Welding apparatus and methods for using ultrasonic sensing

DOEpatents

McJunkin, Timothy R.; Johnson, John A.; Larsen, Eric D.; Smartt, Herschel B.

2006-08-22

A welding apparatus using ultrasonic sensing is described and which includes a movable welder having a selectively adjustable welding head for forming a partially completed weld in a weld seam defined between adjoining metal substrates; an ultrasonic assembly borne by the moveable welder and which is operable to generate an ultrasonic signal which is directed toward the partially completed weld, and is further reflected from same; and a controller electrically coupled with the ultrasonic assembly and controllably coupled with the welding head, and wherein the controller receives information regarding the ultrasonic signal and in response to the information optimally positions the welding head relative to the weld seam.

Multi-mode ultrasonic welding control and optimization

DOEpatents

Tang, Jason C.H.; Cai, Wayne W

2013-05-28

A system and method for providing multi-mode control of an ultrasonic welding system. In one embodiment, the control modes include the energy of the weld, the time of the welding process and the compression displacement of the parts being welded during the welding process. The method includes providing thresholds for each of the modes, and terminating the welding process after the threshold for each mode has been reached, the threshold for more than one mode has been reached or the threshold for one of the modes has been reached. The welding control can be either open-loop or closed-loop, where the open-loop process provides the mode thresholds and once one or more of those thresholds is reached the welding process is terminated. The closed-loop control provides feedback of the weld energy and/or the compression displacement so that the weld power and/or weld pressure can be increased or decreased accordingly.

Apparatus and process for ultrasonic seam welding stainless steel foils

DOEpatents

Leigh, Richard W.

1992-01-01

An ultrasonic seam welding apparatus having a head which is rotated to form contact, preferably rolling contact, between a metallurgically inert coated surface of the head and an outside foil of a plurality of layered foils or work materials. The head is vibrated at an ultrasonic frequency, preferably along a longitudinal axis of the head. The head is constructed to transmit vibration through a contacting surface of the head into each of the layered foils. The contacting surface of the head is preferably coated with aluminum oxide to prevent the head from becoming welded to layered stainless steel foils.

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.

Ultrasonic velocity testing of steel pipeline welded joints

NASA Astrophysics Data System (ADS)

Carreón, Hector

2017-04-01

In general the ultrasonic techniques have been used to determine the mechanical properties of materials on based of their relationship with metallurgical characteristics. In this research work, the relationship between ultrasonic velocity and phased array and the microstructure of steel pipeline welded joints is investigated. Measurements of ultrasonic wave velocity were made as a function of the location across the weld. Hardness measurements were performated in an attempt to correlate with ultrasonic response. In addition, the coarse and dendritic grain structure of the weld material is extreme and unpredictably anisotropic. Thus, due to the acoustic anisotropy of the crystal itself weld material of studied joints is anisotropic, too. 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 conventional ultrasonic phased array techniques becomes desirable.

Quality evaluation and control of end cap welds in PHWR fuel elements by ultrasonic examination

NASA Astrophysics Data System (ADS)

Choi, M. S.; Yang, M. S.

1991-02-01

The current quality control procedure of nuclear fuel end cap weld is mainly dependent on the destructive metallographic examination. A nondestructive examination technique, i.e., ultrasonic examination, has been developed to identify and evaluate weld discontinuities. A few interesting results of the weld quality evaluation by applying the developed ultrasonic examination technique to PHWR fuel welds are presented. In addition, the feasibility of the weld quality control by the ultrasonic examination is discussed. This study shows that the ultrasonic examination is effective and reliable method for detecting abnormal weld contours and weld discontinuities such as micro-fissure, crack, upset split and expulsion, and can be used as a quality control tool for the end cap welding process.

The Detection of Burn-Through Weld Defects Using Noncontact Ultrasonics

PubMed Central

Abbasi, Zeynab; Yuhas, Donald; Zhang, Lu; Basantes, Alexandra-Del-Carmen; Tehrani, Niloofar Nabili; Ozevin, Didem; Indacochea, Ernesto

2018-01-01

Nearly all manufactured products in the metal industry involve welding. The detection and correction of defects during welding improve the product reliability and quality, and prevent unexpected failures. Nonintrusive process control is critical for avoiding these defects. This paper investigates the detection of burn-through damage using noncontact, air-coupled ultrasonics, which can be adapted to the immediate and in-situ inspection of welded samples. The burn-through leads to a larger volume of degraded weld zone, providing a resistance path for the wave to travel which results in lower velocity, energy ratio, and amplitude. Wave energy dispersion occurs due to the increase of weld burn-through resulting in higher wave attenuation. Weld sample micrographs are used to validate the ultrasonic results. PMID:29342875

Ultrasonically-assisted Thermal Stir Welding System

NASA Technical Reports Server (NTRS)

Ding, R. Jeffrey (Inventor)

2014-01-01

A welding head assembly has a work piece disposed between its containment plates' opposing surfaces with the work piece being maintained in a plastic state thereof at least in a vicinity of the welding head assembly's stir rod as the rod is rotated about its longitudinal axis. The welding head assembly and the work piece experience relative movement there between in a direction perpendicular to the rod's longitudinal axis as the work piece is subjected to a compressive force applied by the containment plates. A first source coupled to the first containment plate applies a first ultrasonic wave thereto such that the first ultrasonic wave propagates parallel to the direction of relative movement. A second source coupled to the second containment plate applies a second ultrasonic wave thereto such that the second ultrasonic wave propagates parallel to the direction of relative movement.propagates parallel to the direction of relative movement.

Method for the concurrent ultrasonic inspection of partially completed welds

DOEpatents

Johnson, John A.; Larsen, Eric D.; Miller, Karen S.; Smartt, Herschel B.; McJunkin, Timothy R.

2002-01-01

A method for the concurrent ultrasonic inspection of partially completed welds is disclosed and which includes providing a pair of transducers which are individually positioned on the opposite sides of a partially completed weld to be inspected; moving the transducers along the length of and laterally inwardly and outwardly relative to the partially completed weld; pulsing the respective transducers to produce an ultrasonic signal which passes through or is reflected from the partially completed weld; receiving from the respective transducers ultrasonic signals which pass through or are reflected from the partially completed welds; and analyzing the ultrasonic signal which has passed through or is reflected from the partially completed weld to determine the presence of any weld defects.

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

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

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

2014-02-18

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

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

NASA Astrophysics Data System (ADS)

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

2014-02-01

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

Ultrasonic Welding of Thin Alumina and Aluminum Using Inserts

NASA Astrophysics Data System (ADS)

Ishikuro, Tomoaki; Matsuoka, Shin-Ichi

This paper describes an experimental study of ultrasonic welding of thin ceramics and metals using inserts. Ultrasonic welding has enable the joining of various thick ceramics, such as Al2O3 and ZrO2, to aluminum at room temperature quickly and easily as compared to other welding methods. However, for thin ceramics, which are brittle, welding is difficult to perform without causing damage. In this study, aluminum anodized oxide with different anodizing time was used as thin alumina ceramic. Vapor deposition of aluminum alloys was used to create an effective binder layer for welding at a low pressure and within a short duration in order to prevent damage to the anodic oxide film formed with a short anodizing time. For example, ultrasonic welding of thin Al2O3/Al was accomplished under the following conditions: ultrasonic horn tip amplitude of 30µm, welding pressure of 5MPa, and required duration of 0.1s. However, since the vapor deposition film tends to exfoliate as observed in the anodic oxide film formed with a long anodizing time, welding was difficult.

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

Relation between hardness and ultrasonic velocity on pipeline steel welded joints

NASA Astrophysics Data System (ADS)

Carreón, H.; Barrera, G.; Natividad, C.; Salazar, M.; Contreras, A.

2016-04-01

In general, the ultrasonic techniques have been used to determine the mechanical properties of materials based on their relationship with metallurgical characteristics. In this research work, the relationship between ultrasonic wave velocity, hardness and the microstructure of steel pipeline welded joints is investigated. Measurements of ultrasonic wave velocity were made as a function of the location across the weld. Hardness measurements were performed in an attempt to correlate with ultrasonic response. In addition, the coarse and dendritic grain structure of the weld material is extreme and unpredictably anisotropic. Thus, due to the acoustic anisotropy of the crystal, weld material of studied joints is anisotropic too. 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 conventional ultrasonic phased array techniques becomes desirable. This technique is proposed to assist pipeline operators in estimating the hardness through ultrasonic measures to evaluate the susceptibility to stress sulphide cracking and hydrogen-induced cracking due to hard spots in steel pipeline welded joints in service. Sound wave velocity and hardness measurements have been carried out on a steel welded joint. For each section of the welding, weld bead, fusion zone, heat affected zone and base metal were found to correspond particular values of the ultrasound velocity. These results were correlated with electron microscopy observations of the microstructure and sectorial scan view of welded joints by ultrasonic phased array.

Identification of the Quality Spot Welding used Non Destructive Test-Ultrasonic Testing: (Effect of Welding Time)

NASA Astrophysics Data System (ADS)

Sifa, A.; Endramawan, T.; Badruzzaman

2017-03-01

Resistance Spot Welding (RSW) is frequently used as one way of welding is used in the manufacturing process, especially in the automotive industry [4][5][6][7]. Several parameters influence the process of welding points. To determine the quality of a welding job needs to be tested, either by damaging or testing without damage, in this study conducted experimental testing the quality of welding or identify quality of the nugget by using Non-Destructive Test (NDT) -Ultrasonic Testing (UT), in which the identification of the quality of the welding is done with parameter thickness of worksheet after welding using NDT-UT with use same material worksheet and have more thickness of worksheet, the thickness of the worksheet single plate 1mm, with the capability of propagation Ultrasonic Testing (UT) standard limited> 3 mm [1], welding process parameters such as the time difference between 1-10s and the welding current of 8 KV, visually Heat Affected Zone ( HAZ ) have different results due to the length of time of welding. UT uses a probe that is used with a frequency of 4 MHz, diameter 10 mm, range 100 and the couplant used is oil. Identification techniques using drop 6dB, with sound velocity 2267 m / s of Fe, with the result that the effect of the Welding time affect the size of the HAZ, identification with the lowest time 1s show results capable identified joined through NDT - UT.

The evolution of microstructures, corrosion resistance and mechanical properties of AZ80 joints using ultrasonic vibration assisted welding process

NASA Astrophysics Data System (ADS)

Li, Hui; Zhang, Jiansheng

2017-12-01

The evolution of microstructures, corrosion resistance and mechanical properties of AZ80 joints using an ultrasonic vibration assisted welding process is investigated. The results show that, with ultrasonic vibration treatment, a reliable AZ80 joint without defects is obtained. The coarsening α-Mg grains are refined to about 83.5  ±  3.3 µm and the continuous β-Mg17Al12 phases are broken to granular morphology, owing to the acoustic streaming effect and the cavitation effect evoked by ultrasonic vibration. Both immersion and electrochemical test results indicate that the corrosion resistance of the AZ80 joint welded with ultrasonic vibration is improved, attributed to microstructure evolution. With ultrasonic power of 900 W, the maximum tensile strength of an AZ80 specimen is 261  ±  7.5 MPa and fracture occurs near the heat affected zone of the joint.

Real-time ultrasonic weld evaluation system

NASA Astrophysics Data System (ADS)

Katragadda, Gopichand; Nair, Satish; Liu, Harry; Brown, Lawrence M.

1996-11-01

Ultrasonic testing techniques are currently used as an alternative to radiography for detecting, classifying,and sizing weld defects, and for evaluating weld quality. Typically, ultrasonic weld inspections are performed manually, which require significant operator expertise and time. Thus, in recent years, the emphasis is to develop automated methods to aid or replace operators in critical weld inspections where inspection time, reliability, and operator safety are major issues. During this period, significant advances wee made in the areas of weld defect classification and sizing. Very few of these methods, however have found their way into the market, largely due to the lack of an integrated approach enabling real-time implementation. Also, not much research effort was directed in improving weld acceptance criteria. This paper presents an integrated system utilizing state-of-the-art techniques for a complete automation of the weld inspection procedure. The modules discussed include transducer tracking, classification, sizing, and weld acceptance criteria. Transducer tracking was studied by experimentally evaluating sonic and optical position tracking techniques. Details for this evaluation are presented. Classification is obtained using a multi-layer perceptron. Results from different feature extraction schemes, including a new method based on a combination of time and frequency-domain signal representations are given. Algorithms developed to automate defect registration and sizing are discussed. A fuzzy-logic acceptance criteria for weld acceptance is presented describing how this scheme provides improved robustness compared to the traditional flow-diagram standards.

Characterization of inhomogeneous and anisotropic steel welds by ultrasonic array measurements

NASA Astrophysics Data System (ADS)

Fan, Z.; Lowe, M. J. S.

2013-01-01

Austenitic welds are difficult to inspect non-destructively by ultrasound due to the anisotropic and inhomogeneous material in the weld, which causes spatial deviation of ultrasonic beams. A common way to describe such material is to consider it as transversely isotropic, in which the plane perpendicular to the direction of the grain growth is considered to be isotropic. Therefore a weld performance map which indicates the orientation of the grain growth can be used to describe the material properties in the weld. In our work, we have chosen a weld map based on the parameters of the MINA model which uses the information of the welding procedure and rules for crystalline growth to predict the orientations, and thus has a good physical foundation. We have compared the measured grain orientations for a realistic weld with the predictions from the model. With this model, only a small number of parameters are used to describe the weld properties, therefore enabling the possibility of a well conditioned refining process to determine the weld map from ultrasonic measurements. We have demonstrated the feasibility of doing this, using a ray tracing model, and both simulated and experimental measurements.

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.

Ultrasonic Welding of Graphite/Thermoplastic Composite

NASA Technical Reports Server (NTRS)

Hardy, S. S.; Page, D. B.

1982-01-01

Ultrasonic welding of graphite/thermoplastic composite materials eliminates need for fasteners (which require drilling or punching, add weight, and degrade stiffness) and can be totally automated in beam fabrication and assembly jigs. Feasibility of technique has been demonstrated in laboratory tests which show that neither angular orientation nor vacuum affect weld quality.

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.

Accelerated Post-Weld Natural Ageing in Ultrasonic Welding Aluminium 6111-T4 Automotive Sheet

NASA Astrophysics Data System (ADS)

Chen, Ying-Chun; Prangnell, Phil

In contrast to previously published reports, it is shown that there is an observable HAZ when ultrasonic spot welding (USW) automotive alloys, like AA6111-T4, the severity of which depends on the welding energy. Immediately after welding, softening is seen relative to the T4 condition, but this is rapidly recovered by natural ageing, which masks the presence of a HAZ, and the weld strength eventually exceeds that of the parent material. This behaviour is caused by dissolution of the solute clusters/GPZs in the T4 sheet, due to the high weld temperatures (> 400 °C), combined with accelerated post-weld natural ageing to a more advanced state than in the parent material. Modelling has demonstrated that this accelerated natural ageing behaviour can be attributed to an excess vacancy concentration generated by the USW process.

Effect of acoustic field parameters on arc acoustic binding during ultrasonic wave-assisted arc welding.

PubMed

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

2016-03-01

As a newly developed arc welding method, power ultrasound has been successfully introduced into arc and weld pool during ultrasonic wave-assisted arc welding process. The advanced process for molten metals can be realized by utilizing additional ultrasonic field. Under the action of the acoustic wave, the plasma arc as weld heat source is regulated and its characteristics make an obvious change. Compared with the conventional arc, the ultrasonic wave-assisted arc plasma is bound significantly and becomes brighter. To reveal the dependence of the acoustic binding force on acoustic field parameters, a two-dimensional acoustic field model for ultrasonic wave-assisted arc welding device is established. The influences of the radiator height, the central pore radius, the radiator radius, and curvature radius or depth of concave radiator surface are discussed using the boundary element method. Then the authors analyze the resonant mode by this relationship curve between acoustic radiation power and radiator height. Furthermore, the best acoustic binding ability is obtained by optimizing the geometric parameters of acoustic radiator. In addition, three concave radiator surfaces including spherical cap surface, paraboloid of revolution, and rotating single curved surface are investigated systematically. Finally, both the calculation and experiment suggest that, to obtain the best acoustic binding ability, the ultrasonic wave-assisted arc welding setup should be operated under the first resonant mode using a radiator with a spherical cap surface, a small central pore, a large section radius and an appropriate curvature radius. Copyright © 2015 Elsevier B.V. All rights reserved.

Ultrasonic test of resistance spot welds based on wavelet package analysis.

PubMed

Liu, Jing; Xu, Guocheng; Gu, Xiaopeng; Zhou, Guanghao

2015-02-01

In this paper, ultrasonic test of spot welds for stainless steel sheets has been studied. It is indicated that traditional ultrasonic signal analysis in either time domain or frequency domain remains inadequate to evaluate the nugget diameter of spot welds. However, the method based on wavelet package analysis in time-frequency domain can easily distinguish the nugget from the corona bond by extracting high-frequency signals in different positions of spot welds, thereby quantitatively evaluating the nugget diameter. The results of ultrasonic test fit the actual measured value well. Mean value of normal distribution of error statistics is 0.00187, and the standard deviation is 0.1392. Furthermore, the quality of spot welds was evaluated, and it is showed ultrasonic nondestructive test based on wavelet packet analysis can be used to evaluate the quality of spot welds, and it is more reliable than single tensile destructive test. Copyright © 2014 Elsevier B.V. All rights reserved.

Optimization of Aluminium-to-Magnesium Ultrasonic Spot Welding

NASA Astrophysics Data System (ADS)

Panteli, A.; Chen, Y.-C.; Strong, D.; Zhang, Xiaoyun; Prangnell, P. B.

2012-03-01

The ability to join dissimilar materials in the automotive industry will result in more efficient multimaterial structures. However, welding of aluminium (Al) to magnesium (Mg) alloys is problematic because of the rapid formation of brittle intermetallic phases at the weld interface. Ultrasonic welding (USW) is a solid-state joining technology that may offer a potential solution, but USW of Al to Mg is currently not well understood. Here, we have investigated the effect of process variables and energy input on joint formation between Al-6111 and Mg-AZ31 alloys, and we report on the optimum welding conditions, heat generation, and the formation of a significant intermetallic reaction layer. Furthermore, the factors influencing the interface reaction rate and the advantages of precoating the Mg with Al are discussed.

Ultrasonic Processing of Materials

NASA Astrophysics Data System (ADS)

Han, Qingyou

2015-08-01

Irradiation of high-energy ultrasonic vibration in metals and alloys generates oscillating strain and stress fields in solids, and introduces nonlinear effects such as cavitation, acoustic streaming, and radiation pressure in molten materials. These nonlinear effects can be utilized to assist conventional material processing processes. This article describes recent research at Oak Ridge National Labs and Purdue University on using high-intensity ultrasonic vibrations for degassing molten aluminum, processing particulate-reinforced metal matrix composites, refining metals and alloys during solidification process and welding, and producing bulk nanostructures in solid metals and alloys. Research results suggest that high-intensity ultrasonic vibration is capable of degassing and dispersing small particles in molten alloys, reducing grain size during alloy solidification, and inducing nanostructures in solid metals.

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.

Real-time nondestructive monitoring of the gas tungsten arc welding (GTAW) process by combined airborne acoustic emission and non-contact ultrasonics

NASA Astrophysics Data System (ADS)

Zhang, Lu; Basantes-Defaz, Alexandra-Del-Carmen; Abbasi, Zeynab; Yuhas, Donald; Ozevin, Didem; Indacochea, Ernesto

2018-03-01

Welding is a key manufacturing process for many industries and may introduce defects into the welded parts causing significant negative impacts, potentially ruining high-cost pieces. Therefore, a real-time process monitoring method is important to implement for avoiding producing a low-quality weld. Due to high surface temperature and possible contamination of surface by contact transducers, the welding process should be monitored via non-contact transducers. In this paper, airborne acoustic emission (AE) transducers tuned at 60 kHz and non-contact ultrasonic testing (UT) transducers tuned at 500 kHz are implemented for real time weld monitoring. AE is a passive nondestructive evaluation method that listens for the process noise, and provides information about the uniformity of manufacturing process. UT provides more quantitative information about weld defects. One of the most common weld defects as burn-through is investigated. The influences of weld defects on AE signatures (time-driven data) and UT signals (received signal energy, change in peak frequency) are presented. The level of burn-through damage is defined by using single method or combine AE/UT methods.

Inspection of thick welded joints using laser-ultrasonic SAFT.

PubMed

Lévesque, D; Asaumi, Y; Lord, M; Bescond, C; Hatanaka, H; Tagami, M; Monchalin, J-P

2016-07-01

The detection of defects in thick butt joints in the early phase of multi-pass arc welding would be very valuable to reduce cost and time in the necessity of reworking. As a non-contact method, the laser-ultrasonic technique (LUT) has the potential for the automated inspection of welds, ultimately online during manufacturing. In this study, testing has been carried out using LUT combined with the synthetic aperture focusing technique (SAFT) on 25 and 50mm thick butt welded joints of steel both completed and partially welded. EDM slits of 2 or 3mm height were inserted at different depths in the multi-pass welding process to simulate a lack of fusion. Line scans transverse to the weld are performed with the generation and detection laser spots superimposed directly on the surface of the weld bead. A CCD line camera is used to simultaneously acquire the surface profile for correction in the SAFT processing. All artificial defects but also real defects are visualized in the investigated thick butt weld specimens, either completed or partially welded after a given number of passes. The results obtained clearly show the potential of using the LUT with SAFT for the automated inspection of arc welds or hybrid laser-arc welds during manufacturing. Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

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

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

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

1988-01-01

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

3D Ultrasonic Non-destructive Evaluation of Spot Welds Using an Enhanced Total Focusing Method

NASA Astrophysics Data System (ADS)

Jasiuniene, Elena; Samaitis, Vykintas; Mazeika, Liudas; Sanderson, Ruth

2015-02-01

Spot welds are used to join sheets of metals in the automotive industry. When spot weld quality is evaluated using conventional ultrasonic manual pulse-echo method, the reliability of the inspection is affected by selection of the probe diameter and the positioning of the probe in the weld center. The application of a 2D matrix array is a potential solution to the aforementioned problems. The objective of this work was to develop a signal processing algorithm to reconstruct the 3D spot weld volume showing the size of the nugget and the defects in it. In order to achieve this, the conventional total focusing method was enhanced by taking into account the directivities of the single elements of the array and the divergence of the ultrasonic beam due to the propagation distance. Enhancements enabled a reduction in the background noise and uniform sensitivity at different depths to be obtained. The proposed algorithm was verified using a finite element model of ultrasonic wave propagation simulating three common spot weld conditions: a good weld, an undersized weld, and a weld containing a pore. The investigations have demonstrated that proposed method enables the determination of the size of the nugget and detection of discontinuities.

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.

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

Parametric Investigation on Microstructure and Mechanical Properties of Ultrasonic spot welded Aluminium to Copper sheets

NASA Astrophysics Data System (ADS)

Prasad Satpathy, Mantra; Das Mohapatra, Kasinath; Sahoo, Ananda Kumar; Sahoo, Susanta Kumar

2018-03-01

Ultrasonic welding is one of the promising solid state welding methods which have been widely used to join highly conductive materials like aluminum and copper. Despite these applications in the automotive field, other industries also have a strong interest to adopt this process for joining of various advanced alloys. In some of its applications, poor weld strength and sticking of the workpiece to the tool are issues. Thus, an attempt has been taken in the present study to overcome these issues by performing experiments with a suitable range of weld parameters. The major objectives of this study are to obtain a good joint strength with a reduced sticking phenomenon and microstructure of Al-Cu weld coupons. The results uncovered the mechanical strength of the joint increased up to 0.34 sec of weld time and afterward, it gradually decreased. Meantime, the plastic deformation in the weld zone enhanced the formation of an intermetallic layer of 1.5 μm thick, and it is composed of mainly Al2Cu compound. The temperature evolved during the welding process is also measured by thermocouples to show its relationship with the plastic deformation. The present work exemplifies a finer understanding of the failure behavior of joints and provides an insight of ultrasonic welding towards the improvement in the quality of weld.

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.

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.

High-Powered, Ultrasonically Assisted Thermal Stir Welding

NASA Technical Reports Server (NTRS)

Ding, Robert

2013-01-01

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.

Experimental Investigation on Acoustic Control Droplet Transfer in Ultrasonic-Wave-Assisted Gas Metal Arc Welding

NASA Astrophysics Data System (ADS)

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

2018-02-01

Ultrasonic-wave-assisted gas metal arc welding (U-GMAW) is a new, advanced arc welding method that uses an ultrasonic wave emitted from an ultrasonic radiator above the arc. However, it remains unclear how the ultrasonic wave affects the metal droplet, hindering further application of U-GMAW. In this paper, an improved U-GMAW system was used and its superiority was experimentally demonstrated. Then a series of experiments were designed and performed to study how the ultrasonic wave affects droplet transfer, including droplet size, velocity, and motion trajectory. The behavior of droplet transfer was observed in high-speed images. The droplet transfer is closely related to the distribution of the acoustic field, determined by the ultrasonic current. Moreover, by analyzing the variably accelerated motion of the droplet, the acoustic control of the droplet transfer was intuitively demonstrated. Finally, U-GMAW was successfully used in vertical-up and overhead welding experiments, showing that U-GMAW is promising for use in welding in all positions.

Spatially resolved ultrasonic attenuation in resistance spot welds: implications for nondestructive testing.

PubMed

Mozurkewich, George; Ghaffari, Bita; Potter, Timothy J

2008-09-01

Spatial variation of ultrasonic attenuation and velocity has been measured in plane parallel specimens extracted from resistance spot welds. In a strong weld, attenuation is larger in the nugget than in the parent material, and the region of increased attenuation is surrounded by a ring of decreased attenuation. In the center of a stick weld, attenuation is even larger than in a strong weld, and the low-attenuation ring is absent. These spatial variations are interpreted in terms of differences in grain size and martensite formation. Measured frequency dependences indicate the presence of an additional attenuation mechanism besides grain scattering. The observed attenuations do not vary as commonly presumed with weld quality, suggesting that the common practice of using ultrasonic attenuation to indicate weld quality is not a reliable methodology.

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

Evaluation of microstructure stability at the interfaces of Al-6061 welds fabricated using ultrasonic additive manufacturing

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

Sridharan, Niyanth S.; Gussev, Maxim N.; Parish, Chad M.

Here, ultrasonic additive manufacturing (UAM) is a solid-state additive manufacturing process that uses fundamental principles of ultrasonic welding and sequential layering of tapes to fabricate complex three-dimensional (3-D) components. One of the factors limiting the use of this technology is the poor tensile strength along the z-axis. Recent work has demonstrated the improvement of the z-axis properties after post-processing treatments. The abnormally high stability of the grains at the interface during post-weld heat treatments is, however, not yet well understood. In this work we use multiscale characterization to understand the stability of the grains during post-weld heat treatments. Aluminum alloymore » (6061) builds, fabricated using ultrasonic additive manufacturing, were post-weld heat treated at 180, 330 and 580 °C. The grains close to the tape interfaces are stable during post-weld heat treatments at high temperatures (i.e., 580 °C). This is in contrast to rapid grain growth that takes place in the bulk. Transmission electron microscopy and atom-probe tomography display a significant enrichment of oxygen and magnesium near the stable interfaces. Based on the detailed characterization, two mechanisms are proposed and evaluated: nonequilibrium nano-dispersed oxides impeding the grain growth due to grain boundary pinning, or grain boundary segregation of magnesium and oxygen reducing the grain boundary energy.« less

Evaluation of microstructure stability at the interfaces of Al-6061 welds fabricated using ultrasonic additive manufacturing

DOE PAGES

Sridharan, Niyanth S.; Gussev, Maxim N.; Parish, Chad M.; ...

2018-03-06

Here, ultrasonic additive manufacturing (UAM) is a solid-state additive manufacturing process that uses fundamental principles of ultrasonic welding and sequential layering of tapes to fabricate complex three-dimensional (3-D) components. One of the factors limiting the use of this technology is the poor tensile strength along the z-axis. Recent work has demonstrated the improvement of the z-axis properties after post-processing treatments. The abnormally high stability of the grains at the interface during post-weld heat treatments is, however, not yet well understood. In this work we use multiscale characterization to understand the stability of the grains during post-weld heat treatments. Aluminum alloymore » (6061) builds, fabricated using ultrasonic additive manufacturing, were post-weld heat treated at 180, 330 and 580 °C. The grains close to the tape interfaces are stable during post-weld heat treatments at high temperatures (i.e., 580 °C). This is in contrast to rapid grain growth that takes place in the bulk. Transmission electron microscopy and atom-probe tomography display a significant enrichment of oxygen and magnesium near the stable interfaces. Based on the detailed characterization, two mechanisms are proposed and evaluated: nonequilibrium nano-dispersed oxides impeding the grain growth due to grain boundary pinning, or grain boundary segregation of magnesium and oxygen reducing the grain boundary energy.« less

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.

Ultrasonic seam welding on thin silicon solar cells

NASA Technical Reports Server (NTRS)

Stofel, E. J.

1982-01-01

The ultrathin silicon solar cell has progressed to where it is a serious candidate for future light weight or radiation tolerant spacecraft. The ultrasonic method of producing welds was found to be satisfactory. These ultrathin cells could be handled without breakage in a semiautomated welding machine. This is a prototype of a machine capable of production rates sufficiently large to support spacecraft array assembly needs. For comparative purposes, this project also welded a variety of cells with thicknesses up to 0.23 mm as well as the 0.07 mm ultrathin cells. There was no electrical degradation in any cells. The mechanical pull strength of welds on the thick cells was excellent when using a large welding force. The mechanical strength of welds on thin cells was less since only a small welding force could be used without cracking these cells. Even so, the strength of welds on thin cells appears adequate for array application. The ability of such welds to survive multiyear, near Earth orbit thermal cycles needs to be demonstrated.

Sensing the gas metal arc welding process

NASA Technical Reports Server (NTRS)

Carlson, N. M.; Johnson, J. A.; Smartt, H. B.; Watkins, A. D.; Larsen, E. D.; Taylor, P. L.; Waddoups, M. A.

1994-01-01

Control of gas metal arc welding (GMAW) requires real-time sensing of the process. Three sensing techniques for GMAW are being developed at the Idaho National Engineering Laboratory (INEL). These are (1) noncontacting ultrasonic sensing using a laser/EMAT (electromagnetic acoustic transducer) to detect defects in the solidified weld on a pass-by-pass basis, (2) integrated optical sensing using a CCD camera and a laser stripe to obtain cooling rate and weld bead geometry information, and (3) monitoring fluctuations in digitized welding voltage data to detect the mode of metal droplet transfer and assure that the desired mass input is achieved.

Sensing the gas metal arc welding process

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

Carlson, N.M.; Johnson, J.A.; Smartt, H.B.

1992-01-01

Control of gas metal arc welding (GMAW) requires real-time sensing of the process. Three sensing techniques for GMAW are being developed at the Idaho National Engineering Laboratory (INEL). These are (1) noncontacting ultrasonic sensing using a laser/EMAT (electromagnetic acoustic transducer) to detect defects in the solidified weld on a pass-bypass basis, (2) integrated optical sensing using a CCD camera and a laser stripe to obtain cooling rate and weld bead geometry information, and (3) monitoring fluctuations in digitized welding voltage data to detect the mode of metal droplet transfer and assure that the desired mass input is achieved.

Sensing the gas metal arc welding process

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

Carlson, N.M.; Johnson, J.A.; Smartt, H.B.

1992-10-01

Control of gas metal arc welding (GMAW) requires real-time sensing of the process. Three sensing techniques for GMAW are being developed at the Idaho National Engineering Laboratory (INEL). These are (1) noncontacting ultrasonic sensing using a laser/EMAT (electromagnetic acoustic transducer) to detect defects in the solidified weld on a pass-bypass basis, (2) integrated optical sensing using a CCD camera and a laser stripe to obtain cooling rate and weld bead geometry information, and (3) monitoring fluctuations in digitized welding voltage data to detect the mode of metal droplet transfer and assure that the desired mass input is achieved.

Insights Gained from Ultrasonic Testing of Piping Welds Subjected to the Mechanical Stress Improvement Process

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

Anderson, Michael T.; Cinson, Anthony D.; Crawford, Susan L.

2010-12-01

Pacific Northwest National Laboratory (PNNL) is assisting the United States Nuclear Regulatory Commission (NRC) in developing a position on the management of primary water stress corrosion cracking (PWSCC) in leak-before-break piping systems. Part of this involves determining whether inspections alone, or inspections plus mitigation, are needed. This work addresses the reliability of ultrasonic testing (UT) of cracks that have been mitigated by the mechanical stress improvement process (MSIP). The MSIP has been approved by the NRC (NUREG-0313) since 1986 and modifies residual stresses remaining after welding with compressive, or neutral, stresses near the inner diameter surface of the pipe. Thismore » compressive stress is thought to arrest existing cracks and inhibit new crack formation. To evaluate the effectiveness of the MSIP and the reliability of ultrasonic inspections, flaws were evaluated both before and after MSIP application. An initial investigation was based on data acquired from cracked areas in 325-mm-diameter piping at the Ignalina Nuclear Power Plant (INPP) in Lithuania. In a follow-on exercise, PNNL acquired and evaluated similar UT data from a dissimilar metal weld (DMW) specimen containing implanted thermal fatigue cracks. The DMW specimen is a carbon steel nozzle-to-safe end-to-stainless steel pipe section that simulates a pressurizer surge nozzle. The flaws were implanted in the nozzle-to-safe end Alloy 82/182 butter region. Results are presented on the effects of MSIP on specimen surfaces, and on UT flaw responses.« less

Modelling welded material for ultrasonic testing using MINA: Theory and applications

NASA Astrophysics Data System (ADS)

Moysan, J.; Corneloup, G.; Chassignole, B.; Gueudré, C.; Ploix, M. A.

2012-05-01

Austenitic steel multi-pass welds exhibit a heterogeneous and anisotropic structure that causes difficulties in the ultrasonic testing. Increasing the material knowledge is a long term research field for LCND laboratory and EDF Les Renardières in France. A specific model has been developed: the MINA model (Modelling an Isotropy from Notebook of Arc welding). Welded material is described in 2D for flat position arc welding with shielded electrode (SMAW) at a functional scale for UT modeling. The grain growth is the result of three physical phenomena: epitaxial growth, influence of temperature gradient, and competition between the grains. The model uses phenomenological rules to combine these three phenomena. A limited number of parameters is used to make the modelling possible from the information written down in a notebook of arc welding. We present all these principles with 10 years' hindsight. To illustrate the model's use, we present conclusions obtained with two recent applications. In conclusion we give also insights on other research topics around this model : inverse problem using a F.E.M. code simulating the ultrasonic propagation, in position welding, 3D prospects, GTAW.

Development Of Ultrasonic Testing Based On Delphi Program As A Learning Media In The Welding Material Study Of Detection And Welding Disables In The Environment Of Vocational Education

NASA Astrophysics Data System (ADS)

Dwi Cahyono, Bagus; Ainur, Chandra

2018-04-01

The development of science and technology has a direct impact on the preparation of qualified workers, including the preparation of vocational high school graduates. Law Number 20 the Year 2003 on National Education System explains that the purpose of vocational education is to prepare learners to be ready to work in certain fields. One of the learning materials in Vocational High School is welding and detecting welding defects. Introduction of welding and detecting welding defects, one way that can be done is by ultrasonic testing will be very difficult if only capitalize the book only. Therefore this study aims to adopt ultrasonic testing in a computer system. This system is called Delphi Program-based Ultrasonic Testing Expert System. This system is used to determine the classification and type of welding defects of the welded defect indicator knew. In addition to the system, there is a brief explanation of the notion of ultrasonic testing, calibration procedures and inspection procedures ultrasonic testing. In this system, ultrasonic input data testing that shows defects entered into the computer manually. This system is built using Delphi 7 software and Into Set Up Compiler as an installer. The method used in this research is Research and Development (R & D), with the following stages: (1) preliminary research; (2) manufacture of software design; (3) materials collection; (4) early product development; (5) validation of instructional media experts; (6) product analysis and revision; (8) media trials in learning; And (9) result of end product of instructional media. The result of the research shows that: (1) the result of feasibility test according to ultrasonic material testing expert that the system is feasible to be used as instructional media in welding material subject and welding defect detection in vocational education environment, because it contains an explanation about detection method of welding defect using method Ultrasonic testing in detail; (2

Welding characteristics of 27, 40 and 67 kHz ultrasonic plastic welding systems using fundamental- and higher-resonance frequencies.

PubMed

Tsujino, Jiromaru; Hongoh, Misugi; Yoshikuni, Masafumi; Hashii, Hidekazu; Ueoka, Tetsugi

2004-04-01

The welding characteristics of 27, 40 and 67 kHz ultrasonic plastic welding systems that are driven at only the fundamental-resonance frequency vibration were compared, and also those of the welding systems that were driven at the fundamental and several higher resonance frequencies simultaneously were studied. At high frequency, welding characteristics can be improved due to the larger vibration loss of plastic materials. For welding of rather thin or small specimens, as the fundamental frequency of these welding systems is higher and the numbers of driven higher frequencies are driven simultaneously, larger welded area and weld strength were obtained.

Ultrasonic Non-destructive Prediction of Spot Welding Shear Strength

NASA Astrophysics Data System (ADS)

Himawan, R.; Haryanto, M.; Subekti, R. M.; Sunaryo, G. R.

2018-02-01

To enhance a corrosion resistant of ferritic steel in reactor pressure vessel, stainless steel was used as a cladding. Bonding process between these two steels may result a inhomogenity either sub-clad crack or un-joined part. To ensure the integrity, effective inspection method is needed for this purpose. Therefore, in this study, an experiment of ultrasonic test for inspection of two bonding plate was performed. The objective of this study is to develop an effective method in predicting the shear fracture load of the join. For simplicity, these joined was modelled with two plate of stainless steel with spot welding. Ultrasonic tests were performed using contact method with 5 MHz in frequency and 10 mm in diameter of transducer. Amplitude of reflected wave from intermediate layer was used as a quantitative parameter. A set of experiment results show that shear fracture load has a linear correlation with amplitude of reflected wave. Besides, amplitude of reflected wave also has relation with nugget diameter. It could be concluded that ultrasonic contact method could be applied in predicting a shear fracture load.

Quality status display for a vibration welding process

DOEpatents

Spicer, John Patrick; Abell, Jeffrey A.; Wincek, Michael Anthony; Chakraborty, Debejyo; Bracey, Jennifer; Wang, Hui; Tavora, Peter W.; Davis, Jeffrey S.; Hutchinson, Daniel C.; Reardon, Ronald L.; Utz, Shawn

2017-03-28

A system includes a host machine and a status projector. The host machine is in electrical communication with a collection of sensors and with a welding controller that generates control signals for controlling the welding horn. The host machine is configured to execute a method to thereby process the sensory and control signals, as well as predict a quality status of a weld that is formed using the welding horn, including identifying any suspect welds. The host machine then activates the status projector to illuminate the suspect welds. This may occur directly on the welds using a laser projector, or on a surface of the work piece in proximity to the welds. The system and method may be used in the ultrasonic welding of battery tabs of a multi-cell battery pack in a particular embodiment. The welding horn and welding controller may also be part of the system.

Assessment of weld quality of aerospace grade metals by using ultrasonic matrix phased array technology

NASA Astrophysics Data System (ADS)

Na, Jeong K.; Gleeson, Sean T.

2014-03-01

Advantages of two dimensional electronic ultrasonic beam focusing, steering and scanning with the matrix phased array (MPA) technology has been used to visualize the conditions of resistance spot welds in auto vehicle grade advanced high strength steel carbon steels nondestructively. Two of the commonly used joining techniques, resistance spot welding and resistance seam welding, for thin aerospace grade plates made of aluminum, titanium, and stainless steels have also been inspected with the same MPA NDE system. In this study, a detailed discussions of the current MPA based ultrasonic real time imaging methodology has been made followed by some of the NDT results obtained with various welded test coupons.

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.

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

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

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

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

The Effectiveness of Surface Coatings on Preventing Interfacial Reaction During Ultrasonic Welding of Aluminum to Magnesium

NASA Astrophysics Data System (ADS)

Panteli, Alexandria; Robson, Joseph D.; Chen, Ying-Chun; Prangnell, Philip B.

2013-12-01

High power ultrasonic spot welding (USW) is a solid-state joining process that is advantageous for welding difficult dissimilar material couples, like magnesium to aluminum. USW is also a useful technique for testing methods of controlling interfacial reaction in welding as the interface is not greatly displaced by the process. However, the high strain rate deformation in USW has been found to accelerate intermetallic compound (IMC) formation and a thick Al12Mg17 and Al3Mg2 reaction layer forms after relatively short welding times. In this work, we have investigated the potential of two approaches for reducing the IMC reaction rate in dissimilar Al-Mg ultrasonic welds, both involving coatings on the Mg sheet surface to (i) separate the join line from the weld interface, using a 100- μm-thick Al cold spray coating, and (ii) provide a diffusion barrier layer, using a thin manganese physical vapor deposition (PVD) coating. Both methods were found to reduce the level of reaction and increase the failure energy of the welds, but their effectiveness was limited due to issues with coating attachment and survivability during the welding cycle. The effect of the coatings on the joint's interface microstructure, and the fracture behavior have been investigated in detail. Kinetic modeling has been used to show that the benefit of the cold spray coating can be attributed to the reaction rate reverting to that expected under static conditions. This reduces the IMC growth rate by over 50 pct because at the weld line, the high strain rate dynamic deformation in USW normally enhances diffusion through the IMC layer. In comparison, the thin PVD barrier coating was found to rapidly break up early in USW and become dispersed throughout the deformation layer reducing its effectiveness.

The Mechanism of Ultrasonic Vibration on Grain Refining and Degassing in GTA Spot Welding of Copper Joints.

PubMed

Al-Ezzi, Salih; Quan, Gaofeng; Elrayah, Adil

2018-05-07

This paper examines the effect of ultrasonic vibration (USV) on grain size and interrupted porosity in Gas Tungsten Arc (GTA) spot-welded copper. Grain size was refined by perpendicularly attaching a transducer to the welded sheet and applying USV to the weld pool for a short time (0, 2, 4, and 6 s) in addition improvements to the degassing process. Results illustrate a significant reduction of grain size (57%). Notably, USV provided interaction between reformations (fragmentation) and provided nucleation points (detaching particles from the fusion line) for grains in the nugget zone and the elimination of porosity in the nugget zone. The GTA spot welding process, in conjunction with USV, demonstrated an improvement in the corrosion potential for a copper spot-welded joint in comparison to the joint welded without assistance of USV. Finally, welding of copper by GTA spot welding in conjunction with ultrasound for 2 s presented significant mechanical properties.

The Mechanism of Ultrasonic Vibration on Grain Refining and Degassing in GTA Spot Welding of Copper Joints

PubMed Central

Quan, Gaofeng

2018-01-01

This paper examines the effect of ultrasonic vibration (USV) on grain size and interrupted porosity in Gas Tungsten Arc (GTA) spot-welded copper. Grain size was refined by perpendicularly attaching a transducer to the welded sheet and applying USV to the weld pool for a short time (0, 2, 4, and 6 s) in addition improvements to the degassing process. Results illustrate a significant reduction of grain size (57%). Notably, USV provided interaction between reformations (fragmentation) and provided nucleation points (detaching particles from the fusion line) for grains in the nugget zone and the elimination of porosity in the nugget zone. The GTA spot welding process, in conjunction with USV, demonstrated an improvement in the corrosion potential for a copper spot-welded joint in comparison to the joint welded without assistance of USV. Finally, welding of copper by GTA spot welding in conjunction with ultrasound for 2 s presented significant mechanical properties. PMID:29735894

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

Defense Waste Processing Facility Canister Closure Weld Current Validation Testing

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

Korinko, P. S.; Maxwell, D. N.

Two closure welds on filled Defense Waste Processing Facility (DWPF) canisters failed to be within the acceptance criteria in the DWPF operating procedure SW4-15.80-2.3 (1). In one case, the weld heat setting was inadvertently provided to the canister at the value used for test welds (i.e., 72%) and this oversight produced a weld at a current of nominally 210 kA compared to the operating procedure range (i.e., 82%) of 240 kA to 263 kA. The second weld appeared to experience an instrumentation and data acquisition upset. The current for this weld was reported as 191 kA. Review of the datamore » from the Data Acquisition System (DAS) indicated that three of the four current legs were reading the expected values, approximately 62 kA each, and the fourth leg read zero current. Since there is no feasible way by further examination of the process data to ascertain if this weld was actually welded at either the target current or the lower current, a test plan was executed to provide assurance that these Nonconforming Welds (NCWs) meet the requirements for strength and leak tightness. Acceptance of the welds is based on evaluation of Test Nozzle Welds (TNW) made specifically for comparison. The TNW were nondestructively and destructively evaluated for plug height, heat tint, ultrasonic testing (UT) for bond length and ultrasonic volumetric examination for weld defects, burst pressure, fractography, and metallography. The testing was conducted in agreement with a Task Technical and Quality Assurance Plan (TTQAP) (2) and applicable procedures.« less

A support vector machine approach for classification of welding defects from ultrasonic signals

NASA Astrophysics Data System (ADS)

Chen, Yuan; Ma, Hong-Wei; Zhang, Guang-Ming

2014-07-01

Defect classification is an important issue in ultrasonic non-destructive evaluation. A layered multi-class support vector machine (LMSVM) classification system, which combines multiple SVM classifiers through a layered architecture, is proposed in this paper. The proposed LMSVM classification system is applied to the classification of welding defects from ultrasonic test signals. The measured ultrasonic defect echo signals are first decomposed into wavelet coefficients by the wavelet packet transform. The energy of the wavelet coefficients at different frequency channels are used to construct the feature vectors. The bees algorithm (BA) is then used for feature selection and SVM parameter optimisation for the LMSVM classification system. The BA-based feature selection optimises the energy feature vectors. The optimised feature vectors are input to the LMSVM classification system for training and testing. Experimental results of classifying welding defects demonstrate that the proposed technique is highly robust, precise and reliable for ultrasonic defect classification.

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

The algorithm of verification of welding process for plastic pipes

NASA Astrophysics Data System (ADS)

Rzasinski, R.

2017-08-01

The study analyzes the process of butt welding of PE pipes in terms of proper selection of connector parameters. The process was oriented to the elements performed as a series of types of pipes. Polymeric materials commonly referred to as polymers or plastics, synthetic materials are produced from oil products in the polyreaction compounds of low molecular weight, called monomers. During the polyreactions monomers combine to build a macromolecule material monomer named with the prefix poly polypropylene, polyethylene or polyurethane, creating particles in solid state on the order of 0,2 to 0,4 mm. Finished products from polymers of virtually any shape and size are obtained by compression molding, injection molding, extrusion, laminating, centrifugal casting, etc. Weld can only be a thermoplastic that softens at an elevated temperature, and thus can be connected via a clamp. Depending on the source and method of supplying heat include the following welding processes: welding contact, radiant welding, friction welding, dielectric welding, ultrasonic welding. The analysis will be welding contact. In connection with the development of new generation of polyethylene, and the production of pipes with increasing dimensions (diameter, wall thickness) is important to select the correct process.

Computational modeling and experimental studies of the dynamic performance of ultrasonic horn profiles used in plastic welding.

PubMed

Roopa Rani, M; Rudramoorthy, R

2013-03-01

Ultrasonic horns are tuned components designed to vibrate in a longitudinal mode at ultrasonic frequencies. Reliable performance of such horns is normally decided by the uniformity of vibration amplitude at the working surface and the stress developed during loading condition. The horn design engineer must pay particular attention to designing a tool that will produce the desired amplitude without fracturing. The present work discusses horn configurations which satisfy these criteria and investigates the design requirements of horns in ultrasonic system. Different horn profiles for ultrasonic welding of thermoplastics have been characterized in terms of displacement amplitude and von-Mises stresses using modal and harmonic analysis. To validate the simulated results, five different horns are fabricated from Aluminum, tested and tuned to the operating frequency. Standard ABS plastic parts are welded using these horns. Temperature developed during the welding of ABS test parts using different horns is recorded using sensors and National Instruments (NIs) data acquisition system. The recorded values are compared with the predicted values. Experimental results show that welding using a Bezier horn has a high interface temperature and the welded joints had higher strength as compared to the other horn profiles. Copyright © 2012 Elsevier B.V. All rights reserved.

Catalytic effect on ultrasonic decomposition of cellulose

NASA Astrophysics Data System (ADS)

Nomura, Shinfuku; Wakida, Kousuke; Mukasa, Shinobu; Toyota, Hiromichi

2018-07-01

Cellulase used as a catalyst is introduced into the ultrasonic welding method for cellulose decomposition in order to obtain glucose. By adding cellulase in the welding process, filter paper decomposes cellulose into glucose, 5-hydroxymethylfurfural (5-HMF), furfural, and oligosaccharides. The amount of glucose from hydrolysis was increased by ultrasonic welding in filter paper immersed in water. Most glucose was obtained by 100 W ultrasonic irradiation; however, when was applied 200 W, the dehydration of the glucose itself occurred, and was converted into 5-HMF owing to the thermolysis of ultrasonics. Therefore, there is an optimum welding power for the production of glucose from cellulose decomposition.

The ultrasonic characteristics of high frequency modulated arc and its application in material processing.

PubMed

He, Longbiao; Yang, Ping; Li, Luming; Wu, Minsheng

2014-12-01

To solve the difficulty of introducing traditional ultrasonic transducers to welding molten pool, high frequency current is used to modulate plasma arc and ultrasonic wave is excited successfully. The characteristics of the excited ultrasonic field are studied. The results show that the amplitude-frequency response of the ultrasonic emission is flat. The modulating current is the main factor influencing the ultrasonic power and the sound pressure depends on the variation of arc plasma stream force. Experimental study of the welding structure indicates grain refinement by the ultrasonic emission of the modulated arc and the test results showed there should be an energy region for the arc ultrasonic to get best welding joints. Copyright © 2014 Elsevier B.V. All rights reserved.

Structure and properties of fixed joints formed by ultrasonic-assisted friction-stir welding

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

Fortuna, S. V., E-mail: s-fortuna@ispms.ru; Ivanov, K. V., E-mail: ikv@ispms.ru; Eliseev, A. A., E-mail: alan@ispms.ru

2015-10-27

This paper deals with structure and properties of aluminum alloy 7475 and its joints obtained by friction stir welding including under ultrasonic action. Microhardness measurements show that ultrasonic action increases strength properties of the joints. Optical and transmission electron microscopy reveals that this effect is related to the precipitation of tertiary coherent S-and T-phase particles.

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

NASA Astrophysics Data System (ADS)

Endramawan, T.; Sifa, A.

2018-02-01

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

Detection and assessment of flaws in friction stir welded joints using ultrasonic guided waves: experimental and finite element analysis

NASA Astrophysics Data System (ADS)

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

2018-02-01

Ultrasonic guided waves (GWs), e.g. Lamb waves, have been proven effective in the detection of defects such as corrosion, cracking, delamination, and debonding in both composite and metallic structures. They are a significant tool employed in structural health monitoring. In this study, the ability of ultrasonic GWs to assess the quality of friction stir welding (FSW) was investigated. Four friction stir welded AZ31B magnesium plates processed with different welding parameters and a non-welded plate were used. The fundamental symmetric (S0) Lamb wave mode was excited using piezoelectric wafers (PZTs). Further, the S0 mode was separated using the "Improved complete ensemble empirical mode decomposition with adaptive noise (Improved CEEMDAN)" technique. A damage index (DI) was defined based on the variation in the amplitude of the captured wave signals in order to detect the presence and asses the severity of damage resulting from the welding process. As well, computed tomography (CT) scanning was used as a non-destructive testing (NDT) technique to assess the actual weld quality and validate predictions based on the GW approach. The findings were further confirmed using finite element analysis (FEA). To model the actual damage profile in the welds, "Mimics" software was used for the 3D reconstruction of the CT scans. The built 3D models were later used for evaluation of damage volume and for FEA. The damage volumes were correlated to the damage indices computed from both experimental and numerical data. The proposed approach showed high sensitivity of the S0 mode to internal flaws within the friction stir welded joints. This methodology has great potential as a future classification method of FSW quality.

Microstructure and Mechanical Properties of an Ultrasonic Spot Welded Aluminum Alloy: The Effect of Welding Energy

PubMed Central

Peng, He; Chen, Daolun; Jiang, Xianquan

2017-01-01

The aim of this study is to evaluate the microstructures, tensile lap shear strength, and fatigue resistance of 6022-T43 aluminum alloy joints welded via a solid-state welding technique–ultrasonic spot welding (USW)–at different energy levels. An ultra-fine necklace-like equiaxed grain structure is observed along the weld line due to the occurrence of dynamic crystallization, with smaller grain sizes at lower levels of welding energy. The tensile lap shear strength, failure energy, and critical stress intensity of the welded joints first increase, reach their maximum values, and then decrease with increasing welding energy. The tensile lap shear failure mode changes from interfacial fracture at lower energy levels, to nugget pull-out at intermediate optimal energy levels, and to transverse through-thickness (TTT) crack growth at higher energy levels. The fatigue life is longer for the joints welded at an energy of 1400 J than 2000 J at higher cyclic loading levels. The fatigue failure mode changes from nugget pull-out to TTT crack growth with decreasing cyclic loading for the joints welded at 1400 J, while TTT crack growth mode remains at all cyclic loading levels for the joints welded at 2000 J. Fatigue crack basically initiates from the nugget edge, and propagates with “river-flow” patterns and characteristic fatigue striations. PMID:28772809

Microstructure and Mechanical Properties of an Ultrasonic Spot Welded Aluminum Alloy: The Effect of Welding Energy.

PubMed

Peng, He; Chen, Daolun; Jiang, Xianquan

2017-04-25

The aim of this study is to evaluate the microstructures, tensile lap shear strength, and fatigue resistance of 6022-T43 aluminum alloy joints welded via a solid-state welding technique-ultrasonic spot welding (USW)-at different energy levels. An ultra-fine necklace-like equiaxed grain structure is observed along the weld line due to the occurrence of dynamic crystallization, with smaller grain sizes at lower levels of welding energy. The tensile lap shear strength, failure energy, and critical stress intensity of the welded joints first increase, reach their maximum values, and then decrease with increasing welding energy. The tensile lap shear failure mode changes from interfacial fracture at lower energy levels, to nugget pull-out at intermediate optimal energy levels, and to transverse through-thickness (TTT) crack growth at higher energy levels. The fatigue life is longer for the joints welded at an energy of 1400 J than 2000 J at higher cyclic loading levels. The fatigue failure mode changes from nugget pull-out to TTT crack growth with decreasing cyclic loading for the joints welded at 1400 J, while TTT crack growth mode remains at all cyclic loading levels for the joints welded at 2000 J. Fatigue crack basically initiates from the nugget edge, and propagates with "river-flow" patterns and characteristic fatigue striations.

Characteristics of coated copper wire specimens using high frequency ultrasonic complex vibration welding equipments.

PubMed

Tsujino, J; Ihara, S; Harada, Y; Kasahara, K; Sakamaki, N

2004-04-01

Welding characteristic of thin coated copper wires were studied using 40, 60, 100 kHz ultrasonic complex vibration welding equipments with elliptical to circular vibration locus. The complex vibration systems consisted of a longitudinal-torsional vibration converter and a driving longitudinal vibration system. Polyurethane coated copper wires of 0.036 mm outer diameter and copper plates of 0.3 mm thickness and the other dimension wires were used as welding specimens. The copper wire part is completely welded on the copper substrate and the insulated coating material is driven from welded area to outsides of the wire specimens by high frequency complex vibration.

Ultrasonic Spot Welding of a Rare-Earth Containing ZEK100 Magnesium Alloy: Effect of Welding Energy

NASA Astrophysics Data System (ADS)

Macwan, A.; Chen, D. L.

2016-04-01

Ultrasonic spot welding was used to join a low rare-earth containing ZEK100 Mg alloy at different levels of welding energy, and tensile lap shear tests were conducted to evaluate the failure strength in relation to the microstructural changes. It was observed that dynamic recrystallization occurred in the nugget zone; the grain size increased and microhardness decreased with increasing welding energy arising from the increasing interface temperature and strain rate. The weld interface experienced severe plastic deformation at a high strain rate from ~500 to ~2100 s-1 with increasing welding energy from 500 to 2000 J. A relationship between grain size and Zener-Hollomon parameter, and a Hall-Petch-type relationship between microhardness and grain size were established. The tensile lap shear strength and failure energy were observed to first increase with increasing welding energy, reach the maximum values at 1500 J, and then decrease with a further increase in the welding energy. The samples welded at a welding energy ≤1500 J exhibited an interfacial failure mode, while nugget pull-out occurred in the samples welded at a welding energy above 1500 J. The fracture surfaces showed typical shear failure. Low-temperature tests at 233 K (-40 °C) showed no significant effect on the strength and failure mode of joints welded at the optimal welding energy of 1500 J. Elevated temperature tests at 453 K (180 °C) revealed a lower failure load but a higher failure energy due to the increased deformability, and showed a mixed mode of partial interfacial failure and partial nugget pull-out.

Lay-Up and Consolidation of a Composite Pipe by In Situ Ultrasonic Welding of a Thermoplastic Matrix Composite Tape.

PubMed

Dell'Anna, Riccardo; Lionetto, Francesca; Montagna, Francesco; Maffezzoli, Alfonso

2018-05-11

In this work, the potential of preformed thermoplastic matrix composite tapes for the manufacturing of composite pipes by filament winding assisted by in situ ultrasonic welding was evaluated. Unidirectional tapes of E-glass-reinforcedamorphous poly (ethylene terephthalate) were laid up and consolidated in a filament winding machine that was modified with a set-up enabling ultrasonic welding. The obtained composite specimens were characterized by means of morphological and dynamic mechanical analysis as well as void content evaluation, in order to correlate welding parameters to composite properties.

Design of advanced ultrasonic transducers for welding devices.

PubMed

Parrini, L

2001-11-01

A new high frequency ultrasonic transducer has been conceived, designed, prototyped, and tested. In the design phase, an advanced approach was used and established. The method is based on an initial design estimate obtained with finite element method (FEM) simulations. The simulated ultrasonic transducers and resonators are then built and characterized experimentally through laser interferometry and electrical resonance spectra. The comparison of simulation results with experimental data allows the parameters of FEM models to be adjusted and optimized. The achieved FEM simulations exhibit a remarkably high predictive potential and allow full control of the vibration behavior of the transducer. The new transducer is mounted on a wire bonder with a flange whose special geometry was calculated by means of FEM simulations. This flange allows the transducer to be attached on the wire bonder, not only in longitudinal nodes, but also in radial nodes of the ultrasonic field excited in the horn. This leads to a total decoupling of the transducer to the wire bonder, which has not been achieved so far. The new approach to mount ultrasonic transducers on a welding device is of major importance, not only for wire bonding, but also for all high power ultrasound applications and has been patented.

Lay-Up and Consolidation of a Composite Pipe by In Situ Ultrasonic Welding of a Thermoplastic Matrix Composite Tape

PubMed Central

Dell’Anna, Riccardo; Montagna, Francesco

2018-01-01

In this work, the potential of preformed thermoplastic matrix composite tapes for the manufacturing of composite pipes by filament winding assisted by in situ ultrasonic welding was evaluated. Unidirectional tapes of E-glass-reinforcedamorphous poly (ethylene terephthalate) were laid up and consolidated in a filament winding machine that was modified with a set-up enabling ultrasonic welding. The obtained composite specimens were characterized by means of morphological and dynamic mechanical analysis as well as void content evaluation, in order to correlate welding parameters to composite properties. PMID:29751693

Automated flaw detection scheme for cast austenitic stainless steel weld specimens using Hilbert-Huang transform of ultrasonic phased array data

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

Khan, Tariq; Majumdar, Shantanu; Udpa, Lalita

2012-05-17

The objective of this work is to develop processing algorithms to detect and localize flaws using ultrasonic phased-array data. Data was collected on cast austenitic stainless stell (CASS) weld specimens onloan from the U.S. nuclear power industry' Pressurized Walter Reactor Owners Group (PWROG) traveling specimen set. Each specimen consists of a centrifugally cast stainless stell (CCSS) pipe section welded to a statically cst(SCSS) or wrought (WRSS) section. The paper presents a novel automated flaw detection and localization scheme using low frequency ultrasonic phased array inspection singals from the weld and heat affected zone of the based materials. The major stepsmore » of the overall scheme are preprocessing and region of interest (ROI) detection followed by the Hilbert-Huang transform (HHT) of A-scans in the detected ROIs. HHT offers time-frequency-energy distribution for each ROI. The Accumulation of energy in a particular frequency band is used as a classification feature for the particular ROI.« less

Ultrasonic Stir Welding Development for Ground-Based and In Situ Fabrication and Repair for In-Space Propulsion Systems/Commercial Space Sector

NASA Technical Reports Server (NTRS)

Ding, Jeff

2015-01-01

The completed Center Innovation Fund (CIF) project used the upgraded Ultrasonic Stir Weld (USW) Prototype System (built in 2013/2014) to begin characterizing the weld process using 2219 aluminum (fig. 1). This work is being done in Bldg. 4755 at NASA Marshall Space Flight Center (MSFC). The capabilities of the USW system provides the means to precisely control and document individual welding parameters. The current upgraded system has the following capabilities: (1) Ability to 'pulse' ultrasonic (US) energy on and off and adjust parameters real-time (travel speed, spindle rpm, US amplitude, X and Z axis positions, and plunge and pin axis force; (2) Means to measure draw force; (3) Ability to record US power versus time; (4) Increasing stiffness of Z axis drive and reduce head deflection using laser technology; (5) Adding linear encoder to better control tool penetration setting; (6) Ultrasonic energy integrated into stir rod and containment plate; (7) Maximum 600 rpm; (8) Maximum Z force 15,000 lb; (9) Real-time data acquisition and logging capabilities at a minimum frequency of 10 Hz; and (10) Two separate transducer power supplies operating at 4.5 kW power.

Ultrasonic probe system for the bore-side inspection of tubes and welds therein

DOEpatents

Cook, K. Von; Koerner, Dan W.; Cunningham, Jr., Robert A.; Murrin, Jr., Horace T.

1977-07-26

A probe system is provided for the bore-side inspection of tube-to-header welds and the like for small diameter tubes. The probe head of the system includes an ultrasonic transmitter-receiver transducer, a separate ultrasonic receiver, a reflector associated with the transducer to properly orient the ultrasonic signal with respect to a tube wall, a baffle to isolate the receiver from the transducer, and means for maintaining the probe head against the tube wall under investigation. Since the probe head must rotate to inspect along a helical path, special ultrasonic signal connections are employed. Through the use of the probe, flaws at either the inner or outer surfaces may be detected.

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.

Method and system having ultrasonic sensor movable by translation device for ultrasonic profiling of weld samples

DOEpatents

Panyard, James; Potter, Timothy; Charron, William; Hopkins, Deborah; Reverdy, Frederic

2010-04-06

A system for ultrasonic profiling of a weld sample includes a carriage movable in opposite first and second directions. An ultrasonic sensor is coupled to the carriage to move over the sample as the carriage moves. An encoder determines the position of the carriage to determine the position of the sensor. A spring is connected at one end of the carriage. Upon the carriage being moved in the first direction toward the spring such that the carriage and the sensor are at a beginning position and the spring is compressed the spring decompresses to push the carriage back along the second direction to move the carriage and the sensor from the beginning position to an ending position. The encoder triggers the sensor to take the ultrasonic measurements of the sample when the sensor is at predetermined positions while the sensor moves over the sample between the beginning and positions.

Ultrasonic technique for inspection of GPHS capsule girth weld integrity

NASA Astrophysics Data System (ADS)

Placr, Arnost

1993-05-01

An innovative nondestructive examination (NDE) technique for the inspection of integrity of General Purpose Heat Source (GPHS) capsule girth welds was developed employing a Lamb wave as the mode of the sound propagation. Reliability of the Lamb wave technique was tested on GPHS capsules using plutonium pallet simulators. All ten capsules, which were previously rejected, passed ultrasonic (UT) inspection using the Lamb wave technique.

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.

Use of Ultrasound in Reconditioning by Welding of Tools Used in the Process of Regenerating Rubber.

PubMed

Dobrotă, Dan; Petrescu, Valentin

2018-02-10

Addressing the problem of reconditioning large parts is of particular importance, due to their value and to the fact that the technologies for their reconditioning are very complex. The tools used to refine regenerated rubber which measure 660 mm in diameter and 2130 mm in length suffer from a rather fast dimensional wear. Within this research, the authors looked for a welding reconditioning procedure that would allow a very good adhesion between the deposited material layer and the base material. In this regard, the MAG (Metal Active Gas) welding process was used, but the ultrasonic activation of the welding process was also considered. Thus, the wire used for welding was activated considering a variation of the frequency of ultrasounds in the range f = 18-22 kHz respectively of the oscillation amplitude A = 30-60 μm. Under these conditions it was found that the presence of ultrasonic waves during the welding cladding process results in uniform deposition of hard carbons at the grain boundary and in the elimination of any existing oxides on the deposition surface, but at the same time increases the adhesion between the base material and the additional material, all of which positively influence the wear and corrosion resistance of the tools used to refine the regenerated rubber.

Determination of the Order of Passes of AN Austenitic Weld by Optimization of AN Inversion Process of Ultrasound Data

NASA Astrophysics Data System (ADS)

Gueudré, C.; Marrec, L. Le; Chekroun, M.; Moysan, J.; Chassignole, B.; Corneloup, G.

2011-06-01

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 challenge the ultrasonic non-destructive testing. The simulation in this type of structure is now possible thanks to the MINA code which allows the grain orientation modeling taking into account the welding process, and the ATHENA code to exactly simulate the ultrasonic propagation. We propose studying the case where the order of the passes is unknown to estimate the possibility of reconstructing this important parameter by ultrasound measures. The first results are presented.

Thermo-mechanical process for treatment of welds

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

Malik, R K

1980-03-01

Benefits from thermo-mechanical processing (TMP) of austenitic stainless steel weldments, analogous to hot isostatic pressing (HIP) of castings, most likely result from compressive plastic deformation, enhanced diffusion, and/or increased dislocation density. TMP improves ultrasonic inspectability of austenitic stainless steel welds owing to: conversion of cast dendrites into equiaxed austenitic grains, reduction in size and number of stringers and inclusions, and reduction of delta ferrite content. TMP induces structural homogenization and healing of void-type defects and thus contributes to an increase in elongation, impact strength, and fracture toughness as well as a significant reduction in data scatter for these properties. Anmore » optimum temperature for TMP or HIP of welds is one which causes negligible grain growth and an acceptable reduction in yield strength, and permits healing of porosity.« less

Robotic Welding and Inspection System

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

H. B. Smartt; D. P. Pace; E. D. Larsen

2008-06-01

This paper presents a robotic system for GTA welding of lids on cylindrical vessels. The system consists of an articulated robot arm, a rotating positioner, end effectors for welding, grinding, ultrasonic and eddy current inspection. Features include weld viewing cameras, modular software, and text-based procedural files for process and motion trajectories.

Quality Enhancement of Ultrasonic TOFD Signals from Carbon Steel Weld Pad with Notches.

PubMed

Manjula, K; Vijayarekha, K; Venkatraman, B

2018-03-01

Welding is an integral part of component fabrication in industry. Even though the science and art of welding are more than 100 years old, defects continue to occur during welding. Codes of practice require that the welds be tested and evaluated. Conventionally ultrasonic testing has been widely applied in industry for the detection and evaluation of the flaws/defects in the weldments. With advances in sensor and signal analysis technologies, the last two decades have seen extensive developments in the field of ultrasonic testing. We have advanced techniques such as Time of Flight Diffraction (TOFD) which has better probability of detection for linear defects. A major irritant during the application of TOFD, especially for the testing of carbon steel weldments, is the presence of noise. A variety of approaches has been used internationally for the suppression of such noise and each has its own merits and demerits. This paper focuses on a method of enhancing the TOFD A-scan signals in carbon steel weldments by suppressing the noise from them using the discrete wavelet transform (DWT). The analysis clearly indicates that the DWT gives better signal-to-noise ratio improvement using higher-order wavelet filters with 4-level DWT decomposition. However the computational cost of this signal enhancement depends on the wavelet filter chosen along with the chosen level of DWT decomposition. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

Use of Ultrasound in Reconditioning by Welding of Tools Used in the Process of Regenerating Rubber

PubMed Central

Dobrotă, Dan; Petrescu, Valentin

2018-01-01

Addressing the problem of reconditioning large parts is of particular importance, due to their value and to the fact that the technologies for their reconditioning are very complex. The tools used to refine regenerated rubber which measure 660 mm in diameter and 2130 mm in length suffer from a rather fast dimensional wear. Within this research, the authors looked for a welding reconditioning procedure that would allow a very good adhesion between the deposited material layer and the base material. In this regard, the MAG (Metal Active Gas) welding process was used, but the ultrasonic activation of the welding process was also considered. Thus, the wire used for welding was activated considering a variation of the frequency of ultrasounds in the range f = 18–22 kHz respectively of the oscillation amplitude A = 30–60 μm. Under these conditions it was found that the presence of ultrasonic waves during the welding cladding process results in uniform deposition of hard carbons at the grain boundary and in the elimination of any existing oxides on the deposition surface, but at the same time increases the adhesion between the base material and the additional material, all of which positively influence the wear and corrosion resistance of the tools used to refine the regenerated rubber. PMID:29439400

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

Computer automation of ultrasonic testing. [inspection of ultrasonic welding

NASA Technical Reports Server (NTRS)

Yee, B. G. W.; Kerlin, E. E.; Gardner, A. H.; Dunmyer, D.; Wells, T. G.; Robinson, A. R.; Kunselman, J. S.; Walker, T. C.

1974-01-01

Report describes a prototype computer-automated ultrasonic system developed for the inspection of weldments. This system can be operated in three modes: manual, automatic, and computer-controlled. In the computer-controlled mode, the system will automatically acquire, process, analyze, store, and display ultrasonic inspection data in real-time. Flaw size (in cross-section), location (depth), and type (porosity-like or crack-like) can be automatically discerned and displayed. The results and pertinent parameters are recorded.

Development of an ultrasonic weld inspection system based on image processing and neural networks

NASA Astrophysics Data System (ADS)

Roca Barceló, Fernando; Jaén del Hierro, Pedro; Ribes Llario, Fran; Real Herráiz, Julia

2018-04-01

Several types of discontinuities and defects may be present on a weld, thus leading to a considerable reduction of its resistance. Therefore, ensuring a high welding quality and reliability has become a matter of key importance for many construction and industrial activities. Among the non-destructive weld testing and inspection techniques, the time-of-flight diffraction (TOFD) arises as a very safe (no ionising radiation), precise, reliable and versatile practice. However, this technique presents a relevant drawback, associated to the appearance of speckle noise that should be addressed. In this regard, this paper presents a new, intelligent and automatic method for weld inspection and analysis, based on TOFD, image processing and neural networks. The developed system is capable of detecting weld defects and imperfections with accuracy, and classify them into different categories.

Advanced Welding Concepts

NASA Technical Reports Server (NTRS)

Ding, Robert J.

2010-01-01

Four advanced welding techniques and their use in NASA are briefly reviewed in this poster presentation. The welding techniques reviewed are: Solid State Welding, Friction Stir Welding (FSW), Thermal Stir Welding (TSW) and Ultrasonic Stir Welding.

Applying a nonlinear, pitch-catch, ultrasonic technique for the detection of kissing bonds in friction stir welds.

PubMed

Delrue, Steven; Tabatabaeipour, Morteza; Hettler, Jan; Van Den Abeele, Koen

2016-05-01

Friction stir welding (FSW) is a promising technology for the joining of aluminum alloys and other metallic admixtures that are hard to weld by conventional fusion welding. Although FSW generally provides better fatigue properties than traditional fusion welding methods, fatigue properties are still significantly lower than for the base material. Apart from voids, kissing bonds for instance, in the form of closed cracks propagating along the interface of the stirred and heat affected zone, are inherent features of the weld and can be considered as one of the main causes of a reduced fatigue life of FSW in comparison to the base material. The main problem with kissing bond defects in FSW, is that they currently are very difficult to detect using existing NDT methods. Besides, in most cases, the defects are not directly accessible from the exposed surface. Therefore, new techniques capable of detecting small kissing bond flaws need to be introduced. In the present paper, a novel and practical approach is introduced based on a nonlinear, single-sided, ultrasonic technique. The proposed inspection technique uses two single element transducers, with the first transducer transmitting an ultrasonic signal that focuses the ultrasonic waves at the bottom side of the sample where cracks are most likely to occur. The large amount of energy at the focus activates the kissing bond, resulting in the generation of nonlinear features in the wave propagation. These nonlinear features are then captured by the second transducer operating in pitch-catch mode, and are analyzed, using pulse inversion, to reveal the presence of a defect. The performance of the proposed nonlinear, pitch-catch technique, is first illustrated using a numerical study of an aluminum sample containing simple, vertically oriented, incipient cracks. Later, the proposed technique is also applied experimentally on a real-life friction stir welded butt joint containing a kissing bond flaw. Copyright © 2016

Determination of Flaw Type and Location Using an Expert Module in Ultrasonic Nondestructive Testing for Weld Inspection

NASA Astrophysics Data System (ADS)

Shahriari, D.; Zolfaghari, A.; Masoumi, F.

2011-01-01

Nondestructive evaluation is explained as nondestructive testing, nondestructive inspection, and nondestructive examination. It is a desire to determine some characteristic of the object or to determine whether the object contains irregularities, discontinuities, or flaws. Ultrasound based inspection techniques are used extensively throughout industry for detection of flaws in engineering materials. The range and variety of imperfections encountered is large, and critical assessment of location, size, orientation and type is often difficult. In addition, increasing quality requirements of new standards and codes of practice relating to fitness for purpose are placing higher demands on operators. Applying of an expert knowledge-based analysis in ultrasonic examination is a powerful tool that can help assure safety, quality, and reliability; increase productivity; decrease liability; and save money. In this research, an expert module system is coupled with ultrasonic examination (A-Scan Procedure) to determine and evaluate type and location of flaws that embedded during welding parts. The processing module of this expert system is implemented based on EN standard to classify welding defects, acceptance condition and measuring of their location via echo static pattern and image processing. The designed module introduces new system that can automate evaluating of the results of A-scan method according to EN standard. It can simultaneously recognize the number and type of defects, and determine flaw position during each scan.

Process Control and Development for Ultrasonic Additive Manufacturing with Embedded Fibers

NASA Astrophysics Data System (ADS)

Hehr, Adam J.

Ultrasonic additive manufacturing (UAM) is a recent additive manufacturing technology which combines ultrasonic metal welding, CNC machining, and mechanized foil layering to create large gapless near net-shape metallic parts. The process has been attracting much attention lately due to its low formation temperature, the capability to join dissimilar metals, and the ability to create complex design features not possible with traditional subtractive processes alone. These process attributes enable light-weighting of structures and components in an unprecedented way. However, UAM is currently limited to niche areas due to the lack of quality tracking and inadequate scientific understanding of the process. As a result, this thesis work is focused on improving both component quality tracking and process understanding through the use of average electrical power input to the welder. Additionally, the understanding and application space of embedding fibers into metals using UAM is investigated, with particular focus on NiTi shape memory alloy fibers.

Modelling and control for laser based welding processes: modern methods of process control to improve quality of laser-based joining methods

NASA Astrophysics Data System (ADS)

Zäh, Ralf-Kilian; Mosbach, Benedikt; Hollwich, Jan; Faupel, Benedikt

2017-02-01

To ensure the competitiveness of manufacturing companies it is indispensable to optimize their manufacturing processes. Slight variations of process parameters and machine settings have only marginally effects on the product quality. Therefore, the largest possible editing window is required. Such parameters are, for example, the movement of the laser beam across the component for the laser keyhole welding. That`s why it is necessary to keep the formation of welding seams within specified limits. Therefore, the quality of laser welding processes is ensured, by using post-process methods, like ultrasonic inspection, or special in-process methods. These in-process systems only achieve a simple evaluation which shows whether the weld seam is acceptable or not. Furthermore, in-process systems use no feedback for changing the control variables such as speed of the laser or adjustment of laser power. In this paper the research group presents current results of the research field of Online Monitoring, Online Controlling and Model predictive controlling in laser welding processes to increase the product quality. To record the characteristics of the welding process, tested online methods are used during the process. Based on the measurement data, a state space model is ascertained, which includes all the control variables of the system. Depending on simulation tools the model predictive controller (MPC) is designed for the model and integrated into an NI-Real-Time-System.

Propagation characteristics of ultrasonic guided waves in continuously welded rail

NASA Astrophysics Data System (ADS)

Yao, Wenqing; Sheng, Fuwei; Wei, Xiaoyuan; Zhang, Lei; Yang, Yuan

2017-07-01

Rail defects cause numerous railway accidents. Trains are derailed and serious consequences often occur. Compared to traditional bulk wave testing, ultrasonic guided waves (UGWs) can provide larger monitoring ranges and complete coverage of the waveguide cross-section. These advantages are of significant importance for the non-destructive testing (NDT) of the continuously welded rail, and the technique is therefore widely used in high-speed railways. UGWs in continuous welded rail (CWR) and their propagation characteristics have been discussed in this paper. Finite element methods (FEMs) were used to accomplish a vibration modal analysis, which is extended by a subsequent dispersion analysis. Wave structure features were illustrated by displacement profiles. It was concluded that guided waves have the ability to detect defects in the rail via choice of proper mode and frequency. Additionally, thermal conduction that is caused by temperature variation in the rail is added into modeling and simulation. The results indicated that unbalanced thermal distribution may lead to the attenuation of UGWs in the rail.

Dynamics of ultrasonic additive manufacturing.

PubMed

Hehr, Adam; Dapino, Marcelo J

2017-01-01

Ultrasonic additive manufacturing (UAM) is a solid-state technology for joining similar and dissimilar metal foils near room temperature by scrubbing them together with ultrasonic vibrations under pressure. Structural dynamics of the welding assembly and work piece influence how energy is transferred during the process and ultimately, part quality. To understand the effect of structural dynamics during UAM, a linear time-invariant model is proposed to relate the inputs of shear force and electric current to resultant welder velocity and voltage. Measured frequency response and operating performance of the welder under no load is used to identify model parameters. Using this model and in-situ measurements, shear force and welder efficiency are estimated to be near 2000N and 80% when welding Al 6061-H18 weld foil, respectively. Shear force and welder efficiency have never been estimated before in UAM. The influence of processing conditions, i.e., welder amplitude, normal force, and weld speed, on shear force and welder efficiency are investigated. Welder velocity was found to strongly influence the shear force magnitude and efficiency while normal force and weld speed showed little to no influence. The proposed model is used to describe high frequency harmonic content in the velocity response of the welder during welding operations and coupling of the UAM build with the welder. Copyright © 2016 Elsevier B.V. All rights reserved.

Thermal Stir Welding: A New Solid State Welding Process

NASA Technical Reports Server (NTRS)

Ding, R. Jeffrey

2003-01-01

Thermal stir welding is a new welding process developed at NASA's Marshall Space Flight Center in Huntsville, AL. Thermal stir welding is similar to friction stir welding in that it joins similar or dissimilar materials without melting the parent material. However, unlike friction stir welding, the heating, stirring and forging elements of the process are all independent of each other and are separately controlled. Furthermore, the heating element of the process can be either a solid-state process (such as a thermal blanket, induction type process, etc), or, a fusion process (YG laser, plasma torch, etc.) The separation of the heating, stirring, forging elements of the process allows more degrees of freedom for greater process control. This paper introduces the mechanics of the thermal stir welding process. In addition, weld mechanical property data is presented for selected alloys as well as metallurgical analysis.

Thermal Stir Welding: A New Solid State Welding Process

NASA Technical Reports Server (NTRS)

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

2002-01-01

Thermal stir welding is a new welding process developed at NASA's Marshall Space Flight Center in Huntsville, AL. Thermal stir welding is similar to friction stir welding in that it joins similar or dissimilar materials without melting the parent material. However, unlike friction stir welding, the heating, stirring and forging elements of the process are all independent of each other and are separately controlled. Furthermore, the heating element of the process can be either a solid-state process (such as a thermal blanket, induction type process, etc), or, a fusion process (YG laser, plasma torch, etc.) The separation of the heating, stirring, forging elements of the process allows more degrees of freedom for greater process control. This paper introduces the mechanics of the thermal stir welding process. In addition, weld mechanical property data is presented for selected alloys as well as metallurgical analysis.

Immersion probe arrays for rapid pipeline weld inspection

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

Lebsack, S.; Heckhauser, H.

In 1992, F.H. Gottfeld, Herne, Germany, a member of the SGA Group (Societe Generale de Surveillance) and Krautkramer Branson, Koin, undertook production of a rapid automated ultrasonic testing (UT) system to inspect manually and machine welded pipeline girth welds. The result of the project is a system called MIPA, or multiple immersion probe array. The advantages of using UT to detect certain weld defects have been realized for many years, however for some applications the time required for UT has been a limiting factor. Where time has not been a factor, automated ultrasonic technology has advanced a reliable solution tomore » many inspection problems across a broad industrial base. The recent past has seen the entrance of automated ultrasonic technology into the harsh and demanding environment of pipelay operations, However, the use of these systems has been focused on automated welding processes. Their effectiveness for manual pipeline welding inspection is contested. This is due to the infinite variability of the joint alignment and shape that is unavoidable even when highly skilled welders are used.« less

Effect of Zinc Coatings on Joint Properties and Interfacial Reactions in Aluminum to Steel Ultrasonic Spot Welding

NASA Astrophysics Data System (ADS)

Haddadi, F.; Strong, D.; Prangnell, P. B.

2012-03-01

Dissimilar joining of aluminum to steel sheet in multimaterial automotive structures is an important potential application of ultrasonic spot welding (USW). Here, the weldability of different zinc-coated steels with aluminum is discussed, using a 2.5-kW USW welder. Results show that soft hot-dipped zinc (DX56-Z)-coated steel results in better weld performance than hard (galv-annealed) zinc coatings (DX53-ZF). For Al to hard galv-annealed-coated steel welds, lap shear strengths reached a maximum of ~80% of the strength of an Al-Al joint after a 1.0 s welding time. In comparison, welds between Al6111-T4 and hot dipped soft zinc-coated steel took longer to achieve the same maximum strength, but nearly matched the Al-Al joint properties. The reasons for these different behaviors are discussed in terms of the interfacial reactions between the weld members.

Comparison of ultrasonic suture welding and traditional knot tying in a rabbit rotator cuff repair model.

PubMed

Nho, Shane J; Cole, Brian J; Mazzocca, Augustus D; Williams, James M; Romeo, Anthony A; Bush-Joseph, Charles A; Bach, Bernard R; Hallab, Nadim J

2006-01-01

The purpose of this study is to evaluate ultrasonic suture welding of monofilament suture in an animal model of rotator cuff repair with biomechanical and histologic analyses. We randomly assigned 46 shoulders in 23 rabbits to 1 of 3 treatment groups: sham-operated (n = 15), knotted (n = 15), and welded (n = 16). Supraspinatus defects were surgically created and acutely repaired with suture anchors loaded with either No. 2-0 Ethibond for knotted group or No. 2-0 nylon for welded shoulders. Eighteen weeks postoperatively, all animals were killed, and the shoulders underwent either biomechanical testing or histologic analysis. The maximum stress of the sham-operated group (20.6 N/mm2) was significantly greater than that of both the knotted (10.2 N/mm2) and welded (8.3 N/mm2) groups (P < .05), but no differences were observed between the knotted and welded groups. Although some histologic changes were noted, none was considered to be significant to distinguish either group.

Thermal Stir Welding: A New Solid State Welding Process

NASA Technical Reports Server (NTRS)

Ding, R. Jeffery; Munafo, Paul M. (Technical Monitor)

2002-01-01

Thermal Stir Shielding is a revolutionary new welding process developed at NASA's Marshall Space Flight Center in Huntsville, AL. Thermal stir welding is similar to friction stir welding in that it joins similar or dissimilar materials without melting the parent material. However, unlike friction stir welding, the heating and stirring functions are independent allowing more degrees of freedom for greater process control. This paper introduces the mechanics of the thermal stir welding process. In addition, weld mechanical property data is presented for selected alloys as well as metallurgical analysis.

Effect of Brass Interlayer Sheet on Microstructure and Joint Performance of Ultrasonic Spot-Welded Copper-Steel Joints

NASA Astrophysics Data System (ADS)

Satpathy, Mantra Prasad; Kumar, Abhishek; Sahoo, Susanta Kumar

2017-07-01

Solid-state ultrasonic spot welding (USW) inevitably offers a potential solution for joining dissimilar metal combination like copper (Cu) and steel (SS). In this study, the USW has been performed on Cu (UNS C10100) and SS (AISI 304) with brass interlayer by varying various welding parameters, aiming to identify the interfacial reaction, changes in microstructure and weld strength. The highest tensile shear and T-peel failure loads of 1277 and 174 N are achieved at the optimum conditions like 68 µm of vibration amplitude, 0.42 MPa of weld pressure and 1 s of weld time. The fractured surface analysis of brass interlayer and AISI 304 stainless steel samples reveals the features like swirls, voids and intermetallic compounds (IMCs). These IMCs are composed of CuZn and FeZn composite-like structures with 1.0 μm thickness. This confirms that the weld quality is specifically sensitive to the levels of input parameter combinations as well as the type of material present on the sonotrode side.

Welding induced residual stress evaluation using laser-generated Rayleigh waves

NASA Astrophysics Data System (ADS)

Ye, Chong; Zhou, Yuanlai; Reddy, Vishnu V. B.; Mebane, Aaron; Ume, I. Charles

2018-04-01

Welding induced residual stress could affect the dimensional stability, fatigue life, and chemical resistance of the weld joints. Ultrasonic method serves as an important non-destructive tool for the residual stress evaluation due to its easy implementation, low cost and wide application to different materials. Residual stress would result in the ultrasonic wave velocity variation, which is the so called acoustoelastic effect. In this paper, Laser/EMAT ultrasonic technique was proposed to experimentally study the relative velocity variation ΔV/V of Rayleigh wave, which has the potential to evaluate surface/subsurface longitudinal residual stress developed during the Gas Metal Arc Welding process. Broad band ultrasonic waves were excited by pulsed Q-Switched Nd: YAG laser. An electromagnetic acoustic transducer (EMAT) attached to the welded plates was used to capture the Rayleigh wave signals propagating along the weld seam direction. Different time of flight measurements were conducted by varying the distance between the weld seam and Rayleigh wave propagating path in the range of 0 to 45 mm. The maximum relative velocity difference was found on the weld seam. With the increasing distance away from the weld seam, the relative velocity difference sharply decreased to negative value. With further increase in distance, the relative velocity difference slowly increased and approached zero. The distribution of relative velocity variations indicates that tensile stress appears in the melted zone as it becomes compressive near the heat-affected zone.

Survey of welding processes.

DOT National Transportation Integrated Search

2003-07-01

The current KYTC SPECIAL PROVISION NO. 4 WELDING STEEL BRIDGES prohibits the use of welding processes other than shielded metal arc welding (SMAW) and submerged arc welding (SAW). Nationally, bridge welding is codified under ANSI/AASHTO/AWS D1....

Pearson's Functions to Describe FSW Weld Geometry

NASA Astrophysics Data System (ADS)

Lacombe, D.; Gutierrez-Orrantia, M. E.; Coupard, D.; Tcherniaeff, S.; Girot, F.

2011-01-01

Friction stir welding (FSW) is a relatively new joining technique particularly for aluminium alloys that are difficult to fusion weld. In this study, the geometry of the weld has been investigated and modelled using Pearson's functions. It has been demonstrated that the Pearson's parameters (mean, standard deviation, skewness, kurtosis and geometric constant) can be used to characterize the weld geometry and the tensile strength of the weld assembly. Pearson's parameters and process parameters are strongly correlated allowing to define a control process procedure for FSW assemblies which make radiographic or ultrasonic controls unnecessary. Finally, an optimisation using a Generalized Gradient Method allows to determine the geometry of the weld which maximises the assembly tensile strength.

Sustainability of Welding Process through Bobbin Friction Stir Welding

NASA Astrophysics Data System (ADS)

Sued, M. K.; Samsuri, S. S. M.; Kassim, M. K. A. M.; Nasir, S. N. N. M.

2018-03-01

Welding process is in high demand, which required a competitive technology to be adopted. This is important for sustaining the needs of the joining industries without ignoring the impact of the process to the environment. Friction stir welding (FSW) is stated to be benefitting the environment through low energy consumption, which cannot be achieved through traditional arc welding. However, this is not well documented, especially for bobbin friction stir welding (BFSW). Therefore, an investigation is conducted by measuring current consumption of the machine during the BFSW process. From the measurement, different phases of BFSW welding process and its electrical demand are presented. It is found that in general total energy in BFSW is about 130kW inclusive of all identified process phases. The phase that utilise for joint formation is in weld phase that used the highest total energy of 120kWs. The recorded total energy is still far below the traditional welding technology and the conventional friction stir welding (CFSW) energy demand. This indicates that BFSW technology with its vast benefit able to sustain the joining technology in near future.

Effect of Interfacial Reaction on the Mechanical Performance of Steel to Aluminum Dissimilar Ultrasonic Spot Welds

NASA Astrophysics Data System (ADS)

Xu, Lei; Wang, Li; Chen, Ying-Chun; Robson, Joe D.; Prangnell, Philip B.

2016-01-01

The early stages of formation of intermetallic compounds (IMC) have been investigated in dissimilar aluminum to steel welds, manufactured by high power (2.5 kW) ultrasonic spot welding (USW). To better understand the influence of alloy composition, welds were produced between a low-carbon steel (DC04) and two different aluminum alloys (6111 and 7055). The joint strengths were measured in lap shear tests and the formation and growth behavior of IMCs at the weld interface were characterized by electron microscopy, for welding times from 0.2 to 2.4 seconds. With the material combinations studied, the η (Fe2Al5) intermetallic phase was found to form first, very rapidly in the initial stage of welding, with a discontinuous island morphology. Continuous layers of η and then θ (FeAl3) phase were subsequently seen to develop on extending the welding time to greater than 0.7 second. The IMC layer formed in the DC04-AA7055 combination grew thicker than for the DC04-AA6111 welds, despite both weld sets having near identical thermal histories. Zinc was also found to be dissolved in the IMC phases when welding with the AA7055 alloy. After post-weld aging of the aluminum alloy, fracture in the lap shear tests always occurred along the joint interface; however, the DC04-AA6111 welds had higher fracture energy than the DC04-AA7055 combination.

Fusion welding process

DOEpatents

Thomas, Kenneth C.; Jones, Eric D.; McBride, Marvin A.

1983-01-01

A process for the fusion welding of nickel alloy steel members wherein a ferrite containing pellet is inserted into a cavity in one member and melted by a welding torch. The resulting weld nugget, a fusion of the nickel containing alloy from the members to be welded and the pellet, has a composition which is sufficiently low in nickel content such that ferrite phases occur within the weld nugget, resulting in improved weld properties. The steel alloys encompassed also include alloys containing carbon and manganese, considered nickel equivalents.

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.

Signal quality enhancement using higher order wavelets for ultrasonic TOFD signals from austenitic stainless steel welds.

PubMed

Praveen, Angam; Vijayarekha, K; Abraham, Saju T; Venkatraman, B

2013-09-01

Time of flight diffraction (TOFD) technique is a well-developed ultrasonic non-destructive testing (NDT) method and has been applied successfully for accurate sizing of defects in metallic materials. This technique was developed in early 1970s as a means for accurate sizing and positioning of cracks in nuclear components became very popular in the late 1990s and is today being widely used in various industries for weld inspection. One of the main advantages of TOFD is that, apart from fast technique, it provides higher probability of detection for linear defects. Since TOFD is based on diffraction of sound waves from the extremities of the defect compared to reflection from planar faces as in pulse echo and phased array, the resultant signal would be quite weak and signal to noise ratio (SNR) low. In many cases the defect signal is submerged in this noise making it difficult for detection, positioning and sizing. Several signal processing methods such as digital filtering, Split Spectrum Processing (SSP), Hilbert Transform and Correlation techniques have been developed in order to suppress unwanted noise and enhance the quality of the defect signal which can thus be used for characterization of defects and the material. Wavelet Transform based thresholding techniques have been applied largely for de-noising of ultrasonic signals. However in this paper, higher order wavelets are used for analyzing the de-noising performance for TOFD signals obtained from Austenitic Stainless Steel welds. It is observed that higher order wavelets give greater SNR improvement compared to the lower order wavelets. Copyright © 2013 Elsevier B.V. All rights reserved.

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

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

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

2014-08-01

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

Deconvoluting the Friction Stir Weld Process for Optimizing Welds

NASA Technical Reports Server (NTRS)

Schneider, Judy; Nunes, Arthur C.

2008-01-01

In the friction stir welding process, the rotating surfaces of the pin and shoulder contact the weld metal and force a rotational flow within the weld metal. Heat, generated by the metal deformation as well as frictional slippage with the contact surface, softens the metal and makes it easier to deform. As in any thermo-mechanical processing of metal, the flow conditions are critical to the quality of the weld. For example, extrusion of metal from under the shoulder of an excessively hot weld may relax local pressure and result in wormhole defects. The trace of the weld joint in the wake of the weld may vary geometrically depending upon the flow streamlines around the tool with some geometry more vulnerable to loss of strength from joint contamination than others. The material flow path around the tool cannot be seen in real time during the weld. By using analytical "tools" based upon the principles of mathematics and physics, a weld model can be created to compute features that can be observed. By comparing the computed observations with actual data, the weld model can be validated or adjusted to get better agreement. Inputs to the model to predict weld structures and properties include: hot working properties ofthe metal, pin tool geometry, travel rate, rotation and plunge force. Since metals record their prior hot working history, the hot working conditions imparted during FSW can be quantified by interpreting the final microstructure. Variations in texture and grain size result from variations in the strain accommodated at a given strain rate and temperature. Microstructural data from a variety of FSWs has been correlated with prior marker studies to contribute to our understanding of the FSW process. Once this stage is reached, the weld modeling process can save significant development costs by reducing costly trial-and-error approaches to obtaining quality welds.

Detection and assessment of flaws in friction stir welded metallic plates

NASA Astrophysics Data System (ADS)

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

2017-04-01

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

Effects of Ultrasonic Nanocrystal Surface Modification on the Residual Stress, Microstructure, and Corrosion Resistance of 304 Stainless Steel Welds

NASA Astrophysics Data System (ADS)

Ye, Chang; Telang, Abhishek; Gill, Amrinder; Wen, Xingshuo; Mannava, Seetha R.; Qian, Dong; Vasudevan, Vijay K.

2018-03-01

In this study, ultrasonic nanocrystal surface modification (UNSM) of 304 stainless steel welds was carried out. UNSM effectively eliminates the tensile stress generated during welding and imparts beneficial compressive residual stresses. In addition, UNSM can effectively refine the grains and increase hardness in the near-surface region. Corrosion tests in boiling MgCl2 solution demonstrate that UNSM can significantly improve the corrosion resistance due to the compressive residual stresses and changes in the near-surface microstructure.

Artificial Intelligence Assists Ultrasonic Inspection

NASA Technical Reports Server (NTRS)

Schaefer, Lloyd A.; Willenberg, James D.

1992-01-01

Subtle indications of flaws extracted from ultrasonic waveforms. Ultrasonic-inspection system uses artificial intelligence to help in identification of hidden flaws in electron-beam-welded castings. System involves application of flaw-classification logic to analysis of ultrasonic waveforms.

Robot welding process control

NASA Technical Reports Server (NTRS)

Romine, Peter L.

1991-01-01

This final report documents the development and installation of software and hardware for Robotic Welding Process Control. Primary emphasis is on serial communications between the CYRO 750 robotic welder, Heurikon minicomputer running Hunter & Ready VRTX, and an IBM PC/AT, for offline programming and control and closed-loop welding control. The requirements for completion of the implementation of the Rocketdyne weld tracking control are discussed. The procedure for downloading programs from the Intergraph, over the network, is discussed. Conclusions are made on the results of this task, and recommendations are made for efficient implementation of communications, weld process control development, and advanced process control procedures using the Heurikon.

Laser welding process in PP moulding parts: Evaluation of seam performance

NASA Astrophysics Data System (ADS)

Oliveira, N.; Pontes, A. J.

2015-12-01

The Polypropylene is one of the most versatile polymer materials used in the industry. Due to this versatility, it is possible to use it in different products. This material can also be mixed with several additives namely glass fiber, carbon nanotubes, etc. This compatibility with different additives allows also obtaining products with characteristics that goes from an impact absorber to an electricity conductor. When is necessary to join components in PP they could be welded through hot plate, ultrasonic weld and also by laser. This study had the objective of study the influence of several variables, capable of influence the final quality of the seam. In this case were studied variables of the injection molding process as mold temperature and cooling time. Was also studied laser welding variables and different materials. The results showed that the variables that have the most influence were mould temperature, laser velocity and laser diameter. The seams were analyzed using Optical Microscopy technique. The seams showed perfect contact between the materials analyzed, despite the high standard variation presented in the mechanical testes.

Studies on thermo-elastic heating of horns used in ultrasonic plastic welding.

PubMed

Roopa Rani, M; Prakasan, K; Rudramoorthy, R

2015-01-01

Ultrasonic welding horn is half wavelength section or tool used to focus the ultrasonic vibrations to the components being welded. The horn is designed in such a way that it maximizes the amplitude of the sound wave passing through it. The ends of the horn represent the displacement anti-nodes and the center the 'node' of the wave. As the horns perform 20,000 cycles of expansion and contraction per second, they are highly stressed at the nodes and are heated owing to thermo-elastic effects. Considerable temperature rise may be observed in the horn, at the nodal region when working at high amplitudes indicating high stress levels leading to failure of horns due to cyclic loading. The limits for amplitude must therefore be evaluated for the safe working of the horn. Horns made of different materials have different thermo-elastic behaviors and hence different temperatures at the nodes and antinodes. This temperature field can be used as a control mechanism for setting the amplitude/weld parameters. Safe stress levels can be predicted using modal and harmonic analyses followed by a stress analysis to study the effect of cyclic loads. These are achieved using 'Ansys'. The maximum amplitude level obtained from the stress analysis is used as input for 'Comsol' to predict the temperature field. The actual temperature developed in the horn during operation is measured using infrared camera and compared with the simulated temperature. From experiments, it is observed that horn made of titanium had the lowest temperature rise at the critical region and can be expected to operate at amplitudes up to 77 μm without suffering failure due to cyclic loading. The method of predicting thermo-elastic stresses and temperature may be adopted by the industry for operating the horn within the safe stress limits thereby extending the life of the horn. Copyright © 2014 Elsevier B.V. All rights reserved.

Processing ultrasonic inspection data from multiple scan patterns for turbine rotor weld build-up evaluations

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

Guan, Xuefei; Zhou, S. Kevin; Rasselkorde, El Mahjoub

The study presents a data processing methodology for weld build-up using multiple scan patterns. To achieve an overall high probability of detection for flaws with different orientations, an inspection procedure with three different scan patterns is proposed. The three scan patterns are radial-tangential longitude wave pattern, axial-radial longitude wave pattern, and tangential shear wave pattern. Scientific fusion of the inspection data is implemented using volume reconstruction techniques. The idea is to perform spatial domain forward data mapping for all sampling points. A conservative scheme is employed to handle the case that multiple sampling points are mapped to one grid location.more » The scheme assigns the maximum value for the grid location to retain the largest equivalent reflector size for the location. The methodology is demonstrated and validated using a realistic ring of weld build-up. Tungsten balls and bars are embedded to the weld build-up during manufacturing process to represent natural flaws. Flat bottomed holes and side drilled holes are installed as artificial flaws. Automatic flaw identification and extraction are demonstrated. Results indicate the inspection procedure with multiple scan patterns can identify all the artificial and natural flaws.« less

Processing ultrasonic inspection data from multiple scan patterns for turbine rotor weld build-up evaluations

NASA Astrophysics Data System (ADS)

Guan, Xuefei; Rasselkorde, El Mahjoub; Abbasi, Waheed; Zhou, S. Kevin

2015-03-01

The study presents a data processing methodology for weld build-up using multiple scan patterns. To achieve an overall high probability of detection for flaws with different orientations, an inspection procedure with three different scan patterns is proposed. The three scan patterns are radial-tangential longitude wave pattern, axial-radial longitude wave pattern, and tangential shear wave pattern. Scientific fusion of the inspection data is implemented using volume reconstruction techniques. The idea is to perform spatial domain forward data mapping for all sampling points. A conservative scheme is employed to handle the case that multiple sampling points are mapped to one grid location. The scheme assigns the maximum value for the grid location to retain the largest equivalent reflector size for the location. The methodology is demonstrated and validated using a realistic ring of weld build-up. Tungsten balls and bars are embedded to the weld build-up during manufacturing process to represent natural flaws. Flat bottomed holes and side drilled holes are installed as artificial flaws. Automatic flaw identification and extraction are demonstrated. Results indicate the inspection procedure with multiple scan patterns can identify all the artificial and natural flaws.

Inspection apparatus for evaluating a partially completed weld

DOEpatents

Smartt, Herschel B.; Larsen, Eric D.; Johnson, Jonn A.

2001-01-01

An inspection apparatus for evaluating a partially completed weld is described and which is utilized in combination with an automated movable welder which moves across a supporting surface, and wherein the inspection apparatus includes a coupling member mounted on the welder; a frame member mounted on the coupling member; an ultrasonic sensor mounted on the frame member and disposed in ultrasonic sound transmitting relation relative to the partially completed weld; and a drive assembly for adjusting the position of the ultrasonic sensor relative to the partially completed weld.

Novel Round Energy Director for Use with Servo-driven Ultrasonic Welder

NASA Astrophysics Data System (ADS)

Savitski, Alex; Klinstein, Leo; Holt, Kenneth

Increasingly stringent process repeatability and precision of assembly requirements are common for high-volume manufacturing for electronic, automotive and especially medical device industries, in which components for disposable medication delivery devices are produced in hundreds of millions annually. Ultrasonic welding, one of the most efficient of plastic welding processes often joins these small plastic parts together, and quite possibly, the one most broadly adopted for high volume assembly. The very fundamental factor in ultrasonic welding process performance is a proper joint design, the most common of which is a design utilizing an energy director. Keeping the energy director size and shape consistent on a part-to-part basis in high volume, multi-cavity operations presents a constant challenge to molded part vendors, as dimensional variations from cavity to cavity and variations in the molding process are always present. A newly developed concept of energy director design, when the tip of the energy director is round, addresses these problems, as the round energy director is significantly easier to mold and maintain its dimensional consistency. It also eliminates a major source of process variability for assembly operations. Materializing the benefits of new type of joint design became possible with the introduction of servo-driven ultrasonic welders, which allow an unprecedented control of material flow during the welding cycle and results in significantly improved process repeatability. This article summarizes results of recent studies focused on evaluating performance of round energy director and investigating the main factors responsible for the joint quality.

Laser ablated micropillar energy directors for ultrasonic welding of microfluidic systems

NASA Astrophysics Data System (ADS)

Esben Poulsen, Carl; Kistrup, Kasper; Korsgaard Andersen, Nis; Taboryski, Rafael; Fougt Hansen, Mikkel; Wolff, Anders

2016-06-01

We present a new type of energy director (ED) for ultrasonic welding of microfluidic systems. These micropillar EDs are based on the replication of cone like protrusion structures introduced using a pico-second laser and may therefore be added to any mould surface accessible to a pico-second laser beam. The technology is demonstrated on an injection moulded microfluidic device featuring high-aspect ratio (h  ×  w  =  2000 μm  ×  550 μm) and free-standing channel walls, where bonding is achieved with no detectable channel deformation. The bonding strength is similar to conventional EDs and the fabricated system can withstand pressures of over 9.5 bar.

Experiment and numerical simulation for laser ultrasonic measurement of residual stress.

PubMed

Zhan, Yu; Liu, Changsheng; Kong, Xiangwei; Lin, Zhongya

2017-01-01

Laser ultrasonic is a most promising method for non-destructive evaluation of residual stress. The residual stress of thin steel plate is measured by laser ultrasonic technique. The pre-stress loading device is designed which can easily realize the condition of the specimen being laser ultrasonic tested at the same time in the known stress state. By the method of pre-stress loading, the acoustoelastic constants are obtained and the effect of different test directions on the results of surface wave velocity measurement is discussed. On the basis of known acoustoelastic constants, the longitudinal and transverse welding residual stresses are measured by the laser ultrasonic technique. The finite element method is used to simulate the process of surface wave detection of welding residual stress. The pulsed laser is equivalent to the surface load and the relationship between the physical parameters of the laser and the load is established by the correction coefficient. The welding residual stress of the specimen is realized by the ABAQUS function module of predefined field. The results of finite element analysis are in good agreement with the experimental method. The simple and effective numerical and experimental methods for laser ultrasonic measurement of residual stress are demonstrated. Copyright © 2016. Published by Elsevier B.V.

Emissions of fluorides from welding processes.

PubMed

Szewczyńska, Małgorzata; Pągowska, Emilia; Pyrzyńska, Krystyna

2015-11-01

The levels of fluoride airborne particulates emitted from welding processes were investigated. They were sampled with the patented IOM Sampler, developed by J. H. Vincent and D. Mark at the Institute of Occupational Medicine (IOM), personal inhalable sampler for simultaneous collection of the inhalable and respirable size fractions. Ion chromatography with conductometric detection was used for quantitative analysis. The efficiency of fluoride extraction from the cellulose filter of the IOM sampler was examined using the standard sample of urban air particle matter SRM-1648a. The best results for extraction were obtained when water and the anionic surfactant N-Cetyl-N-N-N-trimethylammonium bromide (CTAB) were used in an ultrasonic bath. The limits of detection and quantification for the whole procedure were 8μg/L and 24μg/L, respectively. The linear range of calibration was 0.01-10mg/L, which corresponds to 0.0001-0.1mg of fluorides per m(3) in collection of a 20L air sample. The concentration of fluorides in the respirable fraction of collected air samples was in the range of 0.20-1.82mg/m(3), while the inhalable fraction contained 0.23-1.96mg/m(3) of fluorides during an eight-hour working day in the welding room. Copyright © 2015. Published by Elsevier B.V.

Microstructure and Fatigue Properties of Ultrasonic Spot Welded Joints of Aluminum 5754 Alloy

NASA Astrophysics Data System (ADS)

Mirza, F. A.; Macwan, A.; Bhole, S. D.; Chen, D. L.

2016-05-01

The purpose of this investigation was to evaluate the microstructural change, lap shear tensile load, and fatigue resistance of ultrasonic spot welded joints of aluminum 5754 alloy for automotive applications. A unique "necklace"-type structure with very fine equiaxed grains was observed to form along the weld line due to the mechanical interlocking coupled with the occurrence of dynamic recrystallization. The maximum lap shear tensile strength of 85 MPa and the fatigue limit of about 0.5 kN (at 1 × 107 cycles) were achieved. The tensile fracture occurred at the Al/Al interface in the case of lower energy inputs, and at the edge of nugget zone in the case of higher energy inputs. The maximum cyclic stress for the transition of fatigue fracture mode from the transverse through-thickness crack growth to the interfacial failure increased with increasing energy input. Fatigue crack propagation was mainly characterized by the formation of fatigue striations, which usually appeared perpendicular to the fatigue crack propagation.

[New welding processes and health effects of welding].

PubMed

La Vecchia, G Marina; Maestrelli, Piero

2011-01-01

This paper describes some of the recent developments in the control technology to enhance capability of Pulse Gas Metal Arc Welding. Friction Stir Welding (FSW) processing has been also considered. FSW is a new solid-state joining technique. Heat generated by friction at the rotating tool softens the material being welded. FSW can be considered a green and energy-efficient technique without deleterious fumes, gas, radiation, and noise. Application of new welding processes is limited and studies on health effects in exposed workers are lacking. Acute and chronic health effects of conventional welding have been described. Metal fume fever and cross-shift decline of lung function are the main acute respiratory effects. Skin and eyes may be affected by heat, electricity and UV radiations. Chronic effects on respiratory system include chronic bronchitis, a benign pneumoconiosis (siderosis), asthma, and a possible increase in the incidence of lung cancer. Pulmonary infections are increased in terms of severity, duration, and frequency among welders.

Semiconductor measurement technology: Microelectronic ultrasonic bonding

NASA Technical Reports Server (NTRS)

Harman, G. G. (Editor)

1974-01-01

Information for making high quality ultrasonic wire bonds is presented as well as data to provide a basic understanding of the ultrasonic systems used. The work emphasizes problems and methods of solving them. The required measurement equipment is first introduced. This is followed by procedures and techniques used in setting up a bonding machine, and then various machine- or operator-induced reliability problems are discussed. The characterization of the ultrasonic system and its problems are followed by in-process bonding studies and work on the ultrasonic bonding (welding) mechanism. The report concludes with a discussion of various effects of bond geometry and wire metallurgical characteristics. Where appropriate, the latest, most accurate value of a particular measurement has been substituted for an earlier reported one.

Ultrasonic weld testing.

DOT National Transportation Integrated Search

1970-12-01

The study was broken down into two phases. Phase I consisted of a laboratory investigation of test specimens to determine the reliability of the ultrasonic equipment and testing procedure. Phase II was a field study where the knowledge, skills and ab...

Welds in thermoplastic composite materials

NASA Astrophysics Data System (ADS)

Taylor, N. S.

Welding methods are reviewed that can be effectively used for joining of thermoplastic composites and continuous-fiber thermoplastics. Attention is given to the use of ultrasonic, vibration, hot-plate, resistance, and induction welding techniques. The welding techniques are shown to provide complementary weld qualities for the range of thermoplastic materials that are of interest to industrial and technological applications.

Thermal stir welding process

NASA Technical Reports Server (NTRS)

Ding, R. Jeffrey (Inventor)

2012-01-01

A welding method is provided for forming a weld joint between first and second elements of a workpiece. The method includes heating the first and second elements to form an interface of material in a plasticized or melted state interface between the elements. The interface material is then allowed to cool to a plasticized state if previously in a melted state. The interface material, while in the plasticized state, is then mixed, for example, using a grinding/extruding process, to remove any dendritic-type weld microstructures introduced into the interface material during the heating process.

Welding process modelling and control

NASA Technical Reports Server (NTRS)

Romine, Peter L.; Adenwala, Jinen A.

1993-01-01

The research and analysis performed, and software developed, and hardware/software recommendations made during 1992 in development of the PC-based data acquisition system for support of Welding Process Modeling and Control is reported. A need was identified by the Metals Processing Branch of NASA Marshall Space Flight Center, for a mobile data aquisition and analysis system, customized for welding measurement and calibration. Several hardware configurations were evaluated and a PC-based system was chosen. The Welding Measurement System (WMS) is a dedicated instrument, strictly for the use of data aquisition and analysis. Although the WMS supports many of the functions associated with the process control, it is not the intention for this system to be used for welding process control.

The development of recent high-power ultrasonic transducers for Near-well ultrasonic processing technology.

PubMed

Wang, Zhenjun; Xu, Yuanming

2017-07-01

With the reduction of crude oil throughout the world, enhance oil recovery technology has become a major oil research topics, which can greatly increase the recovery ratio of the crude oil before the dawning of renewable energy era. Near-well ultrasonic processing technology, as one new method, has attracted more attention for Enhanced Oil Recovery due to its low cost, good applicability and no environmental pollution in recent rears. There are two important relevant aspects about Near-well ultrasonic processing technology: (a) how to enhance the oil flow through the rocks into the pumping pool and (b) how to reduce the oil viscosity so that it can be easier to pump. Therefore, how to design a high-power ultrasonic equipment with excellent performance is crucial for Near-well ultrasonic processing technology. In this paper, recent new high-power ultrasonic transducers for Near-well ultrasonic processing technology are summarized. Each field application of them are also given. The purpose of this paper is to provide reference for the further development of Near-well ultrasonic processing technology. With the reduction of crude oil throughout the world, enhance oil recovery technology has become a major oil research topics, which can greatly increase the recovery ratio of the crude oil before the dawning of renewable energy era. Near-well ultrasonic processing technology, as one new method, has attracted more attention for Enhanced Oil Recovery due to its low cost, good applicability and no environmental pollution in recent rears. There are two important relevant aspects about Near-well ultrasonic processing technology: (a) how to enhance the oil flow through the rocks into the pumping pool and (b) how to reduce the oil viscosity so that it can be easier to pump. Therefore, how to design a high-power ultrasonic equipment with excellent performance is crucial for Near-well ultrasonic processing technology. In this paper, recent new high-power ultrasonic transducers

Analysis of droplet transfer mode and forming process of weld bead in CO 2 laser-MAG hybrid welding process

NASA Astrophysics Data System (ADS)

Liu, Shuangyu; Liu, Fengde; Zhang, Hong; Shi, Yan

2012-06-01

In this paper, CO 2 laser-metal active gas (MAG) hybrid welding technique is used to weld high strength steel and the optimized process parameters are obtained. Using LD Pumped laser with an emission wavelength of 532 nm to overcome the strong interference from the welding arc, a computer-based system is developed to collect and visualize the waveforms of the electrical welding parameters and metal transfer processes in laser-MAG. The welding electric signals of hybrid welding processes are quantitatively described and analyzed using the ANALYSATOR HANNOVER. The effect of distance between laser and arc ( DLA) on weld bead geometry, forming process of weld shape, electric signals, arc characteristic and droplet transfer behavior is investigated. It is found that arc characteristic, droplet transfer mode and final weld bead geometry are strongly affected by the distance between laser and arc. The weld bead geometry is changed from "cocktail cup" to "cone-shaped" with the increasing DLA. The droplet transfer mode is changed from globular transfer to projected transfer with the increasing DLA. Projected transfer mode is an advantage for the stability of hybrid welding processes.

Solid State Welding Development at Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Ding, Robert J.; Walker, Bryant

2012-01-01

What is TSW and USW? TSW is a solid state weld process consisting of an induction coil heating source, a stir rod, and non-rotating containment plates Independent heating, stirring and forging controls Decouples the heating, stirring and forging process elements of FSW. USW is a solid state weld process consisting of an induction coil heating source, a stir rod, and a non-rotating containment plate; Ultrasonic energy integrated into non-rotating containment plate and stir rod; Independent heating, stirring and forging controls; Decouples the heating, stirring and forging process elements of FSW.

Plasma Processes of Cutting and Welding

DTIC Science & Technology

1976-02-01

TIG process. 2.2.2 Keyhole Welding In plasma arc welding , the term...Cutting 3 3 4 4 4 2.2 Plasma Arc Welding 5 2.2.1 Needle Arc Welding 2.2.2 Keyhole Welding 5 6 3. Applications 8 93.1 Economics 4. Environmental Aspects of...Arc Lengths III. Needle Arc Welding Conditions IV. Keyhole Welding Conditions v. Chemical Analyses of Plates Used - vii - 1. 2. 3. 4. 5. 6. 7. 8.

Welding of Thin Steel Plates by Hybrid Welding Process Combined TIG Arc with YAG Laser

NASA Astrophysics Data System (ADS)

Kim, Taewon; Suga, Yasuo; Koike, Takashi

TIG arc welding and laser welding are used widely in the world. However, these welding processes have some advantages and problems respectively. In order to improve problems and make use of advantages of the arc welding and the laser welding processes, hybrid welding process combined the TIG arc with the YAG laser was studied. Especially, the suitable welding conditions for thin steel plate welding were investigated to obtain sound weld with beautiful surface and back beads but without weld defects. As a result, it was confirmed that the shot position of the laser beam is very important to obtain sound welds in hybrid welding. Therefore, a new intelligent system to monitor the welding area using vision sensor is constructed. Furthermore, control system to shot the laser beam to a selected position in molten pool, which is formed by TIG arc, is constructed. As a result of welding experiments using these systems, it is confirmed that the hybrid welding process and the control system are effective on the stable welding of thin stainless steel plates.

Friction stir welding tool and process for welding dissimilar materials

DOEpatents

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

2013-05-07

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

Quality improvement of polymer parts by laser welding

NASA Astrophysics Data System (ADS)

Puetz, Heidrun; Treusch, Hans-Georg; Welz, M.; Petring, Dirk; Beyer, Eckhard; Herziger, Gerd

1994-09-01

The growing significance of laser technology in industrial manufacturing is also observed in case of plastic industry. Laser cutting and marking are established processes. Laser beam welding is successfully practiced in processes like joining foils or winding reinforced prepregs. Laser radiation and its significant advantages of contactless and local heating could even be an alternative to conventional welding processes using heating elements, vibration or ultrasonic waves as energy sources. Developments in the field of laser diodes increase the interest in laser technology for material processing because in the near future they will represent an inexpensive energy source.

Experimental investigation on the weld pool formation process in plasma keyhole arc welding

NASA Astrophysics Data System (ADS)

Van Anh, Nguyen; Tashiro, Shinichi; Van Hanh, Bui; Tanaka, Manabu

2018-01-01

This paper seeks to clarify the weld pool formation process in plasma keyhole arc welding (PKAW). We adopted, for the first time, the measurement of the 3D convection inside the weld pool in PKAW by stereo synchronous imaging of tungsten tracer particles using two sets of x-ray transmission systems. The 2D convection on the weld pool surface was also measured using zirconia tracer particles. Through these measurements, the convection in a wide range of weld pools from the vicinity of the keyhole to the rear region was successfully visualized. In order to discuss the heat transport process in a weld pool, the 2D temperature distribution on the weld pool surface was also measured by two-color pyrometry. The results of the comprehensive experimental measurement indicate that the shear force due to plasma flow is found to be the dominant driving force in the weld pool formation process in PKAW. Thus, heat transport in a weld pool is considered to be governed by two large convective patterns near the keyhole: (1) eddy pairs on the surface (perpendicular to the torch axis), and (2) eddy pairs on the bulk of the weld pool (on the plane of the torch). They are formed with an equal velocity of approximately 0.35 m s-1 and are mainly driven by shear force. Furthermore, the flow velocity of the weld pool convection becomes considerably higher than that of other welding processes, such as TIG welding and GMA welding, due to larger plasma flow velocity.

Development of a pseudo phased array technique using EMATs for DM weld testing

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

Cobb, Adam C., E-mail: adam.cobb@swri.org; Fisher, Jay L., E-mail: adam.cobb@swri.org; Shiokawa, Nobuyuki

2015-03-31

Ultrasonic inspection of dissimilar metal (DM) welds in piping with cast austenitic stainless steel (CASS) has been an area ongoing research for many years given its prevalence in the petrochemical and nuclear industries. A typical inspection strategy for pipe welds is to use an ultrasonic phased array system to scan the weld from a sensor located on the outer surface of the pipe. These inspection systems generally refract either longitudinal or shear vertical (SV) waves at varying angles to inspect the weld radially. In DM welds, however, the welding process can produce a columnar grain structure in the CASS materialmore » in a specific orientation. This columnar grain structure can skew ultrasonic waves away from their intended path, especially for SV and longitudinal wave modes. Studies have shown that inspection using the shear horizontal (SH) wave mode significantly reduces the effect of skewing. Electromagnetic acoustic transducers (EMATs) are known to be effective for producing SH waves in field settings. This paper presents an inspection strategy that seeks to reproduce the scanning and imaging capabilities of a commercial phase array system using EMATs. A custom-built EMAT was used to collect data at multiple propagation angles, and a processing strategy known as the synthetic aperture focusing technique (SAFT) was used to combine the data to produce an image. Results are shown using this pseudo phased array technique to inspect samples with a DM weld and artificial defects, demonstrating the potential of this approach in a laboratory setting. Recommendations for future work to transition the technique to the field are also provided.« less

Thermo-Mechanical Processing in Friction Stir Welds

NASA Technical Reports Server (NTRS)

Schneider, Judy

2003-01-01

Friction stir welding is a solid-phase joining, or welding process that was invented in 1991 at The Welding Institute (TWI). The process is potentially capable of joining a wide variety of aluminum alloys that are traditionally difficult to fusion weld. The friction stir welding (FSW) process produces welds by moving a non-consumable rotating pin tool along a seam between work pieces that are firmly clamped to an anvil. At the start of the process, the rotating pin is plunged into the material to a pre-determined load. The required heat is produced by a combination of frictional and deformation heating. The shape of the tool shoulder and supporting anvil promotes a high hydrostatic pressure along the joint line as the tool shears and literally stirs the metal together. To produce a defect free weld, process variables (RPM, transverse speed, and downward force) and tool pin design must be chosen carefully. An accurate model of the material flow during the process is necessary to guide process variable selection. At MSFC a plastic slip line model of the process has been synthesized based on macroscopic images of the resulting weld material. Although this model appears to have captured the main features of the process, material specific interactions are not understood. The objective of the present research was to develop a basic understanding of the evolution of the microstructure to be able to relate it to the deformation process variables of strain, strain rate, and temperature.

Diffractive beam shaping for enhanced laser polymer welding

NASA Astrophysics Data System (ADS)

Rauschenberger, J.; Vogler, D.; Raab, C.; Gubler, U.

2015-03-01

Laser welding of polymers increasingly finds application in a large number of industries such as medical technology, automotive, consumer electronics, textiles or packaging. More and more, it replaces other welding technologies for polymers, e. g. hot-plate, vibration or ultrasonic welding. At the same rate, demands on the quality of the weld, the flexibility of the production system and on processing speed have increased. Traditionally, diode lasers were employed for plastic welding with flat-top beam profiles. With the advent of fiber lasers with excellent beam quality, the possibility to modify and optimize the beam profile by beam-shaping elements has opened. Diffractive optical elements (DOE) can play a crucial role in optimizing the laser intensity profile towards the optimal M-shape beam for enhanced weld seam quality. We present results on significantly improved weld seam width constancy and enlarged process windows compared to Gaussian or flat-top beam profiles. Configurations in which the laser beam diameter and shape can be adapted and optimized without changing or aligning the laser, fiber-optic cable or optical head are shown.

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

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.

Ultrasonic cavitation erosion of 316L steel weld joint in liquid Pb-Bi eutectic alloy at 550°C.

PubMed

Lei, Yucheng; Chang, Hongxia; Guo, Xiaokai; Li, Tianqing; Xiao, Longren

2017-11-01

Liquid lead-bismuth eutectic alloy (LBE) is applied in the Accelerator Driven transmutation System (ADS) as the high-power spallation neutron targets and coolant. A 19.2kHz ultrasonic device was deployed in liquid LBE at 550°C to induce short and long period cavitation erosion damage on the surface of weld joint, SEM and Atomic force microscopy (AFM) were used to map out the surface properties, and Energy Dispersive Spectrometer (EDS) was applied to the qualitative and quantitative analysis of elements in the micro region of the surface. The erosion mechanism for how the cavitation erosion evolved by studying the element changes, their morphology evolution, the surface hardness and the roughness evolution, was proposed. The results showed that the pits, caters and cracks appeared gradually on the erode surface after a period of cavitation. The surface roughness increased along with exposure time. Work hardening by the bubbles impact in the incubation stage strengthened the cavitation resistance efficiently. The dissolution and oxidation corrosion and cavitation erosion that simultaneously happened in liquid LBE accelerated corrosion-erosion process, and these two processes combined to cause more serious damage on the material surface. Contrast to the performance of weld metal, base metal exhibited a much better cavitation resistance. Copyright © 2017. Published by Elsevier B.V.

Performance Improvement of Friction Stir Welds by Better Surface Finish

NASA Technical Reports Server (NTRS)

Russell, Sam; Nettles, Mindy

2015-01-01

The as-welded friction stir weld has a cross section that may act as a stress concentrator. The geometry associated with the stress concentration may reduce the weld strength and it makes the weld challenging to inspect with ultrasound. In some cases, the geometry leads to false positive nondestructive evaluation (NDE) indications and, in many cases, it requires manual blending to facilitate the inspection. This study will measure the stress concentration effect and develop an improved phased array ultrasound testing (PAUT) technique for friction stir welding. Post-welding, the friction stir weld (FSW) tool would be fitted with an end mill that would machine the weld smooth, trimmed shaved. This would eliminate the need for manual weld preparation for ultrasonic inspections. Manual surface preparation is a hand operation that varies widely depending on the person preparing the welds. Shaving is a process that can be automated and tightly controlled.

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

NASA Astrophysics Data System (ADS)

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

2010-10-01

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

Development of the weld-braze joining process

NASA Technical Reports Server (NTRS)

Bales, T. T.; Royster, D. M.; Arnold, W. E., Jr.

1973-01-01

A joining process, designated weld-brazing, was developed which combines resistance spot welding and brazing. Resistance spot welding is used to position and aline the parts, as well as to establish a suitable faying-surface gap for brazing. Fabrication is then completed at elevated temperature by capillary flow of the braze alloy into the joint. The process was used successfully to fabricate Ti-6Al-4V alloy joints by using 3003 aluminum braze alloy and should be applicable to other metal-braze systems. Test results obtained on single-overlap and hat-stiffened panel specimens show that weld-brazed joints were superior in tensile shear, stress rupture, fatigue, and buckling compared with joints fabricated by conventional means. Another attractive feature of the process is that the brazed joint is hermetically sealed by the braze material, which may eliminate many of the sealing problems encountered with riveted or spot welded structures. The relative ease of fabrication associated with the weld-brazing process may make it cost effective over conventional joining techniques.

Optimization of Gas Metal Arc Welding Process Parameters

NASA Astrophysics Data System (ADS)

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

2016-09-01

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

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

Fabrication and characterization of metal-packaged fiber Bragg grating sensor by one-step ultrasonic welding

NASA Astrophysics Data System (ADS)

Zhang, Yumin; Zhu, Lianqing; Luo, Fei; Dong, Mingli; Ding, Xiangdong; He, Wei

2016-06-01

A metallic packaging technique of fiber Bragg grating (FBG) sensors is developed for measurement of strain and temperature, and it can be simply achieved via one-step ultrasonic welding. The average strain transfer rate of the metal-packaged sensor is theoretically evaluated by a proposed model aiming at surface-bonded metallic packaging FBG. According to analytical results, the metallic packaging shows higher average strain transfer rate compared with traditional adhesive packaging under the same packaging conditions. Strain tests are performed on an elaborate uniform strength beam for both tensile and compressive strains; strain sensitivities of approximately 1.16 and 1.30 pm/μɛ are obtained for the tensile and compressive situations, respectively. Temperature rising and cooling tests are also executed from 50°C to 200°C, and the sensitivity of temperature is 36.59 pm/°C. All the measurements of strain and temperature exhibit good linearity and stability. These results demonstrate that the metal-packaged sensors can be successfully fabricated by one-step welding technique and provide great promise for long-term and high-precision structural health monitoring.

Resistance welding graphite-fiber composites

NASA Technical Reports Server (NTRS)

Lamoureux, R. T.

1980-01-01

High-strength joints are welded in seconds in carbon-reinfored thermoplastic beams. Resistance-welding electrode applies heat and pressure to joint and is spring-loaded to follow softening material to maintain contact; it also holds parts together for cooling and hardening. Both transverse and longitudinal configurations can be welded. Adhesive bonding and encapsulation are more time consuming methods and introduce additional material into joint, while ultrasonic heating can damage graphite fibers in composite.

Possibilities in optical monitoring of laser welding process

NASA Astrophysics Data System (ADS)

Horník, Petr; Mrňa, Libor; Pavelka, Jan

2016-11-01

Laser welding is a modern, widely used but still not really common method of welding. With increasing demands on the quality of the welds, it is usual to apply automated machine welding and with on-line monitoring of the welding process. The resulting quality of the weld is largely affected by the behavior of keyhole. However, its direct observation during the welding process is practically impossible and it is necessary to use indirect methods. At ISI we have developed optical methods of monitoring the process. Most advanced is an analysis of radiation of laser-induced plasma plume forming in the keyhole where changes in the frequency of the plasma bursts are monitored and evaluated using Fourier and autocorrelation analysis. Another solution, robust and suitable for industry, is based on the observation of the keyhole inlet opening through a coaxial camera mounted in the welding head and the subsequent image processing by computer vision methods. A high-speed camera is used to understand the dynamics of the plasma plume. Through optical spectroscopy of the plume, we can study the excitation of elements in a material. It is also beneficial to monitor the gas flow of shielding gas using schlieren method.

Quality status display for a vibration welding process

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

Spicer, John Patrick; Abell, Jeffrey A.; Wincek, Michael Anthony

A method includes receiving, during a vibration welding process, a set of sensory signals from a collection of sensors positioned with respect to a work piece during formation of a weld on or within the work piece. The method also includes receiving control signals from a welding controller during the process, with the control signals causing the welding horn to vibrate at a calibrated frequency, and processing the received sensory and control signals using a host machine. Additionally, the method includes displaying a predicted weld quality status on a surface of the work piece using a status projector. The methodmore » may include identifying and display a quality status of a suspect weld. The laser projector may project a laser beam directly onto or immediately adjacent to the suspect welds, e.g., as a red, green, blue laser or a gas laser having a switched color filter.« 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.

Evaluation of the AISI 904L Alloy Weld Overlays Obtained by GMAW and Electro-Slag Welding Processes

NASA Astrophysics Data System (ADS)

Jorge, Jorge C. F.; Meira, O. G.; Madalena, F. C. A.; de Souza, L. F. G.; Araujo, L. S.; Mendes, M. C.

2017-05-01

The use of superaustenitic stainless steels (SASS) as an overlay replacement for nickel-based alloys can be an interesting alternative for the oil and gas industries, due to its lower cost, when compared to superalloys. Usually, the deposition is made with several welding passes by using conventional arc welding processes, such as gas tungsten arc welding (GTAW) or gas metal arc welding (GMAW) processes. In this respect, electro-slag welding (ESW), which promotes high heat inputs and low dilution of the welds, can also be attractive for this application, as it provides a higher productivity, once only one layer is needed for the deposition of the minimum thickness required. The present work evaluates the behavior of an AISI 904L SASS weld overlay deposited on a carbon steel ASTM A516 Grade 70 by ESW and GMAW processes. Both as-welded and heat-treated conditions were evaluated and compared. A multipass welding by GMAW process with three layers and 48 passes was performed on 12.5 × 200 × 250 mm steel plates with average welding energy of 1.0 kJ/mm. For ESW process, only one layer was deposited on 50 × 400 × 400 mm steel plates with average welding energy of 11.7 kJ/mm. After welding, a post-weld heat treatment (PWHT) at 620 °C for 10 h was performed in half of the steel plate, in order to allow the comparison between this condition and the as-welded one. For both processes, the austenitic microstructure of the weld deposits was characterized by optical microscopy and scanning electron microscopy with electron backscatter diffraction. A low proportion of secondary phases were observed in all conditions, and the PWHT did not promote significant changes on the hardness profile. Martensite for GMAW process and bainite for ESW process were the microstructural constituents observed at the coarse grain heat-affected zone, due to the different cooling rates. For ESW process, no evidences of partially diluted zones were found. As a consequence of the microstructural

WELDING PROCESS

DOEpatents

Zambrow, J.; Hausner, H.

1957-09-24

A method of joining metal parts for the preparation of relatively long, thin fuel element cores of uranium or alloys thereof for nuclear reactors is described. The process includes the steps of cleaning the surfaces to be jointed, placing the sunfaces together, and providing between and in contact with them, a layer of a compound in finely divided form that is decomposable to metal by heat. The fuel element members are then heated at the contact zone and maintained under pressure during the heating to decompose the compound to metal and sinter the members and reduced metal together producing a weld. The preferred class of decomposable compounds are the metal hydrides such as uranium hydride, which release hydrogen thus providing a reducing atmosphere in the vicinity of the welding operation.

Shimmed electron beam welding process

DOEpatents

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

2002-01-01

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

Matrix phased array (MPA) imaging technology for resistance spot welds

NASA Astrophysics Data System (ADS)

Na, Jeong K.; Gleeson, Sean T.

2014-02-01

A three-dimensional MPA probe has been incorporated with a high speed phased array electronic board to visualize nugget images of resistance spot welds. The primary application area of this battery operated portable MPA ultrasonic imaging system is in the automotive industry which a conventional destructive testing process is commonly adopted to check the quality of resistance spot welds in auto bodies. Considering an average of five-thousand spot welds in a medium size passenger vehicle, the amount of time and effort given to popping the welds and measuring nugget size are immeasurable in addition to the millions of dollars' worth of scrap metals recycled per plant per year. This wasteful labor intensive destructive testing process has become less reliable as auto body sheet metal has transitioned from thick and heavy mild steels to thin and light high strength steels. Consequently, the necessity of developing a non-destructive inspection methodology has become inevitable. In this paper, the fundamental aspects of the current 3-D probe design, data acquisition algorithms, and weld nugget imaging process are discussed.

Matrix phased array (MPA) imaging technology for resistance spot welds

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

Na, Jeong K.; Gleeson, Sean T.

2014-02-18

A three-dimensional MPA probe has been incorporated with a high speed phased array electronic board to visualize nugget images of resistance spot welds. The primary application area of this battery operated portable MPA ultrasonic imaging system is in the automotive industry which a conventional destructive testing process is commonly adopted to check the quality of resistance spot welds in auto bodies. Considering an average of five-thousand spot welds in a medium size passenger vehicle, the amount of time and effort given to popping the welds and measuring nugget size are immeasurable in addition to the millions of dollars' worth ofmore » scrap metals recycled per plant per year. This wasteful labor intensive destructive testing process has become less reliable as auto body sheet metal has transitioned from thick and heavy mild steels to thin and light high strength steels. Consequently, the necessity of developing a non-destructive inspection methodology has become inevitable. In this paper, the fundamental aspects of the current 3-D probe design, data acquisition algorithms, and weld nugget imaging process are discussed.« less

Recent Developments for Ultrasonic-Assisted Friction Stir Welding: Joining, Testing, Corrosion - an Overview

NASA Astrophysics Data System (ADS)

Thomä, M.; Wagner, G.; Straß, B.; Conrad, C.; Wolter, B.; Benfer, S.; Fürbeth, W.

2016-03-01

Due to the steadily increasing demand on innovative manufacturing processes, modern lightweight construction concepts become more and more important. Especially joints of dissimilar metals offer a variety of advantages due to their high potential for lightweight construction. The focus of the investigations was Al/Mg-joints. Friction Stir Welding (FSW) is an efficient process to realize high strength joints between these materials in ductile condition. Furthermore, for a simultaneous transmission of power ultrasound during the FSW-process (US-FSW) a positive effect on the achievable tensile strength of the Al/Mg-joints was proven. In the present work the industrial used die cast alloys EN AC-48000 (AlSi12CuNiMg) and AZ80 (MgAl8Zn) were joined by a machining center modified especially for Ultrasound Supported Friction Stir Welding. The appearing welding zone and the formation of intermetallic phases under the influence of power ultrasound were examined in particular. In order to identify optimal process parameters extensive preliminary process analyzes have been carried out. Following this, an ultrasound-induced more intensive stirring of the joining zone and as a result of this a considerably modified intermetallic zone was detected. At the same time an increase of the tensile strength of about 25% for US-FSW-joints and for fatigue an up to three times higher number of cycles to failure in comparison to a conventional welding process was observed. Moreover, detailed corrosion analyzes have shown that especially the welding zone was influenced by the corrosive attack. To expand and deepen the knowledge of the US-FSW-process further material combinations such as Ti/Steel and Al/Steel will be considered in future.

Development of Inspection for Friction Stir Welds for Rocket Fuel Tanks

NASA Technical Reports Server (NTRS)

Russell, Samuel S.

2012-01-01

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

Process Model for Friction Stir Welding

NASA Technical Reports Server (NTRS)

Adams, Glynn

1996-01-01

Friction stir welding (FSW) is a relatively new process being applied for joining of metal alloys. The process was initially developed by The Welding Institute (TWI) in Cambridge, UK. The FSW process is being investigated at NASA/MSEC as a repair/initial weld procedure for fabrication of the super-light-weight aluminum-lithium shuttle external tank. The FSW investigations at MSFC were conducted on a horizontal mill to produce butt welds of flat plate material. The weldment plates are butted together and fixed to a backing plate on the mill bed. A pin tool is placed into the tool holder of the mill spindle and rotated at approximately 400 rpm. The pin tool is then plunged into the plates such that the center of the probe lies at, one end of the line of contact, between the plates and the shoulder of the pin tool penetrates the top surface of the weldment. The weld is produced by traversing the tool along the line of contact between the plates. A lead angle allows the leading edge of the shoulder to remain above the top surface of the plate. The work presented here is the first attempt at modeling a complex phenomenon. The mechanical aspects of conducting the weld process are easily defined and the process itself is controlled by relatively few input parameters. However, in the region of the weld, plasticizing and forging of the parent material occurs. These are difficult processes to model. The model presented here addresses only variations in the radial dimension outward from the pin tool axis. Examinations of the grain structure of the weld reveal that a considerable amount of material deformation also occurs in the direction parallel to the pin tool axis of rotation, through the material thickness. In addition, measurements of the axial load on the pin tool demonstrate that the forging affect of the pin tool shoulder is an important process phenomenon. Therefore, the model needs to be expanded to account for the deformations through the material thickness and the

Optimization of process parameters in welding of dissimilar steels using robot TIG welding

NASA Astrophysics Data System (ADS)

Navaneeswar Reddy, G.; VenkataRamana, M.

2018-03-01

Robot TIG welding is a modern technique used for joining two work pieces with high precision. Design of Experiments is used to conduct experiments by varying weld parameters like current, wire feed and travelling speed. The welding parameters play important role in joining of dissimilar stainless steel SS 304L and SS430. In this work, influences of welding parameter on Robot TIG Welded specimens are investigated using Response Surface Methodology. The Micro Vickers hardness tests of the weldments are measured. The process parameters are optimized to maximize the hardness of the weldments.

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

NASA Astrophysics Data System (ADS)

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

2006-01-01

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

Peculiarities of metal welding process modelling for the Arctic

NASA Astrophysics Data System (ADS)

Lagunov, Alexey; Fofanov, Andrey; Losunov, Anton

2017-09-01

M etal being rather tough has been used in the Arctic for a long time. In severe weather conditions metal construction is subject to strong corrosion and erosion. These processes affect the welds particular strongly. Violation of weld integrity leads to the different industrial accidents. Therefore, the welding quality is given such a strong focus. M ost high-quality welding is obtained if welding zone is provided with gas what eliminates the influence of oxygen on the process. But in this case it is very difficult to find the right concentration, gas pressure, direction of the jet. Study of the welding process using video and photography is expensive, in terms of money and time. Mathematical modelling of welding process using the program FlowVision enables to solve this issue at less cost. It's essential that obtained results qualitatively conform to the experimental ones and can be used in real application.

Ultrasonic Phased Array Evaluation of Control Rod Drive Mechanism (CRDM) Nozzle Interference Fit and Weld Region

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

Cinson, Anthony D.; Crawford, Susan L.; MacFarlan, Paul J.

2011-07-31

Ultrasonic phased array data were collected on a removed-from-service CRDM nozzle specimen to assess a previously reported leak path. First a mock-up CRDM specimen was evaluated that contained two 0.076-mm (3.0-mil) interference fit regions formed from an actual Inconel CRDM tube and two 152.4-mm (6.0-in.) thick carbon steel blocks. One interference fit region has a series of precision crafted electric discharge machining (EDM) notches at various lengths, widths, depths, and spatial separations for establishing probe sensitivity, resolution and calibration. The other interference fit has zones of boric acid (crystal form) spaced periodically between the tube and block to represent anmore » actively leaking CRDM nozzle assembly in the field. Ultrasonic phased-array evaluations were conducted using an immersion 8-element annular 5.0-MHz probe from the tube inner diameter (ID). A variety of focal laws were employed to evaluate the interference fit regions and J grove weld, where applicable. Responses from the mock-up specimen were evaluated to determine detection limits and characterization ability as well as contrast the ultrasonic response differences with the presence of boric acid in the fit region. Nozzle 63, from the North Anna Unit-2 nuclear power plant, was evaluated to assess leakage path(s) and was destructively dismantled to allow a visual verification of the leak path(s).« less

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

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

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.

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.

Thin Wall Pipe Ultrasonic Inspection through Paint Coating

NASA Astrophysics Data System (ADS)

Predoi, Mihai Valentin; Petre, Cristian Cătălin

Classical ultrasonic inspection of welds is currently done for plates thicker than 8 mm. The inspection of but welds in thin walled pipes has considerable implementation difficulties, due to guided waves dominating ultrasonic pulses propagation. Generation of purely symmetric modes, either torsional or longitudinal, requires a circumferential uniform distribution of transducers and dedicated inspection equipment, which are increasing the inspection costs. Moreover, if the surface is paint coated, the received signals are close to the detection level. The present work implies a single transducer, coupled to the painted surface. The proper choice of the guided mode and frequency range, allows the detection of a standard, small diameter through thickness hole. In this way, the inspection of pipe welds can use the same equipment as for thick materials, with only wedge adaptation.

High-power ultrasonic processing: Recent developments and prospective advances

NASA Astrophysics Data System (ADS)

Gallego-Juarez, Juan A.

2010-01-01

Although the application of ultrasonic energy to produce or to enhance a wide variety of processes have been explored since about the middle of the 20th century, only a reduced number of ultrasonic processes have been established at industrial level. However, during the last ten years the interest in ultrasonic processing has revived particularly in industrial sectors where the ultrasonic technology may represent a clean and efficient tool to improve classical existing processes or an innovation alternative for the development of new processes. Such seems to be the case of relevant sectors such as food industry, environment, pharmaceuticals and chemicals manufacture, machinery, mining, etc where power ultrasound is becoming an emerging technology for process development. The possible major problem in the application of high-intensity ultrasound on industrial processing is the design and development of efficient power ultrasonic systems (generators and reactors) capable of large scale successful operation specifically adapted to each individual process. In the area of ultrasonic processing in fluid media and more specifically in gases, the development of the steppedplate transducers and other power ge with extensive radiating surface has strongly contributed to the implementation at semi-industrial and industrial stage of several commercial applications, in sectors such as food and beverage industry (defoaming, drying, extraction, etc), environment (air cleaning, sludge filtration, etc...), machinery and process for manufacturing (textile washing, paint manufacture, etc). The development of different cavitational reactors for liquid treatment in continuous flow is helping to introduce into industry the wide potential of the area of sonochemistry. Processes such as water and effluent treatment, crystallization, soil remediation, etc have been already implemented at semi-industrial and/or industrial stage. Other single advances in sectors like mining or energy have

Nondestructive Evaluation of Friction Stir-Welded Aluminum Alloy to Coated Steel Sheet Lap Joint

NASA Astrophysics Data System (ADS)

Das, H.; Kumar, A.; Rajkumar, K. V.; Saravanan, T.; Jayakumar, T.; Pal, Tapan Kumar

2015-11-01

Dissimilar lap joints of aluminum sheet (AA 6061) of 2 mm thickness and zinc-coated steel sheet of 1 mm thickness were produced by friction stir welding with different combinations of rotational speed and travel speed. Ultrasonic C- and B-scanning, and radiography have been used in a complementary manner for detection of volumetric (cavity and flash) and planar (de bond) defects as the defects are in micron level. Advanced ultrasonic C-scanning did not provide any idea about the defects, whereas B-scanning cross-sectional image showed an exclusive overview of the micron-level defects. A digital x-ray radiography methodology is proposed for quality assessment of the dissimilar welds which provide three-fold increase in signal-to-noise ratio with improved defect detection sensitivity. The present study clearly shows that the weld tool rotational speed and travel speed have a decisive role on the quality of the joints obtained by the friction stir welding process. The suitability of the proposed NDE techniques to evaluate the joint integrity of dissimilar FSW joints is thus established.

Product development using process monitoring and NDE data fusion

NASA Astrophysics Data System (ADS)

Peterson, Todd; Bossi, Richard H.

1998-03-01

Composite process/product development relies on both process monitoring information and nondestructive evaluation measurements for determining application suitability. In the past these activities have been performed and analyzed independently. Our present approach is to present the process monitoring and NDE data together in a data fusion workstation. This methodology leads to final product acceptance based on a combined process monitoring and NDE criteria. The data fusion work station combines process parameter and NDE data in a single workspace enabling all the data to be used in the acceptance/rejection decision process. An example application is the induction welding process, a unique joining method for assembling primary composite structure, that offers significant cost and weight advantages over traditional fasted structure. The determination of the required time, temperature and pressure conditions used in the process to achieve a complete weld is being aided by the use of ultrasonic inspection techniques. Full waveform ultrasonic inspection data is employed to evaluate the quality of spar cap to skin fit, an essential element of the welding process, and is processed to find a parameter that can be used for weld acceptance. Certification of the completed weld incorporates the data fusion methodology.

Process Simulation of Gas Metal Arc Welding Software

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

Murray, Paul E.

2005-09-06

ARCWELDER is a Windows-based application that simulates gas metal arc welding (GMAW) of steel and aluminum. The software simulates the welding process in an accurate and efficient manner, provides menu items for process parameter selection, and includes a graphical user interface with the option to animate the process. The user enters the base and electrode material, open circuit voltage, wire diameter, wire feed speed, welding speed, and standoff distance. The program computes the size and shape of a square-groove or V-groove weld in the flat position. The program also computes the current, arc voltage, arc length, electrode extension, transfer ofmore » droplets, heat input, filler metal deposition, base metal dilution, and centerline cooling rate, in English or SI units. The simulation may be used to select welding parameters that lead to desired operation conditions.« less

Ultrasonic imaging system for in-process fabric defect detection

DOEpatents

Sheen, Shuh-Haw; Chien, Hual-Te; Lawrence, William P.; Raptis, Apostolos C.

1997-01-01

An ultrasonic method and system are provided for monitoring a fabric to identify a defect. A plurality of ultrasonic transmitters generate ultrasonic waves relative to the fabric. An ultrasonic receiver means responsive to the generated ultrasonic waves from the transmitters receives ultrasonic waves coupled through the fabric and generates a signal. An integrated peak value of the generated signal is applied to a digital signal processor and is digitized. The digitized signal is processed to identify a defect in the fabric. The digitized signal processing includes a median value filtering step to filter out high frequency noise. Then a mean value and standard deviation of the median value filtered signal is calculated. The calculated mean value and standard deviation are compared with predetermined threshold values to identify a defect in the fabric.

An evaluation of welding processes to reduce hexavalent chromium exposures and reduce costs by using better welding techniques.

PubMed

Keane, Michael J

2014-01-01

A group of stainless steel arc welding processes was compared for emission rates of fume and hexavalent chromium, and costs per meter length of weld. The objective was to identify those with minimal emissions and also compare relative labor and consumables costs. The selection included flux-cored arc welding (FCAW), shielded-metal arc welding (SMAW), and multiple gas metal arc welding (GMAW) processes. Using a conical chamber, fumes were collected, and fume generation rates and hexavalent chromium (Cr(6+)) were measured. GMAW processes used were short-circuit (SC) and pulsed-spray modes. Flux-cored welding used gas shielding. Costs were estimated per meter of a 6.3-mm thick horizontal butt weld. Emission rates of Cr(6+) were lowest for GMAW processes and highest for SMAW; several GMAW processes had less than 2% of the SMAW generation rate. Labor and consumable costs for the processes studied were again highest for SMAW, with those of several GMAW types about half that cost. The results show that use of any of the GMAW processes (and flux-cored welding) could substantially reduce fume and Cr(6+) emissions, and greatly reduce costs relative to SMAW.

An Evaluation of Welding Processes to Reduce Hexavalent Chromium Exposures and Reduce Costs by Using Better Welding Techniques

PubMed Central

Keane, Michael J

2014-01-01

A group of stainless steel arc welding processes was compared for emission rates of fume and hexavalent chromium, and costs per meter length of weld. The objective was to identify those with minimal emissions and also compare relative labor and consumables costs. The selection included flux-cored arc welding (FCAW), shielded-metal arc welding (SMAW), and multiple gas metal arc welding (GMAW) processes. Using a conical chamber, fumes were collected, and fume generation rates and hexavalent chromium (Cr6+) were measured. GMAW processes used were short-circuit (SC) and pulsed-spray modes. Flux-cored welding used gas shielding. Costs were estimated per meter of a 6.3-mm thick horizontal butt weld. Emission rates of Cr6+ were lowest for GMAW processes and highest for SMAW; several GMAW processes had less than 2% of the SMAW generation rate. Labor and consumable costs for the processes studied were again highest for SMAW, with those of several GMAW types about half that cost. The results show that use of any of the GMAW processes (and flux-cored welding) could substantially reduce fume and Cr6+ emissions, and greatly reduce costs relative to SMAW. PMID:25574138

Ultrasonic fingerprinting by phased array transducer

NASA Astrophysics Data System (ADS)

Sednev, D.; Kataeva, O.; Abramets, V.; Pushenko, P.; Tverdokhlebova, T.

2016-06-01

Increasing quantity of spent nuclear fuel that must be under national and international control requires a novel approach to safeguard techniques and equipment. One of the proposed approaches is utilize intrinsic features of casks with spent fuel. In this article an application of a phased array ultrasonic method is considered. This study describes an experimental results on ultrasonic fingerprinting of austenitic steel seam weld.

Selecting Processes to Minimize Hexavalent Chromium from Stainless Steel Welding: Eight welding processes/shielding gas combinations were assessed for generation of hexavalent chromium in stainless steel welding fumes.

PubMed

Keane, M; Siert, A; Stone, S; Chen, B; Slaven, J; Cumpston, A; Antonini, J

2012-09-01

Eight welding processes/shielding gas combinations were assessed for generation of hexavalent chromium (Cr 6+ ) in stainless steel welding fumes. The processes examined were gas metal arc welding (GMAW) (axial spray, short circuit, and pulsed spray modes), flux cored arc welding (FCAW), and shielded metal arc welding (SMAW). The Cr 6+ fractions were measured in the fumes; fume generation rates, Cr 6+ generation rates, and Cr 6+ generation rates per unit mass of welding wire were determined. A limited controlled comparison study was done in a welding shop including SMAW, FCAW, and three GMAW methods. The processes studied were compared for costs, including relative labor costs. Results indicate the Cr 6+ in the fume varied widely, from a low of 2800 to a high of 34,000 ppm. Generation rates of Cr 6+ ranged from 69 to 7800 μg/min, and Cr 6+ generation rates per unit of wire ranged from 1 to 270 μg/g. The results of field study were similar to the findings in the laboratory. The Cr 6+ (ppm) in the fume did not necessarily correlate with the Cr 6+ generation rate. Physical properties were similar for the processes, with mass median aerodynamic diameters ranging from 250 to 336 nm, while the FCAW and SMAW fumes were larger (360 and 670 nm, respectively). The pulsed axial spray method was the best choice of the processes studied based on minimal fume generation, minimal Cr 6+ generation, and cost per weld. This method is usable in any position, has a high metal deposition rate, and is relatively simple to learn and use.

Advances in ultrasonic testing of austenitic stainless steel welds. Towards a 3D description of the material including attenuation and optimisation by inversion

NASA Astrophysics Data System (ADS)

Moysan, J.; Gueudré, C.; Ploix, M.-A.; Corneloup, G.; Guy, Ph.; Guerjouma, R. El; Chassignole, B.

In the case of multi-pass welds, the material is very difficult to describe due to its anisotropic and heterogeneous properties. Anisotropy results from the metal solidification and is correlated with the grain orientation. A precise description of the material is one of the key points to obtain reliable results with wave propagation codes. A first advance is the model MINA which predicts the grain orientations in multi-pass 316-L steel welds. For flat position welding, good predictions of the grains orientations were obtained using 2D modelling. In case of welding in position the resulting grain structure may be 3D oriented. We indicate how the MINA model can be improved for 3D description. A second advance is a good quantification of the attenuation. Precise measurements are obtained using plane waves angular spectrum method together with the computation of the transmission coefficients for triclinic material. With these two first advances, the third one is now possible: developing an inverse method to obtain the material description through ultrasonic measurements at different positions.

Apparatus for the concurrent inspection of partially completed welds

DOEpatents

Smartt, Herschel B.; Johnson, John A.; Larsen, Eric D.; Bitsoi, Rodney J.; Perrenoud, Ben C.; Miller, Karen S.; Pace, David P.

2002-01-01

An apparatus for the concurrent inspection of partially completed welds is described in which is utilized in combination with a moveable welder for forming a partially completed weld, and an ultrasonic generator mounted on a moveable welder in which is reciprocally moveable along a path of travel which is laterally disposed relative to the partially completed weld.

Physical characteristics of welding arc ignition process

NASA Astrophysics Data System (ADS)

Shi, Linan; Song, Yonglun; Xiao, Tianjiao; Ran, Guowei

2012-07-01

The existing research of welding arc mainly focuses on the stable combustion state and the research on the mechanism of welding arc ignition process is quite lack. The tungsten inert gas(TIG) touch arc ignition process is observed via a high speed camera and the high time resolution spectral diagnosis system. The changing phenomenon of main ionized element provided the electrons in the arc ignition is found. The metallic element is the main contributor to provide the electrons at the beginning of the discharging, and then the excitated shielding gas element replaces the function of the metallic element. The electron density during the period of the arc ignition is calculated by the Stark-broadened lines of Hα. Through the discussion with the repeatability in relaxation phenomenon, the statistical regularity in the arc ignition process is analyzed. The similar rules as above are observed through the comparison with the laser-assisted arc ignition experiments and the metal inert gas(MIG) arc ignition experiments. This research is helpful to further understanding on the generation mechanism of welding arc ignition and also has a certain academic and practical significance on enriching the welding physical theoretical foundation and improving the precise monitoring on automatic arc welding process.

Sustainability assessment of shielded metal arc welding (SMAW) process

NASA Astrophysics Data System (ADS)

Alkahla, Ibrahim; Pervaiz, Salman

2017-09-01

Shielded metal arc welding (SMAW) process is one of the most commonly employed material joining processes utilized in the various industrial sectors such as marine, ship-building, automotive, aerospace, construction and petrochemicals etc. The increasing pressure on manufacturing sector wants the welding process to be sustainable in nature. The SMAW process incorporates several types of inputs and output streams. The sustainability concerns associated with SMAW process are linked with the various input and output streams such as electrical energy requirement, input material consumptions, slag formation, fumes emission and hazardous working conditions associated with the human health and occupational safety. To enhance the environmental performance of the SMAW welding process, there is a need to characterize the sustainability for the SMAW process under the broad framework of sustainability. Most of the available literature focuses on the technical and economic aspects of the welding process, however the environmental and social aspects are rarely addressed. The study reviews SMAW process with respect to the triple bottom line (economic, environmental and social) sustainability approach. Finally, the study concluded recommendations towards achieving economical and sustainable SMAW welding process.

The effect of advanced ultrasonic forging on fatigue fracture mechanisms of welded Ti-6A1-4V alloy

NASA Astrophysics Data System (ADS)

Smirnova, A.; Pochivalov, Yu.; Panin, V.; Panin, S.; Eremin, A.; Gorbunov, A.

2017-12-01

The current study is devoted to application of advanced postwelding ultrasonic forging to joints formed by laser welding of Ti-6A1-4V alloy in order to enhance their mechanical properties and fatigue durability. Low cycle fatigue tests were performed via digital image correlation technique used to obtain strain fields and in situ characterization of deformation, crack growth and fracture. Fracture surfaces were studied by SEM analysis accompanied with calculation of fracture patterns percentage. The fatigue tests demonstrate the high increase in the number of cycles until fracture (from 17 000 to 32 000 cycles) which could be explained by high ductility of welded material after treatment. This leads to lower fatigue crack growth rate due to higher energy dissipation. The obtained effect is attributable only for small cracks on micro-/mesoscales and fails to play a significant role for macro cracks.

Metallic-packaging fiber Bragg grating sensor based on ultrasonic welding for strain-insensitive temperature measurement

NASA Astrophysics Data System (ADS)

Zhu, Lianqing; Yang, Runtao; Zhang, Yumin; Dong, Mingli; Lou, Xiaoping

2018-04-01

In this paper, a metallic-packaging fiber Bragg grating temperature sensor characterized by a strain insensitive design is demonstrated. The sensor is fabricated by the one-step ultrasonic welding technique using type-II fiber Bragg grating combined with an aluminum alloy substrate. Finite element analysis is used to perform theoretical evaluation. The result of the experiment illustrates that the metallic-packaging temperature sensor is insensitive to longitudinal strain. The sensor's temperature sensitivity is 36 pm/°C over the range of 50-110 °C, with the correlation coefficient (R2) being 0.999. The sensor's temporal response is 40 s at a sudden temperature change from 21 °C to 100 °C. The proposed sensor can be applied on reliable and precise temperature measurement.

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.

Welding processes for Inconel 718- A brief review

NASA Astrophysics Data System (ADS)

Tharappel, Jose Tom; Babu, Jalumedi

2018-03-01

Inconel 718 is being extensively used for high-temperature applications, rocket engines, gas turbines, etc. due to its ability to maintain high strength at temperatures range 450-700°C complimented by excellent oxidation and corrosion resistance and its outstanding weldability in either the age hardened or annealed condition. Though alloy 718 is reputed to possess good weldability in the context of their resistance to post weld heat treatment cracking, heat affected zone (HAZ) and weld metal cracking problems persist. This paper presents a brief review on welding processes for Inconel 718 and the weld defects, such as strain cracking during post weld heat treatment, solidification cracking, and liquation cracking. The effect of alloy chemistry, primary and secondary processing on the HAZ cracking susceptibility, influence of post/pre weld heat treatments on precipitation, segregation reactions, and effect of grain size etc. discussed and concluded with future scope for research.

Literature Review: Theory and Application of In-Line Inspection Technologies for Oil and Gas Pipeline Girth Weld Defection

PubMed Central

Feng, Qingshan; Li, Rui; Nie, Baohua; Liu, Shucong; Zhao, Lianyu; Zhang, Hong

2016-01-01

Girth weld cracking is one of the main failure modes in oil and gas pipelines; girth weld cracking inspection has great economic and social significance for the intrinsic safety of pipelines. This paper introduces the typical girth weld defects of oil and gas pipelines and the common nondestructive testing methods, and systematically generalizes the progress in the studies on technical principles, signal analysis, defect sizing method and inspection reliability, etc., of magnetic flux leakage (MFL) inspection, liquid ultrasonic inspection, electromagnetic acoustic transducer (EMAT) inspection and remote field eddy current (RFDC) inspection for oil and gas pipeline girth weld defects. Additionally, it introduces the new technologies for composite ultrasonic, laser ultrasonic, and magnetostriction inspection, and provides reference for development and application of oil and gas pipeline girth weld defect in-line inspection technology. PMID:28036016

Butt Welding Joint of Aluminum Alloy by Space GHTA Welding Process in Vacuum

NASA Astrophysics Data System (ADS)

Suita, Yoshikazu; Shinike, Shuhei; Ekuni, Tomohide; Terajima, Noboru; Tsukuda, Yoshiyuki; Imagawa, Kichiro

Aluminum alloys have been used widely in constructing various space structures including the International Space Station (ISS) and launch vehicles. For space applications, welding experiments on aluminum alloy were performed using the GHTA (Gas Hollow Tungsten Arc) welding process using a filler wire feeder in a vacuum. We investigated the melting phenomenon of the base metal and filler wire, bead formation, and the effects of wire feed speed on melting characteristics. The melting mechanism in the base metal during the bead on a plate with wire feed was similar to that for the melt run without wire feed. We clarified the effects of wire feed speed on bead sizes and configurations. Furthermore, the butt welded joint welded using the optimum wire feed speed, and the joint tensile strengths were evaluated. The tensile strength of the square butt joint welded by the pulsed DC GHTA welding with wire feed in a vacuum is nearly equal to that of the same joint welded by conventional GTA (Gas Tungsten Arc) welding in air.

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

NASA Astrophysics Data System (ADS)

Yan, Qi; Guo, Ruiquan

2005-01-01

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

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

PubMed

Wang, Lin; Gao, Xiangdong; Chen, Ziqin

2018-01-08

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

Influence of Welding Process and Post Weld Heat Treatment on Microstructure and Pitting Corrosion Behavior of Dissimilar Aluminium Alloy Welds

NASA Astrophysics Data System (ADS)

Venkata Ramana, V. S. N.; Mohammed, Raffi; Madhusudhan Reddy, G.; Srinivasa Rao, K.

2018-03-01

Welding of dissimilar Aluminum alloy welds is becoming important in aerospace, shipbuilding and defence applications. In the present work, an attempt has been made to weld dissimilar aluminium alloys using conventional gas tungsten arc welding (GTAW) and friction stir welding (FSW) processes. An attempt was also made to study the effect of post weld heat treatment (T4 condition) on microstructure and pitting corrosion behaviour of these welds. Results of the present investigation established the differences in microstructures of the base metals in T4 condition and in annealed conditions. It is evident that the thickness of the PMZ is relatively more on AA2014 side than that of AA6061 side. In FS welds, lamellar like shear bands are well noticed on the top of the stir zone. The concentration profile of dissimilar friction stir weld in T4 condition revealed that no diffusion has taken place at the interface. Poor Hardness is observed in all regions of FS welds compared to that of GTA welds. Pitting corrosion resistance of the dissimilar FS welds in all regions was improved by post weld heat treatment.

Weld-brazing - a new joining process. [combination resistance spot welding and brazing of titanium alloys

NASA Technical Reports Server (NTRS)

Bales, T. T.; Royster, D. M.; Arnold, W. E., Jr.

1972-01-01

A joining process designated weld brazing which combines resistance spot welding and brazing has been developed. Resistance spot welding is used to position and align the parts as well as to establish a suitable faying surface gap for brazing. Fabrication is then completed by capillary flow of the braze alloy into the joint. The process has been used successfully to fabricate Ti-6Al-4V titanium alloy joints using 3003 aluminum braze alloy. Test results obtained on single overlap and hat-stiffened structural specimens show that weld brazed joints are superior in tensile shear, stress rupture, fatigue, and buckling than joint fabricated by spotwelding or brazing. Another attractive feature of the process is that the brazed joints is hermetically sealed by the braze material.

Alternate Welding Processes for In-Service Welding

DOT National Transportation Integrated Search

2009-04-24

Conducting weld repairs and attaching hot tap tees onto pressurized pipes has the advantage of avoiding loss of service and revenue. However, the risks involved with in-service welding need to be managed by ensuring that welding is performed in a rep...

Evaluation of ultrasonics and optimized radiography for 2219-T87 aluminum weldments

NASA Technical Reports Server (NTRS)

Clotfelter, W. N.; Hoop, J. M.; Duren, P. C.

1975-01-01

Ultrasonic studies are described which are specifically directed toward the quantitative measurement of randomly located defects previously found in aluminum welds with radiography or with dye penetrants. Experimental radiographic studies were also made to optimize techniques for welds of the thickness range to be used in fabricating the External Tank of the Space Shuttle. Conventional and innovative ultrasonic techniques were applied to the flaw size measurement problem. Advantages and disadvantages of each method are discussed. Flaw size data obtained ultrasonically were compared to radiographic data and to real flaw sizes determined by destructive measurements. Considerable success was achieved with pulse echo techniques and with 'pitch and catch' techniques. The radiographic work described demonstrates that careful selection of film exposure parameters for a particular application must be made to obtain optimized flaw detectability. Thus, film exposure techniques can be improved even though radiography is an old weld inspection method.

In Process Measurement of Hydrogen in Welding

DTIC Science & Technology

1986-09-01

Specimen Geometry.........40 Figure 4.8 GTAW Diffusible Hydrogen Specimen Geometry .......... 40 Figure 4.9 Schematic of Specimen Outgassing Container for... GTAW ) and gas metal arc welding (GMAW) have the lowest potentials for hydrogen pickup, while -. the flux-cored arc welding (FCAW) and submerged arc...wire during welding which is the major source of hydrogen in GMAW and GTAW . Although the FCAW process was originally considered an intrinsi- cally low

Numerical simulation of the laser welding process for the prediction of temperature distribution on welded aluminium aircraft components

NASA Astrophysics Data System (ADS)

Tsirkas, S. A.

2018-03-01

The present investigation is focused to the modelling of the temperature field in aluminium aircraft components welded by a CO2 laser. A three-dimensional finite element model has been developed to simulate the laser welding process and predict the temperature distribution in T-joint laser welded plates with fillet material. The simulation of the laser beam welding process was performed using a nonlinear heat transfer analysis, based on a keyhole formation model analysis. The model employs the technique of element ;birth and death; in order to simulate the weld fillet. Various phenomena associated with welding like temperature dependent material properties and heat losses through convection and radiation were accounted for in the model. The materials considered were 6056-T78 and 6013-T4 aluminium alloys, commonly used for aircraft components. The temperature distribution during laser welding process has been calculated numerically and validated by experimental measurements on different locations of the welded structure. The numerical results are in good agreement with the experimental measurements.

46 CFR 154.650 - Cargo tank and process pressure vessel welding.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Cargo tank and process pressure vessel welding. 154.650... Equipment Construction § 154.650 Cargo tank and process pressure vessel welding. (a) Cargo tank and process pressure vessel welding must meet Subpart 54.05 and Part 57 of this chapter. (b) Welding consumables used...

46 CFR 154.650 - Cargo tank and process pressure vessel welding.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Cargo tank and process pressure vessel welding. 154.650... Equipment Construction § 154.650 Cargo tank and process pressure vessel welding. (a) Cargo tank and process pressure vessel welding must meet Subpart 54.05 and Part 57 of this chapter. (b) Welding consumables used...

46 CFR 154.650 - Cargo tank and process pressure vessel welding.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Cargo tank and process pressure vessel welding. 154.650... Equipment Construction § 154.650 Cargo tank and process pressure vessel welding. (a) Cargo tank and process pressure vessel welding must meet Subpart 54.05 and Part 57 of this chapter. (b) Welding consumables used...

46 CFR 154.650 - Cargo tank and process pressure vessel welding.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Cargo tank and process pressure vessel welding. 154.650... Equipment Construction § 154.650 Cargo tank and process pressure vessel welding. (a) Cargo tank and process pressure vessel welding must meet Subpart 54.05 and Part 57 of this chapter. (b) Welding consumables used...

46 CFR 154.650 - Cargo tank and process pressure vessel welding.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Cargo tank and process pressure vessel welding. 154.650... Equipment Construction § 154.650 Cargo tank and process pressure vessel welding. (a) Cargo tank and process pressure vessel welding must meet Subpart 54.05 and Part 57 of this chapter. (b) Welding consumables used...

Phased Array Ultrasonic Examination of Reactor Coolant System (Carbon Steel-to-CASS) Dissimilar Metal Weld Mockup Specimen

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

Crawford, S. L.; Cinson, A. D.; Diaz, A. A.

2015-11-23

In the summer of 2009, Pacific Northwest National Laboratory (PNNL) staff traveled to the Electric Power Research Institute (EPRI) NDE Center in Charlotte, North Carolina, to conduct phased-array ultrasonic testing on a large bore, reactor coolant pump nozzle-to-safe-end mockup. This mockup was fabricated by FlawTech, Inc. and the configuration originated from the Port St. Lucie nuclear power plant. These plants are Combustion Engineering-designed reactors. This mockup consists of a carbon steel elbow with stainless steel cladding joined to a cast austenitic stainless steel (CASS) safe-end with a dissimilar metal weld and is owned by Florida Power & Light. The objectivemore » of this study, and the data acquisition exercise held at the EPRI NDE Center, were focused on evaluating the capabilities of advanced, low-frequency phased-array ultrasonic testing (PA-UT) examination techniques for detection and characterization of implanted circumferential flaws and machined reflectors in a thick-section CASS dissimilar metal weld component. This work was limited to PA-UT assessments using 500 kHz and 800 kHz probes on circumferential flaws only, and evaluated detection and characterization of these flaws and machined reflectors from the CASS safe-end side only. All data were obtained using spatially encoded, manual scanning techniques. The effects of such factors as line-scan versus raster-scan examination approaches were evaluated, and PA-UT detection and characterization performance as a function of inspection frequency/wavelength, were also assessed. A comparative assessment of the data is provided, using length-sizing root-mean-square-error and position/localization results (flaw start/stop information) as the key criteria for flaw characterization performance. In addition, flaw signal-to-noise ratio was identified as the key criterion for detection performance.« less

A Non-Intrusive GMA Welding Process Quality Monitoring System Using Acoustic Sensing.

PubMed

Cayo, Eber Huanca; Alfaro, Sadek Crisostomo Absi

2009-01-01

Most of the inspection methods used for detection and localization of welding disturbances are based on the evaluation of some direct measurements of welding parameters. This direct measurement requires an insertion of sensors during the welding process which could somehow alter the behavior of the metallic transference. An inspection method that evaluates the GMA welding process evolution using a non-intrusive process sensing would allow not only the identification of disturbances during welding runs and thus reduce inspection time, but would also reduce the interference on the process caused by the direct sensing. In this paper a nonintrusive method for weld disturbance detection and localization for weld quality evaluation is demonstrated. The system is based on the acoustic sensing of the welding electrical arc. During repetitive tests in welds without disturbances, the stability acoustic parameters were calculated and used as comparison references for the detection and location of disturbances during the weld runs.

A Non-Intrusive GMA Welding Process Quality Monitoring System Using Acoustic Sensing

PubMed Central

Cayo, Eber Huanca; Alfaro, Sadek Crisostomo Absi

2009-01-01

Most of the inspection methods used for detection and localization of welding disturbances are based on the evaluation of some direct measurements of welding parameters. This direct measurement requires an insertion of sensors during the welding process which could somehow alter the behavior of the metallic transference. An inspection method that evaluates the GMA welding process evolution using a non-intrusive process sensing would allow not only the identification of disturbances during welding runs and thus reduce inspection time, but would also reduce the interference on the process caused by the direct sensing. In this paper a nonintrusive method for weld disturbance detection and localization for weld quality evaluation is demonstrated. The system is based on the acoustic sensing of the welding electrical arc. During repetitive tests in welds without disturbances, the stability acoustic parameters were calculated and used as comparison references for the detection and location of disturbances during the weld runs. PMID:22399990

The variable polarity plasma arc welding process: Characteristics and performance

NASA Technical Reports Server (NTRS)

Hung, R. J.; Zhu, G. J.

1991-01-01

Significant advantages of the Variable Polarity Plasma Arc (VPPA) Welding Process include faster welding, fewer repairs, less joint preparation, reduced weldment distortion, and absence of porosity. The power distribution was analyzed for an argon plasma gas flow constituting the fluid in the VPPA Welding Process. The major heat loss at the torch nozzle is convective heat transfer; in the space between the outlet of the nozzle and the workpiece; radiative heat transfer; and in the keyhole in the workpiece, convective heat transfer. The power absorbed at the workpiece produces the molten puddle that solidifies into the weld bead. Crown and root widths, and crown and root heights of the weld bead are predicted. The basis is provided for an algorithm for automatic control of VPPA welding machine parameters to obtain desired weld bead dimensions.

Decreasing biotoxicity of fume particles produced in welding process.

PubMed

Yu, Kuei-Min; Topham, Nathan; Wang, Jun; Kalivoda, Mark; Tseng, Yiider; Wu, Chang-Yu; Lee, Wen-Jhy; Cho, Kuk

2011-01-30

Welding fumes contain heavy metals, such as chromium, manganese, and nickel, which cause respiratory diseases and cancer. In this study, a SiO(2) precursor was evaluated as an additive to the shielding gas in an arc welding process to reduce the biotoxicity caused by welding fume particles. Transmission electron micrographic images show that SiO(2) coats on the surface of welding fume particles and promotes particle agglomeration. Energy dispersive X-ray spectroscopy further shows that the relative amount of silicon in these SiO(2)-coated agglomerates is higher than in baseline agglomerates. In addition, Escherichia coli (E. coli) exposed to different concentrations of pure SiO(2) particles generated from the arc welding process exhibits similar responses, suggesting that SiO(2) does not contribute to welding fume particle toxicity. The trend of E. coli growth in different concentrations of baseline welding fume particle shows the most significant inhibition occurs in higher exposure concentrations. The 50% lethal logarithmic concentrations for E. coli in arc welding particles of baseline, 2%, and 4.2% SiO(2) precursor additives were 823, 1605, and 1800 mg/L, respectively. Taken together, these results suggest that using SiO(2) precursors as an additive to arc welding shielding gas can effectively reduce the biotoxicity of welding fume. Copyright © 2010 Elsevier B.V. All rights reserved.

Unraveling the Processing Parameters in Friction Stir Welding

NASA Technical Reports Server (NTRS)

Schneider, Judy; Nunes, Arthur C., Jr.

2005-01-01

In friction stir welding (FSW), a rotating threaded pin tool is translated along a weld seam, literally stirring the edges of the seam together. To determine optimal processing parameters for producing a defect free weld, a better understanding of the resulting metal deformation flow path or paths is required. In this study, various markers are used to trace the flow paths of the metal. X-ray radiographs record the segmentation and position of the wire. Several variations in the trajectories can be differentiated within the weld zone.

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.

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

Seam-weld quality of modern ERW/HFI line pipe

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

Groeneveld, T.P.; Barnes, C.R.

1991-09-01

This study was undertaken to determine whether the seam-weld quality of modern ERW (electric resistance-welded)/HFI (high-frequency induction) welded pipe has been improved and justifies more widespread use of this type of pipe in critical applications. Wider use of ERW/HFI line pipe in gas-transmission lines would be expected to reduce construction costs. Five recently produced, heavy wall pipes fabricated using high-frequency electric-resistance welding (ERW) processes to make the seam weld and one pipe fabricated using the high-frequency induction (HFI) welding process to make the seam weld were studied. Four of the pipes were Grade X-60, one was Grade X-65, and onemore » was Grade X-70. All of the pipes were produced from microalloyed, controlled-rolled steels, and the weld zones were post-weld normalized. Ultrasonic inspection of the seam welds in the six pipe sections evaluated revealed no indications of defects. The tensile properties of all of the weld zones exceeded the minimum specified yield strengths for the respective grades of pipe and all of the pipes exhibited ductile failures either in the weld zone or in the base metal. Five of the six pipes exhibited ductile failures either in the weld zone or in the base metal. Five of the six pipes exhibited relatively low 85% shear area transition temperatures and relatively high upper-shelf energy absorptions as determined with Charpy V-notch specimens. In addition, for two of the three joints of pipe for which the properties were determined at both ends of the pipe, the tensile and impact properties showed little variation from end-to-end. However, for the other joint of pipe, the impact properties varied substantially from one end to the other.« less

Identification of the Thickness of Nugget on Worksheet Spot Welding Using Non Destructive Test (NDT) - Effect of Pressure

NASA Astrophysics Data System (ADS)

Sifa, A.; Baskoro, A. S.; Sugeng, S.; Badruzzaman, B.; Endramawan, T.

2018-02-01

Resistance Spot Welding (RSW) is a process of connecting between two worksheet with thermomechanical loading process, RSW is widely used in automotive industry, the quality of splicing spot welding is influenced by several factors. One of the factors at the time of the welding process is pressure. The quality of welding on the nuggets can be determined by undertaking non-destructive testing by using Non Destructive Test (NDT) - Ultrasonic Test. In the NDT test is done by detecting the thickness of the nugget area, the purpose of research conducted to determine the effect of pressure to welding quality with Nugget thickness gauge measurement with Non Destructive Test method and manual measurement with micrometer, Experimental welding process by entering the welding parameters that have been specified and pressure variables 1 -5 bars on the worksheet thickness of 1 mm. The results of testing with NDT show there is addition of thickness in nugget superiority after compare with measurement result of thickness of nugget with micrometer which slightly experience thickness in nugget area, this indicates that the welding results have a connection between worksheet 1 and worksheet 2.

Method of noncontacting ultrasonic process monitoring

DOEpatents

Garcia, Gabriel V.; Walter, John B.; Telschow, Kenneth L.

1992-01-01

A method of monitoring a material during processing comprising the steps of (a) shining a detection light on the surface of a material; (b) generating ultrasonic waves at the surface of the material to cause a change in frequency of the detection light; (c) detecting a change in the frequency of the detection light at the surface of the material; (d) detecting said ultrasonic waves at the surface point of detection of the material; (e) measuring a change in the time elapsed from generating the ultrasonic waves at the surface of the material and return to the surface point of detection of the material, to determine the transit time; and (f) comparing the transit time to predetermined values to determine properties such as, density and the elastic quality of the material.

Computational simulation of weld microstructure and distortion by considering process mechanics

NASA Astrophysics Data System (ADS)

Mochizuki, M.; Mikami, Y.; Okano, S.; Itoh, S.

2009-05-01

Highly precise fabrication of welded materials is in great demand, and so microstructure and distortion controls are essential. Furthermore, consideration of process mechanics is important for intelligent fabrication. In this study, the microstructure and hardness distribution in multi-pass weld metal are evaluated by computational simulations under the conditions of multiple heat cycles and phase transformation. Because conventional CCT diagrams of weld metal are not available even for single-pass weld metal, new diagrams for multi-pass weld metals are created. The weld microstructure and hardness distribution are precisely predicted when using the created CCT diagram for multi-pass weld metal and calculating the weld thermal cycle. Weld distortion is also investigated by using numerical simulation with a thermal elastic-plastic analysis. In conventional evaluations of weld distortion, the average heat input has been used as the dominant parameter; however, it is difficult to consider the effect of molten pool configurations on weld distortion based only on the heat input. Thus, the effect of welding process conditions on weld distortion is studied by considering molten pool configurations, determined by temperature distribution and history.

Toward practical 3D radiography of pipeline girth welds

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

Wassink, Casper, E-mail: casper.wassink@applusrtd.com; Hol, Martijn, E-mail: martijn.hol@applusrtd.com; Flikweert, Arjan, E-mail: martijn.hol@applusrtd.com

2015-03-31

Digital radiography has made its way into in-the-field girth weld testing. With recent generations of detectors and x-ray tubes it is possible to reach the image quality desired in standards as well as the speed of inspection desired to be competitive with film radiography and automated ultrasonic testing. This paper will show the application of these technologies in the RTD Rayscan system. The method for achieving an image quality that complies with or even exceeds prevailing industrial standards will be presented, as well as the application on pipeline girth welds with CRA layers. A next step in development will bemore » to also achieve a measurement of weld flaw height to allow for performing an Engineering Critical Assessment on the weld. This will allow for similar acceptance limits as currently used with Automated Ultrasonic Testing of pipeline girth welds. Although a sufficient sizing accuracy was already demonstrated and qualified in the TomoCAR system, testing in some applications is restricted to time limits. The paper will present some experiments that were performed to achieve flaw height approximation within these time limits.« less

Passively damped vibration welding system and method

DOEpatents

Tan, Chin-An; Kang, Bongsu; Cai, Wayne W.; Wu, Tao

2013-04-02

A vibration welding system includes a controller, welding horn, an anvil, and a passive damping mechanism (PDM). The controller generates an input signal having a calibrated frequency. The horn vibrates in a desirable first direction at the calibrated frequency in response to the input signal to form a weld in a work piece. The PDM is positioned with respect to the system, and substantially damps or attenuates vibration in an undesirable second direction. A method includes connecting the PDM having calibrated properties and a natural frequency to an anvil of an ultrasonic welding system. Then, an input signal is generated using a weld controller. The method includes vibrating a welding horn in a desirable direction in response to the input signal, and passively damping vibration in an undesirable direction using the PDM.

Friction stir welding process to repair voids in aluminum alloys

NASA Technical Reports Server (NTRS)

Rosen, Charles D. (Inventor); Litwinski, Edward (Inventor); Valdez, Juan M. (Inventor)

1999-01-01

The present invention provides an in-process method to repair voids in an aluminum alloy, particularly a friction stir weld in an aluminum alloy. For repairing a circular void or an in-process exit hole in a weld, the method includes the steps of fabricating filler material of the same composition or compatible with the parent material into a plug form to be fitted into the void, positioning the plug in the void, and friction stir welding over and through the plug. For repairing a longitudinal void (30), the method includes machining the void area to provide a trough (34) that subsumes the void, fabricating filler metal into a strip form (36) to be fitted into the trough, positioning the strip in the trough, and rewelding the void area by traversing a friction stir welding tool longitudinally through the strip. The method is also applicable for repairing welds made by a fusing welding process or voids in aluminum alloy workpieces themselves.

Influence of tool geometry and processing parameters on welding defects and mechanical properties for friction stir welding of 6061 Aluminium alloy

NASA Astrophysics Data System (ADS)

Daneji, A.; Ali, M.; Pervaiz, S.

2018-04-01

Friction stir welding (FSW) is a form of solid state welding process for joining metals, alloys, and selective composites. Over the years, FSW development has provided an improved way of producing welding joints, and consequently got accepted in numerous industries such as aerospace, automotive, rail and marine etc. In FSW, the base metal properties control the material’s plastic flow under the influence of a rotating tool whereas, the process and tool parameters play a vital role in the quality of weld. In the current investigation, an array of square butt joints of 6061 Aluminum alloy was to be welded under varying FSW process and tool geometry related parameters, after which the resulting weld was evaluated for the corresponding mechanical properties and welding defects. The study incorporates FSW process and tool parameters such as welding speed, pin height and pin thread pitch as input parameters. However, the weld quality related defects and mechanical properties were treated as output parameters. The experimentation paves way to investigate the correlation between the inputs and the outputs. The correlation between inputs and outputs were used as tool to predict the optimized FSW process and tool parameters for a desired weld output of the base metals under investigation. The study also provides reflection on the effect of said parameters on a welding defect such as wormhole.

Evaluation Of Four Welding Arc Processes Applied To 6061 Aluminium Alloy

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

Benoit, A.; Laboratoire de Genie des Materiaux et Procedes Associes; Paillard, P.

At a time when greenhouse gas emissions must be reduced, the use of the aluminium alloys is expanding, in particular in the transportation industry. In order to extend the possibilities of aluminium assembly design, new Metal Inert Gas (MIG) welding processes have been conceived. They work at lower temperatures than usual arc processes (classic MIG or Tungsten Inert Gas). This study compares four arc welding processes, applied to the 6061 aluminium alloy. These four weld processes have been studied through the metallurgical analysis of the weld beads. Metallography, micro-hardness testings, X Ray radiography have been carried out on the producedmore » weld beads. The processes are classified according to the quality of the beads like geometry of beads, size of the heat affected zone and presence of defects.« less

Plastic deformation and wave formation on the interface of metals welded by ultrasound-assisted explosive welding

NASA Astrophysics Data System (ADS)

Kuz'min, E. V.; Kuz'min, S. V.; Lysak, V. I.; Lata, A. N.

2017-10-01

This paper presents the influence of the effect of ultrasound on the wave formation and plastic deformation in the metals welded by ultrasound-assisted explosive welding. It has been established that the influence of high-frequency acoustic waves on the metal leads to a reduction of the dynamic yield stress, which in turn leads to changes in the properties of the surface layers of metal and in the conditions of bonding between the collided plates upon 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 is 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 behind the point of contact.

Number size distribution of fine and ultrafine fume particles from various welding processes.

PubMed

Brand, Peter; Lenz, Klaus; Reisgen, Uwe; Kraus, Thomas

2013-04-01

Studies in the field of environmental epidemiology indicate that for the adverse effect of inhaled particles not only particle mass is crucial but also particle size is. Ultrafine particles with diameters below 100 nm are of special interest since these particles have high surface area to mass ratio and have properties which differ from those of larger particles. In this paper, particle size distributions of various welding and joining techniques were measured close to the welding process using a fast mobility particle sizer (FMPS). It turned out that welding processes with high mass emission rates (manual metal arc welding, metal active gas welding, metal inert gas welding, metal inert gas soldering, and laser welding) show mainly agglomerated particles with diameters above 100 nm and only few particles in the size range below 50 nm (10 to 15%). Welding processes with low mass emission rates (tungsten inert gas welding and resistance spot welding) emit predominantly ultrafine particles with diameters well below 100 nm. This finding can be explained by considerably faster agglomeration processes in welding processes with high mass emission rates. Although mass emission is low for tungsten inert gas welding and resistance spot welding, due to the low particle size of the fume, these processes cannot be labeled as toxicologically irrelevant and should be further investigated.

Efficiency of the Inertia Friction Welding Process and Its Dependence on Process Parameters

NASA Astrophysics Data System (ADS)

Senkov, O. N.; Mahaffey, D. W.; Tung, D. J.; Zhang, W.; Semiatin, S. L.

2017-07-01

It has been widely assumed, but never proven, that the efficiency of the inertia friction welding (IFW) process is independent of process parameters and is relatively high, i.e., 70 to 95 pct. In the present work, the effect of IFW parameters on process efficiency was established. For this purpose, a series of IFW trials was conducted for the solid-state joining of two dissimilar nickel-base superalloys (LSHR and Mar-M247) using various combinations of initial kinetic energy ( i.e., the total weld energy, E o), initial flywheel angular velocity ( ω o), flywheel moment of inertia ( I), and axial compression force ( P). The kinetics of the conversion of the welding energy to heating of the faying sample surfaces ( i.e., the sample energy) vs parasitic losses to the welding machine itself were determined by measuring the friction torque on the sample surfaces ( M S) and in the machine bearings ( M M). It was found that the rotating parts of the welding machine can consume a significant fraction of the total energy. Specifically, the parasitic losses ranged from 28 to 80 pct of the total weld energy. The losses increased (and the corresponding IFW process efficiency decreased) as P increased (at constant I and E o), I decreased (at constant P and E o), and E o (or ω o) increased (at constant P and I). The results of this work thus provide guidelines for selecting process parameters which minimize energy losses and increase process efficiency during IFW.

Physicochemical and toxicological characteristics of welding fume derived particles generated from real time welding processes.

PubMed

Chang, Cali; Demokritou, Philip; Shafer, Martin; Christiani, David

2013-01-01

Welding fume particles have been well studied in the past; however, most studies have examined welding fumes generated from machine models rather than actual exposures. Furthermore, the link between physicochemical and toxicological properties of welding fume particles has not been well understood. This study aims to investigate the physicochemical properties of particles derived during real time welding processes generated during actual welding processes and to assess the particle size specific toxicological properties. A compact cascade impactor (Harvard CCI) was stationed within the welding booth to sample particles by size. Size fractionated particles were extracted and used for both off-line physicochemical analysis and in vitro cellular toxicological characterization. Each size fraction was analyzed for ions, elemental compositions, and mass concentration. Furthermore, real time optical particle monitors (DustTrak™, TSI Inc., Shoreview, Minn.) were used in the same welding booth to collect real time PM2.5 particle number concentration data. The sampled particles were extracted from the polyurethane foam (PUF) impaction substrates using a previously developed and validated protocol, and used in a cellular assay to assess oxidative stress. By mass, welding aerosols were found to be in coarse (PM 2.5–10), and fine (PM 0.1–2.5) size ranges. Most of the water soluble (WS) metals presented higher concentrations in the coarse size range with some exceptions such as sodium, which presented elevated concentration in the PM 0.1 size range. In vitro data showed size specific dependency, with the fine and ultrafine size ranges having the highest reactive oxygen species (ROS) activity. Additionally, this study suggests a possible correlation between welders' experience, the welding procedure and equipment used and particles generated from welding fumes. Mass concentrations and total metal and water soluble metal concentrations of welding fume particles may be

Real-time monitoring of the laser hot-wire welding process

NASA Astrophysics Data System (ADS)

Liu, Wei; Liu, Shuang; Ma, Junjie; Kovacevic, Radovan

2014-04-01

The laser hot-wire welding process was investigated in this work. The dynamics of the molten pool during welding was visualized by using a high-speed charge-coupled device (CCD) camera assisted by a green laser as an illumination source. It was found that the molten pool is formed by the irradiation of the laser beam on the filler wire. The effect of the hot-wire voltage on the stability of the welding process was monitored by using a spectrometer that captured the emission spectrum of the laser-induced plasma plume. The spectroscopic study showed that when the hot-wire voltage is above 9 V a great deal of spatters occur, resulting in the instability of the plasma plume and the welding process. The effect of spatters on the plasma plume was shown by the identified spectral lines of the element Mn I. The correlation between the Fe I electron temperature and the weld-bead shape was studied. It was noted that the electron temperature of the plasma plume can be used to real-time monitor the variation of the weld-bead features and the formation of the weld defects.

Correlation analysis of the variation of weld seam and tensile strength in laser welding of galvanized steel

NASA Astrophysics Data System (ADS)

Sinha, Amit Kumar; Kim, Duck Young; Ceglarek, Darek

2013-10-01

Many advantages of laser welding technology such as high speed and non-contact welding make the use of the technology more attractive in the automotive industry. Many studies have been conducted to search the optimal welding condition experimentally that ensure the joining quality of laser welding that relies both on welding system configuration and welding parameter specification. Both non-destructive and destructive techniques, for example, ultrasonic inspection and tensile test are widely used in practice for estimating the joining quality. Non-destructive techniques are attractive as a rapid quality testing method despite relatively low accuracy. In this paper, we examine the relationship between the variation of weld seam and tensile shear strength in the laser welding of galvanized steel in a lap joint configuration in order to investigate the potential of the variation of weld seam as a joining quality estimator. From the experimental analysis, we identify a trend in between maximum tensile shear strength and the variation of weld seam that clearly supports the fact that laser welded parts having larger variation in the weld seam usually have lower tensile strength. The discovered relationship leads us to conclude that the variation of weld seam can be used as an indirect non-destructive testing method for estimating the tensile strength of the welded parts.

Tomographical process monitoring of laser transmission welding with OCT

NASA Astrophysics Data System (ADS)

Ackermann, Philippe; Schmitt, Robert

2017-06-01

Process control of laser processes still encounters many obstacles. Although these processes are stable, a narrow process parameter window during the process or process deviations have led to an increase on the requirements for the process itself and on monitoring devices. Laser transmission welding as a contactless and locally limited joining technique is well-established in a variety of demanding production areas. For example, sensitive parts demand a particle-free joining technique which does not affect the inner components. Inline integrated non-destructive optical measurement systems capable of providing non-invasive tomographical images of the transparent material, the weld seam and its surrounding areas with micron resolution would improve the overall process. Obtained measurement data enable qualitative feedback into the system to adapt parameters for a more robust process. Within this paper we present the inline monitoring device based on Fourier-domain optical coherence tomography developed within the European-funded research project "Manunet Weldable". This device, after adaptation to the laser transmission welding process is optically and mechanically integrated into the existing laser system. The main target lies within the inline process control destined to extract tomographical geometrical measurement data from the weld seam forming process. Usage of this technology makes offline destructive testing of produced parts obsolete. 1,2,3,4

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.

Diffusion welding. [heat treatment of nickel alloys following single step vacuum welding process

NASA Technical Reports Server (NTRS)

Holko, K. H. (Inventor)

1974-01-01

Dispersion-strengthened nickel alloys are sanded on one side and chemically polished. This is followed by a single-step welding process wherein the polished surfaces are forced into intimate contact at 1,400 F for one hour in a vacuum. Diffusion, recrystallization, and grain growth across the original weld interface are obtained during postheating at 2,150 F for two hours in hydrogen.

Digital Signal Processing Methods for Ultrasonic Echoes.

PubMed

Sinding, Kyle; Drapaca, Corina; Tittmann, Bernhard

2016-04-28

Digital signal processing has become an important component of data analysis needed in industrial applications. In particular, for ultrasonic thickness measurements the signal to noise ratio plays a major role in the accurate calculation of the arrival time. For this application a band pass filter is not sufficient since the noise level cannot be significantly decreased such that a reliable thickness measurement can be performed. This paper demonstrates the abilities of two regularization methods - total variation and Tikhonov - to filter acoustic and ultrasonic signals. Both of these methods are compared to a frequency based filtering for digitally produced signals as well as signals produced by ultrasonic transducers. This paper demonstrates the ability of the total variation and Tikhonov filters to accurately recover signals from noisy acoustic signals faster than a band pass filter. Furthermore, the total variation filter has been shown to reduce the noise of a signal significantly for signals with clear ultrasonic echoes. Signal to noise ratios have been increased over 400% by using a simple parameter optimization. While frequency based filtering is efficient for specific applications, this paper shows that the reduction of noise in ultrasonic systems can be much more efficient with regularization methods.

Infrared welding process on composite: Effect of interdiffusion at the welding interface

NASA Astrophysics Data System (ADS)

Asseko, André Chateau Akué; Lafranche, Éric; Cosson, Benoît; Schmidt, Fabrice; Le Maoult, Yannick

2016-10-01

In this study, the effects of the welding temperature field developed during the infrared assembly process on the joining properties of glass fibre reinforced polycarbonate/ unreinforced polycarbonate with carbon black were investigated. The temperature field and the contact time govern together the quality of the adhesion at the welding interface. The effect of the semi-transparent glass fibre reinforced polycarbonate composite / unreinforced polycarbonate composite with carbon black interface was quantified in term of quadratic distance of diffusion or diffusion depth through the welding interface. The microstructural characterizations were investigated in order to inspect the welding zones quality and to observe their failure modes. The diffusion theory has then been applied to calculate the variation of the quadratic distance of diffusion versus time at different locations. The complete self-diffusion is supposed occurring only at temperature above the polycarbonate glass transition temperature (140°C) and with a quadratic distance of diffusion superior to the mean square end-to-end distance.

Selecting Processes to Minimize Hexavalent Chromium from Stainless Steel Welding

PubMed Central

KEANE, M.; SIERT, A.; STONE, S.; CHEN, B.; SLAVEN, J.; CUMPSTON, A.; ANTONINI, J.

2015-01-01

Eight welding processes/shielding gas combinations were assessed for generation of hexavalent chromium (Cr6+) in stainless steel welding fumes. The processes examined were gas metal arc welding (GMAW) (axial spray, short circuit, and pulsed spray modes), flux cored arc welding (FCAW), and shielded metal arc welding (SMAW). The Cr6+ fractions were measured in the fumes; fume generation rates, Cr6+ generation rates, and Cr6+ generation rates per unit mass of welding wire were determined. A limited controlled comparison study was done in a welding shop including SMAW, FCAW, and three GMAW methods. The processes studied were compared for costs, including relative labor costs. Results indicate the Cr6+ in the fume varied widely, from a low of 2800 to a high of 34,000 ppm. Generation rates of Cr6+ ranged from 69 to 7800 μg/min, and Cr6+ generation rates per unit of wire ranged from 1 to 270 μg/g. The results of field study were similar to the findings in the laboratory. The Cr6+ (ppm) in the fume did not necessarily correlate with the Cr6+ generation rate. Physical properties were similar for the processes, with mass median aerodynamic diameters ranging from 250 to 336 nm, while the FCAW and SMAW fumes were larger (360 and 670 nm, respectively). Conclusion: The pulsed axial spray method was the best choice of the processes studied based on minimal fume generation, minimal Cr6+ generation, and cost per weld. This method is usable in any position, has a high metal deposition rate, and is relatively simple to learn and use. PMID:26690276

Contemporary ultrasonic signal processing approaches for nondestructive evaluation of multilayered structures

NASA Astrophysics Data System (ADS)

Zhang, Guang-Ming; Harvey, David M.

2012-03-01

Various signal processing techniques have been used for the enhancement of defect detection and defect characterisation. Cross-correlation, filtering, autoregressive analysis, deconvolution, neural network, wavelet transform and sparse signal representations have all been applied in attempts to analyse ultrasonic signals. In ultrasonic nondestructive evaluation (NDE) applications, a large number of materials have multilayered structures. NDE of multilayered structures leads to some specific problems, such as penetration, echo overlap, high attenuation and low signal-to-noise ratio. The signals recorded from a multilayered structure are a class of very special signals comprised of limited echoes. Such signals can be assumed to have a sparse representation in a proper signal dictionary. Recently, a number of digital signal processing techniques have been developed by exploiting the sparse constraint. This paper presents a review of research to date, showing the up-to-date developments of signal processing techniques made in ultrasonic NDE. A few typical ultrasonic signal processing techniques used for NDE of multilayered structures are elaborated. The practical applications and limitations of different signal processing methods in ultrasonic NDE of multilayered structures are analysed.

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.

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

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 Processing Parameters on the Flow Path in Friction Stir Welding

NASA Technical Reports Server (NTRS)

Schneider, J. A.; Nunes, A. C., Jr.

2006-01-01

Friction stir welding (FSW) is a solid phase welding process that unites thermal and mechanical aspects to produce a high quality joint. The process variables are rpm, translational weld speed, and downward plunge force. The strain-temperature history of a metal element at each point on the cross-section of the weld is determined by the individual flow path taken by the particular filament of metal flowing around the tool as influenced by the process variables. The resulting properties of the weld are determined by the strain-temperature history. Thus to control FSW properties, improved understanding of the processing parameters on the metal flow path is necessary.

Sensing of metal-transfer mode for process control of GMAW (gas metal arc welding)

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

Carlson, N.M.; Johnson, J.A.; Smartt, H.B.

1989-01-01

One of the requirements of a sensing system for feedback control of gas metal arc welding (GMAW) is the capability to determine the metal-transfer mode. Because the operating boundary for the desired transfer mode, expressed as a function of mass input and heat input, may vary due to conditions beyond the control of the system, a means of detecting the transfer mode during welding is necessary. A series of sensing experiments was performed during which the ultrasonic emissions, audio emissions, welding current fluctuations and welding voltage fluctuations were recorded as a function of the transfer mode. In addition, high speedmore » movies (5000 frames/s) of the droplet formation and detachment were taken synchronously with the sensing data. An LED mounted in the camera was used to mark the film at the beginning and end of the data acquisition period. A second LED was pulsed at a 1 kHz rate and the pulses recorded on film and with the sensor data. Thus events recorded on the film can be correlated with the sensor data. Data acquired during globular transfer, spray transfer, and stiff spray or streaming transfer were observed to correlate with droplet detachment and arc shorting. The audio, current, and voltage data can be used to discriminate among these different transfer modes. However, the current and voltage data are also dependent on the characteristic of the welding power supply. 5 refs., 3 figs., 1 tab.« less

Investigation of Laser Welding of Ti Alloys for Cognitive Process Parameters Selection.

PubMed

Caiazzo, Fabrizia; Caggiano, Alessandra

2018-04-20

Laser welding of titanium alloys is attracting increasing interest as an alternative to traditional joining techniques for industrial applications, with particular reference to the aerospace sector, where welded assemblies allow for the reduction of the buy-to-fly ratio, compared to other traditional mechanical joining techniques. In this research work, an investigation on laser welding of Ti⁻6Al⁻4V alloy plates is carried out through an experimental testing campaign, under different process conditions, in order to perform a characterization of the produced weld bead geometry, with the final aim of developing a cognitive methodology able to support decision-making about the selection of the suitable laser welding process parameters. The methodology is based on the employment of artificial neural networks able to identify correlations between the laser welding process parameters, with particular reference to the laser power, welding speed and defocusing distance, and the weld bead geometric features, on the basis of the collected experimental data.

Investigation of Laser Welding of Ti Alloys for Cognitive Process Parameters Selection

PubMed Central

2018-01-01

Laser welding of titanium alloys is attracting increasing interest as an alternative to traditional joining techniques for industrial applications, with particular reference to the aerospace sector, where welded assemblies allow for the reduction of the buy-to-fly ratio, compared to other traditional mechanical joining techniques. In this research work, an investigation on laser welding of Ti–6Al–4V alloy plates is carried out through an experimental testing campaign, under different process conditions, in order to perform a characterization of the produced weld bead geometry, with the final aim of developing a cognitive methodology able to support decision-making about the selection of the suitable laser welding process parameters. The methodology is based on the employment of artificial neural networks able to identify correlations between the laser welding process parameters, with particular reference to the laser power, welding speed and defocusing distance, and the weld bead geometric features, on the basis of the collected experimental data. PMID:29677114

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

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

[Treatment of carbonization effluent by the ultrasonic radiation and activated sludge process].

PubMed

Ning, Ping; Xu, Jinqiu; Huang, Dongbin; Ma, Xiaoli; Xu, Xiaojun; Li, Ziyan

2003-05-01

The paper deals with the degradation of organic pollutants by the ultrasonic irradiation-activated sludge process. The treatment of the real coking wastewater of Kunming coke making-gas plant was studied with the water quality model. Using the ultrasonic irradiation-activated sludge process the organic pollutants in the real coking wastewater can be degraded effectively. The influence factors of the ultrasonic degradation effect such as initial concentration, aerated gas and ultrasonic density were investigated and mechanism was explored. The result shows that the ultrasonic degradation effect was high with the decrease of initial concentration of the CODCr, the presence of aerated gas and the increase of ultrasonic density. At the initial CODCr concentration of 807 mg/L, when air acted as aerated gas and only air itself (no ultrasound) was exerted on the wastewater, the degradation rate of the CODCr will be 4.5%. However, when the ultrasound of the intensity of 119.4 kW/m2 was exerted on the wastewater, the degradation rate of the CODCr will be 65%. Compared with the activated sludge process alone, the combination of the ultrasonic irradiation and activated sludge process can increase the degradation rate of the CODCr from 45% to 81%. The oxygen consumption rate of the carbonization effluent obviously decreased in the presence of the activated sludge. This shows the carbonization effluent is not biotoxic behind the ultrasonic irradiation.

Optimization of Gas Metal Arc Welding (GMAW) Process for Maximum Ballistic Limit in MIL A46100 Steel Welded All-Metal Armor

NASA Astrophysics Data System (ADS)

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

2015-01-01

Our recently developed multi-physics computational model for the conventional gas metal arc welding (GMAW) joining process has been upgraded with respect to its predictive capabilities regarding the process optimization for the attainment of maximum ballistic limit within the weld. The original model consists of six modules, each dedicated to handling a specific aspect of the GMAW process, i.e., (a) electro-dynamics of the welding gun; (b) radiation-/convection-controlled heat transfer from the electric arc to the workpiece and mass transfer from the filler metal consumable electrode to the weld; (c) prediction of the temporal evolution and the spatial distribution of thermal and mechanical fields within the weld region during the GMAW joining process; (d) the resulting temporal evolution and spatial distribution of the material microstructure throughout the weld region; (e) spatial distribution of the as-welded material mechanical properties; and (f) spatial distribution of the material ballistic limit. In the present work, the model is upgraded through the introduction of the seventh module in recognition of the fact that identification of the optimum GMAW process parameters relative to the attainment of the maximum ballistic limit within the weld region entails the use of advanced optimization and statistical sensitivity analysis methods and tools. The upgraded GMAW process model is next applied to the case of butt welding of MIL A46100 (a prototypical high-hardness armor-grade martensitic steel) workpieces using filler metal electrodes made of the same material. The predictions of the upgraded GMAW process model pertaining to the spatial distribution of the material microstructure and ballistic limit-controlling mechanical properties within the MIL A46100 butt weld are found to be consistent with general expectations and prior observations.

Ultrasonic Sensor Signals and Optimum Path Forest Classifier for the Microstructural Characterization of Thermally-Aged Inconel 625 Alloy

PubMed Central

de Albuquerque, Victor Hugo C.; Barbosa, Cleisson V.; Silva, Cleiton C.; Moura, Elineudo P.; Rebouças Filho, Pedro P.; Papa, João P.; Tavares, João Manuel R. S.

2015-01-01

Secondary phases, such as laves and carbides, are formed during the final solidification stages of nickel-based superalloy coatings deposited during the gas tungsten arc welding cold wire process. However, when aged at high temperatures, other phases can precipitate in the microstructure, like the γ” and δ phases. This work presents an evaluation of the powerful optimum path forest (OPF) classifier configured with six distance functions to classify background echo and backscattered ultrasonic signals from samples of the inconel 625 superalloy thermally aged at 650 and 950 °C for 10, 100 and 200 h. The background echo and backscattered ultrasonic signals were acquired using transducers with frequencies of 4 and 5 MHz. The potentiality of ultrasonic sensor signals combined with the OPF to characterize the microstructures of an inconel 625 thermally aged and in the as-welded condition were confirmed by the results. The experimental results revealed that the OPF classifier is sufficiently fast (classification total time of 0.316 ms) and accurate (accuracy of 88.75% and harmonic mean of 89.52) for the application proposed. PMID:26024416

Ultrasonic sensor signals and optimum path forest classifier for the microstructural characterization of thermally-aged inconel 625 alloy.

PubMed

de Albuquerque, Victor Hugo C; Barbosa, Cleisson V; Silva, Cleiton C; Moura, Elineudo P; Filho, Pedro P Rebouças; Papa, João P; Tavares, João Manuel R S

2015-05-27

Secondary phases, such as laves and carbides, are formed during the final solidification stages of nickel-based superalloy coatings deposited during the gas tungsten arc welding cold wire process. However, when aged at high temperatures, other phases can precipitate in the microstructure, like the γ'' and δ phases. This work presents an evaluation of the powerful optimum path forest (OPF) classifier configured with six distance functions to classify background echo and backscattered ultrasonic signals from samples of the inconel 625 superalloy thermally aged at 650 and 950 °C for 10, 100 and 200 h. The background echo and backscattered ultrasonic signals were acquired using transducers with frequencies of 4 and 5 MHz. The potentiality of ultrasonic sensor signals combined with the OPF to characterize the microstructures of an inconel 625 thermally aged and in the as-welded condition were confirmed by the results. The experimental results revealed that the OPF classifier is sufficiently fast (classification total time of 0.316 ms) and accurate (accuracy of 88.75%" and harmonic mean of 89.52) for the application proposed.

Hot-crack test for aluminium alloys welds using TIG process

NASA Astrophysics Data System (ADS)

Niel, A.; Deschaux-Beaume, F.; Bordreuil, C.; Fras, G.

2010-06-01

Hot cracking is a critical defect frequently observed during welding of aluminium alloys. In order to better understand the interaction between cracking phenomenon, process parameters, mechanical factors and microstructures resulting from solidification after welding, an original hot-cracking test during welding is developed. According to in-situ observations and post mortem analyses, hot cracking mechanisms are investigated, taking into account the interaction between microstructural parameters, depending on the thermal cycles, and mechanical parameters, depending on geometry and clamping conditions of the samples and on the thermal field on the sample. Finally, a process map indicating the limit between cracking and non-cracking zones according to welding parameters is presented.

Evaluation of near-surface stress distributions in dissimilar welded joint by scanning acoustic microscopy.

PubMed

Kwak, Dong Ryul; Yoshida, Sanichiro; Sasaki, Tomohiro; Todd, Judith A; Park, Ik Keun

2016-04-01

This paper presents the results from a set of experiments designed to ultrasonically measure the near surface stresses distributed within a dissimilar metal welded plate. A scanning acoustic microscope (SAM), with a tone-burst ultrasonic wave frequency of 200 MHz, was used for the measurement of near surface stresses in the dissimilar welded plate between 304 stainless steel and low carbon steel. For quantitative data acquisition such as leaky surface acoustic wave (leaky SAW) velocity measurement, a point focus acoustic lens of frequency 200 MHz was used and the leaky SAW velocities within the specimen were precisely measured. The distributions of the surface acoustic wave velocities change according to the near-surface stresses within the joint. A three dimensional (3D) finite element simulation was carried out to predict numerically the stress distributions and compare with the experimental results. The experiment and FE simulation results for the dissimilar welded plate showed good agreement. This research demonstrates that a combination of FE simulation and ultrasonic stress measurements using SAW velocity distributions appear promising for determining welding residual stresses in dissimilar material joints. Copyright © 2016 Elsevier B.V. All rights reserved.

Process of welding gamma prime-strengthened nickel-base superalloys

DOEpatents

Speigel, Lyle B.; White, Raymond Alan; Murphy, John Thomas; Nowak, Daniel Anthony

2003-11-25

A process for welding superalloys, and particularly articles formed of gamma prime-strengthened nickel-base superalloys whose chemistries and/or microstructures differ. The process entails forming the faying surface of at least one of the articles to have a cladding layer of a filler material. The filler material may have a composition that is different from both of the articles, or the same as one of the articles. The cladding layer is machined to promote mating of the faying surfaces, after which the faying surfaces are mated and the articles welded together. After cooling, the welded assembly is free of thermally-induced cracks.

Welding of Aluminum Alloys to Steels: An Overview

DTIC Science & Technology

2013-08-01

and deformations are a few examples of the unwanted consequences which somehow would lead to brittle fracture, fatigue fracture, shape instability...was made under the copper tips of the spot welding machine. The fatigue results showed higher fatigue strength of the joints with transition layer...kHz ultrasonic butt welding system with a vibration source applying eight bolt-clamped Langevin type PZT transducers and a 50 kW static induction

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.

High-frequency ultrasonic wire bonding systems

PubMed

Tsujino; Yoshihara; Sano; Ihara

2000-03-01

The vibration characteristics of longitudinal-complex transverse vibration systems with multiple resonance frequencies of 350-980 kHz for ultrasonic wire bonding of IC, LSI or electronic devices were studied. The complex vibration systems can be applied for direct welding of semiconductor tips (face-down bonding, flip-chip bonding) and packaging of electronic devices. A longitudinal-complex transverse vibration bonding system consists of a complex transverse vibration rod, two driving longitudinal transducers 7.0 mm in diameter and a transverse vibration welding tip. The vibration distributions along ceramic and stainless-steel welding tips were measured at up to 980 kHz. A high-frequency vibration system with a height of 20.7 mm and a weight of less than 15 g was obtained.

Modeling of ultrasonic processes utilizing a generic software framework

NASA Astrophysics Data System (ADS)

Bruns, P.; Twiefel, J.; Wallaschek, J.

2017-06-01

Modeling of ultrasonic processes is typically characterized by a high degree of complexity. Different domains and size scales must be regarded, so that it is rather difficult to build up a single detailed overall model. Developing partial models is a common approach to overcome this difficulty. In this paper a generic but simple software framework is presented which allows to coupe arbitrary partial models by slave modules with well-defined interfaces and a master module for coordination. Two examples are given to present the developed framework. The first one is the parameterization of a load model for ultrasonically-induced cavitation. The piezoelectric oscillator, its mounting, and the process load are described individually by partial models. These partial models then are coupled using the framework. The load model is composed of spring-damper-elements which are parameterized by experimental results. In the second example, the ideal mounting position for an oscillator utilized in ultrasonic assisted machining of stone is determined. Partial models for the ultrasonic oscillator, its mounting, the simplified contact process, and the workpiece’s material characteristics are presented. For both applications input and output variables are defined to meet the requirements of the framework’s interface.

Digital ultrasonic signal processing: Primary ultrasonics task and transducer characterization use and detailed description

NASA Technical Reports Server (NTRS)

Hammond, P. L.

1979-01-01

This manual describes the use of the primary ultrasonics task (PUT) and the transducer characterization system (XC) for the collection, processing, and recording of data received from a pulse-echo ultrasonic system. Both PUT and XC include five primary functions common to many real-time data acquisition systems. Some of these functions are implemented using the same code in both systems. The solicitation and acceptance of operator control input is emphasized. Those operations not under user control are explained.

Spectroscopic analysis technique for arc-welding process control

NASA Astrophysics Data System (ADS)

Mirapeix, Jesús; Cobo, Adolfo; Conde, Olga; Quintela, María Ángeles; López-Higuera, José-Miguel

2005-09-01

The spectroscopic analysis of the light emitted by thermal plasmas has found many applications, from chemical analysis to monitoring and control of industrial processes. Particularly, it has been demonstrated that the analysis of the thermal plasma generated during arc or laser welding can supply information about the process and, thus, about the quality of the weld. In some critical applications (e.g. the aerospace sector), an early, real-time detection of defects in the weld seam (oxidation, porosity, lack of penetration, ...) is highly desirable as it can reduce expensive non-destructive testing (NDT). Among others techniques, full spectroscopic analysis of the plasma emission is known to offer rich information about the process itself, but it is also very demanding in terms of real-time implementations. In this paper, we proposed a technique for the analysis of the plasma emission spectrum that is able to detect, in real-time, changes in the process parameters that could lead to the formation of defects in the weld seam. It is based on the estimation of the electronic temperature of the plasma through the analysis of the emission peaks from multiple atomic species. Unlike traditional techniques, which usually involve peak fitting to Voigt functions using the Levenberg-Marquardt recursive method, we employ the LPO (Linear Phase Operator) sub-pixel algorithm to accurately estimate the central wavelength of the peaks (allowing an automatic identification of each atomic species) and cubic-spline interpolation of the noisy data to obtain the intensity and width of the peaks. Experimental tests on TIG-welding using fiber-optic capture of light and a low-cost CCD-based spectrometer, show that some typical defects can be easily detected and identified with this technique, whose typical processing time for multiple peak analysis is less than 20msec. running in a conventional PC.

Portable spectrometer monitors inert gas shield in welding process

NASA Technical Reports Server (NTRS)

Grove, E. L.

1967-01-01

Portable spectrometer using photosensitive readouts, monitors the amount of oxygen and hydrogen in the inert gas shield of a tungsten-inert gas welding process. A fiber optic bundle transmits the light from the welding arc to the spectrometer.

In situ laser-induced breakdown spectroscopy measurements of chemical compositions in stainless steels during tungsten inert gas welding

NASA Astrophysics Data System (ADS)

Taparli, Ugur Alp; Jacobsen, Lars; Griesche, Axel; Michalik, Katarzyna; Mory, David; Kannengiesser, Thomas

2018-01-01

A laser-induced breakdown spectroscopy (LIBS) system was combined with a bead-on-plate Tungsten Inert Gas (TIG) welding process for the in situ measurement of chemical compositions in austenitic stainless steels during welding. Monitoring the weld pool's chemical composition allows governing the weld pool solidification behavior, and thus enables the reduction of susceptibility to weld defects. Conventional inspection methods for weld seams (e.g. ultrasonic inspection) cannot be performed during the welding process. The analysis system also allows in situ study of the correlation between the occurrence of weld defects and changes in the chemical composition in the weld pool or in the two-phase region where solid and liquid phase coexist. First experiments showed that both the shielding Ar gas and the welding arc plasma have a significant effect on the selected Cr II, Ni II and Mn II characteristic emissions, namely an artificial increase of intensity values via unspecific emission in the spectra. In situ investigations showed that this artificial intensity increase reached a maximum in presence of weld plume. Moreover, an explicit decay has been observed with the termination of the welding plume due to infrared radiation during sample cooling. Furthermore, LIBS can be used after welding to map element distribution. For austenitic stainless steels, Mn accumulations on both sides of the weld could be detected between the heat affected zone (HAZ) and the base material.

Physics-based process model approach for detecting discontinuity during friction stir welding

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

Shrivastava, Amber; Pfefferkorn, Frank E.; Duffie, Neil A.

2015-02-12

The goal of this work is to develop a method for detecting the creation of discontinuities during friction stir welding. This in situ weld monitoring method could significantly reduce the need for post-process inspection. A process force model and a discontinuity force model were created based on the state-of-the-art understanding of flow around an friction stir welding (FSW) tool. These models are used to predict the FSW forces and size of discontinuities formed in the weld. Friction stir welds with discontinuities and welds without discontinuities were created, and the differences in force dynamics were observed. In this paper, discontinuities weremore » generated by reducing the tool rotation frequency and increasing the tool traverse speed in order to create "cold" welds. Experimental force data for welds with discontinuities and welds without discontinuities compared favorably with the predicted forces. The model currently overpredicts the discontinuity size.« less

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.

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

Graphite composite truss welding and cap section forming subsystems. Volume 1: Executive summary. [large space structures

NASA Technical Reports Server (NTRS)

1980-01-01

A rolltrusion process was developed for forming of a hybrid, single-ply woven graphite and glass fiber cloth, impregnated with a polysulfone resin and coated with TI02 pigmented P-1700 resin into strips for the on-orbit fabrication of triangular truss segments. Ultrasonic welding in vacuum showed no identifiable effects on weld strength or resin flow characteristics. An existing bench model cap roll forming machine was modified and used to roll form caps for the prototype test truss and for column test specimens in order to test local buckling and torsional instability characteristics.

Effect of welding process on the microstructure and properties of dissimilar weld joints between low alloy steel and duplex stainless steel

NASA Astrophysics Data System (ADS)

Wang, Jing; Lu, Min-xu; Zhang, Lei; Chang, Wei; Xu, Li-ning; Hu, Li-hua

2012-06-01

To obtain high-quality dissimilar weld joints, the processes of metal inert gas (MIG) welding and tungsten inert gas (TIG) welding for duplex stainless steel (DSS) and low alloy steel were compared in this paper. The microstructure and corrosion morphology of dissimilar weld joints were observed by scanning electron microscopy (SEM); the chemical compositions in different zones were detected by energy-dispersive spectroscopy (EDS); the mechanical properties were measured by microhardness test, tensile test, and impact test; the corrosion behavior was evaluated by polarization curves. Obvious concentration gradients of Ni and Cr exist between the fusion boundary and the type II boundary, where the hardness is much higher. The impact toughness of weld metal by MIG welding is higher than that by TIG welding. The corrosion current density of TIG weld metal is higher than that of MIG weld metal in a 3.5wt% NaCl solution. Galvanic corrosion happens between low alloy steel and weld metal, revealing the weakness of low alloy steel in industrial service. The quality of joints produced by MIG welding is better than that by TIG welding in mechanical performance and corrosion resistance. MIG welding with the filler metal ER2009 is the suitable welding process for dissimilar metals jointing between UNS S31803 duplex stainless steel and low alloy steel in practical application.

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.

The effect of the welding direction on the plasma and metal transfer behavior of CO2 laser+GMAW-P hybrid welding processes

NASA Astrophysics Data System (ADS)

Zhang, Wang; Hua, Xueming; Liao, Wei; Li, Fang; Wang, Min

2014-07-01

During laser-arc hybrid welding, the welding direction exerts direct effects on the plasma properties, the transient behavior of the droplet, the weld pool behavior, and the temperature field. Ultimately, it will affect the welding process and the weld quality. However, the behavior of the CO2 laser+GMAW-P hybrid welding process has not been systematically studied. In this paper, the current-voltage characteristics of different welding processes were analyzed and compared. The dynamics of the droplet transfer, the plasma behavior, and the weld pool behavior were observed by using two high-speed camera systems. Moreover, an optical emission spectroscopy was applied to analyze the plasma temperature and the electron number density. The results indicated that the electrical resistance of the arc plasma reduced in the laser leading mode. For the same pulse duration, the metal transfer mode was the spray type with the laser leading arrangement. The temperature and electron density distribution showed bimodal behavior in the case of arc leading mode, while this phenomenon does not exist in the caser of laser leading mode. The double elliptic-planar distribution which conventional simulation process used was not applicable in the laser leading mode.

Microscopic Evaluation of Friction Plug Welds- Correlation to a Processing Analysis

NASA Technical Reports Server (NTRS)

Rabenberg, Ellen M.; Chen, Poshou; Gorti, Sridhar

2017-01-01

Recently an analysis of dynamic forge load data from the friction plug weld (FPW) process and the corresponding tensile test results showed that good plug welds fit well within an analytically determined processing parameter box. There were, however, some outliers that compromised the predictions. Here the microstructure of the plug weld material is presented in view of the load analysis with the intent of further understanding the FPW process and how it is affected by the grain structure and subsequent mechanical properties.

Optimization of process parameters of pulsed TIG welded maraging steel C300

NASA Astrophysics Data System (ADS)

Deepak, P.; Jualeash, M. J.; Jishnu, J.; Srinivasan, P.; Arivarasu, M.; Padmanaban, R.; Thirumalini, S.

2016-09-01

Pulsed TIG welding technology provides excellent welding performance on thin sections which helps to increase productivity, enhance weld quality, minimize weld costs, and boost operator efficiency and this has drawn the attention of the welding society. Maraging C300 steel is extensively used in defence and aerospace industry and thus its welding becomes an area of paramount importance. In pulsed TIG welding, weld quality depends on the process parameters used. In this work, Pulsed TIG bead-on-plate welding is performed on a 5mm thick maraging C300 plate at different combinations of input parameters: peak current (Ip), base current (Ib) and pulsing frequency (HZ) as per box behnken design with three-levels for each factor. Response surface methodology is utilized for establishing a mathematical model for predicting the weld bead depth. The effect of Ip, Ib and HZ on the weld bead depth is investigated using the developed model. The weld bead depth is found to be affected by all the three parameters. Surface and contour plots developed from regression equation are used to optimize the processing parameters for maximizing the weld bead depth. Optimum values of Ip, Ib and HZ are obtained as 259 A, 120 A and 8 Hz respectively. Using this optimum condition, maximum bead depth of the weld is predicted to be 4.325 mm.

Optimization of Friction Stir Welding Tool Advance Speed via Monte-Carlo Simulation of the Friction Stir Welding Process

PubMed Central

Fraser, Kirk A.; St-Georges, Lyne; Kiss, Laszlo I.

2014-01-01

Recognition of the friction stir welding process is growing in the aeronautical and aero-space industries. To make the process more available to the structural fabrication industry (buildings and bridges), being able to model the process to determine the highest speed of advance possible that will not cause unwanted welding defects is desirable. A numerical solution to the transient two-dimensional heat diffusion equation for the friction stir welding process is presented. A non-linear heat generation term based on an arbitrary piecewise linear model of friction as a function of temperature is used. The solution is used to solve for the temperature distribution in the Al 6061-T6 work pieces. The finite difference solution of the non-linear problem is used to perform a Monte-Carlo simulation (MCS). A polynomial response surface (maximum welding temperature as a function of advancing and rotational speed) is constructed from the MCS results. The response surface is used to determine the optimum tool speed of advance and rotational speed. The exterior penalty method is used to find the highest speed of advance and the associated rotational speed of the tool for the FSW process considered. We show that good agreement with experimental optimization work is possible with this simplified model. Using our approach an optimal weld pitch of 0.52 mm/rev is obtained for 3.18 mm thick AA6061-T6 plate. Our method provides an estimate of the optimal welding parameters in less than 30 min of calculation time. PMID:28788627

Optimization of Friction Stir Welding Tool Advance Speed via Monte-Carlo Simulation of the Friction Stir Welding Process.

PubMed

Fraser, Kirk A; St-Georges, Lyne; Kiss, Laszlo I

2014-04-30

Recognition of the friction stir welding process is growing in the aeronautical and aero-space industries. To make the process more available to the structural fabrication industry (buildings and bridges), being able to model the process to determine the highest speed of advance possible that will not cause unwanted welding defects is desirable. A numerical solution to the transient two-dimensional heat diffusion equation for the friction stir welding process is presented. A non-linear heat generation term based on an arbitrary piecewise linear model of friction as a function of temperature is used. The solution is used to solve for the temperature distribution in the Al 6061-T6 work pieces. The finite difference solution of the non-linear problem is used to perform a Monte-Carlo simulation (MCS). A polynomial response surface (maximum welding temperature as a function of advancing and rotational speed) is constructed from the MCS results. The response surface is used to determine the optimum tool speed of advance and rotational speed. The exterior penalty method is used to find the highest speed of advance and the associated rotational speed of the tool for the FSW process considered. We show that good agreement with experimental optimization work is possible with this simplified model. Using our approach an optimal weld pitch of 0.52 mm/rev is obtained for 3.18 mm thick AA6061-T6 plate. Our method provides an estimate of the optimal welding parameters in less than 30 min of calculation time.

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.

[Hygienic evaluation of new welding processes and welding materials].

PubMed

Gorban', L N

1990-01-01

The possibility of contaminating the breathing air zone with hazardous substances in manual and semi-automated welding increases with the intensity of their formation in the arc zone. This necessitates more comprehensive data on both the specific excreta and the formation intensity of the most hazardous substances, such as hard and gaseous compounds of welding aerosols, with due account of the welding regimen used and electrode diameter, wires, etc. When calculating the effectiveness of both local and general ventilation systems in welding shops, a possibility of a specific one-way hazardous action of some chemical substances (e.g. chromium, fluorine, etc.) should be taken into account.

Design of signal reception and processing system of embedded ultrasonic endoscope

NASA Astrophysics Data System (ADS)

Li, Ming; Yu, Feng; Zhang, Ruiqiang; Li, Yan; Chen, Xiaodong; Yu, Daoyin

2009-11-01

Embedded Ultrasonic Endoscope, based on embedded microprocessor and embedded real-time operating system, sends a micro ultrasonic probe into coelom through the biopsy channel of the Electronic Endoscope to get the fault histology features of digestive organs by rotary scanning, and acquires the pictures of the alimentary canal mucosal surface. At the same time, ultrasonic signals are processed by signal reception and processing system, forming images of the full histology of the digestive organs. Signal Reception and Processing System is an important component of Embedded Ultrasonic Endoscope. However, the traditional design, using multi-level amplifiers and special digital processing circuits to implement signal reception and processing, is no longer satisfying the standards of high-performance, miniaturization and low power requirements that embedded system requires, and as a result of the high noise that multi-level amplifier brought, the extraction of small signal becomes hard. Therefore, this paper presents a method of signal reception and processing based on double variable gain amplifier and FPGA, increasing the flexibility and dynamic range of the Signal Reception and Processing System, improving system noise level, and reducing power consumption. Finally, we set up the embedded experiment system, using a transducer with the center frequency of 8MHz to scan membrane samples, and display the image of ultrasonic echo reflected by each layer of membrane, with a frame rate of 5Hz, verifying the correctness of the system.

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

PubMed

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

2016-09-15

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

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

PubMed Central

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

2016-01-01

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

Energy reduction for the spot welding process in the automotive industry

NASA Astrophysics Data System (ADS)

Cullen, J. D.; Athi, N.; Al-Jader, M. A.; Shaw, A.; Al-Shamma'a, A. I.

2007-07-01

When performing spot welding on galvanised metals, higher welding force and current are required than on uncoated steels. This has implications for the energy usage when creating each spot weld, of which there are approximately 4300 in each passenger car. The paper presented is an overview of electrode current selection and its variance over the lifetime of the electrode tip. This also describes the proposed analysis system for the selection of welding parameters for the spot welding process, as the electrode tip wears.

Cold pressure welding of aluminium-steel blanks: Manufacturing process and electrochemical surface preparation

NASA Astrophysics Data System (ADS)

Schmidt, Hans Christian; Homberg, Werner; Orive, Alejandro Gonzalez; Grundmeier, Guido; Hordych, Illia; Maier, Hans Jürgen

2018-05-01

In this study the manufacture of aluminium-steel blanks by cold pressure welding and their preparation for a welding process through electrochemical surface treatment are investigated and discussed. The cold pressure welding process was done with an incremental rolling tool that allows for the partial pressure welding of two blanks along a prepared path. The influence of the surface preparation by electrochemical deposition of bond promoting organosilane-based agents and roughening on a nano-scale is investigated and compared to conventional surface treatments. Coating the surfaces with a thin organosilane-based film incorporating specific functional groups should promote additional bonding between the mating oxide layers; its influence on the total weld strength is studied. Pressure welding requires suitable process strategies, and the current advances in the proposed incremental rolling process for the combination of mild steel and aluminium are presented.

Modifying welding process parameters can reduce the neurotoxic potential of manganese-containing welding fumes.

PubMed

Sriram, Krishnan; Lin, Gary X; Jefferson, Amy M; Stone, Samuel; Afshari, Aliakbar; Keane, Michael J; McKinney, Walter; Jackson, Mark; Chen, Bean T; Schwegler-Berry, Diane; Cumpston, Amy; Cumpston, Jared L; Roberts, Jenny R; Frazer, David G; Antonini, James M

2015-02-03

Welding fumes (WF) are a complex mixture of toxic metals and gases, inhalation of which can lead to adverse health effects among welders. The presence of manganese (Mn) in welding electrodes is cause for concern about the potential development of Parkinson's disease (PD)-like neurological disorder. Consequently, from an occupational safety perspective, there is a critical need to prevent adverse exposures to WF. As the fume generation rate and physicochemical characteristics of welding aerosols are influenced by welding process parameters like voltage, current or shielding gas, we sought to determine if changing such parameters can alter the fume profile and consequently its neurotoxic potential. Specifically, we evaluated the influence of voltage on fume composition and neurotoxic outcome. Rats were exposed by whole-body inhalation (40 mg/m(3); 3h/day × 5 d/week × 2 weeks) to fumes generated by gas-metal arc welding using stainless steel electrodes (GMA-SS) at standard/regular voltage (25 V; RVSS) or high voltage (30 V; HVSS). Fumes generated under these conditions exhibited similar particulate morphology, appearing as chain-like aggregates; however, HVSS fumes comprised of a larger fraction of ultrafine particulates that are generally considered to be more toxic than their fine counterparts. Paradoxically, exposure to HVSS fumes did not elicit dopaminergic neurotoxicity, as monitored by the expression of dopaminergic and PD-related markers. We show that the lack of neurotoxicity is due to reduced solubility of Mn in HVSS fumes. Our findings show promise for process control procedures in developing prevention strategies for Mn-related neurotoxicity during welding; however, it warrants additional investigations to determine if such modifications can be suitably adapted at the workplace to avert or reduce adverse neurological risks. Published by Elsevier Ireland Ltd.

Modifying welding process parameters can reduce the neurotoxic potential of manganese-containing welding fumes

PubMed Central

Sriram, Krishnan; Lin, Gary X.; Jefferson, Amy M.; Stone, Samuel; Afshari, Aliakbar; Keane, Michael J.; McKinney, Walter; Jackson, Mark; Chen, Bean T.; Schwegler-Berry, Diane; Cumpston, Amy; Cumpston, Jared L.; Roberts, Jenny R.; Frazer, David G.; Antonini, James M.

2015-01-01

Welding fumes (WF) are a complex mixture of toxic metals and gases, inhalation of which can lead to adverse health effects among welders. The presence of manganese (Mn) in welding electrodes is cause for concern about the potential development of Parkinson’s disease (PD)-like neurological disorder. Consequently, from an occupational safety perspective, there is a critical need to prevent adverse exposures to WF. As the fume generation rate and physicochemical characteristics of welding aerosols are influenced by welding process parameters like voltage, current or shielding gas, we sought to determine if changing such parameters can alter the fume profile and consequently its neurotoxic potential. Specifically, we evaluated the influence of voltage on fume composition and neurotoxic outcome. Rats were exposed by whole-body inhalation (40 mg/m3; 3 h/day × 5 d/week × 2 weeks) to fumes generated by gas–metal arc welding using stainless steel electrodes (GMA-SS) at standard/regular voltage (25 V; RVSS) or high voltage (30 V; HVSS). Fumes generated under these conditions exhibited similar particulate morphology, appearing as chain-like aggregates; however, HVSS fumes comprised of a larger fraction of ultrafine particulates that are generally considered to be more toxic than their ne counterparts. Paradoxically, exposure to HVSS fumes did not elicit dopaminergic neurotoxicity, as monitored by the expression of dopaminergic and PD-related markers. We show that the lack of neurotoxicity is due to reduced solubility of Mn in HVSS fumes. Our findings show promise for process control procedures in developing prevention strategies for Mn-related neurotoxicity during welding; however, it warrants additional investigations to determine if such modifications can be suitably adapted at the workplace to avert or reduce adverse neurological risks. PMID:25549921

Improvement of Landfill Leachate Biodegradability with Ultrasonic Process

PubMed Central

Mahvi, Amir Hossein; Roodbari, Ali Akbar; Nabizadeh Nodehi, Ramin; Nasseri, Simin; Dehghani, Mohammad Hadil; Alimohammadi, Mahmood

2012-01-01

Landfills leachates are known to contain recalcitrant and/or non-biodegradable organic substances and biological processes are not efficient in these cases. A promising alternative to complete oxidation of biorecalcitrant leachate is the use of ultrasonic process as pre-treatment to convert initially biorecalcitrant compounds to more readily biodegradable intermediates. The objectives of this study are to investigate the effect of ultrasonic process on biodegradability improvement. After the optimization by factorial design, the ultrasonic were applied in the treatment of raw leachates using a batch wise mode. For this, different scenarios were tested with regard to power intensities of 70 and 110 W, frequencies of 30, 45 and 60 KHz, reaction times of 30, 60, 90 and 120 minutes and pH of 3, 7 and 10. For determining the effects of catalysts on sonication efficiencies, 5 mg/l of TiO2 and ZnO have been also used. Results showed that when applied as relatively brief pre-treatment systems, the sonocatalysis processes induce several modifications of the matrix, which results in significant enhancement of its biodegradability. For this reason, the integrated chemical–biological systems proposed here represent a suitable solution for the treatment of landfill leachate samples. PMID:22829863

Research on the processing technology of elongated holes based on rotary ultrasonic drilling

NASA Astrophysics Data System (ADS)

Tong, Yi; Chen, Jianhua; Sun, Lipeng; Yu, Xin; Wang, Xin

2014-08-01

The optical glass is hard, brittle and difficult to process. Based on the method of rotating ultrasonic drilling, the study of single factor on drilling elongated holes was made in optical glass. The processing equipment was DAMA ultrasonic machine, and the machining tools were electroplated with diamond. Through the detection and analysis on the processing quality and surface roughness, the process parameters (the spindle speed, amplitude, feed rate) of rotary ultrasonic drilling were researched, and the influence of processing parameters on surface roughness was obtained, which will provide reference and basis for the actual processing.

Modeling of laser transmission contour welding process using FEA and DoE

NASA Astrophysics Data System (ADS)

Acherjee, Bappa; Kuar, Arunanshu S.; Mitra, Souren; Misra, Dipten

2012-07-01

In this research, a systematic investigation on laser transmission contour welding process is carried out using finite element analysis (FEA) and design of experiments (DoE) techniques. First of all, a three-dimensional thermal model is developed to simulate the laser transmission contour welding process with a moving heat source. The commercial finite element code ANSYS® multi-physics is used to obtain the numerical results by implementing a volumetric Gaussian heat source, and combined convection-radiation boundary conditions. Design of experiments together with regression analysis is then employed to plan the experiments and to develop mathematical models based on simulation results. Four key process parameters, namely power, welding speed, beam diameter, and carbon black content in absorbing polymer, are considered as independent variables, while maximum temperature at weld interface, weld width, and weld depths in transparent and absorbing polymers are considered as dependent variables. Sensitivity analysis is performed to determine how different values of an independent variable affect a particular dependent variable.

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.

An Evaluation of Former Soviet Union Welding Processes on Commercially Pure Titanium

DTIC Science & Technology

2001-12-01

welding (GTAW), gas metal arc welding ( GMAW ), and plasma arc welding (PAW) being the most widely used techniques. Of these, the GTAW process is much...quality welds, is free of the spatter that may occur with GMAW , and can be used with or without filler material, depending on the specific application

Online quality monitoring of welding processes by means of plasma optical spectroscopy

NASA Astrophysics Data System (ADS)

Ferrara, Michele; Ancona, Antonio; Lugara, Pietro M.; Sibilano, Michele

2000-02-01

An optical monitoring system for the welding process has been developed; it is based on the study of the optical emission of the welding plasma plume, created during the welding of stainless steels and other iron-based materials. In the first approach a continuous wave CO2 laser of 2500-Watt maximum power, available at the INFM Research Unit labs in Bari University, has been used as welding source. A detailed spectroscopic study of the visible and UV welding plasma emission has been carried out; many transition lines corresponding to the elements composing the material to be welded have been found. By means of an appropriate selection of these lines and suitable algorithms, the electronic temperature of the plasma plume has been calculated and its evolution recorded as a function of several welding parameters. The behavior of the registered signal has resulted to be correlated to the welded joint quality. These findings have allowed to design and assemble a portable, non-intrusive and real-time welding quality optical sensor which has been successfully tested for laser welding of metals in different geometrical configurations; it has been capable of detecting a wide range of weld defects normally occurring during industrial laser metal-working. This sensor has also been tested in arc welding industrial processes (TIG) with promising results.

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

Advanced Bode Plot Techniques for Ultrasonic Transducers

NASA Astrophysics Data System (ADS)

DeAngelis, D. A.; Schulze, G. W.

The Bode plot, displayed as either impedance or admittance versus frequency, is the most basic test used by ultrasonic transducer designers. With simplicity and ease-of-use, Bode plots are ideal for baseline comparisons such as spacing of parasitic modes or impedance, but quite often the subtleties that manifest as poor process control are hard to interpret or are nonexistence. In-process testing of transducers is time consuming for quantifying statistical aberrations, and assessments made indirectly via the workpiece are difficult. This research investigates the use of advanced Bode plot techniques to compare ultrasonic transducers with known "good" and known "bad" process performance, with the goal of a-priori process assessment. These advanced techniques expand from the basic constant voltage versus frequency sweep to include constant current and constant velocity interrogated locally on transducer or tool; they also include up and down directional frequency sweeps to quantify hysteresis effects like jumping and dropping phenomena. The investigation focuses solely on the common PZT8 piezoelectric material used with welding transducers for semiconductor wire bonding. Several metrics are investigated such as impedance, displacement/current gain, velocity/current gain, displacement/voltage gain and velocity/voltage gain. The experimental and theoretical research methods include Bode plots, admittance loops, laser vibrometry and coupled-field finite element analysis.

Investigation on edge joints of Inconel 625 sheets processed with laser welding

NASA Astrophysics Data System (ADS)

Caiazzo, F.; Alfieri, V.; Cardaropoli, F.; Sergi, V.

2017-08-01

Laser welding of Inconel 625 edge joint beads in square groove configuration was investigated. The use of different weld geometries in new aerospace solutions explains research on edge joints. A structured plan was carried out in order to characterize the process defining the influence of laser power and welding speed and to study possible interactions among the governing factors. As weld pool protection is crucial in order to obtain sound joints when processing superalloys, a special glove box for gas supply was designed to upgrade the welding head. Welded joints were characterized referring to bead profile, microstructure and X-rays. It was found that heat input plays an important role as it affects welding stability, porosity content and bead shape. Results suggest operating with low values of heat input to reduce porosity and guarantee stable bead conformation. Furthermore, a decrease in the grain size has been observed as a consequence of decreasing heat input.

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

PubMed

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

2005-01-01

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

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.

Displaced electrode process for welding

DOEpatents

Heichel, L.J.

1975-08-26

A method is described for the butt-welding of a relatively heavy mass to a relatively small mass such as a thin-wall tube. In butt-welding heat is normally applied at the joint between the two pieces which are butt-welded together. The application of heat at the joint results in overheating the tube which causes thinning of the tube walls and porosity in the tube material. This is eliminated by displacing the welding electrode away from the seam toward the heavier mass so that heat is applied to the heavy mass and not at the butt seam. Examples of the parameters used in welding fuel rods are given. The cladding and end plugs were made of Zircalloy. The electrode used was of 2 percent thoriated tungsten. (auth)

Novel Real-Time Diagnosis of the Freezing Process Using an Ultrasonic Transducer

PubMed Central

Tseng, Yen-Hsiang; Cheng, Chin-Chi; Cheng, Hong-Ping; Lee, Dasheng

2015-01-01

The freezing stage governs several critical parameters of the freeze drying process and the quality of the resulting lyophilized products. This paper presents an integrated ultrasonic transducer (UT) in a stainless steel bottle and its application to real-time diagnostics of the water freezing process. The sensor was directly deposited onto the stainless steel bottle using a sol-gel spray technique. It could operate at temperature range from −100 to 400 °C and uses an ultrasonic pulse-echo technique. The progression of the freezing process, including water-in, freezing point and final phase change of water, were all clearly observed using ultrasound. The ultrasonic signals could indicate the three stages of the freezing process and evaluate the cooling and freezing periods under various processing conditions. The temperature was also adopted for evaluating the cooling and freezing periods. These periods increased with water volume and decreased with shelf temperature (i.e., speed of freezing). This study demonstrates the effectiveness of the ultrasonic sensor and technology for diagnosing and optimizing the process of water freezing to save energy. PMID:25946629

Generation of sonic power during welding

NASA Technical Reports Server (NTRS)

Mc Campbell, W. M.

1969-01-01

Generation of intense sonic and ultrasonic power in the weld zone, close to the puddle, reduces the porosity and refinement of the grain. The ac induction brazing power supply is modified with long cables for deliberate addition of resistance to that circuit. The concept is extensible to the molding of metals and plastics.

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

NASA Astrophysics Data System (ADS)

Ahmadi, E.; Ebrahimi, A. R.

2015-02-01

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

Analysis Method of Friction Torque and Weld Interface Temperature during Friction Process of Steel Friction Welding

NASA Astrophysics Data System (ADS)

Kimura, Masaaki; Inoue, Haruo; Kusaka, Masahiro; Kaizu, Koichi; Fuji, Akiyoshi

This paper describes an analysis method of the friction torque and weld interface temperature during the friction process for steel friction welding. The joining mechanism model of the friction welding for the wear and seizure stages was constructed from the actual joining phenomena that were obtained by the experiment. The non-steady two-dimensional heat transfer analysis for the friction process was carried out by calculation with FEM code ANSYS. The contact pressure, heat generation quantity, and friction torque during the wear stage were calculated using the coefficient of friction, which was considered as the constant value. The thermal stress was included in the contact pressure. On the other hand, those values during the seizure stage were calculated by introducing the coefficient of seizure, which depended on the seizure temperature. The relationship between the seizure temperature and the relative speed at the weld interface in the seizure stage was determined using the experimental results. In addition, the contact pressure and heat generation quantity, which depended on the relative speed of the weld interface, were solved by taking the friction pressure, the relative speed and the yield strength of the base material into the computational conditions. The calculated friction torque and weld interface temperatures of a low carbon steel joint were equal to the experimental results when friction pressures were 30 and 90 MPa, friction speed was 27.5 s-1, and weld interface diameter was 12 mm. The calculation results of the initial peak torque and the elapsed time for initial peak torque were also equal to the experimental results under the same conditions. Furthermore, the calculation results of the initial peak torque and the elapsed time for initial peak torque at various friction pressures were equal to the experimental results.

Temperature compensation of ultrasonic velocity during the malolactic fermentation process

NASA Astrophysics Data System (ADS)

Amer, M. A.; Novoa-Díaz, D.; Chávez, J. A.; Turó, A.; García-Hernández, M. J.; Salazar, J.

2015-12-01

Ultrasonic properties of materials present a strong dependence on temperature and in turn the ultrasonic velocity of propagation in the material under test. It is precisely for this reason that most ultrasonic measurements are often carried out with thermostated samples by using either water tanks or climate chambers. This approach is viable in a laboratory and when the measured or characterized samples are relatively small. However, this procedure is highly improbable to be applied when in situ measurements in industrial environments must be performed. This goes for the case of, for example, ultrasonic velocity measurements in wine while it is performing malolactic fermentation inside a tank of hundreds of thousands of litres. In this paper two different practical approaches to temperature compensation are studied. Then, the two temperature compensation methods are applied to the measured ultrasonic velocity values along a whole malolactic fermentation process. The results of each method are discussed.

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.

Microstructure and fatigue resistance of high strength dual phase steel welded with gas metal arc welding and plasma arc welding processes

NASA Astrophysics Data System (ADS)

Ahiale, Godwin Kwame; Oh, Yong-Jun; Choi, Won-Doo; Lee, Kwang-Bok; Jung, Jae-Gyu; Nam, Soo Woo

2013-09-01

This study presents the microstructure and high cycle fatigue performance of lap shear joints of dual phase steel (DP590) welded using gas metal arc welding (GMAW) and plasma arc welding (PAW) processes. High cycle fatigue tests were conducted on single and double lap joints under a load ratio of 0.1 and a frequency of 20 Hz. In order to establish a basis for comparison, both weldments were fabricated to have the same weld depth in the plate thickness. The PAW specimens exhibited a higher fatigue life, a gentle S-N slope, and a higher fatigue limit than the GMAW specimens. The improvement in the fatigue life of the PAW specimens was primarily attributed to the geometry effect that exhibited lower and wider beads resulting in a lower stress concentration at the weld toe where cracks initiate and propagate. Furthermore, the microstructural constituents in the heat-affected zone (HAZ) of the PAW specimens contributed to the improvement. The higher volume fraction of acicular ferrite in the HAZ beneath the weld toe enhanced the PAW specimen's resistance to fatigue crack growth. The double lap joints displayed a higher fatigue life than the single lap joints without changing the S-N slope.

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.

Linear friction weld process monitoring of fixture cassette deformations using empirical mode decomposition

NASA Astrophysics Data System (ADS)

Bakker, O. J.; Gibson, C.; Wilson, P.; Lohse, N.; Popov, A. A.

2015-10-01

Due to its inherent advantages, linear friction welding is a solid-state joining process of increasing importance to the aerospace, automotive, medical and power generation equipment industries. Tangential oscillations and forge stroke during the burn-off phase of the joining process introduce essential dynamic forces, which can also be detrimental to the welding process. Since burn-off is a critical phase in the manufacturing stage, process monitoring is fundamental for quality and stability control purposes. This study aims to improve workholding stability through the analysis of fixture cassette deformations. Methods and procedures for process monitoring are developed and implemented in a fail-or-pass assessment system for fixture cassette deformations during the burn-off phase. Additionally, the de-noised signals are compared to results from previous production runs. The observed deformations as a consequence of the forces acting on the fixture cassette are measured directly during the welding process. Data on the linear friction-welding machine are acquired and de-noised using empirical mode decomposition, before the burn-off phase is extracted. This approach enables a direct, objective comparison of the signal features with trends from previous successful welds. The capacity of the whole process monitoring system is validated and demonstrated through the analysis of a large number of signals obtained from welding experiments.

Discontinuity Detection in the Shield Metal Arc Welding Process

PubMed Central

Cocota, José Alberto Naves; Garcia, Gabriel Carvalho; da Costa, Adilson Rodrigues; de Lima, Milton Sérgio Fernandes; Rocha, Filipe Augusto Santos; Freitas, Gustavo Medeiros

2017-01-01

This work proposes a new methodology for the detection of discontinuities in the weld bead applied in Shielded Metal Arc Welding (SMAW) processes. The detection system is based on two sensors—a microphone and piezoelectric—that acquire acoustic emissions generated during the welding. The feature vectors extracted from the sensor dataset are used to construct classifier models. The approaches based on Artificial Neural Network (ANN) and Support Vector Machine (SVM) classifiers are able to identify with a high accuracy the three proposed weld bead classes: desirable weld bead, shrinkage cavity and burn through discontinuities. Experimental results illustrate the system’s high accuracy, greater than 90% for each class. A novel Hierarchical Support Vector Machine (HSVM) structure is proposed to make feasible the use of this system in industrial environments. This approach presented 96.6% overall accuracy. Given the simplicity of the equipment involved, this system can be applied in the metal transformation industries. PMID:28489045

Discontinuity Detection in the Shield Metal Arc Welding Process.

PubMed

Cocota, José Alberto Naves; Garcia, Gabriel Carvalho; da Costa, Adilson Rodrigues; de Lima, Milton Sérgio Fernandes; Rocha, Filipe Augusto Santos; Freitas, Gustavo Medeiros

2017-05-10

This work proposes a new methodology for the detection of discontinuities in the weld bead applied in Shielded Metal Arc Welding (SMAW) processes. The detection system is based on two sensors-a microphone and piezoelectric-that acquire acoustic emissions generated during the welding. The feature vectors extracted from the sensor dataset are used to construct classifier models. The approaches based on Artificial Neural Network (ANN) and Support Vector Machine (SVM) classifiers are able to identify with a high accuracy the three proposed weld bead classes: desirable weld bead, shrinkage cavity and burn through discontinuities. Experimental results illustrate the system's high accuracy, greater than 90% for each class. A novel Hierarchical Support Vector Machine (HSVM) structure is proposed to make feasible the use of this system in industrial environments. This approach presented 96.6% overall accuracy. Given the simplicity of the equipment involved, this system can be applied in the metal transformation industries.

Process Parameter Optimization for Wobbling Laser Spot Welding of Ti6Al4V Alloy

NASA Astrophysics Data System (ADS)

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

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

Influencing the arc and the mechanical properties of the weld metal in GMA-welding processes by additive elements on the wire electrode surface

NASA Astrophysics Data System (ADS)

Wesling, V.; Schram, A.; Müller, T.; Treutler, K.

2016-03-01

Under the premise of an increasing scarcity of raw materials and increasing demands on construction materials, the mechanical properties of steels and its joints are gaining highly important. In particular high- and highest-strength steels are getting in the focus of the research and the manufacturing industry. To the same extent, the requirements for filler metals are increasing as well. At present, these low-alloy materials are protected by a copper coating (<1μm) against corrosion. In addition, the coating realizes a good ohmic contact and good sliding properties between the welding machine and the wire during the welding process. By exchanging the copper with other elements it should be possible to change the mechanical properties of the weld metal and the arc stability during gas metal arc welding processes and keep the basic functions of the coating nearly untouched. On a laboratory scale solid wire electrodes with coatings of various elements and compounds such as titanium oxide were made and processed with a Gas Metal Arc Welding process. During the processing a different process behavior between the wire electrodes, coated and original, could be observed. The influences ranges from greater/shorter arc-length over increasing/decreasing droplets to larger/smaller arc foot point. Furthermore, the weld metal of the coated electrodes has significantly different mechanical and technological characteristics as the weld metal from the copper coated ground wire. The yield strength and tensile strength can be increased by up to 50%. In addition, the chemical composition of the weld metal was influenced by the application of coatings with layer thicknesses to 15 microns in the lower percentage range (up to about 3%). Another effect of the coating is a modified penetration. The normally occurring “argon finger” can be suppressed or enhanced by the choice of the coating. With the help of the presented studies it will be shown that Gas Metal Arc Welding processes

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 promises to be an important welding process for any industries where welds of optimal quality are demanded. This article provides an introduction to the FSW process. The chief concern is the physical effect of the tool on the weld metal: how weld seam bonding takes place, what kind of weld structure is generated, potential problems, possible defects for example, and implications for process parameters and tool design. Weld properties are determined by structure, and the structure of friction stir welds is determined by the weld metal flow field in the vicinity of the weld tool. Metal flow in the vicinity of the weld tool is explained through a simple kinematic flow model that decomposes the flow field into three basic component flows: a uniform translation, a rotating solid cylinder, and a ring vortex encircling the tool. The flow components, superposed to construct the flow model, can be related to particular aspects of weld process parameters and tool design; they provide a bridge to an understanding of a complex-at-first-glance weld structure. Torques and forces are also discussed. Some simple mathematical models of structural aspects, torques, and forces are included.

Mondani intraoral welding: historical process and main practical applications.

PubMed

Dal Carlo, L; Pasqualini, M E; Mondani, P M; Rossi, F; Moglioni, E; Shulman, M

2017-01-01

The intraoral welder was invented by Dr. Pierluigi Mondani during the early 70’s to weld titanium needle implants to a titanium bar in patient’s mouth and to load them immediately by means of resin prosthesis. The clinical use documented dates back to 1972. Over the years, many practical applications have been added to the initial one, which have expanded the use of this device. In this scientific work, main applications are described. The aim of the work was to trace the historical process of intra-oral welding according to Mondani and describe the main practical applications. Intra-oral welding is a process introduced by dr. Pier Luigi Mondani of Genova (Italy) which allows to firmly conjoin titanium implants of any shape by means of a titanium bar or also directly between them in the mouth during surgery. The immediate stabilization achieved by intraoral welding increases implants success rate, allows immediate loading even in situations of bone atrophy, saves implants that are running into failure, re-evaluates fractured implants, allows to stabilize submerged implants postponing prosthesis management, allows to achieve efficient rehabilitation protocols to deal with difficult cases. The 40-years’ experience with intra-oral welding described in this article, confirms the ease of use and efficiency in providing immediate stabilization of titanium implants of all types.

Ultrasonic processing for recovery of chicken erythrocyte hemoglobin

USDA-ARS?s Scientific Manuscript database

Hemoglobin from chicken blood has been shown to be a good substitute for synthetic polymeric flocculants. One stage of processing the blood entails breaking open the cells and releasing the cytoplasmic contents; in the present study, we investigate the use of ultrasonic processing at this stage. Was...

Effect of Multipass TIG and Activated TIG Welding Process on the Thermo-Mechanical Behavior of 316LN Stainless Steel Weld Joints

NASA Astrophysics Data System (ADS)

Ganesh, K. C.; Balasubramanian, K. R.; Vasudevan, M.; Vasantharaja, P.; Chandrasekhar, N.

2016-04-01

The primary objective of this work was to develop a finite element model to predict the thermo-mechanical behavior of an activated tungsten inert gas (ATIG)-welded joint. The ATIG-welded joint was fabricated using 10 mm thickness of 316LN stainless steel plates in a single pass. To distinguish the merits of ATIG welding process, it was compared with manual multipass tungsten inert gas (MPTIG)-welded joint. The ATIG-welded joint was fabricated with square butt edge configuration using an activating flux developed in-house. The MPTIG-welded joint was fabricated in thirteen passes with V-groove edge configuration. The finite element model was developed to predict the transient temperature, residual stress, and distortion of the welded joints. Also, microhardness, impact toughness, tensile strength, ferrite measurement, and microstructure were characterized. Since most of the recent publications of ATIG-welded joint was focused on the molten weld pool dynamics, this research work gives an insight on the thermo-mechanical behavior of ATIG-welded joint over MPTIG-welded joint.

The Influence of Friction Stir Weld Tool Form and Welding Parameters on Weld Structure and Properties: Nugget Bulge in Self-Reacting Friction Stir Welds

NASA Technical Reports Server (NTRS)

Schneider, Judy; Nunes, Arthur C., Jr.; Brendel, Michael S.

2010-01-01

Although friction stir welding (FSW) was patented in 1991, process development has been based upon trial and error and the literature still exhibits little understanding of the mechanisms determining weld structure and properties. New concepts emerging from a better understanding of these mechanisms enhance the ability of FSW engineers to think about the FSW process in new ways, inevitably leading to advances in the technology. A kinematic approach in which the FSW flow process is decomposed into several simple flow components has been found to explain the basic structural features of FSW welds and to relate them to tool geometry and process parameters. Using this modelling approach, this study reports on a correlation between the features of the weld nugget, process parameters, weld tool geometry, and weld strength. This correlation presents a way to select process parameters for a given tool geometry so as to optimize weld strength. It also provides clues that may ultimately explain why the weld strength varies within the sample population.

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.

Profiling mild steel welding processes to reduce fume emissions and costs in the workplace.

PubMed

Keane, Michael J; Siert, Arlen; Chen, Bean T; Stone, Samuel G

2014-05-01

To provide quantitative information to choose the best welding processes for minimizing workplace emissions, nine gas metal arc welding (GMAW) processes for mild steel were assessed for fume generation rates, normalized fume generation rates (milligram fume per gram of electrode consumed), and normalized generation rates for elemental manganese, nickel, and iron. Shielded metal arc welding (SMAW) and flux-cored arc-welding (FCAW) processes were also profiled. The fumes were collected quantitatively in an American Welding Society-type fume chamber and weighed, recovered, homogenized, and analyzed by inductively coupled atomic emission spectroscopy for total metals. The processes included GMAW with short circuit, globular transfer, axial spray, pulsed spray, Surface Tension Transfer™, Regulated Metal Deposition™, and Cold Metal Transfer™ (CMT) modes. Flux-cored welding was gas shielded, and SMAW was a single rod type. Results indicate a wide range of fume emission factors for the process variations studied. Fume emission rates per gram of electrode consumed were highest for SMAW (~13 mg fume g(-1) electrode) and lowest for GMAW processes such as pulsed spray (~1.5mg g(-1)) and CMT (~1mg g(-1)). Manganese emission rates per gram of electrode consumed ranged from 0.45 mg g(-1) (SMAW) to 0.08 mg g(-1) (CMT). Nickel emission rates were generally low and ranged from ~0.09 (GMAW short circuit) to 0.004 mg g(-1) (CMT). Iron emission rates ranged from 3.7 (spray-mode GMAW) to 0.49 mg g(-1) (CMT). The processes studied have significantly different costs, and cost factors are presented based on a case study to allow comparisons between processes in specific cost categories. Costs per linear meter of weld were $31.07 (SMAW), $12.37 (GMAW short circuit), and $10.89 (FCAW). Although no single process is the best for minimizing fume emissions and costs while satisfying the weld requirements, there are several processes that can minimize emissions. This study provides

Profiling Mild Steel Welding Processes to Reduce Fume Emissions and Costs in the Workplace

PubMed Central

Keane, Michael J.; Siert, Arlen; Chen, Bean T.; Stone, Samuel G.

2015-01-01

To provide quantitative information to choose the best welding processes for minimizing workplace emissions, nine gas metal arc welding (GMAW) processes for mild steel were assessed for fume generation rates, normalized fume generation rates (milligram fume per gram of electrode consumed), and normalized generation rates for elemental manganese, nickel, and iron. Shielded metal arc welding (SMAW) and flux-cored arc-welding (FCAW) processes were also profiled. The fumes were collected quantitatively in an American Welding Society-type fume chamber and weighed, recovered, homogenized, and analyzed by inductively coupled atomic emission spectroscopy for total metals. The processes included GMAW with short circuit, globular transfer, axial spray, pulsed spray, Surface Tension Transfer™, Regulated Metal Deposition™, and Cold Metal Transfer™ (CMT) modes. Flux-cored welding was gas shielded, and SMAW was a single rod type. Results indicate a wide range of fume emission factors for the process variations studied. Fume emission rates per gram of electrode consumed were highest for SMAW (~13 mg fume g−1 electrode) and lowest for GMAW processes such as pulsed spray (~1.5 mg g−1) and CMT (~1 mg g−1). Manganese emission rates per gram of electrode consumed ranged from 0.45 mg g−1 (SMAW) to 0.08 mg g−1 (CMT). Nickel emission rates were generally low and ranged from ~0.09 (GMAW short circuit) to 0.004 mg g−1 (CMT). Iron emission rates ranged from 3.7 (spray-mode GMAW) to 0.49 mg g−1 (CMT). The processes studied have significantly different costs, and cost factors are presented based on a case study to allow comparisons between processes in specific cost categories. Costs per linear meter of weld were $31.07 (SMAW), $12.37 (GMAW short circuit), and $10.89 (FCAW). Although no single process is the best for minimizing fume emissions and costs while satisfying the weld requirements, there are several processes that can minimize emissions. This study provides

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.

Novel Real-Time Temperature Diagnosis of Conventional Hot-Embossing Process Using an Ultrasonic Transducer

PubMed Central

Cheng, Chin-Chi; Yang, Sen-Yeu; Lee, Dasheng

2014-01-01

This paper presents an integrated high temperature ultrasonic transducer (HTUT) on a sensor insert and its application for real-time diagnostics of the conventional hot embossing process to fabricate V-cut patterns. The sensor was directly deposited onto the sensor insert of the hot embossing mold by using a sol-gel spray technique. It could operate at temperatures higher than 400 °C and uses an ultrasonic pulse-echo technique. The ultrasonic velocity could indicate the three statuses of the hot embossing process and also evaluate the replication of V-cut patterns on a plastic plate under various processing conditions. The progression of the process, including mold closure, plastic plate softening, cooling and plate detachment inside the mold, was clearly observed using ultrasound. For an ultrasonic velocity range from 2197.4 to 2435.9 m/s, the height of the V-cut pattern decreased from 23.0 to 3.2 μm linearly, with a ratio of −0.078 μm/(m/s). The incompleteness of the replication of the V-cut patterns could be indirectly observed by the ultrasonic signals. This study demonstrates the effectiveness of the ultrasonic sensors and technology for diagnosing the replicating condition of microstructures during the conventional hot embossing process. PMID:25330051

Adaptive weld control for high-integrity welding applications

NASA Technical Reports Server (NTRS)

Powell, Bradley W.

1993-01-01

An advanced adaptive control weld system for high-integrity welding applications is presented. The system consists of a state-of-the-art weld control subsystem, motion control subsystem, and sensor subsystem which closes the loop on the process. The adaptive control subsystem (ACS), which is required to totally close the loop on weld process control, consists of a multiprocessor system, data acquisition hardware, and three welding sensors which provide measurements from all areas around the torch in real time. The ACS acquires all 'measurables' and feeds offset trims back into the weld control and motion control subsystems to modify the 'controllables' in order to maintain a previously defined weld quality.

Folded Resonant Horns for Power Ultrasonic Applications

NASA Technical Reports Server (NTRS)

Sherrit, Stewart; Askins, Stephen; Gradziel, Michael; Bao, Xiaoqi; Chang, Zensheu; Dolgin, Benjamin; Bar-Cohen, Yoseph; Peterson, Tom

2003-01-01

Folded horns have been conceived as alternatives to straight horns used as resonators and strain amplifiers in power ultrasonic systems. Such systems are used for cleaning, welding, soldering, cutting, and drilling in a variety of industries. In addition, several previous NASA Tech Briefs articles have described instrumented drilling, coring, and burrowing machines that utilize combinations of sonic and ultrasonic vibrational actuation. The main advantage of a folded horn, relative to a straight horn of the same resonance frequency, is that the folded horn can be made shorter (that is, its greatest linear dimension measured from the outside can be made smaller). Alternatively, for a given length, the resonance frequency can be reduced. Hence, the folded-horn concept affords an additional degree of design freedom for reducing the length of an ultrasonic power system that includes a horn.

Welding Metallurgy and Processing Issues for Joining of Power Sources

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

Lienert, Thomas J.; Reardon, Patrick T.

2012-08-14

Weldability issues with the pertinent alloys have been reviewed and preliminary results of our work on Haynes 25 have been presented. Further results on the mechanical properties and metallography on the EB welds are imminent. Hot-ductility experiments will commence within a few weeks. Aging studies on the effects of heat treatment using the Gleeble are also planned. MST-6 has extensive background in the welding metallurgy of the pertinent alloys. We also have considerable experience with the various welding processes to be used.

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

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.

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

Elimination of Two Hormones by Ultrasonic and Ozone Combined Processes

NASA Astrophysics Data System (ADS)

Mingcan Cui,; Younggyu Son,; Myunghee Lim,; Seungmin Na,; Jeehyeong Khim,

2010-07-01

A direct ultrasonic (US) and ozone (O3) combination (US/O3) process for the removal of two hormones, estrone (E1) and estriol (E3), in aqueous solutions was investigated. These two hormones were detected in a wastewater treatment plant effluent in Korea. It was found that the ultrasonic/ozone process showed a higher removal performance than the US and O3 process even though the O3 process also showed approximately the same removal efficiency after 60 min. Chemical oxygen demand/total organic carbon (CODcr/TOC) ratios for E1 and E3 decreased, indicating that biodegradability could be increased significantly in the US/O3 process. The optimal pH condition was determined above the neutral pH condition.

Friction Stir Welding and Processing

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

Hovanski, Yuri; Carsley, John; Clarke, Kester D.

2015-05-01

With nearly twenty years of international research and collaboration in friction stir welding (FSW) and processing industrial applications have spread into nearly every feasible market. Currently applications exist in aerospace, railway, automotive, personal computers, technology, marine, cutlery, construction, as well as several other markets. Implementation of FSW has demonstrated diverse opportunities ranging from enabling new materials to reducing the production costs of current welding technologies by enabling condensed packaging solutions for traditional fabrication and assembly. TMS has sponsored focused instruction and communication in this technology area for more than fifteen years, with leadership from the Shaping and Forming Committee, whichmore » organizes a biannual symposium each odd year at the annual meeting. A focused publication produced from each of these symposia now comprises eight volumes detailing the primary research and development activities in this area over the last two decades. The articles assembled herein focus on both recent developments and technology reviews of several key markets from international experts in this area.« less

More About Arc-Welding Process for Making Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Benavides, Jeanette M.; Leidecker, Henning

2005-01-01

High-quality batches of carbon nanotubes are produced at relatively low cost in a modified atmospheric-pressure electric-arc welding process that does not include the use of metal catalysts. What would normally be a welding rod and a weldment are replaced by an amorphous carbon anode rod and a wider, hollow graphite cathode rod. Both electrodes are water-cooled. The cathode is immersed in ice water to about 0.5 cm from the surface. The system is shielded from air by flowing helium during arcing. As the anode is consumed during arcing at 20 to 25 A, it is lowered to maintain it at an approximately constant distance above the cathode. The process causes carbon nanotubes to form on the lowest 5 cm of the anode. The arcing process is continued until the anode has been lowered to a specified height. The nanotube-containing material is then harvested. The additional information contained in the instant report consists mostly of illustrations of carbon nanotubes and a schematic diagram of the arc-welding setup, as modified for the production of carbon nanotubes.

Configurations of high-frequency ultrasonics complex vibration systems for packaging in microelectronics.