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Sample records for fusion welding improvements

  1. 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.

  2. Physics of Fusion Welding

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.

    1986-01-01

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

  3. Aluminum Lithium Alloy 2195 Fusion Welding Improvements with New Filler Wire

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  4. Aluminum Lithium Alloy 2195 Fusion Welding Improvements with New Filler Wire

    NASA Technical Reports Server (NTRS)

    Russell, C.

    2001-01-01

    The objective of this research was to assess the B218 weld filler wire for Super Lightweight External Tank production, which could improve current production welding and repair productivity. We took the following approaches: (1) Perform a repair weld quick look evaluation between 4043/B218 and B218/B218 weld filler wire combinations and evaluation tensile properties for planished and unplanished conditions; and (2) Perform repair weld evaluation on structural simulation panel using 4043-B218 and B218/B218 weld filler wire combinations and evaluation tensile and simulated service fracture properties for planished and unplanished conditions.

  5. U-Groove aluminum weld strength improvement

    NASA Technical Reports Server (NTRS)

    Verderaime, V.; Vaughan, R.

    1996-01-01

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

  6. U-groove aluminum weld strength improvement

    NASA Technical Reports Server (NTRS)

    Verderaime, V.; Vaughan, R.

    1995-01-01

    Though butt-welds are among the most preferred joining methods in aerostructures, their strength dependence on inelastic mechanics is generally the least understood. This study investigated experimental strain distributions across a thick aluminum U-grooved weld and identified two weld process considerations for improving the multipass weld strength. The extreme thermal expansion and contraction gradient of the fusion heat input across the groove tab thickness produces severe peaking which induces bending under uniaxial loading. The filler strain-hardening deceased with increasing filler pass sequence, producing the weakest welds on the last pass side. Current welding schedules unknowingly compound these effects which reduce the weld strength. A de-peaking index model was developed to select filler pass thicknesses, pass numbers, and sequences to improve de-peaking in the welding process. Intent is to combine the strongest weld pass side with the peaking induced bending tension to provide a more uniform stress and stronger weld under axial tensile loading.

  7. FUSION WELDING METHOD AND APPARATUS

    DOEpatents

    Wyman, W.L.; Steinkamp, W.I.

    1961-01-17

    An apparatus for the fusion welding of metal pieces at a joint is described. The apparatus comprises a highvacuum chamber enclosing the metal pieces and a thermionic filament emitter. Sufficient power is applied to the emitter so that when the electron emission therefrom is focused on the joint it has sufficient energy to melt the metal pieces, ionize the metallic vapor abcve the molten metal, and establish an arc discharge between the joint and the emitter.

  8. U-Groove Aluminum Weld Strength Improvement

    NASA Technical Reports Server (NTRS)

    Verderaime, V.; Vaughan, R.

    1997-01-01

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

  9. Fusion welding. (Latest citations from the EI Compendex*plus database). Published Search

    SciTech Connect

    Not Available

    1994-11-01

    The bibliography contains citations concerning the fusion welding of metals and non-metals. Among the materials cited are aluminum alloys, stainless steel, high density polyethylenes, titanium, ceramic fibers, and glass. Improvement of fusion welding through modeling and real-time control, studies on the bloating mechanism of shales, and prevention of fusion welding are also examined. (Contains a minimum of 53 citations and includes a subject term index and title list.)

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  11. An Improved Method of Capturing the Surface Boundary of a Ti-6Al-4V Fusion Weld Bead for Finite Element Modeling

    NASA Astrophysics Data System (ADS)

    Turner, R. P.; Villa, M.; Sovani, Y.; Panwisawas, C.; Perumal, B.; Ward, R. M.; Brooks, J. W.; Basoalto, H. C.

    2016-02-01

    Weld simulation methods have often employed mathematical functions to describe the size and shape of the molten pool of material transiently present in a weld. However, while these functions can sometimes accurately capture the fusion boundary for certain welding parameters in certain materials, they do not necessarily offer a robust methodology for the more intricate weld pool shapes that can be produced in materials with a very low thermal conductivity, such as the titanium alloy Ti-6Al-4V. Cross-sections of steady-state welds can be observed which contain a dramatic narrowing of the pool width at roughly half way in to the depth of the plate of material, and a significant widening again at the base. These effects on the weld pool are likely to do with beam focusing height. However, the resultant intricacy of the pool means that standard formulaic methods to capture the shape may prove relatively unsuccessful. Given how critical the accuracy of pool shape is in determining the mechanical response to the heating, an alternative method is presented. By entering weld pool width measurements for a series of depths in a Cartesian co-ordinate system using FE weld simulation software Sysweld, a more representative weld pool size and shape can be predicted, compared to the standard double ellipsoid method. Results have demonstrated that significant variations in the mid-depth thermal profile are observed between the two, even though the same values for top and bottom pool-widths are entered. Finally, once the benefits of the Cartesian co-ordinate method are demonstrated, the robustness of this approach to predict a variety of weld pool shapes has been demonstrated upon a series of nine weld simulations, where the two key process parameters (welding laser power and travel speed) are explored over a design space ranging from 1.5 to 3 kW and 50 to 200 mm/s. Results suggest that for the faster travel speeds, the more detailed Cartesian co-ordinate method is better, whereas

  12. 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.

  13. Tailoring defect free fusion welds based on phenomenological modeling

    NASA Astrophysics Data System (ADS)

    Kumar, Amit

    In the last few decades, phenomenological models of fusion welding have provided important understanding and information about the welding processes and welded materials. For example, numerical calculations of heat transfer and fluid flow in welding have enabled accurate quantitative calculations of thermal cycles and fusion zone geometry in fusion welding. In many simple systems such as gas tungsten arc (GTA) butt welding, the computed thermal cycles have been used to quantitatively understand weld metal phase compositions, grain sizes and inclusion structure. However, fabrication of defect free welds with prescribed attributes based on scientific principles still remains to be achieved. In addition, higher fabrication speeds are often limited by the occurrence of humping defects which are characterized by periodic bead-like appearance. Furthermore, phenomenological models have not been applied to tailor welds with given attributes. The goal of the present work is to apply the principles of heat transfer and fluid flow to attain defects free welds with prescribed attributes. Since there are a large number of process variables in welding, the desired weld attributes such as the weld geometry and structure are commonly produced by empirically adjusting the welding variables. However, this approach does not always produce optimum welds and inappropriate choice of variables can lead to poor welds. The existing transport phenomena based models of welding can only predict weld characteristics for a given set of input welding variables. What is needed, and not currently available, is a capability to systematically determine multiple paths to tailor weld geometry and assess robustness of each individual solution to achieve safe, defect free welds. Therefore, these heat transfer and fluid flow based models are restructured to predict the welding conditions to achieve the defect free welds with desired attributes. Systematic tailoring of weld attributes based on scientific

  14. Modeling of Heat and Mass Transfer in Fusion Welding

    SciTech Connect

    Zhang, Wei

    2011-01-01

    In fusion welding, parts are joined together by melting and subsequent solidification. Although this principle is simple, complex transport phenomena take place during fusion welding, and they determine the final weld quality and performance. The heat and mass transfer in the weld pool directly affect the size and shape of the pool, the solidification microstructure, the formation of weld defects such as porosity and humping, and the temperature distribution in the fusion zone and heat-affected zone (HAZ). Furthermore, the temperature evolution affects the kinetics and extent of various solid-state phase transformations, which in turn determine the final weld microstructure and mechanical properties. The formation of residual stresses and distortion originates from the thermal expansion and contraction during welding heating and cooling, respectively.

  15. Microstructure Improvement in Weld Metal under the Ultrasonic Application

    SciTech Connect

    Cui, Yan; Xu, Cailu; Han, Qingyou

    2007-01-01

    When considering the operational performance of weldments in the engineering projects, the most important issues to be considered are weld metal mechanical properties, integrity of the welded joint, and weldability 1 . These issues are closely related to the microstructure of the weld metal. A significant amount of research has been carried out to alter the process variables and to use external devices to obtain microstructure control of the weldments. It has been reported that grain refined microstructure not only reduces cracking behavior of alloys including solidification cracking, cold cracking and reheat cracking, 2 - 5 but also improves the mechanical properties of the weld metal, such as toughness, ductility, strength, and fatigue life. 6, 7 Weld pool stirring, 8 arc oscillation, 9, 10 arc pulsation, 11 , and magnetic arc oscillator 12, 13 have been applied to fusion welding to refine the microstructures. This article describes initial experimental results on the use of power ultrasonic vibration to refine the microstructure of weld metals.

  16. Diffusion welding in air. [solid state welding of butt joint by fusion welding, surface cleaning, and heating

    NASA Technical Reports Server (NTRS)

    Moore, T. J.; Holko, K. H. (Inventor)

    1974-01-01

    Solid state welding a butt joint by fusion welding the peripheral surfaces to form a seal is described along with, autogenetically cleaning the faying or mating surfaces of the joint by heating the abutting surfaces to 1,200 C and heating to the diffusion welding temperature in air.

  17. Fusion welding of a modern borated stainless steel

    SciTech Connect

    Robino, C.V.; Cieslak, M.J.

    1997-01-01

    Experiments designed to assess the fabrication and service weldability of 304B4A borated stainless steel were conducted. Welding procedures and parameters for manual gas tungsten arc (GTA) welding, autogenous electron beam (EB) welding and filler-added EB welding were developed and found to be similar to those for austenitic stainless steels. Following the procedure development, four test welds were produced and evaluated by microstructural analysis and Charpy impact testing. Further samples were used for determination of the postweld heat treatment (PWHT) response of the welds. The fusion zone structure of welds in this alloy consists of primary austenite dendrites with an interdendritic eutectic-like austenite/boride constituent. Welds also show an appreciable partially molten zone that consists of the austenite/boride eutectic surrounding unmelted austenite islands. The microstructure of the EB welds was substantially finer than that of the GTA welds, and boride coarsening was not observed in the solid state heat-affected zone (HAZ) of either weld type. The impact toughness of as-welded samples was found to be relatively poor, averaging less than 10 J for both GTA and EB welds. For fusion zone notched GTA and EB samples and centerline notched EB samples, fracture generally occurred along the boundary between the partially molten and solid-state regions of the HAZ. The results of the PWHT study were very encouraging, with typical values of the impact energy for HAZ notched samples approaching 40 J, or twice the minimum code-acceptable value.

  18. Sensor fusion using neural network in the robotic welding

    SciTech Connect

    Ohshima, Kenji; Yabe, Masaaki; Akita, Kazuya; Kugai, Katsuya; Yamane, Satoshi; Kubota, Takefumi

    1995-12-31

    It is important to realize intelligent welding robots to obtain a good quality of the welding results. For this purpose, it is required to detect the torch height, the torch attitude, the deviation from the center of the gap. In order to simultaneously detect those, the authors propose the sensor fusion by using the neural network, i.e., the information concerning the welding torch is detected by using both the welding current and the welding voltage. First, the authors deal with the welding phenomena as the melting phenomena in the electrode wire of the MIG welding and the CO{sub 2} short circuiting welding. Next, the training data of the neutral networks are made from the numerical simulations. The neuro arc sensor is trained so as to get the desired performance of the sensor. By using it, the seam tracking is carried out in the T-joint.

  19. Classification of weld defect based on information fusion technology for radiographic testing system

    NASA Astrophysics Data System (ADS)

    Jiang, Hongquan; Liang, Zeming; Gao, Jianmin; Dang, Changying

    2016-03-01

    Improving the efficiency and accuracy of weld defect classification is an important technical problem in developing the radiographic testing system. This paper proposes a novel weld defect classification method based on information fusion technology, Dempster-Shafer evidence theory. First, to characterize weld defects and improve the accuracy of their classification, 11 weld defect features were defined based on the sub-pixel level edges of radiographic images, four of which are presented for the first time in this paper. Second, we applied information fusion technology to combine different features for weld defect classification, including a mass function defined based on the weld defect feature information and the quartile-method-based calculation of standard weld defect class which is to solve a sample problem involving a limited number of training samples. A steam turbine weld defect classification case study is also presented herein to illustrate our technique. The results show that the proposed method can increase the correct classification rate with limited training samples and address the uncertainties associated with weld defect classification.

  20. Classification of weld defect based on information fusion technology for radiographic testing system.

    PubMed

    Jiang, Hongquan; Liang, Zeming; Gao, Jianmin; Dang, Changying

    2016-03-01

    Improving the efficiency and accuracy of weld defect classification is an important technical problem in developing the radiographic testing system. This paper proposes a novel weld defect classification method based on information fusion technology, Dempster-Shafer evidence theory. First, to characterize weld defects and improve the accuracy of their classification, 11 weld defect features were defined based on the sub-pixel level edges of radiographic images, four of which are presented for the first time in this paper. Second, we applied information fusion technology to combine different features for weld defect classification, including a mass function defined based on the weld defect feature information and the quartile-method-based calculation of standard weld defect class which is to solve a sample problem involving a limited number of training samples. A steam turbine weld defect classification case study is also presented herein to illustrate our technique. The results show that the proposed method can increase the correct classification rate with limited training samples and address the uncertainties associated with weld defect classification. PMID:27036822

  1. Fatigue strength improvement of MIG-welded joint by shot peening

    NASA Astrophysics Data System (ADS)

    Azida Che Lah, Nur; Ali, Aidy

    2011-02-01

    In this study, the effect of controlled shot peening (CSP) treatment on the fatigue strength of an ASTM A516 grade 70 carbon steel MIG-welded joint has been studied quantitatively. Metallurgical modifications, hardness, elemental compositions, and internal discontinuities, such as porosity and inclusions found in treated and untreated fusion welded joints, were characterized. The fatigue results of as-welded and peened skimmed joints were compared. It was observed that the effect of the CSP and skimming processes improved the fatigue life of the fusion weld by 63% on MIG-welded samples.

  2. Repair welding of fusion reactor components

    SciTech Connect

    Chin, B.A.

    1993-05-15

    Experiments have shown that irradiated Type 316 stainless steel is susceptible to heat-affected-zone (HAZ) cracking upon cooling when welded using the gas tungsten arc (GTA) process under lateral constraint. The cracking has been hypothesized to be caused by stress-assisted helium bubble growth and rupture at grain boundaries. This study utilized an experimental welding setup which enabled different compressive stresses to be applied to the plates during welding. Autogenous GTA welds were produced in Type 316 stainless steel doped with 256 appm helium. The application of a compressive stress, 55 MPa, during welding suppressed the previously observed catastrophic cracking. Detailed examinations conducted after welding showed a dramatic change in helium bubble morphology. Grain boundary bubble growth along directions parallel to the weld was suppressed. Results suggest that stress-modified welding techniques may be used to suppress or eliminate helium-induced cracking during joining of irradiated materials.

  3. Chamber free fusion welding root side purging method and apparatus

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  4. Chamber free fusion welding root side purging method and apparatus

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  5. Final Report: A Transport Phenomena Based Approach to Probe Evolution of Weld Macro and Microstructures and A Smart Bi-directional Model of Fusion Welding

    SciTech Connect

    Dr. Tarasankar DebRoy

    2009-12-11

    In recent years, applications of numerical heat transfer and fluid flow models of fusion welding have resulted in improved understanding of both the welding processes and welded materials. They have been used to accurately calculate thermal cycles and fusion zone geometry in many cases. Here we report the following three major advancements from this project. First, we show how microstructures, grain size distribution and topology of welds of several important engineering alloys can be computed starting from better understanding of the fusion welding process through numerical heat transfer and fluid flow calculations. Second, we provide a conclusive proof that the reliability of numerical heat transfer and fluid flow calculations can be significantly improved by optimizing several uncertain model parameters. Third, we demonstrate how the numerical heat transfer and fluid flow models can be combined with a suitable global optimization program such as a genetic algorithm for the tailoring of weld attributes such as attaining a specified weld geometry or a weld thermal cycle. The results of the project have been published in many papers and a listing of these are included together with a list of the graduate thesis that resulted from this project. The work supported by the DOE award has resulted in several important national and international awards. A listing of these awards and the status of the graduate students are also presented in this report.

  6. Improving fatigue performance of rail thermite welds

    NASA Astrophysics Data System (ADS)

    Jezzini-Aouad, M.; Flahaut, P.; Hariri, S.; Winiar, L.

    2010-06-01

    Rail transport development offers economic and ecological interests. Nevertheless, it requires heavy investments in rolling material and infrastructure. To be competitive, this transportation means must rely on safe and reliable infrastructure, which requires optimization of all implemented techniques and structure. Rail thermite (or aluminothermic) welding is widely used within the railway industry for in-track welding during re-rail and defect replacement. The process provides numerous advantages against other welding technology commonly used. Obviously, future demands on train traffic are heavier axle loads, higher train speeds and increased traffic density. Thus, a new enhanced weld should be developed to prevent accidents due to fracture of welds and to lower maintenance costs. In order to improve such assembly process, a detailed metallurgical study coupled to a thermomechanical modelling of the phenomena involved in the thermite welding process is carried out. Obtained data enables us to develop a new improved thermite weld (type A). This joint is made by modifying the routinely specified procedure (type B) used in a railway rail by a standard gap alumino-thermic weld. Joints of type A and B are tested and compared. Based on experimental temperature measurements, a finite element analysis is used to calculate the thermal residual stresses induced. In the vicinity of the weld, the residual stress patterns depend on the thermal conditions during welding as it also shown by litterature [1, 2]. In parallel, X-Ray diffraction has been used to map the residual stress field that is generated in welded rail of types A and B. Their effect on fatigue crack growth in rail welds is studied. An experimental study based on fatigue tests of rails welded by conventional and improved processes adjudicates on the new advances and results will be shown.

  7. Fusion Welding of AerMet 100 Alloy

    SciTech Connect

    ENGLEHART, DAVID A.; MICHAEL, JOSEPH R.; NOVOTNY, PAUL M.; ROBINO, CHARLES V.

    1999-08-01

    A database of mechanical properties for weldment fusion and heat-affected zones was established for AerMet{reg_sign}100 alloy, and a study of the welding metallurgy of the alloy was conducted. The properties database was developed for a matrix of weld processes (electron beam and gas-tungsten arc) welding parameters (heat inputs) and post-weld heat treatment (PWHT) conditions. In order to insure commercial utility and acceptance, the matrix was commensurate with commercial welding technology and practice. Second, the mechanical properties were correlated with fundamental understanding of microstructure and microstructural evolution in this alloy. Finally, assessments of optimal weld process/PWHT combinations for cotildent application of the alloy in probable service conditions were made. The database of weldment mechanical properties demonstrated that a wide range of properties can be obtained in welds in this alloy. In addition, it was demonstrated that acceptable welds, some with near base metal properties, could be produced from several different initial heat treatments. This capability provides a means for defining process parameters and PWHT's to achieve appropriate properties for different applications, and provides useful flexibility in design and manufacturing. The database also indicated that an important region in welds is the softened region which develops in the heat-affected zone (HAZ) and analysis within the welding metallurgy studies indicated that the development of this region is governed by a complex interaction of precipitate overaging and austenite formation. Models and experimental data were therefore developed to describe overaging and austenite formation during thermal cycling. These models and experimental data can be applied to essentially any thermal cycle, and provide a basis for predicting the evolution of microstructure and properties during thermal processing.

  8. Repair welding of fusion reactor components. Final technical report

    SciTech Connect

    Chin, B.A.; Wang, C.A.

    1997-09-30

    The exposure of metallic materials, such as structural components of the first wall and blanket of a fusion reactor, to neutron irradiation will induce changes in both the material composition and microstructure. Along with these changes can come a corresponding deterioration in mechanical properties resulting in premature failure. It is, therefore, essential to expect that the repair and replacement of the degraded components will be necessary. Such repairs may require the joining of irradiated materials through the use of fusion welding processes. The present ITER (International Thermonuclear Experimental Reactor) conceptual design is anticipated to have about 5 km of longitudinal welds and ten thousand pipe butt welds in the blanket structure. A recent study by Buende et al. predict that a failure is most likely to occur in a weld. The study is based on data from other large structures, particularly nuclear reactors. The data used also appear to be consistent with the operating experience of the Fast Flux Test Facility (FFTF). This reactor has a fuel pin area comparable with the area of the ITER first wall and has experienced one unanticipated fuel pin failure after two years of operation. The repair of irradiated structures using fusion welding will be difficult due to the entrapped helium. Due to its extremely low solubility in metals, helium will diffuse and agglomerate to form helium bubbles after being trapped at point defects, dislocations, and grain boundaries. Welding of neutron-irradiated type 304 stainless steels has been reported with varying degree of heat-affected zone cracking (HAZ). The objectives of this study were to determine the threshold helium concentrations required to cause HAZ cracking and to investigate techniques that might be used to eliminate the HAZ cracking in welding of helium-containing materials.

  9. Optimization of Fiber Laser Welding of DP980 Steels Using RSM to Improve Weld Properties for Formability

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, K.; Panda, S. K.; Saha, P.

    2016-06-01

    The effect of laser parameters on weld quality is a critical laboratory study before implementation of newly developed high-strength dual-phase steels in fabrication of auto-bodies. In present work, dual-phase steels having tensile strength of 980 MPa (DP980) were welded using different welding speeds by Yb-fiber laser source to fabricate similar material combinations laser-welded blanks (LWBs). The weld zone microhardness, microstructure, and formability of DP980 LWBs were compared with those of the DP600 and micro-alloyed interstitial free high-strength steel (IFHS) LWBs. It was found that the formation of soft zone at the outer side of the HAZ was responsible for significant reduction in formability of DP980 LWBs due to strain localization and premature failure. Hence, response surface methodology based on Box-Behnken design was implemented to establish a mathematical model which could correlate the influence of laser process parameters such as power, welding speed, and focal position on weld quality in terms of aspect ratio of fusion zone, width of the soft zone, and surface roughness of weld to improve formability. The model was successfully implemented to optimize the laser parameters, and approximately 13.58% improvement in Erichsen cup height was achieved due to complete weld penetration with simultaneous 67% reduction in soft zone width and 55% reduction in softening. However, the failure was still observed to occur in the soft zone propagating parallel to weld in radial direction.

  10. Improving fatigue strength of welded joints

    NASA Astrophysics Data System (ADS)

    Takamori, Hiroyuki

    One series of fatigue tests was carried out on coverplated bridge girders with small fatigue cracks that had been treated in 1976. The treatment and preconditions were reported in NCHRP Report 206. The Category E' coverplated. beams that were removed from the Yellow Mill Pond Bridge in 1997 had been retrofitted in 1976 by either air hammer peening or GTA remelting the weld toe. Most of the details had small fatigue cracks at the time the retrofit was carried out. No detectable fatigue cracking was observed at the treated coverplate ends after 20 years of service on I-95 and an estimated 56 million truck passages. All beams were tested at a stress range of 69 MPa (10 ksi). Cracks eventually developed from the root of the transverse end welds and propagated through the weld throat and from there into the beam flange via the longitudinal welds. The fatigue resistance of the treated weld toe details was improved to Category C. The one GTA remelted detail that recracked at the weld toe exceeded Category D. The second series of tests was carried out on large scale HPS-485W steel plate girders with as-welded and ultrasonic impact treated (UIT) details. The UIT treatment was applied to the weld toe of transverse stiffeners welded to the web and flanges (Category C details) and to coverplated ends (Category E' details). The as-welded details cracked as expected at their corresponding fatigue resistance. All UIT treated details were improved. The treated transverse stiffeners achieved Category B fatigue resistance. The treated coverplated details achieved Category C. The third series of tests was conducted on large scale HPS-485W steel plate girders with undermatched groove welded details at flange transition. The objectives of using undermatched weld materials compared to the base material is to reduce the potentiality of hydrogen cracking at flange groove welds and to improve the fatigue strength of the welded joints. Fatigue strength of undermatched welded joints was

  11. Simulating weld-fusion boundary microstructures in aluminum alloys

    NASA Astrophysics Data System (ADS)

    Kostrivas, Anastasios D.; Lippold, John C.

    2004-02-01

    A fundamental study of weld-fusion boundary microstructure evolution in aluminum alloys was conducted in an effort to understand equiaxed grain zone formation and fusion boundary nucleation and growth phenomena. In addition to commercial aluminum alloys, experimental Mg-bearing alloys with Zr and Sc additions were studied along with the widely used Cu- and Licontaining alloy 2195-T8. This article describes work conducted to clarify the interrelation among composition, base metal substrate, and temperature as they relate to nucleation and growth phenomena at the fusion boundary.

  12. Stainless steel submerged arc weld fusion line toughness

    SciTech Connect

    Rosenfield, A.R.; Held, P.R.; Wilkowski, G.M.

    1995-04-01

    This effort evaluated the fracture toughness of austenitic steel submerged-arc weld (SAW) fusion lines. The incentive was to explain why cracks grow into the fusion line in many pipe tests conducted with cracks initially centered in SAWS. The concern was that the fusion line may have a lower toughness than the SAW. It was found that the fusion line, Ji. was greater than the SAW toughness but much less than the base metal. Of greater importance may be that the crack growth resistance (JD-R) of the fusion line appeared to reach a steady-state value, while the SAW had a continually increasing JD-R curve. This explains why the cracks eventually turn to the fusion line in the pipe experiments. A method of incorporating these results would be to use the weld metal J-R curve up to the fusion-line steady-state J value. These results may be more important to LBB analyses than the ASME flaw evaluation procedures, since there is more crack growth with through-wall cracks in LBB analyses than for surface cracks in pipe flaw evaluations.

  13. Improving Fatigue Performance of AHSS Welds

    SciTech Connect

    Feng, Zhili; Yu, Xinghua; Erdman, III, Donald L.; Wang, Yanli; Kelly, Steve; Hou, Wenkao; Yan, Benda; Wang, Zhifeng; Yu, Zhenzhen; Liu, Stephen

    2015-03-01

    Reported herein is technical progress on a U.S. Department of Energy CRADA project with industry cost-share aimed at developing the technical basis and demonstrate the viability of innovative in-situ weld residual stresses mitigation technology that can substantially improve the weld fatigue performance and durability of auto-body structures. The developed technology would be costeffective and practical in high-volume vehicle production environment. Enhancing weld fatigue performance would address a critical technology gap that impedes the widespread use of advanced high-strength steels (AHSS) and other lightweight materials for auto body structure light-weighting. This means that the automotive industry can take full advantage of the AHSS in strength, durability and crashworthiness without the concern of the relatively weak weld fatigue performance. The project comprises both technological innovations in weld residual stress mitigation and due-diligence residual stress measurement and fatigue performance evaluation. Two approaches were investigated. The first one was the use of low temperature phase transformation (LTPT) weld filler wire, and the second focused on novel thermo-mechanical stress management technique. Both technical approaches have resulted in considerable improvement in fatigue lives of welded joints made of high-strength steels. Synchrotron diffraction measurement confirmed the reduction of high tensile weld residual stresses by the two weld residual stress mitigation techniques.

  14. DETECTION OF LACK OF FUSION WELD DEFECTS BY RADIOGRAPHY

    SciTech Connect

    Souza, M. P.; Almeida, R. M.; Rebello, J. M. A.

    2009-03-03

    In this work, radiography was employed as the NDT technique for detection of flaws in circumferential girth welds of steel pipelines used in offshore installations in the petroleum industry. The kind of defect specifically focused was lack of fusion. It is currently accepted in the literature that radiography is not as sensitive as ultrasonics to detect lack of fusion defects. Unfortunately, the radiographic inspection can barely detect lack of fusion and only when it is associated to inclusions and voids of considerable size. However, in a previous article ('Reliability of radiographic inspection of steel pipeline girth welds', QNDE Conference, 2007), the authors showed that it is possible to detect lack of fusion defects if, in the radiographic tests, the angle of incidence is the same angle that the weld bevel makes with the test piece surface, which means lowering the angle of disorientation between the flaw and the radiographic beam. However, no concerns were made to sizing the defects. Computational simulation was used with XRSIM software to establish the optimal radiographic parameters to reach the lower limit for detection for this kind of defect.

  15. Improvement of Weld Characteristics by Laser-Arc Double-Sided Welding Compared to Single Arc Welding

    NASA Astrophysics Data System (ADS)

    Lei, Zhenglong; Zhang, Kezhao; Hu, Xue; Yang, Yuhe; Chen, Yanbin; Wu, Yichao

    2015-11-01

    The single arc welding and laser-arc double-sided welding (LADSW) processes are investigated by virtue of test welds. The impacts of the laser beam during the LADSW process on the weld characteristics are studied from weld geometry, crystal morphology, and the mechanical properties of the joints. Compared with the single arc welding, the LADSW process improves the energy density and reduces the range of arc action, which together leads to a doubling of weld penetration depth. When penetrated by the laser beam, the liquid metal of the arc welding pool experiences severe fluctuations, leading to a finer grain size in the range of 17-26 μm in the LADSW weld, a reduction of nearly 63% compared to the grains in the single arc weld. The tensile strength and elongation-to-failure of the LADSW weld were increased by nearly 10 and 100% over the single arc welding, respectively.

  16. Ultrasonic vibration aided laser welding of Al alloys: Improvement of laser-welding quality

    SciTech Connect

    Kim, J.S.; Watanabe, T.; Yoshida, Y.

    1995-03-01

    Using a pulsed YAG laser, meltability of Al-Mg and Al-Mg-Si alloys were investigated by a single-pass irradiation. In order to improve the quality in laser welding, the effectiveness of the Ultrasonic Vibration Laser Welding (UVLW) method proposed in this paper was investigated experimentally. The proposed method was also compared with the traditional welding methods of Normal Laser Welding (NLW) and preHeating Laser Welding (HLW). The welding methods were evaluated from the geometry in the melt zone generated by a single pulse of the laser beam. It was suggested that ultrasonic vibration suppressed welding defects and improved the melt characteristics due to cavitation effects and dispersion of particles in the molten pool during laser welding. The influence on melt characteristics of the melt zone by preheating was also investigated. In these experiments, UVLW was the most useful laser welding method from the point of view of improving the laser welding quality of Al alloys.

  17. TRANSMISSION ELECTRON MICROSCOPY STUDY OF HELIUM BEARING FUSION WELDS

    SciTech Connect

    Tosten, M; Michael Morgan, M

    2008-12-12

    A transmission electron microscopy (TEM) study was conducted to characterize the helium bubble distributions in tritium-charged-and-aged 304L and 21Cr-6Ni-9Mn stainless steel fusion welds containing approximately 150 appm helium-3. TEM foils were prepared from C-shaped fracture toughness test specimens containing {delta} ferrite levels ranging from 4 to 33 volume percent. The weld microstructures in the low ferrite welds consisted mostly of austenite and discontinuous, skeletal {delta} ferrite. In welds with higher levels of {delta} ferrite, the ferrite was more continuous and, in some areas of the 33 volume percent sample, was the matrix/majority phase. The helium bubble microstructures observed were similar in all samples. Bubbles were found in the austenite but not in the {delta} ferrite. In the austenite, bubbles had nucleated homogeneously in the grain interiors and heterogeneously on dislocations. Bubbles were not found on any austenite/austenite grain boundaries or at the austenite/{delta} ferrite interphase interfaces. Bubbles were not observed in the {delta} ferrite because of the combined effects of the low solubility and rapid diffusion of tritium through the {delta} ferrite which limited the amount of helium present to form visible bubbles.

  18. Improved diffusion welding and roll welding of titanium alloys

    NASA Technical Reports Server (NTRS)

    Holko, K. H.

    1973-01-01

    Auto-vacuum cleaning technique was applied to titanium parts prior to welding. This provides oxide-free welding surfaces. Diffusion welding can be accomplished in as little as five minutes of hot pressing. Roll welding can be accomplished with only ten percent deformation.

  19. METHOD OF OBTAINING AN IMPROVED WELD IN INERT ARC WELDING

    DOEpatents

    Correy, T.B.

    1962-12-11

    A method is reported for inert arc welding. An a-c welding current is applied to the workpiece and welding electrode such that the positive portion of each cycle thereof, with the electrode positive, has only sufficient energy to clean the surface of the workpiece and the negative portion of each cycle thereof, with the electrode negative, contains the energy required to weld. (AEC)

  20. Pre-weld heat treatment improves welds in Rene 41

    NASA Technical Reports Server (NTRS)

    Prager, M.

    1968-01-01

    Cooling of Rene 41 prior to welding reduces the incidence of cracking during post-weld heat treatment. The microstructure formed during the slow cooling rate favors elevated temperature ductility. Some vestiges of this microstructure are apparently retained during welding and thus enhance strain-age crack resistance in air.

  1. "Foreign material" to verify root fusion in welded joints

    NASA Technical Reports Server (NTRS)

    Kleint, R. E.

    1980-01-01

    Foil or thin wire at weld root is used to verify weld penetration. When weld is adequate, material mixes with weld and traces of it diffuse to weld crown. Spectroscopic analysis of samples identifies foreign material and verifies root has fused. Weld roots are usually inaccessible to visual inspection, and X-ray and ultrasonic inspection techniques are not always reliable. Good results are obtained with use of gold/nickel alloy.

  2. An improved diffusion welding technique for TD-NiCr

    NASA Technical Reports Server (NTRS)

    Holko, K. H.

    1973-01-01

    An improved diffusion welding technique has been developed for TD-NiCr sheet. In the most preferred form, the improved technique consists of diffusion welding 320-grit sanded plus chemically polished surfaces of unrecrystallized TD-NiCr at 760 C under 140 MN/m2 pressure for 1hr followed by postheating at 1180 C for 2hr. Compared to previous work, this improved technique has the advantages of shorter welding time, lower welding temperature, lower welding pressure, and a simpler and more reproducible surface preparation procedure. Weldments were made that had parent-metal creep-rupture shear strength at 1100 C.

  3. Microstructures and microhardness at fusion boundary of 316 stainless steel/Inconel 182 dissimilar welding

    SciTech Connect

    Wang, Wei; Lu, Yonghao; Ding, Xianfei; Shoji, Tetsuo

    2015-09-15

    Microstructures and microhardness at fusion boundary of a weld joint were investigated in a 316 stainless steel/Inconel 182 dissimilar weldment. The results showed that there were two alternately distributed typical fusion boundaries, a narrow random boundary (possessed 15% in length) with a clear sharp interface and an epitaxial fusion one with (100){sub BM}//(100){sub WM} at the joint interface. The composition transition, microstructure and hardness across the fusion boundary strongly depended on the type of the fusion boundary. For the random boundary, there was a clear sharp interface and the composition transition with a width of 100 μm took place symmetrically across the grain boundary. For the epitaxial fusion one, however, there were Type-I and Type-II grain boundaries perpendicular and parallel to the epitaxial fusion boundary, respectively. The composition transition took place in the Inconel 182 weld side. Σ3 boundaries in the HAZ of 316SS side and Σ5 grain boundaries in weld metal were usually observed, despite the type of fusion boundary, however the former was much more in epitaxial fusion boundary. Microhardness was continuously decreased across the random fusion boundary from the side of Inconel 182 to 316SS, but a hardening phenomenon appeared in the epitaxial fusion boundary zone because of its fine cellular microstructure. - Highlights: • Two typical fusion boundaries alternately distributed in the fusion interface • The microstructure, composition and hardness across fusion boundary depended on its type. • Different regions in welded joint have different special CSL value boundaries. • Hardening phenomenon only appeared in the epitaxial fusion boundary.

  4. Improved Abutting Edges For Welding In Keyhole Mode

    NASA Technical Reports Server (NTRS)

    Harwing, Dennis D.; Sanders, John M.

    1994-01-01

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

  5. Filler wire for aluminum alloys and method of welding

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  6. Repair welding of fusion reactor components. Second year technical report

    SciTech Connect

    Chin, B.A.

    1993-05-15

    Experiments have shown that irradiated Type 316 stainless steel is susceptible to heat-affected-zone (HAZ) cracking upon cooling when welded using the gas tungsten arc (GTA) process under lateral constraint. The cracking has been hypothesized to be caused by stress-assisted helium bubble growth and rupture at grain boundaries. This study utilized an experimental welding setup which enabled different compressive stresses to be applied to the plates during welding. Autogenous GTA welds were produced in Type 316 stainless steel doped with 256 appm helium. The application of a compressive stress, 55 MPa, during welding suppressed the previously observed catastrophic cracking. Detailed examinations conducted after welding showed a dramatic change in helium bubble morphology. Grain boundary bubble growth along directions parallel to the weld was suppressed. Results suggest that stress-modified welding techniques may be used to suppress or eliminate helium-induced cracking during joining of irradiated materials.

  7. Fusion welding studies using laser on Ti-SS dissimilar combination

    NASA Astrophysics Data System (ADS)

    Shanmugarajan, B.; Padmanabham, G.

    2012-11-01

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

  8. Fusion welding experiments under low-gravity conditions using aircraft

    NASA Astrophysics Data System (ADS)

    Masubuchi, Koichi; Nayama, Michisuke

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

  9. Microstructure characterization of laser welded Ti-6Al-4V fusion zones

    SciTech Connect

    Xu, Pei-quan; Li, Leijun Zhang, Chunbo

    2014-01-15

    The as-welded microstructure of laser-welded Ti-6Al-4V is characterized as a function of CO2 key-hole mode laser welding speed. Martensitic α′ is the predominant phase, with some α and retained β. Phase transformation is affected by the cooling rate through laser welding speed. A higher welding speed of 1.6 to 2.0 m/min produced more martensite α′ and less retained β in the welds. 1.4 m/min welding speed produced small amounts of α, besides the martensite α′. A trace of δ titanium hydride phase seems to have formed in the weld fusion zone. Moiré fringes are a common feature in the TEM microstructure, due to abundance of multi-phase interfaces. Tensile twins and clusters of dislocations indicate that plastic deformation has happened in the as-welded microstructure, indicating the local stress levels to be approaching the yield stress on-cooling during laser welding.

  10. Verifying root fusion in electron-beam welds

    NASA Technical Reports Server (NTRS)

    Becker, F. L.; Doctor, S.; Kleint, R. E.

    1980-01-01

    Ultrasonic equipment and x-y recorder indicate where back side of joint is properly welded. Wire waveguide placed in groove at root of joint to be welded is fused when joint is adequately penetrated. Ultransonic signal moving down waveguide is reflected where guide is melted. Change in reflected-signal arrival time with change in weld-head position is nearly constant unless joint is incompletely penetrated. Method permits determination of penetration depth in preweld samples without opening vacuum chamber and sectioning weld. Technique is particularly valuable when back side of joint is inaccessible.

  11. Reduced heat input keyhole welding through improved joint design

    NASA Technical Reports Server (NTRS)

    Sanders, John M. (Inventor); Harwig, Dennis D. (Inventor)

    1993-01-01

    An improved high energy density welding method for reducing input keyhole welding prepares the weld joint (8) between two edges (10, 14) of at least one member by separating the edges (10, 14) of the member (12, 16) with a controllable gap (22) by a projecting portion (24) selectively positioned on one edge (10, 14) of the member (12, 16). The projecting portion (24) closely abuts the other edge of the member for maintaining the controlled distance (d) of the controllable gap (22) to enhance the welding method.

  12. Effect of minor chemistry elements on GTA weld fusion zone characteristics of a commercial grade titanium

    SciTech Connect

    Marya, S.K.

    1996-06-01

    Gas Tungsten Arc Welding (GTAW) is the most common technique employed in the fabrication of rolled thin tubes. One of the major manufacturing problems concerns the stability of weld fusion zone on materials from different casts, notwithstanding stringent monitoring of the process parameters -- current, voltage and travel speed. These parameters determine the theoretical weld heat and are expected to control the instantaneous mass of melt. According to the data compiled by Sahoo et al., oxygen is known to reduce the surface tension of most of the metals. However, investigations on the role of minor changes in concentrations of elements like sulphur, oxygen, selenium, bismuth, aluminium, and titanium in steels have very often attributed the cast to cast variations to different temperature gradients of surface tension over the weldpool. To the author`s knowledge, no reported work so far has revealed changing weld profiles in autogeneous mechanized GTA welds on titanium due to minor composition changes.

  13. Basic study of heat flow in fusion welding. Progress report, March 1, 1980-February 28, 1981

    SciTech Connect

    Szekely, J.; Eagar, T.W.

    1981-01-01

    During the past year the study of electroslag welding was essentially completed with good agreement between the experimental and the theoretical results. It is concluded that the ESW process has certain inherent limitations which were not appreciated previously. The study has expanded into a more complete analysis of heat and fluid flow in arc welding. It has been shown that the heat affected zone and fusion zone sizes are not simple functions of the net heat input as predicted by all current theories. This will affect the choice of welding parameters. For example, in single pass arc welds, the smallest HAZ is usually desirable, while in multipass welding large HAZ's may be desirable to provide tempering of the previous weld beads. It may be possible to achieve both these goals at equivalent heat input by proper adjustment of the welding parameters (such as voltage, current and travel speed). Goal of the current study is to predict which combinations of parameters maximize or minimize the size of the heat affected zone and fusion zone at equal heat input.

  14. 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.

  15. Defect Detectability Improvement for Conventional Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Hill, Chris

    2013-01-01

    This research was conducted to evaluate the effects of defect detectability via phased array ultrasound technology in conventional friction stir welds by comparing conventionally prepped post weld surfaces to a machined surface finish. A machined surface is hypothesized to improve defect detectability and increase material strength.

  16. Fracture evaluations of fusion line cracks in nuclear pipe bimetallic welds

    SciTech Connect

    Scott, P.; Francini, R.; Rahman, S.; Rosenfield, A.; Wilkowski, G.

    1995-04-01

    In both BWRs and PWRs there are many locations where carbon steel pipe or components are joined to stainless steel pipe or components with a bimetallic weld. The objective of the research described in this report was to assess the accuracy of current fracture analyses for the case of a crack along a carbon steel to austenitic weld fusion line. To achieve the program objective, material property data and data from a large-diameter pipe fracture experiment were developed to assess current analytical methods. The bimetallic welds evaluated in this program were bimetallic welds obtained from a cancelled Combustion Engineering plant. The welds joined sections of the carbon steel cold-leg piping system to stainless steel safe ends that were to be welded to stainless steel pump housings. The major conclusion drawn as a result of these efforts was that the fracture behavior of the bimetallic weld evaluated in this program could be evaluated with reasonable accuracy using the strength and toughness properties of the carbon steel pipe material in conjunction with conventional elastic-plastic fracture mechanics or limit-load analyses. This may not be generally true for all bimetallic welds, as discussed in this report.

  17. Fusion zone microstructure and porosity in electron beam welds of an {alpha} + {beta} titanium alloy

    SciTech Connect

    Mohandas, T.; Banerjee, D.; Kutumba Rao, V.V.

    1999-03-01

    The effect of electron beam welding parameters on fusion zone (FZ) microstructure and porosity in a Ti-6.8 Al-3.42 Mo-1.9 Zr-0.21 Si alloy (Russian designation VT 9) has been investigated. It has been observed that the FZ grain width increased continuously with increase in heat input when the base metal was in the {beta} heat-treated condition, while in the {alpha} + {beta} heat-treated base metal welds, the FZ grain width increased only after a threshold energy input. The difference is attributed to both the weld thermal cycle and the pinning effect of equiaxed primary alpha on grain growth in the heat-affected zone (HAZ) of {alpha} + {beta} heat-treated base metal. Postweld heat treatment (PWHT) in the subtransus and supertransus regions did not alter the columnar grain morphology in the FZ, possibly due to the lack of enough driving force for the formation of new grains by the breaking up of the columnar grains and grain boundary movement for grain growth. The highest porosity was observed at intermediate welding speeds. At low speeds, a majority of pores formed at the fusion boundary, while at high speeds, occurrence of porosity was maximum at the weld center. The trends on porosity can be explained on the basis of solubility of hydrogen in titanium as a function of temperature and the influence of weld thermal cycle on nucleation, growth, and escape of hydrogen gas bubbles. The porosity at slow welding speeds is low because sufficient time exists for the nucleation, growth, and escape of hydrogen gas bubbles, while insufficient time exists for the nucleation of gas bubbles at high welding speeds. The effect of pickling of joint surface, vacuum annealing of the base metal, and successive remelting of the weld metal has also been investigated.

  18. Swirl Ring Improves Performance Of Welding Torch

    NASA Technical Reports Server (NTRS)

    Mcgee, William F.; Rybicki, Daniel J.

    1995-01-01

    Plasma-arc welding torch modified to create vortex in plasma gas to focus arc into narrower and denser column. Swirl ring contains four channels with angled exit holes to force gas to swirl as it flows out of torch past tip of electrode. Degradation of electrode and orifice more uniform and need to rotate torch during operation to compensate for asymmetry in arc reduced or eliminated. Used in both keyhole and nonkeyhole welding modes.

  19. Solid-state and fusion resistance spot welding of TD-NiCr sheet

    NASA Technical Reports Server (NTRS)

    Moore, T. J.

    1973-01-01

    By using specially processed TD-NiCr sheet in both 0.4-mm (0.015-in.) and 1.6-mm (0.062-in.) thicknesses and carefully selected welding procedures, solid state resistance spot welds were produced which, after postheating at 1200 C, were indistinguishable from the parent material. Stress-rupture shear tests of single-spot lap joints in 0.4-mm (0.015-in.) thick sheet showed that these welds were as strong as the parent material. Similar results were obtained in tensile-shear tests at room temperature and 1100 C and in fatigue tests. Conventional fusion spot welds in commercial sheet were unsatisfactory because of poor stress-rupture shear properties resulting from metallurgical damage to the parent material.

  20. [Element distribution analysis of welded fusion zone by laser-induced breakdown spectroscopy].

    PubMed

    Yang, Chun; Zhang, Yong; Jia, Yun-Hai; Wang, Hai-Zhou

    2014-04-01

    Over the past decade there has been intense activity in the study and development of laser-induced breakdown spectroscopy (LIBS). As a new tool for surface microanalysis, it caused widespread in materials science because of the advantage of rapid and high sensitivity. In the present paper, the distribution of Ni, Mn, C and Si near weld fusion line was analyzed on two kinds of weld sample. Line scanning mode analysis was carried out by three different kinds of methods, namely laser-induced breakdown spectroscopy (LIBS), scanning electron microscope/energy dispersive spectrometer (SEM/EDS) and electron probe X-ray microanalyser (EPMA). The concentration variation trend of Ni and Mn acquired by LIBS is coincident with SEM/EDS and EPMA. The result shows that the content of Ni and Mn was significantly different between weld seam and base metal on both the samples. The content of Ni and Mn was much higher in weld seam than in base metal, and a sharp concentration gradient was analyzed in the fusion zone. According to the distribution of Ni and Mn, all the three methods got a similar value of welded fusion zone width. The concentration variation trend of C and Si acquired by LIBS is not coincident with SEM/EDS and EPMA. The concentration difference between weld seam and base metal was analyzed by LIBS, but had not by SEM/EDS and EPMA, because of the low concentration and slight difference. The concentration gradient of C and Si in fusion zone was shows clearly by LIBS. For higher sensitivity performance, LIBS is much more adapted to analyze low content element than SEM/EDS and EPMA. PMID:25007635

  1. Microstructural evolution of fusion zone in laser beam welds of pure titanium

    SciTech Connect

    Liu, H.; Nakata, K.; Zhang, J.X.; Yamamoto, N.; Liao, J.

    2012-03-15

    Microstructural evolution of fusion zone in laser beam welds of pure titanium was studied by means of electron backscattering diffraction. The microstructural evolution is strongly affected by the {beta} {yields} {alpha} transformation mechanism dependent on the cooling rate during phase transformation. The long-range diffusional transformation mainly occurs in the fusion zone at the low cooling rate, and the massive transformation dominantly takes place at the high cooling rate. For this reason, the grain morphologies probably change from the granular-like to columnar-like grains with the cooling rate increasing. - Highlights: Black-Right-Pointing-Pointer Microstructures of fusion zone in laser beam welds of pure titanium are studied. Black-Right-Pointing-Pointer Increasing cooling rate changes grain morphology from granular to columnar one. Black-Right-Pointing-Pointer Final microstructures depend on the {beta}{yields}{alpha} transformation mechanisms.

  2. Improved Assembly for Gas Shielding During Welding or Brazing

    NASA Technical Reports Server (NTRS)

    Gradl, Paul; Baker, Kevin; Weeks, Jack

    2009-01-01

    An improved assembly for inert-gas shielding of a metallic joint is designed to be useable during any of a variety of both laser-based and traditional welding and brazing processes. The basic purpose of this assembly or of a typical prior related assembly is to channel the flow of a chemically inert gas to a joint to prevent environmental contamination of the joint during the welding or brazing process and, if required, to accelerate cooling upon completion of the process.

  3. Microtextures and grain boundary misorientation distributions in controlled heat input titanium alloy fusion welds

    NASA Astrophysics Data System (ADS)

    Leary, R.; Merson, E.; Brydson, R.

    2010-07-01

    Microstructures, macrotextures and microtextures in commercial purity titanium and Ti-6Al-4V fusion welds produced by the InterPulse gas tungsten constricted arc welding (GTCAW) technique have been characterised. At the cooling rates associated with the InterPulse technique, α variants sharing a common 1120 pole are found to cluster together into groups within prior β grains, leading to large areas where all variants are separated by a misorientation of 60°. These present potential easy slip paths, hence increasing the "effective structural unit size." Characterisation of these microtextures may provide new insight into microtexture-properties relations and the mechanisms of microtextural evolution.

  4. Microstructural analysis of laser weld fusion zone in Haynes 282 superalloy

    SciTech Connect

    Osoba, L.O.; Ding, R.G.; Ojo, O.A.

    2012-03-15

    Analytical electron microscopy and spectroscopy analyses of the fusion zone (FZ) microstructure in autogenous laser beam welded Haynes 282 (HY 282) superalloy were performed. The micro-segregation patterns observed in the FZ indicate that Co, Cr and Al exhibited a nearly uniform distribution between the dendrite core and interdendritic regions while Ti and Mo were rejected into the interdendritic liquid during the weld solidification. Transmission electron diffraction analysis and energy dispersive X-ray microanalysis revealed the second phase particles formed along the FZ interdendritic region to be Ti-Mo rich MC-type carbide particles. Weld FZ solidification cracking, which is sometimes associated with the formation of {gamma}-{gamma}' eutectic in {gamma}' precipitation strengthened nickel-base superalloys, was not observed in the HY 282 superalloy. Modified primary solidification path due to carbon addition in the newly developed superalloy is used to explain preclusion of weld FZ solidification cracking in the material. - Highlights: Black-Right-Pointing-Pointer A newly developed superalloy was welded by CO{sub 2} laser beam joining technique. Black-Right-Pointing-Pointer Electron microscopy characterization of the weld microstructure was performed. Black-Right-Pointing-Pointer Identified interdendritic microconstituents consist of MC-type carbides. Black-Right-Pointing-Pointer Modification of primary solidification path is used to explain cracking resistance.

  5. Microstructure and mechanical properties of weld fusion zones in modified 9Cr-1Mo steel

    NASA Astrophysics Data System (ADS)

    Sireesha, M.; Sundaresan, S.; Albert, Shaju K.

    2001-06-01

    Modified 9Cr-1Mo steel finds increasing application in power plant construction because of its excellent high-temperature properties. While it has been shown to be weldable and resistant to all types of cracking in the weld metal and heat-affected zone (HAZ), the achievement of optimum weld metal properties has often caused concern. The design of appropriate welding consumables is important in this regard. In the present work, plates of modified 9Cr-1Mo steel were welded with three different filler materials: standard 9Cr-1Mo steel, modified 9Cr-1Mo, and nickel-base alloy Inconel 182. Post-weld heat treatment (PWHT) was carried out at 730 and 760 °C for periods of 2 and 6 h. The joints were characterized in detail by metallography. Hardness, tensile properties, and Charpy toughness were evaluated. Among the three filler materials used, although Inconel 182 resulted in high weld metal toughness, the strength properties were too low. Between modified and standard 9Cr-1Mo, the former led to superior hardness and strength in all conditions. However, with modified 9Cr-1Mo, fusion zone toughness was low and an acceptable value could be obtained only after PWHT for 6 h at 760 °C. The relatively poor toughness was correlated to the occurrence of local regions of untransformed ferrite in the microstructure.

  6. Fusion welding of advanced borated stainless steels. Final report: CRADA No. CR1042

    SciTech Connect

    Robino, C.V.; Cieslak, M.J.

    1994-02-01

    This work addressed two major areas concerning joining of advanced borated stainless steels. These areas included the development of a understanding of the physical metallurgy of borated stainless steels and the development of welding processes and post-weld heat treatments for these alloys. Differential thermal analysis experiments were conducted on ten heats of borated stainless steel to determine the transformation temperatures and melting behavior of the alloys. On-heating solidus temperatures were measured for all of the alloys and were used to define the temperatures associated with the fusion line during welding. Isothermal heat treatments designed to evaluate the effects of elevated temperature exposures on the toughness of the borated grades were conducted. These tests were used to determine if significant changes in the microstructure or mechanical properties of weld heat-affected zones (HAZ) occur. Specifically, the tests addressed the solid-state region of the HAZ. The test matrix included a variety of alloy compositions and thermal exposures at temperatures near the on-heating solidus (as determined by the DTA experiments). Welding experiments designed to assess the mechanical properties and microstructure of gas-tungsten arc and electron beam welds were conducted.

  7. Fusion zone microstructure and porosity in electron beam welds of an α+β titanium alloy

    NASA Astrophysics Data System (ADS)

    Mohandas, T.; Banerjee, D.; Kutumba Rao, V. V.

    1999-03-01

    The effect of electron beam welding parameters on fusion zone (FZ) microstructure and porosity in a Ti -6.8 Al -3.42 Mo -1.9 Zr -0.21 Si alloy (Russian designation VT 9) has been investigated. It has been observed that the FZ grain width increased continuously with increase in heat input when the base metal was in the β heat-treated condition, while in the α+β heat-treated base metal welds, the FZ grain width increased only after a threshold energy input. The difference is attributed to both the weld thermal cycle and the pinning effect of equiaxed primary alpha on grain growth in the heat-affected zone (HAZ) of α+β heat-treated base metal. Postweld heat treatment (PWHT) in the subtransus and supertransus regions did not alter the columnar grain morphology in the FZ, possibly due to the lack of enough driving force for the formation of new grains by the breaking up of the columnar grains and grain boundary movement for grain growth. As the PWHTs were conducted in a furnace, the role of thermal gradients can be ruled out. Intragranular microstructure in the aswelded condition consisted of hexagonal martensite. The scale of the martensite laths depended on welding speed. The highest porosity was observed at intermediate welding speeds. At low speeds, a majority of pores formed at the fusion boundary, while at high speeds, occurrence of porosity was maximum at the weld center. The trends on porosity can be explained on the basis of solubility of hydrogen in titanium as a function of temperature and the influence of weld thermal cycle on nucleation, growth, and escape of hydrogen gas bubbles. The porosity at slow welding speeds is low because sufficient time exists for the nucleation, growth, and escape of hydrogen gas bubbles, while insufficient time exists for the nucleation of gas bubbles at high welding speeds. The effect of pickling of joint surface, vacuum annealing of the base metal, and successive remelting of the weld metal has also been investigated.

  8. Controlled temperature tissue fusion: Ho:YAG laser welding of rat intestine in vivo

    NASA Astrophysics Data System (ADS)

    Cilesiz, Inci F.; Chan, Eric K.; Welch, Ashley J.; Thomsen, Sharon L.

    1995-05-01

    The results of a closed loop thermal feedback controlled laser-assisted tissue welding study in vivo are reported. A series of experiments was carried out to study and compare the weld strength and healing response of sutured and laser welded rat enterotomies with and without temperature feedback control (TFC) using a cryogenically cooled Ho:YAG laser. Although assignment of animals to three groups (control sutured, laser welded with and without TFC) and four observation periods (1, 3, 7, and 21 days) was randomized, several laser welded enterotomies without TFC had complications resulting in death of the animals. Those experiments were repeated. From the failure rates encountered, it is shown that TFC improves the quality of laser-assisted enterotomy closures.

  9. Welding.

    ERIC Educational Resources Information Center

    South Carolina State Dept. of Education, Columbia. Office of Vocational Education.

    This curriculum guide is designed for use by South Carolina vocational education teachers as a continuing set of lesson plans for a two-year course on welding. Covered in the individual sections of the guide are the following topics: an orientation to welding, oxyacetylene welding, advanced oxyacetylene welding, shielded metal arc welding, TIG…

  10. Microstructural Study Of Fusion Welds in 304L and 21Cr-6Ni-9Mn Stainless Steels (U)

    SciTech Connect

    MICHAEL, TOSTEN

    2005-03-01

    Light-optical and transmission electron microscopy (TEM) have been employed to characterize the microstructures of a series of fusion welds made on 304L and 21-6-9 stainless steels. The materials investigated in this study included high-energy-rate-forged 304L, conventionally forged 21-6-9, and 304L weld critical plate (higher ferrite potential). The weld critical plate contained an electron beam weld (no filler wire) while other specimens were welded with various combinations of 308L, 309L modified (MOD) and 312 MOD stainless steel filler wires to produce samples with a range of delta ferrite contents (4 to 33 percent) in the resulting welds. TEM specimens were prepared from broken arc-shaped, mechanical property test specimens that had been used to measure fracture toughness of the fusion welds. Specimens were prepared from regions of the weld heat-affected zones as well as from areas within the weld metal, including areas close to the fracture surface (plastically deformed regions). The observed microstructures varied according to the amount of ferrite in each weld. At the lowest ferrite levels the microstructure consisted of austenite and skeletal ferrite with austenite being the majority (matrix) phase. At intermediate levels of ferrite, lathy austenite/ferrite was observed and the ferrite became continuous throughout the specimens examined. In the weld with the most ferrite, many austenite morphologies were observed and ferrite was the matrix phase. Closest to the fracture surface an increase in dislocation density in both the ferrite and austenite were observed in all welds. Deformation twinning was also observed in the austenite. Many of the welds contained a large number of non-metallic inclusions (oxide particles) which most likely originated from impurities in the weld wires.

  11. Customized orbital welding meets the challenge of titanium welding

    SciTech Connect

    1996-12-01

    Titanium has emerged as the material of choice for tubing used in surface condensers around the world in both new and retrofit configurations. A major worldwide supplier of steam surface condensers to the electric utility industry, Senior Engineering is finding an increased use of titanium tubes and tube sheets in condenser specifications. When compared to other alloys, titanium`s light weight is efficient in design, handling, transportation and installation activities. Additionally, it maintains a stable price structure. Senior Engineering implements an orbital welding process using fusion gas tungsten arc welding (GTAW) for its titanium tube-to-tube sheet welding. Orbital welding involves the use of a welding apparatus placed inside a tube or pipe to automatically and precisely weld a 360-deg joint. When welding manually, a welder stops several times during the weld due to the large amount of time and fatigue involved in achieving 360-deg welds, which results in lack of fusion. An automated orbital welding system, however, can accomplish the task as one continuous weld. This reduces process time and decreases lack of fusion. The orbital welding systems, featuring a microprocessor-based controller, an inverter-based power supply, an expandable mandrel and a customized torch shroud, reduced welding labor by 35%. The improved labor efficiency justified the addition of two more of the systems in January 1996.

  12. Microstructural Evolution of INCONEL® Alloy 740H® Fusion Welds During Creep

    NASA Astrophysics Data System (ADS)

    Bechetti, Daniel H.; DuPont, John N.; de Barbadillo, John J.; Baker, Brian A.; Watanabe, Masashi

    2015-02-01

    Electron microscopy techniques have been used to investigate the cause of premature creep failure in the fusion zone of INCONEL® Alloy 740H® (INCONEL and 740H are registered trademarks of Special Metals Corporation) welds. The reduced creep rupture lives of all-weld-metal and cross-weld creep specimens (relative to base metal specimens) have been attributed to the presence of large grain boundary regions that were denuded in fine γ' but contained coarse, elongated particles. Investigation of creep rupture specimens has revealed four factors that influence the formation of these coarsened zones, and the large particles found within them have been identified as γ'. Comparisons of the microstructural characteristics of these zones to the characteristics that are typical of denuded zones formed by a variety of mechanisms identified in the literature have been made. It is concluded that the mechanism of γ'-denuded zone formation in alloy 740H is discontinuous coarsening of the γ' phase. The discontinuous reaction is catalyzed by the grain boundary migration and sliding which occur during creep and likely promoted by the inhomogeneous weld metal microstructure that results from solute segregation during solidification. The increased susceptibility to the formation of the observed γ'-denuded zones in the weld metal as compared to the base metal is discussed in the context of differences in the contributions to the driving force for the discontinuous coarsening reaction.

  13. Material property evaluations of bimetallic welds, stainless steel saw fusion lines, and materials affected by dynamic strain aging

    SciTech Connect

    Rudland, D.; Scott, P.; Marschall, C.; Wilkowski, G.

    1997-04-01

    Pipe fracture analyses can often reasonably predict the behavior of flawed piping. However, there are material applications with uncertainties in fracture behavior. This paper summarizes work on three such cases. First, the fracture behavior of bimetallic welds are discussed. The purpose of the study was to determine if current fracture analyses can predict the response of pipe with flaws in bimetallic welds. The weld joined sections of A516 Grade 70 carbon steel to F316 stainless steel. The crack was along the carbon steel base metal to Inconel 182 weld metal fusion line. Material properties from tensile and C(T) specimens were used to predict large pipe response. The major conclusion from the work is that fracture behavior of the weld could be evaluated with reasonable accuracy using properties of the carbon steel pipe and conventional J-estimation analyses. However, results may not be generally true for all bimetallic welds. Second, the toughness of austenitic steel submerged-arc weld (SAW) fusion lines is discussed. During large-scale pipe tests with flaws in the center of the SAW, the crack tended to grow into the fusion line. The fracture toughness of the base metal, the SAW, and the fusion line were determined and compared. The major conclusion reached is that although the fusion line had a higher initiation toughness than the weld metal, the fusion-line J-R curve reached a steady-state value while the SAW J-R curve increased. Last, carbon steel fracture experiments containing circumferential flaws with periods of unstable crack jumps during steady ductile tearing are discussed. These instabilities are believed to be due to dynamic strain aging (DSA). The paper discusses DSA, a screening criteria developed to predict DSA, and the ability of the current J-based methodologies to assess the effect of these crack instabilities. The effect of loading rate on the strength and toughness of several different carbon steel pipes at LWR temperatures is also discussed.

  14. Microstructural Evolution and Creep Rupture Behavior of INCONEL RTM Alloy 740H Fusion Welds

    NASA Astrophysics Data System (ADS)

    Bechetti, Daniel H., Jr.

    Electron microscopy techniques were used to investigate the causes of reduced creep-rupture life in INCONEL® alloy 740H ® fusion welds with a specific focus on understanding the formation and evolution of γ'-free zones along grain boundaries. Investigation of creep-rupture specimens revealed four operational factors that influence the formation of these precipitate-free zones, and the identity of large second phase particles typically found within them has been determined. A stress-free aging has demonstrated the influence of stress on the formation of the precipitate-free regions and has illustrated what appear to be the initial stages of their development. It is concluded that the mechanism of precipitate-free zone formation in alloy 740H is moderate discontinuous precipitation accompanied by significant discontinuous growth of the γ' phase. These discontinuous reactions are likely exacerbated by microsegregation within the welded microstructure and by the mechanical deformation associated with grain boundary sliding during creep. Thermodynamic and kinetic modeling were used to determine appropriate heat treatment schedules for homogenization and second phase dissolution of welds in alloy 740H. Following these simulations, a two-step heat treatment process was applied to specimens from a single pass gas tungsten arc weld (GTAW). Scanning electron microscopy (SEM) has been used to assess the changes in the distribution of alloying elements as well as changes in the fraction of second phase particles within the fusion zone. Experimental results demonstrate that homogenization of alloy 740H weld metal can be achieved by an 1100°C/4hr treatment. Complete dissolution of second phase particles could not be completely achieved, even at exposure to temperatures near the alloy's solidus temperature. These results are in good agreement with thermodynamic and kinetic predictions.

  15. Fusion boundary precipitation in thermally aged dissimilar metal welds studied by atom probe tomography and nanoindentation

    NASA Astrophysics Data System (ADS)

    Choi, Kyoung Joon; Kim, Taeho; Yoo, Seung Chang; Kim, Seunghyun; Lee, Jae Hyuk; Kim, Ji Hyun

    2016-04-01

    In this study, microstructural and mechanical characterizations were performed to investigate the effect of long-term thermal aging on the fusion boundary region between low-alloy steel and Nickel-based weld metal in dissimilar metal welds used in operating power plant systems. The effects of thermal aging treatment on the low-alloy steel side near the fusion boundary were an increase in the ratio of Cr constituents and Cr-rich precipitates and the formation and growth of Cr23C6. Cr concentrations were calculated using atom probe tomography. The accuracy of simulations of thermal aging effects of heat treatment was verified, and the activation energy for Cr diffusion in the fusion boundary region was calculated. The mechanical properties of fusion boundary region changed based on the distribution of Cr-rich precipitates, where the material initially hardened with the formation of Cr-rich precipitates and then softened because of the reduction of residual strain or coarsening of Cr-rich precipitates.

  16. Transition material improves spot welding of aluminum to steel

    SciTech Connect

    Not Available

    1994-06-01

    Weight is one of the primary enemies of improved fuel economy in automobiles. To help address this problem, a simple yet highly effective clad metal transition material has been developed. It allows automotive engineers to spot weld aluminum to steel using existing conventional production equipment and practices, thereby enabling them to use aluminum in place of heavier steel without expensive changes in production methods. The idea of the new materials technology is to permit the joining of aluminum to steel using conventional spot welding techniques. Numerous welding and corrosion studies have been conducted on the clad transition material approach by auto manufacturers, industry suppliers and various independent organizations. The success of these tests has prompted manufacturers in the US, Europe and Japan to accelerate production and field testing of clad transition materials on cars with an eye toward volume application.

  17. Effects of Fusion Zone Size and Failure Mode on Peak Load and Energy Absorption of Advanced High Strength Steel Spot Welds under Lap Shear Loading Conditions

    SciTech Connect

    Sun, Xin; Stephens, Elizabeth V.; Khaleel, Mohammad A.

    2008-06-01

    This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS) under lap shear loading condition. DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. Static weld strength tests using lap shear samples were performed on the joint populations with various fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied for all the weld populations using statistical data analysis tools. The results in this study show that AHSS spot welds with conventionally required fusion zone size of can not produce nugget pullout mode for both the DP800 and TRIP800 welds under lap shear loading. Moreover, failure mode has strong influence on weld peak load and energy absorption for all the DP800 welds and the TRIP800 small welds: welds failed in pullout mode have statistically higher strength and energy absorption than those failed in interfacial fracture mode. For TRIP800 welds above the critical fusion zone level, the influence of weld failure modes on peak load and energy absorption diminishes. Scatter plots of peak load and energy absorption versus weld fusion zone size were then constructed, and the results indicate that fusion zone size is the most critical factor in weld quality in terms of peak load and energy absorption for both DP800 and TRIP800 spot welds.

  18. Sensoring Fusion Data from the Optic and Acoustic Emissions of Electric Arcs in the GMAW-S Process for Welding Quality Assessment

    PubMed Central

    Alfaro, Sadek Crisóstomo Absi; Cayo, Eber Huanca

    2012-01-01

    The present study shows the relationship between welding quality and optical-acoustic emissions from electric arcs, during welding runs, in the GMAW-S process. Bead on plate welding tests was carried out with pre-set parameters chosen from manufacturing standards. During the welding runs interferences were induced on the welding path using paint, grease or gas faults. In each welding run arc voltage, welding current, infrared and acoustic emission values were acquired and parameters such as arc power, acoustic peaks rate and infrared radiation rate computed. Data fusion algorithms were developed by assessing known welding quality parameters from arc emissions. These algorithms have showed better responses when they are based on more than just one sensor. Finally, it was concluded that there is a close relation between arc emissions and quality in welding and it can be measured from arc emissions sensing and data fusion algorithms. PMID:22969330

  19. Sensoring fusion data from the optic and acoustic emissions of electric arcs in the GMAW-S process for welding quality assessment.

    PubMed

    Alfaro, Sadek Crisóstomo Absi; Cayo, Eber Huanca

    2012-01-01

    The present study shows the relationship between welding quality and optical-acoustic emissions from electric arcs, during welding runs, in the GMAW-S process. Bead on plate welding tests was carried out with pre-set parameters chosen from manufacturing standards. During the welding runs interferences were induced on the welding path using paint, grease or gas faults. In each welding run arc voltage, welding current, infrared and acoustic emission values were acquired and parameters such as arc power, acoustic peaks rate and infrared radiation rate computed. Data fusion algorithms were developed by assessing known welding quality parameters from arc emissions. These algorithms have showed better responses when they are based on more than just one sensor. Finally, it was concluded that there is a close relation between arc emissions and quality in welding and it can be measured from arc emissions sensing and data fusion algorithms. PMID:22969330

  20. Welding Using Chilled-Inert-Gas Purging

    NASA Technical Reports Server (NTRS)

    Mcgee, William F.; Rybicki, Daniel J.

    1995-01-01

    Report describes study of fusion welding using chilled inert gas. Marked improvement shown in welding of aluminum using chilled helium gas. Chilling inert gas produces two additional benefits: 1) creation of ultradense inert atmosphere around welds; 2) chilled gas cools metal more quickly down to temperature at which metals not reactive.

  1. A method for studying weld fusion boundary microstructure evolution in aluminum alloys

    SciTech Connect

    Kostrivas, A.; Lippold, J.C.

    2000-01-01

    Aluminum alloys may exhibit a variety of microstructures within the fusion zone adjacent to the fusion boundary. Under conventional weld solidification conditions, epitaxial nucleation occurs off grains in the heat-affected zone (HAZ) and solidification proceeds along preferred growth directions. In some aluminum alloys, such as those containing Li and Zr, a nondendritic equiaxed grain zone (EQZ) has been observed along the fusion boundary that does not nucleate epitaxially from the HAZ substrate. The EQZ has been the subject of considerable study because of its susceptibility to cracking during initial fabrication and repair. The motivation of this investigation was to develop a technique that would allow the nature and evolution of the fusion boundary to be studied under controlled thermal conditions. A melting technique was developed to simulate the fusion boundary of aluminum alloys using the Gleeble{reg{underscore}sign} thermal simulator. Using a steel sleeve to contain the aluminum, samples wee heated to incremental temperatures above the solidus temperature of a number of alloys. In Alloy 2195, a 4Cu-1Li alloy, an EQZ could be formed by heating in the temperature range approximately from 630--640 C. At temperatures above 640 C, solidification occurred by the normal epitaxial nucleation and growth mechanism. Fusion boundary behavior was also studied in Alloys 5454-H34, 6061-T6 and 2219-T8. Nucleation in these alloys was observed to be epitaxial. Details of the technique and its effectiveness for performing controlled melting experiments at incremental temperatures above the solidus are described.

  2. Microstructural Evolution and Mechanical Properties of Fusion Welds in an Iron-Copper-Based Multicomponent Steel

    NASA Astrophysics Data System (ADS)

    Farren, Jeffrey D.; Hunter, Allen H.; Dupont, John N.; Seidman, David N.; Robino, Charles V.; Kozeschnik, Ernst

    2012-11-01

    NUCu-140 is a copper-precipitation-strengthened steel that exhibits excellent mechanical properties with a relatively simple chemical composition and processing schedule. As a result, NUCu-140 is a candidate material for use in many naval and structural applications. Before NUCu-140 can be implemented as a replacement for currently used materials, the weldability of this material must be determined under a wide range of welding conditions. This research represents an initial step toward understanding the microstructural and mechanical property evolution that occurs during fusion welding of NUCu-140. Microhardness traverses and tensile testing using digital image correlation show local softening in the heat-affected zone (HAZ). Microstructural characterization using light optical microscopy (LOM) revealed very few differences in the softened regions compared with the base metal. Local-electrode atom-probe (LEAP) tomography demonstrates that local softening occurs as a result of dissolution of the Cu-rich precipitates. MatCalc kinetic simulations (Vienna, Austria) were combined with welding heat-flow calculations to model the precipitate evolution within the HAZ. Reasonably good agreement was obtained between the measured and calculated precipitate radii, number density, and volume fraction of the Cu-rich precipitates in the weld. These results were used with a precipitate-strengthening model to understand strength variations within the HAZ.

  3. Nature and evolution of the fusion boundary in ferritic-austenitic dissimilar weld metals. Part 1 -- Nucleation and growth

    SciTech Connect

    Nelson, T.W.; Lippold, J.C.; Mills, M.J.

    1999-10-01

    A fundamental investigation of fusion boundary microstructure evolution in dissimilar-metal welds (DMWs) between ferritic base metals and a face-centered-cubic (FCC) filler metal was conducted. The objective of the work presented here was to characterize the nature and character of the elevated-temperature fusion boundary to determine the nucleation and growth characteristics of DMWs. Type 409 ferritic stainless steel and 1080 pearlitic steel were utilized as base metal substrates, and Monel (70Ni-30Cu) was used as the filler metal. The Type 409 base metal provided a fully ferritic or body-centered-cubic (BCC) substrate at elevated temperatures and exhibited no on-cooling phase transformations to mask or disguise the original character of the fusion boundary. The 1080 pearlitic steel was selected because it is austenitic at the solidus temperature, providing an austenite substrate at the fusion boundary. The weld microstructure generated with each of the base metals in combination with Monel was fully austenitic. In the Type 409/Monel system, there was no evidence of epitaxial nucleation and growth as normally observed in homogeneous weld metal combinations. The fusion boundary in this system exhibited random grain boundary misorientations between the heat-affected zone (HAZ) and weld metal grains. In the 1080/Monel system, evidence of normal epitaxial growth was observed at the fusion boundary, where solidification and HAZ grain boundaries converged. The fusion boundary morphologies are a result of the crystal structure present along the fusion boundary during the initial stages of solidification. Based on the results of this investigation, a model for heterogeneous nucleation along the fusion boundary is proposed when the base and weld metals exhibit ferritic (BCC) and FCC crystal structures, respectively.

  4. Microstructural Evolution and Creep-Rupture Behavior of A-USC Alloy Fusion Welds

    NASA Astrophysics Data System (ADS)

    Bechetti, Daniel H.; DuPont, John N.; Siefert, John A.; Shingledecker, John P.

    2016-06-01

    Characterization of the microstructural evolution of fusion welds in alloys slated for use in advanced ultrasupercritical (A-USC) boilers during creep has been performed. Creep-rupture specimens involving INCONEL® 740, NIMONIC® 263 (INCONEL and NIMONIC are registered trademarks of Special Metals Corporation), and Haynes® 282® (Haynes and 282 are registered trademarks of Haynes International) have been analyzed via light optical microscopy, scanning electron microscopy, X-ray diffraction, and thermodynamic and kinetic modeling. Focus has been given to the microstructures that develop along the grain boundaries in these alloys during creep at temperatures relevant to the A-USC process cycle, and particular attention has been paid to any evidence of the formation of local γ'-denuded or γ'-free zones. This work has been performed in an effort to understand the microstructural changes that lead to a weld strength reduction factor (WSRF) in these alloys as compared to solution annealed and aged alloy 740 base metal. γ' precipitate-free zones have been identified in alloy 740 base metal, solution annealed alloy 740 weld metal, and alloy 263 weld metal after creep. Their development during long-term thermal exposure is correlated with the stabilization of phases that are rich in γ'-forming elements (e.g., η and G) and is suppressed by precipitation of phases that do not contain the γ' formers (e.g., M23C6 and μ). The location of failure and creep performance in terms of rupture life and WSRF for each welded joint is presented and discussed.

  5. Microstructural Evolution and Creep-Rupture Behavior of A-USC Alloy Fusion Welds

    NASA Astrophysics Data System (ADS)

    Bechetti, Daniel H.; DuPont, John N.; Siefert, John A.; Shingledecker, John P.

    2016-09-01

    Characterization of the microstructural evolution of fusion welds in alloys slated for use in advanced ultrasupercritical (A-USC) boilers during creep has been performed. Creep-rupture specimens involving INCONEL® 740, NIMONIC® 263 (INCONEL and NIMONIC are registered trademarks of Special Metals Corporation), and Haynes® 282® (Haynes and 282 are registered trademarks of Haynes International) have been analyzed via light optical microscopy, scanning electron microscopy, X-ray diffraction, and thermodynamic and kinetic modeling. Focus has been given to the microstructures that develop along the grain boundaries in these alloys during creep at temperatures relevant to the A-USC process cycle, and particular attention has been paid to any evidence of the formation of local γ'-denuded or γ'-free zones. This work has been performed in an effort to understand the microstructural changes that lead to a weld strength reduction factor (WSRF) in these alloys as compared to solution annealed and aged alloy 740 base metal. γ' precipitate-free zones have been identified in alloy 740 base metal, solution annealed alloy 740 weld metal, and alloy 263 weld metal after creep. Their development during long-term thermal exposure is correlated with the stabilization of phases that are rich in γ'-forming elements ( e.g., η and G) and is suppressed by precipitation of phases that do not contain the γ' formers ( e.g., M23C6 and μ). The location of failure and creep performance in terms of rupture life and WSRF for each welded joint is presented and discussed.

  6. Microstructural Evolution and Creep-Rupture Behavior of Fusion Welds Involving Alloys for Advanced Ultrasupercritical Power Generation

    NASA Astrophysics Data System (ADS)

    Bechetti, Daniel H., Jr.

    determine the correlation of discontinuous coarsening of the gamma' phase with time at temperature, creep strain, plastic prestrain, post-weld heat treatment, and compositional modification. The discontinuous coarsening reaction was shown to depend most strongly on the total strain experienced during creep. Post-weld homogenization and compositional modification had mixed effects on fusion weld rupture life and the rate of discontinuous coarsening. The differences in rupture life and discontinuous coarsening across a large matrix of creep specimens were related to the differences in strain at rupture and the relative ease of grain boundary motion in the samples. Finally, in-depth characterization of the discontinuous coarsening reaction products in alloy 740H creep specimens was performed. The effects of solute partitioning during non-equilibrium solidification on the variation in the volume fraction of strengthening precipitates along the length of the grain boundaries has been linked to the propensity for discontinuous coarsening. Evidence for the preferential development of discontinuous coarsening along grain boundary segments with sharp variations in gamma' content was presented. In addition, evidence for the preferred growth of colonies of discontinuous coarsening into regions of lower gamma' content was documented. Scanning transmission electron microscopy determined the compositions of the matrix and precipitate phases within the colonies and quantified the segregation of alloying elements to the reaction front. Thermodynamic and kinetic modeling using commercially available software packages were leaned on extensively throughout this research, both as a way to provide theoretical bases for experimental observations and as a way to design and guide experimentation. Overall, the results presented in this work offer detailed observations on the evolution of deleterious grain boundary features in A-USC alloy fusion welds and provide insight for changes that may improve

  7. Welding.

    ERIC Educational Resources Information Center

    Lehigh County Area Vocational-Technical School, Schnecksville, PA.

    This curriculum guide provides materials for a 12-unit secondary course in welding. Purpose stated for the flexible entry and exit course is to help students master manipulative skills to develop successful welding techniques and to gain an understanding of the specialized tools and equipment used in the welding field. Units cover oxyacetylene…

  8. Sensor fusion for improved indoor navigation

    NASA Astrophysics Data System (ADS)

    Emilsson, Erika; Rydell, Joakim

    2012-09-01

    A reliable indoor positioning system providing high accuracy has the potential to increase the safety of first responders and military personnel significantly. To enable navigation in a broad range of environments and obtain more accurate and robust positioning results, we propose a multi-sensor fusion approach. We describe and evaluate a positioning system, based on sensor fusion between a foot-mounted inertial measurement unit (IMU) and a camera-based system for simultaneous localization and mapping (SLAM). The complete system provides accurate navigation in many relevant environments without depending on preinstalled infrastructure. The camera-based system uses both inertial measurements and visual data, thereby enabling navigation also in environments and scenarios where one of the sensors provides unreliable data during a few seconds. When sufficient light is available, the camera-based system generally provides good performance. The foot-mounted system provides accurate positioning when distinct steps can be detected, e.g., during walking and running, even in dark or smoke-filled environments. By combining the two systems, the integrated positioning system can be expected to enable accurate navigation in almost all kinds of environments and scenarios. In this paper we present results from initial tests, which show that the proposed sensor fusion improves the navigation solution considerably in scenarios where either the foot-mounted or camera-based system is unable to navigate on its own.

  9. Welding and cutting characteristics of blanket/first wall module to back plate for fusion experimental reactor

    SciTech Connect

    Kuroda, T.; Furuya, K.; Sato, S.

    1995-12-31

    A modular blanket/first wall has been proposed for a fusion experimental reactor, e.g., International Thermonuclear Experimental Reactor (ITER), with support ribs connecting to a strong back plate. For the connection method, a welding approach has been investigated. Welding and cutting tests of the support ribs have been performed with three types of test specimens; flat plate (200 mm x 400 mm), partial model (700 mm x 200 mm), and full-box model (600 mm x 1000 mm x 430 mm). The support ribs were made of type 316L austenitic stainless steel with the thickness of 50 mm in all these tests. The welding method applied to these tests was narrow gap TIG, and water jet for cutting. Through these tests, engineering data including optimum welding conditions, welding distortion, and welding/cutting speeds have been obtained. Transverse shrinkage was about 10 mm for the welding of 50 mm thick rib. However, the difference in distortion at the first wall surface was within 1--2 mm. Therefore, the blanket/first wall module can be installed with quite a high accuracy by taking into account the module moving to the back plate during the welding.

  10. Effects of Fusion Zone Size and Failure Mode on Peak Load and Energy Absorption of Advanced High Strength Steel Spot Welds

    SciTech Connect

    Sun, Xin; Stephens, Elizabeth V.; Khaleel, Mohammad A.

    2007-01-01

    This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS). DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. The critical fusion zone sizes to ensure nugget pull-out failure mode are developed for both DP800 and TRIP800 using limit load based analytical model and micro-hardness measurements of the weld cross sections. Static weld strength tests using cross tension samples were performed on the joint populations with controlled fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied for all the weld populations using statistical data analysis tools. The results in this study show that AHSS spot welds with fusion zone size of can not produce nugget pullout mode for both the DP800 and TRIP800 materials examined. The critical fusion zone size for nugget pullout shall be derived for individual materials based on different base metal properties as well as different heat affected zone (HAZ) and weld properties resulted from different welding parameters.

  11. Improved techniques of parallel gap welding and monitoring

    NASA Technical Reports Server (NTRS)

    Mardesich, N.; Gillanders, M. S.

    1984-01-01

    Welding programs which show that parallel gas welding is a reliable process are discussed. When monitoring controls and nondestructive tests are incorporated into the process, parallel gap welding becomes more reliable and cost effective. The panel fabrication techniques and the HAC thermal cycling test indicate reliable product integrity. The design and building of automated tooling and fixturing for welding are discussed.

  12. Improved torch increases weld quality in refractory metals

    NASA Technical Reports Server (NTRS)

    Lessman, G. G.; Sprecace, R.

    1968-01-01

    Specially designed torch welds refractory metals in a vacuum purged, inert gas backfilled welding chamber /weld box/ with practically zero contamination resulting from its use. Included in the torch design is a radiation shield to protect the operators hands when welding at high amperages.

  13. Welding for testability: An approach aimed at improving the ultrasonic testing of thick-walled austenitic and dissimilar metal welds

    NASA Astrophysics Data System (ADS)

    Wagner, Sabine; Dugan, Sandra; Barth, Martin; Schubert, Frank; Köhler, Bernd

    2014-02-01

    Austenitic and dissimilar welds in thick walled components show a coarse grained, dendritic microstructure. Therefore, ultrasonic testing has to deal with beam refraction, scattering and mode conversion effects. As a result, the testing techniques typically applied for isotropic materials yield dissatisfying results. Most approaches for improvement of ultrasonic testing have been based on modeling and improved knowledge of the complex wave propagation phenomena. In this paper, we discuss an alternative approach: is it possible to use a modified welding technology which eliminates the cause of the UT complications, i.e. the large-grained structure of the weld seams? Various modification parameters were tested, including: TIG current pulsing, additional DC and AC magnetic fields, and also additional external vibrations during welding. For all welds produced under different conditions, the grain structure of the weld seam was characterized by optical and GIUM microstructure visualizations on cross sections, wave field propagation measurements, and ultrasonic tests of correct detectability of flaws. The mechanical properties of the welds were also tested.

  14. Welding for testability: An approach aimed at improving the ultrasonic testing of thick-walled austenitic and dissimilar metal welds

    SciTech Connect

    Wagner, Sabine; Dugan, Sandra; Barth, Martin; Schubert, Frank; Köhler, Bernd

    2014-02-18

    Austenitic and dissimilar welds in thick walled components show a coarse grained, dendritic microstructure. Therefore, ultrasonic testing has to deal with beam refraction, scattering and mode conversion effects. As a result, the testing techniques typically applied for isotropic materials yield dissatisfying results. Most approaches for improvement of ultrasonic testing have been based on modeling and improved knowledge of the complex wave propagation phenomena. In this paper, we discuss an alternative approach: is it possible to use a modified welding technology which eliminates the cause of the UT complications, i.e. the large-grained structure of the weld seams? Various modification parameters were tested, including: TIG current pulsing, additional DC and AC magnetic fields, and also additional external vibrations during welding. For all welds produced under different conditions, the grain structure of the weld seam was characterized by optical and GIUM microstructure visualizations on cross sections, wave field propagation measurements, and ultrasonic tests of correct detectability of flaws. The mechanical properties of the welds were also tested.

  15. Taguchi Optimization of Pulsed Current GTA Welding Parameters for Improved Corrosion Resistance of 5083 Aluminum Welds

    NASA Astrophysics Data System (ADS)

    Rastkerdar, E.; Shamanian, M.; Saatchi, A.

    2013-04-01

    In this study, the Taguchi method was used as a design of experiment (DOE) technique to optimize the pulsed current gas tungsten arc welding (GTAW) parameters for improved pitting corrosion resistance of AA5083-H18 aluminum alloy welds. A L9 (34) orthogonal array of the Taguchi design was used, which involves nine experiments for four parameters: peak current ( P), base current ( B), percent pulse-on time ( T), and pulse frequency ( F) with three levels was used. Pitting corrosion resistance in 3.5 wt.% NaCl solution was evaluated by anodic polarization tests at room temperature and calculating the width of the passive region (∆ E pit). Analysis of variance (ANOVA) was performed on the measured data and S/ N (signal to noise) ratios. The "bigger is better" was selected as the quality characteristic (QC). The optimum conditions were found as 170 A, 85 A, 40%, and 6 Hz for P, B, T, and F factors, respectively. The study showed that the percent pulse-on time has the highest influence on the pitting corrosion resistance (50.48%) followed by pulse frequency (28.62%), peak current (11.05%) and base current (9.86%). The range of optimum ∆ E pit at optimum conditions with a confidence level of 90% was predicted to be between 174.81 and 177.74 mVSCE. Under optimum conditions, the confirmation test was carried out, and the experimental value of ∆ E pit of 176 mVSCE was in agreement with the predicted value from the Taguchi model. In this regard, the model can be effectively used to predict the ∆ E pit of pulsed current gas tungsten arc welded joints.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  17. Microstructural characteristics and mechanism of toughness improvement of laser and electron-beam welds of V-4Cr-4Ti following postwelding heat-treatment

    SciTech Connect

    Chung, H.M.; Park, J.H.; Gazda, J.; Smith, D.L.

    1996-10-01

    The authors are conducting a program to develop an optimal laser welding procedure for large-scale fusion-reactor structural components to be fabricated from vanadium-base alloys. Microstructural characteristics were investigated by optical microscopy, X-ray diffraction, transmission electron microscopy, and chemical analysis to provide an understanding of the mechanism of the drastic improvement of impact toughness of laser and electron-beam (EB) welds of V-4Cr-4Ti following postwelding annealing at 1000{degrees}C. Transmission electron microscopy (TEM) revealed that annealed weld zones were characterized by extensive networks of fine V(C,O,N) precipitates, which appear to clean away O, C, and N from grain matrices. This process is accompanied by simultaneous annealing-out of the dense dislocations present in the weld fusion zone. It seems possible to produce high-quality welds under practical conditions by controlling and adjusting the cooling rate of the weld zone by some innovative method to maximize the precipitation of V(C,O,N).

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  19. Microstructure evolution in the fusion welding of heat-treatable Al-Cu-Li alloys. Ph.D. Thesis

    SciTech Connect

    Hou, K.

    1994-01-01

    Aluminum alloys 2090 and 2195 and Al-2.5Cu were welded autogenously using the gas tungsten-arc (GTA) and CO2 laser beam (LB) welding processes. Relationships between microstructure and mechanical properties in the fusion zone (FZ) and the heat-affected zone (HAZ) in both the as-welded and the postweld heat-treated conditions were studied. Solute segregation due to non-equilibrium solidification in the FZ and its effect on precipitation after postweld aging was quantitatively investigated. After aging treatment, precipitates were found surrounding eutectic regions where higher solute content was measured. Fast cooling LB weld exhibited narrower solute enriched regions and narrower precipitate segregation zones (PSZ`s) adjacent to the eutectic. A partial recovery of strength and hardness in the FZ`s was achieved by postweld aging at 160 C and 190 C for 16 hours. A higher Li/Cu ratio in 2090 promoted the formation of uniformly distributed delta(prime) precipitates in the as-welded HAZ. An evident reduction in the FZ ductility occurred in the 2195 LB welds due to the existence of porosity and shrinkage cavities, and the constraint effect from narrower FZ`s. GTA welds in both 2090 and 2195 alloys exhibited a hardness recovery in the near HAZ, which was not obvious in the LB welds. Postweld aging enhanced this hardness variation. Overaging, dissolution and reprecipitation of various strengthening precipitates occurred in the different regions of the HAZ, and consequently induced the hardness variation. Higher heat inputs increased the HAZ width and enhanced the hardness increase in the near HAZ. Aged HAZ microstructure was affected by the precipitation in the as-welded condition. The formation of Li-containing precipitates in the GTA HAZ, especially alpha(prime) in Li-lean 2195, consumed Li from the matrix. Consequently, the precipitation of T1 was affected.

  20. Modeling solute redistribution and microstructural development in fusion welds of multi-component alloys

    SciTech Connect

    Dupont, J.N.; Robino, C.V.; Newbury, B.D.

    1999-12-15

    Solute redistribution and microstructural evolution have been modeled for gas tungsten arc fusion welds in experimental Ni base superalloys. The multi-component alloys were modeled as a pseudo-ternary {gamma}-Nb-C system. The variation in fraction liquid and liquid composition during the primary L {r{underscore}arrow} {gamma} and eutectic type L {r{underscore}arrow} ({gamma} + NbC) stages of solidification were calculated for conditions of negligible Nb diffusion and infinitely rapid C diffusion in the solid phase. Input parameters were estimated by using the Thermo-Calc NiFe Alloy data base and compared to experimentally determined solidification parameters. The solidification model results provide useful information for qualitatively interpreting the influence of alloy composition on weld microstructure. The quantitative comparisons indicate that, for the alloy system evaluated, the thermodynamic database provides sufficiently accurate values for the distribution coefficients of Nb and C. The calculated position of the {gamma}-NbC two-fold saturation line produces inaccurate results when used as inputs for the model, indicating further refinement to the database is needed for quantitative estimates.

  1. Microstructural analysis of solid-state resistance welds

    SciTech Connect

    Kanne, W.R.Jr.

    1993-07-01

    No melting is present in solid-state welds and the microstructure is therefore very different from the solidification structures found in fusion welds. Improved properties of the weld result from the solid-state metallurgical structure. Solid-state resistance welding therefore has advantages compared to fusion welding processes. Different types of solid-state resistance welds have been developed for several unique applications ranging from small tube closure welds to vessel fabrication welds. Solid-state resistance upset welds have a hot worked microstructure, usually with recrystallization near the mating surfaces. Quality of the weld can be related to the metallographic appearance of the bond line at the mating surfaces. Impurities such as oxidation effect both the appearance of the bond line and weld quality. Microstructural examination of flow lines can provide a remarkably clear picture of the deformation pattern, or upsetting, that occurs during welding. Unusual effects such as multiple interfaces can be clearly seen from microstructural examination. Hardness traverses across metallographic sections are used to relate weld area strength to microstructural characteristics. Solid-state weld and heat-affected zone strengths have been compared to base metal and to fusion weld strengths using hardness data.

  2. Microstructural analysis of solid-state resistance welds

    SciTech Connect

    Kanne, W.R.Jr.

    1993-01-01

    No melting is present in solid-state welds and the microstructure is therefore very different from the solidification structures found in fusion welds. Improved properties of the weld result from the solid-state metallurgical structure. Solid-state resistance welding therefore has advantages compared to fusion welding processes. Different types of solid-state resistance welds have been developed for several unique applications ranging from small tube closure welds to vessel fabrication welds. Solid-state resistance upset welds have a hot worked microstructure, usually with recrystallization near the mating surfaces. Quality of the weld can be related to the metallographic appearance of the bond line at the mating surfaces. Impurities such as oxidation effect both the appearance of the bond line and weld quality. Microstructural examination of flow lines can provide a remarkably clear picture of the deformation pattern, or upsetting, that occurs during welding. Unusual effects such as multiple interfaces can be clearly seen from microstructural examination. Hardness traverses across metallographic sections are used to relate weld area strength to microstructural characteristics. Solid-state weld and heat-affected zone strengths have been compared to base metal and to fusion weld strengths using hardness data.

  3. 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.

  4. Development of an improved GTA (gas tungsten arc) weld temperature monitor fixture

    SciTech Connect

    Hollar, D.L.

    1990-05-01

    An initial design weld temperature control fixture was implemented into final closure of an electronic assembly in November 1986. Use of this fixture indicated several areas that could be improved. Review of these areas with the process engineer and the weld operator provided the ideas to be incorporated into the new design Phase 2 fixture. Some primary areas of change and improvement included fixture mobility to provide better accessibility to the weld joint area, automatic timed blow cooling of the weld joint, and a feature to assure proper thermocouple placement. The resulting Phase 2 fixture design provided all of the essential weld temperature monitoring features in addition to several significant improvements. Technology developed during this project will pave the way to similar process monitoring of other manual gas tungsten arc (GTA) welding applications. 9 figs.

  5. Basic study of heat flow in fusion welding. Progress report to the US Department of Energy, October 1, 1980-October 1, 1982

    SciTech Connect

    Szekely, J.; Eagar, T.W.

    1981-10-15

    Progress is reported in an investigation whose purpose is the development of a fundamental understanding of heat and fluid flow in fusion welding operations and of the role played by heat and fluid flow in determining the mechanical and structural properties of the welds produced. To date, a good quantitative description has been developed of the temperature profiles for electroslag welding systems and an understanding has been derived of factors that determine the size of the heat-affected zone (HAZ). Mathematical models of heat and fluid flow in the weld pool and of the temperature distribution in weldments using a moving heat source were developed. Experiments were performed to determine the effects of welding process parameters on the size and shape of the weld pool and of the HAZ. An unexpected finding was that the size of the HAZ was not markedly dependent on any of the welding process parameters. (LCL)

  6. Feasibility study on welding and cutting methods for thick plate in fusion reactor

    SciTech Connect

    Osaki, T.; Nakayama, Y.; Kobayashi, T.

    1995-12-31

    Application of tungsten-arc inert-gas (TIG) welding with narrow gap has been considered as a hopeful joint method to suppress post welding deformation for thick plates. The authors studied some parameters to predict the post-welding deformation for the narrow gap shape of TIG welding. As for cutting methods, the water jet method was applied for weld joints in this study. Reweld tests by using the TIG welding method were successfully performed under the condition of cutting surface as it was. Results of tensile tests for reweld joints showed no reduction in strength. This reveals a good prospect of providing reweld groove surface without any machining on site.

  7. Welding.

    ERIC Educational Resources Information Center

    Baldwin, Harold; Whitney, Gregory

    This curriculum guide is intended to assist vocational instructors in preparing students for entry-level employment as welders and preparing them for advanced training in the workplace. The package contains an overview of new and emerging welding technologies, a competency/skill and task list, an instructor's guide, and an annotated bibliography.…

  8. Welding.

    ERIC Educational Resources Information Center

    Cowan, Earl; And Others

    The curriculum guide for welding instruction contains 16 units presented in six sections. Each unit is divided into the following areas, each of which is color coded: terminal objectives, specific objectives, suggested activities, and instructional materials; information sheet; transparency masters; assignment sheet; test; and test answers. The…

  9. Improvement in fusion reactor performance due to ion channeling

    SciTech Connect

    Emmert, G.A.; El-Guebaly, L.A.; Kulcinski, G.L.; Santarius, J.F.; Sviatoslavsky, I.N.; Meade, D.M.

    1994-11-01

    Ion channeling is a recent idea for improving the performance of fusion reactors by increasing the fraction of the fusion power deposited in the ions. In this paper the authors assess the effect of ion channeling on D-T and D-{sup 3}He reactors. The figures of merit used are the fusion power density and the cost of electricity. It is seen that significant ion channeling can lead to about a 50-65% increase in the fusion power density. For the Apollo D-{sup 3}He reactor concept the reduction in the cost of electricity can be as large as 30%.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  11. Improved electron beam weld design and control with beam current profile measurements

    NASA Astrophysics Data System (ADS)

    Giedt, Warren H.

    The determination of machine settings for making an electron beam weld still involves trial and error tests. Also, even after settings are selected, serious variations in penetration may occur. Results are presented to demonstrate that improved weld consistency and quality can be obtained with measurement of the beam size and intensity distribution.

  12. Welding Research

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Welding fabrication and welding processes were studied. The following research projects are reported: (1) welding fabrication; (2) residual stresses and distortion in structural weldments in high strength steels; (3) improvement of reliability of welding by in process sensing and control (development of smart welding machines for girth welding of pipes); (4) development of fully automated and integrated welding systems for marine applications; (5) advancement of welding technology; (6) research on metal working by high power laser (7) flux development; (8) heat and fluid flow; (9) mechanical properties developments.

  13. Narrow groove gas tungsten arc welding of ASTM A508 Class 4 steel for improved toughness properties

    SciTech Connect

    Penik, M.A. Jr.

    1997-04-01

    Welding of heavy section steel has traditionally used the automatic submerged arc welding (ASAW) process because of the high deposition rates achievable. However, the properties, particularly fracture toughness, of the weld are often inferior when compared to base material. This project evaluated the use of narrow groove gas tungsten arc welding (GTAW) to improve weld material properties. The welding procedures were developed for ASTM A508 Class 4 base material using a 1% Ni filler material complying to AWS Specification A.23-90-EF3-F3-N. A narrow groove joint preparation was used in conjunction with the GTAW process so competitive fabrication rates could be achieved when compared to the ASAW process. Weld procedures were developed to refine weld substructure to achieve better mechanical properties. Two heaters of weld wire were used to examine the effects of minor filler metal chemistry differences on weld mechanical properties. Extensive metallographic evaluations showed excellent weld quality with a refined microstructure. Chemical analysis of the weld metal showed minimal weld dilution by the base metal. Mechanical testing included bend and tensile tests to ensure weld quality and strength. A Charpy impact energy curve versus temperature and fracture toughness curve versus temperature were developed for each weld wire heat. Results of fracture toughness and Charpy impact testing indicated an improved transition temperature closer to that of the base material properties.

  14. Using Feedback Strategies to Improve Peer-Learning in Welding

    ERIC Educational Resources Information Center

    Chan, Selena; Leijten, Flip

    2012-01-01

    Due to safety considerations, students' practice and learning of welding is conducted within individual welding booths. The booth setting presents some challenges to student learning as collaborative learning within a workshop learning environment is compromised. The project reported in this paper, established peer-learning (i.e., students…

  15. Alternative fusion concepts and the prospects for improved reactors

    NASA Astrophysics Data System (ADS)

    Krakowski, R. A.

    1985-05-01

    Past trends, present status, and future directions in the search for an improved fusion reactor are reviewed, and promising options available to both the principle tokamak and other supporting concept are summarized.

  16. An Improved Plasticity-Based Distortion Analysis Method for Large Welded Structures

    NASA Astrophysics Data System (ADS)

    Yang, Yu-Ping; Athreya, Badrinarayan P.

    2013-05-01

    The plasticity-based distortion prediction method was improved to address the computationally intensive nature of welding simulations. Plastic strains, which are typically first computed using either two-dimensional (2D) or three-dimensional (3D) thermo-elastic-plastic analysis (EPA) on finite element models of simple weld geometry, are mapped to the full structure finite element model to predict distortion by conducting a linear elastic analysis. To optimize welding sequence to control distortion, a new theory was developed to consider the effect of weld interactions on plastic strains. This improved method was validated with experimental work on a Tee joint and tested on two large-scale welded structures—a light fabrication and a heavy fabrication—by comparing against full-blown distortion predictions using thermo-EPA. 3D solid and shell models were used for the heavy and light fabrications, respectively, to compute plastic strains due to each weld. Quantitative comparisons between this method and thermo-EPA indicate that this method can predict distortions fairly accurately—even for different welding sequences—and is roughly 1-2 orders of magnitude faster. It was concluded from these findings that, with further technical development, this method can be an ideal solver for optimizing welding sequences.

  17. Investigation of real-time microstructure evolution in steep thermal gradients using in-situ spatially resolved X-ray diffraction: A case study for Ti fusion welds

    SciTech Connect

    Ressler, T.; Wong, J.; Elmer, J.W. |

    1998-12-24

    A recently developed spatially resolved X-ray diffraction (SRXRD) technique utilizing intense synchrotron radiation has been refined to yield phase and microstructural information down to 200 {micro}m in spatial extent in materials subjected to steep thermal gradients during processing. This SRXRD technique has been applied to map completely the phases and their solid-state transformation in the so-called heat-affected zone (HAZ) in titanium fusion welds in situ during the welding process. Detailed profile analysis of the SRXRD patterns revealed four principal microstructural regions at temperature in the vicinity of the HAZ surrounding the liquid weld pool: (i) a completely transformed {beta}-Ti zone 2--3 mm adjacent to the liquid weld pool; (ii) a mixed {alpha} + {beta}-it region surrounding the pure {beta}-Ti zone, (iii) a back-transformed {alpha}-Ti zone on the backside of the HAZ where pure {beta}-Ti once existed at temperature well above the {alpha} {r_arrow} {beta} transformation isotherm, and (iv) a more diffused region outside the HAZ where annealing and recrystallization of the {alpha}-it base metal occur. The high-temperature microstructures so derived corroborate well the expected transformation kinetics in pure titanium, and the observed phase transformation boundaries are in good agreement with those predicted from the transformation isotherms calculated from a simplified heat-flow model. Based on a detailed assessment of the SRXRD setup employed, improved experimentations such as a smaller beam spot emitted from third generation synchrotron sources, better mechanical stability (tighter scattering geometry), and use of an area detector would enable more quantitative structural information for future phase dynamics studies exemplified by this work.

  18. 49 CFR 179.300-9 - Welding.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... joints must be fusion welded. Head-to-shell joints must be forge welded on class DOT-106A tanks and fusion welded on class DOT-110A tanks. Welding procedures, welders and fabricators must be approved in...) Fusion-welded joints must be in compliance with the requirements of AAR Specifications for Tank...

  19. Improved Heat-of-Fusion Energy Storage

    NASA Technical Reports Server (NTRS)

    Chen, K. H.; Manvi, R.

    1982-01-01

    Alkali metal/alkali-halide mixtures proposed for preventing solid buildup during energy recovery. When mixture melts (by absorption of heat of fusion), it forms two immiscible liquids. Salt-rich phase is heavier and has higher melting/recrysallization temperature; so during energy recovery salt crystallizes in this phase first. Since heat exchanger for energy recovery is in lighter metal-rich phase, solids do not form and there is no reduction of heat-recovery efficiency.

  20. Inverter-based GTA welding machines improve fabrication

    SciTech Connect

    Sammons, M.

    2000-05-01

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

  1. 49 CFR 179.300-9 - Welding.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... fusion welded. Head-to-shell joints must be forge welded on class DOT-106A tanks and fusion welded on... AAR Specifications for Tank Cars, appendix W (IBR, see § 171.7 of this subchapter). (b)...

  2. [An improved medical image fusion algorithm and quality evaluation].

    PubMed

    Chen, Meiling; Tao, Ling; Qian, Zhiyu

    2009-08-01

    Medical image fusion is of very important value for application in medical image analysis and diagnosis. In this paper, the conventional method of wavelet fusion is improved,so a new algorithm of medical image fusion is presented and the high frequency and low frequency coefficients are studied respectively. When high frequency coefficients are chosen, the regional edge intensities of each sub-image are calculated to realize adaptive fusion. The choice of low frequency coefficient is based on the edges of images, so that the fused image preserves all useful information and appears more distinctly. We apply the conventional and the improved fusion algorithms based on wavelet transform to fuse two images of human body and also evaluate the fusion results through a quality evaluation method. Experimental results show that this algorithm can effectively retain the details of information on original images and enhance their edge and texture features. This new algorithm is better than the conventional fusion algorithm based on wavelet transform. PMID:19813594

  3. Improving cerebellar segmentation with statistical fusion

    NASA Astrophysics Data System (ADS)

    Plassard, Andrew J.; Yang, Zhen; Prince, Jerry L.; Claassen, Daniel O.; Landman, Bennett A.

    2016-03-01

    The cerebellum is a somatotopically organized central component of the central nervous system well known to be involved with motor coordination and increasingly recognized roles in cognition and planning. Recent work in multiatlas labeling has created methods that offer the potential for fully automated 3-D parcellation of the cerebellar lobules and vermis (which are organizationally equivalent to cortical gray matter areas). This work explores the trade offs of using different statistical fusion techniques and post hoc optimizations in two datasets with distinct imaging protocols. We offer a novel fusion technique by extending the ideas of the Selective and Iterative Method for Performance Level Estimation (SIMPLE) to a patch-based performance model. We demonstrate the effectiveness of our algorithm, Non- Local SIMPLE, for segmentation of a mixed population of healthy subjects and patients with severe cerebellar anatomy. Under the first imaging protocol, we show that Non-Local SIMPLE outperforms previous gold-standard segmentation techniques. In the second imaging protocol, we show that Non-Local SIMPLE outperforms previous gold standard techniques but is outperformed by a non-locally weighted vote with the deeper population of atlases available. This work advances the state of the art in open source cerebellar segmentation algorithms and offers the opportunity for routinely including cerebellar segmentation in magnetic resonance imaging studies that acquire whole brain T1-weighted volumes with approximately 1 mm isotropic resolution.

  4. Improving Cerebellar Segmentation with Statistical Fusion

    PubMed Central

    Plassard, Andrew J.; Yang, Zhen; Prince, Jerry L.; Claassen, Daniel O.; Landman, Bennett A.

    2016-01-01

    The cerebellum is a somatotopically organized central component of the central nervous system well known to be involved with motor coordination and increasingly recognized roles in cognition and planning. Recent work in multi-atlas labeling has created methods that offer the potential for fully automated 3-D parcellation of the cerebellar lobules and vermis (which are organizationally equivalent to cortical gray matter areas). This work explores the trade offs of using different statistical fusion techniques and post hoc optimizations in two datasets with distinct imaging protocols. We offer a novel fusion technique by extending the ideas of the Selective and Iterative Method for Performance Level Estimation (SIMPLE) to a patch-based performance model. We demonstrate the effectiveness of our algorithm, Non-Local SIMPLE, for segmentation of a mixed population of healthy subjects and patients with severe cerebellar anatomy. Under the first imaging protocol, we show that Non-Local SIMPLE outperforms previous gold-standard segmentation techniques. In the second imaging protocol, we show that Non-Local SIMPLE outperforms previous gold standard techniques but is outperformed by a non-locally weighted vote with the deeper population of atlases available. This work advances the state of the art in open source cerebellar segmentation algorithms and offers the opportunity for routinely including cerebellar segmentation in magnetic resonance imaging studies that acquire whole brain T1-weighted volumes with approximately 1 mm isotropic resolution. PMID:27127334

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

    SciTech Connect

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

    2015-05-22

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  7. Microstructural Evolution and Mechanical Properties of Fusion Welds and Simulated Heat-Affected Zones in an Iron-Copper Based Multi-Component Steel

    NASA Astrophysics Data System (ADS)

    Farren, Jeffrey David

    -affected zone (HAZ) as a result of either full or partial dissolution of the copper-rich precipitates responsible for strengthening. Re-precipitation of the copper-rich precipitates was observed during the cooling portion of the weld thermal cycle but the resultant precipitate phase fractions were too low to fully recover the lost strength. The coarse-grained HAZ and fusion zone exhibited an acicular type microstructure which led to improved tensile properties when compared to the other regions of the HAZ. MatCalc simulations displayed excellent agreement with the precipitate parameters measured experimentally using the LEAP. The R-B model was shown to provide reasonable agreement under select conditions, but in general was determined to be overly sensitive to small variations in precipitate parameters. As a result in should be considered a qualitative tool only for precipitate radii less than ˜2 nm. Finally, it was determined that the current generation of MatCalc software was unable to accurately capture the precipitate evolution of various binary iron-copper alloys when experimental data sets were not available for calibration of the model parameters.

  8. Kinect Fusion improvement using depth camera calibration

    NASA Astrophysics Data System (ADS)

    Pagliari, D.; Menna, F.; Roncella, R.; Remondino, F.; Pinto, L.

    2014-06-01

    Scene's 3D modelling, gesture recognition and motion tracking are fields in rapid and continuous development which have caused growing demand on interactivity in video-game and e-entertainment market. Starting from the idea of creating a sensor that allows users to play without having to hold any remote controller, the Microsoft Kinect device was created. The Kinect has always attract researchers in different fields, from robotics to Computer Vision (CV) and biomedical engineering as well as third-party communities that have released several Software Development Kit (SDK) versions for Kinect in order to use it not only as a game device but as measurement system. Microsoft Kinect Fusion control libraries (firstly released in March 2013) allow using the device as a 3D scanning and produce meshed polygonal of a static scene just moving the Kinect around. A drawback of this sensor is the geometric quality of the delivered data and the low repeatability. For this reason the authors carried out some investigation in order to evaluate the accuracy and repeatability of the depth measured delivered by the Kinect. The paper will present a throughout calibration analysis of the Kinect imaging sensor, with the aim of establishing the accuracy and precision of the delivered information: a straightforward calibration of the depth sensor in presented and then the 3D data are correct accordingly. Integrating the depth correction algorithm and correcting the IR camera interior and exterior orientation parameters, the Fusion Libraries are corrected and a new reconstruction software is created to produce more accurate models.

  9. Effect of oxide inclusions on the solid state transformation in low-alloy steel fusion welds

    SciTech Connect

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

    1995-12-31

    Non-metallic inclusions are known to influence the properties of low alloy steel weld metal by altering the microstructure development. Isothermal transformation kinetics of austenite to acicular ferrite and allotriomorphic ferrite were measured in reheated low alloy steel weld deposits with similar weld compositions and austenite grain size but different inclusion characteristics. Accelerated kinetics of the transformation to acicular ferrite were observed in the weld metal containing coarser titanium-rich inclusions. The results are also discussed in relation to the predictions of inclusion model. The kinetics of the transformation to allotriomorphic ferrite were not influenced by a change in the inclusion characteristics, but, rather, by a change in austenite grain size. A theoretical analysis of austenite grain development during weld cooling is considered in this work. The austenite grain size was found to depend on the driving force for transformation from 6 ferrite to austenite ({Delta}G{sup {sigma}->{gamma}}) calculated from ThermoCalc{trademark} software.

  10. Quality improvement of polymer parts by laser welding

    NASA Astrophysics Data System (ADS)

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

    1994-09-01

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

  11. Ultrasonic Impact Treatment to Improve Stress Corrosion Cracking Resistance of Welded Joints of Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Yu, J.; Gou, G.; Zhang, L.; Zhang, W.; Chen, H.; Yang, Y. P.

    2016-06-01

    Stress corrosion cracking is one of the major issues for welded joints of 6005A-T6 aluminum alloy in high-speed trains. High residual stress in the welded joints under corrosion results in stress corrosion cracking. Ultrasonic impact treatment was used to control the residual stress of the welded joints of 6005A-T6 aluminum alloy. Experimental tests show that ultrasonic impact treatment can induce compressive longitudinal and transverse residual stress in the welded joint, harden the surface, and increase the tensile strength of welded joints. Salt-fog corrosion tests were conducted for both an as-welded sample and an ultrasonic impact-treated sample. The surface of the treated sample had far fewer corrosion pits than that of the untreated sample. The treated sample has higher strength and lower tensile residual stress than the untreated sample during corrosion. Therefore, ultrasonic impact treatment is an effective technique to improve the stress corrosion cracking resistance of the welded joints of 6005A-T6 aluminum alloy.

  12. Ultrasonic Impact Treatment to Improve Stress Corrosion Cracking Resistance of Welded Joints of Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Yu, J.; Gou, G.; Zhang, L.; Zhang, W.; Chen, H.; Yang, Y. P.

    2016-07-01

    Stress corrosion cracking is one of the major issues for welded joints of 6005A-T6 aluminum alloy in high-speed trains. High residual stress in the welded joints under corrosion results in stress corrosion cracking. Ultrasonic impact treatment was used to control the residual stress of the welded joints of 6005A-T6 aluminum alloy. Experimental tests show that ultrasonic impact treatment can induce compressive longitudinal and transverse residual stress in the welded joint, harden the surface, and increase the tensile strength of welded joints. Salt-fog corrosion tests were conducted for both an as-welded sample and an ultrasonic impact-treated sample. The surface of the treated sample had far fewer corrosion pits than that of the untreated sample. The treated sample has higher strength and lower tensile residual stress than the untreated sample during corrosion. Therefore, ultrasonic impact treatment is an effective technique to improve the stress corrosion cracking resistance of the welded joints of 6005A-T6 aluminum alloy.

  13. Friction plug welding

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  14. Laser Assisted Plasma Arc Welding

    SciTech Connect

    FUERSCHBACH,PHILLIP W.

    1999-10-05

    Experiments have been performed using a coaxial end-effecter to combine a focused laser beam and a plasma arc. The device employs a hollow tungsten electrode, a focusing lens, and conventional plasma arc torch nozzles to co-locate the focused beam and arc on the workpiece. Plasma arc nozzles were selected to protect the electrode from laser generated metal vapor. The project goal is to develop an improved fusion welding process that exhibits both absorption robustness and deep penetration for small scale (< 1.5 mm thickness) applications. On aluminum alloys 6061 and 6111, the hybrid process has been shown to eliminate hot cracking in the fusion zone. Fusion zone dimensions for both stainless steel and aluminum were found to be wider than characteristic laser welds, and deeper than characteristic plasma arc welds.

  15. Recent ATR and fusion algorithm improvements for multiband sonar imagery

    NASA Astrophysics Data System (ADS)

    Aridgides, Tom; Fernández, Manuel

    2009-05-01

    An improved automatic target recognition processing string has been developed. The overall processing string consists of pre-processing, subimage adaptive clutter filtering, normalization, detection, data regularization, feature extraction, optimal subset feature selection, feature orthogonalization and classification processing blocks. The objects that are classified by the 3 distinct ATR strings are fused using the classification confidence values and their expansions as features, and using "summing" or log-likelihood-ratio-test (LLRT) based fusion rules. The utility of the overall processing strings and their fusion was demonstrated with new high-resolution three-frequency band sonar imagery. The ATR processing strings were individually tuned to the corresponding three-frequency band data, making use of the new processing improvement, data regularization; this improvement entails computing the input data mean, clipping the data to a multiple of its mean and scaling it, prior to feature extraction and resulted in a 3:1 reduction in false alarms. Two significant fusion algorithm improvements were made. First, a nonlinear exponential Box-Cox expansion (consisting of raising data to a to-be-determined power) feature LLRT fusion algorithm was developed. Second, a repeated application of a subset Box-Cox feature selection / feature orthogonalization / LLRT fusion block was utilized. It was shown that cascaded Box-Cox feature LLRT fusion of the ATR processing strings outperforms baseline "summing" and single-stage Box-Cox feature LLRT algorithms, yielding significant improvements over the best single ATR processing string results, and providing the capability to correctly call the majority of targets while maintaining a very low false alarm rate.

  16. Improvements of welding characteristics of aluminum alloys with YAG laser and TIG arc hybrid system

    NASA Astrophysics Data System (ADS)

    Fujinaga, Shigeki; Ohashi, Ryoji; Katayama, Seiji; Matsunawa, Akira

    2003-03-01

    In high power YAG laser welding of steels, a rectangularly modulated beam with high peak power is usually used to get deep penetration. On the other hand, many spatters and solidification cracks are generated when some aluminum alloys are welded with a rectangularly modulated beam because of its high heat conductivity, high reflectivity, low surface tension, large contraction, wide solidification temperature range, etc. Therefore, a properly modulated beam or a continuous beam is usually used in aluminum alloy welding, although the penetration depth is shallow. In this research, sinusoidal wave or rectangularly modulated wave of YAG laser combined with TIG arc was tried to improve the weldability of A6061 aluminum alloy. As a result, when TIG arc was superimposed behind the YAG laser beam, deeply penetrated weld beads with good surface appearances were produced without spatter losses and cracks.

  17. Welding deformation analysis based on improved equivalent strain method to cover external constraint during cooling stage

    NASA Astrophysics Data System (ADS)

    Kim, Tae-Jun; Jang, Beom-Seon; Kang, Sung-Wook

    2015-09-01

    In the present study, external restraints imposed normal to the plate during the cooling stage were determined to be effective for reduction of the angular distortion of butt-welded or fillet-welded plate. A welding analysis model under external force during the cooling stage was idealized as a prismatic member subjected to pure bending. The external restraint was represented by vertical force on both sides of the work piece and bending stress forms in the transverse direction. The additional bending stress distribution across the plate thickness was reflected in the improved inherent strain model, and a set of inherent strain charts with different levels of bending stress were newly calculated. From an elastic linear FE analysis using the inherent strain values taken from the chart and comparing them with those from a 3D thermal elasto-plastic FE analysis, welding deformation can be calculated.

  18. Friction stir welding of F82H steel for fusion applications

    NASA Astrophysics Data System (ADS)

    Noh, Sanghoon; Ando, Masami; Tanigawa, Hiroyasu; Fujii, Hidetoshi; Kimura, Akihiko

    2016-09-01

    In the present study, friction stir welding was employed to join F82H steels and develop a potential joining technique for a reduced activation ferritic/martensitic steel. The microstructures and mechanical properties on the joint region were investigated to evaluate the applicability of friction stir welding. F82H steel sheets were successfully butt-joined with various welding parameters. In welding conditions, 100 rpm and 100 mm/min, the stirred zone represented a comparable hardness distribution with a base metal. Stirred zone induced by 100 rpm reserved uniformly distributed precipitates and very fine ferritic grains, whereas the base metal showed a typical tempered martensite with precipitates on the prior austenite grain boundary and lath boundary. Although the tensile strength was decreased at 550 °C, the stirred zone treated at 100 rpm showed comparable tensile behavior with base metal up to 500 °C. Therefore, friction stir welding is considered a potential welding method to preserve the precipitates of F82H steel.

  19. Welding of Materials for Energy Applications

    NASA Astrophysics Data System (ADS)

    DuPont, John N.; Babu, Suresh; Liu, Stephen

    2013-07-01

    Materials will play a critical role in power generation from both new and existing plants that rely on coal, nuclear, and oil/gas as energy supplies. High efficiency power plants are currently being designed that will require materials with improved mechanical properties and corrosion resistance under conditions of elevated temperature, stress, and aggressive gaseous environments. Most of these materials will require welding during initial fabrication and plant maintenance. The severe thermal and strain cycles associated with welding can produce large gradients in microstructure and composition within the heat-affected and fusion zones of the weld, and these gradients are commonly accompanied by deleterious changes to properties. Thus, successful use of materials in energy applications hinges on the ability to understand, predict, and control the processing-microstructure-property relations during welding. This article highlights some of the current challenges associated with fusion welding of materials for energy applications.

  20. Hydrogen-Assisted Crack Propagation in Austenitic Stainless Steel Fusion Welds

    NASA Astrophysics Data System (ADS)

    Somerday, B. P.; Dadfarnia, M.; Balch, D. K.; Nibur, K. A.; Cadden, C. H.; Sofronis, P.

    2009-10-01

    The objective of this study was to characterize hydrogen-assisted crack propagation in gas-tungsten arc (GTA) welds of the nitrogen-strengthened, austenitic stainless steel 21Cr-6Ni-9Mn (21-6-9), using fracture mechanics methods. The fracture initiation toughness and crack growth resistance curves were measured using fracture mechanics specimens that were thermally precharged with 230 wppm (1.3 at. pct) hydrogen. The fracture initiation toughness and slope of the crack growth resistance curve for the hydrogen-precharged weld were reduced by as much as 60 and 90 pct, respectively, relative to the noncharged weld. A physical model for hydrogen-assisted crack propagation in the welds was formulated from microscopy evidence and finite-element modeling. Hydrogen-assisted crack propagation proceeded by a sequence of microcrack formation at the weld ferrite, intense shear deformation in the ligaments separating microcracks, and then fracture of the ligaments. One salient role of hydrogen in the crack propagation process was promoting microcrack formation at austenite/ferrite interfaces and within the ferrite. In addition, hydrogen may have facilitated intense shear deformation in the ligaments separating microcracks. The intense shear deformation could be related to the development of a nonuniform distribution of hydrogen trapped at dislocations between microcracks, which in turn created a gradient in the local flow stress.

  1. Improved UXO detection via sensor fusion

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Li, Jing; Carin, Lawrence; Collins, Leslie M.

    2000-08-01

    Traditional algorithms for UXO remediation experience severe difficulties distinguishing buried targets from anthropic clutter, and in most cases UXO items are found among extensive surface clutter and shrapnel from ordnance operations. These problems render site mediation a very slow, labor intensive, and efficient process. While sensors have improved significantly over the past several years in their ability to detect conducting and/or permeable targets, reduction of the false alarm rate has proven to be a significantly more challenging problem. Our work has focused on the development of optimal signal processing algorithms that rigorously incorporate the underlying physics characteristics of the sensor and the anticipated UXO target in order to address the false alarm issue. In this paper, we describe several techniques for discriminating targets from clutter that have been applied to data obtained with the Multi-sensor Towed Array Detection System (MTADS) that has been developed by the Naval Research Laboratory. MTADS includes both EMI and magnetometer sensors. We describe a variety of signal processing techniques which incorporate physics-based models that have been applied to the data measured by MTADS during field demonstrations. We will compare and contrast the performance of the various algorithms as well as discussing tradeoffs, such as training requirements. The result of this analysis quantify the utility of fusing magnetometer and EMI dat. For example, the JPG-IV test, at the False Positive level obtained by NRL, one of our algorithms achieved a 13 percent improvement in True Positive level over the algorithm traditionally used for processing MTADS data.

  2. Investigations for the improvement of space shuttle main engine electron beam welding equipment

    NASA Technical Reports Server (NTRS)

    Smock, R. A.; Taylor, R. A.; Wall, W. A., Jr.

    1977-01-01

    Progress made in the testing, evaluation, and correction of MSFC's 7.5 kW electron beam welder in support of space shuttle main engine component welding is summarized. The objective of this project was to locate and correct the deficiencies in the welder. Some 17 areas were deficient in the 7.5 kW ERI welding system and the associated corrective action was taken to improve its operational performance. An overall improvement of 20 times the original reliability was obtained at full rated capacity after the modifications were made.

  3. Laser Peening Effects on Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Hatamleh, Omar

    2011-01-01

    Friction Stir Welding (FSW) is a welding technique that uses frictional heating combined with forging pressure to produce high strength bonds. It is attractive for aerospace applications. Although residual stresses in FSW are generally lower when compared to conventional fusion welds, recent work has shown that significant tensile residual stresses can be present in the weld after fabrication. Therefore, laser shock peening was investigated as a means of moderating the tensile residual stresses produced during welding. This slide presentation reviews the effect of Laser Peening on the weld, in tensile strength, strain, surface roughness, microhardness, surface wear/friction, and fatigue crack growth rates. The study concluded that the laser peening process can result in considerable improvement to crack initiaion, propagation and mechanical properties in FSW.

  4. Advanced Welding Applications

    NASA Technical Reports Server (NTRS)

    Ding, Robert J.

    2010-01-01

    Some of the applications of advanced welding techniques are shown in this poster presentation. Included are brief explanations of the use on the Ares I and Ares V launch vehicle and on the Space Shuttle Launch vehicle. Also included are microstructural views from four advanced welding techniques: Variable Polarity Plasma Arc (VPPA) weld (fusion), self-reacting friction stir welding (SR-FSW), conventional FSW, and Tube Socket Weld (TSW) on aluminum.

  5. Sensor and information fusion for improved hostile fire situational awareness

    NASA Astrophysics Data System (ADS)

    Scanlon, Michael V.; Ludwig, William D.

    2010-04-01

    A research-oriented Army Technology Objective (ATO) named Sensor and Information Fusion for Improved Hostile Fire Situational Awareness uniquely focuses on the underpinning technologies to detect and defeat any hostile threat; before, during, and after its occurrence. This is a joint effort led by the Army Research Laboratory, with the Armaments and the Communications and Electronics Research, Development, and Engineering Centers (CERDEC and ARDEC) partners. It addresses distributed sensor fusion and collaborative situational awareness enhancements, focusing on the underpinning technologies to detect/identify potential hostile shooters prior to firing a shot and to detect/classify/locate the firing point of hostile small arms, mortars, rockets, RPGs, and missiles after the first shot. A field experiment conducted addressed not only diverse modality sensor performance and sensor fusion benefits, but gathered useful data to develop and demonstrate the ad hoc networking and dissemination of relevant data and actionable intelligence. Represented at this field experiment were various sensor platforms such as UGS, soldier-worn, manned ground vehicles, UGVs, UAVs, and helicopters. This ATO continues to evaluate applicable technologies to include retro-reflection, UV, IR, visible, glint, LADAR, radar, acoustic, seismic, E-field, narrow-band emission and image processing techniques to detect the threats with very high confidence. Networked fusion of multi-modal data will reduce false alarms and improve actionable intelligence by distributing grid coordinates, detection report features, and imagery of threats.

  6. Sensor and information fusion for improved hostile threat situational awareness

    NASA Astrophysics Data System (ADS)

    Scanlon, Michael V.; Ludwig, William D.

    2011-06-01

    The U.S. Army Research Laboratory (ARL) has recently concluded a research experiment to study the benefits of multimodal sensor fusion for improved hostile-fire-defeat (HFD) in an urban setting. This joint effort was led by ARL in partnership with other R&D centers and private industry. The primary goals were to detect hostile fire events (small arms, mortars, rockets, IEDs) and hostile human activities by providing solutions before, during, and after the events to improve sensor networking technologies; to develop multimodal sensor data fusion; and to determine effective dissemination techniques for the resultant actionable intelligence. Technologies included ultraviolet, infrared, retroreflection, visible, glint, Laser Detection and Ranging (LADAR), radar, acoustic, seismic, E-field, magnetic, and narrowband emission technologies; all were found to provide useful performance. The experiment demonstrated that combing data and information from diverse sensor modalities can significantly improve the accuracy of threat detections and the effectiveness of the threat response. It also demonstrated that dispersing sensors over a wide range of platforms (fixed site, ground vehicles, unmanned ground and aerial vehicles, aerostat, Soldier-worn) added flexibility and agility in tracking hostile actions. In all, the experiment demonstrated that multimodal fusion will improve hostile event responses, strike force efficiency, and force protection effectiveness.

  7. METAL FUSION AND FABRICATION WELDING. AGRICULTURAL MACHINERY--SERVICE OCCUPATIONS, MODULE, NUMBER 6.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center for Vocational and Technical Education.

    ONE IN A SERIES DESIGNED TO HELP TEACHERS PREPARE POSTSECONDARY STUDENTS FOR THE AGRICULTURAL MACHINERY SERVICE OCCUPATIONS AS PARTS MEN, MECHANICS, MECHANIC'S HELPERS, OR SERVICE SUPERVISORS, THIS GUIDE AIMS TO DEVELOP STUDENT UNDERSTANDING OF WELDING EQUIPMENT AND SUPPLIES, AND ABILITY TO PERFORM SKILLS REQUIRED OF AGRICULTURAL MECHANICS. IT WAS…

  8. Self-assessed performance improves statistical fusion of image labels

    SciTech Connect

    Bryan, Frederick W. Xu, Zhoubing; Asman, Andrew J.; Allen, Wade M.; Reich, Daniel S.; Landman, Bennett A.

    2014-03-15

    . Statistical fusion resulted in statistically indistinguishable performance from self-assessed weighted voting. The authors developed a new theoretical basis for using self-assessed performance in the framework of statistical fusion and demonstrated that the combined sources of information (both statistical assessment and self-assessment) yielded statistically significant improvement over the methods considered separately. Conclusions: The authors present the first systematic characterization of self-assessed performance in manual labeling. The authors demonstrate that self-assessment and statistical fusion yield similar, but complementary, benefits for label fusion. Finally, the authors present a new theoretical basis for combining self-assessments with statistical label fusion.

  9. Self-assessed performance improves statistical fusion of image labels

    PubMed Central

    Bryan, Frederick W.; Xu, Zhoubing; Asman, Andrew J.; Allen, Wade M.; Reich, Daniel S.; Landman, Bennett A.

    2014-01-01

    . Statistical fusion resulted in statistically indistinguishable performance from self-assessed weighted voting. The authors developed a new theoretical basis for using self-assessed performance in the framework of statistical fusion and demonstrated that the combined sources of information (both statistical assessment and self-assessment) yielded statistically significant improvement over the methods considered separately. Conclusions: The authors present the first systematic characterization of self-assessed performance in manual labeling. The authors demonstrate that self-assessment and statistical fusion yield similar, but complementary, benefits for label fusion. Finally, the authors present a new theoretical basis for combining self-assessments with statistical label fusion. PMID:24593721

  10. Laser welding in space

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  13. Surface preparation effects on GTA weld shape in JBK-75 stainless steel

    SciTech Connect

    Campbell, R.D.; Robertson, A.M. ); Heiple, C.R. ); Sturgill, P.L.; Jamsay, R.

    1993-02-01

    The results of a study are reported here on the effects of surface preparation on the shape of autogenous gas tungsten arc (GTA) welds in JBK-75, an austenitic precipitation hardenable stainless steel similar to A286. Minor changes in surface preparation produced substantial changes in the fusion zone shape and welding behavior of this alloy. Increased and more consistent depth of fusion (higher d/w ratios) along with improved arc stability and less arc wander resulted from wire brushing and other abrasive surface preparations, although chemical and machining methods did not produce any increase in depth of fusion. Abrasive treatments roughen the surface, increase the surface area, increase the surface oxide thickness, and entrap oxide. The increased weld d/w ratio is attributed to oxygen added to the weld pool from the surface oxide on the base metal. The added oxygen alters the surface-tension-driven fluid flow pattern in the weld pool. Increased depth of fusion in wire-fed U-groove weld joints also resulted when welding wire with a greater surface oxide thickness was used. Increasing the amount of wire brushing produced even deeper welds. However, a maximum in depth of fusion was observed with further wire brushing, beyond which weld fusion depth decreased.

  14. Improvement of ultrasonic characteristics in butt-welded joint of austenitic stainless steel using magnetic stirring method

    SciTech Connect

    Tanosaki, M.; Yoshikawa, K.; Arakawa, T.

    1995-08-01

    Magnetic Stirring Method of Tungsten Inert Gas(TIG) Welding are applied to butt-welded joint of austenitic stainless steel. The purpose of this method is to refine the welded structure and to improve the ultrasonic characteristics. In the conventional method of ultrasonic test in austenitic stainless steel weldments, dendritic solidification structure of weldment prevents smooth ultrasonic beam transmission. The tests are performed in three welding conditions; One is conventional TIG welding (without magnetic stirring), the other two are TIG welding using magnetic stirring method. Each test piece is evaluated by observing macro structure of cross section and by several ultrasonic tests examining pulse amplitudes, beam path length and proceeding beam direction. The detectability of artificial notches in weldment is also investigated and compared.

  15. Improved Controls for Fusion RF Systems. Final technical report

    SciTech Connect

    Casey, Jeffrey A.

    2011-11-08

    We have addressed the specific requirements for the integrated systems controlling an array of klystrons used for Lower Hybrid Current Drive (LHCD). The immediate goal for our design was to modernize the transmitter protection system (TPS) for LHCD on the Alcator C-Mod tokamak at the MIT Plasma Science and Fusion Center (MIT-PSFC). Working with the Alcator C-Mod team, we have upgraded the design of these controls to retrofit for improvements in performance and safety, as well as to facilitate the upcoming expansion from 12 to 16 klystrons. The longer range goals to generalize the designs in such a way that they will be of benefit to other programs within the international fusion effort was met by designing a system which was flexible enough to address all the MIT system requirements, and modular enough to adapt to a large variety of other requirements with minimal reconfiguration.

  16. Innovative Tools Advance Revolutionary Weld Technique

    NASA Technical Reports Server (NTRS)

    2009-01-01

    (no toxic smoke or shielding gas, liquid metal splatter, arcing, dangerous voltage, or radiation), and environmentally sound (no consumables, fumes, or noise) than fusion welding. Under computer control, an automated FSW machine can create welds with high reproducibility, improving efficiency and overall quality of manufactured materials. The process also allows for welding dissimilar metals as well as those metals considered to be "unweldable" such as the 7xxx series aluminum alloys. Its effectiveness and versatility makes FSW useful for aerospace, rail, automotive, marine, and military applications. A downside to FSW, however, is the keyhole opening left in the weld when the FSW pin tool exits the weld joint. This is a significant problem when using the FSW process to join circumferential structures such as pipes and storage containers. Furthermore, weld joints that taper in material thickness also present problems when using the conventional FSW pin tool, because the threaded pin rotating within the weld joint material is a fixed length. There must be capability for the rotating pin to both increase and decrease in length in real time while welding the tapered material. (Both circumferential and tapered thickness weldments are found in the space shuttle external tank.) Marshall engineers addressed both the keyhole and tapered material thickness problems by developing the auto-adjustable pin tool. This unique piece of equipment automatically withdraws the pin into the tool s shoulder for keyhole closeout. In addition, the auto-adjustable pin tool retracts, or shortens, the rotating pin while welding a weld joint that tapers from one thickness to a thinner thickness. This year, the impact of the Marshall innovation was recognized with an "Excellence in Technology Transfer Award" from the Federal Laboratory Consortium.

  17. Analysis of Microstructural Changes in the Heat-Affected Zone and Fusion Zone of a Fiber Laser Welded DP980 Steel

    NASA Astrophysics Data System (ADS)

    Zhang, Jianqi; Khan, Abdul; Ojo, Olanrewaju A.; Zhou, Norman; Chen, Daolun

    2015-08-01

    Dual phase (DP) steels are designed to consist of hard martensite dispersed in a relatively soft ferrite matrix, which offers a favorable combination of high strength with good deformability. Fiber laser welding (FLW) is becoming increasingly important for joining advanced materials due to its flexibility and deep penetration. In this study, the microstructure of a DP steel, DP980, welded by FLW technique was carefully analyzed. Gleeble thermo-mechanical simulation coupled with analytical transmission electron microscopy revealed that the FLW process produced significant microstructural changes in a narrow heat-affected zone (HAZ) and fusion zone (FZ), which can result in dramatic changes in mechanical properties. This is reflected in the micro-hardness profile obtained across the welded material. The salient phase transitions induced by the FLW, including the formation of new martensite grains in the upper-critical HAZ and FZ, are discussed.

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

    SciTech Connect

    Tang, Wei; Chen, Gaoqiang; Chen, Jian; Yu, Xinghua; Frederick, David Alan; Feng, Zhili

    2015-01-01

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

  19. A Power Factor Corrected SMPS with Improved Power Quality for Welding Applications

    NASA Astrophysics Data System (ADS)

    Narula, Swati; Singh, Bhim; Bhuvaneswari, G.; Pandey, Rahul

    2015-04-01

    This paper presents the analysis, design and implementation of a power factor corrected Arc Welding Power Supply (AWPS) with a boost converter at the front end and three full-bridge (FB) converters connected in parallel at the load end. The modular arrangement of the FB converters offers several meritorious features like usage of power devices with comparatively lower voltage and current ratings, ease of power expandability, easy maintenance, etc. The boost converter operates in continuous conduction mode minimizing the input current ripple and leading to the lowest RMS current thereby improving the input power quality. Individual control loops are designed for each power stage. A dual loop control scheme is employed to incorporate over-current limit on the proposed AWPS which ensures excellent weld bead quality. The proposed AWPS is implemented to validate its performance over a wide range of line/load variations. Test results confirm its fast parametrical response to load and source voltage variations and over-current protection leading to improved welding performance and weld bead quality. The system is found to perform extremely well with very low input current THD and unity power factor, adhering to international power quality norms.

  20. Mathematical modeling and experimental validation of gas metal arc welding of aluminum alloys

    NASA Astrophysics Data System (ADS)

    Guo, Hao

    2004-11-01

    Both mathematical modeling and experiments have been conducted on the GMAW of aluminum alloys. Transient weld shapes and distributions of temperature and velocity were calculated by a three-dimensional numerical model. The final weld bead shape and dimensions and peak temperature in the heat-affected zone (HAZ) were obtained. Metallurgical characterizations including microscopy and Knoop micro-hardness measurements were performed on experimental samples. The experimental weld bead shape and dimensions were in agreement with modeling predictions. It was found that a crater-shaped weld pool was formed as a result of weld pool dynamics. The combined effect of a series of droplet impingements and hydrostatic force caused the fluid level at the rear end of weld pool to vary periodically to form ripples on the weld bead. Also, the high peak temperature near the fusion line caused the HAZ softening. The lack of penetration in the cold weld is due to the lack of pre-heating by the welding arc. Three techniques were then proposed to increase the energy input at the initial stage of welding and improve cold weld penetration. The crater formation at the end of the welding process is due to the rapid solidification of the weld pool. The crater was filled and crater cracking was reduced by reducing welding current and reversing the welding direction at the same time before terminating the arc.

  1. Laser assisted arc welding for aluminum alloys

    SciTech Connect

    Fuerschbach, P.W.

    2000-01-01

    Experiments have been performed using a coaxial end-effector to combine a focused laser beam and a plasma arc. The device employs a hollow tungsten electrode, a focusing lens, and conventional plasma arc torch nozzles to co-locate the focused beam and arc on the workpiece. Plasma arc nozzles were selected to protect the electrode from laser generated metal vapor. The project goal is to develop an improved fusion welding process that exhibits both absorption robustness and deep penetration for small scale (<1.5 mm thickness) applications. On aluminum alloys 6061 and 6111, the hybrid process has been shown to eliminate hot cracking in the fusion zone. Fusion zone dimensions for both stainless steel and aluminum were found to be wider than characteristic laser welds, and deeper than characteristic plasma arc welds.

  2. Improving Higgs coupling measurements through ZZ Fusion at the ILC

    DOE PAGESBeta

    Han, Tao; Liu, Zhen; Qian, Zhuoni; Sayre, Joshua

    2015-06-17

    In this study, we evaluate the e-e+ → e-e+ + h process through the ZZ fusion channel at the International Linear Collider operating at 500 GeV and 1 TeV center-of-mass energies. We perform realistic simulations on the signal process and background processes. With judicious kinematic cuts, we find that the inclusive cross section can be measured to 2.9% after combining the 500 GeV at 500 fb-1 and 1 TeV at 1 ab-1 runs. A multivariate log-likelihood analysis further improves the precision of the cross section measurement to 2.3%. We discuss the overall improvement to model-independent Higgs width and coupling determinations and demonstrate the usemore » of different channels in distinguishing new physics effects in Higgs physics. Our study demonstrates the importance of the ZZ fusion channel to Higgs precision physics, which has often been neglected in the literature.« less

  3. Improving Higgs coupling measurements through ZZ Fusion at the ILC

    SciTech Connect

    Han, Tao; Liu, Zhen; Qian, Zhuoni; Sayre, Joshua

    2015-06-17

    In this study, we evaluate the e-e+ → e-e+ + h process through the ZZ fusion channel at the International Linear Collider operating at 500 GeV and 1 TeV center-of-mass energies. We perform realistic simulations on the signal process and background processes. With judicious kinematic cuts, we find that the inclusive cross section can be measured to 2.9% after combining the 500 GeV at 500 fb-1 and 1 TeV at 1 ab-1 runs. A multivariate log-likelihood analysis further improves the precision of the cross section measurement to 2.3%. We discuss the overall improvement to model-independent Higgs width and coupling determinations and demonstrate the use of different channels in distinguishing new physics effects in Higgs physics. Our study demonstrates the importance of the ZZ fusion channel to Higgs precision physics, which has often been neglected in the literature.

  4. Dynamics of near-alpha titanium welding

    NASA Astrophysics Data System (ADS)

    Neuberger, Brett William

    Typically, when gas tungsten arc welding (GTAW) is employed to join near-alpha titanium alloys, the resulting weld fusion zone (FZ) is much harder than that of the base metal (BM), thereby leading to lost ductility. The aim of this investigation was to improve FZ ductility of Ti-5Al-1Sn-1V-1Zr-0.8Mo by modifying filler metal chemistry. In this regard, metallic yttrium was added to the filler metal and aluminum concentration reduced. It was believed that additions of yttrium would lead to formation of yttria in the weld melt, thereby promoting heterogeneous nucleation. Since oxygen and aluminum both act as alpha-stabilizers, expected pickup of oxygen during the welding process will be offset by the aluminum reduction. Tensile testing indicated that modified filler metal welds showed a dramatic increase in ductility of the FZ. Fracture toughness testing showed that while JIC values decreased in all welds, the tearing modulus, T, in modified filler metal welds was significantly higher than that of matching filler metal welds. Microhardness mapping of the weld zones illustrated that modified filler metal welds were significantly softer than matching filler metal welds. Microstructural examinations were completed through the use of optical, SEM and TEM studies, indicating that there was a presence of nano-particles in the weld FZ. XPS analysis identified these particles as yttrium oxysulfate. WDS analysis across the welds' heat affected zones demonstrated that there is an internal diffusion of oxygen from the BM into the FZ. Research results indicate yttrium oxysulfide particles form in the weld pool, act as a drag force on the solidification front and limit growth of prior-beta grain boundaries. The reduced prior-beta grain size and removal of interstitial oxygen from the matrix in modified filler metal welds, further enhanced by oxidation of yttrium oxysulfide to yttrium oxysulfate, leads to increased ductility in the weld's FZ. Addition of yttrium to the weld also

  5. Improvement of localised corrosion resistance of AISI 2205 Duplex Stainless Steel joints made by gas metal arc welding under electromagnetic interaction of low intensity

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    The resistance to localised corrosion of AISI 2205 duplex stainless steel plates joined by Gas Metal Arc Welding (GMAW) under the effect of electromagnetic interaction of low intensity (EMILI) was evaluated with sensitive electrochemical methods. Welds were made using two shielding gas mixtures: 98% Ar + 2% O2 (M1) and 97% Ar + 3% N2 (M2). Plates were welded under EMILI using the M1 gas with constant welding parameters. The modified microstructural evolution in the high temperature heat affected zone and at the fusion zone induced by application of EMILI during welding is associated with the increase of resistance to localised corrosion of the welded joints. Joints made by GMAW using the shielding gas M2 without the application of magnetic field presented high resistance to general corrosion but high susceptibility to undergo localised attack.

  6. Target detection and recognition improvements by use of spatiotemporal fusion.

    PubMed

    Chen, Hai-Wen; Sutha, Surachai; Olson, Teresa

    2004-01-10

    We developed spatiotemporal fusion techniques for improving target detection and automatic target recognition. We also investigated real IR (infrared) sensor clutter noise. The sensor noise was collected by an IR (256 x 256) sensor looking at various scenes (trees, grass, roads, buildings, etc.). More than 95% of the sensor pixels showed near-stationary sensor clutter noise that was uncorrelated between pixels as well as across time frames. However, in a few pixels (covering the grass near the road) the sensor noise showed nonstationary properties (with increasing or decreasing mean across time frames). The natural noise extracted from the IR sensor, as well as the computer-generated noise with Gaussian and Rayleigh distributions, was used to test and compare different spatiotemporal fusion strategies. Finally, we proposed two advanced detection schemes: the double-thresholding the reverse-thresholding techniques. These techniques may be applied to complicated clutter situations (e.g., very-high clutter or nonstationary clutter situations) where the traditional constant-false-alarm-ratio technique may fail. PMID:14735959

  7. 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.

  8. Web-enabled Landsat Data (WELD): Demonstration of MODIS-Landsat Data Fusion to Provide a Consistent, Long-term, Large-area Data Record for the Terrestrial User Community

    NASA Astrophysics Data System (ADS)

    Roy, D.; Ju, J.; Vermote, E. F.; Zhang, C.; Egorov, A.; Kovalskyy, V.; Loveland, T. R.; Hansen, M. C.; Scaramuzza, P. L.; Kline, K.; Yeom, J.; Kommadreddy, I.

    2009-12-01

    Consistent long-term and large-area Landsat data records are needed to monitor land cover change and study Earth system functioning. The objective of NASA’s Making Earth Science Data Records for Use in Research Environments (MEaSUREs) program is to provide Earth science data products and services driven by NASA’s Earth science goals and to advance NASA’s “missions to measurements” concept. This MEaSUREs WELD project contributes to the Land measurement theme by systematically generating radiometrically consistent Landsat Enhanced Thematic Mapper Plus (ETM+) mosaics of the conterminous USA (CONUS) and Alaska. The U.S. Department of Interior / U.S. Geological Survey (USGS) has been providing terrain-corrected Landsat ETM+ data at no cost since January 2008. In the WELD project every USGS Landsat ETM+ acquisition with cloud cover less than 60% is used to generate monthly, seasonal and annual composited mosaics. The consistency and quality of the ETM+ data is improved through a fusion with standard MODIS land products, including the MODIS BRDF reflectance anisotropy product to radiometrically normalize and fill missing (cloudy and SLC-off) Landsat pixels, the MODIS atmospheric characterization data to systematically atmospherically correct the Landsat data, and the MODIS vegetation continuous field product to provide training for Landsat scale land cover characterization. The WELD mosaics are defined at 30 m and include spectral reflectance, brightness temperature, normalized difference vegetation index, the date each composited pixel was acquired on, per-band radiometric saturation status, cloud mask values, and land cover characterization information. Results for the CONUS, algorithm insights, and information on how to access the WELD data products via the internet from the USGS Landsat project are presented.

  9. Improved Magnetic Fusion Energy Economics via Massive Resistive Electromagnets

    SciTech Connect

    Woolley, R.D.

    1998-08-19

    Abandoning superconductors for magnetic fusion reactors and instead using resistive magnet designs based on cheap copper or aluminum conductor material operating at "room temperature" (300 K) can reduce the capital cost per unit fusion power and simplify plant operations. By increasing unit size well beyond that of present magnetic fusion energy conceptual designs using superconducting electromagnets, the recirculating power fraction needed to operate resistive electromagnets can be made as close to zero as needed for economy without requiring superconductors. Other advantages of larger fusion plant size, such as very long inductively driven pulses, may also help reduce the cost per unit fusion power.

  10. Application of Pre-heating to Improve the Consistency and Quality in AA5052 Resistance Spot Welding

    NASA Astrophysics Data System (ADS)

    Luo, Zhen; Ao, Sansan; Chao, Yuh Jin; Cui, Xuetuan; Li, Yang; Lin, Ye

    2015-10-01

    Making consistent resistance spot welds of aluminum alloy with good quality and at high volume has several obstacles in automotive industry. One of the difficult issues arises from the presence of a tough non-conducting oxide film on the aluminum sheet surface. The oxide film develops over time and often is non-uniform across the surface of the aluminum alloy sheet, which makes the contact resistance characteristics irregular at the faying interface during welding. The consistency in quality of the final spot welds is therefore problematic to control. To suppress the effect of the irregular oxide film on the spot weld quality, application of a pre-heating treatment in the welding schedule for aluminum alloy 5052 is investigated in this present work. The current level of the pre-heating required to reduce the scatter of the contact resistance at the W/W (workpiece-to-workpiece) faying interface is quantified experimentally. The results indicate that the contact resistance at the W/W faying interface with a pre-heating treatment becomes much consistent and can be reduced by two orders of magnitude. Having the uncertain variation of the contact resistance at the W/W faying surface virtually reduced or removed, the quality of the spot welds in terms of the peak load and nugget diameter is examined and shows a great improvement. The proposed method may provide a robust method for high-volume spot welding of aluminum alloy sheets in auto industry.

  11. Aluminum U-groove weld enhancement based on experimental stress analyses

    NASA Technical Reports Server (NTRS)

    Verderaime, V.; Vaughan, R.

    1995-01-01

    Though butt-welds are among the most preferred joining methods in aerostructures because of their sealing and assembly integrity and general elastic performance; their inelastic mechanics are generally the least understood. This study investigated experimental strain distributions across a thick aluminum U-grooved weld and identified two weld process considerations for improving the multipass weld strength. The extreme thermal expansion and contraction gradient of the fusion heat input across the tab thickness between the grooves produce severe peaking, which induces bending moment under uniaxial loading. The filler strain hardening decreased with increasing filler pass sequence. These combined effects reduce the weld strength, and a depeaking index model was developed to select filler pass thicknesses, pass numbers, and sequences to improve the welding process results over the current normal weld schedule.

  12. Potential Methods for Improving Pedestal Temperatures and Fusion Performance

    SciTech Connect

    G.W. Hammett; M. Kotschenreuther; M.A. Beer; W. Dorland

    1999-10-01

    The physics of the tokamak edge is very complicated, and the scaling of the H-mode transport barrier pedestal has significant uncertainties. Evidence from the largest tokamaks appears to support a model in which the H-mode pedestal width scales linearly with the poloidal gyroradius and the gradient scales with ideal MHD ballooning limits. However, there appears to be significant variability in the data from different tokamaks, including observations on DIII-D that indicate a regime where the pedestal is in second stability and the width is independent of poloidal gyroradius, which would give a more favorable scaling to reactor scales. An important question is the role of the bootstrap current in the pedestal, and another is how far can the improvements in edge stability be p shed with higher triangularity and elongation. Even with the more pessimistic model, where the pedestal width is proportional to the poloidal gyroradius, the results presented here suggest that pedestal temperatures, and thus the fusion performance, may be significantly improved by designs with stronger plasma shaping higher triangularity and elongation, moderate density peaking, and higher magnetic field (and thus reduced size), such as in ARIES-RS, FIRE, and some of the new ITER-RC designs.

  13. Welding development for V-Cr-Ti alloys

    SciTech Connect

    King, J.F.; Goodwin, G.M.; Alexander, D.J.

    1995-04-01

    A vanadium structure, cooled with helium, is a favored concept for an advanced breeding blanket for fusion systems. The objective of this task is to develop the metallurgical and technological base for the welding of thick sections of V-Cr-Ti. The subsize Charpy test results for electron beam weld metal from the V-5Cr-5Ti alloy has shown significant improvement in Charpy fracture energy compared to both gas tungsten arc weld metal and the base metal itself. These results are preliminary, however, and additional confirmation testing and analysis will be required to explain this improvement in properties.

  14. Improved microstructure and mechanical properties in gas tungsten arc welded aluminum joints by using graphene nanosheets/aluminum composite filler wires.

    PubMed

    Fattahi, M; Gholami, A R; Eynalvandpour, A; Ahmadi, E; Fattahi, Y; Akhavan, S

    2014-09-01

    In the present study, different amounts of graphene nanosheets (GNSs) were added to the 4043 aluminum alloy powders by using the mechanical alloying method to produce the composite filler wires. With each of the produced composite filler wires, one all-weld metal coupon was welded using the gas tungsten arc (GTA) welding process. The microstructure, mechanical properties and fracture surface morphology of the weld metals have been evaluated and the results are compared. As the amount of GNSs in the composition of filler wire is increased, the microstructure of weld metal was changed from the dendritic structure to fine equiaxed grains. Furthermore, the tensile strength and microhardness of weld metal was improved, and is attributed to the augmented nucleation and retarded growth. From the results, it was seen that the GNSs/Al composite filler wire can be used to improve the microstructure and mechanical properties of GTA weld metals of aluminum and its alloys. PMID:24981209

  15. Toward Improving the Type IV Cracking Resistance in Cr-Mo Steel Weld Through Thermo-Mechanical Processing

    DOE PAGESBeta

    Shassere, Benjamin A.; Yamamoto, Yukinori; Babu, Sudarsanam Suresh

    2016-02-23

    Detailed microstructure characterization of Grade 91 (Modified 9Cr-1Mo, ASTM A387) steel subjected to a thermo-mechanical treatment (TMT) process was performed to rationalize the cross-weld creep properties. A series of thermo-mechanical processing in the austenite phase region, followed by isothermal aging at temperatures at 973 to 1173 K (700 to 900ºC) was applied to the Grade 91 steel to promote precipitation kinetics of MX (M: Nb and V, X: C and N) in the austenite matrix. Detailed characterization of the base metals after standard tempering confirmed the presence of fine MX dispersion within the tempered martensitic microstructure in steels processed at/andmore » above 1073 K (800 ºC). Relatively low volume fraction of M23C6 precipitates was observed after processing at 1073 K (800 ºC). The cross-weld creep strength after processing was increased with respect to the increase of MX dispersion, indicating that these MX precipitates maintained during weld thermal cycles in the fine grained heat affected zone (FGHAZ) region and thereby contribute to improved creep resistant of welds in comparison to the welds made with the standard “normalization and tempering” processes. Lastly, the steels processed in this specific processing condition showed improved cross-weld creep resistance and sufficient room-temperature toughness. The above data is also analysed based on existing theories of creep deformation based on dislocation climb mechanism.« less

  16. Toward Improving the Type IV Cracking Resistance in Cr-Mo Steel Weld Through Thermo-Mechanical Processing

    NASA Astrophysics Data System (ADS)

    Shassere, Benjamin A.; Yamamoto, Yukinori; Babu, Sudarsanam Suresh

    2016-05-01

    Detailed microstructure characterization of Grade 91 (Modified 9Cr-1Mo, ASTM A387) steel subjected to a thermo-mechanical treatment process was performed to rationalize the cross-weld creep properties. A series of thermo-mechanical processing in the austenite phase region, followed by isothermal aging at temperatures at 973 K to 1173 K (700 °C to 900 °C), was applied to the Grade 91 steel to promote precipitation kinetics of MX (M: Nb and V, X: C and N) in the austenite matrix. Detailed characterization of the base metals after standard tempering confirmed the presence of fine MX dispersion within the tempered martensitic microstructure in steels processed at/and above 1073 K (800 °C). Relatively low volume fraction of M23C6 precipitates was observed after processing at 1073 K (800 °C). The cross-weld creep strength after processing was increased with respect to the increase of MX dispersion, indicating that these MX precipitates maintained during weld thermal cycles in the fine-grained heat-affected zone region and thereby contribute to improved creep resistant of welds in comparison to the welds made with the standard "normalization and tempering" processes. The steels processed in this specific processing condition showed improved cross-weld creep resistance and sufficient room temperature toughness. The above data are also analyzed based on existing theories of creep deformation based on dislocation climb mechanism.

  17. Metallurgical and mechanical properties of laser welded high strength low alloy steel

    PubMed Central

    Oyyaravelu, Ramachandran; Kuppan, Palaniyandi; Arivazhagan, Natarajan

    2016-01-01

    The study aimed at investigating the microstructure and mechanical properties of Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser welded high strength low alloy (HSLA) SA516 grade 70 boiler steel. The weld joint for a 4 mm thick plate was successfully produced using minimum laser power of 2 kW by employing a single pass without any weld preheat treatment. The micrographs revealed the presence of martensite phase in the weld fusion zone which could be due to faster cooling rate of the laser weldment. A good correlation was found between the microstructural features of the weld joints and their mechanical properties. The highest hardness was found to be in the fusion zone of cap region due to formation of martensite and also enrichment of carbon. The hardness results also showed a narrow soft zone at the heat affected zone (HAZ) adjacent to the weld interface, which has no effect on the weld tensile strength. The yield strength and ultimate tensile strength of the welded joints were 338 MPa and 549 MPa, respectively, which were higher than the candidate metal. These tensile results suggested that the laser welding process had improved the weld strength even without any weld preheat treatment and also the fractography of the tensile fractured samples showed the ductile mode of failure. PMID:27222751

  18. Metallurgical and mechanical properties of laser welded high strength low alloy steel.

    PubMed

    Oyyaravelu, Ramachandran; Kuppan, Palaniyandi; Arivazhagan, Natarajan

    2016-05-01

    The study aimed at investigating the microstructure and mechanical properties of Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser welded high strength low alloy (HSLA) SA516 grade 70 boiler steel. The weld joint for a 4 mm thick plate was successfully produced using minimum laser power of 2 kW by employing a single pass without any weld preheat treatment. The micrographs revealed the presence of martensite phase in the weld fusion zone which could be due to faster cooling rate of the laser weldment. A good correlation was found between the microstructural features of the weld joints and their mechanical properties. The highest hardness was found to be in the fusion zone of cap region due to formation of martensite and also enrichment of carbon. The hardness results also showed a narrow soft zone at the heat affected zone (HAZ) adjacent to the weld interface, which has no effect on the weld tensile strength. The yield strength and ultimate tensile strength of the welded joints were 338 MPa and 549 MPa, respectively, which were higher than the candidate metal. These tensile results suggested that the laser welding process had improved the weld strength even without any weld preheat treatment and also the fractography of the tensile fractured samples showed the ductile mode of failure. PMID:27222751

  19. Improvement of the control of a gas metal arc welding process

    NASA Astrophysics Data System (ADS)

    Gött, Gregor; Schöpp, Heinz; Hofmann, Frank; Heinz, Gerd

    2010-02-01

    Up to now, the use of the electrical characteristics for process control is state of the art in gas metal arc welding (GMAW). The aim of the work is the improvement of GMAW processes by using additional information from the arc. Therefore, the emitted light of the arc is analysed spectroscopically and compared with high-speed camera images. With this information, a conclusion about the plasma arc and the droplet formation is reasonable. With the correlation of the spectral and local information of the plasma, a specific control of the power supply can be applied. A corresponding spectral control unit (SCU) is introduced.

  20. Resistance Spot Welding of Aluminum Alloy to Steel with Transition Material - Part II: Finite Element Analyses of Nugget Growth

    SciTech Connect

    Sun, Xin; Khaleel, Mohammad A.

    2004-07-01

    This paper summarizes work on finite element modeling of nugget growth for resistance spot welding of aluminum alloy to steel. It is a sequel to a previous paper on experimental studies of resistance spot welding of aluminum to steel using a transition material. Since aluminum alloys and steel cannot be readily fusion welded together due to their drastically different thermal physical properties, a cold-rolled clad material was introduced as a transition to aid the resistance welding process. Coupled electrical-thermal-mechanical finite element analyses were performed to simulate the nugget growth and heat generation patterns during the welding process. The predicted nugget growth results were compared to the experimental weld cross sections. Reasonable comparisons of nugget size were achieved. The finite element simulation procedures were also used in the electrode selection state to help reduce weld expulsion and improve weld quality.

  1. Development of laser welding techniques for vanadium alloys

    SciTech Connect

    Strain, R.V.; Leong, K.H.; Smith, D.L.

    1996-10-01

    Laser welding is potentially advantageous because of its flexibility and the reduced amount of material affected by the weld. Bead-on-plate and butt welds were previously performed to depths of about 4 mm with a 6-kW CO{sub 2} laser on V-4%Cr-4%Ti and V-5%Cr-5%Ti alloys. These welds were made at a speed of 0.042 m/s using argon purging at a flow rate of 2.8 m{sup 3}/s. The purge was distributed with a diffuser nozzle aimed just behind the laser beam during the welding operation. The fusion zones of welds made under these conditions consisted of very fine, needle-shaped grains and were also harder than the bulk metal (230-270 dph, compared to {approx}180 dph for the bulk metal). A limited number of impact tests showed that the as-welded ductile-brittle transition temperatures (DBTT) was above room temperature, but heat treatment at 1000{degrees}C for 1 h in vacuum reduced the DBTT to <{minus}25{degrees}C. Activities during this reporting period focused on improvements in the purging system and determination of the effect of welding speed on welds. A 2-kW continuous YAG laser at Lumonics Corp. in Livonia, MI, was used to make 34 test welds for this study.

  2. Improving Secondary Ion Mass Spectrometry Image Quality with Image Fusion

    PubMed Central

    Tarolli, Jay G.; Jackson, Lauren M.; Winograd, Nicholas

    2014-01-01

    The spatial resolution of chemical images acquired with cluster secondary ion mass spectrometry (SIMS) is limited not only by the size of the probe utilized to create the images, but also by detection sensitivity. As the probe size is reduced to below 1 µm, for example, a low signal in each pixel limits lateral resolution due to counting statistics considerations. Although it can be useful to implement numerical methods to mitigate this problem, here we investigate the use of image fusion to combine information from scanning electron microscope (SEM) data with chemically resolved SIMS images. The advantage of this approach is that the higher intensity and, hence, spatial resolution of the electron images can help to improve the quality of the SIMS images without sacrificing chemical specificity. Using a pan-sharpening algorithm, the method is illustrated using synthetic data, experimental data acquired from a metallic grid sample, and experimental data acquired from a lawn of algae cells. The results show that up to an order of magnitude increase in spatial resolution is possible to achieve. A cross-correlation metric is utilized for evaluating the reliability of the procedure. PMID:24912432

  3. 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

  4. Study on microstructures and mechanical properties of laser-arc hybrid welded S355J2W+N steel

    NASA Astrophysics Data System (ADS)

    Zhen, Shu; Duan, Zhenzhen; Sun, Daqian; Li, Yexiong; Gao, Dandan; Li, Hongmei

    2014-07-01

    The technology of laser-MAG hybrid welding was used on 16 mm thick plate of weathering steel S355J2W+N. Under the welding parameters used in the experiment, full penetration weld without flaws such as pores, cracks and lack of fusion was obtained by a three-layer and three-pass welding technique. In this study, the outstanding advantages of laser-arc hybrid welding were summarized by comparison with welded joint of traditional MAG welding. The microstructure of hybrid welded joint has also been detailed investigated. Besides, the mechanical property tests were performed according to corresponding European standards. Furthermore, the tensile and impact strength of laser-MAG hybrid welded joint turned out to be almost as good as base metal. Most of the hybrid welded joints had a good bending property, but for some sample, there was a micro-crack with the length of 0.9 mm emerging within the transition region where contraction stress would accumulate and remain, being one of the most vulnerable zones in weld metal. The results show that laser-MAG hybrid welding technology is appropriate for S355J2W+N thick plate welding, in favor of not only improving the product performance, but also lowering the production cost and improving the productivity.

  5. Probing Reliability of Transport Phenomena Based Heat Transfer and Fluid Flow Analysis in Autogeneous Fusion Welding Process

    NASA Astrophysics Data System (ADS)

    Bag, S.; de, A.

    2010-09-01

    The transport phenomena based heat transfer and fluid flow calculations in weld pool require a number of input parameters. Arc efficiency, effective thermal conductivity, and viscosity in weld pool are some of these parameters, values of which are rarely known and difficult to assign a priori based on the scientific principles alone. The present work reports a bi-directional three-dimensional (3-D) heat transfer and fluid flow model, which is integrated with a real number based genetic algorithm. The bi-directional feature of the integrated model allows the identification of the values of a required set of uncertain model input parameters and, next, the design of process parameters to achieve a target weld pool dimension. The computed values are validated with measured results in linear gas-tungsten-arc (GTA) weld samples. Furthermore, a novel methodology to estimate the overall reliability of the computed solutions is also presented.

  6. EVALUATION OF CONSTANT CURRENT WELD CONTROL FOR PINCH WELDING

    SciTech Connect

    Korinko, P; STANLEY, S; HOWARD, H

    2005-10-11

    Modern weld controllers typically use current to control the weld process. SRS uses a legacy voltage control method. This task was undertaken to determine if the improvements in the weld control equipment could be implemented to provide improvements to the process control. The constant current mode of operation will reduce weld variability by about a factor of 4. The constant voltage welds were slightly hotter than the constant current welds of the same nominal current. The control mode did not appear to adversely affect the weld quality, but appropriate current ranges need to be established and a qualification methodology for both welding and shunt calibrations needs to be developed and documented.

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

    SciTech Connect

    Anderson, Michael T.; Cinson, Anthony D.; Crawford, Susan L.; Diaz, Aaron A.; Moran, Traci L.

    2010-12-01

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

  8. Penetration in GTA welding

    SciTech Connect

    Heiple, C.R.; Burgardt, P.

    1990-01-01

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

  9. Fusion

    NASA Astrophysics Data System (ADS)

    Herman, Robin

    1990-10-01

    The book abounds with fascinating anecdotes about fusion's rocky path: the spurious claim by Argentine dictator Juan Peron in 1951 that his country had built a working fusion reactor, the rush by the United States to drop secrecy and publicize its fusion work as a propaganda offensive after the Russian success with Sputnik; the fortune Penthouse magazine publisher Bob Guccione sank into an unconventional fusion device, the skepticism that met an assertion by two University of Utah chemists in 1989 that they had created "cold fusion" in a bottle. Aimed at a general audience, the book describes the scientific basis of controlled fusion--the fusing of atomic nuclei, under conditions hotter than the sun, to release energy. Using personal recollections of scientists involved, it traces the history of this little-known international race that began during the Cold War in secret laboratories in the United States, Great Britain and the Soviet Union, and evolved into an astonishingly open collaboration between East and West.

  10. Development of a Comprehensive Weld Process Model

    SciTech Connect

    Radhakrishnan, B.; Zacharia, T.

    1997-05-01

    . The timing results illustrate the potential of the modified computer model for the analysis of large-scale welding simulations. 2. The kinetics of grain structure evolution in the weld heat affected zone (HAZ) has been simulated with reasonable accuracy by coupling an improved MC grain growth algorithm with a methodology for converting the MC parameters of grain size and time to real parameters. The simulations effectively captured the thermal pinning phenomenon that has been reported in the weld HAZ. 3. A cellular automaton (CA) code has been developed to simulate the solidification microstructure in the weld fusion zone. The simulations effectively captured the epitaxial growth of the HAZ grains, the grain selection mechanism, and the formation of typical grain structures observed in the weld t%sion zone. 4. The point heat source used in the LMES welding code has ben replaced with a distributed heat source to better capture the thermal characteristics and energy distributions in a commercial welding heat source. 5. Coupled thermal-mechanical and metallurgical models have been developed to accurately predict the weld residual stresses, and 6. Attempts have been made to integrate the newly developed computational capabilities into a comprehensive weld design tool.

  11. Model of Layered Weld Formation Under Narrow Gap Pulse Welding

    NASA Astrophysics Data System (ADS)

    Krampit, A. G.

    2016-04-01

    The model parameters of narrow gap pulse welding can be divided into input, internal and output ones. The breadth of gap, that is, clearance breadth between upright edges is one of key parameters securing high quality of a weld joint. The paper presents theoretical outcomes for the model of layered weld formation under narrow gap pulse welding. Based on these studies is developed model of processes, which occur in the weld pool under pulse grove welding. It comprises the scheme of liquid metal motion in the weld pool, scheme of fusion with the side edge and in the bottom part, and the scheme of welding current impulse effect on the structure of a weld joint.

  12. Microstructure evolution of Al/Mg butt joints welded by gas tungsten arc with Zn filler metal

    SciTech Connect

    Liu Fei; Zhang Zhaodong; Liu Liming

    2012-07-15

    Based on the idea of alloying welding seam, Gas tungsten arc welding method with pure Zn filler metal was chosen to join Mg alloy and Al alloy. The microstructures, phases, element distribution and fracture morphology of welding seams were examined. The results indicate that there was a transitional zone in the width of 80-100 {mu}m between the Mg alloy substrate and fusion zone. The fusion zone was mainly composed of MgZn{sub 2}, Zn-based solid solution and Al-based solid solution. The welding seam presented distinct morphology in different location owning to the quite high cooling rate of the molten pool. The addition of Zn metal could prevent the formation of Mg-Al intermetallics and form the alloyed welding seam during welding. Therefore, the tensile strengths of joints have been significantly improved compared with those of gas tungsten arc welded joints without Zn metal added. Highlights: Black-Right-Pointing-Pointer Mg alloy AZ31B and Al alloy 6061 are welded successfully. Black-Right-Pointing-Pointer Zinc wire is employed as a filler metal to form the alloyed welding seam. Black-Right-Pointing-Pointer An alloyed welding seam is benefit for improving of the joint tensile strength.

  13. 49 CFR 178.58 - Specification 4DA welded steel cylinders for aircraft use.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... § 171.7 of this subchapter). (2) All seams of the sphere or cylinders must be fusion welded. Seams must... of the joint. (e) Welding. Attachments to the container are authorized by fusion welding provided... to the container by fusion welding. (2) Attachments to a fitting, boss, or pad must be adequate...

  14. Genetic Nature, Stability, and Improved Virulence of Hybrids from Protoplast Fusion in Beauveria

    PubMed

    Couteaudier; Viaud; Riba

    1996-07-01

    Genetic improvement of two different strains of the entomopathogenic fungus Beauveria bassiana for more effective control of Ostrinia nubilalis and Leptinotarsa decemlineata was obtained by crosses with the insecticidal toxin-producing strain Beauveria sulfurescens. Protoplast fusion between diauxotrophic mutants resulted in the recovery of some stable prototrophic fusion products. The low levels of virulence of the wild type strain B. bassiana 28 isolated originally from L. decemlineata were enhanced both on L. decemlineata and O. nubilalis for one of the hybrids obtained (FP 8) from the cross B. bassiana 28xB. sulfurescens 2. Fusion product 25 obtained from the cross between B. sulfurescens and the highly pathogenic strain B. bassiana 147 showed a three-day reduction in the LT50 towards O. nubilalis. Southern blot hybridization with nine probe-enzyme combinations were conducted on genomic DNAs from the original wild strains, parental mutant strains, and fusion products. Additive banding patterns or unique banding pattern of either parental strain was observed in five hybrids, indicating their status as recombinant and/or partially diploid. Combination of RFLP markers indicative of both parental genomes was never observed with fusion product FP 25. The stability of the virulence following passage through insect-host and stability of molecular structure for the fusion products FP 8 and FP 25 suggest that asexual genetic recombination by protoplast fusion may provide an attractive method for the genetic improvement of biocontrol efficiency in entomopathogenic fungi. PMID:8661542

  15. An improved fusion algorithm for infrared and visible images based on multi-scale transform

    NASA Astrophysics Data System (ADS)

    Li, He; Liu, Lei; Huang, Wei; Yue, Chao

    2016-01-01

    In this paper, an improved fusion algorithm for infrared and visible images based on multi-scale transform is proposed. First of all, Morphology-Hat transform is used for an infrared image and a visible image separately. Then two images were decomposed into high-frequency and low-frequency images by contourlet transform (CT). The fusion strategy of high-frequency images is based on mean gradient and the fusion strategy of low-frequency images is based on Principal Component Analysis (PCA). Finally, the final fused image is obtained by using the inverse contourlet transform (ICT). The experiments and results demonstrate that the proposed method can significantly improve image fusion performance, accomplish notable target information and high contrast and preserve rich details information at the same time.

  16. Vacuum Gas Tungsten Arc Welding

    NASA Technical Reports Server (NTRS)

    Weeks, J. L.; Todd, D. T.; Wooten, J. R.

    1997-01-01

    A two-year program investigated vacuum gas tungsten arc welding (VGTAW) as a method to modify or improve the weldability of normally difficult-to-weld materials. After a vacuum chamber and GTAW power supply were modified, several difficult-to-weld materials were studied and key parameters developed. Finally, Incoloy 903 weld overlays were produced without microfissures.

  17. Alternating-Polarity Arc Welding

    NASA Technical Reports Server (NTRS)

    Schwinghamer, R. J.

    1987-01-01

    Brief reversing polarity of welding current greatly improves quality of welds. NASA technical memorandum recounts progress in art of variable-polarity plasma-arc (VPPA) welding, with emphasis on welding of aluminum-alloy tanks. VPPA welders offer important advantages over conventional single-polarity gas/tungsten arc welders.

  18. Improvements of the welding performance of plasma arcs by a superimposed fibre laser beam

    NASA Astrophysics Data System (ADS)

    Mahrle, Achim; Rose, Sascha; Schnick, Michael; Pinder, Thomas; Beyer, Eckhard; Füssel, Uwe

    2012-03-01

    Details and results of experimental investigations of a laser-supported plasma arc welding process are presented. The particular feature of the realized experimental set-up is the coaxial arrangement of a single-mode fibre laser beam through a hollow tungsten electrode in combination with a modified plasma welding torch. The analysis of the welding capabilities of the combined laser-arc source comprises high-speed video recordings of the arc shape and size, corresponding simultaneous measurements of the arc voltage as well as an evaluation of the resultant weld seam geometries. Results of welding trials on different types of steel and aluminum alloys are discussed. The corresponding investigations reveal that a fibre laser beam with a wavelength of 1.07 microns can have a crucial impact on the arc and welding characteristics for both categories of materials even at very low laser power output levels. Beneficial effects are especially observed with high welding speeds. In that particular case the arc root and therefore arc column can be substantially stabilized and guided by the laser-induced hot spot.

  19. Use of fusion-welding techniques in fabrication of a superconducting-magnet thermal-shield system

    SciTech Connect

    Dalder, E.N.C.; Berkey, J.H.; Chang, Y.; Johnson, G.L.; Lathrop, G.H.; Podesta, D.L.; Van Sant, J.H.

    1983-06-10

    Success of the thermal shield system was demonstrated by the results of acceptance tests performed with the magnet and all its ancillary equipment. During these tests the thermal shield system was: (1) thermally cycled several times from 300/sup 0/K to 77/sup 0/K; (2) pressure cycled several times from 0 to 5 atmospheres; (3) operated for more than 500 hours at 77/sup 0/K and in a vacuum environment of less than 10/sup -5/ torr; (4) operated in a magnetic field up to 6.0 Telsa; (5) exposed to a rapidly collapsing magnetic field of more than 250 gauss per second; (6) drained of all LN/sub 2/ in a few minutes, without any weld failures. The successful (and relatively problem free) operation of the magnet system validates the choice of the welding processes used, as well as their execution in both shop and field environments.

  20. A study of the solid-liquid interface in cobalt base alloy (Stellite) coatings deposited by fusion welding (TIG)

    SciTech Connect

    Molleda, F. . E-mail: fmolleda@etsin.upm.es; Mora, J.; Molleda, F.J.; Mora, E.; Carrillo, E.; Mellor, B.G.

    2006-12-15

    Microstructural features present at the interface between a weld deposited Stellite 6 hard facing and an austenitic stainless steel substrate are described. Elemental X-ray maps indicate that diffusion of carbon from the liquid Stellite to the austenitic stainless steel takes place along grain boundaries resulting in the formation of chromium carbide 'arms' that penetrate along the austenite grain boundaries in the interfacial region.

  1. 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.

  2. 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.

  3. Improving the recognition of fingerprint biometric system using enhanced image fusion

    NASA Astrophysics Data System (ADS)

    Alsharif, Salim; El-Saba, Aed; Stripathi, Reshma

    2010-04-01

    Fingerprints recognition systems have been widely used by financial institutions, law enforcement, border control, visa issuing, just to mention few. Biometric identifiers can be counterfeited, but considered more reliable and secure compared to traditional ID cards or personal passwords methods. Fingerprint pattern fusion improves the performance of a fingerprint recognition system in terms of accuracy and security. This paper presents digital enhancement and fusion approaches that improve the biometric of the fingerprint recognition system. It is a two-step approach. In the first step raw fingerprint images are enhanced using high-frequency-emphasis filtering (HFEF). The second step is a simple linear fusion process between the raw images and the HFEF ones. It is shown that the proposed approach increases the verification and identification of the fingerprint biometric recognition system, where any improvement is justified using the correlation performance metrics of the matching algorithm.

  4. Heat Treatment of Friction-Stir-Welded 7050 Aluminum Plates

    NASA Technical Reports Server (NTRS)

    Petter, George E.; Figert, John D.; Rybicki, Daniel J.; Burns, Timothy

    2006-01-01

    A method of heat treatment has been developed to reverse some of the deleterious effects of friction stir welding of plates of aluminum alloy 7050. This alloy is considered unweldable by arc and high-energy-density beam fusion welding processes. The alloy can be friction stir welded, but as-welded workpieces exhibit low ductility, low tensile and yield strengths, and low resistance to stress corrosion cracking. Heat treatment according to the present method increases tensile and yield strengths, and minimizes or eliminates stress corrosion cracking. It also increases ductility. This method of heat treatment is a superior alternative to a specification-required heat treatment that caused the formation of large columnar grains, which are undesired. Workpieces subjected to the prior heat treatment exhibited elongations <2 percent, and standard three-point bend specimens shattered. The development of the present heat treatment method was guided partly by the principles that (1) by minimizing grain sizes and relieving deformation stresses, one can minimize or eliminate stress corrosion cracking and (2) the key to maximizing strength and eliminating residual stresses is to perform post-weld solution heating for as long a time as possible while incurring little or no development of large columnar grains in friction stir weld nuggets. It is necessary to perform some of the solution heat treatment (to soften the alloy and improve machine welding parameters) before welding. The following is an example of thickness- dependent pre- and post-weld heat treatments according to the present method: For plates 0.270 in. (approx.6.86 mm) thick milled from plates 4.5 in. (114.3 mm) thick, perform pre-weld solution heating at 890 F (477 C) for 1 hour, then cool in air. After friction stir welding, perform solution heating for 10 minutes, quench, hold at room temperature for 96 hours, then age at 250 F (121 C) for 5 hours followed by 325 F (163 C) for 27 hours.

  5. Improved Continuous Tube Welding Due to Unique Process Sensor System and Process Control

    NASA Astrophysics Data System (ADS)

    Dorsch, F.; Pfitzner, D.; Braun, H.

    A unique camera-based triple sensor system increases productivity, yield and quality of continuous welding of tubes and profiles. It combines high-precision seam tracking and beam positioning with weld spot visualization and characterization, and seam geometry measurement. The higher overall precision allows operating the process closer to its limits, online quality monitoring detects faults immediately. The process setup time is greatly reduced, and also the waste during startup is reduced. Finally, full documentation sets the basis for data traceability.

  6. Method for welding chromium molybdenum steels

    DOEpatents

    Sikka, Vinod K.

    1986-01-01

    Chromium-molybdenum steels exhibit a weakening after welding in an area adjacent to the weld. This invention is an improved method for welding to eliminate the weakness by subjecting normalized steel to a partial temper prior to welding and subsequently fully tempering the welded article for optimum strength and ductility.

  7. Improving Agent Based Models and Validation through Data Fusion

    PubMed Central

    Laskowski, Marek; Demianyk, Bryan C.P.; Friesen, Marcia R.; McLeod, Robert D.; Mukhi, Shamir N.

    2011-01-01

    This work is contextualized in research in modeling and simulation of infection spread within a community or population, with the objective to provide a public health and policy tool in assessing the dynamics of infection spread and the qualitative impacts of public health interventions. This work uses the integration of real data sources into an Agent Based Model (ABM) to simulate respiratory infection spread within a small municipality. Novelty is derived in that the data sources are not necessarily obvious within ABM infection spread models. The ABM is a spatial-temporal model inclusive of behavioral and interaction patterns between individual agents on a real topography. The agent behaviours (movements and interactions) are fed by census / demographic data, integrated with real data from a telecommunication service provider (cellular records) and person-person contact data obtained via a custom 3G Smartphone application that logs Bluetooth connectivity between devices. Each source provides data of varying type and granularity, thereby enhancing the robustness of the model. The work demonstrates opportunities in data mining and fusion that can be used by policy and decision makers. The data become real-world inputs into individual SIR disease spread models and variants, thereby building credible and non-intrusive models to qualitatively simulate and assess public health interventions at the population level. PMID:23569606

  8. Multi-model data fusion to improve an early warning system for hypo-/hyperglycemic events.

    PubMed

    Botwey, Ransford Henry; Daskalaki, Elena; Diem, Peter; Mougiakakou, Stavroula G

    2014-01-01

    Correct predictions of future blood glucose levels in individuals with Type 1 Diabetes (T1D) can be used to provide early warning of upcoming hypo-/hyperglycemic events and thus to improve the patient's safety. To increase prediction accuracy and efficiency, various approaches have been proposed which combine multiple predictors to produce superior results compared to single predictors. Three methods for model fusion are presented and comparatively assessed. Data from 23 T1D subjects under sensor-augmented pump (SAP) therapy were used in two adaptive data-driven models (an autoregressive model with output correction - cARX, and a recurrent neural network - RNN). Data fusion techniques based on i) Dempster-Shafer Evidential Theory (DST), ii) Genetic Algorithms (GA), and iii) Genetic Programming (GP) were used to merge the complimentary performances of the prediction models. The fused output is used in a warning algorithm to issue alarms of upcoming hypo-/hyperglycemic events. The fusion schemes showed improved performance with lower root mean square errors, lower time lags, and higher correlation. In the warning algorithm, median daily false alarms (DFA) of 0.25%, and 100% correct alarms (CA) were obtained for both event types. The detection times (DT) before occurrence of events were 13.0 and 12.1 min respectively for hypo-/hyperglycemic events. Compared to the cARX and RNN models, and a linear fusion of the two, the proposed fusion schemes represents a significant improvement. PMID:25571076

  9. Grain Refinement in Al-Mg-Si Alloy TIG Welds Using Transverse Mechanical Arc Oscillation

    NASA Astrophysics Data System (ADS)

    Biradar, N. S.; Raman, R.

    2012-11-01

    Reduction in grain size in weld fusion zones (FZs) presents the advantages of increased resistance to solidification cracking and improvement in mechanical properties. Transverse mechanical arc oscillation was employed to obtain grain refinement in the weldment during tungsten inert gas welding of Al-Mg-Si alloy. Electron backscattered diffraction analysis was carried out on AA6061-AA4043 filler metal tungsten inert gas welds. Grain size, texture evolution, misorientation distribution, and aspect ratio of weld metal, PMZ, and BM have been observed at fixed arc oscillation amplitude and at three different frequencies levels. Arc oscillation showed grain size reduction and texture formation. Fine-grained arc oscillated welds exhibited better yield and ultimate tensile strengths and significant improvement in percent elongation. The obtained results were attributed to reduction in equivalent circular diameter of grains and increase in number of subgrain network structure of low angle grain boundaries.

  10. Improved computational methods for simulating inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    Fatenejad, Milad

    This dissertation describes the development of two multidimensional Lagrangian code for simulating inertial confinement fusion (ICF) on structured meshes. The first is DRACO, a production code primarily developed by the Laboratory for Laser Energetics. Several significant new capabilities were implemented including the ability to model radiative transfer using Implicit Monte Carlo [Fleck et al., JCP 8, 313 (1971)]. DRACO was also extended to operate in 3D Cartesian geometry on hexahedral meshes. Originally the code was only used in 2D cylindrical geometry. This included implementing thermal conduction and a flux-limited multigroup diffusion model for radiative transfer. Diffusion equations are solved by extending the 2D Kershaw method [Kershaw, JCP 39, 375 (1981)] to three dimensions. The second radiation-hydrodynamics code developed as part of this thesis is Cooper, a new 3D code which operates on structured hexahedral meshes. Cooper supports the compatible hydrodynamics framework [Caramana et al., JCP 146, 227 (1998)] to obtain round-off error levels of global energy conservation. This level of energy conservation is maintained even when two temperature thermal conduction, ion/electron equilibration, and multigroup diffusion based radiative transfer is active. Cooper is parallelized using domain decomposition, and photon energy group decomposition. The Mesh Oriented datABase (MOAB) computational library is used to exchange information between processes when domain decomposition is used. Cooper's performance is analyzed through direct comparisons with DRACO. Cooper also contains a method for preserving spherical symmetry during target implosions [Caramana et al., JCP 157, 89 (1999)]. Several deceleration phase implosion simulations were used to compare instability growth using traditional hydrodynamics and compatible hydrodynamics with/without symmetry modification. These simulations demonstrate increased symmetry preservation errors when traditional hydrodynamics

  11. An Improved High Frequency Modulating Fusion Method Based on Modulation Transfer Function Filters

    NASA Astrophysics Data System (ADS)

    Jia, Y.; Wu, M.; Zhang, X.

    2012-07-01

    GeoEye-1 is the most advanced and highest resolution commercial earth imaging satellite in the world today. It provides multispectral images (MS) and Panchromatic image (PAN) with spatial resolutions of 2.0 m and 0.5 m respectively. Image fusion is very important for mapping and image interpretation because it can take advantage of the complementary spatial/spectral resolution characteristics of remote sensing imagery. So an improved high frequency modulation fusion method based on MTF is proposed. Modulation transfer functions (MTF) are firstly measured from GeoEye-1 images, and then the degraded images based on MTF filters are obtained. Secondly, modulating parameter is obtained based on Minimum Mean Square Error, and image fusion is performed and measured in the degraded version. Finally, fused images with the high spatial resolution are produced by using the proposed method. Compared with fusion methods of weighted high passing filtering(w-HPF) in ERDAS IMAGINE and general image fusion based on MTF( MTF-GIF), The results of fused GeoEye-1 images show that the proposed method is an efficient way for GeoEye-1 image fusion, which can keep spectral information with the high spatial resolution.

  12. Simulation of metal transfer and weld pool development in gas metal arc welding of thin sheet metals

    NASA Astrophysics Data System (ADS)

    Wang, Fang

    Gas metal arc welding (GMAW) is the most commonly used arc welding method in industry for joining steels and aluminum alloys. But due to the mathematical difficulties associated with the free surface motion of the molten droplet and the weld pool, the process is not well understood and the development of new welding procedures in the manufacturing industry highly depends on expensive, time-consuming and experience-based trial and error. In this dissertation, numerical methods are developed to overcome the difficulties and to simulate the metal transfer and weld pool development in the GMAW of sheet metals. The simulations are validated by experiments and used to study an industrial welding process. A numerical procedure is first developed to model the free surface motion in fusion welding processes. Thermal and electromagnetic models are integrated with the fluid models. Recommendations are made on the selection and improvement of publicly available numerical algorithms, while alternative methods are also reviewed. A model combining the enthalpy, effective-viscosity and volume-of-fluid methods is then developed to simulate the metal transfer process in globular, spray and short-circuiting transfer modes. The model not only describes the influence of gravity, electromagnetic force and surface tension on droplet profile and transfer frequency, but also models the nonisothermal phenomena such as heat transfer and phase change. The melting front motion, the droplet detachment and oscillation, the satellite formation and the fluid convection within the droplet are analyzed. It has been found that the taper formation in spray transfer is closely related to the heat input on the unmelted portion of the welding wire, and the taper formation affects the globular-spray transition by decelerating the transfer process. Experiments with a high-speed motion analyzer validate the simulation results. The model is then extended to simulate the initiation, development and

  13. 49 CFR 179.220-10 - Welding.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Welding. 179.220-10 Section 179.220-10...-Pressure Tank Car Tanks (Classes DOT-111AW and 115AW) § 179.220-10 Welding. (a) All joints must be fusion... subchapter). Welding procedures, welders, and fabricators shall be approved. (b) Radioscopy of the...

  14. 49 CFR 179.200-10 - Welding.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Welding. 179.200-10 Section 179.200-10...-Pressure Tank Car Tanks (Classes DOT-111AW and 115AW) § 179.200-10 Welding. (a) All joints shall be fusion... § 171.7 of this subchapter). Welding procedures, welders and fabricators shall be approved. (b)...

  15. 49 CFR 179.200-10 - Welding.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Welding. 179.200-10 Section 179.200-10...-Pressure Tank Car Tanks (Classes DOT-111AW and 115AW) § 179.200-10 Welding. (a) All joints shall be fusion... § 171.7 of this subchapter). Welding procedures, welders and fabricators shall be approved. (b)...

  16. 49 CFR 179.200-10 - Welding.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Welding. 179.200-10 Section 179.200-10...-Pressure Tank Car Tanks (Classes DOT-111AW and 115AW) § 179.200-10 Welding. (a) All joints shall be fusion... § 171.7 of this subchapter). Welding procedures, welders and fabricators shall be approved. (b)...

  17. 49 CFR 179.200-10 - Welding.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Welding. 179.200-10 Section 179.200-10...-Pressure Tank Car Tanks (Classes DOT-111AW and 115AW) § 179.200-10 Welding. (a) All joints shall be fusion... § 171.7 of this subchapter). Welding procedures, welders and fabricators shall be approved. (b)...

  18. 49 CFR 179.220-10 - Welding.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Welding. 179.220-10 Section 179.220-10...-Pressure Tank Car Tanks (Classes DOT-111AW and 115AW) § 179.220-10 Welding. (a) All joints must be fusion... subchapter). Welding procedures, welders, and fabricators shall be approved. (b) Radioscopy of the...

  19. 49 CFR 179.220-10 - Welding.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Welding. 179.220-10 Section 179.220-10...-Pressure Tank Car Tanks (Classes DOT-111AW and 115AW) § 179.220-10 Welding. (a) All joints must be fusion... subchapter). Welding procedures, welders, and fabricators shall be approved. (b) Radioscopy of the...

  20. 49 CFR 179.220-10 - Welding.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Welding. 179.220-10 Section 179.220-10...-Pressure Tank Car Tanks (Classes DOT-111AW and 115AW) § 179.220-10 Welding. (a) All joints must be fusion... subchapter). Welding procedures, welders, and fabricators shall be approved. (b) Radioscopy of the...

  1. Weld Wire Investigation Summary

    SciTech Connect

    Cunningham, M.A.

    1999-03-22

    After GTA welding reservoir A production/process prove-in assemblies, X-ray examination detected a lack of sidewall fusion. After examining several possible causes, it was determined that the weld wire filler metal was responsible, particularly the wire cleaning process. The final conclusion was that the filler wire must be abrasively cleaned in a particular manner to perform as required. The abrasive process was incorporated into the wire material specification, ensuring consistency for all reservoir GTA welding at AlliedSignal Federal Manufacturing and Technologies (FM and T).

  2. The Measurement of the Specific Latent Heat of Fusion of Ice: Two Improved Methods.

    ERIC Educational Resources Information Center

    Mak, S. Y.; Chun, C. K. W.

    2000-01-01

    Suggests two methods for measuring the specific latent heat of ice fusion for high school physics laboratories. The first method is an ice calorimeter which is made from simple materials. The second method improves the thermal contact and allows for a more accurate measurement. Lists instructions for both methods. (Author/YDS)

  3. 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.

  4. 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.

  5. Fast, automatically darkening welding filter offering an improved level of safety

    NASA Astrophysics Data System (ADS)

    Palmer, Stephen

    1996-03-01

    A mode of operation is introduced for the standard 90 degrees twisted nematic (TN) liquid-crystal cell when placed together with an interference filter and positioned between crossed polarizers such that a small stimulating voltage of between 2.0 and 3.0 V is required in order to attain the light state. Further incrementation of the driving electronics reverts the system back to a darker phase. Such cells offer advantages over those of the standard 90 degrees TN device operating in the normally white mode, in that the unit maintains the fast response time from the light to the dark state associated with the employment of TN cells placed between crossed polarizers. In addition, a low transmittance state is achieved when the unit is in the inactivated phase; this is an effect usually correlated with the normally black mode of operation. These cells are therefore ideal candidates for incorporation into fast, automatically darkening, welding filters that are designed to change rapidly from the light to the dark protective state, while offering an improved level of safety by not holding in a potentially hazardous light state should the controlling electronics malfunction. The requirement for this phenomenon to be observed is that the cell displays a low optical transmittance over the green wavelengths of the visible spectrum when in the inactivated phase and placed between crossed polarizers. The presence of an interference filter that possesses a peak transmittance over the central part of the visible spectrum is also necessary. It is shown that there are only two possible cell types that satisfy this criteria, and the optical properties of such cells are analyzed in some detail.

  6. Fusion of multispectral and panchromatic images using improved GIHS and PCA mergers based on contourlet

    NASA Astrophysics Data System (ADS)

    Yang, Shuyuan; Zeng, Liang; Jiao, Licheng; Xiao, Jing

    2007-11-01

    Since Chavez proposed the highpass filtering procedure to fuse multispectral and panchromatic images, several fusion methods have been developed based on the same principle: to extract from the panchromatic image spatial detail information to later inject it into the multispectral one. In this paper, we present new fusion alternatives based on the same concept, using the multiresolution contourlet decomposition to execute the detail extraction phase and the generalized intensity-hue-saturation (GIHS) and principal component analysis (PCA) procedures to inject the spatial detail of the panchromatic image into the multispectral one. Experimental results show the new fusion method have better performance than GIHS, PCA, wavelet and the method of improved GIHS and PCA mergers based on wavelet decomposition.

  7. Improving image classification in a complex wetland ecosystem through image fusion techniques

    NASA Astrophysics Data System (ADS)

    Kumar, Lalit; Sinha, Priyakant; Taylor, Subhashni

    2014-01-01

    The aim of this study was to evaluate the impact of image fusion techniques on vegetation classification accuracies in a complex wetland system. Fusion of panchromatic (PAN) and multispectral (MS) Quickbird satellite imagery was undertaken using four image fusion techniques: Brovey, hue-saturation-value (HSV), principal components (PC), and Gram-Schmidt (GS) spectral sharpening. These four fusion techniques were compared in terms of their mapping accuracy to a normal MS image using maximum-likelihood classification (MLC) and support vector machine (SVM) methods. Gram-Schmidt fusion technique yielded the highest overall accuracy and kappa value with both MLC (67.5% and 0.63, respectively) and SVM methods (73.3% and 0.68, respectively). This compared favorably with the accuracies achieved using the MS image. Overall, improvements of 4.1%, 3.6%, 5.8%, 5.4%, and 7.2% in overall accuracies were obtained in case of SVM over MLC for Brovey, HSV, GS, PC, and MS images, respectively. Visual and statistical analyses of the fused images showed that the Gram-Schmidt spectral sharpening technique preserved spectral quality much better than the principal component, Brovey, and HSV fused images. Other factors, such as the growth stage of species and the presence of extensive background water in many parts of the study area, had an impact on classification accuracies.

  8. Recovery of Mechanical Properties of a 6061-T6 Aluminum Weld by Heat Treatment After Welding

    NASA Astrophysics Data System (ADS)

    Pérez, Javier Serrano; Ambriz, Ricardo Rafael; López, Francisco Fernando Curiel; Vigueras, David Jaramillo

    2016-07-01

    The dilution effects in welds of a 6061-T6 (Al-Si-Mg) alloy obtained by the modified indirect electric arc (MIEA), using an ER4043 filler metal (Al-Si), and postweld heat treatment (PWHT) were analyzed. The soft zone (55 to 70 HV0.1) formed by the microstructural transformation in the heat-affected zone (HAZ) was eliminated. The hardness measurements were presented on a traditional microhardness profile and mapping representation. A hardening effect of the fusion zone was observed; the hardness values were above 120 HV0.1 and tended to be uniform. This behavior could be attributed to the chemical composition of the filler metal, the Mg migration from the base to the weld metal, and the reversible process of the PWHT, which promotes precipitation hardening. Improvement for yield (260 MPa) and tensile strength (310 MPa) of the MIEA joints was observed; these values were similar to those obtained for the base metal. However, the presence of porosity in the fusion zone limits the ductility of the joints (4.3 pct). Even though the yield and tensile strengths of the base metal and welded joints were similar, the stress concentration due to porosity in the weld metal generated data dispersion in fatigue life. As a consequence, the high-cycle fatigue life decreases with respect to the base metal. In contrast, when the crack propagates under elastic conditions, the crack-tip singularity is affected by the porosity in the weld metal (stress liberator). This aspect, in conjunction with the hardening effect in joints subjected to PWHT, improves the fatigue crack growth rate when compared to the as-welded condition.

  9. Recovery of Mechanical Properties of a 6061-T6 Aluminum Weld by Heat Treatment After Welding

    NASA Astrophysics Data System (ADS)

    Pérez, Javier Serrano; Ambriz, Ricardo Rafael; López, Francisco Fernando Curiel; Vigueras, David Jaramillo

    2016-05-01

    The dilution effects in welds of a 6061-T6 (Al-Si-Mg) alloy obtained by the modified indirect electric arc (MIEA), using an ER4043 filler metal (Al-Si), and postweld heat treatment (PWHT) were analyzed. The soft zone (55 to 70 HV0.1) formed by the microstructural transformation in the heat-affected zone (HAZ) was eliminated. The hardness measurements were presented on a traditional microhardness profile and mapping representation. A hardening effect of the fusion zone was observed; the hardness values were above 120 HV0.1 and tended to be uniform. This behavior could be attributed to the chemical composition of the filler metal, the Mg migration from the base to the weld metal, and the reversible process of the PWHT, which promotes precipitation hardening. Improvement for yield (260 MPa) and tensile strength (310 MPa) of the MIEA joints was observed; these values were similar to those obtained for the base metal. However, the presence of porosity in the fusion zone limits the ductility of the joints (4.3 pct). Even though the yield and tensile strengths of the base metal and welded joints were similar, the stress concentration due to porosity in the weld metal generated data dispersion in fatigue life. As a consequence, the high-cycle fatigue life decreases with respect to the base metal. In contrast, when the crack propagates under elastic conditions, the crack-tip singularity is affected by the porosity in the weld metal (stress liberator). This aspect, in conjunction with the hardening effect in joints subjected to PWHT, improves the fatigue crack growth rate when compared to the as-welded condition.

  10. A study of weld quality in ultrasonic spot welding of similar and dissimilar metals

    NASA Astrophysics Data System (ADS)

    Al-Sarraf, Z.; Lucas, M.

    2012-08-01

    Several difficulties are faced in joining thinner sheets of similar and dissimilar materials from fusion welding processes such as resistance welding and laser welding. Ultrasonic metal welding overcomes many of these difficulties by using high frequency vibration and applied pressure to create a solid-state weld. Ultrasonic metal welding is an effective technique in joining small components, such as in wire bonding, but is also capable of joining thicker sheet, depending on the control of welding conditions. This study presents the design, characterisation and test of a lateral-drive ultrasonic metal welding device. The ultrasonic welding horn is modelled using finite element analysis and its vibration behaviour is characterised experimentally to ensure ultrasonic energy is delivered to the weld coupon. The welding stack and fixtures are then designed and mounted on a test machine to allow a series of experiments to be conducted for various welding and ultrasonic parameters. Weld strength is subsequently analysed using tensile-shear tests. Control of the vibration amplitude profile through the weld cycle is used to enhance weld strength and quality, providing an opportunity to reduce part marking. Optical microscopic examination and scanning electron microscopy (SEM) were employed to investigate the weld quality. The results show how the weld quality is particularly sensitive to the combination of clamping force and vibration amplitude of the welding tip.

  11. 49 CFR 178.57 - Specification 4L welded insulated cylinders.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...) Type, size, service pressure, and design service temperature. A DOT 4L cylinder is a fusion welded...: (1) All seams of the cylinder must be fusion welded. A means must be provided for accomplishing... and heads of the cylinder must be by fusion welding and must be of a weldable material complying...

  12. 49 CFR 178.57 - Specification 4L welded insulated cylinders.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...) Type, size, service pressure, and design service temperature. A DOT 4L cylinder is a fusion welded...: (1) All seams of the cylinder must be fusion welded. A means must be provided for accomplishing... and heads of the cylinder must be by fusion welding and must be of a weldable material complying...

  13. 49 CFR 178.57 - Specification 4L welded insulated cylinders.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...) Type, size, service pressure, and design service temperature. A DOT 4L cylinder is a fusion welded...: (1) All seams of the cylinder must be fusion welded. A means must be provided for accomplishing... and heads of the cylinder must be by fusion welding and must be of a weldable material complying...

  14. 49 CFR 178.47 - Specification 4DS welded stainless steel cylinders for aircraft use.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...-3 (IBR, see § 171.7 of this subchapter). All seams of the sphere or cylinder must be fusion welded... joint. (e) Attachments. Attachments to the container are authorized by fusion welding provided that such... stainless steel securely attached to the container by fusion welding. (2) Attachments to a fitting, boss,...

  15. Fracture toughness of Ti-6Al-4V after welding and postweld heat treatment

    SciTech Connect

    Murthy, K.K.; Sundaresan, S.

    1997-02-01

    The fracture toughness (J{sub IC}) of the fusion zone of Ti-6Al-4V alloy welds was studied in terms of microstructural changes in the as-welded condition and following postweld heat treatment. Gas tungsten arc and electron beam welds were produced in sheet material over a limited range of heat input and subsequently heat treated at 700 C and 900 C. In the as-welded condition, the weld microstructure was a mixture of diffusional and martensitic alpha phases, whose proportion varied wit heat input and cooling rate. The fusion zone exhibited low ductility resulting from the highly acicular microstructure and a large prior-beta grain size. Postweld heat treatment tempered the martensite and coarsened the microstructure, but a beneficial effect on ductility was realized only after treatment at 900 C. Fracture toughness in the as-welded condition was greater than for the base metal and was attributed to the lamellar microstructure of the fusion zone and absence of continuous alpha film along the grain boundaries. Postweld heat treatment at 700 C reduced the fracture toughness considerably and, as in the case of ductility, it was necessary to heat treat at 900 C to produce an improvement.

  16. 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.

  17. 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.

  18. Weld electrode cooling study

    NASA Astrophysics Data System (ADS)

    Masters, Robert C.; Simon, Daniel L.

    1999-03-01

    The U.S. auto/truck industry has been mandated by the Federal government to continuously improve their fleet average gas mileage, measured in miles per gallon. Several techniques are typically used to meet these mandates, one of which is to reduce the overall mass of cars and trucks. To help accomplish this goal, lighter weight sheet metal parts, with smaller weld flanges, have been designed and fabricated. This paper will examine the cooling characteristics of various water cooled weld electrodes and shanks used in resistance spot welding applications. The smaller weld flanges utilized in modern vehicle sheet metal fabrications have increased industry's interest in using one size of weld electrode (1/2 inch diameter) for certain spot welding operations. The welding community wants more data about the cooling characteristics of these 1/2 inch weld electrodes. To hep define the cooling characteristics, an infrared radiometer thermal vision system (TVS) was used to capture images (thermograms) of the heating and cooling cycles of several size combinations of weld electrodes under typical production conditions. Tests results will show why the open ended shanks are more suitable for cooling the weld electrode assembly then closed ended shanks.

  19. Improving CAD performance by fusion of the bilateral mammographic tissue asymmetry information

    NASA Astrophysics Data System (ADS)

    Wang, Xingwei; Li, Lihua; Liu, Wei; Xu, Weidong; Lederman, Dror; Zheng, Bin

    2012-03-01

    Bilateral mammographic tissue density asymmetry could be an important factor in assessing risk of developing breast cancer and improving the detection of the suspicious lesions. This study aims to assess whether fusion of the bilateral mammographic density asymmetrical information into a computer-aided detection (CAD) scheme could improve CAD performance in detecting mass-like breast cancers. A testing dataset involving 1352 full-field digital mammograms (FFDM) acquired from 338 cases was used. In this dataset, half (169) cases are positive containing malignant masses and half are negative. Two computerized schemes were first independently applied to process FFDM images of each case. The first single-image based CAD scheme detected suspicious mass regions on each image. The second scheme detected and computed the bilateral mammographic tissue density asymmetry for each case. A fusion method was then applied to combine the output scores of the two schemes. The CAD performance levels using the original CAD-generated detection scores and the new fusion scores were evaluated and compared using a free-response receiver operating characteristic (FROC) type data analysis method. By fusion with the bilateral mammographic density asymmetrical scores, the case-based CAD sensitivity was increased from 79.2% to 84.6% at a false-positive rate of 0.3 per image. CAD also cued more "difficult" masses with lower CAD-generated detection scores while discarded some "easy" cases. The study indicated that fusion between the scores generated by a single-image based CAD scheme and the computed bilateral mammographic density asymmetry scores enabled to increase mass detection sensitivity in particular to detect more subtle masses.

  20. Noise temperature improvement for magnetic fusion plasma millimeter wave imaging systems.

    PubMed

    Lai, J; Domier, C W; Luhmann, N C

    2014-03-01

    Significant progress has been made in the imaging and visualization of magnetohydrodynamic and microturbulence phenomena in magnetic fusion plasmas [B. Tobias et al., Plasma Fusion Res. 6, 2106042 (2011)]. Of particular importance have been microwave electron cyclotron emission imaging and microwave imaging reflectometry systems for imaging T(e) and n(e) fluctuations. These instruments have employed heterodyne receiver arrays with Schottky diode mixer elements directly connected to individual antennas. Consequently, the noise temperature has been strongly determined by the conversion loss with typical noise temperatures of ~60,000 K. However, this can be significantly improved by making use of recent advances in Monolithic Microwave Integrated Circuit chip low noise amplifiers to insert a pre-amplifier in front of the Schottky diode mixer element. In a proof-of-principle design at V-Band (50-75 GHz), significant improvement of noise temperature from the current 60,000 K to measured 4000 K has been obtained. PMID:24689579

  1. Multi-sensor fusion with interacting multiple model filter for improved aircraft position accuracy.

    PubMed

    Cho, Taehwan; Lee, Changho; Choi, Sangbang

    2013-01-01

    The International Civil Aviation Organization (ICAO) has decided to adopt Communications, Navigation, and Surveillance/Air Traffic Management (CNS/ATM) as the 21st century standard for navigation. Accordingly, ICAO members have provided an impetus to develop related technology and build sufficient infrastructure. For aviation surveillance with CNS/ATM, Ground-Based Augmentation System (GBAS), Automatic Dependent Surveillance-Broadcast (ADS-B), multilateration (MLAT) and wide-area multilateration (WAM) systems are being established. These sensors can track aircraft positions more accurately than existing radar and can compensate for the blind spots in aircraft surveillance. In this paper, we applied a novel sensor fusion method with Interacting Multiple Model (IMM) filter to GBAS, ADS-B, MLAT, and WAM data in order to improve the reliability of the aircraft position. Results of performance analysis show that the position accuracy is improved by the proposed sensor fusion method with the IMM filter. PMID:23535715

  2. Improved Guided Image Fusion for Magnetic Resonance and Computed Tomography Imaging

    PubMed Central

    Jameel, Amina

    2014-01-01

    Improved guided image fusion for magnetic resonance and computed tomography imaging is proposed. Existing guided filtering scheme uses Gaussian filter and two-level weight maps due to which the scheme has limited performance for images having noise. Different modifications in filter (based on linear minimum mean square error estimator) and weight maps (with different levels) are proposed to overcome these limitations. Simulation results based on visual and quantitative analysis show the significance of proposed scheme. PMID:24695586

  3. Multi-focus image fusion based on improved spectral graph wavelet transform

    NASA Astrophysics Data System (ADS)

    Yan, Xiang; Qin, Hanlin; Chen, Zhimin; Zhou, Huixin; Li, Jia; Zong, Jingguo

    2015-10-01

    Due to the limited depth-of-focus of optical lenses in imaging camera, it is impossible to acquire an image with all parts of the scene in focus. To make up for this defect, fusing the images at different focus settings into one image is a potential approach and many fusion methods have been developed. However, the existing methods can hardly deal with the problem of image detail blur. In this paper, a novel multiscale geometrical analysis called the directional spectral graph wavelet transform (DSGWT) is proposed, which integrates the nonsubsampled directional filter bank with the traditional spectral graph wavelet transform. Through combines the feature of efficiently representing the image containing regular or irregular areas of the spectral graph wavelet transform with the ability of capturing the directional information of the directional filter bank, the DSGWT can better represent the structure of images. Given the feature of the DSGWT, it is introduced to multi-focus image fusion to overcome the above disadvantage. On the one hand, using the high frequency subbands of the source images are obtained by the DSGWT, the proposed method efficiently represents the source images. On the other hand, using morphological filter to process the sparse feature matrix obtained by sum-modified-Laplacian focus measure criterion, the proposed method generates the fused subbands by morphological filtering. Comparison experiments have been performed on different image sets, and the experimental results demonstrate that the proposed method does significantly improve the fusion performance compared to the existing fusion methods.

  4. Study of Mechanical Properties and Characterization of Pipe Steel welded by Hybrid (Friction Stir Weld + Root Arc Weld) Approach

    SciTech Connect

    Lim, Yong Chae; Sanderson, Samuel; Mahoney, Murray; Wasson, Andrew J; Fairchild, Doug P; Wang, Yanli; Feng, Zhili

    2015-01-01

    Friction stir welding (FSW) has recently attracted attention as an alternative construction process for gas/oil transportation applications due to advantages compared to fusion welding techniques. A significant advantage is the ability of FSW to weld the entire or nearly the entire wall thickness in a single pass, while fusion welding requires multiple passes. However, when FSW is applied to a pipe or tube geometry, an internal back support anvil is required to resist the plunging forces exerted during FSW. Unfortunately, it may not be convenient or economical to use internal backing support due to limited access for some applications. To overcome this issue, ExxonMobil recently developed a new concept, combining root arc welding and FSW. That is, a root arc weld is made prior to FSW that supports the normal loads associated with FSW. In the present work, mechanical properties of a FSW + root arc welded pipe steel are reported including microstructure and microhardness.

  5. 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.

  6. Electric arc welding gun

    DOEpatents

    Luttrell, Edward; Turner, Paul W.

    1978-01-01

    This invention relates to improved apparatus for arc welding an interior joint formed by intersecting tubular members. As an example, the invention is well suited for applications where many similar small-diameter vertical lines are to be welded to a long horizontal header. The improved apparatus includes an arc welding gun having a specially designed welding head which is not only very compact but also produces welds that are essentially free from rolled-over solidified metal. The welding head consists of the upper end of the barrel and a reversely extending electrode holder, or tip, which defines an acute angle with the barrel. As used in the above-mentioned example, the gun is positioned to extend upwardly through the vertical member and the joint to be welded, with its welding head disposed within the horizontal header. Depending on the design of the welding head, the barrel then is either rotated or revolved about the axis of the vertical member to cause the electrode to track the joint.

  7. An Improved WiFi Indoor Positioning Algorithm by Weighted Fusion

    PubMed Central

    Ma, Rui; Guo, Qiang; Hu, Changzhen; Xue, Jingfeng

    2015-01-01

    The rapid development of mobile Internet has offered the opportunity for WiFi indoor positioning to come under the spotlight due to its low cost. However, nowadays the accuracy of WiFi indoor positioning cannot meet the demands of practical applications. To solve this problem, this paper proposes an improved WiFi indoor positioning algorithm by weighted fusion. The proposed algorithm is based on traditional location fingerprinting algorithms and consists of two stages: the offline acquisition and the online positioning. The offline acquisition process selects optimal parameters to complete the signal acquisition, and it forms a database of fingerprints by error classification and handling. To further improve the accuracy of positioning, the online positioning process first uses a pre-match method to select the candidate fingerprints to shorten the positioning time. After that, it uses the improved Euclidean distance and the improved joint probability to calculate two intermediate results, and further calculates the final result from these two intermediate results by weighted fusion. The improved Euclidean distance introduces the standard deviation of WiFi signal strength to smooth the WiFi signal fluctuation and the improved joint probability introduces the logarithmic calculation to reduce the difference between probability values. Comparing the proposed algorithm, the Euclidean distance based WKNN algorithm and the joint probability algorithm, the experimental results indicate that the proposed algorithm has higher positioning accuracy. PMID:26334278

  8. An Improved WiFi Indoor Positioning Algorithm by Weighted Fusion.

    PubMed

    Ma, Rui; Guo, Qiang; Hu, Changzhen; Xue, Jingfeng

    2015-01-01

    The rapid development of mobile Internet has offered the opportunity for WiFi indoor positioning to come under the spotlight due to its low cost. However, nowadays the accuracy of WiFi indoor positioning cannot meet the demands of practical applications. To solve this problem, this paper proposes an improved WiFi indoor positioning algorithm by weighted fusion. The proposed algorithm is based on traditional location fingerprinting algorithms and consists of two stages: the offline acquisition and the online positioning. The offline acquisition process selects optimal parameters to complete the signal acquisition, and it forms a database of fingerprints by error classification and handling. To further improve the accuracy of positioning, the online positioning process first uses a pre-match method to select the candidate fingerprints to shorten the positioning time. After that, it uses the improved Euclidean distance and the improved joint probability to calculate two intermediate results, and further calculates the final result from these two intermediate results by weighted fusion. The improved Euclidean distance introduces the standard deviation of WiFi signal strength to smooth the WiFi signal fluctuation and the improved joint probability introduces the logarithmic calculation to reduce the difference between probability values. Comparing the proposed algorithm, the Euclidean distance based WKNN algorithm and the joint probability algorithm, the experimental results indicate that the proposed algorithm has higher positioning accuracy. PMID:26334278

  9. Recent processing string and fusion algorithm improvements for automated sea mine classification in shallow water

    NASA Astrophysics Data System (ADS)

    Aridgides, Tom; Fernandez, Manuel F.; Dobeck, Gerald J.

    2003-09-01

    A novel sea mine computer-aided-detection / computer-aided-classification (CAD/CAC) processing string has been developed. The overall CAD/CAC processing string consists of pre-processing, adaptive clutter filtering (ACF), normalization, detection, feature extraction, feature orthogonalization, optimal subset feature selection, classification and fusion processing blocks. The range-dimension ACF is matched both to average highlight and shadow information, while also adaptively suppressing background clutter. For each detected object, features are extracted and processed through an orthogonalization transformation, enabling an efficient application of the optimal log-likelihood-ratio-test (LLRT) classification rule, in the orthogonal feature space domain. The classified objects of 4 distinct processing strings are fused using the classification confidence values as features and logic-based, "M-out-of-N", or LLRT-based fusion rules. The utility of the overall processing strings and their fusion was demonstrated with new shallow water high-resolution sonar imagery data. The processing string detection and classification parameters were tuned and the string classification performance was optimized, by appropriately selecting a subset of the original feature set. A significant improvement was made to the CAD/CAC processing string by utilizing a repeated application of the subset feature selection / LLRT classification blocks. It was shown that LLRT-based fusion algorithms outperform the logic based and the "M-out-of-N" ones. The LLRT-based fusion of the CAD/CAC processing strings resulted in up to a nine-fold false alarm rate reduction, compared to the best single CAD/CAC processing string results, while maintaining a constant correct mine classification probability.

  10. 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.