EB welding of launch vehicles

NASA Astrophysics Data System (ADS)

Szabo, Attila

While large structural components can be electron beam (EB) welded, equipment and operating costs increase with the requisite vacuum chamber's size. Attention is presently given to cost-effective ways of EB welding launch-vehicle assemblies without compromise of weld quality in such alloys as 2219, 2090, Weldalite, and HP9-4-30/20. Weld strengths at both room and cryogenic temperatures that were 50 percent higher than those obtainable for such materials with arc welding have been demonstrated. Fracture toughnesses were also 40-50 percent higher than arc-welded values. Attention is given to EB joint fit-up allowables for 2219-T87 Al alloy.

Model-Based Structural Health Monitoring of Fatigue Damage Test-Bed Specimens

DTIC Science & Technology

2011-11-15

the hull welds or notches along component edges are good initial candidates for the hypothetical damage initiation areas. The branching process adds...to it off-center. The base plate and the stiffener plate are rigidly welded by a tungsten inert gas ( TIG ) weld . Three different crack paths...shown in Figure 9(a), an 18 in long stiffener plate has been welded to each of the tested plates with 0.625 in long discrete TIG welds at 5 locations

Assessment of delta ferrite in multipass TIG welds of 40 mm thick SS 316L: A comparative study of ferrite number (FN) prediction and measurements

NASA Astrophysics Data System (ADS)

Buddu, Ramesh Kumar; Raole, P. M.; Sarkar, B.

2017-04-01

Austenitic stainless steels are widely used in the fabrication of fusion reactor major systems like vacuum vessel, divertor, cryostat and other structural components development. Multipass welding is used for the development of thick plates for the structural components fabrication. Due to the repeated weld thermal cycles, the microstructure adversely alters owing to the presence of complex phases like austenite, ferrite and delta ferrite and subsequently influences the mechanical properties like tensile and impact toughness of joints. The present paper reports the detail analysis of delta ferrite phase in welded region of 40 mm thick SS316L plates welded by special design multipass narrow groove TIG welding process under three different heat input conditions. The correlation of delta ferrite microstructure of different type structures acicular and vermicular is observed. The chemical composition of weld samples was used to predict the Ferrite Number (FN), which is representative form of delta ferrite in welds, with Schaeffler’s, WRC-1992 diagram and DeLong techniques by calculating the Creq and Nieq ratios and compared with experimental data of FN from Feritescope measurements. The low heat input conditions (1.67 kJ/mm) have produced higher FN (7.28), medium heat input (1.72 kJ/mm) shown FN (7.04) where as high heat input (1.87 kJ/mm) conditions has shown FN (6.68) decreasing trend and FN data is compared with the prediction methods.

A Weld Position Recognition Method Based on Directional and Structured Light Information Fusion in Multi-Layer/Multi-Pass Welding.

PubMed

Zeng, Jinle; Chang, Baohua; Du, Dong; Wang, Li; Chang, Shuhe; Peng, Guodong; Wang, Wenzhu

2018-01-05

Multi-layer/multi-pass welding (MLMPW) technology is widely used in the energy industry to join thick components. During automatic welding using robots or other actuators, it is very important to recognize the actual weld pass position using visual methods, which can then be used not only to perform reasonable path planning for actuators, but also to correct any deviations between the welding torch and the weld pass position in real time. However, due to the small geometrical differences between adjacent weld passes, existing weld position recognition technologies such as structured light methods are not suitable for weld position detection in MLMPW. This paper proposes a novel method for weld position detection, which fuses various kinds of information in MLMPW. First, a synchronous acquisition method is developed to obtain various kinds of visual information when directional light and structured light sources are on, respectively. Then, interferences are eliminated by fusing adjacent images. Finally, the information from directional and structured light images is fused to obtain the 3D positions of the weld passes. Experiment results show that each process can be done in 30 ms and the deviation is less than 0.6 mm. The proposed method can be used for automatic path planning and seam tracking in the robotic MLMPW process as well as electron beam freeform fabrication process.

Improving Stiffness-to-weight Ratio of Spot-welded Structures based upon Nonlinear Finite Element Modelling

NASA Astrophysics Data System (ADS)

Zhang, Shengyong

2017-07-01

Spot welding has been widely used for vehicle body construction due to its advantages of high speed and adaptability for automation. An effort to increase the stiffness-to-weight ratio of spot-welded structures is investigated based upon nonlinear finite element analysis. Topology optimization is conducted for reducing weight in the overlapping regions by choosing an appropriate topology. Three spot-welded models (lap, doubt-hat and T-shape) that approximate “typical” vehicle body components are studied for validating and illustrating the proposed method. It is concluded that removing underutilized material from overlapping regions can result in a significant increase in structural stiffness-to-weight ratio.

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.

Analytical simulation of weld effects in creep range

NASA Technical Reports Server (NTRS)

Dhalla, A. K.

1985-01-01

The inelastic analysis procedure used to investigate the effect of welding on the creep rupture strength of a typical Liquid Metal Fast Breeder Reactor (LMFBR) nozzle is discussed. The current study is part of an overall experimental and analytical investigation to verify the inelastic analysis procedure now being used to design LMFBR structural components operating at elevated temperatures. Two important weld effects included in the numerical analysis are: (1) the residual stress introduced in the fabrication process; and (2) the time-independent and the time-dependent material property variations. Finite element inelastic analysis was performed on a CRAY-1S computer using the ABAQUS program with the constitutive equations developed for the design of LMFBR structural components. The predicted peak weld residual stresses relax by as much as 40% during elevated temperature operation, and their effect on creep-rupture cracking of the nozzle is considered of secondary importance.

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.

Influence of deformation on structural-phase state of weld material in St3 steel

NASA Astrophysics Data System (ADS)

Smirnov, Alexander; Kozlov, Eduard; Ababkov, Nicolay; Popova, Natalya; Nikonenko, Elena; Ozhiganov, Yevgeniy; Zboykova, Nadezhda; Koneva, Nina

2016-01-01

The structural-phase condition of the weld material subjected to the plastic deformation was investigated using the translucent diffraction electron microscopy method. The investigations were carried out near the joint of the weld and the base metal. The seam was done by the method of manual arc welding without artificial defects. The St3 steel was taken as the welded material. Influence of the plastic deformation on morphology, phase composition, defect structure and its parameters of weld metal was revealed. All investigations were done at the distance of 0.5 mm from the joint of the weld and the base metal at the deformation degrees from 0 to 5% and after destruction of a sample. It was established that deformation of the sample did not lead to qualitative changes in the structure (the structure is still presented by ferrite-pearlite mixture) but changed the quantitative parameters of the structure, namely, with the increase of plastic deformation a part of the pearlite component becomes more and more imperfect. In the beginning it turns into the destroyed pearlite then into ferrite, the volume fraction of pearlite is decreased. The polarization of dislocation structure takes place but it doesn't lead to the internal stresses that can destroy the sample.

Ultrasonic Phased Array Simulations of Welded Components at NASA

NASA Technical Reports Server (NTRS)

Roth, D. J.; Tokars, R. P.; Martin, R. E.; Rauser, R. W.; Aldrin, J. C.

2009-01-01

Comprehensive and accurate inspections of welded components have become of increasing importance as NASA develops new hardware such as Ares rocket segments for future exploration missions. Simulation and modeling will play an increasing role in the future for nondestructive evaluation in order to better understand the physics of the inspection process, to prove or disprove the feasibility for an inspection method or inspection scenario, for inspection optimization, for better understanding of experimental results, and for assessment of probability of detection. This study presents simulation and experimental results for an ultrasonic phased array inspection of a critical welded structure important for NASA future exploration vehicles. Keywords: nondestructive evaluation, computational simulation, ultrasonics, weld, modeling, phased array

ManTech Affordability for Defense Weapon Systems

DTIC Science & Technology

2009-11-01

the Virginia Class Submarine Development of Friction Stir Welding for Navy Expeditionary Fighting Vehicle (EFV) Hull Components Procurement...Tile 2007 – Translational Friction Stir Welding 2006 – Engine Rotor Life Extension 2006 – Uncooled Focal Plane Array Producibility 2005 – Large...DDG 1000 with Hybrid Laser Arc Welding The Problem: T-Beam stiffeners, used extensively for decks, bulkheads, and other ship structures, are being

Experimental assessment of the influence of welding process parameters on Lamb wave transmission across ultrasonically welded thermoplastic composite joints

NASA Astrophysics Data System (ADS)

Ochôa, Pedro; Fernandez Villegas, Irene; Groves, Roger M.; Benedictus, Rinze

2018-01-01

One of the advantages of thermoplastic composites relative to their thermoset counterparts is the possibility of assembling components through welding. Ultrasonic welding in particular is very promising for industrialization. However, uncertainty in the fatigue and fracture behaviour of composites is still an obstacle to the full utilisation of these materials. Health monitoring is then of vital importance, and Lamb wave techniques have been widely recognised as some of the most promising approaches for that end. This paper presents the first experimental study about the influence of welding travel on the transmission of Lamb waves across ultrasonically welded thermoplastic composite joints in single-lap configuration. The main aim of this research is to start to understand how guided waves interact with the internal structure of ultrasonic welds, so that benign, manufacturing-related structural features can be distinguished from damaging ones in signal interpretation. The power transmission coefficient and the correlation coefficient proved to be suitable for analysing the wave propagation phenomena, allowing quantitative identification of small variations of weld-line thickness and intermolecular diffusion at the weld interface. The conclusions are used to develop a tentative damage detection criterion which can later on assist the design of a Lamb wave based structural health monitoring system for thermoplastic composite structures. The Lamb wave test results are backed up by phased-array inspections, which also provide some extra insight on the internal structure of ultrasonic welds.

Plasma arc welding repair of space flight hardware

NASA Technical Reports Server (NTRS)

Hoffman, David S.

1993-01-01

Repair and refurbishment of flight and test hardware can extend the useful life of very expensive components. A technique to weld repair the main combustion chamber of space shuttle main engines has been developed. The technique uses the plasma arc welding process and active cooling to seal cracks and pinholes in the hot-gas wall of the main combustion chamber liner. The liner hot-gas wall is made of NARloyZ, a copper alloy previously thought to be unweldable using conventional arc welding processes. The process must provide extensive heat input to melt the high conductivity NARloyZ while protecting the delicate structure of the surrounding material. The higher energy density of the plasma arc process provides the necessary heat input while active water cooling protects the surrounding structure. The welding process is precisely controlled using a computerized robotic welding system.

Investigation of plasma arc welding as a method for the additive manufacturing of titanium-(6)aluminum-(4)vanadium alloy components

NASA Astrophysics Data System (ADS)

Stavinoha, Joe N.

The process of producing near net-shape components by material deposition is known as additive manufacturing. All additive manufacturing processes are based on the addition of material with the main driving forces being cost reduction and flexibility in both manufacturing and product design. With wire metal deposition, metal is deposited as beads side-by-side and layer-by-layer in a desired pattern to build a complete component or add features on a part. There are minimal waste products, low consumables, and an efficient use of energy and feedstock associated with additive manufacturing processes. Titanium and titanium alloys are useful engineering materials that possess an extraordinary combination of properties. Some of the properties that make titanium advantageous for structural applications are its high strength-to-weight ratio, low density, low coefficient of thermal expansion, and good corrosion resistance. The most commonly used titanium alloy, Ti-6Al-4V, is typically used in aerospace applications, pressure vessels, aircraft gas turbine disks, cases and compressor blades, and surgical implants. Because of the high material prices associated with titanium alloys, the production of near net-shape components by additive manufacturing is an attractive option for the manufacturing of Ti-6Al-4V alloy components. In this thesis, the manufacturing of cylindrical Ti-6Al-4V alloy specimens by wire metal deposition utilizing the plasma arc welding process was demonstrated. Plasma arc welding is a cost effective additive manufacturing technique when compared to other current additive manufacturing methods such as laser beam welding and electron beam welding. Plasma arc welding is considered a high-energy-density welding processes which is desirable for the successful welding of titanium. Metal deposition was performed using a constant current plasma arc welding power supply, flow-purged welding chamber, argon shielding and orifice gas, ERTi-5 filler metal, and Ti-6Al-4V alloy substrates. Cylindrical weld metal deposits were built by employing an automatic wire feeder, turntable positioner, and vertical torch positioner. A total of four cylindrical weld metal specimens were built with various combinations of essential plasma arc welding process parameters. The temperature of the weld metal deposit was taken with a thermocouple after allowing a specified amount of time to pass before depositing the next weld track. An analytical heat flow model was created that estimated the temperature of the weld metal deposit in relation to the number of tracks deposited. The analytical heat flow model was adjusted to match the experimental data that was obtained and revealed that the rate of production could be increased if the rate of thermal energy losses from the deposit were increased. Cross-sections of the weld metal deposits were examined to observe the effects of thermal energy input on the weld metal macrostructure, microstructure, and grain size. Results from the metallographic inspections revealed an increase in grain size and coarsening of the structure as the number of weld tracks in the deposit increased.

Evaluation of Residual Stress Measurements Before and After Post-Weld Heat Treatment in the Weld Repairs

NASA Astrophysics Data System (ADS)

Pardowska, Anna M.; Price, John W. H.; Finlayson, Trevor R.; Ibrahim, R.

2010-11-01

Welding repairs are increasingly a structural integrity concern for aging pressure vessel and piping components. It has been demonstrated that the residual stress distribution near repair welds can be drastically different from that of the original weld. Residual stresses have a significant effect on the lifetime performance of a weld, and a reduction of these stresses is normally desirable. The aim of this paper is to investigate residual stresses in various weld repair arrangements using the non-destructive neutron diffraction technique. This research is focused on characterization of the residual stress distribution: (i) in the original weld; (ii) in a shallow toe weld repair; and (iii) after conventional post-weld heat treatment. The focus of the measurements is on the values of the subsurface strain/stress variations across the weld.

The Study of Complex (Ti, Zr, Cs) Nanopowder Influencing the Effective Ionization Potential of Arc Discharge When Mma Welding

NASA Astrophysics Data System (ADS)

Sapozhkov, S. B.; Burakova, E. M.

2016-08-01

Strength is one of the most important characteristics of a weld joint. Mechanical properties of a weld metal can be improved in a variety of ways. One of the possibilities is to add a nanopowder to the weld metal. Authors of the paper suggest changing the production process of MMA welding electrodes via adding nanopowder Ti, Zr, Cs to electrode components through liquid glass. Theoretical research into the nanopowder influence on the effective ionization potential (Ueff) of welding arc discharge is also necessitated. These measures support arcing stability, improve strength of a weld joint, as the consequence, ensure quality enhancing of a weld joint and the structure on the whole.

Application of welding simulation to block joints in shipbuilding and assessment of welding-induced residual stresses and distortions

NASA Astrophysics Data System (ADS)

Fricke, Wolfgang; Zacke, Sonja

2014-06-01

During ship design, welding-induced distortions are roughly estimated as a function of the size of the component as well as the welding process and residual stresses are assumed to be locally in the range of the yield stress. Existing welding simulation methods are very complex and time-consuming and therefore not applicable to large structures like ships. Simplified methods for the estimation of welding effects were and still are subject of several research projects, but mostly concerning smaller structures. The main goal of this paper is the application of a multi-layer welding simulation to the block joint of a ship structure. When welding block joints, high constraints occur due to the ship structure which are assumed to result in accordingly high residual stresses. Constraints measured during construction were realized in a test plant for small-scale welding specimens in order to investigate their and other effects on the residual stresses. Associated welding simulations were successfully performed with fine-mesh finite element models. Further analyses showed that a courser mesh was also able to reproduce the welding-induced reaction forces and hence the residual stresses after some calibration. Based on the coarse modeling it was possible to perform the welding simulation at a block joint in order to investigate the influence of the resulting residual stresses on the behavior of the real structure, showing quite interesting stress distributions. Finally it is discussed whether smaller and idealized models of definite areas of the block joint can be used to achieve the same results offering possibilities to consider residual stresses in the design process.

Acoustic Emission Weld Monitoring in the 2195 Aluminum-Lithium Alloy

NASA Technical Reports Server (NTRS)

Walker, James L.

2005-01-01

Due to its low density, the 2195 aluminum-lithium alloy was developed as a replacement for alloy 2219 in the Space Shuttle External Tank (ET). The external tank is the single largest component of the space shuttle system. It is 154 feet long and 27.6 feet in diameter, and serves as the structural backbone for the shuttle during launch, absorbing most of the 7 million plus pounds of thrust produced. The almost 4% decrease in density between the two materials provides an extra 7500 pounds of payload capacity necessary to put the International Space Station components into orbit. The ET is an all-welded structure; hence, the requirement is for up to five rewelds without hot cracking. Unfortunately, hot cracking during re-welding or repair operations was occurring and had to be dealt with before the new super lightweight tank could be used. Weld metal porosity formation was also of concern because it leads to hot cracking during weld repairs. Accordingly, acoustic emission (AE) nondestructive testing was employed to monitor the formation of porosity and hot cracks in order to select the best filler metal and optimize the weld schedule. The purpose of this work is to determine the feasibility of detecting hot cracking in welded aluminum-lithium (Al-Li) structures through the analysis of acoustic emission data. By acoustically characterizing the effects of reheating during a repair operation, the potential for hidden flaws coalescing and becoming "unstable" as the panel is repaired could be reduced. Identification of regions where microcrack growth is likely to occur and the location of active flaw growth in the repair weld will provide the welder with direct feedback as to the current weld quality enabling adjustments to the repair process be made in the field. An acoustic emission analysis of the source mechanisms present during welding has been conducted with the goals of locating regions in the weld line that are susceptible to damage from a repair operation, identifying the formation of critically sized flaws and providing accept/reject criteria for the quality of a weld as it is performed.

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.

Monitoring of surface-fatigue crack propagation in a welded steel angle structure using guided waves and principal component analysis

NASA Astrophysics Data System (ADS)

Lu, Mingyu; Qu, Yongwei; Lu, Ye; Ye, Lin; Zhou, Limin; Su, Zhongqing

2012-04-01

An experimental study is reported in this paper demonstrating monitoring of surface-fatigue crack propagation in a welded steel angle structure using Lamb waves generated by an active piezoceramic transducer (PZT) network which was freely surface-mounted for each PZT transducer to serve as either actuator or sensor. The fatigue crack was initiated and propagated in welding zone of a steel angle structure by three-point bending fatigue tests. Instead of directly comparing changes between a series of specific signal segments such as S0 and A0 wave modes scattered from fatigue crack tips, a variety of signal statistical parameters representing five different structural status obtained from marginal spectrum in Hilbert-huang transform (HHT), indicating energy progressive distribution along time period in the frequency domain including all wave modes of one wave signal were employed to classify and distinguish different structural conditions due to fatigue crack initiation and propagation with the combination of using principal component analysis (PCA). Results show that PCA based on marginal spectrum is effective and sensitive for monitoring the growth of fatigue crack although the received signals are extremely complicated due to wave scattered from weld, multi-boundaries, notch and fatigue crack. More importantly, this method indicates good potential for identification of integrity status of complicated structures which cause uncertain wave patterns and ambiguous sensor network arrangement.

Avoidance of crack inducement when laser welding hot-formed car body components - a variable analysis

NASA Astrophysics Data System (ADS)

Larsson, Johnny K.

The Volvo XC60 car body contains numerous parts in Ultra High Strength Steels (UHSS) in order to guarantee the structural integrity of the car in the event of a crash situation. Most of the parts are manufactured in a hot-forming process, so called presshardening, resulting in component tensile strength in the range of 1,500 MPa. As this type of material also presents fairly high carbon content (˜0.22%) it brings a challenge when it comes to welding. The Volvo XC60 car body is at the same time to a large extent assembled by laser welding technology. In early development stages of the project (Y413), it was observed that laser welding of hot-formed components presented a number of challenges due to the unique conditions offered by this welding method. The presentation will thoroughly describe the modes of procedure how to avoid crack inducement during the welding operation. A variable analysis approach was used based on the present circumstances at the production facility in the Gent plant. Crucial variables at laser welding such as gap between sheets, focal point position, welding speed and laser weld position relative to the flange edge were included in a test matrix and welding trials were carried out accordingly in the Pilot Plant in Gothenburg. The paper will discuss those welding results, the subsequent analysis and plausible theoretic explanations. From the lessons learnt in this research, the optimum laser welding parameters were then transferred to the laser welding stations in the Gent plant. There it has been proven, that also at high volume automotive manufacturing, it is possible to provide an outstanding weld quality also at such difficult pre-conditions. The presentation ends with some facts and figures and experiences from high volume series production, which also includes aspects on quality assurance.

Multiscale characterization and mechanical modeling of an Al-Zn-Mg electron beam weld

NASA Astrophysics Data System (ADS)

Puydt, Quentin; Flouriot, Sylvain; Ringeval, Sylvain; Parry, Guillaume; De Geuser, Frédéric; Deschamps, Alexis

Welding of precipitation hardening alloys results in multi-scale microstructural heterogeneities, from the hardening nano-scale precipitates to the micron-scale solidification structures and to the component geometry. This heterogeneity results in a complex mechanical response, with gradients in strength, stress triaxiality and damage initiation sites.

Limit load solution for electron beam welded joints with single edge weld center crack in tension

NASA Astrophysics Data System (ADS)

Lu, Wei; Shi, Yaowu; Li, Xiaoyan; Lei, Yongping

2012-05-01

Limit loads are widely studied and several limit load solutions are proposed to some typical geometry of weldments. However, there are no limit load solutions exist for the single edge crack weldments in tension (SEC(T)), which is also a typical geometry in fracture analysis. The mis-matching limit load for thick plate with SEC(T) are investigated and the special limit load solutions are proposed based on the available mis-matching limit load solutions and systematic finite element analyses. The real weld configurations are simplified as a strip, and different weld strength mis-matching ratio M, crack depth/width ratio a/ W and weld width 2H are in consideration. As a result, it is found that there exists excellent agreement between the limit load solutions and the FE results for almost all the mis-matching ration M, a/ W and ligament-to-weld width ratio ( W-a)/ H. Moreover, useful recommendations are given for evaluating the limit loads of the EBW structure with SEC(T). For the EBW joints with SEC(T), the mis-matching limit loads can be obtained assuming that the components are wholly made of base metal, when M changing from 1.6 to 0.6. When M decreasing to 0.4, the mis-matching limit loads can be obtained assuming that the components are wholly made of base metal only for large value of ( W-a)/ H. The recommendations may be useful for evaluating the limit loads of the EBW structures with SEC(T). The engineering simplifications are given for assessing the limit loads of electron beam welded structure with SEC(T).

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.

Gas Shielding Technology for Welding and Brazing

NASA Technical Reports Server (NTRS)

Nunes, Arthur J.; Gradl, Paul R.

2012-01-01

Welding is a common method that allows two metallic materials to be joined together with high structural integrity. When joints need to be leak-tight, light-weight, or free of contaminant-trapping seams or surface asperities, welding tends to be specified. There are many welding techniques, each with its own advantages and disadvantages. Some of these techniques include Forge Welding, Gas Tungsten Arc Welding, Friction Stir Welding, and Laser Beam Welding to name a few. Whichever technique is used, the objective is a structural joint that meets the requirements of a particular component or assembly. A key practice in producing quality welds is the use of shielding gas. This article discusses various weld techniques, quality of the welds, and importance of shielding gas in each of those techniques. Metallic bonds, or joints, are produced when metals are put into intimate contact. In the solid-state "blacksmith welding" process, now called Forge Welding (FOW), the site to be joined is pounded into intimate contact. The surfaces to be joined usually need to be heated to make it easier to deform the metal. The surfaces are sprinkled with a flux to melt surface oxides and given a concave shape so that surface contamination can be squeezed out of the joint as the surfaces are pounded together; otherwise the surface contamination would be trapped in the joint and would weaken the weld. In solid-state welding processes surface oxides or other contamination are typically squeezed out of the joint in "flash."

Laser Beam Welding of Nitride Steel Components

NASA Astrophysics Data System (ADS)

Gu, Hongping; Yin, Guobin; Shulkin, Boris

Laser beam welding is a joining technique that has many advantages over conventional GMAW welding, such as low heat input, short cycle time as well as good cosmetic welds. Laser beam welding has been widely used for welding powertrain components in automotive industry. When welding nitride steel components, however, laser beam welding faces a great challenge. The difficulty lies in the fact that the nitride layer in the joint releases the nitrogen into the weld pool, resulting in a porous weld. This research presents an industrial ready solution to prevent the nitrogen from forming gas bubbles in the weld.

New Equipment for Testing the Fatigue Strength of Riveted and Welded Joints

NASA Technical Reports Server (NTRS)

Muller, W

1940-01-01

The mechanical and electrical construction of a new experimental instrument for fatigue testing riveted and welded joints is described. This experimental device has the advantage of being able to stress, even with comparatively low magnetic exciter force, structural components in alternate bending by resonance vibrations up to incipient fatigue failure.

75 FR 60480 - In the Matter of Certain Bulk Welding Wire Containers and Components Thereof and Welding Wire...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-30

... Welding Wire Containers and Components Thereof and Welding Wire; Notice of Commission Determination To... within the United States after importation of certain bulk welding wire containers, components thereof, and welding wire by reason of infringement of certain claims of United States Patent Nos. 6,260,781; 6...

Ultrasonic Phased Array Inspection Simulations of Welded Components at NASA

NASA Technical Reports Server (NTRS)

Roth, D. J.; Tokars, R. P.; Martin, R. E.; Rauser, R. W.; Aldrin, J. C.; Schumacher, E. J.

2009-01-01

Comprehensive and accurate inspections of welded components have become of increasing importance as NASA develops new hardware such as Ares rocket segments for future exploration missions. Simulation and modeling will play an increased role in the future for nondestructive evaluation in order to better understand the physics of the inspection process and help explain the experimental results. It will also help to prove or disprove the feasibility for an inspection method or inspection scenario, help optimize inspections, and allow to a first approximation limits of detectability. This study presents simulation and experimental results for an ultrasonic phased array inspection of a critical welded structure important for NASA future exploration vehicles.

Detection and Sizing of Defects in Structural Components of a Nuclear Power Plant by ECT

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

Chen Zhenmao; Miya, Kenzo

2005-04-09

In this paper, progress of ECT technique for inspection of stress corrosion cracks in a structural component of a nuclear power plant is reported. Access and scanning vehicle (robot), advanced probes for SG tube inspection, development and evaluation of new probes for welding joint, and ECT based crack sizing technique are described respectively. Based on these new techniques, it is clarified that ECT can play as a supplement of UT for the welding zone inspection. It is also proved in this work that new ECT sensors are efficient even for a stainless plate as thick as 15mm.

Metallurgical effects on titanium by laser welding on dental stone.

PubMed

Fujioka, Sonosuke; Kakimoto, Kazutoshi; Inoue, Taro; Okazaki, Joji; Komasa, Yutaka

2003-12-01

It is not known for certain that dental stone components influence titanium welding. In this study, we investigated metallurgical problems caused by laser welding on dental stones using wrought commercial pure (CP) titanium. A pulsed Nd:YAG laser irradiated a number of specimens' surfaces which were fixed on either a dental hard stone or a titanium plate. The metallurgical properties of the weld were evaluated using the Vickers hardness test, microstructure observation, fractured surface observation and quantitative analysis of oxygen and hydrogen. In the weld formed on the dental stone there was an increase in hardness, the existence of an acicular structure and a brittle fractured surface, and an increase in the oxygen and hydrogen concentrations compared with base metal. In the weld formed on the titanium plate, these changes were not observed. Therefore, it was demonstrated that laser welding on dental stones made the welds brittle.

Quantification of Microtexture at Weld Nugget of Friction Stir-Welded Carbon Steel

NASA Astrophysics Data System (ADS)

Husain, Md M.; Sarkar, R.; Pal, T. K.; Ghosh, M.; Prabhu, N.

2017-05-01

Friction stir welding of C-Mn steel was carried out under 800-1400 rpm tool rotation. Tool traversing speed of 50 mm/min remained same for all joints. Effect of thermal state and deformation on texture and microstructure at weld nugget was investigated. Weld nugget consisted of ferrite + bainite/Widmanstatten ferrite with different matrix grain sizes depending on peak temperature. A texture around ( ϕ 2 = 0°, φ = 30°, ϕ 2 = 45°) was developed at weld nugget. Grain boundary misorientation at weld nugget indicated that continuous dynamic recrystallization influenced the development of fine equiaxed grain structure. Pole figures and orientation distribution function were used to determine crystallographic texture at weld nugget and base metal. Shear texture components D1, D2 and F were present at weld nugget. D1 shear texture was more prominent among all. Large number of high-angle grain boundaries ( 60-70%) was observed at weld nugget and was the resultant of accumulation of high amount of dislocation, followed by subgrain formation.

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.

Weldability of AA 5052 H32 aluminium alloy by TIG welding and FSW process - A comparative study

NASA Astrophysics Data System (ADS)

Shanavas, S.; Raja Dhas, J. Edwin

2017-10-01

Aluminium 5xxx series alloys are the strongest non-heat treatable aluminium alloy. Its application found in automotive components and body structures due to its good formability, good strength, high corrosion resistance, and weight savings. In the present work, the influence of Tungsten Inert Gas (TIG) welding parameters on the quality of weld on AA 5052 H32 aluminium alloy plates were analyzed and the mechanical characterization of the joint so produced was compared with Friction stir (FS) welded joint. The selected input variable parameters are welding current and inert gas flow rate. Other parameters such as welding speed and arc voltage were kept constant throughout the study, based on the response from several trial runs conducted. The quality of the weld is measured in terms of ultimate tensile strength. A double side V-butt joints were fabricated by double pass on one side to ensure maximum strength of TIG welded joints. Macro and microstructural examination were conducted for both welding process.

Through-Thickness Residual Stress Profiles in Austenitic Stainless Steel Welds: A Combined Experimental and Prediction Study

NASA Astrophysics Data System (ADS)

Mathew, J.; Moat, R. J.; Paddea, S.; Francis, J. A.; Fitzpatrick, M. E.; Bouchard, P. J.

2017-12-01

Economic and safe management of nuclear plant components relies on accurate prediction of welding-induced residual stresses. In this study, the distribution of residual stress through the thickness of austenitic stainless steel welds has been measured using neutron diffraction and the contour method. The measured data are used to validate residual stress profiles predicted by an artificial neural network approach (ANN) as a function of welding heat input and geometry. Maximum tensile stresses with magnitude close to the yield strength of the material were observed near the weld cap in both axial and hoop direction of the welds. Significant scatter of more than 200 MPa was found within the residual stress measurements at the weld center line and are associated with the geometry and welding conditions of individual weld passes. The ANN prediction is developed in an attempt to effectively quantify this phenomenon of `innate scatter' and to learn the non-linear patterns in the weld residual stress profiles. Furthermore, the efficacy of the ANN method for defining through-thickness residual stress profiles in welds for application in structural integrity assessments is evaluated.

Correlation Between Microstructure and Low-Temperature Impact Toughness of Simulated Reheated Zones in the Multi-pass Weld Metal of High-Strength Steel

NASA Astrophysics Data System (ADS)

Kang, Yongjoon; Park, Gitae; Jeong, Seonghoon; Lee, Changhee

2018-01-01

A large fraction of reheated weld metal is formed during multi-pass welding, which significantly affects the mechanical properties (especially toughness) of welded structures. In this study, the low-temperature toughness of the simulated reheated zone in multi-pass weld metal was evaluated and compared to that of the as-deposited zone using microstructural analyses. Two kinds of high-strength steel welds with different hardenabilities were produced by single-pass, bead-in-groove welding, and both welds were thermally cycled to peak temperatures above Ac3 using a Gleeble simulator. When the weld metals were reheated, their toughness deteriorated in response to the increase in the fraction of detrimental microstructural components, i.e., grain boundary ferrite and coalesced bainite in the weld metals with low and high hardenabilities, respectively. In addition, toughness deterioration occurred in conjunction with an increase in the effective grain size, which was attributed to the decrease in nucleation probability of acicular ferrite; the main cause for this decrease changed depending on the hardenability of the weld metal.

Characterisation of metallic glass incorporated Zircaloy-2 weldments

NASA Astrophysics Data System (ADS)

Mishra, S.; Savalia, R. T.; Bhanumurthy, K.; Dey, G. K.; Banerjee, S.

1995-12-01

In this study the effect of incorporation of Zr based Fe and Ni bearing metallic glass in spot welds in Zircaloy components has been examined. A comparison of strength and microstructure of the welded joint with and without glass has been carried out. The welded joint with metallic glass has been found to be stronger than the one without metallic glass. The microstructure of the welded region with metallic glass has been found to comprise a large region having martensite. This large martensitic region has also been found to have considerable amount of excess solute (Fe, Ni). The higher strength of the weld with metallic glass seems to originate due to solid solution strengthening, small grain size and the presence of martensitic structure over a large region.

Transformation and Precipitation Reactions by Metal Active Gas Pulsed Welded Joints from X2CrNiMoN22-5-3 Duplex Stainless Steels

PubMed Central

Utu, Ion-Dragos; Mitelea, Ion; Urlan, Sorin Dumitru; Crăciunescu, Corneliu Marius

2016-01-01

The high alloying degree of Duplex stainless steels makes them susceptible to the formation of intermetallic phases during their exposure to high temperatures. Precipitation of these phases can lead to a decreasing of the corrosion resistance and sometimes of the toughness. Starting from the advantages of the synergic Metal Active Gas (MAG) pulsed welding process, this paper analyses the structure formation particularities of homogeneous welded joints from Duplex stainless steel. The effect of linear welding energy on the structure morphology of the welded joints was revealed by macro- and micrographic examinations, X-ray energy dispersion analyses, measurements of ferrite proportion and X-ray diffraction analysis. The results obtained showed that the transformation of ferrite into austenite is associated with the chromium, nickel, molybdenum and nitrogen distribution between these two phases and their redistribution degree is closely linked to the overall heat cycle of the welding process. The adequate control of the energy inserted in the welded components provides an optimal balance between the two microstructural constituents (Austenite and Ferrite) and avoids the formation of undesirable intermetallic phases. PMID:28773727

Transformation and Precipitation Reactions by Metal Active Gas Pulsed Welded Joints from X2CrNiMoN22-5-3 Duplex Stainless Steels.

PubMed

Utu, Ion-Dragos; Mitelea, Ion; Urlan, Sorin Dumitru; Crăciunescu, Corneliu Marius

2016-07-21

The high alloying degree of Duplex stainless steels makes them susceptible to the formation of intermetallic phases during their exposure to high temperatures. Precipitation of these phases can lead to a decreasing of the corrosion resistance and sometimes of the toughness. Starting from the advantages of the synergic Metal Active Gas (MAG) pulsed welding process, this paper analyses the structure formation particularities of homogeneous welded joints from Duplex stainless steel. The effect of linear welding energy on the structure morphology of the welded joints was revealed by macro- and micrographic examinations, X-ray energy dispersion analyses, measurements of ferrite proportion and X-ray diffraction analysis. The results obtained showed that the transformation of ferrite into austenite is associated with the chromium, nickel, molybdenum and nitrogen distribution between these two phases and their redistribution degree is closely linked to the overall heat cycle of the welding process. The adequate control of the energy inserted in the welded components provides an optimal balance between the two microstructural constituents (Austenite and Ferrite) and avoids the formation of undesirable intermetallic phases.

Modeling of the fracture behavior of spot welds using advanced micro-mechanical damage models

NASA Astrophysics Data System (ADS)

Sommer, Silke

2010-06-01

This paper presents the modeling of deformation and fracture behavior of resistance spot welded joints in DP600 steel sheets. Spot welding is still the most commonly used joining technique in automotive engineering. In overloading situations like crash joints are often the weakest link in a structure. For those reasons, crash simulations need reliable and applicable tools to predict the load bearing capacity of spot welded components. Two series of component tests with different spot weld diameters have shown that the diameter of the weld nugget is the main influencing factor affecting fracture mode (interfacial or pull-out fracture), load bearing capacity and energy absorption. In order to find a correlation between nugget diameter, load bearing capacity and fracture mode, the spot welds are simulated with detailed finite element models containing base metal, heat affected zone and weld metal in lap-shear loading conditions. The change in fracture mode from interfacial to pull-out or peel-out fracture with growing nugget diameter under lap-shear loading was successfully modeled using the Gologanu-Leblond model in combination with the fracture criteria of Thomason and Embury. A small nugget diameter is identified to be the main cause for interfacial fracture. In good agreement with experimental observations, the calculated pull-out fracture initiates in the base metal at the boundary to the heat affected zone.

Low distortion laser welding of cylindrical components

NASA Astrophysics Data System (ADS)

Kittel, Sonja

2011-02-01

Automotive components are for the most part cylindrical and thus the weld seams are of radial shape. Radial weld seams are usually produced by starting at a point on the component's surface rotating the component resulting in an overlap zone at the start/end of the weld. In this research, it is shown that the component's distortion strongly depends on the overlap of weld start and end. A correlation between overlap zone and distortion is verified by an experimental study. In order to reduce distortion generated by the overlap zone a special optics is used which allows shaping the laser beam into a ring shape which is then focused on the cylindrical surface and produces a radial ring weld seam simultaneously by one laser pulse. In doing this, the overlap zone is eliminated and distortion can be reduced. Radial weld seams are applied on precision samples and distortion is measured after welding. The distortion of the precision samples is measured by a tactile measuring method and a comparison of the results of welding with the ring optics to reference welds is done.

Welding abilities of UFG metals

NASA Astrophysics Data System (ADS)

Morawiński, Łukasz; Chmielewski, Tomasz; Olejnik, Lech; Buffa, Gianluca; Campanella, Davide; Fratini, Livan

2018-05-01

Ultrafine Grained (UFG) metals are characterized by an average grain size of <1 µm and mostly high angle grain boundaries. These materials exhibit exceptional improvements in strength, superplastic behaviour and in some cases enhanced biocompatibility. UFG metals barstock can be fabricated effectively by means of Severe Plastic Deformation (SPD) methods. However, the obtained welded joints with similar properties to the base of UFG material are crucial for the production of finished engineering components. Conventional welding methods based on local melting of the joined edges cannot be used due to the UFG microstructure degradation caused by the heat occurrence in the heat affected zone. Therefore, the possibility of obtaining UFG materials joints with different shearing plane (SP) positions by means of friction welded processes, which do not exceed the melting temperature during the process, should be investigated. The article focuses on the Linear Friction Welding (LFW) method, which belongs to innovative welding processes based on mixing of the friction-heated material in the solid state. LFW is a welding process used to joint bulk components. In the process, the friction forces work due to the high frequency oscillation and the pressure between the specimens is converted in thermal energy. Character and range of recrystallization can be controlled by changing LFW parameters. Experimental study on the welded UFG 1070 aluminum alloy by means of FLW method, indicates the possibility of reducing the UFG structure degradation in the obtained joint. A laboratory designed LFW machine has been used to weld the specimens with different contact pressure and oscillation frequency.

49 CFR 192.153 - Components fabricated by welding.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 3 2010-10-01 2010-10-01 false Components fabricated by welding. 192.153 Section....153 Components fabricated by welding. (a) Except for branch connections and assemblies of standard... welding, whose strength cannot be determined, must be established in accordance with paragraph UG-101 of...

49 CFR 192.153 - Components fabricated by welding.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 3 2014-10-01 2014-10-01 false Components fabricated by welding. 192.153 Section....153 Components fabricated by welding. (a) Except for branch connections and assemblies of standard... welding, whose strength cannot be determined, must be established in accordance with paragraph UG-101 of...

49 CFR 192.153 - Components fabricated by welding.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Components fabricated by welding. 192.153 Section....153 Components fabricated by welding. (a) Except for branch connections and assemblies of standard... welding, whose strength cannot be determined, must be established in accordance with paragraph UG-101 of...

49 CFR 192.153 - Components fabricated by welding.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Components fabricated by welding. 192.153 Section....153 Components fabricated by welding. (a) Except for branch connections and assemblies of standard... welding, whose strength cannot be determined, must be established in accordance with paragraph UG-101 of...

49 CFR 192.153 - Components fabricated by welding.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 3 2012-10-01 2012-10-01 false Components fabricated by welding. 192.153 Section....153 Components fabricated by welding. (a) Except for branch connections and assemblies of standard... welding, whose strength cannot be determined, must be established in accordance with paragraph UG-101 of...

Understanding Friction Stir Welding

NASA Technical Reports Server (NTRS)

Nunes, A. C., Jr.

2018-01-01

This Technical Memorandum explains the friction stir welding process in terms of two basic concepts: the concentration of deformation in a shear surface enveloping the tool and the composition of the overall plastic flow field around the tool from simple flow field components. It is demonstrated how weld structure may be understood and torque, drag, and lateral tool forces may be estimated using these concepts. Some discrepancies between computations and accompanying empirical data are discussed in the text. This work is intended to be helpful to engineers in diagnosing problems and advancing technology.

Microstructure and Porosity of Laser Welds in Cast Ti-6Al-4V with Addition of Boron

NASA Astrophysics Data System (ADS)

Tolvanen, Sakari; Pederson, Robert; Klement, Uta

2018-03-01

Addition of small amounts of boron to cast Ti-6Al-4V alloy has shown to render a finer microstructure and improved mechanical properties. For such an improved alloy to be widely applicable for large aerospace structural components, successful welding of such castings is essential. In the present work, the microstructure and porosity of laser welds in a standard grade cast Ti-6Al-4V alloy as well as two modified alloy versions with different boron concentrations have been investigated. Prior-β grain reconstruction revealed the prior-β grain structure in the weld zones. In fusion zones of the welds, boron was found to refine the grain size significantly and rendered narrow elongated grains. TiB particles in the prior-β grain boundaries in the cast base material restricted grain growth in the heat-affected zone. The TiB particles that existed in the as cast alloys decreased in size in the fusion zones of welds. The hardness in the weld zones was higher than in the base material and boron did not have a significant effect on hardness of the weld zones. The fusion zones were smaller in the boron-modified alloys as compared with Ti-6Al-4V without boron. Computed tomography X-ray investigations of the laser welds showed that pores in the FZ of the boron modified alloys were confined to the lower part of the welds, suggesting that boron addition influences melt pool flow.

Advanced Near Net Shape Technology

NASA Technical Reports Server (NTRS)

Vickers, John

2015-01-01

The objective of the Advanced Near Net Shape Technology (ANNST) project is to radically improve near net shape manufacturing methods from the current Technology/ Manufacturing Readiness Levels (TRL/MRL 3-4) to the point where they are viable candidates (TRL/ MRL-6) for shortening the time and cost for insertion of new aluminum alloys and revolutionary manufacturing methods into the development/improvement of space structures. Conventional cyrotank manufacturing processes require fabrication of multiple pieces welded together to form a complete tank. A variety of near net shape manufacturing processes has demonstrated excellent potential for enabling single-piece construction of components such as domes, barrels, and ring frames. Utilization of such processes can dramatically reduce the extent of welding and joining needed to construct cryogenic tanks and other aerospace structures. The specific focus of this project is to successfully mature the integrally stiffened cylinder (ISC) process in which a single-piece cylinder with integral stiffeners is formed in one spin/flow forming process. Structural launch vehicle components, like cryogenic fuel tanks (e.g., space shuttle external tank), are currently fabricated via multipiece assembly of parts produced through subtractive manufacturing techniques. Stiffened structural panels are heavily machined from thick plate, which results in excessive scrap rates. Multipiece construction requires welds to assemble the structure, which increases the risk for defects and catastrophic failures.

Microstructures and Mechanical Properties of Friction Tapered Stud Overlap Welding for X65 Pipeline Steel Under Wet Conditions

NASA Astrophysics Data System (ADS)

Xu, Y. C.; Jing, H. Y.; Han, Y. D.; Xu, L. Y.

2017-08-01

This paper exhibits a novel in situ remediation technique named friction tapered stud overlap welding (FTSOW) to repair a through crack in structures and components in extremely harsh environments. Furthermore, this paper presents variations in process data, including rotational speed, stud displacement, welding force, and torque for a typical FTSOW weld. In the present study, the effects of welding parameters on the microstructures and mechanical properties of the welding joints were investigated. Inapposite welding parameters consisted of low rotational speeds and welding forces, and when utilized, they increased the occurrence of a lack of bonding and unfilled defects within the weld. The microstructures with a welding zone and heat-affected zone mainly consisted of upper bainite. The hardness value was highest in the welding zone and lowest in the base material. During the pull-out tests, all the welds failed in the stud. Moreover, the defect-free welds broke at the interface of the lap plate and substrate during the cruciform uniaxial tensile test. The best tensile test results at different depths and shear tests were 721.6 MPa and 581.9 MPa, respectively. The favorable Charpy impact-absorbed energy was 68.64 J at 0 °C. The Charpy impact tests revealed a brittle fracture characteristic with a large area of cleavage.

Particulate and gaseous emissions when welding aluminum alloys.

PubMed

Cole, Homer; Epstein, Seymour; Peace, Jon

2007-09-01

Fabrication and repair of aluminum components and structures commonly involves the use of electric arc welding. The interaction of the arc and the metal being welded generates ultraviolet radiation, metallic oxides, fumes, and gases. Aluminum is seldom used as the pure metal but is often alloyed with other metals to improve strength and other physical properties. Therefore, the exact composition of any emissions will depend on the welding process and the particular aluminum alloy being welded. To quantify such emissions, The Aluminum Association sponsored several studies to characterize arc welding emissions by the gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW) processes for various combinations of base and filler alloys. In all cases, the tests were conducted under conditions that could be found in a production weld shop without forced ventilation. The concentrations of each analyte that a welder could be exposed to were greatly affected by the welding process, the composition of the base and filler alloys, the position of the welder, and the welding helmet. The results obtained can be used by employers to identify and control potential hazards associated with the welding of aluminum alloys and can provide the basis for hazard communication to employees involved in the welding of these alloys.

Effect of electromagnetic interaction during fusion welding of AISI 2205 duplex stainless steel on the corrosion resistance

NASA Astrophysics Data System (ADS)

García-Rentería, M. A.; López-Morelos, V. H.; González-Sánchez, J.; García-Hernández, R.; Dzib-Pérez, L.; Curiel-López, F. F.

2017-02-01

The effect of electromagnetic interaction of low intensity (EMILI) applied during fusion welding of AISI 2205 duplex stainless steel on the resistance to localised corrosion in natural seawater was investigated. The heat affected zone (HAZ) of samples welded under EMILI showed a higher temperature for pitting initiation and lower dissolution under anodic polarisation in chloride containing solutions than samples welded without EMILI. The EMILI assisted welding process developed in the present work enhanced the resistance to localised corrosion due to a modification on the microstructural evolution in the HAZ and the fusion zone during the thermal cycle involved in fusion welding. The application of EMILI reduced the size of the HAZ, limited coarsening of the ferrite grains and promoted regeneration of austenite in this zone, inducing a homogeneous passive condition of the surface. EMILI can be applied during fusion welding of structural or functional components of diverse size manufactured with duplex stainless steel designed to withstand aggressive environments such as natural seawater or marine atmospheres.

Gas metal arc welding in refurbishment of cobalt base superalloys

NASA Astrophysics Data System (ADS)

Shahriary, M. S.; Miladi Gorji, Y.; Kolagar, A. M.

2017-01-01

Refurbishments of superalloys which are used in manufacturing gas turbine hot components usually consists of removing cracks and other defects by blending and then repair welding in order to reconstruct damaged area. In this study, the effects of welding parameters on repair of FSX-414 superalloy, as the most applicable cobalt base superalloy in order to manufacture gas turbine nozzles, by use of Gas Metal Arc Welding (GMAW) technic were investigated. Results then were compared by Gas Tungsten Arc Welding (GTAW). Metallographic and SEM studies of the microstructure of the weld and HAZ showed that there are no noticeable defects in the microstructure by use of GMAW. Also, chemical analysis and morphologies of carbide in both methods are similar. Hardness profile of the GM AW structure then also compared with GTAW and no noticeable difference was observed between the profiles. Also, proper tensile properties, compared with GTAW, can be achieved by use of optimum parameters that can be obtained by examining the current and welding speed. Tensile properties of optimized condition of the GMAW then were compared with GTAW. It was seen that the room and high temperature tensile properties of the GMAW structure is very similar and results confirmed that changing the technic did not have any significant influence on the properties.

Structural Properties of EB-Welded AlSi10Mg Thin-Walled Pressure Vessels Produced by AM-SLM Technology

NASA Astrophysics Data System (ADS)

Nahmany, Moshe; Stern, Adin; Aghion, Eli; Frage, Nachum

2017-10-01

Additive manufacturing of metals by selective laser melting (AM-SLM) is hampered by significant limitations in product size due to the limited dimensions of printing trays. Electron beam welding (EBW) is a well-established process that results in relatively minor metallurgical modifications in workpieces due to the ability of EBW to pass high-density energy to the related substance. The present study aims to evaluate structural properties of EB-welded AlSi10Mg thin-walled pressure vessels produced from components prepared by SLM technology. Following the EB welding process, leak and burst tests were conducted, as was fractography analysis. The welded vessels showed an acceptable holding pressure of 30 MPa, with a reasonable residual deformation up to 2.3% and a leak rate better than 1 × 10-8 std-cc s-1 helium. The failures that occurred under longitudinal stresses reflected the presence of two weak locations in the vessels, i.e., the welded joint region and the transition zone between the vessel base and wall. Fractographic analysis of the fracture surfaces of broken vessels displayed the ductile mode of the rupture, with dimples of various sizes, depending on the failure location.

Comparative Studies on microstructure, mechanical and corrosion behaviour of DMR 249A Steel and its welds

NASA Astrophysics Data System (ADS)

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

2018-03-01

DMR249A Medium strength (low carbon) Low-alloy steels are used as structural components in naval applications due to its low cost and high availability. An attempt has been made to weld the DMR 249A steel plates of 8mm thickness using shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW). Welds were characterized for metallography to carry out the microstructural changes, mechanical properties were evaluated using vickers hardness tester and universal testing machine. Potentio-dynamic polarization tests were carried out to determine the pitting corrosion behaviour. Constant load type Stress corrosion cracking (SCC) testing was done to observe the cracking tendency of the joints in a 3.5%NaCl solution. Results of the present study established that SMA welds resulted in formation of relatively higher amount of martensite in ferrite matrix when compared to gas tungsten arc welding (GTAW). It is attributed to faster cooling rates achieved due to high thermal efficiency. Improved mechanical properties were observed for the SMA welds and are due to higher amount of martensite. Pitting corrosion and stress corrosion cracking resistance of SMA welds were poor when compared to GTA welds.

New Tool Creates a Big Stir

NASA Technical Reports Server (NTRS)

2001-01-01

A new self-adjusting, retractable pin tool for friction stir welding is now used in the manufacturing of components for NASA Space Shuttles. Friction stir welding is a process that makes straight-line welds without bringing the parent material to a liquid state. This is accomplished through high-speed rotation, which generates frictional heat between the welding tool and the piece being welded. This heat causes the material to soften to the point of plasticity without allowing it to melt. The plasticized material is then transferred from the front edge of the welding tool to the trail edge, where it joins the pieces being welded. However, a major flaw of this method is its reliance on a single-piece pin tool. The weld is left unfinished and a hole remains where the pin was inserted. The hole must be covered with a rivet in order to preserve the integrity of the weld. The NASA-developed pin tool, however, eliminates the need for this finishing step, as its retraction allows continuous rewelding at lesser depths, until the hole is completely closed. With this NASA technology, welding of higher strength alloys, as well as non-planer and variable thickness structures can be achieved.

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.

Manufacturing Challenges Associated with the Use of Metal Matrix Composites in Aerospace Structures

NASA Technical Reports Server (NTRS)

Prater, Tracie

2014-01-01

Metal Matrix Composites (MMCs) consist of a metal alloy reinforced with ceramic particles or fibers. These materials possess a very high strength to weight ratio, good resistance to impact and wear, and a number of other properties which make them attractive for use in aerospace and defense applications. MMCs have found use in the space shuttle orbiter's structural tubing, the Hubble Space Telescope's antenna mast, control surfaces and propulsion systems for aircraft, and tank armors. The size of MMC components is severely limited by difficulties encountered in joining these materials using fusion welding. Melting of the material results in formation of an undesirable phase (formed when molten Aluminum reacts with the reinforcement) which leaves a strength depleted region along the joint line. Friction Stir Welding (FSW) is a relatively nascent solid state joining technique developed at The Welding Institute (TWI) in 1991. The process was first used at NASA to weld the super lightweight external tank for the Space Shuttle. Today FSW is used to join structural components of the Delta IV, Atlas V, and Falcon IX rockets as well as NASA's Orion Crew Exploration Vehicle and Space Launch System. A current focus of FSW research is to extend the process to new materials, such as MMCs, which are difficult to weld using conventional fusion techniques. Since Friction Stir Welding occurs below the melting point of the workpiece material, this deleterious phase is absent in FSW-ed MMC joints. FSW of MMCs is, however, plagued by rapid wear of the welding tool, a consequence of the large discrepancy in hardness between the steel tool and the reinforcement material. This chapter summarizes the challenges encountered when joining MMCs to themselves or to other materials in structures. Specific attention is paid to the influence of process variables in Friction Stir Welding on the wear process characterizes the effect of process parameters (spindle speed, traverse rate, and length of joint) on the wear process. A phenomenological model of the wear process was constructed based on the rotating plug model of Friction Stir Welding. The effectiveness of harder tool materials (such as Tungsten Carbide, high speed steel, and tools with diamond coatings) to combat abrasive wear is also explored. In-process force, torque, and vibration signals are analyzed to assess the feasibility of in situ monitoring of tool shape changes as a result of wear (an advancement which would eliminate the need for off-line evaluation of tool condition during joining). Monitoring, controlling, and reducing tool wear in FSW of MMCs is essential to implementation of these materials in structures (such as launch vehicles) where they would be of maximum benefit. The work presented here is extendable to machining of MMCs, where wear of the tool is also a limiting factor.

Welding studs detection based on line structured light

NASA Astrophysics Data System (ADS)

Geng, Lei; Wang, Jia; Wang, Wen; Xiao, Zhitao

2018-01-01

The quality of welding studs is significant for installation and localization of components of car in the process of automobile general assembly. A welding stud detection method based on line structured light is proposed. Firstly, the adaptive threshold is designed to calculate the binary images. Then, the light stripes of the image are extracted after skeleton line extraction and morphological filtering. The direction vector of the main light stripe is calculated using the length of the light stripe. Finally, the gray projections along the orientation of the main light stripe and the vertical orientation of the main light stripe are computed to obtain curves of gray projection, which are used to detect the studs. Experimental results demonstrate that the error rate of proposed method is lower than 0.1%, which is applied for automobile manufacturing.

Experimental Modal Analysis and Dynamic Component Synthesis. Volume 2. Measurement Techniques for Experimental Modal Analysis

DTIC Science & Technology

1987-12-01

A- -- HZ LIN 3.0 . Be-I. •,% •4’ 20.. 0-p -4 -0 30a 4a j0 O0 100a 10 4140 iSo 130 20C. 2210 140 M* LIN g•" %g Figur 19. Cyli Avergin (N4,M 0 -3- 40...shows that the degree of nonlinearity of a structure varies according to the characteristics of the system. That is, welded structures will usually...exhibit a linear response; where a riveted or spot welded structure exhibits a very nonlinear response [52]. As an example of a nonlinear system

On the microstructure analysis of FSW joints of aluminium components made via direct metal laser sintering

NASA Astrophysics Data System (ADS)

Scherillo, Fabio; Astarita, Antonello; di Martino, Daniela; Contaldi, Vincenzo; di Matteo, Luca; di Petta, Paolo; Casarin, Renzo; Squillace, Antonino; Langella, Antonio

2017-10-01

Additive Manufacturing (AM), applied to metal industry, is a family of processes that allow complex shape components to be realized from raw materials in the form of powders. The compaction of the powders can be achieved by local melting of the powder bed or by solid state sintering. Direct Metal Laser Sintering (DMLS) is an additive manufacturing process in which a focalized laser beam is the heat source that allows the powders to be compacted. By DMLS it is possible to realize complex shape components. One of the limits of DMLS, as for every additive layer manufacturing techniques, is the unfeasibility to realize large dimension parts. Due to this limit the study of joining process of parts made via ALM is of great interest. One of the most promising options is the Friction Stir Welding (FSW), a solid state welding technique that has been proven to be very effective in the welding of metals difficult to weld, above all aluminium alloys. Since FSW is a solid-state technique, the microstructure of the various zone of the weld bead depends not only by the process itself but also by the parent microstruct ure of the parts to be welded. Furthermore, parts made of aluminium alloy via DMLS have a particular microstructure that is the result of repeated severe thermal cycles. In the present work the authors, starting from the description of the parent microstructure of parts made of AlSi10Mg aluminium alloy, study the microstructure evolution occurred within the joint made by Friction Stir Welding, analysing in details the microstructure of the main well recognized zone of the weld bead. The structure of the parent material is characterized by the presence of melting pools with a very fine microstructure. In the joint the recrystallization, the grain refinement and, above all, the redistribution of intermetallic phases occurs, resulting in an homogenization of the microstructure and in an increase of micro hardness.

Investigation of the interaction of the solder components for laser welding of biological tissues

NASA Astrophysics Data System (ADS)

Ryabki, Dmitrii I.; Gerasimenko, Alexander Yu.; Kvasnov, Bogdan A.; Pyankov, Evgeny S.; Pyanov, Ivan V.; Telyshev, Dmitry V.; Podgaetsky, Vitaly M.

2017-07-01

Increase the weld strength is main directions of development of laser welding technology. Laser solders are used to increase tensile strength of welds and reduce of tissue temperature necrosis. Soldering components interaction effect the solder tensile strength characteristics of laser welds. Tensile strengths for welds obtained using of solder various concentration BSA and SWCNT was measured. Dimensions laser solder aggregates were measured. The dependence between the dimensions of the aggregates of laser solder and the tensile strength of the weld has been revealed.

Friction Stir Welding of Metal Matrix Composites for use in aerospace structures

NASA Astrophysics Data System (ADS)

Prater, Tracie

2014-01-01

Friction Stir Welding (FSW) is a relatively nascent solid state joining technique developed at The Welding Institute (TWI) in 1991. The process was first used at NASA to weld the super lightweight external tank for the Space Shuttle. Today FSW is used to join structural components of the Delta IV, Atlas V, and Falcon IX rockets as well as the Orion Crew Exploration Vehicle. A current focus of FSW research is to extend the process to new materials which are difficult to weld using conventional fusion techniques. Metal Matrix Composites (MMCs) consist of a metal alloy reinforced with ceramics and have a very high strength to weight ratio, a property which makes them attractive for use in aerospace and defense applications. MMCs have found use in the space shuttle orbiter's structural tubing, the Hubble Space Telescope's antenna mast, control surfaces and propulsion systems for aircraft, and tank armors. The size of MMC components is severely limited by difficulties encountered in joining these materials using fusion welding. Melting of the material results in formation of an undesirable phase (formed when molten Aluminum reacts with the reinforcement) which leaves a strength depleted region along the joint line. Since FSW occurs below the melting point of the workpiece material, this deleterious phase is absent in FSW-ed MMC joints. FSW of MMCs is, however, plagued by rapid wear of the welding tool, a consequence of the large discrepancy in hardness between the steel tool and the reinforcement material. This work characterizes the effect of process parameters (spindle speed, traverse rate, and length of joint) on the wear process. Based on the results of these experiments, a phenomenological model of the wear process was constructed based on the rotating plug model for FSW. The effectiveness of harder tool materials (such as Tungsten Carbide, high speed steel, and tools with diamond coatings) to combat abrasive wear is explored. In-process force, torque, and vibration signals are analyzed to assess the feasibility of on-line monitoring of tool shape changes as a result of wear (an advancement which would eliminate the need for off-line evaluation of tool condition during joining). Monitoring, controlling, and reducing tool wear in FSW of MMCs is essential to the implementation of these materials in structures (such as launch vehicles) where they would be of maximum benefit.

Hot Forging of a Cladded Component by Automated GMAW Process

NASA Astrophysics Data System (ADS)

Rafiq, Muhammad; Langlois, Laurent; Bigot, Régis

2011-01-01

Weld cladding is employed to improve the service life of engineering components by increasing corrosion and wear resistance and reducing the cost. The acceptable multi-bead cladding layer depends on single bead geometry. Hence, in first step, the relationship between input process parameters and the single bead geometry is studied and in second step a comprehensive study on multi bead clad layer deposition is carried out. This paper highlights an experimental study carried out to get single layer cladding deposited by automated Gas Metal Arc Welding (GMAW) process and to find the possibility of hot forming of the cladded work piece to get the final hot formed improved structure. GMAW is an arc welding process that uses an arc between a consumable electrode and the welding pool with an external shielding gas and the cladding is done by alongside deposition of weld beads. The experiments for single bead were conducted by varying the three main process parameters wire feed rate, arc voltage and welding speed while keeping other parameters like nozzle to work distance, shielding gas and its flow rate and torch angle constant. The effect of bead spacing and torch orientation on the cladding quality of single layer from the results of single bead deposition was studied. Effect of the dilution rate and nominal energy on the cladded layer hot bending quality was also performed at different temperatures.

Alternative welding reconditioning solutions without post welding heat treatment of pressure vessel

NASA Astrophysics Data System (ADS)

Cicic, D. T.; Rontescu, C.; Bogatu, A. M.; Dijmărescu, M. C.

2017-08-01

In pressure vessels, working on high temperature and high pressure may appear some defects, cracks for example, which may lead to failure in operation. When these nonconformities are identified, after certain examination, testing and result interpretation, the decision taken is to repair or to replace the deteriorate component. In the current legislation it’s stipulated that any repair, alteration or modification to an item of pressurised equipment that was originally post-weld heat treated after welding (PWHT) should be post-weld heat treated again after repair, requirement that cannot always be respected. For that reason, worldwide, there were developed various welding repair techniques without PWHT, among we find the Half Bead Technique (HBT) and Controlled Deposition Technique (CDT). The paper presents the experimental results obtained by applying the welding reconditioning techniques HBT and CDT in order to restore as quickly as possible the pressure vessels made of 13CrMo4-5. The effects of these techniques upon the heat affected zone are analysed, the graphics of the hardness variation are drawn and the resulted structures are compared in the two cases.

Failure investigations of failed valve plug SS410 steel due to cracking

NASA Astrophysics Data System (ADS)

Kalyankar, V. D.; Deshmukh, D. D.

2017-12-01

Premature and sudden in service failure of a valve plug due to crack formation, applied in power plant has been investigated. The plug was tempered and heat treated, the crack was originated at centre, developed along the axis and propagates radially towards outer surface of plug. The expected life of the component is 10-15 years while, the component had failed just after the installation that is, within 3 months of its service. No corrosion products were observed on the crack interface and on the failed surface; hence, causes of corrosion failure are neglected. This plug of level separator control valve, is welded to the stem by means of plasma-transferred arc welding and as there is no crack observed at the welding zone, the failure due to welding residual stresses are also neglected. The failed component discloses exposed surface of a crack interface that originated from centre and propagates radially. The micro-structural observation, hardness testing, and visual observation are carried out of the specimen prepared from the failed section and base portion. The microstructure from the cracked interface showed severe carbide formation along the grain boundaries. From the microstructural analysis of the failed sample, it is observed that there is a formation of acicular carbides along the grain boundaries due to improper tempering heat treatment.

Fabricating Structural Stiffeners By Superplastic Forming

NASA Technical Reports Server (NTRS)

Bales, Thomas T.; Shinn, Joseph M., Jr.; Hales, Stephen J.; James, William F.

1994-01-01

Superplastic forming (SPF) of aluminum alloys effective technique for making strong, lightweight structural components conforming to close dimensional tolerances. Technique applied in experimental fabrication of prototypes of stiffening ribs for cylindrical tanks. When making structural panel, stiffening ribs spot-welded to metal skin. Use of discrete eliminates machining waste, and use of SPF. Cost of fabrication reduced.

Effects of Welding Parameters on Mechanical Properties in Electron Beam Welded CuCrZr Alloy Plates

NASA Astrophysics Data System (ADS)

Jaypuria, Sanjib; Doshi, Nirav; Pratihar, Dilip Kumar

2018-03-01

CuCrZr alloys are attractive structural materials for plasma-facing components (PFC) and heat sink element in the International Thermonuclear Experimental Reactor (ITER) fusion reactors. This material has gained so much attention because of its high thermal conductivity and fracture toughness, high resistance to radiation damage and stability at elevated temperatures. The objective of this work is to study the effects of electron beam welding parameters on the mechanical strength of the butt welded CuCrZr joint. Taguchi method is used as the design of experiments to optimize the input parameters, such as accelerating voltage, beam current, welding speed, oscillation amplitude and frequency. The joint strength and ductility are the desired responses, which are measured through ultimate tensile strength and percent elongation, respectively. Accelerating voltage and welding speed are found to have significant influence on the strength. A combination of low amplitude and high-frequency oscillation is suggested for the higher joint strength and ductility. There is a close agreement between Taguchi predicted results and experimental ones. Fractographic analysis of joint and weld zone analysis are carried out to study the failure behaviour and microstructural variation in the weld zone, respectively.

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.

Design criteria monograph for metal tanks and tank components

NASA Technical Reports Server (NTRS)

1975-01-01

Significant elements in detail tank design are wall and end structures, weld joints at bulkhead and attachment junctures, and ports and access openings. Additional design considerations are influence and effect of fabrication processes on tank component design, and finally, testing and inspection that are required to establish confidence in tank design.

Microstructure Evolution and Mechanical Properties of Underwater Dry and Local Dry Cavity Welded Joints of 690 MPa Grade High Strength Steel

PubMed Central

Sun, Kun; Cui, Shuwan; Zeng, Min; Yi, Jianglong; Shen, Xiaoqin; Yi, Yaoyong

2018-01-01

Q690E high strength low alloy (HSLA) steel plays an important role in offshore structures. In addition, underwater local cavity welding (ULCW) technique was widely used to repair important offshore constructions. However, the high cooling rate of ULCW joints results in bad welding quality compared with underwater dry welding (UDW) joints. Q690E high strength low alloy steels were welded by multi-pass UDW and ULCW techniques, to study the microstructural evolution and mechanical properties of underwater welded joints. The microstructure and fracture morphology of welded joints were observed by scanning electron microscope and optical microscope. The elemental distribution in the microstructure was determined with an Electron Probe Microanalyzer. The results indicated that the microstructure of both two welded joints was similar. However, martensite and martensite-austenite components were significantly different with different underwater welding methods such that the micro-hardness of the HAZ and FZ in the ULCW specimen was higher than that of the corresponding regions in UDW joint. The yield strength and ultimate tensile strength of the ULCW specimen are 109 MPa lower and 77 MPa lower, respectively, than those of the UDW joint. The impact toughness of the UDW joint was superior to those of the ULCW joint. PMID:29361743

Microstructure Evolution and Mechanical Properties of Underwater Dry and Local Dry Cavity Welded Joints of 690 MPa Grade High Strength Steel.

PubMed

Shi, Yonghua; Sun, Kun; Cui, Shuwan; Zeng, Min; Yi, Jianglong; Shen, Xiaoqin; Yi, Yaoyong

2018-01-22

Q690E high strength low alloy (HSLA) steel plays an important role in offshore structures. In addition, underwater local cavity welding (ULCW) technique was widely used to repair important offshore constructions. However, the high cooling rate of ULCW joints results in bad welding quality compared with underwater dry welding (UDW) joints. Q690E high strength low alloy steels were welded by multi-pass UDW and ULCW techniques, to study the microstructural evolution and mechanical properties of underwater welded joints. The microstructure and fracture morphology of welded joints were observed by scanning electron microscope and optical microscope. The elemental distribution in the microstructure was determined with an Electron Probe Microanalyzer. The results indicated that the microstructure of both two welded joints was similar. However, martensite and martensite-austenite components were significantly different with different underwater welding methods such that the micro-hardness of the HAZ and FZ in the ULCW specimen was higher than that of the corresponding regions in UDW joint. The yield strength and ultimate tensile strength of the ULCW specimen are 109 MPa lower and 77 MPa lower, respectively, than those of the UDW joint. The impact toughness of the UDW joint was superior to those of the ULCW joint.

Fatigue assessment for selected connections of structural steel bridge components using the finite elements method

NASA Astrophysics Data System (ADS)

Śledziewski, Krzysztof

2018-01-01

Material fatigue it is one of the most frequent causes of steel bridge failures, particularly the bridges already existing. Thus, the procedure of fatigue life assessment is one of the most relevant procedures in a comprehensive assessment of load-carrying capacity and service life of the structure. A reliable assessment of the fatigue life is predominantly decisive for estimation of the remaining service life. Hitherto, calculation methods of welded joints took into account only stresses occurring in cross sections of whole elements and did not take into account stress concentration occurring in the vicinity of the weld, caused by geometrical aspects of the detail. At present, use of the Finite Element Analysis, makes possible looking for more accurate approach to the fatigue design of steel structures. The method of geometrical stresses is just such approach which is based on definition of stresses which take into account geometry of the detail. The study presents fatigue assessment of a representative type of welded joint in welded bridge structures. The testing covered longitudinal attachments. The main analyses were carried out on the basis of FEM and the method of local stresses, so-called "hot-spot" stresses. The obtained values of stresses were compared with the values obtained in accordance with the method of nominal stress.

Advanced ultrasonic techniques for nondestructive testing of austenitic and dissimilar welds in nuclear facilities

NASA Astrophysics Data System (ADS)

Juengert, Anne; Dugan, Sandra; Homann, Tobias; Mitzscherling, Steffen; Prager, Jens; Pudovikov, Sergey; Schwender, Thomas

2018-04-01

Austenitic stainless steel welds as well as dissimilar metal welds with nickel alloy filler material, used in safety relevant parts of nuclear power plants, still challenge the ultrasonic inspection. The weld material forms large oriented grains that lead, on the one hand, to high sound scattering and, on the other hand, to inhomogeneity and to the acoustic anisotropy of the weld structure. The ultrasonic wave fronts do not propagate linearly, as in ferritic weld joints, but along the curves, which depend on the specific grain structure of the weld. Due to the influence of these phenomena, it is difficult to analyze the inspection results and to classify the ultrasonic indications, which could be both from the weld geometry and from the material defects. A correct flaw sizing is not possible. In an ongoing research project, different techniques to improve the reliability of ultrasonic testing at these kinds of welds are investigated. In a first step (in the previous research project) two ultrasonic inspection techniques were developed and validated on plane test specimens with artificial and realistic flaws. In the ongoing project, these techniques are applied to circumferential pipe welds with longitudinal and transverse flaws. The technique developed at the Federal Institute for Materials Research and Testing (BAM) in Germany uses a combination of ray tracing and synthetic aperture focusing technique (SAFT). To investigate the unknown grain structure, the velocity distribution of weld-transmitting ultrasound waves is measured and used to model the weld by ray tracing. The second technique, developed at the Fraunhofer Institute for Nondestructive Testing (IZFP) in Germany, uses Sampling Phased Array (Full Matrix Capture) combined with the reverse phase matching (RPM) and the gradient elastic constant descent algorithm (GECDM). This inspection method is able to estimate the elastic constants of the columnar grains in the weld and offers an improvement of the reliability of ultrasonic testing through the correction of the sound field distortion. The unknown inhomogeneity and anisotropy are investigated using a reference indication and the special optimization algorithm. Both reconstruction techniques give quantitative inspection results and allow the defect sizing. They have been compared to conventional ultrasonic testing with techniques that are state of the art for components in nuclear power plants. The improvement will be quantified by the comparison of the probability of detection (POD) of each technique.

Experimental and numerical studies on the issues in laser welding of light-weight alloys in a zero-gap lap joint configuration

NASA Astrophysics Data System (ADS)

Harooni, Masoud

It is advantageous for the transportation industry to use lightweight components in the structure in order to save mass and reduce CO2 emissions. One of the lightest structural metals, magnesium, fulfills the need for mass reduction within the automotive industry. Many of the body structure components in the automotive industry are assembled using joining processes such as fusion welding. Furthermore, laser welding offers a low heat impact, high process rate, joining method which is becoming increasingly popular as the cost for laser systems continues to decrease. However, there is a limited body of work investigating the laser welding of magnesium and therefore, in the current study, different techniques and methods for laser welding of magnesium alloys are numerically and experimentally studied in order to optimize process parameters to achieve high quality welds. A feasibility study was designed in order to study the effect of various laser welding process parameters (such as laser power levels and welding speeds) on weld quality. Three regression models were developed to find the best fit model that relates process parameters to the shear load of the weld. Furthermore, to understand the effect of laser welding parameters on temperature distribution in laser welding of AZ31B magnesium alloy, a numerical model was developed. A rotary Gaussian volumetric body heat source was applied in this study to obtain the temperature history during the laser welding process. Cross-sectional views of the weld beads, temperature history recorded by thermocouples, and temperature history recorded by infrared camera were used to validate the numerical model. In order to study the real-time dynamic behavior of the molten pool and the keyhole during the welding process, a high speed charge-coupled device (CCD) assisted with a green laser as an illumination source was used. In order to observe the presence of pores, prior studies destructively evaluated the weld bead however; in the current study a non-destructive evaluation method based on spectroscopy is proposed to detect the presence of pores in the lap joint of laser welded AZ31B magnesium alloy. The electron temperature that is calculated by the Boltzmann plot method is correlated to the presence of pores in the weld bead. A separate series of experiments was performed to evaluate the effect of an oxide coating layer on the dynamic behavior of the molten pool in the laser welding of an AZ31B magnesium alloy in a zero-gap lap joint configuration. A high speed CCD camera assisted with a green laser as an illumination source was selected to record the weld pool dynamics. Another technique used in this study was two-pass laser welding process to join AZ31B magnesium sheet in a zero-gap, lap-shear configuration. Two groups of samples including one pass laser welding (OPLW) and two pass laser welding (TPLW) were studied. In the two pass laser welding procedure, the first pass is performed by a defocused laser beam on the top of the two overlapped sheets in order to preheat the faying surface prior to laser welding, while the second pass is applied to melt and eventually weld the samples. Tensile and microhardness tests were used to measure the mechanical properties of the laser welded samples. A spectrometer was also used in real-time to correlate pore formation with calculated electron temperature using the Boltzmann plot method. The results of calculated electron temperature confirmed the previous results in earlier chapter. Magnesium and aluminum are two alloys which are used in different industries mainly due to their light weight. The main use of these two alloys is in automotive industry. Since different parts of the automobiles can be manufactured with each of these two alloys, it is essential to evaluate the joining feasibility of dissimilar metals such as aluminum to magnesium. A 4 kW fiber laser is used to join AZ31B magnesium alloy to AA 6014 using an overlap joint configuration. Two different methods including focused beam laser welding (FBLW) and defocused beam laser welding (DBLW) are performed. The cross-sections of the welds were studied using an optical microscope, scanning electron microscope (SEM) as well as energy-dispersive X-ray spectroscopy (EDS) to reveal the quality of the obtained dissimilar welds. The mechanical properties of the welds were studied using a tensile test and microhardness testing machines. The results show that the defocused laser welding process could help to achieve a better quality of weld. (Abstract shortened by UMI.)

Residual Stress Analysis in Welded Component.

NASA Astrophysics Data System (ADS)

Rouhi, Shahab; Yoshida, Sanichiro; Miura, Fumiya; Sasaki, Tomohiro

Due to local heating, thermal stresses occur during welding; and residual stress and distortion result remain welding. Welding distortion has negative effects on the accuracy of assembly, exterior appearance, and various strengths of the welded structures. Up to date, a lot of experiments and numerical analysis have been developed to assess residual stress. However, quantitative estimation of residual stress based on experiment may involve massive uncertainties and complexity of the measurement process. To comprehensively understand this phenomena, it is necessary to do further researches by means of both experiment and numerical simulation. In this research, we conduct Finite Element Analysis (FEA) for a simple butt-welded metal plate specimen. Thermal input and resultant expansion are modeled with a thermal expansion FEA module and the resultant constitutive response of the material is modeled with a continuous mechanic FEA module. The residual stress is modeled based on permanent deformation occurring during the heating phase of the material. Experiments have also been carried out to compare with the FEA results. Numerical and experimental results show qualitative agreement. The present work was supported by the Louisiana Board of Regents (LEQSF(2016-17)-RD-C-13).

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.

Structure of welded joints obtained by contact weld in nanostructured titanium

NASA Astrophysics Data System (ADS)

Klimenov, V. A.; Klopotov, A. A.; Gnysov, S. F.; Vlasov, V. A.; Lychagin, D. V.; Chumaevskii, A. V.

2015-10-01

The paper presents the research of the weld structure of two Ti specimens of the type VT6 that have nano- and submicrocrystalline structures. Electrical contact welding is used to obtain welds. The acicular structure is formed in the weld area. Two types of defects are detected, namely micropores and microcracks.

Toughness of 2,25Cr-1Mo steel and weld metal

NASA Astrophysics Data System (ADS)

Acarer, Mustafa; Arici, Gökhan; Acar, Filiz Kumdali; Keskinkilic, Selcuk; Kabakci, Fikret

2017-09-01

2,25Cr-1Mo steel is extensively used at elevated temperature structural applications in fossil fire power plants for steam pipes, nozzle chambers and petrochemical industry for hydrocracking unit due to its excellent creep resistance and good redundant to oxidation. Also they should have acceptable weldability and toughness. The steels are supplied in quenched and tempered condition and their welded components are subjected to post-weld heat treatment (PWHT). Tempering process is carried out at 690-710°C to improve toughness properties. However they are sensitive to reheat cracking and temper embrittlement. To measure temper embrittlement of the steels and their weld metal, temper embrittlement factor and formula (J factor - Watanabe and X formula- Bruscato) are used. Step cooling heat treatment is also applied to determine temper embrittlement. In this study, toughness properties of Cr Mo (W) steels were reviewed. Also transition temperature curves of 2,25Cr-1Mo steel and its weld metal were constructed before and after step cool heat treatment as experimental study. While 2,25Cr-1Mo steel as base metal was supplied, all weld metal samples were produced in Gedik Welding Company. Hardness measurements and microstructure evaluation were also carried out.

Critical evaluation of sequential leaching procedures for the determination of Ni and Mn species in welding fumes.

PubMed

Berlinger, B; Náray, M; Sajó, I; Záray, G

2009-06-01

In this work, welding fume samples were collected in a welding plant, where corrosion-resistant steel and unalloyed structural steel were welded by gas metal arc welding (GMAW) and manual metal arc welding (MMAW) techniques. The welding fumes were sampled with a fixed-point sampling strategy applying Higgins-Dewell cyclones. The following solutions were used to dissolve the different species of Ni and Mn: ammonium citrate solution [1.7% (m/v) diammonium hydrogen citrate and 0.5% (m/v) citric acid monohydrate] for 'soluble' Ni, 50:1 methanol-bromine solution for metallic Ni, 0.01 M ammonium acetate for soluble Mn, 25% acetic acid for Mn(0) and Mn(2+) and 0.5% hydroxylammonium chloride in 25% acetic acid for Mn(3+) and Mn(4+). 'Insoluble' Ni and Mn contents of the samples were determined after microwave-assisted digestion with the mixture of concentrated (cc). HNO(3), cc. HCl and cc. HF. The sample solutions were analysed by inductively coupled plasma quadrupole mass spectrometry and inductively coupled plasma atomic emission spectrometry. The levels of total Ni and Mn measured in the workplace air were different because of significant differences of the fume generation rates and the distributions of the components in the welding fumes between the welding processes. For quality control of the leaching process, dissolution of the pure stoichiometric Mn and Ni compounds and their mixtures weighing was investigated using the optimized leaching conditions. The results showed the adequacy of the procedure for the pure metal compounds. Based on the extraction procedures, the predominant oxidation states of Ni and Mn proved to be very different depending on the welding techniques and type of the welded steels. The largest amount of Mn in GMAW fumes were found as insoluble Mn (46 and 35% in case of corrosion-resistant steel and unalloyed structural steel, respectively), while MMAW fumes contain mainly soluble Mn, Mn(0) and Mn(2+) (78%) and Mn(3+) and Mn(4+) (54%) in case of corrosion-resistant steel and unalloyed structural steel, respectively. According to the results of the leaching procedures, GMAW fumes are rich in oxidic Ni (79%), while Ni compounds in welding fumes generated during MMAW are mainly in easily soluble form (44%). The crystalline phases were identified in each welding fume by X-ray powder diffraction (XRPD) technique as well. From the XRPD spectra, it is clear that GMAW fumes contain predominantly magnetite (FeFe(2)O(4)). In case of structural steel welding, there was a little amount of ferrite (alpha-Fe) also found. Welding fume generated during MMAW of structural steel contained a complex alkali-alkali earth fluoride phase (KCaF(3)-CaF(2)) and some magnetite and jakobsite (MnFe(2)O(4)). The XRPD results did not fully confirm the ones obtained from the extraction experiments. However, some results, for example the rate of soluble Ni and Mn compounds compared to the total, can be useful for further investigations of welding fumes.

Friction Stir Welding in Wrought and Cast Aluminum Alloys: Weld Quality Evaluation and Effects of Processing Parameters on Microstructure and Mechanical Properties

NASA Astrophysics Data System (ADS)

Pan, Yi; Lados, Diana A.

2017-04-01

Friction stir welding (FSW) is a solid-state process widely used for joining similar and dissimilar materials for critical applications in the transportation sector. Understanding the effects of the process on microstructure and mechanical properties is critical in design for structural integrity. In this study, four aluminum alloy systems (wrought 6061-T651 and cast A356, 319, and A390) were processed in both as-fabricated and pre-weld heat-treated (T6) conditions using various processing parameters. The effects of processing and heat treatment on the resulting microstructures, macro-/micro-hardness, and tensile properties were systematically investigated and mechanistically correlated to changes in grain size, characteristic phases, and strengthening precipitates. Tensile tests were performed at room temperature both along and across the welding zones. A new method able to evaluate weld quality (using a weld quality index) was developed based on the stress concentration calculated under tensile loading. Optimum processing parameter domains that provide both defect-free welds and good mechanical properties were determined for each alloy and associated with the thermal history of the process. These results were further related to characteristic microstructural features, which can be used for component design and materials/process optimization.

Nuclear reactor I

DOEpatents

Ference, Edward W.; Houtman, John L.; Waldby, Robert N.

1977-01-01

A nuclear reactor, particularly a liquid-metal breeder reactor whose upper internals include provision for channeling the liquid metal flowing from the core-component assemblies to the outlet plenum in vertical paths in direction generally along the direction of the respective assemblies. The metal is channeled by chimneys, each secured to, and extending from, a grid through whose openings the metal emitted by a plurality of core-component assemblies encompassed by the grid flows. To reduce the stresses resulting from structural interaction, or the transmissive of thermal strains due to large temperature differences in the liquid metal emitted from neighboring core-component assemblies, throughout the chimneys and the other components of the upper internals, the grids and the chimneys are supported from the heat plate and the core barrel by support columns (double portal support) which are secured to the head plate at the top and to a member, which supports the grids and is keyed to the core barrel, at the bottom. In addition to being restrained from lateral flow by the chimneys, the liquid metal is also restrained from flowing laterally by a peripheral seal around the top of the core. This seal limits the flow rate of liquid metal, which may be sharply cooled during a scram, to the outlet nozzles. The chimneys and the grids are formed of a highly-refractory, high corrosion-resistant nickel-chromium-iron alloy which can withstand the stresses produced by temperature differences in the liquid metal. The chimneys are supported by pairs of plates, each pair held together by hollow stubs coaxial with, and encircling, the chimneys. The plates and stubs are a welded structure but, in the interest of economy, are composed of stainless steel which is not weld compatible with the refractory metal. The chimneys and stubs are secured together by shells of another nickel-chromium-iron alloy which is weld compatible with, and is welded to, the stubs and has about the same coefficient of expansion as the highly-refractory, high corrosion-resistant alloy.

Experimental Investigation of Tensile Test on Connection of Cold-formed Cut-curved Steel Section

NASA Astrophysics Data System (ADS)

Sani, Mohd Syahrul Hisyam Mohd; Muftah, Fadhluhartini; Rahman, Nurul Farraheeda Abdul; Fakri Muda, Mohd

2017-08-01

Cold-formed steel (CFS) is widely used as structural and non-structural components such as roof trusses and purlin. A CFS channel section with double intermediate web stiffener and lipped is chosen based on the broader usage in roof truss construction. CFS section is cut to form cold-formed pre-cut-curved steel section and lastly strengthened by several types of method or likely known as connection to establish the cold-formed cut-curved steel (CFCCS) section. CFCCS is proposed to be used as a top chord section in the roof truss system. The CFCCS is to resist the buckling phenomena of the roof truss structure and reduced the compression effect on the top chord. The tensile test connection of CFCCS section, especially at the flange element with eight types of connection by welding, plate with self-drilling screw and combination is investigated. The flange element is the weakest part that must be solved first other than the web element because they are being cut totally, 100% of their length for curving process. The testing is done using a universal testing machine for a tensile load. From the experiment, specimen with full welding has shown as a good result with an ultimate load of 13.37 kN and reported having 35.41% when compared with normal specimen without any of connection methods. Furthermore, the experimental result is distinguished by using Eurocode 3. The failure of a full welding specimen is due to breaking at the welding location. Additionally, all specimens with either full weld or spot weld or combination failed due to breaking on weld connection, but specimen with flange plate and self-drilling screw failed due to tilting and bearing. Finally, the full welding specimen is chosen as a good connection to perform the strengthening method of CFCCS section.

General Mechanical Repair. Welding. Volume 2. Teacher's Guide.

ERIC Educational Resources Information Center

East Texas State Univ., Commerce. Occupational Curriculum Lab.

Five units on welding are presented in this teacher's guide. The units are the following: introduction to oxyacetylene welding, oxyacetylene welding positions and applications, use of the cutting torch, introduction to shielded metal arc welding, and welding joints and positions. Each instructional unit generally contains eight components:…

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.

The Evolution of Friction Stir Welding Theory at Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Nunes, Arthur C.

2012-01-01

From 1995 to the present the friction stir welding (FSW) process has been under study at Marshall Space Flight Center (MSFC). This is an account of the progressive emergence of a set of conceptual tools beginning with the discovery of the shear surface, wiping metal transfer, and the invention of a kinematic model and making possible a treatment of both metallurgical structure formation and process dynamics in friction stir welding from a unified point of view. It is generally observed that the bulk of the deformation of weld metal around the FSW pin takes place in a very narrow, almost discontinuous zone with high deformation rates characteristic of metal cutting. By 1999 it was realized that this zone could be treated as a shear surface like that in simple metal cutting models. At the shear surface the seam is drawn out and compressed and pressure and flow conditions determine whether or not a sound weld is produced. The discovery of the shear surface was followed by the synthesis of a simple 3- flow kinematic model of the FSW process. Relative to the tool the flow components are: (1) an approaching translational flow at weld speed V, (2) a rotating cylindrical plug flow with the angular velocity of the tool , and (3) a relatively slow ring vortex flow (like a smoke ring) encircling the tool and driven by shoulder scrolls and pin threads. The rotating plug flow picks up an element of weld metal, rotates it around with the tool, and deposits it behind the tool ( wiping metal transfer ); it forms plan section loops in tracers cut through by the tool. Radially inward flow from the ring vortex component retains metal longer in the rotating plug and outward flow expels metal earlier; this interaction forms the looping weld seam trace and the tongue and groove bimetallic weld contour. The radial components of the translational and ring vortex flows introduce parent metal intrusions into the small grained nugget material close to the tool shoulder; if this feature is pronounced, nugget collapse may result. Certain weld features, in particular internal banding seen in transverse section as onion rings and associated surface ridges called tool marks , have long implied an oscillation flow component, but have only recently been attributed in the literature to tool eccentricity. Rotating plug shape, typically a hollow cylinder flared at the end where it sticks to the shoulder, varies as pressure distribution on the tool determines where sticking occurs. Simplified power input estimates balanced against heat loss estimates give reasonable temperature estimates, explain why the power requirement changes hardly at all over a wide range of RPM s, and yield isotherms that seem to fall along boundaries of parameter windows of operation.

Micro friction stir lap welding of AISI 430 ferritic stainless steel: a study on the mechanical properties, microstructure, texture and magnetic properties

NASA Astrophysics Data System (ADS)

Mostaan, Hossein; Safari, Mehdi; Bakhtiari, Arash

2018-04-01

In this study, the effect of friction stir welding of AISI 430 (X6Cr17, material number 1.4016) ferritic stainless steel is examined. Two thin sheets with dimensions of 0.4 × 50 × 200 mm3 are joined in lap configuration. Optical microscopy and field emission electron microscopy were used in order to microstructural evaluations and fracture analysis, respectively. Tensile test and microhardness measurements are employed in order to study the mechanical behaviors of welds. Also, vibrational sample magnetometry (VSM) is employed for characterizing magnetic properties of welded samples. Texture analysis is carried out in order to clarify the change mechanism of magnetic properties in the welded area. The results show that AISI 430 sheets are successfully joined considering both, the appearance of the welding bead and the strength of the welded joint. It is found that by friction stir welding of AISI 430 sheets, texture components with easy axes magnetization have been replaced by texture components with harder magnetization axes. VSM analysis showed that friction stir welding leads to increase in residual induction (Br) and coercivity (Hc). This increase is attributed to the grain refining due the friction stir welding and formation of texture components with harder axes of magnetizations.

Molecular dynamics study on welding a defected graphene by a moving fullerene

NASA Astrophysics Data System (ADS)

Cai, Kun; Wan, Jing; Yu, Jingzhou; Cai, Haifang; Qin, Qinghua

2016-07-01

When a composite nanostructure is fabricated through van der Waals interaction only, the interaction among components may be sensitive to environmental conditions. To endow such a structure with relative stability, new covalent bonds should be applied. In this paper, a welding method for welding a circular graphene with a defect gap through a moving fullerene (C240 or C540 buckyball) is presented. When the buckyball moves above the gap, the two faces of the gap are attracted to each other and the distance between the two faces is shortened. When the dangling carbon atoms on both faces of the gap are excited to form new normal sp2-sp2 carbon bonds, the gap can be sewn up quickly. Molecular dynamics simulations are presented to demonstrate the welding process. When the gap is a sector, an ideal cone can be fabricated using the present method.

Atomic force microscopy and transmission electron microscopy analyses of low-temperature laser welding of the cornea.

PubMed

Matteini, Paolo; Sbrana, Francesca; Tiribilli, Bruno; Pini, Roberto

2009-07-01

Low-temperature laser welding of the cornea is a technique used to facilitate the closure of corneal cuts. The procedure consists of staining the wound with a chromophore (indocyanine green), followed by continuous wave irradiation with an 810 nm diode laser operated at low power densities (12-16 W/cm(2)), which induces local heating in the 55-65 degrees C range. In this study, we aimed to investigate the ultrastructural modifications in the extracellular matrix following laser welding of corneal wounds by means of atomic force microscopy and transmission electron microscopy. The results evidenced marked disorganization of the normal fibrillar assembly, although collagen appeared not to be denatured under the operating conditions we employed. The mechanism of low-temperature laser welding may be related to some structural modifications of the nonfibrillar extracellular components of the corneal stroma.

Unique methods for on-orbit structural repair, maintenance, and assembly

NASA Technical Reports Server (NTRS)

Anderson, Ray; Fuson, Phil

1994-01-01

This paper reviews the MDA independent research and development (IRAD) efforts since 1986 in the development of two distinctly different approaches to on-orbit tube repair: (1) one-piece mechanical tube fittings that are forced, under pressure, onto the tube outer surface to effect the repair; and (2) electron beam weldings as demonstrated with the Paton-developed universal hand tool (UHT) space welding system for the repair of fluid lines and tubular components. Other areas of potential on-orbit repair using the UHT include damage to the flat or curved surfaces of habitation modules and truss assemblies. This paper will also address MDA evaluation of the Paton UHT system for on-orbit coating, cleaning, brazing, and cutting of metals. MDA development of an on-orbit compatible nondestructive evaluation (NDE) system for the inspection of tube welds is an important part of this complete space welding capability and will be discussed in a separate paper.

Measurement of Laser Weld Temperatures for 3D Model Input

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

Dagel, Daryl; Grossetete, Grant; Maccallum, Danny O.

Laser welding is a key joining process used extensively in the manufacture and assembly of critical components for several weapons systems. Sandia National Laboratories advances the understanding of the laser welding process through coupled experimentation and modeling. This report summarizes the experimental portion of the research program, which focused on measuring temperatures and thermal history of laser welds on steel plates. To increase confidence in measurement accuracy, researchers utilized multiple complementary techniques to acquire temperatures during laser welding. This data serves as input to and validation of 3D laser welding models aimed at predicting microstructure and the formation of defectsmore » and their impact on weld-joint reliability, a crucial step in rapid prototyping of weapons components.« less

Thermal Recovery of Plastic Deformation in Dissimilar Metal Weld

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

Qiao, Dongxiao; Yu, Xinghua; Zhang, Wei

Stainless steel has been widely used in challenging environments typical to nuclear power plant structures, due its excellent corrosion resistance. Nickel filler metals containing high chromium concentration, including Alloy 82/182, are used for joining stainless steel to carbon steel components to achieve similar high resistance to stress corrosion cracking. However, the joint usually experience weld metal stress corrosion cracking (SCC), which affects the safety and structural integrity of light water nuclear reactor systems. A primary driving force for SCC is the high tensile residual stress in these welds. Due to large dimension of pressure vessel and limitations in the field,more » non-destructive residual stress measurement is difficult. As a result, finite element modeling has been the de facto method to evaluate the weld residual stresses. Recent studies on this subject from researchers worldwide report different residual stress value in the weldments [5]. The discrepancy is due to the fact that most of investigations ignore or underestimate the thermal recovery in the heat-affect zone or reheated region in the weld. In this paper, the effect of heat treatment on thermal recovery and microhardness is investigated for materials used in dissimilar metal joint. It is found that high equivalent plastic strains are predominately accumulated in the buttering layer, the root pass, and the heat affected zone, which experience multiple welding thermal cycles. The final cap passes, experiencing only one or two welding thermal cycles, exhibit less plastic strain accumulation. Moreover, the experimental residual plastic strains are compared with those predicted using an existing weld thermo-mechanical model with two different strain hardening rules. The importance of considering the dynamic strain hardening recovery due to high temperature exposure in welding is discussed for the accurate simulation of weld residual stresses and plastic strains. In conclsuion, the experimental result reveals that the typical post-buttering heat treatment for residual stress relief may not be adequate to completely eliminate the residual plastic strains in the buttering layer.« less

Electrolyzer assembly method and system

DOEpatents

Swala, Dana Ray; Bourgeois, Richard Scott; Paraszczak, Steven; Buckley, Donald Joseph

2017-05-23

The present techniques provide a novel electrolyzer and methods for welding components of such electrolyzers. The techniques may use conductors, such as resistance wires, placed in paths around the internal structural features and edges of the components. The conductors may be incorporated into the components during manufacture by injection molding, or other molding techniques, or may be tacked or otherwise applied to the surface of the components after manufacture. When current, a field or other excitation is applied to the conductors, the plastic surrounding the wire is melted. If this plastic is in direct contact with an adjoining component, a strong, hermetic seal may be formed between the two components, including the internal structural features.

Nine percent nickel steel heavy forging weld repair study. [National Transonic Wind Tunnel fan components

NASA Technical Reports Server (NTRS)

Young, C. P., Jr.; Gerringer, A. H.; Brooks, T. G.; Berry, R. F., Jr.

1978-01-01

The feasibility of making weld repairs on heavy section 9% nickel steel forgings such as those being manufactured for the National Transonic Facility fan disk and fan drive shaft components was evaluated. Results indicate that 9% nickel steel in heavy forgings has very good weldability characteristics for the particular weld rod and weld procedures used. A comparison of data for known similar work is included.

Simulation model of Al-Ti dissimilar laser welding-brazing and its experimental verification

NASA Astrophysics Data System (ADS)

Behúlová, M.; Babalová, E.; Nagy, M.

2017-02-01

Formation of dissimilar weld joints of light metals and alloys including Al-Ti joints is interesting mainly due to demands on the weight reduction and corrosion resistance of components and structures in automotive, aircraft, aeronautic and other industries. Joining of Al-Ti alloys represents quite difficult problem. Generally, the fusion welding of these materials can lead to the development of different metastable phases and formation of brittle intermetallic compounds. The paper deals with numerical simulation of the laser welding-brazing process of titanium Grade 2 and EN AW 5083 aluminum alloy sheets using the 5087 aluminum filler wire. Simulation model for welding-brazing of testing samples with the dimensions of 50 × 100 × 2 mm was developed in order to perform numerical experiments applying variable welding parameters and to design proper combination of these parameters for formation of sound Al-Ti welded-brazed joints. Thermal properties of welded materials in the dependence on temperature were computed using JMatPro software. The conical model of the heat source was exploited for description of the heat input to the weld due to the moving laser beam source. The sample cooling by convection and radiation to the surrounding air and shielding argon gas was taken into account. Developed simulation model was verified by comparison of obtained results of numerical simulation with the temperatures measured during real experiments of laser welding-brazing by the TruDisk 4002 disk laser.

Electron Beam Welding to Join Gamma Titanium Aluminide Articles

NASA Technical Reports Server (NTRS)

Kelly, Thomas Joseph (Inventor)

2008-01-01

A method is provided for welding two gamma titanium aluminide articles together. The method includes preheating the two articles to a welding temperature of from about 1700 F to about 2100 F, thereafter electron beam welding the two articles together at the welding temperature and in a welding vacuum to form a welded structure, and thereafter annealing the welded structure at an annealing temperature of from about 1800 F to about 2200 F, to form a joined structure.

Feasibility of remotely manipulated welding in space. A step in the development of novel joining technologies

NASA Technical Reports Server (NTRS)

Masubuchi, K.; Agapakis, J. E.; Debiccari, A.; Vonalt, C.

1983-01-01

In order to establish permanent human presence in space technologies of constructing and repairing space stations and other space structures must be developed. Most construction jobs are performed on earth and the fabricated modules will then be delivered to space by the Space Shuttle. Only limited final assembly jobs, which are primarily mechanical fastening, will be performed on site in space. Such fabrication plans, however, limit the designs of these structures, because each module must fit inside the transport vehicle and must withstand launching stresses which are considerably high. Large-scale utilization of space necessitates more extensive construction work on site. Furthermore, continuous operations of space stations and other structures require maintenance and repairs of structural components as well as of tools and equipment on these space structures. Metal joining technologies, and especially high-quality welding, in space need developing.

Effects of Post-Weld Heat Treatment on the Microstructure and Toughness of Flash Butt Welded High-Strength Low-Alloy Steel

NASA Astrophysics Data System (ADS)

Shajan, Nikhil; Arora, Kanwer Singh; Asati, Brajesh; Sharma, Vikram; Shome, Mahadev

2018-04-01

Effect of post-weld heat treatment on the weld microstructure, texture, and its correlation to the toughness of flash butt welded joints were investigated. Upon flash butt welding, the α and γ-fiber in the parent material converted to Goss (110)[001], rotated Goss (110)[1 \\bar{1} 0], and rotated cube (001)[1 \\bar{1} 0], (001)[ \\overline{11} 0] textures along the fracture plane. Formation of these detrimental texture components was a result of shear deformation and recrystallization of austenite at temperatures above T nr resulting in a drop of toughness at the weld zone. Inter-critical and sub-critical annealing cycles proved to be less effective in reducing the Goss (110)[001], rotated Goss (110)[1 \\bar{1} 0], and rotated cube (001)[1 \\bar{1} 0], (001)[ \\overline{11} 0] texture components, and therefore, toughness values remained unaffected. Post-weld heat treatment in the austenite phase field at 1000 °C for 5 seconds resulted in the formation of new grains with different orientations leading to a reduction in the texture intensities of both Goss and rotated Goss components and therefore improved weld zone toughness. Prolonged annealing time was found to be ineffective in improving the toughness due to grain growth.

Influence of low nickel (0.09 wt%) content on microstructure and toughness of P91 steel welds

NASA Astrophysics Data System (ADS)

Arivazhagan, B.; Vasudevan, M.; Kamaraj, M.

2015-05-01

Modified 9Cr-1Mo (P91) steel is widely used as a high temperature structural material in the fabrication of power plant components. Alloying elements significantly influences the microstructure and mechanical properties of P91 steel weldments. The alloying elements manganese and nickel significantly influence the lower critical phase transformation temperature (AC1) as well as tempering response of welds. In the existing published information there was wide spread use of high Mn+Ni filler wire. In the present study, weldment preparation was completed using GTA filler wire having low Nickel content (Mn+Ni of 0.58 wt% including nickel content of 0.09 wt%). Microstructure and mechanical properties characterization was done. There is a requirement on minimum toughness of 47 Joules for P91 steel tempered welds at room temperature. Microstructural observation revealed that the GTA welds have low δ-ferrite content (<0.5%) in the martensite matrix. In the as-weld condition, the toughness was 28 Joules whereas after PWHT at 760 °C-2 h it was 115 Joules. In the present study, toughness of low nickel weld was higher due to low δ-ferrite content (<0.5%), multipass grain refinement and weld metal deposition of single pass per layer of weldment.

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.

Microstructural and Mechanical Aspects of Reinforcement Welds for Lightweight Components Produced by Friction Hydro Pillar Processing

NASA Astrophysics Data System (ADS)

Pinheiro, Gustavo; dos Santos, Jorge; Hort, Norbert; Kainer, Karl Ulrich

The development of new creep resistant and cost effective die casting magnesium alloys such as AE, MRI, MEZ, ACM, AXJ, AJ, WE have emerged as an alternative to fulfil the actual demands in structural relevant applications as engines blocks, gear and converter boxes. However, magnesium components are in most of the cases screwed with aluminium and steel bolts, which lead the screwed joint to lose the preload force due to relaxation. This barrier limits thus the broad use of magnesium within this segment and should somehow find an adequate solution to be implemented and to help overcoming this limitation. In this context Friction Welding (FW) and particularly Friction Hydro Pillar Processing (FHPP), which can be described as a drill and fill process, appears as an alternative to widespread the use of magnesium. In this context, FHPP is intended to be used to locally reinforce mechanical fastened magnesium components.

Use of Infrared Thermography for the Inspection of Welds in the Shop and Field [Summary

DOT National Transportation Integrated Search

2018-02-01

Steel bridges are created by welding steel components. The quality of these welds is critical to the integrity of the bridge. Weld defects can lead to expensive repairs or mechanical failure. However, weld defects are often below the steel surface an...

Modelling the attenuation in the ATHENA finite elements code for the ultrasonic testing of austenitic stainless steel welds.

PubMed

Chassignole, B; Duwig, V; Ploix, M-A; Guy, P; El Guerjouma, R

2009-12-01

Multipass welds made in austenitic stainless steel, in the primary circuit of nuclear power plants with pressurized water reactors, are characterized by an anisotropic and heterogeneous structure that disturbs the ultrasonic propagation and makes ultrasonic non-destructive testing difficult. The ATHENA 2D finite element simulation code was developed to help understand the various physical phenomena at play. In this paper, we shall describe the attenuation model implemented in this code to give an account of wave scattering phenomenon through polycrystalline materials. This model is in particular based on the optimization of two tensors that characterize this material on the basis of experimental values of ultrasonic velocities attenuation coefficients. Three experimental configurations, two of which are representative of the industrial welds assessment case, are studied in view of validating the model through comparison with the simulation results. We shall thus provide a quantitative proof that taking into account the attenuation in the ATHENA code dramatically improves the results in terms of the amplitude of the echoes. The association of the code and detailed characterization of a weld's structure constitutes a remarkable breakthrough in the interpretation of the ultrasonic testing on this type of component.

Superplastic Forming/Adhesive Bonding of Aluminum (SPF/AB) Multi-Sheet Structures

NASA Technical Reports Server (NTRS)

Wagner, John A. (Technical Monitor); Will, Jeff D.; Cotton, James D.

2003-01-01

A significant fraction of airframe structure consists of stiffened panels that are costly and difficult to fabricate. This program explored a potentially lower-cost processing route for producing such panels. The alternative process sought to apply concurrent superplastic forming and adhesive bonding of aluminum alloy sheets. Processing conditions were chosen to balance adequate superplasticity of the alloy with thermal stability of the adhesive. As a first objective, an air-quenchable, superplastic aluminum-lithium alloy and a low-volatile content, low-viscosity adhesive with compatible forming/curing cycles were identified. A four-sheet forming pack was assembled which consisted of a welded two-sheet core separated from the face sheets by a layer of adhesive. Despite some preliminary success, of over 30 forming trials none was completely successful. The main problem was inadequate superplasticity in the heat-affected zones of the rib welds, which generally fractured prior to completion of the forming cycle. The welds are a necessary component in producing internal ribs by the 'four-sheet' process. Other challenges, such as surface preparation and adhesive bonding, were adequately solved. But without the larger issue of tearing at the weld locations, complex panel fabrication by SPF/AB does not appear viable.

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.

Advanced fusion welding processes, solid state joining and a successful marriage. [production of aerospace structures

NASA Technical Reports Server (NTRS)

Miller, F. R.

1972-01-01

Joining processes for aerospace systems combine fusion welding and solid state joining during production of metal structures. Detailed characteristics of electron beam welding, plasma arc welding, diffusion welding, inertia welding and weldbond processes are discussed.

Seal welded cast iron nuclear waste container

DOEpatents

Filippi, Arthur M.; Sprecace, Richard P.

1987-01-01

This invention identifies methods and articles designed to circumvent metallurgical problems associated with hermetically closing an all cast iron nuclear waste package by welding. It involves welding nickel-carbon alloy inserts which are bonded to the mating plug and main body components of the package. The welding inserts might be bonded in place during casting of the package components. When the waste package closure weld is made, the most severe thermal effects of the process are restricted to the nickel-carbon insert material which is far better able to accommodate them than is cast iron. Use of nickel-carbon weld inserts should eliminate any need for pre-weld and post-weld heat treatments which are a problem to apply to nuclear waste packages. Although the waste package closure weld approach described results in a dissimilar metal combination, the relative surface area of nickel-to-iron, their electrochemical relationship, and the presence of graphite in both materials will act to prevent any galvanic corrosion problem.

Vacuum chamber translation/positioning mechanism and welding power supply controller

NASA Technical Reports Server (NTRS)

Smith, James E., Jr.; Cashon, John L.

1992-01-01

Welding in the vacuum of space represents an important and fundamental problem for space exploration. Repairs or connection of metal components on orbit or during travel to the moon or distant planets may be required. Cracks or holes in spacecraft skin or supporting structures external to the pressurized section will require some type of repair that must be permanently made to the skin or support by welding. The development of a translation/positioning system that will permit research into welding of metal samples in a small vacuum chamber located at Marshall Space Flight Center (MSFC) is addressed. The system and associated software was tested to the extent possible without the availability of the welder power supply or control computer that must be supplied by MSFC. Software has been developed for straight line welding. More extensive and varied translations are possible with simple alterations to the operating software to use the full capabilities of this three axes system. The source code 'VW.BAS' has been provided to serve as an example for further development of the vacuum welder translation system.

Welded tie plate feasibility study for ITER central solenoid structure

NASA Astrophysics Data System (ADS)

Walsh, R.; McRae, D.; Dalder, E.; Litherland, S.; Goddard, R.; Han, K.; Trosen, M.; Kuhlmann, D. D.

2014-01-01

The result of a Nitronic 50 (N50) weld-screening program conducted in support of CS-Tie Plate Structure Design and Development is reported here. The goal of this program is to evaluate four different weld practices and to select the best weld practice for thick section welding of the N50 tie plate structure. The structure design specifies both the weld and base metals have the same minimum mechanical properties requirements. The criteria for selecting the best weld practice are based on the combination of the 295 K tensile properties and the 4 K-tensile, fatigue, and fracture-toughness properties.

Friction stir welding and processing of oxide dispersion strengthened (ODS) alloys

DOEpatents

Ren, Weiju

2014-11-11

A method of welding including forming a filler material of a first oxide dispersoid metal, the first oxide dispersoid material having first strengthening particles that compensate for decreases in weld strength of friction stir welded oxide dispersoid metals; positioning the filler material between a first metal structure and a second metal structure each being comprised of at least a second oxide dispersoid metal; and friction welding the filler material, the first metal structure and the second metal structure to provide a weld.

Study of weld offset in longitudinally welded SSME HPFTP inlet

NASA Technical Reports Server (NTRS)

Min, J. B.; Spanyer, K. S.; Brunair, R. M.

1992-01-01

Welded joints are an essential part of rocket engine structures such as the Space Shuttle Main Engine (SSME) turbopumps. Defects produced in the welding process can be detrimental to weld performance. Recently, review of the SSME high pressure fuel turbopump (HPFTP) titanium inlet X-rays revealed several weld discrepancies such as penetrameter density issues, film processing discrepancies, weld width discrepancies, porosity, lack of fusion, and weld offsets. Currently, the sensitivity of welded structures to defects is of concern. From a fatigue standpoint, weld offset may have a serious effect since local yielding, in general, aggravates cyclic stress effects. Therefore, the weld offset issue is considered in this report. Using the FEM and beamlike plate approximations, parametric studies were conducted to determine the influence of weld offsets and a variation of weld widths in longitudinally welded cylindrical structures with equal wall thicknesses on both sides of the joint. Following the study, some conclusions are derived for the weld offsets.

46 CFR 154.180 - Contiguous hull structure: Welding procedure.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Contiguous hull structure: Welding procedure. 154.180 Section 154.180 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS... Equipment Hull Structure § 154.180 Contiguous hull structure: Welding procedure. Welding procedure tests for...

46 CFR 154.180 - Contiguous hull structure: Welding procedure.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Contiguous hull structure: Welding procedure. 154.180 Section 154.180 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS... Equipment Hull Structure § 154.180 Contiguous hull structure: Welding procedure. Welding procedure tests for...

46 CFR 154.180 - Contiguous hull structure: Welding procedure.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Contiguous hull structure: Welding procedure. 154.180 Section 154.180 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS... Equipment Hull Structure § 154.180 Contiguous hull structure: Welding procedure. Welding procedure tests for...

46 CFR 154.180 - Contiguous hull structure: Welding procedure.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Contiguous hull structure: Welding procedure. 154.180 Section 154.180 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS... Equipment Hull Structure § 154.180 Contiguous hull structure: Welding procedure. Welding procedure tests for...

Low temperature corneal laser welding investigated by atomic force microscopy

NASA Astrophysics Data System (ADS)

Matteini, Paolo; Sbrana, Francesca; Tiribilli, Bruno; Pini, Roberto

2009-02-01

The structural modifications in the stromal matrix induced by low-temperature corneal laser welding were investigated by atomic force microscopy (AFM). This procedure consists of staining the wound with Indocyanine Green (ICG), followed by irradiation with a near-infrared laser operated at low-power densities. This induces a local heating in the 55-65 °C range. In welded tissue, extracellular components undergo heat-induced structural modifications, resulting in a joining effect between the cut edges. However, the exact mechanism generating the welding, to date, is not completely understood. Full-thickness cuts, 3.5 mm in length, were made in fresh porcine cornea samples, and these were then subjected to laser welding operated at 16.7 W/cm2 power density. AFM imaging was performed on resin-embedded semi-thin slices once they had been cleared by chemical etching, in order to expose the stromal bulk of the tissue within the section. We then carried out a morphological analysis of characteristic fibrillar features in the laser-treated and control samples. AFM images of control stromal regions highlighted well-organized collagen fibrils (36.2 +/- 8.7 nm in size) running parallel to each other as in a typical lamellar domain. The fibrils exhibited a beaded pattern with a 22-39 nm axial periodicity. Laser-treated corneal regions were characterized by a significant disorganization of the intralamellar architecture. At the weld site, groups of interwoven fibrils joined the cut edges, showing structural properties that were fully comparable with those of control regions. This suggested that fibrillar collagen is not denatured by low-temperature laser welding, confirming previous transmission electron microscopy (TEM) observations, and thus it is probably not involved in the closure mechanism of corneal cuts. The loss of fibrillar organization may be related to some structural modifications in some interfibrillar substance as proteoglycans or collagen VI. Furthermore, AFM imaging was demonstrated to be a suitable tool for attaining three-dimensional information on the fibrillar assembly of corneal stroma. The results suggested that AFM analyses of resin-embedded histological sections subjected to chemical etching provide a rapid and cost-effective response, with an imaging resolution that is quite similar to that of TEM.

Structural and mechanical properties of welded joints of reduced activation martensitic steels

NASA Astrophysics Data System (ADS)

Filacchioni, G.; Montanari, R.; Tata, M. E.; Pilloni, L.

2002-12-01

Gas tungsten arc welding and electron beam welding methods were used to realise welding pools on plates of reduced activation martensitic steels. Structural and mechanical features of these simulated joints have been investigated in as-welded and post-welding heat-treated conditions. The research allowed to assess how each welding technique affects the original mechanical properties of materials and to find suitable post-welding heat treatments. This paper reports results from experimental activities on BATMAN II and F82H mod. steels carried out in the frame of the European Blanket Project - Structural Materials Program.

Space Fabrication Demonstration System

NASA Technical Reports Server (NTRS)

1978-01-01

Progress in the mechanical/structural assembly of the beam builder is reported. The following structures were investigated: cross brace magazine/dispenser subsystem; and rolling mill supply reel, guide, and drive. The fabrication facility design and a detail design of all major subsystem components are discussed. The number of spot welds per structural joint were reduced which enables the doubling of length of truss which can be produced within known electrode life limits.

Demonstration of a Large-Scale Tank Assembly via Circumferential Friction Stir Welds

NASA Technical Reports Server (NTRS)

Jones, Clyde S.; Adams, Glynn; Colligan, Kevin

2000-01-01

A collaborative effort between NASA/Marshall Space Flight Center and the Michoud Unit of Lockheed Martin Space Systems Company was undertaken to demonstrate assembly of a large-scale aluminum tank using circumferential friction stir welds. The hardware used to complete this demonstration was fabricated as a study of near-net- shape technologies. The tooling used to complete this demonstration was originally designed for assembly of a tank using fusion weld processes. This presentation describes the modifications and additions that were made to the existing fusion welding tools required to accommodate circumferential friction stir welding, as well as the process used to assemble the tank. The tooling modifications include design, fabrication and installation of several components. The most significant components include a friction stir weld unit with adjustable pin length capabilities, a continuous internal anvil for 'open' circumferential welds, a continuous closeout anvil, clamping systems, an external reaction system and the control system required to conduct the friction stir welds and integrate the operation of the tool. The demonstration was intended as a development task. The experience gained during each circumferential weld was applied to improve subsequent welds. Both constant and tapered thickness 14-foot diameter circumferential welds were successfully demonstrated.

46 CFR 154.180 - Contiguous hull structure: Welding procedure.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Contiguous hull structure: Welding procedure. 154.180... Equipment Hull Structure § 154.180 Contiguous hull structure: Welding procedure. Welding procedure tests for contiguous hull structure designed for a temperature colder than −18 °C (0 °F) must meet § 54.05-15 and...

LDEF mechanical systems

NASA Technical Reports Server (NTRS)

Spear, W. Steve; Dursch, Harry W.

1992-01-01

Following LDEF retrieval, a number of studies were made of mechanical hardware and structure flown on the LDEF. The primary objectives are to determine the effects of long term space exposure on (1) mechanisms either used on LDEF or as part of individual experiments; (2) LDEF structural components; and (3) fasteners. Results from examination and testing of LDEF structure, fasteners, LDEF end support beam, environment exposure control canisters, experiment tray clamps, LDEF grapple fixtures, and viscous damper are presented. The most significant finding is the absence of space exposure related cold welding. The instances of seizure or removal difficulties initially attributed to cold welding were shown to have resulted from installation galling damage or improper removal techniques. Widespread difficulties encountered with removal of stainless steel fasteners underscore the need for effective thread lubrication schemes to ensure successful application of proposed orbital replacement units onboard Space Station Freedom.

[Assessment of occupational exposure of welders based on determination of fumes and their components produced during stainless steel welding].

PubMed

Stanisławska, Magdalena; Janasik, Beata; Trzcinka-Ochocka, Małgorzata

2011-01-01

Occupational exposure to welding fumes is a known health hazard. The aim of this study was to determine concentrations of welding fumes components such as: iron, manganese, nickel and chromium (including chromium speciation) to assess exposure of stainless steel welders. The survey covered 14 workers of two metallurgic plants engaged in welding stainless steel (18% Cr and 8% Ni) by different techniques: manual metal arc (MMA), metal inert gas (MIG) and tungsten inert gas (TIG). Personal air samples were collected in the welders' breathing zone over a period of about 6-7 h (dust was collected on a membrane and glass filter) to determine time weighted average (TWA) concentration of welding fumes and its components. The concentrations of welding fumes (total particulate) were determined with use of the gravimetric method. Concentrations and welding fume components, such as: iron, manganese, nickel and chromium were determined by ICP-MS technique. The total hexavalent chromium was analyzed by applying the spectrophotometry method according to NIOSH. The water-soluble chromium species were analyzed by HPLC-ICP-MS. Time weighted average concentrations of the welding fumes and its components at the worker's breathing zone were (mg/m3): dust, 0.14-10.7; iron, 0.004-2.9; manganese, 0.001-1.12; nickel, < 0.001-0.2; and chromium <0.002-0.85 (mainly Cr(III) and insoluble Cr(VI)). The maximum admissible limits for workplace pollutants (TLV-TWA) were exceeded for manganese and for insoluble chromium Cr (VI). For Cr (III) the limit was exceeded in individual cases. The assessment of the workers' occupational exposure, based on the determined time weighted average (TWA) of fumes and their components, shows that the stainless steel welders worked in conditions harmful to their health owing to the significantly exceeded maximum admissible limits for manganese and the exceeded TLV value for insoluble chromium (VI).

Fabricating Superior NiAl Bronze Components through Wire Arc Additive Manufacturing.

PubMed

Ding, Donghong; Pan, Zengxi; van Duin, Stephen; Li, Huijun; Shen, Chen

2016-08-03

Cast nickel aluminum bronze (NAB) alloy is widely used for large engineering components in marine applications due to its excellent mechanical properties and corrosion resistance. Casting porosity, as well as coarse microstructure, however, are accompanied by a decrease in mechanical properties of cast NAB components. Although heat treatment, friction stir processing, and fusion welding were implemented to eliminate porosity, improve mechanical properties, and refine the microstructure of as-cast metal, their applications are limited to either surface modification or component repair. Instead of traditional casting techniques, this study focuses on developing NAB components using recently expanded wire arc additive manufacturing (WAAM). Consumable welding wire is melted and deposited layer-by-layer on substrates producing near-net shaped NAB components. Additively-manufactured NAB components without post-processing are fully dense, and exhibit fine microstructure, as well as comparable mechanical properties, to as-cast NAB alloy. The effects of heat input from the welding process and post-weld-heat-treatment (PWHT) are shown to give uniform NAB alloys with superior mechanical properties revealing potential marine applications of the WAAM technique in NAB production.

Fabricating Superior NiAl Bronze Components through Wire Arc Additive Manufacturing

PubMed Central

Ding, Donghong; Pan, Zengxi; van Duin, Stephen; Li, Huijun; Shen, Chen

2016-01-01

Cast nickel aluminum bronze (NAB) alloy is widely used for large engineering components in marine applications due to its excellent mechanical properties and corrosion resistance. Casting porosity, as well as coarse microstructure, however, are accompanied by a decrease in mechanical properties of cast NAB components. Although heat treatment, friction stir processing, and fusion welding were implemented to eliminate porosity, improve mechanical properties, and refine the microstructure of as-cast metal, their applications are limited to either surface modification or component repair. Instead of traditional casting techniques, this study focuses on developing NAB components using recently expanded wire arc additive manufacturing (WAAM). Consumable welding wire is melted and deposited layer-by-layer on substrates producing near-net shaped NAB components. Additively-manufactured NAB components without post-processing are fully dense, and exhibit fine microstructure, as well as comparable mechanical properties, to as-cast NAB alloy. The effects of heat input from the welding process and post-weld-heat-treatment (PWHT) are shown to give uniform NAB alloys with superior mechanical properties revealing potential marine applications of the WAAM technique in NAB production. PMID:28773774

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.

Overall interior view of structures shop (11 shop) located on ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Overall interior view of structures shop (11 shop) located on west side of building 57 - looking north; the south end of the structures shop was devoted to welding heavy plate foundations and ship components; the floor is fabricated of case steel and features a grillwork of 1 1/2 fabricated holes which are used as sockets for gripping position pins. - Naval Base Philadelphia-Philadelphia Naval Shipyard, Structure Shop, League Island, Philadelphia, Philadelphia County, PA

New Possibilities in the Fabrication of Hybrid Components with Big Dimensions by Means of Selective Laser Melting (SLM)

NASA Astrophysics Data System (ADS)

Ascari, A.; Fortunato, A.; Liverani, E.; Gamberoni, A.; Tomesani, L.

The application of laser technology to welding of dissimilar AISI316 stainless steel components manufactured with selective laser melting (SLM) and traditional methods has been investigated. The role of laser parameters on weld bead formation has been studied experimentally, with particular attention placed on effects occurring at the interface between the two parts. In order to assess weld bead characteristics, standardised tensile tests were carried out on suitable specimens and the fracture zone was analysed. The results highlighted the possibility of exploiting suitable process parameters to appropriately shape the heat affected and fusion zones in order to maximise the mechanical performance of the component and minimise interactions between the two parent metals in the weld bead.

Materials Design for Joinable, High Performance Aluminum Alloys

NASA Astrophysics Data System (ADS)

Glamm, Ryan James

An aluminum alloy compatible with friction stir welding is designed for automotive and aerospace structural applications. Current weldable automotive aluminum alloys do not possess the necessary strength to meet safety standards and therefore are not able to replace steel in the automotive body. Significant weight savings could be achieved if steel components are replaced with aluminum. Current aerospace alloys are not weldable, requiring machining of large pieces that are then riveted together. If an aerospace alloy could be friction stir welded, smaller pieces could be welded, reducing material waste. Using a systems approach for materials design, property goals are set from performance objectives. From previous research and computational predictions, a structure is designed for a prototype alloy containing dynamic precipitates to readily dissolve and re-precipitate and high stability precipitates to resist dissolution and coarsening in the weld region. It is found that a Ag modified Al-3.9Mg-0.04Cu (at. %) alloy enhanced the rate and magnitude of hardening during ageing, both beneficial effects for dynamic precipitation. In the same alloy, ageing at 350°C results in hardening from Al 3(Sc,Zr) precipitates. Efforts to effectively precipitate both populations simultaneously are unsuccessful. The Al3(Sc,Zr) precipitation hardened prototype is friction stir processed and no weak zones are found in the weld hardness profile. An aerospace alloy design is proposed, utilizing the dual precipitate structure shown in the prototype. The automotive alloy is designed using a basic strength model with parameters determined from the initial prototype alloy analysis. After ageing to different conditions, the alloy is put through a simulated heat affected zone thermal cycle with a computer controlled induction heater. The aged samples lose hardness from the weld cycle but recover hardness from a post weld heat treatment. Atom probe tomography and transmission electron microscopy are used to characterize the composition, size, and phase fraction evolution for the automotive alloy strengthening precipitates. It is determined that the dominant precipitate at peak hardness is a metastable T' phase. The automotive alloy is friction stir processed and found to lose hardness in the heat affected zones surrounding the nugget. A post weld heat treatment nearly recovers the heat affected zones to base hardness. The post weld heat treatment is compatible with the current automotive paint bake step, showing design for processability. Tensile tests confirm the base alloy strength meets the automotive strength goal.

Friction Stir Welding Development at NASA, Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

McGill, Preston; Gentz, Steve (Technical Monitor)

2001-01-01

Friction stir welding (FSW) is a solid state process that pan be used to join materials without melting. The process was invented by The Welding Institute (TWI), Cambridge, England. Friction stir welding exhibits several advantages over fusion welding in that it produces welds with fewer defects and higher joint efficiency and is capable of joining alloys that are generally considered non-weldable with a fusion weld process. In 1994, NASA-Marshall began collaborating with TWI to transform FSW from a laboratory curiosity to a viable metal joining process suitable for manufacturing hardware. While teamed with TWI, NASA-Marshall began its own FSW research and development effort to investigate possible aerospace applications for the FSW process. The work involved nearly all aspects of FSW development, including process modeling, scale-up issues, applications to advanced materials and development of tooling to use FSW on components of the Space Shuttle with particular emphasis on aluminum tanks. The friction stir welding process involves spinning a pin-tool at an appropriate speed, plunging it into the base metal pieces to be joined, and then translating it along the joint of the work pieces. In aluminum alloys the rotating speed typically ranges from 200 to 400 revolutions per minute and the translation speed is approximately two to five inches per minute. The pin-tool is inserted at a small lead angle from the axis normal to the work piece and requires significant loading along the axis of the tool. An anvil or reaction structure is required behind the welded material to react the load along the axis of the pin tool. The process requires no external heat input, filler material, protective shielding gas or inert atmosphere typical of fusion weld processes. The FSW solid-state weld process has resulted in aluminum welds with significantly higher strengths, higher joint efficiencies and fewer defects than fusion welds used to join similar alloys.

Comparative study on the welded structure fatigue strength assessment method

NASA Astrophysics Data System (ADS)

Hu, Tao

2018-04-01

Due to the welding structure is widely applied in various industries, especially the pressure container, motorcycle, automobile, aviation, ship industry, such as large crane steel structure, so for welded structure fatigue strength evaluation is particularly important. For welded structure fatigue strength evaluation method mainly has four kinds of, the more from the use of two kinds of welded structure fatigue strength evaluation method, namely the nominal stress method and the hot spot stress evaluation method, comparing from its principle, calculation method for the process analysis and research, compare the similarities and the advantages and disadvantages, the analysis of practical engineering problems to provide the reference for every profession and trade, as well as the future welded structure fatigue strength and life evaluation method put forward outlook.

Portable Weld Tester.

ERIC Educational Resources Information Center

Eckert, Douglas

This training manual, which was developed for employees of an automotive plant, is designed to teach trainees to operate a portable weld tester (Miyachi MM-315). In chapter 1, the weld tester's components are illustrated and described, and the procedure for charging its batteries is explained. Chapter 2 illustrates the weld tester's parts,…

Capillary flow weld-bonding

NASA Technical Reports Server (NTRS)

Vaughan, R. W.; Jones, R. J. (Inventor)

1976-01-01

The invention of a weld-bonding technique for titanium plates was described. This involves fastening at least two plates of titanium together using spot-welding and applying a bead of adhesive along the edge of the resistance spot-welded joint which upon heating, flows and fills the separation between the joint components.

Innovative Tools Advance Revolutionary Weld Technique

NASA Technical Reports Server (NTRS)

2009-01-01

The iconic, orange external tank of the space shuttle launch system not only contains the fuel used by the shuttle s main engines during liftoff but also comprises the shuttle s backbone, supporting the space shuttle orbiter and solid rocket boosters. Given the tank s structural importance and the extreme forces (7.8 million pounds of thrust load) and temperatures it encounters during launch, the welds used to construct the tank must be highly reliable. Variable polarity plasma arc welding, developed for manufacturing the external tank and later employed for building the International Space Station, was until 1994 the best process for joining the aluminum alloys used during construction. That year, Marshall Space Flight Center engineers began experimenting with a relatively new welding technique called friction stir welding (FSW), developed in 1991 by The Welding Institute, of Cambridge, England. FSW differs from traditional fusion welding in that it is a solid-state welding technique, using frictional heat and motion to join structural components without actually melting any of the material. The weld is created by a shouldered pin tool that is plunged into the seam of the materials to be joined. The tool traverses the line while rotating at high speeds, generating friction that heats and softens but does not melt the metal. (The heat produced approaches about 80 percent of the metal s melting temperature.) The pin tool s rotation crushes and stirs the plasticized metal, extruding it along the seam as the tool moves forward. The material cools and consolidates, resulting in a weld with superior mechanical properties as compared to those weld properties of fusion welds. The innovative FSW technology promises a number of attractive benefits. Because the welded materials are not melted, many of the undesirables associated with fusion welding porosity, cracking, shrinkage, and distortion of the weld are minimized or avoided. The process is more energy efficient, safe (no toxic smoke or shielding gas, liquid metal splatter, arcing, dangerous voltage, or radiation), and environmentally sound (no consumables, fumes, or noise) than fusion welding. Under computer control, an automated FSW machine can create welds with high reproducibility, improving efficiency and overall quality of manufactured materials. The process also allows for welding dissimilar metals as well as those metals considered to be "unweldable" such as the 7xxx series aluminum alloys. Its effectiveness and versatility makes FSW useful for aerospace, rail, automotive, marine, and military applications. A downside to FSW, however, is the keyhole opening left in the weld when the FSW pin tool exits the weld joint. This is a significant problem when using the FSW process to join circumferential structures such as pipes and storage containers. Furthermore, weld joints that taper in material thickness also present problems when using the conventional FSW pin tool, because the threaded pin rotating within the weld joint material is a fixed length. There must be capability for the rotating pin to both increase and decrease in length in real time while welding the tapered material. (Both circumferential and tapered thickness weldments are found in the space shuttle external tank.) Marshall engineers addressed both the keyhole and tapered material thickness problems by developing the auto-adjustable pin tool. This unique piece of equipment automatically withdraws the pin into the tool s shoulder for keyhole closeout. In addition, the auto-adjustable pin tool retracts, or shortens, the rotating pin while welding a weld joint that tapers from one thickness to a thinner thickness. This year, the impact of the Marshall innovation was recognized with an "Excellence in Technology Transfer Award" from the Federal Laboratory Consortium.

Residual stress determination in an overlay dissimilar welded pipe by neutron diffraction

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

Woo, Wan Chuck; Em, Vyacheslav; Hubbard, Camden R

2011-01-01

Residual stresses were determined through the thickness of a dissimilar weld overlay pipe using neutron diffraction. The specimen has a complex joining structure consisting of a ferritic steel (SA508), austenitic steel (F316L), Ni-based consumable (Alloy 182), and overlay of Ni-base superalloy (Alloy 52M). It simulates pressurized nozzle components, which have been a critical issue under the severe crack condition of nuclear power reactors. Two neutron diffractometers with different spatial resolutions have been utilized on the identical specimen for comparison. The macroscopic 'stress-free' lattice spacing (d{sub o}) was also obtained from both using a 2-mm width comb-like coupon. The results showmore » significant changes in residual stresses from tension (300-400 MPa) to compression (-600 MPa) through the thickness of the dissimilar weld overlay pipe specimen.« less

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

Five-Axis Ultrasonic Additive Manufacturing for Nuclear Component Manufacture

NASA Astrophysics Data System (ADS)

Hehr, Adam; Wenning, Justin; Terrani, Kurt; Babu, Sudarsanam Suresh; Norfolk, Mark

2017-03-01

Ultrasonic additive manufacturing (UAM) is a three-dimensional metal printing technology which uses high-frequency vibrations to scrub and weld together both similar and dissimilar metal foils. There is no melting in the process and no special atmosphere requirements are needed. Consequently, dissimilar metals can be joined with little to no intermetallic compound formation, and large components can be manufactured. These attributes have the potential to transform manufacturing of nuclear reactor core components such as control elements for the High Flux Isotope Reactor at Oak Ridge National Laboratory. These components are hybrid structures consisting of an outer cladding layer in contact with the coolant with neutron-absorbing materials inside, such as neutron poisons for reactor control purposes. UAM systems are built into a computer numerical control (CNC) framework to utilize intermittent subtractive processes. These subtractive processes are used to introduce internal features as the component is being built and for net shaping. The CNC framework is also used for controlling the motion of the welding operation. It is demonstrated here that curved components with embedded features can be produced using a five-axis code for the welder for the first time.

Five-axis ultrasonic additive manufacturing for nuclear component manufacture

DOE PAGES

Hehr, Adam; Wenning, Justin; Terrani, Kurt A.; ...

2016-01-01

Ultrasonic additive manufacturing (UAM) is a three-dimensional metal printing technology which uses high-frequency vibrations to scrub and weld together both similar and dissimilar metal foils. There is no melting in the process and no special atmosphere requirements are needed. Consequently, dissimilar metals can be joined with little to no intermetallic compound formation, and large components can be manufactured. These attributes have the potential to transform manufacturing of nuclear reactor core components such as control elements for the High Flux Isotope Reactor at Oak Ridge National Laboratory. These components are hybrid structures consisting of an outer cladding layer in contact withmore » the coolant with neutron-absorbing materials inside, such as neutron poisons for reactor control purposes. UAM systems are built into a computer numerical control (CNC) framework to utilize intermittent subtractive processes. These subtractive processes are used to introduce internal features as the component is being built and for net shaping. The CNC framework is also used for controlling the motion of the welding operation. Lastly, it is demonstrated here that curved components with embedded features can be produced using a five-axis code for the welder for the first time.« less

Experiments and simulation for 6061-T6 aluminum alloy resistance spot welded lap joints

NASA Astrophysics Data System (ADS)

Florea, Radu Stefanel

This comprehensive study is the first to quantify the fatigue performance, failure loads, and microstructure of resistance spot welding (RSW) in 6061-T6 aluminum (Al) alloy according to welding parameters and process sensitivity. The extensive experimental, theoretical and simulated analyses will provide a framework to optimize the welding of lightweight structures for more fuel-efficient automotive and military applications. The research was executed in four primary components. The first section involved using electron back scatter diffraction (EBSD) scanning, tensile testing, laser beam profilometry (LBP) measurements, and optical microscopy(OM) images to experimentally investigate failure loads and deformation of the Al-alloy resistance spot welded joints. Three welding conditions, as well as nugget and microstructure characteristics, were quantified according to predefined process parameters. Quasi-static tensile tests were used to characterize the failure loads in specimens based upon these same process parameters. Profilometer results showed that increasing the applied welding current deepened the weld imprints. The EBSD scans revealed the strong dependency between the grain sizes and orientation function on the process parameters. For the second section, the fatigue behavior of the RSW'ed joints was experimentally investigated. The process optimization included consideration of the forces, currents, and times for both the main weld and post-heating. Load control cyclic tests were conducted on single weld lap-shear joint coupons to characterize the fatigue behavior in spot welded specimens. Results demonstrate that welding parameters do indeed significantly affect the microstructure and fatigue performance for these welds. The third section comprised residual strains of resistance spot welded joints measured in three different directions, denoted as in-plane longitudinal, in-plane transversal, and normal, and captured on the fusion zone, heat affected zone and base metal of the joints. Neutron diffraction results showed residual stresses in the weld are approximately 40% lower than the yield strength of the parent material, with maximum variation occurring in the vertical position of the specimen because of the orientation of electrode clamping forces that produce a non-uniform solidification pattern. In the final section a theoretical continuum modeling framework for 6061-T6 aluminum resistance spot welded joints is presented.

Method and design for externally applied laser welding of internal connections in a high power electrochemical cell

DOEpatents

Martin, Charles E; Fontaine, Lucien; Gardner, William H

2014-01-21

An electrochemical cell includes components that are welded from an external source after the components are assembled in a cell canister. The cell canister houses electrode tabs and a core insert. An end cap insert is disposed opposite the core insert. An external weld source, such as a laser beam, is applied to the end cap insert, such that the end cap insert, the electrode tabs, and the core insert are electrically coupled by a weld which extends from the end cap insert to the core insert.

Predicting Welding Distortion in a Panel Structure with Longitudinal Stiffeners Using Inherent Deformations Obtained by Inverse Analysis Method

PubMed Central

Liang, Wei; Murakawa, Hidekazu

2014-01-01

Welding-induced deformation not only negatively affects dimension accuracy but also degrades the performance of product. If welding deformation can be accurately predicted beforehand, the predictions will be helpful for finding effective methods to improve manufacturing accuracy. Till now, there are two kinds of finite element method (FEM) which can be used to simulate welding deformation. One is the thermal elastic plastic FEM and the other is elastic FEM based on inherent strain theory. The former only can be used to calculate welding deformation for small or medium scale welded structures due to the limitation of computing speed. On the other hand, the latter is an effective method to estimate the total welding distortion for large and complex welded structures even though it neglects the detailed welding process. When the elastic FEM is used to calculate the welding-induced deformation for a large structure, the inherent deformations in each typical joint should be obtained beforehand. In this paper, a new method based on inverse analysis was proposed to obtain the inherent deformations for weld joints. Through introducing the inherent deformations obtained by the proposed method into the elastic FEM based on inherent strain theory, we predicted the welding deformation of a panel structure with two longitudinal stiffeners. In addition, experiments were carried out to verify the simulation results. PMID:25276856

Predicting welding distortion in a panel structure with longitudinal stiffeners using inherent deformations obtained by inverse analysis method.

PubMed

Liang, Wei; Murakawa, Hidekazu

2014-01-01

Welding-induced deformation not only negatively affects dimension accuracy but also degrades the performance of product. If welding deformation can be accurately predicted beforehand, the predictions will be helpful for finding effective methods to improve manufacturing accuracy. Till now, there are two kinds of finite element method (FEM) which can be used to simulate welding deformation. One is the thermal elastic plastic FEM and the other is elastic FEM based on inherent strain theory. The former only can be used to calculate welding deformation for small or medium scale welded structures due to the limitation of computing speed. On the other hand, the latter is an effective method to estimate the total welding distortion for large and complex welded structures even though it neglects the detailed welding process. When the elastic FEM is used to calculate the welding-induced deformation for a large structure, the inherent deformations in each typical joint should be obtained beforehand. In this paper, a new method based on inverse analysis was proposed to obtain the inherent deformations for weld joints. Through introducing the inherent deformations obtained by the proposed method into the elastic FEM based on inherent strain theory, we predicted the welding deformation of a panel structure with two longitudinal stiffeners. In addition, experiments were carried out to verify the simulation results.

Laser-GMA Hybrid Pipe Welding System

DTIC Science & Technology

2007-11-01

Experimental Results.................................................................................................34 Autogenous Laser Welds...APPENDIX B. Training Manual – Overview of System Components and Software...................... APPENDIX C. NASSCO...17. Autogenous laser welds in different joint configurations (10 mm thick mild steel, 5 mm land

Improvement of the reliability of laser beam microwelding as interconnection technique

NASA Astrophysics Data System (ADS)

Glasmacher, Mathias; Pucher, Hans-Joerg; Geiger, Manfred

1996-04-01

The requirements of actual trends for joining within modern electronics production can be met with the technique of laser beam micro welding, which is the topic of this paper. Thereby component leads are welded directly to the conducting tracks of the circuit board. This technique is not limited to electronics, because fine mechanical parts can be joined with the same equipment, too. The advantages as high temperature strength, reduced manufacturing time and simplified material separation at the end of the life cycle are noted. Furthermore the drawbacks of laser beam micro welding as a competitive joining technique to soldering are discussed. The reasons for the unstable process behavior of different welding scenarios can be understood by taking the changes of some process parameters into account. Since the process reliability can be improved by a proper process design as well as by closed-loop-control, results of finite element calculations of the temperature field as well as experimental setup for the determination of the melting point are presented. Future work is stated to spread the applicability of this joining technique as well as to develop an on-line control for high performance welding of locally restricted structures.

Friction Stir Weld System for Welding and Weld Repair

NASA Technical Reports Server (NTRS)

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

2001-01-01

A friction stir weld system for welding and weld repair has a base foundation unit connected to a hydraulically controlled elevation platform and a hydraulically adjustable pin tool. The base foundation unit may be fixably connected to a horizontal surface or may be connected to a mobile support in order to provide mobility to the friction stir welding system. The elevation platform may be utilized to raise and lower the adjustable pin tool about a particular axis. Additional components which may be necessary for the friction stir welding process include back plate tooling, fixturing and/or a roller mechanism.

Effects of Pulse Parameters on Weld Microstructure and Mechanical Properties of Extra Pulse Current Aided Laser Welded 2219 Aluminum Alloy Joints.

PubMed

Zhang, Xinge; Li, Liqun; Chen, Yanbin; Yang, Zhaojun; Chen, Yanli; Guo, Xinjian

2017-09-15

In order to expand the application range of laser welding and improve weld quality, an extra pulse current was used to aid laser-welded 2219 aluminum alloy, and the effects of pulse current parameters on the weld microstructure and mechanical properties were investigated. The effect mechanisms of the pulse current interactions with the weld pool were evaluated. The results indicated that the coarse dendritic structure in the weld zone changed to a fine equiaxed structure using an extra pulse current, and the pulse parameters, including medium peak current, relatively high pulse frequency, and low pulse duty ratio benefited to improving the weld structure. The effect mechanisms of the pulse current were mainly ascribed to the magnetic pinch effect, thermal effect, and electromigration effect caused by the pulse current. The effect of the pulse parameters on the mechanical properties of welded joints were consistent with that of the weld microstructure. The tensile strength and elongation of the optimal pulse current-aided laser-welded joint increased by 16.4% and 105%, respectively, compared with autogenous laser welding.

Effects of Pulse Parameters on Weld Microstructure and Mechanical Properties of Extra Pulse Current Aided Laser Welded 2219 Aluminum Alloy Joints

PubMed Central

Zhang, Xinge; Li, Liqun; Chen, Yanbin; Yang, Zhaojun; Chen, Yanli; Guo, Xinjian

2017-01-01

In order to expand the application range of laser welding and improve weld quality, an extra pulse current was used to aid laser-welded 2219 aluminum alloy, and the effects of pulse current parameters on the weld microstructure and mechanical properties were investigated. The effect mechanisms of the pulse current interactions with the weld pool were evaluated. The results indicated that the coarse dendritic structure in the weld zone changed to a fine equiaxed structure using an extra pulse current, and the pulse parameters, including medium peak current, relatively high pulse frequency, and low pulse duty ratio benefited to improving the weld structure. The effect mechanisms of the pulse current were mainly ascribed to the magnetic pinch effect, thermal effect, and electromigration effect caused by the pulse current. The effect of the pulse parameters on the mechanical properties of welded joints were consistent with that of the weld microstructure. The tensile strength and elongation of the optimal pulse current-aided laser-welded joint increased by 16.4% and 105%, respectively, compared with autogenous laser welding. PMID:28914825

Repair welding of gamma titanium aluminide castings

NASA Astrophysics Data System (ADS)

Kelly, T. J.

This paper examines the GTA repair welding of cast Ti-48Al-2Cr-2Nb gamma titanium aluminide. Pre-weld heat treatment, preheat and welding parameters are evaluated and discussed. A wide range of GTAW parameters is demonstrated for use with this alloy and the resulting weld structure is examined. The effects of postweld heat treatment on the structure of the weld deposit is also determined.

A Brief Introduction to the Theory of Friction Stir Welding

NASA Technical Reports Server (NTRS)

Nunes, Arthur C., Jr.

2008-01-01

Friction stir welding (FSW) is a solid state welding process invented in 1991 at The Welding Institute in the United Kingdom. A weld is made in the FSW process by translating a rotating pin along a weld seam so as to stir the sides of the seam together. FSW avoids deleterious effects inherent in melting and is already an important welding process for the aerospace industry, where welds of optimal quality are demanded. The structure of welds determines weld properties. The structure of friction stir welds is determined by the flow field in the weld metal in the vicinity of the weld tool. A simple kinematic model of the FSW flow field developed at Marshall Space Flight Center, which enables the basic features of FSW microstructure to be understood and related to weld process parameters and tool design, is explained.

Introduction to Construction Welding. Instructor Edition. Introduction to Construction Series.

ERIC Educational Resources Information Center

Oklahoma State Dept. of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.

This instructor's guide contains the materials required to teach a competency-based introductory course in construction welding to students who have chosen to explore careers in construction. It contains three units: welding materials, welding tools, and applied skills. Each instructional unit includes some or all of the basic components of a unit…

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

Klimenov, V. A., E-mail: klimenov@tpu.ru; National Research Tomsk Polytechnic University, 30 Lenin Av., Tomsk, 634050; Kurgan, K. A., E-mail: kirill-k2.777@mail.ru

The structure of weld joints of the titanium alloy Ti-6Al-4V in the initial ultrafine-grained state, obtained by resistance spot welding, is studied using the optical and scanning electron microscopy method and the X-ray structure analysis. The carried out studies show the relationship of the metal structure in the weld zone with main joint zones. The structure in the core zone and the heat affected zone is represented by finely dispersed grains of needle-shaped martensite, differently oriented in these zones. The change in the microhardness in the longitudinal section of the weld joint clearly correlates with structural changes during welding.

Investigation on the Effect of Initial Welding Imperfection on Fatigue strength of Tubular Member by FEM

NASA Astrophysics Data System (ADS)

Chang, Kyong-Ho; Shin, Wang Sub; Nguyen Van Vuong, Do; Lee, Chin Hyeong

2018-04-01

Steel tube structure is used for steel structure such as offshore platform, bridges and so on. Also, all circular members of tubular structures are mainly connected by welding. When the steel tubular structures are subjected to repeated loading, not only the load carrying capacity is reduced but also fatigue cracks may develop at the joint part of steel tubular members which are connected by welding. Carrying out welding, welding initial imperfection such as welding deformation and residual stress are inevitably generated at weld part. It was well known that the effect of welding residual and welding deformation on fatigue strength. However, It’s not clear which affects fatigue strength more. However, it’s difficult to clear the effect on fatigue strength by experiment. To clarify these effect, fatigue analysis was carried out by FEM which is based on continuum damage mechanics. On the other hand, coupled three-dimensional non-steady heat conduction analysis, and the thermal elastic-plastic analysis was carried out to reproduce the initial weld state of tubular member. From the result, not only the fatigue strength of welded tubular member but also the fatigue life could be found by FEM fatigue analysis.

Reactor Materials Program - Baseline Material Property Handbook - Mechanical Properties of 1950's Vintage Stainless Steel Weldment Components, Task Number 89-23-A-1

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

Stoner, K.J.

1999-11-05

The Process Water System (primary coolant) piping of the nuclear production reactors constructed in the 1950''s at Savannah River Site is comprised primarily of Type 304 stainless steel with Type 308 stainless steel weld filler. A program to measure the mechanical properties of archival PWS piping and weld materials (having approximately six years of service at temperatures between 25 and 100 degrees C) has been completed. The results from the mechanical testing has been synthesized to provide a mechanical properties database for structural analyses of the SRS piping.

73rd American Welding Society annual meeting

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

Not Available

1992-01-01

The volume includes the abstracts of papers presented at the 73rd American Welding Society Annual Meeting. Detailed summaries are given for 118 technical sessions papers discussing computer and control applications in welding, stainless steel, nickel and nickel alloys, weld metal microstructure, shipbuilding, consumables, structural welding, investigations in arc welding and cutting, arc welding processes, weldability testing, piping and tubing, high energy beam welding processes, welding metallurgy of structural steels, new applications, weld metal behavior, NDT certification, aluminum welding, submerged arc welding, modeling studies, resistance welding, friction welding, and safety and health. The 23rd International AWS Brazing and Soldering Conference wasmore » also held during this meeting. The topics presented in 24 papers included recent developments in soldering technology, brazing of stainless steel, brazing of ceramics and nickel material, filler metal developments for torch brazing, and developments in diffusion and induction brazing.« less

Parametric study in weld mismatch of longitudinally welded SSME HPFTP inlet

NASA Technical Reports Server (NTRS)

Min, J. B.; Spanyer, K. L.; Brunair, R. M.

1991-01-01

Welded joints are an essential part of pressure vessels such as the Space Shuttle Main Engine (SSME) Turbopumps. Defects produced in the welding process can be detrimental to weld performance. Recently, review of the SSME high pressure fuel turbopump (HPFTP) titanium inlet x rays revealed several weld discrepancies such as penetrameter density issues, film processing discrepancies, weld width discrepancies, porosity, lack of fusion, and weld offsets. Currently, the sensitivity of welded structures to defects is of concern. From a fatigue standpoint, weld offset may have a serious effect since local yielding, in general, aggravates cyclic stress effects. Therefore, the weld offset issue is considered. Using the finite element method and mathematical formulations, parametric studies were conducted to determine the influence of weld offsets and a variation of weld widths in longitudinally welded cylindrical structures with equal wall thickness on both sides of the joint. From the study, the finite element results and theoretical solutions are presented.

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.

The seam visual tracking method for large structures

NASA Astrophysics Data System (ADS)

Bi, Qilin; Jiang, Xiaomin; Liu, Xiaoguang; Cheng, Taobo; Zhu, Yulong

2017-10-01

In this paper, a compact and flexible weld visual tracking method is proposed. Firstly, there was the interference between the visual device and the work-piece to be welded when visual tracking height cannot change. a kind of weld vision system with compact structure and tracking height is researched. Secondly, according to analyze the relative spatial pose between the camera, the laser and the work-piece to be welded and study with the theory of relative geometric imaging, The mathematical model between image feature parameters and three-dimensional trajectory of the assembly gap to be welded is established. Thirdly, the visual imaging parameters of line structured light are optimized by experiment of the weld structure of the weld. Fourth, the interference that line structure light will be scatters at the bright area of metal and the area of surface scratches will be bright is exited in the imaging. These disturbances seriously affect the computational efficiency. The algorithm based on the human eye visual attention mechanism is used to extract the weld characteristics efficiently and stably. Finally, in the experiment, It is verified that the compact and flexible weld tracking method has the tracking accuracy of 0.5mm in the tracking of large structural parts. It is a wide range of industrial application prospects.

Effects of various conditions in cold-welding of copper nanowires: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Zhou, Hongjian; Wu, Wen-ping; Wu, Runni; Hu, Guoming; Xia, Re

2017-11-01

Cold-welding possesses such desirable environment as low temperature and low applied stress, thus becoming the prime candidate for nanojointing and nanoassembly techniques. To explore the welding mechanism of nanoscale structures, here, molecular dynamics was performed on copper nanowires under different welding conditions and various original characteristics to obtain an atomic-level depiction of their cold-welding behavior. By analyzing the mechanical properties of as-welded nanowires, the relations between welding quality and welding variables are revealed and identified. This comparison study will be of great importance to future mechanical processing and structural assembly of metallic nanowires.

High-Powered, Ultrasonically Assisted Thermal Stir Welding

NASA Technical Reports Server (NTRS)

Ding, Robert

2013-01-01

This method is a solid-state weld process capable of joining metallic alloys without melting. The weld workpieces to be joined by thermal stir welding (TSW) are drawn, by heavy forces, between containment plates past the TSW stir tool that then causes joining of the weld workpiece. TSW is similar to friction stir welding (FSW) in that material is heated into a plastic state (not melted) and stirred using a stir rod. The FSW pin tool is an integrated geometrical structure consisting of a large-diameter shoulder, and a smaller-diameter stir pin protruding from the shoulder. When the pin is plunged into a weld workpiece, the shoulder spins on the surface of the weld workpiece, thus inducing frictional heat into the part. The pin stirs the fraying surfaces of the weld joint, thus joining the weld workpiece into one structure. The shoulder and stir pin of the FSW pin tool must rotate together at a desired rotational speed. The induced frictional energy control and stir pin control of the pin tool cannot be de-coupled. The two work as one integrated unit. TSW, on the other hand, de-couples the heating and stirring of FSW, and allows for independent control of each process element. A uniquely designed induction coil heats the weld workpiece to a desired temperature, and once heated, the part moves into a stir rod whose RPM is also independently controlled. As the weld workpiece moves into the stir rod, the piece is positioned, or sandwiched, between upper and lower containment plates. The plate squeezes together, thus compressing the upper and lower surfaces of the weld workpiece. This compressive force, also called consolidation force, consolidates the plastic material within the weld nugget material as it is being stirred by the stir rod. The stir rod is positioned through the center of the top containment plate and protrudes midway through the opposite lower containment plate where it is mechanically captured. The upper and lower containment plates are separated by a distance equal to the thickness of the material being welded. The TSW process can be significantly improved by reducing the draw forces. This can be achieved by reducing the friction forces between the weld workpieces and the containment plates. High-power ultrasonic (HPU) vibrations of the containment plates achieve friction reduction in the TSW process. Furthermore, integration of the HPU energy into the TSW stir rod can increase tool life of the stir rod, and can reduce shear forces to which the stir rod is subjected during the welding process. TSW has been used to successfully join 0.500-in (˜13-mm) thick commercially pure (CP) titanium, titanium 6AL- 4V, and titanium 6AL-4V ELI in weld joint lengths up to 9 ft (˜2.75-m) long. In addition, the TSW process was used to fabricate a sub-scale hexagonally shaped gun turret component for the U.S. Navy. The turret is comprised of six 0.5000-in (˜13-mm) thick angled welds. Each angled weld joint was prepared by machining the mating surfaces to 120deg. The angled weld joint was then fixtured using an upper and lower containment plate of the same geometry of the angled weld joint. The weld joint was then stirred by the stir rod as it and the upper and lower containment plates traverse through the angled joint prep.

Properties of the welded joints of manganese steel made by low-frequency pulsed arc welding

NASA Astrophysics Data System (ADS)

Saraev, Yu. N.; Bezborodov, V. P.; Gladovskii, S. V.; Golikov, N. I.

2017-04-01

The structure, the mechanical properties, the impact toughness, and the fracture mechanisms of the welded joints made of steel 09G2S plates by direct current welding and pulsed arc welding with a modulated arc current in the frequency range 0.25-5.0 Hz are studied. The application of low-frequency pulsed arc welding allowed us to form welded joints with a fine-grained structure in the weld metal and the heat-affected zone and to achieve a higher impact toughness and a longer cyclic fatigue life as compared to the welded joints fabricated by direct current welding. The achieved effect manifests itself over the entire testing range from 20 to-60°C.

Study of the ultraviolet emission of the electrode coatings of arc welding.

PubMed

Garcia-Guinea, J; Correcher, V; Lombardero, M; Gonzalez-Martin, R

2004-08-01

The optical emission properties of several minerals components employed in electrode coatings of arc welding have been investigated. The X-ray diffraction analysis shows that the composition of 14 commercial electrode coatings collected from different countries (Spain, France, UK, Poland, Argentina and Germany), consists of quartz, calcite, sodium and potassium rich feldspars, muscovite and rutile. The natural thermal stimulated luminescence (TSL) of these mineral phases, measured in the range of 200-800 nm at different temperatures (from room temperature to 400 degrees C) displays UV-A (wavelengths of 320 nm to 400 nm) and UV-B (from 280 nm to 320 nm) emissions, with the exception of rutile. The UV-B radiation, commonly described as the most dangerous form of radiation to human life, is here associated with structural defects in the crystallographic lattice of the mineral components of electrode coatings.

Temperature Histories of Structural Steel Laser and Hybrid Laser-GMA Welds Calculated Using Multiple Constraints

DTIC Science & Technology

2015-12-10

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--15-9665 Temperature Histories of Structural Steel Laser and Hybrid Laser-GMA Welds ...NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Temperature Histories of Structural Steel Laser and Hybrid Laser-GMA Welds Calculated Using Multiple...structures. These analyses provide parametric representations of weld temperature histories that can be adopted as input data to various types of

Temperature Histories of Structural Steel Laser and Hybrid Laser-GMA Welds Calculated Using Multiple Constraints

DTIC Science & Technology

2015-12-10

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--15-9665 Temperature Histories of Structural Steel Laser and Hybrid Laser-GMA Welds ...NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Temperature Histories of Structural Steel Laser and Hybrid Laser-GMA Welds Calculated Using Multiple...202) 767-2601 Inverse thermal analyses of structural steel deep-penetration welds are presented. These analyses employ a methodology that is in terms of

Theoretical prediction of welding distortion in large and complex structures

NASA Astrophysics Data System (ADS)

Deng, De-An

2010-06-01

Welding technology is widely used to assemble large thin plate structures such as ships, automobiles, and passenger trains because of its high productivity. However, it is impossible to avoid welding-induced distortion during the assembly process. Welding distortion not only reduces the fabrication accuracy of a weldment, but also decreases the productivity due to correction work. If welding distortion can be predicted using a practical method beforehand, the prediction will be useful for taking appropriate measures to control the dimensional accuracy to an acceptable limit. In this study, a two-step computational approach, which is a combination of a thermoelastic-plastic finite element method (FEM) and an elastic finite element with consideration for large deformation, is developed to estimate welding distortion for large and complex welded structures. Welding distortions in several representative large complex structures, which are often used in shipbuilding, are simulated using the proposed method. By comparing the predictions and the measurements, the effectiveness of the two-step computational approach is verified.

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.

Microstructure, crystallographic texture and mechanical properties of friction stir welded AA2017A

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

Ahmed, M.M.Z., E-mail: mohamed_ahmed4@s-petrol.suez.edu.eg; Department of Metallurgical and Materials Engineering, Suez Canal University, Suez 43721; Wynne, B.P.

2012-02-15

In this study a thick section (20 mm) friction stir welded AA2017A-T451 has been characterized in terms of microstructure, crystallographic texture and mechanical properties. For microstructural analysis both optical and scanning electron microscopes have been used. A detailed crystallographic texture analysis has been carried out using the electron back scattering diffraction technique. Crystallographic texture has been examined in both shoulder and probe affected regions of the weld NG. An entirely weak texture is observed at the shoulder affected region which is mainly explained by the effect of the sequential multi pass deformation experienced by both tool probe and tool shoulder.more » The texture in the probe dominated region at the AS side of the weld is relatively weak but still assembles the simple shear texture of FCC metals with B/B{sup Macron} and C components existing across the whole map. However, the texture is stronger at the RS than at the AS of the weld, mainly dominated byB/B{sup Macron} components and with C component almost absent across the map. An alternating bands between (B) components and (B{sup Macron }) component are observed only at the AS side of the weld. - Highlights: Black-Right-Pointing-Pointer Detailed investigation of microstructure and crystallographic texture. Black-Right-Pointing-Pointer The grain size is varied from the top to the bottom of the NG. Black-Right-Pointing-Pointer An entirely weak texture is observed at the shoulder affected region. Black-Right-Pointing-Pointer The texture in the probe affected region is dominated by simple shear texture.« less

Automated Laser Ultrasonic Testing (ALUT) of Hybrid Arc Welds for Pipeline Construction, #272

DOT National Transportation Integrated Search

2009-12-22

One challenge in developing new gas reserves is the high cost of pipeline construction. Welding costs are a major component of overall construction costs. Industry continues to seek advanced pipeline welding technologies to improve productivity and s...

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.

Analysis of Solid State Bonding in the Extrusion Process of Magnesium Alloys --Numerical Prediction and Experimental Verification

NASA Astrophysics Data System (ADS)

Alharthi, Nabeel H.

The automotive industry developments focused on increasing fuel efficiency are accomplished by weight reduction of vehicles, which consequently results in less negative environmental impact. Usage of low density materials such as Magnesium alloys is an approach to replace heavier structural components. One of the challenges in deformation processing of Magnesium is its low formability attributed to the hexagonal close packed (hcp) crystal structure. The extrusion process is one of the most promising forming processes for Magnesium because it applies a hydrostatic compression state of stress during deformation resulting in improved workability. Many researchers have attempted to fully understand solid state bonding during deformation in different structural materials such as Aluminum, Copper and other metals and alloys. There is a lack of sufficient understanding of the extrusion welding in these materials as well as very limited knowledge on this subject for hollow profiles made from Magnesium alloys. The weld integrity and the characteristic of the welding microstructure are generally unknown. In this dissertation three related research projects are investigated by using different tools such as microstructure characterization, mechanical testing, thermo-mechanical physical simulation and finite element numerical modeling. Project 1: Microstructure characterization supported by mechanical testing of the extrusion welding regions in Magnesium alloy AM30 extrudate. The microstructure characterization was conducted using Light Optical Microscopy (LOM), in addition to LOM the electron backscattered diffraction (EBSD) technique was implemented to characterize in depth the deformed and welded microstructure. Project 2: Finite element numerical simulation of AM30 extrudate to model different process parameters and their influence on localized state variables such as strain, strain rate, temperature and normal pressure within the weld zone. Project 3: Physical simulation of the extrusion welding by using Gleeble 3500 thermo-mechanical simulator to create deformation welds in Magnesium alloy AM30 samples in compression test under various temperatures and strain rates conditions. Based on the obtained results from the performed research projects and literature review, a new qualitative criterion of extrusion welding has been introduced as contribution to the field. The criterion and its analysis have provided better understanding of material response to processing parameters and assisted in selecting the processing windows for good practices in the extrusion process. In addition, the new approach contributed to better understanding and evaluating the quality of the solid state bonding of Mg alloy. Accordingly, the criteria help to avoiding formation of potential mechanical and metallurgical imperfections.

Layer Structure of a Refractory Multilayer Ti/Al Composite After Pressure Diffusion Welding

NASA Astrophysics Data System (ADS)

Karpov, M. I.; Korzhov, V. P.; Zheltyakova, I. S.

2016-05-01

A composite refractory material with layer structure obtained by the method of pressure diffusion welding of multilayer Ti/Al packets composed of Ti- and Al-foils is studied. The welding temperature of the packets does not exceed 1200 - 1250°C. A layer structure forms in the process of interdiffusion of titanium and aluminum during welding of the packets.

Structure formation and properties of a copper-aluminum joint produced by ultrasound-assisted explosive welding

NASA Astrophysics Data System (ADS)

Kuz'min, E. V.; Peev, A. P.; Kuz'min, S. V.; Lysak, V. I.

2017-08-01

The effect of ultrasound-assisted explosive welding on the structure formation and the properties of copper-aluminum joints is studied. Ultrasound-assisted explosive welding improves the quality of formed copper-aluminum joints, i.e., enhances their strength and significantly reduces the amount of fused metal over the entire weldability range. It is shown that ultrasound-assisted explosive welding can noticeably extend the weldability range of the copper-aluminum pair to obtain equal-in-strength joints with minimum structural heterogeneity in the wide welding range.

Effect of the Grain Size of the Initial Structure of 1565chM Alloy on the Structure and Properties of the Joints Fabricated by Friction Stir Welding

NASA Astrophysics Data System (ADS)

Ovchinnikov, V. V.; Drits, A. M.; Gureeva, M. A.; Malov, D. V.

2017-12-01

The effect of the initial grain size in the structure of the aluminum 1565chM alloy on the mechanical properties of the welded joints formed by friction stir welding and on the grain size in the weld core is studied. It is shown that the design of tool and, especially, the parameters of a screw groove exert a great effect on the grain size in the weld core.

On-Site Evaluation of Large Components Using Saft and Tofd Ultrasonic Imaging

NASA Astrophysics Data System (ADS)

Spies, M.; Rieder, H.; Dillhöfer, A.

2011-06-01

This contribution addresses ultrasonic inspection and evaluation of welds in large components. An approach has been developed in order to enhance the reliability of welded ship propellers. The Synthetic Aperture Focusing Technique (SAFT) has been modified with regard to the curved surfaces and the sound attenuation of cast Ni-Al bronzes. For weld inspection in steels the Time-of-Flight Diffraction technique (TOFD) can provide additional information for specific defect orientations. Both techniques have been combined in view of the determination of defect sizes and shapes in longitudinal welds of pipes with diameters of up to 48 inches. Details on the inspection and evaluation concepts as well as experimental results are presented.

Improved Accuracy of the Inherent Shrinkage Method for Fast and More Reliable Welding Distortion Calculations

NASA Astrophysics Data System (ADS)

Mendizabal, A.; González-Díaz, J. B.; San Sebastián, M.; Echeverría, A.

2016-07-01

This paper describes the implementation of a simple strategy adopted for the inherent shrinkage method (ISM) to predict welding-induced distortion. This strategy not only makes it possible for the ISM to reach accuracy levels similar to the detailed transient analysis method (considered the most reliable technique for calculating welding distortion) but also significantly reduces the time required for these types of calculations. This strategy is based on the sequential activation of welding blocks to account for welding direction and transient movement of the heat source. As a result, a significant improvement in distortion prediction is achieved. This is demonstrated by experimentally measuring and numerically analyzing distortions in two case studies: a vane segment subassembly of an aero-engine, represented with 3D-solid elements, and a car body component, represented with 3D-shell elements. The proposed strategy proves to be a good alternative for quickly estimating the correct behaviors of large welded components and may have important practical applications in the manufacturing industry.

Microstructure and Microhardness of 17-4PH Deposited with Co-based Alloy Hardfacing Coating

NASA Astrophysics Data System (ADS)

Deng, D. W.; Zhang, C. P.; Chen, R.; Xia, H. F.

Hardfacing is widely used to improve the performance of components exposed to severe service conditions. In this paper, the surface modification was evaluated for precipitation hardening martensitic stainless steel 17-4PH deposited with Co-based alloy stellite12 by the plasma-transferred arc welding (PTAW). The microstructure and microhardness of coating and heat affected zone(HAZ) of base metal were characterized by optical microscope (OM), scanning electron scanning microscope (SEM), X-ray diffractometer and hardness tester. The results show that the interface between weld metal and base metal is favorable without pore and crack, at the same time elements diffusion is observed in the fusion area. However, as the distance from the interface increases, HAZ comprises three different microstructural zones, namely, zones of coarse overheated structures, quenching martensite and martensite, ferrite. The microhardness decreases gradually from the HAZ near interface to the base metal, except the zone of coarse overheated structures. The microhardness of the coating improves a lot and fluctuates in a definitive range, and microstructural gradient is observed including the fusion area (the planar region and the bulky dendrite in a direction perpendicular to the weld interface), the transition zone (the dendrite in a multi-direction way) and the fine grain zone near the surface in the coating (fine equiaxial structure).

Design of a welded joint for robotic, on-orbit assembly of space trusses

NASA Astrophysics Data System (ADS)

Rule, William K.

1992-12-01

In the future, some spacecraft will be so large that they must be assembled on-orbit. These spacecraft will be used for such tasks as manned missions to Mars or used as orbiting platforms for monitoring the Earth or observing the universe. Some large spacecraft will probably consist of planar truss structures to which will be attached special purpose, self-contained modules. The modules will most likely be taken to orbit fully outfitted and ready for use in heavy-lift launch vehicles. The truss members will also similarly be taken to orbit, but most unassembled. The truss structures will need to be assembled robotically because of the high costs and risks of extra-vehicular activities. Some missions will involve very large loads. To date, very few structures of any kind have been constructed in space. Two relatively simple trusses were assembled in the Space Shuttle bay in late 1985. Here the development of a design of a welded joint for on-orbit, robotic truss assembly is described. Mechanical joints for this application have been considered previously. Welded joints have the advantage of allowing the truss members to carry fluids for active cooling or other purposes. In addition, welded joints can be made more efficient structurally than mechanical joints. Also, welded joints require little maintenance (will not shake loose), and have no slop which would cause the structure to shudder under load reversal. The disadvantages of welded joints are that a more sophisticated assembly robot is required, weld flaws may be difficult to detect on-orbit, the welding process is hazardous, and welding introduces contamination to the environment. In addition, welded joints provide less structural damping than do mechanical joints. Welding on-orbit was first investigated aboard a Soyuz-6 mission in 1969 and then during a Skylab electron beam welding experiment in 1973. A hand held electron beam welding apparatus is currently being prepared for use on the MIR space station.

[Mechanical properties of weld area soldered by lasers and structural changes in hot reaction zone].

PubMed

Wu, H; Cui, Y; Mu, W

2001-05-01

To analyse and measure the welding depths and strengths of three kinds of welding materials under different laser welding conditions as well as the structural changes of the heat affected zone. Under different voltages and pulse duration three kinds of measuring sticks, including Co-Cr alloy, Ni-Cr alloy and pure titanium were welded and their strengths were compared with that of control group. At the same time, the structure of the heat-affected zone was analysed by means of the gold-phase method. The welding depth and strength of Co-Cr alloy were in direct proportion to the setting voltage, with averages of 335MPa (250V) to 573MPa(330V). At the heat-affected zone, the crystal particle was small and the end point of welding by laser bean presented the shape of the mountain peak and the interval of finger shape. The center of measuring sticks had a black zone with the circle shape. The setting voltage was in direct proportion to the welding depth of pure titanium and in inverse proportion to the welding strength with averages of 221MPa(250V) to 154MPa (330V). The crystal particle in the heat affected zone grew large and the solid phase expanded, the interval of the crystal oxidised, and the structure showed honeycomb changes. The laser welding is favourable to the welding properties of Co-Cr and Ni-Cr alloys, but its effect on the welding properties of pure titanium needs further discussion.

Hybrid/Tandem Laser-Arc Welding of Thick Low Carbon Martensitic Stainless Steel Plates =

NASA Astrophysics Data System (ADS)

Mirakhorli, Fatemeh

High efficiency and long-term life of hydraulic turbines and their assemblies are of utmost importance for the hydropower industry. Usually, hydroelectric turbine components are made of thick-walled low carbon martensitic stainless steels. The assembly of large hydroelectric turbine components has been a great challenge. The use of conventional welding processes involves typical large groove design and multi-pass welding to fill the groove which exposes the weld to a high heat input creating relatively large fusion zone and heat affected zone. The newly-developed hybrid/tandem laser-arc welding technique is believed to offer a highly competitive solution to improve the overall hydro-turbine performance by combining the high energy density and fast welding speed of the laser welding technology with the good gap bridging and feeding ability of the gas metal arc welding process to increase the productivity and reduce the consumable material. The main objective of this research work is to understand different challenges appearing during hybrid laser-arc welding (HLAW) of thick gauge assemblies of low carbon 13%Cr- 4%Ni martensitic stainless steel and find a practical solution by adapting and optimizing this relatively new welding process in order to reduce the number of welding passes necessary to fill the groove gap. The joint integrity was evaluated in terms of microstructure, defects and mechanical properties in both as-welded and post-welded conditions. A special focus was given to the hybrid and tandem laser-arc welding technique for the root pass. Based on the thickness of the low carbon martensitic stainless steel plates, this work is mainly focused on the following two tasks: • Single pass hybrid laser-arc welding of 10-mm thick low carbon martensitic stainless steel. • Multi-pass hybrid/tandem laser-arc welding of 25-mm thick martensitic stainless steel.

Out of the SHADOW: watch parts in the spotlight -- laser beam microwelding of delicate watch components

NASA Astrophysics Data System (ADS)

Kramer, Thorsten; Olowinsky, Alexander M.

2003-07-01

Conventional joining techniques like press fitting or crimping require the application of mechanical forces to the parts which, in combination with the tolerances of both parts to be joined, lead to imprecision and poor tensile strength. In contrast, laser beam micro welding provides consistent joining and high flexibility and it acts as an alternative as long as press fitting, crimping, screwing or gluing are not capable of batch production. Different parts and even different metals can be joined in a non-contact process at feed rates of up to 60 m/min and with weld seam lengths from 0.6 mm to 15.7 mm. Due to the low energy input, typically 1 J to 6 J, a weld width as small as 50 μm and a weld depth as small as 20 μm have been attained. This results in low distortion of the joined watch components. Since the first applications of laser beam micro welding of watch components showed promising results, the process has further been enhanced using the SHADOW technique. Aspects of the technique such as tensile strength, geometry and precision of the weld seam as well as the acceptance amongst the -mostly conservative- watch manufacturers have been improved.

Automated generation of weld path trajectories.

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

Sizemore, John M.; Hinman-Sweeney, Elaine Marie; Ames, Arlo Leroy

2003-06-01

AUTOmated GENeration of Control Programs for Robotic Welding of Ship Structure (AUTOGEN) is software that automates the planning and compiling of control programs for robotic welding of ship structure. The software works by evaluating computer representations of the ship design and the manufacturing plan. Based on this evaluation, AUTOGEN internally identifies and appropriately characterizes each weld. Then it constructs the robot motions necessary to accomplish the welds and determines for each the correct assignment of process control values. AUTOGEN generates these robot control programs completely without manual intervention or edits except to correct wrong or missing input data. Most shipmore » structure assemblies are unique or at best manufactured only a few times. Accordingly, the high cost inherent in all previous methods of preparing complex control programs has made robot welding of ship structures economically unattractive to the U.S. shipbuilding industry. AUTOGEN eliminates the cost of creating robot control programs. With programming costs eliminated, capitalization of robots to weld ship structures becomes economically viable. Robot welding of ship structures will result in reduced ship costs, uniform product quality, and enhanced worker safety. Sandia National Laboratories and Northrop Grumman Ship Systems worked with the National Shipbuilding Research Program to develop a means of automated path and process generation for robotic welding. This effort resulted in the AUTOGEN program, which has successfully demonstrated automated path generation and robot control. Although the current implementation of AUTOGEN is optimized for welding applications, the path and process planning capability has applicability to a number of industrial applications, including painting, riveting, and adhesive delivery.« less

76 FR 14108 - Notice of Issuance of Regulatory Guide

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-15

..., Revision 1, ``Control of Preheat Temperature for Welding of Low-Alloy Steel.'' FOR FURTHER INFORMATION... for Welding of Low-Alloy Steel,'' was issued with a temporary identification as Draft Regulatory Guide... implementing regulatory requirements related to the control of welding for low-alloy steel components during...

46 CFR 154.182 - Contiguous hull structure: Production weld test.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Contiguous hull structure: Production weld test. 154.182... Equipment Hull Structure § 154.182 Contiguous hull structure: Production weld test. If a portion of the contiguous hull structure is designed for a temperature colder than −34 °C (−30 °F) and is not part of the...

46 CFR 154.182 - Contiguous hull structure: Production weld test.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Contiguous hull structure: Production weld test. 154.182... Equipment Hull Structure § 154.182 Contiguous hull structure: Production weld test. If a portion of the contiguous hull structure is designed for a temperature colder than −34 °C (−30 °F) and is not part of the...

46 CFR 154.182 - Contiguous hull structure: Production weld test.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Contiguous hull structure: Production weld test. 154.182... Equipment Hull Structure § 154.182 Contiguous hull structure: Production weld test. If a portion of the contiguous hull structure is designed for a temperature colder than −34 °C (−30 °F) and is not part of the...

46 CFR 154.182 - Contiguous hull structure: Production weld test.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Contiguous hull structure: Production weld test. 154.182... Equipment Hull Structure § 154.182 Contiguous hull structure: Production weld test. If a portion of the contiguous hull structure is designed for a temperature colder than −34 °C (−30 °F) and is not part of the...

46 CFR 154.182 - Contiguous hull structure: Production weld test.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Contiguous hull structure: Production weld test. 154.182... Equipment Hull Structure § 154.182 Contiguous hull structure: Production weld test. If a portion of the contiguous hull structure is designed for a temperature colder than −34 °C (−30 °F) and is not part of the...

Numerical and Experimental Evaluation on the Residual Stresses of Welded Joints

NASA Astrophysics Data System (ADS)

Huh, Sun Chul; Park, Wonjo; Yang, Haesug; Jung, Haeyoung; Kim, Chuyoung

Wings for the defense industry such as fighters, missiles, and rockets should show no deformation or damage on the structure. The structures of existing wings had holes for weight reduction. The plates and frames were fixed with rivets or screws, which limited the weight reduction possible. In this study, an improvement was made in jointing methods through EB welding and laser welding. Welding strength was measured through tension testing. In addition, finite element analysis was performed for the welding process so as to deduce the optimum welding condition.

Accurate modelling of anisotropic effects in austenitic stainless steel welds

NASA Astrophysics Data System (ADS)

Nowers, O. D.; Duxbury, D. J.; Drinkwater, B. W.

2014-02-01

The ultrasonic inspection of austenitic steel welds is challenging due to the formation of highly anisotropic and heterogeneous structures post-welding. This is due to the intrinsic crystallographic structure of austenitic steel, driving the formation of dendritic grain structures on cooling. The anisotropy is manifested as both a `steering' of the ultrasonic beam and the back-scatter of energy due to the macroscopic granular structure of the weld. However, the quantitative effects and relative impacts of these phenomena are not well-understood. A semi-analytical simulation framework has been developed to allow the study of anisotropic effects in austenitic stainless steel welds. Frequency-dependent scatterers are allocated to a weld-region to approximate the coarse grain-structures observed within austenitic welds and imaged using a simulated array. The simulated A-scans are compared against an equivalent experimental setup demonstrating excellent agreement of the Signal to Noise (S/N) ratio. Comparison of images of the simulated and experimental data generated using the Total Focusing Method (TFM) indicate a prominent layered effect in the simulated data. A superior grain allocation routine is required to improve upon this.

Diffusion welding of Cassegrainian concentrator cell stack assemblies. M.S. Thesis Final Report, Jun. 1983 - Sep. 1985

NASA Technical Reports Server (NTRS)

Gangl, K. J.

1985-01-01

Development of a procedure to join the components of the Cassegrainian concentrator photovoltaic cell stack assembly was studied. Diffusion welding was selected as the most promising process, and was concentrated on exclusively. All faying surfaces were coated with silver to promote welding. The first phase of the study consisted of developing the relationship between process parameters and joint strength using silver plated steel samples and an isostatic pressure system. In the second phase, mockups of the cell stack assembly were welded in a hot isostatic press. Excellent joint strength was achieved with parameters of 350 C and 10 ksi, but the delicate GaAs component could not survive the welding cycle without cracking. The tendency towards cracking was found to be affected by both temperature and pressure. Further work will be required in the future to solve this problem.

FE Simulation Models for Hot Stamping an Automobile Component with Tailor-Welded High-Strength Steels

NASA Astrophysics Data System (ADS)

Tang, Bingtao; Wang, Qiaoling; Wei, Zhaohui; Meng, Xianju; Yuan, Zhengjun

2016-05-01

Ultra-high-strength in sheet metal parts can be achieved with hot stamping process. To improve the crash performance and save vehicle weight, it is necessary to produce components with tailored properties. The use of tailor-welded high-strength steel is a relatively new hot stamping process for saving weight and obtaining desired local stiffness and crash performance. The simulation of hot stamping boron steel, especially tailor-welded blanks (TWBs) stamping, is more complex and challenging. Information about thermal/mechanical properties of tools and sheet materials, heat transfer, and friction between the deforming material and the tools is required in detail. In this study, the boron-manganese steel B1500HS and high-strength low-alloy steel B340LA are tailor welded and hot stamped. In order to precisely simulate the hot stamping process, modeling and simulation of hot stamping tailor-welded high-strength steels, including phase transformation modeling, thermal modeling, and thermal-mechanical modeling, is investigated. Meanwhile, the welding zone of tailor-welded blanks should be sufficiently accurate to describe thermal, mechanical, and metallurgical parameters. FE simulation model using TWBs with the thickness combination of 1.6 mm boron steel and 1.2 mm low-alloy steel is established. In order to evaluate the mechanical properties of the hot stamped automotive component (mini b-pillar), hardness and microstructure at each region are investigated. The comparisons between simulated results and experimental observations show the reliability of thermo-mechanical and metallurgical modeling strategies of TWBs hot stamping process.

Effect of rhenium on the structure and properties of the weld metal of a molybdenum alloy

NASA Technical Reports Server (NTRS)

Dyachenko, V. V.; Morozov, B. P.; Tylkina, M. A.; Savitskiy, Y. M.; Nikishanov, V. V.

1984-01-01

The structure and properties of welds made in molybdenum alloy VM-1 as a function of rhenium concentrations in the weld metal were studied. Rhenium was introduced into the weld using rhenium wire and tape or wires of Mo-47Re and Mo-52Re alloys. The properties of the weld metal were studied by means of metallographic techniques, electron microscopy, X-ray analysis, and autoradiography. The plasticity of the weld metal sharply was found to increase with increasing concentration of rhenium up to 50%. During welding, a decarburization process was observed which was more pronounced at higher concentrations of rhenium.

Evaluation of the Low Heat Input Process for Weld Repair of Nickel-Base Superalloys

NASA Astrophysics Data System (ADS)

Durocher, J.; Richards, N. L.

2011-10-01

The repair of turbine blades and vanes commonly involves gas tungsten arc welding or an equivalent process, but unfortunately these components are often susceptible to heat-affected zone (HAZ) cracking during the weld repair process. This is a major problem especially in cast alloys due to their coarse-grain size and where the (Al + Ti) contents is in excess of 3-4%; vacuum brazing is also used but mainly on low stress non-rotating components such as vanes. Micro-welding has the potential to deposit small amounts of filler at low heat input levels with minimum HAZ and thus is an attractive process for depositing a quality weld. As with conventional fusion processes, the filler alloy is deposited by the generation of a low power arc between a consumable electrode and the substrate. The low heat input of this process offers unique advantages over more common welding processes such as gas tungsten arc, plasma arc, laser, and electron beam welding. In this study, the low heat input characteristic of micro-welding has been used to simulate weld repair using Inconel (IN) (Inconel and IN are trademarks of INCO Alloys International) 625, Rene (Rene is a trademark of General Electric Company) 41, Nimonic (Nimonic is a trademark of INCO Alloys International) 105 and Inconel 738LC filler alloys, to a cast Inconel 738LC substrate. The effect of micro-welding process parameters on the deposition rate, coating quality, and substrate has been investigated.

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.

76 FR 4373 - In the Matter of Certain Composite Wear Components and Welding Products Containing Same; Notice...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-25

... INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-644] In the Matter of Certain Composite Wear Components and Welding Products Containing Same; Notice of Commission Determination to Temporarily Rescind Its Limited Exclusion Order and Cease and Desist Order Entered on November 24, 2009 Pending...

Cold Spray Repair of Martensitic Stainless Steel Components

NASA Astrophysics Data System (ADS)

Faccoli, M.; Cornacchia, G.; Maestrini, D.; Marconi, G. P.; Roberti, R.

2014-12-01

The possibility of using cold spray as repair technique of martensitic stainless steel components was evaluated through laboratory investigations. An austenitic stainless steel feedstock powder was chosen, instead of soft metals powders like nickel, copper, or aluminum, used for repairing components made in light alloy or cast iron. The present study directly compares the microstructure, the residual stresses, and the micro-hardness of repairs obtained by cold spray and by TIG welding, that is commonly used as repair technique in large steel components. XRD and optical metallographic analysis of the repairs showed that cold spray offers some advantages, inducing compressive residual stresses in the repair and avoiding alterations of the interface between repair and base material. For these reasons, a heat treatment after the cold spray repair is not required to restore the base material properties, whereas a post-weld heat treatment is needed after the welding repair. Cold spray repair also exhibits a higher micro-hardness than the welding repair. In addition, the cavitation erosion resistance of a cold spray coating was investigated through ultrasonic cavitation tests, and the samples worn surfaces were observed by scanning electron microscopy.

Effect of shielding gas composition on the properties of hyperbaric GMA welds in duplex steels

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

Ware, N.; Dos Santos, J.F.; Richardson, I.

1994-12-31

By using Ar/He based shielding gas mixtures with a variety of oxygen and nitrogen additions the absorption of active gas components into duplex stainless steels welded under hyperbaric conditions was examined. The pressure levels used corresponded to seawater depths of 100m, 200m and 300m. The GMAW process in the short circuit transfer mode was used for all tests. Both bead-on-plate and ``V`` butt joints were carried out. The effect of variations in the weld metal active gas components on the weld metal chemical composition and phase balance was investigated. In a second set of tests the effect of varying heatmore » inputs on the phase balance and microstructure was assessed.« less

Formation of Gradient Structures in the Zone of Joining a Deformable Nickel Alloy and a Single-Crystal Intermetallic Alloy during Thermodiffusion Pressure Welding and Subsequent Heat Treatment

NASA Astrophysics Data System (ADS)

Povarova, K. B.; Valitov, V. A.; Drozdov, A. A.; Bazyleva, O. A.; Galieva, E. V.; Arginbaeva, E. G.

2018-01-01

The possibility of formation of a high-quality solid-phase joint of an Ni3Al-based single-crystal intermetallic VKNA-25 blade alloy with a high-temperature deformable EP975 disk alloy by pressure welding is studied to create high-performance one-piece blisk unit for the next-generation aviation gas turbine engines and to decrease the unit mass. The influence of the conditions of thermodiffusion pressure welding under the hightemperature superplasticity of the disk alloy and the influence of heat treatment of welded joints on the gradient structures in the welded joint zone and the structure at the periphery of the welded samples are investigated.

Discussion on Influence of High Strength Bolt’s Parameters on the Weld Reinforced Combined Connection with Bolts and Welds

NASA Astrophysics Data System (ADS)

Ma, Jiansuo; Wang, Yuanqing; Li, Mingfeng; Bai, Runshan; Ban, Huiyong

2018-03-01

In the process of existing steel structure operation, in order to prevent the bolted joints from being damaged by insufficient carrying capacity, welds can be used for reinforcement. Weld reinforced combined connection with bolts and weld consists with high strength bolts and side fillet weld composition. The parameters and properties of high strength bolts and fillet welds have a direct effect on the connection. Based on the test results, We explore the influence that welding seam reinforcement and the performance of the connection between the number of high strength bolts and specifications changes in this paper. It will provide a theoretical reference for the design of connection nodes of steel structure reinforcement project.

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.

Towards Real Time Diagnostics of Hybrid Welding Laser/GMAW

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

Timothy Mcjunkin; Dennis C. Kunerth; Corrie Nichol

2013-07-01

Methods are currently being developed towards a more robust system real time feedback in the high throughput process combining laser welding with gas metal arc welding. A combination of ultrasonic, eddy current, electronic monitoring, and visual techniques are being applied to the welding process. Initial simulation and bench top evaluation of proposed real time techniques on weld samples are presented along with the concepts to apply the techniques concurrently to the weld process. Consideration for the eventual code acceptance of the methods and system are also being researched as a component of this project. The goal is to detect defectsmore » or precursors to defects and correct when possible during the weld process.« less

Towards real time diagnostics of Hybrid Welding Laser/GMAW

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

McJunkin, T. R.; Kunerth, D. C.; Nichol, C. I.

2014-02-18

Methods are currently being developed towards a more robust system real time feedback in the high throughput process combining laser welding with gas metal arc welding. A combination of ultrasonic, eddy current, electronic monitoring, and visual techniques are being applied to the welding process. Initial simulation and bench top evaluation of proposed real time techniques on weld samples are presented along with the concepts to apply the techniques concurrently to the weld process. Consideration for the eventual code acceptance of the methods and system are also being researched as a component of this project. The goal is to detect defectsmore » or precursors to defects and correct when possible during the weld process.« less

Towards real time diagnostics of Hybrid Welding Laser/GMAW

NASA Astrophysics Data System (ADS)

McJunkin, T. R.; Kunerth, D. C.; Nichol, C. I.; Todorov, E.; Levesque, S.

2014-02-01

Methods are currently being developed towards a more robust system real time feedback in the high throughput process combining laser welding with gas metal arc welding. A combination of ultrasonic, eddy current, electronic monitoring, and visual techniques are being applied to the welding process. Initial simulation and bench top evaluation of proposed real time techniques on weld samples are presented along with the concepts to apply the techniques concurrently to the weld process. Consideration for the eventual code acceptance of the methods and system are also being researched as a component of this project. The goal is to detect defects or precursors to defects and correct when possible during the weld process.

A novel post-weld-shift measurement and compensation technique in butterfly-type laser module packages

NASA Astrophysics Data System (ADS)

Hsu, Yi-Cheng, Sr.; Tsai, Y. C.; Hung, Y. S.; Cheng, W. H.

2005-08-01

One of the greatest challenges in the packaging of laser modules using laser welding technique is to use a reliable and accurate joining process. However, during welding, due to the material property difference between welded components, the rapid solidification of the welded region and the associated material shrinkage often introduced a post-weld-shift (PWS) between welded components. For a typical single-mode fiber application, if the PWS induced fiber alignment shift by the laser welding joining process is even a few micrometers, up to 50 % or greater loss in the coupled power may occur. The fiber alignment shift of the PWS effect in the laser welding process has a significant impact on the laser module package yield. Therefore, a detailed understanding of the effects of PWS on the fiber alignment shifts in laser-welded laser module packages and then the compensation of the fiber alignment shifts due to PWS effects are the key research subjects in laser welding techniques for optoelectronic packaging applications. Previously, the power losses due to PWS in butterfly-type laser module packages have been qualitatively corrected by applying the laser hammering technique to the direction of the detected shift. Therefore, by applying an elastic deformation to the welded components and by observing the corresponding power variation, the direction and magnitude of the PWS may be predicted. Despite numerous studies on improving the fabrication yields of laser module packaging using the PWS correction in laser welding techniques by a qualitative estimate, limited information is available for the quantitative understanding of the PWS induced fiber alignment shift which can be useful in designing and fabricating high-yield and high-performance laser module packages. The purpose of this paper is to present a quantitative probing of the PWS induced fiber alignment shift in laser-welded butterfly-type laser module packaging by employing a novel technique of a high-magnification camera with image capture system (HMCICS). The benefit of using the HMCICS technique to determine the fiber alignment shift are quantitatively measure and compensate the PWS direction and magnitude during the laser-welded laser module packages. This study makes it possible to probe the nonlinear behavior of the PWS by using a novel HMCICS technique that results in a real time quantitative compensation of the PWS in butterfly-type laser module packages, when compared to the currently available qualitatively estimated techniques to correct the PWS2. Therefore, the reliable butterfly-type laser modules with high yield and high performance used in lightwave transmission systems may thus be developed and fabricated.

Tailored Welding Technique for High Strength Al-Cu Alloy for Higher Mechanical Properties

NASA Astrophysics Data System (ADS)

Biradar, N. S.; Raman, R.

AA2014 aluminum alloy, with 4.5% Cu as major alloying element, offers highest strength and hardness values in T6 temper and finds extensive use in aircraft primary structures. However, this alloy is difficult to weld by fusion welding because the dendritic structure formed can affect weld properties seriously. Among the welding processes, AC-TIG technique is largely used for welding. As welded yield strength was in the range of 190-195 MPa, using conventional TIG technique. Welding metallurgy of AA2014 was critically reviewed and factors responsible for lower properties were identified. Square-wave AC TIG with Transverse mechanical arc oscillation (TMAO) was postulated to improve the weld strength. A systematic experimentation using 4 mm thick plates produced YS in the range of 230-240 MPa, has been achieved. Through characterization including optical and SEM/EDX was conducted to validate the metallurgical phenomena attributable to improvement in weld properties.

A comparison of LBW and GTAW processes in miniature closure welds

NASA Astrophysics Data System (ADS)

Knorovsky, G. A.; Fuerschbach, P. W.; Gianoulakis, S. E.; Burchett, S. N.

When small electronic components with glass-to-metal seals are closure welded, the residual stresses that develop in the glass are of concern. If these stresses exceed allowable tensile levels' the resulting weld-induced seal failure may cause the entire component to be scrapped or reworked at a substantial cost. Conventional wisdom says the best welding process for these applications is that which provides the least heat input, and so in that respect, Laser Beam Welding (LBW) provides less heat input than Gas Tungsten Arc Welding (GTAW), however, other concerns, such as weld fit-up, part variability, and material weldability, can modify the final choice of a welding process. In this paper, we compare the characteristic levels of heat input and the residual stresses generated in glass seals for two processes (as calculated by a 3D Finite Element Analysis) as a function of heat input and travel speed, and contrast some of the other manufacturing decisions that must be made in choosing a production process. The geometry chosen is that of a standing edge corner weld in a cylindrical container about 20 mm diameter by 35 mm tall. Four metal pins are glassed into the part lid. The stresses calculated from the resulting from continuous wave CO2 LBW are compared with those resulting from GTAW. The total energy required by the laser weld is significantly less than that needed for the equivalent size GTA weld. The energy input requirements for a given size weld is inversely proportional to the travel speed, but approaches a saturation level as the travel speed increases. LBW travel speeds ranging from 10 mm/s to 50 mm/s were examined.

Influence of Filler Alloy Composition and Process Parameters on the Intermetallic Layer Thickness in Single-Sided Cold Metal Transfer Welding of Aluminum-Steel Blanks

NASA Astrophysics Data System (ADS)

Silvayeh, Zahra; Vallant, Rudolf; Sommitsch, Christof; Götzinger, Bruno; Karner, Werner; Hartmann, Matthias

2017-11-01

Hybrid components made of aluminum alloys and high-strength steels are typically used in automotive lightweight applications. Dissimilar joining of these materials is quite challenging; however, it is mandatory in order to produce multimaterial car body structures. Since especially welding of tailored blanks is of utmost interest, single-sided Cold Metal Transfer butt welding of thin sheets of aluminum alloy EN AW 6014 T4 and galvanized dual-phase steel HCT 450 X + ZE 75/75 was experimentally investigated in this study. The influence of different filler alloy compositions and welding process parameters on the thickness of the intermetallic layer, which forms between the weld seam and the steel sheet, was studied. The microstructures of the weld seam and of the intermetallic layer were characterized using conventional optical light microscopy and scanning electron microscopy. The results reveal that increasing the heat input and decreasing the cooling intensity tend to increase the layer thickness. The silicon content of the filler alloy has the strongest influence on the thickness of the intermetallic layer, whereas the magnesium and scandium contents of the filler alloy influence the cracking tendency. The layer thickness is not uniform and shows spatial variations along the bonding interface. The thinnest intermetallic layer (mean thickness < 4 µm) is obtained using the silicon-rich filler Al-3Si-1Mn, but the layer is more than twice as thick when different low-silicon fillers are used.

Defects diagnosis in laser brazing using near-infrared signals based on empirical mode decomposition

NASA Astrophysics Data System (ADS)

Cheng, Liyong; Mi, Gaoyang; Li, Shuo; Wang, Chunming; Hu, Xiyuan

2018-03-01

Real-time monitoring of laser welding plays a very important role in the modern automated production and online defects diagnosis is necessary to be implemented. In this study, the status of laser brazing was monitored in real time using an infrared photoelectric sensor. Four kinds of braze seams (including healthy weld, unfilled weld, hole weld and rough surface weld) along with corresponding near-infrared signals were obtained. Further, a new method called Empirical Mode Decomposition (EMD) was proposed to analyze the near-infrared signals. The results showed that the EMD method had a good performance in eliminating the noise on the near-infrared signals. And then, the correlation coefficient was developed for selecting the Intrinsic Mode Function (IMF) more sensitive to the weld defects. A more accurate signal was reconstructed with the selected IMF components. Simultaneously, the spectrum of selected IMF components was solved using fast Fourier transform, and the frequency characteristics were clearly revealed. The frequency energy of different frequency bands was computed to diagnose the defects. There was a significant difference in four types of weld defects. This approach has been proved to be an effective and efficient method for monitoring laser brazing defects.

Electroacoustics modeling of piezoelectric welders for ultrasonic additive manufacturing processes

NASA Astrophysics Data System (ADS)

Hehr, Adam; Dapino, Marcelo J.

2016-04-01

Ultrasonic additive manufacturing (UAM) is a recent 3D metal printing technology which utilizes ultrasonic vibrations from high power piezoelectric transducers to additively weld similar and dissimilar metal foils. CNC machining is used intermittent of welding to create internal channels, embed temperature sensitive components, sensors, and materials, and for net shaping parts. Structural dynamics of the welder and work piece influence the performance of the welder and part quality. To understand the impact of structural dynamics on UAM, a linear time-invariant model is used to relate system shear force and electric current inputs to the system outputs of welder velocity and voltage. Frequency response measurements are combined with in-situ operating measurements of the welder to identify model parameters and to verify model assumptions. The proposed LTI model can enhance process consistency, performance, and guide the development of improved quality monitoring and control strategies.

Validating a Model for Welding Induced Residual Stress Using High-Energy X-ray Diffraction

NASA Astrophysics Data System (ADS)

Mach, J. C.; Budrow, C. J.; Pagan, D. C.; Ruff, J. P. C.; Park, J.-S.; Okasinski, J.; Beaudoin, A. J.; Miller, M. P.

2017-05-01

Integrated computational materials engineering (ICME) provides a pathway to advance performance in structures through the use of physically-based models to better understand how manufacturing processes influence product performance. As one particular challenge, consider that residual stresses induced in fabrication are pervasive and directly impact the life of structures. For ICME to be an effective strategy, it is essential that predictive capability be developed in conjunction with critical experiments. In the present work, simulation results from a multi-physics model for gas metal arc welding are evaluated through x-ray diffraction using synchrotron radiation. A test component was designed with intent to develop significant gradients in residual stress, be representative of real-world engineering application, yet remain tractable for finely spaced strain measurements with positioning equipment available at synchrotron facilities. The experimental validation lends confidence to model predictions, facilitating the explicit consideration of residual stress distribution in prediction of fatigue life.

The Light Plane Calibration Method of the Laser Welding Vision Monitoring System

NASA Astrophysics Data System (ADS)

Wang, B. G.; Wu, M. H.; Jia, W. P.

2018-03-01

According to the aerospace and automobile industry, the sheet steels are the very important parts. In the recent years, laser welding technique had been used to weld the sheet steel part. The seam width between the two parts is usually less than 0.1mm. Because the error of the fixture fixed can’t be eliminated, the welding parts quality can be greatly affected. In order to improve the welding quality, the line structured light is employed in the vision monitoring system to plan the welding path before welding. In order to improve the weld precision, the vision system is located on Z axis of the computer numerical control (CNC) tool. The planar pattern is placed on the X-Y plane of the CNC tool, and the structured light is projected on the planar pattern. The vision system stay at three different positions along the Z axis of the CNC tool, and the camera shoot the image of the planar pattern at every position. Using the calculated the sub-pixel center line of the structure light, the world coordinate of the center light line can be calculated. Thus, the structured light plane can be calculated by fitting the structured light line. Experiment result shows the effective of the proposed method.

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

Self-Reacting Friction Stir Welding for Aluminum Alloy Circumferential Weld Applications

NASA Technical Reports Server (NTRS)

Bjorkman, Gerry; Cantrell, Mark; Carter, Robert

2003-01-01

Friction stir welding is an innovative weld process that continues to grow in use, in the commercial, defense, and space sectors. It produces high quality and high strength welds in aluminum alloys. The process consists of a rotating weld pin tool that plasticizes material through friction. The plasticized material is welded by applying a high weld forge force through the weld pin tool against the material during pin tool rotation. The high weld forge force is reacted against an anvil and a stout tool structure. A variation of friction stir welding currently being evaluated is self-reacting friction stir welding. Self-reacting friction stir welding incorporates two opposing shoulders on the crown and root sides of the weld joint. In self-reacting friction stir welding, the weld forge force is reacted against the crown shoulder portion of the weld pin tool by the root shoulder. This eliminates the need for a stout tooling structure to react the high weld forge force required in the typical friction stir weld process. Therefore, the self-reacting feature reduces tooling requirements and, therefore, process implementation costs. This makes the process attractive for aluminum alloy circumferential weld applications. To evaluate the application of self-reacting friction stir welding for aluminum alloy circumferential welding, a feasibility study was performed. The study consisted of performing a fourteen-foot diameter aluminum alloy circumferential demonstration weld using typical fusion weld tooling. To accomplish the demonstration weld, weld and tack weld development were performed and fourteen-foot diameter rings were fabricated. Weld development consisted of weld pin tool selection and the generation of a process map and envelope. Tack weld development evaluated gas tungsten arc welding and friction stir welding for tack welding rings together for circumferential welding. As a result of the study, a successful circumferential demonstration weld was produced leading the way for future circumferential weld implementation.

Electron beam weld development on a Filter Pack Assembly

NASA Astrophysics Data System (ADS)

Dereskiewicz, J. P.

1994-06-01

A continuous electron beam welding procedure was developed to replace the manual gas tungsten arc welding procedure on the Filter Pack Assembly. A statistical study was used to evaluate the feasibility of electron beam welding 6061-T6 aluminum covers to A356 cast weldments throughout the joint tolerance range specified on product drawings. Peak temperature exposures were not high enough to degrade the heat sensitive electrical components inside the cast weldment. Actual weldments with alodine coating on the weld joint area were successfully cleaned using a nonmetallic fiberglass brush cleaning method.

Welding, Bonding and Fastening, 1984

NASA Technical Reports Server (NTRS)

Buckley, J. D. (Editor); Stein, B. A. (Editor)

1985-01-01

A compilation of papers presented in a joint NASA, American Society for Metals, The George Washington University, American Welding Soceity, and Society of Manufacturing Engineers conference on Welding, Bonding, and Fastening at Langley Research Center, Hampton, VA, on October 23 to 25, 1984 is given. Papers were presented on technology developed in current research programs relevant to welding, bonding, and fastening of structural materials required in fabricating structures and mechanical systems used in the aerospace, hydrospace, and automotive industries. Topics covered in the conference included equipment, hardware and materials used when welding, brazing, and soldering, mechanical fastening, explosive welding, use of unique selected joining techniques, adhesives bonding, and nondestructive evaluation. A concept of the factory of the future was presented, followed by advanced welding techniques, automated equipment for welding, welding in a cryogenic atmosphere, blind fastening, stress corrosion resistant fasteners, fastening equipment, explosive welding of different configurations and materials, solid-state bonding, electron beam welding, new adhesives, effects of cryogenics on adhesives, and new techniques and equipment for adhesive bonding.

Structure and Microhardness of Cu-Ta Joints Produced by Explosive Welding

PubMed Central

Maliutina, Iu. N.; Mali, V. I.; Bataev, I. A.; Bataev, A. A.; Esikov, M. A.; Smirnov, A. I.; Skorokhod, K. A.

2013-01-01

The structure and microhardness of Cu-Ta joints produced by explosive welding were studied. It was found that, during explosive welding, an intermediate layer 20⋯40 μm thick with a finely dispersed heterophase structure, formed between the welded copper and tantalum plates. The structure of the layer was studied by scanning and transmission electron microscopy. Microvolumes with tantalum particles distributed in a copper matrix and microvolumes of copper particles in a tantalum matrix were detected. The tantalum particles in copper have a size of 5⋯500 nm, with a predominance of 5⋯50 nm particles. A mechanism for the formation of the finely dispersed heterophase structure in explosive welding is proposed. The microhardness of interlayers with the heterophase structure reaches 280 HV, which far exceeds the microhardness of copper (~130 HV) and tantalum (~160 HV). Many twins of deformation origin were found in the structure of the copper plate. The effect of heating temperature in the range from 100 to 900°C on the microhardness of copper, tantalum, and the Cu-Ta welded joint was studied. Upon heating to 900°C, the microhardness of the intermediate layer decreases from 280 to 150 HV. The reduction in the strength properties of the weld material is mainly due to structural transformations in copper. PMID:24453818

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.

Simulation of Weld Mechanical Behavior to Include Welding-Induced Residual Stress and Distortion: Coupling of SYSWELD and Abaqus Codes

DTIC Science & Technology

2015-11-01

induced residual stresses and distortions from weld simulations in the SYSWELD software code in structural Finite Element Analysis ( FEA ) simulations...performed in the Abaqus FEA code is presented. The translation of these results is accomplished using a newly developed Python script. Full details of...Local Weld Model in Structural FEA ....................................................15 CONCLUSIONS

Summary of Results of Tests Made by Aluminum Research Laboratories of Spot-welded Joints and Structural Elements

NASA Technical Reports Server (NTRS)

HARTMANN E C; Stickley, G W

1942-01-01

Available information concerning spot welding as a means of joining aluminum-alloy parts has been summarized and comparisons have been made of the relative merits of spot-welded and riveted aluminum-alloy structural elements. The results indicated that spot welding was as satisfactory as riveting insofar as resistance to static loads is concerned. Spot welds showed slightly lower resistance to impact loads but definitely lower resistance to repeated loads than rivets.

Investigation the Amplitude Uniformity on the Surface of the Wide-Blade Ultrasonic Plastic Welding Horn

NASA Astrophysics Data System (ADS)

Hai Nguyen, Thanh; Thanh Quang, Quang; Luat Tran, Cong; Loc Nguyen, Huu

2017-10-01

Ultrasonic welding has been applied for joining thermoplastic components due to their advantages such as clean, fast and reliable. The basic principle is to use the mechanical energy of ultrasonic frequency vibration to produce the molten pool at the interface of the joined components under high pressure to create solid-state welding joints. Depending on the specific application, the ultrasonic horn is designed to generate suitable amplitudes on the surface of the welding zone. Uniformity of the amplitudes can be a challenge as the welding area increases. Therefore, design a welding horn in order to obtain the uniform amplitudes at the large area is significant difficult. This work presents a method for obtaining the uniform amplitudes at the working surface of the stepped wide-blade horn. Finite element method is used to analyze the amplitude distribution at the horn surface of 250 × 34 mm2 with working frequency of 15 kHz and aluminum alloy 7075. The uniformity of amplitude is obtained by changing the shape of the horn.

Microstructural investigation of hardfacing weld deposit obtained from CrB paste

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

Kr. Ray, S.; Sarker, B.; Kr. Bhattacharya, S.

Hardfacing weld deposits are used as a protective layer on engineering components and tools subjected to different modes of wear. Cheaper iron-based alloys with chromium and carbon or relatively expensive alloys with some niobium or titanium have long been used as standard hardfacing materials. In recent years boron has substituted the costlier alloying elements and the newly developed Fe-B-C alloys have shown encouraging results. The microstructure of the welded hardfacing deposit is one of the most important factors that determine its performance. The amount, size, distribution and hardness of the individual constituents play important roles in imparting the desired properties.more » Recently Colomonoy sweat on paste containing fine CrB particles (of about 12 {mu}m average size) suspended in an organic binder has been marketed as the new generation hardfacing material. A thin coating of the paste is applied on the component surface, allowed to dry and welded. The welded deposit has been found to offer good wear resistance in many industrial applications. This paper reports the microstructural investigation of the welded deposit obtained from this paste.« less

Engineering aspects of the application of structural materials in the 5 MW-ESS-mercury-target

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

Guttek, B.

1996-06-01

A main problem of the ESS-Hg-target development and the design of the components of its primary Hg-circuit is the choice of structural materials. As designing, calculations and experiments with elected materials take time and are very costy, a preview on their successful application has to be done before as detailed as possible. One aspect on this is to have the knowledge of characteristics values of the structural material candidates under the occuring mechanical and thermal loads, irradiation, corrosion and erosion. Another point is the technology of engineering concerning the manufacturing, welding, surface treatment, and quality control of such parts andmore » components under the demand to reach maximum lifetime.« less

Research on Ultrasonic Flaw Detection of Steel Weld in Spatial Grid Structure

NASA Astrophysics Data System (ADS)

Du, Tao; Sun, Jiandong; Fu, Shengguang; Zhang, Changquan; Gao, Qing

2017-06-01

The welding quality of spatial grid member is an important link in quality control of steel structure. The paper analyzed the reasons that the welding seam of small-bore pipe with thin wall grid structure is difficult to be detected by ultrasonic wave from the theoretical and practical aspects. A series of feasible detection methods was also proposed by improving probe and operation approaches in this paper, and the detection methods were verified by project cases. Over the years, the spatial grid structure is widely used the engineering by virtue of its several outstanding characteristics such as reasonable structure type, standard member, excellent space integrity and quick installation. The wide application of spatial grid structure brings higher requirements on nondestructive test of grid structure. The implementation of new Code for Construction Quality Acceptance of Steel Structure Work GB50205-2001 strengthens the site inspection of steel structure, especially the site inspection of ultrasonic flaw detection in steel weld. The detection for spatial grid member structured by small-bore and thin-walled pipes is difficult due to the irregular influence of sound pressure in near-field region of sound field, sound beam diffusion generated by small bore pipe and reduction of sensitivity. Therefore, it is quite significant to select correct detecting conditions. The spatial grid structure of welding ball and bolt ball is statically determinate structure with high-order axial force which is connected by member bars and joints. It is welded by shrouding or conehead of member bars and of member bar and bolt-node sphere. It is obvious that to ensure the quality of these welding positions is critical to the quality of overall grid structure. However, the complexity of weld structure and limitation of ultrasonic detection method cause many difficulties in detection. No satisfactory results will be obtained by the conventional detection technology, so some special approaches must be used.

In mold laser welding for high precision polymer based optical components

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

Oliveira, N., E-mail: id2694@alunos.uminho.pt, E-mail: pontes@dep.uminho.pt; Pontes, A. J., E-mail: id2694@alunos.uminho.pt, E-mail: pontes@dep.uminho.pt

2014-05-15

To assemble a complete subsystem as a rear lamp, is necessary to have different machines and to perform several tasks. This necessity obliges the companies to have large structures to support all the assembling process. These huge structures are very costly and have as a consequence the reduction of the competitiveness of the companies. The process presented in this document has the intention of reducing the number of tasks needed to produce the final subsystem/product. To achieve this goal were combined several technologies, as in-mould assembling, laser welding and LEDs (light-emitting diode). One of the advantages of this process wasmore » the utilization of only one injection molding machine with three injection units to do all the assembling process. To achieve the main objective, firstly, the rear lamp was designed according to with the legislation of UNECE Vehicle Regulations - 1958 Agreements; Regulation No. 50 -Rev.2 - Position lamps, stop lamps, direction indicators for motorcycles. Posterior several polymeric materials were studied at different levels. Initial were studied several concentrations of carbon nanotubes mixed with PC (polycarbonate). This had the objective of determine, if these materials are suitable to conduct the necessary electric current to turn on the different LEDs. One of the main advantages of this process is the use of the laser transmission welded process. Since, with this welding technology is possible reduce the complexity of the final part. To understand the potentialities of this technology a combination of two materials was studied. The studied showed that all materials presented a high transparency to the laser beam. In terms of weld process, the study showed that the best welding conditions are the lowest velocity, diameter and power. With these studies was possible conclude that this new process is suitable to be implemented at the industrial level.« less

Accurate modelling of anisotropic effects in austenitic stainless steel welds

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

Nowers, O. D.; Duxbury, D. J.; Drinkwater, B. W.

2014-02-18

The ultrasonic inspection of austenitic steel welds is challenging due to the formation of highly anisotropic and heterogeneous structures post-welding. This is due to the intrinsic crystallographic structure of austenitic steel, driving the formation of dendritic grain structures on cooling. The anisotropy is manifested as both a ‘steering’ of the ultrasonic beam and the back-scatter of energy due to the macroscopic granular structure of the weld. However, the quantitative effects and relative impacts of these phenomena are not well-understood. A semi-analytical simulation framework has been developed to allow the study of anisotropic effects in austenitic stainless steel welds. Frequency-dependent scatterersmore » are allocated to a weld-region to approximate the coarse grain-structures observed within austenitic welds and imaged using a simulated array. The simulated A-scans are compared against an equivalent experimental setup demonstrating excellent agreement of the Signal to Noise (S/N) ratio. Comparison of images of the simulated and experimental data generated using the Total Focusing Method (TFM) indicate a prominent layered effect in the simulated data. A superior grain allocation routine is required to improve upon this.« less

Weldability of an iron meteorite by Friction Stir Spot Welding: A contribution to in-space manufacturing

NASA Astrophysics Data System (ADS)

Evans, William Todd; Neely, Kelsay E.; Strauss, Alvin M.; Cook, George E.

2017-11-01

Friction Stir Welding has been proposed as an efficient and appropriate method for in space welding. It has the potential to serve as a viable option for assembling large scale space structures. These large structures will require the use of natural in space materials such as those available from iron meteorites. Impurities present in most iron meteorites limit its ability to be welded by other space welding techniques such as electron beam laser welding. This study investigates the ability to weld pieces of in situ Campo del Cielo meteorites by Friction Stir Spot Welding. Due to the rarity of the material, low carbon steel was used as a model material to determine welding parameters. Welded samples of low carbon steel, invar, and Campo del Cielo meteorite were compared and found to behave in similar ways. This study shows that meteorites can be Friction Stir Spot Welded and that they exhibit properties analogous to that of FSSW low carbon steel welds. Thus, iron meteorites can be regarded as another viable option for in-space or Martian construction.

Nickel-hydrogen. [metal hydrides, electrochemical corrosion, and structural design

NASA Technical Reports Server (NTRS)

Mchenry, E. J.

1977-01-01

Because of the disintegration of LaNi5 as the lattice expands on absorbing hydrogen, a nickel hydrogen cell similar to a nickel cadmium cell was designed. The positive electrode is wrapped in a microporous separator and the leads are insulated. A negative conducting grid is inserted and welded to the top of the can into an open ended container which is then turned upside down and filled so that LiNa5 powder occupies all the space not used by the rest of the components. The bottom of the can is then welded on. A fill tube is located either on the bottom or on the top of the can. When welded shut, the cell is put into a pressure bomb and the lanthanum nickel is activated at about 1,000 pounds of hydrogen. Electrolytes are added to the cell as well as whatever amount of hydrogen precharge desired, and the cell is sealed. Advantages and disadvantages of the cell are discussed.

Cracking in dissimilar laser welding of tantalum to molybdenum

NASA Astrophysics Data System (ADS)

Zhou, Xingwen; Huang, Yongde; Hao, Kun; Chen, Yuhua

2018-06-01

Dissimilar joining of tantalum (Ta) to molybdenum (Mo) is of great interest in high temperature structural component applications. However, few reports were found about joining of these two hard-to-weld metals. The objective of this experimental study was to assess the weldability of laser butt joining of 0.2 mm-thick Ta and Mo. In order to study cracking mechanism in Ta/Mo joint, similar Ta/Ta and Mo/Mo joints were compared under the same welding conditions. An optical microscope observation revealed presence of intergranular cracks in the Mo/Mo joint, while both transgranular and intergranular cracks were observed in Ta/Mo joint. The cracking mechanism of the Ta/Mo joint was investigated further by micro-hardness testing, micro X-ray diffraction and scanning electron microscopy. The results showed that solidification cracking tendency of Mo is a main reason for crack initiation in the Ta/Mo joint. Low ductility feature in fusion zone most certainly played a role in the transgranular propagation of cracking.

Stress Analysis of Bolted, Segmented Cylindrical Shells Exhibiting Flange Mating-Surface Waviness

NASA Technical Reports Server (NTRS)

Knight, Norman F., Jr.; Phillips, Dawn R.; Raju, Ivatury S.

2009-01-01

Bolted, segmented cylindrical shells are a common structural component in many engineering systems especially for aerospace launch vehicles. Segmented shells are often needed due to limitations of manufacturing capabilities or transportation issues related to very long, large-diameter cylindrical shells. These cylindrical shells typically have a flange or ring welded to opposite ends so that shell segments can be mated together and bolted to form a larger structural system. As the diameter of these shells increases, maintaining strict fabrication tolerances for the flanges to be flat and parallel on a welded structure is an extreme challenge. Local fit-up stresses develop in the structure due to flange mating-surface mismatch (flange waviness). These local stresses need to be considered when predicting a critical initial flaw size. Flange waviness is one contributor to the fit-up stress state. The present paper describes the modeling and analysis effort to simulate fit-up stresses due to flange waviness in a typical bolted, segmented cylindrical shell. Results from parametric studies are presented for various flange mating-surface waviness distributions and amplitudes.

Effect of weld line positions on the tensile deformation of two-component metal injection moulding

NASA Astrophysics Data System (ADS)

Manonukul, Anchalee; Songkuea, Sukrit; Moonchaleanporn, Pongporn; Tange, Makiko

2017-12-01

Knowledge of the mechanical properties of two-component parts is critical for engineering functionally graded components. In this study, mono- and two-component tensile test specimens were metal injection moulded. Three different weld line positions were generated in the two-component specimens. Linear shrinkage of the two-component specimens was greater than that of the mono-component specimens because the incompatibility of sintering shrinkage of both materials causes biaxial stresses and enhances sintering. The mechanical properties of 316L stainless steel were affected by the addition of a coloured pigment used to identify the weld line position after injection moulding. For the two-component specimens, the yield stress and ultimate tensile stress were similar to those of 316L stainless steel. Because 316L and 630 (also known as 17-4PH) stainless steels were well-sintered at the interface, the mechanical properties of the weaker material (316L stainless steel) were dominant. However, the elongations of the two-component specimens were lower than those of the mono-component specimens. An interfacial zone with a microstructure that differed from those of the mono-material specimens was observed; its different microstructure was attributed to the gradual diffusion of nickel and copper.

Pulmonary adverse effects of welding fume in automobile assembly welders.

PubMed

Sharifian, Seyed Akbar; Loukzadeh, Ziba; Shojaoddiny-Ardekani, Ahmad; Aminian, Omid

2011-01-01

Welding is one of the key components of numerous manufacturing industries, which has potential physical and chemical health hazards. Many components of welding fumes can potentially affect the lung function. This study investigates the effects of welding fumes on lung function and respiratory symptoms among welders of an automobile manufacturing plant in Iran. This historical cohort study assesses 43 male welders and 129 office workers by a questionnaire to record demographic data, smoking habits, work history and respiratory symptoms as well as lung function status by spirometry. The average pulmonary function values of welders were lower relative to controls with dose-effect relationship between work duration and pulmonary function impairment. The prevalence of chronic bronchitis was higher in welders than controls. Our findings suggest that welders are at risk for pulmonary disease.

A Cross Structured Light Sensor and Stripe Segmentation Method for Visual Tracking of a Wall Climbing Robot

PubMed Central

Zhang, Liguo; Sun, Jianguo; Yin, Guisheng; Zhao, Jing; Han, Qilong

2015-01-01

In non-destructive testing (NDT) of metal welds, weld line tracking is usually performed outdoors, where the structured light sources are always disturbed by various noises, such as sunlight, shadows, and reflections from the weld line surface. In this paper, we design a cross structured light (CSL) to detect the weld line and propose a robust laser stripe segmentation algorithm to overcome the noises in structured light images. An adaptive monochromatic space is applied to preprocess the image with ambient noises. In the monochromatic image, the laser stripe obtained is recovered as a multichannel signal by minimum entropy deconvolution. Lastly, the stripe centre points are extracted from the image. In experiments, the CSL sensor and the proposed algorithm are applied to guide a wall climbing robot inspecting the weld line of a wind power tower. The experimental results show that the CSL sensor can capture the 3D information of the welds with high accuracy, and the proposed algorithm contributes to the weld line inspection and the robot navigation. PMID:26110403

Isothermal Calorimetric Observations of the Effect of Welding on Compatibility of Stainless Steels with High-Test Hydrogen Peroxide Propellant

NASA Technical Reports Server (NTRS)

Gostowski, Rudy

2003-01-01

High-Test Hydrogen Peroxide (HTP) is receiving renewed interest as a monopropellant and as the oxidizer for bipropellant systems. HTP is hydrogen peroxide having concentrations ranging from 70 to 98%. In these applications the energy and oxygen released during decomposition of HTP is used for propulsion. In propulsion systems components must be fabricated and connected using available joining processes. Welding is a common joining method for metallic components. The goal of this study was to compare the HTP compatibility of welded vs. unwelded stainless steel.

Development of sensor augmented robotic weld systems for aerospace propulsion system fabrication

NASA Technical Reports Server (NTRS)

Jones, C. S.; Gangl, K. J.

1986-01-01

In order to meet stringent performance goals for power and reuseability, the Space Shuttle Main Engine was designed with many complex, difficult welded joints that provide maximum strength and minimum weight. To this end, the SSME requires 370 meters of welded joints. Automation of some welds has improved welding productivity significantly over manual welding. Application has previously been limited by accessibility constraints, requirements for complex process control, low production volumes, high part variability, and stringent quality requirements. Development of robots for welding in this application requires that a unique set of constraints be addressed. This paper shows how robotic welding can enhance production of aerospace components by addressing their specific requirements. A development program at the Marshall Space Flight Center combining industrial robots with state-of-the-art sensor systems and computer simulation is providing technology for the automation of welds in Space Shuttle Main Engine production.

Electron Beam Welding: study of process capability and limitations towards development of nuclear components

NASA Astrophysics Data System (ADS)

Vadolia, Gautam R.; Premjit Singh, K.

2017-04-01

Electron Beam Welding (EBW) technology is an established and widely adopted technique in nuclear research and development area. Electron beam welding was thought of as a candidate process for ITER Vacuum Vessel Fabrication. Dhruva Reactor at BARC, Mumbai and Niobium superconducting accelerator cavity at BARC has adopted the EB welding technique as a fabrication route. Study of process capability and limitations based on available literature is consolidated in this short review paper.

Welding and Weldability of AZ31B by Gas Tungsten Arc and Laser Beam Welding Processes

NASA Astrophysics Data System (ADS)

Lathabai, S.; Barton, K. J.; Harris, D.; Lloyd, P. G.; Viano, D. M.; McLean, A.

Welding will play an important role in the fabrication of modular lightweight structures based on magnesium alloy die castings, extrusion profiles and wrought products. Minimisation of rejection rates during fabrication requires that satisfactory weldability be established for a particular combination of materials and welding procedures. In this paper, we present the results of a study to quantify the weldability of wrought alloy AZ31B by gas tungsten arc (GTA) and laser beam (LB) welding processes. The susceptibility to weld metal solidification cracking was evaluated using the Circular Patch weldability test. Operating windows of welding parameters for crack-free and porosity-free GTA and LB welding were identified, based on which welding procedures were developed for sheet and plate AZ31B. The microstructure and mechanical properties of welded test plates were assessed, leading to a better understanding of microstructurat development and structure-property relationships in GTA and LB weldments in AZ31B.

The effects of short pulse laser surface cleaning on porosity formation and reduction in laser welding of aluminium alloy for automotive component manufacture

NASA Astrophysics Data System (ADS)

AlShaer, A. W.; Li, L.; Mistry, A.

2014-12-01

Laser welding of aluminium alloys typically results in porosity in the fusion zones, leading to poor mechanical and corrosion performances. Mechanical and chemical cleaning of surfaces has been used previously to remove contaminants for weld joint preparations. However, these methods are slow, ineffective (e.g. due to hydrogen trapping) or lead to environmental hazards. This paper reports the effects of short pulsed laser surface cleaning on porosity formation and reduction in laser welding of AC-170PX (AA6014) aluminium sheets (coated with Ti/Zr and lubricated using a dry lubricant AlO70) with two types of joints: fillet edge and flange couch, using an AA4043 filler wire for automotive component assembly. The effect of laser cleaning on porosity reduction during laser welding using a filler wire has not been reported before. In this work, porosity and weld fusion zone geometry were examined prior to and after laser cleaning. The nanosecond pulsed Nd:YAG laser cleaning was found to reduce porosity significantly in the weld fusion zones. For the fillet edge welds, porosity was reduced to less than 0.5% compared with 10-80% without laser cleaning. For flange couch welds, porosity was reduced to 0.23-0.8% with laser cleaning from 0.7% to 4.3% without laser cleaning. This has been found to be due to the elimination of contaminations and oxide layers that contribute to the porosity formation. The laser cleaning is based on thermal ablation. This research focuses on porosity reduction in laser welding of aluminium alloy. Weld quality was investigated for two joints, fillet edge and flange couch joints. The effect of laser cleaning on porosity reduction after welding was investigated. It was found that laser cleaning reduced porosity less than 1% in both joints. Weld dimensions and strength were evaluated and discussed for both types of joints.

Improving Processes of Mechanized Pulsed Arc Welding of Low-Frequency Range Variation of Mode Parameters

NASA Astrophysics Data System (ADS)

Saraev, Yu N.; Solodskiy, S. A.; Ulyanova, O. V.

2016-04-01

A new technology of low-frequency modulation of the arc current in MAG and MIG welding is presented. The technology provides control of thermal and crystallization processes, stabilizes the time of formation and crystallization of the weld pool. Conducting theoretical studies allowed formulating the basic criteria for obtaining strong permanent joints for high-duty structures, providing conditions for more equilibrium structure of the deposited metal and the smaller width of the HAZ. The stabilization of time of the formation and crystallization of the weld pool improves the formation of the weld and increases productivity in welding thin sheet metal.

Experimental Investigation on Laser Impact Welding of Fe-Based Amorphous Alloys to Crystalline Copper

PubMed Central

Wang, Xiao; Luo, Yapeng; Huang, Tao; Liu, Huixia

2017-01-01

Recently, amorphous alloys have attracted many researchers’ attention for amorphous structures and excellent properties. However, the welding of amorphous alloys to traditional metals in the microscale is not easy to realize in the process with amorphous structures unchanged, which restrains the application in industry. In this paper, a new method of welding Fe-based amorphous alloys (GB1K101) to crystalline copper by laser impact welding (LIW) is investigated. A series of experiments was conducted under different laser energies, during which Fe-based amorphous alloys and crystalline copper were welded successfully by LIW. In addition, the microstructure and mechanical properties of welding joints were observed and measured, respectively. The results showed that the surface wave and springback were observed on the flyer plate after LIW. The welding interface was straight or wavy due to different plastic deformation under different laser energies. The welding interface was directly bonded tightly without visible defects. No visible element diffusion and intermetallic phases were found in the welding interface. The Fe-based amorphous alloys retained amorphous structures after LIW under the laser energy of 835 mJ. The nanoindentation hardness across the welding interface showed an increase on both sides of the welding interface. The results of the lap shearing test showed that the fracture position was on the side of copper coil. PMID:28772886

Experimental Investigation on Laser Impact Welding of Fe-Based Amorphous Alloys to Crystalline Copper.

PubMed

Wang, Xiao; Luo, Yapeng; Huang, Tao; Liu, Huixia

2017-05-12

Recently, amorphous alloys have attracted many researchers' attention for amorphous structures and excellent properties. However, the welding of amorphous alloys to traditional metals in the microscale is not easy to realize in the process with amorphous structures unchanged, which restrains the application in industry. In this paper, a new method of welding Fe-based amorphous alloys (GB1K101) to crystalline copper by laser impact welding (LIW) is investigated. A series of experiments was conducted under different laser energies, during which Fe-based amorphous alloys and crystalline copper were welded successfully by LIW. In addition, the microstructure and mechanical properties of welding joints were observed and measured, respectively. The results showed that the surface wave and springback were observed on the flyer plate after LIW. The welding interface was straight or wavy due to different plastic deformation under different laser energies. The welding interface was directly bonded tightly without visible defects. No visible element diffusion and intermetallic phases were found in the welding interface. The Fe-based amorphous alloys retained amorphous structures after LIW under the laser energy of 835 mJ. The nanoindentation hardness across the welding interface showed an increase on both sides of the welding interface. The results of the lap shearing test showed that the fracture position was on the side of copper coil.

Effect of welding structure and δ-ferrite on fatigue properties for TIG welded austenitic stainless steels at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Yuri, Tetsumi; Ogata, Toshio; Saito, Masahiro; Hirayama, Yoshiaki

2000-04-01

High-cycle and low-cycle fatigue properties of base and weld metals for SUS304L and SUS316L and the effects of welding structure and δ-ferrite on fatigue properties were investigated at cryogenic temperatures in order to evaluate the long-life reliability of the structural materials to be used in liquid hydrogen supertankers and storage tanks and to develop a welding process for these applications. The S-N curves of the base and weld metals shifted towards higher levels, i.e., the longer life side, with decreasing test temperatures. High-cycle fatigue tests demonstrated the ratios of fatigue strength at 10 6 cycles to tensile strength of the weld metals to be 0.35-0.7, falling below those of base metals with decreasing test temperatures. Fatigue crack initiation sites in SUS304L weld metals were mostly at blowholes with diameters of 200-700 μm, and those of SUS316L weld metals were at weld pass interface boundaries. Low-cycle fatigue tests revealed the fatigue lives of the weld metals to be somewhat lower than those of the base metals. Although δ-ferrite reduces the toughness of austenitic stainless steels at cryogenic temperatures, the effects of δ-ferrite on high-cycle and low-cycle fatigue properties are not clear or significant.

Quasi-Rayleigh waves in butt-welded thick steel plate

NASA Astrophysics Data System (ADS)

Kamas, Tuncay; Giurgiutiu, Victor; Lin, Bin

2015-03-01

This paper discusses theoretical and experimental analyses of weld guided surface acoustic waves (SAW) through the guided wave propagation (GWP) analyses. The GWP analyses have been carried out by utilizing piezoelectric wafer active sensors (PWAS) for in situ structural inspection of a thick steel plate with butt weld as the weld bead is ground flush. Ultrasonic techniques are commonly used for validation of welded structures in many in-situ monitoring applications, e.g. in off-shore structures, in nuclear and pressure vessel industries and in a range of naval applications. PWAS is recently employed in such ultrasonic applications as a resonator as well as a transducer. Quasi-Rayleigh waves a.k.a. SAW can be generated in relatively thick isotropic elastic plate having the same phase velocity as Rayleigh waves whereas Rayleigh waves are a high frequency approximation of the first symmetric (S0) and anti-symmetric (A0) Lamb wave modes. As the frequency becomes very high the S0 and the A0 wave speeds coalesce, and both have the same value. This value is exactly the Rayleigh wave speed and becomes constant along the frequency i.e. Rayleigh waves are non-dispersive guided surface acoustic waves. The study is followed with weld-GWP tests through the pitch-catch method along the butt weld line. The tuning curves of quasi-Rayleigh wave are determined to show the tuning and trapping effect of the weld bead that has higher thickness than the adjacent plates on producing a dominant quasi-Rayleigh wave mode. The significant usage of the weld tuned and guided quasi-Rayleigh wave mode is essentially discussed for the applications in the in-situ inspection of relatively thick structures with butt weld such as naval offshore structures. The paper ends with summary, conclusions and suggestions for future work.

Heat treatment stabilizes welded aluminum jigs and tool structures

NASA Technical Reports Server (NTRS)

Mehnert, R. S.

1966-01-01

Heat treatment processes, applied after welding but before machining, imparts above normal stability to welded aluminum jigs and tool structures. Weight saving will not be realized in these tools if rigidity equal to that of a comparable steel tool is required.

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.

Testing of Military Towbars

DTIC Science & Technology

2016-09-28

pin diameters, lunette diameter, clevis end details, cross section, and overall tube length and straightness. b. Weld failures, voids, cracks...etc., should be considered failures if they are identified visually or using a nondestructive weld inspection test method, per the applicable American... Welding Society standard for the specific material being inspected. c. Broken or cracked components, or catastrophic damage should be considered

A Review of Tribological Coatings for Control Drive Mechanisms in Space Reactors

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

CJ Larkin; JD Edington; BJ Close

2006-02-21

Tribological coatings must provide lubrication for moving components of the control drive mechanism for a space reactor and prevent seizing due to friction or diffusion welding to provide highly reliable and precise control of reflector position over the mission lifetime. Several coatings were evaluated based on tribological performance at elevated temperatures and in ultrahigh vacuum environments. Candidates with proven performance in the anticipated environment are limited primarily to disulfide materials. Irradiation data for these coatings is nonexistent. Compatibility issues between coating materials and structural components may require the use of barrier layers between the solid lubricant and structural components tomore » prevent deleterious interactions. It would be advisable to consider possible lubricant interactions prior to down-selection of structural materials. A battery of tests was proposed to provide the necessary data for eventual solid lubricant/coating selection.« less

Evaluation of Weldability for MAG and LASER with Galvannealed Steel.

PubMed

Kim, Jong-Hee; Bang, Han-Sur; Bang, Hee-Seon

2018-03-01

Lower-arm, one of the components in automotive suspension module, has been fabricated by MAG welding in general which is lap jointed with 2 mm thick galvannealed steel sheet (SGAPH440). This welding process produces some problems such as significantly much spatters and weld defects of porosity in welded joint, which degrades productivity and weldability. Therefore, in order to solve these problems, this study has been tried to apply two types of solid wires with different chemical composition rate of Si and Mn, in MAG welding process. Moreover, the laser welding process has been adopted to fabricate the low-arm and compared with those of MAG welding, in terms of mechanical and metallurgical characteristics. It was observed that in MAG welded joints, much more spatters were occurred in using solid wire with higher Si and Mn contains. The maximum tensile-shear strength in laser welded joints was approximately 16.7 kN, which was almost equal to that of in MAG welded joints. The microstructure showed ferrite and martensite in weld metal in MAG and laser welded joints indicating no significantly grain size change.

Nano- and Microparticles in Welding Aerosol: Granulometric Analysis

NASA Astrophysics Data System (ADS)

Kirichenko, K. Yu.; Drozd, V. A.; Chaika, V. V.; Gridasov, A. V.; Kholodov, A. S.; Golokhvast, K. S.

The paper presents the first results of the study of the size of particles appearing in the welding process by means of laser granulometry. It is shown that welding aerosol is the source of nano-and micro-sized particles extremely dangerous for human and animal health. Particle size distribution in the microrange was from 1 to 10 μm and up to 100%. It is shown that in 9 cases out of 28 with the use of various welding modes, welding rods and components the emission of aerosol with nano-sized particles (from 45.5% to 99.4%) is observed.

Implementation of an Outer Can Welding System for Savannah River Site FB-Line

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

Howard, S.R.

2003-03-27

This paper details three phases of testing to confirm use of a Gas Tungsten Arc (GTA) system for closure welding the 3013 outer container used for stabilization/storage of plutonium metals and oxides. The outer container/lid closure joint was originally designed for laser welding, but for this application, the gas tungsten arc (GTA) welding process has been adapted. The testing progressed in three phases: (1) system checkout to evaluate system components for operational readiness, (2) troubleshooting to evaluate high weld failure rates and develop corrective techniques, and (3) pre-installation acceptance testing.

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.

Joining technologies for the 1990s: Welding, brazing, soldering, mechanical, explosive, solid-state, adhesive

NASA Technical Reports Server (NTRS)

Buckley, John D. (Editor); Stein, Bland A. (Editor)

1986-01-01

A compilation of papers presented in a joint NASA, American Society for Metals, The George Washington University, American Welding Society, and Society of Manufacturing Engineers Conference on Welding, Bonding, and Fastening at Langley Research Center, Hampton, VA, on October 23 to 25, 1984 is given. Papers were presented on technology developed in current research programs relevant to welding, bonding, and fastening of structural materials required in fabricating structures and mechanical systems used in the aerospace, hydrospace, and automotive industries. Topics covered in the conference included equipment, hardware and materials used when welding, brazing, and soldering, mechanical fastening, explosive welding, use of unique selected joining techniques, adhesives bonding, and nondestructive evaluation. A concept of the factory of the future was presented, followed by advanced welding techniques, automated equipment for welding, welding in a cryogenic atmosphere, blind fastening, stress corrosion resistant fasteners, fastening equipment, explosive welding of different configurations and materials, solid-state bonding, electron beam welding, new adhesives, effects of cryogenics on adhesives, and new techniques and equipment for adhesive bonding.

Studying heat-affected zone deformations of electric arc welding

NASA Astrophysics Data System (ADS)

Suleimanov, R. I.; Zainagalina, L. Z.; Khabibullin, M. Ya; Zaripova, L. M.; Kovalev, N. O.

2018-03-01

The paper studies the influence of the most common defects in permanent electric arc welds made during the welding butt joints in infield oil pipelines, onto the strength characteristics of the welded pipe material around the heat-affected zone. A specimen of a butt weld with an obvious defect was used as a subject of the study. The changes in the geometric parameters of the weld were measured with the standard means; Rockwell hardness in the heat-affected zone was determined in certain areas with justification for the weld process modes. The cause of softening was found to be an increased width of the hot spot on the one side of the weld, where an enlarged crystalline structure appears as a result of the pipe material recrystallization under the influence of heat. Changes in the geometry of the thermal action area are determined by accumulation of molten filler on the one side of the weld when the welding rate is decreased. Some recommendations are given to prevent destruction of the welded structures and appearance of emergencies in infield oil pipelines.

U-Groove Aluminum Weld Strength Improvement

NASA Technical Reports Server (NTRS)

Verderaime, V.; Vaughan, R.

1997-01-01

Though butt-welds are among the most preferred joining methods in aerostructures, their strength dependence on inelastic mechanics is generally the least understood. This study investigated experimental strain distributions across a thick aluminum U-grooved weld and identified two weld process considerations for improving the multipass weld strength. One is the source of peaking in which the extreme thermal expansion and contraction gradient of the fusion heat input across the groove tab thickness produces severe angular distortion that induces bending under uniaxial loading. The other is the filler strain hardening decreasing with increasing filler pass sequences, producing the weakest welds on the last weld pass side. Both phenomena are governed by weld pass sequences. Many industrial welding schedules unknowingly compound these effects, which reduce the weld strength. A depeaking index model was developed to select filler pass thickness, pass numbers, and sequences to improve depeaking in the welding process. The result was to select the number and sequence of weld passes to reverse the peaking angle such as to combine the strongest weld pass side with the peaking induced bending tension component side to provide a more uniform stress and stronger weld under axial tensile loading.

Enabling high speed friction stir welding of aluminum tailor welded blanks

NASA Astrophysics Data System (ADS)

Hovanski, Yuri

Current welding technologies for production of aluminum tailor-welded blanks (TWBs) are utilized in low-volume and niche applications, and have yet to be scaled for the high-volume vehicle market. This study targeted further weight reduction, part reduction, and cost savings by enabling tailor-welded blank technology for aluminum alloys at high-volumes. While friction stir welding (FSW) has traditionally been applied at linear velocities less than one meter per minute, high volume production applications demand the process be extended to higher velocities more amenable to cost sensitive production environments. Unfortunately, weld parameters and performance developed and characterized at low to moderate welding velocities do not directly translate to high speed linear friction stir welding. Therefore, in order to facilitate production of high volume aluminum FSW components, parameters were developed with a minimum welding velocity of three meters per minute. With an emphasis on weld quality, welded blanks were evaluated for post-weld formability using a combination of numerical and experimental methods. Evaluation across scales was ultimately validated by stamping full-size production door inner panels made from dissimilar thickness aluminum tailor-welded blanks, which provided validation of the numerical and experimental analysis of laboratory scale tests.

Lasers in automobile production

NASA Astrophysics Data System (ADS)

Pizzi, P.

There is a trend in mechanical equipment to replace complicated mechanical components with electronics, especially microprocessors, laser technology represents an important new tool. The effects of laser technology can be seen in production systems concerned with cutting, welding, heat treatment, and the alloying of mechanical components. Applications in the automobile industry today are not very widespread and are concerned essentially with welding and cutting.

Effect of a microstructure and surface hydrogen alloying of a VT6 alloy on diffusion welding

NASA Astrophysics Data System (ADS)

Senkevich, K. S.; Skvortsova, S. V.; Kudelina, I. M.; Knyazev, M. I.; Zasypkin, V. V.

2014-01-01

The effect of a structural type (lamellar, fine, gradient) and additional surface alloying with hydrogen on the diffusion bonding of titanium alloy VT6 samples is studied. It is shown that the surface alloying of VT6 alloy parts with hydrogen allows one to decrease the diffusion welding temperature by 50-100°C, to obtain high-quality pore-free bonding, and to remove the "structural" boundary between materials to be welded that usually forms during welding of titanium alloys with a lamellar structure.

Effect of water-cooling treatment times on properties of friction stir welded joints of 7N01-T4 aluminum alloy

NASA Astrophysics Data System (ADS)

Zhang, T. H.; Wang, Y.; Fang, X. F.; Liang, P.; Zhao, Y.; Li, Y. H.; Liu, X. M.

2018-02-01

Due to the deformation caused by residual stress in the welding process, welded components need treatment to reduce welding distortion. In this paper, several different times of flame-heating and water-cooling treatment were subjected to the friction stir welding joints of 15mm thick 7N01P-T4 aluminum alloy sheets to study the microstructure variation of friction stir welding joints of 7N01P-T4 aluminum alloy, and to analyze the effect on micro-hardness, tensile and fracture mechanical properties. This investigation will be helpful to optimize treatment methods and provide instruction on industrial production.

Effect of Welding Processes on the Microstructure, Mechanical Properties and Residual Stresses of Plain 9Cr-1Mo Steel Weld Joints

NASA Astrophysics Data System (ADS)

Nagaraju, S.; Vasantharaja, P.; Brahadees, G.; Vasudevan, M.; Mahadevan, S.

2017-12-01

9Cr-1Mo steel designated as P9 is widely used in the construction of power plants and high-temperature applications. It is chosen for fabricating hexcan fuel subassembly wrapper components of fast breeder reactors. Arc welding processes are generally used for fabricating 9Cr-1Mo steel weld joints. A-TIG welding process is increasingly being adopted by the industries. In the present study, shielded metal arc (SMA), tungsten inert gas (TIG) and A-TIG welding processes are used for fabricating the 9Cr-1Mo steel weld joints of 10 mm thickness. Effect of the above welding processes on the microstructure evolution, mechanical properties and residual stresses of the weld joints has been studied in detail. All the three weld joints exhibited comparable strength and ductility values. 9Cr-1Mo steel weld joint fabricated by SMAW process exhibited lower impact toughness values caused by coarser grain size and inclusions. 9Cr-1Mo steel weld joint fabricated by TIG welding exhibited higher toughness due to finer grain size, while the weld joint fabricated by A-TIG welding process exhibited adequate toughness values. SMA steel weld joint exhibited compressive residual stresses in the weld metal and HAZ, while TIG and A-TIG weld joint exhibited tensile residual stresses in the weld metal and HAZ.

An evaluation of GTAW-P versus GTA welding of alloy 718

NASA Technical Reports Server (NTRS)

Gamwell, W. R.; Kurgan, C.; Malone, T. W.

1991-01-01

Mechanical properties were evaluated to determine statistically whether the pulsed current gas tungsten arc welding (GTAW-P) process produces welds in alloy 718 with room temperature structural performance equivalent to current Space Shuttle Main Engine (SSME) welds manufactured by the constant current GTAW-P process. Evaluations were conducted on two base metal lots, two filler metal lots, two heat input levels, and two welding processes. The material form was 0.125-inch (3.175-mm) alloy 718 sheet. Prior to welding, sheets were treated to either the ST or STA-1 condition. After welding, panels were left as welded or heat treated to the STA-1 condition, and weld beads were left intact or machined flush. Statistical analyses were performed on yield strength, ultimate tensile strength (UTS), and high cycle fatigue (HCF) properties for all the post welded material conditions. Analyses of variance were performed on the data to determine if there were any significant effects on UTS or HCF life due to variations in base metal, filler metal, heat input level, or welding process. Statistical analyses showed that the GTAW-P process does produce welds with room temperature structural performance equivalent to current SSME welds manufactured by the GTAW process, regardless of prior material condition or post welding condition.

A novel ultrasonic NDE for shrink fit welded structures using interface waves.

PubMed

Lee, Jaesun; Park, Junpil; Cho, Younho

2016-05-01

Reactor vessel inspection is a critical part of safety maintenance in a nuclear power plant. The inspection of shrink fit welded structures in a reactor nozzle can be a challenging task due to the complicated geometry. Nozzle inspection using pseudo interface waves allows us to inspect the nozzle from outside of the nuclear reactor. In this study, layered concentric pipes were manufactured with perfect shrink fit conditions using stainless steel 316. The displacement distributions were calculated with boundary conditions for a shrink fit welded structure. A multi-transducer guided wave phased array system was employed to monitor the welding quality of the nozzle end at a distance from a fixed position. The complicated geometry of a shrink fit welded structure can be overcome by using the pseudo interface waves in identifying the location and size of defects. The experimental results demonstrate the feasibility of detecting weld delamination and defects. Copyright © 2016 Elsevier B.V. All rights reserved.

46 CFR 56.95-5 - Rights of access of marine inspectors.

Code of Federal Regulations, 2010 CFR

2010-10-01

... includes manufacture, fabrication, assembly, erection, and testing of the piping or system components... requirements of § 56.95-1, including certified qualifications for welders, welding operators, and welding...

Use of photostress to characterize the mechanical behavior of weldments

NASA Technical Reports Server (NTRS)

Gambrell, S. C., Jr.

1992-01-01

Welded aluminum is an important part of many space structures. Knowledge of the properties and behavior of weld material and the material surrounding the weld is important for modeling and design of the structures. Photoelastic coatings (Photostress) and strain gages were used to determine behavior of heat treated and as welded joints made from 2219T87 parent material and 2319 weld material subjected to tensile loads. TIG welds of 1/8, 1/2, and 1.4 inches thickness were investigated. Discontinuous yielding was observed in all tests and highly non-uniform behavior through the weld thickness was observed in joints having welds 1.4 inches thick. Joints having welds 1/8 and 1/2 inches thick had only small differences in behavior through the thickness of the weld. Joints in the 1/2 inch thick material contained distinct zones of constant strain within the normal strain gradient extending outward from the weld centerline. These zones had different thickness and locations. Points at the weld centerline, and for a distance of nearly one inch from the centerline, exhibited very nonlinear behavior during the first loading but exhibited near perfect strain hardening during the second loading.

Automatic programming of arc welding robots

NASA Astrophysics Data System (ADS)

Padmanabhan, Srikanth

Automatic programming of arc welding robots requires the geometric description of a part from a solid modeling system, expert weld process knowledge and the kinematic arrangement of the robot and positioner automatically. Current commercial solid models are incapable of storing explicitly product and process definitions of weld features. This work presents a paradigm to develop a computer-aided engineering environment that supports complete weld feature information in a solid model and to create an automatic programming system for robotic arc welding. In the first part, welding features are treated as properties or attributes of an object, features which are portions of the object surface--the topological boundary. The structure for representing the features and attributes is a graph called the Welding Attribute Graph (WAGRAPH). The method associates appropriate weld features to geometric primitives, adds welding attributes, and checks the validity of welding specifications. A systematic structure is provided to incorporate welding attributes and coordinate system information in a CSG tree. The specific implementation of this structure using a hybrid solid modeler (IDEAS) and an object-oriented programming paradigm is described. The second part provides a comprehensive methodology to acquire and represent weld process knowledge required for the proper selection of welding schedules. A methodology of knowledge acquisition using statistical methods is proposed. It is shown that these procedures did little to capture the private knowledge of experts (heuristics), but helped in determining general dependencies, and trends. A need was established for building the knowledge-based system using handbook knowledge and to allow the experts further to build the system. A methodology to check the consistency and validity for such knowledge addition is proposed. A mapping shell designed to transform the design features to application specific weld process schedules is described. A new approach using fixed path modified continuation methods is proposed in the final section to plan continuously the trajectory of weld seams in an integrated welding robot and positioner environment. The joint displacement, velocity, and acceleration histories all along the path as a function of the path parameter for the best possible welding condition are provided for the robot and the positioner to track various paths normally encountered in arc welding.

Nondestructive Evaluation of the Friction Weld Process on 2195/2219 Grade Aluminum

NASA Technical Reports Server (NTRS)

Suits, Michael W.; Clark, Linda S.; Cox, Dwight E.

1999-01-01

In 1996, NASA's Marshall Space Flight Center began an ambitious program designed to find alternative methods of repairing conventional TIG (Tungsten Inert Gas) welds and VPPA (Variable Polarity Plasma Arc) welds on the Space Shuttle External Tank without producing additional heat-related anomalies or conditions. Therefore, a relatively new method, invented by The Welding Institute (TWI) in Cambridge, England, called Friction Stir Welding (FSW), was investigated for use in this application, as well as being used potentially as an initial weld process. As with the conventional repair welding processes, nondestructive evaluation (NDE) plays a crucial role in the verification of these repairs. Since it was feared that conventional NDE might have trouble with this type of weld structure (due to shape of nugget, grain structure, etc.) it was imperative that a complete study be performed to address the adequacy of the NDE process. This paper summarizes that process.

Robotic Manufacturing of 5.5 Meter Cryogenic Fuel Tank Dome Assemblies for the NASA Ares I Rocket

NASA Technical Reports Server (NTRS)

Jones, Ronald E.

2012-01-01

The Ares I rocket is the first launch vehicle scheduled for manufacture under the National Aeronautic and Space Administration's (NASA's) Constellation program. A series of full-scale Ares I development articles have been constructed on the Robotic Weld Tool at the NASA George C. Marshall Space Flight Center in Huntsville, Alabama. The Robotic Weld Tool is a 100 ton, 7-axis, robotic manufacturing system capable of machining and friction stir welding large-scale space hardware. This presentation will focus on the friction stir welding of 5.5m diameter cryogenic fuel tank components; specifically, the liquid hydrogen forward dome (LH2 MDA), the common bulkhead manufacturing development articles (CBMDA) and the thermal protection system demonstration dome (TPS Dome). The LH2 MDA was the first full-scale, flight-like Ares I hardware produced under the Constellation Program. It is a 5.5m diameter elliptical dome assembly consisting of eight gore panels, a y-ring stiffener and a manhole fitting. All components are made from aluminumlithium alloy 2195. Conventional and self-reacting friction stir welding was used on this article. An overview of the manufacturing processes will be discussed. The LH2 MDA is the first known fully friction stir welded dome ever produced. The completion of four Common Bulkhead Manufacturing Development Articles (CBMDA) and the TPS Dome will also be highlighted. Each CBMDA and the TPS Dome consists of a 5.5m diameter spun-formed dome friction stir welded to a y-ring stiffener. The domes and y-rings are made of aluminum 2014 and 2219 respectively. The TPS Dome has an additional aluminum alloy 2195 barrel section welded to the y-ring. Manufacturing solutions will be discussed including "fixtureless" welding with self reacting friction stir welding.

High-Speed Friction-Stir Welding To Enable Aluminum Tailor-Welded Blanks

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

Hovanski, Yuri; Upadhyay, Piyush; Carsley, John

Current joining technologies for automotive aluminum alloys are utilized in low-volume and niche applications, and have yet to be scaled for the high-volume vehicle market. This study targeted further weight reduction, part reduction, and cost savings by enabling tailor-welded blank technology for aluminum alloys at high-volumes. While friction stir welding has been traditionally applied at linear velocities less than one meter per minute, high volume production applications demand the process be extended to higher velocities more amenable to cost sensitive production environments. Unfortunately, weld parameters and performance developed and characterized at low to moderate welding velocities do not directly translatemore » to high speed linear friction stir welding. Therefore, in order to facilitate production of high volume aluminum welded components, parameters were developed with a minimum welding velocity of three meters per minute. With an emphasis on weld quality, welded blanks were evaluated for post-weld formability utilizing a combination of numerical and experimental methods. Evaluation across scales was ultimately validated by stamping full-size production door inner panels made from dissimilar thickness aluminum tailor-welded blanks, which provided validation of the numerical and experimental analysis of laboratory scale tests.« less

Flaws detection and localization in weld structure using the topological energy method

NASA Astrophysics Data System (ADS)

Lubeigt, Emma; Mensah, Serge; Rakotonarivo, Sandrine; Chaix, Jean-François; Gobillot, Gilles; Baqué, François

2017-02-01

The non-destructive testing of austenitic welds using ultrasound plays an important role in the assessment of the structural integrity and safety of critical structures in a nuclear reactor. The bedspring and the deck are complex welded structures of very restricted access; the ability to reliably detect and locate defects like cracks is therefore a difficult challenge. Ultrasonic testing is a well-recognized non-invasive technique which exhibits high characterization performances in homogeneous media (steel). However, its capabilities are hampered when operating in heterogeneous and anisotropic austenitic welds because of deviation and splitting of the ultrasonic beam. In order to rise to this important challenge, a model-based method is proposed, which takes into account a prior knowledge corresponding to the welding procedure specifications that condition the austenitic grains orientation within the weld and thus the wave propagation. The topological imaging method implemented is a differential approach which, compares signals from the reference defect-free medium to the inspected medium. It relies on combinations of two computed ultrasonic fields, one forward and one adjoint. Numerical simulations and experiments have been carried out to validate the practical relevance of this approach to detect and locate a flaw in a weld.

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.

Development of electromagnetic welding facility of flat plates for nuclear industry

NASA Astrophysics Data System (ADS)

Kumar, Rajesh; Sahoo, Subhanarayan; Sarkar, Biswanath; Shyam, Anurag

2017-04-01

Electromagnetic pulse welding (EMPW) process, one of high speed welding process uses electromagnetic force from discharged current through working coil, which develops a repulsive force between the induced current flowing parallel and in opposite direction. For achieving the successful weldment using this process the design of working coil is the most important factor due to high magnetic field on surface of work piece. In case of high quality flat plate welding factors such as impact velocity, angle of impact standoff distance, thickness of flyer and overlap length have to be chosen carefully. EMPW has wide applications in nuclear industry, automotive industry, aerospace, electrical industries. However formability and weldability still remain major issues. Due to ease in controlling the magnetic field enveloped inside tubes, the EMPW has been widely used for tube welding. In case of flat components control of magnetic field is difficult. Hence the application of EMPW gets restricted. The present work attempts to make a novel contribution by investigating the effect of process parameters on welding quality of flat plates. The work emphasizes the approaches and engineering calculations required to effectively use of actuator in EMPW of flat components.

A density-adaptive SPH method with kernel gradient correction for modeling explosive welding

NASA Astrophysics Data System (ADS)

Liu, M. B.; Zhang, Z. L.; Feng, D. L.

2017-09-01

Explosive welding involves processes like the detonation of explosive, impact of metal structures and strong fluid-structure interaction, while the whole process of explosive welding has not been well modeled before. In this paper, a novel smoothed particle hydrodynamics (SPH) model is developed to simulate explosive welding. In the SPH model, a kernel gradient correction algorithm is used to achieve better computational accuracy. A density adapting technique which can effectively treat large density ratio is also proposed. The developed SPH model is firstly validated by simulating a benchmark problem of one-dimensional TNT detonation and an impact welding problem. The SPH model is then successfully applied to simulate the whole process of explosive welding. It is demonstrated that the presented SPH method can capture typical physics in explosive welding including explosion wave, welding surface morphology, jet flow and acceleration of the flyer plate. The welding angle obtained from the SPH simulation agrees well with that from a kinematic analysis.

HEAT INPUT AND POST WELD HEAT TREATMENT EFFECTS ON REDUCED-ACTIVATION FERRITIC/MARTENSITIC STEEL FRICTION STIR WELDS

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

Tang, Wei; Chen, Gaoqiang; Chen, Jian

Reduced-activation ferritic/martensitic (RAFM) steels are an important class of structural materials for fusion reactor internals developed in recent years because of their improved irradiation resistance. However, they can suffer from welding induced property degradations. In this paper, a solid phase joining technology friction stir welding (FSW) was adopted to join a RAFM steel Eurofer 97 and different FSW parameters/heat input were chosen to produce welds. FSW response parameters, joint microstructures and microhardness were investigated to reveal relationships among welding heat input, weld structure characterization and mechanical properties. In general, FSW heat input results in high hardness inside the stir zonemore » mostly due to a martensitic transformation. It is possible to produce friction stir welds similar to but not with exactly the same base metal hardness when using low power input because of other hardening mechanisms. Further, post weld heat treatment (PWHT) is a very effective way to reduce FSW stir zone hardness values.« less

Effect of welding on creep damage evolution in P91B steel

NASA Astrophysics Data System (ADS)

Baral, J.; Swaminathan, J.; Chakrabarti, D.; Ghosh, R. N.

2017-07-01

Study of creep behavior of base metal (without weld) and welded specimens of P91B steel over a range of temperatures (600-650 °C) and stresses (50-180 MPa) showed similar values of minimum creep-rates for both specimens at higher stress regime (>100 MPa) whilst, significantly higher creep rates in the case of welded specimens at lower stress regime. Considering that welded specimen is comprised of two distinct structural regimes, i.e. weld affected zone and base metal, a method has been proposed for estimating the material parameters describing creep behavior of those regimes. Stress-strain distribution across welded specimen predicted from finite element analysis based on material parameters revealed preferential accumulation of stress and creep strain at the interface between weld zone and base metal. This is in-line with the experimental finding that creep rupture preferentially occurs at inter-critical heat affected zone in welded specimens owing to ferrite-martensite structure with coarse Cr23C6 particles.

Electron Backscatter Diffraction Analysis of Joints Between AISI 316L Austenitic/UNS S32750 Dual-Phase Stainless Steel

NASA Astrophysics Data System (ADS)

Shamanian, Morteza; Mohammadnezhad, Mahyar; Amini, Mahdi; Zabolian, Azam; Szpunar, Jerzy A.

2015-08-01

Stainless steels are among the most economical and highly practicable materials widely used in industrial areas due to their mechanical and corrosion resistances. In this study, a dissimilar weld joint consisting of an AISI 316L austenitic stainless steel (ASS) and a UNS S32750 dual-phase stainless steel was obtained under optimized welding conditions by gas tungsten arc welding technique using AWS A5.4:ER2594 filler metal. The effect of welding on the evolution of the microstructure, crystallographic texture, and micro-hardness distribution was also studied. The weld metal (WM) was found to be dual-phased; the microstructure is obtained by a fully ferritic solidification mode followed by austenite precipitation at both ferrite boundaries and ferrite grains through solid-state transformation. It is found that welding process can affect the ferrite content and grain growth phenomenon. The strong textures were found in the base metals for both steels. The AISI 316L ASS texture is composed of strong cube component. In the UNS S32750 dual-phase stainless steel, an important difference between the two phases can be seen in the texture evolution. Austenite phase is composed of a major cube component, whereas the ferrite texture mainly contains a major rotated cube component. The texture of the ferrite is stronger than that of austenite. In the WM, Kurdjumov-Sachs crystallographic orientation relationship is found in the solidification microstructure. The analysis of the Kernel average misorientation distribution shows that the residual strain is more concentrated in the austenite phase than in the other phase. The welding resulted in a significant hardness increase in the WM compared to initial ASS.

Thermal and infrared-diode laser effects on indocyanine-green-treated corneal collagen

NASA Astrophysics Data System (ADS)

Timberlake, George T.; Patmore, Ann; Shallal, Assaad; McHugh, Dominic; Marshall, John

1993-07-01

It has been suggested that laser welds of collagenous tissues form by interdigitation and chemical bonding of thermally 'unraveled' collagen fibrils. We investigated this proposal by attempting to weld highly collagenous, avascular corneal tissue with an infrared (IR) diode laser as follows. First, the temperature at which corneal collagen shrinks and collagen fibrils 'split' into subfibrillary components was determined. Second, since use of a near-IR laser wavelength necessitated addition of an absorbing dye (indocyanine green (ICG) to the cornea, we measured absorption spectra of ICG-treated tissue to ensure that peak ICG absorbance did not change markedly when ICG was present in the cornea. Third, using gel electrophoresis of thermally altered corneal collagen, we searched for covalently crosslinked compounds predicted by the proposed welding mechanism. Finally, we attempted to weld partial thickness corneal incisions infused with ICG. Principal experimental findings were as follows: (1) Human corneal (type I) collagen splits into subfibrillary components at approximately 63 degree(s)C, the same temperature that produces collagen shrinkage. (2) Peak ICG absorption does not change significantly in corneal stroma or with laser heating. (3) No evidence was found for the formation of novel compounds or the loss of proteins as a result of tissue heating. All tissue treated with ICG, however, exhibited a novel 244 kD protein band indicating chemical activity between collagen and corneal stromal components. (4) Laser welding corneal incisions was unsuccessful possibly due to shrinkage of the sides of the incision, lack of incision compression during heating, or a less than optimal combination of ICG concentration and radiant exposure. In summary, these experiments demonstrate the biochemical and morphological complexity of ICG-enhanced IR laser-tissue welding and the need for further investigation of laser welding mechanisms.

Formation of austenite in high Cr ferritic/martensitic steels by high fluence neutron irradiation

NASA Astrophysics Data System (ADS)

Lu, Z.; Faulkner, R. G.; Morgan, T. S.

2008-12-01

High Cr ferritic/martensitic steels are leading candidates for structural components of future fusion reactors and new generation fission reactors due to their excellent swelling resistance and thermal properties. A commercial grade 12%CrMoVNb ferritic/martensitic stainless steel in the form of parent plate and off-normal weld materials was fast neutron irradiated up to 33 dpa (1.1 × 10 -6 dpa/s) at 400 °C and 28 dpa (1.7 × 10 -6 dpa/s) at 465 °C, respectively. TEM investigation shows that the fully martensitic weld metal transformed to a duplex austenite/ferrite structure due to high fluence neutron irradiation, the austenite was heavily voided (˜15 vol.%) and the ferrite was relatively void-free; whilst no austenite phases were detected in plate steel. Thermodynamic and phase equilibria software MTDATA has been employed for the first time to investigate neutron irradiation-induced phase transformations. The neutron irradiation effect is introduced by adding additional Gibbs free energy into the system. This additional energy is produced by high energy neutron irradiation and can be estimated from the increased dislocation loop density caused by irradiation. Modelling results show that neutron irradiation reduces the ferrite/austenite transformation temperature, especially for high Ni weld metal. The calculated results exhibit good agreement with experimental observation.

Space Fabrication Demonstration System

NASA Technical Reports Server (NTRS)

1977-01-01

Progress on fabrication facility (beam builder) support structure control, clamp/weld block, and welding and truss cut off is discussed. The brace attachment design was changed and the design of the weld mechanism was modified which achieved the following system benefits: (1) simplified weld electrode life; (2) reduced weld power requirements; and (3) simplified brace attachment mechanisms. Static and fatigue characteristics of spot welded 2024T3 aluminum joints are evaluated.

Microstructure and mechanical properties of friction stir welded and laser welded high entropy alloy CrMnFeCoNi

NASA Astrophysics Data System (ADS)

Jo, Min-Gu; Kim, Han-Jin; Kang, Minjung; Madakashira, Phaniraj P.; Park, Eun Soo; Suh, Jin-Yoo; Kim, Dong-Ik; Hong, Sung-Tae; Han, Heung Nam

2018-01-01

The high entropy alloy CrMnFeCoNi has been shown to have promising structural properties. For a new alloy to be used in a structural application it should be weldable. In the present study, friction stir welding (FSW) and laser welding (LW) techniques were used to butt weld thin plates of CrMnFeCoNi. The microstructure, chemical homogeneity and mechanical behavior of the welds were characterized and compared with the base metal. The tensile stress-strain behavior of the welded specimens were reasonable when compared with that of the base metal. FSW refined the grain size in the weld region by a factor of ˜14 when compared with the base metal. High-angle annular dark field transmission electron microscopy in combination with energy dispersive X-ray spectroscopy showed chemical inhomogeneity between dendritic and interdendritic regions in the fusion zone of LW. Large fluctuations in composition (up to 15 at%) did not change the crystal structure in the fusion zone. Hardness measurements were carried out in the weld cross section and discussed in view of the grain size, low angle grain boundaries and twin boundaries in FSW specimens and the dendritic microstructure in LW specimens.

Microstructure and Plastic Deformation of the As-Welded Invar Fusion Zones

NASA Astrophysics Data System (ADS)

Yao, D. J.; Zhou, D. R.; Xu, P. Q.; Lu, F. G.

2017-05-01

The as-welded Invar fusion zones were fabricated between cemented carbides and carbon steel using a Fe-Ni Invar interlayer and laser welding method. Three regions in the as-welded Invar fusion zones were defined to compare microstructures, and these were characterized and confirmed by scanning electron microscopy and X-ray diffractometry. The structure and plastic deformation mechanism for initial Invar Fe-Ni alloys and the as-welded Invar fusion zones are discussed. (1) After undergoing high-temperature thermal cycles, the microstructure of the as-welded Invar fusion zones contains γ-(Fe, Ni) solid solution (nickel dissolving in γ-Fe) with a face-centered cubic (fcc) crystal structure and mixed carbides (eutectic colonies, mixed carbides between two adjacent grains). The mixed carbides exhibited larger, coarser eutectic microstructures with a decrease in welding speed and an increase in heat input. (2) The structure of the initial Invar and the as-welded Invar is face-centered cubic γ-(Fe, Ni). (3) The as-welded Invar has a larger plastic deformation than initial Invar with an increase in local strain field and dislocation density. Slip deformation is propagated along the (111) plane. This finding helps us to understand microstructure and the formation of dislocation and plastic deformation when the Invar Fe-Ni alloy undergoes a high-temperature process.

The Mechanical Metallurgy of Armour Steels

DTIC Science & Technology

2016-10-01

21 7.A. Cracking associated with Welding ...associated with Welding A range of defects, including cracks can be caused by welding processes, examples of which are shown in Figure 19, many of...which can lead to structural cracking problems. The avoidance of weld defects, particularly cracking, is the reason why armour steel welding processes

Solid State Joining of Dissimilar Titanium Alloys

NASA Astrophysics Data System (ADS)

Morton, Todd W.

Solid state joining of titanium via friction stir welding and diffusion bonding have emerged as enablers of efficient monolithic structural designs by the eliminations fasteners for the aerospace industry. As design complexity and service demands increase, the need for joints of dissimilar alloys has emerged. Complex thermomechanical conditions in friction stir weld joints and high temperature deformation behavior differences between alloys used in dissimilar joints gives rise to a highly variable flow pattern within a stir zone. Experiments performed welding Ti-6Al-4V to beta21S show that mechanical intermixing of the two alloys is the primary mechanism for the generation of the localized chemistry and microstructure, the magnitude of which can be directly related to pin rotation and travel speed weld parameters. Mechanical mixing of the two alloys is heavily influenced by strain rate softening phenomena, and can be used to manipulate weld nugget structure by switching which alloy is subjected to the advancing side of the pin. Turbulent mixing of a weld nugget and a significant reduction in defects and weld forces are observed when the beta21S is put on the advancing side of the weld where higher strain rates are present. Chemical diffusion driven by the heat of weld parameters is characterized using energy dispersive x-ray spectroscopy (EDS) and is shown to be a secondary process responsible for generating short-range chemical gradients that lead to a gradient of alpha particle structures. Diffusion calculations are inconsistent with an assumption of steady-state diffusion and show that material interfaces in the weld nugget evolve through the break-down of turbulent interface features generated by material flows. A high degree of recrystallization is seen throughout the welds, with unique, hybrid chemistry grains that are generated at material interfaces in the weld nugget that help to unify the crystal structure of dissimilar alloys. The degree of recrystallization is tied to the localized thermal profile in the weld nugget as well as the heating rates of a given set of weld parameters. Slow kinetics of alpha dissolution relative to the heating rate and process times of friction stir welding suggest an alpha-particle assisted super-transus recrystallization process contributes to a refined grain size in weld parameters utilizing high travel speed.

On-orbit NDE: A novel approach to tube weld inspection

NASA Technical Reports Server (NTRS)

Michaels, Kerry; Hughes, Greg

1994-01-01

The challenge of fabrication and repair of structures in space must be met if we are to utilize and maintain long-duration space facilities. Welding techniques have been demonstrated to provide the most reliable means to accomplish this task. Over the past few years, methods have been developed to perform orbital tube welding employing space-based welding technology pioneered by the former Soviet Union. Welding can result in the formation of defects, which threaten the structural integrity of the welded joint. Implementation of welding on-orbit, therefore, must also include methods to evaluate the quality and integrity of the welded joints. To achieve this goal, the development of an on-orbit tube weld inspection system, utilizing alternating current field measurement (ACFM) technology, has been under taken. This paper describes the development of the ACFM on-orbit tube weld inspection tool. Topics discussed include: requirements for on-orbit NDE, basic theory of ACFM, its advantages over other NDE methods for on-orbit applications, and the ACFM NDE system design. System operation and trial inspection results are also discussed. Future work with this technology is also considered.

Structural Degradation of the Welded Joint of the Gas Main after a Long-Term Operation in Sub-Acid Soil

NASA Astrophysics Data System (ADS)

Maruschak, P. O.; Bishchak, R. T.; Maruschak, O. V.; Panin, S. V.

2018-01-01

The authors investigated the main regularities in the structural and mechanical degradation of steel and a welded joint of the “Soyuz” gas main in operation. It is established that the defect accumulation kinetics in welds are determined both by technological disruptions in their manufacture and by hydrogenation of the weld during a long operating time. A weakening of the mechanical properties of the weld after a prolonged operation is shown, which in some cases led to the appearance of cracks and fracture of the gas main.

Vibration stress relief of DH 36 rectangle welded plates

NASA Astrophysics Data System (ADS)

Li, Shuqi; Fang, Hongyuan

2018-03-01

Vibration stress relief (VSR) is widely used in reducing residual stress in welded structures. However, the effectiveness of this method is still instable in some circumstance. In this study, a covert negative treatment phenomenon was investigated, i.e. natural frequency of welded structures decreased after VSR but residual stress in one direction increased. When the alteration of natural frequency after VSR is significant, the residual stresses in both the longitudinal and transversal directions shall decrease. Otherwise, residual stresses may increase on one direction. Thus, sufficient power shall be applied to the welded structures to avoid negative results.

Production and fabrication of vanadium alloys for the radiative divertor program of DIII-D

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

Johnson, W.R.; Smith, J.P.; Trester, P.W.

1997-04-01

V-4Cr-4Ti alloy has been selected for use in the manufacture of a portion of the DIII-D Radiative Divertor upgrade. The production of a 1200-kg ingot of V-4Cr-4Ti alloy, and processing into final sheet and rod product forms suitable for components of the DIII-D Radiative Divertor structure, has been completed at Wah Chang (formerly Teledyne Wah Chang) of Albany, Oregon (WCA). Joining of V-4Cr-4Ti alloy has been identified as the most critical fabrication issue for its use in the RD Program, and research into several joining methods for fabrication of the RD components, including resistance seam, friction, and electron beam welding,more » is continuing. Preliminary trials have been successful in the joining of V-alloy to itself by electron beam, resistance, and friction welding processes, and to Inconel 625 by friction welding. An effort to investigate the explosive bonding of V-4Cr-4Ti alloy to Inconel 625 has also been initiated, and results have been encouraging. In addition, preliminary tests have been completed to evaluate the susceptibility of V-4Cr-4Ti alloy to stress corrosion cracking in DIII-D cooling water, and the effects of exposure to DIII-D bakeout conditions on the tensile and fracture behavior of V-4Cr-4Ti alloy.« less

Programmable Automated Welding System (PAWS)

NASA Technical Reports Server (NTRS)

Kline, Martin D.

1994-01-01

An ambitious project to develop an advanced, automated welding system is being funded as part of the Navy Joining Center with Babcock & Wilcox as the prime integrator. This program, the Programmable Automated Welding System (PAWS), involves the integration of both planning and real-time control activities. Planning functions include the development of a graphical decision support system within a standard, portable environment. Real-time control functions include the development of a modular, intelligent, real-time control system and the integration of a number of welding process sensors. This paper presents each of these components of the PAWS and discusses how they can be utilized to automate the welding operation.

Weld failure detection

DOEpatents

Pennell, William E.; Sutton, Jr., Harry G.

1981-01-01

Method and apparatus for detecting failure in a welded connection, particrly applicable to not readily accessible welds such as those joining components within the reactor vessel of a nuclear reactor system. A preselected tag gas is sealed within a chamber which extends through selected portions of the base metal and weld deposit. In the event of a failure, such as development of a crack extending from the chamber to an outer surface, the tag gas is released. The environment about the welded area is directed to an analyzer which, in the event of presence of the tag gas, evidences the failure. A trigger gas can be included with the tag gas to actuate the analyzer.

Control of microstructure in soldered, brazed, welded, plated, cast or vapor deposited manufactured components

DOEpatents

Ripley, Edward B.; Hallman, Russell L.

2015-11-10

Disclosed are methods and systems for controlling of the microstructures of a soldered, brazed, welded, plated, cast, or vapor deposited manufactured component. The systems typically use relatively weak magnetic fields of either constant or varying flux to affect material properties within a manufactured component, typically without modifying the alloy, or changing the chemical composition of materials or altering the time, temperature, or transformation parameters of a manufacturing process. Such systems and processes may be used with components consisting of only materials that are conventionally characterized as be uninfluenced by magnetic forces.

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.

Coil Welding Aid

NASA Technical Reports Server (NTRS)

Wiesenbach, W. T.; Clark, M. C.

1983-01-01

Positioner holds coil inside cylinder during tack welding. Welding aid spaces turns of coil inside cylinder and applies contact pressure while coil is tack-welded to cylinder. Device facilitates fabrication of heat exchangers and other structures by eliminating hand-positioning and clamping of individual coil turns.

Characteristics of Laser Beam and Friction Stir Welded AISI 409M Ferritic Stainless Steel Joints

NASA Astrophysics Data System (ADS)

Lakshminarayanan, A. K.; Balasubramanian, V.

2012-04-01

This article presents the comparative evaluation of microstructural features and mechanical properties of friction stir welded (solid-state) and laser beam welded (high energy density fusion welding) AISI 409M grade ferritic stainless steel joints. Optical microscopy, microhardness testing, transverse tensile, and impact tests were performed. The coarse ferrite grains in the base material were changed to fine grains consisting duplex structure of ferrite and martensite due to the rapid cooling rate and high strain induced by severe plastic deformation caused by frictional stirring. On the other hand, columnar dendritic grain structure was observed in fusion zone of laser beam welded joints. Tensile testing indicates overmatching of the weld metal relative to the base metal irrespective of the welding processes used. The LBW joint exhibited superior impact toughness compared to the FSW joint.

Phenomenological Models and Animations of Welding and their Impact

NASA Astrophysics Data System (ADS)

DebRoy, Tarasankar

Professor Robertson's recognized research on metallurgical thermodynamics and kinetics for over 40 years facilitated the emergence of rigorous quantitative understanding of many complex metallurgical processes. The author had the opportunity to work with Professor Robertson on liquid metals in the 1970s. This paper is intended to review the advances in the quantitative understanding of welding processes and weld metal attributes in recent decades. Over this period, phenomenological models have been developed to better understand and control various welding processes and the structure and properties of welded materials. Numerical models and animations of melting, solidification and the evolution of micro and macro-structural features will be presented to critically examine their impact on the practice of welding and the underlying science.

Welding at the Kennedy Space Center.

NASA Technical Reports Server (NTRS)

Clautice, W. E.

1973-01-01

Brief description of the nature of the mechanical equipment at a space launch complex from a welding viewpoint. including an identification of the major welding applications used in the construction of this complex. The role played by welding in the ground support equipment is noted, including the welded structures and systems required in the vehicle assembly building, the mobile launchers, transporters, mobile service structure, launch pad and launch site, the propellants system, the pneumatics system, and the environmental control system. The welding processes used at the Kennedy Space Center are reviewed, and a particularly detailed account is given of the design and fabrication of the liquid hydrogen and liquid oxygen storage spheres and piping. Finally, the various methods of testing and inspecting the storage spheres are cited.

Plasma arc welding repair of space flight hardware

NASA Technical Reports Server (NTRS)

Hoffman, David S.

1993-01-01

A technique to weld repair the main combustion chamber of Space Shuttle Main Engines has been developed. The technique uses the plasma arc welding process and active cooling to seal cracks and pinholes in the hot-gas wall of the main combustion chamber liner. The liner hot-gas wall is made of NARloy-Z, a copper alloy previously thought to be unweldable using conventional arc welding processes. The process must provide extensive heat input to melt the high conductivity NARloy-Z while protecting the delicate structure of the surrounding material. The higher energy density of the plasma arc process provides the necessary heat input while active water cooling protects the surrounding structure. The welding process is precisely controlled using a computerized robotic welding system.

SNL/SRNL Joint Project on degradation of mechanical properties in structural metals and welds for GTS reservoirs.

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

Ronevich, Joseph Allen; Balch, Dorian K.; San Marchi, Christopher W.

2015-12-01

This project was intended to enable SNL-CA to produce appropriate specimens of relevant stainless steels for testing and perform baseline testing of weld heat-affected zone and weld fusion zone. One of the key deliverables in this project was to establish a procedure for fracture testing stainless steel weld fusion zone and heat affected zones that were pre-charged with hydrogen. Following the establishment of the procedure, a round robin was planned between SNL-CA and SRNL to ensure testing consistency between laboratories. SNL-CA and SRNL would then develop a comprehensive test plan, which would include tritium exposures of several years at SRNLmore » on samples delivered by SNL-CA. Testing would follow the procedures developed at SNL-CA. SRNL will also purchase tritium charging vessels to perform the tritium exposures. Although comprehensive understanding of isotope-induced fracture in GTS reservoir materials is a several year effort, the FY15 work would enabled us to jump-start the tests and initiate long-term tritium exposures to aid comprehensive future investigations. Development of a procedure and laboratory testing consistency between SNL-CA and SNRL ensures reliability in results as future evaluations are performed on aluminum alloys and potentially additively-manufactured components.« less

Status of Fuel Development and Manufacturing for Space Nuclear Reactors at BWX Technologies

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

Carmack, W.J.; Husser, D.L.; Mohr, T.C.

2004-02-04

New advanced nuclear space propulsion systems will soon seek a high temperature, stable fuel form. BWX Technologies Inc (BWXT) has a long history of fuel manufacturing. UO2, UCO, and UCx have been fabricated at BWXT for various US and international programs. Recent efforts at BWXT have focused on establishing the manufacturing techniques and analysis capabilities needed to provide a high quality, high power, compact nuclear reactor for use in space nuclear powered missions. To support the production of a space nuclear reactor, uranium nitride has recently been manufactured by BWXT. In addition, analytical chemistry and analysis techniques have been developedmore » to provide verification and qualification of the uranium nitride production process. The fabrication of a space nuclear reactor will require the ability to place an unclad fuel form into a clad structure for assembly into a reactor core configuration. To this end, BWX Technologies has reestablished its capability for machining, GTA welding, and EB welding of refractory metals. Specifically, BWX Technologies has demonstrated GTA welding of niobium flat plate and EB welding of niobium and Nb-1Zr tubing. In performing these demonstration activities, BWX Technologies has established the necessary infrastructure to manufacture UO2, UCx, or UNx fuel, components, and complete reactor assemblies in support of space nuclear programs.« less

Evaluating the SCC resistance of underwater welds in sodium tetrathionate

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

White, R.A.; Angeliu, T.M.

1997-12-01

The susceptibility of welds to stress corrosion cracking (SCC) is enhanced by the surface residual tensile stresses generated by the typical welding process. However, underwater plasma transferred arc (PTA) welding has been shown to produce compressive surface residual stresses, an encouraging result if repairs of cracked boiling water reactor (BWR) components are to be made without further endangering them to SCC. This program was designed to verify that underwater PTA welds are resistant to SCC and to determine if underwater PTA welding could mitigate SCC in potentially susceptible welds. This was achieved by exposing various welds on solution annealed (SA)more » and SA + thermally sensitized 304 stainless steel at 25 C in a solution of 1.5 gm/liter of sodium sulfide added to 0.05M sodium tetrathionate, titrated to a pH of 1.25 with H{sub 2}SO{sub 4}. The autogeneous welds were produced using gas tungsten arc (GTA) and plasma transferred arc (PTA) welding under atmospheric conditions, and PTA welding underwater. After 1 hour of sodium tetrathionate exposure, GTA and air PTA welds exhibited SCC while the underwater PTA weld heat affected zones were more resistant. Underwater PTA welds bisecting a GTA weld eliminated the cracking in the GTA weld heat affected zone under certain conditions. The lack of IG cracking in the region influenced by the underwater PTA weld is consistent with the measurement of compressive surface residual stresses inherent to the underwater welding process.« less

Advanced Metalworking Solutions For Naval Systems That Go In Harm’s Way

DTIC Science & Technology

2015-01-01

destroyers USS Momsen (DDG 92) and USS Preble (DDG 88) are underway in formation. U.S. Navy photo Front cover: Ingalls Shipbuilding welding photo...applies a variety of innovative welding technologies to address the challenges associated with joining weapon system components. Joining Technologies...friction stir welding process to manufacture edge-cooled naval electronic cold plate assemblies. The modular, high- performance, and scalable

Technological Advances in Joining

DTIC Science & Technology

1981-08-01

automotive industry, and similar robots are being equipped to perform many arc welding functions in areas where high production rates must be...nonvacuum electron-beam welding favor the use of this process by the automotive industry. For example, this process has been used to join the component...metal additions were not needed. This process has been also used to weld various assemblies for automotive transmissions (e.g., annulus gear assemblies

Circulating adhesion molecules after short-term exposure to particulate matter among welders.

PubMed

Fang, S C; Eisen, E A; Cavallari, J M; Mittleman, M A; Christiani, D C

2010-01-01

Studies from several countries indicate that welders experience increased risk of mortality and morbidity from ischaemic heart disease. Although the underlying mechanisms are unclear, vascular responses to particulate matter contained in welding fumes may play a role. To investigate this, we studied the acute effects of welding fume exposure on the endothelial component of vascular function, as measured by circulating adhesion molecules involved in leukocyte adhesion (sICAM-1 and sVCAM-1) and coagulation (vWF). A panel of 26 male welders was studied repeatedly across a 6 h work-shift on a high exposure welding day and/or a low exposure non-welding day. Personal PM(2.5) exposure was measured throughout the work-shift. Blood samples were collected in the morning (baseline) prior to the exposure period, immediately after the exposure period, and the following morning. To account for the repeated measurements, we used linear mixed models to evaluate the effects of welding (binary) and PM(2.5) (continuous) exposure on each blood marker, adjusting for baseline blood marker concentration, smoking, age and time of day. Welding and PM(2.5) exposure were significantly associated with a decrease in sVCAM-1 in the afternoon and the following morning and an increase in vWF in the afternoon. The data suggest that welding and short-term occupational exposure to PM(2.5) may acutely affect the endothelial component of vascular function.

Grain refinement control in gas-shielded arc welding of aluminum tubing

NASA Technical Reports Server (NTRS)

Iceland, W. F.; Whiffen, E. L.

1974-01-01

When sections are being welded, operator varies pulse rate of power supply and simultaneously monitors signal on oscilloscope until rate is found which produces maximum arc gas voltage. Remainder of welding is performed with power supply set at this pulse rate, producing desired maximum weld puddle agitation and fine uniform weld of grain structure.

Modeling and characterization of as-welded microstructure of solid solution strengthened Ni-Cr-Fe alloys resistant to ductility-dip cracking part I: Numerical modeling

NASA Astrophysics Data System (ADS)

Unfried-Silgado, Jimy; Ramirez, Antonio J.

2014-03-01

This work aims the numerical modeling and characterization of as-welded microstructure of Ni-Cr-Fe alloys with additions of Nb, Mo and Hf as a key to understand their proven resistance to ductility-dip cracking. Part I deals with as-welded structure modeling, using experimental alloying ranges and Calphad methodology. Model calculates kinetic phase transformations and partitioning of elements during weld solidification using a cooling rate of 100 K.s-1, considering their consequences on solidification mode for each alloy. Calculated structures were compared with experimental observations on as-welded structures, exhibiting good agreement. Numerical calculations estimate an increase by three times of mass fraction of primary carbides precipitation, a substantial reduction of mass fraction of M23C6 precipitates and topologically closed packed phases (TCP), a homogeneously intradendritic distribution, and a slight increase of interdendritic Molybdenum distribution in these alloys. Incidences of metallurgical characteristics of modeled as-welded structures on desirable characteristics of Ni-based alloys resistant to DDC are discussed here.

Calculation of optimal modes for electric-contact welding of rails of mine haulage tracks

NASA Astrophysics Data System (ADS)

Shevchenko, R. A.; Kozyrev, N. A.; Usoltsev, A. A.; Kriukov, R. E.; Shishkin, P. E.

2017-09-01

The choice of thermal regime is based on the exclusion of formation of quenching structures (martensite and bainite), causing additional stresses and cracks which lead to the destruction of rails. After welded joint upset and cooling at the time of reaching the required temperature it is proposed to perform quasi-isothermal exposure by passing pulses of alternating current through the welded joint. The method for calculating the quasi-isothermal exposure is described that depends on the strength of the welding current and different rails section. It is suggested that after welding the rails during quenching, a quasi-isothermal holding is carried out in the temperature range of the formation of the fine-dispersed structure by passing pulses of alternating electric current through the welded joint maintaining this temperature until the end of the transformation. It is shown that the use of quasi-isothermal exposure at a chosen temperature of 600 - 650 °C makes it possible to obtain a finely dispersed structure of the welded seam of rails of mine haulage tracks without additional heat treatment.

Local Laser Strengthening of Steel Sheets for Load Adapted Component Design in Car Body Structures

NASA Astrophysics Data System (ADS)

Jahn, Axel; Heitmanek, Marco; Standfuss, Jens; Brenner, Berndt; Wunderlich, Gerd; Donat, Bernd

The current trend in car body construction concerning light weight design and car safety improvement increasingly requires an adaption of the local material properties on the component load. Martensitic hardenable steels, which are typically used in car body components, show a significant hardening effect, for instance in laser welded seams. This effect can be purposefully used as a local strengthening method. For several steel grades the local strengthening, resulting from a laser remelting process was investigated. The strength in the treated zone was determined at crash relevant strain rates. A load adapted design of complex reinforcement structures was developed for compression and bending loaded tube samples, using numerical simulation of the deformation behavior. Especially for bending loaded parts, the crash energy absorption can be increased significantly by local laser strengthening.

Characterization of Nitinol Laser-Weld Joints by Nondestructive Testing

NASA Astrophysics Data System (ADS)

Wohlschlögel, Markus; Gläßel, Gunter; Sanchez, Daniela; Schüßler, Andreas; Dillenz, Alexander; Saal, David; Mayr, Peter

2015-12-01

Joining technology is an integral part of today's Nitinol medical device manufacturing. Besides crimping and riveting, laser welding is often applied to join components made from Nitinol to Nitinol, as well as Nitinol components to dissimilar materials. Other Nitinol joining techniques include adhesive bonding, soldering, and brazing. Typically, the performance of joints is assessed by destructive mechanical testing, on a process validation base. In this study, a nondestructive testing method—photothermal radiometry—is applied to characterize small Nitinol laser-weld joints used to connect two wire ends via a sleeve. Two different wire diameters are investigated. Effective joint connection cross sections are visualized using metallography techniques. Results of the nondestructive testing are correlated to data from destructive torsion testing, where the maximum torque at fracture is evaluated for the same joints and criteria for the differentiation of good and poor laser-welding quality by nondestructive testing are established.

Quasi-Rayleigh waves in butt-welded thick steel plate

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

Kamas, Tuncay, E-mail: kamas@email.sc.edu, E-mail: victorg@sc.edu, E-mail: linbin@cec.sc.edu; Giurgiutiu, Victor, E-mail: kamas@email.sc.edu, E-mail: victorg@sc.edu, E-mail: linbin@cec.sc.edu; Lin, Bin, E-mail: kamas@email.sc.edu, E-mail: victorg@sc.edu, E-mail: linbin@cec.sc.edu

2015-03-31

This paper discusses theoretical and experimental analyses of weld guided surface acoustic waves (SAW) through the guided wave propagation (GWP) analyses. The GWP analyses have been carried out by utilizing piezoelectric wafer active sensors (PWAS) for in situ structural inspection of a thick steel plate with butt weld as the weld bead is ground flush. Ultrasonic techniques are commonly used for validation of welded structures in many in-situ monitoring applications, e.g. in off-shore structures, in nuclear and pressure vessel industries and in a range of naval applications. PWAS is recently employed in such ultrasonic applications as a resonator as wellmore » as a transducer. Quasi-Rayleigh waves a.k.a. SAW can be generated in relatively thick isotropic elastic plate having the same phase velocity as Rayleigh waves whereas Rayleigh waves are a high frequency approximation of the first symmetric (S0) and anti-symmetric (A0) Lamb wave modes. As the frequency becomes very high the S0 and the A0 wave speeds coalesce, and both have the same value. This value is exactly the Rayleigh wave speed and becomes constant along the frequency i.e. Rayleigh waves are non-dispersive guided surface acoustic waves. The study is followed with weld-GWP tests through the pitch-catch method along the butt weld line. The tuning curves of quasi-Rayleigh wave are determined to show the tuning and trapping effect of the weld bead that has higher thickness than the adjacent plates on producing a dominant quasi-Rayleigh wave mode. The significant usage of the weld tuned and guided quasi-Rayleigh wave mode is essentially discussed for the applications in the in-situ inspection of relatively thick structures with butt weld such as naval offshore structures. The paper ends with summary, conclusions and suggestions for future work.« less

An integrated optical sensor for GMAW feedback control

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

Taylor, P.L.; Watkins, A.D.; Larsen, E.D.

1992-08-01

The integrated optical sensor (IOS) is a multifunction feedback control sensor for arc welding, that is computer automated and independent of significant operator interaction. It is based on three major ``off-the-shelf`` components: a charged coupled device (CCD) camera, a diode laser, and a processing computer. The sensor head is compact and lightweight to avoid interference with weld head mobility, hardened to survive the harsh operating environment, and free of specialized cooling and power requirements. The sensor is positioned behind the GMAW torch and measures weld pool position and width, standoff distance, and postweld centerline cooling rate. Weld pool position andmore » width are used in a feedback loop, by the weld controller, to track the weld pool relative to the weld joint, thus allowing compensation for such phenomena as arc blow. Sensor stand off distance is used in a feedback loop to control the contact tip to base metal distance during the welding process. Cooling rate information is used to infer the final metallurgical state of the weld bead and heat affected zone, thereby providing a means of controlling post weld mechanical properties.« less

An integrated optical sensor for GMAW feedback control

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

Taylor, P.L.; Watkins, A.D.; Larsen, E.D.

1992-01-01

The integrated optical sensor (IOS) is a multifunction feedback control sensor for arc welding, that is computer automated and independent of significant operator interaction. It is based on three major off-the-shelf'' components: a charged coupled device (CCD) camera, a diode laser, and a processing computer. The sensor head is compact and lightweight to avoid interference with weld head mobility, hardened to survive the harsh operating environment, and free of specialized cooling and power requirements. The sensor is positioned behind the GMAW torch and measures weld pool position and width, standoff distance, and postweld centerline cooling rate. Weld pool position andmore » width are used in a feedback loop, by the weld controller, to track the weld pool relative to the weld joint, thus allowing compensation for such phenomena as arc blow. Sensor stand off distance is used in a feedback loop to control the contact tip to base metal distance during the welding process. Cooling rate information is used to infer the final metallurgical state of the weld bead and heat affected zone, thereby providing a means of controlling post weld mechanical properties.« less

Development of low-cost welding procedures for thick sections of HY-150 steel

NASA Technical Reports Server (NTRS)

Schmidt, P. M.; Snow, R. S.

1972-01-01

Low cost welding procedures were developed for welding 6-inch thick HY-150 steel to be used in the manufacture of large diameter motor case Y rings and nozzle attachment flanges. An extensive investigation was made of the mechanical and metallurgical properties and fracture toughness of HY-150 base plate and welds made with manual shielded metal arc process and semi-automatic gas metal arc process in the flat position. Transverse tensiles, all-weld metal tensiles, Charpy V-notch specimens and edge notched bend specimens were tested in the course of the program. In addition metallographic studies and hardness tests were performed on the weld, weld HAZ and base metal. The results of the work performed indicate that both the shielded metal arc and gas metal arc processes are capable of producing consistently sound welds as determined by radiographic and ultrasonic inspection. In addition, the weld metal, deposited by each process was found to exhibit a good combination of strength and toughness such that the selection of a rolled and welded procedure for fabricating rocket motor case components would appear to be technically feasible.

Manufacture of micro fluidic devices by laser welding using thermal transfer printing techniques

NASA Astrophysics Data System (ADS)

Klein, R.; Klein, K. F.; Tobisch, T.; Thoelken, D.; Belz, M.

2016-03-01

Micro-fluidic devices are widely used today in the areas of medical diagnostics and drug research, as well as for applications within the process, electronics and chemical industry. Microliters of fluids or single cell to cell interactions can be conveniently analyzed with such devices using fluorescence imaging, phase contrast microscopy or spectroscopic techniques. Typical micro-fluidic devices consist of a thermoplastic base component with chambers and channels covered by a hermetic fluid and gas tight sealed lid component. Both components are usually from the same or similar thermoplastic material. Different mechanical, adhesive or thermal joining processes can be used to assemble base component and lid. Today, laser beam welding shows the potential to become a novel manufacturing opportunity for midsize and large scale production of micro-fluidic devices resulting in excellent processing quality by localized heat input and low thermal stress to the device during processing. For laser welding, optical absorption of the resin and laser wavelength has to be matched for proper joining. This paper will focus on a new approach to prepare micro-fluidic channels in such devices using a thermal transfer printing process, where an optical absorbing layer absorbs the laser energy. Advantages of this process will be discussed in combination with laser welding of optical transparent micro-fluidic devices.

A Review of Similar and Dissimilar Micro-joining of Nitinol

NASA Astrophysics Data System (ADS)

Deepan Bharathi Kannan, T.; Ramesh, T.; Sathiya, P.

2016-04-01

NiTinol belongs to a class of smart materials which has a wide range of applications in the field of automotive, aerospace, biomedical, robotics, etc., owing to the growing trend in miniaturization of components. Micro-joining is becoming one of the important and familiar processes in the fabrication of miniaturized components. Recently, effective micro-joining of thin sheets has been gaining a lot of interest among researchers. In this article, the research and progress in micro-joining of NiTinol to itself and other metals are reviewed at different aspects. To date, laser welding, tungsten inert gas welding, and resistance welding have been used to a large extent in investigating the weldability of NiTinol alloys. Some important welding parameters used in micro joining by various researchers and their effects on weld qualities are detailed in this review. Metallurgical aspects, mechanical properties and corrosion aspects of micro-joined NiTinol sheets/wires are discussed. The aim of this report is to review the recent progress in micro-joining of NiTinol and to provide a basis for follow-on research.

Validating a Model for Welding Induced Residual Stress Using High-Energy X-ray Diffraction

DOE PAGES

Mach, J. C.; Budrow, C. J.; Pagan, D. C.; ...

2017-03-15

Integrated computational materials engineering (ICME) provides a pathway to advance performance in structures through the use of physically-based models to better understand how manufacturing processes influence product performance. As one particular challenge, consider that residual stresses induced in fabrication are pervasive and directly impact the life of structures. For ICME to be an effective strategy, it is essential that predictive capability be developed in conjunction with critical experiments. In the present paper, simulation results from a multi-physics model for gas metal arc welding are evaluated through x-ray diffraction using synchrotron radiation. A test component was designed with intent to developmore » significant gradients in residual stress, be representative of real-world engineering application, yet remain tractable for finely spaced strain measurements with positioning equipment available at synchrotron facilities. Finally, the experimental validation lends confidence to model predictions, facilitating the explicit consideration of residual stress distribution in prediction of fatigue life.« less

Validating a Model for Welding Induced Residual Stress Using High-Energy X-ray Diffraction

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

Mach, J. C.; Budrow, C. J.; Pagan, D. C.

Integrated computational materials engineering (ICME) provides a pathway to advance performance in structures through the use of physically-based models to better understand how manufacturing processes influence product performance. As one particular challenge, consider that residual stresses induced in fabrication are pervasive and directly impact the life of structures. For ICME to be an effective strategy, it is essential that predictive capability be developed in conjunction with critical experiments. In the present paper, simulation results from a multi-physics model for gas metal arc welding are evaluated through x-ray diffraction using synchrotron radiation. A test component was designed with intent to developmore » significant gradients in residual stress, be representative of real-world engineering application, yet remain tractable for finely spaced strain measurements with positioning equipment available at synchrotron facilities. Finally, the experimental validation lends confidence to model predictions, facilitating the explicit consideration of residual stress distribution in prediction of fatigue life.« less

Modelling grain-scattered ultrasound in austenitic stainless-steel welds: A hybrid model

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

Nowers, O.; Duxbury, D. J.; Velichko, A.

2015-03-31

The ultrasonic inspection of austenitic stainless steel welds can be challenging due to their coarse grain structure, charaterised by preferentially oriented, elongated grains. The anisotropy of the weld is manifested as both a ‘steering’ of the beam and the back-scatter of energy due to the macroscopic granular structure of the weld. However, the influence of weld properties, such as mean grain size and orientation distribution, on the magnitude of scattered ultrasound is not well understood. A hybrid model has been developed to allow the study of grain-scatter effects in austenitic welds. An efficient 2D Finite Element (FE) method is usedmore » to calculate the complete scattering response from a single elliptical austenitic grain of arbitrary length and width as a function of the specific inspection frequency. A grain allocation model of the weld is presented to approximate the characteristic structures observed in austenitic welds and the complete scattering behaviour of each grain calculated. This model is incorporated into a semi-analytical framework for a single-element inspection of a typical weld in immersion. Experimental validation evidence is demonstrated indicating excellent qualitative agreement of SNR as a function of frequency and a minimum SNR difference of 2 dB at a centre frequency of 2.25 MHz. Additionally, an example Monte-Carlo study is presented detailing the variation of SNR as a function of the anisotropy distribution of the weld, and the application of confidence analysis to inform inspection development.« less

Improvement of bonding properties of laser transmission welded, dissimilar thermoplastics by plasma surface treatment

NASA Astrophysics Data System (ADS)

Hopmann, Ch.; Weber, M.; Schöngart, M.; Sooriyapiragasam, S.; Behm, H.; Dahlmann, R.

2015-05-01

Compared to different welding methods such as ultrasonic welding, laser transmission welding is a relatively new technology to join thermoplastic parts. The most significant advantages over other methods are the contactless energy input which can be controlled very precisely and the low mechanical loads on the welded parts. Therefore, laser transmission welding is used in various areas of application, for example in medical technology or for assembling headlights in the automotive sector. However, there are several challenges in welding dissimilar thermoplastics. This may be due to different melting points on the one hand and different polarities on the other hand. So far these problems are faced with the intermediate layer technique. In this process a layer bonding together the two components is placed between the components. This means that an additional step in the production is needed to apply the extra layer. To avoid this additional step, different ways of joining dissimilar thermoplastics are investigated. In this regard, the improvement in the weldability of the dissimilar thermoplastics polyamide 6 (PA 6) and polypropylene (PP) by means of plasma surface modification and contour welding is examined. To evaluate the influence of the plasma surface modification process on the subsequent welding process of the two dissimilar materials, the treatment time as well as the storage time between treatment and welding are varied. The treatment time in pulsed micro wave excited oxygen plasmas with an electron density of about 1x1017 m-3 is varied from 0.5 s to 120 s and the time between treatment and welding is varied from a few minutes up to a week. As reference, parts being made of the same polymer (PP and PA 6) are welded and tested. For the evaluation of the results of the welding experiments, short-time tensile tests are used to determine the bond strength. Without plasma treatment the described combination of PA 6/PP cannot be welded with sufficient bond strength to withstand handling of the samples. In contrast, the tear-out force of previously plasma treated samples can be determined to up to 1400 N. The achieved bond strengths are higher than of untreated PP/PP welded parts (about 1000 N).

Improvement of bonding properties of laser transmission welded, dissimilar thermoplastics by plasma surface treatment

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

Hopmann, Ch.; Weber, M.; Schöngart, M.

2015-05-22

Compared to different welding methods such as ultrasonic welding, laser transmission welding is a relatively new technology to join thermoplastic parts. The most significant advantages over other methods are the contactless energy input which can be controlled very precisely and the low mechanical loads on the welded parts. Therefore, laser transmission welding is used in various areas of application, for example in medical technology or for assembling headlights in the automotive sector. However, there are several challenges in welding dissimilar thermoplastics. This may be due to different melting points on the one hand and different polarities on the other hand.more » So far these problems are faced with the intermediate layer technique. In this process a layer bonding together the two components is placed between the components. This means that an additional step in the production is needed to apply the extra layer. To avoid this additional step, different ways of joining dissimilar thermoplastics are investigated. In this regard, the improvement in the weldability of the dissimilar thermoplastics polyamide 6 (PA 6) and polypropylene (PP) by means of plasma surface modification and contour welding is examined. To evaluate the influence of the plasma surface modification process on the subsequent welding process of the two dissimilar materials, the treatment time as well as the storage time between treatment and welding are varied. The treatment time in pulsed micro wave excited oxygen plasmas with an electron density of about 1x10{sup 17} m{sup −3} is varied from 0.5 s to 120 s and the time between treatment and welding is varied from a few minutes up to a week. As reference, parts being made of the same polymer (PP and PA 6) are welded and tested. For the evaluation of the results of the welding experiments, short-time tensile tests are used to determine the bond strength. Without plasma treatment the described combination of PA 6/PP cannot be welded with sufficient bond strength to withstand handling of the samples. In contrast, the tear-out force of previously plasma treated samples can be determined to up to 1400 N. The achieved bond strengths are higher than of untreated PP/PP welded parts (about 1000 N)« less

Patterns of residual stresses due to welding

NASA Technical Reports Server (NTRS)

Botros, B. M.

1983-01-01

Residual stresses caused by welding result from the nonuniform rate of cooling and the restrained thermal contraction or non-uniform plastic deformation. From the zone of extremely high temperature at the weld, heat flows into both the adjoining cool body and the surrounding atmosphere. The weld metal solidifies under very rapid cooling. The plasticity of the hot metal allows adjustment initially, but as the structure cools the rigidity of the surrounding cold metal inhibits further contraction. The zone is compressed and the weld is put under tensile stresses of high magnitude. The danger of cracking in these structural elements is great. Change in specific volume is caused by the change in temperature.

Manufacturing of 5.5 Meter Diameter Cryogenic Fuel Tank Domes for the NASA Ares I Rocket

NASA Technical Reports Server (NTRS)

Jones, Ronald E.; Carter, Robert W.

2012-01-01

The Ares I rocket is the first launch vehicle scheduled for manufacture under the National Aeronautic and Space Administration s (NASA s) Constellation program. A series of full-scale Ares I development articles have been constructed on the Robotic Weld Tool at the NASA George C. Marshall Space Flight Center in Huntsville, Alabama. The Robotic Weld Tool is a 100 ton, 7-axis, robotic manufacturing system capable of machining and friction stir welding large-scale space hardware. This presentation will focus on the friction stir welding of 5.5m diameter cryogenic fuel tank components; specifically, the liquid hydrogen forward dome (LH2 MDA) and the common bulkhead manufacturing development articles (CBMDA). The LH2 MDA was the first full-scale, flight-like Ares I hardware produced under the Constellation Program. It is a 5.5m diameter elliptical dome assembly consisting of eight gore panels, a y-ring stiffener and a manhole fitting. All components are made from aluminum-lithium alloy 2195. Conventional and self-reacting friction stir welding was used on this article. Manufacturing solutions will be discussed including the implementation of photogrammetry, an advanced metrology technique, as well as fixtureless welding. The LH2 MDA is the first known fully friction stir welded dome ever produced. The completion of four Common Bulkhead Manufacturing Development Articles (CBMDA) will also be highlighted. Each CBMDA consists of a 5.5m diameter spun-formed dome friction stir welded to a y-ring stiffener. The domes and y-rings are made of aluminum 2014 and 2219 respectively. An overview of CBMDA manufacturing processes and the effect of tooling on weld defect formation will be discussed.

Ultrasonic Spot and Torsion Welding of Aluminum to Titanium Alloys: Process, Properties and Interfacial Microstructure

NASA Astrophysics Data System (ADS)

Balle, Frank; Magin, Jens

Hybrid lightweight structures shape the development of future vehicles in traffic engineering and the aerospace industry. For multi-material concepts made out of aluminum and titanium alloys, the ultrasonic welding technique is an alternative effective joining technology. The overlapped structures can be welded in the solid state, even without gas shielding. In this paper the conventional ultrasonic spot welding with longitudinal oscillation mode is compared to the recent ultrasonic torsion welding with a torsional mode at 20 kHz working frequency. For each technique the process parameters welding force, welding energy and oscillation amplitude were optimized for the hybrid joints using design of experiments. Relationships between the process parameters, mechanical properties and related welding zone should be understood. Central aspects of the research project are microscopic studies of the joining zone in cross section and extensive fracture surface analysis. Detailed electron microscopy and spectroscopy of the hybrid interface help to understand the interfacial formation during ultrasonic welding as well as to transfer the gained knowledge for further multi-metal joints.

The Effect of Ultrasonic Peening on Service Life of the Butt-Welded High-Temperature Steel Pipes

NASA Astrophysics Data System (ADS)

Daavari, Morteza; Vanini, Seyed Ali Sadough

2015-09-01

Residual stresses introduced by manufacturing processes such as casting, forming, machining, and welding have harmful effects on the mechanical behavior of the structures. In addition to the residual stresses, weld toe stress concentration can play a determining effect. There are several methods to improve the mechanical properties such as fatigue behavior of the welded structures. In this paper, the effects of ultrasonic peening on the fatigue life of the high-temperature seamless steel pipes, used in the petrochemical environment, have been investigated. These welded pipes are fatigued due to thermal and mechanical loads caused by the cycle of cooling, heating, and internal pressure fluctuations. Residual stress measurements, weld geometry estimation, electrochemical evaluations, and metallography investigations were done as supplementary examinations. Results showed that application of ultrasonic impact treatment has led to increased fatigue life, fatigue strength, and corrosion resistance of A106-B welded steel pipes in petrochemical corrosive environment.

29 CFR 1915.54 - Welding, cutting and heating of hollow metal containers and structures not covered by § 1915.12.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 29 Labor 7 2010-07-01 2010-07-01 false Welding, cutting and heating of hollow metal containers and... STANDARDS FOR SHIPYARD EMPLOYMENT Welding, Cutting and Heating § 1915.54 Welding, cutting and heating of... which have contained flammable substances shall, before welding, cutting, or heating is undertaken on...

29 CFR 1915.54 - Welding, cutting and heating of hollow metal containers and structures not covered by § 1915.12.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 29 Labor 7 2011-07-01 2011-07-01 false Welding, cutting and heating of hollow metal containers and... STANDARDS FOR SHIPYARD EMPLOYMENT Welding, Cutting and Heating § 1915.54 Welding, cutting and heating of... which have contained flammable substances shall, before welding, cutting, or heating is undertaken on...

29 CFR 1915.54 - Welding, cutting and heating of hollow metal containers and structures not covered by § 1915.12.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 29 Labor 7 2012-07-01 2012-07-01 false Welding, cutting and heating of hollow metal containers and... STANDARDS FOR SHIPYARD EMPLOYMENT Welding, Cutting and Heating § 1915.54 Welding, cutting and heating of... which have contained flammable substances shall, before welding, cutting, or heating is undertaken on...

29 CFR 1915.54 - Welding, cutting and heating of hollow metal containers and structures not covered by § 1915.12.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 29 Labor 7 2013-07-01 2013-07-01 false Welding, cutting and heating of hollow metal containers and... STANDARDS FOR SHIPYARD EMPLOYMENT Welding, Cutting and Heating § 1915.54 Welding, cutting and heating of... which have contained flammable substances shall, before welding, cutting, or heating is undertaken on...

29 CFR 1915.54 - Welding, cutting and heating of hollow metal containers and structures not covered by § 1915.12.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 29 Labor 7 2014-07-01 2014-07-01 false Welding, cutting and heating of hollow metal containers and... STANDARDS FOR SHIPYARD EMPLOYMENT Welding, Cutting and Heating § 1915.54 Welding, cutting and heating of... which have contained flammable substances shall, before welding, cutting, or heating is undertaken on...

Metallurgy and mechanical properties variation with heat input,during dissimilar metal welding between stainless and carbon steel

NASA Astrophysics Data System (ADS)

Ramdan, RD; Koswara, AL; Surasno; Wirawan, R.; Faturohman, F.; Widyanto, B.; Suratman, R.

2018-02-01

The present research focus on the metallurgy and mechanical aspect of dissimilar metal welding.One of the common parameters that significantly contribute to the metallurgical aspect on the metal during welding is heat input. Regarding this point, in the present research, voltage, current and the welding speed has been varied in order to observe the effect of heat input on the metallurgical and mechanical aspect of both welded metals. Welding was conducted by Gas Metal Arc Welding (GMAW) on stainless and carbon steel with filler metal of ER 309. After welding, hardness test (micro-Vickers), tensile test, macro and micro-structure characterization and Energy Dispersive Spectroscopy (EDS) characterization were performed. It was observed no brittle martensite observed at HAZ of carbon steel, whereas sensitization was observed at the HAZ of stainless steel for all heat input variation at the present research. Generally, both HAZ at carbon steel and stainless steel did not affect tensile test result, however the formation of chromium carbide at the grain boundary of HAZ structure (sensitization) of stainless steel, indicate that better process and control of welding is required for dissimilar metal welding, especially to overcome this issue.

High-Speed Friction-Stir Welding to Enable Aluminum Tailor-Welded Blanks

NASA Astrophysics Data System (ADS)

Hovanski, Yuri; Upadhyay, Piyush; Carsley, John; Luzanski, Tom; Carlson, Blair; Eisenmenger, Mark; Soulami, Ayoub; Marshall, Dustin; Landino, Brandon; Hartfield-Wunsch, Susan

2015-05-01

Current welding technologies for production of aluminum tailor-welded blanks (TWBs) are utilized in low-volume and niche applications, and they have yet to be scaled for the high-volume vehicle market. This study targeted further weight reduction, part reduction, and cost savings by enabling tailor-welded blank technology for aluminum alloys at high volumes. While friction-stir welding (FSW) has been traditionally applied at linear velocities less than 1 m/min, high-volume production applications demand the process be extended to higher velocities more amenable to cost-sensitive production environments. Unfortunately, weld parameters and performance developed and characterized at low-to-moderate welding velocities do not directly translate to high-speed linear FSW. Therefore, to facilitate production of high-volume aluminum FSW components, parameters were developed with a minimum welding velocity of 3 m/min. With an emphasis on weld quality, welded blanks were evaluated for postweld formability using a combination of numerical and experimental methods. An evaluation across scales was ultimately validated by stamping full-size production door inner panels made from dissimilar thickness aluminum TWBs, which provided validation of the numerical and experimental analysis of laboratory-scale tests.

Characteristics comparison of weld metal zones welded to cast and forged steels for piston crown material

NASA Astrophysics Data System (ADS)

Moon, Kyung-Man; Kim, Yun-Hae; Lee, Myeong-Hoon; Baek, Tae-Sil

2015-03-01

An optimum repair welding for the piston crown which is one of the engine parts exposed to the combustion chamber is considered to be very important to prolong the engine lifetime from an economical point of view. In this study, two types of filler metals such as 1.25Cr-0.5Mo, 0.5Mo were welded with SMAW method and the other two types of filler metals such as Inconel 625 and 718 were welded with GTAW method, respectively, and the used base metals were the cast and forged steels of the piston crown material. The weld metal zones welded with Inconel 625 and 718 filler metals exhibited higher corrosion resistance compared to 1.25Cr-0.5Mo and 0.5Mo filler metals. In particular, the weld metal zone welded with Inconel 718 and 0.5Mo, filler metals indicated the best and worst corrosion resistance, respectively. Consequently, it is suggested that the corrosion resistance of the weld metal zone surely depends on the chemical components of each filler metal and welding method irrespective of the types of piston crown material.

Effects of Post-Weld Heat Treatment on the Mechanical Properties of Similar- and Dissimilar-Alloy Friction Stir Welded Blanks

NASA Astrophysics Data System (ADS)

Zadpoor, Amir Abbas; Sinke, Jos

2011-01-01

Friction stir welding is a solid state joining process with relatively low welding temperatures. Nevertheless, the mechanical properties of friction stir welded blanks are degraded after welding. Indeed, both strength and ductility of the welds are decreased after welding. Often, the resulting friction stir welded blanks need to be formed to their final structural shape. Therefore, the formability of friction stir welded blanks is of primary importance in the manufacturing of structural parts. This paper studies how the mechanical properties and particularly formability of friction stir welded blanks can be improved by applying a post weld heat treatment. Two aluminum alloys from 2000 and 7000 series, namely 2024-T3 and 7075-T6, are selected for the study. The sheet thickness of both materials is 2,0 mm. The selected alloys are welded in three configurations: 2024-T3 and 2024-T3, 7075-T6 and 7075-T6, and 2024-T3 and 7075-T6. The resulting welds are naturally aged for a few months. Three sets of standard dog bone shape tensile test specimens are then machined from the welds. The first set of the specimens is tested without any heat treatment. The second set of the specimens is solution heat treated and quenched before testing. The third set of the specimens is solution heat treated, quenched, and naturally aged for a week before testing. The mechanical properties of the three different sets of specimens are compared with each other. It is shown that careful selection of post weld heat-treatment can greatly improve the formability of friction stir welded blanks.

Friction Stir Weld Failure Mechanisms in Aluminum-Armor Structures Under Ballistic Impact Loading Conditions

DTIC Science & Technology

2013-01-01

REPORT Friction Stir Weld Failure Mechanisms in Aluminum -Armor Structures Under Ballistic Impact Loading Conditions 14. ABSTRACT 16. SECURITY...Stir Weld Failure Mechanisms in Aluminum -Armor Structures Under Ballistic Impact Loading Conditions M. Grujicic, B. Pandurangan, A. Arakere, C-F. Yen...K.O. Pedersen, Fracture Mechanisms of Aluminum Alloy AA7075-T651 Under Various Loading Conditions , Int. J. Impact Eng., 2010, 37, p 537–551 24. T

Numerical simulation of linear fiction welding (LFW) processes

NASA Astrophysics Data System (ADS)

Fratini, L.; La Spisa, D.

2011-05-01

Solid state welding processes are becoming increasingly important due to a large number of advantages related to joining "unweldable" materials and in particular light weight alloys. Linear friction welding (LFW) has been used successfully to bond non-axisymmetric components of a range of materials including titanium alloys, steels, aluminum alloys, nickel, copper, and also dissimilar material combinations. The technique is useful in the research of quality of the joints and in reducing costs of components and parts of the aeronautic and automotive industries. LFW involves parts to be welded through the relative reciprocating motion of two components under an axial force. In such process the heat source is given by the frictional forces work decaying into heat determining a local softening of the material and proper bonding conditions due to both the temperature increase and the local pressure of the two edges to be welded. This paper is a comparative test between the numerical model in two dimensions, i.e. in plane strain conditions, and in three dimensions of a LFW process of AISI1045 steel specimens. It must be observed that the 3D model assures a faithful simulation of the actual threedimensional material flow, even if the two-dimensional simulation computational times are very short, a few hours instead of several ones as the 3D model. The obtained results were compared with experimental values found out in the scientific literature.

Aircraft landing dynamics facility carriage weld test program

NASA Technical Reports Server (NTRS)

Lawson, A. G.

1984-01-01

A welded tubular structure constructed of low alloy high strength quenched and tempered steel was tested. The consistency of the mechanical strengths and chemical composition and the degree of difficulty of obtaining full strength welds with these steels is characterized. The results of constructing and testing two typical connections which are used in the structure design are reported.

Review of Literature on Probability of Detection for Magnetic Particle Nondestructive Testing

DTIC Science & Technology

2013-01-01

4 3.2 Offshore welded structures..................................................................................... 8 3.3 Aerospace...presented in Section 6. 2. Overview of Magnetic Particle Testing MPT is used in heavy engineering to inspect welds for surface-breaking... welded structures, and concluding with a summary of reliability information embedded in aerospace standards. 3.1 Aerospace It appears that the

Microstructural characterization and hardness properties of electric resistance welding titanium joints for dental applications.

PubMed

Ceschini, Lorella; Boromei, Iuri; Morri, Alessandro; Nardi, Diego; Sighinolfi, Gianluca; Degidi, Marco

2015-06-01

The electric resistance welding procedure is used to join a titanium bar with specific implant abutments in order to produce a framework directly in the oral cavity of the patient. This investigation studied the effects of the welding process on microstructure and hardness properties of commercially pure (CP2 and CP4) Ti components. Different welding powers and cooling procedures were applied to bars and abutments, normally used to produce the framework, in order to simulate the clinical intraoral welding procedure. The analyses highlighted that the joining process did not induce appreciable changes in the geometry of the abutments. However, because of unavoidable microstructural modifications in the welded zones, the hardness decreased to values lower than those of the unwelded CP2 and CP4 Ti grades, irrespective of the welding environments and parameters. © IMechE 2015.

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

Eisazadeh, Hamid; Goldak, John A.; Aidun, Daryush K.

Residual strain distributions in similar and dissimilar welds were measured using neutron diffraction (ND) method. Then, using three strain components, three-dimensional stress states were calculated. The results were used to determine the effect of the martensitic phase transformation and material properties on residual stress (RS) distribution. It was observed that smaller longitudinal RS was induced in the low carbon steel side of dissimilar weld when compared to its similar weld. Also, it was found that the transverse RS near and within the weld zone (WZ) in dissimilar weld exhibited a distinctive trend, with tensile mode reaching the yield strength ofmore » the base metal (BM). In order to characterize the WZ in dissimilar weld, we deployed optical microscopy, hardness, and energy dispersive X-ray spectroscopy (EDAX). This study not only provides further insight into the RS state in similar and dissimilar welds; it also delivers important consequences of phase transformation in the latter case.« less

A summary of phase analysis on Apollo 14 samples

NASA Technical Reports Server (NTRS)

Fredriksson, K.; Nelen, J.; Noonan, A.; Kraut, F.

1971-01-01

The results of an analysis of lunar samples from Apollo 14 are presented. The large number of breccias returned from the Fra Mauro formation show that impact events are an important rock forming mechanism on the moon. Larger rocks as well as micro breccias bear structural resemblance to brecciated chondrites and terrestrial impactites. Many show evidence of repetitious events of break-up and accumulation welding. The surface of the regolith has become thoroughly mixed by this process. Most components however appear locally derived from basalts rich in feldspar and Kreep components, similar to rocks such as 14310.

Summary of Prior Work on Joining of Oxide Dispersion-Strengthened Alloys

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

Wright, Ian G; Tatlock, Gordon J; Badairy, H.

2009-08-01

There is a range of joining techniques available for use with ODS alloys, but care should be exercised in matching the technique to the final duty requirements of the joint. The goal for joining ODS alloys is a joint with no local disruption of the distribution of the oxide dispersion, and no significant change in the size and orientation of the alloy microstructure. Not surprisingly, the fusion welding processes typically employed with wrought alloys produce the least satisfactory results with ODS alloys, but some versions, such as fusion spot welding, and the laser and electron-beam welding technologies, have demonstrated potentialmore » for producing sound joints. Welds made using solid-state spot welding reportedly have exhibited parent metal properties. Thus, it is possible to employ processes that result in significant disruption of the alloy microstructure, as long as the processing parameters are adjustment to minimize the extent of or influence of the changes in the alloy microstructure. Selection among these joining approaches largely depends on the particular application and component configuration, and an understanding of the relationships among processing, alloy microstructure, and final properties is key. Recent developments have resulted in friction welding evolving to be a prime method for joining ODS sheet products, and variants of brazing/diffusion bonding have shown excellent promise for use with tubes and pipes. The techniques that come closest to the goal defined above involve solid-state diffusion bonding and, in particular, it has been found that secondary recrystallization of joints made by pulsed plasma-assisted diffusion can produce the desired, continuous, large alloy grain structure through the joint. Such joints have exhibited creep rupture failure at >82% of the load needed to fail the monolithic parent alloy at 1000 C.« less

Weld residual stresses and plastic deformation

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

Rybicki, E.; Shiratori, M.

1989-01-01

Residual stresses due to welding can play a primary role in the performance of piping systems and pressure vessels. The stresses are high, in the range of the yield stress of the material, and can influence the fatigue and fracture behavior as well as component service life. Thus, it is important to have an understanding of weld residual stresses. The papers in this section address the important topic of residual stresses and failure analysis. The paper by Boyles reviews computer simulation in the prediction and analysis of fatigue, fracture, and creep of welded structures. The growing use of expert systemsmore » for these purposes is also covered. Karisson, et al, determine the deformations and stresses during the butt-welding of a pipe. The determination of residual deformations and stresses is also presented. Oddy, Goldak, and McDill propose a method to incorporate transformation plasticity in a finite element program. A three-dimensional analysis of a short longitudinal pipe weld in a typical pressure vessel steel is presented. Chaaban, Morin, Ma, and Bazergui study the influence of ligament thickness, strain hardening, expansion sequence, and level of applied expansion pressure on the interference fit in a model of a tube-to-tubesheet joint in a heat exchanger. This section contains papers dealing with models for plastic deformation. Imatani, Teraura, and Inoue formulate a viscoplastic constitutive model based on an anisotropic yield criterion. Comparisons with experimental results obtained using thin walled tubular specimens made from SUS 304 stainless steel show that the present yield criterion adequately accounts for prior deformation history. Niitsu, Horiguchi, and Ikegami investigate the plastic behavior of S25C mild steel tubular specimens subjected to combined axial and torsional loading at both constant and variable temperatures.« less

Characterization of the Microstructures and the Cryogenic Mechanical Properties of Electron Beam Welded Inconel 718

NASA Astrophysics Data System (ADS)

Kwon, Soon Il; Bae, Sang Hyun; Do, Jeong Hyeon; Jo, Chang Yong; Hong, Hyun Uk

2016-02-01

The microstructures and the cryogenic mechanical properties of electron beam (EB) welds between cast and forged Inconel 718 superalloys with a thickness of 10 mm were investigated in comparison with gas tungsten arc (GTA) welds. EB welding with a heat input lower than 250 J/mm caused the formation of liquation microfissuring in the cast-side heat-affected-zone (HAZ) of the EB welds. HAZ liquation microfissuring appeared to be associated with the constitutional liquation of primary NbC carbides at the grain boundaries. Compared with the GTA welding process, the EB welding produced welds with superior microstructure, exhibiting fine dendritic structure associated with the reduction in size and fraction of the Laves phase due to the rapid cooling rate. This result was responsible for the superior mechanical properties of the EB welds at 77 K (-196 °C). Laves particles in both welds were found to provide the preferential site for the crack initiation and propagation, leading to a significant decrease in the Charpy impact toughness at 77 K (-196 °C). Crack initiation and propagation induced by Charpy impact testing were discussed in terms of the dendrite arm spacing, the Laves size and the dislocation structure ahead of the crack arisen from the fractured Laves phase in the two welds.

Advanced Metalworking Solutions for Naval Systems that Go in Harm’s Way

DTIC Science & Technology

2010-11-10

TECHNOLOGIES An NMC project team designed, built, and demonstrated at Concurrent Technologies Corporation a low-cost, transportable friction stir welding (LC...technologies for use in shipbuilding applications. For example, NMC and its team members are currently advancing friction stir welding (FSW...lower the cost of Navy ships and improve the quality of ship components. NMC is modifying its previously designed low-cost friction stir welding

Influence of the parameters of a high-frequency acoustic wave on the structure, properties, and plastic flow of metal in the zone of a joint of materials welded by ultrasound-assisted explosive welding

NASA Astrophysics Data System (ADS)

Peev, A. P.; Kuz'min, S. V.; Lysak, V. I.; Kuz'min, E. V.; Dorodnikov, A. N.

2017-05-01

The results of an investigation of the influence of the parameters of high-frequency acoustic wave on the structure and properties of the zone of joint of homogeneous metals bonded by explosive welding under the action of ultrasound have been presented. The influence of the frequency and amplitude of ultrasonic vibrations on the structure and properties of the explosively welded joints compared with the samples welded without the application of ultrasound has been established. The action of high-frequency acoustic waves on the metal leads to a reduction in the dynamic yield stress, which changes the properties of the surface layers of the metal and the conditions of the formation of the joint of the colliding plates upon the explosive welding. It has been shown that the changes in the length and amplitude of waves that arise in the weld joint upon the explosive welding with the simultaneous action of ultrasonic vibrations are connected with a decrease in the magnitude of the deforming pulse and time of action of the compressive stresses that exceed the dynamic yield stress beyond the point of contact.

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.

New welding fluxes based on silicomanganese slag for deposition and welding of canopies and crib bed of mine support

NASA Astrophysics Data System (ADS)

Kryukov, R. E.; Kozyrev, N. A.; Usoltsev, A. A.; Kozyreva, O. E.

2017-09-01

The paper considers the possibility of efficient use of silicomanganese slag for the production of welding fluxes. The results of studying the use of metallurgical wastes as components of welding fluxes are given. Analysis of the results of mechanical properties of the samples made it possible to determine the optimum content of the pulverized fraction less than 0.45 mm in the flux. The composition and technology of manufacturing a new welding flux using slag of silicomanganese production was developed. The effect of fractional composition on the welding-technological properties of fluxes was studied. The optimal content of liquid glass in the flux, which allows a favorable complex of mechanical properties to be obtained, is 20-30%. To reduce the level of contamination of the weld metal with non-metallic oxide inclusions and to increase the mechanical properties of the welded joint, it is proposed to introduce a carbon-fluorine-containing additive FD-UFS into fluxes based on the slag.

Influence of Joint Configuration on the Strength of Laser Welded Presshardened Steel

NASA Astrophysics Data System (ADS)

Kügler, H.; Mittelstädt, C.; Vollertsen, F.

Presshardened steel is used in nowadays automotive production. Due to its high strength, sheet thicknesses can be reduced which results in decreasing weight of car body components. However, because of microstructure softening and coating agglomerations in the seam, welding is still a challenge. In this paper laser beam welding of 22MnB5 with varying energy input per irradiated area is presented. It is found that increasing energy input per seam length reduces tensile strength. Using a small spot size of 200 μm, tensile strength of 1434 N/mm2 can be reached in bead on plate welds. In lap welds tensile strength is limited because of coating particles agglomerating at the melt pool border line. However, the resulting strength is higher when using several small weld seams than using one seam with the same total seam width. With three weld seams, each 0.5mm in width, tensile strength of 911N/mm2 is reached in lap welding.

A residual stress study in similar and dissimilar welds

DOE PAGES

Eisazadeh, Hamid; Goldak, John A.; Aidun, Daryush K.; ...

2016-04-01

Residual strain distributions in similar and dissimilar welds were measured using neutron diffraction (ND) method. Then, using three strain components, three-dimensional stress states were calculated. The results were used to determine the effect of the martensitic phase transformation and material properties on residual stress (RS) distribution. It was observed that smaller longitudinal RS was induced in the low carbon steel side of dissimilar weld when compared to its similar weld. Also, it was found that the transverse RS near and within the weld zone (WZ) in dissimilar weld exhibited a distinctive trend, with tensile mode reaching the yield strength ofmore » the base metal (BM). In order to characterize the WZ in dissimilar weld, we deployed optical microscopy, hardness, and energy dispersive X-ray spectroscopy (EDAX). This study not only provides further insight into the RS state in similar and dissimilar welds; it also delivers important consequences of phase transformation in the latter case.« less

78 FR 13856 - Notice of Petitions by Firms for Determination of Eligibility To Apply for Trade Adjustment...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-01

... & Welding, Inc.... 600 E. Commerce Road, 2/21/2013 Company's articles are made from Lexington, NE 68850. metals, using metal fabrication processes: Cutting, bending, welding, and other. Components are then used...

46 CFR 52.05-1 - General (modifies PW-1 through PW-54).

Code of Federal Regulations, 2010 CFR

2010-10-01

... BOILERS Requirements for Boilers Fabricated by Welding § 52.05-1 General (modifies PW-1 through PW-54). (a) Boilers and component parts, including piping, that are fabricated by welding shall be as indicated in PW...

46 CFR 52.05-1 - General (modifies PW-1 through PW-54).

Code of Federal Regulations, 2011 CFR

2011-10-01

... BOILERS Requirements for Boilers Fabricated by Welding § 52.05-1 General (modifies PW-1 through PW-54). (a) Boilers and component parts, including piping, that are fabricated by welding shall be as indicated in PW...

46 CFR 52.05-1 - General (modifies PW-1 through PW-54).

Code of Federal Regulations, 2014 CFR

2014-10-01

... BOILERS Requirements for Boilers Fabricated by Welding § 52.05-1 General (modifies PW-1 through PW-54). (a) Boilers and component parts, including piping, that are fabricated by welding shall be as indicated in PW...

46 CFR 52.05-1 - General (modifies PW-1 through PW-54).

Code of Federal Regulations, 2013 CFR

2013-10-01

... BOILERS Requirements for Boilers Fabricated by Welding § 52.05-1 General (modifies PW-1 through PW-54). (a) Boilers and component parts, including piping, that are fabricated by welding shall be as indicated in PW...

46 CFR 52.05-1 - General (modifies PW-1 through PW-54).

Code of Federal Regulations, 2012 CFR

2012-10-01

... BOILERS Requirements for Boilers Fabricated by Welding § 52.05-1 General (modifies PW-1 through PW-54). (a) Boilers and component parts, including piping, that are fabricated by welding shall be as indicated in PW...

Laser welded steel sandwich panel bridge deck development : finite element analysis and stake weld strength tests.

DOT National Transportation Integrated Search

2009-09-01

This report summarizes the analysis of laser welded steel sandwich panels for use in bridge structures and : static testing of laser stake welded lap shear coupons. Steel sandwich panels consist of two face sheets : connected by a relatively low-dens...

High-precision and high-speed laser microjoining for electronics and microsystems

NASA Astrophysics Data System (ADS)

Gillner, Arnold; Olowinsky, Alexander; Klages, Kilian; Gedicke, Jens; Sari, Fahri

2006-02-01

The joining processes in electronic device manufacturing are today still dominated by conventional joining techniques like press fitting, crimping and resistance welding. Laser beam joining techniques have been under intensive investigations and subsequently new processes for mass manufacturing and high accuracy assembling were established. With the newly developed SHADOW (R) welding technology technical aspects such as tensile strength, geometry and precision of the weld could be improved. This technology provides highest flexibility in weld geometry with a minimum welding time as well as new possibilities in using application adapted materials. Different parts and even different metals can be joined by a non-contact process. The application of a relative movement between the laser beam and the part to be joined at feed rates of up to 60 m/min produces weld seams with a length from 0.6 mm to 15.7 mm using a pulsed Nd:YAG laser with a pulse duration of up to 50 ms. Due to the low energy input, typically 1 J to 6 J, a weld width as small as 50 μm and a weld depth as small as 20 pm have been attained. This results in low distortion of the joined watch components. Within this paper this new welding process will be explained and several examples of joined components will be presented with respect to fundamentals and the sustainable implementation of the SHADOW (R) welding technique into watch manufacturing and electronic industry. For microsystem applications the laser joining technology is modified to join even silicon and glass parts without any melting based on the formation of a thermally induced oxygen bond. New fields of applications for joining different materials such as steel to brass or steel to copper for electrical interconnects will be discussed. Here the SHADOW (R) welding technique offers new possibilities for the combination of good electrical properties of copper with high mechanical stiffness of steel. The paper will give a closer look to microjoining applications especially using the SHADOW (R) welding technique. Basics of the process as well as its application on dedicated examples will be shown for small parts such as axis-wheel combinations and electrical connectors.

Joining of polypropylene/polypropylene and glass fiber reinforced polypropylene composites

NASA Astrophysics Data System (ADS)

Zhang, Jianguang

Joining behavior of polypropylene (PP) to PP and long glass fiber reinforced polypropylene (LFT) to LFT were investigated. Adhesive bonding was used to join PP/PP. Both adhesive bonding and ultrasonic welding were used to join LFT/LFT. Single-lap shear testing and low velocity impact (LVI) testing were used to evaluate the performance of bonded structures. The two-part acrylic adhesive DP8005 was determined to be the best among the three adhesive candidates, which was attributed to its low surface energy. The impact resistance of LFT/LFT joints, normalized with respect to thickness, was higher than that of PP/PP joints because of higher stiffness of LFT/LFT joints. The stress states in the adhesive layer of adhesively bonded structures were analyzed using ANSYS and LS-DYNA to simulate the single-lap shear testing and LVI testing, respectively. The shear and peel stresses peaked at the edges of the adhesive layer. Compared to LFT/LFT joints, higher peel stress occurred in the adhesive layer in the PP/PP joints in tension. Impact response of adhesively bonded structures as evaluated by LS-DYNA showed good agreement with the experimental results. The effect of weld time and weld pressure on the shear strength of ultrasonically welded LFT/LFT was evaluated. With higher weld pressure, less time was required to obtain a complete weld. At longer weld times, lower weld pressure was required. From the 15 weld conditions studied, a weld map was obtained that provides conditions to achieve a complete weld. Nanoindentation was used to evaluate the effect of ultrasonic weld on the modulus and hardness of the PP matrix. Modulus and hardness of the PP matrix were slightly decreased by ultrasonic welding possibly due to the decrease in the molecular weight. The temperature profile in LFT/LFT in the transverse direction during ultrasonic welding was analyzed by two ANSYS-based thermal models: (a) one in which heat generated by interfacial friction was treated as a heat flux and (b) one in which heat was generated in a thin slab at the interface. The weld map obtained from the thin slab model was closer to the one obtained experimentally.

The Influence of the Heat-Affected Zone Mechanical Properties on the Behaviour of the Welding in Transverse Plate-to-Tube Joints.

PubMed

Lozano, Miguel; Serrano, Miguel A; López-Colina, Carlos; Gayarre, Fernando L; Suárez, Jesús

2018-02-09

Eurocode 3 establishes the component method to analytically characterize the structural joints between beam and columns. When one of the members involved in the joint is a hollow section (i.e., a tube) there is a lack of information for the specific components present in the joint. There are two different ways to bridge the gap: experimental testing on the actual beam column joints involving tubular sections; or numerical modelization, typically by means of finite element analysis. For this second option, it is necessary to know the actual mechanical properties of the material. As long as the joint implies a welding process, there is a concern related to how the mechanical properties in the heat-affected zone (HAZ) influence the behavior of the joint. In this work, some coupons were extracted from the HAZ of the beam-column joint. The coupons were tested and the results were implemented in the numerical model of the joint, in an attempt to bring it closer to the experimental results of the tested joints.

A fundamental study on the structural integrity of magnesium alloys joined by friction stir welding

NASA Astrophysics Data System (ADS)

Rao, Harish Mangebettu

The goal of this research is to study the factors that influence the physical and mechanical properties of lap-shear joints produced using friction stir welding. This study focuses on understanding the effect of tool geometry and weld process parameters including the tool rotation rate, tool plunge depth and dwell time on the mechanical performance of similar magnesium alloy and dissimilar magnesium to aluminum alloy weld joints. A variety of experimental activities were conducted including tensile and fatigue testing, fracture surface and failure analysis, microstructure characterization, hardness measurements and chemical composition analysis. An investigation on the effect of weld process conditions in friction stir spot welding of magnesium to magnesium produced in a manner that had a large effective sheet thickness and smaller interfacial hook height exhibited superior weld strength. Furthermore, in fatigue testing of friction stir spot welded of magnesium to magnesium alloy, lap-shear welds produced using a triangular tool pin profile exhibited better fatigue life properties compared to lap-shear welds produced using a cylindrical tool pin profile. In friction stir spot welding of dissimilar magnesium to aluminum, formation of intermetallic compounds in the stir zone of the weld had a dominant effect on the weld strength. Lap-shear dissimilar welds with good material mixture and discontinues intermetallic compounds in the stir zone exhibited superior weld strength compared to lap-shear dissimilar welds with continuous formation of intermetallic compounds in the stir zone. The weld structural geometry like the interfacial hook, hook orientation and bond width also played a major role in influencing the weld strength of the dissimilar lap-shear friction stir spot welds. A wide scatter in fatigue test results was observed in friction stir linear welds of aluminum to magnesium alloys. Different modes of failure were observed under fatigue loading including crack propagation into the top sheet, into the bottom sheet, and interfacial separation. Investigation of the tested welds revealed that the voids in the weld nugget reduced the weld strength, resulting in lower fatigue life. A thin layer of IMCs formed along the faying surface which accelerated the fatigue failure.

Structure formation of 5083 alloy during friction stir welding

NASA Astrophysics Data System (ADS)

Zaikina, A. A.; Kolubaev, A. V.; Sizova, O. V.; Ivanov, K. V.; Filippov, A. V.; Kolubaev, E. A.

2017-12-01

This paper provides a comparative study of structures obtained by friction stir welding and sliding friction of 5083 Al alloy. Optical and electron microscopy reveals identical fine-grained structures with a grain size of ˜5 µm both in the weld nugget zone and subsurface layer in friction independently of the initial grain size of the alloy. It has been suggested that the grain boundary sliding is responsible for the specific material flow pattern in both techniques considered.

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

High Power Laser Welding. [of stainless steel and titanium alloy structures

NASA Technical Reports Server (NTRS)

Banas, C. M.

1972-01-01

A review of recent developments in high power, carbon dixoide laser welding is presented. Deep penetration welding in stainless steel to 0.5-in. thick, high speed welding in thin gage rimmed steel and gas shielded welding in Ti-6Al-4V alloy are described. The effects of laser power, power density, focusing optics, gas-shielding techniques, material properties and weld speed on weld quality and penetration are discussed. It is shown that laser welding performance in thin materials is comparable to that of electron beams. It is further shown that high quality welds, as evidenced by NDT, mechanical and metal-lographic tests, can be achieved. The potential of the laser for industrial welding applications is indicated.

Comparison between hybrid laser-MIG welding and MIG welding for the invar36 alloy

NASA Astrophysics Data System (ADS)

Zhan, Xiaohong; Li, Yubo; Ou, Wenmin; Yu, Fengyi; Chen, Jie; Wei, Yanhong

2016-11-01

The invar36 alloy is suitable to produce mold of composite materials structure because it has similar thermal expansion coefficient with composite materials. In the present paper, the MIG welding and laser-MIG hybrid welding methods are compared to get the more appropriate method to overcome the poor weldability of invar36 alloy. According to the analysis of the experimental and simulated results, it has been proved that the Gauss and cone combined heat source model can characterize the laser-MIG hybrid welding heat source well. The total welding time of MIG welding is 8 times that of hybrid laser-MIG welding. The welding material consumption of MIG welding is about 4 times that of hybrid laser-MIG welding. The stress and deformation simulation indicate that the peak value of deformation during MIG welding is 3 times larger than that of hybrid laser-MIG welding.

Mechanical Characteristics of Welded Joints of Aluminum Alloy 6061 T6 Formed by Arc and Friction Stir Welding

NASA Astrophysics Data System (ADS)

Astarita, A.; Squillace, A.; Nele, L.

2016-01-01

Butt welds formed by arc welding in inert gas with nonconsumable electrode (tungsten inert gas (TIG) welding) and by friction stir welding (FSW) from aluminum alloy AA6061 T6 are studied. Comparative analysis of the structures and mechanical properties of the welded joints is performed using the results of optical and electron microscopy, tensile tests, tests for residual bending ductility, and measurements of microhardness. The changes in the microstructure in different zones and the degrees of degradation of the mechanical properties after the welding are determined. It is shown that the size of the tool for the friction stir welding affects the properties of the welds. Quantitative results showing the relation between the microscopic behavior of the alloy and the welding-induced changes in the microstructure are obtained. Friction stir welding is shown to provide higher properties of the welds.

A reliability analysis framework with Monte Carlo simulation for weld structure of crane's beam

NASA Astrophysics Data System (ADS)

Wang, Kefei; Xu, Hongwei; Qu, Fuzheng; Wang, Xin; Shi, Yanjun

2018-04-01

The reliability of the crane product in engineering is the core competitiveness of the product. This paper used Monte Carlo method analyzed the reliability of the weld metal structure of the bridge crane whose limit state function is mathematical expression. Then we obtained the minimum reliable welding feet height value for the welds between cover plate and web plate on main beam in different coefficients of variation. This paper provides a new idea and reference for the growth of the inherent reliability of crane.

Creep behavior and in-depth microstructural characterization of dissimilar joints

PubMed Central

Kauffmann, F; Klein, T; Klenk, A; Maile, K

2013-01-01

The 700 °C power plants currently under development will utilize Ni-base alloys such as alloy 617 for components to be operated at temperatures >650 °C. Due to economic reasons for components or parts of components which are subjected to temperatures <650 °C, 2% Cr or 9–12% Cr steels is used, depending on the required mechanical properties. This makes the dissimilar joining of Ni-base alloys and Cr steels a necessity in these plants. Experimental investigations show that these joints have to be identified as weak points with regard to damage development under creep and creep-fatigue loading. The present investigation focuses on welds between the alloy 617 and 2% Cr steel. Under creep load the fracture occurs near the fusion line between the 2% Cr steel base metal and alloy 617 weld metal. To explain the reasons for this fracture location, the microstructure of this fusion line was investigated using TEM and FIB techniques after welding and after creep loading. The TEM investigations have shown a small zone in the weld metal near the fusion line exhibiting chromium depletion and clearly reduced amounts of chromium carbides, leading to a weakening of this zone. PMID:27877551

The Preignition and Autoignition Oxidation of Alternatives to Petroleum Derived JP-8 and their Surrogate Components in a Pressurized Flow Reactor and Single Cylinder Research Engine

DTIC Science & Technology

2009-09-01

sample probe consisted of TIG welding the 3/8” sample probe shaft to the sample probe tip (Koert, 1990 and Lenhert, 2004b). Silver solder was...was performed in the Drexel University Machine Shop. Conventional TIG welding was sufficient for welding the 3/8” O.D. tube to the sample probe tip...However, to TIG weld the thermocouple and the glass lined tube to the sample probe tip, extreme care had to be taken so as not to damage the

Advances in welding science: A perspective

NASA Astrophysics Data System (ADS)

David, S. A.; Vitek, J. M.; Babu, S. S.; Debroy, T.

The ultimate goal of welding technology is to improve the joint integrity and increase productivity. Over the years, welding has been more of an art than a science, but in the last few decades major advances have taken place in welding science and technology. With the development of new methodologies at the crossroads of basic and applied sciences, enormous opportunities and potential exist to develop a science-based tailoring of composition, structure, and properties of welds with intelligent control and automation of the welding processes.

Properties of welded joints in laser welding of aeronautic aluminum-lithium alloys

NASA Astrophysics Data System (ADS)

Malikov, A. G.; Orishich, A. M.

2017-01-01

The work presents the experimental investigation of the laser welding of the aluminum-lithium alloys (system Al-Mg-Li) and aluminum alloy (system Al-Cu-Li) doped with Sc. The influence of the nano-structuring of the surface layer welded joint by the cold plastic deformation method on the strength properties of the welded joint is determined. It is founded that, regarding the deformation degree over the thickness, the varying value of the welded joint strength is different for these aluminum alloys.

A Comparative Study of Fracture Toughness at Cryogenic Temperature of Austenitic Stainless Steel Welds

NASA Astrophysics Data System (ADS)

Aviles Santillana, I.; Boyer, C.; Fernandez Pison, P.; Foussat, A.; Langeslag, S. A. E.; Perez Fontenla, A. T.; Ruiz Navas, E. M.; Sgobba, S.

2018-03-01

The ITER magnet system is based on the "cable-in-conduit" conductor (CICC) concept, which consists of stainless steel jackets filled with superconducting strands. The jackets provide high strength, limited fatigue crack growth rate and fracture toughness properties to counteract the high stress imposed by, among others, electromagnetic loads at cryogenic temperature. Austenitic nitrogen-strengthened stainless steels have been chosen as base material for the jackets of the central solenoid and the toroidal field system, for which an extensive set of cryogenic mechanical property data are readily available. However, little is published for their welded joints, and their specific performance when considering different combinations of parent and filler metals. Moreover, the impact of post-weld heat treatments that are required for Nb3Sn formation is not extensively treated. Welds are frequently responsible for cracks initiated and propagated by fatigue during service, causing structural failure. It becomes thus essential to select the most suitable combination of parent and filler material and to assess their performance in terms of strength and crack propagation at operation conditions. An extensive test campaign has been conducted at 7 K comparing tungsten inert gas (TIG) welds using two fillers adapted to cryogenic service, EN 1.4453 and JK2LB, applied to two different base metals, AISI 316L and 316LN. A large set of fracture toughness data are presented, and the detrimental effect on fracture toughness of post-weld heat treatments (unavoidable for some of the components) is demonstrated. In this study, austenitic stainless steel TIG welds with various filler metals have undergone a comprehensive fracture mechanics characterization at 7 K. These results are directly exploitable and contribute to the cryogenic fracture mechanics properties database of the ITER magnet system. Additionally, a correlation between the impact in fracture toughness and microstructure resulting from the above treatment is provided.

Development of explosive welding procedures to fabricate channeled nozzle structures

NASA Technical Reports Server (NTRS)

Pattee, H. E.; Linse, V. D.

1976-01-01

Research was conducted to demonstrate the feasibility of fabricating a large contoured structure with complex internal channeling by explosive welding procedures. Structures or nozzles of this nature for wind tunnel applications were designed. Such nozzles vary widely in their complexity. However, in their simplest form, they consist of a grooved base section to which a cover sheet is attached to form a series of internal cooling passages. The cover sheet attachment can be accomplished in various ways: fusion welding, brazing, and diffusion welding. The cover sheet has also been electroformed in place. Of these fabrication methods, brazing has proved most successful in producing nozzles with complex contoured surfaces and a multiplicity of internal channels.

Two examples of subaqueously welded ash-flow tuffs: the Visean of southern Vosges (France) and the Upper Cretaceous of northern Anatolia (Turkey)

NASA Astrophysics Data System (ADS)

Schneider, Jean-Luc; Fourquin, Claude; Paicheler, Jean-Claude

1992-02-01

Pyroclastic deposits interpreted as subaqueous ash-flow tuff have been recognized within Archean to Recent marine and lacustrine sequences. Several authors proposed a high-temperature emplacement for some of these tuffs. However, the subaqueous welding of pyroclastic deposits remains controversial. The Visean marine volcaniclastic formations of southern Vosges (France) contain several layers of rhyolitic and rhyodacitic ash-flow tuff. These deposits include, from proximal to distal settings, breccia, lapilli and fine-ash tuff. The breccia and lapilli tuff are partly welded, as indicated by the presence of fiamme, fluidal and axiolitic structures. The lapilli tuff form idealized sections with a lower, coarse and welded unit and an upper, bedded and unwelded fine-ash tuff. Sedimentary structures suggest that the fine-ash tuff units were deposited by turbidity currents. Welded breccias, interbedded in a thick submarine volcanic complex, indicate the close proximity of the volcanic source. The lapilli and fine-ash tuff are interbedded in a thick marine sequence composed of alternating sandstones and shales. Presence of a marine stenohaline fauna and sedimentary structures attest to a marine depositional environment below storm-wave base. In northern Anatolia, thick massive sequences of rhyodacitic crystal tuff are interbedded with the Upper Cretaceous marine turbidites of the Mudurnu basin. Some of these tuffs are welded. As in southern Vosges, partial welding is attested by the presence of fiamme and fluidal structures. The latter are frequent in the fresh vitric matrix. These tuff units contain a high proportion of vitroclasis, and were emplaced by ash flows. Welded tuff units are associated with non-welded crystal tuff, and contain abundant bioclasts which indicate mixing with water during flowage. At the base, basaltic breccia beds are associated with micritic beds containing a marine fauna. The welded and non-welded tuff sequences are interbedded in an alternation of limestones and marls. These limestones are rich in pelagic microfossils. The evidence above strongly suggest that in both examples, tuff beds are partly welded and were emplaced at high temperature by subaqueous ash flows in a permanent marine environment. The sources of the pyroclastic material are unknown in both cases. We propose that the ash flows were produced during submarine fissure eruptions. Such eruptions could produce non-turbulent flows which were insulated by a steam carapace before deposition and welding. The welded ash-flow tuff deposits of southern Vosges and northern Anatolia give strong evidence for existence of subaqueous welding.

Finite element normal mode analysis of resistance welding jointed of dissimilar plate hat structure

NASA Astrophysics Data System (ADS)

Nazri, N. A.; Sani, M. S. M.

2017-10-01

Structural joints offer connection between structural element (beam, plate, solid etc.) in order to build a whole assembled structure. The complex behaviour of connecting elements plays a valuable role in characteristics of dynamic such as natural frequencies and mode shapes. In automotive structures, the trustworthiness arrangement of the structure extremely depends on joints. In this paper, top hat structure is modelled and designed with spot welding joint using dissimilar materials which is mild steel 1010 and stainless steel 304, using finite element software. Different types of connector elements such as rigid body element (RBE2), welding joint element (CWELD), and bar element (CBAR) are applied to represent real connection between two dissimilar plates. Normal mode analysis is simulated with different types of joining element in order to determine modal properties. Natural frequencies using RBE2, CBAR and CWELD are compared to equivalent rigid body method. Connection that gives the lowest percentage error among these three will be selected as the most reliable joining for resistance spot weld. From the analysis, it is shown that CWELD is better compared to others in term of weld joining among dissimilar plate materials. It is expected that joint modelling of finite element plays significant role in structural dynamics.

Multi objective Taguchi optimization approach for resistance spot welding of cold rolled TWIP steel sheets

NASA Astrophysics Data System (ADS)

Tutar, Mumin; Aydin, Hakan; Bayram, Ali

2017-08-01

Formability and energy absorption capability of a steel sheet are highly desirable properties in manufacturing components for automotive applications. TWinning Induced Plastisity (TWIP) steels are, new generation high Mn alloyed steels, attractive for the automotive industry due to its outstanding elongation (%40-45) and tensile strength (~1000MPa). So, TWIP steels provide excellent formability and energy absorption capability. Another required property from the steel sheets is suitability for manufacturing methods such as welding. The use of the steel sheets in the automotive applications inevitably involves welding. Considering that there are 3000-5000 welded spots on a vehicle, it can be interpreted that one of the most important manufacturing method is Resistance Spot Welding (RSW) for the automotive industry. In this study; firstly, TWIP steel sheet were cold rolled to 15% reduction in thickness. Then, the cold rolled TWIP steel sheets were welded with RSW method. The welding parameters (welding current, welding time and electrode force) were optimized for maximizing the peak tensile shear load and minimizing the indentation of the joints using a Taguchi L9 orthogonal array. The effect of welding parameters was also evaluated by examining the signal-to-noise ratio and analysis of variance (ANOVA) results.

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

Effect of Continuous and Pulsed Current Gas Tungsten Arc Welding on Dissimilar Weldments Between Hastelloy C-276/AISI 321 Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Sharma, Sumitra; Taiwade, Ravindra V.; Vashishtha, Himanshu

2017-03-01

In the present investigation, an attempt has been made to join Hastelloy C-276 nickel-based superalloy and AISI 321 austenitic stainless steel using ERNiCrMo-4 filler. The joints were fabricated by continuous and pulsed current gas tungsten arc welding processes. Experimental studies to ascertain the structure-property co-relationship with or without pulsed current mode were carried out using an optical microscope and scanning electron microscope. Further, the energy-dispersive spectroscope was used to evaluate the extent of microsegregation. The microstructure of fusion zone was obtained as finer cellular dendritic structure for pulsed current mode, whereas columnar structure was formed with small amount of cellular structure for continuous current mode. The scanning electron microscope examination witnessed the existence of migrated grain boundaries at the weld interfaces. Moreover, the presence of secondary phases such as P and μ was observed in continuous current weld joints, whereas they were absent in pulsed current weld joints, which needs to be further characterized. Moreover, pulsed current joints resulted in narrower weld bead, refined morphology, reduced elemental segregation and improved strength of the welded joints. The outcomes of the present investigation would help in obtaining good quality dissimilar joints for industrial applications and AISI 321 ASS being cheaper consequently led to cost-effective design also.

Re-weldability tests of irradiated 316L(N) stainless steel using laser welding technique

NASA Astrophysics Data System (ADS)

Yamada, Hirokazu; Kawamura, Hiroshi; Tsuchiya, Kunihiko; Kalinin, George; Kohno, Wataru; Morishima, Yasuo

2002-12-01

SS316L(N)-IG is the candidate material for the in-vessel and ex-vessel components of fusion reactors such as ITER (International Thermonuclear Experimental Reactor). This paper describes a study on re-weldability of un-irradiated and/or irradiated SS316L(N)-IG and the effect of helium generation on the mechanical properties of the weld joint. The laser welding process is used for re-welding of the water cooling branch pipeline repairs. It is clarified that re-welding of SS316L(N)-IG irradiated up to about 0.2 dpa (3.3 appm He) can be carried out without a serious deterioration of tensile properties due to helium accumulation. Therefore, repair of the ITER blanket cooling pipes can be performed by the laser welding process.

Shear strength of fillet welds in aluminum alloy 2219. [for use on the solid rocket motor and external tank

NASA Technical Reports Server (NTRS)

Lovoy, C. V.

1978-01-01

Fillet size is discussed in terms of theoretical or design dimensions versus as-welded dimensions, drawing attention to the inherent conservatism in the design load sustaining capabilities of fillet welds. Emphasis is placed on components for the solid rocket motor, external tank, and other aerospace applications. Problems associated with inspection of fillet welds are addresses and a comparison is drawn between defect counts obtained by radiographic inspection and by visual examination of the fracture plane. Fillet weld quality is related linearly to ultimate shear strength. Correlation coefficients are obtained by simple straight line regression analysis between the variables of ultimate shear strength and accumulative discontinuity summation. Shear strength allowables are found to be equivalent to 57 percent of butt weld A allowables (F sub tu.)

Friction Stir Welding of ODS and RAFM Steels

DOE PAGES

Yu, Zhenzhen; Feng, Zhili; Hoelzer, David; ...

2015-09-14

Advanced structural materials such as oxide dispersion strengthened steels and reduced-activation ferritic/martensitic steels are desired in fusion reactors as primary candidate materials for first wall and blanket structures, due to their excellent radiation and high-temperature creep resistance. However, their poor fusion weldability has been the major technical challenge limiting practical applications. For this reason, solid-state friction stir welding (FSW) has been considered for such applications. In this paper, the effect of FSW parameters on joining similar and dissimilar advanced structural steels was investigated. Scanning electron microscopy and electron backscatter diffraction methods were used to reveal the effects of FSW onmore » grain size, micro-texture distribution, and phase stability. Hardness mapping was performed to evaluate mechanical properties. Finally, post weld heat treatment was also performed to tailor the microstructure in the welds in order to match the weld zone mechanical properties to the base material.« less

Information flow analysis and Petri-net-based modeling for welding flexible manufacturing cell

NASA Astrophysics Data System (ADS)

Qiu, T.; Chen, Shanben; Wang, Y. T.; Wu, Lin

2000-10-01

Due to the development of advanced manufacturing technology and the introduction of Smart-Manufacturing notion in the field of modern industrial production, welding flexible manufacturing system (WFMS) using robot technology has become the inevitable developing direction on welding automation. In WFMS process, the flexibility for different welding products and the realizing on corresponding welding parameters control are the guarantees for welding quality. Based on a new intelligent arc-welding flexible manufacturing cell (WFMC), the system structure and control policies are studied in this paper. Aiming at the different information flows among every subsystem and central monitoring computer in this WFMC, Petri net theory is introduced into the process of welding manufacturing. With its help, a discrete control model of WFMC has been constructed, in which the system status is regarded as place and the control process is regarded as transition. Moreover, grounded on automation Petri net principle, the judging and utilizing of information obtained from welding sensors are imported into net structure, which extends the traditional Petri net concepts. The control model and policies researched in this paper have established foundation for further intelligent real-time control on WFMC and WFMS.

Microstructural development at weld interface between Zr-based glassy alloy and stainless steel by resistance microwelding

NASA Astrophysics Data System (ADS)

Fukumoto, S.; Minami, M.; Soeda, A.; Matsushima, M.; Takahashi, M.; Yokoyama, Y.; Fujimoto, K.

2012-08-01

Zr-based bulk metallic glasses are expected to be welded to conventional structural alloys. Dissimilar welding of metallic glasses to stainless steel was carried out by resistance microwelding. The metallurgical analysis of the weld interface revealed the welding mechanism. A thin reaction layer was formed between the two liquid materials. The melting of stainless steel should be limited to obtain sound joints.

Naval Research Reviews. Volume XXXIII. Number 2,

DTIC Science & Technology

1981-01-01

and filler metal addition. ratio weld is a characteristic of a keyhole -produced The most distinctive feature of LB welding , weld . T /h III laser Ii...evolved from these radiation for precision operation, such as hole-drill- efforts include a 3kW CO. laser /workstation system ing, trimming, and welding ...asso- Laser Surface Modifications ciated with thick-section welding of naval structure and surface modification for improved corrosion and The high

Improving Fatigue Performance of AHSS Welds

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

Feng, Zhili; Yu, Xinghua; Erdman, III, Donald L.

Reported herein is technical progress on a U.S. Department of Energy CRADA project with industry cost-share aimed at developing the technical basis and demonstrate the viability of innovative in-situ weld residual stresses mitigation technology that can substantially improve the weld fatigue performance and durability of auto-body structures. The developed technology would be costeffective and practical in high-volume vehicle production environment. Enhancing weld fatigue performance would address a critical technology gap that impedes the widespread use of advanced high-strength steels (AHSS) and other lightweight materials for auto body structure light-weighting. This means that the automotive industry can take full advantage ofmore » the AHSS in strength, durability and crashworthiness without the concern of the relatively weak weld fatigue performance. The project comprises both technological innovations in weld residual stress mitigation and due-diligence residual stress measurement and fatigue performance evaluation. Two approaches were investigated. The first one was the use of low temperature phase transformation (LTPT) weld filler wire, and the second focused on novel thermo-mechanical stress management technique. Both technical approaches have resulted in considerable improvement in fatigue lives of welded joints made of high-strength steels. Synchrotron diffraction measurement confirmed the reduction of high tensile weld residual stresses by the two weld residual stress mitigation techniques.« less

Brittle crack arrestability of thick steel plate welds in large structure

NASA Astrophysics Data System (ADS)

An, Gyu Baek; Park, Joon Sik

2011-10-01

Recently, there has been such a critical issue in shipbuilding industry that much larger and stronger ships are required to develop oil and gas in the Arctic region. Attention has been paid to obtaining high strength, good toughness at low temperature, and good weldability. An experimental study was performed to evaluate the brittle crack arrest toughness value (Kca) and brittle crack arrest method of welded joints using EH40 grade steel with a thickness of 80 mm. The test specimens were made by both flux cored arc welding (FCAW) and combined welding (EGW+FCAW) processes. Temperature gradient ESSO test was performed to measure the Kca of the base metal. Also, a constant temperature (-10 °C) ESSO test was performed to establish a brittle crack arrest method using high toughness welding consumable with real structural specimens. The research aims in this study were to investigate the effect of joint design and welding consumable for the crack arrestability of thick steel plates using EH40 grade shipbuilding steel of straight block joint weld line with two kinds of welding processes.

Microstructure, texture, and mechanical properties of friction stir welded commercial brass alloy

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

Heidarzadeh, A., E-mail: ak.hz62@gmail.com

Microstructural evolution during friction stir welding of single-phase brass and corresponding mechanical properties were investigated. For this purpose, 2 mm thick brass plate was friction stir welded at a rotational speed of 450 rpm and traverse speed of 100 mm/min. The microstructure of the joint was studied using optical microscopy, scanning electron microscopy equipped with electron back scattered diffraction system, and scanning transmission electron microscopy. The mechanical properties were measured using hardness and tensile tests. The formation of subgrains and their transformation into new grains in conjunction with existence of A{sub 1}{sup ⁎}, A{sub 2}{sup ⁎} and C texture componentsmore » revealed that the continuous dynamic recrystallization plays a dominant role in the microstructural evolution. However, grain boundary bulging, along with the formation of twin boundaries, and presence of the G texture component showed that the discontinues dynamic recrystallization may participate in the new grain formation. Furthermore, the different strengthening mechanisms, which caused the higher strength of the joint, were discussed. - Highlights: •Microstructural evolution during FSW of a single phase brass was investigated. •CDRX and DDRX were the main mechanisms of the grain structure formation during FSW. •GDRX and SRX were not contributed in grain structure formation. •The lamellas TBs were formed in the SZ of the joints. •Grain boundary, dislocation, and texture effects resulted in higher strength.« less

Optimization and Prediction of Angular Distortion and Weldment Characteristics of TIG Square Butt Joints

NASA Astrophysics Data System (ADS)

Narang, H. K.; Mahapatra, M. M.; Jha, P. K.; Biswas, P.

2014-05-01

Autogenous arc welds with minimum upper weld bead depression and lower weld bead bulging are desired as such welds do not require a second welding pass for filling up the upper bead depressions (UBDs) and characterized with minimum angular distortion. The present paper describes optimization and prediction of angular distortion and weldment characteristics such as upper weld bead depression and lower weld bead bulging of TIG-welded structural steel square butt joints. Full factorial design of experiment was utilized for selecting the combinations of welding process parameter to produce the square butts. A mathematical model was developed to establish the relationship between TIG welding process parameters and responses such as upper bead width, lower bead width, UBD, lower bead height (bulging), weld cross-sectional area, and angular distortions. The optimal welding condition to minimize UBD and lower bead bulging of the TIG butt joints was identified.

The Effect of Welding Energy on the Microstructural and Mechanical Properties of Ultrasonic-Welded Copper Joints

PubMed Central

Yang, Jingwei; Cao, Biao; Lu, Qinghua

2017-01-01

The effects of welding energy on the mechanical and microstructural characteristics of ultrasonic-welded pure copper plates were investigated. Complex dynamic recrystallization and grain growth occurred inside the weld zone during ultrasonic welding. At a low welding energy, a thin band of straight weld interfaces was observed and had an ultra-fine grain structure. With an increase in welding energy, the weld interface progressively changed from flat to sinusoidal, and eventually turned into a convoluted wavy pattern, bearing similarities to shear instabilities, as observed in fluid dynamics. The lap shear load of the joints initially increased and then remained stable as the welding energy increased. The tensile characteristics of the joints significantly depended on the development of plastic deformation at the interface. The influence of the microstructure on the hardness was also discussed. PMID:28772553

The Effect of Welding Energy on the Microstructural and Mechanical Properties of Ultrasonic-Welded Copper Joints.

PubMed

Yang, Jingwei; Cao, Biao; Lu, Qinghua

2017-02-16

The effects of welding energy on the mechanical and microstructural characteristics of ultrasonic-welded pure copper plates were investigated. Complex dynamic recrystallization and grain growth occurred inside the weld zone during ultrasonic welding. At a low welding energy, a thin band of straight weld interfaces was observed and had an ultra-fine grain structure. With an increase in welding energy, the weld interface progressively changed from flat to sinusoidal, and eventually turned into a convoluted wavy pattern, bearing similarities to shear instabilities, as observed in fluid dynamics. The lap shear load of the joints initially increased and then remained stable as the welding energy increased. The tensile characteristics of the joints significantly depended on the development of plastic deformation at the interface. The influence of the microstructure on the hardness was also discussed.

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.

Aluminum Lithium Alloy 2195 Fusion Welding Improvements with New Filler Wire

NASA Technical Reports Server (NTRS)

Russell, C.

2001-01-01

The objective of this research was to assess the B218 weld filler wire for Super Lightweight External Tank production, which could improve current production welding and repair productivity. We took the following approaches: (1) Perform a repair weld quick look evaluation between 4043/B218 and B218/B218 weld filler wire combinations and evaluation tensile properties for planished and unplanished conditions; and (2) Perform repair weld evaluation on structural simulation panel using 4043-B218 and B218/B218 weld filler wire combinations and evaluation tensile and simulated service fracture properties for planished and unplanished conditions.

Diode Lasers used in Plastic Welding and Selective Laser Soldering - Applications and Products

NASA Astrophysics Data System (ADS)

Reinl, S.

Aside from conventional welding methods, laser welding of plastics has established itself as a proven bonding method. The component-conserving and clean process offers numerous advantages and enables welding of sensitive assemblies in automotive, electronic, medical, human care, food packaging and consumer electronics markets. Diode lasers are established since years within plastic welding applications. Also, soft soldering using laser radiation is becoming more and more significant in the field of direct diode laser applications. Fast power controllability combined with a contactless temperature measurement to minimize thermal damage make the diode laser an ideal tool for this application. These advantages come in to full effect when soldering of increasingly small parts in temperature sensitive environments is necessary.

Analysis of rail welding methods for mine rail access with the use of modern technologies

NASA Astrophysics Data System (ADS)

Usoltsev, A. A.; Shevchenko, R. A.; Kozyrev, N. A.; Kriukov, R. E.; Shishkin, P. E.

2017-09-01

Welded joint zones are weak sections of the railway track for all traffic cases (in the case of high-speed traffic and heavy traffic). In the paper advantages and disadvantages of the basic ways of rails welding, which are widely used today, are considered: electrocontact and aluminothermic. Carefully selected mode of differentially thermally strengthened rails string will allow the process of correction after heat treatment to be minimized and internal residual compressive stresses to be kept. Particular attention should be paid to the method of rails welding, in which after rails welding during their cooling it is offered to perform quasi-isothermal exposure in the temperature range of fine structure formation by passing pulses of alternating electric current through the welded joint maintaining this temperature until the end of the transformation. The use of quasi-isothermal exposure at a temperature of 600 - 650 °C makes it possible to obtain a finely dispersed structure of the welded seam of rails without additional heat treatment.

Extracting natural dyes from wool--an evaluation of extraction methods.

PubMed

Manhita, Ana; Ferreira, Teresa; Candeias, António; Dias, Cristina Barrocas

2011-05-01

The efficiency of eight different procedures used for the extraction of natural dyes was evaluated using contemporary wool samples dyed with cochineal, madder, woad, weld, brazilwood and logwood. Comparison was made based on the LC-DAD peak areas of the natural dye's main components which had been extracted from the wool samples. Among the tested methods, an extraction procedure with Na(2)EDTA in water/DMF (1:1, v/v) proved to be the most suitable for the extraction of the studied dyes, which presented a wide range of chemical structures. The identification of the natural dyes used in the making of an eighteenth century Arraiolos carpet was possible using the Na(2)EDTA/DMF extraction of the wool embroidery samples and an LC-DAD-MS methodology. The effectiveness of the Na(2)EDTA/DMF extraction method was particularly observed in the extraction of weld dye components. Nine flavone derivatives previously identified in weld extracts could be identified in a single historical sample, confirming the use of this natural dye in the making of Arraiolos carpets. Indigo and brazilwood were also identified in the samples, and despite the fact that these natural dyes were referred in the historical recipes of Arraiolos dyeing, it is the first time that the use of brazilwood is confirmed. Mordant analysis by ICP-MS identified the widespread use of alum in the dyeing process, but in some samples with darker hues, high amounts of iron were found instead.

Metallography of Battery Resistance Spot Welds

NASA Technical Reports Server (NTRS)

Martinez, J. E.; Johannes, L. B.; Gonzalez, D.; Yayathi, S.; Figuered, J. M.; Darcy, E. C.; Bilc, Z. M.

2015-01-01

Li-ion cells provide an energy dense solution for systems that require rechargeable electrical power. However, these cells can undergo thermal runaway, the point at which the cell becomes thermally unstable and results in hot gas, flame, electrolyte leakage, and in some cases explosion. The heat and fire associated with this type of event is generally violent and can subsequently cause damage to the surrounding system or present a dangerous risk to the personnel nearby. The space flight environment is especially sensitive to risks particularly when it involves potential for fire within the habitable volume of the International Space Station (ISS). In larger battery packs such as Robonaut 2 (R2), numerous Li-ion cells are placed in parallel-series configurations to obtain the required stack voltage and desired run-time or to meet specific power requirements. This raises a second and less obvious concern for batteries that undergo certification for space flight use: the joining quality at the resistance spot weld of battery cells to component wires/leads and battery tabs, bus bars or other electronic components and assemblies. Resistance spot welds undergo materials evaluation, visual inspection, conductivity (resistivity) testing, destructive peel testing, and metallurgical examination in accordance with applicable NASA Process Specifications. Welded components are cross-sectioned to ensure they are free of cracks or voids open to any exterior surface. Pore and voids contained within the weld zone but not open to an exterior surface, and are not determined to have sharp notch like characteristics, shall be acceptable. Depending on requirements, some battery cells are constructed of aluminum canisters while others are constructed of steel. Process specific weld schedules must be developed and certified for each possible joining combination. The aluminum canisters' positive terminals were particularly difficult to weld due to a bi-metal strip that comes ultrasonically pre-welded by the manufacturer. This was further complicated as the maximum electrode force was limited to low-electrode force to prevent deflection of the aluminum can during welding. Other Li-ion cells are comprised of smaller diameter cylindrical steel canisters which are inherently capable of handling greater force from the electrodes. Allowing higher-electrode forces aids greatly in insuring a consistent resistance network for the weld. Overall lessons learned: developing good jigs is critical to insure the parts and electrodes are planer to one another and the location of the weld sites remains accurate and repeatable; maintaining strict control over materials is critical--materials must be of a specific hardness and chemical composition to insure that a weld schedule is repeatable; accuracy of the die used to stamp the projections is critical and worth the investment; and proper seasoning of the electrodes is critical to producing consistent welds--once the electrodes have been properly seasoned, cleaning/dressing should be avoided until it is absolutely necessary.

Investigations on Laser Beam Welding of Different Dissimilar Joints of Steel and Aluminum Alloys for Automotive Lightweight Construction

NASA Astrophysics Data System (ADS)

Seffer, Oliver; Pfeifer, Ronny; Springer, André; Kaierle, Stefan

Due to the enormous potential of weight saving, and the consequential reduction of pollutant emissions, the use of hybrid components made of steel and aluminum alloys is increasing steadily, especially concerning automotive lightweight construction. However, thermal joining of steel and aluminum is still being researched, due to a limited solubility of the binary system of iron and aluminum causing the formation of hard and brittle intermetallic phases, which decrease the strength and the formability of the dissimilar seam. The presented results show the investigation of laser beam welding for joining different dissimilar hybrid components of the steel materials HX220LAD+Z100, 22MnB5+AS150 and 1.4301, as well as the aluminum alloy AA6016-T4 as a lap joint. Among other things, the influences of the energy per unit length, the material grade, the sheet thickness t, the weld type (lap weld, fillet weld) and the arrangement of the base materials in a lap joint (aluminum-sided irradiation, steel-sided irradiation) on the achievable strengths are analyzed. The characterization of the dissimilar joints includes tensile shear tests and metallographic analyses, depending on the energy per unit length.

Final Assessment of Manual Ultrasonic Examinations Applied to Detect Flaws in Primary System Dissimilar Metal Welds at North Anna Power Station

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

Anderson, Michael T.; Diaz, Aaron A.; Cinson, Anthony D.

2014-03-24

PNNL conducted a technical assessment of the NDE issues and protocols that led to missed detections of several axially oriented flaws in a steam generator primary inlet dissimilar metal weld at North Anna Power Station, Unit 1 (NAPS-1). This particular component design exhibits a significant outside-diameter (OD) taper that is not included as a blind performance demonstration mock-up within the industry’s Performance Demonstration Initiative, administered by EPRI. For this reason, the licensee engaged EPRI to assist in the development of a technical justification to support the basis for a site-specific qualification. The service-induced flaws at NAPS-1 were eventually detected asmore » a result of OD surface machining in preparation for a full structural weld overlay. The machining operation uncovered the existence of two through-wall flaws, based on the observance of primary water leaking from the dissimilar metal weld. A total of five axially oriented flaws were detected in varied locations around the weld circumference. The field volumetric examination that was conducted at NAPS-1 was a non-encoded, real-time manual ultrasonic examination. PNNL conducted both an initial assessment, and subsequently, a more rigorous technical evaluation (reported here), which has identified an array of NDE issues that may have led to the subject missed detections. These evaluations were performed through technical reviews and discussions with NRC staff, EPRI NDE Center personnel, industry and ISI vendor personnel, and ultrasonic transducer manufacturers, and laboratory tests, to better understand the underlying issues at North Anna.« less

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.

Structural Phase Evolution in Ultrasonic-Assisted Friction Stir Welded 2195 Aluminum Alloy Joints

NASA Astrophysics Data System (ADS)

Eliseev, A. A.; Fortuna, S. V.; Kalashnikova, T. A.; Chumaevskii, A. V.; Kolubaev, E. A.

2017-10-01

The authors examined the structural and phase state of fixed joints produced by method of friction stir welding (FSW) and ultrasonic-assisted friction stir welding (UAFSW) from extruded profile of aluminum alloy AA2195. In order to identify the role of ultrasonic application in the course of welding, such characteristics, as volume fraction and average size of secondary particles are compared in the base material and stir zones of FSW and UAFSW joints. By applying the methods of SEM and TEM analysis, researchers established the complex character of phase transitions as a result of ultrasonic application.

Temperature profiles induced by a stationary CW laser beam in a multi-layer structure - Application to solar cell interconnect welding

NASA Astrophysics Data System (ADS)

Oh, J. E.; Ianno, N. J.; Ahmed, A. U.

A three-dimensional heat transfer model for heating of a multilayer structure by a stationary Gaussian CW CO2 laser beam is developed and applied to solar cell interconnect welding. This model takes into account the temperature dependence of the thermal conductivity and diffusivity as well as free carrier absorption of the incident beam in the silicon where appropriate. Finally, the theoretical temperature profiles are used to determine the weld spot size and these values are compared to results obtained from a simple welding experiment, where excellent agreement is obtained.

High Power Laser Beam Welding of Thick-walled Ferromagnetic Steels with Electromagnetic Weld Pool Support

NASA Astrophysics Data System (ADS)

Fritzsche, André; Avilov, Vjaceslav; Gumenyuk, Andrey; Hilgenberg, Kai; Rethmeier, Michael

The development of modern high power laser systems allows single pass welding of thick-walled components with minimal distortion. Besides the high demands on the joint preparation, the hydrostatic pressure in the melt pool increases with higher plate thicknesses. Reaching or exceeding the Laplace pressure, drop-out or melt sagging are caused. A contactless electromagnetic weld support system was used for laser beam welding of thick ferromagnetic steel plates compensating these effects. An oscillating magnetic field induces eddy currents in the weld pool which generate Lorentz forces counteracting the gravity forces. Hysteresis effects of ferromagnetic steels are considered as well as the loss of magnetization in zones exceeding the Curie temperature. These phenomena reduce the effective Lorentz forces within the weld pool. The successful compensation of the hydrostatic pressure was demonstrated on up to 20 mm thick plates of duplex and mild steel by a variation of the electromagnetic power level and the oscillation frequency.

Ultrasonic sensing of GMAW: Laser/EMAT defect detection system. [Gas Metal Arc Welding (GMAW), Electromagnetic acoustic transducer (EMAT)

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

Carlson, N.M.; Johnson, J.A.; Larsen, E.D.

1992-01-01

In-process ultrasonic sensing of welding allows detection of weld defects in real time. A noncontacting ultrasonic system is being developed to operate in a production environment. The principal components are a pulsed laser for ultrasound generation and an electromagnetic acoustic transducer (EMAT) for ultrasound reception. A PC-based data acquisition system determines the quality of the weld on a pass-by-pass basis. The laser/EMAT system interrogates the area in the weld volume where defects are most likely to occur. This area of interest is identified by computer calculations on a pass-by-pass basis using weld planning information provided by the off-line programmer. Themore » absence of a signal above the threshold level in the computer-calculated time interval indicates a disruption of the sound path by a defect. The ultrasonic sensor system then provides an input signal to the weld controller about the defect condition. 8 refs.« less

Gas-tungsten arc welding of aluminum alloys

DOEpatents

Frye, Lowell D.

1984-01-01

A gas-tungsten arc welding method for joining together structures formed of aluminum alloy with these structures disposed contiguously to a heat-damagable substrate of a metal dissimilar to the aluminum alloy. The method of the present invention is practiced by diamond machining the fay surfaces of the aluminum alloy structures to provide a mirror finish thereon having a surface roughness in the order of about one microinch. The fay surfaces are aligned and heated sufficiently by the tungsten electrode to fuse the aluminum alloy contiguous to the fay surfaces to effect the weld joint. The heat input used to provide an oxide-free weld is significantly less than that required if the fay surfaces were prepared by using conventional chemical and mechanical practices.

Design of reinforcement welding machine within steel framework for marine engineering

NASA Astrophysics Data System (ADS)

Wang, Gang; Wu, Jin

2017-04-01

In this project, a design scheme that reinforcement welding machine is added within the steel framework is proposed according to the double-side welding technology for box-beam structure in marine engineering. Then the design and development of circuit and transmission mechanism for new welding equipment are completed as well with one sample machine being made. Moreover, the trial running is finished finally. Main technical parameters of the equipment are: the working stroke: ≥1500mm, the welding speed: 8˜15cm/min and the welding sheet thickness: ≥20mm.

Grain refinement control in TIG arc welding

NASA Technical Reports Server (NTRS)

Iceland, W. F.; Whiffen, E. L. (Inventor)

1975-01-01

A method for controlling grain size and weld puddle agitation in a tungsten electrode inert gas welding system to produce fine, even grain size and distribution is disclosed. In the method the frequency of dc welding voltage pulses supplied to the welding electrode is varied over a preselected frequency range and the arc gas voltage is monitored. At some frequency in the preselected range the arc gas voltage will pass through a maximum. By maintaining the operating frequency of the system at this value, maximum weld puddle agitation and fine grain structure are produced.

Investigation of Hot Cracking Behavior in Transverse Mechanically Arc Oscillated Autogenous AA2014 T6 TIG Welds

NASA Astrophysics Data System (ADS)

Biradar, N. S.; Raman, R.

2012-09-01

Hot cracking studies on autogenous AA2014 T6 TIG welds were carried out. Significant cracking was observed during linear and circular welding test (CWT) on 4-mm-thick plates. Weld metal grain structure and amount of liquid distribution during the terminal stages of solidification were the key cause for hot cracking in aluminum welds. Square-wave AC TIG welding with transverse mechanical arc oscillation (TMAO) was employed to study the cracking behavior during linear and CWT. TMAO welds with amplitude = 0.9 mm and frequency = 0.5 Hz showed significant reduction in cracking tendency. The increase in cracking resistance in the arc-oscillated weld was attributed to grain refinement and improved weld bead morphology, which improved the weld metal ductility and uniformity, respectively, of residual tensile stresses that developed during welding. The obtained results were comparable to those of reported favorable results of electromagnetic arc oscillation.

The effect of travel speed on thermal response in CO2 laser welding of small electronic components

NASA Astrophysics Data System (ADS)

Gianoulakis, S. E.; Burchett, S. N.; Fuerschbach, P. W.; Knorovsky, G. A.

A comprehensive three-dimensional numerical investigation of the effect of beat source travel speed on temperatures and resulting thermal stresses was performed for CO2-laser welding. The test specimen was a small thermal battery header containing several stress-sensitive glass-to-metal seals surrounding the electrical connections and a temperature sensitive ignitor located under the header near the center. Predictions of the thermal stresses and temperatures in the battery header were made for several travel speeds of the laser. The travel speeds examined ranged from 10mm/sec to 50mm/sec. The results indicate that faster weld speeds result in lower temperatures and stresses for the same size weld. This is because the higher speed welds are more efficient, requiring less energy to produce a given weld. Less energy absorbed by the workpiece results in lower temperatures, which results in lower stresses.

Ultrasonic sensing of GMAW: Laser/EMAT defect detection system

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

Carlson, N.M.; Johnson, J.A.; Larsen, E.D.

1992-08-01

In-process ultrasonic sensing of welding allows detection of weld defects in real time. A noncontacting ultrasonic system is being developed to operate in a production environment. The principal components are a pulsed laser for ultrasound generation and an electromagnetic acoustic transducer (EMAT) for ultrasound reception. A PC-based data acquisition system determines the quality of the weld on a pass-by-pass basis. The laser/EMAT system interrogates the area in the weld volume where defects are most likely to occur. This area of interest is identified by computer calculations on a pass-by-pass basis using weld planning information provided by the off-line programmer. Themore » absence of a signal above the threshold level in the computer-calculated time interval indicates a disruption of the sound path by a defect. The ultrasonic sensor system then provides an input signal to the weld controller about the defect condition. 8 refs.« less

Damage Tolerance Assessment of Friction Pull Plug Welds in an Aluminum Alloy

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 cryogenic propellant tanks. Self-reacting friction stir welding is one variation of the friction stir weld process being developed for manufacturing tanks. Friction pull plug welding is used to seal the exit hole that remains in a circumferential self-reacting friction stir weld. A friction plug weld placed in a self-reacting friction stir weld results in a non-homogenous weld joint where the initial weld, plug weld, their respective heat affected zones and the base metal all interact. The welded joint is a composite plastically deformed material system with a complex residual stress field. In order to address damage tolerance concerns associated with friction plug welds in safety critical structures, such as propellant tanks, 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 relating residual strength capability to flaw size in an aluminum alloy friction plug weld will be presented.

Microscopic analysis of structural changes in diode-laser-welded corneal stroma

NASA Astrophysics Data System (ADS)

Matteini, Paolo; Rossi, Francesca; Menabuoni, Luca; Pini, Roberto

2007-02-01

Diode laser welding of the cornea is a technique used to provide immediate sealing of corneal wounds: the cut is stained with a water solution of Indocyanine Green and is then irradiated with an 810 nm laser at low power densities (12-16 W/cm2), which induces a localized heating of the stroma in the range 55-66 °C range. In this study, we present a microscopic analysis aimed at evaluating the structural modifications induced in the stromal collagen of pig eyes during the laser welding of corneal wounds. Cornea samples obtained from twenty freshly-enucleated eyes were cut with a pre-calibrated knife and subjected to the laser welding procedure. Histological slices of the laser-welded stroma were examined by means of optical and transmission electron microscopy. These analyses indicated that bridges of lamellar structures crossed the wound edges with no presence of a coagulation effect. After laser welding, collagen fibrils appeared differently oriented among themselves in comparison with those of the control samples, but with similar mean fibril diameters. The laser-induced effect appeared to be confined to the ICG stained area of the cut walls, and no heat damage was observed at the operative power levels of laser corneal welding.

Casting of weldable graphite/magnesium metal matrix composites with built-in metallic inserts

NASA Technical Reports Server (NTRS)

Lee, Jonathan A.; Kashalikar, Uday; Majkowski, Patricia

1994-01-01

Technology innovations directed at the advanced development of a potentially low cost and weldable graphite/magnesium metal matrix composites (MMC) through near net shape pressure casting are described. These MMC components uniquely have built-in metallic inserts to provide an innovative approach for joining or connecting other MMC components through conventional joining techniques such as welding, brazing, mechanical fasteners, etc. Moreover, the metallic inserts trapped within the MMC components can be made to transfer the imposed load efficiently to the continuous graphite fiber reinforcement thus producing stronger, stiffer, and more reliable MMC components. The use of low pressure near net shape casting is economical compared to other MMC fabrication processes. These castable and potentially weldable MMC components can provide great payoffs in terms of high strength, high stiffness, low thermal expansion, lightweight, and easily joinable MMC components for several future NASA space structural, industrial, and commercial applications.

The technology and welding joint properties of hybrid laser-tig welding on thick plate

NASA Astrophysics Data System (ADS)

Shenghai, Zhang; Yifu, Shen; Huijuan, Qiu

2013-06-01

The technologies of autogenous laser welding and hybrid laser-TIG welding are used on thick plate of high strength lower alloy structural steel 10CrNiMnMoV in this article. The unique advantages of hybrid laser-TIG welding is summarized by comparing and analyzing the process parameters and welding joints of autogenous laser welding laser welding and hybrid laser-TIG welding. With the optimal process parameters of hybrid welding, the good welding joint without visible flaws can be obtained and its mechanical properties are tested according to industry standards. The results show that the hybrid welding technology has certain advantages and possibility in welding thick plates. It can reduce the demands of laser power, and it is significant for lowering the aspect ratio of weld during hybrid welding, so the gas in the molten pool can rise and escape easily while welding thick plates. Therefore, the pores forming tendency decreases. At the same time, hybrid welding enhances welding speed, and optimizes the energy input. The transition and grain size of the microstructure of hybrid welding joint is better and its hardness is higher than base material. Furthermore, its tensile strength and impact toughness is as good as base material. Consequently, the hybrid welding joint can meet the industry needs completely.

The high frequency characteristics of laser reflection and visible light during solid state disk laser welding

NASA Astrophysics Data System (ADS)

Gao, Xiangdong; You, Deyong; Katayama, Seiji

2015-07-01

Optical properties are related to weld quality during laser welding. Visible light radiation generated from optical-induced plasma and laser reflection is considered a key element reflecting weld quality. An in-depth analysis of the high-frequency component of optical signals is conducted. A combination of a photoelectric sensor and an optical filter helped to obtain visible light reflection and laser reflection in the welding process. Two groups of optical signals were sampled at a high sampling rate (250 kHz) using an oscilloscope. Frequencies in the ranges 1-10 kHz and 10-125 kHz were investigated respectively. Experimental results showed that there was an obvious correlation between the high-frequency signal and the laser power, while the high-frequency signal was not sensitive to changes in welding speed. In particular, when the defocus position was changed, only a high frequency of the visible light signal was observed, while the high frequency of the laser reflection signal remained unchanged. The basic correlation between optical features and welding status during the laser welding process is specified, which helps to provide a new research focus for investigating the stability of welding status.

Effects of active flux on plasma behavior and weld shape in laser welding of X5CrNi189 stainless steel

NASA Astrophysics Data System (ADS)

Dai, Hongbin; Peng, Jun

2016-11-01

In this paper, stainless steel was welded by active flux-aided laser welding method. The effects of single active flux (Cr2O3, SiO2 and TiO2) and composite active flux on laser welding were studied. In the welding process, laser plasma behavior was recorded by a high-speed imaging system. The results show that, with the addition of active flux, the absorption of laser energy and melting efficiency increase. In the laser power of 750 W, effects of active flux on weld depth to width ratio are given by the order: composite active flux > SiO2 > Cr2O3 > TiO2. The effect of composite active flux is the most significant and it can increase the weld depth to width ratio to 85%. Active flux can restrict the laser plasma. With the addition of composite active flux, the projected area of laser plasma obtained obviously reduced, and it can be reduced by 41.39%. Active flux cannot obviously change the main components in weld zone, but can change the grains of austenite and ferrite.

Microstructure and Mechanical Performance of Friction Stir Spot-Welded Aluminum-5754 Sheets

NASA Astrophysics Data System (ADS)

Pathak, N.; Bandyopadhyay, K.; Sarangi, M.; Panda, Sushanta Kumar

2013-01-01

Friction stir spot welding (FSSW) is a recent trend of joining light-weight sheet metals while fabricating automotive and aerospace body components. For the successful application of this solid-state welding process, it is imperative to have a thorough understanding of the weld microstructure, mechanical performance, and failure mechanism. In the present study, FSSW of aluminum-5754 sheet metal was tried using tools with circular and tapered pin considering different tool rotational speeds, plunge depths, and dwell times. The effects of tool design and process parameters on temperature distribution near the sheet-tool interface, weld microstructure, weld strength, and failure modes were studied. It was found that the peak temperature was higher while welding with a tool having circular pin compared to tapered pin, leading to a bigger dynamic recrystallized stir zone (SZ) with a hook tip bending towards the upper sheet and away from the keyhole. Hence, higher lap shear separation load was observed in the welds made from circular pin compared to those made from tapered pin. Due to influence of size and hardness of SZ on crack propagation, three different failure modes of weld nugget were observed through optical cross-sectional micrograph and SEM fractographs.

Prospects of very high power CO{sub 2} laser in welding

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

Goussain, J.C.; Vire, S.

1996-12-31

A 45 kW laser system was recently installed at Institut de Soudure (IS) in France in order to evaluate the possibilities of such high power beams in welding. Some results of welding various materials (Ta6V, C-steel, Cr-Ni alloys), different thicknesses (>30 mm) and large components (several meters) are presented. Some recent installations of high power laser equipment already integrated into production site or under development in shipbuilding and steel fabrication are described. Finally the objectives of an important R and D program launched recently for exploring the different aspects of laser welding in thick section steel fabrication is outlined.

Metal-Matrix Composite Parts With Metal Inserts

NASA Technical Reports Server (NTRS)

Majkowski, T.; Kashalikar, U.

1995-01-01

Developmental fabrication process produces metal-matrix composite (MMC) parts with integral metal inserts. With inserts, MMC parts readily joined to similar parts by use of brazing, welding, or mechanical fasteners. Process conceived to make strong, lightweight components of structures erected in outer space. Also useful on Earth, in such automotive parts as rocker arms, cylinder liners, and pistons. Potential industrial applications include parts subjected to high stresses at high temperatures, as in power-generation, mining, and oil-drilling equipment.

Improved simulation method of automotive spot weld failure with an account of the mechanical properties of spot welds

NASA Astrophysics Data System (ADS)

Wu, H.; Meng, X. M.; Fang, R.; Huang, Y. F.; Zhan, S.

2017-12-01

In this paper, the microstructure and mechanical properties of spot weld were studied, the hardness of nugget and heat affected zone (HAZ) were also tested by metallographic microscope and microhardness tester. The strength of the spot weld with the different parts' area has been characterized. According to the experiments result, CAE model of spot weld with HAZ structure was established, and simulation results of different lap-shear CAE models were analyzed. The results show that the spot weld model which contained the HAZ has good performance and more suitable for engineering application in spot weld simulation.

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.

Manufacturing Methods and Technology Application of High Energy Laser Welding Process.

DTIC Science & Technology

1980-08-01

surface appearance and the lowest porosity of the three beam shapes evaluated. Welds made with the pure annular beam resembled a TIG weld in both surface...improper starts and stops when welding with a conventional MIG or TIG process. Figure 16 left and center illustrates cracking due to fast freezing conditions...REPORT RL-82-2 0 MANUFACTURING METHODS AND TECHNOLOGY APPLICATION _OF HIGH ENERGY LASER WELDING PROCESS 0John V. Melonas Structures Directorate, U S

Fibre Laser Welding of HY-80 Steel: Procedure Development and Testing

DTIC Science & Technology

2010-09-01

2 Welding The material used in this study was quenched and tempered martensitic HY80 steel which conforms to MIL-S-1621 [2]. The testing...Journal, 1977. [4] AWS, D1.6 in Structural Welding Code Stainless Steel . 2007, American Welding Society: Miami Florida. [5] DefStan, 02-770 Part 2...Canada Fibre Laser Welding of HY-80 Steel Proceedure Development and Testing Christopher Bayley DLP Neil Aucoin DLP Xinjin Cao NRC IAR AMTC Technical

Hot cracking of Structural Steel during Laser Welding

NASA Astrophysics Data System (ADS)

Pineda Huitron, Rosa M.; Vuorinen, Esa

2017-10-01

Laser welding is an important technique in many industries due to its high precision in operation, its local and fast processing, narrow welds and its good weld surface quality. However, the process can involve some complications due to the rapid heating and cooling of the material processed, resulting in physical and metallurgical effects as thermal contraction during solidification, giving as a result the presence of residual stresses in the narrow weld. Formation of defects during the process is an important topic to be evaluated in order to achieve better performance of the steels in use. In the present work, defects formed during laser welding of a structural steel have been investigated. The defects formed have been identified and the causes of the defects are discussed. Possible strategies for improvement of the welding procedure and final weld result are proposed. The defects were analysed by optical and scanning electron microscopy and hardness measurement. Cracks were located in the middle of the fusion zone and followed both inter-granular and trans-granular paths. Impurities as manganese sulphides were found along the welding direction, and could act as sites for crack formation. The cracks formed during solidification of the weld are identified as solidification cracks. This kind of cracks is usually caused by solidification shrinkage and thermal contractions during the process, which appear in the fusion zone and sometimes in the heat affected zone.

Effects of various tool pin profiles on mechanical and metallurgical properties of friction stir welded joints of cryorolled AA2219 aluminium alloy

NASA Astrophysics Data System (ADS)

Kamal Babu, Karupannan; Panneerselvam, Kavan; Sathiya, Paulraj; Noorul Haq, Abdul Haq; Sundarrajan, Srinivasan; Mastanaiah, Potta; Srinivasa Murthy, Chunduri Venkata

2018-02-01

Friction stir welding (FSW) process was conducted on cryorolled (CR) AA2219 plate using different tool pin profiles such as cylindrical pin, threaded cylindrical pin, square pin and hexagonal pin profiles. The FSW was carried out with pairs of 6 mm thick CR aluminium plates with different tool pin profiles. The different tool pin profile weld portions' behaviors like mechanical (tensile strength, impact and hardness) and metallurgical characteristics were analyzed. The results of the mechanical analysis revealed that the joint made by the hexagonal pin tool had good strength compared to other pin profiles. This was due to the pulsating action and material flow of the tool resulting in dynamic recrystallization in the weld zone. This was confirmed by the ultra fine grain structure formation in Weld Nugget (WN) of hexagonal pin tool joint with a higher percentage of precipitate dissolution. The fractograph of the hexagonal tool pin weld portion confirmed the finer dimple structure morphology without having any interior defect compared to other tool pin profiles. The lowest weld joint strength was obtained from cylindrical pin profile weld joint due to insufficient material flow during welding. The Transmission Electron Microscope and EDX analysis showed the dissolution of the metastable θ″, θ' (Al2Cu) partial precipitates in the WN and proved the influence of metastable precipitates on enhancement of mechanical behavior of weld. The XRD results also confirmed the Al2Cu precipitation dissolution in the weld zone.

Investigation on fibrous collagen modifications during corneal laser welding by second harmonic generation microscopy

NASA Astrophysics Data System (ADS)

Matteini, Paolo; Ratto, Fulvio; Rossi, Francesca; Cicchi, Riccardo; Stringari, Chiara; Kapsokalyvas, Dimitrios; Pavone, Francesco S.; Pini, Roberto

2009-02-01

The structural modifications in the collagen lattice of corneal stroma induced by near-infrared laser welding were investigated with second-harmonic generation (SHG) imaging. The corneal laser welding procedure is performed by staining the wound edges with a saturated water solution of Indocyanine Green (ICG) followed by irradiation with a 810 nm diode laser operated in continuous (CWLW: continuous wave laser welding) or pulsed (PLW: pulsed laser welding) mode. Both these procedures can provide closure of corneal wounds by inducing different structural modifications in the extracellular matrix. SHG imaging of native corneal stroma revealed collagen bundles composed of many regularly aligned collagen fibrils. After CWLW the regular lamellar arrangement was lost; collagen bundles appeared densely packed with an increasing disordered arrangement toward the welded cut. The weld was characterized by a loss of details; nevertheless, the observation of the second harmonic signal at this site indicated the lack of collagen denaturation. By contrast, PLW mode produced welding spots at the interface between donor and recipient corneal layers, which were characterized by a severe loss of the SHG signal, suggesting the occurrence of a complete collagen denaturation. SHG imaging appeared to be a powerful tool for visualizing the supramolecular morphological modifications in the collagen matrix after laser welding.

Quantitative ultrasonic testing of acoustically anisotropic materials with verification on austenitic and dissimilar weld joints

NASA Astrophysics Data System (ADS)

Boller, C.; Pudovikov, S.; Bulavinov, A.

2012-05-01

Austenitic stainless steel materials are widely used in a variety of industry sectors. In particular, the material is qualified to meet the design criteria of high quality in safety related applications. For example, the primary loop of the most of the nuclear power plants in the world, due to high durability and corrosion resistance, is made of this material. Certain operating conditions may cause a range of changes in the integrity of the component, and therefore require nondestructive testing at reasonable intervals. These in-service inspections are often performed using ultrasonic techniques, in particular when cracking is of specific concern. However, the coarse, dendritic grain structure of the weld material, formed during the welding process, is extreme and unpredictably anisotropic. Such structure is no longer direction-independent to the ultrasonic wave propagation; therefore, the ultrasonic beam deflects and redirects and the wave front becomes distorted. Thus, the use of conventional ultrasonic testing techniques using fixed beam angles is very limited and the application of ultrasonic Phased Array techniques becomes desirable. The "Sampling Phased Array" technique, invented and developed by Fraunhofer IZFP, allows the acquisition of time signals (A-scans) for each individual transducer element of the array along with fast image reconstruction techniques based on synthetic focusing algorithms. The reconstruction considers the sound propagation from each image pixel to the individual sensor element. For anisotropic media, where the sound beam is deflected and the sound path is not known a-priori, a novel phase adjustment technique called "Reverse Phase Matching" is implemented. By taking into account the anisotropy and inhomogeneity of the weld structure, a ray tracing algorithm for modeling the acoustic wave propagation and calculating the sound propagation time is applied. This technique can be utilized for 2D and 3D real time image reconstruction. The "Gradient Constant Descent Method" (GECDM), an iterative algorithm, is implemented, which is essential for examination of inhomogeneous anisotropic media having unknown properties (elastic constants). The Sampling Phased Array technique with Reverse Phase Matching extended by GECDM-technique determines unknown elastic constants and provides reliable and efficient quantitative flaw detection in the austenitic welds. The validation of ray-tracing algorithm and GECDM-method is performed by number of experiments on test specimens with artificial as well as natural material flaws. A mechanized system for ultrasonic testing of stainless steel and dissimilar welds is developed. The system works on both conventional and Sampling Phased Array techniques. The new frontend ultrasonic unit with optical data link allows the 3D visualization of the inspection results in real time.

Development and Testing of a Hydropneumatic Suspension System on a USMC AAV7A1

DTIC Science & Technology

1991-07-30

original material, SAE 4140 steel alloy hardened to 30/34 Rc, has a yield strength of 130,000 psi. All of the ISU’s were disassembled and were reassembled...plugged and welded in place. Aluminum I-beams were welded in place in the water jet tunnels to act as jounce stops for the aft suspension units. The...following Is a tabulation of components attributed to the vehicle: 1000 Hull, Welded & machined 1100 Bow Plane 2000 Powertrain 3000 Transmission 4000

40 CFR 63.11519 - What are my notification, recordkeeping, and reporting requirements?

Code of Federal Regulations, 2010 CFR

2010-07-01

..., a brief characterization of the types of products (e.g., aerospace components, sports equipment, etc... of emissions opacity. (9) Site-specific Welding Emissions Management Plan reporting. You must submit...-Specific Welding Emissions Management Plan and any subsequent revisions to the plan pursuant to § 63.11516...

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.

Metal Flow in Friction Stir Welding

NASA Technical Reports Server (NTRS)

Nunes, Arthur C., Jr.

2006-01-01

The plastic deformation field in Friction Stir Welding (FSW) is compared to that in metal cutting. A shear surface around the FSW tool analogous to the metal cutting shear plane is identified and comprises the basis of the "rotating plug" flow field model and the "wiping" model of tool interaction with weld metal. Within the context of these models: The FSW shear rate is estimated to be comparable to metal cutting shear rates. The effect of tool geometry on the FSW shear surface is discussed and related to published torque measurements. Various FS W structural features are explained, including a difference in structure of bimetallic welds when alloys on the advancing and retreating sides of the weld seam are exchanged. The joining mechanism and critical parameters of the FSW process are made clear.

Changes in type I collagen following laser welding.

PubMed

Bass, L S; Moazami, N; Pocsidio, J; Oz, M C; LoGerfo, P; Treat, M R

1992-01-01

Selection of ideal laser parameters for tissue welding is inhibited by poor understanding of the mechanism. We investigated structural changes in collagen molecules extracted from rat tail tendon (> 90% type I collagen) after tissue welding using an 808 nm diode laser and indocyanine green dye applied to the weld site. Mobility patterns on SDS-PAGE were identical in the lasered and untreated tendon extracts with urea or acetic acid. Pepsin incubation after acetic acid extraction revealed a reduction of collagen alpha and beta bands in lasered compared with untreated specimens. Circular dichroism studies of rat tail tendon showed absence of helical structure in collagen from lasered tendon. No evidence for covalent bonding was present in laser-treated tissues. Collagen molecules are denatured by the laser wavelength and parameters used in this study. No significant amount of helical structure is regenerated on cooling. We conclude that non-covalent interactions between denatured collagen molecules may be responsible for the creation of tissue welding.

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

Acoustic emission investigation of cold cracking in gas metal-arc welding of AISI 4340 steel

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

Fang, C.K.; Kannatey-Asibu, E. Jr.; Barber, J.R.

1995-06-01

Acoustic emission (AE) has been used to investigate the propagation of a finite crack in a weldment subjected to nonuniform longitudinal residual stresses during gas metal arc welding (GMAW). Cold cracking in selected weldments was accelerated using the electrochemical method to cathodically charge the weldments with hydrogen in order to induce hydrogen embrittlement. Cold cracking was observed about 40 min after charging in the specimen subjected to hydrogen embrittlement, while it was observed two days after welding for the one that was left in the atmosphere. The AE signals were generated as the specimen cracked and were recorded, and themore » effects from structure and instrumentation were removed from the measured signals by deconvolution in the frequency domain. Most of the high-amplitude signal components were found to be clustered in the frequency range below 200 kHz. The experimentally obtained spectrum was compared with theoretical results derived in earlier work, and reasonable agreement with theoretical surface displacement in both time and frequency domains was obtained. The envelopes for both spectra were found to decrease with increasing frequency, while the fluctuations in each curve diminished at high frequencies.« less

Glue-free assembly of glass fiber reinforced thermoplastics using laser light

NASA Astrophysics Data System (ADS)

Binetruy, C.; Clement, S.; Deleglise, M.; Franz, C.; Knapp, W.; Oumarou, M.; Renard, J.; Roesner, A.

2011-05-01

The use of laser light for bonding of continuous fiber reinforced thermoplastic composites (CFTPC) offers new possibilities to overcome the constraints of conventional joining technologies. Laser bonding is environmentally friendly as no chemical additive or glue is necessary. Accuracy and flexibility of the laser process as well as the quality of the weld seams provide benefits which are already used in many industrial applications. Laser transmission welding has already been introduced in manufacturing of short fiber thermoplastic composites. The laser replaces hot air in tapelaying systems for pre-preg carbon fiber placement. The paper provides an overview concerning the technical basics of the joining process and outline some material inherent characteristics to be considered when using continuous glass fiber reinforced composites The technical feasibility and the mechanical characterization of laser bonded CFTPC are demonstrated. The influence of the different layer configurations on the laser interaction with the material is investigated and the dependency on the mechanical strength of the weld seem is analyzed. The results show that the laser provides an alternative joining technique and offers new perspectives to assemble structural components emerging in automotive or aeronautical manufacturing. It overcomes the environmental and technical difficulties related to existing gluing processes.

Gas-tungsten arc welding of aluminum alloys

DOEpatents

Frye, L.D.

1982-03-25

The present invention is directed to a gas-tungsten arc welding method for joining together structures formed of aluminum alloy with these structures disposed contiguously to a heat-damagable substrate of a metal dissimilar to the aluminum alloy. The method of the present invention is practiced by diamond machining the fay surfaces of the aluminum alloy structures to profice a mirror finish thereon having a surface roughness in the order of about one microinch. The fay surface are aligned and heated sufficiently by the tungsten electrode to fuse the aluminum alloy continguous to the fay surfaces to effect the weld joint. The heat input used to provide an oxide-free weld is significantly less than that required if the fay surfaces were prepared by using conventional chemical and mechanical practices.

Design of a welded joint for robotic, on-orbit assembly of space trusses

NASA Astrophysics Data System (ADS)

Rule, W. K.; Thomas, F. P.

1992-10-01

A preliminary design for a weldable truss joint for on-orbit assembly of large space structures is described. The joint was designed for ease of assembly, for structural efficiency, and to allow passage of fluid (for active cooling or other purposes) along the member through the joint. The truss members were assumed to consist of graphite/epoxy tubes to which were bonded 2219-T87 aluminum alloy end fittings for welding on-orbit to truss nodes of the same alloy. A modified form of gas tungsten arc welding was assumed to be the welding process. The joint was designed to withstand the thermal and structural loading associated with a 120-ft diameter tetrahedral truss intended as an aerobrake for a mission to Mars.

Design of a welded joint for robotic, on-orbit assembly of space trusses

NASA Technical Reports Server (NTRS)

Rule, W. K.; Thomas, F. P.

1992-01-01

A preliminary design for a weldable truss joint for on-orbit assembly of large space structures is described. The joint was designed for ease of assembly, for structural efficiency, and to allow passage of fluid (for active cooling or other purposes) along the member through the joint. The truss members were assumed to consist of graphite/epoxy tubes to which were bonded 2219-T87 aluminum alloy end fittings for welding on-orbit to truss nodes of the same alloy. A modified form of gas tungsten arc welding was assumed to be the welding process. The joint was designed to withstand the thermal and structural loading associated with a 120-ft diameter tetrahedral truss intended as an aerobrake for a mission to Mars.

Microstructural Evolution and Fracture Behavior of Friction-Stir-Welded Al-Cu Laminated Composites

NASA Astrophysics Data System (ADS)

Beygi, R.; Kazeminezhad, Mohsen; Kokabi, A. H.

2014-01-01

In this study, we attempt to characterize the microstructural evolution during friction stir butt welding of Al-Cu-laminated composites and its effect on the fracture behavior of the joint. Emphasis is on the material flow and particle distribution in the stir zone. For this purpose, optical microscopy and scanning electron microscopy (SEM) images, energy-dispersive spectroscopy EDS and XRD analyses, hardness measurements, and tensile tests are carried out on the joints. It is shown that intermetallic compounds exist in lamellas of banding structure formed in the advancing side of the welds. In samples welded from the Cu side, the banding structure in the advancing side and the hook formation in the retreating side determine the fracture behavior of the joint. In samples welded from the Al side, a defect is formed in the advancing side of the weld, which is attributed to insufficient material flow. It is concluded that the contact surface of the laminate (Al or Cu) with the shoulder of the FSW tool influences the material flow and microstructure of welds.

HAZ and Structural Defects Control in Key-Hole Welding of Titanium Using a Reptitively-Pulsed Nd: Yag Laser

NASA Astrophysics Data System (ADS)

Hamudi, Walid K.

1996-12-01

HAZ, porosity and cracks were investigated when welding 0.9 mm thick titanium sheets using a 10 J pulsed Nd: Yag laser. The effects of welding speed, joints fit-up, shielding gas, and laser parameters are presented. For optimum welding quality, 0.25 m/min scanning speed, 10 ℓ/min gas flow rate and 72 Watt average power were used. Welds of narrow heat affected zone (HAZ) with small level of porosity were obtained.

An online real time ultrasonic NDT system for the quality control of spot welding in the automotive industry

NASA Astrophysics Data System (ADS)

Athi, N.; Wylie, S. R.; Cullen, J. D.; Al-Jader, M.; Al-Shamma'a, A. I.; Shaw, A.

2009-07-01

Resistance spot welding is the main joining technique used for the fabrication of body-in-white structures in the automotive industry. The quality of the welds depends on the profile of the spot welding electrode cap. The increased use of zinc coated steel in the industry increases wear rate of the caps, making quality control more difficult. This paper presents a novel online real time ultrasonic NDE system for resistance spot welding which evaluates every weld as it is formed. SEM results are presented to show the alloying of the electrode caps.

Milestones in welding technology

NASA Astrophysics Data System (ADS)

Dolby, Richard E.

2013-09-01

Sir Alan's PhD thesis describes his research into cracking during arc welding of armour steels. Throughout his career, he had a strong interest in defects of all types, how they formed in metallic structures and how the larger ones could be detected and sized by non-destructive techniques. He was also vitally concerned with how defects impacted on the engineering integrity of welded structures, particularly the risk of fracture in nuclear plant. This study presents a view of some of the major milestones in global welding technology that took place over the 60 or more years of Sir Alan's career and highlights those where he had a personal and direct involvement.

Modelling Polymer Deformation and Welding Behaviour during 3D Printing

NASA Astrophysics Data System (ADS)

McIlroy, Claire; Olmsted, Peter

2016-11-01

3D printing has the potential to transform manufacturing processes, yet improving the strength of printed parts, to equal that of traditionally-manufactured parts, remains an underlying issue. The most common method, fused deposition modelling, involves melting a thermoplastic, followed by layer-by-layer extrusion of the material to fabricate a three-dimensional object. The key to the ensuring strength at the weld between these layers is successful inter-diffusion. However, as the printed layer cools towards the glass transition temperature, the time available for diffusion is limited. In addition, the extrusion process significantly deforms the polymer micro-structure prior to welding and consequently affects how the polymers "re-entangle" across the weld. We have developed a simple model of the non-isothermal printing process to explore the effects that typical printing conditions and amorphous polymer rheology have on the ultimate weld structure. In particular, we incorporate both the stretch and orientation of the polymer using the Rolie-Poly constitutive equation to examine how the melt flows through the nozzle and is deposited onto the build plate. We then address how this deformation relaxes and contributes to the thickness and structure of the weld. National Institute for Standards and Technology (NIST) and Georgetown University.

Development of a Robust and Cost-Effective Friction Stir Welding Process for Use in Advanced Military Vehicles

NASA Astrophysics Data System (ADS)

Grujicic, M.; Arakere, G.; Pandurangan, B.; Hariharan, A.; Yen, C.-F.; Cheeseman, B. A.

2011-02-01

To respond to the advent of more lethal threats, recently designed aluminum-armor-based military-vehicle systems have resorted to an increasing use of higher strength aluminum alloys (with superior ballistic resistance against armor piercing (AP) threats and with high vehicle-light weighing potential). Unfortunately, these alloys are not very amenable to conventional fusion-based welding technologies and in-order to obtain high-quality welds, solid-state joining technologies such as Friction stir welding (FSW) have to be employed. However, since FSW is a relatively new and fairly complex joining technology, its introduction into advanced military vehicle structures is not straight forward and entails a comprehensive multi-step approach. One such (three-step) approach is developed in the present work. Within the first step, experimental and computational techniques are utilized to determine the optimal tool design and the optimal FSW process parameters which result in maximal productivity of the joining process and the highest quality of the weld. Within the second step, techniques are developed for the identification and qualification of the optimal weld joint designs in different sections of a prototypical military vehicle structure. In the third step, problems associated with the fabrication of a sub-scale military vehicle test structure and the blast survivability of the structure are assessed. The results obtained and the lessons learned are used to judge the potential of the current approach in shortening the development time and in enhancing reliability and blast survivability of military vehicle structures.

Welding of a corrosion-resistant composite material based on VT14 titanium alloy obtained using an electron beam emitted into the atmosphere

NASA Astrophysics Data System (ADS)

Golkovski, M. G.; Samoylenko, V. V.; Polyakov, I. A.; Lenivtseva, O. G.; Chakin, I. K.; Komarov, P. N.; Ruktuev, A. A.

2017-01-01

The study investigates the possibility of inert gas arc welding of a double layer composite material on a titanium base with an anti-corrosive layer obtained by fused deposition of a powder mix containing tantalum and niobium over a titanium base using an electron beam emitted into the atmosphere. Butt welding and fillet welding options were tested with two types of edge preparation. Welds were subjected to a metallographic examination including a structural study and an analysis of the chemical and phase composition of the welds. A conclusion was made regarding the possibility of using welding for manufacturing of items from the investigated composite material.

Damage Tolerance Assessment of Friction Pull Plug Welds

NASA Technical Reports Server (NTRS)

McGill, Preston; Burkholder, Jonathan

2012-01-01

Friction stir welding is a solid state welding process developed and patented by The Welding Institute in Cambridge, England. Friction stir welding has been implemented in the aerospace industry in the fabrication of longitudinal welds in pressurized cryogenic propellant tanks. As the industry looks to implement friction stir welding in circumferential welds in pressurized cryogenic propellant tanks, techniques to close out the termination hole associated with retracting the pin tool are being evaluated. Friction pull plug welding is under development as a one means of closing out the termination hole. A friction pull plug weld placed in a friction stir weld results in a non-homogenous weld joint where the initial weld, plug weld, their respective heat affected zones and the base metal all interact. The welded joint is a composite, plastically deformed material system with a complex residual stress field. In order to address damage tolerance concerns associated with friction plug welds in safety critical structures, such as propellant tanks, 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 in the test or service environments. Test data relating residual strength capability to flaw size in two aluminum alloy friction plug weld configurations is presented.

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.

Proton-irradiation technology for high-frequency high-current silicon welding diode manufacturing

NASA Astrophysics Data System (ADS)

Lagov, P. B.; Drenin, A. S.; Zinoviev, M. A.

2017-05-01

Different proton irradiation regimes were tested to provide more than 20 kHz-frequency, soft reverse recovery “snap-less” behavior, low forward voltage drop and leakage current for 50 mm diameter 7 kA/400 V welding diode Al/Si/Mo structure. Silicon diode with such parameters is very suitable for high frequency resistance welding machines of new generation for robotic welding.

An intelligent approach to welding robot selection

NASA Astrophysics Data System (ADS)

Milano, J.; Mauk, S. D.; Flitter, L.; Morris, R.

1993-10-01

In a shipyard where multiple stationary and mobile workcells are employed in the fabrication of components of complex sub-assemblies,efficient operation requires an intelligent method of scheduling jobs and selecting workcells based on optimum throughput and cost. The achievement of this global solution requires the successful organization of resource availability,process requirements,and process constraints. The Off-line Planner (OLP) of the Programmable Automated Weld Systemd (PAWS) is capable of advanced modeling of weld processes and environments as well as the generation of complete weld procedures. These capabilities involve the integration of advanced Computer Aided Design (CAD), path planning, and obstacle detection and avoidance techniques as well as the synthesis of complex design and process information. These existing capabilities provide the basis of the functionality required for the successful implementation of an intelligent weld robot selector and material flow planner. Current efforts are focused on robot selection via the dynamic routing of components to the appropriate work cells. It is proposed that this problem is a variant of the “Traveling Salesman Problem” (TSP) that has been proven to belong to a larger set of optimization problems termed nondeterministic polynomial complete (NP complete). In this paper, a heuristic approach utilizing recurrent neural networks is explored as a rapid means of producing a near optimal, if not optimal, bdweld robot selection.

Characterization of Tungsten Inert Gas (TIG) Welding Fume Generated by Apprentice Welders

PubMed Central

Graczyk, Halshka; Lewinski, Nastassja; Zhao, Jiayuan; Concha-Lozano, Nicolas; Riediker, Michael

2016-01-01

Tungsten inert gas welding (TIG) represents one of the most widely used metal joining processes in industry. Its propensity to generate a greater portion of welding fume particles at the nanoscale poses a potential occupational health hazard for workers. However, current literature lacks comprehensive characterization of TIG welding fume particles. Even less is known about welding fumes generated by welding apprentices with little experience in welding. We characterized TIG welding fume generated by apprentice welders (N = 20) in a ventilated exposure cabin. Exposure assessment was conducted for each apprentice welder at the breathing zone (BZ) inside of the welding helmet and at a near-field (NF) location, 60cm away from the welding task. We characterized particulate matter (PM4), particle number concentration and particle size, particle morphology, chemical composition, reactive oxygen species (ROS) production potential, and gaseous components. The mean particle number concentration at the BZ was 1.69E+06 particles cm−3, with a mean geometric mean diameter of 45nm. On average across all subjects, 92% of the particle counts at the BZ were below 100nm. We observed elevated concentrations of tungsten, which was most likely due to electrode consumption. Mean ROS production potential of TIG welding fumes at the BZ exceeded average concentrations previously found in traffic-polluted air. Furthermore, ROS production potential was significantly higher for apprentices that burned their metal during their welding task. We recommend that future exposure assessments take into consideration welding performance as a potential exposure modifier for apprentice welders or welders with minimal training. PMID:26464505

Laser beam welding of Waspaloy: Characterization and corrosion behavior evaluation

NASA Astrophysics Data System (ADS)

Shoja Razavi, Reza

2016-08-01

In this work, a study on Nd:YAG laser welding of Waspaloy sheets has been made. Microstructures, phase changes and hardness of the laser joint were investigated using optical microscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD) and vickers microhardness (HV0.3). Corrosion behavior of the weldment at low temperature in 3.5%wt NaCl solution at room temperature was also investigated using open circuit potential and cyclic potentiodynamic polarization tests. Hot corrosion studies were conducted on samples in the molten salt environment (Na2SO4-60%V2O5) at 900 °C for 50 h. Results indicated that the microstructure of weld zone was mainly dendritic grown epitaxially in the direction perpendicular to the weld boundary and heat transfer. Moreover, the Ti-Mo carbide particles were observed in the structure of the weld zone and base metal. The average size of carbides formed in the base metal (2.97±0.5 μm) was larger than that of the weld zone (0.95±0.2 μm). XRD patterns of the weld zone and base metal showed that the laser welding did not alter the phase structure of the weld zone, being in γ-Ni(Cr) single phase. Microhardness profile showed that the hardness values of the weld zone (210-261 HV) were lower than that of the base metal (323-330 HV). Electrochemical and hot corrosion tests indicated that the corrosion resistance of the weld metal was greater than the base metal in both room and high temperatures.

Development of Probabilistic Structural Analysis Integrated with Manufacturing Processes

NASA Technical Reports Server (NTRS)

Pai, Shantaram S.; Nagpal, Vinod K.

2007-01-01

An effort has been initiated to integrate manufacturing process simulations with probabilistic structural analyses in order to capture the important impacts of manufacturing uncertainties on component stress levels and life. Two physics-based manufacturing process models (one for powdered metal forging and the other for annular deformation resistance welding) have been linked to the NESSUS structural analysis code. This paper describes the methodology developed to perform this integration including several examples. Although this effort is still underway, particularly for full integration of a probabilistic analysis, the progress to date has been encouraging and a software interface that implements the methodology has been developed. The purpose of this paper is to report this preliminary development.

A Micro-Electrochemical Study of Friction Stir Welded Aluminum 6061-T6

NASA Technical Reports Server (NTRS)

Hintze, Paul E.; Calle, Luz M.

2005-01-01

The corrosion behavior of friction stir welded Aluminum alloy 606 1-T6 was studied using a micro-electrochemical cell. The micro-electrochemical cell has a measurement area of about 0.25 square mm which allows for measurement of corrosion properties at a very small scale. The corrosion and breakdown potentials were measured at many points inside and outside the weld along lines perpendicular to the weld. The breakdown potential is approximately equal inside and outside the weld; however, it is lower in the narrow border between the weld and base material. The results of electrochemical measurements were correlated to micro-structural analysis. The corrosion behavior of the friction stir welded samples was compared to tungsten inert gas (TIG) welded samples of the same material.

Size effect on cold-welding of gold nanowires investigated using molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Wu, Cheng-Da; Fang, Te-Hua; Wu, Chung-Chin

2016-03-01

The size effect on the cold-welding mechanism and mechanical properties of Au nanowires (NWs) in head-to-head contact are studied using molecular dynamics simulations based on the second-moment approximation of the many-body tight-binding potential. The results are discussed in terms of atomic trajectories, slip vectors, stress, radial distribution function, and weld strength ratio. Simulation results show that during the cold-welding process, a few disordered atoms/defects in the jointing area rearrange themselves and transform into a face-centered cubic crystalline structure. With an increase in contact between the two NWs, dislocations gradually form on the (111) slip plane and then on a twin plane, leading to an increase in the lateral deformation of 4-nm-wide NWs. The effect of structural instability increases with decreasing NW width, making the alignment of the two NWs more difficult. The elongation ability of the welded NWs increases with increasing NW width. Smaller NWs have better weld strength.

Robotic Manufacturing of 18-ft (5.5m) Diameter Cryogenic Fuel Tank Dome Assemblies for the NASA Ares I Rocket

NASA Technical Reports Server (NTRS)

Jones, Ronald E.; Carter, Robert W.

2012-01-01

The Ares I rocket was the first launch vehicle scheduled for manufacture under the National Aeronautic and Space Administration's Constellation program. A series of full-scale Ares I development articles were constructed on the Robotic Weld Tool at the NASA George C. Marshall Space Flight Center in Huntsville, Alabama. The Robotic Weld Tool is a 100 ton, 7- axis, robotic manufacturing system capable of machining and friction stir welding large-scale space hardware. This paper will focus on the friction stir welding of 18-ft (5.5m) diameter cryogenic fuel tank components; specifically, the liquid hydrogen forward dome and two common bulkhead manufacturing development articles.

Manufacturing Technology Support (MATES II) Task Order 0005: Manufacturing Integration and Technology Evaluation to Enable Technology Transition. Subtask Phase 0 Study Task: Manufacturing Technology (ManTech) and Systems Engineering For Quick Reaction Systems

DTIC Science & Technology

2014-10-01

Porosity from gas entrapment & shrinkage 4 Continuous Fiber Ti Metal Matrix Composites (Aircraft panels and rotor components) [14...process models for casting, forging, and welding , and software capability to integrate various independent models with design, thermal, and structural...Applications, Ph.D. Thesis, Queen’s College, University of Oxford, (2007). 14. S.A. Singerman and J.J. Jackson, Titanium Metal Matrix Composites for

The Microstructure and Gamma Prime Distributions in Inertia Friction Welded Joint of P/M Superalloy FGH96

NASA Astrophysics Data System (ADS)

Zhang, Chi; Shen, Wenfei; Zhang, Liwen; Xia, Yingnan; Li, Ruiqin

2017-04-01

A gamma prime ( γ') precipitation ( 35% in volume)-hardened powder metallurgy (P/M) superalloy FGH96 was welded using inertia friction welding (IFW). The microstructure and γ' distributions in the joints in two conditions, hot isostatic pressed state and solution-treated and aged state, were characterized. The recrystallization of grains, the dissolution and re-precipitation of γ' in the joints were discussed in terms of the temperature evolutions which were calculated by finite element model analysis. Regardless of the initial states, fully recrystallized fine grain structure formed at welded zone. Meanwhile, very fine γ' precipitations were re-precipitated at the welded zone. These recrystallized grain structure and fine re-precipitated γ' resulted in increasing hardness of IFW joint while making the hardness dependent on the microstructure and γ' precipitation.

Frequency dependence of excitation-contraction of multicellular smooth muscle preparations: the relevance to bipolar electrosurgery.

PubMed

Vladimirova, Irina A; Lankin, Yuri N; Philyppov, Igor B; Sushiy, Lyudmyla F; Shuba, Yaroslav M

2014-01-01

Bipolar electrosurgical tissue welding uses forceps-like electrodes for grasping the tissues and delivering high-frequency electric current (HFEC) to produce local heat, desiccation, and protein denaturation, resulting in the fusion of the contacting tissues. Although in this technique no electric current is flowing through the whole body to cause electric injury, depending on the frequency of applied energy, it may produce local excitation of intramural nerves, which can propagate beyond the surgical site potentially causing harmful effects. The effects of varying frequency of HFEC on tissue excitability in bipolar electrosurgical modality were studied in vitro using electric field stimulation (EFS) method on multicellular smooth muscle strips of rat vas deferens. Contractile response to 5-s-long sine wave EFS train was taken as the measure of excitation of intramural nerves. EFS-induced contraction consisted of phasic and tonic components. The amplitude of both components decreased with increasing frequency, with tonic component disappearing at about 10 kHz and phasic component at about 50 kHz. Because components of EFS-induced contraction depend on different neurotransmitters, this indicates that various neurotransmitter systems are characterized by distinct frequency dependence, but above 50 kHz they all become inactivated. Bipolar electrosurgical sealing of porcine gut showed no difference in the structure of seal area at HFEC of 67 and 533 kHz. EFS frequency of 50 kHz represents the upper limit for excitation. HFEC above 50 kHz is safe to use for bipolar electrosurgical tissue welding without concerns of excitation propagating beyond the surgical site. Copyright © 2014 Elsevier Inc. All rights reserved.

Influence of Ti addition on fracture behaviour of HSLA steel using TIG melting technique

NASA Astrophysics Data System (ADS)

Musa, M. H. A.; Maleque, M. A.; Ali, M. Y.

2017-03-01

The welding process is a critical stage in the production of structural parts and the microstructure and mechanical properties of the welded joints must be appropriate in order to guarantee the reliability and durability of the components. The fracture toughness behaviour, which accounts for the residual strength of the component in the presence of flaws or cracks, is one of the most important properties to be evaluated in terms of microstructure and mechanical properties. In this present study, the surface of high strength low alloy (HSLA) steel was surface modified with the preplacement of pure Titanium (Ti) powder using a tungsten inert gas (TIG) arc heat source, at 100 ampere current with a voltage 30 V and a constant traversing speed of 1.0 mm/s using Argon shielded gas. The effect of preplaced Ti powder on the strength and toughness properties of the modified HSLA steel surface was investigated. The results indicated that the tensile and yield strength of HSLA steel decreased by ∼12% and ∼14%, respectively. While the impact toughness increased by ∼33% and the ductility decreased by ∼50%. The fractography analysis results by scanning electron microscopy (SEM) were also presented in this paper.

Quantitative Residual Strain Analyses on Strain Hardened Nickel Based Alloy

NASA Astrophysics Data System (ADS)

Yonezawa, Toshio; Maeguchi, Takaharu; Goto, Toru; Juan, Hou

Many papers have reported about the effects of strain hardening by cold rolling, grinding, welding, etc. on stress corrosion cracking susceptibility of nickel based alloys and austenitic stainless steels for LWR pipings and components. But, the residual strain value due to cold rolling, grinding, welding, etc. is not so quantitatively evaluated.

Welding. Pre-Apprenticeship Phase 1 Training. Instructor's Guide.

ERIC Educational Resources Information Center

Lane Community Coll., Eugene, OR.

This instructor's guide accompanies the self-paced student training modules on welding, three of which are available separately as CE 032 889-891. Introductory materials include a description of the components of the pre-apprenticeship project, a discussion of the teacher's role in conducting the course, and scope and contents of the four phases…

Copper Gas Diffusers For Purging Line-Focus Laser Welds

NASA Technical Reports Server (NTRS)

Fonteyne, Steve L.; Hosking, Timothy J.; Shelley, D. Mark

1996-01-01

Modified flow diffusers built for inert-gas purging of welds made with 5-kW CO(2) lasers operating with line-focus optics in conduction mode instead of with point-focus optics in customary keyhole mode. Diffusers made of copper components brazed together, robust enough to withstand strong reflections of line-focused laser energy.

Special Features of Structure Formation in an Explosion-Welded Magnesium-Aluminum Composite Under Deformation and Subsequent Heat Treatment

NASA Astrophysics Data System (ADS)

Gurevich, L. M.; Arisova, V. N.; Trykov, Yu. P.; Ponomareva, I. A.; Trudov, A. F.

2016-07-01

The effect of bending deformation and subsequent heat treatment on the variation of microhardness and structure of explosion-welded magnesium-aluminum layered composite material MA2-1 - AD1 is studied.

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.

The defects and microstructure in the fusion zone of multipass laser welded joints with Inconel 52M filler wire for nuclear power plants

NASA Astrophysics Data System (ADS)

Li, Gang; Lu, Xiaofeng; Zhu, Xiaolei; Huang, Jian; Liu, Luwei; Wu, Yixiong

2017-09-01

The defects and microstructure in the fusion zone of multipass laser welded joints with Inconel 52M filler wire are investigated for nuclear power plants. Experimental results indicate that the incomplete fusion forms as the deposited metals do not completely cover the groove during multipass laser welding. The dendritic morphologies are observed on the inner surface of the porosity in the fusion zone. Many small cellular are found in the zones near the fusion boundary. With solidification preceding, cellular gradually turn into columnar dendrites and symmetrical columnar dendrites are exhibited in the weld center of the fusion zone. The fine equiaxed grains form and columnar dendrites disappear in the remelted zone of two passes. The dendrite arm spacing in the fusion zone becomes widened with increasing welding heat input. Nb-rich carbides/carbonitrides are preferentially precipitated in the fusion zone of multipass laser welded joints. In respect to high cooling rate during multipass laser welding, element segregation could be insufficient to achieve the component of Laves phase.

Microstructure and Mechanical Properties of Resistance Spot Welding Joints of Carbonitrided Low-Carbon Steels

NASA Astrophysics Data System (ADS)

Taweejun, Nipon; Poapongsakorn, Piyamon; Kanchanomai, Chaosuan

2017-04-01

Carbonitrided low-carbon steels are resistance welded in various engineering components. However, there are no reports on the microstructure and mechanical properties of their resistance spot welding (RSW) joints. Therefore, various carbonitridings were performed on the low-carbon steel sheets, and then various RSWs were applied to these carbonitrided sheets. The metallurgical and mechanical properties of the welding joint were investigated and discussed. The peak load and failure energy increased with the increases of welding current and fusion zone (FZ) size. At 11 kA welding current, the carbonitrided steel joint had the failure energy of 16 J, i.e., approximately 84 pct of untreated steel joint. FZ of carbonitrided steel joint consisted of ferrite, Widmanstatten ferrite, and untempered martensite, i.e., the solid-state transformation products, while the microstructure at the outer surfaces consisted of untempered martensite and retained austenite. The surface hardening of carbonitrided steel after RSW could be maintained, i.e., approximately 810 HV. The results can be applied to carbonitriding and RSW to achieve a good welding joint.

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

Wang, Yiyu; Kannan, Rangasayee; Li, Leijun, E-mail

Non-equilibrium microstructure of the heat-affected zone (HAZ) in the as-welded modified 9Cr–1Mo–V–Nb pipe steel (P91) weldment deposited by gas tungsten arc welding (GTAW) and flux core arc welding (FCAW) has been characterized by field-emission scanning electron microscope (FESEM) and electron backscatter diffraction (EBSD). The heterogeneous structures in the sub-layers of the as-welded HAZ are attributable to phase transformations caused by the welding thermal cycles and the local structure variations in the as-received base metal. Coarse-grained heat-affected zone (CGHAZ) has a prior austenite grain (PAG) size of 20 μm. Fine uniformly-distributed precipitates and a higher fraction of MX carbonitrides are observedmore » in the CGHAZ. Fine-grained heat-affected zone (FGHAZ) consists of the finest grains (1.22 μm measured by EBSD, 5 μm PAG size), coarse undissolved M{sub 23}C{sub 6} carbides within the PAG boundaries and fine nucleated M{sub 23}C{sub 6} particles within the martensite laths. Inter-critical heat-affected zone (ICHAZ) consists of partially austenitized grains and over-tempered martensite laths. EBSD kernel average misorientation (KAM) map in the FGHAZ close to the ICHAZ illustrates the greatest local strain variations with a moderate normalized KAM value of 0.92°. The majority (88.1%) of the matrix grains in the CGHAZ are classified as deformed grains by EBSD grain average misorientation (GAM) evaluation. The FGHAZ close to the ICHAZ has the most recrystallized grains with an area fraction of 14.4%. The highest density variation of precipitates within grains in the FGHAZ originates from the inhomogeneous chemistry in the base metal. - Highlights: •A comprehensive characterization of the as-welded HAZ of P91 weldment is conducted. •Structural features in the each layer of the HAZ are quantified by EBSD. •Structural heterogenities in HAZ are due to welding cycle and base metal structure. •FGHAZ contains the finest grain structure and largest precipitate density variation.« less

Lamb wave line sensing for crack detection in a welded stiffener.

PubMed

An, Yun-Kyu; Kim, Jae Hong; Yim, Hong Jae

2014-07-18

This paper proposes a novel Lamb wave line sensing technique for crack detection in a welded stiffener. The proposed technique overcomes one of the biggest technical challenges of Lamb wave crack detection for real structure applications: crack-induced Lamb waves are often mixed with multiple reflections from complex waveguides. In particular, crack detection in a welded joint, one of the structural hot spots due to stress concentration, is accompanied by reflections from the welded joint as well as a crack. Extracting and highlighting crack-induced Lamb wave modes from Lamb wave responses measured at multi-spatial points along a single line can be accomplished through a frequency-wavenumber domain analysis. The advantages of the proposed technique enable us not only to enhance the crack detectability in the welded joint but also to minimize false alarms caused by environmental and operational variations by avoiding the direct comparison with the baseline data previously accumulated from the pristine condition of a target structure. The proposed technique is experimentally and numerically validated in vertically stiffened metallic structures, revealing that it successfully identifies and localizes subsurface cracks, regardless of the coexistence with the vertical stiffener.

Manufacture of a four-sheet complex component from different titanium alloys by superplastic forming

NASA Astrophysics Data System (ADS)

Allazadeh, M. R.; Zuelli, N.

2017-10-01

A superplastic forming (SPF) technology process was deployed to form a complex component with eight-pocket from a four-sheet sandwich panel sheetstock. Six sheetstock packs were composed of two core sheets made of Ti-6Al-4V or Ti-5Al-4Cr-4Mo-2Sn-2Zr titanium alloy and two skin sheets made of Ti-6Al-4V or Ti-6Al-2Sn-4Zr-2Mo titanium alloy in three different combinations. The sheets were welded with two subsequent welding patterns over the core and skin sheets to meet the required component's details. The applied welding methods were intermittent and continuous resistance seam welding for bonding the core sheets to each other and the skin sheets over the core panel, respectively. The final component configuration was predicted based on the die drawings and finite element method (FEM) simulations for the sandwich panels. An SPF system set-up with two inlet gas pipe feeding facilitated the trials to deliver two pressure-time load cycles acting simultaneously which were extracted from FEM analysis for specific forming temperature and strain rate. The SPF pressure-time cycles were optimized via GOM scanning and visually inspecting some sections of the packs in order to assess the levels of core panel formation during the inflation process of the sheetstock. Two sets of GOM scan results were compared via GOM software to inspect the surface and internal features of the inflated multisheet packs. The results highlighted the capability of the tested SPF process to form complex components from a flat multisheet pack made of different titanium alloys.

The tensile strength characteristics study of the laser welds of biological tissue using the nanocomposite solder

NASA Astrophysics Data System (ADS)

Rimshan, I. B.; Ryabkin, D. I.; Savelyev, M. S.; Zhurbina, N. N.; Pyanov, I. V.; Eganova, E. M.; Pavlov, A. A.; Podgaetsky, V. M.; Ichkitidze, L. P.; Selishchev, S. V.; Gerasimenko, A. Y.

2016-04-01

Laser welding device for biological tissue has been developed. The main device parts are the radiation system and adaptive thermal stabilization system of welding area. Adaptive thermal stabilization system provided the relation between the laser radiation intensity and the weld temperature. Using atomic force microscopy the structure of composite which is formed by the radiation of laser solder based on aqua- albuminous dispersion of multi-walled carbon nanotubes was investigated. AFM topograms nanocomposite solder are mainly defined by the presence of pores in the samples. In generally, the surface structure of composite is influenced by the time, laser radiation power and MWCNT concentration. Average size of backbone nanoelements not exceeded 500 nm. Bulk density of nanoelements was in the range 106-108 sm-3. The data of welding temperature maintained during the laser welding process and the corresponding tensile strength values were obtained. Maximum tensile strength of the suture was reached in the range 50-55°C. This temperature and the pointwise laser welding technology (point area ~ 2.5mm) allows avoiding thermal necrosis of healthy section of biological tissue and provided reliable bonding construction of weld join. In despite of the fact that tensile strength values of the samples are in the range of 15% in comparison with unbroken strips of pigskin leather. This situation corresponds to the initial stage of the dissected tissue connection with a view to further increasing of the joint strength of tissues with the recovery of tissue structure; thereby achieved ratio is enough for a medical practice in certain cases.

Influence of scandium on the microstructure and strength properties of the welded joint at the laser welding of aluminum-lithium alloys

NASA Astrophysics Data System (ADS)

Malikov, A. G.; Golyshev, A. A.; Ivanova, M. Yu.

2017-10-01

Today, aeronautical equipment manufacture involves up-to-date high-strength aluminum alloys of decreased density resulting from lithium admixture. Various technologies of fusible welding of these alloys are being developed. Serious demands are imposed to the welded joints of aluminum alloys in respect to their strength characteristics. The paper presents experimental investigations of the optimization of the laser welding of aluminum alloys with the scandium-modified welded joint. The effect of scandium on the micro-and macro-structure has been studied as well as the strength characteristics of the welded joint. It has been found that scandium under in the laser welding process increases the welded joint elasticity for the system Al-Mg-Li, aluminum alloy 1420 by 20 %, and almost doubles the same for the system Al-Cu-Li, aluminum alloy 1441.

Microstructure and Mechanical Properties of Laser Welded Titanium 6Al-4V

NASA Astrophysics Data System (ADS)

Mazumder, J.; Steen, W. M.

1982-05-01

Laser butt welds were fabricated in a titanium alloy (Ti-6A1-4V, AMS 4911-Tal0 BSS, annealed) using a Control Laser 2 kW CW CO2 laser. The relationships between the weld microstructure and mechanical properties are described and compared to the theoretical thermal history of the weld zone as calculated from a three-dimensional heat transfer model of the process. The structure of the weld zone was examined by radiography to detect any gross porosity as well as by both optical and electron microscopy in order to identify the microstructure. The oxygen pick-up during gas shielded laser welding was analyzed to correlate further with the observed mechanical properties. It was found that optimally fabricated laser welds have a very good combination of weld microstructure and mechanical properties, ranking this process as one which can produce high quality welds.

Probing heat transfer, fluid flow and microstructural evolution during fusion welding of alloys

NASA Astrophysics Data System (ADS)

Zhang, Wei

The composition, geometry, structure and properties of the welded joints are affected by the various physical processes that take place during fusion welding. Understanding these processes has been an important goal in the contemporary welding research to achieve structurally sound and reliable welds. In the present thesis research, several important physical processes including the heat transfer, fluid flow and microstructural evolution in fusion welding were modeled based on the fundamentals of transport phenomena and phase transformation theory. The heat transfer and fluid flow calculation is focused on the predictions of the liquid metal convection in the weld pool, the temperature distribution in the entire weldment, and the shape and size of the fusion zone (FZ) and heat affected zone (HAZ). The modeling of microstructural evolution is focused on the quantitative understanding of phase transformation kinetics during welding of several important alloys under both low and high heating and cooling conditions. Three numerical models were developed in the present thesis work: (1) a three-dimensional heat transfer and free surface flow model for the gas metal arc (GMA) fillet welding considering the complex weld joint geometry, (2) a phase transformation model based on the Johnson-Mehl-Avrami (JMA) theory, and (3) a one-dimensional numerical diffusion model considering multiple moving interfaces. To check the capabilities of the developed models, several cases were investigated, in which the predictions from the models were compared with the experimental results. The cases studied are the follows. For the modeling of heat transfer and fluid flow, the welding processes studied included gas tungsten arc (GTA) linear welding, GTA transient spot welding, and GMA fillet welding. The calculated weldment geometry and thermal cycles was validated against the experimental data under various welding conditions. For the modeling of microstructural evolution, the welded materials investigated included AISI 1005 low-carbon steel, 1045 medium-carbon steel, 2205 duplex stainless steel (DSS) and Ti-6Al-4V alloy. The calculated phase transformation kinetics were compared with the experimental results obtained using an x-ray diffraction technique by Dr. John W. Elmer of Lawrence Livermore National Laboratory. (Abstract shortened by UMI.)

CRADA Final Report: Weld Predictor App

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

Billings, Jay Jay

Welding is an important manufacturing process used in a broad range of industries and market sectors, including automotive, aerospace, heavy manufacturing, medical, and defense. During welded fabrication, high localized heat input and subsequent rapid cooling result in the creation of residual stresses and distortion. These residual stresses can significantly affect the fatigue resistance, cracking behavior, and load-carrying capacity of welded structures during service. Further, additional fitting and tacking time is often required to fit distorted subassemblies together, resulting in non-value added cost. Using trial-and-error methods to determine which welding parameters, welding sequences, and fixture designs will most effectively reduce distortionmore » is a time-consuming and expensive process. For complex structures with many welds, this approach can take several months. For this reason, efficient and accurate methods of mitigating distortion are in-demand across all industries where welding is used. Analytical and computational methods and commercial software tools have been developed to predict welding-induced residual stresses and distortion. Welding process parameters, fixtures, and tooling can be optimized to reduce the HAZ softening and minimize weld residual stress and distortion, improving performance and reducing design, fabrication and testing costs. However, weld modeling technology tools are currently accessible only to engineers and designers with a background in finite element analysis (FEA) who work with large manufacturers, research institutes, and universities with access to high-performance computing (HPC) resources. Small and medium enterprises (SMEs) in the US do not typically have the human and computational resources needed to adopt and utilize weld modeling technology. To allow an engineer with no background in FEA and SMEs to gain access to this important design tool, EWI and the Ohio Supercomputer Center (OSC) developed the online weld application software tool “WeldPredictor” ( https://eweldpredictor.ewi.org ). About 1400 users have tested this application. This project marked the beginning of development on the next version of WeldPredictor that addresses many outstanding features of the original, including 3D models, allow more material hardening laws, model material phase transformation, and uses open source finite element solvers to quickly solve problems (as opposed to expensive commercial tools).« less

Microstructural Characteristics and Mechanical Properties of Friction Stir Welded Thick 5083 Aluminum Alloy

NASA Astrophysics Data System (ADS)

Imam, Murshid; Sun, Yufeng; Fujii, Hidetoshi; Ma, Ninshu; Tsutsumi, Seiichiro; Murakawa, Hidekazu

2017-01-01

Joining thick sections of aluminum alloys by friction stir welding (FSW) in a single pass needs to overcome many challenges before it comes to full-scale industrial use. Important parameters controlling the structure-properties relationships both across weld cross-section and through thickness direction were investigated through mechanical testing, electron backscatter diffraction technique, transmission electron microscopy, and occurrence of serrated plastic flow. The evolution of the properties in the weld cross-section shows that the presence of undissolved and fragmented Al_6MnFe particles cause discrepancies in establishing the Hall-Petch relationship, and derive the strengthening from the Orowan strengthening mechanism. A `stop action' friction stir weld has been prepared to understand the role of geometrical features of the tool probe in the development of the final microstructure after complete weld. Sectioning through the `stop action' weld with the probe in situ displays the individual effect of thread and flat on the grain structure formation. The material at the thread surface experiences more severe deformation than the material at flat surface. Both the high-angle boundaries and mean grain size are found to be higher at the thread surface. The strain hardening capacity, stress serration amplitude, and frequency are observed to be higher in the stir zone than other weld regions.

Pulsed infrared thermography for assessment of ultrasonic welds

NASA Astrophysics Data System (ADS)

McGovern, Megan E.; Rinker, Teresa J.; Sekol, Ryan C.

2018-03-01

Battery packs are a critical component in electric vehicles. During pack assembly, the battery cell tab and busbar are ultrasonically welded. The properties of the welds ultimately affect battery pack durability. Quality inspection of these welds is important to ensure durable battery packs. Pack failure is detrimental economically and could also pose a safety hazard, such as thermal runaway. Ultrasonic welds are commonly checked by measuring electrical resistance or auditing using destructive mechanical testing. Resistance measurements are quick, but sensitive to set-up changes. Destructive testing cannot represent the entire weld set. It is possible for a weak weld to satisfy the electrical requirement check, because only sufficient contact between the tabs and busbar is required to yield a low resistance measurement. Laboratory techniques are often not suitable for inline inspection, as they may be time-consuming, use couplant, or are only suitable for coupons. The complex surface geometry also poses difficulties for conventional nondestructive techniques. A method for inspection of ultrasonic welds is proposed using pulsed infrared thermography to identify discrepant welds in a manufacturing environment. Thermal measurements of welds were compared to electrical and mechanical measurements. The heat source distribution was calculated to obtain thermal images with high temporal and spatial resolution. All discrepant welds were readily identifiable using two thermographic techniques: pixel counting and the gradient image. A positive relationship between pixel count and mechanical strength was observed. The results demonstrate the potential of pulsed thermography for inline inspection, which can complement, or even replace, conventional electrical resistance measurements.

Friction Stir Welding of Large Scale Cryogenic Tanks for Aerospace Applications

NASA Technical Reports Server (NTRS)

Russell, Carolyn; Ding, R. Jeffrey

1998-01-01

The Marshall Space Flight Center (MSFC) has established a facility for the joining of large-scale aluminum cryogenic propellant tanks using the friction stir welding process. Longitudinal welds, approximately five meters in length, have been made by retrofitting an existing vertical fusion weld system, designed to fabricate tank barrel sections ranging from two to ten meters in diameter. The structural design requirements of the tooling, clamping and travel system will be described in this presentation along with process controls and real-time data acquisition developed for this application. The approach to retrofitting other large welding tools at MSFC with the friction stir welding process will also be discussed.

High-strength laser welding of aluminum-lithium scandium-doped alloys

NASA Astrophysics Data System (ADS)

Malikov, A. G.; Ivanova, M. Yu.

2016-11-01

The work presents the experimental investigation of laser welding of an aluminum alloy (system Al-Mg-Li) and aluminum alloy (system Al-Cu-Li) doped with Sc. The influence of nano-structuring of the surface layer welded joint by cold plastic deformation on the strength properties of the welded joint is determined. It is founded that, regarding the deformation degree over the thickness, the varying value of the welded joint strength is different for these aluminum alloys. The strength of the plastically deformed welded joint, aluminum alloys of the Al-Mg-Li and Al-Cu-Li systems reached 0.95 and 0.6 of the base alloy strength, respectively.

Assessment of the LC-2 Prelaunch Fatigue Spectra of the CM-to-SM Flange Weld

NASA Technical Reports Server (NTRS)

Dawicke, David S.; Newman, John A.

2008-01-01

The pad stay and rollout components of the Ares I-X life cycle can generate cyclic stress oscillations to the vehicle that could initiate and grow fatigue cracks from weld defects. The Ares I-X Project requested that a study be performed to determine if stabilization of the vehicle is required to reduce the stresses that could initiate and grow fatigue cracks at the flange-to-skin weld of the Command Module (CM) and Service Module (SM) interface. A fatigue crack growth analysis was conducted that used loads (LC-2) and stress analyses developed by the Ares I-X Project and utilized material data and analysis methods developed by a critical initial flaw size (CIFS) analysis conducted by NASA Engineering and Safety Center (NESC) for the Upper Stage Simulator (USS) of the Ares I-X vehicle. A full CIFS analysis for the CM-to-SM flange-to-skin weld was not performed because the full flight spectrum was not provided and was not necessary to answer the question posed by the Ares I-X Project. Instead, an approach was developed to determine if the crack growth due to the pad stay and rollout components of the flight spectrum would adversely influence the CIFS. The approach taken used a number of conservative assumptions that eliminated the need for high-fidelity analyses and additional material testing, but still provided a bounding solution for the uncertainties of the problem. The results from this analysis indicate that the LC-2 pad stay and rollout spectrum components would not produce significant fatigue crack growth on the CM-to-SM flange-to-skin weld. Thus, from a fatigue crack growth standpoint, no stabilization is required to reduce the LC-2 pad stay and rollout cyclic stresses on the CM-to-SM flange-to-skin weld.

Application of laser in seam welding of dissimilar steel to aluminium joints for thick structural components

NASA Astrophysics Data System (ADS)

Meco, S.; Pardal, G.; Ganguly, S.; Williams, S.; McPherson, N.

2015-04-01

Laser welding-brazing technique, using a continuous wave (CW) fibre laser with 8000 W of maximum power, was applied in conduction mode to join 2 mm thick steel (XF350) to 6 mm thick aluminium (AA5083-H22), in a lap joint configuration with steel on the top. The steel surface was irradiated by the laser and the heat was conducted through the steel plate to the steel-aluminium interface, where the aluminium melts and wets the steel surface. The welded samples were defect free and the weld micrographs revealed presence of a brittle intermetallic compounds (IMC) layer resulting from reaction of Fe and Al atoms. Energy Dispersive Spectroscopy (EDS) analysis indicated the stoichiometry of the IMC as Fe2Al5 and FeAl3, the former with maximum microhardness measured of 1145 HV 0.025/10. The IMC layer thickness varied between 4 to 21 μm depending upon the laser processing parameters. The IMC layer showed an exponential growth pattern with the applied specific point energy (Esp) at a constant power density (PD). Higher PD values accelerate the IMC layer growth. The mechanical shear strength showed a narrow band of variation in all the samples (with the maximum value registered at 31.3 kN), with a marginal increase in the applied Esp. This could be explained by the fact that increasing the Esp results into an increase in the wetting and thereby the bonded area in the steel-aluminium interface.

Systems and Methods for Fabricating Structures Including Metallic Glass-Based Materials Using Ultrasonic Welding

NASA Technical Reports Server (NTRS)

Hofmann, Douglas C. (Inventor); Roberts, Scott N. (Inventor)

2017-01-01

Systems and methods in accordance with embodiments of the invention fabricate objects including metallic glass-based materials using ultrasonic welding. In one embodiment, a method of fabricating an object that includes a metallic glass-based material includes: ultrasonically welding at least one ribbon to a surface; where at least one ribbon that is ultrasonically welded to a surface has a thickness of less than approximately 150.mu.m; and where at least one ribbon that is ultrasonically welded to a surface includes a metallic glass-based material.

Effect of heat treatment and diffusion welding conditions on the structure and properties of porous material workpieces made of titanium fibers

NASA Astrophysics Data System (ADS)

Kollerov, M. Yu.; Shlyapin, S. D.; Gusev, D. E.; Senkevich, K. S.; Runova, Yu. E.

2015-11-01

The effect of the diffusion welding conditions on the structure and properties of a porous material (PM) made of titanium fibers is studied. It is shown that the use of fibers produced by melt quenching and then joined to form workpieces or articles by diffusion welding can be a promising trend in the production of PMs for medicine applications. A change in the solidification rate of fibers and their contact substantially affects the mechanical properties of PM workpieces. As the diffusion welding temperature of both sheet and cylindrical workpieces increases, the strength of PM increases and the plasticity of PM decreases.

An investigation into underwater wet welding using the flux cored arc welding process

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

Brydon, A.M.; Nixon, J.H.

1995-12-31

For the last two years, Cranfield has been carrying out a program of process investigations into wet underwater welding (Graham and Nixon 1993, Nixon and Webb 1994), and has demonstrated that it is possible to markedly improve the stability and consistency of the process by using control techniques developed for hyperbaric welding. In the project reported below, an initial evaluation of wet flux cored arc welding was undertaken. Although there continues to be considerable resistance to the use of wet welding on structures in the North Sea, continued pressure to reduce repair and maintenance costs is causing the industry tomore » re-examine techniques previously discounted, such as wet welding (Anon 1993).« less

Structure and constitution of glass and steel compound in glass-metal composite

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

Lyubimova, Olga N.; Morkovin, Andrey V.; Dryuk, Sergey A.

2014-11-14

The research using methods of optical and scanning electronic microscopy was conducted and it discovered common factors on structures and diffusing zone forming after welding glass C49-1 and steel Ct3sp in technological process of creating new glass-metal composite. Different technological modes of steel surface preliminary oxidation welded with and without glass were investigated. The time of welding was varied from minimum encountering time to the time of stabilizing width of diffusion zone.

Investigations for the improvement of space shuttle main engine electron beam welding equipment

NASA Technical Reports Server (NTRS)

Smock, R. A.; Taylor, R. A.; Wall, W. A., Jr.

1977-01-01

Progress made in the testing, evaluation, and correction of MSFC's 7.5 kW electron beam welder in support of space shuttle main engine component welding is summarized. The objective of this project was to locate and correct the deficiencies in the welder. Some 17 areas were deficient in the 7.5 kW ERI welding system and the associated corrective action was taken to improve its operational performance. An overall improvement of 20 times the original reliability was obtained at full rated capacity after the modifications were made.

Uranium nitride fuel fabrication for SP-100 reactors

NASA Technical Reports Server (NTRS)

Mason, Richard E.; Chidester, Kenneth M.; Hoth, Carl W.; Matthews, Bruce R.

1987-01-01

Fuel pins of uranium mononitride clad in Nb-1 percent Zr were fabricated for irradiation tests in EBR-II. Laboratory scale process parameters to synthesize UN powders and fabricate UN pellets were developed. Uranium mononitride was prepared by converting UO2 to UN. Fuel pellets were prepared by communition of UN briquettes, uniaxial pressing, and high temperature sintering. Techniques for machining, cleaning, and welding Nb-1 percent Zr cladding components were developed. End caps were electron beam welded to the tubing. Helium back-fill holes were sealed with a laser weld.

Uranium nitride fuel fabrication for SP-100 reactors

NASA Astrophysics Data System (ADS)

Mason, Richard E.; Chidester, Kenneth M.; Hoth, Carl W.; Matthews, Bruce R.

Fuel pins of uranium mononitride clad in Nb-1 percent Zr were fabricated for irradiation tests in EBR-II. Laboratory scale process parameters to synthesize UN powders and fabricate UN pellets were developed. Uranium mononitride was prepared by converting UO2 to UN. Fuel pellets were prepared by communition of UN briquettes, uniaxial pressing, and high temperature sintering. Techniques for machining, cleaning, and welding Nb-1 percent Zr cladding components were developed. End caps were electron beam welded to the tubing. Helium back-fill holes were sealed with a laser weld.