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

NASA Astrophysics Data System (ADS)

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

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

Development of Microstructure and Crystallographic Texture in a Double-Sided Friction Stir Welded Microalloyed Steel

NASA Astrophysics Data System (ADS)

Rahimi, S.; Wynne, B. P.; Baker, T. N.

2017-01-01

The evolution of microstructure and crystallographic texture has been investigated in double-sided friction stir welded microalloyed steel, using electron backscatter diffraction (EBSD). The microstructure analyses show that the center of stirred zone reached a temperature between Ac1 and Ac3 during FSW, resulting in a dual-phase austenitic/ ferritic microstructure. The temperatures in the thermo-mechanically affected zone and the overlapped area between the first and second weld pass did not exceed the Ac1. The shear generated by the rotation probe occurs in austenitic/ferritic phase field where the austenite portion of the microstructure is transformed to a bainitic ferrite, on cooling. Analysis of crystallographic textures with regard to shear flow lines generated by the probe tool shows the dominance of simple shear components across the whole weld. The austenite texture at Ac1 - Ac3 is dominated by the B { {1bar{1}2} }< 110rangle and bar{B} { {bar{1}1bar{2}} }< bar{1}bar{1}0rangle simple shear texture components, where the bainite phase textures formed on cooling were inherited from the shear textures of the austenite phase with relatively strong variant selection. The ferrite portion of the stirred zone and the ferrites in the thermo-mechanically affected zones and the overlapped area underwent shear deformation with textures dominated by the D1 { {bar{1}bar{1}2} }< 111rangle and D2 { {11bar{2}} }< 111rangle simple shear texture components. The formation of ultrafine equiaxed ferrite with submicron grain size has been observed in the overlapped area between the first and second weld pass. This is due to continuous dynamic strain-induced recrystallization as a result of simultaneous severe shear deformation and drastic undercooling.

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.

2195 Aluminum-Copper-Lithium Friction Plug Welding Development

NASA Technical Reports Server (NTRS)

Takeshita, Rike P.; Hartley, Paula J.; Baker, Kent S.

1997-01-01

Technology developments and applications of friction plug welding is presented. This friction repair welding technology is being studied for implementation on the Space Transportation System's Super Light Weight External Tank. Single plug repairs will be used on a vast majority of weld defects, however, linear defects of up to several inches can be repaired by overlapping plug welds. Methods and results of tensile, bend, simulated service, surface crack tension and other tests at room and cryogenic temperatures is discussed. Attempts to implement Friction Plug Welding has led to both tool and process changes in an attempt to minimize expansive tooling and lengthy implementation times. Process control equipment and data storage methods intended for large scale production will also be addressed. Benefits include increased strength and toughness, decreased weld repair time, automated and highly reliable process, and a lower probability of having to re-repair defect locations.

Tubular hydrogen permeable metal foil membrane and method of fabrication

DOEpatents

Paglieri, Stephen N.; Birdsell, Stephen A.; Barbero, Robert S.; Snow, Ronny C.; Smith, Frank M.

2006-04-04

A tubular hydrogen permeable metal membrane and fabrication process comprises obtaining a metal alloy foil having two surfaces, coating the surfaces with a metal or metal alloy catalytic layer to produce a hydrogen permeable metal membrane, sizing the membrane into a sheet with two long edges, wrapping the membrane around an elongated expandable rod with the two long edges aligned and overlapping to facilitate welding of the two together, placing the foil wrapped rod into a surrounding fixture housing with the two aligned and overlapping foil edges accessible through an elongated aperture in the surrounding fixture housing, expanding the elongated expandable rod within the surrounding fixture housing to tighten the foil about the expanded rod, welding the two long overlapping foil edges to one another generating a tubular membrane, and removing the tubular membrane from within the surrounding fixture housing and the expandable rod from with the tubular membrane.

Microstructure and Hardness Profiles of Bifocal Laser-Welded DP-HSLA Steel Overlap Joints

NASA Astrophysics Data System (ADS)

Grajcar, A.; Matter, P.; Stano, S.; Wilk, Z.; Różański, M.

2017-04-01

The article presents results related to the bifocal laser welding of overlap joints made of HSLA and DP high-strength steels. The joints were made using a disk laser and a head enabling the 50-50% distribution of laser power. The effects of the laser welding rates and the distance between laser spots on morphological features and hardness profiles were analyzed. It was established that the positioning of beams at angles of 0° or 90° determined the hardness of the individual zones of the joints, without causing significant differences in microstructures of the steels. Microstructural features were inspected using scanning electron microscopy. Both steels revealed primarily martensitic-bainitic microstructures in the fusion zone and in the heat-affected zone. Mixed multiphase microstructures were revealed in the inter-critical heat-affected zone of the joint. The research involved the determination of parameters making it possible to reduce the hardness of joints and prevent the formation of the soft zone in the dual-phase steel.

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

NASA Astrophysics Data System (ADS)

Balle, Frank; Magin, Jens

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

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.

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

NASA Astrophysics Data System (ADS)

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

2015-03-01

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

Weld pool oscillation during pulsed GTA welding

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

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

1996-12-31

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

Welding Experiments of Aluminum Alloy by Space GHTA Welding in the ISS Orbital Pressure

NASA Astrophysics Data System (ADS)

Suita, Yoshikazu; Takai, Daisuke; Sugiyama, Satoshi; Terajima, Noboru; Tsukuda, Yoshiyuki; Fujisawa, Shoichiro; Imagawa, Kichiro

As a feasible welding method in space, the authors have previously proposed the space GHTA (Gas Hollow Tungsten Arc) welding process. The space GHTA welding with high frequency power source for the arc starting may cause the electro-magnetic noise problems of computer equipments placed on the ISS. Therefore, in this paper the welding experiments of aluminum alloy by the space GHTA welding with DC high voltage power source for the arc starting was carried out in the ISS orbital pressure 10-5Pa. It is made clear that there is the shifting phenomenon in which the spark discharge changes to the glow or arc discharge at starting phenomenon of the space GHTA welding in high vacuum condition, and the features of those starting phenomenon are demonstrated. And the space GHTA welding with DC high voltage power source can be used for welding in the ISS orbital pressure.

Method for welding an article and terminating the weldment within the perimeter of the article

NASA Technical Reports Server (NTRS)

Snyder, John H. (Inventor); Smashey, Russell W. (Inventor); Boerger, Eric J. (Inventor); Borne, Bruce L. (Inventor)

2000-01-01

An article is welded, as in weld repair of a defect, by positioning a weld lift-off block at a location on the surface of the article adjacent to the intended location of the end of the weldment on the surface of the article. The weld lift-off block has a wedge shape including a base contacting the surface of the article, and an upper face angled upwardly from the base from a base leading edge. A weld pool is formed on the surface of the article by directly heating the surface of the article using a heat source. The heat source is moved relative to the surface of the article and onto the upper surface of the weld lift-off block by crossing the leading edge of the wedge, without discontinuing the direct heating of the article by the heat source. The heating of the article with the heat source is discontinued only after the heat source is directly heating the upper face of the weld lift-off block, and not the article.

Alloying Elements Transition Into the Weld Metal When Using an Inventor Power Source

NASA Astrophysics Data System (ADS)

Mamadaliev, R. A.; Kuskov, V. N.; Popova, A. A.; Valuev, D. V.

2016-04-01

The temperature distribution over the surface of the welded 12Kh18N10T steel plates using the inventor power source ARC-200 has been calculated. In order to imitate multipass welding when conducting the thermal analysis the initial temperature was changed from 298K up to 798K in 100K increments. It has been determined that alloying elements transition into the weld metal depends on temperature. Using an inventor power source facilitates a uniform distribution of alloying elements along the length and height of the weld seam.

Effect of Inverter Power Source Characteristics on Welding Stability and Heat Affected Zone Dimensions

NASA Astrophysics Data System (ADS)

Il'yaschenko, D. P.; Chinakhov, D. A.; Mamadaliev, R. A.

2018-01-01

The paper presents results the research in the effect of power sources dynamic characteristics on stability of melting and electrode metal transfer to the weld pool shielded metal arc welding. It is proved that when applying inverter-type welding power sources, heat and mass transfer characteristics change, arc gap short-circuit time and drop generation time are reduced. This leads to reduction of weld pool heat content and contraction of the heat-affected zone by 36% in comparison the same parameters obtained using a diode rectifier.

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

NASA Astrophysics Data System (ADS)

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

2016-11-01

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

Nanosecond pulsed laser welding of high carbon steels

NASA Astrophysics Data System (ADS)

Ascari, Alessandro; Fortunato, Alessandro

2014-03-01

The present paper deals with the possibility to exploit low-cost, near infra-red, nanosecond pulsed laser sources in welding of high carbon content thin sheets. The exploitation of these very common sources allows to achieve sound weld beads with a good depth-to-width ratio and very small heat affected zones when the proper process parameters are involved. In particular the role of pulse frequency, pulse duration, peak power and welding speed on the characteristics of the weld beads is studied and the advantage of the application of short-pulse laser sources over traditional long-pulse or continuous wave one is assessed.

Effect of temporal pulse shaping on the reduction of laser weld defects in a Pd-Ag-Sn dental alloy.

PubMed

Bertrand, C; Poulon-Quintin, A

2011-03-01

To describe the influence of pulse shaping on the behavior of a palladium-based dental alloy during laser welding and to show how its choice is effective to promote good weld quality. Single spots, weld beads and welds with 80% overlapping were performed on Pd-Ag-Sn cast plates. A pulsed Nd:Yag laser was used with a specific welding procedure using all the possibilities for pulse-shaping: (1) the square pulse shape as the default setting, (2) a rising edge slope for gradual heating, (3) a falling edge slope to slow the cooling and (4) a combination of a rising and falling edges called bridge shape. The optimization of the pulse shape is supposed to enhance weldability and produce defect-free welds (cracks, pores…) Vickers microhardness measurements were made on cross sections of the welds. A correlation between laser welding parameters and microstructure evolution was found. Hot cracking and internal porosities were systematically detected when using rapid cooling. The presence of these types of defects was significantly reduced with the slow cooling of the molten pool. The best weld quality was obtained with the use of the bridge shape. The use of a slow cooling ramp is the only way to significantly reduce the presence of typical defects within the welds for this Pd-based alloy studied. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Physics of Fusion Welding

NASA Technical Reports Server (NTRS)

Nunes, A. C., Jr.

1986-01-01

Applicabilities and limitations of three techniques analyzed. NASA technical memorandum discusses physics of electron-beam, gas/ tungsten-arc, and laser-beam welding. From comparison of capabilities and limitations of each technique with regard to various welding conditions and materials, possible to develop criteria for selecting best welding technique in specific application. All three techniques classified as fusion welding; small volume of workpiece melted by intense heat source. Heat source moved along seam, leaving in wake solid metal that joins seam edges together.

Fine-tuned Remote Laser Welding of Aluminum to Copper with Local Beam Oscillation

NASA Astrophysics Data System (ADS)

Fetzer, Florian; Jarwitz, Michael; Stritt, Peter; Weber, Rudolf; Graf, Thomas

Local beam oscillation in remote laser welding of aluminum to copper was investigated. Sheets of 1 mm thickness were welded in overlap configuration with aluminum as top material. The laser beam was scanned in a sinusoidal mode perpendicular to the direction of feed and the influence of the oscillation parameters frequency and amplitude on the weld geometry was investigated. Scanning frequencies up to 1 kHz and oscillation amplitudes in the range from 0.25 mm to 1 mm were examined. Throughout the experiments the laser power and the feed rate were kept constant. A decrease of welding depth with amplitude and frequency is found. The scanning amplitude had a strong influence and allowed coarse setting of the welding depth into the lower material, while the frequency allowed fine tuning in the order of 10% of the obtained depth. The oscillation parameters were found to act differently on the aluminum sheet compared to copper sheet regarding the amount of fused material. It is possible to influence the geometry of the fused zones separately for both sheets. Therefore the average composition in the weld can be set with high precision via the oscillation parameters. A setting of the generated intermetallics in the weld zone is possible without adjustment of laser power and feed rate.

Demonstration of pharmaceutical tablet coating process by injection molding technology.

PubMed

Puri, Vibha; Brancazio, David; Harinath, Eranda; Martinez, Alexander R; Desai, Parind M; Jensen, Keith D; Chun, Jung-Hoon; Braatz, Richard D; Myerson, Allan S; Trout, Bernhardt L

2018-01-15

We demonstrate the coating of tablets using an injection molding (IM) process that has advantage of being solvent free and can provide precision coat features. The selected core tablets comprising 10% w/w griseofulvin were prepared by an integrated hot melt extrusion-injection molding (HME-IM) process. Coating trials were conducted on a vertical injection mold machine. Polyethylene glycol and polyethylene oxide based hot melt extruded coat compositions were used. Tablet coating process feasibility was successfully demonstrated using different coating mold designs (with both overlapping and non-overlapping coatings at the weld) and coat thicknesses of 150 and 300 μm. The resultant coated tablets had acceptable appearance, seal at the weld, and immediate drug release profile (with an acceptable lag time). Since IM is a continuous process, this study opens opportunities to develop HME-IM continuous processes for transforming powder to coated tablets. Copyright © 2017 Elsevier B.V. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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

2016-10-01

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

Investigation of precipitation and hardening response of maraging stainless steels 17-4 and 13-8+Mo during multi-pass welding

NASA Astrophysics Data System (ADS)

Hamlin, Robert J.

Martensitic precipitation strengthened stainless steels 17-4 and 13-8+Mo are candidate alloys for high strength military applications. These applications will require joining by fusion welding processes thus, it is necessary to develop an understanding of microstructural and mechanical property changes that occur during welding. Previous investigations on these materials have demonstrated that significant softening occurs in the heat affected zone (HAZ) during welding, due to dissolution of the strengthen precipitates. It was also observed that post weld heat treatments (PWHT's) were required to restore the properties. However, PWHT's are expensive and cannot be applied when welding on a large scale or making a repair in the field. Thus, the purpose of the current work is to gain a fundamental understanding of the precipitation kinetics in these systems so that optimized welding procedures can be developed that do not require a PWHT. Multi-pass welding provides an opportunity to restore the strengthening precipitates that dissolve during primary weld passes using the heat from secondary weld passes. Thus, a preliminary investigation was performed to determine whether the times and temperatures associated with welding thermal cycles were sufficient to restore the strength in these systems. A Gleeble thermo-mechanical simulator was used to perform multi-pass welding simulations on samples of each material using a 1000 J/mm and 2000 J/mm heat input. Additionally, base metal and weld metal samples were used as starting conditions to evaluate the difference in precipitation response between each. Hardness measurements were used to estimate the extent of precipitate dissolution and growth. Microstructures were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). It was determined that precipitate dissolution occurred during primary welding thermal cycles and that significant hardening could be achieved using secondary welding thermal cycles for both heat inputs. Additionally, it was observed that the weld metal and base metal had similar precipitation responses. The preliminary multi-pass welding simulations demonstrated that the times and temperatures associated with welding thermal cycles were sufficient to promote precipitation in each system. Furthermore, these findings indicate that controlled weld metal deposition may be a viable method for optimizing welding procedures and eliminating the need for a PWHT. Next, an in-depth Gleeble study was performed to develop a fundamental understanding of the reactions that occur in 17-4 and 13-8+Mo during exposure to times and temperatures representative of multi-pass welding. Samples of each material were subjected to a series of short isothermal holds at high temperatures and hardness measurements were recorded to investigate the dissolution behavior of each alloy. Additional secondary isothermal experiments were performed on samples that had been subjected to a high temperature primary thermal cycle and hardness measurements were recorded. Matrix microstructures were characterized by LOM and reverted austenite measurements were recorded using X-ray diffraction techniques. The hardness data from the secondary heating tests was used in combination with Avrami kinetics equations to develop a relationship between the hardness and fraction transformed of the strengthening precipitates. It was determined that the Avrami relationships provide a useful approximation of the precipitation behavior at times and temperatures representative of welding thermal cycles. Finally, an autogenous gas tungsten arc (GTA) welding study was performed to demonstrate the utility of multi-pass welding for strength restoration in these alloys. Dual-pass welds were made on samples of each material using a range of heat inputs and secondary weld pass overlap percentages. Hardness mapping was then performed to estimate the extent of precipitate growth and dissolution. It was determined that significant softening occurs after primary weld passes and that secondary weld passes, using a high heat input, restored much of the strength. Furthermore, optimal weld overlap percentages were approximated. It was concluded that controlled weld metal deposition can significantly improve the properties of 17-4 and 13-8+Mo and potentially eliminate the need for costly PWHT's.

The effect of weld stresses on weld quality. [stress fields and metal cracking

NASA Technical Reports Server (NTRS)

Chihoski, R. A.

1972-01-01

A narrow heat source raises the temperature of a spot on a solid piece of material like metal. The high temperature of the spot decreases with distance from the spot. This is true whether the heat source is an arc, a flame, an electron beam, a plasma jet, a laser beam, or any other source of intense, narrowly defined heat. Stress and strain fields around a moving heat source are organized into a coherent visible system. It is shown that five stresses act across the weld line in turn as an arc passes. Their proportions and positions are considerably altered by weld parameters or condition changes. These pushes and pulls affect the metallurgical character and integrity of the weld area even when there is no apparent difference between after-the-fact examples.

Development of electromagnetic welding facility of flat plates for nuclear industry

NASA Astrophysics Data System (ADS)

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

2017-04-01

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

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

NASA Astrophysics Data System (ADS)

Echer, L.; Marczak, R. J.

2018-02-01

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

Laser heat treatment of welds for various stainless steels

NASA Astrophysics Data System (ADS)

Dontu, O.; Ganatsios, S.; Alexandrescu, N.; Predescu, C.

2008-03-01

The paper presents a study concerning the post - weld heat treatment of a duplex stainless steel. Welded joint samples were surface - treated using the same laser source adopted during welding in order to counterbalance the excess of ferrite formed in the welding process.

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

NASA Astrophysics Data System (ADS)

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

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

Modeling of plasma and thermo-fluid transport in hybrid welding

NASA Astrophysics Data System (ADS)

Ribic, Brandon D.

Hybrid welding combines a laser beam and electrical arc in order to join metals within a single pass at welding speeds on the order of 1 m min -1. Neither autonomous laser nor arc welding can achieve the weld geometry obtained from hybrid welding for the same process parameters. Depending upon the process parameters, hybrid weld depth and width can each be on the order of 5 mm. The ability to produce a wide weld bead increases gap tolerance for square joints which can reduce machining costs and joint fitting difficulty. The weld geometry and fast welding speed of hybrid welding make it a good choice for application in ship, pipeline, and aerospace welding. Heat transfer and fluid flow influence weld metal mixing, cooling rates, and weld bead geometry. Cooling rate affects weld microstructure and subsequent weld mechanical properties. Fluid flow and heat transfer in the liquid weld pool are affected by laser and arc energy absorption. The laser and arc generate plasmas which can influence arc and laser energy absorption. Metal vapors introduced from the keyhole, a vapor filled cavity formed near the laser focal point, influence arc plasma light emission and energy absorption. However, hybrid welding plasma properties near the opening of the keyhole are not known nor is the influence of arc power and heat source separation understood. A sound understanding of these processes is important to consistently achieving sound weldments. By varying process parameters during welding, it is possible to better understand their influence on temperature profiles, weld metal mixing, cooling rates, and plasma properties. The current literature has shown that important process parameters for hybrid welding include: arc power, laser power, and heat source separation distance. However, their influence on weld temperatures, fluid flow, cooling rates, and plasma properties are not well understood. Modeling has shown to be a successful means of better understanding the influence of processes parameters on heat transfer, fluid flow, and plasma characteristics for arc and laser welding. However, numerical modeling of laser/GTA hybrid welding is just beginning. Arc and laser welding plasmas have been previously analyzed successfully using optical emission spectroscopy in order to better understand arc and laser plasma properties as a function of plasma radius. Variation of hybrid welding plasma properties with radial distance is not known. Since plasma properties can affect arc and laser energy absorption and weld integrity, a better understanding of the change in hybrid welding plasma properties as a function of plasma radius is important and necessary. Material composition influences welding plasma properties, arc and laser energy absorption, heat transfer, and fluid flow. The presence of surface active elements such as oxygen and sulfur can affect weld pool fluid flow and bead geometry depending upon the significance of heat transfer by convection. Easily vaporized and ionized alloying elements can influence arc plasma characteristics and arc energy absorption. The effects of surface active elements on heat transfer and fluid flow are well understood in the case of arc and conduction mode laser welding. However, the influence of surface active elements on heat transfer and fluid flow during keyhole mode laser welding and laser/arc hybrid welding are not well known. Modeling has been used to successfully analyze the influence of surface active elements during arc and conduction mode laser welding in the past and offers promise in the case of laser/arc hybrid welding. A critical review of the literature revealed several important areas for further research and unanswered questions. (1) The understanding of heat transfer and fluid flow during hybrid welding is still beginning and further research is necessary. (2) Why hybrid welding weld bead width is greater than that of laser or arc welding is not well understood. (3) The influence of arc power and heat source separation distance on cooling rates during hybrid welding are not known. (4) Convection during hybrid welding is not well understood despite its importance to weld integrity. (5) The influence of surface active elements on weld geometry, weld pool temperatures, and fluid flow during high power density laser and laser/arc hybrid welding are not known. (6) Although the arc power and heat source separation distance have been experimentally shown to influence arc stability and plasma light emission during hybrid welding, the influence of these parameters on plasma properties is unknown. (7) The electrical conductivity of hybrid welding plasmas is not known, despite its importance to arc stability and weld integrity. In this study, heat transfer and fluid flow are analyzed for laser, gas tungsten arc (GTA), and laser/GTA hybrid welding using an experimentally validated three dimensional phenomenological model. By evaluating arc and laser welding using similar process parameters, a better understanding of the hybrid welding process is expected. The role of arc power and heat source separation distance on weld depth, weld pool centerline cooling rates, and fluid flow profiles during CO2 laser/GTA hybrid welding of 321 stainless steel are analyzed. Laser power is varied for a constant heat source separation distance to evaluate its influence on weld temperatures, weld geometry, and fluid flow during Nd:YAG laser/GTA hybrid welding of A131 structural steel. The influence of oxygen and sulfur on keyhole and weld bead geometry, weld temperatures, and fluid flow are analyzed for high power density Yb doped fiber laser welding of (0.16 %C, 1.46 %Mn) mild steel. Optical emission spectroscopy was performed on GTA, Nd:YAG laser, and Nd:YAG laser/GTA hybrid welding plasmas for welding of 304L stainless steel. Emission spectroscopy provides a means of determining plasma temperatures and species densities using deconvoluted measured spectral intensities, which can then be used to calculate plasma electrical conductivity. In this study, hybrid welding plasma temperatures, species densities, and electrical conductivities were determined using various heat source separation distances and arc currents using an analytical method coupled calculated plasma compositions. As a result of these studies heat transfer by convection was determined to be dominant during hybrid welding of steels. The primary driving forces affecting hybrid welding fluid flow are the surface tension gradient and electromagnetic force. Fiber laser weld depth showed a negligible change when increasing the (0.16 %C, 1.46 %Mn) mild steel sulfur concentration from 0.006 wt% to 0.15 wt%. Increasing the dissolved oxygen content in weld pool from 0.0038 wt% to 0.0257 wt% increased the experimental weld depth from 9.3 mm to 10.8 mm. Calculated partial pressure of carbon monoxide increased from 0.1 atm to 0.75 atm with the 0.0219 wt% increase in dissolved oxygen in the weld metal and may explain the increase in weld depth. Nd:YAG laser/GTA hybrid welding plasma temperatures were calculated to be approximately between 7927 K and 9357 K. Increasing the Nd:YAG laser/GTA hybrid welding heat source separation distance from 4 mm to 6 mm reduced plasma temperatures between 500 K and 900 K. Hybrid welding plasma total electron densities and electrical conductivities were on the order of 1 x 1022 m-3 and 3000 S m-1, respectively.

High-power industrial pulsed CO2 laser

NASA Astrophysics Data System (ADS)

Levin, G. I.

1983-12-01

The use of a pulsed TEA CO2 laser (with maximum average power 1.0 kW; maximum pulse energy 3.5 J; repetition frequency 400-600 Hz; half-width pulse duration 15 microsec; circular-coupling-aperture beam diameter 6, 8, or 12 mm; and beam divergence 10 mrad) in industrial welding applications is investigated experimentally in carbon and stainless steels, Zr, Ti, and Ni of various thicknesses. The power required to melt the metals is found to be about 120-200 W/sq cm, or 5-6 times less than that for CW lasers. It is shown that deep narrow-seam welds with mechanical properties identical to those of the bulk metal can be obtained with little or no intercrystalline corrosion or thermal distortion of the surrounding area. Disadvantages such as the 65-dB noise level, low welding speed, formation of an overlap at the top and a crater at the bottom of the weld, and root porosity are considered the primary limitations on the applicability of the device tested.

Increased risk of parkinsonism associated with welding exposure.

PubMed

Racette, Brad A; Criswell, Susan R; Lundin, Jessica I; Hobson, Angela; Seixas, Noah; Kotzbauer, Paul T; Evanoff, Bradley A; Perlmutter, Joel S; Zhang, Jing; Sheppard, Lianne; Checkoway, Harvey

2012-10-01

Manganese (Mn), an established neurotoxicant, is a common component of welding fume. The neurological phenotype associated with welding exposures has not been well described. Prior epidemiologic evidence linking occupational welding to parkinsonism is mixed, and remains controversial. This was a cross-sectional and nested case-control study to investigate the prevalence and phenotype of parkinsonism among 811 shipyard and fabrication welders recruited from trade unions. Two reference groups included 59 non-welder trade workers and 118 newly diagnosed, untreated idiopathic PD patients. Study subjects were examined by a movement disorders specialist using the Unified Parkinson Disease Rating Scale motor subsection 3 (UPDRS3). Parkinsonism cases were defined as welders with UPDRS3 score ≥15. Normal was defined as UPDRS3<6. Exposure was classified as intensity adjusted, cumulative years of welding. Adjusted prevalence ratios for parkinsonism were calculated in relation to quartiles of welding years. The overall prevalence estimate of parkinsonism was 15.6% in welding exposed workers compared to 0% in the reference group. Among welders, we observed a U-shaped dose-response relation between weighted welding exposure-years and parkinsonism. UPDRS3 scores for most domains were similar between welders and newly diagnosed idiopathic Parkinson disease (PD) patients, except for greater frequency of rest tremor and asymmetry in PD patients. This work-site based study among welders demonstrates a high prevalence of parkinsonism compared to nonwelding-exposed workers and a clinical phenotype that overlaps substantially with PD. Copyright © 2012 Elsevier Inc. All rights reserved.

Increased risk of parkinsonism associated with welding exposure

PubMed Central

Racette, Brad A.; Criswell, Susan R.; Lundin, Jessica I.; Hobson, Angela; Seixas, Noah; Kotzbauer, Paul T.; Evanoff, Bradley A.; Perlmutter, Joel S.; Zhang, Jing; Sheppard, Lianne; Checkoway, Harvey

2013-01-01

Objective Manganese (Mn), an established neurotoxicant, is a common component of welding fume. The neurological phenotype associated with welding exposures has not been well described. Prior epidemiologic evidence linking occupational welding to parkinsonism is mixed, and remains controversial. Methods This was a cross-sectional and nested case–control study to investigate the prevalence and phenotype of parkinsonism among 811 shipyard and fabrication welders recruited from trade unions. Two reference groups included 59 non-welder trade workers and 118 newly diagnosed, untreated idiopathic PD patients. Study subjects were examined by a movement disorders specialist using the Unified Parkinson Disease Rating Scale motor subsection 3 (UPDRS3). Parkinsonism cases were defined as welders with UPDRS3 score ≥15. Normal was defined as UPDRS3 < 6. Exposure was classified as intensity adjusted, cumulative years of welding. Adjusted prevalence ratios for parkinsonism were calculated in relation to quartiles of welding years. Results The overall prevalence estimate of parkinsonism was 15.6% in welding exposed workers compared to 0% in the reference group. Among welders, we observed a U-shaped dose–response relation between weighted welding exposure-years and parkinsonism. UPDRS3 scores for most domains were similar between welders and newly diagnosed idiopathic Parkinson disease (PD) patients, except for greater frequency of rest tremor and asymmetry in PD patients. Conclusion This work-site based study among welders demonstrates a high prevalence of parkinsonism compared to nonwelding-exposed workers and a clinical phenotype that overlaps substantially with PD. PMID:22975422

Integration of NASA-sponsored studies on aluminum welding

NASA Technical Reports Server (NTRS)

Masubuchi, K.

1972-01-01

The results are presented of numerous studies relating to aluminum alloy welding. The subjects covered include: (1) effects of porosity on weld joint performance, (2) sources of porosity, (3) weld thermal effects, (4) residual stresses and distortion, and (5) manufacturing process system control.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Physical Nature of the Processes in Structure Forming, Phase and Chemical Composition of pipe Permanent Joints when MMA Welding

NASA Astrophysics Data System (ADS)

Il'yaschenko, D. P.; Chinakhov, D. A.; Danilov, V. I.; Sadykov, I. D.

2016-04-01

The paper outlines peculiarities of structure formation, phase and chemical composition in regard to heat content in molten electrode metal beads when pipe steel (steel 09G2S) welding using power sources with various energy characteristics. Mathematical calculations indicate an inverter power source provides minor heat content into the bead of electrode metal when welding. Experimental research has pointed at 4-9 % increase in impact strength of joints produced using an inverter power source in comparison with samples produced applying a diode rectifier. The following factors can possibly give rise to the increasing impact strength: difference in microstructures of weld joints, up to 50% shortening ferritic plates in metal of weld joint, change in dimensions of ferritic grains in the heat-affected zone by as much as 17.5 %, and decrease in the extent of heat-affected zone by 50%.

Feasibility evaluations for the integration of laser butt welding of tubes in industrial pipe coil production lines

NASA Astrophysics Data System (ADS)

Penasa, Mauro; Colombo, Enrico; Giolfo, Mauro

1994-09-01

Due to the good performance shown by laser welded joints, to the quality and repeatability achievable by this welding technique and to its high process productivity, a feature inherent to the laser technology which, together with its high flexibility, allows different operations to be performed by a single source, consistent savings in a production line may be obtained. Therefore laser welding techniques may be of high relevance for industrial applications, provided that a sufficient attention is paid to avoiding a low utilization time to the operating laser source. The paper describes a feasibility study for the integration of a laser source as an automatic unit for circumferential butt welding of tubes in production lines of pipe coils, just before the cold bending station. Using a 6 kW CO2 source, thickness ranging from 3.5 to 11.2 mm in carbon, low alloyed Cr-Mo and austenitic stainless steels, have been successfully welded. Cr-Mo steels require on line preheating treatment, which however can be achieved by laser defocused passes just before welding. The results of the preliminary qualification performed on laser welded joints of the involved topologies of product (materials, diameters and thicknesses) are described together with technological tests required for approval: laser circumferential butt welding of tubes has proven to be effective, with satisfactory and repeatable results and good joint performances. An exhaustive comparison with current welding techniques (TIG, MIG) is then carried out, along with a detailed analysis of the potential advantages and benefits which may be expected by using the laser welding technique, as well as with a first estimation of the investments and running costs. Since laser productivity is saturated only at a rough 35% during the year, an accurate analysis of other possible applications and of a possible lay out of a laser working cell integrated in the factory production lines is performed. Usually little attention is given to this problem and this is one of the causes of uncertainty when investments in a laser are planned. In most cases a source is devoted to a single application, even if effective working time is really low due to laser fast processing. Therefore potential benefits are substantially reduced to a minimum amount of what can be expected by this flexible technology.

Mechanisms of hydrogen-assisted fracture in austenitic stainless steel welds.

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

Balch, Dorian K.; Sofronis, Petros; Somerday, Brian P.

2005-03-01

The objective of this study was to quantify the hydrogen-assisted fracture susceptibility of gas-tungsten arc (GTA) welds in the nitrogen-strengthened, austenitic stainless steels 21Cr-6Ni-9Mn (21-6-9) and 22Cr-13Ni-5Mn (22-13-5). In addition, mechanisms of hydrogen-assisted fracture in the welds were identified using electron microscopy and finite-element modeling. Elastic-plastic fracture mechanics experiments were conducted on hydrogen-charged GTA welds at 25 C. Results showed that hydrogen dramatically lowered the fracture toughness from 412 kJ/m{sup 2} to 57 kJ/m{sup 2} in 21-6-9 welds and from 91 kJ/m{sup 2} to 26 kJ/m{sup 2} in 22-13-5 welds. Microscopy results suggested that hydrogen served two roles in themore » fracture of welds: it promoted the nucleation of microcracks along the dendritic structure and accelerated the link-up of microcracks by facilitating localized deformation. A continuum finite-element model was formulated to test the notion that hydrogen could facilitate localized deformation in the ligament between microcracks. On the assumption that hydrogen decreased local flow stress in accordance with the hydrogen-enhanced dislocation mobility argument, the finite-element results showed that deformation was localized in a narrow band between two parallel, overlapping microcracks. In contrast, in the absence of hydrogen, the finite-element results showed that deformation between microcracks was more uniformly distributed.« less

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

DOEpatents

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

2014-01-21

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

Shielded Metal Arc Welding. Welding Module 4. Instructor's Guide.

ERIC Educational Resources Information Center

Missouri Univ., Columbia. Instructional Materials Lab.

This guide is intended to assist vocational educators in teaching an eight-unit module in shielded metal arc welding. The module is part of a welding curriculum that has been designed to be totally integrated with Missouri's Vocational Instruction Management System. The following topics are covered in the module: safety; theory, power sources, and…

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.

Optical penetration sensor for pulsed laser welding

DOEpatents

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

2000-01-01

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

Virtual welding equipment for simulation of GMAW processes with integration of power source regulation

NASA Astrophysics Data System (ADS)

Reisgen, Uwe; Schleser, Markus; Mokrov, Oleg; Zabirov, Alexander

2011-06-01

A two dimensional transient numerical analysis and computational module for simulation of electrical and thermal characteristics during electrode melting and metal transfer involved in Gas-Metal-Arc-Welding (GMAW) processes is presented. Solution of non-linear transient heat transfer equation is carried out using a control volume finite difference technique. The computational module also includes controlling and regulation algorithms of industrial welding power sources. The simulation results are the current and voltage waveforms, mean voltage drops at different parts of circuit, total electric power, cathode, anode and arc powers and arc length. We describe application of the model for normal process (constant voltage) and for pulsed processes with U/I and I/I-modulation modes. The comparisons with experimental waveforms of current and voltage show that the model predicts current, voltage and electric power with a high accuracy. The model is used in simulation package SimWeld for calculation of heat flux into the work-piece and the weld seam formation. From the calculated heat flux and weld pool sizes, an equivalent volumetric heat source according to Goldak model, can be generated. The method was implemented and investigated with the simulation software SimWeld developed by the ISF at RWTH Aachen University.

A simple 2-d thermal model for GMA welds

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

Matteson, M.A.; Franke, G.L.; Vassilaros, M.G.

1996-12-31

The Rosenthal model of heat distribution from a moving source has been used in many applications to predict the temperature distribution during welding. The equation has performed well in its original form or as modified. The expression has a significant limitation for application to gas metal arc welds (GMAW) that have a papilla extending from the root of the weld bead. The shape of the fusion line between the papilla and the plate surface has a concave shape rather than the expected convex shape. However, at some distance from the fusion line the heat affected zone (HAZ) made visible bymore » etching has the expected convex shape predicted by the Rosenthal expression. This anomaly creates a limitation to the use of the Rosenthal expression for predicting GMAW bead shapes or HAZ temperature histories. Current research at the Naval Surface Warfare Center--Carderock Division (NSWC--CD) to develop a computer based model to predict the microstructure of multi-pass GMAW requires a simple expression to predict the fusion line and temperature history of the HAZ for each weld pass. The solution employed for the NSWC--CD research is a modified Rosenthal expression that has a dual heat source. One heat source is a disk source above the plate surface supplying the majority of the heat. The second heat source is smaller and below the surface of the plate. This second heat source helps simulate the penetration power of many GMAW welds that produces the papilla. The assumptions, strengths and limitations of the model are presented along with some applications.« less

Dissimilar material joining using laser (aluminum to steel using zinc-based filler wire)

NASA Astrophysics Data System (ADS)

Mathieu, Alexandre; Shabadi, Rajashekar; Deschamps, Alexis; Suery, Michel; Matteï, Simone; Grevey, Dominique; Cicala, Eugen

2007-04-01

Joining steel with aluminum involving the fusion of one or both materials is possible by laser beam welding technique. This paper describes a method, called laser braze welding, which is a suitable process to realize this structure. The main problem with thermal joining of steel/aluminum assembly with processes such as TIG or MIG is the formation of fragile intermetallic phases, which are detrimental to the mechanical performances of such joints. Braze welding permits a localized fusion of the materials resulting in a limitation on the growth of fragile phases. This article presents the results of a statistical approach for an overlap assembly configuration using a filler wire composed of 85% Zn and 15% Al. Tensile tests carried on these assemblies demonstrate a good performance of the joints. The fracture mechanisms of the joints are analyzed by a detailed characterization of the seams.

Hybrid Welding Possibilities of Thick Sections for Arctic Applications

NASA Astrophysics Data System (ADS)

Bunaziv, Ivan; Akselsen, Odd M.; Ren, Xiaobo; Salminen, Antti

The arctic shelf contains about 20% of all undiscovered hydrocarbons on our planet, therefore oil and gas industry requires advanced steels to be used which withstand appropriate fracture toughness up to -60 °C and suitable welding technologies. High brightness laser with combination with arc source can be appropriate joining process even for very high strength advanced steels above 700 MPa for low temperature applications. Hybrid welding has improved each year becoming more standardized and reliable welding process. However, until now, its application was limited to shipbuilding and pipeline industry. Due to many reasonable advantages, hybrid welding, especially when it is combined with MIG/MAG, can be used in every possible industry. Inherent filler wire addition from the MIG/MAG source can improve fracture toughness at lower temperatures and increase overall productivity. This paper provides information about recent breakthrough in hybrid welding of thick section high-strength steels.

What Voc Ed Administrators Should Know About the Welding Program

ERIC Educational Resources Information Center

Godley, M. Andrew

1976-01-01

Information on the development of a welding program and curriculum is presented to assist instructors and administrators in the implementation of a training program. The American Welding Society is recommended as an authoritative source for assistance. (EC)

78 FR 16180 - Seaway Regulations and Rules: Periodic Update, Various Categories

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-14

... flame or than can produce a source of ignition, cutting or welding, can be carried out on any vessels at... source of ignition, cutting or welding, is carried out by any vessel on any designated St. Lawrence...

Evolution of Welding-Fume Aerosols with Time and Distance from the Source: A study was conducted on the spatiotemporal variability in welding-fume concentrations for the characterization of first- and second-hand exposure to welding fumes.

PubMed

Cena, L G; Chen, B T; Keane, M J

2016-08-01

Gas metal arc welding fumes were generated from mild-steel plates and measured near the arc (30 cm), representing first-hand exposure of the welder, and farther away from the source (200 cm), representing second-hand exposure of adjacent workers. Measurements were taken during 1-min welding runs and at subsequent 5-min intervals after the welding process was stopped. Number size distributions were measured in real time. Particle mass distributions were measured using a micro-orifice uniform deposition impactor, and total mass concentrations were measured with polytetrafluorothylene filters. Membrane filters were used for collecting morphology samples for electron microscopy. Average mass concentrations measured near the arc were 45 mg/m 3 and 9 mg/m 3 at the farther distance. The discrepancy in concentrations at the two distances was attributed to the presence of spatter particles, which were observed only in the morphology samples near the source. As fumes aged over time, mass concentrations at the farther distance decreased by 31% (6.2 mg/m 3 ) after 5 min and an additional 13% (5.4 mg/m 3 ) after 10 min. Particle number and mass distributions during active welding were similar at both distances, indicating similar exposure patterns for welders and adjacent workers. Exceptions were recorded for particles smaller than 50 nm and larger than 3 μm, where concentrations were higher near the arc, indicating higher exposures of welders. These results were confirmed by microscopy analysis. As residence time increased, number concentrations decreased dramatically. In terms of particle number concentrations, second-hand exposures to welding fumes during active welding may be as high as first-hand exposures.

Laser welding of polypropylene using two different sources

NASA Astrophysics Data System (ADS)

Mandolfino, Chiara; Brabazon, Dermot; McCarthy, Éanna; Lertora, Enrico; Gambaro, Carla; Ahad, Inam Ul

2017-10-01

In this paper, laser weldability of neutral polypropylene has been investigated using fibre and carbon dioxide lasers. A design of experiment (DoE) was conducted in order to establish the influence of the main working parameters on the welding strength of the two types of laser. The welded samples were characterized by carrying out visual and microscopic inspection for the welding morphology and cross-section, and by distinguishing the tensile strength. The resulting weld quality was investigated by means of optical microscopy at weld cross-sections. The tensile strength of butt-welded materials was measured and compared to that of a corresponding bulk material.

Off-line programming motion and process commands for robotic welding of Space Shuttle main engines

NASA Technical Reports Server (NTRS)

Ruokangas, C. C.; Guthmiller, W. A.; Pierson, B. L.; Sliwinski, K. E.; Lee, J. M. F.

1987-01-01

The off-line-programming software and hardware being developed for robotic welding of the Space Shuttle main engine are described and illustrated with diagrams, drawings, graphs, and photographs. The menu-driven workstation-based interactive programming system is designed to permit generation of both motion and process commands for the robotic workcell by weld engineers (with only limited knowledge of programming or CAD systems) on the production floor. Consideration is given to the user interface, geometric-sources interfaces, overall menu structure, weld-parameter data base, and displays of run time and archived data. Ongoing efforts to address limitations related to automatic-downhand-configuration coordinated motion, a lack of source codes for the motion-control software, CAD data incompatibility, interfacing with the robotic workcell, and definition of the welding data base are discussed.

Studying of welding aerosol using laser granulometry

NASA Astrophysics Data System (ADS)

Kirichenko, K. Y.; Gridasov, A. V.; Drozd, V. A.; Golokhvast, K. S.

2016-11-01

The paper presents results of a study of the size of the particles that arise during the welding process using laser granulometry method. It is shown that the welding aerosol - extremely dangerous for human and animal health and the source of nano- and micro-sized particles.

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

NASA Astrophysics Data System (ADS)

Behúlová, M.; Babalová, E.; Nagy, M.

2017-02-01

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

Dual-beam laser welding of AZ31B magnesium alloy in zero-gap lap joint configuration

NASA Astrophysics Data System (ADS)

Harooni, Masoud; Carlson, Blair; Kovacevic, Radovan

2014-03-01

Porosity within laser welds of magnesium alloys is one of the main roadblocks to achieving high quality joints. One of the causes of pore formation is the presence of pre-existing coatings on the surface of magnesium alloy such as oxide or chromate layers. In this study, single-beam and dual-beam laser heat sources are investigated in relation to mitigation of pores resulting from the presence of the as-received oxide layer on the surface of AZ31B-H24 magnesium alloy during the laser welding process. A fiber laser with a power of up to 4 kW is used to weld samples in a zero-gap lap joint configuration. The effect of dual-beam laser welding with different beam energy ratios is studied on the quality of the weld bead. The purpose of this paper is to identify the beam ratio that best mitigates pore formation in the weld bead. The laser molten pool and the keyhole condition, as well as laser-induced plasma plume are monitored in real-time by use of a high speed charge-coupled device (CCD) camera assisted with a green laser as an illumination source. Tensile and microhardness tests were used to measure the mechanical properties of the laser welded samples. Results showed that a dual-beam laser configuration can effectively mitigate pore formation in the weld bead by a preheating-welding mechanism.

Fusion welding experiments under low-gravity conditions using aircraft

NASA Astrophysics Data System (ADS)

Masubuchi, Koichi; Nayama, Michisuke

A series of gas tungsten arc welding experiments under low-gravity conditions created using parabolic flight of aircraft were performed. The materials used were aluminum and 2219 aluminum alloy. Welding was conducted in a small chamber filled with 100 percent argon gas, and the power source was a set of storage batteries. While welding was conducted, CCD image of welding phenomena, welding current, voltage, and the gravity level of the welding table were recorded continuously. It was found that sound welds can be obtained under low-gravity conditions. The bead appearance of the weld bead made under low-gravity conditions was very smooth and flat with no ripple lines which normally exist in welds made on the earth. The observed shape of the arc plasma under low-gravity conditions was larger than that made under normal gravity condition, but the difference was not so significant. Welds made under low-gravity conditions tend to contain more porosity compared with welds made under the earth conditions.

Improving the reliability of inverter-based welding machines

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

Schiedermayer, M.

1997-02-01

Although inverter-based welding power sources have been available since the late 1980s, many people hesitated to purchase them because of reliability issues. Unfortunately, their hesitancy had a basis, until now. Recent improvements give some inverters a reliability level that approaches that of traditional, transformer-based industrial welding machines, which have a failure rate of about 1%. Acceptance of inverter-based welding machines is important because, for many welding applications, they provide capabilities that solid-state, transformer-based machines cannot deliver. These advantages include enhanced pulsed gas metal arc welding (GMAW-P), lightweight portability, an ultrastable arc, and energy efficiency--all while producing highly aesthetic weld beadsmore » and delivering multiprocess capabilities.« less

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

Viewing Welds By Computer Tomography

NASA Technical Reports Server (NTRS)

Pascua, Antonio G.; Roy, Jagatjit

1990-01-01

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

Inverter-based GTA welding machines improve fabrication

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

Sammons, M.

2000-05-01

While known as precision process, many fabricators using the gas tungsten arc welding (GTAW) process fight several common problems that hinder quality, slow production, frustrate the operator and otherwise prevent the process from achieving its full potential. These include a limited ability to tailor the weld bead profile, poor control of the arc direction and arc wandering, poor arc starting, unstable or inconsistent arcs in the AC mode, high-frequency interference with electronics and tungsten contamination. Fortunately, new GTA welding technology--made possible by advances with inverter-based power sources and micro-processor controls--can eliminate common productivity gremlins. Further, new AC/DC inverter-based GTA powermore » sources provide advanced arc shaping capabilities. As a result, many fabricators adopting this new technology have experienced phenomenal production increases, taken on new types of projects and reduced costs. Most importantly, the operators enjoy welding more.« less

The Role of Zinc Layer During Wetting of Aluminium on Zinc-coated Steel in Laser Brazing and Welding

NASA Astrophysics Data System (ADS)

Gatzen, M.; Radel, T.; Thomy, C.; Vollertsen, F.

The zinc layer of zinc-coated steel is known to be a crucial factor for the spreading of liquid aluminium on the coated surface. For industrial brazing and welding processes these zinc-coatings enable a fluxless joining between aluminium and steel in many cases. Yet, the reason for the beneficial effect of the zinc to the wetting process is not completely understood. Fundamental investigations on the wetting behaviour of single aluminium droplets on different zinc-coated steel surfaces have revealed a distinct difference between coated surfaces at room temperature and at elevated temperature regarding the influence of different coating thicknesses. In this paper the case of continuous laser brazing and welding processes of aluminium and commercial galvanized zinc-coated steel sheets are presented. It is shown that in the case of bead-on-plate laser beam brazing, the coating thickness has a measureable effect on the resulting wetting angle and length but does not have a significant impact in case of overlap laser beam welding. This might be linked to different heat transfer conditions. The results also strongly indicate that proper initialbreakup of oxide layers is still required to accomplish good wetting on zinc-coated surfaces.

Development of forming and joining technology for TD-NiCr sheet

NASA Technical Reports Server (NTRS)

Torgerson, R. T.

1973-01-01

Forming joining techniques and properties data were developed for thin-gage TD-NiCr sheet in the recrystallized and unrecrystallized conditions. Theoretical and actual forming limit data are presented for several gages of each type of material for five forming processes: brake forming, corrugation forming, joggling, dimpling and beading. Recrystallized sheet can be best formed at room temperature, but unrecrystallized sheet requires forming at elevated temperature. Formability is satisfactory with most processes for the longitudinal orientation but poor for the transverse orientation. Dimpling techniques require further development for both material conditions. Data on joining techniques and joint properties are presented for four joining processes: resistance seam welding (solid-state), resistance spot welding (solid-state), resistance spot welding (fusion) and brazing. Resistance seam welded (solid-state) joints with 5t overlap were stronger than parent material for both material conditions when tested in tensile-shear and stress-rupture. Brazing studies resulted in development of NASA 18 braze alloy (Ni-16Cr-15Mo-8Al-4Si) with several properties superior to baseline TD-6 braze alloy, including lower brazing temperture, reduced reaction with Td-Ni-Cr, and higher stress-rupture properties.

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.

Remote Laser Welding of Zinc Coated Steel Sheets in an Edge Lap Configuration with Zero Gap

NASA Astrophysics Data System (ADS)

Roos, Christian; Schmidt, Michael

Remote Laser Welding (RLW) of zinc-coated steel sheets is a great challenge for the automotive industry but offers high potentials with respect to flexibility and costs. In state of the art applications, sheets are joined in overlap configuration with a preset gap for a stable zinc degassing. This paper investigates RLW of fillets without a preset gap and conditions for a stable process. The influence of process parameters on weld quality and process stability is shown. Experimental data give evidence, that the degassing of zinc through the capillary and the rear melt pool are the major degassing mechanisms. Furthermore the paper gives experimental validation of the zinc degassing in advance of the process zone to the open side of the fillet. Chemical analysis of the hot-dip galvanized zinc coating proof the iron-zinc-alloys to be the reason for a limited effectiveness of this mechanism in comparison to pure zinc as intermediate.

Reactor vessels: weld cladding - base metal interaction

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

Mager, T.R.; Landerman, E.; Kubit, C.J.

1971-07-01

An underclad anomaly first observed during magnetic particle inspection of a European steam generator and subsequently discovered during inspection of certain reactor vessels manufactured in both the United States and in Europe is shown to be inconsequential for the intended application because of its small size and insignificant expected growth. Metallurgical investigation identifies the anomaly as grain boundary separations in the base metal, restricted in extent to the grain coarsened part of the weld heat-affected zone beneath the weld bead overlap. In all cases the depth of the separations was less than the maximum depth (0.125 inches) of the grainmore » coarsened area. The occurrence of the anomaly depends on the specific weld overlay process. It has been found generally after post-weld stress relief in forging and plate material (SA508 Class 2 composition). Fracture mechanics evaluation of the affected materials shows that the expected growth of the grain boundary separations during the lifetime of the plant is insignificant, being only 0.004 inches maximum as calculated based on conservative assumptions verified by the metallurgical investigation. Since the original size of the grain boundary separations is negligible and its growth is insignificant during the 40-year plant life, the structural integrity of the vessels has not been compromised and the affected vessels are suitable for the use intended.« less

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

NASA Astrophysics Data System (ADS)

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

2017-07-01

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

27 CFR 555.209 - Construction of type 3 magazines.

Code of Federal Regulations, 2010 CFR

2010-04-01

... Construction of type 3 magazines. A type 3 magazine is a “day-box” or other portable magazine. It must be fire...-type hardboard. Doors must overlap sides by at least one inch. Hinges and hasps are to be attached by welding, riveting or bolting (nuts on inside). One steel padlock (which need not be protected by a steel...

27 CFR 555.209 - Construction of type 3 magazines.

Code of Federal Regulations, 2014 CFR

2014-04-01

... Construction of type 3 magazines. A type 3 magazine is a “day-box” or other portable magazine. It must be fire...-type hardboard. Doors must overlap sides by at least one inch. Hinges and hasps are to be attached by welding, riveting or bolting (nuts on inside). One steel padlock (which need not be protected by a steel...

Guidelines for Controlling Indoor Air Quality Problems Associated with Kilns, Copiers, and Welding in Schools. Technical Bulletin.

ERIC Educational Resources Information Center

Turner, Ronald W.; And Others

Guidelines for controlling indoor air quality problems associated with kilns, copiers, and welding in schools are provided in this document. Individual sections on kilns, duplicating equipment, and welding operations contain information on the following: sources of contaminants; health effects; methods of control; ventilation strategies; and…

29 CFR 1915.51 - Ventilation and protection in welding, cutting and heating.

Code of Federal Regulations, 2012 CFR

2012-07-01

...) When inert-gas metal-arc welding is being performed on stainless steel, the requirements of paragraph... the number of air changes necessary to maintain welding fumes and smoke within safe limits. (iii... as to remove fumes and smoke at the source and keep the concentration of them in the breathing zone...

29 CFR 1915.51 - Ventilation and protection in welding, cutting and heating.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) When inert-gas metal-arc welding is being performed on stainless steel, the requirements of paragraph... the number of air changes necessary to maintain welding fumes and smoke within safe limits. (iii... as to remove fumes and smoke at the source and keep the concentration of them in the breathing zone...

29 CFR 1915.51 - Ventilation and protection in welding, cutting and heating.

Code of Federal Regulations, 2014 CFR

2014-07-01

...) When inert-gas metal-arc welding is being performed on stainless steel, the requirements of paragraph... the number of air changes necessary to maintain welding fumes and smoke within safe limits. (iii... as to remove fumes and smoke at the source and keep the concentration of them in the breathing zone...

29 CFR 1915.51 - Ventilation and protection in welding, cutting and heating.

Code of Federal Regulations, 2013 CFR

2013-07-01

...) When inert-gas metal-arc welding is being performed on stainless steel, the requirements of paragraph... the number of air changes necessary to maintain welding fumes and smoke within safe limits. (iii... as to remove fumes and smoke at the source and keep the concentration of them in the breathing zone...

U-Groove Aluminum Weld Strength Improvement

NASA Technical Reports Server (NTRS)

Verderaime, V.; Vaughan, R.

1997-01-01

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

The numerical simulation of heat transfer during a hybrid laser-MIG welding using equivalent heat source approach

NASA Astrophysics Data System (ADS)

Bendaoud, Issam; Matteï, Simone; Cicala, Eugen; Tomashchuk, Iryna; Andrzejewski, Henri; Sallamand, Pierre; Mathieu, Alexandre; Bouchaud, Fréderic

2014-03-01

The present study is dedicated to the numerical simulation of an industrial case of hybrid laser-MIG welding of high thickness duplex steel UR2507Cu with Y-shaped chamfer geometry. It consists in simulation of heat transfer phenomena using heat equivalent source approach and implementing in finite element software COMSOL Multiphysics. A numerical exploratory designs method is used to identify the heat sources parameters in order to obtain a minimal required difference between the numerical results and the experiment which are the shape of the welded zone and the temperature evolution in different locations. The obtained results were found in good correspondence with experiment, both for melted zone shape and thermal history.

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.

Nano- and Microparticles in Welding Aerosol: Granulometric Analysis

NASA Astrophysics Data System (ADS)

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

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

29 CFR 1926.353 - Ventilation and protection in welding, cutting, and heating.

Code of Federal Regulations, 2013 CFR

2013-07-01

... welding is being performed on stainless steel, the requirements of paragraph (c)(2) of this section shall... the number of air changes necessary to maintain welding fumes and smoke within safe limits, as defined... sufficient capacity and so arranged as to remove fumes and smoke at the source and keep the concentration of...

29 CFR 1926.353 - Ventilation and protection in welding, cutting, and heating.

Code of Federal Regulations, 2014 CFR

2014-07-01

... welding is being performed on stainless steel, the requirements of paragraph (c)(2) of this section shall... the number of air changes necessary to maintain welding fumes and smoke within safe limits, as defined... sufficient capacity and so arranged as to remove fumes and smoke at the source and keep the concentration of...

29 CFR 1926.353 - Ventilation and protection in welding, cutting, and heating.

Code of Federal Regulations, 2012 CFR

2012-07-01

... welding is being performed on stainless steel, the requirements of paragraph (c)(2) of this section shall... the number of air changes necessary to maintain welding fumes and smoke within safe limits, as defined... sufficient capacity and so arranged as to remove fumes and smoke at the source and keep the concentration of...

29 CFR 1926.353 - Ventilation and protection in welding, cutting, and heating.

Code of Federal Regulations, 2011 CFR

2011-07-01

... welding is being performed on stainless steel, the requirements of paragraph (c)(2) of this section shall... the number of air changes necessary to maintain welding fumes and smoke within safe limits, as defined... sufficient capacity and so arranged as to remove fumes and smoke at the source and keep the concentration of...

Literature Review: Weldability of Iridium DOP-26 Alloy for General Purpose Heat Source

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

Burgardt, Paul; Pierce, Stanley W.

The basic purpose of this paper is to provide a literature review relative to fabrication of the General Purpose Heat Source (GPHS) that is used to provide electrical power for deep space missions of NASA. The particular fabrication operation to be addressed here is arc welding of the GPHS encapsulation. A considerable effort was made to optimize the fabrication of the fuel pellets and of other elements of the encapsulation; that work will not be directly addressed in this paper. This report consists of three basic sections: 1) a brief description of the GPHS will be provided as background informationmore » for the reader; 2) mechanical properties and the optimization thereof as relevant to welding will be discussed; 3) a review of the arc welding process development and optimization will be presented. Since the welding equipment must be upgraded for future production, some discussion of the historical establishment of relevant welding variables and possible changes thereto will also be discussed.« less

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.

Decomposition of cellulose by ultrasonic welding in water

NASA Astrophysics Data System (ADS)

Nomura, Shinfuku; Miyagawa, Seiya; Mukasa, Shinobu; Toyota, Hiromichi

2016-07-01

The use of ultrasonic welding in water to decompose cellulose placed in water was examined experimentally. Filter paper was used as the decomposition material with a horn-type transducer 19.5 kHz adopted as the ultrasonic welding power source. The frictional heat at the point where the surface of the tip of the ultrasonic horn contacts the filter paper decomposes the cellulose in the filter paper into 5-hydroxymethylfurfural (5-HMF), furfural, and oligosaccharide through hydrolysis and thermolysis that occurs in the welding process.

The effect of impurity gasses on variable polarity plasma arc welded 2219 aluminum

NASA Technical Reports Server (NTRS)

Mcclure, John C.; Torres, Martin R.; Gurevitch, Alan C.; Newman, Robert A.

1989-01-01

Variable polarity plasma arc (VPPA) welding has been used with considerable success by NASA for the welds on the Space Shuttle External Tank as well as by others concerned with high quality welded structures. The effects of gaseous contaminants on the appearance of VPPA welds on 2219 aluminum are examined so that a welder can recognize that such contamination is present and take corrective measures. There are many possible sources of such contamination including, contaminated gas bottles, leaks in the gas plumbing, inadequate shield gas flow, condensed moisture in the gas lines or torch body, or excessive contaminants on the workpiece. The gasses chosen for study in the program were nitrogen, oxygen, methane, and hydrogen. Welds were made in a carefully controlled environment and comparisons were made between welds with various levels of these contaminants and welds made with research purity (99.9999 percent) gasses. Photographs of the weld front and backside as well as polished and etched cross sections are presented.

Characterization of lap joints laser beam welding of thin AA 2024 sheets with Yb:YAG disk-laser

NASA Astrophysics Data System (ADS)

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

2012-06-01

Lap joints obtained by overlapping two plates are widely diffused in aerospace industry. Nevertheless, because of natural aging, adhesively bonded and riveted aircraft lap joints may be affected by cracks from rivets, voids or corrosion. Friction stir welding has been proposed as a valid alternative, although large heat affected zones are produced both in the top and the bottom plate due to the pin diameter. Interest has therefore been shown in studying laser lap welding as the laser beam has been proved to be competitive since it allows to concentrate the thermal input and increases productivity and quality. Some challenges arise as a consequence of aluminum low absorptance and high thermal conductivity; furthermore, issues are due to metallurgical challenges such as both micro and macro porosity formation and softening in the fused zone. Welding of AA 2024 thin sheets in a lap joint configuration is discussed in this paper: tests are carried out using a recently developed Trumpf TruDisk 2002 Yb:YAG disk-laser with high beam quality which allows to produce beads with low plates distortion and better penetration. The influence of the processing parameters is discussed considering the fused zone extent and the bead shape. The porosity content as well as the morphological features of the beads have been examined.

A Precise Visual Method for Narrow Butt Detection in Specular Reflection Workpiece Welding

PubMed Central

Zeng, Jinle; Chang, Baohua; Du, Dong; Hong, Yuxiang; Chang, Shuhe; Zou, Yirong

2016-01-01

During the complex path workpiece welding, it is important to keep the welding torch aligned with the groove center using a visual seam detection method, so that the deviation between the torch and the groove can be corrected automatically. However, when detecting the narrow butt of a specular reflection workpiece, the existing methods may fail because of the extremely small groove width and the poor imaging quality. This paper proposes a novel detection method to solve these issues. We design a uniform surface light source to get high signal-to-noise ratio images against the specular reflection effect, and a double-line laser light source is used to obtain the workpiece surface equation relative to the torch. Two light sources are switched on alternately and the camera is synchronized to capture images when each light is on; then the position and pose between the torch and the groove can be obtained nearly at the same time. Experimental results show that our method can detect the groove effectively and efficiently during the welding process. The image resolution is 12.5 μm and the processing time is less than 10 ms per frame. This indicates our method can be applied to real-time narrow butt detection during high-speed welding process. PMID:27649173

A Precise Visual Method for Narrow Butt Detection in Specular Reflection Workpiece Welding.

PubMed

Zeng, Jinle; Chang, Baohua; Du, Dong; Hong, Yuxiang; Chang, Shuhe; Zou, Yirong

2016-09-13

During the complex path workpiece welding, it is important to keep the welding torch aligned with the groove center using a visual seam detection method, so that the deviation between the torch and the groove can be corrected automatically. However, when detecting the narrow butt of a specular reflection workpiece, the existing methods may fail because of the extremely small groove width and the poor imaging quality. This paper proposes a novel detection method to solve these issues. We design a uniform surface light source to get high signal-to-noise ratio images against the specular reflection effect, and a double-line laser light source is used to obtain the workpiece surface equation relative to the torch. Two light sources are switched on alternately and the camera is synchronized to capture images when each light is on; then the position and pose between the torch and the groove can be obtained nearly at the same time. Experimental results show that our method can detect the groove effectively and efficiently during the welding process. The image resolution is 12.5 μm and the processing time is less than 10 ms per frame. This indicates our method can be applied to real-time narrow butt detection during high-speed welding process.

Modelling of fluid flow phenomenon in laser+GMAW hybrid welding of aluminum alloy considering three phase coupling and arc plasma shear stress

NASA Astrophysics Data System (ADS)

Xu, Guoxiang; Li, Pengfei; Cao, Qingnan; Hu, Qingxian; Gu, Xiaoyan; Du, Baoshuai

2018-03-01

The present study aims to develop a unified three dimensional numerical model for fiber laser+GMAW hybrid welding, which is used to study the fluid flow phenomena in hybrid welding of aluminum alloy and the influence of laser power on weld pool dynamic behavior. This model takes into account the coupling of gas, liquid and metal phases. Laser heat input is described using a cone heat source model with changing peak power density, its height being determined based on the keyhole size. Arc heat input is modeled as a double ellipsoid heat source. The arc plasma flow and droplet transfer are simulated through the two simplified models. The temperature and velocity fields for different laser powers are calculated. The computed results are in general agreement with the experimental data. Both the peak and average values of fluid flow velocity during hybrid welding are much higher than those of GMAW. At a low level of laser power, both the arc force and droplet impingement force play a relatively large role on fluid flow in the hybrid welding. Keyhole depth always oscillates within a range. With an increase in laser power, the weld pool behavior becomes more complex. An anti-clockwise vortex is generated and the stability of keyhole depth is improved. Besides, the effects of laser power on different driving forces of fluid flow in weld pool are also discussed.

A Monte Carlo model for 3D grain evolution during welding

NASA Astrophysics Data System (ADS)

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

2017-09-01

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

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.

Gravitational effects on the weld pool shape and microstructural evolution during gas tungsten arc and laser beam welding of 304 stainless steel and Al-4 wt% Cu alloy.

PubMed

Kang, Namhyun; Singh, Jogender; Kulkarni, Anil K

2004-11-01

Effects of gravitational acceleration were investigated on the weld pool shape and microstructural evolution for 304 stainless steel and Al-4wt% Cu alloy. Effects of welding heat source were investigated by using laser beam welding (LBW) and gas tungsten arc welding (GTAW). As the gravitational level was increased from low gravity (LG approximately 1.2 g) to high gravity (HG approximately 1.8 g) using a NASA KC-135 aircraft, the weld pool shape for 304 stainless steel was influenced considerably during GTAW. However, insignificant change in the microstructure and solute distribution was observed at gravitational levels between LG and HG. The GTAW on Al-4 wt% Cu alloy was used to investigate the effect of gravitational orientation on the weld solidification behavior. Gravitational orientation was manipulated by varying the welding direction with respect to gravity vector; that is, by welding upward opposing gravity ( ||-U) and downward with gravity ( ||-D) on a vertical weld piece and welding perpendicular to gravity (perpendicular) on a horizontal weld piece. Under the same welding conditions, a larger primary dendrite spacing in the ||-U weld was observed near the weld pool surface and the fusion boundary than in the case of perpendicular or ||-D welds. The ||-D weld exhibited different solidification morphology and abnormal S shape of solidification rate curve during its growth. For 304 stainless steel GTAW, significant effects of gravitational orientation were observed on the weld pool shape that was associated with weld surface morphology and convection flow. However, the weld pool shape for LBW was mostly constant with respect to the gravitational orientation.

Definition of the Mathematical Model Coefficients on the Weld Size of Butt Joint Without Edge Preparation

NASA Astrophysics Data System (ADS)

Sidorov, Vladimir P.; Melzitdinova, Anna V.

2017-10-01

This paper represents the definition methods for thermal constants according to the data of the weld width under the normal-circular heat source. The method is based on isoline contouring of “effective power - temperature conductivity coefficient”. The definition of coefficients provides setting requirements to the precision of welding parameters support with the enough accuracy for an engineering practice.

Fabrication of fine-grain tantalum diffusion barrier tube for Nb3Sn conductors

NASA Astrophysics Data System (ADS)

Hartwig, K. T.; Balachandran, S.; Mezyenski, R.; Seymour, N.; Robinson, J.; Barber, R. E.

2014-01-01

Diffusion barriers used in Nb3Sn wire are often fabricated by wrapping Ta sheet into a tube with an overlap seam. A common result of such practice is non-uniform deformation in the Ta sheet as it thins by wire drawing because of non-uniform grain size and texture in the original Ta sheet. Seamless Ta tube with a fine-grain and uniform microstructure would be much better for the diffusion barrier application, but such material is expensive and difficult to manufacture. This report presents results on a new fabrication strategy for Ta tube that shows promise for manufacture of less costly tube with an improved microstructure. The fabrication method begins with seam-welded tube but gives a fine-grain uniform microstructure with little difference between the longitudinal seam weld region and the parent metal after post-weld processing. Severe plastic deformation processing (SPD) applied by area reduction extrusion and tube equal channel angular extrusion (tECAE) are used to refine and homogenize the microstructure. Microstructure and mechanical property results are presented for Ta tubes fabricated by this new processing strategy.

Moisture contamination and welding parameter effects on flux cored arc welding diffusible hydrogen

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

Kiefer, J.J.

1994-12-31

Gas metal arc (GMAW) and flux cored arc (FCAW) welding are gas shielded semiautomatic processes widely used for achieving high productivity in steel fabrication. Contamination of the shielding has can occur due to poorly maintained gas distribution systems. Moisture entering as a gas contaminant is a source of hydrogen that can cause delayed cold cracking in welds. Limiting heat-affected zone hardness is one method of controlling cracking. Even this is based on some assumptions about the hydrogen levels in the weld. A study was conducted to investigate the effect of shielding gas moisture contamination and welding parameters on the diffusiblemore » hydrogen content of gas shielded flux cored arc welding. The total wire hydrogen of various electrodes was also tested and compared to the diffusible weld hydrogen. An empirical equation has been developed that estimates the diffusible hydrogen in weld metal for gas shielded flux cored arc welding. The equation is suitable for small diameter electrodes and welding parameter ranges commonly used for out-of-position welding. by combining this with the results from the total wire hydrogen tests, it is possible to estimate diffusible hydrogen directly from measured welding parameters, shielding gas dew point, and total hydrogen of the consumable. These equations are also useful for evaluating the effect of welding procedure variations from known baseline conditions.« less

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.

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

NASA Technical Reports Server (NTRS)

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

2007-01-01

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

Laser welding of fused quartz

DOEpatents

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

2003-06-10

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

Effect of Microstructure on Stress Corrosion Cracking Behaviour of High Nitrogen Stainless Steel Gas Tungsten Arc Welds

NASA Astrophysics Data System (ADS)

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

2018-03-01

Present work is aimed to improve stress corrosion cracking resistance of high nitrogen steel and its welds. An attempt to weld high nitrogen steel of 5 mm thick plate using gas tungsten arc welding (GTAW) with three high strength age hardenable fillers i.e., 11-10 PH filler, PH 13- 8Mo and maraging grade of MDN 250 filler is made. Welds were characterized by optical microscopy and scanning electron microscopy. Vickers hardness testing of the welds was carried out to study the mechanical behaviour of welds. Potentio-dynamic polarization studies were done to determine pitting corrosion resistance in aerated 3.5% NaCl solution. Stress corrosion cracking (SCC) testing was carried out using constant load type machine with applied stress of 50% yield strength and in 45% MgCl2 solution boiling at 155°C. The results of the present investigation established that improvement in resistance to stress corrosion cracking was observed for PH 13- 8Mo GTA welds when compared to 11-10 PH and MDN 250 GTA welds. However, All GTA welds failed in the weld interface region. This may be attributed to relatively lower pitting potential in weld interface which acts as active site and the initiation source of pitting.

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

NASA Astrophysics Data System (ADS)

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

2015-07-01

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

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

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

NASA Astrophysics Data System (ADS)

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

2017-09-01

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

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.

Experimental investigations of tungsten inert gas assisted friction stir welding of pure copper plates

NASA Astrophysics Data System (ADS)

Constantin, M. A.; Boșneag, A.; Nitu, E.; Iordache, M.

2017-10-01

Welding copper and its alloys is usually difficult to join by conventional fusion welding processes because of high thermal diffusivity of the copper, alloying elements, necessity of using a shielding gas and a clean surface. To overcome this inconvenience, Friction Stir Welding (FSW), a solid state joining process that relies on frictional heating and plastic deformation, is used as a feasible welding process. In order to achieve an increased welding speed and a reduction in tool wear, this process is assisted by another one (WIG) which generates and adds heat to the process. The aim of this paper is to identify the influence of the additional heat on the process parameters and on the welding joint properties (distribution of the temperature, hardness and roughness). The research includes two experiments for the FSW process and one experiment for tungsten inert gas assisted FSW process. The outcomes of the investigation are compared and analysed for both welding variants. Adding a supplementary heat source, the plates are preheated and are obtain some advantages such as reduced forces used in process and FSW tool wear, faster and better plasticization of the material, increased welding speed and a proper weld quality.

A Monte Carlo model for 3D grain evolution during welding

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

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

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

A Monte Carlo model for 3D grain evolution during welding

DOE PAGES

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

2017-08-04

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

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

NASA Technical Reports Server (NTRS)

Adams, Glynn; Venable, Richard; Lawless, Kirby

2003-01-01

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

Effect of process parameters on temperature distribution in twin-electrode TIG coupling arc

NASA Astrophysics Data System (ADS)

Zhang, Guangjun; Xiong, Jun; Gao, Hongming; Wu, Lin

2012-10-01

The twin-electrode TIG coupling arc is a new type of welding heat source, which is generated in a single welding torch that has two tungsten electrodes insulated from each other. This paper aims at determining the distribution of temperature for the coupling arc using the Fowler-Milne method under the assumption of local thermodynamic equilibrium. The influences of welding current, arc length, and distance between both electrode tips on temperature distribution of the coupling arc were analyzed. Based on the results, a better understanding of the twin-electrode TIG welding process was obtained.

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

NASA Astrophysics Data System (ADS)

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

1992-02-01

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

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

PubMed

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

2018-01-05

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

A hot-cracking mitigation technique for welding high-strength aluminum alloy

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

Yang, Y.P.; Dong, P.; Zhang, J.

2000-01-01

A hot-cracking mitigation technique for gas tungsten arc welding (GTAW) of high-strength aluminum alloy 2024 is presented. The proposed welding technique incorporates a trailing heat sink (an intense cooling source) with respect to the welding torch. The development of the mitigation technique was based on both detailed welding process simulation using advanced finite element techniques and systematic laboratory experiments. The finite element methods were used to investigate the detailed thermomechanical behavior of the weld metal that undergoes the brittle temperature range (BTR) during welding. As expected, a tensile deformation zone within the material BTR region was identified behind the weldmore » pool under conventional GTA welding process conventional GTA welding process conditions for the aluminum alloy studied. To mitigate hot cracking, the tensile zone behind the weld pool must be eliminated or reduce to a satisfactory level if the weld metal hot ductility cannot be further improved. With detailed computational modeling, it was found that by the introduction of a trailing heat sink at some distance behind the welding arc, the tensile strain rate with respect to temperature in the zone encompassing the BTR region can be significantly reduced. A series of parametric studies were also conducted to derive optimal process parameters for the trailing heat sink. The experimental results confirmed the effectiveness of the trailing heat sink technique. With a proper implementation of the trailing heat sink method, hot cracking can be completely eliminated in welding aluminum alloy 2024 (AA 2024).« less

Weld radiograph enigmas

NASA Technical Reports Server (NTRS)

Jemian, Wartan A.

1986-01-01

Weld radiograph enigmas are features observed on X-ray radiographs of welds. Some of these features resemble indications of weld defects, although their origin is different. Since they are not understood, they are a source of concern. There is a need to identify their causes and especially to measure their effect on weld mechanical properties. A method is proposed whereby the enigmas can be evaluated and rated, in relation to the full spectrum of weld radiograph indications. Thie method involves a signature and a magnitude that can be used as a quantitive parameter. The signature is generated as the diference between the microdensitometer trace across the radiograph and the computed film intensity derived from a thickness scan along the corresponding region of the sample. The magnitude is the measured difference in intensity between the peak and base line values of the signature. The procedure is demonstated by comparing traces across radiographs of a weld sample before and after the introduction of a hole and by a system based on a MacIntosh mouse used for surface profiling.

Effect of carbon black on temperature field and weld profile during laser transmission welding of polymers: A FEM study

NASA Astrophysics Data System (ADS)

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

2012-04-01

The influence of the carbon black on temperature distribution and weld profile, during laser transmission welding of polymers, is investigated in the present research work. A transient numerical model, based on conduction mode heat transfer, is developed to analyze the process. The heat input to the model is considered to be the volumetric Gaussian heat source. The computation of temperature field during welding is carried out for polycarbonates having different proportion of carbon black in polymer matrix. The temperature dependent material properties of polycarbonate are taken into account for modeling. The finite element code ANSYS ® is employed to obtain the numerical results. The numerically computed results of weld pool dimensions are compared with the experimental results. The comparison shows a fair agreement between them, which gives confidence to use the developed model for intended investigation with acceptable accuracy. The results obtained have revealed that the carbon black has considerable influence on the temperature field distribution and the formation of the weld pool geometry.

Effects of stress concentration on the fatigue strength of 7003-T5 aluminum alloy butt joints with weld reinforcement

NASA Astrophysics Data System (ADS)

Zhu, Zongtao; Li, Yuanxing; Zhang, Mingyue; Hui, Chen

2015-03-01

7003-T5 Aluminum (Al) alloy plates with a thickness of 5 mm are welded by gas metal arc welding (GMAW) method in this work. In order to investigate the influence of stress concentration introduced by weld reinforcement on fatigue strength, the stress concentration factor of the butt joint is calculated. Microscopic and X-ray techniques were utilized to make sure there are no weld defects with large size in butt weld, which can induce extra stress concentration. The cyclic stress - number of cycles to failure (S-N) curves of the joints with and without the welder were obtained by fatigue testing, and the results show that the fatigue strength of 7003-T5 Al alloy butt joints with the weld reinforcement is 50 MPa, which is only 45% of the joints without the weld reinforcement. Fracture surface observation indicated that the fatigue source and propagation are dissimilar for the specimens with and without the welder due to the stress concentration at the weld root. The stress concentration with a factor of 1.7 has great effect on the fatigue strength, but little influence on the tensile strength.

Hybrid Welding of 45 mm High Strength Steel Sections

NASA Astrophysics Data System (ADS)

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

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

The effect of travel speed on thermal response in CO2 laser welding of small electronic components

NASA Astrophysics Data System (ADS)

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

A comprehensive three-dimensional numerical investigation of the effect of beat source travel speed on temperatures and resulting thermal stresses was performed for CO2-laser welding. The test specimen was a small thermal battery header containing several stress-sensitive glass-to-metal seals surrounding the electrical connections and a temperature sensitive ignitor located under the header near the center. Predictions of the thermal stresses and temperatures in the battery header were made for several travel speeds of the laser. The travel speeds examined ranged from 10mm/sec to 50mm/sec. The results indicate that faster weld speeds result in lower temperatures and stresses for the same size weld. This is because the higher speed welds are more efficient, requiring less energy to produce a given weld. Less energy absorbed by the workpiece results in lower temperatures, which results in lower stresses.

Thermomechanically coupled conduction mode laser welding simulations using smoothed particle hydrodynamics

NASA Astrophysics Data System (ADS)

Hu, Haoyue; Eberhard, Peter

2017-10-01

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

Sensor Fusion to Estimate the Depth and Width of the Weld Bead in Real Time in GMAW Processes

PubMed Central

Sampaio, Renato Coral; Vargas, José A. R.

2018-01-01

The arc welding process is widely used in industry but its automatic control is limited by the difficulty in measuring the weld bead geometry and closing the control loop on the arc, which has adverse environmental conditions. To address this problem, this work proposes a system to capture the welding variables and send stimuli to the Gas Metal Arc Welding (GMAW) conventional process with a constant voltage power source, which allows weld bead geometry estimation with an open-loop control. Dynamic models of depth and width estimators of the weld bead are implemented based on the fusion of thermographic data, welding current and welding voltage in a multilayer perceptron neural network. The estimators were trained and validated off-line with data from a novel algorithm developed to extract the features of the infrared image, a laser profilometer was implemented to measure the bead dimensions and an image processing algorithm that measures depth by making a longitudinal cut in the weld bead. These estimators are optimized for embedded devices and real-time processing and were implemented on a Field-Programmable Gate Array (FPGA) device. Experiments to collect data, train and validate the estimators are presented and discussed. The results show that the proposed method is useful in industrial and research environments. PMID:29570698

Sensor Fusion to Estimate the Depth and Width of the Weld Bead in Real Time in GMAW Processes.

PubMed

Bestard, Guillermo Alvarez; Sampaio, Renato Coral; Vargas, José A R; Alfaro, Sadek C Absi

2018-03-23

The arc welding process is widely used in industry but its automatic control is limited by the difficulty in measuring the weld bead geometry and closing the control loop on the arc, which has adverse environmental conditions. To address this problem, this work proposes a system to capture the welding variables and send stimuli to the Gas Metal Arc Welding (GMAW) conventional process with a constant voltage power source, which allows weld bead geometry estimation with an open-loop control. Dynamic models of depth and width estimators of the weld bead are implemented based on the fusion of thermographic data, welding current and welding voltage in a multilayer perceptron neural network. The estimators were trained and validated off-line with data from a novel algorithm developed to extract the features of the infrared image, a laser profilometer was implemented to measure the bead dimensions and an image processing algorithm that measures depth by making a longitudinal cut in the weld bead. These estimators are optimized for embedded devices and real-time processing and were implemented on a Field-Programmable Gate Array (FPGA) device. Experiments to collect data, train and validate the estimators are presented and discussed. The results show that the proposed method is useful in industrial and research environments.

3D construction and repair from welding and material science perspectives

NASA Astrophysics Data System (ADS)

Marya, Surendar; Hascoet, Jean-Yves

2016-10-01

Additive manufacturing, based on layer-by-layer deposition of a feedstock material from a 3D data, can be mechanistically associated to welding. With feedstock fusion based processes, both additive manufacturing and welding implement similar heat sources, feedstock materials and translation mechanisms. From material science perspectives, additive manufacturing can take clue from lessons learned by millennium old welding technology to rapidly advance in its quest to generate fit for service metallic parts. This paper illustrates material science highlights extracted from the fabrication of a 316 L air vent and the functional repair of a Monel K500 (UNS N0500) with Inconel 625.

Holographic measurement of distortion during laser melting: Additive distortion from overlapping pulses

NASA Astrophysics Data System (ADS)

Haglund, Peter; Frostevarg, Jan; Powell, John; Eriksson, Ingemar; Kaplan, Alexander F. H.

2018-03-01

Laser - material interactions such as welding, heat treatment and thermal bending generate thermal gradients which give rise to thermal stresses and strains which often result in a permanent distortion of the heated object. This paper investigates the thermal distortion response which results from pulsed laser surface melting of a stainless steel sheet. Pulsed holography has been used to accurately monitor, in real time, the out-of-plane distortion of stainless steel samples melted on one face by with both single and multiple laser pulses. It has been shown that surface melting by additional laser pulses increases the out of plane distortion of the sample without significantly increasing the melt depth. The distortion differences between the primary pulse and subsequent pulses has also been analysed for fully and partially overlapping laser pulses.

Near infrared laser-tissue welding using nanoshells as an exogenous absorber.

PubMed

Gobin, Andre M; O'Neal, D Patrick; Watkins, Daniel M; Halas, Naomi J; Drezek, Rebekah A; West, Jennifer L

2005-08-01

Gold nanoshells are a new class of nanoparticles that can be designed to strongly absorb light in the near infrared (NIR). These particles provide much larger absorption cross-sections and efficiency than can be achieved with currently used chemical chromophores without photobleaching. In these studies, we have investigated the use of gold nanoshells as exogenous NIR absorbers to facilitate NIR laser-tissue welding. Gold nanoshells with peak extinction matching the NIR wavelength of the laser being used were manufactured and suspended in an albumin solder. Optimization work was performed on ex vivo muscle samples and then translated into testing in an in vivo rat skin wound-healing model. Mechanical testing of the muscle samples was immediately performed and compared to intact tissue mechanical properties. In the in vivo study, full thickness incisions in the dorsal skin of rats were welded, and samples of skin were excised at 0, 5, 10, 21, and 32 days for analysis of strength and wound healing response. Mechanical testing of nanoshell-solder welds in muscle revealed successful fusion of tissues with tensile strengths of the weld site equal to the uncut tissue. No welding was accomplished with this light source when using solder formulations without nanoshells. Mechanical testing of the skin wounds showed sufficient strength for closure and strength increased over time. Histological examination showed good wound-healing response in the soldered skin. The use of nanoshells as an exogenous absorber allows the usage of light sources that are minimally absorbed by tissue components, thereby, minimizing damage to surrounding tissue and allowing welding of thicker tissues. (c) 2005 Wiley-Liss, Inc.

Heat Source - Materials Interactions during Fusion Welding.

DTIC Science & Technology

1982-04-30

calcium, chromium and tungsten lines have been identified. In the titanium spectra (Figure 6), argon, titanium, aluminum, calcium and tungsten lines have...Stainless Steel," Weld J.,5(12), 1974, p. 5 4 9 -r. 3. C. B. Shaw, Jr. "Diagnostic Studies of the GTAW Arc," Weld J. 54(2), p.33-s. 4. J. F. Key, M. E...black body radiation curve. The diagram is valid only in the manganese m.p.-b.p. range. Fig.-8 Chromium isopleths plotted against log of pressure, log

An Investigation into the Comparative Costs of Additive Manufacture vs. Machine from Solid for Aero Engine Parts

DTIC Science & Technology

2006-05-01

welding power sources are not totally efficient at converting power drawn from the wall into heat energy used for the welding process . TIG sources are...Powder bed + Laser • Wire + Laser • Wire + Electron Beam • Wire + TIG Each system has its own unique attributes in terms of process variables...relative economics of producing a near net shape by Additive Manufacturing (AM) processes compared with traditional machine from solid processes (MFS

NonDestructive Evaluation for Industrial & Development Applications

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

Hunter, James F.

2016-10-12

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

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.

Emissions of chromium (VI) from arc welding.

PubMed

Heung, William; Yun, Myoung-Jin; Chang, Daniel P Y; Green, Peter G; Halm, Chris

2007-02-01

The presence of Cr in the +6 oxidation state (Cr[VI]) is still observed in ambient air samples in California despite steps taken to reduce emissions from plating operations. One known source of emission of Cr(VI) is welding, especially with high Cr-content materials, such as stainless steels. An experimental effort was undertaken to expand and update Cr(VI) emission factors by conducting tests on four types of arc-welding operations: gas-metal arc welding (GMAW), shielded metal arc welding (SMAW), fluxcore arc welding, and pulsed GMAW. Standard American Welding Society hood results were compared with a total enclosure method that permitted isokinetic sampling for particle size-cut measurement, as well as total collection of the aerosol. The fraction of Cr(VI) emitted per unit mass of Cr electrode consumed was determined. Consistent with AP-42 data, initial results indicate that a significant fraction of the total Cr in the aerosol is in the +6 oxidation state. The fraction of Cr(VI) and total aerosol mass produced by the different arc welding methods varies with the type of welding process used. Self-shielded electrodes that do not use a shield gas, for example, SMAW, produce greater amounts of Cr(VI) per unit mass of electrode consumed. The formation of Cr(VI) from standard electrode wires used for welding mild steel was below the method detection limit after eliminating an artifact in the analytical method used.

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.

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

PubMed Central

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

2015-01-01

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

Welding current and melting rate in GMAW of aluminium

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

Pandey, S.; Rao, U.R.K.; Aghakhani, M.

1996-12-31

Studies on GMAW of aluminium and its alloy 5083, revealed that the welding current and melting rate were affected by any change in wire feed rate, arc voltage, nozzle to plate distance, welding speed and torch angle. Empirical models have been presented to determine accurately the welding current and melting rate for any set of these parameters. These results can be utilized for determining accurately the heat input into the workpiece from which reliable predictions can be made about the mechanical and the metallurgical properties of a welded joint. The analysis of the model also helps in providing a vitalmore » information about the static V-I characteristics of the welding power source. The models were developed using a two-level fractional factorial design. The adequacy of the model was tested by the use of analysis of variance technique and the significance of the coefficients was tested by the student`s t test. The estimated and observed values of the welding current and melting rate have been shown on a scatter diagram and the interaction effects of different parameters involved have been presented in graphical forms.« less

Intelligent Weld Manufacturing: Role of Integrated Computational Welding Engineering

DOE PAGES

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

2017-12-02

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

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.

Intelligent Weld Manufacturing: Role of Integrated Computational Welding Engineering

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

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

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

Conceptual design of modular fixture for frame welding and drilling process integration case study: Student chair in UNS industrial engineering integrated practicum

NASA Astrophysics Data System (ADS)

Darmawan, Tofiq Dwiki; Priadythama, Ilham; Herdiman, Lobes

2018-02-01

Welding and drilling are main processes of making chair frame from metal material. Commonly, chair frame construction includes many arcs which bring difficulties for its welding and drilling process. In UNS industrial engineering integrated practicum there are welding fixtures which use to fixing frame component position for welding purpose. In order to achieve exact holes position for assembling purpose, manual drilling processes were conducted after the frame was joined. Unfortunately, after it was welded the frame material become hard and increase drilling tools wear rate as well as reduce holes position accuracy. The previous welding fixture was not equipped with clamping system and cannot accommodate drilling process. To solve this problem, our idea is to reorder the drilling process so that it can be execute before welding. Thus, this research aims to propose conceptual design of modular fixture which can integrate welding and drilling process. We used Generic Product Development Process to address the design concept. We collected design requirements from 3 source, jig and fixture theoretical concepts, user requirements, and clamping part standards. From 2 alternatives fixture tables, we propose the first which equipped with mounting slots instead of holes. We test the concept by building a full sized prototype and test its works by conducting welding and drilling of a student chair frame. Result from the welding and drilling trials showed that the holes are on precise position after welding. Based on this result, we conclude that the concept can be a consideration for application in UNS Industrial Engineering Integrated Practicum.

Plasmonic welded single walled carbon nanotubes on monolayer graphene for sensing target protein

NASA Astrophysics Data System (ADS)

Kim, Jangheon; Kim, Gi Gyu; Kim, Soohyun; Jung, Wonsuk

2016-05-01

We developed plasmonic welded single walled carbon nanotubes (SWCNTs) on monolayer graphene as a biosensor to detect target antigen molecules, fc fusion protein without any treatment to generate binder groups for linker and antibody. This plasmonic welding induces atomic networks between SWCNTs as junctions containing carboxylic groups and improves the electrical sensitivity of a SWCNTs and the graphene membrane to detect target protein. We investigated generation of the atomic networks between SWCNTs by field-emission scanning electron microscopy and atomic force microscopy after plasmonic welding process. We compared the intensity ratios of D to G peaks from the Raman spectra and electrical sheet resistance of welded SWCNTs with the results of normal SWCNTs, which decreased from 0.115 to 0.086 and from 10.5 to 4.12, respectively. Additionally, we measured the drain current via source/drain voltage after binding of the antigen to the antibody molecules. This electrical sensitivity of the welded SWCNTs was 1.55 times larger than normal SWCNTs.

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

NASA Astrophysics Data System (ADS)

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

2016-07-01

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

Numerical Simulation and Artificial Neural Network Modeling for Predicting Welding-Induced Distortion in Butt-Welded 304L Stainless Steel Plates

NASA Astrophysics Data System (ADS)

Narayanareddy, V. V.; Chandrasekhar, N.; Vasudevan, M.; Muthukumaran, S.; Vasantharaja, P.

2016-02-01

In the present study, artificial neural network modeling has been employed for predicting welding-induced angular distortions in autogenous butt-welded 304L stainless steel plates. The input data for the neural network have been obtained from a series of three-dimensional finite element simulations of TIG welding for a wide range of plate dimensions. Thermo-elasto-plastic analysis was carried out for 304L stainless steel plates during autogenous TIG welding employing double ellipsoidal heat source. The simulated thermal cycles were validated by measuring thermal cycles using thermocouples at predetermined positions, and the simulated distortion values were validated by measuring distortion using vertical height gauge for three cases. There was a good agreement between the model predictions and the measured values. Then, a multilayer feed-forward back propagation neural network has been developed using the numerically simulated data. Artificial neural network model developed in the present study predicted the angular distortion accurately.

40 CFR 63.11516 - What are my standards and management practices?

Code of Federal Regulations, 2010 CFR

2010-07-01

... Testing Air-Cleaning Devices Used in General Ventilation for Removing Particulate Matter, June 4, 1992... requirements of this section and be re-certified every 5 years. (e) [Reserved] (f) Standards for welding. If you own or operate a new or existing welding affected source, you must comply with the requirements in...

Electrode cartridge for pulse welding

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

Bonnen, John Joseph Francis; Golovashchenko, Sergey Fedorovich; Mamutov, Alexander

A cartridge assembly for a tool includes a cartridge body or casing that contains a conductor. A conductor is connected to a pulse generator or source of stored charge that is discharged to vaporize the conductor and create an electro-hydraulic or electro-magnetic shockwave that is used to impact or pulse weld two parts together.

Truss Assembly and Welding by Intelligent Precision Jigging Robots

NASA Technical Reports Server (NTRS)

Komendera, Erik; Dorsey, John T.; Doggett, William R.; Correll, Nikolaus

2014-01-01

This paper describes an Intelligent Precision Jigging Robot (IPJR) prototype that enables the precise alignment and welding of titanium space telescope optical benches. The IPJR, equipped with micron accuracy sensors and actuators, worked in tandem with a lower precision remote controlled manipulator. The combined system assembled and welded a 2 m truss from stock titanium components. The calibration of the IPJR, and the difference between the predicted and the truss dimensions as-built, identified additional sources of error that should be addressed in the next generation of IPJRs in 2D and 3D.

Development and fabrication of a diffusion welded Columbium alloy heat exchanger. [for space power generation

NASA Technical Reports Server (NTRS)

Zimmerman, W. F.; Duderstadt, E. C.; Wein, D.; Titran, R. H.

1978-01-01

A Mini Brayton space power generation system required the development of a Columbium alloy heat exchanger to transfer heat from a radioisotope heat source to a He/Xe working fluid. A light-weight design featured the simultaneous diffusion welding of 148 longitudinal fins in an annular heat exchanger about 9-1/2 in. in diameter, 13-1/2 in. in length and 1/4 in. in radial thickness. To complete the heat exchanger, additional gas ducting elements and attachment supports were added by GTA welding in a vacuum-purged inert atmosphere welding chamber. The development required the modification of an existing large size hot isostatic press to achieve HIP capabilities of 2800 F and 10,000 psi for at least 3 hr. Excellent diffusion welds were achieved in a high-quality component which met all system requirements.

Effect of Local Post Weld Heat Treatment on Tensile Properties in Friction Stir Welded 2219-O Al Alloy

NASA Astrophysics Data System (ADS)

Chu, Guannan; Sun, Lei; Lin, Caiyuan; Lin, Yanli

2017-11-01

To improve the formability of the aluminum alloy welds and overcome the size limitation of the bulk post weld heat treatment (BPWHT) on large size friction stir welded joints, a local post weld heat treatment method (LPWHT) was proposed. In this method, the resistance heating as the moving heat source is adopted to only heat the weld seam. The temperature field of LPWHT and its influence on the mechanical properties and formability of FSW 2219-O Al alloy joints was investigated. The evaluation of the tensile properties of FSW samples was also examined by mapping the global and local strain distribution using the digital image correlation methodology. The results indicated that the formability was improved greatly after LPWHT, while the hardness distribution of the FSW joint was homogenized. The maximum elongation can reach 1.4 times that of as-welded joints with increase the strength and the strain of the nugget zone increased from 3 to 8% when annealing at 300 °C. The heterogeneity on the tensile deformation of the as-welded joints was improved by the nugget zone showing large local strain value and the reason was given according to the dimple fracture characteristics at different annealing temperatures. The tensile strength and elongation of LPWHT can reach 93.3 and 96.1% of the BPWHT, respectively. Thus, the LPWHT can be advantageous compared to the BPWHT for large size welds.

Numerical analysis of the heat source characteristics of a two-electrode TIG arc

NASA Astrophysics Data System (ADS)

Ogino, Y.; Hirata, Y.; Nomura, K.

2011-06-01

Various kinds of multi-electrode welding processes are used to ensure high productivity in industrial fields such as shipbuilding, automotive manufacturing and pipe fabrication. However, it is difficult to obtain the optimum welding conditions for a specific product, because there are many operating parameters, and because welding phenomena are very complicated. In the present research, the heat source characteristics of a two-electrode TIG arc were numerically investigated using a 3D arc plasma model with a focus on the distance between the two electrodes. The arc plasma shape changed significantly, depending on the electrode spacing. The heat source characteristics, such as the heat input density and the arc pressure distribution, changed significantly when the electrode separation was varied. The maximum arc pressure of the two-electrode TIG arc was much lower than that of a single-electrode TIG. However, the total heat input of the two-electrode TIG arc was nearly constant and was independent of the electrode spacing. These heat source characteristics of the two-electrode TIG arc are useful for controlling the heat input distribution at a low arc pressure. Therefore, these results indicate the possibility of a heat source based on a two-electrode TIG arc that is capable of high heat input at low pressures.

Pulsed welding plasma source

NASA Astrophysics Data System (ADS)

Knyaz'kov, A.; Pustovykh, O.; Verevkin, A.; Terekhin, V.; Shachek, A.; Tyasto, A.

2016-04-01

It is shown that in order to form the current pulse of a near rectangular shape, which provides conversion of the welding arc into a dynamic mode, it is rational to connect a forming element made on the basis of an artificial forming line in series to the welding DC circuit. The paper presents a diagram of a pulsed device for welding with a non-consumable electrode in argon which was developed using the forming element. The conversion of the arc into the dynamic mode is illustrated by the current and voltage oscillograms of the arc gap and the dynamic characteristic of the arc within the interval of one pulse generation time in the arc gap. The background current travels in the interpulse interval.

Strategies for risk assessment and control in welding: challenges for developing countries.

PubMed

Hewitt, P J

2001-06-01

Metal arc welding ranges from primitive (manual) to increasingly complex automated welding processes. Welding occupies 1% of the labour force in some industrialised countries and increasing knowledge of health risks, necessitating improved assessment strategies and controls have been identified by the International Institute of Welding (IIW), ILO, WHO and other authoritative bodies. Challenges for developing countries need to be addressed. For small scale production and repair work, predominantly by manual metal arc on mild steel, the focus in developing economies has correctly been on control of obvious physical and acute health affects. Development introduces more sophisticated processes and hazards. Work pieces of stainless steel and consumables with chromium, nickel and manganese constituents are used with increasingly complex semi-manual or automated systems involving variety of fluxes or gasses. Uncritical adoption of new welding technologies by developing countries potentiates future health problems. Control should be integral at the design stage, otherwise substantive detriments and later costs can ensue. Developing countries need particular guidance on selection of the optimised welding consumables and processes to minimise such detriments. The role of the IIW and the MFRU are described. Applications of occupational hygiene principals of prevention and control of welding fume at source by process modification are presented.

Microstructure Evolution and Selective Corrosion Resistance in Underwater Multi-pass 2101 Duplex Stainless Steel Welding Joints

NASA Astrophysics Data System (ADS)

Hu, Yu; Shi, Yonghua; Shen, Xiaoqin; Wang, Zhongmin

2018-05-01

A recently developed promising material, 2101 lean duplex stainless steel, represents an alternative to 304 austenite stainless steel. In this work, multi-pass 2101 weld joints were fabricated using the flux-cored arc welding method in a hyperbaric chamber. The pressure varied from 0 to 0.75 MPa. The evolution of the welding process and microstructure was investigated. γ 2 formation in the reheated zones of the WM and HAZ was not uniform. The closer the reheated zone is to the subsequent heat source, the greater the γ 2 formation in the reheated zone. Sufficient primary austenite transformation inhibited Cr2N precipitation and the subsequent intragranular γ 2 formation in the reheated weld passes of the 0.45 MPa weld metal. The localized corrosion resistance of each zone of the 0.45 MPa DSS joint was measured using non-destructive double-loop electrochemical potentiokinetic reactivation tests. The localized corrosion was induced by γ 2 and Cr2N. The root region of the 0.45 MPa weld metal underwent two subsequent welding thermal cycles, which induced increased γ 2 formation and lower resistance to corrosion because of the decreased pitting resistance value of γ 2. The correlation between microstructure evolution and the distribution of selective corrosion was determined.

Numerical Simulation and Experimental Validation of MIG Welding of T-Joints of Thin Aluminum Plates for Top Class Vehicles

NASA Astrophysics Data System (ADS)

Bonazzi, Enrico; Colombini, Elena; Panari, Davide; Vergnano, Alberto; Leali, Francesco; Veronesi, Paolo

2017-01-01

The integration of experiments with numerical simulations can efficiently support a quick evaluation of the welded joint. In this work, the MIG welding operation on aluminum T-joint thin plate has been studied by the integration of both simulation and experiments. The aim of the paper is to enlarge the global database, to promote the use of thin aluminum sheets in automotive body industries and to provide new data. Since the welding of aluminum thin plates is difficult to control due to high speed of the heat source and high heat flows during heating and cooling, a simulation model could be considered an effective design tool to predict the real phenomena. This integrated approach enables new evaluation possibilities on MIG-welded thin aluminum T-joints, as correspondence between the extension of the microstructural zones and the simulation parameters, material hardness, transient 3D temperature distribution on the surface and inside the material, stresses, strains, and deformations. The results of the mechanical simulations are comparable with the experimental measurements along the welding path, especially considering the variability of the process. The results could well predict the welding-induced distortion, which together with local heating during welding must be anticipated and subsequently minimized and counterbalance.

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

PubMed Central

Tseng, Kuang-Hung; Lin, Po-Yu

2014-01-01

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

A novel weld seam detection method for space weld seam of narrow butt joint in laser welding

NASA Astrophysics Data System (ADS)

Shao, Wen Jun; Huang, Yu; Zhang, Yong

2018-02-01

Structured light measurement is widely used for weld seam detection owing to its high measurement precision and robust. However, there is nearly no geometrical deformation of the stripe projected onto weld face, whose seam width is less than 0.1 mm and without misalignment. So, it's very difficult to ensure an exact retrieval of the seam feature. This issue is raised as laser welding for butt joint of thin metal plate is widely applied. Moreover, measurement for the seam width, seam center and the normal vector of the weld face at the same time during welding process is of great importance to the welding quality but rarely reported. Consequently, a seam measurement method based on vision sensor for space weld seam of narrow butt joint is proposed in this article. Three laser stripes with different wave length are project on the weldment, in which two red laser stripes are designed and used to measure the three dimensional profile of the weld face by the principle of optical triangulation, and the third green laser stripe is used as light source to measure the edge and the centerline of the seam by the principle of passive vision sensor. The corresponding image process algorithm is proposed to extract the centerline of the red laser stripes as well as the seam feature. All these three laser stripes are captured and processed in a single image so that the three dimensional position of the space weld seam can be obtained simultaneously. Finally, the result of experiment reveals that the proposed method can meet the precision demand of space narrow butt joint.

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

PubMed

Tseng, Kuang-Hung; Lin, Po-Yu

2014-06-20

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

[The evaluation of the consequences of electromagnetic irradiation of hands in operators of high-frequency welding devices].

PubMed

Rudakov, M L

2000-01-01

Method of secondary sources (method of integral equations) was applied to calculate specific absorbed intensity in hands of operators working at non-shielded high-frequency (27.12 Mhz) welding devices. The authors present calculations for "female" and "male" hand sizes, give recommendations on lower level of specific absorption.

Real-time monitoring of laser welding of galvanized high strength steel in lap joint configuration

NASA Astrophysics Data System (ADS)

Kong, Fanrong; Ma, Junjie; Carlson, Blair; Kovacevic, Radovan

2012-10-01

Two different cases regarding the zinc coating at the lap joint faying surface are selected for studying the influence of zinc vapor on the keyhole dynamics of the weld pool and the final welding quality. One case has the zinc coating fully removed at the faying surface; while the other case retains the zinc coating on the faying surface. It is found that removal of the zinc coating at the faying surface produces a significantly better weld quality as exemplified by a lack of spatters whereas intense spatters are present when the zinc coating is present at the faying surface. Spectroscopy is used to detect the optical spectra emitted from a laser generated plasma plume during the laser welding of galvanized high strength DP980 steel in a lap-joint configuration. A correlation between the electron temperature and defects within the weld bead is identified by using the Boltzmann plot method. The laser weld pool keyhole dynamic behavior affected by a high-pressure zinc vapor generated at the faying surface of galvanized steel lap-joint is monitored in real-time by a high speed charge-coupled device (CCD) camera assisted with a green laser as an illumination source.

Design and Manufacturing Criteria for Beam Position Monitor (BPM) of Taiwan Photon Source (TPS)

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

Hsueh, H. P.; Chang, C. C.; Hsu, S. N.

2010-06-23

There are quite some considerations when the button feedthrough is designed and manufactured in a new 3rd generation synchrotron light source like the to-be-constructed TPS. It is the responsibility of the button feedthrough designer to design a feedthrough with the lowest probable HOM problem. It is also required for the designer to analyze the consequences for each possible mechanical error during manufacturing and therefore set standards of tolerance. We have been using MAFIA to optimize the design of feedthrough including flange type on bending chamber section and primary BPM on insertion device section. We also have set some criteria formore » feedthrough manufacturing, inspection, and welding based on hands-on experience on feedthrough electrical properties measuring, sorting, inspection, and laser welding. Here we will present the MAFIA results, electrical measurement results, and laser welding results and analysis. Criteria based on these results will also be presented.« less

Design and Manufacturing Criteria for Beam Position Monitor (BPM) of Taiwan Photon Source (TPS)

NASA Astrophysics Data System (ADS)

Hsueh, H. P.; Chang, C. C.; Hsu, S. N.; Huang, I. T.; Chen, Y. B.; Kuan, C. K.; Hsiung, G. Y.; Chen, J. R.

2010-06-01

There are quite some considerations when the button feedthrough is designed and manufactured in a new 3rd generation synchrotron light source like the to-be-constructed TPS. It is the responsibility of the button feedthrough designer to design a feedthrough with the lowest probable HOM problem. It is also required for the designer to analyze the consequences for each possible mechanical error during manufacturing and therefore set standards of tolerance. We have been using MAFIA to optimize the design of feedthrough including flange type on bending chamber section and primary BPM on insertion device section. We also have set some criteria for feedthrough manufacturing, inspection, and welding based on hands-on experience on feedthrough electrical properties measuring, sorting, inspection, and laser welding. Here we will present the MAFIA results, electrical measurement results, and laser welding results and analysis. Criteria based on these results will also be presented.

[Study of the effect of heat source separation distance on plasma physical properties in laser-pulsed GMAW hybrid welding based on spectral diagnosis technique].

PubMed

Liao, Wei; Hua, Xue-Ming; Zhang, Wang; Li, Fang

2014-05-01

In the present paper, the authors calculated the plasma's peak electron temperatures under different heat source separation distance in laser- pulse GMAW hybrid welding based on Boltzmann spectrometry. Plasma's peak electron densities under the corresponding conditions were also calculated by using the Stark width of the plasma spectrum. Combined with high-speed photography, the effect of heat source separation distance on electron temperature and electron density was studied. The results show that with the increase in heat source separation distance, the electron temperatures and electron densities of laser plasma did not changed significantly. However, the electron temperatures of are plasma decreased, and the electron densities of are plasma first increased and then decreased.

CRADA Final Report: Weld Predictor App

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

Billings, Jay Jay

Welding is an important manufacturing process used in a broad range of industries and market sectors, including automotive, aerospace, heavy manufacturing, medical, and defense. During welded fabrication, high localized heat input and subsequent rapid cooling result in the creation of residual stresses and distortion. These residual stresses can significantly affect the fatigue resistance, cracking behavior, and load-carrying capacity of welded structures during service. Further, additional fitting and tacking time is often required to fit distorted subassemblies together, resulting in non-value added cost. Using trial-and-error methods to determine which welding parameters, welding sequences, and fixture designs will most effectively reduce distortionmore » is a time-consuming and expensive process. For complex structures with many welds, this approach can take several months. For this reason, efficient and accurate methods of mitigating distortion are in-demand across all industries where welding is used. Analytical and computational methods and commercial software tools have been developed to predict welding-induced residual stresses and distortion. Welding process parameters, fixtures, and tooling can be optimized to reduce the HAZ softening and minimize weld residual stress and distortion, improving performance and reducing design, fabrication and testing costs. However, weld modeling technology tools are currently accessible only to engineers and designers with a background in finite element analysis (FEA) who work with large manufacturers, research institutes, and universities with access to high-performance computing (HPC) resources. Small and medium enterprises (SMEs) in the US do not typically have the human and computational resources needed to adopt and utilize weld modeling technology. To allow an engineer with no background in FEA and SMEs to gain access to this important design tool, EWI and the Ohio Supercomputer Center (OSC) developed the online weld application software tool “WeldPredictor” ( https://eweldpredictor.ewi.org ). About 1400 users have tested this application. This project marked the beginning of development on the next version of WeldPredictor that addresses many outstanding features of the original, including 3D models, allow more material hardening laws, model material phase transformation, and uses open source finite element solvers to quickly solve problems (as opposed to expensive commercial tools).« less

Development of a chromium-free consumable for joining stainless steels

NASA Astrophysics Data System (ADS)

Sowards, Jeffrey William

Government regulations in the United States (OSHA Standards: 1910; 1915; 1917; 1918; 1926) and abroad are decreasing allowable exposure levels of hexavalent chromium to welding related personnel. The latest OSHA ruling in 2006 reduced the permissible exposure limit of airborne hexavalent chromium from 52 to 5 mug m-3. Achieving the new level may not be practical from an engineering controls standpoint during the fabrication of tightly enclosed stainless steel components such as the inside of ship hulls and boiler vessels. One method of addressing this problem is to implement a chromium-free welding consumable that provides equivalent mechanical performance and corrosion characteristics to current stainless steel welding consumables. This project was aimed at developing such a consumable and evaluating its suitability for replacement of current stainless steel consumables such as E308L-16. A new shielded metal arc welding (SMAW) consumable based on the Ni-Cu-Ru system was developed for austenitic stainless steel welding. The focus of this work was evaluating the mechanical properties, weldability, and fume formation characteristics of the various iterations of consumables developed. Welds deposited on Type 304 stainless steel were evaluated with weldability tests including: mechanical testing, hot ductility testing, Strain-to-fracture testing, Transverse Varestraint testing, and button melting. Mechanical properties of weld deposits of each consumable were found to exceed minimum values of Type 304 stainless steel based on tensile testing. Guide bend testing showed that weld deposits met minimum weld ductility requirements for stainless steel consumables, such as E308-16. Hot ductility testing revealed a narrow crack susceptible region (33 to 54°C) indicating a low susceptibility to weld metal liquation cracking. GTA welds exhibited superior ductility when compared to SMA welds. This was attributed to a lack of slag inclusions in the weld deposit, which are effective weld strengtheners. Varestraint testing revealed that weld deposits have a higher solidification cracking susceptibility than stainless steel consumables used to join Type 304. Higher cracking susceptibility was attributed to austenitic solidification of the weld metal resulting in increased weld segregation and stabilization of a TiC eutectic reaction at the end of solidification. No solidification cracks were observed in actual weld deposits. Evaluation of weld microsegregation patterns showed higher dilutions of Type 304 increased segregation of Ti, promoting a TiC eutectic reaction at the end of solidification. Thermodynamic modeling techniques were used to describe the solidification the Ni-Cu weld deposits as a function of dilution with Type 304. Solidification cracking susceptibility was shown to increase with dilution during evaluation with the Cast Pin Tear Test indicating high dilution welds should be avoided to minimize solidification cracking during welding. The Strain-to-fracture test was used to examine DDC cracking susceptibility, and revealed that this alloy has a higher susceptibility to solid-state weld cracking than austenitic stainless alloys such as 304. Threshold strain levels necessary to initiate cracking in the weld deposits were in the range of 2 to 3%. These values are comparable to other Ni-base alloys with a moderate to high susceptibility to DDC. Fume generation rates (FGR) of the new consumable were measured and bulk fume phases were analyzed with X-ray diffraction. FGR values were found to be similar to current SMAW and flux cored arc welding consumables. No chromium bearing compounds were observed during X-ray diffraction measurements, and the bulk fume consisted primarily of halides and metallic-oxides. Fume generated by the new consumable was subjected to colorimetric testing showing hexavalent Cr content (0.02 wt-%) was reduced by two orders of magnitude compared to E308-16 (2.6 wt-%). The source of this hexavalent chromium was from evaporation of the base metal due to the welding heat source. The consumable developed in this study, having a nominal composition of Ni-7.5Cu-1Ru-0.5Al-0.5Ti-0.02C, met virtually all the design criteria that were initially established. Work performed by the Fontana Corrosion Center showed that the weld deposits met corrosion design criteria to prevent localized attack of the weld metal. Work performed in this study showed that mechanical properties were comparable to stainless steel consumables, and weld cracking susceptibility was comparable to Ni-base welding consumables. The consumable was also found to have good operability characteristics. (Abstract shortened by UMI.)

Thermal regulation in multiple-source arc welding involving material transformations

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

Doumanidis, C.C.

1995-06-01

This article addresses regulation of the thermal field generated during arc welding, as the cause of solidification, heat-affected zone and cooling rate related metallurgical transformations affecting the final microstructure and mechanical properties of various welded materials. This temperature field is described by a dynamic real-time process model, consisting of an analytical composite conduction expression for the solid region, and a lumped-state, double-stream circulation model in the weld pool, integrated with a Gaussian heat input and calibrated experimentally through butt joint GMAW tests on plain steel plates. This model serves as the basis of an in-process thermal control system employing feedbackmore » of part surface temperatures measured by infrared pyrometry; and real-time identification of the model parameters with a multivariable adaptive control strategy. Multiple heat inputs and continuous power distributions are implemented by a single time-multiplexed torch, scanning the weld surface to ensure independent, decoupled control of several thermal characteristics. Their regulation is experimentally obtained in longitudinal GTAW of stainless steel pipes, despite the presence of several geometrical, thermal and process condition disturbances of arc welding.« less

Hardness analysis of welded joints of austenitic and duplex stainless steels

NASA Astrophysics Data System (ADS)

Topolska, S.

2016-08-01

Stainless steels are widely used in the modern world. The continuous increase in the use of stainless steels is caused by getting greater requirements relating the corrosion resistance of all types of devices. The main property of these steels is the ability to overlap a passive layer of an oxide on their surface. This layer causes that they become resistant to oxidation. One of types of corrosion-resistant steels is ferritic-austenitic steel of the duplex type, which has good strength properties. It is easily formable and weldable as well as resistant to erosion and abrasive wear. It has a low susceptibility to stress-corrosion cracking, to stress corrosion, to intercrystalline one, to pitting one and to crevice one. For these reasons they are used, among others, in the construction of devices and facilities designed for chemicals transportation and for petroleum and natural gas extraction. The paper presents the results which shows that the particular specimens of the ][joint representing both heat affected zones (from the side of the 2205 steel and the 316L one) and the weld are characterized by higher hardness values than in the case of the same specimens for the 2Y joint. Probably this is caused by machining of edges of the sections of metal sheets before the welding process, which came to better mixing of native materials and the filler metal. After submerged arc welding the 2205 steel still retains the diphase, austenitic-ferritic structure and the 316L steel retains the austenitic structure with sparse bands of ferrite σ.

Silicic, high- to extremely high-grade ignimbrites and associated deposits from the Paraná Magmatic Province, southern Brazil

NASA Astrophysics Data System (ADS)

Luchetti, Ana Carolina F.; Nardy, Antonio J. R.; Madeira, José

2018-04-01

The Cretaceous trachydacites and dacites of Chapecó type (ATC) and dacites and rhyolites of Palmas type (ATP) make up 2.5% of the 800.000 km3 of volcanic pile in the Paraná Magmatic Province (PMP), emplaced at the onset of Gondwana breakup. Together they cover extensive areas in southern Brazil, overlapping volcanic sequences of tholeiitic basalts and andesites; occasional mafic units are also found within the silicic sequence. In the central region of the PMP silicic volcanism comprises porphyritic ATC-type, trachydacite high-grade ignimbrites (strongly welded) overlying aphyric ATP-type, rhyolite high- to extremely high-grade ignimbrites (strongly welded to lava-like). In the southwestern region strongly welded to lava-like high-grade ignimbrites overlie ATP lava domes, while in the southeast lava domes are found intercalated within the ignimbrite sequence. Characteristics of these ignimbrites are: widespread sheet-like deposits (tens to hundreds of km across); absence of basal breccias and basal fallout layers; ubiquitous horizontal to sub-horizontal sheet jointing; massive, structureless to horizontally banded-laminated rock bodies locally presenting flow folding; thoroughly homogeneous vitrophyres or with flow banding-lamination; phenocryst abundance presenting upward and lateral decrease; welded glass blobs in an 'eutaxitic'-like texture; negligible phenocryst breakage; vitroclastic texture locally preserved; scarcity of lithic fragments. These features, combined with high eruption temperatures (≥ 1000 °C), low water content (≤ 2%) and low viscosities (104-7 Pa s) suggest that the eruptions were characterized by low fountaining, little heat loss during collapse, and high mass fluxes producing extensive deposits.

Microstructure and Fatigue Properties of Laser Welded DP590 Dual-Phase Steel Joints

NASA Astrophysics Data System (ADS)

Xie, Chaojie; Yang, Shanglei; Liu, Haobo; Zhang, Qi; Cao, Yaming; Wang, Yuan

2017-08-01

In this paper, cold-rolled DP590 dual-phase steel sheets with 1.5 mm thickness were butt-welded by a fiber laser, and the evolution and effect on microhardness, tensile property and fatigue property of the welded joint microstructure were studied. The results showed that the base metal is composed of ferrite and martensite, with the martensite dispersed in the ferrite matrix in an island manner. The microstructure of the weld zone was lath-shaped martensite that can be refined further by increasing the welding speed, while the heat-affected zone was composed of ferrite and tempered martensite. The microhardness increased with increasing welding speed, and the hardness reached its highest value—393.8 HV—when the welding speed was 5 m/min. Static tensile fracture of the welded joints always occurred in the base metal, and the elongation at break was more than 16%. The conditional fatigue limits of the base metal and the weld joints were 354.2 and 233.6 MPa, respectively, under tension-tension fatigue tests with a stress rate of 0.1. After observation of the fatigue fracture morphology, it was evident that the fatigue crack of the base metal had sprouted into the surface pits and that its expansion would be accelerated under the action of a secondary crack. The fatigue source of the welded joint was generated in the weld zone and expanded along the martensite, forming a large number of fatigue striations. Transient breaking, which occurred in the heat-affected zone of the joint as a result of the formation of a large number of dimples, reflected the obvious characteristics of ductile fracture.

Charpy V-notch properties and microstructures of narrow gap ferritic welds of a quenched and tempered steel plate

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

Powell, G.L.F.; Herfurth, G.

1998-11-01

Multipass welds of quenched and tempered 50-mm-thick steel plate have been deposited by a single wire narrow gap process using both gas metal arc welding (GMAW) and submerged arc welding (SAW). Of the five welds, two reported much lower Charpy V-notch (CVN) values when tested at {minus} 20 C. The CVN toughness did not correlate with either the welding process or whether the power source was pulsed or nonpulsed. The only difference in the ferritic microstructure between the two welds of low Charpy values and the three of high values was the percentage of acicular ferrite. There was no effectmore » of the percentage of as-deposited reheated zones intersected by the Charpy notch or the microhardness of the intercellular-dendritic regions. In all welds, austenite was the microconstituent between the ferrite laths. The percentage of acicular ferrite correlated with the presence of MnO, TiO{sub 2}, {gamma} Al{sub 2}O{sub 3}, or MnO. Al{sub 2}O{sub 3} as the predominant crystalline compound in the oxide inclusions. In turn, the crystalline compound depended on the aluminum-to-titanium ratio in both the weld deposits and the oxide inclusions. In addition to the presence of less acicular ferrite, the two welds that showed lower Charpy values also reported more oxide inclusions greater than 1 {micro}m in diameter. The combination of more oxide inclusions greater than 1 {micro}m and less acicular ferrite is considered to be the explanation for the lower Charpy values.« less

The use of conduction model in laser weld profile computation

NASA Astrophysics Data System (ADS)

Grabas, Bogusław

2007-02-01

Profiles of joints resulting from deep penetration laser beam welding of a flat workpiece of carbon steel were computed. A semi-analytical conduction model solved with Green's function method was used in computations. In the model, the moving heat source was attenuated exponentially in accordance with Beer-Lambert law. Computational results were compared with those in the experiment.

Illusion induced overlapped optics.

PubMed

Zang, XiaoFei; Shi, Cheng; Li, Zhou; Chen, Lin; Cai, Bin; Zhu, YiMing; Zhu, HaiBin

2014-01-13

The traditional transformation-based cloak seems like it can only hide objects by bending the incident electromagnetic waves around the hidden region. In this paper, we prove that invisible cloaks can be applied to realize the overlapped optics. No matter how many in-phase point sources are located in the hidden region, all of them can overlap each other (this can be considered as illusion effect), leading to the perfect optical interference effect. In addition, a singular parameter-independent cloak is also designed to obtain quasi-overlapped optics. Even more amazing of overlapped optics is that if N identical separated in-phase point sources covered with the illusion media, the total power outside the transformation region is N2I0 (not NI0) (I0 is the power of just one point source, and N is the number point sources), which seems violating the law of conservation of energy. A theoretical model based on interference effect is proposed to interpret the total power of these two kinds of overlapped optics effects. Our investigation may have wide applications in high power coherent laser beams, and multiple laser diodes, and so on.

Heat sink effects in variable polarity plasma arc welding

NASA Technical Reports Server (NTRS)

Abdelmessih, Amanie N.

1991-01-01

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

Statistical modeling to determine sources of variability in exposures to welding fumes.

PubMed

Liu, Sa; Hammond, S Katharine; Rappaport, Stephen M

2011-04-01

Exposures to total particulate matter (TP) and manganese (Mn) received by workers during welding and allied hot processes were analyzed to assess the sources and magnitudes of variability. Compilation of data from several countries identified 2065 TP and 697 Mn measurements for analysis. Linear mixed models were used to determine fixed effects due to different countries, industries and trades, process characteristics, and the sampling regimen, and to estimate components of variance within workers (both intraday and interday), between workers (within worksites), and across worksites. The fixed effects explained 55 and 49% of variation in TP and Mn exposures, respectively. The country, industry/trade, type of ventilation, and type of work/welding process were the major factors affecting exposures to both agents. Measurements in the USA were generally higher than those in other countries. Exposure to TP was 67% higher in enclosed spaces and 43% lower with local exhaust ventilation (LEV), was higher among boilermakers and was higher when either a mild-steel base metal or a flux cored consumable was used. Exposure to Mn was 750% higher in enclosed spaces and 67% lower when LEV was present. Air concentrations of Mn were significantly affected by the welding consumables but not by the base metal. Resistance welding produced significantly lower TP and Mn exposures compared to other welding processes. Interestingly, exposures to TP had not changed over the 40 years of observation, while those of Mn showed (non-significant) reductions of 3.6% year(-1). After controlling for fixed effects, variance components between worksites and between-individual workers within a worksite were reduced by 89 and 57% for TP and 75 and 63% for Mn, respectively. The within-worker variation (sum of intraday and interday variance components) of Mn exposure was three times higher than that of TP exposure. The estimated probabilities of exceeding occupational exposure limits were very high (generally much >10%) for both agents. Welding exposures to TP and Mn vary considerably across the world and across occupational groups. Exposures to both contaminants have been and continue to be unacceptably high in most sectors of industry. Because exposures to the two agents have different sources and characteristics, separate control strategies should be considered to reduce welders' exposures to TP and Mn.

Physical and Theoretical Models of Heat Pollution Applied to Cramped Conditions Welding Taking into Account the Different Types of Heat

NASA Astrophysics Data System (ADS)

Bulygin, Y. I.; Koronchik, D. A.; Legkonogikh, A. N.; Zharkova, M. G.; Azimova, N. N.

2017-05-01

The standard k-epsilon turbulence model, adapted for welding workshops, equipped with fixed workstations with sources of pollution took into account only the convective component of heat transfer, which is quite reasonable for large-volume rooms (with low density distribution of sources of pollution) especially the results of model calculations taking into account only the convective component correlated well with experimental data. For the purposes of this study, when we are dealing with a small confined space where necessary to take account of the body heated to a high temperature (for welding), located next to each other as additional sources of heat, it can no longer be neglected radiative heat exchange. In the task - to experimentally investigate the various types of heat transfer in a limited closed space for welding and behavior of a mathematical model, describing the contribution of the various components of the heat exchange, including radiation, influencing the formation of fields of concentration, temperature, air movement and thermal stress in the test environment. Conducted field experiments to model cubic body, allowing you to configure and debug the model of heat and mass transfer processes with the help of the developed approaches, comparing the measurement results of air flow velocity and temperature with the calculated data showed qualitative and quantitative agreement between process parameters, that is an indicator of the adequacy of heat and mass transfer model.

Electron Beam Welding of Duplex Steels with using Heat Treatment

NASA Astrophysics Data System (ADS)

Schwarz, Ladislav; Vrtochová, Tatiana; Ulrich, Koloman

2010-01-01

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

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.

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

PubMed

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

2014-11-01

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

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

NASA Astrophysics Data System (ADS)

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

2011-01-01

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

Effects of beam configurations on wire melting and transfer behaviors in dual beam laser welding with filler wire

NASA Astrophysics Data System (ADS)

Ma, Guolong; Li, Liqun; Chen, Yanbin

2017-06-01

Butt joints of 2 mm thick stainless steel with 0.5 mm gap were fabricated by dual beam laser welding with filler wire technique. The wire melting and transfer behaviors with different beam configurations were investigated detailedly in a stable liquid bridge mode and an unstable droplet mode. A high speed video system assisted by a high pulse diode laser as an illumination source was utilized to record the process in real time. The difference of welding stability between single and dual beam laser welding with filler wire was also compartively studied. In liquid bridge transfer mode, the results indicated that the transfer process and welding stability were disturbed in the form of "broken-reformed" liquid bridge in tandem configuration, while improved by stabilizing the molten pool dynamics with a proper fluid pattern in side-by-side configuration, compared to sigle beam laser welding with filler wire. The droplet transfer period and critical radius were studied in droplet transfer mode. The transfer stability of side-by-side configuration with the minium transfer period and critical droplet size was better than the other two configurations. This was attributed to that the action direction and good stability of the resultant force which were beneficial to transfer process in this case. The side-by-side configuration showed obvious superiority on improving welding stability in both transfer modes. An acceptable weld bead was successfully generated even in undesirable droplet transfer mode under the present conditions.

Modelling of Strains During SAW Surfacing Taking into Heat of the Weld in Temperature Field Description and Phase Transformations

NASA Astrophysics Data System (ADS)

Winczek, J.; Makles, K.; Gucwa, M.; Gnatowska, R.; Hatala, M.

2017-08-01

In the paper, the model of the thermal and structural strain calculation in a steel element during single-pass SAW surfacing is presented. The temperature field is described analytically assuming a bimodal volumetric model of heat source and a semi-infinite body model of the surfaced (rebuilt) workpiece. The electric arc is treated physically as one heat source. Part of the heat is transferred by the direct impact of the electric arc, while another part of the heat is transferred to the weld by the melted material of the electrode. Kinetics of phase transformations during heating is limited by temperature values at the beginning and at the end of austenitic transformation, while the progress of phase transformations during cooling is determined on the basis of TTT-welding diagramand JMA-K law for diffusive transformations, and K-M law for martensitic transformation. Totalstrains equal to the sum ofthermaland structuralstrainsinduced by phasetransformationsin weldingcycle.

High-bandwidth continuous-flow arc furnace

DOEpatents

Hardt, David E.; Lee, Steven G.

1996-01-01

A high-bandwidth continuous-flow arc furnace for stream welding applications includes a metal mass contained in a crucible having an orifice. A power source charges an electrode for generating an arc between the electrode and the mass. The arc heats the metal mass to a molten state. A pressurized gas source propels the molten metal mass through the crucible orifice in a continuous stream. As the metal is ejected, a metal feeder replenishes the molten metal bath. A control system regulates the electrode current, shielding gas pressure, and metal source to provide a continuous flow of molten metal at the crucible orifice. Independent control over the electrode current and shield gas pressure decouples the metal flow temperature and the molten metal flow rate, improving control over resultant weld characteristics.

High-bandwidth continuous-flow arc furnace

DOEpatents

Hardt, D.E.; Lee, S.G.

1996-08-06

A high-bandwidth continuous-flow arc furnace for stream welding applications includes a metal mass contained in a crucible having an orifice. A power source charges an electrode for generating an arc between the electrode and the mass. The arc heats the metal mass to a molten state. A pressurized gas source propels the molten metal mass through the crucible orifice in a continuous stream. As the metal is ejected, a metal feeder replenishes the molten metal bath. A control system regulates the electrode current, shielding gas pressure, and metal source to provide a continuous flow of molten metal at the crucible orifice. Independent control over the electrode current and shield gas pressure decouples the metal flow temperature and the molten metal flow rate, improving control over resultant weld characteristics. 4 figs.

Laser transmission welding of polylactide to aluminium thin films for applications in the food-packaging industry

NASA Astrophysics Data System (ADS)

Pagano, Nunziante; Campana, Giampaolo; Fiorini, Maurizio; Morelli, Raffaele

2017-06-01

Laser transmission welding is a suitable technology to join thin films of similar or dissimilar materials without any addition of chemical solvents or adhesives. This process represents a very important opportunity in the case of packaging applications (for example in food and pharmaceutical sectors) where the realisation of strong welds by avoiding the contact between the thermal source and the processed materials and, furthermore, without using any third material that could contaminate the contents, is reliable and relevant. The aim of this paper is to prove the feasibility of the laser transmission welding of polylactide to aluminium thin films by means of laser transmission welding through the use of a low power pulsed wave fibre laser. Laser joint samples were realised, analysed by optical microscopy to reveal possible defects and to evaluate the weld width and tested to measure the mechanical tensile strength. An accurate relationship between the joint quality and both the welding speed and the k-factor, which represents the delivered energy per unit length and affects the bonding mechanism at the interface, was determined. The achieved feasibility area is extremely narrow and possible only for the higher value of the average power. The joint tensile strength was proven to be in a proportional relationship with the effective bonded area and reached satisfactory values.

High power x-ray welding of metal-matrix composites

DOEpatents

Rosenberg, Richard A.; Goeppner, George A.; Noonan, John R.; Farrell, William J.; Ma, Qing

1999-01-01

A method for joining metal-matrix composites (MMCs) by using high power x-rays as a volumetric heat source is provided. The method involves directing an x-ray to the weld line between two adjacent MMCs materials to create an irradiated region or melt zone. The x-rays have a power density greater than about 10.sup.4 watts/cm.sup.2 and provide the volumetric heat required to join the MMC materials. Importantly, the reinforcing material of the metal-matrix composites remains uniformly distributed in the melt zone, and the strength of the MMCs are not diminished. In an alternate embodiment, high power x-rays are used to provide the volumetric heat required to weld metal elements, including metal elements comprised of metal alloys. In an alternate embodiment, high power x-rays are used to provide the volumetric heat required to weld metal elements, including metal elements comprised of metal alloys.

Laser based spot weld characterization

NASA Astrophysics Data System (ADS)

Jonietz, Florian; Myrach, Philipp; Rethmeier, Michael; Suwala, Hubert; Ziegler, Mathias

2016-02-01

Spot welding is one of the most important joining technologies, especially in the automotive industry. Hitherto, the quality of spot welded joints is tested mainly by random destructive tests. A nondestructive testing technique offers the benefit of cost reduction of the testing procedure and optimization of the fabrication process, because every joint could be examined. This would lead to a reduced number of spot welded joints, as redundancies could be avoided. In the procedure described here, the spot welded joint between two zinc-coated steel sheets (HX340LAD+Z100MB or HC340LA+ZE 50/50) is heated optically on one side. Laser radiation and flash light are used as heat sources. The melted zone, the so called "weld nugget" provides the mechanical stability of the connection, but also constitutes a thermal bridge between the sheets. Due to the better thermal contact, the spot welded joint reveals a thermal behavior different from the surrounding material, where the heat transfer between the two sheets is much lower. The difference in the transient thermal behavior is measured with time resolved thermography. Hence, the size of the thermal contact between the two sheets is determined, which is directly correlated to the size of the weld nugget, indicating the quality of the spot weld. The method performs well in transmission with laser radiation and flash light. With laser radiation, it works even in reflection geometry, thus offering the possibility of testing with just one-sided accessibility. By using heating with collimated laser radiation, not only contact-free, but also remote testing is feasible. A further convenience compared to similar thermographic approaches is the applicability on bare steel sheets without any optical coating for emissivity correction. For this purpose, a proper way of emissivity correction was established.

Vacuum chamber translation/positioning mechanism and welding power supply controller

NASA Technical Reports Server (NTRS)

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

1992-01-01

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

M551 metals melting experiment. [space manufacturing of aluminum alloys, tantalum alloys, stainless steels

NASA Technical Reports Server (NTRS)

Li, C. H.; Busch, G.; Creter, C.

1976-01-01

The Metals Melting Skylab Experiment consisted of selectively melting, in sequence, three rotating discs made of aluminum alloy, stainless steel, and tantalum alloy. For comparison, three other discs of the same three materials were similarly melted or welded on the ground. The power source of the melting was an electron beam unit. Results are presented which support the concept that the major difference between ground base and Skylab samples (i.e., large elongated grains in ground base samples versus nearly equiaxed and equal sized grains in Skylab samples) can be explained on the basis of constitutional supercooling, and not on the basis of surface phenomena. Microstructural observations on the weld samples and present explanations for some of these observations are examined. In particular, ripples and their implications to weld solidification were studied. Evidence of pronounced copper segregation in the Skylab A1 weld samples, and the tantalum samples studied, indicates a weld microhardness (and hence strength) that is uniformly higher than the ground base results, which is in agreement with previous predictions. Photographs are shown of the microstructure of the various alloys.

Space processing applications of ion beam technology. [surface finishing, welding, milling and film deposition

NASA Technical Reports Server (NTRS)

Grodzka, P. G.

1977-01-01

Ion thruster engines for spacecraft propulsion can serve as ion beam sources for potential space processing applications. The advantages of space vacuum environments and the possible gravity effects on thruster ion beam materials operations such as thin film growth, ion milling, and surface texturing were investigated. The direct gravity effect on sputter deposition and vapor deposition processes are discussed as well as techniques for cold and warm welding.

Contributions to study of the stability of the electric welding arc under the action of acoustic pressure

NASA Technical Reports Server (NTRS)

Petru, S.

1974-01-01

During the treatment of an electric welding arc with ultrasonic oscillations, an improvement was found in overall source-arc stability. Theoretical explanations are provided for this phenomenon and formulas of equivalence between the classical arc and the treated arc are derived, taking stability as their criterion. A knowledge of this phenomenon can be useful in extending the applications of ultrasounds to different forms of electric arcs.

A Comparison Between Mechanical And Electrochemical Tests on Ti6Al4V Welded By LBW

NASA Astrophysics Data System (ADS)

Serroni, G.; Bitondo, C.; Astarita, A.; Scala, A.; Gloria, A.; Prisco, U.; Squillace, A.; Bellucci, F.

2011-05-01

Titanium and its alloys are nowadays widely used in many sectors: in the medical field (orthopedic and dental ones), in the architectural field, in the chemical plants field and in aeronautic. In this last field it is more and more used both for its contribution to make lightweight and time durable structures and for its compatibility with new materials, first of all Carbon Fiber Reinforced Plastics (CFRP). To this aim, lots of researches are now focusing on new and emerging technologies capable to make titanium objects and, at the same time, reducing the scrap, since titanium alloys for aeronautic application are very expensive. This paper examines Grade 5 Titanium Alloy (Ti6Al4V) welded by Laser Beam (LBW) in butt-joint configuration. The source was Nd:YAG laser, moreover two inert gases were used, in order to provide a shield both on the top and on the bottom of the weld bead. The joints were studied by varying two process parameters: welding speed and power of the laser beam. It was not possible to realize a full experimental plan, due to technological limits in making titanium laser beam welds. The joints were tested to measure their mechanical properties and the corrosion resistance. The process parameters do not significantly affect the maximum static strength of the joints. Microscopic analysis showed that welds made with high power and low welding speed have a uniform weld bead, and no macroscopic defect occurs. Fatigue test results, instead, show a marked influence of the morphology of the weld bead: the occurrence of some defects, such as the undercut, both on the top and on the bottom of the weld bead, dramatically reduced fatigue resistance of the joints. Corrosion resistance was studied using the electrochemical micro cell technique, which allows to distinguish electrochemical properties of each zone of the weld bead, even when, as in this case, they are very narrow. By a general point of view, it has been demonstrated that the joints showing the best mechanical performances also possess better electrochemical properties. What's more, in these cases, the weld bead shows a cathodic behavior with respect to the parent material.

Acoustic Emission Weld Monitoring in the 2195 Aluminum-Lithium Alloy

NASA Technical Reports Server (NTRS)

Walker, James L.

2005-01-01

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

Electromagnetic characteristic of twin-wire indirect arc welding

NASA Astrophysics Data System (ADS)

Shi, Chuanwei; Zou, Yong; Zou, Zengda; Wu, Dongting

2015-01-01

Traditional welding methods are limited in low heat input to workpiece and high welding wire melting rate. Twin-wire indirect arc(TWIA) welding is a new welding method characterized by high melting rate and low heat input. This method uses two wires: one connected to the negative electrode and another to the positive electrode of a direct-current(DC) power source. The workpiece is an independent, non-connected unit. A three dimensional finite element model of TWIA is devised. Electric and magnetic fields are calculated and their influence upon TWIA behavior and the welding process is discussed. The results show that with a 100 A welding current, the maximum temperature reached is 17 758 K, arc voltage is 14.646 V while maximum current density was 61 A/mm2 with a maximum Lorene force of 84.5 μN. The above mentioned arc parameters near the cathode and anode regions are far higher than those in the arc column region. The Lorene force is the key reason for plasma velocity direction deviated and charged particles flowed in the channel formed by the cathode, anode and upper part of arc column regions. This led to most of the energy being supplied to the polar and upper part of arc column regions. The interaction between electric and magnetic fields is a major determinant in shaping TWIA as well as heat input on the workpiece. This is a first study of electromagnetic characteristics and their influences in the TWIA welding process, and it is significant in both a theoretical and practical sense.

Human biomonitoring of aluminium after a single, controlled manual metal arc inert gas welding process of an aluminium-containing worksheet in nonwelders.

PubMed

Bertram, Jens; Brand, Peter; Hartmann, Laura; Schettgen, Thomas; Kossack, Veronika; Lenz, Klaus; Purrio, Ellwyn; Reisgen, Uwe; Kraus, Thomas

2015-10-01

Several existing field studies evaluate aluminium welding works but no thoroughly controlled exposure scenario for welding fume has been described yet. This study provides information about the uptake and elimination of aluminium from welding fumes under controlled conditions. In the Aachen Workplace Simulation Laboratory, we are able to generate welding fumes of a defined particle mass concentration. We exposed 12, until then occupationally unexposed participants with aluminium-containing welding fumes of a metal inert gas (MIG) welding process of a total dust mass concentration of 2.5 mg/m(3) for 6 h. Room air filter samples were collected, and the aluminium concentration in air derived. Urine and plasma samples were collected directly before and after the 6-h lasting exposure, as well as after 1 and 7 days. Human biomonitoring methods were used to determine the aluminium content of the samples with high-resolution continuum source atomic absorption spectrometry. Urinary aluminium concentrations showed significant changes after exposure compared to preexposure levels (mean t(1) (0 h) 13.5 µg/L; mean t(2) (6 h) 23.5 µg/L). Plasma results showed the same pattern but pre-post comparison did not reach significance. We were able to detect a significant increase of the internal aluminium burden of a single MIG aluminium welding process in urine, while plasma failed significance. Biphasic elimination kinetic can be observed. The German BAT of 60 µg/g creatinine was not exceeded, and urinary aluminium returned nearly to baseline concentrations after 7 days.

Study of issues in difficult-to-weld thick materials by hybrid laser arc welding

NASA Astrophysics Data System (ADS)

Mazar Atabaki, Mehdi

There is a high interest for the high strength-to-weight ratio with good ductility for the welds of advanced alloys. The concern about the welding of thick materials (Advanced high strength steels (AHSS) and 5xxx and 6xxx series of aluminum alloys) has stimulated the development of manufacturing processes to overcome the associated issues. The need to weld the dissimilar materials (AHSS and aluminum alloys) is also required for some specific applications in different industries. Hence, the requirement in the development of a state-of-the-art welding procedure can be helpful to fulfill the constraints. Among the welding methods hybrid laser/arc welding (HLAW) has shown to be an effective method to join thick and difficult-to-weld materials. This process benefits from both advantages of the gas metal arc welding (GMAW) and laser welding processes. The interaction of the arc and laser can help to have enough penetration of weld in thick plates. However, as the welding of dissimilar aluminum alloys and steels is very difficult because of the formation of brittle intermetallics the present work proposed a procedure to effectively join the alloys. The reports showed that the explosively welded aluminum alloys to steels have the highest toughness, and that could be used as an "insert" (TRICLAD) for welding the thick plates of AHSS to aluminum alloys. Therefore, the HLAW of the TRICLAD-Flange side (Aluminum alloy (AA 5456)) to the Web side (Aluminum alloys (AA 6061 and AA 5456)) and the TRICLAD-Flange side (ASTM A516) to the Web side (AHSS) was studied in the present work. However, there are many issues related to HLAW of the dissimilar steels as well as dissimilar aluminum alloys that have to be resolved in order to obtain sound welds. To address the challenges, the most recent welding methods for joining aluminum alloys to steels were studied and the microstructural development, mechanical properties, and on-line monitoring of the welding processes were discussed as well. The heat and mass transfer and the issues in joining of dissimilar alloys by the hybrid laser/arc welding process (HLAW) were explicitly explained in details. A finite element model was developed to simulate the heat transfer in HLAW of the aluminum alloys. Two double-ellipsoidal heat source models were considered to describe the heat input of the gas metal arc welding and laser welding processes. An experimental procedure was also developed for joining thick advanced high strength steel plates by using the HLAW, by taking into consideration different butt joint configurations. The geometry of the weld groove was optimized according to the requirements of ballistic test, where the length of the softened heat affected zone should be less than 15.9 mm measured from the weld centerline. Since the main issue in HLAW of the AHSS was the formation of the pores, the possible mechanisms of the pores formation and their mitigation methods during the welding process were investigated. Mitigation methods were proposed to reduce the pores inside in the weld area and the influence of each method on the process stability was investigated by an on-line monitoring system of the HLAW process. The groove angle was optimized for the welding process based on the allowed amount of heat input along the TRICLADRTM interface generated by an explosive welding. The weld was fractured in the heat affected zone of the aluminum side in the tensile test. The microharness was shown that the temperature variation caused minor softening in the heat affected zone satisfying the requirement that the width of the softened heat affected zone in the steel side falls within 15.9 mm far away from the weld centerline. The microstructure analysis showed the presence of tempered martensite at the vicinity of the weld area, which it was a cause of softening in the heat affected zone.

Prediction and Measurement of X-Ray Spectral and Intensity Distributions from Low Energy Electron Impact Sources

NASA Technical Reports Server (NTRS)

Edwards, David L.

1999-01-01

In-vacuum electron beam welding is a technology that NASA considered as a joining technique for manufacture of space structures. The interaction of energetic electrons with metal produces x-rays. The radiation exposure to astronauts performing the in-vacuum electron beam welding must be characterized and minimized to insure safe operating conditions. This investigation characterized the x-ray environment due to operation of an in-vacuum electron beam welding tool. NASA, in a joint venture with the Russian Space Agency, was scheduled to perform a series of welding in space experiments on board the United States Space Shuttle. This series of experiments was named the International Space Welding Experiment (ISWE). The hardware associated with the ISWE was leased to NASA, by the Paton Welding Institute (PWI) in Ukraine, for ground based welding experiments in preparation for flight. Two tests were scheduled, using the ISWE electron beam welding tool, to characterize the radiation exposure to an astronaut during the operation of the ISWE. These radiation exposure tests consisted of Thermoluminescence Dosimeters (TLD's) shielded with material currently used by astronauts during Extra Vehicular Activities (EVA) and exposed to x-ray radiation generated by operation of an in-vacuum electron beam welding tool. This investigation was the first known application of TLD's to measure absorbed dose from x-rays of energy less than 10 KeV. The ISWE hardware was returned to Ukraine before the issue of adequate shielding for the astronauts was verified. Therefore, alternate experimental and analytical methods were developed to measure and predict the x-ray spectral and intensity distribution generated by electron impact with metal. These x-ray spectra were used to calculate the absorbed radiation dose to astronauts. These absorbed dose values were compared to TLD measurements obtained during actual operation of the in-vacuum electron beam welding tool. The calculated absorbed dose values were found to be in good agreement with the TLD values.

Investigation and development of friction stir welding process for unreinforced polyphenylene sulfide and reinforced polyetheretherketone

NASA Astrophysics Data System (ADS)

Ahmed, Hossain

The joining of thermoplastics through welding, a specific form of fusion bonding, offers numerous advantages over mechanical joining. It eliminates the use of costly fasteners and has only a limited effect on the strength of the parts being joined since it does not require the introduction of holes and loading pins, and it does not create significant stress concentrations. A specific form of welding, Friction Stir Welding, was investigated for the creation of butt joints of unreinforced polyphenylene sulfide (PPS) and short carbon fiber reinforced polyetheretherketone (PEEK) plates. Friction stir welding requires a rotating pin, a shoulder arrangement, relative movement between the tool and the weld piece and a clamping mechanism to hold the weld piece in place. Analytical models and experimental results show that the heat generated by the FSW tool is insufficient to produce the heat required to weld thermoplastic materials which makes FSW of polymers different from FSW of metals. A second heat source is required for preheating the thermoplastic parts prior to welding. A resistance type surface heater was placed at the bottom of two identical weld pieces for the experiments. Two types of shoulder design i.e. a rotating shoulder and a stationary shoulder were developed. Taguchi's Design of Experiment method was utilized to investigate the welding process, where duration of heating, process temperature, tool rotational speed and tool traverse speed were used as the welding parameters. The quality of the welding process was assumed to be indicated by the weld strength. DoE revealed that one of the process parameters, tool traverse speed, had significant influence on the tensile strength of PPS samples. While PPS sample showed relatively lower tensile strength with higher traverse speed, short carbon fiber reinforced PEEK samples had higher tensile strength with higher traverse speeds. In addition to tensile tests on dog bone shaped specimen, fracture toughness tests were performed for both PPS and PEEK samples to identify the fracture toughness of these materials. Presence of un-welded section in the welded specimen due to the setup of the experiments yielded notched tensile strengths during the tensile test process. With the help of fracture toughness values of these materials, notched tensile strengths of the welded samples were compared with the notched tensile strengths or residual tensile strengths of the base materials. In this study, residual joint efficiency of PEEK samples was found higher than that of PPS samples. Additionally, notched tensile strengths of the welded samples were compared with un-notched tensile strengths of the materials. The notched tensile strengths of PPS and PEEK were found about 80% and 75% of the respective base materials. Micrographs of PEEK samples showed the presence of more voids and cracks in the weld line compared to the un-welded samples. In this study, continuous friction stir welding process has been developed for butt joining of unreinforced PPS and short carbon fiber reinforced PEEK. The process parameters and the experimental setup can be utilized to investigate the weldability of different types of thermoplastic composites and various types of joint configurations.

Carbon monoxide poisoning--Weld County, Colorado, 1993.

PubMed

1994-10-28

In March 1993, the Colorado Department of Public Health and Environment (CDPHE) was notified that six family members residing in a home in Weld County had suffered carbon monoxide (CO) poisoning; five of the persons died. An investigation indicated that the source of CO had been a van parked in the garage of the home; the van had been left running, and the exhaust fumes leaked into the home. This report summarizes the investigation of this incident.

An Overview of Ni Base Additive Fabrication Technologies for Aerospace Applications (Preprint)

DTIC Science & Technology

2011-03-01

fusion welding processes that have the ability to add filler material can be used as additive manufacturing processes . The majority of the work in the...Laser Additive Manufacturing (LAM) The LAM process uses a conventional laser welding heat source (CO2 or solid state laser) combined with a...wrought properties. The LAM process typically has a lower deposition rate (0.5 – 10 lbs/hr) compared to EB, PTA or TIG based processes , although as

Analytical Modeling of Weld Bead Shape in Dry Hyperbaric GMAW Using Ar-He Chamber Gas Mixtures

NASA Astrophysics Data System (ADS)

Azar, Amin S.; Ås, Sigmund K.; Akselsen, Odd M.

2013-03-01

Hyperbaric arc welding is a special application of joining the pipeline steels under seawater. In order to analyze the behavior of the arc under ambient pressure, a model is required to estimate the arc efficiency. A distributed point heat source model was employed. The simulated isotherms were calibrated iteratively to fit the actual bead cross section. Basic gas mixture rules and models were used to calculate the thermal properties of the low-temperature shielding gas under the ambient pressure of 10 bar. Nine bead-on-plate welds were deposited each of which under different Ar-He chamber gas compositions. The well-known correlation between arc efficiency (delivered heat) and the thermal conductivity was established for different gas mixtures. The arc efficiency was considered separately for the transverse and perpendicular heat sources. It was found that assigning single heat efficiency factor for the entire arc, which is usually below unity, causes a noticeable underestimation for the heat transfer in the perpendicular direction and a little overestimation in the transverse direction.

Artificial Optical Radiation photobiological hazards in arc welding.

PubMed

Gourzoulidis, G A; Achtipis, A; Topalis, F V; Kazasidis, M E; Pantelis, D; Markoulis, A; Kappas, C; Bourousis, C A

2016-08-01

Occupational Health and Safety (OHS) is associated with crucial social, economic, cultural and technical issues. A highly specialized OHS sector deals with the photobiological hazards from artificial optical radiation (AOR), which is divided into visible light, UV and IR emitted during various activities and which is legally covered by European Directive 2006/25/EC. Among the enormous amount of sources emitting AOR, the most important non-coherent ones to consider for health effects to the whole optical range, are arcs created during metal welding. This survey presents the effort to assess the complicated exposure limits of the Directive in the controlled environment of a welding laboratory. Sensors covering the UV and blue light range were set to measure typical welding procedures reproduced in the laboratory. Initial results, apart from apparently justifying the use of Personal Protective Equipment (PPE) due to even subsecond overexposures measured, also set the basis to evaluate PPE's properties and support an integrated risk assessment of the complex welding environment. These results can also improve workers' and employer's information and training about radiation hazards, which is a crucial OHS demand. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

GTA weld penetration and the effects of deviations in machine variables

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

Giedt, W.H.

1987-07-01

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

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

NASA Astrophysics Data System (ADS)

Hemmer, H.; Grong, Ø.; Klokkehaug, S.

2000-03-01

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

State-of-the-art survey of joinability of materials for OTEC heat exchangers

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

Beaver, R. J.

1978-12-01

Literature and industrial sources were surveyed to assess, on the basis of apparent economics and reliability, the joinability of both shell-and-tube and compact ocean thermal energy conversion (OTEC) heat exchangers. A no-leak requirement is mandatory to prevent mixing seawater and the ammonia working fluid. The operating temperature range considered is 7 to 28/sup 0/C (45 to 82/sup 0/F). Materials evaluated were aluminum, titanium, copper--nickel, AL-6X austenitic stainless steel, singly and in combination with steel and concrete. Many types of welding and brazing processes, roller expansion, magnaforming, O-ring sealing, and adhesive bonding were considered. The automatic gas tungsten-arc welding process andmore » explosion welding processes are the only two joining processes that now appear to offer the high reliability required of no-leak shell-and-tube heat exchangers. Of these two processes, the gas tungsten-arc welding process appears to be the more economically attractive.« less

Welding/sealing glass-enclosed space in a vacuum

DOEpatents

Tracy, C.E.; Benson, D.K.

1996-02-06

A method of welding and sealing the edges of two juxtaposed glass sheets together to seal a vacuum space between the sheets comprises the steps of positioning a radiation absorbent material, such as FeO, VO{sub 2}, or NiO, between the radiation transmissive glass sheets adjacent the edges and then irradiating the absorbent material, preferably with a laser beam, through at least one of the glass sheets. Heat produced by the absorbed radiation in the absorbent material melts glass in the portions of both glass sheets that are adjacent the absorbent material, and the melted glass from both sheets flows together to create the weld when the melted glass cools and hardens. The absorbent material can be dissolved and diffused into the melted glass to the extent that it no longer absorbs enough energy to keep the glass melted, thus, with appropriate proportioning of absorbent material to source energy power and welding heat needed, the process can be made self-stopping. 8 figs.

Welding/sealing glass-enclosed space in a vacuum

DOEpatents

Tracy, C. Edwin; Benson, David K.

1996-01-01

A method of welding and sealing the edges of two juxtaposed glass sheets together to seal a vacuum space between the sheets comprises the steps of positioning a radiation absorbant material, such as FeO, VO.sub.2, or NiO, between the radiation transmissive glass sheets adjacent the edges and then irradiating the absorbant material, preferably with a laser beam, through at least one of the glass sheets. Heat produced by the absorbed radiation in the absorbant material melts glass in the portions of both glass sheets that are adjacent the absorbant material, and the melted glass from both sheets flows together to create the weld when the melted glass cools and hardens. The absorbant material can be dissolved and diffused into the melted glass to the extent that it no longer absorbs enough energy to keep the glass melted, thus, with appropriate proportioning of absorbant material to source energy power and welding heat needed, the process can be made self-stopping.

Method for laser spot welding monitoring

NASA Astrophysics Data System (ADS)

Manassero, Giorgio

1994-09-01

As more powerful solid state laser sources appear on the market, new applications become technically possible and important from the economical point of view. For every process a preliminary optimization phase is necessary. The main parameters, used for a welding application by a high power Nd-YAG laser, are: pulse energy, pulse width, repetition rate and process duration or speed. In this paper an experimental methodology, for the development of an electrooptical laser spot welding monitoring system, is presented. The electromagnetic emission from the molten pool was observed and measured with appropriate sensors. The statistical method `Parameter Design' was used to obtain an accurate analysis of the process parameter that influence process results. A laser station with a solid state laser coupled to an optical fiber (1 mm in diameter) was utilized for the welding tests. The main material used for the experimental plan was zinc coated steel sheet 0.8 mm thick. This material and the related spot welding technique are extensively used in the automotive industry, therefore, the introduction of laser technology in production line will improve the quality of the final product. A correlation, between sensor signals and `through or not through' welds, was assessed. The investigation has furthermore shown the necessity, for the modern laser production systems, to use multisensor heads for process monitoring or control with more advanced signal elaboration procedures.

Comparative study of pulsed Nd:YAG laser welding of AISI 304 and AISI 316 stainless steels

NASA Astrophysics Data System (ADS)

Kumar, Nikhil; Mukherjee, Manidipto; Bandyopadhyay, Asish

2017-02-01

Laser welding is a potentially useful technique for joining two pieces of similar or dissimilar materials with high precision. In the present work, comparative studies on laser welding of similar metal of AISI 304SS and AISI 316SS have been conducted forming butt joints. A robotic control 600 W pulsed Nd:YAG laser source has been used for welding purpose. The effects of laser power, scanning speed and pulse width on the ultimate tensile strength and weld width have been investigated using the empirical models developed by RSM. The results of ANOVA indicate that the developed models predict the responses adequately within the limits of input parameters. 3-D response surface and contour plots have been developed to find out the combined effects of input parameters on responses. Furthermore, microstructural analysis as well as hardness and tensile behavior of the selected weld of 304SS and 316SS have been carried out to understand the metallurgical and mechanical behavior of the weld. The selection criteria are based on the maximum and minimum strength achieved by the respective weld. It has been observed that the current pulsation, base metal composition and variation in heat input have significant influence on controlling the microstructural constituents (i.e. phase fraction, grain size etc.). The result suggests that the low energy input pulsation generally produce fine grain structure and improved mechanical properties than the high energy input pulsation irrespective of base material composition. However, among the base materials, 304SS depict better microstructural and mechanical properties than the 316SS for a given parametric condition. Finally, desirability function analysis has been applied for multi-objective optimization for maximization of ultimate tensile strength and minimization of weld width simultaneously. Confirmatory tests have been conducted at optimum parametric conditions to validate the optimization techniques.

Electromagnetic interference from welding and motors on implantable cardioverter-defibrillators as tested in the electrically hostile work site.

PubMed

Fetter, J G; Benditt, D G; Stanton, M S

1996-08-01

This study was designed to determine the susceptibility of an implanted cardioverter-defibrillator to electromagnetic interference in an electrically hostile work site environment, with the ultimate goal of allowing the patient to return to work. Normal operation of an implanted cardioverter-defibrillator depends on reliable sensing of the heart's electrical activity. Consequently, there is concern that external electromagnetic interference from external sources in the work place, especially welding equipment or motor-generator systems, may be sensed and produce inappropriate shocks or abnormal reed switch operation, temporarily suspending detection of ventricular tachycardia or ventricular fibrillation. The effects of electromagnetic interference on the operation of one type of implantable cardioverter-defibrillator (Medtronic models 7217 and 7219) was measured by using internal event counter monitoring in 10 patients operating arc welders at up to 900 A or working near 200-hp motors and 1 patient close to a locomotive starter drawing up to 400 A. The electromagnetic interference produced two sources of potential interference on the sensing circuit or reed switch operation, respectively: 1) electrical fields with measured frequencies up to 50 MHz produced by the high currents during welding electrode activation, and 2) magnetic fields produced by the current in the welding electrode and cable. The defibrillator sensitivity was programmed to the highest (most sensitive) value: 0.15 mV (model 7219) or 0.3 mV (model 7217). The ventricular tachycardia and ventricular fibrillation therapies were temporarily turned off but the detection circuits left on. None of the implanted defibrillators tested were affected by oversensing of the electric field as verified by telemetry from the detection circuits. The magnetic field from 225-A welding current produced a flux density of 1.2 G; this density was not adequate to close the reed switch, which requires approximately 10 G. Our testing at the work site revealed no electrical interference with this type of defibrillator. Patients were allowed to return to work. The following precautions should be observed by the patient: 1) maintain a minimal distance of 2 ft (61 cm) from the welding arc and cables or large motors, 2) do not exceed tested currents with the welding equipment, 3) wear insulated gloves while operating electrical equipment, 4) verify that electrical equipment is properly grounded, and 5) stop welding and leave the work area immediately if a therapy is delivered or a feeling of lightheadedness is experienced.

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.

Welding of unique and advanced alloys for space and high-temperature applications: welding and weldability of iridium and platinum alloys

DOE PAGES

David, Stan A.; Miller, Roger G.; Feng, Zhili

2016-08-31

Advances have been made in developing alloys for space power systems for spacecraft that travel long distances to various planets. The spacecraft are powered by radioisotope thermoelectric generators (RTGs) and the fuel element in RTGs is plutonia. For safety and containment of the radioactive fuel element, the heat source is encapsulated in iridium or platinum alloys. Ir and Pt alloys are the alloys of choice for encapsulating radioisotope fuel pellets. Ir and Pt alloys were chosen because of their high-temperature properties and compatibility with the oxide fuel element and the graphite impact shells. This review addresses the alloy design andmore » welding and weldability of Ir and Pt alloys for use in RTGs.« less

Welding of unique and advanced alloys for space and high-temperature applications: welding and weldability of iridium and platinum alloys

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

David, Stan A.; Miller, Roger G.; Feng, Zhili

Advances have been made in developing alloys for space power systems for spacecraft that travel long distances to various planets. The spacecraft are powered by radioisotope thermoelectric generators (RTGs) and the fuel element in RTGs is plutonia. For safety and containment of the radioactive fuel element, the heat source is encapsulated in iridium or platinum alloys. Ir and Pt alloys are the alloys of choice for encapsulating radioisotope fuel pellets. Ir and Pt alloys were chosen because of their high-temperature properties and compatibility with the oxide fuel element and the graphite impact shells. This review addresses the alloy design andmore » welding and weldability of Ir and Pt alloys for use in RTGs.« less

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

Crowder, Jeff; Cornish, Neil J.; Reddinger, J. Lucas

This work presents the first application of the method of genetic algorithms (GAs) to data analysis for the Laser Interferometer Space Antenna (LISA). In the low frequency regime of the LISA band there are expected to be tens of thousands of galactic binary systems that will be emitting gravitational waves detectable by LISA. The challenge of parameter extraction of such a large number of sources in the LISA data stream requires a search method that can efficiently explore the large parameter spaces involved. As signals of many of these sources will overlap, a global search method is desired. GAs representmore » such a global search method for parameter extraction of multiple overlapping sources in the LISA data stream. We find that GAs are able to correctly extract source parameters for overlapping sources. Several optimizations of a basic GA are presented with results derived from applications of the GA searches to simulated LISA data.« less

A pilot study to characterize fine particles in the environment of an automotive machining facility.

PubMed

Sioutas, C

1999-04-01

The main goal of this study was to characterize fine particles (e.g., smaller than about 3 microns) in an automotive machining environment. The Toledo Machining Plant of Chrysler Corporation was selected for this purpose. The effect of local mechanical processes as aerosol sources was a major part of this investigation. To determine the size-dependent mass concentration of particles in the plant, the Micro-Orifice Uniform Deposit Impactor (MOUDI Model 100, MSP Corp., Minneapolis, Minnesota) was used. The MOUDI was placed at central locations in departments with sources inside the plant, so that the obtained information on the size distribution realistically represents the aerosol to which plant workers are exposed. Sampling was conducted over a 4-day period, and during three periods per day, each matching the work shifts. A special effort was made to place the MOUDI at a central location of a department with relatively homogeneous particle sources. The selected sampling sites included welding, grinding, steel machining, and heat treating processes. The average 24-hour mass concentrations of particles smaller than 3.2 microns in aerodynamic diameter were 167.8, 103.9, 201.7, and 112.7 micrograms/m3 for welding, grinding, mild steel, and heat treating processes, respectively. Finally, the mass median diameters of welding, heat treatment, machining, and grinding operations were approximately 0.5, 0.5, 0.6, and 0.8 micron, respectively.

The Landsat Phenology Study (LaPS): Preliminary CONUS Results for 2008

NASA Astrophysics Data System (ADS)

Henebry, Geoffrey M.; Roy, David P.; Ju, Junchang; Kovalskyy, Valeriy

2010-05-01

Most studies of land surface phenology (LSP) have used time series derived from moderate spatial resolution satellite sensor data (e.g., AVHRR, MODIS, VEGETATION) because these data are freely available and because they provide an acceptable trade-off between higher, near daily, temporal frequency of observation needed to reduce cloud contamination against lower (500m-5km) spatial resolution. The recent opening of the USGS Landsat archive to web-enabled access presents the opportunity to explore how well Landsat time series can portray LSPs at high spatial resolution. The NASA Web-enabled Landsat data (WELD) project (http://landsat.usgs.gov/WELD.php) has produced 30m composited mosaics for all the conterminous US (CONUS) from Landsat 7 ETM+ data. The composited mosaics are generated on monthly, seasonal, and annual basis and include spectral reflectance, normalized difference vegetation index (NDVI), and the acquisition date of each composited pixel. The WELD compositing approach is designed to select valid land surface observations with minimal cloud, snow, and atmospheric contamination. We extracted 30m pixel time series from the twelve monthly WELD composited mosaics for 2008 at 320 locations across the CONUS where we have ground phenological observations that are heterogeneous with respect to the types of plants observed, the phenophases recorded (predominantly spring green-up) and the ground sampling protocols used. The ground data came from several sources, including the cloned lilac/honeysuckle network, the Phenocam network, five LTER sites (H.J. Andrews, Harvard Forest, Jornada, Konza Prairie, and Sevilleta), and a private woodlot in Maine. Temporal profiles of the 30m WELD Landsat NDVI, the green NDVI (GNDVI), the normalized difference infrared index (NDII) derived from the composited reflectances, are compared to the ground observations. Results show that (i) inclusion of the Landsat acquisition date for each pixel improves the characterization of the LSP, (ii) the use of the NDII and GNDVI in conjunction with the NDVI improves identification of the onset both of canopy development and senescence, and (iii) the WELD compositing approach and the resulting mosaics provide a rich new data source for phenological investigations.

[A functional orthodontic magnetic appliance (FOMA) after Vardimon. 1. A three-dimensional analysis of the force system of the attractive magnets].

PubMed

Bourauel, C; Vardimon, A D; Drescher, D; Schmuth, G P

1995-09-01

The functional magnetic system (FMS) is a removable functional appliance which induces mandibular advance by means of mandibular and maxillary magnets in an attracting configuration. The maxillary and mandibular plates are each equipped with 2 cylindrically shaped cobalt-samarium magnets, 4 mm in diameter and 3 mm in height, which are welded into stainless steel housings. The force system of this magnetic configuration was analyzed using the orthodontic measurement and simulation system (OMSS). OMSS simulated the mandibular jaw movements by separating the installed magnets vertically, corresponding to a mouth opening of X = -10 mm, transversally (right excursion, +/left excursion, -) at Y = +/- 10 mm and sagittally (anterior displacement, +/posterior displacement, -) at Z = +/- 10 mm. The resulting 2D and 3D force/displacement diagrams elucidate the outstanding centripetal-spatial orientation characteristics of the functional magnetic appliance in reference to the full overlap brought about by the attraction of the mandibular magnet by the maxillary magnet. The maximum centripetal forces reached a value of approximately FY, max = 0.65 N for the vertical attracting force at full overlap of the mandibular and maxillary magnets (X = 0.55 mm, Y = Z = 0 mm), a value of FY, max = 0.65 N for the medial shearing force at a partial transversal overlap Z = 0, Y = +/- 2 mm and Y = +/- 6 mm), and for the sagittal shearing force a value of FZ, max = 1.2 N at a partial sagittal overlap of the magnets (Y = 0 mm, Z = +/- 2 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

Investigations on laser transmission welding of absorber-free thermoplastics

NASA Astrophysics Data System (ADS)

Mamuschkin, Viktor; Olowinsky, Alexander; Britten, Simon W.; Engelmann, Christoph

2014-03-01

Within the plastic industry laser transmission welding ranks among the most important joining techniques and opens up new application areas continuously. So far, a big disadvantage of the process was the fact that the joining partners need different optical properties. Since thermoplastics are transparent for the radiation of conventional beam sources (800- 1100 nm) the absorbance of one of the joining partners has to be enhanced by adding an infrared absorber (IR-absorber). Until recently, welding of absorber-free parts has not been possible. New diode lasers provide a broad variety of wavelengths which allows exploiting intrinsic absorption bands of thermoplastics. The use of a proper wavelength in combination with special optics enables laser welding of two optically identical polymer parts without absorbers which can be utilized in a large number of applications primarily in the medical and food industry, where the use of absorbers usually entails costly and time-consuming authorization processes. In this paper some aspects of the process are considered as the influence of the focal position, which is crucial when both joining partners have equal optical properties. After a theoretical consideration, an evaluation is carried out based on welding trials with polycarbonate (PC). Further aspects such as gap bridging capability and the influence of thickness of the upper joining partner are investigated as well.

Computer modeling of the stress-strain state of welded construction

NASA Astrophysics Data System (ADS)

Nurguzhin, Marat; Danenova, Gulmira; Akhmetzhanov, Talgat

2017-11-01

At the present time the maintenance of the welded construction serviceability over normative service life is provided by the maintenance system on the basis of the guiding documents according to the concept of "fail safe". However, technology factors relating to welding such as high residual stresses and significant plastic strains are not considered in the guiding documents. The design procedure of the stressed-strained state of welded constructions is suggested in the paper. The procedure investigates welded constructions during welding and the external load using the program ANSYS. In this paper, the model of influence of the residual stress strain state on the factor of stress intensity is proposed. The calculation method of the residual stressed-strained state (SSS) taking into account the phase transition is developed by the authors. Melting and hardening of a plate material during heating and cooling is considered. The thermomechanical problem of heating a plate by a stationary heat source is solved. The setup of the heating spot center on distance (190 mm) from the crack top in a direction of its propagation leads to the fact that the value of total factor of stress intensity will considerably decrease under action of the specified residual compressing stresses. It can lower the speed of the crack propagation to zero. The suggested method of survivability maintenance can be applied during operation with the purpose of increasing the service life of metal constructions up to running repair of technological machines.

Digital control and data acquisition for high-value GTA welding

NASA Astrophysics Data System (ADS)

George, T. G.; Franco-Ferreira, E. A.

Electric power for the Cassini space probe will be provided by radioisotope thermoelectric generators (RTG's) thermally driven by General-Purpose Heat Source (GPHS) modules. Each GPHS module contains four, 150-g, pellets of Pu-238O2, and each of the four pellets is encapsulated within a thin-wall iridium-alloy shell. GTA girth welding of these capsules is performed at Los Alamos National Laboratory (LANL) on an automated, digitally-controlled welding system. Baseline design considerations for system automation and strategies employed to maximize process yield, improve process consistency, and generate required quality assurance information are discussed. Design of the automated girth welding system was driven by a number of factors which militated for precise parametric control and data acquisition. Foremost among these factors was the extraordinary value of the capsule components. In addition, DOE order 5700.6B, which took effect on 23 Sep. 1986, required that all operations adhere to strict levels of process quality assurance. A detailed technical specification for the GPHS welding system was developed on the basis of a joint LANL/Westinghouse Savannah River Company (WSRC) design effort. After a competitive bidding process, Jetline Engineering, Inc., of Irvine, California, was selected as the system manufacturer. During the period over which four identical welding systems were fabricated, very close liason was maintained between the LANL/WSRC technical representatives and the vendor. The level of rapport was outstanding, and the end result was the 1990 delivery of four systems that met or exceeded all specification requirements.

Numerical simulation of heat transfer and fluid flow during double-sided laser beam welding of T-joints for aluminum aircraft fuselage panels

NASA Astrophysics Data System (ADS)

Yang, Zhibin; Tao, Wang; Li, Liqun; Chen, Yanbin; Shi, Chunyuan

2017-06-01

In comparison with conventional laser beam welding, double-sided laser beam welding has two laser heat sources simultaneously and symmetrically loaded from both sides makes it to be a more complicated coupled heat transport and fluid flow process. In this work, in order to understand the heat transfer and fluid flow, a three-dimensional model was developed and validated with the experimental results. The temperature field, fluid flow field, and keyhole characteristic were calculated using the developed model by FLUENT software. Calculated results indicated that the temperature and fluid flow fields were bilateral symmetry along the stringer center, and the molten pool maximum length was located near the keyhole intersection position. The skin side had higher temperature and faster cooling speed. Several characteristic flow patterns in the weld pool cross section, including the vortexes flows near the keyhole opening position, the convection flows above the keyhole intersection location, the regularity downward flows at the molten pool bottom. And in the lengthwise section, a distinct vortex flow below the keyhole, and the liquid metal behind the keyhole first flowed to near the molten pool maximum length location and then to the molten pool surface. Perpendicular to and along welding direction the keyhole liquid metal flowed to the weld molten pool surface and around the keyhole, respectively. The special temperature fields and fluid flow patterns were closely related to the effects of the double sides' laser energy coupling and enhancement. The calculated weld pool geometry basically in good agreement with the experimental results indicated that the developed model was validity and reasonable.

Workplace exposure to nanoparticles from gas metal arc welding process

NASA Astrophysics Data System (ADS)

Zhang, Meibian; Jian, Le; Bin, Pingfan; Xing, Mingluan; Lou, Jianlin; Cong, Liming; Zou, Hua

2013-11-01

Workplace exposure to nanoparticles from gas metal arc welding (GMAW) process in an automobile manufacturing factory was investigated using a combination of multiple metrics and a comparison with background particles. The number concentration (NC), lung-deposited surface area concentration (SAC), estimated SAC and mass concentration (MC) of nanoparticles produced from the GMAW process were significantly higher than those of background particles before welding ( P < 0.01). A bimodal size distribution by mass for welding particles with two peak values (i.e., 10,000-18,000 and 560-320 nm) and a unimodal size distribution by number with 190.7-nm mode size or 154.9-nm geometric size were observed. Nanoparticles by number comprised 60.7 % of particles, whereas nanoparticles by mass only accounted for 18.2 % of the total particles. The morphology of welding particles was dominated by the formation of chain-like agglomerates of primary particles. The metal composition of these welding particles consisted primarily of Fe, Mn, and Zn. The size distribution, morphology, and elemental compositions of welding particles were significantly different from background particles. Working activities, sampling distances from the source, air velocity, engineering control measures, and background particles in working places had significant influences on concentrations of airborne nanoparticle. In addition, SAC showed a high correlation with NC and a relatively low correlation with MC. These findings indicate that the GMAW process is able to generate significant levels of nanoparticles. It is recommended that a combination of multiple metrics is measured as part of a well-designed sampling strategy for airborne nanoparticles. Key exposure factors, such as particle agglomeration/aggregation, background particles, working activities, temporal and spatial distributions of the particles, air velocity, engineering control measures, should be investigated when measuring workplace exposure to nanoparticles.

High Power High Efficiency Diode Laser Stack for Processing

NASA Astrophysics Data System (ADS)

Gu, Yuanyuan; Lu, Hui; Fu, Yueming; Cui, Yan

2018-03-01

High-power diode lasers based on GaAs semiconductor bars are well established as reliable and highly efficient laser sources. As diode laser is simple in structure, small size, longer life expectancy with the advantages of low prices, it is widely used in the industry processing, such as heat treating, welding, hardening, cladding and so on. Respectively, diode laser could make it possible to establish the practical application because of rectangular beam patterns which are suitable to make fine bead with less power. At this power level, it can have many important applications, such as surgery, welding of polymers, soldering, coatings and surface treatment of metals. But there are some applications, which require much higher power and brightness, e.g. hardening, key hole welding, cutting and metal welding. In addition, High power diode lasers in the military field also have important applications. So all developed countries have attached great importance to high-power diode laser system and its applications. This is mainly due their low performance. In this paper we will introduce the structure and the principle of the high power diode stack.

Validation of Assessment Methods for Production Scale Girth Welding of High Strength Steel Pipelines with Multiple Pipe Sources

DOT National Transportation Integrated Search

2012-03-01

There is an increasing need to deliver energy from sources in remote areas to demand centers. For example, in North America, the delivery of gas from Alaska to demand centers in the lower 48 states is of major economic and strategic interest. This wi...

Predicting mesoscale microstructural evolution in electron beam welding

DOE PAGES

Rodgers, Theron M.; Madison, Jonathan D.; Tikare, Veena; ...

2016-03-16

Using the kinetic Monte Carlo simulator, Stochastic Parallel PARticle Kinetic Simulator, from Sandia National Laboratories, a user routine has been developed to simulate mesoscale predictions of a grain structure near a moving heat source. Here, we demonstrate the use of this user routine to produce voxelized, synthetic, three-dimensional microstructures for electron-beam welding by comparing them with experimentally produced microstructures. When simulation input parameters are matched to experimental process parameters, qualitative and quantitative agreement for both grain size and grain morphology are achieved. The method is capable of simulating both single- and multipass welds. As a result, the simulations provide anmore » opportunity for not only accelerated design but also the integration of simulation and experiments in design such that simulations can receive parameter bounds from experiments and, in turn, provide predictions of a resultant microstructure.« less

Characterization of weld (Reseda luteola L.) and spurge flax (Daphne gnidium L.) by high-performance liquid chromatography-diode array detection-mass spectrometry in Arraiolos historical textiles.

PubMed

Marques, Rita; Sousa, Micaela M; Oliveira, Maria C; Melo, Maria J

2009-02-27

The natural dyes, and dye sources, in two seventeenth century Arraiolos carpets from the National Museum of Machado de Castro were analysed by high-performance liquid chromatography with UV-vis diode array detection (HPLC-DAD) and HPLC-mass spectrometry (LC-MS). Weld (Reseda luteola L.), indigo and spurge flax (Daphne gnidium L.) were found to be the dye sources, in agreement with original dyeing recipes collected during the nineteenth century. In order to fully characterize the plant sources, LC-MS conditions were optimized with plant extracts and the chromatographic separation and mass detection were enhanced. Extraction of the dyes, in the Arraiolos carpet samples, was performed using mild conditions that avoid glycoside decomposition. For the blues a dimethylformamide solution proved to be efficient for indigotin recovery. For all the other colours, an improved mild extraction method (with oxalic acid, methanol, acetone and water) was used, enabling to obtain the full dye source fingerprint, namely the flavonoid glycosides in the yellow dyes.

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

NASA Astrophysics Data System (ADS)

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

2017-10-01

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

Joining of polymer composite materials

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

Magness, F.H.

1990-11-01

Under ideal conditions load bearing structures would be designed without joints, thus eliminating a source of added weight, complexity and weakness. In reality the need for accessibility, repair, and inspectability, added to the size limitations imposed by the manufacturing process and transportation/assembly requirements mean that some minimum number of joints will be required in most structures. The designer generally has two methods for joining fiber composite materials, adhesive bonding and mechanical fastening. As the use of thermoplastic materials increases, a third joining technique -- welding -- will become more common. It is the purpose of this document to provide amore » review of the available sources pertinent to the design of joints in fiber composites. The primary emphasis is given to adhesive bonding and mechanical fastening with information coming from documentary sources as old as 1961 and as recent as 1989. A third, shorter section on composite welding is included in order to provide a relatively comprehensive treatment of the subject.« less

Thermoplastic Ribbon-Ply Bonding Model

NASA Technical Reports Server (NTRS)

Hinkley, Jeffrey A.; Marchello, Joseph M.; Messier, Bernadette C.

1996-01-01

The aim of the present work was to identify key variables in rapid weldbonding of thermoplastic tow (ribbon) and their relationship to matrix polymer properties and to ribbon microstructure. Theoretical models for viscosity, establishment of ply-ply contact, instantaneous (Velcro) bonding, molecular interdiffusion (healing), void growth suppression, and gap filling were reviewed and synthesized. Consideration of the theoretical bonding mechanisms and length scales and of the experimental weld/peel data allow the prediction of such quantities as the time and pressure required to achieve good contact between a ribbon and a flat substrate, the time dependence of bond strength, pressures needed to prevent void growth from dissolved moisture and conditions for filling gaps and smoothing overlaps.

Gravitational effects on the development of weld-pool and solidification microstructures

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

Boatner, L.A.; David, S.A.; Workman, G.

1994-09-01

This research effort has as its objective the development of a quantitative understanding of the effects of both low- and high-g environments on the solidification microstructures and morphologies that are produced in alloy single crystals during a variety of melting and solidification processes. The overall goal of the effort is to delineate the nature of the roles played by natural convection, surface-tension-driven convection, and mass transport effects due to interactions associated with various heating methods that are used to form melt pools in practical, commercially important alloy systems. The experimental and theoretical investigations comprising this effort encompass the study ofmore » configurations in which stationary heat sources are employed as well as melt pools formed by moving heat sources like those frequently used in fusion-welding processes.« less

Dismantling of Radium-226 Coal Level Gauges: Encountered Problems and How to Solve

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

Punnachaiya, M.; Nuanjan, P.; Moombansao, K.

2006-07-01

This paper describes the techniques for dismantling of disused-sealed Radium-226 (Ra-226) coal level gauges which the source specifications and documents were not available, including problems occurred during dismantling stage and the decision making in solving all those obstacles. The 2 mCi (20 pieces), 6 mCi (20 pieces) and 6.6 mCi (30 pieces) of Ra-226 hemi-spherically-shaped with lead-filled coal level gauges were used in industrial applications for electric power generation. All sources needed to be dismantled for further conditioning as requested by the International Atomic Energy Agency (IAEA). One of the 2 mCi Ra-226 source was dismantled under the supervision ofmore » IAEA expert. Before conditioning period, each of the 6 mCi and 6.6 mCi sources were dismantled and inspected. It was found that coal level gauges had two different source types: the sealed cylindrical source (diameter 2 cm x 2 cm length) locked with spring in lead housing for 2 mCi and 6.6 mCi; while the 6 mCi was an embedded capsule inside source holder stud assembly in lead-filled housing. Dismantling Ra-226 coal level gauges comprised of 6 operational steps: confirmation of the surface dose rate on each source activity, calculation of working time within the effective occupational dose limit, cutting the weld of lead container by electrical blade, confirmation of the Ra-226 embedded capsule size using radiation scanning technique and gamma radiography, automatic sawing of the source holder stud assembly, and transferring the source to store in lead safe box. The embedded length of 6 mCi Ra-226 capsule in its diameter 2 cm x 14.7 cm length stud assembly was identified, the results from scanning technique and radiographic film revealed the embedded source length of about 2 cm, therefore all the 6 mCi sources were safely cut at 3 cm using the automatic saw. Another occurring problem was one of the 6.6 mCi spring type source stuck inside its housing because the spring was deformed and there was previously a leakage on inner source housing. Thus, during manufacturing the filled-lead for shielding passed through this small hole and fixed the deformed spring together with the source. The circular surface of inner hole was measured and slowly drilled at a diameter 2.2 cm behind shielding, till the spring and the fixed lead sheet were cut, therefore the source could be finally hammered out. The surface dose rate of coal level gauges before weld cutting was 10-15 mR/hr and the highest dose rate at the position of the weld cutter was 2.5 mR/hr. The total time for each weld cutting and automatic sawing was 2-3 minutes and 1 minute, respectively. The source was individually and safely transferred to store in lead safe box using a 1-meter length tong and a light container with 1 meter length handle. The total time for Ra-226 (70 pieces) dismantling, including the encountered problems and their troubles shooting took 4 days operation in which the total dose obtained by 18 operators were ranged from 1-38 {mu}Sv. The dismantling team safely completed the activities within the effective dose limit for occupational exposure of 20 mSv/year (80 {mu}Sv/day). (authors)« less

Laser-Assisted Stir Welding of 25-mm-Thick HSLA-65 Plate

NASA Astrophysics Data System (ADS)

Williamson, Keith M.

2002-12-01

Laser-assisted stir welding is a hybrid process that combines energy from a laser with functional heating and mechanical energy to join materials in the solid state. The technology is an adaptation of friction stir welding which is particularly suited for joining thick plates. Aluminum plates up to 75 mm thick have been successfully joined using friction stir welding. Since joining occurs in the solid state, stir technology offers the capability for fabricating full penetration joints in thick plates with better mechanical properties and less weld distortion than is possible by fusion processes. Currently friction stir welding is being used in several industries to improve productivity, reduce weight, and increase the strength of welded structures. Examples include: (a) the aircraft/aerospace industry where stir technology is currently being used to fabricate the space shuttle's external tank as well as components of the Delta family of rockets; (b) the shipping industry where container manufacturers are using stir technology to produce lighter containers with more payload capacity; and (c) the oil industry where offshore platform manufactures are using automated stir welding plants to fabricate large panels and structures up to 16 meters long with widths as required. In all these cases, stir technology has been restricted to aluminum alloys; however, stainless and HSLA 65 steels have been recently stir welded with friction as the primary heat source. One of the difficulties in adapting stir welding to steel is tool wear aggravated by the high tool rubbing velocities needed to provide frictional heat input into the material. Early work showed that the tool shoulder reached temperatures above 1000 C and the weld seam behind the tool stayed within this temperature range for up to 25 mm behind the tool. Cross sections of stir welded samples showed that the heat-affected zone is relatively wide and follows the profile of the tool shoulder. Besides minimizing the tool wear by increasing the energy into the material, another benefit of the proposed Laser Assisted Stir Welding (LASW is to reduce the width of the heat affected zone which typically has the lowest hardness in the weld region. Additionally, thermal modeling of the friction stir process shows that the heat input is asymmetric and suggests that the degree of asymmetry could improve the efficiency of the process. These asymmetries occur because the leading edge of the tool supplies heat to cold material while the trailing edge provides heat to material already preheated by the leading edge. As a result, flow stresses on the advancing side of the joint are lower than corresponding values on the retreating side. The proposed LASW process enhances these asymmetries by providing directional heating to increase the differential in flow stress across the joint and improve the stir tool efficiency. Theoretically the LASW process can provide the energy input to allow the flow stresses on the advancing side to approach zero and the stir efficiency to approach 100 percent. Reducing the flow stresses on the advancing side of the weld creates the greatest pressure differential across the stir weld and eliminates the possibility of voids on the advancing side of the joint. Small pressure differentials result in poor stir welds because voids on the advancing side are not filled by the plastic flow of material from the retreating side.

Exposure assessment of aluminum arc welding radiation.

PubMed

Peng, Chiung-yu; Lan, Cheng-hang; Juang, Yow-jer; Tsao, Ta-ho; Dai, Yu-tung; Liu, Hung-hsin; Chen, Chiou-jong

2007-10-01

The purpose of this study is to evaluate the non-ionizing radiation (NIR) exposure, especially optical radiation levels, and potential health hazard from aluminum arc welding processes based on the American Conference of Governmental Industrial Hygienists (ACGIH) method. The irradiance from the optical radiation emissions can be calculated with various biological effective parameters [i.e., S(lambda), B(lambda), R(lambda)] for NIR hazard assessments. The aluminum arc welding processing scatters bright light with NIR emission including ultraviolet radiation (UVR), visible, and infrared spectra. The UVR effective irradiance (Eeff) has a mean value of 1,100 microW cm at 100 cm distance from the arc spot. The maximum allowance time (tmax) is 2.79 s according to the ACGIH guideline. Blue-light hazard effective irradiance (EBlue) has a mean value of 1840 microW cm (300-700 nm) at 100 cm with a tmax of 5.45 s exposure allowance. Retinal thermal hazard effective calculation shows mean values of 320 mW cm(-2) sr(-1) and 25.4 mW (cm-2) (380-875 nm) for LRetina (spectral radiance) and ERetina (spectral irradiance), respectively. From this study, the NIR measurement from welding optical radiation emissions has been established to evaluate separate types of hazards to the eye and skin simultaneously. The NIR exposure assessment can be applied to other optical emissions from industrial sources. The data from welding assessment strongly suggest employees involved in aluminum welding processing must be fitted with appropriate personal protection devices such as masks and gloves to prevent serious injuries of the skin and eyes upon intense optical exposure.

Digital control and data acquisition for high-value GTA welding

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

George, T.G.; Franco-Ferreira, E.A.

1993-10-01

Electric power for the Cassini space probe wig be provided by radioisotope thermoelectric generators (RTGs) thermally driven by General-Purpose Heat Source (GPHS) modules. Each GPHS module contains four, 150-g, pellets of {sup 238}PuO{sub 2}, and each of the four pellets is encapsulated within a thin-wall iridium-alloy shell. GTA girth welding of these capsules is performed at Los Alamos National Laboratory (LANL) on an automated, digitally-controlled welding system. This paper discusses baseline design considerations for system automation and strategies employed to maximize process yield, improve process consistency, and generate required quality assurance information. Design of the automated girth welding system wasmore » driven by a number of factors which militated for precise parametric control and data acquisition. Foremost among these factors was the extraordinary value of the capsule components. In addition, DOE order 5700.6B, which took effect on 23 September 1986, required that all operations adhere to strict levels of process quality assurance. A detailed technical specification for the GPHS welding system was developed on the basis of a joint Lanl/Westinghouse Savannah River Company (WSRC) design effort. After a competitive bidding process, Jetline Engineering, Inc., of Irvine, California, was selected as the system manufacturer. During the period over which four identical welding systems were fabricated, very close liason was maintained between the LANL/WSRC technical representatives and the vendor. The level of rapport was outstanding, and the end result was the 1990 delivery of four systems that met or exceeded all specification requirements.« less

Analysis of High-Power Diode Laser Heating Effects on HY-80 Steel for Laser Assisted Friction Stir Welding Applications

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

Wiechec, Maxwell; Baker, Brad; McNelley, Terry

In this research, several conditions of high power diode laser heated HY-80 steel were characterized to determine the viability of using such lasers as a preheating source before friction stir welding in order to reduce frictional forces thereby reducing tool wear and increasing welding speeds. Differences in microstructures within heat affected zones were identified at specific laser powers and traverse speeds. Vickers hardness values were recorded and analyzed to validate the formation of additional martensite in diode laser heated regions of HY-80 steel. Conditions that produced little to no additional martensite were identified and relationships among high power diode lasermore » power, traverse speed, and martensite formation were determined. The development of heat affected zones, change in grain structure, and creation of additional martensite in HY-80 can be prevented through the optimization of laser amperage and transverse speed.« less

The risk of cataract in relation to metal arc welding.

PubMed

Slagor, Rebekka Michaelsen; La Cour, Morten; Bonde, Jens Peter

2016-09-01

There are indications that solar ultraviolet radiation (UVR) increases the risk of cataract, but there is only circumstantial evidence that metal welding, an important occupational source of UVR exposure, is a risk factor. The objective of this study is to unravel if metal welding increases the risk of cataract. We compared the risk of being diagnosed with cataract from 1987-2012 in a historic cohort of 4288 male metal arc welders against a reference group comprised of Danish skilled and unskilled male workers with similar age distribution. For the welders' cohort, information on welding was collected from questionnaires and, for both cohorts, information about cataract diagnosis and operation was gathered from Danish national registers. Using Cox regression analysis, the hazard ratio (HR) for cataract diagnosis and/or operation was calculated in the follow-up period adjusted for baseline data regarding age, diabetes, and social group. There were 266 welders and 29 007 referents with a diagnosis and/or operation for cataract. The unadjusted HR for cataract comparing ever-welders with referents was 1.07 [95% confidence interval (95% CI) 0.95-1.21] and the adjusted HR was 1.08 (95% CI 0.95-1.22). Age and diabetes were as expected strong risk factors. We found no increased risk of developing cataract among Danish metal welders who worked with arc welding from 1950-1985. This may be attributed to the effectiveness of personal safety equipment.

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.

The porosity formation mechanism in the laser-MIG hybrid welded joint of Invar alloy

NASA Astrophysics Data System (ADS)

Zhan, Xiaohong; Gao, Qiyu; Gu, Cheng; Sun, Weihua; Chen, Jicheng; Wei, Yanhong

2017-10-01

The porosity formation mechanism in the laser-metal inter gas (MIG) multi-layer hybrid welded (HW) joint of 19.05 mm thick Invar alloy is investigated. The microstructure characteristics and energy dispersive spectroscopy (EDS) are analyzed. The phase identification was conducted by the X-ray diffractometer (XRD). Experimental results show that the generation of porosity is caused by the relatively low laser power in the root pass and low current in the cover pass. It is also indicated that the microstructures of the welded joints are mainly observed to be columnar crystal and equiaxial crystal, which are closely related to the porosity formation. The EDS results show that oxygen content is significantly high in the inner wall of the porosity. The XRD results indicate that the BM and the WB of laser-MIG HW all are composed of Fe0.64Ni0.36 and γ-(Fe,Ni). When the weld pool is cooled quickly, [NiO] [FeO] and [MnO] are formed that react on C to generate CO/CO2 gases. The porosity of laser-MIG HW for Invar alloy is oxygen pore. The root source of metallurgy porosity formation is that the dissolved gases are hard to escape sufficiently and thus exist in the weld pool. Furthermore, 99.99% pure Argon is recommended as protective gas in the laser-MIG HW of Invar alloy.

Instruction manual for UTEP weld gas hydrogen detector

NASA Technical Reports Server (NTRS)

Mcclure, John; Pang, Tonghui

1992-01-01

The instrument described in this manual was developed at the University of Texas at El Paso under contract from the National Aeronautics and Space Administration Marshall Space Flight Center. The instrument has been used to detect hydrogen in the shielding gas of Variable Polarity Plasma Arc (VPPA) welds at concentrations of less than 100 ppm. The instrument makes measurements in real time during the welding operation and provides the operator with an easily readable graphic display of the present level of hydrogen in the arc as well as the level of hydrogen over the past approximately five minutes. In this way the welder can not only tell if the present level of hydrogen is excessive, but can see what changes in weld parameters have done to the level of hydrogen. The welder can set the level of hydrogen that is considered critical and the instrument display will indicate when that level has been exceeded. All detection is from the torch side. All needed equipment is supplied by the developer except for an IBM PC compatible computer which must be supplied by the user. Source code is supplied in this manual so that the user can modify the control program as desired.

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

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

Bransch, H.N.

1994-12-31

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

High Strain Rate Testing of Welded DOP-26 Iridium

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

Schneibel, J. H.; Miller, R. G.; Carmichael, C. A.

The iridium alloy DOP-26 is used to produce Clad Vent Set cups that protect the radioactive fuel in radioisotope thermoelectric generators (RTGs) which provide electric power for spacecraft and rovers. In a previous study, the tensile properties of DOP-26 were measured over a wide range of strain rates and temperatures and reported in ORNL/TM-2007/81. While that study established the properties of the base material, the fabrication of the heat sources requires welding, and the mechanical properties of welded DOP-26 have not been extensively characterized in the past. Therefore, this study was undertaken to determine the mechanical properties of DOP-26 specimensmore » containing a transverse weld in the center of their gage sections. Tensile tests were performed at room temperature, 750, 900, and 1090°C and engineering strain rates of 1×10 -3 and 10 s -1. Room temperature testing was performed in air, while testing at elevated temperatures was performed in a vacuum better than 1×10 -4 Torr. The welded specimens had a significantly higher yield stress, by up to a factor of ~2, than the non-welded base material. The yield stress did not depend on the strain rate except at 1090°C, where it was slightly higher for the faster strain rate. The ultimate tensile stress, on the other hand, was significantly higher for the faster strain rate at temperatures of 750°C and above. At 750°C and above, the specimens deformed at 1×10 -3 s -1 showed pronounced necking resulting sometimes in perfect chisel-edge fracture. The specimens deformed at 10 s -1 exhibited this fracture behavior only at the highest test temperature, 1090°C. Fracture occurred usually in the fusion zone of the weld and was, in most cases, primarily intergranular.« less

Manufacturing High-Quality Carbon Nanotubes at Lower Cost

NASA Technical Reports Server (NTRS)

Benavides, Jeanette M.; Lidecker, Henning

2004-01-01

A modified electric-arc welding process has been developed for manufacturing high-quality batches of carbon nanotubes at relatively low cost. Unlike in some other processes for making carbon nanotubes, metal catalysts are not used and, consequently, it is not necessary to perform extensive cleaning and purification. Also, unlike some other processes, this process is carried out at atmospheric pressure under a hood instead of in a closed, pressurized chamber; as a result, the present process can be implemented more easily. Although the present welding-based process includes an electric arc, it differs from a prior electric-arc nanotube-production process. The welding equipment used in this process includes an AC/DC welding power source with an integral helium-gas delivery system and circulating water for cooling an assembly that holds one of the welding electrodes (in this case, the anode). The cathode is a hollow carbon (optionally, graphite) rod having an outside diameter of 2 in. (approximately equal to 5.1 cm) and an inside diameter of 5/8 in. (approximately equal to 1.6 cm). The cathode is partly immersed in a water bath, such that it protrudes about 2 in. (about 5.1 cm) above the surface of the water. The bottom end of the cathode is held underwater by a clamp, to which is connected the grounding cable of the welding power source. The anode is a carbon rod 1/8 in. (approximately equal to 0.3 cm) in diameter. The assembly that holds the anode includes a thumbknob- driven mechanism for controlling the height of the anode. A small hood is placed over the anode to direct a flow of helium downward from the anode to the cathode during the welding process. A bell-shaped exhaust hood collects the helium and other gases from the process. During the process, as the anode is consumed, the height of the anode is adjusted to maintain an anode-to-cathode gap of 1 mm. The arc-welding process is continued until the upper end of the anode has been lowered to a specified height above the surface of the water bath. The process causes carbon nanotubes to form in the lowest 2.5 cm of the anode. It also causes a deposit reminiscent of a sandcastle to form on the cathode. The nanotube-containing material is harvested. The cathode and anode can then be cleaned (or the anode is replaced, if necessary) and the process repeated to produce more nanotubes. Tests have shown that the process results in approximately equal to 50-percent yield of carbon nanotubes (mostly of the single-wall type) of various sizes. Whereas the unit cost of purified single-wall carbon nanotubes produced by other process is about $1,000/g in the year 2000, it has been estimated that for the present process, the corresponding cost would be about $10/g.

Automated lung sound analysis for detecting pulmonary abnormalities.

PubMed

Datta, Shreyasi; Dutta Choudhury, Anirban; Deshpande, Parijat; Bhattacharya, Sakyajit; Pal, Arpan

2017-07-01

Identification of pulmonary diseases comprises of accurate auscultation as well as elaborate and expensive pulmonary function tests. Prior arts have shown that pulmonary diseases lead to abnormal lung sounds such as wheezes and crackles. This paper introduces novel spectral and spectrogram features, which are further refined by Maximal Information Coefficient, leading to the classification of healthy and abnormal lung sounds. A balanced lung sound dataset, consisting of publicly available data and data collected with a low-cost in-house digital stethoscope are used. The performance of the classifier is validated over several randomly selected non-overlapping training and validation samples and tested on separate subjects for two separate test cases: (a) overlapping and (b) non-overlapping data sources in training and testing. The results reveal that the proposed method sustains an accuracy of 80% even for non-overlapping data sources in training and testing.

Laser Cladding of Ultra-Thin Nickel-Based Superalloy Sheets.

PubMed

Gabriel, Tobias; Rommel, Daniel; Scherm, Florian; Gorywoda, Marek; Glatzel, Uwe

2017-03-10

Laser cladding is a well-established process to apply coatings on metals. However, on substrates considerably thinner than 1 mm it is only rarely described in the literature. In this work 200 µm thin sheets of nickel-based superalloy 718 are coated with a powder of a cobalt-based alloy, Co-28Cr-9W-1.5Si, by laser cladding. The process window is very narrow, therefore, a precisely controlled Yb fiber laser was used. To minimize the input of energy into the substrate, lines were deposited by setting single overlapping points. In a design of experiments (DoE) study, the process parameters of laser power, laser spot area, step size, exposure time, and solidification time were varied and optimized by examining the clad width, weld penetration, and alloying depth. The microstructure of the samples was investigated by optical microscope (OM) and scanning electron microscopy (SEM), combined with electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDX). Similarly to laser cladding of thicker substrates, the laser power shows the highest influence on the resulting clad. With a higher laser power, the clad width and alloying depth increase, and with a larger laser spot area the weld penetration decreases. If the process parameters are controlled precisely, laser cladding of such thin sheets is manageable.

Laser Cladding of Ultra-Thin Nickel-Based Superalloy Sheets

PubMed Central

Gabriel, Tobias; Rommel, Daniel; Scherm, Florian; Gorywoda, Marek; Glatzel, Uwe

2017-01-01

Laser cladding is a well-established process to apply coatings on metals. However, on substrates considerably thinner than 1 mm it is only rarely described in the literature. In this work 200 µm thin sheets of nickel-based superalloy 718 are coated with a powder of a cobalt-based alloy, Co–28Cr–9W–1.5Si, by laser cladding. The process window is very narrow, therefore, a precisely controlled Yb fiber laser was used. To minimize the input of energy into the substrate, lines were deposited by setting single overlapping points. In a design of experiments (DoE) study, the process parameters of laser power, laser spot area, step size, exposure time, and solidification time were varied and optimized by examining the clad width, weld penetration, and alloying depth. The microstructure of the samples was investigated by optical microscope (OM) and scanning electron microscopy (SEM), combined with electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDX). Similarly to laser cladding of thicker substrates, the laser power shows the highest influence on the resulting clad. With a higher laser power, the clad width and alloying depth increase, and with a larger laser spot area the weld penetration decreases. If the process parameters are controlled precisely, laser cladding of such thin sheets is manageable. PMID:28772639

Dynamic load environment of bridge-mounted sign support structures : research implementation plan.

DOT National Transportation Integrated Search

2005-09-01

Welded aluminum highway sign support trusses must withstand in-service dynamic loads, which largely : constitute the fatigue environment. Sources of these dynamic loads include the natural wind and seismic : environment, the artificial wind environme...

Percolation flux and Transport velocity in the unsaturated zone, Yucca Mountain, Nevada

USGS Publications Warehouse

Yang, I.C.

2002-01-01

The percolation flux for borehole USW UZ-14 was calculated from 14C residence times of pore water and water content of cores measured in the laboratory. Transport velocity is calculated from the depth interval between two points divided by the difference in 14C residence times. Two methods were used to calculate the flux and velocity. The first method uses the 14C data and cumulative water content data directly in the incremental intervals in the Paintbrush nonwelded unit and the Topopah Spring welded unit. The second method uses the regression relation for 14C data and cumulative water content data for the entire Paintbrush nonwelded unit and the Topopah Spring Tuff/Topopah Spring welded unit. Using the first method, for the Paintbrush nonwelded unit in boreholeUSW UZ-14 percolation flux ranges from 2.3 to 41.0 mm/a. Transport velocity ranges from 1.2 to 40.6 cm/a. For the Topopah Spring welded unit percolation flux ranges from 0.9 to 5.8 mm/a in the 8 incremental intervals calculated. Transport velocity ranges from 1.4 to 7.3 cm/a in the 8 incremental intervals. Using the second method, average percolation flux in the Paintbrush nonwelded unit for 6 boreholes ranges from 0.9 to 4.0 mm/a at the 95% confidence level. Average transport velocity ranges from 0.6 to 2.6 cm/a. For the Topopah Spring welded unit and Topopah Spring Tuff, average percolation flux in 5 boreholes ranges from 1.3 to 3.2 mm/a. Average transport velocity ranges from 1.6 to 4.0 cm/a. Both the average percolation flux and average transport velocity in the PTn are smaller than in the TS/TSw. However, the average minimum and average maximum values for the percolation flux in the TS/TSw are within the PTn average range. Therefore, differences in the percolation flux in the two units are not significant. On the other hand, average, average minimum, and average maximum transport velocities in the TS/TSw unit are all larger than the PTn values, implying a larger transport velocity for the TS/TSw although there is a small overlap.

Ultrafast Microwave Welding/Reinforcing Approach at the Interface of Thermoplastic Materials.

PubMed

Poyraz, Selcuk; Zhang, Lin; Schroder, Albrecht; Zhang, Xinyu

2015-10-14

As an attempt to address the needs and tackle the challenges in welding of thermoplastic materials (TPMs), a novel process was performed via short-term microwave (MW) heating of a specific composite, made up of conducting polypyrrole nanogranule (PPy NG) coated carbon and catalyst source precursor (ferrocene) fine particles, at substrate polypropylene (PP) dog bone pieces' interface. Upon vigorous interactions between MWs and electromagnetic absorbent PPy NG coating, the energy was transformed into a large amount of heat leading to a drastic temperature increase that was simultaneously used for the instant carbonization of PPy and the decomposition of fine ferrocene particles, which resulted in multiwalled carbon nanotubes (CNTs) growth at the interface. Meanwhile, the as-grown CNTs on the surface conveyed the heat into the adjacent bulk PP and caused locally molten surface layers' formation. Eventually, the light pressure applied at the interface during the heating process squeezed the molten layers together and a new weld was generated. The method is considerably advantageous compared to other alternatives due to (i) its fast, straightforward, and affordable nature, (ii) its applicability at ambient conditions without the need of any extra equipment or chemicals, and also (iii) its ability to provide clean, durable, and functional welds, via precisely controlling process parameters, without causing any thermal distortion or physical alterations in the bulk TPM. Thus, it is believed that this novel welding process will become much preferable for the manufacturing of next-generation TPM composites in large scale, through short-term MW heating.

Apparatus and Method for Cold Welding Thin Wafers to Hard Substrates

NASA Technical Reports Server (NTRS)

Oeftering, Richard C. (Inventor); Smith, Floyd A. (Inventor)

1996-01-01

An apparatus for coating and bonding parts in a vacuum includes a floating mount assembly holding one part and applying a bonding load to the parts. A pivoting mount assembly holds one part and is pivoted between a coating position and a bonding position. At least one coating source is provided for depositing a thin film of a metal onto a surface of each of the parts to improve the cold weld between the two parts. A restraining lever controls the application of the bonding load to the parts. The coating and bonding process occurs in a vacuum chamber with a single set-up.

Towards Fast Tracking of the Keyhole Geometry

NASA Astrophysics Data System (ADS)

Brock, C.; Hohenstein, R.; Schmidt, M.

We describe a sensor principle permitting the fast online measurement of the position of the optical process emissions in deep penetration laser welding. Experiments show a strong correlation between the position of the vapour plume and the keyhole geometry, demonstrated here by varying the penetration depth of the weld. In order to achieve an absolute position measurement, the sensor was calibrated using a light source with well defined characteristics. The setup for the calibration measurements and the corresponding data evaluation methods are discussed. The precision of the calibration with a green LED is 6 μm in lateral and 55 μm in axial direction, for a working distance of 200 mm.

Occupational health concerns in the welding industry.

PubMed

Korczynski, R E

2000-12-01

The Workplace Safety and Health Branch initiated a proactive study in the welding industry in Manitoba. Eight welding companies participated in this study. Health concerns raised by welders were welders' flash, sore/red/teary eyes, headaches, nosebleeds, and a black mucous discharge from their nasal membrane. Most welders expressed concern regarding excessive smoke levels in the workplace and inadequate ventilation. Types of welding identified were MIG mild steel, MIG stainless steel, and TIG aluminum. Monitoring involved an assessment of noise levels, fume composition, and carbon monoxide and ozone concentrations. Metal analyses were according to National Institute for Occupational Safety and Health (NIOSH) Method 7300. Noise dosimeters used were the Quest model 100 and Micro 14 & 15. Carbon monoxide was monitored using the Gastech Model 4700 and ozone using the AID Portable Ozone Meter Model 560. In Manitoba, a hearing conservation program is required when the equivalent sound exposure level (normalized Lex 8-hr) exceeds 80 dBA-weighted. The American Conference of Governmental Industrial Hygienists' threshold limit value-time weighted average (ACGIH TLV-TWA) for iron is 5.0 mg/m3, manganese is 0.2 mg/m3, carbon monoxide is 25 ppm, and ozone is 0.05 ppm (heavy work), 0.08 ppm (moderate work), and 0.1 ppm (light work). Welders' personal exposures to manganese ranged from 0.01-4.93 mg/m3 (N = 42; AM = 0.5; GM = 0.2; SD +/- 0.9; GSD +/- 3.2) and to iron ranged from 0.04-16.29 mg/m3 (N = 42; AM = 3.0; GM = 1.4; SD +/- 3.5; GSD +/- 2.5). Noise exposures ranged from 79-98 dBA (N = 44; AM = 88.9; GM = 88.8; SD +/- 4.2; GSD +/- 1.0). Carbon monoxide levels were less than 5.0 ppm (at source) and ozone levels varied from 0.4-0.6 ppm (at source). Ventilation upgrades in the workplace were required in most welding shops. Only 7 percent of the welders wore respiratory protection. A hearing conservation program and hearing protection were required at all monitored workplaces.

The Landsat Phenology Study (LaPS): Preliminary CONUS Results for 2008

NASA Astrophysics Data System (ADS)

Henebry, G. M.; Roy, D.; Ju, J.; Kovalskyy, V.

2009-12-01

Most studies of land surface phenology (LSP) have used time series derived from moderate spatial resolution satellite sensor data (e.g., AVHRR, MODIS, VEGETATION) because these data are freely available and because they provide an acceptable trade-off between higher, near daily, temporal frequency of observation needed to reduce cloud contamination against lower (500m-5km) spatial resolution. The recent opening of the USGS Landsat archive to web-enabled access presents the opportunity to explore how well Landsat time series can portray LSPs at high spatial resolution. The NASA Web-enabled Landsat data (WELD) project has produced 30m composited mosaics for all the conterminous US (CONUS) from Landsat 7 ETM+ data. The composited mosaics are generated on monthly, seasonal, and annual basis and include spectral reflectance, normalized difference vegetation index (NDVI), and the acquisition date of each composited pixel. The WELD compositing approach is designed to select valid land surface observations with minimal cloud, snow, and atmospheric contamination. We extracted 30m pixel time series from the twelve monthly WELD composited mosaics for 2008 at 320 locations across the CONUS where we have ground phenological observations that are heterogeneous with respect to the types of plants observed, the phenophases recorded (predominantly spring green-up) and the ground sampling protocols used. The ground data came from several sources, including the cloned lilac/honeysuckle network, the Phenocam network, five LTER sites (H.J. Andrews, Harvard Forest, Jornada, Konza Prairie, and Sevilleta), and a private woodlot in New Hampshire. Temporal profiles of the 30m WELD Landsat NDVI and the normalized difference infrared index (NDII) derived from the composited reflectances, are compared to the ground observations. Results show that (i) inclusion of the Landsat acquisition date for each pixel improves the characterization of the LSP, (ii) the use of the NDII in conjunction with the NDVI improves identification of the onset both of canopy development and senescence, and (iii) the WELD compositing approach and the resulting mosaics provide a rich new data source for phenological investigations.

Intertidal Sandbar Welding as a Primary Source of Sediment for Dune Growth: Evidence from a Large Scale Field Experiment

NASA Astrophysics Data System (ADS)

Cohn, N.; Ruggiero, P.; de Vries, S.

2016-12-01

Dunes provide the first line of defense from elevated water levels in low-lying coastal systems, limiting potentially major flooding, economic damages, and loss of livelihood. Despite the well documented importance of healthy dunes, our predictive ability of dune growth, particularly following erosive storm events, remains poor - resulting in part from traditionally studying the wet and dry beach as separate entities. In fact, however, dune recovery and growth is closely tied to the subtidal morphology and the nearshore hydrodynamic conditions, necessitating treating the entire coastal zone from the shoreface to the backshore as an integrated system. In this context, to further improve our understanding of the physical processes allowing for beach and dune growth during fair weather conditions, a large field experiment, the Sandbar-aEolian Dune EXchange EXperiment, was performed in summer 2016 in southwestern Washington, USA. Measurements of nearshore and atmospheric hydrodynamics, in-situ sediment transport, and morphology change provide insight into the time and space scales of nearshore-beach-dune exchanges along a rapidly prograding stretch of coast over a 6 week period. As part of this experiment, the hypothesis that dune growth is limited by the welding of intertidal sandbars to the shoreline (Houser, 2009) was tested. Using laser particle counters, bed elevation sensors (sonar altimeters and Microsoft Kinect), continuously logging sediment traps, RGB and IR cameras, and repeat morphology surveys (terrestrial lidar, kite based structure from motion, and RTK GPS), spatial and temporal trends in aeolian sediment transport were assessed in relation to the synoptic onshore migration and welding of intertidal sandbars. Observations from this experiment demonstrate that (1) the intertidal zone is the primary source of sediment to the dunes during non-storm conditions, (2) rates of saltation increase during later stages of bar welding but equivalent wind conditions, and (3) alongshore variability in rates of backshore fluxes appear to be related to alongshore variability in intertidal morphology. These observations quantitatively support the Houser (2009) bar welding hypothesis and provide valuable new insights on nearshore-beach-dune sediment exchanges

Dual wire welding torch and method

DOEpatents

Diez, Fernando Martinez; Stump, Kevin S.; Ludewig, Howard W.; Kilty, Alan L.; Robinson, Matthew M.; Egland, Keith M.

2009-04-28

A welding torch includes a nozzle with a first welding wire guide configured to orient a first welding wire in a first welding wire orientation, and a second welding wire guide configured to orient a second welding wire in a second welding wire orientation that is non-coplanar and divergent with respect to the first welding wire orientation. A method of welding includes moving a welding torch with respect to a workpiece joint to be welded. During moving the welding torch, a first welding wire is fed through a first welding wire guide defining a first welding wire orientation and a second welding wire is fed through a second welding wire guide defining a second welding wire orientation that is divergent and non-coplanar with respect to the first welding wire orientation.

Quantitative assessment of the expanding complementarity between public and commercial databases of bioactive compounds.

PubMed

Southan, Christopher; Várkonyi, Péter; Muresan, Sorel

2009-07-06

Since 2004 public cheminformatic databases and their collective functionality for exploring relationships between compounds, protein sequences, literature and assay data have advanced dramatically. In parallel, commercial sources that extract and curate such relationships from journals and patents have also been expanding. This work updates a previous comparative study of databases chosen because of their bioactive content, availability of downloads and facility to select informative subsets. Where they could be calculated, extracted compounds-per-journal article were in the range of 12 to 19 but compound-per-protein counts increased with document numbers. Chemical structure filtration to facilitate standardised comparisons typically reduced source counts by between 5% and 30%. The pair-wise overlaps between 23 databases and subsets were determined, as well as changes between 2006 and 2008. While all compound sets have increased, PubChem has doubled to 14.2 million. The 2008 comparison matrix shows not only overlap but also unique content across all sources. Many of the detailed differences could be attributed to individual strategies for data selection and extraction. While there was a big increase in patent-derived structures entering PubChem since 2006, GVKBIO contains over 0.8 million unique structures from this source. Venn diagrams showed extensive overlap between compounds extracted by independent expert curation from journals by GVKBIO, WOMBAT (both commercial) and BindingDB (public) but each included unique content. In contrast, the approved drug collections from GVKBIO, MDDR (commercial) and DrugBank (public) showed surprisingly low overlap. Aggregating all commercial sources established that while 1 million compounds overlapped with PubChem 1.2 million did not. On the basis of chemical structure content per se public sources have covered an increasing proportion of commercial databases over the last two years. However, commercial products included in this study provide links between compounds and information from patents and journals at a larger scale than current public efforts. They also continue to capture a significant proportion of unique content. Our results thus demonstrate not only an encouraging overall expansion of data-supported bioactive chemical space but also that both commercial and public sources are complementary for its exploration.

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

NASA Technical Reports Server (NTRS)

Bjorkman, Gerry; Cantrell, Mark; Carter, Robert

2003-01-01

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

Heterojunction fully depleted SOI-TFET with oxide/source overlap

NASA Astrophysics Data System (ADS)

Chander, Sweta; Bhowmick, B.; Baishya, S.

2015-10-01

In this work, a hetero-junction fully depleted (FD) Silicon-on-Insulator (SOI) Tunnel Field Effect Transistor (TFET) nanostructure with oxide overlap on the Germanium-source region is proposed. Investigations using Synopsys Technology Computer Aided Design (TCAD) simulation tools reveal that the simple oxide overlap on the Germanium-source region increases the tunneling area as well as the tunneling current without degrading the band-to-band tunneling (BTBT) and improves the device performance. More importantly, the improvement is independent of gate overlap. Simulation study shows improvement in ON current, subthreshold swing (SS), OFF current, ION/IOFF ration, threshold voltage and transconductance. The proposed device with hafnium oxide (HfO2)/Aluminium Nitride (AlN) stack dielectric material offers an average subthreshold swing of 22 mV/decade and high ION/IOFF ratio (∼1010) at VDS = 0.4 V. Compared to conventional TFET, the Miller capacitance of the device shows the enhanced performance. The impact of the drain voltage variation on different parameters such as threshold voltage, subthreshold swing, transconductance, and ION/IOFF ration are also found to be satisfactory. From fabrication point of view also it is easy to utilize the existing CMOS process flows to fabricate the proposed device.

Parameter optimization of flux-aided backing-submerged arc welding by using Taguchi method

NASA Astrophysics Data System (ADS)

Pu, Juan; Yu, Shengfu; Li, Yuanyuan

2017-07-01

Flux-aided backing-submerged arc welding has been conducted on D36 steel with thickness of 20 mm. The effects of processing parameters such as welding current, voltage, welding speed and groove angle on welding quality were investigated by Taguchi method. The optimal welding parameters were predicted and the individual importance of each parameter on welding quality was evaluated by examining the signal-to-noise ratio and analysis of variance (ANOVA) results. The importance order of the welding parameters for the welding quality of weld bead was: welding current > welding speed > groove angle > welding voltage. The welding quality of weld bead increased gradually with increasing welding current and welding speed and decreasing groove angle. The optimum values of the welding current, welding speed, groove angle and welding voltage were found to be 1050 A, 27 cm/min, 40∘ and 34 V, respectively.

Feasibility of EB Welded Hastelloy X and Combination of Refractory Metals

NASA Technical Reports Server (NTRS)

Martinez, Diana A.

2004-01-01

As NASA continues to expand its horizon, exploration and discovery creates the need of advancement in technology. The Jupiter Icy Moon Orbiter's (JIMO) mission to explore and document the outer surfaces, rate the possibility of holding potential life forms, etc. within the three moons (Callisto, Ganymede, and Europa) proves to be challenging. The orbiter itself consists of many sections including: the nuclear reactor and the power conversion system, the radiator panels, and the thrusters and antenna. The nuclear reactor serves as a power source, and if successfully developed, can operate for extended periods. During the duration of my tenure at NASA Glenn Research Center's (NASA GRC) Advanced Metallics Branch, I was assigned to assist Frank J. Ritzert on analyzing the feasibility of the Electron Beam Welded Hastelloy X (HX), a nickel-based superalloy, to Niobium- 1 %Zirconium (Nb-1 Zr) and other refractory metals/alloys including Tantalum, Molybdenum, Tungsten, and Rhenium alloys. This welding technique is going to be used for the nuclear reactor within JIMO.

Laser Spot Welding of Copper-aluminum Joints Using a Pulsed Dual Wavelength Laser at 532 and 1064 nm

NASA Astrophysics Data System (ADS)

Stritt, Peter; Hagenlocher, Christian; Kizler, Christine; Weber, Rudolf; Rüttimann, Christoph; Graf, Thomas

A modulated pulsed laser source emitting green and infrared laser light is used to join the dissimilar metals copper and aluminum. The resultant dynamic welding process is analyzed using the back reflected laser light and high speed video observations of the interaction zone. Different pulse shapes are applied to influence the melt pool dynamics and thereby the forming grain structure and intermetallic phases. The results of high-speed images and back-reflections prove that a modulation of the pulse shape is transferred to oscillations of the melt pool at the applied frequency. The outcome of the melt pool oscillation is shown by the metallurgically prepared cross-section, which indicates different solidification lines and grain shapes. An energy-dispersivex-ray analysis shows the mixture and the resultant distribution of the two metals, copper and aluminum, within the spot weld. It can be seen that the mixture is homogenized the observed melt pool oscillations.

Single-sensor multispeaker listening with acoustic metamaterials

PubMed Central

Xie, Yangbo; Tsai, Tsung-Han; Konneker, Adam; Popa, Bogdan-Ioan; Brady, David J.; Cummer, Steven A.

2015-01-01

Designing a “cocktail party listener” that functionally mimics the selective perception of a human auditory system has been pursued over the past decades. By exploiting acoustic metamaterials and compressive sensing, we present here a single-sensor listening device that separates simultaneous overlapping sounds from different sources. The device with a compact array of resonant metamaterials is demonstrated to distinguish three overlapping and independent sources with 96.67% correct audio recognition. Segregation of the audio signals is achieved using physical layer encoding without relying on source characteristics. This hardware approach to multichannel source separation can be applied to robust speech recognition and hearing aids and may be extended to other acoustic imaging and sensing applications. PMID:26261314

Welding fumes from stainless steel gas metal arc processes contain multiple manganese chemical species.

PubMed

Keane, Michael; Stone, Samuel; Chen, Bean

2010-05-01

Fumes from a group of gas metal arc welding (GMAW) processes used on stainless steel were generated using three different metal transfer modes and four different shield gases. The objective was to identify and measure manganese (Mn) species in the fumes, and identify processes that are minimal generators of Mn species. The robotic welding system was operated in short-circuit (SC) mode (Ar/CO2 and He/Ar), axial spray (AXS) mode (Ar/O2 and Ar/CO2), and pulsed axial-spray (PAXS) mode (Ar/O2). The fumes were analyzed for Mn by a sequential extraction process followed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analysis, and by X-ray diffraction (XRD). Total elemental Mn, iron (Fe), chromium (Cr) and nickel (Ni) were separately measured after aqua regia digestion and ICP-AES analysis. Soluble Mn2+, Fe2+, Fe3+, and Ni2+ in a simple biological buffer (phosphate-buffered saline) were determined at pH 7.2 and 5.0 after 2 h incubation at 37 C by ion chromatography. Results indicate that Mn was present in soluble form, acid-soluble form, and acid-soluble form after reduction by hydroxylamine, which represents soluble Mn0 and Mn2+ compounds, other Mn2+ compounds, and (Mn3+ and Mn4+) compounds, respectively. The dominant fraction was the acid-soluble Mn2+ fraction, but results varied with the process and shield gas. Soluble Mn mass percent in the fume ranged from 0.2 to 0.9%, acid-soluble Mn2+ compounds ranged from 2.6 to 9.3%, and acid plus reducing agent-soluble (Mn3+ and Mn4+) compounds ranged from 0.6 to 5.1%. Total Mn composition ranged from 7 to 15%. XRD results showed fumes had a crystalline content of 90-99% Fe3O4, and showed evidence of multiple Mn oxides, but overlaps and weak signals limited identification. Small amounts of the Mn2+ in the fume (<0.01 to ≈ 1% or <0.1 to ≈ 10 microg ml(-1)) and Ni2+ (<0.01 to ≈ 0.2% or <0.1 to ≈ 2 mg ml(-1)) ions were found in biological buffer media, but amounts were highly dependent on pH and the welding process. Mn generation rates for the fractions were tabulated, and the influence of ozone is discussed. The conclusions are that exposures to welding fumes include multiple Mn species, both soluble and insoluble, and that exposures to Mn species vary with specific processes and shield gases.

Submillimeter bolt location in car bodywork for production line quality inspection

NASA Astrophysics Data System (ADS)

Altamirano-Robles, Leopoldo; Arias-Estrada, Miguel; Alviso-Quibrera, Samuel; Lopez-Lopez, Aurelio

2000-03-01

In the automotive industry, a vehicle begins with the construction of the vehicle floor. Later on, several robots weld a series of bolts to this floor which are used to fix other parts. Due to several problems, like welding tools wearing, robot miscalibration or momentary low power supply, among others, some bolts are incorrectly positioned or are not present at all, bringing problems and delays in the next work cells. Therefore, it is of importance to verify the quality of welded parts before the following assembly steps. A computer vision system is proposed in order to locate autonomously the presence and quality of the bolts. The system should carry on the inspection in real time at the car assembly line under the following conditions: without touching the bodywork, with a precision in the submillimeter range and in few seconds. In this paper we present a basic computer vision system for bolt location in the submillimeter range. We analyze three arrangements of the system components (camera and illumination sources) that produce different results in the localization. Results are presented and compared for the three approaches obtained under laboratory conditions. The algorithms were tested in the assembling line. Variations up to one millimeter in the welded position of the bolts were observed.

Underwater laser weld bowing distortion behavior and mechanism of thin 304 stainless steel plates

NASA Astrophysics Data System (ADS)

Huang, ZunYue; Luo, Zhen; Ao, Sansan; Cai, YangChuan

2018-10-01

Underwater laser weld bowing distortion behavior and mechanism of thin 304 stainless steel plates are studied in the paper. The influence of underwater laser welding parameters (such as laser power, welding speed, defocusing distance and gas flow rate) on weld bowing distortion was investigated through central composite rotatable design and an orthogonal test. A quadratic response model was established to evaluate the underwater laser weld bowing distortion by central composite rotatable design and the order of the impacts of the welding parameters on weld bowing distortion was studied by an orthogonal test. The weld bowing distortion after welding was determined by the digital image correlation technique. The weld bowing distortion of in-air laser welding and underwater laser welding were compared and it revealed that the shape of the in-air and underwater laser welded specimens are the same, but the weld bowing distortion amount of in-air welding is larger than that of underwater welding. Weld bowing distortion mechanism was studied by the digital image correlation technique, and it was demonstrated that weld bowing distortion is associated with the welding plate temperature gradient during laser welding. The wider weld width also resulted in larger weld bowing distortion.

A Low-Cost, Effective, Fumes Exhaust System.

ERIC Educational Resources Information Center

Jacobs, C. O.

1979-01-01

Discusses the importance of avoiding welding fumes. The sources of these fumes are presented in a table. Criticizes currently used ventilation systems and reviews the Occupational Safety and Health Act requirements. Describes a low-cost exhaust system developed for agricultural mechanics laboratories. (LRA)

Target/error overlap in jargonaphasia: The case for a one-source model, lexical and non-lexical summation, and the special status of correct responses.

PubMed

Olson, Andrew; Halloran, Elizabeth; Romani, Cristina

2015-12-01

We present three jargonaphasic patients who made phonological errors in naming, repetition and reading. We analyse target/response overlap using statistical models to answer three questions: 1) Is there a single phonological source for errors or two sources, one for target-related errors and a separate source for abstruse errors? 2) Can correct responses be predicted by the same distribution used to predict errors or do they show a completion boost (CB)? 3) Is non-lexical and lexical information summed during reading and repetition? The answers were clear. 1) Abstruse errors did not require a separate distribution created by failure to access word forms. Abstruse and target-related errors were the endpoints of a single overlap distribution. 2) Correct responses required a special factor, e.g., a CB or lexical/phonological feedback, to preserve their integrity. 3) Reading and repetition required separate lexical and non-lexical contributions that were combined at output. Copyright © 2015 Elsevier Ltd. All rights reserved.

New stratigraphic, chronologic, and magnetic fabric constraints for Neogene and Quaternary ignimbrites in the Central Andes (South Peru)

NASA Astrophysics Data System (ADS)

De La Rupelle, A.; Thouret, J. C.; Cubukcu, H. E.; Jicha, B.; Bréard, E.; Gerbe, M.-C.; Le Pennec, J.-L.; Diot, H.; Boivin, P.

2012-04-01

Central Andean deformation history in southern Peru is recorded in Neogene volcanic units of Ocoña and Cotahuasi canyons that cut across the western Cordillera. Acceleration (<25 Ma) of uplift in the region is reflected in the Neogene epiclastic deposits with interspersed and subsequent rhyolitic ignimbrites between 24.6 and 1.37 Ma. Large-volume (>100 km3) Nazca (c.24.6 Ma), Alpabamba (19.4-18.0 Ma), and Huaylillas (14.25-12.7 Ma) ignimbrite sheets preceded the canyon incision, whereas sheets of smaller volume (<50 km3), Caraveli (9.5-8.9 Ma), Lower (5.13-3.6 Ma) and Upper Sencca (c.2 Ma) and Las Lomas (c.1.56-1.37 Ma), were deposited during canyon incision and are interspersed with Lower and Upper Barroso lava flows. The Alpabamba compound ignimbrite sheets comprise a vitrophyre at the base, grading into a strongly welded, eutaxitic, crystal-rich facies overlain by a thick, multi-bedded ash-flow tuff and a lithic-rich, indurated flow unit. The Huaylillas ignimbrite sheet comprises a strongly welded, crystal-rich, lithic-poor, columnar lithofacies, with devitrified pumice. The Caraveli ignimbrite sheet has a jointed vitrophyre overlain by a welded, blocky, crystal-rich flow unit. A vacuolar, saccharolytic unit forms the top of the sequence. The Lower Sencca ignimbrite sheet comprises of a basal vitrophyre and a slightly welded, fibrous pumice-rich flow unit, which grades into a welded, vapor-phase unit that contains more crystals than pumice and lithics. The Upper Sencca ignimbrite sheet consists of a black vitrophyre, grading into a strongly welded, crystal-rich, eutaxitic cooling unit. The latter is capped by a slightly welded unit, and an indurated pumice-rich, crystal-poor vapour-phase facies. Quaternary valley-fill termed Las Lomas consists of unwelded, crystal-poor pumice-flow deposits. Eighteen new 40Ar/39Ar analyses have been carried out on feldspar/glass separates from pumice and lavas. Results for the Caraveli ignimbrite (9.35±0.06 Ma), Upper Barroso lavas (2.24±0.45 Ma) and Upper Sencca ignimbrite (2.00-2.06±0.09 Ma) are in good agreement with previous data. New ages for the Lower Barroso lavas (7.32±0.05; 5.36±0.12 Ma) and Lower Sencca ignimbrites (5.13±0.01, 5.09±0.03, 4.65±0.11, 4.36 ± 0.16) extend their temporal history towards older times. Lower Barroso lava flow activity occurred as early as~7.3 and lasted until 5.4 Ma just before the Lower Sencca eruptions. The Lower Sencca ignimbrites spanned at least 1.5 Ma and are larger and more widespread than the Upper Sencca ignimbrites, which may have formed in one pulse around 2 Ma. The Anisotropy of Magnetic Susceptibility (AMS) method and the magnetic fabric at 24 sites have been used to indicate flow directions and to infer the source location of the rhyolitic ignimbrites. Mean directions and confidence cones were calculated using Bingham statistics. Most AMS ellipsoids are oblate with near-vertical, slightly imbricated minimum susceptibility directions. The magnetic signal is dominantly carried by coarse multi-domain and a few fine single-domain grains of titanomagnetite. Inferred transport directions based on AMS results reveal that the source of Huaylillas, Lower Sencca and Upper Sencca units is probably located below the Nevado Coropuna volcano. The source of the Caraveli unit points to a depression W of Nevado Sara Sara. The Alpabamba source could not be clearly determined. Keywords: ignimbrites, Peru, stratigraphy, chronology, AMS, fabric, Neogene, Quaternary.

Toward a complete dataset of drug-drug interaction information from publicly available sources.

PubMed

Ayvaz, Serkan; Horn, John; Hassanzadeh, Oktie; Zhu, Qian; Stan, Johann; Tatonetti, Nicholas P; Vilar, Santiago; Brochhausen, Mathias; Samwald, Matthias; Rastegar-Mojarad, Majid; Dumontier, Michel; Boyce, Richard D

2015-06-01

Although potential drug-drug interactions (PDDIs) are a significant source of preventable drug-related harm, there is currently no single complete source of PDDI information. In the current study, all publically available sources of PDDI information that could be identified using a comprehensive and broad search were combined into a single dataset. The combined dataset merged fourteen different sources including 5 clinically-oriented information sources, 4 Natural Language Processing (NLP) Corpora, and 5 Bioinformatics/Pharmacovigilance information sources. As a comprehensive PDDI source, the merged dataset might benefit the pharmacovigilance text mining community by making it possible to compare the representativeness of NLP corpora for PDDI text extraction tasks, and specifying elements that can be useful for future PDDI extraction purposes. An analysis of the overlap between and across the data sources showed that there was little overlap. Even comprehensive PDDI lists such as DrugBank, KEGG, and the NDF-RT had less than 50% overlap with each other. Moreover, all of the comprehensive lists had incomplete coverage of two data sources that focus on PDDIs of interest in most clinical settings. Based on this information, we think that systems that provide access to the comprehensive lists, such as APIs into RxNorm, should be careful to inform users that the lists may be incomplete with respect to PDDIs that drug experts suggest clinicians be aware of. In spite of the low degree of overlap, several dozen cases were identified where PDDI information provided in drug product labeling might be augmented by the merged dataset. Moreover, the combined dataset was also shown to improve the performance of an existing PDDI NLP pipeline and a recently published PDDI pharmacovigilance protocol. Future work will focus on improvement of the methods for mapping between PDDI information sources, identifying methods to improve the use of the merged dataset in PDDI NLP algorithms, integrating high-quality PDDI information from the merged dataset into Wikidata, and making the combined dataset accessible as Semantic Web Linked Data. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Cable attachment for a radioactive brachytherapy source capsule

DOEpatents

Gross, Ian G; Pierce, Larry A

2006-07-18

In cancer brachytherapy treatment, a small californium-252 neutron source capsule is attached to a guide cable using a modified crimping technique. The guide cable has a solid cylindrical end, and the attachment employs circumferential grooves micromachined in the solid cable end. The attachment was designed and tested, and hardware fabricated for use inside a radioactive hot cell. A welding step typically required in other cable attachments is avoided.

Design considerations for near-infrared filter photometry: effects of noise sources and selectivity.

PubMed

Tarumi, Toshiyasu; Amerov, Airat K; Arnold, Mark A; Small, Gary W

2009-06-01

Optimal filter design of two-channel near-infrared filter photometers is investigated for simulated two-component systems consisting of an analyte and a spectrally overlapping interferent. The degree of overlap between the analyte and interferent bands is varied over three levels. The optimal design is obtained for three cases: a source or background flicker noise limited case, a shot noise limited case, and a detector noise limited case. Conventional photometers consist of narrow-band optical filters with their bands located at discrete wavelengths. However, the use of broadband optical filters with overlapping responses has been proposed to obtain as much signal as possible from a weak and broad analyte band typical of near-infrared absorptions. One question regarding the use of broadband optical filters with overlapping responses is the selectivity achieved by such filters. The selectivity of two-channel photometers is evaluated on the basis of the angle between the analyte and interferent vectors in the space spanned by the relative change recorded for each of the two detector channels. This study shows that for the shot noise limited or detector noise limited cases, the slight decrease in selectivity with the use of broadband optical filters can be compensated by the higher signal-to-noise ratio afforded by the use of such filters. For the source noise limited case, the best quantitative results are obtained with the use of narrow-band non-overlapping optical filters.

Evaluating optical hazards from plasma arc cutting.

PubMed

Glassford, Eric; Burr, Gregory

2018-01-01

The Health Hazard Evaluation Program of the National Institute for Occupational Safety and Health evaluated a steel building materials manufacturer. The employer requested the evaluation because of concerns about optical radiation hazards from a plasma arc cutting system and the need to clarify eye protection requirements for plasma operators, other employees, and visitors. The strength of the ultraviolet radiation, visible radiation (light), and infrared radiation generated by the plasma arc cutter was measured at various distances from the source and at different operating amperages. Investigators also observed employees performing the plasma arc cutting. Optical radiation above safe levels for the unprotected eyes in the ultraviolet-C, ultraviolet-B, and visible light ranges were found during plasma arc cutting. In contrast, infrared and ultraviolet-A radiation levels during plasma arc cutting were similar to background levels. The highest non-ionizing radiation exposures occurred when no welding curtains were used. A plasma arc welding curtain in place did not eliminate optical radiation hazards to the plasma arc operator or to nearby employees. In most instances, the measured intensities for visible light, UV-C, and UV-B resulted in welding shade lens numbers that were lower than those stipulated in the OSHA Filter Lenses for Protection Against Radiant Energy table in 29 CFR 1910.133(a)(5). [1] Investigators recommended using a welding curtain that enclosed the plasma arc, posting optical radiation warning signs in the plasma arc cutter area, installing audible or visual warning cues when the plasma arc cutter was operating, and using welding shades that covered the plasma arc cutter operator's face to protect skin from ultraviolet radiation hazards.

Study of Compatibility of Stainless Steel Weld Joints with Liquid Sodium-Potassium Coolants for Fission Surface Power Reactors for Lunar and Space Applications

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

Grossbeck, Martin; Qualls, Louis

To make a manned mission to the surface of the moon or to Mars with any significant residence time, the power requirements will make a nuclear reactor the most feasible source of energy. To prepare for such a mission, NASA has teamed with the DOE to develop Fission Surface Power technology with the goal of developing viable options. The Fission Surface Power System (FSPS) recommended as the initial baseline design includes a liquid metal reactor and primary coolant system that transfers heat to two intermediate liquid metal heat transfer loops. Each intermediate loop transfers heat to two Stirling heat exchangersmore » that each power two Stirling converters. Both the primary and the intermediate loops will use sodium-potassium (NaK) as the liquid metal coolant, and the primary loop will operate at temperatures exceeding 600°C. The alloy selected for the heat exchangers and piping is AISI Type 316L stainless steel. The extensive experience with NaK in breeder reactor programs and with earlier space reactors for unmanned missions lends considerable confidence in using NaK as a coolant in contact with stainless steel alloys. However, the microstructure, chemical segregation, and stress state of a weld leads to the potential for corrosion and cracking. Such failures have been experienced in NaK systems that have operated for times less than the eight year goal for the FSPS. For this reason, it was necessary to evaluate candidate weld techniques and expose welds to high-temperature, flowing NaK in a closed, closely controlled system. The goal of this project was to determine the optimum weld configuration for a NaK system that will withstand service for eight years under FSPS conditions. Since the most difficult weld to make and to evaluate is the tube to tube sheet weld in the intermediate heat exchangers, it was the focus of this research. A pumped loop of flowing NaK was fabricated for exposure of candidate weld specimens at temperatures of 600°C, the expected temperature within the intermediate heat exchangers. Since metal transfer from a high-temperature region to a cooler region is a predominant mode of corrosion in liquid metal systems, specimens were placed at zones in the loop at the above temperature to evaluate the effects of both alloy component leaching and metal deposition. Microstructural analysis was performed to evaluate weld performance on control weld specimens. The research was coordinated with Oak Ridge National Laboratory (ORNL) where most of the weld samples were prepared. In addition, ORNL participated in the loop operation to assist in keeping the testing relevant to the project and to take advantage of the extensive experience in liquid metal research at ORNL.« less

Visualising inter-subject variability in fMRI using threshold-weighted overlap maps

NASA Astrophysics Data System (ADS)

Seghier, Mohamed L.; Price, Cathy J.

2016-02-01

Functional neuroimaging studies are revealing the neural systems sustaining many sensory, motor and cognitive abilities. A proper understanding of these systems requires an appreciation of the degree to which they vary across subjects. Some sources of inter-subject variability might be easy to measure (demographics, behavioural scores, or experimental factors), while others are more difficult (cognitive strategies, learning effects, and other hidden sources). Here, we introduce a simple way of visualising whole-brain consistency and variability in brain responses across subjects using threshold-weighted voxel-based overlap maps. The output quantifies the proportion of subjects activating a particular voxel or region over a wide range of statistical thresholds. The sensitivity of our approach was assessed in 30 healthy adults performing a matching task with their dominant hand. We show how overlap maps revealed many effects that were only present in a subsample of our group; we discuss how overlap maps can provide information that may be missed or misrepresented by standard group analysis, and how this information can help users to understand their data. In particular, we emphasize that functional overlap maps can be particularly useful when it comes to explaining typical (or atypical) compensatory mechanisms used by patients following brain damage.

40 CFR 420.71 - Specialized definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... tube mill means those steel hot forming operations that produce butt welded or seamless tubular steel... AND STANDARDS IRON AND STEEL MANUFACTURING POINT SOURCE CATEGORY Hot Forming Subcategory § 420.71 Specialized definitions. (a) The term hot forming means those steel operations in which solidified, heated...

Hydrogen mitigation in submerged arc welding

NASA Astrophysics Data System (ADS)

Klimowicz, Steven

With the role of hydrogen in weld metal well understood in its relation to cold cracking, there has been a push to produce welds with lower and lower diffusible hydrogen contents. The push for lower diffusible hydrogen contents has placed pressure on consumables manufactures to create consumables that can achieve the requirements for lower diffusible hydrogen content. Currently EM12K flux is produced so that it can achieve below 4 ml of diffusible hydrogen for every 100g of weld metal deposited (ml/100g) for submerged arc welding (SAW). The recent trend for industry is to preferentially achieve diffusible hydrogen contents below 3 ml/100g. Making it necessary to find a way to modify the flux to achieve a lower diffusible hydrogen content for the welds it produces. To achieve this goal a two phase plan was developed. The first phase was to characterize the entire welding system for hydrogen. Since the goal of the project is hydrogen mitigation, any amount of hydrogen that could be reduced is helpful and therefore must first be discovered. Sources of hydrogen may be found by analyzing the welding wire and base metal, as well as breaking the flux down into its components and production steps. The wire was analyzed for total hydrogen content as was the base metal. The flux and its components were analyzed using differential thermal analysis-simultaneous thermal analysis (DTA-STA) and later vacuum degassing for moisture content. The analysis of the wire showed that the copper coating on the wire was the largest contributor of hydrogen. There was lubricant present on the wire surface as well, but it did not contribute as much as the copper coating. It was found that a simple low temperature baking of the wire was enough to remove the lubricant and coating moisture. The base metal was found to have a similar total hydrogen content to that of the wire. The breakdown of the flux and production process for moisture content analysis revealed that the production process removes the moisture that is added by the water based binder. The second phase of the project was to modify the flux with fluoride additions to remove hydrogen from the arc while welding. The introduction of fluorine into the arc would lower the amount of hydrogen that may be absorbed as diffusible hydrogen by the weld metal. To select the fluorides a series of thermodynamic calculations were performed as well as simple tests to determine the fluorides behavior in a welding arc and flux. From these tests the following fluorides were selected to be used to be added to EM12K flux as oneweight percent additions: SrF 2, K2TiF6, K2SiF6, and LiF. Welds were then run with the experimental fluxes according to AWS A4.3 standard for diffusible hydrogen testing. From these tests it was found that none experimental fluxes were able to achieve a diffusible hydrogen content lower than the original EM12K flux. It was also found that fluoride reduction in a simple flux is a better predictor of fluoride effectiveness than decomposition temperature.

The influence of process parameters on porosity formation in hybrid LASER-GMA welding of AA6082 aluminum alloy

NASA Astrophysics Data System (ADS)

Ascari, Alessandro; Fortunato, Alessandro; Orazi, Leonardo; Campana, Giampaolo

2012-07-01

This paper deals with an experimental campaign carried out on AA6082 8 mm thick plates in order to investigate the role of process parameters on porosity formation in hybrid LASER-GMA welding. Bead on plate weldments were obtained on the above mentioned aluminum alloy considering the variation of the following process parameters: GMAW current (120 and 180 A for short-arc mode, 90 and 130 A for pulsed-arc mode), arc transfer mode (short-arc and pulsed-arc) and mutual distance between arc and LASER sources (0, 3 and 6 mm). Porosities occurring in the fused zone were observed by means of X-ray inspection and measured exploiting an image analysis software. In order to understand the possible correlation between process parameters and porosity formation an analysis of variance statistical approach was exploited. The obtained results pointed out that GMAW current is significant on porosity formation, while the distance between the sources do not affect this aspect.

Underclad cracking of pressure vessel steels for light-water reactors

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

Lopez, H.F.

1987-06-01

Although fracture mechanics analyses have shown that underclad cracks have no detrimental effect on the integrity of thick walled pressure vessels (40 year service), in order to avoid unexpected failures the US Nuclear Regulatory Commission has issued Regulatory Guide 1.43 which sets limits on the extent of fissures permitted and describes acceptable means of controlling the weld cladding processes. Cavitation and intergranular fissuring in SA508-2 and 22NiMoCr37 steels can occur in the presence or absence of intergranular particles. The observations of intergranular fissuring and cavitation in those HAZ free from overlapping effects are attributed to grain boundary segregation. Other probablemore » void nucleation sites are the grain boundary-lath interface intersections which facilitate the formation of grain boundary discontinuities.« less

Investigation on mechanical properties of welded material under different types of welding filler (shielded metal arc welding)

NASA Astrophysics Data System (ADS)

Tahir, Abdullah Mohd; Lair, Noor Ajian Mohd; Wei, Foo Jun

2018-05-01

The Shielded Metal Arc Welding (SMAW) is (or the Stick welding) defined as a welding process, which melts and joins metals with an arc between a welding filler (electrode rod) and the workpieces. The main objective was to study the mechanical properties of welded metal under different types of welding fillers and current for SMAW. This project utilized the Design of Experiment (DOE) by adopting the Full Factorial Design. The independent variables were the types of welding filler and welding current, whereas the other welding parameters were fixed at the optimum value. The levels for types of welding filler were by the models of welding filler (E6013, E7016 and E7018) used and the levels for welding current were 80A and 90A. The responses were the mechanical properties of welded material, which include tensile strength and hardness. The experiment was analyzed using the two way ANOVA. The results prove that there are significant effects of welding filler types and current levels on the tensile strength and hardness of the welded metal. At the same time, the ANOVA results and interaction plot indicate that there are significant interactions between the welding filler types and the welding current on both the hardness and tensile strength of the welded metals, which has never been reported before. This project found that when the amount of heat input with increase, the mechanical properties such as tensile strength and hardness decrease. The optimum tensile strength for welded metal is produced by the welding filler E7016 and the optimum of hardness of welded metal is produced by the welding filler E7018 at welding current of 80A.

Study of Gravity Effects on Titanium Laser Welding in the Vertical Position

PubMed Central

Yuan, Zhang; Pu, Haitao; Li, Haigang; Cheng, Hao; Du, Dong; Shan, Jiguo

2017-01-01

To obtain satisfactory welds in positional laser beam welding, it is necessary to know how process parameters will influence the quality of welds in different welding positions. In this study, the titanium alloy Ti6Al4V sheets were laser welded in two vertical welding positions (vertical up and vertical down), and the appearance, porosity, strength, and ductility of the laser joints were evaluated. Results show that undercuts of the vertical up welds were greater than that of vertical down welds, while the porosity contents were much higher in vertical down welds than that in vertical up welds. When welding with a higher heat input, the vertical up welding position resulted in poor weld profiles (undercuts and burn-through holes), whereas the vertical down welding position led to excessive porosity contents in welds. Both severe undercut and excessive porosity were detrimental to the tensile properties of the welds. Weld appearance was improved and porosity contents were reduced by using a lower heat input, achieving better weld quality. Therefore, it is suggested that process parameter settings with relatively high laser powers and welding speeds, which can result in lower heat inputs, are used when laser welding the Ti6Al4V titanium alloys vertically. PMID:28885573

Study of Gravity Effects on Titanium Laser Welding in the Vertical Position.

PubMed

Chang, Baohua; Yuan, Zhang; Pu, Haitao; Li, Haigang; Cheng, Hao; Du, Dong; Shan, Jiguo

2017-09-08

To obtain satisfactory welds in positional laser beam welding, it is necessary to know how process parameters will influence the quality of welds in different welding positions. In this study, the titanium alloy Ti6Al4V sheets were laser welded in two vertical welding positions (vertical up and vertical down), and the appearance, porosity, strength, and ductility of the laser joints were evaluated. Results show that undercuts of the vertical up welds were greater than that of vertical down welds, while the porosity contents were much higher in vertical down welds than that in vertical up welds. When welding with a higher heat input, the vertical up welding position resulted in poor weld profiles (undercuts and burn-through holes), whereas the vertical down welding position led to excessive porosity contents in welds. Both severe undercut and excessive porosity were detrimental to the tensile properties of the welds. Weld appearance was improved and porosity contents were reduced by using a lower heat input, achieving better weld quality. Therefore, it is suggested that process parameter settings with relatively high laser powers and welding speeds, which can result in lower heat inputs, are used when laser welding the Ti6Al4V titanium alloys vertically.

[Spectra and thermal analysis of the arc in activating flux plasma arc welding].

PubMed

Chai, Guo-Ming; Zhu, Yi-Feng

2010-04-01

In activating flux plasma arc welding the welding arc was analyzed by spectra analysis technique, and the welding arc temperature field was measured by the infrared sensing and computer image technique. The distribution models of welding arc heat flow density of activating flux PAW welding were developed. The composition of welding arc affected by activated flux was studied, and the welding arc temperature field was studied. The results show that the spectral lines of argon atom and ionized argon atom of primary ionization are the main spectra lines of the conventional plasma welding arc. The spectra lines of weld metal are inappreciable in the spectra lines of the conventional plasma welding arc. The gas particle is the main in the conventional plasma welding arc. The conventional plasma welding arc is gas welding arc. The spectra lines of argon atom and ionized argon atom of primary ionization are intensified in the activating flux plasma welding arc, and the spectra lines of Ti, Cr and Fe elements are found in the activating flux plasma welding arc. The welding arc temperature distribution in activating flux plasma arc welding is compact, the outline of the welding arc temperature field is narrow, the range of the welding arc temperature distribution is concentrated, the welding arc radial temperature gradient is large, and the welding arc radial temperature gradient shows normal Gauss distribution.

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

NASA Astrophysics Data System (ADS)

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

2016-11-01

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

Comparing Laser Welding Technologies with Friction Stir Welding for Production of Aluminum Tailor-Welded Blanks

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

Hovanski, Yuri; Carsley, John; Carlson, Blair

2014-01-15

A comparison of welding techniques was performed to determine the most effective method for producing aluminum tailor-welded blanks for high volume automotive applications. Aluminum sheet was joined with an emphasis on post weld formability, surface quality and weld speed. Comparative results from several laser based welding techniques along with friction stir welding are presented. The results of this study demonstrate a quantitative comparison of weld methodologies in preparing tailor-welded aluminum stampings for high volume production in the automotive industry. Evaluation of nearly a dozen welding variations ultimately led to down selecting a single process based on post-weld quality and performance.

On the ground state of Yang-Mills theory

NASA Astrophysics Data System (ADS)

Bakry, Ahmed S.; Leinweber, Derek B.; Williams, Anthony G.

2011-08-01

We investigate the overlap of the ground state meson potential with sets of mesonic-trial wave functions corresponding to different gluonic distributions. We probe the transverse structure of the flux tube through the creation of non-uniform smearing profiles for the string of glue connecting two color sources in Wilson loop operator. The non-uniformly UV-regulated flux-tube operators are found to optimize the overlap with the ground state and display interesting features in the ground state overlap.

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.

GTA welding and heat treating of high purity aluminum. [-452/sup 0/F

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

Voigt, R.C.; Loper, C.R. Jr.

1979-01-01

Gas tungsten arc welding is a suitable way to join high purity aluminum with only small increases in the electrical resistivity at 4.2 K (i.e., -269 C or -452 F) if proper welding procedures are used. High purity aluminum weld zone properties, useful for the design of cryogenic superconducting devices, are now available. The additional electrical resistivity caused by welding is independent of original base metal resistivity and can be decreased significantly by heat treatments as low as 260 C (500 F) for 30 minutes. Tungsten contamination caused from welding is small (on the order of 0.2 ppM) but itmore » is a significant contribution to weld zone resistivity. This suggests that other welding techniques such as laser welding or electron beam welding may be successful alternatives. Additional GTA welding tests for various welding conditions and welding procedures would lead to a greater understanding of the tungsten emission levels during welding. Perturbations during GTA welding such as electrode spitting or electrode contact with the weld metal must be eliminated to successfully weld high purity aluminum. Improper welding techniques causing arc instabilities, for any reason, cause highly resistive welds that must be properly repaired.« less

Adoption of High Performance Computational (HPC) Modeling Software for Widespread Use in the Manufacture of Welded Structures

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

Brust, Frederick W.; Punch, Edward F.; Twombly, Elizabeth Kurth

This report summarizes the final product developed for the US DOE Small Business Innovation Research (SBIR) Phase II grant made to Engineering Mechanics Corporation of Columbus (Emc 2) between April 16, 2014 and August 31, 2016 titled ‘Adoption of High Performance Computational (HPC) Modeling Software for Widespread Use in the Manufacture of Welded Structures’. Many US companies have moved fabrication and production facilities off shore because of cheaper labor costs. A key aspect in bringing these jobs back to the US is the use of technology to render US-made fabrications more cost-efficient overall with higher quality. One significant advantage thatmore » has emerged in the US over the last two decades is the use of virtual design for fabrication of small and large structures in weld fabrication industries. Industries that use virtual design and analysis tools have reduced material part size, developed environmentally-friendly fabrication processes, improved product quality and performance, and reduced manufacturing costs. Indeed, Caterpillar Inc. (CAT), one of the partners in this effort, continues to have a large fabrication presence in the US because of the use of weld fabrication modeling to optimize fabrications by controlling weld residual stresses and distortions and improving fatigue, corrosion, and fracture performance. This report describes Emc 2’s DOE SBIR Phase II final results to extend an existing, state-of-the-art software code, Virtual Fabrication Technology (VFT®), currently used to design and model large welded structures prior to fabrication - to a broader range of products with widespread applications for small and medium-sized enterprises (SMEs). VFT® helps control distortion, can minimize and/or control residual stresses, control welding microstructure, and pre-determine welding parameters such as weld-sequencing, pre-bending, thermal-tensioning, etc. VFT® uses material properties, consumable properties, etc. as inputs. Through VFT®, manufacturing companies can avoid costly design changes after fabrication. This leads to the concept of joint design/fabrication where these important disciplines are intimately linked to minimize fabrication costs. Finally service performance (such as fatigue, corrosion, and fracture/damage) can be improved using this product. Emc 2’s DOE SBIR Phase II effort successfully adapted VFT® to perform efficiently in an HPC environment independent of commercial software on a platform to permit easy and cost effective access to the code. This provides the key for SMEs to access this sophisticated and proven methodology that is quick, accurate, cost effective and available “on-demand” to address weld-simulation and fabrication problems prior to manufacture. In addition, other organizations, such as Government agencies and large companies, may have a need for spot use of such a tool. The open source code, WARP3D, a high performance finite element code used in fracture and damage assessment of structures, was significantly modified so computational weld problems can be solved efficiently on multiple processors and threads with VFT®. The thermal solver for VFT®, based on a series of closed form solution approximations, was extensively enhanced for solution on multiple processors greatly increasing overall speed. In addition, the graphical user interface (GUI) was re-written to permit SMEs access to an HPC environment at the Ohio Super Computer Center (OSC) to integrate these solutions with WARP3D. The GUI is used to define all weld pass descriptions, number of passes, material properties, consumable properties, weld speed, etc. for the structure to be modeled. The GUI was enhanced to make it more user-friendly so that non-experts can perform weld modeling. Finally, an extensive outreach program to market this capability to fabrication companies was performed. This access will permit SMEs to perform weld modeling to improve their competitiveness at a reasonable cost.« less

The technology and welding joint properties of hybrid laser-tig welding on thick plate

NASA Astrophysics Data System (ADS)

Shenghai, Zhang; Yifu, Shen; Huijuan, Qiu

2013-06-01

The technologies of autogenous laser welding and hybrid laser-TIG welding are used on thick plate of high strength lower alloy structural steel 10CrNiMnMoV in this article. The unique advantages of hybrid laser-TIG welding is summarized by comparing and analyzing the process parameters and welding joints of autogenous laser welding laser welding and hybrid laser-TIG welding. With the optimal process parameters of hybrid welding, the good welding joint without visible flaws can be obtained and its mechanical properties are tested according to industry standards. The results show that the hybrid welding technology has certain advantages and possibility in welding thick plates. It can reduce the demands of laser power, and it is significant for lowering the aspect ratio of weld during hybrid welding, so the gas in the molten pool can rise and escape easily while welding thick plates. Therefore, the pores forming tendency decreases. At the same time, hybrid welding enhances welding speed, and optimizes the energy input. The transition and grain size of the microstructure of hybrid welding joint is better and its hardness is higher than base material. Furthermore, its tensile strength and impact toughness is as good as base material. Consequently, the hybrid welding joint can meet the industry needs completely.

Friction Stir Welding of Magnesium Alloy Type AZ 31

NASA Astrophysics Data System (ADS)

Kupec, Tomáš; Behúlová, Mária; Turňa, Milan; Sahul, Miroslav

The paper deals with welding of Mg alloy of the type AZ 31 by Friction Stir Welding technology (FSW). The FSW technology is at present predominantly used for welding light metals and alloys, as aluminium, magnesium and their alloys. Experimental part consists of performing the simulation and fabrication of welded joints on a new-installed welding equipment available at the Welding Research Institute — Industrial Institute of SR Bratislava. Welding tools made of tool steel type H 13 were used for welding experiments. Geometry of welding tools was designed on the base of literature knowledge. Suitable welding parameters and conditions were determined using numerical simulation. Main emphasis was laid upon the tool revolutions, welding speed and tool bevel angle. The effect of welding parameters on the quality of welded joints was assessed. Assessment of welded joints was carried out by radiography, light microscopy, hardness measurement and EDX microanalysis. Static tensile test was employed for mechanical testing.

40 CFR 420.71 - Specialized definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... means those steel hot forming operations that produce butt welded or seamless tubular steel products. (f... STANDARDS IRON AND STEEL MANUFACTURING POINT SOURCE CATEGORY Hot Forming Subcategory § 420.71 Specialized definitions. (a) The term hot forming means those steel operations in which solidified, heated steel is shaped...

40 CFR 420.71 - Specialized definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... means those steel hot forming operations that produce butt welded or seamless tubular steel products. (f... STANDARDS IRON AND STEEL MANUFACTURING POINT SOURCE CATEGORY Hot Forming Subcategory § 420.71 Specialized definitions. (a) The term hot forming means those steel operations in which solidified, heated steel is shaped...

40 CFR 420.71 - Specialized definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... means those steel hot forming operations that produce butt welded or seamless tubular steel products. (f... STANDARDS IRON AND STEEL MANUFACTURING POINT SOURCE CATEGORY Hot Forming Subcategory § 420.71 Specialized definitions. (a) The term hot forming means those steel operations in which solidified, heated steel is shaped...

40 CFR 420.71 - Specialized definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... means those steel hot forming operations that produce butt welded or seamless tubular steel products. (f... STANDARDS IRON AND STEEL MANUFACTURING POINT SOURCE CATEGORY Hot Forming Subcategory § 420.71 Specialized definitions. (a) The term hot forming means those steel operations in which solidified, heated steel is shaped...

Contribution to applications of EBW in instrument techniques

NASA Astrophysics Data System (ADS)

Hrabovsky, Miroslav

1999-07-01

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

Aluminum Lithium Alloy 2195 Fusion Welding Improvements with New Filler Wire

NASA Technical Reports Server (NTRS)

Russell, Carolyn; Bjorkman, Gerry; McCool, Carolyn (Technical Monitor)

2000-01-01

A viewgraph presentation outlines NASA Marshall Space Flight Center, Lockheed Martin Michoud Space Systems, and McCook Metals' development an aluminum-copper weld filler wire for fusion welding 2195 aluminum lithium. The aluminum-copper based weld filler wire has been identified as B218, which is the result of six years of weld filler wire development funded by NASA, Lockheed Martin, and McCook Metals. The Super Lightweight External Tank for the NASA Space Shuttle Program consists of 2195 welded with 4043 aluminum-silicon weld filler wire. The B218 filler wire chemistry was developed to produce enhanced 2195 weld and repair weld mechanical properties. An initial characterization of the B218 weld filler wire was performed consisting of initial weld and repair weld evaluation comparing B218 and 4043. The testing involved room temperature and cryogenic tensile testing along with fracture toughness testing. B218 weld filler wire proved to produce enhanced initial and repair weld tensile and fracture properties over 4043. B218 weld filler wire has proved to be a superior weld filler wire for welding 2195 and other aluminum lithium alloys over 4043.

In vitro laser nerve repair: protein solder strip irradiation or irradiation alone?

PubMed

Trickett, I; Dawes, J M; Knowles, D S; Lanzetta, M; Owen, E R

1997-01-01

This study investigated the potential of sutureless nerve repair using two promising laser fusion methods: direct 2 microns irradiation of the epineurium, and protein solder assisted epineurial fusion using a 800 nm laser. Laser anastomosis of the rat sciatic nerve was performed in vitro without stay sutures in two groups of six animals. In the first group, direct laser fusion used a pulsed Cr, Tm: YAG laser. In the second group an albumin-based fluid solder containing the dye indocyanine green was applied to the epineurium, then irradiated with a diode laser. These two techniques were compared with regards to coaptation success and axonal damage. Direct laser welding produced weak bonds despite microscopic investigation of the irradiated nerves showing fusion of the epineurium. The unsatisfactory bonding can be attributed to poor tissue overlap and insufficient protein in the thin epineurium denaturation of underlying axons was also observed. In contrast, the laser solder method produced successful welds with greatly reduced axonal damage, and significantly improved the tensile strength. This study confirmed the technical possibilities of sutureless nerve anastomosis. Laser activated solders enable stronger bonds, by the addition of protein to the anastomosis site, and less thermal damage to underlying tissue through selective absorption of laser energy by dye in the solder. Further in vivo studies are required before drawing final conclusions.

Fundamentals and advances in the development of remote welding fabrication systems

NASA Technical Reports Server (NTRS)

Agapakis, J. E.; Masubuchi, K.; Von Alt, C.

1986-01-01

Operational and man-machine issues for welding underwater, in outer space, and at other remote sites are investigated, and recent process developments are described. Probable remote welding missions are classified, and the essential characteristics of fundamental remote welding tasks are analyzed. Various possible operational modes for remote welding fabrication are identified, and appropriate roles for humans and machines are suggested. Human operator performance in remote welding fabrication tasks is discussed, and recent advances in the development of remote welding systems are described, including packaged welding systems, stud welding systems, remotely operated welding systems, and vision-aided remote robotic welding and autonomous welding systems.

Deformation of allochthonous salt and evolution of related salt-structural systems, eastern Louisiana Gulf Coast

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

Schuster, D.C.

1996-12-31

Salt tectonics in the northern Gulf of Mexico involves both vertical diapirism and lateral silling or flow of salt into wings and tablets (sheets). Combinations of these two modes of salt deformation, concurrent with sediment loading and salt evacuation, have produced complex structures in the coastal and offshore region of southeastern Louisiana, a prolific oil and gas province. Many large growth faults and salt domes in the study area root into intra-Tertiary salt welds that were formerly occupied by allochthonous salt tablets. Two end-member structural systems involving evacuation of former tabular salt are recognized: roho systems and stepped counter-regional systems.more » Both end-member systems share a similar multi-staged evolution, including (1) initial formation of a south-leaning salt dome or wall sourced from the Jurassic salt level; (2) progressive development into a semi-tabular allochthonous salt body; and (3) subsequent loading, evacuation, and displacement of the tabular salt into secondary domes. In both systems, it is not uncommon to find salt displaced as much as 16-24 km south of its autochthonous source, connected by a horizontal salt weld to an updip, deflated counter-regional feeder. Although both end-member structural systems may originate before loading of allochthonous salt having grossly similar geometry, their final structural configurations after loading and salt withdrawal are distinctly different. Roho systems are characterized by large-displacement, listric, south-dipping growth faults that sole into intra-Tertiary salt welds marked by high-amplitude reflections continuous with residual salt masses. Salt from the former salt tablets has been loaded and squeezed laterally and downdip. Stepped counter-regional systems, in contrast, comprise large salt domes and adjacent large-displacement, north-dipping growth faults that sole into intra-Tertiary salt welds before stepping down again farther north.« less

Two-dimensional time-resolved x-ray diffraction study of dual phase rapid solidification in steels

NASA Astrophysics Data System (ADS)

Yonemura, Mitsuharu; Osuki, Takahiro; Terasaki, Hidenori; Komizo, Yuichi; Sato, Masugu; Toyokawa, Hidenori; Nozaki, Akiko

2010-01-01

The high intensity heat source used for fusion welding creates steep thermal gradients of 100 °C/s from 1800 °C. Further, the influence of preferred orientation is important for the observation of a directional solidification that follows the dendrite growth along the ⟨100⟩ direction toward the moving heat source. In the present study, we observed the rapid solidification of weld metal at a time resolution of 0.01-0.1 s by a two-dimensional time-resolved x-ray diffraction (2DTRXRD) system for real welding. The diffraction rings were dynamically observed by 2DTRXRD with synchrotron energy of 18 keV while the arc passes over the irradiation area of the x-rays. The arc power output was 10 V-150 A, and the scan speed of the arc was 1.0 mm/s. The temperature rise in instruments was suppressed by a water-cooled copper plate under the specimen. Further, the temperature distribution of the weld metal was measured by a thermocouple and correlated with the diffraction patterns. Consequently, solidification and solid phase transformation of low carbon steels and stainless steels were observed during rapid cooling by 2DTRXRD. In the low carbon steel, the microstructure is formed in a two step process, (i) formation of crystallites and (ii) increase of crystallinity. In stainless steel, the irregular interface layer of δ/γ in the quenched metal after solidification is expected to show the easy movement of dendrites at a lower temperature. In carbide precipitation stainless steel, it is easy for NbC to grow on δ phase with a little undercooling. Further, a mistlike pattern, which differs from the halo pattern, in the fusion zone gave some indication of the possibilities to observe the nucleation and the early solidification by 2DTRXRD.

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.

Soldadura (Welding). Spanish Translations for Welding.

ERIC Educational Resources Information Center

Hohhertz, Durwin

Thirty transparency masters with Spanish subtitles for key words are provided for a welding/general mechanical repair course. The transparency masters are on such topics as oxyacetylene welding; oxyacetylene welding equipment; welding safety; different types of welds; braze welding; cutting torches; cutting with a torch; protective equipment; arc…

Numerical and experimental determination of weld pool shape during high-power diode laser welding

NASA Astrophysics Data System (ADS)

Klimpel, Andrzej; Lisiecki, Aleksander; Szymanski, Andrzej; Hoult, Anthony P.

2003-10-01

In this paper, results of investigations on the shape of weld pool during High Power Diode Laser (HPDL) welding are presented. The results of tests showed that the shape of weld pool and mechanism of laser welding with a rectangular pattern of 808 nm laser radiation differs distinctly from previous laser welding mechanisms. For all power densities the conduction mode welds were observed and weld pool geometry depends significantly on the welding parameters.

A Brief Introduction to the Theory of Friction Stir Welding

NASA Technical Reports Server (NTRS)

Nunes, Arthur C., Jr.

2008-01-01

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

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

NASA Astrophysics Data System (ADS)

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

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

Sources and Seasonality of Volatile Organic Compounds in the Northern Front Range Metropolitan Area

NASA Astrophysics Data System (ADS)

Abeleira, A.; Pollack, I. B.; Sive, B. C.; Zaragoza, J.; Lindaas, J.; Fischer, E. V.; Farmer, D.

2016-12-01

The Northern Front Range Metropolitan Area (NFRMA) of Colorado, with a growing population of over 3 million, was deemed an ozone (O3) nonattainment area (NAA) in 2008 despite continued work on NOx reductions. Ground-level O3 is produced from photochemical catalytic cycles initiated by the OH oxidation of volatile organic compounds (VOCs), and propagated through reactions involving peroxy (HO2+RO2) and NOx (NO + NO2) radicals. We measured a suite of speciated VOCs during two 8-week deployments (March-May 2015, July-September 2015) at the Boulder Atmospheric Observatory in Erie, CO. The spring deployment overlapped with the NOAA SONGNEX (Shale Oil and Natural Gas Nexus) campaign. The BAO site lies at an urban-rural interface in the NFRMA with multiple urban centers surrounding the site, a major interstate highway within 2 miles, local suburban development in Erie, agricultural operations in the surrounding counties, and recent rapid expansion of oil and gas development in adjacent Weld County. VOCs were measured hourly with a custom-built online gas chromatography system along with measurements of O3, NOx, PAN, CO, and CH4. VOC measurements included C2-C8 hydrocarbons (NMHCs), C1-C5 alkyl nitrates, C1-C2 halocarbons, and several oxygenated species (OVOCs: methyl ethyl ketone, acetone, acetaldehyde). Using Positive Matrix Factorization (PMF) we have identified four distinct VOC sources in the spring and five in the summer: 1) Oil and Natural Gas (ONG, e.g. C2 - C5 alkanes), 2) Traffic (e.g. ethyne & aromatics), 3) Background species (e.g. long-lived halogenated species), 4) Secondary production (e.g. C3-C5 alkyl nitrates & OVOCs), and for summer 5) Biogenic (e.g. isoprene). Using the source factors generated from the PMF analysis we calculated the VOC reactivity (VOCr) of each source. For both seasons, the ONG factor dominates VOCr in the mornings. In spring afternoons, a combination of background species and secondary products make up a large percentage of VOCr as primary species are photochemically removed. During summer afternoons, the Biogenic factor is a major contributor to VOCr, with an average diurnal peak up to 47% of VOCr in the late (6 - 8 pm) afternoon. This diel cycle of source contribution to VOCr indicates that both anthropogenic and biogenic VOC sources contribute to O3 production in the NFRMA.

49 CFR 195.228 - Welds and welding inspection: Standards of acceptability.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 3 2010-10-01 2010-10-01 false Welds and welding inspection: Standards of... SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Construction § 195.228 Welds and welding inspection: Standards of acceptability. (a) Each weld and welding must be inspected to insure compliance with...

49 CFR 195.228 - Welds and welding inspection: Standards of acceptability.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Welds and welding inspection: Standards of... SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Construction § 195.228 Welds and welding inspection: Standards of acceptability. (a) Each weld and welding must be inspected to insure compliance with...

49 CFR 195.228 - Welds and welding inspection: Standards of acceptability.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Welds and welding inspection: Standards of... SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Construction § 195.228 Welds and welding inspection: Standards of acceptability. (a) Each weld and welding must be inspected to insure compliance with...

49 CFR 195.228 - Welds and welding inspection: Standards of acceptability.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 3 2012-10-01 2012-10-01 false Welds and welding inspection: Standards of... SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Construction § 195.228 Welds and welding inspection: Standards of acceptability. (a) Each weld and welding must be inspected to insure compliance with...

49 CFR 195.228 - Welds and welding inspection: Standards of acceptability.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 3 2014-10-01 2014-10-01 false Welds and welding inspection: Standards of... SAFETY TRANSPORTATION OF HAZARDOUS LIQUIDS BY PIPELINE Construction § 195.228 Welds and welding inspection: Standards of acceptability. (a) Each weld and welding must be inspected to insure compliance with...

Research and application of self - propagating welding technology

NASA Astrophysics Data System (ADS)

Ma, Yunhe; Li, Zhizun; Wang, Jianjiang; Sun, Liming

2018-04-01

Self-propagating welding is an important application area of self-propagating high-temperature synthesis technology (SHS technology), suitable for special environment and special materials welding. This paper briefly introduces the principle of self - propagating welding and its technical characteristics, and briefly summarizes the current research and application of SHS welding around three aspects of thin film welding, welding of refractory welding and emergency welding of battlefield.

Laser Beam Welding of Nitride Steel Components

NASA Astrophysics Data System (ADS)

Gu, Hongping; Yin, Guobin; Shulkin, Boris

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

Friction plug welding

NASA Technical Reports Server (NTRS)

Takeshita, Riki (Inventor); Hibbard, Terry L. (Inventor)

2001-01-01

Friction plug welding (FPW) usage is advantageous for friction stir welding (FSW) hole close-outs and weld repairs in 2195 Al--Cu--Li fusion or friction stir welds. Current fusion welding methods of Al--Cu--Li have produced welds containing varied defects. These areas are found by non-destructive examination both after welding and after proof testing. Current techniques for repairing typically small (<0.25) defects weaken the weldment, rely heavily on welders' skill, and are costly. Friction plug welding repairs increase strength, ductility and resistance to cracking over initial weld quality, without requiring much time or operator skill. Friction plug welding while pulling the plug is advantageous because all hardware for performing the weld can be placed on one side of the workpiece.

Optimization of tribological performance of SiC embedded composite coating via Taguchi analysis approach

NASA Astrophysics Data System (ADS)

Maleque, M. A.; Bello, K. A.; Adebisi, A. A.; Akma, N.

2017-03-01

Tungsten inert gas (TIG) torch is one of the most recently used heat source for surface modification of engineering parts, giving similar results to the more expensive high power laser technique. In this study, ceramic-based embedded composite coating has been produced by precoated silicon carbide (SiC) powders on the AISI 4340 low alloy steel substrate using TIG welding torch process. A design of experiment based on Taguchi approach has been adopted to optimize the TIG cladding process parameters. The L9 orthogonal array and the signal-to-noise was used to study the effect of TIG welding parameters such as arc current, travelling speed, welding voltage and argon flow rate on tribological response behaviour (wear rate, surface roughness and wear track width). The objective of the study was to identify optimal design parameter that significantly minimizes each of the surface quality characteristics. The analysis of the experimental results revealed that the argon flow rate was found to be the most influential factor contributing to the minimum wear and surface roughness of the modified coating surface. On the other hand, the key factor in reducing wear scar is the welding voltage. Finally, a convenient and economical Taguchi approach used in this study was efficient to find out optimal factor settings for obtaining minimum wear rate, wear scar and surface roughness responses in TIG-coated surfaces.

Computational Analysis of Material Flow During Friction Stir Welding of AA5059 Aluminum Alloys

NASA Astrophysics Data System (ADS)

Grujicic, M.; Arakere, G.; Pandurangan, B.; Ochterbeck, J. M.; Yen, C.-F.; Cheeseman, B. A.; Reynolds, A. P.; Sutton, M. A.

2012-09-01

Workpiece material flow and stirring/mixing during the friction stir welding (FSW) process are investigated computationally. Within the numerical model of the FSW process, the FSW tool is treated as a Lagrangian component while the workpiece material is treated as an Eulerian component. The employed coupled Eulerian/Lagrangian computational analysis of the welding process was of a two-way thermo-mechanical character (i.e., frictional-sliding/plastic-work dissipation is taken to act as a heat source in the thermal-energy balance equation) while temperature is allowed to affect mechanical aspects of the model through temperature-dependent material properties. The workpiece material (AA5059, solid-solution strengthened and strain-hardened aluminum alloy) is represented using a modified version of the classical Johnson-Cook model (within which the strain-hardening term is augmented to take into account for the effect of dynamic recrystallization) while the FSW tool material (AISI H13 tool steel) is modeled as an isotropic linear-elastic material. Within the analysis, the effects of some of the FSW key process parameters are investigated (e.g., weld pitch, tool tilt-angle, and the tool pin-size). The results pertaining to the material flow during FSW are compared with their experimental counterparts. It is found that, for the most part, experimentally observed material-flow characteristics are reproduced within the current FSW-process model.

Design of Friction Stir Spot Welding Tools by Using a Novel Thermal-Mechanical Approach

PubMed Central

Su, Zheng-Ming; Qiu, Qi-Hong; Lin, Pai-Chen

2016-01-01

A simple thermal-mechanical model for friction stir spot welding (FSSW) was developed to obtain similar weld performance for different weld tools. Use of the thermal-mechanical model and a combined approach enabled the design of weld tools for various sizes but similar qualities. Three weld tools for weld radii of 4, 5, and 6 mm were made to join 6061-T6 aluminum sheets. Performance evaluations of the three weld tools compared fracture behavior, microstructure, micro-hardness distribution, and welding temperature of welds in lap-shear specimens. For welds made by the three weld tools under identical processing conditions, failure loads were approximately proportional to tool size. Failure modes, microstructures, and micro-hardness distributions were similar. Welding temperatures correlated with frictional heat generation rate densities. Because the three weld tools sufficiently met all design objectives, the proposed approach is considered a simple and feasible guideline for preliminary tool design. PMID:28773800

Design of Friction Stir Spot Welding Tools by Using a Novel Thermal-Mechanical Approach.

PubMed

Su, Zheng-Ming; Qiu, Qi-Hong; Lin, Pai-Chen

2016-08-09

A simple thermal-mechanical model for friction stir spot welding (FSSW) was developed to obtain similar weld performance for different weld tools. Use of the thermal-mechanical model and a combined approach enabled the design of weld tools for various sizes but similar qualities. Three weld tools for weld radii of 4, 5, and 6 mm were made to join 6061-T6 aluminum sheets. Performance evaluations of the three weld tools compared fracture behavior, microstructure, micro-hardness distribution, and welding temperature of welds in lap-shear specimens. For welds made by the three weld tools under identical processing conditions, failure loads were approximately proportional to tool size. Failure modes, microstructures, and micro-hardness distributions were similar. Welding temperatures correlated with frictional heat generation rate densities. Because the three weld tools sufficiently met all design objectives, the proposed approach is considered a simple and feasible guideline for preliminary tool design.

Method and apparatus for assessing weld quality

DOEpatents

Smartt, Herschel B.; Kenney, Kevin L.; Johnson, John A.; Carlson, Nancy M.; Clark, Denis E.; Taylor, Paul L.; Reutzel, Edward W.

2001-01-01

Apparatus for determining a quality of a weld produced by a welding device according to the present invention includes a sensor operatively associated with the welding device. The sensor is responsive to at least one welding process parameter during a welding process and produces a welding process parameter signal that relates to the at least one welding process parameter. A computer connected to the sensor is responsive to the welding process parameter signal produced by the sensor. A user interface operatively associated with the computer allows a user to select a desired welding process. The computer processes the welding process parameter signal produced by the sensor in accordance with one of a constant voltage algorithm, a short duration weld algorithm or a pulsed current analysis module depending on the desired welding process selected by the user. The computer produces output data indicative of the quality of the weld.

73rd American Welding Society annual meeting

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

Not Available

1992-01-01

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

Parametric study in weld mismatch of longitudinally welded SSME HPFTP inlet

NASA Technical Reports Server (NTRS)

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

1991-01-01

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

Study of weld offset in longitudinally welded SSME HPFTP inlet

NASA Technical Reports Server (NTRS)

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

1992-01-01

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

Neural Overlap in Item Representations Across Episodes Impairs Context Memory.

PubMed

Kim, Ghootae; Norman, Kenneth A; Turk-Browne, Nicholas B

2018-06-12

We frequently encounter the same item in different contexts, and when that happens, memories of earlier encounters can get reactivated. We examined how existing memories are changed as a result of such reactivation. We hypothesized that when an item's initial and subsequent neural representations overlap, this allows the initial item to become associated with novel contextual information, interfering with later retrieval of the initial context. Specifically, we predicted a negative relationship between representational similarity across repeated experiences of an item and subsequent source memory for the initial context. We tested this hypothesis in an fMRI study, in which objects were presented multiple times during different tasks. We measured the similarity of the neural patterns in lateral occipital cortex that were elicited by the first and second presentations of objects, and related this neural overlap score to subsequent source memory. Consistent with our hypothesis, greater item-specific pattern similarity was linked to worse source memory for the initial task. In contrast, greater reactivation of the initial context was associated with better source memory. Our findings suggest that the influence of novel experiences on an existing context memory depends on how reliably a shared component (i.e., item) is represented across these episodes.

Weld analysis and control system

NASA Technical Reports Server (NTRS)

Kennedy, Larry Z. (Inventor); Rodgers, Michael H. (Inventor); Powell, Bradley W. (Inventor); Burroughs, Ivan A. (Inventor); Goode, K. Wayne (Inventor)

1994-01-01

The invention is a Weld Analysis and Control System developed for active weld system control through real time weld data acquisition. Closed-loop control is based on analysis of weld system parameters and weld geometry. The system is adapted for use with automated welding apparatus having a weld controller which is capable of active electronic control of all aspects of a welding operation. Enhanced graphics and data displays are provided for post-weld analysis. The system provides parameter acquisition, including seam location which is acquired for active torch cross-seam positioning. Torch stand-off is also monitored for control. Weld bead and parent surface geometrical parameters are acquired as an indication of weld quality. These parameters include mismatch, peaking, undercut, underfill, crown height, weld width, puddle diameter, and other measurable information about the weld puddle regions, such as puddle symmetry, etc. These parameters provide a basis for active control as well as post-weld quality analysis and verification. Weld system parameters, such as voltage, current and wire feed rate, are also monitored and archived for correlation with quality parameters.

B218 Weld Filler Wire Characterization for Al-Li Alloy 2195

NASA Technical Reports Server (NTRS)

Bjorkman, Gerry; Russell, Carolyn

2000-01-01

NASA Marshall Space Flight Center, Lockheed Martin Space Systems- Michoud Operations, and McCook Metals have developed an aluminum-copper weld filler wire for fusion welding aluminum lithium alloy 2195. The aluminum-copper based weld filler wire has been identified as B218, a McCook Metals designation. B218 is the result of six years of weld filler wire development funded by NASA, Lockheed Martin, and McCook Metals. The filler wire chemistry was developed to produce enhanced 2195 weld and repair weld mechanical properties over the 4043 aluminum-silicon weld filler wire, which is currently used to weld 2195 on the Super Lightweight External Tank for the NASA Space Shuttle Program. An initial characterization was performed consisting of a repair weld evaluation using B218 and 4043 weld filler wires. The testing involved room temperature and cryogenic repair weld tensile testing along with fracture toughness testing. From the testing, B218 weld filler wire produce enhanced repair weld tensile strength, ductility, and fracture properties over 4043. B218 weld filler wire has proved to be a superior weld filler wire for welding aluminum lithium alloy 2195 over 4043.

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

NASA Astrophysics Data System (ADS)

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

2012-07-01

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

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

An 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.

Ultrafast Synthetic Transmit Aperture Imaging Using Hadamard-Encoded Virtual Sources With Overlapping Sub-Apertures.

PubMed

Ping Gong; Pengfei Song; Shigao Chen

2017-06-01

The development of ultrafast ultrasound imaging offers great opportunities to improve imaging technologies, such as shear wave elastography and ultrafast Doppler imaging. In ultrafast imaging, there are tradeoffs among image signal-to-noise ratio (SNR), resolution, and post-compounded frame rate. Various approaches have been proposed to solve this tradeoff, such as multiplane wave imaging or the attempts of implementing synthetic transmit aperture imaging. In this paper, we propose an ultrafast synthetic transmit aperture (USTA) imaging technique using Hadamard-encoded virtual sources with overlapping sub-apertures to enhance both image SNR and resolution without sacrificing frame rate. This method includes three steps: 1) create virtual sources using sub-apertures; 2) encode virtual sources using Hadamard matrix; and 3) add short time intervals (a few microseconds) between transmissions of different virtual sources to allow overlapping sub-apertures. The USTA was tested experimentally with a point target, a B-mode phantom, and in vivo human kidney micro-vessel imaging. Compared with standard coherent diverging wave compounding with the same frame rate, improvements on image SNR, lateral resolution (+33%, with B-mode phantom imaging), and contrast ratio (+3.8 dB, with in vivo human kidney micro-vessel imaging) have been achieved. The f-number of virtual sources, the number of virtual sources used, and the number of elements used in each sub-aperture can be flexibly adjusted to enhance resolution and SNR. This allows very flexible optimization of USTA for different applications.

THE CHANDRA SURVEY OF THE COSMOS FIELD. II. SOURCE DETECTION AND PHOTOMETRY

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

Puccetti, S.; Vignali, C.; Cappelluti, N.

2009-12-01

The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that covers the central contiguous {approx}0.92 deg{sup 2} of the COSMOS field. C-COSMOS is the result of a complex tiling, with every position being observed in up to six overlapping pointings (four overlapping pointings in most of the central {approx}0.45 deg{sup 2} area with the best exposure, and two overlapping pointings in most of the surrounding area, covering an additional {approx}0.47 deg{sup 2}). Therefore, the full exploitation of the C-COSMOS data requires a dedicated and accurate analysis focused on three main issues: (1) maximizing the sensitivity when themore » point-spread function (PSF) changes strongly among different observations of the same source (from {approx}1 arcsec up to {approx}10 arcsec half-power radius); (2) resolving close pairs; and (3) obtaining the best source localization and count rate. We present here our treatment of four key analysis items: source detection, localization, photometry, and survey sensitivity. Our final procedure consists of a two step procedure: (1) a wavelet detection algorithm to find source candidates and (2) a maximum likelihood PSF fitting algorithm to evaluate the source count rates and the probability that each source candidate is a fluctuation of the background. We discuss the main characteristics of this procedure, which was the result of detailed comparisons between different detection algorithms and photometry tools, calibrated with extensive and dedicated simulations.« less

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

NASA Astrophysics Data System (ADS)

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

2012-02-01

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

Detection and quantification of fugitive emissions from Colorado oil and gas production operations using remote monitoring

EPA Science Inventory

Western states contain vast amounts of oil and gas production. For example, Weld County Colorado contains approximately 25,000 active oil and gas well sites with associated production operations. There is little information on the air pollutant emission potential from this source...

Spot-Welding Gun Is Easy To Use

NASA Technical Reports Server (NTRS)

Morgan, Gene E.; Nguyen, Francis H.

1991-01-01

Electrical-resistance spot-welding gun designed to produce more welds per unit time by decreasing technician's effort and fatigue. Vacuum cups on frame secure welding gun to workpiece while compressed air drives welding tip against workpiece to make spot resistance weld. When weld completed, vacuum in frame cups released so frame and gun moved to position of next spot weld.

Characterizing Shipyard Welding Emissions and Associated Control Options (The National Shipbuilding Research Program)

DTIC Science & Technology

1995-08-01

TRl) Occupational Health and Safety Administration (OSHA) Air Quality Legislation Hexavalent Chromium and the Legislation List-of-list Chemicals and...2.2.7 2.2.8 Shielded Metal Arc Welding (SMAW) Submerged Arc Welding (SAW) Gas Metal Arc Welding (GMAW) Gas Tungsten Arc Welding ( GTAW ) Flux Core Arc... GTAW Welding Processes Advantages and Disadvantages of FCAW Welding Processes Welding Process Comparison Matrix Diagram of SMAW Welding Process

Effects of Fusion Tack Welds on Self-Reacting Friction Stir Welds

NASA Technical Reports Server (NTRS)

Nunes, A. C., Jr.; Pendleton, M. L.; Brooke, S. A.; Russell, C. K.

2012-01-01

In order to know whether fusion tack welds would affect the strength of self-reacting friction stir seam welds in 2195-T87 aluminum alloy, the fracture stresses of 144 tensile test coupons cut from 24 welded panels containing segments of friction stir welds were measured. Each of the panels was welded under unique processing conditions. A measure of the effect of the tack welds for each panel was devised. An analysis of the measures of the tack weld effect supported the hypothesis that fusion tack welds do not affect the strength of self-reacting friction stir welds to a 5% level of confidence.

Research on the Effect of Welding Speed on the Quality of Welding Seam Based on the Local Dry Underwater Welding

NASA Astrophysics Data System (ADS)

Liu, Lei; Chen, Wu; Wang, Huagang; Ba, Jinyu; Li, Bing

2017-12-01

The repair of nuclear spent fuel pool has a high requirement for the quality of welding, the welding speed directly affects the quality of the weld when local dry automatic underwater welding is used to repair the damaged surface. Under the condition of the same condition, the local dry automatic underwater welding test was carried out under the condition of the same welding condition. Taking the 20cm as the experimental condition, after massive experiments show that when the welding speed is approximately 48cm/min the weld quality is high, meeting the design requirements, based on the double layer shrinkage nozzle chamber of local dry underwater automatic welding.

Gravimetric and analytical evaluation of welding fume in an automobile part manufacturing factory.

PubMed

Mansouri, N; Atbi, F; Moharamnezhad, N; Rahbaran, D A; Alahiari, M

2008-12-28

Welding is one of the most exercised industrial processes which welders are exposed to chemical and physical Hazardous agents. This study was conducted to evaluate occupational and environmental exposures to aerosols generated by welding processes in a factory. A total of 28 samples of aerosols were collected at 4 different locations including indoor, outdoor, source of welding and the stacks using a high volume pump with a volumetric flow rate of 112 lit/min calibrated with a dry gas meter. The samples were collected on round 110 mm fiber glass filters, measured gravimetrically, extracted using nitric acid and analyzed with atomic absorption spectroscopy method for heavy metals including Fe, Mn, Ni, Cr3+, Cr+6, Co, and Zn. Gravimetric measuring has shown the mean values of indoor air: 1.33 mg/m3, breathing zone of the welders using coated electrodes and CO2: 7.25 mg/m3 and 6.45 mg/m3 respectively and in ventilation exhausts: 95.07 mg/m3. The mean values of Fe, Mn, and Ni were 0.8, 0.041, and 0.00 mg/m3 in indoor air, 2.7, 0.18, and 0.15 mg/m3 in breathing zone of welders used coated electrodes, and 1.75, 0.08, and 0.22 mg/m3 in breathing zone of welders used CO2 welding respectively. The concentrations of Cr3+, Cr+6, Co, and Zn were too low to be detected. The welders were exposed to high concentration of metallic fumes, which raise the risk of pulmonary dysfunction and other health disorders. Using suitable respiratory masks and Appling the effective local ventilation system may improve the working condition.

Effect of welding position on porosity formation in aluminum alloy welds

NASA Technical Reports Server (NTRS)

Haryung, J.; Wroth, R. S.

1967-01-01

Program investigates the effects of varied welding positions on weld qualities. Progressive changes in bead geometry occur as the weld plane angle is varied from upslope to downslope. The gravitational effect on the weld puddle varies greatly with welding position.

Latest MIG, TIG arc-YAG laser hybrid welding systems for various welding products

NASA Astrophysics Data System (ADS)

Ishide, Takashi; Tsubota, Shuho; Watanabe, Masao

2003-03-01

Laser welding is capable of high-efficiency low-strain welding, and so its applications are started to various products. We have also put the high-power YAG laser of up to 10 kW to practical welding use for various products. On the other hand the weakest point of this laser welding is considered to be strict in the welding gap aiming allowance. In order to solve this problem, we have developed hybrid welding of TIG, MIG arc and YAG laser, taking the most advantages of both the laser and arc welding. Since the electrode is coaxial to the optical axis of the YAG laser in this process, it can be applied to welding of various objects. In the coaxial MIG, TIG-YAG welding, in order to make irradiation positions of the YAG laser beams having been guided in a wire or an electrode focused to the same position, the beam transmitted in fibers is separated to form a space between the separated beams, in which the laser is guided. With this method the beam-irradiating area can be brought near or to the arc-generating point. This enables welding of all directions even for the member of a three-dimensional shape. This time we carried out welding for various materials and have made their welding of up to 1 mm or more in welding groove gap possible. We have realized high-speed 1-pass butt welding of 4m/min in welding speed with the laser power of 3 kW for an aluminum alloy plate of approximately 4 mm thick. For a mild steel plate also we have realized butt welding of 1m/min with 5 kW for 6 mm thick. Further, in welding of stainless steel we have shown its welding possibility, by stabilizing the arc with the YAG laser in the welding atmosphere of pure argon, and shown that this welding is effective in high-efficiency welding of various materials. Here we will report the fundamental welding performances and applications to various objects for the coaxial MIG, TIG-YAG welding we have developed.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Damage Tolerance Assessment of Friction Pull Plug Welds

NASA Technical Reports Server (NTRS)

McGill, Preston; Burkholder, Jonathan

2012-01-01

Friction stir welding is a solid state welding process developed and patented by The Welding Institute in Cambridge, England. Friction stir welding has been implemented in the aerospace industry in the fabrication of longitudinal welds in pressurized cryogenic propellant tanks. As the industry looks to implement friction stir welding in circumferential welds in pressurized cryogenic propellant tanks, techniques to close out the termination hole associated with retracting the pin tool are being evaluated. Friction pull plug welding is under development as a one means of closing out the termination hole. A friction pull plug weld placed in a friction stir weld results in a non-homogenous weld joint where the initial weld, plug weld, their respective heat affected zones and the base metal all interact. The welded joint is a composite, plastically deformed material system with a complex residual stress field. In order to address damage tolerance concerns associated with friction plug welds in safety critical structures, such as propellant tanks, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size in the test or service environments. Test data relating residual strength capability to flaw size in two aluminum alloy friction plug weld configurations is presented.

Studying the Issues in Laser Joining of Lightweight Materials in a Coach-Peel Joint Configuration

NASA Astrophysics Data System (ADS)

Yang, Guang

In the automotive industry, aluminum alloys have been widely used and partially replaced the conventional steel structures in order to decrease the weight of a car and improve its fuel efficiency. This Thesis focuses on the development of laser joining of light-weight materials, such as aluminum alloys and high-strength galvanized steels. Among different joint types, the coach-peel configuration is of a specific design that requires a heat source capable of heating up a large surface area of the joint. Coach-peel joints applied on the visible exterior of a car require a smooth transition from the weld surface to the panel surface and low surface roughness without any need for post-processing. Although these joints are used as non-load-bearing components, a desirable strength of the weld is also needed. A fusion-brazing process using a dual-beam laser allows the automotive components such as the roof and side member panels to be joined in a coach-peel configuration with a high surface quality as well as an acceptable strength of the weld. To improve the weld surface quality, processing parameters such as laser beam configuration, laser-wire position, and shielding gas parameters were optimized for joining of aluminum alloy to aluminum alloy. Laser power was optimized for dual-beam laser joining of aluminum alloy to galvanized steel at high speed. The feasibility of joining as-received panels with lubricant was also explored. The identification of strain hardening models of aluminum alloys was conducted for the mechanical finite element analysis of the joint. Control of the molten pool solidification through the selection of laser beam configuration is one approach to improve joint quality. Laser joining of aluminum alloy AA 6111-T4 coach peel panels with the addition of AA 4047 filler wire was investigated using three configurations of laser beam: a single beam, dual beams in-line with the weld bead, and dual beams aligned perpendicular to the weld bead (herein referred to as cross-beam). To compare the three joining processes, the transient heat distribution, cooling rates, and solidification rates were analyzed by three-dimensional finite element models using ANSYS. Microstructure evolution, tensile strength, fracture mechanisms, and surface roughness of joints were investigated accordingly. To improve the weld surface quality of aluminum joints, the laser-wire position and the gas parameters were optimized. Visualization of the gas flow by a CCD camera revealed the effects of nozzle shape, flow rate, inclination angle of the gas tube, nozzle position, and gas compositions (argon and helium) on the weld surface quality. The suppression of plasma plume and the effects of oxidation on the molten pool were illustrated in detail. With an optimized set of processing parameters, the weld surface roughness (Ra) of approximately 1 microm can be achieved. The feasibility of fabricating the aluminum alloy panel joint in the as-received condition, i.e., with stamping lubricant, by using the cross-beam laser was investigated. Two commercial mineral oils, Bonderite L-FM MP-404 and Ferrocote 61 MAL HCL, were applied onto clean panels prior to joining in order to simulate the conditions of the production environment. The formation and growth of hydrogen bubbles inside the molten pool, the stability of welding process, and the possible energy absorption capability of the porous weld were explained. Besides joining of similar materials, cross-beam laser was applied to join aluminum alloy 6111 to hot-dip galvanized steel in the coach-peel configuration. The filler material was not only brazed onto the galvanized steel but also partially fusion-welded with the aluminum panel. Through adjusting the laser power to 3.4 kW, a desirable wetting and spreading of filler wire on both panel surfaces could be achieved, and the thickness of intermetallic layer in the middle section of the interface between the weld bead and steel was less than 2 microm. To better understand the solid/liquid interfacial reaction at the brazing interface, two rotary Gaussian heat source models were introduced to simulate the temperature distribution in the molten pool by using the finite element method. Joint properties were examined in terms of microstructure and mechanical properties. Simulation of the mechanical response of a coach-peel joint is instructive for improvement of the joining process. The effective true stress-strain curve of fusion-brazed AA 4047 was difficult to obtain experimentally. Therefore, the von Mises isotropic flow function of the weld bead was inversely derived by image-based finite element analysis. Through iterative correction, the predicted tensile response of the coach-peel joint matched well with the experiment. The von Mises fracture stresses at the fusion zone boundary and the brazing interface were identified, respectively.

Automated Welding System

NASA Technical Reports Server (NTRS)

Bayless, E. O.; Lawless, K. G.; Kurgan, C.; Nunes, A. C.; Graham, B. F.; Hoffman, D.; Jones, C. S.; Shepard, R.

1993-01-01

Fully automated variable-polarity plasma arc VPPA welding system developed at Marshall Space Flight Center. System eliminates defects caused by human error. Integrates many sensors with mathematical model of the weld and computer-controlled welding equipment. Sensors provide real-time information on geometry of weld bead, location of weld joint, and wire-feed entry. Mathematical model relates geometry of weld to critical parameters of 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.

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

NASA Astrophysics Data System (ADS)

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

2016-11-01

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

Damage Tolerance Assessment of Friction Pull Plug Welds in an Aluminum Alloy

NASA Technical Reports Server (NTRS)

McGill, Preston; Burkholder, Jonathan

2012-01-01

Friction stir welding is a solid state welding process used in the fabrication of cryogenic propellant tanks. Self-reacting friction stir welding is one variation of the friction stir weld process being developed for manufacturing tanks. Friction pull plug welding is used to seal the exit hole that remains in a circumferential self-reacting friction stir weld. A friction plug weld placed in a self-reacting friction stir weld results in a non-homogenous weld joint where the initial weld, plug weld, their respective heat affected zones and the base metal all interact. The welded joint is a composite plastically deformed material system with a complex residual stress field. In order to address damage tolerance concerns associated with friction plug welds in safety critical structures, such as propellant tanks, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size. Test data relating residual strength capability to flaw size in an aluminum alloy friction plug weld will be presented.

Automatic orbital GTAW welding: Highest quality welds for tomorrow's high-performance systems

NASA Technical Reports Server (NTRS)

Henon, B. K.

1985-01-01

Automatic orbital gas tungsten arc welding (GTAW) or TIG welding is certain to play an increasingly prominent role in tomorrow's technology. The welds are of the highest quality and the repeatability of automatic weldings is vastly superior to that of manual welding. Since less heat is applied to the weld during automatic welding than manual welding, there is less change in the metallurgical properties of the parent material. The possibility of accurate control and the cleanliness of the automatic GTAW welding process make it highly suitable to the welding of the more exotic and expensive materials which are now widely used in the aerospace and hydrospace industries. Titanium, stainless steel, Inconel, and Incoloy, as well as, aluminum can all be welded to the highest quality specifications automatically. Automatic orbital GTAW equipment is available for the fusion butt welding of tube-to-tube, as well as, tube to autobuttweld fittings. The same equipment can also be used for the fusion butt welding of up to 6 inch pipe with a wall thickness of up to 0.154 inches.

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.

Assessment of Stress Corrosion Cracking Resistance of Activated Tungsten Inert Gas-Welded Duplex Stainless Steel Joints

NASA Astrophysics Data System (ADS)

Alwin, B.; Lakshminarayanan, A. K.; Vasudevan, M.; Vasantharaja, P.

2017-12-01

The stress corrosion cracking behavior of duplex stainless steel (DSS) weld joint largely depends on the ferrite-austenite phase microstructure balance. This phase balance is decided by the welding process used, heat input, welding conditions and the weld metal chemistry. In this investigation, the influence of activated tungsten inert gas (ATIG) and tungsten inert gas (TIG) welding processes on the stress corrosion cracking (SCC) resistance of DSS joints was evaluated and compared. Boiling magnesium chloride (45 wt.%) environment maintained at 155 °C was used. The microstructure and ferrite content of different weld zones are correlated with the outcome of sustained load, SCC test. Irrespective of the welding processes used, SCC resistance of weld joints was inferior to that of the base metal. However, ATIG weld joint exhibited superior resistance to SCC than the TIG weld joint. The crack initiation and final failure were in the weld metal for the ATIG weld joint; they were in the heat-affected zone for the TIG weld joint.

Weld pool oscillation during GTA welding of mild steel

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

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

1993-08-01

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

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

NASA Astrophysics Data System (ADS)

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

2016-01-01

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

Improving the Quality of Welding Seam of Automatic Welding of Buckets Based on TCP

NASA Astrophysics Data System (ADS)

Hu, Min

2018-02-01

Since February 2014, the welding defects of the automatic welding line of buckets have been frequently appeared. The average repair time of each bucket is 26min, which seriously affects the production efficiency and welding quality. We conducted troubleshooting, and found the main reasons for the welding defects of the buckets were the deviations of the center points of the robot tools and the poor quality of the locating welding. We corrected the gripper, welding torch, and accuracy of repeat positioning of robots to control the quality of positioning welding. The welding defect rate of buckets was reduced greatly, ensuring the production efficiency and welding quality.

Computerized adaptive control weld skate with CCTV weld guidance project

NASA Technical Reports Server (NTRS)

Wall, W. A.

1976-01-01

This report summarizes progress of the automatic computerized weld skate development portion of the Computerized Weld Skate with Closed Circuit Television (CCTV) Arc Guidance Project. The main goal of the project is to develop an automatic welding skate demonstration model equipped with CCTV weld guidance. The three main goals of the overall project are to: (1) develop a demonstration model computerized weld skate system, (2) develop a demonstration model automatic CCTV guidance system, and (3) integrate the two systems into a demonstration model of computerized weld skate with CCTV weld guidance for welding contoured parts.

Parametrization study of the land multiparameter VTI elastic waveform inversion

NASA Astrophysics Data System (ADS)

He, W.; Plessix, R.-É.; Singh, S.

2018-06-01

Multiparameter inversion of seismic data remains challenging due to the trade-off between the different elastic parameters and the non-uniqueness of the solution. The sensitivity of the seismic data to a given subsurface elastic parameter depends on the source and receiver ray/wave path orientations at the subsurface point. In a high-frequency approximation, this is commonly analysed through the study of the radiation patterns that indicate the sensitivity of each parameter versus the incoming (from the source) and outgoing (to the receiver) angles. In practice, this means that the inversion result becomes sensitive to the choice of parametrization, notably because the null-space of the inversion depends on this choice. We can use a least-overlapping parametrization that minimizes the overlaps between the radiation patterns, in this case each parameter is only sensitive in a restricted angle domain, or an overlapping parametrization that contains a parameter sensitive to all angles, in this case overlaps between the radiation parameters occur. Considering a multiparameter inversion in an elastic vertically transverse isotropic medium and a complex land geological setting, we show that the inversion with the least-overlapping parametrization gives less satisfactory results than with the overlapping parametrization. The difficulties come from the complex wave paths that make difficult to predict the areas of sensitivity of each parameter. This shows that the parametrization choice should not only be based on the radiation pattern analysis but also on the angular coverage at each subsurface point that depends on geology and the acquisition layout.

Syllabus in Trade Welding.

ERIC Educational Resources Information Center

New York State Education Dept., Albany. Bureau of Secondary Curriculum Development.

The syllabus outlines material for a course two academic years in length (minimum two and one-half hours daily experience) leading to entry-level occupational ability in several welding trade areas. Fourteen units covering are welding, gas welding, oxyacetylene welding, cutting, nonfusion processes, inert gas shielded-arc welding, welding cast…

Filler wire for aluminum alloys and method of welding

NASA Technical Reports Server (NTRS)

Bjorkman, Jr., Gerald W. O. (Inventor); Cho, Alex (Inventor); Russell, Carolyn K. (Inventor)

2003-01-01

A weld filler wire chemistry has been developed for fusion welding 2195 aluminum-lithium. The weld filler wire chemistry is an aluminum-copper based alloy containing high additions of titanium and zirconium. The additions of titanium and zirconium reduce the crack susceptibility of aluminum alloy welds while producing good weld mechanical properties. The addition of silver further improves the weld properties of the weld filler wire. The reduced weld crack susceptibility enhances the repair weldability, including when planishing is required.

Programmable Positioner For Spot Welding

NASA Technical Reports Server (NTRS)

Roden, William A.

1989-01-01

Welding station mechanized by installing preset indexing system and gear drive. Mechanism includes a low-cost, versatile, single-axis motion control and motor drive to provide fully-automatic weld sequencing and spot-to-spot spacing. Welding station relieves operator of some difficult, tedious tasks and increases both productivity and quality of welds. Results in welds of higher quality and greater accuracy, fewer weld defects, and faster welding operation.

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

NASA Astrophysics Data System (ADS)

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

2016-03-01

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

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.

Evaluating the SCC resistance of underwater welds in sodium tetrathionate

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

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

1997-12-01

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

Production of ozone and reactive oxygen species after welding.

PubMed

Liu, H H; Wu, Y C; Chen, H L

2007-11-01

Many toxic substances including heavy metals, ozone, carbon monoxide, carbon dioxide, and nitrogen oxides are generated during welding. Ozone (O(3)) is a strong oxidant that generates reactive oxygen species (ROS) in tissue, and ambient ROS exposure associated with particles has been determined to cause DNA damage. Ozone is produced within 30 seconds during welding. However, the length of time that O(3) remains in the air after welding is completed (post-welding) is unknown. The current study aimed to assess the distributions of ambient ROS and O(3) before the start of welding (pre-welding), during welding, and after welding. The highest O(3) levels, equal to 195 parts per billion (ppb), appeared during welding. Ozone levels gradually decreased to 60 ppb 10 minutes after the welding was completed. The highest ROS level was found in samples taken during welding, followed by samples taken after the welding was completed. The lowest ROS level was found in samples taken before the welding had started. Ozone and ROS levels were poorly correlated, but a similar trend was found for O(3) and ROS levels in particles (microM/mg). Although particles were not generated after welding, ROS and O(3) still persisted for more than 10 minutes. Meanwhile, because O(3) continues after welding, how long the occupational protective system should be used depends on the welding materials and the methods used. In addition, the relationship between metal fumes and ROS generation during the welding process should be further investigated.

Automatic welding systems for large ship hulls

NASA Astrophysics Data System (ADS)

Arregi, B.; Granados, S.; Hascoet, JY.; Hamilton, K.; Alonso, M.; Ares, E.

2012-04-01

Welding processes represents about 40% of the total production time in shipbuilding. Although most of the indoor welding work is automated, outdoor operations still require the involvement of numerous operators. To automate hull welding operations is a priority in large shipyards. The objective of the present work is to develop a comprehensive welding system capable of working with several welding layers in an automated way. There are several difficulties for the seam tracking automation of the welding process. The proposed solution is the development of a welding machine capable of moving autonomously along the welding seam, controlling both the position of the torch and the welding parameters to adjust the thickness of the weld bead to the actual gap between the hull plates.

Effect of friction stir welding parameters on defect formation

NASA Astrophysics Data System (ADS)

Tarasov, S. Yu.; Rubtsov, V. E.; Eliseev, A. A.; Kolubaev, E. A.; Filippov, A. V.; Ivanov, A. N.

2015-10-01

Friction stir welding is a perspective method for manufacturing automotive parts, aviation and space technology. One of the major problems is the formation of welding defects and weld around the welding zone. The formation of defect is the main reason failure of the joint. A possible way to obtain defect-free welded joints is the selection of the correct welding parameters. Experimental results describing the effect of friction stir welding process parameters on the defects of welded joints on aluminum alloy AMg5M have been shown. The weld joint defects have been characterized using the non-destructive radioscopic and ultrasound phase array methods. It was shown how the type and size of defects determine the welded joint strength.

Non-destructive Magnetic Evaluation of Laser Weld Quality in Hot Rolled Coils

NASA Astrophysics Data System (ADS)

Mohapatra, J. N.; Chakradhar, I.; Rao, K. R. C.; Rao, V. V. L.; Kaza, Marutiram

2015-06-01

Weld quality evaluation was conducted on laser welded thin sectsions (2 mm) of hot-rolled (HR) low-carbon steel coils during cold rolling process. The analysis revealed that the poor welds consisting of the weld defects like incomplete fusion, cluster of porosity, and large difference in hardness between the weld zone and base metal were responsible for the weld failures. Experiments were conducted by varying the welding parameters; laser power and welding speed to optimize the parameters for minimizing the weld defects. The optimized weld process parameters have helped elimination of weld defects and the results are verified with microscopy and microhardness measurements. As destructive evaluation techniques are time consuming and not always permitted in industrial applications, attempts have been made in the present investigation for the utilization of suitable non-destructive techniques for the evaluation of weld quality. Non-destructive magnetic techniques of magnetic hysteresis loop and magnetic Barkhausen emissions were used in the present investigation to establish possible correlations of magnetic properties across the weld seam with the mechanical property (microhardness) for evaluation of weld quality. It is inferred that the magnetic properties of coercivity and inverse of root mean square voltage can be effectively utilized to determine weld quality in HR steel coils.

Tool For Friction Stir Tack Welding of Aluminum Alloys

NASA Technical Reports Server (NTRS)

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

2003-01-01

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

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.

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

NASA Astrophysics Data System (ADS)

Yun, Seok-Chul; Kim, Jae-Woong

2010-12-01

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

Recent Developments and Research Progress on Friction Stir Welding of Titanium Alloys: An Overview

NASA Astrophysics Data System (ADS)

Karna, Sivaji; Cheepu, Muralimohan; Venkateswarulu, D.; Srikanth, V.

2018-03-01

Titanium and its alloys are joined by various welding processes. However, Fusion welding of titanium alloys resulted solidification problems like porosity, segregation and columnar grains. The problems occurred in conventional welding processes can be resolved using a solid state welding i.e. friction stir welding. Aluminium and Magnesium alloys were welded by friction stir welding. However alloys used for high temperature applications such as titanium alloys and steels are arduous to weld using friction stir welding process because of tool limitations. Present paper summarises the studies on joining of Titanium alloys using friction stir welding with different tool materials. Selection of tool material and effect of welding conditions on mechanical and microstructure properties of weldments were also reported. Major advantage with friction stir welding is, we can control the welding temperature above or below β-transus temperature by optimizing the process parameters. Stir zone in below beta transus condition consists of bi-modal microstructure and microstructure in above β-transus condition has large prior β- grains and α/β laths present in the grain. Welding experiments conducted below β- transus condition has better mechanical properties than welding at above β-transus condition. Hardness and tensile properties of weldments are correlated with the stir zone microstructure.

Comparison of Tensile Damage Evolution in Ti6A14V Joints Between Laser Beam Welding and Gas Tungsten Arc Welding

NASA Astrophysics Data System (ADS)

Gao, Xiao-Long; Zhang, Lin-Jie; Liu, Jing; Zhang, Jian-Xun

2014-12-01

The present paper studied the evolution of tensile damage in joints welded using laser beam welding (LBW) and gas tungsten arc welding (TIG) under a uniaxial tensile load. The damage evolution in the LBW joints and TIG-welded joints was studied by using digital image correlation (DIC) technology and monitoring changes in Young's modulus during tensile testing. To study the mechanism of void nucleation and growth in the LBW joints and TIG-welded joints, test specimens with various amounts of plastic deformation were analyzed using a scanning electron microscope (SEM). Compared with TIG-welded joints, LBW-welded joints have a finer microstructure and higher microhardness in the fusion zone. The SEM analysis and DIC test results indicated that the critical strain of void nucleation was greater in the LBW-welded joints than in the TIG-welded joints, while the growth rate of voids was lower in the LBW-welded joints than in the TIG-welded joints. Thus, the damage ratio in the LBW joints was lower than that in the TIG-welded joints during tensile testing. This can be due to the coarser martensitic α' and the application of TC-1 welding rods in the TIG-welded joint.

Dry Sliding Tribological Studies of AA6061-B4C-Gr Hybrid Composites

NASA Astrophysics Data System (ADS)

Monikandan, V. V.; Joseph, M. A.; Rajendrakumar, P. K.

2016-10-01

The dry sliding behavior of stir-cast AA6061-10 wt.% B4C composites containing 2.5, 5 and 7.5 wt.% graphite particles was studied as a function of applied load, sliding speed and sliding distance on a pin-on-disk tribotester. The wear rate and friction coefficient increased with increase in applied load and sliding distance. The increase in graphite addition reduced the increase in wear rate and friction coefficient in the sliding speed range 2-2.5 m/s. Scanning electron microscopy of the worn pin revealed a graphite tribolayer, and transmission electron microscopy revealed overlapping deformation bands under 30 N applied load. Upon increasing the applied load to 40 N, welded region with fine crystalline structure was formed due to dynamic recrystallization of AA6061 alloy matrix.

Joining dissimilar materials using Friction Stir scribe technique

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

Upadhyay, Piyush; Hovanski, Yuri; Jana, Saumyadeep

2016-10-03

The ability to effectively join materials with vastly different melting points like Aluminum-Steel, Polymer composites - metals has been one of the road blocks in realizing multi-material components for light weighting efforts. Friction stir scribe (FSS) technique is a promising method that produces continuous overlap joint between materials with vastly different melting regimes and high temperature flow characteristics. FSS uses an offset cutting tool at the tip of the FSW pin to create an insitu mechanical interlock between material interfaces. With investments from Vehicle Technology office, US DOE and several automotive manufacturers and suppliers PNNL is developing the FSS processmore » and has demonstrated viability of joining several material combinations. Details of welding trails, unique challenges and mitigation strategies in different material combinations will be discussed. Joint characterization including mechanical tests and joint performances will also be presented.« less

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.

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.

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

NASA Astrophysics Data System (ADS)

Vasantharaja, P.; Vasudevan, M.

2012-02-01

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

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....

Extending RTM Imaging With a Focus on Head Waves

NASA Astrophysics Data System (ADS)

Holicki, Max; Drijkoningen, Guy

2016-04-01

Conventional industry seismic imaging predominantly focuses on pre-critical reflections, muting post-critical arrivals in the process. This standard approach neglects a lot of information present in the recorded wave field. This negligence has been partially remedied with the inclusion of head waves in more advanced imaging techniques, like Full Waveform Inversion (FWI). We would like to see post-critical information leave the realm of labour-intensive travel-time picking and tomographic inversion towards full migration to improve subsurface imaging and parameter estimation. We present a novel seismic imaging approach aimed at exploiting post-critical information, using the constant travel path for head-waves between shots. To this end, we propose to generalize conventional Reverse Time Migration (RTM) to scenarios where the sources for the forward and backward propagated wave-fields are not coinciding. RTM functions on the principle that backward propagated receiver data, due to a source at some locations, must overlap with the forward propagated source wave field, from the same source location, at subsurface scatterers. Where the wave-fields overlap in the subsurface there is a peak at the zero-lag cross-correlation, and this peak is used for the imaging. For the inclusion of head waves, we propose to relax the condition of coincident sources. This means that wave-fields, from non-coincident-sources, will not overlap properly in the subsurface anymore. We can make the wave-fields overlap in the subsurface again, by time shifting either the forward or backward propagated wave-fields until the wave-fields overlap. This is the same as imaging at non-zero cross-correlation lags, where the lag is the travel time difference between the two wave-fields for a given event. This allows us to steer which arrivals we would like to use for imaging. In the simplest case we could use Eikonal travel-times to generate our migration image, or we exclusively image the subsurface with the head wave from the nth-layer. To illustrate the method we apply it to a layered Earth model with five layers and compare it to conventional RTM. We will show that conventional RTM highlights interfaces, while our head-wave based images highlight layers, producing fundamentally different images. We also demonstrate that our proposed imaging scheme is more sensitive to the velocity model than conventional RTM, which is important for improved velocity model building in the future.

Effect of Shielding Gas on the Properties of AW 5083 Aluminum Alloy Laser Weld Joints

NASA Astrophysics Data System (ADS)

Vyskoč, Maroš; Sahul, Miroslav; Sahul, Martin

2018-04-01

The paper deals with the evaluation of the shielding gas influence on the properties of AW 5083 aluminum alloy weld joints produced with disk laser. Butt weld joints were produced under different shielding gas types, namely Ar, He, Ar + 5 vol.% He, Ar + 30 vol.% He and without shielding weld pool. Light and electron microscopy, computed tomography, microhardness measurements and tensile testing were used for evaluation of weld joint properties. He-shielded weld joints were the narrowest ones. On the other hand, Ar-shielded weld joints exhibited largest weld width. The choice of shielding gas had significant influence on the porosity level of welds. The lowest porosity was observed in weld joint produced in Ar with the addition of 5 vol.% He shielding atmosphere (only 0.03%), while the highest level of porosity was detected in weld joint produced in pure He (0.24%). Except unshielded aluminum alloy weld joint, the lowest tensile strength was recorded in He-shielded weld joints. On the contrary, the highest average microhardness was measured in He-shielded weld joints.

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.

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

NASA Astrophysics Data System (ADS)

Rao, Harish Mangebettu

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

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

NASA Astrophysics Data System (ADS)

Kang, Namhyun

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

Fast, Nonspattering Inert-Gas Welding

NASA Technical Reports Server (NTRS)

Gilbert, Jeffrey L.

1991-01-01

Proposed welding technique combines best features of metal (other than tungsten)/inert-gas welding, plasma arc welding, and tungsten/inert-gas welding. Advantages include: wire fed to weld joint preheated, therefore fed at high speed without spattering; high-frequency energy does not have to be supplied to workpiece to initiate welding; size of arc gap not critical, power-supply control circuit adjusts voltage across gap to compensate for changes; only low gas-flow rate needed; welding electrode replaced easily as prefabricated assembly; external wire-feeding manipulator not needed; and welding process relatively forgiving of operator error.

Characteristics of Extra Narrow Gap Weld of HSLA Steel Welded by Single-Seam per Layer Pulse Current GMA Weld Deposition

NASA Astrophysics Data System (ADS)

Agrawal, B. P.; Ghosh, P. K.

2017-03-01

Butt weld joints are produced using pulse current gas metal arc welding process by employing the technique of centrally laid multi-pass single-seam per layer weld deposition in extra narrow groove of thick HSLA steel plates. The weld joints are prepared by using different combination of pulse parameters. The selection of parameter of pulse current gas metal arc welding is done considering a summarized influence of simultaneously interacting pulse parameters defined by a dimensionless hypothetical factor ϕ. The effect of diverse pulse parameters on the characteristics of weld has been studied. Weld joint is also prepared by using commonly used multi-pass multi-seam per layer weld deposition in conventional groove. The extra narrow gap weld joints have been found much superior to the weld joint prepared by multi-pass multi-seam per layer deposition in conventional groove with respect to its metallurgical characteristics and mechanical properties.

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.

Effects of conventional welding and laser welding on the tensile strength, ultimate tensile strength and surface characteristics of two cobalt-chromium alloys: a comparative study.

PubMed

Madhan Kumar, Seenivasan; Sethumadhava, Jayesh Raghavendra; Anand Kumar, Vaidyanathan; Manita, Grover

2012-06-01

The purpose of this study was to evaluate the efficacy of laser welding and conventional welding on the tensile strength and ultimate tensile strength of the cobalt-chromium alloy. Samples were prepared with two commercially available cobalt-chromium alloys (Wironium plus and Diadur alloy). The samples were sectioned and the broken fragments were joined using Conventional and Laser welding techniques. The welded joints were subjected to tensile and ultimate tensile strength testing; and scanning electron microscope to evaluate the surface characteristics at the welded site. Both on laser welding as well as on conventional welding technique, Diadur alloy samples showed lesser values when tested for tensile and ultimate tensile strength when compared to Wironium alloy samples. Under the scanning electron microscope, the laser welded joints show uniform welding and continuous molt pool all over the surface with less porosity than the conventionally welded joints. Laser welding is an advantageous method of connecting or repairing cast metal prosthetic frameworks.

Effect of FSW welding speed on microstructure and microhardness of Al-0.84Mg-0.69Si-0.76Fe alloy at moderate rotational tool velocity

NASA Astrophysics Data System (ADS)

Chand, Suresh; Vineetha, S.; Madhusudhan, D.; Sai Krishna, CH; Kusuma Devi, G.; Bhawani; Hemarao, K.; Ganesh Naidu, G.

2018-03-01

The plate of 7.0 mm thickness was double side welded using friction stir welding is investigated. The rotational velocity of friction stir welding tool is used 1400 rpm. The influence of welding speed on the microstructure and microhardness values of Al-0.84Mg-0.69Si-0.76Fe aluminum alloy is presented. Two welding speeds 25 mm/min and 31.5 mm/min are used. The microhardness values of friction stir weld are measured at various locations from the weld interface. The microhardness values in stir zone of weld are found larger than lower welding speed at constant rotational velocity of 1400 rpm of friction stir welding tool. The similar effects on microhardness values are found in the thermo-mechanically affected zone and heat affected zone. The fine microstructure is observed at 31.5 mm/min welding speed compared to the 25 mm/min welding speed at 1400 rpm.

Bronchial reactions to exposure to welding fumes.

PubMed Central

Contreras, G R; Chan-Yeung, M

1997-01-01

OBJECTIVES: To study the airway response and its mechanism to welding fumes in six welders with respiratory symptoms. METHODS: Methacholine and welding challenge tests were carried out. The concentration of welding fumes during the exposure test was measured. On two subjects who developed bronchoconstricition to welding challenge, additional tests were carried out including prick, patch, and inhalation challenges with metal salt solutions. RESULTS: Three subjects developed immediate bronchial reaction to exposure to welding fume; one to mild steel and stainless steel welding, another to mild steel and galvanised welding, and one only to galvanised welding. They all had a moderate to pronounced degree of non-specific bronchial hyperresponsiveness. The concentration of fumes during welding tests, particularly to galvanised welding, was high. An inhalation challenge test with zinc chloride salt solution in two subjects who reacted to galvanised welding was negative. Prick and patch tests with zinc chloride were also negative. CONCLUSION: The airway response to welding in these subjects is non-specific and is due to irritation rather than to sensitisation. PMID:9538358

Bronchial reactions to exposure to welding fumes.

PubMed

Contreras, G R; Chan-Yeung, M

1997-11-01

To study the airway response and its mechanism to welding fumes in six welders with respiratory symptoms. Methacholine and welding challenge tests were carried out. The concentration of welding fumes during the exposure test was measured. On two subjects who developed bronchoconstricition to welding challenge, additional tests were carried out including prick, patch, and inhalation challenges with metal salt solutions. Three subjects developed immediate bronchial reaction to exposure to welding fume; one to mild steel and stainless steel welding, another to mild steel and galvanised welding, and one only to galvanised welding. They all had a moderate to pronounced degree of non-specific bronchial hyperresponsiveness. The concentration of fumes during welding tests, particularly to galvanised welding, was high. An inhalation challenge test with zinc chloride salt solution in two subjects who reacted to galvanised welding was negative. Prick and patch tests with zinc chloride were also negative. The airway response to welding in these subjects is non-specific and is due to irritation rather than to sensitisation.

Automatic hot wire GTA welding of pipe offers speed and increased deposition

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

Sykes, I.; Digiacomo, J.

1995-07-01

Heavy-wall pipe welding for the power and petrochemical industry must meet code requirements. Contractors strive to meet these requirements in the most productive way possible. The challenge put to orbital welding equipment manufacturers is to produce pipe welding equipment that cost-effectively produces code-quality welds. Orbital welding equipment using the GTA process has long produced outstanding quality results but has lacked the deposition rate to compete cost effectively with other manual and semiautomatic processes such as SMAW, FCAW and GMAW. In recent years, significant progress has been made with the use of narrow-groove weld joint designs to reduce weld joint volumemore » and improve welding times. Astro Arc Polysoude, an orbital welding equipment manufacturer based in Sun Valley, Calif., and Nantes, France, has combined the hot wire GTAW process with orbital welding equipment using a narrow-groove weld joint design. Field test results show this process and procedure is a good alternative for many heavy-wall-pipe welding applications.« less

Monitoring the quality of welding based on welding current and ste analysis

NASA Astrophysics Data System (ADS)

Mazlan, Afidatusshimah; Daniyal, Hamdan; Izzani Mohamed, Amir; Ishak, Mahadzir; Hadi, Amran Abdul

2017-10-01

Qualities of welding play an important part in industry especially in manufacturing field. Post-welding non-destructive test is one of the importance process to ensure the quality of welding but it is time consuming and costly. To reduce the chance of defects, online monitoring had been utilized by continuously sense some of welding parameters and predict welding quality. One of the parameters is welding current, which is rich of information but lack of study focus on extract them at signal analysis level. This paper presents the analysis of welding current using Short Time Energy (STE) signal processing to quantify the pattern of the current. GMAW set with carbon steel specimens are used in this experimental study with high-bandwidth and high sampling rate oscilloscope capturing the welding current. The results indicate welding current as signatures have high correlation with the welding process. Continue with STE analysis, the value below 5000 is declare as good welding, meanwhile the STE value more than 6000 is contained defect.

Sensors control gas metal arc welding

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

Siewert, T.A.; Madigan, R.B.; Quinn, T.P.

1997-04-01

The response time of a trained welder from the time a weld problem is identified to the time action is taken is about one second--especially after a long, uneventful period of welding. This is acceptable for manual welding because it is close to the time it takes for the weld pool to solidify. If human response time were any slower, manual welding would not be possible. However, human response time is too slow to respond to some weld events, such as melting of the contact tube in gas metal arc welding (GMAW), and only automated intelligent control systems can reactmore » fast enough to correct or avoid these problems. Control systems incorporate welding knowledge that enables intelligent decisions to be made about weld quality and, ultimately, to keep welding parameters in the range where only high-quality welds are produced. This article discusses the correlation of electrical signals with contact-tube wear, changes in shielding gas, changes in arc length, and other weld process data.« less

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.

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.

Influence of the Gap Width on the Geometry of the Welded Joint in Hybrid Laser-Arc Welding

NASA Astrophysics Data System (ADS)

Turichin, G.; Tsibulskiy, I.; Kuznetsov, M.; Akhmetov, A.; Mildebrath, M.; Hassel, T.

The aim of this research was the experimental investigation of the influence of the gap width and speed of the welding wire on the changes of the geometry in the welded joint in the hybrid laser-arc welding of shipbuilding steel RS E36. The research was divided into three parts. First, in order to understand the influence of the gap width on the welded joint geometry, experimental research was done using continuous wave fiber laser IPG YLS-15000 with arc rectifier VDU-1500DC. The second part involved study of the geometry of the welded joint and hardness test results. Three macrosections from each welded joint were obtained. Influence of the gap width and welding wire speed on the welded joint geometry was researched in the three lines: in the right side of the plates, middle welded joint and in the root welded joint.

The effects of welded joint characteristics on its properties in HDPE thermal fusion welding

NASA Astrophysics Data System (ADS)

Dai, Hongbin; Peng, Jun

2017-05-01

In this paper, PE100 pipes with the diameter of 200 mm and the thickness of 11.9 mm were used as material. The welded joints were obtained in different welding pressures with the optimal welding temperature of 220∘C. Reheating process on the welded joints with the temperature of 130∘C was carried out. The joints exhibited X-type, and the cause of X-type joints was discussed. The temperature field in the forming process of welded joints was measured, and tensile and bending tests on welded joints were carried out. The fracture surface of welded joints was observed by scanning electron microscopy (SEM), and crystallinity calculation was taken by X-ray diffraction (XRD). The mechanism of X-type weld profile effects on welded joints properties was analyzed. It was concluded that the mechanical properties of welded joints decrease with the reduced X distance between lines.

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.

Optimization and Prediction of Angular Distortion and Weldment Characteristics of TIG Square Butt Joints

NASA Astrophysics Data System (ADS)

Narang, H. K.; Mahapatra, M. M.; Jha, P. K.; Biswas, P.

2014-05-01

Autogenous arc welds with minimum upper weld bead depression and lower weld bead bulging are desired as such welds do not require a second welding pass for filling up the upper bead depressions (UBDs) and characterized with minimum angular distortion. The present paper describes optimization and prediction of angular distortion and weldment characteristics such as upper weld bead depression and lower weld bead bulging of TIG-welded structural steel square butt joints. Full factorial design of experiment was utilized for selecting the combinations of welding process parameter to produce the square butts. A mathematical model was developed to establish the relationship between TIG welding process parameters and responses such as upper bead width, lower bead width, UBD, lower bead height (bulging), weld cross-sectional area, and angular distortions. The optimal welding condition to minimize UBD and lower bead bulging of the TIG butt joints was identified.

Creep rupture strength of activated-TIG welded 316L(N) stainless steel

NASA Astrophysics Data System (ADS)

Sakthivel, T.; Vasudevan, M.; Laha, K.; Parameswaran, P.; Chandravathi, K. S.; Mathew, M. D.; Bhaduri, A. K.

2011-06-01

316L(N) stainless steel plates were joined using activated-tungsten inert gas (A-TIG) welding and conventional TIG welding process. Creep rupture behavior of 316L(N) base metal, and weld joints made by A-TIG and conventional TIG welding process were investigated at 923 K over a stress range of 160-280 MPa. Creep test results showed that the enhancement in creep rupture strength of weld joint fabricated by A-TIG welding process over conventional TIG welding process. Both the weld joints fractured in the weld metal. Microstructural observation showed lower δ-ferrite content, alignment of columnar grain with δ-ferrite along applied stress direction and less strength disparity between columnar and equiaxed grains of weld metal in A-TIG joint than in MP-TIG joint. These had been attributed to initiate less creep cavitation in weld metal of A-TIG joint leading to improvement in creep rupture strength.

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

Stine, Andrew Martin; Pierce, Stanley W.; Moniz, Paul F.

The welding equipment used for welding iridium containers (clads) at Los Alamos National Laboratory is twenty five years old and is undergoing an upgrade. With the upgrade, there is a requirement for requalification of the welding process, and the opportunity for process improvement. Testing of the new system and requalification will require several welds on iridium test parts and clads, and any efforts to improve the process will add to the need for iridium parts. The extreme high cost of iridium imposes a severe limitation on the extent of test welding that can be done. The 2 inch diameter, 0.027more » inch thick, iridium blank disc that the clad cup is formed from, is useful for initial weld trials, but it costs $5000. The development clad sets needed for final tests and requalification cost $15,000 per set. A solution to iridium cost issue would be to do the majority of the weld development on a less expensive surrogate metal with similar weld characteristics. One such metal is molybdenum. Since its melting index (melting temperature x thermal conductivity) is closest to iridium, welds on molybdenum should be similar in size for a given weld power level. Molybdenum is inexpensive; a single 2 inch molybdenum disc costs only $9. In order to evaluate molybdenum as a surrogate for iridium, GTA welds were first developed to provide full penetration on 0.030 inch thick molybdenum discs at speeds of 20, 25, and 30 inches per minute (ipm). These weld parameters were then repeated on the standard 0.027 inch thick iridium blanks. The top surface and bottom surface (root) width and grain structure of the molybdenum and iridium welds were compared, and similarities were evident between the two metals. Due to material and thickness differences, the iridium welds were approximately 35% wider than the molybdenum welds. A reduction in iridium weld current of 35% produce welds slightly smaller than the molybdenum welds yet showed that current could be scaled according to molybdenum/iridium weld width ratio to achieve similar welds. Further weld trials using various thicknesses of molybdenum determined that 0.024 inch thick molybdenum material would best match the 0.027 inch thick iridium in achieving comparable welds when using the same welding parameters. Across the range of welding speeds, the characteristic weld pool shape and solidification grain structure in the two materials was also similar. With the similarity of welding characteristics confirmed, and the appropriate thickness of molybdenum determined, it has been concluded that the use of molybdenum discs and tube sections will greatly expand the weld testing opportunities prior to iridium weld qualification« less

Development of an intelligent system for cooling rate and fill control in GMAW. [Gas Metal Arc Welding (GMAW)

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

Einerson, C.J.; Smartt, H.B.; Johnson, J.A.

1992-01-01

A control strategy for gas metal arc welding (GMAW) is developed in which the welding system detects certain existing conditions and adjusts the process in accordance to pre-specified rules. This strategy is used to control the reinforcement and weld bead centerline cooling rate during welding. Relationships between heat and mass transfer rates to the base metal and the required electrode speed and welding speed for specific open circuit voltages are taught to a artificial neural network. Control rules are programmed into a fuzzy logic system. TRADITOINAL CONTROL OF THE GMAW PROCESS is based on the use of explicit welding proceduresmore » detailing allowable parameter ranges on a pass by pass basis for a given weld. The present work is an exploration of a completely different approach to welding control. In this work the objectives are to produce welds having desired weld bead reinforcements while maintaining the weld bead centerline cooling rate at preselected values. The need for this specific control is related to fabrication requirements for specific types of pressure vessels. The control strategy involves measuring weld joint transverse cross-sectional area ahead of the welding torch and the weld bead centerline cooling rate behind the weld pool, both by means of video (2), calculating the required process parameters necessary to obtain the needed heat and mass transfer rates (in appropriate dimensions) by means of an artificial neural network, and controlling the heat transfer rate by means of a fuzzy logic controller (3). The result is a welding machine that senses the welding conditions and responds to those conditions on the basis of logical rules, as opposed to producing a weld based on a specific procedure.« less

[Study on the arc spectral information for welding quality diagnosis].

PubMed

Li, Zhi-Yong; Gu, Xiao-Yan; Li, Huan; Yang, Li-Jun

2009-03-01

Through collecting the spectral signals of TIG and MIG welding arc with spectrometer, the arc light radiations were analyzed based on the basic theory of plasma physics. The radiation of welding arc distributes over a broad range of frequency, from infrared to ultraviolet. The arc spectrum is composed of line spectra and continuous spectra. Due to the variation of metal density in the welding arc, there is great difference between the welding arc spectra of TIG and MIG in both their intensity and distribution. The MIG welding arc provides more line spectra of metal and the intensity of radiation is greater than TIG. The arc spectrum of TIG welding is stable during the welding process, disturbance factors that cause the spectral variations can be reflected by the spectral line related to the corresponding element entering the welding arc. The arc spectrum of MIG welding will fluctuate severely due to droplet transfer, which produces "noise" in the line spectrum aggregation zone. So for MIG welding, the spectral zone lacking spectral line is suitable for welding quality diagnosis. According to the characteristic of TIG and MIG, special spectral zones were selected for welding quality diagnosis. For TIG welding, the selected zone is in ultraviolet zone (230-300 nm). For MIG welding, the selected zone is in visible zone (570-590 nm). With the basic theory provided for welding quality diagnosis, the integral intensity of spectral signal in the selected zone of welding process with disturbing factor was studied to prove the theory. The results show that the welding quality and disturbance factors can be diagnosed with good signal to noise ratio in the selected spectral zone compared with signal in other spectral zone. The spectral signal can be used for real-time diagnosis of the welding quality.

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

NASA Astrophysics Data System (ADS)

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

2017-08-01

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

Clamp force and alignment checking device

DOEpatents

Spicer, John Patrick; Cai, Wayne W.; Chakraborty, Debejyo; Mink, Keith

2017-04-11

A check fixture measures a total clamp force applied by a welder device. The welder device includes a welding horn having a plurality of weld pads and welding anvil having a plurality of weld pads. The check fixture includes a base member operatively supporting a plurality of force sensors. The base member and the force sensors are received between the weld pads of the welding horn and the anvil pads of the welding anvil. Each force sensor is configured to measure an individual clamp force applied thereto by corresponding weld and anvil pads when the base member is received between the welding horn and the welding anvil and the welder device is in the clamped position. The individual clamp forces are used to determine whether the weld and/or anvil pads are worn or misaligned.

Automated GMA welding of austenitic stainless steel pipe

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

Tahash, G.J.

1996-12-31

The study focused on reducing weld cycle times of rotatable subassemblies (spools) using automated welding equipment. A unique automatic Gas Metal Arc Welding (GMAW) system was used to produce a series of pipe to pipe welds on 141 mm (5 in.) schedule 80 seamless stainless steel pipe. After manual tack welding, the adaptive control system welded the root pass of the argon gas backed open vee groove circumferential butt joints in the IG rotated position with short circuiting transfer GMAW. The fill and cover passes were welded automatically with spray transfer GMAW. Automatic welding cycle times were found to bemore » 50--80 percent shorter than the current techniques of roll welding with Shielded Metal Arc Welding and manual Gas Tungsten Arc Welding. Weld costs ({Brit_pounds}/m), including amortization, for the various systems were compared. The cost of automated GMA welds was virtually equivalent to the most competitive methods while depositing 75% more filler metal per year. Also investigated were metallurgical effects generated by weld thermal cycling, and the associated effects on mechanical properties of the weld joint. Mechanical properties of the welds met or exceeded those of the base metal. Sensitization of the pipe did not occur in the heat affected zone (HAZ), based on the absence of evidence of intergranular attack in modified Strauss corrosion tests and despite the fact of interpass temperatures well above recommended maximums. Cooling rates of 3--5 C/s in the heat affected zone of the four pass welds were measured by thermocouple technique and found to be within the non-sensitizing range for this alloy.« less

49 CFR 195.230 - Welds: Repair or removal of defects.

Code of Federal Regulations, 2012 CFR

2012-10-01

... adversely affect the quality of the weld repair. After repair, the segment of the weld that was repaired... welding procedure used to make the original weld are met upon completion of the final weld repair. [Amdt...

49 CFR 195.230 - Welds: Repair or removal of defects.

Code of Federal Regulations, 2014 CFR

2014-10-01

... adversely affect the quality of the weld repair. After repair, the segment of the weld that was repaired... welding procedure used to make the original weld are met upon completion of the final weld repair. [Amdt...

49 CFR 195.230 - Welds: Repair or removal of defects.

Code of Federal Regulations, 2011 CFR

2011-10-01

... adversely affect the quality of the weld repair. After repair, the segment of the weld that was repaired... welding procedure used to make the original weld are met upon completion of the final weld repair. [Amdt...

49 CFR 195.230 - Welds: Repair or removal of defects.

Code of Federal Regulations, 2013 CFR

2013-10-01

... adversely affect the quality of the weld repair. After repair, the segment of the weld that was repaired... welding procedure used to make the original weld are met upon completion of the final weld repair. [Amdt...

49 CFR 195.230 - Welds: Repair or removal of defects.

Code of Federal Regulations, 2010 CFR

2010-10-01

... adversely affect the quality of the weld repair. After repair, the segment of the weld that was repaired... welding procedure used to make the original weld are met upon completion of the final weld repair. [Amdt...

Arc Welding of Mg Alloys: Oxide Films, Irregular Weld Shape and Liquation Cracking

NASA Astrophysics Data System (ADS)

Chai, Xiao

The use of Mg alloys for vehicle weight reduction has been increasing rapidly worldwide. Gas-metal arc welding (GMAW) has the potential for mass-production welding of Mg alloys. Recently, the University of Wisconsin demonstrated in bead-on-plate GMAW of Mg alloys that severe spatter can be eliminated by using controlled short circuiting (CSC), and severe hydrogen porosity can be eliminated by removing Mg(OH)2. The present study aimed at actual butt and lap welding of Mg alloys by CSC-GMAW and susceptibility of Mg alloys to weld-edge cracking using the circular-patch welding test. Sound welds were made without spatter and hydrogen porosity butt and lap welding of AZ 31 Mg using CSC-GMAW , with butt welds approaching 100% of the base-metal strength. However, three new significant issues were found to occur easily and degrade the weld quality significantly: 1. formation of oxide films inside butt welds, 2. formation of high crowns on butt welds, and 3. formation of fingers from lap welds. The mechanisms of their formation were established, and the methods for their elimination or reduction were demonstrated. Circular-patch welds were made on most widely used Mg casting alloy AZ91, the most widely used Mg wrought alloy AZ31 with three different Mg filler wires AZ31, AZ61 and AZ92. The susceptibility to cracking along the weld edge was predicted and compared against the experimental results. Such a prediction has not been made for welds of Mg alloys before.

Tailor-welded blanks and their production

NASA Astrophysics Data System (ADS)

Yan, Qi

2005-01-01

Tailor welded blanks had been widely used in the automobile industry. A tailor welded blank consists of several flat sheets that were laser welded together before stamping. A combination of different materials, thickness, and coatings could be welded together to form a blank for stamping car body panels. As for the material for automobile industry, this technology was one of the development trend for automobile industry because of its weight reduction, safety improvement and economical use of materials. In this paper, the characters and production of tailor welded blanks in the market were discussed in detail. There had two major methods to produce tailor welded blanks. Laser welding would replace mesh seam welding for the production of tailor welded blanks in the future. The requirements on the edge preparation of unwelded blanks for tailor welded blanks were higher than the other steel processing technology. In order to produce the laser welded blank, there had the other process before the laser welding in the factory. In the world, there had three kinds of patterns for the large volume production of tailor welded blanks. In China, steel factory played the important role in the promotion of the application of tailor welded blanks. The competition for the supply of tailor welded blanks to the automobile industry would become fierce in the near future. As a result, the demand for the quality control on the production of tailor welded blanks would be the first priority concern for the factory.

Forming Completely Penetrated Welded T-joints when Pulsed Arc Welding

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

Geochemical and Depth Variations at the Galápagos 93.25˚W Propagating Rift

NASA Astrophysics Data System (ADS)

Rotella, M.; Sinton, J.; Mahoney, J.; Chazey, W.

2006-12-01

The 93.25°W propagating rift on the Galápagos Spreading Center (GSC) differs markedly from the better-known propagator at 95.5°W in having the morphology of a classic overlapping spreading center (~24 km of overlap and 7.5 km of offset). It has a higher propagation rate (70 vs 48 mm/yr) [Wilson & Hey, JGR v. 100, 1995] and is breaking through younger crust (260 vs 910 ka); overall magma supply is ~20% greater, as the area is closer to the Galápagos hotspot. The overlapping limbs lack pronounced bathymetric lows, instead they are up to 150 m shallower than the surrounding axial ridges away from the offset. Lavas are T-MORB; failing rift lavas show a slight increase in Mg within the overlap zone but propagating rift lavas lack the strong fractionation anomaly that characterizes the propagating limb at 95.5°W and many other propagating rifts. New major and trace element data on 28 samples from 24 dredge stations along a 175 km section of the GSC spanning the 93.25°W offset indicate significant, systematic variations in mantle sources and melting processes on each limb of the system. Fractionation-corrected ratios of highly to moderately incompatible elements (e.g. La/Yb, Sm/Yb, Zr/Y) show constant values along the propagating rift east of 93.2°W, but within the overlap zone these ratios increase sharply up to a factor of 1.5, then gradually decline to the west. In contrast, the failing rift shows constant to moderately increasing ratios as the overlap zone is approached from the west, with lower overall ratios within the zone. These variations could be interpreted to reflect a counter-intuitive relationship of gradually increasing extent of partial melting with progressive failure of the dying rift, consistent with the striking shoaling of the failing limb, or melting of incompatible-element depleted mantle. Variations along the eastern, propagating rift suggest either a sharp decrease in extent of melting or tapping of a more incompatible-element-enriched mantle source within the overlap zone. Limited Nd-Pb-Sr isotopic data suggest source variations are required in addition to variations in extent of melting. Thus, in contrast to other well-documented propagators where geochemical variations are dominated by magma chamber effects, variations around the 93.25°W system appear to be dominated by melting and source.

Control of Gas Tungsten Arc welding pool shape by trace element addition to the weld pool

DOEpatents

Heiple, C.R.; Burgardt, P.

1984-03-13

An improved process for Gas Tungsten Arc welding maximizes the depth/width ratio of the weld pool by adding a sufficient amount of a surface active element to insure inward fluid flow, resulting in deep, narrow welds. The process is especially useful to eliminate variable weld penetration and shape in GTA welding of steels and stainless steels, particularly by using a sulfur-doped weld wire in a cold wire feed technique.

Electron Beam Welding to Join Gamma Titanium Aluminide Articles

NASA Technical Reports Server (NTRS)

Kelly, Thomas Joseph (Inventor)

2008-01-01

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

Friction Stir Process Mapping Methodology

NASA Technical Reports Server (NTRS)

Kooney, Alex; Bjorkman, Gerry; Russell, Carolyn; Smelser, Jerry (Technical Monitor)

2002-01-01

In FSW (friction stir welding), the weld process performance for a given weld joint configuration and tool setup is summarized on a 2-D plot of RPM vs. IPM. A process envelope is drawn within the map to identify the range of acceptable welds. The sweet spot is selected as the nominal weld schedule. The nominal weld schedule is characterized in the expected manufacturing environment. The nominal weld schedule in conjunction with process control ensures a consistent and predictable weld performance.

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.

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

NASA Astrophysics Data System (ADS)

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

2018-04-01

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

The Implementation and Demonstration of Flame Detection and Wireless Communications in a Consumer Appliance to Improve Fire Detection Capabilities

DTIC Science & Technology

2007-06-08

Temperature Detectors (RTDs), thermistors , bimetallic devices, liquid expansion devices, and change-of-state devices. Liquid expansion, change-of...sterilization lamps, halogen lamps, direct or reflected sunlight on the sensor, electrical or welding sparks, radiation sources and high 7 Figure 1, Standard

Sources of Influence on Students' Enrollment Decision in Post-Secondary Vocational-Technical Education.

ERIC Educational Resources Information Center

Sandford, Brian A.; Torres, Robert M.

Descriptive survey research methodology was used to explore and describe factors--demographic, influential, or informational--that influenced student enrollment decisions in entry-level Welding Technology Program (WTP) courses. The target population included 38 students enrolled in the first semester courses offered by the WTP at Dona Ana…

29 CFR 1910.252 - General requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... to prevent ignition. (x) Noncombustible walls. If welding is to be done on a metal wall, partition... is incorporated by reference as specified in § 1910.6. (vii) X-ray inspection. The use of X-rays and... American National Standard Safety Standard for Non-Medical X-ray and Sealed Gamma-Ray Sources, ANSI Z54.1...

Lorentz force detuning analysis of the Spallation Neutron Source (SNS) accelerating cavities.

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

Mitchell, R.R.; Matsumoto, K. Y.; Ciovati, G.

2001-01-01

The Spallation Neutron Source (SNS) project incorporates a superconducting radio-frequency (SRF) accelerator for the final section of the pulsed mode linac. Cavities with geometrical {beta} values of {beta}=0.61 and {beta}=0.81 are utilized in the SRF section, and are constructed out of thin-walled niobium with stiffener rings welded between the cells near the iris. The welded titanium helium vessel and tuner assembly restrains the cavity beam tubes. Cavities with {beta} values less than one have relatively steep and flat side-walls making the cavities susceptible to Lorentz force detuning. In addition, the pulsed RF induces cyclic Lorentz pressures that mechanically excite themore » cavities, producing a dynamic Lorentz force detuning different from a continuous RF system. The amplitude of the dynamic detuning for a given cavity design is a function of the mechanical damping, stiffness of the tuner/helium vessel assembly, RF pulse profile, and the RF pulse rate. This paper presents analysis and testing results to date, and indicates areas where more investigation is required.« less

Weld procedure produces quality welds for thick sections of Hastelloy-X

NASA Technical Reports Server (NTRS)

Flens, F. J.; Fletcher, C. W.; Glasier, L. F., Jr.

1967-01-01

Welding program produces premium quality, multipass welds in heavy tube sections of Hastelloy-X. It develops semiautomatic tungsten/inert gas procedures, weld wire procurement specifications material weld properties, welder-operator training, and nondestructive testing inspection techniques and procedures.

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

NASA Astrophysics Data System (ADS)

Yang, Yang

2017-05-01

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

Fusion welding studies using laser on Ti-SS dissimilar combination

NASA Astrophysics Data System (ADS)

Shanmugarajan, B.; Padmanabham, G.

2012-11-01

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

Thermo-Mechanical Analysis of a Single-Pass Weld Overlay and Girth Welding in Lined Pipe

NASA Astrophysics Data System (ADS)

Obeid, Obeid; Alfano, Giulio; Bahai, Hamid

2017-08-01

The paper presents a nonlinear heat-transfer and mechanical finite-element (FE) analyses of a two-pass welding process of two segments of lined pipe made of a SUS304 stainless steel liner and a C-Mn steel pipe. The two passes consist of the single-pass overlay welding (inner lap weld) of the liner with the C-Mn steel pipe for each segment and the single-pass girth welding (outer butt weld) of the two segments. A distributed power density of the moving welding torch and a nonlinear heat-transfer coefficient accounting for both radiation and convection have been used in the analysis and implemented in user subroutines for the FE code ABAQUS. The modeling procedure has been validated against previously published experimental results for stainless steel and carbon steel welding separately. The model has been then used to determine the isotherms induced by the weld overlay and the girth welding and to clarify their influence on the transient temperature field and residual stress in the lined pipe. Furthermore, the influence of the cooling time between weld overlay and girth welding and of the welding speed have been examined thermally and mechanically as they are key factors that can affect the quality of lined pipe welding.

Welded joints integrity analysis and optimization for fiber laser welding of dissimilar materials

NASA Astrophysics Data System (ADS)

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

2016-11-01

Dissimilar materials welded joints provide many advantages in power, automotive, chemical, and spacecraft industries. The weld bead integrity which is determined by process parameters plays a significant role in the welding quality during the fiber laser welding (FLW) of dissimilar materials. In this paper, an optimization method by taking the integrity of the weld bead and weld area into consideration is proposed for FLW of dissimilar materials, the low carbon steel and stainless steel. The relationships between the weld bead integrity and process parameters are developed by the genetic algorithm optimized back propagation neural network (GA-BPNN). The particle swarm optimization (PSO) algorithm is taken for optimizing the predicted outputs from GA-BPNN for the objective. Through the optimization process, the desired weld bead with good integrity and minimum weld area are obtained and the corresponding microstructure and microhardness are excellent. The mechanical properties of the optimized joints are greatly improved compared with that of the un-optimized welded joints. Moreover, the effects of significant factors are analyzed based on the statistical approach and the laser power (LP) is identified as the most significant factor on the weld bead integrity and weld area. The results indicate that the proposed method is effective for improving the reliability and stability of welded joints in the practical production.

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

NASA Astrophysics Data System (ADS)

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

2017-03-01

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

Electronic imaging system and technique

DOEpatents

Bolstad, J.O.

1984-06-12

A method and system for viewing objects obscurred by intense plasmas or flames (such as a welding arc) includes a pulsed light source to illuminate the object, the peak brightness of the light reflected from the object being greater than the brightness of the intense plasma or flame; an electronic image sensor for detecting a pulsed image of the illuminated object, the sensor being operated as a high-speed shutter; and electronic means for synchronizing the shutter operation with the pulsed light source.

Electronic imaging system and technique

DOEpatents

Bolstad, Jon O.

1987-01-01

A method and system for viewing objects obscurred by intense plasmas or flames (such as a welding arc) includes a pulsed light source to illuminate the object, the peak brightness of the light reflected from the object being greater than the brightness of the intense plasma or flame; an electronic image sensor for detecting a pulsed image of the illuminated object, the sensor being operated as a high-speed shutter; and electronic means for synchronizing the shutter operation with the pulsed light source.

Ultrabright femtosecond source of biphotons based on a spatial mode inverter.

PubMed

Jarutis, Vygandas; Juodkazis, Saulius; Mizeikis, Vygantas; Sasaki, Keiji; Misawa, Hiroaki

2005-02-01

A method of enhancing the efficiency of entangled biphoton sources based on a type II femtosecond spontaneous parametric downconversion (SPDC) process is proposed and implemented experimentally. Enhancement is obtained by mode inversion of one of the SPDC output beams, which allows the beams to overlap completely, thus maximizing the number of SPDC photon pairs with optimum spatiotemporal overlap. By use of this method, biphoton count rates as high as 16 kHz from a single 0.5-mm-long beta-barium borate crystal pumped by second-harmonic radiation from a Ti:sapphire laser were obtained.

30 CFR 250.110 - What must I include in my welding plan?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What must I include in my welding plan? 250.110... must I include in my welding plan? You must include all of the following in the Welding Plan that you... qualified personnel weld; (c) Practices and procedures for safe welding that address: (1) Welding in...

Fluid Flow Phenomena during Welding

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

Zhang, Wei

2011-01-01

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

Enabling high speed friction stir welding of aluminum tailor welded blanks

NASA Astrophysics Data System (ADS)

Hovanski, Yuri

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

Automatic welding of stainless steel tubing

NASA Technical Reports Server (NTRS)

Clautice, W. E.

1978-01-01

The use of automatic welding for making girth welds in stainless steel tubing was investigated as well as the reduction in fabrication costs resulting from the elimination of radiographic inspection. Test methodology, materials, and techniques are discussed, and data sheets for individual tests are included. Process variables studied include welding amperes, revolutions per minute, and shielding gas flow. Strip chart recordings, as a definitive method of insuring weld quality, are studied. Test results, determined by both radiographic and visual inspection, are presented and indicate that once optimum welding procedures for specific sizes of tubing are established, and the welding machine operations are certified, then the automatic tube welding process produces good quality welds repeatedly, with a high degree of reliability. Revised specifications for welding tubing using the automatic process and weld visual inspection requirements at the Kennedy Space Center are enumerated.

Integrated optical sensor

DOEpatents

Watkins, Arthur D.; Smartt, Herschel B.; Taylor, Paul L.

1994-01-01

An integrated optical sensor for arc welding having multifunction feedback control. The sensor, comprising generally a CCD camera and diode laser, is positioned behind the arc torch for measuring weld pool position and width, standoff distance, and post-weld centerline cooling rate. Computer process information from this sensor is passed to a controlling computer for use in feedback control loops to aid in the control of the welding process. Weld pool position and width are used in a feedback loop, by the weld controller, to track the weld pool relative to the weld joint. Sensor standoff distance is used in a feedback loop to control the contact tip to base metal distance during the welding process. Cooling rate information is used to determine the final metallurgical state of the weld bead and heat affected zone, thereby controlling post-weld mechanical properties.

Integrated optical sensor

DOEpatents

Watkins, A.D.; Smartt, H.B.; Taylor, P.L.

1994-01-04

An integrated optical sensor for arc welding having multifunction feedback control is described. The sensor, comprising generally a CCD camera and diode laser, is positioned behind the arc torch for measuring weld pool position and width, standoff distance, and post-weld centerline cooling rate. Computer process information from this sensor is passed to a controlling computer for use in feedback control loops to aid in the control of the welding process. Weld pool position and width are used in a feedback loop, by the weld controller, to track the weld pool relative to the weld joint. Sensor standoff distance is used in a feedback loop to control the contact tip to base metal distance during the welding process. Cooling rate information is used to determine the final metallurgical state of the weld bead and heat affected zone, thereby controlling post-weld mechanical properties. 6 figures.

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

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

NASA Astrophysics Data System (ADS)

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

2010-11-01

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

The 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.

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.

Grinding Parts For Automatic Welding

NASA Technical Reports Server (NTRS)

Burley, Richard K.; Hoult, William S.

1989-01-01

Rollers guide grinding tool along prospective welding path. Skatelike fixture holds rotary grinder or file for machining large-diameter rings or ring segments in preparation for welding. Operator grasps handles to push rolling fixture along part. Rollers maintain precise dimensional relationship so grinding wheel cuts precise depth. Fixture-mounted grinder machines surface to quality sufficient for automatic welding; manual welding with attendant variations and distortion not necessary. Developed to enable automatic welding of parts, manual welding of which resulted in weld bead permeated with microscopic fissures.

Method for controlling gas metal arc welding

DOEpatents

Smartt, Herschel B.; Einerson, Carolyn J.; Watkins, Arthur D.

1989-01-01

The heat input and mass input in a Gas Metal Arc welding process are controlled by a method that comprises calculating appropriate values for weld speed, filler wire feed rate and an expected value for the welding current by algorithmic function means, applying such values for weld speed and filler wire feed rate to the welding process, measuring the welding current, comparing the measured current to the calculated current, using said comparison to calculate corrections for the weld speed and filler wire feed rate, and applying corrections.

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

PubMed

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

2017-09-15

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

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

PubMed Central

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

2017-01-01

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

Active weld control

NASA Technical Reports Server (NTRS)

Powell, Bradley W.; Burroughs, Ivan A.

1994-01-01

Through the two phases of this contract, sensors for welding applications and parameter extraction algorithms have been developed. These sensors form the foundation of a weld control system which can provide action weld control through the monitoring of the weld pool and keyhole in a VPPA welding process. Systems of this type offer the potential of quality enhancement and cost reduction (minimization of rework on faulty welds) for high-integrity welding applications. Sensors for preweld and postweld inspection, weld pool monitoring, keyhole/weld wire entry monitoring, and seam tracking were developed. Algorithms for signal extraction were also developed and analyzed to determine their application to an adaptive weld control system. The following sections discuss findings for each of the three sensors developed under this contract: (1) weld profiling sensor; (2) weld pool sensor; and (3) stereo seam tracker/keyhole imaging sensor. Hardened versions of these sensors were designed and built under this contract. A control system, described later, was developed on a multiprocessing/multitasking operating system for maximum power and flexibility. Documentation for sensor mechanical and electrical design is also included as appendices in this report.

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

NASA Astrophysics Data System (ADS)

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

2012-09-01

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

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.

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

NASA Astrophysics Data System (ADS)

Kutsuna, Muneharu; Chen, Liang

2003-03-01

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

Upgraded HFIR Fuel Element Welding System

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

Sease, John D

2010-02-01

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

Development of an intelligent system for cooling rate and fill control in GMAW

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

Einerson, C.J.; Smartt, H.B.; Johnson, J.A.

1992-09-01

A control strategy for gas metal arc welding (GMAW) is developed in which the welding system detects certain existing conditions and adjusts the process in accordance to pre-specified rules. This strategy is used to control the reinforcement and weld bead centerline cooling rate during welding. Relationships between heat and mass transfer rates to the base metal and the required electrode speed and welding speed for specific open circuit voltages are taught to a artificial neural network. Control rules are programmed into a fuzzy logic system. TRADITOINAL CONTROL OF THE GMAW PROCESS is based on the use of explicit welding proceduresmore » detailing allowable parameter ranges on a pass by pass basis for a given weld. The present work is an exploration of a completely different approach to welding control. In this work the objectives are to produce welds having desired weld bead reinforcements while maintaining the weld bead centerline cooling rate at preselected values. The need for this specific control is related to fabrication requirements for specific types of pressure vessels. The control strategy involves measuring weld joint transverse cross-sectional area ahead of the welding torch and the weld bead centerline cooling rate behind the weld pool, both by means of video (2), calculating the required process parameters necessary to obtain the needed heat and mass transfer rates (in appropriate dimensions) by means of an artificial neural network, and controlling the heat transfer rate by means of a fuzzy logic controller (3). The result is a welding machine that senses the welding conditions and responds to those conditions on the basis of logical rules, as opposed to producing a weld based on a specific procedure.« less

Development of automatic pre-tracking system for fillet weld based on laser trigonometry

NASA Astrophysics Data System (ADS)

Shen, Xiaoqin; Yu, Fusheng

2005-01-01

In this paper, an automatic fillet weld pre-tracking system for welding the work piece of lorry back boards with several bend in haul automobile is developed basing on laser trigonometry. The optical measuring head based on laser-PSD trigonometry is used as position sensor. It is placed in front of the traveling direction of welding wire to get the distances from welding wire to the two side boards of the welding lines, upper board and bottom board of the fillet weld respectively. A chip of AT89S52 is used as the micro controller in this system. The AC servomotors, ball-screws and straight guide rails constitute the sliding table to take welding wire move. The laser-PSD sensors pass through the vertical board, upper board and bottom board of the fillet weld when welding wire moves and then get the distance. The laser-PSD sensors output the analog signals. After A/D conversion, the digital signal is input into AT89S52 and calculated. Then the information of the position and lateral deviation of the welding wire when welding a certain position are gotten to control welding wires. So the weld pre-tracking for welding the work piece with long distance and large bend in haul automobile is realized. The position information is input into EEPROM to be saved for short time after handled by AT89S52. The information is as the welding position information as well as the speed adjusting data of the welding wire when it welds the several bend of the work piece. The practice indicates that this system has high pre-tracking precision, good anti-disturb ability, excellent reliability, easy operating ability and good adaptability to the field of production.

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

NASA Astrophysics Data System (ADS)

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

2017-04-01

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

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

NASA Technical Reports Server (NTRS)

Banas, C. M.

1972-01-01

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

On the hot cracking susceptibility of a semisolid aluminium 6061 weld: Application of a coupled solidification- thermomechanical model

NASA Astrophysics Data System (ADS)

Zareie Rajani, H. R.; Phillion, A. B.

2015-06-01

A coupled solidification-thermomechanical model is presented that investigates the hot tearing susceptibility of an aluminium 6061 semisolid weld. Two key phenomena are considered: excessive deformation of the semisolid weld, initiating a hot tear, and the ability of the semisolid weld to heal the hot tear by circulation of the molten metal. The model consists of two major modules: weld solidification and thermomechanical analysis. 1) By means of a multi-scale model of solidification, the microstructural evolution of the semisolid weld is simulated in 3D. The semisolid structure, which varies as a function of welding parameters, is composed of solidifying grains and a network of micro liquid channels. The weld solidification module is utilized to obtain the solidification shrinkage. The size of the micro liquid channels is used as an indicator to assess the healing ability of the semisolid weld. 2) Using the finite element method, the mechanical interaction between the weld pool and the base metal is simulated to capture the transient force field deforming the semisolid weld. Thermomechanical stresses and shrinkage stresses are both considered in the analysis; the solidification contractions are extracted from the weld solidification module and applied to the deformation simulation as boundary conditions. Such an analysis enables characterization of the potential for excessive deformation of the weld. The outputs of the model are used to study the effect of welding parameters including welding current and speed, and also welding constraint on the hot cracking susceptibility of an aluminium alloy 6061 semisolid weld.

49 CFR 192.225 - Welding procedures.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 3 2010-10-01 2010-10-01 false Welding procedures. 192.225 Section 192.225... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.225 Welding procedures. (a) Welding must be performed by a qualified welder in accordance with welding procedures...

49 CFR 192.225 - Welding procedures.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Welding procedures. 192.225 Section 192.225... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.225 Welding procedures. (a) Welding must be performed by a qualified welder in accordance with welding procedures...

49 CFR 192.225 - Welding procedures.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 3 2014-10-01 2014-10-01 false Welding procedures. 192.225 Section 192.225... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.225 Welding procedures. (a) Welding must be performed by a qualified welder in accordance with welding procedures...

49 CFR 192.225 - Welding procedures.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 3 2012-10-01 2012-10-01 false Welding procedures. 192.225 Section 192.225... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.225 Welding procedures. (a) Welding must be performed by a qualified welder in accordance with welding procedures...

49 CFR 192.225 - Welding procedures.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Welding procedures. 192.225 Section 192.225... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.225 Welding procedures. (a) Welding must be performed by a qualified welder in accordance with welding procedures...

Effect of rotation speed and welding speed on Friction Stir Welding of AA1100 Aluminium alloy

NASA Astrophysics Data System (ADS)

Raja, P.; Bojanampati, S.; Karthikeyan, R.; Ganithi, R.

2018-04-01

Aluminum AA1100 is the most widely used grade of Aluminium due to its excellent corrosion resistance, high ductility and reflective finish, the selected material was welded with Friction Stir Welding (FSW) process on a CNC machine, using a combination of different tool rotation speed (1500 rpm, 2500 rpm, 3500 rpm) and welding speed (10 mm/min, 30 mm/min, 50 mm/min) as welding parameters. The effect of FSW using this welding parameter was studied by measuring the ultimate tensile strength of the welded joints. A high-speed steel tool was prepared for welding the Aluminium AA1100 alloy having an 8mm shoulder diameter and pin dimension of 4mm diameter and 2.8 mm length. The welded joints were tested using the universal testing machine. It was found that Ultimate Tensile Strength of FSW specimen was highest with a value of 98.08 MPa when the weld was performed at rotation speed of 1500 RPM and welding speed of 50 mm/min.

Hardness variation of welded boron steel using continuous wave (CW) and pulse wave (PW) mode of fiber laser

NASA Astrophysics Data System (ADS)

Yaakob, K. I.; Ishak, M.; Idris, S. R. A.; Aiman, M. H.; Khalil, N. Z.

2017-09-01

Recent car manufacturer requirement in lightweight and optimum safety lead to utilization of boron steel with tailor welded blank approach. Laser welding process in tailor welded blank (TWB) production can be applied in continuous wave (CW) of pulse wave (PW) which produce different thermal experience in welded area. Instead of microstructure identification, hardness properties also can determine the behavior of weld area. In this paper, hardness variation of welded boron steel using PW and CW mode is investigated. Welding process is conducted using similar average power for both welding mode. Hardness variation across weld area is observed. The result shows similar hardness pattern across weld area for both welding mode. Hardness degradation at fusion zone (FZ) is due to ferrite formation existence from high heat input applied. With additional slower cooling rate for CW mode, the hardness degradation is become obvious. The normal variation of hardness behavior with PW mode might lead to good strength.

Laser welding on trough panel: 3D body part

NASA Astrophysics Data System (ADS)

Shirai, Masato; Hisano, Hirohiko

2003-03-01

Laser welding for automotive bodies has been introduced mainly by European car manufacturers since more than 10 years ago. Their purposes of laser welding introduction were mainly vehicle performance improvement and lightweight. And laser welding was applied to limited portion where shapes of panels are simple and easy to fit welded flanges. Toyota also has introduced laser welding onto 3 dimensional parts named trough panel since 1999. Our purpose of the introduction was common use of equipment. Trough panel has a complex shape and different shapes in each car type. In order to realize common use of welding equipment, we introduced parts locating equipment which had unique, small & simple jigs fo each car type and NC (Numerical Controlled) locators and air-cooled small laser head developed by ourselves to the trough welding process. Laser welding replaced spot welding and was applied linearly like stitches. Length of laser welding was determined according to comparison with statistic tensile strength and fatigue strength of spot welding.

An optimization method for defects reduction in fiber laser keyhole welding

NASA Astrophysics Data System (ADS)

Ai, Yuewei; Jiang, Ping; Shao, Xinyu; Wang, Chunming; Li, Peigen; Mi, Gaoyang; Liu, Yang; Liu, Wei

2016-01-01

Laser welding has been widely used in automotive, power, chemical, nuclear and aerospace industries. The quality of welded joints is closely related to the existing defects which are primarily determined by the welding process parameters. This paper proposes a defects optimization method that takes the formation mechanism of welding defects and weld geometric features into consideration. The analysis of welding defects formation mechanism aims to investigate the relationship between welding defects and process parameters, and weld features are considered to identify the optimal process parameters for the desired welded joints with minimum defects. The improved back-propagation neural network possessing good modeling for nonlinear problems is adopted to establish the mathematical model and the obtained model is solved by genetic algorithm. The proposed method is validated by macroweld profile, microstructure and microhardness in the confirmation tests. The results show that the proposed method is effective at reducing welding defects and obtaining high-quality joints for fiber laser keyhole welding in practical production.

The effect of welding parameters on penetration in GTA welds

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

Shirali, A.A.; Mills, K.C.

1993-07-01

The effect of various welding parameters on the penetration of GTA welds has been investigated. Increases in welding speed were found to reduce penetration; however, increases in welding current were observed to increase the penetration in high sulfur (HS) casts and decrease penetration in low sulfur (LS) steels. Plots of penetration as a function of increasing linear energy (the heat supplied per unit length of weld) revealed a similar trend with increased penetration in HS casts, but the penetration in LS casts was unaffected by increases in linear energy. These results support the Burgardt-Heiple proposition that changes in welding parametersmore » on penetration can be explained in terms of their effect, sequentially, on the temperature gradient and the Marangoni forces operating in the weld pool. Increases in arc length were found to decrease weld penetration regardless of the sulfur concentration of the steel, and the effects of electrode geometry and welding position on weld penetration were also investigated.« less

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

NASA Astrophysics Data System (ADS)

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

2014-01-01

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

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.

Content Integration across Multiple Documents Reduces Memory for Sources

ERIC Educational Resources Information Center

Braasch, Jason L. G.; McCabe, Rebecca M.; Daniel, Frances

2016-01-01

The current experiments systematically examined semantic content integration as a mechanism for explaining source inattention and forgetting when reading-to-remember multiple texts. For all 3 experiments, degree of semantic overlap was manipulated amongst messages provided by various information sources. In Experiment 1, readers' source…

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.

Effects of welding technology on welding stress based on the finite element method

NASA Astrophysics Data System (ADS)

Fu, Jianke; Jin, Jun

2017-01-01

Finite element method is used to simulate the welding process under four different conditions of welding flat butt joints. Welding seams are simulated with birth and death elements. The size and distribution of welding residual stress is obtained in the four kinds of welding conditions by Q345 manganese steel plate butt joint of the work piece. The results shown that when using two-layers welding,the longitudinal and transverse residual stress were reduced;When welding from Middle to both sides,the residual stress distribution will change,and the residual stress in the middle of the work piece was reduced.

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.

U-Groove aluminum weld strength improvement

NASA Technical Reports Server (NTRS)

Verderaime, V.; Vaughan, R.

1996-01-01

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

Investigation of Hot Cracking Behavior in Transverse Mechanically Arc Oscillated Autogenous AA2014 T6 TIG Welds

NASA Astrophysics Data System (ADS)

Biradar, N. S.; Raman, R.

2012-09-01

Hot cracking studies on autogenous AA2014 T6 TIG welds were carried out. Significant cracking was observed during linear and circular welding test (CWT) on 4-mm-thick plates. Weld metal grain structure and amount of liquid distribution during the terminal stages of solidification were the key cause for hot cracking in aluminum welds. Square-wave AC TIG welding with transverse mechanical arc oscillation (TMAO) was employed to study the cracking behavior during linear and CWT. TMAO welds with amplitude = 0.9 mm and frequency = 0.5 Hz showed significant reduction in cracking tendency. The increase in cracking resistance in the arc-oscillated weld was attributed to grain refinement and improved weld bead morphology, which improved the weld metal ductility and uniformity, respectively, of residual tensile stresses that developed during welding. The obtained results were comparable to those of reported favorable results of electromagnetic arc oscillation.

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.

Thermo-Mechanical Calculations of Hybrid Rotary Friction Welding at Equal Diameter Copper Bars and Effects of Essential Parameters on Dependent Special Variables

NASA Astrophysics Data System (ADS)

Parsa, M. H.; Davari, H.; Hadian, A. M.; Ahmadabadi, M. Nili

2007-05-01

Hybrid Rotary Friction Welding is a modified type of common rotary friction welding processes. In this welding method parameters such as pressure, angular velocity and time of welding control temperature, stress, strain and their variations. These dependent factors play an important rule in defining optimum process parameters combinations in order to improve the design and manufacturing of welding machines and quality of welded parts. Thermo-mechanical simulation of friction welding has been carried out and it has been shown that, simulation is an important tool for prediction of generated heat and strain at the weld interface and can be used for prediction of microstructure and evaluation of quality of welds. For simulation of Hybrid Rotary Friction Welding, a commercial finite element program has been used and the effects of pressure and rotary velocity of rotary part on temperature and strain variations have been investigated.

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

Welding.

ERIC Educational Resources Information Center

South Carolina State Dept. of Education, Columbia. Office of Vocational Education.

This curriculum guide is designed for use by South Carolina vocational education teachers as a continuing set of lesson plans for a two-year course on welding. Covered in the individual sections of the guide are the following topics: an orientation to welding, oxyacetylene welding, advanced oxyacetylene welding, shielded metal arc welding, TIG…

Automatic, nondestructive test monitors in-process weld quality

NASA Technical Reports Server (NTRS)

Deal, F. C.

1968-01-01

Instrument automatically and nondestructively monitors the quality of welds produced in microresistance welding. It measures the infrared energy generated in the weld as the weld is made and compares this energy with maximum and minimum limits of infrared energy values previously correlated with acceptable weld-strength tolerances.

Dual wire weld feed proportioner

NASA Technical Reports Server (NTRS)

Nugent, R. E.

1968-01-01

Dual feed mechanism enables proportioning of two different weld feed wires during automated TIG welding to produce a weld alloy deposit of the desired composition. The wires are fed into the weld simultaneously. The relative feed rates of the wires and the wire diameters determine the weld deposit composition.

Investigation of mechanical dissipation in CO2 laser-drawn fused silica fibres and welds

NASA Astrophysics Data System (ADS)

Heptonstall, Alastair; Barton, Mark; Cantley, Caroline; Cumming, Alan; Cagnoli, Geppo; Hough, James; Jones, Russell; Kumar, Rahul; Martin, Iain; Rowan, Sheila; Torrie, Calum; Zech, Steven

2010-02-01

The planned upgrades to the LIGO gravitational wave detectors include monolithic mirror suspensions to reduce thermal noise. The mirrors will be suspended using CO2 laser-drawn fused silica fibres. We present here measurements of mechanical dissipation in synthetic fused silica fibres drawn using a CO2 laser. The level of dissipation in the surface layer is investigated and is found to be at a similar level to fibres produced using a gas flame. Also presented is a method for examining dissipation at welded interfaces, showing clear evidence of the existence of this loss mechanism which forms an additional component of the total detector thermal noise. Modelling of a typical detector suspension configuration shows that the thermal noise contribution from this loss source will be negligible.

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.

Influence of PWHT on Toughness of High Chromium and Nickel Containing Martensitic Stainless Steel Weld Metals

NASA Astrophysics Data System (ADS)

Divya, M.; Das, Chitta Ranjan; Mahadevan, S.; Albert, S. K.; Pandian, R.; Kar, Sujoy Kumar; Bhaduri, A. K.; Jayakumar, T.

2015-06-01

Commonly used 12.5Cr-5Ni consumable specified for welding of martensitic stainless steels is compared with newly designed 14.5Cr-5Ni consumable in terms of their suitability for repair welding of 410 and 414 stainless steels by gas tungsten arc welding process. Changes in microstructure and austenite evolution were investigated using optical, scanning electron microscopy, X-ray diffraction techniques and Thermo-Calc studies. Microstructure of as-welded 12.5Cr-5Ni weld metal revealed only lath martensite, whereas as-welded 14.5Cr-5Ni weld metal revealed delta-ferrite, retained austenite, and lath martensite. Toughness value of as-welded 12.5Cr-5Ni weld metal is found to be significantly higher (216 J) than that of the 14.5Cr-5Ni weld metal (15 J). The welds were subjected to different PWHTs: one at 923 K (650 °C) for 1, 2, 4 hours (single-stage PWHT) and another one at 923 K (650 °C)/4 h followed by 873 K (600 °C)/2 h or 873 K (600 °C)/4 h (two-stage heat treatment). Hardness and impact toughness of the weld metals were measured for these weld metals and correlated with the microstructure. The study demonstrates the importance of avoiding formation of delta-ferrite in the weld metal.

Tensile Properties of Friction Stir Welded Joints of AA 2024-T6 Alloy at Different Welding Speeds

NASA Astrophysics Data System (ADS)

Avula, Dhananjayulu; Devuri, Venkateswarlu; Cheepu, Muralimohan; Dwivedi, Dheerendra Kumar

2018-03-01

The influence of welding speed on the friction stir welded joint properties of hardness, tensile properties, defects and microstructure characterization are studied in the present study. The friction stir welding was conducted on AA2014-T6 heat treated alloy with 5 mm thickness plate in butt joint configuration. The welding speed was varied from 8 mm/min to 120 mm/min at the fixed travel speed and load conditions. It is observed that the welding speeds at higher rate with wide range can be possible to weld this alloy at higher rates of tool revolution suggesting that the inherent capability of friction stir welding technique for aluminum 2014 alloys. The strength of the joints gradually increases with enhancing of welding speed. The micro structural observations exhibited the formation of equiaxed grains in the stir zone and slightly in the thermo-mechanically affected zone. In addition, the size of the grains decreases with increase in welding speed owing to the presence of low heat input. Hence the hardness of the joints slightly increased in the stir zones over the other zones of the weld nugget. The joint strength initially increases with the welding speed and starts to decreases after reaching to the maximum value. The relationship between the welding conditions and friction stir welded joint properties has been discussed.

Grain fragmentation in ultrasonic-assisted TIG weld of pure aluminum.

PubMed

Chen, Qihao; Lin, Sanbao; Yang, Chunli; Fan, Chenglei; Ge, Hongliang

2017-11-01

Under the action of acoustic waves during an ultrasonic-assisted tungsten inert gas (TIG) welding process, a grain of a TIG weld of aluminum alloy is refined by nucleation and grain fragmentation. Herein, effects of ultrasound on grain fragmentation in the TIG weld of aluminum alloy are investigated via systematic welding experiments of pure aluminum. First, experiments involving continuous and fixed-position welding are performed, which demonstrate that ultrasound can break the grain of the TIG weld of pure aluminum. The microstructural characteristics of an ultrasonic-assisted TIG weld fabricated by fixed-position welding are analyzed. The microstructure is found to transform from plane crystal, columnar crystal, and uniform equiaxed crystal into plane crystal, deformed columnar crystal, and nonuniform equiaxed crystal after application of ultrasound. Second, factors influencing ultrasonic grain fragmentation are investigated. The ultrasonic amplitude and welding current are found to have a considerable effect on grain fragmentation. The degree of fragmentation first increases and then decreases with an increase in ultrasonic amplitude, and it increases with an increase in welding current. Measurement results of the vibration of the weld pool show that the degree of grain fragmentation is related to the intensity of acoustic nonlinearity in the weld pool. The greater the intensity of acoustic nonlinearity, the greater is the degree of grain fragmentation. Finally, the mechanism of ultrasonic grain fragmentation in the TIG weld of pure aluminum is discussed. A finite element simulation is used to simulate the acoustic pressure and flow in the weld pool. The acoustic pressure in the weld pool exceeds the cavitation threshold, and cavitation bubbles are generated. The flow velocity in the weld pool does not change noticeably after application of ultrasound. It is concluded that the high-pressure conditions induced during the occurrence of cavitation, lead to grain fragmentation in a pure aluminum TIG weld during an ultrasonic-assisted TIG welding process. Copyright © 2017 Elsevier B.V. All rights reserved.

Quantifying the relative contribution of natural gas fugitive emissions to total methane emissions in Weld County Colorado using δ13CH4 analysis

NASA Astrophysics Data System (ADS)

Rella, C.; Jacobson, G. A.; Crosson, E.; Sweeney, C.; Karion, A.; Petron, G.

2012-12-01

Fugitive emissions of methane into the atmosphere are a major concern facing the natural gas production industry. Given that the global warming potential of methane is many times greater than that of carbon dioxide (Forster et al. 2007), the importance of quantifying methane emissions becomes clear. Companion presentations at this meeting describe efforts to quantify the overall methane emissions in two separate gas producing areas in Colorado and Utah during intensive field campaigns undertaken in 2012. A key step in the process of assessing the emissions arising from natural gas production activities is partitioning the observed methane emissions between natural gas fugitive emissions and other sources of methane, such as from landfills or agricultural activities. One method for assessing the contribution of these different sources is stable isotope analysis. In particular, the δ13CH4 signature of natural gas (-37 permil) is significantly different that the signature of other significant sources of methane, such as landfills or ruminants (-50 to -70 permil). In this paper we present measurements of δ13CH4 in Colorado in Weld County, a region of intense natural gas production, using a mobile δ13CH4¬ analyzer capable of high-precision measurements of the stable isotope ratio of methane at ambient levels. This analyzer was used to make stable isotope measurements at a fixed location near the center of the gas producing region, from which an overall isotope ratio for the regional emissions is determined. In addition, mobile measurements in the nocturnal boundary layer have been made, over a total distance of 150 km throughout Weld County, allowing spatially resolved measurements of this isotope signature. Finally, this analyzer was used to quantify the isotopic signature of those individual sources (natural gas fugitive emissions, concentrated animal feeding operations, and landfills) that constitute the majority of methane emissions in this region, by making measurements of the isotope ratio directly in the downwind plume from each source. These data are combined to establish the fraction of the observed methane emissions that can be attributed to natural gas activities in the region. The results are compared to inventories as well as other measurement techniques, and the uncertainty of the measurement is estimated.

49 CFR 195.234 - Welds: Nondestructive testing.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 3 2010-10-01 2010-10-01 false Welds: Nondestructive testing. 195.234 Section 195... HAZARDOUS LIQUIDS BY PIPELINE Construction § 195.234 Welds: Nondestructive testing. (a) A weld may be... weld. (b) Any nondestructive testing of welds must be performed— (1) In accordance with a written set...

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

ERIC Educational Resources Information Center

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

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

49 CFR 192.235 - Preparation for welding.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 3 2010-10-01 2010-10-01 false Preparation for welding. 192.235 Section 192.235... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.235 Preparation for welding. Before beginning any welding, the welding surfaces must be clean and free of any material that...

Method for welding chromium molybdenum steels

DOEpatents

Sikka, Vinod K.

1986-01-01

Chromium-molybdenum steels exhibit a weakening after welding in an area adjacent to the weld. This invention is an improved method for welding to eliminate the weakness by subjecting normalized steel to a partial temper prior to welding and subsequently fully tempering the welded article for optimum strength and ductility.

49 CFR 192.235 - Preparation for welding.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Preparation for welding. 192.235 Section 192.235... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.235 Preparation for welding. Before beginning any welding, the welding surfaces must be clean and free of any material that...

49 CFR 192.235 - Preparation for welding.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 3 2012-10-01 2012-10-01 false Preparation for welding. 192.235 Section 192.235... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.235 Preparation for welding. Before beginning any welding, the welding surfaces must be clean and free of any material that...

49 CFR 192.235 - Preparation for welding.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Preparation for welding. 192.235 Section 192.235... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.235 Preparation for welding. Before beginning any welding, the welding surfaces must be clean and free of any material that...

49 CFR 192.235 - Preparation for welding.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 3 2014-10-01 2014-10-01 false Preparation for welding. 192.235 Section 192.235... BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.235 Preparation for welding. Before beginning any welding, the welding surfaces must be clean and free of any material that...