Sample records for weld pool size

  1. Determination of a temperature sensor location for monitoring weld pool size in GMAW

    SciTech Connect

    Boo, K.S.; Cho, H.S. (Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Precision Engineering and Mechatronics)

    1994-11-01

    This paper describes a method of determining the optimal sensor location to measure weldment surface temperature, which has a close correlation with weld pool size in the gas metal arc (GMA) welding process. Due to the inherent complexity and nonlinearity in the GMA welding process, the relationship between the weldment surface temperature and the weld pool size varies with the point of measurement. This necessitates an optimal selection of the measurement point to minimize the process nonlinearity effect in estimating the weld pool size from the measured temperature. To determine the optimal sensor location on the top surface of the weldment, the correlation between the measured temperature and the weld pool size is analyzed. The analysis is done by calculating the correlation function, which is based upon an analytical temperature distribution model. To validate the optimal sensor location, a series of GMA bead-on-plate welds are performed on a medium-carbon steel under various welding conditions. A comparison study is given in detail based upon the simulation and experimental results.

  2. Weld pool phenomena

    SciTech Connect

    David, S.A.; Vitek, J.M.; Zacharia, T. [Oak Ridge National Lab., TN (United States); DebRoy, T. [Pennsylvania State Univ., University Park, PA (United States)

    1994-09-01

    During welding, the composition, structure and properties of the welded structure are affected by the interaction of the heat source with the metal. The interaction affects the fluid flow, heat transfer and mass transfer in the weld pool, and the solidification behavior of the weld metal. In recent years, there has been a growing recognition of the importance of the weld pool transport processes and the solid state transformation reactions in determining the composition, structure and properties of the welded structure. The relation between the weld pool transport processes and the composition and structure is reviewed. Recent applications of various solidification theories to welding are examined to understand the special problems of weld metal solidification. The discussion is focussed on the important problems and issues related to weld pool transport phenomena and solidification. Resolution of these problems would be an important step towards a science based control of composition, structure and properties of the weld metal.

  3. Gravitational effects on the GTA weld pool size of a pure metal

    NASA Astrophysics Data System (ADS)

    Domey, Jeffrey John

    Understanding the physical phenomena involved in the welding process is of substantial value to improving the weldability of materials. The nature of arc welding restricts direct observation during the welding process to surface phenomena, and physical observation of the weld is limited to solidified welds. Thus, accurate computational simulations are needed to provide a better understanding of the transient phenomena that are present during the welding process. One of the major factors affecting the motion within the molten weld pool is the gravity-driven buoyancy force. This force opposes the electromagnetic force induced flow for the straight polarity (direct-current electrode negative) GTA weld. The buoyancy force can also act to oppose or enhance the Marangoni convective flow within the weld pool depending on the sign of the surface tension temperature coefficient. An extensive study involving both numerical as well as physical experiments of the GTA welding process covering a variety of gravitational fields has been performed. Numerical experiments, utilizing the WELDER code, were conducted for stationary GTA welds onto an aluminum alloy. It was found that at a g-level of 0.1g, the convective flow was dominated by the electromagnetic force, while at higher g-levels, 1.0g and 2.0g, the convective flow was dominated by the buoyancy force. It was also found that the depth-to-width (d/w) ratio decreased as the g-level increased for 0.1g to 2.0g. Numerical experiments were also performed in the 1.0g to 10.0g range for stationary GTA welds onto commercially pure nickel. It was found that the electro-magnetic force dominated all of the simulations, although as the g-level increased, the buoyancy force increased causing a decrease in the depth of the fusion zone. This decrease in depth caused a decrease in the d/w ratio of the fusion zone as the g-level increased. Physical experiments for GTA welding of commercially pure nickel in the high-g range (up to 10.0g) were conducted in the Multi-Gravitational Research Welding System (MGRWS) at Clarkson University. It was found that the results were consistent with those found numerically. Specifically, the depths decreased as the g-level increased causing a decrease in the d/w ratio. In addition, a trace element of iron was added to the stationary GTA welds of commercially pure nickel. Similar to the previous results, it was found that the d/w ratio decreased with and increase in the g-level, though the decrease was smaller in magnitude. From the stationary GTA welding experiments performed numerically for the aluminum alloy and both physically and numerically for commercially pure nickel, it is concluded that an increase in g-level causes a decrease in the d/w ratio.

  4. Camera Would Monitor Weld-Pool Contours

    NASA Technical Reports Server (NTRS)

    Gordon, Stephen S.; Gutow, David A.

    1990-01-01

    Weld pool illuminated and viewed coaxially along welding torch. Proposed monitoring subsystem for arc welder provides image in which horizontal portions of surface of weld pool highlighted. Monitoring and analyzing subsystems integrated into overall control system of robotic welder. Control system sets welding parameters to adapt to changing conditions, maintaining surface contour giving desired pattern of reflections.

  5. The study of surface active element on weld pool development in A-TIG welding

    NASA Astrophysics Data System (ADS)

    Zhao, Yuzhen; Zhou, Heping; Shi, Yaowu

    2006-04-01

    A 3D mathematical model was developed to simulate the weld pool development in a moving A-TIG weld pool with different oxygen and sulfur concentrations. It is shown that the surface active elements—oxygen and sulfur, which change the temperature coefficient of surface tension from a negative value to a positive one, can cause significant changes in fluid flow patterns and the weld penetration. When surface active element content increases, the weld penetration and depth/width ratio increase sharply and then remain nearly a constant. Positive temperature coefficient of surface tension dominates the fluid flow and the weld pool is narrow and deep. The further increasing surface active element content leads to an inappreciable difference in the weld pool size and shape when the oxygen content increases beyond 280 ppm and sulfur content beyond 125 ppm. Positive and negative temperature coefficients of surface tension co-exist in the weld pool when surface active element content is less than the critical value. The fluid flows in the weld pool change apparently with different surface active element. Depending upon the oxygen and sulfur concentrations, three, one or two vortexes that have different positions, strength and directions may be found in the weld pool. The vortexes with opposite direction caused by positive temperature coefficient of surface tension can efficiently transfer the thermal energy from the arc, creating a deep weld pool.

  6. Neural control of weld pool in the robotic welding

    Microsoft Academic Search

    Yasuyoshi Kaneko; Satoshi Yamane; Katsuya Kugai; Kenji Ohshima

    1994-01-01

    This paper deals with some problems concerning the controlling of the weld pool shape. The model of the weld pool is represented by using the RC circuit, where the resistance R corresponds to the thermal resistance. The authors try to keep the voltage across the capacitor C constant, regardless of the variation of R, by controlling the applied voltage to

  7. 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.

  8. A keyhole volumetric model for weld pool analysis in Nd:YAG pulsed laser welding

    NASA Astrophysics Data System (ADS)

    Kuang, Jao-Hwa; Hung, Tsung-Pin; Chen, Chih-Kuan

    2012-07-01

    This study presents a new model for analyzing the temperature distribution and weld pool shape in Nd:YAG pulsed laser welding. In the proposed approach, a surface flux heat transfer model is applied in the low laser energy intensity region of the weld, while a keyhole heat transfer model based on a volumetric heat source is applied in the high laser energy intensity region of the weld. The correlation between the intensity of the laser input energy and the geometric parameters of the volumetric heat source is derived experimentally. A series of MARC finite element simulations based on the proposed single pulse model are performed to investigate the shape and size of the weld pool given different laser energy intensities. A good agreement is observed between the simulation results and the experimental results obtained under equivalent single pulse welding conditions. Thus, the basic validity of the proposed model is confirmed.

  9. Weld Pool Stability in the Flat Position

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.; Coan, B.

    1999-01-01

    The Soft Plasma Arc (SPA) process was devised to avoid interactions between backshield and full penetration mode plasma jet in welding 2195 aluminum-lithium alloy. Occasional sudden and mysterious losses in penetration were encountered in flat position SPA welding. To understand what was happening a model of the dynamics of the molten metal meniscus at the root of the weld was worked out. When the power input to the weld P(sub in) exceeds the power leakage P(sub out) the difference in power is absorbed by an increase in the molten weld pool volume V, Rho X L(SUB m) X (d(V)/dt)) = P(sub in) - P(sub out) where rho is the density and L(sub m) the specific heat of the weld metal.

  10. Heat and fluid flow in pulsed current GTA weld pool

    Microsoft Academic Search

    W.-H. Kim; S.-J. Na

    1998-01-01

    In this study the heat transfer, fluid flow and phase change of the weld pool in pulsed current gas tungsten arc (GTA) welding were investigated. Transporting phenomena from the welding arc to the base material surface, such as current density, heat flux, arc pressure and shear stress acting on the weld pool surface, were taken from the simulation results of

  11. Vision detection of weld pool shape parameters and numerical simulation

    NASA Astrophysics Data System (ADS)

    Yuan, Youzhi; Liu, Nansheng; Wang, Yanfeng; Luo, Wei; Liu, Xiaorui

    2008-12-01

    An active vision sensing system which established by low power laser and common CCD is used to shoot GTAW welding pool images. Based on choose the appropriate LASER and filters, projected angle of laser and shoot angle of CCD, we avoid the disturbance of arc effectively and obtain clear images of the welding pool. The shape parameters of welding pool can obtain by demarcated and calculated. And then a three-dimentional numerical model of GTAW welding pool is established based on the theories of fluid dynamics and heat transfer. It considered the convection heat transfer of liquid metal and heat conduction of solid metal. And FLUENT software is used for simulate the GTAW welding pool. Extract the weld pool shape parameters and done comparative study with the vision detection of pool. This will be beneficial to avoid repeat experiments and improve work efficiency.

  12. Sensing and control of weld pool by fuzzy-neural network in robotic welding system

    Microsoft Academic Search

    A. Hirai; Y. Kaneko; T. Hosoda; S. Yamane; K. Oshima

    2001-01-01

    It is important to control the penetration depth of the weld pool during welding, so as to obtain a good-quality weld, but it may be difficult to detect the penetration depth directly by using a visual sensor. In order to detect the penetration depth, the authors propose a penetration depth model based on a neural network. During welding, a fuzzy

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

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

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

  14. CHANGES OF WELD POOL SHAPE BY VARIATIONS IN THE DISTRIBUTION OF HEAT SOURCE IN ARC WELDING

    E-print Network

    Eagar, Thomas W.

    of Technology Cambridge, HA 02139 USA Summar y Weld width , penetr ation, and cross-sectional ar ea were · convection and surface depression in weld pool (8]. Although Christensen's experimental results indicate

  15. Process parameter selection for optimizing the weld pool geometry in the tungsten inert gas welding of stainless steel

    Microsoft Academic Search

    S. C Juang; Y. S Tarng

    2002-01-01

    In this paper, the selection of process parameters for obtaining an optimal weld pool geometry in the tungsten inert gas (TIG) welding of stainless steel is presented. Basically, the geometry of the weld pool has several quality characteristics, for example, the front height, front width, back height and back width of the weld pool. To consider these quality characteristics together

  16. Dynamic behavior of the weld pool in stationary GMAW

    NASA Astrophysics Data System (ADS)

    Chapuis, J.; Romero, E.; Bordreuil, C.; Soulié, F.; Fras, G.

    2010-06-01

    Because hump formation limits welding productivity, better understanding of the humping phenomena during the welding process is needed to access to process modifications that decrease the tendency for hump formation and then allow higher productivity welding. From a physical point of view, the mechanism identified is the Rayleigh instability initiated by strong surface tension gradient which induces a variation of kinetic flow. But the causes of the appearance of this instability are not yet well explained. Because of the phenomena complex and multi-physics, we chose in first step to conduct an analysis of the characteristic times involved in weld pool in pulsed stationary GMAW. The goal is to study the dynamic behavior of the weld pool, using our experimental multi physics approach. The experimental tool and methodology developed to understand these fast phenomena are presented first: frames acquisition with high speed digital camera and specific optical devices, numerical library. The analysis of geometric parameters of the weld pool during welding operation are presented in the last part: we observe the variations of wetting angles (or contact lines angles), the base and the height of the weld pool (macro-drop) versus weld time.

  17. Modeling of laser ultrasound generation in a weld pool

    NASA Astrophysics Data System (ADS)

    Johnson, J. A.

    Finite element techniques are used to model laser generation of ultrasound and its propagation through a weld pool. The laser generation is modeled by assuming the reactive force to the laser ablation of the liquid is a stress perpendicular to the surface of the pool. The boundary of the pool is assumed to be spherical. The propagation of the sound waves from the laser source through the boundary into the solid metal is calculated assuming homogeneous properties in both the liquid and solid metal and temperature gradient effects are neglected. The results are compared to a series of experiments on real and simulated weld pools.

  18. Real time polarization imaging of weld pool surface

    NASA Astrophysics Data System (ADS)

    Stolz, C.; Coniglio, N.; Mathieu, A.; Aubreton, O.

    2015-04-01

    The search for an efficient on-line monitoring system focused on the real-time analysis of arc welding quality is an active area of research. The topography and the superficial temperature field of the weld pool can provide important information which can be used to regulate the welding parameters for depositing consistent welds. One difficulty relies on accessing this information despite the bright dazzling welding arc. In the present work, Stokes polarimetry and associated shape-from-polarization methods are applied for the analysis of the weld pool through its 810 nm-wavelength infrared emissions. The obtained information can provide a better understanding of the process, such as the usage of the topography to seek Marangoni flows direction, or to have a denser 3D map to improve numerical simulation models.

  19. A study of arc force, pool depression and weld penetration during gas tungsten arc welding

    SciTech Connect

    Rokhlin, S.I.; Guu, A.C. (Ohio State Univ., Columbus, OH (United States). Dept. of Welding Engineering)

    1993-08-01

    Weld pool depression, arc force, weld penetration, and their interrelations have been studied as a function of welding current. Pool depression and welding arc force have been measured simultaneously using a recently developed technique. The authors found quadratic dependence of arc force on current, confirming similar findings in previous studies. Pool depression is essentially zero below a threshold level of current (200 A in this experiment) and then increases quadratically with current. A perfectly linear relation between arc force and pool depression was found in the current range from 200 to 350 A, with pool depression onset at about 0.35 g force (0.34 [center dot] 10[sup [minus]2]N). The total surface tension and gravitational forces were calculated, from the measured surface topography, and found to be about five times that required to balance the arc force at 300 A. Thus electromagnetic and hydrodynamic forces must be taken into account to explain the measured levels of pool depression. The relation between weld penetration and pool depression for different welding currents has been established. Three distinct regimes of weld penetration on weld current were found.

  20. Influence of Arc Pressure on Weld Pool Geometry

    E-print Network

    Eagar, Thomas W.

    as a possible mechanism to explain the deep surface depression encountered at currents over 300 amperes ABSTRACT. At currents over 300 amperes, the surface of the weld pool becomes markedly depressed and the assumption depression under the action of the arc pressure has been calculated. At currents of 300 amperes, it is found

  1. Stability of Full Penetration, Flat Position Weld Pools

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.; Coan, Al. B.

    1999-01-01

    The dynamics of the dropthrough distance of a full penetration, flat position weld pool is described. Close to incipient root side penetration the dropthrough is metastable, so that a small drop in power can cause a loss of penetration if not followed soon enough by a compensating rise in power. The SPA (Soft Plasma Arc) process with higher pressure on top of the weld pool loses penetration more quickly than the GTA (Gas Tungsten Arc) process. 2195 aluminum-lithium alloy with a lower surface tension loses penetration more quickly than 2219 aluminum alloy. An instance of loss of penetration of a SPA weld in 2195 aluminum-lithium alloy is discussed in the light of the model.

  2. Mathematical formulation and simulation of specular reflection based measurement system for gas tungsten arc weld pool surface

    Microsoft Academic Search

    G Saeed; Y M Zhang

    2003-01-01

    Weld pool surface can change dynamically during welding and is indicative of information critical to controlling the process. Research has picked up in the field of observing the weld pool surface to understand the dynamics of the welding process. This paper will help visualize and understand the physics involved in observing the weld pool surface. A study of laser properties,

  3. Reflection of illumination laser from gas metal arc weld pool surface

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoji; Zhang, Yu Ming

    2009-11-01

    The weld pool is the core of the welding process where complex welding phenomena originate. Skilled welders acquire their process feedback primarily from the weld pool. Observation and measurement of the three-dimensional weld pool surface thus play a fundamental role in understanding and future control of complex welding processes. To this end, a laser line is projected onto the weld pool surface in pulsed gas metal arc welding (GMAW) and an imaging plane is used to intercept its reflection from the weld pool surface. Resultant images of the reflected laser are analyzed and it is found that the weld pool surface in GMAW does specularly reflect the projected laser as in gas tungsten arc welding (GTAW). Hence, the weld pool surface in GMAW is also specular and it is in principle possible that it may be observed and measured by projecting a laser pattern and then intercepting and imaging the reflection from it. Due to high frequencies of surface fluctuations, GMAW requires a relatively short time to image the reflected laser.

  4. Using Taguchi method to optimize welding pool of dissimilar laser-welded components

    NASA Astrophysics Data System (ADS)

    Anawa, E. M.; Olabi, A. G.

    2008-03-01

    In the present work, CO 2 continuous laser welding process was successfully applied and optimized for joining a dissimilar AISI 316 stainless-steel and AISI 1009 low carbon steel plates. Laser power, welding speed and defocusing distance combinations were carefully selected with the objective of producing welded joint with complete penetration, minimum fusion zone size and acceptable welding profile. Fusion zone area and shape of dissimilar austenitic stainless-steel with ferritic low carbon steel were evaluated as a function of the selected laser welding parameters. Taguchi approach was used as statistical design of experiment (DOE) technique for optimizing the selected welding parameters in terms of minimizing the fusion zone. Mathematical models were developed to describe the influence of the selected parameters on the fusion zone area and shape, to predict its value within the limits of the variables being studied. The result indicates that the developed models can predict the responses satisfactorily.

  5. Alloying element vaporization and weld pool temperature during laser welding of AlSl 202 stainless steel

    Microsoft Academic Search

    P. A. A. Khan; T. Debroy

    1984-01-01

    Alloying element vaporization rates, plasma composition, and the changes in weld composition during laser welding of 202 stainless\\u000a steel are discussed in this paper. Iron, manganese, and chromium were the most dominant species in the plasma. During laser\\u000a welding it is always a difficult task to measure the temperature of the weld pool since this region is surrounded by hot

  6. THESIS FOR THE DEGREE OF LICENTIATE OF PHILOSOPHY Weld Pool Simulations

    E-print Network

    Patriksson, Michael

    pointing in the directions of the surface normal. Printed in G¨oteborg, Sweden 2008 #12;iii #12;Weld Pool accurate prediction of the quality of the weldment that is created once the pool has solidified. Keywords

  7. A smart model to estimate effective thermal conductivity and viscosity in the weld pool

    NASA Astrophysics Data System (ADS)

    De, A.; DebRoy, T.

    2004-05-01

    Calculations of fluid flow and heat transfer in the weld pool are strongly influenced by the values of effective thermal conductivity and effective viscosity of the liquid metal. The values of these variables are uncertain since the welding conditions and the fluid flow characteristics within the weld pool influence them. Following an inverse modeling approach, the present work develops a smart model that embodies a multivariable optimization scheme within the framework of a phenomenological heat transfer and fluid flow model to estimate the uncertain parameters necessary for weld pool modeling. The optimization scheme considers the sensitivity of the calculated weld geometry with respect to the unknown parameters. To avoid unrealistic optimized solutions, the smart model is internally guided to look for only the physically significant solutions. The model could estimate the effective thermal conductivity and effective viscosity for conduction mode laser welding as a function of nondimensional heat input from six sets of experimental measurements of weld pool depth and width.

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

    NASA Astrophysics Data System (ADS)

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

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

  9. Three-dimensional reconstruction of specular surface for a gas tungsten arc weld pool

    NASA Astrophysics Data System (ADS)

    Song, Hong Sheng; Zhang, Yu Ming

    2007-12-01

    Observing the weld pool and measuring its geometrical parameters are key issues for developing the next generation intelligent welding machine and modeling the complex welding process. In the past few years, different techniques have been applied, but the dynamic specular weld pool surface and the strong weld arc complicate these approaches and make observation difficult. To resolve the problem, a new three-dimensional sensing system using structured light is proposed for a gas tungsten arc welding (GTAW) process. In the system, a dot-matrix laser pattern is projected on the specular weld pool surface, which can reflect light onto an imaging plane. The reflected images are captured by a high-speed camera and can successfully be processed by image processing algorithms developed. With the acquired information, a three-dimensional reconstruction scheme is proposed and discussed in this paper. A surface reconstruction method with several slope-based algorithms is first developed to rebuild the region of weld pool surface which reflects the laser pattern. Then a two-dimensional piecewise model is provided to calculate weld pool boundary by utilizing the edge condition. Finally the optimal estimate of the three-dimensional weld pool surface is synthesized. The acceptable accuracy of the results verified the effectiveness of the reconstruction scheme.

  10. Convection in Arc Weld Pools Electromagnetic and surface tension forces are shown to

    E-print Network

    Eagar, Thomas W.

    Convection in Arc Weld Pools Electromagnetic and surface tension forces are shown to dominate flow and heat flow in weld pools is of considerable practical interest because convective heat flow will affect majority of heat flow analyses, no allowance has been made for convective heat flow in the melt

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

    SciTech Connect

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

    1988-01-01

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

  12. Development of maintenance technology with underwater TIG welding for spent fuel storage pool

    Microsoft Academic Search

    Takeshi Obana; Yasumitsu Hamada; Toshihiro Ootsuka; Seiichi Toyoda; Atsushi Hosogane; Kaoru Ooeda; Masahide Katou

    2009-01-01

    The core technology of an underwater TIG welding process has been developed and a welding equipment system has been manufactured for application to the maintenance of the spent fuel storage pool of Rokkasho reprocessing plant. Basic experiments for understanding the conditions of the dry area and the range of welding conditions was performed, and mock examination for simulation of the

  13. In situ observations of weld pool solidification using transparent metal-analog systems

    NASA Astrophysics Data System (ADS)

    Trivedi, R.; David, S. A.; Eshelman, M. A.; Vitek, J. M.; Babu, S. S.; Hong, T.; DebRoy, T.

    2003-04-01

    The dynamics of weld solidification were observed in situ using a laser welding process on transparent organic materials systems. Succinonitrile was used to simulate a pure metal system and succinonitrile with 1.2 wt. % acetone was used to simulate an alloy system. Observed weld pool shapes in succinonitrile were in good agreement with theoretical heat transfer calculations. The dynamics of weld pool shape in the succinonitrile-acetone system were related to complex interactions between grain orientation, grain selection, and dendrite orientations, which depend strongly on welding speed. An increase in welding speed leads to a transition from a steady-state to a nonsteady-state weld pool shape. Several other phenomena, including epitaxial growth, grain selection process, grain boundary melting, and porosity formation, were also observed.

  14. Neural network model for predicting the backside dimension of weld pool during pulsed GTAW process

    NASA Astrophysics Data System (ADS)

    Zhao, Dongbin; Lou, Yajun; Chen, Shanben; Wu, Lin

    1998-10-01

    Pulsed GTAW was used widely in butt welding of thin plate. Top surface depression occurred without filler wire in full penetration, while reinforcement height was assured with filler wire. Currently butt welding process control of thin plate welding during pulsed GTAW with filler wire was depended on manual experience and the consistency of seam shape was hardly attained. Based on self-developed vision sensor, double-side images of weld pool were captured simultaneously in a frame. By image processing the topside dimension and shape of weld pool, such as area, length, maximum width, the similarity of reinforcement, and the coefficients of multinomial regression of boundary, and the backside dimension such as area, length, maximum width and the similarity of height were calculated. A fractional factorial technique was used to design the experiment. Artificial neural network was applied to establish the steady model for predicting backside dimension of weld pool. The input of the model was the topside dimension, shape of weld pool and welding parameters, such as pulse current, base current, arc voltage, pulse duty ratio, welding speed, and wire feeding rate. The output of the model was the backside dimension of weld pool. Finally the variance method was used to test the validity of the model.

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

    NASA Astrophysics Data System (ADS)

    Naito, Yasuaki; Katayama, Seiji; Matsunawa, Akira

    2003-03-01

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

  16. Analytical real-time measurement of a three-dimensional weld pool surface

    NASA Astrophysics Data System (ADS)

    Zhang, WeiJie; Wang, XueWu; Zhang, YuMing

    2013-11-01

    The ability to observe and measure weld pool surfaces in real-time is the core of the foundation for next generation intelligent welding that can partially imitate skilled welders who observe the weld pool to acquire information on the welding process. This study aims at the real-time measurement of the specular three-dimensional (3D) weld pool surface under a strong arc in gas tungsten arc welding (GTAW). An innovative vision system is utilized in this study to project a dot-matrix laser pattern on the specular weld pool surface. Its reflection from the surface is intercepted at a distance from the arc by a diffuse plane. The intercepted laser dots illuminate this plane producing an image showing the reflection pattern. The deformation of this reflection pattern from the projected pattern (e.g. the dot matrix) is used to derive the 3D shape of the reflection surface, i.e., the weld pool surface. Based on careful analysis, the underlying reconstruction problem is formulated mathematically. An analytic solution is proposed to solve this formulated problem resulting in the weld pool surface being reconstructed on average in 3.04 ms during welding experiments. A vision-based monitoring system is thus established to measure the weld pool surface in GTAW in real-time. In order to verify the effectiveness of the proposed reconstruction algorithm, first numerical simulation is conducted. The proposed algorithm is then tested on a spherical convex mirror with a priori knowledge of its geometry. The detailed analysis of the measurement error validates the accuracy of the proposed algorithm. Results from the real-time experiments verify the robustness of the proposed reconstruction algorithm.

  17. Experimental characterization of the weld pool flow in a TIG configuration

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  18. Use of Aria to simulate laser weld pool dynamics for neutron generator production.

    SciTech Connect

    Noble, David R.; Notz, Patrick K.; Martinez, Mario J.; Kraynik, Andrew Michael

    2007-09-01

    This report documents the results for the FY07 ASC Integrated Codes Level 2 Milestone number 2354. The description for this milestone is, 'Demonstrate level set free surface tracking capabilities in ARIA to simulate the dynamics of the formation and time evolution of a weld pool in laser welding applications for neutron generator production'. The specialized boundary conditions and material properties for the laser welding application were implemented and verified by comparison with existing, two-dimensional applications. Analyses of stationary spot welds and traveling line welds were performed and the accuracy of the three-dimensional (3D) level set algorithm is assessed by comparison with 3D moving mesh calculations.

  19. Weld pool penetration measurement using ultrasound with thermal gradient correction factors

    NASA Astrophysics Data System (ADS)

    Anderton, John Martin

    Weld penetration is critical to final weld performance. There are many techniques for determining surface parameters of weld pools but the transient nature of the pools, high temperatures and intense electromagnetic energy make direct measurement of the penetration of weld pools difficult. In order to determine weld pool penetration ultrasonically from below the weld pool it is necessary to compensate for the variation in the time of flight of the ultrasound wave due to temperature gradients. This requires both a precise understanding of the location and magnitude of the temperature gradients and the time of flight of ultrasound at the range of temperatures seen in the gradients. Given this information it is possible to develop a correction factor to an ultrasonic time of flight reading that accurately represents the actual penetration of a weld pool. This research examines the electroslag surfacing (ESS) processing of AISI 1005 low carbon steel clad onto a ductile iron substrate. The high temperature cladding on low temperature substrate provides a deep weld penetration. Ultrasonic time of flight measurements were made from a piezoelectric transducer on the backside of the substrate to the solid/liquid interface of the weld pool during welding. The speed of ultrasound over a range of temperatures was determined from furnace heated ductile iron substrates. The sample was stepped and contact piezoelectric methods used to determine time of flight. A finite element model was developed and analyzed to predict thermal gradients in the substrate around the weld pool. The model was correlated to thermocouple data of substrate heating during welding. The predicted thermal gradients and speed/temperature curves are combined with the time of flight measurement to determine the location of the solid/liquid weld interface. An automated seam tracking system for ESS was also developed. This system utilizes a line laser at right angles to the view of a CCD camera which illuminates the relief of the existing bead for the camera. Optimas software was used to locate the edge of the bead and determine the correct location for the weld head to overlap the existing bead.

  20. A three-dimensional sharp interface model for self-consistent keyhole and weld pool dynamics in deep penetration laser welding

    NASA Astrophysics Data System (ADS)

    Pang, Shengyong; Chen, Liliang; Zhou, Jianxin; Yin, Yajun; Chen, Tao

    2011-01-01

    A three-dimensional sharp interface model is proposed to investigate the self-consistent keyhole and weld pool dynamics in deep penetration laser welding. The coupling of three-dimensional heat transfer, fluid flow and keyhole free surface evolutions in the welding process is simulated. It is theoretically confirmed that under certain low heat input welding conditions deep penetration laser welding with a collapsing free keyhole could be obtained and the flow directions near the keyhole wall are upwards and approximately parallel to the keyhole wall. However, significantly different weld pool dynamics in a welding process with an unstable keyhole are numerically found. Many flow patterns in the welding process with an unstable keyhole, verified by x-ray transmission experiments, were successfully simulated and analysed. Periodical keyhole collapsing and bubble formation processes are also successfully simulated and believed to be in good agreement with experiments. The mechanisms of keyhole instability are found to be closely associated with the behaviour of humps on the keyhole wall, and it is found that the welding speed and surface tension are closely related to the formation of humps on the keyhole wall. It is also shown that the weld pool dynamics in laser welding with an unstable keyhole are closely associated with the transient keyhole instability and therefore modelling keyhole and weld pool in a self-consistent way is significant to understand the physics of laser welding.

  1. Monitoring of high-power fiber laser welding based on principal component analysis of a molten pool configuration

    NASA Astrophysics Data System (ADS)

    Xiangdong, Gao; Qian, Wen

    2013-12-01

    There exists plenty of welding quality information on a molten pool during high-power fiber laser welding. An approach for monitoring the high-power fiber laser welding status based on the principal component analysis (PCA) of a molten pool configuration is investigated. An infrared-sensitive high-speed camera was used to capture the molten pool images during laser butt-joint welding of Type 304 austenitic stainless steel plates with a high-power (10 kW) continuous wave fiber laser. In order to study the relationship between the molten pool configuration and the welding status, a new method based on PCA is proposed to analyze the welding stability by comparing the situation when the laser beam spot moves along, and when it deviates from the weld seam. Image processing techniques were applied to process the molten pool images and extract five characteristic parameters. Moreover, the PCA method was used to extract a composite indicator which is the linear combination of the five original characteristics to analyze the different status during welding. Experimental results showed that the extracted composite indicator had a close relationship with the actual welding results and it could be used to evaluate the status of the high-power fiber laser welding, providing a theoretical basis for the monitoring of laser welding quality.

  2. INFLUENCE OF SURFACE DEPRESSION AND CONVECTION ON ARC WELD POOL GEOMETRY

    E-print Network

    Eagar, Thomas W.

    ) ) INFLUENCE OF SURFACE DEPRESSION AND CONVECTION ON ARC WELD POOL GEOMETRY M. L. Lin and T. W. Eagar Materials Processing Center Massachusetts Institute of Technology Cambridge, Massachusetts ABSTRACT The relative importance of surface depression and convection in determining the depth of wel

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

    PubMed

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

    2014-05-01

    In the present paper, Boltzmann plot method was applied to analyze the temperature distributions of the are plasma when the gas pool coupled activating TIG welding was at different coupling degrees with the outer gas being O2. Based on this study of temperature distributions, the changing regularities of are voltage and are appearance were studied. The result shows that compared with traditional TIG welding, the introduction of O2 makes the welding arc constricted slightly, the temperature of the are center build up, and the are voltage increase. When argon being the inner gas, oxygen serving as the outer gas instead of argon makes the are constricted more obviously. When the coupling degree increases from 0 to 2, the temperature of the are center and the are voltage both increase slightly. In the gas pool coupled activating TIG welding the are is constricted not obviously, and the reason why the weld penetration is improved dramatically in the welding of stainless steel is not are constriction. PMID:25095400

  4. Effect of Shoulder Size on Weld Properties of Dissimilar Metal Friction Stir Welds

    NASA Astrophysics Data System (ADS)

    Akinlabi, E. T.

    2012-07-01

    This article reports a research study that shows the effect of shoulder diameter size on the resulting weld properties of dissimilar friction stir welds between 5754 aluminum alloy (AA) and C11000 copper (Cu). Welds were produced using three different shoulder diameter tools: 15, 18, and 25 mm by varying the rotational speed between 600 and 1200 rpm and the traverse speed between 50 and 300 mm/min to achieve the best result. Each parameter combination was chosen to represent different heat input conditions (low, intermediates and high). The welds were characterized through microstructural evaluation, tensile testing, microhardness measurements, x-ray diffraction analysis, and electrical resistivity. Microstructural evaluation of the welds revealed that the welds produced consisted of all the friction stir welding (FSW) microstructure zones with organized flow lines comprising mixture layers of aluminum (Al) and copper (Cu) at the Stir Zones. The average Ultimate Tensile Strength (UTS) of the welds considered ranged from 178 to 208 MPa. Higher Vickers microhardness values were measured at the joint interfaces of all the welds because of the presence of intermetallic compounds in these regions. The x-ray diffraction analysis revealed the presence of Al4Cu9 and Al2Cu intermetallics at the interfacial regions, and low electrical resistivities were obtained at the joint interfaces. An optimized parameter setting for FSW of Al and Cu was obtained at the weld produced at 950 rpm and 50 mm/min with the 18-mm shoulder diameter tool.

  5. Invertebrate community structure along a habitat-patch size gradient within a bog pool complex 

    E-print Network

    Towers, Naomi M.

    This thesis characterises species richness and community structure over a habitat-patch size gradient of a typical bog-pool complex, investigating the effect of pool size on aquatic invertebrate communities. In this study, twenty-two pools were...

  6. Taurocholate pool size and distribution in the fetal rat.

    PubMed Central

    Little, J M; Richey, J E; Van Thiel, D H; Lester, R

    1979-01-01

    Taurocholate concentrations in fetal and neonatal rats were determined by radioimmunoassay. Total body taurocholate pool size varied from 0.0049 +/- 0.0008 to 203 +/- 8 nmol/g body weight from day 5 of gestation to 5 d after birth. A 50-fold increase in taurocholate pool size was observed between days 15 and 19 of gestation. The distribution of taurocholate between liver, intestine, and the remainder of the carcass was determined for rats of gestational age 19 d to 5 d after birth. The major fraction of total body taurocholate was in the liver and intestine, with less than 15% in the remainder of the carcass. The ratio of taurocholate in intestine to taurocholate in liver, which was 1:17 at 19 d of gestation, had altered substantially to a ratio of 6:1 by 5 d after birth. Treatment of pregnant rats with 60 microgram/d of dexamethasone from gestational day 9 until sacrifice increased fetal taurocholate pool size by 80% at 15 d, 40% at 19 d, and 16% at 1 d after birth. Administration of dexamethasone to the mother also changed the ratio of taurocholate in intestine to taurocholate in liver. At 19 d of gestation, dexamethasone-treated mothers had fetuses with approximately equal amounts of taurocholate in intestine and liver. This suggested that adrenocorticosteroids stimulate the early maturation of factors controlling taurocholate pool size and tissue distribution in the rat fetus. PMID:447826

  7. WELDING RESEARCH -s85WELDING JOURNAL

    E-print Network

    Zhang, YuMing

    Welding is a labor-intensive operation. Although welding robots can provide con- sistent motion to help skilled human welders can achieve good weld quality through observing the weld pool, the pool surface mustWELDING RESEARCH -s85WELDING JOURNAL ABSTRACT. Measurement of weld pool surface is a difficult

  8. Gravity and Heater Size Effects on Pool Boiling Heat Transfer

    NASA Technical Reports Server (NTRS)

    Kim, Jungho; Raj, Rishi

    2014-01-01

    The current work is based on observations of boiling heat transfer over a continuous range of gravity levels between 0g to 1.8g and varying heater sizes with a fluorinert as the test liquid (FC-72/n-perfluorohexane). Variable gravity pool boiling heat transfer measurements over a wide range of gravity levels were made during parabolic flight campaigns as well as onboard the International Space Station. For large heaters and-or higher gravity conditions, buoyancy dominated boiling and heat transfer results were heater size independent. The power law coefficient for gravity in the heat transfer equation was found to be a function of wall temperature under these conditions. Under low gravity conditions and-or for smaller heaters, surface tension forces dominated and heat transfer results were heater size dependent. A pool boiling regime map differentiating buoyancy and surface tension dominated regimes was developed along with a unified framework that allowed for scaling of pool boiling over a wide range of gravity levels and heater sizes. The scaling laws developed in this study are expected to allow performance quantification of phase change based technologies under variable gravity environments eventually leading to their implementation in space based applications.

  9. Ultra-fast in-situ X-ray studies of evolving columnar dendrites in solidifying steel weld pools

    NASA Astrophysics Data System (ADS)

    Mirihanage, W. U.; Di Michiel, M.; Mathiesen, R. H.

    2015-06-01

    High-brilliance polychromatic synchrotron radiation has been used to conduct in-situ studies of the solidification microstructure evolution during simulated welding. The welding simulations were realized by rapidly fusing ? 5 mm spot in Fe-Cr-Ni steel. During the solid- liquid-solid phase transformations, a section of the weld pool was placed in an incident 50-150 keV polychromatic synchrotron X-ray beam, in a near-horizontal position at a very low inclination angle. Multiple high-resolution 2D detectors with very high frame rates were utilized to capture time resolved X-ray diffraction data from suitably oriented solid dendrites evolving in the weld pool. Comprehensive analysis of the diffraction data revealed individual and overall dendritic growth characteristics and relevant melt and solid flow dynamics during weld pool solidification, which was completed within 1.5 s. Columnar dendrite tip velocities were estimated from the experimental data and during early stages of solidification were exceeded 4 mm/s. The most remarkable observation revealed through the time-resolved reciprocal space observations are correlated to significant tilting of columnar type dendrites at their root during solidification, presumably caused by convective currents in the weld pool. When the columnar dendrite tilting are transformed to respective metric linear tilting velocities at the dendrite tip; tilting velocities are found to be in the same order of magnitude as the columnar tip growth velocities, suggesting a highly transient nature of growth conditions.

  10. Effects of shielding gas composition on arc profile and molten pool dynamics in gas metal arc welding of steels

    NASA Astrophysics Data System (ADS)

    Wang, L. L.; Lu, F. G.; Wang, H. P.; Murphy, A. B.; Tang, X. H.

    2014-11-01

    In gas metal arc welding, gases of different compositions are used to produce an arc plasma, which heats and melts the workpiece. They also protect the workpiece from the influence of the air during the welding process. This paper models gas metal arc welding (GMAW) processes using an in-house simulation code. It investigates the effects of the gas composition on the temperature distribution in the arc and on the molten pool dynamics in gas metal arc welding of steels. Pure argon, pure CO2 and different mixtures of argon and CO2 are considered in the study. The model is validated by comparing the calculated weld profiles with physical weld measurements. The numerical calculations reveal that gas composition greatly affects the arc temperature profile, heat transfer to the workpiece, and consequently the weld dimension. As the CO2 content in the shielding gas increases, a more constricted arc plasma with higher energy density is generated as a result of the increased current density in the arc centre and increased Lorentz force. The calculation also shows that the heat transferred from the arc to the workpiece increases with increasing CO2 content, resulting in a wider and deeper weld pool and decreased reinforcement height.

  11. Plasma-weld pool interaction in tungsten inert-gas configuration

    NASA Astrophysics Data System (ADS)

    Mougenot, J.; Gonzalez, J.-J.; Freton, P.; Masquère, M.

    2013-04-01

    A three-dimensional (3D) transient model of a transferred argon arc in interaction with an anode material is presented and the results discussed. The model based on a finite volume method is developed using the open software @Saturne distributed by Electricité de France. The 3D model includes the characterization of the plasma gas and of the work piece with a current continuity resolution in the whole domain. Transport and thermodynamic properties are dependent on the local temperature and on the vapours emitted by the eroded material due to the heat flux transferred by the plasma. Drag force, Marangoni force, Laplace and gravity forces are taken into account on the weld pool description. The plasma and the weld pool characteristics are presented and compared with experimental and theoretical results from the literature. For a distance between the two electrodes of d = 5 mm and an applied current intensity of I = 200 A, the vapour concentration is weak. The influence of the parameters used in the Marangoni formulation is highlighted. Finally, in agreement with some authors, we show with this global transient 3D model that it is not necessary to include the voltage drop in the energy balance.

  12. Possibility of Underwater Explosive Welding for Making Large-Sized Thin Metal Plate Clad by Overlapping Plates

    Microsoft Academic Search

    Kazuyuki Hokamoto; Akihisa Mori; Masahiro Fujita

    2008-01-01

    The authors have developed a new method of explosive welding using underwater shock wave for the welding of thin plate on a substrate. Considering the size limitation of the welding area in using the technique, the possibility of overlapping thin plates to make large-sized welding area is investigated. In general, the results for the welding of Inconel 600 on 304

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

    PubMed

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

    2013-04-01

    Studies in the field of environmental epidemiology indicate that for the adverse effect of inhaled particles not only particle mass is crucial but also particle size is. Ultrafine particles with diameters below 100 nm are of special interest since these particles have high surface area to mass ratio and have properties which differ from those of larger particles. In this paper, particle size distributions of various welding and joining techniques were measured close to the welding process using a fast mobility particle sizer (FMPS). It turned out that welding processes with high mass emission rates (manual metal arc welding, metal active gas welding, metal inert gas welding, metal inert gas soldering, and laser welding) show mainly agglomerated particles with diameters above 100 nm and only few particles in the size range below 50 nm (10 to 15%). Welding processes with low mass emission rates (tungsten inert gas welding and resistance spot welding) emit predominantly ultrafine particles with diameters well below 100 nm. This finding can be explained by considerably faster agglomeration processes in welding processes with high mass emission rates. Although mass emission is low for tungsten inert gas welding and resistance spot welding, due to the low particle size of the fume, these processes cannot be labeled as toxicologically irrelevant and should be further investigated. PMID:23028013

  14. Inorganic pyrophosphate pool size and turnover rate in arthritic joints.

    PubMed Central

    Camerlain, M; McCarty, D J; Silcox, D C; Jung, A

    1975-01-01

    Recent studies have shown elevated inorganic pyrophosphate (PPi) levels in most knee joint fluid supernates from patients with pseudogout (PG) or osteoarthritis (OA) and more modestly elevated levels in some supernates from patients with gout or rheumatoid arthritis (RA) relative to PPi levels found in the venous blood plasma of normal or arthritic subjects. We measured the intraarticular PPi pool and its rate of turnover to better understand the significance of the joint fluid-plasma PPi gradient. Preliminary studies in rabbits showed that (32-P)PPi passed from joint space to blood and vice versa without detectable hydrolysis. Incubation of natural or synthetic calcium pyrophosphate dihydrate (CPPD) microcrystals with synovial fluid in vitro in the presence of (32P)PPi tracer showed no change in PPi specific activity in the supernate over a 19-h period so that exchange of PPi in solution with that in CPPD microcrystals could be ignored. Clearance rates of (32P)PPi and of (33P)Pi, as determined by serially sampling the catheterized knee joints of volunteers with various types of arthritis over a 3-h period, were nearly identical. The (32P)PPi/(32P)Pi was determined in each sample. A mixture of a large excess of cold PPi did not influence the clearance rate of either nuclide. The quantity of PPi turned over per hous was calculated from the pool size as determined by isotope dilution and the turnover rate. The residual joint fluid nuclide was shown to be (32P)PPi. The PPi pool was generally smaller and the rate of turnover was greater in clinically inflamed joints. The mean plus or minus SEM pool size (mu-moles) and turnover rate (percent/hour) in PG knees was 0.23 plus or minus 0.07 and 117 plus or minus 11.9, hydrolysis rate (%/h) to Pi was 27.7 plus or minus 13.2; in OA knees: 0.45 plus or minus 0.26 and 72 plus or minus 9.2, hydrolysis 6.9 plus or minus 0.9; in gouty knees: 0.8 plus or minus 0.41 and 50 plus or minus 11.6, hydrolysis 9.8 plus or minus 2.8; and in RA knees: 0.14 plus or minus 0.14 and 114 plus or minus 35.8, hydrolysis 236 plus or minus 116. PPi turnover (mumoles/hour) correlated with the degree of OA change present in the joint as graded by radiologic criteria irrespective of the clinical diagnosis. Mean PPi turnover in joints with advanced OA was greater than in those with mild or moderate changes (P smaller than 0.001), but the mild and moderate groups showed no significant difference. We conclude that synovial PPi turnover and elevated PPi fluid concentrations are not specific for PG patients, and that these factors alone cannot be the only determinants of CPPD crystal deposition. PMID:166095

  15. Effects of pressure, orientation, and heater size on pool boiling of water with nanocoated heaters

    Microsoft Academic Search

    Sang M. Kwark; Miguel Amaya; Ratan Kumar; Gilberto Moreno; Seung M. You

    2010-01-01

    Parametric tests were experimentally conducted to observe the role of average nanoparticle size, pressure, heater orientation, and heater size during pool boiling of water using Al2O3 nanoparticle coated flat heaters. Results indicate that pool boiling performance is dependent on the parameters tested, except the nanoparticle size, for both uncoated and nanocoated surfaces. The nanoparticle coated heater consistently produced dramatic Critical

  16. An optical sensing system for seam tracking and weld pool control in gas metal arc welding of steel pipe

    Microsoft Academic Search

    K.-Y. Bae; T.-H. Lee; K.-C. Ahn

    2002-01-01

    A visual sensing system was developed for automatic gas metal arc welding (GMAW) of the root pass of steel pipe. The system consisted of a vision sensor that consisted of a charge-coupled device (CCD) camera and lenses, a frame grabber, image processing algorithms, and a computer controller. A specially designed five-axis manipulator was used to position the welding torch and

  17. Influence of the Diadinoxanthin Pool Size on Photoprotection in the Marine Planktonic Diatom Phaeodactylum tricornutum

    Microsoft Academic Search

    Johann Lavaud; Bernard Rousseau; Hans J. van Gorkom; Anne-Lise Etienne

    2002-01-01

    The pool size of the xanthophyll cycle pigment diadinoxanthin (DD) in the diatom Phaeodactylum tricornutum depends on illumination conditions during culture. Intermittent light caused a doubling of the DD pool without significant change in other pigment contents and photosynthetic parameters, including the photosystem II (PSII) antenna size. On exposure to high-light intensity, extensive de-epoxidation of DD to diatoxanthin (DT) rapidly

  18. REGULATION OF TRACHEBRONCHIAL TISSUE SPECIFIC STEM CELL POOL SIZE

    PubMed Central

    Ghosh, Moumita; Smith, Russell W.; Runkle, Christine M.; Hicks, Douglas A.; Helm, Karen M.; Reynolds, Susan D.

    2013-01-01

    Tissue specific stem cell (TSC) number is tightly regulated in normal individuals but can change following severe injury. We previously showed that tracheobronchial epithelial TSC number increased after severe naphthalene (NA)-injury and then returned to normal. The present study focused on the fate of the supernumerary TSC and the signals that regulate TSC pool size. We used the Keratin 5-rTA/Histone 2B:GFP model to purify basal cells that proliferated infrequently (GFPbright) or frequently (GFPdim) after NA-injury. Both populations contained TSC but TSC were 8.5-fold more abundant in the GFPbright population. Interestingly, both populations also contained a unipotential basal progenitor (UPB), a mitotic basal cell subtype whose daughters were terminally-differentiated basal cells. The ratio of TSC to UBP was 5:1 in the GFPbright population and 1:5 in the GFPdim population. These data suggested that TSC proliferation in vivo promoted TSC-to-UPB differentiation. To evaluate this question, we cloned TSC from the GFPbright and GFPdim populations and passaged the clones 7 times. We found that TSC number decreased and UPB number increased at each passage. Reciprocal changes in TSC and UPB frequency were more dramatic in the GFPdim lineage. Gene expression analysis showed that ?-catenin and Notch pathway genes were differentially expressed in freshly-isolated TSC derived from GFPbright and GFPdim populations. We conclude that: 1) TSC and UPB are members of a single lineage; 2) TSC proliferation in vivo or in vitro promotes TSC-to-UPB differentiation; and 3) an interaction between the ?-catenin and Notch pathways regulates the TSC-to-UPB differentiation process. PMID:23712882

  19. Neural network model for predicting the backside dimension of weld pool during pulsed GTAW process

    Microsoft Academic Search

    Dongbin Zhao; Yajun Lou; Shanben Chen; Lin Wu

    1998-01-01

    Pulsed GTAW was used widely in butt welding of thin plate. Top surface depression occurred without filler wire in full penetration, while reinforcement height was assured with filler wire. Currently butt welding process control of thin plate welding during pulsed GTAW with filler wire was depended on manual experience and the consistency of seam shape was hardly attained. Based on

  20. Surfactant phosphatidylcholine pool size in human neonates with congenital diaphragmatic hernia requiring ECMO

    Microsoft Academic Search

    Daphne J. M. T. Janssen; Dick Tibboel; Virgilio P. Carnielli; Esther van Emmen; Ingrid H. T. Luijendijk; J. L. Darcos Wattimena; Luc J. I. Zimmermann

    2003-01-01

    Objective We measured surfactant phosphatidylcholine (PC) pool size and half-life in human congenital diaphragmatic hernia (CDH) patients who required extracorporeal membrane oxygenation (ECMO). Study design Surfactant PC pool size and half-life were measured by endotracheal administration of deuterium-labeled dipalmitoylphosphatidylcholine in 8 neonates with CDH on ECMO (CDH-ECMO), in 7 neonates with meconium aspiration syndrome on ECMO (MAS-ECMO), and in 6

  1. Survey on nucleate pool boiling of nanofluids: the effect of particle size relative to roughness

    Microsoft Academic Search

    Sarit K. Das; G. Prakash Narayan; Anoop K. Baby

    2008-01-01

    Pool boiling heat transfer using nanofluids (which are suspensions of nano-sized particles in a base fluid) has been a subject\\u000a of many investigations and incoherent results have been reported in literature regarding the same. In the past, experiments\\u000a were conducted in nucleate pool boiling with varying parameters such as particle size, concentration, surface roughness etc.\\u000a and all sort of results

  2. Variations of bile salt pool size and secretion rate in rats according to the modes of sterilization and preparation

    E-print Network

    Paris-Sud XI, Université de

    amount of water. The bile salt pool increased from the first to the third treatment. That effect to explain the relationship between the form of the diet and bile salt pool size and secre- tionVariations of bile salt pool size and secretion rate in rats according to the modes

  3. Grain size, chemistry, and structure of fine and ultrafine particles in stainless steel welding fumes

    Microsoft Academic Search

    B. Moroni; C. Viti

    2009-01-01

    A combined SEM–TEM study was performed on samples of metal inert gas (MIG) stainless steel (SS) arc welding fumes to characterize fine and ultrafine particle fractions in terms of size distributions, crystal structures, and chemistry. Overall observations indicate that welding fumes consist of a complex mixture of magnetite-like nanocrystals and non-spinel particles in different phases, with distinguishing grain size distributions

  4. Possibility of Underwater Explosive Welding for Making Large-Sized Thin Metal Plate Clad by Overlapping Plates

    NASA Astrophysics Data System (ADS)

    Hokamoto, Kazuyuki; Mori, Akihisa; Fujita, Masahiro

    The authors have developed a new method of explosive welding using underwater shock wave for the welding of thin plate on a substrate. Considering the size limitation of the welding area in using the technique, the possibility of overlapping thin plates to make large-sized welding area is investigated. In general, the results for the welding of Inconel 600 on 304 stainless steel show a macroscopically successful weld, but the microstructure shows some melting spots caused due to the trapping of metal jet during the welding process when the welding condition is changed. The welding process is discussed based on the experimental results in comparison with some numerically simulated results obtained by AUTODYN-2D code.

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

    NASA Astrophysics Data System (ADS)

    Shenghai, Zhang; Yifu, Shen; Huijuan, Qiu

    2013-06-01

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

  6. Robotic Vision for Welding

    NASA Technical Reports Server (NTRS)

    Richardson, R. W.

    1986-01-01

    Vision system for robotic welder looks at weld along axis of welding electrode. Gives robot view of most of weld area, including yet-unwelded joint, weld pool, and completed weld bead. Protected within welding-torch body, lens and fiber bundle give robot closeup view of weld in progress. Relayed to video camera on robot manipulator frame, weld image provides data for automatic control of robot motion and welding parameters.

  7. Synapse Clusters Are Preferentially Formed by Synapses with Large Recycling Pool Sizes

    PubMed Central

    Jung, Jasmin; Kohler, Eva M.; Svetlitchny, Alexei; Henkel, Andreas W.; Kornhuber, Johannes; Groemer, Teja W.

    2010-01-01

    Synapses are distributed heterogeneously in neural networks. The relationship between the spatial arrangement of synapses and an individual synapse's structural and functional features remains to be elucidated. Here, we examined the influence of the number of adjacent synapses on individual synaptic recycling pool sizes. When measuring the discharge of the styryl dye FM1–43 from electrically stimulated synapses in rat hippocampal tissue cultures, a strong positive correlation between the number of neighbouring synapses and recycling vesicle pool sizes was observed. Accordingly, vesicle-rich synapses were found to preferentially reside next to neighbours with large recycling pool sizes. Although these synapses with large recycling pool sizes were rare, they were densely arranged and thus exhibited a high amount of release per volume. To consolidate these findings, functional terminals were marked by live-cell antibody staining with anti-synaptotagmin-1-cypHer or overexpression of synaptopHluorin. Analysis of synapse distributions in these systems confirmed the results obtained with FM 1–43. Our findings support the idea that clustering of synapses with large recycling pool sizes is a distinct developmental feature of newly formed neural networks and may contribute to functional plasticity. PMID:20976002

  8. Xanthophyll cycle pool size and composition in relation to the nitrogen content of apple leaves.

    PubMed

    Cheng, Lailiang

    2003-01-01

    The objective of this study was to determine xanthophyll cycle pool size and composition in response to N status and their relationships to non-photochemical quenching in apple leaves. Bench-grafted Fuji/M.26 trees were fertilized with different N concentrations (0-20 mM) in a modified Hoagland's solution for 6 weeks to create a wide range of leaf N status (1-4.4 g m(-2)). Chlorophyll content, xanthophyll cycle pool size, lutein, total carotene, and neoxanthin on a leaf area basis all increased linearly with increasing leaf N. However, only the ratios of the xanthophyll cycle pool and of lutein to chlorophyll were higher in low N leaves than in high N leaves. Under high light at midday, both zeaxanthin (Z), expressed on a chlorophyll basis, and the percentage of the xanthophyll cycle pool present as Z, increased as leaf N decreased. Thermal dissipation of excitation energy, measured as non-photochemical quenching of chlorophyll fluorescence, was positively related to, whereas efficiency of excitation transfer and photosystem II quantum efficiency were negatively related to, Z, expressed on a chlorophyll basis or on a xanthophyll cycle pool basis. It is concluded that both xanthophyll cycle pool size (on a chlorophyll basis) and conversion of violaxanthin to zeaxanthin are enhanced in response to N limitation to dissipate excessive absorbed light under high irradiance. PMID:12493867

  9. Welding and Lung Cancer in a Pooled Analysis of Case-Control Studies

    PubMed Central

    Kendzia, Benjamin; Behrens, Thomas; Jöckel, Karl-Heinz; Siemiatycki, Jack; Kromhout, Hans; Vermeulen, Roel; Peters, Susan; Van Gelder, Rainer; Olsson, Ann; Brüske, Irene; Wichmann, H.-Erich; Stücker, Isabelle; Guida, Florence; Tardón, Adonina; Merletti, Franco; Mirabelli, Dario; Richiardi, Lorenzo; Pohlabeln, Hermann; Ahrens, Wolfgang; Landi, Maria Teresa; Caporaso, Neil; Consonni, Dario; Zaridze, David; Szeszenia-Dabrowska, Neonila; Lissowska, Jolanta; Gustavsson, Per; Marcus, Michael; Fabianova, Eleonora; ‘t Mannetje, Andrea; Pearce, Neil; Tse, Lap Ah; Yu, Ignatius Tak-sun; Rudnai, Peter; Bencko, Vladimir; Janout, Vladimir; Mates, Dana; Foretova, Lenka; Forastiere, Francesco; McLaughlin, John; Demers, Paul; Bueno-de-Mesquita, Bas; Boffetta, Paolo; Schüz, Joachim; Straif, Kurt; Pesch, Beate; Brüning, Thomas

    2013-01-01

    Several epidemiologic studies have indicated an increased risk of lung cancer among welders. We used the SYNERGY project database to assess welding as a risk factor for developing lung cancer. The database includes data on 15,483 male lung cancer cases and 18,388 male controls from 16 studies in Europe, Canada, China, and New Zealand conducted between 1985 and 2010. Odds ratios and 95% confidence intervals between regular or occasional welding and lung cancer were estimated, with adjustment for smoking, age, study center, and employment in other occupations associated with lung cancer risk. Overall, 568 cases and 427 controls had ever worked as welders and had an odds ratio of developing lung cancer of 1.44 (95% confidence interval: 1.25, 1.67) with the odds ratio increasing for longer duration of welding. In never and light smokers, the odds ratio was 1.96 (95% confidence interval: 1.37, 2.79). The odds ratios were somewhat higher for squamous and small cell lung cancers than for adenocarcinoma. Another 1,994 cases and 1,930 controls had ever worked in occupations with occasional welding. Work in any of these occupations was associated with some elevation of risk, though not as much as observed in regular welders. Our findings lend further support to the hypothesis that welding is associated with an increased risk of lung cancer. PMID:24052544

  10. Relationships between plasma lipoprotein cholesterol concentrations and the pool size and metabolism of cholesterol in man.

    PubMed

    Miller, N E; Nestel, P J; Clifton-Bligh, P

    1976-01-01

    The plasma concentration of unesterified and esterified cholesterol within very low density (VLDL), low density (LDL) and high density (HDL) lipoproteins have been examined in relation to the metabolism and pool size of cholesterol in normal and hyperlipidaemic subjects. Cholesterol metabolism was assessed as faecal endogenous neutral and acidic steroid excretion, a 2-pool model of cholesterol turnover, and in vitro plasma cholesterol esterifying activity. VLDL total cholesterol (TC) concentration was positively correlated with cholesterol turnover, endogenous neutral steroid excretion, bile acid excretion and the absolute rate of plasma cholestrol esterification. The correlations with cholesterol turnover and neutral steroid excretion, but not that with bile acid excretion, remained significant when these were corrected for their relationships to body weight. LDL-TC was negatively correlated with the fractional rate of plasma cholesterol esterification and, in subjects with primary type IIa hyperlipoproteinaemia, also with the rate constant for cholesterol elimination from the rapidly exchanging cholesterol pool. No correlation was found between LDL-TC concentration and bile acid excretion. HDL-TC concentration was negatively correlated with both the rapidly and slowly exchanging pools of tissue cholesterol, after correction for their relationships to body weight and adiposity. In contrast, cholesterol pool sizes were not correlated with the concentration of VLDL or LDL-TC; nor was there any relationship to plasma cholesterol esterifying activity. No correlation was found between the relative proportions of unesterified cholesterol within any lipoprotein fraction and either the pool size or metabolism of cholesterol. These findings accord with previous reports of enhanced cholesterol metabolism in subjects with elevated VLDL concentrations and of impaired plasma LDL and cholesterol clearance in patients with primary type IIa hyperlipoproteinaemia. The demonstration that HDL-TC concentration is negatively correlated with body cholesterol pool size supports in vitro evidence for a role of HDL IN TISSUE CHOLESTEROL CLEARENCE. PMID:178328

  11. Moral hazard, risk sharing, and the optimal pool size Frauke von Bieberstein

    E-print Network

    Fernando, Jose F.

    Moral hazard, risk sharing, and the optimal pool size Frauke von Bieberstein , Eberhard Feess levels, and moral hazard, we derive two main results: First, for all mixed risk averse utility functions. JEL Classification: D81, G22 Keywords: risk sharing, moral hazard, partnerships, mutuals We thank

  12. Planktonic phosphorus pool sizes and cycling efficiency in coastal and interior British Columbia lakes

    E-print Network

    Mazumder, Asit

    Planktonic phosphorus pool sizes and cycling efficiency in coastal and interior British Columbia long acknowledged the importance of phosphorus (P) in determining the organism biomass and productivity of precise measurements of the dissolved inorganic phosphorus (PO3À 4 ) and (2) accurate or complete

  13. Synapse Clusters Are Preferentially Formed by Synapses with Large Recycling Pool Sizes

    Microsoft Academic Search

    Oliver Welzel; Carsten H. Tischbirek; Jasmin Jung; Eva M. Kohler; Alexei Svetlitchny; Andreas W. Henkel; Johannes Kornhuber; Teja W. Groemer; Jialin Charles Zheng

    2010-01-01

    Synapses are distributed heterogeneously in neural networks. The relationship between the spatial arrangement of synapses and an individual synapse's structural and functional features remains to be elucidated. Here, we examined the influence of the number of adjacent synapses on individual synaptic recycling pool sizes. When measuring the discharge of the styryl dye FM1–43 from electrically stimulated synapses in rat hippocampal

  14. Swimming Pools.

    ERIC Educational Resources Information Center

    Ministry of Housing and Local Government, London (England).

    Technical and engineering data are set forth on the design and construction of swimming pools. Consideration is given to site selection, pool construction, the comparative merits of combining open air and enclosed pools, and alternative uses of the pool. Guidelines are presented regarding--(1) pool size and use, (2) locker and changing rooms, (3)…

  15. TOWARDS AN FVEFAC METHOD FOR DETERMINING THERMOCAPILLARY EFFECTS ON WELD POOL SHAPE

    E-print Network

    , near the solid­liquid interface, the full conduction­convection solution will require extremely fine in the liquid metal is driven primarily by thermocapillary forces, and even in cases where other forces growth, involve a pool of molten metal with a free surface, with strong temperature gradients along

  16. Experimental and numerical investigation of temperature distribution and melt pool geometry during pulsed laser welding of Ti6Al4V alloy

    NASA Astrophysics Data System (ADS)

    Akbari, Mohammad; Saedodin, Seyfolah; Toghraie, Davood; Shoja-Razavi, Reza; Kowsari, Farshad

    2014-07-01

    This paper reports on a numerical and experimental investigation of laser welding of titanium alloy (Ti6Al4V) for modeling the temperature distribution to predict the heat affected zone (HAZ), depth and width of the molten pool. This is a transient three-dimensional problem in which, because of simplicity, the weld pool surface is considered flat. The complex physical phenomenon causing the formation of keyhole has not been considered. The temperature histories of welding process were studied. It was observed that the finite volume thermal model was in good agreement with the experimental data. Also, we predicted the temperature as a function of distance at different laser welding speeds and saw that at each welding speed, the temperature profile was decreased sharply in points close to the laser beam center, and then decreased slightly in the far region from the laser beam center. The model prediction error was found to be in the 2-17% range with most numerical values falling within 7% of the experimental values.

  17. Size effects on residual stress and fatigue crack growth in friction stir welded 2195-T8 aluminium – Part I: Experiments

    Microsoft Academic Search

    Yu E. Ma; P. Staron; T. Fischer; P. E. Irving

    2011-01-01

    Residual stress fields were measured in three different sizes of Compact-Tension (C(T)) and eccentrically loaded single edge notch (ESE(T)) specimens containing transverse or longitudinal welds. The effect of size on residual stress profiles was studied. Fatigue crack growth tests were carried out with cracks growing into or away from the weld line, as well as growing along the weld centre

  18. Nitrogen stress affects the turnover and size of nitrogen pools supplying leaf growth in a grass.

    PubMed

    Lehmeier, Christoph Andreas; Wild, Melanie; Schnyder, Hans

    2013-08-01

    The effect of nitrogen (N) stress on the pool system supplying currently assimilated and (re)mobilized N for leaf growth of a grass was explored by dynamic ¹?N labeling, assessment of total and labeled N import into leaf growth zones, and compartmental analysis of the label import data. Perennial ryegrass (Lolium perenne) plants, grown with low or high levels of N fertilization, were labeled with ¹?NO??/¹?NO?? from 2 h to more than 20 d. In both treatments, the tracer time course in N imported into the growth zones fitted a two-pool model (r² > 0.99). This consisted of a "substrate pool," which received N from current uptake and supplied the growth zone, and a recycling/mobilizing "store," which exchanged with the substrate pool. N deficiency halved the leaf elongation rate, decreased N import into the growth zone, lengthened the delay between tracer uptake and its arrival in the growth zone (2.2 h versus 0.9 h), slowed the turnover of the substrate pool (half-life of 3.2 h versus 0.6 h), and increased its size (12.4 ?g versus 5.9 ?g). The store contained the equivalent of approximately 10 times (low N) and approximately five times (high N) the total daily N import into the growth zone. Its turnover agreed with that of protein turnover. Remarkably, the relative contribution of mobilization to leaf growth was large and similar (approximately 45%) in both treatments. We conclude that turnover and size of the substrate pool are related to the sink strength of the growth zone, whereas the contribution of the store is influenced by partitioning between sinks. PMID:23757403

  19. A Preferentially Segregated Recycling Vesicle Pool of Limited Size Supports Neurotransmission in Native Central Synapses

    PubMed Central

    Marra, Vincenzo; Burden, Jemima J.; Thorpe, Julian R.; Smith, Ikuko T.; Smith, Spencer L.; Häusser, Michael; Branco, Tiago; Staras, Kevin

    2012-01-01

    Summary At small central synapses, efficient turnover of vesicles is crucial for stimulus-driven transmission, but how the structure of this recycling pool relates to its functional role remains unclear. Here we characterize the organizational principles of functional vesicles at native hippocampal synapses with nanoscale resolution using fluorescent dye labeling and electron microscopy. We show that the recycling pool broadly scales with the magnitude of the total vesicle pool, but its average size is small (?45 vesicles), highly variable, and regulated by CDK5/calcineurin activity. Spatial analysis demonstrates that recycling vesicles are preferentially arranged near the active zone and this segregation is abolished by actin stabilization, slowing the rate of activity-driven exocytosis. Our approach reveals a similarly biased recycling pool distribution at synapses in visual cortex activated by sensory stimulation in vivo. We suggest that in small native central synapses, efficient release of a limited pool of vesicles relies on their favored spatial positioning within the terminal. PMID:23141069

  20. Increases in plasma pool size of lipoprotein components in copper-deficient hamsters

    SciTech Connect

    Al-Othman, A.A.; Rosenstein, F.; Lei, K.Y. (Univ. of Arizona, Tucson (United States))

    1991-03-15

    Twenty-four male Golden Syrian hamsters, were randomly assigned to 2 dietary copper (Cu) treatments; deficient and adequate. Reductions in weight gain, hematocrit and liver Cu as well as increases in heart weight and plasma volume were observed in CD hamsters after 7 weeks of treatment. Plasma very low (VLDL), low (LDL) and high (HDL) density lipoproteins were isolated by ultracentrifugation and Sepharose column chromatography. The percentage of total plasma cholesterol carried by LDL was increased from 20 to 24% but was reduced from 71 to 68% for HDL as a result of Cu deficiency. In LDL the % composition of triglycerides (TG) and phospholipids (PL) was increased by 25% but that of cholesterol was reduced by 13%. The % composition of protein was reduced 24% but that of TG was increased 18% in VLDL by Cu deficiency. Since plasma volume was increased 50% in CD hamsters, the data were expressed as the amount present in the plasma pool corrected for body weight. With the exceptions of smaller increased in VLDL protein and PL as well as the more than threefold increases in LDL TG and PL plasma pool size, the pool size for the rest of the lipoprotein components were increased about twofold in CD hamsters. The lipoprotein data further indicate that Cu deficiency increased the particle number of VLDL, LDL and HDL but enlarged the size of only VLDL and LDL.

  1. Physical-chemical model for cellular uptake of fatty acids: prediction of intracellular pool sizes

    SciTech Connect

    Cooper, R.; Noy, N.; Zakim, D.

    1987-09-08

    If the uptake of fatty acids by liver is a physical, not a biological, process, then the size and location of the intrahepatic pool of fatty acids can be predicted from uptake rates and thermodynamic data. The purpose of the experiments in this paper was to test the accuracy of this idea. Rat livers were perfused with (/sup 3/H) palmitate bound to (/sup 14/C) albumin, and the total amounts of palmitate removed from the perfusate were measured at 3-s intervals. The intrahepatic pools of palmitate calculated from these data were 13.8 and 23.0 nmol/g of liver at ratios of palmitate/albumin (mol/mol) (afferent side) of 2/1 and 4/1, respectively, in the steady state. The intrahepatic pools of palmitate calculated from the distributions of palmitate between membranes, H/sub 2/O, albumin, and fatty acid binding protein and the measured first-order rate constants for acyl-CoA ligases in mitochondria and microsomes were 12.1 and 34.6 nmol/g for perfusate ratios of palmitate/albumin of 2/1 and 4/1, in the steady state. Intrahepatic pools of palmitate measured after establishment of a steady-state rate of uptake were 15.0 and 31.8 nmol/g for these ratios of palmitate/albumin of 2/1 and 4/1.

  2. Modeling of Heat and Mass Transfer in Fusion Welding

    SciTech Connect

    Zhang, Wei [ORNL

    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.

  3. Analysing the influences of weld size on fatigue life prediction of FCAW cruciform joints by strain energy concept

    Microsoft Academic Search

    V Balasubramanian; B Guha

    1999-01-01

    The effect of weld size on fatigue life of flux cored arc welded (FCAW) cruciform joints containing lack of penetration (LOP) defect has been analysed by using the strain energy density factor (SEDF) concept. Moreover, new fracture mechanics equations have been developed to predict the fatigue life of the cruciform joints. Load carrying cruciform joints were fabricated from ASTM 517

  4. Origin of stray grain formation in single-crystal superalloy weld pools from heat transfer and fluid flow modeling

    Microsoft Academic Search

    T. D. Anderson; J. N. DuPont; T. DebRoy

    2010-01-01

    Stray grain formation in laser and electron beam welds on single-crystal alloy CMSX-4 was investigated through heat transfer and fluid flow simulations. The results were combined with a single-crystal growth model and stray grain calculations to investigate the influence of welding parameters on stray grain formation. Stray grain contents were also experimentally measured on laser and electron beam welds prepared

  5. Monitoring Weld Penetration Optically From Within Torch

    NASA Technical Reports Server (NTRS)

    Smith, Matthew A.; Gilbert, Jeffrey L.; Linsacum, Deron L.; Gutlow, David A.

    1993-01-01

    Photodetector or optical fiber leading to photodetector mounted inside gas/tungsten arc welding torch to monitor arc light reflected from oscillating surface of weld pool. Proposed optical monitoring components preserve compact profile of welding torch, maintained in fixed aim at weld-pool position at end of welding torch, and protected against bumping external objects.

  6. Intelligent Technologies for Robotic Welding

    Microsoft Academic Search

    S. B. Chen; T. Qiu; T. Lin; L. Wu; J. S. Tian; W. X. Lv; Y. Zhang

    This paper discusses intelligent technologies for the robotic welding, which contains computer vision sensing, automatic programming for weld path and technical parameters, guiding and tracking seam, intelligent control of welding pool dynamics and quality. Such an welding robotic systems with some artificial intelligent functions could realize collision-free path planning for complex curve seam, detecting welding surroundings by laser scanning technology,

  7. WELDING RESEARCH -s57WELDING JOURNAL

    E-print Network

    Zhang, YuMing

    WELDING RESEARCH -s57WELDING JOURNAL ABSTRACT. Low heat input is typically desired for welding high welding. However, a high current, and thus a high heat input, is required to melt more wire to achieve the HAZ size, microstructure, and the hard- ness of high-strength steel ASTM A514 welded by DE

  8. Heat transfer, fluid flow and mass transfer in laser welding of stainless steel with small length scale

    NASA Astrophysics Data System (ADS)

    He, Xiuli

    Nd: YAG Laser welding with hundreds of micrometers in laser beam diameter is widely used for assembly and closure of high reliability electrical and electronic packages for the telecommunications, aerospace and medical industries. However, certain concerns have to be addressed to obtain defect-free and structurally sound welds. During laser welding, Because of the high power density used, the pressures at the weld pool surface can be greater than the ambient pressure. This excess pressure provides a driving force for the vaporization to take place. As a result of vaporization for different elements, the composition in the weld pool may differ from that of base metal, which can result in changes in the microstructure and degradation of mechanical properties of weldments. When the weld pool temperatures are very high, the escaping vapor exerts a large recoil force on the weld pool surface, and as a consequence, tiny liquid metal particles may be expelled from the weld pool. Vaporization of alloying elements and liquid metal expulsion are the two main mechanisms of material loss. Besides, for laser welds with small length scale, heat transfer and fluid flow are different from those for arc welds with much larger length scale. Because of small weld pool size, rapid changes of temperature and very short duration of the laser welding process, physical measurements of important parameters such as temperature and velocity fields, weld thermal cycles, solidification and cooling rates are very difficult. The objective of the research is to quantitatively understand the influences of various factors on the heat transfer, fluid flow, vaporization of alloying elements and liquid metal expulsion in Nd:YAG laser welding with small length scale of 304 stainless steel. In this study, a comprehensive three dimensional heat transfer and fluid flow model based on the mass, momentum and energy conservation equations is relied upon to calculate temperature and velocity fields in the weld pool, weld thermal cycle, weld pool geometry and solidification parameters. Surface tension and buoyancy forces were considered for the calculation of transient weld pool convection. Very fine grids and small time steps were used to achieve accuracy in the calculations. The calculated weld pool dimensions were compared with the corresponding measured values to validate the model. (Abstract shortened by UMI.)

  9. The Bruchpilot cytomatrix determines the size of the readily releasable pool of synaptic vesicles

    PubMed Central

    Matkovic, Tanja; Siebert, Matthias; Knoche, Elena; Depner, Harald; Mertel, Sara; Owald, David; Schmidt, Manuela; Thomas, Ulrich; Sickmann, Albert; Kamin, Dirk; Hell, Stefan W.; Bürger, Jörg; Hollmann, Christina; Mielke, Thorsten

    2013-01-01

    Synaptic vesicles (SVs) fuse at a specialized membrane domain called the active zone (AZ), covered by a conserved cytomatrix. How exactly cytomatrix components intersect with SV release remains insufficiently understood. We showed previously that loss of the Drosophila melanogaster ELKS family protein Bruchpilot (BRP) eliminates the cytomatrix (T bar) and declusters Ca2+ channels. In this paper, we explored additional functions of the cytomatrix, starting with the biochemical identification of two BRP isoforms. Both isoforms alternated in a circular array and were important for proper T-bar formation. Basal transmission was decreased in isoform-specific mutants, which we attributed to a reduction in the size of the readily releasable pool (RRP) of SVs. We also found a corresponding reduction in the number of SVs docked close to the remaining cytomatrix. We propose that the macromolecular architecture created by the alternating pattern of the BRP isoforms determines the number of Ca2+ channel-coupled SV release slots available per AZ and thereby sets the size of the RRP. PMID:23960145

  10. Development of a comprehensive weld process model

    SciTech Connect

    Radhakrishnan, B.; Zacharia, T.; Paul, A.

    1997-05-01

    This cooperative research and development agreement (CRADA) between Concurrent Technologies Corporation (CTC) and Lockheed Martin Energy Systems (LMES) combines CTC`s expertise in the welding area and that of LMES to develop computer models and simulation software for welding processes. This development is of significant impact to the industry, including materials producers and fabricators. The main thrust of the research effort was to develop a comprehensive welding simulation methodology. A substantial amount of work has been done by several researchers to numerically model several welding processes. The primary drawback of most of the existing models is the lack of sound linkages between the mechanistic aspects (e.g., heat transfer, fluid flow, and residual stress) and the metallurgical aspects (e.g., microstructure development and control). A comprehensive numerical model which can be used to elucidate the effect of welding parameters/conditions on the temperature distribution, weld pool shape and size, solidification behavior, and microstructure development, as well as stresses and distortion, does not exist. It was therefore imperative to develop a comprehensive model which would predict all of the above phenomena during welding. The CRADA built upon an already existing three-dimensional (3-D) welding simulation model which was developed by LMES which is capable of predicting weld pool shape and the temperature history in 3-d single-pass welds. However, the model does not account for multipass welds, microstructural evolution, distortion and residual stresses. Additionally, the model requires large resources of computing time, which limits its use for practical applications. To overcome this, CTC and LMES have developed through this CRADA the comprehensive welding simulation model described above.

  11. A study of the effects of heater size, subcooling, and gravity level on pool boiling heat transfer

    E-print Network

    Kim, Jungho

    was measured. Steady- state boiling data in low-g and high-g were obtained for various bulk fluid subcoolings subcooling had a negligible impact on boiling performance and a characteristically low heat flux was observedA study of the effects of heater size, subcooling, and gravity level on pool boiling heat transfer

  12. Determination of welding fume size with time using E7018 electrodes and A131B base metal

    E-print Network

    Owen, Richard James

    1976-01-01

    DETERMINATION OF WELDING FUME SIZE WITH TIME USING E7018 ELECTRODES AND A131B BASE METAL A Thesis by RICHARD JAMES OWEN Submitted to the Graduate College of Texas AILM University in partial fulfillment of the requirement for the degree... of MASTER OF SCIENCE December 1976 Major Subject: Industrial Hygiene DETERMINATION OF WELDING FUME SIZE WITH TIME USING E7018 ELECTRODES AND Al 318 BASE METAL A Thesis by RICHARD JAMES OWEN Approved as to style and content by: Cha&rman of Comm t ad...

  13. Solidification of underwater wet welds

    SciTech Connect

    Pope, A.M.; Medeiros, R.C. de; Liu, S. [Colorado School of Mines, Golden, CO (United States). Center for Welding and Joining Research

    1995-12-31

    It is well known that the shape of a weld pool can influence the microstructure and segregation pattern of the final solidified weld metal. Mechanical properties and susceptibility to defects are consequently affected by the solidification mode of the weld. In this work the solidification behavior of weld beads deposited in air and underwater wet welding using rutile electrodes were compared. The welds were deposited by gravity feed, on low carbon, manganese steel plates using similar welding conditions. Macroscopic observation of the weld craters showed that welds deposited in air presented an elliptical weld pool. The underwater wet welds, on the other hand, solidified with a tear drop shape. Although the welds differed in shape, their lengths were approximately the same. Microscopic examinations carried out on transverse, normal and longitudinal sections revealed a coarser columnar grain structure in the underwater welds. These results suggest that the tear-drop shaped pool induced solidification in a preferred orientation with segregation more likely in welds deposited under wet conditions. This change in weld pool geometry can be explained by the surface heat loss conditions that occur in a wet weld: slower when covered by the steam bubble and faster in the region in contact with water behind the pool.

  14. Laser welding in space

    NASA Astrophysics Data System (ADS)

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

    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.

  15. Low-Temperature Sensitization Behavior of Base, Heat-Affected Zone, and Weld Pool in AISI 304LN

    Microsoft Academic Search

    Raghuvir Singh; Gautam Das; P. K. Singh; I. Chattoraj

    2009-01-01

    Present investigations were focused on low-temperature sensitization (LTS) behavior of 304LN stainless steels considered from\\u000a pipes of two different thicknesses. The specimens for the present study were taken from solution-annealed pipes (of varying\\u000a thicknesses) and welded pipes (including the heat-affected zone (HAZ)). The specimens were subjected to thermal aging at 400 °C\\u000a and 450 °C for different durations ranging from 125 to

  16. Optically controlled welding system

    NASA Technical Reports Server (NTRS)

    Gordon, Stephen S. (Inventor)

    1989-01-01

    An optically controlled welding system (10) wherein a welding torch (12) having through-the-torch viewing capabilities is provided with an optical beam splitter (56) to create a transmitted view and a reflective view of a welding operation. These views are converted to digital signals which are then processed and utilized by a computerized robotic welder (15) to make the welding torch responsive thereto. Other features includes an actively cooled electrode holder (26) which minimizes a blocked portion of the view by virtue of being constructed of a single spoke or arm (28) and a weld pool contour detector (14) comprising a laser beam directed onto the weld pool with the position of specular radiation reflected therefrom being characteristic of a penetrated or unpenetrated condition of the weld pool.

  17. Optically controlled welding system

    NASA Technical Reports Server (NTRS)

    Gordon, Stephen S. (inventor)

    1988-01-01

    An optically controlled welding system wherein a welding torch having through-the-torch viewing capabilities is provided with an optical beam splitter to create a transmitted view and a reflective view of a welding operation. These views are converted to digital signals which are then processed and utilized by a computerized robotic welder to make the welding torch responsive thereto. Other features include an actively cooled electrode holder which minimizes a blocked portion of the view by virtue of being constructed of a single spoke or arm, and a weld pool contour detector comprising a laser beam directed onto the weld pool with the position of specular radiation reflected therefrom, being characteristic of a penetrated or unpenetrated condition of the weld pool.

  18. Orphan G Protein–Coupled Receptor GPR116 Regulates Pulmonary Surfactant Pool Size

    PubMed Central

    Ludwig, Marie-Gabrielle; Mueller, Matthias; Kinzel, Bernd; Sato, Atsuyasu; Xu, Yan; Whitsett, Jeffrey A.; Ikegami, Machiko

    2013-01-01

    Pulmonary surfactant levels within the alveoli are tightly regulated to maintain lung volumes and promote efficient gas exchange across the air/blood barrier. Quantitative and qualitative abnormalities in surfactant are associated with severe lung diseases in children and adults. Although the cellular and molecular mechanisms that control surfactant metabolism have been studied intensively, the critical molecular pathways that sense and regulate endogenous surfactant levels within the alveolus have not been identified and constitute a fundamental knowledge gap in the field. In this study, we demonstrate that expression of an orphan G protein–coupled receptor, GPR116, in the murine lung is developmentally regulated, reaching maximal levels 1 day after birth, and is highly expressed on the apical surface of alveolar type I and type II epithelial cells. To define the physiological role of GPR116 in vivo, mice with a targeted mutation of the Gpr116 locus, Gpr116?exon17, were generated. Gpr116?exon17 mice developed a profound accumulation of alveolar surfactant phospholipids at 4 weeks of age (12-fold) that was further increased at 20 weeks of age (30-fold). Surfactant accumulation in Gpr116?exon17 mice was associated with increased saturated phosphatidylcholine synthesis at 4 weeks and the presence of enlarged, lipid-laden macrophages, neutrophilia, and alveolar destruction at 20 weeks. mRNA microarray analyses indicated that P2RY2, a purinergic receptor known to mediate surfactant secretion, was induced in Gpr116?exon17 type II cells. Collectively, these data support the concept that GPR116 functions as a molecular sensor of alveolar surfactant lipid pool sizes by regulating surfactant secretion. PMID:23590306

  19. Heat transfer and fluid flow during laser spot welding of 304 stainless steel

    NASA Astrophysics Data System (ADS)

    He, X.; Fuerschbach, P. W.; Roy, T. Deb

    2003-06-01

    The evolution of temperature and velocity fields during laser spot welding of 304 stainless steel was studied using a transient, heat transfer and fluid flow model based on the solution of the equations of conservation of mass, momentum and energy in the weld pool. The weld pool geometry, weld thermal cycles and various solidification parameters were calculated. The fusion zone geometry, calculated from the transient heat transfer and fluid flow model, was in good agreement with the corresponding experimentally measured values for various welding conditions. Dimensional analysis was used to understand the importance of heat transfer by conduction and convection and the roles of various driving forces for convection in the weld pool. During solidification, the mushy zone grew at a rapid rate and the maximum size of the mushy zone was reached when the pure liquid region vanished. The solidification rate of the mushy zone/liquid interface was shown to increase while the temperature gradient in the liquid zone at this interface decreased as solidification of the weld pool progressed. The heating and cooling rates, temperature gradient and the solidification rate at the mushy zone/liquid interface for laser spot welding were much higher than those for the moving and spot gas tungsten arc welding.

  20. On the hot cracking susceptibility of a semisolid aluminium 6061 weld: Application of a coupled solidification- thermomechanical model

    NASA Astrophysics Data System (ADS)

    Zareie Rajani, H. R.; Phillion, A. B.

    2015-06-01

    A coupled solidification-thermomechanical model is presented that investigates the hot tearing susceptibility of an aluminium 6061 semisolid weld. Two key phenomena are considered: excessive deformation of the semisolid weld, initiating a hot tear, and the ability of the semisolid weld to heal the hot tear by circulation of the molten metal. The model consists of two major modules: weld solidification and thermomechanical analysis. 1) By means of a multi-scale model of solidification, the microstructural evolution of the semisolid weld is simulated in 3D. The semisolid structure, which varies as a function of welding parameters, is composed of solidifying grains and a network of micro liquid channels. The weld solidification module is utilized to obtain the solidification shrinkage. The size of the micro liquid channels is used as an indicator to assess the healing ability of the semisolid weld. 2) Using the finite element method, the mechanical interaction between the weld pool and the base metal is simulated to capture the transient force field deforming the semisolid weld. Thermomechanical stresses and shrinkage stresses are both considered in the analysis; the solidification contractions are extracted from the weld solidification module and applied to the deformation simulation as boundary conditions. Such an analysis enables characterization of the potential for excessive deformation of the weld. The outputs of the model are used to study the effect of welding parameters including welding current and speed, and also welding constraint on the hot cracking susceptibility of an aluminium alloy 6061 semisolid weld.

  1. Pool size measurements facilitate the determination of fluxes at branching points in non-stationary metabolic flux analysis: the case of Arabidopsis thaliana

    PubMed Central

    Heise, Robert; Fernie, Alisdair R.; Stitt, Mark; Nikoloski, Zoran

    2015-01-01

    Pool size measurements are important for the estimation of absolute intracellular fluxes in particular scenarios based on data from heavy carbon isotope experiments. Recently, steady-state fluxes estimates were obtained for central carbon metabolism in an intact illuminated rosette of Arabidopsis thaliana grown photoautotrophically (Szecowka et al., 2013; Heise et al., 2014). Fluxes were estimated therein by integrating mass-spectrometric data of the dynamics of the unlabeled metabolic fraction, data on metabolic pool sizes, partitioning of metabolic pools between cellular compartments and estimates of photosynthetically inactive pools, with a simplified model of plant central carbon metabolism. However, the fluxes were determined by treating the pool sizes as fixed parameters. Here we investigated whether and, if so, to what extent the treatment of pool sizes as parameters to be optimized in three scenarios may affect the flux estimates. The results are discussed in terms of benchmark values for canonical pathways and reactions, including starch and sucrose synthesis as well as the ribulose-1,5-bisphosphate carboxylation and oxygenation reactions. In addition, we discuss pathways emerging from a divergent branch point for which pool sizes are required for flux estimation, irrespective of the computational approach used for the simulation of the observable labeling pattern. Therefore, our findings indicate the necessity for development of techniques for accurate pool size measurements to improve the quality of flux estimates from non-stationary flux estimates in intact plant cells in the absence of alternative flux measurements.

  2. Pool size measurements facilitate the determination of fluxes at branching points in non-stationary metabolic flux analysis: the case of Arabidopsis thaliana.

    PubMed

    Heise, Robert; Fernie, Alisdair R; Stitt, Mark; Nikoloski, Zoran

    2015-01-01

    Pool size measurements are important for the estimation of absolute intracellular fluxes in particular scenarios based on data from heavy carbon isotope experiments. Recently, steady-state fluxes estimates were obtained for central carbon metabolism in an intact illuminated rosette of Arabidopsis thaliana grown photoautotrophically (Szecowka et al., 2013; Heise et al., 2014). Fluxes were estimated therein by integrating mass-spectrometric data of the dynamics of the unlabeled metabolic fraction, data on metabolic pool sizes, partitioning of metabolic pools between cellular compartments and estimates of photosynthetically inactive pools, with a simplified model of plant central carbon metabolism. However, the fluxes were determined by treating the pool sizes as fixed parameters. Here we investigated whether and, if so, to what extent the treatment of pool sizes as parameters to be optimized in three scenarios may affect the flux estimates. The results are discussed in terms of benchmark values for canonical pathways and reactions, including starch and sucrose synthesis as well as the ribulose-1,5-bisphosphate carboxylation and oxygenation reactions. In addition, we discuss pathways emerging from a divergent branch point for which pool sizes are required for flux estimation, irrespective of the computational approach used for the simulation of the observable labeling pattern. Therefore, our findings indicate the necessity for development of techniques for accurate pool size measurements to improve the quality of flux estimates from non-stationary flux estimates in intact plant cells in the absence of alternative flux measurements. PMID:26082786

  3. Acoustic-Emission Weld-Penetration Monitor

    NASA Technical Reports Server (NTRS)

    Maram, J.; Collins, J.

    1986-01-01

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

  4. Active weld control

    NASA Technical Reports Server (NTRS)

    Powell, Bradley W.; Burroughs, Ivan A.

    1994-01-01

    Through the two phases of this contract, sensors for welding applications and parameter extraction algorithms have been developed. These sensors form the foundation of a weld control system which can provide action weld control through the monitoring of the weld pool and keyhole in a VPPA welding process. Systems of this type offer the potential of quality enhancement and cost reduction (minimization of rework on faulty welds) for high-integrity welding applications. Sensors for preweld and postweld inspection, weld pool monitoring, keyhole/weld wire entry monitoring, and seam tracking were developed. Algorithms for signal extraction were also developed and analyzed to determine their application to an adaptive weld control system. The following sections discuss findings for each of the three sensors developed under this contract: (1) weld profiling sensor; (2) weld pool sensor; and (3) stereo seam tracker/keyhole imaging sensor. Hardened versions of these sensors were designed and built under this contract. A control system, described later, was developed on a multiprocessing/multitasking operating system for maximum power and flexibility. Documentation for sensor mechanical and electrical design is also included as appendices in this report.

  5. Establishing Mathematical Models to Predict Grain Size and Hardness of the Friction Stir-Welded AA 7020 Aluminum Alloy Joints

    NASA Astrophysics Data System (ADS)

    Rahimzadeh Ilkhichi, A.; Soufi, R.; Hussain, G.; Vatankhah Barenji, R.; Heidarzadeh, A.

    2015-02-01

    In this study, response surface methodology in conjunction with a central composite design was applied to predict the grain size and hardness of friction stir-welded AA 7020 aluminum alloy joints. For this purpose, three welding parameters, including tool rotational speed, traverse speed, and tool axial force, at five levels and 20 runs were considered. In order to validate the predicted models, the analysis of variance was performed. Hardness and microstructural features of the joints were investigated using microhardness test and optical microscopy, respectively. In addition, the influences of friction stir welding parameters on grain size and hardness of the joints were examined thoroughly. The analysis of variance results revealed that the developed models were significant and accurate to predict the responses. Furthermore, with increasing the heat input, the hardness of the joints decreased, where the grain size increased continuously. In addition, the optimized condition for achieving the lowest grain size and highest hardness of the joints was reached as 800 rpm, 125 mm/min and 8 kN.

  6. A Scanning Transmission Electron Microscopy Method for Determining Manganese Composition in Welding Fume as a Function of Primary Particle Size.

    PubMed

    Richman, Julie D; Livi, Kenneth J T; Geyh, Alison S

    2011-06-01

    Increasing evidence suggests that the physicochemical properties of inhaled nanoparticles influence the resulting toxicokinetics and toxicodynamics. This report presents a method using scanning transmission electron microscopy (STEM) to measure the Mn content throughout the primary particle size distribution of welding fume particle samples collected on filters for application in exposure and health research. Dark field images were collected to assess the primary particle size distribution and energy-dispersive X-ray and electron energy loss spectroscopy were performed for measurement of Mn composition as a function of primary particle size. A manual method incorporating imaging software was used to measure the primary particle diameter and to select an integration region for compositional analysis within primary particles throughout the size range. To explore the variation in the developed metric, the method was applied to 10 gas metal arc welding (GMAW) fume particle samples of mild steel that were collected under a variety of conditions. The range of Mn composition by particle size was -0.10 to 0.19 %/nm, where a positive estimate indicates greater relative abundance of Mn increasing with primary particle size and a negative estimate conversely indicates decreasing Mn content with size. However, the estimate was only statistically significant (p<0.05) in half of the samples (n=5), which all had a positive estimate. In the remaining samples, no significant trend was measured. Our findings indicate that the method is reproducible and that differences in the abundance of Mn by primary particle size among welding fume samples can be detected. PMID:21625364

  7. A Scanning Transmission Electron Microscopy Method for Determining Manganese Composition in Welding Fume as a Function of Primary Particle Size

    PubMed Central

    Richman, Julie D.; Livi, Kenneth J.T.; Geyh, Alison S.

    2011-01-01

    Increasing evidence suggests that the physicochemical properties of inhaled nanoparticles influence the resulting toxicokinetics and toxicodynamics. This report presents a method using scanning transmission electron microscopy (STEM) to measure the Mn content throughout the primary particle size distribution of welding fume particle samples collected on filters for application in exposure and health research. Dark field images were collected to assess the primary particle size distribution and energy-dispersive X-ray and electron energy loss spectroscopy were performed for measurement of Mn composition as a function of primary particle size. A manual method incorporating imaging software was used to measure the primary particle diameter and to select an integration region for compositional analysis within primary particles throughout the size range. To explore the variation in the developed metric, the method was applied to 10 gas metal arc welding (GMAW) fume particle samples of mild steel that were collected under a variety of conditions. The range of Mn composition by particle size was ?0.10 to 0.19 %/nm, where a positive estimate indicates greater relative abundance of Mn increasing with primary particle size and a negative estimate conversely indicates decreasing Mn content with size. However, the estimate was only statistically significant (p<0.05) in half of the samples (n=5), which all had a positive estimate. In the remaining samples, no significant trend was measured. Our findings indicate that the method is reproducible and that differences in the abundance of Mn by primary particle size among welding fume samples can be detected. PMID:21625364

  8. Solar heating for a commercial-sized swimming pool. Final report

    SciTech Connect

    Kane, J.M.

    1983-11-12

    The task of the project was to build a solar heating system for a large community pool. Racks for the sixty collectors were constructed of redwood as described in the section on carpentry work. The plumbing section details the ease of putting together the collectors as well as the difficulty of hooking up the pipe to the pumps and inline filters. An automatic controller unit turns the pumps on and off depending on the availability of sunlight. After two years of work, the system is operable, but the pool cover purchased in the first year may be more effective than the entire solar heating system. Optimal solar efficiency may not be practical. The details of this finding are discussed in the section on conclusions, pitfalls, and recommendations.

  9. Forage intake, N and NDF flow to the abomasum and rumen pool sizes of NDF in Bos indicus (Boran) steers fed oat,

    E-print Network

    Boyer, Edmond

    detergent fibre) and N flow to the abomasum and rumen pool sizes of NDF in Boran steers fed oat ((0) Avena sativa) hay, lablab ((L) Lablab purpureus) hay, or grass ((G) Andropogon sp, Danthonia subulata) hay

  10. Stem cell repopulation efficiency but not pool size is governed by p27kip1

    Microsoft Academic Search

    Neil Rodrigues; David Dombkowski; Sebastian Stier; Tao Cheng; David T. Scadden

    2000-01-01

    Sustained blood cell production requires preservation of a quiescent, multipotential stem cell pool that intermittently gives rise to progenitors with robust proliferative potential. The ability of cells to shift from a highly constrained to a vigorously active proliferative state is critical for maintaining stem cells while providing the responsiveness necessary for host defense. The cyclin-dependent kinase inhibitor (CDKI), p21cip1\\/waf1 (p21)

  11. Systematic Heterogeneity of Fractional Vesicle Pool Sizes and Release Rates of Hippocampal Synapses

    Microsoft Academic Search

    Oliver Welzel; Andreas W. Henkel; Armin M. Stroebel; Jasmin Jung; Carsten H. Tischbirek; Katrin Ebert; Johannes Kornhuber; Silvio O. Rizzoli; Teja W. Groemer

    2011-01-01

    Hippocampal neurons in tissue culture develop functional synapses that exhibit considerable variation in synaptic vesicle content (20–350 vesicles). We examined absolute and fractional parameters of synaptic vesicle exocytosis of individual synapses. Their correlation to vesicle content was determined by activity-dependent discharge of FM-styryl dyes. At high frequency stimulation (30 Hz), synapses with large recycling pools released higher amounts of dye, but

  12. Laser Beam Welding of Nitride Steel Components

    NASA Astrophysics Data System (ADS)

    Gu, Hongping; Yin, Guobin; Shulkin, Boris

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

  13. Development of a Comprehensive Weld Process Model

    SciTech Connect

    Radhakrishnan, B.; Zacharia, T.

    1997-05-01

    This cooperative research and development agreement (CRADA) between Concurrent Technologies Corporation (CTC) and Lockheed Martin Energy Systems (LMES) combines CTC's expertise in the welding area and that of LMES to develop computer models and simulation software for welding processes. This development is of significant impact to the industry, including materials producers and fabricators. The main thrust of the research effort was to develop a comprehensive welding simulation methodology. A substantial amount of work has been done by several researchers to numerically model several welding processes. The primary drawback of most of the existing models is the lack of sound linkages between the mechanistic aspects (e.g., heat transfer, fluid flow, and residual stress) and the metallurgical aspects (e.g., microstructure development and control). A comprehensive numerical model which can be used to elucidate the effect of welding parameters/conditions on the temperature distribution, weld pool shape and size, solidification behavior, and microstructure development, as well as stresses and distortion, does not exist. It was therefore imperative to develop a comprehensive model which would predict all of the above phenomena during welding. The CRADA built upon an already existing three- dimensional (3-D) welding simulation model which was developed by LMES which is capable of predicting weld pool shape and the temperature history in 3-d single-pass welds. However, the model does not account for multipass welds, microstructural evolution, distortion and residual stresses. Additionally, the model requires large resources of computing time, which limits its use for practical applications. To overcome this, CTC and LMES have developed through this CRADA the comprehensive welding simulation model described above. The following technical tasks have been accomplished as part of the CRADA. 1. The LMES welding code has been ported to the Intel Paragon parallel computer at ORNL. 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.

  14. X-ray and neutron diffraction measurements of dislocation density and subgrain size in a friction stir welded aluminum alloy

    SciTech Connect

    Claussen, Bjorn [Los Alamos National Laboratory; Woo, Wanchuck [ORNL; Zhili, Feng [ORNL; Edward, Kenik [ORNL; Ungar, Tamas [EOTVOS UNIV.

    2009-01-01

    The dislocation density and subgrain size were determined in the base material and friction-stir welds of 6061-T6 aluminum alloy. High-resolution X-ray diffraction measurement was performed in the base material. The result of the line profile analysis of the X-ray diffraction peak shows that the dislocation density is about 4.5 x 10{sup 14} m{sup 02} and the subgrain size is about 200 nm. Meanwhile, neutron diffraction measurements have been performed to observe the diffraction peaks during friction-stir welding (FSW). The deep penetration capability of the neutron enables us to measure the peaks from the midplane of the Al plate underneath the tool shoulder of the friction-stir welds. The peak broadening analysis result using the Williamson-Hall method shows the dislocation density of about 3.2 x 10{sup 15} m{sup -2} and subgrain size of about 160 nm. The significant increase of the dislocation density is likely due to the severe plastic deformation during FSW. This study provides an insight into understanding the transient behavior of the microstructure under severe thermomechanical deformation.

  15. Laser beam welding of any metal.

    SciTech Connect

    Leong, K. H.

    1998-10-01

    The effect of a metal's thermophysical properties on its weldability are examined. The thermal conductivity, melting point, absorptivity and thermal diffusivity of the metal and the laser beam focused diameter and welding speed influence the minimum beam irradiance required for melting and welding. Beam diameter, surface tension and viscosity of the molten metal affect weld pool stability and weld quality. Lower surface tension and viscosity increases weld pool instability. With larger beam diameters causing wider welds, dropout also increases. Effects of focused beam diameter and joint fitup on weldability are also examined. Small beam diameters are sensitive to beam coupling problems in relation to fitup precision in addition to beam alignment to the seam. Welding parameters for mitigating weld pool instability and increasing weld quality are derived from the above considerations. Guidelines are presented for the tailoring of welding parameters to achieve good welds. Weldability problems can also be anticipated from the properties of a metal.

  16. Effects of defect size in root region on fatigue strength of fillet welded joints—root failure of non?load?carrying cruciform fillet welded joints due to toe treatment (2 report)

    Microsoft Academic Search

    S. Ohta; H. Kitamura

    1994-01-01

    This paper describes an investigation of the effects of the defect size in the root region on the fatigue strength of non?load?carrying cruciform fillet welded joints by FEM analysis, fatigue tests, and hardness tests. The results may be summarised as follows. 1. Through TIG dressing of the toe region of fillet welded joints, joints have a fatigue limit of 1.4?2.5

  17. NAD kinase regulates the size of the NADPH pool and insulin secretion in pancreatic ?-cells.

    PubMed

    Gray, Joshua P; Alavian, Kambiz N; Jonas, Elizabeth A; Heart, Emma A

    2012-07-15

    NADPH is an important component of the antioxidant defense system and a proposed mediator in glucose-stimulated insulin secretion (GSIS) from pancreatic ?-cells. An increase in the NADPH/NADP(+) ratio has been reported to occur within minutes following the rise in glucose concentration in ?-cells. However, 30 min following the increase in glucose, the total NADPH pool also increases through a mechanism not yet characterized. NAD kinase (NADK) catalyzes the de novo formation of NADP(+) by phosphorylation of NAD(+). NAD kinases have been shown to be essential for redox regulation, oxidative stress defense, and survival in bacteria and yeast. However, studies on NADK in eukaryotic cells are scarce, and the function of this enzyme has not been described in ?-cells. We employed INS-1 832/13 cells, an insulin-secreting rat ?-cell line, and isolated rodent islets to investigate the role of NADK in ?-cell metabolic pathways. Adenoviral-mediated overexpression of NADK resulted in a two- to threefold increase in the total NADPH pool and NADPH/NADP(+) ratio, suggesting that NADP(+) formed by the NADK-catalyzed reaction is rapidly reduced to NADPH via cytosolic reductases. This increase in the NADPH pool was accompanied by an increase in GSIS in NADK-overexpressing cells. Furthermore, NADK overexpression protected ?-cells against oxidative damage by the redox cycling agent menadione and reversed menadione-mediated inhibition of GSIS. Knockdown of NADK via shRNA exerted the opposite effect on all these parameters. These data suggest that NADK kinase regulates intracellular redox and affects insulin secretion and oxidative defense in the ?-cell. PMID:22550069

  18. Fluid Flow Phenomena during Welding

    SciTech Connect

    Zhang, Wei [ORNL

    2011-01-01

    MOLTEN WELD POOLS are dynamic. Liquid in the weld pool in acted on by several strong forces, which can result in high-velocity fluid motion. Fluid flow velocities exceeding 1 m/s (3.3 ft/s) have been observed in gas tungsten arc (GTA) welds under ordinary welding conditions, and higher velocities have been measured in submerged arc welds. Fluid flow is important because it affects weld shape and is related to the formation of a variety of weld defects. Moving liquid transports heat and often dominates heat transport in the weld pool. Because heat transport by mass flow depends on the direction and speed of fluid motion, weld pool shape can differ dramatically from that predicted by conductive heat flow. Temperature gradients are also altered by fluid flow, which can affect weld microstructure. A number of defects in GTA welds have been attributed to fluid flow or changes in fluid flow, including lack of penetration, top bead roughness, humped beads, finger penetration, and undercutting. Instabilities in the liquid film around the keyhole in electron beam and laser welds are responsible for the uneven penetration (spiking) characteristic of these types of welds.

  19. Body size and multiple myeloma mortality: a pooled analysis of 20 prospective studies.

    PubMed

    Teras, Lauren R; Kitahara, Cari M; Birmann, Brenda M; Hartge, Patricia A; Wang, Sophia S; Robien, Kim; Patel, Alpa V; Adami, Hans-Olov; Weiderpass, Elisabete; Giles, Graham G; Singh, Pramil N; Alavanja, Michael; Beane Freeman, Laura E; Bernstein, Leslie; Buring, Julie E; Colditz, Graham A; Fraser, Gary E; Gapstur, Susan M; Gaziano, J Michael; Giovannucci, Edward; Hofmann, Jonathan N; Linet, Martha S; Neta, Gila; Park, Yikyung; Peters, Ulrike; Rosenberg, Philip S; Schairer, Catherine; Sesso, Howard D; Stampfer, Meir J; Visvanathan, Kala; White, Emily; Wolk, Alicja; Zeleniuch-Jacquotte, Anne; de González, Amy Berrington; Purdue, Mark P

    2014-09-01

    Multiple myeloma (MM) is a rare but highly fatal malignancy. High body weight is associated with this cancer, but several questions remain regarding the aetiological relevance of timing and location of body weight. To address these questions, we conducted a pooled analysis of MM mortality using 1·5 million participants (including 1388 MM deaths) from 20 prospective cohorts in the National Cancer Institute Cohort Consortium. Proportional hazards regression was used to calculate pooled multivariate hazard ratios (HRs) and 95% confidence intervals (CIs). Associations with elevated MM mortality were observed for higher early-adult body mass index (BMI; HR = 1·22, 95% CI: 1·09-1·35 per 5 kg/m(2) ) and for higher cohort-entry BMI (HR 1·09, 95% CI: 1·03-1·16 per 5 kg/m(2) ) and waist circumference (HR = 1·06, 95% CI: 1·02-1·10 per 5 cm). Women who were the heaviest, both in early adulthood (BMI 25+) and at cohort entry (BMI 30+) were at greater risk compared to those with BMI 18·5 ? 25 at both time points (HR = 1·95, 95% CI: 1·33-2·86). Waist-to-hip ratio and height were not associated with MM mortality. These observations suggest that overall, and possibly also central, obesity influence myeloma mortality, and women have the highest risk of death from this cancer if they remain heavy throughout adulthood. PMID:24861847

  20. Systematic Heterogeneity of Fractional Vesicle Pool Sizes and Release Rates of Hippocampal Synapses

    PubMed Central

    Welzel, Oliver; Henkel, Andreas W.; Stroebel, Armin M.; Jung, Jasmin; Tischbirek, Carsten H.; Ebert, Katrin; Kornhuber, Johannes; Rizzoli, Silvio O.; Groemer, Teja W.

    2011-01-01

    Hippocampal neurons in tissue culture develop functional synapses that exhibit considerable variation in synaptic vesicle content (20–350 vesicles). We examined absolute and fractional parameters of synaptic vesicle exocytosis of individual synapses. Their correlation to vesicle content was determined by activity-dependent discharge of FM-styryl dyes. At high frequency stimulation (30 Hz), synapses with large recycling pools released higher amounts of dye, but showed a lower fractional release compared to synapses that contained fewer vesicles. This effect gradually vanished at lower frequencies when stimulation was triggered at 20 Hz and 10 Hz, respectively. Live-cell antibody staining with anti-synaptotagmin-1-cypHer 5, and overexpression of synaptopHluorin as well as photoconversion of FM 1-43 followed by electron microscopy, consolidated the findings obtained with FM-styryl dyes. We found that the readily releasable pool grew with a power function with a coefficient of 2/3, possibly indicating a synaptic volume/surface dependency. This observation could be explained by assigning the rate-limiting factor for vesicle exocytosis at high frequency stimulation to the available active zone surface that is proportionally smaller in synapses with larger volumes. PMID:21281573

  1. Fracture mechanics for weld acceptance

    NASA Technical Reports Server (NTRS)

    Bolstad, C. A.; Loechel, L. W.

    1976-01-01

    Criteria include specifications for allowable cracklike defect lengths, undercut, underfill, suckback, mismatch, peaking in butt welds, root penetration, weld beam dimensions, lap joint dimensions, and acceptable defect sizes and densities for double and single fillet welds.

  2. Chronic treatment with lithium and pretreatment with excess inositol reduce inositol pool size in astrocytes by different mechanisms.

    PubMed

    Wolfson, M; Hertz, E; Belmaker, R H; Hertz, L

    1998-03-16

    Chronic treatment with a lithium salt is the classical treatment for manic-depressive disorder. It is hypothesized that the therapeutic action of lithium is caused by its inhibition of inositol phosphatases which leads to a relative deficiency of inositol and, therefore, an impairment of inositol recycling and production of precursor for the second messengers inositol triphosphate (IP3) and diacylglycerol (DAG). However, peculiarly enough, treatment with high doses of inositol also has an antidepressant effect. In the present work, we have studied the acute and chronic effects of lithium and of excess inositol, in separation or together, on accumulation of 50 microM [3H]inositol (a physiologically relevant concentration) into primary cultures of mouse astrocytes. Two parameters were investigated: (1) rate of unidirectional uptake across the cell membrane (measured during short-term exposure to the radioisotope), and (2) magnitude of the intracellular pool of inositol, equilibrating with extracellular inositol (measured during long-term exposure to the radioisotope). Inositol uptake was highly concentrative and occurred with a Km of approximately 500 microM and a Vmax of 1.5 nmol/min/mg protein. The uptake rate was not affected by either acute or chronic treatment with LiCl (or both), but it was substantially reduced ('down-regulated') after pretreatment with a high concentration of inositol. The inositol pool size was decreased to a similar extent as the uptake rate by previous exposure to excess inositol. In spite of the fact that inositol uptake rate was unaffected by lithium, the magnitude of the inositol pool was significantly decreased by chronic treatment with a pharmacologically relevant concentration of LiCl (1 mM), but not by treatment with lower concentrations. This decrease is likely to reflect a reduction in either inositol synthesis or replenishment of inositol from IP3, due to the inhibition of inositol phosphatases by the lithium ion. In agreement with the different mechanisms by which lithium and pretreatment with excess inositol appear to reduce the pool size of inositol, the effects of pretreatment with excess inositol and of LiCl were additive. It is noteworthy that both effects could be observed in astrocytes, suggesting that there might be a significant astrocytic target during clinical treatment. PMID:9518542

  3. gone early, a Novel Germline Factor, Ensures the Proper Size of the Stem Cell Precursor Pool in the Drosophila Ovary

    PubMed Central

    Matsuoka, Shinya; Gupta, Swati; Suzuki, Emiko; Hiromi, Yasushi; Asaoka, Miho

    2014-01-01

    In order to sustain lifelong production of gametes, many animals have evolved a stem cell–based gametogenic program. In the Drosophila ovary, germline stem cells (GSCs) arise from a pool of primordial germ cells (PGCs) that remain undifferentiated even after gametogenesis has initiated. The decision of PGCs to differentiate or remain undifferentiated is regulated by somatic stromal cells: specifically, epidermal growth factor receptor (EGFR) signaling activated in the stromal cells determines the fraction of germ cells that remain undifferentiated by shaping a Decapentaplegic (Dpp) gradient that represses PGC differentiation. However, little is known about the contribution of germ cells to this process. Here we show that a novel germline factor, Gone early (Goe), limits the fraction of PGCs that initiate gametogenesis. goe encodes a non-peptidase homologue of the Neprilysin family metalloendopeptidases. At the onset of gametogenesis, Goe was localized on the germ cell membrane in the ovary, suggesting that it functions in a peptidase-independent manner in cell–cell communication at the cell surface. Overexpression of Goe in the germline decreased the number of PGCs that enter the gametogenic pathway, thereby increasing the proportion of undifferentiated PGCs. Inversely, depletion of Goe increased the number of PGCs initiating differentiation. Excess PGC differentiation in the goe mutant was augmented by halving the dose of argos, a somatically expressed inhibitor of EGFR signaling. This increase in PGC differentiation resulted in a massive decrease in the number of undifferentiated PGCs, and ultimately led to insufficient formation of GSCs. Thus, acting cooperatively with a somatic regulator of EGFR signaling, the germline factor goe plays a critical role in securing the proper size of the GSC precursor pool. Because goe can suppress EGFR signaling activity and is expressed in EGF-producing cells in various tissues, goe may function by attenuating EGFR signaling, and thereby affecting the stromal environment. PMID:25420147

  4. Robotic Welding Systems with Vision-Sensing and Self-learning Neuron Control of Arc Welding Dynamic Process

    Microsoft Academic Search

    S. B. Chen; Y. Zhang; T. Qiu; T. Lin

    2003-01-01

    This paper addresses the vision sensing and neuron control techniques for real-time sensing and control of weld pool dynamics during robotic arc welding. Current teaching playback welding robots are not provided with this real-time function for sensing and control of the welding process. In our research, using composite filtering technology, a computer vision sensing system was established and clear weld

  5. Visible Light Emissions during Gas Tungsten Arc Welding and Its Application to Weld

    E-print Network

    Eagar, Thomas W.

    \\ Visible Light Emissions during Gas Tungsten· Arc Welding and Its Application to Weld Image established, providing for the possibility of an improved weld pool image BY E. W. KIM, C. ALLEMAND AND T. W using 24 combi- nations of weld parameters. Data were collected with a computer-interfaced double

  6. Flow Dynamics in Arc Welding

    SciTech Connect

    Lowke, John J. [CSIRO Materials Science and Engineering, PO Box 218, Lindfield, Sydney NSW 2070 (Australia); Tanaka, Manabu [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki (Japan)

    2008-02-21

    The state of the art for numerical computations has now advanced so that the capability is within sight of calculating weld shapes for any arc current, welding gas, welding material or configuration. Inherent in these calculations is 'flow dynamics' applied to plasma flow in the arc and liquid metal flow in the weld pool. Examples of predictions which are consistent with experiment, are discussed for (1) conventional tungsten inert gas welding, (2) the effect of a fraction of a percent of sulfur in steel, which can increase weld depth by more than a factor of two through changes in the surface tension, (3) the effect of a flux, which can produce increased weld depth due to arc constriction, (4) use of aluminium instead of steel, when the much larger thermal conductivity of aluminium greatly reduces the weld depth and (5) addition of a few percent of hydrogen to argon, which markedly increases weld depth.

  7. Method for enhanced control of welding processes

    SciTech Connect

    Sheaffer, D.A.; Renzi, R.F.; Tung, D.M.; Schroder, K.

    2000-07-04

    Method and system for producing high quality welds in welding processes, in general, and gas tungsten arc (GTA) welding, in particular by controlling weld penetration are disclosed. Light emitted from a weld pool is collected from the backside of a workpiece by optical means during welding and transmitted to a digital video camera for further processing, after the emitted light is first passed through a short wavelength pass filter to remove infrared radiation. By filtering out the infrared component of the light emitted from the backside weld pool image, the present invention provides for the accurate determination of the weld pool boundary. Data from the digital camera is fed to an imaging board which focuses on a 100 x 100 pixel portion of the image. The board performs a thresholding operation and provides this information to a digital signal processor to compute the backside weld pool dimensions and area. This information is used by a control system, in a dynamic feedback mode, to automatically adjust appropriate parameters of a welding system, such as the welding current, to control weld penetration and thus, create a uniform weld bead and high quality weld.

  8. Method for enhanced control of welding processes

    DOEpatents

    Sheaffer, Donald A. (Livermore, CA); Renzi, Ronald F. (Tracy, CA); Tung, David M. (Livermore, CA); Schroder, Kevin (Pleasanton, CA)

    2000-01-01

    Method and system for producing high quality welds in welding processes, in general, and gas tungsten arc (GTA) welding, in particular by controlling weld penetration. Light emitted from a weld pool is collected from the backside of a workpiece by optical means during welding and transmitted to a digital video camera for further processing, after the emitted light is first passed through a short wavelength pass filter to remove infrared radiation. By filtering out the infrared component of the light emitted from the backside weld pool image, the present invention provides for the accurate determination of the weld pool boundary. Data from the digital camera is fed to an imaging board which focuses on a 100.times.100 pixel portion of the image. The board performs a thresholding operation and provides this information to a digital signal processor to compute the backside weld pool dimensions and area. This information is used by a control system, in a dynamic feedback mode, to automatically adjust appropriate parameters of a welding system, such as the welding current, to control weld penetration and thus, create a uniform weld bead and high quality weld.

  9. Biliary lipid output during three meals and an overnight fast. I. Relationship to bile acid pool size and cholesterol saturation of bile in gallstone and control subjects.

    PubMed Central

    Northfield, T C; Hofmann, A F

    1975-01-01

    Using a duodenal perfusion technique, the biliary output of bile acids, phospholipid, and cholesterol was measured hourly during three meals and an overnight fast in seven Caucasians with radiolucent gallstones in a functioning gallbladder, and in seven health controls without gallstones, closely matched for age, sex, and weight. Before the perfusion, bile acid kinetics were defined by an isotope dilution procedure, and the biliary lipid composition of fasting gallbladder bile was determined. Total daily biliary lipid output was similar in gallstone and control subjects, and was unrelated to cholesterol saturation of fasting gallbladder bile and to bile acid pool size. There was an inverse relationship between the size and recycling frequency of the bile acid pool, so that secretion rate and hepatic return of bile acids remained constant, despite a wide range of pool sizes. The finding of a normal bile acid synthesis rate in subjects with a small pool size therefore indicated normal feedback regulation of bile acid synthesis. Hourly measurements of biliary lipid output showed a linear relationship between bile acid and cholesterol output, with a similar regression line for gallstone and control subjects, but a non-linear relationship between bile acid and phospholipid output. Consequently, samples from all subjects were consistently supersaturated with cholesterol at low bile acid outputs, especially during overnight fasting, but not at high bile acid outputs. These findings indicate that hepatic secretion of bile supersaturated with cholesterol is physiological in man at low bile acid outputs, that bile acid pool size is probably determined in part by its recycling frequency, and that cholesterol cholelithiasis in some Caucasians may be due to an underlying extrahepatic abnormality. PMID:806491

  10. Effects of fenofibrate on biliary lipids and bile acid pool size in patients with type IV hyperlipoproteinemia.

    PubMed

    Podda, M; Zuin, M

    1985-05-01

    Lipid-lowering drugs, notably clofibrate, may induce a supersaturation of bile with cholesterol, thus favouring the development of cholelithiasis. In order to see whether or not fenofibrate, a clofibrate analogue, has any influence on biliary cholesterol saturation, we determined the lipid composition of gallbladder bile and the bile acid pool size in 15 patients with type IV hyperlipoproteinemia before and after 6-8 weeks of treatment with a daily dose of 300 mg of the drug. At the end of treatment plasma triglycerides were markedly decreased, whereas no detectable influence on liver cell integrity or bile excretory function could be demonstrated in any patient by comparing the pre- and post-treatment serum levels of liver enzymes, bilirubin and bile acids. The mean bile cholesterol saturation index did not significantly change and cholic acid was the only bile acid to increase significantly. In the 3 patients with an initial saturation index of less than 1, bile became supersaturated with cholesterol. However, in no case were the limits of the metastable phase for cholesterol solubility in bile exceeded. Though only long-term prospective studies may give a definitive answer about the lithogenic potential of fenofibrate, our data on gallbladder bile composition in patients with type IV hyperlipoproteinemia indicate that it is not very likely that fenofibrate administration will increase the risk of gallstone formation in severely hyperlipidemic patients. PMID:4004987

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

    NASA Astrophysics Data System (ADS)

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

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

  12. Nutrient demand interacts with legume particle length to affect digestion responses and rumen pool sizes in dairy cows.

    PubMed

    Kammes, K L; Ying, Y; Allen, M S

    2012-05-01

    Effects of legume particle length on dry matter intake (DMI), milk production, ruminal fermentation and pool sizes, and digestion and passage kinetics, and the relationship of these effects with preliminary DMI (pDMI) were evaluated using 13 ruminally and duodenally cannulated Holstein cows in a crossover design with a 14-d preliminary period and two 19-d treatment periods. During the preliminary period, pDMI of individual cows ranged from 22.8 to 32.4 kg/d (mean=26.5 kg/d) and 3.5% fat-corrected milk yield ranged from 22.9 to 62.4 kg/d (mean=35.1 kg/d). Experimental treatments were diets containing alfalfa silage chopped to (1) 19 mm (long cut, LC) or (2) 10 mm (short cut, SC) theoretical length of cut as the sole forage. Alfalfa silages contained approximately 43% neutral detergent fiber (NDF); diets contained approximately 47% forage and 20% forage NDF. Preliminary DMI, an index of nutrient demand, was determined during the last 4 d of the preliminary period, when cows were fed a common diet, and used as a covariate. Main effects of legume particle length and their interaction with pDMI were tested by ANOVA. Alfalfa particle length and its interaction with pDMI did not affect milk yield or rumen pH. The LC diet decreased milk fat concentration more per kilogram of pDMI increase than the SC diet and increased yields of milk fat and fat-corrected milk less per kilogram of pDMI increase than the SC diet, resulting in a greater benefit for LC at low pDMI and for SC at high pDMI. The LC diet tended to decrease DMI compared with the SC diet. Ruminal digestion and passage rates of feed fractions did not differ between LC and SC and were not related to level of intake. The LC diet tended to decrease the rate of ruminal turnover for NDF but increased NDF rumen pools at a slower rate than the SC diet as pDMI increased. This indicated that the faster NDF turnover rate did not counterbalance the higher DMI for SC, resulting in larger NDF rumen pools for SC than LC. As pDMI increased, LC increased ruminal digestibility of potentially digestible NDF and total NDF, and SC decreased them, but total-tract digestibilities of potentially digestible NDF, total NDF, organic matter, and dry matter were lower for LC than for SC. Ruminal digestibilities of starch and organic matter interacted quadratically with level of intake. When legume silage was the only source of forage in the diet, increasing chop length from 10 to 19 mm tended to decrease DMI but did not negatively affect productivity of cows. PMID:22541490

  13. Nitrogen Stress Affects the Turnover and Size of Nitrogen Pools Supplying Leaf Growth in a Grass1[C][W][OPEN

    PubMed Central

    Lehmeier, Christoph Andreas; Wild, Melanie; Schnyder, Hans

    2013-01-01

    The effect of nitrogen (N) stress on the pool system supplying currently assimilated and (re)mobilized N for leaf growth of a grass was explored by dynamic 15N labeling, assessment of total and labeled N import into leaf growth zones, and compartmental analysis of the label import data. Perennial ryegrass (Lolium perenne) plants, grown with low or high levels of N fertilization, were labeled with 15NO3?/14NO3? from 2 h to more than 20 d. In both treatments, the tracer time course in N imported into the growth zones fitted a two-pool model (r2 > 0.99). This consisted of a “substrate pool,” which received N from current uptake and supplied the growth zone, and a recycling/mobilizing “store,” which exchanged with the substrate pool. N deficiency halved the leaf elongation rate, decreased N import into the growth zone, lengthened the delay between tracer uptake and its arrival in the growth zone (2.2 h versus 0.9 h), slowed the turnover of the substrate pool (half-life of 3.2 h versus 0.6 h), and increased its size (12.4 ?g versus 5.9 ?g). The store contained the equivalent of approximately 10 times (low N) and approximately five times (high N) the total daily N import into the growth zone. Its turnover agreed with that of protein turnover. Remarkably, the relative contribution of mobilization to leaf growth was large and similar (approximately 45%) in both treatments. We conclude that turnover and size of the substrate pool are related to the sink strength of the growth zone, whereas the contribution of the store is influenced by partitioning between sinks. PMID:23757403

  14. Developing mathematical models to predict grain size and hardness of argon tungsten pulse current arc welded titanium alloy

    Microsoft Academic Search

    M. Balasubramanian; V. Jayabalan; V. Balasubramanian

    2008-01-01

    Titanium (Ti–6Al–4V) alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to-weight ratio, such as transportable bridge girders, military vehicles, road tankers and railway transport systems. The frequently preferred welding process of titanium alloy is argon tungsten arc welding due to its comparatively easier applicability and better economy. In case of single pass welding

  15. Optical penetration sensor for pulsed laser welding

    DOEpatents

    Essien, Marcelino (Albuquerque, NM); Keicher, David M. (Albuquerque, NM); Schlienger, M. Eric (Albuquerque, NM); Jellison, James L. (Albuquerque, NM)

    2000-01-01

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

  16. A Study on the Welding Characteristics of Tailor Welded Blank Metal Sheets Using GTAW and Laser Welding

    NASA Astrophysics Data System (ADS)

    Thasanaraphan, Pornsak

    In this study, a computational and experimental effort was carried out to qualitatively understand the weld pool shape, distortion and residual stress for continuous laser welding and manual pulsed gas metal arc welding. For all the welding simulations given in this dissertation, a welding specific finite element package, SYSWELD, is used. This research focuses on the welding behavior observed in light-weight metal structures known as the tailor-welded blanks, TWBs. They are a combination of two or more metal sheets with different thickness and/or different materials that are welded together in a single plane prior to forming, e.g., stamping. They made from the low carbon steel. As laser welding experiment results show, the weld pool shape at the top and bottom surface, is strongly influenced by surface tension, giving it a characteristic hourglass shape. In order to simulate the hourglass shape, a new volumetric heat source model was developed to predict the transient temperature profile and weld pool shape, including the effect of surface tension. Tailor welded blanks with different thicknesses were examined in the laser welding process. All major physical phenomena such as thermal conduction, heat radiation and convection heat losses are taken into account in the model development as well as temperature-dependant thermal and mechanical material properties. The model is validated for the case of butt joint welding of cold rolled steel sheets. The results of the numerical simulations provide temperature distributions representing the shape of the molten pool, distortion and residual stress with varying laser beam power and welding speed. It is demonstrated that the finite element simulation results are in good agreement with the experiment results. This includes the weld pool shape and sheet metal distortion. While there is no experimental data to compare directly with residual stress results, the distorted shape provides an indirect measure of the welding residual stresses. The welding details such as clamping, butt joint configuration, material, sample thickness are similar for both the laser welding process and the manual pulsed GTAW process. Also as same metallurgical investigation, the weld pool shape displays wider full penetration without the effect of surface tension. The double ellipsoid volumetric heat source is applied in the finite element simulation to determine the temperature distribution, distortion and residual stress. The simulation results are compared with the experimental results and show good agreement. In addition, the results from the laser welding process are compared to the equivalent results from the GTAW process in the order to better understand the fundamental differences between these two welding processes.

  17. Effect of the conditions of the welding thermal cycle on the structure and properties of weld metal in titanium alloys

    Microsoft Academic Search

    V. I. Muravev; O. N. Kleshnina; A. A. Kuznetsov; P. V. Bakhmatov

    2011-01-01

    The results of investigations of the effect of the welding thermal cycle on the structure and properties of welded joints VT20 titanium alloy are presented. It is shown that the removal of capillary-condensed moisture from the surface of the welded components and degassing of the weld pool prevent the formation of pores and result in a large reduction of the

  18. Effect of the conditions of the welding thermal cycle on the structure and properties of weld metal in titanium alloys

    Microsoft Academic Search

    V. I. Muravev; O. N. Kleshnina; A. A. Kuznetsov; P. V. Bakhmatov

    2012-01-01

    The results of investigations of the effect of the welding thermal cycle on the structure and properties of welded joints VT20 titanium alloy are presented. It is shown that the removal of capillary-condensed moisture from the surface of the welded components and degassing of the weld pool prevent the formation of pores and result in a large reduction of the

  19. Neurofuzzy Model-Based Weld Fusion State Estimation

    E-print Network

    Zhang, YuMing

    . The fusion state can be specified using the outline of the cross-sectional solidified weld bead. Extraction or- der to directly observe the weld pool, the intensive arc light should be avoided or eliminated

  20. HPLC analysis of nonprotein thiols in planktonic diatoms: pool size, redox state and response to copper and cadmium exposure

    Microsoft Academic Search

    J. W. Rijstenbil; J. A. Wijnholds

    1996-01-01

    A sensitive method was developed to analyze low molecular weight thiols involved in metal homeostasis and detoxification in phytoplankton. The aims of this study were to (1) separate and measure all relevant thiols in a single HPLC run, (2) measure redox states of the thiols and (3) identify specific responses of thiols (pools, redox) to heavy metals by testing diatoms

  1. Processing Welding Images For Robot Control

    NASA Technical Reports Server (NTRS)

    Richardson, Richard W.

    1988-01-01

    Image data from two distinct windows used to locate weld features. Analyzer part of vision system described in companion article, "Image Control in Automatic Welding Vision System" (MFS-26035). Horizontal video lines define windows for viewing unwelded joint and weld pool. Data from picture elements outside windows not processed. Widely-separated local features carry no significance, but closely spaced features indicate welding feature. Image processor assigns confidence level to group of local features according to spacing and pattern.

  2. X-Ray and Neutron Diffraction Measurements of Dislocation Density and Subgrain Size in a Friction-Stir-Welded Aluminum Alloy

    SciTech Connect

    Woo, Wan Chuck [ORNL; Ungar, Prof Tomas [Eotvos University, Budapest, Hungary; Feng, Zhili [ORNL; Kenik, Edward A [ORNL; Clausen, B [Los Alamos National Laboratory (LANL)

    2009-01-01

    The dislocation density and subgrain size were determined in the base material and friction-stir welds of 6061-T6 aluminum alloy. High-resolution X-ray diffraction measurement was performed in the base material. The result of the line profile analysis of the X-ray diffraction peak shows that the dislocation density is about 4.5 x 10{sup 14} m{sup -2} and the subgrain size is about 200 nm. Meanwhile, neutron diffraction measurements have been performed to observe the diffraction peaks during friction-stir welding (FSW). The deep penetration capability of the neutron enables us to measure the peaks from the midplane of the Al plate underneath the tool shoulder of the friction-stir welds. The peak broadening analysis result using the Williamson-Hall method shows the dislocation density of about 3.2 x 10{sup 15} m{sup -2} and subgrain size of about 160 nm. The significant increase of the dislocation density is likely due to the severe plastic deformation during FSW. This study provides an insight into understanding the transient behavior of the microstructure under severe thermomechanical deformation.

  3. CHANGES IN SOLIDIFICATION MODE, AND THE MEASUREMENT OF COOLING RATES FOLLOWING SOLIDIFICATION DURING ARC WELDING

    E-print Network

    Cambridge, University of

    SOLIDIFICATION DURING ARC WELDING 2.1 INTRODUCTION The solidification process in a weld pool has been shown to have a considerable in- fluence upon the properties of the resultant weld. It influences elements, and hence the homogeneity of the weld. Previous work on the cooling behaviour of welds (Garland

  4. 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.

  5. Proteasome Inhibition Triggers Activity-Dependent Increase in the Size of the Recycling Vesicle Pool in Cultured Hippocampal Neurons

    PubMed Central

    Willeumier, Kristen; Pulst, Stefan M.; Schweizer, Felix E.

    2008-01-01

    The ubiquitin proteasome system, generally known for its function in protein degradation, also appears to play an important role in regulating membrane trafficking. A role for the proteasome in regulating presynaptic release and vesicle trafficking has been proposed for invertebrates, but it remains to be tested in mammalian presynaptic terminals. We used the fluorescent styrylpyridinium dye FM4-64 to visualize changes in the recycling pool of vesicles in hippocampal culture under pharmacological inhibition of the proteasome. We found that a 2 h inhibition increases the recycling pool of vesicles by 76%, with no change in the rate or total amount of dye release. Interestingly, enhancement did not depend on protein synthesis but did depend on synaptic activity; blocking action potentials during proteasome inhibition abolished the effect whereas increasing neuronal activity accelerated the effect with an increased recycling pool evident after 15 min. We propose that the proteasome acts as a negative-feedback regulator of synaptic transmission, possibly serving a homeostatic role. PMID:17079661

  6. AMINO ACID SYNTHESIS IN PHOTO-SYNTHESIZING SPINACH CELLS. EFFECTS OF AMMONIA ON POOL SIZES AND RATES OF LABELING FROM {sup 14}CO{sub 2}

    SciTech Connect

    Larsen, Peder Olesen; Cornwell, Karen L.; Gee, Sherry L.; Bassham, James A.

    1980-10-01

    Isolated cells from leaves of Spinacea oleracea have been maintained in a state capable of high rates of photosynthetic CO{sub 2} fixation for more than 60 h. The incorporation of {sup 14}CO{sub 2} under saturating CO{sub 2} conditions into carbohydrates, carboxylic acids, and amino acids, and the effect of ammonia on this incorporation have been studied. Total incorporation, specific radioactivity and pool size have been determined as a function of time for most of the protein amino acids and for {gamma}-aminobutyric acid. the measurements of specific activities and of the approaches to {sup 14}C "saturation" of some amino acids indicate the presence and relative sizes of metabolically active and passive pools of these amino acids. Added ammonia decreased carbon fixation into carbohydrates and increased fixation into carboxylic acids and amino acids. Different amino acids were, however, affected in different and highly specific ways. Ammonia caused large stimulatory effects in incorporation of {sup 14}C into glutamine (a factor of 16), No effect or slight decreases were seen in glycine, serine, phenylalanine, and tyrosine labeling, In.the case of glutamate, {sup 14}C-labeling decreased, but specific activity increased. The production of labeled {gamma}-aminobutyric acid was virtually stopped by ammonia. The results indicate that added ammonia stimulates the reactions mediated by pyruvate kinase and phosphoenolpyruvate carboxylase, as seen with other plant systems. The data on the effects of added ammonia on total labeling, pool sizes, and specific activities of several amino acids provides a number of indications about the intracellular sites of principal synthesis from carbon skeletons of these amino acids and the selective nature of effects of increased intracellular ammonia concentration on such synthesis.

  7. Fast, Nonspattering Inert-Gas Welding

    NASA Technical Reports Server (NTRS)

    Gilbert, Jeffrey L.

    1991-01-01

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

  8. Investigation of molten pool oscillation during GMAW-P process based on a 3D model

    NASA Astrophysics Data System (ADS)

    Wang, L. L.; Lu, F. G.; Cui, H. C.; Tang, X. H.

    2014-11-01

    In order to better reveal the oscillation mechanism of the pulsed gas metal arc welding (GMAW-P) process due to an alternately varied welding current, arc plasma and molten pool oscillation were simulated through a self-consistent three-dimensional model. Based on an experimental analysis of the dynamic variation of the arc plasma and molten pool captured by a high-speed camera, the model was validated by comparison of the measured and predicted results. The calculated results showed that arc pressure was the key factor causing the molten pool to oscillate. The variation in arc size and temperature from peak time to base time resulted in a great difference in the heat input and arc pressure acting on the molten pool. The surface deformation of the molten pool due to the varying degrees of arc pressure induced alternate displacement and backflow in the molten metal. The periodic iteration of deeper and shallower surface deformation, drain and backflow of molten metal caused the molten pool to oscillate at a certain frequency. In this condition, the arc pressure at the peak time is more than six times higher than that at the base time, and the maximum surface depression is 1.4?mm and 0.6?mm, respectively, for peak time and base time.

  9. The particle size distribution, density, and specific surface area of welding fumes from SMAW and GMAW mild and stainless steel consumables.

    PubMed

    Hewett, P

    1995-02-01

    Particle size distributions were measured for fumes from mild steel (MS) and stainless steel (SS); shielded metal arc welding (SMAW) and gas metal arc welding (GMAW) consumables. Up to six samples of each type of fume were collected in a test chamber using a micro-orifice uniform deposit (cascade) impactor. Bulk samples were collected for bulk fume density and specific surface area analysis. Additional impactor samples were collected using polycarbonate substrates and analyzed for elemental content. The parameters of the underlying mass distributions were estimated using a nonlinear least squares analysis method that fits a smooth curve to the mass fraction distribution histograms of all samples for each type of fume. The mass distributions for all four consumables were unimodal and well described by a lognormal distribution; with the exception of the GMAW-MS and GMAW-SS comparison, they were statistically different. The estimated mass distribution geometric means for the SMAW-MS and SMAW-SS consumables were 0.59 and 0.46 micron aerodynamic equivalent diameter (AED), respectively, and 0.25 micron AED for both the GMAW-MS and GMAW-SS consumables. The bulk fume densities and specific surface areas were similar for the SMAW-MS and SMAW-SS consumables and for the GMAW-MS and GMAW-SS consumables, but differed between SMAW and GMAW. The distribution of metals was similar to the mass distributions. Particle size distributions and physical properties of the fumes were considerably different when categorized by welding method. Within each welding method there was little difference between MS and SS fumes. PMID:7856513

  10. Metabolic engineering of the purine biosynthetic pathway in Corynebacterium glutamicum results in increased intracellular pool sizes of IMP and hypoxanthine

    PubMed Central

    2012-01-01

    Background Purine nucleotides exhibit various functions in cellular metabolism. Besides serving as building blocks for nucleic acid synthesis, they participate in signaling pathways and energy metabolism. Further, IMP and GMP represent industrially relevant biotechnological products used as flavor enhancing additives in food industry. Therefore, this work aimed towards the accumulation of IMP applying targeted genetic engineering of Corynebacterium glutamicum. Results Blocking of the degrading reactions towards AMP and GMP lead to a 45-fold increased intracellular IMP pool of 22 ?mol gCDW-1. Deletion of the pgi gene encoding glucose 6-phosphate isomerase in combination with the deactivated AMP and GMP generating reactions, however, resulted in significantly decreased IMP pools (13 ?mol gCDW-1). Targeted metabolite profiling of the purine biosynthetic pathway further revealed a metabolite shift towards the formation of the corresponding nucleobase hypoxanthine (102 ?mol gCDW-1) derived from IMP degradation. Conclusions The purine biosynthetic pathway is strongly interconnected with various parts of the central metabolism and therefore tightly controlled. However, deleting degrading reactions from IMP to AMP and GMP significantly increased intracellular IMP levels. Due to the complexity of this pathway further degradation from IMP to the corresponding nucleobase drastically increased suggesting additional targets for future strain optimization. PMID:23092390

  11. The radial diffusivity and magnetization transfer pool size ratio are sensitive markers for demyelination in a rat model of type III multiple sclerosis (MS) lesions

    PubMed Central

    Janve, Vaibhav A.; Zu, Zhongliang; Yao, Song-Yi; Li, Ke; Zhang, Fang Lin; Wilson, Kevin; Ou, Xiawei; Does, Mark D.; Subramaniam, Sriram; Gochberg, Daniel F.

    2013-01-01

    Determining biophysical sensitivity and specificity of quantitative magnetic resonance imaging is essential to develop effective imaging metrics of neurodegeneration. Among these metrics apparent pool size ratio (PSR) from quantitative magnetization transfer (qMT) imaging and radial diffusivity (RD) from diffusion tensor imaging (DTI) are both known to relate to histological measure of myelin density and integrity. However their relative sensitivities towards quantitative myelin detection are unknown. In this study, we correlated high-resolution quantitative magnetic resonance imaging measures of subvoxel tissue structures with corresponding quantitative myelin histology in a lipopolysacharide (LPS) mediated animal model of MS. Specifically, we acquired quantitative magnetization transfer (qMT) and diffusion tensor imaging (DTI) metrics (on the same tissue sample) in an animal model system of type III oligodendrogliopathy which lacked prominent lymphocytic infiltration, a system that had not been previously examined with quantitative MRI. We find that the qMT measured apparent pool size ratio (PSR) showed the strongest correlation with a histological measure of myelin content. DTI measured RD showed the next strongest correlation, and other DTI and relaxation parameters (such as the longitudinal relaxation rate (R1f) or fractional anisotropy (FA)) showed considerably weaker correlations with myelin content. PMID:23481461

  12. Electrode formulation to reduce weld metal hydrogen and porosity

    SciTech Connect

    Liu, S.; Olson, D.L. [Colorado School of Mines, Golden, CO (United States). Center for Welding and Joining Research; Ibarra, S. [Amoco Corporation Research, Naperville, IL (United States)

    1994-12-31

    Residual weld metal hydrogen is a major concern in high strength steel welding, especially when the weld is performed under high cooling rate conditions. In the case of underwater wet welding, weld metal porosity is also of importance because of the water environment. The control of both problems can be achieved by means of pyrochemical reactions in the weld pool. The hydrogen-oxygen reaction and carbon-oxygen reaction are fundamental in the control of residual hydrogen in the weld metal and the amount of gas pores entrapped. A simple model was proposed to estimate weld metal residual hydrogen content by monitoring the weld pool deoxidation reactions. Potent deoxidizers such as aluminum will first react with oxygen in the liquid weld pool, followed by other elements present such as silicon and manganese. Carbon and hydrogen will be the last ones to react with oxygen prior to the iron atoms. The Ellingham-Richardson diagram frequently applied in describing steel and iron making processes was used in the modeling. Following the sequence of deoxidation, the chemical make-up of the gas pores and the amount of each chemical species in the pores could be estimated. Carbon monoxide and hydrogen were determined to be the major components in the weld pores. To minimize the amount of weld metal porosity and residual hydrogen content, specially designed consumables that will control the oxygen potential of the weld pool must be developed.

  13. Effects of varying subatmospheric pressure on stationary plasma arc welds

    NASA Technical Reports Server (NTRS)

    Chin, J. J.; Rubinsky, B.

    1991-01-01

    An experimental study was performed examining the variation of penetration, fluid behavior, heat-affected zone and arc in plasma arc welding (PAW) with respect to subatmospheric ambient pressure. The results reveal nonlinear variation of keyhole size, time of penetration, and size of the heat-affected zone with pressure. In a restricted range of pressure, dynamic components of fluid flow directed out of the molten pool appear and have a profound effect on keyhole formation. The generated plasma arc is observed to decrease in intensity with decreasing pressure, resulting in a reduction of penetration at lower pressures.

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

    NASA Astrophysics Data System (ADS)

    Kim, Taewon; Suga, Yasuo; Koike, Takashi

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

  15. Delineation of biochemical, molecular, and physiological changes accompanying bile acid pool size restoration in Cyp7a1?/? mice fed low levels of cholic acid

    PubMed Central

    Jones, Ryan D.; Repa, Joyce J.; Russell, David W.; Dietschy, John M.

    2012-01-01

    Cholesterol 7?-hydroxylase (CYP7A1) is the initiating and rate-limiting enzyme in the neutral pathway that coverts cholesterol to primary bile acids (BA). CYP7A1-deficient (Cyp7a1?/?) mice have a depleted BA pool, diminished intestinal cholesterol absorption, accelerated fecal sterol loss, and increased intestinal cholesterol synthesis. To determine the molecular and physiological effects of restoring the BA pool in this model, adult female Cyp7a1?/? mice and matching Cyp7a1+/+ controls were fed diets containing cholic acid (CA) at modest levels [0.015, 0.030, and 0.060% (wt/wt)] for 15–18 days. A level of just 0.03% provided a CA intake of ?12 ?mol (4.8 mg) per day per 100 g body wt and was sufficient in the Cyp7a1?/? mice to normalize BA pool size, fecal BA excretion, fractional cholesterol absorption, and fecal sterol excretion but caused a significant rise in the cholesterol concentration in the small intestine and liver, as well as a marked inhibition of cholesterol synthesis in these organs. In parallel with these metabolic changes, there were marked shifts in intestinal and hepatic expression levels for many target genes of the BA sensor farnesoid X receptor, as well as genes involved in cholesterol transport, especially ATP-binding cassette (ABC) transporter A1 (ABCA1) and ABCG8. In Cyp7a1+/+ mice, this level of CA supplementation did not significantly disrupt BA or cholesterol metabolism, except for an increase in fecal BA excretion and marginal changes in mRNA expression for some BA synthetic enzymes. These findings underscore the importance of using moderate dietary BA levels in studies with animal models. PMID:22628034

  16. Contribution to study of heat transfer and fluid flow during GTA welding

    NASA Astrophysics Data System (ADS)

    Koudadje, Koffi; Delalondre, Clarisse; Médale, Marc; Carpreau, Jean-Michel

    2014-06-01

    In this paper, the effect of surface-active elements especially sulfur on weld pool shape has been reported. In our contribution, we analyze the influence of the weld pool chemical composition (Mn, Si, …), welding energy, sulphur gradient and electromagnetic effect. The computed results are in good agreement with the corresponding experimental results, indicating the validity of the modeling approach.

  17. 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.

  18. The keyhole region in VPPA welds

    NASA Technical Reports Server (NTRS)

    Walsh, Daniel W.

    1988-01-01

    The morphology and properties of the Variable Polarity Plasma Arc (VPPA) weld composite zone are intimately related to the physical processes associated with the keyhole. The effects of microsegregation and transient weld stress on macrosegregation in the weld tool are examined. In addition the electrical character of straight and reverse polarity portions of the arc cycle were characterized. The results of the former study indicate that alloy 2219 is weldable because large liquid volumes are available during latter stages of weld solidification. Strains in the pool region, acting in conjunction with weld microsegregation can produce macrosegregation great enough to produce radiographic contrast effects in welds. Mechanisms of surface copper enrichment were identified. The latter study has demonstrated that increased heat is delivered to workpieces if the reverse polarity proportion of the weld cycle is increased. Current in the straight polarity portion of the welding cycle increased as the reverse cycle proportion increased. Voltage during reverse polarity segments is large.

  19. Thermochemical Analysis of Hydrogen Absorption in Welding

    E-print Network

    Eagar, Thomas W.

    the amount of hy- drogen initially absorbed by the weld pool. Diffusible hydrogen measurements can be converted to initially absorbed hy· drogen values by using Terasaki's theo· retical analysis {Ref. 3

  20. ABSTRACT. Keyhole plasma arc welding is a unique arc welding process for deep

    E-print Network

    Zhang, YuMing

    ABSTRACT. Keyhole plasma arc welding is a unique arc welding process for deep penetration. To ensure the quality of the welds, the presence of the keyhole is crit- ical. Understanding of the keyhole will certainly benefit the improvement of the process and weld quality. Currently, the size of the keyhole

  1. Pool Purification

    NASA Technical Reports Server (NTRS)

    1988-01-01

    Caribbean Clear, Inc. used NASA's silver ion technology as a basis for its automatic pool purifier. System offers alternative approach to conventional purification chemicals. Caribbean Clear's principal markets are swimming pool owners who want to eliminate chlorine and bromine. Purifiers in Caribbean Clear System are same silver ions used in Apollo System to kill bacteria, plus copper ions to kill algae. They produce spa or pool water that exceeds EPA Standards for drinking water.

  2. Fatigue life prediction of gas tungsten arc welded AISI 304L cruciform joints with different LOP sizes

    Microsoft Academic Search

    P. Johan Singh; D. R. G Achar; B Guha; Hans Nordberg

    2003-01-01

    Fatigue life evaluations have been carried out on gas tungsten arc welded (GTAW) load-carrying cruciform joints of AISI 304L stainless steel with lack of penetration (LOP) using conventional S-N and crack initiation-propagation (I-P) methods. The crack process normally comprises two major phases: (1) the crack initiation life (Ni): and (2) the crack propagation life (Np). The local stress-life approach is

  3. Effect of Pin Length on Hook Size and Joint Properties in Friction Stir Lap Welding of 7B04 Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Wang, Min; Zhang, Huijie; Zhang, Jingbao; Zhang, Xiao; Yang, Lei

    2014-05-01

    Friction stir lap welding of 7B04 aluminum alloy was conducted in the present paper, and the effect of pin length on hook size and joint properties was investigated in detail. It is found that for each given set of process parameters, the size of hook defect on the advancing side shows an "M" type evolution trend as the pin length is increased. The affecting characteristics of pin length on joint properties are dependent on the heat input levels. When the heat input is low, the fracture strength is firstly increased to a peak value and then shows a decrease. When the heat input is relatively high, the evolution trend of fracture strength tends to exhibit a "W" type with increasing the pin length.

  4. Welding I.

    ERIC Educational Resources Information Center

    Allegheny County Community Coll., Pittsburgh, PA.

    Instructional objectives and performance requirements are outlined in this course guide for Welding I, a performance-based course offered at the Community College of Allegheny County to introduce students to shielded arc welding procedures involving stringer beads, butt welds, and lap welds. After introductory material outlining course objectives,…

  5. Optical Monitoring of Weld Penetration

    NASA Technical Reports Server (NTRS)

    Maram, J.

    1986-01-01

    Robotic welding controlled by reliable, relatively-noise-free optoelectronic unit. Bounding off meniscus of pool of molten metal, laser beam impinges on position-sensitive photodetector. Beam diameter adjusted for width of weld. Optical filters screen out light from arc. Made from small, low-cost components and utilizing optical fibers to conduct signals, system immune to electromagnetic interference common in industrial environments. Aimed for automatic welders, robot welders in particular and also adaptable to other types of welding, including tungsten/inert-gas, laser, and electron-beam techniques.

  6. Laser Sensor For Adaptive Welding

    NASA Astrophysics Data System (ADS)

    Beranek, Bretislav; Boillot, Jean-Paul; Ferrie, F. P.

    1986-10-01

    An autosynchronized laser scanning mechanism is integrated in a compact, mobile unit mounted on a six axis, articulated robot wrist. This camera combines a new geometrical arrangement for improving the performance of optical triangulation with the latest solid-state laser and CCD sensor technology. The camera enables in-process, 3D mea-surements of the welded workpiece and the optimization of the robotic arc welding process. Joint and weld geometry analysis can be performed in real time with high precision, even during high current arc welding. This provides information about weld joint geometry in front of the arc (e.g. seam tracking) and behind the weld pool (e.g. inspection of finished welds), both of which are required for closed loop adaptive welding. High dimensional resolution combined with high signal to noise ratio provides an ideal tool for the further development of expert welding systems. Furthermore, the vision system can be used for the generation of 3D object data, which can be used in conjunction with a computer graphics system for offline robot programming.

  7. Slag-Metal Reactions during Welding: Part Ill. Verification of the Theory

    E-print Network

    Eagar, Thomas W.

    , Slag-Metal Reactions during Welding: Part Ill. Verification of the Theory U. MITRA and T.W. EAGAR. The transfer of carbon and oxygen is also discussed. It is shown that the transfer of oxygen into the weld of inclusions in the solidifying weld pool. Methods of applying this analysis to multipass welds and active

  8. Friction Stir Welding Development

    NASA Technical Reports Server (NTRS)

    Romine, Peter L.

    1998-01-01

    The research of this summer was a continuation of work started during the previous summer faculty fellowship period. The Friction Stir Welding process (FSW) patented by The Welding Institute (TWI), in Great Britain, has become a popular topic at the Marshall Space Flight Center over the past year. Last year it was considered a novel approach to welding but few people took it very seriously as a near term solution. However, due to continued problems with cracks in the new aluminum-lithium space shuttle external tank (ET), the friction stir process is being mobilized at full speed in an effort to mature this process for the potential manufacture of flight hardware. It is now the goal of NASA and Lockheed-Martin Corporation (LMC) to demonstrate a full-scale friction stir welding system capable of welding ET size barrel sections. The objectives this summer were: (1) Implementation and validation of the rotating dynamometer on the MSFC FSW system; (2) Collection of data for FSW process modeling efforts; (3) Specification development for FSW implementation on the vertical weld tool; (4) Controls and user interface development for the adjustable pin tool; and (5) Development of an instrumentation system for the planishing process. The projects started this summer will lead to a full scale friction stir welding system that is expected to produce a friction stir welded shuttle external tank type barrel section. The success of this could lead to the implementation of the friction stir process for manufacturing future shuttle external tanks.

  9. Full penetration detection in Nd:YAG laser welding by analysis of oscillatory optical signals: application to overlap weld-seam tracking

    NASA Astrophysics Data System (ADS)

    Hand, Duncan P.; Haran, Frank M.; Jones, Julian D. C.; Peters, Christopher

    1997-04-01

    We describe a non-intrusive optical sensor for process monitoring of Nd:YAG laser welding, using light returned through the core of the power delivery optical fiber. This sensor is referred to as the core power monitor (core PM), and uses the delivery fiber to collect the broadband light generated in the process, which is then divided into spectral bands (designated as UV/visible and IR). These optical signals exhibit a characteristic oscillatory intensity modulation within the frequency range 2 - 5 kHz, which is believed to arise from a combination of keyhole, and weld pool oscillations. The frequency content may be related to the size and shape of the welding keyhole, and an alarm system for overlap weeding has been developed based on this principle. This can detect both misalignment of the focused laser spot off the seam, and any excessive gap between the plates.

  10. Vision processing and control of robotic Arc welding system

    Microsoft Academic Search

    R. S. Baheti

    1985-01-01

    A microprocessor-based control system is presented for a Gas Tungsten Arc Welding (GTAW) process to join thin sheet metal parts. The system uses a welding robot, a vision sensor, and an image processor to control the welding torch in real-time. A vision-processing algorithm is developed to compute weld puddle geometry parameters from the noisy image of the molten pool. The

  11. Sensors control gas metal arc welding

    SciTech Connect

    Siewert, T.A.; Madigan, R.B.; Quinn, T.P. [National Inst. of Standards and Technology, Boulder, CO (United States)

    1997-04-01

    The response time of a trained welder from the time a weld problem is identified to the time action is taken is about one second--especially after a long, uneventful period of welding. This is acceptable for manual welding because it is close to the time it takes for the weld pool to solidify. If human response time were any slower, manual welding would not be possible. However, human response time is too slow to respond to some weld events, such as melting of the contact tube in gas metal arc welding (GMAW), and only automated intelligent control systems can react fast enough to correct or avoid these problems. Control systems incorporate welding knowledge that enables intelligent decisions to be made about weld quality and, ultimately, to keep welding parameters in the range where only high-quality welds are produced. This article discusses the correlation of electrical signals with contact-tube wear, changes in shielding gas, changes in arc length, and other weld process data.

  12. Advanced Welding Concepts

    NASA Technical Reports Server (NTRS)

    Ding, Robert J.

    2010-01-01

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

  13. Development and application of specially-focused ultrasonic transducers to location and sizing of defects in 75 mm- to 127 mm-thick austenitic stainless steel weld metals

    SciTech Connect

    Dalder, E.N.C.; Benson, S.; McKinley, B.J.; Carodiskey, T.

    1992-08-01

    Special UT transducer parts, capable of focusing incident signals within a 25 mm {times} 25 mm {times} 25 mm volume in an austenitic stainless weld metal at depths that varied from 25 mm to 127 mm, were developed and demonstrated to be capable of detecting a defect with cross section equivalent to that of a 4.76 mm-dia flat-bottom hole. Defect length sizing could be accomplished to {plus_minus}50% for 100% of the time and to {plus_minus}25% on selected defect types as follows: porosity groups, 100%; cracks, 67%; combined slag and porosity, 60%; and linear slag indications, 59%. Extensive linear elastic-fracture-mechanics analyses were performed to establish allowable defect sizes at functions of stress, based on a cyclic-life criterion of 10{sup 3} full power cycles of the MFTF-B magnet system. These defect sizes were used to determine which UT indicating were to be removed and repaired and which were to be retained and their recorded sizes and locations.

  14. Examination of the physical processes associated with the keyhole region of variable polarity plasma arc welds in aluminum alloy 2219

    NASA Technical Reports Server (NTRS)

    Walsh, Daniel W.

    1987-01-01

    The morphology and properties of the Variable Polarity Plasma Arc (VPPA) weld composite zone are intimately related to the physical processes associated with the keyhole. This study examined the effects of oxide, halide, and sulfate additions to the weld plate on the keyhole and the weld pool. Changes in both the arc plasma character and the bead morphology were correlated to the chemical environment of the weld. Pool behavior was observed by adding flow markers to actual VPPA welds. A low temperature analog to the welding process was developed. The results of the study indicate that oxygen, even at low partial pressures, can disrupt the stable keyhole and weld pool. The results also indicate that the Marangoni surface tension driven flows dominate the weld pool over the range of welding currents studied.

  15. Effects of shielding gas compositions on arc plasma and metal transfer in gas metal arc welding

    SciTech Connect

    Rao, Z. H. [School of Energy Science and Engineering, Central South University, Changsha 410083 (China); Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States); Liao, S. M. [School of Energy Science and Engineering, Central South University, Changsha 410083 (China); Tsai, H. L. [Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States)

    2010-02-15

    This article presents the effects of shielding gas compositions on the transient transport phenomena, including the distributions of temperature, flow velocity, current density, and electromagnetic force in the arc and the metal, and arc pressure in gas metal arc welding of mild steel at a constant current input. The shielding gas considered includes pure argon, 75% Ar, 50% Ar, and 25% Ar with the balance of helium. It is found that the shielding gas composition has significant influences on the arc characteristics; droplet formation, detachment, transfer, and impingement onto the workpiece; and weld pool dynamics and weld bead profile. As helium increases in the shielding gas, the droplet size increases but the droplet detachment frequency decreases. For helium-rich gases, the current converges at the workpiece with a 'ring' shape which produces non-Gaussian-like distributions of arc pressure and temperature along the workpiece surface. Detailed explanations to the physics of the very complex but interesting transport phenomena are given.

  16. Palmitate increases L-type Ca2+ currents and the size of the readily releasable granule pool in mouse pancreatic beta-cells.

    PubMed

    Olofsson, Charlotta S; Salehi, Albert; Holm, Cecilia; Rorsman, Patrik

    2004-06-15

    We have investigated the in vitro effects of the saturated free fatty acid palmitate on mouse pancreatic beta-cells by a combination of electrophysiological recordings, intracellular Ca(2+) ([Ca(2+)](i)) microfluorimetry and insulin release measurements. Addition of palmitate (1 mm, bound to fatty acid-free albumin) to intact islets exposed to 15 mm glucose increased the [Ca(2+)](i) by approximately 30% and insulin secretion 2-fold. Palmitate remained capable of increasing [Ca(2+)](i) and insulin release in the presence of tolbutamide and in islets depolarized by high K(+) in combination with diazoxide, indicating that the stimulation occurs independently of closure of ATP-regulated K(+) channels (K(ATP) channels). Palmitate (0.5 mm) augmented exocytosis (measured as an increase in cell capacitance) in single beta-cells and increased the size of the readily releasable pool (RRP) of granules 2-fold. Whole-cell peak Ca(2+) currents rose by approximately 25% following addition of 0.5 mm palmitate, an effect that was abolished in the presence of 10 microm isradipine indicating that the free fatty acid specifically acts on L-type Ca(2+) channels. The actions of palmitate on exocytosis and Ca(2+) currents were not mimicked by intracellular application of palmitoyl-CoA. We conclude that palmitate increases insulin secretion by a K(ATP) channel-independent mechanism exerted at the level of exocytosis and that involves both augmentation of L-type Ca(2+) currents and an increased size of the RRP. PMID:15090611

  17. Three-dimensional transient model for arc welding process

    NASA Astrophysics Data System (ADS)

    Zacharia, T.; Eraslan, A. H.; Aidun, D. K.; David, S. A.

    1989-10-01

    A direct computer simulation technique, discrete element analysis (DEA), was utilized in the development of a transient multidimensional (2-D and 3-D) mathematical model for investi-gating coupled conduction and convection heat transfer problems associated with stationary and moving arc welding processes. The mathematical formulation considers buoyancy, electro-magnetic, and surface tension driving forces in the solution of the overall heat transfer conditions in the specimen. Furthermore, the formulation of the model allows realistic consideration of the geometrical variations in the workpiece. The model treats the -weld pool surface as a truly deformable free surface, allowing for the prediction of the weld surface deformations such as the “weld crown.? A marked element formulation was employed to monitor the transient de-velopment of the weld pool as determined by the latent heat considerations and the calculated velocities in the weld pool. The model was utilized to simulate the heat and fluid flows in the weld pool that occur during stationary (spot) and moving (linear) gas tungsten-arc welding. Also, the present analysis considers a simple rectangular specimen and a geometrically complex specimen to demonstrate the capability of the model to simulate realistic 3-D arc welding prob-lems. The results of the present investigation clearly demonstrate the significant influence of the heat and fluid flows and the specimen geometry on the development of the weld. Comparison of the predicted and the experimentally observed fusion zone and heat-affected zone (HAZ) geometries indicate good agreement.

  18. The Effects of Droplet Size and Injection Orientation on Water Mist Suppression of Low and High Boiling Point Liquid Pool Fires

    Microsoft Academic Search

    CHUKA C. NDUBIZU; RAMAGOPAL ANANTH; PATRICIA A. TATEM

    2000-01-01

    This paper presents the results of an experimental parametric study of water mist suppression of large-scale liquid pool fires. The experiments were conducted with 50cm diameter pan heptane and JP8 pool fires. Mist was injected into the fire from the base at 90 and 45 and from the top at 90. The results show that base injection of droplets enhanced

  19. GLD-4-Mediated Translational Activation Regulates the Size of the Proliferative Germ Cell Pool in the Adult C. elegans Germ Line

    PubMed Central

    Millonigg, Sophia; Eckmann, Christian R.

    2014-01-01

    To avoid organ dysfunction as a consequence of tissue diminution or tumorous growth, a tight balance between cell proliferation and differentiation is maintained in metazoans. However, cell-intrinsic gene expression mechanisms controlling adult tissue homeostasis remain poorly understood. By focusing on the adult Caenorhabditis elegans reproductive tissue, we show that translational activation of mRNAs is a fundamental mechanism to maintain tissue homeostasis. Our genetic experiments identified the Trf4/5-type cytoplasmic poly(A) polymerase (cytoPAP) GLD-4 and its enzymatic activator GLS-1 to perform a dual role in regulating the size of the proliferative zone. Consistent with a ubiquitous expression of GLD-4 cytoPAP in proliferative germ cells, its genetic activity is required to maintain a robust proliferative adult germ cell pool, presumably by regulating many mRNA targets encoding proliferation-promoting factors. Based on translational reporters and endogenous protein expression analyses, we found that gld-4 activity promotes GLP-1/Notch receptor expression, an essential factor of continued germ cell proliferation. RNA-protein interaction assays documented also a physical association of the GLD-4/GLS-1 cytoPAP complex with glp-1 mRNA, and ribosomal fractionation studies established that GLD-4 cytoPAP activity facilitates translational efficiency of glp-1 mRNA. Moreover, we found that in proliferative cells the differentiation-promoting factor, GLD-2 cytoPAP, is translationally repressed by the stem cell factor and PUF-type RNA-binding protein, FBF. This suggests that cytoPAP-mediated translational activation of proliferation-promoting factors, paired with PUF-mediated translational repression of differentiation factors, forms a translational control circuit that expands the proliferative germ cell pool. Our additional genetic experiments uncovered that the GLD-4/GLS-1 cytoPAP complex promotes also differentiation, forming a redundant translational circuit with GLD-2 cytoPAP and the translational repressor GLD-1 to restrict proliferation. Together with previous findings, our combined data reveals two interconnected translational activation/repression circuitries of broadly conserved RNA regulators that maintain the balance between adult germ cell proliferation and differentiation. PMID:25254367

  20. Underwater welding

    Microsoft Academic Search

    D. J. Lythall; E. M. Wilson

    1977-01-01

    A process is described for arc welding in an under-water environment wherein a welding chamber is positioned adjacent a workpiece, and an arc welding torch is positioned therein. A gas under pressure is introduced into the chamber to displace the water, and a gas is supplied to the torch at a pressure greater than the pressure of the gas in

  1. Shielding conditions of local cavity for underwater arc spot welding

    SciTech Connect

    Ogawa, Y. [Shikoku National Industrial Research Inst., Takamatsu, Kagawa (Japan); Koga, H. [Industrial Technology Institute, Yamaguchi City, Yamaguchi (Japan)

    1996-12-01

    Arc spot welding to join lapped plates is an effective maintenance operation for emergent recovering technique of defects under water. The welding operation is easy and effective except for an excessive amount of weld metal for deep penetration. A special nozzle for CO{sub 2} arc spot welding was designed to maintain this defect. A large amount of swirl shielding gas flow is adopted to discharge the excessive weld metal and to reduce digging action of weld pool. An additional high speed air jet is supplied to reinforce these effects. Almost flat weld bead is obtained by using of this nozzle. The effect of swirl shielding flow and additional air jet on the pressure is studied. When an excessive axial gas flow is used, a pressure at the weld pool becomes high enough to press down the weld surface below original surface level of base plate, and some molten metal is splashed out. Then, it is difficult to get a sound weld geometry. A swirl gas flow is tried to reduce the static pressure on the weld pool. The pressure on the weld pool by the swirl flow becomes much lower compared to the case by axial flow. When the swirl flow is used, a flat bead can be obtained. But some molten metal which is blown out by the swirl gas is resolidified at the edge of the nozzle. The additional high speed air jet is required to blow out the splashed metal from the nozzle completely. It has a suction effect itself. The pressure on the weld pool is also decreased. But the interaction between the swirl flow and the additional jet shows a complicated manner. This paper discusses the interaction between main shielding gas flow and the additional air jet to guarantee the good shielding condition for underwater use.

  2. Optimization of Weld Conditions and Alloy Composition for Welding of Single-Crystal Nickel-Based Superalloys

    SciTech Connect

    Vitek, John Michael [ORNL; David, Stan A [ORNL; Babu, Sudarsanam S [ORNL

    2007-01-01

    Calculations were carried out to identify optimum welding conditions and weld alloy compositions to avoid stray grain formation during welding of single-crystal nickel-based superalloys. The calculations were performed using a combination of three models: a thermal model to describe the weld pool shape and the local thermal gradient and solidification front velocity; a geometric model to identify the local active dendrite growth variant, and a nucleation and growth model to describe the extent of stray grain formation ahead of the advancing solidification front. Optimum welding conditions (low weld power, high weld speed) were identified from the model calculations. Additional calculations were made to determine potential alloy modifications that reduce the solidification temperature range while maintaining high gamma prime content. The combination of optimum weld conditions and alloy compositions should allow for weld repair of single-crystal nickel-based superalloys without sacrificing properties or performance.

  3. Real-time ultrasonic sensing of arc welding processes

    SciTech Connect

    Lott, L.A.; Johnson, J.A.; Smartt, H.B.

    1983-01-01

    NDE techniques are being investigated for fusion zone sensing of arc welding processes for closed-loop process control. An experimental study of pulse-echo ultrasonics for sensing the depth of penetration of molten weld pools in structural metals during welding indicates that real-time ultrasonic sensing is feasible. Results on the detection of liquid/solid weld pool interfaces, the determination of interface location, and effects of high temperature gradients near the molten zones on ultrasonic wave propagation are presented. Additional work required and problems associated with practical application of the techniques are discussed.

  4. A walk-through programmed robot for welding in shipyards

    Microsoft Academic Search

    Marcelo H. Ang Jr; Wei Lin; Ser-Yong Lim

    1999-01-01

    Automating the welding process for the shipbuilding industry is very challenging and important, as this industry relies heavily on quality welds. Conventional robotic welding systems are seldom used because the welding tasks in shipyards are characterised by non-standardised workpieces which are large but small in batch sizes. Furthermore, geometries and locations of the workpieces are uncertain. To tackle the problem,

  5. Small-scale resistance spot welding of austenitic stainless steels

    Microsoft Academic Search

    Shinji Fukumoto; Kana Fujiwara; Shin Toji; Atsushi Yamamoto

    2008-01-01

    Small-scale resistance spot welding (SSRSW) was carried out for austenitic stainless steels. A weld lobe that shows the process window for making sound joints was obtained for type 304 stainless steel thin sheets, and the effects of welding current, force and weld time on joint strength and nugget size were investigated. The cooling rate that was estimated from the solidification

  6. Oscillation of Molten Pool by Pulsed Assist Gas Oscillating Method and Penetration Control Using Peculiar Frequency

    NASA Astrophysics Data System (ADS)

    Jianbin, Ju; Hasegawa, Hiroyuki; Suga, Yasuo

    In automatic butt welding of relatively thin plates, it is important to control welding conditions in order to obtain a sound full penetration weld. Recently, it was reported that there was an intimate relationship between the oscillation of the molten pool and penetration. Therefore, the oscillation phenomena of the weld molten pool were analyzed and the estimation of penetration by detecting frequency of the molten pool was attempted. In this study, a new oscillating method, Pulsed Assist Gas (PAG) oscillating method is proposed. The natural frequency of molten pool was measured from the molten pool oscillation detected by arc sensor. A control system, which controled welding current on the basis of oscillation frequency measured, was constructed. Main results obtained are summarized as follows: 1) In order to oscillate molten pool during TIG arc welding of thin steel plate, Pulsed Assist Gas (PAG) oscillating method was proposed and effectiveness of this method was confirmed. 2) The PAG oscillating method was superior to conventional pulsed current oscillating (PC) method in amplitude of oscillation and robustness of frequency measurement. 3) Applying PAG oscillating method and detecting oscillation of arc voltage, the peculiar frequency of the oscillation of molten pool could be detected. 4) A system to control weld penetration using the principle of detecting the peculiar frequency of the molten pool was constructed and the effectiveness of the system was demonstrated.

  7. Cave Pool

    USGS Multimedia Gallery

    A pool in the Caverns of Sonora. This cave, like many others, was formed by water combining with carbon dioxide to create a weak carbonic acid. This acid then dissolved the limestone to carve out chambers. The dissolved calcium from the limestone then combined with the carbon dioxide to create calci...

  8. 46 CFR 52.05-30 - Minimum requirements for attachment welds (modifies PW-16).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...false Minimum requirements for attachment welds (modifies PW-16). ...05-30 Minimum requirements for attachment welds (modifies PW-16). (a) The location and minimum size of attachment welds for nozzles and...

  9. 46 CFR 52.05-30 - Minimum requirements for attachment welds (modifies PW-16).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...false Minimum requirements for attachment welds (modifies PW-16). ...05-30 Minimum requirements for attachment welds (modifies PW-16). (a) The location and minimum size of attachment welds for nozzles and...

  10. Ultrasound in arc welding: a review.

    PubMed

    da Cunha, Tiago Vieira; Bohórquez, Carlos Enrique Niño

    2015-02-01

    During the last decade, the introduction of ultrasound techniques in arc welding with the intention of improving the operational performance and technical characteristics of the welding processes have been studied intensively. In this work is presented a broad review of the literature surrounding the utilization of this technique. Firstly, we discuss the use of traditional mechanical transducers to generate ultrasound in arc welding. Furthermore, we describe the various methods and their application in arc-welding processes. After, is presented a recent method of introducing ultrasonic energy in arc welding, which forms a potential alternative to the use of traditional mechanical type transducers. This method was originally developed in the late 1990s and is called arc with ultrasonic excitation of current. Here, the arc acts not only as a thermal source but also as an emission mechanism for ultrasound, acting directly on the weld pool. We presented and discussed various innovative concepts based on this method, which allows the introduction of ultrasonic energy in the arc welding without the need of any auxiliary device of welding. In addition, we also presented the variations of this method reported in the literature. Finally, we have described the respective effects attributed to the use of this method in the welding of different materials using various welding processes. PMID:25455190

  11. Investigation of underwater welding of steel

    SciTech Connect

    Shannon, G.J.; Watson, J.; Deans, W.F. (Univ. of Aberdeen (United Kingdom). Dept. of Engineering)

    1994-12-01

    The preliminary underwater welding study described forms part of a European funded research program (EUREKA EU194) which involves a feasibility study into laser welding applications in the offshore oil industry. An investigation was undertaken using a 1.2 KW carbon dioxide laser for underwater butt welding of BS 4360 43A and 50D steel, in order to assess the quality of the welds and to achieve an understanding of the laser/water/material interaction. Using a high-speed camera, the temporal behavior of the melt pool and ''plasma'' dynamics surrounded by an aqueous environment were monitored. Experiments were undertaken to characterize the attenuation of the laser beam in the water as a function of various focal length optics and depth of water. The effect of energy input conditions on the weld bead appearance and mechanical properties were also examined. The interaction of the laser beam with water produced a wave-guiding mechanism in which the focused beam instantaneously vaporizes the water and directs the beam on to the workpiece. The underwater weld beads exhibited sound microstructures over a range of weld energy inputs, mainly due to the formation of a ''dry region'' during welding. Metallurgical analysis of the welds showed a slight increase in hardness, though other post-weld mechanical strengths were similar to in-air results.

  12. Fundamental study of molten pool depth measurement method using an ultrasonic phased array system

    NASA Astrophysics Data System (ADS)

    Mizota, Hirohisa; Nagashima, Yoshiaki; Obana, Takeshi

    2015-07-01

    The molten pool depth measurement method using an ultrasonic phased array system has been developed. The molten pool depth distribution is evaluated by comparing the times taken by the ultrasonic wave to propagate through a molten pool and a solid-phase and through only the solid-phase near the molten pool. Maximum molten pool depths on a flat type-304 stainless-steel plate, formed with a gas tungsten arc welding machine for different welding currents from 70 to 150 A, were derived within an error of ±0.5 mm.

  13. WELDING RESEARCH -s11WELDING JOURNAL

    E-print Network

    Zhang, YuMing

    WELDING RESEARCH -s11WELDING JOURNAL ABSTRACT. Double-electrode gas metal arc welding (DE-GMAW) is a novel weld- ing process recently developed to increase welding productivity while maintaining the base its non- consumable tungsten electrode with a consumable welding wire electrode result- ing in a new

  14. WELDING RESEARCH -s229WELDING JOURNAL

    E-print Network

    Zhang, YuMing

    WELDING RESEARCH -s229WELDING JOURNAL ABSTRACT. Dual-bypass gas metal arc welding (DB agrees with experimental data. Introduction Gas metal arc welding (GMAW) is an arc welding process- minum alloy welded structures have been widely applied. The use of aluminum as an alternative material

  15. An Assessment of Molten Metal Detachment Hazards During Electron Beam Welding in Space

    NASA Technical Reports Server (NTRS)

    Fragomeni, James M.; Nunes, Arthur C., Jr.

    1998-01-01

    The safety issue has been raised with regards to potential molten metal detachments from the weld pool and cold filler wire during electron beam welding in space. This investigation was undertaken to evaluate if molten metal could detach and come in contact with astronauts and burn through the fabric of the astronauts' Extravehicular Mobility Unit (EMU) during electron beam welding in space. Molten metal detachments from either the weld/cut substrate or weld wire could present harm to a astronaut if the detachment was to burn through the fabric of the EMU. Theoretical models were developed to predict the possibility and size of the molten metal detachment hazards during the electron beam welding exercises at Low Earth Orbit (LEO). The primary molten metal detachment concerns were those cases of molten metal separation from the metal surface due to metal cutting, weld pool splashing, entrainment and release of molten metal due to filler wire snap-out from the weld puddle, and molten metal accumulation and release from the end of the weld wire. Some possible ways of obtaining molten metal drop detachments would include an impulse force, or bump, to the weld sample, cut surface, or filler wire. Theoretical models were developed for these detachment concerns from principles of impact and kinetic energies, surface tension, drop geometry, surface energies, and particle dynamics. The surface tension represents the force opposing the liquid metal drop from detaching whereas the weight of the liquid metal droplet represents a force that is tending to detach the molten metal drop. Theoretical calculations have indicated that only a small amount of energy is required to detach a liquid metal drop; however, much of the energy of an impact is absorbed in the sample or weld plate before it reaches the metal drop on the cut edge or surface. The tendency for detachment is directly proportional to the weld pool radius and metal density and inversely proportional to the surface tension of the liquid metal. For a detachment the initial kinetic energy of the weld pool with respect to the plate has to exceed the energy to form the extra surface required for the detachment of the pool. The difficulty is in transferring the energy from the point of impact through the plate and sample to the cut edge. It is likely that not all of the kinetic energy is available for detaching the pool; some may be sequestered in weld pool oscillations. The coefficient of restitution for the collision will be lower than one if irreversible deformation, for example plastic flow deformation, takes place during the collision. Thus determining the amount of energy from an impact that actually reaches the molten metal droplet is critical. Various molten metal detachment scenarios were tested experimentally in an enclosed vacuum chamber using the Ukrainian Universal Hand Tool, an electron beam welder designed for space welding. The experimental testing was performed in a 4 ft. X 4 ft. vacuum chamber at Marshall Space Flight Center, evacuated to vacuum levels of at least 50 microTorr, and also some welding garment material was utilized to observe the effect of the molten metal detachments on the material. A "carillon" apparatus consisting of four pendulum hammer strikers, each weighing approximately 3.65 lbs, raised to predetermined specific heights was used to apply an impact force to the weld sample/plate during electron beam welding and cutting exercises. The strikers were released by switching on an electric motor to rotate a pin holding wires retaining the strikers at desired heights. The specimens were suspended so as to be free to respond to the blows with a sudden velocity increment. The specimens were mounted on a hinged plate for minimizing effective mass with the option to fasten it down so as to raise its effective mass closer to that anticipated for an actual space welding scenario. Measurements were made of the impact energy and the horizontal fling distances of the detached metal drops. It was not particularly easy to generate the detachments fo

  16. Virginia Tech - Buffer Pool

    NSDL National Science Digital Library

    Cliff Shaffer

    Allows user to select from FIFO, LRU, and LFU page replacement strategies. User then gives a series of page requests and the AV shows the decisions made regarding page replacement. Simple to use, clearly shows the process. It would be nice if the user could pick the size of the backing memory and the buffer pool. Recommended as lecture aide, standalone, self-study suppliment to tutorial or lecture.

  17. Plasma arc welding weld imaging

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    A welding torch for plasma arc welding apparatus has a transparent shield cup disposed about the constricting nozzle, the cup including a small outwardly extending polished lip. A guide tube extends externally of the torch and has a free end adjacent to the lip. First and second optical fiber bundle assemblies are supported within the guide tube. Light from a strobe light is transmitted along one of the assemblies to the free end and through the lip onto the weld site. A lens is positioned in the guide tube adjacent to the second assembly and focuses images of the weld site onto the end of the fiber bundle of the second assembly and these images are transmitted along the second assembly to a video camera so that the weld site may be viewed continuously for monitoring the welding process.

  18. Pool & Spa Safety Act

    MedlinePLUS

    ... Safely > The Pool & Spa Safety Act The Pool & Spa Safety Act Download the Act 2008 Pool & Spa ... Act Format: PDF The Virginia Graeme Baker Pool & Spa Safety Act (P&SS Act) was enacted by Congress ...

  19. Coaxial monitoring of the fibre laser lap welding of Zn-coated steel sheets using an auxiliary illuminant

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Zhang, Chenglei; Tan, Lipeng; Li, Shichun

    2013-09-01

    In the laser welding process, weld defects are often caused by many factors, such as variations in the laser power, welding speed and gaps between two workpieces. In an auto-welding system, the on-line monitoring of the welding quality is very important in avoiding weld defects. In this paper, an on-line coaxial monitoring system with an auxiliary illuminant was built for the fibre laser welding of galvanised steel; images of the weld pool were taken during the welding process. Profiles of the weld pool and the keyhole were obtained by processing the images using the region-growing algorithm and the Canny algorithm. In this research, we used the on-line monitored weld pool width to monitor the weld surface width. The weld penetration status was divided into the three categories of incompletely penetrated, moderately penetrated and over-penetrated using the value of d (diameter at the bottom of the keyhole)/D (diameter at the top of the keyhole). Thus, the weld width and weld penetration status of fibre laser welding can be monitored on-line.

  20. Is Your Pool Safe?

    MedlinePLUS

    ... without an adult; the pool area is off limits without adult supervision. ? Keep toys that are not in use away from the pool and out of sight. Toys can attract young children into the pool. ? Pool covers and pool alarms can be used as added layers of protection. Set rules for the pool and ...

  1. Problems of Pore Formation in Welded Joints of Titanium Alloys

    Microsoft Academic Search

    V. I. Murav'ev

    2005-01-01

    Special features of formation of the connection zone in front of the front of molten pool and changes in the macro- and microstructure of the weld metal are considered for conditions of fusion welding of titanium alloys on an example of pseudo-?-titanium alloy VT20.Ways for forming macrotexture on the surface of joined preforms are determined with the aim of obtaining

  2. 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 principles still remains an important milestone in changing welding from almost an empirical art to a mainstream science-based technology. The ability to determine multiple welding variable sets to achieve desired weld attributes, based on scientific principles, would be an important step to achieve this goal. Furthermore, no comprehensive unified theoretical model exists today that can predict the formation of commonly occurring humping defects considering the effects of important welding variables such as the arc current, voltage, welding speed, nature of the shielding gas, electrode geometry, torch angle and ambient pressure. In this research work, a model is developed to achieve desired weld attributes and avoid high speed weld defects like humping. (Abstract shortened by UMI.)

  3. Welding superalloy sheet for superconducting cable jackets

    SciTech Connect

    Summers, L.T.; Strum, M.J.; Morris, J.W. Jr.

    1983-08-01

    Autogenous gas tungsten arc welds produced in A-286 exhibit significantly lower yield and ultimate tensile strengths than comparably heat-treated base metal. Deformation in the aged weld metal is highly localized and delineates the dendritic microstructure. The observed mechanical properties are caused by the formation of precipitate-free regions located at the dendrite cores. These regions form as the result of titanium segregation during weld pool solidification which yields dendrite cores sufficiently lean in titanium as to prevent nucleation of the hardening phase.

  4. WELDING RESEARCH -s231WELDING JOURNAL

    E-print Network

    Zhang, YuMing

    WELDING RESEARCH -s231WELDING JOURNAL ABSTRACT. Double-electrode gas metal arc welding (DE the welding wire and the bypass torch. To control the base metal current at the desired level, a group. Introduction Gas metal arc welding (GMAW) is a major process for metals joining. Conventional GMAW is normally

  5. WELDING RESEARCH -s87WELDING JOURNAL

    E-print Network

    Eagar, Thomas W.

    WELDING RESEARCH -s87WELDING JOURNAL ABSTRACT. Welding fume contains ele- ments that, in their pure of welding fume must be examined when considering fume toxicity. Various chemical analysis techniques are pre techniques to analyze the chemistry of mild steel welding fume. X-ray diffraction (XRD) shows that mild steel

  6. WELDING RESEARCH -S237WELDING JOURNAL

    E-print Network

    Cambridge, University of

    WELDING RESEARCH -S237WELDING JOURNAL We depend in our everyday life on the performance of vast the tallest building in the world -- Fig. 1. These are all made from steel and rely on welding for their assembly. Weld Design: Experiment or Model? A weld is a heterogeneity introduced into a carefully

  7. Weld defect formation in rail thermite welds

    Microsoft Academic Search

    Y Chen; F V Lawrence; C P L Barkan; J A Dantzig

    2006-01-01

    A previously developed heat transfer model is used to study the influence of welding parameters on weld defect development in thermite welds. Weld defect formation maps are constructed from a series of heat transfer simulations. For the current normal rail thermite weld- ing conditions, it is found that shrinkage cavity formation can be avoided but cold-lap and centre-line defects are

  8. The size of the intracellular beta 1-integrin precursor pool regulates maturation of beta 1-integrin subunit and associated alpha-subunits.

    PubMed Central

    Koivisto, L; Heino, J; Häkkinen, L; Larjava, H

    1994-01-01

    A large pool of precursor beta 1-integrin subunits is frequently found intracellularly. During malignant transformation this pool often disappears. Concomitantly, integrin-mediated cell-adhesion functions are disturbed, even though no change in the number of beta 1-integrin receptors on the cell surface can be observed. Here, we have studied the role of an intracellular pre-beta 1-integrin pool by transfecting human MG-63 osteosarcoma cells with plasmid construction producing an antisense RNA for the beta 1-integrin subunit. Stable cell clones expressing beta 1-integrin antisense RNA were shown to have a reduced intracellular pool of pre-beta 1-integrin subunits. In the antisense-transfected cells, the synthesis of the beta 1-integrin chain was reduced by 65% compared with non-transfected or vector-transfected MG-63 cells. The decreased synthesis of the beta 1-integrin chain was associated with accelerated maturation of the beta 1-integrin chain (half-maturation time about 5 h in antisense-transfected cells compared with about 10.5 h in control cells), whereas maturation of the alpha-integrin chain slowed down. The amount of beta 1-integrins on the cell surface, however, remained unaltered. Cell clones with the largest decrease in the relative amount of the pre-beta 1-integrin subunit also showed altered integrin function. They were found to synthesize fibronectin, but were unable to assemble it into a fibronectin matrix on the cell surface. Thus we conclude that the repression of biosynthesis of the beta 1-integrin chain leads to alterations in receptor maturation and may be connected with altered receptor function. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 PMID:8010959

  9. Welding and Weldability of Thorium-Doped Iridium Alloys

    SciTech Connect

    David, S.A.; Ohriner, E.K.; King, J.F.

    2000-03-12

    Ir-0.3%W alloys doped with thorium are currently used as post-impact containment material for radioactive fuel in thermoelectric generators that provide stable electrical power for a variety of outer planetary space exploration missions. Welding and weldability of a series of alloys was investigated using arc and laser welding processes. Some of these alloys are prone to severe hot-cracking during welding. Weldability of these alloys was characterized using Sigmajig weldability test. Hot-cracking is influenced to a great extent by the fusion zone microstructure and composition. Thorium content and welding atmosphere were found to be very critical. The weld cracking behavior in these alloys can be controlled by modifying the fusion zone microstructure. Fusion zone microstructure was found to be controlled by welding process, process parameters, and the weld pool shape.

  10. Increasing Productivity of Welding 

    E-print Network

    Uhrig, J. J.

    1983-01-01

    It is universally recognized that welding is the most economical way to permanently join metals. Recent advances in welding, specifically, the continuous electrode wire processes make welding even more attractive for manufacturing. As welding...

  11. Increasing Productivity of Welding

    E-print Network

    Uhrig, J. J.

    1983-01-01

    It is universally recognized that welding is the most economical way to permanently join metals. Recent advances in welding, specifically, the continuous electrode wire processes make welding even more attractive for manufacturing. As welding...

  12. On-line predication of underwater welding penetration depth based on multi-sensor data fusion

    Microsoft Academic Search

    Weimin Zhang; Guorong Wang; Yonghua Shi; Biliang Zhong

    2008-01-01

    Using least squares support vector machines (LS-SVM) technology, a new multi-sensor data fusion model for online predication of underwater flux-cored arc welding (FCAW) penetration depth is presented. In this model, welding speed, wire feed rate, arc voltage, contact-tube-to-work distance (CTWD), and weld pool width are used as inputs, while the depth of welding penetration as output. The radial basis function

  13. Numerical simulation of variable polarity vertical-up plasma arc welding process

    Microsoft Academic Search

    H. X. Wang; Y. H. Wei; C. L. Yang

    2007-01-01

    Three-dimensional transient governing equations were developed based on conservation laws of energy, momentum and mass. These equations described physical phenomena of convection in weld pool and heat transfer in workpiece during variable polarity vertical-up plasma arc welding process. Boundary conditions for the developed governing equations were given. Welding energy input for variable polarity vertical-up plasma arc welding process was quantitatively

  14. MHD MELT CONTROL SYSTEMS FOR HIGH-POWER BEAM WELDING OF METALS

    Microsoft Academic Search

    V. V. Avilov; G. Ambrosy; P. Berger

    Introduction. One of the major advantages of high-power laser as well as electron beam welding is its tremendous penetration. The width of the penetration pattern is extremely narrow with a depth-to-width ratio up to 20:1 for laser beam welding and much more for electron beam welding. The weld pool and the heat affected zone are much smaller than those of

  15. WELDING RESEARCH ~----------------------~--~ SUPPLEMENT TO THE WELDING JOURNAL. FEBRUARY 1990

    E-print Network

    Eagar, Thomas W.

    J ) WELDING RESEARCH ~----------------------~--~ SUPPLEMENT TO THE WELDING JOURNAL. FEBRUARY 1990 Sponsored by the American Welding Society and the Welding Research Council All papers published in the Welding Journal's Welding Research Supplement undergo Peer Review before publication for: I) originality

  16. Mechanical and Metallurgical Behavior of Weld-Bonds of 6061 Aluminum Alloy

    Microsoft Academic Search

    M. D. Faseeulla Khan; D. K. Dwivedi

    2012-01-01

    This article presents the microstructure and mechanical properties of spot weld and weld-bond of 2 mm thick 6061 aluminum alloy sheets. The fracture surfaces of the adhesive joints, spot welds, and weld-bonds were studied under scanning electron microscope (SEM). Optical microscopy was carried out to study the microstructure of the joints and nugget size of resistance spot weld and weld-bond of

  17. Smaller Coaxial-View Welding Torch

    NASA Technical Reports Server (NTRS)

    Gangl, Kenneth J.

    1991-01-01

    Coaxial-view torch for gas/tungsten arc welding has only two-thirds length and width of its predecessor. Shape and size similar to that of commercial arc-welding torch (Linde HW-27 or equivalent), even though it contains lens system. Collet that holds electrode has unique design allowing greater passage of light. Used in small spaces previously inaccessible, also introduced into production welding operations with minimum of disturbance.

  18. Electrode carrying wire for GTAW welding

    NASA Technical Reports Server (NTRS)

    Morgan, Gene E. (inventor); Dyer, Gerald E. (inventor)

    1990-01-01

    A welding torch for gas tungsten arc welding apparatus has a hollow tungsten electrode including a ceramic liner and forms the filler metal wire guide. The wire is fed through the tungsten electrode thereby reducing the size of the torch to eliminate clearance problems which exist with external wire guides. Since the wire is preheated from the tungsten more wire may be fed into the weld puddle, and the wire will not oxidize because it is always within the shielding gas.

  19. Dynamic stresses in weld metal hot cracking

    Microsoft Academic Search

    Zacharia

    1994-01-01

    This paper presents the results of a study aimed at understanding the influence of dynamic stresses, induced by thermal and mechanical loading, on weld metal hot cracking. The study attempts to resolve the relationship between the dynamic stress distribution in the specimen, particularly near the trailing edge of the pool, and the observed cracking behavior in a Sigmajig test specimen.

  20. Tool For Friction Stir Tack Welding of Aluminum Alloys

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  2. Minimization of welding residual stress and distortion in large structures

    E-print Network

    Michaleris, Panagiotis

    1 Minimization of welding residual stress and distortion in large structures P. Michaleris at Champaign Urbana, Urbana, IL Abstract Welding distortion in large structures is usually caused by buckling due to the residual stress. In cases where the design is fixed and minimum weld size requirements

  3. A PARANETRIC STlJDY OF THE ELECTROSLAG WELDING PROCESS

    E-print Network

    Eagar, Thomas W.

    ) ) A PARANETRIC STlJDY OF THE ELECTROSLAG WELDING PROCESS by W. S. Ricci and T. W. Eagar conducted on electroslag welds to statistically evaluate the effect of i ndependent process variables upon dependent process responses consisting of heat affected zone size, dilution, form factor, welding speed

  4. Ferritic, martensitic, and precipitation hardening stainless steel laser weldings

    Microsoft Academic Search

    Giuseppe Daurelio; Antonio D. Ludovico; Christos N. Panagopoulos; Corrado Tundo

    1998-01-01

    Even if many steels and alloys have been welded on the last years, nowadays there are some other stainless steel alloys that need a further comprehension when they have to be welded. Typically these alloys are martensitic and precipitation hardening ones that still present some problems to be weld, i.e. hot cracks, fragile beads, an excessive grain size and other

  5. Evaluation of electrode shape and nondestructive evaluation method for welded solar cell interconnects

    NASA Technical Reports Server (NTRS)

    Baraona, C. R.; Klima, S. J.; Moore, T. J.; Frey, W. E.; Forestieri, A. F.

    1982-01-01

    Resistance welds of solar cell interconnect tabs were evaluated. Both copper-silver and silver-silver welds were made with various heat inputs and weld durations. Parallel gap and annular gap weld electrode designs were used. The welds were analyzed by light microscope, electron microprobe and scanning laser acoustic microscope. These analyses showed the size and shape of the weld, the relationship between the acoustic micrographs, the visible electrode footprint, and the effect of electrode misalignment. The effect of weld heat input on weld microstructure was also shown.

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

    SciTech Connect

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

    2000-01-01

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

  7. Preliminary Study on the Formability of a Laser-Welded Superplastic Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Sorgente, D.; Corizzo, O.; Brandizzi, M.; Tricarico, L.

    2014-11-01

    In this work, the effect of the laser-material interaction on the formability of a superplastic aluminum alloy was investigated. In applications such as Tailor-Welded Blanks and in the manufacturing of very large components with a complex shape, laser welding combined with superplastic forming may be a very fitting industrial tool. Bead on plate tests were carried out in order to simulate the laser-welding process and then, free inflation tests were performed to evaluate the compatibility of these two processing techniques. The Al-Mg alloy used in this work has a very small grain size which ensures the superplastic behavior. With the aim of preserving this peculiarity, the following aspects on the formability were investigated: (i) the surface condition of the bead before the forming test (with and without the removal of the excess of metal); (ii) the effect of the travel speed of the laser source on the mean grain size; (iii) the introduction of a refiner, commonly used in aluminum casts, in the molten pool in order to further reduce the mean grain size.

  8. An Assessment of Molten Metal Detachment Hazards for Electron Beam Welding in the Space Environment: Analysis and Test Results

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.; Russell, C.; Bhat, B.; Fragomeni, J. M.

    1998-01-01

    Conditions under which molten metal detachments might occur in a space welding environment are analyzed. A weld pool detachment parameter specifying conditions for pool detachment by impact is derived and corroborated by experimental evidence. Impact detachment for the pool is unlikely. Impact detachment for a drop of metal on the end of the weld wire may be possible under extreme conditions. Other potential causes of molten metal detachment considered, vaporization pressure forces and wire flickout from the pool, did not appear to present significant detachment threats.

  9. Weld repair method for aluminum lithium seam

    NASA Technical Reports Server (NTRS)

    McGee, William Floyd (Inventor); Rybicki, Daniel John (Inventor)

    1998-01-01

    Aluminum-lithium plates are butt-welded by juxtaposing the plates and making a preliminary weld from the rear or root side of the seam. An initial weld is then made from the face side of the seam, which may cause a defect in the root portion. A full-size X-ray is made and overlain over the seam to identify the defects. The defect is removed from the root side, and rewelded. Material is then removed from the face side, and the cavity is rewelded. The procedure repeats, alternating from the root side to the face side, until the weld is sound.

  10. Pulsed magnetic welding

    SciTech Connect

    Sheely, W.F.

    1986-11-20

    Solid state welding techniques are an alternative to fusion welding. Two solid state welding techniques are pulsed magnetic welding and explosive bonding. Both achieve bonds by impacting the metals to be joined at high velocity. Development of the pulsed magnetic welding process by Hanford Engineers for fuel fabrication may make this process useful for a variety of other applications. Hanford engineers have developed advanced equipment for pulsed magnetic welding and have defined conditions for reliably welding stainless steel fuel pins using this equipment.

  11. Welding Curtains

    NASA Astrophysics Data System (ADS)

    1984-01-01

    Concept of transparent welding curtains made of heavy duty vinyl originated with David F. Wilson, President of Wilson Sales Company. In 1968, Wilson's curtains reduced glare of welding arc and blocked ultraviolet radiation. When later research uncovered blue light hazards, Wilson sought improvement of his products. He contracted Dr. Charles G. Miller and James B. Stephens, both of Jet Propulsion Laboratory (JPL), and they agreed to undertake development of a curtain capable of filtering out harmful irradiance, including ultraviolet and blue light and provide protection over a broad range of welding operation. Working on their own time, the JPL pair spent 3 years developing a patented formula that includes light filtering dyes and small particles of zinc oxide. The result was the Wilson Spectra Curtain.

  12. WELDING RESEARCH -s77WELDING JOURNAL

    E-print Network

    DuPont, John N.

    WELDING RESEARCH -s77WELDING JOURNAL ABSTRACT. The microstructure of AL- 6XN plates joined via a double-sided fric- tion stir weld has been investigated. The microstructural zones that develop during friction stir welding (FSW) reflect de- creasing strains and less severe thermal cy- cles with increasing

  13. WELDING RESEARCH -s281WELDING JOURNAL

    E-print Network

    DuPont, John N.

    WELDING RESEARCH -s281WELDING JOURNAL ABSTRACT. Superaustenitic stainless steel alloys can often pose difficulties dur- ing fusion welding due to the unavoidable microsegregation of Mo and tramp ele. A method of producing austenitic welds is proposed that can po- tentially circumvent these issues by de

  14. WELDING RESEARCH -s51WELDING JOURNAL

    E-print Network

    DuPont, John N.

    WELDING RESEARCH -s51WELDING JOURNAL ABSTRACT. Electron microprobe analy- sis was utilized to examine the gradient of alloying elements across the weld inter- face of austenitic/ferritic dissimilar alloy welds. The concentration gradients were converted to martensite start (Ms) tem- perature gradients

  15. WELDING RESEARCH -S125WELDING JOURNAL

    E-print Network

    DuPont, John N.

    WELDING RESEARCH -S125WELDING JOURNAL ABSTRACT. Microstructural evolution and solidification cracking susceptibility of dissimilar metal welds between AL- 6XN super austenitic stainless steel and two, differential thermal analysis, and Varestraint testing tech- niques. Welds were prepared over the en- tire

  16. WELDING RESEARCH -s55WELDING JOURNAL

    E-print Network

    DuPont, John N.

    between the carbon steel and stainless steel end members to permit the deposition of two similar welds corrosion conditions that require the use of austenitic stainless steels. A dissimi- lar metal weld (DMWWELDING RESEARCH -s55WELDING JOURNAL ABSTRACT. Dissimilar metal weld (DMW) failures between carbon

  17. Automatic Welding of Stainless Steel Tubing

    NASA Technical Reports Server (NTRS)

    Clautice, W. E.

    1978-01-01

    To determine if the use of automatic welding would allow reduction of the radiographic inspection requirement, and thereby reduce fabrication costs, a series of welding tests were performed. In these tests an automatic welder was used on stainless steel tubing of 1/2, 3/4, and 1/2 inch diameter size. The optimum parameters were investigated to determine how much variation from optimum in machine settings could be tolerate and still result in a good quality weld. The process variables studied were the welding amperes, the revolutions per minute as a function of the circumferential weld travel speed, and the shielding gas flow. The investigation showed that the close control of process variables in conjunction with a thorough visual inspection of welds can be relied upon as an acceptable quality assurance procedure, thus permitting the radiographic inspection to be reduced by a large percentage when using the automatic process.

  18. Influence of Aluminum Content on Grain Refinement and Strength of AZ31 Magnesium GTA Weld Metal

    SciTech Connect

    Babu, N. Kishore [Singapore Institute of Manufacturing Technology; Cross, Carl E. [Los Alamos National Laboratory

    2012-06-28

    The goal is to characterize the effect of Al content on AZ31 weld metal, the grain size and strength, and examine role of Al on grain refinement. The approach is to systematically vary the aluminum content of AZ31 weld metal, Measure average grain size in weld metal, and Measure cross-weld tensile properties and hardness. Conclusions are that: (1) increased Al content in AZ31 weld metal results in grain refinement Reason: higher undercooling during solidification; (2) weld metal grain refinement resulted in increased strength & hardness Reason: grain boundary strengthening; and (3) weld metal strength can be raised to wrought base metal levels.

  19. Elucidation of high-power fibre laser welding phenomena of stainless steel and effect of factors on weld geometry

    NASA Astrophysics Data System (ADS)

    Kawahito, Yousuke; Mizutani, Masami; Katayama, Seiji

    2007-10-01

    The fibre laser has been receiving great attention due to its advantages of high efficiency, high power and high beam quality, and is expected to be one of the most desirable heat sources for high-speed and deep-penetration welding. In this study, therefore, in bead-on-plate welding of Type 304 stainless steel plates with 6 kW fibre laser, the effects of laser power, power density and welding speed on the formation of sound welds were investigated with four laser beams of 130, 200, 360 and 560 µm in spot diameter, and their welding phenomena were clarified with high-speed video cameras and an x-ray transmission real-time imaging system. The weld beads showed a keyhole type of penetration at any diameter, and the maximum penetration of 11 mm in depth was obtained at 130 µm spot diameter and 0.6 m min-1 welding speed. It was found that the laser power density exerted a remarkable effect on the increase in weld penetration at higher welding speeds, and sound partially penetrated welds without welding defects such as porosity, underfilling or humping could be produced at wide process windows of welding speeds between 4.5 and 10 m min-1 with fibre laser beams of 360 µm or 560 µm in spot diameter. The high-speed video observation pictures and the x-ray images of the welding phenomena at 6 m min-1 welding speed and 360 µm spot diameter show that a sound weld bead was formed owing to a long molten pool suppressing and accommodating spattering and a stable keyhole generating no bubbles from the tip, respectively.

  20. Narrow gap laser welding

    DOEpatents

    Milewski, J.O.; Sklar, E.

    1998-06-02

    A laser welding process including: (a) using optical ray tracing to make a model of a laser beam and the geometry of a joint to be welded; (b) adjusting variables in the model to choose variables for use in making a laser weld; and (c) laser welding the joint to be welded using the chosen variables. 34 figs.

  1. Narrow gap laser welding

    DOEpatents

    Milewski, John O. (Santa Fe, NM); Sklar, Edward (Santa Fe, NM)

    1998-01-01

    A laser welding process including: (a) using optical ray tracing to make a model of a laser beam and the geometry of a joint to be welded; (b) adjusting variables in the model to choose variables for use in making a laser weld; and (c) laser welding the joint to be welded using the chosen variables.

  2. Underwater welding test chamber

    Microsoft Academic Search

    Berghof

    1975-01-01

    An apparatus is described which is capable of testing a small hand-held welding chamber for use in underwater welding. Specifically, the apparatus includes 2 interconnected chambers, one being elevated above the other. Within the lower chamber, there is a plate on which is positioned a workpiece to be welded. The welding chamber, a tubular welding housing having a side aperture

  3. Heat and mass transfer in laser dissimilar welding of stainless steel and nickel

    NASA Astrophysics Data System (ADS)

    Hu, Yaowu; He, Xiuli; Yu, Gang; Ge, Zhifu; Zheng, Caiyun; Ning, Weijian

    2012-05-01

    Laser spot welding of stainless steel-nickel dissimilar couple has been studied experimentally and numerically. A three-dimensional heat and mass transfer model is used to simulate the welding process, based on the solution of the equations of mass, momentum, energy conservation and solute transport in weld pool. The calculated fusion zone geometry and element distributions are in good agreement with the corresponding experimental results. The role of fluid flow on temperature field and its evolution is analyzed by comparing two cases with and without considering convection. Temperature fields far away from the weld pool are quite similar, but exhibit large difference close to the heat source. During the early stage after formation of weld pool, the distribution of element Fe in weld pool is non-uniform, due to insufficient time for mixing. The speed for mass transport is the highest during the initial stage of weld pool formation and it decreases with time. Both heat and mass transport are significantly influenced by convection during laser spot welding of stainless steel and nickel.

  4. Development and application of specially-focused ultrasonic transducers to location and sizing of defects in 75 mm- to 127 mm-thick austenitic stainless steel weld metals

    Microsoft Academic Search

    E. N. C. Dalder; S. Benson; B. J. McKinley; T. Carodiskey

    1992-01-01

    Special ultrasonic transducer (UT) parts, capable of focusing incident signals within a 25 mm x 25 mm x 25 mm volume in an austenitic stainless weld metal at depths that varied from 25 mm to 127 mm, were developed and demonstrated to be capable of detecting a defect with cross section equivalent to that of a 4.76 mm-dia flat-bottom hole.

  5. Effects of laser-weld joint opening size on fatigue strength of Ti-6Al-4V structures with several diameters.

    PubMed

    Nuñez-Pantoja, J M C; Vaz, L G; Nóbilo, M A A; Henriques, G E P; Mesquita, M F

    2011-03-01

    This study was conducted to evaluate the fatigue strength of Ti-6Al-4V laser-welded joints with several diameters and joint openings. Sixty dumbbell rods were machined in Ti-6Al-4V alloy with central diameters of 1·5, 2·0 and 3·5 mm. The specimens were sectioned and then welded using two joint openings (0·0 and 0·6 mm). The combination of variables created six groups, which when added to the intact groups made a total of nine groups (n = 10). Laser welding was executed as follows: 360 V per 8 ms (1·5 and 2·0 mm) and 380 V per 9 ms (3·5 mm) with focus and frequency regulated to zero. The joints were finished, polished and submitted to radiographic examination to be analysed visually for the presence of porosity. The specimens were then subjected to a mechanical cyclic test, and the number of cycles until failure was recorded. The fracture surface was examined with a scanning electron microscope (SEM). The Kruskal-Wallis test and Dunn test (? = 0·05) indicated that the number of cycles required for fracture was lower for all specimens with joint openings of 0·6 mm, and for 3·5-mm-diameter specimens with joint openings of 0·0 mm. The Spearman correlation coefficient (? = 0·05) indicated that there was a negative correlation between the number of cycles and the presence of porosity. So, laser welding of Ti-6Al-4V structures with a thin diameter provides the best conditions for the juxtaposition of parts. Radiographic examination allows for the detection of internal voids in titanium joints. PMID:20678101

  6. The role of thermocapillary instability in heat transfer in a liquid metal pool

    Microsoft Academic Search

    Valerian A. Nemchinsky

    1997-01-01

    During the treatment of metal with concentrated heat sources (plasma and laser welding, cutting etc.), high temperature gradients are created within the liquid metal pool. A capillary wave propagating along this pool carries non-uniformly heated metal out to the surface. Since the surface tension coefficient ? depends on temperature, surface forces arise, which are directed from these spots with low

  7. Modeling of plasma and thermo-fluid transport in hybrid welding

    NASA Astrophysics Data System (ADS)

    Ribic, Brandon D.

    Hybrid welding combines a laser beam and electrical arc in order to join metals within a single pass at welding speeds on the order of 1 m min -1. Neither autonomous laser nor arc welding can achieve the weld geometry obtained from hybrid welding for the same process parameters. Depending upon the process parameters, hybrid weld depth and width can each be on the order of 5 mm. The ability to produce a wide weld bead increases gap tolerance for square joints which can reduce machining costs and joint fitting difficulty. The weld geometry and fast welding speed of hybrid welding make it a good choice for application in ship, pipeline, and aerospace welding. Heat transfer and fluid flow influence weld metal mixing, cooling rates, and weld bead geometry. Cooling rate affects weld microstructure and subsequent weld mechanical properties. Fluid flow and heat transfer in the liquid weld pool are affected by laser and arc energy absorption. The laser and arc generate plasmas which can influence arc and laser energy absorption. Metal vapors introduced from the keyhole, a vapor filled cavity formed near the laser focal point, influence arc plasma light emission and energy absorption. However, hybrid welding plasma properties near the opening of the keyhole are not known nor is the influence of arc power and heat source separation understood. A sound understanding of these processes is important to consistently achieving sound weldments. By varying process parameters during welding, it is possible to better understand their influence on temperature profiles, weld metal mixing, cooling rates, and plasma properties. The current literature has shown that important process parameters for hybrid welding include: arc power, laser power, and heat source separation distance. However, their influence on weld temperatures, fluid flow, cooling rates, and plasma properties are not well understood. Modeling has shown to be a successful means of better understanding the influence of processes parameters on heat transfer, fluid flow, and plasma characteristics for arc and laser welding. However, numerical modeling of laser/GTA hybrid welding is just beginning. Arc and laser welding plasmas have been previously analyzed successfully using optical emission spectroscopy in order to better understand arc and laser plasma properties as a function of plasma radius. Variation of hybrid welding plasma properties with radial distance is not known. Since plasma properties can affect arc and laser energy absorption and weld integrity, a better understanding of the change in hybrid welding plasma properties as a function of plasma radius is important and necessary. Material composition influences welding plasma properties, arc and laser energy absorption, heat transfer, and fluid flow. The presence of surface active elements such as oxygen and sulfur can affect weld pool fluid flow and bead geometry depending upon the significance of heat transfer by convection. Easily vaporized and ionized alloying elements can influence arc plasma characteristics and arc energy absorption. The effects of surface active elements on heat transfer and fluid flow are well understood in the case of arc and conduction mode laser welding. However, the influence of surface active elements on heat transfer and fluid flow during keyhole mode laser welding and laser/arc hybrid welding are not well known. Modeling has been used to successfully analyze the influence of surface active elements during arc and conduction mode laser welding in the past and offers promise in the case of laser/arc hybrid welding. A critical review of the literature revealed several important areas for further research and unanswered questions. (1) The understanding of heat transfer and fluid flow during hybrid welding is still beginning and further research is necessary. (2) Why hybrid welding weld bead width is greater than that of laser or arc welding is not well understood. (3) The influence of arc power and heat source separation distance on cooling rates during hybrid welding are not known. (4) Convect

  8. Effect of welding parameters on high-power diode laser welding on thin sheet

    NASA Astrophysics Data System (ADS)

    Salminen, Antti; Jansson, Anssi; Kujanpaa, Veli

    2003-06-01

    High power diode laser (HPDL) is the newest laser tool for industrial manufacturing. The most promising areas of application of HPDL are thin sheet welding and hardening. The HPDL has several advantages and disadvantages compared to lasers CO2 and Nd:YAG lasers currently used for welding. There is quite a few industrial applications in which diode laser is the most suitable laser. A typical industrial installation consists of a HPDL, an industrial robot, work piece manipulation and safety enclosures. The HPDL welding process is at this moment conduction limited and has therefore different parameters than the keyhole welding. In this study the basic HPDL welding parameters and the effect of the parameters on the welding process, weld quality and efficiency are examined. Joint types tested are butt joint and fillet lap joint. The parameters tested are beam intensity, welding speed, spot size, beam impingement angle. The materials tested are common carbon steel and stainless steel. By the experiments carried out it can be seen that all of these parameters have an effect on the weld quality and the absorption of the laser power during welding. The higher the beam intensity is the shorter also the throughput time is. However, in case of fillet joint the maximum welding speed and best visual out look are achieved with totally different set of parameters. Based on these experiments it can, however, be seen that reliable welding parameters can be established for the welding of various industrial products. The beam quality of the diode laser is not optimum for high speed keyhole welding but it is a flexible tool to be used for different joint types.

  9. Fiber laser welding of nickel-based superalloy inconel 718

    NASA Astrophysics Data System (ADS)

    Oshobe, Omudhohwo Emaruke

    Inconel 718 (IN 718) is widely used in applications, such as aircraft and power turbine components. Recently, fiber laser welding has become an attractive joining technique in industry for fabrication and repair of service-damaged components. However, a major limitation in the laser welding of IN 718 is that liquation cracking occurs. In the present work, autogenous fiber laser welding of IN 718 was used to study the effects of welding parameters and different pre-weld heat treatments on liquation cracking. Contrary to previous studies, a dual effect of heat input on cracking is observed. A rarely reported effect of heat input is attributed to process instability. Liquation cracking increases with pre-weld heat treatment temperatures that increase grain size and/or, possibly, intregranular boron segregation. The study shows that pre-weld heat treatment at 950oC can be used for repair welding of IN 718 without significant loss in cracking resistance.

  10. A Quantitative Model of Keyhole Instability Induced Porosity in Laser Welding of Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Pang, Shengyong; Chen, Weidong; Wang, Wen

    2014-06-01

    Quantitative prediction of the porosity defects in deep penetration laser welding has generally been considered as a very challenging task. In this study, a quantitative model of porosity defects induced by keyhole instability in partial penetration CO2 laser welding of a titanium alloy is proposed. The three-dimensional keyhole instability, weld pool dynamics, and pore formation are determined by direct numerical simulation, and the results are compared to prior experimental results. It is shown that the simulated keyhole depth fluctuations could represent the variation trends in the number and average size of pores for the studied process conditions. Moreover, it is found that it is possible to use the predicted keyhole depth fluctuations as a quantitative measure of the average size of porosity. The results also suggest that due to the shadowing effect of keyhole wall humps, the rapid cooling of the surface of the keyhole tip before keyhole collapse could lead to a substantial decrease in vapor pressure inside the keyhole tip, which is suggested to be the mechanism by which shielding gas enters into the porosity.

  11. Explosive welding of pipes

    Microsoft Academic Search

    O. Drennov; O. Burtseva; A. Kitin

    2006-01-01

    For connection by welding it is suggested to use the explosive welding method. This method is rather new. Nevertheless, it has become commonly used among the technological developments. This method can be advantageous (saving material and physical resources) comparing to its statical analogs (electron-beam welding, argon-arc welding, plasma welding, gas welding, etc.), in particular, in hard-to-reach areas due to their

  12. Explosive Welding of Pipes

    Microsoft Academic Search

    Olga Burtseva

    2007-01-01

    For connection by welding it is suggested to use the explosive welding method. This method is rather new. Nevertheless, it has become commonly used among the technological developments. This method can be advantageous (saving material and physical resources) comparing to its statical analogs (electron-beam welding, argon-arc welding, plasma welding, gas welding, etc.), in particular, in hard-to-reach areas due to their

  13. Modeling of thermal stresses in welds

    SciTech Connect

    Zacharia, T.; Aramayo, G.A.

    1993-12-31

    The transient stress distribution in a Sigmajig test specimen resulting from mechanical and thermal loading was calculated for a Type 316 stainless steel specimen using finite element analysis. The study attempted to resolve the relationship between the dynamic stress distribution, particularly near the trailing edge of the pool, and the observed cracking behavior in the test specimen. The initiation and propagation of the crack during welding was visually monitored using a stroboscopic vision system. The numerical results were used to understand the initiation and propagation of hot-cracks during controlled welding of a specimen subjected to external restraint.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  16. Inertia welding nickel-based superalloy: Part I. Metallurgical characterization

    Microsoft Academic Search

    M. Preuss; P. J. Withers; J. W. L. Pang; G. J. Baxter

    2002-01-01

    This article describes a quantitative study of the microstructure of nickel-based superalloy RR1000 tube structures joined\\u000a by inertia welding. One as-welded and three post weld heat-treated (PWHT) conditions have been investigated. The samples were\\u000a characterized mechanically by measuring the hardness profiles and microstructurally in terms of ? grain size, ?? precipitate size and volume fraction, stored energy, and microtexture. Electron

  17. Development of closed-loop control of robotic welding processes

    Microsoft Academic Search

    John P. H. Steele; Chris Mnich; Chris Debrunner; Tyrone Vincent; Stephen Liu

    2005-01-01

    Purpose – The purpose of this research is to develop closed-loop control of robotic welding processes. Design\\/methodology\\/approach – The approach being developed is the creation of three-dimensional models of the weld pool using stereo imagining. These models will be used in a model-based feedback control system. Fusion of more than one sensor type in the controller is used. Findings –

  18. Friction Stir Weld System for Welding and Weld Repair

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  19. Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.

    2008-01-01

    Friction stir welding (FSW) is a solid state welding process invented in 1991 at The Welding Institute in the United Kingdom. A weld is made in the FSW process by translating a rotating pin along a weld seam so as to stir the sides of the seam together. FSW avoids deleterious effects inherent in melting and promises to be an important welding process for any industries where welds of optimal quality are demanded. This article provides an introduction to the FSW process. The chief concern is the physical effect of the tool on the weld metal: how weld seam bonding takes place, what kind of weld structure is generated, potential problems, possible defects for example, and implications for process parameters and tool design. Weld properties are determined by structure, and the structure of friction stir welds is determined by the weld metal flow field in the vicinity of the weld tool. Metal flow in the vicinity of the weld tool is explained through a simple kinematic flow model that decomposes the flow field into three basic component flows: a uniform translation, a rotating solid cylinder, and a ring vortex encircling the tool. The flow components, superposed to construct the flow model, can be related to particular aspects of weld process parameters and tool design; they provide a bridge to an understanding of a complex-at-first-glance weld structure. Torques and forces are also discussed. Some simple mathematical models of structural aspects, torques, and forces are included.

  20. Virtual Tide Pool

    NSDL National Science Digital Library

    Science NetLinks (PBS; )

    2003-04-29

    Virtual Tide Pool features a three dimensional view of a tide pool during both low and high tides. Students can see animals that live under, above, and at the waters surface. This site offers the ability to pan the tide pool for a 360 degree view, with zoom options, and gives descriptions of the animals found during both low and high tides.

  1. Finite volume methods applied to the computational modelling of welding phenomena

    Microsoft Academic Search

    Gareth A. TAYLOR; Michael Hughes; Nadia Strusevich; Koulis Pericleous

    2002-01-01

    This paper presents the computational modelling of welding phenomena within a versatile numerical framework. The framework embraces models from both the fields of computational fluid dynamics (CFD) and computational solid mechanics (CSM). With regard to the CFD modelling of the weld pool fluid dynamics, heat transfer and phase change, cell-centred finite volume (FV) methods are employed. Additionally, novel vertex-based FV

  2. CO 2 laser-micro plasma arc hybrid welding for galvanized steel sheets

    Microsoft Academic Search

    C. H. KIM; Y. N. AHN; J. H. KIM

    2011-01-01

    A laser lap welding process for zinc-coated steel has a well-known unsolved problem-porosity formation. The boiling temperature of coated zinc is lower than the melting temperature of the base metal, which is steel. In the autogenous laser welding, the zinc vapor generates from the lapped surfaces expels the molten pool and the expulsion causes numerous weld defects, such as spatters

  3. Inspection of Austenitic Weld with Emats

    NASA Astrophysics Data System (ADS)

    Gao, H.; Ali, S. M.; Lopez, B.

    2010-02-01

    Nondestructive testing of austenitic welds is very important for nuclear, petrochemical, and many other industries. Due to the strong material anisotropy and coarse grain size in the dendritic weld zone, shear horizontal (SH) wave mode is much superior to conventional shear vertical (SV) and longitudinal wave modes. In this paper, an electromagnetic acoustic transducer (EMAT) is designed and used for the inspection of two austenitic weld samples. Compared with piezoelectric transducers, EMAT has lower efficiency in sound generation due to low conductivity of austenitic stainless steel material and strong attenuation in the weld zone. However, using our EMAT probe and cutting edge pulser and receiver, good signal to noise ratio is achieved in our testing. The angle beam EMAT probe successfully detected all defects in the samples with good signal to noise ratio including a 2% defect. The capability of detection a defect across a 2? inch thick and 2? wide austenitic weld zone is also demonstrated in the paper.

  4. Fusion welding process

    Microsoft Academic Search

    E. D. Jones; M. A. Mcbride; K. C. Thomas

    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

  5. Combinatorial optimization of welding

    E-print Network

    Sóbester, András

    C E D C Combinatorial optimization of welding sequences The problem Combinatorial optimization a welding example of a tail bearing housing vanes ­ Figure 1. The major structural details are the outer ring, the inner ring and the vanes. The vanes are welded to the rings using TIG welding. Fig. 1: Tail

  6. Finding the Optimum Parameters for Ultrasonic Welding of Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Imai, Hisashi; Matsuoka, Shin-Ichi

    The ultrasonic welding method has been expected to replace other welding and brazing processes, and this paper is concerned with an experimental study on the ultrasonic welding of an aluminum alloy onto other three aluminum alloys. In this study the relation between energy density and welding pressure in welding certain types of aluminum alloys was clarified. For example, the ultrasonic welding of an aluminum alloy can be accomplished under the condition E=K1Pn1welding pressure, K, n: coefficients). The welding energy increases with an increasing in welding pressure, and decreases with a decrease in the size of the material on the anvil side. The welding energy is effectively used in the ultrasonic welding of a flexible, narrow material with a narrow pressurization area. Weldability can be evaluated by observing the amount of subduction of the welding material. Furthermore, the oxide film and organic coating are periodically removed from bonded interfaces by ultrasonic wave vibration.

  7. Optical Welding Torch

    NASA Technical Reports Server (NTRS)

    Richardson, R. W.

    1987-01-01

    Gas/tungsten-arc welding torch supports electrode at center while enabling viewing of weld area along torch axis. Gas torch accommodates lens and optical fibers, all part of vision system for welding robot. Welding torch includes spoked structure in central bore of optical body. Structure supports welding electrode, carries electric current to it, and takes heat away from it. Spokes formed by drilling six holes 60 degrees apart around center line of torch.

  8. Television Monitoring System for Welding

    NASA Technical Reports Server (NTRS)

    Vallow, K.; Gordon, S.

    1986-01-01

    Welding process in visually inaccessible spots viewed and recorded. Television system enables monitoring of welding in visually inaccessible locations. System assists welding operations and provide video record, used for weld analysis and welder training.

  9. Internal wire guide for GTAW welding

    NASA Technical Reports Server (NTRS)

    Morgan, Gene E. (inventor); Dyer, Gerald E. (inventor)

    1989-01-01

    A welding torch for gas tungsten arc welding apparatus has a filler metal wire guide positioned within the torch, and within the shielding gas nozzle. The wire guide is adjacent to the tungsten electrode and has a ceramic liner through which the wire is fed. This reduces the size of the torch and eliminates the outside clearance problems that exit with external wire guides. Additionally, since the wire is always within the shielding gas, oxidizing of the wire is eliminated.

  10. WELDING RESEARCH SUPPLEMENT TO THE WELDING JOURNAL, JUNE, 1982

    E-print Network

    Eagar, Thomas W.

    ) WELDING RESEARCH SUPPLEMENT TO THE WELDING JOURNAL, JUNE, 1982 Sponsored by the American Welding Society .1mJ the Welding Research Council The Effect of Electrical Resistance on Nugget Formation During Spot Welding Applying a higher resistance coating to HSLA steel increases the welding current range

  11. WELDING RESEARCH ~------------~-~ SUPPLEMENT TO THE WELDING JOURNAL, AUGUST 1989

    E-print Network

    Eagar, Thomas W.

    ) ) WELDING RESEARCH ·~------------~-~ SUPPLEMENT TO THE WELDING JOURNAL, AUGUST 1989 Sponsored by the American Welding Society and the Welding Research Council All papers published in the Welding Journal's Welding Research Supplement undergo Peer Review before publication for: 1) originality of the contribution

  12. Low-temperature friction-stir welding of 2024 aluminum

    SciTech Connect

    Benavides, S.; Li, Y.; Murr, L.E.; Brown, D.; McClure, J.C. [Univ. of Texas, El Paso, TX (United States). Dept. of Metallurgical and Materials Engineering] [Univ. of Texas, El Paso, TX (United States). Dept. of Metallurgical and Materials Engineering

    1999-09-10

    Solid-state, friction-stir welding (FSW) has been demonstrated to involve dynamic recrystallization producing ultra-fine, equiaxed grain structures to facilitate superplastic deformation as the welding or joining mechanism. Since the recrystallization temperature also decreases with increasing strain rate, the FSW process is somewhat complicated because the ambient temperature, the frictional heating fraction, and the adiabatic heating fraction (proportional to the product of strain and strain-rate) will all influence both the recrystallization and grain growth within the FSW zone. Significantly reducing the ambient temperature of the base metal or work pieces to be welded would be expected to reduce the residual weld-zone grain size. The practical consequences of this temperature reduction would be the achievement of low-temperature welding. This study compares the residual grain sizes and microstructures in 2024 Al friction-stir welded at room temperature ({approximately} 30 C) and low temperature ({minus} 30 C).

  13. Linear dimension establishes weld integrity

    NASA Technical Reports Server (NTRS)

    Lewis, J. C.

    1978-01-01

    Study finds that when automatic in-place tube-welding head is used to butt-weld two stainless-steel tubes together, welding process can be made so reliable that when weld exceeds a certain minimum dimension, penetration of weld can be assumed to be complete. Detailed procedure for tube welding considers effects of arc gap, shielding gas, welding speed, and other parameters related to weld reliability.

  14. Intelligent Welding Controller

    NASA Technical Reports Server (NTRS)

    Cook, George E.; Kumar, Ramaswamy; Prasad, Tanuji; Andersen, Kristinn; Barnett, Robert J.

    1989-01-01

    Control system adapts to changing design requirements and operating conditions. Proposed control system for gas/tungsten arc welding requires only that operator specifies such direct parameters of welds as widths and depths of penetration. In control system for robotic welder, components and functions intimately connected with welding process assigned to controller domain. More general functions assigned to supervisor domain. Initial estimate of indirect parameters of welding process applied to system only at beginning of weld (t=0); after start of welding, outputs from multivariable controller takes place of estimate.

  15. Fanfares & Fireworks Pool Party

    E-print Network

    Pilyugin, Sergei S.

    Highlights Fanfares & Fireworks Pool Party Notes from the Office Class Photo TheELIWeekly Fireworks & Pool Party This is a very exciting week! We have two activities for you to participate in. As always, feel free to bring your family and conversation partners. Fanfares & Fireworks On Tuesday, we

  16. Fanfares & Fireworks Pool Party

    E-print Network

    Pilyugin, Sergei S.

    Highlights Fanfares & Fireworks Pool Party Ramadan Reminder ELI Places of Origin Notes from the Office Birthdays TheELIWeekly Fireworks & Pool Party This is a very exciting week! We have two. Fanfares & Fireworks On Wednesday, we will be going to Fanfares and Fireworks. Come listen

  17. Calculation of weld metal composition change in high-power conduction mode carbon dioxide laser-welded stainless steels

    NASA Astrophysics Data System (ADS)

    Mundra, K.; Debroy, T.

    1993-02-01

    The use of high-power density laser beam for welding of many important alloys often leads to appreciable changes in the composition and properties of the weld metal. The main difficulties in the estimation of laser-induced vaporization rates and the resulting composition changes are the determination of the vapor condensation rates and the incorporation of the effect of the welding plasma in suppressing vaporization rates. In this article, a model is presented to predict the weld metal composition change during laser welding. The velocity and temperature fields in the weld pool are simulated through numerical solution of the Navier-Stokes equation and the equation of conservation of energy. The computed temperature fields are coupled with ve-locity distribution functions of the vapor molecules and the equations of conservation of mass, momentum, and the translational kinetic energy in the gas phase for the calculation of the evap-oration and the condensation rates. Results of carefully controlled physical modeling experi-ments are utilized to include the effect of plasma on the metal vaporization rate. The predicted area of cross section and the rates of vaporization are then used to compute the resulting com-position change. The calculated vaporization rates and the weld metal composition change for the welding of high-manganese 201 stainless steels are found to be in fair agreement with the corresponding experimental results.

  18. Swimming pool. View of aisle between swimming pool and seating ...

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

    Swimming pool. View of aisle between swimming pool and seating area. Non-original spa pool is partially visible on right. - Jewish Community Center of San Francisco, 3200 California Street, San Francisco, San Francisco County, CA

  19. Thermocapillary and arc phenomena in stainless steel welding

    SciTech Connect

    Pierce, S.W.; Olson, D.L. [Colorado School of Mines, Golden, CO (United States); Burgardt, P. [Los Alamos National Lab., NM (United States)

    1999-02-01

    This investigation characterized the effects of power level and Gaussian heat source size on thermocapillary-induced weld shape and estimated the relative influence of various possible arc phenomena in determining weld shape. Welds made with the CTAW process were compared with similar ones made with a conduction-mode EBW process and the differences were related to arc effects. Evidence of thermocapillary flow was readily apparent in both the GTA welds and the conduction-mode EB welds and was qualitatively similar in both. The similarity between the results obtained with the two processes serves to demonstrate that thermocapillary convection is the dominant factor in heat-to-heat weld shape variability. However, a similar one-to-one correspondence between welds produced with the two processes does not exist. Especially at high power, the EB welds showed stronger thermocapillary convection than the GTA welds. One important arc factor that limits thermocapillary flow in ar welds appears to be an increase in arc size with arc length and arc current. A non-Gaussian arc power distribution in GTAW seems to be most important in limiting the fluid flow. Apparently, the arc power distribution is more nearly rectangular in shape for an argon gas arc. At higher currents, above 200 A, plasma shear force may also be an important contributor to weld shape development. The conduction-mode EB welds demonstrate that thermocapillary flow reversal probably does not occur in welds made with a simple Gaussian heat source. The complex shape behavior is likely a result of an arc effect such as plasma shear.

  20. Effect of Pre- and Post-weld Heat Treatments on Linear Friction Welded Ti-5553

    NASA Astrophysics Data System (ADS)

    Wanjara, Priti; Dalgaard, Elvi; Gholipour, Javad; Cao, Xinjin; Cuddy, Jonathan; Jonas, John J.

    2014-10-01

    Linear friction welding allows solid-state joining of near-beta ( ?) titanium alloy Ti-5553 (Ti-5Al-5V-5Mo-3Cr). In the as-welded condition, the weld zone (WZ) exhibits ? grain refinement and marked softening as compared with Ti-5553 in the solution heat treated and aged condition. The softening of the weldment is attributed to the depletion of the strengthening alpha ( ?) phase in the WZ and the adjacent thermo-mechanically affected zone (TMAZ). Specifically, in near- ? titanium alloys, the strength of the material mainly depends on the shape, size, distribution, and fraction of the primary ? and other decomposition products of the ? phase. Hence, a combination of pre- and post-weld heat treatments were applied to determine the conditions that allow mitigating the ? phase depletion in the WZ and TMAZ of the welds. The mechanical response of the welded samples to the heat treatments was determined by performing microhardness measurements and tensile testing at room temperature with an automated 3D deformation measurement system. It was found that though the joint efficiency in the as-welded condition was high (96 pct), strain localization and failure occurred in the TMAZ. The application of post-weld solution heat treatment with aging was effective in restoring ?, increasing the joint efficiency (97 to 99 pct) and inducing strain localization and failure in the parent material region.

  1. Microhardness Testing of Aluminum Alloy Welds

    NASA Technical Reports Server (NTRS)

    Bohanon, Catherine

    2009-01-01

    A weld is made when two pieces of metal are united or fused together using heat or pressure, and sometimes both. There are several different types of welds, each having their own unique properties and microstructure. Strength is a property normally used in deciding which kind of weld is suitable for a certain metal or joint. Depending on the weld process used and the heat required for that process, the weld and the heat-affected zone undergo microstructural changes resulting in stronger or weaker areas. The heat-affected zone (HAZ) is the region that has experienced enough heat to cause solid-state microstructural changes, but not enough to melt the material. This area is located between the parent material and the weld, with the grain structure growing as it progresses respectively. The optimal weld would have a short HAZ and a small fluctuation in strength from parent metal to weld. To determine the strength of the weld and decide whether it is suitable for the specific joint certain properties are looked at, among these are ultimate tensile strength, 0.2% offset yield strength and hardness. Ultimate tensile strength gives the maximum load the metal can stand while the offset yield strength gives the amount of stress the metal can take before it is 0.2% longer than it was originally. Both of these are good tests, but they both require breaking or deforming the sample in some way. Hardness testing, however, provides an objective evaluation of weld strengths, and also the difference or variation in strength across the weld and HAZ which is difficult to do with tensile testing. Hardness is the resistance to permanent or plastic deformation and can be taken at any desired point on the specimen. With hardness testing, it is possible to test from parent metal to weld and see the difference in strength as you progress from parent material to weld. Hardness around grain boundaries and flaws in the material will show how these affect the strength of the metal while still retaining the sample. This makes hardness testing a good test for identifying grain size and microstructure.

  2. Underwater Welding Techniques & Technologies

    Microsoft Academic Search

    R. Holdsworth

    1986-01-01

    The variety and amount of both wet and dry U\\/W welding taking place today in the offshore oil and inland sectors are such that a broader basic understanding of U\\/W welding techniques and technologies are needed to progress the integrity and quality of all U\\/W welding. To understand the problems which initiated the development of U\\/W welding, the solutions U\\/W

  3. RRR Degradation and Gas Absorption in the Electron Beam Welding Area of High Purity

    E-print Network

    in a vacuum chamber [2]. Performance degradation due to weld imperfections has been observed in some cavities the requirements for the welding of niobium cavities for TESLA. High vacuum (between 2×10-8 and 2×10-6 mbar. 370-380. The distribution of RRR, gases, grain size and thermal conductivity in the welding area

  4. IMPROVEMENT OF PROPERTIES OF WELDED JOINTS OF CIRCULAR COMPONENTS FOR GAS TURBINE ENGINES

    Microsoft Academic Search

    E. N. Eremin

    Method of electroslag welding with the combined electrode under ANF-21 flux, resulting in high-quality melting of the edges and satisfactory formation of the welded joint is described. In order to increase the properties of the weld metal, the latter was modified with the ultrafine powder of titanium carbonitride. The results of metallographic examination the zone or failure, the grain size,

  5. SYNTHETICALLY FOCUSED IMAGING TECHNIQUES IN SIMULATED AUSTENITIC STEEL WELDS USING AN ULTRASONIC PHASED ARRAY

    Microsoft Academic Search

    G. D. Connolly; M. J. S. Lowe; S. I. Rokhlin; J. A. G. Temple

    2010-01-01

    In austenitic steel welds employed in safety-critical applications, detection of defects that may propagate during service or may have occurred during welding is particularly important. In this study, synthetically focused imaging techniques are applied to the echoes received by phased arrays in order to reconstruct images of the interior of a simulated austenitic steel weld, with application to sizing and

  6. Synthetically Focused Imaging Techniques in Simulated Austenitic Steel Welds Using AN Ultrasonic Phased Array

    Microsoft Academic Search

    G. D. Connolly; M. J. S. Lowe; S. I. Rokhlin; J. A. G. Temple

    2010-01-01

    In austenitic steel welds employed in safety-critical applications, detection of defects that may propagate during service or may have occurred during welding is particularly important. In this study, synthetically focused imaging techniques are applied to the echoes received by phased arrays in order to reconstruct images of the interior of a simulated austenitic steel weld, with application to sizing and

  7. Welding Plutonium Storage Containers

    SciTech Connect

    HUDLOW, SL

    2004-04-20

    The outer can welder (OCW) in the FB-Line Facility at the Savannah River Site (SRS) is a Gas Tungsten Arc Weld (GTAW) system used to create outer canisters compliant with the Department of Energy 3013 Standard, DOE-STD-3013-2000, Stabilization, Packaging, and Storage of Plutonium-Bearing Materials. The key welding parameters controlled and monitored on the outer can welder Data Acquisition System (DAS) are weld amperage, weld voltage, and weld rotational speed. Inner 3013 canisters from the Bagless Transfer System that contain plutonium metal or plutonium oxide are placed inside an outer 3013 canister. The canister is back-filled with helium and welded using the outer can welder. The completed weld is screened to determine if it is satisfactory by reviewing the OCW DAS key welding parameters, performing a helium leak check, performing a visual examination by a qualified weld inspector, and performing digital radiography of the completed weld. Canisters with unsatisfactory welds are cut open and repackaged. Canisters with satisfactory welds are deemed compliant with the 3013 standard for long-term storage.

  8. Variable polarity arc welding

    NASA Technical Reports Server (NTRS)

    Bayless, E. O., Jr.

    1991-01-01

    Technological advances generate within themselves dissatisfactions that lead to further advances in a process. A series of advances in welding technology which culminated in the Variable Polarity Plasma Arc (VPPA) Welding Process and an advance instituted to overcome the latest dissatisfactions with the process: automated VPPA welding are described briefly.

  9. Pooling annotated corpora for clinical concept extraction

    PubMed Central

    2013-01-01

    Background The availability of annotated corpora has facilitated the application of machine learning algorithms to concept extraction from clinical notes. However, high expenditure and labor are required for creating the annotations. A potential alternative is to reuse existing corpora from other institutions by pooling with local corpora, for training machine taggers. In this paper we have investigated the latter approach by pooling corpora from 2010 i2b2/VA NLP challenge and Mayo Clinic Rochester, to evaluate taggers for recognition of medical problems. The corpora were annotated for medical problems, but with different guidelines. The taggers were constructed using an existing tagging system MedTagger that consisted of dictionary lookup, part of speech (POS) tagging and machine learning for named entity prediction and concept extraction. We hope that our current work will be a useful case study for facilitating reuse of annotated corpora across institutions. Results We found that pooling was effective when the size of the local corpus was small and after some of the guideline differences were reconciled. The benefits of pooling, however, diminished as more locally annotated documents were included in the training data. We examined the annotation guidelines to identify factors that determine the effect of pooling. Conclusions The effectiveness of pooling corpora, is dependent on several factors, which include compatibility of annotation guidelines, distribution of report types and size of local and foreign corpora. Simple methods to rectify some of the guideline differences can facilitate pooling. Our findings need to be confirmed with further studies on different corpora. To facilitate the pooling and reuse of annotated corpora, we suggest that – i) the NLP community should develop a standard annotation guideline that addresses the potential areas of guideline differences that are partly identified in this paper; ii) corpora should be annotated with a two-pass method that focuses first on concept recognition, followed by normalization to existing ontologies; and iii) metadata such as type of the report should be created during the annotation process. PMID:23294871

  10. How to map your industry's profit pool.

    PubMed

    Gadiesh, O; Gilbert, J L

    1998-01-01

    Many managers chart strategy without a full understanding of the sources and distribution of profits in their industry. Sometimes they focus their sights on revenues instead of profits, mistakenly assuming that revenue growth will eventually translate into profit growth. In other cases, they simply lack the data or the analytical tools required to isolate and measure variations in profitability. In this Manager's Tool Kit, the authors present a way to think clearly about where the money's being made in any industry. They describe a framework for analyzing how profits are distributed among the activities that form an industry's value chain. Such an analysis can provide a company's managers with a rich understanding of their industry's profit structure--what the authors call its profit pool--enabling them to identify which activities are generating disproportionately large or small shares of profits. Even more important, a profit-pool map opens a window onto the underlying structure of the industry, helping managers see the various forces that are determining the distribution of profits. As such, a profit-pool map provides a solid basis for strategic thinking. Mapping a profit pool involves four steps: defining the boundaries of the pool, estimating the pool's overall size, estimating the size of each value-chain activity in the pool, and checking and reconciling the calculations. The authors briefly describe each step and then apply the process by providing a detailed example of a hypothetical retail bank. They conclude by looking at ways of organizing the data in chart form as a first step toward plotting a profit-pool strategy. PMID:10179650

  11. The study of surface-active element oxygen on flow patterns and penetration in A-TIG welding

    NASA Astrophysics Data System (ADS)

    Zhao, Yuzhen; Shi, Yaowu; Lei, Yongping

    2006-06-01

    A three-dimensional mathematical model was developed to simulate the flow patterns and temperature distributions in a moving A-TIG weld pool of 304 stainless steels with different oxygen content using PHOENICS software. It is shown that the surface-active element, oxygen, is important, because it affects the weld shape by changing the flow patterns in the weld pool. The weld bead penetration and the depth/width ratio increase first sharply and then remain nearly a constant with increasing oxygen content. Depending upon the oxygen contents, three, one, or two vortexes that have different positions, strength, and directions may be found in the weld pool. Oxygen can cause significant changes in the weld shape by varying the sign of the surface tension coefficient. The situation with the maximum surface tension moves from the edge to the center with increasing oxygen content. As oxygen content exceeds a critical value, a positive surface tension coefficient dominates the flow patterns. The vortexes with opposite directions caused by positive surface tension coefficient can efficiently transfer the thermal energy from the arc, creating a deep weld pool. The critical oxygen content increases with the increase of the welding current.

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

    SciTech Connect

    Campbell, R.D.; Robertson, A.M. (AWS Precision Joining Center, Wheat Ridge, CO (United States)); Heiple, C.R. (EG and G Rocky Flats Plant, Golden (Colombia)); 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.

  13. Effect of Welding Atmosphere at Bottom Surface on Welding Phenomenan in Full Penetration Laser Welding of Thick Plate

    NASA Astrophysics Data System (ADS)

    Arakane, Goro; Tsukamoto, Susumu; Honda, Hiroshi; Kuroda, Seiji; Fukushima, Takeshi

    The keyhole behaviour and bubble formation were investigated in the full penetration laser welding of 11 and 15 mm thick plate with various kinds of atmosphere at the bottom side. Prevention of some defects was also attempted. Back surface atmosphere was controlled using a shielding box fixed on the sample back surface to avoid contamination from the air and also the effect of gas flow on the keyhole behaviour. A lot of bubbles were formed during welding with the back surface atmosphere of nitrogen and air. This was deduced to be caused by supersaturation of nitrogen, which was dissolved from the backside molten pool. The critical nitrogen concentration in the weld metal to form the porosity was independent of the back surface atmosphere. Oxygen enhanced the porosity formation, since the nitrogen concentration increased in the presence of oxygen. The keyhole was significantly perturbed and hot cracking occurred in the inert gas back shielding. It was shown that the keyhole stability determined by solubility of the shielding gas in the molten steel. Aluminum coating on the sample back surface was effective in preventing the porosity due to denitrification of the molten pool and hot cracking.

  14. A dimensionless parameter model for arc welding processes

    NASA Astrophysics Data System (ADS)

    Fuerschbach, P. W.

    A dimensionless parameter model previously developed for CO2 laser beam welding has been shown to be applicable to GTAW and PAW autogenous arc welding processes. The model facilitates estimates of weld size, power, and speed based on knowledge of the material's thermal properties. The dimensionless parameters can also be used to estimate the melting efficiency, which eases development of weld schedules with lower heat input to the weldment. The mathematical relationship between the dimensionless parameters in the model has been shown to be dependent on the heat flow geometry in the weldment.

  15. Welding Technician National Core Curriculum

    NSDL National Science Digital Library

    The National Center for Welding Education and Training (Weld-Ed) created this document to help educational institutions develop or review welding technician programs. This core curriculum provides a validated listing of the core of what students should know and be able to do after completing a welding technician program. Experts consulted in the creation of this curriculum included Weld-Ed regional centers and a validation panel of education and industry representatives from across the country.

  16. The effect of quenching on the solidification structure and transformation behavior of stainless steel welds

    NASA Astrophysics Data System (ADS)

    Kou, S.; Le, Y.

    1982-07-01

    Weld solidification structure of three different types of stainless steel, i.e., 310 austenitic, 309 and 304 semiaustenitic, and 430 ferritic, was investigated. Welds of each material were made without any quenching, with water quenching, and with liquid-tin quenching during welding. The weld micro-structure obtained was explained with the help of the pseudobinary phase diagrams for Fe-Cr-Ni and Fe-Cr-C systems. It was found that, due to the postsolidification 5 ? ? phase transformation in 309 and 304 stainless steels and the rapid homogenization of microsegregation in 430 stainless steel, their weld solidification structure could not be observed unless quenched from the solidification range with liquid tin. Moreover, the formation of acicular austenite, and hence, martensite, at the grain boundaries of 430 stainless steel welds was eliminated completely when quenched with liquid tin. The weld solidification structure of 310 stainless steel, on the other hand, was essentially unaffected by quenching. Based upon the observations made, the weld microstructure of these stainless steels was summarized. The effect of cooling rate on the formation of primary austenite in 309 stainless steel welds was discussed. Finally, a simple method for determining the relationship between the secondary dendrite arm spacing and the solidification time, based on welding speeds and weld pool configurations, was suggested.

  17. Simulation of deep water wet weld microstructures using electrodes with high oxidizing potential

    SciTech Connect

    Pope, A.M.; Liu, S.; Olson, D.L. [Colorado School of Mines, Golden, CO (United States)

    1994-12-31

    The properties of underwater wet (UWW) welds are greatly affected by water depth. Ibarra and Olson [1] showed that the oxygen content of the weld increases with increasing depth while the amount of deoxidants such as Mn and Si decreases. This change in chemical composition adversely affects both the tensile strength and toughness of the weld. The present research was designed to understand the influence of oxidizing ingredients in the electrode covering on the chemical composition, weld bead appearance and microstructure of wet welds. Changes in the ability of the electrode to supply oxygen to the weld pool were made through modifications of the hematite to rutile (Fe{sub 2}O{sub 3}/TiO{sub 2}) ratio in the covering.The weld deposited by the rutile electrode (no hematite addition) presented the lowest oxygen content (1700 ppm). When the oxidizing character of the electrode increased the concentration of inclusions, mainly FeO, in the weld also increased. However, the increase in oxygen pickup was not monotonous but reached a `saturation` value at approximately 2100 ppm. These results suggest that the microstructure and properties of wet welds deposited at great depths by rutile electrodes will be similar to those made by oxidizing electrodes at much shallower depths. Hence studying oxidizing electrodes and improving their properties will help the development of electrodes for wet welding at greater depths. It is also a much cheaper way of `simulating` welding at higher pressures.

  18. Reliability-based optimization of multi-component welded structures

    SciTech Connect

    Cramer, E.H. (Univ. of California, Berkeley, CA (United States). Dept. of Naval Architecture and Offshore Engineering); Friis-Hansen, P. (Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Ocean Engineering)

    1994-11-01

    Sufficient safety of welded structures against fatigue damage is achieved through the use of several safety procedures, design of the structure, quality control of the welding procedure during fabrication, and inspection for fatigue cracks with subsequent repair of detected cracks. Each safety procedure has a certain cost, and it is important to minimize the total expected cost over the lifetime of the structure. The present paper presents a probability-based optimization procedure defining optimal initial design, quality of welding procedure at fabrication, time of inspections, quality of inspections, and length of weld to be inspected at each inspection for a continuous weld. The cost considered in the optimization is cost-related to initial design, cost of fabrication, cost of inspection, expected repair cost, and expected failure cost. The probabilistic optimization problem is formulated for a homogeneous continuously welded structure containing hazardous material for which no leakage is permissible. The weld seam considered has multiple potential crack initiation sites from weld defects, where all the crack initiation sites are exposed to the same stochastic loading condition. Two models are applied to define the distribution of weld defects over the weld seam: a model where the locations of the crack initiation sites are known, and a model where the locations and number of crack initiation sites are unknown and described through a homogeneous Poisson distribution process. Uncertainties in the long-term stochastic load process, the fatigue strength, and the crack size of the different initial defects are considered in the procedure.

  19. Microstructure mapping in friction stir welds of 7449 aluminium alloy using SAXS

    Microsoft Academic Search

    M. Dumont; A. Steuwer; A. Deschamps; M. Peel; P. J. Withers

    2006-01-01

    This paper describes the microstructural response of an age-hardenable, high-strength 7449 aluminium alloy to friction stir welding. Plates in the naturally aged (T3) and over-aged (T79) conditions were welded using two weld tool translation speeds. Maps of precipitate volume fraction and size were obtained by spatially resolved small-angle X-ray scattering over a cross-section of the welded plate, complemented by direct

  20. Evaluation of solar cell welds by scanning acoustic microscopy

    NASA Technical Reports Server (NTRS)

    Klima, S. J.; Frey, W. E.; Baraona, C. R.

    1982-01-01

    Scanning laser acoustic microscopy was used to nondestructively evaluate solar cell interconnect bonds made by resistance welding. Both copper-silver and silver-silver welds were analyzed. The bonds were produced either by a conventional parallel-gap welding technique using rectangular electrodes or new annular gap design with a circular electrode cross section. With the scanning laser acoustic microscope, it was possible to produce a real time television image which reveales the weld configuration as it relates to electrode geometry. The effect of electrode misalinement with the surface of the cell was also determined. A preliminary metallographic analysis was performed on selected welds to establish the relationship between actual size and shape of the weld area and the information available from acoustic micrographs.

  1. Method for welding beryllium

    DOEpatents

    Dixon, Raymond D. (Los Alamos, NM); Smith, Frank M. (Espanola, NM); O'Leary, Richard F. (Los Alamos, NM)

    1997-01-01

    A method is provided for joining beryllium pieces which comprises: depositing aluminum alloy on at least one beryllium surface; contacting that beryllium surface with at least one other beryllium surface; and welding the aluminum alloy coated beryllium surfaces together. The aluminum alloy may be deposited on the beryllium using gas metal arc welding. The aluminum alloy coated beryllium surfaces may be subjected to elevated temperatures and pressures to reduce porosity before welding the pieces together. The aluminum alloy coated beryllium surfaces may be machined into a desired welding joint configuration before welding. The beryllium may be an alloy of beryllium or a beryllium compound. The aluminum alloy may comprise aluminum and silicon.

  2. Friction Stir Welding in HSLA-65 Steel: Part I. Influence of Weld Speed and Tool Material on Microstructural Development

    NASA Astrophysics Data System (ADS)

    Barnes, S. J.; Bhatti, A. R.; Steuwer, A.; Johnson, R.; Altenkirch, J.; Withers, P. J.

    2012-07-01

    A systematic set of single-pass full penetration friction stir bead-on-plate and butt-welds in HSLA-65 steel were produced using a range of different traverse speeds (50 to 500 mm/min) and two tool materials (W-Re and PCBN). Microstructural analysis of the welds was carried out using optical microscopy, and hardness variations were also mapped across the weld-plate cross sections. The maximum and minimum hardnesses were found to be dependent upon both welding traverse speed and tool material. A maximum hardness of 323 Hv(10) was observed in the mixed martensite/bainite/ferrite microstructure of the weld nugget for a welding traverse speed of 200 mm/min using a PCBN tool. A minimum hardness of 179 Hv(10) was found in the outer heat-affected zone (OHAZ) for welding traverse speed of 50 mm/min using a PCBN tool. The distance from the weld centerline to the OHAZ increased with decreasing weld speed due to the greater heat input into the weld. Likewise for similar energy inputs, the size of the transformed zone and the OHAZ increased on moving from a W-Re tool to a PCBN tool probably due to the poorer thermal conductivity of the PCBN tool. The associated residual stresses are reported in Part II of this series of articles.

  3. Swimming pool granuloma

    MedlinePLUS

    Aquarium granuloma; Fish tank granuloma ... Risks include exposure to swimming pools, salt water aquariums, or ocean fish. ... Wash hands and arms thoroughly after cleaning aquariums. Or, wear rubber gloves when cleaning.

  4. Swimming Pool Safety

    MedlinePLUS

    ... closing/self-latching Window guards Pool alarms Swimming Lessons - Where We Stand Children need to learn to ... Some factors you may consider before starting swimming lessons for younger children include: Frequency of exposure to ...

  5. (Welding under extreme conditions)

    SciTech Connect

    Davis, S.A.

    1989-09-29

    The traveler was an invited member of the United States delegation and representative of the Basic Energy Science Welding Science program at the 42nd Annual International Institute of Welding (IIW) Assembly and Conference held in Helsinki, Finland. The conference and the assembly was attended by about 600 delegates representing 40 countries. The theme of the conference was welding under extreme conditions. The conference program contained several topics related to welding in nuclear, arctic petrochemical, underwater, hyperbaric and space environments. At the annual assembly the traveler was a delegate (US) to two working groups of the IIW, namely Commission IX and welding research study group 212. Following the conference the traveler visited the Danish Welding Institute in Copenhagen and the Risoe National Laboratory in Roskilde. Prior to the conference the traveler visited Lappeenranta University of Technology and presented an invited seminar entitled Recent Advances in Welding Science and Technology.''

  6. Mechanism of laser welding on dissimilar metals between stainless steel and W-Cu alloy

    NASA Astrophysics Data System (ADS)

    Chen, Kai; Wang, Zhiyong; Xiao, Rongshi; Zuo, Tiechuan

    2006-05-01

    CO2 laser is employed to join a piece of powder metallurgical material (PMM) to a stainless steel in butt joint welding mode. The powder Ni35, as a filler powder, is used. The weld metal comes from three parts of stainless steel, powder Ni35, and Cu in W-Cu PMM. It is indicated that some parts of the W-Cu base metal are heated by laser and the metal Cu at the width of 0.06-0.12 mm from the edge is melted into the melting pool in the laser welding process. The formation of firm weld joint is just because that the melting liquid metal could fill the position occupied by metal Cu and surround the metal W granules fully. The analysis results indicate that the mechanism of the laser welding for stainless steel and W-Cu alloy is a special mode of fusion-brazing welding.

  7. CW/PW dual-beam YAG laser welding of steel/aluminum alloy sheets

    NASA Astrophysics Data System (ADS)

    Yan, Shi; Hong, Zhang; Watanabe, Takehiro; Jingguo, Tang

    2010-07-01

    The lap welding of JSC270CC steel and A6111-T4 aluminum alloys were carried out by a dual-beam YAG laser with the continuous wave (CW) and pulse wave (PW) modes. The microstructure of the welded joints were examined with SEM, EPMA while the properties were checked with microhardness tester and tensile testing machine. It was shown that the dual-beam laser welding can effectively reduce or avoid the formation of the blowholes in the welded joints. The PW laser beam penetrated the welding pool, leading to the root-shape structures with enhanced bonding strength at the weld interface. A 10 ?m intermetallic compound (IMC) layer was generated at the interface. The shearing strength of lap joint was measured to be 128 MPa.

  8. Processing-Microstructure Relationships in Friction Stir Welding of MA956 Oxide Dispersion Strengthened Steel

    NASA Astrophysics Data System (ADS)

    Baker, Bradford W.; Menon, E. Sarath K.; McNelley, Terry R.; Brewer, Luke N.; El-Dasher, Bassem; Farmer, Joseph C.; Torres, Sharon G.; Mahoney, Murray W.; Sanderson, Samuel

    2014-12-01

    A comprehensive set of processing-microstructure relationships is presented for friction stir welded oxide dispersion strengthened MA956 steel. Eight rotational speed/traverse speed combinations were used to produce friction stir welds on MA956 plates using a polycrystalline cubic boron nitride tool. Weld conditions with high thermal input produced defect-free, full-penetration welds. Electron backscatter diffraction results showed a significant increase in grain size, a persistent body centered cubic torsional texture in the stir zone, and a sharp transition in grain size across the thermo-mechanically affected zone sensitive to weld parameters. Micro-indentation showed an asymmetric reduction in hardness across a transverse section of the weld. This gradient in hardness was greatly increased with higher heat inputs. The decrease in hardness after welding correlates directly with the increase in grain size and may be explained with a Hall-Petch type relationship.

  9. Measurement and modelling of residual stresses in a TIG weld

    NASA Astrophysics Data System (ADS)

    Webster, P. J.; Ananthaviravakumar, N.; Hughes, D. J.; Mills, G.; Preston, R. V.; Shercliff, H. R.; Withers, P. J.

    Residual stresses due to TIG welding have been measured using neutron diffraction and the results compared with a finite element model calculation. Measurements were made on a single-pass, autogenous, bead-on-plate TIG weld made along the centre line of an aluminium alloy rectangular plate of dimensions 172×150×3mm3. The weld is 150mm long with the start and end pools centred approximately 12mm from the plate edges. There is an 8mm wide molten band on the crown surface of the weld. Measurements were made at a neutron wavelength of 1.51Å using the aluminium (311) reflection and a gauge volume 2×2×2mm3. Scans were made along three transverse lines, across the centre of the weld, 40mm from the start and 40mm from the end at mid-thickness. Stresses were derived using data collected in the three orthogonal symmetry directions. A finite-element model was generated using ABAQUS. The agreement between the calculated and measured results is good. Longitudinal residual stresses are strongly tensile (approaching 200MPa) in the weld, falling to zero at around 15mm from the weld line with balancing compression towards the edges.

  10. Robotic Welding Of Injector Manifold

    NASA Technical Reports Server (NTRS)

    Gilbert, Jeffrey L.; Shelley, D. Mark

    1992-01-01

    Brief report presents history, up through October 1990, of continuing efforts to convert from manual to robotic gas/tungsten arc welding in fabrication of main injector inlet manifold of main engine of Space Shuttle. Includes photographs of welding machinery, welds, and weld preparations. Of interest to engineers considering establishment of robotic-welding facilities.

  11. Bobbin-Tool Friction-Stir Welding of Thick-Walled Aluminum Alloy Pressure Vessels

    SciTech Connect

    Dalder, E C; Pastrnak, J W; Engel, J; Forrest, R S; Kokko, E; Ternan, K M; Waldron, D

    2007-06-06

    It was desired to assemble thick-walled Al alloy 2219 pressure vessels by bobbin-tool friction-stir welding. To develop the welding-process, mechanical-property, and fitness-for-service information to support this effort, extensive friction-stir welding-parameter studies were conducted on 2.5 cm. and 3.8 cm. thick 2219 Al alloy plate. Starting conditions of the plate were the fully-heat-treated (-T62) and in the annealed (-O) conditions. The former condition was chosen with the intent of using the welds in either the 'as welded' condition or after a simple low-temperature aging treatment. Since preliminary stress-analyses showed that stresses in and near the welds would probably exceed the yield-strength of both 'as welded' and welded and aged weld-joints, a post-weld solution-treatment, quenching, and aging treatment was also examined. Once a suitable set of welding and post-weld heat-treatment parameters was established, the project divided into two parts. The first part concentrated on developing the necessary process information to be able to make defect-free friction-stir welds in 3.8 cm. thick Al alloy 2219 in the form of circumferential welds that would join two hemispherical forgings with a 102 cm. inside diameter. This necessitated going to a bobbin-tool welding-technique to simplify the tooling needed to react the large forces generated in friction-stir welding. The bobbin-tool technique was demonstrated on both flat-plates and plates that were bent to the curvature of the actual vessel. An additional issue was termination of the weld, i.e. closing out the hole left at the end of the weld by withdrawal of the friction-stir welding tool. This was accomplished by friction-plug welding a slightly-oversized Al alloy 2219 plug into the termination-hole, followed by machining the plug flush with both the inside and outside surfaces of the vessel. The second part of the project involved demonstrating that the welds were fit for the intended service. This involved determining the room-temperature tensile and elastic-plastic fracture-toughness properties of the bobbin-tool friction-stir welds after a post-weld solution-treatment, quenching, and aging heat-treatment. These mechanical properties were used to conduct fracture-mechanics analyses to determine critical flaw sizes. Phased-array and conventional ultrasonic non-destructive examination was used to demonstrate that no flaws that match or exceed the calculated critical flaw-sizes exist in or near the friction-stir welds.

  12. The Transportable Auxin Pool 1

    PubMed Central

    de la Fuente, R. K.; Leopold, A. C.

    1970-01-01

    Evidences from experiments with stem sections of sunflower seedlings suggest that the transport of auxin may be limited by a restricted pool size of transportable auxin and restrictions in the availability of transport sites. A steady state of transport is observed over a range of lengths of stem sections, and over a wide range of auxin contents. The capacity of the sections to transport a pulse of auxin declines with aging after cutting, 50% decline occurring at about 10+ hours; the transportability of a pulse of auxin declines rapidly after the completion of uptake, 50% decline occurring at about 1 hour. A chase treatment with unlabeled auxin does not alter transport, but a pretreatment with auxin depressed subsequent transport for about 1 hour. In depleted tissues such pretreatment is not inhibitory but rather is promotive of transport. The interpretation offered is that transport is limited by the pool size and transport sites, and roles for these factors are suggested in relation to the auxin transport gradient and the tropistic responses. PMID:16657273

  13. DROWNING IN DISINFECTION BY-PRODUCTS? ASSESSING SWIMMING POOL WATER

    EPA Science Inventory

    The development of treated water for swimming pools has made swimming a year round activity, widely enjoyed for leisure as well as exercise. Swimming pools can be found in different kinds and sizes in public areas, hotels and spas, or at private homes. In Germany ~250-300 million...

  14. Vernal Pool Lessons and Activities.

    ERIC Educational Resources Information Center

    Childs, Nancy; Colburn, Betsy

    This curriculum guide accompanies Certified: A Citizen's Step-by-Step Guide to Protecting Vernal Pools which is designed to train volunteers in the process of identifying vernal pool habitat so that as many of these pools as possible can be certified by the Massachusetts Natural Heritage and Endangered Species Program. Vernal pools are a kind of…

  15. Low-Temperature Friction-Stir Welding of 2024 Aluminum

    NASA Technical Reports Server (NTRS)

    Benavides, S.; Li, Y.; Murr, L. E.; Brown, D.; McClure, J. C.

    1998-01-01

    Solid state friction-stir welding (FSW) has been demonstrated to involve dynamic recrystallization producing ultra-fine, equiaxed grain structures to facilitate superplastic deformation as the welding or joining mechanism. However, the average residual, equiaxed, grain size in the weld zone has ranged from roughly 0.5 micron to slightly more than 10 micron, and the larger weld zone grain sizes have been characterized as residual or static grain growth as a consequence of the temperatures in the weld zone (where center-line temperatures in the FSW of 6061 Al have been shown to be as high as 480C or -0.8 T(sub M) where T(sub M) is the absolute melting temperature)). In addition, the average residual weld zone grain size has been observed to increase near the top of the weld, and to decrease with distance on either side of the weld-zone centerline, an d this corresponds roughly to temperature variations within the weld zone. The residual grain size also generally decreases with decreasing FSW tool rotation speed. These observations are consistent with the general rules for recrystallization where the recrystallized grain size decreases with increasing strain (or deformation) at constant strain rate, or with increasing strain-rate, or with increasing strain rate at constant strain; especially at lower ambient temperatures, (or annealing temperatures). Since the recrystallization temperature also decreases with increasing strain rate, the FSW process is somewhat complicated because the ambient temperature, the frictional heating fraction, and the adiabatic heating fraction )proportional to the product of strain and strain-rate) will all influence both the recrystallization and growth within the FSW zone. Significantly reducing the ambient temperature of the base metal or work pieces to be welded would be expected to reduce the residual weld-zone grain size. The practical consequences of this temperature reduction would be the achievement of low temperature welding. This study compares the residual grain sizes and microstructures in 2024 Al friction-stir welded at room temperature (about 30C and low temperature (-30C).

  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. Detection of weld line and automatic seam tracking by ultrasonic sensing robot for underwater wet welding

    SciTech Connect

    Suga, Yasuo; Machida, Akira [Keio Univ., Yokohama (Japan)

    1994-12-31

    An underwater wet welding robot with an ultrasonic sensor was developed to detect the weld line and to track the weld line automatically. The robot can move the welding torch toward X and Y directions and the ultrasonic sensor can oscillate along the X direction. As the ultrasonic sensor, an immersion type probe of 9.0 mm in diameter was used. The frequency of the ultrasonic wave is 5.0 MHz. The spot size of the ultrasonic beam is approximately 2 mm at a water distance of 50 mm. As the result of the detecting experiment of weld line by the ultrasonic method, there was no problem in the case of as-received steel plate. However, when the surface condition of the base metal is poor, the robot sometimes makes misjudgment. In the tracking test of the butt weld line of steel plates, which has the angle of 30{degree} to the Y-axis, the tracking error was about 0.5 mm. As the result of the experiments, it was made clear that the robot system is effective on the automatic seam tracking of underwater wet welding.

  18. Automated Weld Characterization Using the Thermoelectric Method

    NASA Technical Reports Server (NTRS)

    Fulton, J. P.; Wincheski, B.; Namkung, M.

    1992-01-01

    The effective assessment of the integrity of welds is a complicated NDE problem that continues to be a challenge. To be able to completely characterize a weld, detailed knowledge of its tensile strength, ductility, hardness, microstructure, macrostructure, and chemical composition is needed. NDE techniques which can provide information on any of these features are extremely important. In this paper, we examine a seldom used approach based on the thermoelectric (TE) effect for characterizing welds and their associated heat affected zone (HAZ). The thermoelectric method monitors the thermoelectric power which is sensitive to small changes in the kinetics of the conduction electrons near the Fermi surface that can be caused by changes in the local microstructure. The technique has been applied to metal sorting, quality testing, flaw detection, thickness gauging of layers, and microscopic structural analysis. To demonstrate the effectiveness of the technique for characterizing welds, a series of tungsten-inert-gas welded Inconel-718 samples were scanned with a computer controlled TE probe. The samples were then analyzed using a scanning electron microscope and Rockwell hardness tests to characterize the weld and the associated HAZ. We then correlated the results with the TE measurements to provide quantitative information on the size of the HAZ and the degree of hardness of the material in the weld region. This provides potentially valuable information on the strength and fatigue life of the weld. We begin the paper by providing a brief review of the TE technique and then highlight some of the factors that can effect the measurements. Next, we provide an overview of the experimental procedure and discuss the results. Finally, we summarize our findings and consider areas for future research.

  19. Associations of welding and manganese exposure with Parkinson disease

    PubMed Central

    Borenstein, Amy R.; Nelson, Lorene M.

    2012-01-01

    Objective: To examine associations of welding and manganese exposure with Parkinson disease (PD) using meta-analyses of data from cohort, case-control, and mortality studies. Methods: Epidemiologic studies related to welding or manganese exposure and PD were identified in a PubMed search, article references, published reviews, and abstracts. Inclusion criteria were 1) cohort, case-control, or mortality study with relative risk (RR), odds ratio (OR), or mortality OR (MOR) and 95 confidence intervals (95% CI); 2) RR, OR, and MOR matched or adjusted for age and sex; 3) valid study design and analysis. When participants of a study were a subgroup of those in a larger study, only results of the larger study were included to assure independence of datasets. Pooled RR/OR estimates and 95% CIs were obtained using random effects models; heterogeneity of study effects were evaluated using the Q statistic and I2 index in fixed effect models. Results: Thirteen studies met inclusion criteria for the welding meta-analysis and 3 studies for the manganese exposure meta-analysis. The pooled RR for the association between welding and PD for all study designs was 0.86 (95% CI 0.80–0.92), with absence of between-study heterogeneity (I2 = 0.0). Effect measures for cohort, case-control, and mortality studies were similar (0.91, 0.82, 0.87). For the association between manganese exposure and PD, the pooled OR was 0.76 (95% CI 0.41–1.42). Conclusions: Welding and manganese exposure are not associated with increased PD risk. Possible explanations for the inverse association between welding and PD include confounding by smoking, healthy worker effect, and hormesis. PMID:22965675

  20. Two-Pulse Stitch Welding

    NASA Technical Reports Server (NTRS)

    Torborg, C. J.

    1985-01-01

    Second welding pulse at about 20 percent higher energy repairs bad single-pulse welds. Method used successfully to weld polytetrafluoroethyleneinsulated nickel wire to stainless-steel terminals in back-plane wiring.

  1. Welding skate with computerized controls

    NASA Technical Reports Server (NTRS)

    Wall, W. A., Jr.

    1968-01-01

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

  2. Cleaning Internal-Weld Splatter

    NASA Technical Reports Server (NTRS)

    Snodgrass, R.

    1982-01-01

    Splattered metal produced by welding can be easily removed from inaccessible areas by method resembling ball milling. Hard steel balls are vibrated inside welded unit so that they "scrub away" excess metal on interior side of weld joint.

  3. 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.

  4. Friction Stir Welding

    NSDL National Science Digital Library

    Leske, Cavin.

    Probably the best resource to learn about friction stir welding (FSW) comes from the entity that developed the technology. The Welding Institute (1) offers a thorough overview of FSW and its advantages over other types of welding. The University of Cambridge (2) maintains another informative Web site about FSW. This is a more visual resource, allowing the visitor to view images and video clips that show FSW equipment and how the process works. Three introductory slide presentations are also available. For those who are unfamiliar with other types of welding, the Joining Technologies company (3) has an online welding reference center. Of particular interest is the Weld Defects section, which describes many of the problems of conventional welding that FSW solves. The American Welding Society published this research paper (4) in the January 2003 issue of the Welding Journal. The nine-page document presents experimental results of FSW tests, showing that defect-free welds can be achieved with a material such as mild steel. Automobile design is a prime application area for FSW, as is noted in a fact sheet from the National Transportation Research Center (5). It states that while other welding methods are suitable for standard metals in automobiles, new lightweight materials cannot be effectively joined unless a technique like FSW is used. A research paper that will be presented at an international conference in July 2003 (6) discusses the residual stresses resulting from a weld created with the FSW process. While welds of this type are typically much stronger than others, it is important to note how the performance of a weld is degraded by such residual stresses. NASA has devised a new technique, called thermal stir welding, that improves upon FSW. This breakthrough is presented in a two-page summary (7) that briefly explains the differences between thermal stir welding and other advanced methods. A new friction stir welding center was announced in November 2002, and it will be used in the construction of a new jet airplane. FSW will replace over half of the rivets traditionally used to hold planes together. This development, and its importance for jet manufacturing, are outlined in a press release from Eclipse Aviation (8).

  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. Welding in Space Workshop

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.

    1990-01-01

    The potential was discussed for welding in space, its advantages and disadvantages, and what type of programs can benefit from the capability. Review of the various presentations and comments made in the course of the workshop suggests several routes to obtaining a better understanding of how welding processes can be used in NASA's initiatives in space. They are as follows: (1) development of a document identifying well processes and equipment requirements applicable to space and lunar environments; (2) more demonstrations of welding particular hardware which are to be used in the above environments, especially for space repair operations; (3) increased awareness among contractors responsible for building space equipment as to the potential for welding operations in space and on other planetary bodies; and (4) continuation of space welding research projects is important to maintain awareness within NASA that welding in space is viable and beneficial.

  7. LPT. EBOR (TAN646) interior, installing reactor in STF pool ("vault"). ...

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

    LPT. EBOR (TAN-646) interior, installing reactor in STF pool ("vault"). Pressure vessel shows core barrel and outlet nozzle (next to man below) to inner duct weld, which is prepared and in position for stress relieving. Camera facing southeast. Photographer: Comiskey. Date: January 20, 1965. INEEL negative no. 65-239 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  8. Determination of pool boiling Critical Heat Flux enhancement in nanofluids

    E-print Network

    Truong, Bao H. (Bao Hoai)

    2007-01-01

    Nanofluids are engineered colloids composed of nano-size particles dispersed in common fluids such as water or refrigerants. Using an electrically controlled wire heater, pool boiling Critical Heat Flux (CHF) of Alumina ...

  9. Underwater Stud Welding

    Microsoft Academic Search

    K. Masubuchi; H. Ozaki; J. Chiba

    1978-01-01

    Stud welding is a simple process which requires no skill of the operator. Experiments were conducted to determine whether underwater stud welding could be made. Most experiments were made with mild-steel studs 3\\/4 inch in diameter. Base plates used were mild steel and HY-80 steel, 1\\/2 and 1 inch (6.4 and 25.4 mm) thick. It was found that stud welding

  10. Dual wire welding torch and method

    DOEpatents

    Diez, Fernando Martinez (Peoria, IL); Stump, Kevin S. (Sherman, IL); Ludewig, Howard W. (Groveland, IL); Kilty, Alan L. (Peoria, IL); Robinson, Matthew M. (Peoria, IL); Egland, Keith M. (Peoria, IL)

    2009-04-28

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

  11. Explosive Welding of Pipes

    NASA Astrophysics Data System (ADS)

    Drennov, Oleg; Drennov, Andrey; Burtseva, Olga

    2013-06-01

    For connection by welding it is suggested to use the explosive welding method. This method is rather new. Nevertheless, it has become commonly used among the technological developments. This method can be advantageous (saving material and physical resources) comparing to its statical analogs (electron-beam welding, argon-arc welding, plasma welding, gas welding, etc.), in particular, in hard-to-reach areas due to their geographic and climatic conditions. Explosive welding of cylindrical surfaces is performed by launching of welded layer along longitudinal axis of construction. During this procedure, it is required to provide reliable resistance against radial convergent strains. The traditional method is application of fillers of pipe cavity, which are dense cylindrical objects having special designs. However, when connecting pipes consecutively in pipelines by explosive welding, removal of the fillers becomes difficult and sometimes impossible. The suggestion is to use water as filler. The principle of non-compressibility of liquid under quasi-dynamic loading is used. In one-dimensional gasdynamic and elastic-plastic calculations we determined non-deformed mass of water (perturbations, which are moving in the axial direction with sound velocity, should not reach the layer end boundaries for 5-7 circulations of shock waves in the radial direction). Linear dimension of the water layer from the zone of pipe coupling along axis in each direction is >= 2R, where R is the internal radius of pipe.

  12. Robot welding process control

    NASA Technical Reports Server (NTRS)

    Romine, Peter L.

    1991-01-01

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

  13. Superplastic Forming of Aluminum Multisheet Structures Fabricated Using Friction Stir Welding and Refill Friction Stir Spot Welding

    SciTech Connect

    Grant, Glenn J.; Herling, Darrell R.; Arbegast, William J.; Allen, Casey D.; Degen, Cassandra M.

    2006-12-20

    Superplastically-formed structural panels are growing in their applications in aerospace, aircraft, automotive, and other industries. Generally, monolithic sheets are employed, limiting the size and complexity of the final part. However, more complex and larger final geometries are possible if individual sheet materials can be joined together through an appropriate joining technology, then SPF formed to final shape. The primary challenge in this type of SPF fabrication has been making a joint between the sheets that will survive the SPF forming event and display the correct amount of elongation in the joint relative to the base materials being formed. Friction Stir Welding is an ideal joining technology for SPF applications because the forming response of the weld metal at SPF conditions is adjustable by selecting different weld process parameters during initial joining. This allows the SPF deformation in the weld metal to be “tuned” to the deformation of the parent sheet to prevent early failure from occurring in either the weld metal or the parent sheet due to mismatched SPF flow stresses. Industrial application of the concept of matching flow stresses is currently being pursued on a program at the Pacific Northwest National Laboratory on room temperature formed friction stir welded tailor welded blanks for heavy truck applications. Flow stress matching and process parameter “tuning” is also important in the fabrication of SPF multisheet structural panels. These panels are fabricated by joining three sheets together with alternating welds top and bottom, so that each weld penetrates only two of the three sheets. This sheet pack is then sealed with a weld seam around the outside and hot gas is introduced between the sheets through a welded tube. Under SPF conditions the sheet pack inflates to produce an internally supported structure. In this paper we presents results on an investigation into using FSW and Refill Friction Stir Spot Welding to fabricated 5083 aluminum multisheet packs that can be SPF formed into 3-D structural or integrally stiffened panels. Several configurations of 3-sheet egg crate and truss structures were friction stir welded and hot gas SPF formed in a parallel-platen SPF press. Data on weld conditions for optimum SPF forming as well as pre- and post- forming microstructures will be presented. It is found that FSW process conditions are a key feature of a successful SPF forming operation and the nugget microstructures and other features of the weld zone can be optimized to produce a wide range of weld region elongations. Friction Stir Welding may prove to be the enabler that allows aluminum to be considered in multisheet and integrally stiffened SPF Aluminum structures.

  14. Defect distributions in weld-deposited cladding

    SciTech Connect

    Li, Y.Y.; Mabe, W.R.

    1998-11-01

    Defect distributions in stainless steel and nickel-chromium alloy weld-deposited cladding over a low alloy steel base were characterized by destructive evaluation (DE). An evaluation of the observed defects was conducted to characterize the defects by type or classification. Size distributions of cladding defect types were developed from the information obtained. This paper presents the results of the cladding evaluation.

  15. Effects of Sealing Run Welding with Defocused Laser Beam on the Quality of T-joint Fillet Weld

    NASA Astrophysics Data System (ADS)

    Unt, Anna; Poutiainen, Ilkka; Salminen, Antti

    Fillet weld is the predominant weld type used for connecting different elements e.g. in shipbuilding, offshore and bridge structures. One of prevalent research questions is the structural integrity of the welded joint. Post weld improvement techniques are being actively researched, as high stress areas like an incomplete penetration on the root side or fluctuations in penetration depth cannot be avoided. Development of laser and laser-arc hybrid welding processes have greatly contributed to increase of production capacity and reduction of heat-induced distortions by producing single pass full penetration welds in thin- and medium thickness structural steel parts. Present study addresses the issue of how to improve the quality of the fillet welds by welding the sealing run on the root side with defocused laser beam. Welds having incomplete or excessive penetration were produced with several beam angles and laser beam spot sizes on surface. As a conclusion, significant decrease or even complete elimination of the seam irregularities, which act as the failure starting points during service, is achieved.

  16. Manually Operated Welding Wire Feeder

    NASA Technical Reports Server (NTRS)

    Rybicki, Daniel J. (Inventor)

    2001-01-01

    A manual welding wire feeder apparatus comprising a bendable elongate metal frame with a feed roller mounted at the center thereof for rotation about an axis transverse to the longitudinal axis of the frame. The frame ends are turned up as tabs and each provided with openings in alignment with each other and the mid-width center of the roller surface. The tab openings are sized to accommodate welding wire and each extends to a side edge of the tab, both opening on the same side of the frame, whereby welding wire can be side-loaded onto the frame. On the side of the frame, opposite the roller a lock ring handle is attached tangentially and is rotatable about the attachment point and an axis perpendicular to the frame. The device is grasped in the hand normally used to hold the wire. A finger is placed through the loop ring and the frame positioned across the palm and lower fingers. The thumb is positioned atop the wire so it can be moved from the back of the frame across the roller, and towards the front. In doing so, the wire is advanced at a steady rate in axial alignment with the tab openings and roller. To accommodate different wire diameters the frame is bendable about its center in the plane of the frame axis and wire so as to keep the wire in sufficient tension against the roller and to keep the wire fixed when the frame is tilted and thumb pressure released.

  17. Simulation of inverse heat conduction problems in fusion welding with extended analytical heat source models

    Microsoft Academic Search

    V. A. Karkhin; A. Pittner; C. Schwenk; M. Rethmeier

    2011-01-01

    The paper presents bounded volume heat sources and the corresponding functional-analytical expressions for the temperature\\u000a field. The power density distributions considered here are normal, exponential and parabolic. The sources model real heat\\u000a sources like the welding arc, laser beam, electron beam, etc., the convection in the weld pool as well as the latent heat\\u000a due to fusion and solidification. The

  18. Aircraft observations of cold pools under marine stratocumulus

    NASA Astrophysics Data System (ADS)

    Terai, C. R.; Wood, R.

    2013-10-01

    Although typically associated with precipitating cumuli, cold pools also form under shallower stratocumulus. This study presents cold-pool observations as sampled by the NSF/NCAR C-130, which made cloud and boundary-layer measurements over the southeast Pacific stratocumulus region at an altitude of approximately 150 m during the VOCALS Regional Experiment. Ninety edges of cold pools are found in the C-130 measurements by identifying step-like changes in the potential temperature. Examination of their mesoscale environment shows that the observed cold pools tend to form under heavier precipitation, thicker clouds, and in cleaner environments. Cold pools are also found to form under clouds with high LWP values over the night of or before sampling. When they form, cold pools often form in clusters or on top of each other, rather than as separate, individual entities. Their sizes range from 2 km to 16 km (middle 50th percentile), where the largest of cold pools are associated with the greatest drops in temperature. Composites of various observed thermodynamic and chemical variables along the cold-pool edges indicate increased humidity, equivalent potential temperature, coarse-mode aerosol, and dimethyl sulfide concentration inside cold pools. The enhancements inside cold pools are consistent with increased static stability that traps fluxes from the ocean surface in the lowest levels of the boundary layer. By using pressure perturbations, the average cold pool is estimated to be approximately 300 m deep. The temperature depression in cold pools also leads to density-driven flows that drive convergence of horizontal winds and measurable, mechanically driven vertical wind velocity at the edges of cold pools.

  19. Stochastic pooling networks

    NASA Astrophysics Data System (ADS)

    McDonnell, Mark D.; Amblard, Pierre-Olivier; Stocks, Nigel G.

    2009-01-01

    We introduce and define the concept of a stochastic pooling network (SPN), as a model for sensor systems where redundancy and two forms of 'noise'—lossy compression and randomness—interact in surprising ways. Our approach to analysing SPNs is information theoretic. We define an SPN as a network with multiple nodes that each produce noisy and compressed measurements of the same information. An SPN must combine all these measurements into a single further compressed network output, in a way dictated solely by naturally occurring physical properties—i.e. pooling—and yet cause no (or negligible) reduction in mutual information. This means that SPNs exhibit redundancy reduction as an emergent property of pooling. The SPN concept is applicable to examples in biological neural coding, nanoelectronics, distributed sensor networks, digital beamforming arrays, image processing, multiaccess communication networks and social networks. In most cases the randomness is assumed to be unavoidably present rather than deliberately introduced. We illustrate the central properties of SPNs for several case studies, where pooling occurs by summation, including nodes that are noisy scalar quantizers, and nodes with conditionally Poisson statistics. Other emergent properties of SPNs and some unsolved problems are also briefly discussed.

  20. Cable Pool - Cherryfield

    USGS Multimedia Gallery

    The USGS monitors the Narraguagus River at Cherryfield, Maine at a location called Cable Pool. This spot was once renowned for Atlantic salmon, where anglers would line the banks, waiting their turn to cast a line into the water. In fact, posts along the river bank to hold the waiting anglers rods e...

  1. Modeling of heat transfer and fluid flow in keyhole mode welding

    NASA Astrophysics Data System (ADS)

    Rai, Rohit

    In this work, computationally efficient numerical models have been developed for linear keyhole mode LBW and EBW processes. The models combine an energy balance based model for keyhole geometry calculation with a well tested 3D heat transfer and fluid flow model. For LBW, keyhole wall temperatures are assumed to be equal to the boiling point of the alloy at 1 atm pressure. Keyhole wall temperatures in EBW are calculated from the equilibrium vapor pressure versus temperature relation for the work-piece material. The vapor pressure is, in turn, calculated from a force balance at the keyhole walls between the surface tension, vapor pressure and hydrostatic forces. A turbulence model is used to estimate the effective values of viscosity and thermal conductivity to account for the enhanced heat and mass transport in the turbulent weld pool due to the fluctuating components of velocities in both LBW and EBW. The proposed model for LBW has been tested for materials with wide ranging thermo-physical properties under varying input powers and welding speeds covering both partial and full penetration welds. The tested materials include Al 5754 alloy, A131 steel, 304L stainless steel, Ti-6Al-4V, tantalum, and vanadium. These materials vary significantly in their thermo-physical properties, including boiling point, thermal conductivity, and specific heat. The EBW model was tested for 21Cr-6Ni-9Mn steel, 304L stainless steel, and Ti-6Al-4V for different input powers and power density distributions. To improve the agreement between the calculated and experimental results, a methodology is presented to estimate the values of uncertain input parameters like absorption coefficient and beam radius using a genetic algorithm with the numerical model and limited amount of experimental data. Finally, a genetic algorithm is used with the numerical model to prescribe welding conditions that would result in a desired weld attribute. The computed weld cross-sectional geometries and thermal cycles agreed reasonably well with the experimental observations. The weld pool shapes depended on the convective heat transport within the weld pool. Convective heat transfer was more important for materials with low thermal diffusivity. The calculated solidification parameters showed that criterion for plane front stability was not satisfied for the alloys and the range of welding conditions considered in this work. Higher peak temperatures were found in the EBW of Ti-6Al-4V welds compared to similar locations in 21Cr-6Ni-9Mn stainless steel welds due to the higher boiling point and lower solid state thermal conductivity of the former. Non-dimensional analysis showed that convective heat transfer was very significant and Lorentz force was small compared to Marangoni force. Comparison of calculated weld geometries for electron beam and laser beam welds for similar process parameters showed that lower keyhole wall temperatures in EBW tend to make the welds deeper and narrower compared to laser beam welds. A genetic algorithm was used to optimize the values of absorption coefficient and beam radius based on limited volume of experimental data for 5182 Al-Mg alloy welds. The weld geometry calculated using the optimized values of absorption coefficient and beam radius was in good agreement with experimental observations. The optimized values of absorption coefficient and beam radius were then used to prescribe sets of welding conditions to obtain specified weld geometry. These sets of welding conditions differed significantly but resulted in the same weld geometry. The results show that a widely applicable and computationally efficient 3D model of heat transfer and fluid flow can be developed by combining an energy balance based keyhole calculation sub model with a 3D convective heat transfer model. The modeling results can improve the understanding of the keyhole mode welding process. The results also show that by combining numerical models with an optimizing algorithm, the model results can be made more reliable. Finally, systematic tailoring of weld attributes v

  2. SUMMER BAT ACTIVITY AT WOODLAND SEASONAL POOLS IN THE NORTHERN GREAT LAKES REGION

    Microsoft Academic Search

    Karen E. Francl

    2008-01-01

    Woodland seasonal pools in the northern Great Lakes region, limited in this study to northern Wisconsin and Michigan's Upper Peninsula, are potentially important sites for bat feeding and drinking. In order to determine the influence of pool size, hydroperiod, and structural complexity on relative bat activity, I surveyed pools (17 in 2004, eight in 2005 and 2006) at approximately two-week

  3. Item Pool Design for an Operational Variable-Length Computerized Adaptive Test

    ERIC Educational Resources Information Center

    He, Wei; Reckase, Mark D.

    2014-01-01

    For computerized adaptive tests (CATs) to work well, they must have an item pool with sufficient numbers of good quality items. Many researchers have pointed out that, in developing item pools for CATs, not only is the item pool size important but also the distribution of item parameters and practical considerations such as content distribution…

  4. Stochastic modelling of plasma reflection during keyhole arc welding

    NASA Astrophysics Data System (ADS)

    Zhang, Y. M.; Ma, Y.

    2001-11-01

    Keyhole arc welding (KAW), including the keyhole double-sided arc welding process being developed at the University of Kentucky and keyhole plasma arc welding, can achieve much deeper narrower penetration than all other arc welding processes. If it could be controlled such that the heat input and weld pool are minimized while at the same time the desired full penetration is guaranteed, it could become an effective yet affordable technology to improve productivity in welding thick materials. However, the key in developing such a controlled KAW technology is the sensor which can detect the evolution of the keyhole. Preliminary study shows that the plasma reflection could lead to a practical yet accurate sensor. In this study, the dynamic behaviour of the plasma reflection is described using the reflection arc angle (RAA). It is found that the RAA series can be considered an autoregressive moving-average (ARMA) process. The orders of the ARMA model are determined using auto-correlation and partial auto-correlation functions. The parameters of the ARMA are recursively estimated using the extended least squares algorithm. It is found that the recursive estimates of the model parameters change as the state of the keyhole changes. A discriminator has been proposed to determine the state of the keyhole based on the recursive estimates of the model parameters.

  5. Evaluation of various solar-cell-to-interconnector welds by means of scanning laser acoustic microscopy and metallography

    Microsoft Academic Search

    B. D. Dunn; W. R. Burke

    1982-01-01

    The quality of electrical resistance welds uniting spacecraft solar array components, such as solar cells, interconnectors, shunt diodes and bus bars cannot be assessed by visual inspection. A variety of welded samples, some joined in typical spacecraft configurations and following environmental testing, were examined by nondestructive testing and metallography. The size of the welds was determined and their position located

  6. Low cycle fatigue behavior of electron beam and friction welded joints of an α-β titanium alloy

    Microsoft Academic Search

    T. Mohandas; V. K. Varma; D. Banerjee; V. V. Kutumbarao

    1996-01-01

    Fusion welds in titanium alloys, with intermediate β stabilizing additions, show poor mechanical properties due to large fusion zone grain size coupled with a brittle plate martensitic microstructure and hydrogen induced microporosity. These problems, associated with fusion welding, have been reported to be overcome by friction welding. The alloy used in this study is a Soviet composition (VT9) of the

  7. 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.

  8. Design and fabrication of reactor components: welding

    Microsoft Academic Search

    Vannan

    1973-01-01

    Common problems that are encountered during the welding of reactor ; components and the measures to be taken to tackle these problems are examined. ; Consumable insert welding, weld edge preparation, preheat, interpass temperature ; control, weld distortion, post weld heat treatment, distortion control, electrode ; storage, non-destructive testing requirements, socket welding, and welding of ; stainless steel types AISI

  9. Vocational Preparation Curriculum: Welding.

    ERIC Educational Resources Information Center

    Usoro, Hogan

    Designed to be a workable guide for instructors serving the occupational needs of various categories of disadvantaged and handicapped students, this welding curriculum contains fourteen units of self-paced and self-contained instructional materials. The instructional units cover the following topics: job opportunities in welding, safety rules in…

  10. Sorting Titanium Welding Rods

    NASA Technical Reports Server (NTRS)

    Ross, W. D., Jr.; Brown, R. L.

    1985-01-01

    Three types of titanium welding wires identified by their resistance to current flow. Welding-wire tester quickly identifies unknown titaniumalloy wire by touching wire with test probe, and comparing meter response with standard response. Before touching wire, tip of test probe dipped into an electrolyte.

  11. Weld-Fill Program

    NASA Technical Reports Server (NTRS)

    Maslakowski, John E.

    1994-01-01

    ROCKFILL is software that calculates key robot weld information. Its easy-to-use menu system enables robot operator to estimate better number of passes, amount of wire, arc time, and amount of heat put into particular weld. Designed to operate on work-cell personal computer of robot and requires no documentation or training. Written in C language.

  12. Robotic friction stir welding

    Microsoft Academic Search

    George E. Cook; Reginald Crawford; Denis E. Clark; Alvin M. Strauss

    2004-01-01

    The forces and torques associated with friction stir welding (FSW) are discussed as they relate to implementation of the welding process with industrial robots. Experimental results are presented that support the conclusions drawn from models developed by others. It is shown that even with heavy-duty industrial robots with high stiffness, force feedback is important for successful robotic FSW. Methods of

  13. Method for welding beryllium

    DOEpatents

    Dixon, R.D.; Smith, F.M.; O`Leary, R.F.

    1997-04-01

    A method is provided for joining beryllium pieces which comprises: depositing aluminum alloy on at least one beryllium surface; contacting that beryllium surface with at least one other beryllium surface; and welding the aluminum alloy coated beryllium surfaces together. The aluminum alloy may be deposited on the beryllium using gas metal arc welding. The aluminum alloy coated beryllium surfaces may be subjected to elevated temperatures and pressures to reduce porosity before welding the pieces together. The aluminum alloy coated beryllium surfaces may be machined into a desired welding joint configuration before welding. The beryllium may be an alloy of beryllium or a beryllium compound. The aluminum alloy may comprise aluminum and silicon. 9 figs.

  14. EFFECT OF MINOR ADDITIONS OF HYDROGEN TO ARGON SHIELDING GAS WHEN WELDING AUSTENITIC STAINLESS STEEL WITH THE GTAW PROCESS

    SciTech Connect

    CANNELL, G.R.

    2004-12-15

    This paper provides the technical basis to conclude that the use of hydrogen containing shielding gases during welding of austenitic stainless steels will not lead to hydrogen induced cracking (HIC) of the weld or weld heat affected zone. Argon-hydrogen gas mixtures, with hydrogen additions up to 35% [1], have been successfully used as the shielding gas in gas tungsten arc welding (GTAW) of austenitic stainless steels. The addition of hydrogen improves weld pool wettability, bead shape control, surface cleanliness and heat input. The GTAW process is used extensively for welding various grades of stainless steel and is preferred when a very high weld quality is desired, such as that required for closure welding of nuclear materials packages. The use of argon-hydrogen gas mixtures for high-quality welding is occasionally questioned, primarily because of concern over the potential for HIC. This paper was written specifically to provide a technical basis for using an argon-hydrogen shielding gas in conjunction with the development, at the Savannah River Technology Center (SRTC), of an ''optimized'' closure welding process for the DOE standardized spent nuclear fuel canister [2]. However, the basis developed here can be applied to other applications in which the use of an argon-hydrogen shielding gas for GTAW welding of austenitic stainless steels is desired.

  15. The effects of hydrogen on the fracture toughness properties of upset welded stainless steel

    SciTech Connect

    Morgan, M.T.

    1995-06-01

    The effects of hydrogen on the fracture toughness properties of upset welded Type 304L stainless steel were measured and compared to those measured previously for as-received and as-welded steels. The results showed that the upset welded steels had good fracture toughness properties, but values were lower than the as-received material. The fracture toughness value of the base material was 6420 in-lbs/sq. in., while the welded steels averaged 3660 in-lbs/sq. in. Hydrogen exposure lowered the fracture toughness values of the as-received steel by 43 % to 3670 in-lbs/sq. in. and the welded steels by 21 % to 2890 in-lbs/sq. in. The fracture morphologies of the unexposed steels showed that ductile fracture occurred by the microvoid nucleation and growth process. The size of the microvoids on the fracture surfaces of the welded steels were much smaller and more closely spaced that those found on the base material fracture surfaces. The change in the size and spacing of the microvoids indicates that the fracture toughness properties of the welded steels were lower than the base steels because of the higher concentration of microscopic precipitates on the weld plane. The welds examined thus far have been {open_quotes}good{close_quotes} welds and the presence of these precipitates was not apparent in standard {open_quotes}low{close_quotes}-magnification metallographic sections of the weld planes. The results indicate that hydrogen did not weaken greatly the solid-state welds but that other inclusions or impurities present prior to welding did. Improvements in surface cleaning and preparation prior to welding should be explored as a way to improve the strength of solid-state welded joints.

  16. Residual stresses in welded structures

    Microsoft Academic Search

    R. H. Leggatt

    2008-01-01

    The nature of residual stresses in welded structures is discussed in terms of their magnitude, directionality, spatial distribution, range and variability. The effects of the following factors on the residual stresses are considered: material properties, material manufacture, structural geometry, fabrication procedure, welding procedure, post-weld treatments and service conditions.Examples are given of residual stress distributions in plate butt welds, circumferential butt

  17. Comparison Between Keyhole Weld Model and Laser Welding Experiments

    Microsoft Academic Search

    B C Wood; T A Palmer; J W Elmer

    2002-01-01

    A series of laser welds were performed using a high-power diode-pumped continuous-wave Nd:YAG laser welder. In a previous study, the experimental results of those welds were examined, and the effects that changes in incident power and various welding parameters had on weld geometry were investigated. In this report, the fusion zones of the laser welds are compared with those predicted

  18. Slag-metal reactions during welding: Part III. Verification of the Theory

    NASA Astrophysics Data System (ADS)

    Mitra, U.; Eagar, T. W.

    1991-02-01

    A previously developed kinetic model of alloy transfer (Part II)[1] is tested experimentally for transfer of Mn, Si, Cr, P, S, Ni, Cu, and Mo. The results show very good agreement between theory and experiment. The transfer of carbon and oxygen is also discussed. It is shown that the transfer of oxygen into the weld metal occurs in the zone of droplet reactions, whereas oxygen is lost by formation and separation of inclusions in the solidifying weld pool. Methods of applying this analysis to multipass welds and active fluxes containing ferroalloy additions are also described.

  19. Mechanical Properties, Microstructure and Crystallographic Texture of Magnesium AZ91-D Alloy Welded by Friction Stir Welding (FSW)

    NASA Astrophysics Data System (ADS)

    Kouadri-Henni, A.; Barrallier, L.

    2014-10-01

    The objective of the study was to characterize the properties of a magnesium alloy welded by friction stir welding. The results led to a better understanding of the relationship between this process and the microstructure and anisotropic properties of alloy materials. Welding principally leads to a large reduction in grain size in welded zones due to the phenomenon of dynamic recrystallization. The most remarkable observation was that crystallographic textures appeared from a base metal without texture in two zones: the thermo-mechanically affected and stir-welded zones. The latter zone has the peculiarity of possessing a marked texture with two components on the basal plane and the pyramidal plane. These characteristics disappeared in the thermo-mechanically affected zone (TMAZ), which had only one component following the basal plane. These modifications have been explained by the nature of the plastic deformation in these zones, which occurs at a moderate temperature in the TMAZ and high temperature in the SWZ.

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

    NASA Astrophysics Data System (ADS)

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

    2005-02-01

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

  1. Effects of habitat isolation on the recovery of fish assemblages in experimentally defaunated stream pools in Arkansas

    Microsoft Academic Search

    David George Lonzarich; Mary Ruth Elger Lonzarich

    1998-01-01

    We removed fish from pools in two Arkansas streams to determine recolonization rates and the effects of isolation (i.e., riffle length, riffle depth, distance to large source pools, and location), pool area, and assemblage size on recovery. To determine pool-specific recovery rates, we repeatedly snorkeled 12 pools over a 40-day recovery period. Results indicated the effects of isolation on percent

  2. Robotic weld overlay coatings for erosion control

    NASA Astrophysics Data System (ADS)

    Levin, B. F.; Dupont, J. N.; Marder, A. R.

    1994-01-01

    Research is being conducted to develop criteria for selecting weld overlay coatings for erosion mitigation in circulated fluidized beds. Twelve weld overlay alloys were deposited on 1018 steel substrates using plasma arc welding. Ten samples from each coating were prepared for erosion testing. All selected coatings were erosion tested at 400C and their erosion resistance and microstructure evaluated. Steady state erosion rates were similar for several weld overlay coatings (Ultimet, Inconel-625, Iron-Aluminide, 316L SS, and High Chromium Cast Iron) and were considerably lower than the remaining coating evaluated. These coatings had different base (Co, Fe, Ni-base). No correlations were found between room temperature microhardness of the weld overlay coatings and their erosion resistance at elevated temperature, although this criteria is often thought to be an indicator of erosion resistance. It was suggested that the coatings that showed similar erosion rates may have similar mechanical properties such as fracture strength, toughness and work hardening rates at this temperature. During the past quarter, Iron-Aluminide, Inconel-625, and 316L SS coatings were selected for more detailed investigations based upon the preliminary erosion test results. Microhardness tests were performed on eroded samples to determine the size of the work hardened zone and change in coatings hardness due to erosion. The work hardened zone was correlated with erosion resistance of the coatings. Additional Iron-Aluminide, Inconel-625, and 316L SS coatings were deposited on 1018 steel substrates.

  3. Aircraft observations of cold pools under marine stratocumulus

    NASA Astrophysics Data System (ADS)

    Terai, C. R.; Wood, R.

    2013-04-01

    Although typically associated with precipitating cumuli, cold pools also form under shallower stratocumulus. The NSF/NCAR C-130 made cloud and boundary layer measurements over the southeast Pacific stratocumulus region at an altitude of approximately 150 m during the VOCALS Regional Experiment. Ninety edges of cold pools are found in the C-130 measurements by identifying step-like decreases in the potential temperature. Examination of their mesoscale environment shows that the observed cold pools tend to form under heavier precipitation, thicker clouds, and in cleaner environments. Cold pools are also found to form under clouds with high LWP values over the night of or before sampling. When they form, cold pools often form in clusters or on top of each other, rather than as separate, individual entities. Their sizes range from 2 km to 16 km (middle 50th percentile), where the largest of cold pools are associated with the greatest drops in temperature. Composites of various observed thermodynamic and chemical variables along the cold pool edges indicate increased humidity, equivalent potential temperature, coarse-mode aerosol, and dimethyl sulfide concentration inside cold pools. The enhancements inside cold pools are consistent with increased static stability that traps fluxes from the ocean surface in the lowest levels of the boundary layer. By using pressure perturbations, the average cold pool is estimated to be approximately 300 m deep. The temperature depression in cold pools leads to density-driven flows that drive convergence of horizontal winds and measurable, mechanically-driven vertical wind velocity at the edges of cold pools.

  4. Capabilities of infrared weld monitor

    SciTech Connect

    Sanders, P.G.; Keske, J.S.; Leong, K.H.; Kornecki, G.

    1997-11-01

    A non-obtrusive pre-aligned, solid-state device has been developed to monitor the primary infrared emissions during laser welding. The weld monitor output is a 100-1000 mV signal that depends on the beam power and weld characteristics. The DC level of this signal is related to weld penetration, while AC portions of the output can be correlated with surface irregularities and part misalignment or contamination. Changes in DC behavior are also noted for both full and deep penetration welds. Full penetration welds are signified by an abrupt reduction in the weld monitor output. Bead on plate welds were made on steel, aluminum, and magnesium with both a CW CO{sub 2} laser and a pulsed Nd:YAG laser to explore the relationships between the weld characteristics and the weld monitor output.

  5. A three-pool model dissecting readily releasable pool replenishment at the calyx of held.

    PubMed

    Guo, Jun; Ge, Jian-long; Hao, Mei; Sun, Zhi-cheng; Wu, Xin-sheng; Zhu, Jian-bing; Wang, Wei; Yao, Pan-tong; Lin, Wei; Xue, Lei

    2015-01-01

    Although vesicle replenishment is critical in maintaining exo-endocytosis recycling, the underlying mechanisms are not well understood. Previous studies have shown that both rapid and slow endocytosis recycle into a very large recycling pool instead of within the readily releasable pool (RRP), and the time course of RRP replenishment is slowed down by more intense stimulation. This finding contradicts the calcium/calmodulin-dependence of RRP replenishment. Here we address this issue and report a three-pool model for RRP replenishment at a central synapse. Both rapid and slow endocytosis provide vesicles to a large reserve pool (RP) ~42.3 times the RRP size. When moving from the RP to the RRP, vesicles entered an intermediate pool (IP) ~2.7 times the RRP size with slow RP-IP kinetics and fast IP-RRP kinetics, which was responsible for the well-established slow and rapid components of RRP replenishment. Depletion of the IP caused the slower RRP replenishment observed after intense stimulation. These results establish, for the first time, a realistic cycling model with all parameters measured, revealing the contribution of each cycling step in synaptic transmission. The results call for modification of the current view of the vesicle recycling steps and their roles. PMID:25825223

  6. Contribution to arc plasma modeling for welding TIG application

    NASA Astrophysics Data System (ADS)

    Borel, Damien; Delalondre, Clarisse; Carpreau, Jean-Michel; Chéron, B. G.; Boubert, J.-P.

    2014-06-01

    In this paper we present a numerical model that simulates transferred energy by a welding thermal plasma to the weld pool. This energy transfer allows materials melting. The originality of our model is to include the modeling of transition zones and the vaporization of the anode. The cathodic and anodic areas are taken into account in the model by means of heat balance at the gas-solid interfaces. We report the heating and cooling effects they induce on the solid (cathode, anode) and plasma. Code_Saturne® the CFD software developed at EDF R&D is used for this work Comparisons between simulations and measurements of temperature and electron density confirm the model assumptions for TIG welding.

  7. Cellular neural networks for welding arc thermograms segmentation

    NASA Astrophysics Data System (ADS)

    Jamrozik, Wojciech

    2014-09-01

    Machine vision systems are used in many areas for monitoring of technological processes. Among this processes welding takes important place, where often infrared cameras are used. Besides reliable hardware, successful application of vision systems requires suitable software based on proper algorithms. One of most important group of image processing algorithms is connected to image segmentation. Obtainment of exact boundary of an object that changes shape in time, such as the welding arc, represented on a thermogram is not a trivial task. In the paper a segmentation method using supervised approach based on a cellular neural networks is presented. Simulated annealing and genetic algorithm were used for training of the network (template optimization). Comparison of proposed method to a well elaborated segmentation method based on region growing approach was made. Obtained results prove that the cellular neural network can be a valuable tool for infrared welding pool images segmentation.

  8. Laser Vascular Welding

    NASA Astrophysics Data System (ADS)

    White, Rodney A.; Kopchok, George; White, Geoffrey H.

    1988-06-01

    Vascular tissue fusion by lasers is performed by directing a low energy beam at the apposed edges of the repair. The tissues are approximated with stay sutures or non-reflective instruments and laser energy is passed back-and-forth over the anastomotic site until fusion is achieved. Vessel welding is apparent to the trained eye, as is nonunion caused by inadequate energy delivery. Conversely, excessive energy delivery results in obvious tissue coagulation or vaporization. Fiberoptic laser transmission and hand-eye coordination are adequate for repair or anastomosis of vessels with diameters greater than 3 mm, whereas magnification and precise mechanical control of the laser beam are necessary for microanastomoses of smaller vessels. The laser power (watts, W), and the amount of energy and time required (energy fluence or power density) vary according to the type of laser and the size of the vessels. Although laser repairs can be fashioned in time intervals equal to or slightly longer than those required for suture repairs, the optimum wavelengths and laser parameters for different types of seals are not yet established.

  9. Pool octanes via oxygenates

    SciTech Connect

    Prezelj, M.

    1987-09-01

    Increasingly stringent antipollution regulations placed on automobile exhaust gases with consequent reduction or complete lead ban from motor gasoline result in octane shortage at many manufacturing sites. Attractive solutions to this problem, especially in conjunction with abundant methanol supplies, are the hydration and etherification of olefins contained in light product streams from cracking unit or produced by field gas dehydrogenation. A comparison is made between oxygenates octane-volume pool contributions and established refinery technologies. Process reviews for bulk manufacture of fuel-grade isopropanol (IPA), secondary butanol (SBA), tertiary butanol (TBA), methyl tertiary butyl ether (MTBE) and tertiary amyl methyl ether (TAME) are presented together with the characteristic investment and operating data. The implantation of these processes into a typical FCCU refinery complex with the resulting octane-pool improvement possibilities is descried.

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

    PubMed Central

    Pesch, Beate

    2012-01-01

    This investigation aims to explore determinants of exposure to particle size-specific welding fume. Area sampling of ultrafine particles (UFP) was performed at 33 worksites in parallel with the collection of respirable particles. Personal sampling of respirable and inhalable particles was carried out in the breathing zone of 241 welders. Median mass concentrations were 2.48 mg m?3 for inhalable and 1.29 mg m?3 for respirable particles when excluding 26 users of powered air-purifying respirators (PAPRs). Mass concentrations were highest when flux-cored arc welding (FCAW) with gas was applied (median of inhalable particles: 11.6 mg m?3). Measurements of particles were frequently below the limit of detection (LOD), especially inside PAPRs or during tungsten inert gas welding (TIG). However, TIG generated a high number of small particles, including UFP. We imputed measurements welding fume. Concentrations were mainly predicted by the welding process and were significantly higher when local exhaust ventilation (LEV) was inefficient or when welding was performed in confined spaces. Substitution of high-emission techniques like FCAW, efficient LEV, and using PAPRs where applicable can reduce exposure to welding fume. However, harmonizing the different exposure metrics for UFP (as particle counts) and for the respirable or inhalable fraction of the welding fume (expressed as their mass) remains challenging. PMID:22539559

  11. Allergic to Pool Water

    PubMed Central

    2012-01-01

    To identify the allergy problem of a 36-year old swimming instructor, who experiences heavy itching and rashes whenever she comes in contact with pool water. Patch tests were performed with European standard series and materials from the work floor. A positive patch test to aluminum chloride and flocculant was observed. Occupational dermatitis is, based on a contact allergy to aluminum chloride in the flocculant. PMID:22993713

  12. Calibration Fixture For Welding Robot

    NASA Technical Reports Server (NTRS)

    Holly, Krisztina J.

    1990-01-01

    Compact, lightweight device used in any position or orientation. Calibration fixture designed for use on robotic gas/tungsten-arc welding torch equipped with vision-based seam-tracking system. Through optics in hollow torch cylinder, video camera obtains image of weld, viewing along line of sight coaxial with welding electrode. Attaches to welding-torch cylinder in place of gas cup normally attached in use. By use of longer or shorter extension tube, fixture accommodates welding electrode of unusual length.

  13. Weld analysis and control system

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  14. Microstructure of Laser-MAG Hybrid Welds of Sintered P/M Steel

    NASA Astrophysics Data System (ADS)

    Liu, Shuangyu; Zhang, Hong; Hu, Jiandong; Shi, Yan

    2013-01-01

    The microstructure and mechanical properties of iron-based powder metallurgical steels jointed by CO2 laser-metal active gas (MAG) hybrid welding were investigated. The cross-sectional morphology of hybrid weld bead consisted of arc zone and laser zone. The microstructure of arc zone consisted of columnar dendrite and fine acicular dendrite between the columnar dendrites, but that of laser zone was composed of fine equiaxed dendrite. The MAG weld had obvious heat-affected zone (HAZ) zone, while hybrid weld had very narrow HAZ zone because of the rapid cooling rate. The phase constitutions of the joint determined by x-ray diffraction were ?-Fe (ferrite) and Cu. The 2? value of ?-Fe (200) peaks of hybrid weld was smaller than that of sintering compact. Compared to MAG weld, hybrid weld had finer grain size, higher micro-hardness, and higher micro-strain, which was caused by the difference of cooling rate and crystallizing.

  15. New England salt marsh pools: A quantitative analysis of geomorphic and geographic features

    USGS Publications Warehouse

    Adamowicz, S.C.; Roman, C.T.

    2005-01-01

    New England salt marsh pools provide important wildlife habitat and are the object of on-going salt marsh restoration projects; however, they have not been quantified in terms of their basic geomorphic and geographic traits. An examination of 32 ditched and unditched salt marshes from the Connecticut shore of Long Island Sound to southern Maine, USA, revealed that pools from ditched and unditched marshes had similar average sizes of about 200 m2, averaged 29 cm in depth, and were located about 11 m from the nearest tidal flow. Unditched marshes had 3 times the density (13 pools/ha), 2.5 times the pool coverage (83 m pool/km transect), and 4 times the total pool surface area per hectare (913 m2 pool/ha salt marsh) of ditched sites. Linear regression analysis demonstrated that an increasing density of ditches (m ditch/ha salt marsh) was negatively correlated with pool density and total pool surface area per hectare. Creek density was positively correlated with these variables. Thus, it was not the mere presence of drainage channels that were associated with low numbers of pools, but their type (ditch versus creek) and abundance. Tidal range was not correlated with pool density or total pool surface area, while marsh latitude had only a weak relationship to total pool surface area per hectare. Pools should be incorporated into salt marsh restoration planning, and the parameters quantified here may be used as initial design targets.

  16. Eddy current inspection of weld defects in tubing

    NASA Technical Reports Server (NTRS)

    Katragadda, G.; Lord, W.

    1992-01-01

    An approach using differential probes for the inspection of weld defects in tubing is studied. Finite element analysis is used to model the weld regions and defects. Impedance plane signals are predicted for different weld defect types and compared wherever possible with signals from actual welds in tubing. Results show that detection and sizing of defects in tubing is possible using differential eddy current techniques. The phase angle of the impedance plane trajectory gives a good indication of the sizing of the crack. Data on the type of defect can be obtained from the shape of the impedance plane trajectory and the phase. Depending on the skin depth, detection of outer wall, inner wall, and subsurface defects is possible.

  17. Thermal stir welding process

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor)

    2012-01-01

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

  18. Thermal stir welding apparatus

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor)

    2011-01-01

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

  19. Fiber Laser Welded AZ31 Magnesium Alloy: The Effect of Welding Speed on Microstructure and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Chowdhury, S. H.; Chen, D. L.; Bhole, S. D.; Powidajko, E.; Weckman, D. C.; Zhou, Y.

    2012-06-01

    This study was aimed at characterizing microstructural change and evaluating tensile and fatigue properties of fiber laser welded AZ31B-H24 Mg alloy with special attention to the effect of welding speed. Laser welding led to the formation of equiaxed dendrites in the fusion zone and columnar dendrites near the fusion zone boundary along with divorced eutectic Mg17Al12 particles and recrystallized grains in the heat-affected zone. The lowest hardness across the weld appeared in the fusion zone. Although the yield strength, ductility, and fatigue life decreased, the hardening capacity increased after laser welding, with a joint efficiency reaching about 90 pct. A higher welding speed resulted in a narrower fusion zone, smaller grain size, higher yield strength, and longer fatigue life, as well as a slightly lower strain-hardening capacity mainly because of the smaller grain sizes. Tensile fracture occurred in the fusion zone, whereas fatigue failure appeared essentially in between the heat-affected zone and the fusion zone. Fatigue cracks initiated from the near-surface welding defects and propagated by the formation of fatigue striations together with secondary cracks.

  20. Remaining life assessment of welded pipes containing cracks

    Microsoft Academic Search

    Robert Peace; Heloísa Cunha Furtado; Iain Le May

    2006-01-01

    The presence of flaws, their size and location in the welded region affects the safe service life of pressure pipes operating at elevated temperature. A remaining life assessment was required to determine the probable remaining safe life of pressure pipes in a high-temperature steam distribution system in which crack-like defects had been identified in many welds. The crack-like defects indicated

  1. Specs add confidence in use of wet welding. [Underwater welding

    SciTech Connect

    Not Available

    1984-02-01

    Underwater wet welding can now be utilized with the same confidence as dry welding, provided certain guidelines are followed. A new electrode is discussed that has been delivering exceptionally high quality welds by a diving firm in Houston. With the issuance of the American Welding Society's specifications (ANS/LAWS D3.6-83) much of the confusion surrounding underwater welding should be eliminated. The new specifications establish the levels of quality for underwater welding and gives everyone in the business a common language.

  2. A simplified model of decontamination by BWR steam suppression pools

    SciTech Connect

    Powers, D.A.

    1997-05-01

    Phenomena that can decontaminate aerosol-laden gases sparging through steam suppression pools of boiling water reactors during reactor accidents are described. Uncertainties in aerosol properties, aerosol behavior within gas bubbles, and bubble behavior in plumes affect predictions of decontamination by steam suppression pools. Uncertainties in the boundary and initial conditions that are dictated by the progression of severe reactor accidents and that will affect predictions of decontamination by steam suppression pools are discussed. Ten parameters that characterize boundary and initial condition uncertainties, nine parameters that characterize aerosol property and behavior uncertainties, and eleven parameters that characterize uncertainties in the behavior of bubbles in steam suppression pools are identified. Ranges for the values of these parameters and subjective probability distributions for parametric values within the ranges are defined. These uncertain parameters are used in Monte Carlo uncertainty analyses to develop uncertainty distributions for the decontamination that can be achieved by steam suppression pools and the size distribution of aerosols that do emerge from such pools. A simplified model of decontamination by steam suppression pools is developed by correlating features of the uncertainty distributions for total decontamination factor, DF(total), mean size of emerging aerosol particles, d{sub p}, and the standard deviation of the emerging aerosol size distribution, {sigma}, with pool depth, H. Correlations of the median values of the uncertainty distributions are suggested as the best estimate of decontamination by suppression pools. Correlations of the 10 percentile and 90 percentile values of the uncertainty distributions characterize the uncertainty in the best estimates. 295 refs., 121 figs., 113 tabs.

  3. Underwater wet welding of steel

    SciTech Connect

    Ibarra, S. [Amoco Corporation Research, Naperville, IL (United States); Liu, S.; Olson, D.L. [Colorado School of Mines, Golden, CO (United States)

    1995-05-01

    Underwater wet welding is conducted directly in water with the shielded metal arc (SMA) and flux cored arc (FCA) welding processes. Underwater wet welding has been demonstrated as an acceptable repair technique down to 100 meters (325 ft.) in depth, but wet welds have been attempted on carbon steel structures down to 200 meters (650 ft.). The primary purpose of this interpretive report is to document and evaluate current understanding of metallurgical behavior of underwater wet welds so that new welding consumables can be designed and new welding practices can be developed for fabrication and repair of high strength steel structures at greater depths. First the pyrometallurgical and physical metallurgy behaviors of underwater weldments are discussed. Second, modifications of the welding consumables and processes are suggested to enhance the ability to apply wet welding techniques.

  4. Evaluation of Superplastic Forming and Weld-brazing for Fabrication of Titanium Compression Panels

    NASA Technical Reports Server (NTRS)

    Royster, D. M.; Bales, T. T.; Davis, R. C.

    1985-01-01

    The two titanium processing procedures, superplastic forming and weld brazing, are successfully combined to fabricate titanium skin stiffened structural panels. Stiffeners with complex shapes are superplastically formed using simple tooling. These stiffeners are formed to the desired configuration and required no additional sizing or shaping following removal from the mold. The weld brazing process by which the stiffeners are attached to the skins utilize spot welds to maintain alignment and no additional tooling is required for brazing. The superplastic formed/weld brazed panels having complex shaped stiffeners develop up to 60 percent higher buckling strengths than panels with conventional shaped stiffeners. The superplastic forming/weld brazing process is successfully scaled up to fabricate full size panels having multiple stiffeners. The superplastic forming/weld brazing process is also successfully refined to show its potential for fabricating multiple stiffener compression panels employing unique stiffener configurations for improved structural efficiency.

  5. Friction stir welding tool

    DOEpatents

    Tolle, Charles R. (Idaho Falls, ID); Clark, Denis E. (Idaho Falls, ID); Barnes, Timothy A. (Ammon, ID)

    2008-04-15

    A friction stir welding tool is described and which includes a shank portion; a shoulder portion which is releasably engageable with the shank portion; and a pin which is releasably engageable with the shoulder portion.

  6. Investigation of electromagnetic welding

    E-print Network

    Pressl, Daniel G. (Daniel Gerd)

    2009-01-01

    We propose several methodologies to study and optimize the electromagnetic process for Electromagnetic Forming (EMF) and Welding (EMW), thereby lowering the necessary process energy up to a factor of three and lengthening ...

  7. Welding Qualification Sharing

    SciTech Connect

    Newton, Bruce [Welding Services, Inc., 2225 Skyland Court, Norcross, GA 30071 (United States)

    2002-07-01

    ASME Section IX, 'Welding Qualifications', requires that each organization qualify its own welders and welding procedures. Qualification responsibility cannot be subcontracted, and qualifications administered by one organization cannot be transferred to another organization. This requirement has become the subject of close scrutiny as the demand for efficiency, particularly among nuclear plant owners, has increased. Two recent Code Cases change procedure and performance qualification requirements for the better. The first, N-573, enables nuclear plant owners to share welding procedure qualifications. The second, N-600, enables nuclear plant owners to share welder performance qualifications. Several owners have reduced costs using N-573. N-600, because it is relatively new, has not yet been implemented. Its potential for cost savings, though, is equivalent to that afforded by N-573. This paper discusses ASME Section IX's procedure and performance qualification philosophy, assesses that philosophy in light of today's welding environment, and discusses implementation of Code Cases N-573 and N-600. (authors)

  8. Controls on Filling and Evacuation of Sediment in Waterfall Plunge Pools

    NASA Astrophysics Data System (ADS)

    Scheingross, J. S.; Lamb, M. P.

    2014-12-01

    Many waterfalls are characterized by the presence of deep plunge pools that experience periods of sediment fill and evacuation. These cycles of sediment fill are a first order control on the relative magnitude of lateral versus vertical erosion at the base of waterfalls, as vertical incision requires cover-free plunge pools to expose the bedrock floor, while lateral erosion can occur when pools are partially filled and plunge-pool walls are exposed. Currently, there exists no mechanistic model describing sediment transport through waterfall plunge pools, limiting our ability to predict waterfall retreat. To address this knowledge gap, we performed detailed laboratory experiments measuring plunge-pool sediment transport capacity (Qsc_pool) under varying waterfall and plunge-pool geometries, flow hydraulics, and sediment size. Our experimental plunge-pool sediment transport capacity measurements match well with a mechanistic model we developed which combines existing waterfall jet theory with a modified Rouse profile to predict sediment transport capacity as a function of water discharge and suspended sediment concentration at the plunge-pool lip. Comparing the transport capacity of plunge pools to lower gradient portions of rivers (Qsc_river) shows that, for transport limited conditions, plunge pools fill with sediment under modest water discharges when Qsc_river > Qsc_pool, and empty to bedrock under high discharges when Qsc_pool > Qsc_river. These results are consistent with field observations of sand-filled plunge pools with downstream boulder rims, implying filling and excavation of plunge pools over single-storm timescales. Thus, partial filling of waterfall plunge pools may provide a mechanism to promote lateral undercutting and retreat of waterfalls in homogeneous rock in which plunge-pool vertical incision occurs during brief large floods that expose bedrock, whereas lateral erosion may prevail during smaller events.

  9. Welding Plutonium Storage Containers

    Microsoft Academic Search

    2004-01-01

    The outer can welder (OCW) in the FB-Line Facility at the Savannah River Site (SRS) is a Gas Tungsten Arc Weld (GTAW) system used to create outer canisters compliant with the Department of Energy 3013 Standard, DOE-STD-3013-2000, Stabilization, Packaging, and Storage of Plutonium-Bearing Materials. The key welding parameters controlled and monitored on the outer can welder Data Acquisition System (DAS)

  10. Friction stir weld tools

    NASA Technical Reports Server (NTRS)

    Carter, Robert W. (Inventor); Payton, Lewis N. (Inventor)

    2007-01-01

    A friction stir weld tool sleeve is supported by an underlying support pin. The pin material is preferably selected for toughness and fracture characteristics. The pin sleeve preferably has a geometry which employs the use of an interrupted thread, a plurality of flutes and/or eccentric path to provide greater flow through. Paddles have been found to assist in imparting friction and directing plastic metal during the welding process.

  11. Friction Stir Weld Tools

    NASA Technical Reports Server (NTRS)

    Carter, Robert W. (Inventor); Payton, Lewis N. (Inventor)

    2007-01-01

    A friction stir weld tool sleeve is supported by an underlying support pin. The pin material is preferably selected for toughness and fracture characteristics. The pin sleeve preferably has a geometry which employs the use of an interrupted thread, a plurality of flutes and/or eccentric path to provide greater flow through. Paddles have been found to assist in imparting friction and directing plastic metal during the welding process.

  12. Weld braze technique

    DOEpatents

    Kanne, Jr., William R. (Aiken, SC); Kelker, Jr., John W. (North Augusta, SC); Alexander, Robert J. (Aiken, SC)

    1982-01-01

    High-strength metal joints are formed by a combined weld-braze technique. A hollow cylindrical metal member is forced into an undersized counterbore in another metal member with a suitable braze metal disposed along the bottom of the counterbore. Force and current applied to the members in an evacuated chamber results in the concurrent formation of the weld along the sides of the counterbore and a braze along the bottom of the counterbore in one continuous operation.

  13. Customized orbital welding meets the challenge of titanium welding

    SciTech Connect

    NONE

    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.

  14. Mitigating Abnormal Grain Growth for Friction Stir Welded Al-Li 2195 Spun Formed Domes

    NASA Technical Reports Server (NTRS)

    Chen, Po-Shou; Russell, Carolyn

    2012-01-01

    Formability and abnormal grain growth (AGG) are the two major issues that have been encountered for Al alloy spun formed dome development using friction stir welded blanks. Material properties that have significant influence on the formability include forming range and strain hardening exponent. In this study, tensile tests were performed for two 2195 friction stir weld parameter sets at 400 F to study the effects of post weld anneal on the forming range and strain hardening exponent. It was found that the formability can be enhanced by applying a newly developed post weld anneal to heat treat the friction stir welded panels. This new post weld anneal leads to a higher forming range and much improved strain hardening exponent. AGG in the weld nugget is known to cause a significant reduction of ductility and fracture toughness. This study also investigated how AGG may be influenced by the heating rate to the solution heat treatment temperature. After post-weld annealing, friction stir welds were strained to 15% and 39% by compression at 400 F before they were subjected to SHT at 950 F for 1 hour. Salt bath SHT is very effective in reducing the grain size as it helps arrest the onset of AGG and promote normal recrystallization and grain growth. However, heat treating a 18 ft dome using a salt bath is not practical. Efforts are continuing at Marshall Space Flight Center to identify the welding parameters and heat treating parameters that can help mitigate the AGG in the friction stir welds.

  15. Welding of tailored blanks of different materials

    Microsoft Academic Search

    J. Tušek; Z. Kampuš; M. Suban

    2001-01-01

    This paper treats welding of tailored blanks made of different materials. In general, fusion welding and welding with pressure, practically without fusion, are described. Fusion welding may be carried out with or without the addition of filler material. In Section 3, general characteristics of tailored blanks are described. In Section 4, MIG welding and laser welding of austenitic stainless steel

  16. [Measuring the calibration factor of a light scattering dust monitor for CO2 arc welding fumes].

    PubMed

    Ojima, Jun

    2002-12-01

    In Japan, a light scattering type digital dust monitor is most commonly used for dust concentration measurement in a working environment. In this study, the calibration factors of a digital dust monitor (K-factor) for several welding fumes were measured in a laboratory. During the experiment, fumes were generated from CO2 arc welding performed by an automatic welding robot. The examined welding wires were JIS Z 3312, Z 3313, Z 3315, Z 3317 and Z 3320. The mass and relative concentrations of the welding fumes were measured simultaneously by a total/respirable (TR) dust sampler and a digital dust monitor at a welding current of 100 A, 150 A, 200 A, 250 A and 300 A. The particle size distributions of welding fumes were measured by a low pressure impactor at a welding current of 100 A and 300 A. A significant effect of the welding current on the K-factor was recognized for all the examined wires. In the most remarkable case, a four-fold difference in the K-factors was found when the fumes were generated from a flux cored wire for mild steel (JIS Z 3313). The particle size distributions of fumes were also affected by the welding current. The coefficients of variation in the measured K-factor were 7.8-40.5%. PMID:12506861

  17. Concurrent ultrasonic weld evaluation system

    DOEpatents

    Hood, D.W.; Johnson, J.A.; Smartt, H.B.

    1985-09-04

    A system for concurrent, non-destructive evaluation of partially completed welds for use in conjunction with an automated welder. The system utilizes real time, automated ultrasonic inspection of a welding operation as the welds are being made by providing a transducer which follows a short distance behind the welding head. Reflected ultrasonic signals are analyzed utilizing computer based digital pattern recognition techniques to discriminate between good and flawed welds on a pass by pass basis. The system also distinguishes between types of weld flaws.

  18. Concurrent ultrasonic weld evaluation system

    DOEpatents

    Hood, Donald W. (Idaho Falls, ID); Johnson, John A. (Idaho Falls, ID); Smartt, Herschel B. (Idaho Falls, ID)

    1987-01-01

    A system for concurrent, non-destructive evaluation of partially completed welds for use in conjunction with an automated welder. The system utilizes real time, automated ultrasonic inspection of a welding operation as the welds are being made by providing a transducer which follows a short distance behind the welding head. Reflected ultrasonic signals are analyzed utilizing computer based digital pattern recognition techniques to discriminate between good and flawed welds on a pass by pass basis. The system also distinguishes between types of weld flaws.

  19. Automatic Welding System

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Robotic welding has been of interest to industrial firms because it offers higher productivity at lower cost than manual welding. There are some systems with automated arc guidance available, but they have disadvantages, such as limitations on types of materials or types of seams that can be welded; susceptibility to stray electrical signals; restricted field of view; or tendency to contaminate the weld seam. Wanting to overcome these disadvantages, Marshall Space Flight Center, aided by Hayes International Corporation, developed system that uses closed-circuit TV signals for automatic guidance of the welding torch. NASA granted license to Combined Technologies, Inc. for commercial application of the technology. They developed a refined and improved arc guidance system. CTI in turn, licensed the Merrick Corporation, also of Nashville, for marketing and manufacturing of the new system, called the CT2 Optical Trucker. CT2 is a non-contracting system that offers adaptability to broader range of welding jobs and provides greater reliability in high speed operation. It is extremely accurate and can travel at high speed of up to 150 inches per minute.

  20. In-situ spatially resolved x-ray diffraction mapping of the alpha to beta to alpha transformation in commercially pure titanium arc welds

    SciTech Connect

    Elmer, J. W., LLNL

    1998-05-15

    Spatially Resolved X-Ray Diffraction (SRXRD) is used to map the {alpha}{r_arrow}{beta}{r_arrow}{alpha} phase transformation in the heat affected zone (HAZ) of commercially pure titanium gas tungsten arc welds. In-situ SRXRD experiments were conducted on arc welds using a 200 pm diameter x-ray beam at Stanford Synchrotron Radiation Laboratory (SSRL). A map was created which identifies six HAZ microstructural regions that exist between the liquid weld pool and the base metal during welding. The first region is single phase {beta}-Ti that forms in a 2- to 3-mm band adjacent to the liquid weld pool. The second region is back transformed {alpha}-Ti that forms behind the portion of the HAZ where {beta}-Ti was once present at higher temperatures. The third region is completely recrystallized {alpha}-Ti that forms in a 2- to 3-mm band surrounding the single phase {beta}-Ti region. Recrystallized {alpha}-Ti was observed by itself and also with varying amounts of {beta}-Ti. The fourth region of the weld is the partially transformed zone where {alpha}-Ti and {beta}-Ti coexist during welding. The fifth region is directly behind the partially transformed zone and consists of a mixture of recrystallized and back transformed {alpha}-Ti The sixth region is farthest from the weld pool and consists of {alpha}-Ti that is undergoing annealing and recrystallization. Annealing of the base metal was observed to some degree in all of the SRXRD patterns, showing that annealing exceeded 13 mm from the centerline of the weld. Although the microstructure consisted predominantly of {alpha}-Ti, both prior to the weld and after the weld, the (002) texture of the starting material was altered during welding to produce a predominantly (101) texture within the resulting HAZ.

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

    Microsoft Academic Search

    Taewon Kim; Yasuo Suga; Takashi Koike

    2003-01-01

    TIG arc welding and laser welding are used widely in the world. However, these welding processes have some advantages and problems respectively. In order to improve problems and make use of advantages of the arc welding and the laser welding processes, hybrid welding process combined the TIG arc with the YAG laser was studied. Especially, the suitable welding conditions for

  2. The Productive Ligurian Pool

    E-print Network

    Casella, E; Couvelard, X; Caldeira, R M A

    2011-01-01

    In contrast with the behavior of the eddies in the open-ocean, the sub-mesoscale eddies generated in the constricted Ligurian Basin (NW Mediterranean), are unproductive but their combined effect, arranged in a rim-like fashion, contributes to the containment of a Productive Ligurian Pool (PLP). Data de- rived from MODIS satellite sensor showed persistent higher chlorophyll con- centrations in the centre of the basin, concurrent with high EKE values in its surroundings, derived from AVISO altimetry merged products. This sug- gested that this 'productive pool' is maintained by the intense (sub)mesoscale eddy activity in the rim. Numerical realistic experiments, using a Regional Ocean Model System, forced by MERCATOR and by a high-resolution COSMO- l7 atmospheric model, also showed that most of the sub-mesoscale eddies, during 2009 and 2010, are concentrated in the rim surrounding the basin, contributing to the formation of a basin-scale cyclonic gyre. We hypothesized that the interaction between eddies in the r...

  3. Stud arc welding in a magnetic field – Investigation of the influences on the arc motion

    NASA Astrophysics Data System (ADS)

    Hartz-Behrend, K.; Marqués, J. L.; Forster, G.; Jenicek, A.; Müller, M.; Cramer, H.; Jilg, A.; Soyer, H.; Schein, J.

    2014-11-01

    Stud arc welding is widely used in the construction industry. For welding of studs with a diameter larger than 14 mm a ceramic ferrule is usually necessary in order to protect the weld pool. Disadvantages of using such a ferrule are that more metal is molten than necessary for a high quality welded joint and that the ferrule is a consumable generally thrown away after the welding operation. Investigations show that the ferrule can be omitted when the welding is carried out in a radially symmetric magnetic field within a shielding gas atmosphere. Due to the Lorentz force the arc is laterally shifted so that a very uniform and controlled melting of the stud contact surface as well as of the work piece can be achieved. In this paper a simplified physical model is presented describing how the parameters welding current, flux density of the magnetic field, radius of the arc and mass density of the shielding gas influence the velocity of the arc motion. The resulting equation is subsequently verified by comparing it to optical measurements of the arc motion. The proposed model can be used to optimize the required field distribution for the magnetic field stud welding process.

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

    NASA Astrophysics Data System (ADS)

    Tashiro, Shinichi; Tanaka, Manabu

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

  5. Monitoring of TIG welding using laser and diode illumination sources: A comparison study

    Microsoft Academic Search

    B. M. Abdullah; J. S. Smith; W. Lucas; J. Lucas; F. Malek

    2008-01-01

    This paper presents a vision system based on the use of a CMOS camera. The vision system has demonstrated its potential for applications of weld pool monitoring. It has been demonstrated in this study that the arc light can be successfully eliminated and that a substantial amount of information can be obtained in real time e.g. metal transfer in TIG

  6. Effect of enhanced convection on the microstructure of Al-Cu-Li welds

    SciTech Connect

    Aidun, D.K.; Dean, J.P.

    1999-10-01

    The effects of enhanced convection induced by a high-gravity environment on the resulting weld microstructure of a 2195-T8 (Al-Cu-Li) alloy have been investigated. Stationary (spot) bead-on-plate gas tungsten arc welds were performed at 1, 5, and 10 g (1 g = 9.8 m/s{sup 2}) using the multigravity research welding system (MGRWS). Of particular interest was the gradual disappearance of a narrow band of fine equiaxed grains (EQ) located along the fusion boundary of the weld as g level increased. The presence of this equiaxed zone (EQZ) may affect weld mechanical properties and therefore compromise structures incorporating welds of Al-Cu-Li alloys. The qualitative verification of a proposed mechanism for equiaxed grain formation along the fusion boundary of Al-Cu-Li alloy welds by Gutierrez and Lippold is also presented. The high-g environment causing enhanced convection is believed to alter the thermal and fluid flow conditions within the weld pool, thereby creating an environment in which there is neither a stagnant boundary layer nor an unmixed zone. Furthermore, the precipitates aiding in the precipitation of the fine, equiaxed grains are believed to be swept into the weld pool at high-g and completely dissolved. As a result, the environment for equiaxed grain formation has been eliminated. The analysis of the microstructural evolution from 1 to 5 to 10 g qualitatively verifies this proposed mechanism. At 1 g, a prominent EQZ formed; at 5 g, the EQZ was scattered in location along the fusion boundary and of reduced width; at 10 g, the EQZ had completely disappeared leaving a near perfect line separating the large grains of the heat-affected zone from the fine dendrites of the fusion zone.

  7. Corium quench in deep pool mixing experiments

    SciTech Connect

    Spencer, B.W.; McUmber, L.; Gregorash, D.; Aeschlimann, R.; Sienicki, J.J.

    1985-01-01

    The results of two recent corium-water thermal interaction (CWTI) tests are described in which a stream of molten corium was poured into a deep pool of water in order to determine the mixing behavior, the corium-to-water heat transfer rates, and the characteristic sizes of the quenched debris. The corium composition was 60% UO/sub 2/, 16% ZrO/sub 2/, and 24% stainless steel by weight; its initial temperature was 3080 K, approx.160 K above the oxide phase liquidus temperature. The corium pour stream was a single-phase 2.2 cm dia liquid column which entered the water pool in film boiling at approx.4 m/s. The water subcooling was 6 and 75C in the two tests. Test results showed that with low subcooling, rapid steam generation caused the pool to boil up into a high void fraction regime. In contrast, with large subcooling no net steam generation occurred, and the pool remained relatively quiescent. Breakup of the jet appeared to occur by surface stripping. In neither test was the breakup complete during transit through the 32 cm deep water pool, and molten corium channeled to the base where it formed a melt layer. The characteristic heat transfer rates measured 3.5 MJ/s and 2.7 MJ/s during the fall stage for small and large subcooling, respectively; during the initial stage of bed quench, the surface heat fluxes measured 2.4 MW/m/sup 2/ and 3.7 MW/m/sup 2/, respectively. A small mass of particles was formed in each test, measuring typically 0.1 to 1 mm and 1 to 5 mm dia for the large and small subcooling conditions, respectively. 9 refs., 13 figs., 1 tab.

  8. Weld line detection and process control for welding automation

    NASA Astrophysics Data System (ADS)

    Yang, Sang-Min; Cho, Man-Ho; Lee, Ho-Young; Cho, Taik-Dong

    2007-03-01

    Welding has been widely used as a process to join metallic parts. But because of hazardous working conditions, workers tend to avoid this task. Techniques to achieve the automation are the recognition of joint line and process control. A CCD (charge coupled device) camera with a laser stripe was applied to enhance the automatic weld seam tracking in GMAW (gas metal arc welding). The adaptive Hough transformation having an on-line processing ability was used to extract laser stripes and to obtain specific weld points. The three-dimensional information obtained from the vision system made it possible to generate the weld torch path and to obtain information such as the width and depth of the weld line. In this study, a neural network based on the generalized delta rule algorithm was adapted to control the process of GMAW, such as welding speed, arc voltage and wire feeding speed. The width and depth of the weld joint have been selected as neurons in the input layer of the neural-network algorithm. The input variables, the width and depth of the weld joint, are determined by image information. The voltage, weld speed and wire feed rate are represented as the neurons in the output layer. The results of the neural-network learning applied to the welding are as follows: learning ratio 0.5, momentum ratio 0.7, the number of hidden layers 2 and the number of hidden units 8. They have significant influence on the weld quality.

  9. Certification of a weld produced by friction stir welding

    DOEpatents

    Obaditch, Chris; Grant, Glenn J

    2013-10-01

    Methods, devices, and systems for providing certification of friction stir welds are disclosed. A sensor is used to collect information related to a friction stir weld. Data from the sensor is compared to threshold values provided by an extrinsic standard setting organizations using a certification engine. The certification engine subsequently produces a report on the certification status of the weld.

  10. Microstructure-Fracture Behavior Relationships of Slot-Welded Rail Steels

    NASA Astrophysics Data System (ADS)

    Allie, Aldinton; Aglan, Heshmat; Fateh, Mahmood

    2011-09-01

    Microstructural analyses of the parent pearlitic and bainitic rail steels were performed, and the results were compared with the microstructure of the welded pearlitic and bainitic steels. An increase in the ASTM grain size number of the heat-affected zone (HAZ) for both pearlitic and bainitic slot welds was observed. The microstructural features that were identified in the weldment of both slot-welded steels were very similar. This was expected since the same welding wire was used to weld both rail steels. The weld consisted of mainly ferrite and had similar grain size. The fusion zones of the welded pearlitic and bainitic rail steels were examined after flexural tests to determine if there were any cracks present due to improper or weak fusion. Examination of the entire fusion zone under high optical magnification revealed no cracks, indicating that a perfect fusion was achieved. The three-point flexural behavior of the parent pearlitic and bainitic steels was evaluated and compared with that of the slot-welded steels. It was found that that the welded pearlitic steel has superior fracture resistance properties when compared to the parent pearlitic steel. The average fracture resistance of the parent pearlitic steel was 79 MPa?m compared to 119 MPa?m for the welded pearlitic steel. The slot-welded bainitic steel, however, showed similar fracture resistance properties to the parent bainitic steel with average values of 121 and 128 MPa?m, respectively. The failure mechanism of the welded and parent pearlitic and bainitic steels was also identified. Microvoid coalescence was observed in both welded rail steel samples. This was manifested by dimpled features, which are associated with ductile failure.

  11. Conceptual design for spacelab pool boiling experiment

    NASA Technical Reports Server (NTRS)

    Lienhard, J. H.; Peck, R. E.

    1978-01-01

    A pool boiling heat transfer experiment to be incorporated with a larger two-phase flow experiment on Spacelab was designed to confirm (or alter) the results of earth-normal gravity experiments which indicate that the hydrodynamic peak and minimum pool boiling heat fluxes vanish at very low gravity. Twelve small sealed test cells containing water, methanol or Freon 113 and cylindrical heaters of various sizes are to be built. Each cell will be subjected to one or more 45 sec tests in which the surface heat flux on the heaters is increased linearly until the surface temperature reaches a limiting value of 500 C. The entire boiling process will be photographed in slow-motion. Boiling curves will be constructed from thermocouple and electric input data, for comparison with the motion picture records. The conduct of the experiment will require no more than a few hours of operator time.

  12. 1. OVERVIEW OF POOLE POWERHOUSE COMPLEX SETTING. POOLE POWERHOUSE AND ...

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

    1. OVERVIEW OF POOLE POWERHOUSE COMPLEX SETTING. POOLE POWERHOUSE AND TRIPLEX COTTAGE ARE VISIBLE AT PHOTO CENTER IN SMALL CLEARING AMONG TREES IN LEE VINING CREEK VALLEY. VIEW TO SOUTH EAST. - Lee Vining Creek Hydroelectric System, Triplex Cottage, Lee Vining Creek, Lee Vining, Mono County, CA

  13. Welding and Brazing Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Moore, T. J.

    1986-01-01

    Hot isostatic pressing and conventional furnace brazing effective under right conditions. Study performed showed feasibility of welding SiC using several welding and brazing techniques. Use of SiC improves engine efficiency by allowing increase in operating temperature. SiC successfully hot-pressure-welded at 3,550 degrees F (1,950 degrees C) in argon. Refinements of solid-state welding and brazing procedures used sufficient for some specific industrial applications.

  14. Theoretical Foundation for Weld Modeling

    NASA Technical Reports Server (NTRS)

    Traugott, S.

    1986-01-01

    Differential equations describe physics of tungsten/inert-gas and plasma-arc welding in aluminum. Report collects and describes necessary theoretical foundation upon which numerical welding model is constructed for tungsten/inert gas or plasma-arc welding in aluminum without keyhole. Governing partial differential equations for flow of heat, metal, and current given, together with boundary conditions relevant to welding process. Numerical estimates for relative importance of various phenomena and required properties of 2219 aluminum included

  15. Modelling of sound fields through austenitic welds

    NASA Astrophysics Data System (ADS)

    Schmitz, V.; Kröning, M.; Chakhlov, S.

    2000-05-01

    The propagation paths of ultrasonic waves through austenitic weld material can not be predicted due to the anisotropic and inhomogeneous structure of the weld. To support an NDT-inspector Ogilvy's ray tracing algorithm has been implemented to follow virtually in three dimensions longitudinal, horizontal and vertical polarized shear wave propagation from the basic material through the cladding. The algorithm has been implemented in a software package "3D-CAD-Ray" which allows to model the experiment in a 3D-CAD drawing and to visualize the rays including reflections from lack of side wall fusions or inner surface connected cracks. The defects can be placed, sized or oriented arbitrarily which allows to perform a parametric study. Results of the algorithm are presented and checked against the experiment. The measured elastic constants and the orientation of the grains taken from micrographs have been entered properly into the CAD-model. The spreading effect for the sound field perpendicular to the orientation of the weld—observed during the experiments—could be confirmed for the SH-, SV- and longitudinal waves by the theoretical predictions. Animations are shown for fixed probe positions where rays and mode converted rays are shown marching on in time and for scans in pulse echo technique where the probe is moved towards the weld.

  16. CONTROLLED-ATMOSPHERE ARC WELDING

    Microsoft Academic Search

    N. E. Weare; R. E. Monroe

    1958-01-01

    Many of the new engineering metals coming into widespread use in welding ; applications are sensitive to contamination by gaseous impurities such as oxygen, ; nitrogen or hydrogen. These metals and alloys may become embrittled or less ; resistant to corrosion because of gaseous impurities picked up during welding. ; Carefully controlled welding atmospheres are required to prevent harmful ;

  17. Welding. Performance Objectives. Basic Course.

    ERIC Educational Resources Information Center

    Vincent, Kenneth

    Several intermediate performance objectives and corresponding criterion measures are listed for each of eight terminal objectives for a basic welding course. The materials were developed for a 36-week (2 hours daily) course developed to teach the fundamentals of welding shop work, to become familiar with the operation of the welding shop…

  18. Orbital friction stir weld system

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor); Carter, Robert W. (Inventor)

    2001-01-01

    This invention is an apparatus for joining the ends of two cylindrical (i.e., pipe-shaped) sections together with a friction stir weld. The apparatus holds the two cylindrical sections together and provides back-side weld support as it makes a friction stir weld around the circumference of the joined ends.

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

    NASA Technical Reports Server (NTRS)

    Bjorkman, Gerry; Cantrell, Mark; Carter, Robert

    2003-01-01

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

  20. Contstraint effects of shallow cracks in structures containing fillet weld toe cracks 

    E-print Network

    Neligon, Melinda T

    1995-01-01

    for structures containing a/W--O.l and a/W--O.5 fillet weld toe cracks. The Anderson-Dodds scaling model is applied to quantify the effects of finite size on J contour integral values for structures containing a/W=O.l and a/W=0.5 fillet weld toe cracks loaded...

  1. Capabilities of Ultrasonic Phased Arrays for FarSide Examinations of Austenitic Stainless Steel Piping Welds

    Microsoft Academic Search

    Michael T. Anderson; Stephen E. Cumblidge; Steven R

    2006-01-01

    A study was conducted to assess the ability of advanced ultrasonic techniques to detect and accurately determine the size of flaws from the far-side of wrought austenitic piping welds. Far-side inspections of nuclear system austenitic piping welds are currently performed on a best effort basis and do not conform to ASME Code Section XI Appendix VIII performance demonstration requirements for

  2. Capabilities of Ultrasonic Techniques for the FarSide Examination of Austenitic Stainless Steel Piping Welds

    Microsoft Academic Search

    Michael T. Anderson; Aaron A. Diaz; Stephen E. Cumblidge; Steven R

    2006-01-01

    A study was conducted to assess the ability of advanced ultrasonic techniques to detect and accurately determine the size of flaws from the far-side of wrought austenitic piping welds. Far-side inspections of nuclear system piping welds are currently performed on a best effort basis and do not conform to ASME Code Section XI Appendix VIII performance demonstration requirements. For this

  3. Synthetically Focused Imaging Techniques in Simulated Austenitic Steel Welds Using AN Ultrasonic Phased Array

    NASA Astrophysics Data System (ADS)

    Connolly, G. D.; Lowe, M. J. S.; Rokhlin, S. I.; Temple, J. A. G.

    2010-02-01

    In austenitic steel welds employed in safety-critical applications, detection of defects that may propagate during service or may have occurred during welding is particularly important. In this study, synthetically focused imaging techniques are applied to the echoes received by phased arrays in order to reconstruct images of the interior of a simulated austenitic steel weld, with application to sizing and location of simplified defects. Using a ray-tracing approach through a previously developed weld model, we briefly describe and then apply three focusing techniques. Results generated via both ray-tracing theory and finite element simulations will be shown.

  4. Electron beam welding, laser beam welding and gas tungsten arc welding of titanium sheet

    Microsoft Academic Search

    Qi Yunlian; Deng Ju; Hong Quan; Zeng Liying

    2000-01-01

    Microstructures, properties and technical parameters of welding specimen of 0.5 mm thick sheets of commercial purity titanium (C.P. Ti) have been studied via high vacuum electron beam welding (EBW-HV), CO2 laser beam welding (LBW) and gas tungsten arc welding (TIG), as well as optical microscope (OM) observation and microhardness measuring. The results indicate that the EBW is more suitable for

  5. Study of inertia welding: the sensitivity of weld configuration and strength to variations in welding parameters

    SciTech Connect

    Mote, M.W.

    1981-12-01

    An experiment is described which is designed to demonstrate the forgiveness of inertia welding, that is, the relative insensitivity of weld strength to variations in energy (rotational speed of parts) and axial force. Although easily observed variations in the welding parameters produced easily observed changes in weldment configuration and changes in dimension (upset), only extremes in parameters produced changes in weld strength. Consequently, process monitoring and product inspection would be sufficient for quality assurance in a production environment.

  6. Element pool changes within a scrub-oak ecosystem after 11 years of elevated CO2 exposure

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Elevated CO2 effects on soil element pool size and fluxes are equivocal. We measured above and belowground pools of non-nitrogen macro and micronutrients in a Florida scrub-oak ecosystem exposed to twice-ambient CO2 concentrations for 11 years. We quantified element pools in above ground biomass of ...

  7. Program for Heat Flow in Welding

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.; Graham, M.

    1986-01-01

    Program contains numerical model of temperature distribution in vicinity of weld. Weld model used to produce estimated welding power requirements, welding-power-loss analysis, heat-affected-zone temperature history, and weld-puddle cross-section plots. Applied to gas/tungsten-arc, plasma-arc, electron-beam, and laser-beam welds on wide plates under steady conditions. User predicts power requirements and temperature distributions. Weld model written in BASIC.

  8. Radiation and annealing response of WWER 440 beltline welding seams

    NASA Astrophysics Data System (ADS)

    Viehrig, Hans-Werner; Houska, Mario; Altstadt, Eberhard

    2015-01-01

    The focus of this paper is on the irradiation response and the effect of thermal annealing in weld materials extracted from decommissioned WWER 440 reactor pressure vessels of the nuclear power plant Greifswald. The characterisation is based on the measurement of the hardness, the yield stress, the Master Curve reference temperature, T0, and the Charpy-V transition temperature through the thickness of multi-layer beltline welding seams in the irradiated and the thermally annealed condition. Additionally, the weld bead structure was characterised by light microscopic studies. We observed a large variation in the through thickness T0 values in the irradiated as well as in thermally annealed condition. The T0 values measured with the T-S-oriented Charpy size SE(B) specimens cut from different thickness locations of the multilayer welding seams strongly depend on the intrinsic weld bead structure along the crack tip. The Master Curve, T0, and Charpy-V, TT47J, based ductile-to-brittle transition temperature progressions through the thickness of the multi-layer welding seam do not correspond to the forecast according to the Russian code. In general, the fracture toughness values at cleavage failure, KJc, measured on SE(B) specimens from the irradiated and large-scale thermally annealed beltline welding seams follow the Master Curve description, but more than the expected number lie outside the curves for 2% and 98% fracture probability. In this case the test standard ASTM E1921 indicates the investigated multi-layer weld metal as not uniform. The multi modal Master Curve based approach describes the temperature dependence of the specimen size adjusted KJc-1T values well. Thermal annealing at 475 °C for 152 h results in the expected decrease of the hardness and tensile strength and the shift of Master Curve and Charpy-V based ductile-to-brittle transition temperatures to lower values.

  9. Modelling of laser welding of flat parts using the modifying nanopowders

    NASA Astrophysics Data System (ADS)

    Cherepanov, A. N.; Shapeev, V. P.

    2013-06-01

    A mathematical model is formulated to describe thermophysical processes at laser welding of metal plates for the case when the modifying nanoparticles of refractory compounds have been introduced in the weld pool (the nanopowder seed cultrure fermenters — NSCF). Specially prepared nanoparticles of refractory compounds serve the crystallization centers that is they are in fact the exogenous primers, on the surface of which the individual clusters are grouped. Owing to this, one can control the process of the crystallization of the alloy and the formation of its structure and, consequently, the joint weld properties. As an example, we present the results of computing the butt welding of two plates of aluminum alloy and steel. Computed and experimental data are compared.

  10. Extravehicular activity welding experiment

    NASA Technical Reports Server (NTRS)

    Watson, J. Kevin

    1989-01-01

    The In-Space Technology Experiments Program (INSTEP) provides an opportunity to explore the many critical questions which can only be answered by experimentation in space. The objective of the Extravehicular Activity Welding Experiment definition project was to define the requirements for a spaceflight experiment to evaluate the feasibility of performing manual welding tasks during EVA. Consideration was given to experiment design, work station design, welding hardware design, payload integration requirements, and human factors (including safety). The results of this effort are presented. Included are the specific objectives of the flight test, details of the tasks which will generate the required data, and a description of the equipment which will be needed to support the tasks. Work station requirements are addressed as are human factors, STS integration procedures and, most importantly, safety considerations. A preliminary estimate of the cost and the schedule for completion of the experiment through flight and postflight analysis are given.

  11. Characterization of Stainless Steel and Refractory Metal Welds Made using a Diode-Pumped, Continuous Wave Nd: Yag Laser

    SciTech Connect

    Palmer, T A; Wood, B; Elmer, J W; Westrich, C; Milewski, J O; Piltch, M; Barbe, M; Carpenter, R

    2001-10-19

    A series of laser welds have been made on several materials using a Rofin-Sinar DY-033, 3.3 kW, Diode-Pumped Continuous Wave (CW) Nd:YAG laser system, located at Los Alamos National Laboratory. Materials welded in these experiments include 21-6-9 stainless steel, 304L stainless steel, vanadium, and tantalum. The effects of changes in the power input at a constant travel speed on the depth, width, aspect ratio, and total melted area of the welds have been analyzed. Increases in the measured weld pool dimensions as a function of power input are compared for each of the base metals investigated. These results provide a basis for further examining the characteristics of diode pumped CW Nd:YAG laser systems in welding applications.

  12. The science and practice of welding. 8th ed. Vol. 2: The practice of welding

    SciTech Connect

    Davies, A.C.

    1984-01-01

    This book includes sections on underwater welding and cutting, cold pressure welding, the application of mixed gases to various welding processes, and robot welding. The author uses photographs, tables, figures, and illustrations to explain the text and provides examination questions.

  13. Investigation in welding technology for pipelines at a nuclear plant by holographic interferometry

    NASA Astrophysics Data System (ADS)

    Obraztsov, Vladimir S.; Odintsev, Igor N.; Zakharzhevsky, Yu. O.; Pavlov, M. A.; Tsykin, A. V.

    2004-06-01

    Effect of the standard size of pipes made from 08x18H10T austenitic chromium-nickel steel on the level of residual weld stresses on the inner surface in the weld junction area were experimentally studied by holographic interferometry. The results obtained in the course of experimental investigations reveal that one can control the level of residual stresses within the certain limits by matching diameter and wall thickness of the pipes. For the welding practice accepted for pipes 300 mm in passage diameter made from 08 x 18H10T austenitic chromium-nickel steel it is better to use pipes ? 273 x 11 mm. In this case the tension welding stress does not exceed 110 MPa, while it makes up 325 MPa in the heating area of the weld for pipes 325 x 12 mm. Technique and instrumentation for holographic inspection of residual welding stresses is described.

  14. Controlling conditions for wet welding

    SciTech Connect

    Hill, M.

    1985-11-01

    Wet welding is finding increased use for repairing and maintaining vessel hulls around the world. Users are developing new methods and procedures to expand the technology. A wet welded joint underwater can be made as strong as one welded in a dry habitat, but at a greatly reduced cost. The design of the joint for wet welding and the procedures that need to be followed are outlined. In designing for wet welding, high tensile strength, ease of access, and over-design should be considered.

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

    PubMed

    Dasch, Jean; D'Arcy, James

    2008-07-01

    Airborne particles were characterized from six welding operations in three automotive plants, including resistance spot welding, metal inert gas (MIG) welding and tungsten inert gas (TIG) welding of aluminum and resistance spot welding, MIG welding and weld-through sealer of galvanized steel. Particle levels were measured throughout the process area to select a sampling location, followed by intensive particle sampling over one working shift. Temporal trends were measured, and particles were collected on filters to characterize their size and chemistry. In all cases, the particles fell into a bimodal size distribution with very large particles >20 mum in diameter, possibly emitted as spatter or metal expulsions, and very small particles about 1 mum in diameter, possibly formed from condensation of vaporized metal. The mass median aerodynamic diameter was about 1 mum, with only about 7% of the particle mass present as ultrafine particles <100 nm. About half the mass of aluminum welding particles could be accounted for by chemical analysis, with the remainder possibly present as oxygen. Predominant species were organic carbon, elemental carbon, iron, and aluminum. More than 80% of the particle mass could be accounted for from steel welding, primarily present as iron, organic carbon, zinc, and copper. Particle concentrations and elemental concentrations were compared with allowable concentrations as recommended by the Occupational Safety and Health Administration and the American Conference of Governmental Industrial Hygienists. In all cases, workplace levels were at least 11 times lower than recommended levels. PMID:18464098

  16. Effect of Welding Parameters on the Microstructure and Strength of Friction Stir Weld Joints in Twin Roll Cast EN AW Al-Mn1Cu Plates

    NASA Astrophysics Data System (ADS)

    Birol, Yucel; Kasman, Sefika

    2013-10-01

    Twin roll cast EN AW Al-Mn1Cu plates were butt welded with the friction stir welding process which employed a non-consumable tool, tilted by 1.5° and 3° with respect to the plate normal, rotated in a clockwise direction at 400 and 800 rpm, while traversing at a fixed rate of 80 mm/min along the weld line. Microstructural observations and microhardness tests were performed on sections perpendicular to the tool traverse direction. Tensile tests were carried out at room temperature on samples cut perpendicular to the weld line. The ultimate tensile strength of the welded EN AW Al-Mn1Cu plates improved with increasing tool rotation speed and decreasing tool tilt angle. This marked improvement in ultimate tensile strength is attributed to the increase in the heat input owing to an increased frictional heat generation. There appears to be a perfect correlation between the ultimate tensile strength and the size of the weld zone. The fracture surfaces of the base plate and the welded plates are distinctly different. The former is dominated by dimples typical of ductile fractures. A vast majority of the intermetallic particles inside the weld zones are too small to generate dimples during a tensile test. The fracture surface of the welded plates is thus characterized by occasional dimples that are elongated in the same direction suggesting a tensile tearing mechanism.

  17. Effects of residual stress, weld toe notch and weld defects on fatigue of welded steel structures

    NASA Astrophysics Data System (ADS)

    Shen, Wenyu

    In studying the fatigue behavior of fillet welded railroad tank car shell structures, the effects of welding residual stress, weld toe notch, and weld defects on the fatigue of fillet welded A515 steel specimens were evaluated. Both hole-drilling and sectioning measurement techniques were used to obtain residual stress information. Pad-on-plate weld specimens were designed to simulate the tank car structure for welding residual stress measurement. Simple bead-on-plate and fillet weld specimens, which have similar welding residual stresses near the weld end toe to the pad-on-plate specimens, were designed to be as compact as possible for fatigue testing. As-welded and stress-relieved simple weld specimens were tested under pulsed tension and alternating cyclic load conditions to determine stress-life and fatigue crack propagation properties. Weld toe stress concentration effects were determined by strain gage measurement. Fracture surface features and crack initiation sites were studied by visual analysis, scanning electron microscopy, and optical microscopy. Welding residual stresses were found to be biaxial tension-compression near the weld end toe and biaxial tension-tension near the weld center toe. Longitudinal tensile residual stress was significantly relieved when the applied longitudinal tensile cyclic load was greater than 14 Ksi. Test results did not show a consistent effect of tensile residual stress on the fatigue strength under pulsed tension loads. However, tensile residual stress had a significant influence on the fatigue strength under alternating cyclic loads. The weld end toe was associated with a stress concentration factor of approximately 3 and was the most critical factor in initiating fatigue cracks. Weld defects, such as slag inclusions, lack of fusion, and porosity were found to significantly affect the fatigue strength of a welded joint when the load magnitude or mean stress was low. An equivalent crack concept, based on linear elastic fracture mechanics theory, was introduced to quantify the weld toe stress concentration effect. This concept was shown to be effective for fatigue design life prediction of welded structures.

  18. Unique Cryogenic Welded Structures

    SciTech Connect

    Yushchenko, K.A.; Monko, G.G. [E.O. Paton Electric Welding Institute, Kiev 03680 (Ukraine)

    2004-06-28

    For the last few decades, the E. O. Paton Electric Welding Institute has been active in the field of cryogenic materials science. Integrated research on development of new grades of steels and alloys for cryogenic engineering was carried out in collaboration with the leading institutions of Russia, Ukraine, and Georgia. Commercially applied welding technologies and consumables were developed. They include large, spherical tanks for storage of liquefied gases (from oxygen to helium) under high pressures; space simulators with a capacity of 10 000 m3 and more; and load-carrying elements of superconducting fusion magnetic systems for the TOKAMAK, MGD, and ITER series.

  19. Visual-based spatter detection during high-power disk laser welding

    NASA Astrophysics Data System (ADS)

    You, Deyong; Gao, Xiangdong; Katayama, Seiji

    2014-03-01

    The spatters created during laser welding are considered as essential information for welding quality inspection. This paper proposes a laser welding quality inspection method based on the high-speed visual detection. A high-power (10 kW) disk laser bead-on-plate welding of Type 304 austenitic stainless workpiece was carried out and two high-speed cameras were used to capture the spatter images. The first one was used to measure the near infrared (IR) light emitted from a molten pool, and the second was utilized to measure the ultraviolet (UV) light and visible light. By comparing the images captured from two different cameras, it was found that the measurement of UV light and visible light was more appropriate for spatter detection. Based on image process technology, a novel spatter detection algorithm was presented. A shape similarity function and angle similarity function of the spatters were established for spatter recognition by defining the spatter features, such as centroid position, gray-value, average gray-value and radius. The spatter volume, spatter gray-value and spatter radius were used to evaluate the welding quality. By comparing the spatter information with the molten pool width, this paper investigates the internal relationship between the welding quality and the spatter feature parameters. Experimental results proved that the proposed spatter feature extraction method could guarantee an accurate evaluation on the quality of high-power disk laser welding. In addition it was demonstrated in this study that, by using high-speed visual detection and image processing technology, the quantities and feature of spatters could be measured during the welding process.

  20. Laser welding of INCONEL 600

    NASA Astrophysics Data System (ADS)

    Daurelio, G.; Dionoro, G.; Memola Capece Minutolo, F.

    1991-02-01

    Laser beam welding exhibits features typical of autogenous welding by fusion with very concentrated heat sources: narrow deep weld, restrict heat affected zone (HAZ), negligible residual.stresses etc. All these aspects are of great importance in welding special purpose alloys such as corrosion resistant nickel base alloys. In this work, a nickel base alloy INCONEIl 600 has been welded by means of a 2 kW C02 cw laser. In order to evaluate the influence of the basic welding parameters on heat affected zone, weld structure and weld geometry, an accurate analysis has been carried out. The experimental results show a strict correlation between the power beam and the welding speed vs. the weld bead geometry. As the speed increases, so penetration decays. Microhardness tests, micro and macrograph examinations did not reveal, in the range of experimental parameters, any significant alteration in weld bead structure nor the presence of a HAZ. In order to assess process efficiency, the experimental data were processed using the Line Source Model (LSM) which permits to calculate the Melting Ratio (MR) and Energy Transfer Efficiency (ETE).

  1. Weld penetration and defect control

    SciTech Connect

    Chin, B.A.

    1992-05-15

    Highly engineered designs increasingly require the use of improved materials and sophisticated manufacturing techniques. To obtain optimal performance from these engineered products, improved weld properties and joint reliability are a necessarily. This requirement for improved weld performance and reliability has led to the development of high-performance welding systems in which pre-programmed parameters are specified before any welding takes place. These automated systems however lack the ability to compensate for perturbations which arise during the welding process. Hence the need for systems which monitor and control the in-process status of the welding process. This report discusses work carried out on weld penetration indicators and the feasibility of using these indicators for on-line penetration control.

  2. Development of Space DL Welding Process for Construction and Repair of Space Structures in Space

    NASA Astrophysics Data System (ADS)

    Suita, Yoshikazu; Tabakodani, Eiji; Sugiyama, Satoshi; Terajima, Noboru; Tsukuda, Yoshiyuki; Fujisawa, Shoichiro; Imagawa, Kichiro

    An ultra-high vacuum diode laser welding system capable of performing a diode laser (DL) welding experiment at the International Space Station orbital pressure of 10-5 Pa was developed for investigating the effect of environmental pressure on DL welding phenomena. A DL welding experiment with a power density of about 100 kW/cm2 was conducted on 304 stainless steel at pressure levels between 105 Pa and 10-5 Pa. Although a laser-induced plasma plume was observed during welding at environmental pressures, 105 Pa and 103 Pa, no laser-induced plasma plume was found in the pressure range from 10 Pa to 10-5 Pa. The mode of the melting process (weld pool shape) under these experimental conditions was a keyhole-type melting mode or a transition-type melting mode at environmental pressures of 105 Pa and 103 Pa. However, the melting mode at pressures lower than 10 Pa changed to a heat-conduction-type melting mode. Although the penetration depth decreased when the environmental pressure was dropped to 103 Pa, it did not change at pressures lower than 10 Pa. We also determined that the prevention technology of metal vapor deposition on optical devices needs to be developed for DL welding technologies used in space.

  3. Development of Space DL Welding Process for Construction and Repair of Space Structures in Space

    NASA Astrophysics Data System (ADS)

    Suita, Yoshikazu; Tabakodani, Eiji; Sugiyama, Satoshi; Terajima, Noboru; Tsukuda, Yoshiyuki; Fujisawa, Shoichiro; Imagawa, Kichiro

    An ultra high vacuum diode laser welding(UHVDLW) system in which a diode laser(DL) welding can be performed in the ISS orbital pressure 10-5Pa was developed for investigating the effect of an environmental pressure on a DL welding phenomenon. The DL welding experiments with power density around 100kW/cm2 were conducted on 304 stainless steel in pressure levels between 105Pa and 10-5Pa. Although a laser-induced plasma plume is observed during welding in the environmental pressure 105Pa and 103Pa, no laser-induced plasma plume is found in the pressure ranging 10Pa to 10-5Pa. A formation of melting process(weld pool shape) with this experimental condition is a keyhole melting type or a transition melting type in the environmental pressure 105Pa and 103Pa. But, a melting process in the pressure lower than 10Pa changes to a heat conduction melting type. The penetration depth showed a decrease with the environmental pressure down to 103Pa and then appears to no change in a pressure lower than 10Pa. Establishment of space DL welding technology needs to develop a suppression technology of a metal vapor deposition to an optical device.

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  5. Laser Beam Welding of Thick Titanium Sheets in the Field of Marine Technology

    NASA Astrophysics Data System (ADS)

    Schneider, André; Gumenyuk, Andrey; Lammers, Marco; Malletschek, Andreas; Rethmeier, Michael

    The ever larger requirements of the material selection in the range of maritime industry necessitate the application of high-tech materials. Titanium because of its excellent mechanical properties at low weight is an attractive alternative for the construction of ships. The goal of this investigation was to design a welding method for joining samples of 16 mm thick Ti3Al2.5 V. The welding experiments with a 20 kW Yb-fiber laser source and varying combinations of parameters were intended to qualify the laser beam welding process. The welding results were analyzed by non-destructive and destructive testing. In addition, the welding tests were recorded with two high-speed cameras to observe the weld pool and the vapor plume. The evaluation of the high-speed images in correlation with the results of non-destructive testing shows, that a significant improvement of process stability and weld quality can be achieved by the suppression of the vapor plume.

  6. A Distributed Pool Architecture for Genetic Algorithms

    E-print Network

    Roy, Gautam

    2011-02-22

    individuals which are possible solutions to our distributed GA is represented in the code by a shared global array of length n. Let u be the per-thread population size. The threads (each representing one processor in the real scenario) run their own GA... for synchronous operation of threads, in which each participating thread finishes generation N before any thread begins generation N +1. This lock step behavior is achieved using barrier synchronization in pthreads. The Pool GA was tested on the following real...

  7. Welding technology transfer task/laser based weld joint tracking system for compressor girth welds

    NASA Technical Reports Server (NTRS)

    Looney, Alan

    1991-01-01

    Sensors to control and monitor welding operations are currently being developed at Marshall Space Flight Center. The laser based weld bead profiler/torch rotation sensor was modified to provide a weld joint tracking system for compressor girth welds. The tracking system features a precision laser based vision sensor, automated two-axis machine motion, and an industrial PC controller. The system benefits are elimination of weld repairs caused by joint tracking errors which reduces manufacturing costs and increases production output, simplification of tooling, and free costly manufacturing floor space.

  8. Pooling techniques for bioassay screening

    SciTech Connect

    Sun, L.C.; Baum, J.W.; Kaplan, E; Moorthy, A.R.

    1996-03-01

    Pooling techniques commonly are used to increase the throughput of samples used for screening purposes. While the advantages of such techniques are increased analytical efficiency and cost savings, the sensitivity of measurements decreases because it is inversely proportional to the number of samples in the pools. Consequently, uncertainties in estimates of dose and risk which are based on the results of pooled samples increase as the number of samples in the pools increases in all applications. However, sensitivities may not be seriously degraded, for example, in urinalysis, if the samples in the pools are of known time duration, or if the fraction of some attribute of the grab urine samples to that in a 24-hour composite is known (e.g., mass, specific gravity, creatinine, or volume, per 24-h interval). This paper presents square and cube pooling schemes that greatly increase throughput and can considerably reduce analytical costs (on a sample basis). The benefit-cost ratios for 5{times}5 square and 5{times}5{times}5 cube pooling schemes are 2.5 and 8.3, respectively. Three-dimensional and higher arrayed pooling schemes would result in even greater economies; however, significant improvements in analytical sensitivity are required to achieve these advantages. These are various other considerations for designing a pooling scheme, where the number of dimensions and of samples in the optimum array are influenced by: (1) the minimal detectable amount (MDA) of the analytical processes, (2) the screening dose-rate requirements, (3) the maximum masses or volumes of the composite samples that can be analyzed, (4) the information already available from results of composite analysis, and (5) the ability of an analytical system to guard against both false negative and false positive results. Many of these are beyond the scope of this paper but are being evaluated.

  9. Underwater wet welding made simple: benefits of Hammerhead ® wet-spot welding process

    Microsoft Academic Search

    David J Keats

    2009-01-01

    A new method of wet welding was investigated to evaluate potential improvements in weld quality, ease of use, increased welding speed and the elimination of welding skill. The new welding process, which has been called Hammerhead 'wet-spot' welding, eliminates the need for skilled welder-divers as well as traditional cleaning and preparation techniques normally associated with conventional manual metal arc (MMA)

  10. Masatsu kakuhan setsugo "Friction Stir Welding Complete aspects of FSW" Japan Welding Society

    E-print Network

    Cambridge, University of

    Masatsu kakuhan setsugo ­ "Friction Stir Welding ­ Complete aspects of FSW" Japan Welding Society years ago that the Friction Stir Welding (FSW) method was proposed by TWI. Because FSW is a solid state welding method, the peak temperature reached during FSW welding is lower than the traditional welding

  11. The influence of welding parameters on the joint strength of resistance spot-welded titanium sheets

    Microsoft Academic Search

    Nizamettin Kahraman

    2007-01-01

    In this study, commercially pure (CP) titanium sheets (ASTM Grade 2) were welded by resistance spot welding at different welding parameters and under different welding environments. The welded joints were subjected to tensile-shearing tests in order to determine the strength of the welded zones. In addition, hardness and microstructural examinations were carried out in order to examine the influence of

  12. Efficient weld seam detection for robotic welding based on local image processing

    Microsoft Academic Search

    Fanhuai Shi; Tao Lin; Shanben Chen

    2009-01-01

    Purpose – The weld seam detection is required for a welding robot to preplan the weld seam track before the actual welding. The purpose of this paper is to investigate this subject in natural lighting conditions. Design\\/methodology\\/approach – This paper presents an efficient algorithm of weld seam detection for butt joint welding from a single image. The basic idea of

  13. Influence of weld discontinuities on strain controlled fatigue behavior of 308 stainless steel weld metal

    Microsoft Academic Search

    K. Bhanu Sankara Rao; M. Valsan; R. Sandhya; S. L. Mannan; P. Rodriguez

    1994-01-01

    Detailed investigations have been performed for assessing the importance of weld discontinuities in strain controlled low cycle fatigue (LCF) behavior of 308 stainless steel (SS) welds. The LCF behavior of 308 SS welds containing defects was compared with that of type 304 SS base material and 308 SS sound weld metal. Weld pads were prepared by shielded metal arc welding

  14. 13 CFR 120.1704 - Pool Loans eligible for Pooling.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...financing the acquisition, construction or renovation of an aquarium, zoo, golf course, or swimming pool; or (iv) To a business covered...713910 (“Golf Courses and Country Clubs”); or aquariums and zoos—712130 (“Zoos and Botanical Gardens”)....

  15. 13 CFR 120.1704 - Pool Loans eligible for Pooling.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...financing the acquisition, construction or renovation of an aquarium, zoo, golf course, or swimming pool; or (iv) To a business covered...713910 (“Golf Courses and Country Clubs”); or aquariums and zoos—712130 (“Zoos and Botanical Gardens”)....

  16. 49 CFR 179.300-9 - Welding.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... (a) Longitudinal 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...171.7 of this subchapter). (b) Fusion-welded joints must be in...

  17. 49 CFR 179.300-9 - Welding.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... (a) Longitudinal 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...171.7 of this subchapter). (b) Fusion-welded joints must be in...

  18. 49 CFR 179.300-9 - Welding.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... (a) Longitudinal 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...171.7 of this subchapter). (b) Fusion-welded joints must be in...

  19. Toolbox Safety Talk Welding & Metal Work Safety

    E-print Network

    Pawlowski, Wojtek

    Toolbox Safety Talk Welding & Metal Work Safety Environmental Health & Safety Facilities Safety or harmful emission giving metals. Welding Safety When welding outside of a designated welding booth, ensure injury. Avoid welding on materials such as galvanized or stainless steel in order to minimize toxic fume

  20. Preliminary Study on Arc Welding in Vacuum

    Microsoft Academic Search

    H. Toya; K. Hieda; T. Saitou

    2006-01-01

    Welding technology in space is required to repair the space station. Arc welding in vacuum should be more conventional than electron beam welding because of low voltage operation. Preliminary study on vacuum arc welding is presented in this paper. Arc was ignited by separating an arcing electrode (cathode) from the welding piece (anode). The former is composed of a rod

  1. Tool For Robotic Resistive Roll Welding

    NASA Technical Reports Server (NTRS)

    Gilber, Jeffrey L.

    1991-01-01

    Roll-welding attachment for robot simple, inexpensive device incorporating modified commercial resistance-welding gun. Modified welding gun easily attaches to end effector of robot. Robot applies welding force and moves electrode wheel along prescribed path. Resistance-welding current starts and stops automatically according to force exerted against workpiece. Used to apply brazing foil to workpiece.

  2. Analysis of residual stresses at weld repairs

    Microsoft Academic Search

    P. Dong; J. K. Hong; P. J. Bouchard

    2005-01-01

    In contrast to initial fabrication welds, residual stresses associated with finite length weld repairs tend to exhibit some important invariant features, regardless of actual component configurations, materials, and to some degree, welding procedures. Such invariant features are associated with the severe restraint conditions present in typical repair welding situations. In this paper, residual stress results from several weld repair case

  3. Preventing weld hot cracking by synchronous rolling during welding

    SciTech Connect

    Liu, W. [Dalian Railway Inst. (China). Dept. of Materials Science and Engineering; Tian, X.; Zhang, X. [School of Materials Science and Engineering, Harbin (China)

    1996-09-01

    Based on the mechanical point of view of hot cracking in weldments, a new method, accomplished by synchronous rolling during welding (SRDW) along both sides of the weld at a suitable distance behind the welding arc, has been developed for preventing weld hot cracking. The theory behind this method was also examined. Three-dimensional simulative computations of displacement and strain fields produced by SRDW were carried out by means of the finite element method to reveal the mechanism of the new method and provide a theoretical basis for parameter choice. With a specially developed equipment for welding and synchronous rolling, experiments were performed to investigate the effectiveness and feasibility of this method in preventing weld hot cracking in high-strength aluminum alloy 2024-T4. Results show that weld hot cracking in 2024-Al alloy can be effectively prevented and the mechanical properties of welded joints can also be improved by the new method. It is an important new solution to weld hot cracking in welding of sheet metals.

  4. REACTORS NEED SUPERLATIVE WELDING

    Microsoft Academic Search

    1962-01-01

    Discussion is given on Tig, Mig, stick, and electron beam welding of ; atomic reactors using austenitic and ferritic stainless steel, stainless clad ; steel, Inconel, carbon steel, Zr, the precipitation hardening steels, and others. ; Testing by x ray, dye penetration, and magnetic particles is also included. ; (P.C.H.);

  5. Tube welding and brazing

    NASA Technical Reports Server (NTRS)

    Poorman, R. M.

    1969-01-01

    Brochures outline the tools, equipment, materials, and techniques used for joining tubes by automatic and semiautomatic welding and brazing. A few of the metals being joined are stainless steels of various diameters and thickness. Techniques have been developed for on-site or work-bench repair.

  6. Welding of Stainless Materials

    NASA Technical Reports Server (NTRS)

    Bull, H; Johnson, Lawrence

    1929-01-01

    It would appear that welds in some stainless steels, heat-treated in some practicable way, will probably be found to have all the resistance to corrosion that is required for aircraft. Certainly these structures are not subjected to the severe conditions that are found in chemical plants.

  7. Welding Rustproof Steels

    NASA Technical Reports Server (NTRS)

    Hoffmann, W

    1929-01-01

    The following experimental results will perhaps increase the knowledge of the process of welding rustproof steels. The experiments were made with two chrome-steel sheets and with two chrome-steel-nickel sheets having the composition shown in Table I.

  8. Welding. Student Learning Guide.

    ERIC Educational Resources Information Center

    Palm Beach County Board of Public Instruction, West Palm Beach, FL.

    This student learning guide contains 30 modules for completing a course in welding. It is designed especially for use in secondary schools in Palm Beach County, Florida. Each module covers one task, and consists of a purpose, performance objective, enabling objectives, learning activities keyed to resources, information sheets, student self-check…

  9. Welding. Student Learning Guides.

    ERIC Educational Resources Information Center

    Ridge Vocational-Technical Center, Winter Haven, FL.

    These 23 learning guides are self-instructional packets for 23 tasks identified as essential for performance on an entry-level job in welding. Each guide is based on a terminal performance objective (task) and 1-4 enabling objectives. For each enabling objective, some or all of these materials may be presented: learning steps (outline of student…

  10. Magnetic pulse welding technology

    Microsoft Academic Search

    Ahmad K. Jassim

    2010-01-01

    In this paper, the benefits of using Magnetic Pulse machine which is belong to Non-conventional machine instead of conventional machine. Magnetic Pulse Technology is used for joining dissimilar metals, and for forming and cutting metals. It is a non contact technique. Magnetic field is used to generate impact magnetic pressure for welding and forming the work piece by converted the

  11. Robot welding in shipbuilding

    Microsoft Academic Search

    Brian Rooks

    1997-01-01

    Examines the challenges facing the shipbuilding industry today and details the solution offered by a consortium of three German companies. It is based on the prefabrication of sub-assemblies on production lines in which automation is critical to the economics. Describes welding robots playing a key role in this approach and the robot systems supplied to one German shipbuilder. Also important

  12. Welding nozzle position manipulator

    NASA Technical Reports Server (NTRS)

    Gilbert, Jeffrey L. (inventor); Gutow, David A. (inventor)

    1994-01-01

    The present invention is directed to a welding nozzle position manipulator. The manipulator consists of an angle support to which the remaining components of the device are attached either directly or indirectly. A pair of pivotal connections attach a weld nozzle holding link to the angle support and provide a two axis freedom of movement of the holding link with respect to the support angle. The manipulator is actuated by a pair of adjusting screws angularly mounted to the angle support. These screws contact a pair of tapered friction surfaces formed on the upper portion of the welding nozzle holding link. A spring positioned between the upper portions of the support angle and the holding link provides a constant bias engagement between the friction surfaces of the holding link and the adjustment screws, so as to firmly hold the link in position and to eliminate any free play in the adjustment mechanism. The angular relationships between the adjustment screws, the angle support and the tapered friction surfaces of the weld nozzle holding link provide a geometric arrangement which permits precision adjustment of the holding link with respect to the angle support and also provides a solid holding link mount which is resistant to movement from outside forces.

  13. Summer bat activity at Woodland seasonal pools in the northern Great Lakes region

    Microsoft Academic Search

    Karen E. Francl

    2008-01-01

    Woodland seasonal pools in the northern Great Lakes region, limited in this study to northern Wisconsin and Michigan’s Upper\\u000a Peninsula, are potentially important sites for bat feeding and drinking. In order to determine the influence of pool size,\\u000a hydroperiod, and structural complexity on relative bat activity, I surveyed pools (17 in 2004, eight in 2005 and 2006) at\\u000a approximately two-week

  14. Process for optimizing titanium and zirconium additions to aluminum welding consumables

    SciTech Connect

    Dvornak, M.J.; Frost, R.H.

    1992-04-14

    This patent describes a process for manufacturing an aluminum welding consumable. It comprises: creating an aluminum melt; adding to the aluminum melt solid pieces of a master alloy, comprising aluminum and a weld-enhancing additive to form a mixture, wherein the weld-enhancing additive being a material selected from the group consisting of titanium and zirconium, so that the weld-enhancing additive exists in the alloy prior to addition to the melt in the form of intermetallic particles relatively large in size and small in number, and after addition to the melt the weld-enhancing additive exists in the form of fractured intermetallic particles of refined size having dissolved fractured interfaces, casting the mixture into a chill mold to form an ingot; reducing the ingot to rods of rough wire dimension by cold rolling; annealing the reduced rods; and drawing the rods into wire.

  15. Detailed characterization of welding fumes in personal exposure samples

    NASA Astrophysics Data System (ADS)

    Quémerais, B.; Mino, James; Amin, M. R.; Golshahi, H.; Izadi, H.

    2015-05-01

    The objective of the project was to develop a method allowing for detailed characterization of welding particles including particle number concentration, size distribution, surface chemistry and chemical composition of individual particles, as well as metal concentration of various welding fumes in personal exposure samples using regular sampling equipment. A sample strategy was developed to evaluate the variation of the collection methods on mass concentration. Samples were collected with various samplers and filters at two different locations using our collection system. The first location was using a robotic welding system while the second was manual welding. Collected samples were analysed for mass concentration using gravimetryand metal concentration using ICP/OES. More advanced analysis was performed on selected filters using X-Ray Photoelectron Spectroscopy to determine surface composition of the particles, and X-Ray Diffraction to determine chemical composition of the fumes. Results showed that the robotic system had a lot of variation in space when the collection system was located close to the weld. Collection efficiency was found to be quite variable depending upon the type of filter. As well, metal concentrations in blank filters were dependent upon the type of filter with MCE presenting with the highest blank values. Results obtained with the XRD and XPS systems showed that it was possible to analyse a small of powdered welding fume sample but results on filters were not conclusive.

  16. CAR POOL POLICY Program Goals

    E-print Network

    Meyers, Steven D.

    CAR POOL POLICY Program Goals · To reduce traffic congestion and improve air quality in and around, Emergency Ride Home (ERH) and WeCar participants · To provide a benefit for USF faculty, staff and students

  17. Hybrid laser–TIG welding, laser beam welding and gas tungsten arc welding of AZ31B magnesium alloy

    Microsoft Academic Search

    Liu Liming; Wang Jifeng; Song Gang

    2004-01-01

    Welding of AZ31B magnesium alloy was carried out using hybrid laser–TIG (LATIG) welding, laser beam welding (LBW) and gas tungsten arc (TIG) welding. The weldability and microstructure of magnesium AZ31B alloy welded using LATIG, LBW and TIG were investigated by OM and EMPA. The experimental results showed that the welding speed of LATIG was higher than that of TIG, which

  18. Influence of Post-Weld Annealing on Transformation Behavior and Mechanical Properties of Laser-Welded NiTi Alloy Wires

    NASA Astrophysics Data System (ADS)

    Yan, Xiaojun; Ge, Yuli

    2014-10-01

    The influence of annealing on the transformation behavior, mechanical, and functional properties of laser-welded NiTi wires was investigated. The results show that Ti3Ni4 precipitates occur after post-weld annealing and coarsen with increasing annealing temperature. The as-welded specimen exhibits one-step B2 ? B19' transformation, while the annealed ones show two-step B2 ? R ? B19' transformation. Annealing at 400 °C for 1 h can improve the tensile strength and superelasticity of the welded joints. However, these properties decrease when annealing at 500 °C for 1 h. The change of mechanical and functional properties after annealing is attributed to the different size of Ti3Ni4 precipitates. Annealing to produce smaller coherent precipitates (10 nm) improves the mechanical and functional properties of the welded joints. As the Ti3Ni4 precipitates coarsen, the mechanical and functional properties decrease.

  19. On the Microstructural and Mechanical Characterization of Hybrid Laser-Welded Al-Zn-Mg-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Wu, S. C.; Hu, Y. N.; Song, X. P.; Xue, Y. L.; Peng, J. F.

    2015-04-01

    Butt-welded 2-mm-thick high-strength aluminum alloys have been welded using a hybrid fiber laser and pulsed arc heat source system with the ER5356 filler. The microstructure, size of precipitates, texture, grain size and shape, change of strengthening elements, mechanical properties, and surface-based fatigue fracture characteristics of hybrid-welded joints were investigated in detail. The results indicate that the hybrid welds and the unaffected base materials have the lowest and largest hardness values, respectively, compared with the heat-affected zone. It is resonably believed that the elemental loss, coarse grains, and changed precipitates synthetically produce the low hardness and tensile strengths of hybrid welds. Meanwhile, the weaker grain boundary inside welds appears to initiate a microcrack. Besides, there exists an interaction of fatigue cracks and gas pores and microstructures.

  20. Modeling the effects of tool shoulder and probe profile geometries on friction stirred aluminum welds using response surface methodology

    NASA Astrophysics Data System (ADS)

    Mohanty, H. K.; Mahapatra, M. M.; Kumar, P.; Biswas, P.; Mandal, N. R.

    2012-12-01

    The present paper discusses the modeling of tool geometry effects on the friction stir aluminum welds using response surface methodology. The friction stir welding tools were designed with different shoulder and tool probe geometries based on a design matrix. The matrix for the tool designing was made for three types of tools, based on three types of probes, with three levels each for defining the shoulder surface type and probe profile geometries. Then, the effects of tool shoulder and probe geometries on friction stirred aluminum welds were experimentally investigated with respect to weld strength, weld cross section area, grain size of weld and grain size of thermo-mechanically affected zone. These effects were modeled using multiple and response surface regression analysis. The response surface regression modeling were found to be appropriate for defining the friction stir weldment characteristics.

  1. Arc Welding and Hybrid Laser-Arc Welding

    Microsoft Academic Search

    Ian Richardson

    2009-01-01

    Laser-arc hybrid welding has developed into a viable industrial technology in recent years, and is attracting increasing commercial\\u000a interest. The physics of the underlying interactions is quite complex. In order to explore the relationships involved, it\\u000a is useful to consider important aspects of laser and arc welding separately. The physics of laser welding has already been\\u000a examined in Chaps. 3

  2. Effect of Welding and Post-weld Heat Treatment on Tensile Properties of Nimonic 263 at Room and Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Jeon, Minwoo; Lee, Jae-Hyun; Woo, Ta Kwan; Kim, Sangshik

    2011-04-01

    Nimonic 263 has been developed for the improved ductility in welded assemblies and is a candidate material for gas turbine combustor and transition pieces along with its good weldability and mechanical properties at room and elevated temperatures. In this study, the tensile behavior of an as-welded Nimonic 263 specimen at room temperature and 1053 K (780 °C) was examined in conjunction with microstructural evolution during welding and postweld heat treatment (PWHT). With the welding and the PWHT, the yield strength (YS), ultimate tensile strength (UTS), and tensile elongation of Nimonic 263 varied in a complex manner. It was observed that the PWHT of resolutionization at 1423 K (1150 °C) for 2 hours gave the highest YS and UTS values, whereas the tensile elongation was the lowest, at both testing temperatures. With increasing resolutionization time, the YS and UTS tended to decrease along with the increase in tensile ductility. The tensile behaviors of as-welded Nimonic 263 specimens was affected by several factors, including grain size, residual stress, possible microsegregation of ?' forming elements, a tendency for interdendritic or intergranular fracture and a morphological change in both M23C6 and MC type carbides, depending on the testing temperature and the PWHT. The complex changes in tensile properties of Nimonic 263 with welding and PWHT at room temperature and 1053 K (780 °C) were discussed based on the micrographic and fractographic observations.

  3. Lightweight, High-Current Welding Gun

    NASA Technical Reports Server (NTRS)

    Starck, Thomas F.; Brennan, Andrew D.

    1989-01-01

    Lighweight resistance-welding, hand-held gun supplies alternating or direct current over range of 600 to 4,000 A and applies forces from 40 to 60 lb during welding. Used to weld metal sheets in multilayered stacks.

  4. Torch kit for welding in difficult areas

    NASA Technical Reports Server (NTRS)

    Stein, J. A.

    1971-01-01

    Miniature tungsten inert gas welding torch, used with variously formed interchangeable soft copper tubing extensions, provides inexpensive, accurate welding capability for inaccessible joints. Kit effectively welds stainless steel tubing 0.089 cm thick. Other applications are cited.

  5. Closed circuit TV system monitors welding operations

    NASA Technical Reports Server (NTRS)

    Gilman, M.

    1967-01-01

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

  6. Correlates of vernal pool occurrence in the Massachusetts USA, landscape

    USGS Publications Warehouse

    Grant, E.H.C.

    2005-01-01

    Vernal pool wetlands are at risk of destruction across the northeast United States, due in part to their diminutive size and short hydroperiods. These characteristics make it difficult to locate vernal pool habitats in the landscape during much of the year, and no efficient method exists for predicting their occurrence. A logistic regression procedure was used to identify large-scale variables that influence the presence of a potential vernal pool, including surficial geology, land use and land cover, soil classification, topography, precipitation, and surficial hydrologic features. The model was validated with locations of field-verified vernal pools. The model demonstrated that the probability of potential vernal pool occurrence is positively related to slope, negatively related to till/bedrock surficial geology, and negatively related to the proportion of cropland, urban/commercial, and high density residential development in the landscape. The relationship between vernal pool occurrence and large-scale variables suggests that these habitats do not occur at random in the landscape, and thus, protection in situ should be considered.

  7. Array imaging of austenitic welds by measuring weld material map

    NASA Astrophysics Data System (ADS)

    Fan, Z.; Lowe, M.

    2014-02-01

    It is difficult to inspect for defects in austenitic welds ultrasonically due to complicated material properties inside the weld. Weld microstructures typically lead to weld stiffnesses that are both anisotropic and inhomogeneous, so that ultrasonic waves tend to deviate and scatter. A weld performance map is commonly used to describe how the material properties vary throughout the weld, and this idea has been applied to wave propagation models. In this work, we developed a non-destructive method to measure this map using ultrasonic arrays. A material model (previously published by others) with a small number of parameters has been applied to describe the weld performance map. It uses the information of the welding procedure and rules for crystalline growth to predict the orientations, therefore it has a good physical foundation. An inverse model has then been developed to measure the weld performance map based on the matching of predictions by the ray tracing method to selected experimental array measurements. The process is validated by both finite element models and experiments. The results have been applied to correct array images to compensate for deviations of the ultrasonic rays.

  8. Expansion of IgG+ B-Cells during Mitogen Stimulation for Memory B-Cell ELISpot Analysis Is Influenced by Size and Composition of the B-Cell Pool

    PubMed Central

    Langhorne, Jean; Sauerwein, Robert W.

    2014-01-01

    The memory B-cell (MBC) ELISpot assay is the main technique used to measure antigen-specific MBCs as a readout of humoral immune memory. This assay relies on the ability of MBCs to differentiate into antibody-secreting cells (ASC) upon polyclonal stimulation. The total number of IgG+ ASCs generated by mitogen-stimulation is often used as a reference point; alternatively antigen-specific MBCs are expressed as a frequency of post-culture peripheral blood mononuclear cells (PBMC) as a surrogate for absolute frequencies. Therefore, it is important to know whether IgG+ B-cells are uniformly expanded during the preceding mitogen-culture as a true reflection of MBC frequencies ex vivo. We systematically compared B-cell phenotype and proportions before and after mitogen stimulation in cultures of 269 peripheral blood mononuclear cell samples from 62 volunteers by flow cytometry and analyzed the number of resulting ASCs. Our data show that the number of total IgG+ ASCs detected by ELISpot after mitogen stimulation correlates with the proportion of IgG+ MBCs ex vivo, highlighting its general robustness for comparisons of study cohorts at group level. The expansion of total and IgG+ B-cells during mitogen-stimulation, however, was not identical in all cultures, but influenced by size and composition of the ex vivo B-cell compartment. The uncorrected readout of antigen-specific MBCs per million post-culture PBMCs therefore only preserves the quality, but not the magnitude of differences in the ex vivo MBC response between groups or time points, particularly when comparing samples where the B-cell compartment substantially differs between cohorts or over time. Therefore, expressing antigen-specific cells per total IgG+ ASCs is currently the best measure to correct for mitogen-culture effects. Additionally, baseline information on the size and composition of the ex vivo B-cell compartment should be supplied to additionally inform about differences or changes in the size and composition of the ex vivo MBC compartment. PMID:25050555

  9. Ontogenic growth of the haemopoietic stem cell pool in humans

    Microsoft Academic Search

    David Dingli; Jorge M. Pacheco

    2007-01-01

    Recently, the size of the active stem cell pool has been predicted to scale allometrically with the adult mass of mammalian species with a 3\\/4 power exponent, similar to what has been found to occur for the resting metabolic rate across species. Here we investigate the allometric scaling of human haemopoietic stem cells (HSCs) during ontogenic growth and predict a

  10. Using Airborne Sensing to Map Pools in Rivers

    E-print Network

    Walker, Jeff

    appropriate instrumentation ­ Disadvantages: Reliability uncertain, may need ground observation to calibrate ground surveys of pool size and location #12;Instrumentation #12;Flight Path Valley Length: 14 km River-Spectral Line Scanner 1.0m pixels 1250m swath width Raster files #12;LIDAR 1m point spacing 600m swath width

  11. The Past and Future of the British Football Pools

    Microsoft Academic Search

    David Forrest

    1999-01-01

    The introduction of the treble chance game in 1946 allowed the football (soccer) pools industry to flourish in Britain for nearly fifty years. The focus on size of jackpot led to very high concentration in the sector. The near-monopoly situation facilitated a much higher take-out rate than in other gambling media, a situation fully exploited by the government through the

  12. A COMPACT NANOSTRUCTURE INTEGRATED POOL BOILER FOR MICROSCALE COOLING APPLICATIONS

    Microsoft Academic Search

    Cem Baha Akkartal; Tansel Karabacak

    2009-01-01

    An efficient cooling system consisting of a plate, on which copper nanorods (nanorods of size ~100nm) are integrated to copper thin film (which is deposited on Silicon substrate), a heater, the Aluminum base, and a pool was developed. This high efficiency heat transfer equipment has a base of dimensions 6cmx6cm. The base is specially designed to enhance heat transfer with

  13. Strength of welded copper joints

    SciTech Connect

    Kuzyukova, A.N.; Fedorenko, M.I.; Kovalenko, N.I.; Zelik, E.I.

    1983-07-01

    A coefficient of the strength of welded joints in structures of copper and its alloys made by manual arc welding are known. At the Severedonetsk Branch of the Institute of Chemical Engineering the strength coefficients were determined for welded joints made of MZR (phosphorous-deoxydized) copper produced by manual argonarc welding. Optimum welding regimes were selected, and specimens of strips tested for tensile strength. Metallographic investigations showed significant grain growth in the zone of thermal influence. The results of mechanical tests are given. The results are verified by the fabrication of nine models. All the models ruptured in the zone of thermal influence, confirming results that the zone of thermal influence was the weak point in the welded joints in copper.

  14. Allometric Scaling of the Active Hematopoietic Stem Cell Pool across Mammals

    Microsoft Academic Search

    David Dingli; Jorge M. Pacheco; Christopher Arendt

    2006-01-01

    BackgroundMany biological processes are characterized by allometric relations of the type Y = Y0Mb between an observable Y and body mass M, which pervade at multiple levels of organization. In what regards the hematopoietic stem cell pool, there is experimental evidence that the size of the hematopoietic stem cell pool is conserved in mammals. However, demands for blood cell formation

  15. ESTIMATING THE TERRESTIAL CARBON POOLS OF THE FORMER SOVIET UNION, CONTERMINOUS U.S., AND BRAZIL

    EPA Science Inventory

    Terrestrial-carbon (C) pool sizes are of interest in relation to quantifying current sources and sinks of C, and evaluating the possibilities for future C sequestration or release by the biosphere. In this study, the C pools in the terrestrial ecosystems of the former Soviet Unio...

  16. Pool boiling heat transfer on small heaters: effect of gravity and subcooling

    E-print Network

    Kim, Jungho

    Abstract Measurements of space and time resolved subcooled pool boiling of FC-72 in low, earth, and high to increase in size with bulk fluid temperature. Boiling curves at various subcoolings and gravity levelsPool boiling heat transfer on small heaters: effect of gravity and subcooling Jungho Kim a,*, John

  17. DROWNING IN DISINFECTION BY-PRODUCTS? SWIMMING POOL WATER QUALITY RECONSIDERED.

    EPA Science Inventory

    The development of treated water for swimming pools has made swimming a year ¬round activity, widely enjoyed for leisure as well as exercise. Swimming pools can be found in different kinds and sizes in public areas, hotels and spas, or at private homes. In Germany ~250-300 millio...

  18. The 1980-81 AFE Pool: The End of an Era.

    ERIC Educational Resources Information Center

    Knight, Peter

    1981-01-01

    The Advanced Further Education (AFE) Pool was conceived in Britain in the 1950s to distribute public funds for higher education. The 1980-81 pool broke with tradition by having a fixed amount to be apportioned by local authorities rather than having a size determined by institutional needs. The change is seen as fundamentally political. (SE)

  19. Laser beam welding of dissimilar ferritic/martensitic stainless steels in a butt joint configuration

    NASA Astrophysics Data System (ADS)

    Khan, M. M. A.; Romoli, L.; Dini, G.

    2013-07-01

    This paper investigates laser beam welding of dissimilar AISI430F and AISI440C stainless steels. A combined welding and pre-and-postweld treatment technique was developed and used successfully to avoid micro-crack formation. This paper also examined the effects of laser welding parameters and line energy on weld bead geometry and tried to obtain an optimized laser-welded joint using a full factorial design of experiment technique. The models developed were used to find optimal parameters for the desired geometric criteria. All the bead characteristics varied positively as laser power increased or welding speed decreased. Penetration size factor decreased rapidly due to keyhole formation for line energy input in the range of 15-20 kJ/m. Laser power of 790-810 W and welding speed of 3.6-4.0 m/min were the optimal parameters providing an excellent welded component. Whatever the optimization criteria, beam incident angle was around its limiting value of 15° to achieve optimal geometrical features of the weld.

  20. Effect of multiple repairs in girth welds of pipelines on the mechanical properties

    SciTech Connect

    Vega, O.E.; Hallen, J.M. [Departamento de Ingenieria Metalurgica, ESIQIE-IPN, Laboratorios Pesados de Metalurgia, UPALM, Zacatenco, C.P. 07738, Mexico D.F. (Mexico); Villagomez, A. [Construcciones Maritimas Mexicanas, CMM-PROTEXA, Av. Periferica s/n, Fracc. Lomas de Holche, C.P. 24120, Cd. del Carmen, Campeche (Mexico); Contreras, A. [Instituto Mexicano del Petroleo, Investigacion en Ductos, Corrosion y Materiales, Eje Central Lazaro Cardenas Norte 152 Col. San Bartolo Atepehuacan, C.P. 07730, Mexico D.F. (Mexico)], E-mail: acontrer@imp.mx

    2008-10-15

    This work presents the results of multiple weld repairs in the same area in seamless API X-52 microalloyed steel pipe. Four conditions of shielded metal arc welding repairs and one as-welded specimen of the girth weld were characterized to determine changes in the microstructure, grain size in the heat affected zone, and to evaluate their effect on the mechanical properties of the weld joints. The mechanical properties by means of tension tests, Charpy-V impact resistance and Vickers hardness of the welds were analyzed. The results indicate that significant changes are not generated in the microstructural constituents of the heat affected zone. Grain growth in the heat affected zone at the specimen mid-thickness with the number of repairs was observed. Tensile strength of the weld joints meets the requirement of the API 1104 standard even after the fourth weld repair. Significant reduction in Charpy-V impact resistance with the number of weld repairs was found when the notch location was in the intersection of the fusion line with the specimen mid-thickness. A significant increase in the Vickers hardness of the heat affected zone occurred after the first repair and a gradual decrease in the Vickers hardness occurred as the number of repairs increases.