[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.

Experimental Investigation and Optimization of TIG Welding Parameters on Aluminum 6061 Alloy Using Firefly Algorithm

NASA Astrophysics Data System (ADS)

Kumar, Rishi; Mevada, N. Ramesh; Rathore, Santosh; Agarwal, Nitin; Rajput, Vinod; Sinh Barad, AjayPal

2017-08-01

To improve Welding quality of aluminum (Al) plate, the TIG Welding system has been prepared, by which Welding current, Shielding gas flow rate and Current polarity can be controlled during Welding process. In the present work, an attempt has been made to study the effect of Welding current, current polarity, and shielding gas flow rate on the tensile strength of the weld joint. Based on the number of parameters and their levels, the Response Surface Methodology technique has been selected as the Design of Experiment. For understanding the influence of input parameters on Ultimate tensile strength of weldment, ANOVA analysis has been carried out. Also to describe and optimize TIG Welding using a new metaheuristic Nature - inspired algorithm which is called as Firefly algorithm which was developed by Dr. Xin-She Yang at Cambridge University in 2007. A general formulation of firefly algorithm is presented together with an analytical, mathematical modeling to optimize the TIG Welding process by a single equivalent objective function.

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.

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

PubMed

Tseng, Kuang-Hung; Chen, Kuan-Lung

2012-08-01

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

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.

Final Report of Project Curriculum Development: Pulsed Tig Welding, 1978-1979.

ERIC Educational Resources Information Center

Atlantic County Area Vocational-Technical School, NJ.

Designed to help unemployed and disadvantaged workers find new career opportunities, this curriculum provides vocational students with a basic course of instruction in pulsed tungsten inert gas (TIG) welding. The first of four sections provides a general background of welding, the welding industry, and welding processes. Section 2 focuses on…

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.

Manufacturing Methods and Technology Application of High Energy Laser Welding Process.

DTIC Science & Technology

1980-08-01

surface appearance and the lowest porosity of the three beam shapes evaluated. Welds made with the pure annular beam resembled a TIG weld in both surface...improper starts and stops when welding with a conventional MIG or TIG process. Figure 16 left and center illustrates cracking due to fast freezing conditions...REPORT RL-82-2 0 MANUFACTURING METHODS AND TECHNOLOGY APPLICATION _OF HIGH ENERGY LASER WELDING PROCESS 0John V. Melonas Structures Directorate, U S

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.

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.

Thick SS316 materials TIG welding development activities towards advanced fusion reactor vacuum vessel applications

NASA Astrophysics Data System (ADS)

Kumar, B. Ramesh; Gangradey, R.

2012-11-01

Advanced fusion reactors like ITER and up coming Indian DEMO devices are having challenges in terms of their materials design and fabrication procedures. The operation of these devices is having various loads like structural, thermo-mechanical and neutron irradiation effects on major systems like vacuum vessel, divertor, magnets and blanket modules. The concept of double wall vacuum vessel (VV) is proposed in view of protecting of major reactor subsystems like super conducting magnets, diagnostic systems and other critical components from high energy 14 MeV neutrons generated from fusion plasma produced by D-T reactions. The double walled vacuum vessel is used in combination with pressurized water circulation and some special grade borated steel blocks to shield these high energy neutrons effectively. The fabrication of sub components in VV are mainly used with high thickness SS materials in range of 20 mm- 60 mm of various grades based on the required protocols. The structural components of double wall vacuum vessel uses various parts like shields, ribs, shells and diagnostic vacuum ports. These components are to be developed with various welding techniques like TIG welding, Narrow gap TIG welding, Laser welding, Hybrid TIG laser welding, Electron beam welding based on requirement. In the present paper the samples of 20 mm and 40 mm thick SS 316 materials are developed with TIG welding process and their mechanical properties characterization with Tensile, Bend tests and Impact tests are carried out. In addition Vickers hardness tests and microstructural properties of Base metal, Heat Affected Zone (HAZ) and Weld Zone are done. TIG welding application with high thick SS materials in connection with vacuum vessel requirements and involved criticalities towards welding process are highlighted.

Analysis of the Corrosion Behavior of an A-TIG Welded SS 409 Weld Fusion Zone

NASA Astrophysics Data System (ADS)

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

2017-11-01

AISI 409 (SS 409) ferritic stainless steel is generally used as the thick gauge section in freight train wagons, in ocean containers, and in sugar refinery equipment. Activating the flux tungsten inert gas (A-TIG) welding process can reduce the welding cost during fabrication of thick sections. However, corrosion behavior of the A-TIG weld fusion zone is a prime concern for this type of steel. In the present work, the effect of the A-TIG welding process parameters on the corrosion behavior of a weld fusion zone made of 8-mm-thick AISI 409 ferritic stainless-steel plate has been analyzed. Potentiodynamic polarization tests were performed to evaluate the corrosion behavior. The maximum corrosion potential ( E corr) was shown by the weld made using a welding current of 215 A, a welding speed of 95 mm/min, and a flux coating density of 0.81 mg/cm2. The minimum E corr was observed in the weld made using a welding current of 190 A, a welding speed of 120 mm/min, and a flux coating density of 1.40 mg/cm2. The current study also presents the inclusive microstructure-corrosion property relationships using the collective techniques of scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction.

Study of 2219 aluminum alloy using direct current A-TIG welding

NASA Astrophysics Data System (ADS)

Li, Hui; Zou, Jiasheng

2017-07-01

Direct current A-TIG (DCEN A-TIG) welding using special active agent had eliminated the pores and the oxidation of 2219 high-strength aluminum alloy in welding. Addition of AlF3-25% LiF active agent to DCEN A-TIG welding and arc morphology showed a trailing phenomenon. However, the change in arc morphology was not remarkable when AlF3-75% LiF active agent was added. Addition of AlF3-75% LiF active agent can refine the grain size of DCEN A-TIG joint. The mechanical properties of the weld were optimal at 10% AlF3-75% LiF active agent. Compared with AC TIG and AC A-TIG welding, DCEN A-TIG welding yielded better results for 2219 Al alloy.

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.

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.

Environmental Assessment (EA): Proposed Aircraft Power Systems Repair Transformation Facility, Hill Air Force Base, Utah

DTIC Science & Technology

2007-05-16

and silicon carbide; spent elastic abrasive media; rags and wipes from the NDI process ; and unused scraps of TIG welding wire. Dust from the thermal...used, which would not be expected to produce regulated air emissions. For this process , no air quality permit updates are anticipated. • Welding ...The electron beam welding equipment would not be expected to produce regulated air emissions. The tungsten inert gas ( TIG ) welding equipment would

[Calculation and analysis of arc temperature field of pulsed TIG welding based on Fowler-Milne method].

PubMed

Xiao, Xiao; Hua, Xue-Ming; Wu, Yi-Xiong; Li, Fang

2012-09-01

Pulsed TIG welding is widely used in industry due to its superior properties, and the measurement of arc temperature is important to analysis of welding process. The relationship between particle densities of Ar and temperature was calculated based on the theory of spectrum, the relationship between emission coefficient of spectra line at 794.8 nm and temperature was calculated, arc image of spectra line at 794.8 nm was captured by high speed camera, and both the Abel inversion and Fowler-Milne method were used to calculate the temperature distribution of pulsed TIG welding.

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

NASA Astrophysics Data System (ADS)

Shanavas, S.; Raja Dhas, J. Edwin

2017-10-01

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

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

NASA Astrophysics Data System (ADS)

Subashini, L.; Vasudevan, M.

2012-02-01

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

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

NASA Astrophysics Data System (ADS)

Biradar, N. S.; Raman, R.

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

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.

Analysis and Comparison of Aluminum Alloy Welded Joints Between Metal Inert Gas Welding and Tungsten Inert Gas Welding

NASA Astrophysics Data System (ADS)

Zhao, Lei; Guan, Yingchun; Wang, Qiang; Cong, Baoqiang; Qi, Bojin

2015-09-01

Surface contamination usually occurs during welding processing and it affects the welds quality largely. However, the formation of such contaminants has seldom been studied. Effort was made to study the contaminants caused by metal inert gas (MIG) welding and tungsten inert gas (TIG) welding processes of aluminum alloy, respectively. SEM, FTIR and XPS analysis was carried out to investigate the microstructure as well as surface chemistry. These contaminants were found to be mainly consisting of Al2O3, MgO, carbide and chromium complexes. The difference of contaminants between MIG and TIG welds was further examined. In addition, method to minimize these contaminants was proposed.

Effect of Friction Stir Processing on Microstructure and Mechanical Properties of AZ91C Magnesium Cast Alloy Weld Zone

NASA Astrophysics Data System (ADS)

Hassani, Behzad; Karimzadeh, Fathallah; Enayati, Mohammad Hossein; Sabooni, Soheil; Vallant, Rudolf

2016-07-01

In this study, friction stir processing (FSP) was applied to the GTAW (TIG)-welded AZ91C cast alloy to refine the microstructure and optimize the mechanical properties of the weld zone. Microstructural investigation of the samples was performed by optical microscopy and the phases in the microstructure were determined by x-ray diffraction (XRD). The microstructural evaluations showed that FSP destroys the coarse dendritic microstructure. Furthermore, it dissolves the secondary hard and brittle β-Mg17Al12 phase existing at grain boundaries of the TIG weld zone. The closure and decrease in amount of porosities along with the elimination of the cracks in the microstructure were observed. These changes were followed by a significant grain refinement to an average value of 11 µm. The results showed that the hardness values increased to the mean ones, respectively, for as-cast (63 Hv), TIG weld zone (67 Hv), and stir zone (79 Hv). The yield and ultimate strength were significantly enhanced after FSP. The fractography evaluations, by scanning electron microscopy (SEM), indicated to a transition from brittle to ductile fracture surface after applying FSP to the TIG weld zone.

Increase in oxidative stress levels following welding fume inhalation: a controlled human exposure study.

PubMed

Graczyk, Halshka; Lewinski, Nastassja; Zhao, Jiayuan; Sauvain, Jean-Jacques; Suarez, Guillaume; Wild, Pascal; Danuser, Brigitta; Riediker, Michael

2016-06-10

Tungsten inert gas (TIG) welding represents one of the most widely used metal joining processes in industry. It has been shown to generate a large majority of particles at the nanoscale and to have low mass emission rates when compared to other types of welding. Despite evidence that TIG fume particles may produce reactive oxygen species (ROS), limited data is available for the time course changes of particle-associated oxidative stress in exposed TIG welders. Twenty non-smoking male welding apprentices were exposed to TIG welding fumes for 60 min under controlled, well-ventilated settings. Exhaled breathe condensate (EBC), blood and urine were collected before exposure, immediately after exposure, 1 h and 3 h post exposure. Volunteers participated in a control day to account for oxidative stress fluctuations due to circadian rhythm. Biological liquids were assessed for total reducing capacity, hydrogen peroxide (H2O2), malondialdehyde (MDA), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) concentrations at each time point. A linear mixed model was used to assess within day and between day differences. Significant increases in the measured biomarkers were found at 3 h post exposure. At 3 h post exposure, we found a 24 % increase in plasma-H2O2 concentrations ([95%CI: 4 % to 46 %], p = 0.01); a 91 % increase in urinary-H2O2 ([2 % to 258 %], p = 0.04); a 14 % increase in plasma-8-OHdG ([0 % to 31 %], p = 0.049); and a 45 % increase in urinary-8-OHdG ([3 % to 105 %], p = 0.03). Doubling particle number concentration (PNC) exposure was associated with a 22 % increase of plasma-8-OHdG at 3 h post exposure (p = 0.01). A 60-min exposure to TIG welding fume in a controlled, well-ventilated setting induced acute oxidative stress at 3 h post exposure in healthy, non-smoking apprentice welders not chronically exposed to welding fumes. As mass concentration of TIG welding fume particles is very low when compared to other types of welding, it is recommended that additional exposure metrics such as PNC are considered for occupational risk assessments. Our findings highlight the importance of increasing awareness of TIG welding fume toxicity, especially given the realities of welding workplaces that may lack ventilation; and beliefs among interviewed welders that TIG represents a cleaner and safer welding process.

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

DTIC Science & Technology

2011-11-15

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

Characterization of Tungsten Inert Gas (TIG) Welding Fume Generated by Apprentice Welders

PubMed Central

Graczyk, Halshka; Lewinski, Nastassja; Zhao, Jiayuan; Concha-Lozano, Nicolas; Riediker, Michael

2016-01-01

Tungsten inert gas welding (TIG) represents one of the most widely used metal joining processes in industry. Its propensity to generate a greater portion of welding fume particles at the nanoscale poses a potential occupational health hazard for workers. However, current literature lacks comprehensive characterization of TIG welding fume particles. Even less is known about welding fumes generated by welding apprentices with little experience in welding. We characterized TIG welding fume generated by apprentice welders (N = 20) in a ventilated exposure cabin. Exposure assessment was conducted for each apprentice welder at the breathing zone (BZ) inside of the welding helmet and at a near-field (NF) location, 60cm away from the welding task. We characterized particulate matter (PM4), particle number concentration and particle size, particle morphology, chemical composition, reactive oxygen species (ROS) production potential, and gaseous components. The mean particle number concentration at the BZ was 1.69E+06 particles cm−3, with a mean geometric mean diameter of 45nm. On average across all subjects, 92% of the particle counts at the BZ were below 100nm. We observed elevated concentrations of tungsten, which was most likely due to electrode consumption. Mean ROS production potential of TIG welding fumes at the BZ exceeded average concentrations previously found in traffic-polluted air. Furthermore, ROS production potential was significantly higher for apprentices that burned their metal during their welding task. We recommend that future exposure assessments take into consideration welding performance as a potential exposure modifier for apprentice welders or welders with minimal training. PMID:26464505

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

PubMed Central

Tseng, Kuang-Hung; Lin, Po-Yu

2014-01-01

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

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

PubMed

Tseng, Kuang-Hung; Lin, Po-Yu

2014-06-20

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

Characterization of Tungsten Inert Gas (TIG) Welding Fume Generated by Apprentice Welders.

PubMed

Graczyk, Halshka; Lewinski, Nastassja; Zhao, Jiayuan; Concha-Lozano, Nicolas; Riediker, Michael

2016-03-01

Tungsten inert gas welding (TIG) represents one of the most widely used metal joining processes in industry. Its propensity to generate a greater portion of welding fume particles at the nanoscale poses a potential occupational health hazard for workers. However, current literature lacks comprehensive characterization of TIG welding fume particles. Even less is known about welding fumes generated by welding apprentices with little experience in welding. We characterized TIG welding fume generated by apprentice welders (N = 20) in a ventilated exposure cabin. Exposure assessment was conducted for each apprentice welder at the breathing zone (BZ) inside of the welding helmet and at a near-field (NF) location, 60cm away from the welding task. We characterized particulate matter (PM4), particle number concentration and particle size, particle morphology, chemical composition, reactive oxygen species (ROS) production potential, and gaseous components. The mean particle number concentration at the BZ was 1.69E+06 particles cm(-3), with a mean geometric mean diameter of 45nm. On average across all subjects, 92% of the particle counts at the BZ were below 100nm. We observed elevated concentrations of tungsten, which was most likely due to electrode consumption. Mean ROS production potential of TIG welding fumes at the BZ exceeded average concentrations previously found in traffic-polluted air. Furthermore, ROS production potential was significantly higher for apprentices that burned their metal during their welding task. We recommend that future exposure assessments take into consideration welding performance as a potential exposure modifier for apprentice welders or welders with minimal training. © The Author 2015. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

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

NASA Astrophysics Data System (ADS)

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

2007-03-01

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

Laser-TIG Welding of Titanium Alloys

NASA Astrophysics Data System (ADS)

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

2016-08-01

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

Effects of different brazing and welding methods on the fracture load of various orthodontic joining configurations.

PubMed

Bock, Jens J; Bailly, Jacqueline; Fuhrmann, Robert A

2009-06-01

The aim of this study was to compare the fracture load of different joints made by conventional brazing, tungston inert gas (TIG) and laser welding. Six standardized joining configurations of spring hard quality orthodontic wire were investigated: end-to-end, round, cross, 3 mm length, 9 mm length and 6.5 mm to orthodontic band. The joints were made by five different methods: brazing with universal silver solder, two TIG and two laser welding devices. The fracture loads were measured with a universal testing machine (Zwick 005). Data were analysed with the Mann-Whitney-Wilcoxon and Kruskal-Wallis tests. The significance level was set at P<0.05). In all cases brazed joints were ruptured at a low level of fracture load (186-407 N). Significant differences between brazing and TIG or laser welding (P<0.05) were found. The highest mean fracture loads were observed for laser welding (826 N). No differences between the various TIG or laser welding devices were demonstrated, although it was not possible to join an orthodontic wire to an orthodontic band using TIG welding. For orthodontic purposes laser and TIG welding are solder free alternatives. TIG welding and laser welding showed similar results. The laser technique is an expensive, but sophisticated and simple method.

Influence of different brazing and welding methods on tensile strength and microhardness of orthodontic stainless steel wire.

PubMed

Bock, Jens Johannes; Fraenzel, Wolfgang; Bailly, Jacqueline; Gernhardt, Christian Ralf; Fuhrmann, Robert Andreas Werner

2008-08-01

The aim of this study was to compare the mechanical strength and microhardness of joints made by conventional brazing and tungsten inert gas (TIG) and laser welding. A standardized end-to-end joint configuration of the orthodontic wire material in spring hard quality was used. The joints were made using five different methods: brazing (soldering > 450 degrees C) with universal silver solder, two TIG, and two laser welders. Laser parameters and welding conditions were used according to the manufacturers' guidance. The tensile strengths were measured with a universal testing machine (Zwick 005). The microhardness measurements were carried out with a hardness tester (Zwick 3202). Data were analysed using one-way analysis of variance and Bonferroni's post hoc correction (P < 0.05). In all cases, brazing joints ruptured at low levels of tensile strength (198 +/- 146 MPa). Significant differences (P < 0.001) between brazing and TIG or laser welding were found. The highest means were observed for TIG welding (699-754 MPa). Laser welding showed a significantly lower mean tensile strength (369-520 MPa) compared with TIG welding. Significant differences (P < 0.001) were found between the original orthodontic wire and the mean microhardness at the centre of the welded area. The mean microhardness differed significantly between brazing (1.99 GPa), TIG (2.22-2.39 GPa) and laser welding (2.21-2.68 GPa). For orthodontic purposes, laser and TIG welding are solder-free alternatives to joining metal. TIG welding with a lower investment cost is comparable with laser welding. However, while expensive, the laser technique is a sophisticated and simple method.

Parameter Design in Fusion Welding of AA 6061 Aluminium Alloy using Desirability Grey Relational Analysis (DGRA) Method

NASA Astrophysics Data System (ADS)

Adalarasan, R.; Santhanakumar, M.

2015-01-01

In the present work, yield strength, ultimate strength and micro-hardness of the lap joints formed with Al 6061 alloy sheets by using the processes of Tungsten Inert Gas (TIG) welding and Metal Inert Gas (MIG) welding were studied for various combinations of the welding parameters. The parameters taken for study include welding current, voltage, welding speed and inert gas flow rate. Taguchi's L9 orthogonal array was used to conduct the experiments and an integrated technique of desirability grey relational analysis was disclosed for optimizing the welding parameters. The ignored robustness in desirability approach is compensated by the grey relational approach to predict the optimal setting of input parameters for the TIG and MIG welding processes which were validated through the confirmation experiments.

Experimental characterization of the weld pool flow in a TIG configuration

NASA Astrophysics Data System (ADS)

Stadler, M.; Masquère, M.; Freton, P.; Franceries, X.; Gonzalez, J. J.

2014-11-01

Tungsten Inert Gas (TIG) welding process relies on heat transfer between plasma and work piece leading to a metallic weld pool. Combination of different forces produces movements on the molten pool surface. One of our aims is to determine the velocity on the weld pool surface. This provides a set of data that leads to a deeper comprehension of the flow behavior and allows us to validate numerical models used to study TIG parameters. In this paper, two diagnostic methods developed with high speed imaging for the determination of velocity of an AISI 304L stainless steel molten pool are presented. Application of the two methods to a metallic weld pool under helium with a current intensity of 100 A provides velocity values around 0.70 m/s which are in good agreement with literature works.

A study of thorium exposure during tungsten inert gas welding in an airline engineering population.

PubMed

McElearney, N; Irvine, D

1993-07-01

To investigate the theoretic possibility of excessive exposure to thorium during the process of tungsten inert gas (TIG) welding using thoriated rods we carried out a cross-sectional study of TIG welders and an age- and skill-matched group. We measured the radiation doses from inhaled thorium that was retained in the body and investigated whether any differences in health or biologic indices could have been attributable to the welding and tip-grinding process. Sixty-four TIG welders, 11 non-TIG welders, and 61 control subjects from an airline engineering population participated. All of the subjects were interviewed for biographic, occupational history and morbidity details. All of the welders and eight control subjects carried out large-volume urine sampling to recover thorium 232 and thorium 228; this group also had chest radiographs. All of the subjects had a blood sample taken to estimate liver enzymes, and they provided small-volume urine samples for the estimation of retinol-binding protein and beta 2-microglobulin. We found no excess of morbidity among the TIG or non-TIG welding groups, and the levels of retinol-binding protein and beta 2-microglobulin were the same for both groups. There was a higher aspartate aminotransferase level in the control group. The internal radiation doses were estimated at less than an annual level of intake in all cases, and considerably less if the exposure (as was the case) was assumed to be chronic over many years. Some additional precautionary measures are suggested to reduce further any potential hazard from this process.

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.

Evaluation of Surface Roughness by Image Processing of a Shot-Peened, TIG-Welded Aluminum 6061-T6 Alloy: An Experimental Case Study

PubMed Central

Rawashdeh, Nathir A.

2018-01-01

Visual inspection through image processing of welding and shot-peened surfaces is necessary to overcome equipment limitations, avoid measurement errors, and accelerate processing to gain certain surface properties such as surface roughness. Therefore, it is important to design an algorithm to quantify surface properties, which enables us to overcome the aforementioned limitations. In this study, a proposed systematic algorithm is utilized to generate and compare the surface roughness of Tungsten Inert Gas (TIG) welded aluminum 6061-T6 alloy treated by two levels of shot-peening, high-intensity and low-intensity. This project is industrial in nature, and the proposed solution was originally requested by local industry to overcome equipment capabilities and limitations. In particular, surface roughness measurements are usually only possible on flat surfaces but not on other areas treated by shot-peening after welding, as in the heat-affected zone and weld beads. Therefore, those critical areas are outside of the measurement limitations. Using the proposed technique, the surface roughness measurements were possible to obtain for weld beads, high-intensity and low-intensity shot-peened surfaces. In addition, a 3D surface topography was generated and dimple size distributions were calculated for the three tested scenarios: control sample (TIG-welded only), high-intensity shot-peened, and low-intensity shot-peened TIG-welded Al6065-T6 samples. Finally, cross-sectional hardness profiles were measured for the three scenarios; in all scenarios, lower hardness measurements were obtained compared to the base metal alloy in the heat-affected zone and in the weld beads even after shot-peening treatments. PMID:29748520

Evaluation of Surface Roughness by Image Processing of a Shot-Peened, TIG-Welded Aluminum 6061-T6 Alloy: An Experimental Case Study.

PubMed

Atieh, Anas M; Rawashdeh, Nathir A; AlHazaa, Abdulaziz N

2018-05-10

Visual inspection through image processing of welding and shot-peened surfaces is necessary to overcome equipment limitations, avoid measurement errors, and accelerate processing to gain certain surface properties such as surface roughness. Therefore, it is important to design an algorithm to quantify surface properties, which enables us to overcome the aforementioned limitations. In this study, a proposed systematic algorithm is utilized to generate and compare the surface roughness of Tungsten Inert Gas (TIG) welded aluminum 6061-T6 alloy treated by two levels of shot-peening, high-intensity and low-intensity. This project is industrial in nature, and the proposed solution was originally requested by local industry to overcome equipment capabilities and limitations. In particular, surface roughness measurements are usually only possible on flat surfaces but not on other areas treated by shot-peening after welding, as in the heat-affected zone and weld beads. Therefore, those critical areas are outside of the measurement limitations. Using the proposed technique, the surface roughness measurements were possible to obtain for weld beads, high-intensity and low-intensity shot-peened surfaces. In addition, a 3D surface topography was generated and dimple size distributions were calculated for the three tested scenarios: control sample (TIG-welded only), high-intensity shot-peened, and low-intensity shot-peened TIG-welded Al6065-T6 samples. Finally, cross-sectional hardness profiles were measured for the three scenarios; in all scenarios, lower hardness measurements were obtained compared to the base metal alloy in the heat-affected zone and in the weld beads even after shot-peening treatments.

Microprobe investigation of brittle segregates in aluminum MIG and TIG welds

NASA Technical Reports Server (NTRS)

Larssen, P. A.; Miller, E. L.

1968-01-01

Quantitative microprobe analysis of segregated particles in aluminum MIG /Metal Inert Gas/ and TIG /Tungsten Inert Gas/ welds indicated that there were about ten different kinds of particles, corresponding to ten different intermetallic compounds. Differences between MIG and TIG welds related to the individual cooling rates of these welds.

Effect of laser power on clad metal in laser-TIG combined metal cladding

NASA Astrophysics Data System (ADS)

Utsumi, Akihiro; Hino, Takanori; Matsuda, Jun; Tasoda, Takashi; Yoneda, Masafumi; Katsumura, Munehide; Yano, Tetsuo; Araki, Takao

2003-03-01

TIG arc welding has been used to date as a method for clad welding of white metal as bearing material. We propose a new clad welding process that combines a CO2 laser and a TIG arc, as a method for cladding at high speed. We hypothesized that this method would permit appropriate control of the melted quantity of base metal by varying the laser power. We carried out cladding while varying the laser power, and investigated the structure near the boundary between the clad layer and the base metal. Using the laser-TIG combined cladding, we found we were able to control appropriately the degree of dilution with the base metal. By applying this result to subsequent cladding, we were able to obtain a clad layer of high quality, which was slightly diluted with the base metal.

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

Tungsten inert gas (TIG) welding of Ni-rich NiTi plates: functional behavior

NASA Astrophysics Data System (ADS)

Oliveira, J. P.; Barbosa, D.; Braz Fernandes, F. M.; Miranda, R. M.

2016-03-01

It is often reported that, to successfully join NiTi shape memory alloys, fusion-based processes with reduced thermal affected regions (as in laser welding) are required. This paper describes an experimental study performed on the tungsten inert gas (TIG) welding of 1.5 mm thick plates of Ni-rich NiTi. The functional behavior of the joints was assessed. The superelasticity was analyzed by cycling tests at maximum imposed strains of 4, 8 and 12% and for a total of 600 cycles, without rupture. The superelastic plateau was observed, in the stress-strain curves, 30 MPa below that of the base material. Shape-memory effect was evidenced by bending tests with full recovery of the initial shape of the welded joints. In parallel, uniaxial tensile tests of the joints showed a tensile strength of 700 MPa and an elongation to rupture of 20%. The elongation is the highest reported for fusion-welding of NiTi, including laser welding. These results can be of great interest for the wide-spread inclusion of NiTi in complex shaped components requiring welding, since TIG is not an expensive process and is simple to operate and implement in industrial environments.

Microstructural Characterization of a Polycrystalline Nickel-Based Superalloy Processed via Tungsten-Intert-Gas-Shaped Metal Deposition

NASA Astrophysics Data System (ADS)

Clark, Daniel; Bache, Martin R.; Whittaker, Mark T.

2010-12-01

Recent trials have produced tungsten-inert-gas (TIG)-welded structures of a suitable scale to allow an evaluation of the technique as an economic and commercial process for the manufacture of complex aeroengine components. The employment of TIG welding is shown to have specific advantages over alternative techniques based on metal inert gas (MIG) systems. Investigations using the nickel-based superalloy 718 have shown that TIG induces a smaller weld pool with less compositional segregation. In addition, because the TIG process involves a pulsed power source, a faster cooling rate is achieved, although this rate, in turn, compromises the deposition rate. The microstructures produced by the two techniques differ significantly, with TIG showing an absence of the detrimental delta and Laves phases typically produced by extended periods at a high temperature using MIG. Instead, an anisotropic dendritic microstructure was evident with a preferred orientation relative to the axis of epitaxy. Niobium was segregated to the interdendritic regions. A fine-scale porosity was evident within the microstructure with a maximum diameter of approximately 5 μm. This porosity often was found in clusters and usually was associated with the interdendritic regions. Subsequent postdeposition heat treatment was shown to have no effect on preexisting porosity and to have a minimal effect on the microstructure.

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.

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

DTIC Science & Technology

1986-10-13

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

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.

Tensile and flexural strength of commercially pure titanium submitted to laser and tungsten inert gas welds.

PubMed

Atoui, Juliana Abdallah; Felipucci, Daniela Nair Borges; Pagnano, Valéria Oliveira; Orsi, Iara Augusta; Nóbilo, Mauro Antônio de Arruda; Bezzon, Osvaldo Luiz

2013-01-01

This study evaluated the tensile and flexural strength of tungsten inert gas (TIG) welds in specimens made of commercially pure titanium (CP Ti) compared with laser welds. Sixty cylindrical specimens (2 mm diameter x 55 mm thick) were randomly assigned to 3 groups for each test (n=10): no welding (control), TIG welding (10 V, 36 A, 8 s) and Nd:YAG laser welding (380 V, 8 ms). The specimens were radiographed and subjected to tensile and flexural strength tests at a crosshead speed of 1.0 mm/min using a load cell of 500 kgf applied on the welded interface or at the middle point of the non-welded specimens. Tensile strength data were analyzed by ANOVA and Tukey's test, and flexural strength data by the Kruskal-Wallis test (α=0.05). Non-welded specimens presented significantly higher tensile strength (control=605.84 ± 19.83) (p=0.015) and flexural strength (control=1908.75) (p=0.000) than TIG- and laser-welded ones. There were no significant differences (p>0.05) between the welding types for neither the tensile strength test (TIG=514.90 ± 37.76; laser=515.85 ± 62.07) nor the flexural strength test (TIG=1559.66; laser=1621.64). As far as tensile and flexural strengths are concerned, TIG was similar to laser and could be suitable to replace laser welding in implant-supported rehabilitations.

Determination of airborne nanoparticles from welding operations.

PubMed

Gomes, João Fernando Pereira; Albuquerque, Paula Cristina Silva; Miranda, Rosa Maria Mendes; Vieira, Maria Teresa Freire

2012-01-01

The aim of this study is to assess the levels of airborne ultrafine particles emitted in welding processes (tungsten inert gas [TIG], metal active gas [MAG] of carbon steel, and friction stir welding [FSW] of aluminum) in terms of deposited area in pulmonary alveolar tract using a nanoparticle surface area monitor (NSAM) analyzer. The obtained results showed the dependence of process parameters on emitted ultrafine particles and demonstrated the presence of ultrafine particles compared to background levels. Data indicated that the process that resulted in the lowest levels of alveolar deposited surface area (ADSA) was FSW, followed by TIG and MAG. However, all tested processes resulted in significant concentrations of ultrafine particles being deposited in humans lungs of exposed workers.

Effect of current and travel speed variation of TIG welding on microstructure and hardness of stainless steel SS 316L

NASA Astrophysics Data System (ADS)

Jatimurti, Wikan; Abdillah, Fakhri Aulia; Kurniawan, Budi Agung; Rochiem, Rochman

2018-04-01

One of the stainless steel types that widely used in industry is SS 316L, which is austenitic stainless steel. One of the welding methods to join stainless steel is Tungsten Inert Gas (TIG), which can affect its morphology, microstructure, strength, hardness, and even lead to cracks in the weld area due to the given heat input. This research has a purpose of analyzing the relationship between microstructure and hardness value of SS 316L stainless steel after TIG welding with the variation of current and travel speed. The macro observation shows a distinct difference in the weld metal and base metal area, and the weld form is not symmetrical. The metallographic test shows the phases that formed in the specimen are austenite and ferrite, which scattered in three welding areas. The hardness test showed that the highest hardness value found in the variation of travel speed 12 cm/min with current 100 A. Welding process and variation were given do not cause any defects in the microstructure, such as carbide precipitation and sigma phase, means that it does not affect the hardness and corrosion resistance of all welded specimen.

Clamp and Gas Nozzle for TIG Welding

NASA Technical Reports Server (NTRS)

Gue, G. B.; Goller, H. L.

1982-01-01

Tool that combines clamp with gas nozzle is aid to tungsten/inert-gas (TIG) welding in hard-to-reach spots. Tool holds work to be welded while directing a stream of argon gas at weld joint, providing an oxygen-free environment for tungsten-arc welding.

Internal Stress Distribution Measurement of TIG Welded SUS304 Samples Using Neutron Diffraction Technique

NASA Astrophysics Data System (ADS)

Muslih, M. Refai; Sumirat, I.; Sairun; Purwanta

2008-03-01

The distribution of residual stress of SUS304 samples that were undergone TIG welding process with four different electric currents has been measured. The welding has been done in the middle part of the samples that was previously grooved by milling machine. Before they were welded the samples were annealed at 650 degree Celsius for one hour. The annealing process was done to eliminate residual stress generated by grooving process so that the residual stress within the samples was merely produced from welding process. The calculation of distribution of residual stress was carried out by measuring the strains within crystal planes of Fe(220) SUS304. Strain, Young modulus, and Poisson ratio of Fe(220) SUS304 were measured using DN1-M neutron diffractometer. Young modulus and Poisson ratio of Fe(220) SUS304 sample were measured in-situ. The result of calculations showed that distribution of residual stress of SUS304 in the vicinity of welded area is influenced both by treatments given at the samples-making process and by the electric current used during welding process.

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.

Compatibility of martensitic/austenitic steel welds with liquid lead bismuth eutectic environment

NASA Astrophysics Data System (ADS)

Van den Bosch, J.; Almazouzi, A.

2009-04-01

The high-chromium ferritic/martensitic steel T91 and the austenitic stainless steel 316L are to be used in contact with liquid lead-bismuth eutectic (LBE), under high irradiation doses. Both tungsten inert gas (TIG) and electron beam (EB) T91/316L welds have been examined by means of metallography, scanning electron microscopy (SEM-EDX), Vickers hardness measurements and tensile testing both in inert gas and in LBE. Although the T91/316L TIG weld has very good mechanical properties when tested in air, its properties decline sharply when tested in LBE. This degradation in mechanical properties is attributed to the liquid metal embrittlement of the 309 buttering used in TIG welding of T91/316L welds. In contrast to mixed T91/316L TIG welding, the mixed T91/316L EB weld was performed without buttering. The mechanical behaviour of the T91/316L EB weld was very good in air after post weld heat treatment but deteriorated when tested in LBE.

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

PubMed

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

2015-05-01

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

Amélioration des performances du procédé de soudage TIG sur un acier au carbone et un alliage d'aluminium par dépôt de silice

NASA Astrophysics Data System (ADS)

Sire, Stéphane; Marya, Surendar

This Note presents ways to improve the weld penetration potential of TIG process by optimising silica application around the joints in a plain carbon steel and an aluminium alloy 5086. Whereas for plain carbon steels, full coverage of joint improves penetration, the presence of a blank zone around the joint in the flux coating on aluminium 5086 using AC-TIG seems to be the best solution for cosmetic and deep welds. To cite this article: S. Sire, S. Marya, C. R. Mecanique 330 (2002) 83-89.

[The vision of welders in France].

PubMed

Boissin, J P; Peyresblanques, J; Rollin, J P; Marini, F; Beaufils, D

2002-10-01

A study was conducted to measure the impact of welding on the vision of welders. This study was conducted in France by the occupational medicine staff of large companies on 1.131 people, namely 850 welders and 281 control subjects. This investigation included two examinations at the beginning and the end of a year. The investigative procedure examined the different welding processes, the percentage of working time spent on welding activity, the length of exposure in years, as well as the medical variables: the optical correction type and history of ocular traumatology. The Visiotest or the Ergovision were used for the visual examination, equipment in common use by occupational medicine departments. The welders were comparatively young (59.53% of them were less than 45 years old). Moreover, for 69.75% of the welders, more than 75% of their activity was devoted to welding. All currently used welding processes were represented, including the modern PLASMA-TIG welding process. No excessive blood alcohol levels were observed in all subjects, but welders did smoke slightly more than the control subjects (40% vs 33%). Self-medication was rather less frequent among the welders, except as regards the use of eye drops, where the proportions were clearly inverted. Optical correction for hyperopia was similar between the two groups; however, as regards myopia, the welders were corrected less often. Lastly, contact lens use was exceptional among the welders. Nearsightedness varied logically with age, but also, inexplicably, with the welding processes. Vision recovery time after exposure to glare was much longer among the welders, except for the PLASMA-TIG processes. No difference was observed in the other parameters of the study. No change in the visual functions studied was noted between the two examinations. The examination techniques used showed no impairment of the studied visual functions, probably because companies use protective and preventive eye care methods. Moreover this study is the first to examine the type of welding used by workers and particularly the modern PLASMA-TIG process. The vision recovery time after exposure to glare seems better for the PLASMA-TIG process may be the result of the lower luminous intensity of this process. This study was conducted for preventive purposes to contribute to better monitoring of safety and comfort for welding workers and has shown no alteration of the visual function among welders in general.

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.

Evaluation of anodic behavior of commercially pure titanium in tungsten inert gas and laser welds.

PubMed

Orsi, Iara Augusta; Raimundo, Larica B; Bezzon, Osvaldo Luiz; Nóbilo, Mauro Antonio de Arruda; Kuri, Sebastião E; Rovere, Carlos Alberto D; Pagnano, Valeria Oliveira

2011-12-01

This study evaluated the resistance to corrosion in welds made with Tungsten Inert Gas (TIG) in specimens made of commercially pure titanium (cp Ti) in comparison with laser welds. A total of 15 circular specimens (10-mm diameter, 2-mm thick) were fabricated and divided into two groups: control group-cp Ti specimens (n = 5); experimental group-cp Ti specimens welded with TIG (n = 5) and with laser (n = 5). They were polished mechanically, washed with isopropyl alcohol, and dried with a drier. In the anodic potentiodynamic polarization assay, measurements were taken using a potentiostat/galvanostat in addition to CorrWare software for data acquisition and CorrView for data visualization and treatment. Three curves were made for each working electrode. Corrosion potential values were statistically analyzed by the Student's t-test. Statistical analysis showed that corrosion potentials and passive current densities of specimens welded with TIG are similar to those of the control group, and had lower values than laser welding. TIG welding provided higher resistance to corrosion than laser welding. Control specimens welded with TIG were more resistant to local corrosion initiation and propagation than those with laser welding, indicating a higher rate of formation and growth of passive film thickness on the surfaces of these alloys than on specimens welded with laser, making it more difficult for corrosion to occur. © 2011 by the American College of Prosthodontists.

[Stress-corrosion test of TIG welded CP-Ti].

PubMed

Li, H; Wang, Y; Zhou, Z; Meng, X; Liang, Q; Zhang, X; Zhao, Y

2000-12-01

In this study TIG (Tungsten Inert Gas) welded CP-Ti were subjected to stress-corrosion test under 261 MPa in artificial saliva of 37 degrees C for 3 months. No significant difference was noted on mechanical test (P > 0.05). No color-changed and no micro-crack on the sample's surface yet. These results indicate that TIG welded CP-Ti offers excellent resistance to stress corrosion.

Optical Arc-Length Sensor For TIG Welding

NASA Technical Reports Server (NTRS)

Smith, Matthew A.

1990-01-01

Proposed subsystem of tungsten/inert-gas (TIG) welding system measures length of welding arc optically. Viewed by video camera, in one of three alternative optical configurations. Length of arc measured instead of inferred from voltage.

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.

On post-weld heat treatment cracking in tig welded superalloy ATI 718Plus

NASA Astrophysics Data System (ADS)

Asala, G.; Ojo, O. A.

The susceptibility of heat affected zone (HAZ) to cracking in Tungsten Inert Gas (TIG) welded Allvac 718Plus superalloy during post-weld heat treatment (PWHT) was studied. Contrary to the previously reported case of low heat input electron beam welded Allvac 718Plus, where HAZ cracking occurred during PWHT, the TIG welded alloy is crack-free after PWHT, notwithstanding the presence of similar micro-constituents that caused cracking in the low input weld. Accordingly, the formation of brittle HAZ intergranular micro-constituents may not be a sufficient factor to determine cracking propensity, the extent of heat input during welding may be another major factor that influences HAZ cracking during PWHT of the aerospace superalloy Allvac 718Plus.

Mechanical Properties and Microstructure of TIG and FSW Joints of a New Al-Mg-Mn-Sc-Zr Alloy

NASA Astrophysics Data System (ADS)

Xu, Guofu; Qian, Jian; Xiao, Dan; Deng, Ying; Lu, Liying; Yin, Zhimin

2016-04-01

A new Al-5.8%Mg-0.4%Mn-0.25%Sc-0.10%Zr (wt.%) alloy was successfully welded by tungsten inert gas (TIG) and friction stir welding (FSW) techniques, respectively. The mechanical properties and microstructure of the welded joints were investigated by microhardness measurements, tensile tests, and microscopy methods. The results show that the ultimate tensile strength, yield strength, and elongation to failure are 358, 234 MPa, and 27.6% for TIG welded joint, and 376, 245 MPa and 31.9% for FSW joint, respectively, showing high strength and superior ductility. The TIG welded joint fails in the heat-affected zone and the fracture of FSW joint is located in stirred zone. Al-Mg-Mn-Sc-Zr alloy is characterized by lots of dislocation tangles and secondary coherent Al3(Sc,Zr) particles. The superior mechanical properties of the TIG and FSW joints are mainly derived from the Orowan strengthening and grain boundary strengthening caused by secondary coherent Al3(Sc,Zr) nano-particles (20-40 nm). For new Al-Mg-Mn-Sc-Zr alloy, the positive effect from secondary Al3(Sc, Zr) particles in the base metal can be better preserved in FSW joint than in TIG welded joint.

Optimized design on condensing tubes high-speed TIG welding technology magnetic control based on genetic algorithm

NASA Astrophysics Data System (ADS)

Lu, Lin; Chang, Yunlong; Li, Yingmin; Lu, Ming

2013-05-01

An orthogonal experiment was conducted by the means of multivariate nonlinear regression equation to adjust the influence of external transverse magnetic field and Ar flow rate on welding quality in the process of welding condenser pipe by high-speed argon tungsten-arc welding (TIG for short). The magnetic induction and flow rate of Ar gas were used as optimum variables, and tensile strength of weld was set to objective function on the base of genetic algorithm theory, and then an optimal design was conducted. According to the request of physical production, the optimum variables were restrained. The genetic algorithm in the MATLAB was used for computing. A comparison between optimum results and experiment parameters was made. The results showed that the optimum technologic parameters could be chosen by the means of genetic algorithm with the conditions of excessive optimum variables in the process of high-speed welding. And optimum technologic parameters of welding coincided with experiment results.

Effect of current and speed on porosity in autogenous Tungsten Inert Gas (TIG) welding of aluminum alloys A1100 butt joint

NASA Astrophysics Data System (ADS)

Milyardi, Indra; Sunar Baskoro, Ario

2018-04-01

Autogenous Tungsten Inert Gas (TIG) welding has been conducted on aluminum alloy A1100. The purpose of this research is to determine the proper current and speed of autogenous TIG welding with butt joint pattern. Variations on welding current are 150 A, 155 A, and 160 A with the variations on welding speed are 1 mm/seconds, 1.1 mm/seconds, 1.2 mm/seconds. The welded results were tested using non-destructive test (NDT) method using X-Ray radiography. After the test, it is found that the appropriate current for the best result without porosity can be achieved using the welding parameter of welding current of 160 A and the welding speed of 1.1 mm seconds.

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

PubMed

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

2014-05-01

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

Influence of the arc plasma parameters on the weld pool profile in TIG welding

NASA Astrophysics Data System (ADS)

Toropchin, A.; Frolov, V.; Pipa, A. V.; Kozakov, R.; Uhrlandt, D.

2014-11-01

Magneto-hydrodynamic simulations of the arc and fluid simulations of the weld pool can be beneficial in the analysis and further development of arc welding processes and welding machines. However, the appropriate coupling of arc and weld pool simulations needs further improvement. The tungsten inert gas (TIG) welding process is investigated by simulations including the weld pool. Experiments with optical diagnostics are used for the validation. A coupled computational model of the arc and the weld pool is developed using the software ANSYS CFX. The weld pool model considers the forces acting on the motion of the melt inside and on the surface of the pool, such as Marangoni, drag, electromagnetic forces and buoyancy. The experimental work includes analysis of cross-sections of the workpieces, highspeed video images and spectroscopic measurements. Experiments and calculations have been performed for various currents, distances between electrode and workpiece and nozzle diameters. The studies show the significant impact of material properties like surface tension dependence on temperature as well as of the arc structure on the weld pool behaviour and finally the weld seam depth. The experimental weld pool profiles and plasma temperatures are in good agreement with computational results.

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.

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.

Mechanical Properties of Steel P92 Welded Joints Obtained By TIG Technology

NASA Astrophysics Data System (ADS)

Mohyla, P.; Havelka, L.; Schmidová, E.; Vontorová, J.

2017-11-01

Mechanical properties of P92 steel welded joints obtained using the TIG (141) technology have been studied upon post-welding heat treatment (PWHT). The microhardness, tensile strength, and impact toughness of metal in the weld and heat-affected zone are determined. The PWHT is shown to be obligatory.

Dredge Mooring Study Recommended Design, Phase 2 Report

DTIC Science & Technology

1992-05-01

processes are acceptable under this Specification: a. Shielded Metal Arc Welding (SMAW). b. Gas Tungsten-Arc Welding ( GTAW or TIG). c. Gas Metal-Arc...the GTAW process. 11.3.9.3 For welding of stainless steel pipe, the GTAW process shall be used on the root pass of open butt joints welded from one...whichever is greater, from each edge of the weld (t = wall thickness of the thickest part being welded). 11.3.11.5 Postweld heat treatment for chromium

Thermodynamic, Transport and Chemical Properties of Reference JP-8

DTIC Science & Technology

2006-06-01

external diameter, 0.18 cm internal diameter) that are sealed on one end with a stainless steel plug welded by a clean tungsten-inert-gas ( TIG ) 15...tubing with an internal diameter of 0.02 cm, also TIG welded to the cell. Each cell and valve is capable of withstanding a pressure in excess of 105... process . Each cell is connected to a high-pressure high-temperature valve at the other end with a short length of 0.16 cm diameter 316 stainless steel

Microstructure characteristics and mechanical properties of laser-TIG hybrid welded dissimilar joints of Ti-22Al-27Nb and TA15

NASA Astrophysics Data System (ADS)

Zhang, Kezhao; Lei, Zhenglong; Chen, Yanbin; Liu, Ming; Liu, Yang

2015-10-01

Laser-TIG-hybrid-welding (TIG - tungsten inert gas) process was successfully applied to investigate the microstructure and tensile properties of Ti-22Al-27Nb/TA15 dissimilar joints. The HAZ of the arc zone in Ti-22Al-27Nb was characterized by three different regions: single B2, B2+α2 and B2+α2+O, while the single B2 phase region was absent in the HAZ of the laser zone. As for the HAZ in TA15 alloy, the microstructure mainly contained acicular α‧ martensites near the fusion line and partially remained the lamellar structure near the base metal. The fusion zone consisted of B2 phase due to the relatively high content of β phase stabilizing elements and fast cooling rate during the welding process. The tensile strength of the welds was higher than that of TA15 alloy because of the fully B2 microstructure in the fusion zone, and the fracture preferentially occurred on the base metal of TA15 alloy during the tensile tests at room temperature and 650 °C.

Nuclear Technology. Course 28: Welding Inspection. Module 28-3, Tungsten Inert Gas (TIG), Metal Inert Gas (MIG) and Submerged Arc Welding.

ERIC Educational Resources Information Center

Espy, John

This third in a series of ten modules for a course titled Welding Inspection presents the apparatus, process techniques, procedures, applications, associated defects, and inspection for the tungsten inert gas, metal inert gas, and submerged arc welding processes. The module follows a typical format that includes the following sections: (1)…

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

DTIC Science & Technology

2009-09-01

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

A simplified model for TIG-dressing numerical simulation

NASA Astrophysics Data System (ADS)

Ferro, P.; Berto, F.; James, M. N.

2017-04-01

Irrespective of the mechanical properties of the alloy to be welded, the fatigue strength of welded joints is primarily controlled by the stress concentration associated with the weld toe or weld root. In order to reduce the effects of such notch defects in welds, which are influenced by tensile properties of the alloy, post-weld improvement techniques have been developed. The two most commonly used techniques are weld toe grinding and TIG dressing, which are intended to both remove toe defects such as non-metallic intrusions and to re-profile the weld toe region to give a lower stress concentration. In the case of TIG dressing the weld toe is re-melted to provide a smoother transition between the plate and the weld crown and to beneficially modify the residual stress redistribution. Assessing the changes to weld stress state arising from TIG-dressing is most easily accomplished through a complex numerical simulation that requires coupled thermo-fluid dynamics and solid mechanics. However, this can be expensive in terms of computational cost and time needed to reach a solution. The present paper therefore proposes a simplified numerical model that overcomes such drawbacks and which simulates the remelted toe region by means of the activation and deactivation of elements in the numerical model.

Distribution of Argon Arc Contaminated with Nitrogen as Function of Frequency in Pulsed TIG Welding

NASA Astrophysics Data System (ADS)

Takahashi, Hiroki; Tanaka, Tatsuro; Yamamoto, Shinji; Iwao, Toru

2016-09-01

TIG arc welding is the high-quality and much applicable material joining technology. However, the current has to be small because the cathode melting should be prevented. In this case, the heat input to the welding pool becomes low, then, the welding defect sometimes occurs. The pulsed TIG arc welding is used to improve this disadvantage This welding can be controlled by some current parameters such as frequency However, few report has reported the distribution of argon arc contaminated with nitrogen It is important to prevent the contamination of nitrogen because the melting depth increases in order to prevent the welding defects. In this paper, the distribution of argon arc contaminated as function of frequency with nitrogen in pulsed TIG welding is elucidated. The nitrogen concentration, the radial flow velocity, the arc temperature were calculated using the EMTF simulation when the time reached at the base current. As a result, the nitrogen concentration into the arc became low with increasing the frequency The diffusion coefficient decreased because of the decrement of temperature over 4000 K. In this case, the nitrogen concentration became low near the anode. Therefore, the nitrogen concentration became low because the frequency is high.

10-kW-class YAG laser application for heavy components

NASA Astrophysics Data System (ADS)

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

2000-02-01

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

Study of the effect of low-power pulse laser on arc plasma and magnesium alloy target in hybrid welding by spectral diagnosis technique

NASA Astrophysics Data System (ADS)

Liu, Liming; Hao, Xinfeng

2008-10-01

In order to study the effect of laser pulses on arc plasma and target metal in the hybrid welding process, the spectra of the plasmas in the welding process of magnesium alloys are analysed in this paper. The acquisition system of plasma spectra is set up and the spectral lines of welding plasma are acquired. Compared with tungsten-inert gas (TIG) welding, the intensities of the spectral lines of magnesium increase sharply while those of Ar decrease for strong evaporation and ionization of magnesium alloys in low-power laser/arc hybrid welding. The electron temperature and density are estimated by the Boltzmann plot method and the Stark broadening effect. The result shows that the electron temperature of arc plasma in the hybrid welding process is much lower than that in TIG welding, especially in the laser beam-affected zone. In contrast, the electron density of the plasma is enhanced. The influences of laser parameters on electron temperature are also studied. The changes in electron temperature and density indicate that the effect of laser pulse on the target metal is the dominant factor influencing the electron temperature and density in low-power laser/arc hybrid welding.

Fracture strength of different soldered and welded orthodontic joining configurations with and without filling material.

PubMed

Bock, Jens Johannes; Bailly, Jacqueline; Gernhardt, Christian Ralf; Fuhrmann, Robert Andreas Werner

2008-01-01

The aim of this study was to compare the mechanical strength of different joints made by conventional brazing, TIG and laser welding with and without filling material. Five standardized joining configurations of orthodontic wire in spring hard quality were used: round, cross, 3 mm length, 9 mm length and 7 mm to orthodontic band. The joints were made by five different methods: brazing, tungsten inert gas (TIG) and laser welding with and without filling material. For the original orthodontic wire and for each kind of joint configuration or connecting method 10 specimens were carefully produced, totalizing 240. The fracture strengths were measured with a universal testing machine (Zwick 005). Data were analyzed by ANOVA (p=0.05) and Bonferroni post hoc test (p=0.05). In all cases, brazing joints were ruptured on a low level of fracture strength (186-407 N). Significant differences between brazing and TIG or laser welding (p<0.05, Bonferroni post hoc test) were found in each joint configuration. The highest fracture strength means were observed for laser welding with filling material and 3 mm joint length (998 N). Using filling materials, there was a clear tendency to higher mean values of fracture strength in TIG and laser welding. However, statistically significant differences were found only in the 9-mm long joints (p<0.05, Bonferroni post hoc test). In conclusion, the fracture strength of welded joints was positively influenced by the additional use of filling material. TIG welding was comparable to laser welding except for the impossibility of joining orthodontic wire with orthodontic band.

FRACTURE STRENGTH OF DIFFERENT SOLDERED AND WELDED ORTHODONTIC JOINING CONFIGURATIONS WITH AND WITHOUT FILLING MATERIAL

PubMed Central

Bock, Jens Johannes; Bailly, Jacqueline; Gernhardt, Christian Ralf; Fuhrmann, Robert Andreas Werner

2008-01-01

The aim of this study was to compare the mechanical strength of different joints made by conventional brazing, TIG and laser welding with and without filling material. Five standardized joining configurations of orthodontic wire in spring hard quality were used: round, cross, 3 mm length, 9 mm length and 7 mm to orthodontic band. The joints were made by five different methods: brazing, tungsten inert gas (TIG) and laser welding with and without filling material. For the original orthodontic wire and for each kind of joint configuration or connecting method 10 specimens were carefully produced, totalizing 240. The fracture strengths were measured with a universal testing machine (Zwick 005). Data were analyzed by ANOVA (p=0.05) and Bonferroni post hoc test (p=0.05). In all cases, brazing joints were ruptured on a low level of fracture strength (186-407 N). Significant differences between brazing and TIG or laser welding (p<0.05, Bonferroni post hoc test) were found in each joint configuration. The highest fracture strength means were observed for laser welding with filling material and 3 mm joint length (998 N). Using filling materials, there was a clear tendency to higher mean values of fracture strength in TIG and laser welding. However, statistically significant differences were found only in the 9-mm long joints (p<0.05, Bonferroni post hoc test). In conclusion, the fracture strength of welded joints was positively influenced by the additional use of filling material. TIG welding was comparable to laser welding except for the impossibility of joining orthodontic wire with orthodontic band. PMID:19089229

Numerical Modeling of Fluid Flow, Heat Transfer and Arc-Melt Interaction in Tungsten Inert Gas Welding

NASA Astrophysics Data System (ADS)

Li, Linmin; Li, Baokuan; Liu, Lichao; Motoyama, Yuichi

2017-04-01

The present work develops a multi-region dynamic coupling model for fluid flow, heat transfer and arc-melt interaction in tungsten inert gas (TIG) welding using the dynamic mesh technique. The arc-weld pool unified model is developed on basis of magnetohydrodynamic (MHD) equations and the interface is tracked using the dynamic mesh method. The numerical model for arc is firstly validated by comparing the calculated temperature profiles and essential results with the former experimental data. For weld pool convection solution, the drag, Marangoni, buoyancy and electromagnetic forces are separately validated, and then taken into account. Moreover, the model considering interface deformation is adopted in a stationary TIG welding process with SUS304 stainless steel and the effect of interface deformation is investigated. The depression of weld pool center and the lifting of pool periphery are both predicted. The results show that the weld pool shape calculated with considering the interface deformation is more accurate.

A new technique for the strengthening of aluminum tungsten inert gas weld metals: using carbon nanotube/aluminum composite as a filler metal.

PubMed

Fattahi, M; Nabhani, N; Rashidkhani, E; Fattahi, Y; Akhavan, S; Arabian, N

2013-01-01

The effect of multi-walled carbon nanotube (MWCNT) on the mechanical properties of aluminum multipass weld metal prepared by the tungsten inert gas (TIG) welding process was investigated. High energy ball milling was used to disperse MWCNT in the aluminum powder. Carbon nanotube/aluminum composite filler metal was fabricated for the first time by hot extrusion of ball-milled powders. After welding, the tensile strength, microhardness and MWCNT distribution in the weld metal were investigated. The test results showed that the tensile strength and microhardness of weld metal was greatly increased when using the filler metal containing 1.5 wt.% MWCNT. Therefore, according to the results presented in this paper, it can be concluded that the filler metal containing MWCNT can serve as a super filler metal to improve the mechanical properties of TIG welds of Al and its alloys. Copyright © 2013 Elsevier Ltd. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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

2013-03-01

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

Numerical Simulation of Stationary AC Tungsten Inert Gas Welding of Aluminum Plate in Consideration of Oxide Layer Cleaning

NASA Astrophysics Data System (ADS)

Tashiro, Shinichi; Tanaka, Manabu

An unified numerical simulation model of AC TIG welding of the aluminum plate considering energy balance among the electrode, the arc and the base metal and employing an analytical model for calculating cleaning rate of the oxide layer has been developed for investigating heat transport properties and weld pool formation process in AC TIG welding of aluminum plate. As a result of this simulation, it was shown that although the heat flux from the arc onto the base metal increases in EN (Electrode Negative) phase due to the electron condensation, that in EP (Electrode Positive) phase conversely decreases because mainly of cooling caused by the electron emission. Furthermore, the validity of the simulation model was confirmed by comparing to experimental results such as the arc voltage, the area of cleaning zone and the shape of weld pool.

Effects on the efficiency of activated carbon on exposure to welding fumes

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

Ghosh, D.

1995-02-01

It is the intention of this paper to document that certain types of welding fumes have little or no effect on the effectiveness of the carbon filter air filtration efficiency when directly exposed to a controlled amount of welding fumes for a short-term period. The welding processes studied were restricted to shielded metal arc welding (SMAW), flux cored arc welding (FCAW), gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) processes. Contrary to the SMAW and FCAW processes, the GTAW (or TIG) and the GMAW (or MIG) welding processes do not require the use of flux as partmore » of the overall process. Credit was taken for these processes occurring in inert gas environments and producing minimal amount of smoke. It was concluded that a study involving the SMAW process would also envelop the effects of the TIG and MIG welding processes. The quantity of welding fumes generated during the arc welding process is a function of the particular process, the size and type of electrode, welding machine amperage, and operator proficiency. For this study, the amount of welding for specific testing was equated to the amount of welding normally conducted during plant unit outages. Different welding electrodes were also evaluated, and the subsequent testing was limited to an E7018 electrode which was judged to be representative of all carbon and stainless steel electrodes commonly used at the site. The effect of welding fumes on activated charcoal was tested using a filtration unit complete with prefilters, upstream and downstream high efficiency particulate air (HEPA) filters, and a carbon adsorber section. The complete system was field tested in accordance with ANSI N510 standards prior to exposing the filters and the adsorber bed to welding fumes. The carbon samples were tested at an established laboratory using ASTM D3803-1989 standards.« less

Corrosion studies using potentiodynamic and EIS electrochemical techniques of welded lean duplex stainless steel UNS S82441

NASA Astrophysics Data System (ADS)

Brytan, Z.; Niagaj, J.; Reiman, Ł.

2016-12-01

The corrosion characterisation of lean duplex stainless steel (1.4662) UNS S82441 welded joints using the potentiodynamic test and electrochemical impedance spectroscopy in 1 M NaCl solution are discussed. The influence of autogenous TIG welding parameters (amount of heat input and composition of shielding gases like Ar and Ar-N2 and an Ar-He mixture), as well as A-TIG welding was studied. The influence of welding parameters on phase balance, microstructural changes and the protective properties of passive oxide films formed at the open circuit potential or during the anodic polarisation were studied. From the results of the potentiodynamic test and electrochemical impedance spectroscopy of TIG and A-TiG, welded joints show a lower corrosion resistance compared to non-welded parent metal, but introducing heat input properly during welding and applying shielding gases rich in nitrogen or helium can increase austenitic phase content, which is beneficial for corrosion resistance, and improves surface oxide layer resistance in 1 M NaCl solution.

NASA Astrophysics Data System (ADS)

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

Prediction Analysis of Weld-Bead and Heat Affected Zone in TIG welding using Artificial Neural Networks

NASA Astrophysics Data System (ADS)

Saldanha, Shamith L.; Kalaichelvi, V.; Karthikeyan, R.

2018-04-01

TIG Welding is a high quality form of welding which is very popular in industries. It is one of the few types of welding that can be used to join dissimilar metals. Here a weld joint is formed between stainless steel and monel alloy. It is desired to have control over the weld geometry of such a joint through the adjustment of experimental parameters which are welding current, wire feed speed, arc length and the shielding gas flow rate. To facilitate the automation of the same, a model of the welding system is needed. However the underlying welding process is complex and non-linear, and analytical methods are impractical for industrial use. Therefore artificial neural networks (ANN) are explored for developing the model, as they are well-suited for modelling non-linear multi-variate data. Feed-forward neural networks with backpropagation training algorithm are used, and the data for training the ANN taken from experimental work. There are four outputs corresponding to the weld geometry. Different training and testing phases were carried out using MATLAB software and ANN approximates the given data with minimum amount of error.

Melting of SiC powders preplaced duplex stainless steel using TIG welding

NASA Astrophysics Data System (ADS)

Maleque, M. A.; Afiq, M.

2018-01-01

TIG torch welding technique is a conventional melting technique for the cladding of metallic materials. Duplex stainless steels (DSS) show decrease in performance under aggressive environment which may lead to unanticipated failure due to poor surface properties. In this research, surface modification is done by using TIG torch method where silicon carbide (SiC) particles are fused into DSS substrate in order to form a new intermetallic compound at the surface. The effect of particle size, feed rate of SiC preplacement, energy input and shielding gas flow rate on surface topography, microstructure, microstructure and hardness are investigated. Deepest melt pool (1.237 mm) is produced via TIG torch with highest energy input of 1080 J/mm. Observations of surface topography shows rippling marks which confirms that re-solidification process has taken place. Melt microstructure consist of dendritic and globular carbides precipitate as well as partially melted silicon carbides (SiC) particles. Micro hardness recorded at value ranging from 316 HV0.5 to 1277 HV0.5 which shows increment from base hardness of 260 HV0.5kgf. The analyzed result showed that incorporation of silicon carbide particles via TIG Torch method increase the hardness of DSS.

An Investigation of TIG welding parameters on microhardness and microstructure of heat affected zone of HSLA steel

NASA Astrophysics Data System (ADS)

Musa, M. H. A.; Maleque, M. A.; Ali, M. Y.

2018-01-01

Nowadays a wide variety of metal joining methods are used in fabrication industries. In this study, the effect of various welding parameters of the TIG welding process on microhardness, depth, and microstructure of the heat-affected zone (HAZ) of L450 HSLA steel and optimizing these process parameters following Taguchi experimental design was investigated. The microhardness tended to increase significantly with the increase of welding speed from 1.0 to 2.5 mm/s whereas the width of HAZ decreased. The current and arc voltage was found to be less significant in relative comparison. Microstructures of the welded samples were also studied to analyze the changes in the microstructure of the material in terms of ferrite, pearlite, bainite, and martensite formations. Welding speed was found to be the most significant factors leading to changes in microhardness and metallurgical properties. The increase of welding heat input caused an increase in width (depth) of HAZ and the growth of prior austenite grains and then enlarged the grain size of coarse grain heat affected zone (CGHAZ). However, the amount of martensite in the HAZ decreased accompanied by an opposite change of paint. It was observed that the hardness properties and the microstructural feature of HAZ area was strongly affected by the welding parameters.

Continuous internal channels formed in aluminum fusion welds

NASA Technical Reports Server (NTRS)

Gault, J.; Sabo, W.

1967-01-01

Process produces continuous internal channel systems on a repeatable basis in 2014-T6 aluminum. Standard machining forms the initial channel, which is filled with tungsten carbide powder. TIG machine fusion welding completes formation of the channel. Chem-mill techniques enlarge it to the desired size.

Electron temperature and density measurement of tungsten inert gas arcs with Ar-He shielding gas mixture

NASA Astrophysics Data System (ADS)

Kühn-Kauffeldt, M.; Marques, J.-L.; Forster, G.; Schein, J.

2013-10-01

The diagnostics of atmospheric welding plasma is a well-established technology. In most cases the measurements are limited to processes using pure shielding gas. However in many applications shielding gas is a mixture of various components including metal vapor in gas metal arc welding (GMAW). Shielding gas mixtures are intentionally used for tungsten inert gas (TIG) welding in order to improve the welding performance. For example adding Helium to Argon shielding gas allows the weld geometry and porosity to be influenced. Yet thermal plasmas produced with gas mixtures or metal vapor still require further experimental investigation. In this work coherent Thomson scattering is used to measure electron temperature and density in these plasmas, since this technique allows independent measurements of electron and ion temperature. Here thermal plasmas generated by a TIG process with 50% Argon and 50% Helium shielding gas mixture have been investigated. Electron temperature and density measured by coherent Thomson scattering have been compared to the results of spectroscopic measurements of the plasma density using Stark broadening of the 696.5 nm Argon spectral line. Further investigations of MIG processes using Thomson scattering technique are planned.

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

NASA Astrophysics Data System (ADS)

Liu, Bo

2017-03-01

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

Surface Effect Ship Structural Producibility. Part 1.

DTIC Science & Technology

1980-05-14

Effort should be made to produce welds whose root pass does not have a re-entrant toe angle. Studies have been made that indicate that a TIG root pass...been called TIG welding , a noapref erred term.) GOVERNMENT INSPECTOR (REPRESENTATIVE). Government official who is charged with the responsibility for...INTRODUCTION 1-1 2 / RECOMMENDATIONS/OBSERVATIONS 2-1 2.1 Welding & Fabrication Technology Summary Report ......... ................... 2-1 2.2 SES-10OAl

Comparing Reactivation Behavior of TIG and Laser Beam Welded Alloy 690

NASA Astrophysics Data System (ADS)

Abraham, Geogy J.; Bhambroo, Rajan; Kain, V.; Dey, G. K.; Raja, V. S.

2013-02-01

The nickel base Alloy 690 was subjected to simulated autogenous welding treatment employing two different techniques, laser beam welding (LBW) and tungsten inert gas (TIG) welding. The resultant weld fusion zone (WFZ) and heat-affected zone (HAZ) were compared by studying the reactivation behavior. The chromium depletion effect was assessed by measuring the degree of sensitization (DOS) from the electrochemical potentiodynamic reactivation (EPR) test. A double-loop EPR test for Alloy 690 was employed to measure the DOS at different regions of weldments by masking the remaining regions. The results clearly demonstrated that Alloy 690 showed no sensitization in the parent material and the WFZ region of both TIG and laser weldments. However, it exhibited reactivation in the HAZ region of both the weldments. The DOS values measured for Alloy 690 were very low for all the regions of the LBW weldment as compared to that in the TIG weldment. The HAZ region of the LBW weldment showed the highest DOS value in any region of the weldment but even this value was quite low indicating absence of sensitization in LBW weldment. The attack along the grain boundaries for the weldments after EPR experiments were studied using optical and scanning electron microscopy.

Automatic Welding System of Aluminum Pipe by Monitoring Backside Image of Molten Pool Using Vision Sensor

NASA Astrophysics Data System (ADS)

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

An automatic welding system using Tungsten Inert Gas (TIG) welding with vision sensor for welding of aluminum pipe was constructed. This research studies the intelligent welding process of aluminum alloy pipe 6063S-T5 in fixed position and moving welding torch with the AC welding machine. The monitoring system consists of a vision sensor using 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. Neural network model for welding speed control were constructed to perform the process automatically. From the experimental results it shows the effectiveness of the control system confirmed by good detection of molten pool and sound weld of experimental result.

Fatigue strength: effect of welding type and joint design executed in Ti-6Al-4V structures.

PubMed

Pantoja, Juliana M C Nuñez; Farina, Ana P; Vaz, Luis G; Consani, Rafael L X; Nóbilo, Mauro A de Arruda; Mesquita, Marcelo F

2012-06-01

This study evaluated the fatigue strength of Ti-6Al-4V-machined structures submitted to laser (L)-welding and TIG (TIG)-welding procedures, varying the joint designs. Seventy dumbbell rods were machined in Ti-6Al-4V alloy with central diameters of 3.5 mm. The specimens were sectioned and welded using TIG or L and three joint designs {'I' design, varying welding distances [0.0 mm (I00) or 0.6 mm (I06)], or 'X' [X] design}. The combinations of variables created six groups, which, when added to the intact group, made a total of seven groups (n = 10). L was executed as follows: 360 V/8 ms (X) and 390 V/9 ms (I00 and I06), with focus and frequency regulated to zero. TIG was executed using 2:2 (X) and 3:2 (I00 and I06) as welding parameters. Joints were finished, polished and submitted to radiographic examination to be analysed visually for the presence of porosity. The specimens were then subjected to mechanical cyclic tests, and the number of cycles completed until failure was recorded. The fracture surface was examined using a scanning electron microscope. The Kruskal-Wallis and Dunn test (α = 0.05) indicated that the number of cycles resisted for fracture was higher to X for both welding procedures. To L, I06 was as resistant as X. The Mann-Whitney U-test (α = 0.05) indicated that L joints were more resistant than TIG to I00 and I06. Spearman's correlation coefficient (α = 0.05) indicated a negative correlation between the number of cycles and presence of porosity. Thus, to weld Ti-6Al-4V structures, the best condition is X, independent of the welding method employed. © 2011 The Gerodontology Society and John Wiley & Sons A/S.

[Occupational exposure of welders to ultraviolet and "blue light" radiation emitted during TIG and MMA welding based on field measurements].

PubMed

Wolska, Agnieszka

2013-01-01

The aim of the study was to present the results of welders' occupational exposure to "blue light" and UV radiation carried out at industrial workstations during TIG and MMA welding. Measurements were performed at 13 workstations (TIG welding: 6; MMA welding: 7), at which different welding parameters and materials were used. The radiation level was measured using a wide-range radiometer and a set of detectors, whose spectral responses were adequately fit to particular hazard under study. The measurement points corresponded with the location of eye and hand. The highest values of eye irradiance were found for aluminum TIG welding. Effective irradiance of actinic UV was within the range E(s) = 7.79-37.6 W/m2; UVA total irradiance, E(UVA) = 18-53.1 W/m2 and effective blue-light irradiance E(B) = 35-67 W/m2. The maximum allowance time ranged from 1.7 to 75 s, which means that in some cases even unintentional very short eye exposure can exceed MPE. The influence of welded material and the type of electrode coating on the measured radiation level were evidenced. The exceeded value of MPE for photochemical hazard arising for the eyes and skin was found at all measured workstations. Welders should use appropriately the eye and face protective equipment and avoid direct staring at welding arc when starting an arc-welding operation. Besides, the lack of head and neck skin protection can induce acute and chronic harmful health effects. Therefore, an appropriate wear of personal protective equipment is essential for welders' health.

Hot-crack test for aluminium alloys welds using TIG process

NASA Astrophysics Data System (ADS)

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

2010-06-01

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

Microstructural Aspects in FSW and TIG Welding of Cast ZE41A Magnesium Alloy

NASA Astrophysics Data System (ADS)

Carlone, Pierpaolo; Astarita, Antonello; Rubino, Felice; Pasquino, Nicola

2016-04-01

In this paper, magnesium ZE41A alloy plates were butt joined through friction stir welding (FSW) and Tungsten Inert Gas welding processes. Process-induced microstructures were investigated by optical and SEM observations, EDX microanalysis and microhardness measurements. The effect of a post-welded T5 heat treatment on FSW joints was also assessed. Sound joints were produced by means of both techniques. Different elemental distributions and grain sizes were found, whereas microhardness profiles reflect microstructural changes. Post-welding heat treatment did not induce significant alterations in elemental distribution. The FSW-treated joint showed a more homogeneous hardness profile than the as-welded FSW joint.

Abrasive wear response of TIG-melted TiC composite coating: Taguchi approach

NASA Astrophysics Data System (ADS)

Maleque, M. A.; Bello, K. A.; Adebisi, A. A.; Dube, A.

2017-03-01

In this study, Taguchi design of experiment approach has been applied to assess wear behaviour of TiC composite coatings deposited on AISI 4340 steel substrates by novel powder preplacement and TIG torch melting processes. To study the abrasive wear behaviour of these coatings against alumina ball at 600° C, a Taguchi’s orthogonal array is used to acquire the wear test data for determining optimal parameters that lead to the minimization of wear rate. Composite coatings are developed based on Taguchi’s L-16 orthogonal array experiment with three process parameters (welding current, welding speed, welding voltage and shielding gas flow rate) at four levels. In this technique, mean response and signal-to-noise ratio are used to evaluate the influence of the TIG process parameters on the wear rate performance of the composite coated surfaces. The results reveal that welding voltage is the most significant control parameter for minimizing wear rate while the current presents the least contribution to the wear rate reduction. The study also shows the best optimal condition has been arrived at A3 (90 A), B4 (2.5 mm/s), C3 (30 V) and D3 (20 L/min), which gives minimum wear rate in TiC embedded coatings. Finally, a confirmatory experiment has been conducted to verify the optimized result and shows that the error between the predicted values and the experimental observation at the optimal condition lies within the limit of 4.7 %. Thus, the validity of the optimum condition for the coatings is established.

Process and Energy Optimization Assessment, Tobyhanna Army Depot, PA

DTIC Science & Technology

2006-04-17

assembly of electronic-communication components, different welding processes are performed at TYAD. It uses shielded arc, metal inert gas (MIG...tungsten inert gas ( TIG ), and silver braz- ing oxygen/acetylene cutting plasma arc methods to complete mission re- quirements. Major welding jobs are...ER D C/ CE R L TR -0 6 -1 1 Process and Energy Optimization Assessment Tobyhanna Army Depot, PA Mike C.J. Lin, Alexander M. Zhivov

Significance of the Resonance Condition for Controlling the Seam Position in Laser-assisted TIG Welding

NASA Astrophysics Data System (ADS)

Emde, B.; Huse, M.; Hermsdorf, J.; Kaierle, S.; Wesling, V.; Overmeyer, L.; Kozakov, R.; Uhrlandt, D.

As an energy-preserving variant of laser hybrid welding, laser-assisted arc welding uses laser powers of less than 1 kW. Recent studies have shown that the electrical conductivity of a TIG welding arc changes within the arc in case of a resonant interaction between laser radiation and argon atoms. This paper presents investigations on how to control the position of the arc root on the workpiece by means of the resonant interaction. Furthermore, the influence on the welding result is demonstrated. The welding tests were carried out on a cooled copper plate and steel samples with resonant and non-resonant laser radiation. Moreover, an analysis of the weld seam is presented.

Fracture Mechanics Evaluation of B-1 Materials. Volume I. Text

DTIC Science & Technology

1976-10-01

4V Microstructures 2-37 P.4-1 TIG Welding Setup 2-60 2.4-2 Macrographs Showing Transverse Cross- 2-61 Sections of Typical Weld Joints 2.4-3 Diffusion...concavity. k. PAW welding parameters were: Keyhole Mode (First Pass) 1fWelding-Amperage - 185 Pilot Arc Amperage - P5 1/5" Diameter Tungsten -P% Thoria...of tooling employed. 2. •𔃼󈧿 r a • 4 .fA A A ~ . - 4N. I 141Eb,~..0 1171 :41ýI t4, 1. r "I j, O~ vN;I ___4 A Ad2 Figuire 2.4-1i TIG Welding , Setup

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

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

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

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

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

Automatic visual monitoring of welding procedure in stainless steel kegs

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

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

NASA Technical Reports Server (NTRS)

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

1999-01-01

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

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

NASA Astrophysics Data System (ADS)

Song, Gang; Luo, Zhimin

2011-01-01

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

Welding skate with computerized controls

NASA Technical Reports Server (NTRS)

Wall, W. A., Jr.

1968-01-01

New welding skate concept for automatic TIG welding of contoured or double-contoured parts combines lightweight welding apparatus with electrical circuitry which computes the desired torch angle and positions a torch and cold-wire guide angle manipulator.

Effect of Cryogenic Treatment on Sensitization of 304 Stainless Steel in TIG Welding

NASA Astrophysics Data System (ADS)

Singh, Rupinder; Slathia, Ravinder Singh

2016-04-01

Stainless steel (SS) is sensitized by a thermal treatment in the range of 400-850 °C and inter-granular attack would occur upon subsequent exposure to certain media. In many practical situations, such as welding, sensitization is best studied by continuous cooling through the sensitizing temperature range wherein the variables are the peak temperature reached and the cooling rate in contrast to temperature and time of the isothermal hold which has been the customary practice. There are also various methods of controlling the inter-granular corrosion viz. lowering the carbon content, adding stabilizers and applying solution heat treatment but all these methods are either costly or difficult to apply. This study is focussed on the effect of cryogenically treated tungsten electrode of TIG welding on the sensitization behaviour of 304SS by taking into consideration the weld properties (like: hardness, tensile strength, percentage elongation and micro-structure). The parameters of significance are current, pulse frequency and gas flow rate. Further the study suggested that the results of non cryo treated electrode were better than the treated one on sensitization of welded joints during TIG welding within the range of selected parameters.

Exposure to Inhalable, Respirable, and Ultrafine Particles in Welding Fume

PubMed Central

Pesch, Beate

2012-01-01

This investigation aims to explore determinants of exposure to particle size-specific welding fume. Area sampling of ultrafine particles (UFP) was performed at 33 worksites in parallel with the collection of respirable particles. Personal sampling of respirable and inhalable particles was carried out in the breathing zone of 241 welders. Median mass concentrations were 2.48 mg m−3 for inhalable and 1.29 mg m−3 for respirable particles when excluding 26 users of powered air-purifying respirators (PAPRs). Mass concentrations were highest when flux-cored arc welding (FCAW) with gas was applied (median of inhalable particles: 11.6 mg m−3). Measurements of particles were frequently below the limit of detection (LOD), especially inside PAPRs or during tungsten inert gas welding (TIG). However, TIG generated a high number of small particles, including UFP. We imputed measurements

Exposure to inhalable, respirable, and ultrafine particles in welding fume.

PubMed

Lehnert, Martin; Pesch, Beate; Lotz, Anne; Pelzer, Johannes; Kendzia, Benjamin; Gawrych, Katarzyna; Heinze, Evelyn; Van Gelder, Rainer; Punkenburg, Ewald; Weiss, Tobias; Mattenklott, Markus; Hahn, Jens-Uwe; Möhlmann, Carsten; Berges, Markus; Hartwig, Andrea; Brüning, Thomas

2012-07-01

This investigation aims to explore determinants of exposure to particle size-specific welding fume. Area sampling of ultrafine particles (UFP) was performed at 33 worksites in parallel with the collection of respirable particles. Personal sampling of respirable and inhalable particles was carried out in the breathing zone of 241 welders. Median mass concentrations were 2.48 mg m(-3) for inhalable and 1.29 mg m(-3) for respirable particles when excluding 26 users of powered air-purifying respirators (PAPRs). Mass concentrations were highest when flux-cored arc welding (FCAW) with gas was applied (median of inhalable particles: 11.6 mg m(-3)). Measurements of particles were frequently below the limit of detection (LOD), especially inside PAPRs or during tungsten inert gas welding (TIG). However, TIG generated a high number of small particles, including UFP. We imputed measurements

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).

Tungsten Carbide Grain Size Computation for WC-Co Dissimilar Welds

NASA Astrophysics Data System (ADS)

Zhou, Dongran; Cui, Haichao; Xu, Peiquan; Lu, Fenggui

2016-06-01

A "two-step" image processing method based on electron backscatter diffraction in scanning electron microscopy was used to compute the tungsten carbide (WC) grain size distribution for tungsten inert gas (TIG) welds and laser welds. Twenty-four images were collected on randomly set fields per sample located at the top, middle, and bottom of a cross-sectional micrograph. Each field contained 500 to 1500 WC grains. The images were recognized through clustering-based image segmentation and WC grain growth recognition. According to the WC grain size computation and experiments, a simple WC-WC interaction model was developed to explain the WC dissolution, grain growth, and aggregation in welded joints. The WC-WC interaction and blunt corners were characterized using scanning and transmission electron microscopy. The WC grain size distribution and the effects of heat input E on grain size distribution for the laser samples were discussed. The results indicate that (1) the grain size distribution follows a Gaussian distribution. Grain sizes at the top of the weld were larger than those near the middle and weld root because of power attenuation. (2) Significant WC grain growth occurred during welding as observed in the as-welded micrographs. The average grain size was 11.47 μm in the TIG samples, which was much larger than that in base metal 1 (BM1 2.13 μm). The grain size distribution curves for the TIG samples revealed a broad particle size distribution without fine grains. The average grain size (1.59 μm) in laser samples was larger than that in base metal 2 (BM2 1.01 μm). (3) WC-WC interaction exhibited complex plane, edge, and blunt corner characteristics during grain growth. A WC ( { 1 {bar{{1}}}00} ) to WC ( {0 1 1 {bar{{0}}}} ) edge disappeared and became a blunt plane WC ( { 10 1 {bar{{0}}}} ) , several grains with two- or three-sided planes and edges disappeared into a multi-edge, and a WC-WC merged.

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.

Closed circuit TV system monitors welding operations

NASA Technical Reports Server (NTRS)

Gilman, M.

1967-01-01

TV camera system that has a special vidicon tube with a gradient density filter is used in remote monitoring of TIG welding of stainless steel. The welding operations involve complex assembly welding tools and skates in areas of limited accessibility.

Arc-Welding Spectroscopic Monitoring based on Feature Selection and Neural Networks.

PubMed

Garcia-Allende, P Beatriz; Mirapeix, Jesus; Conde, Olga M; Cobo, Adolfo; Lopez-Higuera, Jose M

2008-10-21

A new spectral processing technique designed for application in the on-line detection and classification of arc-welding defects is presented in this paper. A noninvasive fiber sensor embedded within a TIG torch collects the plasma radiation originated during the welding process. The spectral information is then processed in two consecutive stages. A compression algorithm is first applied to the data, allowing real-time analysis. The selected spectral bands are then used to feed a classification algorithm, which will be demonstrated to provide an efficient weld defect detection and classification. The results obtained with the proposed technique are compared to a similar processing scheme presented in previous works, giving rise to an improvement in the performance of the monitoring system.

Keyhole behavior and liquid flow in molten pool during laser-arc hybrid welding

NASA Astrophysics Data System (ADS)

Naito, Yasuaki; Katayama, Seiji; Matsunawa, Akira

2003-03-01

Hybrid welding was carried out on Type 304 stainless steel plate under various conditions using YAG laser combined with TIG arc. During arc and laser-arc hybrid welding, arc voltage variation was measured, and arc plasma, laser-induced plume and evaporation spots as well as keyhole behavior and liquid flow in the molten pool were observed through CCD camera and X-ray real-time transmission apparatus. It was consequently found that hybrid welding possessed many features in comparison with YAG laser welding. The deepest weld bead could be produced when the YAG laser beam of high power density was shot on the molten pool made beforehand stably with TIG arc. A keyhole was long and narrow, and its behavior was rather stable inside the molten pool. It was also confirmed that porosity was reduced by the suppression of bubble formation in hybrid welding utilizing a laser of a moderate power density.

Design and Fabrication of Quadrupole Ion Mass Spectrometer for Upper Atmosphere.

DTIC Science & Technology

1981-09-30

34 diameter con-flat flange were T.I.G. welded to the end of each of three bowls. All bowls were then electro- polished, cleaned and sent out to have...plated surface was .0001" to .0002" thick. After gold plating, the hemispheres were mated and T.I.G. welded to form a sphere with a con-flat flange at...Valve Rotatable Conflat to fit k" Swage Lock Weld Adaptors. 5 2 3/4" Conflat Flanges machined to fit Swage Lock unions. 12 10-24 x 2 " Brass Screws necket

Temperature and emissivity determination of liquid steel S235

NASA Astrophysics Data System (ADS)

Schöpp, H.; Sperl, A.; Kozakov, R.; Gött, G.; Uhrlandt, D.; Wilhelm, G.

2012-06-01

Temperature determination of liquid metals is difficult but a necessary tool for improving materials and processes such as arc welding in the metal-working industry. A method to determine the surface temperature of the weld pool is described. A TIG welding process and absolute calibrated optical emission spectroscopy are used. This method is combined with high-speed photography. 2D temperature profiles are obtained. The emissivity of the radiating surface has an important influence on the temperature determination. A temperature dependent emissivity for liquid steel is given for the spectral region between 650 and 850 nm.

Fatigue Behavior of Inconel 718 TIG Welds

NASA Astrophysics Data System (ADS)

Alexopoulos, Nikolaos D.; Argyriou, Nikolaos; Stergiou, Vasillis; Kourkoulis, Stavros K.

2014-08-01

Mechanical behavior of reference and TIG-welded Inconel 718 specimens was examined in the present work. Tensile, constant amplitude fatigue, and fracture toughness tests were performed in ambient temperature for both, reference and welded specimens. Microstructure revealed the presence of coarse and fine-grained heat-affected zones. It has been shown that without any post-weld heat treatment, welded specimens maintained their tensile strength properties while their ductility decreased by more than 40%. It was found that the welded specimens had lower fatigue life and this decrease was a function of the applied fatigue maximum stress. A 30% fatigue life decrease was noticed in the high cycle fatigue regime for the welded specimens while this decrease exceeded 50% in the low cycle fatigue regime. Cyclic stress-strain curves showed that Inconel 718 experiences a short period of hardening followed by softening for all fatigue lives. Cyclic fatigue response of welded specimens' exhibited cyclically stable behavior. Finally, a marginal decrease was noticed in the Mode I fracture toughness of the welded specimens.

Wear behavior of the surface alloyed AISI 1020 steel with Fe-Nb-B by TIG welding technique

NASA Astrophysics Data System (ADS)

Kilinc, B.; Durmaz, M.; Abakay, E.; Sen, U.; Sen, S.

2015-03-01

Weld overlay coatings also known as hardfacing is a method which involves melting of the alloys and solidification for applied coatings. Recently hardfacing by welding has become a commonly used technique for improvement of material performance in extreme (high temperature, impact/abrasion, erosion, etc.) conditions.In the present study, the coatings were produced from a mixture of ferrous niobium, ferrous boron and iron powders in the ranges of -45µm particle size with different ratio. Fe12Nb5B3 and Fe2NbBalloys were coated on the AISI 1020 steel surface by TIG welding. The phases formed in the coated layer are Fe2B, NbB2, NbFeB and Fe0,2 Nb0,8 phases. The hardness of the presence phases are changing between 1689±85 HV0.01, and 181±7 HV0.1. Microstructural examinations were realized by optical and scanning electron microscopy. The wear and friction behaviors of Fe12Nb5B3 and Fe2NbB realized on the AISI 1020 steel were investigated by the technique of TIG welding by using ball-on-disk arrangement against alumina ball.

Assessment of biological chromium among stainless steel and mild steel welders in relation to welding processes.

PubMed

Edmé, J L; Shirali, P; Mereau, M; Sobaszek, A; Boulenguez, C; Diebold, F; Haguenoer, J M

1997-01-01

Air and biological monitoring were used for assessing external and internal chromium exposure among 116 stainless steel welders (SS welders) using manual metal arc (MMA), metal inert gas (MIG) and tungsten inert gas (TIG) welding processes (MMA: n = 57; MIG: n = 37; TIG: n = 22) and 30 mild steel welders (MS welders) using MMA and MIG welding processes (MMA: n = 14; MIG: n = 16). The levels of atmospheric total chromium were evaluated after personal air monitoring. The mean values for the different groups of SS welders were 201 micrograms/m3 (MMA) and 185 micrograms/m3 (MIG), 52 micrograms/m3 (TIG) and for MS welders 8.1 micrograms/m3 (MMA) and 7.3 micrograms/m3 (MIG). The curve of cumulative frequency distribution from biological monitoring among SS welders showed chromium geometric mean concentrations in whole blood of 3.6 micrograms/l (95th percentile = 19.9), in plasma of 3.3 micrograms/l (95th percentile = 21.0) and in urine samples of 6.2 micrograms/l (95th percentile = 58.0). Among MS welders, mean values in whole blood and plasma were rather more scattered (1.8 micrograms/l, 95th percentile = 9.3 and 1.3 micrograms/l, 95th percentile = 8.4, respectively) and in urine the value was 2.4 micrograms/l (95th percentile = 13.3). The analysis of variance of chromium concentrations in plasma previously showed a metal effect (F = 29.7, P < 0.001), a process effect (F = 22.2, P < 0.0001) but no metal-process interaction (F = 1.3, P = 0.25). Concerning urinary chromium concentration, the analysis of variance also showed a metal effect (F = 30, P < 0.0001), a process effect (F = 72, P < 0.0001) as well as a metal-process interaction (F = 13.2, P = 0.0004). Throughout the study we noted any significant differences between smokers and non-smokers among welders. Taking in account the relationships between chromium concentrations in whole, plasma or urine and the different welding process. MMA-SS is definitely different from other processes because the biological values are clearly higher. These higher levels are due to the very significant concentrations of total soluble chromium, mainly hexavalent chromium, in welding fumes.

Refractory metals welded or brazed with tungsten inert gas equipment

NASA Technical Reports Server (NTRS)

Wisner, J. P.

1965-01-01

Appropriate brazing metals and temperatures facilitate the welding or brazing of base metals with tungsten inert gas equipment. The highest quality bond is obtained when TIG welding is performed in an inert atmosphere.

Weld Repair of Thin Aluminum Sheet

NASA Technical Reports Server (NTRS)

Beuyukian, C. S.; Mitchell, M. J.

1986-01-01

Weld repairing of thin aluminum sheets now possible, using niobium shield and copper heat sinks. Refractory niobium shield protects aluminum adjacent to hole, while copper heat sinks help conduct heat away from repair site. Technique limits tungsten/inert-gas (TIG) welding bombardment zone to melt area, leaving surrounding areas around weld unaffected. Used successfully to repair aluminum cold plates on Space Shuttle, Commercial applications, especially in sealing fractures, dents, and holes in thin aluminum face sheets or clad brazing sheet in cold plates, heat exchangers, coolers, and Solar panels. While particularly suited to thin aluminum sheet, this process also used in thicker aluminum material to prevent surface damage near weld area.

Tungsten Inert Gas and Friction Stir Welding Characteristics of 4-mm-Thick 2219-T87 Plates at Room Temperature and -196 °C

NASA Astrophysics Data System (ADS)

Lei, Xuefeng; Deng, Ying; Yin, Zhimin; Xu, Guofu

2014-06-01

2219-T87 aluminum alloy is widely used for fabricating liquid rocket propellant storage tank, due to its admirable cryogenic property. Welding is the dominant joining method in the manufacturing process of aerospace components. In this study, the tungsten inert gas welding and friction stir welding (FSW) characteristics of 4-mm-thick 2219-T87 alloy plate at room temperature (25 °C) and deep cryogenic temperature (-196 °C) were investigated by property measurements and microscopy methods. The studied 2219 base alloy exhibits a low strength plane anisotropy and excellent room temperature and cryogenic mechanical properties. The ultimate tensile strength values of TIG and FSW welding joints can reach 265 and 353 MPa at room temperature, and 342 and 438 MPa at -196 °C, respectively. The base metal consists of elongated deformed grains and many nano-scaled θ (Al2Cu) aging precipitates. Fusion zone and heat-affected zone (HAZ) of the TIG joint are characterized by coarsening dendritic grains and equiaxed recrystallized grains, respectively. The FSW-welded joint consists of the weld nugget zone, thermo-mechanically affected zone (TMAZ), and HAZ. In the weld nugget zone, a micro-scaled sub-grain structure is the main microstructure characteristic. The TMAZ and HAZ are both characterized by coarsened aging precipitates and elongated deformed grains. The excellent FSW welding properties are attributed to the preservation of the working structures and homogenous chemical compositions.

Acoustic-Emission Weld-Penetration Monitor

NASA Technical Reports Server (NTRS)

Maram, J.; Collins, J.

1986-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2017-04-01

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

Ceramic backup ring prevents undesirable weld-metal buildup

NASA Technical Reports Server (NTRS)

Leonard, G. E.

1971-01-01

Removable ceramic backup material butted against weld zone back prevents weld metal buildup at that site. Method is successful with manual tungsten-inert gas /TIG/ welding of 316 corrosion resistant steel /CRES/ pieces with 0.76 cm throat diameter and 1.57 cm pipe internal diameter.

Corrosion in artificial saliva of a Ni-Cr-based dental alloy joined by TIG welding and conventional brazing.

PubMed

Matos, Irma C; Bastos, Ivan N; Diniz, Marília G; de Miranda, Mauro S

2015-08-01

Fixed prosthesis and partial dental prosthesis frameworks are usually made from welded Ni-Cr-based alloys. These structures can corrode in saliva and have to be investigated to establish their safety. The purpose of this study was to evaluate the corrosion behavior of joints joined by tungsten inert gas (TIG) welding and conventional brazing in specimens made of commercial Ni-Cr alloy in Fusayama artificial saliva at 37°C (pH 2.5 and 5.5). Eighteen Ni-Cr base metal specimens were cast and welded by brazing or tungsten inert gas methods. The specimens were divided into 3 groups (base metal, 2 welded specimens), and the composition and microstructure were qualitatively evaluated. The results of potential corrosion and corrosion current density were analyzed with a 1-way analysis of variance and the Tukey test for pairwise comparisons (α=.05). Base metal and tungsten inert gas welded material showed equivalent results in electrochemical corrosion tests, while the air-torched specimens exhibited low corrosion resistance. The performance was worst at pH 2.5. These results suggest that tungsten inert gas is a suitable welding process for use in dentistry, because the final microstructure does not reduce the corrosion resistance in artificial saliva at 37°C, even in a corrosion-testing medium that facilitates galvanic corrosion processes. Moreover, the corrosion current density of brazed Ni-Cr alloy joints was significantly higher (P<.001) than the base metal and tungsten inert gas welded joints. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Methodology for Estimating Thermal and Neutron Embrittlement of Austenitic Stainless Steel Welds During Service in Light Water Reactors

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

Chopra, O. K.; Rao, A. S.

The effect of thermal aging on the degradation of fracture toughness and Charpy-impact properties of austenitic stainless steel (SS) welds has been characterized at reactor temperatures. The solidification behavior and the distribution and morphology of the ferrite phase in SS welds are described. Thermal aging of the welds results in moderate decreases in Charpy-impact strength and fracture toughness. The upper-shelf Charpy-impact energy of aged welds decreases by 50–80 J/cm2. The decrease in fracture toughness J-R curve, or JIc is relatively small. Thermal aging has minimal effect on the tensile strength. The fracture properties of SS welds are insensitive to fillermore » metal; the welding process has a significant effect. The large variability in the data makes it difficult to establish the effect of the welding process on fracture properties of SS welds. Consequently, the approach used for evaluating thermal and neutron embrittlement of austenitic SS welds relies on establishing a lower-bound fracture toughness J-R curve for unaged and aged, and non-irradiated and irradiated, SS welds. The existing fracture toughness J-R curve data for SS welds have been reviewed and evaluated to define lower-bound J-R curve for submerged arc (SA)/shielded metal arc (SMA)/manual metal arc (MMA) welds and gas tungsten arc (GTA)/tungsten inert gas (TIG) welds in the unaged and aged conditions. At reactor temperatures, the fracture toughness of GTA/TIG welds is a factor of about 2.3 higher than that of SA/SMA/MMA welds. Thermal aging decreases the fracture toughness by about 20%. The potential combined effects of thermal and neutron embrittlement of austenitic SS welds are also described. Lower-bound curves are presented that define the change in coefficient C and exponent n of the power-law J-R curve and the JIc value for SS welds as a function of neutron dose. The potential effects of reactor coolant environment on the fracture toughness of austenitic SS welds are also discussed.« less

The effects of welding parameters on ultra-violet light emissions, ozone and CrVI formation in MIG welding.

PubMed

Dennis, J H; Mortazavi, S B; French, M J; Hewitt, P J; Redding, C R

1997-01-01

This paper describes the relationships between ultra-violet emission, ozone generation and CrVI production in MIG welding which were measured as a function of shield gas flow rate, welding voltage, electrode stick-out and shield gas composition using an automatic welding rig that permitted MIG welding under reproducible conditions. The experimental results are interpreted in terms of the physico-chemical processes occurring in the micro- and macro-environments of the arc as part of research into process modification to reduce occupational exposure to ozone and CrVI production rates in MIG welding. We believe the techniques described here, and in particular the use of what we have termed u.v.-ozone measurements, will prove useful in further study of ozone generation and CrVI formation and may be applied in the investigation of engineering control of occupational exposure in MIG and other welding process such as Manual Metal Arc (MMA) and Tungsten Inert Gas (TIG).

Arc-welding quality assurance by means of embedded fiber sensor and spectral processing combining feature selection and neural networks

NASA Astrophysics Data System (ADS)

Mirapeix, J.; García-Allende, P. B.; Cobo, A.; Conde, O.; López-Higuera, J. M.

2007-07-01

A new spectral processing technique designed for its application in the on-line detection and classification of arc-welding defects is presented in this paper. A non-invasive fiber sensor embedded within a TIG torch collects the plasma radiation originated during the welding process. The spectral information is then processed by means of two consecutive stages. A compression algorithm is first applied to the data allowing real-time analysis. The selected spectral bands are then used to feed a classification algorithm, which will be demonstrated to provide an efficient weld defect detection and classification. The results obtained with the proposed technique are compared to a similar processing scheme presented in a previous paper, giving rise to an improvement in the performance of the monitoring system.

Welding. Performance Objectives. Intermediate Course.

ERIC Educational Resources Information Center

Vincent, Kenneth

Several intermediate performance objectives and corresponding criterion measures are listed for each of nine terminal objectives for an intermediate welding course. The materials were developed for a 36-week (3 hours daily) course designed to prepare the student for employment in the field of welding. Electric welding and specialized (TIG & MIG)…

Wear behavior of the surface alloyed AISI 1020 steel with Fe-Nb-B by TIG welding technique

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

Kilinc, B., E-mail: bkilinc@sakarya.edu.tr; Durmaz, M.; Abakay, E.

Weld overlay coatings also known as hardfacing is a method which involves melting of the alloys and solidification for applied coatings. Recently hardfacing by welding has become a commonly used technique for improvement of material performance in extreme (high temperature, impact/abrasion, erosion, etc.) conditions.In the present study, the coatings were produced from a mixture of ferrous niobium, ferrous boron and iron powders in the ranges of -45µm particle size with different ratio. Fe{sub 12}Nb{sub 5}B{sub 3} and Fe{sub 2}NbBalloys were coated on the AISI 1020 steel surface by TIG welding. The phases formed in the coated layer are Fe{sub 2}B,more » NbB{sub 2}, NbFeB and Fe0,2 Nb{sub 0,8} phases. The hardness of the presence phases are changing between 1689±85 HV{sub 0.01}, and 181±7 HV{sub 0.1}. Microstructural examinations were realized by optical and scanning electron microscopy. The wear and friction behaviors of Fe{sub 12}Nb{sub 5}B{sub 3} and Fe2NbB realized on the AISI 1020 steel were investigated by the technique of TIG welding by using ball-on-disk arrangement against alumina ball.« less

3D finite element simulation of TIG weld pool

NASA Astrophysics Data System (ADS)

Kong, X.; Asserin, O.; Gounand, S.; Gilles, P.; Bergheau, J. M.; Medale, M.

2012-07-01

The aim of this paper is to propose a three-dimensional weld pool model for the moving gas tungsten arc welding (GTAW) process, in order to understand the main factors that limit the weld quality and improve the productivity, especially with respect to the welding speed. Simulation is a very powerful tool to help in understanding the physical phenomena in the weld process. A 3D finite element model of heat and fluid flow in weld pool considering free surface of the pool and traveling speed has been developed for the GTAW process. Cast3M software is used to compute all the governing equations. The free surface of the weld pool is calculated by minimizing the total surface energy. The combined effects of surface tension gradient, buoyancy force, arc pressure, arc drag force to drive the fluid flow is included in our model. The deformation of the weld pool surface and the welding speed affect fluid flow, heat flow and thus temperature gradients and molten pool dimensions. Welding trials study is presented to compare our numerical results with macrograph of the molten pool.

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

NASA Astrophysics Data System (ADS)

Dai, Hongbin; Shen, Xiuqiang; Wang, Haoran

2018-06-01

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

Effects Of Welding On The Fatigue Behaviour Of Commercial Aluminum AA-1100 Joints

NASA Astrophysics Data System (ADS)

Uthayakumar, M.; Balasubramanian, V.; Rani, Ahmad Majdi Abdul; Hadzima, Branislav

2018-04-01

Friction Stir Welding (FSW) is an budding solid state welding process, which is frequently used for joining aluminum alloys where materials can be joined without melt and recast. Therefore, when welding alloys through FSW the phase transformations occurs will be in the solid state form. The present work is aimed in evaluating the fatigue life of friction stir welded commercial grade aluminum alloy joints. The commercial grade AA1100 aluminum alloy of 12mm thickness plate is welded and the specimens are tested using a rotary beam fatigue testing machine at different stress levels. The stress versus number of cycles (S-N) curves was plotted using the data points. The Fatigue life of tungsten inert gas (TIG) and metal inert gas (MIG) welded joints was compared. The fatigue life of the weld joints was interrelated with the tensile properties, microstructure and micro hardness properties. The effects of the notches and welding processes are evaluated and reported.

Space storable propulsion components development

NASA Technical Reports Server (NTRS)

Hagler, R., Jr.

1982-01-01

The current development status of components to control the flow of propellants (liquid fluorine and hydrazine) in a demonstration space storable propulsion system is discussed. The criteria which determined the designs for the pressure regulator, explosive-actuated valves, propellant shutoff valve, latching solenoid-actuated valve and propellant filter are presented. The test philosophy that was followed during component development is outlined. The results from compatibility demonstrations for reusable connectors, flange seals, and CRES/Ti-6Al4V transition tubes and the evaluations of processes for welding (hand-held TIG, automated TIG, and EB), cleaning for fluorine service, and decontamination after fluorine exposure are described.

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.

Role of heat equation in lap joint for welding process

NASA Astrophysics Data System (ADS)

Kumar, P.; Rohit, Sooraj

2017-07-01

Welding is predominantly used in industrial purposes and growth in their industry, which gives exact welding and more efficient. The major advantage of using this welding technique at initial stage it takes very low heat to weld the portion and gives a good result of low distortion in modules. In this context, two dissimilar metals copper and nickel are chosen for analysis in tungsten inert gas welding (TIG) in which length is 300 mm and breadth is 100 mm thickness 15 mm welded at room temperature a welded portion zone is formed simulation analysis has done on CATIA® and ANSYS®and MATLAB® code is generated for calculating temperatures at each node to calculate temperature at each node a new technique is used tri-diagonal matrix algorithm is used (TDMA) Steady state one dimension heat is calculated results compared between simulation analysis and analytical analysis temperature at each node is calculated both the temperatures are equal with error.

Results of the Experiment: Welding of Aluminium Alloy in Microgravity

NASA Astrophysics Data System (ADS)

Ferretti, S.; Amadori, K.; Boccalatte, A.; Alessandrini, M.; Freddi, A.; Persiani, F.; Poli, G.

2002-01-01

An experiment on "dendritic growth in aluminium alloy welding" was performed by the UNIBO team during the 3rd Student Parabolic Flight Campaign and the 30th Professional Parabolic Flight Campaign organised by ESA. Its purpose was to achieve a better understanding of crystal growth during tungsten inert gas (TIG) welding of an aluminium alloy to define the main parameters affecting the process under microgravity condition. The experiment had 4 phases : The paper discusses different aspects of the research, paying particularly attention not only to the influence of gravity, but also to other factors influencing welding microstructure, such as the Marangoni effect and the thermal transfer from the electrode to the material. The paper conclude the dissertation of the results offering new perspectives for welding studies and proposing a new approach to the scientific community to investigate this materials processes for manufacturing.

Evaluation of occupational exposure to toxic metals released in the process of aluminum welding.

PubMed

Matczak, Wanda; Gromiec, Jan

2002-04-01

The objective of this study was to evaluate occupational exposure to welding fumes and its elements on aluminum welders in Polish industry. The study included 52 MIG/Al fume samples and 18 TIG/Al samples in 3 plants. Air samples were collected in the breathing zone of welders (total and respirable dust). Dust concentration was determined gravimetrically, and the elements in the collected dust were determined by AAS. Mean time-weighted average (TWA) concentrations of the welding dusts/fumes and their components in the breathing zone obtained for different welding processes were, in mg/m3: MIG/Al fumes mean 6.0 (0.8-17.8), Al 2.1 (0.1-7.7), Mg 0.2 (< 0.1-0.9), Mn 0.014 (0.002-0.049), Cu 0.011 (0.002-0.092), Zn 0.016 (0.002-0.14), Pb 0.009 (0.005-0.025), Cr 0.003 (0.002-0.007), and TIG/Al fumes 0.7 (0.3-1.4), Al 0.17 (0.07-0.50). A correlation has been found between the concentration of the main components and the fume/dust concentrations in MIG/Al and TIG/Al fumes. Mean percentages of the individual components in MIG/Al fumes/dusts were Al: 30 (9-56) percent; Mg: 3 (1-5.6) percent; Mn: 0.2 (0.1-0.3) percent; Cu: 0.2 (< 0.1-1.8) percent; Zn: 0.2 (< 0.1-0.8) percent; Pb: 0.2 (< 0.1-1) percent; Cr: < 0.1 percent. The proportion of the respirable fraction in the fumes and their constituents varied between 10 percent and 100 percent. The results showed that MIG/Al fumes concentration was 1.2 times higher than the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV), and the index of the combined exposure to the determined agents was 2.3 (0.4-8.0), mostly because of high Al2O3 contribution. The background concentrations of the components (ca. 5-10 times lower than those in the breathing zone of the welders) did not exceed the Polish MAC value. The elemental composition of total and respirable fume/dust may differ considerably depending on welding methods, the nature of welding-related operations, and work environment conditions.

Factors Influencing the Microstructural and Mechanical Properties of ULCB Steel Weldments

DTIC Science & Technology

1991-12-01

18 3. Molybdenum.................................... 19 4. Chromium ...................................... 19 5...WELDING METHODS UTILIZED IN ANALYSIS 1. Tungsten Inert Gas (TIG) Tungsten inert gas welding, also known as gas tungsten arc welding ( GTAW ), produces a weld...Abson, Pargeter, 1986, p.166). The role of molybdenum and chromium is not fully understood but the formation of molybdenum or chromium carbides may

Welding of AM350 and AM355 steel

NASA Technical Reports Server (NTRS)

Davis, R. J.; Wroth, R. S.

1967-01-01

A series of tests was conducted to establish optimum procedures for TIG welding and heat treating of AM350 and AM355 steel sheet in thicknesses ranging from 0.010 inch to 0.125 inch. Statistical analysis of the test data was performed to determine the anticipated minimum strength of the welded joints.

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.

Novel low-cost vision-sensing technology with controllable of exposal time for welding

NASA Astrophysics Data System (ADS)

Zhang, Wenzeng; Wang, Bin; Chen, Nian; Cao, Yipeng

2005-02-01

In the process of robot Welding, position of welding seam and welding pool shape is detected by CCD camera for quality control and seam tracking in real-time. It is difficult to always get a clear welding image in some welding methods, such as TIG welding. A novel idea that the exposal time of CCD camera is automatically controlled by arc voltage or arc luminance is proposed to get clear welding image. A set of special device and circuits are added to a common industrial CCD camera in order to flexibly control the CCD to start or close exposal by control of the internal clearing signal of the accumulated charge. Two special vision sensors according to the idea are developed. Their exposal grabbing can be triggered respectively by the arc voltage and the variety of the arc luminance. Two prototypes have been designed and manufactured. Experiments show that they can stably grab clear welding images at appointed moment, which is a basic for the feedback control of automatic welding.

Adhesion of Salmonella Enteritidis and Listeria monocytogenes on stainless steel welds.

PubMed

Casarin, Letícia Sopeña; Brandelli, Adriano; de Oliveira Casarin, Fabrício; Soave, Paulo Azevedo; Wanke, Cesar Henrique; Tondo, Eduardo Cesar

2014-11-17

Pathogenic microorganisms are able to adhere on equipment surfaces, being possible to contaminate food during processing. Salmonella spp. and Listeria monocytogenes are important pathogens that can be transmitted by food, causing severe foodborne diseases. Most surfaces of food processing industry are made of stainless steel joined by welds. However currently, there are few studies evaluating the influence of welds in the microorganism's adhesion. Therefore the purpose of the present study was to investigate the adhesion of Salmonella Enteritidis and L. monocytogenes on surface of metal inert gas (MIG), and tungsten inert gas (TIG) welding, as well as to evaluate the cell and surface hydrophobicities. Results demonstrated that both bacteria adhered to the surface of welds and stainless steel at same levels. Despite this, bacteria and surfaces demonstrated different levels of hydrophobicity/hydrophilicity, results indicated that there was no correlation between adhesion to welds and stainless steel and the hydrophobicity. Copyright © 2014 Elsevier B.V. All rights reserved.

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.

Structure and Corrosion Resistance of Welded Joints of Alloy 1151 in Marine Atmosphere

NASA Astrophysics Data System (ADS)

Bakulo, A. V.; Yakushin, B. F.; Puchkov, Yu. A.

2017-07-01

The corrosion behavior of joints formed by TIG and IMIG welding from clad sheets of heat-hardenable aluminum alloy 1151 of the Al - Cu - Mg system is studied. The corrosion tests are performed in an aqueous solution of NaCl in a salt-spray chamber. The welded joints are subjected to a metallographic analysis.

The mechanical properties of high speed GTAW weld and factors of nonlinear multiple regression model under external transverse magnetic field

NASA Astrophysics Data System (ADS)

Lu, Lin; Chang, Yunlong; Li, Yingmin; He, Youyou

2013-05-01

A transverse magnetic field was introduced to the arc plasma in the process of welding stainless steel tubes by high-speed Tungsten Inert Gas Arc Welding (TIG for short) without filler wire. The influence of external magnetic field on welding quality was investigated. 9 sets of parameters were designed by the means of orthogonal experiment. The welding joint tensile strength and form factor of weld were regarded as the main standards of welding quality. A binary quadratic nonlinear regression equation was established with the conditions of magnetic induction and flow rate of Ar gas. The residual standard deviation was calculated to adjust the accuracy of regression model. The results showed that, the regression model was correct and effective in calculating the tensile strength and aspect ratio of weld. Two 3D regression models were designed respectively, and then the impact law of magnetic induction on welding quality was researched.

Microstructure and mechanical properties of China low activation martensitic steel joint by TIG multi-pass welding with a new filler wire

NASA Astrophysics Data System (ADS)

Huang, Bo; Zhang, Junyu; Wu, Qingsheng

2017-07-01

Tungsten Inner Gas (TIG) welding is employed for joining of China low activation martensitic (CLAM) steel. A new filler wire was proposed, and the investigation on welding with various heat input and welding passes were conducted to lower the tendency towards the residual of δ ferrite in the joint. With the optimized welding parameters, a butt joint by multi-pass welding with the new filler wire was prepared to investigate the microstructure and mechanical properties. The microstructure of the joint was observed by optical microscope (OM) and scanning electron microscope (SEM). The hardness, Charpy impact and tensile tests of the joint were implemented at room temperature (25 °C). The results revealed that almost full martensite free from ferrite in the joints were obtained by multipass welding with the heat input of 2.26 kJ/mm. A certain degree of softening occurred at the heat affected zone of the joint according to the results of tensile and hardness tests. The as welded joints showed brittle fracture in the impact tests. However, the joints showed toughness fracture after tempering and relatively better comprehensive performance were achieved when the joints were tempered at 740 °C for 2 h.

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

NASA Astrophysics Data System (ADS)

Liu, Liming; Hao, Xinfeng

2009-11-01

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

Physical characteristics of welding arc ignition process

NASA Astrophysics Data System (ADS)

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

2012-07-01

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

Development of welding technologies for the manufacturing of European Tritium Breeder blanket modules

NASA Astrophysics Data System (ADS)

Poitevin, Y.; Aubert, Ph.; Diegele, E.; de Dinechin, G.; Rey, J.; Rieth, M.; Rigal, E.; von der Weth, A.; Boutard, J.-L.; Tavassoli, F.

2011-10-01

Europe has developed two reference Tritium Breeder Blankets concepts for a DEMO fusion reactor: the Helium-Cooled Lithium-Lead and the Helium-Cooled Pebble-Bed. Both are using the reduced-activation ferritic-martensitic EUROFER-97 steel as structural material and will be tested in ITER under the form of test blanket modules. The fabrication of their EUROFER structures requires developing welding processes like laser, TIG, EB and diffusion welding often beyond the state-of-the-art. The status of European achievements in this area is reviewed, illustrating the variety of processes and key issues behind retained options, in particular with respect to metallurgical aspects and mechanical properties. Fabrication of mock-ups is highlighted and their characterization and performances with respect to design requirements are reviewed.

Thermal Stir Welding Development at Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Ding, Robert J.

2008-01-01

Solid state welding processes have become the focus of welding process development at NASA's Marshall Space Flight Center. Unlike fusion weld processes such as tungsten inert gas (TIG), variable polarity plasma arc (VPPA), electron beam (EB), etc., solid state welding processes do not melt the material during welding. The resultant microstructure can be characterized as a dynamically recrystallized morphology much different than the casted, dentritic structure typical of fusion weld processes. The primary benefits of solid state processes over fusion weld processes include superior mechanic properties and the elimination of thermal distortion and residual stresses. These solid state processes attributes have profoundly influenced the direction of advanced welding research and development within the NASA agency. Thermal Stir Welding (TSW) is a new solid state welding process being developed at the Marshall Space Flight Center. Unlike friction stir welding, the heating, stirring and forging elements of the weld process can be decoupled for independent control. An induction coil induces energy into a workpiece to attain a desired plastic temperature. An independently controlled stir rod, captured within non-rotating containment plates, then stirs the plasticized material followed by forging plates/rollers that work the stirred weld joint. The independent control (decoupling) of heating, stirring and forging allows, theoretically, for the precision control of microstructure morphology. The TSW process is being used to evaluate the solid state joining of Haynes 230 for ARES J-2X applications. It is also being developed for 500-in (12.5 mm) thick commercially pure grade 2 titanium for navy applications. Other interests include Inconel 718 and stainless steel. This presentation will provide metallurgical and mechanical property data for these high melting temperature alloys.

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

Grain refinement control in TIG arc welding

NASA Technical Reports Server (NTRS)

Iceland, W. F.; Whiffen, E. L. (Inventor)

1975-01-01

A method for controlling grain size and weld puddle agitation in a tungsten electrode inert gas welding system to produce fine, even grain size and distribution is disclosed. In the method the frequency of dc welding voltage pulses supplied to the welding electrode is varied over a preselected frequency range and the arc gas voltage is monitored. At some frequency in the preselected range the arc gas voltage will pass through a maximum. By maintaining the operating frequency of the system at this value, maximum weld puddle agitation and fine grain structure are produced.

Intakes of thorium while using thoriated tungsten electrodes for TIG welding.

PubMed

Ludwig, T; Schwass, D; Seitz, G; Siekmann, H

1999-10-01

Thoriated electrodes are used in TIG welding. TIG welders, along with persons who grind thoriated electrodes and persons located near relevant welding and grinding sites, might be at risk of thorium intake. The isotopes of radiological relevance are 232Th, 230Th, and 228Th. The studies described in the literature do not provide a consistent picture of the actual hazards, and changes in European and German radiological protection laws have now made it necessary to determine the risks. To accomplish this, a field test was conducted under real working conditions in 26 different welding shops. The airborne activity generated through welding, and through grinding of electrodes, was measured using personal air samplers. Stationary samplers were also used. The filters' samples were evaluated by means of direct alpha spectrometry with proportional counting and by means of gamma spectrometry following neutron activation. The results clearly showed that considerable intake can occur during both alternating-current welding and electrode grinding, if no suction systems are used. The range of 232Th intakes to welders were estimated from 0.1 Bq y(-1) to 144 Bq y(-1) during welding and from 0.02 Bq y(-1) to 30.2 Bq y(-1) during grinding. In 6 of the 26 cases the recent annual limit on intake derived from the most recent ICRP publications was exceeded--in the worst case it was exceeded by a factor of 10--if it is assumed that the persons studied were not exposed workers (not routinely monitored for radiation exposure). When the significantly more restrictive German limits are applied, the amounts by which the limits were exceeded were even greater. Because many qualified welders have very long careers, the risks can thus be considerable. The paper also discusses parameters that influence exposure, and it presents a catalogue of recommended measures for dosage reduction.

Utilization of Low Temperatures in Electrical Machines,

DTIC Science & Technology

1983-09-08

quality 8 | | -. . * - . * . . .. . . . - * , . . , . . . . . * of the obtained junctions. For welding of steels, we used the TIG * method which is the...most frequently used technique for joining alloy steels. We studied the effects of the chemical composition of the * weld , linear energy of welding and...disappearance of resistance in certain metals and alloys at very low temperatures, in the vicinity of abso- lute zero. This fact enables currents to

Elementary TIG Welding Skills.

ERIC Educational Resources Information Center

Pierson, John E., III

The text was prepared to help deaf students develop the skills needed by an employed welder. It uses simplified language and illustrations to present concepts which should be reinforced by practical experience with welding skills. Each of the 12 lessons contains: (1) an information section with many illustrations which presents a concept or…

Heat Pipe and Thermal Energy Storage and Corrosion Studies (1988)

DTIC Science & Technology

1989-06-01

of air environment melting and end cap TIG welding [2]. Because of its severity, vacuum thermal cycling of the salt clad capsules between salt eutectic...melting of the salt under an inert gas atmosphere and welding of the specimen capsules by electron beam welding in contrast to previously used methods...electron beam welding . However, no ill effects were believed to have occurred on the overall testing program. Ultrapure fluoride salts LiF, MgF2, NaF

Discrete element weld model, phase 2

NASA Technical Reports Server (NTRS)

Prakash, C.; Samonds, M.; Singhal, A. K.

1987-01-01

A numerical method was developed for analyzing the tungsten inert gas (TIG) welding process. The phenomena being modeled include melting under the arc and the flow in the melt under the action of buoyancy, surface tension, and electromagnetic forces. The latter entails the calculation of the electric potential and the computation of electric current and magnetic field therefrom. Melting may occur at a single temperature or over a temperature range, and the electrical and thermal conductivities can be a function of temperature. Results of sample calculations are presented and discussed at length. A major research contribution has been the development of numerical methodology for the calculation of phase change problems in a fixed grid framework. The model has been implemented on CHAM's general purpose computer code PHOENICS. The inputs to the computer model include: geometric parameters, material properties, and weld process parameters.

Contribution For Arc Temperature Affected By Current Increment Ratio At Peak Current In Pulsed Arc

NASA Astrophysics Data System (ADS)

Kano, Ryota; Mitubori, Hironori; Iwao, Toru

2015-11-01

Tungsten Inert Gas (TIG) Welding is one of the high quality welding. However, parameters of the pulsed arc welding are many and complicated. if the welding parameters are not appropriate, the welding pool shape becomes wide and shallow.the convection of driving force contributes to the welding pool shape. However, in the case of changing current waveform as the pulse high frequency TIG welding, the arc temperature does not follow the change of the current. Other result of the calculation, in particular, the arc temperature at the reaching time of peak current is based on these considerations. Thus, the accurate measurement of the temperature at the time is required. Therefore, the objective of this research is the elucidation of contribution for arc temperature affected by current increment ratio at peak current in pulsed arc. It should obtain a detail knowledge of the welding model in pulsed arc. The temperature in the case of increment of the peak current from the base current is measured by using spectroscopy. As a result, when the arc current increases from 100 A to 150 A at 120 ms, the transient response of the temperature didn't occur during increasing current. Thus, during the current rise, it has been verified by measuring. Therefore, the contribution for arc temperature affected by current increment ratio at peak current in pulsed arc was elucidated in order to obtain more knowledge of welding model of pulsed arc.

Low activation steels welding with PWHT and coating for ITER test blanket modules and DEMO

NASA Astrophysics Data System (ADS)

Aubert, P.; Tavassoli, F.; Rieth, M.; Diegele, E.; Poitevin, Y.

2011-02-01

EUROFER weldability is investigated in support of the European material properties database and TBM manufacturing. Electron Beam, Hybrid, laser and narrow gap TIG processes have been carried out on the EUROFER-97 steel (thickness up to 40 mm), a reduced activation ferritic-martensitic steel developed in Europe. These welding processes produce similar welding results with high joint coefficients and are well adapted for minimizing residual distortions. The fusion zones are typically composed of martensite laths, with small grain sizes. In the heat-affected zones, martensite grains contain carbide precipitates. High hardness values are measured in all these zones that if not tempered would degrade toughness and creep resistance. PWHT developments have driven to a one-step PWHT (750 °C/3 h), successfully applied to joints restoring good material performances. It will produce less distortion levels than a full austenitization PWHT process, not really applicable to a complex welded structure such as the TBM. Different tungsten coatings have been successfully processed on EUROFER material. It has shown no really effect on the EUROFER base material microstructure.

Fast algorithm for spectral processing with application to on-line welding quality assurance

NASA Astrophysics Data System (ADS)

Mirapeix, J.; Cobo, A.; Jaúregui, C.; López-Higuera, J. M.

2006-10-01

A new technique is presented in this paper for the analysis of welding process emission spectra to accurately estimate in real-time the plasma electronic temperature. The estimation of the electronic temperature of the plasma, through the analysis of the emission lines from multiple atomic species, may be used to monitor possible perturbations during the welding process. Unlike traditional techniques, which usually involve peak fitting to Voigt functions using the Levenberg-Marquardt recursive method, sub-pixel algorithms are used to more accurately estimate the central wavelength of the peaks. Three different sub-pixel algorithms will be analysed and compared, and it will be shown that the LPO (linear phase operator) sub-pixel algorithm is a better solution within the proposed system. Experimental tests during TIG-welding using a fibre optic to capture the arc light, together with a low cost CCD-based spectrometer, show that some typical defects associated with perturbations in the electron temperature can be easily detected and identified with this technique. A typical processing time for multiple peak analysis is less than 20 ms running on a conventional PC.

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.

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

[Calculating the stark broadening of welding arc spectra by Fourier transform method].

PubMed

Pan, Cheng-Gang; Hua, Xue-Ming; Zhang, Wang; Li, Fang; Xiao, Xiao

2012-07-01

It's the most effective and accurate method to calculate the electronic density of plasma by using the Stark width of the plasma spectrum. However, it's difficult to separate Stark width from the composite spectrum linear produced by several mechanisms. In the present paper, Fourier transform was used to separate the Lorentz linear from the spectrum observed, thus to get the accurate Stark width. And we calculated the distribution of the TIG welding arc plasma. This method does not need to measure arc temperature accurately, to measure the width of the plasma spectrum broadened by instrument, and has the function to reject the noise data. The results show that, on the axis, the electron density of TIG welding arc decreases with the distance from tungsten increasing, and changes from 1.21 X 10(17) cm(-3) to 1.58 x 10(17) cm(-3); in the radial, the electron density decreases with the distance from axis increasing, and near the tungsten zone the biggest electronic density is off axis.

High temperature aircraft research furnace facilities

NASA Technical Reports Server (NTRS)

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

1992-01-01

Focus is on the design, fabrication, and development of the High Temperature Aircraft Research Furnace Facilities (HTARFF). The HTARFF was developed to process electrically conductive materials with high melting points in a low gravity environment. The basic principle of operation is to accurately translate a high temperature arc-plasma gas front as it orbits around a cylindrical sample, thereby making it possible to precisely traverse the entire surface of a sample. The furnace utilizes the gas-tungsten-arc-welding (GTAW) process, also commonly referred to as Tungsten-Inert-Gas (TIG). The HTARFF was developed to further research efforts in the areas of directional solidification, float-zone processing, welding in a low-gravity environment, and segregation effects in metals. The furnace is intended for use aboard the NASA-JSC Reduced Gravity Program KC-135A Aircraft.

Quick Reaction Evaluation of Materials and Processes. Delivery Order 0011: Engineering Properties, Fatigue, and Crack Growth Data on SCS-6/Ti-6Al-4V Titanium Matrix Composite (16 Ply) Panels

DTIC Science & Technology

2009-05-01

tabs were bonded to the specimen using a TIG welding process to ensure adhesion of the tabs throughout the experiment. The shear specimens and the...AFRL-RX-WP-TR-2010-4175 QUICK REACTION EVALUATION OF MATERIALS AND PROCESSES Delivery Order 0011: Engineering Properties, Fatigue, and Crack...From - To) May 2009 Final 03 April 2006 – 29 May 2009 4. TITLE AND SUBTITLE QUICK REACTION EVALUATION OF MATERIALS AND PROCESSES Delivery Order

Interactions between laser and arc plasma during laser-arc hybrid welding of magnesium alloy

NASA Astrophysics Data System (ADS)

Liu, Liming; Chen, Minghua

2011-09-01

This paper presents the results of the investigation on the interactions between laser and arc plasma during laser-arc hybrid welding on magnesium alloy AZ31B using the spectral diagnose technique. By comparably analyzing the variation in plasma information (the shape, the electron temperature and density) of single tungsten inert gas (TIG) welding with the laser-arc hybrid welding, it is found that the laser affects the arc plasma through the keyhole forming on the workpiece. Depending on the welding parameters there are three kinds of interactions taking place between laser and arc plasma.

Design of Gages for Direct Skin Friction Measurements in Complex Turbulent Flows with Shock Impingement Compensation

DTIC Science & Technology

2007-06-07

100 kW/m2 for 0.1 s. Along with the material change, an oil leak problem required a geometric change. Initially, we considered TIG welding or...shear and moment, is addressed through the design, development, and testing of the CF1 and CF2 gages. Chapter 3 presents the evolutionary process ...a shock. Chapter 4 examines the performance of each gage to the nominal load conditions. Through this process , objective 2 is met. The best

Combustion Joining for Composite Fabrication

DTIC Science & Technology

2009-10-25

Inert preheating Process beginning T e m p e r a t u r e , o C Time, s I = 600 Amps D = 10 mm Joule preheating only up to Tig UNCLASSIFIED • C...Honeywell Corp (South Bend, IN) • Currently build aircraft brake disks from carbon fibers • use a long (~ 100 day) CVD process to densify • Brake wear...oxidation with every landing A380 -rejected take off test C-C brakes UNCLASSIFIED Joining C-Based Materials • Difficult task – Carbon cannot be welded

The Tungsten Inert GAS (TIG) Process of Welding Aluminium in Microgravity: Technical and Economic Considerations

NASA Astrophysics Data System (ADS)

Ferretti, S.; Amadori, K.; Boccalatte, A.; Alessandrini, M.; Freddi, A.; Persiani, F.; Poli, G.

2002-01-01

The UNIBO team composed of students and professors of the University of Bologna along with technicians and engineers from Alenia Space Division and Siad Italargon Division, took part in the 3rd Student Parabolic Flight Campaign of the European Space Agency in 2000. It won the student competition and went on to take part in the Professional Parabolic Flight Campaign of May 2001. The experiment focused on "dendritic growth in aluminium alloy weldings", and investigated topics related to the welding process of aluminium in microgravity. The purpose of the research is to optimise the process and to define the areas of interest that could be improved by new conceptual designs. The team performed accurate tests in microgravity to determine which phenomena have the greatest impact on the quality of the weldings with respect to penetration, surface roughness and the microstructures that are formed during the solidification. Various parameters were considered in the economic-technical optimisation, such as the type of electrode and its tip angle. Ground and space tests have determined the optimum chemical composition of the electrodes to offer longest life while maintaining the shape of the point. Additionally, the power consumption has been optimised; this offers opportunities for promoting the product to the customer as well as being environmentally friendly. Tests performed on the Al-Li alloys showed a significant influence of some physical phenomena such as the Marangoni effect and thermal diffusion; predictions have been made on the basis of observations of the thermal flux seen in the stereophotos. Space transportation today is a key element in the construction of space stations and future planetary bases, because the volumes available for launch to space are directly related to the payload capacity of rockets or the Space Shuttle. The research performed gives engineers the opportunity to consider completely new concepts for designing structures for space applications. In fact, once the optimised parameters are defined for welding in space, it could be possible to weld different parts directly in orbit to obtain much larger sizes and volumes, for example for space tourism habitation modules. The second relevant aspect is technology transfer obtained by the optimisation of the TIG process on aluminium which is often used in the automotive industry as well as in mass production markets.

The effects of alloying elements on microstructures and mechanical properties of tungsten inert gas welded AZ80 magnesium alloys joint

NASA Astrophysics Data System (ADS)

Li, Hui; Zhang, Jiansheng; Ding, Rongrong

2017-11-01

The effects of alloying elements on the macrostructures, microstructures and tensile strength of AZ80 Mg alloy weldments were studied in the present study. The results indicate that with the decrease of Al element content of filler wire, the welding defects of seam are gradually eliminated and the β-Mg17Al12 phases at α-Mg boundaries are refined and become discontinuous, which are beneficial to the improvement of tensile strength. With AZ31 Mg alloy filler wire, the maximum tensile strength of AZ80 weldment is 220 MPa and fracture occurs at the welding seam of joint. It is experimentally proved that robust AZ80 Mg alloy joints can be obtained by tungsten inert gas (TIG) welding process with AZ31 Mg alloy filler wire. However, further study is required to improve the microstructures and reduce welding defects of joint in order to further improve the joining strength of AZ80 Mg alloy joint.

Characteristics of AZ31 Mg alloy joint using automatic TIG welding

NASA Astrophysics Data System (ADS)

Liu, Hong-tao; Zhou, Ji-xue; Zhao, Dong-qing; Liu, Yun-teng; Wu, Jian-hua; Yang, Yuan-sheng; Ma, Bai-chang; Zhuang, Hai-hua

2017-01-01

The automatic tungsten-inert gas welding (ATIGW) of AZ31 Mg alloys was performed using a six-axis robot. The evolution of the microstructure and texture of the AZ31 auto-welded joints was studied by optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction. The ATIGW process resulted in coarse recrystallized grains in the heat affected zone (HAZ) and epitaxial growth of columnar grains in the fusion zone (FZ). Substantial changes of texture between the base material (BM) and the FZ were detected. The {0002} basal plane in the BM was largely parallel to the sheet rolling plane, whereas the c-axis of the crystal lattice in the FZ inclined approximately 25° with respect to the welding direction. The maximum pole density increased from 9.45 in the BM to 12.9 in the FZ. The microhardness distribution, tensile properties, and fracture features of the AZ31 auto-welded joints were also investigated.

Comparative analysis of different joining techniques to improve the passive fit of cobalt-chromium superstructures.

PubMed

Barbi, Francisco C L; Camarini, Edevaldo T; Silva, Rafael S; Endo, Eliana H; Pereira, Jefferson R

2012-12-01

The influence of different joining techniques on passive fit at the interface structure/abutment of cobalt-chromium (Co-Cr) superstructures has not yet been clearly established. The purpose of this study was to compare 3 different techniques of joining Co-Cr superstructures by measuring the resulting marginal misfit in a simulated prosthetic assembly. A specially designed metal model was used for casting, sectioning, joining, and measuring marginal misfit. Forty-five cast bar-type superstructures were fabricated in a Co-Cr alloy and randomly assigned by drawing lots to 3 groups (n=15) according to the joining method used: conventional gas-torch brazing (G-TB), laser welding (LW), and tungsten inert gas welding (TIG). Joined specimens were assembled onto abutment analogs in the metal model with the 1-screw method. The resulting marginal misfit was measured with scanning electron microscopy (SEM) at 3 different points: distal (D), central (C), and mesial (M) along the buccal aspect of both abutments: A (tightened) and B (without screw). The Levene test was used to evaluate variance homogeneity and then the Welsch ANOVA for heteroscedastic data (α=.05). Significant differences were found on abutment A between groups G-TB and LW (P=.013) measured mesially and between groups G-TB and TIG (P=.037) measured centrally. On abutment B, significant differences were found between groups G-TB and LW (P<.001) and groups LW and TIG (P<.001) measured mesially; groups G-TB and TIG (P=.007) measured distally; and groups G-TB and TIG (P=.001) and LW and TIG (P=.007) measured centrally. The method used for joining Co-Cr prosthetic structures had an influence on the level of resulting passive fit. Structures joined by the tungsten inert gas method produced better mean results than did the brazing or laser method. Copyright © 2012 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Influence of Ti addition on fracture behaviour of HSLA steel using TIG melting technique

NASA Astrophysics Data System (ADS)

Musa, M. H. A.; Maleque, M. A.; Ali, M. Y.

2017-03-01

The welding process is a critical stage in the production of structural parts and the microstructure and mechanical properties of the welded joints must be appropriate in order to guarantee the reliability and durability of the components. The fracture toughness behaviour, which accounts for the residual strength of the component in the presence of flaws or cracks, is one of the most important properties to be evaluated in terms of microstructure and mechanical properties. In this present study, the surface of high strength low alloy (HSLA) steel was surface modified with the preplacement of pure Titanium (Ti) powder using a tungsten inert gas (TIG) arc heat source, at 100 ampere current with a voltage 30 V and a constant traversing speed of 1.0 mm/s using Argon shielded gas. The effect of preplaced Ti powder on the strength and toughness properties of the modified HSLA steel surface was investigated. The results indicated that the tensile and yield strength of HSLA steel decreased by ∼12% and ∼14%, respectively. While the impact toughness increased by ∼33% and the ductility decreased by ∼50%. The fractography analysis results by scanning electron microscopy (SEM) were also presented in this paper.

Influence of Zn Interlayer on Interfacial Microstructure and Mechanical Properties of TIG Lap-Welded Mg/Al Joints

NASA Astrophysics Data System (ADS)

Gao, Qiong; Wang, Kehong

2016-03-01

This study explored 6061 Al alloy and AZ31B Mg alloy joined by TIG lap welding with Zn foils of varying thicknesses, with the additional Zn element being imported into the fusion zone to alloy the weld seam. The microstructures and chemical composition in the fusion zone near the Mg substrate were examined by SEM and EDS, and tensile shear strength tests were conducted to investigate the mechanical properties of the Al/Mg joints, as well as the fracture surfaces, and phase compositions. The results revealed that the introduction of an appropriate amount of Zn transition layer improves the microstructure of Mg/Al joints and effectively reduces the formation of Mg-Al intermetallic compounds (IMCs). The most common IMCs in the fusion zone near the Mg substrate were Mg-Zn and Mg-Al-Zn IMCs. The type and distribution of IMCs generated in the weld zone differed according to Zn additions; Zn interlayer thickness of 0.4 mm improved the sample's mechanical properties considerably compared to thicknesses of less than 0.4 mm; however, any further increase in Zn interlayer thickness of above 0.4 mm caused mechanical properties to deteriorate.

Weld geometry strength effect in 2219-T87 aluminum

NASA Technical Reports Server (NTRS)

Nunes, A. C., Jr.; Novak, H. L.; Mcilwain, M. C.

1981-01-01

A theory of the effect of geometry on the mechanical properties of a butt weld joint is worked out based upon the soft interlayer weld model. Tensile tests of 45 TIG butt welds and 6 EB beads-on-plate in 1/4-in. 2219-T87 aluminum plate made under a wide range of heat sink and power input conditions are analyzed using this theory. The analysis indicates that purely geometrical effects dominate in determining variations in weld joint strength with heat sink and power input. Variations in weld dimensions with cooling rate are significant as well as with power input. Weld size is suggested as a better indicator of the condition of a weld joint than energy input.

A Decade of Friction Stir Welding R and D at NASA's Marshall Space Flight Center and a Glance into the Future

NASA Technical Reports Server (NTRS)

Ding, Jeff; Carter, Bob; Lawless, Kirby; Nunes, Arthur; Russell, Carolyn; Suites, Michael; Schneider, Judy

2006-01-01

Welding at NASA's Marshall Space Flight Center (MSFC), Huntsville, Alabama, has taken a new direction through the last 10 years. Fusion welding processes, namely variable polarity plasma arc (VPPA) and tungsten inert gas (TIG) were once the corner stone of welding development in the Space Flight Center's welding laboratories, located in the part of MSFC know as National Center for Advanced Manufacturing (NCM). Developed specifically to support the Shuttle Program's External Tank and later International Space Station manufacturing programs, was viewed as the paragon of welding processes for joining aluminum alloys. Much has changed since 1994, however, when NASA's Jeff Ding brought the FSW process to the NASA agency. Although, at that time, FSW was little more than a "lab curiosity", NASA researchers started investigating where the FSW process would best fit NASA manufacturing programs. A laboratory FSW system was procured and the first welds were made in fall of 1995. The small initial investment NASA made into the first FSW system has certainly paid off for the NASA agency in terms of cost savings, hardware quality and notoriety. FSW is now a part of Shuttle External Tank (ET) production and the preferred weld process for the manufacturing of components for the new Crew Launch Vehicle (CLV) and Heavy Lift Launch Vehicle (HLLV) that will take this country back to the moon. It is one of the solid state welding processes being considered for on-orbit space welding and repair, and is of considerable interest for Department of Defense @OD) manufacturing programs. MSFC involvement in these and other programs makes NASA a driving force in this country's development of FSW and other solid state welding technologies. Now, a decade later, almost the entire on-going welding R&D at MSFC now focuses on FSW and other more advanced solid state welding processes.

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

NASA Astrophysics Data System (ADS)

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

2016-01-01

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

A Micro-Electrochemical Study of Friction Stir Welded Aluminum 6061-T6

NASA Technical Reports Server (NTRS)

Hintze, Paul E.; Calle, Luz M.

2005-01-01

The corrosion behavior of friction stir welded Aluminum alloy 606 1-T6 was studied using a micro-electrochemical cell. The micro-electrochemical cell has a measurement area of about 0.25 square mm which allows for measurement of corrosion properties at a very small scale. The corrosion and breakdown potentials were measured at many points inside and outside the weld along lines perpendicular to the weld. The breakdown potential is approximately equal inside and outside the weld; however, it is lower in the narrow border between the weld and base material. The results of electrochemical measurements were correlated to micro-structural analysis. The corrosion behavior of the friction stir welded samples was compared to tungsten inert gas (TIG) welded samples of the same material.

[Welding arc temperature field measurements based on Boltzmann spectrometry].

PubMed

Si, Hong; Hua, Xue-Ming; Zhang, Wang; Li, Fang; Xiao, Xiao

2012-09-01

Arc plasma, as non-uniform plasma, has complicated energy and mass transport processes in its internal, so plasma temperature measurement is of great significance. Compared with absolute spectral line intensity method and standard temperature method, Boltzmann plot measuring is more accurate and convenient. Based on the Boltzmann theory, the present paper calculates the temperature distribution of the plasma and analyzes the principle of lines selection by real time scanning the space of the TIG are measurements.

ESPRESSO optical bench: from mind to reality

NASA Astrophysics Data System (ADS)

Tenegi, F.; Santana, S.; Gómez, J.; Rodilla, E.; Hughes, I.; Mégevand, D.; Rebolo, R.; Riva, M.; Luis-Simoes, R.

2016-07-01

ESPRESSO [1] is a high-resolution spectrograph under development for the VLT telescope. In general, the Optical Bench (OB) structure can be considered as a 3D one, conformed by welding thin plates of Structural Steel (St-52) with a nickelplated surface treatment, combined for getting maximum stiffness and minimum weight, that will be finally re-machined to get stringent geometrical and dimensional tolerances at I/Fs positions. TIG conventional welding procedure has been selected to minimize the cost and facilitate the own welding process. This solution follows the inheritance from HARPS [2] due to its success to achieve the required performance for the bench. This paper contains an overview of the whole process of designing and manufacturing the Optical Bench of ESPRESSO, from the very first beginning with the specifications to the current status of the bench with its integration on the Spectrograph (including the Finite Element Models and the delivery of the final structure by the supplier) and lessons learned.

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

NASA Astrophysics Data System (ADS)

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

2000-04-01

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

Conversion of continuous-direct-current TIG welder to pulse-arc operation

NASA Technical Reports Server (NTRS)

Lien, D. R.

1969-01-01

Electronics package converts a continuous-dc tungsten-inert gas welder for pulse-arc operation. Package allows presetting of the pulse rate, duty cycle, and current value, and enables welding of various alloys and thicknesses of materials.

Microstructural characterization of weld joints of 9Cr reduced activation ferritic martensitic steel fabricated by different joining methods

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

Thomas Paul, V.; Saroja, S.; Albert, S.K.

This paper presents a detailed electron microscopy study on the microstructure of various regions of weldment fabricated by three welding methods namely tungsten inert gas welding, electron beam welding and laser beam welding in an indigenously developed 9Cr reduced activation ferritic/martensitic steel. Electron back scatter diffraction studies showed a random micro-texture in all the three welds. Microstructural changes during thermal exposures were studied and corroborated with hardness and optimized conditions for the post weld heat treatment have been identified for this steel. Hollomon–Jaffe parameter has been used to estimate the extent of tempering. The activation energy for the tempering processmore » has been evaluated and found to be corresponding to interstitial diffusion of carbon in ferrite matrix. The type and microchemistry of secondary phases in different regions of the weldment have been identified by analytical transmission electron microscopy. - Highlights: • Comparison of microstructural parameters in TIG, electron beam and laser welds of RAFM steel • EBSD studies to illustrate the absence of preferred orientation and identification of prior austenite grain size using phase identification map • Optimization of PWHT conditions for indigenous RAFM steel • Study of kinetics of tempering and estimation of apparent activation energy of the process.« less

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.

Study on the special vision sensor for detecting position error in robot precise TIG welding of some key part of rocket engine

NASA Astrophysics Data System (ADS)

Zhang, Wenzeng; Chen, Nian; Wang, Bin; Cao, Yipeng

2005-01-01

Rocket engine is a hard-core part of aerospace transportation and thrusting system, whose research and development is very important in national defense, aviation and aerospace. A novel vision sensor is developed, which can be used for error detecting in arc length control and seam tracking in precise pulse TIG welding of the extending part of the rocket engine jet tube. The vision sensor has many advantages, such as imaging with high quality, compactness and multiple functions. The optics design, mechanism design and circuit design of the vision sensor have been described in detail. Utilizing the mirror imaging of Tungsten electrode in the weld pool, a novel method is proposed to detect the arc length and seam tracking error of Tungsten electrode to the center line of joint seam from a single weld image. A calculating model of the method is proposed according to the relation of the Tungsten electrode, weld pool, the mirror of Tungsten electrode in weld pool and joint seam. The new methodologies are given to detect the arc length and seam tracking error. Through analyzing the results of the experiments, a system error modifying method based on a linear function is developed to improve the detecting precise of arc length and seam tracking error. Experimental results show that the final precision of the system reaches 0.1 mm in detecting the arc length and the seam tracking error of Tungsten electrode to the center line of joint seam.

Welding Emissions in Shipbuilding and Repair (Briefing Charts)

DTIC Science & Technology

2009-09-03

not just about Hexavalent Chromium • http://www.weldinglawsuits.com/ 5 Naval Facilities Engineering Command/ Engineering Service Center Driving...Regulations ( the Dry Stuff) • OSHA 1910.1026 – Hexavalent Chromium Regulation • OSHA 1910.1000 – Limits for Air Contaminants – e.g. Manganese, Nickel...gas – GTAW –uses shield gas, but low emissions –aka TIG – SAW – lowest rate, solid wire weld covered with flux material 7 Naval Facilities

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

NASA Astrophysics Data System (ADS)

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

1998-07-01

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

Assessment of the influence of surface finishing and weld joints on the corrosion/oxidation behaviour of stainless steels in lead bismuth eutectic

NASA Astrophysics Data System (ADS)

Martín-Muñoz, F. J.; Soler-Crespo, L.; Gómez-Briceño, D.

2011-09-01

The objective of this paper is to gain some insight into the influence of the surface finishing in the oxidation/corrosion behaviour of 316L and T91 steels in lead bismuth eutectic (LBE). Specimens of both materials with different surface states were prepared (as-received, grinded, grinded and polished, and electrolitically polished) and oxidation tests were carried out at 775 and 825 K from 100 to 2000 h for two different oxygen concentrations and for H 2/H 2O molar ratios of 3 and 0.03. The general conclusion for these tests is that the effect of surface finishing on the corrosion/protection processes is not significant under the tested conditions. In addition the behaviour of weld joints, T91-T91 Tungsten Inert Gas (TIG) and T91-316L have been also studied under similar conditions. The conclusions are that, whereas T91-T91 welded joint shows the same corrosion properties as the parent materials for the conditions tested, AISI 316L-T91 welded joint, present an important dissolution over seam area that it associated to the electrode 309S used for the fabrication process.

Portable Rapid Test Fuel Tank Leak Detection System

DTIC Science & Technology

2010-04-01

polished. Lid is tig welded . Media: Water Result: Bubbles (encircled in red) only at threaded port and at top of the center as shown in Picture 2...bimetallic strip ( ) quartz crystal ( ) thermistor ( ) other (describe briefly) B-3 If product temperature is not

Softening Behavior of a New Al-Zn-Mg-Cu Alloy Due to TIG Welding

NASA Astrophysics Data System (ADS)

Zhang, Liang; Li, Xiaoyan; Nie, Zuoren; Huang, Hui; Sun, Jiantong

2016-05-01

A new Al-Zn-Mg-Cu alloy with T6 temper was welded by TIG welding, and the softening behavior of the joint was evaluated. Results show that the ultimate tensile strength of the joint is 436.2 ± 26.4 MPa which is about 64.5% of that of the base metal (BM). Fusion zone (FZ) is the weakest region even though its microhardness increases from 107.6 to 131.3 HV within 90 days after welding. Microhardness of the heat-affected zone (HAZ) adjacent to FZ increases from 125.2 to 162.3 HV within 90 days. However, a valley value of microhardness appears in the rest of the HAZ that increases from 112.1 to 128.1 HV within 90 days. The variation of grain size and precipitates is regarded as the main cause of softening in both FZ and HAZ. The grain size of FZ is about 33.9 μm, whereas 8.7 and 8.4 μm for HAZ and BM, respectively. A large number of η' phases distribute dispersively in BM, whereas precipitates in FZ identified as GPI zones are finer and fewer. Besides, precipitates in HAZ adjacent to FZ are also GPI zones. Precipitates in HAZ far away from FZ are coarser and fewer than those in BM and η phases begin to emerge.

Weld bead reinforcement removal: A method of improving the strength and ductility of peaked welds in 2219-T87 aluminum alloy plate

NASA Technical Reports Server (NTRS)

Lovoy, C. V.

1979-01-01

The results of a study to determine the degree to which the ductility and tensile properties of peaked welds could be enhanced by removing the reinforcing bead and fairing the weld nugget into the adjacent parent metal are presented. The study employed 2219-T87 aluminum alloy plate, tungsten inert gas (TIG) welding, and 2319 filler wire. The study concluded that significant improvements in peak weld, ultimate strength, and ductility can be obtained through removal and fairing of the weld reinforcing bead. The specimens so treated and tested in this program exhibited ultimate strength improvements of 2 to 3 percent for peak angles of 5.8 to 10 degrees and 10 to 22 percent for welds with peak angles of 11.7 to 16.9 degrees. It was also determined that removal of the weld bead enhanced the ability of peaked welds to straighten when exposed to cyclic loading at stress levels above the yield strength.

Spectroscopic analysis technique for arc-welding process control

NASA Astrophysics Data System (ADS)

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

2005-09-01

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

Effect of zirconium addition on welding of aluminum grain refined by titanium plus boron

NASA Astrophysics Data System (ADS)

Zaid, A. I. O.

2014-06-01

Aluminum oxidizes freely in ordinary atmosphere which makes its welding difficult and weak, particularly it solidifies in columnar structure with large grains. Therefore, it is anticipated that the effect of addition of some grain refiners to its melt before solidification is worth while investigating as it may enhance its weldabilty and improve its mechanical strength. In this paper, the effect of addition of zirconium at a weight of 0.1% (which corresponds to the peretictic limit on the aluminum-zirconium base phase diagram) to commercially pure aluminum, grain refined by Ti+B on its weldability, using gas tungsten arc welding, GTAW, method which was formerly known as TIG. A constant current level of 30 AC Ampere was used because it removes the oxides during the welding process. Metallographic examination of the weldments of the different combinations of Al with Al and Al with its microalloys: in the heat affected zone, HAZ, and away from it was carried out and examined for HAZ width, porosity, cracks and microhardness. It was found that grain refining by Ti+B or Zr resulted in enhancement of the weldment.

Effect of Alternate Supply of Shielding Gases of Tungsten Inert Gas Welding on Mechanical Properties of Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Shinde, Neelam Vilas; Telsang, Martand Tamanacharya

2016-07-01

In the present study, an attempt is made to study the effect of alternate supply of the shielding gas in comparison with the conventional method of TIG welding with pure argon gas. The two sets of combination are used as 10-10 and 40-20 s for alternate supply of the Argon and Helium shielding gas respectively. The effect of alternate supply of shielding gas is studied on the mechanical properties like bend test, tensile test and impact test. The full factorial experimental design is applied for three set of combinations. The ANOVA is used to find significant parameters for the process and regression analysis used to develop the mathematical model. The result shows that the alternate supply of the shielding gas for 10-10 s provides better result for the bend, tensile and impact test as compared with the conventional argon gas and the alternate supply of 40-20 s argon and helium gas respectively. Welding speed can be increased for alternate supply of the shielding gas that can reduce the total welding cost.

Modelling the transient behaviour of pulsed current tungsten-inert-gas weldpools

NASA Astrophysics Data System (ADS)

Wu, C. S.; Zheng, W.; Wu, L.

1999-01-01

A three-dimensional model is established to simulate the pulsed current tungsten-inert-gas (TIG) welding process. The goal is to analyse the cyclic variation of fluid flow and heat transfer in weldpools under periodic arc heat input. To this end, an algorithm, which is capable of handling the transience, nonlinearity, multiphase and strong coupling encountered in this work, is developed. The numerical simulations demonstrate the transient behaviour of weldpools under pulsed current. Experimental data are compared with numerical results to show the effectiveness of the developed model.

Physical and chemical characterization of airborne particles from welding operations in automotive plants.

PubMed

Dasch, Jean; D'Arcy, James

2008-07-01

Airborne particles were characterized from six welding operations in three automotive plants, including resistance spot welding, metal inert gas (MIG) welding and tungsten inert gas (TIG) welding of aluminum and resistance spot welding, MIG welding and weld-through sealer of galvanized steel. Particle levels were measured throughout the process area to select a sampling location, followed by intensive particle sampling over one working shift. Temporal trends were measured, and particles were collected on filters to characterize their size and chemistry. In all cases, the particles fell into a bimodal size distribution with very large particles >20 mum in diameter, possibly emitted as spatter or metal expulsions, and very small particles about 1 mum in diameter, possibly formed from condensation of vaporized metal. The mass median aerodynamic diameter was about 1 mum, with only about 7% of the particle mass present as ultrafine particles <100 nm. About half the mass of aluminum welding particles could be accounted for by chemical analysis, with the remainder possibly present as oxygen. Predominant species were organic carbon, elemental carbon, iron, and aluminum. More than 80% of the particle mass could be accounted for from steel welding, primarily present as iron, organic carbon, zinc, and copper. Particle concentrations and elemental concentrations were compared with allowable concentrations as recommended by the Occupational Safety and Health Administration and the American Conference of Governmental Industrial Hygienists. In all cases, workplace levels were at least 11 times lower than recommended levels.

Protected, high-temperature connecting cable

NASA Technical Reports Server (NTRS)

Engdahl, R. E.

1967-01-01

Ceramic insulated, swaged stainless steel, sheathed, protective atmosphere cable admits electrical leads into an 1800 deg F air-environment test chamber. The cable has some bending capability and provides for nine niobium alloy conductors. An argon purge during the TIG weld closure protects internal wires from oxidation and embrittlement.

Electrical characteristics of TIG arcs in argon from non-equilibrium modelling and experiment

NASA Astrophysics Data System (ADS)

Baeva, Margarita; Uhrlandt, Dirk; Siewert, Erwan

2016-09-01

Electric arcs are widely used in industrial processes so that a thorough understanding of the arc characteristics is highly important to industrial research and development. TIG welding arcs operated with pointed electrodes made of tungsten, doped with cerium oxide, have been studied in order to analyze in detail the electric field and the arc voltage. Newly developed non-equilibrium model of the arc is based on a complete diffusion treatment of particle fluxes, a generalized form of Ohm's law, and boundary conditions accounting for the space-charge sheaths within the magneto-hydrodynamic approach. Experiments have been carried out for electric currents in the range 5-200 A. The electric arc has been initiated between a WC20 cathode and a water-cooled copper plate placed 0.8 mm from each other. The arc length has been continuously increased by 0.1 mm up to 15 mm and the arc voltage has been simultaneously recorded. Modelling and experimental results will be presented and discussed.

[The reconstruction of welding arc 3D electron density distribution based on Stark broadening].

PubMed

Zhang, Wang; Hua, Xue-Ming; Pan, Cheng-Gang; Li, Fang; Wang, Min

2012-10-01

The three-dimensional electron density is very important for welding arc quality control. In the present paper, Side-on characteristic line profile was collected by a spectrometer, and the lateral experimental data were approximated by a polynomial fitting. By applying an Abel inversion technique, the authors obtained the radial intensity distribution at each wavelength and thus constructed a profile for the radial positions. The Fourier transform was used to separate the Lorentz linear from the spectrum reconstructed, thus got the accurate Stark width. And we calculated the electronic density three-dimensional distribution of the TIG welding are plasma.

Residual stress characterization of steel TIG welds by neutron diffraction and by residual magnetic stray field mappings

NASA Astrophysics Data System (ADS)

Stegemann, Robert; Cabeza, Sandra; Lyamkin, Viktor; Bruno, Giovanni; Pittner, Andreas; Wimpory, Robert; Boin, Mirko; Kreutzbruck, Marc

2017-03-01

The residual stress distribution of tungsten inert gas welded S235JRC+C plates was determined by means of neutron diffraction (ND). Large longitudinal residual stresses with maxima around 600 MPa were found. With these results as reference, the evaluation of residual stress with high spatial resolution GMR (giant magneto resistance) sensors was discussed. The experiments performed indicate a correlation between changes in residual stresses (ND) and the normal component of local residual magnetic stray fields (GMR). Spatial variations in the magnetic field strength perpendicular to the welds are in the order of the magnetic field of the earth.

Design of Boiler Welding for Improvement of Lifetime and Cost Control.

PubMed

Thong-On, Atcharawadi; Boonruang, Chatdanai

2016-11-03

Fe-2.25Cr-1Mo a widely used material for headers and steam tubes of boilers. Welding of steam tube to header is required for production of boiler. Heat affected zone of the weld can have poor mechanical properties and poor corrosion behavior leading to weld failure. The cost of material used for steam tube and header of boiler should be controlled. This study propose a new materials design for boiler welding to improve the lifetime and cost control, using tungsten inert gas (TIG) welding of Fe-2.25Cr-1Mo tube to carbon steel pipe with chromium-containing filler. The cost of production could be reduced by the use of low cost material such as carbon steel pipe for boiler header. The effect of chromium content on corrosion behavior of the weld was greater than that of the microstructure. The lifetime of the welded boiler can be increased by improvement of mechanical properties and corrosion behavior of the heat affected zone.

Design of Boiler Welding for Improvement of Lifetime and Cost Control

PubMed Central

Thong-On, Atcharawadi; Boonruang, Chatdanai

2016-01-01

Fe-2.25Cr-1Mo a widely used material for headers and steam tubes of boilers. Welding of steam tube to header is required for production of boiler. Heat affected zone of the weld can have poor mechanical properties and poor corrosion behavior leading to weld failure. The cost of material used for steam tube and header of boiler should be controlled. This study propose a new materials design for boiler welding to improve the lifetime and cost control, using tungsten inert gas (TIG) welding of Fe-2.25Cr-1Mo tube to carbon steel pipe with chromium-containing filler. The cost of production could be reduced by the use of low cost material such as carbon steel pipe for boiler header. The effect of chromium content on corrosion behavior of the weld was greater than that of the microstructure. The lifetime of the welded boiler can be increased by improvement of mechanical properties and corrosion behavior of the heat affected zone. PMID:28774014

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

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

Dry sliding wear behavior of TIG welding clad WC composite coatings

NASA Astrophysics Data System (ADS)

Buytoz, Soner; Ulutan, Mustafa; Yildirim, M. Mustafa

2005-12-01

In this study, melted tungsten carbide powders on the surface of AISI 4340 steel was applied by using tungsten inert gas (TIG) method. It was observed that it has been solidified in different microstructures depending on the production parameters. As a result of microstructure examinations, in the surface modified layers an eutectic and dendrite solidification was observed together with WC, W 2C phases. In the layer produced, the hardness values varied between 950 and 1200 HV. The minimum mass loss was observed in the sample, which was treated in 1.209 mm/s production rate, 0.5 g/s powder feed rate and 13.9 kJ/cm heat input.

The Influence of TIG Welding Thermal Cycles on HSLA-100 Steel Plate

DTIC Science & Technology

1993-11-01

8217 1.0’ 1,i 1.0’ 10’ TZ•ME. Secznas Figure 15. CCT diagram for a HSLA-100 steel with composition similar to that of the present work from Wilson...cooling rate through the transformation and ends up with a HAZ hardness of 345 HV which indicates a predominantly martensitic structure, on the CCT ... diagram . This is confirmed by the TEM micrograph of the HAZ taken close to fusion boundary, figure 14. On the other hand, the high heat input weld 1, with

Fabrication of seamless calandria tubes by cold pilgering route using 3-pass and 2-pass schedules

NASA Astrophysics Data System (ADS)

Saibaba, N.

2008-12-01

Calandria tube is a large diameter, extremely thin walled zirconium alloy tube which has diameter to wall thickness ratio as high as 90-95. Such tubes are conventionally produced by the 'welded route', which involves extrusion of slabs followed by a series of hot and cold rolling passes, intermediate anneals, press forming of sheets into circular shape and closing the gap by TIG welding. Though pilgering is a well established process for the fabrication of seamless tubes, production of extremely thin walled tubes offers several challenges during pilgering. Nuclear fuel complex (NFC), Hyderabad, has successfully developed a process for the production of Zircaloy-4 calandria tubes by adopting the 'seamless route' which involves hot extrusion of mother blanks followed by three-pass pilgering or two-pass pilgering schedules. This paper deals with standardization of the seamless route processes for fabrication of calandria tubes, comparison between the tubes produced by 2-pass and 3-pass pilgering schedules, role of ultrasonic test charts for control of process parameters, development of new testing methods for burst testing and other properties.

Use of photostress and strain gages to analyze behavior of weldments and use of photostress and strain gages to analyze behavior of an aft skirt test specimen

NASA Technical Reports Server (NTRS)

Gambrell, S. C.; Karr, Gerald R.

1993-01-01

Previous work using Photostress on TIG welded, heat treated specimens of 2219-T87 parent material and 2319 weld material indicated that behavior of the joint can be highly irregular and non-uniform. Welded joints 1.40 inches thick exhibited a totally non-uniform behavior through the weld thickness with the 'wide' side of the weld being much more ductile than the 'narrow' side. It is believed that this difference in behavior through the weld is, in part, caused by procedures used when laying the weld bead. Joints similar to weldments in references 1 and 2 are an integral part of the aft skirt of the SRB of the shuttle. Since the ultimate safety factor for the lower portion of the weld is below the minimum required safety factor, a photostress analysis of this lower portion will be conducted in the vicinity of the weld. A test program using photostress will be conducted in accordance with the project planning document entitled 'Photostress Evaluation Requirements for AFT Skirt Test Article No. 4'.

Use of photostress to characterize the mechanical behavior of weldments

NASA Technical Reports Server (NTRS)

Gambrell, S. C., Jr.

1992-01-01

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

Improved TIG weld joint strength in aluminum alloy 2219-T87 by filler metal substitution

NASA Technical Reports Server (NTRS)

Poorman, R. M.; Lovoy, C. V.

1972-01-01

The results of an investigation on weld joint characteristics of aluminum alloy 2219-T87 are given. Five different alloys were utilized as filler material. The mechanical properties of the joints were determined at ambient and cryogenic temperatures for weldments in the as-welded condition and also, for weldments after elevated temperature exposures. Other evaluations included hardness surveys, stress corrosion susceptibility, and to a limited extent, the internal metallurgical weld structures. The overall results indicate that M-943 filler weldments are superior in strength to weldments containing either the standard 2319 filler or fillers 2014, 2020, and a dual wire feed consisting of three parts 2319 and one part 5652. In addition, no deficiencies were evident in M-934 filler weldments with regard to ductility, joint strength after elevated temperature exposure, weld hardness, metallographic structures, or stress corrosion susceptibility.

Biomarkers of exposure to stainless steel tungsten inert gas welding fumes and the effect of exposure on exhaled breath condensate.

PubMed

Riccelli, Maria Grazia; Goldoni, Matteo; Andreoli, Roberta; Mozzoni, Paola; Pinelli, Silvana; Alinovi, Rossella; Selis, Luisella; Mutti, Antonio; Corradi, Massimo

2018-08-01

The respiratory tract is the main target organ of the inhaled hexavalent chromium (Cr-VI) and nickel (Ni) contained in stainless steel (SS) welding fumes (WFs). The aim of this study was to investigate the Cr and Ni content of the exhaled breath condensate (EBC) of SS tungsten inert gas (TIG) welders, and relate their concentrations with oxidative stress and inflammatory biomarkers. EBC and urine from 100 SS TIG welders were collected pre-(T 0 ) and post-shift (T 1 ) on a Friday, and pre-shift (T 2 ) on the following Monday morning. Both EBC and urinary Cr concentrations were higher at T 1 (0.08 μg/L and 0.71 μg/g creatinine) and T 0 (0.06 μg/L and 0.74 μg/g creatinine) than at T 2 (below the limit of detection [LOD] and 0.59 μg/g creatinine), and EBC Ni concentrations generally remained

The Effect of Dilution on Microsegregation in AWS ER NiCrMo-14 Alloy Welding Claddings

NASA Astrophysics Data System (ADS)

Miná, Émerson Mendonça; da Silva, Yuri Cruz; Dille, Jean; Silva, Cleiton Carvalho

2016-12-01

Dilution and microsegregation are phenomena inherent to claddings, which, in turn, directly affect their main properties. This study evaluated microsegregation in the fusion zone with different dilution levels. The overlays were welded by the TIG cold wire feed process. Dilution was calculated from the geometric characteristics of the claddings and from the conservation of mass equation using chemical composition measurements. Microsegregation was calculated using energy dispersive X-ray spectroscopy measurements of the dendrites and the chemical composition of the fusion zone. The dilution of the claddings was increased by reducing the wire feed rate. Fe showed potential to be incorporated into the solid phase ( k > 1), and this increased with the increase of dilution. Mo, in turn, was segregated into the liquid phase ( k < 1) and also increased with the increase of dilution. However, Cr and W showed a slight decrease in their partition coefficients ( k) with the increase of dilution.

Confined Tube Crimp Using Portable Hand Tools

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

Reynolds, Joseph James; Pereyra, R. A.; Archuleta, Jeffrey Christopher

2016-04-04

The Lawrence Radiation Laboratory developed handheld tools that crimp a 1/16 inch OD tube, forming a leak tight seal1 (see Figure 1). The leak tight seal forms by confining the 1/16 inch OD tubing inside a die while applying crimp pressure. Under confined pressure, the tube walls weld at the crimp. The purpose of this study was to determine conditions for fabricating a leak tight tube weld. The equipment was used on a trial-and-error basis, changing the conditions after each attempt until successful welds were fabricated. To better confine the tube, the die faces were polished. Polishing removed a fewmore » thousandths of an inch from the die face, resulting in a tighter grip on the tubing wall. Using detergent in an ultrasonic bath, the tubing was cleaned. Also, the time under crimp pressure was increased to 30 seconds. With these modifications, acceptable cold welds were fabricated. After setting the conditions for an acceptable cold weld, the tube was TIG welded across the crimped face.« less

Corrosion behavior of stainless steel weldments in physiological solutions

NASA Astrophysics Data System (ADS)

Farooq, A.; Azam, M.; Deen, K. M.

2018-01-01

In this study corrosion behavior of TIG welded 316L stainless steel plates in simulated biological solutions is investigated. The mechanical testing results showed slight decrease in ductility after welding and the fracture surface represented mixed cleavage and inclusions containing dimple structure. The heat affected and weld zone (WZ) demonstrated higher corrosion potential and relatively large pitting tendency than base metal (BM) in both Hank’s and Ringer’s solution. The formation of delta (δ) ferrite in the heat affected and WZ decreased the corrosion resistance as confirmed from potentiodynamic Tafel scans. The decrease in pitting resistance and lower protection tendency of the WZ compared to BM and heat affected zone was also quantified from the cyclic polarization trends.

Long arc stabilities with various arc gas flow rates

NASA Astrophysics Data System (ADS)

Maruyama, K.; Takeda, K.; Sugimoto, M.; Noguchi, Y.

2014-11-01

A new arc torch for use in magnetically driven arc device was developed with a commercially available TIG welding arc torch. The torch has a water-cooling system to the torch nozzle and has a nozzle nut to supply a swirling-free plasma gas flow. Its endurance against arc thermal load is examined. Features of its generated arc are investigated.

Stress distribution in Co-Cr implant frameworks after laser or TIG welding.

PubMed

de Castro, Gabriela Cassaro; de Araújo, Cleudmar Amaral; Mesquita, Marcelo Ferraz; Consani, Rafael Leonardo Xediek; Nóbilo, Mauro Antônio de Arruda

2013-01-01

Lack of passivity has been associated with biomechanical problems in implant-supported prosthesis. The aim of this study was to evaluate the passivity of three techniques to fabricate an implant framework from a Co-Cr alloy by photoelasticity. The model was obtained from a steel die simulating an edentulous mandible with 4 external hexagon analog implants with a standard platform. On this model, five frameworks were fabricated for each group: a monoblock framework (control), laser and TIG welding frameworks. The photoelastic model was made from a flexible epoxy resin. On the photoelastic analysis, the frameworks were bolted onto the model for the verification of maximum shear stress at 34 selected points around the implants and 5 points in the middle of the model. The stresses were compared all over the photoelastic model, between the right, left, and center regions and between the cervical and apical regions. The values were subjected to two-way ANOVA, and Tukey's test (α=0.05). There was no significant difference among the groups and studied areas (p>0.05). It was concluded that the stresses generated around the implants were similar for all techniques.

Numerical investigations of arc behaviour in gas metal arc welding using ANSYS CFX

NASA Astrophysics Data System (ADS)

Schnick, M.; Fuessel, U.; Hertel, M.; Spille-Kohoff, A.; Murphy, A. B.

2011-06-01

Current numerical models of gas metal arc welding (GMAW) are trying to combine magnetohydrodynamics (MHD) models of the arc and volume of fluid (VoF) models of metal transfer. They neglect vaporization and assume an argon atmosphere for the arc region, as it is common practice for models of gas tungsten arc welding. These models predict temperatures above 20 000 K and a temperature distribution similar to tungsten inert gas (TIG) arcs. However, current spectroscopic temperature measurements in GMAW arcs demonstrate much lower arc temperatures. In contrast to TIG arcs they found a central local minimum of the radial temperature distribution. The paper presents a GMAW arc model that considers metal vapour and which is in a very good agreement with experimentally observed temperatures. Furthermore, the model is able to predict the local central minimum in the radial temperature and the radial electric current density distributions for the first time. The axially symmetric model of the welding torch, the work piece, the wire and the arc (fluid domain) implements MHD as well as turbulent mixing and thermal demixing of metal vapour in argon. The mass fraction of iron vapour obtained from the simulation shows an accumulation in the arc core and another accumulation on the fringes of the arc at 2000 to 5000 K. The demixing effects lead to very low concentrations of iron between these two regions. Sensitive analyses demonstrate the influence of the transport and radiation properties of metal vapour, and the evaporation rate relative to the wire feed. Finally the model predictions are compared with the measuring results of Zielińska et al.

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.

Dynamic analysis of I cross beam section dissimilar plate joined by TIG welding

NASA Astrophysics Data System (ADS)

Sani, M. S. M.; Nazri, N. A.; Rani, M. N. Abdul; Yunus, M. A.

2018-04-01

In this paper, finite element (FE) joint modelling technique for prediction of dynamic properties of sheet metal jointed by tungsten inert gas (TTG) will be presented. I cross section dissimilar flat plate with different series of aluminium alloy; AA7075 and AA6061 joined by TTG are used. In order to find the most optimum set of TTG welding dissimilar plate, the finite element model with three types of joint modelling were engaged in this study; bar element (CBAR), beam element and spot weld element connector (CWELD). Experimental modal analysis (EMA) was carried out by impact hammer excitation on the dissimilar plates that welding by TTG method. Modal properties of FE model with joints were compared and validated with model testing. CWELD element was chosen to represent weld model for TTG joints due to its accurate prediction of mode shapes and contains an updating parameter for weld modelling compare to other weld modelling. Model updating was performed to improve correlation between EMA and FEA and before proceeds to updating, sensitivity analysis was done to select the most sensitive updating parameter. After perform model updating, average percentage of error of the natural frequencies for CWELD model is improved significantly.

Strengthening of Aluminum Wires Treated with A206/Alumina Nanocomposites.

PubMed

Florián-Algarín, David; Marrero, Raúl; Li, Xiaochun; Choi, Hongseok; Suárez, Oscar Marcelo

2018-03-10

This study sought to characterize aluminum nanocomposite wires that were fabricated through a cold-rolling process, having potential applications in TIG (tungsten inert gas) welding of aluminum. A206 (Al-4.5Cu-0.25Mg) master nanocomposites with 5 wt % γAl₂O₃ nanoparticles were first manufactured through a hybrid process combining semi-solid mixing and ultrasonic processing. A206/1 wt % γAl₂O₃ nanocomposites were fabricated by diluting the prepared master nanocomposites with a monolithic A206 alloy, which was then added to a pure aluminum melt. The fabricated Al-γAl₂O₃ nanocomposite billet was cold-rolled to produce an Al nanocomposite wire with a 1 mm diameter and a transverse area reduction of 96%. Containing different levels of nanocomposites, the fabricated samples were mechanically and electrically characterized. The results demonstrate a significantly higher strength of the aluminum wires with the nanocomposite addition. Further, the addition of alumina nanoparticles affected the wires' electrical conductivity compared with that of pure aluminum and aluminum-copper alloys. The overall properties of the new material demonstrate that these wires could be an appealing alternative for fillers intended for aluminum welding.

Strengthening of Aluminum Wires Treated with A206/Alumina Nanocomposites

PubMed Central

Marrero, Raúl; Li, Xiaochun; Choi, Hongseok

2018-01-01

This study sought to characterize aluminum nanocomposite wires that were fabricated through a cold-rolling process, having potential applications in TIG (tungsten inert gas) welding of aluminum. A206 (Al-4.5Cu-0.25Mg) master nanocomposites with 5 wt % γAl2O3 nanoparticles were first manufactured through a hybrid process combining semi-solid mixing and ultrasonic processing. A206/1 wt % γAl2O3 nanocomposites were fabricated by diluting the prepared master nanocomposites with a monolithic A206 alloy, which was then added to a pure aluminum melt. The fabricated Al–γAl2O3 nanocomposite billet was cold-rolled to produce an Al nanocomposite wire with a 1 mm diameter and a transverse area reduction of 96%. Containing different levels of nanocomposites, the fabricated samples were mechanically and electrically characterized. The results demonstrate a significantly higher strength of the aluminum wires with the nanocomposite addition. Further, the addition of alumina nanoparticles affected the wires’ electrical conductivity compared with that of pure aluminum and aluminum–copper alloys. The overall properties of the new material demonstrate that these wires could be an appealing alternative for fillers intended for aluminum welding. PMID:29534441

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.

Slow fatigue testing of titanium grade 29 in air and seawater

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

Atteraas, L.; Hersvik, G.; Solbakken, H.

1999-07-01

ASTM Grade 29 titanium has been fatigue tested in air and seawater at 110 C at a low frequency. The possible influence of seawater is completely masked by the fact that all the specimens of welded titanium, and most of the parent metal samples, had internal fracture initiations. Compared to the parent metal, the welded pipe specimens (5G orbital TIG) had a significantly lower fatigue life at the relatively high cyclic stress levels employed ({sigma}{sub max} = 0.85 {sigma}{sub y}). This is attributed to the presence of pores. Fractographic studies of failed weld metal specimens indicate that the fracture initiationmore » takes place in the material immediately surrounding a pore, with an abrupt crack formation, marking the beginning of the crack growth phase. The duration of the crack initiation phase shows large variations, whereas the growth phase duration varies little.« less

Surface Modification of Micro-Alloyed High-Strength Low-Alloy Steel by Controlled TIG Arcing Process

NASA Astrophysics Data System (ADS)

Ghosh, P. K.; Kumar, Ravindra

2015-02-01

Surface modification of micro-alloyed HSLA steel plate has been carried out by autogenous conventional and pulse current tungsten inert gas arcing (TIGA) processes at different welding parameters while the energy input was kept constant. At a given energy input the influence of pulse parameters on the characteristics of surface modification has been studied in case of employing single and multi-run procedure. The role of pulse parameters has been studied by considering their summarized influence defined by a factor Φ. The variation in Φ and pulse frequency has been found to significantly affect the thermal behavior of fusion and accordingly the width and penetration of the modified region along with its microstructure, hardness and wear characteristics. It is found that pulsed TIGA is relatively more advantageous over the conventional TIGA process, as it leads to higher hardness, improved wear resistance, and a better control over surface characteristics.

Exposure to hexavalent chromium in welders: Results of the WELDOX II field study.

PubMed

Pesch, Beate; Lehnert, Martin; Weiss, Tobias; Kendzia, Benjamin; Menne, Eleonore; Lotz, Anne; Heinze, Evelyn; Behrens, Thomas; Gabriel, Stefan; Schneider, Wolfgang; Brüning, Thomas

2018-03-12

Exposure to hexavalent chromium (Cr(VI)) has been primarily studied in chromate production. Here, we measured personal exposure to respirable Cr(VI) together with airborne and urinary Cr and Ni in welders to explore levels and associations between various measures of exposure. Shift concentrations of Cr(VI), Cr, and Ni were measured in respirable welding fumes in 50 men who used either gas metal arc welding (GMAW) (n = 24) or tungsten inert gas welding (TIG) (n = 19) as their major technique. Cr and Ni were determined in pre- and post-shift urine samples. Concentrations below the limit of quantification (LOQ) were multiply imputed. Spearman correlation coefficients (rs) were calculated with 95% confidence intervals (CIs) to explore associations between the exposure variables, and regression models were applied to estimate the effect of the parent metal on the urinary concentration. Regarding the respirable Cr(VI), 62% of the measurements were below the LOQ, the 75th percentile was 0.50 µg m-3, and 8 out of 50 (16%) welders exceeded 1 µg m-3. The highest shift concentration that occurred as a result of shielded metal arc welding (SMAW) was 180 µg m-3. The Cr(VI) content in total Cr ranged from 4 to 82% (median 20%), although the concentration correlated with total Cr (rs 0.55, 95% CI 0.46; 0.64). The correlation between Cr(VI) and Ni was weaker (rs 0.42, 95% CI 0.34; 0.51) than that between total Cr and Ni in welding fumes (rs 0.83, 95% CI 0.74; 0.92). Both Cr(VI) and total Cr influenced the urinary Cr concentrations in post-shift samples (P = 0.0008 and P ≤ 0.0001, respectively). The airborne shift exposure was a weaker determinant than the Cr content in pre-shift urine samples, which strongly correlated with post-shift urinary Cr (rs 0.78, 95% CI 0.69; 0.87). The Cr(VI) content in total Cr varied considerably in welding fumes. The majority of welders using GMAW or TIG presented with shift concentrations of respirable Cr(VI) below 1 µg m-3. However, very high Cr(VI) concentrations may occur, for example in SMAW. The urinary concentration of total Cr, cannot be used to precisely determine the shift concentration of respirable Cr(VI) in welders.

A review of the use of Al-alloy vacuum components for operation at 10-13 Torr

NASA Astrophysics Data System (ADS)

Ishimaru, Hajime

1990-02-01

An extremely high vacuum (XHV) chamber was fabricated and tested. The vacuum chamber was made of special surface finished (EX-process) aluminum alloy in oxygen and argon atmosphere. The chamber was assembled using TIG welding in an argon atmosphere and by electron beam welding. The system was evacuated with a turbo-backed 300 l/s turbomolecular pump separated from the main chamber using a right angle valve. The liquid nitrogen shroud is installed inside the main vacuum chamber. The XHV is maintained by two 300 l/s sputter ion pumps and a titanium sublimation pump with a liquid nitrogen shroud. These pumps are also made of aluminum alloys. An ultimate pressure of 3×10-13 Torr was measured with a point collector gauge with a spherical anode mounted on an Al-flange. Residual gas analysis in the order 10-13 Torr was performed by a newly developed Q-mass filter. To suppress outgassing from the quadrupole electrode, the ion source is mounted on an Al-flange separated from the quadrupole electrode.

Evolution of Microstructure and Stress Corrosion Cracking Behavior of AA2219 Plate to Ring Weld Joints in 3.5 Wt Pct NaCl Solution

NASA Astrophysics Data System (ADS)

Venugopal, A.; Narayanan, P. Ramesh; Sharma, S. C.

2016-04-01

AA2219 aluminum alloy plate (T87) and ring (T851) were joined by tungsten inert gas (TIG) welding using multi-pass welding. The mechanical properties and stress corrosion cracking (SCC) resistance of the above base metals (BMs) in different directions (L, LT, and ST) were examined. Similarly, the weld metal joined by plate to plate and plate to ring (PR) joints was evaluated. The results revealed that the mechanical properties of the ring were comparatively lower than the plate. This was found to be due to the extremely coarse grain size of the ring along with severe Cu-rich segregation along the grain boundaries when compared to the plate material. The SCC resistance of the base and weldments were found to be good and not susceptible to SCC. This was shown to be due to high values of SCC index (>0.9) and the typical ductile cracking morphology of the BM and the weld joints after SCC test in the environment (3.5 wt pct NaCl) when compared to test performed in the control environment (air). However, the corrosion resistance of the weld interface between the FZ and ring was inferior to the FZ-plate interface.

Cold Spray Repair of Martensitic Stainless Steel Components

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

Microstructure and Mechanical Properties of Three-Layer TIG-Welded 2219 Aluminum Alloys with Dissimilar Heat Treatments

NASA Astrophysics Data System (ADS)

Zhang, Dengkui; Li, Quan; Zhao, Yue; Liu, Xianli; Song, Jianling; Wang, Guoqing; Wu, Aiping

2018-05-01

2219-C10S and 2219-CYS aluminum alloys are 2219 aluminum alloys with different heat treatment processes, and they have been widely used in the aerospace industry. In the present study, 2219-C10S and 2219-CYS aluminum alloys were butt-welded by three-layer tungsten inert gas arc welding (with the welding center of the third layer shifted toward the CYS side), and the microstructure characteristics and mechanical properties of the welded joint were investigated. The lamellar θ' phases, the bulk or rod θ phases, and the coarse rod-shaped or pancake-shaped Al-Cu-Fe-Mn phases coexisted in the two aluminum alloys. The Cu content of the α-Al matrix and the distribution of eutectic structures of different welding layers in the weld zone (WZ) were varied, implying that the segregation degrees of the Cu element were different due to the different welding thermal cycles in different welding layers. The microhardness values of the CYS side were much higher than those of the C10S side in each region on both sides of the joint. The tensile test deformation was concentrated mainly in the regions of WZ and the over aged zone (OAZ), where the microhardness values were relatively low. The main deformation concentrated region was transferred from the CYS side to the C10S side with the increase in the tensile load during the tensile test. The fracture behavior of the tensile test showed that the macroscopic crack initiated near the front weld toe had gone through the crack blunt region, the shear fracture region of the partially melted zone (PMZ), and the shear fracture region of OAZ. Meanwhile, the fracture characteristics gradually evolved from brittle to ductile. The concentrated stress and the dense eutectic structure in the region near the front weld toe of the C10S side contributed to the fracture of the joint. The shift of the welding center of the third layer to the CYS side resulted in two effects: (i) the microhardness values from the middle layer to the top layer in the PMZ of the CYS side were the most significantly increased and (ii) the distance between the front weld toe and the fusion line of the CYS side was significantly larger.

Pyrometer mount for a closed-circuit thermal medium cooled gas turbine

DOEpatents

Jones, Raymond Joseph; Kirkpatrick, Francis Lawrence; Burns, James Lee; Fulton, John Robert

2002-01-01

A steam-cooled second-stage nozzle segment has an outer band and an outer cover defining a plenum therebetween for receiving cooling steam for flow through the nozzles to the inner band and cover therefor and return flow through the nozzles. To measure the temperature of the buckets of the stage forwardly of the nozzle stage, a pyrometer boss is electron beam-welded in an opening through the outer band and TIG-welded to the outer cover plate. By machining a hole through the boss and seating a linearly extending tube in the boss, a line of sight between a pyrometer mounted on the turbine frame and the buckets is provided whereby the temperature of the buckets can be ascertained. The welding of the boss to the outer band and outer cover enables steam flow through the plenum without leakage, while providing a line of sight through the outer cover and outer band to measure bucket temperature.

Stress Corrosion Cracking Behavior of Multipass TIG-Welded AA2219 Aluminum Alloy in 3.5 wt pct NaCl Solution

NASA Astrophysics Data System (ADS)

Venugopal, A.; Sreekumar, K.; Raja, V. S.

2012-09-01

The stress corrosion cracking (SCC) behavior of the AA2219 aluminum alloy in the single-pass (SP) and multipass (MP) welded conditions was examined and compared with that of the base metal (BM) in 3.5 wt pct NaCl solution using a slow-strain-rate technique (SSRT). The reduction in ductility was used as a parameter to evaluate the SCC susceptibility of both the BM and welded joints. The results showed that the ductility ratio ( ɛ NaCl/( ɛ air) was 0.97 and 0.96, respectively, for the BM and MP welded joint, and the same was marginally reduced to 0.9 for the SP welded joint. The fractographic examination of the failed samples revealed a typical ductile cracking morphology for all the base and welded joints, indicating the good environmental cracking resistance of this alloy under all welded conditions. To understand the decrease in the ductility of the SP welded joint, preexposure SSRT followed by microstructural observations were made, which showed that the decrease in ductility ratio of the SP welded joint was caused by the electrochemical pitting that assisted the nucleation of cracks in the form of corrosion induced mechanical cracking rather than true SCC failure of the alloy. The microstructural examination and polarization tests demonstrated a clear grain boundary (GB) sensitization of the PMZ, resulting in severe galvanic corrosion of the SP weld joint, which initiated the necessary conditions for the localized corrosion and cracking along the PMZ. The absence of PMZ and a refined fusion zone (FZ) structure because of the lesser heat input and postweld heating effect improved the galvanic corrosion resistance of the MP welded joint greatly, and thus, failure occurred along the FZ.

The role of welding techniques in the biomechanical behavior of implant-supported prostheses.

PubMed

Rodrigues, Sabrina Alessandra; Presotto, Anna Gabriella Camacho; Barão, Valentim Adelino Ricardo; Consani, Rafael Leonardo Xediek; Nóbilo, Mauro Antônio Arruda; Mesquita, Marcelo Ferraz

2017-09-01

This in vitro study investigated the role of welding techniques of implant-supported prostheses in the 2D and 3D marginal misfits of prosthetic frameworks, strain induced on the mini abutment, and detorque of prosthetic screws. The correlations between the analyzed variables were also investigated. Frameworks were cast in commercially pure titanium (cp-Ti). A marginal misfit of 200μm was simulated in the working models (control group) (n=20). The 2D marginal misfit was analyzed according to the single-screw test protocol using a precision optical microscope. The 3D marginal misfit was performed by X-ray microtomography. Strain gauge analysis was performed to investigate the strain induced on the mini abutment. A digital torque meter was used for analysis of the detorque and the mean value was calculated for each framework. Afterwards, the frameworks were divided into two experimental groups (n=10): Laser (L) and TIG (T). The welding techniques were performed according to the following parameters: L (390V/9ms); T (36A/60ms). The L and T groups were reevaluated according to the marginal misfit, strain, and detorque. The results were submitted to one-way ANOVA followed by Tukey's HSD test and Person correlation analysis (α=0.05). Welding techniques statistically reduced the 2D and 3D marginal misfits of prosthetic frameworks (p<0.001), the strain induced on the mini abutment replicas (p=0.006), and improved the screw torque maintenance (p<0.001). Similar behavior was noted between L and T groups for all dependent variables (p>0.05). Positive correlations were observed between 2D and 3D marginal misfit reading methods (r=0.943, p<0.0001) and between misfit and strain (2D r=0.844, p<0.0001 and 3D r=0.864, p<0.0001). Negative correlation was observed between misfit and detorque (2D r=-0.823, p=0.003 and 3D r=-0.811, p=0.005). In conclusion, the welding techniques improved the biomechanical behavior of the implant-supported system. TIG can be an acceptable and affordable technique to reduce the misfit of 3-unit Ti frameworks. Copyright © 2017 Elsevier B.V. All rights reserved.

Thermal cooling effects in the microstructure and properties of cast cobalt-base biomedical alloys

NASA Astrophysics Data System (ADS)

Vega Valer, Vladimir

Joint replacement prosthesis is widely used in the biomedical field to provide a solution for dysfunctional human body joints. The demand for orthopedic knee and hip implants motivate scientists and manufacturers to develop novel materials or to increase the life of service and efficiency of current materials. Cobalt-base alloys have been investigated by various researchers for biomedical implantations. When these alloys contain Chromium, Molybdenum, and Carbon, they exhibit good tribological and mechanical properties, as well as excellent biocompatibility and corrosion resistance. In this study, the microstructure of cast Co-Cr-Mo-C alloy is purposely modified by inducing rapid solidification through fusion welding processes and solution annealing heat treatment (quenched in water at room temperature. In particular the effect of high cooling rates on the athermal phase transformation FCC(gamma)↔HCP(epsilon) on the alloy hardness and corrosion resistance is investigated. The Co-alloy microstructures were characterized using metallography and microscopy techniques. It was found that the as cast sample typically dendritic with dendritic grain sizes of approximately 150 microm and containing Cr-rich coarse carbide precipitates along the interdendritic boundaries. Solution annealing gives rise to a refined microstructure with grain size of 30 microm, common among Co-Cr-Mo alloys after heat treating. Alternatively, an ultrafine grain structure (between 2 and 10 microm) was developed in the fusion zone for specimens melted using Laser and TIG welding methods. When laser surface modification treatments were implemented, the developed solidification microstructure shifted from dendritic to a fine cellular morphology, with possible nanoscale carbide precipitates along the cellular boundaries. In turn, the solidified regions exhibited high hardness values (461.5HV), which exceeds by almost 110 points from the alloy in the as-cast condition. The amount of developed athermal epsilon-martensite phase was determined using X-ray diffractrometry. It was found that the amount of epsilon-martensite increases significantly from 2% for the Laser surface processing to 13% in the as cast specimen, 24% in the annealed specimen, and 51% for the TIG surface processing. Moreover, the corrosion rate in Ringer solution was calculated by applying the Tafel extrapolation method on each alloy condition. The lowest corrosion rate (0.435 microm/year) was achieved in the Laser treated alloy and it is attributed to the lack of appreciable athermal epsilon-martensite. The highest corrosion rate (15.5 microm/year) was found to occur in the TIG treated alloy, which possesses the largest amount of epsilon-martensite. In turn, this suggests that surface modification through melting induces variable amounts of athermal epsilon-martensite in the as-cast Co-Cr-Mo-C alloys. Apparently, rapid solidification of melted surfaces in the Co-alloy is highly effective in modifying the induced amounts of HCP phase, and hence, the exhibited properties.

A study of the bio-accessibility of welding fumes.

PubMed

Berlinger, Balázs; Ellingsen, Dag G; Náray, Miklós; Záray, Gyula; Thomassen, Yngvar

2008-12-01

The respiratory bio-accessibility of a substance is the fraction that is soluble in the respiratory environment and is available for absorption. In the case of respiratory exposure the amount of absorbed substance plays a main role in the biological effects. Extensive bio-accessibility studies have always been an essential requirement for a better understanding of the biological effects of different workplace aerosols, such as welding fumes. Fumes generated using three different welding techniques, manual metal arc (MMA) welding, metal inert gas (MIG) welding, and tungsten inert gas (TIG) welding were investigated in the present study. Each technique was used for stainless steel welding. Welding fumes were collected on PVC membrane filters in batches of 114 using a multiport air sampler. Three different fluids were applied for the solubility study: deionised water and two kinds of lung fluid simulants: lung epithelial lining fluid simulant (Gamble's solution) and artificial lung lining fluid simulant (Hatch's solution). In order to obtain sufficient data to study the tendencies in solubility change with time, seven different leaching periods were used (0.5, 1, 2, 4, 8, 16, 24 h), each of them with three replicates. The effect of dissolution temperature was also studied. The total amounts of selected metals in the three different welding fumes were determined after microwave-assisted digestion with the mixture of aqua regia and hydrofluoric acid. The most obvious observation yielded by the results is that the solubility of individual metals varies greatly depending on the welding technique, the composition of the leaching fluid and leaching time. This study shows that the most reasonable choice as a media for the bio-assessment of solubility might be Hatch's solution by a dissolution time of 24 h.

Selection And Evaluation Of An Alloy For Nozzle Application

NASA Technical Reports Server (NTRS)

Pandey, A. B.; Shah, S.; Shadoan, M.; Lyles, Garry (Technical Monitor)

2003-01-01

The present work includes results on material characterization conducted under COBRA Hydrogen Cooled Nozzle Program and was funded by NASA MSFC. The nozzle requires a material that has high strength at ambient and high (up to l200 F) temperatures in air and hydrogen. Presently, a precipitation hardened steel; A-286 is used in nozzles for Space Shuttle Engines. The A-286 alloy has limited hydrogen compatibility and weldability. The present work focused on selection and characterization of JBK-75 alloy that has significantly higher capability in hydrogen and weldability in addition to other attributes. The alloy was evaluated at different temperatures and environments. Tungsten Inert Gas (TIG) and Electron Beam welding techniques were used to evaluate the weldability of material. Brazing was also conducted on the alloy and evaluated. The characterization of base JBK-75 alloy, welded and brazed alloy included tensile properties, low cycle fatigue and crack growth resistance at different temperatures in air and hydrogen environments. The results indicated that JBK-75 has excellent tensile and fatigue properties in air and hydrogen. The welded and brazed alloy also showed very good properties.

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

NASA Astrophysics Data System (ADS)

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

2016-10-01

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

Correlation of stress-wave-emission characteristics with fracture aluminum alloys

NASA Technical Reports Server (NTRS)

Hartbower, C. E.; Reuter, W. G.; Morais, C. F.; Crimmins, P. P.

1972-01-01

A study to correlate stress wave emission characteristics with fracture in welded and unwelded aluminum alloys tested at room and cryogenic temperature is reported. The stress wave emission characteristics investigated were those which serve to presage crack instability; viz., a marked increase in:(1) signal amplitude; (2) signal repetition rate; and (3) the slope of cumulative count plotted versus load. The alloys were 7075-T73, 2219-T87 and 2014-T651, welded with MIG and TIG using 2319 and 4043 filler wire. The testing was done with both unnotched and part-through-crack (PTC) tension specimens and with 18-in.-dia subscale pressure vessels. In the latter testing, a real time, acoustic emission, triangulation system was used to locate the source of each stress wave emission. With such a system, multiple emissions from a given location were correlated with defects found by conventional nondestructive inspection.

Effect of Repair Welding on Electrochemical Corrosion and Stress Corrosion Cracking Behavior of TIG Welded AA2219 Aluminum Alloy in 3.5 Wt Pct NaCl Solution

NASA Astrophysics Data System (ADS)

Venugopal, A.; Sreekumar, K.; Raja, V. S.

2010-12-01

The stress corrosion cracking (SCC) behavior of AA2219 aluminum alloy in the as-welded (AW) and repair-welded (RW) conditions was examined and compared with that of the base metal (BM) in 3.5 wt pct NaCl solution using the slow strain rate technique (SSRT). The reduction in ductility was used as a parameter to evaluate the SCC susceptibility of both BM and welded joints. The results show that the ductility ratio ( ɛ NaCl/( ɛ air)) of the BM was close to one (0.97) and reduced to 0.9 for the AW joint. This value further reduced to 0.77 after carrying out one repair welding operation. However, the RW specimen exhibited higher ductility than the single-weld specimens even in 3.5 wt pct NaCl solution. SSRT results obtained using pre-exposed samples followed by post-test metallographic observations clearly showed localized pitting corrosion along the partially melted zone (PMZ), signifying that the reduction in ductility ratio of both the AW and RW joints was more due to mechanical overload failure, caused by the localized corrosion and a consequent reduction in specimen thickness, than due to SCC. Also, the RW joint exhibited higher ductility than the AW joint both in air and the environment, although SCC index (SI) for the former is lower than that of the latter. Fractographic examination of the failed samples, in general, revealed a typical ductile cracking morphology for all the base and welded joints, indicating the good environmental cracking resistance of this alloy. Microstructural examination and polarization tests further demonstrate grain boundary melting along the PMZ, and that provided the necessary electrochemical condition for the preferential cracking on that zone of the weldment.

Microstructural response to heat affected zone cracking of prewelding heat-treated Inconel 939 superalloy

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

Gonzalez, M.A., E-mail: mgonzalez@comimsa.com.mx; Martinez, D.I., E-mail: dorairma@yahoo.com; Perez, A., E-mail: betinperez@hotmail.com

2011-12-15

The microstructural response to cracking in the heat-affected zone (HAZ) of a nickel-based IN 939 superalloy after prewelding heat treatments (PWHT) was investigated. The PWHT specimens showed two different microstructures: 1) spherical ordered {gamma} Prime precipitates (357-442 nm), with blocky MC and discreet M{sub 23}C{sub 6} carbides dispersed within the coarse dendrites and in the interdendritic regions; and 2) ordered {gamma} Prime precipitates in 'ogdoadically' diced cube shapes and coarse MC carbides within the dendrites and in the interdendritic regions. After being tungsten inert gas welded (TIG) applying low heat input, welding speed and using a more ductile filler alloy,more » specimens with microstructures consisting of spherical {gamma} Prime precipitate particles and dispersed discreet MC carbides along the grain boundaries, displayed a considerably improved weldability due to a strong reduction of the intergranular HAZ cracking associated with the liquation microfissuring phenomena. - Highlights: Black-Right-Pointing-Pointer Homogeneous microstructures of {gamma} Prime spheroids and discreet MC carbides of Ni base superalloys through preweld heat treatments. Black-Right-Pointing-Pointer {gamma} Prime spheroids and discreet MC carbides reduce the intergranular HAZ liquation and microfissuring of Nickel base superalloys. Black-Right-Pointing-Pointer Microstructure {gamma} Prime spheroids and discreet blocky type MC carbides, capable to relax the stress generated during weld cooling. Black-Right-Pointing-Pointer Low welding heat input welding speeds and ductile filler alloys reduce the HAZ cracking susceptibility.« less

Manufacturing Methods and Technology. Project Summary Reports.

DTIC Science & Technology

1980-06-01

Tung- sten Inert Gas (TIG) welding of aluminum components. 41 X 4 (,B)IRAIt AW k A r A’I 4 " 6 A T A k I, A ., : , . Figure 1 - Modular Packages for...Telescope and M134 Mount 75 6 M102 Howitzer M113 Panoramic Telescope and M134 Mount 100 4 )21l4 Quiadrant 1.50 2 XM11A Elbow Telescope 130 5 M29...No. Temperature( OF) Time at temperature(min.) 1 200 30 2 200 6o 3 300 30 4 300 60 5 4DO 30 6 4 +0 60 Springs compressed to a stress level of 150,000

Nurturing Professional Growth: A Peer Review Model for Independent Evaluators

ERIC Educational Resources Information Center

Bond, Sally L.; Ray, Marilyn L.

2006-01-01

There has been a recent groundswell of support in the American Evaluation Association's Independent Consulting Topical Interest Group (IC TIG) for evaluating evaluators' work just as evaluators evaluate the work of their clients. To facilitate this self-evaluation, the IC TIG elected to create a peer review process that focuses on written…

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

PubMed

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

2011-01-01

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

Corrosion-Resistant Ti- xNb- xZr Alloys for Nitric Acid Applications in Spent Nuclear Fuel Reprocessing Plants

NASA Astrophysics Data System (ADS)

Manivasagam, Geetha; Anbarasan, V.; Kamachi Mudali, U.; Raj, Baldev

2011-09-01

This article reports the development, microstructure, and corrosion behavior of two new alloys such as Ti-4Nb-4Zr and Ti-2Nb-2Zr in boiling nitric acid environment. The corrosion test was carried out in the liquid, vapor, and condensate phases of 11.5 M nitric acid, and the potentiodynamic anodic polarization studies were performed at room temperature for both alloys. The samples subjected to three-phase corrosion testing were characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDAX). As Ti-2Nb-2Zr alloy exhibited inferior corrosion behavior in comparison to Ti-4Nb-4Zr in all three phases, weldability and heat treatment studies were carried out only on Ti-4Nb-4Zr alloy. The weldability of the new alloy was evaluated using tungsten inert gas (TIG) welding processes, and the welded specimen was thereafter tested for its corrosion behavior in all three phases. The results of the present investigation revealed that the newly developed near alpha Ti-4Nb-4Zr alloy possessed superior corrosion resistance in all three phases and excellent weldability compared to conventional alloys used for nitric acid application in spent nuclear reprocessing plants. Further, the corrosion resistance of the beta heat-treated Ti-4Nb-4Zr alloy was superior when compared to the sample heat treated in the alpha + beta phase.

Creep Deformation and Rupture Behavior of Single- and Dual-Pass 316LN Stainless-Steel-Activated TIG Weld Joints

NASA Astrophysics Data System (ADS)

Vijayanand, V. D.; Vasudevan, M.; Ganesan, V.; Parameswaran, P.; Laha, K.; Bhaduri, A. K.

2016-06-01

Creep deformation and rupture behavior of single-pass and dual-pass 316LN stainless steel (SS) weld joints fabricated by an autogenous activated tungsten inert gas welding process have been assessed by performing metallography, hardness, and conventional and impression creep tests. The fusion zone of the single-pass joint consisted of columnar zones adjacent to base metals with a central equiaxed zone, which have been modified extensively by the thermal cycle of the second pass in the dual-pass joint. The equiaxed zone in the single-pass joint, as well as in the second pass of the dual-pass joint, displayed the lowest hardness in the joints. In the dual-pass joint, the equiaxed zone of the first pass had hardness comparable to the columnar zone. The hardness variations in the joints influenced the creep deformation. The equiaxed and columnar zone in the first pass of the dual-pass joint was more creep resistant than that of the second pass. Both joints possessed lower creep rupture life than the base metal. However, the creep rupture life of the dual-pass joint was about twofolds more than that of the single-pass joint. Creep failure in the single-pass joint occurred in the central equiaxed fusion zone, whereas creep cavitation that originated in the second pass was blocked at the weld pass interface. The additional interface and strength variation between two passes in the dual-pass joint provides more restraint to creep deformation and crack propagation in the fusion zone, resulting in an increase in the creep rupture life of the dual-pass joint over the single-pass joint. Furthermore, the differences in content, morphology, and distribution of delta ferrite in the fusion zone of the joints favors more creep cavitation resistance in the dual-pass joint over the single-pass joint with the enhancement of creep rupture life.

Establishment of human induced pluripotent stem cell lines from normal fibroblast TIG-1.

PubMed

Kumazaki, Tsutomu; Kurata, Sayaka; Matsuo, Taira; Mitsui, Youji; Takahashi, Tomoko

2011-06-01

Normal human cells have a replicative life span and therefore senesce. Usually, normal human cell strains are differentiated cells and reach a terminally differentiated state after a number of cell divisions. At present, definitive differences are not known between replicative senescence and terminal differentiation. TIG-1 is a human fibroblast strain established from fetal lung and has been used extensively in studies of cellular senescence, and numerous data were accumulated at the molecular level. Recently, a method for generating induced pluripotent stem cells (iPSCs) was developed. Using the method, we introduced four reprogramming genes to TIG-1 fibroblasts and succeeded in isolating colonies that had embryonic stem cell (ESC)-like morphologies. They showed alkaline phosphatase activity and expressed ESC markers, as shown by immunostaining of OCT4, SOX2, SSEA4, and TRA-1-81 as well as reverse-transcription polymerase chain reaction (RT-PCR) for OCT4 and NANOG transcripts. Thus, we succeeded in establishing iPSC clones from TIG-1. The iPSC clones could differentiate to cells originated from all three germ-cell layers, as shown by RT-PCR, for messenger RNA (mRNA) expression of α-fetoprotein (endoderm), MSX1 (mesoderm) and microtubule-associated protein 2 (ectoderm), and by immunostaining for α-fetoprotein (endoderm), α-smooth muscle actin (mesoderm), and β-III-tubulin (ectoderm). The iPSCs formed teratoma containing the structures developed from all three germ-cell layers in severe combined immune-deficiency mice. Thus, by comparing the aging process of parental TIG-1 cells and the differentiation process of iPSC-derived fibrocytes to fibroblasts, we can reveal the exact differences in processes between senescence and terminal differentiation.

Crack Growth of D6 Steel in Air and High Pressure Oxygen

NASA Technical Reports Server (NTRS)

Bixler, W. D.; Engstrom, W. L.

1971-01-01

Fracture and subcritical flaw growth characteristics were experimentally deter­mined for electroless nickel plated D6 steel in dry air and high pressure oxygen environments as applicable to the Lunar Module/Environmental Control System (LM/ECS) descent gaseous oxygen (GOX) tank. The material tested included forgings, plate, and actual LM/ECS descent GOX tank material. Parent metal and TIG (tungsten inert gas) welds were tested. Tests indicate that proof testing the tanks at 4000 pounds per square inch or higher will insure safe operation at 3060 pounds per square inch. Although significant flaw growth can occur during proofing, subsequent growth of flaws during normal tank operation is negligible.

Respiratory symptoms and lung function change in welders: are they associated with workplace exposures?

PubMed

Fishwick, David; Bradshaw, Lisa; Slater, Tania; Curran, Andrew; Pearce, Neil

2004-05-07

This study investigates whether work-related respiratory symptoms and acute falls in forced expiratory volume in 1 second (FEV1), previously observed in current welders, are related to measured workplace exposures to total fume and metals. At four work sites in New Zealand, changes in pulmonary function (and reported respiratory symptoms) were recorded in 49 welding workers (and 26 non-welders) exposed to welding fume. We also determined the personal breathing zone levels of total fume and various metals. Work-related respiratory symptoms were reported by 26.5% of welders and 11.5% of non-welders. These symptoms were related significantly to their personal breathing zone nickel exposure--with an adjusted odds ratio (OR) and 95% confidence interval [CI] of the high exposure group (compared to a low exposure group of 7.0 [1.3-36.6]). There were non-significant associations with total fume exposure (OR = 2.6, 95% CI 0.6-12.2), and exposure index of greater than 10 years (OR=2.8, 95% CI 0.5-15.0). A fall in FEV1 of at least 5% after 15 minutes of work was significantly associated with aluminium exposure (OR=5.8, 95% CI 1.7-20.6). Nickel exposure from metal inert gas (MIG) and tungsten inert gas (TIG) welding is associated with work-related respiratory symptoms and aluminium exposure from welding is associated with a fall in FEV1 of at least 5 % after 15 minutes of work.

Upgrade of the LHC magnet interconnections thermal shielding

NASA Astrophysics Data System (ADS)

Musso, Andrea; Barlow, Graeme; Bastard, Alain; Charrondiere, Maryline; Chrul, Anna; Damianoglou, Dimitrios; Deferne, Guy; Dib, Gaëlle; Duret, Max; Guinchard, Michael; Prin, Hervé; Strychalski, Michał; Craen, Arnaud Vande; Villiger, Gilles; Wright, Loren

2014-01-01

The about 1700 interconnections (ICs) between the Large Hadron Collider (LHC) superconducting magnets include thermal shielding at 50-75 K, providing continuity to the thermal shielding of the magnet cryostats to reduce the overall radiation heat loads to the 1.9 K helium bath of the magnets. The IC shield, made of aluminum, is conduction-cooled via a welded bridge to the thermal shield of the adjacent magnets which is actively cooled. TIG welding of these bridges made in the LHC tunnel at installation of the magnets induced a considerable risk of fire hazard due to the proximity of the multi-layer insulation of the magnet shields. A fire incident occurred in one of the machine sectors during machine installation, but fortunately with limited consequences thanks to prompt intervention of the operators. LHC is now undergoing a 2 years technical stop during which all magnet's ICs will have to be opened to consolidate the magnet electrical connections. The IC thermal shields will therefore have to be removed and re-installed after the work is completed. In order to eliminate the risk of fire hazard when re-welding, it has been decided to review the design of the IC shields, by replacing the welded bridges with a mechanical clamping which also preserves its thermal function. An additional advantage of this new solution is the ease in dismantling for maintenance, and eliminating weld-grinding operations at removal needing radioprotection measures because of material activation after long-term operation of the LHC. This paper describes the new design of the IC shields and in particular the theoretical and experimental validation of its thermal performance. Furthermore a status report of the on-going upgrade work in the LHC is given.

Impaired ATP6V0A2 expression contributes to Golgi dispersion and glycosylation changes in senescent cells.

PubMed

Udono, Miyako; Fujii, Kaoru; Harada, Gakuro; Tsuzuki, Yumi; Kadooka, Keishi; Zhang, Pingbo; Fujii, Hiroshi; Amano, Maho; Nishimura, Shin-Ichiro; Tashiro, Kosuke; Kuhara, Satoru; Katakura, Yoshinori

2015-11-27

Many genes and signaling pathways have been found to be involved in cellular senescence program. In the present study, we have identified 16 senescence-associated genes by differential proteomic analysis of the normal human diploid fibroblast cell line, TIG-1, and focused on ATP6V0A2. The aim of this study is to clarify the role of ATP6V0A2, the causal gene for ARCL2, a syndrome of abnormal glycosylation and impaired Golgi trafficking, in cellular senescence program. Here we showed that ATP6V0A2 is critical for cellular senescence; impaired expression of ATP6V0A2 disperses the Golgi structure and triggers senescence, suggesting that ATP6V0A2 mediates these processes. FITC-lectin staining and glycoblotting revealed significantly different glycosylation structures in presenescent (young) and senescent (old) TIG-1 cells; reducing ATP6V0A2 expression in young TIG-1 cells yielded structures similar to those in old TIG-1 cells. Our results suggest that senescence-associated impaired expression of ATP6V0A2 triggers changes in Golgi structure and glycosylation in old TIG-1 cells, which demonstrates a role of ATP6V0A2 in cellular senescence program.

Impaired ATP6V0A2 expression contributes to Golgi dispersion and glycosylation changes in senescent cells

PubMed Central

Udono, Miyako; Fujii, Kaoru; Harada, Gakuro; Tsuzuki, Yumi; Kadooka, Keishi; Zhang, Pingbo; Fujii, Hiroshi; Amano, Maho; Nishimura, Shin-Ichiro; Tashiro, Kosuke; Kuhara, Satoru; Katakura, Yoshinori

2015-01-01

Many genes and signaling pathways have been found to be involved in cellular senescence program. In the present study, we have identified 16 senescence-associated genes by differential proteomic analysis of the normal human diploid fibroblast cell line, TIG-1, and focused on ATP6V0A2. The aim of this study is to clarify the role of ATP6V0A2, the causal gene for ARCL2, a syndrome of abnormal glycosylation and impaired Golgi trafficking, in cellular senescence program. Here we showed that ATP6V0A2 is critical for cellular senescence; impaired expression of ATP6V0A2 disperses the Golgi structure and triggers senescence, suggesting that ATP6V0A2 mediates these processes. FITC-lectin staining and glycoblotting revealed significantly different glycosylation structures in presenescent (young) and senescent (old) TIG-1 cells; reducing ATP6V0A2 expression in young TIG-1 cells yielded structures similar to those in old TIG-1 cells. Our results suggest that senescence-associated impaired expression of ATP6V0A2 triggers changes in Golgi structure and glycosylation in old TIG-1 cells, which demonstrates a role of ATP6V0A2 in cellular senescence program. PMID:26611489

The Stress Corrosion Resistance and the Cryogenic Temperature Mechanical Behavior of 18-3 Mn (Nitronic 33) Stainless Steel Parent and Welded Material

NASA Technical Reports Server (NTRS)

Montano, J. W.

1976-01-01

The ambient and cryogenic temperature mechanical properties and the ambient temperature stress corrosion results of 18-3 Mn (Nitronic 33)stainless steel, longitudinal and transverse, as received and as welded (TIG) material specimens manufactured from 0.063 inch thick sheet material, were described. The tensile test results indicate an increase in ultimate tensile and yield strengths with decreasing temperature. The elongation remained fairly constant to -200 F, but below that temperature the elongation decreased to less than 6.0% at liquid hydrogen temperature. The notched tensile strength (NTS) for the parent metal increased with decreasing temperature to liquid nitrogen temperature. Below -320 F the NTS decreased rapidly. The notched/unnotched (N/U) tensile ratio of the parent material specimens remained above 0.9 from ambient to -200 F, and decreased to approximately 0.65 and 0.62, respectively, for the longitudinal and transverse directions at liquid hydrogen temperature. After 180 days of testing, only those specimens exposed to the salt spray indicated pitting and some degradation of mechanical properties.

A Three-Stage Mechanistic Model for Solidification Cracking During Welding of Steel

NASA Astrophysics Data System (ADS)

Aucott, L.; Huang, D.; Dong, H. B.; Wen, S. W.; Marsden, J.; Rack, A.; Cocks, A. C. F.

2018-03-01

A three-stage mechanistic model for solidification cracking during TIG welding of steel is proposed from in situ synchrotron X-ray imaging of solidification cracking and subsequent analysis of fracture surfaces. Stage 1—Nucleation of inter-granular hot cracks: cracks nucleate inter-granularly in sub-surface where maximum volumetric strain is localized and volume fraction of liquid is less than 0.1; the crack nuclei occur at solute-enriched liquid pockets which remain trapped in increasingly impermeable semi-solid skeleton. Stage 2—Coalescence of cracks via inter-granular fracture: as the applied strain increases, cracks coalesce through inter-granular fracture; the coalescence path is preferential to the direction of the heat source and propagates through the grain boundaries to solidifying dendrites. Stage 3—Propagation through inter-dendritic hot tearing: inter-dendritic hot tearing occurs along the boundaries between solidifying columnar dendrites with higher liquid fraction. It is recommended that future solidification cracking criterion shall be based on the application of multiphase mechanics and fracture mechanics to the failure of semi-solid materials.

Rapid emergence of high-level tigecycline resistance in Escherichia coli strains harbouring blaNDM-5 in vivo.

PubMed

Li, Xi; Mu, Xinli; Yang, Yunxing; Hua, Xiaoting; Yang, Qing; Wang, Nanfei; Du, Xiaoxing; Ruan, Zhi; Shen, Xiaoqiang; Yu, Yunsong

2016-04-01

Tigecycline (TIG) resistance is a growing concern because this antibiotic is regarded as one of the last resorts to treat infections caused by multidrug-resistant and extensively drug-resistant (XDR) bacteria. Information regarding TIG-resistant Escherichia coli isolates is scarce. In this study, we report the emergence of high-level TIG resistance in a longitudinal series of XDR E. coli isolates collected during TIG treatment. Whole-genome sequencing was performed for six E. coli strains harbouring bla(NDM-5) and genomic comparison revealed two amino acid substitutions. Mutation in rpsJ could be a significant factor conferring TIG resistance in these isolates. The fitness cost of TIG resistance in resistant strains was evaluated by determining the relative growth rate, indicating that TIG resistance reduced fitness by ca. 7%. This study is the first report to demonstrate high-level TIG resistance in E. coli in vivo. In addition, we report the first treatment-emergent minimum inhibitory concentration (MIC) development of TIG from 1mg/L to 64 mg/L in E. coli. Clinicians should be aware of the risk of an increase in the MIC of TIG under therapy. Copyright © 2016 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

Susceptibility of Candida albicans biofilms to azithromycin, tigecycline and vancomycin and the interaction between tigecycline and antifungals.

PubMed

Ku, Tsun Sheng N; Palanisamy, Suresh K A; Lee, Samuel A

2010-11-01

Despite growing data on antimicrobial lock therapy (ALT) in treating bacterial catheter-related bloodstream infections (CR-BSIs), ALT has not been established as a treatment option for CR-BSI caused by Candida albicans. Based on our finding that high-dose doxycycline exhibited antifungal activity against mature C. albicans biofilms, we evaluated additional antibacterial agents with Gram-positive activity [azithromycin, tigecycline (TIG) and vancomycin]. After screening these antibiotics, it was found that TIG had substantial antifungal activity against mature C. albicans biofilms. Therefore, TIG was assayed alone and in combination with fluconazole (FLC), amphotericin B (AmB) or caspofungin (CAS). TIG at 2048 μg/mL resulted in a >50% reduction in the growth of planktonic C. albicans cells. TIG inhibited the formation of biofilms from 128 μg/mL. Against mature biofilms, 2048 μg/mL TIG reduced metabolic activity by 84.2%. Furthermore, addition of 512 μg/mL TIG to FLC at all concentrations tested provided additional reduction in the metabolic activity of mature biofilms. However, this was not superior to 512 μg/mL TIG alone. TIG at 512 μg/mL increased the antifungal effect of lower concentrations of AmB (0.03125-0.25 μg/mL), but at 0.03125 μg/mL and 0.0625 μg/mL this effect was not superior to 512 μg/mL TIG alone. TIG inhibited the antifungal effect of higher concentrations of AmB (≥ 2 μg/mL). TIG at 512 μg/mL inhibited the antifungal activity of CAS at lower concentrations (0.25-8 μg/mL). These data indicate that high-dose TIG is highly active in vitro against planktonic cells, forming biofilms and mature biofilms of C. albicans. Published by Elsevier B.V.

Development and trial manufacturing of 1/2-scale partial mock-up of blanket box structure for fusion experimental reactor

NASA Astrophysics Data System (ADS)

Hashimoto, Toshiyuki; Takatsu, Hideyuki; Sato, Satoshi

1994-07-01

Conceptual design of breeding blanket has been discussed during the CDA (Conceptual Design Activities) of ITER (International Thermonuclear Experimental Reactor). Structural concept of breeding blanket is based on box structure integrated with first wall and shield, which consists of three coolant manifolds for first wall, breeding and shield regions. The first wall must have cooling channels to remove surface heat flux and nuclear heating. The box structure includes plates to form the manifolds and stiffening ribs to withstand enormous electromagnetic load, coolant pressure and blanket internal (purge gas) pressure. A 1/2-scale partial model of the blanket box structure for the outboard side module near midplane is manufactured to estimate the fabrication technology, i.e. diffusion bonding by HIP (Hot Isostatic Pressing) and EBW (Electron Beam Welding) procedure. Fabrication accuracy is a key issue to manufacture first wall panel because bending deformation during HIP may not be small for a large size structure. Data on bending deformation during HIP was obtained by preliminary manufacturing of HIP elements. For the shield structure, it is necessary to reduce the welding strain and residual stress of the weldment to establish the fabrication procedure. Optimal shape of the parts forming the manifolds, welding locations and welding sequence have been investigated. In addition, preliminary EBW tests have been performed in order to select the EBW conditions, and fundamental data on built-up shield have been obtained. Especially, welding deformation by joining the first wall panel to the shield has been measured, and total deformation to build-up shield by EBW has been found to be smaller than 2 mm. Consequently, the feasibility of fabrication technologies has been successfully demonstrated for a 1m-scaled box structure including the first wall with cooling channels by means of HIP, EBW and TIG (Tungsten Inert Gas arc)-welding.

The emergence of clinical resistance to tigecycline.

PubMed

Sun, Yan; Cai, Yun; Liu, Xu; Bai, Nan; Liang, Beibei; Wang, Rui

2013-02-01

Tigecycline (TIG) exhibits broad-spectrum activity against many Gram-positive and Gram-negative pathogens. However, clinical resistance has emerged recently and has been detected following treatment with TIG. This observation suggests that long-term monotherapy may carry a high risk for TIG resistance. TIG resistance is observed most frequently in Acinetobacter baumannii and Enterobacteriaceae, especially in multidrug-resistant strains. Resistance-nodulation-cell division (RND)-type transporters and other efflux pumps may be factors for decreased sensitivity to TIG. Therefore, TIG should be cautiously used in the clinic, and efflux-mediated resistance should be closely monitored in order to prolong the lifespan of this useful antibiotic. Copyright © 2012 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

Lewis lung carcinoma progression is facilitated by TIG-3 fibroblast cells.

PubMed

Yamauchi, Yoshikane; Izumi, Yotaro; Asakura, Keisuke; Kawai, Kenji; Wakui, Masatoshi; Ohmura, Mitsuyo; Suematsu, Makoto; Nomori, Hiroaki

2013-09-01

The interactions of tumor cells with stromal fibroblasts influence tumor biology, but the exact mechanisms involved are still unclear. In the present study, we evaluated the effects of a human lung fibroblast cell line, TIG-3, on Lewis lung carcinoma (LLC) cells both in vitro and in vivo. LLC and TIG-3 cells were co-cultured/co-implanted in vitro and in vivo. Cell invasion was assayed. Local tumor growth, as well as lung metastasis, were evaluated after subcutaneous cell co-implantation into NOD/SCID/γ-null (NOG) mice. LLC, and TIG-3 cells were pre-treated with either SB431542, a small molecule TGF-β receptor antagonist, or siRNA for transforming growth factor (TGF)-β before co-culture or co-implantation, and the effects of pre-treatments were compared both in cell culture and in mice. Subcutaneous LLC tumor growth (L group) in NOG mice was significantly increased by co-implantation of TIG-3 cells (L+T group) at four weeks. The number of macroscopic lung metastases was also significantly increased in the L+T group in comparison to the L group. In vitro cell invasion was significantly increased in the L+T group in comparison to the L group. In vitro expression of phosphorylated-SMAD3 was significantly increased in the L+T group in comparison to the L group. Furthermore, pre-treatment with either SB431542 or siRNA for TGF-β reduced the invasiveness both in culture and in mice. This study suggested that in vitro as well as in vivo progression of LLC was facilitated by co-culture/co-implantation with TIG-3 cells, and that this process was at least in part dependent on TGF-β-mediated interactions.

Cooperative role of calnexin and TigA in Aspergillus oryzae glycoprotein folding.

PubMed

Wang, Ning; Seko, Akira; Takeda, Yoichi; Kikuma, Takashi; Ito, Yukishige

2015-10-01

Calnexin (CNX), known as a lectin chaperone located in the endoplasmic reticulum (ER), specifically recognizes G1M9GN2-proteins and facilitates their proper folding with the assistance of ERp57 in mammalian cells. However, it has been left unidentified how CNX works in Aspergillus oryzae, which is a filamentous fungus widely exploited in biotechnology. In this study, we found that a protein disulfide isomerase homolog TigA can bind with A. oryzae CNX (AoCNX), which was revealed to specifically recognize monoglucosylated glycans, similarly to CNX derived from other species, and accelerate the folding of G1M9GN2-ribonuclease (RNase) in vitro. For refolding experiments, a homogeneous monoglucosylated high-mannose-type glycoprotein G1M9GN2-RNase was chemoenzymatically synthesized from G1M9GN-oxazoline and GN-RNase. Denatured G1M9GN2-RNase was refolded with highest efficiency in the presence of both soluble form of AoCNX and TigA. TigA contains two thioredoxin domains with CGHC motif, mutation analysis of which revealed that the one in N-terminal regions is involved in binding to AoCNX, while the other in catalyzing protein refolding. The results suggested that in glycoprotein folding process of A. oryzae, TigA plays a similar role as ERp57 in mammalian cells, as a partner protein of AoCNX. © The Author 2015. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Reduced susceptibility of Enterococcus spp. isolates from Cairo University Hospital to tigecycline: Highlight on the influence of proton pump inhibitors.

PubMed

Hassan, Reem Mostafa; Ghaith, Doaa Mohammad; Ismail, Dalia Kadry; Zafer, Mai Mahmoud

2018-03-01

The incidence of reduced susceptibility to tigecycline (TIG) is increasing. This study aimed to analyse the in vitro activity of TIG against Enterococcus spp. isolates recovered from hospitalised patients and to evaluate the effect of omeprazole on the in vitro antimicrobial activity of TIG against several enterococcal species. A total of 67 Enterococcus clinical isolates were identified by MALDI-TOF/MS and multiplex PCR. Minimum inhibitory concentrations (MICs) of TIG alone and in combination with omeprazole (10, 30 and 60mg/L) were determined by broth microdilution. Antibiotic susceptibility to other antibiotics was determined by disk diffusion. The presence of van, tet(X) and tet(X1) genes was tested by multiplex PCR. Of the 67 Enterococcus isolates, 2 (3.0%) were resistant to TIG and 13 (19.4%) were intermediate-resistant according to EUCAST. The frequencies of resistance to norfloxacin (80.6%), doxycycline (80.6%), levofloxacin (74.6%) and ciprofloxacin (71.6%) were highest, whilst that of vancomycin (25.4%) was lowest. The vanA gene was detected in 11 Enterococcus isolates (8 Enterococcus faecalis, 3 Enterococcus faecium), vanB in 3 Enterococcus isolates (2 E. faecium, 1 E. faecalis) and vanC-2/3 in 3 Enterococcus casseliflavus. Nine isolates (13.4%) were positive for tet(X1). TIG resistance occurred both in patients receiving or not TIG and/or omeprazole. Omeprazole increased TIG MICs by 4-128-fold. The possibility of selection of TIG-non-susceptible Enterococcus in the gut may occur with long-term use of omeprazole. Omeprazole influenced TIG activity in a concentration-dependent manner. To our knowledge; this is the first report of TIG-non-susceptible Enterococcus spp. in Egypt. Copyright © 2017 International Society for Chemotherapy of Infection and Cancer. Published by Elsevier Ltd. All rights reserved.

TBCRC 019: A Phase II Trial of Nanoparticle Albumin-Bound Paclitaxel with or without the Anti-Death Receptor 5 Monoclonal Antibody Tigatuzumab in Patients with Triple-Negative Breast Cancer.

PubMed

Forero-Torres, Andres; Varley, Katherine E; Abramson, Vandana G; Li, Yufeng; Vaklavas, Christos; Lin, Nancy U; Liu, Minetta C; Rugo, Hope S; Nanda, Rita; Storniolo, Anna M; Traina, Tiffany A; Patil, Sujata; Van Poznak, Catherine H; Nangia, Julie R; Irvin, William J; Krontiras, Helen; De Los Santos, Jennifer F; Haluska, Paul; Grizzle, William; Myers, Richard M; Wolff, Antonio C

2015-06-15

Tigatuzumab (TIG), an agonistic anti-DR5 antibody, triggers apoptosis in DR5(+) human tumor cells without crosslinking. TIG has strong in vitro/in vivo activity against basal-like breast cancer cells enhanced by chemotherapy agents. This study evaluates activity of TIG and chemotherapy in patients with metastatic triple-negative breast cancer (TNBC). Randomized 2:1 phase II trial of albumin-bound paclitaxel (nab-PAC) ± TIG in patients with TNBC stratified by prior chemotherapy. Patients received nab-PAC weekly × 3 ± TIG every other week, every 28 days. Primary objective was within-arm objective response rate (ORR). Secondary objectives were safety, progression-free survival (PFS), clinical benefit, and TIG immunogenicity. Metastatic research biopsies were required. Among 64 patients (60 treated; TIG/nab-PAC n = 39 and nab-PAC n = 21), there were 3 complete remissions (CR), 8 partial remissions (PR; 1 almost CR), 11 stable diseases (SD), and 17 progressive diseases (PD) in the TIG/nab-PAC arm (ORR, 28%), and no CRs, 8 PRs, 4 SDs, and 9 PDs in the nab-PAC arm (ORR, 38%). There was a numerical increase in CRs and several patients had prolonged PFS (1,025+, 781, 672, 460, 334) in the TIG/nab-PAC arm. Grade 3 toxicities were 28% and 29%, respectively, with no grade 4-5. Exploratory analysis suggests an association of ROCK1 gene pathway activation with efficacy in the TIG/nab-PAC arm. ORR and PFS were similar in both. Preclinical activity of TIG in basal-like breast cancer and prolonged PFS in few patients in the combination arm support further investigation of anti-DR5 agents. ROCK pathway activation merits further evaluation. ©2015 American Association for Cancer Research.

In vitro activity of tigecycline and comparators against gram-negative bacteria isolated from a tertiary hospital in Alexandria, Egypt.

PubMed

Mohamed, Nelly M; Youssef, Alaa A F

2011-12-01

The emergence of infections caused by multidrug-resistant Gram-negative bacteria, in particular Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae, has necessitated the search for alternative therapy by either introducing new agents or renewing interest in old agents. This study compares the in vitro activity of tigecycline (TIG), recently introduced to Egyptian market, to other potentially active antimicrobials as Colistin (COL), imipenem (IPM), levofloxacin (LEV), and piperacillin/tazobactam (PIP/TAZ) against 67 Gram-negative clinical isolates obtained from El- Meery Hospital in Alexandria, Egypt. El-Meery Hospital is a 1,500-bed tertiary teaching hospital where TIG has not been previously used. Based on MIC(90)s, TIG was found to be a comparator to IPM and COL (MIC(90)= 8 μg/ml). LEV and PIP/TAZ were less active than TIG exhibiting high MIC(90)s. TIG inhibited 100% of Escherichia coli and K. pneumoniae and 60% of Ps. aeruginosa and A. baumannii isolates. In time-kill studies against IPM-resistant isolates, TIG showed bactericidal activity after 6 hours of contact against the Enterobacteriaceae isolates and after 3 hours for the tested Ps. aeruginosa isolates at 4× and 8× MIC. Against A. baumannii, TIG exerted a bacteriostatic effect. TIG demonstrated variable ability to suppress biofilm formation affecting mainly E. coli and A. baumannii isolates. These results point TIG to be a promising agent in treatment of infections caused by strains for which adequate therapy has been limited. As far as we know, this is the first report evaluating the in vitro activity of TIG against Egyptian clinical isolates.

The Antibiotic Drug Tigecycline: A Focus on its Promising Anticancer Properties

PubMed Central

Xu, Zhijie; Yan, Yuanliang; Li, Zhi; Qian, Long; Gong, Zhicheng

2016-01-01

Tigecycline (TIG), the first member of glycylcycline bacteriostatic agents, has been approved to treat complicated infections in the clinic because of its expanded-spectrum antibiotic potential. Recently, an increasing number of studies have emphasized the anti-tumor effects of TIG. The inhibitory effects of TIG on cancer depend on several activating signaling pathways and abnormal mitochondrial function in cancer cells. The aim of this review is to summarize the cumulative anti-tumor evidence supporting TIG activity against different cancer types, including acute myeloid leukemia (AML), glioma, non-small cell lung cancer (NSCLC), among others. In addition, the efficacy and side effects of TIG in cancer patients are summarized in detail. Future clinical trials are also to be discussed that will evaluate the security and validate the underlying the tumor-killing properties of TIG. PMID:27994551

The Antibiotic Drug Tigecycline: A Focus on its Promising Anticancer Properties.

PubMed

Xu, Zhijie; Yan, Yuanliang; Li, Zhi; Qian, Long; Gong, Zhicheng

2016-01-01

Tigecycline (TIG), the first member of glycylcycline bacteriostatic agents, has been approved to treat complicated infections in the clinic because of its expanded-spectrum antibiotic potential. Recently, an increasing number of studies have emphasized the anti-tumor effects of TIG. The inhibitory effects of TIG on cancer depend on several activating signaling pathways and abnormal mitochondrial function in cancer cells. The aim of this review is to summarize the cumulative anti-tumor evidence supporting TIG activity against different cancer types, including acute myeloid leukemia (AML), glioma, non-small cell lung cancer (NSCLC), among others. In addition, the efficacy and side effects of TIG in cancer patients are summarized in detail. Future clinical trials are also to be discussed that will evaluate the security and validate the underlying the tumor-killing properties of TIG.

Molecular characterization of a feline calicivirus isolated from tiger and its pathogenesis in cats.

PubMed

Tian, Jin; Liu, Dafei; Liu, Yongxiang; Wu, Hongxia; Jiang, Yanmei; Zu, Shaopo; Liu, Chunguo; Sun, Xue; Liu, Jiasen; Qu, Liandong

2016-08-30

Feline calicivirus (FCV) is a virus that causes respiratory disease in cats. In this study, the FCV TIG-1 was isolated from Siberian tiger feces collected in 2014 in Heilongjiang Province, China. Phylogenetic analysis among TIG-1 and other FCVs showed that TIG-1 does not share the same lineage with other FCV isolates from Heilongjiang or other regions in China but is located in the same cluster with the FCV strain Urbana, which was isolated from the United States. The growth kinetics in vitro and the pathogenicity in cats between TIG-1 and the domestic cat-origin FCV strain F9 (vaccine strain) and strain 2280 were compared. We found that the growth kinetics of strains TIG-1 and 2280 were faster than that of strain F9 from 12h to 36h post-infection, indicating that strains TIG-1 and 2280 produce infectious virions and reach peak yields earlier. Challenge experiments in cats showed that TIG-1 grew faster than the other two strains in the lungs of cats and that TIG-1 is a virulent FCV with 100% morbidity and lethality. In addition, the histopathological results showed that the virulent TIG-1 strain directly led to severe lung tissue damage and indirectly led to intestinal damage. The results presented here show that a tiger-origin FCV exhibits high virulence in cats. Copyright © 2016 Elsevier B.V. All rights reserved.

Single Center Retrospective Analysis of Conventional and Radial TIG Catheters for Transradial Diagnostic Coronary Angiography.

PubMed

Vorpahl, Marc; Koehler, Till; Foerst, Jason; Panagiotopoulos, Spyridon; Schleiting, Heinrich; Koss, Klaus; Ziegler, Gunda; Brinkmann, Hilmar; Seyfarth, Melchior; Tiroch, Klaus

2015-01-01

Current guidelines favor the radial approach for coronary angiography. Therefore, specialty radial diagnostic catheters were designed to engage both coronary arteries with a single device. However, it is unclear if single catheters are superior to conventional catheters. A retrospective analysis was performed of consecutive right radial coronary angiographies to determine catheter use, fluoroscopy time, radiation dosage, and consumption of contrast. Procedures were performed with a single TIG catheter or conventional catheters (CONV). Procedures with coronary artery bypass grafts or ventricular angiographies were excluded. 273 transradial procedures were performed successfully. 95 procedures were performed with CONV and 178 procedures with a TIG. Crossover to additional catheters was higher in TIG (15.2%) compared to CONV (5.3%, p = 0.02). Fluoroscopy time was comparable between CONV and TIG, without crossover (2.2 ± 1.2 min versus 2.3 ± 1.2 min; n.s.), however, greater in the case of crossover for CONV (5.8 ± 0.7) and TIG (7.6 ± 3.0; p = 0.0001). Radiation dosage was similar in CONV and the TIG, without crossover (1419 ± 1075, cGy∗cm(2) versus 1690 ± 1138; n.s.), however, greater for CONV (2374 ± 620) and TIG (3733 ± 2281, p = 0.05) with crossover. Overall, the amount of contrast was greater in TIG (56 ± 13 mL) versus CONV (48 ± 3 mL; p = 0.0003). CONV femoral catheters may be the primary choice for radial approach.

Effect of Heat Input on Microstructural Changes and Corrosion Behavior of Commercially Pure Titanium Welds in Nitric Acid Medium

NASA Astrophysics Data System (ADS)

Ravi Shankar, A.; Gopalakrishnan, G.; Balusamy, V.; Kamachi Mudali, U.

2009-11-01

Commercially pure titanium (Ti) has been selected for the fabrication of dissolver for the proposed fast reactor fuel reprocessing plant at Kalpakkam, India. In the present investigation, microstructural changes and corrosion behavior of tungsten inert gas (TIG) welds of Ti grade-1 and grade-2 with different heat inputs were carried out. A wider heat affected zone was observed with higher heat inputs and coarse grains were observed from base metal toward the weld zone with increasing heat input. Fine and more equiaxed prior β grains were observed at lower heat input and the grain size increased toward fusion zone. The results indicated that Ti grade-1 and grade-2 with different heat inputs and different microstructures were insensitive to corrosion in liquid, vapor, and condensate phases of 11.5 M nitric acid tested up to 240 h. The corrosion rate in boiling liquid phase (0.60-0.76 mm/year) was higher than that in vapor (0.012-0.039 mm/year) and condensate phases (0.04-0.12 mm/year) of nitric acid for Ti grade-1 and grade-2, as well as for base metal for all heat inputs. Potentiodynamic polarization experiment carried out at room temperature indicated higher current densities and better passivation in 11.5 M nitric acid. SEM examination of Ti grade-1 welds for all heat inputs exposed to liquid phase after 240 h showed corrosion attack on the surface, exposing Widmanstatten microstructure containing acicular alpha. The continuous dissolution of the liquid-exposed samples was attributed to the heterogeneous microstructure and non-protective passive film formation.

Single Center Retrospective Analysis of Conventional and Radial TIG Catheters for Transradial Diagnostic Coronary Angiography

PubMed Central

Vorpahl, Marc; Koehler, Till; Foerst, Jason; Panagiotopoulos, Spyridon; Schleiting, Heinrich; Koss, Klaus; Ziegler, Gunda; Brinkmann, Hilmar; Seyfarth, Melchior; Tiroch, Klaus

2015-01-01

Current guidelines favor the radial approach for coronary angiography. Therefore, specialty radial diagnostic catheters were designed to engage both coronary arteries with a single device. However, it is unclear if single catheters are superior to conventional catheters. A retrospective analysis was performed of consecutive right radial coronary angiographies to determine catheter use, fluoroscopy time, radiation dosage, and consumption of contrast. Procedures were performed with a single TIG catheter or conventional catheters (CONV). Procedures with coronary artery bypass grafts or ventricular angiographies were excluded. 273 transradial procedures were performed successfully. 95 procedures were performed with CONV and 178 procedures with a TIG. Crossover to additional catheters was higher in TIG (15.2%) compared to CONV (5.3%, p = 0.02). Fluoroscopy time was comparable between CONV and TIG, without crossover (2.2 ± 1.2 min versus 2.3 ± 1.2 min; n.s.), however, greater in the case of crossover for CONV (5.8 ± 0.7) and TIG (7.6 ± 3.0; p = 0.0001). Radiation dosage was similar in CONV and the TIG, without crossover (1419 ± 1075, cGy∗cm2 versus 1690 ± 1138; n.s.), however, greater for CONV (2374 ± 620) and TIG (3733 ± 2281, p = 0.05) with crossover. Overall, the amount of contrast was greater in TIG (56 ± 13 mL) versus CONV (48 ± 3 mL; p = 0.0003). CONV femoral catheters may be the primary choice for radial approach. PMID:26435876

Is there any difference in tetanus IgG levels of diabetic patientswith respect to the presence of foot ulcers?

PubMed

Tekin, Fatih; Sürmeli, Mehmet; Çizmeci, Zeynep; Tekin, Özlem; Işik, Ergin; Taner, Ömer Faruk; Ertuğrul, Derun Taner

2017-02-27

The aim of this study was to reveal the tetanus immunization status of diabetic patients and to determine whether diabetic patients with foot ulcers have different TIG levels. A cross-sectional study was designed that included diabetic patients with foot ulcers (n = 30) and diabetic patients without ulcers (n = 30). The groups were compared for serum TIG levels along with total serum protein, albumin, C-reactive protein (CRP), and total immunoglobulin G (Ig G). For diabetic patients without foot ulcers, 17 of 30 (56.6%) patients were found to have nonprotective TIG levels whereas for diabetic patients with foot ulcers, 28 of 30 (93.3%) patients were found to have nonprotective TIG levels. The mean value of TIG for diabetic patients without foot ulcers was 0.345 ± 0.281 IU/mL and for diabetic patients with foot ulcers the mean TIG value was 0.055 ± 0.033 IU/mL. Statistically significant differences were observed in TIG (P = 0.008), total protein (P < 0.001), albumin (P < 0.001), and CRP levels (P < 0.001) between the two groups. The majority of the diabetic patients had low TIG levels and they were significantly lower in diabetic patients with ulcers. A booster dose of tetanus vaccine should be considered for diabetic patients with and without diabetic foot ulcers.

Efficacy versus health risks: An in vitro evaluation of power-driven scalers.

PubMed

Graetz, Christian; Plaumann, Anna; Bielfeldt, Jule; Tillner, Anica; Sälzer, Sonja; Dörfer, Christof Edmund

2015-01-01

Power-driven instrumentation of root surfaces during supportive periodontal therapy is an alternative to hand instrumentation. The purpose of this pilot in vitro study was to investigate the efficacy of sub- and supragingival plaque removal with a sonic (AIR: Synea, W and H, Bürmoos, Austria) and two ultrasonic devices (TIG: Tigon+, W and H, Bürmoos, Austria; VEC: Vector, Dürr, Bietigheim-Bissingen, Germany) as well as the health-risk for dental professionals during treatment. The power-driven devices were utilized to remove plaque from model teeth in dummy heads. The percentage of residual artificial plaque after 2 min of supra- or subgingival instrumentation was calculated by means of image-processing techniques at four sites (n = 576) of each tooth. The Health-Risk-Index (HRI: spatter/residual plaque quotient) with the different power-driven devices was assessed during treatment. The smallest amounts of residual plaque were found for the sonic device AIR (8.89% ± 10.92%) and the ultrasonic scaler TIG (8.72% ± 12.02%) (P = 0.707). Significantly more plaque was remained after the use of the ultrasonic scaler VEC (18.76% ± 18.07%) (P < 0.001). Irrespectively of the scaler, efficacy was similar sub- (10.7% ± 11.6%) and supragingivally (13.5% ± 17.2%) (P = 0.901). AIR/TIG demonstrated equal residual amounts of plaque sub- (P = 0.831) as well as supragingivally (P = 0.510). However, AIR/VEC and TIG/VEC were significantly in favor of AIR and TIG (P < 0.001). In contrast, the lowest HRI was found after using VEC (0.0043) and differed considerably for AIR (0.2812) and TIG (0.0287). Sonic devices are as effective as ultrasonic devices in the removal of biofilm but bear a higher risk to the dental professional's health concerning the formation of spatter.

A novel glutamine-rich putative transcriptional adaptor protein (TIG-1), preferentially expressed in placental and bone-marrow tissues.

PubMed

Abraham, S; Solomon, W B

2000-09-19

We used a subtractive hybridization protocol to identify novel expressed sequence tags (ESTs) corresponding to mRNAs whose expression was induced upon exposure of the human leukemia cell line K562 to the phorbol ester 12-O-tetradecanolyphorbol-13-acetate (TPA). The complete open reading frame of one of the novel ESTs, named TIG-1, was obtained by screening K562 cell and placental cDNA libraries. The deduced open reading frame of the TIG-1 cDNA encodes for a glutamine repeat-rich protein with a predicted molecular weight of 63kDa. The predicted open reading frame also contains a consensus bipartite nuclear localization signal, though no specific DNA-binding domain is found. The corresponding TIG-1 mRNA is ubiquitously expressed. Placental tissue expresses the TIG-1 mRNA 200 times more than the lowest expressing tissues such as kidney and lung. There is also preferential TIG-1 mRNA expression in cells of bone-marrow lineage.In-vitro transcription/translation of the TIG-1 cDNA yielded a polypeptide with an apparent molecular weight of 97kDa. Using polyclonal antibodies obtained from a rabbit immunized with the carboxy-terminal portion of bacterially expressed TIG-1 protein, a polypeptide with molecular weight of 97kDa was identified by Western blot analyses of protein lysates obtained from K562 cells. Cotransfection assays of K562 cells, using a GAL4-TIG-1 fusion gene and GAL4 operator-CAT, indicate that the TIG-1 protein may have transcriptional regulatory activity when tethered to DNA. We hypothesize that this novel glutamine-rich protein participates in a protein complex that regulates gene transcription. It has been demonstrated by Naar et al. (Naar, A.M., Beaurang, P.A., Zhou, S., Abraham, S., Solomon, W.B., Tjian, R., 1999, Composite co-activator ARC mediates chromatin-directed transcriptional activation. Nature 398, 828-830) that the amino acid sequences of peptide fragments obtained from a polypeptide found in a complex of proteins that alters chromatin structure (ARC) are identical to portions of the deduced open reading frame of TIG-1 mRNA.

Genomic Analysis of Reduced Susceptibility to Tigecycline in Enterococcus faecium

PubMed Central

Isnard, Christophe; Cosquer, Thibaud; Odhiambo, Arlène; Bucquet, Fiona; Guérin, François; Giard, Jean-Christophe

2014-01-01

Tigecycline (TIG) is approved for use for the treatment of complicated intra-abdominal infections, skin and skin structure infections, as well as pneumonia. Acquired resistance or reduced susceptibility to TIG has been observed in Gram-negative rods, has seldom been reported in Gram-positive organisms, and has not yet been reported in Enterococcus faecium. Using the serial passage method, in vitro mutant AusTig and in vitro mutants HMtig1 and HMtig2 with decreased TIG susceptibility (MICs, 0.25 μg/ml) were obtained from strains E. faecium Aus0004 and HM1070 (MICs, 0.03 μg/ml), respectively. In addition, two vancomycin-resistant E. faecium clinical isolates (EF16 and EF22) with reduced susceptibility to TIG (MICs, 0.5 and 0.25 μg/ml, respectively) were studied. Compared to the wild-type strains, the in vitro mutants also showed an increase in the MICs of other tetracyclines. An efflux mechanism did not seem to be involved in the reduced TIG susceptibility, since the presence of efflux pump inhibitors (reserpine or pantoprazole) did not affect the MICs of TIG. Whole-genome sequencing of AusTig was carried out, and genomic comparison with the Aus0004 genome was performed. Four modifications leading to an amino acid substitution were found. These mutations affected the rpsJ gene (efau004_00094, coding for the S10 protein of the 30S ribosomal subunit), efau004_01228 (encoding a cation transporter), efau004_01636 (coding for a hypothetical protein), and efau004_02455 (encoding the l-lactate oxidase). The four other strains exhibiting reduced TIG susceptibility were screened for the candidate mutations. This analysis revealed that three of them showed an amino acid substitution in the same region of the RpsJ protein. In this study, we characterized for the first time genetic determinants linked to reduced TIG susceptibility in enterococci. PMID:25348531

Genomic analysis of reduced susceptibility to tigecycline in Enterococcus faecium.

PubMed

Cattoir, Vincent; Isnard, Christophe; Cosquer, Thibaud; Odhiambo, Arlène; Bucquet, Fiona; Guérin, François; Giard, Jean-Christophe

2015-01-01

Tigecycline (TIG) is approved for use for the treatment of complicated intra-abdominal infections, skin and skin structure infections, as well as pneumonia. Acquired resistance or reduced susceptibility to TIG has been observed in Gram-negative rods, has seldom been reported in Gram-positive organisms, and has not yet been reported in Enterococcus faecium. Using the serial passage method, in vitro mutant AusTig and in vitro mutants HMtig1 and HMtig2 with decreased TIG susceptibility (MICs, 0.25 μg/ml) were obtained from strains E. faecium Aus0004 and HM1070 (MICs, 0.03 μg/ml), respectively. In addition, two vancomycin-resistant E. faecium clinical isolates (EF16 and EF22) with reduced susceptibility to TIG (MICs, 0.5 and 0.25 μg/ml, respectively) were studied. Compared to the wild-type strains, the in vitro mutants also showed an increase in the MICs of other tetracyclines. An efflux mechanism did not seem to be involved in the reduced TIG susceptibility, since the presence of efflux pump inhibitors (reserpine or pantoprazole) did not affect the MICs of TIG. Whole-genome sequencing of AusTig was carried out, and genomic comparison with the Aus0004 genome was performed. Four modifications leading to an amino acid substitution were found. These mutations affected the rpsJ gene (efau004_00094, coding for the S10 protein of the 30S ribosomal subunit), efau004_01228 (encoding a cation transporter), efau004_01636 (coding for a hypothetical protein), and efau004_02455 (encoding the l-lactate oxidase). The four other strains exhibiting reduced TIG susceptibility were screened for the candidate mutations. This analysis revealed that three of them showed an amino acid substitution in the same region of the RpsJ protein. In this study, we characterized for the first time genetic determinants linked to reduced TIG susceptibility in enterococci. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Trigger factor of Streptococcus suis is involved in stress tolerance and virulence.

PubMed

Wu, Tao; Zhao, Zhanqin; Zhang, Lin; Ma, Hongwei; Lu, Ka; Ren, Wen; Liu, Zhengya; Chang, Haitao; Bei, Weicheng; Qiu, Yinsheng; Chen, Huanchun

2011-01-01

Streptococcus suis serotype 2 is an important zoonotic pathogen that causes serious diseases such as meningitis, septicemia, endocarditis, arthritis and septic shock in pigs and humans. Little is known about the regulation of virulence gene expression in S. suis serotype 2. In this study, we cloned and deleted the entire tig gene from the chromosome of S. suis serotype 2 SC21 strain, and constructed a mutant strain (Δtig) and a complementation strain (CΔtig). The results demonstrated that the tig gene, encoding trigger factor from S. suis serotype 2 SC21, affects the stress tolerance and the expression of a few virulence genes of S. suis serotype 2. Deletion of the tig gene of S. suis serotype 2 resulted in mutant strain, ΔTig, which exhibited a significant decrease in adherence to cell line HEp-2, and lacked hemolytic activity. Tig deficiency diminishes stresses tolerance of S. suis serotype 2 such as survive thermal, oxidative and acid stresses. Quantification of expression levels of known S. suis serotype 2 SC21 virulence genes by real-time polymerase chain reaction in vitro revealed that trigger factor influences the expression of epf, cps, adh, rpob, fbps, hyl, sly, mrp and hrcA virulence-associated genes. ΔTig was shown to be attenuated in a LD50 assay and bacteriology, indicating that trigger factor plays an important part in the pathogenesis and stress tolerance of. S. suis serotype 2 infection. Mutant ΔTig was 100% defective in virulence in CD1 mice at up to 107 CFU, and provided 100% protection when challenged with 107 CFU of the SC21 strain. Copyright © 2010. Published by Elsevier India Pvt Ltd.

Genetic characterisation of tigecycline-resistant Enterobacter spp. in blood isolates causing bacteraemia.

PubMed

Cha, Min Kyeong; Kang, Cheol-In; Park, Ga Eun; Kim, So Hyun; Chung, Doo Ryeon; Peck, Kyong Ran; Song, Jae-Hoon

2018-01-05

Tigecycline (TIG) is one of the most important antimicrobial agents used to treat infections by multidrug-resistant bacteria. However, rates of TIG-resistant pathogens have increased recently. This study was conducted to identify the antimicrobial susceptibility profiles and to investigate the role of efflux pumps in high-level TIG-resistant Enterobacter spp. isolates causing bacteraemia. A total of 323 Enterobacter spp. causing bacteraemia were collected from eight hospitals in various regions of South Korea. Minimum inhibitory concentrations (MICs) were determined by the broth microdilution method and Etest. Expression levels of the efflux pump gene acrA and its regulators (ramA and rarA) were examined by quantitative real-time PCR. Isolate relatedness was determined by multilocus sequence typing (MLST). Among the 323 clinical isolates included in this study, 37 (11.5%) were TIG-non-susceptible, of which 8 isolates were highly resistant to TIG with MICs of 8mg/L (4 isolates) or 16mg/L (4 isolates). All high-level TIG-resistant isolates showed increased expression of acrA (0.93-13.3-fold) and ramA (1.4-8.2-fold). Isolates with a tigecycline MIC of 16mg/L also showed overexpression of rarA compared with TIG-susceptible isolates. In this study, overexpression of acrA, ramA and rarA was observed in high-level TIG-resistant Enterobacter spp. isolates. We suggest that rarA might be involved in the regulation of acrA overexpression in high-level TIG-resistant Enterobacter spp. isolates. Efflux pump-mediated resistance should be closely monitored because it could be indirectly attributed to the use of other antibiotics transported by the same efflux pump. Copyright © 2017. Published by Elsevier Ltd.

Dissecting molecular and physiological response mechanisms to high solar radiation in cyanic and acyanic leaves: a case study on red and green basil.

PubMed

Tattini, Massimiliano; Sebastiani, Federico; Brunetti, Cecilia; Fini, Alessio; Torre, Sara; Gori, Antonella; Centritto, Mauro; Ferrini, Francesco; Landi, Marco; Guidi, Lucia

2017-04-01

Photosynthetic performance and the expression of genes involved in light signaling and the biosynthesis of isoprenoids and phenylpropanoids were analysed in green ('Tigullio', TIG) and red ('Red Rubin', RR) basil. The aim was to detect the physiological and molecular response mechanisms to high sunlight. The attenuation of blue-green light by epidermal anthocyanins was shown to evoke shade-avoidance responses with consequential effects on leaf morpho-anatomical traits and gas exchange performance. Red basil had a lower mesophyll conductance, partially compensated by the less effective control of stomatal movements, in comparison with TIG. Photosynthesis decreased more in TIG than in RR in high sunlight, because of larger stomatal limitations and the transient impairment of PSII photochemistry. The methylerythritol 4-phosphate pathway promoted above all the synthesis and de-epoxidation of violaxanthin-cycle pigments in TIG and of neoxanthin and lutein in RR. This enabled the green leaves to process the excess radiant energy effectively, and the red leaves to optimize light harvesting and photoprotection. The greater stomatal closure observed in TIG than in RR was due to enhanced abscisic acid (ABA) glucose ester deglucosylation and reduced ABA oxidation, rather than to superior de novo ABA synthesis. This study shows a strong competition between anthocyanin and flavonol biosynthesis, which occurs at the level of genes regulating the oxidation of the C2-C3 bond in the dihydro-flavonoid skeleton. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Regional Resistance Surveillance Program Results for 12 Asia-Pacific Nations (2011)

PubMed Central

Mendes, Rodrigo E.; Mendoza, Myrna; Banga Singh, Kirnpal K.; Castanheira, Mariana; Bell, Jan M.; Turnidge, John D.; Lin, Stephen S. F.

2013-01-01

The Regional Resistance Surveillance program monitored susceptibility rates and developing resistance by geographic region, including 12 Asia-Pacific (APAC) countries. Reference broth microdilution methods for susceptibility/interpretations were applied, processing 5,053 strains. Among Staphylococcus aureus isolates (37% methicillin-resistant S. aureus [MRSA], highest in South Korea [73%]), linezolid (LZD), tigecycline (TIG), and vancomycin were 100% active, but 33 and 34% of strains were levofloxacin (LEV) or macrolide resistant, respectively. Streptococcus pneumoniae was most resistant to β-lactams and macrolides (45%) but was LZD, LEV, and TIG susceptible (>98%). Extended-spectrum β-lactamase (ESBL) phenotype rates in Escherichia coli and Klebsiella spp. were 48 and 47%, respectively, and were highest in Taiwan, at 75 to 91%. The best anti-ESBL-phenotype agents were amikacin (81 to 96% susceptible), colistin (COL; >98%), TIG (>98%), and carbapenems (81 to 97%). Pseudomonas aeruginosa showed ≥20% resistance to all drugs except COL (99% susceptible). In conclusion, endemic evolving antimicrobial resistances in APAC nations show compromised roles for many commonly used antimicrobials. PMID:23959306

Teaching Team Invasion Games and Motivational Climate

ERIC Educational Resources Information Center

Gray, Shirley; Sproule, John; Morgan, Kevin

2009-01-01

Team invasion games (TIG) make up a large part of the PE curriculum in Scottish schools. It is important, therefore, to understand the environmental conditions that contribute to pupils' motivation to learn to play TIG. Consequently, this study aimed to identify the teaching behaviours exhibited when teaching TIG using a game-based approach and a…

In vitro synergistic activity of tigecycline and colistin against XDR-Acinetobacter baumannii.

PubMed

Dizbay, Murat; Tozlu, Derya Keten; Cirak, Meltem Yalinay; Isik, Yasemin; Ozdemir, Kevser; Arman, Dilek

2010-02-01

The emergence of extensive drug-resistant (XDR) Acinetobacter baumannii limits the therapeutic options and leads to high mortality in intensive care units. Combined antibiotic therapy is frequently recommended for the treatment of these infections. Colistin (CO) and tigecycline (TIG), alone or in combination with other antimicrobials, are the most commonly used antibiotics in the treatment of these resistant infections. In this study, the in vitro synergistic activity of TIG and CO were tested for 25 XDR-A. baumannii strains isolated from ventilator-associated pneumonia by the Etest method. Resistance to CO was not detected, whereas 8% of the strains were resistant to TIG. The TIG-CO combination was more synergistic than TIG-rifampin and CO-rifampin according to the fractional inhibitory concentration index. No antagonism was detected between the drugs in the study. There was no strong correlation between the activity of the combinations with reference to strains or genotypes. Our results suggest that the combined use of TIG and CO may be useful for the treatment of XDR-A. baumannii infections.

Intrathecal tetanus immunoglobulins in the management of tetanus.

PubMed

Geeta, M G; Krishnakumar, P; Mathews, Lulu

2007-01-01

To study the clinical profile, treatment and outcome of tetanus in children treated with intrathecal tetanus immunoglobulin. (TIG) METHODS: Retrospective analysis of hospital records of tetaus cases admitted to the pediatric ICU during the five year period between 1999 to 2004 was done. There were 66 cases of tetanus treated with intrathecal TIG. Children below 5 years formed 53% of cases and 47% were above 5 years. Totally unimmunized children constituted 82% of cases and 18% partially immunized children. The portal of entry was otogenic in 58% of cases and injury in30% of cases. The common complications observed included thrombophlebitis, aspiration pneumonia, laryngospasm and autonomic system involvement. There were no complications specific to intrathecal administration of TIG. The mortality due to tetanus was 9%. Mortality and morbidity due to tetanus was less in the present study compared to other centers where TIG is given intramuscularly. Intrathecal TIG is effective in the treatment of mild and moderate tetanus. Randomized controlled clinical trials are needed to evaluate the efficacy of intrathecal TIG in the management of severe tetanus.

Design of time interval generator based on hybrid counting method

NASA Astrophysics Data System (ADS)

Yao, Yuan; Wang, Zhaoqi; Lu, Houbing; Chen, Lian; Jin, Ge

2016-10-01

Time Interval Generators (TIGs) are frequently used for the characterizations or timing operations of instruments in particle physics experiments. Though some "off-the-shelf" TIGs can be employed, the necessity of a custom test system or control system makes the TIGs, being implemented in a programmable device desirable. Nowadays, the feasibility of using Field Programmable Gate Arrays (FPGAs) to implement particle physics instrumentation has been validated in the design of Time-to-Digital Converters (TDCs) for precise time measurement. The FPGA-TDC technique is based on the architectures of Tapped Delay Line (TDL), whose delay cells are down to few tens of picosecond. In this case, FPGA-based TIGs with high delay step are preferable allowing the implementation of customized particle physics instrumentations and other utilities on the same FPGA device. A hybrid counting method for designing TIGs with both high resolution and wide range is presented in this paper. The combination of two different counting methods realizing an integratable TIG is described in detail. A specially designed multiplexer for tap selection is emphatically introduced. The special structure of the multiplexer is devised for minimizing the different additional delays caused by the unpredictable routings from different taps to the output. A Kintex-7 FPGA is used for the hybrid counting-based implementation of a TIG, providing a resolution up to 11 ps and an interval range up to 8 s.

Tazarotene-induced gene 3 is suppressed in basal cell carcinomas and reversed in vivo by tazarotene application.

PubMed

Duvic, Madeleine; Ni, Xiao; Talpur, Rakhashandra; Herne, Kelly; Schulz, Claudia; Sui, Dawen; Ward, Staci; Joseph, Aaron; Hazarika, Parul

2003-10-01

Basal cell carcinomas are the most common form of skin cancer. Tazarotene is a retinoic acid receptor selective retinoid that upregulates a tumor suppressor, tazarotene-induced gene 3 (TIG-3), in keratinocytes and psoriasis. Expression of TIG-3 in basal cell carcinomas was studied in an opened-label pilot biomarker study of 22 patients with basal cell carcinomas who applied tazarotene 0.1% gel for up to 12 wk prior to excision. Nineteen paired baseline and treated specimens were compared using immunohistochemistry and in situ hybridization. Compared to overlying normal epidermis, TIG-3 protein and mRNA were decreased in 14 and 18 of 19 basal cell carcinomas (74% and 95%), respectively (p < 0.001). Tazarotene treatment was associated with increased TIG-3 protein and mRNA expression in basal cell carcinomas compared to baseline levels (p < or = 0.001 and p = 0.028, respectively). Sixty percent of basal cell carcinomas treated with tazarotene decreased in size by at least 25%. Ten of 19 lesions improved histologically, including three complete responses. There was a correlation between the increased expression of TIG-3 protein and histologic improvement (p = 0.020), suggesting that suppression of TIG-3 may underlie the development of basal cell carcinomas. This association suggests that reversal of TIG-3 expression may help to explain the mechanism of retinoid action in epidermal differentiation and chemoprevention.

A new human male diploid cell strain, TIG-7: its age-related changes and comparison with a matched female TIG-1 cell strain.

PubMed

Yamamoto, K; Kaji, K; Kondo, H; Matsuo, M; Shibata, Y; Tasaki, Y; Utakoji, T; Ooka, H

1991-01-01

A new human diploid cell strain, TIG-7, which has the male karyotype, was established and characterized. Isozyme and histocompatibility typing of the cell strain was performed. The average in vitro life span of the cells is 73 population doublings. Changes in cell volume, doubling time, saturation density, the efficiency of cell attachment, plating efficiency, and relative DNA content were examined during in vitro cellular aging. Hydrocortisone slightly prolongs the life span of the cell strain when the hormone is administered to the cultures during middle passages. The age-related changes in the parameters of TIG-7 are not appreciably different from those of the previously established TIG-1 cell strain. These results show that this cell strain is useful for research on cellular aging; further profit is anticipated from research using a combination of these two sexually different cell strains.

Activity of Antimicrobial Combinations against KPC-2-Producing Klebsiella pneumoniae in a Rat Model and Time-Kill Assay

PubMed Central

Aranha Junior, Ayrton Alves; Arend, Lavinia Nery; Ribeiro, Vanessa; Zavascki, Alexandre Prehn; Tuon, Felipe Francisco

2015-01-01

This study evaluated the efficacy of tigecycline (TIG), polymyxin B (PMB), and meropenem (MER) in 80 rats challenged with Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae infection. A time-kill assay was performed with the same strain. Triple therapy and PMB+TIG were synergistic, promoted 100% survival, and produced negative peritoneal cultures, while MER+TIG showed lower survival and higher culture positivity than other regimens (P = 0.018) and was antagonistic. In vivo and in vitro studies showed that combined regimens, except MER+TIG, were more effective than monotherapies for this KPC-producing strain. PMID:25896686

Highly flexible SRAM cells based on novel tri-independent-gate FinFET

NASA Astrophysics Data System (ADS)

Liu, Chengsheng; Zheng, Fanglin; Sun, Yabin; Li, Xiaojin; Shi, Yanling

2017-10-01

In this paper, a novel tri-independent-gate (TIG) FinFET is proposed for highly flexible SRAM cells design. To mitigate the read-write conflict, two kinds of SRAM cells based on TIG FinFETs are designed, and high tradeoff are obtained between read stability and speed. Both cells can offer multi read operations for frequency requirement with single voltage supply. In the first TIG FinFET SRAM cell, the strength of single-fin access transistor (TIG FinFET) can be flexibly adjusted by selecting five different modes to meet the needs of dynamic frequency design. Compared to the previous double-independent-gate (DIG) FinFET SRAM cell, 12.16% shorter read delay can be achieved with only 1.62% read stability decrement. As for the second TIG FinFET SRAM cell, pass-gate feedback technology is applied and double-fin TIG FinFETs are used as access transistors to solve the severe write-ability degradation. Three modes exist to flexibly adjust read speed and stability, and 68.2% larger write margin and 51.7% shorter write delay are achieved at only the expense of 26.2% increase in leakage power, with the same layout area as conventional FinFET SRAM cell.

Improvement of Productivity in TIG Welding Plant by Equipment Design in Orbit

NASA Astrophysics Data System (ADS)

Gnanavel, C.; Saravanan, R.; Chandrasekaran, M.; Jayakanth, J. J.

2017-03-01

Measurements and improvements are very indispensable task at all levels of management. Here some samples are, at operator level: Measuring operating parameters to ensure OEE (Overall Equipment Effectiveness) and measuring Q components performance to ensure quality, at supervisory level: measuring operator’s performance to ensure labour utility at managerial level: production and productivity measurements and at top level capital and capacity utilization. An often accepted statement is “Improvement is impossible without measurement”. Measurements often referred as observation. The case study was conducted at Government Boiler factory in India. The scientific approach followed for indentifying non value added activities. Personalised new equipment designed and installed to achieve productivity improvement of 85% for a day. The new equipment can serve 360o around its axis hence it simplified loading and unloading procedures as well as reduce their times and ensured effective space and time.

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.

Activity of antimicrobial combinations against KPC-2-producing Klebsiella pneumoniae in a rat model and time-kill assay.

PubMed

Toledo, Paula Virginia Michelon; Aranha Junior, Ayrton Alves; Arend, Lavinia Nery; Ribeiro, Vanessa; Zavascki, Alexandre Prehn; Tuon, Felipe Francisco

2015-07-01

This study evaluated the efficacy of tigecycline (TIG), polymyxin B (PMB), and meropenem (MER) in 80 rats challenged with Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae infection. A time-kill assay was performed with the same strain. Triple therapy and PMB+TIG were synergistic, promoted 100% survival, and produced negative peritoneal cultures, while MER+TIG showed lower survival and higher culture positivity than other regimens (P = 0.018) and was antagonistic. In vivo and in vitro studies showed that combined regimens, except MER+TIG, were more effective than monotherapies for this KPC-producing strain. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Tazarotene-Induced Gene 1 Interacts with DNAJC8 and Regulates Glycolysis in Cervical Cancer Cells.

PubMed

Wang, Chun-Hua; Shyu, Rong-Yaun; Wu, Chang-Chieh; Chen, Mao-Liang; Lee, Ming-Cheng; Lin, Yi-Yin; Wang, Lu-Kai; Jiang, Shun-Yuan; Tsai, Fu-Ming

2018-06-14

The tazarotene-induced gene 1 (TIG1) protein is a retinoidinducible growth regulator and is considered a tumor suppressor. Here, we show that DnaJ heat shock protein family member C8 (DNAJC8) is a TIG1 target that regulates glycolysis. Ectopic DNAJC8 expression induced the translocation of pyruvate kinase M2 (PKM2) into the nucleus, subsequently inducing glucose transporter 1 (GLUT1) expression to promote glucose uptake. Silencing either DNAJC8 or PKM2 alleviated the upregulation of GLUT1 expression and glucose uptake induced by ectopic DNAJC8 expression. TIG1 interacted with DNAJC8 in the cytosol, and this interaction completely blocked DNAJC8-mediated PKM2 translocation and inhibited glucose uptake. Furthermore, increased glycose uptake was observed in cells in which TIG1 was silenced. In conclusion, TIG1 acts as a pivotal repressor of DNAJC8 to enhance glucose uptake by partially regulating PKM2 translocation.

Vitamin E improves the in vivo efficacy of tigecycline and daptomycin in an animal model of wounds infected with meticillin-resistant Staphylococcus aureus.

PubMed

Provinciali, Mauro; Cirioni, Oscar; Orlando, Fiorenza; Pierpaoli, Elisa; Barucca, Alessandra; Silvestri, Carmela; Ghiselli, Roberto; Scalise, Alessandro; Brescini, Lucia; Guerrieri, Mario; Giacometti, Andrea

2011-12-01

A relevant bacterial load in cutaneous wounds significantly interferes with the normal process of healing. Vitamin E (VE) is a known immunomodulator and immune enhancer. Here, it was shown that administration of VE before infection was effective at increasing the antimicrobial activity of daptomycin (DAP) or tigecycline (TIG) in a mouse model of wound infection caused by meticillin-resistant Staphylococcus aureus (MRSA). A wound was established through the panniculus carnosus of mice and inoculated with MRSA. Mice were assigned to six groups: a VE pre-treated group with no antibiotics given after MRSA challenge; two VE pre-treated groups with DAP or TIG given after MRSA challenge; two groups treated with DAP or TIG only after MRSA challenge; and a control group that did not receive any treatment. Mice receiving each antibiotic alone showed a 3 log decrease in the number of c.f.u. recovered compared with the control group, mice treated with VE plus TIG had a 4 log decrease, whilst mice treated with VE plus DAP had the largest decrease in c.f.u. recovered (5 logs). The increased antimicrobial effect seen from treatment with VE plus antibiotics was associated with increased levels of natural killer cell cytotoxicity, with a more pronounced increase in leukocyte populations in mice treated with VE plus DAP. These data suggest that treatment with VE prior to infection and subsequent antibiotic treatment act in synergy. © 2011 SGM

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.

Controlled cell morphology and liver-specific function of engineered primary hepatocytes by fibroblast layer cell densities.

PubMed

Sakai, Yusuke; Koike, Makiko; Kawahara, Daisuke; Hasegawa, Hideko; Murai, Tomomi; Yamanouchi, Kosho; Soyama, Akihiko; Hidaka, Masaaki; Takatsuki, Mitsuhisa; Fujita, Fumihiko; Kuroki, Tamotsu; Eguchi, Susumu

2018-03-05

Engineered primary hepatocytes, including co-cultured hepatocyte sheets, are an attractive to basic scientific and clinical researchers because they maintain liver-specific functions, have reconstructed cell polarity, and have high transplantation efficiency. However, co-culture conditions regarding engineered primary hepatocytes were suboptimal in promoting these advantages. Here we report that the hepatocyte morphology and liver-specific function levels are controlled by the normal human diploid fibroblast (TIG-118 cell) layer cell density. Primary rat hepatocytes were plated onto TIG-118 cells, previously plated 3 days before at 1.04, 5.21, and 26.1×10 3  cells/cm 2 . Hepatocytes plated onto lower TIG-118 cell densities expanded better during the early culture period. The hepatocytes gathered as colonies and only exhibited small adhesion areas because of the pushing force from proliferating TIG-118 cells. The smaller areas of each hepatocyte result in the development of bile canaliculi. The highest density of TIG-118 cells downregulated albumin synthesis activity of hepatocytes. The hepatocytes may have undergone apoptosis associated with high TGF-β1 concentration and necrosis due to a lack of oxygen. These occurrences were supported by apoptotic chromatin condensation and high expression of both proteins HIF-1a and HIF-1b. Three types of engineered hepatocyte/fibroblast sheets comprising different TIG-118 cell densities were harvested after 4 days of hepatocyte culture and showed a complete cell sheet format without any holes. Hepatocyte morphology and liver-specific function levels are controlled by TIG-118 cell density, which helps to design better engineered hepatocytes for future applications such as in vitro cell-based assays and transplantable hepatocyte tissues. Copyright © 2018 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Determination of tigecycline in turkey plasma by LC-MS/MS: validation and application in a pharmacokinetic study.

PubMed

Jasiecka-Mikołajczyk, A; Jaroszewski, J J

2017-03-01

Tigecycline (TIG), a novel glycylcycline antibiotic, plays an important role in the management of complicated skin and intra-abdominal infections. The available data lack any description of a method for determination of TIG in avian plasma. In our study, a selective, accurate and reversed-phase high performance liquid chromatography-tandem mass spectrometry method was developed for the determination of TIG in turkey plasma. Sample preparation was based on protein precipitation and liquid-liquid extraction using 1,2-dichloroethane. Chromatographic separation of TIG and minocycline (internal standard, IS) was achieved on an Atlantis T3 column (150 mm × 3.0 mm, 3.0 μm) using gradient elution. The selected reaction monitoring transitions were performed at 293.60 m/z → 257.10 m/z for TIG and 458.00 m/z → 441.20 m/z for IS. The developed method was validated in terms of specificity, selectivity, linearity, lowest limit of quantification, limit of detection, precision, accuracy, matrix effect, carry-over effect, extraction recovery and stability. All parameters of the method submitted to validation met the acceptance criteria. The assay was linear over the concentration range of 0.01-100 μg/ml. This validated method was successfully applied to a TIG pharmacokinetic study in turkey after intravenous and oral administration at a dose of 10 mg/kg at various time-points.

Large anomalous Hall effect in Pt interfaced with perpendicular anisotropy ferrimagnetic insulator

NASA Astrophysics Data System (ADS)

Tang, Chi; Sellappan, Pathikumar; Liu, Yawen; Garay, Javier; Shi, Jing; Shines Team

We demonstrate the strain induced perpendicular magnetic anisotropy (PMA) in a ferrimagnetic insulator (FMI), Tm3Fe5O12 (TIG) and the first observation of large anomalous Hall effect (AHE) in TIG/Pt bilayers. Atomically flat TIG films were deposited by a laser molecular beam epitaxy system on (111)-orientated substituted gadolinium gallium garnet substrates. The strength of PMA could be effectively tuned by controlling the oxygen pressure during deposition. Sharp squared anomalous Hall hysteresis loops were observed in bilayers of TIG/Pt over a range of thicknesses of Pt, with the maximum AHE conductivity reaching 1 S/cm at room temperature. The AHE vanishes when a 5 nm Cu layer was inserted between Pt and TIG, strongly indicating the proximity-induced ferromagnetism in Pt. The large AHE in the bilayer structures demonstrates a potential use of PMA-FMI related heterostructures in spintronics. This work was supported as part of the SHINES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # SC0012670.

The effect of tigecycline and ertapenem against clinical isolates of Brucella melitensis detected by E-test on different media.

PubMed

Tanyel, E; Coban, A Y; Fisgin, N Tasdelen; Tulek, N

2010-01-01

In this study, in vitro activity of tigecycline (TIG) and ertapenem (ERT) against clinical isolates of Brucella melitensis and the effect of different media on in vitro test results were investigated. The in vitro effects of TIG and ERT to 38 B. melitensis isolates were comparatively investigated in brucella agar and 5% sheep blood agar. MIC value of ERT was 0.032 μg/mL in 23 of 38 and 20 of 38 isolates on blood and brucella agar, respectively. Minimum inhibitory concentration values of TIG were substantially different ranging between 0.064-0.25 μg/mL on blood agar. However, MIC values of TIG were similar on brucella agar with 0.25 μg/mL in 15 of 38 isolates and 0.5 μg/mL in 10 of 38 isolates. In conclusion, although ERT and TIG were effective against B. melitensis isolates in vitro, further studies are needed in order to determine the use of these novel drugs in treatment of brucellosis.

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

75 FR 67396 - Sunshine Act Meeting Notice

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-02

... report on the Technology Initiatives Grants (``TIG'') program.\\1\\ \\1\\ Any portion of the closed session... Technology Initiatives Grants (``TIG'') program. 5. Consider and act on proposal regarding a research project...

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.

75 FR 70704 - Sunshine Act Meeting of the Board of Directors

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-18

... audit report on the Technology Initiatives Grants (``TIG'') program.\\1\\/ \\1\\ Any portion of the closed... Inspector General's audit report regarding the Technology Initiatives Grants (``TIG'') program. 9. Consider...

Traditional Indigenous Games promoting physical activity and cultural connectedness in primary schools--cluster randomised control trial.

PubMed

Kiran, Asha; Knights, Janice

2010-08-01

This study investigated the effectiveness of Traditional Indigenous Games (TIG) to improve physical activity and cultural connectedness among primary school students in the community renewal areas of Townsville in North Queensland. A cluster randomised control trial was conducted in four primary schools in 2007. Baseline and post implementation surveys were conducted in two intervention and two control schools and the results were compared. TIG delivered in primary schools every week over period of three months did not contribute to any statistically significant improvement in intervention and control groups in physical activity levels or cultural connectedness. Further research specifically in terms of intensity and duration of TIG may inform whether physical activity may be improved. Enhancing the Indigenous cultural features of the existing TIG kit might positively influence Indigenous cultural connectedness.

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.

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.

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.

Thermal Stir Welding: A New Solid State Welding Process

NASA Technical Reports Server (NTRS)

Ding, R. Jeffrey

2003-01-01

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

Thermal Stir Welding: A New Solid State Welding Process

NASA Technical Reports Server (NTRS)

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

2002-01-01

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

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.

Welding Development: Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Ding, Jeff

2007-01-01

This paper presents the basic understanding of the friction stir welding process. It covers process description, pin tool operation and materials, metal flow theory, mechanical properties, and materials welded using the process. It also discusses the thermal stir welding process and the differences between thermal stir and friction stir welding. MSFC weld tools used for development are also presented.

Automated analysis of high-throughput B-cell sequencing data reveals a high frequency of novel immunoglobulin V gene segment alleles.

PubMed

Gadala-Maria, Daniel; Yaari, Gur; Uduman, Mohamed; Kleinstein, Steven H

2015-02-24

Individual variation in germline and expressed B-cell immunoglobulin (Ig) repertoires has been associated with aging, disease susceptibility, and differential response to infection and vaccination. Repertoire properties can now be studied at large-scale through next-generation sequencing of rearranged Ig genes. Accurate analysis of these repertoire-sequencing (Rep-Seq) data requires identifying the germline variable (V), diversity (D), and joining (J) gene segments used by each Ig sequence. Current V(D)J assignment methods work by aligning sequences to a database of known germline V(D)J segment alleles. However, existing databases are likely to be incomplete and novel polymorphisms are hard to differentiate from the frequent occurrence of somatic hypermutations in Ig sequences. Here we develop a Tool for Ig Genotype Elucidation via Rep-Seq (TIgGER). TIgGER analyzes mutation patterns in Rep-Seq data to identify novel V segment alleles, and also constructs a personalized germline database containing the specific set of alleles carried by a subject. This information is then used to improve the initial V segment assignments from existing tools, like IMGT/HighV-QUEST. The application of TIgGER to Rep-Seq data from seven subjects identified 11 novel V segment alleles, including at least one in every subject examined. These novel alleles constituted 13% of the total number of unique alleles in these subjects, and impacted 3% of V(D)J segment assignments. These results reinforce the highly polymorphic nature of human Ig V genes, and suggest that many novel alleles remain to be discovered. The integration of TIgGER into Rep-Seq processing pipelines will increase the accuracy of V segment assignments, thus improving B-cell repertoire analyses.

Friction Stir Process Mapping Methodology

NASA Technical Reports Server (NTRS)

Bjorkman, Gerry; Kooney, Alex; Russell, Carolyn

2003-01-01

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.

Metabolic Adaptation to Chronic Inhibition of Mitochondrial Protein Synthesis in Acute Myeloid Leukemia Cells

PubMed Central

Jhas, Bozhena; Sriskanthadevan, Shrivani; Skrtic, Marko; Sukhai, Mahadeo A.; Voisin, Veronique; Jitkova, Yulia; Gronda, Marcela; Hurren, Rose; Laister, Rob C.; Bader, Gary D.; Minden, Mark D.; Schimmer, Aaron D.

2013-01-01

Recently, we demonstrated that the anti-bacterial agent tigecycline preferentially induces death in leukemia cells through the inhibition of mitochondrial protein synthesis. Here, we sought to understand mechanisms of resistance to tigecycline by establishing a leukemia cell line resistant to the drug. TEX leukemia cells were treated with increasing concentrations of tigecycline over 4 months and a population of cells resistant to tigecycline (RTEX+TIG) was selected. Compared to wild type cells, RTEX+TIG cells had undetectable levels of mitochondrially translated proteins Cox-1 and Cox-2, reduced oxygen consumption and increased rates of glycolysis. Moreover, RTEX+TIG cells were more sensitive to inhibitors of glycolysis and more resistant to hypoxia. By electron microscopy, RTEX+TIG cells had abnormally swollen mitochondria with irregular cristae structures. RNA sequencing demonstrated a significant over-representation of genes with binding sites for the HIF1α:HIF1β transcription factor complex in their promoters. Upregulation of HIF1α mRNA and protein in RTEX+TIG cells was confirmed by Q-RTPCR and immunoblotting. Strikingly, upon removal of tigecycline from RTEX+TIG cells, the cells re-established aerobic metabolism. Levels of Cox-1 and Cox-2, oxygen consumption, glycolysis, mitochondrial mass and mitochondrial membrane potential returned to wild type levels, but HIF1α remained elevated. However, upon re-treatment with tigecycline for 72 hours, the glycolytic phenotype was re-established. Thus, we have generated cells with a reversible metabolic phenotype by chronic treatment with an inhibitor of mitochondrial protein synthesis. These cells will provide insight into cellular adaptations used to cope with metabolic stress. PMID:23520503

Metabolic adaptation to chronic inhibition of mitochondrial protein synthesis in acute myeloid leukemia cells.

PubMed

Jhas, Bozhena; Sriskanthadevan, Shrivani; Skrtic, Marko; Sukhai, Mahadeo A; Voisin, Veronique; Jitkova, Yulia; Gronda, Marcela; Hurren, Rose; Laister, Rob C; Bader, Gary D; Minden, Mark D; Schimmer, Aaron D

2013-01-01

Recently, we demonstrated that the anti-bacterial agent tigecycline preferentially induces death in leukemia cells through the inhibition of mitochondrial protein synthesis. Here, we sought to understand mechanisms of resistance to tigecycline by establishing a leukemia cell line resistant to the drug. TEX leukemia cells were treated with increasing concentrations of tigecycline over 4 months and a population of cells resistant to tigecycline (RTEX+TIG) was selected. Compared to wild type cells, RTEX+TIG cells had undetectable levels of mitochondrially translated proteins Cox-1 and Cox-2, reduced oxygen consumption and increased rates of glycolysis. Moreover, RTEX+TIG cells were more sensitive to inhibitors of glycolysis and more resistant to hypoxia. By electron microscopy, RTEX+TIG cells had abnormally swollen mitochondria with irregular cristae structures. RNA sequencing demonstrated a significant over-representation of genes with binding sites for the HIF1α:HIF1β transcription factor complex in their promoters. Upregulation of HIF1α mRNA and protein in RTEX+TIG cells was confirmed by Q-RTPCR and immunoblotting. Strikingly, upon removal of tigecycline from RTEX+TIG cells, the cells re-established aerobic metabolism. Levels of Cox-1 and Cox-2, oxygen consumption, glycolysis, mitochondrial mass and mitochondrial membrane potential returned to wild type levels, but HIF1α remained elevated. However, upon re-treatment with tigecycline for 72 hours, the glycolytic phenotype was re-established. Thus, we have generated cells with a reversible metabolic phenotype by chronic treatment with an inhibitor of mitochondrial protein synthesis. These cells will provide insight into cellular adaptations used to cope with metabolic stress.

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

NASA Astrophysics Data System (ADS)

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

2012-06-01

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

Thermal Stir Welding: A New Solid State Welding Process

NASA Technical Reports Server (NTRS)

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

2002-01-01

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

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

PubMed

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

2013-04-01

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

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.

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 parameter optimization of alloy material by friction stir welding using Taguchi approach and design of experiments

NASA Astrophysics Data System (ADS)

Karwande, Amit H.; Rao, Seeram Srinivasa

2018-04-01

Friction stir welding (FSW) a welding process in which metals are joint by melting them at their solid state. In different engineering areas such as civil, mechanical, naval and aeronautical engineering beams are widely used of the magnesium alloys for different applications and that are joined by conventional inert gas welding process. Magnesium metal has less density and low melting point for that reason large heat generation in the common welding process so its necessity to adapt new welding process. FSW process increases the weld quality which observed under various mechanical testing by using different tool size.

In vitro selection of Staphylococcus aureus mutants resistant to tigecycline with intermediate susceptibility to vancomycin.

PubMed

Herrera, Melina; Di Gregorio, Sabrina; Fernandez, Silvina; Posse, Graciela; Mollerach, Marta; Di Conza, José

2016-03-08

Tigecycline (TIG) is an antibiotic belonging to the glycylcyclines class and appears to be a good choice to fight infections caused by Staphylococcus aureus. To date, TIG exhibits good activity against this microorganism. The aim of this work was to obtain in vitro mutants of S. aureus resistant to TIG and evaluate possible changes in their susceptibility patterns to other antibiotics. Two mutants of S. aureus resistant to TIG (MIC = 16 µg/mL) were selected in vitro from clinical isolates of methicillin-resistant S. aureus. In both mutants, corresponding to different lineage (ST5 and ST239), an increase of efflux activity against TIG was detected. One mutant also showed a reduced susceptibility to vancomycin, corresponding to the VISA phenotype (MIC = 4 µg/mL), with a loss of functionality of the agr locus. The emergence of the VISA phenotype was accompanied by an increase in oxacillin and cefoxitin MICs. This study demonstrates that, under selective pressure, the increase of efflux activity in S. aureus is one of the mechanisms that may be involved in the emergence of tigecycline resistance. The emergence of this phenotype may eventually be associated to changes in susceptibility to other antibiotics such oxacillin and vancomycin.

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

NASA Technical Reports Server (NTRS)

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

2010-01-01

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

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....

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

NASA Technical Reports Server (NTRS)

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

1991-01-01

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

Developing Pupils' Performance in Team Invasion Games

ERIC Educational Resources Information Center

Gray, Shirley; Sproule, John

2011-01-01

Background: To develop pupils' team invasion games (TIG) performance within physical education (PE), practitioners have traditionally adopted teacher-centred, skill-focused approaches. Teaching Games for Understanding and the Tactical approach are alternative approaches to TIG teaching that aim to develop overall game performance, including…

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

NASA Astrophysics Data System (ADS)

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

2017-05-01

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

Enhanced in vitro activity of tigecycline in the presence of chelating agents.

PubMed

Deitchman, Amelia N; Singh, Ravi Shankar Prasad; Rand, Kenneth H; Derendorf, Hartmut

2018-05-01

The lack of availability of novel antibiotic agents and the rise of resistance to existing therapies has led clinicians to utilise combination therapy to adequately treat bacterial infections. Here we examined how chelators may impact the in vitro activity of tigecycline (TIG) against Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae. Minimum inhibitory concentrations (MICs) were determined by broth dilution with and without various combinations of chelators (EDTA and other tetracyclines) and metal ions (i.e. calcium, magnesium). Trimethoprim (TMP) was used as a non-chelating control. Addition of metal ions led to increases in MICs, whilst addition of EDTA led to decreases in MICs. The chelating effects of EDTA were reversed by addition of magnesium and most profoundly calcium. Similar effects of EDTA and calcium were observed for tetracycline (TET) and TMP. When other tetracyclines (TET, oxytetracycline (OXY) and chlortetracycline (CHL)) were used as chelators at concentrations below their MICs, TIG MICs decreased for P. aeruginosa but not for E. coli. Some decreases in TIG MICs were observed for K. pneumoniae when TET and CHL were added. A dose-dependent decrease in TIG MIC was observed for TET and was reversed by the addition of calcium. The presence of effects of EDTA and calcium on TMP MICs indicates that mechanisms outside of TIG chelation likely play a role in enhanced activity. Full characterisation of an unexpected interaction such as TIG-TET with different microorganisms could provide valuable insights into the underlying mechanisms and design of physiologically viable chelators as candidates for future combinations regimens. Copyright © 2018 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.

State-of-technology for joining TD-NiCr sheet

NASA Technical Reports Server (NTRS)

Holko, K. H.; Moore, T. J.; Gyorgak, C. A.

1972-01-01

At the current state-of-technology there are many joining processes that can be used to make sound welds in TD-NiCr sheet. Some of these that are described in this report are electron beam welding, gas-tungsten arc welding, diffusion welding, resistance spot welding, resistance seam welding, and brazing. The strengths of the welds made by the various processes show considerable variation, especially at elevated temperatures. Most of the fusion welding processes tend to give weak welds at elevated temperatures (with the exception of fusion-type resistance spotwelds). However, solid-state welds have been made with parent metal properties. The process used for a specific application will be dictated by the specific joint requirements. In highly stressed joints at elevated temperatures, one of the solid-state processes, such as DFW, RSW (solid-state or fusion), and RSEW, offer the most promise.

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

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.

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

Code of Federal Regulations, 2010 CFR

2010-10-01

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

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

Code of Federal Regulations, 2012 CFR

2012-10-01

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

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

Code of Federal Regulations, 2014 CFR

2014-10-01

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

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

Code of Federal Regulations, 2011 CFR

2011-10-01

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

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

Code of Federal Regulations, 2013 CFR

2013-10-01

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

Ultrasonic Welding of Thermoplastic Composite Coupons for Mechanical Characterization of Welded Joints through Single Lap Shear Testing.

PubMed

Villegas, Irene F; Palardy, Genevieve

2016-02-11

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ultrasonic welding process described in this paper is based on three main pillars. Firstly, flat energy directors are used for preferential heat generation at the joining interface during the welding process. A flat energy director is a neat thermoplastic resin film that is placed between the parts to be joined prior to the welding process and heats up preferentially owing to its lower compressive stiffness relative to the composite substrates. Consequently, flat energy directors provide a simple solution that does not require molding of resin protrusions on the surfaces of the composite substrates, as opposed to ultrasonic welding of unreinforced plastics. Secondly, the process data provided by the ultrasonic welder is used to rapidly define the optimum welding parameters for any thermoplastic composite material combination. Thirdly, displacement control is used in the welding process to ensure consistent quality of the welded joints. According to this method, thermoplastic-composite flat coupons are individually welded in a single lap configuration. Mechanical testing of the welded coupons allows determining the apparent lap shear strength of the joints, which is one of the properties most commonly used to quantify the strength of thermoplastic composite welded joints.

Ultrasonic Welding of Thermoplastic Composite Coupons for Mechanical Characterization of Welded Joints through Single Lap Shear Testing

PubMed Central

Villegas, Irene F.; Palardy, Genevieve

2016-01-01

This paper presents a novel straightforward method for ultrasonic welding of thermoplastic-composite coupons in optimum processing conditions. The ultrasonic welding process described in this paper is based on three main pillars. Firstly, flat energy directors are used for preferential heat generation at the joining interface during the welding process. A flat energy director is a neat thermoplastic resin film that is placed between the parts to be joined prior to the welding process and heats up preferentially owing to its lower compressive stiffness relative to the composite substrates. Consequently, flat energy directors provide a simple solution that does not require molding of resin protrusions on the surfaces of the composite substrates, as opposed to ultrasonic welding of unreinforced plastics. Secondly, the process data provided by the ultrasonic welder is used to rapidly define the optimum welding parameters for any thermoplastic composite material combination. Thirdly, displacement control is used in the welding process to ensure consistent quality of the welded joints. According to this method, thermoplastic-composite flat coupons are individually welded in a single lap configuration. Mechanical testing of the welded coupons allows determining the apparent lap shear strength of the joints, which is one of the properties most commonly used to quantify the strength of thermoplastic composite welded joints. PMID:26890931

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

PubMed

Wang, Lin; Gao, Xiangdong; Chen, Ziqin

2018-01-08

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

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

NASA Astrophysics Data System (ADS)

Yan, Qi; Guo, Ruiquan

2005-01-01

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

Mechanical Properties of Aluminum-Based Dissimilar Alloy Joints by Power Beams, Arc and FSW Processes

NASA Astrophysics Data System (ADS)

Okubo, Michinori; Kon, Tomokuni; Abe, Nobuyuki

Dissimilar smart joints are useful. In this research, welded quality of dissimilar aluminum alloys of 3 mm thickness by various welding processes and process parameters have been investigated by hardness and tensile tests, and observation of imperfection and microstructure. Base metals used in this study are A1050-H24, A2017-T3, A5083-O, A6061-T6 and A7075-T651. Welding processes used are YAG laser beam, electron beam, metal inert gas arc, tungsten inert gas arc and friction stir welding. The properties of weld zones are affected by welding processes, welding parameters and combination of base metals. Properties of high strength aluminum alloy joints are improved by friction stir welding.

Alar-columellar and lateral nostril changes following tongue-in-groove rhinoplasty.

PubMed

Shah, Ajul; Pfaff, Miles; Kinsman, Gianna; Steinbacher, Derek M

2015-04-01

Repositioning the medial crura cephalically onto the caudal septum (tongue-in-groove; TIG) allows alteration of the columella, ala, and nasal tip to address alar-columellar disproportion as seen from the lateral view. To date, quantitative analysis of nostril dimension, alar-columellar relationship, and nasal tip changes following the TIG rhinoplasty technique have not been described. The present study aims to evaluate post-operative lateral morphometric changes following TIG. Pre- and post-operative lateral views of a series of consecutive patients who underwent TIG rhinoplasty were produced from 3D images at multiple time points (≤2 weeks, 4-10 weeks, and >10 weeks post-operatively) for analysis. The 3D images were converted to 2D and set to scale. Exposed lateral nostril area, alar-columellar disproportion (divided into superior and inferior heights), nasolabial angle, nostril height, and nostril length were calculated and statistically analyzed using a pairwise t test. A P ≤ 0.05 was considered statistically significant. Ninety-four lateral views were analyzed from 20 patients (16 females; median age: 31.8). One patient had a history of current tobacco cigarette use. Lateral nostril area decreased at all time points post-operatively, in a statistically significant fashion. Alar-columellar disproportion was reduced following TIG at all time points. The nasolabial angle significantly increased post-operatively at ≤2 weeks, 4-10 weeks, and >10, all in a statistically significant fashion. Nostril height and nostril length decreased at all post-operative time points. Morphometric analysis reveals reduction in alar-columellar disproportion and lateral nostril shows following TIG rhinoplasty. Tip rotation, as a function of nasolabial angle, also increased. These results provide quantitative substantiation for qualitative descriptions attributed to the TIG technique. Future studies will focus on area and volumetric measurements, and assessment of long-term stability. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

The Tongue-in-Groove Technique in Primary and Revision Rhinoplasty.

PubMed

Datema, Frank R; Lohuis, Peter J F M

2016-08-01

The tongue-in-groove (TIG) is a conservative but powerful surgical suture technique to control tip rotation and projection, to set an appropriate alar-columellar relationship, to straighten a caudal septal deviation, and to stabilize the nasal base. TIG is suitable in primary and most revision cases and is easily combined with other surgical techniques. Seventeen years after its popularization, the TIG technique is embedded in modern-day rhinoplasty literature and teaching material. This article describes indications and considerations during external primary and revision rhinoplasty, based on clinical experience and the available literature. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

AE9/AP9/SMP: New Models for Radiation Belt And Space Plasma Specification

DTIC Science & Technology

2014-05-09

1 A ut ho rs •B ob J oh ns to n A ir Fo rc e R es ea rc h La b (P rin ci pa l I nv es tig at or ) •P au l O ’B rie n A er os pa ce C or p...P rin ci pa l I nv es tig at or ) •G re go ry G in et M IT L in co ln L ab (P rin ci pa l I nv es tig at or ) •S tu ar t H us to n A tm os

Advances in Solid State Joining of High Temperature Alloys

NASA Technical Reports Server (NTRS)

Ding, Jeff; Schneider, Judy

2011-01-01

Many of the metals used in the oil and gas industry are difficult to fusion weld including Titanium and its alloys. Solid state joining processes are being pursued as an alternative process to produce robust structures more amenable to high pressure applications. Various solid state joining processes include friction stir welding (FSW) and a patented modification termed thermal stir welding (TSW). The configuration of TSWing utilizes an induction coil to preheat the material minimizing the burden on the weld tool extending its life. This provides the ability to precisely select and control the temperature to avoid detrimental changes to the microstructure. The work presented in this presentation investigates the feasibility of joining various titanium alloys using the solid state welding processes of FSW and TSW. Process descriptions and attributes of each weld process will be presented. Weld process set ]up and welding techniques will be discussed leading to the challenges experienced. Mechanical property data will also be presented.

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

PubMed

Keane, Michael J

2014-01-01

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

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

PubMed Central

Keane, Michael J

2014-01-01

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

Lead-acid battery

NASA Technical Reports Server (NTRS)

Edwards, Dean B. (Inventor); Rippel, Wally E. (Inventor)

1986-01-01

A sealed, low maintenance battery (10, 100) is formed of a casing (14, 102) having a sealed lid (12, 104) enclosing cell compartments (22, 110) formed by walls (24, 132). The cells comprise a stack (26) of horizontally disposed negative active plates (30) and positive active plates (28) interspersed with porous, resilient separator sheets (30). Each plate has a set of evenly spaced tigs (40, 41) disposed on one side thereof; like polarity tigs being disposed on one side and opposite polarity tigs on the other. Columns of tigs are electrically and mechanically joined by vertical bus bars (46). The bus bars contain outwardly projecting arms (56) of opposite polarity which are electrically joined at each partition wall (24) to electrically connect the cells in series. The stack is compressed by biasing means such as resilient pad (58) attached to the lid or by joining the tigs (52) to the post (48) at a distance less than the thickness of the mat (124). The end bus bars (46) are joined to straps (60, 62) which connect to the terminals (16, 18). The negative plates contain more capacity than the positive plates and the starved electrolyte imbibed in the separator sheets permits pressurized operation during which oxygen diffuses through the separator sheet to the negative plate where it recombines. Excess pressure is relieved through the vent and pressure relief valve (20).

Design of the helium cooled lithium lead breeding blanket in CEA: from TBM to DEMO

NASA Astrophysics Data System (ADS)

Aiello, G.; Aubert, J.; Forest, L.; Jaboulay, J.-C.; Li Puma, A.; Boccaccini, L. V.

2017-04-01

The helium cooled lithium lead (HCLL) blanket concept was originally developed in CEA at the beginning of 2000: it is one of the two European blanket concepts to be tested in ITER in the form of a test blanket module (TBM) and one of the four blanket concepts currently being considered for the DEMOnstration reactor that will follow ITER. The TBM is a highly optimized component for the ITER environment that will provide crucial information for the development of the DEMO blanket, but its design needs to be adapted to the DEMO reactor. With respect to the TBM design, reduction of the steel content in the breeding zone (BZ) is sought in order to maximize tritium breeding reactions. Different options are being studied, with the potential of reaching tritium breeding ratio (TBR) values up to 1.21. At the same time, the design of the back supporting structure (BSS), which is a DEMO specific component that has to support the blanket modules inside the vacuum vessel (VV), is ongoing with the aim of maximizing the shielding power and minimizing pumping power. This implies a re-engineering of the modules’ attachment system. Design changes however, will have an impact on the manufacturing and assembly sequences that are being developed for the HCLL-TBM. Due to the differences in joint configurations, thicknesses to be welded, heat dissipation and the various technical constraints related to the accessibility of the welding tools and implementation of non-destructive examination (NDE), the manufacturing procedure should be adapted and optimized for DEMO design. Laser welding instead of TIG could be an option to reduce distortions. The time-of-flight diffraction (TOFD) technique is being investigated for NDE. Finally, essential information expected from the HCLL-TBM program that will be needed to finalize the DEMO design is discussed.

Comparison of joining processes for Haynes 230 nickel based super alloy

NASA Astrophysics Data System (ADS)

Williston, David Hugh

Haynes 230 is a nickel based, solid-solution strengthened alloy that is used for high-temperature applications in the aero-engine and power generation industries. The alloy composition is balanced to avoid precipitation of undesirable topologically closed-packed (TCP) intermetallic phases, such as Sigma, Mu, or Laves-type, that are detrimental to mechanical and corrosion properties. This material is currently being used for the NASA's J2X upper stage rocket nozzle extension. Current fabrication procedures use fusion welding processes to join blanks that are subsequently formed. Cracks have been noted to occur in the fusion welded region during the forming operations. Use of solid state joining processes, such as friction stir welding are being proposed to eliminate the fusion weld cracks. Of interest is a modified friction stir welding process called thermal stir welding. Three welding process: Gas Metal Arc Welding (GMAW), Electron Beam Welding (EBW), and Thermal Stir Welding (TSWing) are compared in this study.

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.

Hybrid laser arc welding: State-of-art review

NASA Astrophysics Data System (ADS)

Acherjee, Bappa

2018-02-01

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

Sustainability of Welding Process through Bobbin Friction Stir Welding

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy

PubMed Central

Campanelli, Sabina Luisa; Casalino, Giuseppe; Casavola, Caterina; Moramarco, Vincenzo

2013-01-01

Friction Stir Welding (FSW) is a solid-state joining process; i.e., no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW) is a combination in which the FSW is the dominant welding process and the laser pre-heats the weld. In this work FSW and LAFSW tests were conducted on 6 mm thick 5754H111 aluminum alloy plates in butt joint configuration. LAFSW is studied firstly to demonstrate the weldability of aluminum alloy using that technique. Secondly, process parameters, such as laser power and temperature gradient are investigated in order to evaluate changes in microstructure, micro-hardness, residual stress, and tensile properties. Once the possibility to achieve sound weld using LAFSW is demonstrated, it will be possible to explore the benefits for tool wear, higher welding speeds, and lower clamping force. PMID:28788430

Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy.

PubMed

Campanelli, Sabina Luisa; Casalino, Giuseppe; Casavola, Caterina; Moramarco, Vincenzo

2013-12-18

Friction Stir Welding (FSW) is a solid-state joining process; i.e. , no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW) is a combination in which the FSW is the dominant welding process and the laser pre-heats the weld. In this work FSW and LAFSW tests were conducted on 6 mm thick 5754H111 aluminum alloy plates in butt joint configuration. LAFSW is studied firstly to demonstrate the weldability of aluminum alloy using that technique. Secondly, process parameters, such as laser power and temperature gradient are investigated in order to evaluate changes in microstructure, micro-hardness, residual stress, and tensile properties. Once the possibility to achieve sound weld using LAFSW is demonstrated, it will be possible to explore the benefits for tool wear, higher welding speeds, and lower clamping force.

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

NASA Astrophysics Data System (ADS)

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

2018-04-01

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

Ultrashort pulse laser micro-welding of cyclo-olefin copolymers

NASA Astrophysics Data System (ADS)

Roth, Gian-Luca; Rung, Stefan; Hellmann, Ralf

2017-06-01

We report on the joining of transparent thermoplastic polymers using infrared femtosecond laser pulses. Due to nonlinear absorption, the developed micro-welding process for cyclo-olefin copolymers does not require any intermediate absorbing layers or any surface pre-processing of the welding partners. In view of an optimized and stable micro-welding process, the influence of the welding speed and focal position on both, the quality and shear force strength are investigated. We highlight that welding seam widths of down to 65 μm are feasible for welding speeds of up to 75 mm/s. However, a variation of the welding speed affects the required focal position for a successful joining process. The shear force strength of the welding seam is determined to 37 MPa, which corresponds to 64% of the shear strength of the bulk material and is not affected by the welding speed.

The Community Psychology Evaluation Nexus

ERIC Educational Resources Information Center

Sheldon, Jeffrey A.; Wolfe, Susan M.

2015-01-01

In 2012, the American Evaluation Association (AEA) added community psychology (CP) to its roster of topical interests groups (TIG). One of the highlights of the CP TIG program at the 2012 AEA Conference and the genesis of this "American Journal of Evaluation" Forum was a panel of accomplished community psychologists and evaluation…

Current and Developing Conceptions of Use: Evaluation Use TIG Survey Results.

ERIC Educational Resources Information Center

Preskill, Hallie; Caracelli, Valerie

1997-01-01

A survey was sent to members of the Evaluation Use Topical Interest Group (TIG) to determine their perceptions about and experiences with evaluation use. Responses from 282 members show agreement on the major purposes of evaluation and an increased use of performance-results oriented and formative evaluations. (SLD)

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

NASA Astrophysics Data System (ADS)

Unt, Anna; Poutiainen, Ilkka; Salminen, Antti

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

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

NASA Astrophysics Data System (ADS)

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

2015-11-01

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

Research on High-Strength Steels with an Improved Resistance against Weld Cracking.

DTIC Science & Technology

1984-06-01

rate. The cooling rate is also dependent upon the welding process selected. Gas Tungsten Arc Welding ( GTAW ), Gas Metal Arc Welding (GMAW), and Shielded...displacement (COD) was used to measure the magnitude 45 GTAW , GMAW, SMAW - SAW j ESW APPROXIMATE RANGES FOR WELDING PROCESSES Increased Martensite...following processes when joining metal, in order of decreasing frequency: GMAW, SMAW, GTAW , SAW, FCAW, and Electrogas welding. 0 The various regulatory

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.

An Optimized Trajectory Planning for Welding Robot

NASA Astrophysics Data System (ADS)

Chen, Zhilong; Wang, Jun; Li, Shuting; Ren, Jun; Wang, Quan; Cheng, Qunchao; Li, Wentao

2018-03-01

In order to improve the welding efficiency and quality, this paper studies the combined planning between welding parameters and space trajectory for welding robot and proposes a trajectory planning method with high real-time performance, strong controllability and small welding error. By adding the virtual joint at the end-effector, the appropriate virtual joint model is established and the welding process parameters are represented by the virtual joint variables. The trajectory planning is carried out in the robot joint space, which makes the control of the welding process parameters more intuitive and convenient. By using the virtual joint model combined with the B-spline curve affine invariant, the welding process parameters are indirectly controlled by controlling the motion curve of the real joint. To solve the optimal time solution as the goal, the welding process parameters and joint space trajectory joint planning are optimized.

Efficacy of dry-ice blasting in preventive maintenance of auto robotic assemblies

NASA Astrophysics Data System (ADS)

Baluch, Nazim; Mohtar, Shahimi; Abdullah, Che Sobry

2016-08-01

Welding robots are extensively applied in the automotive assemblies and `Spot Welding' is the most common welding application found in the auto stamping assembly manufacturing. Every manufacturing process is subject to variations - with resistance welding, these include; part fit up, part thickness variations, misaligned electrodes, variations in coating materials or thickness, sealers, weld force variations, shunting, machine tooling degradation; and slag and spatter damage. All welding gun tips undergo wear; an elemental part of the process. Though adaptive resistance welding control automatically compensates to keep production and quality up to the levels needed as gun tips undergo wear so that the welds remain reliable; the system cannot compensate for deterioration caused by the slag and spatter on the part holding fixtures, sensors, and gun tips. To cleanse welding robots of slag and spatter, dry-ice blasting has proven to be an effective remedy. This paper describes Spot welding process, analyses the slag and spatter formation during robotic welding of stamping assemblies, and concludes that the dry ice blasting process's utility in cleansing of welding robots in auto stamping plant operations is paramount and exigent.

Weld bonding of titanium with polyimide adhesives

NASA Technical Reports Server (NTRS)

Vaughan, R. W.; Sheppard, C. H.; Orell, M. K.

1975-01-01

A conductive adhesive primer and a capillary flow adhesive were developed for weld bonding titanium alloy joints. Both formulations contained ingredients considered to be non-carcinogenic. Lap-shear joint test specimens and stringer-stiffened panels were weld bonded using a capillary flow process to apply the adhesive. Static property information was generated for weld bonded joints over the temperature range of 219K (-65 F) to 561K (550 F). The capillary flow process was demonstrated to produce weld bonded joints of equal strength to the weld through weld bonding process developed previously.

Ultrasonic Stir Welding

NASA Technical Reports Server (NTRS)

Nabors, Sammy

2015-01-01

NASA Marshall Space Flight Center (MSFC) developed Ultrasonic Stir Welding (USW) to join large pieces of very high-strength metals such as titanium and Inconel. USW, a solid-state weld process, improves current thermal stir welding processes by adding high-power ultrasonic (HPU) energy at 20 kHz frequency. The addition of ultrasonic energy significantly reduces axial, frictional, and shear forces; increases travel rates; and reduces wear on the stir rod, which results in extended stir rod life. The USW process decouples the heating, stirring, and forging elements found in the friction stir welding process allowing for independent control of each process element and, ultimately, greater process control and repeatability. Because of the independent control of USW process elements, closed-loop temperature control can be integrated into the system so that a constant weld nugget temperature can be maintained during welding.

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.

A laser-based vision system for weld quality inspection.

PubMed

Huang, Wei; Kovacevic, Radovan

2011-01-01

Welding is a very complex process in which the final weld quality can be affected by many process parameters. In order to inspect the weld quality and detect the presence of various weld defects, different methods and systems are studied and developed. In this paper, a laser-based vision system is developed for non-destructive weld quality inspection. The vision sensor is designed based on the principle of laser triangulation. By processing the images acquired from the vision sensor, the geometrical features of the weld can be obtained. Through the visual analysis of the acquired 3D profiles of the weld, the presences as well as the positions and sizes of the weld defects can be accurately identified and therefore, the non-destructive weld quality inspection can be achieved.

A Laser-Based Vision System for Weld Quality Inspection

PubMed Central

Huang, Wei; Kovacevic, Radovan

2011-01-01

Welding is a very complex process in which the final weld quality can be affected by many process parameters. In order to inspect the weld quality and detect the presence of various weld defects, different methods and systems are studied and developed. In this paper, a laser-based vision system is developed for non-destructive weld quality inspection. The vision sensor is designed based on the principle of laser triangulation. By processing the images acquired from the vision sensor, the geometrical features of the weld can be obtained. Through the visual analysis of the acquired 3D profiles of the weld, the presences as well as the positions and sizes of the weld defects can be accurately identified and therefore, the non-destructive weld quality inspection can be achieved. PMID:22344308

Application of TRIZ Methodology in Diffusion Welding System Optimization

NASA Astrophysics Data System (ADS)

Ravinder Reddy, N.; Satyanarayana, V. V.; Prashanthi, M.; Suguna, N.

2017-12-01

Welding is tremendously used in metal joining processes in the manufacturing process. In recent years, diffusion welding method has significantly increased the quality of a weld. Nevertheless, diffusion welding has some extent short research and application progress. Therefore, diffusion welding has a lack of relevant information, concerned with the joining of thick and thin materials with or without interlayers, on welding design such as fixture, parameters selection and integrated design. This article intends to combine innovative methods in the application of diffusion welding design. This will help to decrease trial and error or failure risks in the welding process being guided by the theory of inventive problem solving (TRIZ) design method. This article hopes to provide welding design personnel with innovative design ideas under research and for practical application.

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.

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.

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.

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.

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

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

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.

Independent Consulting Topical Interest Group: 2004 Industry Survey

ERIC Educational Resources Information Center

Jarosewich, Tania; Essenmacher, Victoria L.; Lynch, Christina Olenik; Williams, Jennifer E.; Doino-Ingersoll, Jo Ann

2006-01-01

The American Evaluation Association's (AEA) Independent Consulting Topical Interest Group (IC TIG) has a membership of over eight hundred individuals who generally work as sole proprietors, in partnerships, or in small consulting firms. Well over a decade ago, the IC TIG conducted a survey of its membership (Bonnet, 1992). To gather current data…

Influence of Processing Parameters on the Flow Path in Friction Stir Welding

NASA Technical Reports Server (NTRS)

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

2006-01-01

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

Peculiarities of metal welding process modelling for the Arctic

NASA Astrophysics Data System (ADS)

Lagunov, Alexey; Fofanov, Andrey; Losunov, Anton

2017-09-01

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

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.

Towards Real Time Diagnostics of Hybrid Welding Laser/GMAW

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

Timothy Mcjunkin; Dennis C. Kunerth; Corrie Nichol

2013-07-01

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

Towards real time diagnostics of Hybrid Welding Laser/GMAW

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

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

2014-02-18

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

Towards real time diagnostics of Hybrid Welding Laser/GMAW

NASA Astrophysics Data System (ADS)

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

2014-02-01

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

Friction Stir Welding of Steel Alloys

NASA Technical Reports Server (NTRS)

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

2001-01-01

The friction stir welding process has been developed primarily for the welding of aluminum alloys. Other higher melting allows such, as steels are much more difficult to join. Special attention must be given to pin tool material selection and welding techniques. This paper addresses the joining of steels and other high melting point materials using the friction stir welding process. Pin tool material and welding parameters will be presented. Mechanical properties of weldments will also be presented. Significance: There are many applications for the friction stir welding process other than low melting aluminum alloys. The FSW process can be expanded for use with high melting alloys in the pressure vessel, railroad and ship building industries.

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.

Friction Stir Welding Development at NASA, Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

McGill, Preston; Gentz, Steve (Technical Monitor)

2001-01-01

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

An RpoS-dependent sRNA regulates the expression of a chaperone involved in protein folding

PubMed Central

Silva, Inês Jesus; Ortega, Álvaro Darío; Viegas, Sandra Cristina; García-del Portillo, Francisco; Arraiano, Cecília Maria

2013-01-01

Small noncoding RNAs (sRNAs) are usually expressed in the cell to face a variety of stresses. In this report we disclose the first target for SraL (also known as RyjA), a sRNA present in many bacteria, which is highly induced in stationary phase. We also demonstrate that this sRNA is directly transcribed by the major stress σ factor σS (RpoS) in Salmonella enterica serovar Typhimurium. We show that SraL sRNA down-regulates the expression of the chaperone Trigger Factor (TF), encoded by the tig gene. TF is one of the three major chaperones that cooperate in the folding of the newly synthesized cytosolic proteins and is the only ribosome-associated chaperone known in bacteria. By use of bioinformatic tools and mutagenesis experiments, SraL was shown to directly interact with the 5′ UTR of the tig mRNA a few nucleotides upstream of the Shine-Dalgarno region. Namely, point mutations in the sRNA (SraL*) abolished the repression of tig mRNA and could only down-regulate a tig transcript target with the respective compensatory mutations. We have also validated in vitro that SraL forms a stable duplex with the tig mRNA. This work constitutes the first report of a small RNA affecting protein folding. Taking into account that both SraL and TF are very well conserved in enterobacteria, this work will have important repercussions in the field. PMID:23893734

An RpoS-dependent sRNA regulates the expression of a chaperone involved in protein folding.

PubMed

Silva, Inês Jesus; Ortega, Alvaro Darío; Viegas, Sandra Cristina; García-Del Portillo, Francisco; Arraiano, Cecília Maria

2013-09-01

Small noncoding RNAs (sRNAs) are usually expressed in the cell to face a variety of stresses. In this report we disclose the first target for SraL (also known as RyjA), a sRNA present in many bacteria, which is highly induced in stationary phase. We also demonstrate that this sRNA is directly transcribed by the major stress σ factor σ(S) (RpoS) in Salmonella enterica serovar Typhimurium. We show that SraL sRNA down-regulates the expression of the chaperone Trigger Factor (TF), encoded by the tig gene. TF is one of the three major chaperones that cooperate in the folding of the newly synthesized cytosolic proteins and is the only ribosome-associated chaperone known in bacteria. By use of bioinformatic tools and mutagenesis experiments, SraL was shown to directly interact with the 5' UTR of the tig mRNA a few nucleotides upstream of the Shine-Dalgarno region. Namely, point mutations in the sRNA (SraL*) abolished the repression of tig mRNA and could only down-regulate a tig transcript target with the respective compensatory mutations. We have also validated in vitro that SraL forms a stable duplex with the tig mRNA. This work constitutes the first report of a small RNA affecting protein folding. Taking into account that both SraL and TF are very well conserved in enterobacteria, this work will have important repercussions in the field.

Process Parameter Optimization for Wobbling Laser Spot Welding of Ti6Al4V Alloy

NASA Astrophysics Data System (ADS)

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

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

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

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

During final preparations for start of the PDCF Inner Can (IC) qualification effort, welding was performed on an automated weld system known as the PICN. During the initial weld, using a pedigree canister and plug, a weld defect was observed. The defect resulted in a hole in the sidewall of the canister, and it was observed that the plug sidewall had not been consumed. This was a new type of failure not seen during development and production of legacy Bagless Transfer Cans (FB-Line/Hanford). Therefore, a team was assembled to determine the root cause and to determine if the process couldmore » be improved. After several brain storming sessions (MS and T, R and D Engineering, PDC Project), an evaluation matrix was established to direct this effort. The matrix identified numerous activities that could be taken and then prioritized those activities. This effort was limited by both time and resources (the number of canisters and plugs available for testing was limited). A discovery process was initiated to evaluate the Vendor's IC fabrication process relative to legacy processes. There were no significant findings, however, some information regarding forging/anneal processes could not be obtained. Evaluations were conducted to compare mechanical properties of the PDC canisters relative to the legacy canisters. Some differences were identified, but mechanical properties were determined to be consistent with legacy materials. A number of process changes were also evaluated. A heat treatment procedure was established that could reduce the magnetic characteristics to levels similar to the legacy materials. An in-situ arc annealing process was developed that resulted in improved weld characteristics for test articles. Also several tack welds configurations were addressed, it was found that increasing the number of tack welds (and changing the sequence) resulted in decreased can to plug gaps and a more stable weld for test articles. Incorporating all of the process improvements for the actual can welding process, however, did not result in an improved weld geometry. Several possibilities for the lack of positive response exist, some of which are that (1) an insufficient number of test articles were welded under prototypic conditions, (2) the process was not optimized so that significant improvements were observable over the 'noise', and (3) the in-situ arc anneal closed the gap down too much so the can was unable to exhaust pressure ahead of the weld. Several operational and mechanical improvements were identified. The weld clamps were changed to a design consistent with those used in the legacy operations. A helium puff operation was eliminated; it is believed that this operation was the cause of the original weld defect. Also, timing of plug mast movement was found to correspond with weld irregularities. The timing of the movement was changed to occur during weld head travel between tacks. In the end a three sequential tack weld process followed by a pulse weld at the same current and travel speed as was used for the legacy processes was suggested for use during the IC qualification effort. Relative to legacy welds, the PDC IC weld demonstrates greater fluctuation in the region of the weld located between tack welds. However, canister weld response (canister to canister) is consistent and with the aid of the optical mapping system (for targeting the cut position) is considered adequate. DR measurements and METs show the PDC IC welds to have sufficient ligament length to ensure adequate canister pressure/impact capacity and to ensure adequate stub function. The PDC welding process has not been optimized as a result of this effort. Differences remain between the legacy BTC welds and the PDC IC weld, but these differences are not sufficient to prevent resumption of the current PDC IC qualification effort. During the PDC IC qualification effort, a total of 17 cans will be welded and a variety of tests/inspections will be performed. The extensive data collected during that qualification effort should be of a sufficient population to determine if additional weld process optimization is necessary prior to production release.« less

Efficacy of telephone and mail intervention in patient compliance with antihypertensive drugs in hypertension. ETECUM-HTA study.

PubMed

Márquez Contreras, Emilio; Vegazo García, Onofre; Martel Claros, Nieves; Gil Guillén, Vicente; de la Figuera von Wichmann, Mariano; Casado Martínez, José Joaquín; Fernández, Raúl

2005-01-01

To study the efficacy of telephone and mail intervention in therapeutic compliance among patients with mild to moderate hypertension. A prospective controlled multicenter clinical trial. Eighty-five primary care centers in Spain, with a duration of 6 months. A total of 636 patients with newly diagnosed or uncontrolled hypertension were included. Interventions. The patients were randomized and distributed between the following groups: (i) control (CG) - under routine clinical management; (ii) mail intervention (MIG) - received a mailed message reinforcing compliance and reminding of the visits (15 days, 2 and 4 months); (iii) telephone intervention (TIG) - received a telephone call at 15 days, then at 7 and 15 weeks. Five visits were scheduled, with the measurement of blood pressure and counting of tablets. Compliers were defined as subjects showing 80-110% drug consumption. Calculations were made of mean percentage compliance (MPC) and compliers, mean blood pressure and percentage controlled subjects. Five hundred and thirty-eight patients completed the study (261 males); 85.5% were compliers (CI = 82.5-88.5; n = 460). The MPC was 95.1+/-19.6% (CI = 93.28-96.92). The CG consisted of 182 individuals, MIG = 172 and TIG = 184. Compliers represented 69.2% of the CG (CI 62.5-75.9%), 91.3% (CI = 87.1-95.5) of the MIG (p = 0.0001) and 96.2% of the TIG (CI 93.5-98.9%); the final MPC was 89.6%+/-15 in CG, 96.6%+/-12 in MIG and 99.1+/-26.8 in TIG (p = 0.0001). The percentage of controlled subjects was 47.2% in CG (CI = 40-54.4), 61.3% in MIG (CI = 54.1-68.5%) and 63.3% in TIG (CI = 56.4-70.2%) (p<0.05). TIG and MIG are effective measures for improving patient compliance in hypertension.

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.

Mathematical Model Of Variable-Polarity Plasma Arc Welding

NASA Technical Reports Server (NTRS)

Hung, R. J.

1996-01-01

Mathematical model of variable-polarity plasma arc (VPPA) welding process developed for use in predicting characteristics of welds and thus serves as guide for selection of process parameters. Parameters include welding electric currents in, and durations of, straight and reverse polarities; rates of flow of plasma and shielding gases; and sizes and relative positions of welding electrode, welding orifice, and workpiece.

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.

Variable polarity arc welding

NASA Technical Reports Server (NTRS)

Bayless, E. O., Jr.

1991-01-01

Technological advances generate within themselves dissatisfactions that lead to further advances in a process. A series of advances in welding technology which culminated in the Variable Polarity Plasma Arc (VPPA) Welding Process and an advance instituted to overcome the latest dissatisfactions with the process: automated VPPA welding are described briefly.

Comparison of grain to grain orientation and stiffness mapping by spatially resolved acoustic spectroscopy and EBSD.

PubMed

Mark, A F; Li, W; Sharples, S; Withers, P J

2017-07-01

Our aim was to establish the capability of spatially resolved acoustic spectroscopy (SRAS) to map grain orientations and the anisotropy in stiffness at the sub-mm to micron scale by comparing the method with electron backscatter diffraction (EBSD) undertaken within a scanning electron microscope. In the former the grain orientations are deduced by measuring the spatial variation in elastic modulus; conversely, in EBSD the elastic anisotropy is deduced from direct measurements of the crystal orientations. The two test-cases comprise mapping the fusion zones for large TIG and MMA welds in thick power plant austenitic and ferritic steels, respectively; these are technologically important because, among other things, elastic anisotropy can cause ultrasonic weld inspection methods to become inaccurate because it causes bending in the paths of sound waves. The spatial resolution of SRAS is not as good as that for EBSD (∼100 μm vs. ∼a few nm), nor is the angular resolution (∼1.5° vs. ∼0.5°). However the method can be applied to much larger areas (currently on the order of 300 mm square), is much faster (∼5 times), is cheaper and easier to perform, and it could be undertaken on the manufacturing floor. Given these advantages, particularly to industrial users, and the on-going improvements to the method, SRAS has the potential to become a standard method for orientation mapping, particularly in cases where the elastic anisotropy is important over macroscopic/component length scales. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Water corrosion of F82H-modified in simulated irradiation conditions by heat treatment

NASA Astrophysics Data System (ADS)

Lapeña, J.; Blázquez, F.

2000-12-01

This paper presents results of testing carried out on F82H in water at 260°C with 2 ppm H 2 and the addition of 0.27 ppm Li in the form of LiOH. Uniform corrosion tests have been carried out on as-received material and on specimens from welded material [TIG and electron beam (EB)]. Stress corrosion cracking (SCC) tests have been carried out in as-received material and in material heat treated to simulate neutron irradiation hardening (1075°C/30' a.c. and 1040°C/30' + 625°C/1 h a.c.) with hardness values of 405 and 270 HV30, respectively. Results for uniform corrosion after 2573 h of testing have shown weight losses of about 60 mg/dm 2. Compact tension (CT) specimens from the as-received material tested under constant load have not experienced crack growth. However, in the simulated irradiation conditions for a stress intensity factor between 40 and 80 MPa√m, crack growth rates of about 7×10 -8 m/s have been measured.

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

NASA Astrophysics Data System (ADS)

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

2015-01-01

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

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.

Multiphysics Modeling and Simulations of Mil A46100 Armor-Grade Martensitic Steel Gas Metal Arc Welding Process

NASA Astrophysics Data System (ADS)

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

2013-10-01

A multiphysics computational model has been developed for the conventional Gas Metal Arc Welding (GMAW) joining process and used to analyze butt-welding of MIL A46100, a prototypical high-hardness armor martensitic steel. The model consists of five distinct modules, each covering a specific aspect of the GMAW process, i.e., (a) dynamics of welding-gun behavior; (b) heat transfer from the electric arc and mass transfer from the electrode to the weld; (c) development of thermal and mechanical fields during the GMAW process; (d) the associated evolution and spatial distribution of the material microstructure throughout the weld region; and (e) the final spatial distribution of the as-welded material properties. To make the newly developed GMAW process model applicable to MIL A46100, the basic physical-metallurgy concepts and principles for this material have to be investigated and properly accounted for/modeled. The newly developed GMAW process model enables establishment of the relationship between the GMAW process parameters (e.g., open circuit voltage, welding current, electrode diameter, electrode-tip/weld distance, filler-metal feed speed, and gun travel speed), workpiece material chemistry, and the spatial distribution of as-welded material microstructure and properties. The predictions of the present GMAW model pertaining to the spatial distribution of the material microstructure and properties within the MIL A46100 weld region are found to be consistent with general expectations and prior observations.

Self-Reacting Friction Stir Welding for Aluminum Complex Curvature Applications

NASA Technical Reports Server (NTRS)

Brown, Randy J.; Martin, W.; Schneider, J.; Hartley, P. J.; Russell, Carolyn; Lawless, Kirby; Jones, Chip

2003-01-01

This viewgraph representation provides an overview of sucessful research conducted by Lockheed Martin and NASA to develop an advanced self-reacting friction stir technology for complex curvature aluminum alloys. The research included weld process development for 0.320 inch Al 2219, sucessful transfer from the 'lab' scale to the production scale tool and weld quality exceeding strenght goals. This process will enable development and implementation of large scale complex geometry hardware fabrication. Topics covered include: weld process development, weld process transfer, and intermediate hardware fabrication.

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

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

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

2015-02-12

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

Examination of the physical processes associated with the keyhole region of variable polarity plasma arc welds in aluminum alloy 2219

NASA Technical Reports Server (NTRS)

Walsh, Daniel W.

1987-01-01

The morphology and properties of the Variable Polarity Plasma Arc (VPPA) weld composite zone are intimately related to the physical processes associated with the keyhole. This study examined the effects of oxide, halide, and sulfate additions to the weld plate on the keyhole and the weld pool. Changes in both the arc plasma character and the bead morphology were correlated to the chemical environment of the weld. Pool behavior was observed by adding flow markers to actual VPPA welds. A low temperature analog to the welding process was developed. The results of the study indicate that oxygen, even at low partial pressures, can disrupt the stable keyhole and weld pool. The results also indicate that the Marangoni surface tension driven flows dominate the weld pool over the range of welding currents studied.

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

PubMed

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

2016-09-15

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

Friction Pull Plug Welding in Aluminum Alloys

NASA Technical Reports Server (NTRS)

Brooke, Shane A.; Bradford, Vann

2012-01-01

NASA's Marshall Space Flight Center (MSFC) has recently invested much time and effort into the process development of Friction Pull Plug Welding (FPPW). FPPW, is a welding process similar to Friction Push Plug Welding in that, there is a small rotating part (plug) being spun and simultaneously pulled (forged) into a larger part. These two processes differ, in that push plug welding requires an internal reaction support, while pull plug welding reacts to the load externally. FPPW was originally conceived as a post proof repair technique for the Space Shuttle fs External Tank. FPPW was easily selected as the primary weld process used to close out the termination hole on the Constellation Program's ARES I Upper Stage circumferential Self-Reacting Friction Stir Welds (SR-FSW). The versatility of FPPW allows it to also be used as a repair technique for both SR-FSW and Conventional Friction Stir Welds. To date, all MSFC led development has been concentrated on aluminum alloys (2195, 2219, and 2014). Much work has been done to fully understand and characterize the process's limitations. A heavy emphasis has been spent on plug design, to match the various weldland thicknesses and alloy combinations. This presentation will summarize these development efforts including weld parameter development, process control, parameter sensitivity studies, plug repair techniques, material properties including tensile, fracture and failure analysis.

Process Optimization of Dual-Laser Beam Welding of Advanced Al-Li Alloys Through Hot Cracking Susceptibility Modeling

NASA Astrophysics Data System (ADS)

Tian, Yingtao; Robson, Joseph D.; Riekehr, Stefan; Kashaev, Nikolai; Wang, Li; Lowe, Tristan; Karanika, Alexandra

2016-07-01

Laser welding of advanced Al-Li alloys has been developed to meet the increasing demand for light-weight and high-strength aerospace structures. However, welding of high-strength Al-Li alloys can be problematic due to the tendency for hot cracking. Finding suitable welding parameters and filler material for this combination currently requires extensive and costly trial and error experimentation. The present work describes a novel coupled model to predict hot crack susceptibility (HCS) in Al-Li welds. Such a model can be used to shortcut the weld development process. The coupled model combines finite element process simulation with a two-level HCS model. The finite element process model predicts thermal field data for the subsequent HCS hot cracking prediction. The model can be used to predict the influences of filler wire composition and welding parameters on HCS. The modeling results have been validated by comparing predictions with results from fully instrumented laser welds performed under a range of process parameters and analyzed using high-resolution X-ray tomography to identify weld defects. It is shown that the model is capable of accurately predicting the thermal field around the weld and the trend of HCS as a function of process parameters.

Method for controlling gas metal arc welding

DOEpatents

Smartt, H.B.; Einerson, C.J.; Watkins, A.D.

1987-08-10

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. 3 figs., 1 tab.

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.

Real time computer controlled weld skate

NASA Technical Reports Server (NTRS)

Wall, W. A., Jr.

1977-01-01

A real time, adaptive control, automatic welding system was developed. This system utilizes the general case geometrical relationships between a weldment and a weld skate to precisely maintain constant weld speed and torch angle along a contoured workplace. The system is compatible with the gas tungsten arc weld process or can be adapted to other weld processes. Heli-arc cutting and machine tool routing operations are possible applications.

Independent Consulting and the American Evaluation Association: Twenty Years Later

ERIC Educational Resources Information Center

Bonnet, Deborah G.

2006-01-01

This article reviews the evolution of American Evaluation Association's (AEA) Independent Consulting Topical Interest Group (IC TIG). The TIG goes back a joint meeting held in San Francisco in 1984 of the Evaluation Network (ENet) and the Evaluation Research Society (ERS), two years before the organizations merged to become the AEA. On the fringes…

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.

Optimization of hybrid laser arc welding of 42CrMo steel to suppress pore formation

NASA Astrophysics Data System (ADS)

Zhang, Yan; Chen, Genyu; Mao, Shuai; Zhou, Cong; Chen, Fei

2017-06-01

The hybrid laser arc welding (HLAW) of 42CrMo quenched and tempered steel was conducted. The effect of the processing parameters, such as the relative positions of the laser and the arc, the shielding gas flow rate, the defocusing distance, the laser power, the wire feed rate and the welding speed, on the pore formation was analyzed, the morphological characteristics of the pores were analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that the majority of the pores were invasive. The pores formed at the leading a laser (LA) welding process were fewer than those at the leading a arc (AL) welding process. Increasing the shielding gas flow rate could also facilitate the reduction of pores. The laser power and the welding speed were two key process parameters to reduce the pores. The flow of the molten pool, the weld cooling rate and the pore escaping rate as a result of different parameters could all affect pore formation. An ideal pore-free weld was obtained for the optimal welding process parameters.

Vacuum vapor deposition: A spinoff of space welding development

NASA Technical Reports Server (NTRS)

Poorman, R. M.

1991-01-01

A vapor deposition process has been defined through a spinoff effort of space welding development. In this development for welding in a space environment, a hollow electrode was used to add gas precisely at the welding arc. This provides gas for ionization which carries the welding arc current. During this welding development metal vapor coatings were observed. These coatings are unique in that they are produced by a new process. Some coatings produced and the potential of this new and innovative vapor deposition process are characterized. Advantages over prior art are discussed.

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

NASA Astrophysics Data System (ADS)

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

2018-03-01

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

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.

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.

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

PubMed

Caiazzo, Fabrizia; Caggiano, Alessandra

2018-04-20

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

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

PubMed Central

2018-01-01

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

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

DTIC Science & Technology

2001-12-01

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

The Mechanical Metallurgy of Armour Steels

DTIC Science & Technology

2016-10-01

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

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

NASA Astrophysics Data System (ADS)

Tsirkas, S. A.

2018-03-01

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

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

NASA Technical Reports Server (NTRS)

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

1972-01-01

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

Optimization of Gas Metal Arc Welding Process Parameters

NASA Astrophysics Data System (ADS)

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

2016-09-01

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

Experimental study of hot cracking at circular welding joints of 42CrMo steel

NASA Astrophysics Data System (ADS)

Zhang, Yan; Chen, Genyu; Chen, Binghua; Wang, Jinhai; Zhou, Cong

2017-12-01

The hot cracking at circular welding joints of quenched and tempered 42CrMo steel were studied. The flow of the molten pool and the solidification process of weld were observed with a high-speed video camera. The information on the variations in the weld temperature was collected using an infrared (IR) thermal imaging system. The metallurgical factors of hot cracking were analyzed via metallographic microscope and scanning electron microscope (SEM). The result shows that leading laser laser-metal active gas (MAG) hybrid welding process has a smaller solid-liquid boundary movement rate (VSL) and a smaller solid-liquid boundary temperature gradient (GSL) compared with leading arc laser-MAG hybrid welding process and laser welding process. Additionally, the metal in the molten pool has superior permeability while flowing toward the dendritic roots and can compensate for the inner-dendritic pressure balance. Therefore, leading laser laser-MAG hybrid welding process has the lowest hot cracking susceptibility.

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

NASA Astrophysics Data System (ADS)

Durocher, J.; Richards, N. L.

2011-10-01

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

Thermo-Mechanical Processing in Friction Stir Welds

NASA Technical Reports Server (NTRS)

Schneider, Judy

2003-01-01

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

Friction stir welding tool and process for welding dissimilar materials

DOEpatents

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

2013-05-07

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

Fusion welding process

DOEpatents

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

1983-01-01

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

49 CFR 195.222 - Welders: Qualification of welders.

Code of Federal Regulations, 2010 CFR

2010-10-01

... under that earlier edition. (b) No welder may weld with a welding process unless, within the preceding 6 calendar months, the welder has— (1) Engaged in welding with that process; and (2) Had one welded tested...

Mutagenicity of fume particles from metal arc welding on stainless steel in the Salmonella/microsome test.

PubMed

Maxild, J; Andersen, M; Kiel, P

1978-01-01

Mutagenic activity of fume particles produced by metal arc welding on stainless steel (ss) is demonstrated by using the Salmonella/microsome mutagenicity test described by Ames et al., with strain TA100 (base-pair substitution) and TA98 (frame-shift reversion). Results of a representative but limited selection of processes and materials show that mutagenic activity is a function of process and process parameters. Welding on stainless steel produces particles that are mutagenic, whereas welding on mild steel (ms) produces particles that are not. Manual metal arc (MMA) welding on stainless steel produces particles of higher mutagenic activity than does metal inert gas (MIG) welding, and fume particles produced by MIG welding under short-arc transfer. Further studies of welding fumes (both particles and gases) must be performed to determine process parameters of significance for the mutagenic activity.

Quality status display for a vibration welding process

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

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

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

Analysis And Control System For Automated Welding

NASA Technical Reports Server (NTRS)

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

1994-01-01

Automated variable-polarity plasma arc (VPPA) welding apparatus operates under electronic supervision by welding analysis and control system. System performs all major monitoring and controlling functions. It acquires, analyzes, and displays weld-quality data in real time and adjusts process parameters accordingly. Also records pertinent data for use in post-weld analysis and documentation of quality. System includes optoelectronic sensors and data processors that provide feedback control of welding process.

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

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

Dowden, J.; Kapadia, P.

1996-12-31

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

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.

Evaluation of Weldability for MAG and LASER with Galvannealed Steel.

PubMed

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

2018-03-01

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

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

NASA Astrophysics Data System (ADS)

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

2017-10-01

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

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.

Plasma arc welding repair of space flight hardware

NASA Technical Reports Server (NTRS)

Hoffman, David S.

1993-01-01

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

Guidelines in the Choice of Parameters for Hybrid Laser Arc Welding with Fiber Lasers

NASA Astrophysics Data System (ADS)

Eriksson, I.; Powell, J.; Kaplan, A.

Laser arc hybrid welding has been a promising technology for three decades and laser welding in combination with gas metal arc welding (GMAW) has shown that it is an extremely promising technique. On the other hand the process is often considered complicated and difficult to set up correctly. An important factor in setting up the hybrid welding process is an understanding of the GMAW process. It is especially important to understand how the wire feed rate and the arc voltage (the two main parameters) affect the process. In this paper the authors show that laser hybrid welding with a 1 μm laser is similar to ordinary GMAW, and several guidelines are therefore inherited by the laser hybrid process.

Minimum deltaV Burn Planning for the International Space Station Using a Hybrid Optimization Technique, Level 1

NASA Technical Reports Server (NTRS)

Brown, Aaron J.

2015-01-01

The International Space Station's (ISS) trajectory is coordinated and executed by the Trajectory Operations and Planning (TOPO) group at NASA's Johnson Space Center. TOPO group personnel routinely generate look-ahead trajectories for the ISS that incorporate translation burns needed to maintain its orbit over the next three to twelve months. The burns are modeled as in-plane, horizontal burns, and must meet operational trajectory constraints imposed by both NASA and the Russian Space Agency. In generating these trajectories, TOPO personnel must determine the number of burns to model, each burn's Time of Ignition (TIG), and magnitude (i.e. deltaV) that meet these constraints. The current process for targeting these burns is manually intensive, and does not take advantage of more modern techniques that can reduce the workload needed to find feasible burn solutions, i.e. solutions that simply meet the constraints, or provide optimal burn solutions that minimize the total DeltaV while simultaneously meeting the constraints. A two-level, hybrid optimization technique is proposed to find both feasible and globally optimal burn solutions for ISS trajectory planning. For optimal solutions, the technique breaks the optimization problem into two distinct sub-problems, one for choosing the optimal number of burns and each burn's optimal TIG, and the other for computing the minimum total deltaV burn solution that satisfies the trajectory constraints. Each of the two aforementioned levels uses a different optimization algorithm to solve one of the sub-problems, giving rise to a hybrid technique. Level 2, or the outer level, uses a genetic algorithm to select the number of burns and each burn's TIG. Level 1, or the inner level, uses the burn TIGs from Level 2 in a sequential quadratic programming (SQP) algorithm to compute a minimum total deltaV burn solution subject to the trajectory constraints. The total deltaV from Level 1 is then used as a fitness function by the genetic algorithm in Level 2 to select the number of burns and their TIGs for the next generation. In this manner, the two levels solve their respective sub-problems separately but collaboratively until a burn solution is found that globally minimizes the deltaV across the entire trajectory. Feasible solutions can also be found by simply using the SQP algorithm in Level 1 with a zero cost function. This paper discusses the formulation of the Level 1 sub-problem and the development of a prototype software tool to solve it. The Level 2 sub-problem will be discussed in a future work. Following the Level 1 formulation and solution, several look-ahead trajectory examples for the ISS are explored. In each case, the burn targeting results using the current process are compared against a feasible solution found using Level 1 in the proposed technique. Level 1 is then used to find a minimum deltaV solution given the fixed number of burns and burn TIGs. The optimal solution is compared with the previously found feasible solution to determine the deltaV (and therefore propellant) savings. The proposed technique seeks to both improve the current process for targeting ISS burns, and to add the capability to optimize ISS burns in a novel fashion. The optimal solutions found using this technique can potentially save hundreds of kilograms of propellant over the course of the ISS mission compared to feasible solutions alone. While the software tool being developed to implement this technique is specific to ISS, the concept is extensible to other long-duration, central-body orbiting missions that must perform orbit maintenance burns to meet operational trajectory constraints.

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

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

Intelligent Weld Manufacturing: Role of Integrated Computational Welding Engineering

DOE PAGES

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

2017-12-02

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

Intelligent Weld Manufacturing: Role of Integrated Computational Welding Engineering

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

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

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

Online monitoring of thermo-cycles and its correlation with microstructure in laser cladding of nickel based super alloy

NASA Astrophysics Data System (ADS)

Muvvala, Gopinath; Patra Karmakar, Debapriya; Nath, Ashish Kumar

2017-01-01

Laser cladding, basically a weld deposition technique, is finding applications in many areas including surface coatings, refurbishment of worn out components and generation of functionally graded components owing to its various advantages over conventional methods like TIG, PTA etc. One of the essential requirements to adopt this technique in industrial manufacturing is to fulfil the increasing demand on product quality which could be controlled through online process monitoring and correlating the signals with the mechanical and metallurgical properties. Rapid thermo-cycle i.e. the fast heating and cooling rates involved in this process affect above properties of the deposited layer to a great extent. Therefore, the current study aims to monitor the thermo-cycles online, understand its variation with process parameters and its effect on different quality aspects of the clad layer, like microstructure, elemental segregations and mechanical properties. The effect of process parameters on clad track geometry is also studied which helps in their judicious selection to deposit a predefined thickness of coating. In this study Inconel 718, a nickel based super alloy is used as a clad material and AISI 304 austenitic steel as a substrate material. The thermo-cycles during the cladding process were recorded using a single spot monochromatic pyrometer. The heating and cooling rates were estimated from the recorded thermo-cycles and its effects on microstructures were characterised using SEM and XRD analyses. Slow thermo-cycles resulted in severe elemental segregations favouring Laves phase formation and increased γ matrix size which is found to be detrimental to the mechanical properties. Slow cooling also resulted in termination of epitaxial growth, forming equiaxed grains near the surface, which is not preferred for single crystal growth. Heat treatment is carried out and the effect of slow cooling and the increased γ matrix size on dissolution of segregated elements in metal matrix is studied.

Empirical first-line treatment with tigecycline for febrile episodes following abdominal surgery in cancer patients.

PubMed

Secondo, Giovanni; Vassallo, Francesca; Solari, Nicola; Moresco, Luciano; Percivale, Pierluigi; Zappi, Lucia; Cafiero, Ferdinando; De Maria, Andrea

2010-11-01

Cancer patients with complicated infections following abdominal surgery represent one of the worst clinical scenarios that is useful for testing the efficacy of empirical antimicrobial therapy. No study so far has evaluated the performance of tigecycline (TIG) when administered as empirical first-line treatment in a homogeneous population of surgical cancer patients with a febrile episode. An observational review of the data records of 24 sequential patients receiving TIG for a febrile episode following a major abdominal procedure in a single cancer institute was performed. Large bowel surgery represented 68% of all procedures, followed by gastric surgery (16%) and urinary-gynaecologic-biliary surgery (16%). Complications following surgery were observed in 68% of febrile episodes, with peritonitis and sepsis accounting for 59% and 24% of complications, respectively. Eight patients needed repeat surgery for source control. The mean duration of TIG treatment was 8 days. Causative pathogens were detected in 16 episodes (64%), and a total of 44 microorganisms were recovered (29% Escherichia coli, 9% Enterococcus faecalis and 9% coagulase-negative staphylococci). TIG was effective in 12 episodes (48%). The success rate was 67% when infectious episodes sustained by intrinsically resistant bacteria and fungi were excluded. Treatment failure was associated with the presence of complications and with microbiologically documented infection. TIG may be useful as a first-line treatment option in cancer patients requiring antibiotic treatment following surgery when complications are not present or suspected on clinical grounds and when local microbial epidemiology shows a low incidence of primary resistant bacteria. Copyright © 2010 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

H2O2 accelerates cellular senescence by accumulation of acetylated p53 via decrease in the function of SIRT1 by NAD+ depletion.

PubMed

Furukawa, Ayako; Tada-Oikawa, Saeko; Kawanishi, Shosuke; Oikawa, Shinji

2007-01-01

It has been reported that p53 acetylation, which promotes cellular senescence, can be regulated by the NAD(+)-dependent deacetylase SIRT1, the human homolog of yeast Sir2, a protein that modulates lifespan. To clarify the role of SIRT1 in cellular senescence induced by oxidative stress, we treated normal human diploid fibroblast TIG-3 cells with H(2)O(2) and examined DNA cleavage, depletion of intracellular NAD(+), expression of p21, SIRT1, and acetylated p53, cell cycle arrest, and senescence-associated beta-galactosidase (SA-beta-gal) activity. DNA cleavage was observed immediately in TIG-3 cells treated with H(2)O(2), though no cell death was observed. NAD(+) levels in TIG-3 cells treated with H(2)O(2) were also decreased significantly. Pre-incubation with the poly (ADP-ribose) polymerase (PARP) inhibitor resulted in preservation of intracellular NAD(+) levels. The amount of acetylated p53 was increased in TIG-3 cells at 4h after H(2)O(2) treatment, while there was little to no decrease in SIRT1 protein expression. The expression level of p21 was increased at 12h and continued to increase for up to 24h. Additionally, exposure of TIG-3 cells to H(2)O(2) induced cell cycle arrest at 24h and increased SA-beta-gal activity at 48h. This pathway likely plays an important role in the acceleration of cellular senescence by oxidative stress.

Socket welds in nuclear facilities

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

Anderson, P.A.; Torres, L.L.

1995-12-31

Socket welds are easier and faster to make than are butt welds. However, they are often not used in nuclear facilities because the crevices between the pipes and the socket sleeves may be subject to crevice corrosion. If socket welds can be qualified for wider use in facilities that process nuclear materials, the radiation exposures to welders can be significantly reduced. The current tests at the Idaho Chemical Processing Plant (ICPP) are designed to determine if socket welds can be qualified for use in the waste processing system at a nuclear fuel processing plant.

The variable polarity plasma arc welding process: Its application to the Space Shuttle external tank

NASA Technical Reports Server (NTRS)

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

1983-01-01

The technical history of the variable polarity plasma arc (VPPA) welding process being introduced as a partial replacement for the gas shielded tungsten arc process in assembly welding of the space shuttle external tank is described. Interim results of the weld strength qualification studies, and plans for further work on the implementation of the VPPA process are included.

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

NASA Astrophysics Data System (ADS)

Pan, Yi; Lados, Diana A.

2017-04-01

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

Saturn S-2 production operations techniques: Production welding. Volume 1: Bulkhead welding

NASA Technical Reports Server (NTRS)

Abel, O. G.

1970-01-01

The complex Saturn S-2 welding processes and procedures required considerable development and refinement to establish a production capability that could consistently produce aluminum alloy welds within specified requirements. The special processes and techniques are defined that were established for the welding of gore-to-gore and manhole- or closeout-to-gore.

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.

VPPA weld model evaluation

NASA Technical Reports Server (NTRS)

Mccutcheon, Kimble D.; Gordon, Stephen S.; Thompson, Paul A.

1992-01-01

NASA uses the Variable Polarity Plasma Arc Welding (VPPAW) process extensively for fabrication of Space Shuttle External Tanks. This welding process has been in use at NASA since the late 1970's but the physics of the process have never been satisfactorily modeled and understood. In an attempt to advance the level of understanding of VPPAW, Dr. Arthur C. Nunes, Jr., (NASA) has developed a mathematical model of the process. The work described in this report evaluated and used two versions (level-0 and level-1) of Dr. Nunes' model, and a model derived by the University of Alabama at Huntsville (UAH) from Dr. Nunes' level-1 model. Two series of VPPAW experiments were done, using over 400 different combinations of welding parameters. Observations were made of VPPAW process behavior as a function of specific welding parameter changes. Data from these weld experiments was used to evaluate and suggest improvements to Dr. Nunes' model. Experimental data and correlations with the model were used to develop a multi-variable control algorithm for use with a future VPPAW controller. This algorithm is designed to control weld widths (both on the crown and root of the weld) based upon the weld parameters, base metal properties, and real-time observation of the crown width. The algorithm exhibited accuracy comparable to that of the weld width measurements for both aluminum and mild steel welds.

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

PubMed Central

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

2016-01-01

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

Rapid fabricating technique for multi-layered human hepatic cell sheets by forceful contraction of the fibroblast monolayer.

PubMed

Sakai, Yusuke; Koike, Makiko; Hasegawa, Hideko; Yamanouchi, Kosho; Soyama, Akihiko; Takatsuki, Mitsuhisa; Kuroki, Tamotsu; Ohashi, Kazuo; Okano, Teruo; Eguchi, Susumu

2013-01-01

Cell sheet engineering is attracting attention from investigators in various fields, from basic research scientists to clinicians focused on regenerative medicine. However, hepatocytes have a limited proliferation potential in vitro, and it generally takes a several days to form a sheet morphology and multi-layered sheets. We herein report our rapid and efficient technique for generating multi-layered human hepatic cell (HepaRG® cell) sheets using pre-cultured fibroblast monolayers derived from human skin (TIG-118 cells) as a feeder layer on a temperature-responsive culture dish. Multi-layered TIG-118/HepaRG cell sheets with a thick morphology were harvested on day 4 of culturing HepaRG cells by forceful contraction of the TIG-118 cells, and the resulting sheet could be easily handled. In addition, the human albumin and alpha 1-antitrypsin synthesis activities of TIG-118/HepaRG cells were approximately 1.2 and 1.3 times higher than those of HepaRG cells, respectively. Therefore, this technique is considered to be a promising modality for rapidly fabricating multi-layered human hepatocyte sheets from cells with limited proliferation potential, and the engineered cell sheet could be used for cell transplantation with highly specific functions.

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

NASA Astrophysics Data System (ADS)

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

2014-07-01

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

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.

Design of a robust fuzzy controller for the arc stability of CO(2) welding process using the Taguchi method.

PubMed

Kim, Dongcheol; Rhee, Sehun

2002-01-01

CO(2) welding is a complex process. Weld quality is dependent on arc stability and minimizing the effects of disturbances or changes in the operating condition commonly occurring during the welding process. In order to minimize these effects, a controller can be used. In this study, a fuzzy controller was used in order to stabilize the arc during CO(2) welding. The input variable of the controller was the Mita index. This index estimates quantitatively the arc stability that is influenced by many welding process parameters. Because the welding process is complex, a mathematical model of the Mita index was difficult to derive. Therefore, the parameter settings of the fuzzy controller were determined by performing actual control experiments without using a mathematical model of the controlled process. The solution, the Taguchi method was used to determine the optimal control parameter settings of the fuzzy controller to make the control performance robust and insensitive to the changes in the operating conditions.

49 CFR 178.61 - Specification 4BW welded steel cylinders with electric-arc welded longitudinal seam.

Code of Federal Regulations, 2014 CFR

2014-10-01

.... Cylinders closed in by spinning process are not authorized. (b) Authorized steel. Steel used in the.... Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced... seams must be of the butt welded type. Welds must be made by a machine process including automatic feed...

49 CFR 178.61 - Specification 4BW welded steel cylinders with electric-arc welded longitudinal seam.

Code of Federal Regulations, 2013 CFR

2013-10-01

.... Cylinders closed in by spinning process are not authorized. (b) Authorized steel. Steel used in the.... Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced... seams must be of the butt welded type. Welds must be made by a machine process including automatic feed...

49 CFR 178.61 - Specification 4BW welded steel cylinders with electric-arc welded longitudinal seam.

Code of Federal Regulations, 2012 CFR

2012-10-01

.... Cylinders closed in by spinning process are not authorized. (b) Authorized steel. Steel used in the.... Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced... seams must be of the butt welded type. Welds must be made by a machine process including automatic feed...

Evaluation Of Four Welding Arc Processes Applied To 6061 Aluminium Alloy

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

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

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

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

NASA Astrophysics Data System (ADS)

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

2011-01-01

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

Possibilities in optical monitoring of laser welding process

NASA Astrophysics Data System (ADS)

Horník, Petr; Mrňa, Libor; Pavelka, Jan

2016-11-01

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

Automatic Control Of Length Of Welding Arc

NASA Technical Reports Server (NTRS)

Iceland, William F.

1991-01-01

Nonlinear relationships among current, voltage, and length stored in electronic memory. Conceptual microprocessor-based control subsystem maintains constant length of welding arc in gas/tungsten arc-welding system, even when welding current varied. Uses feedback of current and voltage from welding arc. Directs motor to set position of torch according to previously measured relationships among current, voltage, and length of arc. Signal paths marked "calibration" or "welding" used during those processes only. Other signal paths used during both processes. Control subsystem added to existing manual or automatic welding system equipped with automatic voltage control.

Friction Pull Plug Welding in Aluminum Alloys

NASA Technical Reports Server (NTRS)

Brooke, Shane A.; Bradford, Vann; Burkholder, Jonathon

2011-01-01

NASA fs Marshall Space Flight Center (MSFC) has recently invested much time and effort into the process development of Friction Pull Plug Welding (FPPW). FPPW, is a welding process similar to Friction Push Plug Welding in that, there is a small rotating part (plug) being spun and simultaneously pulled (forged) into a larger part. These two processes differ, in that push plug welding requires an internal reaction support, while pull plug welding reacts to the load externally. FPPW was originally conceived as a post proof repair technique for External Tank. FPPW was easily selected as the primary process used to close out the termination hole on the Constellation Program fs ARES I Upper Stage circumferential Self ] Reacting Friction Stir Welds (SR ]FSW). The versatility of FPPW allows it to also be used as a repair technique for both SR ]FSW and Conventional Friction Stir Welds. To date, all MSFC led development has been concentrated on aluminum alloys (2195, 2219, and 2014). Much work has been done to fully understand and characterize the process fs limitations. A heavy emphasis has been spent on plug design, to match the various weldland thicknesses and alloy combinations. This presentation will summarize these development efforts including weld parameter development, process control, parameter sensitivity studies, plug repair techniques, material properties including tensile, fracture and failure analysis.

Effect of Mg and Cu on mechanical properties of high-strength welded joints of aluminum alloys obtained by laser welding

NASA Astrophysics Data System (ADS)

Annin, B. D.; Fomin, V. M.; Karpov, E. V.; Malikov, A. G.; Orishich, A. M.

2017-09-01

Results of experimental investigations of welded joints of high-strength aluminum-lithium alloys of the Al-Cu-Li and Al-Mg-Li systems are reported. The welded joints are obtained by means of laser welding and are subjected to various types of processing for obtaining high-strength welded joints. A microstructural analysis is performed. The phase composition and mechanical properties of the welded joints before and after heat treatment are studied. It is found that combined heat treatment of the welded joint (annealing, quenching, and artificial ageing) increases the joint strength, but appreciably decreases the alloy strength outside the region thermally affected by the welding process.

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

NASA Astrophysics Data System (ADS)

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

2011-02-01

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

Welding arc plasma physics

NASA Technical Reports Server (NTRS)

Cain, Bruce L.

1990-01-01

The problems of weld quality control and weld process dependability continue to be relevant issues in modern metal welding technology. These become especially important for NASA missions which may require the assembly or repair of larger orbiting platforms using automatic welding techniques. To extend present welding technologies for such applications, NASA/MSFC's Materials and Processes Lab is developing physical models of the arc welding process with the goal of providing both a basis for improved design of weld control systems, and a better understanding of how arc welding variables influence final weld properties. The physics of the plasma arc discharge is reasonably well established in terms of transport processes occurring in the arc column itself, although recourse to sophisticated numerical treatments is normally required to obtain quantitative results. Unfortunately the rigor of these numerical computations often obscures the physics of the underlying model due to its inherent complexity. In contrast, this work has focused on a relatively simple physical model of the arc discharge to describe the gross features observed in welding arcs. Emphasis was placed of deriving analytic expressions for the voltage along the arc axis as a function of known or measurable arc parameters. The model retains the essential physics for a straight polarity, diffusion dominated free burning arc in argon, with major simplifications of collisionless sheaths and simple energy balances at the electrodes.

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.

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.

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