Contribution to applications of EBW in instrument techniques

NASA Astrophysics Data System (ADS)

Hrabovsky, Miroslav

1999-07-01

The electron beam welding belongs to so-called physical methods of welding and it is utilized to welding of most materials, that can be arc welded. It is of use there, where one taxing welding technics and structure technologyableless heavily. As a rule, the quality of weld is better than at most first-rate welds being done by inert gas shielded arc welding (WIG, Argoarc). In plant instrumentation, where the limitation of any welded material distortion is of extraordinary importance, this way of welding is significant at welding of thermal-treated Cu-Be alloys, used in measurement technics, structural members from Ti alloys and stainless steels in branches of biomedicine and cryotechnics. This technology positives, especially high weld purity, narrow and deep root penetration, high welding rate, together with low energy consumption, lead to applications and verification of optimum operating mode at welding of frequent materials. In the contribution the results of this proofs of selected welded materials from viewpoint of weld quality, their physical-mechanic properties and microhardness, are presented.

ICALEO '91 - Laser materials processing; Proceedings of the Meeting, San Jose, CA, Nov. 3-8, 1991

NASA Astrophysics Data System (ADS)

Metzbower, Edward A.; Beyer, Eckhard; Matsunawa, Akira

Consideration is given to new developments in LASERCAV technology, modeling of deep penetration laser welding, the theory of radiative transfer in the plasma of the keyhole in penetration laser welding, a synchronized laser-video camera system study of high power laser material interactions, laser process monitoring with dual wavelength optical sensors, new devices for on-line process diagnostics during laser machining, and the process development for a portable Nd:YAG laser materials processing system. Attention is also given to laser welding of alumina-reinforced 6061 aluminum alloy composite, the new trend of laser materials processing, optimization of the laser cutting process for thin section stainless steels, a new nozzle concept for cutting with high power lasers, rapid solidification effects during laser welding, laser surface modification of a low carbon steel with tungsten carbide and carbon, absorptivity of a polarized beam during laser hardening, and laser surface melting of 440 C tool steel. (No individual items are abstracted in this volume)

Weld pool oscillation during GTA welding of mild steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Y.H.; Ouden, G. den

1993-08-01

In this paper the results are reported of a study dealing with the oscillation behavior of weld pools in the case of GTA bead-on-plate welding of mild steel, Fe 360. During welding, the weld pool was brought into oscillation by applying short current pulses, and the oscillation frequency and amplitude were measured by monitoring the arc voltage. It was found that the oscillation of the partially penetrated weld pool is dominated by one of two different oscillation modes (Mode 1 and Mode 2) depending on the welding conditions, whereas the oscillation of the fully penetrated weld pool is characterized bymore » a third oscillation mode (Mode 3). It is possible to maintain partially penetrated weld pool oscillation in Mode 1 by choosing appropriate welding conditions. Under these conditions, an abrupt decrease in oscillation frequency occurs when the weld pool transfers from partial penetration to full penetration. Thus, weld penetration can be in-process controlled by monitoring the oscillation frequency during welding.« less

Proof test criteria for thin-walled 2219 aluminum pressure vessels. Volume 1: Program summary and data analysis

NASA Technical Reports Server (NTRS)

Finger, R. W.

1976-01-01

This experimental program was undertaken to investigate the crack growth behavior of deep surface flaws in 2219 aluminum. The program included tests of uniaxially loaded surface flaw and center crack panels at temperatures ranging from 20K (-423 F) to ambient. The tests were conducted on both the base metal and as-welded weld metal material. The program was designed to provide data on the mechanisms of failure by ligament penetration, and the residual cyclic life, after proof-testing, of a vessel which has been subjected to incipient penetration by the proof test. The results were compared and analyzed with previously developed data to develop guidelines for the proof testing of thin walled 2219 pressure vessels.

Interaction of trace elements and welding parameters on GTA weld shape. [Variation with penetration and tip angle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burgardt, P.; Heiple, C.R.

1985-01-01

Good penetration and poor penetration steels have different responses to changes in temperature distribution on the weld pool surface. Penetration of 304 SS was varied using S and Se dopants. The weld parameter investigated was the electrode tip angle. Results of bead-on-plate GTA welds show that there is a difference in response of weld pool shape to tip angle depending on penetration: Low penetration base metal showed no dependence, intermediate penetration steel showed a small linear decrease of weld depth-to-width ratio (d/w) with tip angle, while high penetration steel showed an increase of d/w up to a maximum at aboutmore » 50/sup 0/, followed by a decrease in d/w. (DLC)« less

Optimization of laser welding thin-gage galvanized steel via response surface methodology

NASA Astrophysics Data System (ADS)

Zhao, Yangyang; Zhang, Yansong; Hu, Wei; Lai, Xinmin

2012-09-01

The increasing demand of light weight and durability makes thin-gage galvanized steels (<0.6 mm) attractive for future automotive applications. Laser welding, well known for its deep penetration, high speed and small heat affected zone, provides a potential solution for welding thin-gage galvanized steels in automotive industry. In this study, the effect of the laser welding parameters (i.e. laser power, welding speed, gap and focal position) on the weld bead geometry (i.e. weld depth, weld width and surface concave) of 0.4 mm-thick galvanized SAE1004 steel in a lap joint configuration has been investigated by experiments. The process windows of the concerned process parameters were therefore determined. Then, response surface methodology (RSM) was used to develop models to predict the relationship between the processing parameters and the laser weld bead profile and identify the correct and optimal combination of the laser welding input variables to obtain superior weld joint. Under the optimal welding parameters, defect-free weld were produced, and the average aspect ratio increased about 30%, from 0.62 to 0.83.

Research on the welding process of aluminum alloy based on high power fiber laser

NASA Astrophysics Data System (ADS)

Zhang, Jian; Zhang, Wei; Pan, Xiaoming; Huang, Shanshi; Liu, Wenwen

2017-08-01

To research the formation and variation principle of the weld seam and molten pool for aluminum alloy high power fiber laser welding, the welding experiments for 5052 aluminum alloy were carried out. The influences of laser power, scanning velocity and protection gas on the welding process were systematically researched. The results show that with the increase of power and scanning velocity, the depth to width ratio first increases and then decreases. The ratio reaches the maximum value at 2.6 KW and 30 mm/s, respectively. When the power located at 2.6 KW to 2.8 KW or the velocity located at 25 mm/s to 30 mm/s, stable deep penetration welding can be obtained. The weld seam shows relative flat appearance and the molten pool presents typical "T shape" topography. Moreover, the protection gas also influences the appearance of the weld seam. Using the independently designed fixture, the quality of the weld seam can be well improved.

A Quantitative Model of Keyhole Instability Induced Porosity in Laser Welding of Titanium Alloy

NASA Astrophysics Data System (ADS)

Pang, Shengyong; Chen, Weidong; Wang, Wen

2014-06-01

Quantitative prediction of the porosity defects in deep penetration laser welding has generally been considered as a very challenging task. In this study, a quantitative model of porosity defects induced by keyhole instability in partial penetration CO2 laser welding of a titanium alloy is proposed. The three-dimensional keyhole instability, weld pool dynamics, and pore formation are determined by direct numerical simulation, and the results are compared to prior experimental results. It is shown that the simulated keyhole depth fluctuations could represent the variation trends in the number and average size of pores for the studied process conditions. Moreover, it is found that it is possible to use the predicted keyhole depth fluctuations as a quantitative measure of the average size of porosity. The results also suggest that due to the shadowing effect of keyhole wall humps, the rapid cooling of the surface of the keyhole tip before keyhole collapse could lead to a substantial decrease in vapor pressure inside the keyhole tip, which is suggested to be the mechanism by which shielding gas enters into the porosity.

Status analysis of keyhole bottom in laser-MAG hybrid welding process.

PubMed

Wang, Lin; Gao, Xiangdong; Chen, Ziqin

2018-01-08

The keyhole status is a determining factor of weld quality in laser-metal active gas arc (MAG) hybrid welding process. For a better evaluation of the hybrid welding process, three different penetration welding experiments: partial penetration, normal penetration (or full penetration), and excessive penetration were conducted in this work. The instantaneous visual phenomena including metallic vapor, spatters and keyhole of bottom surface were used to evaluate the keyhole status by a double high-speed camera system. The Fourier transform was applied on the bottom weld pool image for removing the image noise around the keyhole, and then the bottom weld pool image was reconstructed through the inverse Fourier transform. Lastly, the keyhole bottom was extracted from the de-noised bottom weld pool image. By analyzing the visual features of the laser-MAG hybrid welding process, mechanism of the closed and opened keyhole bottom were revealed. The results show that the stable opened or closed status of keyhole bottom is directly affected by the MAG droplet transition in the normal penetration welding process, and the unstable opened or closed status of keyhole bottom would appear in excessive penetration welding and partial penetration welding. The analysis method proposed in this paper could be used to monitor the keyhole stability in laser-MAG hybrid welding process.

A Study to Increase Weld Penetration in P91 Steel During TIG Welding by using Activating Fluxes

NASA Astrophysics Data System (ADS)

Singh, Akhilesh Kumar; Kumar, Mayank; Dey, Vidyut; Naresh Rai, Ram

2017-08-01

Activated Flux TIG (ATIG) welding is a unique joining process, invented at Paton Institute of electric welding in 1960. ATIG welding process is also known as flux zoned TIG (FZTIG). In this process, a thin layer of activating flux is applied along the line on the surface of the material where the welding is to be carries out. The ATIG process aids to increase the weld penetration in thick materials. Activating fluxes used in the literature show the use of oxides like TiO2, SiO2, Cr2O3, ZnO, CaO, Fe2O3, and MnO2 during welding of steels. In the present study, ATIG was carried out on P-91 steel. Though, Tungsten Inert Gas welding gives excellent quality welds, but the penetration obtained in such welding is still demanding. P91 steel which is ferritic steel is used in high temperature applications. As this steel is, generally, used in thick sections, fabrication of such structures with TIG welding is limited, due to its low depth of penetration. To increase the depth of penetration in P91while welding with ATIG, the role of various oxides were investigated. Apart from the oxides mentioned above, in the present study the role of B2O3, V2O5 and MgO, during ATIG welding of P91 was investigated. It was seen that, compared to TIG welding, there was phenomenal increase in weld penetration during ATIG welding. Amongst all the oxides used in this study, maximum penetration was achieved in case of B2O3. The measurements of weld penetration, bead width and heat affected zone of the weldings were carried out using an image analysis technique.

Prediction of Weld Penetration in FCAW of HSLA steel using Artificial Neural Networks

NASA Astrophysics Data System (ADS)

Asl, Y. Dadgar; Mostafa, N. B.; Panahizadeh R., V.; Seyedkashi, S. M. H.

2011-01-01

Flux-cored arc welding (FCAW) is a semiautomatic or automatic arc welding process that requires a continuously-fed consumable tubular electrode containing a flux. The main FCAW process parameters affecting the depth of penetration are welding current, arc voltage, nozzle-to-work distance, torch angle and welding speed. Shallow depth of penetration may contribute to failure of a welded structure since penetration determines the stress-carrying capacity of a welded joint. To avoid such occurrences; the welding process parameters influencing the weld penetration must be properly selected to obtain an acceptable weld penetration and hence a high quality joint. Artificial neural networks (ANN), also called neural networks (NN), are computational models used to express complex non-linear relationships between input and output data. In this paper, artificial neural network (ANN) method is used to predict the effects of welding current, arc voltage, nozzle-to-work distance, torch angle and welding speed on weld penetration depth in gas shielded FCAW of a grade of high strength low alloy steel. 32 experimental runs were carried out using the bead-on-plate welding technique. Weld penetrations were measured and on the basis of these 32 sets of experimental data, a feed-forward back-propagation neural network was created. 28 sets of the experiments were used as the training data and the remaining 4 sets were used for the testing phase of the network. The ANN has one hidden layer with eight neurons and is trained after 840 iterations. The comparison between the experimental results and ANN results showed that the trained network could predict the effects of the FCAW process parameters on weld penetration adequately.

Weld pool oscillation during pulsed GTA welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aendenroomer, A.J.R.; Ouden, G. den

1996-12-31

This paper deals with weld pool oscillation during pulsed GTA welding and with the possibility to use this oscillation for in-process control of weld penetration. Welding experiments were carried out under different welding conditions. During welding the weld pool was triggered into oscillation by the normal welding pulses or by extra current pulses. The oscillation frequency was measured both during the pulse time and during the base time by analyzing the arc voltage variation using a Fast Fourier Transformation program. Optimal results are obtained when full penetration occurs during the pulse time and partial penetration during the base time. Undermore » these conditions elliptical overlapping spot welds are formed. In the case of full penetration the weld pool oscillates in a low frequency mode (membrane oscillation), whereas in the case of partial penetration the weld pool oscillates in a high frequency mode (surface oscillation). Deviation from the optimal welding conditions occurs when high frequency oscillation is observed during both pulse time and base time (underpenetration) or when low frequency oscillation is observed during both pulse time and base time (overpenetration). In line with these results a penetration sensing system with feedback control was designed, based on the criterion that optimal weld penetration is achieved when two peaks are observed in the frequency distribution. The feasibility of this sensing system for orbital tube welding was confirmed by the results of experiments carried out under various welding conditions.« less

An Approach to Maximize Weld Penetration During TIG Welding of P91 Steel Plates by Utilizing Image Processing and Taguchi Orthogonal Array

NASA Astrophysics Data System (ADS)

Singh, Akhilesh Kumar; Debnath, Tapas; Dey, Vidyut; Rai, Ram Naresh

2017-10-01

P-91 is modified 9Cr-1Mo steel. Fabricated structures and components of P-91 has a lot of application in power and chemical industry owing to its excellent properties like high temperature stress corrosion resistance, less susceptibility to thermal fatigue at high operating temperatures. The weld quality and surface finish of fabricated structure of P91 is very good when welded by Tungsten Inert Gas welding (TIG). However, the process has its limitation regarding weld penetration. The success of a welding process lies in fabricating with such a combination of parameters that gives maximum weld penetration and minimum weld width. To carry out an investigation on the effect of the autogenous TIG welding parameters on weld penetration and weld width, bead-on-plate welds were carried on P91 plates of thickness 6 mm in accordance to a Taguchi L9 design. Welding current, welding speed and gas flow rate were the three control variables in the investigation. After autogenous (TIG) welding, the dimension of the weld width, weld penetration and weld area were successfully measured by an image analysis technique developed for the study. The maximum error for the measured dimensions of the weld width, penetration and area with the developed image analysis technique was only 2 % compared to the measurements of Leica-Q-Win-V3 software installed in optical microscope. The measurements with the developed software, unlike the measurements under a microscope, required least human intervention. An Analysis of Variance (ANOVA) confirms the significance of the selected parameters. Thereafter, Taguchi's method was successfully used to trade-off between maximum penetration and minimum weld width while keeping the weld area at a minimum.

Acoustic-Emission Weld-Penetration Monitor

NASA Technical Reports Server (NTRS)

Maram, J.; Collins, J.

1986-01-01

Weld penetration monitored by detection of high-frequency acoustic emissions produced by advancing weld pool as it melts and solidifies in workpiece. Acoustic emission from TIG butt weld measured with 300-kHz resonant transducer. Rise in emission level coincides with cessation of weld penetration due to sudden reduction in welding current. Such monitoring applied to control of automated and robotic welders.

Relationship between spatter formation and dynamic molten pool during high-power deep-penetration laser welding

NASA Astrophysics Data System (ADS)

Li, Shichun; Chen, Genyu; Katayama, Seiji; Zhang, Yi

2014-06-01

The spatter and the molten pool behavior, which were the important phenomena concerned with the welding quality, were observed and studied by using the high-speed camera and the X-ray transmission imaging system during laser welding under different welding parameters. The formation mechanism of spatter and the corresponding relationships between the spatter and molten pool behavior were investigated. The increase of laser power could cause more intense evaporation and lead to more spatter. When the focal position of laser beam was changed, different forms of spatter were generated, as well as the flow trends of molten metal on the front keyhole wall and at the rear molten pool were changed. The results revealed that the behavior of molten pool, which could be affected by the absorbed energy distribution in the keyhole, was the key factor to determine the spatter formation during laser welding. The relatively sound weld seam could be obtained during laser welding with the focal position located inside the metal.

Microstructure and Porosity of Laser-welded Dissimilar Material Joints of HR-2 and J75

NASA Astrophysics Data System (ADS)

Shen, Xianfeng; Teng, Wenhua; Zhao, Shuming; He, Wenpei

Dissimilar laser welding of HR-2 and J75 has a wide range of applications in high-and low-temperature hydrogen storage. The porosity distributions of the welded joints were investigated at different line energies, penetration status, and welding positions (1G, 2G, and 3G). The effect of the welding position on the welding appearance was evident only at high line energies because of the essential effect of gravity of the larger and longer dwelling molten pool. The porosity of the welded joints between the solutionised and aged J75 and HR-2 at the 3G position and partial penetration was located at the weld centre line, while the porosity at the 2G position with full penetration was distributed at the weld edges, which is consistent with the distribution of floating slag. Full keyhole penetration resulted in minimum porosity, partial penetration resulted in moderate porosity, and periodic molten pool penetration resulted in maximum porosity.

Effect of oxygen on weld shape and crystallographic orientation of duplex stainless steel weld using advanced A-TIG (AA-TIG) welding method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zou, Ying, E-mail: yingzou@jwri.osaka-u.ac.jp; Ueji, Rintaro; Fujii, Hidetoshi

The double-shielded advanced A-TIG (AA-TIG) welding method was adopted in this study for the welding of the SUS329J4L duplex stainless steel with the shielding gases of different oxygen content levels. The oxygen content in the shielding gas was controlled by altering the oxygen content in the outer layer gas, while the inner layer remained pure argon to suppress oxidation on the tungsten electrode. As a result, a deep weld penetration was obtained due to the dissolution of oxygen into the weld metals. Additionally, the microstructure of the weld metal was changed by the dissolution of oxygen. The austenite phase atmore » the ferrite grain boundary followed a Kurdjumov–Sachs (K–S) orientation relationship with the ferrite matrix phase at any oxide content. On the other hand, the orientation relationship between the intragranular austenite phase and the ferrite matrix phase exhibited different patterns under different oxygen content levels. When there was little oxide in the fusion zone, only a limited part of the intragranular austenite phase and the ferrite matrix phase followed the K–S orientation relationship. With the increase of the oxide, the correspondence of the K–S relationship increased and fit very well in the 2.5% O{sub 2} shielded sample. The investigation of this phenomenon was carried out along with the nucleation mechanisms of the intragranular austenite phases. - Highlights: • Weld penetration increased with the increase of the oxygen content. • Average diameter and number density of oxide were changed by the oxygen content. • K-S relationship of Widmanstätten austenite/ferrite wasn’t varied by oxide. • Orientation relationship of intragranular austenite/ferrite was varied by oxide.« less

Adaptive Neuro-Fuzzy Inference System (ANFIS)-Based Models for Predicting the Weld Bead Width and Depth of Penetration from the Infrared Thermal Image of the Weld Pool

NASA Astrophysics Data System (ADS)

Subashini, L.; Vasudevan, M.

2012-02-01

Type 316 LN stainless steel is the major structural material used in the construction of nuclear reactors. Activated flux tungsten inert gas (A-TIG) welding has been developed to increase the depth of penetration because the depth of penetration achievable in single-pass TIG welding is limited. Real-time monitoring and control of weld processes is gaining importance because of the requirement of remoter welding process technologies. Hence, it is essential to develop computational methodologies based on an adaptive neuro fuzzy inference system (ANFIS) or artificial neural network (ANN) for predicting and controlling the depth of penetration and weld bead width during A-TIG welding of type 316 LN stainless steel. In the current work, A-TIG welding experiments have been carried out on 6-mm-thick plates of 316 LN stainless steel by varying the welding current. During welding, infrared (IR) thermal images of the weld pool have been acquired in real time, and the features have been extracted from the IR thermal images of the weld pool. The welding current values, along with the extracted features such as length, width of the hot spot, thermal area determined from the Gaussian fit, and thermal bead width computed from the first derivative curve were used as inputs, whereas the measured depth of penetration and weld bead width were used as output of the respective models. Accurate ANFIS models have been developed for predicting the depth of penetration and the weld bead width during TIG welding of 6-mm-thick 316 LN stainless steel plates. A good correlation between the measured and predicted values of weld bead width and depth of penetration were observed in the developed models. The performance of the ANFIS models are compared with that of the ANN models.

Optical penetration sensor for pulsed laser welding

DOEpatents

Essien, Marcelino; Keicher, David M.; Schlienger, M. Eric; Jellison, James L.

2000-01-01

An apparatus and method for determining the penetration of the weld pool created from pulsed laser welding and more particularly to an apparatus and method of utilizing an optical technique to monitor the weld vaporization plume velocity to determine the depth of penetration. A light source directs a beam through a vaporization plume above a weld pool, wherein the plume changes the intensity of the beam, allowing determination of the velocity of the plume. From the velocity of the plume, the depth of the weld is determined.

Influence of Oxides on Microstructures and Mechanical Properties of High-Strength Steel Weld Joint

NASA Astrophysics Data System (ADS)

Cai, Yangchuan; Luo, Zhen; Huang, Zunyue; Zeng, Yida

2016-11-01

A comprehensive investigation was conducted into the effect of oxides on penetrations, microstructures and mechanical properties of BS700MC super steel weld bead. Boron oxide changed the penetration of weld bead by changing the Marangoni convection in the weld pool and contracting the welding arc. Chromium oxide only changed the Marangoni convection in the weld pool to increase the penetration of super steel. Thus, the super steel weld bead has higher penetration coated with flux boron oxide than that coated with chromium oxide. In other words, the activating flux TIG (A-TIG) welding with flux boron oxide has less welding heat input than the A-TIG welding with flux chromium oxide. As a result, on the one hand, there existed more fine and homogeneous acicular ferrites in the microstructure of welding heat-affected zone when the super steel was welded by A-TIG with flux boron oxide. Thus, the weld beads have higher value of low-temperature impact toughness. On the other hand, the softening degree of welding heat-affected zone, welded by A-TIG with flux boron oxide, will be decreased for the minimum value of welding heat input.

Stability of Full Penetration, Flat Position Weld Pools

NASA Technical Reports Server (NTRS)

Nunes, Arthur C., Jr.; Coan, Al. B.

1999-01-01

The dynamics of the dropthrough distance of a full penetration, flat position weld pool is described. Close to incipient root side penetration the dropthrough is metastable, so that a small drop in power can cause a loss of penetration if not followed soon enough by a compensating rise in power. The SPA (Soft Plasma Arc) process with higher pressure on top of the weld pool loses penetration more quickly than the GTA (Gas Tungsten Arc) process. 2195 aluminum-lithium alloy with a lower surface tension loses penetration more quickly than 2219 aluminum alloy. An instance of loss of penetration of a SPA weld in 2195 aluminum-lithium alloy is discussed in the light of the model.

Dynamic characteristics and mechanisms of compressible metallic vapor plume behaviors in transient keyhole during deep penetration fiber laser welding

NASA Astrophysics Data System (ADS)

Pang, Shengyong; Shao, Xinyu; Li, Wen; Chen, Xin; Gong, Shuili

2016-07-01

The compressible metallic vapor plume or plasma plume behaviors in the keyhole during deep penetration laser welding have significant effects on the joint quality. However, these behaviors and their responses to process parameter variations have not been well understood. In this paper, we first systematically study the dynamic characteristics and mechanisms of compressible metallic vapor plume behaviors in transient keyhole during fiber laser welding of 304 stainless steels based on a multiple timescale multiphase model. The time-dependent temperature, pressure, velocity and Mach number distributions of vapor plume under different process parameters are theoretically predicted. It is found that the distributions of the main physical characteristics of vapor plume such as pressure, velocity as well as Mach number in keyhole are usually highly uneven and highly time dependent. The peak difference of the velocity, pressure, temperature and Mach number of the vapor plume in a keyhole could be greater than 200 m/s, 20 kPa, 1000 K and 0.6 Mach, respectively. The vapor plume characteristics in a transient keyhole can experience significant changes within several hundreds of nanoseconds. The formation mechanisms of these dynamic characteristics are mainly due to the mesoscale keyhole hump (sized in several tens of microns) dynamics. It is also demonstrated that it is possible to suppress the oscillations of compressible vapor plume in the keyhole by improving the keyhole stability through decreasing the heat input. However, stabilizing the keyhole could only weaken, but not eliminate, the observed highly uneven and transient characteristics. This finding may pose new challenges for accurate experimental measurements of vapor plume induced by laser welding.

Intelligent Modeling Combining Adaptive Neuro Fuzzy Inference System and Genetic Algorithm for Optimizing Welding Process Parameters

NASA Astrophysics Data System (ADS)

Gowtham, K. N.; Vasudevan, M.; Maduraimuthu, V.; Jayakumar, T.

2011-04-01

Modified 9Cr-1Mo ferritic steel is used as a structural material for steam generator components of power plants. Generally, tungsten inert gas (TIG) welding is preferred for welding of these steels in which the depth of penetration achievable during autogenous welding is limited. Therefore, activated flux TIG (A-TIG) welding, a novel welding technique, has been developed in-house to increase the depth of penetration. In modified 9Cr-1Mo steel joints produced by the A-TIG welding process, weld bead width, depth of penetration, and heat-affected zone (HAZ) width play an important role in determining the mechanical properties as well as the performance of the weld joints during service. To obtain the desired weld bead geometry and HAZ width, it becomes important to set the welding process parameters. In this work, adaptative neuro fuzzy inference system is used to develop independent models correlating the welding process parameters like current, voltage, and torch speed with weld bead shape parameters like depth of penetration, bead width, and HAZ width. Then a genetic algorithm is employed to determine the optimum A-TIG welding process parameters to obtain the desired weld bead shape parameters and HAZ width.

Process characteristics of the combination of laser beam- and gas metal arc welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalla, G.; Neuenhahn, J.; Koerber, C.

1994-12-31

In this presentation, experiences regarding the combination of laser beam-and gas metal arc welding are discussed. The combination of both techniques offers the possibility of using the specific advantages include the deep penetration effect and the concentrated heat input. Additionally, the gas metal arc welding (GMAW) process is characterized by several advantages, such as high thermal efficiency and good gap-bridging ability. Beyond these characteristics, the combination leads to additional advantages concerning process, technique, and quality. Improvement of seam quality and properties are of special note. Adaptation of the GMAW parameters reduces the hardness of the seam weld at increasing weldingmore » speed. This is possible by adapting the efficiency of metal deposition and by the suitable choice of wire material composition. Another advantage is an improvement of surface topology. The surface of the weld seam and the connection to the base material are very smooth. This leads to advantages with regard to the fatigue strength of the seam.« less

Laser-ultrasonic inspection of hybrid laser-arc welded HSLA-65 steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lévesque, D.; Rousseau, G.; Monchalin, J.-P.

2014-02-18

The hybrid laser-arc welding (HLAW) process is a relatively low heat input joining technology that combines the synergistic qualities of both the high energy density laser beam for deep penetration and the arc for wide fit-up gap tolerance. This process is especially suitable for the shipbuilding industry where thick-gauge section, long steel plates have been widely used in a butt joint configuration. In this study, preliminary exploration was carried out to detect and visualize the welding defects using laser ultrasonics combined with the synthetic aperture focusing technique (SAFT). Results obtained on 9.3 mm thick butt-welded HSLA-65 steel plates indicated thatmore » the laser-ultrasonic SAFT inspection technique can successfully detect and visualize the presence of porosity, lack of fusion and internal crack defects. This was further confirmed by X-ray digital radiography and metallography. The results obtained clearly show the potential of using the laser-ultrasonic technology for the automated inspection of hybrid laser-arc welds.« less

Laser-ultrasonic inspection of hybrid laser-arc welded HSLA-65 steel

NASA Astrophysics Data System (ADS)

Lévesque, D.; Rousseau, G.; Wanjara, P.; Cao, X.; Monchalin, J.-P.

2014-02-01

The hybrid laser-arc welding (HLAW) process is a relatively low heat input joining technology that combines the synergistic qualities of both the high energy density laser beam for deep penetration and the arc for wide fit-up gap tolerance. This process is especially suitable for the shipbuilding industry where thick-gauge section, long steel plates have been widely used in a butt joint configuration. In this study, preliminary exploration was carried out to detect and visualize the welding defects using laser ultrasonics combined with the synthetic aperture focusing technique (SAFT). Results obtained on 9.3 mm thick butt-welded HSLA-65 steel plates indicated that the laser-ultrasonic SAFT inspection technique can successfully detect and visualize the presence of porosity, lack of fusion and internal crack defects. This was further confirmed by X-ray digital radiography and metallography. The results obtained clearly show the potential of using the laser-ultrasonic technology for the automated inspection of hybrid laser-arc welds.

Plasma Charge Current for Controlling and Monitoring Electron Beam Welding with Beam Oscillation

PubMed Central

Trushnikov, Dmitriy; Belenkiy, Vladimir; Shchavlev, Valeriy; Piskunov, Anatoliy; Abdullin, Aleksandr; Mladenov, Georgy

2012-01-01

Electron beam welding (EBW) shows certain problems with the control of focus regime. The electron beam focus can be controlled in electron-beam welding based on the parameters of a secondary signal. In this case, the parameters like secondary emissions and focus coil current have extreme relationships. There are two values of focus coil current which provide equal value signal parameters. Therefore, adaptive systems of electron beam focus control use low-frequency scanning of focus, which substantially limits the operation speed of these systems and has a negative effect on weld joint quality. The purpose of this study is to develop a method for operational control of the electron beam focus during welding in the deep penetration mode. The method uses the plasma charge current signal as an additional informational parameter. This parameter allows identification of the electron beam focus regime in electron-beam welding without application of additional low-frequency scanning of focus. It can be used for working out operational electron beam control methods focusing exactly on the welding. In addition, use of this parameter allows one to observe the shape of the keyhole during the welding process. PMID:23242276

Plasma charge current for controlling and monitoring electron beam welding with beam oscillation.

PubMed

Trushnikov, Dmitriy; Belenkiy, Vladimir; Shchavlev, Valeriy; Piskunov, Anatoliy; Abdullin, Aleksandr; Mladenov, Georgy

2012-12-14

Electron beam welding (EBW) shows certain problems with the control of focus regime. The electron beam focus can be controlled in electron-beam welding based on the parameters of a secondary signal. In this case, the parameters like secondary emissions and focus coil current have extreme relationships. There are two values of focus coil current which provide equal value signal parameters. Therefore, adaptive systems of electron beam focus control use low-frequency scanning of focus, which substantially limits the operation speed of these systems and has a negative effect on weld joint quality. The purpose of this study is to develop a method for operational control of the electron beam focus during welding in the deep penetration mode. The method uses the plasma charge current signal as an additional informational parameter. This parameter allows identification of the electron beam focus regime in electron-beam welding without application of additional low-frequency scanning of focus. It can be used for working out operational electron beam control methods focusing exactly on the welding. In addition, use of this parameter allows one to observe the shape of the keyhole during the welding process.

Effects of Sealing Run Welding with Defocused Laser Beam on the Quality of T-joint Fillet Weld

NASA Astrophysics Data System (ADS)

Unt, Anna; Poutiainen, Ilkka; Salminen, Antti

Fillet weld is the predominant weld type used for connecting different elements e.g. in shipbuilding, offshore and bridge structures. One of prevalent research questions is the structural integrity of the welded joint. Post weld improvement techniques are being actively researched, as high stress areas like an incomplete penetration on the root side or fluctuations in penetration depth cannot be avoided. Development of laser and laser-arc hybrid welding processes have greatly contributed to increase of production capacity and reduction of heat-induced distortions by producing single pass full penetration welds in thin- and medium thickness structural steel parts. Present study addresses the issue of how to improve the quality of the fillet welds by welding the sealing run on the root side with defocused laser beam. Welds having incomplete or excessive penetration were produced with several beam angles and laser beam spot sizes on surface. As a conclusion, significant decrease or even complete elimination of the seam irregularities, which act as the failure starting points during service, is achieved.

Thermomechanically coupled conduction mode laser welding simulations using smoothed particle hydrodynamics

NASA Astrophysics Data System (ADS)

Hu, Haoyue; Eberhard, Peter

2017-10-01

Process simulations of conduction mode laser welding are performed using the meshless Lagrangian smoothed particle hydrodynamics (SPH) method. The solid phase is modeled based on the governing equations in thermoelasticity. For the liquid phase, surface tension effects are taken into account to simulate the melt flow in the weld pool, including the Marangoni force caused by a temperature-dependent surface tension gradient. A non-isothermal solid-liquid phase transition with the release or absorption of additional energy known as the latent heat of fusion is considered. The major heat transfer through conduction is modeled, whereas heat convection and radiation are neglected. The energy input from the laser beam is modeled as a Gaussian heat source acting on the initial material surface. The developed model is implemented in Pasimodo. Numerical results obtained with the model are presented for laser spot welding and seam welding of aluminum and iron. The change of process parameters like welding speed and laser power, and their effects on weld dimensions are investigated. Furthermore, simulations may be useful to obtain the threshold for deep penetration welding and to assess the overall welding quality. A scalability and performance analysis of the implemented SPH algorithm in Pasimodo is run in a shared memory environment. The analysis reveals the potential of large welding simulations on multi-core machines.

Camera Based Closed Loop Control for Partial Penetration Welding of Overlap Joints

NASA Astrophysics Data System (ADS)

Abt, F.; Heider, A.; Weber, R.; Graf, T.; Blug, A.; Carl, D.; Höfler, H.; Nicolosi, L.; Tetzlaff, R.

Welding of overlap joints with partial penetration in automotive applications is a challenging process, since the laser power must be set very precisely to achieve a proper connection between the two joining partners without damaging the backside of the sheet stack. Even minor changes in welding conditions can lead to bad results. To overcome this problem a camera based closed loop control for partial penetration welding of overlap joints was developed. With this closed loop control it is possible to weld such configurations with a stable process result even under changing welding conditions.

Effect of A-TIG Welding Process on the Weld Attributes of Type 304LN and 316LN Stainless Steels

NASA Astrophysics Data System (ADS)

Vasudevan, M.

2017-03-01

The specific activated flux has been developed for enhancing the penetration performance of TIG welding process for autogenous welding of type 304LN and 316LN stainless steels through systematic study. Initially single-component fluxes were used to study their effect on depth of penetration and tensile properties. Then multi-component activated flux was developed which was found to produce a significant increase in penetration of 10-12 mm in single-pass TIG welding of type 304LN and 316LN stainless steels. The significant improvement in penetration achieved using the activated flux developed in the present work has been attributed to the constriction of the arc and as well as reversal of Marangoni flow in the molten weld pool. The use of activated flux has been found to overcome the variable weld penetration observed in 316LN stainless steel with <50 ppm of sulfur. There was no degradation in the microstructure and mechanical properties of the A-TIG welds compared to that of the welds produced by conventional TIG welding on the contrary the transverse strength properties of the 304LN and 316LN stainless steel welds produced by A-TIG welding exceeded the minimum specified strength values of the base metals. Improvement in toughness values were observed in 316LN stainless steel produced by A-TIG welding due to refinement in the weld microstructure in the region close to the weld center. Thus, activated flux developed in the present work has greater potential for use during the TIG welding of structural components made of type 304LN and 316LN stainless steels.

Elucidation of Metallic Plume and Spatter Characteristics Based on SVM During High-Power Disk Laser Welding

NASA Astrophysics Data System (ADS)

Gao, Xiangdong; Liu, Guiqian

2015-01-01

During deep penetration laser welding, there exist plume (weak plasma) and spatters, which are the results of weld material ejection due to strong laser heating. The characteristics of plume and spatters are related to welding stability and quality. Characteristics of metallic plume and spatters were investigated during high-power disk laser bead-on-plate welding of Type 304 austenitic stainless steel plates at a continuous wave laser power of 10 kW. An ultraviolet and visible sensitive high-speed camera was used to capture the metallic plume and spatter images. Plume area, laser beam path through the plume, swing angle, distance between laser beam focus and plume image centroid, abscissa of plume centroid and spatter numbers are defined as eigenvalues, and the weld bead width was used as a characteristic parameter that reflected welding stability. Welding status was distinguished by SVM (support vector machine) after data normalization and characteristic analysis. Also, PCA (principal components analysis) feature extraction was used to reduce the dimensions of feature space, and PSO (particle swarm optimization) was used to optimize the parameters of SVM. Finally a classification model based on SVM was established to estimate the weld bead width and welding stability. Experimental results show that the established algorithm based on SVM could effectively distinguish the variation of weld bead width, thus providing an experimental example of monitoring high-power disk laser welding quality.

Laser-based welding of 17-4 PH martensitic stainless steel in a tubular butt joint configuration with a built-in backing bar

NASA Astrophysics Data System (ADS)

Ma, Junjie; Atabaki, Mehdi Mazar; Liu, Wei; Pillai, Raju; Kumar, Biju; Vasudevan, Unnikrishnan; Kovacevic, Radovan

2016-08-01

Laser-based welding of thick 17-4 precipitation hardening (PH) martensitic stainless steel (SS) plates in a tubular butt joint configuration with a built-in backing bar is very challenging because the porosity and cracks are easily generated in the welds. The backing bar blocked the keyhole opening at the bottom surface through which the entrapped gas could escape, and the keyhole was unstable and collapsed overtime in a deep partially penetrated welding conditions resulting in the formation of pores easily. Moreover, the fast cooling rate prompted the ferrite transform to austenite which induced cracking. Two-pass welding procedure was developed to join 17-4 PH martensitic SS. The laser welding assisted by a filler wire, as the first pass, was used to weld the groove shoulder. The added filler wire could absorb a part of the laser beam energy; resulting in the decreased weld depth-to-width ratio and relieved intensive restraint at the weld root. A hybrid laser-arc welding or a gas metal arc welding (GMAW) was used to fill the groove as the second pass. Nitrogen was introduced to stabilize the keyhole and mitigate the porosity. Preheating was used to decrease the cooling rate and mitigate the cracking during laser-based welding of 17-4 PH martensitic SS plates.

Process stability during fiber laser-arc hybrid welding of thick steel plates

NASA Astrophysics Data System (ADS)

Bunaziv, Ivan; Frostevarg, Jan; Akselsen, Odd M.; Kaplan, Alexander F. H.

2018-03-01

Thick steel plates are frequently used in shipbuilding, pipelines and other related heavy industries, and are usually joined by arc welding. Deep penetration laser-arc hybrid welding could increase productivity but has not been thoroughly investigated, and is therefore usually limited to applications with medium thickness (5-15 mm) sections. A major concern is process stability, especially when using modern welding consumables such as metal-cored wire and advanced welding equipment. High speed imaging allows direct observation of the process so that process behavior and phenomena can be studied. In this paper, 45 mm thick high strength steel was welded (butt joint double-sided) using the fiber laser-MAG hybrid process utilizing a metal-cored wire without pre-heating. Process stability was monitored under a wide range of welding parameters. It was found that the technique can be used successfully to weld thick sections with appropriate quality when the parameters are optimized. When comparing conventional pulsed and the more advanced cold metal transfer pulse (CMT+P) arc modes, it was found that both can provide high quality welds. CMT+P arc mode can provide more stable droplet transfer over a limited range of travel speeds. At higher travel speeds, an unstable metal transfer mechanism was observed. Comparing leading arc and trailing arc arrangements, the leading arc configuration can provide higher quality welds and more stable processing at longer inter-distances between the heat sources.

Surface preparation effects on GTA (gas tungsten arc) weld penetration in JBK-75 stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, R.D.; Heiple, C.R.; Sturgill, P.L.

1989-01-01

The results of a study are reported here on the effects of surface preparation on the shape of GTA welds on JBK-75, an austenitic precipitation hardenable stainless steel similar to A286. Minor changes in surface (weld groove) preparation produced substantial changes in the penetration characteristics and welding behavior of this alloy. Increased and more consistent weld penetration (higher d/w ratios) along with improved arc stability and less arc wander result from wire brushing and other abrasive surface preparations, although chemical and machining methods did not produce any improvement in penetration. Abrasive treatments roughen the surface, increase the surface area, andmore » increase the surface oxide thickness. The increased weld d/w ratio is attributed to oxygen added to the weld pool from the surface oxide on the base metal. The added oxygen alters the surface-tension driven fluid flow pattern in the weld pool. Similar results were observed with changes in filler wire surface oxide thickness, caused by changes in wire production conditions. 15 refs., 14 figs., 4 tabs.« less

Interaction of both plasmas in CO2 laser-MAG hybrid welding of carbon steel

NASA Astrophysics Data System (ADS)

Kutsuna, Muneharu; Chen, Liang

2003-03-01

Researches and developments of laser and arc hybrid welding has been curried out since in 1978. Especially, CO2 laser and TIG hybrid welding has been studied for increasing the penetration depth and welding speed. Recently laser and MIG/MAG/Plasma hybrid welding processes have been developed and applied to industries. It was recognized as a new welding process that promote the flexibility of the process for increasing the penetration depth, welding speed and allowable joint gap and improving the quality of the welds. In the present work, CO2 Laser-MAG hybrid welding of carbon steel (SM490) was investigated to make clear the phenomenon and characteristics of hybrid welding process comparing with laser welding and MAG process. The effects of many process parameters such as welding current, arc voltage, welding speed, defocusing distance, laser-to-arc distance on penetration depth, bead shape, spatter, arc stability and plasma formation were investigated in the present work. Especially, the interaction of laser plasma and MAG arc plasma was considered by changing the laser to arc distance (=DLA).

On-line welding quality inspection system for steel pipe based on machine vision

NASA Astrophysics Data System (ADS)

Yang, Yang

2017-05-01

In recent years, high frequency welding has been widely used in production because of its advantages of simplicity, reliability and high quality. In the production process, how to effectively control the weld penetration welding, ensure full penetration, weld uniform, so as to ensure the welding quality is to solve the problem of the present stage, it is an important research field in the field of welding technology. In this paper, based on the study of some methods of welding inspection, a set of on-line welding quality inspection system based on machine vision is designed.

Thermo-Mechanical Modeling of Laser-Mig Hybrid Welding (lmhw)

NASA Astrophysics Data System (ADS)

Kounde, Ludovic; Engel, Thierry; Bergheau, Jean-Michel; Boisselier, Didier

2011-01-01

Hybrid welding is a combination of two different technologies such as laser (Nd: YAG, CO2…) and electric arc welding (MIG, MAG / TIG …) developed to assemble thick metal sheets (over 3 mm) in order to reduce the required laser power. As a matter of fact, hybrid welding is a lso used in the welding of thin materials to benefit from process, deep penetration and gap limit. But the thermo-mechanical behaviour of thin parts assembled by LMHW technology for railway cars production is far from being controlled the modeling and simulation contribute to the assessment of the causes and effects of the thermo mechanical behaviour in the assembled parts. In order to reproduce the morphology of melted and heat-affected zones, two analytic functions were combined to model the heat source of LMHW. On one hand, we applied a so-called "diaboloïd" (DB) which is a modified hyperboloid, based on experimental parameters and the analysis of the macrographs of the welds. On the other hand, we used a so-called "double ellipsoïd" (DE) which takes the MIG only contribution including the bead into account. The comparison between experimental result and numerical result shows a good agreement.

Fluid Flow Phenomena during Welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Wei

2011-01-01

MOLTEN WELD POOLS are dynamic. Liquid in the weld pool in acted on by several strong forces, which can result in high-velocity fluid motion. Fluid flow velocities exceeding 1 m/s (3.3 ft/s) have been observed in gas tungsten arc (GTA) welds under ordinary welding conditions, and higher velocities have been measured in submerged arc welds. Fluid flow is important because it affects weld shape and is related to the formation of a variety of weld defects. Moving liquid transports heat and often dominates heat transport in the weld pool. Because heat transport by mass flow depends on the direction andmore » speed of fluid motion, weld pool shape can differ dramatically from that predicted by conductive heat flow. Temperature gradients are also altered by fluid flow, which can affect weld microstructure. A number of defects in GTA welds have been attributed to fluid flow or changes in fluid flow, including lack of penetration, top bead roughness, humped beads, finger penetration, and undercutting. Instabilities in the liquid film around the keyhole in electron beam and laser welds are responsible for the uneven penetration (spiking) characteristic of these types of welds.« less

Welding with the thin disc laser: new processing and application potentials

NASA Astrophysics Data System (ADS)

Hügel, H.; Ruβ, A.; Weberpals, J.; Dausinger, F.

2005-09-01

Thin disc lasers represent a new class of welding lasers in that they combine the beneficial characteristics of CO2- and Nd:YAG-lasers. Their good focusability--values of M2 around 20 are typical for devices in the multi kW power range--can be utilized in several ways to improve the welding performance: compared to lamp-pumped Nd:YAG-lasers, the laser power required at the threshold to the deep penetration regime can be reduced, the welding depth can be increased and far higher values of traverse speed are applicable at prescribed welding depths. Alternatively, the high beam quality allows the use of focusing optics with large focal lengths, hence enabling the realization of "remote welding" concepts. At the same time, a wavelength of 1.03 μm (Yb:YAG) provides, in comparison to CO2-lasers, a high absorptivity at metallic workpieces and a low sensitivity against plasma production; both effects contribute to the efficiency, stability and achievable quality of the welding process. Further, beam delivery via flexible glass fibers with core diameters of 100 μm to 150 μm is possible. With these features and an overall (plug) efficiency of more than 20 %, this laser offers a large potential for many applications.

Forming Completely Penetrated Welded T-joints when Pulsed Arc Welding

NASA Astrophysics Data System (ADS)

Krampit, N. Yu; Krampit, M. A.; Sapozhkov, A. S.

2016-04-01

The paper is focused on revealing the influence of welding parameters on weld formation when pulsed arc welding. As an experimental sample a T-joint over 10 mm was selected. Welding was carried out in flat position, which required no edge preparation but provided mono-directional guaranteed root penetration. The following parameters of welding were subjected to investigation: gap in the joint, wire feed rate and incline angles of the torch along and across the weld axis. Technological recommendations have been made with respect to pulsed arc welding; the cost price of product manufacturing can be reduced on their basis due to reduction of labor input required by machining, lowering consumption of welding materials and electric power.

Application of lap laser welding technology on stainless steel railway vehicles

NASA Astrophysics Data System (ADS)

Wang, Hongxiao; Wang, Chunsheng; He, Guangzhong; Li, Wei; Liu, Liguo

2016-10-01

Stainless steel railway vehicles with so many advantages, such as lightweight, antirust, low cost of maintenance and simple manufacturing process, so the production of high level stainless steel railway vehicles has become the development strategy of European, American and other developed nations. The current stainless steel railway vehicles body and structure are usually assembled by resistance spot welding process. The weak points of this process are the poor surface quality and bad airtight due to the pressure of electrodes. In this study, the partial penetration lap laser welding process was investigated to resolve the problems, by controlling the laser to stop at the second plate in the appropriate penetration. The lap laser welding joint of stainless steel railway vehicle car body with partial penetration has higher strength and surface quality than those of resistance spot welding joint. The biggest problem of lap laser welding technology is to find the balance of the strength and surface quality with different penetrations. The mechanism of overlap laser welding of stainless steel, mechanical tests, microstructure analysis, the optimization of welding parameters, analysis of fatigue performance, the design of laser welding stainless steel railway vehicles structure and the development of non-destructive testing technology were systematically studied before lap laser welding process to be applied in manufacture of railway vehicles. The results of the experiments and study show that high-quality surface state and higher fatigue strength can be achieved by the partial penetration overlap laser welding of the side panel structure, and the structure strength of the car body can be higher than the requirements of En12663, the standard of structural requirements of railway vehicles bodies. Our company has produced the stainless steel subway and high way railway vehicles by using overlap laser welding technology. The application of lap laser welding will be a big change of railway vehicles manufacturing technology.

Nondestructive and Destructive Examination Studies on Removed-from-Service Control Rod Drive Mechanism Penetrations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cumblidge, Stephen E.; Crawford, Susan L.; Doctor, Steven R.

2007-06-07

Studies conducted at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington, focused on assessing the effectiveness of nondestructive examination (NDE) techniques for inspecting control rod drive mechanism (CRDM) nozzles and J-groove weldments. The primary objectives of this work are to provide information to the U.S. Nuclear Regulatory Commission (NRC) on the effectiveness of NDE methods as related to the in-service inspection of CRDM nozzles and J-groove weldments and to enhance the knowledge base of primary water stress corrosion cracking (PWSCC) through destructive characterization of the CRDM assemblies. Two CRDM assemblies were removed from service, decontaminated, and then used inmore » a series of NDE and destructive examination (DE) measurements; this report addresses the following questions: 1) What did each NDE technique detect? 2) What did each NDE technique miss? 3) How accurately did each NDE technique characterize the detected flaws? 4) Why did the NDE techniques perform or not perform? Two CRDM assemblies including the CRDM nozzle, the J-groove weld, buttering, and a portion of the ferritic head material were selected for this study. This report focuses on a CRDM assembly that contained suspected PWSCC, based on in-service inspection data and through-wall leakage. The NDE measurements used to examine the CRDM assembly followed standard industry techniques for conducting in-service inspections of CRDM nozzles and the crown of the J-groove welds and buttering. These techniques included eddy current testing (ET), time-of-flight diffraction ultrasound, and penetrant testing. In addition, laboratory-based NDE methods were employed to conduct inspections of the CRDM assembly with particular emphasis on inspecting the J-groove weld and buttering. These techniques included volumetric ultrasonic inspection of the J-groove weld metal and visual testing via replicant material of the J-groove weld. The results from these NDE studies were used to guide the development of the destructive characterization plan. The NDE studies found several crack-like indications. The NDE and DE studies determined that one of these was a through-weld, radially oriented PWSCC crack in the wetted surface of the J-groove weld, located at the transition point between the weld and the buttering. The crack was 6 mm long on the surface and quickly grew to 25 mm long at a depth of 8 mm, covering the length of the weld between the penetration tube and the carbon steel. The NDE studies found that only ET was able to detect the through-weld crack. The crack was oriented poorly for the ultrasonic testing and was too tight for accurate dye penetrant testing or visual testing. The ET voltage response of the through-wall crack was 30% of the response from a deep electrical discharge machined notch. Destructive examination showed the crack is PWSCC and that it initiated on the wetted surface, grew and expanded through the weld metal, and exited into the annulus. The crack was branched and discontinuous along its length.« less

Controlling Force and Depth in Friction Stir Welding

NASA Technical Reports Server (NTRS)

Adams, Glynn; Loftus, Zachary; McCormac, Nathan; Venable, Richard

2005-01-01

Feedback control of the penetration force applied to a pin tool in friction stir welding has been found to be a robust and reliable means for controlling the depth of penetration of the tool. This discovery has made it possible to simplify depth control and to weld with greater repeatability, even on workpieces with long weld joints. Prior to this discovery, depths of penetration in friction stir welding were controlled by hard-tooled roller assemblies or by depth actuators controlled by feedback from such external sensors as linear variable-differential transformers or laser-based devices. These means of control are limited: A hard-tooled roller assembly confines a pin tool to a preset depth that cannot be changed easily during the welding process. A measurement by an external sensor is only an indirect indicative of the depth of penetration, and computations to correlate such a measurement with a depth of penetration are vulnerable to error. The present force-feedback approach exploits the proportionality between the depth and the force of penetration Unlike a depth measurement taken by an external sensor, a force measurement can be direct because it can be taken by a sensor coupled directly to the pin tool. The reading can be processed through a modern electronic servo control system to control an actuator to keep the applied penetration force at the desired level. In comparison with the older depth-control methods described above, this method offers greater sensitivity to plasticizing of the workpiece metal and is less sensitive to process noise, resulting in a more consistent process. In an experiment, a tapered panel was friction stir welded while controlling the force of penetration according to this method. The figure is a plot of measurements taken during the experiment, showing that force was controlled with a variation of 200 lb (890 N), resulting in control of the depth of penetration with a variation of 0.004 in. (0.1 mm).

Welding Penetration Control of Fixed Pipe in TIG Welding Using Fuzzy Inference System

NASA Astrophysics Data System (ADS)

Baskoro, Ario Sunar; Kabutomori, Masashi; Suga, Yasuo

This paper presents a study on welding penetration control of fixed pipe in Tungsten Inert Gas (TIG) welding using fuzzy inference system. The welding penetration control is essential to the production quality welds with a specified geometry. For pipe welding using constant arc current and welding speed, the bead width becomes wider as the circumferential welding of small diameter pipes progresses. Having welded pipe in fixed position, obviously, the excessive arc current yields burn through of metals; in contrary, insufficient arc current produces imperfect welding. In order to avoid these errors and to obtain the uniform weld bead over the entire circumference of the pipe, the welding conditions should be controlled as the welding proceeds. This research studies the intelligent welding process of aluminum alloy pipe 6063S-T5 in fixed position using the AC welding machine. The monitoring system used a charge-coupled device (CCD) camera to monitor backside image of molten pool. The captured image was processed to recognize the edge of molten pool by image processing algorithm. Simulation of welding control using fuzzy inference system was constructed to simulate the welding control process. The simulation result shows that fuzzy controller was suitable for controlling the welding speed and appropriate to be implemented into the welding system. A series of experiments was conducted to evaluate the performance of the fuzzy controller. The experimental results show the effectiveness of the control system that is confirmed by sound welds.

Study on Dynamic Development of Three-dimensional Weld Pool Surface in Stationary GTAW

NASA Astrophysics Data System (ADS)

Huang, Jiankang; He, Jing; He, Xiaoying; Shi, Yu; Fan, Ding

2018-04-01

The weld pool contains abundant information about the welding process. In particular, the type of the weld pool surface shape, i. e., convex or concave, is determined by the weld penetration. To detect it, an innovative laser-vision-based sensing method is employed to observe the weld pool surface of the gas tungsten arc welding (GTAW). A low-power laser dots pattern is projected onto the entire weld pool surface. Its reflection is intercepted by a screen and captured by a camera. Then the dynamic development process of the weld pool surface can be detected. By observing and analyzing, the change of the reflected laser dots reflection pattern, for shape of the weld pool surface shape, was found to closely correlate to the penetration of weld pool in the welding process. A mathematical model was proposed to correlate the incident ray, reflected ray, screen and surface of weld pool based on structured laser specular reflection. The dynamic variation of the weld pool surface and its corresponding dots laser pattern were simulated and analyzed. By combining the experimental data and the mathematical analysis, the results show that the pattern of the reflected laser dots pattern is closely correlated to the development of weld pool, such as the weld penetration. The concavity of the pool surface was found to increase rapidly after the surface shape was changed from convex to concave during the stationary GTAW process.

The influence of laser pulse waveform on laser-TIG hybrid welding of AZ31B magnesium alloy

NASA Astrophysics Data System (ADS)

Song, Gang; Luo, Zhimin

2011-01-01

By dividing laser pulse duration into two parts, three kinds of laser waveforms are designed, including a high power density pulse (HPDP) laser in a short duration set at the beginning of the laser waveform. This paper aims to find out the laser pulse waveform and idiographic critical values of HPDP, which can affect the magnesium penetration in laser-tungsten inert gas (TIG) hybrid welding. Results show that when the laser pulse duration of HPDP is not more than 0.4 ms, the welding penetration values of lasers with HPDP are larger than otherwise. Also, the welding penetration values of laser with HPDP have increased by up to 26.1%. It has been found that with HPDP, the laser can form the keyhole more easily because the interaction between laser and the plate is changed, when the TIG arc preheats the plate. Besides, the laser with high power density and short duration strikes on the plates so heavily that the corresponding background power can penetrate into the bottom of the keyhole and maintain the keyhole open, which facilitates the final welding penetration.

Viewing Welds By Computer Tomography

NASA Technical Reports Server (NTRS)

Pascua, Antonio G.; Roy, Jagatjit

1990-01-01

Computer tomography system used to inspect welds for root penetration. Source illuminates rotating welded part with fan-shaped beam of x rays or gamma rays. Detectors in circular array on opposite side of part intercept beam and convert it into electrical signals. Computer processes signals into image of cross section of weld. Image displayed on video monitor. System offers only nondestructive way to check penetration from outside when inner surfaces inaccessible.

Partially melted zone in aluminum welds

NASA Astrophysics Data System (ADS)

Huang, Chen-Che

The partially melted zone (PMZ) is a region immediately outside the weld metal where grain boundary (GB) liquation can occur and cause intergranular cracking. Aluminum alloys are known to be susceptible to liquation and liquation cracking. The PMZ of alloy 2219 (essentially Al-6.3Cu) was studied. Liquation is initiated eutectically. Solidification of the GB liquid was directional---upward and toward the weld as a result of the temperature gradients across the PMZ. The liquated material solidifies with severe segregation into a low-strength, low-ductility structure consisting of a solute-depleted ductile phase and a solute-rich brittle eutectic. In tensile testing the maximum load and displacement before failure were both far below those of the base metal. The GB eutectic fractured while the adjacent Cu-depleted a deformed readily under tension. The solidification mode of the grain boundary liquid was mostly planar. However, cellular solidification was also observed near the bottom of partial-penetration welds, where temperature gradients were lowest. The liquation mechanisms in wrought multicomponent aluminum alloys during welding were also studied. Three mechanisms were identified. They cover most, if not all, wrought aluminum alloys. Liquation cracking in the PMZ was investigated in full-penetration aluminum welds. Liquation cracking occurs because the solidifying PMZ is pulled by a solidifying and thus contracting weld metal that is stronger than the PMZ. Liquation cracking can occur if there is significant liquation in the PMZ, if there is no solidification cracking in the adjacent weld metal, and if the PMZ becomes lower in solid fraction (and hence strength) during its terminal solidification than the solidifying weld metal. Liquation cracking in the PMZ was also investigated in partial-penetration aluminum welds. The papillary (nipple) type penetration common in welding with spray transfer of the filler wire actually oscillates along the weld and promotes cracking regardless of the filler metal used. The fast-solidifying weld metal immediately behind the penetration tip contracts and pulls the PMZ near the tip and, regardless of the weld-metal composition, cracking can occur if PMZ liquation is significant.

Friction Stir Welding of Line-Pipe Steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanderson, Samuel; Mahoney, Murray; Feng, Zhili

Friction stir welding (FSW) offers both economic and technical advantages over conventional fusion welding practices for welding line-pipe. For offshore line-pipe construction, the economic savings has been shown to be considerable, approaching a calculated 25%. Offshore pipe is relatively small diameter but heavy wall compared to onshore pipe. One concern is the ability to achieve consistent full weld penetration in an on-site offshore FSW operation, e.g., on a lay-barge. In addition, depending on the size and morphology of the unwelded zone, lack of penetration at the weld root can be difficult if not impossible to detect by conventional NDE methods.more » Thus, an approach to assure consistent full penetration via process control is required for offshore line-pipe construction using FSW. For offshore construction, an internal structural mandrel can be used offering the opportunity to use a sacrificial anvil FSW approach. With this approach, a small volume of sacrificial material can be inserted into the structural anvil. The FSW tool penetrates into the sacrificial anvil, beyond the inner diameter of the pipe wall, thus assuring full penetration. The sacrificial material is subsequently removed from the pipe inner wall. In the work presented herein, FSW studies were completed on both 6 mm and 12 mm wall thickness line-pipe. Lastly, post-FSW evaluations including radiography, root-bend tests, and metallography demonstrated the merits of the sacrificial anvil approach to achieve consistent full penetration.« less

Study on Microstructure and Mechanical Properties of 304 Stainless Steel Joints by Tig-Mig Hybrid Welding

NASA Astrophysics Data System (ADS)

Ogundimu, Emmanuel O.; Akinlabi, Esther T.; Erinosho, Mutiu F.

Stainless steel is a family of Fe-based alloys having excellent resistance to corrosion and as such has been used imperatively for kitchen utensils, transportation, building constructions and much more. This paper presents the work conducted on the material characterizations of a tungsten inert gas (TIG)-metal inert gas (MIG) hybrid welded joint of type 304 austenitic stainless steel. The welding processes were conducted in three phases. The phases of welding employed are MIG welding using a current of 170A, TIG welding using a current of 190A, and a hybrid TIG-MIG welding with currents of 190/170A, respectively. The MIG, TIG, and hybrid TIG-MIG weldments were characterized with incomplete penetration, full penetration and excess penetration of weld. Intergranular austenite was created toward transition and heat affected zones. The thickness of the delta ferrite (δ-Fe) formed in the microstructures of the TIG weld is more than the thickness emerged in the microstructures of MIG and hybrid TIG-MIG welds. A TIG-MIG hybrid weld of specimen welded at the currents of 190/170A has the highest ultimate tensile strength value and percentage elongation of 397.72MPa and 35.7%. The TIG-MIG hybrid welding can be recommended for high-tech industrial applications such as nuclear, aircraft, food processing, and automobile industry.

Penetration in GTA welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heiple, C.R.; Burgardt, P.

1990-01-01

The size and shape of the weld bead produced in GTA welding depends on the magnitude and distribution of the energy incident on the workpiece surfaces as well as the dissipation of that energy in the workpiece. The input energy is largely controllable through the welding parameters selected, however the dissipation of that energy in the workpiece is less subject to control. Changes in energy dissipation can produce large changes in weld shape or penetration. Heat transport away from the weld pool is almost entirely by conduction, but heat transport in the weld pool is more complicated. Heat conduction throughmore » the liquid is an important component, but heat transport by convection (mass transport) is often the dominant mechanism. Convective heat transport is directional and changes the weld pool shape from that produced by conduction alone. Surface tension gradients are often the dominant forces driving fluid flow in GTA weld pools. These gradients are sensitive functions of weld pool chemistry and the energy input distribution to the weld. Experimental and theoretical work conducted primarily in the past decade has greatly enhanced our understanding of weld pool fluid flow, the forces which drive it, and its effects on weld pool shape. This work is reviewed here. While less common, changes in energy dissipation through the unmelted portion of the workpiece can also affect fusion zone shape or penetration. These effects are also described. 41 refs., 9 figs.« less

Method for defect free keyhole plasma arc welding

NASA Technical Reports Server (NTRS)

Harwig, Dennis D. (Inventor); Hunt, James F. (Inventor); Ryan, Patrick M. (Inventor); Fisher, Walter J. (Inventor)

1993-01-01

A plasma arc welding process for welding metal of increased thickness with one pass includes operating the plasma arc welding apparatus at a selected plasma gas flow rate, travel speed and arc current, to form a weld having a penetration ratio to weld height to weld width, and maintaining the penetration ratio at less than 0.74. Parameters for the plasma gas flow rate, travel speed and arc current are adjusted to a steady state condition during a start up period and maintained during the steady state condition to complete a weld. During a terminal stopping period, the travel speed is stopped and instantaneously replaced by filler wire which adds material to fill the keyhole that had been formed by the welding process. Parameters are subsequently adjusted during the stopping period to terminate the weld in a sound manner.

Effect of Pulse Parameters on Weld Quality in Pulsed Gas Metal Arc Welding: A Review

NASA Astrophysics Data System (ADS)

Pal, Kamal; Pal, Surjya K.

2011-08-01

The weld quality comprises bead geometry and its microstructure, which influence the mechanical properties of the weld. The coarse-grained weld microstructure, higher heat-affected zone, and lower penetration together with higher reinforcement reduce the weld service life in continuous mode gas metal arc welding (GMAW). Pulsed GMAW (P-GMAW) is an alternative method providing a better way for overcoming these afore mentioned problems. It uses a higher peak current to allow one molten droplet per pulse, and a lower background current to maintain the arc stability. Current pulsing refines the grains in weld fusion zone with increasing depth of penetration due to arc oscillations. Optimum weld joint characteristics can be achieved by controlling the pulse parameters. The process is versatile and easily automated. This brief review illustrates the effect of pulse parameters on weld quality.

SMAW Ceramic Weld Backing Evaluation

DTIC Science & Technology

1982-03-01

marked similarity to the open root technique in that the " keyhole " technique, commnly used to maxmize penetration with SMAW open root welding , was also...melt into the sides of the bevel and penetrate into the root opening to form a keyhole . Once the keyhole was established, normal welding current was...hot start to melt through the taper, welding proceeded to the keyhole . Once in the keyhole , the electrode was positioned in front of the puddle but not

Hybrid Welding of 45 mm High Strength Steel Sections

NASA Astrophysics Data System (ADS)

Bunaziv, Ivan; Frostevarg, Jan; Akselsen, Odd M.; Kaplan, Alexander F.

Thick section welding has significant importance for oil and gas industry in low temperature regions. Arc welding is usually employed providing suitable quality joints with acceptable toughness at low temperatures with very limited productivity compared to modern high power laser systems. Laser-arc hybrid welding (LAHW) can enhance the productivity by several times due to higher penetration depth from laser beam and combined advantages of both heat sources. LAHW was applied to join 45 mm high strength steel with double-sided technique and application of metal cored wire. The process was captured by high speed camera, allowing process observation in order to identify the relation of the process stability on weld imperfections and efficiency. Among the results, it was found that both arc power and presence of a gap increased penetration depth, and that higher welding speeds cause unstable processing and limits penetration depth. Over a wide range of heat inputs, the welds where found to consist of large amounts of fine-grained acicular ferrite in the upper 60-75% part of welds. At the root filler wire mixing was less and cooling faster, and thus found to have bainitic transformation. Toughness of deposited welds provided acceptable toughness at -50 °C with some scattering.

Effect of Heat Input on Geometry of Austenitic Stainless Steel Weld Bead on Low Carbon Steel

NASA Astrophysics Data System (ADS)

Saha, Manas Kumar; Hazra, Ritesh; Mondal, Ajit; Das, Santanu

2018-05-01

Among different weld cladding processes, gas metal arc welding (GMAW) cladding becomes a cost effective, user friendly, versatile method for protecting the surface of relatively lower grade structural steels from corrosion and/or erosion wear by depositing high grade stainless steels onto them. The quality of cladding largely depends upon the bead geometry of the weldment deposited. Weld bead geometry parameters, like bead width, reinforcement height, depth of penetration, and ratios like reinforcement form factor (RFF) and penetration shape factor (PSF) determine the quality of the weld bead geometry. Various process parameters of gas metal arc welding like heat input, current, voltage, arc travel speed, mode of metal transfer, etc. influence formation of bead geometry. In the current experimental investigation, austenite stainless steel (316) weld beads are formed on low alloy structural steel (E350) by GMAW using 100% CO2 as the shielding gas. Different combinations of current, voltage and arc travel speed are chosen so that heat input increases from 0.35 to 0.75 kJ/mm. Nine number of weld beads are deposited and replicated twice. The observations show that weld bead width increases linearly with increase in heat input, whereas reinforcement height and depth of penetration do not increase with increase in heat input. Regression analysis is done to establish the relationship between heat input and different geometrical parameters of weld bead. The regression models developed agrees well with the experimental data. Within the domain of the present experiment, it is observed that at higher heat input, the weld bead gets wider having little change in penetration and reinforcement; therefore, higher heat input may be recommended for austenitic stainless steel cladding on low alloy steel.

Lack of Penetration in Friction Stir Welds: Effects on Mechanical Properties and NDE Feasibility

NASA Technical Reports Server (NTRS)

Kinchen, David G.; Adams, Glynn P.

2000-01-01

This presentation reviews the issue of lack of penetration (LOP) in Friction Stir Welding and the feasibility of using non-destructive tests to detect . Friction Stir Welding takes place in the solid phase below the melting point of the materials to be joined. It thus gives the ability to join materials which are difficult to fusion weld, for example 2000 and 7000 aluminium alloys. This process though can result in a lack of penetration, due to an incomplete penetration of the DXZ. This is frequently referred to as a "kissing bond", which requires micro examination to detect. The presentation then discusses the surface crack tension tests. It then reviews the simulated service test and results. It then discusses the feasibility of using non-destructive examination to detect LOP, the forms of test which can be used, and the results the tests.

Influence of shielding gas pressure on welding characteristics in CO2 laser-MIG hybrid welding process

NASA Astrophysics Data System (ADS)

Chen, Yanbin; Lei, Zhenglong; Li, Liqun; Wu, Lin

2006-01-01

The droplet transfer behavior and weld characteristics have been investigated under different pressures of shielding gas in CO2 laser and metal inert/active gas (laser-MIG) hybrid welding process. The experimental results indicate that the inherent droplet transfer frequency and stable welding range of conventional MIG arc are changed due to the interaction between CO2 laser beam and MIG arc in laser-MIG hybrid welding process, and the shielding gas pressure has a crucial effect on welding characteristics. When the pressure of shielding gas is low in comparison with MIG welding, the frequency of droplet transfer decreases, and the droplet transfer becomes unstable in laser-MIG hybrid welding. So the penetration depth decreases, which shows the characteristic of unstable hybrid welding. However, when the pressure of shielding gas increases to a critical value, the hybrid welding characteristic is changed from unstable hybrid welding to stable hybrid welding, and the frequency of droplet transfer and the penetration depth increase significantly.

Friction Stir Welding of Tapered Thickness Welds Using an Adjustable Pin Tool

NASA Technical Reports Server (NTRS)

Adams, Glynn; Venable, Richard; Lawless, Kirby

2003-01-01

Friction stir welding (FSW) can be used for joining weld lands that vary in thickness along the length of the weld. An adjustable pin tool mechanism can be used to accomplish this in a single-pass, full-penetration weld by providing for precise changes in the pin length relative to the shoulder face during the weld process. The difficulty with this approach is in accurately adjusting the pin length to provide a consistent penetration ligament throughout the weld. The weld technique, control system, and instrumentation must account for mechanical and thermal compliances of the tooling system to conduct tapered welds successfully. In this study, a combination of static and in-situ measurements, as well as active control, is used to locate the pin accurately and maintain the desired penetration ligament. Frictional forces at the pin/shoulder interface were a source of error that affected accurate pin position. A traditional FSW pin tool design that requires a lead angle was used to join butt weld configurations that included both constant thickness and tapered sections. The pitch axis of the tooling was fixed throughout the weld; therefore, the effective lead angle in the tapered sections was restricted to within the tolerances allowed by the pin tool design. The sensitivity of the FSW process to factors such as thickness offset, joint gap, centerline offset, and taper transition offset were also studied. The joint gap and the thickness offset demonstrated the most adverse affects on the weld quality. Two separate tooling configurations were used to conduct tapered thickness welds successfully. The weld configurations included sections in which the thickness decreased along the weld, as well as sections in which the thickness increased along the weld. The data presented here include weld metallography, strength data, and process load data.

Characterization the microstructure of pulsed Nd:YAG welding method in low frequencies; correlation with tensile and fracture behavior in laser-welded nitinol joints

NASA Astrophysics Data System (ADS)

Shojaei Zoeram, Ali; Rahmani, Aida; Asghar Akbari Mousavi, Seyed Ali

2017-05-01

The precise controllability of heat input in pulsed Nd:YAG welding method provided by two additional parameters, frequency and pulse duration, has made this method very promising for welding of alloys sensitive to heat input. The poor weldability of Ti-rich nitinol as a result of the formation of Ti2Ni IMC has deprived us of the unique properties of this alloy. In this study, to intensify solidification rate during welding of Ti-rich nitinol, pulsed Nd:YAG laser beam in low frequency was employed in addition to the employment of a copper substrate. Specific microstructure produced in this condition was characterized and the effects of this microstructure on tensile and fracture behavior of samples welded by two different procedures, full penetration and double-sided method with halved penetration depth for each side were investigated. The investigations revealed although the combination of low frequencies, the use of a high thermal conductor substrate and double-sided method eliminated intergranular fracture and increased tensile strength, the particular microstructure, built in the pulsed welding method in low frequencies, results to the formation of the longitudinal cracks during the first stages of tensile test at weld centerline. This degrades tensile strength of welded samples compared to base metal. The results showed samples welded in double-sided method performed much better than samples welded in full penetration mode.

Effect of Travel Speed and Beam Focus on Porosity in Alloy 690 Laser Welds

NASA Astrophysics Data System (ADS)

Tucker, Julie D.; Nolan, Terrance K.; Martin, Anthony J.; Young, George A.

2012-12-01

Advances in laser welding technology, including fiber optic delivery and high power density, are increasing the applicability of this joining technique. The inherent benefits of laser welding include small heat-affected zones, minimal distortion, and limited susceptibility to cracking. These advantages are of special interest to next-generation nuclear power systems where welding solute-rich alloys is expected to increase. Alloy 690 (A690) is an advanced corrosion-resistant structural material used in many replacement components and in construction of new commercial power plants. However, the application of A690 is hindered by its difficult weldability using conventional arc welding, and laser welding is a promising alternate. This work studies the effects of travel speed and beam focus on porosity formation in partial penetration, autogenous A690 laser welds. Porosity has been characterized by light optical microscopy and x-ray computed tomography to quantify its percent volume in the welds. This work describes the tradeoff between weld penetration and defect density as a function of beam defocus and travel speed. Additionally, the role of shield gas in porosity formation is discussed to provide a mitigation strategy for A690 laser welding. A process map is provided that shows the optimal combinations of travel speed and beam defocus to minimize porosity and maximize weld penetration at a laser power of 4 kW.

Effect of Activated Flux on the Microstructure, Mechanical Properties, and Residual Stresses of Modified 9Cr-1Mo Steel Weld Joints

NASA Astrophysics Data System (ADS)

Maduraimuthu, V.; Vasudevan, M.; Muthupandi, V.; Bhaduri, A. K.; Jayakumar, T.

2012-02-01

A novel variant of tungsten inert gas (TIG) welding called activated-TIG (A-TIG) welding, which uses a thin layer of activated flux coating applied on the joint area prior to welding, is known to enhance the depth of penetration during autogenous TIG welding and overcomes the limitation associated with TIG welding of modified 9Cr-1Mo steels. Therefore, it is necessary to develop a specific activated flux for enhancing the depth of penetration during autogeneous TIG welding of modified 9Cr-1Mo steel. In the current work, activated flux composition is optimized to achieve 6 mm depth of penetration in single-pass TIG welding at minimum heat input possible. Then square butt weld joints are made for 6-mm-thick and 10-mm-thick plates using the optimized flux. The effect of flux on the microstructure, mechanical properties, and residual stresses of the A-TIG weld joint is studied by comparing it with that of the weld joints made by conventional multipass TIG welding process using matching filler wire. Welded microstructure in the A-TIG weld joint is coarser because of the higher peak temperature in A-TIG welding process compared with that of multipass TIG weld joint made by a conventional TIG welding process. Transverse strength properties of the modified 9Cr-1Mo steel weld produced by A-TIG welding exceeded the minimum specified strength values of the base materials. The average toughness values of A-TIG weld joints are lower compared with that of the base metal and multipass weld joints due to the presence of δ-ferrite and inclusions in the weld metal caused by the flux. Compressive residual stresses are observed in the fusion zone of A-TIG weld joint, whereas tensile residual stresses are observed in the multipass TIG weld joint.

Effect of joint design and welding type on the flexural strength and weld penetration of Ti-6Al-4V alloy bars.

PubMed

Simamoto Júnior, Paulo Cézar; Resende Novais, Veridiana; Rodrigues Machado, Asbel; Soares, Carlos José; Araújo Raposo, Luís Henrique

2015-05-01

Framework longevity is a key factor for the success of complete-arch prostheses and commonly depends on the welding methods. However, no consensus has been reached on the joint design and welding type for improving framework resistance. The purpose of this study was to assess the effect of different joint designs and welding methods with tungsten inert gas (TIG) or laser to join titanium alloy bars (Ti-6Al-4V). Seventy titanium alloy bar specimens were prepared (3.18 mm in diameter × 40.0 mm in length) and divided into 7 groups (n=10): the C-control group consisting of intact specimens without joints and the remaining 6 groups consisting of specimens sectioned perpendicular to the long-axis and rejoined using an I-, X30-, or X45-shaped joint design with TIG welding (TI, TX30, and TX45) or laser welding (LI, LX30, and LX45). The specimens were tested with 3-point bending. The fracture surfaces were first evaluated with stereomicroscopy to measure the weld penetration area and then analyzed with scanning electron microscopy (SEM). The data were statistically analyzed with 2-way ANOVA and the Tukey post hoc test, 1-way ANOVA and the Dunnett test, and the Pearson correlation test (α=.05). Specimens from the X30 and X45 groups showed higher flexural strength (P<.05) and welded area (P<.05) than specimens from the I groups, regardless of the welding type. TIG welded groups showed significantly higher flexural strength than the laser groups (P<.05), regardless of the joint design. TIG welding also resulted in higher welded areas than laser welding for the I-shaped specimens. No significant differences were found for the weld penetration area in the X45 group, either for laser or TIG welding. SEM analysis showed more pores at the fracture surfaces of the laser specimens. Fracture surfaces indicative of regions of increased ductility were detected for the TIG specimens. TIG welding resulted in higher flexural strength for the joined titanium specimens than laser welding. For both welding methods, X30- and X45-shaped joint designs resulted in higher flexural strength and welding penetration than the I-shaped joint design. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Method for enhanced control of welding processes

DOEpatents

Sheaffer, Donald A.; Renzi, Ronald F.; Tung, David M.; Schroder, Kevin

2000-01-01

Method and system for producing high quality welds in welding processes, in general, and gas tungsten arc (GTA) welding, in particular by controlling weld penetration. Light emitted from a weld pool is collected from the backside of a workpiece by optical means during welding and transmitted to a digital video camera for further processing, after the emitted light is first passed through a short wavelength pass filter to remove infrared radiation. By filtering out the infrared component of the light emitted from the backside weld pool image, the present invention provides for the accurate determination of the weld pool boundary. Data from the digital camera is fed to an imaging board which focuses on a 100.times.100 pixel portion of the image. The board performs a thresholding operation and provides this information to a digital signal processor to compute the backside weld pool dimensions and area. This information is used by a control system, in a dynamic feedback mode, to automatically adjust appropriate parameters of a welding system, such as the welding current, to control weld penetration and thus, create a uniform weld bead and high quality weld.

Digital Radiography Using Digital Detector Arrays Fulfills Critical Applications for Offshore Pipelines

NASA Astrophysics Data System (ADS)

Moreira, EdsonVasques; Barbosa Rabello, JoséMaurício; Pereira, MarcelodosSantos; Lopes, RicardoTadeu; Zscherpel, Uwe

2010-12-01

Digital radiography in the inspection of welded pipes to be installed under deep water offshore gas and oil pipelines, like a presalt in Brazil, in the paper has been investigated. The aim is to use digital radiography for nondestructive testing of welds as it is already in use in the medical, aerospace, security, automotive, and petrochemical sectors. Among the current options, the DDA (Digital Detector Array) is considered as one of the best solutions to replace industrial films, as well as to increase the sensitivity to reduce the inspection cycle time. This paper shows the results of this new technique, comparing it to radiography with industrial films systems. In this paper, 20 test specimens of longitudinal welded pipe joints, specially prepared with artificial defects like cracks, lack of fusion, lack of penetration, and porosities and slag inclusions with varying dimensions and in 06 different base metal wall thicknesses, were tested and a comparison of the techniques was made. These experiments verified the purposed rules for parameter definitions and selections to control the required digital radiographic image quality as described in the draft international standard ISO/DIS 10893-7. This draft is first standard establishing the parameters for digital radiography on weld seam of welded steel pipes for pressure purposes to be used on gas and oil pipelines.

Effect of Nd:YAG laser parameters on the penetration depth of a representative Ni-Cr dental casting alloy.

PubMed

Al Jabbari, Youssef S; Koutsoukis, Theodoros; Barmpagadaki, Xanthoula; El-Danaf, Ehab A; Fournelle, Raymond A; Zinelis, Spiros

2015-02-01

The effects of voltage and laser beam (spot) diameter on the penetration depth during laser beam welding in a representative nickel-chromium (Ni-Cr) dental alloy were the subject of this study. The cast alloy specimens were butted against each other and laser welded at their interface using various voltages (160-390 V) and spot diameters (0.2-1.8 mm) and a constant pulse duration of 10 ms. After welding, the laser beam penetration depths in the alloy were measured. The results were plotted and were statistically analyzed with a two-way ANOVA, employing voltage and spot diameter as the discriminating variables and using Holm-Sidak post hoc method (a = 0.05). The maximum penetration depth was 4.7 mm. The penetration depth increased as the spot diameter decreased at a fixed voltage and increased as the voltage increased at a fixed spot diameter. Varying the parameters of voltage and laser spot diameter significantly affected the depth of penetration of the dental cast Ni-Cr alloy. The penetration depth of laser-welded Ni-Cr dental alloys can be accurately adjusted based on the aforementioned results, leading to successfully joined/repaired dental restorations, saving manufacturing time, reducing final cost, and enhancing the longevity of dental prostheses.

Models for selecting GMA Welding Parameters for Improving Mechanical Properties of Weld Joints

NASA Astrophysics Data System (ADS)

Srinivasa Rao, P.; Ramachandran, Pragash; Jebaraj, S.

2016-02-01

During the process of Gas Metal Arc (GMAW) welding, the weld joints mechanical properties are influenced by the welding parameters such as welding current and arc voltage. These parameters directly will influence the quality of the weld in terms of mechanical properties. Even small variation in any of the cited parameters may have an important effect on depth of penetration and on joint strength. In this study, S45C Constructional Steel is taken as the base metal to be tested using the parameters wire feed rate, voltage and type of shielding gas. Physical properties considered in the present study are tensile strength and hardness. The testing of weld specimen is carried out as per ASTM Standards. Mathematical models to predict the tensile strength and depth of penetration of weld joint have been developed by regression analysis using the experimental results.

Surface-active element effects on the shape of GTA, laser, and electron-beam welds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heiple, C.R.; Roper, J.R.; Stagner, R.T.

1983-03-01

Laser and electron-beam welds were passed across selenium-doped zones in 21-6-9 stainless steel. The depth/width (d/w) ratio of a defocused laser weld with a weld pool shape similar to a GTA weld increased by over 200% in a zone where 66 ppm selenium had been added. Smaller increases were observed in selenium-doped zones for a moderately defocused electron beam weld with a higher d/w ratio in undoped base metal. When laser or electron beam weld penetration was by a keyhole mechanism, no change in d/w ratio occurred in selenium-doped zones. The results confirm the surface-tension-driven fluid-flow model for the effectmore » of minor elements on GTA weld pool shape. Other experimental evidence bearing on the effect of minor elements on GTA weld penetration is summarized.« less

Welding polarity effects on weld spatters and bead geometry of hyperbaric dry GMAW

NASA Astrophysics Data System (ADS)

Xue, Long; Wu, Jinming; Huang, Junfen; Huang, Jiqiang; Zou, Yong; Liu, Jian

2016-03-01

Welding polarity has influence on welding stability to some extent, but the specific relationship between welding polarity and weld quality has not been found, especially under the hyperbaric environment. Based on a hyperbaric dry welding experiment system, gas metal arc welding(GMAW) experiments with direct current electrode positive(DCEP) and direct current electrode negative(DCEN) operations are carried out under the ambient pressures of 0.1 MPa, 0.4 MPa, 0.7 MPa and 1.0 MPa to find the influence rule of different welding polarities on welding spatters and weld bead geometry. The effects of welding polarities on the weld bead geometry such as the reinforcement, the weld width and the penetration are discussed. The experimental results show that the welding spatters gradually grow in quantity and size for GMAW with DCEP, while GMAW with DCEN can produce fewer spatters comparatively with the increase of the ambient pressure. Compared with DCEP, the welding current and arc voltage waveforms for DCEN is more stable and the distribution of welding current probability density for DCEN is more concentrated under the hyperbaric environment. When the ambient pressure is increased from 0.1 MPa to 1.0 MPa, the effects of welding polarities on the reinforcement, the weld width and the penetration are as follows: an increase of 0.8 mm for the weld reinforcement is produced by GMAW with DCEN and 1.3 mm by GMAW with DCEP, a decrease of 7.2 mm for the weld width is produced by DCEN and 6.1 mm by DCEP; and an increase of 3.9 mm for the penetration is produced by DCEN and 1.9 mm by DCEP. The proposed research indicates that the desirable stability in the welding procedure can be achieved by GMAW with DCEN operation under the hyperbaric environment.

Penetration Effects of the Compound Vortex in Gas Metal-Arc Welding

DTIC Science & Technology

1988-05-01

steel plate using constant current GMAW equipment and argon + 2;. oxygen shielding gas. After welding, the plates were cut, ground, polished and etched...49 14. Typical time plot of current used in pulsed GMAW ..... 51 15. The experimental apparatus ........................... 54 16. Plot...this phenomenon could be employed in some manner to yield high penetration welds with low average current. 2. Pulsed GMAW . KolodziejczaK [26] studied

Fabrication of elliptical SRF cavities

NASA Astrophysics Data System (ADS)

Singer, W.

2017-03-01

The technological and metallurgical requirements of material for high-gradient superconducting cavities are described. High-purity niobium, as the preferred metal for the fabrication of superconducting accelerating cavities, should meet exact specifications. The content of interstitial impurities such as oxygen, nitrogen, and carbon must be below 10 μg g-1. The hydrogen content should be kept below 2 μg g-1 to prevent degradation of the quality factor (Q-value) under certain cool-down conditions. The material should be free of flaws (foreign material inclusions or cracks and laminations) that can initiate a thermal breakdown. Traditional and alternative cavity mechanical fabrication methods are reviewed. Conventionally, niobium cavities are fabricated from sheet niobium by the formation of half-cells by deep drawing, followed by trim machining and electron beam welding. The welding of half-cells is a delicate procedure, requiring intermediate cleaning steps and a careful choice of weld parameters to achieve full penetration of the joints. A challenge for a welded construction is the tight mechanical and electrical tolerances. These can be maintained by a combination of mechanical and radio-frequency measurements on half-cells and by careful tracking of weld shrinkage. The main aspects of quality assurance and quality management are mentioned. The experiences of 800 cavities produced for the European XFEL are presented. Another cavity fabrication approach is slicing discs from the ingot and producing cavities by deep drawing and electron beam welding. Accelerating gradients at the level of 35-45 MV m-1 can be achieved by applying electrochemical polishing treatment. The single-crystal option (grain boundary free) is discussed. It seems that in this case, high performance can be achieved by a simplified treatment procedure. Fabrication of the elliptical resonators from a seamless pipe as an alternative is briefly described. This technology has yielded good performance and is already available for multi-cell structures.

Fiber laser welding of nickel based superalloy Inconel 625

NASA Astrophysics Data System (ADS)

Janicki, Damian M.

2013-01-01

The paper describes the application of single mode high power fiber laser (HPFL) for the welding of nickel based superalloy Inconel 625. Butt joints of Inconel 625 sheets 0,8 mm thick were laser welded without an additional material. The influence of laser welding parameters on weld quality and mechanical properties of test joints was studied. The quality and mechanical properties of the joints were determined by means of tensile and bending tests, and micro hardness tests, and also metallographic examinations. The results showed that a proper selection of laser welding parameters provides non-porous, fully-penetrated welds with the aspect ratio up to 2.0. The minimum heat input required to achieve full penetration butt welded joints with no defect was found to be 6 J/mm. The yield strength and ultimate tensile strength of the joints are essentially equivalent to that for the base material.

Pipe penetration inspection and repair equipment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eckert, G.; Gebrath, D.; Schlusen, H.J.

Kraftwerk Union (KWU) has developed an in-pipe inspection and repair equipment package for use on pipe welds inside drywell penetrations since these welds are susceptible to integranular stress corrosion cracking (IGSCC) attack. The following paper does not give a detailed description of inspection and repair techniques (e.g., nondestructive examination (NDE), milling, or welding) but is aimed at providing information on recent developments at KWU with regard to in-pipe inspection and repair equipment.

Laser-welded Dissimilar Steel-aluminum Seams for Automotive Lightweight Construction

NASA Astrophysics Data System (ADS)

Schimek, M.; Springer, A.; Kaierle, S.; Kracht, D.; Wesling, V.

By reducing vehicle weight, a significant increase in fuel efficiency and consequently a reduction in CO 2 emissions can be achieved. Currently a high interest in the production of hybrid weld seams between steel and aluminum exists. Previous methods as laser brazing are possible only by using fluxes and additional materials. Laser welding can be used to join steel and aluminum without the use of additives. With a low penetration depth increases in tensile strength can be achieved. Recent results from laser welded overlap seams show that there is no compromise in strength by decreasing penetration depth in the aluminum.

Feasibility of using acoustic method in monitoring the penetration status during the Pulse Mode Laser Welding process

NASA Astrophysics Data System (ADS)

Yusof, M. F. M.; Ishak, M.; Ghazali, M. F.

2017-09-01

In this paper, the feasibility of using acoustic method to monitor the depth of penetration was investigated by determine the characteristic of the acquired sound throughout the pulse mode laser welding process. To achieve the aim, the sound signal was acquired during the pulsed laser welding process on the 2 mm structural carbon steel plate. During the experiment, the laser peak power and pulse width was set to be varied while welding speed was constantly at 2 mm/s. Result from the experiment revealed that the sound pressure level of the acquired sound was linearly related to the pulse energy as well as the depth of penetration for welding process using 2ms pulse width. However, as the pulse width increase, the sound pressure level show insignificant change with respect to the change in the depth of penetration when the pulse energy reaches certain values. The reported result shows that this was happen due to the occurrence of spatter which suppressed the information associated with the generation of plasma plume as the product of high pulse energy. In this work, it was demonstrated that in some condition, the acoustic method was found to be potentially suitable to be used as a medium to monitor the depth of weld on online basis. To increase the robustness of this method to be used in wider range of parameter, it was believed that some other post processing method is needed in order to extract the specific information associated with the depth of penetration from the acquired sound.

Self-Aligning Sensor-Mounting Fixture

NASA Technical Reports Server (NTRS)

Gilbert, Jeffrey L.; Mills, Rhonda J.

1991-01-01

Optical welding sensors replaced without realignment. Mounting fixture for optical weld-penetration sensor enables accurate and repeatable alignment. Simple and easy to use. Assembled on welding torch, it holds sensor securely and keeps it pointed toward weld pool. Designed for use on gas/tungsten arc-welding torch, fixture replaces multipiece bracket.

The effect of laser pulse tailored welding of Inconel 718

NASA Technical Reports Server (NTRS)

Mccay, T. Dwayne; Mccay, Mary Helen; Sharp, C. Michael; Womack, Michael G.

1990-01-01

Pulse tailored laser welding has been applied to wrought, wrought grain grown, and cast Inconel 718 using a CO2 laser. Prior to welding, the material was characterized metallographically and the solid state transformation regions were identified using Differential Scanning Calorimetry and high temperature x-ray diffraction. Bead on plate welds (restrained and unrestrained) were then produced using a matrix of pulse duty cycles and pulsed average power. Subsequent characterization included heat affected zone width, penetration and underbead width, the presence of cracks, microfissures and porosity, fusion zone curvature, and precipitation and liquated region width. Pedigree welding on three selected processing conditions was shown by microstructural and dye penetrant analysis to produce no microfissures, a result which strongly indicates the viability of pulse tailored welding for microfissure free IN 718.

Mechanism and Microstructure of Oxide Fluxes for Gas Tungsten Arc Welding of Magnesium Alloy

NASA Astrophysics Data System (ADS)

Liu, L. M.; Zhang, Z. D.; Song, G.; Wang, L.

2007-03-01

Five single oxide fluxes—MgO, CaO, TiO2, MnO2, and Cr2O3—were used to investigate the effect of active flux on the depth/width ratio in AZ31B magnesium alloy. The microstructure and mechanical property of the tungsten inert gas (TIG) welding seam were studied. The oxygen content in the weld seam and the arc images during the TIG welding process were analyzed. A series of emission spectroscopy of weld arc for TIG welding for magnesium with and without flux were developed. The results showed that for the five single oxide fluxes, all can increase the weld penetration effectively and grain size in the weld seam of alternating current tungsten inert gas (ACTIG) welding of the Mg alloy. The oxygen content of the welds made without flux is not very different from those produced with oxide fluxes not considering trapped oxide. However, welds that have the best penetration have a relatively higher oxygen content among those produced with flux. It was found that the arc images with the oxide fluxes were only the enlarged form of the arc images without flux; the arc constriction was not observed. The detection of arc spectroscopy showed that the metal elements in the oxides exist as the neutral atom or the first cation in the weld arc. This finding would influence the arc properties. When TIG simulation was carried out on a plate with flux applied only on one side, the arc image video showed an asymmetric arc, which deviated toward the flux free side. The thermal stability, the dissociation energy, and the electrical conductivity of oxide should be considered when studying the mechanism for increased TIG flux weld penetration.

Accelerated crack growth, residual stress, and a cracked zinc coated pressure shell

NASA Technical Reports Server (NTRS)

Dittman, Daniel L.; Hampton, Roy W.; Nelson, Howard G.

1987-01-01

During a partial inspection of a 42 year old, operating, pressurized wind tunnel at NASA-Ames Research Center, a surface connected defect 114 in. long having an indicated depth of a 0.7 in. was detected. The pressure shell, constructed of a medium carbon steel, contains approximately 10 miles of welds and is cooled by flowing water over its zinc coated external surface. Metallurgical and fractographic analysis showed that the actual detect was 1.7 in. deep, and originated from an area of lack of weld penetration. Crack growth studies were performed on the shell material in the laboratory under various loading rates, hold times, and R-ratios with a simulated shell environment. The combination of zinc, water with electrolyte, and steel formed an electrolytic cell which resulted in an increase in cyclic crack growth rate by as much as 500 times over that observed in air. It was concluded that slow crack growth occurred in the pressure shell by a combination of stress corrosion cracking due to the welding residual stress and corrosion fatigue due to the cyclic operating stress.

Fluid Flow Characteristics and Porosity Behavior in Full Penetration Laser Welding of a Titanium Alloy

NASA Astrophysics Data System (ADS)

Chang, Baohua; Allen, Chris; Blackburn, Jon; Hilton, Paul; Du, Dong

2015-04-01

In this paper, a computational fluid mechanics model is developed for full penetration laser welding of titanium alloy Ti6Al4V. This has been used to analyze possible porosity formation mechanisms, based on predictions of keyhole behavior and fluid flow characteristics in the weld pool. Numerical results show that when laser welding 3 mm thickness titanium alloy sheets with given laser beam focusing optics, keyhole depth oscillates before a full penetration keyhole is formed, but thereafter keyhole collapses are not predicted numerically. For lower power, lower speed welding, the fluid flow behind the keyhole is turbulent and unstable, and vortices are formed. Molten metal is predicted to flow away from the center plane of the weld pool, and leave a gap or void within the weld pool behind the keyhole. For higher power, higher speed welding, fluid flow is less turbulent, and such vortices are not formed. Corresponding experimental results show that porosity was absent in the melt runs made at higher power and higher welding speed. In contrast, large pores were present in melt runs made at lower power and lower welding speed. Based on the combination of experimental results and numerical predictions, it is proposed that porosity formation when keyhole laser welding may result from turbulent fluid flow behind the keyhole, with the larger the value of associated Reynolds number, the higher the possibility of porosity formation. For such fluid flow controlled porosities, measures to decrease Reynolds number of the fluid flow close to the keyhole could prove effective in reducing or avoiding porosity.

Selection of optimal welding condition for GTA pulse welding in root-pass of V-groove butt joint

NASA Astrophysics Data System (ADS)

Yun, Seok-Chul; Kim, Jae-Woong

2010-12-01

In the manufacture of high-quality welds or pipeline, a full-penetration weld has to be made along the weld joint. Therefore, root-pass welding is very important, and its conditions have to be selected carefully. In this study, an experimental method for the selection of optimal welding conditions is proposed for gas tungsten arc (GTA) pulse welding in the root pass which is done along the V-grooved butt-weld joint. This method uses response surface analysis in which the width and height of back bead are chosen as quality variables of the weld. The overall desirability function, which is the combined desirability function for the two quality variables, is used as the objective function to obtain the optimal welding conditions. In our experiments, the target values of back bead width and height are 4 mm and zero, respectively, for a V-grooved butt-weld joint of a 7-mm-thick steel plate. The optimal welding conditions could determine the back bead profile (bead width and height) as 4.012 mm and 0.02 mm. From a series of welding tests, it was revealed that a uniform and full-penetration weld bead can be obtained by adopting the optimal welding conditions determined according to the proposed method.

Characterization of disk-laser dissimilar welding of titanium alloy Ti-6Al-4V to aluminum alloy 2024

NASA Astrophysics Data System (ADS)

Caiazzo, Fabrizia; Alfieri, Vittorio; Cardaropoli, Francesco; Corrado, Gaetano; Sergi, Vincenzo

2013-02-01

Both technical and economic reasons suggest to join dissimilar metals, benefiting from the specific properties of each material in order to perform flexible design. Adhesive bonding and mechanical joining have been traditionally used although adhesives fail to be effective in high-temperature environments and mechanical joining are not adequate for leak-tight joints. Friction stir welding is a valid alternative, even being difficult to perform for specific joint geometries and thin plates. The attention has therefore been shifted to laser welding. Interest has been shown in welding titanium to aluminum, especially in the aviation industry, in order to benefit from both corrosive resistance and strength properties of the former, and low weight and cost of the latter. Titanium alloy Ti-6Al-4V and aluminum alloy 2024 are considered in this work, being them among the most common ones in aerospace and automotive industries. Laser welding is thought to be particularly useful in reducing the heat affected zones and providing deep penetrative beads. Nevertheless, many challenges arise in welding dissimilar metals and the aim is further complicated considering the specific features of the alloys in exam, being them susceptible to oxidation on the upper surface and porosity formation in the fused zone. As many variables are involved, a systematic approach is used to perform the process and to characterize the beads referring to their shape and mechanical features, since a mixture of phases and structures is formed in the fused zone after recrystallization.

Reed Valve Regulates Welding Back-Purge Pressure

NASA Technical Reports Server (NTRS)

Coby, J. Ben, Jr.; Weeks, Jack L.

1991-01-01

Simple modification yields welds of better quality. Reed valve halves fluctuations in pressure in back-purge chamber attached to workpiece undergoing keyhole plasma arc welding. Identical to one used in fuel system of two-cycle gasoline engine. Backbead smoother, and weld penetrates more uniformly.

Transient Response of Arc Temperature and Iron Vapor Concentration Affected by Current Frequency with Iron Vapor in Pulsed Arc

NASA Astrophysics Data System (ADS)

Tanaka, Tatsuro; Maeda, Yoshifumi; Yamamoto, Shinji; Iwao, Toru

2016-10-01

TIG arc welding is chemically a joining technology with melting the metallic material and it can be high quality. However, this welding should not be used in high current to prevent cathode melting. Thus, the heat transfer is poor. Therefore, the deep penetration cannot be obtained and the weld defect sometimes occurs. The pulsed arc welding has been used for the improvement of this defect. The pulsed arc welding can control the heat flux to anode. The convention and driving force in the weld pool are caused by the arc. Therefore, it is important to grasp the distribution of arc temperature. The metal vapor generate from the anode in welding. In addition, the pulsed current increased or decreased periodically. Therefore, the arc is affected by such as a current value and current frequency, the current rate of increment and the metal vapor. In this paper, the transient response of arc temperature and the iron vapor concentration affected by the current frequency with iron vapor in pulsed arc was elucidated by the EMTF (ElectroMagnetic Thermal Fluid) simulation. As a result, the arc temperature and the iron vapor were transient response as the current frequency increase. Thus, the temperature and the electrical conductivity decreased. Therefore, the electrical field increased in order to maintain the current continuity. The current density and electromagnetic force increased at the axial center. In addition, the electronic flow component of the heat flux increased at the axial center because the current density increased. However, the heat conduction component of the heat flux decreased.

UNS S31603 Stainless Steel Tungsten Inert Gas Welds Made with Microparticle and Nanoparticle Oxides

PubMed Central

Tseng, Kuang-Hung; Lin, Po-Yu

2014-01-01

The purpose of this study was to investigate the difference between tungsten inert gas (TIG) welding of austenitic stainless steel assisted by microparticle oxides and that assisted by nanoparticle oxides. SiO2 and Al2O3 were used to investigate the effects of the thermal stability and the particle size of the activated compounds on the surface appearance, geometric shape, angular distortion, delta ferrite content and Vickers hardness of the UNS S31603 stainless steel TIG weld. The results show that the use of SiO2 leads to a satisfactory surface appearance compared to that of the TIG weld made with Al2O3. The surface appearance of the TIG weld made with nanoparticle oxide has less flux slag compared with the one made with microparticle oxide of the same type. Compared with microparticle SiO2, the TIG welding with nanoparticle SiO2 has the potential benefits of high joint penetration and less angular distortion in the resulting weldment. The TIG welding with nanoparticle Al2O3 does not result in a significant increase in the penetration or reduction of distortion. The TIG welding with microparticle or nanoparticle SiO2 uses a heat source with higher power density, resulting in a higher ferrite content and hardness of the stainless steel weld metal. In contrast, microparticle or nanoparticle Al2O3 results in no significant difference in metallurgical properties compared to that of the C-TIG weld metal. Compared with oxide particle size, the thermal stability of the oxide plays a significant role in enhancing the joint penetration capability of the weld, for the UNS S31603 stainless steel TIG welds made with activated oxides. PMID:28788704

UNS S31603 Stainless Steel Tungsten Inert Gas Welds Made with Microparticle and Nanoparticle Oxides.

PubMed

Tseng, Kuang-Hung; Lin, Po-Yu

2014-06-20

The purpose of this study was to investigate the difference between tungsten inert gas (TIG) welding of austenitic stainless steel assisted by microparticle oxides and that assisted by nanoparticle oxides. SiO₂ and Al₂O₃ were used to investigate the effects of the thermal stability and the particle size of the activated compounds on the surface appearance, geometric shape, angular distortion, delta ferrite content and Vickers hardness of the UNS S31603 stainless steel TIG weld. The results show that the use of SiO₂ leads to a satisfactory surface appearance compared to that of the TIG weld made with Al₂O₃. The surface appearance of the TIG weld made with nanoparticle oxide has less flux slag compared with the one made with microparticle oxide of the same type. Compared with microparticle SiO₂, the TIG welding with nanoparticle SiO₂ has the potential benefits of high joint penetration and less angular distortion in the resulting weldment. The TIG welding with nanoparticle Al₂O₃ does not result in a significant increase in the penetration or reduction of distortion. The TIG welding with microparticle or nanoparticle SiO₂ uses a heat source with higher power density, resulting in a higher ferrite content and hardness of the stainless steel weld metal. In contrast, microparticle or nanoparticle Al₂O₃ results in no significant difference in metallurgical properties compared to that of the C-TIG weld metal. Compared with oxide particle size, the thermal stability of the oxide plays a significant role in enhancing the joint penetration capability of the weld, for the UNS S31603 stainless steel TIG welds made with activated oxides.

Weld-Bead Shaver

NASA Technical Reports Server (NTRS)

Guirguis, Kamal; Price, Daniel S.

1990-01-01

Hand-held power tool shaves excess metal from inside circumference of welded duct. Removes excess metal deposited by penetration of tungsten/inert-gas weld or by spatter from electron-beam weld. Produces smooth transition across joint. Easier to use and not prone to overshaving. Also cuts faster, removing 35 in. (89 cm) of weld bead per hour.

Influence of M-TIG and A-TIG Welding Process on Microstructure and Mechanical Behavior of 409 Ferritic Stainless Steel

NASA Astrophysics Data System (ADS)

Vidyarthy, R. S.; Dwivedi, D. K.; Vasudevan, M.

2017-03-01

The current study investigates the effects of activating flux tungsten inert gas welding (A-TIG) and multipass tungsten inert gas welding (M-TIG) on the weld morphology, angular distortion, microstructures and mechanical properties when welding 8-mm-thick 409 ferritic stainless steel (FSS). SiO2 was used as activating flux for A-TIG welding, while SUPERTIG ER309L was used as filler for M-TIG welding. Bead-on-plate weld trials were carried out to obtain the full penetration by using different combinations of flux coating density, welding speed and welding current. An optical microscope, field emission scanning microscope (FESEM), and x-ray diffractometer were used for the metallurgical characterizations. Vickers hardness, tensile test, Charpy toughness test, and creep behavior test were carried out to evaluate the mechanical properties of the base and weld metals. Experimental results indicate that the A-TIG process can increase the joint penetration and tends to reduce the angular distortion of the 409 FSS weldment. The A-TIG welded joint also exhibited greater mechanical strength. However, a critically low Charpy toughness was measured for the A-TIG weld fusion zone, which was later sufficiently improved after post weld heat treatment (PWHT). It was concluded that PWHT is mandatory for A-TIG welded 409 FSS.

Non Destructive Test Dye Penetrant and Ultrasonic on Welding SMAW Butt Joint with Acceptance Criteria ASME Standard

NASA Astrophysics Data System (ADS)

Endramawan, T.; Sifa, A.

2018-02-01

The purpose of this research is to know the type of discontinuity of SMAW welding result and to determine acceptance criteria based on American Society of Mechanical Engineer (ASME) standard. Material used is mild steel 98,71% Fe and 0,212% C with hardness 230 VHN with specimen diameter 20 cm and thickness 1.2 cm which is welded use SMAW butt joint with electrode for rooting LB 52U diameter 2.6 mm, current 70 Ampere and voltage 380 volt, filler used LB 5218 electrode diameter 3.2 mm with current 80 Ampere and 380 volt. The method used to analyze the welded with non destructive test dye penetrant (PT) method to see indication on the surface of the object and Ultrasonic (UT) to see indication on the sub and inner the surface of the object, the result is discontinuity recorded and analyzed and then the discontinuity is determine acceptance criteria based on the American Society of Mechanical Engineer (ASME) standards. The result show the discontinuity of porosity on the surface of the welded and inclusion on sub material used ultrasonic test, all indication on dye penetrant or ultrasonic test if there were rejected of result of welded that there must be gouging on part which rejected and then re-welding.

Influence of Filler Wire Feed Rate in Laser-Arc Hybrid Welding of T-butt Joint in Shipbuilding Steel with Different Optical Setups

NASA Astrophysics Data System (ADS)

Unt, Anna; Poutiainen, Ilkka; Salminen, Antti

In this paper, a study of laser-arc hybrid welding featuring three different process fibres was conducted to build knowledge about process behaviour and discuss potential benefits for improving the weld properties. The welding parameters affect the weld geometry considerably, as an example the increase in welding speed usually decreases the penetration and a larger beam diameter usually widens the weld. The laser hybrid welding system equipped with process fibres with 200, 300 and 600 μm core diameter were used to produce fillet welds. Shipbuilding steel AH36 plates with 8 mm thickness were welded with Hybrid-Laser-Arc-Welding (HLAW) in inversed T configuration, the effects of the filler wire feed rate and the beam positioning distance from the joint plane were investigated. Based on the metallographic cross-sections, the effect of process parameters on the joint geometry was studied. Joints with optimized properties (full penetration, soundness, smooth transition from bead to base material) were produced with 200 μm and 600 μm process fibres, while fiber with 300 μm core diameter produced welds with unacceptable levels of porosity.

Welding of 316L Austenitic Stainless Steel with Activated Tungsten Inert Gas Process

NASA Astrophysics Data System (ADS)

Ahmadi, E.; Ebrahimi, A. R.

2015-02-01

The use of activating flux in TIG welding process is one of the most notable techniques which are developed recently. This technique, known as A-TIG welding, increases the penetration depth and improves the productivity of the TIG welding. In the present study, four oxide fluxes (SiO2, TiO2, Cr2O3, and CaO) were used to investigate the effect of activating flux on the depth/width ratio and mechanical property of 316L austenitic stainless steel. The effect of coating density of activating flux on the weld pool shape and oxygen content in the weld after the welding process was studied systematically. Experimental results indicated that the maximum depth/width ratio of stainless steel activated TIG weld was obtained when the coating density was 2.6, 1.3, 2, and 7.8 mg/cm2 for SiO2, TiO2, Cr2O3, and CaO, respectively. The certain range of oxygen content dissolved in the weld, led to a significant increase in the penetration capability of TIG welds. TIG welding with active fluxes can increase the delta-ferrite content and improves the mechanical strength of the welded joint.

Studies on the Parametric Effects of Plasma Arc Welding of 2205 Duplex Stainless Steel

NASA Astrophysics Data System (ADS)

Selva Bharathi, R.; Siva Shanmugam, N.; Murali Kannan, R.; Arungalai Vendan, S.

2018-03-01

This research study attempts to create an optimized parametric window by employing Taguchi algorithm for Plasma Arc Welding (PAW) of 2 mm thick 2205 duplex stainless steel. The parameters considered for experimentation and optimization are the welding current, welding speed and pilot arc length respectively. The experimentation involves the parameters variation and subsequently recording the depth of penetration and bead width. Welding current of 60-70 A, welding speed of 250-300 mm/min and pilot arc length of 1-2 mm are the range between which the parameters are varied. Design of experiments is used for the experimental trials. Back propagation neural network, Genetic algorithm and Taguchi techniques are used for predicting the bead width, depth of penetration and validated with experimentally achieved results which were in good agreement. Additionally, micro-structural characterizations are carried out to examine the weld quality. The extrapolation of these optimized parametric values yield enhanced weld strength with cost and time reduction.

Effect of adding powder on joint properties of laser penetration welding for dual phase steel and aluminum alloy

NASA Astrophysics Data System (ADS)

Zhou, D. W.; Liu, J. S.; Lu, Y. Z.; Xu, S. H.

2017-09-01

The experiments of laser penetration welding for dual phase steel and aluminum alloy were carried out, and the effect of adding Mn or Si powder on mechanical properties and microstructure of the weld was investigated. Some defects, such as spatter, inclusion, cracks and softening in heat affected zone (HAZ), can be avoided in welding joints, and the increased penetration depth is obtained by adding Mn or Si powder. The average tensile-shear strength of Si-added joint is 3.84% higher than that of Mn-added joint, and the strength of both joints exceeds that of no-added joint. In the case of adding Mn powder, small amount of liquid Al is mixed into steel molten pool, and the Al content increases in both sides of the weld, which leads to the increased weld width in aluminum molten pool. Thus, transverse area increases in jointing steel to aluminum, which is significant for the improved tensile-shear strength of joints. As far as adding Si powder is concerned, it is not the case, the enhancement of the joint properties benefits from improvement of metallurgical reaction.

Characterization of bond line discontinuities in a high-Mn TWIP steel pipe welded by HF-ERW

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Gitae; Kim, Bongyoon; Kang, Yongjoon

In this work, the microstructure and defects in a high-frequency electrical resistance welded (HF-ERW) pipe of high-Mn twinning-induced plasticity (TWIP) steel were characterized. The microstructure of the base metal and the bond line were examined using both optical microscopy and scanning electron microscopy. The features of the bond line were similar to those of conventional steel. Simultaneously, the circumferential ductility was evaluated via a flaring test. It was concluded that the deterioration of the circumferential ductility in a high-Mn TWIP steel pipe was caused by irregular shaped oxide defects and a penetrator that had been formed during welding. Specifically, themore » penetrator, which is composed of MnO and Mn{sub 2}SiO{sub 4}, was found to be the most influential on the circumferential ductility of the welded pipe. The penetrator was analyzed using both an electron probe micro analyzer and transmission electron microscopy, and the formation sequence of the penetrator was evaluated. - Highlights: •This study focused on applying the HF-ERW process to the seam welding of expandable pipe using TWIP steels. •For improvement of the circumferential ductility, deterioration factors were characterized. •Penetrator which would mainly deteriorate the circumferential ductility consisted of round MnO and Mn{sub 2}SiO{sub 4}. •Metallurgical evidence of existing theory regarding the mechanism of defect formation during the HF-ERW was characterized.« less

Laser welding aluminum without filler metal using continuous wave and pulsed Nd:YAG lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bransch, H.N.

1994-12-31

A problem with automotive aluminum tubing applications, particularly for air conditioning heat exchanger assemblies, is terminating the tube reliably and inexpensively. An alternative to upsetting and mchining threads to the tube end is welding a nut (made from a stronger, easily machinable alloy such as Al 5456 or Al 6061) to lengths of tubing (made from a softer alloy such as Al 3003). Laser welding was investigated in order to reduce heat input and increase process speeds copared to brazing or gas metal arc welding (GMAW). Nd:YAG lasers were selected as beam source because of better absorptivity of the wavelengthmore » compared to CO{sub 2} lasers and simplified tooling with fiber optic beam delivery. It wa determined that a pulsed Nd:YAG laser produced 1.0 mm penetration at 0.3 m/min with 400 W average power, and 1.0 mm penetration at 0.75 m/min with 1000 W average power, however, an Al 4047 filler metal was required to eliminate solidification cracking. A 1900 W CW laser could weld the Al 3003 tube to the Al 5456 nut without filler metal, however, there was insufficient penetration (0.25 mm) to meet the mechanical and hermeticity requirements. To enhance penetration, but still reduce the tendency for hot cracking, the 1900 W average power beam was sine wave modulated from 400 W to 3600 W at 250 Hz and usd to weld the Al 3003 directly to the Al 5456. These parameters produced 1.2 mm penetration at 1.2 m/min without significant cracking and without using a filler metal. In addition, the welds passed all hermeticity and tensile strength tests. This combination of materials, joint design, and laser parameters produced tube assemblies that passed a leak check (300 psi nitrogen in 60{degrees}C water for 1 min) and tensile (tube breakage 100 mm from the joint, 5.2 kN tensile strength).« less

Study of the Performance of Stainless Steel A-TIG Welds

NASA Astrophysics Data System (ADS)

Shyu, S. W.; Huang, H. Y.; Tseng, K. H.; Chou, C. P.

2008-04-01

The purpose of the present work was to investigate the effect of oxide fluxes on weld morphology, arc voltage, mechanical properties, angular distortion and hot cracking susceptibility obtained with TIG welding, which applied to the welding of 5 mm thick austenitic stainless steel plates. A novel variant of the autogenous TIG welding process, oxide powders (Al2O3, Cr2O3, TiO2, SiO2 and CaO) was applied on a type 304 stainless steel through a thin layer of the flux to produce a bead on plate welds. The experimental results indicated that the increase in the penetration is significant with the use of Cr2O3, TiO2, and SiO2. A-TIG welding can increase the weld depth to bead-width ratio, and tends to reduce the angular distortion of the weldment. It was also found that A-TIG welding can increase the retained delta-ferrite content of stainless steel 304 welds and, in consequence, the hot-cracking susceptibility of as-welded is reduced. Physically constricting the plasma column and reducing the anode spot are the possible mechanism for the effect of certain flux on A-TIG penetration.

Closed loop control of penetration depth during CO₂ laser lap welding processes.

PubMed

Sibillano, Teresa; Rizzi, Domenico; Mezzapesa, Francesco P; Lugarà, Pietro Mario; Konuk, Ali Riza; Aarts, Ronald; Veld, Bert Huis In 't; Ancona, Antonio

2012-01-01

In this paper we describe a novel spectroscopic closed loop control system capable of stabilizing the penetration depth during laser welding processes by controlling the laser power. Our novel approach is to analyze the optical emission from the laser generated plasma plume above the keyhole, to calculate its electron temperature as a process-monitoring signal. Laser power has been controlled by using a quantitative relationship between the penetration depth and the plasma electron temperature. The sensor is able to correlate in real time the difference between the measured electron temperature and its reference value for the requested penetration depth. Accordingly the closed loop system adjusts the power, thus maintaining the penetration depth.

Closed Loop Control of Penetration Depth during CO2 Laser Lap Welding Processes

PubMed Central

Sibillano, Teresa; Rizzi, Domenico; Mezzapesa, Francesco P.; Lugarà, Pietro Mario; Konuk, Ali Riza; Aarts, Ronald; Veld, Bert Huis in 't; Ancona, Antonio

2012-01-01

In this paper we describe a novel spectroscopic closed loop control system capable of stabilizing the penetration depth during laser welding processes by controlling the laser power. Our novel approach is to analyze the optical emission from the laser generated plasma plume above the keyhole, to calculate its electron temperature as a process-monitoring signal. Laser power has been controlled by using a quantitative relationship between the penetration depth and the plasma electron temperature. The sensor is able to correlate in real time the difference between the measured electron temperature and its reference value for the requested penetration depth. Accordingly the closed loop system adjusts the power, thus maintaining the penetration depth. PMID:23112646

Process control of laser conduction welding by thermal imaging measurement with a color camera.

PubMed

Bardin, Fabrice; Morgan, Stephen; Williams, Stewart; McBride, Roy; Moore, Andrew J; Jones, Julian D C; Hand, Duncan P

2005-11-10

Conduction welding offers an alternative to keyhole welding. Compared with keyhole welding, it is an intrinsically stable process because vaporization phenomena are minimal. However, as with keyhole welding, an on-line process-monitoring system is advantageous for quality assurance to maintain the required penetration depth, which in conduction welding is more sensitive to changes in heat sinking. The maximum penetration is obtained when the surface temperature is just below the boiling point, and so we normally wish to maintain the temperature at this level. We describe a two-color optical system that we have developed for real-time temperature profile measurement of the conduction weld pool. The key feature of the system is the use of a complementary metal-oxide semiconductor standard color camera leading to a simplified low-cost optical setup. We present and discuss the real-time temperature measurement and control performance of the system when a defocused beam from a high power Nd:YAG laser is used on 5 mm thick stainless steel workpieces.

Exploring infrared sensoring for real time welding defects monitoring in GTAW.

PubMed

Alfaro, Sadek C A; Franco, Fernand Díaz

2010-01-01

This paper presents an evaluation of an infrared sensor for monitoring the welding pool temperature in a Gas Tungsten Arc Welding (GTAW) process. The purpose of the study is to develop a real time system control. It is known that the arc welding pool temperature is related to the weld penetration depth; therefore, by monitoring the temperature, the arc pool temperature and penetration depth are also monitored. Various experiments were performed; in some of them the current was varied and the temperature changes were registered, in others, defects were induced throughout the path of the weld bead for a fixed current. These simulated defects resulted in abrupt changes in the average temperature values, thus providing an indication of the presence of a defect. The data has been registered with an acquisition card. To identify defects in the samples under infrared emissions, the timing series were analyzed through graphics and statistic methods. The selection of this technique demonstrates the potential for infrared emission as a welding monitoring parameter sensor.

Exploring Infrared Sensoring for Real Time Welding Defects Monitoring in GTAW

PubMed Central

Alfaro, Sadek C. A.; Franco, Fernand Díaz

2010-01-01

This paper presents an evaluation of an infrared sensor for monitoring the welding pool temperature in a Gas Tungsten Arc Welding (GTAW) process. The purpose of the study is to develop a real time system control. It is known that the arc welding pool temperature is related to the weld penetration depth; therefore, by monitoring the temperature, the arc pool temperature and penetration depth are also monitored. Various experiments were performed; in some of them the current was varied and the temperature changes were registered, in others, defects were induced throughout the path of the weld bead for a fixed current. These simulated defects resulted in abrupt changes in the average temperature values, thus providing an indication of the presence of a defect. The data has been registered with an acquisition card. To identify defects in the samples under infrared emissions, the timing series were analyzed through graphics and statistic methods. The selection of this technique demonstrates the potential for infrared emission as a welding monitoring parameter sensor. PMID:22219697

Effects of activating fluxes on the weld penetration and corrosion resistant property of laser welded joint of ferritic stainless steel

NASA Astrophysics Data System (ADS)

Wang, Yonghui; Hu, Shengsun; Shen, Junqi

2015-10-01

This study was based on the ferritic stainless steel SUS430. Under the parallel welding conditions, the critical penetration power values (CPPV) of 3mm steel plates with different surface-coating activating fluxes were tested. Results showed that, after coating with activating fluxes, such as ZrO2, CaCO3, CaF2 and CaO, the CPPV could reduce 100~250 W, which indicating the increases of the weld penetrations (WP). Nevertheless, the variation range of WP with or without activating fluxes was less than 16.7%. Compared with single-component ones, a multi-component activating flux composed of 50% ZrO2, 12.09% CaCO3, 10.43% CaO, and 27.49% MgO was testified to be much more efficient, the WP of which was about 2.3-fold of that without any activating fluxes. Furthermore, a FeCl3 spot corrosion experiment was carried out with samples cut from weld zone to test the effects of different activating fluxes on the corrosion resistant (CR) property of the laser welded joints. It was found that all kinds of activating fluxes could improve the CR of the welded joints. And, it was interesting to find that the effect of the mixed activating fluxes was inferior to those single-component ones. Among all the activating fluxes, the single-component of CaCO3 seemed to be the best in resisting corrosion. By means of Energy Dispersive Spectrometer (EDS) testing, it was found that the use of activating fluxes could effectively restrain the loss of Cr element of weld zone in the process of laser welding, thus greatly improving the CR of welded joints.

Nonstationary plasma-thermo-fluid dynamics and transition in processes of deep penetration laser beam-matter interaction

NASA Astrophysics Data System (ADS)

Golubev, Vladimir S.; Banishev, Alexander F.; Azharonok, V. V.; Zabelin, Alexandre M.

1994-09-01

A qualitative analysis of the role of some hydrodynamic flows and instabilities by the process of laser beam-metal sample deep penetration interaction is presented. The forces of vapor pressure, melt surface tension and thermocapillary forces can determined a number of oscillatory and nonstationary phenomena in keyhole and weld pool. Dynamics of keyhole formation in metal plates has been studied under laser beam pulse effect ((lambda) equals 1.06 micrometers ). Velocities of the keyhole bottom motion have been determined at 0.5 X 105 - 106 W/cm2 laser power densities. Oscillatory regime of plate break- down has been found out. Small-dimensional structures with d-(lambda) period was found on the frozen cavity walls, which, in our opinion, can contribute significantly to laser beam absorption. A new form of periodic structure on the frozen pattern being a helix-shaped modulation of the keyhole walls and bottom relief has been revealed. Temperature oscillations related to capillary oscillations in the melt layer were discovered in the cavity. Interaction of the CW CO2 laser beam and the matter by beam penetration into a moving metal sample has been studied. The pulsed and thermodynamic parameters of the surface plasma were investigated by optical and spectroscopic methods. The frequencies of plasma jets pulsations (in 10 - 105 Hz range) are related to possible melt surface instabilities of the keyhole.

Effects of fabrication procedures and weld melt-through on fatigue resistance of orthotropic steel deck welds.

DOT National Transportation Integrated Search

2008-12-01

A common practice for the fabrication of orthotropic bridge deck in the US involves using 80% partial-joint-penetration groove welds (PJP) to join : closed ribs to a deck plate. Avoiding weld melt-through with the thin rib plate may be difficult to a...

Effect of laser pulse on alternative current arc discharge during laser-arc hybrid welding of magnesium alloy

NASA Astrophysics Data System (ADS)

Chen, Minghua; Xin, Lijun; Zhou, Qi; He, Lijia; Wu, Fufa

2018-01-01

The coupling effect between a laser and arc plasma was studied in situations in which the laser acts at the positive and negative waveforms of the arc discharge during the laser-arc hybrid welding of magnesium alloy. Using the methods of direct observation, high speed imaging, and spectral analysis, the surface status of weld seams, weld penetration depths, plasma behavior, and spectral characteristics of welding plasma were investigated, respectively. Results show that, as compared with the laser pulse acting at the negative waveform of the arc plasma discharge, a better weld seam formation can be achieved when the laser pulse acts at the positive waveform of the arc discharge. At the same time, the radiation intensity of Mg atoms in the arc plasma increases significantly. However, the weld penetration depth is weaker. The findings show that when the laser pulse is acting at the negative waveform of the arc plasma discharge, the position of the arc plasma discharge on the workpiece can be restrained by the laser action point, which improves the energy density of the welding arc.

An investigation on capability of hybrid Nd:YAG laser-TIG welding technology for AA2198 Al-Li alloy

NASA Astrophysics Data System (ADS)

Faraji, Amir Hosein; Moradi, Mahmoud; Goodarzi, Massoud; Colucci, Pietro; Maletta, Carmine

2017-09-01

This paper surveys the capability of the hybrid laser-arc welding in comparison with lone laser welding for AA2198 aluminum alloy experimentally. In the present research, a continuous Nd:YAG laser with a maximum power of 2000 W and a 350 A electric arc were used as two combined welding heat sources. In addition to the lone laser welding experiments, two strategies were examined for hybrid welding; the first one was low laser power (100 W) accompanied by high arc energy, and the second one was high laser power (2000 W) with low arc energy. Welding speed and arc current varied in the experiments. The influence of heat input on weld pool geometry was surveyed. The macrosection, microhardness profile and microstructure of the welded joints were studied and compared. The results indicated that in lone laser welding, conduction mode occurred and keyhole was not formed even in low welding speeds and thus the penetration depth was so low. It was also found that the second approach (high laser power accompanied with low arc energy) is superior to the first one (low laser power accompanied with high arc energy) in hybrid laser-arc welding of Al2198, since lower heat input was needed for full penetration weld and as a result a smaller HAZ was created.

Nonchamber, Root-Side, Inert-Gas Purging During Welding

NASA Technical Reports Server (NTRS)

Mcgee, William F.; Rybicki, Daniel J.

1995-01-01

Improved apparatus distributes inert gas to protect against oxidation on root side of weld during welding and after welding while joint remains hot. Simple and lightweight; readily moved along weld path in synchronism with torch. Because it concentrates inert gas where needed, consumes gas at relatively low rate, and not necessary to monitor oxygen content of protective atmosphere. Apparatus does not obscure view of root side of weld. Used for full-penetration plasma-arc welding of such reactive metals as aluminum/lithium alloys and titanium.

Friction stir welding tool and process for welding dissimilar materials

DOEpatents

Hovanski, Yuri; Grant, Glenn J; Jana, Saumyadeep; Mattlin, Karl F

2013-05-07

A friction stir welding tool and process for lap welding dissimilar materials are detailed. The invention includes a cutter scribe that penetrates and extrudes a first material of a lap weld stack to a preselected depth and further cuts a second material to provide a beneficial geometry defined by a plurality of mechanically interlocking features. The tool backfills the interlocking features generating a lap weld across the length of the interface between the dissimilar materials that enhances the shear strength of the lap weld.

Fatigue behavior of 5Ni-Cr-Mo-V steel weldments containing fabrication discontinuities

NASA Technical Reports Server (NTRS)

Gill, Steven J.; Hauser, Joseph A., II; Crooker, Thomas W.; Kruse, Brian J.; Menon, Ravi

1988-01-01

The applicability of linear elastic fracture mechanics to characterize the fatigue behavior of high-strength steel weldments containing lack-of-penetration (LOP) and slag/lack-of-fusion (S/LOF) discontinuities is explored. Full penetration, double-V butt welds with reinforcements removed were tested under zero-to-tension axial loading. Various filler metals and welding techniques were used. Both sound welds and welds containing discontinuities were cycled to failure. Where possible, cycles to crack initiation were estimated by strain gage measurements. The fracture mechanics approach was successful in correlating the fatigue lifetimes of specimens containing single LOP discontinuities of varying size. However, the fatigue behavior of specimens containing multiple S/LOF discontinuities proved to be much more complex and difficult to analyze.

Three-dimensional transient thermoelectric currents in deep penetration laser welding of austenite stainless steel

NASA Astrophysics Data System (ADS)

Chen, Xin; Pang, Shengyong; Shao, Xinyu; Wang, Chunming; Xiao, Jianzhong; Jiang, Ping

2017-04-01

The existence of thermoelectric currents (TECs) in workpieces during the laser welding of metals has been common knowledge for more than 15 years. However, the time-dependent evolutions of TECs in laser welding remain unclear. The present study developed a novel three-dimensional theoretical model of thermoelectric phenomena in the fiber laser welding of austenite stainless steel and used it to observe the time-dependent evolutions of TECs for the first time. Our model includes the complex physical effects of thermal, electromagnetic, fluid and phase transformation dynamics occurring at the millimeter laser ablated zone, which allowed us to simulate the TEC, self-induced magnetic field, Lorentz force, keyhole and weld pool behaviors varying with the welding time for different parameters. We found that TECs are truly three-dimensional, time-dependent, and uneven with a maximum current density of around 107 A/m2 located at the liquid-solid (L/S) interface near the front or bottom part of the keyhole at a laser power of 1.5 kW and a welding speed of 3 m/min. The TEC formed three-dimensional circulations moving from the melting front to solidification front in the solid part of workpiece, after which the contrary direction was followed in the liquid part. High frequency oscillation characteristics (2.2-8.5 kHz) were demonstrated in the TEC, which coincides with that of the keyhole instability (2.0-5.0 kHz). The magnitude of the self-induced magnetic field and Lorentz force can reach 0.1 mT and 1 kN/m3, respectively, which are both consistent with literature data. The predicted results of the weld dimensions by the proposed model agree well with the experimental results. Our findings could enhance the fundamental understanding of thermoelectric phenomena in laser welding.

Hybrid Laser-Arc Welding of 10-mm-Thick Cast Martensitic Stainless Steel CA6NM: As-Welded Microstructure and Mechanical Properties

NASA Astrophysics Data System (ADS)

Mirakhorli, Fatemeh; Cao, Xinjin; Pham, Xuan-Tan; Wanjara, Priti; Fihey, Jean-Luc

2016-07-01

Cast CA6NM martensitic stainless steel plates, 10 mm in thickness, were welded using hybrid laser-arc welding. The effect of different welding speeds on the as-welded joint integrity was characterized in terms of the weld bead geometry, defects, microstructure, hardness, ultimate tensile strength, and impact energy. Significant defects such as porosity, root humping, underfill, and excessive penetration were observed at a low welding speed (0.5 m/min). However, the underfill depth and excessive penetration in the joints manufactured at welding speeds above 0.75 m/min met the specifications of ISO 12932. Characterization of the as-welded microstructure revealed untempered martensite and residual delta ferrite dispersed at prior-austenite grain boundaries in the fusion zone. In addition, four different heat-affected zones in the weldments were differentiated through hardness mapping and inference from the Fe-Cr-Ni ternary phase diagram. The tensile fracture occurred in the base metal for all the samples and fractographic analysis showed that the crack path is within the martensite matrix, along primary delta ferrite-martensite interfaces and within the primary delta ferrite. Additionally, Charpy impact testing demonstrated slightly higher fracture energy values and deeper dimples on the fracture surface of the welds manufactured at higher welding speeds due to grain refinement and/or lower porosity.

Effects of SO/sub 2/ shielding gas additions on GTA weld shape

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heiple, C.R.; Burgardt, P.

1985-06-01

Substantial increases in GTA weld depth/width ratio resulted from small additions of sulfur dioxide (SO/sub 2/) to the torch shielding gas when welding two stainless steels. The improvement was demonstrated on both Types 304 and 21-6-9 austenitic stainless steels, but would be expected for iron-base alloys generally. The weld pool shape achieved was essentially independent of variations in both SO/sub 2/ content of the torch gas and base metal composition when SO/sub 2/ in the shielding gas was in the range of 500 to 1400 ppm. With 700 ppm SO/sub 2/ in the torch gas, less than 30 ppm sulfurmore » was added to an autogenous weld bead. For alloys where this additional sulfur can be tolerated and appropriate measures can be taken to handle the toxic SO/sub 2/, this technique offers a promising way to improve GTA weld joint penetration while suppressing variable penetration.« less

Improving Keyhole Stability by External Magnetic Field in Full Penetration Laser Welding

NASA Astrophysics Data System (ADS)

Li, Min; Xu, Jiajun; Huang, Yu; Rong, Youmin

2018-05-01

An external magnetic field was used to improve the keyhole stability in full penetration laser welding 316L steel. The increase of magnetic field strength gave rise to a shorter flying time of the spatter, a weaker size and brightness of the spatter, and a larger spreading area of vapor plume. This suggested that the dynamic behavior of the keyhole was stabilized by the external magnetic field. In addition, a stronger magnetic field could result in a more homogeneous distribution of laser energy, which increased the width of the weld zone, and the height of the bottom weld zone from 381 μm (0 mT) to 605 μm (50 mT). Dendrite and cellular crystal near the weld center disappeared, and grain size was refined. The external magnetic field was beneficial to the keyhole stability and improved the joint quality, because the weld pool was stirred by a Lorentz force resulting from the coupling effect of the magnetic field and inner thermocurrent.

Laser welding in space

NASA Technical Reports Server (NTRS)

Kaukler, W. F.; Workman, G. L.

1991-01-01

Autogenous welds in 304 stainless steel were performed by Nd-YAG laser heating in a simulated space environment. Simulation consists of welding on the NASA KC-135 aircraft to produce the microgravity and by containing the specimen in a vacuum chamber. Experimental results show that the microgravity welds are stronger, harder in the fusion zone, have deeper penetration and have a rougher surface rippling of the weld pool than one-g welds. To perform laser welding in space, a solar-pumped laser concept that significantly increases the laser conversion efficiency and makes welding viable despite the limited power availability of spacecraft is proposed.

NDE and DE of PWSCC Found in the J-Groove Weld of a Removed-From-Service Control Rod Drive Mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cumblidge, Stephen E.; Doctor, Steven R.; Schuster, George J.

2008-01-01

Studies conducted at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington focused on assessing the effectiveness of nondestructive examination (NDE) techniques for inspecting control rod drive mechanism (CRDM) nozzles and J-groove weldments. The primary objective of this work is to provide information to the United States Nuclear Regulatory Commission (US NRC) on the effectiveness of NDE methods as related to the in-service inspection of CRDM nozzles and J-groove weldments, and to enhance the knowledge base of primary water stress corrosion cracking (PWSCC) through destructive characterization of the CRDM assemblies. Two CRDM assemblies were removed from service, decontaminated, and thenmore » used in a series of laboratory NDE and DE measurements; this report addresses the following questions: 1) What did each NDE technique detect?, 2) What did each NDE technique miss?, 3) How accurately did each NDE technique characterize the detected flaws?, and finally 4) What were the basis for the NDE techniques performance? Two CRDM assemblies including the CRDM nozzle, the J-groove weld, buttering, and a portion of the ferritic head material were selected for this study. This paper focuses on a CRDM assembly that contained suspected PWSCC, based on in-service inspection data and through-wall leakage. The laboratory NDE measurements used to examine the CRDM assembly followed standard industry techniques for conducting in-service inspections of CRDM nozzles and the crown of the J-groove welds and buttering. These techniques included eddy current testing, time of flight diffraction ultrasound, and penetrant testing. In addition, other laboratory-based NDE methods were employed to conduct inspections of the CRDM assembly with particular emphasis on inspecting the J-groove weld and buttering. These techniques included volumetric ultrasonic inspection of the J-groove weld metal, visual testing via replicant material of the J-groove weld and high resolution photography of the J-groove weld crown and buttering. The results from these NDE studies were used to guide the development of the destructive characterization plan. The NDE studies found several crack-like indications. The NDE and DE studies determined that one of these was a through-weld radially-oriented PWSCC crack in the wetted surface of the J-groove weld, located at the transition point between the weld and the buttering. The crack was 6 mm long on the surface and quickly grew to 25 mm long at a depth of 8 mm, covering the length of the weld between the penetration tube and the carbon steel. The NDE studies found that only ET was able to detect the through-weld crack. The crack was oriented poorly for the ultrasonic testing, and was too tight for accurate PT or VT. The ET voltage response of the flaw was 30% that of a deep EDM notch. The DE performed on the crack consisted of slicing the crack into thin sections, polishing the sections, and then using optical and scanning electron microscopy (SEM) to characterize the crack. DE shows the crack was PWSCC and that it initiated on the wetted surface, grew and expanded through the weld metal, and exited into the annulus. The SEM examinations showed the crack followed the weld grain boundaries as it progressed through the weld. The crack was branched and discontinuous along its length.« less

Post-weld Tempered Microstructure and Mechanical Properties of Hybrid Laser-Arc Welded Cast Martensitic Stainless Steel CA6NM

NASA Astrophysics Data System (ADS)

Mirakhorli, Fatemeh; Cao, Xinjin; Pham, Xuan-Tan; Wanjara, Priti; Fihey, Jean-Luc

2016-12-01

Manufacturing of hydroelectric turbine components involves the assembly of thick-walled stainless steels using conventional multi-pass arc welding processes. By contrast, hybrid laser-arc welding may be an attractive process for assembly of such materials to realize deeper penetration depths, higher production rates, narrower fusion, and heat-affected zones, and lower distortion. In the present work, single-pass hybrid laser-arc welding of 10-mm thick CA6NM, a low carbon martensitic stainless steel, was carried out in the butt joint configuration using a continuous wave fiber laser at its maximum power of 5.2 kW over welding speeds ranging from 0.75 to 1.2 m/minute. The microstructures across the weldment were characterized after post-weld tempering at 873 K (600 °C) for 1 hour. From microscopic examinations, the fusion zone was observed to mainly consist of tempered lath martensite and some residual delta-ferrite. The mechanical properties were evaluated in the post-weld tempered condition and correlated to the microstructures and defects. The ultimate tensile strength and Charpy impact energy values of the fully penetrated welds in the tempered condition were acceptable according to ASTM, ASME, and industrial specifications, which bodes well for the introduction of hybrid laser-arc welding technology for the manufacturing of next generation hydroelectric turbine components.

NASA Astrophysics Data System (ADS)

Tube to tube-sheet joints in heat exchangers are currently welded by the orbital TIG process characterized by very high quality of the weld beads and good repeatability. However, due to high number of welds, a reduction in the welding cycle time would have an interesting impact on manufacturing costs and delays and laser welding technology is aimed to improve this factor. The main disadvantage is the positioning accuracy required by the laser welding process since beam deviations from real joint cause lack of penetration. It is expected that the Orbital laser welding head developed under the European project ORBITAL will avoid this drawback.

Inspecting Pipe Radiographically Through Asbestos Insulation

NASA Technical Reports Server (NTRS)

Gianettino, David P.

1994-01-01

Welds between sections of insulated steampipe located and inspected radiographically. Unless need to repair defective weld, one avoids cost, time, and hazard of removing asbestos insulation. Enables inspectors to locate and evaluate nondestructively any weld in pipe system, without shutting down steam. Hidden weld joints first located by use of low-power fluoroscope, moved along pipe while technician observes fluoroscopic image. Low-energy x rays from fluoroscope penetrate insulation but not pipe. Weld bead appears in silhouette on fluoroscope screen. Technician then accurately marks weld sites on insulation for later inspection.

Improved Abutting Edges For Welding In Keyhole Mode

NASA Technical Reports Server (NTRS)

Harwing, Dennis D.; Sanders, John M.

1994-01-01

Welds of better quality made, and/or heat input reduced. Improved shapes devised for abutting edges of metal pieces to be joined by plasma arc welding in keyhole mode, in which gas jet maintains molten hole ("keyhole") completely through thickness of weld joint. Edges of metal pieces to be welded together machined to provide required combination gap and shaped, thin sections. Shapes and dimensions chosen to optimize weld in various respects; e.g., to enhance penetration of keyhole or reduce heat input to produce joint of given thickness.

Improved Back-Side Purge-Gas Chambers For Plasma Arc Welding

NASA Technical Reports Server (NTRS)

Ezell, Kenneth G.; Mcgee, William F.; Rybicki, Daniel J.

1995-01-01

Improved chambers for inert-gas purging of back sides of workpieces during plasma arc welding in keyhole (full-penetration) mode based on concept of directing flows of inert gases toward, and concentrating them on, hot weld zones. Tapered chamber concentrates flow of inert gas on plasma arc plume and surrounding metal.

Gravitational effects on weld pool shape and microstructural evolution during gas tungsten arc and laser beam welding on 304 stainless steel, nickel, and aluminum-4 wt.% copper alloy

NASA Astrophysics Data System (ADS)

Kang, Namhyun

The objective of the present work was to investigate effects of gravitational (acceleration) level and orientation on Ni 200 alloy (99.5% Ni purity), 304 stainless steel, and Al-4 wt.% Cu alloy during gas tungsten arc welding (GTAW) and laser beam welding (LBW). Main characterization was focused on the weld pool shape, microstructure, and solute distribution as a function of gravitational level and orientation. The welds were divided into two classes, i.e., 'stable' and 'unstable' welds, in view of the variation of weld pool shape as a function of gravitational level and orientation. In general, higher arc current and translational GTAW produced more significant effects of gravitational orientation on the weld pool shape than the case of lower arc current and spot welding. Cross-sectional area (CSA) was a secondary factor in determining the stability of weld pool shape. For the 'stable' weld of 304 stainless steel GTAW, the II-U weld showed less convexity in the pool bottom and more depression of the free surface, therefore producing deeper penetration (10--20%) than the case of II-D weld. The II-D weld of 304 stainless steel showed 31% deeper penetration, 28% narrower width, and more hemispherical shape of the weld pool than the case of II-U weld. For GTAW on 304 stainless steel, gravitational level variation from low gravity (LG ≈ 1.2 go) to high gravity (HG ≈ 1.8 go) caused 10% increase in width and 10% decrease in depth while maintaining the overall weld pool volume. Furthermore, LBW on 304 stainless steels showed mostly constant shape of weld pool as a function of gravitational orientation. GTAW on Ni showed similar trends of weld pool shape compared with GTAW on 304 stainless steel, i.e., the weld pool became unstable by showing more penetration in the II-D weld for slower arc translational velocity (V a) and larger weld pool size. However, the Ni weld pool shape had greater stability of the weld pool shape with respect to the gravitational orientation than the case of 304 stainless steel, i.e., higher current boundary and no humping. Regardless of the gravitational level, the ferrite content and the distribution of the solutes (Cr and Ni) remained constant for GTAW on 304 stainless steel. However, for GTAW on Al-4 wt.% Cu alloys, the gravitational orientation changed the weld pool shape associated with convection flows. In summary, gravity influenced the weld pool shape that was associated with convection flows and weld surface deformation for specific welding conditions. The variation of convection flows and weld pool shape played a role in modifying VS and GL. Solidification orientation and morphology were affected because VS and GL were changed as a function of gravity. Studies of gravity on the welding process are expected to play a significant role in the space-station construction and circumferential pipe welding on the earth. (Abstract shortened by UMI.)

Effects of Cr2O3 Activating Flux on the Plasma Plume in Pulsed Laser Welding

NASA Astrophysics Data System (ADS)

Yi, Luo; Yunfei, Du; Xiaojian, Xie; Rui, Wan; Liang, Zhu; Jingtao, Han

2016-11-01

The effects of Cr2O3 activating flux on pulsed YAG laser welding of stainless steel and, particularly, on the behavior of the plasma plume in the welding process were investigated. According to the acoustic emission (AE) signals detected in the welding process, the possible mechanism for the improvement in penetration depth was discussed. The results indicated that the AE signals detected in the welding process reflected the behavior of the plasma plume as pulsed laser energy affecting the molten pool. The root-mean-square (RMS) waveform, AE count, and power spectrum of AE signals were three effective means to characterize the behavior of the plasma plume, which indicated the characteristics of energy released by the plasma plume. The activating flux affected by the laser beam helped to increase the duration and intensity of energy released by the plasma plume, which improved the recoil force and thermal effect transferred from the plasma plume to the molten pool. These results were the main mechanism for Cr2O3 activating flux addition improving the penetration depth in pulsed YAG laser welding.

The detection of tightly closed flaws by nondestructive testing (NDT) methods. [fatigue crack formation in aluminum alloy test specimens

NASA Technical Reports Server (NTRS)

Rummel, W. D.; Rathke, R. A.; Todd, P. H., Jr.; Mullen, S. J.

1975-01-01

Liquid penetrant, ultrasonic, eddy current and X-radiographic techniques were optimized and applied to the evaluation of 2219-T87 aluminum alloy test specimens in integrally stiffened panel, and weld panel configurations. Fatigue cracks in integrally stiffened panels, lack-of-fusion in weld panels, and fatigue cracks in weld panels were the flaw types used for evaluation. A 2319 aluminum alloy weld filler rod was used for all welding to produce the test specimens. Forty seven integrally stiffened panels containing a total of 146 fatigue cracks, ninety three lack-of-penetration (LOP) specimens containing a total of 239 LOP flaws, and one-hundred seventeen welded specimens containing a total of 293 fatigue cracks were evaluated. Nondestructive test detection reliability enhancement was evaluated during separate inspection sequences in the specimens in the 'as-machined or as-welded', post etched and post proof loaded conditions. Results of the nondestructive test evaluations were compared to the actual flaw size obtained by measurement of the fracture specimens after completing all inspection sequences. Inspection data were then analyzed to provide a statistical basis for determining the flaw detection reliability.

Optimization of operator and physical parameters for laser welding of dental materials.

PubMed

Bertrand, C; le Petitcorps, Y; Albingre, L; Dupuis, V

2004-04-10

Interactions between lasers and materials are very complex phenomena. The success of laser welding procedures in dental metals depends on the operator's control of many parameters. The aims of this study were to evaluate factors relating to the operator's dexterity and the choice of the welding parameters (power, pulse duration and therefore energy), which are recognized determinants of weld quality. In vitro laboratory study. FeNiCr dental drawn wires were chosen for these experiments because their properties are well known. Different diameters of wires were laser welded, then tested in tension and compared to the control material as extruded, in order to evaluate the quality of the welding. Scanning electron microscopy of the fractured zone and micrograph observations perpendicular and parallel to the wire axis were also conducted in order to analyse the depth penetration and the quality of the microstructure. Additionally, the micro-hardness (Vickers type) was measured both in the welded and the heat-affected zones and then compared to the non-welded alloy. Adequate combination of energy and pulse duration with the power set in the range between 0.8 to 1 kW appears to improve penetration depth of the laser beam and success of the welding procedure. Operator skill is also an important variable. The variation in laser weld quality in dental FeNiCr wires attributable to operator skill can be minimized by optimization of the physical welding parameters.

Detection of lack of fusion using opaque additives

NASA Technical Reports Server (NTRS)

Cook, J. L.

1973-01-01

Reliable nondestructive inspection for incomplete weldment penetration and rapid oxidation of aluminum surfaces when exposed to the atmosphere are currently two major problems in welded aluminum spacecraft structure. Incomplete-penetration defects are extremely difficult to detect and can lead to catastrophic failure of the structure. The moisture absorbed by aluminum oxide on the surface can cause weldment porosity if the surface is not cleaned before welding. The approach employed in this program to solve both problems was to employ copper as a coating to prevent oxidation of the aluminum. Also, copper was used as an opaque additive in the weldment to enhance X-ray detection in the event of incomplete penetration.

Effect of Welding Process on Microstructure, Mechanical and Pitting Corrosion Behaviour of 2205 Duplex Stainless Steel Welds

NASA Astrophysics Data System (ADS)

Mohammed, Raffi; Madhusudhan Reddy, G.; Srinivasa Rao, K.

2018-03-01

An attempt has been made to weld 2205 Duplex stainless steel of 6mm thick plate using conventional gas tungsten arc welding (GTAW) and activated gas tungsten arc welding (A- GTAW) process using silica powder as activated flux. Present work is aimed at studying the effect of welding process on depth of penetration, width of weld zone of 2205 duplex stainless steel. It also aims to observe the microstructural changes and its effect on mechanical properties and pitting corrosion resistance of 2205 duplex stainless steel welds. Metallography is done to observe the microstructural changes of the welds using image analyzer attached to the optical microscopy. Hardness studies, tensile and ductility bend tests were evaluated for mechanical properties. Potentio-dynamic polarization studies were carried out using a basic GillAC electro-chemical system in 3.5% NaCl solution to observe the pitting corrosion behaviour. Results of the present investigation established that increased depth of penetration and reduction of weld width in a single pass by activated GTAW with the application of SiO2 flux was observed when compared with conventional GTAW process. It may be attributed to the arc constriction effect. Microstructure of the weld zones for both the welds is observed to be having combination of austenite and delta ferrite. Grain boundary austenite (GBA) with Widmanstatten-type austenite (WA) of plate-like feature was nucleated from the grain boundaries in the weld zone of A-GTAW process. Mechanical properties are relatively low in activated GTAW process and are attributed to changes in microstructural morphology of austenite. Improved pitting corrosion resistance was observed for the welds made with A-GTAW process.

Parametric optimisation and microstructural analysis on high power Yb-fibre laser welding of Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Ahn, J.; Chen, L.; Davies, C. M.; Dear, J. P.

2016-11-01

In this work thin sheets of Ti-6Al-4V were full penetration welded using a 5 kW fibre laser in order to evaluate the effectiveness of high power fibre laser as a welding processing tool for welding Ti-6Al-4V with the requirements of the aircraft industry and to determine the effect of welding parameters including laser power, welding speed and beam focal position on the weld microstructure, bead profile and weld quality. It involved establishing an understanding of the influence of welding parameters on microstructural change, welding defects, and the characteristics of heat affected zone (HAZ) and weld metal (WM) of fibre laser welded joints. The optimum range of welding parameters which produced welds without cracking and porosity were identified. The influence of the welding parameters on the weld joint heterogeneity was characterised by conducting detailed microstructural analysis.

The use of electromagnetic body forces to enhance the quality of laser welds

NASA Astrophysics Data System (ADS)

Ambrosy, Guenter; Berger, P.; Huegel, H.; Lindenau, D.

2003-11-01

The use of electromagnetic body forces in laser beam welding of aluminum alloys is a new method to shape the geometry and to enhance the quality of the weld seams. In this new approach, electromagnetic volume forces are utilized by applying magnetic fields and electric currents of various origins. Acting in the liquid metal, they directly affect the flow field and can lead to favourable conditions for the melt dynamics and energy coupling. Numerous welds with full and partial penetration using both CO2 and Nd:YAG lasers demonstrate that this method directly influences the seam geometry and top-bead topography as well as the penetration depth and the evolution of pores and cracks. In the case of full penetration, it is also possible to lift or to lower the weld pool. The method, therefore, can be used to shape the geometry and to enhance the quality of the weld seam. Depending on the orientation of an external magnetic field, significant impacts are achieved in CO2 welding, even without an external current: the shape of the cross-sectional area can be increased of up to 50% and also the seam width is changed. Whereas for such conditions with Nd:YAG lasers no significant effect could be observed, it turned out that, when an external electric current is applied, similar effects are present with both wavelengths. In further investigations, the effect of electromagnetic body forces resulting from the interaction of an external current and its self-induced magnetic field was studied. Hereby, the current was fed into the workpiece via a tungsten electrode or a filler wire. The resulting phenomena are the same independent from wavelength and means of current feed.

Nickel aluminide-copper backing for butt joint welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raghavan, S.; Muszynski, M.; Chin, B.A.

1996-12-31

Single-side full penetration welding is the primary welding process in shipbuilding. This process requires the use of a backing to support the molten metal. Conventionally, copper has been used as the backing material in the shop and ceramic tiles for jobs on the field. However, copper has shown to contaminate the weld and produce adverse effects and ceramics have shown to produce porosities in the weld. A new backing with an intermetallic layer (NiAl) on the copper surface has been fabricated. The results indicate that this backing could alleviate the contamination problems and produce quality welds.

Comparison on welding mode characteristics of arc heat source for heat input control in hybrid welding of aluminum alloy

NASA Astrophysics Data System (ADS)

Song, Moo-Keun; Kim, Jong-Do; Oh, Jae-Hwan

2015-03-01

Presently in shipbuilding, transportation and aerospace industries, the potential to apply welding using laser and laser-arc hybrid heat sources is widely under research. This study has the purpose of comparing the weldability depending on the arc mode by varying the welding modes of arc heat sources in applying laser-arc hybrid welding to aluminum alloy and of implementing efficient hybrid welding while controlling heat input. In the experimental study, we found that hybrid welding using CMT mode produced deeper penetration and sounder bead surface than those characteristics produced during only laser welding, with less heat input compared to that required in pulsed arc mode.

Optically controlled welding system

NASA Technical Reports Server (NTRS)

Gordon, Stephen S. (Inventor)

1988-01-01

An optically controlled welding system wherein a welding torch having through-the-torch viewing capabilities is provided with an optical beam splitter to create a transmitted view and a reflective view of a welding operation. These views are converted to digital signals which are then processed and utilized by a computerized robotic welder to make the welding torch responsive thereto. Other features include an actively cooled electrode holder which minimizes a blocked portion of the view by virtue of being constructed of a single spoke or arm, and a weld pool contour detector comprising a laser beam directed onto the weld pool with the position of specular radiation reflected therefrom, being characteristic of a penetrated or unpenetrated condition of the weld pool.

Comparison of pressure drop and filtration efficiency of particulate respirators using welding fumes and sodium chloride.

PubMed

Cho, Hyun-Woo; Yoon, Chung-Sik; Lee, Jin-Ho; Lee, Seung-Joo; Viner, Andrew; Johnson, Erik W

2011-07-01

Respirators are used to help reduce exposure to a variety of contaminants in workplaces. Test aerosols used for certification of particulate respirators (PRs) include sodium chloride (NaCl), dioctyl phthalate, and paraffin oil. These aerosols are generally assumed to be worst case surrogates for aerosols found in the workplace. No data have been published to date on the performance of PRs with welding fumes, a hazardous aerosol that exists in real workplace settings. The aim of this study was to compare the performance of respirators and filters against a NaCl aerosol and a welding fume aerosol and determine whether or not a correlation between the two could be made. Fifteen commercial PRs and filters (seven filtering facepiece, two replaceable single-type filters, and six replaceable dual-type filters) were chosen for investigation. Four of the filtering facepiece respirators, one of the single-type filters, and all of the dual-type filters contained carbon to help reduce exposure to ozone and other vapors generated during the welding process. For the NaCl test, a modified National Institute for Occupational Safety and Health protocol was adopted for use with the TSI Model 8130 automated filter tester. For the welding fume test, welding fumes from mild steel flux-cored arcs were generated and measured with a SIBATA filter tester (AP-634A, Japan) and a manometer in the upstream and downstream sections of the test chamber. Size distributions of the two aerosols were measured using a scanning mobility particle sizer. Penetration and pressure drop were measured over a period of aerosol loading onto the respirator or filter. Photos and scanning electron microscope images of clean and exposed respirators were taken. The count median diameter (CMD) and mass median diameter (MMD) for the NaCl aerosol were smaller than the welding fumes (CMD: 74 versus 216 nm; MMD: 198 versus 528 nm, respectively). Initial penetration and peak penetration were higher with the NaCl aerosol. However, pressure drop increased much more rapidly in the welding fume test than the NaCl aerosol test. The data and images clearly show differences in performance trends between respirator models. Therefore, general correlations between NaCl and weld fume data could not be made. These findings suggest that respirators certified with a surrogate test aerosol such as NaCl are appropriate for filtering welding fume (based on penetration). However, some respirators may have a more rapid increase in pressure drop from the welding fume accumulating on the filter. Therefore, welders will need to choose which models are easier to breathe through for the duration of their use and replace respirators or filters according to the user instructions and local regulations.

Melting Efficiency During Plasma Arc Welding

NASA Technical Reports Server (NTRS)

McClure, J.C.; Evans, D. M.; Tang, W.; Nunes, A. C.

1999-01-01

A series of partial penetration Variable Polarity Plasma Arc welds were made at equal power but various combinations of current and voltage on 2219 aluminum. Arc Efficiency was measured calorimetrically and ranged between 48% and 66%. Melting efficiency depends on the weld pool shape. Increased current increases the melting efficiency as it increases the depth to width ratio of the weld pool. Higher currents are thought to raise arc pressure and depress the liquid at the bottom of the weld pool causing a more nearly two dimensional heat flow condition.

Laser-TIG Welding of Titanium Alloys

NASA Astrophysics Data System (ADS)

Turichin, G.; Tsibulsky, I.; Somonov, V.; Kuznetsov, M.; Akhmetov, A.

2016-08-01

The article presents the results of investigation the technological opportunity of laser-TIG welding of titanium alloys. The experimental stand for implementation of process with the capability to feed a filler wire was made. The research of the nature of transfer the filler wire into the welding pool has been demonstrated. The influence of distance between the electrode and the surface of the welded plates on the stability of the arc was shown. The relationship between welding velocity, the position of focal plane of the laser beam and the stability of penetration of plates was determined.

Method and apparatus for real time weld monitoring

DOEpatents

Leong, Keng H.; Hunter, Boyd V.

1997-01-01

An improved method and apparatus are provided for real time weld monitoring. An infrared signature emitted by a hot weld surface during welding is detected and this signature is compared with an infrared signature emitted by the weld surface during steady state conditions. The result is correlated with weld penetration. The signal processing is simpler than for either UV or acoustic techniques. Changes in the weld process, such as changes in the transmitted laser beam power, quality or positioning of the laser beam, change the resulting weld surface features and temperature of the weld surface, thereby resulting in a change in the direction and amount of infrared emissions. This change in emissions is monitored by an IR sensitive detecting apparatus that is sensitive to the appropriate wavelength region for the hot weld surface.

Hybrid FSWeld-bonded joint fatigue behaviour

NASA Astrophysics Data System (ADS)

Lertora, Enrico; Mandolfino, Chiara; Gambaro, Carla; Pizzorni, Marco

2018-05-01

Aluminium alloys, widely used in aeronautics, are increasingly involved in the automotive industry due to the good relationship between mechanical strength and specific weight. The lightening of the structures is the first objective, which allows the decreasing in the weight in motion. The use of aluminium alloys has also seen the introduction of the Friction Stir Welding (FSW) technique for the production of structural overlapping joints. FSW allows us to weld overlap joints free from defects, but with the presence of a structural notch further aggravated by the presence of a "hook" defect near the edge of the weld. Furthermore, FSW presents a weld penetration area connected to the tool geometry and penetration. The experimental activity will be focused on the combination of two different joining techniques, which can synergistically improve the final joint resistance. In particular, the welding and bonding process most commonly known as weld-bonding is defined as a hybrid process, as it combines two different junction processes. In this paper we analyse FSWelded AA6082 aluminium alloy overlapped joint with the aim of quantitatively evaluating the improvement provided by the presence of an epoxy adhesive between the plates. After optimising the weld-bonding process, the mechanical behaviour of welded joints will be analysed by static and dynamic tests. The presence of the adhesive should limit the negative effect of the structural notch inevitable in a FSW overlapped joint.

Fatigue strength of socket welded pipe joint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Higuchi, Makoto; Hayashi, Makoto; Yamauchi, Takayoshi

1995-12-01

Fully reversed four point bending fatigue tests were carried out on small diameter socket welded joints made of carbon steels. Experimental parameters were pipe diameter, thicknesses of pipe and socket wall, throat depth and shape of fillet welds, slip-on and diametral gaps in the socket welding, lack of penetration at the root of fillet welds, and peening of fillet welds. In most cases a fatigue crack started from the root of the fillet, but in the case of higher stress amplitude, it tended to start from the toe of fillet. The standard socket welded joint for a pipe with amore » 50 mm nominal diameter showed a relatively low fatigue strength of 46 MPa in stress amplitude at the 10{sup 7} cycles failure life. This value corresponds to about 1/5 of that for the smoothed base metal specimens in axial fatigue. The fatigue strength decreased with increasing pipe diameter, and increased with increasing thickness of the pipe and socket wall. The effects of throat depth and shape of fillet welds on fatigue strength were not significant. Contrary to expectation, the fatigue strength of a socket welded joint without slip-on gap is Higher than that of the joint with a normal gap. A lack of penetration at the root deleteriously reduced fatigue strength, showing 14 MPa in stress amplitude at the 10{sup 7} cycles failure life for the 50 mm diameter socket joint.« less

Comparative study on interactions between laser and arc plasma during laser-GTA welding and laser-GMA welding

NASA Astrophysics Data System (ADS)

Chen, Minghua; Xu, Jiannan; Xin, Lijun; Zhao, Zuofu; Wu, Fufa

2016-10-01

This paper describes an investigation on differences in interactions between laser and arc plasma during laser-gas tungsten arc (LT) welding and laser-gas metal arc (LM) welding. The characteristics of LT heat source and LM heat source, such as plasma behavior, heat penetration ability and spectral information were comparably studied. Based on the plasma discharge theory, the interactions during plasma discharge were modeled and analyzed. Results show that in both LT and LM welding, coupling discharge between the laser keyhole plasma and arc happens, which strongly enhance the arc. But, the enhancing effect in LT welding is much more sensitive than that in LM welding when parameters are adjusted.

Optically controlled welding system

NASA Technical Reports Server (NTRS)

Gordon, Stephen S. (Inventor)

1989-01-01

An optically controlled welding system (10) wherein a welding torch (12) having through-the-torch viewing capabilities is provided with an optical beam splitter (56) to create a transmitted view and a reflective view of a welding operation. These views are converted to digital signals which are then processed and utilized by a computerized robotic welder (15) to make the welding torch responsive thereto. Other features includes an actively cooled electrode holder (26) which minimizes a blocked portion of the view by virtue of being constructed of a single spoke or arm (28) and a weld pool contour detector (14) comprising a laser beam directed onto the weld pool with the position of specular radiation reflected therefrom being characteristic of a penetrated or unpenetrated condition of the weld pool.

Laser penetration spike welding: a welding tool enabling novel process and design opportunities

NASA Astrophysics Data System (ADS)

Dijken, Durandus K.; Hoving, Willem; De Hosson, J. Th. M.

2002-06-01

A novel method for laser welding for sheet metal. is presented. This laser spike welding method is capable of bridging large gaps between sheet metal plates. Novel constructions can be designed and manufactured. Examples are light weight metal epoxy multi-layers and constructions having additional strength with respect to rigidity and impact resistance. Its capability to bridge large gaps allows higher dimensional tolerances in production. The required laser systems are commercially available and are easily implemented in existing production lines. The lasers are highly reliable, the resulting spike welds are quickly realized and the cost price per weld is very low.

High power laser welding of thick steel plates in a horizontal butt joint configuration

NASA Astrophysics Data System (ADS)

Atabaki, M. Mazar; Yazdian, N.; Ma, J.; Kovacevic, R.

2016-09-01

In this investigation, two laser-based welding techniques, autogenous laser welding (ALW) and laser welding assisted with a cold wire (LWACW), were applied to join thick plates of a structural steel (A36) in a horizontal narrow gap butt joint configuration. The main practical parameters including welding method and laser power were varied to get the sound weld with a requirement to achieve a full penetration with the reinforcement at the back side of weld in just one pass. The weld-bead shape, cross-section and mechanical properties were evaluated by profilometer, micro-hardness test and optical microscope. In order to investigate the stability of laser-induced plasma plume, the emitted optical spectra was detected and analyzed by the spectroscopy analysis. It was found that at the laser power of 7 kW a fully penetrated weld with a convex back side of weld could be obtained by the LWACW. The microstructural examinations showed that for the ALW the acicular ferrite and for the LWACW the pearlite were formed in the heat affected zone (HAZ). The prediction of microstructure based on continuous cooling transformation (CCT) diagram and cooling curves obtained by thermocouple measurement were in good agreement with each other. According to the plasma ionization values obtained from the spectroscopy analysis the plume for both processes was recognized as dominated weakly ionized plasma including the main vaporized elemental composition. At the optimum welding condition (LWACW at the laser power of 7 kW) the fluctuation of the electron temperature was reduced. The spectroscopy analysis demonstrated that at the higher laser power more of the elemental compositions such as Mn and Fe were evaporated.

Mixing weld gases offers advantages

NASA Technical Reports Server (NTRS)

May, J. L.; Mendenhall, M. M.

1969-01-01

Argon added to helium during gas tungsten arc cover-pass welding in the horizontal position results in a better controlled wider bead width, increased arc stability, and reduction in heat input. Adequate filler material wetness and penetration pass coverage is possible with only one pass.

The feasibility of producing aluminum-lithium structures for cryogenic tankage applications by laser beam welding

NASA Technical Reports Server (NTRS)

Martukanitz, R. P.; Lysher, K. G.

1993-01-01

Aluminum-lithium alloys exhibit high strength, high elastic modulus, and low density as well as excellent cryogenic mechanical properties making them ideal material candidates for cryogenic tanks. NASA has proposed the use of 'built-up' structure for panels fabricated into cryogenic tanks replacing current conventional machining. Superplastically formed stiffeners would be joined to sheet (tank skin) that had been roll formed to the radius of the tank in order to produce panels. Aluminum-lithium alloys of interest for producing the built-up structure include alloy 2095-T6 stiffeners to 2095-T8 sheet and alloy 8090-T6 stiffeners to 2090-T83 sheet. Laser welding, with comparable joint properties, offers the following advantages over conventional welding: higher production rates, minimal degradation within the heat affected zones, and full process automation. This study established process parameters for laser beam welding, mechanical property determinations, metallographic characterization, and fabrication of prototype panels. Tensile tests representing partial penetration of the skin alloys provided joint efficiencies between 65 and 77 percent, depending upon alloy and degree of penetration. Results of tension shear tests of lap welds indicated that the combination of 2095-T6 to 2090-T8 exhibited significantly higher weld shear strength at the interface in comparison to welds of 8090-T6 to 2090-T83. The increased shear strength associated with 2095 is believed to be due to the alloy's ability to precipitation strengthening (naturally age) after welding.

Role of Oxygen as Surface-Active Element in Linear GTA Welding Process

NASA Astrophysics Data System (ADS)

Yadaiah, Nirsanametla; Bag, Swarup

2013-11-01

Although the surface-active elements such as oxygen and sulfur have an adverse effect on momentum transport in liquid metals during fusion welding, such elements can be used beneficially up to a certain limit to increase the weld penetration in the gas tungsten arc (GTA) welding process. The fluid flow pattern and consequently the weld penetration and width change due to a change in coefficient of surface tension from a negative value to a positive value. The present work is focused on the analysis of possible effects of surface-active elements to change the weld pool dimensions in linear GTA welding. A 3D finite element-based heat transfer and fluid flow model is developed to study the effect of surface-active elements on stainless steel plates. A velocity in the order of 180 mm/s due to surface tension force is estimated at an optimum concentration of surface-active elements. Further, the differential evolution-based global optimization algorithm is integrated with the numerical model to estimate uncertain model parameters such as arc efficiency, effective arc radius, and effective values of material properties at high temperatures. The effective values of thermal conductivity and viscosity are estimated to be enhanced nine and seven times, respectively, over corresponding room temperature values. An error analysis is also performed to find out the overall reliability of the computed results, and a maximum reliability of 0.94 is achieved.

Numerical simulation of spatter formation during fiber laser welding of 5083 aluminum alloy at full penetration condition

NASA Astrophysics Data System (ADS)

Wu, Dongsheng; Hua, Xueming; Huang, Lijin; Zhao, Jiang

2018-03-01

The droplet escape condition in laser welding is established in this paper. A three-dimensional numerical model is developed to study the weld pool convection and spatter formation at full penetration during the fiber laser welding of 5083 aluminum alloy. It is found that when laser power is 9 kW, the bottom of the keyhole is dynamically opened and closed. When the bottom of the keyhole is closed, the molten metal at the bottom of the back keyhole wall flows upwards along the fusion line. When the bottom of the keyhole is opened, few spatters can be seen around the keyhole at the top surface, two flow patterns exists in the rear part of the keyhole: a portion of molten metal flows upwards along the fusion line, other portion of molten metal flows to the bottom of the keyhole, which promote the spatter formation at the bottom of the keyhole rear wall.

Optical Sensor for real-time Monitoring of CO(2) Laser Welding Process.

PubMed

Ancona, A; Spagnolo, V; Lugarà, P M; Ferrara, M

2001-11-20

An optical sensor for real-time monitoring of laser welding based on a spectroscopic study of the optical emission of plasma plumes has been developed. The welding plasma's electron temperature was contemporarily monitored for three of the chemical species that constitute the plasma plume by use of related emission lines. The evolution of electron temperature was recorded and analyzed during several welding procedures carried out under various operating conditions. A clear correlation between the mean value and the standard deviation of the plasma's electron temperature and the quality of the welded joint has been found. We used this information to find optimal welding parameters and for real-time detection of weld defects such as crater formation, lack of penetration, weld disruptions, and seam oxidation.

Preliminary study on detection technology of the cladding weld of spent fuel storage pool

NASA Astrophysics Data System (ADS)

Qi, Pan; Cui, Hongyan; Feng, Meiming; Shao, Wenbin; Liao, Shusheng; Li, Wei

2018-04-01

As the first barrier of the Spent fuel storage pool, the steel cladding using different sizes (length×width) of 304L stainless steel with 3˜6mm thickness plate argon arc welded together which is direct contacted with boric acid water. Environmental humidity between the back of steel cladding and concrete, makes phosphate, chloride ion overflowed from the concrete that corroded on the weld zone with different mechanism. Part of the corrosion defects can penetrate leaded to leakage of boric acid water in penetration position accelerated crack propagation. In view of the above situation and combined with the actual needs of the power plant, the development of effective underwater nondestructive testing means of the weld area for periodic inspection and monitoring is necessary. A single method may lead to the missing of defects detection due to weld reinforcement unpolished. In this paper, eddy current array (ARRAY) and Alternating Current Field Measurement (ACFM) are adapted to test the limit sensitivity and resolution through by the specimens with artificial defects which make their detection abilities close to satisfy engineering requirements. The preliminary study found that Φ0.5mm through-wall hole and with 2mm length and 0.3mm width through-wall crack in the weld can be good inspected.

System for Controlling the Stirring Pin of a Friction Stir Welding Apparatus

NASA Technical Reports Server (NTRS)

Ding, R. Jeffrey (Inventor); Romine, Peter L. (Inventor); Oelgoetz, Peter A. (Inventor)

2002-01-01

A control is provided for a friction stir welding apparatus comprising a pin tool which includes a shoulder and a rotating pin extending outwardly from the shoulder of the pin tool and which, in use, is plunged into a workpiece formed contacting workpiece members to stir weld the members together. The control system controls the penetration of the pin tool into the workpiece members which are mounted on a support anvil. The control system includes a pin length controller for controlling pin length relative to the shoulder and for producing a corresponding pin length signal. A pin force sensor senses the force being exerted on the pin during welding and produces a corresponding actual pin force signal. A probe controller controls a probe extending outwardly from the pin, senses a parameter related to the distance between the probe and the supporting anvil and produces a corresponding probe signal. A workpiece standoff sensor senses the standoff distance between the workpiece and the standoff sensor and produces a corresponding standoff signal. A control unit receives the various signals, together with a weld schedule, and, based on these signals and the weld schedule, controls the pin length controller so as to control pin penetration into the workpiece.

Metal flow of a tailor-welded blank in deep drawing process

NASA Astrophysics Data System (ADS)

Yan, Qi; Guo, Ruiquan

2005-01-01

Tailor welded blanks were used in the automotive industry to consolidate parts, reduce weight, and increase safety. In recent years, this technology was developing rapidly in China. In Chinese car models, tailor welded blanks had been applied in a lot of automobile parts such as rail, door inner, bumper, floor panel, etc. Concerns on the properties of tailor welded blanks had become more and more important for automobile industry. A lot of research had shown that the strength of the welded seam was higher than that of the base metal, such that the weld failure in the aspect of strength was not a critical issue. However, formability of tailor welded blanks in the stamping process was complex. Among them, the metal flow of tailor welded blanks in the stamping process must be investigated thoroughly in order to reduce the scrap rate during the stamping process in automobile factories. In this paper, the behavior of metal flow for tailor welded blanks made by the laser welding process with two types of different thickness combinations were studied in the deep drawing process. Simulations and experiment verification of the movement of weld line for tailor welded blanks were discussed in detail. Results showed that the control on the movement of welded seam during stamping process by taking some measures in the aspect of blank holder was effective.

GTA weld penetration and the effects of deviations in machine variables

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giedt, W.H.

1987-07-01

Analytical models for predicting the temperature distribution during GTA welding are reviewed with the purpose of developing a procedure for investigating the effects of deviations in machine parameters. The objective was to determine the accuracy required in machine settings to obtain reproducible results. This review revealed a wide range of published values (21 to 90%) for the arc heating efficiency. Low values (21 to 65%) were associated with evaluation of efficiency using constant property conduction models. Values from 75 to 90% were determined from calorimetric type measurements and are applicable for more accurate numerical solution procedures. Although numerical solutions canmore » yield better overall weld zone predictions, calculations are lengthy and complex. In view of this and the indication that acceptable agreement with experimental measurements can be achieved with the moving-point-source solution, it was utilized to investigate the effects of deviations or errors in voltage, current, and travel speed on GTA weld penetration. Variations resulting from welding within current goals for voltage (+-0.1 V), current (+-3.0 A), and travel speed (+-2.0%) were found to be +-2 to 4%, with voltage and current being more influential than travel speed.« less

Effects of Flux Precoating and Process Parameter on Welding Performance of Inconel 718 Alloy TIG Welds

NASA Astrophysics Data System (ADS)

Lin, Hsuan-Liang; Wu, Tong-Min; Cheng, Ching-Min

2014-01-01

The purpose of this study is to investigate the effect of activating flux on the depth-to-width ratio (DWR) and hot cracking susceptibility of Inconel 718 alloy tungsten inert gas (TIG) welds. The Taguchi method is employed to investigate the welding parameters that affect the DWR of weld bead and to achieve optimal conditions in the TIG welds that are coated with activating flux in TIG (A-TIG) process. There are eight single-component fluxes used in the initial experiment to evaluate the penetration capability of A-TIG welds. The experimental results show that the Inconel 718 alloy welds precoated with 50% SiO2 and 50% MoO3 flux were provided with better welding performance such as DWR and hot cracking susceptibility. The experimental procedure of TIG welding process using mixed-component flux and optimal conditions not only produces a significant increase in DWR of weld bead, but also decreases the hot cracking susceptibility of Inconel 718 alloy welds.

The Effect of Weld Penetration on Blast Performance of Welded Panels

DTIC Science & Technology

2014-08-01

requirements of blast and ballistic protection, structural strength, fatigue resistance, unit mass and production cost. The testing described in this report...UNCLASSIFIED 7 TETRA S 20 9 3-G is an austenitic filler material often selected for welding high strength armour steels to control hydrogen induced...repeatability, lower cost, faster test turnaround and a reduced number of variables to control . Figure 30 is an illustration of the simplifications made

Thermal Analysis and Microhardness Mapping in Hybrid Laser Welds in a Structural Steel

DTIC Science & Technology

2003-01-01

conditions. Via the keyhole the laser beam brings about easier ignition of the arc, stabilization of the arc welding process, and penetration of the...with respect to the conventional GMAW or GTAW processes without the need for very close fit-up. This paper will compare an autogenous laser weld to a...UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP017864 TITLE: Thermal Analysis and Microhardness Mapping in Hybrid Laser

NonDestructive Evaluation for Industrial & Development Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hunter, James F.

2016-10-12

Provide overview of weld inspection for Non-Destructive Testing at LANL. This includes radiography (RT/DR/CR/CT for x-ray & neutron sources), ultrasonic testing (UT/PAUT), dye penetrant inspection (PT), eddy current inspection (ET) and magnetic particle testing (MT). Facilities and capabilities for weld inspection will be summarized with examples.

Simulation and Technology of Hybrid Welding of Thick Steel Parts with High Power Fiber Laser

NASA Astrophysics Data System (ADS)

Turichin, Gleb; Valdaytseva, Ekaterina; Tzibulsky, Igor; Lopota, Alexander; Velichko, Olga

The article devoted to steady state and dynamic simulation of melt pool behavior during hybrid laser-arc welding of pipes and shipbuilding sections. The quasi-stationary process-model was used to determine an appropriate welding mode. The dynamical model of laser welding was used for investigation of keyhole depth and width oscillations. The experiments of pipe steel and stainless steel hybrid laser-MAG welding have been made with 15-kW fiber laser in wide range of welding mode parameters. Comparison of experimentally measured and simulated behavior of penetration depth as well as their oscillation spectra approved the self-oscillation nature of melt pool behavior. The welding mode influence of melt pool stability has also been observed. The technological peculiarities, which allow provide high quality weld seam, has been discussed also.

Investigation of defect rate of lap laser welding of stainless steel railway vehicles car body

NASA Astrophysics Data System (ADS)

Wang, Hongxiao

2015-02-01

In order to resolve the disadvantages such as poor appearance quality, poor tightness, low efficiency of resistance spot welding of stainless steel rail vehicles, partial penetration lap laser welding process was investigated widely. But due to the limitation of processing technology, there will be local incomplete fusion in the lap laser welding seam. Defect rate is the ratio of the local incomplete fusion length to the weld seam length. The tensile shear strength under different defect rate and its effect on the car body static strength are not clear. It is necessary to find the biggest defect rate by numerical analysis of effects of different defect rates on the laser welding stainless steel rail vehicle body structure strength ,and tests of laser welding shear tensile strength.

Optimization of hybrid laser - TIG welding of 316LN steel using response surface methodology (RSM)

NASA Astrophysics Data System (ADS)

Ragavendran, M.; Chandrasekhar, N.; Ravikumar, R.; Saxena, Rajesh; Vasudevan, M.; Bhaduri, A. K.

2017-07-01

In the present study, the hybrid laser - TIG welding parameters for welding of 316LN austenitic stainless steel have been investigated by combining a pulsed laser beam with a TIG welding heat source at the weld pool. Laser power, pulse frequency, pulse duration, TIG current were presumed as the welding process parameters whereas weld bead width, weld cross-sectional area and depth of penetration (DOP) were considered as the process responses. Central composite design was used to complete the design matrix and welding experiments were conducted based on the design matrix. Weld bead measurements were then carried out to generate the dataset. Multiple regression models correlating the process parameters with the responses have been developed. The accuracy of the models were found to be good. Then, the desirability approach optimization technique was employed for determining the optimum process parameters to obtain the desired weld bead profile. Validation experiments were then carried out from the determined optimum process parameters. There was good agreement between the predicted and measured values.

Prediction and Verification of Ductile Crack Growth from Simulated Defects in Strength Overmatched Butt Welds

NASA Technical Reports Server (NTRS)

Nishioka, Owen S.

1997-01-01

Defects that develop in welds during the fabrication process are frequently manifested as embedded flaws from lack of fusion or lack of penetration. Fracture analyses of welded structures must be able to assess the effect of such defects on the structural integrity of weldments; however, the transferability of R-curves measured in laboratory specimens to defective structural welds has not been fully examined. In the current study, the fracture behavior of an overmatched butt weld containing a simulated buried, lack-of-penetration defect is studied. A specimen designed to simulate pressure vessel butt welds is considered; namely, a center crack panel specimen, of 1.25 inch by 1.25 inch cross section, loaded in tension. The stress-relieved double-V weld has a yield strength 50% higher than that of the plate material, and displays upper shelf fracture behavior at room temperature. Specimens are precracked, loaded monotonically while load-CMOD measurements are made, then stopped and heat tinted to mark the extent of ductile crack growth. These measurements are compared to predictions made using finite element analysis of the specimens using the fracture mechanics code Warp3D, which models void growth using the Gurson-Tvergaard dilitant plasticity formulation within fixed sized computational cells ahead of the crack front. Calibrating data for the finite element analyses, namely cell size and initial material porosities are obtained by matching computational predictions to experimental results from tests of welded compact tension specimens. The R-curves measured in compact tension specimens are compared to those obtained from multi-specimen weld tests, and conclusions as to the transferability of R-curves is discussed.

Alternate Design of ITER Cryostat Skirt Support System

NASA Astrophysics Data System (ADS)

Pandey, Manish Kumar; Jha, Saroj Kumar; Gupta, Girish Kumar; Bhattacharya, Avik; Jogi, Gaurav; Bhardwaj, Anil Kumar

2017-04-01

The skirt support of ITER cryostat is a support system which takes all the load of cryostat cylinder and dome during normal and operational condition. The present design of skirt support has full penetration weld joints at the bottom (shell to horizontal plate joint). To fulfil the requirements of tolerances and control the welding distortions, we have proposed to change the full penetration weld into fillet weld. A detail calculation is done to check the feasibility and structural impact due to proposed design. The calculations provide the size requirements of fillet weld. To verify the structural integrity during most severe load case, finite element analysis (FEA) has been done in line with ASME section VIII division 2 [1]. By FEA ‘Plastic Collapse’ and ‘Local Failure’ modes has been assessed. 5° sector of skirt clamp has been modelled in CATIA V5 R21 and used in FEA. Fillet weld at shell to horizontal plate joint has been modelled and symmetry boundary condition at ± 2.5° applied. ‘Elastic Plastic Analysis’ has been performed for the most severe loading case i.e. Category IV loading. The alternate design of Cryostat Skirt support system has been found safe by analysis against Plastic collapse and Local Failure Modes with load proportionality factor 2.3. Alternate design of Cryostat skirt support system has been done and validated by FEA. As per alternate design, the proposal of fillet weld has been implemented in manufacturing.

Interfacial microstructure and properties of copper clad steel produced using friction stir welding versus gas metal arc welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Z.; Chen, Y.; Haghshenas, M., E-mail: mhaghshe@uwaterloo.ca

A preliminary study compares the feasibility and microstructures of pure copper claddings produced on a pressure vessel A516 Gr. 70 steel plate, using friction stir welding versus gas metal arc welding. A combination of optical and scanning electron microscopy is used to characterize the grain structures in both the copper cladding and heat affected zone in the steel near the fusion line. The friction stir welding technique produces copper cladding with a grain size of around 25 μm, and no evidence of liquid copper penetration into the steel. The gas metal arc welding of copper cladding exhibits grain sizes overmore » 1 mm, and with surface microcracks as well as penetration of liquid copper up to 50 μm into the steel substrate. Transmission electron microscopy reveals that metallurgical bonding is produced in both processes. Increased diffusion of Mn and Si into the copper cladding occurs when using gas metal arc welding, although some nano-pores were detected in the FSW joint interface. - Highlights: • Cladding of steel with pure copper is possible using either FSW or GMAW. • The FSW yielded a finer grain structure in the copper, with no evidence of cracking. • The FSW joint contains some evidence of nano-pores at the interface of the steel/copper. • Copper cladding by GMAW contained surface cracks attributed to high thermal stresses. • The steel adjacent to the fusion line maintained a hardness value below 248 HV.« less

Fatigue Microcrack Behavior under the Influence of Surface Residual Stresses.

DTIC Science & Technology

1982-11-01

Stress Surface Crack Opening Displacement Technique * Brine Environment Stress Intensity Weld Microstructure W. *O ABSTRACT (Continue on reverse aide If...discussed. The results of preliminary optical metallography of the microstructural development in three types of welding processes for one inch thick...of Gas-Metal Arc Weld (GMA) 35 14 Macrograph of Extended Electrode Weld (EE) 35 15 Macrograpb of Deep Gas-Tungsten Arc Weld (DTIG) 36 16

Evaluation of a 6-wire thermocouple psychrometer for determination of in-situ water potentials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loskot, C.L.; Rousseau, J.P.; Kurzmack, M.A.

1994-12-31

The US Geological Survey has been conducting investigations at Yucca Mountain, Nevada, to provide information about the hydrologic and geologic suitability of this site for storing high-level nuclear wastes in an underground mined repository. Test drilling and instrumentation are a principal method of investigation. The main objectives of the deep unsaturated-zone testhole program are: (1) to determine the flux of water moving through the unsaturated welded and nonwelded tuff units, (2) to determine the vertical and lateral distribution of moisture content, water potential, and other important geohydrologic characteristics in the rock units penetrated, and (3) to monitor stability and changesmore » in in-situ fluid potentials with time. Thermocouple psychrometers will be used to monitor in-situ water potentials.« less

Highly efficient 400  W near-fundamental-mode green thin-disk laser.

PubMed

Piehler, Stefan; Dietrich, Tom; Rumpel, Martin; Graf, Thomas; Ahmed, Marwan Abdou

2016-01-01

We report on the efficient generation of continuous-wave, high-brightness green laser radiation. Green lasers are particularly interesting for reliable and reproducible deep-penetration welding of copper or for pumping Ti:Sa oscillators. By intracavity second-harmonic generation in a thin-disk laser resonator designed for fundamental-mode operation, an output power of up to 403 W is demonstrated at a wavelength of 515 nm with almost diffraction-limited beam quality. The unprecedented optical efficiency of 40.7% of green output power with respect to the pump power of the thin-disk laser is enabled by the intracavity use of a highly efficient grating waveguide mirror, which combines the functions of wavelength stabilization and spectral narrowing, as well as polarization selection in a single element.

System for evaluating weld quality using eddy currents

DOEpatents

Todorov, Evgueni I.; Hay, Jacob

2017-12-12

Electromagnetic and eddy current techniques for fast automated real-time and near real-time inspection and monitoring systems for high production rate joining processes. An eddy current system, array and method for the fast examination of welds to detect anomalies such as missed seam (MS) and lack of penetration (LOP) the system, array and methods capable of detecting and sizing surface and slightly subsurface flaws at various orientations in connection with at least the first and second weld pass.

Optical sensor for real-time weld defect detection

NASA Astrophysics Data System (ADS)

Ancona, Antonio; Maggipinto, Tommaso; Spagnolo, Vincenzo; Ferrara, Michele; Lugara, Pietro M.

2002-04-01

In this work we present an innovative optical sensor for on- line and non-intrusive welding process monitoring. It is based on the spectroscopic analysis of the optical VIS emission of the welding plasma plume generated in the laser- metal interaction zone. Plasma electron temperature has been measured for different chemical species composing the plume. Temperature signal evolution has been recorded and analyzed during several CO2-laser welding processes, under variable operating conditions. We have developed a suitable software able to real time detect a wide range of weld defects like crater formation, lack of fusion, excessive penetration, seam oxidation. The same spectroscopic approach has been applied for electric arc welding process monitoring. We assembled our optical sensor in a torch for manual Gas Tungsten Arc Welding procedures and tested the prototype in a manufacturing industry production line. Even in this case we found a clear correlation between the signal behavior and the welded joint quality.

Friction stir scribe welding technique for dissimilar joining of aluminium and galvanised steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Tianhao; Sidhar, Harpreet; Mishra, Rajiv S.

Friction stir scribe technology, a derivative of friction stir welding, was applied for the dissimilar lap welding of an aluminum alloy and galvanized mild steel sheets. During the process, the rotating tool with a cobalt steel scribe first penetrated the top material — aluminum — and then the scribe cut the bottom material — steel. The steel was displaced into the upper material to produce a characteristic hook feature. Lap welds were shear tested, and their fracture paths were studied. Welding parameters affected the welding features including hook height, which turned out to be highly related to fracture position. Therefore,more » in this paper, the relationships among welding parameters, hook height, joint strength and fracture position are presented. In addition, influence of zinc coating on joint strength was also studied. Keywords: friction stir scribe technology; dissimilar material welding; zinc coating; hook height; joint strength; fracture position« less

Definition of Beam Diameter for Electron Beam Welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burgardt, Paul; Pierce, Stanley W.; Dvornak, Matthew John

It is useful to characterize the dimensions of the electron beam during process development for electron beam welding applications. Analysis of the behavior of electron beam welds is simplest when a single number can be assigned to the beam properties that describes the size of the beam spot; this value we generically call the “beam diameter”. This approach has worked well for most applications and electron beam welding machines with the weld dimensions (width and depth) correlating well with the beam diameter. However, in recent weld development for a refractory alloy, Ta-10W, welded with a low voltage electron beam machinemore » (LVEB), it was found that the weld dimensions (weld penetration and weld width) did not correlate well with the beam diameter and especially with the experimentally determined sharp focus point. These data suggest that the presently used definition of beam diameter may not be optimal for all applications. The possible reasons for this discrepancy and a suggested possible alternative diameter definition is the subject of this paper.« less

Autogeneous Friction Stir Weld Lack-of-Penetration Defect Detection and Sizing Using Directional Conductivity Measurements with MWM Eddy Current Sensor

NASA Technical Reports Server (NTRS)

Goldfine, Neil; Zilberstei, Vladimir; Lawson, Ablode; Kinchen, David; Arbegast, William

2000-01-01

Al 2195-T8 plate specimens containing Friction Stir Welds (FSW), provided by Lockheed Martin, were inspected using directional conductivity measurements with the MWM sensor. Sensitivity to lack-of-penetration (LOP) defect size has been demonstrated. The feature used to determine defect size was the normalized longitudinal component of the MWM conductivity measurements. This directional conductivity component was insensitive to the presence of a discrete crack. This permitted correlation of MWM conductivity measurements with the LOP defect size as changes in conductivity were apparently associated with metallurgical features within the first 0.020 in. of the LOP defect zone. Transverse directional conductivity measurements also provided an indication of the presence of discrete cracks. Continued efforts are focussed on inspection of a larger set of welded panels and further refinement of LOP characterization tools.

The effect of electron beam welding on the creep rupture properties of a Nb-Zr-C alloy

NASA Technical Reports Server (NTRS)

Moore, T. J.; Titran, R. H.; Grobstein, T. L.

1986-01-01

Creep rupture tests of electron beam welded PWC-11 sheet were conducted at 1350 K. Full penetration, single pass welds were oriented transverse to the testing direction in 1 mm thick sheet. With this orientation, stress was imposed equally on the base metal, weld metal, and heat-affected zone. Tests were conducted in both the postweld annealed and aged conditions. Unwelded specimens with similar heat treatments were tested for comparative purposes. It was found that the weld region is stronger than the base metal for both the annealed and aged conditions and that the PWC-11 material is stronger in the annealed condition than in the aged condition.

Automatic visual monitoring of welding procedure in stainless steel kegs

NASA Astrophysics Data System (ADS)

Leo, Marco; Del Coco, Marco; Carcagnì, Pierluigi; Spagnolo, Paolo; Mazzeo, Pier Luigi; Distante, Cosimo; Zecca, Raffaele

2018-05-01

In this paper a system for automatic visual monitoring of welding process, in dry stainless steel kegs for food storage, is proposed. In the considered manufacturing process the upper and lower skirts are welded to the vessel by means of Tungsten Inert Gas (TIG) welding. During the process several problems can arise: 1) residuals on the bottom 2) darker weld 3) excessive/poor penetration and 4) outgrowths. The proposed system deals with all the four aforementioned problems and its inspection performances have been evaluated by using a large set of kegs demonstrating both the reliability in terms of defect detection and the suitability to be introduced in the manufacturing system in terms of computational costs.

Automatic Detection of Welding Defects using Deep Neural Network

NASA Astrophysics Data System (ADS)

Hou, Wenhui; Wei, Ye; Guo, Jie; Jin, Yi; Zhu, Chang'an

2018-01-01

In this paper, we propose an automatic detection schema including three stages for weld defects in x-ray images. Firstly, the preprocessing procedure for the image is implemented to locate the weld region; Then a classification model which is trained and tested by the patches cropped from x-ray images is constructed based on deep neural network. And this model can learn the intrinsic feature of images without extra calculation; Finally, the sliding-window approach is utilized to detect the whole images based on the trained model. In order to evaluate the performance of the model, we carry out several experiments. The results demonstrate that the classification model we proposed is effective in the detection of welded joints quality.

Acceptance criteria for welds in ASTM A106 grade B steel pipe and plate

NASA Technical Reports Server (NTRS)

Hudson, C. M.; Wright, D. B., Jr.; Leis, B. N.

1986-01-01

Based on the RECERT Program findings, NASA-Langley funded a fatigue study of code-unacceptable welds. Usage curves were developed which were based on the structural integrity of the welds. The details of this study are presented in NASA CR-178114. The information presented is a condensation and reinterpretation of the information in NASA CR-178114. This condensation and reinterpretation generated usage curves for welds having: (1) indications 0.20 -inch deep by 0.40-inch long, and (2) indications 0.195-inch deep by 8.4-inches long. These curves were developed using the procedures used in formulating the design curves in Section VIII, Division 2 of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code.

Magnetically-Guided Penetrant Applicator

NASA Technical Reports Server (NTRS)

Molina, Orlando G.

1990-01-01

Small wheeled vehicle moved inside nonmagnetic enclosure. Miniature magnetically guided truck uses foam-rubber sponge pads to apply penetrant fluid for inspection of welds in hidden surfaces of nonmagnetic tubes. Risk of explosion less than if electric motor used to drive vehicle. Inexpensive to make and made in range of sizes.

Studies on A-TIG welding of Low Activation Ferritic/Martensitic (LAFM) steel

NASA Astrophysics Data System (ADS)

Vasantharaja, P.; Vasudevan, M.

2012-02-01

Low Activation Ferritic-Martensitic steels (LAFM) are chosen as the candidate material for structural components in fusion reactors. The structural components are generally fabricated by welding processes. Activated Tungsten Inert Gas (A-TIG) welding is an emerging process for welding of thicker components. In the present work, attempt was made to develop A-TIG welding technology for LAFM steel plates of 10 mm thick. Activated flux was developed for LAFM steel by carrying out various bead-on-plate TIG welds without flux and with flux. The optimum flux was identified as one which gave maximum depth of penetration at minimum heat input values. With the optimized flux composition, LAFM steel plate of 10 mm thickness was welded in square butt weld joint configuration using double side welding technique. Optical and Scanning Electron Microscopy was used for characterizing the microstructures. Microhardness measurements were made across the weld cross section for as welded and post weld heat treated samples. Tensile and impact toughness properties were determined. The mechanical properties values obtained in A-TIG weld joint were comparable to that obtained in weld joints of LAFM steel made by Electron beam welding process.

The Role of the Plasma during Laser-Gas Laser-Metal Interactions.

DTIC Science & Technology

1986-10-13

argument will be treated in Chap. 5. It 50 Ushlo and Matsuda [421 assessed the target transport in an argon TIG welding assembly. The TIG process involves...i 3 1. LITERATURE SURVEY 1.1 Introduction The most widespread commercial use of the laser is in cutting, welding , drilling, and heat treatment. Many...targets was presented by Locke, et al. [1]. The authors were concerned with the non-uniform penetration depths in laser welding . Half inch thick 304

Shimmed electron beam welding process

DOEpatents

Feng, Ganjiang; Nowak, Daniel Anthony; Murphy, John Thomas

2002-01-01

A modified electron beam welding process effects welding of joints between superalloy materials by inserting a weldable shim in the joint and heating the superalloy materials with an electron beam. The process insures a full penetration of joints with a consistent percentage of filler material and thereby improves fatigue life of the joint by three to four times as compared with the prior art. The process also allows variable shim thickness and joint fit-up gaps to provide increased flexibility for manufacturing when joining complex airfoil structures and the like.

A highly efficient and compact long pulse Nd:YAG rod laser with 540 J of pulse energy for welding application.

PubMed

Choubey, Ambar; Vishwakarma, S C; Misra, Pushkar; Jain, R K; Agrawal, D K; Arya, R; Upadhyaya, B N; Oak, S M

2013-07-01

We have developed an efficient and high average power flash lamp pumped long pulse Nd:YAG laser capable of generating 1 kW of average output power with maximum 540 J of single pulse energy and 20 kW of peak power. The laser pulse duration can be varied from 1 to 40 ms and repetition rate from 1 to 100 Hz. A compact and robust laser pump chamber and resonator was designed to achieve this high average and peak power. It was found that this laser system provides highest single pulse energy as compared to other long pulsed Nd:YAG laser systems of similar rating. A slope efficiency of 5.4% has been achieved, which is on higher side for typical lamp pumped solid-state lasers. This system will be highly useful in laser welding of materials such as aluminium and titanium. We have achieved 4 mm deep penetration welding of these metals under optimized conditions of output power, pulse energy, and pulse duration. The laser resonator was optimized to provide stable operation from single shot to 100 Hz of repetition rate. The beam quality factor was measured to be M(2) ~ 91 and pulse-to-pulse stability of ±3% for the multimode operation. The laser beam was efficiently coupled through an optical fiber of 600 μm core diameter and 0.22 numerical aperture with power transmission of 90%.

Influence of the welding temperature and the welding speed on the mechanical properties of friction stir welds in EN AW-2219-T87

NASA Astrophysics Data System (ADS)

Bachmann, A.; Krutzlinger, M.; Zaeh, M. F.

2018-06-01

Friction Stir Welding (FSW) is an innovative joining technique, which has proven to produce high quality joints in high strength aluminum alloys. Consequently, it is commonly used to manufacture lightweight aerospace structures with stringent requirements. For these structures, it is necessary to ensure a high ultimate tensile strength (UTS). Various studies have reported that the UTS is significantly influenced by the welding parameters. Samples welded with different parameter sets showed a considerably different UTS, despite being free from detectable welding defects (e.g. tunnel defect, voids, or lack of penetration). Based on the observations in the literature, a hypothesis was posed. The welding temperature along with the welding speed determine the UTS of the weld. This study aims to prove this hypothesis experimentally by using temperature-controlled FSW to join plates of EN AW-2219-T87 in butt joint configuration. The welded samples were examined using visual inspection, metallography, X-ray imaging, and uniaxial tensile tests. Finally, a statistical analysis was conducted. Hereby, the hypothesis was confirmed.

Experimental design approach to the process parameter optimization for laser welding of martensitic stainless steels in a constrained overlap configuration

NASA Astrophysics Data System (ADS)

Khan, M. M. A.; Romoli, L.; Fiaschi, M.; Dini, G.; Sarri, F.

2011-02-01

This paper presents an experimental design approach to process parameter optimization for the laser welding of martensitic AISI 416 and AISI 440FSe stainless steels in a constrained overlap configuration in which outer shell was 0.55 mm thick. To determine the optimal laser-welding parameters, a set of mathematical models were developed relating welding parameters to each of the weld characteristics. These were validated both statistically and experimentally. The quality criteria set for the weld to determine optimal parameters were the minimization of weld width and the maximization of weld penetration depth, resistance length and shearing force. Laser power and welding speed in the range 855-930 W and 4.50-4.65 m/min, respectively, with a fiber diameter of 300 μm were identified as the optimal set of process parameters. However, the laser power and welding speed can be reduced to 800-840 W and increased to 4.75-5.37 m/min, respectively, to obtain stronger and better welds.

Hot cracking during welding and casting

NASA Astrophysics Data System (ADS)

Cao, Guoping

Aluminum welds are susceptible to liquation cracking in the partially melted zone (PMZ). Using the multicomponent Scheil model, curves of temperature vs. fraction solid (T-fS) during solidification were calculated for the PMZ and weld metals (WMs). These curves were used to predict the crack susceptibility by checking if the harmful condition of WM fS > PMZ fS exists during PMZ solidification and reduce the susceptibility by minimizing this condition. This approach was tested against full-penetration welds of alloys 7075 and 2024 and it can be used to guide the selection or development of filler metals. Liquation cracking in the PMZ in welds of Al-Si cast alloys was also investigated. The crack susceptibility was evaluated by circular-patch test, and full-penetration welds made with filler metals 1100, 4043, 4047 and 5356. Liquation cracking was significant with filler metals 1100 and 5356 but slight with filler metals 4043 and 4047. In all welds, liquation cracks were completely backfilled, instead of open as in full-penetration welds of wrought alloys 2219 and 6061. The T-fS curves showed that alloy A357 has a much higher fraction liquid for backfilling before PMZ solidification was essentially over. Hot tearing in Mg-xAl-yCa alloys was studied by constrained rod casting (CRC) in a steel mold. The hot tearing susceptibility decreased significantly with increasing Ca content (y) but did not change much with the Al content (x). An instrumented CRC with a steel mold was developed to detect the onset of hot tearing. The secondary phases, eutectic content, solidification path, and freezing range were examined. Hot tearing in Mg-Al-Sr alloys was also studied by CRC in a steel mold. With Mg-(4,6,8)Al-1.5Sr alloys, the hot tearing susceptibility decreased significantly with increasing Al content. With Mg-(4,6,8)Al-3Sr alloys, the trend was similar but not as significant. At the same Al content, the hot tearing susceptibility decreased significantly with increasing Sr content. Instrumented CRC with a steel mold was also used to test hot tearing of Mg-Al-Sr alloys. Cracking occurred at a higher temperature in alloys most susceptible to cracking than in alloys least susceptible.

Process control of GMAW by detection of discontinuities in the molten weld pool

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlson, N.M.; Kunerth, D.C.; Johnson, J.A.

1988-01-01

The use of ultrasonic sensors to detect discontinuities associated with the molten pool is one phase of a project to automate the welding process. In this work, ultrasonic sensors were used to interrogate the region around the molten/solid interface during gas metal arc welding (GMAW). The ultrasonic echoes from the interface and the molten pool provide information about the quality of the fusion zone and the molten pool. This information can be sent to a controller that can vary the welding parameters to correct the process. Previously ultrasonic shear waves were used to determine if the geometry of the molten/solidmore » interface was indicative of an acceptable weld. In this work, longitudinal waves were used to interrogate the molten weld pool for discontinuities. Unacceptable welding conditions that can result in porosity, incomplete penetration, or undercut were detected. 8 refs., 4 figs.« less

Development of a CCTV system for welder training and monitoring of Space Shuttle Main Engine welds

NASA Technical Reports Server (NTRS)

Gordon, S. S.; Flanigan, L. A.; Dyer, G. E.

1987-01-01

A Weld Operator's Remote Monitoring System (WORMS) for remote viewing of manual and automatic GTA welds has been developed for use in Space Shuttle Main Engine (SSME) manufacturing. This system utilizes fiberoptics to transmit images from a receiving lens to a small closed-circuit television (CCTV) camera. The camera converts the image to an electronic signal, which is sent to a videotape recorder (VTR) and a monitor. The overall intent of this system is to provide a clearer, more detailed view of welds than is available by direct observation. This system has six primary areas of application: (1) welder training; (2) viewing of joint penetration; (3) viewing visually inaccessible welds; (4) quality control and quality assurance; (5) remote joint tracking and adjustment of variables in machine welds; and (6) welding research and development. This paper describes WORMS and how it applies to each application listed.

Study of Radiographic Linear Indications and Subsequent Microstructural Features in Gas Tungsten Arc Welds of Inconel 718

NASA Technical Reports Server (NTRS)

Walley, J. L.; Nunes, A. C.; Clounch, J. L.; Russell, C. K.

2007-01-01

This study presents examples and considerations for differentiating linear radiographic indications produced by gas tungsten arc welds in a 0.05-in-thick sheet of Inconel 718. A series of welds with different structural features, including the enigma indications and other defect indications such as lack of fusion and penetration, were produced, radiographed, and examined metallographically. The enigma indications were produced by a large columnar grain running along the center of the weld nugget occurring when the weld speed was reduced sufficiently below nominal. Examples of respective indications, including the effect of changing the x-ray source location, are presented as an aid to differentiation. Enigma, nominal, and hot-weld specimens were tensile tested to demonstrate the harmlessness of the enigma indication. Statistical analysis showed that there is no difference between the strengths of these three weld conditions.

Optimization of the A-TIG welding for stainless steels

NASA Astrophysics Data System (ADS)

Jurica, M.; Kožuh, Z.; Garašić, I.; Bušić, M.

2018-03-01

The paper presents the influence of the activation flux and shielding gas on tungsten inert gas (A-TIG) welding of the stainless steel. In introduction part, duplex stainless steel was analysed. The A-TIG process was explained and the possibility of welding stainless steels using the A-TIG process to maximize productivity and the cost-effectiveness of welded structures was presented. In the experimental part duplex, 7 mm thick stainless steel has been welded in butt joint. The influence of activation flux chemical composition upon the weld penetration has been investigated prior the welding. The welding process was performed by a robot with TIG equipment. With selected A-TIG welding technology preparation of plates and consumption of filler material (containing Cr, Ni and Mn) have been avoided. Specimens sectioned from the produced welds have been subjected to tensile strength test, macrostructure analysis and corrosion resistance analysis. The results have confirmed that this type of stainless steel can be welded without edge preparation and addition of filler material containing critical raw materials as Cr, Ni and Mn when the following welding parameters are set: current 200 A, welding speed 9,1 cm/min, heat input 1,2 kJ/mm and specific activation flux is used.

Tool For Friction Stir Tack Welding of Aluminum Alloys

NASA Technical Reports Server (NTRS)

Bjorkman, Gerald W.; Dingler, Johnny W.; Loftus, Zachary

2003-01-01

A small friction-stir-welding tool has been developed for use in tack welding of aluminum-alloy workpieces. It is necessary to tack-weld the workpieces in order to hold them together during friction stir welding because (1) in operation, a full-size friction-stir-welding tool exerts a large force that tends to separate the workpieces and (2) clamping the workpieces is not sufficient to resist this force. It is possible to tack the pieces together by gas tungsten arc welding, but the process can be awkward and time-consuming and can cause sufficient damage to necessitate rework. Friction stir tack welding does not entail these disadvantages. In addition, friction stir tack welding can be accomplished by use of the same automated equipment (except for the welding tool) used in subsequent full friction stir welding. The tool for friction stir tack welding resembles the tool for full friction stir welding, but has a narrower shoulder and a shorter pin. The shorter pin generates a smaller workpiece-separating force so that clamping suffices to keep the workpieces together. This tool produces a continuous or intermittent partial-penetration tack weld. The tack weld is subsequently consumed by action of the larger tool used in full friction stir welding tool.

Dual beam Nd:YAG laser welding: influence of lubricants to lap joint welding of steel sheets

NASA Astrophysics Data System (ADS)

Geiger, M.; Merklein, M.; Otto, A.; Blankl, A.

2007-05-01

Laser welding is applied in large-volume production since the late eighties and has revolutionized the possibilities of designing and engineering products. Nevertheless, problems appear during application because the operational conditions in industrial environments fluctuate and can influence the welding process negatively. Contaminations, like lubricants and organic solids, are an example of changing conditions in laser beam welding. If a lap joint is welded, these materials have to be removed from the sheets, otherwise pores and surface failures may appear due to keyhole instabilities induced by uncontrolled outgassing. One possibility for solving this problem is the use of two separate laser beams. For producing these two beams several systems are available for all different kind of lasers. A bifocal optic is such a solution for an Nd:YAG laser. By using this system, the laser beam is divided after collimation with a prism. Afterwards the two beams are focussed with a lens to the surface of the sheet and two single spots are produced. If the distance between the two spots is low, one common, elliptical keyhole is created. With this system two different welding strategies are possible. The spots can be oriented parallel or normal to the feed direction. For stabilizing the laser welding of contaminated steel sheets the parallel arrangement is better, because the amount of contamination is nearly the same as in single spot welding but the total volume of the keyhole is greater and so pressure variations due to uncontrolled evaporation of contaminations are lower. In order to prove this theory and to determine the exact effects some investigations were made at the Chair of Manufacturing Technology of the University of Erlangen-Nuremberg. A 4 kW Nd:YAG laser with a beam parameter product of 25 mm*mrad and a focal distance of 200 mm was used to weld two 1 mm DC04 steel sheets together with a lap joint. Between the sheets a deep drawing lubricant, Castrol FST 6, was used to simulate the contaminations. The sheets were welded with mono- and bifocal optic, whereas with bifocal the power distribution between the two beams was varied. After welding, the seams were qualified by analyzing surface defects and mechanical properties. The results of the investigations show that the adoption of a bifocal optic can increase the stability of the welding process. The distribution between the two single spots has an essential influence on the welding result. In order to get a higher penetration and failure free seams, a 30 % to 70 % distribution between the two spots is better. Furthermore the blade angle has another slight impact on the welding result. For monofocus and bifocus a towing angle between the sheets and the beam produces better welding results. Considering these results it can be resumed that the application of a bifocal optic is a possibility to increase the quality and the stability of lap joint welding but the parameter settings for good results can only be varied in a tight tolerance zone.

Hybrid laser arc welding: State-of-art review

NASA Astrophysics Data System (ADS)

Acherjee, Bappa

2018-02-01

Hybrid laser arc welding simultaneously utilizes the arc welding and the laser welding, in a common interaction zone. The synergic effects of laser beam and eclectic arc in the same weld pool results in an increase of welding speed and penetration depth along with the enhancement of gap bridging capability and process stability. This paper presents the current status of this hybrid technique in terms of research, developments and applications. Effort is made to present a comprehensive technical know-how about this process through a systematic review of research articles, industrial catalogues, technical notes, etc. In the introductory part of the review, an overview of the hybrid laser arc welding is presented, including operation principle, process requirements, historical developments, benefits and drawbacks of the process. This is followed by a detailed discussion on control parameters those govern the performance of hybrid laser arc welding process. Thereafter, a report of improvements of performance and weld qualities achieved by using hybrid welding process is presented based on review of several research papers. The succeeding sections furnish the examples of industrial applications and the concluding remarks.

Chamber free fusion welding root side purging method and apparatus

NASA Technical Reports Server (NTRS)

Mcgee, William F. (Inventor); Rybicki, Daniel J. (Inventor)

1993-01-01

A method and apparati are presented for non-chamber root side purging in fusion welding of oxygen reactive metals which require that the molten weld zone and local solid areas of the weld seam remaining at high temperatures be shielded from normal atmosphere to prevent degradation of the welded area. The apparati provide an inert atmosphere to the root side of a weld joint through a porous medium whereby the jet-like thrust of the plasma arc actually draws the continuously supplied inert atmosphere into the path of the molten or high temperature solid weld zone. The porous medium is configured so it can be placed at the borders of the weld seam and substantially parallel to the seam without restricting the view of the root side of the seam. The inert gas is dispersed evenly through the porous media and across the weld seam, at the point of arc penetration and in front of and behind the arc. The apparati can be constructed so as to limit the amount of inert gas flow and can be mobile and travel synchronously with the welding arc.

Chamber free fusion welding root side purging method and apparatus

NASA Technical Reports Server (NTRS)

Dailey, J. R. (Inventor); Mcgee, William F. (Inventor); Rybicki, Daniel J. (Inventor)

1995-01-01

A method and apparati are presented for non-chamber root side purging in fusion welding of oxygen reactive metals which require that the molten weld zone and local solid areas of the weld seam remaining at high temperatures be shielded from normal atmosphere to prevent degradation of the welded area. The apparati provide an inert atmosphere to the root side of a weld joint through a porous medium whereby the jet-like thrust of the plasma arc actually draws the continuously supplied inert atmosphere into the path of the molten or high temperature solid weld zone. The porous medium is configured so it can be placed at the borders of the weld seam and substantially parallel to the seam without restricting the view of the root side of the seam. The inert gas is dispersed evenly through the porous media and across the weld seam, at the point of arc penetration and in front of and behind the arc. The apparati can be constructed so as to limit the amount of inert gas flow and can be mobile and travel synchronously with the welding arc.

Fusion welding studies using laser on Ti-SS dissimilar combination

NASA Astrophysics Data System (ADS)

Shanmugarajan, B.; Padmanabham, G.

2012-11-01

Laser welding investigations were carried out on dissimilar Ti-SS combination. The study is aimed to improve the weld strength and ductility by minimizing harmful intermetallics and taking advantage of high cooling rates in laser welding. Results of continuous wave 3.5 kW CO2 laser welding of totally dissimilar combination of Titanium and stainless steel (304) have been discussed. Bead on plate welding experiments were conducted to identify the laser welding parameters using depth of penetration as criteria. The welding of dissimilar combination has been attempted both autogenously and with interlayers such as Vanadium (V) and Tantalum (Ta) in the form of laser cladding as well as strip. Autogenous welds were carried out by varying the laser power, welding speed and position of the laser beam with respect to the joint centre. The resultant welds are characterized by macrostructure analysis, SEM/EDAX and XRD and as welded tensile test in UTM. The autogenous welds have exhibited extensive cracking even when welded at high speeds or by manipulating the beam position with respect to the joint. Similarly Vandaium as interlayer could not achieve crack free joint. A joint with 40 MPa strength could be made with Ta as interlayer. Results and analysis of these variants of laser welded joints are reported and discussed.

Study the Effect of SiO2 Based Flux on Dilution in Submerged Arc Welding

NASA Astrophysics Data System (ADS)

kumar, Aditya; Maheshwari, Sachin

2017-08-01

This paper highlights the method for prediction of dilution in submerged arc welding (SAW). The most important factors of weld bead geometry are governed by the weld dilution which controls the chemical and mechanical properties. Submerged arc welding process is used generally due to its very easy control of process variables, good penetration, high weld quality, and smooth finish. Machining parameters, with suitable weld quality can be achieved with the different composition of the flux in the weld. In the present study Si02-Al2O3-CaO flux system was used. In SiO2 based flux NiO, MnO, MgO were mixed in various proportions. The paper investigates the relationship between the process parameters like voltage, % of flux constituents and dilution with the help of Taguchi’s method. The experiments were designed according to Taguchi L9 orthogonal array, while varying the voltage at two different levels in addition to alloying elements. Then the optimal results conditions were verified by confirmatory experiments.

Coupling of Laser with Plasma Arc to Facilitate Hybrid Welding of Metallic Materials: A Review

NASA Astrophysics Data System (ADS)

Zhiyong, Li; Srivatsan, T. S.; Yan, LI; Wenzhao, Zhang

2013-02-01

Hybrid laser arc welding combines the advantages of laser welding and arc welding. Ever since its origination in the late 1970s, this technique has gained gradual attention and progressive use due to a combination of high welding speed, better formation of weld bead, gap tolerance, and increased penetration coupled with less distortion. In hybrid laser arc welding, one of the reasons for the observed improvement is an interaction or coupling effect between the plasma arc, laser beam, droplet transfer, and the weld pool. Few researchers have made an attempt to study different aspects of the process to facilitate a better understanding. It is difficult to get a thorough understanding of the process if only certain information in a certain field is provided. In this article, an attempt to analyze the coupling effect of the process was carried out based on a careful review of the research work that has been done which provides useful information from a different prospective.

Laser welding of fused quartz

DOEpatents

Piltch, Martin S.; Carpenter, Robert W.; Archer, III, McIlwaine

2003-06-10

Refractory materials, such as fused quartz plates and rods are welded using a heat source, such as a high power continuous wave carbon dioxide laser. The radiation is optimized through a process of varying the power, the focus, and the feed rates of the laser such that full penetration welds may be accomplished. The process of optimization varies the characteristic wavelengths of the laser until the radiation is almost completely absorbed by the refractory material, thereby leading to a very rapid heating of the material to the melting point. This optimization naturally occurs when a carbon dioxide laser is used to weld quartz. As such this method of quartz welding creates a minimum sized heat-affected zone. Furthermore, the welding apparatus and process requires a ventilation system to carry away the silicon oxides that are produced during the welding process to avoid the deposition of the silicon oxides on the surface of the quartz plates or the contamination of the welds with the silicon oxides.

Optimization of Gas Metal Arc Welding Process Parameters

NASA Astrophysics Data System (ADS)

Kumar, Amit; Khurana, M. K.; Yadav, Pradeep K.

2016-09-01

This study presents the application of Taguchi method combined with grey relational analysis to optimize the process parameters of gas metal arc welding (GMAW) of AISI 1020 carbon steels for multiple quality characteristics (bead width, bead height, weld penetration and heat affected zone). An orthogonal array of L9 has been implemented to fabrication of joints. The experiments have been conducted according to the combination of voltage (V), current (A) and welding speed (Ws). The results revealed that the welding speed is most significant process parameter. By analyzing the grey relational grades, optimal parameters are obtained and significant factors are known using ANOVA analysis. The welding parameters such as speed, welding current and voltage have been optimized for material AISI 1020 using GMAW process. To fortify the robustness of experimental design, a confirmation test was performed at selected optimal process parameter setting. Observations from this method may be useful for automotive sub-assemblies, shipbuilding and vessel fabricators and operators to obtain optimal welding conditions.

Comparisons between TiO2- and SiO2-flux assisted TIG welding processes.

PubMed

Tseng, Kuang-Hung; Chen, Kuan-Lung

2012-08-01

This study investigates the effects of flux compounds on the weld shape, ferrite content, and hardness profile in the tungsten inert gas (TIG) welding of 6 mm-thick austenitic 316 L stainless steel plates, using TiO2 and SiO2 powders as the activated fluxes. The metallurgical characterizations of weld metal produced with the oxide powders were evaluated using ferritoscope, optical microscopy, and Vickers microhardness test. Under the same welding parameters, the penetration capability of TIG welding with TiO2 and SiO2 fluxes was approximately 240% and 292%, respectively. A plasma column made with SiO2 flux exhibited greater constriction than that made with TiO2 flux. In addition, an anode root made with SiO2 flux exhibited more condensation than that made with TiO2 flux. Results indicate that energy density of SiO2-flux assisted TIG welding is higher than that of TiO2-flux assisted TIG welding.

Closed-Loop Control System for Friction Stir Welding Retractable Pin Tool

NASA Technical Reports Server (NTRS)

Ding, R. Jeffrey; Romine, Peter L.; Munafo, Paul M. (Technical Monitor)

2001-01-01

NASA invention disclosure, NASA Case No. MFS-31413, entitled "System for Controlling the Stirring Pin of a Friction Stir Welding Apparatus", (Patent Pending) authored by Jeff Ding, Dr Peter Romine and Pete Oelgoetz, addresses the precision control of the friction stir welding process. The closed-loop control system automatically adjusts the spinning welding pin, real-time, to maintain a precise penetration ligament (i.e., distance between pin-tip and weld panel backside surface). A specific pin length can be maintained while welding constant thickness or tapered material thickness weld panels. The closed-loop control system provides operator data and information relative to the exact position of the welding pin inside the weld joint. This paper presents the closed-loop RPT control system that operates using the auto-feedback of force signals sensed by the tip and shoulder of the welding pin. Significance: The FSW process can be successfully used in a production environment only if there is a method or technique that informs the FSW operator the precise location of the welding pin inside the weld joint. This is essential for applications in aerospace, automotive, pressure vessel, commercial aircraft and other industries.

The influence of TIG-Arc physical characteristics on the penetration and weld width under different Ar and He supply conditions

NASA Astrophysics Data System (ADS)

Dai, Hongbin; Shen, Xiuqiang; Wang, Haoran

2018-06-01

In the paper, the 5A03 aluminium alloy was employed to study the influence of TIG arc on the penetration and the weld width. And the split anode method with water-cooled copper plate was used to measure and record the distribution of arc current, under different flow ratio of argon and helium conditions. And a gas supply device controlled by a solenoid valve was employed to obtain the stable TIG welding arc of gas supply alternately at the frequency of 1 Hz and 4 Hz, and then collected the phenomenon of arc alternate by the high-speed camera. The experimental results indicated that the current density at the arc anode center of argon and helium supply alternately with different mixing ratio is lower than that of the pure argon-arc center. Nonetheless, the former is more uniform in current density within 2 mm from the arc center. Furthermore, it presented as a component arc of argon-arc and helium-arc switched, with the condition of argon and helium supply alternately at a frequency of 1 Hz and the arc power density is greater and concentrated, leading to the wider and deeper weld.

Processing, Microstructure, and Material Property Relationships Following Friction Stir Welding of Oxide Dispersion Strengthened Steels

DTIC Science & Technology

2013-09-01

2.75), (b) 400 RPM/100 MMPM (HI= 4 ), (c) 300 RPM/50 MMPM (HI= 6 ), and (d) 500 RPM/25 MMPM (HI=10) showing increase in grain size as HI is increased...Heat Index Weld Quality Weld Penetration 200 50 4 Lack of Consolidation Incomplete 300 50 6 Defect-free Full 300 100 3 Lack of Consolidation...Specifically, the grain size for HI= 6 (300 RPM/50 MMPM) is less than the grain size for HI= 4 (400 RPM/100 MMPM); however, grain size did

[Submicron particles in smoke resulting from welding alloys and cast alloy in metalworking industry].

PubMed

Avino, P; Manigrasso, M; Fanizza, Carla; Carrai, P; Solfanelli, Linda

2013-01-01

The toxicity of welding fumes depends on both chemical composition and ability to penetrate and deposit deeply in the lungs. Their penetration and deposition in the regions of the respiratory system is mainly determined by their size. The knowledge of the size distribution of welding fumes is a crucial information towards the estimate of the doses of toxic compounds delivered into the respiratory tract. Particle number size distribution was continuously measured during different welding operations by means of a Fast Mobility Particle Sizer, which counts and classifies particles, according to their electrical mobility, in 32 size-channels, in the range from 5.6 to 523 nm, with is time resolution. The temporal evolution of submicrometric particles (6-523 nm), nucleation mode particles (6-16 nm) and the fraction 19-523 nm before, during and after the welding operations performed with/without local exhaust ventilation are reported and extensively discussed. Before welding, nucleation mode particles represent about 7% of submicrometric particles; after about 40 s from the welding start, the percent contribution of nucleation mode particles increases to 60%. Total and nucleation mode particle concentrations increase from 2.1 x 10(4) to 2.0 x 10(6) and from 1.6 x 10(3) to 1.0 x 10(6), respectively. The temporal variation of the particle number size distribution across the peaks, evidences the strong and fast-evolving contribution of nucleation mode particles: peak values are maintained for less than 10 s. The implication of such contribution on human health is linked to high deposition efficiency of the submicrometric particles in the alveolar interstitial region of the human respiratory system, where gas exchange occurs.

Microstructures and Mechanical Properties of Weld Metal and Heat-Affected Zone of Electron Beam-Welded Joints of HG785D Steel

NASA Astrophysics Data System (ADS)

Zhang, Qiang; Han, Jianmin; Tan, Caiwang; Yang, Zhiyong; Wang, Junqiang

2016-12-01

Vacuum electron beam welding (EBW) process was employed to butt weld 10-mm-thick HG785D high-strength steels. The penetration into the steel was adjusted by beam current. Microstructures at weld metal and heat-affected zone (HAZ) regions were comparatively observed. Mechanical properties of the EBWed joints including Vickers hardness, tensile and Charpy impact tests were evaluated. The results indicated that microstructures at the weld metal consisted of coarse lath martensite and a small amount of acicular martensite, while that in the HAZ was tempered sorbite and martensite. The grain size in the weld metal was found to be larger than that in the HAZ, and its proportion in weld metal was higher. The hardness in the weld metal was higher than the HAZ and base metal. The tensile strength and impact toughness in the HAZ was higher than that in the weld metal. All the behaviors were related to microstructure evolution caused by higher cooling rates and state of base metal. The fracture surfaces of tensile and impact tests on the optimized joint were characterized by uniform and ductile dimples. The results differed significantly from that obtained using arc welding process.

Detection and assessment of flaws in friction stir welded metallic plates

NASA Astrophysics Data System (ADS)

Fakih, Mohammad Ali; Mustapha, Samir; Tarraf, Jaafar; Ayoub, Georges; Hamade, Ramsey

2017-04-01

Investigated is the ability of ultrasonic guided waves to detect flaws and assess the quality of friction stir welds (FSW). AZ31B magnesium plates were friction stir welded. While process parameters of spindle speed and tool feed were fixed, shoulder penetration depth was varied resulting in welds of varying quality. Ultrasonic waves were excited at different frequencies using piezoelectric wafers and the fundamental symmetric (S0) mode was selected to detect the flaws resulting from the welding process. The front of the first transmitted wave signal was used to capture the S0 mode. A damage index (DI) measure was defined based on the amplitude attenuation after wave interaction with the welded zone. Computed Tomography (CT) scanning was employed as a nondestructive testing (NDT) technique to assess the actual weld quality. Derived DI values were plotted against CT-derived flaw volume resulting in a perfectly linear fit. The proposed approach showed high sensitivity of the S0 mode to internal flaws within the weld. As such, this methodology bears great potential as a future predictive method for the evaluation of FSW weld quality.

Keyhole and weld shapes for plasma arc welding under normal and zero gravity

NASA Technical Reports Server (NTRS)

Keanini, R. G.; Rubinsky, B.

1990-01-01

A first order study of the interfacial (keyhole) shape between a penetrating argon plasma arc jet and a stationary liquid metal weld pool is presented. The interface is determined using the Young-Laplace equation by assuming that the plasma jet behaves as a one-dimensional ideal gas flow and by neglecting flow within the weld pool. The solution for the keyhole shape allows an approximate determination of the liquid-solid metal phase boundary location based on the assumption that the liquid melt is a stagnant thermal boundary layer. Parametric studies examine the effect of plasma mass flow rate, initial plasma enthalpy, liquid metal surface tension, and jet shear on weldment shape under both normal and zero gravity. Among the more important findings of this study is that keyhole and weld geometries are minimally affected by gravity, suggesting that data gathered under gravity can be used in planning in-space welding.

Grain Refinement of AZ31 Magnesium Alloy Weldments by AC Pulsing Technique

NASA Astrophysics Data System (ADS)

Kishore Babu, N.; Cross, C. E.

2012-11-01

The current study has investigated the influence of alternating current pulsing on the structure and mechanical properties of AZ31 magnesium alloy gas tungsten arc (GTA) weldments. Autogenous full penetration bead-on-plate GTA welds were made under a variety of conditions including variable polarity (VP), variable polarity mixed (VPM), alternating current (AC), and alternating current pulsing (ACPC). AC pulsing resulted in significant refinement of weld metal when compared with the unpulsed conditions. AC pulsing leads to relatively finer and more equiaxed grain structure in GTA welds. In contrast, VP, VPM, and AC welding resulted in predominantly columnar grain structures. The reason for this grain refinement may be attributed to the periodic variations in temperature gradient and solidification rate associated with pulsing as well as weld pool oscillation observed in the ACPC welds. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, tensile strength, and ductility.

Process modeling and parameter optimization using radial basis function neural network and genetic algorithm for laser welding of dissimilar materials

NASA Astrophysics Data System (ADS)

Ai, Yuewei; Shao, Xinyu; Jiang, Ping; Li, Peigen; Liu, Yang; Yue, Chen

2015-11-01

The welded joints of dissimilar materials have been widely used in automotive, ship and space industries. The joint quality is often evaluated by weld seam geometry, microstructures and mechanical properties. To obtain the desired weld seam geometry and improve the quality of welded joints, this paper proposes a process modeling and parameter optimization method to obtain the weld seam with minimum width and desired depth of penetration for laser butt welding of dissimilar materials. During the process, Taguchi experiments are conducted on the laser welding of the low carbon steel (Q235) and stainless steel (SUS301L-HT). The experimental results are used to develop the radial basis function neural network model, and the process parameters are optimized by genetic algorithm. The proposed method is validated by a confirmation experiment. Simultaneously, the microstructures and mechanical properties of the weld seam generated from optimal process parameters are further studied by optical microscopy and tensile strength test. Compared with the unoptimized weld seam, the welding defects are eliminated in the optimized weld seam and the mechanical properties are improved. The results show that the proposed method is effective and reliable for improving the quality of welded joints in practical production.

Weld bead profile of laser welding dissimilar joints stainless steel

NASA Astrophysics Data System (ADS)

Mohammed, Ghusoon R.; Ishak, M.; Aqida, S. N.; Abdulhadi, Hassan A.

2017-10-01

During the process of laser welding, the material consecutively melts and solidifies by a laser beam with a peak high power. Several parameters such as the laser energy, pulse frequency, pulse duration, welding power and welding speed govern the mode of the welding process. The aim of this paper is to investigate the effect of peak power, incident angle, and welding speed on the weld bead geometry. The first investigation in this context was conducted using 2205-316L stainless steel plates through the varying of the welding speed from 1.3 mm/s to 2.1 mm/s. The second investigation was conducted by varying the peak power from 1100 W to 1500 W. From the results of the experiments, the welding speed and laser power had a significant effect on the geometry of the weld bead, and the variation in the diameter of the bead pulse-size. Due to the decrease in the heat input, welding speed affected penetration depth more than bead width, and a narrow width of heat affected zone was achieved ranging from 0.2 to 0.5 mm. Conclusively, weld bead geometry dimensions increase as a function of peak power; at over 1350 W peak power, the dimensions lie within 30 μm.

Influence of Mn contents in 0Cr18Ni10Ti thin wall stainless steel tube on TIG girth weld quality

NASA Astrophysics Data System (ADS)

Liu, Bo

2017-03-01

Three kinds of cold worked 0Cr18Ni10Ti thin wall stainless steel tubes with the manganese contents of 1.27%, 1.35% and 1.44% and the cold worked 0Cr18Ni10Ti stainless steel end plug with manganese content of 1.35% were used for TIG girth welding in the present investigation. The effect of different manganese contents in stainless steel tube on weld quality was studied. The results showed that under the same welding conditions, the metallographic performance of the girth weld for the thin wall stainless steel tube with the manganese element content 1.44% welded with end plug was the best. Under the appropriate welding conditions, the quality of the girth weld increased with the increase of the manganese content till 1.44%. It was found that in the case of the Mn content of 1.44%, and under the proper welding condition the welding defects, such as welding cracks were effectively avoided, and the qualified weld penetration can be obtained.. It is concluded that the appropriate increase of the manganese content can significantly improve the TIG girth weld quality of the cold worked 0Cr18Ni10Ti stainless steel tube.

Electron Beam Welding of Duplex Steels with using Heat Treatment

NASA Astrophysics Data System (ADS)

Schwarz, Ladislav; Vrtochová, Tatiana; Ulrich, Koloman

2010-01-01

This contribution presents characteristics, metallurgy and weldability of duplex steels with using concentrated energy source. The first part of the article describes metallurgy of duplex steels and the influence of nitrogen on their solidification. The second part focuses on weldability of duplex steels with using electron beam aimed on acceptable structure and corrosion resistance performed by multiple runs of defocused beam over the penetration weld.

Laser welding in penetrating keratoplasty and cataract surgery in pediatric patients: early results.

PubMed

Buzzonetti, Luca; Capozzi, Paolo; Petrocelli, Gianni; Valente, Paola; Petroni, Sergio; Menabuoni, Luca; Rossi, Francesca; Pini, Roberto

2013-12-01

To evaluate the efficacy of diode laser welding to close corneal wounds in penetrating keratoplasty (PKP) and cataract surgery in pediatric patients. Ophthalmology Department, Bambino Gesù Children's Hospital, Rome, Italy. Prospective observational study. Patients had surgery for congenital cataract (Group 1) or femtosecond laser-assisted PKP (Group 2). The surgery was followed by corneal wound closure using diode laser welding of the stroma. In Group 1, no standard suturing was used. In Group 2, the donor button was sutured onto the recipient using 8 single nylon sutures or a 10-0 nylon running suture (12 passages). Laser welding was then used as an adjunct to the traditional suturing procedure. Group 1 comprised 7 eyes (7 patients; mean age 8.1 years ± 5.3 [SD], range 1 to 15 years) and Group 2, 5 eyes (5 patients; mean age 10.6 ± 3.3 years, range 6 to 15 years). The adhesion of the laser-welded tissues was perfect; there were no collateral effects, and restoration of the treated tissues was optimum. Seidel testing showed no wound leakage during the follow-up. Postoperative astigmatism did not change significantly from the first day after cataract surgery and shifted moderately 3 months after PKP. Laser welding of corneal tissue appeared to be safe and effective in children for whom a sutureless surgical procedure is important to reduce the use of anesthesia for suture management, prevent endophthalmitis, and improve the antiamblyopic effect. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Laser welding in penetrating keratoplasty and cataract surgery of pediatric patients: early results

NASA Astrophysics Data System (ADS)

Rossi, Francesca; Pini, Roberto; Menabuoni, Luca; Malandrini, Alex; Canovetti, Annalisa; Lenzetti, Ivo; Capozzi, Paolo; Valente, Paola; Buzzonetti, Luca

2013-03-01

Diode laser welding of ocular tissues is a procedure that enables minimally invasive closure of a corneal wound. This procedure is based on a photothermal effect: a water solution of Indocyanine Green (ICG) is inserted in the surgical wound, in order to stain the corneal tissue walls. The stained tissue is then irradiated with a low power infrared diode laser, delivering laser light through a 300-μm core diameter optical fiber. This procedure enables an immediate closure of the wounds: it is thus possible to reduce or to substitute the use of surgical threads. This is of particular interest in children, because the immediate closure improves refractive outcome and anti-amblyopic effect; moreover this procedure avoids several general anaesthesia for suture management. In this work, we present the first use of diode laser welding procedure in paediatric patients. 5 selected patients underwent cataract surgery (Group 1), while 4 underwent fs-laserassisted penetrating keratoplasty (Group 2). In Group 1 the conventional surgery procedure was performed, while no stitches were used for the closure of the surgical wounds: these were laser welded and immediately closed. In Group 2 the donor button was sutured upon the recipient by 8 single stitches, instead of 16 single stitches or a running suture. The laser welding procedure was performed in order to join the donor tissue to the recipient bed. Objective observations in the follow up study evidenced a perfect adhesion of the laser welded tissues, no collateral effects and an optimal restoration of the treated tissues.

Experimental Investigation of Mechanical Properties of Welded Corten Steel A588 Grade Plate Using ER70S - 6 Filler Material for Construction Application

NASA Astrophysics Data System (ADS)

Deepak, J. R.; Bupesh Raja, V. K.; Janardhan Guptha, Mittapalli; Durga Prasad, Palaparthi Hari; Sriram, V.

2017-05-01

ASTM A588 Grade A steel plate is a high strength, low alloy structural steel with 0.19 % of carbon content. When exposed to the atmosphere, A588 Grade A is suitable for construction in the bare (paint - free) condition. The main problems are lack of fusion, lack of penetration and corrosion on heat affected zone. In this research work Corten ASTM A588 Grade steel of 3mm thickness is electroplated with copper and then both raw and copper electroplated are welded by GMAW welding process with ER70S-6 as a filler material. The welded ASTM A588 is cut according to ASTM size for further testing of mechanical properties. Considering its welding strength after the process of electroplating, this research clearly states the metal can be utilized for better results in any given field. Here both the tensile and hardness are higher in copper electroplated welded when compare to raw welded.

Optimization of laser butt welding parameters with multiple performance characteristics

NASA Astrophysics Data System (ADS)

Sathiya, P.; Abdul Jaleel, M. Y.; Katherasan, D.; Shanmugarajan, B.

2011-04-01

This paper presents a study carried out on 3.5 kW cooled slab laser welding of 904 L super austenitic stainless steel. The joints have butts welded with different shielding gases, namely argon, helium and nitrogen, at a constant flow rate. Super austenitic stainless steel (SASS) normally contains high amount of Mo, Cr, Ni, N and Mn. The mechanical properties are controlled to obtain good welded joints. The quality of the joint is evaluated by studying the features of weld bead geometry, such as bead width (BW) and depth of penetration (DOP). In this paper, the tensile strength and bead profiles (BW and DOP) of laser welded butt joints made of AISI 904 L SASS are investigated. The Taguchi approach is used as a statistical design of experiment (DOE) technique for optimizing the selected welding parameters. Grey relational analysis and the desirability approach are applied to optimize the input parameters by considering multiple output variables simultaneously. Confirmation experiments have also been conducted for both of the analyses to validate the optimized parameters.

[Impact of introduction of O2 on the welding arc of gas pool coupled activating TIG].

PubMed

Huang, Yong; Wang, Yan-Lei; Zhang, Zhi-Guo

2014-05-01

In the present paper, Boltzmann plot method was applied to analyze the temperature distributions of the are plasma when the gas pool coupled activating TIG welding was at different coupling degrees with the outer gas being O2. Based on this study of temperature distributions, the changing regularities of are voltage and are appearance were studied. The result shows that compared with traditional TIG welding, the introduction of O2 makes the welding arc constricted slightly, the temperature of the are center build up, and the are voltage increase. When argon being the inner gas, oxygen serving as the outer gas instead of argon makes the are constricted more obviously. When the coupling degree increases from 0 to 2, the temperature of the are center and the are voltage both increase slightly. In the gas pool coupled activating TIG welding the are is constricted not obviously, and the reason why the weld penetration is improved dramatically in the welding of stainless steel is not are constriction.

Effects of aging treatment and heat input on the microstructures and mechanical properties of TIG-welded 6061-T6 alloy joints

NASA Astrophysics Data System (ADS)

Peng, Dong; Shen, Jun; Tang, Qin; Wu, Cui-ping; Zhou, Yan-bing

2013-03-01

Aging treatment and various heat input conditions were adopted to investigate the microstructural evolution and mechanical properties of TIG welded 6061-T6 alloy joints by microstructural observations, microhardness tests, and tensile tests. With an increase in heat input, the width of the heat-affected zone (HAZ) increases and grains in the fusion zone (FZ) coarsen. Moreover, the hardness of the HAZ decreases, whereas that of the FZ decreases initially and then increases with an increase in heat input. Low heat input results in the low ultimate tensile strength of the welded joints due to the presence of partial penetrations and pores in the welded joints. After a simple artificial aging treatment at 175°C for 8 h, the microstructure of the welded joints changes slightly. The mechanical properties of the welded joints enhance significantly after the aging process as few precipitates distribute in the welded seam.

Improvement of laser keyhole formation with the assistance of arc plasma in the hybrid welding process of magnesium alloy

NASA Astrophysics Data System (ADS)

Liu, Liming; Hao, Xinfeng

2009-11-01

In the previous work, low-power laser/arc hybrid welding technique is used to weld magnesium alloy and high-quality weld joints are obtained. In order to make clear the interactions between low-power laser pulse and arc plasma, the effect of arc plasma on laser pulse is studied in this article. The result shows that the penetration of low-power laser welding with the assistance of TIG arc is more than two times deeper than that of laser welding alone and laser welding transforms from thermal-conduction mode to keyhole mode. The plasma behaviors and spectra during the welding process are studied, and the transition mechanism of laser-welding mode is analyzed in detail. It is also found that with the assistance of arc plasma, the threshold value of average power density to form keyhole welding for YAG laser is only 3.3×10 4 W/cm 2, and the average peak power density is 2.6×10 5 W/cm 2 in the present experiment. Moreover, the distribution of energy density during laser pulse is modulated to improve the formation and stability of laser keyholes.

Predicting laser weld reliability with stochastic reduced-order models. Predicting laser weld reliability

DOE PAGES

Emery, John M.; Field, Richard V.; Foulk, James W.; ...

2015-05-26

Laser welds are prevalent in complex engineering systems and they frequently govern failure. The weld process often results in partial penetration of the base metals, leaving sharp crack-like features with a high degree of variability in the geometry and material properties of the welded structure. Furthermore, accurate finite element predictions of the structural reliability of components containing laser welds requires the analysis of a large number of finite element meshes with very fine spatial resolution, where each mesh has different geometry and/or material properties in the welded region to address variability. We found that traditional modeling approaches could not bemore » efficiently employed. Consequently, a method is presented for constructing a surrogate model, based on stochastic reduced-order models, and is proposed to represent the laser welds within the component. Here, the uncertainty in weld microstructure and geometry is captured by calibrating plasticity parameters to experimental observations of necking as, because of the ductility of the welds, necking – and thus peak load – plays the pivotal role in structural failure. The proposed method is exercised for a simplified verification problem and compared with the traditional Monte Carlo simulation with rather remarkable results.« less

Low temperature heat treatments of AA5754-Ti6Al4V dissimilar laser welds: Microstructure evolution and mechanical properties

NASA Astrophysics Data System (ADS)

Leo, P.; D'Ostuni, S.; Casalino, G.

2018-03-01

This paper presents the effects of the post welding heat treatments (PWHT) performed at 350 °C and 450 °C on the microstructure evolution and mechanical properties of AA5754 and Ti6Al4V dissimilar laser welds. The microstructure and tensile properties of the welds before and after low temperature treatment were analyzed. The off-set welding technique was applied to limit the formation of brittle intermetallic compounds during the welding process. The laser beam was directed onto the titanium side at a small distance from the aluminum edge. The keyhole formed and the full penetration was reached in the titanium side of the weld. Thereafter, the aluminum side melted as the heat that formed the keyhole transferred from the titanium fused zone. Two different energy lines (32 J/mm and 76 J/mm) were used. In this manner, a fused and a heat affected zones was revealed on both sides of the weld. Several intermetallic compounds formed in the intermetallic layer between the two metals. The thickness and the composition of the intermetallic layer depended on the welding parameters and the post welding heat treatment. The hardness and tensile properties of the welds before and after the post welding heat treatment were measured and analyzed.

The fatigue life of a cobalt-chromium alloy after laser welding.

PubMed

Al-Bayaa, Nabil Jalal Ahmad; Clark, Robert K F; Juszczyk, Andrzej S; Radford, David R

2011-03-01

The aim of this study was to investigate the fatigue life of laser welded joints in a commercially available cast cobalt-chromium alloy. Twenty rod shaped specimens (40 mm x 1.5 mm) were cast and sand blasted. Ten specimens were used as controls and the remaining ten were sectioned and repaired using a pulsed Nd: YAG laser welder. All specimens were subjected to fatigue testing (30N - 2Hz) in a controlled environment. A statistically significant difference in median fatigue life was found between as-cast and laser welded specimens (p < 0.001). Consequently, the technique may not be appropriate for repairing cobalt chromium clasps on removable partial dentures. Scanning electron microscopy indicated the presence of cracks, pores and constriction of the outer surface in the welded specimens despite 70% penetration of the weld.

Investigation on the Effect of Pulsed Energy on Strength of Fillet Lap Laser Welded AZ31B Magnesium Alloys

NASA Astrophysics Data System (ADS)

Salleh, M. N. M.; Ishak, M.; Aiman, M. H.; Idris, S. R. A.; Romlay, F. R. M.

2017-09-01

AZ31B magnesium alloy have been hugely applied in the aerospace, automotive, and electronic industries. However, welding thin sheet AZ31B was challenging due to its properties which is easily to evaporated especially using conventional fusion welding method such as metal inert gas (MIG). Laser could be applied to weld this metal since it produces lower heat input. The application of fiber laser welding has been widely since this type of laser could produce better welding product especially in the automotive sectors. Low power fiber laser was used to weld this non-ferrous metal where pulse wave (PW) mode was used. Double fillet lap joint was applied to weld as thin as 0.6 mm thick of AZ31B and the effect of pulsed energy on the strength was studied. Bond width, throat length, and penetration depth also was studied related to the pulsed energy which effecting the joint. Higher pulsed energy contributes to the higher fracture load with angle of irradiation lower than 3 °

Research on the microstructure and properties of laser-MIG hybrid welded joint of Invar alloy

NASA Astrophysics Data System (ADS)

Zhan, Xiaohong; Zhang, Dan; Wei, Yanhong; Wang, Yuhua

2017-12-01

In order to solve the problem of large deformation, low production efficiency and high tendency of hot cracking in welding 19.05 mm thick plates of Fe36Ni Invar alloy, laser-MIG hybrid multi-layer welding technique (LMHMW) has been developed. To investigate the influence of different welding parameters on the joint properties, optical microscope observation, SEM, EDS and microhardness measurement were conducted. Experimental results illustrated that different matching of welding parameters significantly affected the depth-to-width ratio, formation of defects and HAZ width. Besides, weld zone were consisted of two regions according to the different grain shape. The region near center of weld seam (region 1) was columnar dendrite induced by laser, while the region far away from weld seam center (region 2) was cellular dendrite which was mainly caused by MIG arc. The peak value of microhardness appeared at the center of weld seam since the grains in region 1 were relatively fine, and the lowest hardness value was obtained in HAZ. In addition, results showed that the sheets can be welded at optimum process parameters, with few defects such as, surface oxidation, porosity, cracks and lack of penetration in the welding seam: laser power of backing weld P = 5500 W, welding current I = 240 A, welding speed v = 1 m/min. laser power of filling weld P = 2000 W, welding current I = 220 A, welding speed v = 0.35 m/min. laser power of cosmetic weld P = 2000 W, welding current I = 300 A, welding speed v = 0.35 m/min.

Space-dependent characterization of laser-induced plasma plume during fiber laser welding

NASA Astrophysics Data System (ADS)

Xiao, Xianfeng; Song, Lijun; Xiao, Wenjia; Liu, Xingbo

2016-12-01

The role of a plasma plume in high power fiber laser welding is of considerable interest due to its influence on the energy transfer mechanism. In this study, the space-dependent plasma characteristics including spectrum intensity, plasma temperature and electron density were investigated using optical emission spectroscopy technique. The plasma temperature was calculated using the Boltzmann plot of atomic iron lines, whereas the electron density was determined from the Stark broadening of the Fe I line at 381.584 nm. Quantitative analysis of plasma characteristics with respect to the laser radiation was performed. The results show that the plasma radiation increases as the laser power increases during the partial penetration mode, and then decreases sharply after the initiation of full penetration. Both the plasma temperature and electron density increase with the increase of laser power until they reach steady state values after full penetration. Moreover, the hottest core of the plasma shifts toward the surface of the workpiece as the penetration depth increases, whereas the electron density is more evenly distributed above the surface of the workpiece. The results also indicate that the absorption and scattering of nanoparticles in the plasma plume is the main mechanism for laser power attenuation.

Optimization of Laser Keyhole Welding Strategies of Dissimilar Metals by FEM Simulation

NASA Astrophysics Data System (ADS)

Garcia Navas, Virginia; Leunda, Josu; Lambarri, Jon; Sanz, Carmen

2015-07-01

Laser keyhole welding of dissimilar metals has been simulated to study the effect of welding strategies (laser beam displacements and tilts) and combination of metals to be welded on final quality of the joints. Molten pool geometry and welding penetration have been studied but special attention has been paid to final joint material properties, such as microstructure/phases and hardness, and especially to the residual stress state because it greatly conditions the service life of laser-welded components. For a fixed strategy (laser beam perpendicular to the joint) austenitic to carbon steel laser welding leads to residual stresses at the joint area very similar to those obtained in austenitic to martensitic steel welding, but welding of steel to Inconel 718 results in steeper residual stress gradients and higher area at the joint with detrimental tensile stresses. Therefore, when the difference in thermo-mechanical properties of the metals to be welded is higher, the stress state generated is more detrimental for the service life of the component, and consequently more relevant is the optimization of welding strategy. In laser keyhole welding of austenitic to martensitic stainless steel and austenitic to carbon steel, the optimum welding strategy is displacing the laser beam 1 mm toward the austenitic steel. In the case of austenitic steel to Inconel welding, the optimum welding strategy consists in setting the heat source tilted 45 deg and moved 2 mm toward the austenitic steel.

Reduction of Focal Shift Effects in Industrial Laser Beam Welding by Means of Innovative Protection Glass Concept

NASA Astrophysics Data System (ADS)

Hemmerich, Malte; Thiel, Christiane; Lupp, Friedrich; Hanebuth, Henning; Weber, Rudolf; Graf, Thomas

High-power laser beam welding in industrial environment often suffers from process induced contamination of laser focusing optics. Especially exposed to this contamination is the plane protection glass which is positioned directly above the process to protect the expensive lenses from contaminations such as spatter and metal vapor. Locally increased absorption due to con-tamination leads to a temperature rise in the protection glass and a corresponding change of its optical characteristics. This results in a reduced beam quality and a shift of the focus position. Both effects lead to a reduced intensity of radiation on the workpiece causing a lower welding penetration depth. In this article we present laser beam measurements using laser processing optics with protection glasses of different materials and different grades of contamination. Welds in mild steel illustrate the extraordinary advantage of sapphire protection glasses, allowing a constant welding depth even when they are strongly contaminated. Welding results, beam caustic measurements and an estimation of economic efficiency will be shown.

Investigation on Microstructure and Mechanical Properties of ATIG welded alloy C-276 with Fe2O3 flux

NASA Astrophysics Data System (ADS)

Surve, Angad; Bhosage, Sharnappa; Mehta, Akshay; Srikanth, A.; Arivarasu, M.; Manikandan, M.; Gokulkumar, K.; Rajan, Deva. N.

2018-02-01

Alloy C-276 susceptible to hot cracking. The microsegregation occurs during solidification is the largely responsible for the hot cracking in the alloy. The present study investigates the microstructure and mechanical properties of alloy C-276 weld joint fabricated by ATIG welding technique. The macro examination was carried out assess the defects in the weld joints. Optical and scanning electron microscope examination was carried out to see the structural changes in the fusion zone. The tensile test was performed to evaluate the strength of the weld joints. The results show the defect free welding was achieved in the established process parameters. The macrograph shows the full depth of penetration was obtained in the single pass by the effect of Marangoni convection. Energy Dispersive X-ray spectroscopy (EDS) analysis illustrates the absence of microsegregation in the interdendritic zone. The tensile test shows the improved mechanical properties compared to the base metal.

Laboratory Investigation of a Leaking Type 316 Socket Weld in a Boron Injection Tank Sampling Line

NASA Astrophysics Data System (ADS)

Xu, Hongqing; Fyfitch, Steve; Hosier, Ryan; Hyres, James

A leak was discovered in a Type 316 stainless steel socket weld in the sampling line for the boron injection tank. A section of the pipeline containing the leaking weld was removed for laboratory investigation that included visual and Stereovisual inspections, liquid penetrant (PT) testing, metallography, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and ferrite content determinations. The leak path was a through-wall transgranular crack in the socket weld. Cracking initiated along the weld-metal-to-base-metal interface at the tip of the crevice between the socket and pipe. The crevice was exposed to oxygenated boron solution at <180°F. Shallow intergranular attack (IGA) was found in the exposed base metal inside the crevice. Based on the investigation results, it was concluded that transgranular stress corrosion cracking (TGSCC) is the primary cracking mechanism.

Weld pool development during GTA and laser beam welding of Type 304 stainless steel; Part II-experimental correlation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zacharia, T.; David, S.A.; Vitek, J.M.

1989-12-01

In part I of the paper, the results of the heat flow and the fluid flow analysis were presented. Here, in Part II of the paper, predictions of the computational model are verified by comparing the numerically predicted and experimentally observed fusion zone size and shape. Stationary gas tungsten arc and laser beam welds were made on Type 304 stainless steel for different times to provide a variety of solidification conditions such as cooling rate and temperature gradient. Calculated temperatures and cooling rates are correlated with the experimentally observed fusion zone structure. In addition, the effect of sulfur on GTAmore » weld penetration was quantitatively evaluated by considering two heats of 304 stainless steel containing 90 and 240 ppm sulfur. Sulfur, as expected, increased the depth/width ratio by altering the surface tension gradient driven flow in the weld pool.« less

Damage Tolerance Behavior of Friction Stir Welds in Aluminum Alloys

NASA Technical Reports Server (NTRS)

McGill, Preston; Burkholder, Jonathan

2012-01-01

Friction stir welding is a solid state welding process used in the fabrication of various aerospace structures. Self-reacting and conventional friction stir welding are variations of the friction stir weld process employed in the fabrication of cryogenic propellant tanks which are classified as pressurized structure in many spaceflight vehicle architectures. In order to address damage tolerance behavior associated with friction stir welds in these safety critical structures, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size. Test data describing fracture behavior, residual strength capability, and cyclic mission life capability of friction stir welds at ambient and cryogenic temperatures have been generated and will be presented in this paper. Fracture behavior will include fracture toughness and tearing (R-curve) response of the friction stir welds. Residual strength behavior will include an evaluation of the effects of lack of penetration on conventional friction stir welds, the effects of internal defects (wormholes) on self-reacting friction stir welds, and an evaluation of the effects of fatigue cycled surface cracks on both conventional and selfreacting welds. Cyclic mission life capability will demonstrate the effects of surface crack defects on service load cycle capability. The fracture data will be used to evaluate nondestructive inspection and proof test requirements for the welds.

Validation of a Computational Model for Autogenous Arc Welding

DTIC Science & Technology

1990-03-01

Structure of Austenitic Stainless Steels ." M1etallurgical 7Tansactions A, v.20A, May 1989. Zacharia. T., Eraslan. A.l.. and Aidun. D.K., "Modeling of...Figure 4. Temperature profiles for low and high conductivity flaws ........... 13 Figure 5. Rosenthal verification results...The sulfur contents (90 ppm and 24() ppn’n had a significant effect on the weld penetration for the GTA process for 304 stainless steel , however, there

Real-Time Measurement of Width and Height of Weld Beads in GMAW Processes.

PubMed

Pinto-Lopera, Jesús Emilio; S T Motta, José Mauricio; Absi Alfaro, Sadek Crisostomo

2016-09-15

Associated to the weld quality, the weld bead geometry is one of the most important parameters in welding processes. It is a significant requirement in a welding project, especially in automatic welding systems where a specific width, height, or penetration of weld bead is needed. This paper presents a novel technique for real-time measuring of the width and height of weld beads in gas metal arc welding (GMAW) using a single high-speed camera and a long-pass optical filter in a passive vision system. The measuring method is based on digital image processing techniques and the image calibration process is based on projective transformations. The measurement process takes less than 3 milliseconds per image, which allows a transfer rate of more than 300 frames per second. The proposed methodology can be used in any metal transfer mode of a gas metal arc welding process and does not have occlusion problems. The responses of the measurement system, presented here, are in a good agreement with off-line data collected by a common laser-based 3D scanner. Each measurement is compare using a statistical Welch's t-test of the null hypothesis, which, in any case, does not exceed the threshold of significance level α = 0.01, validating the results and the performance of the proposed vision system.

Van Allen Probes Measurements of Energetic Particle Deep Penetration Into the Low L Region (L < 4) During the Storm on 8 April 2016

NASA Astrophysics Data System (ADS)

Zhao, H.; Baker, D. N.; Califf, S.; Li, X.; Jaynes, A. N.; Leonard, T.; Kanekal, S. G.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.; Turner, D. L.; Reeves, G. D.; Spence, H. E.

2017-12-01

Using measurements from the Van Allen Probes, a penetration event of tens to hundreds of keV electrons and tens of keV protons into the low L shells (L < 4) is studied. Timing and magnetic local time (MLT) differences of energetic particle deep penetration are unveiled and underlying physical processes are examined. During this event, both proton and electron penetrations are MLT asymmetric. The observed MLT difference of proton penetration is consistent with convection of plasma sheet protons, suggesting enhanced convection during geomagnetic active times to be the cause of energetic proton deep penetration during this event. The observed MLT difference of tens to hundreds of keV electron penetration is completely different from tens of keV protons and cannot be well explained by inward radial diffusion, convection of plasma sheet electrons, or transport of trapped electrons by enhanced convection electric field represented by the Volland-Stern model or a uniform dawn-dusk electric field model based on the electric field measurements. It suggests that the underlying physical mechanism responsible for energetic electron deep penetration, which is very important for fully understanding energetic electron dynamics in the low L shells, should be MLT localized.

Automatic laser welding and milling with in situ inline coherent imaging.

PubMed

Webster, P J L; Wright, L G; Ji, Y; Galbraith, C M; Kinross, A W; Van Vlack, C; Fraser, J M

2014-11-01

Although new affordable high-power laser technologies enable many processing applications in science and industry, depth control remains a serious technical challenge. In this Letter we show that inline coherent imaging (ICI), with line rates up to 312 kHz and microsecond-duration capture times, is capable of directly measuring laser penetration depth, in a process as violent as kW-class keyhole welding. We exploit ICI's high speed, high dynamic range, and robustness to interference from other optical sources to achieve automatic, adaptive control of laser welding, as well as ablation, achieving 3D micron-scale sculpting in vastly different heterogeneous biological materials.

Thick section aluminum weldments for SRB structures

NASA Technical Reports Server (NTRS)

Bayless, E.; Sexton, J.

1978-01-01

The Space Shuttle Solid Rocket Booster (SRB) forward and aft skirts were designed with fracture control considerations used in the design data. Fracture control is based on reliance upon nondestructive evaluation (NDE) techniques to detect potentially critical flaws. In the aerospace industry, welds on aluminum in the thicknesses (0.500 to 1.375 in.) such as those encountered on the SRB skirts are normally welded from both sides to minimize distortion. This presents a problem with the potential presence of undefined areas of incomplete fusion and the inability to detect these potential flaws by NDE techniques. To eliminate the possibility of an undetectable defect, weld joint design was revised to eliminate blind root penetrations. Weld parameters and mechanical property data were developed to verify the adequacy of the new joint design.

NUCLEAR REACTOR FUEL ELEMENT ASSEMBLY

DOEpatents

Stengel, F.G.

1963-12-24

A method of fabricating nuclear reactor fuel element assemblies having a plurality of longitudinally extending flat fuel elements in spaced parallel relation to each other to form channels is presented. One side of a flat side plate is held contiguous to the ends of the elements and a welding means is passed along the other side of the platertransverse to the direction of the longitudinal extension of the elements. The setting and speed of travel of the welding means is set to cause penetration of the side plate with welds at bridge the gap in each channel between adjacent fuel elements with a weld-through bubble of predetermined size. The fabrication of a high strength, dependable fuel element is provided, and the reduction of distortion and high production costs are facilitated by this method. (AEC)

Investigation of the structure and properties of a composite insert applied at laser welding of steel with titanium

NASA Astrophysics Data System (ADS)

Pugacheva, N. B.; Cherepanov, A. N.; Orishich, A. M.; Malikov, A. G.; Drozdov, V. O.; Mali, V. I.; Senaeva, E. I.

2017-10-01

Production of welded bimetallic structures of titanium and steel using a laser beam is a very urgent and important task in the shipbuilding, airspace and power engineering. Laser welding using an intermediate insert is one of the ways to solve this problem. In this paper, we present the results of experimental studies of formation of the structure and properties of composite insert, obtained by explosion welding, after its application at laser welding steel with titanium. A study of a four-layer composite insert obtained by explosion welding showed that it has no brittle intermetallic phases and defects in the form of cracks and pores. The boundaries between the plates to be welded in the composite insert have a characteristic wavy structure with narrow zones of mutual diffusion penetration of elements of the adjacent metals. It is established that the strength of the composite insert is comparable with the maximum strength of Grade 4 alloy, and the destruction of the product during the tensile tests in most cases occurred along the weakest component of the composite insert, i.e. the copper layer, whose strength was significantly increased due to the hardening that took place in the explosion welding.

Upgraded HFIR Fuel Element Welding System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sease, John D

2010-02-01

The welding of aluminum-clad fuel plates into aluminum alloy 6061 side plate tubing is a unique design feature of the High Flux Isotope Reactor (HFIR) fuel assemblies as 101 full-penetration circumferential gas metal arc welds (GMAW) are required in the fabrication of each assembly. In a HFIR fuel assembly, 540 aluminum-clad fuel plates are assembled into two nested annular fuel elements 610 mm (24-inches) long. The welding process for the HFIR fuel elements was developed in the early 1960 s and about 450 HFIR fuel assemblies have been successfully welded using the GMAW process qualified in the 1960 s. Inmore » recent years because of the degradation of the electronic and mechanical components in the old HFIR welding system, reportable defects in plate attachment or adapter welds have been present in almost all completed fuel assemblies. In October 2008, a contract was awarded to AMET, Inc., of Rexburg, Idaho, to replace the old welding equipment with standard commercially available welding components to the maximum extent possible while maintaining the qualified HFIR welding process. The upgraded HFIR welding system represents a major improvement in the welding system used in welding HFIR fuel elements for the previous 40 years. In this upgrade, the new inner GMAW torch is a significant advancement over the original inner GMAW torch previously used. The innovative breakthrough in the new inner welding torch design is the way the direction of the cast in the 0.762 mm (0.030-inch) diameter aluminum weld wire is changed so that the weld wire emerging from the contact tip is straight in the plane perpendicular to the welding direction without creating any significant drag resistance in the feeding of the weld wire.« less

Effects of electrode bevel angle on argon arc properties and weld shape

NASA Astrophysics Data System (ADS)

Dong, W. C.; Lu, S. P.; Li, D. Z.; Y Li, Y.

2012-07-01

A numerical modeling of coupled welding arc with weld pool is established using FLUENT software for moving shielded GTA welding to systematically investigate the effects of electrode bevel angle on the argon arc properties as well as the weld shape on SUS304 stainless steel. The calculated results show that the argon arc is constricted and the peak values of heat flux and shear stress on the weld pool decrease with increasing electrode bevel angle, while the radial distribution of heat flux and shear stress varying slightly. The weld shape is controlled by the pool flow patterns driving by the surface tension, gas shear stress, electromagnetic force and buoyancy. The Marangoni convection induced by surface tension plays an important role on weld shapes. All the weld shapes are wide and shallow with low weld metal oxygen content, while the narrow and deep weld shapes form under high weld metal oxygen content, which is related with the oxygen concentration in the shielding gas. The weld depth/width (D/W) ratio increases with increasing electrode bevel angle for high weld metal oxygen content and is not sensitive to the electrode bevel angle under low weld metal oxygen content. The calculated results for the weld shape, weld size and weld D/W ratio agree well with the experimental ones.

Process Parameter Optimization for Wobbling Laser Spot Welding of Ti6Al4V Alloy

NASA Astrophysics Data System (ADS)

Vakili-Farahani, F.; Lungershausen, J.; Wasmer, K.

Laser beam welding (LBW) coupled with "wobble effect" (fast oscillation of the laser beam) is very promising for high precision micro-joining industry. For this process, similarly to the conventional LBW, the laser welding process parameters play a very significant role in determining the quality of a weld joint. Consequently, four process parameters (laser power, wobble frequency, number of rotations within a single laser pulse and focused position) and 5 responses (penetration, width, heat affected zone (HAZ), area of the fusion zone, area of HAZ and hardness) were investigated for spot welding of Ti6Al4V alloy (grade 5) using a design of experiments (DoE) approach. This paper presents experimental results showing the effects of variating the considered most important process parameters on the spot weld quality of Ti6Al4V alloy. Semi-empirical mathematical models were developed to correlate laser welding parameters to each of the measured weld responses. Adequacies of the models were then examined by various methods such as ANOVA. These models not only allows a better understanding of the wobble laser welding process and predict the process performance but also determines optimal process parameters. Therefore, optimal combination of process parameters was determined considering certain quality criteria set.

Material Interactions in a Novel Pinless Tool Approach to Friction Stir Spot Welding Thin Aluminum Sheet

NASA Astrophysics Data System (ADS)

Bakavos, Dimitrios; Chen, Yingchun; Babout, Laurent; Prangnell, Phil

2011-05-01

The requirement for a probe, or pin, in friction stir spot welding (FSSW) leads to an undesirable keyhole and "hooking," which can influence the fracture path and weld strength. Furthermore, the full weld cycle for FSSW is typically longer than ideal for the automotive industry, being 2 to 5 seconds. Here, it is shown that using a novel pinless tool design it is possible to achieve high lap shear strength (~3.4 kN) in thin aluminum sheet (~1 mm thick), with short weld cycle times (<1 second). Several techniques have been exploited to study the material flow and mechanisms of weld formation in pinless FSSW, including high-resolution X-ray tomography, to understand the role of the tool design and weld parameters. Despite the "simple" nature of a pinless tool, material flow in the weld zone was found to be surprisingly complex and strongly influenced by surface features on the tool, which greatly increased the penetration of the plastic zone into the bottom sheet. Because of the rapid thermal cycle and high level of grain refinement, the weld zone was found to develop a higher strength than the parent material with little evidence of a heat affected zone (HAZ) after postweld natural aging.

Modern fiber laser beam welding of the newly-designed precipitation-strengthened nickel-base superalloys

NASA Astrophysics Data System (ADS)

Naffakh Moosavy, Homam; Aboutalebi, Mohammad-Reza; Seyedein, Seyed Hossein; Goodarzi, Massoud; Khodabakhshi, Meisam; Mapelli, Carlo; Barella, Silvia

2014-04-01

In the present research, the modern fiber laser beam welding of newly-designed precipitation-strengthened nickel-base superalloys using various welding parameters in constant heat input has been investigated. Five nickel-base superalloys with various Ti and Nb contents were designed and produced by Vacuum Induction Melting furnace. The fiber laser beam welding operations were performed in constant heat input (100 J mm-2) and different welding powers (400 and 1000 W) and velocities (40 and 100 mm s-1) using 6-axis anthropomorphic robot. The macro- and micro-structural features, weld defects, chemical composition and mechanical property of 3.2 mm weldments were assessed utilizing optical and scanning electron microscopes equipped with EDS analysis and microhardness tester. The results showed that welding with higher powers can create higher penetration-to-width ratios. The porosity formation was increased when the welding powers and velocities were increased. None of the welds displayed hot solidification and liquation cracks in 400 and 1000 W welding powers, but liquation phenomenon was observed in all the heat-affected zones. With increasing the Nb content of the superalloys the liquation length was increased. The changing of the welding power and velocity did not alter the hardness property of the welds. The hardness of welds decreased when the Ti content declined in the composition of superalloys. Finally, the 400 and 1000 W fiber laser powers with velocity of 40 and 100 m ms-1 have been offered for hot crack-free welding of the thin sheet of newly-designed precipitation-strengthened nickel-base superalloys.

Micro-Welding of Copper Plate by Frequency Doubled Diode Pumped Pulsed Nd:YAG Laser

NASA Astrophysics Data System (ADS)

Nakashiba, Shin-Ichi; Okamoto, Yasuhiro; Sakagawa, Tomokazu; Takai, Sunao; Okada, Akira

A pulsed laser of 532 nm wavelength with ms range pulse duration was newly developed by second harmonic generation of diode pumped pulsed Nd:YAG laser. High electro-optical conversion efficiency more than 13% could be achieved, and 1.5 kW peak power green laser pulse was put in optical fiber of 100 μm in diameter. In micro- welding of 1.0 mm thickness copper plate, a keyhole welding was successfully performed by 1.0 kW peak power at spot diameter less than 200 μm. The frequency doubled pulsed laser improved the processing efficiency of copper welding, and narrow and deep weld bead was stably obtained.

Behavior of Ti-5Al-2.5Sn ELI titanium alloy sheet parent and weld metal in the presence of cracks at 20 K

NASA Technical Reports Server (NTRS)

Sullivan, T. L.

1971-01-01

Through- and surface-cracked specimens of two thicknesses were tested in uniaxial tension. Surface-cracked specimens were generally found to be stronger than through-cracked specimens with the same crack length. Apparent surface-crack fracture toughness calculated using the Anderson modified Irwin equation remained relatively constant for cracks as deep as 90 percent of the sheet thickness. Subcritical growth of surface cracks was investigated. Comparison of chamber and open air welds showed chamber welds to be slightly tougher. Both methods produced welds with toughness that compared favorably with that of the parent metal. Weld efficiencies were above 94 percent.

Grain structure, texture and mechanical property evolution of automotive aluminium sheet during high power ultrasonic welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haddadi, Farid, E-mail: farid.haddadi@gmail.com

High power ultrasonic spot welding (HPUSW) is a joining technique which is performed within less than a second and provides a more energy-efficient alternative to friction stir spot welding (FSSW), which is considered a longer cycle manufacturing process for joining automotive alloys. To date, only a few reports exist on the deformation mechanisms that take place during high power ultrasonic spot welding. In this work, dynamic recrystallization and grain growth were examined using electron backscatter diffraction (EBSD). HPUSW causes extensive deformation within the weld zone where the temperature increases to 440 °C. An ultra-fine grain structure was observed in amore » thin band of flat weld interface within a short welding time of 0.10 s. With increasing welding time the interface was displaced and ‘folds’ or ‘crests’ appeared together with shear bands. The weld interface progressively changed from flat to sinusoidal and eventually to a convoluted wave-like pattern when the tool fully penetrated the workpiece, having a wavelength of ~ 1 mm after 0.40 s. Finally, the microstructure and texture varied significantly depending on the location within the weld. Although the texture near the weld interface was relatively weak, a shift was observed with increasing welding time from an initially Cube-dominated texture to one where the typical β-fibre Brass component prevailed. - Highlights: •Lap shear strength of ~2.9 kN was achieved in 0.30 sec welding time. •Temperature approached 440 °C along the weld centreline for the highest welding time. •The texture near the teeth was dominated by Brass, P and S components at optimum condition. •The weld interface showed typical β-fibre deformation texture at optimum condition.« less

Real-Time Measurement of Width and Height of Weld Beads in GMAW Processes

PubMed Central

Pinto-Lopera, Jesús Emilio; S. T. Motta, José Mauricio; Absi Alfaro, Sadek Crisostomo

2016-01-01

Associated to the weld quality, the weld bead geometry is one of the most important parameters in welding processes. It is a significant requirement in a welding project, especially in automatic welding systems where a specific width, height, or penetration of weld bead is needed. This paper presents a novel technique for real-time measuring of the width and height of weld beads in gas metal arc welding (GMAW) using a single high-speed camera and a long-pass optical filter in a passive vision system. The measuring method is based on digital image processing techniques and the image calibration process is based on projective transformations. The measurement process takes less than 3 milliseconds per image, which allows a transfer rate of more than 300 frames per second. The proposed methodology can be used in any metal transfer mode of a gas metal arc welding process and does not have occlusion problems. The responses of the measurement system, presented here, are in a good agreement with off-line data collected by a common laser-based 3D scanner. Each measurement is compare using a statistical Welch’s t-test of the null hypothesis, which, in any case, does not exceed the threshold of significance level α = 0.01, validating the results and the performance of the proposed vision system. PMID:27649198

10-kW-class YAG laser application for heavy components

NASA Astrophysics Data System (ADS)

Ishide, Takashi; Tsubota, S.; Nayama, Michisuke; Shimokusu, Yoshiaki; Nagashima, Tadashi; Okimura, K.

2000-02-01

The authors have put the YAG laser of the kW class to practical use for repair welding of nuclear power plant steam generator heat exchanger tubes, all-position welding of pipings, etc. This paper describes following developed methods and systems of high power YAG laser processing. First, we apply the 6 kW to 10 kW YAG lasers for welding and cutting in heavy components. The beam guide systems we have used are optical fibers which core diameter is 0.6 mm to 0.8 mm and its length is 200 m as standard one. Using these system, we can get the 1 pass penetration of 15 mm to 20 mm and multi pass welding for more thick plates. Cutting of 100 mm thickness plate data also described for dismantling of nuclear power plants. In these systems we carried out the in-process monitoring by using CCD camera image processing and monitoring fiber which placed coaxial to the YAG optical lens system. In- process monitoring by the monitoring fiber, we measured the light intensity from welding area. Further, we have developed new hybrid welding with the TIG electrode at the center of lens for high power. The hybrid welding with TIG-YAG system aims lightening of welding groove allowances and welding of high quality. Through these techniques we have applied 7 kW class YAG laser for welding in the components of nuclear power plants.

Dye-enhanced laser welding for skin closure.

PubMed

DeCoste, S D; Farinelli, W; Flotte, T; Anderson, R R

1992-01-01

The use of a laser to weld tissue in combination with a topical photosensitizing dye permits selective delivery of energy to the target tissue. A combination of indocyanine green (IG), absorption peak 780 nm, and the near-infrared (IR) alexandrite laser was studied with albino guinea pig skin. IG was shown to bind to the outer 25 microns of guinea pig dermis and appeared to be bound to collagen. The optical transmittance of full-thickness guinea pig skin in the near IR was 40% indicating that the alexandrite laser should provide adequate tissue penetration. Laser "welding" of skin in vivo was achieved at various concentrations of IG from 0.03 to 3 mg/cc using the alexandrite at 780 nm, 250-microseconds pulse duration, 8 Hz, and a 4-mm spot size. A spectrum of welds was obtained from 1- to 20-W/cm2 average irradiance. Weak welds occurred with no thermal damage obtained at lower irradiances: stronger welds with thermal damage confined to the weld site occurred at higher irradiances. At still higher irradiances, local vaporization occurred with failure to "weld." Thus, there was an optimal range of irradiances for "welding," which varied inversely with dye concentration. Histology confirmed the thermal damage results that were evident clinically. IG dye-enhanced laser welding is possible in skin and with further optimization may have practical application.

Real-time focus controller for laser welding with fibre optic noninvasive capture of light

NASA Astrophysics Data System (ADS)

Cobo, Adolfo; Bardin, F.; Hand, Duncan P.; Jones, Julian D.; Collin, O.; Aubry, P.; Dubois, Thierry; Hoegstroem, M.; Nylen, P.; Jonsson, P.; Lopez-Higuera, Jose M.

2004-06-01

Laser welding is being introduced in the aerospace industry due to its many advantages over traditional techniques. However, welding of parts with complex shapes requires precise control of the focal point of the laser in order to achieve full penetration over the entire seam. In this paper, we present an improved control system for real-time adjustment of the correct focal position, which is based on the monitoring of the light emitted by the process in two different spectral bands. The reported system has been optimized for use in a real environment: it is robust, compact, easy to operate, able to adjust itself to different welding conditions, materials and laser setups, and includes a direct connection to an external PC. Results from recent field trials on complex aerospace structures are provided.

Using Phased Array Ultrasonic Testing in Lieu of Radiography for Acceptance of Carbon Steel Piping Welds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moran, Traci L.; Anderson, Michael T.; Cinson, Anthony D.

2014-08-01

The Pacific Northwest National Laboratory (PNNL) is conducting studies for the U.S. Nuclear Regulatory Commission (NRC) to assess the capability, effectiveness, and reliability of ultrasonic testing (UT) as a replacement method for radiographic testing (RT) for volumetric examination of nuclear power plant (NPP) components. This particular study focused on evaluating the use of UT on carbon steel plate welds. Welding fabrication flaws included a combination of planar and volumetric types, e.g., incomplete fusion, lack of penetration, cracks, porosity, and slag inclusions. The examinations were conducted using phased-array (PA) UT techniques applied primarily for detection and flaw type characterization. This papermore » will discuss the results of using UT in lieu of RT for detection and classification of fabrication flaws in carbon steel plate welds.« less

Influence of shielding gas on the mechanical and metallurgical properties of DP-GMA-welded 5083-H321 aluminum alloy

NASA Astrophysics Data System (ADS)

Koushki, Amin Reza; Goodarzi, Massoud; Paidar, Moslem

2016-12-01

In the present research, 6-mm-thick 5083-H321 aluminum alloy was joined by the double-pulsed gas metal arc welding (DP-GMAW) process. The objective was to investigate the influence of the shielding gas composition on the microstructure and properties of GMA welds. A macrostructural study indicated that the addition of nitrogen and oxygen to the argon shielding gas resulted in better weld penetration. Furthermore, the tensile strength and bending strength of the welds were improved when oxygen and nitrogen (at concentrations as high as approximately 0.1vol%) were added to the shielding gas; however, these properties were adversely affected when the oxygen and nitrogen contents were increased further. This behavior was attributed to the formation of excessive brown and black oxide films on the bead surface, the formation of intermetallic compounds in the weld metal, and the formation of thicker oxide layers on the bead surface with increasing nitrogen and oxygen contents in the argon-based shielding gas. Analysis by energy-dispersive X-ray spectroscopy revealed that most of these compounds are nitrides or oxides.

ARC and Melting Efficiency of Plasma ARC Welds

NASA Technical Reports Server (NTRS)

McClure, J. C.; Nunes, A. C.; Evans, D. M.

1999-01-01

A series of partial penetration Variable Polarity Plasma Arc welds were made at equal power but various combinations of current and voltage on 2219 Aluminum. Arc efficiency was measured calorimetrically and ranged between 48% and 66% for the conditions of the welds. Arc efficiency depends in different ways on voltage and current. The voltage effect dominates. Raising voltage while reducing current increases arc efficiency. Longer, higher voltage arcs are thought to transfer a greater portion of arc power to the workpiece through shield gas convection. Melting efficiency depends upon weld pool shape as well as arc efficiency. Increased current increases the melting efficiency as it increases the depth to width ratio of the weld pool. Increased plasma gas flow does the same thing. Higher currents are thought to raise arc pressure and depress liquid at the bottom of the weld pool. More arc power then transfers to the workpiece through increasing plasma gas convection. If the power is held constant, the reduced voltage lowers the arc efficiency, while the pool shape change increases the melting efficiency,

Benefit from NASA

NASA Image and Video Library

1998-12-01

Two companies have successfully commercialized a specialized welding tool developed at the Marshall Space Flight Center (MSFC). Friction stir welding uses the high rotational speed of a tool and the resulting frictional heat created from contact to crush, "stir" together, and forge a bond between two metal alloys. It has had a major drawback, reliance on a single-piece pin tool. The pin is slowly plunged into the joint between two materials to be welded and rotated as high speed. At the end of the weld, the single-piece pin tool is retracted and leaves a "keyhole," something which is unacceptable when welding cylindrical objects such as drums, pipes and storage tanks. Another drawback is the requirement for different-length pin tools when welding materials of varying thickness. An engineer at the MSFC helped design an automatic retractable pin tool that uses a computer-controlled motor to automatically retract the pin into the shoulder of the tool at the end of the weld, preventing keyholes. This design allows the pin angle and length to be adjusted for changes in material thickness and results in a smooth hole closure at the end of the weld. Benefits of friction stir welding, using the MSFC retractable pin tool technology, include the following: The ability to weld a wide range of alloys, including previously unweldable and composite materials; provision of twice the fatigue resistance of fusion welds and no keyholes; minimization of material distortion; no creation of hazards such as welding fumes, radiation, high voltage, liquid metals, or arcing; automatic retraction of the pin at the end of the weld; and maintaining full penetration of the pin.

Method of beam welding metallic parts together and apparatus for doing same

DOEpatents

Lewandowski, Edward F.; Cassidy, Dale A.; Sommer, Robert G.

1987-01-01

The disclosed method provides for temporarily clamping a metallic piece to one side of a metallic plate while leaving the opposite side of the plate exposed, and providing a heat conductive heat sink body configured to engage the adjacent portions of such one side of the plate and the piece at all regions proximate to but not at the interface between these components. Such exposed side of such plate is then subjected to an electron welding beam, in exact registry with but opposite to the piece. The electron welding beam is supplied with adequate energy for penetrating through the plate, across the interface, and into the piece, whereby the electron welding beam produces molten material from both the plate and the piece in the region of the interface. The molten material flows into any interstices that may exist in the interface, and upon cooling solidifies to provide a welded joint between the plate and piece, where the interface was, virtually without any interstices. The heat sink material prevents the molten material from extruding beyond what was the interface, to provide a clean welded joint. The heat sink body also mechanically holds the plate and piece together prior to the actual welding.

Method of beam welding metallic parts together and apparatus for doing same

DOEpatents

Lewandowski, E.F.; Cassidy, D.A.; Sommer, R.G.

1985-11-29

This method provides for temporarily clamping a metallic piece to one side of a metallic plate while leaving the opposite side of the plate exposed, and providing a heat conductive heat sink body configured to engage the adjacent portions of such one side of the plate and the piece at all regions proximate to but not at the interface between these components. The exposed side of such plate is then subjected to an electron welding beam, in exact registry with but opposite to the piece. The electron welding beam is supplied with adequate energy for penetrating through the plate, across the interface, and into the piece, whereby the electron welding beam produces molten material from both the plate and the piece in the region of the interface. The molten material flows into any interstices that may exist in the interface, and upon cooling solidifies to provide a welded joint between the plate and piece, where the interface was, virtually without any interstices. The heat sink material prevents the molten material from extrucing beyond what was the interface, to provide a clean welded joint. The heat sink body also mechanically holds the plate and piece together prior to the actual welding.

Experimental study on the healing process following laser welding of the cornea.

PubMed

Rossi, Francesca; Pini, Roberto; Menabuoni, Luca; Mencucci, Rita; Menchini, Ugo; Ambrosini, Stefano; Vannelli, Gabriella

2005-01-01

An experimental study evaluating the application of laser welding of the cornea and the subsequent healing process is presented. The welding of corneal wounds is achieved after staining the cut walls with a solution of the chromophore indocyanine green, and irradiating them with a diode laser (810 nm) operating at low power (60 to 90 mW). The result is a localized heating of the cut, inducing controlled welding of the stromal collagen. In order to optimize this technique and to study the healing process, experimental tests, simulating cataract surgery and penetrating keratoplasty, were performed on rabbits: conventional and laser-induced suturing of corneal wounds were thus compared. A follow-up study 7 to 90 days after surgery was carried out by means of objective and histological examinations, in order to optimize the welding technique and to investigate the subsequent healing process. The analyses of the laser-welded corneas evidenced a faster and more effective restoration of the architecture of the stroma. No thermal damage of the welded stroma was detected, nor were there foreign body reactions or other inflammatory processes. Copyright 2005 Society of Photo-Optical Instrumentation Engineers.

Gas Metal Arc Welding Parameters Effect on Properties of Tailored Orbital Weld of SS304 and BS1387

NASA Astrophysics Data System (ADS)

Ayof, M. N.; Hussein, N. I. S.; Noh, M. Z. Mohd

2017-09-01

Dissimilar material pipes in a power plant boiler water piping system are used to transmit water at various temperatures, either in extremely high temperature water or room temperature water. In this study, tailored orbital welding of dissimilar material of Stainless Steel (SS) 304 and British Steel (BS) 1387 were performed by Gas Metal Arc Welding (GMAW) with automated fixed nozzle-rotational jig. This study focused on GMAW parameters variation effects on mechanical properties of SS304 and BS1387 dissimilar material tailored orbital welding. The weldment quality was tested by performing non-destructive dye penetrant test. The tensile strength and microhardness were studied to verify the influence of welding parameters variations. Design of Experiment (DOE) was employed to generate process parameter using Response Surface Methodology (RSM) method. Welding parameters that were arc current, arc voltage and travel speed as input response, whilst, tensile strength and microhardness as output response. Results from non-destructive test showed no major defect occurred. The tensile strength and microhardness increased when arc current and voltage increased and travel speed decreased. Microhardness at weldment was higher than base material.

Intelligent Weld Manufacturing: Role of Integrated Computational Welding Engineering

DOE PAGES

David, Stan A.; Chen, Jian; Feng, Zhili; ...

2017-12-02

A master welder uses his sensory perceptions to evaluate the process and connect them with his/her knowledge base to take the necessary corrective measures with his/her acquired skills to make a good weld. All these actions must take place in real time. Success depends on intuition and skills, and the procedure is labor-intensive and frequently unreliable. The solution is intelligent weld manufacturing. The ultimate goal of intelligent weld manufacturing would involve sensing and control of heat source position, weld temperature, weld penetration, defect formation and ultimately control of microstructure and properties. This involves a solution to a problem (welding) withmore » many highly coupled and nonlinear variables. The trend is to use an emerging tool known as intelligent control. This approach enables the user to choose a desirable end factor such as properties, defect control, or productivity to derive the selection of process parameters such as current, voltage, or speed to provide for appropriate control of the process. Important elements of intelligent manufacturing are sensing and control theory and design, process modeling, and artificial intelligence. Significant progress has been made in all these areas. Integrated computational welding engineering (ICWE) is an emerging field that will aid in the realization of intelligent weld manufacturing. The paper will discuss the progress in process modeling, microstructure, properties, and process control and automation and the importance of ICWE. Also, control and automation strategies for friction stir welding will be discussed.« less

Intelligent Weld Manufacturing: Role of Integrated Computational Welding Engineering

DOE Office of Scientific and Technical Information (OSTI.GOV)

David, Stan A.; Chen, Jian; Feng, Zhili

A master welder uses his sensory perceptions to evaluate the process and connect them with his/her knowledge base to take the necessary corrective measures with his/her acquired skills to make a good weld. All these actions must take place in real time. Success depends on intuition and skills, and the procedure is labor-intensive and frequently unreliable. The solution is intelligent weld manufacturing. The ultimate goal of intelligent weld manufacturing would involve sensing and control of heat source position, weld temperature, weld penetration, defect formation and ultimately control of microstructure and properties. This involves a solution to a problem (welding) withmore » many highly coupled and nonlinear variables. The trend is to use an emerging tool known as intelligent control. This approach enables the user to choose a desirable end factor such as properties, defect control, or productivity to derive the selection of process parameters such as current, voltage, or speed to provide for appropriate control of the process. Important elements of intelligent manufacturing are sensing and control theory and design, process modeling, and artificial intelligence. Significant progress has been made in all these areas. Integrated computational welding engineering (ICWE) is an emerging field that will aid in the realization of intelligent weld manufacturing. The paper will discuss the progress in process modeling, microstructure, properties, and process control and automation and the importance of ICWE. Also, control and automation strategies for friction stir welding will be discussed.« less

A Monte Carlo model for 3D grain evolution during welding

NASA Astrophysics Data System (ADS)

Rodgers, Theron M.; Mitchell, John A.; Tikare, Veena

2017-09-01

Welding is one of the most wide-spread processes used in metal joining. However, there are currently no open-source software implementations for the simulation of microstructural evolution during a weld pass. Here we describe a Potts Monte Carlo based model implemented in the SPPARKS kinetic Monte Carlo computational framework. The model simulates melting, solidification and solid-state microstructural evolution of material in the fusion and heat-affected zones of a weld. The model does not simulate thermal behavior, but rather utilizes user input parameters to specify weld pool and heat-affect zone properties. Weld pool shapes are specified by Bézier curves, which allow for the specification of a wide range of pool shapes. Pool shapes can range from narrow and deep to wide and shallow representing different fluid flow conditions within the pool. Surrounding temperature gradients are calculated with the aide of a closest point projection algorithm. The model also allows simulation of pulsed power welding through time-dependent variation of the weld pool size. Example simulation results and comparisons with laboratory weld observations demonstrate microstructural variation with weld speed, pool shape, and pulsed-power.

Hot Corrosion of Inconel 625 Overlay Weld Cladding in Smelting Off-Gas Environment

NASA Astrophysics Data System (ADS)

Mohammadi Zahrani, E.; Alfantazi, A. M.

2013-10-01

Degradation mechanisms and hot corrosion behavior of weld overlay alloy 625 were studied. Phase structure, morphology, thermal behavior, and chemical composition of deposited salt mixture on the weld overlay were characterized utilizing XRD, SEM/EDX, DTA, and ICP/OES, respectively. Dilution level of Fe in the weldment, dendritic structure, and degradation mechanisms of the weld were investigated. A molten phase formed on the weld layer at the operating temperature range of the boiler, which led to the hot corrosion attack in the water wall and the ultimate failure. Open circuit potential and weight-loss measurements and potentiodynamic polarization were carried out to study the hot corrosion behavior of the weld in the simulated molten salt medium at 873 K, 973 K, and 1073 K (600 °C, 700 °C, and 800 °C). Internal oxidation and sulfidation plus pitting corrosion were identified as the main hot corrosion mechanisms in the weld and boiler tubes. The presence of a significant amount of Fe made the dendritic structure of the weld susceptible to preferential corrosion. Preferentially corroded (Mo, Nb)-depleted dendrite cores acted as potential sites for crack initiation from the surface layer. The penetration of the molten phase into the cracks accelerated the cracks' propagation mainly through the dendrite cores and further crack branching/widening.

Deep Dyspareunia in Endometriosis: A Proposed Framework Based on Pain Mechanisms and Genito-Pelvic Pain Penetration Disorder.

PubMed

Yong, Paul J

2017-10-01

Endometriosis is a common chronic disease affecting 1 in 10 women of reproductive age, with half of women with endometriosis experiencing deep dyspareunia. A review of research studies on endometriosis indicates a need for a validated question or questionnaire for deep dyspareunia. Moreover, placebo-controlled randomized trials have yet to demonstrate a clear benefit for traditional treatments of endometriosis for the outcome of deep dyspareunia. The reason some patients might not respond to traditional treatments is the multifactorial nature of deep dyspareunia in endometriosis, which can include comorbid conditions (eg, interstitial cystitis and bladder pain syndrome) and central sensitization underlying genito-pelvic pain penetration disorder. In general, there is a lack of a framework that integrates these multifactorial causes to provide a standardized approach to deep dyspareunia in endometriosis. To propose a clinical framework for deep dyspareunia based on a synthesis of pain mechanisms with genito-pelvic pain penetration disorder according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. Narrative review after literature search with the terms (endometriosis AND dyspareunia) OR (dyspareunia AND deep) and after analysis of placebo-controlled randomized trials. Deep dyspareunia presence or absence or deep dyspareunia severity on a numeric rating scale or visual analog scale. Four types of deep dyspareunia are proposed in women with endometriosis: type I that is directly due to endometriosis; type II that is related to a comorbid condition; type III in which genito-pelvic pain penetration disorder is primary; and type IV that is secondary to a combination of types I to III. Four types of deep dyspareunia in endometriosis are proposed, which can be used as a framework in research studies and in clinical practice. Research trials could phenotype or stratify patients by each type. The framework also could give rise to more personalized care for patients by targeting appropriate treatments to each deep dyspareunia type. Yong PJ. Deep Dyspareunia in Endometriosis: A Proposed Framework Based on Pain Mechanisms and Genito-Pelvic Pain Penetration Disorder. Sex Med Rev 2017;5:495-507. Copyright © 2017 International Society for Sexual Medicine. Published by Elsevier Inc. All rights reserved.

Retractable Pin Tools for the Friction Stir Welding Process

NASA Technical Reports Server (NTRS)

1998-01-01

Two companies have successfully commercialized a specialized welding tool developed at the Marshall Space Flight Center (MSFC). Friction stir welding uses the high rotational speed of a tool and the resulting frictional heat created from contact to crush, 'stir' together, and forge a bond between two metal alloys. It has had a major drawback, reliance on a single-piece pin tool. The pin is slowly plunged into the joint between two materials to be welded and rotated as high speed. At the end of the weld, the single-piece pin tool is retracted and leaves a 'keyhole,' something which is unacceptable when welding cylindrical objects such as drums, pipes and storage tanks. Another drawback is the requirement for different-length pin tools when welding materials of varying thickness. An engineer at the MSFC helped design an automatic retractable pin tool that uses a computer-controlled motor to automatically retract the pin into the shoulder of the tool at the end of the weld, preventing keyholes. This design allows the pin angle and length to be adjusted for changes in material thickness and results in a smooth hole closure at the end of the weld. Benefits of friction stir welding, using the MSFC retractable pin tool technology, include the following: The ability to weld a wide range of alloys, including previously unweldable and composite materials; provision of twice the fatigue resistance of fusion welds and no keyholes; minimization of material distortion; no creation of hazards such as welding fumes, radiation, high voltage, liquid metals, or arcing; automatic retraction of the pin at the end of the weld; and maintaining full penetration of the pin.

Effect of Compositional Variation in TiO2-Based Flux-Cored Arc Welding Fluxes on the Thermo-physical Properties and Mechanical Behavior of a Weld Zone

NASA Astrophysics Data System (ADS)

Kim, J. B.; Lee, T. H.; Sohn, I.

2018-04-01

The effect of compositional variation in TiO2-based flux-cored arc welding fluxes on viscosity, wettability, and electronegativity was studied. The thermo-physical properties of the retrieved fluxes and their relationship with the mechanical properties of the weld zone, including tensile strength and micro-Vickers hardness, after welding were identified. Microstructural observation under similar welding conditions revealed significant grain coarsening at a corrected optical basicity (Λcorr) of 0.62, resulting in reduced strength and hardness due to greater heat transfer. Welding fluxes containing TiO2-based simple structural units should result in greater heat transfer due to the deficiency in complex [AlO4]5-- and [SiO4]4--based structural units, as identified through spectroscopic analyses using fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The electronegativity of the retrieved fluxes was also evaluated since higher electronegativity results in greater absorption of electrons in the arc, resulting in arc condensation towards the center direction. Consequently, deeper penetration could be obtained, where the highest electronegativity was identified to be approximately 0.62 of the corrected optical basicity. Thus, both the thermal conductivity and electronegativity of the welding fluxes were identified to determine the heat transfer phenomenon during flux-cored arc welding.

Effect of Compositional Variation in TiO2-Based Flux-Cored Arc Welding Fluxes on the Thermo-physical Properties and Mechanical Behavior of a Weld Zone

NASA Astrophysics Data System (ADS)

Kim, J. B.; Lee, T. H.; Sohn, I.

2018-07-01

The effect of compositional variation in TiO2-based flux-cored arc welding fluxes on viscosity, wettability, and electronegativity was studied. The thermo-physical properties of the retrieved fluxes and their relationship with the mechanical properties of the weld zone, including tensile strength and micro-Vickers hardness, after welding were identified. Microstructural observation under similar welding conditions revealed significant grain coarsening at a corrected optical basicity (Λcorr) of 0.62, resulting in reduced strength and hardness due to greater heat transfer. Welding fluxes containing TiO2-based simple structural units should result in greater heat transfer due to the deficiency in complex [AlO4]5-- and [SiO4]4--based structural units, as identified through spectroscopic analyses using fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The electronegativity of the retrieved fluxes was also evaluated since higher electronegativity results in greater absorption of electrons in the arc, resulting in arc condensation towards the center direction. Consequently, deeper penetration could be obtained, where the highest electronegativity was identified to be approximately 0.62 of the corrected optical basicity. Thus, both the thermal conductivity and electronegativity of the welding fluxes were identified to determine the heat transfer phenomenon during flux-cored arc welding.

Repair welding of cast iron coated electrodes

NASA Astrophysics Data System (ADS)

Żuk, M.; Górka, J.; Dojka, R.; Czupryński, A.

2017-08-01

Welding cast iron is a complex production procedure. Repair welding was used to repair damaged or poorly made castings. This is due to a tendency to cracking of the material during welding as well as after it. Welding cast iron can be carried out on hot or on cold. Hot welding requires high heat material and the use of welding material in the form of cast iron. In the case of cold welding, it is possible to use different materials. Mostly used filler metals are nickel and copper based. The work shows the course of research concerning repairmen of ductile iron with arc welding method. For the reparation process four types of ESAB company coated electrodes dedicated for cast iron were used with diameter 3.2 and 4 mm: ES 18-8-6B (4mm), EB 150 (4mm), OK NiCl, EŻM. In the cast iron examined during the testing grooves were made using plasma methods, in order to simulate the removed casting flaws. Then the welding process with coated electrodes was executed. The process utilized low welding current row of 100A, so there would only be a small amount of heat delivered to the heat affected zone (HAZ). Short stitches were made, after welding it was hammered, in order to remove stresses. After the repair welding the part of studies commenced which purpose was finding surface defects using visual testing (VT) and penetration testing (PT). In the second part, a series of macro and microscopic studies were executed witch the purpose of disclosuring the structure. Then the hardness tests for welds cross sections were performed. An important aspect of welding cast iron is the colour of the padding weld after welding, more precisely the difference between the base material and padding weld, the use of different materials extra gives the extra ability to select the best variant. The research of four types of coated electrode was executed, based on the demands the best option in terms of aesthetic, strength and hardness.

Electron beam welding passes initial test

DOE Office of Scientific and Technical Information (OSTI.GOV)

de Sirvy, B.

1979-11-01

Once the new electron-beam welding process is coupled with vertical or J-curve pipelaying techniques, Total-Compagnie Francaise des Petroles (Gestion and Recherches) will be able to offer a system capable of laying up to 36-in. pipe in deep water (1000-9900 ft) at a pace competitive with the best performance of a shallow-water barge: 8200 ft in 24 hr. Electron-beam welding provides the fast, single-station joining needed to make J-curve laying economical. Tests recently demonstrated that this welding technique can join 1.25-in.-wall, 24-in. pipe in less than 3 min; conventional processes require 1-1 1/2 hr.

PARENT Quick Blind Round-Robin Test Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braatz, Brett G.; Heasler, Patrick G.; Meyer, Ryan M.

The U.S. Nuclear Regulatory Commission has established the Program to Assess the Reliability of Emerging Nondestructive Techniques (PARENT) whose goal is to investigate the effectiveness of current and novel nondestructive examination procedures and techniques to find flaws in nickel-alloy welds and base materials. This is to be done by conducting a series of open and blind international round-robin tests on a set of piping components that include large-bore dissimilar metal welds, small-bore dissimilar metal welds, and bottom-mounted instrumentation penetration welds. The blind testing is being conducted in two segments, one is called Quick-Blind and the other is called Blind. Themore » Quick-Blind testing and destructive analysis of the test blocks has been completed. This report describes the four Quick-Blind test blocks used, summarizes their destructive analysis, gives an overview of the nondestructive evaluation (NDE) techniques applied, provides an analysis inspection data, and presents the conclusions drawn.« less

Development of a high power electron beam welding gun with replaceable high voltage feed-through insulators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saha, T.K; Mascarenhas, M.; Kandaswamy, E., E-mail: tanmay@barc.gov.in

Ceramic to metal sealed feed-through insulators are commonly used in electron beam welding gun. The above feed-through insulators are susceptible to failure, as the brazing joints in them are not always very strong. Failure in one of these feed-through could render the complete gun unusable. This problem has already been faced in BARC, which led to the development of the electron gun with replaceable feed through insulators. A 24 kW Electron Beam Welding (EBW) gun with indigenous designed replaceable insulators is fabricated in BARC. Emphasis during the design of the gun had been to reduce the use of imported componentsmore » to zero. This paper describes the design and fabrication of this gun and reports various simulations and tests performed. Beam trajectory of the gun is numerically computed and presented. Weld passes were carried out on stainless steel plates show satisfactory penetrations. (author)« less

Modeling of the Weld Shape Development During the Autogenous Welding Process by Coupling Welding Arc with Weld Pool

NASA Astrophysics Data System (ADS)

Dong, Wenchao; Lu, Shanping; Li, Dianzhong; Li, Yiyi

2010-10-01

A numerical model of the welding arc is coupled to a model for the heat transfer and fluid flow in the weld pool of a SUS304 stainless steel during a moving GTA welding process. The described model avoids the use of the assumption of the empirical Gaussian boundary conditions, and at the same time, provides reliable boundary conditions to analyze the weld pool. Based on the two-dimensional axisymmetric numerical modeling of the argon arc, the heat flux to workpiece, the input current density, and the plasma drag stress are obtained. The arc temperature contours, the distributions of heat flux, and current density at the anode are in fair agreement with the reported experimental results. Numerical simulation and experimental studies to the weld pool development are carried out for a moving GTA welding on SUS304 stainless steel with different oxygen content from 30 to 220 ppm. The calculated result show that the oxygen can change the Marangoni convection from outward to inward direction on the liquid pool surface and make the wide shallow weld shape become narrow deep one. The calculated result for the weld shape and weld D/W ratio agrees well with the experimental one.

Mechanical properties of thin films of laser-welded titanium and their associated welding defects.

PubMed

Wu, Yulu; Xin, Haitao; Zhang, Chunbao; Tang, Zhongbin; Zhang, Zhiyuan; Wang, Weifeng

2014-11-01

The aim of this study was to evaluate the mechanical properties of thin films of laser-welded cast titanium using an interference strain/displacement gauge (ISDG) and to analyze factors that affect laser welding. Dog-bone-shaped small specimens of cast titanium were prepared by wire cutting after they were laser-welded. The specimens were divided into three groups according to the gap distance of the laser weld; the control was non-welded titanium. Small specimens without cast defects detected by X-ray screening were measured by a tensile test machine using ISDG, and stress-strain curves were drawn. Finally, the fracture texture was analyzed. The ultimate tensile strengths (UTSs) of specimens with a gap distance of 0.00, 0.25, and 0.50 mm were 492.16 ± 33.19, 488.09 ± 43.18, and 558.45 ± 10.80 MPa, respectively. There were no significant differences in UTS between the test groups and the control group (p > 0.05). However, the plastic deformation and the percent elongation increased as the gap distance increased. Incomplete penetration defects appeared in groups that had small gap distances, which may have affected the properties of the laser-welded titanium. However, the welding material was still pure titanium. These results suggest that an appropriate gap distance should be maintained to improve the application of dental laser welding.

Safety assessment for In-service Pressure Bending Pipe Containing Incomplete Penetration Defects

NASA Astrophysics Data System (ADS)

Wang, M.; Tang, P.; Xia, J. F.; Ling, Z. W.; Cai, G. Y.

2017-12-01

Incomplete penetration defect is a common defect in the welded joint of pressure pipes. While the safety classification of pressure pipe containing incomplete penetration defects, according to periodical inspection regulations in present, is more conservative. For reducing the repair of incomplete penetration defect, a scientific and applicable safety assessment method for pressure pipe is needed. In this paper, the stress analysis model of the pipe system was established for the in-service pressure bending pipe containing incomplete penetration defects. The local finite element model was set up to analyze the stress distribution of defect location and the stress linearization. And then, the applicability of two assessment methods, simplified assessment and U factor assessment method, to the assessment of incomplete penetration defects located at pressure bending pipe were analyzed. The results can provide some technical supports for the safety assessment of complex pipelines in the future.

A Monte Carlo model for 3D grain evolution during welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodgers, Theron M.; Mitchell, John A.; Tikare, Veena

Welding is one of the most wide-spread processes used in metal joining. However, there are currently no open-source software implementations for the simulation of microstructural evolution during a weld pass. Here we describe a Potts Monte Carlo based model implemented in the SPPARKS kinetic Monte Carlo computational framework. The model simulates melting, solidification and solid-state microstructural evolution of material in the fusion and heat-affected zones of a weld. The model does not simulate thermal behavior, but rather utilizes user input parameters to specify weld pool and heat-affect zone properties. Weld pool shapes are specified by Bezier curves, which allow formore » the specification of a wide range of pool shapes. Pool shapes can range from narrow and deep to wide and shallow representing different fluid flow conditions within the pool. Surrounding temperature gradients are calculated with the aide of a closest point projection algorithm. Furthermore, the model also allows simulation of pulsed power welding through time-dependent variation of the weld pool size. Example simulation results and comparisons with laboratory weld observations demonstrate microstructural variation with weld speed, pool shape, and pulsed-power.« less

A Monte Carlo model for 3D grain evolution during welding

DOE PAGES

Rodgers, Theron M.; Mitchell, John A.; Tikare, Veena

2017-08-04

Welding is one of the most wide-spread processes used in metal joining. However, there are currently no open-source software implementations for the simulation of microstructural evolution during a weld pass. Here we describe a Potts Monte Carlo based model implemented in the SPPARKS kinetic Monte Carlo computational framework. The model simulates melting, solidification and solid-state microstructural evolution of material in the fusion and heat-affected zones of a weld. The model does not simulate thermal behavior, but rather utilizes user input parameters to specify weld pool and heat-affect zone properties. Weld pool shapes are specified by Bezier curves, which allow formore » the specification of a wide range of pool shapes. Pool shapes can range from narrow and deep to wide and shallow representing different fluid flow conditions within the pool. Surrounding temperature gradients are calculated with the aide of a closest point projection algorithm. Furthermore, the model also allows simulation of pulsed power welding through time-dependent variation of the weld pool size. Example simulation results and comparisons with laboratory weld observations demonstrate microstructural variation with weld speed, pool shape, and pulsed-power.« less

Parametric representation of weld fillets using shell finite elements—a proposal based on minimum stiffness and inertia errors

NASA Astrophysics Data System (ADS)

Echer, L.; Marczak, R. J.

2018-02-01

The objective of the present work is to introduce a methodology capable of modelling welded components for structural stress analysis. The modelling technique was based on the recommendations of the International Institute of Welding; however, some geometrical features of the weld fillet were used as design parameters in an optimization problem. Namely, the weld leg length and thickness of the shell elements representing the weld fillet were optimized in such a way that the first natural frequencies were not changed significantly when compared to a reference result. Sequential linear programming was performed for T-joint structures corresponding to two different structural details: with and without full penetration weld fillets. Both structural details were tested in scenarios of various plate thicknesses and depths. Once the optimal parameters were found, a modelling procedure was proposed for T-shaped components. Furthermore, the proposed modelling technique was extended for overlapped welded joints. The results obtained were compared to well-established methodologies presented in standards and in the literature. The comparisons included results for natural frequencies, total mass and structural stress. By these comparisons, it was observed that some established practices produce significant errors in the overall stiffness and inertia. The methodology proposed herein does not share this issue and can be easily extended to other types of structure.

Heat sink effects in variable polarity plasma arc welding

NASA Technical Reports Server (NTRS)

Abdelmessih, Amanie N.

1991-01-01

The Space Shuttle External Tank is fabricated by the variable polarity plasma arc (VPPA) welding process. In VPPA welding, a noble gas, usually argon, is directed through an arc to emerge from the torch as a hot plasma jet. This jet is surrounded by a shielding gas, usually helium, to protect the weld from contamination with air. The high velocity, hot plasma jet completely penetrates the workpiece (resembling a line heat source) when operated in the 'keyhole' mode. The metal melts on touching the side of the jet, as the torch travels in the perpendicular direction to the direction of the jet, and melted metal moves around the plasma jet in the keyhole forming a puddle which solidifies behind the jet. Heat sink effects are observed when there are irregularities in the workpiece configuration, especially, if these irregularities are close to the weld bead. These heat sinks affect the geometry of the weld bead, i.e., in extreme cases they could cause defects such as incomplete fusion. Also, different fixtures seem to have varying heat sink effects. The objective of this research is to study the effect of irregularities in workpiece configuration and fixture differences (heat sink effects) on the weld bead geometry with the ultimate objective to compensate for the heat sink effects and achieve a perfect weld. Experiments were performed on different workpiece geometries and compared to approximate models.

The effect of different rutile electrodes on mechanical properties of underwater wet welded AH-36 steel plates

NASA Astrophysics Data System (ADS)

Winarto, Winarto; Purnama, Dewin; Churniawan, Iwan

2018-04-01

Underwater welding is an important role in the rescue of ships and underwater structures, in case of emergency. In this study, the marine steel plates used are AH-36 steel as parent material. This type of steel is included in the High Strength Low Alloy (HSLA). Electrodes used for welding AH-36 steel plates are commonly the E6013 and E 7024 which are the type of based rutile electrodes. Those electrodes are widely available on the market and they would be compared with the original electrode for underwater which is the type of E7014 with the trade name of Broco UW-CS-1. Welding method used is Shielding Metal Arc Welding (SMAW) with the variation of 5 m and 10 m underwater depth and also varied with the electric current of 120A, 140A and 250A. It was found that hardness value of increased in the area of weld metal and HAZ. HAZ also tends to have the highest hardness compared to both of weld metal and base metal. Non destructive test by radiographed test (RT) on welds showed that there are found welding defects in the form of incomplete penetration on all variations of welding parameters, but there is no porosity defect detected. The results of the hardness tests of underwater wet welded steel plates show that the hardness value of both rutile electrodes (E6013 and E 7024) is apparently similar hardness value compared with the existing commercial electrode (E7014 of Broco UW-CS- 1). The tensile test results of underwater wet welded steel plates show that the use of rutile electrode of E6013 gives a better tensile properties than other rutile electrodes.

Role of the micro/macro structure of welds in crack nucleation and propagation in aerospace aluminum-lithium alloy

NASA Technical Reports Server (NTRS)

Talia, George E.

1996-01-01

Al-Li alloys offer the benefits of increased strength, elastic modulus and lower densities as compared to conventional aluminum alloys. Martin Marietta Laboratories has developed an Al-Li alloy designated 2195 which is designated for use in the cryogenic tanks of the space shuttle. The Variable Polarity Plasma Arc (VPPA) welding process is currently being used to produce these welds [1]. VPPA welding utilizes high temperature ionized gas (plasma) to transfer heat to the workpiece. An inert gas, such as Helium, is used to shield the active welding zone to prevent contamination of the molten base metal with surrounding reactive atmospheric gases. [1] In the Space Shuttle application, two passes of the arc are used to complete a butt-type weld. The pressure of the plasma stream is increased during the first pass to force the arc entirely through the material, a practice commonly referred to as keyholing. Molten metal forms on either side of the arc and surface tension draws this liquid together as the arc passes. 2319 Al alloy filler material may also be fed into the weld zone during this pass. During the second pass, the plasma stream pressure is reduced such that only partial penetration of the base material is obtained. Al 2319 filler material is added during this pass to yield a uniform, fully filled welded joint. This additional pass also acts to alter the grain structure of the weld zone to yield a higher strength joint.

Fatigue flaw growth and NDI evaluation for preventing through cracks in spacecraft tankage structures

NASA Technical Reports Server (NTRS)

Pettit, D. E.; Hoeppner, D. W.

1972-01-01

A program was conducted to determine the fatigue-crack propagation behavior of parent and welded 2219-T87 aluminum alloy sheet under controlled cyclic stress conditions in room temperature air and 300 F air. Specimens possessing an initial surface defect of controlled dimensions were cycled under constant load amplitude until the propagating fatigue crack penetrated the back surface of the specimen. A series of precracked specimens were prepared to determine optimum penetrant, X-ray, ultrasonic, and eddy current nondestructive inspection procedures.

Process Stability of Ultrasonic-Wave-Assisted Gas Metal Arc Welding

NASA Astrophysics Data System (ADS)

Fan, Chenglei; Xie, Weifeng; Yang, Chunli; Lin, Sanbao; Fan, Yangyang

2017-10-01

As a newly developed arc welding method, ultrasonic-wave-assisted arc welding successfully introduced power ultrasound into the arc and weld pool, during which the ultrasonic acts on the top of the arc in the coaxial alignment direction. The advanced process for molten metals can be realized by using an additional ultrasonic field. Compared with the conventional gas metal arc welding (GMAW), the welding arc is compressed, the droplet size is decreased, and the droplet transfer frequency is increased significantly in ultrasonic-wave-assisted GMAW (U-GMAW). However, the stability of the metal transfer has deep influence on the welding quality equally, and the ultrasonic wave effect on the stability of the metal transfer is a phenomenon that is not completely understood. In this article, the stabilities of the short-circuiting transfer process and globular transfer process are studied systematically, and the effect of ultrasonic wave on the metal transfer is analyzed further. The transfer frequency and process stability of the U-GMAW process are much higher than those of the conventional GMAW. Analytical results show that the additional ultrasonic wave is helpful for improving welding stability.

Laser welding of polymers: phenomenological model for a quick and reliable process quality estimation considering beam shape influences

NASA Astrophysics Data System (ADS)

Timpe, Nathalie F.; Stuch, Julia; Scholl, Marcus; Russek, Ulrich A.

2016-03-01

This contribution presents a phenomenological, analytical model for laser welding of polymers which is suited for a quick process quality estimation for the practitioner. Besides material properties of the polymer and processing parameters like welding pressure, feed rate and laser power the model is based on a simple few parameter description of the size and shape of the laser power density distribution (PDD) in the processing zone. The model allows an estimation of the weld seam tensile strength. It is based on energy balance considerations within a thin sheet with the thickness of the optical penetration depth on the surface of the absorbing welding partner. The joining process itself is modelled by a phenomenological approach. The model reproduces the experimentally known process windows for the main process parameters correctly. Using the parameters describing the shape of the laser PDD the critical dependence of the process windows on the PDD shape will be predicted and compared with experiments. The adaption of the model to other laser manufacturing processes where the PDD influence can be modelled comparably will be discussed.

Variable polarity plasma arc welding on the Space Shuttle external tank

NASA Technical Reports Server (NTRS)

Nunes, A. C., Jr.; Bayless, E. O., Jr.; Jones, C. S., III; Munafo, P. M.; Biddle, A. P.; Wilson, W. A.

1984-01-01

Variable polarity plasma arc (VPPA) techniques used at NASA's Marshall Space Flight Center for the fabrication of the Space Shuttle External Tank are presentedd. The high plasma arc jet velocities of 300-2000 m/s are produced by heating the plasma gas as it passes through a constraining orifice, with the plasma arc torch becoming a miniature jet engine. As compared to the GTA jet, the VPPA has the following advantages: (1) less sensitive to contamination, (2) a more symmetrical fusion zone, and (3) greater joint penetration. The VPPA welding system is computerized, operating with a microprocessor, to set welding variables in accordance with set points inputs, including the manipulator and wire feeder, as well as torch control and power supply. Some other VPPA welding technique advantages are: reduction in weld repair costs by elimination of porosity; reduction of joint preparation costs through elimination of the need to scrape or file faying surfaces; reduction in depeaking costs; eventual reduction of the 100 percent-X-ray inspection requirements. The paper includes a series of schematic and block diagrams.

A mathematical model of the chevron-like wave pattern on a weld piece

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dowden, J.; Kapadia, P.

1996-12-31

In welding processes in general the surface of a metallic weld displays a chevron-like pattern. Such a pattern is also clearly seen to be present if welding is carried out using a laser beam. In the welding process a laser beam is directed normally on the metal undergoing translation and usually penetrates it to form a keyhole. The keyhole is surrounded by a molten region, the weld pool. Even if a CO{sub 2} laser is used, there are numerous fluctuations and instabilities that occur, so that the keyhole imposes forcing frequencies on the molten weld pool, additional to vibrations attendantmore » on the process of translation. The weld pool in turn responds by supporting a spectrum of waves of different frequencies involving the natural frequency of the weld pool as well as various forcing frequencies. These waves are surface tension-type capillary waves and previous publications have attempted to model their behavior mathematically, although not all aspects of the problem have always been included. The wave pattern that is manifested in the chevron-like pattern seen on the weld piece is, however, not necessarily identical to the wave pattern present in the weld pool. This is because the chevron-like wave pattern forms as a result of several complicating effects that arise as the weld specimen cools on its surface immediately after the weld has been formed. This process involves the waves on the surface of the weld pool freezing to form the chevron-like wave pattern. A feature that is often ignored is the fact that the waves on the weld pool can only be regarded as irrotational if the translation speed is sufficiently low. This paper describes mathematically the formation of the chevron-like wave pattern based on suitable simplifying assumptions to model the process. The mathematical description of the way in which this chevron-like pattern forms is a step toward a more comprehensive understanding of this process.« less

Ultrasonic Real-Time Quality Monitoring Of Aluminum Spot Weld Process

NASA Astrophysics Data System (ADS)

Perez Regalado, Waldo Josue

The real-time ultrasonic spot weld monitoring system, introduced by our research group, has been designed for the unsupervised quality characterization of the spot welding process. It comprises the ultrasonic transducer (probe) built into one of the welding electrodes and an electronics hardware unit which gathers information from the transducer, performs real-time weld quality characterization and communicates with the robot programmable logic controller (PLC). The system has been fully developed for the inspection of spot welds manufactured in steel alloys, and has been mainly applied in the automotive industry. In recent years, a variety of materials have been introduced to the automotive industry. These include high strength steels, magnesium alloys, and aluminum alloys. Aluminum alloys have been of particular interest due to their high strength-to-weight ratio. Resistance spot welding requirements for aluminum vary greatly from those of steel. Additionally, the oxide film formed on the aluminum surface increases the heat generation between the copper electrodes and the aluminum plates leading to accelerated electrode deterioration. Preliminary studies showed that the real-time quality inspection system was not able to monitor spot welds manufactured with aluminum. The extensive experimental research, finite element modelling of the aluminum welding process and finite difference modeling of the acoustic wave propagation through the aluminum spot welds presented in this dissertation, revealed that the thermodynamics and hence the acoustic wave propagation through an aluminum and a steel spot weld differ significantly. For this reason, the hardware requirements and the algorithms developed to determine the welds quality from the ultrasonic data used on steel, no longer apply on aluminum spot welds. After updating the system and designing the required algorithms, parameters such as liquid nugget penetration and nugget diameter were available in the ultrasonic data acquired during the aluminum welding process. Finally, a fuzzy system was designed to receive these parameters and determine the weld quality.

Application of YAG Laser TIG Arc Hybrid Welding to Thin AZ31B Magnesium Alloy Sheet

NASA Astrophysics Data System (ADS)

Kim, Taewon; Kim, Jongcheol; Hasegawa, Yu; Suga, Yasuo

A magnesium alloy is said to be an ecological material with high ability of recycling and lightweight property. Especially, magnesium alloys are in great demand on account of outstanding material property as a structural material. Under these circumstances, research and development of welding process to join magnesium alloy plates are of great significance for wide industrial application of magnesium. In order to use it as a structure material, the welding technology is very important. TIG arc welding process is the most ordinary process to weld magnesium alloy plates. However, since the heat source by the arc welding process affects the magnesium alloy plates, HAZ of welded joint becomes wide and large distortion often occurs. On the other hand, a laser welding process that has small diameter of heat source seems to be one of the possible means to weld magnesium alloy in view of the qualitative improvement. However, the low boiling point of magnesium generates some weld defects, including porosity and solidification cracking. Furthermore, precise edge preparation is very important in butt-welding by the laser welding process, due to the small laser beam diameter. Laser/arc hybrid welding process that combines the laser beam and the arc is an effective welding process in which these two heat sources influence and assist each other. Using the hybrid welding, a synegistic effect is achievable and the disadvantages of the respective processes can be compensated. In this study, YAG laser/TIG arc hybrid welding of thin magnesium alloy (AZ31B) sheets was investigated. First of all, the effect of the irradiation point and the focal position of laser beam on the quality of a weld were discussed in hybrid welding. Then, it was confirmed that a sound weld bead with sufficient penetration is obtained using appropriate welding conditions. Furthermore, it was made clear that the heat absorption efficiency is improved with the hybrid welding process. Finally, the tensile tests of welded joints were performed, and it was confirmed that they have sufficient mechanical properties. As a result of this study, it is confirmed that, if the appropriate welding conditions are selected, sound welded joints of AZ31B magnesium alloy are obtainable by the YAG laser/TIG arc hybrid welding process.

ARC+(Registered Trademark) and ARC PC Welding Simulators: Teach Welders with Virtual Interactive 3D Technologies

NASA Technical Reports Server (NTRS)

Choquet, Claude

2011-01-01

123 Certification Inc., a Montreal based company, has developed an innovative hands-on welding simulator solution to help build the welding workforce in the most simple way. The solution lies in virtual reality technology, which has been fully tested since the early 90's. President and founder of 123 Certification Inc., Mr. Claude Choquet Ing. Msc. IWE. acts as a bridge between the welding and the programming world. Working in these fields for more than 20 years. he has filed 12 patents world-wide for a gesture control platform with leading edge hardware related to simulation. In the summer of 2006. Mr Choquet was proud to be invited to the annual IIW International Weld ing Congress in Quebec City to launch the ARC+ welding simulator. A 100% virtual reality system and web based training center was developed to simulate multi process. multi-materiaL multi-position and multi pass welding. The simulator is intended to train welding students and apprentices in schools or industries. The welding simulator is composed of a real welding e[eetrode holder (SMAW-GTAW) and gun (GMAW-FCAW). a head mounted display (HMD), a 6 degrees of freedom tracking system for interaction between the user's hands and head. as well as external audio speakers. Both guns and HMD are interacting online and simultaneously. The welding simulation is based on the law of physics and empirical results from detailed analysis of a series of welding tests based on industrial applications tested over the last 20 years. The simulation runs in real-time, using a local logic network to determine the quality and shape of the created weld. These results are based on the orientation distance. and speed of the welding torch and depth of penetration. The welding process and resulting weld bc.1d are displayed in a virtual environment with screenplay interactive training modules. For review. weld quality and recorded process values can be displayed and diagnosed after welding. To help in the le.tming process, a learning curve for each student and each Virtual Welding Class'" can be plotted, for an instructor's review or a required third party evaluation.

49 CFR 178.58 - Specification 4DA welded steel cylinders for aircraft use.

Code of Federal Regulations, 2014 CFR

2014-10-01

..., if water quenched or quenched with a liquid producing a cooling rate in excess of 80 percent of the cooling rate of water, must be inspected by the magnetic particle or dye penetrant method to detect the...

49 CFR 178.58 - Specification 4DA welded steel cylinders for aircraft use.

Code of Federal Regulations, 2012 CFR

2012-10-01

..., if water quenched or quenched with a liquid producing a cooling rate in excess of 80 percent of the cooling rate of water, must be inspected by the magnetic particle or dye penetrant method to detect the...

49 CFR 178.58 - Specification 4DA welded steel cylinders for aircraft use.

Code of Federal Regulations, 2013 CFR

2013-10-01

..., if water quenched or quenched with a liquid producing a cooling rate in excess of 80 percent of the cooling rate of water, must be inspected by the magnetic particle or dye penetrant method to detect the...

Deep-seated intramuscular lipoma penetrates the intercostal muscle

PubMed Central

Hwang, Jinwook; Min, Byoung-Ju; Shin, Jae Seung

2015-01-01

Deep-seated intramuscular lipomas are rare, and most exhibit an infiltrating behavior. This study reports serial radiographs of a lipoma in chest wall muscles which penetrated the intercostal muscle for a 6-year period. Although this lipoma did not involve the parietal pleura, it compressed lung. To the authors’ knowledge, the present study is the first report to show the growth of a deep-seated chest wall lipoma into the thoracic cavity through serial radiographs. We consider the surgical treatment is needed before deep-seated intramuscular chest wall lipoma compress intrathoracic structures. PMID:26623127

Ballistic-Failure Mechanisms in Gas Metal Arc Welds of Mil A46100 Armor-Grade Steel: A Computational Investigation

NASA Astrophysics Data System (ADS)

Grujicic, M.; Snipes, J. S.; Galgalikar, R.; Ramaswami, S.; Yavari, R.; Yen, C.-F.; Cheeseman, B. A.

2014-09-01

In our recent work, a multi-physics computational model for the conventional gas metal arc welding (GMAW) joining process was introduced. The model is of a modular type and comprises five modules, each designed to handle a specific aspect of the GMAW process, i.e.: (i) electro-dynamics of the welding-gun; (ii) radiation-/convection-controlled heat transfer from the electric-arc to the workpiece and mass transfer from the filler-metal consumable electrode to the weld; (iii) prediction of the temporal evolution and the spatial distribution of thermal and mechanical fields within the weld region during the GMAW joining process; (iv) the resulting temporal evolution and spatial distribution of the material microstructure throughout the weld region; and (v) spatial distribution of the as-welded material mechanical properties. In the present work, the GMAW process model has been upgraded with respect to its predictive capabilities regarding the spatial distribution of the mechanical properties controlling the ballistic-limit (i.e., penetration-resistance) of the weld. The model is upgraded through the introduction of the sixth module in the present work in recognition of the fact that in thick steel GMAW weldments, the overall ballistic performance of the armor may become controlled by the (often inferior) ballistic limits of its weld (fusion and heat-affected) zones. To demonstrate the utility of the upgraded GMAW process model, it is next applied to the case of butt-welding of a prototypical high-hardness armor-grade martensitic steel, MIL A46100. The model predictions concerning the spatial distribution of the material microstructure and ballistic-limit-controlling mechanical properties within the MIL A46100 butt-weld are found to be consistent with prior observations and general expectations.

Investigation of dissimilar metal welds by energy-resolved neutron imaging.

PubMed

Tremsin, Anton S; Ganguly, Supriyo; Meco, Sonia M; Pardal, Goncalo R; Shinohara, Takenao; Feller, W Bruce

2016-08-01

A nondestructive study of the internal structure and compositional gradient of dissimilar metal-alloy welds through energy-resolved neutron imaging is described in this paper. The ability of neutrons to penetrate thick metal objects (up to several cm) provides a unique possibility to examine samples which are opaque to other conventional techniques. The presence of Bragg edges in the measured neutron transmission spectra can be used to characterize the internal residual strain within the samples and some microstructural features, e.g. texture within the grains, while neutron resonance absorption provides the possibility to map the degree of uniformity in mixing of the participating alloys and intermetallic formation within the welds. In addition, voids and other defects can be revealed by the variation of neutron attenuation across the samples. This paper demonstrates the potential of neutron energy-resolved imaging to measure all these characteristics simultaneously in a single experiment with sub-mm spatial resolution. Two dissimilar alloy welds are used in this study: Al autogenously laser welded to steel, and Ti gas metal arc welded (GMAW) to stainless steel using Cu as a filler alloy. The cold metal transfer variant of the GMAW process was used in joining the Ti to the stainless steel in order to minimize the heat input. The distributions of the lattice parameter and texture variation in these welds as well as the presence of voids and defects in the melt region are mapped across the welds. The depth of the thermal front in the Al-steel weld is clearly resolved and could be used to optimize the welding process. A highly textured structure is revealed in the Ti to stainless steel joint where copper was used as a filler wire. The limited diffusion of Ti into the weld region is also verified by the resonance absorption.

Weld quality inspection using laser-EMAT ultrasonic system and C-scan method

NASA Astrophysics Data System (ADS)

Yang, Lei; Ume, I. Charles

2014-02-01

Laser/EMAT ultrasonic technique has attracted more and more interests in weld quality inspection because of its non-destructive and non-contact characteristics. When ultrasonic techniques are used to detect welds joining relative thin plates, the dominant ultrasonic waves present in the plates are Lamb waves, which propagate all through the thickness. Traditional Time of Flight(ToF) method loses its power. The broadband nature of laser excited ultrasound plus dispersive and multi-modal characteristic of Lamb waves make the EMAT acquired signals very complicated in this situation. Challenge rises in interpreting the received signals and establishing relationship between signal feature and weld quality. In this paper, the laser/EMAT ultrasonic technique was applied in a C-scan manner to record full wave propagation field over an area close to the weld. Then the effect of weld defect on the propagation field of Lamb waves was studied visually by watching an movie resulted from the recorded signals. This method was proved to be effective to detect the presence of hidden defect in the weld. Discrete wavelet transform(DWT) was applied to characterize the acquired ultrasonic signals and ideal band-pass filter was used to isolate wave components most sensitive to the weld defect. Different interactions with the weld defect were observed for different wave components. Thus this C-Scan method, combined with DWT and ideal band-pass filter, proved to be an effective methodology to experimentally study interactions of various laser excited Lamb Wave components with weld defect. In this work, the method was demonstrated by inspecting a hidden local incomplete penetration in weld. In fact, this method can be applied to study Lamb Wave interactions with any type of structural inconsistency. This work also proposed a ideal filtered based method to effectively reduce the total experimental time.

PWSCC Assessment by Using Extended Finite Element Method

NASA Astrophysics Data System (ADS)

Lee, Sung-Jun; Lee, Sang-Hwan; Chang, Yoon-Suk

2015-12-01

The head penetration nozzle of control rod driving mechanism (CRDM) is known to be susceptible to primary water stress corrosion cracking (PWSCC) due to the welding-induced residual stress. Especially, the J-groove dissimilar metal weld regions have received many attentions in the previous studies. However, even though several advanced techniques such as weight function and finite element alternating methods have been introduced to predict the occurrence of PWSCC, there are still difficulties in respect of applicability and efficiency. In this study, the extended finite element method (XFEM), which allows convenient crack element modeling by enriching degree of freedom (DOF) with special displacement function, was employed to evaluate structural integrity of the CRDM head penetration nozzle. The resulting stress intensity factors of surface cracks were verified for the reliability of proposed method through the comparison with those suggested in the American Society of Mechanical Engineering (ASME) code. The detailed results from the FE analyses are fully discussed in the manuscript.

Fluid flow monitoring device

DOEpatents

McKay, M.D.; Sweeney, C.E.; Spangler, B.S. Jr.

1993-11-30

A flow meter and temperature measuring device are described comprising a tube with a body centered therein for restricting flow and a sleeve at the upper end of the tube to carry several channels formed longitudinally in the sleeve to the appropriate axial location where they penetrate the tube to allow pressure measurements and temperature measurements with thermocouples. The high pressure measurement is made using a channel penetrating the tube away from the body and the low pressure measurement is made at a location at the widest part of the body. An end plug seals the end of the device and holes at its upper end allow fluid to pass from the interior of the tube into a plenum. The channels are made by cutting grooves in the sleeve, the grooves widened at the surface of the sleeve and then a strip of sleeve material is welded to the grooves closing the channels. Preferably the sleeve is packed with powdered graphite before cutting the grooves and welding the strips. 7 figures.

Detection of lack of fusion using opaque additives, phase 1

NASA Technical Reports Server (NTRS)

Cook, J. L.

1972-01-01

Two major problems in welded aluminum spacecraft structure, reliable nondestructive inspection for incomplete weldment penetration and the rapid oxidation of aluminum surfaces left exposed to the atmosphere are investigated. The approach employed to solve both problems was to employ copper as a coating to prevent oxidation of the aluminum and as an opaque additive in the weldment to enhance X-ray detection in the event of incomplete penetration. Both plasma spray and vacuum vapor deposition techniques were evaluated for depositing the copper. A series of welded panels was made using three thicknesses of vacuum-vapor-deposited copper. All weldments were nondestructively inspected by X-ray, then excised into tensile and bend specimens. Mechanical tests were conducted and all data evaluated. It was determined that the vacuum-vapor-deposited coating was superior to a plasma sprayed coating of the same thickness. The vacuum-vapor-deposited coating was more uniform in thickness, provided complete coverage of the aluminum, and was free of cracks and porosity.

Enzyme-triggered size shrink and laser-enhanced NO release nanoparticles for deep tumor penetration and combination therapy.

PubMed

Hu, Chuan; Cun, Xingli; Ruan, Shaobo; Liu, Rui; Xiao, Wei; Yang, Xiaotong; Yang, Yuanyuan; Yang, Chuanyao; Gao, Huile

2018-06-01

Chemotherapy remains restricted by poor drug delivery efficacy due to the heterogenous nature of tumor. Herein, we presented a novel nanoparticle that could not only response to the tumor microenvironment but also modulate it for deep tumor penetration and combination therapy. The intelligent nanoparticle (IDDHN) was engineered by hyaluronidase (HAase)-triggered size shrinkable hyaluronic acid shells, which were modified with NIR laser sensitive nitric oxide donor (HN), small-sized dendrimeric prodrug (IDD) of doxorubicin (DOX) as chemotherapy agent and indocyanine green (ICG) as photothermal agent into a single nanoparticle. IDDHN displayed synergistic deep penetration both in vitro and in vivo, owing to the enzymatically degradable HN shell mediated by HAase and laser-enhanced NO release triggered deep penetration upon strong hyperthermia effect of ICG under the NIR laser irradiation. The therapeutic effect of IDDHN was verified in 4T1 xenograft tumor model, and IDDHN showed a much better antitumor efficiency with few side effects upon NIR laser irradiation. Therefore, the valid of this study might provide a novel tactic for engineering nanoparticles both response to and modulate the tumor microenvironment for improving penetration and heterogeneity distribution of therapeutic agents in tumor. Copyright © 2018 Elsevier Ltd. All rights reserved.

A process model for the heat-affected zone microstructure evolution in duplex stainless steel weldments: Part II. Application to electron beam welding

NASA Astrophysics Data System (ADS)

Hemmer, H.; Grong, Ø.; Klokkehaug, S.

2000-03-01

In the present investigation, a process model for electron beam (EB) welding of different grades of duplex stainless steels (i.e. SAF 2205 and 2507) has been developed. A number of attractive features are built into the original finite element code, including (1) a separate module for prediction of the penetration depth and distribution of the heat source into the plate, (2) adaptive refinement of the three-dimensional (3-D) element mesh for quick and reliable solution of the differential heat flow equation, and (3) special subroutines for calculation of the heat-affected zone (HAZ) microstructure evolution. The process model has been validated by comparison with experimental data obtained from in situ thermocouple measurements and optical microscope examinations. Subsequently, its aptness to alloy design and optimization of welding conditions for duplex stainless steels is illustrated in different numerical examples and case studies pertaining to EB welding of tubular joints.

Hot-wire Laser Welding of Deep and Wide Gaps

NASA Astrophysics Data System (ADS)

Näsström, J.; Frostevarg, J.; Silver, T.

Heavy section Gas Metal Arc Welding (GMAW) usually requires special edge preparation and several passes. One alternative for increased performance is Laser Arc Hybrid Welding (LAHW). For very thick sheets however, imperfections like root drops or solidification cracks can occur. In this study, other techniques are also studied, including multi-pass filling of deep gaps with wire deposition. A laser is then used to melt the filler and base material. The hot- and cold wire laser welding processes are highly sensitive to wire-laser positioning, where controlled melting of the wire is essential. Apart from a comprehensive literature survey, preliminary experiments were also performed in order to find a novel method variant that can successfully fill deep and wide gaps. The method applied uses a defocused laser that generates the melt pool. A resistance heated wire is fed into the melt pool front in a leading position. This is similar to additive manufacturing techniques such as laser direct metal deposition with wire. A layer height of several millimeters can be achieved and rather low laser power can be chosen. The preliminary experiments were observed using high speed imaging and briefly evaluated by visual examination of the resulting beads. Using a defocused laser beam turned out to have two major advantages; 1. It adds heat to the melt pool in a manner that properly fuses the bottom and walls of the base material. 2. It counteracts difficulties due to an irregularly oscillating filler wire. These early results show that this can be a promising technique for joining thick steels with wide gaps.

Medium- and high-pressure gauges and transducers produced by laser welding technology

NASA Astrophysics Data System (ADS)

Daurelio, Giuseppe; Nenci, Fabio; Cinquepalmi, Massimo; Chita, Giuseppe

1998-07-01

Industrial manufacturers produce many types of pressure gauges and transducers according to the applications, for gas or liquid, for high-medium and low pressure ranges. Nowadays the current production technology generally prefers to weld by micro TIG source the metallic corrugated membranes to the gauge or transducer bodies for the products, operating on the low pressure or medium pressure ranges. For the other ones, operating to high pressure range, generally the two components of the transducers are both threaded only and threaded and then circularly welded by micro TIG for the other higher range, till to 1000 bar. In this work the products, operating on the approximately equals 30 divided by 200 bar, are considered. These, when assembled on industrial plants, as an outcome of a non-correct operating sequence, give a 'shifted' electrical signal. This is due to a shift of the 'zero electrical signal' that unbalances the electrical bridge - thin layer sensor - that is the sensitive part of the product. Moreover, for the same problem, often some mechanical settlings of the transducer happen during the first pressure semi-components, with an increasing of the product manufacturing costs. In light of all this, the above referred, in this work the whole transducer has been re-designed according to the specific laser welding technology requirements. On the new product no threaded parts exist but only a circular laser welding with a full penetration depth about 2.5 divided by 3 mm high. Three different alloys have been tested according to the applications and the mechanical properties requested to the transducer. By using a 1.5 KW CO2 laser system many different working parameters have been evaluated for correlating laser parameters to the penetration depths, crown wides, interaction laser-materia times, mechanical and metallurgical properties. Moreover during the laser welding process the measurements of the maximum temperature, reached by the transducer top, has been read and recorded. At least some transducers, before the usual destructive testings, have been undertaken to many pressure test cycles to verify any pressure drops, the transducer sealing and the total quality of the new product.

Study on the activated laser welding of ferritic stainless steel with rare earth elements yttrium

NASA Astrophysics Data System (ADS)

Wang, Yonghui; Hu, Shengsun; Shen, Junqi

2015-10-01

The ferritic stainless steel SUS430 was used in this work. Based on a multi-component activating flux, composed of 50% ZrO2, 12.09 % CaCO3, 10.43 % CaO, and 27.49 % MgO, a series of modified activating fluxes with 0.5%, 1%, 2%, 5%, 10%, 15%, and 20% of rare earth (RE) element yttrium (Y) respectively were produced, and their effects on the weld penetration (WP) and corrosion resistant (CR) property were studied. Results showed that RE element Y hardly had any effects on increasing the WP. In the FeCl3 spot corrosion experiment, the corrosion rates of almost all the samples cut from welded joints turned out to be greater than the parent metal (23.51 g/m2 h). However, there was an exception that the corrosion rate of the sample with 5% Y was only 21.96 g/m2 h, which was even better than parent metal. The further Energy Dispersive Spectrometer (EDS) test showed the existence of elements Zr, Ca, O, and Y in the molten slag near the weld seam while none of them were found in the weld metal, indicating the direct transition of element from activating fluxes to the welding seam did not exist. It was known that certain composition of activating fluxes effectively restrain the loss of Cr element in the process of laser welding, and as a result, the CR of welded joints was improved.

The research of PSD location method in micro laser welding fields

NASA Astrophysics Data System (ADS)

Zhang, Qiue; Zhang, Rong; Dong, Hua

2010-11-01

In the field of micro laser welding, besides the special requirement in the parameter of lasers, the locating in welding points accurately is very important. The article adopt position sensitive detector (PSD) as hard core, combine optic system, electric circuits and PC and software processing, confirm the location of welding points. The signal detection circuits adopt the special integrate circuit H-2476 to process weak signal. It is an integrated circuit for high-speed, high-sensitivity optical range finding, which has stronger noiseproof feature, combine digital filter arithmetic, carry out repair the any non-ideal factors, increasing the measure precision. The amplifier adopt programmable amplifier LTC6915. The system adapt two dimension stepping motor drive the workbench, computer and corresponding software processing, make sure the location of spot weld. According to different workpieces to design the clamps. The system on-line detect PSD 's output signal in the moving processing. At the workbench moves in the X direction, the filaments offset is detected dynamic. Analyze the X axes moving sampling signal direction could be estimate the Y axes moving direction, and regulate the Y axes moving values. The workbench driver adopt A3979, it is a stepping motor driver with insert transducer and operate easily. It adapts the requirement of location in micro laser welding fields, real-time control to adjust by computer. It can be content up 20 μm's laser micro welding requirement on the whole. Using laser powder cladding technology achieve inter-penetration welding of high quality and reliability.

NIR-laser tissue welding in an in vivo guinea pig animal model

NASA Astrophysics Data System (ADS)

Sriramoju, Vidyasagar; Savage, Howard E.; Katz, A.; Chakraverty, Rahul; Budansky, Yuri; Podder, Rakhi; Davatgarzadeh, Naghmeh; Kartazayev, Uladzimir; Rosen, Richard B.; Alfano, R. R.

2008-02-01

Near infrared laser tissue welding (LTW) is achieved by subjecting the closely approximated surgically incised tissues to a laser beam at a wavelength that is absorbed by water in the tissue. Full thickness welds are accomplished with optimum laser power and penetration depths appropriate for the thickness of welded tissues. No extrinsic cross-linking or bonding materials are used. The absorbed laser energy increases the entropy of collagen in the tissue. In LTW, tissue water temperatures transiently rises to approximately 60° C, causing partial denaturing of collagen and other structural proteins due to breaking of hydrogen bonds, electrostatic interactions and some interchain covalent bonds for a short duration of time. This is followed by cross linking of proteins on either side of weld line, with reformation of the above mentioned bonds as the tissue cools, resulting in the formation of water tight full thickness welds. In this study, a cw fiber laser emitting at 1455 nm, corresponding to absorption by a water vibrational overtone, is used for in vivo LTW of surgical incisions made in the skin of guinea pigs under general anesthesia. The tensile strength and healing rates of the welded incisions are compared to suturing of similar incisions. Laser parameters, including power, scanning rates, exposure area, and exposure duration, are optimized to reduce thermal damage while maintaining tensile strength.

Simulation of a manual electric-arc welding in a working gas pipeline. 2. Numerical investigation of the temperature-stress distribution in the wall of a gas pipe

NASA Astrophysics Data System (ADS)

Baikov, V. I.; Gishkelyuk, I. A.; Rus', A. M.; Sidorovich, T. V.; Tonkonogov, B. A.

2010-11-01

A numerical simulation of the action of the current experienced by an electric arc and the rate of gas flow in a pipe of a cross-country gas pipeline on the depth of penetration of the electric arc into the wall of this pipe and on the current and residual stresses arising in the pipe material in the process of electric-arc welding of nonthrough cavity-like defects in it has been carried out for gas pipes with walls of different thickness.

Plate interface rheological switches during subduction infancy: Control on slab penetration and metamorphic sole formation

NASA Astrophysics Data System (ADS)

Agard, P.; Yamato, P.; Soret, M.; Prigent, C.; Guillot, S.; Plunder, A.; Dubacq, B.; Chauvet, A.; Monié, P.

2016-10-01

Subduction infancy corresponds to the first few million years following subduction initiation, when slabs start their descent into the mantle. It coincides with the transient (yet systematic) transfer of material from the top of the slab to the upper plate, as witnessed by metamorphic soles welded beneath obducted ophiolites. Combining structure-lithology-pressure-temperature-time data from metamorphic soles with flow laws derived from experimental rock mechanics, this study highlights two main successive rheological switches across the subduction interface (mantle wedge vs. basalts, then mantle wedge vs. sediments; at ∼800 °C and ∼600 °C, respectively), during which interplate mechanical coupling is maximized by the existence of transiently similar rheologies across the plate contact. We propose that these rheological switches hinder slab penetration and are responsible for slicing the top of the slab and welding crustal pieces (high- then low-temperature metamorphic soles) to the base of the mantle wedge during subduction infancy. This mechanism has implications for the rheological properties of the crust and mantle (and for transient episodes of accretion/exhumation of HP-LT rocks in mature subduction systems) and highlights the role of fluids in enabling subduction to overcome the early resistance to slab penetration.

A Computational approach in optimizing process parameters of GTAW for SA 106 Grade B steel pipes using Response surface methodology

NASA Astrophysics Data System (ADS)

Sumesh, A.; Sai Ramnadh, L. V.; Manish, P.; Harnath, V.; Lakshman, V.

2016-09-01

Welding is one of the most common metal joining techniques used in industry for decades. As in the global manufacturing scenario the products should be more cost effective. Therefore the selection of right process with optimal parameters will help the industry in minimizing their cost of production. SA 106 Grade B steel has a wide application in Automobile chassis structure, Boiler tubes and pressure vessels industries. Employing central composite design the process parameters for Gas Tungsten Arc Welding was optimized. The input parameters chosen were weld current, peak current and frequency. The joint tensile strength was the response considered in this study. Analysis of variance was performed to determine the statistical significance of the parameters and a Regression analysis was performed to determine the effect of input parameters over the response. From the experiment the maximum tensile strength obtained was 95 KN reported for a weld current of 95 Amp, frequency of 50 Hz and peak current of 100 Amp. With an aim of maximizing the joint strength using Response optimizer a target value of 100 KN is selected and regression models were optimized. The output results are achievable with a Weld current of 62.6148 Amp, Frequency of 23.1821 Hz, and Peak current of 65.9104 Amp. Using Die penetration test the weld joints were also classified in to 2 categories as good weld and weld with defect. This will also help in getting a defect free joint when welding is performed using GTAW process.

Bladder welding in rats using controlled temperature CO2 laser system.

PubMed

Lobik, L; Ravid, A; Nissenkorn, I; Kariv, N; Bernheim, J; Katzir, A

1999-05-01

Laser tissue welding has potential advantages over conventional suture closure of surgical wounds. It is a noncontact technique that introduces no foreign body and limits the possibility of infections and complications. The closure could be immediately watertight and the procedure may be less traumatic, faster and easier. In spite of these positives laser welding has not yet been approved for wide use. The problem in the clinical implementation of this technique arises from the difficulty in defining the conditions under which a highly reliable weld is formed. We have assumed that the successful welding of tissues depends on the ability to monitor and control the surface temperature during the procedure, thereby avoiding underheating or overheating. The purpose of this work was to develop a laser system for reliable welding of urinary tract tissues under good temperature control. We have developed a "smart" laser system that is capable of a dual role: transmitting CO2 laser power for tissue heating, and noncontact (radiometric) temperature monitoring and control. Bladder opening (cystotomy) was performed in 38 rats. Thirty-three animals underwent laser welding. In 5 rats (control group) the bladder wound was closed with one layer of continuous 6-0 dexon sutures. Reliable welding was obtained when the surface temperature was kept at 71 + 5C. Quality of weld was controlled immediately after operation. The rats were sacrificed on days 2, 10 and 30 for histological study. Bladder closure using the laser welding system was successful in 31/33 (94%) animals. Histological examination revealed an excellent welding and healing of the tissue. Efficiency of laser welding of urinary bladder in rats was confirmed by high survival rate and quality of scar that was demonstrated by clinical and histological examinations. In the future, optimal laser welding conditions will be studied in larger animals, using CO2 lasers and other lasers, with deeper radiation penetration into tissues.

Real-Time Penetrating Particle Analyzer (PAN)

NASA Astrophysics Data System (ADS)

Wu, X.; Ambrosi, G.; Bertucci, B.

2018-02-01

The PAN can measure penetrating particles with great precision to study energetic particles, solar activities, and the origin and propagation of cosmic rays. The real-time monitoring of penetrating particles is crucial for deep space human travel.

Interfacial Characterization of Dissimilar Joints Between Al/Mg/Al-Trilayered Clad Sheet to High-Strength Low-Alloy Steel

NASA Astrophysics Data System (ADS)

Macwan, A.; Jiang, X. Q.; Chen, D. L.

2015-07-01

Magnesium (Mg) alloys are increasingly used in the automotive and aerospace sectors to reduce vehicle weight. Al/Mg/Al tri-layered clad sheets are deemed as a promising alternative to improve the corrosion resistance and formability of Mg alloys. The structural application of Al/Mg/Al tri-layered clad sheets inevitably involves welding and joining in the multi-material vehicle body manufacturing. This study aimed to characterize the bonding interface microstructure of the Al/Mg/Al-clad sheet to high-strength low-alloy steel with and without Zn coating using ultrasonic spot welding at different levels of welding energy. It was observed that the presence of Zn coating improved the bonding at the interface due to the formation of Al-Zn eutectic structure via enhanced diffusion. At a higher level of welding energy, characteristic flow patterns of Zn into Al-clad layer were observed with an extensive penetration mainly along some high angle grain boundaries. The dissimilar joints without Zn coating made at a high welding energy of 800 J failed partially from the Al/Fe weld interface and partially from the Al/Mg clad interface, while the joints with Zn coating failed from the Al/Mg clad interface due to the presence of brittle Al12Mg17 phase.

Effect of laser welding process on the microstructure, mechanical properties and residual stresses in Ti-5Al-2.5Sn alloy

NASA Astrophysics Data System (ADS)

Junaid, Massab; Khan, Fahd Nawaz; Rahman, Khalid; Baig, Mirza Nadeem

2017-12-01

Pulsed Nd-YAG laser was employed in bead on plate configuration for welding of 1.6 mm thick Ti-5Al-2.5Sn alloy sheet. The effect of laser processing parameters on the weld pool shape, pulse overlap, oxide formation, and microstructure were studied using scanning electron and optical microscope. It was found out that laser peak power had a significant influence on the FZ oxygen contents and grain size whereas, both peak power and heat input per unit length were important in defining the weld pool shape. Processing parameters for full penetration welds with acceptable joint properties and low oxygen contents were selected for further study in terms of residual stresses and mechanical properties. Formation of acicular α and α‧ martensite in fusion and heat affected zone, led to an increase in microhardness by about 55 HV0.2 as compared to base metal. Induced residual stresses were found to be significantly less than the yield strength resulting in plate deformation less than 1 mm. Transverse residual stresses present at different depths below the surface tend to counter effect each other resulting in tensile strength of welded specimen becoming nearly equal to that of the base metal.

Closure of skin incisions by 980-nm diode laser welding.

PubMed

Gulsoy, Murat; Dereli, Zeynep; Tabakoglu, Hasim O; Bozkulak, Ozguncem

2006-04-01

A 980-nm diode laser is proposed to be an alternative welding laser in dermatology due to its optimal penetration in tissue. An in vivo predosimetry study was done to estimate the optimal laser energy delivery conditions (6 W, 400 ms). Next, in vivo experiments were comparatively performed to examine healing of wounds closed either with suture or laser welding. One-centimeter-long, full-thickness incisions were done on the dorsal side of Wistar rats. Wounds were surgically removed at 1, 4, 7, 14, and 21 days postoperatively. Macroscopic examinations showed that welding had minimal scarring and a fine quality healing. According to histological (hematoxylin and eosin staining) results, change of epidermal thickness and granulation tissue formation through 21 days of healing period showed similarities in both methods. Epidermal thickness of welded wounds decreased from 62.46+/-6.87 microm (first day) to 36.49+/-0.92 microm (21st day) and that of sutured wounds decreased from 62.94+/-13.53 microm (first day) to 37.88+/-7.41 microm (21st day). At day 14, epidermal thickness of sutured wounds (61.20+/-6.60 microm) were higher than welded wounds (49.69+/-6.31 microm) (p<0.05). Besides, granulation values were greater for the sutured wounds but the difference was statistically significant (p<0.05) only for the seventh day (197,190.29+/-.89,554.96 microm(2) for sutured wounds, 138,433.1+/-51,077.17 microm(2) for welded wounds). Those differences indicate a faster recovery with laser welding. It is concluded that tissue welding with a 980-nm diode laser can be a good candidate for tissue welding applications with accelerated and improved healing, but further investigations are in progress for clinical use.

Effect of plasma welding parameters on the flexural strength of Ti-6Al-4V alloy.

PubMed

Lyra e Silva, João Paulo; Fernandes Neto, Alfredo Júlio; Raposo, Luís Henrique Araújo; Novais, Veridiana Resende; de Araujo, Cleudmar Amaral; Cavalcante, Luisa de Andrade Lima; Simamoto Júnior, Paulo Cezar

2012-01-01

The aim of this study was to assess the effect of different plasma arc welding parameters on the flexural strength of titanium alloy beams (Ti-6Al-4V). Forty Ti-6Al-4V and 10 NiCr alloy beam specimens (40 mm long and 3.18 mm diameter) were prepared and divided into 5 groups (n=10). The titanium alloy beams for the control group were not sectioned or subjected to welding. Groups PL10, PL12, and PL14 contained titanium beams sectioned and welded at current 3 A for 10, 12 or 14 ms, respectively. Group NCB consisted of NiCr alloy beams welded using conventional torch brazing. After, the beams were subjected to a three-point bending test and the values obtained were analyzed to assess the flexural strength (MPa). Statistical analysis was carried out by one-way ANOVA and Tukey's HSD test at 0.05 confidence level. Significant difference was verified among the evaluated groups (p<0.001), with higher flexural strength for the control group (p<0.05). No significant differences was observed among the plasma welded groups (p>0.05). The NCB group showed the lowest flexural strength, although it was statistically similar to the PL 14 group (p>0.05). The weld depth penetration was not significantly different among the plasma welded groups (p=0.05). Three representative specimens were randomly selected to be evaluated under scanning electron microcopy. The composition of the welded regions was analyzed by energy dispersive X-ray spectroscopy. This study provides an initial set of parameters supporting the use of plasma welding during fabrication of titanium alloy dental frameworks.

Tracking ocean heat uptake during the surface warming hiatus

DOE PAGES

Liu, Wei; Xie, Shang -Ping; Lu, Jian

2016-03-30

Ocean heat uptake is observed to penetrate deep during the recent hiatus1,2,3 of global warming in the Atlantic and Southern Ocean. This has been suggested to indicate that the two regions are the driver of the surface warming hiatus4. We show that the deep heat penetration in the Atlantic and Southern Ocean is not unique to the hiatus but common to the past four decades including the 1970s-90s epoch of accelerated surface warming. Our analyses of a large ensemble simulation5 confirm the deep heat penetration in the Atlantic and Southern Ocean in ensemble members with or without surface warming hiatusmore » in the early 21th century. During the past four decades, the global ocean heat content (OHC) of upper 1500m is dominated by a warming trend, and the depth of anthropogenic heat penetration merely reflects the depth of the mean meridional overturning circulation in the basin. Furthermore, the heat penetration depth is not a valid basis to infer the hiatus mechanism.« less

Tracking ocean heat uptake during the surface warming hiatus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Wei; Xie, Shang -Ping; Lu, Jian

Ocean heat uptake is observed to penetrate deep during the recent hiatus1,2,3 of global warming in the Atlantic and Southern Ocean. This has been suggested to indicate that the two regions are the driver of the surface warming hiatus4. We show that the deep heat penetration in the Atlantic and Southern Ocean is not unique to the hiatus but common to the past four decades including the 1970s-90s epoch of accelerated surface warming. Our analyses of a large ensemble simulation5 confirm the deep heat penetration in the Atlantic and Southern Ocean in ensemble members with or without surface warming hiatusmore » in the early 21th century. During the past four decades, the global ocean heat content (OHC) of upper 1500m is dominated by a warming trend, and the depth of anthropogenic heat penetration merely reflects the depth of the mean meridional overturning circulation in the basin. Furthermore, the heat penetration depth is not a valid basis to infer the hiatus mechanism.« less

Dual-drug nanomedicine with hydrophilic F127-modified magnetic nanocarriers assembled in amphiphilic gelatin for enhanced penetration and drug delivery in deep tumor tissue.

PubMed

Lai, Yen-Ho; Chiang, Chih-Sheng; Kao, Tzu-Hsun; Chen, San-Yuan

2018-01-01

Deep penetration of large-sized drug nanocarriers into tumors is important to improve the efficacy of tumor therapy. In this study, we developed a size-changeable "Trojan Horse" nanocarrier (THNC) composed of paclitaxel (PTX)-loaded Greek soldiers (GSs; ~20 nm) assembled in an amphiphilic gelatin matrix with hydrophilic losartan (LST) added. With amphiphilic gelatin matrix cleavage by matrix metalloproteinase-2, LST showed fast release of up to 60% accumulated drug at 6 h, but a slow release kinetic (~20%) was detected in the PTX from the GSs, indicating that THNCs enable controllable release of LST and PTX drugs for penetration into the tumor tissue. The in vitro cell viability in a 3D tumor spheroid model indicated that the PTX-loaded GSs liberated from THNCs showed deeper penetration as well as higher cytotoxicity, reducing a tumor spheroid to half its original size and collapsing the structure of the tumor microenvironment. The results demonstrate that the THNCs with controlled drug release and deep penetration of magnetic GSs show great potential for cancer therapy.

Mechanical Properties of Laser Beam Welded Ultra-high Strength Chromium Steel with Martensitic Microstructure

NASA Astrophysics Data System (ADS)

Dahmen, Martin; Janzen, Vitalij; Lindner, Stefan; Wagener, Rainer

A new class of steels is going to be introduced into sheet manufacturing. Stainless ferritic and martensitic steels open up opportunities for sheet metal fabrication including hot stamping. A strength of up to 2 GPa at a fracture strain of 15% can be attained. Welding of these materials became apparently a challenge. Energy-reduced welding methods with in-situ heat treatment are required in order to ensure the delicate and complex heat control. Laser beam welding is the joining technique of choice to supply minimum heat input to the fusion process and to apply an efficient heat control. For two application cases, production of tailored blanks in as-rolled condition and welding in assembly in hot stamped conditions, welding processes have been developed. The welding suitability is shown in metallurgical investigations of the welds. Crash tests based on the KSII concept as well as fatigue tests prove the applicability of the joining method. For the case of assembly also joining with deep drawing and manganese boron steel was taken into consideration. The strength of the joint is determined by the weaker partner but can benefit from its ductility.

Hypervelocity penetration against mechanical properties of target materials

NASA Astrophysics Data System (ADS)

Kamarudin, Khairul Hasni; Abdullah, Mohamad Faizal; Zaidi, Ahmad Mujahid Ahmad; Nor, Norazman M.; Ismail, Ariffin; Yusof, Mohammed Alias; Hilmi, Ahmad Humaizi

2018-02-01

This paper study the mechanical properties behavior of metal plates against hypervelocity penetration caused by shaped charge. Five different materials were used as target specimen fabricated from welded stacks of material plates, namely Rolled Homogeneous Armor (RHA), Hardox-500, mild steel, aluminum and brass. Specimens had undergone an initial monolithic test consist of tensile tests and microstructure observations, followed by series of hydrodynamics penetration blast tests using shape charge mechanism. Results from blast test shows that the least penetrated specimen is RHA (58mm) followed by Hardox-500 (92 mm), mild steel (110 mm), Brass (155 mm) and aluminum 238 mm). Comparing these with the specimen yield strength from the tensile test results shows that Hardox-500 has higher yield strength (Sy) followed by RHA, mild steel, brass and aluminum, which are 1370 MPa, 1320 MPa, 280,221 respectively, which are not inversely proportional to the penetration. However, the ultimate tensile strength (Sut) where the RHA were the highest followed by Hardox-500, mild steel, brass and aluminum, were inversely proportional with the depth of penetration. The penetration results also show consistence relation with energy absorption.

Improving the corrosion properties of magnesium AZ31 alloy GTA weld metal using microarc oxidation process

NASA Astrophysics Data System (ADS)

Siva Prasad, M.; Ashfaq, M.; Kishore Babu, N.; Sreekanth, A.; Sivaprasad, K.; Muthupandi, V.

2017-05-01

In this work, the morphology, phase composition, and corrosion properties of microarc oxidized (MAO) gas tungsten arc (GTA) weldments of AZ31 alloy were investigated. Autogenous gas tungsten arc welds were made as full penetration bead-on-plate welding under the alternating-current mode. A uniform oxide layer was developed on the surface of the specimens with MAO treatment in silicate-based alkaline electrolytes for different oxidation times. The corrosion behavior of the samples was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy. The oxide film improved the corrosion resistance substantially compared to the uncoated specimens. The sample coated for 10 min exhibited better corrosion properties. The corrosion resistance of the coatings was concluded to strongly depend on the morphology, whereas the phase composition and thickness were concluded to only slightly affect the corrosion resistance.

Optimization of cladding parameters for resisting corrosion on low carbon steels using simulated annealing algorithm

NASA Astrophysics Data System (ADS)

Balan, A. V.; Shivasankaran, N.; Magibalan, S.

2018-04-01

Low carbon steels used in chemical industries are frequently affected by corrosion. Cladding is a surfacing process used for depositing a thick layer of filler metal in a highly corrosive materials to achieve corrosion resistance. Flux cored arc welding (FCAW) is preferred in cladding process due to its augmented efficiency and higher deposition rate. In this cladding process, the effect of corrosion can be minimized by controlling the output responses such as minimizing dilution, penetration and maximizing bead width, reinforcement and ferrite number. This paper deals with the multi-objective optimization of flux cored arc welding responses by controlling the process parameters such as wire feed rate, welding speed, Nozzle to plate distance, welding gun angle for super duplex stainless steel material using simulated annealing technique. Regression equation has been developed and validated using ANOVA technique. The multi-objective optimization of weld bead parameters was carried out using simulated annealing to obtain optimum bead geometry for reducing corrosion. The potentiodynamic polarization test reveals the balanced formation of fine particles of ferrite and autenite content with desensitized nature of the microstructure in the optimized clad bead.

Development of Inspection for Friction Stir Welds for Rocket Fuel Tanks

NASA Technical Reports Server (NTRS)

Russell, Samuel S.

2012-01-01

During development of the Ares I weld processes nondestructive and destructive testing were used to identify and characterize defects that occurred. These defects were named and character noted. This catalogue of defects and characteristics was then used to develop inspection methods for Self Reacting Friction Stir Welds (SR ]FSW) and Conventional Friction Stir Welds (C ]FSW). Dye penetrant, eddy current, x ]radiography, single element ultrasonic, and phased array ultrasonic (PAUT) inspection procedures were developed to target the expected defects. Once the method procedure was developed a comparison was performed to allow for selection of the best inspection method. Tests of the effectiveness of the inspection were performed on purposely fabricated flawed specimens and electrodischarge machined notches. The initial test results prompted a revisit of the PAUT procedure and a redesign of the inspection. Subsequent testing showed that a multi ]angle PAUT inspection resulted in better detection capability. A discussion of the most effective orientations of the PAUT transducer will be presented. Also, the implementation of the inspection on production hardware will be presented. In some cases the weld tool is used as the transducer manipulator and in some cases a portable scanner is used

Global and Local Mechanical Properties of Autogenously Laser Welded Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Cao, Xinjin; Kabir, Abu Syed H.; Wanjara, Priti; Gholipour, Javad; Birur, Anand; Cuddy, Jonathan; Medraj, Mamoun

2014-03-01

Ti-6Al-4V sheets, 3.2-mm in thickness, were butt welded using a continuous wave 4 kW Nd:YAG laser welding system. The effect of two main process parameters, laser power and welding speed, on the joint integrity was characterized in terms of the joint geometry, defects, microstructure, hardness, and tensile properties. In particular, a digital image correlation technique was used to determine the local tensile properties of the welds. It was determined that a wide range of heat inputs can be used to fully penetrate the Ti-6Al-4V butt joints during laser welding. At high laser power levels, however, significant defects such as underfill and porosity, can occur and cause marked degradation in the joint integrity and performance. At low welding speeds, however, significant porosity occurs due to its growth and the potential collapse of instable keyholes. Intermediate to relatively high levels of heat input allow maximization of the joint integrity and performance by limiting the underfill and porosity defects. In considering the effect of the two main defects on the joint integrity, the underfill defect was found to be more damaging to the mechanical performance of the weldment than the porosity. Specifically, it was determined that the maximum tolerable underfill depth for Ti-6Al-4V is approximately 6 pct of the workpiece thickness, which is slightly stricter than the value of 7 pct specified in AWS D17.1 for fusion welding in aerospace applications. Hence, employing optimized laser process parameters allows the underfill depth to be maintained within the tolerable limit (6 pct), which in turn prevents degradation in both the weld strength and ductility. To this end, the ability to maintain weld ductility in Ti-6Al-4V by means of applying a high energy density laser welding process presents a significant advantage over conventional arc welding for the assembly of aerospace components.

29 CFR 1926.352 - Fire prevention.

Code of Federal Regulations, 2011 CFR

2011-07-01

... penetration of sparks or heat transfer may introduce a fire hazard to an adjacent area, the same precautions... confine the heat, sparks, and slag, and to protect the immovable fire hazards from them. (c) No welding...-consuming device. (h) Except when the contents are being removed or transferred, drums, pails, and other...

Characterization of nitrogen effects in high energy density weldments of Nitronic 40 stainless steel

NASA Astrophysics Data System (ADS)

Pfeif, Erik Andrew

Variation in the welding environment for laser beam welding and electron beam welding can alter the resulting weld chemical composition, microstructure and therefore the mechanical properties. The room temperature mechanical properties of Nitronic 40 stainless steel weld metal from three different heats containing 0.24, 0.28, and 0.31 wt. pct. nitrogen were evaluated for continuous mode Ytterbium doped Fiber laser welds conducted with argon and nitrogen shielding gases, and for electron beam welds. The bulk nitrogen contents were monitored and the resulting properties were then related to microstructural features measured using Electron BackScatter Diffraction (EBSD). Traditional tensile testing of weld metal is conducted on composite tensile bars consisting of base metal and weld metal often leading to failure in the region adjacent to the weld due to strength mismatch at the weld interface. These tests provide composite strength but do not specifically determine the mechanical properties of the heterogeneous weld metal. In this research, microtensile testing was conducted to characterize the properties of the different regions of the weld. The microtensile testing procedures were developed using two geometries of tensile bars measuring the properties through the thickness of 3 mm full penetration welds. In all cases an increase in the strength of the weld metal was found to occur, though the electron beam welds exhibited a higher strength than the laser welds. Standard predictive equations were found to under-predict the strength of the laser welds, even when average grain size or intercept distances were measured. The contribution of nitrogen solid solution strengthening was consistent at approximately 513 MPa per wt. pct. nitrogen. Similar cooling rates and heat inputs allow for a comparison across high energy density welding techniques. Though microstructural differences through the depth of the weld metal were observed as nitrogen vaporization decreased and cooling rates increased. Vermicular ferrite, lacy ferrite and intercellular ferrite were identified as predicted in prior research done on high nitrogen austenitic stainless steels. The resulting laser weld metal microstructures were analyzed with EBSD for grain size and ferrite content measurements, while grain boundary character was determined for a Hansen model used for multi-scale mechanical property measurements. It was found that the low angle grain boundaries were the predominant microstructural feature responsible for strengthening within the weld metal and that this contribution must be accounted for when predicting yield strength of the weld metal.

Microstructure and Ductility-Dip Cracking Susceptibility of Circumferential Multipass Dissimilar Weld Between 20MND5 and Z2CND18-12NS with Ni-Base Filler Metal 52

NASA Astrophysics Data System (ADS)

Qin, Renyao; Duan, Zhaoling; He, Guo

2013-10-01

The large circumferential multipass dissimilar weld between 20MND5 steel and Z2CND18-12NS stainless steel welded with FM52 filler material was investigated in terms of the diluted composition, the grain boundary precipitation, and the ductility-dip cracking (DDC) susceptibility of the weld. The diluted composition of the weld is composed of 37 to 47 pct Ni, 21 to 24 pct Cr, and 28 to 40 pct Fe, which are inhomogeneous along the depth and over the width of the deep weld. The carbon content has a distribution in the region of the surface weld from a high level (~0.20 pct) in the zone near 20MND5 steel to a normal level (~0.03 pct) in the zone near Z2CND18-12NS stainless steel. The carbon distribution is corresponding to the grain boundary carbides. The minimum threshold strains for DDC occur in the temperature range of 1223 K to 1323 K (950 °C to 1050 °C), which are 0.5, 0.35, and 0.4 pct for the root weld, middle region, and the surface weld, respectively. The dissimilar weld has the largest susceptibility to the DDC compared to the filler metal 52 and the Inconel 690.

Comparison between ray-tracing and physical optics for the computation of light absorption in capillaries--the influence of diffraction and interference.

PubMed

Qin, Yuan; Michalowski, Andreas; Weber, Rudolf; Yang, Sen; Graf, Thomas; Ni, Xiaowu

2012-11-19

Ray-tracing is the commonly used technique to calculate the absorption of light in laser deep-penetration welding or drilling. Since new lasers with high brilliance enable small capillaries with high aspect ratios, diffraction might become important. To examine the applicability of the ray-tracing method, we studied the total absorptance and the absorbed intensity of polarized beams in several capillary geometries. The ray-tracing results are compared with more sophisticated simulations based on physical optics. The comparison shows that the simple ray-tracing is applicable to calculate the total absorptance in triangular grooves and in conical capillaries but not in rectangular grooves. To calculate the distribution of the absorbed intensity ray-tracing fails due to the neglected interference, diffraction, and the effects of beam propagation in the capillaries with sub-wavelength diameter. If diffraction is avoided e.g. with beams smaller than the entrance pupil of the capillary or with very shallow capillaries, the distribution of the absorbed intensity calculated by ray-tracing corresponds to the local average of the interference pattern found by physical optics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stine, Andrew Martin; Pierce, Stanley W.; Moniz, Paul F.

The welding equipment used for welding iridium containers (clads) at Los Alamos National Laboratory is twenty five years old and is undergoing an upgrade. With the upgrade, there is a requirement for requalification of the welding process, and the opportunity for process improvement. Testing of the new system and requalification will require several welds on iridium test parts and clads, and any efforts to improve the process will add to the need for iridium parts. The extreme high cost of iridium imposes a severe limitation on the extent of test welding that can be done. The 2 inch diameter, 0.027more » inch thick, iridium blank disc that the clad cup is formed from, is useful for initial weld trials, but it costs $5000. The development clad sets needed for final tests and requalification cost $15,000 per set. A solution to iridium cost issue would be to do the majority of the weld development on a less expensive surrogate metal with similar weld characteristics. One such metal is molybdenum. Since its melting index (melting temperature x thermal conductivity) is closest to iridium, welds on molybdenum should be similar in size for a given weld power level. Molybdenum is inexpensive; a single 2 inch molybdenum disc costs only $9. In order to evaluate molybdenum as a surrogate for iridium, GTA welds were first developed to provide full penetration on 0.030 inch thick molybdenum discs at speeds of 20, 25, and 30 inches per minute (ipm). These weld parameters were then repeated on the standard 0.027 inch thick iridium blanks. The top surface and bottom surface (root) width and grain structure of the molybdenum and iridium welds were compared, and similarities were evident between the two metals. Due to material and thickness differences, the iridium welds were approximately 35% wider than the molybdenum welds. A reduction in iridium weld current of 35% produce welds slightly smaller than the molybdenum welds yet showed that current could be scaled according to molybdenum/iridium weld width ratio to achieve similar welds. Further weld trials using various thicknesses of molybdenum determined that 0.024 inch thick molybdenum material would best match the 0.027 inch thick iridium in achieving comparable welds when using the same welding parameters. Across the range of welding speeds, the characteristic weld pool shape and solidification grain structure in the two materials was also similar. With the similarity of welding characteristics confirmed, and the appropriate thickness of molybdenum determined, it has been concluded that the use of molybdenum discs and tube sections will greatly expand the weld testing opportunities prior to iridium weld qualification« less

Long-term Pavement Performance Program (LTPP) data analysis support : National Pooled Fund Study TPF-5(013). Effects of multiple freeze cycles and deep frost penetration on pavement performance and cost

DOT National Transportation Integrated Search

2006-11-01

The objectives of this study are to: (1) quantify the effects of frost penetration on pavement performance in climates with deep sustained frost as compared to environments with multiple freeze-thaw cycles, (2) investigate the effect that local adapt...

Multi-focus beam shaping of high power multimode lasers

NASA Astrophysics Data System (ADS)

Laskin, Alexander; Volpp, Joerg; Laskin, Vadim; Ostrun, Aleksei

2017-08-01

Beam shaping of powerful multimode fiber lasers, fiber-coupled solid-state and diode lasers is of great importance for improvements of industrial laser applications. Welding, cladding with millimetre scale working spots benefit from "inverseGauss" intensity profiles; performance of thick metal sheet cutting, deep penetration welding can be enhanced when distributing the laser energy along the optical axis as more efficient usage of laser energy, higher edge quality and reduction of the heat affected zone can be achieved. Building of beam shaping optics for multimode lasers encounters physical limitations due to the low beam spatial coherence of multimode fiber-coupled lasers resulting in big Beam Parameter Products (BPP) or M² values. The laser radiation emerging from a multimode fiber presents a mixture of wavefronts. The fiber end can be considered as a light source which optical properties are intermediate between a Lambertian source and a single mode laser beam. Imaging of the fiber end, using a collimator and a focusing objective, is a robust and widely used beam delivery approach. Beam shaping solutions are suggested in form of optics combining fiber end imaging and geometrical separation of focused spots either perpendicular to or along the optical axis. Thus, energy of high power lasers is distributed among multiple foci. In order to provide reliable operation with multi-kW lasers and avoid damages the optics are designed as refractive elements with smooth optical surfaces. The paper presents descriptions of multi-focus optics as well as examples of intensity profile measurements of beam caustics and application results.

Microstructure Characterization of Fiber Laser Welds of S690QL High-Strength Steels

NASA Astrophysics Data System (ADS)

Li, Baoming; Xu, Peiquan; Lu, Fenggui; Gong, Hongying; Cui, Haichao; Liu, Chuangen

2018-02-01

The use of fiber laser welding to join S690QL steels has attracted interest in the field of construction and assembly. Herein, 13-mm-thick S690QL welded joints were obtained without filler materials using the fiber laser. The as-welded microstructures and the impact energies of the joints were characterized and measured using electron microscopy in conjunction with high-resolution transmission electron images, X-ray diffraction, and impact tests. The results indicated that a single-sided welding technique could be used to join S690QL steels up to a thickness of 12 mm (fail to fuse the joint in the root) when the laser power is equal to 12 kW (scan speed 1 m/min). Double-side welding technique allows better weld penetration and better control of heat distribution. Observation of the samples showed that the fusion zone exhibited bainitic and martensitic microstructures with increased amounts of martensites (Ms) compared with the base materials. Also, the grains in the fusion zone increased in coarseness as the heat input was increased. The fusion zone exhibited increased hardness (397 HV0.2) while exhibiting a simultaneous decrease in the impact toughness. The maximum impact energy value of 26 J was obtained from the single-side-welded sample, which is greater than those obtained from the double-side-welded samples (maximum of 18 J). Many more dislocations and plastic deformations were found in the fusion zone than the heat-affected zone in the joint, which hardened the joints and lowered the impact toughness. The microstructures characterized by FTEM-energy-dispersive X-ray spectrometer also exhibited laths of M, as well as stacking faults and dislocations featuring high-density, interfacial structure ledges that occur between the high-angle grain boundaries and the M and bainite.

Modeling macro-and microstructures of Gas-Metal-Arc Welded HSLA-100 steel

NASA Astrophysics Data System (ADS)

Yang, Z.; Debroy, T.

1999-06-01

Fluid flow and heat transfer during gas-metal-arc welding (GMAW) of HSLA-100 steel were studied using a transient, three-dimensional, turbulent heat transfer and fluid flow model. The temperature and velocity fields, cooling rates, and shape and size of the fusion and heat-affected zones (HAZs) were calculated. A continuous-cooling-transformation (CCT) diagram was computed to aid in the understanding of the observed weld metal microstructure. The computed results demonstrate that the dissipation of heat and momentum in the weld pool is significantly aided by turbulence, thus suggesting that previous modeling results based on laminar flow need to be re-examined. A comparison of the calculated fusion and HAZ geometries with their corresponding measured values showed good agreement. Furthermore, “finger” penetration, a unique geometric characteristic of gas-metal-arc weld pools, could be satisfactorily predicted from the model. The ability to predict these geometric variables and the agreement between the calculated and the measured cooling rates indicate the appropriateness of using a turbulence model for accurate calculations. The microstructure of the weld metal consisted mainly of acicular ferrite with small amounts of bainite. At high heat inputs, small amounts of allotriomorphic and Widmanstätten ferrite were also observed. The observed microstructures are consistent with those expected from the computed CCT diagram and the cooling rates. The results presented here demonstrate significant promise for understanding both macro-and microstructures of steel welds from the combination of the fundamental principles from both transport phenomena and phase transformation theory.

A novel spatter detection algorithm based on typical cellular neural network operations for laser beam welding processes

NASA Astrophysics Data System (ADS)

Nicolosi, L.; Abt, F.; Blug, A.; Heider, A.; Tetzlaff, R.; Höfler, H.

2012-01-01

Real-time monitoring of laser beam welding (LBW) has increasingly gained importance in several manufacturing processes ranging from automobile production to precision mechanics. In the latter, a novel algorithm for the real-time detection of spatters was implemented in a camera based on cellular neural networks. The latter can be connected to the optics of commercially available laser machines leading to real-time monitoring of LBW processes at rates up to 15 kHz. Such high monitoring rates allow the integration of other image evaluation tasks such as the detection of the full penetration hole for real-time control of process parameters.

Investigation of dissimilar metal welds by energy-resolved neutron imaging

DOE PAGES

Tremsin, Anton S.; Ganguly, Supriyo; Meco, Sonia M.; ...

2016-06-09

A nondestructive study of the internal structure and compositional gradient of dissimilar metal-alloy welds through energy-resolved neutron imaging is described in this paper. The ability of neutrons to penetrate thick metal objects (up to several cm) provides a unique possibility to examine samples which are opaque to other conventional techniques. The presence of Bragg edges in the measured neutron transmission spectra can be used to characterize the internal residual strain within the samples and some microstructural features, e.g. texture within the grains, while neutron resonance absorption provides the possibility to map the degree of uniformity in mixing of the participatingmore » alloys and intermetallic formation within the welds. In addition, voids and other defects can be revealed by the variation of neutron attenuation across the samples. This paper demonstrates the potential of neutron energy-resolved imaging to measure all these characteristics simultaneously in a single experiment with sub-mm spatial resolution. Two dissimilar alloy welds are used in this study: Al autogenously laser welded to steel, and Ti gas metal arc welded (GMAW) to stainless steel using Cu as a filler alloy. The cold metal transfer variant of the GMAW process was used in joining the Ti to the stainless steel in order to minimize the heat input. The distributions of the lattice parameter and texture variation in these welds as well as the presence of voids and defects in the melt region are mapped across the welds. The depth of the thermal front in the Al–steel weld is clearly resolved and could be used to optimize the welding process. As a result, a highly textured structure is revealed in the Ti to stainless steel joint where copper was used as a filler wire. The limited diffusion of Ti into the weld region is also verified by the resonance absorption.« less

Investigation of dissimilar metal welds by energy-resolved neutron imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tremsin, Anton S.; Ganguly, Supriyo; Meco, Sonia M.

A nondestructive study of the internal structure and compositional gradient of dissimilar metal-alloy welds through energy-resolved neutron imaging is described in this paper. The ability of neutrons to penetrate thick metal objects (up to several cm) provides a unique possibility to examine samples which are opaque to other conventional techniques. The presence of Bragg edges in the measured neutron transmission spectra can be used to characterize the internal residual strain within the samples and some microstructural features, e.g. texture within the grains, while neutron resonance absorption provides the possibility to map the degree of uniformity in mixing of the participatingmore » alloys and intermetallic formation within the welds. In addition, voids and other defects can be revealed by the variation of neutron attenuation across the samples. This paper demonstrates the potential of neutron energy-resolved imaging to measure all these characteristics simultaneously in a single experiment with sub-mm spatial resolution. Two dissimilar alloy welds are used in this study: Al autogenously laser welded to steel, and Ti gas metal arc welded (GMAW) to stainless steel using Cu as a filler alloy. The cold metal transfer variant of the GMAW process was used in joining the Ti to the stainless steel in order to minimize the heat input. The distributions of the lattice parameter and texture variation in these welds as well as the presence of voids and defects in the melt region are mapped across the welds. The depth of the thermal front in the Al–steel weld is clearly resolved and could be used to optimize the welding process. As a result, a highly textured structure is revealed in the Ti to stainless steel joint where copper was used as a filler wire. The limited diffusion of Ti into the weld region is also verified by the resonance absorption.« less

Investigation of dissimilar metal welds by energy-resolved neutron imaging

PubMed Central

Tremsin, Anton S.; Ganguly, Supriyo; Meco, Sonia M.; Pardal, Goncalo R.; Shinohara, Takenao; Feller, W. Bruce

2016-01-01

A nondestructive study of the internal structure and compositional gradient of dissimilar metal-alloy welds through energy-resolved neutron imaging is described in this paper. The ability of neutrons to penetrate thick metal objects (up to several cm) provides a unique possibility to examine samples which are opaque to other conventional techniques. The presence of Bragg edges in the measured neutron transmission spectra can be used to characterize the internal residual strain within the samples and some microstructural features, e.g. texture within the grains, while neutron resonance absorption provides the possibility to map the degree of uniformity in mixing of the participating alloys and intermetallic formation within the welds. In addition, voids and other defects can be revealed by the variation of neutron attenuation across the samples. This paper demonstrates the potential of neutron energy-resolved imaging to measure all these characteristics simultaneously in a single experiment with sub-mm spatial resolution. Two dissimilar alloy welds are used in this study: Al autogenously laser welded to steel, and Ti gas metal arc welded (GMAW) to stainless steel using Cu as a filler alloy. The cold metal transfer variant of the GMAW process was used in joining the Ti to the stainless steel in order to minimize the heat input. The distributions of the lattice parameter and texture variation in these welds as well as the presence of voids and defects in the melt region are mapped across the welds. The depth of the thermal front in the Al–steel weld is clearly resolved and could be used to optimize the welding process. A highly textured structure is revealed in the Ti to stainless steel joint where copper was used as a filler wire. The limited diffusion of Ti into the weld region is also verified by the resonance absorption. PMID:27504075

Langley Research Center Standard for the Evaluation of Socket Welds

NASA Technical Reports Server (NTRS)

Berry, R. F., Jr.

1985-01-01

A specification utilized for the nondestructive evaluation of socket type pipe joints at Langley Research Center (LaRC) is discussed. The scope of hardware shall include, but is not limited to, all common pipe fittings: tees, elbows, couplings, caps, and so forth, socket type flanges, unions, and valves. In addition, the exterior weld of slip on flanges shall be inspected using this specification. At the discretion of the design engineer, standard practice engineer, Fracture Mechanics Engineering Section, Pressure Systems Committee, or other authority, four nondestructive evaluation techniques may be utilized exclusively, or in combination, to inspect socket type welds. These techniques are visual, radiographic, magnetic particle, and dye penetrant. Under special circumstances, other techniques (such as eddy current or ultrasonics) may be required and their application shall be guided by the appropriate sections of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (B&PVC).

Effect of Steel Galvanization on the Microstructure and Mechanical Performances of Planar Magnetic Pulse Welds of Aluminum and Steel

NASA Astrophysics Data System (ADS)

Avettand-Fènoël, M.-N.; Khalil, C.; Taillard, R.; Racineux, G.

2018-07-01

For the first time, planar joints between pure aluminum and galvanized or uncoated DP450 steel joints have been developed via magnetic pulse welding. Both present a wavy interface. The microstructure of the interfacial zone differs according to the joint. With uncoated steel, the interface is composed of discrete 2.5- µm-thick FeAl3 intermetallic compounds and Fe penetration lamellae, whereas the interface of the pure Al-galvanized steel joint is bilayered and composed of a 10-nm-thick (Al)Zn solid solution and a few micrometers thick aggregate of Al- and Zn-based grains, arranged from the Al side to the Zn coating. Even if the nature of the interfacial zone differs with or without the steel coating, both welds present rather similar maximum tensile forces and ductility in shear lap testing.

Evaluation of ultrasonics and optimized radiography for 2219-T87 aluminum weldments

NASA Technical Reports Server (NTRS)

Clotfelter, W. N.; Hoop, J. M.; Duren, P. C.

1975-01-01

Ultrasonic studies are described which are specifically directed toward the quantitative measurement of randomly located defects previously found in aluminum welds with radiography or with dye penetrants. Experimental radiographic studies were also made to optimize techniques for welds of the thickness range to be used in fabricating the External Tank of the Space Shuttle. Conventional and innovative ultrasonic techniques were applied to the flaw size measurement problem. Advantages and disadvantages of each method are discussed. Flaw size data obtained ultrasonically were compared to radiographic data and to real flaw sizes determined by destructive measurements. Considerable success was achieved with pulse echo techniques and with 'pitch and catch' techniques. The radiographic work described demonstrates that careful selection of film exposure parameters for a particular application must be made to obtain optimized flaw detectability. Thus, film exposure techniques can be improved even though radiography is an old weld inspection method.

Effect of Steel Galvanization on the Microstructure and Mechanical Performances of Planar Magnetic Pulse Welds of Aluminum and Steel

NASA Astrophysics Data System (ADS)

Avettand-Fènoël, M.-N.; Khalil, C.; Taillard, R.; Racineux, G.

2018-05-01

For the first time, planar joints between pure aluminum and galvanized or uncoated DP450 steel joints have been developed via magnetic pulse welding. Both present a wavy interface. The microstructure of the interfacial zone differs according to the joint. With uncoated steel, the interface is composed of discrete 2.5-µm-thick FeAl3 intermetallic compounds and Fe penetration lamellae, whereas the interface of the pure Al-galvanized steel joint is bilayered and composed of a 10-nm-thick (Al)Zn solid solution and a few micrometers thick aggregate of Al- and Zn-based grains, arranged from the Al side to the Zn coating. Even if the nature of the interfacial zone differs with or without the steel coating, both welds present rather similar maximum tensile forces and ductility in shear lap testing.

Estimation of regional pulmonary deposition and exposure for fumes from SMAW and GMAW mild and stainless steel consumables.

PubMed

Hewett, P

1995-02-01

The particle size distributions and bulk fume densities for mild steel and stainless steel welding fumes generated using two welding processes (shielded metal arc welding [SMAW] and gas metal arc welding [GMAW]) were used in mathematical models to estimate regional pulmonary deposition (the fraction of each fume expected to deposit in each region of the pulmonary system) and regional pulmonary exposure (the fraction of each fume expected to penetrate to each pulmonary region and would be collected by a particle size-selective sampling device). Total lung deposition for GMAW fumes was estimated at 60% greater than that of SMAW fumes. Considering both the potential for deposition and the fume specific surface areas, it is likely that for equal exposure concentrations GMAW fumes deliver nearly three times the particle surface area to the lungs as SMAW fumes. This leads to the hypothesis that exposure to GMAW fumes constitutes a greater pulmonary hazard than equal exposure to SMAW fumes. The implications of this hypothesis regarding the design of future health studies of welders is discussed.

Literature Review: Weldability of Iridium DOP-26 Alloy for General Purpose Heat Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burgardt, Paul; Pierce, Stanley W.

The basic purpose of this paper is to provide a literature review relative to fabrication of the General Purpose Heat Source (GPHS) that is used to provide electrical power for deep space missions of NASA. The particular fabrication operation to be addressed here is arc welding of the GPHS encapsulation. A considerable effort was made to optimize the fabrication of the fuel pellets and of other elements of the encapsulation; that work will not be directly addressed in this paper. This report consists of three basic sections: 1) a brief description of the GPHS will be provided as background informationmore » for the reader; 2) mechanical properties and the optimization thereof as relevant to welding will be discussed; 3) a review of the arc welding process development and optimization will be presented. Since the welding equipment must be upgraded for future production, some discussion of the historical establishment of relevant welding variables and possible changes thereto will also be discussed.« less

Tensile Behavior of Electron Beam-Welded and Post-Weld Vacuum-Annealed Nb-10% Hf-1% Ti Refractory Alloy Weldments

NASA Astrophysics Data System (ADS)

Anil Kumar, V.; Gupta, R. K.; Venkateswaran, T.; Ram Kumar, P.

2018-02-01

Nb-10% Hf-1% Ti refractory alloy is a high performance material extensively used for high temperature applications. Electron beam welding is one of the most widely used techniques to join refractory and reactive alloys. Bigger sizes of nozzles for rocket propulsion applications can be either made through deep drawing and flow turning route or by roll bending and welding route both using sheets/plates as input material for fabrication. The latter is a more economical option for mass production of the hardware using such exotic and expensive alloys. In view of this, both as-welded (AW) coupon and weld plus post-weld vacuum-annealed (AW + VA) coupon have been prepared to study their mechanical behavior. It has been observed that tensile strength and ductility have not been reduced in both these conditions vis-à-vis the base metal, confirming weld efficiency of the alloy to be 100%. Microhardness is found to be 150-160 VHN in the base metal and 200-225 VHN in the weld fusion zone in AW condition, which became uniform (145-155 VHN) throughout the weldment in AW + VA condition. Microstructure of the weldment in AW condition is found to be consisting of grains solidified by epitaxial mode from base metal toward the weld centre. In AW + VA condition, improvement in tensile elongation is observed, which is found to be due to the presence of homogenized grains/more uniform microstructure near the heat-affected zone as compared to the steep gradient in grain size in different zones in the weld in AW condition.

Targeted Mesoporous Iron Oxide Nanoparticles-Encapsulated Perfluorohexane and a Hydrophobic Drug for Deep Tumor Penetration and Therapy.

PubMed

Su, Yu-Lin; Fang, Jen-Hung; Liao, Chia-Ying; Lin, Chein-Ting; Li, Yun-Ting; Hu, Shang-Hsiu

2015-01-01

A magneto-responsive energy/drug carrier that enhances deep tumor penetration with a porous nano-composite is constructed by using a tumor-targeted lactoferrin (Lf) bio-gate as a cap on mesoporous iron oxide nanoparticles (MIONs). With a large payload of a gas-generated molecule, perfluorohexane (PFH), and a hydrophobic anti-cancer drug, paclitaxel (PTX), Lf-MIONs can simultaneously perform bursting gas generation and on-demand drug release upon high-frequency magnetic field (MF) exposure. Biocompatible PFH was chosen and encapsulated in MIONs due to its favorable phase transition temperature (56 °C) and its hydrophobicity. After a short-duration MF treatment induces heat generation, the local pressure increase via the gasifying of the PFH embedded in MION can substantially rupture the three-dimensional tumor spheroids in vitro as well as enhance drug and carrier penetration. As the MF treatment duration increases, Lf-MIONs entering the tumor spheroids provide an intense heat and burst-like drug release, leading to superior drug delivery and deep tumor thermo-chemo-therapy. With their high efficiency for targeting tumors, Lf-MIONs/PTX-PFH suppressed subcutaneous tumors in 16 days after a single MF exposure. This work presents the first study of using MF-induced PFH gasification as a deep tumor-penetrating agent for drug delivery.

Targeted Mesoporous Iron Oxide Nanoparticles-Encapsulated Perfluorohexane and a Hydrophobic Drug for Deep Tumor Penetration and Therapy

PubMed Central

Su, Yu-Lin; Fang, Jen-Hung; Liao, Chia-Ying; Lin, Chein-Ting; Li, Yun-Ting; Hu, Shang-Hsiu

2015-01-01

A magneto-responsive energy/drug carrier that enhances deep tumor penetration with a porous nano-composite is constructed by using a tumor-targeted lactoferrin (Lf) bio-gate as a cap on mesoporous iron oxide nanoparticles (MIONs). With a large payload of a gas-generated molecule, perfluorohexane (PFH), and a hydrophobic anti-cancer drug, paclitaxel (PTX), Lf-MIONs can simultaneously perform bursting gas generation and on-demand drug release upon high-frequency magnetic field (MF) exposure. Biocompatible PFH was chosen and encapsulated in MIONs due to its favorable phase transition temperature (56 °C) and its hydrophobicity. After a short-duration MF treatment induces heat generation, the local pressure increase via the gasifying of the PFH embedded in MION can substantially rupture the three-dimensional tumor spheroids in vitro as well as enhance drug and carrier penetration. As the MF treatment duration increases, Lf-MIONs entering the tumor spheroids provide an intense heat and burst-like drug release, leading to superior drug delivery and deep tumor thermo-chemo-therapy. With their high efficiency for targeting tumors, Lf-MIONs/PTX-PFH suppressed subcutaneous tumors in 16 days after a single MF exposure. This work presents the first study of using MF-induced PFH gasification as a deep tumor-penetrating agent for drug delivery. PMID:26379789

Laser-assisted corneal welding in cataract surgery: retrospective study.

PubMed

Menabuoni, Luca; Pini, Roberto; Rossi, Francesca; Lenzetti, Ivo; Yoo, Sonia H; Parel, Jean-Marie

2007-09-01

To evaluate the efficacy of laser welding to close corneal wounds in cataract surgery. Department of Ophthalmology, Hospital of Misericordia e Dolce, Prato, Italy. This retrospective nonrandomized interventional case series included 20 eyes of 20 patients. All eyes had cataract with visual acuity worse than 20/200. Ten patients had phacoemulsification surgery, and 10 had extracapsular cataract extraction (ECCE). Surgeries were followed by laser-assisted closure of the corneal wounds by diode laser welding of the stroma using a technique established in animal models. Preoperative and postoperative (1, 3, 7, 30, and 90 days) astigmatism, level of inflammation, Seidel testing, and endothelial cell counts were obtained. There were minor differences in preoperative and postoperative astigmatism except in 1 eye in the ECCE group. The Seidel test showed no wound leakage during the follow-up examinations, and endothelial cell loss was similar to that published for standard surgical cataract procedures. No collateral effects of the laser welding were detected, nor was postoperative inflammation. Astigmatism was slightly affected by the use of laser welding for corneal wound closure after phacoemulsification and ECCE. The laser-assisted corneal sealing procedure was rapid and safe and could serve as an alternative to corneal suturing, with significant potential applications for the closure of longer incisions, such as those used in penetrating keratoplasty.

Manufacturing and assembly of IWS support rib and lower bracket for ITER vacuum vessel

NASA Astrophysics Data System (ADS)

Laad, R.; Sarvaiya, Y.; Pathak, H. A.; Raval, J. R.; Choi, C. H.

2017-04-01

ITER Vacuum Vessel (VV) is made of double walls connected by ribs structure and flexible housings. Space between these walls is filled up with In Wall Shielding (IWS) blocks to (1) shield neutrons streaming out of plasma and (2) reduce toroidal magnetic field ripple. These blocks will be connected to the VV through a supporting structure of Support Rib (SR) and Lower Bracket (LB) assembly. SR and LB are two independent components manufactured from SS 316L(N)-IG, Total 1584 support ribs and 3168 lower bracket of different sizes and shapes will be manufactured for the IWS. Two lower brackets will be welded with one support rib to make an assembly. The welding between SR and LB is a full penetration welding. Total 1584 assemblies of different sizes and shapes will be manufactured. Sufficient experience gained from manufacturing and testing of mock ups, final manufacturing of IWS support rib and lower bracket has been started at the site of IWS manufacturer M/s. Avasarala Technologies Limited (ATL). This paper will describe, optimization of water jet cutting speed on IWS material, selection criteria for K type weld joint, unique features of fixture of assembly, manufacturing of Mock ups, and welding processes with NDTs.

Transitional behaviour of thickness effects in shipbuilding materials (MS plate)

NASA Astrophysics Data System (ADS)

Mahmud, S. M. Ikhtiar; Razib, Amirul Hasan; Rahman, Md. Rabab Raiyatur

2017-12-01

Majority of the crack propagation in ships and offshore structures are caused due to fatigue. Previously, it was known that fatigue strength of notched specimen is dependent on size, but recently it came to light that fatigue strength of some welded joints depends on the thickness. Much investigation is done on the fatigue growth of welded joints. Fatigue often results in fracture accidents, which starts from the sites of structural discontinuities because of the reason that they may induce local stress concentrations. Structural discontinuities include notches, holes, sharp corners, and weld defects. Weld defects include undercut, porosity, lack of fusion, slag inclusion, incomplete weld root penetration, and misalignments. In order to investigate the effects of plate thickness on fatigue strength, semi-elliptical side notches (U and V shaped) in plates are studied in the present research. First consider a simple problem of crack emanating from notches in plates where the solution of stress intensity factor is given by an empirical formula so that the thickness effect on fatigue strength can easily be investigated for a variety of geometrical parameters. The present study aims to investigate the transitional behaviour of thickness effect in plates on fatigue strength. In order to calculate the stress, finite element analysis is carried by using ANSYS.

Modeling macro-and microstructures of gas-metal-arc welded HSLA-100 steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Z.; Debroy, T.

1999-06-01

Fluid flow and heat transfer during gas-metal-arc welding (GMAW) of HSLA-100 steel were studied using a transient, three-dimensional, turbulent heat transfer and fluid flow model. The temperature and velocity fields, cooling rates, and shape and size of the fusion and heat-affected zones (HAZs) were calculated. A continuous-cooling-transformation (CCT) diagram was computed to aid in the understanding of the observed weld metal microstructure. The computed results demonstrate that the dissipation of heat and momentum in the weld pool is significantly aided by turbulence,m thus suggesting that previous modeling results based on laminar flow need to be re-examined. A comparison of themore » calculated fusion and HAZ geometries with their corresponding measured values showed good agreement. Furthermore, finger penetration, a unique geometric characteristic of gas-metal-arc weld pools, could be satisfactorily predicted from the model. The ability to predict these geometric variables and the agreement between the calculated and the measured cooling rates indicate the appropriateness of using a turbulence model for accurate calculations. The microstructure of the weld metal consisted mainly of acicular ferrite with small amounts of bainite. At high heat inputs, small amounts of allotriomorphic and Widmanstaetten ferrite were also observed. The observed microstructures are consistent with those expected from the computed CCT diagram and the cooling rates. The results presented here demonstrate significant promise for understanding both macro-and microstructures of steel welds from the combination of the fundamental principles from both transport phenomena and phase transformation theory.« less

Task IV: Groundshock-Induced Hydrogeologic Response: Volume 2. Hydrologic Response of Deep Based Systems to Blast Loading

DTIC Science & Technology

1994-09-01

north-south. Width of the cap rock is approximately 1.5 miles, length about 3 miles and area about 4.4 square miles. According to Thordarson (1965...The volcanic tuffs making up the mesa are of moderately recent (Miocene) to very recent (Pliocene) origin. Thordarson (1965) identifies 11 layered tuff...various degrees of welded or partially welded tuff can be formed during cooling. The tuff units identified by Thordarson (1965) making up Rainier

Simulator Studies of the Deep Stall

NASA Technical Reports Server (NTRS)

White, Maurice D.; Cooper, George E.

1965-01-01

Simulator studies of the deep-stall problem encountered with modern airplanes are discussed. The results indicate that the basic deep-stall tendencies produced by aerodynamic characteristics are augmented by operational considerations. Because of control difficulties to be anticipated in the deep stall, it is desirable that adequate safeguards be provided against inadvertent penetrations.

Tungsten Inert Gas and Friction Stir Welding Characteristics of 4-mm-Thick 2219-T87 Plates at Room Temperature and -196 °C

NASA Astrophysics Data System (ADS)

Lei, Xuefeng; Deng, Ying; Yin, Zhimin; Xu, Guofu

2014-06-01

2219-T87 aluminum alloy is widely used for fabricating liquid rocket propellant storage tank, due to its admirable cryogenic property. Welding is the dominant joining method in the manufacturing process of aerospace components. In this study, the tungsten inert gas welding and friction stir welding (FSW) characteristics of 4-mm-thick 2219-T87 alloy plate at room temperature (25 °C) and deep cryogenic temperature (-196 °C) were investigated by property measurements and microscopy methods. The studied 2219 base alloy exhibits a low strength plane anisotropy and excellent room temperature and cryogenic mechanical properties. The ultimate tensile strength values of TIG and FSW welding joints can reach 265 and 353 MPa at room temperature, and 342 and 438 MPa at -196 °C, respectively. The base metal consists of elongated deformed grains and many nano-scaled θ (Al2Cu) aging precipitates. Fusion zone and heat-affected zone (HAZ) of the TIG joint are characterized by coarsening dendritic grains and equiaxed recrystallized grains, respectively. The FSW-welded joint consists of the weld nugget zone, thermo-mechanically affected zone (TMAZ), and HAZ. In the weld nugget zone, a micro-scaled sub-grain structure is the main microstructure characteristic. The TMAZ and HAZ are both characterized by coarsened aging precipitates and elongated deformed grains. The excellent FSW welding properties are attributed to the preservation of the working structures and homogenous chemical compositions.

Alternative acceptance criteria of girth weld defects in cross country pipelines. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denys, R.M.; Lefevre, T.

1997-06-01

The failure behaviour of defective girth welds in large diameter pipe lines was assessed using radiographic and mechanised ultrasonic inspection, small scale (tensile, hardness, Charpy and CTOD) and wide plate tests. The specimens were taken from girth welds in API 5LX70 pipe of 1219 mm (48 inches) in diameter by 8,0 mm (0,323 inch) and 13,3 mm (0,524 inch) wall. The test welds were made with the SMAW (8 welds) and GMAW (9 welds) welding processes. Upon completion of the non-destructive tests, 96 curved wide plate specimens were tested to destruction under tensile load. Testing was performed at low temperaturemore » (-50{degrees}C/-58{degrees}F). Defect type, defect position and size were determined from photographs of the fracture face and macro sections (defect characterisation and sizing). In total, 290 typical surface breaking and embedded defects in SMAW or GMAW girth welds have been evaluated. The vast majority of these defects were grossly out of tolerance with respect to current weld quality (workmanship) acceptance levels. To allow the defect tolerance to be determined, the failure strains and stresses were correlated with a defect length determined for an equivalent 3 mm (0, 118 inch) deep defect. This target depth was chosen to represent the average height of one weld pass. The results of this approach have been compared to wall thickness, current workmanship and the EPRG Tier 2 defect limit for planar defects. The defect lengths were derived for rectangular, parabolic and elliptical defect representations.« less

Optimization of Deep Drilling Performance - Development and Benchmark Testing of Advanced Diamond Product Drill Bits & HP/HT Fluids to Significantly Improve Rates of Penetration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alan Black; Arnis Judzis

2005-09-30

This document details the progress to date on the OPTIMIZATION OF DEEP DRILLING PERFORMANCE--DEVELOPMENT AND BENCHMARK TESTING OF ADVANCED DIAMOND PRODUCT DRILL BITS AND HP/HT FLUIDS TO SIGNIFICANTLY IMPROVE RATES OF PENETRATION contract for the year starting October 2004 through September 2005. The industry cost shared program aims to benchmark drilling rates of penetration in selected simulated deep formations and to significantly improve ROP through a team development of aggressive diamond product drill bit--fluid system technologies. Overall the objectives are as follows: Phase 1--Benchmark ''best in class'' diamond and other product drilling bits and fluids and develop concepts for amore » next level of deep drilling performance; Phase 2--Develop advanced smart bit-fluid prototypes and test at large scale; and Phase 3--Field trial smart bit--fluid concepts, modify as necessary and commercialize products. As of report date, TerraTek has concluded all Phase 1 testing and is planning Phase 2 development.« less

A comparative evaluation of laser and GTA welds in a high-strength titanium alloy -- Ti-6-22-22S

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baeslack, W.A. III; Hurley, J.; Paskell, T.

1994-12-31

Titanium alloy Ti-6Al-2Sn-2Zr-2Mo-2Cr-025Si (hereafter designated Ti-6-22-22S)is an alpha-beta titanium alloy developed for deep hardenability, high strength, intermediate temperature creep resistance, and moderate toughness. As a potential structural material for next-generation aircraft and aerospace systems, the weldability of Ti-6-22-22S has recently become a subject of increasing importance and concern. In the welding of titanium sheet, achieving satisfactory ductility is the principal limitation to alloy weldability, with poor ductility promoted by a coarse beta grain structure in the weld fusion and near-heat-affected zones. Square-butt welds were produced in 1.6 mm thick Ti-6-22-22S sheet using automatic GTA and CO{sub 2} laser welding systems.more » Microstructure analysis and DPH hardness traverses were performed on mounted. polished and etched specimens. Three-point bend and tensile tests were performed on transverse-weld and longitudinal-weld oriented specimens. Microstructure analysis of the laser welds revealed a fine, columnar fusion zone beta grain macrostructure and a fully-martensitic transformed-beta microstructure. Consistent with the microstructural similarities, fusion zone hardnesses of the laser welds were comparable (385 and 390 DPG, respectively) and greater than that of the base metal (330 DPH). In general, laser welds did not exhibit markedly superior ductilities relative to the GTAW, which was attributed to differences in the nature of the intragranular transformed-beta microstructures, being coarser and softer for the GTAW, the response of these as-welded microstructures to heat treatment, and interactions between the transformed-beta microstructure and the beta grain macrostructure.« less

Partial liquid-penetration inside a deep trench by film flowing over it

NASA Astrophysics Data System (ADS)

Nguyen, Phuc-Khanh; Dimakopoulos, Yiannis; Tsamopoulos, John

2014-11-01

Liquid film flow along substrates featuring a deep trench may not wet the trench floor, but create a second gas-liquid interface inside the trench. The liquid penetration inside the trench depends on the location and shape of this inner interface. The penetration increases by decreasing the two three-phase contact lines between the inner interface and the two side-walls or the flow rate and depends on the liquid properties. This partial-penetration is studied by employing the Galerkin / finite element method to solve the two-dimensional steady-state Navier-Stokes equations in a physical domain that is adaptively remeshed. Multiple branches of steady solutions connected via turning points are revealed by pseudo arc-length continuation. Flow hysteresis may occur in a certain range of liquid penetration depth, when the interaction of the two interfaces changes qualitatively. This induces an abrupt jump of penetration distance and deformation amplitude of the outer interface. Work supported by the General Secretariat of Research & Technology of Greece through the program ``Excellence'' (Grant No. 1918) in the framework ``Education and Lifelong Learning'' co-funded by the ESF.

Influence of modes of metal transfer on grain structure and direction of grain growth in low nickel austenitic stainless steel weld metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukherjee, Manidipto; Saha, Saptarshi; Pal, Tapan Kumar, E-mail: tkpal.ju@gmail.com

2015-04-15

The present study elaborately discussed the effect of different modes of metal transfer (i.e., short circuit mode, spray mode and pulse mode) on grain structure and direction of grain growth in low nickel austenitic stainless steel weld metals. Electron backscattered diffraction (EBSD) analysis was used to study the grain growth direction and grain structure in weld metals. The changes in grain structure and grain growth direction were found to be essentially varied with the weld pool shape and acting forces induced by modes of metal transfer at a constant welding speed. Short circuit mode of metal transfer owing to highermore » Marangoni force (M{sub a}) and low electromagnetic force (R{sub m}) promotes the lower weld pool volume (Γ) and higher weld pool maximum radius (r{sub m}). Short circuit mode also shows curved and tapered columnar grain structures and the grain growth preferentially occurred in <001> direction. In contrast, spray mode of metal transfer increases the Γ and reduces the r{sub m} values due to very high R{sub m} and typically reveals straight and broad columnar grain structures with preferential growth direction in <111>. In the pulse mode of metal transfer relatively high M{sub a} and R{sub m} simultaneously increase the weld pool width and the primary penetration which might encourage relatively complex grain growth directions in the weld pool and cause a shift of major intensity from <001> to <111> direction. It can also be concluded that the fusion zone grain structure and direction of grain growth are solely dependent on modes of metal transfer and remain constant for a particular mode of metal transfer irrespective of filler wire used. - Highlights: • Welded joints of LNiASS were prepared by varying modes of metal transfer. • Weld pool shape, grain structure and grain growth direction were studied. • Short circuit mode shows curved and tapered grain growth in <001> direction. • Spray mode shows straight and broad columnar grain growth in <111> direction. • Pulse mode shows complex grain growth with a shift in growth direction.« less

Laser welding of biological tissue: experimental studies in ophthalmology

NASA Astrophysics Data System (ADS)

Pini, Roberto; Rossi, Francesca; Menabuoni, Luca

2006-04-01

In this paper we present an original approach to laser welding of ocular media. Attention is focused on laser welding of the cornea and lens capsule. The process is based on the interaction of near infrared diode laser radiation (at 810 nm) with tissue that was previously stained with an Indocyanine Green solution in sterile water. The topical application of the chromophore makes possible a selective heating of the tissue, which results in a homogenous welding effect with low thermal damage to the surrounding tissue. Experimental tests were performed ex vivo on both capsule and cornea, and in vivo (rabbits) only on the cornea, in order to characterize the process as a whole. Spectrophotometric, biomechanical, and thermal measurements were carried out in order to study the laser-tissue interaction, while morphological, histological and auto-florescence microscopy analyses made during a follow-up study provided information on the healing process in welded rabbit corneas. The welding procedure was set up according to the type of tissue, with the staining procedure and irradiation conditions being optimized in each case. Our test indicated that: 1) laser welding of corneal wounds, which is a non contact technique performed at low continuous wave laser power (12 W/cm2), can be proposed as a support to or substitute for the standard suturing technique in cataract surgery and in penetrating keratoplasty (in corneal transplants); 2) laser welding of the lens capsule requires a "contact irradiating technique" in order to be efficiently performed, since the tissue is in underwater conditions, with single spot pulses of about 100 J/cm2 fluence and pulse duration around 100 ms. In the latter case, laser welding was proposed as a tool for assisting closure of the lens capsule after the lens refilling procedure (Phaco-ersatz), or for repairing capsular breaks induced by accidental traumas or produced intraoperatively.

Biasing anisotropic scattering kernels for deep-penetration Monte Carlo calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carter, L.L.; Hendricks, J.S.

1983-01-01

The exponential transform is often used to improve the efficiency of deep-penetration Monte Carlo calculations. This technique is usually implemented by biasing the distance-to-collision kernel of the transport equation, but leaving the scattering kernel unchanged. Dwivedi obtained significant improvements in efficiency by biasing an isotropic scattering kernel as well as the distance-to-collision kernel. This idea is extended to anisotropic scattering, particularly the highly forward Klein-Nishina scattering of gamma rays.

Hydrogeology of rocks penetrated by test well JF-3, Jackass Flats, Nye County, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plume, R.W.; La Camera, R.J.

1996-12-31

The U.S. Department of Energy and U.S. Geological Survey are monitoring water levels in southern Nevada and adjacent parts of California in response to concern about the potential effects of pumping ground water to support the Yucca Mountain Site-Characterization Program. Well JF-3 was drilled in the western part of Jackass Flats for monitoring water levels, for determining the likelihood of a hydraulic connection between well JF-3 and production wells J-12 and J-13, and for measuring the hydraulic properties of the Topopah Spring Tuff. The borehole for JF-3 penetrated about 480 feet of alluvium and 818 feet of underlying volcanic rock.more » The well was finished at a depth of 1,138 feet below land surface near the base of the Topopah Spring Tuff, which is the principal volcanic-rock aquifer in the area. The Topopah Spring Tuff at well JF-3 extends from depths of 580 feet to 1,140 feet and consists of about 10 feet of partly to moderately welded ash-flow tuff; 10 feet of vitrophyre; 440 feet of devitrified, moderately to densely welded ash-flow tuff; 80 feet of densely welded ash-flow tuff; 10 feet of vitric, nonwelded to partly welded ash-flow tuff; and 10 feet of ashfall tuff. Fractures and lithophysae are most common in the devitrified tuff, especially between depths of 600 feet and 1,040 feet. Much of the water produced in well JF-3 probably comes from the sequence of these devitrified tuffs that is below the water table. The transmissivity of the aquifer is an estimated 140,000-160,000 feet squared per day and hydraulic conductivity is 330-370 feet per day. These values exceed estimates made at well J-13 by two orders of magnitude. Such large differences may be accounted for by differences in the development of fractures and lithophysae in the Topopah Spring Tuff at the two wells.« less

Ultrasonic Stir Welding Development for Ground-Based and In Situ Fabrication and Repair for In-Space Propulsion Systems/Commercial Space Sector

NASA Technical Reports Server (NTRS)

Ding, Jeff

2015-01-01

The completed Center Innovation Fund (CIF) project used the upgraded Ultrasonic Stir Weld (USW) Prototype System (built in 2013/2014) to begin characterizing the weld process using 2219 aluminum (fig. 1). This work is being done in Bldg. 4755 at NASA Marshall Space Flight Center (MSFC). The capabilities of the USW system provides the means to precisely control and document individual welding parameters. The current upgraded system has the following capabilities: (1) Ability to 'pulse' ultrasonic (US) energy on and off and adjust parameters real-time (travel speed, spindle rpm, US amplitude, X and Z axis positions, and plunge and pin axis force; (2) Means to measure draw force; (3) Ability to record US power versus time; (4) Increasing stiffness of Z axis drive and reduce head deflection using laser technology; (5) Adding linear encoder to better control tool penetration setting; (6) Ultrasonic energy integrated into stir rod and containment plate; (7) Maximum 600 rpm; (8) Maximum Z force 15,000 lb; (9) Real-time data acquisition and logging capabilities at a minimum frequency of 10 Hz; and (10) Two separate transducer power supplies operating at 4.5 kW power.

Electron beam additive manufacturing with wire - Analysis of the process

NASA Astrophysics Data System (ADS)

Weglowski, Marek St.; Błacha, Sylwester; Pilarczyk, Jan; Dutkiewicz, Jan; Rogal, Łukasz

2018-05-01

The electron beam additive manufacturing process with wire is a part of global trend to find fast and efficient methods for producing complex shapes elements from costly metal alloys such as stainless steels, nickel alloys, titanium alloys etc. whose production by other conventional technologies is unprofitable or technically impossible. Demand for additive manufacturing is linked to the development of new technologies in the automotive, aerospace and machinery industries. The aim of the presented work was to carried out research on electron beam additive manufacturing with a wire as a deposited (filler) material. The scope of the work was to investigate the influence of selected technological parameters such as: wire feed rate, beam current, travelling speed, acceleration voltage on stability of the deposition process and geometric dimensions of the padding welds. The research revealed that, at low beam currents, the deposition process is unstable. The padding weld reinforcement is non-uniform. Irregularity of the width, height and straightness of the padding welds can be observed. At too high acceleration voltage and beam current, burn-through of plate and excess penetration weld can be revealed. The achieved results and gained knowledge allowed to produce, based on EBAM with wire process, whole structure from stainless steel.

Influencing the arc and the mechanical properties of the weld metal in GMA-welding processes by additive elements on the wire electrode surface

NASA Astrophysics Data System (ADS)

Wesling, V.; Schram, A.; Müller, T.; Treutler, K.

2016-03-01

Under the premise of an increasing scarcity of raw materials and increasing demands on construction materials, the mechanical properties of steels and its joints are gaining highly important. In particular high- and highest-strength steels are getting in the focus of the research and the manufacturing industry. To the same extent, the requirements for filler metals are increasing as well. At present, these low-alloy materials are protected by a copper coating (<1μm) against corrosion. In addition, the coating realizes a good ohmic contact and good sliding properties between the welding machine and the wire during the welding process. By exchanging the copper with other elements it should be possible to change the mechanical properties of the weld metal and the arc stability during gas metal arc welding processes and keep the basic functions of the coating nearly untouched. On a laboratory scale solid wire electrodes with coatings of various elements and compounds such as titanium oxide were made and processed with a Gas Metal Arc Welding process. During the processing a different process behavior between the wire electrodes, coated and original, could be observed. The influences ranges from greater/shorter arc-length over increasing/decreasing droplets to larger/smaller arc foot point. Furthermore, the weld metal of the coated electrodes has significantly different mechanical and technological characteristics as the weld metal from the copper coated ground wire. The yield strength and tensile strength can be increased by up to 50%. In addition, the chemical composition of the weld metal was influenced by the application of coatings with layer thicknesses to 15 microns in the lower percentage range (up to about 3%). Another effect of the coating is a modified penetration. The normally occurring “argon finger” can be suppressed or enhanced by the choice of the coating. With the help of the presented studies it will be shown that Gas Metal Arc Welding processes are significantly affected by thin film coatings on solid wire electrodes for Gas Metal Arc welding. The influences are regarding the stability of the arc, the properties of the weld metal in terms of geometric expression, chemical composition and mechanical properties, the composition of the arc-plasma and the dynamics of the molten metal.

The Auto-Gopher: A Wireline Rotary-Percussive Deep Sampler

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph; Zacny, Kris; Badescu, Mircea; Lee, Hyeong Jae; Sherrit, Stewart; Bao, Xiaoqi; Paulsen, Gale L.; Beegle, Luther

2016-01-01

Accessing regions on planetary bodies that potentially preserved biosignatures or are presently habitable is vital to meeting NASA solar system "Search for Life" exploration objectives. To address these objectives, a wireline deep rotary-percussive corer called Auto-Gopher was developed. The percussive action provides effective material fracturing and the rotation provides effective cuttings removal. To increase the drill's penetration rate, the percussive and rotary motions are operated simultaneously. Initially, the corer was designed as a percussive mechanism for sampling ice and was demonstrated in 2005 in Antarctica reaching about 2 m deep. The lessons learned suggested the need to use a combination of rotation and hammering to maximize the penetration rate. This lesson was implemented into the Auto-Gopher-I deep drill which was demonstrated to reach 3-meter deep in gypsum. The average drilling power that was used has been in the range of 100-150 Watt, while the penetration rate was approximately 2.4 m/hr. Recently, a task has started with the goal to develop Auto-Gopher-II that is equipped to execute all the necessary functions in a single drilling unit. These functions also include core breaking, retention and ejection in addition drilling. In this manuscript, the Auto-Gopher-II, its predecessors and their capability are described and discussed.

Laser balloon angioplasty: effect of tissue temperature on weld strength of human postmortem intima-media separations.

PubMed

Jenkins, R D; Sinclair, I N; Anand, R; Kalil, A G; Schoen, F J; Spears, J R

1988-01-01

Dehiscence of portions of atheromatous plaques fractured during percutaneous transluminal coronary angioplasty may contribute to both abrupt reclosure and gradual restenosis. Laser balloon angioplasty has been shown to be effective in welding human plaque-arterial wall separations in vitro by heating tissues with a Nd:YAG laser during balloon inflation. To define the potentially useful therapeutic range of tissue temperature required to achieve thermal welds, 220 1-cm diameter discs of human postmortem atheromatous aortic tissue, the intimal plaque of which had been separated from the media, were exposed to 3-25 watts of Nd:YAG laser radiation delivered over a 12-mm2 nominal spot size for 20 seconds via a 400-micron core optical fiber. As measured with a thermistor, adventitial temperature reflected the temperature at the plaque-media junction to within 10 degrees C. The degree of tissue temperature elevation was related to delivered energy, while effective tissue penetration increased to maximum depth of 3 mm at the highest power density. Strength of tissue welds was defined as the force required to shear opposing layers of welded segments. Adventitial tissue temperatures below 80 degrees C were not associated with appreciable welds, while equilibrium temperatures between 95 degrees C and 140 degrees C were consistently associated with effective mean weld strengths, which increased linearly from 25 to 110 g, respectively. Temperatures greater than 150 degrees C were associated with rapid tissue dehydration and charring. These data suggest that the therapeutic range of tissue temperature that provides effective thermal fusion of intima-media separations is broad and that the depth and degree of thermal coagulation can be controlled by manipulation of laser energy delivery.

Geohydrologic data from test hole USW UZ-7, Yucca Mountain area, Nye County, Nevada

USGS Publications Warehouse

Kume, Jack; Hammermeister, D.P.

1990-01-01

This report contains a description of the methods used in drilling and coring of the test-hole USW UZ-7, a description of the methods used in collecting, handling, and testing of test-hole samples; Lithologic information from the test hole; and water-content, water-potential, bulk-density, grain-density, porosity, and tritium data for the test hole. Test-hole USW UZ-7 was drilled and cored to a total depth of 62.94 m. The drilling was done using air as a drilling fluid to minimize disturbance to the water content of cores, drill-bit cuttings, and borehole wall-rock. Beginning at the land surface, the unsaturated-zone rock that was penetrated consisted of alluvium; welded and partially to nonwelded ash-flow tuff; bedded and reworked ash-fall tuff; nonwelded ash-flow tuff; and welded ash-flow tuff. Values of gravimetric water content and water potential of alluvium were intermediate between the extreme values in welded and nonwelded units of tuff. Gravimetric water content was largest in bedded and nonwelded ash-fall tuffs and was smallest in welded ash-flow tuff. Values of water potential were more negative in densely welded ash-flow tuffs and were less negative in bedded and nonwelded ash-fall tuffs. Bulk density was largest in densely welded ash-flow tuffs and smallest in nonwelded and bedded ash-fall tuffs. Grain density was uniform but was slightly larger in nonwelded and bedded ash-fall tuffs than in welded ash-flow tuffs. Porosity trends were opposite to bulk-density trends. Tritium content in alluvium was smallest near the alluvium-bedrock contact, markedly increased in the middle of the deposit, and decreased in the near-surface zone of the deposit. (Author 's abstract)

Tomography of the subducting Pacific slab and the 2015 Bonin deepest earthquake (Mw 7.9).

PubMed

Zhao, Dapeng; Fujisawa, Moeto; Toyokuni, Genti

2017-03-15

On 30 May 2015 an isolated deep earthquake (~670 km, Mw 7.9) occurred to the west of the Bonin Islands. To clarify its causal mechanism and its relationship to the subducting Pacific slab, we determined a detailed P-wave tomography of the deep earthquake source zone using a large number of arrival-time data. Our results show that this large deep event occurred within the subducting Pacific slab which is penetrating into the lower mantle. In the Izu-Bonin region, the Pacific slab is split at ~28° north latitude, i.e., slightly north of the 2015 deep event hypocenter. In the north the slab becomes stagnant in the mantle transition zone, whereas in the south the slab is directly penetrating into the lower mantle. This deep earthquake was caused by joint effects of several factors, including the Pacific slab's fast deep subduction, slab tearing, slab thermal variation, stress changes and phase transformations in the slab, and complex interactions between the slab and the ambient mantle.

A simple 2-d thermal model for GMA welds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matteson, M.A.; Franke, G.L.; Vassilaros, M.G.

1996-12-31

The Rosenthal model of heat distribution from a moving source has been used in many applications to predict the temperature distribution during welding. The equation has performed well in its original form or as modified. The expression has a significant limitation for application to gas metal arc welds (GMAW) that have a papilla extending from the root of the weld bead. The shape of the fusion line between the papilla and the plate surface has a concave shape rather than the expected convex shape. However, at some distance from the fusion line the heat affected zone (HAZ) made visible bymore » etching has the expected convex shape predicted by the Rosenthal expression. This anomaly creates a limitation to the use of the Rosenthal expression for predicting GMAW bead shapes or HAZ temperature histories. Current research at the Naval Surface Warfare Center--Carderock Division (NSWC--CD) to develop a computer based model to predict the microstructure of multi-pass GMAW requires a simple expression to predict the fusion line and temperature history of the HAZ for each weld pass. The solution employed for the NSWC--CD research is a modified Rosenthal expression that has a dual heat source. One heat source is a disk source above the plate surface supplying the majority of the heat. The second heat source is smaller and below the surface of the plate. This second heat source helps simulate the penetration power of many GMAW welds that produces the papilla. The assumptions, strengths and limitations of the model are presented along with some applications.« less

Cryogenic Treatment of Al-Li Alloys for Improved Weldability, Repairability, and Reduction of Residual Stresses

NASA Technical Reports Server (NTRS)

Malone, Tina W.; Graham, Benny F.; Gentz, Steven J. (Technical Monitor)

2001-01-01

Service performance has shown that cryogenic treatment of some metals provides improved strength, fatigue life, and wear resistance to the processed material. Effects such as these were initially discovered by NASA engineers while evaluating spacecraft that had returned from the cold vacuum of space. Factors such as high cost, poor repairability, and poor machinability are currently prohibitive for wide range use of some aerospace aluminum alloys. Application of a cryogenic treatment process to these alloys is expected provide improvements in weldability and weld properties coupled with a reduction in repairs resulting in a significant reduction in the cost to manufacture and life cycle cost of aerospace hardware. The primary purpose of this effort was to evaluate the effects of deep cryogenic treatment of some aluminum alloy plate products, welds, and weld repairs, and optimize a process for the treatment of these materials. The optimized process is being evaluated for improvements in properties of plate and welds, improvements in weldability and repairability of treated materials, and as an alternative technique for the reduction of residual stresses in repaired welds. This paper will present the results of testing and evaluation conducted in this effort. These results will include assessments of changes in strength, toughness, stress corrosion susceptability, weldability, repairability, and reduction in residual stresses of repaired welds.

Experimental Investigations on Formability of Aluminum Tailor Friction Stir Welded Blanks in Deep Drawing Process

NASA Astrophysics Data System (ADS)

Kesharwani, R. K.; Panda, S. K.; Pal, S. K.

2015-02-01

In the present work, tailor friction stir welded blanks (TFSWBs) were fabricated successfully using 2.0-mm-thick AA5754-H22 and AA5052-H32 sheet metals with optimized tool design and process parameters. Taguchi L9 orthogonal array has been used to design the friction stir welding experiments, and the Grey relational analysis has been applied for the multi objective optimization in order to maximize the weld strength and total elongation reducing the surface roughness and energy consumption. The formability of the TFSWBs and parent materials was evaluated and compared in terms of limiting drawing ratio (LDR) using a conventional circular die. It was found that the formability of the TFSWBs was comparable with that of both the parent materials without failure in the weldment. A modified conical tractrix die (MCTD) was proposed to enhance the LDR of the TFSWBs. It was found that the formability was improved by 27% using the MCTD.

High-power industrial pulsed CO2 laser

NASA Astrophysics Data System (ADS)

Levin, G. I.

1983-12-01

The use of a pulsed TEA CO2 laser (with maximum average power 1.0 kW; maximum pulse energy 3.5 J; repetition frequency 400-600 Hz; half-width pulse duration 15 microsec; circular-coupling-aperture beam diameter 6, 8, or 12 mm; and beam divergence 10 mrad) in industrial welding applications is investigated experimentally in carbon and stainless steels, Zr, Ti, and Ni of various thicknesses. The power required to melt the metals is found to be about 120-200 W/sq cm, or 5-6 times less than that for CW lasers. It is shown that deep narrow-seam welds with mechanical properties identical to those of the bulk metal can be obtained with little or no intercrystalline corrosion or thermal distortion of the surrounding area. Disadvantages such as the 65-dB noise level, low welding speed, formation of an overlap at the top and a crater at the bottom of the weld, and root porosity are considered the primary limitations on the applicability of the device tested.

Gimballed Shoulders for Friction Stir Welding

NASA Technical Reports Server (NTRS)

Carter, Robert; Lawless, Kirby

2008-01-01

In a proposed improvement of tooling for friction stir welding, gimballed shoulders would supplant shoulders that, heretofore, have been fixedly aligned with pins. The proposal is especially relevant to self-reacting friction stir welding. Some definitions of terms, recapitulated from related prior NASA Tech Briefs articles, are prerequisite to a meaningful description of the proposed improvement. In friction stir welding, one uses a tool that includes (1) a rotating shoulder on top (or front) of the workpiece and (2) a pin that rotates with the shoulder and protrudes from the shoulder into the depth of the workpiece. In conventional friction stir welding, the main axial force exerted by the tool on the workpiece is reacted through a ridged backing anvil under (behind) the workpiece. When conventional friction stir welding is augmented with an auto-adjustable pin-tool (APT) capability, the depth of penetration of the pin into the workpiece is varied in real time by a position- or forcecontrol system that extends or retracts the pin as needed to obtain the desired effect. In self-reacting (also known as self-reacted) friction stir welding as practiced heretofore, there are two shoulders: one on top (or front) and one on the bottom (or back) of the workpiece. In this case, a threaded shaft protrudes from the tip of the pin to beyond the back surface of the workpiece. The back shoulder is held axially in place against tension by a nut on the threaded shaft. Both shoulders rotate with the pin and remain aligned coaxially with the pin. The main axial force exerted on the workpiece by the tool and front shoulder is reacted through the back shoulder and the threaded shaft into the friction-stir-welding machine head, so that a backing anvil is no longer needed. A key transmits torque between the bottom shoulder and the threaded shaft, so that the bottom shoulder rotates with the shaft. This concludes the prerequisite definitions of terms.

Characterization of lap joints laser beam welding of thin AA 2024 sheets with Yb:YAG disk-laser

NASA Astrophysics Data System (ADS)

Caiazzo, Fabrizia; Alfieri, Vittorio; Cardaropoli, Francesco; Sergi, Vincenzo

2012-06-01

Lap joints obtained by overlapping two plates are widely diffused in aerospace industry. Nevertheless, because of natural aging, adhesively bonded and riveted aircraft lap joints may be affected by cracks from rivets, voids or corrosion. Friction stir welding has been proposed as a valid alternative, although large heat affected zones are produced both in the top and the bottom plate due to the pin diameter. Interest has therefore been shown in studying laser lap welding as the laser beam has been proved to be competitive since it allows to concentrate the thermal input and increases productivity and quality. Some challenges arise as a consequence of aluminum low absorptance and high thermal conductivity; furthermore, issues are due to metallurgical challenges such as both micro and macro porosity formation and softening in the fused zone. Welding of AA 2024 thin sheets in a lap joint configuration is discussed in this paper: tests are carried out using a recently developed Trumpf TruDisk 2002 Yb:YAG disk-laser with high beam quality which allows to produce beads with low plates distortion and better penetration. The influence of the processing parameters is discussed considering the fused zone extent and the bead shape. The porosity content as well as the morphological features of the beads have been examined.

Laser spot size and beam profile studies for tissue welding applications

NASA Astrophysics Data System (ADS)

Fried, Nathaniel M.; Hung, Vincent C.; Walsh, Joseph T., Jr.

1999-06-01

We evaluated the effect of changes in laser spot size and beam profile on the thermal denaturation zone produced during laser skin welding. Our objective was to limit heating of the tissue surface, while creating enough thermal denaturation in the deeper layers of the dermis to produce full-thickness welds. Two-cm-long, full-thickness incisions were made on the backs of guinea pigs, in vivo. India ink was used as an absorber. Continuous-wave, 1.06-μm, Nd:YAG laser radiation was scanned over the incisions, producing approximately 100 ms pulses. Cooling times of 10.0 s between scans were used. Laser spot diameters of 1, 2, 4, and 6 mm were studied, with powers of 1, 4, 16, and 36 W, respectively. The irradiance remained constant at 127 W/cm2. 1, 2, and 4 mm diameter spots produced thermal denaturation to a depth of 570 +/- 100 μm, 970 +/- 210 μm, and 1470 +/- 190 μm, respectively. The 6-mm- diameter spot produced full-thickness welds (1900 μm), but also burns due to the high incident power. Monte Carlo simulations were also conducted, varying the laser spot diameter and beam profile. The simulations verified that an increase in laser spot diameter result in an increase in the penetration depth of radiation into the tissue.

Tomography of the subducting Pacific slab and the 2015 Bonin deepest earthquake (Mw 7.9)

PubMed Central

Zhao, Dapeng; Fujisawa, Moeto; Toyokuni, Genti

2017-01-01

On 30 May 2015 an isolated deep earthquake (~670 km, Mw 7.9) occurred to the west of the Bonin Islands. To clarify its causal mechanism and its relationship to the subducting Pacific slab, we determined a detailed P-wave tomography of the deep earthquake source zone using a large number of arrival-time data. Our results show that this large deep event occurred within the subducting Pacific slab which is penetrating into the lower mantle. In the Izu-Bonin region, the Pacific slab is split at ~28° north latitude, i.e., slightly north of the 2015 deep event hypocenter. In the north the slab becomes stagnant in the mantle transition zone, whereas in the south the slab is directly penetrating into the lower mantle. This deep earthquake was caused by joint effects of several factors, including the Pacific slab’s fast deep subduction, slab tearing, slab thermal variation, stress changes and phase transformations in the slab, and complex interactions between the slab and the ambient mantle. PMID:28295018

Tomography of the subducting Pacific slab and the 2015 Bonin deepest earthquake (Mw 7.9)

NASA Astrophysics Data System (ADS)

Zhao, Dapeng; Fujisawa, Moeto; Toyokuni, Genti

2017-03-01

On 30 May 2015 an isolated deep earthquake (~670 km, Mw 7.9) occurred to the west of the Bonin Islands. To clarify its causal mechanism and its relationship to the subducting Pacific slab, we determined a detailed P-wave tomography of the deep earthquake source zone using a large number of arrival-time data. Our results show that this large deep event occurred within the subducting Pacific slab which is penetrating into the lower mantle. In the Izu-Bonin region, the Pacific slab is split at ~28° north latitude, i.e., slightly north of the 2015 deep event hypocenter. In the north the slab becomes stagnant in the mantle transition zone, whereas in the south the slab is directly penetrating into the lower mantle. This deep earthquake was caused by joint effects of several factors, including the Pacific slab’s fast deep subduction, slab tearing, slab thermal variation, stress changes and phase transformations in the slab, and complex interactions between the slab and the ambient mantle.

Near-infrared deep brain stimulation via upconversion nanoparticle–mediated optogenetics

NASA Astrophysics Data System (ADS)

Chen, Shuo; Weitemier, Adam Z.; Zeng, Xiao; He, Linmeng; Wang, Xiyu; Tao, Yanqiu; Huang, Arthur J. Y.; Hashimotodani, Yuki; Kano, Masanobu; Iwasaki, Hirohide; Parajuli, Laxmi Kumar; Okabe, Shigeo; Teh, Daniel B. Loong; All, Angelo H.; Tsutsui-Kimura, Iku; Tanaka, Kenji F.; Liu, Xiaogang; McHugh, Thomas J.

2018-02-01

Optogenetics has revolutionized the experimental interrogation of neural circuits and holds promise for the treatment of neurological disorders. It is limited, however, because visible light cannot penetrate deep inside brain tissue. Upconversion nanoparticles (UCNPs) absorb tissue-penetrating near-infrared (NIR) light and emit wavelength-specific visible light. Here, we demonstrate that molecularly tailored UCNPs can serve as optogenetic actuators of transcranial NIR light to stimulate deep brain neurons. Transcranial NIR UCNP-mediated optogenetics evoked dopamine release from genetically tagged neurons in the ventral tegmental area, induced brain oscillations through activation of inhibitory neurons in the medial septum, silenced seizure by inhibition of hippocampal excitatory cells, and triggered memory recall. UCNP technology will enable less-invasive optical neuronal activity manipulation with the potential for remote therapy.

Study of issues in difficult-to-weld thick materials by hybrid laser arc welding

NASA Astrophysics Data System (ADS)

Mazar Atabaki, Mehdi

There is a high interest for the high strength-to-weight ratio with good ductility for the welds of advanced alloys. The concern about the welding of thick materials (Advanced high strength steels (AHSS) and 5xxx and 6xxx series of aluminum alloys) has stimulated the development of manufacturing processes to overcome the associated issues. The need to weld the dissimilar materials (AHSS and aluminum alloys) is also required for some specific applications in different industries. Hence, the requirement in the development of a state-of-the-art welding procedure can be helpful to fulfill the constraints. Among the welding methods hybrid laser/arc welding (HLAW) has shown to be an effective method to join thick and difficult-to-weld materials. This process benefits from both advantages of the gas metal arc welding (GMAW) and laser welding processes. The interaction of the arc and laser can help to have enough penetration of weld in thick plates. However, as the welding of dissimilar aluminum alloys and steels is very difficult because of the formation of brittle intermetallics the present work proposed a procedure to effectively join the alloys. The reports showed that the explosively welded aluminum alloys to steels have the highest toughness, and that could be used as an "insert" (TRICLAD) for welding the thick plates of AHSS to aluminum alloys. Therefore, the HLAW of the TRICLAD-Flange side (Aluminum alloy (AA 5456)) to the Web side (Aluminum alloys (AA 6061 and AA 5456)) and the TRICLAD-Flange side (ASTM A516) to the Web side (AHSS) was studied in the present work. However, there are many issues related to HLAW of the dissimilar steels as well as dissimilar aluminum alloys that have to be resolved in order to obtain sound welds. To address the challenges, the most recent welding methods for joining aluminum alloys to steels were studied and the microstructural development, mechanical properties, and on-line monitoring of the welding processes were discussed as well. The heat and mass transfer and the issues in joining of dissimilar alloys by the hybrid laser/arc welding process (HLAW) were explicitly explained in details. A finite element model was developed to simulate the heat transfer in HLAW of the aluminum alloys. Two double-ellipsoidal heat source models were considered to describe the heat input of the gas metal arc welding and laser welding processes. An experimental procedure was also developed for joining thick advanced high strength steel plates by using the HLAW, by taking into consideration different butt joint configurations. The geometry of the weld groove was optimized according to the requirements of ballistic test, where the length of the softened heat affected zone should be less than 15.9 mm measured from the weld centerline. Since the main issue in HLAW of the AHSS was the formation of the pores, the possible mechanisms of the pores formation and their mitigation methods during the welding process were investigated. Mitigation methods were proposed to reduce the pores inside in the weld area and the influence of each method on the process stability was investigated by an on-line monitoring system of the HLAW process. The groove angle was optimized for the welding process based on the allowed amount of heat input along the TRICLADRTM interface generated by an explosive welding. The weld was fractured in the heat affected zone of the aluminum side in the tensile test. The microharness was shown that the temperature variation caused minor softening in the heat affected zone satisfying the requirement that the width of the softened heat affected zone in the steel side falls within 15.9 mm far away from the weld centerline. The microstructure analysis showed the presence of tempered martensite at the vicinity of the weld area, which it was a cause of softening in the heat affected zone.

Evolution of the conceptual model of unsaturated zone hydrology at Yucca Mountain, Nevada

NASA Astrophysics Data System (ADS)

Flint, Alan L.; Flint, Lorraine E.; Bodvarsson, Gudmundur S.; Kwicklis, Edward M.; Fabryka-Martin, June

2001-06-01

Yucca Mountain is an arid site proposed for consideration as the United States' first underground high-level radioactive waste repository. Low rainfall (approximately 170 mm/yr) and a thick unsaturated zone (500-1000 m) are important physical attributes of the site because the quantity of water likely to reach the waste and the paths and rates of movement of the water to the saturated zone under future climates would be major factors in controlling the concentrations and times of arrival of radionuclides at the surrounding accessible environment. The framework for understanding the hydrologic processes that occur at this site and that control how quickly water will penetrate through the unsaturated zone to the water table has evolved during the past 15 yr. Early conceptual models assumed that very small volumes of water infiltrated into the bedrock (0.5-4.5 mm/yr, or 2-3 percent of rainfall), that much of the infiltrated water flowed laterally within the upper nonwelded units because of capillary barrier effects, and that the remaining water flowed down faults with a small amount flowing through the matrix of the lower welded, fractured rocks. It was believed that the matrix had to be saturated for fractures to flow. However, accumulating evidence indicated that infiltration rates were higher than initially estimated, such as infiltration modeling based on neutron borehole data, bomb-pulse isotopes deep in the mountain, perched water analyses and thermal analyses. Mechanisms supporting lateral diversion did not apply at these higher fluxes, and the flux calculated in the lower welded unit exceeded the conductivity of the matrix, implying vertical flow of water in the high permeability fractures of the potential repository host rock, and disequilibrium between matrix and fracture water potentials. The development of numerical modeling methods and parameter values evolved concurrently with the conceptual model in order to account for the observed field data, particularly fracture flow deep in the unsaturated zone. This paper presents the history of the evolution of conceptual models of hydrology and numerical models of unsaturated zone flow at Yucca Mountain, Nevada ( Flint, A.L., Flint, L.E., Kwicklis, E.M., Bodvarsson, G.S., Fabryka-Martin, J.M., 2001. Hydrology of Yucca Mountain. Reviews of Geophysics in press). This retrospective is the basis for recommendations for optimizing the efficiency with which a viable and robust conceptual model can be developed for a complex site.

Friction Stir Weld Inspection Through Conductivity Imaging Using Shaped Field MWM(Registered Trademark) - Arrays

NASA Technical Reports Server (NTRS)

Goldfine, Neil; Grundy, David; Zilberstein, Vladimir; Kinchen, David G.; McCool, Alex (Technical Monitor)

2002-01-01

Friction Stir Welds (FSW) of Al 2195-T8 and Al 2219-T8, provided by Lockheed Martin Michoud Operations, were inspected for lack-of-penetration (LOP) defects using a custom designed MWM-Array, a multi-element eddy-current sensor. MWM (registered trademark) electrical conductivity mapping demonstrated high sensitivity to LOP as small as 0.75 mm (0.03 in.), as confirmed by metallographic data that characterized the extent of LOP defects. High sensitivity and high spatial resolution was achieved via a 37-element custom designed MWM-Array allowing LOP detection using the normalized longitudinal component of the MWM measured conductivity. This permitted both LOP detection and correlation of MWM conductivity features with the LOP defect size, as changes in conductivity were apparently associated with metallurgical features within the near-surface layer of the LOP defect zone. MWM conductivity mapping reveals information similar to macro-etching as the MWM-Array is sensitive to small changes in conductivity due to changes in microstructure associated with material thermal processing, in this case welding. The electrical conductivity measured on the root side of FSWs varies across the weld due to microstructural differences introduced by the FSW process, as well as those caused by planar flaws. Weld metal, i.e., dynamically recrystallized zone (DXZ), thermomechanically affected zone (TMZ), heat-affected zone (HAZ), and parent metal (PM) are all evident in the conductivity maps. While prior efforts had met with limited success for NDE (Nondestructive Evaluation) of dissimilar alloy, Al2219 to Al2195 FSW, the new custom designed multi-element MWM-Array achieved detection of all LOP defects even in dissimilar metal welds.

Detailed Microstructural Characterization and Restoration Mechanisms of Duplex and Superduplex Stainless Steel Friction-Stir-Welded Joints

NASA Astrophysics Data System (ADS)

Santos, T. F. A.; Torres, E. A.; Lippold, J. C.; Ramirez, A. J.

2016-12-01

Duplex stainless steels are successfully used in a wide variety of applications in areas such as the food industry, petrochemical installations, and sea water desalination plants, where high corrosion resistance and high mechanical strength are required. However, during fusion welding operations, there can be changes to the favorable microstructure of these materials that compromise their performance. Friction stir welding with a non-consumable pin enables welded joints to be obtained in the solid state, which avoids typical problems associated with solidification of the molten pool, such as segregation of alloying elements and the formation of solidification and liquefaction cracks. In the case of superduplex stainless steels, use of the technique can avoid unbalanced proportions of ferrite and austenite, formation of deleterious second phases, or growth of ferritic grains in the heat-affected zone. Consolidated joints with full penetration were obtained for 6-mm-thick plates of UNS S32101 and S32205 duplex stainless steels, and S32750 and S32760 superduplex steels. The welding heat cycles employed avoided the conditions required for formation of deleterious phases, except in the case of the welded joint of the S32760 steel, where SEM images indicated the formation of secondary phases, as corroborated by decreased mechanical performance. Analysis using EBSD and transmission electron microscopy revealed continuous dynamic recrystallization by the formation of cellular arrays of dislocations in the ferrite and discontinuous dynamic recrystallization in the austenite. Microtexture evaluation indicated the presence of fibers typical of shear in the thermomechanically affected zone. These fibers were not obviously present in the stir zone, probably due to the intensity of microstructural reformulation to which this region was subjected.

Spectroscopic analysis technique for arc-welding process control

NASA Astrophysics Data System (ADS)

Mirapeix, Jesús; Cobo, Adolfo; Conde, Olga; Quintela, María Ángeles; López-Higuera, José-Miguel

2005-09-01

The spectroscopic analysis of the light emitted by thermal plasmas has found many applications, from chemical analysis to monitoring and control of industrial processes. Particularly, it has been demonstrated that the analysis of the thermal plasma generated during arc or laser welding can supply information about the process and, thus, about the quality of the weld. In some critical applications (e.g. the aerospace sector), an early, real-time detection of defects in the weld seam (oxidation, porosity, lack of penetration, ...) is highly desirable as it can reduce expensive non-destructive testing (NDT). Among others techniques, full spectroscopic analysis of the plasma emission is known to offer rich information about the process itself, but it is also very demanding in terms of real-time implementations. In this paper, we proposed a technique for the analysis of the plasma emission spectrum that is able to detect, in real-time, changes in the process parameters that could lead to the formation of defects in the weld seam. It is based on the estimation of the electronic temperature of the plasma through the analysis of the emission peaks from multiple atomic species. Unlike traditional techniques, which usually involve peak fitting to Voigt functions using the Levenberg-Marquardt recursive method, we employ the LPO (Linear Phase Operator) sub-pixel algorithm to accurately estimate the central wavelength of the peaks (allowing an automatic identification of each atomic species) and cubic-spline interpolation of the noisy data to obtain the intensity and width of the peaks. Experimental tests on TIG-welding using fiber-optic capture of light and a low-cost CCD-based spectrometer, show that some typical defects can be easily detected and identified with this technique, whose typical processing time for multiple peak analysis is less than 20msec. running in a conventional PC.

Laser Cladding of Ultra-Thin Nickel-Based Superalloy Sheets.

PubMed

Gabriel, Tobias; Rommel, Daniel; Scherm, Florian; Gorywoda, Marek; Glatzel, Uwe

2017-03-10

Laser cladding is a well-established process to apply coatings on metals. However, on substrates considerably thinner than 1 mm it is only rarely described in the literature. In this work 200 µm thin sheets of nickel-based superalloy 718 are coated with a powder of a cobalt-based alloy, Co-28Cr-9W-1.5Si, by laser cladding. The process window is very narrow, therefore, a precisely controlled Yb fiber laser was used. To minimize the input of energy into the substrate, lines were deposited by setting single overlapping points. In a design of experiments (DoE) study, the process parameters of laser power, laser spot area, step size, exposure time, and solidification time were varied and optimized by examining the clad width, weld penetration, and alloying depth. The microstructure of the samples was investigated by optical microscope (OM) and scanning electron microscopy (SEM), combined with electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDX). Similarly to laser cladding of thicker substrates, the laser power shows the highest influence on the resulting clad. With a higher laser power, the clad width and alloying depth increase, and with a larger laser spot area the weld penetration decreases. If the process parameters are controlled precisely, laser cladding of such thin sheets is manageable.

Laser Cladding of Ultra-Thin Nickel-Based Superalloy Sheets

PubMed Central

Gabriel, Tobias; Rommel, Daniel; Scherm, Florian; Gorywoda, Marek; Glatzel, Uwe

2017-01-01

Laser cladding is a well-established process to apply coatings on metals. However, on substrates considerably thinner than 1 mm it is only rarely described in the literature. In this work 200 µm thin sheets of nickel-based superalloy 718 are coated with a powder of a cobalt-based alloy, Co–28Cr–9W–1.5Si, by laser cladding. The process window is very narrow, therefore, a precisely controlled Yb fiber laser was used. To minimize the input of energy into the substrate, lines were deposited by setting single overlapping points. In a design of experiments (DoE) study, the process parameters of laser power, laser spot area, step size, exposure time, and solidification time were varied and optimized by examining the clad width, weld penetration, and alloying depth. The microstructure of the samples was investigated by optical microscope (OM) and scanning electron microscopy (SEM), combined with electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDX). Similarly to laser cladding of thicker substrates, the laser power shows the highest influence on the resulting clad. With a higher laser power, the clad width and alloying depth increase, and with a larger laser spot area the weld penetration decreases. If the process parameters are controlled precisely, laser cladding of such thin sheets is manageable. PMID:28772639

CHARACTERIZATION OF DEFECTS IN ALLOY 152, 52 AND 52M WELDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruemmer, Stephen M.; Toloczko, Mychailo B.; Olszta, Matthew J.

2009-08-27

Defect distributions have been documented by optical metallography, scanning electron microscopy and electron backscatter diffraction in alloy 152 and 52 mockups welds, alloy 52 and 52M overlay mockups and an alloy 52M inlay. Primary defects were small cracks at grain boundaries except for more extensive cracking in the dilution zone of an alloy 52 overlay on 304SS. Detailed characterizations of the dilution zone cracks were performed by analytical transmission electron microscopy identifying grain boundary titanium-nitride precipitation associated with the intergranular separations. I. INTRODUCTION Weldments continue to be a primary location of stress-corrosion cracking (SCC) in light-water reactor systems. While problemsmore » related to heat-affected-zone (HAZ) sensitization and intergranular (IG) SCC of austenitic stainless alloys in boiling-water reactors (BWRs) have been significantly reduced, SCC has now been observed in HAZs of non-sensitized materials and in dissimilar metal welds where Ni-base alloy weld metals are used. IGSCC in weld metals has been observed in both BWRs and pressurized water reactors (PWRs) with recent examples for PWR pressure vessel penetrations producing the most concern. This has led to the replacement of alloy 600/182/82 welds with higher Cr, more corrosion-resistant replacement materials (alloy 690/152/52/52M). Complicating this issue has been a known susceptibility to cracking during welding [1-7] of these weld metals. There is a critical need for an improved understanding of the weld metal metallurgy and defect formation in Ni-base alloy welds to effectively assess long-term performance. A series of macroscopic to microscopic examinations were performed on available mockup welds made with alloy 52 or alloy 152 plus selected overlay and inlay mockups. The intent was to expand our understanding of weld metal structures in simulated LWR service components with a focus on as-welded defects. Microstructural features, defect distributions, defect characteristics and weld residual strains were examined by optical metallography, scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy. Industry-supplied mock-up welds were characterized including alloy 52 and 152 weldments, alloy 52M overlay and inlay welds, and an alloy 52 overlay. II. WELDMENTS II.A. Alloy 52 and 152 Weld Mockups The alloy 52 and 152 weld mockups were fabricated by MHI for the Kewaunee reactor and were obtained from the EPRI NDE Center. The mockups were U-groove welds joining two plates of 304SS as shown in Figure 1. Alloy 152 butter (heat 307380) was placed on the U-groove surface for both mockups by shielded metal arc welding (SMAW). For the alloy 152 weld mockup, the alloy 152 fill (heat 307380) was also applied using SMAW while for the alloy 52 weld mockup, the alloy 52 fill (heat NX2686JK) was applied using gas tungsten arc welding (GTAW). Welding parameters for the fill materials were substantially different with the alloy 152 SMAW having a deposition speed of 4-25 cm/min with a current of 95-145 A and the alloy 52 GTAW having a deposition speed of 4-10 cm/min with a current of 150-300 A. One prominent feature in these mockup welds is the presence of a crack starting at the 304SS butt joint at the bottom of the U-groove and extending up into the weld. It appears that the 304SS plate on either side of the butt joint acted as an anchor for the weld resulting in a stress rise across the slit that drove crack formation and extension up into the fill weld. As will be shown in the next section, the extent of the cracking around this stress riser was much greater in the MHI 52 weld mockup.« less

Detection and evaluation of weld defects in stainless steel using alternating current field measurement

NASA Astrophysics Data System (ADS)

Wei-Li, Ma, Weiping; Pan-Qi, Wen-jiao, Dou; Yuan, Xin'an; Yin, Xiaokang

2018-04-01

Stainless steel is widely used in nuclear power plants, such as various high-radioactive pool, tools storage and fuel transportation channel, and serves as an important barrier to stop the leakage of high-radioactive material. NonDestructive Evaluation (NDE) methods, eddy current testing (ET), ultrasonic examination (UT), penetration testing (PT) and hybrid detection method, etc., have been introduced into the inspection of a nuclear plant. In this paper, the Alternating Current Field Measurement (ACFM) was fully applied to detect and evaluate the defects in the welds of the stainless steel. Simulations were carried out on different defect types, crack lengths, and orientation to reveal the relationship between the signals and dimensions to determine whether methods could be validated by the experiment. A 3-axis ACFM probe was developed and three plates including 16 defects, which served in nuclear plant before, were examined by automatic detection equipment. The result shows that the minimum detectable crack length on the surface is 2mm and ACFM shows excellent inspection results for a weld in stainless steel and gives an encouraging prospect of broader application.

PWSCC Susceptibility in Heat Affected Zones of Alloy 600

NASA Astrophysics Data System (ADS)

Couvant, Thierry; Brossier, Thomas; Cossange, Christian

The recent field experience and several experimental results have shown the possible deleterious effect of a heat affected zone (HAZ) induced by welding on the susceptibility to the stress corrosion cracking (SCC) of Alloy 600 of bottom penetrations exposed to primary water of PWRs. This work tried to quantify the increasing susceptibility to initiation and crack propagation in 600/182 HAZ. The rolled plate did not exhibit any susceptibility to SCC except for a cold work higher than 10% typically. By contrast, the weld metal was well known for its high susceptibility to SCC. Metallurgical and mechanical characterizations of the HAZ indicated a slight gradient of Vickers micro hardness close to the fusion line (up to few mm) and a lack of intergranular precipitates up to 500 µm from the fusion line. SCC tests clearly demonstrated that a non-susceptible plate may exhibit a significant susceptibility to SCC propagation in the HAZ. Results of initiation tests did not allow to observe any SCC in the base metal, due to the high susceptibility to SCC of the weld.

Tensile strength and corrosion resistance of brazed and laser-welded cobalt-chromium alloy joints.

PubMed

Zupancic, Rok; Legat, Andraz; Funduk, Nenad

2006-10-01

The longevity of prosthodontic restorations is often limited due to the mechanical or corrosive failure occurring at the sites where segments of a metal framework are joined together. The purpose of this study was to determine which joining method offers the best properties to cobalt-chromium alloy frameworks. Brazed and 2 types of laser-welded joints were compared for their mechanical and corrosion characteristics. Sixty-eight cylindrical cobalt-chromium dental alloy specimens, 35 mm long and 2 mm in diameter, were cast. Sixteen specimens were selected for electrochemical measurements in an artificial saliva solution and divided into 4 groups (n=4). In the intact group, the specimens were left as cast. The specimens of the remaining 3 groups were sectioned at the center, perpendicular to the long-axis, and were subsequently rejoined by brazing (brazing group) or laser welding using an X- or I-shaped joint design (X laser and I laser groups, respectively). Another 16 specimens were selected for electrochemical measurements in a more acidic artificial saliva solution. These specimens were also divided into 4 groups (n=4) as described above. Electrochemical impedance spectroscopy and potentiodynamic polarization were used to assess corrosion potentials, breakdown potentials, corrosion current densities, total impedances at lowest frequency, and polarization charge-transfer resistances. The remaining 36 specimens were used for tensile testing. They were divided into 3 groups in which specimen pairs (n=6) were joined by brazing or laser welding to form 70-mm-long cylindrical rods. The tensile strength (MPa) was measured using a universal testing machine. Differences between groups were analyzed using 1-way analysis of variance (alpha=.05). The fracture surfaces and corrosion defects were examined with a scanning electron microscope. The average tensile strength of brazed joints was 792 MPa and was significantly greater (P<.05) than the tensile strength of both types of laser-welded joints (404 MPa and 405 MPa). When laser welding was used, successful joining was limited to the peripheral aspects of the weld. The welding technique did not significantly affect the joint tensile strength. Electrochemical measurements indicated that the corrosion resistance of the laser-welded joints was better than of the brazed ones, primarily due to differences in passivation ability. Laser welding provides excellent corrosion resistance to cobalt-chromium alloy joints, but strength is limited due to the shallow weld penetration. Brazed joints are less resistant to corrosion but have higher tensile strength than laser welds.

Influence of nanomodification additives on the properties of multilayer composite coating obtained in laser surfacing

NASA Astrophysics Data System (ADS)

Cherepanov, A. N.; Orishich, A. M.; Ovcharenko, V. E.; Malikov, A. G.; Drozdov, V. O.; Pshenichnikov, A. P.

2017-10-01

The paper presents the results of numerical and experimental studies of the process of obtaining a permanent joint of two plates of heterogeneous metals that cannot be welded in the usual way: alloy Grade 4 and steel AISI 321 using a laser beam and an intermediate composite insert. The composite insert was obtained by explosion welding of four thin plates of titanium (Grade 4), niobium, copper, and steel (AISI 321). The insert was placed between the welded plates of titanium and steel, and the steel plate was welded with the steel part of the insert, and the titanium plate was welded with the titanium part of the insert. The plates were welded using a CO2 laser. The connection of metals with the help of explosion is carried out without their melting, so the formation of the brittle intermetallics does not occur in most cases. This ensures the greatest strength of the joints as compared to the joints obtained by other welding methods. To analyze the distribution of thermal fields in the composite insert and welded plates, a numerical study was conducted of the laser welding of steel and titanium plates with the corresponding parts of the insert. The purpose of the study was to determine the rational parameters of welding (laser beam power, speed of its movement, size and position of the focal spot), at which there was no complete melting of the steel and titanium parts of the insert during through penetration of the welded plates. The experimental part of the work is devoted to analysis of formation of the internal boundaries and microstructure of the composite insert and the strength of the permanent joint. It is shown that as a result of the explosion welding, weld seams of different wavelike configuration are formed. The most pronounced wavelike boundary is observed in the steel-copper connection, since these materials have a face-centered cubic lattice and are easily subjected to plastic deformation. At the contact boundaries of the plates, transition diffusion zones with different widths (from 5 to 40 μm) and element concentrations are formed. The hardness in the boundary diffusion zones is higher than in the connected metals, which is due to the diffusion interaction of the materials adjacent to each other. It has been established that the tensile strength of the composite insert is comparable to the maximum strength of Grade 4 alloy (456-511 MPa), and the failure in most cases occurred over the least durable component of the composite material, which is the copper plate, whose strength was significantly increased by cold hardening during explosion welding and diffusion of elements of the contacting plates.

Unusually Deep Bonin Earthquake (M7.9) of May 30, 2015 Suggests that Stagnant Slab Transforms into Penetration Stage

NASA Astrophysics Data System (ADS)

Obayashi, M.; Fukao, Y.; Yoshimitsu, J.

2015-12-01

A great shock occurred at an unusual depth of 678 km far away from the well-defined Wadati-Benioff zone of the Izu-Bonin arc (Fig.1). To the north of this region the slab is stagnant above the 660 km discontinuity and to the south it penetrates the discontinuity (Fig.2). Thus, the slab in this region can be viewed as in a transitional state from the stagnant to penetrating slab. Here, the steeply dipping part of the slab bends sharply to horizontal and the great shock happened at the lowest corner of this bending. The CMT indicates a pure normal faulting with the trench-normal near horizontal tensional axis and the near vertical compressional axis (Fig.1). We suggest that this mechanism reflects a transitional state of slab deformation from the bending-dominant mode to the penetration-dominant mode. The mechanism is consistent with either of these two two modes. We show that the mechanism is also consistent with the resultant stress field generated by many deep shocks occurring along the Wadati-Benioff zone. The calculated stress field changes rapidly along a trench-normal profile at a depth of 680 km and becomes similar to that generated by the great shock at points near the hypocenter (Fig.3). Thus, the stress field due to the Wadati-Benioff zone earthquakes works to enhance the occurrence of deep shocks of the type of the 2015 great shock, which represents slab deformation associated with the transition from stagnant to penetrating slab.

Influence of Laser Power on the Shape of Single Tracks in Scanner Based Laser Wire Cladding

NASA Astrophysics Data System (ADS)

Barroi, A.; Gonçalves, D. Albertazzi; Hermsdorf, J.; Kaierle, S.; Overmeyer, L.

The shape of the cladding tracks is extremely important for producing layers or structures by adding them sequently. This paper shows the influence of the laser power of a diode laser in the range of 500 to 1000 W on the shapes of single tracks in scanner based laser wire cladding. The scanner was used to oscillate the beam perpendiculary to the welding direction. Stainless steel (ER 318 Si) wire with a 0.6 mm diameter was used as deposition material. Height, width, penetration, molten area and weld seam angles of single tracks were obtained from cross-sections at three different positions of each track. The influence of these different positions on the results depends on the traverse speed. The paper discusses this influence in respect to the heat dissipation in the substrate material.

Semen quality and sex hormones among mild steel and stainless steel welders: a cross sectional study.

PubMed Central

Bonde, J P

1990-01-01

Welding may be detrimental to the male reproductive system. To test this hypothesis, semen quality was examined in 35 stainless steel welders, 46 mild steel welders, and 54 non-welding metal workers and electricians. These figures represent a participation rate of 37.1% in welders and 36.7% in non-welding subjects. The mean exposure to welding fume particulates was 1.3 mg/m3 (SD 0.8) in stainless steel welders using tungsten inert gas, 3.2 mg/m3 (SD 1.0) in low exposed mild steel welders using manual metal arc or metal active gas (n = 31), and 4.7 mg/m3 (SD 2.1) in high exposed mild steel welders (n = 15). The semen quality of each participant was defined in terms of the mean values of the particular semen parameters in three semen samples delivered at monthly intervals in a period with occupational exposure in a steady state. The sperm concentration was not reduced in either mild steel or stainless steel welders. The sperm count per ejaculate, the proportion of normal sperm forms, the degree of sperm motility, and the linear penetration rate of the sperm were significantly decreased and the sperm concentration of follicle stimulating hormone (FSH) was non-significantly increased in mild steel welders. A dose response relation between exposure to welding fumes and these semen parameters (sperm count excepted) was found. Semen quality decreased and FSH concentrations increased with increasing exposure. Significant deteriorations in some semen parameters were also observed in stainless steel welders. An analysis of information from questionnaires obtained from the whole population including subjects who declined to participate indicated an underestimation of effects due to selection bias. Potential confounding was treated by restriction and statistical analysis. The results support the hypothesis that mild steel welding and to a lesser extent stainless steel welding with tungsten inert gas is associated with reduced semen quality at exposure in the range of the Danish process specific threshold limit values of welding. PMID:2118383

Semen quality and sex hormones among mild steel and stainless steel welders: a cross sectional study.

PubMed

Bonde, J P

1990-08-01

Welding may be detrimental to the male reproductive system. To test this hypothesis, semen quality was examined in 35 stainless steel welders, 46 mild steel welders, and 54 non-welding metal workers and electricians. These figures represent a participation rate of 37.1% in welders and 36.7% in non-welding subjects. The mean exposure to welding fume particulates was 1.3 mg/m3 (SD 0.8) in stainless steel welders using tungsten inert gas, 3.2 mg/m3 (SD 1.0) in low exposed mild steel welders using manual metal arc or metal active gas (n = 31), and 4.7 mg/m3 (SD 2.1) in high exposed mild steel welders (n = 15). The semen quality of each participant was defined in terms of the mean values of the particular semen parameters in three semen samples delivered at monthly intervals in a period with occupational exposure in a steady state. The sperm concentration was not reduced in either mild steel or stainless steel welders. The sperm count per ejaculate, the proportion of normal sperm forms, the degree of sperm motility, and the linear penetration rate of the sperm were significantly decreased and the sperm concentration of follicle stimulating hormone (FSH) was non-significantly increased in mild steel welders. A dose response relation between exposure to welding fumes and these semen parameters (sperm count excepted) was found. Semen quality decreased and FSH concentrations increased with increasing exposure. Significant deteriorations in some semen parameters were also observed in stainless steel welders. An analysis of information from questionnaires obtained from the whole population including subjects who declined to participate indicated an underestimation of effects due to selection bias. Potential confounding was treated by restriction and statistical analysis. The results support the hypothesis that mild steel welding and to a lesser extent stainless steel welding with tungsten inert gas is associated with reduced semen quality at exposure in the range of the Danish process specific threshold limit values of welding.

Welding of Vanadium, Tantalum, 304L and 21-6-9 Stainless Steels, and Titanium Alloys at Lawrence Livermore National Laboratory using a Fiber Delivered 2.2 kW Diode Pumped CW Nd:YAG Laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmer, T; Elmer, J; Pong, R

This report summarizes the results of a series of laser welds made between 2003 and 2005 at Lawrence Livermore National Laboratory (LLNL). The results are a compilation of several, previously unpublished, internal LLNL reports covering the laser welding of vanadium, tantalum, 304L stainless steel, 21-6-9 (Nitronic 40) steel, and Ti-6Al-4V. All the welds were made using a Rofin Sinar DY-022 diode pumped continuous wave Nd:YAG laser. Welds are made at sharp focus on each material at various power levels and travel speeds in order to provide a baseline characterization of the performance of the laser welder. These power levels aremore » based on measurements of the output power of the laser system, as measured by a power meter placed at the end of the optics train. Based on these measurements, it appears that the system displays a loss of approximately 10% as the beam passes through the fiber optic cable and laser optics. Since the beam is delivered to the fixed laser optics through a fiber optic cable, the effects of fiber diameter are also briefly investigated. Because the system utilizes 1:1 focusing optics, the laser spot size at sharp focus generally corresponds to the diameter of the fiber with which the laser is delivered. Differences in the resulting weld penetration in the different materials system are prevalent, with the welds produced on the Nitronic 40 material displaying the highest depths (> 5 mm) and minimal porosity. A Primes focusing diagnostic has also been installed on this laser system and used to characterize the size and power density distribution of the beams as a function of both power and focus position. Further work is planned in which this focusing diagnostic will be used to better understand the effects of changes in beam properties on the resulting weld dimensions in these and other materials systems.« less

Comparative study of electromechanical impedance and Lamb wave techniques for fatigue crack detection and monitoring in metallic structures

NASA Astrophysics Data System (ADS)

Lim, Say Ian; Liu, Yu; Soh, Chee Kiong

2012-04-01

Fatigue cracks often initiate at the weld toes of welded steel connections. Usually, these cracks cannot be identified by the naked eyes. Existing identification methods like dye-penetration test and alternating current potential drop (ACPD) may be useful for detecting fatigue cracks at the weld toes. To apply these non-destructive evaluation (NDE) techniques, the potential sites have to be accessible during inspection. Therefore, there is a need to explore other detection and monitoring techniques for fatigue cracks especially when their locations are inaccessible or cost of access is uneconomical. Electro-mechanical Impedance (EMI) and Lamb wave techniques are two fast growing techniques in the Structural Health Monitoring (SHM) community. These techniques use piezoelectric ceramics (PZT) for actuation and sensing. Since the monitoring site is only needed to be accessed once for the instrumentation of the transducers, remote monitoring is made possible. The permanent locations of these transducers also translate to having consistent measurement for monitoring. The main focus of this study is to conduct a comparative investigation on the effectiveness and efficiency of the EMI technique and the Lamb wave technique for successful fatigue crack identification and monitoring of welded steel connections using piezoelectric transducers. A laboratory-sized non-load carrying fillet weld specimen is used in this study. The specimen is subjected to cyclic tensile load and data for both techniques are acquired at stipulated intervals. It can be concluded that the EMI technique is sensitive to the crack initiation phase while the Lamb wave technique correlates well with the crack propagation phase.

Investigation of galvanic corrosion in laser-welded stainless steel sheets

NASA Astrophysics Data System (ADS)

Kwok, Chi-Tat; Fong, Siu Lung; Cheng, Fai Tsun; Man, Hau-Chung

2004-10-01

In the present study, bead-on-plate specimens of 1-mm sheets of austenitic and duplex stainless steels were fabricated by laser penetration welding with a 2.5-kW CW Nd:YAG laser. The galvanic corrosion behavior of laser-weldment (LW) against as-received (AR) specimens with an area rato of 1:1 in 3.5% NaCL solution was studied by means of a zero-resistance ammeter. The free corrosion potentials of as-received specimens were found to be considerably higher than those of laser weldments, indicating that the weldments are more active and always act as anodes. The ranking of galvanic current densities (IG) of the couples in ascending order is: AR S31603-LW S31603 < AR S31803-LW S31803 < AR S32760-LW S32760 < AR S30400-LW S30400. For the galvanic couple between AR S30400 and LW S30400, the IG is the highest (78.6 nA/cm2) because large amount of δ-ferrite in the weld zone acts as active sites. On the other hand, the IG of the galvanic couple between AR S31603 and LW S31603 is the lowest (-26 nA/cm2) because no δ-ferrite is present after laser welding. The recorded IG of all couples revealed constantly low values (in the rnage of nA/cm2) and sometimes stayed negative, which indicated polarity reversal.

Overview of the program to assess the reliability of emerging nondestructive techniques open testing and study of flaw type effect on NDE response

NASA Astrophysics Data System (ADS)

Meyer, Ryan M.; Komura, Ichiro; Kim, Kyung-cho; Zetterwall, Tommy; Cumblidge, Stephen E.; Prokofiev, Iouri

2016-02-01

In February 2012, the U.S. Nuclear Regulatory Commission (NRC) executed agreements with VTT Technical Research Centre of Finland, Nuclear Regulatory Authority of Japan (NRA, former JNES), Korea Institute of Nuclear Safety (KINS), Swedish Radiation Safety Authority (SSM), and Swiss Federal Nuclear Safety Inspectorate (ENSI) to establish the Program to Assess the Reliability of Emerging Nondestructive Techniques (PARENT). The goal of PARENT is to investigate the effectiveness of current emerging and perspective novel nondestructive examination procedures and techniques to find flaws in nickel-alloy welds and base materials. This is done by conducting a series of open and blind international round-robin tests on a set of large-bore dissimilar metal welds (LBDMW), small-bore dissimilar metal welds (SBDMW), and bottom-mounted instrumentation (BMI) penetration weld test blocks. The purpose of blind testing is to study the reliability of more established techniques and included only qualified teams and procedures. The purpose of open testing is aimed at a more basic capability assessment of emerging and novel technologies. The range of techniques applied in open testing varied with respect to maturity and performance uncertainty and were applied to a variety of simulated flaws. This paper will include a brief overview of the PARENT blind and open testing techniques and test blocks and present some of the blind testing results.

Observed Eastward Progression of the Fukushima 134Cs Signal Across the North Pacific

NASA Astrophysics Data System (ADS)

Yoshida, S.; Macdonald, A. M.; Jayne, S. R.; Rypina, I.; Buesseler, K.

2015-12-01

Radionuclide samples taken as part of hydrographic surveys at 30°N in the North Pacific reveal that the easternmost edge of Fukushima-derived 134Cs observed at 174.3°W in 2012 had progressed eastward across the basin to 160.6°W by 2013. The 2013 30°N observations indicate surface 134Cs concentrations of 3-5 Bq/m3 between 160°E and 160°W, slightly lower concentrations west of 160°E and no detectable signal east of 160.6°W. Profile samples show 134Cs penetration to 500 m west of 180° with shoaling penetration depth toward to the east. The near-uniform vertical distribution of 137Cs between 152°W and 121.3°W in the top 500 m is indicative of trace amounts of radionuclides remaining from weapons testing. The physical processes responsible for the deep 134Cs penetration in the western Pacific appear to be related to distinct water mass subduction pathways, however the timing and rapidity of deep penetration over the broad scales observed has yet to be clarified.

Candidate-penetrative-fracture mapping of the Grand Canyon area, Arizona, from spatial correlation of deep geophysical features and surficial lineaments

USGS Publications Warehouse

Gettings, Mark E.; Bultman, Mark W.

2005-01-01

Some aquifers of the southwestern Colorado Plateaus Province are deeply buried and overlain by several impermeable shale layers, and so recharge to the aquifer probably is mainly by seepage down penetrative-fracture systems. The purpose of this 2-year study, sponsored by the U.S. National Park Service, was to map candidate deep penetrative fractures over a 120,000-km2 area, using gravity and aeromagnetic-anomaly data together with surficial-fracture data. The study area was on the Colorado Plateau south of the Grand Canyon and west of Black Mesa; mapping was carried out at a scale of 1:250,000. The resulting database constitutes a spatially registered estimate of deep-fracture locations. Candidate penetrative fractures were located by spatial correlation of horizontal- gradient and analytic-signal maximums of gravity and magnetic anomalies with major surficial lineaments obtained from geologic, topographic, side-looking-airborne-radar, and satellite imagery. The maps define a subset of candidate penetrative fractures because of limitations in the data coverage and the analytical technique. In particular, the data and analytical technique used cannot predict whether the fractures are open or closed. Correlations were carried out by using image-processing software, such that every pixel on the resulting images was coded to uniquely identify which datasets are correlated. The technique correctly identified known and many new deep fracture systems. The resulting penetrative-fracture-distribution maps constitute an objectively obtained, repeatable dataset and a benchmark from which additional studies can begin. The maps also define in detail the tectonic fabrics of the southwestern Colorado Plateaus Province. Overlaying the correlated lineaments on the normalized-density-of-vegetation-index image reveals that many of these lineaments correlate with the boundaries of vegetation zones in drainages and canyons and so may be controlling near-surface water availability in some places. Many derivative products can be produced from the database, such as fracture-density-estimate maps, and maps with the number of correlations color-coded to estimate the possible quality of correlation. The database contained in this report is designed to be used in a geographic information system and image-processing systems, and most data layers are in georeferenced tagged image format (Geotiff) or ARC grids. The report includes 163 map plates and various metadata, supporting, and statistical diagram files.

A Deep Penetration Problem Calculation Using AETIUS:An Easy Modeling Discrete Ordinates Transport Code UsIng Unstructured Tetrahedral Mesh, Shared Memory Parallel

NASA Astrophysics Data System (ADS)

KIM, Jong Woon; LEE, Young-Ouk

2017-09-01

As computing power gets better and better, computer codes that use a deterministic method seem to be less useful than those using the Monte Carlo method. In addition, users do not like to think about space, angles, and energy discretization for deterministic codes. However, a deterministic method is still powerful in that we can obtain a solution of the flux throughout the problem, particularly as when particles can barely penetrate, such as in a deep penetration problem with small detection volumes. Recently, a new state-of-the-art discrete-ordinates code, ATTILA, was developed and has been widely used in several applications. ATTILA provides the capabilities to solve geometrically complex 3-D transport problems by using an unstructured tetrahedral mesh. Since 2009, we have been developing our own code by benchmarking ATTILA. AETIUS is a discrete ordinates code that uses an unstructured tetrahedral mesh such as ATTILA. For pre- and post- processing, Gmsh is used to generate an unstructured tetrahedral mesh by importing a CAD file (*.step) and visualizing the calculation results of AETIUS. Using a CAD tool, the geometry can be modeled very easily. In this paper, we describe a brief overview of AETIUS and provide numerical results from both AETIUS and a Monte Carlo code, MCNP5, in a deep penetration problem with small detection volumes. The results demonstrate the effectiveness and efficiency of AETIUS for such calculations.

Empirical modeling for intelligent, real-time manufacture control

NASA Technical Reports Server (NTRS)

Xu, Xiaoshu

1994-01-01

Artificial neural systems (ANS), also known as neural networks, are an attempt to develop computer systems that emulate the neural reasoning behavior of biological neural systems (e.g. the human brain). As such, they are loosely based on biological neural networks. The ANS consists of a series of nodes (neurons) and weighted connections (axons) that, when presented with a specific input pattern, can associate specific output patterns. It is essentially a highly complex, nonlinear, mathematical relationship or transform. These constructs have two significant properties that have proven useful to the authors in signal processing and process modeling: noise tolerance and complex pattern recognition. Specifically, the authors have developed a new network learning algorithm that has resulted in the successful application of ANS's to high speed signal processing and to developing models of highly complex processes. Two of the applications, the Weld Bead Geometry Control System and the Welding Penetration Monitoring System, are discussed in the body of this paper.

Hydrogeology of the unsaturated zone, North Ramp area of the Exploratory Studies Facility, Yucca Mountain, Nevada

USGS Publications Warehouse

Rousseau, Joseph P.; Kwicklis, Edward M.; Gillies, Daniel C.; Rousseau, Joseph P.; Kwicklis, Edward M.; Gillies, Daniel C.

1999-01-01

Yucca Mountain, in southern Nevada, is being investigated by the U.S. Department of Energy as a potential site for a repository for high-level radioactive waste. This report documents the results of surface-based geologic, pneumatic, hydrologic, and geochemical studies conducted during 1992 to 1996 by the U.S. Geological Survey in the vicinity of the North Ramp of the Exploratory Studies Facility (ESF) that are pertinent to understanding multiphase fluid flow within the deep unsaturated zone. Detailed stratigraphic and structural characteristics of the study area provided the hydrogeologic framework for these investigations. Multiple lines of evidence indicate that gas flow and liquid flow within the welded tuffs of the unsaturated zone occur primarily through fractures. Fracture densities are highest in the Tiva Canyon welded (TCw) and Topopah Spring welded (TSw) hydrogeologic units. Although fracture density is much lower in the intervening nonwelded and bedded tuffs of the Paintbrush nonwelded hydrogeologic unit (PTn), pneumatic and aqueous-phase isotopic evidence indicates that substantial secondary permeability is present locally in the PTn, especially in the vicinity of faults. Borehole air-injection tests indicate that bulk air-permeability ranges from 3.5x10-14 to 5.4x10-11 square meters for the welded tuffs and from 1.2x10-13 to 3.0x10-12 square meters for the non welded and bedded tuffs of the PTn. Analyses of in-situ pneumatic-pressure data from monitored boreholes produced estimates of bulk permeability that were comparable to those determined from the air-injection tests. In many cases, both sets of estimates are two to three orders of magnitude larger than estimates based on laboratory analyses of unfractured core samples. The in-situ pneumatic-pressure records also indicate that the unsaturated-zone pneumatic system consists of four subsystems that coincide with the four major hydrogeologic units of the unsaturated zone at Yucca Mountain. In descending order, these hydrogeologic units are the Tiva Canyon welded (TCw), Paintbrush nonwelded (PTn), Topopah Spring welded (TSw ), and Calico Hills nonwelded (CHn). Deep percolation takes place as episodic pulses of inflow that propagate rapidly to depth and apparently bypass most of the rock matrix. Field-scale and core-scale water potentials throughout much of the PTn and TSw are very high, generally greater than -0.3 megapascals, and are nearly depth invariant. Thus, the imbibition capacity of the densely welded tuffs, at least near fractures, is very small because of low matrix permeabilities and low water-potential gradients across the fracture-matrix interface. The combination of high fracture permeability, high water potentials, high matrix saturations, and low matrix permeabilities results in a percolation environment that favors deep fracture flow. The episodic pulses of inflow are evidenced in the sporadic but nevertheless commonplace occurrence of water with concentrations of radioactive isotopes indicative of origins postdating the atmospheric testing of nuclear weapons. High concentrations of tritium have been detected at many horizons within the PTn and in the top of the TSw. Much lower concentrations of tritium, indicating the mixing of a bomb-pulse component with older water, have been detected in the deeper sections of the TSw and in the CHn. Evidence for fracture flow also is apparent in the widespread occurrence of perched water with chemical and isotopic signatures that indicate a fracture-flow origin for at least some of this water. In the North Ramp area, perched water has been detected at the base of the Topopah Spring Tuff or in the top of the underlying non welded to partially welded tuffs of the Calico Hills Formation in every dry-drilled borehole of sufficient depth to penetrate the Topopah Spring Tuff-Calico Hills Formation contact. The concentrations of the major ions of the perched water are similar to that of TSw pore water at borehole UZ-14, CHn pore water, and saturated-zone water at boreholes NRG-7 a and SD-9. The absolute chloride concentration of the perched water, however, is much lower than the chloride concentration of pore water from either the PTn or the TSw. The chemical and isotopic compositions of perched water indicate that this water was derived primarily from fracture flow, with little or no contribution from water in the matrix of the overlying rock. Carbon-14 ages of perched water range from 3,000 to 7,000 years. Strontium-87 isotope ratios indicate dissolution of surficial pedogenic calcite and calcite fracture fillings, which supports a fracture-flow origin for perched water. Moreover, carbon-13 and deuterium isotope values indicate rapid infiltration into fractures with little or no prior evaporation. Evidence for deep fracture flow into the Calico Hills Formation at UZ-14 is indicated by carbon-14 values that are from 65 and 95 percent modem carbon, equivalent to apparent ages of about 3,500 to 500 years. Some of these ages are younger than age estimates for perched water in the overlying Topopah Spring Tuff and are much younger than any that could be derived from a matrix-flow model. Evidence is lacking for extensive lateral flow within the PTn or for interception and diversion of this flow downward along structural pathways (faults), two key features of the original conceptual model for unsaturated flow at Yucca Mountain. Where data are available to infer lateral flow in the PTn, it is not certain that fracture flow could not have produced the same results. Pneumatic data, derived primarily from analysis of the interference effects from excavation of the North Ramp tunnel, indicate that faults within the Topopah Spring Tuff are open over substantial distances and are very permeable. Tunnel-boring-induced pneumatic disturbances have been propagated along these faults over distances that exceed 500 meters. These disturbances also have been detected in the pneumatic-pressure record of the overlying PTn in the vicinity of these faults. In spite of the apparent high permeability of faults, the existing data have neither confirmed nor refuted the hypothetical role of these faults in intercepting lateral flow from within or from above the PTn and diverting this flow downward into the deeper subsurface. On the basis of measured temperature gradients within the TSw, deep percolation appears to be greatest beneath active channels of major drainages, diminishing toward the margins and hillslopes bordering these channels. Numerical simulations indicate that this downward percolation is accompanied by lateral spreading as the percolation front moves downward through the PTn and across the contact between the PTn and underlying TSw. Temperature data from a well-documented site in Pagany Wash indicate the presence of a significant heat-flow deficit between the PTn and underlying TSw that most likely is due to nonconductive heat-flow processes with substantial capacity to extract heat. Percolation fluxes on the order of 10 to 20 millimeters per year beneath the Pagany Wash channel and on the order of 5 millimeters per year or less beneath the hillslopes bordering this drainage accounted for the apparent heat-flow deficit. Analyses of borehole temperature gradients in Drill Hole Wash indicate similar percolation fluxes and flux distributions within that drainage. An analysis of residence times estimated from uncorrected carbon-14 activities of perched-water samples and estimates for the volume of the structurally controlled reservoir, however, showed that the perched-water reservoir intersected by borehole UZ-14 under Drill Hole Wash could be sustained by percolation fluxes through the TSw of as little as 0.001 to 0.29 millimeter per year. The significance and implications of these findings with respect to waste isolation are discussed in the appendix of this report.

Laser-Assisted Stir Welding of 25-mm-Thick HSLA-65 Plate

NASA Astrophysics Data System (ADS)

Williamson, Keith M.

2002-12-01

Laser-assisted stir welding is a hybrid process that combines energy from a laser with functional heating and mechanical energy to join materials in the solid state. The technology is an adaptation of friction stir welding which is particularly suited for joining thick plates. Aluminum plates up to 75 mm thick have been successfully joined using friction stir welding. Since joining occurs in the solid state, stir technology offers the capability for fabricating full penetration joints in thick plates with better mechanical properties and less weld distortion than is possible by fusion processes. Currently friction stir welding is being used in several industries to improve productivity, reduce weight, and increase the strength of welded structures. Examples include: (a) the aircraft/aerospace industry where stir technology is currently being used to fabricate the space shuttle's external tank as well as components of the Delta family of rockets; (b) the shipping industry where container manufacturers are using stir technology to produce lighter containers with more payload capacity; and (c) the oil industry where offshore platform manufactures are using automated stir welding plants to fabricate large panels and structures up to 16 meters long with widths as required. In all these cases, stir technology has been restricted to aluminum alloys; however, stainless and HSLA 65 steels have been recently stir welded with friction as the primary heat source. One of the difficulties in adapting stir welding to steel is tool wear aggravated by the high tool rubbing velocities needed to provide frictional heat input into the material. Early work showed that the tool shoulder reached temperatures above 1000 C and the weld seam behind the tool stayed within this temperature range for up to 25 mm behind the tool. Cross sections of stir welded samples showed that the heat-affected zone is relatively wide and follows the profile of the tool shoulder. Besides minimizing the tool wear by increasing the energy into the material, another benefit of the proposed Laser Assisted Stir Welding (LASW is to reduce the width of the heat affected zone which typically has the lowest hardness in the weld region. Additionally, thermal modeling of the friction stir process shows that the heat input is asymmetric and suggests that the degree of asymmetry could improve the efficiency of the process. These asymmetries occur because the leading edge of the tool supplies heat to cold material while the trailing edge provides heat to material already preheated by the leading edge. As a result, flow stresses on the advancing side of the joint are lower than corresponding values on the retreating side. The proposed LASW process enhances these asymmetries by providing directional heating to increase the differential in flow stress across the joint and improve the stir tool efficiency. Theoretically the LASW process can provide the energy input to allow the flow stresses on the advancing side to approach zero and the stir efficiency to approach 100 percent. Reducing the flow stresses on the advancing side of the weld creates the greatest pressure differential across the stir weld and eliminates the possibility of voids on the advancing side of the joint. Small pressure differentials result in poor stir welds because voids on the advancing side are not filled by the plastic flow of material from the retreating side.

Fabrication and evaluation of superplastically formed/weld-brazed corrugated compression panels with beaded webs

NASA Technical Reports Server (NTRS)

Royster, D. M.; Davis, R. C.; Shinn, J. M., Jr.; Bales, T. T.; Wiant, H. R.

1985-01-01

A study was made to investigate the feasibility of superplastically forming corrugated panels with beaded webs and to demonstrate the structural integrity of these panels by testing. The test panels in the study consist of superplastically formed titanium alloy Ti-6Al-4V half-hat elements that are joined by weld-brazing to titanium alloy Ti-6Al-4V caps to form either single-corrugation compression panels or multiple-corrugation compression panels. Stretching and subsequent thinning of the titanium sheet during superplastic forming is reduced by approximately 35 percent with a shallow half-hat die concept instead of a deep die concept and results in a more uniform thickness across the beaded webs. The complete panels are tested in end compression at room temperature and the results compared with analysis. The heavily loaded panels failed at loads approaching the yield strength of the titanium material. At maximum load, the caps wrinkled locally accompanied with separation of the weld-braze joint in the wrinkle. None of the panels tested, however, failed catastrophically in the weld-braze joint. Experimental test results are in good agreement with structural analysis of the panels.

Cellular imaging of deep organ using two-photon Bessel light-sheet nonlinear structured illumination microscopy

PubMed Central

Zhao, Ming; Zhang, Han; Li, Yu; Ashok, Amit; Liang, Rongguang; Zhou, Weibin; Peng, Leilei

2014-01-01

In vivo fluorescent cellular imaging of deep internal organs is highly challenging, because the excitation needs to penetrate through strong scattering tissue and the emission signal is degraded significantly by photon diffusion induced by tissue-scattering. We report that by combining two-photon Bessel light-sheet microscopy with nonlinear structured illumination microscopy (SIM), live samples up to 600 microns wide can be imaged by light-sheet microscopy with 500 microns penetration depth, and diffused background in deep tissue light-sheet imaging can be reduced to obtain clear images at cellular resolution in depth beyond 200 microns. We demonstrate in vivo two-color imaging of pronephric glomeruli and vasculature of zebrafish kidney, whose cellular structures located at the center of the fish body are revealed in high clarity by two-color two-photon Bessel light-sheet SIM. PMID:24876996

Energy and technology review: Engineering modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cabayan, H.S.; Goudreau, G.L.; Ziolkowski, R.W.

1986-10-01

This report presents information concerning: Modeling Canonical Problems in Electromagnetic Coupling Through Apertures; Finite-Element Codes for Computing Electrostatic Fields; Finite-Element Modeling of Electromagnetic Phenomena; Modeling Microwave-Pulse Compression in a Resonant Cavity; Lagrangian Finite-Element Analysis of Penetration Mechanics; Crashworthiness Engineering; Computer Modeling of Metal-Forming Processes; Thermal-Mechanical Modeling of Tungsten Arc Welding; Modeling Air Breakdown Induced by Electromagnetic Fields; Iterative Techniques for Solving Boltzmann's Equations for p-Type Semiconductors; Semiconductor Modeling; and Improved Numerical-Solution Techniques in Large-Scale Stress Analysis.

Optimization of Deep Drilling Performance--Development and Benchmark Testing of Advanced Diamond Product Drill Bits & HP/HT Fluids to Significantly Improve Rates of Penetration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alan Black; Arnis Judzis

2003-10-01

This document details the progress to date on the OPTIMIZATION OF DEEP DRILLING PERFORMANCE--DEVELOPMENT AND BENCHMARK TESTING OF ADVANCED DIAMOND PRODUCT DRILL BITS AND HP/HT FLUIDS TO SIGNIFICANTLY IMPROVE RATES OF PENETRATION contract for the year starting October 2002 through September 2002. The industry cost shared program aims to benchmark drilling rates of penetration in selected simulated deep formations and to significantly improve ROP through a team development of aggressive diamond product drill bit--fluid system technologies. Overall the objectives are as follows: Phase 1--Benchmark ''best in class'' diamond and other product drilling bits and fluids and develop concepts for amore » next level of deep drilling performance; Phase 2--Develop advanced smart bit--fluid prototypes and test at large scale; and Phase 3--Field trial smart bit--fluid concepts, modify as necessary and commercialize products. Accomplishments to date include the following: 4Q 2002--Project started; Industry Team was assembled; Kick-off meeting was held at DOE Morgantown; 1Q 2003--Engineering meeting was held at Hughes Christensen, The Woodlands Texas to prepare preliminary plans for development and testing and review equipment needs; Operators started sending information regarding their needs for deep drilling challenges and priorities for large-scale testing experimental matrix; Aramco joined the Industry Team as DEA 148 objectives paralleled the DOE project; 2Q 2003--Engineering and planning for high pressure drilling at TerraTek commenced; 3Q 2003--Continuation of engineering and design work for high pressure drilling at TerraTek; Baker Hughes INTEQ drilling Fluids and Hughes Christensen commence planning for Phase 1 testing--recommendations for bits and fluids.« less

Three dimensional amorphous silicon/microcrystalline silicon solar cells

DOEpatents

Kaschmitter, James L.

1996-01-01

Three dimensional deep contact amorphous silicon/microcrystalline silicon (a-Si/.mu.c-Si) solar cells which use deep (high aspect ratio) p and n contacts to create high electric fields within the carrier collection volume material of the cell. The deep contacts are fabricated using repetitive pulsed laser doping so as to create the high aspect p and n contacts. By the provision of the deep contacts which penetrate the electric field deep into the material where the high strength of the field can collect many of the carriers, thereby resulting in a high efficiency solar cell.

Three dimensional amorphous silicon/microcrystalline silicon solar cells

DOEpatents

Kaschmitter, J.L.

1996-07-23

Three dimensional deep contact amorphous silicon/microcrystalline silicon (a-Si/{micro}c-Si) solar cells are disclosed which use deep (high aspect ratio) p and n contacts to create high electric fields within the carrier collection volume material of the cell. The deep contacts are fabricated using repetitive pulsed laser doping so as to create the high aspect p and n contacts. By the provision of the deep contacts which penetrate the electric field deep into the material where the high strength of the field can collect many of the carriers, thereby resulting in a high efficiency solar cell. 4 figs.

Application of elastic and elastic-plastic fracture mechanics methods to surface flaws

NASA Astrophysics Data System (ADS)

McCabe, Donald E.; Ernst, Hugo A.; Newman, James C., Jr.

Fuel tanks that are a part of the External Tank assembly for the Space Shuttle are made of relatively thin 2219-T87 aluminum plate. These tanks contain about 917 m of fusion weld seam, all of which is nondestructively inspected for flaws and all those found are repaired. The tanks are subsequently proof-tested to a pressure that is sufficiently severe to cause weld metal yielding in a few local regions of the weld seam. The work undertaken in the present project was to develop a capability to predict flaw growth from undetected surface flaws that are assumed to be located in the highly stressed regions. The technical challenge was to develop R-curve prediction capability for surface cracks in specimens that contain the flaws of unusual sizes and shapes deemed to be of interest. The test techniques developed and the elastic-plastic analysis concepts adopted are presented. The flaws of interest were quite small surface cracks that were narrow-deep ellipses that served to exacerbate the technical difficulties involved.

Application of elastic and elastic-plastic fracture mechanics methods to surface flaws

NASA Technical Reports Server (NTRS)

Mccabe, Donald E.; Ernst, Hugo A.; Newman, James C., Jr.

1992-01-01

Fuel tanks that are a part of the External Tank assembly for the Space Shuttle are made of relatively thin 2219-T87 aluminum plate. These tanks contain about 917 m of fusion weld seam, all of which is nondestructively inspected for flaws and all those found are repaired. The tanks are subsequently proof-tested to a pressure that is sufficiently severe to cause weld metal yielding in a few local regions of the weld seam. The work undertaken in the present project was to develop a capability to predict flaw growth from undetected surface flaws that are assumed to be located in the highly stressed regions. The technical challenge was to develop R-curve prediction capability for surface cracks in specimens that contain the flaws of unusual sizes and shapes deemed to be of interest. The test techniques developed and the elastic-plastic analysis concepts adopted are presented. The flaws of interest were quite small surface cracks that were narrow-deep ellipses that served to exacerbate the technical difficulties involved.

Evolution of the conceptual model of unsaturated zone hydrology at Yucca Mountain, Nevada

USGS Publications Warehouse

Flint, Alan L.; Flint, Lorraine E.; Bodvarsson, Gudmundur S.; Kwicklis, Edward M.; Fabryka-Martin, June

2001-01-01

Yucca Mountain is an arid site proposed for consideration as the United States’ first underground high-level radioactive waste repository. Low rainfall (approximately 170 mm/yr) and a thick unsaturated zone (500–1000 m) are important physical attributes of the site because the quantity of water likely to reach the waste and the paths and rates of movement of the water to the saturated zone under future climates would be major factors in controlling the concentrations and times of arrival of radionuclides at the surrounding accessible environment. The framework for understanding the hydrologic processes that occur at this site and that control how quickly water will penetrate through the unsaturated zone to the water table has evolved during the past 15 yr. Early conceptual models assumed that very small volumes of water infiltrated into the bedrock (0.5–4.5 mm/yr, or 2–3 percent of rainfall), that much of the infiltrated water flowed laterally within the upper nonwelded units because of capillary barrier effects, and that the remaining water flowed down faults with a small amount flowing through the matrix of the lower welded, fractured rocks. It was believed that the matrix had to be saturated for fractures to flow. However, accumulating evidence indicated that infiltration rates were higher than initially estimated, such as infiltration modeling based on neutron borehole data, bomb-pulse isotopes deep in the mountain, perched water analyses and thermal analyses. Mechanisms supporting lateral diversion did not apply at these higher fluxes, and the flux calculated in the lower welded unit exceeded the conductivity of the matrix, implying vertical flow of water in the high permeability fractures of the potential repository host rock, and disequilibrium between matrix and fracture water potentials. The development of numerical modeling methods and parameter values evolved concurrently with the conceptual model in order to account for the observed field data, particularly fracture flow deep in the unsaturated zone. This paper presents the history of the evolution of conceptual models of hydrology and numerical models of unsaturated zone flow at Yucca Mountain, Nevada (Flint, A.L., Flint, L.E., Kwicklis, E.M., Bodvarsson, G.S., Fabryka-Martin, J.M., 2001. Hydrology of Yucca Mountain. Reviews of Geophysics in press). This retrospective is the basis for recommendations for optimizing the efficiency with which a viable and robust conceptual model can be developed for a complex site.

Cyclic mechanical loading promotes bacterial penetration along composite restoration marginal gaps

PubMed Central

Khvostenko, D.; Salehi, S.; Naleway, S. E.; Hilton, T. J.; Ferracane, J. L.; Mitchell, J. C.; Kruzic, J. J.

2015-01-01

Objectives Secondary caries is the most common reason for composite restoration replacement and usually forms between dentin and the filling. The objective of this study was to investigate the combined effect of cyclic loading and bacterial exposure on bacterial penetration into gaps at the interface between dentin and resin composite restorative material using a novel bioreactor system and test specimen design. Methods Human molars were machined into 3 mm thick disks with 2 mm deep × 5 mm diameter cavity preparations into which composite restorations were placed. A ∼15-30 micrometer (small) or ∼300 micrometer wide (large) dentin-restoration gap was introduced along half of the interface between the dentin and restoration. Streptococcus mutans UA 159 biofilms were grown on each sample prior to testing in a bioreactor both with and without cyclic loading. Both groups of samples were tested for 2 weeks and post-test biofilm viability was confirmed with a live-dead assay. Samples were fixed, mounted and cross-sectioned to reveal the gaps and observe the depth of bacterial penetration. Results It was shown that for large gap samples the bacteria easily penetrated to the full depth of the gap independent of loading or non-loading conditions. The results for all cyclically loaded small gap samples show a consistently deep bacterial penetration down 100% of the gap while the average penetration depth was only 67% for the non-loaded samples with only two of six samples reaching 100%. Significance A new bioreactor was developed that allows combining cyclic mechanical loading and bacterial exposure of restored teeth for bacterial biofilm and demineralization studies. Cyclic loading was shown to aid bacterial penetration into narrow marginal gaps, which could ultimately promote secondary caries formation. PMID:25900624

Delayed presentation of deep penetrating trauma to the subaxial cervical spine.

PubMed

Zaldivar-Jolissaint, Julien Francisco; Bobinski, Lukas; Van Dommelen, Yaelle; Levivier, Marc; Simon, Christian; Duff, John Michael

2015-05-01

To present a rare case of deep penetrating neck trauma in which a retained foreign body in the cervical spine (a broken knife blade) resulted in delayed radicular injury. We describe the surgical management using a retrojugular approach. Our patient sustained a stab wound to the supraclavicular triangle from a small pocketknife. He was initially managed in a local hospital by simple primary wound closure without any radiological examinations, and was discharged home. The patient re-consulted in a delayed fashion with mild local persistent neck pain. Subsequent radiological investigations revealed a foreign body (the broken blade of a pocket knife) embedded in the left neural foramen between the C6 and C7 vertebrae penetrating the disc space. The blade was lying between the left C7 nerve root and the ipsilateral vertebral artery (VA) at the transition of V1 and V2 segments. Initial neurological evaluation was normal. Some days later, the patient developed a delayed left C7 radicular deficit. We undertook urgent exploration along the wound corridor through a retrojugular, transforaminal approach with successful removal of the blade. To our knowledge, this is a unique case where a retained foreign body penetrated the soft tissues of the neck, embedding deep in the vertebral column without vascular, aerodigestive or significant primary neurological injury, while causing delayed neck pain and delayed onset radicular injury. We describe our surgical management for removal of the retained blade. The retrojugular approach gives excellent access to all of the important anatomical structures of the neck from an anterolateral approach.

A predictive penetrative fracture mapping method from regional potential field and geologic datasets, southwest Colorado Plateau, U.S.A

USGS Publications Warehouse

Gettings, M.E.; Bultman, M.W.

2005-01-01

Some aquifers of the southwest Colorado Plateau, U.S.A., are deeply buried and overlain by several impermeable units, and thus recharge to the aquifer is probably mainly by seepage down penetrative fracture systems. This purpose of this study was to develop a method to map the location of candidate deep penetrative fractures over a 120,000 km2 area using gravity and aeromagnetic anomaly data together with surficial fracture data. The resulting database constitutes a spatially registered estimate of recharge location. Candidate deep fractures were obtained by spatial correlation of horizontal gradient and analytic signal maxima of gravity and magnetic anomalies vertically with major surficial lineaments obtained from geologic, topographic, side-looking airborne radar, and satellite imagery. The maps define a sub-set of possible penetrative fractures because of limitations of data coverage and the analysis technique. The data and techniques employed do not yield any indication as to whether fractures are open or closed. Correlations were carried out using image processing software in such a way that every pixel on the resulting grids was coded to uniquely identify which datasets correlated. The technique correctly identified known deep fracture systems and many new ones. Maps of the correlations also define in detail the tectonic fabrics of the Southwestern Colorado Plateau. Copyright ?? The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.

Conceptual waste packaging options for deep borehole disposal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Jiann -Cherng; Hardin, Ernest L.

This report presents four concepts for packaging of radioactive waste for disposal in deep boreholes. Two of these are reference-size packages (11 inch outer diameter) and two are smaller (5 inch) for disposal of Cs/Sr capsules. All four have an assumed length of approximately 18.5 feet, which allows the internal length of the waste volume to be 16.4 feet. However, package length and volume can be scaled by changing the length of the middle, tubular section. The materials proposed for use are low-alloy steels, commonly used in the oil-and-gas industry. Threaded connections between packages, and internal threads used to sealmore » the waste cavity, are common oilfield types. Two types of fill ports are proposed: flask-type and internal-flush. All four package design concepts would withstand hydrostatic pressure of 9,600 psi, with factor safety 2.0. The combined loading condition includes axial tension and compression from the weight of a string or stack of packages in the disposal borehole, either during lower and emplacement of a string, or after stacking of multiple packages emplaced singly. Combined loading also includes bending that may occur during emplacement, particularly for a string of packages threaded together. Flask-type packages would be fabricated and heat-treated, if necessary, before loading waste. The fill port would be narrower than the waste cavity inner diameter, so the flask type is suitable for directly loading bulk granular waste, or loading slim waste canisters (e.g., containing Cs/Sr capsules) that fit through the port. The fill port would be sealed with a tapered, threaded plug, with a welded cover plate (welded after loading). Threaded connections between packages and between packages and a drill string, would be standard drill pipe threads. The internal flush packaging concepts would use semi-flush oilfield tubing, which is internally flush but has a slight external upset at the joints. This type of tubing can be obtained with premium, low-profile threaded connections at each end. The internal-flush design would be suitable for loading waste that arrives from the originating site in weld-sealed, cylindrical canisters. Internal, tapered plugs with sealing filet welds would seal the tubing at each end. The taper would be precisely machined onto both the tubing and the plug, producing a metal-metal sealing surface that is compressed as the package is subjected to hydrostatic pressure. The lower plug would be welded in place before loading, while the upper plug would be placed and welded after loading. Conceptual Waste Packaging Options for Deep Borehole Disposal July 30, 2015 iv Threaded connections between packages would allow emplacement singly or in strings screwed together at the disposal site. For emplacement on a drill string the drill pipe would be connected directly into the top package of a string (using an adapter sub to mate with premium semi-flush tubing threads). Alternatively, for wireline emplacement the same package designs could be emplaced singly using a sub with wireline latch, on the upper end. Threaded connections on the bottom of the lowermost package would allow attachment of a crush box, instrumentation, etc.« less

Process Model for Friction Stir Welding

NASA Technical Reports Server (NTRS)

Adams, Glynn

1996-01-01

Friction stir welding (FSW) is a relatively new process being applied for joining of metal alloys. The process was initially developed by The Welding Institute (TWI) in Cambridge, UK. The FSW process is being investigated at NASA/MSEC as a repair/initial weld procedure for fabrication of the super-light-weight aluminum-lithium shuttle external tank. The FSW investigations at MSFC were conducted on a horizontal mill to produce butt welds of flat plate material. The weldment plates are butted together and fixed to a backing plate on the mill bed. A pin tool is placed into the tool holder of the mill spindle and rotated at approximately 400 rpm. The pin tool is then plunged into the plates such that the center of the probe lies at, one end of the line of contact, between the plates and the shoulder of the pin tool penetrates the top surface of the weldment. The weld is produced by traversing the tool along the line of contact between the plates. A lead angle allows the leading edge of the shoulder to remain above the top surface of the plate. The work presented here is the first attempt at modeling a complex phenomenon. The mechanical aspects of conducting the weld process are easily defined and the process itself is controlled by relatively few input parameters. However, in the region of the weld, plasticizing and forging of the parent material occurs. These are difficult processes to model. The model presented here addresses only variations in the radial dimension outward from the pin tool axis. Examinations of the grain structure of the weld reveal that a considerable amount of material deformation also occurs in the direction parallel to the pin tool axis of rotation, through the material thickness. In addition, measurements of the axial load on the pin tool demonstrate that the forging affect of the pin tool shoulder is an important process phenomenon. Therefore, the model needs to be expanded to account for the deformations through the material thickness and the forging affect of the shoulder. The energy balance at the boundary of the plastic region with the environment required that energy flow away from the boundary in both radial directions. One resolution to this problem may be to introduce a time dependency into the process model, allowing the energy flow to oscillate across this boundary. Finally, experimental measurements are needed to verify the concepts used here and to aid in improving the model.

Preparing America for Deep Space Exploration Episode 11: Committed to Exploration

NASA Image and Video Library

2015-12-09

Engineers around the country are making progress developing NASA’s Space Launch System, Orion spacecraft and the ground systems at Kennedy Space Center in Florida needed to send astronauts on missions to deep space destinations. Between July and September, progress continued as pieces of Orion’s crew module and the SLS core stage tanks were welded together at NASA’s Michoud Assembly Facility in New Orleans, modifications were made to the mobile launcher at Kennedy, astronauts tested techniques for exiting Orion after a mission, and an RS-25 engine was tested at Stennis Space Center in Mississippi.

Improved Tubulars for Better Economics in Deep Gas Well Drilling using Microwave Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dinesh Agrawal; Paul Gigl; Mahlon Dennis

2006-02-01

The objective of the research program has been to improve the rate-of-penetration in deep hostile environments by improving the life cycle and performance of coiled-tubing, an important component of a deep well drilling system for oil and gas exploration. The current process of the manufacture long tubular steel products consists of shaping the tube from flat strip, welding the seam and sections into lengths that can be miles long, and coiling onto reels. However, the welds, that are a weak point, now limit the performance of the coil tubing. This is not only from a toughness standpoint but also frommore » a corrosion standpoint. By utilizing the latest developments in the sintering of materials with microwave energy and powder metal extrusion technology for the manufacture of seamless coiled tubing and other tubular products, these problems can be eliminated. The project is therefore to develop a continuous microwave process to sinter continuously steel tubulars and butt-join them using microwave/induction process. The program started about three years ago and now we are in the middle of Phase II. In Phase I (which ended in February 2005) a feasibility study of the extrusion process of steel powder and continuously sinter the extruded tubing was conducted. The research program has been based on the development of microwave technology to process tubular specimens of powder metals, especially steels. The existing microwave systems at the Materials Research Laboratory (MRL) and Dennis Tool Company (DTC) were suitably modified to process tubular small specimens. The precursor powder metals were either extruded or cold isostatically pressed (CIP) to form tubular specimens. After conducting an extensive and systematic investigation of extrusion process for producing long tubes, it was determined that there were several difficulties in adopting extrusion process and it cannot be economically used for producing thousands of feet long green tubing. Therefore, in the Phase II the approach was modified to the microwave sintering combined with Cold Isostatic Press (CIP) and joining (by induction or microwave). This process can be developed into a semi-continuous sintering process if the CIP can produce parts fast enough to match the microwave sintering rates. This report summarizes the progress made to-date in this new approach. The final steel composition matching with the Quality tubing's QT-16Cr80 was short listed and used for all experiments. Bonding experiments using 4 different braze powders were conducted and the process optimized to obtain high degree of bonding strength. For fabrication of green tubulars a large CIP unit was acquired and tested. This equipment is located at the Dennis Tool facility in Houston. Microwave sintering experiments for continuous processing of the CIPed tubes are under progress in order to identify the optimum conditions. There have been some reproducibility problems and we are at present working to resolve these problems.« less

Optics for multimode lasers with elongated depth of field

NASA Astrophysics Data System (ADS)

Laskin, Alexander; Laskin, Vadim; Ostrun, Aleksei

2017-02-01

Modern multimode high-power lasers are widely used in industrial applications and control of their radiation, especially by focusing, is of great importance. Because of relatively low optical quality, characterized by high values of specifications Beam Parameter Product (BPP) or M², the depth of field by focusing of multimode laser radiation is narrow. At the same time laser technologies like deep penetration welding, cutting of thick metal sheets get benefits from elongated depth of field in area of focal plane, therefore increasing of zone along optical axis with minimized spot size is important technical task. As a solution it is suggested to apply refractive optical systems splitting an initial laser beam into several beamlets, which are focused in different foci separated along optical axis with providing reliable control of energy portions in each separate focus, independently of beam size or mode structure. With the multi-focus optics, the length of zone of material processing along optical axis is defined rather by distances between separate foci, which are determined by optical design of the optics and can be chosen according to requirements of a particular laser technology. Due to stability of the distances between foci there is provided stability of a technology process. This paper describes some design features of refractive multi-focus optics, examples of real implementations and experimental results will be presented as well.

Nondestructive Evaluation Methods for Characterization of Corrosion: State of the Art Review

DTIC Science & Technology

1988-12-01

form molecules of hydrogen gas damage is characterized by surface discolora- and leave the surface. Under some circum- tion and deep gouges or pits...large electromagnet and low operating granular corrosion without stress-related crack- frequencies resulted in deep penetration of ing can produce a...focus, and then the spray al. (11) showed that thermography was able to and the focus were moved together down the detect 3-mm deep , 50-mm diameter

Current oscillations in semi-insulating GaAs associated with field-enhanced capture of electrons by the major deep donor EL2

NASA Technical Reports Server (NTRS)

Kaminska, M.; Parsey, J. M.; Lagowski, J.; Gatos, H. C.

1982-01-01

Current oscillations thermally activated by the release of electrons from deep levels in undoped semiinsulating GaAs were observed for the first time. They were attributed to electric field-enhanced capture of electrons by the dominant deep donor EL2 (antisite AsGa defect). This enhanced capture is due to the configurational energy barrier of EL2, which is readily penetrated by hot electrons.

Intensified diapycnal mixing in the midlatitude western boundary currents.

PubMed

Jing, Zhao; Wu, Lixin

2014-12-10

The wind work on oceanic near-inertial motions is suggested to play an important role in furnishing the diapycnal mixing in the deep ocean which affects the uptake of heat and carbon by the ocean as well as climate changes. However, it remains a puzzle where and through which route the near-inertial energy penetrates into the deep ocean. Using the measurements collected in the Kuroshio extension region during January 2005, we demonstrate that the diapycnal mixing in the thermocline and deep ocean is tightly related to the shear variance of wind-generated near-inertial internal waves with the diapycnal diffusivity 6 × 10(-5) m(2)s(-1) almost an order stronger than that observed in the circulation gyre. It is estimated that 45%-62% of the local near-inertial wind work 4.5 × 10(-3) Wm(-2) radiates into the thermocline and deep ocean and accounts for 42%-58% of the energy required to furnish mixing there. The elevated mixing is suggested to be maintained by the energetic near-inertial wind work and strong eddy activities causing enhanced downward near-inertial energy flux than earlier findings. The western boundary current turns out to be a key region for the penetration of near-inertial energy into the deep ocean and a hotspot for the diapycnal mixing in winter.

Elaboration and Device Complex Trial for Pipe Production of Raised Quality

NASA Astrophysics Data System (ADS)

Privarnikov, J. K.; Vdovin, V. D.; Privarnikova, I. J.

2002-01-01

Technology and device for production of heightened quality pipes for arterial oil and gas conduits are created and inculcated on factual data of work of Novomoskovsk Pipe Plant. At present such pipes are made with using heat treatment in penetrated sectional stoves. Herewith big volume of natural gas is expended. Besides, it is observed an incomplete removal of residual stresses during heat treatment that adversely affects at operation pipe indexes and durability of welded seam. Researches, which authors have conducted, have shown that offered weakly annealing technology and device provide almost full removal of undesirable residual stresses that considerably raises durability of welded junctions and improves operation pipe indexes. Inculcation of offered technology in Ukraine at the same time will allow to reduce by 40-50 % natural gas expense, to raise ecological safety at the sacrifice of diminish of possible damages at conduits as well as to produce electric welded pipes of heightened quality. I am sending you the abstract of the report Elaboration and device complex trial for pipe production of heightened quality, reference number - IAC-02.V.6./1.7 - ? (Unfortunately number is lost. Please inform us the number of our report once again) authors Privarnikov J.K, Vdovin V.D., Privarnikova I.J. for presentation at the 53rd International Asnronautical Congress/ Professor Yu. Privarnikov

Structural, mechanical and corrosion studies of Cr-rich inclusions in 152 cladding of dissimilar metal weld joint

NASA Astrophysics Data System (ADS)

Li, Yifeng; Wang, Jianqiu; Han, En-Hou; Yang, Chengdong

2018-01-01

Cr-rich inclusions were discovered in 152 cladding at the inner wall of domestic dissimilar metal weld joint, and their morphologies, microstructures, mechanical properties and corrosion behaviors were systematically characterized by SEM, TEM, nanoindentation and FIB. The results indicate that the Cr-rich inclusions originate from large-size Cr particles in 152 welding electrode flux, and they are 50-150 μm in size in most cases, and there is a continuous transition zone of 2-5 μm in width between the Cr inclusion core and 152 cladding matrix, and the transition zone consists of Ni & Fe-rich dendritic austenite and Cr23C6 and Cr matrix. The transition zone has the highest nanoindentation hardness (7.66 GPa), which is much harder than the inclusion core (5.14 GPa) and 152 cladding (3.71 GPa). In-situ microscopic tensile tests show that cracks initialize preferentially in transition zone, and then propagate into the inclusion core, and creep further into 152 cladding after penetrating the core area. The inclusion core and its transition zone both share similar oxide film structure with nickel-base 152 cladding matrix in simulated primary water, while those two parts present better general corrosion resistance than 152 cladding matrix due to higher Cr concentration.

Weldability of Advanced High Strength Steels using Ytterbium:Yttrium Aluminium Garnet high power laser for Tailor-Welded Blank applications

NASA Astrophysics Data System (ADS)

Sharma, Rajashekhar Shivaram

Use of a high power Yb:YAG laser is investigated for joining advanced high strength steel materials for use in tailor-welded blank (TWB) applications. TWB's are materials of different chemistry, coating or thicknesses that are joined before metal forming and other operations such as trimming, assembly and painting are carried out. TWB is becoming an important design tool in the automotive industry for reducing weight, improving fuel economy and passenger safety, while reducing the overall costs for the customer. Three advanced high strength steels, TRIP780, DP980 and USIBOR, which have many unique properties that are conducive to achieving these objectives, along with mild steel, are used in this work. The objective of this work is to ensure that high quality welds can be obtained using Yb:YAG lasers which are also becoming popular for metal joining operations, since they produce high quality laser beams that suffer minimal distortion when transported via fiber optic cables. Various power levels and speeds for the laser beam were used during the investigation. Argon gas was consistently used for shielding purposes during the welding process. After the samples were welded, metallographic examination of the fusion and heat-affected zones using optical and scanning electron microscopes were carried out to determine the microstructures as well as weld defects. Optical and scanning electron microscopes were also used to examine the top of welds as well as fracture surfaces. Additionally, cross-weld microhardness evaluations, tensile tests using Instron tester, limited fatigue tests as well as formability evaluations using OSU plane strain evaluation were carried out. The examinations included a 2-factor full factorial design of experiments to determine the impact of coatings on the surface roughness on the top of the welds. Tensile strengths of DP980, TRIP780 and mild steel materials as well as DP980 welded to TRIP780 and mild steel in the rolling direction as well as transverse direction were evaluated. Metallographic examinations determined that most of the fusion zone is martensitic with small regions of bainite and ferrite. High microhardness values of the order of 550--600 Hv were noted in most joints, which are attributed to high alloy content of the fusion zone as well as high rates of cooling typical of laser welds. During tensile, fatigue and formability tests, no fractures in the fusion or heat affected zones were observed. Geometric variability evaluations indicated that coatings such as aluminum (in the case of USIBOR) and galvanized zinc (TRIP780) can affect the variability of the weld zone and the surface roughness on the top of the weld. Excessive variability in the form of weld concavity in the weld zones can lead to fractures in the weld region, even though higher hardness can, to some extent, compensate for these surface irregularities. The 2-factor design of experiments further confirmed that coatings adversely affect the surface roughness on the top of the welds. Although thickness differentials alone do not make a significant impact on surface roughness, together with coatings, they can have an adverse effect on roughness. Tensile tests in the direction of rolling as well as in the transverse direction indicate that TRIP780 seems weaker in the direction of rolling when compared to transverse direction while mild steel is stronger in the direction of rolling. Weldability analyses revealed that the typical melting efficiency is on the order of 50--70% for full penetration welding. Formability tests showed that TR/MS joints fractured in a direction parallel to the weld line when tested with the loads perpendicular to the weld line. Tests have also confirmed that weld speed and power have no impact on the outcome of formability results. Overall, this work conclusively proves that high power Yb:YAG lasers can effectively join high strength materials such as DP980, TRIP780, USIBOR, as well as mild steel, for use in tailor-welded blank applications, contributing to lighter, more fuel-efficient and safer vehicles.

Development and Application of Laser Peening System for PWR Power Plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masaki Yoda; Itaru Chida; Satoshi Okada

2006-07-01

Laser peening is a process to improve residual stress from tensile to compressive in surface layer of materials by irradiating high-power laser pulses on the material in water. Toshiba has developed a laser peening system composed of Q-switched Nd:YAG laser oscillators, laser delivery equipment and underwater remote handling equipment. We have applied the system for Japanese operating BWR power plants as a preventive maintenance measure for stress corrosion cracking (SCC) on reactor internals like core shrouds or control rod drive (CRD) penetrations since 1999. As for PWRs, alloy 600 or 182 can be susceptible to primary water stress corrosion crackingmore » (PWSCC), and some cracks or leakages caused by the PWSCC have been discovered on penetrations of reactor vessel heads (RVHs), reactor bottom-mounted instrumentation (BMI) nozzles, and others. Taking measures to meet the unconformity of the RVH penetrations, RVHs themselves have been replaced in many PWRs. On the other hand, it's too time-consuming and expensive to replace BMI nozzles, therefore, any other convenient and less expensive measures are required instead of the replacement. In Toshiba, we carried out various tests for laser-peened nickel base alloys and confirmed the effectiveness of laser peening as a preventive maintenance measure for PWSCC. We have developed a laser peening system for PWRs as well after the one for BWRs, and applied it for BMI nozzles, core deluge line nozzles and primary water inlet nozzles of Ikata Unit 1 and 2 of Shikoku Electric Power Company since 2004, which are Japanese operating PWR power plants. In this system, laser oscillators and control devices were packed into two containers placed on the operating floor inside the reactor containment vessel. Laser pulses were delivered through twin optical fibers and irradiated on two portions in parallel to reduce operation time. For BMI nozzles, we developed a tiny irradiation head for small tubes and we peened the inner surface around J-groove welds after laser ultrasonic testing (LUT) as the remote inspection, and we peened the outer surface and the weld for Ikata Unit 2 supplementary. For core deluge line nozzles and primary water inlet nozzles, we peened the inner surface of the dissimilar metal welding, which is of nickel base alloy, joining a safe end and a low alloy metal nozzle. In this paper, the development and the actual application of the laser peening system for PWR power plants will be described. (authors)« less

RGD-conjugated two-photon absorbing near-IR emitting fluorescent probes for tumor vascular imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Belfield, Kevin D.; Yue, Xiling; Morales, Alma R.; Githaiga, Grace W.; Woodward, Adam W.; Tang, Simon; Sawada, Junko; Komatsu, Masanobu; Liu, Xuan

2016-03-01

Observation of the activation and inhibition of angiogenesis processes is important in the progression of cancer. Application of targeting peptides, such as a small peptide that contains adjacent L-arginine (R), glycine (G) and L-aspartic acid (D) residues can afford high selectivity and deep penetration in vessel imaging. To facilitate deep tissue vasculature imaging, probes that can be excited via two-photon absorption (2PA) in the near-infrared (NIR) and subsequently emit in the NIR are essential. In this study, the enhancement of tissue image quality with RGD conjugates was investigated with new NIR-emitting pyranyl fluorophore derivatives in two-photon fluorescence microscopy. Linear and nonlinear photophysical properties of the new probes were comprehensively characterized; significantly the probes exhibited good 2PA over a broad spectral range from 700-1100 nm. Cell and tissue images were then acquired and examined, revealing deep penetration and high contrast with the new pyranyl RGD-conjugates up to 350 μm in tumor tissue.

OPTIMIZATION OF DEEP DRILLING PERFORMANCE--DEVELOPMENT AND BENCHMARK TESTING OF ADVANCED DIAMOND PRODUCT DRILL BITS & HP/HT FLUIDS TO SIGNIFICANTLY IMPROVE RATES OF PENETRATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alan Black; Arnis Judzis

2004-10-01

The industry cost shared program aims to benchmark drilling rates of penetration in selected simulated deep formations and to significantly improve ROP through a team development of aggressive diamond product drill bit--fluid system technologies. Overall the objectives are as follows: Phase 1--Benchmark ''best in class'' diamond and other product drilling bits and fluids and develop concepts for a next level of deep drilling performance; Phase 2--Develop advanced smart bit-fluid prototypes and test at large scale; and Phase 3--Field trial smart bit-fluid concepts, modify as necessary and commercialize products. As of report date, TerraTek has concluded all major preparations for themore » high pressure drilling campaign. Baker Hughes encountered difficulties in providing additional pumping capacity before TerraTek's scheduled relocation to another facility, thus the program was delayed further to accommodate the full testing program.« less

An Assessment of Molten Metal Detachment Hazards During Electron Beam Welding in the Space Shuttle Bay at LEO for the International Space Welding Experiment

NASA Technical Reports Server (NTRS)

Fragomeni, James M.

1996-01-01

In 1997, the United States [NASA] and the Paton Electric Welding Institute are scheduled to cooperate in a flight demonstration on the U.S. Space Shuttle to demonstrate the feasibility of welding in space for a possible repair option for the International Space Station Alpha. This endeavor, known as the International Space Welding Experiment (ISWE), will involve astronauts performing various welding exercises such as brazing, cutting, welding, and coating using an electron beam space welding system that was developed by the E.O. Paton Electric Welding Institute (PWI), Kiev Ukraine. This electron beam welding system known as the "Universal Weld System" consists of hand tools capable of brazing, cutting, autogeneous welding, and coating using an 8 kV (8000 volts) electron beam. The electron beam hand tools have also been developed by the Paton Welding Institute with greater capabilities than the original hand tool, including filler wire feeding, to be used with the Universal Weld System on the U.S. Space Shuttle Bay as part of ISWE. The hand tool(s) known as the Ukrainian Universal Hand [Electron Beam Welding] Tool (UHT) will be utilized for the ISWE Space Shuttle flight welding exercises to perform welding on various metal alloy samples. A total of 61 metal alloy samples, which include 304 stainless steel, Ti-6AI-4V, 2219 aluminum, and 5456 aluminum alloys, have been provided by NASA for the ISWE electron beam welding exercises using the UHT. These samples were chosen to replicate both the U.S. and Russian module materials. The ISWE requires extravehicular activity (EVA) of two astronauts to perform the space shuttle electron beam welding operations of the 61 alloy samples. This study was undertaken to determine if a hazard could exist with ISWE during the electron beam welding exercises in the Space Shuttle Bay using the Ukrainian Universal Weld System with the UHT. The safety issue has been raised with regard to molten metal detachments as a result of several possible causes such as welder procedural error, externally applied impulsive forces(s), filler wire entrainment and snap-out, cutting expulsion, and puddle expulsion. Molten metal detachment from either the weld/cut substrate or weld wire could present harm to a astronaut in the space environment it the detachment was ti burn through the fabric of the astronaut Extravehicular Mobility Unit (EMC). In this paper an experimental test was performed in a 4 ft. x 4 ft. vacuum chamber at MSFC enabling protective garment to be exposed to the molten metal drop detachments to over 12 inches. The chamber was evacuated to vacuum levels of at least 1 x 10(exp -5) torr (50 micro-torr) during operation of the 1.0 kW Universal Hand Tool (UHT). The UHT was manually operated at the power mode appropriate for each material and thickness. The space suit protective welding garment, made of Teflon fabric (10 oz. per yard) with a plain weave, was placed on the floor of the vacuum chamber to catch the molten metal drop detachments. A pendulum release mechanism consisting of four hammers, each weighing approximately 3.65 lbs, was used to apply an impact forces to the weld sample/plate during both the electron beam welding and cutting exercises. Measurements were made of the horizontal fling distances of the detached molten metal drops. The volume of a molten metal drop can also be estimated from the size of the cut. Utilizing equations, calculations were made to determine chande in surafec area (Delat a(surface)) for 304 stainless steel for cutting based on measurements of metal drop sizes at the cut edges. For the cut sample of 304 stainless steel based on measurement of the drop size at the edge, Delta-a(surface) was determined to be 0.0054 2 in . Calculations have indicated only a small amount of energy is required to detach a liquid metal drop. For example, approximately only 0.000005 ft-lb of energy is necessary to detach a liquid metal steel drop based on the above theoretical analysis. However, some of the energy will be absorbed by the plate before it reaches the metal drop. Based on the theoretical calculations, it was determined that during a weld cutting exercise, the titanium alloy would be the most difficult to detach molten metal droplets followed by stainless steel and then by aluminum. The results of the experimental effort have shown that molten metal will detach if large enough of a hammer blow is applied to the weld sample plate during the full penetration welding and cutting exercises. However, no molten metal detachments occurred as a result of the filler wire snap-out tests from the weld puddle since it was too difficult to cause the metal to flick-out from the pool. Molten metal detachments, though not large in size, did result from the direct application of the electron beam on the end of the filler weld wire.

Seismicity, shear failure and modes of deformation in deep subduction zones

NASA Technical Reports Server (NTRS)

Lundgren, Paul R.; Giardini, Domenico

1992-01-01

The joint hypocentral determination method is used to relocate deep seismicity reported in the International Seismological Center catalog for earthquakes deeper than 400 km in the Honshu, Bonin, Mariannas, Java, Banda, and South America subduction zones. Each deep seismic zone is found to display planar features of seismicity parallel to the Harvard centroid-moment tensor nodal planes, which are identified as planes of shear failure. The sense of displacement on these planes is one of resistance to deeper penetration.

Microstructure development and texture evolution of aluminum multi-port extrusion tube during the porthole die extrusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, X.H.

Aluminum multi-port extrusion tube is processed by the porthole die extrusion and the internal tube walls are welded through the solid state metallurgical bonding. In order to observe the development of grains and their orientations under severe plastic deformation and solid state welding, the extrusion butt together with the die is quenched immediately after extrusion to preserve the grain structure in the processing. The forming histories of selected material points are obtained by analyzing the optical microscopy graph. The evolution of the microstructure along the forming path is characterized by electro backscattered diffraction. It is found that geometrical dynamic recrystallizationmore » happens in the process. Grains are elongated, scattered at the transition zone and shear intensive zone, and then pinched off when they are pushed out from the die orifice. The shear-type orientations are predominant at the surface layer on the longitudinal section of the tube web and have penetrated into the intermediate layer. The rolling-type orientations are formed at the central layer. Texture gradient through the thickness of the tube web is observed. And cube orientated grains are found at the seam weld region. - Highlights: •Microstructure of extrusion butt is preserved after the micro scale porthole die extrusion. •Grain morphology history along forming path is investigated. •Texture evolutions on three material flows are present. •Texture gradient exists on the longitudinal section of the internal wall of profile. •Rolling-type and cube textures are found at the solid state welding region.« less

Effect of heat input on microstructure and properties of hybrid fiber laser-arc weld joints of the 800 MPa hot-rolled Nb-Ti-Mo microalloyed steels

NASA Astrophysics Data System (ADS)

Wang, X.-N.; Zhang, S.-H.; Zhou, J.; Zhang, M.; Chen, C.-J.; Misra, R. D. K.

2017-04-01

Hybrid fiber laser-arc welding (HLAW) process was applied to a novel hot-rolled Nb-Ti-Mo microalloyed steels of 8 mm thickness. The steel is primarily used to manufacture automotive and construction machinery components, etc. To elucidate the effect of heat input on geometry, microstructure and mechanical properties, different heat inputs (3.90, 5.20 and 7.75 kJ/cm) were used by changing the welding speeds. With increased heat input, the depth/width of penetration was decreased, and the geometry of fusion zone (FZ) changed to "wine cup-like" shape. In regard to the microstructural constituents, the martensite content was decreased, but granular bainite (GB) content was increased. The main microstructural difference was in the FZ cross-section at 7.75 kJ/cm because of the effect of thermal source on the top and bottom. The microstructure of the top part consisted of GB, grain boundary ferrite, and acicular ferrite, while the bottom part was primarily lath martensite. The hardness distribution was similar for different heat inputs. Hardness in FZ, coarse-grained HAZ and mixed-grained HAZ was higher than the base metal (BM), but for the fine-grained HAZ was similar or marginally less than the base metal (BM). Tensile strain was concentrated in the BM such that the fracture occurred in this region. In summary, the geometry, microstructure, and mechanical properties of weld joints were superior at heat input of 5.20 kJ/cm.

JPRS Report, Science & Technology, USSR: Materials Science

DTIC Science & Technology

1988-03-15

another. It has developed and transferred to design institutes technological schemes of transportation systems for working deep levels at the Sarbay...manuscript received 1 Oct 84, in final version 19 May 86) pp 45-50 [Article by V.V. Shefel, engineer, Energomontazhproyekt Design -Technological...Institute, Moscow] [Abstract] Three variants of automatic argon-arc welding have been developed at the Energomontazh Design -Technological Institute

Drill-back studies examine fractured, heated rock

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wollenberg, H.A.; Flexser, S.; Myer, L.R.

1990-01-01

To investigate the effects of heating on the mineralogical, geochemical, and mechanical properties of rock by high-level radioactive waste, cores are being examined from holes penetrating locations where electric heaters simulated the presence of a waste canister, and from holes penetration natural hydrothermal systems. Results to date indicate the localized mobility and deposition of uranium in an open fracture in heated granitic rock, the mobility of U in a breccia zone in an active hydrothermal system in tuff, and the presence of U in relatively high concentration in fracture-lining material in tuff. Mechanical -- property studies indicate that differences inmore » compressional- and shear-wave parameters between heated and less heated rock can be attributed to differences in the density of microcracks. Emphasis has shifted from initial studies of granitic rock at Stripa, Sweden to current investigations of welded tuff at the Nevada Test Site. 7 refs., 8 figs.« less

Deep penetration of light into biotissue

NASA Astrophysics Data System (ADS)

Bearden, Edward D.; Wilson, James D.; Zharov, Vladimir P.; Lowery, Curtis L.

2001-07-01

The results of a study of deep (several centimeters) light penetration into biological tissue are presented in order to estimate its significance to potentially photosensitive structures and processes including the fetal eyes. In order to accomplish this goal, samples of various tissues (fat, muscle, and uterus) from surgical patients and autopsies were examined with a double integrating sphere arrangement to determine their optical properties. The results were implemented in a Monte Carlo modeling program. Next, optical fiber probes were inserted into the uterus and abdominal wall of patients undergoing laparoscopic procedures. The fibers were couples to a photomultiplier tube with intervening filters allowing measurements of light penetration at various wavelengths. To determine the feasibility of stimulation in utero, a xenon lamp and waveguide were used to transilluminate the abdomen of several labor patients. Light in the range of 630 to 670 nm where the eye sensitivity and penetration depth are well matched, will likely provide the best chance of visual stimulation. Fetal heart rate, fetal movement, and fetal magnetoencephalography (SQUID) and electroencephalography (EEG) were observed in different studies to determine if stimulation has occurred. Since internal organs and the fetus are completely dark adapted, the amount of light required to simulate in our opinion could be on the order of 10(superscript -8 Watts.

Modular detector for deep underwater registration of muons and muon groups

NASA Technical Reports Server (NTRS)

Demianov, A. I.; Sarycheva, L. I.; Sinyov, N. B.; Varadanyan, I. N.; Yershov, A. A.

1985-01-01

Registration and identification of muons and muon groups penetrating into the ocean depth, can be performed using a modular multilayer detector with high resolution bidimensional readout - deep underwater calorimeter (project NADIR). Laboratory testing of a prototype sensor cell with liquid scintillator in light-tight casing, testifies to the practicability of the full-scale experiment within reasonable expences.

Photodynamic tissue adhesion with chlorin(e6) protein conjugates.

PubMed

Khadem, J; Veloso, A A; Tolentino, F; Hasan, T; Hamblin, M R

1999-12-01

To test the hypothesis that a photodynamic laser-activated tissue solder would perform better in sealing scleral incisions when the photosensitizer was covalently linked to the protein than when it was noncovalently mixed. Conjugates and mixtures were prepared between the photosensitizer chlorin(e6) and various proteins (albumin, fibrinogen, and gelatin) in different ratios and used to weld penetrating scleral incisions made in human cadaveric eyes. A blue-green (488-514 nm) argon laser activated the adhesive, and the strength of the closure was measured by increasing the intraocular pressure until the wound showed leakage. Both covalent conjugates and noncovalent mixtures showed a light dose-dependent increase in leaking pressure. A preparation of albumin chlorin(e6) conjugate with additional albumin added (2.5 protein to chlorin(e6) molar ratio) showed significantly higher weld strength than other protein conjugates and mixtures. This is the first report of dye-protein conjugates as tissue solders. These conjugates may have applications in ophthalmology.

Workplace field testing of the pressure drop of particulate respirators using welding fumes.

PubMed

Cho, Hyun-Woo; Yoon, Chung-Sik

2012-10-01

In a previous study, we concluded that respirator testing with a sodium chloride aerosol gave a conservative estimate of filter penetration for welding fume aerosols. A rapid increase in the pressure drop (PD) of some respirators was observed as fumes accumulated on the filters. The present study evaluated particulate respirator PD based on workplace field tests. A field PD tester was designed and validated using the TSI 8130 Automatic Filter Tester, designed in compliance with National Institute for Occupational and Safety and Health regulation 42 CFR part 84. Three models (two replaceable dual-type filters and one replaceable single-type filter) were evaluated against CO(2) gas arc welding on mild steel in confined booths in the workplace. Field tests were performed under four airborne concentrations (27.5, 15.4, 7.9, and 2.1 mg m(-3)). The mass concentration was measured by the gravimetric method, and number concentration was monitored using P-Trak (Model 8525, TSI, USA). Additionally, photos and scanning electron microscopy-energy dispersive X-ray spectroscopy were used to visualize and analyze the composition of welding fumes trapped in the filters. The field PD tester showed no significant difference compared with the TSI tester. There was no significant difference in the initial PD between laboratory and field results. The PD increased as a function of fume load on the respirator filters for all tested models. The increasing PD trend differed by models, and PD increased rapidly at high concentrations because greater amount of fumes accumulated on the filters in a given time. The increase in PD as a function of fume load on the filters showed a similar pattern as fume load varied for a particular model, but different patterns were observed for different models. Images and elemental analyses of fumes trapped on the respirator filters showed that most welding fumes were trapped within the first layer, outer web cover, and second layer, in order, while no fumes were observed beneath the fourth layer of the tested respirators. The current findings contribute substantially to our understanding of respirator PD in the presence of welding fumes.

Stochastic Model of Fracture Frequency Heterogeneity in a Welded Tuff EGS reservoir, Snake River Plain, Idaho, USA

NASA Astrophysics Data System (ADS)

Moody, A.; Fairley, J. P., Jr.

2014-12-01

In light of recent advancements in reservoir enhancement and injection tests at active geothermal fields, there is interest in investigating the geothermal potential of widespread subsurface welded tuffs related to caldera collapse on the Snake River Plain (SRP). Before considering stimulation strategies, simulating heat extraction from the reservoir under in-situ fracture geometries will give a first-order estimation of extractable heat. With only limited deep boreholes drilled on the SRP, few analyses of the bulk hydrologic properties of the tuffs exist. Acknowledging the importance of the spatial heterogeneity of fractures to the permeability and injectivity of reservoirs hosted in impermeable volcanic units, we present fracture distributions from ICDP hole 5036-2A drilled as a part of Project HOTSPOT. The core documents more than 1200 m of largely homogeneous densely welded tuff hosting an isothermal warm-water reservoir at ~60˚ C. Multiple realizations of a hypothetical reservoir are created using sequential indicator algorithms that honor the observed vertical fracture frequency statistics. Results help form criteria for producing geothermal energy from the SRP.

Transurethral illumination probe design for deep photoacoustic imaging of prostate

NASA Astrophysics Data System (ADS)

Ai, Min; Salcudean, Tim; Rohling, Robert; Abolmaesumi, Purang; Tang, Shuo

2018-02-01

Photoacoustic (PA) imaging with internal light illumination through optical fiber could enable imaging of internal organs at deep penetration. We have developed a transurethral probe with a multimode fiber inserted in a rigid cystoscope sheath for illuminating the prostate. At the distal end, the fiber tip is processed to diffuse light circumferentially over 2 cm length. A parabolic cylinder mirror then reflects the light to form a rectangular-shaped parallel beam which has at least 1 cm2 at the probe surface. The relatively large rectangular beam size can reduce the laser fluence rate on the urethral wall and thus reduce the potential of tissue damage. A 3 cm optical penetration in chicken tissue is achieved at a fluence rate around 7 mJ/cm2 . For further validation, a prostate phantom was built with similar optical properties of the human prostate. A 1.5 cm penetration depth is achieved in the prostate mimicking phantom at 10 mJ/cm2 fluence rate. PA imaging of prostate can potentially be carried out in the future by combining a transrectal ultrasound transducer and the transurethral illumination.

The deep Algerian margin structure revisited by the Algerian-French SPIRAL research program, stage 2 : Wide-ange seismic experiment

NASA Astrophysics Data System (ADS)

Klingelhoefer, Frauke; Yellès, Abdelkarim; Bracène, Rabah; Graindorge, David; Ouabadi, Aziouz; Schnürle, Philippe; Scientific Party, Spiral

2010-05-01

During the second leg of the Algerien - French SPIRAL (Sismique Profonde et Investigation Regionale du Nord de l'ALgerie) cruise conducted on the R/V Atalante in October and November 2009 an extensive wide-angle seismic data-set was acquired on 5 regional transects off Algeria, from Arzew bay to the west, to Annaba to the east. The profiles are between 80 and 180 km in length and around 40 ocean-bottom seismometers were deployed on each profile. A 8350 cu. inch tuned airgun array consisting of 10 Bolt airguns was used to generate of deep frequency to allow for a good penetration. All profiles were extended on land up to 150 km by land-stations to better constrain the structure of the margin and the nature of the ocean-continent transition zone. Coincident reflection seismic, gravity and magnetic data were acquired on all profiles during the first leg of the cruise. The resulting data quality is very good with deep penetrating arrivals on most of the instruments. Only on very few instruments a deep salt layer inhibits deeper penetration of the seismic energy. Two instruments were lost and all other yielded useful information on geophone and hydrophone channels. Instruments located close to the coast show arrivals from thick sedimentary layers. Instruments located on oceanic crust indicate a relatively thin crust overlying a mantle layer characterised by seismic velocities of 8 km/s. Forward and inverse modelling of the wide-angle seismic data will help constrain the deep structure of the margin, the nature of the crust and might help to constrain possible existence of a detached slab in the upper mantle. Integration of the wide-angle seismic data with multichannel seismic, gravity and magnetic data will enable us to better understand the tectonic history and the structure of the Algerian margin.

The risk of male subfecundity attributable to welding of metals. Studies of semen quality, infertility, fertility, adverse pregnancy outcome and childhood malignancy.

PubMed

Bonde, J P

1993-08-01

These studies were initiated by the results of two Danish investigations of infertility clients, which indicated the reduced fecundity of male metal welders. The objective was to refute or corroborate the effects of welding on male reproductive capability and--if there was any effect--to identify the causal exposures. The initial hypothesis postulated reduced spermatogenesis, spontaneous abortion, congenital malformation and childhood malignancy following exposure to hexavalent chromium among stainless steel welders. Subsequently, a hypothesis concerned with the significance of exposure to radiant heat on reduced semen quality was put forward. These studies comprised a case-referent study of infertility, cross-sectional and longitudinal studies of semen quality and historical cohort studies of fertility, pregnancy outcome and cancer in offspring. Exposure to welding was reported with a higher frequency during periods of infertility than prior to conception in the case-referent study (OR 2.0, 95% CI 1.0-4.0). This finding is consistent with the main cross-sectional study showing reduced semen quality in welders [average reduction ranging from 8% (sperm penetration rate in eggwhite) to 28% (total sperm count)] and with the cohort study revealing reduced fertility in relation to welding (OR 0.89, 95% CI 0.83-0.97). However, reduced semen quality and fertility were not attributable to the welding of stainless steel but to the welding of mild steel; and no relationship was found between biological measures of exposure to chromium and parameters of semen quality. If the unexpected association between mild steel welding and reduced fecundity is causal, the biological mechanisms involved are obscure. A separate longitudinal study leaves little doubt that moderate radiant heat exposure may cause reversible deterioration of semen quality, but it is not justified to generalize this observation to the entire population of welders. Male-mediated effects on occurrence of congenital malformation and cancer in offspring from stainless steel welding are not indicated by the studies. Weak indications of an increased risk of spontaneous abortion among partners to stainless steel welders (OR 1.9, 95% CI 1.1-3.2) need to be refuted or corroborated in future studies. Suggested effects of mild steel welding on male fecundity should be corroborated by longitudinal controlled studies of semen quality examined before and during exposure and by prospective studies of fecundability in couples trying to conceive a child. On account of the present knowledge it is not possible to recommend rational preventative measures with the exception of elimination of radiant heat exposure in cases of infertility.(ABSTRACT TRUNCATED AT 400 WORDS)

Intensified Diapycnal Mixing in the Midlatitude Western Boundary Currents

PubMed Central

Jing, Zhao; Wu, Lixin

2014-01-01

The wind work on oceanic near-inertial motions is suggested to play an important role in furnishing the diapycnal mixing in the deep ocean which affects the uptake of heat and carbon by the ocean as well as climate changes. However, it remains a puzzle where and through which route the near-inertial energy penetrates into the deep ocean. Using the measurements collected in the Kuroshio extension region during January 2005, we demonstrate that the diapycnal mixing in the thermocline and deep ocean is tightly related to the shear variance of wind-generated near-inertial internal waves with the diapycnal diffusivity 6 × 10−5 m2s−1 almost an order stronger than that observed in the circulation gyre. It is estimated that 45%–62% of the local near-inertial wind work 4.5 × 10−3 Wm−2 radiates into the thermocline and deep ocean and accounts for 42%–58% of the energy required to furnish mixing there. The elevated mixing is suggested to be maintained by the energetic near-inertial wind work and strong eddy activities causing enhanced downward near-inertial energy flux than earlier findings. The western boundary current turns out to be a key region for the penetration of near-inertial energy into the deep ocean and a hotspot for the diapycnal mixing in winter. PMID:25491363

Analysis of induced effects in matter during pulsed Nd:YAG laser welding by flash radiography

NASA Astrophysics Data System (ADS)

Pascal, G.; Noré, D.; Girard, K.; Perret, O.; Naudy, P.

2000-05-01

Tantalum and TA6V (titanium alloy) are respectively used in corrosive chemical product containers and in aircraft and aerospace industries. The objective of this study was to analyze the dynamic behavior of the matter during deep laser spot welding of these materials. The obtained images should allow a better understanding of laser-matter interaction and should validate a model developed for porosities formation. Because of the afterglow of detectors, classical video x-ray systems are not suitable for the analysis of short dynamic effects during and after the laser pulse. An experimental device, based on a flash x-ray generator EUROPULSE 600 kV and a QUANTEL pulsed Nd:YAG laser, has been used. The flash x-ray generator is triggered, after a programmed delay, by the laser shot. The x-ray pulse duration is 30 ns. Welding parameters (pulse duration and energy) yield molten zones of 2 mm depth. Both materials, tantalum and TA6V, have been tested. Radiological films BIOMAX coupled with radioluminescent screens and direct exposure film (DEF) were respectively used for tantalum and TA6V samples. A fine collimation was studied to avoid the scattering effect in the material and in the radioluminescent screen. Radiological test samples, made of tantalum and TA6V, were performed to estimate the images qualities obtained by flash radiography. About 270 laser/x-rays shots were performed. The radiographic images have been digitalized and processed. The results show a deep and narrow capillary hole called "keyhole" which appears a few milliseconds after the beginning of the interaction. The "keyhole" hollows until the end of the laser pulse. After the end of the laser pulse, the molten bath collapses in less than 1 ms, trapping cavities.

Uncertainty quantification methodologies development for stress corrosion cracking of canister welds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dingreville, Remi Philippe Michel; Bryan, Charles R.

2016-09-30

This letter report presents a probabilistic performance assessment model to evaluate the probability of canister failure (through-wall penetration) by SCC. The model first assesses whether environmental conditions for SCC – the presence of an aqueous film – are present at canister weld locations (where tensile stresses are likely to occur) on the canister surface. Geometry-specific storage system thermal models and weather data sets representative of U.S. spent nuclear fuel (SNF) storage sites are implemented to evaluate location-specific canister surface temperature and relative humidity (RH). As the canister cools and aqueous conditions become possible, the occurrence of corrosion is evaluated. Corrosionmore » is modeled as a two-step process: first, pitting is initiated, and the extent and depth of pitting is a function of the chloride surface load and the environmental conditions (temperature and RH). Second, as corrosion penetration increases, the pit eventually transitions to a SCC crack, with crack initiation becoming more likely with increasing pit depth. Once pits convert to cracks, a crack growth model is implemented. The SCC growth model includes rate dependencies on both temperature and crack tip stress intensity factor, and crack growth only occurs in time steps when aqueous conditions are predicted. The model suggests that SCC is likely to occur over potential SNF interim storage intervals; however, this result is based on many modeling assumptions. Sensitivity analyses provide information on the model assumptions and parameter values that have the greatest impact on predicted storage canister performance, and provide guidance for further research to reduce uncertainties.« less

Effect of Processing Parameters on Plastic Flow and Defect Formation in Friction-Stir-Welded Aluminum Alloy

NASA Astrophysics Data System (ADS)

Zeng, X. H.; Xue, P.; Wang, D.; Ni, D. R.; Xiao, B. L.; Ma, Z. Y.

2018-07-01

The effect of processing parameters on material flow and defect formation during friction stir welding (FSW) was investigated on 6.0-mm-thick 2014Al-T6 rolled plates with an artificially thickened oxide layer on the butt surface as the marker material. It was found that the "S" line in the stir zone (SZ) rotated with the pin and stayed on the retreating side (RS) and advancing side (AS) at low and high heat inputs, respectively. When the tool rotation rate was extremely low, the oxide layer under the pin moved to the RS first and then to the AS perpendicular to the welding direction, rather than rotating with the pin. The material flow was driven by the shear stresses produced by the forces at the pin-workpiece interface. With increases of the rotation rate, the depth of the shoulder-affected zone (SAZ) first decreased and then increased due to the decreasing shoulder friction force and increasing heat input. Insufficient material flow appeared in the whole of the SZ at low rotation rates and in the bottom of the SZ at high rotation rates, resulting in the formation of the "S" line. The extremely inadequate material flow is the reason for the lack of penetration and the kissing bonds in the bottom of the SZ at extremely low and low rotation rates, respectively.

Effect of Processing Parameters on Plastic Flow and Defect Formation in Friction-Stir-Welded Aluminum Alloy

NASA Astrophysics Data System (ADS)

Zeng, X. H.; Xue, P.; Wang, D.; Ni, D. R.; Xiao, B. L.; Ma, Z. Y.

2018-04-01

The effect of processing parameters on material flow and defect formation during friction stir welding (FSW) was investigated on 6.0-mm-thick 2014Al-T6 rolled plates with an artificially thickened oxide layer on the butt surface as the marker material. It was found that the "S" line in the stir zone (SZ) rotated with the pin and stayed on the retreating side (RS) and advancing side (AS) at low and high heat inputs, respectively. When the tool rotation rate was extremely low, the oxide layer under the pin moved to the RS first and then to the AS perpendicular to the welding direction, rather than rotating with the pin. The material flow was driven by the shear stresses produced by the forces at the pin-workpiece interface. With increases of the rotation rate, the depth of the shoulder-affected zone (SAZ) first decreased and then increased due to the decreasing shoulder friction force and increasing heat input. Insufficient material flow appeared in the whole of the SZ at low rotation rates and in the bottom of the SZ at high rotation rates, resulting in the formation of the "S" line. The extremely inadequate material flow is the reason for the lack of penetration and the kissing bonds in the bottom of the SZ at extremely low and low rotation rates, respectively.

Numerical investigation of the interaction of positive streamers with bubbles floating on a liquid surface

NASA Astrophysics Data System (ADS)

Babaeva, Natalia Yu.; Naidis, George V.; Kushner, Mark J.

2016-09-01

Streamer discharges in air intersecting with liquids are being investigated to produce reactivity in the liquid. In this talk, we discuss results from a 2-d computational investigation of streamers in air intersecting an isolated liquid, air filled bubble floating on a liquid surface. The 15 mm diameter bubble is conducting water (ɛ /ɛ0 = 80 , σ = 7 . 5 ×10-4Ω-1cm-1) or transformer oil (ɛ /ɛ0 = 2 . 2 , σ = 1 . 5 ×10-13Ω-1cm-1). A needle electrode is positioned d =0-10 mm from the bubble center. With a water bubble (d =0) the streamer slides along the external surface but does not penetrate the bubble due to electric field screening by the conducting shell. If the electrode is shifted (d =3-10 mm) the streamer deviates from the vertical and adheres to the bubble. If the electrode is inserted inside the bubble, the streamer path depends on how deep the electrode penetrates. For shallow penetration, the streamer propagates along the inner surface of the bubble. For deep penetration the streamer takes the shortest path down through the gas. Due to the low conductivity of the oil bubble shell the electric field penetrates into the interior of the bubble. The streamer can then be re-initiated inside the bubble. Charge accumulation on both sides of the bubble shell and perforation of the shell will be also discussed. NYB, GVN supported by Russian Sci. Found. (14-12-01295). MJK by US Natl. Sci. Found. and Dept. of Energy.

Radar attenuation in Europa's ice shell: Obstacles and opportunities for constraining the shell thickness and its thermal structure

NASA Astrophysics Data System (ADS)

Kalousová, Klára; Schroeder, Dustin M.; Soderlund, Krista M.

2017-03-01

Young surface and possible recent endogenic activity make Europa one of the most exciting solar system bodies and a primary target for spacecraft exploration. Future Europa missions are expected to carry ice-penetrating radar instruments designed to investigate its subsurface thermophysical structure. Several authors have addressed the radar sounders' performance at icy moons, often ignoring the complex structure of a realistic ice shell. Here we explore the variation in two-way radar attenuation for a variety of potential thermal structures of Europa's shell (determined by reference viscosity, activation energy, tidal heating, surface temperature, and shell thickness) as well as for low and high loss temperature-dependent attenuation model. We found that (i) for all investigated ice shell thicknesses (5-30 km), the radar sounder will penetrate between 15% and 100% of the total thickness, (ii) the maximum penetration depth varies laterally, with deepest penetration possible through cold downwellings, (iii) direct ocean detection might be possible for shells of up to 15 km thick if the signal travels through cold downwelling ice or the shell is conductive, (iv) even if the ice/ocean interface is not directly detected, penetration through most of the shell could constrain the deep shell structure through returns from deep non-ocean interfaces or the loss of signal itself, and (v) for all plausible ice shells, the two-way attenuation to the eutectic point is ≲30 dB which shows a robust potential for longitudinal investigation of the ice shell's shallow thermophysical structure.

Programmed Nanoparticle-Loaded Nanoparticles for Deep-Penetrating 3D Cancer Therapy.

PubMed

Kim, Jinhwan; Jo, Changshin; Lim, Won-Gwang; Jung, Sungjin; Lee, Yeong Mi; Lim, Jun; Lee, Haeshin; Lee, Jinwoo; Kim, Won Jong

2018-05-18

Tumors are 3D, composed of cellular agglomerations and blood vessels. Therapies involving nanoparticles utilize specific accumulations due to the leaky vascular structures. However, systemically injected nanoparticles are mostly uptaken by cells located on the surfaces of cancer tissues, lacking deep penetration into the core cancer regions. Herein, an unprecedented strategy, described as injecting "nanoparticle-loaded nanoparticles" to address the long-lasting problem is reported for effective surface-to-core drug delivery in entire 3D tumors. The "nanoparticle-loaded nanoparticle" is a silica nanoparticle (≈150 nm) with well-developed, interconnected channels (diameter of ≈30 nm), in which small gold nanoparticles (AuNPs) (≈15 nm) with programmable DNA are located. The nanoparticle (AuNPs)-loaded nanoparticles (silica): (1) can accumulate in tumors through leaky vascular structures by protecting the inner therapeutic AuNPs during blood circulation, and then (2) allow diffusion of the AuNPs for penetration into the entire surface-to-core tumor tissues, and finally (3) release a drug triggered by cancer-characteristic pH gradients. The hierarchical "nanoparticle-loaded nanoparticle" can be a rational design for cancer therapies because the outer large nanoparticles are effective in blood circulation and in protection of the therapeutic nanoparticles inside, allowing the loaded small nanoparticles to penetrate deeply into 3D tumors with anticancer drugs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Single myelin fiber imaging in living rodents without labeling by deep optical coherence microscopy.

PubMed

Ben Arous, Juliette; Binding, Jonas; Léger, Jean-François; Casado, Mariano; Topilko, Piotr; Gigan, Sylvain; Boccara, A Claude; Bourdieu, Laurent

2011-11-01

Myelin sheath disruption is responsible for multiple neuropathies in the central and peripheral nervous system. Myelin imaging has thus become an important diagnosis tool. However, in vivo imaging has been limited to either low-resolution techniques unable to resolve individual fibers or to low-penetration imaging of single fibers, which cannot provide quantitative information about large volumes of tissue, as required for diagnostic purposes. Here, we perform myelin imaging without labeling and at micron-scale resolution with >300-μm penetration depth on living rodents. This was achieved with a prototype [termed deep optical coherence microscopy (deep-OCM)] of a high-numerical aperture infrared full-field optical coherence microscope, which includes aberration correction for the compensation of refractive index mismatch and high-frame-rate interferometric measurements. We were able to measure the density of individual myelinated fibers in the rat cortex over a large volume of gray matter. In the peripheral nervous system, deep-OCM allows, after minor surgery, in situ imaging of single myelinated fibers over a large fraction of the sciatic nerve. This allows quantitative comparison of normal and Krox20 mutant mice, in which myelination in the peripheral nervous system is impaired. This opens promising perspectives for myelin chronic imaging in demyelinating diseases and for minimally invasive medical diagnosis.

Single myelin fiber imaging in living rodents without labeling by deep optical coherence microscopy

NASA Astrophysics Data System (ADS)

Ben Arous, Juliette; Binding, Jonas; Léger, Jean-François; Casado, Mariano; Topilko, Piotr; Gigan, Sylvain; Claude Boccara, A.; Bourdieu, Laurent

2011-11-01

Myelin sheath disruption is responsible for multiple neuropathies in the central and peripheral nervous system. Myelin imaging has thus become an important diagnosis tool. However, in vivo imaging has been limited to either low-resolution techniques unable to resolve individual fibers or to low-penetration imaging of single fibers, which cannot provide quantitative information about large volumes of tissue, as required for diagnostic purposes. Here, we perform myelin imaging without labeling and at micron-scale resolution with >300-μm penetration depth on living rodents. This was achieved with a prototype [termed deep optical coherence microscopy (deep-OCM)] of a high-numerical aperture infrared full-field optical coherence microscope, which includes aberration correction for the compensation of refractive index mismatch and high-frame-rate interferometric measurements. We were able to measure the density of individual myelinated fibers in the rat cortex over a large volume of gray matter. In the peripheral nervous system, deep-OCM allows, after minor surgery, in situ imaging of single myelinated fibers over a large fraction of the sciatic nerve. This allows quantitative comparison of normal and Krox20 mutant mice, in which myelination in the peripheral nervous system is impaired. This opens promising perspectives for myelin chronic imaging in demyelinating diseases and for minimally invasive medical diagnosis.

Impact cratering experiments in brittle targets with variable thickness: Implications for deep pit craters on Mars

NASA Astrophysics Data System (ADS)

Michikami, T.; Hagermann, A.; Miyamoto, H.; Miura, S.; Haruyama, J.; Lykawka, P. S.

2014-06-01

High-resolution images reveal that numerous pit craters exist on the surface of Mars. For some pit craters, the depth-to-diameter ratios are much greater than for ordinary craters. Such deep pit craters are generally considered to be the results of material drainage into a subsurface void space, which might be formed by a lava tube, dike injection, extensional fracturing, and dilational normal faulting. Morphological studies indicate that the formation of a pit crater might be triggered by the impact event, and followed by collapse of the ceiling. To test this hypothesis, we carried out laboratory experiments of impact cratering into brittle targets with variable roof thickness. In particular, the effect of the target thickness on the crater formation is studied to understand the penetration process by an impact. For this purpose, we produced mortar targets with roof thickness of 1-6 cm, and a bulk density of 1550 kg/m3 by using a mixture of cement, water and sand (0.2 mm) in the ratio of 1:1:10, by weight. The compressive strength of the resulting targets is 3.2±0.9 MPa. A spherical nylon projectile (diameter 7 mm) is shot perpendicularly into the target surface at the nominal velocity of 1.2 km/s, using a two-stage light-gas gun. Craters are formed on the opposite side of the impact even when no target penetration occurs. Penetration of the target is achieved when craters on the opposite sides of the target connect with each other. In this case, the cross section of crater somehow attains a flat hourglass-like shape. We also find that the crater diameter on the opposite side is larger than that on the impact side, and more fragments are ejected from the crater on the opposite side than from the crater on the impact side. This result gives a qualitative explanation for the observation that the Martian deep pit craters lack a raised rim and have the ejecta deposit on their floor instead. Craters are formed on the opposite impact side even when no penetration occurs. Penetration is achieved when craters of both sides are connected. Crater diameter on the opposite side is larger than that on the impact side. More fragments are ejected from the opposite side than from the impact side. We present a qualitative explanation for the shapes of Martian deep pit craters.

Use of a Minimally Invasive Retractor System for Retrieval of Intracranial Fragments in Wartime Trauma.

PubMed

Rymarczuk, George N; Davidson, Laurence; Severson, Meryl A; Armonda, Rocco A

2015-10-01

Wartime penetrating brain injury can result in deep-seated parenchymal and intraventicular shrapnel, bullets, and bone. Large fragments pose a risk of secondary injury from migration, infection, and metal toxicity. It has been recommended that aggressive removal of fragments be avoided. The goal of this study is to report our technique of minimally invasive removal of select deep-seated fragments using a tubular retractor system. A retrospective review of our database of service members presenting with penetrating traumatic brain injuries incurred during Operations Iraqi Freedom and Enduring Freedom and treated at the Walter Reed Army Medical Center and the National Naval Medical Center was performed. Six individuals were identified in which the Vycor ViewSite retractor system (Vycor Medical, Boca Raton, Florida, USA) was used to remove a ventricular or deep intraparenchymal fragment. All patients were male and ranged in age from 21 to 29 years. Fragment location included the foramen of Monro; the atrium of the right lateral ventricle; parasagittally within the right occipital lobe; the occipital horn of the right lateral ventricle; the deep white matter of the dominant temporal lobe; and within the posterior right temporal lobe deep to the junction of the transverse and sigmoid dural venous sinuses. Fragments included in-driven bone, shrapnel from improvised explosive devices, and bullets. In all cases the fragment was successfully removed. No patient had worsening of their neurologic condition following surgery. Deep parenchymal and intraventricular fragments can be safely removed using a tubular retractor system. Published by Elsevier Inc.

Space Launch System Launch Vehicle Stage Adapter Hardware Completes Manufacturing

NASA Image and Video Library

2017-08-28

The Launch Vehicle Stage Adapter for the first flight of the Space Launch System, NASA’s new deeps space rocket, recently completed manufacturing at NASA’s Marshal Space Flight Center in Huntsville, Alabama. The LVSA, the largest piece of the rocket welded together in Marshall’s Huntsville manufacturing area, will connect two major sections of SLS – the 27.6-foot diameter core stage and the 16.4-foot interim cryogenic propulsion stage – for the first integrated flight of SLS and the Orion spacecraft. Teledyne Brown Engineering of Huntsville, the prime contractor for the adapter, has completed manufacturing, and engineers are preparing to apply thermal insulation. It will be the largest piece of hardware that Marshall. The LVSA was moved from the NASA welding area to NASA’s Center for Advanced Manufacturing where the thermal protection system will be applied.

Failure Analysis of a Service Tube

NASA Astrophysics Data System (ADS)

Xie, Zhongdong; Cai, Weiguo; Li, Zhenxing; Guan, YiMing; Zhang, Baocheng; Yang, XiaoTong

2017-12-01

One tube was cracked used in the primary reformer furnace in a fertilizer plant for two and half years. In order to find out the causes of cracking, the methods for chemical composition analysis, macro- and microstructure analysis, penetrant testing, weld analysis, crack and surface damage analysis, mechanics property analysis, high temperature endurance performance analysis, stress and wall thickness calculation were adopted. The integrated assessment results showed that the carbon content of the tube was in the lower limit of the standard range; the tube effective wall thickness was too small; local overheating leads to tube cracking in use process.

Tritium analysis of divertor tiles used in JET ITER-like wall campaigns by means of β-ray induced x-ray spectrometry

NASA Astrophysics Data System (ADS)

Hatano, Y.; Yumizuru, K.; Koivuranta, S.; Likonen, J.; Hara, M.; Matsuyama, M.; Masuzaki, S.; Tokitani, M.; Asakura, N.; Isobe, K.; Hayashi, T.; Baron-Wiechec, A.; Widdowson, A.; contributors, JET

2017-12-01

Energy spectra of β-ray induced x-rays from divertor tiles used in ITER-like wall campaigns of the Joint European Torus were measured to examine tritium (T) penetration into tungsten (W) layers. The penetration depth of T evaluated from the intensity ratio of W(Lα) x-rays to W(Mα) x-rays showed clear correlation with poloidal position; the penetration depth at the upper divertor region reached several micrometers, while that at the lower divertor region was less than 500 nm. The deep penetration at the upper part was ascribed to the implantation of high energy T produced by DD fusion reactions. The poloidal distribution of total x-ray intensity indicated higher T retention in the inboard side than the outboard side of the divertor region.

Compact, Deep-Penetrating Geothermal Heat Flow Instrumentation for Lunar Landers

NASA Technical Reports Server (NTRS)

Nagihara, S.; Zacny, K.; Hedlund, M.; Taylor, P. T.

2012-01-01

Geothermal heat flow is obtained as a product of the two separate measurements of geothermal gradient in, and thermal conductivity of, the vertical soi/rock/regolith interval penetrated by the instrument. Heat flow measurements are a high priority for the geophysical network missions to the Moon recommended by the latest Decadal Survey [I] and previously the International Lunar Network [2]. The two lunar-landing missions planned later this decade by JAXA [3] and ESA [4] also consider geothermal measurements a priority.

Filter Enhances Fluorescent-Penetrant-Inspecting Borescope

NASA Technical Reports Server (NTRS)

Molina, Orlando G.

1990-01-01

Slip-on eyepiece for commercial ultraviolet-light borescope reduces both amount of short-wave ultraviolet light that reaches viewer's eye and apparent intensity of unwanted reflections of white light from surfaces undergoing inspection. Fits on stock eyepiece of borescope, which illuminates surface inspected with intense ultraviolet light. Surface, which is treated with fluorescent dye, emits bright-green visible light wherever dye penetrates - in cracks and voids. Eyepiece contains deep-yellow Wratten 15 (G) filter, which attenuates unwanted light strongly but passes yellow-green fluorescence so defects seen clearly.

Geological Engineering Characteristics of the Residual Soil: Implementation for Soil Bearing Capacity at Gayungan, Surabaya, East Java

NASA Astrophysics Data System (ADS)

Rukmana, Y. Y.; Ridwan, M.

2018-01-01

This paper presents the results of soil investigation on the residual soil at Gayungan Surabaya. The methodology of the research consists of Drilling + Standard Penetration Test (ASTM D1586-99), sampling and laboratory test for index properties & mechanical of soil, then analyzed for Soil Bearing Capacity (Meyerhoff, 1976). Field test analysis data showed that Bore Hole.01(BH.01) and Bore Hole.03 (BH.03) were dominated by Sand / Sandy clay layer with Standart Penetration Test (SPT) values: 6-68, whereas in BH.02 was dominated by Clayey sand layer with Standard Penetration Test (SPT) values: 32-68. Based on Soil classification according to Unified Soil Classification System (USCS), the soil type at the research area consisted of ML (Silt with Low plasticity), CL ( Clay with low plasticity), MH (Silt with High plasticity), and SP (Sand with Poor gradation). Based on the borlog data and soil bearing capacity analysis of the research area is recommended: for The Deep foundation to reaches at least 16 meters depth with Qa = 1160.40-2032.80 kN / m2, and Shallow foundation reaches at least 1-2 meters deep with Qa = 718.25 kN / M2.

Corneal transplantation trends in France from 2004 to 2015: A 12-year review.

PubMed

Bigan, Guillaume; Puyraveau, Marc; Saleh, Maher; Gain, Philippe; Martinache, Isabelle; Delbosc, Bernard; Gauthier, Anne-Sophie

2018-04-01

The aim of this study was to report the 12-year longitudinal trends in indication and corneal transplantation techniques in France from 2004 to 2015. The records of all corneal transplantations performed from 2004 to 2015 in France were retrospectively reviewed. The patient indications and types of transplant performed were analyzed. A total of 46,658 corneal transplantations were performed between 2004 and 2015, with 34,187 (73.3%) penetrating keratoplasty and 10,452 (22.4%) lamellar keratoplasty. The leading surgical indications were secondary endothelial failure (24.3%), keratoconus (18.8%), regraft (13.5%), and Fuchs endothelial corneal dystrophy (15.1%). Endothelial keratoplasty became the preferred technique for endothelial diseases and deep anterior lamellar keratoplasty the preferred technique for keratoconus, surpassing penetrating keratoplasty in 2013. Secondary endothelial failure is the top indication for performing a keratoplasty over the 12-year period. There was a shift from penetrating keratoplasty to endothelial keratoplasty performed for Fuchs endothelial corneal dystrophy and secondary endothelial failure, and to deep anterior lamellar keratoplasty, performed for keratoconus. This highlights an important shift in managing corneal diseases toward the application of selective and more conservative surgeries and changes in indications in corneal transplantation.

Instantaneous death due to transorbital reverse penetration of a screw in an accidental fall: unusual autopsy case report and review of the literature.

PubMed

Gioia, Sara; Bacci, Mauro; Lancia, Massimo; Carlini, Luigi; Suadoni, Fabio

2014-03-01

We present a peculiar autopsy case of a transorbital penetrating head injury, in a male worker, after an accidental fall onto a screw not completely stuck into a wooden board. A 13-cm screw entered the cranium 9.5 cm deep, penetrating with the flat end, a condition defined in literature as "reverse penetration." The death was instantaneous and caused by a neurogenic shock due to injuries to the brain stem and the right cerebellar hemisphere. These injuries, enabled by the length of the screw, are generally described in literature as due to nontransorbital penetrations, frequently associated with posterior entry and a large intracranial injury. The ocular globe has been, furthermore, perfectly preserved thanks to its mobility in the orbit. Even the dynamic of the incident is peculiar because of the stationary nature of the penetrating object, which the victim actively fell on by accident. To the best of our knowledge, the matter is therefore a very peculiar mortal case of transorbital intracranial penetration, whose verified injuries and dynamics are absolutely atypical. The case is now under discussion, and a review of pertinent literature is performed.

Linear-array based full-view high-resolution photoacoustic computed tomography of whole mouse brain functions in vivo

NASA Astrophysics Data System (ADS)

Li, Lei; Zhang, Pengfei; Wang, Lihong V.

2018-02-01

Photoacoustic computed tomography (PACT) is a non-invasive imaging technique offering high contrast, high resolution, and deep penetration in biological tissues. We report a photoacoustic computed tomography (PACT) system equipped with a high frequency linear array for anatomical and functional imaging of the mouse whole brain. The linear array was rotationally scanned in the coronal plane to achieve the full-view coverage. We investigated spontaneous neural activities in the deep brain by monitoring the hemodynamics and observed strong interhemispherical correlations between contralateral regions, both in the cortical layer and in the deep regions.

Volcanotectonic history of Crater Flat, southwestern Nevada, as suggested by new evidence from drill hole USW-VH-1 and vicinity

USGS Publications Warehouse

Carr, W.J.

1982-01-01

New evidence for a possible resurgent dome in the caldera related to eruption of the Bullfrog Member of the Crater Flat Tuff has been provided by recent drilling of a 762-meter (2,501-foot) hole in central Crater Flat. Although no new volcanic units were penetrated by the drill hole (USW-VH-1), the positive aeromagnetic anomaly in the vicinity of the drill hole appears to result in part from the unusually thick, densely welded tuff of the Bullfrog. Major units penetrated include alluvium, basalt of Crater Flat, Tiva Canyon and Topopah Spring Members of the Paintbrush Tuff, and Prow Pass and Bullfrog Members of the Crater Flat Tuff. In addition, the drill hole provided the first subsurface hydrologic information for the area. The water table in the hole is at about 180 meters (600 feet), and the temperature gradient appears slightly higher than normal for the region.

Present and future trends of laser materials processing in Japan

NASA Astrophysics Data System (ADS)

Matsunawa, Akira

1991-10-01

Lasers quickly penetrated into Japanese industries in the mid-80s. The paper reviews the present situation of industrial lasers and their applications in Japanese industries for materials removal, joining, and some surface modification technologies as well as their economical evaluation compared with competitive technologies. Laser cutting of metallic and nonmetallic thin sheets is widely prevalent even in small scale industries as a flexible manufacturing tool. As for the laser welding is concerned, industrial applications are rather limited in mass production lines. This mainly comes from the fact that the present laser technologies have not employed the adaptive control because of the lack of sensors, monitoring, and control systems which can tolerate the high-precision and high-speed processing. In spite of this situation, laser welding is rapidly increasing in recent years in industries such as automotive, machinery, electric/electronic, steel, heavy industries, etc. Laser surface modification technologies have attracted significant interest from industrial people, but actual application is very limited today. However, the number of R&D papers is increasing year by year. The paper also reviews these new technology trends in Japan.

Monitoring of tissue modification with optical coherence tomography

NASA Astrophysics Data System (ADS)

Zhang, Wei; Luo, Qingming; Yao, Lei; Cheng, Haiying; Zeng, Shaoqun

2002-04-01

An experimental monitoring of tissue modification of in vitro and in vivo rabbit dura mater with administration of osmotical agents, 40% glucose solution and glycerol, using optical coherence tomography was presented. The preliminary results of experimental study of influence of osmotical liquids (glucose solutions, glycerol) of rabbit dura mater were reported. The significant decreasing of the light from surface and increasing of the light from the deep of dura mater under action of osmotical solutions and the increasing of OCT imaging depth were demonstrated. Experiments showed that administration of osmolytes to dura mater allowed for effective and temporary control of its optical characteristics, which made dura mater more transparent, increased the ability of light penetrating the tissue, and consequently improved the optical imaging depth. It is a significant study, which can improve penetration of optical imaging of cerebral function and acquire more information of the deep brain tissue.

Automated variance reduction for MCNP using deterministic methods.

PubMed

Sweezy, J; Brown, F; Booth, T; Chiaramonte, J; Preeg, B

2005-01-01

In order to reduce the user's time and the computer time needed to solve deep penetration problems, an automated variance reduction capability has been developed for the MCNP Monte Carlo transport code. This new variance reduction capability developed for MCNP5 employs the PARTISN multigroup discrete ordinates code to generate mesh-based weight windows. The technique of using deterministic methods to generate importance maps has been widely used to increase the efficiency of deep penetration Monte Carlo calculations. The application of this method in MCNP uses the existing mesh-based weight window feature to translate the MCNP geometry into geometry suitable for PARTISN. The adjoint flux, which is calculated with PARTISN, is used to generate mesh-based weight windows for MCNP. Additionally, the MCNP source energy spectrum can be biased based on the adjoint energy spectrum at the source location. This method can also use angle-dependent weight windows.

Bending-related faulting and mantle serpentinization at the Middle America trench.

PubMed

Ranero, C R; Morgan, J Phipps; McIntosh, K; Reichert, C

2003-09-25

The dehydration of subducting oceanic crust and upper mantle has been inferred both to promote the partial melting leading to arc magmatism and to induce intraslab intermediate-depth earthquakes, at depths of 50-300 km. Yet there is still no consensus about how slab hydration occurs or where and how much chemically bound water is stored within the crust and mantle of the incoming plate. Here we document that bending-related faulting of the incoming plate at the Middle America trench creates a pervasive tectonic fabric that cuts across the crust, penetrating deep into the mantle. Faulting is active across the entire ocean trench slope, promoting hydration of the cold crust and upper mantle surrounding these deep active faults. The along-strike length and depth of penetration of these faults are also similar to the dimensions of the rupture area of intermediate-depth earthquakes.

The Tungsten Inert GAS (TIG) Process of Welding Aluminium in Microgravity: Technical and Economic Considerations

NASA Astrophysics Data System (ADS)

Ferretti, S.; Amadori, K.; Boccalatte, A.; Alessandrini, M.; Freddi, A.; Persiani, F.; Poli, G.

2002-01-01

The UNIBO team composed of students and professors of the University of Bologna along with technicians and engineers from Alenia Space Division and Siad Italargon Division, took part in the 3rd Student Parabolic Flight Campaign of the European Space Agency in 2000. It won the student competition and went on to take part in the Professional Parabolic Flight Campaign of May 2001. The experiment focused on "dendritic growth in aluminium alloy weldings", and investigated topics related to the welding process of aluminium in microgravity. The purpose of the research is to optimise the process and to define the areas of interest that could be improved by new conceptual designs. The team performed accurate tests in microgravity to determine which phenomena have the greatest impact on the quality of the weldings with respect to penetration, surface roughness and the microstructures that are formed during the solidification. Various parameters were considered in the economic-technical optimisation, such as the type of electrode and its tip angle. Ground and space tests have determined the optimum chemical composition of the electrodes to offer longest life while maintaining the shape of the point. Additionally, the power consumption has been optimised; this offers opportunities for promoting the product to the customer as well as being environmentally friendly. Tests performed on the Al-Li alloys showed a significant influence of some physical phenomena such as the Marangoni effect and thermal diffusion; predictions have been made on the basis of observations of the thermal flux seen in the stereophotos. Space transportation today is a key element in the construction of space stations and future planetary bases, because the volumes available for launch to space are directly related to the payload capacity of rockets or the Space Shuttle. The research performed gives engineers the opportunity to consider completely new concepts for designing structures for space applications. In fact, once the optimised parameters are defined for welding in space, it could be possible to weld different parts directly in orbit to obtain much larger sizes and volumes, for example for space tourism habitation modules. The second relevant aspect is technology transfer obtained by the optimisation of the TIG process on aluminium which is often used in the automotive industry as well as in mass production markets.

Monitoring controlled graves representing common burial scenarios with ground penetrating radar

NASA Astrophysics Data System (ADS)

Schultz, John J.; Martin, Michael M.

2012-08-01

Implementing controlled geophysical research is imperative to understand the variables affecting detection of clandestine graves during real-life forensic searches. This study focused on monitoring two empty control graves (shallow and deep) and six burials containing a small pig carcass (Sus scrofa) representing different burial forensic scenarios: a shallow buried naked carcass, a deep buried naked carcass, a deep buried carcass covered by a layer of rocks, a deep buried carcass covered by a layer of lime, a deep buried carcass wrapped in an impermeable tarpaulin and a deep buried carcass wrapped in a cotton blanket. Multi-frequency, ground penetrating radar (GPR) data were collected monthly over a 12-month monitoring period. The research site was a cleared field within a wooded area in a humid subtropical environment, and the soil consisted of a Spodosol, a common soil type in Florida. This study compared 2D GPR reflection profiles and horizontal time slices obtained with both 250 and 500 MHz dominant frequency antennae to determine the utility of both antennae for grave detection in this environment over time. Overall, a combination of both antennae frequencies provided optimal detection of the targets. Better images were noted for deep graves, compared to shallow graves. The 250 MHz antenna provided better images for detecting deep graves, as less non-target anomalies were produced with lower radar frequencies. The 250 MHz antenna also provided better images detecting the disturbed ground. Conversely, the 500 MHz antenna provided better images when detecting the shallow pig grave. The graves that contained a pig carcass with associated grave items provided the best results, particularly the carcass covered with rocks and the carcass wrapped in a tarpaulin. Finally, during periods of increased soil moisture levels, there was increased detection of graves that was most likely related to conductive decompositional fluid from the carcasses.

An Industry/DOE Program to Develop and Benchmark Advanced Diamond Product Drill Bits and HP/HT Drilling Fluids to Significantly Improve Rates of Penetration

DOE Office of Scientific and Technical Information (OSTI.GOV)

TerraTek

2007-06-30

A deep drilling research program titled 'An Industry/DOE Program to Develop and Benchmark Advanced Diamond Product Drill Bits and HP/HT Drilling Fluids to Significantly Improve Rates of Penetration' was conducted at TerraTek's Drilling and Completions Laboratory. Drilling tests were run to simulate deep drilling by using high bore pressures and high confining and overburden stresses. The purpose of this testing was to gain insight into practices that would improve rates of penetration and mechanical specific energy while drilling under high pressure conditions. Thirty-seven test series were run utilizing a variety of drilling parameters which allowed analysis of the performance ofmore » drill bits and drilling fluids. Five different drill bit types or styles were tested: four-bladed polycrystalline diamond compact (PDC), 7-bladed PDC in regular and long profile, roller-cone, and impregnated. There were three different rock types used to simulate deep formations: Mancos shale, Carthage marble, and Crab Orchard sandstone. The testing also analyzed various drilling fluids and the extent to which they improved drilling. The PDC drill bits provided the best performance overall. The impregnated and tungsten carbide insert roller-cone drill bits performed poorly under the conditions chosen. The cesium formate drilling fluid outperformed all other drilling muds when drilling in the Carthage marble and Mancos shale with PDC drill bits. The oil base drilling fluid with manganese tetroxide weighting material provided the best performance when drilling the Crab Orchard sandstone.« less

Dealing with the Surgical and Medical Challenges of Penetrating Brain Injuries

PubMed Central

Syrmos, Nikolaos; Ganau, Mario; De Carlo, Antonella; Prisco, Lara; Ganau, Laura; Valadakis, Vasileios; Grigoriou, Kostantinos; Iliadis, Charalampos; Arvanitakis, Dimitrios

2013-01-01

Peacetime has reduced the overall incidence of penetrating brain injuries (PBI), and those related to missile penetration are not common anymore at least in western countries. Nevertheless, PBI still occur, and car crashes or work accidents are their main causes. The management of such cases is characterized by many challenges, not only from a surgical and medical point of view, but also for the different and sometimes bizarre dynamics by which they present. Herein we report an unusual deep penetrating brain injury, due to a high-energy crash against a metallic rod in a construction site, with a good surgical outcome despite dramatic clinical conditions on admission. A discussion of the surgical results and functional outcome related to PBI, as found in the English medical literature, is provided. Moreover the most common postoperative complications along with the diagnostic flow charts and therapeutic options useful to prevent inappropriate treatment are highlighted. PMID:23365777

Effect of Mechanical Heterogeneity on the Crack Driving Force of a Reactor Pressure Vessel Outlet Nozzle DMW Joint

NASA Astrophysics Data System (ADS)

Lingyan, Zhao; Yinghao, Cui; He, Xue

2017-12-01

The welding mechanical heterogeneity, load complexity, material and geometrical structure makes it very difficult to assess the structural integrity of dissimilar metal weld (DMW) joints. Based on a numerical simulated approach of the continuous change of material mechanical property in the buttering layer, a reactor pressure vessel (RPV) outlet nozzle DMW joint with service loads is studied, effect of mechanical heterogeneity on the stress-strain field and stress triaxiality at the semi-elliptical surface crack front are discussed. The analyses show that once the crack extends into the high hardness zone of Alloy 182 buttering, the strain decreases sharply, the strain gradient increases and the crack propagation slows down. The influence of strength mismatch on the stress triaxiality at the shallow crack front is greater than that at the deep crack front. The interaction between strength mismatch and crack depth directly affects the crack growth direction.

Subinertial Slope-Trapped Waves in the Northeastern Gulf of Mexico

DTIC Science & Technology

2009-06-01

describe low-frequency varia- bility in the GOM and its interaction with the topo- graphy. Oey and Lee (2002) describe modeled deep eddy kinetic...deep energy can penetrate onto the upper part of the slope in this region; Oey and Lee (2002) state that their model cannot adequately resolve...slope topography in the NE GOM is described by Cames et al. (2008), Hamilton and Lee (2005), and Wang et al. (2003). Hamilton and Lee (2005) found

Experimental studies on nonpenetrating filtration surgery using the CO2 laser.

PubMed

Assia, Ehud I; Rotenstreich, Yigal; Barequet, Irina S; Apple, David J; Rosner, Mordechai; Belkin, Michael

2007-06-01

This study evaluated the use of a CO2 laser for performing deep sclerectomy in nonpenetrating filtration surgery. Three experimental models were performed: enucleated sheep and cow eyes (n=18) to determine optimal irradiation parameters, live rabbit eyes (n=20) to test feasibility, and cadaver eyes (40 procedures in 20 eyes) to study effects in human eyes tissue. After a half-thickness scleral flap was created, deep sclerectomy was performed by CO2 laser applications on the scleral bed down to the trabeculo-Descemet's membrane. Fluid percolation was repeatedly achieved without penetration in sheep and cow eyes using scanned laser energy of 5-10 W at a pulse duration of 200 micros and a working distance of 35 cm. In live rabbits, deep sclerectomy was achieved without perforation in 19/20 eyes. Intraocular pressure was significantly decreased on the first postoperative day (10.3+/-5.1 mmHg lower, on average, than in the nonoperated fellow eye; P<0.001), and this persisted for 21 days. Operations on all cadaver eyes resulted in effective fluid percolation. Penetration of the scleral wall occurred in five cases only after repeated laser applications with high energy. Histologically, a thin sclerocorneal intact wall was demonstrated at the sclerectomy bed. Collateral tissue damage did not extend beyond 100 microm, and adjacent structures remained unharmed. CO2 laser-assisted deep sclerectomy is a feasible and apparently safe procedure.

Final summary report for 1989 inservice inspection (ISI) of SRS (Savannah River Site) 100-P Reactor tank

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morrison, J.M.; Loibl, M.W.

1989-12-15

The integrity of the SRS reactor tanks is a key factor affecting their suitability for continued service since, unlike the external piping system and components, the tanks are virtually irreplaceable. Cracking in various areas of the process water piping systems has occurred beginning in 1960 as a result of several degradation mechanisms, chiefly intergranular stress corrosion cracking (IGSCC) and chloride-induced transgranular cracking. IGSCC, currently the primary degradation mechanism, also occurred in the knuckle'' region (tank wall-to-bottom tube sheet transition piece) unique to C Reactor and was eventually responsible for that reactor being deactivated in 1985. A program of visual examinationsmore » of the SRS reactor tanks was initiated in 1968, which used a specially designed immersible periscope. Under that program the condition of the accessible tank welds and associated heat affected zones (HAZ) was evaluated on a five-year frequency. Prior to 1986, the scope of these inspections comprised approximately 20 percent of the accessible weld area. In late 1986 and early 1987 the scope of the inspections was expanded and a 100 percent visual inspection of accessible welds was performed of the P-, L-, and K-Reactor tanks. Supplemental dye penetrant examinations were performed in L Reactor on selected areas which showed visual indications. No evidence of cracking was detected in any of these inspections of the P-, L-, and K-Reactor tanks. 17 refs., 7 figs.« less

A checklist of the deep sea fishes of the Levant Sea, Mediterranean Sea.

PubMed

Goren, Menachem; Galil, Bella S

2015-08-04

We list sixty five fish species collected at depths greater than 500 m in the Levant Basin, including 10 depth records. The Levantine bathyal ichthyofauna is characterized by its eurybathy, with an upper bathymetric boundary that permitted penetration of the shallow Gibraltar and Siculo-Tunisian sills, and a much lower bathymetric boundary than recorded for conspecifics elsewhere. The opportunistic and resilient ichthyofauna re-colonized recently the deep-sea following the last anoxic event (~ 6 kyr), forming assemblages notably distinct from those in the western Mediterranean. The exploration and production of deep seabed hydrocarbons have raised the specter of severe direct impacts to the deep habitats. There is an urgent need for documenting the full extent of deep-sea biodiversity, and for providing information for the development of competent and pragmatic management plans and effective conservation policies.

Transcranial magnetic stimulation: Improved coil design for deep brain investigation

NASA Astrophysics Data System (ADS)

Crowther, L. J.; Marketos, P.; Williams, P. I.; Melikhov, Y.; Jiles, D. C.; Starzewski, J. H.

2011-04-01

This paper reports on a design for a coil for transcranial magnetic stimulation. The design shows potential for improving the penetration depth of the magnetic field, allowing stimulation of subcortical structures within the brain. The magnetic and induced electric fields in the human head have been calculated with finite element electromagnetic modeling software and compared with empirical measurements. Results show that the coil design used gives improved penetration depth, but also indicates the likelihood of stimulation of additional tissue resulting from the spatial distribution of the magnetic field.

Structure Formation and Properties of Weld Overlay Produced by Laser Cladding under the Influence of Nanoparticles of High-melting Compounds

NASA Astrophysics Data System (ADS)

Murzakov, M.; Petrovskiy, V.; Birukov, V.; Dzhumaev, P.; Polski, V.; Markushov, Y.; Bykovskiy, D.

Researches of flat samples using laser cladding technology were carried out. Nickel-based powders with the addition of nanopowders of tantalum carbide and tungsten carbide with water-based hydroxyethylcellulose as the binder, were used for slip cladding. Powders are fused on under local argon protection. The experiments were carried out to determine minimal base metal penetration depth, microhardness distribution over cross section of substrate and deposited layers, enrichment level of cladding metal with base components depending on power density and deposition rate. Metallographic studies of obtained overlays were conducted using a high-precision analytical equipment.

Cellular uptake and ex vivo urothelial penetration by oligodeoxynucleotides for optimizing treatment of transitional cell carcinoma.

PubMed

Bolenz, Christian; Trojan, Lutz; Gabriel, Ute; Honeck, Patrick; Wendt-Nordahl, Gunnar; Schaaf, Axel; Alken, Peter; Michel, Maurice Stephan

2008-10-01

To evaluate cellular uptake and urothelial penetration of oligodeoxynucleotides (ODNs) in transitional cell carcinoma (TCC) cell lines and in a porcine ex vivo model, respectively. A panel of human TCC cell lines (RT 112, HT 1197 and UM-UC3) were exposed tofluorescein-labeled ODNs. Transfection rates were assessed byfluorescence microscopy and fluorescence-activated cell sorting (FACS). Intravesical treatment with ODNs was performed in a porcine ex vivo model. Urothelial penetration was evaluated using fluorescence microscopy of cryosections. Treatment with ODNs provided transfection rates of at least 96.8% of TCC cells, irrespective of use of a transfection agent. Effective urothelial penetration by ODNs was detected when compared with controls (p = 0.0325). The addition of a liposomal transfection agent significantly increased the penetration depth, allowing affection of deep urothelial cell layers (p = 0.0082). High transfection rates of ODNs can be achieved in TCC cells. Urothelial penetration of ODNs was observed down to the deepest cell layers when a transfection agent is added, suggesting a high potential for complementing the chemoresection effects on residual tumor areas during intravesical therapy of non-muscle-invasive TCC.

The hydrothermal system of Long Valley Caldera, California

USGS Publications Warehouse

Sorey, M.L.; Lewis, Robert Edward; Olmsted, F.H.

1978-01-01

Long Valley caldera, an elliptical depression covering 450 km 2 on the eastern front of the Sierra Nevada in east-central California, contains a hot-water convection system with numerous hot springs and measured and estimated aquifer temperatures at depths of 180?C to 280?C. In this study we have synthesized the results of previous geologic, geophysical, geochemical, and hydrologic investigations of the Long Valley area to develop a generalized conceptual and mathematical model which describes the gross features of heat and fluid flow in the hydrothermal system. Cenozoic volcanism in the Long Valley region began about 3.2 m.y. (million years) ago and has continued intermittently until the present time. The major event that resulted in the formation of the Long Valley caldera took place about 0.7 m.y. ago with the eruption of 600 km 3 or more of Bishop Tuff of Pleistocene age, a rhyolitic ash flow, and subsequent collapse of the roof of the magma chamber along one or more steeply inclined ring fractures. Subsequent intracaldera volcanism and uplift of the west-central part of the caldera floor formed a subcircular resurgent dome about 10 km in diameter surrounded by a moat containing rhyolitic, rhyodacitic, and basaltic rocks ranging in age from 0.5 to 0.05 m.y. On the basis of gravity and seismic studies, we estimate an aver- age thickness of fill of 2.4 km above the precaldera granitic and metamorphic basement rocks. A continuous layer of densely welded Bishop Tuff overlies the basement rocks, with an average thickness of 1.4 km; the fill above the welded Bishop Tuff consists of intercalated volcanic flows and tuffs and fluvial and lacustrine deposits. Assuming the average grain density of the fill is between 2.45 and 2.65 g/cm 3 , we calculate the average bulk porosity of the total fill as from 0.11 to 0.21. Comparison of published values of porosity of the welded Bishop Tuff exposed southeast of the caldera with calculated values indicates average bulk porosity for the welded tuff (including fracture porosity) from 0.05 to 0.10. Because of its continuity and depth and the likelihood of significant fracture permeability in the more competent rocks such as the welded tuff, our model of the hydrothermal system assumes that the Bishop Tuff provides the principal hot-water reservoir. However, because very little direct information exists from drill holes below 300 m, this assumption must be considered tentative. Long Valley caldera is drained by the Owens River and several tributaries which flow into Lake Crowley in the southeast end of the caldera. Streamflow and springflow measurements for water years 1964-74 indicate a total inflow to Lake Crowley of about 10,900 L/s. In contrast, the total discharge of hot water from the hydrothermal reservoir is about 300 L/s. For modeling purposes, the ground-water system is considered as comprising a shallow subsystem in the fill above the densely welded Bishop Tuff containing relatively cold ground water, and a deep subsystem or hydrothermal reservoir in the welded tuff containing relatively hot ground water. Hydrologic, isotopic, and thermal data indicate that recharge to the hydrothermal reservoir occurs in the upper Owens River drainage basin along the western periphery of the caldera. Temperature profiles in a 2.11- km-deep test well drilled by private industry in the southeastern part of the caldera suggest that an additional flux of relatively cool ground water recharges the deep subsystem around the northeast rim. Flow in the shallow ground-water subsystem is neglected in the model except in recharge areas and along Hot Creek gorge, where approximately 80 percent of the hot-water discharge from the hydrothermal reservoir moves upward along faults toward springs in the gorge. Heat-flow data from the Long Valley region indicate that the resurgent dome overlies a residual magma chamber more circular in plan than the original magma chamber that supplied the Bishop Tuff

Elastic-Plastic Fracture Mechanics Analysis of Critical Flaw Size in ARES I-X Flange-to-Skin Welds

NASA Technical Reports Server (NTRS)

Chell, G. Graham; Hudak, Stephen J., Jr.

2008-01-01

NASA's Ares 1 Upper Stage Simulator (USS) is being fabricated from welded A516 steel. In order to insure the structural integrity of these welds it is of interest to calculate the critical initial flaw size (CIFS) to establish rational inspection requirements. The CIFS is in turn dependent on the critical final flaw size (CFS), as well as fatigue flaw growth resulting from transportation, handling and service-induced loading. These calculations were made using linear elastic fracture mechanics (LEFM), which are thought to be conservative because they are based on a lower bound, so called elastic, fracture toughness determined from tests that displayed significant plasticity. Nevertheless, there was still concern that the yield magnitude stresses generated in the flange-to-skin weld by the combination of axial stresses due to axial forces, fit-up stresses, and weld residual stresses, could give rise to significant flaw-tip plasticity, which might render the LEFM results to be non-conservative. The objective of the present study was to employ Elastic Plastic Fracture Mechanics (EPFM) to determine CFS values, and then compare these values to CFS values evaluated using LEFM. CFS values were calculated for twelve cases involving surface and embedded flaws, EPFM analyses with and without plastic shakedown of the stresses, LEFM analyses, and various welding residual stress distributions. For the cases examined, the computed CFS values based on elastic analyses were the smallest in all instances where the failures were predicted to be controlled by the fracture toughness. However, in certain cases, the CFS values predicted by the elastic-plastic analyses were smaller than those predicted by the elastic analyses; in these cases the failure criteria were determined by a breakdown in stress intensity factor validity limits for deep flaws (a greater than 0.90t), rather than by the fracture toughness. Plastic relaxation of stresses accompanying shakedown always increases the calculated CFS values compared to the CFS values determined without shakedown. Thus, it is conservative to ignore shakedown effects.

NDE of copper canisters for long-term storage of spent nuclear fuel from the Swedish nuclear power plants

NASA Astrophysics Data System (ADS)

Stepinski, Tadeusz

2003-07-01

Sweden has been intensively developing methods for long term storage of spent fuel from the nuclear power plants for twenty-five years. A dedicated research program has been initiated and conducted by the Swedish company SKB (Swedish Nuclear Fuels and Waste Management Co.). After the interim storage SKB plans to encapsulate spent nuclear fuel in copper canisters that will be placed at a deep repository located in bedrock. The canisters filled with fuel rods will be sealed by an electron beam weld. This paper presents three complementary NDE techniques used for assessing the sealing weld in copper canisters, radiography, ultrasound, and eddy current. A powerful X-ray source and a digital detector are used for the radiography. An ultrasonic array system consisting of a phased ultrasonic array and a multi-channel electronics is used for the ultrasonic examination. The array system enables electronic focusing and rapid electronic scanning eliminating the use of a complicated mechanical scanner. A specially designed eddy current probe capable of detecting small voids at the depth up to 4 mm in copper is used for the eddy current inspection. Presently, all the NDE techniques are verified in SKB's Canister Laboratory where full scale canisters are welded and examined.