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1

Weld pool phenomena  

SciTech Connect

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.

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

2

A novel control algorithm for weld pool control  

Microsoft Academic Search

Purpose – Quality control of arc welding process is the key component in robotic welding system. The purpose of this paper is to address vision-sensing technology and model-free adaptive control (MFC) of weld pool size during automatic arc welding system. Design\\/methodology\\/approach – The shape and size parameters for the weld pool are used to describe the weld pool geometry, which

Fenglin Lü; Huabin Chen; Chongjian Fan; Shanben Chen

2010-01-01

3

Weld pool oscillation during pulsed GTA welding  

SciTech Connect

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

Aendenroomer, A.J.R.; Ouden, G. den [Delft Univ. of Technology (Netherlands)

1996-12-31

4

A unified model of coupled arc plasma and weld pool for double electrodes TIG welding  

NASA Astrophysics Data System (ADS)

A three-dimensional model containing tungsten electrodes, arc plasma and a weld pool is presented for double electrodes tungsten inert gas welding. The model is validated by available experimental data. The distributions of temperature, velocity and pressure of the coupled arc plasma are investigated. The current density, heat flux and shear stress over the weld pool are highlighted. The weld pool dynamic is described by taking into account buoyance, Lorentz force, surface tension and plasma drag force. The turbulent effect in the weld pool is also considered. It is found that the temperature and velocity distributions of the coupled arc are not rotationally symmetrical. A similar property is also shown by the arc pressure, current density and heat flux at the anode surface. The surface tension gradient is much larger than the plasma drag force and dominates the convective pattern in the weld pool, thus determining the weld penetration. The anodic heat flux and plasma drag force, as well as the surface tension gradient over the weld pool, determine the weld shape and size. In addition, provided the welding current through one electrode increases and that through the other decreases, keeping the total current unchanged, the coupled arc behaviour and weld pool dynamic change significantly, while the weld shape and size show little change. The results demonstrate the necessity of a unified model in the study of the arc plasma and weld pool.

Wang, Xinxin; Fan, Ding; Huang, Jiankang; Huang, Yong

2014-07-01

5

Camera Would Monitor Weld-Pool Contours  

NASA Technical Reports Server (NTRS)

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.

Gordon, Stephen S.; Gutow, David A.

1990-01-01

6

Vision-based weld pool width control  

SciTech Connect

Methods for controlling weld penetration for arc welding processes from top-side measurements have long been sought. One indirect variable that has been reported to correlate with penetration is weld pool geometry. A system which uses weld pool geometry sensing for controlling weld penetration is described in this paper. The system uses a miniature camera mounted in a modified coaxial viewing torch to view the weld pool. A robust machine vision algorithm has been developed for this system to measure weld pool width. The algorithm was designed to locate the edges of the weld pool despite the presence of other edges caused by the heat affected zone, scratches, marks, and weld pool impurities. The algorithm uses a matched edge filter and a majority voting scheme to measure the width of the pool. A control system was developed to regulate weld pool width in the presence of disturbances caused by such items as incorrect parameter settings, small variations in material composition, and material thickness changes. Experiments were conducted to test the control system by simulating some of these disturbances. The experiments demonstrated that for certain classes of materials, this technique works quite well. However, for other materials such as stainless steel 304, surface impurities in the weld pool visually obscure the weld pool and its edges to such a degree that the system fails to lock onto the edges of the pool.

Pietrzak, K.A.; Packer, S.M. (United Technologies Research Center, East Hartford, CT (United States))

1994-02-01

7

Role of welding parameters in determining the geometrical appearance of weld pool  

SciTech Connect

A three-dimensional numerical model is developed to describe the fluid flow and heat transfer in weld pools. Both full penetration and free deformation of the top and bottom weld pool surfaces are considered. Temperature distribution and fluid flow field are obtained. In order to analyze the influence of welding parameters on the geometrical appearance of weld pools, a normalized model is developed to characterize the geometrical appearance of weld pools. It is found that welding current can significantly affect the geometrical shape. When welding current increases, the curvature of the pool boundary at the trailing end increases. The effect of the welding speed on the geometrical appearance is slight, although its influence on the pool size is great. In the interest range of arc length (from 1 mm to 4 mm), the arc length can affect both the size and the shape of the weld pool. However, compared with the welding current and speed, its influences are much weaker, GTA welding experiments are performed to verify the validity of the numerical models. The appearance of weld pools was obtained by using machine vision and a high-shutter speed camera. It is found that the calculated results have a good agreement with the experimental ones.

Kovacevic, R.; Cao, Z.N.; Zhang, Y.M. [Univ. of Kentucky, Lexington, KY (United States). Center for Robotics and Manufacturing Systems

1996-10-01

8

Numerical simulation of weld pool geometry in laser beam welding  

NASA Astrophysics Data System (ADS)

A linear correlation between the depth and the length of the weld pool is found in laser beam welding experiments with varied laser beam power and constant welding speed. On the other hand, the weld pool length changes only slightly with increased welding speed and constant laser beam power. The existing analytical and numerical models fail to explain these dependences. The observed effects are essentially conditioned by the fluid flow in the weld pool caused by the thermocapillary effect, by the friction forces of the metal vapour passing through the capillary and by the convexity of weld pool and fusion zone caused by thermal expansion of the weld pool and the joined workpieces. In order to predict the weld pool length more accurately the model developed by Sudnik et al in 1996 is enlarged by the heat transport produced by the recirculating flow in radial sections of the weld pool. Verification of the model for 16MnCr5 steel with sheet thicknesses of 2 and 6 mm shows that it is suitable for predicting the weld pool geometry and for analysing the thermodynamics of the process. In order to gain a better understanding of the structure of heat transport in the weld pool, the different modes of transport are compared in respect of their contribution to the depth-to-length ratio of the weld pool. A calculation of the weld pool length for welding speeds of 1-8 m min-1 with a laser beam power of 2.5 kW shows that the relative contributions of the transport modes are as follows. Approximately 50-90% of the weld pool length (increasing with welding speed) results from conductive and translatory heat transport (with the fusion zone convexity contributing approximately 20-30%). The remaining 50-10% of the weld pool length (decreasing with welding speed) result from convective heat transport. The model predicts the shoulder in the weld pool trough. It also explains the change in the weld pool length by the effect of the gap width, by the transition from through welding to penetration welding and by improvements in beam quality.

Sudnik, W.; Radaj, D.; Breitschwerdt, S.; Erofeew, W.

2000-03-01

9

Weld pool oscillation during GTA welding of mild steel  

SciTech Connect

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

Xiao, Y.H.; Ouden, G. den (Delft Univ. of Tech., Delft (Netherlands). Dept. of Materials Science and Engineering)

1993-08-01

10

Numerical simulation on interaction between TIG welding arc and weld pool  

Microsoft Academic Search

The interface deformation between welding arc and weld pool is important in dynamic coupling numerical simulation on arc and pool. To reveal the interaction between welding arc and weld pool, unified mathematic model of TIG welding arc and pool was established in this paper. The moving interface was solved by updating the calculation region of arc and weld pool continually.

Fenggui Lu; Xinhua Tang; Hailiang Yu; Shun Yao

2006-01-01

11

Neural control of weld pool in the robotic welding  

Microsoft Academic Search

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

Yasuyoshi Kaneko; Satoshi Yamane; Katsuya Kugai; Kenji Ohshima

1994-01-01

12

Numerical Study for Gta Weld Shape Variation by Coupling Welding Arc and Weld Pool  

Microsoft Academic Search

A numerical modeling of the welding arc and weld pool is studied for moving GTA welding to investigate the effect of the surface active element oxygen and the plasma drag force on the weld shape. Based on the 2D axisymmetric numerical modeling of the argon arc, the heat flux, current density and plasma drag force are obtained under different welding

Wenchao Dong; Shanping Lu; Dianzhong Li; Yiyi Li

2009-01-01

13

Numerical Study for Gta Weld Shape Variation by Coupling Welding Arc and Weld Pool  

NASA Astrophysics Data System (ADS)

A numerical modeling of the welding arc and weld pool is studied for moving GTA welding to investigate the effect of the surface active element oxygen and the plasma drag force on the weld shape. Based on the 2D axisymmetric numerical modeling of the argon arc, the heat flux, current density and plasma drag force are obtained under different welding currents. Numerical calculations to the weld pool development are carried out for moving GTA welding on SUS304 stainless steel with different oxygen contents 30 ppm and 220 ppm, respectively. The results show that the plasma drag force is another dominating driving force affecting the liquid pool flow pattern, except for the Marangoni force. The different welding currents will change the temperature distribution and plasma drag force on the pool surface, and affect the strength of Marangoni convection and the weld shape. The weld D/W ratio initially increases, followed by a constant value around 0.5 with the increasing welding current under high oxygen content. The weld D/W ratio under the low oxygen content slightly decreases with the increasing welding current. The predicted weld shape by simulation agrees well with experimental results.

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

14

Heat and fluid flow in pulsed current GTA weld pool  

Microsoft Academic Search

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

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

1998-01-01

15

A shape optimization formulation of weld pool determination. , A. Ellabibb  

E-print Network

A shape optimization formulation of weld pool determination. A. Chakiba , A. Ellabibb , A modeling a process of welding. We show the existence of an optimal solution. The finite element method technique using a parameterization of the weld pool by B´ezier curves and Genetic algorithms. Keywords

Paris-Sud XI, Université de

16

Influence of Arc Pressure on Weld Pool Geometry  

E-print Network

) ) Influence of Arc Pressure on Weld Pool Geometry A new model of a compound vortex is proposed,7,8) based on the assumption that the arc pressure depresses the sur- face of the weld pool. An analytical scales parabolically with weld current (Ref. 11). Arc pressure also will not explain why one current

Eagar, Thomas W.

17

The effect of the cathode tip angle on the gas tungsten arc welding arc and weld pool: II. The mathematical model for the weld pool  

Microsoft Academic Search

In part I, the effect of the electrode tip angle on the arc properties was investigated. In part II, a mathematical model for the weld pool is developed in order to study the effect of the electrode tip angle on the weld pool properties. The information required to simulate the flow in the weld pool including the heat flux to

Massoud Goodarzi; Roland Choo; Tomio Takasu; James M. Toguri

1998-01-01

18

Weld pool flow visualization studies during gas tungsten arc welding of steel and aluminum. Master's thesis  

SciTech Connect

A flow visualization study of current distribution effects on weld pool stirring in GTA steel welds is presented using a pulsed ultraviolet laser vision system. Weld pool stirring is almost eliminated in HY-80 steel by the use of symmetric current flow path within the weld samples. Periodic radial surface pulses are observed at low currents in stationary welds while flows of turbulent nature are observed at higher currents. Autogenous welds on 17.75 cm by 28.0 cm by 1.27 cm thick 6061 aluminum plates are also studied to determine resulting surface flow characteristics and weld pool growth rates. Clockwise stirring in conjunction with a vertical undulation is noted in stationary welds. Solidified weld zone exhibits a profound crater that was not present in welds on HY-80 Steel.

Schupp, P.E.

1992-03-01

19

A model-free adaptive control of welding pool dynamics during arc welding  

Microsoft Academic Search

Arc welding process is characterized as nonlinear, time varying, and uncertain. So it is very difficult to design an effective control scheme by conventional modeling and control methods. Quality control of arc welding process is the key component in robotic welding system. This paper addresses model-free adaptive control with functional reinforce of Al alloy weld pool dynamics during pulsed gas

F. L. Lu; J. F. Wang; C. J. Fan; S. B. Chen

2008-01-01

20

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

Microsoft Academic Search

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

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

2001-01-01

21

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

NASA Astrophysics Data System (ADS)

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.

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

2010-10-01

22

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

Microsoft Academic Search

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

S. C Juang; Y. S Tarng

2002-01-01

23

Characterizing weld pool surfaces from polarization state of thermal emissions.  

PubMed

In this Letter, a vision-based remote sensing methodology is proposed to measure the topography of weld pool surfaces from one single view. Thermal radiations emitted by the hot liquid metal at a wavelength within the arc plasma blind spectral window are acquired by a wavefront division polarimetric system. The refractive index of the liquid metal and the topography of the weld pool surface are inferred from the polarimetric state of the thermal radiations. PMID:23938985

Coniglio, Nicolas; Mathieu, Alexandre; Aubreton, Olivier; Stolz, Christophe

2013-06-15

24

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

E-print Network

- CHANGES OF WELD POOL SHAPE BY VARIATIONS IN THE DISTRIBUTION OF HEAT SOURCE IN ARC WELDING N. S of Technology Cambridge, HA 02139 USA Summar y Weld width , penetr ation, and cross-sectional ar ea were presented as a function of heat input and arc heat dist ribution parameter in dimensionless forms

Eagar, Thomas W.

25

Bubble flow and the formation of cavity defect in weld pool of vacuum electron beam welding  

Microsoft Academic Search

Seen from gas-liquid two-phase-flow system, the gas phase and liquid phase of bubble flow in weld pool are studied by means of isolated phase based on the conservation of mass and momentum. The two-dimensional fractional flow model of bubble flow in weld pool of vacuum electron beam welding is developed. And the gas distribution and the phenomenon of bubble flow

Yi Luo; Jinhe Liu; Hong Ye

2011-01-01

26

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

SciTech Connect

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.

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

1993-08-01

27

THESIS FOR THE DEGREE OF LICENTIATE OF PHILOSOPHY Weld Pool Simulations  

E-print Network

THESIS FOR THE DEGREE OF LICENTIATE OF PHILOSOPHY Weld Pool Simulations Marcus Edstorp Department;Weld Pool Simulations Marcus Edstorp c Marcus Edstorp, 2008 NO 2008:19 ISSN 1652-9715 Department of a gas metal arc fillet welding process. The shape of the weld pool surface is visualized by arrows

Patriksson, Michael

28

Sensing of the weld pool depth with neural network and fuzzy control of seam tracking  

Microsoft Academic Search

Deals with the problem concerning the sensing of the weld pool and the tracking of the welding line with welding robots. In order to obtain a good quality of the welding result, it is important to control the weld pool depth and to keep the torch posture constant regardless of the external disturbance. First, a new method is proposed for

Y. Kaneko; T. Iisaka; A. Tanaka; Peijun Ma; S. Yamane; K. Ohshima

1993-01-01

29

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

E-print Network

Convection in Arc Weld Pools Electromagnetic and surface tension forces are shown to dominate flow behavior/ in some cases producing double circulation loops in the weld pool BY G. M. OREP.ER, T. W. EAGAR and temperature distributions in sta- tionary arc weld pools driven by buoyan- cy, electromagnetic and surface

Eagar, Thomas W.

30

Stability of Full Penetration, Flat Position Weld Pools  

NASA Technical Reports Server (NTRS)

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.

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

1999-01-01

31

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

Microsoft Academic Search

Gas metal arc welding (GMAW) is the most commonly used arc welding method in industry for joining steels and aluminum alloys. But due to the mathematical difficulties associated with the free surface motion of the molten droplet and the weld pool, the process is not well understood and the development of new welding procedures in the manufacturing industry highly depends

Fang Wang

2003-01-01

32

Weld pool development during GTA and laser beam welding of Type 304 stainless steel; Part II-experimental correlation  

SciTech Connect

In part I of the paper, the results of the heat flow and the fluid flow analysis were presented. Here, in Part II of the paper, predictions of the computational model are verified by comparing the numerically predicted and experimentally observed fusion zone size and shape. Stationary gas tungsten arc and laser beam welds were made on Type 304 stainless steel for different times to provide a variety of solidification conditions such as cooling rate and temperature gradient. Calculated temperatures and cooling rates are correlated with the experimentally observed fusion zone structure. In addition, the effect of sulfur on GTA weld penetration was quantitatively evaluated by considering two heats of 304 stainless steel containing 90 and 240 ppm sulfur. Sulfur, as expected, increased the depth/width ratio by altering the surface tension gradient driven flow in the weld pool.

Zacharia, T.; David, S.A.; Vitek, J.M. (Metals and Ceramics Div., Oak Ridge National Lab, Oak Ridge, TN (USA)); Debroy, T. (Dept. of Materials Science and Engineering, Pennsylvania State Univ, Univ Park, PA (USA))

1989-12-01

33

INFLUENCE OF SURFACE DEPRESSION AND CONVECTION ON ARC WELD POOL GEOMETRY  

E-print Network

) ) INFLUENCE OF SURFACE DEPRESSION AND CONVECTION ON ARC WELD POOL GEOMETRY M. L. Lin and T. W~ penetra- tion in stationary GTA welds has been studied. The results indi cate that a deep crater depr ession forms on the surface of a steel weld pool at currents in excess of 250 amperes. During

Eagar, Thomas W.

34

Reflection of illumination laser from gas metal arc weld pool surface  

NASA Astrophysics Data System (ADS)

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.

Ma, Xiaoji; Zhang, Yu Ming

2009-11-01

35

Electrochemical effects on weld pool chemistry in submerged arc and dc electroslag welding  

SciTech Connect

Electrochemical reactions could be an important factor governing the chemistry of weld pools in dc welding. The anodic reaction at the weld wire-slag interface leads to a relatively high Po/sub 2/ which leads to the formation of an oxide nO/sup 2 -/ + M(metal) ..-->.. MO/sub n/ + 2ne where M is a metal at the weld wire-slag interface and n is related to the valence of M in the oxide. After the molten weld wire forms a droplet which separates from the wire, the electrochemical reaction ceases and the oxide dissolves in the flux. The cathodic reactions at the weld pool lead to the electrodeposition of metals M/sup 2 +/(slag) + 2e ..-->.. M(metal); Si/sup 4 +/(slag) + 4e ..-->.. Si(metal) where M can be Fe/sup 2 +/, Mn/sup 2 +/. or other metals which are electrodeposited at the interface. The relative amounts of all these deposits wil be readjusted by chemical reactions such as Si(metal) + 2MO(slag) ..-->.. SiO/sub 2/(slag) + 2M(metal); Mn(metal) + FeO(slag) ..-->.. MnO(slag) + Fe(metal). The resultant changes in the compositions of the weld metal and the slag depend on the rates of the electrodeposition reactions relative to the rates of the back reactions. If the proposed mechanism is correct, experimental data would indicate that both the electrochemical and back reactions appear to be important. Analogous electrochemical reactions can occur at metal-plasma interfaces.

Blander, M.; Olson, D.L.

1986-01-01

36

Experimental and numerical studies on three dimensional GTA weld pool convection: Non-axisymmetric effects  

SciTech Connect

Observations of surface flow patterns of steel and aluminum GTAW pools have been made using a pulsed laser visualization system. The weld pool convection is found to be three dimensional, with the azimuthal circulation depending on the location of the clamp with respect to the torch. Oscillation of steel pools and undulating motion in aluminum weld pools are also observed even with steady process parameters. Current axisymmetric numerical models are unable to explain such phenomena. A three dimensional computational study is carried out in this study to explain the rotational flow in aluminum weld pools.

Joshi, Y. [Univ. of Maryland, College Park, MD (United States). Dept. of Mechanical Engineering; Dutta, P. [Columbia Univ., New York, NY (United States). Dept. of Mechanical Engineering; Schupp, P.E.; Espinosa, D. [Naval Postgraduate School, Monterey, CA (United States). Dept. of Mechanical Engineering

1995-12-31

37

Weld pool development during GTA and laser beam welding of Type 304 stainless steel; Part I - theoretical analysis  

SciTech Connect

A computational and experimental study was carried out to quantitatively understand the influence of the heat flow and the fluid flow in the transient development of the weld pool during gas tungsten arc (GTA) and laser beam welding of Type 304 stainless steel. Stationary gas tungsten arc and laser beam welds were made on two heats of Type 304 austenitic stainless steels containing 90 ppm sulfur and 240 ppm sulfur. A transient heat transfer model was utilized to simulate the heat flow and fluid flow in the weld pool. In this paper, the results of the heat flow and fluid flow analysis are presented.

Zacharia, T.; David, S.A.; Vitek, J.M. (Metals and Ceramics Div., Oak Ridge National Lab., Oak Ridge, TN (USA)); Debroy, T. (Dept. of Materials Science and Engineering, Pennsylvania State Univ., University Park, PA (USA))

1989-12-01

38

Detectability of penetration depth based on weld pool geometry and process emission spectrum in laser welding of copper  

NASA Astrophysics Data System (ADS)

Laser welding is a promising joining process for copper interconnections. A key criterion of quality for these welds is the penetration depth. The penetration depth is subject to intrinsic variation, i.e. by the nature of the welding process. Online detection of penetration depth enables quality assurance and furthermore welding of joint configurations with tighter tolerances via closed-loop control. Weld pool geometry and keyhole optical emission in the wavelength interval of 400-1100 nm are investigated with regard to how suitable they are for the detection of penetration depth in laser welding of copper Cu-ETP. Different penetration depths were induced by stepwise modulation of laser power in bead-on-plate welds. The welds have been monitored with illuminated high-speed videography of the work piece surface and spectrometry. Increase of the weld pool length (in direction of travel) corresponding to increase in penetration depth has been observed while no noticeable change was observed of the weld pool width (transverse to the direction of travel). No significant lines were observed in the spectrum. The radiant power in VIS-spectrum was observed to increase with increasing penetration depth as well. As future work, with increasing understanding and experimental data, online monitoring by indirectly measuring the penetration depth would be possible. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no 260153 (QCOALA: Quality Control for Aluminium Laser-Welded Assemblies).

Ã-zmert, Alp; Neisser-Deiters, Paul; Drenker, Alexander

2014-05-01

39

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

NASA Astrophysics Data System (ADS)

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.

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

1998-10-01

40

Sizing Multiple Buffer Pools for A thesis submitted to the  

E-print Network

objects to buffer pools and the setting the size for each of the buffer pools, is crucial for achieving wife, Jie Lu, for their love, support, and encouragement in these years. #12;iii Contents Abstract

41

Measurement of laser welding pool geometry using a closed convex active contour model  

NASA Astrophysics Data System (ADS)

The purpose of this study was to develop a computer vision method to measure geometric parameters of the weld pool in a deep penetration CO2 laser welding system. Accurate measurement was achieved by removing a huge amount of interference caused by spatter, arc light and plasma to extract the true weld pool contour. This paper introduces a closed convex active contour (CCAC) model derived from the active contour model (snake model), which is a more robust high-level vision method than the traditional low-level vision methods. We made an improvement by integrating an active contour with the information that the weld pool contour is almost a closed convex curve. An effective thresholding method and an improved greedy algorithm are also given to complement the CCAC model. These influences can be effectively removed by using the CCAC model to acquire and measure the weld pool contour accurately and relatively fast.

Zheng, Rui; Zhang, Pu; Duan, Aiqing; Xiao, Peng

2014-03-01

42

Simulation of grain morphologies and competitive growth in weld pool of Ni-Cr alloy  

NASA Astrophysics Data System (ADS)

Grain morphologies in the weld pool of Ni-Cr alloy are simulated using a multi-scale numerical model based on cellular automaton algorithm. Depending on the CA-FD model with diagonal simulating angle method, the competitive growth process between columnar dendrite grains with different crystallographic orientations and the competitive growth process between columnar grain and equiaxed grain in a finite two-dimension zone of the weld pool are simulated. The simulated results reproduced the grain morphology evolution as well as the solute distribution during the solidification process of the weld pool. It is indicated that the complicated thermal field and solute field can result in complex grain morphologies in the weld pool. The grain boundary segregations in the weld seam are remarkable and they become more severe when there is competitive growth between columnar grains and equiaxed grains.

Zhan, X. H.; Dong, Z. B.; Wei, Y. H.; Ma, R.

2009-12-01

43

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

NASA Astrophysics Data System (ADS)

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.

Zhang, WeiJie; Wang, XueWu; Zhang, YuMing

2013-11-01

44

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

NASA Astrophysics Data System (ADS)

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

Wang, Fang

45

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

SciTech Connect

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.

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

2007-09-01

46

Weld pool penetration measurement using ultrasound with thermal gradient correction factors  

NASA Astrophysics Data System (ADS)

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.

Anderton, John Martin

47

Applications Of Reflective High-Speed Photography In Research Of Welding Molten Pools  

NASA Astrophysics Data System (ADS)

By making comparison between a few types of light sources, a removable and adjustable xenon light source had been successfully trial-produced to take clear photos of welding arc, metal transfer and molten pools. In the procession of investigating the technology of reflective high-speed photography, some problems for taking photos of welding arc, solidification of molten metal, especially the molten pools have been solved. This method has put into use in some research subjects and practical applications, such as "Welding Mechanism Research with Quartz-backing". "Comparison of Electrode Properties for Vertical-downwards Welding", and "Welder's Pressure Vessel-Welding Operating Demonstration", etc. the results were satisfactory and were praised by the profession of welding in China.

Xiaomin, Gu; Yuiiong, Ma

1989-06-01

48

Residual Stresses and Critical Initial Flaw Size Analyses of Welds  

NASA Technical Reports Server (NTRS)

An independent assessment was conducted to determine the critical initial flaw size (CIFS) for the flange-to-skin weld in the Ares I-X Upper Stage Simulator (USS). A series of weld analyses are performed to determine the residual stresses in a critical region of the USS. Weld residual stresses both increase constraint and mean stress thereby having an important effect on the fatigue life. The purpose of the weld analyses was to model the weld process using a variety of sequences to determine the 'best' sequence in terms of weld residual stresses and distortions. The many factors examined in this study include weld design (single-V, double-V groove), weld sequence, boundary conditions, and material properties, among others. The results of this weld analysis are included with service loads to perform a fatigue and critical initial flaw size evaluation.

Brust, Frederick W.; Raju, Ivatury, S.; Dawocke, David S.; Cheston, Derrick

2009-01-01

49

Study on moving GTA weld pool in an externally applied longitudinal magnetic field with experimental and finite element methods  

Microsoft Academic Search

Under the control of external longitudinal magnetic field, substantial changes happen to ordinary gas tungsten arc welding (GTAW) process. In this paper, mathematical models of fluid flow and heat transfer of external longitudinal magnetic field moving GTAW three-dimensional weld pool were established. Current density distribution on weld pool surface was obtained by probe method. Using the multi-coupled analysis function of

Li Yongbing; Lin Zhongqin; Chen Guanlong; Wang Yasheng; Xi Shengyin

2002-01-01

50

TOPICAL REVIEW: Predictions of weld pool profiles using plasma physics  

Microsoft Academic Search

This paper gives a review of recent papers which have led to the capability of the prediction of weld depths for gas tungsten arc welding, for any given arc current, electrode shape or separation and welding gas. The methodology is given for deriving plasma composition as a function of temperature and pressure from basic atomic and molecular properties. Transport coefficients

M. Tanaka; J. J. Lowke

2007-01-01

51

Mitochondrial Deoxyribonucleotides, Pool Sizes, Synthesis, and Regulation*  

E-print Network

the phosphorylation of thymidine by the mt thy- midine kinase. The synthesis of DNA requires a supply with nuclear DNA rep- lication (1). In resting cells the de novo synthesis of deoxyribo- nucleotides is shut in mitochon- dria not in equilibrium with cytosolic dNTP pools serve the synthesis of mt DNA. Seminal reports

Bianchi, Vera

52

Effect of adhesive on molten pool structure and penetration in laser weld bonding of magnesium alloy  

NASA Astrophysics Data System (ADS)

Laser weld bonding (LWB) is a new hybrid technique that combines adhesive bonding with laser seam welding together, and can achieve higher joint strength than adhesive bonding or laser welding individually. Some new physical phenomena have been observed in this welding method, and the phenomena are different from the normal laser welding process, such as a remarkable deeper penetration in LWB than that in laser welding direct (LWD). The adhesive-induced gas can influence the molten pool structure in front of the keyhole, so that less energy is required for laser keyhole through the upper sheet; thus, higher laser power density can interact with the lower sheet, leading to deeper penetration. Simulation comparison experiments are set to indirectly verify these conclusions above.

Liu, L. M.; Ren, D. X.

2010-09-01

53

Temperature and size variabilities of the Western Pacific Warm Pool  

NASA Technical Reports Server (NTRS)

Variabilities in sea-surface temperature and size of the Western Pacific Warm Pool were tracked with 10 years of satellite multichannel sea-surface temperature observations from 1982 to 1991. The results show that both annual mean sea-surface temperature and the size of the warm pool increased from 1983 to 1987 and fluctuated after 1987. Possible causes of these variations include solar irradiance variabilities, El Nino-Southern Oscillaton events, volcanic activities, and global warming.

Yan, Xiao-Hai; Ho, Chung-Ru; Zheng, Quanan; Klemas, Vic

1992-01-01

54

Weld pool temperatures of steel S235 while applying a controlled short-circuit gas metal arc welding process and various shielding gases  

NASA Astrophysics Data System (ADS)

The temperature determination of liquid metals is difficult and depends strongly on the emissivity. However, the surface temperature distribution of the weld pool is an important characteristic of an arc weld process. As an example, short-arc welding of steel with a cold metal transfer (CMT) process is considered. With optical emission spectroscopy in the spectral region between 660 and 840 nm and absolute calibrated high-speed camera images the relation between temperature and emissivity of the weld pool is determined. This method is used to obtain two-dimensional temperature profiles in the pictures. Results are presented for welding materials (wire G3Si1 on base material S235) using different welding CMT processes with CO2 (100%), Corgon 18 (18% CO2 + 82% Ar), VarigonH6 (93.5% Ar + 6.5% H2) and He (100%) as shielding gases. The different gases are used to study their influence on the weld pool temperature.

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

2013-11-01

55

Modeling Methods of Weld Pool Dynamics During Pulsed GTAW  

Microsoft Academic Search

GTAW is a thermal process during which the workpiece melts, solidifies and finally forms the welding seam. As is well known,\\u000a arc welding is influenced by many complex factors, such as material metallurgy, heat conduction, physical chemistry reactions,\\u000a etc. Due to its multi-variable coupling, nonlinear, time-varying, random and uncertain properties, GTAW dynamics is difficult\\u000a to be modelled by classical linear

Shan-Ben Chen; Jing Wu

56

Arc welding robot system with seam tracking and weld pool control based on passive vision  

Microsoft Academic Search

The automatic control in square-wave alternating current (AC) gas tungsten arc welding (GTAW) is significant for a “teach\\u000a and playback” robot to overcome the variation of the seam trajectory and the seam gap in the welding process. This paper presents\\u000a a welding robot system based on the real-time visual measurement in the different levels of the welding current. The primary

Hong-yuan Shen; Jing Wu; Tao Lin; Shan-ben Chen

2008-01-01

57

Dynamic Approach Of The Keyhole And Melt Pool Behavior For Deep Penetration Nd-Yag Laser Welding  

Microsoft Academic Search

This paper contains our last results concerning the understanding of fundamental processes occurring inside metallic melt pool produced during deep penetration CW Nd-Yag laser welding. When the welding speed varies from a few m\\/min to a few tens of m\\/min, one can observe that melt pool behavior has very different and complex hydrodynamics. At low welding speed, the keyhole appears

Rémy Fabbro

2008-01-01

58

Study on image acquisition in 3-D sensor system of arc welding pool surface shape using grating projection  

NASA Astrophysics Data System (ADS)

Detecting 3-D information on welding pool surface shape is difficult due to the arc light interference, high temperature radiation and pool surface specular reflection. The characteristics of mirror like reflection on pool of liquid surface are studied. Besides the way to obtain clear information-rich image of the pool area is discussed under the strong arc light. Because of the strong arc light above the pool will affect the imaging of the relatively weaker laser stripes seriously, we need to choose a suitable shooting angle and shooting distance to achieve well image. According to all these factors, the optimal combination of the sensing structure parameters in theory is deduced. Based on this work, a vision detecting of arc welding pool surface topography system was putted up in our laboratory, also actual measurement was carried out to obtain more clear images of deformation laser stripes in welding pool. This will provide the three-dimensional reconstruction a strong support.

Ai, Xiaopu; Liu, Nansheng; Wei, Yiqing; Hu, Xian; Wei, Sheng; Liu, Xiaorui

2009-11-01

59

Surface temperature distribution of GTA weld pools on thin-plate 304 stainless steel  

SciTech Connect

A transient multidimensional computational model was utilized to study gas tungsten arc (GTA) welding of thin-plate 304 stainless steel (SS). The model eliminates several of the earlier restrictive assumptions including temperature-independent thermal-physical properties. Consequently, all important thermal-physical properties were considered as temperature dependent throughout the range of temperatures experienced by the weld metal. The computational model was used to predict surface temperature distribution of the GTA weld pools in 1.5-mm-thick AISI 304 SS. The welding parameters were chosen so as to correspond with an earlier experimental study that produced high-resolution surface temperature maps. One of the motivations of the present study was to verify the predictive capability of the computational model. Comparison of the numerical predictions and experimental observations indicate excellent agreement, thereby verifying the model.

Zacharia, T.; David, S.A.; Vitek, J.M. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.; Kraus, H.G. [EG and G Idaho, Inc., Idaho Falls, ID (United States). Idaho National Engineering Lab.

1995-11-01

60

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

NASA Astrophysics Data System (ADS)

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.

Akinlabi, E. T.

2012-07-01

61

On the calculation of the free surface temperature of gas-tungsten-arc weld pools from first principles: Part I. modeling the welding arc  

Microsoft Academic Search

A mathematical formulation has been developed and computed results are presented describing the temperature profiles in gas\\u000a tungsten arc welding (GTAW) arcs and, hence, the net heat flux from the welding arc to the weld pool. The formulation consists\\u000a of the statement of Maxwell's equations, coupled to the Navier-Stokes equations and the differential thermal energy balance\\u000a equation. The theoretical predictions

R. T. C. Choo; J. Szekely; R. C. Westhoff

1992-01-01

62

Lin28a regulates germ cell pool size and fertility  

PubMed Central

Overexpression of LIN28A is associated with human germ cell tumors and promotes primordial germ cell (PGC) development from embryonic stem cells in vitro and in chimeric mice. Knockdown of Lin28a inhibits PGC development in vitro, but how constitutional Lin28a deficiency affects the mammalian reproductive system in vivo remains unknown. Here, we generated Lin28a knockout (KO) mice and found that Lin28a deficiency compromises the size of the germ cell pool in both males and females by affecting PGC proliferation during embryogenesis. Interestingly however, in Lin28a KO males the germ cell pool partially recovers during postnatal expansion, while fertility remains impaired in both males and females mated to wild type mice. Embryonic overexpression of let-7, a microRNA negatively regulated by Lin28a, reduces the germ cell pool, corroborating the role of the Lin28a/let-7 axis in regulating the germ lineage. PMID:23378032

Shinoda, Gen; de Soysa, T. Yvanka; Seligson, Marc T.; Yabuuchi, Akiko; Fujiwara, Yuko; Huang, Pei Yi; Hagan, John P.; Gregory, Richard I.; Moss, Eric G.; Daley, George Q.

2013-01-01

63

Penetration in GTA welding  

SciTech Connect

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

Heiple, C.R.; Burgardt, P.

1990-01-01

64

Simulation of grain morphologies and competitive growth in weld pool of Ni–Cr alloy  

Microsoft Academic Search

Grain morphologies in the weld pool of Ni–Cr alloy are simulated using a multi-scale numerical model based on cellular automaton algorithm. Depending on the CA-FD model with diagonal simulating angle method, the competitive growth process between columnar dendrite grains with different crystallographic orientations and the competitive growth process between columnar grain and equiaxed grain in a finite two-dimension zone of

X. H. Zhan; Z. B. Dong; Y. H. Wei; R. Ma

2009-01-01

65

10 CFR 905.32 - Resource extensions and resource pool size.  

Code of Federal Regulations, 2010 CFR

...Resource extensions and resource pool size. 905.32 Section 905.32 Energy DEPARTMENT OF ENERGY ENERGY PLANNING AND MANAGEMENT PROGRAM Power Marketing Initiative § 905.32 Resource extensions and resource pool size....

2010-01-01

66

Relationship between spatter formation and dynamic molten pool during high-power deep-penetration laser welding  

NASA Astrophysics Data System (ADS)

The spatter and the molten pool behavior, which were the important phenomena concerned with the welding quality, were observed and studied by using the high-speed camera and the X-ray transmission imaging system during laser welding under different welding parameters. The formation mechanism of spatter and the corresponding relationships between the spatter and molten pool behavior were investigated. The increase of laser power could cause more intense evaporation and lead to more spatter. When the focal position of laser beam was changed, different forms of spatter were generated, as well as the flow trends of molten metal on the front keyhole wall and at the rear molten pool were changed. The results revealed that the behavior of molten pool, which could be affected by the absorbed energy distribution in the keyhole, was the key factor to determine the spatter formation during laser welding. The relatively sound weld seam could be obtained during laser welding with the focal position located inside the metal.

Li, Shichun; Chen, Genyu; Katayama, Seiji; Zhang, Yi

2014-06-01

67

Dynamic Approach Of The Keyhole And Melt Pool Behavior For Deep Penetration Nd-Yag Laser Welding  

NASA Astrophysics Data System (ADS)

This paper contains our last results concerning the understanding of fundamental processes occurring inside metallic melt pool produced during deep penetration CW Nd-Yag laser welding. When the welding speed varies from a few m/min to a few tens of m/min, one can observe that melt pool behavior has very different and complex hydrodynamics. At low welding speed, the keyhole appears to be quite vertical, embedded inside a large pool that fluctuates due to friction effects induced by the quite vertical ejected plume. At high welding speeds, laser interaction is only localized on the keyhole front whose inclination increases with the welding speed. Induced melt flow then dominates and can generate the humping regime, with severe undercuts. For intermediate welding speeds, it is the interaction of the vapor plume with the melt pool that controls its stability and the final quality of the weld seam. The vapor plume behavior that is ejected from the keyhole, such as its fluctuations or its dynamic pressure, has been also studied as a function of these different operating parameters. Also the behavior of the keyhole and more precisely its front wall is analyzed by using a simple modeling approach that allows us to reproduce its main characteristics such as the penetration depth or the keyhole front wall inclination dependences with operating parameters. The interpretation of these different experiments allows us to confirm that the dynamic pressure of the vapor plume, which is emitted with a variable intensity and direction perpendicularly from the inclined keyhole front, has an essential role for the melt pool stability and its dynamics in deep penetration laser welding.

Fabbro, Rémy

2008-09-01

68

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

69

Computational modeling of stationary gastungsten-arc weld pools and comparison to stainless steel 304 experimental results  

Microsoft Academic Search

A systematic study was carried out to verify the predictions of a transient multidimensional computational model by comparing\\u000a the numerical results with the results of an experimental study. The welding parameters were chosen such that the predictions\\u000a of the model could be correlated with the results of an earlier experimental investigation of the weld pool surface temperatures\\u000a during spot gas-tungsten-arc

T. Zacharia; S. A. David; J. M. Vitek; H. G. Kraus

1991-01-01

70

A unified model of transport phenomena in gas metal arc welding including electrode, arc plasma and molten pool  

Microsoft Academic Search

This paper presents a theoretical model for describing globular transfer in gas metal arc welding. The heat and mass transfer in the electrode, arc plasma and molten pool are considered in one unified model. Using the volume of fluid method, the transport phenomena are dynamically studied in the following processes: droplet formation and detachment, droplet flight in arc plasma, impingement

H. G. Fan; R. Kovacevic

2004-01-01

71

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

PubMed

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

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

2013-04-01

72

Towards and FVE-FAC Method for Determining Thermocapillary Effects on Weld Pool Shape  

NASA Technical Reports Server (NTRS)

Several practical materials processes, e.g., welding, float-zone purification, and Czochralski crystal growth, involve a pool of molten metal with a free surface, with strong temperature gradients along the surface. In some cases, the resulting thermocapillary flow is vigorous enough to convect heat toward the edges of the pool, increasing the driving force in a sort of positive feedback. In this work we examine this mechanism and its effect on the solid-liquid interface through a model problem: a half space of pure substance with concentrated axisymmetric surface heating, where surface tension is strong enough to keep the liquid free surface flat. The numerical method proposed for this problem utilizes a finite volume element (FVE) discretization in cylindrical coordinates. Because of the axisymmetric nature of the model problem, the control volumes used are torroidal prisms, formed by taking a polygonal cross-section in the (r, z) plane and sweeping it completely around the z-axis. Conservation of energy (in the solid), and conservation of energy, momentum, and mass (in the liquid) are enforced globally by integrating these quantities and enforcing conservation over each control volume. Judicious application of the Divergence Theorem and Stokes' Theorem, combined with a Crank-Nicolson time-stepping scheme leads to an implicit algebraic system to be solved at each time step. It is known that near the boundary of the pool, that is, near the solid-liquid interface, the full conduction-convection solution will require extremely fine length scales to resolve the physical behavior of the system. Furthermore, this boundary moves as a function of time. Accordingly, we develop the foundation of an adaptive refinement scheme based on the principles of Fast Adaptive Composite Grid methods (FAC). Implementation of the method and numerical results will appear in a later report.

Canright, David; Henson, Van Emden

1996-01-01

73

Instantaneous liquid release from a rail tanker: the influence of noise shields on pool shape and pool size.  

PubMed

In the Netherlands, the Betuweline is a dedicated freight railway. It will, among other things, be used for transportation of all kinds of hazardous materials from the Port of Rotterdam to the German Hinterland and vice versa. The line is approximately 150 km long. Alongside the line, more than 100 km noise shields have been constructed. The question is how, and to what extent, this noise shield will affect the pool shape and size of an instantaneous release of a flammable liquid, such as liquefied petroleum gas (LPG). In case of an instantaneous release of liquid from a rail tanker (50 m(3)), both risk analysts and emergency responders use a circular pool shape of about 600 m(2) would result. To assess the influence of a noise shield, a full scale test was conducted on an already constructed part of the Betuweline. A rail tanker was filled with 50 m(3) red-colored environmentally safe liquid. The liquid was instantaneously released. A very peculiar pool shape actually results due to the presence of a noise shield. A zone between the rails and the noise shield (2m wide and 90 m long) is within 2-3 min filled with 15 cm of liquid. The total pool size area was about 750 m(2). Both shape and size deviate substantially from the traditional figures. These insights are both relevant to emergency responders for disaster abatement purposes and to risk analysts for effective modeling purposes. The Dutch Ministry of Transport is examining possible strategies to deal with these results. The results of this study are based upon one single instantaneous release test. In addition, it is valuable to find out what the pool shape and size would be in case of a continuous release from the rail tanker near a noise shield. PMID:18849112

Rosmuller, Nils

2009-05-30

74

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

NASA Astrophysics Data System (ADS)

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

Subashini, L.; Vasudevan, M.

2012-02-01

75

Temperature profiles, the size of the heat-affected zone and dilution in electroslag welding  

Microsoft Academic Search

SUMMARY A mathematical model was developed to represent the three-dimensional temperature field in the slag, the metal pool and the baseplate regions in the electroslag welding process. The spatially distributed heat generation patterns used in the calculations were obtained from the solution of the electric field equations. The output from the model were the temperature fields in the baseplate, the

T. DEBROY; J. SZEKELY; T. W. EAGAR

1982-01-01

76

Biquandles of Small Size and some Invariants of Virtual and Welded Knots  

E-print Network

In this paper we give the results of a computer search for biracks of small size and we give various interpretations of these findings. The list includes biquandles, racks and quandles together with new invariants of welded knots and examples of welded knots which are shown to be non-trivial by the new invariants. These can be used to answer various questions concerning virtual and welded knots. As an application we reprove the result that the Burau map from braids to matrices is non injective and give an example of a non-trivial virtual (welded) knot which cannot be distinguished from the unknot by any linear biquandles.

Bartholomew, Andrew

2010-01-01

77

Effects of temperature-dependent material properties and shielding gas on molten pool formation during continuous laser welding of AZ91 magnesium alloy  

NASA Astrophysics Data System (ADS)

Laser welding processes are widely used for fabrications in many engineering applications such as aerospace and automotives. In this paper, a moving distributed heat source model based on Goldak's method [1] has been implemented into finite volume thermal simulations in order to predict temperature distributions during the welding process of a magnesium alloy and to study the effects of variations in thermal properties, absorption coefficient and gas shielding on the computed temperature distributions and weld pool dimensions. The main conclusion is the significant effects of varying the thermal conductivity and absorption coefficient of magnesium. Also, it has been seen that the shielding gas, besides its main role of protection against oxidation, has a significant effect on the width of the weld pool. Finally, the obtained results have been compared to the experimental ones and a satisfactory correlation has been observed, indicating the reliability of the model developed in this study.

Bannour, Sana; Abderrazak, Kamel; Mhiri, Hatem; Le Palec, Georges

2012-11-01

78

The public goods game on homogeneous and heterogeneous networks: investment strategy according to the pool size  

E-print Network

We propose an extended public goods interaction model to study the evolution of cooperation in heterogeneous population. The investors are arranged on the well known scale-free type network, the Barab\\'{a}si-Albert model. Each investor is supposed to preferentially distribute capital to pools in its portfolio based on the knowledge of pool sizes. The extent that investors prefer larger pools is determined by investment strategy denoted by a tunable parameter $\\alpha$, with larger $\\alpha$ corresponding to more preference to larger pools. As comparison, we also study this interaction model on square lattice, and find that the heterogeneity contacts favors cooperation. Additionally, the influence of local topology to the game dynamics under different $\\alpha$ strategies are discussed. It is found that the system with smaller $\\alpha$ strategy can perform comparatively better than the larger $\\alpha$ ones.

Zi-Gang Huang; Zhi-Xi Wu; Jian-Yue Guan; An-Cai Wu; Ying-Hai Wang

2007-08-21

79

Effects of Fusion Zone Size on Failure Modes and Static Strength of Aluminum Resistance Spot Welds  

SciTech Connect

This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of aluminum spot welded samples using a combined experimental, statistical and analytical approach. Static strength tests using coupon configurations of lap shear, cross tension and coach peel were performed on joint populations with a controlled fusion zone size. The resulted peak load and energy absorption levels associated with each failure mode were studied using statistical models. An analytical model was developed to determine the failure mode of an aluminum resistance spot weld based on limit load analyses. It was found that fusion zone size, sheet thickness, and the level and location of weld porosity/defects are the main factors influencing the cross-tension failure mode of an aluminum spot weld.

Sun, Xin; Stephens, Elizabeth V.; Davies, Richard W.; Khaleel, Mohammad A.; Spinella, Donald J.

2004-11-01

80

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

NASA Astrophysics Data System (ADS)

Present investigations were focused on low-temperature sensitization (LTS) behavior of 304LN stainless steels considered from pipes of two different thicknesses. The specimens for the present study were taken from solution-annealed pipes (of varying thicknesses) and welded pipes (including the heat-affected zone (HAZ)). The specimens were subjected to thermal aging at 400 °C and 450 °C for different durations ranging from 125 to 8000 hours, to evaluate their sensitization susceptibility. The aging durations were worked out to simulate the 30-to-100-year life of the studied stainless steel at 300 °C using the Arrheneous equation and considering the activation energy of 150 kJ/mol. The thermally aged specimens were characterized for their degree of sensitization (DOS) and susceptibility to intergranular corrosion (IGC) by double-loop (DL) electrochemical potentiokinetic reactivation (EPR) and by methods given in the ASTM A262 practices A and E. It has been clearly shown that the weld pool is more sensitive to IGC than are the base and the HAZ at both the aging temperatures (LTS), because they showed IGC cracks during the bending subsequent to the boiling in H2SO4-CuSO4 solution. Both the base and the HAZ of the thicker pipe material showed susceptibility to sensitization, as indicated by the increasing DOS and “dual-type” microstructure during electrolytic oxalic acid (EOA) etching; however, they were found safe from IGC for the studied sensitization times. The susceptibility to sensitization and IGC in the weld pool is related to the presence of copious delta ferrite with chromium diffusivity that is accelerated compared to the austenite phase. The time-temperature-sensitization (TTS) curves were prepared accordingly, based on these results.

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

2009-05-01

81

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

PubMed Central

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

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

82

WELDING RESEARCH -s85WELDING JOURNAL  

E-print Network

WELDING RESEARCH -s85WELDING JOURNAL ABSTRACT. Measurement of weld pool surface is a difficult but urgent task in the welding community. It plays an important role not only in developing the next- generation intelligent welding machines but also for modeling complex welding processes. In recent years

Zhang, YuMing

83

Species pool size and invasibility of island communities: a null model of sampling effects  

E-print Network

Correspondence: E-mail: herben@site.cas.cz Abstract The success of alien species on oceanic islands is considered, but this argument needs re-examination. The important difference between islands and mainland is in the size underlie differences in invasibility. Keywords Alien species, population growth rate, species pool, species

Herben, Tomas

84

Kinetics and pool size of chenodeoxycholic acid in cholesterol gallstone patients.  

PubMed

The pool size, half life, and daily production rate of chenodeoxycholic acid (CDCA) was determined by the isotope dilution method upon intravenous injections of about 10 muCI OF 24-14C-CDCA in 7 patients with radiolucent gallstones in functioning gallbladders, and 9 healthy controls. Bile was obtained by duodenal intubation. The method also allowed measurement of the CDCA percentage of total bile acids (TBA) and an indirect calculation of the TBA pool size. The pool size and daily production rate of CDCA were slightly, but not significantly, diminished in the gallstone patients. The half life of CDCA was almost equal in the 2 groups. The CDCA percentage of TBA was significantly higher in the gallstone patients (0.02 less than P less than 0.05), and the TBA pool size was significantly reduced (P less than 0.01) in the gallstone patients. It is concluded that the CDCA metabolism is similar to that of cholic acid in gallstone patients. Thus the formation of gallstones is hardly due to specific alterations in CDCA metabolism, suspected on account of the specific cholelitholytic effect of CDCA ingestion. The significance of increased CDCA percentage in bile is discussed in relation to the results from other study groups, and it is pointed out that a relative increase in the bile content of dihydroxy bile acids may lead to reduced cholesterol holding capacity of bile, and thus favor the formation of gallstones. PMID:1153952

Pedersen, L; Arnfred, T

1975-01-01

85

Association between zinc pool sizes and iron stores in premenopausal women without anaemia.  

PubMed

The simultaneous occurrence of Zn and Fe deficiencies in man has been known since the discovery of human Zn deficiency. However, it is not established that low Fe stores per se or Fe-deficiency anaemia infer low Zn status. Therefore our objective was to identify relationships between Zn and Fe status in premenopausal women without anaemia. We also examined the contribution of food frequencies and blood loss to Zn and Fe status. The subjects were thirty-three apparently healthy premenopausal women without anaemia, who were not taking dietary supplements containing Zn or Fe or oral contraceptives. Main outcomes were Zn kinetic parameters based on the three-compartment mammillary model and serum ferritin (SF) concentration; contributing factors were the frequency of consumption of specific foods and menorrhagia. Lower SF was significantly associated with smaller sizes of Zn pools. The breakpoint in the relationship between SF and the lesser peripheral Zn pool was found to be 21.0 microg SF/l. SF also correlated positively with frequency of beef consumption and negatively with bleeding through menstrual pads (BTMP). Similar to SF, the Zn pool sizes correlated positively with frequency of beef consumption, and negatively with BTMP. In summary, Zn pool sizes and Fe stores were highly correlated in premenopausal women. SF concentrations < 20 microg/l suggest an increased likelihood of low Zn status. PMID:17692150

Yokoi, Katsuhiko; Sandstead, Harold H; Egger, Norman G; Alcock, Nancy W; Sadagopa Ramanujam, V M; Dayal, Hari H; Penland, James G

2007-12-01

86

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

PubMed

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

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

2013-08-01

87

Update of "Biquandles of Small Size and some Invariants of Virtual and Welded Knots"  

E-print Network

In this paper we give the results of a computer search for biracks of small size and we give various interpretations of these findings. The list includes biquandles, racks and quandles together with new invariants of welded knots and examples of welded knots which are shown to be non-trivial by the new invariants. These can be used to answer various questions concerning virtual and welded knots. As an application we reprove the result that the Burau map from braids to matrices is non injective and give an example of a non-trivial virtual (welded) knot which cannot be distinguished from the unknot by any linear biquandles. (This is a revised version of an earlier paper of the same name)

Bartholomew, Andrew

2010-01-01

88

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

E-print Network

A study of the effects of heater size, subcooling, and gravity level on pool boiling heat transfer Martin Hill, College Park, MD 20742, USA Abstract Pool boiling heat transfer measurements from different. Boiling on three heaters of different size (0.65, 2.62, 7.29 mm2 ) was studied. Control circuitry was used

Kim, Jungho

89

Dynamics of space welding impact and corresponding safety welding study.  

PubMed

This study was undertaken in order to be sure that no hazard would exist from impingement of hot molten metal particle detachments upon an astronauts space suit during any future electron beam welding exercises or experiments. The conditions under which molten metal detachments might occur in a space welding environment were analyzed. The safety issue is important during welding with regards to potential molten metal detachments from the weld pool and cold filler wire during electron beam welding in space. 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. 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 determined for these detachment concerns from principles of impact and kinetic energies, surface tension, drop geometry, surface energies, and particle dynamics. A weld pool detachment parameter for specifying the conditions for metal weld pool detachment by impact was derived and correlated to the experimental results. The experimental results were for the most part consistent with the theoretical analysis and predictions. PMID:14740660

Fragomeni, James M; Nunes, Arthur C

2004-03-01

90

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

SciTech Connect

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.

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

1991-03-15

91

Postillumination Isoprene Emission: In Vivo Measurements of Dimethylallyldiphosphate Pool Size and Isoprene Synthase Kinetics in Aspen Leaves1  

PubMed Central

The control of foliar isoprene emission is shared between the activity of isoprene synthase, the terminal enzyme catalyzing isoprene formation from dimethylallyldiphosphate (DMADP), and the pool size of DMADP. Due to limited in vivo information of isoprene synthase kinetic characteristics and DMADP pool sizes, the relative importance of these controls is under debate. In this study, the phenomenon of postillumination isoprene release was employed to develop an in vivo method for estimation of the DMADP pool size and to determine isoprene synthase kinetic characteristics in hybrid aspen (Populus tremula × Populus tremuloides) leaves. The method is based on observations that after switching off the light, isoprene emission continues for 250 to 300 s and that the integral of the postillumination isoprene emission is strongly correlated with the isoprene emission rate before leaf darkening, thus quantitatively estimating the DMADP pool size associated with leaf isoprene emission. In vitro estimates demonstrated that overall leaf DMADP pool was very large, almost an order of magnitude larger than the in vivo pool. Yet, the difference between total DMADP pools in light and in darkness (light-dependent DMADP pool) was tightly correlated with the in vivo estimates of the DMADP pool size that is responsible for isoprene emission. Variation in in vivo DMADP pool size was obtained by varying light intensity and atmospheric CO2 and O2 concentrations. From these experiments, the in vivo kinetic constants of isoprene synthase were determined. In vivo isoprene synthase kinetic characteristics suggested that isoprene synthase mainly operates under substrate limitation and that short-term light, CO2, and O2 dependencies of isoprene emission result from variation in DMADP pool size rather than from modifications in isoprene synthase activity. PMID:19129417

Rasulov, Bahtijor; Copolovici, Lucian; Laisk, Agu; Niinemets, Ülo

2009-01-01

92

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

93

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

94

Heater size and heater aspect ratio effects on subcooled pool boiling heat transfer in low-g  

E-print Network

little to no effect on heat transfer during nucleate boiling in earth gravity [6]. Subcooling effectsHeater size and heater aspect ratio effects on subcooled pool boiling heat transfer in low University, New Brunswick, NJ 08901-8520, USA Abstract Pool boiling heat transfer measurements using heaters

Kim, Jungho

95

Estimation and control of droplet size and frequency in projected spray mode of a gas metal arc welding (GMAW) process.  

PubMed

New estimators are designed based on the modified force balance model to estimate the detaching droplet size, detached droplet size, and mean value of droplet detachment frequency in a gas metal arc welding process. The proper droplet size for the process to be in the projected spray transfer mode is determined based on the modified force balance model and the designed estimators. Finally, the droplet size and the melting rate are controlled using two proportional-integral (PI) controllers to achieve high weld quality by retaining the transfer mode and generating appropriate signals as inputs of the weld geometry control loop. PMID:21444083

Anzehaee, Mohammad Mousavi; Haeri, Mohammad

2011-07-01

96

Welding  

NSDL National Science Digital Library

Teachers' Domain presents this video as part of a series on advanced technological education. Around 500,000 people are currently employed in welding in the United States, and as more highways, bridges and other structures need crucial updates, welders will continue to be in demand. The video clip demonstrates welding techniques, including what constitutes a bad weld and how to recognize one. Careers in welding are also discussed. The video may be viewed online or downloaded. To download the clip, users must create a free login for Teachers' Domain. Running time for this QuickTime video is 3:56. Educators will also find a background essay, discussion questions, and standards alignment for the material.

2010-09-29

97

Effects of Fusion Zone Size on Failure Modes and Performance of Advanced High Strength Steel Spot Welds  

SciTech Connect

This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS). DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. The critical fusion zone sizes to ensure nugget pull-out failure mode are developed for both DP800 and TRIP800 using the limit load based analytical model and the micro-hardness measurements of the weld cross sections. Static weld strength tests using cross tension samples were performed on the joint populations with controlled fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied using statistical data analysis tools. The results in this study show that the conventional weld size of 4 t can not produce nugget pullout mode for both the DP800 and TRIP800 materials. The results also suggest that performance based spot weld acceptance criteria should be developed for different AHSS spot welds.

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

2006-04-28

98

Weld width indicates weld strength  

NASA Technical Reports Server (NTRS)

Width of butt weld in 2219-T87 aluminum has been found to be more reliable indicator of weld strength than more traditional parameters of power input and cooling rate. Yield stress and ultimate tensile strength tend to decrease with weld size. This conclusion supports view of many professional welders who give priority to weld geometry over welding energy or cooling rate as indicator of weld quality.

Nunes, A. C. J.; Novak, H. L.; Mcllwain, M. C.

1982-01-01

99

Computational modeling of GTA (gas tungsten arc) welding with emphasis on surface tension effects  

SciTech Connect

A computational study of the convective heat transfer in the weld pool during gas tungsten arch (GTA) welding of Type 304 stainless steel is presented. The solution of the transport equations is based on a control volume approach which utilized directly, the integral form of the governing equations. The computational model considers buoyancy and electromagnetic and surface tension forces in the solution of convective heat transfer in the weld pool. In addition, the model treats the weld pool surface as a deformable free surface. The computational model includes weld metal vaporization and temperature dependent thermophysical properties. The results indicate that consideration of weld pool vaporization effects and temperature dependent thermophysical properties significantly influence the weld model predictions. Theoretical predictions of the weld pool surface temperature distributions and the cross-sectional weld pool size and shape wee compared with corresponding experimental measurements. Comparison of the theoretically predicted and the experimentally obtained surface temperature profiles indicated agreement with {plus minus} 8%. The predicted weld cross-section profiles were found to agree very well with actual weld cross-sections for the best theoretical models. 26 refs., 8 figs.

Zacharia, T.; David, S.A.

1990-01-01

100

Ultrasonic Phased Array Technique for Accurate Flaw Sizing in Dissimilar Metal Welds  

SciTech Connect

Described is a manual,portable non-destructive technique to determine the through wall height of cracks present in dissimilar metal welds used in the primary coolling systems of pressure water and boiler light water reactors. Current manual methods found in industry have proven not to exhibit the sizing accuracy required by ASME inspection requirement. The technique described demonstrated an accuracy approximately three times that required to ASME Section XI, Appendix 8 qualification.

Jonathan D Buttram

2005-03-11

101

Nonlinear Identification of Laser Welding Process  

Microsoft Academic Search

It has been well recognized that weld pool geometry plays a critical role in fusion welding process such as laser welding. In this study, the authors establish a standard diode laser welding system and perform a series of experiments to investigate correlations between welding parameters and the weld pool geometry. Custom digital camera for image acquisition and software for image

Xiaodong Na; YuMing Zhang; YuSheng Liu; Bruce Walcott

2010-01-01

102

Modeling of Heat and Mass Transfer in Fusion Welding  

SciTech Connect

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.

Zhang, Wei [ORNL

2011-01-01

103

Investigation of mixing and diffusion processes in hybrid spot laser-MIG keyhole welding  

NASA Astrophysics Data System (ADS)

In hybrid laser-MIG keyhole welding, anti-crack elements can be added into the weld pool through a filler metal in anticipation of compensating mass loss, preventing porosity formation and improving compositional and mechanical properties of the welds. Understanding the mixing and diffusion of the filler metal in the molten pool is vital to achieve these desired objectives. In this study, mathematical models and associated numerical techniques have been developed to investigate the mixing and diffusion processes in hybrid laser-MIG keyhole welding. The transient interactions between droplets and weld pool and dynamics of the melt flow are studied. The effects of key process parameters, such as droplet size (wire diameter), droplet generation frequency (wire feed speed) and droplet impinging speed, on mixing/diffusion are systematically investigated. It was found that compositional homogeneity of the weld pool is determined by the competition between the mixing rate and the solidification rate. A small-size filler droplet together with high generation frequency can increase the latitudinal diffusion of the filler metal into the weld pool, while the large-size droplet along with the low generation frequency helps to get more uniform longitudinal diffusion. Increasing the impinging velocity of the filler droplet can improve the latitudinal diffusion of the filler metal. However, a high impinging velocity can cause a lower diffusion zone in the upper part of the welds. This study provides a good foundation for optimizing the hybrid laser-MIG keyhole welding process to achieve quality welds with desired properties.

Zhou, J.; Tsai, H. L.

2009-05-01

104

Information content of incubation experiments for inverse estimation of pools sizes in the Rothamsted carbon model: a Bayesian approach  

NASA Astrophysics Data System (ADS)

Turnover of soil organic matter (SOM) is usually described with multi-compartment models. A model compartment (or pool) contains all carbon compounds with similar functional properties, such as decomposition rate and partitioning of decomposition products. These functionally defined carbon pools do not necessarily correspond to measurable (SOC) fractions in real practice. This not only impairs our ability to rigorously evaluate SOC models, but also makes it difficult to derive accurate initial states. In this study, we test the usefulness and applicability of inverse modeling to derive the various carbon pool sizes in the Rothamsted carbon model (ROTHC) using observed mineralization rate data during incubation of soil samples in the laboratory. In the last decade, inverse modeling has found widespread application and use for environmental model calibration, but this methodology has not yet been tested for assessing carbon pools in multi-compartment SOC models. To appropriately consider data and model uncertainty we consider a Bayesian approach using the recently developed DiffeRential Evolution Adaptive Metropolis (DREAM) algorithm. This Markov Chain Monte Carlo (MCMC) scheme derives the posterior probability density distribution of the initial pool sizes at the start of incubation from measured mineralization rates. Our results show that measured mineralization rates generally provide sufficient information to reliably estimate the sizes of all active carbon pools in the ROTHC model. However, for soils with slow and intermediate carbon turnover an excessively long incubation time is required to appropriately constrain all carbon pools. The explicit use of prior information on microbial biomass provides a way forward to significantly reduce uncertainty and required duration of incubation. Our illustrative case studies show how Bayesian inverse modeling can be used to provide important insights into the information content of incubation experiments for assessing SOC turnover and dynamics.

Scharnagl, B.; Vrugt, J. A.; Vereecken, H.; Herbst, M.

2009-09-01

105

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

SciTech Connect

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

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

2008-06-01

106

Mathematical modelling of GTA girth welding of pipes  

Microsoft Academic Search

This paper describes the development of a three-dimensional numerical model for GTA (TIG) girth welding of pipes. It consists of a heat conduction model and molten pool balance model.In the heat conduction model, the transient temperature distribution and molten pool size are numerically analysed by the finite difference and enthalpy methods to consider the effect of the latent heat of

T. Matsutani; F. Miyasaka; T. Oji; Y. Hirata

1997-01-01

107

New parametric study of nugget size in resistance spot welding process using finite element method  

Microsoft Academic Search

Resistance spot welding process (RSW) is one of important manufacturing processes in automotive industry for assembling bodies. Quality and strength of the welds and therefore body mainly are defined by quality of the weld nuggets. The most effective parameters in this process are: current intensity, welding time, sheet thickness and material, geometry of electrodes, electrode force, and current shunting. In

Hamid Eisazadeh; Mohsen Hamedi; Ayob Halvaee

2010-01-01

108

Probabilistic Estimation of Critical Flaw Sizes in the Primary Structure Welds of the Ares I-X Launch Vehicle  

NASA Technical Reports Server (NTRS)

The primary structure of the Ares I-X Upper Stage Simulator (USS) launch vehicle is constructed of welded mild steel plates. There is some concern over the possibility of structural failure due to welding flaws. It was considered critical to quantify the impact of uncertainties in residual stress, material porosity, applied loads, and material and crack growth properties on the reliability of the welds during its pre-flight and flight. A criterion--an existing maximum size crack at the weld toe must be smaller than the maximum allowable flaw size--was established to estimate the reliability of the welds. A spectrum of maximum allowable flaw sizes was developed for different possible combinations of all of the above listed variables by performing probabilistic crack growth analyses using the ANSYS finite element analysis code in conjunction with the NASGRO crack growth code. Two alternative methods were used to account for residual stresses: (1) The mean residual stress was assumed to be 41 ksi and a limit was set on the net section flow stress during crack propagation. The critical flaw size was determined by parametrically increasing the initial flaw size and detecting if this limit was exceeded during four complete flight cycles, and (2) The mean residual stress was assumed to be 49.6 ksi (the parent material s yield strength) and the net section flow stress limit was ignored. The critical flaw size was determined by parametrically increasing the initial flaw size and detecting if catastrophic crack growth occurred during four complete flight cycles. Both surface-crack models and through-crack models were utilized to characterize cracks in the weld toe.

Pai, Shantaram S.; Hoge, Peter A.; Patel, B. M.; Nagpal, Vinod K.

2009-01-01

109

Correlation of inclusion size and chemistry with weld metal composition and microstructure arc weldments of high strength steels  

NASA Astrophysics Data System (ADS)

Non-metallic inclusions are crucial to the development of acicular ferrite, the desired microstructure for optimal strength and toughness in weld metal. This study focused on obtaining correlation between the size and chemistry of inclusions and weld metal properties, especially the amount of acicular ferrite, in Gas Metal Arc (GMA) and Submerged Arc (SA) weldments in HY-100 and HSLA-100 steel. A strong correlation was found between the amount of acicular ferrite, flux basicity and inclusion composition and volume fraction in SAW weld metal samples. An index developed to consider the effect of chemistry and volume fraction of inclusions on acicular ferrite showed good correlation. The GMA weld samples were found to contain less acicular ferrite than the SAW samples, principally because of their lower oxygen content. However, it was again found possible to correlate inclusion chemistry and volume fraction with acicular ferrite formation. Unfortunately, the large amount of data scatter precluded the development of an index in this case.

Eakes, Mark W.

1994-12-01

110

Computer modeling of arc welds to predict effects of critical variables on weld penetration  

SciTech Connect

In recent years, there have been several attempts to study the effect of critical variables on welding by computational modeling. It is widely recognized that temperature distributions and weld pool shapes are keys to quality weldments. It would be very useful to obtain relevant information about the thermal cycle experienced by the weld metal, the size and shape of the weld pool, and the local solidification rates, temperature distributions in the heat-affected zone (HAZ), and associated phase transformations. The solution of moving boundary problems, such as weld pool fluid flow and heat transfer, that involve melting and/or solidification is inherently difficult because the location of the solid-liquid interface is not known a priori and must be obtained as a part of the solution. Because of non-linearity of the governing equations, exact analytical solutions can be obtained only for a limited number of idealized cases. Therefore, considerable interest has been directed toward the use of numerical methods to obtain time-dependant solutions for theoretical models that describe the welding process. Numerical methods can be employed to predict the transient development of the weld pool as an integral part of the overall heat transfer conditions. The structure of the model allows each phenomenon to be addressed individually, thereby gaining more insight into their competing interactions. 19 refs., 6 figs., 1 tab.

Zacharia, T.; David, S.A.

1991-01-01

111

Intelligent Technologies for Robotic Welding  

Microsoft Academic Search

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,

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

112

WELDING RESEARCH -s57WELDING JOURNAL  

E-print Network

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

Zhang, YuMing

113

Orphan G protein-coupled receptor GPR116 regulates pulmonary surfactant pool size.  

PubMed

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

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

2013-09-01

114

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

E-print Network

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...

Owen, Richard James

2012-06-07

115

Why and when channelling can decrease pool size at constant net flux in a simple dynamic channel  

Microsoft Academic Search

Cornish-Bowden and Cárdenas (Cornish-Bowden, A. and Cárdenas M.L. (1993) Eur. J. Biochem. 213, 87–92) have suggested that simulation results previously published by us (Mendes, P., Kell, D.B. and Westerhoff, H.V. (1992) Eur. J. Biochem. 204, 255–266) which had demonstrated that large reductions of intermediate pool sizes could be accompanied by increasing channel flux in a model metabolic pathway, were an

Pedro Mendes; Douglas B. Kell; Hans V. Westerhoff

1996-01-01

116

Protein Kinase C Enhances Exocytosis from Chromaffin Cells by Increasing the Size of the Readily Releasable Pool of Secretory Granules  

Microsoft Academic Search

We have used membrane capacitance measurements to assay Ca2+-triggered exocytosis in single bovine adrenal chromaffin cells. Brief application of phorbol ester (PMA) enhances depolarization-evoked exocytosis severalfold while actually decreasing the Ca2+ current. Ca2+ metabolism is unchanged. Three different protocols were used to show that PMA increases the size of the readily releasable pool of secretory granules. PMA treatment leads to

Kevin D. Gillis; Rotraut Mößner; Erwin Neher

1996-01-01

117

Litter pool sizes, decomposition, and nitrogen dynamics in Spartina alterniflora -invaded and native coastal marshlands of the Yangtze Estuary  

Microsoft Academic Search

Past studies have focused primarily on the effects of invasive plants on litter decomposition at soil surfaces. In natural\\u000a ecosystems, however, considerable amounts of litter may be at aerial and belowground positions. This study was designed to\\u000a examine the effects of Spartina\\u000a alterniflora invasion on the pool sizes and decomposition of aerial, surficial, and belowground litter in coastal marshlands, the

Cheng Zhang Liao; Yi Qi Luo; Chang Ming Fang; Jia Kuan Chen; Bo Li

2008-01-01

118

Chemical stabilization of organic carbon pools in particle size fractions in no-till and meadow soils  

Microsoft Academic Search

The knowledge about the relevance of physical and chemical fractionation methods to soil organic carbon (SOC) stabilization\\u000a mechanisms is fragmentary but needed to manage the SOC pool. Therefore, our objective was to compare the C contents of the\\u000a particle size fractions coarse and fine sand, silt, and clay of the two uppermost horizons of a soil under three different\\u000a management

K. Lorenz; R. Lal; M. J. Shipitalo

2008-01-01

119

Automated and aluminum welding technology  

NASA Astrophysics Data System (ADS)

Automated welding technology and techniques for welding advanced aluminum alloys with potential for industrial and commercial applications have been developed by the National Aeronautics and Space Administration at the Marshall Space Flight Center. These technologies are being offered to private companies for commercial development, and include: Variable polarity plasma arc welding, a welding process that produces high-quality aluminum welds for fabrication of the space shuttle external tank and space station common module structures. This process uses reverse polarity pulses to produce welds virtually free of internal defects. Advanced weld sensor technology, comprised of machine vision-based weld seam tracking that uses both structured and global laser illumination for finding weld joints, even those difficult to discern by the human eye. Weld pool feedback is accomplished with a vision system to measure arc symmetry and molten weld pool geometry. A weld bead profiler trails the welding torch. It provides feedback to the process control system, which records quality control data.

Jones, Clyde S.

1994-10-01

120

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

SciTech Connect

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

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

2007-01-01

121

Development of a comprehensive weld process model  

SciTech Connect

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.

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

1997-05-01

122

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

SciTech Connect

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

Szekely, J.; Eagar, T.W.

1981-10-15

123

Transport of salts and micron-sized particles entrained from a boiling water pool  

Microsoft Academic Search

The entrainment of soluble (KI, CsI) and non-soluble (Al2O3) substances through droplets, which are produced by disintegrating steam bubbles at the surface of a boiling water pool, is determined in a pilot-scale facility. Integral measurements are conducted at steady-state conditions in an atmosphere of either pure steam or an air–steam mixture. The ratio of the entrained liquid mass flow and

Jérôme O. Cosandey; Axel Günther; Philipp Rudolf von Rohr

2003-01-01

124

Time-dependent calculations of molten pool formation and thermal plasma with metal vapour in gas tungsten arc welding  

NASA Astrophysics Data System (ADS)

A gas tungsten arc (GTA) was modelled taking into account the contamination of the plasma by metal vapour from the molten anode. The whole region of GTA atmosphere including the tungsten cathode, the arc plasma and the anode was treated using a unified numerical model. A viscosity approximation was used to express the diffusion coefficient in terms of viscosity of the shielding gas and metal vapour. The transient two-dimensional distributions of temperature, velocity of plasma flow and iron vapour concentration were predicted, together with the molten pool as a function of time for a 150 A arc current at atmospheric pressure, both for helium and argon gases. It was shown that the thermal plasma in the GTA was influenced by iron vapour from the molten pool surface and that the concentration of iron vapour in the plasma was dependent on the temperature of the molten pool. GTA on high sulfur stainless steel was calculated to discuss the differences between a low sulfur and a high sulfur stainless steel anode. Helium was selected as the shielding gas because a helium GTA produces more metal vapour than an argon GTA. In the GTA on a high sulfur stainless steel anode, iron vapour and current path were constricted. Radiative emission density in the GTA on high sulfur stainless steel was also concentrated in the centre area of the arc plasma together with the iron vapour although the temperature distributions were almost the same as that in the case of a low sulfur stainless steel anode.

Tanaka, M.; Yamamoto, K.; Tashiro, S.; Nakata, K.; Yamamoto, E.; Yamazaki, K.; Suzuki, K.; Murphy, A. B.; Lowke, J. J.

2010-11-01

125

The effect of density-dependent insect visits, flowering phenology, and plant size on seed set of the endangered vernal pool plant Pogogyne abramsii (Lamiaceae) in natural compared to created vernal pools  

Microsoft Academic Search

Pollinator activity, flowering phenology, plant size, and seed set of an endangered annual plant, Pogogyne abramsii, were compared in natural and created vernal pools on Del Mar Mesa, San Diego County, California, USA. The purpose was to\\u000a test the hypothesis that an artificial habitat would have fewer or less effective pollinator visits than natural vernal pools\\u000a and that, as a

Joseph R. Schiller; Paul H. Zedler; Chuck H. Black

2000-01-01

126

Effects of Fusion Zone Size on Failure Modes and Performance of Advanced High Strength Steel Spot Welds (2006-01-0531)  

SciTech Connect

This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS). DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. The critical fusion zone sizes to ensure nugget pull-out failure mode are developed for both DP800 and TRIP800 using the limit load based analytical model and the micro-hardness measurements of the weld cross sections. Static weld strength tests using cross tension samples were performed on the joint populations with controlled fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied using statistical data analysis tools. The results in this study show that the conventional weld size of 4 t1/2 can not produce nugget pullout mode for both the DP800 and TRIP800 materials. The results also suggest that performance based spot weld acceptance criteria should be developed for different AHSS spot welds.

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

2007-03-01

127

ECOLOGICAL STUDIES AND MATHEMATICAL MODELING OF 'CLADOPHORA' IN LAKE HURON: 3. THE DEPENDENCE OF GROWTH RATES ON INTERNAL PHOSPHOROUS POOL SIZE (JOURNAL VERSION)  

EPA Science Inventory

The relationship between growth rate and internal phosphorus pool size was examined using field populations of Cladophora golmerata from Lake Huron. Algal samples, representing a range of internal phosphorus concentrations, were harvested from the lake and used for laboratory mea...

128

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

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

Boyer, Edmond

129

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

PubMed

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

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

2011-06-01

130

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

SciTech Connect

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.

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

2009-01-01

131

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

PubMed

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

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

1998-03-16

132

Active weld control  

NASA Technical Reports Server (NTRS)

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.

Powell, Bradley W.; Burroughs, Ivan A.

1994-01-01

133

Experimental validation of nondestructive damage detection of a 1/32" surface crack in a #6 and #9 size welded rebar splice  

E-print Network

EXPERIMENTAL VALIDATION OF NONDESTRUCTIVE DAMAGE DETECTION OF A I/32" SURFACE CRACK IN A ?6 AND ?9 SIZE WELDED REBAR SPLICE A Thesis by CHARLES ERIC MILLER Submitted to the Office of Graduate Studies of Texas ARM University in partial... fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1999 Major Subject: Mechanical Engineering EXPERIMENTAL VALIDATION OF NONDESTRUCTIVE DAMAGE DETECTION OF A I/32" SURFACE CRACK IN A ?6 AND ?9 SIZE WELDED REBAR SPLICES A Thesis...

Miller, Charles Eric

2012-06-07

134

Acoustic-Emission Weld-Penetration Monitor  

NASA Technical Reports Server (NTRS)

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.

Maram, J.; Collins, J.

1986-01-01

135

Presynaptic calcium influx controls neurotransmitter release in part by regulating the effective size of the readily releasable pool.  

PubMed

The steep calcium dependence of synaptic strength that has been observed at many synapses is thought to reflect a calcium dependence of the probability of vesicular exocytosis (p), with the cooperativity of three to six corresponding to the multiple calcium ion binding sites on the calcium sensor responsible for exocytosis. Here we test the hypothesis that the calcium dependence of the effective size of the readily releasable pool (RRP) also contributes to the calcium dependence of release at the calyx of Held synapse in mice. Using two established methods of quantifying neurotransmitter release evoked by action potentials (effective RRP), we find that when calcium influx is changed by altering the external calcium concentration, the calcium cooperativity of p is insufficient to account for the full calcium dependence of EPSC size; the calcium dependence of the RRP size also contributes. Reducing calcium influx by blocking R-type voltage-gated calcium channels (VGCCs) with Ni(2+), or by blocking P/Q-type VGCCs with ?-agatoxin IVA also changes EPSC amplitude by reducing both p and the effective RRP size. This suggests that the effective RRP size is dependent on calcium influx through VGCCs. Furthermore, activation of GABAB receptors, which reduces presynaptic calcium through VGCCs without other significant effects on release, also reduces the effective RRP size in addition to reducing p. These findings indicate that calcium influx regulates the RRP size along with p, which contributes to the calcium dependence of synaptic strength, and it influences the manner in which presynaptic modulation of presynaptic calcium channels affects neurotransmitter release. PMID:23486937

Thanawala, Monica S; Regehr, Wade G

2013-03-13

136

Development of a Comprehensive Weld Process Model  

SciTech Connect

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.

Radhakrishnan, B.; Zacharia, T.

1997-05-01

137

Sensor controlled robotic welding for nuclear power plant operations: Final progress report  

SciTech Connect

The objective of the proposed research is to apply real time monitoring, artificial intelligence and on-line correction to dynamically control the depth of weld penetration and weld integrity during the welding process. Welding is a major technique used in the fabrication, construction and maintenance of power generating and energy conversion systems. In the welding process, fluctuations in process variables lead to weld defects such as lack of penetration, cracks, porosity and undesirable metallurgical structures. This research will apply advanced infrared sensing techniques which have been successfully used in seam tracking to the equally complex problem of weld defect and weld puddle penetration control. Thermal temperature distributions of plates being welded will be dynamically measured during welding using infrared techniques. These temperature distributions will be used to interpret changes in the size and shape of the molten metal pool and the presence of conditions that may lead to defects in the solidified weld. The ultimate result of this research will be the development of machines which are capable of sensing and altering process variables to eliminate defective welds and increase the productivity of the welding process. Successful completion of this proposed research will lead to potential major improvements in the fabrication, construction and maintenance of advanced nuclear reactors and promote increased safety and reliability while decreasing construction costs. 47 refs., 50 figs.

Chin, B.A.

1989-06-08

138

Prediction of the weld shape in arc welding A numerical modeling example in multiphysics coupling  

Microsoft Academic Search

A numerical model of the arc welding process is presented. It deals with all arc welding process with and without filler metal (Gas Metal Arc Welding and Gas Tungsten Arc Welding). We consider the three dimensional modelling of the stationary weld pool with a free deformable surface. All coupled equations are solved by the finite volume method. We consider heat

Frédéric Roger; Ky Dang Van

2004-01-01

139

Elastic-Plastic Fracture Mechanics Analysis of Critical Flaw Size in ARES I-X Flange-to-Skin Welds  

NASA Technical Reports Server (NTRS)

NASA's Ares 1 Upper Stage Simulator (USS) is being fabricated from welded A516 steel. In order to insure the structural integrity of these welds it is of interest to calculate the critical initial flaw size (CIFS) to establish rational inspection requirements. The CIFS is in turn dependent on the critical final flaw size (CFS), as well as fatigue flaw growth resulting from transportation, handling and service-induced loading. These calculations were made using linear elastic fracture mechanics (LEFM), which are thought to be conservative because they are based on a lower bound, so called elastic, fracture toughness determined from tests that displayed significant plasticity. Nevertheless, there was still concern that the yield magnitude stresses generated in the flange-to-skin weld by the combination of axial stresses due to axial forces, fit-up stresses, and weld residual stresses, could give rise to significant flaw-tip plasticity, which might render the LEFM results to be non-conservative. The objective of the present study was to employ Elastic Plastic Fracture Mechanics (EPFM) to determine CFS values, and then compare these values to CFS values evaluated using LEFM. CFS values were calculated for twelve cases involving surface and embedded flaws, EPFM analyses with and without plastic shakedown of the stresses, LEFM analyses, and various welding residual stress distributions. For the cases examined, the computed CFS values based on elastic analyses were the smallest in all instances where the failures were predicted to be controlled by the fracture toughness. However, in certain cases, the CFS values predicted by the elastic-plastic analyses were smaller than those predicted by the elastic analyses; in these cases the failure criteria were determined by a breakdown in stress intensity factor validity limits for deep flaws (a greater than 0.90t), rather than by the fracture toughness. Plastic relaxation of stresses accompanying shakedown always increases the calculated CFS values compared to the CFS values determined without shakedown. Thus, it is conservative to ignore shakedown effects.

Chell, G. Graham; Hudak, Stephen J., Jr.

2008-01-01

140

Fluid Flow Phenomena during Welding  

SciTech Connect

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.

Zhang, Wei [ORNL

2011-01-01

141

Mathematical modeling of heat transfer, fluid flow, and solidification during linear welding with a pulsed laser beam  

NASA Astrophysics Data System (ADS)

The evolution of temperature and velocity fields during welding of 304 stainless steel with a pulsed laser beam was simulated using a three dimensional numerical heat transfer and fluid flow model. The weld pool solidified between pulses and regions of the weld bead melted and solidified several times during welding. Short laser pulses restricted the width of the weld track and velocities in the weld pool. However, convection still remained an important mechanism of heat transfer in the weld pool. The computed high cooling rates during linear welding with neodymium-doped yttrium aluminum garnet pulsed laser operated at 140W average power, 20Hz frequency, and 5ms pulse duration were consistent with those observed in typical laser welding. After the laser beam was switched off, the mushy zone expanded, reaching its maximum size when no pure liquid region remained. Calculations of solidification parameters indicated that the criterion for plane front solidification was not satisfied. The results demonstrate that the application of numerical transport phenomena can significantly improve the current understanding of linear welding with a pulsed laser beam.

Roy, G. G.; Elmer, J. W.; DebRoy, T.

2006-08-01

142

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

PubMed Central

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

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

2014-01-01

143

EFFECTS OF SURFACE DEPRESSION AND CONVECTION IN GTA WELDING  

E-print Network

EFFECTS OF SURFACE DEPRESSION AND CONVECTION IN GTA WELDING M.L. Lin, T.W. Eagar Materials of the weld pool which are changed by these fact ors . It is shown that, at current s in excess of 300 amperes in a different heat distribution on the weld pool surface . ALTHOUGH THE GAS tungsten arc (GTA) welding process

Eagar, Thomas W.

144

The activity of nitrate reductase and the pool sizes of some amino acids and some sugars in water-stressed maize leaves  

Microsoft Academic Search

The activity of nitrate reductase and the pool sizes of some amino acids and some sugars were measured in relation to the leaf water potential (?) of maize leaves. The activity of nitrate reductase was severely inhibited in water-stressed maize leaves. This was not due to substrate shortage or the presence of an inhibitor at reduced leaf water potential. While

T. W. Becker; H. P. Fock

1986-01-01

145

FatJ acts via the Hippo mediator Yap1 to restrict the size of neural progenitor cell pools  

PubMed Central

The size, composition and functioning of the spinal cord is likely to depend on appropriate numbers of progenitor and differentiated cells of a particular class, but little is known about how cell numbers are controlled in specific cell cohorts along the dorsoventral axis of the neural tube. Here, we show that FatJ cadherin, identified in a large-scale RNA interference (RNAi) screen of cadherin genes expressed in the neural tube, is localised to progenitors in intermediate regions of the neural tube. Loss of function of FatJ promotes an increase in dp4-vp1 progenitors and a concomitant increase in differentiated Lim1+/Lim2+ neurons. Our studies reveal that FatJ mediates its action via the Hippo pathway mediator Yap1: loss of downstream Hippo components can rescue the defect caused by loss of FatJ. Together, our data demonstrate that RNAi screens are feasible in the chick embryonic neural tube, and show that FatJ acts through the Hippo pathway to regulate cell numbers in specific subsets of neural progenitor pools and their differentiated progeny. PMID:21521736

Van Hateren, Nick J.; Das, Raman M.; Hautbergue, Guillaume M.; Borycki, Anne-Gaelle; Placzek, Marysia; Wilson, Stuart A.

2011-01-01

146

The effect of welding parameters on penetration in GTA welds  

SciTech Connect

The effect of various welding parameters on the penetration of GTA welds has been investigated. Increases in welding speed were found to reduce penetration; however, increases in welding current were observed to increase the penetration in high sulfur (HS) casts and decrease penetration in low sulfur (LS) steels. Plots of penetration as a function of increasing linear energy (the heat supplied per unit length of weld) revealed a similar trend with increased penetration in HS casts, but the penetration in LS casts was unaffected by increases in linear energy. These results support the Burgardt-Heiple proposition that changes in welding parameters on penetration can be explained in terms of their effect, sequentially, on the temperature gradient and the Marangoni forces operating in the weld pool. Increases in arc length were found to decrease weld penetration regardless of the sulfur concentration of the steel, and the effects of electrode geometry and welding position on weld penetration were also investigated.

Shirali, A.A. (Univ. of Strathclyde, Glasgow (United Kingdom)); Mills, K.C. (National Physical Lab., Teddington, Middx (United Kingdom))

1993-07-01

147

The effect of nucleus size on mechanical properties in electrical resistance spot welding of sheets used in automotive industry  

Microsoft Academic Search

In this study, the effects of welding current and time on the tensile-peel strength and tensile-shear strength of welding joint in electrical resistance spot welding of chromided micro-alloyed steel sheets having 0.8 mm thickness and galvanized chromided micro-alloyed steel sheets having 1.0 mm thickness were investigated. A timer and current controlled electrical resistance spot welding machine having 120 kVA capacity

S. Aslanlar

2006-01-01

148

Beam Shaping to Control of Weldpool Size in Width and Depth  

NASA Astrophysics Data System (ADS)

The introduction of high power single mode fiber lasers has given deeper and narrower laser welds than seen previously. In some cases the weld becomes too narrow and must be expanded to fit the geometrical shape of a given weld task. It was suggested that instead of using only one beam, the beam was split into multiple beams placed in a pre-specified pattern. In this way the dimensions of the weld pool could be controlled. This gave the ability to control the final weld face width and penetrationdepth independently of each other with minimum heat input. Practical implementation of splitting a beam into a beam pattern with a diffractive optical element (DOE) is presented with results on splitting a beam from a single mode fiber laser into either three or seven individual beams on a row. Basic design rules for controlling the weld pool dimensions are developed. Results show that it is possible to control weldpool in size.

Hansen, K. S.; Kristiansen, M.; Olsen, F. O.

149

Litter pool sizes, decomposition, and nitrogen dynamics in Spartina alterniflora-invaded and native coastal marshlands of the Yangtze Estuary.  

PubMed

Past studies have focused primarily on the effects of invasive plants on litter decomposition at soil surfaces. In natural ecosystems, however, considerable amounts of litter may be at aerial and belowground positions. This study was designed to examine the effects of Spartina alterniflora invasion on the pool sizes and decomposition of aerial, surficial, and belowground litter in coastal marshlands, the Yangtze Estuary, which were originally occupied by two native species, Scirpus mariqueter and Phragmites australis. We collected aerial and surficial litter of the three species once a month and belowground litter once every 2 months. We used the litterbag method to quantify litter decomposition at the aerial, surficial and belowground positions for the three species. Yearly averaged litter mass in the Spartina stands was 1.99 kg m(-2); this was 250 and 22.8% higher than that in the Scirpus (0.57 kg m(-2)) and Phragmites (1.62 kg m(-2)) stands, respectively. The litter in the Spartina stands was primarily distributed in the air (45%) and belowground (48%), while Scirpus and Phragmites litter was mainly allocated to belowground positions (85 and 59%, respectively). The averaged decomposition rates of aerial, surficial, and belowground litter were 0.82, 1.83, and 1.27 year(-1) for Spartina, respectively; these were 52, 62 and 69% of those for Scirpus litter at corresponding positions and 158, 144 and 78% of those for Phragmites litter, respectively. The differences in decomposition rates between Spartina and the two native species were largely due to differences in litter quality among the three species, particularly for the belowground litter. The absolute amount of nitrogen increased during the decomposition of Spartina stem, sheath and root litter, while the amount of nitrogen in Scirpus and Phragmites litter declined during decomposition for all tissue types. Our results suggest that Spartina invasion altered the carbon and nitrogen cycling in the coastal marshlands of China. PMID:18327617

Liao, Cheng Zhang; Luo, Yi Qi; Fang, Chang Ming; Chen, Jia Kuan; Li, Bo

2008-06-01

150

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

PubMed Central

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

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

2013-01-01

151

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

Microsoft Academic Search

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

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

2003-01-01

152

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

E-print Network

\\ 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

Eagar, Thomas W.

153

Flow Dynamics in Arc Welding  

SciTech Connect

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.

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

154

Method for enhanced control of welding processes  

SciTech Connect

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.

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

2000-07-04

155

Local fatigue strength parameters for welded joints based on strain energy density with inclusion of small-size notches  

Microsoft Academic Search

A fatigue strength parameter for (seam-)welded joints is presented which is based on the averaged elastic strain energy density (SED) criterion applied to full circle and semicircular ‘control volumes’, the latter centred by the expected crack path. The parameter is applicable both at weld toes and weld roots, at least in the medium-cycle and high-cycle fatigue range where elastic conditions

D. Radaj; F. Berto; P. Lazzarin

2009-01-01

156

Changes in the size and composition of intracellular pools of nonesterified coenzyme A and coenzyme A thioesters in aerobic and facultatively anaerobic bacteria.  

PubMed Central

Intracellular levels of three coenzyme A (CoA) molecular species, i.e., nonesterified CoA (CoASH), acetyl-CoA, and malonyl-CoA, in a variety of aerobic and facultatively anaerobic bacteria were analyzed by the acyl-CoA cycling method developed by us. It was demonstrated that there was an intrinsic difference between aerobes and facultative anaerobes in the changes in the size and composition of CoA pools. The CoA pools in the aerobic bacteria hardly changed and were significantly smaller than those of the facultatively anaerobic bacteria. On the other hand, in the facultatively anaerobic bacteria, the size and composition of the CoA pool drastically changed within minutes in response to the carbon and energy source provided. Acetyl-CoA was the major component of the CoA pool in the facultative anaerobes grown on sufficient glucose, although CoASH was dominant in the aerobes. Therefore, the acetyl-CoA/CoASH ratios in facultatively anaerobic bacteria were 10 times higher than those in aerobic bacteria. In Escherichia coli K-12 cells, the addition of reagents to inhibit the respiratory system led to a rapid decrease in the amount of acetyl-CoA with a concomitant increase in the amount of CoASH, whereas the addition of cerulenin, a specific inhibitor of fatty acid synthase, triggered the intracellular accumulation of malonyl-CoA. The acylation and deacylation of the three CoA molecular species coordinated with the energy-yielding systems and the restriction of the fatty acid-synthesizing system of cells. These data suggest that neither the accumulation of acetyl-CoA nor that of malonyl-CoA exerts negative feedback on pyruvate dehydrogenase and acetyl-CoA carboxylase, respectively. PMID:9023936

Chohnan, S; Furukawa, H; Fujio, T; Nishihara, H; Takamura, Y

1997-01-01

157

Improvement of reliability of welding by in-process sensing and control (development of smart welding machines for girth welding of pipes). Final report  

SciTech Connect

Closed-loop control of the welding variables represents a promising, cost-effective approach to improving weld quality and therefore reducing the total cost of producing welded structures. The ultimate goal is to place all significant weld variables under direct closed-loop control; this contrasts with preprogrammed machines which place the welding equipment under control. As the first step, an overall strategy has been formulated and an investigation of weld pool geometry control for gas tungsten arc process has been completed. The research activities were divided into the areas of arc phenomena, weld pool phenomena, sensing techniques and control activities.

Hardt, D.E.; Masubuchi, K.; Paynter, H.M.; Unkel, W.C.

1983-04-01

158

Welding wire pressure sensor assembly  

NASA Technical Reports Server (NTRS)

The present invention relates to a device which is used to monitor the position of a filler wire relative to a base material being welded as the filler wire is added to a welding pool. The device is applicable to automated welding systems wherein nonconsumable electrode arc welding processes are utilized in conjunction with a filler wire which is added to a weld pool created by the electrode arc. The invention senses pressure deviations from a predetermined pressure between the filler wire and the base material, and provides electrical signals responsive to the deviations for actuating control mechanisms in an automatic welding apparatus so as to minimize the pressure deviation and to prevent disengagement of the contact between the filler wire and the base material.

Morris, Timothy B. (inventor); Milly, Peter F., Sr. (inventor); White, J. Kevin (inventor)

1994-01-01

159

Melting Efficiency During Plasma Arc Welding  

NASA Technical Reports Server (NTRS)

A series of partial penetration Variable Polarity Plasma Arc welds were made at equal power but various combinations of current and voltage on 2219 aluminum. Arc Efficiency was measured calorimetrically and ranged between 48% and 66%. Melting efficiency depends on the weld pool shape. Increased current increases the melting efficiency as it increases the depth to width ratio of the weld pool. Higher currents are thought to raise arc pressure and depress the liquid at the bottom of the weld pool causing a more nearly two dimensional heat flow condition.

McClure, J.C.; Evans, D. M.; Tang, W.; Nunes, A. C.

1999-01-01

160

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

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.

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

1980-10-01

161

Diets high in resistant starch and arabinoxylan modulate digestion processes and SCFA pool size in the large intestine and faecal microbial composition in pigs.  

PubMed

The effects of a high level of dietary fibre (DF) either as arabinoxylan (AX) or resistant starch (RS) on digestion processes, SCFA concentration and pool size in various intestinal segments and on the microbial composition in the faeces were studied in a model experiment with pigs. A total of thirty female pigs (body weight 63·1 (sem 4·4) kg) were fed a low-DF, high-fat Western-style control diet (WSD), an AX-rich diet (AXD) or a RS-rich diet (RSD) for 3 weeks. Diet significantly affected the digestibility of DM, protein, fat, NSP and NSP components, and the arabinose:xylose ratio, as well as the disappearance of NSP and AX in the large intestine. RS was mainly digested in the caecum. AX was digested at a slower rate than RS. The digesta from AXD-fed pigs passed from the ileum to the distal colon more than twice as fast as those from WSD-fed pigs, with those from RSD-fed pigs being intermediate (P< 0·001). AXD feeding resulted in a higher number of Faecalibacterium prausnitzii, Roseburia intestinalis, Blautia coccoides-Eubacterium rectale, Bifidobacterium spp. and Lactobacillus spp. in the faeces sampled at week 3 of the experimental period (P< 0·05). In the caecum, proximal and mid colon, AXD feeding resulted in a 3- to 5-fold higher pool size of butyrate compared with WSD feeding, with the RSD being intermediate (P <0·001). In conclusion, the RSD and AXD differently affected digestion processes compared with the WSD, and the AXD most efficiently shifted the microbial composition towards butyrogenic species in the faeces and increased the large-intestinal butyrate pool size. PMID:25327182

Nielsen, Tina S; Lærke, Helle N; Theil, Peter K; Sørensen, Jens F; Saarinen, Markku; Forssten, Sofia; Bach Knudsen, Knud E

2014-12-01

162

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

SciTech Connect

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.

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

163

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

NASA Astrophysics Data System (ADS)

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 × 1014 m-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 × 1015 m-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.

Woo, Wanchuck; Ungár, Tamás; Feng, Zhili; Kenik, Edward; Clausen, Bjørn

2010-05-01

164

Three-Dimensional Coaxial Weld Monitoring  

NASA Technical Reports Server (NTRS)

Optical system for coaxial-viewing welding torch enables perception or measurement of depth. Light from welding area passes through beam splitter into two optical trains forming two images, each viewed along line making small angle with axis of torch. Two lines of sight intersect at weld pool. Parallax between two views provides sensation of depth over entire field view.

Gordon, Stephen S.

1989-01-01

165

Optical penetration sensor for pulsed laser welding  

DOEpatents

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.

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

2000-01-01

166

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

NASA Astrophysics Data System (ADS)

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.

Thasanaraphan, Pornsak

167

BDNF increases release probability and the size of a rapidly recycling vesicle pool within rat hippocampal excitatory synapses  

PubMed Central

Exerting its actions pre-, post- and peri-synaptically, brain-derived neurotrophic factor (BDNF) is one of the most potent modulators of hippocampal synaptic function. Here, we examined the effects of BDNF on a rapidly recycling pool (RRP) of vesicles within excitatory synapses. First, we estimated vesicular release in hippocampal cultures by performing FM4-64 imaging in terminals impinging on enhanced green fluorescent protein (eGFP)-labelled dendritic spines – a hallmark of excitatory synapses. Consistent with a modulation of the RRP, BDNF increased the evoked destaining rate of FM4-64 only during the initial phase of field stimulation. Multiphoton microscopy in acute hippocampal slices confirmed these observations by selectively imaging the RRP, which was loaded with FM1-43 by hyperosmotic shock. Slices exposed to BDNF showed an increase in the evoked and spontaneous rates of FM1-43 destaining from terminals in CA1 stratum radiatum, mostly representing excitatory terminals of Schaffer collaterals. Variance-mean analysis of evoked EPSCs in CA1 pyramidal neurons further confirmed that release probability is increased in BDNF-treated slices, without changes in the number of independent release sites or average postsynaptic quantal amplitude. Because BDNF was absent during dye loading, imaging, destaining and whole-cell recordings, these results demonstrate that BDNF induces a long-lasting enhancement in the probability of transmitter release at hippocampal excitatory synapses by modulating the RRP. Since the endogenous BDNF scavenger TrkB-IgG prevented the enhancement of FM1-43 destaining rate caused by induction of long-term potentiation in acute hippocampal slices, the modulation of a rapidly recycling vesicle pool may underlie the role of BDNF in hippocampal long-term synaptic plasticity. PMID:16709633

Tyler, William J; Zhang, Xiao-lei; Hartman, Kenichi; Winterer, Jochen; Muller, Wolfgang; Stanton, Patric K; Pozzo-Miller, Lucas

2006-01-01

168

Dependence of overload performance on weld attributes for resistance spot welded galvanized low carbon steel  

Microsoft Academic Search

Microstructure and failure behavior of galvanized low carbon steel resistance spot welds were investigated. Failure mode, peak load and energy absorption obtained in tensile-shear test were used to describe spot welds performance. It was found that weld fusion zone size, electrode indentation and expulsion can significantly affect the mechanical performance of spot welds. Failure mechanism of spot weld which fail

M. Goodarzi; S. P. H. Marashi; M. Pouranvari

2009-01-01

169

Processing Welding Images For Robot Control  

NASA Technical Reports Server (NTRS)

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.

Richardson, Richard W.

1988-01-01

170

Exciting Pools  

ERIC Educational Resources Information Center

Advocates the creation of swimming pool oscillations as part of a general investigation of mechanical oscillations. Presents the equations, procedure for deriving the slosh modes, and methods of period estimation for exciting swimming pool oscillations. (GS)

Wright, Bradford L.

1975-01-01

171

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

E-print Network

SOLIDIFICATION DURING ARC WELDING 2.1 INTRODUCTION The solidification process in a weld pool has been shown of the thermal cycle experienced in the heat-affected zone (HAZ) during manual-metal-arc (MMA) welding (Baker concentrations as a consequence of the fast cooling rates encountered in arc welding, two bead-on-plate welds

Cambridge, University of

172

Swimming Pool Guidelines. 1997 Edition.  

ERIC Educational Resources Information Center

The state of Alaska, which provides for swimming pools as an eligible project cost in projects approved for state aid, presents guidelines to assist school districts in planning swimming pools, and provides standards for swimming pool size based on the planned educational program and student population. The guidelines are intended to assist school…

Alaska State Dept. of Education, Juneau.

173

Repair welding process of friction stir welding groove defect  

Microsoft Academic Search

The groove defect formed in the friction stir welding dramatically deteriorates weld appearances and mechanical properties of the joints owing to its larger size and penetration. Therefore, the friction stir repair welding was utilized to remove such a groove defect, and the focus was placed on the mechanical properties and microstructural characteristics of the repair joints so as to obtain

Hui-jie LIU; Hui-jie ZHANG

2009-01-01

174

Effect of specimen size and shape on creep rupture behavior of creep strength enhanced ferritic steel welds  

Microsoft Academic Search

The creep strength enhanced ferritic (CSEF) steels such as Grades 91, 92, 122, 911, 23 and 24 have become very important key materials for high efficiency fossil-fired power plants for last decades, however the long-term creep rupture strength and strength reduction in welds due to Type IV failure of these steels are serious problem to be urgently resolved. In order

Fujimitsu Masuyama

2010-01-01

175

Structural and mechanical properties of welded joints of reduced activation martensitic steels  

Microsoft Academic Search

Gas tungsten arc welding and electron beam welding methods were used to realise welding pools on plates of reduced activation martensitic steels. Structural and mechanical features of these simulated joints have been investigated in as-welded and post-welding heat-treated conditions. The research allowed to assess how each welding technique affects the original mechanical properties of materials and to find suitable post-welding

G. Filacchioni; R. Montanari; M. E. Tata; L. Pilloni

2002-01-01

176

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

177

Nicotine enhancement of dopamine release by a calcium-dependent increase in the size of the readily releasable pool of synaptic vesicles.  

PubMed

A major factor underlying compulsive tobacco use is nicotine-induced modulation of dopamine release in the mesolimbic reward pathway (Wise and Rompre, 1989). An established biochemical mechanism for nicotine-enhanced dopamine release is by activating presynaptic nicotinic acetylcholine receptors (nAChRs) (Wonnacott, 1997). Prolonged application of 10(-7) to 10(-5) m nicotine to striatal synaptosomes promoted a sustained efflux of [3H]dopamine. This nicotine effect was mediated by non-alpha7 nAChRs, because it was blocked by 5 mum mecamylamine but was resistant to 100 nm alpha-bungarotoxin (alphaBgTx). Dopamine release was diminished by omitting Na+ or by applying peptide calcium channel blockers, indicating that nAChRs trigger release by depolarizing the nerve terminals. However, because alpha7 receptors rapidly desensitize in the continuous presence of agonists, a repetitive stimulation protocol was used to evaluate the possible significance of desensitization. This protocol produced a transient increase in [3H]dopamine released by depolarization and a significant increase in the response to hypertonic solutions that measure the size of the readily releasable pool (RRP) of synaptic vesicles. The nicotine-induced increase in the size of the readily releasable pool was blocked by alphaBgTx and by the calmodulin antagonist calmidazolium, suggesting that Ca2+ entry through alpha7 nAChRs specifically enhances synaptic vesicle mobilization at dopamine terminals. Thus, nicotine enhances dopamine release by two complementary actions mediated by discrete nAChR subtypes and suggest that the alpha7 nAChR-mediated pathway is tightly and specifically coupled to refilling of the RRP of vesicles in dopamine terminals. PMID:15601939

Turner, Timothy J

2004-12-15

178

Visual sensing and penetration control in aluminum alloy pulsed GTA welding  

Microsoft Academic Search

In this paper, visual sensing and penetration control in aluminum (Al) alloy pulse gas tungsten arc welding were researched.\\u000a Firstly, a three-optical-route visual sensor was designed. The sensor can capture the weld pool from three directions at the\\u000a same time. After analyzing the influences of different factors on weld pool image, serials of clear and stable weld pool images\\u000a were

Chongjian Fan; Fenglin Lv; Shanben Chen

2009-01-01

179

Development of a Three-Dimensional Heat-Transfer Model for the Gas Tungsten Arc Welding Process Using the Finite Element Method Coupled with a Genetic Algorithm Based Identification of Uncertain Input Parameters  

NASA Astrophysics Data System (ADS)

An accurate estimation of the temperature field in weld pool and its surrounding area is important for a priori determination of the weld-pool dimensions and the weld thermal cycles. A finite element based three-dimensional (3-D) quasi-steady heat-transfer model is developed in the present work to compute temperature field in gas tungsten arc welding (GTAW) process. The numerical model considers temperature-dependent material properties and latent heat of melting and solidification. A novelty of the numerical model is that the welding heat source is considered in the form of an adaptive volumetric heat source that confirms to the size and the shape of the weld pool. The need to predefine the dimensions of the volumetric heat source is thus overcome. The numerical model is further integrated with a parent-centric recombination (PCX) operated generalized generation gap (G3) model based genetic algorithm to identify the magnitudes of process efficiency and arc radius that are usually unknown but required for the accurate estimation of the net heat input into the workpiece. The complete numerical model and the genetic algorithm based optimization code are developed indigenously using an Intel Fortran Compiler. The integrated model is validated further with a number of experimentally measured weld dimensions in GTA-welded samples in stainless steels.

Bag, S.; de, A.

2008-11-01

180

Pool Purification  

NASA Technical Reports Server (NTRS)

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.

1988-01-01

181

Evaluation of weld porosity in laser beam seam welds: optimizing continuous wave and square wave modulated processes.  

SciTech Connect

Nd:YAG laser joining is a high energy density (HED) process that can produce high-speed, low-heat input welds with a high depth-to-width aspect ratio. This is optimized by formation of a ''keyhole'' in the weld pool resulting from high vapor pressures associated with laser interaction with the metallic substrate. It is generally accepted that pores form in HED welds due to the instability and frequent collapse of the keyhole. In order to maintain an open keyhole, weld pool forces must be balanced such that vapor pressure and weld pool inertia forces are in equilibrium. Travel speed and laser beam power largely control the way these forces are balanced, as well as welding mode (Continuous Wave or Square Wave) and shielding gas type. A study into the phenomenon of weld pool porosity in 304L stainless steel was conducted to better understand and predict how welding parameters impact the weld pool dynamics that lead to pore formation. This work is intended to aid in development and verification of a finite element computer model of weld pool fluid flow dynamics being developed in parallel efforts and assist in weld development activities for the W76 and future RRW programs.

Ellison, Chad M. (Honeywell FM& T, Kansas City, MO); Perricone, Matthew; Faraone, Kevin M. (Honeywell FM& T, Kansas City, MO); Roach, Robert Allen; Norris, Jerome T.

2007-02-01

182

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

183

Primary Water Stress Corrosion Cracks in Nickel Alloy Dissimilar Metal Welds: Detection and Sizing Using Established and Emerging Nondestructive Examination Techniques  

SciTech Connect

The U.S. Nuclear Regulatory Commission has established the Program to Assess the Reliability of Emerging Nondestructive Techniques (PARENT) as a follow-on to the international cooperative Program for the Inspection of Nickel Alloy Components (PINC). The goal of PINC was to evaluate the capabilities of various nondestructive evaluation (NDE) techniques to detect and characterize surface-breaking primary water stress corrosion cracks in dissimilar-metal welds (DMW) in bottom-mounted instrumentation (BMI) penetrations and small-bore (?400-mm diameter) piping components. A series of international blind round-robin tests were conducted by commercial and university inspection teams. Results from these tests showed that a combination of conventional and phased-array ultrasound techniques provided the highest performance for flaw detection and depth sizing in dissimilar metal piping welds. The effective detection of flaws in BMIs by eddy current and ultrasound shows that it may be possible to reliably inspect these components in the field. The goal of PARENT is to continue the work begun in PINC and apply the lessons learned to a series of open and blind international round-robin tests that will be conducted on a new set of piping components including large-bore (?900-mm diameter) DMWs, small-bore DMWs, and BMIs. Open round-robin testing will engage universities and industry worldwide to investigate the reliability of emerging NDE techniques to detect and accurately size flaws having a wide range of lengths, depths, orientations, and locations. Blind round-robin testing will invite testing organizations worldwide, whose inspectors and procedures are certified by the standards for the nuclear industry in their respective countries, to investigate the ability of established NDE techniques to detect and size flaws whose characteristics range from easy to very difficult to detect and size. This paper presents highlights of PINC and reports on the plans and progress for PARENT round-robin tests.

Braatz, Brett G.; Cumblidge, Stephen E.; Doctor, Steven R.; Prokofiev, Iouri

2012-12-31

184

Numerical analysis of fume formation mechanism in arc welding  

NASA Astrophysics Data System (ADS)

In order to clarify the fume formation mechanism in arc welding, a quantitative investigation based on the knowledge of interaction among the electrode, arc and weld pool is indispensable. A fume formation model consisting of a heterogeneous condensation model, a homogeneous nucleation model and a coagulation model has been developed and coupled with the GTA or GMA welding model. A series of processes from evaporation of metal vapour to fume formation from the metal vapour was totally investigated by employing this simulation model. The aim of this paper is to visualize the fume formation process and clarify the fume formation mechanism theoretically through a numerical analysis. Furthermore, the reliability of the simulation model was also evaluated through a comparison of the simulation result with the experimental result. As a result, it was found that the size of the secondary particles consisting of small particles with a size of several tens of nanometres reached 300 nm at maximum and the secondary particle was in a U-shaped chain form in helium GTA welding. Furthermore, it was also clarified that most part of the fume was produced in the downstream region of the arc originating from the metal vapour evaporated mainly from the droplet in argon GMA welding. The fume was constituted by particles with a size of several tens of nanometres and had similar characteristics to that of GTA welding. On the other hand, if the metal transfer becomes unstable and the metal vapour near the droplet diffuses directly towards the surroundings of the arc not getting into the plasma flow, the size of the particles reaches several hundred nanometres.

Tashiro, Shinichi; Zeniya, Tasuku; Yamamoto, Kentaro; Tanaka, Manabu; Nakata, Kazuhiro; Murphy, Anthony B.; Yamamoto, Eri; Yamazaki, Kei; Suzuki, Keiichi

2010-11-01

185

Investigation of the force characteristics of the three-phase welding arc in deposition of components made of light alloys  

Microsoft Academic Search

Three-phase arc integral pressure measurement data are covered and welding arc power force component effect on the welding bath formation is considered. Effect of welding arc electrodynamic component and gas-kinetic flow on the welding bath formation and shrink crater is determined. Technological guidance to pressure minimization of the active spot on the metal of the weld pool is given.

V. V. Eltsov; O. A. Ditenkov; A. S. Zelenkov; A. Yu. Leipinen

2011-01-01

186

The keyhole region in VPPA welds  

NASA Technical Reports Server (NTRS)

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.

Walsh, Daniel W.

1988-01-01

187

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

188

Modelling Plastic Deformation and Thermal Response in Welding using Smoothed Particle Hydrodynamics  

Microsoft Academic Search

An approach for modelling plastic deformation and t hermal response in a weld pool using the mesh-free Smoothed Particle Hydrodynamics (SPH) method is developed. The proposed modelling technique is illustrated by simulating a simple setup of an arc welding process. The plastic deformation and temperature distribution in the weld pool and the surrounding p arent material are analysed using SPH.

R. Das; P. W. Cleary

189

Neurofuzzy Model-Based Weld Fusion State Estimation  

E-print Network

Neurofuzzy Model-Based Weld Fusion State Estimation Radovan Kovacevic and Yu M. Zhang roper fusion is crucial in Pgenerating a sound weld. Successful control of the fu- sion state requires accurate state from the observed weld pool, a neurofuzzy system is developed to infer the back- side bead width

Zhang, YuMing

190

Variable-Polarity Plasma Arc Welding Of Alloy 2219  

NASA Technical Reports Server (NTRS)

Report presents results of study of variable-polarity plasma arc (VPPA) welding of aluminum alloy 2219. Consists of two parts: Examination of effects of microsegregation and transient weld stress on macrosegregation in weld pool and, electrical characterization of straight- and reverse-polarity portions of arc cycle.

Walsh, Daniel W.; Nunes, Arthur C., Jr.

1989-01-01

191

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

PubMed Central

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

Millonigg, Sophia; Eckmann, Christian R.

2014-01-01

192

Welding I.  

ERIC Educational Resources Information Center

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,…

Allegheny County Community Coll., Pittsburgh, PA.

193

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

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.

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

1992-08-01

194

An analytical thermodynamic model of laser welding  

Microsoft Academic Search

An earlier model of deep-penetration laser welding has been simplified in order to provide a useful model of process analysis. This work involves the modelling of the various energy-absorption mechanisms which determine the keyhole shape and thus the dimensions of the melt pool. The penetration depth and weld width (top and bottom) predicted by the model are shown to be

Conny Lampa; Alexander F. H. Kaplan; John Powell; Claes Magnusson

1997-01-01

195

A novel visual image sensor for CO2 short circuiting arc welding and its application in weld reinforcement detection  

NASA Astrophysics Data System (ADS)

In this paper, a novel visual image sensor was designed to detect the weld pool images during CO2 short circuiting arc welding. Based on a charge coupled device (CCD) camera, the new sensor was smaller than the previous one. As a result, larger operation space is achieved for the welding torch which is attached to it. Moreover, the mismatching problem between the fixed shooting schedule of the CCD camera and the random short circuiting metal transfer during welding was successfully resolved. By eliminating the influences from welding arc and spatter, clear and complete welding pool images were acquired from different angles around the welding torch. Based on these images, the shape parameters of the welding pool were defined and the relationship between these parameters and weld reinforcement was analysed. In addition, the multiple linear regression (MLR) model and the artificial neutral network (ANN) model were proposed and trained, respectively, to detect weld reinforcement from weld pool images. Results of both the MLR model and the ANN model show that weld reinforcement can successfully be detected.

Sun, Zhenguo; Chen, Qiang; Zhang, Wenzeng; Cao, Yipeng; Liu, Pengfei

2006-12-01

196

Optical Monitoring of Weld Penetration  

NASA Technical Reports Server (NTRS)

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.

Maram, J.

1986-01-01

197

Probing heat transfer, fluid flow and microstructural evolution during fusion welding of alloys  

NASA Astrophysics Data System (ADS)

The composition, geometry, structure and properties of the welded joints are affected by the various physical processes that take place during fusion welding. Understanding these processes has been an important goal in the contemporary welding research to achieve structurally sound and reliable welds. In the present thesis research, several important physical processes including the heat transfer, fluid flow and microstructural evolution in fusion welding were modeled based on the fundamentals of transport phenomena and phase transformation theory. The heat transfer and fluid flow calculation is focused on the predictions of the liquid metal convection in the weld pool, the temperature distribution in the entire weldment, and the shape and size of the fusion zone (FZ) and heat affected zone (HAZ). The modeling of microstructural evolution is focused on the quantitative understanding of phase transformation kinetics during welding of several important alloys under both low and high heating and cooling conditions. Three numerical models were developed in the present thesis work: (1) a three-dimensional heat transfer and free surface flow model for the gas metal arc (GMA) fillet welding considering the complex weld joint geometry, (2) a phase transformation model based on the Johnson-Mehl-Avrami (JMA) theory, and (3) a one-dimensional numerical diffusion model considering multiple moving interfaces. To check the capabilities of the developed models, several cases were investigated, in which the predictions from the models were compared with the experimental results. The cases studied are the follows. For the modeling of heat transfer and fluid flow, the welding processes studied included gas tungsten arc (GTA) linear welding, GTA transient spot welding, and GMA fillet welding. The calculated weldment geometry and thermal cycles was validated against the experimental data under various welding conditions. For the modeling of microstructural evolution, the welded materials investigated included AISI 1005 low-carbon steel, 1045 medium-carbon steel, 2205 duplex stainless steel (DSS) and Ti-6Al-4V alloy. The calculated phase transformation kinetics were compared with the experimental results obtained using an x-ray diffraction technique by Dr. John W. Elmer of Lawrence Livermore National Laboratory. (Abstract shortened by UMI.)

Zhang, Wei

198

Automatic welding of stainless steel tubing  

NASA Technical Reports Server (NTRS)

The use of automatic welding for making girth welds in stainless steel tubing was investigated as well as the reduction in fabrication costs resulting from the elimination of radiographic inspection. Test methodology, materials, and techniques are discussed, and data sheets for individual tests are included. Process variables studied include welding amperes, revolutions per minute, and shielding gas flow. Strip chart recordings, as a definitive method of insuring weld quality, are studied. Test results, determined by both radiographic and visual inspection, are presented and indicate that once optimum welding procedures for specific sizes of tubing are established, and the welding machine operations are certified, then the automatic tube welding process produces good quality welds repeatedly, with a high degree of reliability. Revised specifications for welding tubing using the automatic process and weld visual inspection requirements at the Kennedy Space Center are enumerated.

Clautice, W. E.

1978-01-01

199

Joint tracking and adaptive robotic welding using vision sensing of the weld joint geometry  

SciTech Connect

An approach to the vision-guidance of welding robots and the in-process adjustment of welding conditions is presented. The implementation of a complete vision-guided adaptive robotic welding system is described. The vision-guided adaptive welding system described here has been used to track and weld a wide variety of test and production parts ranging in size from 1.6-mm (1/16-in.) sheet steel to 19.1-mm (3/4-in.) steel plate. Both conventional joint types, including square butt, lap, and V-groove, and special types, such as a multipass square butt submerged arc weld with pre-welded root passes or the axle joints were welded. Various welding procedures, such as GMA welding with a variety of shielding gases and submerged arc welding, have also been used.

Agapakis, J.E.; Katz, J.M.; Koifman, M.; Epstein, G.N.; Friedman, J.M.; Eyring, D.O.; Rutishauser, H.J.

1986-11-01

200

Vision processing and control of robotic Arc welding system  

Microsoft Academic Search

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

R. S. Baheti

1985-01-01

201

Robotic welding  

SciTech Connect

The purpose of this book is to provide the reader with the latest up-to-date information on robotic welding, associated components, and systems. This information has been compiled on automatic robotic arc welding systems which are presently employed and being worked on for future applications along with various adaptive control techniques and welt joint seam,-tracking systems being investigated for continuous robotic arc welding. In addition to arc welding, robotic resistance welding and laser welding systems and applications are presented with the idea of illustrating detailed knowledge on the most established and the newest robotic integrated systems, respectively.

Lane, J.D.

1986-01-01

202

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

NASA Astrophysics Data System (ADS)

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

Guo, Hao

2004-11-01

203

Establishing empirical relationships to predict grain size and tensile strength of friction stir welded AA 6061-T6 aluminium alloy joints  

Microsoft Academic Search

AA 6061-T6 aluminium alloy (Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of light weight structures requiring a high specific strength and good corrosion resistance. Compared with the fusion welding processes that are routinely used for joining structural aluminium alloys, friction stir welding (FSW) process is an emerging solid state joining process in which the material welded does not

S. RAJAKUMAR; C. MURALIDHARAN; V. BALASUBRAMANIAN

2010-01-01

204

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)

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.

Walsh, Daniel W.

1987-01-01

205

Absorbed zinc and exchangeable zinc pool size are greater in Pakistani infants receiving traditional complementary foods with zinc-fortified micronutrient powder.  

PubMed

Adequacy of zinc intake from breast milk alone becomes marginal in relation to infant requirements by around 6 mo of age. Simple and cost-effective strategies are needed at the population level to ensure adequate intakes of zinc in infants and toddlers in populations at risk of zinc deficiency. We determined the amount of absorbed zinc (AZ) from a micronutrient powder (MNP) without and with 10 mg of zinc (MNP+Zn) added to local complementary foods used in Pakistan and the impact on the exchangeable zinc pool (EZP) size. As a nested study within a large, prospective, cluster randomized trial, 6-mo-old infants were randomly assigned to receive MNP or MNP+Zn. Stable isotope methodology was applied after ?3 and 9 mo of use to measure AZ from MNP-fortified test meals of rice-lentils (khitchri) and EZP. Nineteen infants per group completed the first metabolic studies and 14 and 17 infants in the MNP and MNP+Zn groups, respectively, completed the follow-up studies. AZs were (mean ± SD) 0.1 ± 0.1 and 1.2 ± 0.5 mg at the first point for the MNP and MNP+Zn groups, respectively (P < 0.001); results were nearly identical at the follow-up measurement. EZP did not differ between groups at the first measurement but was less in the MNP group (3.7 ± 0.6 mg/kg) than in the MNP+Zn group (4.5 ± 1.0 mg/kg) at the second measurement (P = 0.01). These data confirm that the MNP+Zn in khitchri were well absorbed and after 1 y of home fortification, zinc status assessed by EZP was significantly better for the MNP+Zn group. Additional field studies may be necessary to ascertain the adequacy of this dose for infants at high risk of deficiency. This trial was registered at ClinicalTrials.gov as NCT00705445. PMID:24225451

Ariff, Shabina; Krebs, Nancy F; Soofi, Sajid; Westcott, Jamie; Bhatti, Zaid; Tabassum, Farhana; Bhutta, Zulfiqar A

2014-01-01

206

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

NASA Astrophysics Data System (ADS)

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.

Rao, Z. H.; Liao, S. M.; Tsai, H. L.

2010-02-01

207

Welding Technician  

ERIC Educational Resources Information Center

About 95% of all manufactured goods in this country are welded or joined in some way. These welded products range in nature from bicycle handlebars and skyscrapers to bridges and race cars. The author discusses what students need to know about careers for welding technicians--wages, responsibilities, skills needed, career advancement…

Smith, Ken

2009-01-01

208

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

209

Effects of different gas environments on CO2 and Nd:YAG laser welding process efficiencies  

NASA Astrophysics Data System (ADS)

When laser welding mild steel under high power densities, vaporized material is ejected from the keyhole and forms a plume/plasma above the weld pool. In previous studies on plume formation and extent of ionization, the influence of the laser wavelength and the gas environment has been observed. In this study a comparison between CO2 and Nd:YAG laser welding has been performed using the same energy density (approximately 1.24 MW/cm2, produced using 3.5 kW of power and a focal spot size of 0.6 mm) in He, Ar and N2 gas environments and in vacuum. Plume/plasma evolution was recorded with high-speed video at 9000 frames/second and these images have been correlated with the characteristics of the weld cross-section. The fusion and heat-affected zone profiles have been measured to analyze the melting efficiency at different processing speeds. The temperatures and electron densities in the plume/plasma have also been calculated by spectroscopic methods to estimate the losses caused by the plume/plasma development. By analyzing the differences in the weld shape profiles and the plume/plasma behavior, the temporal evolution of the laser welding process efficiency was also obtained.

Greses, Jose; Barlow, Claire Y.; Hilton, Paul A.; Steen, William M.

2003-03-01

210

Mechanical properties and microstructures of a magnesium alloy gas tungsten arc welded with a cadmium chloride flux  

SciTech Connect

Gas tungsten arc (GTA) welds were prepared on 5-mm thick plates of wrought magnesium AZ31B alloy, using an activated flux. The microstructural characteristics of the weld joint were investigated using optical and scanning microscopy, and the fusion zone microstructure was compared with that of the base metal. The elemental distribution was also investigated by electron probe microanalysis (EPMA). Mechanical properties were determined by standard tensile tests on small-scale specimens. The as-welded fusion zone prepared using a CdCl{sub 2} flux exhibited a larger grain size than that prepared without flux; the microstructure consisted of matrix {alpha}-Mg, eutectic {alpha}-Mg and {beta}-Al{sub 12}Mg{sub 17}. The HAZ was observed to be slightly wider for the weld prepared with a CdCl{sub 2} flux compared to that prepared without flux; thus the tensile strength was lower for the flux-prepared weld. The fact that neither Cd nor Cl was detected in the weld seam by EPMA indicates that the CdCl{sub 2} flux has a small effect on convection in the weld pool.

Zhang, Z.D. [State Key Laboratory of Material Surface Modification by Laser, Ion, and Beams, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Liu, L.M. [State Key Laboratory of Material Surface Modification by Laser, Ion, and Beams, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China)], E-mail: liulm@dlut.edu.cn; Shen, Y.; Wang, L. [State Key Laboratory of Material Surface Modification by Laser, Ion, and Beams, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China)

2008-01-15

211

Deconvoluting the Friction Stir Weld Process for Optimizing Welds  

NASA Technical Reports Server (NTRS)

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

Schneider, Judy; Nunes, Arthur C.

2008-01-01

212

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

SciTech Connect

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.

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

2007-01-01

213

A walk-through programmed robot for welding in shipyards  

Microsoft Academic Search

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,

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

1999-01-01

214

A Parametric Study of the Electroslag Welding Process  

E-print Network

A Parametric Study of the Electroslag Welding Process Heat input and HAZ size are found ABSTRACT. Screening experiments were conducted on electroslag welds to statis- tically evaluate the effect, dilution, form factor, welding speedand heat input. The results of multiple electrode electroslag welds

Eagar, Thomas W.

215

An experimental and theoretical study of gas tungsten arc welding of stainless steel plates with different sulfur concentrations  

Microsoft Academic Search

During fusion welding, the presence of sulfur in steel often affects heat and fluid flow in the weld pool and its geometry. While the role of sulfur during welding of stainless steel plates with the same sulfur content is well understood, welding of stainless steel plates containing different concentrations of sulfur has not yet received proper attention. Here we report

S. Mishra; T. J. Lienert; M. Q. Johnson; T. DebRoy

2008-01-01

216

Infrared sensing techniques for adaptive robotic welding  

SciTech Connect

The objective of this research is to investigate the feasibility of using infrared sensors to monitor the welding process. Data were gathered using an infrared camera which was trained on the molten metal pool during the welding operation. Several types of process perturbations which result in weld defects were then intentionally induced and the resulting thermal images monitored. Gas tungsten arc using ac and dc currents and gas metal arc welding processes were investigated using steel, aluminum and stainless steel plate materials. The thermal images obtained in the three materials and different welding processes revealed nearly identical patterns for the same induced process perturbation. Based upon these results, infrared thermography is a method which may be very applicable to automation of the welding process.

Lin, T.T.; Groom, K.; Madsen, N.H.; Chin, B.A.

1986-01-01

217

Hatching phenology, life history and egg bank size of fairy shrimp Branchipodopsis spp. (Branchiopoda, Crustacea) in relation to the ephemerality of their rock pool habitat  

Microsoft Academic Search

In temporary aquatic habitats, permanence and the severe disturbance associated with desiccation are strong selective agents\\u000a expected to lead to differentiation in life history strategies in populations experiencing different disturbance regimes.\\u000a Besides optimal timing of hatching of dormant life stages, maturation and reproduction, pool inhabitants also benefit from\\u000a the acquisition of reliable cues for the quality of the ambient environment.

Bram Vanschoenwinkel; Maitland Seaman; Luc Brendonck

2010-01-01

218

The physics of welding  

Microsoft Academic Search

Greater understanding of the physics of welding is leading to improved application and control of welding processes. Further gains in welding productivity could follow. Electric arc welding, high energy density welding and future developments are described

J. F. Lancaster

1984-01-01

219

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

Code of Federal Regulations, 2010 CFR

... Minimum requirements for attachment welds (modifies PW-16). 52.05-30... Minimum requirements for attachment welds (modifies PW-16). (a) The location and minimum size of attachment welds for nozzles and other...

2010-10-01

220

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

Code of Federal Regulations, 2012 CFR

... Minimum requirements for attachment welds (modifies PW-16). 52.05-30... Minimum requirements for attachment welds (modifies PW-16). (a) The location and minimum size of attachment welds for nozzles and other...

2012-10-01

221

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

Code of Federal Regulations, 2013 CFR

... Minimum requirements for attachment welds (modifies PW-16). 52.05-30... Minimum requirements for attachment welds (modifies PW-16). (a) The location and minimum size of attachment welds for nozzles and other...

2013-10-01

222

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

Code of Federal Regulations, 2011 CFR

... Minimum requirements for attachment welds (modifies PW-16). 52.05-30... Minimum requirements for attachment welds (modifies PW-16). (a) The location and minimum size of attachment welds for nozzles and other...

2011-10-01

223

WELDING RESEARCH -s11WELDING JOURNAL  

E-print Network

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

Zhang, YuMing

224

Soldadura (Welding). Spanish Translations for Welding.  

ERIC Educational Resources Information Center

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

Hohhertz, Durwin

225

WELDING RESEARCH -s229WELDING JOURNAL  

E-print Network

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

Zhang, YuMing

226

Structure and mechanical properties of 1570C alloy welds produced by friction stir welding  

NASA Astrophysics Data System (ADS)

The effect of the conditions of friction stir welding (FSW) of 1570C aluminum alloy sheets on the structure and mechanical properties of the welded joints is studied. A recrystallized fine-grained structure with a grain size changing with the rate of welding tool rotation forms in a weld during FSW. As compared to the base metal, the yield strength of the weld metal decreases by 9-22% depending on the rate of welding tool rotation, and the ultimate tensile strength is almost independent of the FSW conditions and accounts for ˜90% of the ultimate tensile strength of the base metal. The plasticity of the weld metal is >13% for all rates of welding tool rotation. The microstructure and mechanical properties of the weld zone are discussed.

Malopheyev, S. S.; Kulitskiy, V. A.

2012-09-01

227

A mathematical model of the chevron-like wave pattern on a weld piece  

SciTech Connect

In welding processes in general the surface of a metallic weld displays a chevron-like pattern. Such a pattern is also clearly seen to be present if welding is carried out using a laser beam. In the welding process a laser beam is directed normally on the metal undergoing translation and usually penetrates it to form a keyhole. The keyhole is surrounded by a molten region, the weld pool. Even if a CO{sub 2} laser is used, there are numerous fluctuations and instabilities that occur, so that the keyhole imposes forcing frequencies on the molten weld pool, additional to vibrations attendant on the process of translation. The weld pool in turn responds by supporting a spectrum of waves of different frequencies involving the natural frequency of the weld pool as well as various forcing frequencies. These waves are surface tension-type capillary waves and previous publications have attempted to model their behavior mathematically, although not all aspects of the problem have always been included. The wave pattern that is manifested in the chevron-like pattern seen on the weld piece is, however, not necessarily identical to the wave pattern present in the weld pool. This is because the chevron-like wave pattern forms as a result of several complicating effects that arise as the weld specimen cools on its surface immediately after the weld has been formed. This process involves the waves on the surface of the weld pool freezing to form the chevron-like wave pattern. A feature that is often ignored is the fact that the waves on the weld pool can only be regarded as irrotational if the translation speed is sufficiently low. This paper describes mathematically the formation of the chevron-like wave pattern based on suitable simplifying assumptions to model the process. The mathematical description of the way in which this chevron-like pattern forms is a step toward a more comprehensive understanding of this process.

Dowden, J.; Kapadia, P. [Univ. of Essex (United Kingdom)

1996-12-31

228

CO2 laser welding process in reduced-pressure atmosphere  

NASA Astrophysics Data System (ADS)

Laser welding study under vacuum conditions was performed. Plasma parameters (particulary electronic density and temperature) were measured. They were correlated to the molten pool analysis, and give informations on the energy deposition process inside the keyhole.

Poueyo-Verwaerde, Anne; Deshors, G.; Fabbro, Remy

1994-08-01

229

CO2 laser welding process in reduced-pressure atmosphere  

Microsoft Academic Search

Laser welding study under vacuum conditions was performed. Plasma parameters (particulary electronic density and temperature) were measured. They were correlated to the molten pool analysis, and give informations on the energy deposition process inside the keyhole.

Anne Poueyo-Verwaerde; G. Deshors; Remy Fabbro

1994-01-01

230

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

231

Welding III.  

ERIC Educational Resources Information Center

Instructional objectives and performance requirements are outlined in this course guide for Welding III, an advanced course in arc welding offered at the Community College of Allegheny County to provide students with the proficiency necessary for industrial certification. The course objectives, which are outlined first, specify that students will…

Allegheny County Community Coll., Pittsburgh, PA.

232

Welding II.  

ERIC Educational Resources Information Center

Instructional objectives and performance requirements are outlined in this course guide for Welding II, a performance-based course offered at the Community College of Allegheny County to introduce students to out-of-position shielded arc welding with emphasis on proper heats, electrode selection, and alternating/direct currents. After introductory…

Allegheny County Community Coll., Pittsburgh, PA.

233

Damage Tolerance Assessment of Friction Pull Plug Welds  

NASA Technical Reports Server (NTRS)

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

McGill, Preston; Burkholder, Jonathan

2012-01-01

234

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

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

235

Measurement of fusion boundary energy transport during Arc welding  

Microsoft Academic Search

An experimental technique is presented to identify fusion boundary (liquid\\/solid interface) energy transport mechanisms during welding procedures. The gas-tungsten-arc-spot-welding procedure, using a low melting (point specimen material (lead), was chosen to demonstrate the methods. Vaporization energy losses were found to be important during the growth of the fusion boundary. Significant thermal convection was absent within the weld pool for applied

C. S. Landram

1983-01-01

236

Simulation and Technology of Hybrid Welding of Thick Steel Parts with High Power Fiber Laser  

NASA Astrophysics Data System (ADS)

The article devoted to steady state and dynamic simulation of melt pool behavior during hybrid laser-arc welding of pipes and shipbuilding sections. The quasi-stationary process-model was used to determine an appropriate welding mode. The dynamical model of laser welding was used for investigation of keyhole depth and width oscillations. The experiments of pipe steel and stainless steel hybrid laser-MAG welding have been made with 15-kW fiber laser in wide range of welding mode parameters. Comparison of experimentally measured and simulated behavior of penetration depth as well as their oscillation spectra approved the self-oscillation nature of melt pool behavior. The welding mode influence of melt pool stability has also been observed. The technological peculiarities, which allow provide high quality weld seam, has been discussed also.

Turichin, Gleb; Valdaytseva, Ekaterina; Tzibulsky, Igor; Lopota, Alexander; Velichko, Olga

237

Welding superalloy sheet for superconducting cable jackets  

SciTech Connect

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.

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

1983-08-01

238

Towards the Prediction of Weld Metal Properties  

E-print Network

, respectively Ms, Bs, Wsand Th, and the allotriomorphic ferrite finish temperature, Tl, to be calculated. Knowing the allotriomorphic ferrite half-thickness, q, and the cooling rate of the weld over the temperature range 800 -t 500°C, the time taken for the weld... by the mode of solidification, whether this involves the formation of 8-ferrite or austenite as the primary phase, and the solid- ification stage determines the extent of chemical segregation and growth processes within the weld pool. Experimental work has...

Sugden, Alastair Allen Brockbank

1989-01-31

239

Tailoring defect free fusion welds based on phenomenological modeling  

NASA Astrophysics Data System (ADS)

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.)

Kumar, Amit

240

Hydrogen Transport and Rationalization of Porosity Formation during Welding of Titanium Alloys  

Microsoft Academic Search

The transport of hydrogen during fusion welding of the titanium alloy Ti-6Al4V is analyzed. A coupled thermodynamic\\/kinetic treatment is proposed for the mass transport within and around the weld pool. The modeling indicates that hydrogen accumulates in the weld pool as a consequence of the thermodynamic driving forces that arise; a region of hydrogen depletion exists in cooler, surrounding regions

Jianglin Huang; Nils Warnken; Jean-Christophe Gebelin; Martin Strangwood; Roger C. Reed

2012-01-01

241

Vaccum Gas Tungsten Arc Welding, phase 1  

NASA Astrophysics Data System (ADS)

This two year program will investigate Vacuum Gas Tungsten Arc Welding (VGTAW) as a method to modify or improve the weldability of normally difficult-to-weld materials. VGTAW appears to offer a significant improvement in weldability because of the clean environment and lower heat input needed. The overall objective of the program is to develop the VGTAW technology and implement it into a manufacturing environment that will result in lower cost, better quality and higher reliability aerospace components for the space shuttle and other NASA space systems. Phase 1 of this program was aimed at demonstrating the process's ability to weld normally difficult-to-weld materials. Phase 2 will focus on further evaluation, a hardware demonstration and a plan to implement VGTAW technology into a manufacturing environment. During Phase 1, the following tasks were performed: (1) Task 11000 Facility Modification - an existing vacuum chamber was modified and adapted to a GTAW power supply; (2) Task 12000 Materials Selection - four difficult-to-weld materials typically used in the construction of aerospace hardware were chosen for study; (3) Task 13000 VGTAW Experiments - welding experiments were conducted under vacuum using the hollow tungsten electrode and evaluation. As a result of this effort, two materials, NARloy Z and Incoloy 903, were downselected for further characterization in Phase 2; and (4) Task 13100 Aluminum-Lithium Weld Studies - this task was added to the original work statement to investigate the effects of vacuum welding and weld pool vibration on aluminum-lithium alloys.

Weeks, J. L.; Krotz, P. D.; Todd, D. T.; Liaw, Y. K.

1995-03-01

242

An analytical thermodynamic model of laser welding  

NASA Astrophysics Data System (ADS)

An earlier model of deep-penetration laser welding has been simplified in order to provide a useful model of process analysis. This work involves the modelling of the various energy-absorption mechanisms which determine the keyhole shape and thus the dimensions of the melt pool. The penetration depth and weld width (top and bottom) predicted by the model are shown to be in close agreement with experimental results. The widening of the top of the weld seam as a result of Marangoni flow is accurately modelled by introducing an artificially enhanced value for the workpiece's thermal conductivity towards the top of the weld. The model allows analysis of the dependence of the weld profile on the process parameters.

Lampa, Conny; Kaplan, Alexander F. H.; Powell, John; Magnusson, Claes

1997-05-01

243

WELDING RESEARCH -s87WELDING JOURNAL  

E-print Network

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

Eagar, Thomas W.

244

WELDING RESEARCH -S237WELDING JOURNAL  

E-print Network

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

Cambridge, University of

245

WELDING RESEARCH -s231WELDING JOURNAL  

E-print Network

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

Zhang, YuMing

246

WELDING RESEARCH -S25WELDING JOURNAL  

E-print Network

-service material may be welded during repairs. In such applica- tions, preheat and/or postweld heat treat- mentsWELDING RESEARCH -S25WELDING JOURNAL ABSTRACT. Stress-relief cracking is a major cause of weld conventional TEM and STEM techniques. The results of this study form a basis for heat treatment and welding

DuPont, John N.

247

Heat transfer and fluid flow in fusion type PA-GTA double-sided welding  

NASA Astrophysics Data System (ADS)

In comparison with conventional single-sided arc welding, double-sided arc welding powered by a single power supply has remarkable advantages in enhancing penetration, minimizing distortion and improving welding production. In this paper, a three-dimensional steady numerical model is developed for the heat transfer and fluid flow in a fusion type plasma arc (PA)-gas tungsten arc (GTA) double-sided welding process. Based on the numerical model, the distributions of the fluid flow and temperature field are calculated. Numerical results show that the peak temperature and temperature gradient in the weld pool in the PA side are higher than the values in the GTA side. Within the weld pool, the electromagnetic force drives the melted metal to move from two sides to the central part of the weld pool, and this effect is positive to penetrating the workpiece. The fluid flow of the melted metal in the free surface of the weld pool is fiercer than the flow within the weld pool, and the biggest flow velocity of the melted metal occurs in the free surface in the PA side. A comparison of the cross section of the weld bead with the experimental result shows that the numerical model's accuracy is reasonable.

Honggang, Dong; Hongming, Gao; Lin, Wu

2005-12-01

248

Surface-active element effects on the shape of GTA, laser, and electron-beam welds  

SciTech Connect

Laser and electron-beam welds were passed across selenium-doped zones in 21-6-9 stainless steel. The depth/width (d/w) ratio of a defocused laser weld with a weld pool shape similar to a GTA weld increased by over 200% in a zone where 66 ppm selenium had been added. Smaller increases were observed in selenium-doped zones for a moderately defocused electron beam weld with a higher d/w ratio in undoped base metal. When laser or electron beam weld penetration was by a keyhole mechanism, no change in d/w ratio occurred in selenium-doped zones. The results confirm the surface-tension-driven fluid-flow model for the effect of minor elements on GTA weld pool shape. Other experimental evidence bearing on the effect of minor elements on GTA weld penetration is summarized.

Heiple, C.R.; Roper, J.R.; Stagner, R.T.; Aden, R.J.

1983-03-01

249

Keyhole and weld shapes for plasma arc welding under normal and zero gravity  

NASA Technical Reports Server (NTRS)

A first order study of the interfacial (keyhole) shape between a penetrating argon plasma arc jet and a stationary liquid metal weld pool is presented. The interface is determined using the Young-Laplace equation by assuming that the plasma jet behaves as a one-dimensional ideal gas flow and by neglecting flow within the weld pool. The solution for the keyhole shape allows an approximate determination of the liquid-solid metal phase boundary location based on the assumption that the liquid melt is a stagnant thermal boundary layer. Parametric studies examine the effect of plasma mass flow rate, initial plasma enthalpy, liquid metal surface tension, and jet shear on weldment shape under both normal and zero gravity. Among the more important findings of this study is that keyhole and weld geometries are minimally affected by gravity, suggesting that data gathered under gravity can be used in planning in-space welding.

Keanini, R. G.; Rubinsky, B.

1990-01-01

250

Wonder Weld  

SciTech Connect

Engineers at the U.S. Department of Energy's Princeton Plasma Physics Laboratory are using the process shown here to create a super-strong weld for the upgrade of a key component of the Lab's experimental nuclear fusion reactor.

None

2012-01-01

251

Robotic welding  

Microsoft Academic Search

The purpose of this book is to provide the reader with the latest up-to-date information on robotic welding, associated components, and systems. This information has been compiled on automatic robotic arc welding systems which are presently employed and being worked on for future applications along with various adaptive control techniques and welt joint seam,-tracking systems being investigated for continuous robotic

1986-01-01

252

Microstructure Improvement in Weld Metal under the Ultrasonic Application  

SciTech Connect

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

Cui, Yan [University of Tennessee, Knoxville (UTK); Xu, Cailu [University of Tennessee, Knoxville (UTK); Han, Qingyou [ORNL

2007-01-01

253

Microstructures and mechanical properties of Inconel 718 welds by CO 2 laser welding  

Microsoft Academic Search

CO2 laser welding characteristics of Inconel 718, heat treatment effects on microstructures, and tensile\\/fatigue properties were researched. CO2 laser welding was carried out on 5mm thick plates having two different grain sizes, ASTM #4 and #10. For the fine-grain sized specimens (ASTM #10), the optimum laser welding conditions without defects were 6kW with 2.5m\\/min and 8kW with 4.0m\\/min. However, on

J. K. Hong; J. H. Park; N. K. Park; I. S. Eom; M. B. Kim; C. Y. Kang

2008-01-01

254

Effects of CO 2 shielding gas additions and welding speed on GTA weld shape  

Microsoft Academic Search

Gas tungsten arc (GTA) welding with deep penetration for high efficiency has long been of concern in industry. Experimental\\u000a results showed that the small addition of carbon dioxide to the argon shielding gas produces an increase in the weld metal\\u000a oxygen content, which is one of the compositional variables that strongly influence the Marangoni convection on the pool surface\\u000a and

Lu Shanping; Fujii Hidetoshi; Nogi Kiyoshi

2005-01-01

255

Simulation and Technology of Hybrid Welding of Thick Steel Parts with High Power Fiber Laser  

Microsoft Academic Search

The article devoted to steady state and dynamic simulation of melt pool behavior during hybrid laser-arc welding of pipes and shipbuilding sections. The quasi-stationary process-model was used to determine an appropriate welding mode. The dynamical model of laser welding was used for investigation of keyhole depth and width oscillations. The experiments of pipe steel and stainless steel hybrid laser-MAG welding

Gleb Turichin; Ekaterina Valdaytseva; Igor Tzibulsky; Alexander Lopota; Olga Velichko

2011-01-01

256

Stochastic modeling of pool-to-pool structure in small Nevada rangeland streams  

NASA Astrophysics Data System (ADS)

We developed, calibrated, and verified a compound Poisson process model of pool-to-pool spacing and size using an exponential distribution for spacing and gamma distributions for length and width on 12 rangeland streams in Nevada. Neither distribution parameter varied with simple stream morphologic or vegetation characteristics. We verified the model by comparing the first three moments and distributions of stream simulations with observed streams using two transect-based sampling schemes. Very small errors stemmed from an inability to reproduce autocorrelation of width at short distances, pool cyclicity, and additional density at the tails. We conclude that the presented model is accurate for small, Nevada, rangeland streams and for pools located randomly on small streams with forced pool-riffle or step-pool sequences and regularly on larger, pool-riffle systems. Simulated streams may be used for testing stream survey procedures and hypotheses regarding pool habitat, spacing, and length.

Myers, Thomas J.; Swanson, Sherman

1997-04-01

257

Shielding gas selection for increased weld penetration and productivity in GTA welding  

SciTech Connect

The effects of hydrogen and helium additions to the argon shielding gas on GTA weld pool profiles in the case of two austenitic stainless steel sheets 3 mm thick are investigated here in detail. One of the test steels shows good weldability, with a relatively deep, narrow weld pool profile, but the other is poorly weldable, with a shallow, wide weld pool when argon shielding gas is used. Bead-on-plate test welds were produced with arc shields of argon, argon with hydrogen additions of 2 to 18.2% and argon with helium additions of 20 to 80%. The hydrogen additions increases the depth of weld penetration in both test steels, but productivity with respect to maximum welding speed can be improved to an accepted level only with steel sheets of good weldability in terms of a relatively high depth/width (D/W) ratio. The depth of penetration in the test steel of good weldability increased somewhat with helium additions and the D/W ratio remained unchanged, while these parameters increased markedly in the poorly weldable steel when a He-20% Ar shielding gas was used and resembled those of the more weldable steel.

Leinonen, J.I. [Univ. of Oulu (Finland)

1996-12-31

258

RESISTANCE SPOT WELDING BERYLLIUM SHEET  

Microsoft Academic Search

It was determined that beryllium cross-rolled sheet can be resistance ; welded. Pre- and post-heating reduced the tendency for cracking by reducing the ; residual stress level during cooling. The cast nugget grain size was dependent ; on base metal grain size. Electrode sticking was reduced by improved surface ; finish. Beryllium weldments showed adequate strength only if proper design

Jahnle

1962-01-01

259

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

PubMed

Welding fume particles have been well studied in the past; however, most studies have examined welding fumes generated from machine models rather than actual exposures. Furthermore, the link between physicochemical and toxicological properties of welding fume particles has not been well understood. This study aims to investigate the physicochemical properties of particles derived during real time welding processes generated during actual welding processes and to assess the particle size specific toxicological properties. A compact cascade impactor (Harvard CCI) was stationed within the welding booth to sample particles by size. Size fractionated particles were extracted and used for both off-line physicochemical analysis and in vitro cellular toxicological characterization. Each size fraction was analyzed for ions, elemental compositions, and mass concentration. Furthermore, real time optical particle monitors (DustTrak™, TSI Inc., Shoreview, Minn.) were used in the same welding booth to collect real time PM2.5 particle number concentration data. The sampled particles were extracted from the polyurethane foam (PUF) impaction substrates using a previously developed and validated protocol, and used in a cellular assay to assess oxidative stress. By mass, welding aerosols were found to be in coarse (PM 2.5–10), and fine (PM 0.1–2.5) size ranges. Most of the water soluble (WS) metals presented higher concentrations in the coarse size range with some exceptions such as sodium, which presented elevated concentration in the PM 0.1 size range. In vitro data showed size specific dependency, with the fine and ultrafine size ranges having the highest reactive oxygen species (ROS) activity. Additionally, this study suggests a possible correlation between welders' experience, the welding procedure and equipment used and particles generated from welding fumes. Mass concentrations and total metal and water soluble metal concentrations of welding fume particles may be greatly influenced by these factors. Furthermore, the results also confirmed the hypothesis that smaller particles generate more ROS activity and should be evaluated carefully for risk assessment. PMID:24592438

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

2013-01-01

260

Phase transformations and microstructure development in low alloy steel welds  

SciTech Connect

Microstructure development in low alloy steel welds depends on various phase transformations that are a function of weld heating and cooling. The phase changes include non-metallic oxide inclusion formation in the liquid state, weld pool solidification, and solid state transformations. In this paper the mechanism of inclusion formation during low alloy steel welding is considered and the model predictions are compared with published results. The effect of inclusions on the austenite to ferrite transformation kinetics is measured and the mechanisms of transformation are discussed. The austenite gain development is related to the driving force for transformation of {delta} ferrite to austenite.

Babu, S.S.; David, S.A.; Vitek, J.M. [and others

1995-07-01

261

An Lmx1b-miR135a2 Regulatory Circuit Modulates Wnt1/Wnt Signaling and Determines the Size of the Midbrain Dopaminergic Progenitor Pool  

PubMed Central

MicroRNAs regulate gene expression in diverse physiological scenarios. Their role in the control of morphogen related signaling pathways has been less studied, particularly in the context of embryonic Central Nervous System (CNS) development. Here, we uncover a role for microRNAs in limiting the spatiotemporal range of morphogen expression and function. Wnt1 is a key morphogen in the embryonic midbrain, and directs proliferation, survival, patterning and neurogenesis. We reveal an autoregulatory negative feedback loop between the transcription factor Lmx1b and a newly characterized microRNA, miR135a2, which modulates the extent of Wnt1/Wnt signaling and the size of the dopamine progenitor domain. Conditional gain of function studies reveal that Lmx1b promotes Wnt1/Wnt signaling, and thereby increases midbrain size and dopamine progenitor allocation. Conditional removal of Lmx1b has the opposite effect, in that expansion of the dopamine progenitor domain is severely compromised. Next, we provide evidence that microRNAs are involved in restricting dopamine progenitor allocation. Conditional loss of Dicer1 in embryonic stem cells (ESCs) results in expanded Lmx1a/b+ progenitors. In contrast, forced elevation of miR135a2 during an early window in vivo phenocopies the Lmx1b conditional knockout. When En1::Cre, but not Shh::Cre or Nes::Cre, is used for recombination, the expansion of Lmx1a/b+ progenitors is selectively reduced. Bioinformatics and luciferase assay data suggests that miR135a2 targets Lmx1b and many genes in the Wnt signaling pathway, including Ccnd1, Gsk3b, and Tcf7l2. Consistent with this, we demonstrate that this mutant displays reductions in the size of the Lmx1b/Wnt1 domain and range of canonical Wnt signaling. We posit that microRNA modulation of the Lmx1b/Wnt axis in the early midbrain/isthmus could determine midbrain size and allocation of dopamine progenitors. Since canonical Wnt activity has recently been recognized as a key ingredient for programming ESCs towards a dopaminergic fate in vitro, these studies could impact the rational design of such protocols. PMID:24348261

Anderegg, Angela; Lin, Hsin-Pin; Chen, Jun-An; Caronia-Brown, Giuliana; Cherepanova, Natalya; Yun, Beth; Joksimovic, Milan; Rock, Jason; Harfe, Brian D.; Johnson, Randy; Awatramani, Rajeshwar

2013-01-01

262

Recent progress on gas tungsten arc welding of vanadium alloys  

SciTech Connect

Emphasis has been placed on welding 6.4 mm plate, primarily by gas tungsten arc (GTA) welding. The weld properties were tested using blunt notch Charpy testing to determine the ductile to brittle transition temperature (DBTT). Erratic results were attributed to hydrogen and oxygen contamination of the welds. An improved gas clean-up system was installed on the welding glove box and the resulting high purity welds had Charpy impact properties similar to those of electron beam welds with similar grain size. A post-weld heat treatment (PWHT) of 950{degrees}C for two hours did not improve the properties of the weld in cases where low concentrations of impurities were attained. Further improvements in the gas clean-up system are needed to control hydrogen contamination.

Grossbeck, M.L.; King, J.F.; Alexander, D.J. [Oak Ridge National Lab., TN (United States)] [and others

1997-08-01

263

Welding Curtains  

NASA Technical Reports Server (NTRS)

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.

1984-01-01

264

Characterisation of fume from hyperbaric welding operations  

Microsoft Academic Search

We report preliminary work characterising dust from hyperbaric welding trials carried out at increased pressure in a helium and oxygen atmosphere. Particle size and concentration were measured during welding. Samples for quartz and metal analysis and toxicity assessment were taken from a filter in the local fume extraction system. The residue of dust after metal extraction by nitric acid in

John A. S. Ross; Sean Semple; Rodger Duffin; Frank Kelly; Joerg Seldmann; Andrea Raab

2009-01-01

265

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

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

266

Static and fatigue behavior of spot-welded 5182-0 aluminum alloys sheet  

SciTech Connect

There is a strong interest in the use of aluminum alloy sheet for vehicle applications, particularly the body, where resistance spot welding is the principal joining method. It is important that the particular discontinuities that are often found in aluminum alloy spot welds do not adversely affect the weld properties. The objectives of this work were to provide information about the effect of excessive porosity and surface indentation and the effect of weld size on the fatigue performance of spot welds in aluminum alloy sheet. Trials were conducted on 1.2-mm-thick 5182-0 aluminum alloy in the mill-finished condition. Static shear and fatigue tests were conducted on welds over a range of welding conditions to simulate severe weld discontinuities. The work indicated that nugget porosity, up to about 40% of the weld diameter, deep surface indentation and variation in weld size had no major impact on the fatigue properties of the welds.

Gean, A.; Kucza, J.C.; Ehrstrom, J.C. [Pechiney CRV, Voreppe (France); Westgate, S.A. [TWI, Abington (United Kingdom)

1999-03-01

267

WELDING RESEARCH -s51WELDING JOURNAL  

E-print Network

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

DuPont, John N.

268

WELDING RESEARCH -s77WELDING JOURNAL  

E-print Network

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

DuPont, John N.

269

WELDING RESEARCH -S249WELDING JOURNAL  

E-print Network

WELDING RESEARCH -S249WELDING JOURNAL ABSTRACT. Double-sided arcing uses two torches on the opposite sides of the workpiece to force the welding current to flow through the thickness. If a keyhole is established through the thickness, part of the welding current will flow through the keyhole and maintain

Zhang, YuMing

270

WELDING RESEARCH -S125WELDING JOURNAL  

E-print Network

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

DuPont, John N.

271

WELDING RESEARCH -s281WELDING JOURNAL  

E-print Network

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

DuPont, John N.

272

Prediction of weld strength and seam width for laser transmission welding of thermoplastic using response surface methodology  

Microsoft Academic Search

In the present work, a study is made to investigate the effects of process parameters, namely, laser power, welding speed, size of the laser beam and clamp pressure, on the lap-shear strength and weld-seam width for laser transmission welding of acrylic (polymethyl methacrylate), using a diode laser system. Response surface methodology (RSM) is employed to develop mathematical relationships between the

Bappa Acherjee; Dipten Misra; Dipankar Bose; K. Venkadeshwaran

2009-01-01

273

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

SciTech Connect

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).

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

2000-01-01

274

Multi-physical Simulation of Laser Welding  

NASA Astrophysics Data System (ADS)

Laser welding is a highly demanded technology for manufacturing of body parts in the automotive industry. Application of powerful multi-physical simulation models permits detailed investigation of the laser process avoiding intricate experimental setups and procedures. Features like the degree of power coupling, keyhole evolution or currents inside the melt pool can be analyzed easily. The implementation of complex physical phenomena, like multi-reflection absorption provides insight into process characteristics under selectable conditions and yields essential information concerning the driving mechanisms. The implementation of additional physical models e. g. for diffusion discloses new potential for investigating welding of dissimilar materials. In this paper we present a computational study of laser welding for different conditions. Applied to a real case model predictions show good agreement with experimental results. Initial tests including species diffusion during welding of dissimilar materials are also presented.

Vázquez, Rodrigo Gómez; Koch, Holger M.; Otto, Andreas

275

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

276

Automatic Welding of Stainless Steel Tubing  

NASA Technical Reports Server (NTRS)

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.

Clautice, W. E.

1978-01-01

277

Weld-Ed Research, Publications, and Presentations  

NSDL National Science Digital Library

This page contains the research, publications, and presentations by the Nation Center for Welding Education and Training or its contractors. Publications include "Careers in Welding - InDemand," "The Welding Industry: A National Perspective on Workforce Trends and Challenges," and "The Welding Industry: A Regional Perspective on Workforce Trends and Challenges." Many presentations are also listed such as "Aligning NSF Advanced Technology Education (ATE) Center Programs with the Workforce System" and "Virtual Welding Trainers."

2011-10-07

278

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

SciTech Connect

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.

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

2012-06-28

279

RESISTANCE SPOT REPAIR WELDING OF SPOT WELDED STEEL SHEET  

Microsoft Academic Search

Repeated resistance spot repair welding over the poor spot weld and interface fractured spot weld of low carbon steel sheet has been studied. The repair welding has been carried out at different parameters to optimize the welding current, weld time, and electrode force as the primary welding parameters for maximum joint strength. The optimum strengths of the repaired weld under

P. K. Ghosh; Vinay Kumar Patel

2005-01-01

280

Effect of multiple repairs in girth welds of pipelines on the mechanical properties  

Microsoft Academic Search

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

O. E. Vega; J. M. Hallen; A. Villagomez; A. Contreras

2008-01-01

281

LASER WELDING -Literature Review Materials Science and Metallurgy Department, University of Cambridge, England. July 2002.  

E-print Network

industry to produce seam or stitch welds, as alternatives to conventional resistance spot welding, which over resistance spot welding result from the smallness of the laser spot size, the large penetration changes, unlike that used for resistance spot welding.1 Potential benefits realised by the application

Cambridge, University of

282

Narrow gap laser welding  

DOEpatents

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.

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

1998-01-01

283

Narrow gap laser welding  

DOEpatents

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.

Milewski, J.O.; Sklar, E.

1998-06-02

284

Survey of Welding Processes  

National Technical Information Service (NTIS)

The current KYTC 'Special Provision No.4 Welding Steel Bridges' prohibits the use of welding processes other than shielded metal arc welding (SMAW) and submerged arc welding (SAW). Nationally, bridge welding is codified under ANSI/AASHTO/AWS D1.5:2002 Bri...

T. Hopwood

2003-01-01

285

Swimming pool granuloma  

MedlinePLUS

A swimming pool granuloma is a long-term (chronic) skin infection. It is caused by the bacteria Mycobacterium marinum . ... A swimming pool granuloma occurs when water containing Mycobacterium marinum bacteria enters a break in the skin. Signs of ...

286

Swimming pool cleaner poisoning  

MedlinePLUS

Swimming pool cleaner poisoning occurs when someone swallows these substances, touches the chemicals and acids in them, ... breathes in their fumes. Chlorine, a chemical in swimming pool cleaners, is more likely than the acids ...

287

Virtual Tide Pool  

NSDL National Science Digital Library

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.

Science NetLinks (PBS;)

2003-04-29

288

Laser Beam Welding of Brass  

NASA Astrophysics Data System (ADS)

Up to date the evaporation process in laser beam welding of alloys with volatile elements is not completely understood. This paper discusses the phenomena occurring at the welding process of brass with 37m% zinc. Since copper has a solidification temperature of 1,087 °C and zinc vaporizes at a temperature of 907 °C, a strong evaporation takes place and anelongation of the keyhole can be observed. Depending upon welding velocity, the ratio of keyhole length to width is between one and six. Furthermore it is observed that a defect free weld seam is formed. Since the melt pool does not leak also for high ratios of keyhole length to width, the conventional keyhole model with a dynamic flow around the laser beam has to be adapted to a model in which the melt flow at the side of the capillary is stabilized also outside of the interaction zone of the laser beam with the melt due to strong evaporation at the flank of the keyhole.

Hugger, Florian; Hofmann, Konstantin; Stein, Stefan; Schmidt, Michael

289

Field comparison of three inhalable samplers (IOM, PGP-GSP 3.5 and Button) for welding fumes.  

PubMed

Inhalable sampler efficiency depends on the aerodynamic size of the airborne particles to be sampled and the wind speed. The aim of this study was to compare the behaviour of three personal inhalable samplers for welding fumes generated by Manual Metal Arc (MMA) and Metal Active Gas (MAG) processes. The selected samplers were the ones available in Spain when the study began: IOM, PGP-GSP 3.5 (GSP) and Button. Sampling was carried out in a welding training center that provided a homogeneous workplace environment. The static sampling assembly used allowed the placement of 12 samplers and 2 cascade impactors simultaneously. 183 samples were collected throughout 2009 and 2010. The range of welding fumes' mass concentrations was from 2 mg m(-3) to 5 mg m(-3). The pooled variation coefficients for the three inhalable samplers were less than or equal to 3.0%. Welding particle size distribution was characterized by a bimodal log-normal distribution, with MMADs of 0.7 ?m and 8.2 ?m. For these welding aerosols, the Button and the GSP samplers showed a similar performance (P = 0.598). The mean mass concentration ratio was 1.00 ± 0.01. The IOM sampler showed a different performance (P < 0.001). The mean mass concentration ratios were 0.90 ± 0.01 for Button/IOM and 0.92 ± 0.02 for GSP/IOM. This information is useful to consider the measurements accomplished by the IOM, GSP or Button samplers together, in order to assess the exposure at workplaces over time or to study exposure levels in a specific industrial activity, as welding operations. PMID:22037834

Zugasti, Agurtzane; Montes, Natividad; Rojo, José M; Quintana, M José

2012-02-01

290

Electroslag and electrogas welding  

NASA Technical Reports Server (NTRS)

These two new joining methods perform welding in the vertical position, and therein lies the secret of their impressive advantages in material handling, in weld preparation, in welding speed, in freedom from distortion, and in weld soundness. Once the work has been set in the proper vertical position for welding, no further plate handling is required. The molten filler metal is held in place by copper shoes or dams, and the weld is completed in one pass.

Campbell, H. C.

1972-01-01

291

Fiber laser welding of nickel-based superalloy inconel 718  

NASA Astrophysics Data System (ADS)

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.

Oshobe, Omudhohwo Emaruke

292

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

NASA Astrophysics Data System (ADS)

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.

Pang, Shengyong; Chen, Weidong; Wang, Wen

2014-06-01

293

Autonomous Mobile Robot System for Monitoring and Control of Penetration during Fixed Pipes Welding  

NASA Astrophysics Data System (ADS)

In order to obtain sound welded joints in the welding of horizontal fixed pipes, it is important to control the back bead width in the first pass. However, it is difficult to obtain optimum back bead width, because the proper welding conditions change with welding position. In this paper, in order to fully automatize the welding of fixed pipes, a new method is developed to control the back bead width with monitoring the shape and dimensions of the molten pool from the reverse side by autonomous mobile robot system. This robot has spherical shape so as to move in a complex route including curved pipe, elbow joint and so on. It has also a camera to observe inner surface of pipe and recognize a route in which the robot moves. The robot moves to welding point in the pipe, and monitors the reverse side shape of molten pool during welding. The host computer processes the images of molten pool acquired by the robot vision system, and calculates the optimum welding conditions to realize adaptive control of welding. As a result of the welding control experiments, the effectiveness of this system for the penetration control of fixed pipes is demonstrated.

Muramatsu, Masahiro; Suga, Yasuo; Mori, Kazuhiro

294

Friction Stir Weld System for Welding and Weld Repair  

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

295

Friction plug welding  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

296

Effects of process parameters on the bead geometry of laser beam butt welded stainless steel sheets  

Microsoft Academic Search

Laser beam welding (LBW) is a field of growing importance in industry with respect to traditional welding methodologies due\\u000a to lower dimension and shape distortion of components and greater processing velocity. Because of its high weld strength to\\u000a weld size ratio, reliability and minimal heat affected zone, laser welding has become important for varied industrial applications.\\u000a With increased use of

K. Manonmani; N. Murugan; G. Buvanasekaran

2007-01-01

297

Texture development in Ti–6Al–4V linear friction welds  

Microsoft Academic Search

Microstructure and microtexture development in as-welded and post weld heat treated (PWHT) lab-scale (LS) and full-scale (FS) Ti–6Al–4V linear friction welds have been characterized using scanning electron microscopy and electron back-scatter diffraction (EBSD). The full-scale specimens exhibited a plastically affected zone (PAZ) about twice the size compared to lab-scale test welds. At the weld line a region of very fine

M. Karadge; M. Preuss; C. Lovell; P. J. Withers; S. Bray

2007-01-01

298

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

Microsoft Academic Search

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

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

2002-01-01

299

Slag Metal Reactions during Submerged Arc Welding of Alloy Steels  

Microsoft Academic Search

The transfer of Cr, Si, Mn, P, S, C, Ni, and Mo between the slag and the weld pool has been studied for submerged arc welds\\u000a made with calcium silicate and manganese silicate fluxes. The results show a strong interaction between Cr and Si transfer\\u000a but no interaction with Mn. The manganese silicate flux produces lower residual sulfur while the

U. Mitra; T. W. Eagar

1984-01-01

300

Understanding heat and fluid flow in linear GTA welds  

SciTech Connect

A transient heat flow and fluid flow model was used to predict the development of gas tungsten arc (GTA) weld pools in 1.5 mm thick AISI 304 SS. The welding parameters were chosen so as to correspond to an earlier experimental study which produced high-resolution surface temperature maps. The motivation of the present study was to verify the predictive capability of the computational model. Comparison of the numerical predictions and experimental observations indicate good agreement.

Zacharia, T.; David, S.A.; Vitek, J.M.

1992-01-01

301

Understanding heat and fluid flow in linear GTA welds  

SciTech Connect

A transient heat flow and fluid flow model was used to predict the development of gas tungsten arc (GTA) weld pools in 1.5 mm thick AISI 304 SS. The welding parameters were chosen so as to correspond to an earlier experimental study which produced high-resolution surface temperature maps. The motivation of the present study was to verify the predictive capability of the computational model. Comparison of the numerical predictions and experimental observations indicate good agreement.

Zacharia, T.; David, S.A.; Vitek, J.M.

1992-12-31

302

Development of closed-loop control of robotic welding processes  

Microsoft Academic Search

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 –

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

2005-01-01

303

Manganese in occupational arc welding fumes--aspects on physiochemical properties, with focus on solubility.  

PubMed

Physicochemical properties, such as particle sizes, composition, and solubility of welding fumes are decisive for the bioaccessibility of manganese and thereby for the manganese cytotoxic and neurotoxic effects arising from various welding fumes. Because of the diverse results within the research on welding fume solubility, this article aims to review and discuss recent literature on physicochemical properties of gas metal arc welding, shielded metal arc welding, and flux-cored arc welding fumes, with focus on solubility properties. This article also presents a short introduction to the literature on arc welding techniques, health effects from manganese, and occupational exposure to manganese among welders. PMID:22997412

Taube, Fabian

2013-01-01

304

Automated Spot Weld Inspection using Infrared Thermography  

SciTech Connect

An automated non-contact and non-destructive resistance spot weld inspection system based on infrared (IR) thermography was developed for post-weld applications. During inspection, a weld coupon was heated up by an auxiliary induction heating device from one side of the weld, while the resulting thermal waves on the other side were observed by an IR camera. The IR images were analyzed to extract a thermal signature based on normalized heating time, which was then quantitatively correlated to the spot weld nugget size. The use of normalized instead of absolute IR intensity was found to be useful in minimizing the sensitivity to the unknown surface conditions and environment interference. Application of the IR-based inspection system to different advanced high strength steels, thickness gauges and coatings were discussed.

Chen, Jian [ORNL] [ORNL; Zhang, Wei [ORNL] [ORNL; Yu, Zhenzhen [ORNL] [ORNL; Feng, Zhili [ORNL] [ORNL

2012-01-01

305

Combinatorial optimization of welding  

E-print Network

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

Sóbester, András

306

Heat flow during the autogenous GTA welding of pipes  

SciTech Connect

A theoretical and experimental study of heat flow during the welding of pipes was carried out. The theoretical part of the study involves the development of two finite difference computer models: one for describing steady state, 3-dimensional heat flow during seam welding, the other for describing unsteady state, 3-dimensional heat flow during girth welding. The experimental part of the study, on the other hand, includes: measurement of the thermal response of the pipe with a high speed data acquisition system, determination of the arc efficiency with a calorimeter, and examination of the fusion boundary of the resultant weld. The experimental results were compared with the calculated ones, and the agreement was excellent in the case of seam welding and reasonably good in the case of girth welding. Both the computer models and experiments confirmed that, under a constant heat input and welding speed, the size of the fusion zone remains unchanged in seam welding but continues to increase in girth welding of pipes of small diameters. It is expected that the unsteady state model developed can be used to provide optimum conditions for girth welding, so that uniform weld beads can be obtained and weld defects such as lack of fusion and sagging can be avoided.

Kou, S.; Le, Y.

1984-06-01

307

Heat Flow during the Autogenous GTA Welding of Pipes  

NASA Astrophysics Data System (ADS)

A theoretical and experimental study of heat flow during the welding of pipes was carried out. The theoretical part of the study involves the development of two finite difference computer models: one for describing steady state, 3-dimensional heat flow during seam welding, the other for describing unsteady state, 3-dimensional heat flow during girth welding. The experimental part of the study, on the other hand, includes: measurement of the thermal response of the pipe with a high speed data acquisition system, determination of the arc efficiency with a calorimeter, and examination of the fusion boundary of the resultant weld. The experimental results were compared with the calculated ones, and the agreement was excellent in the case of seam welding and reasonably good in the case of girth welding. Both the computer models and experiments confirmed that, under a constant heat input and welding speed, the size of the fusion zone remains unchanged in seam welding but continues to increase in girth welding of pipes of small diameters. It is expected that the unsteady state model developed can be used to provide optimum conditions for girth welding, so that uniform weld beads can be obtained and weld defects such as lack of fusion and sagging can be avoided.

Kou, Sindo; Le, Y.

1984-06-01

308

Integration of an optical profile sensor in a welding equipment using an industrial robot  

NASA Astrophysics Data System (ADS)

A sensor controlled arc welding system using an industrial robot, and an optical profile sensor was designed and partially realized. An important obstacle is the on-line communication facilities for the robot controller. Despite this a system that meets all the requirements was constructed, using an IBM-PC as central computer. Experiments for controlling the welding parameters depending upon the measured size of the welding seam, were performed. The results show that welding quality can be improved by compensating for the size of the seam, despite the complex nature of the welding process. Plans for achieving a fully sensor controlled welding system are presented.

Vanvelthoven, Johan L.

1986-01-01

309

Optical Welding Torch  

NASA Technical Reports Server (NTRS)

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.

Richardson, R. W.

1987-01-01

310

Development of models for welding applications  

SciTech Connect

The modeling of welding processes offers considerable potential for help with manufacturing problems but a complete definition of any welding process offers many challenges. However, the modular structure of MARC, and the diverse range of capabilities offered, create a good opportunity for development in this area. This paper discusses these problems and describes techniques used to overcome some of them. Models have been developed to simulate gas tungsten arc (GTA) and electron beam (EB) welding with a moving heat source. Fortran routines for subroutines FLUX and FORCDT have been written to generate a moving heat source. Sequential element activation has permitted the simulation of GTA welding with cold wire feed (CWF), as in filling of a machined weld groove. A program which generates History Definition blocks necessary for this type of welding model is also described in this paper. Semi-infinite heat transfer elements were used to get accurate temperature histories while keeping the size of the model manageable. Time-temperature histories and isothermal contours compare well with experimental measurements, although many areas for improvement and refinement remain. Results have been used to anticipate the necessity for weld parameter changes after part redesign, and the electron beam model relates closely to situations in which information is needed for the minimization of peak temperatures on the underside of the welded part. 8 refs., 11 figs.

Roper, J.R.; Hayer, L.K.

1990-01-01

311

Physicochemical characterisation of different welding aerosols.  

PubMed

Physicochemical properties important in exposure characterisation of four different welding aerosols were investigated. Particle number size distributions were determined by scanning mobility particle sizer (SMPS), mass size distributions by separation and weighing the individual size fractions of an 11-stage cascade impactor. The size distribution of the primary particles of agglomerates, chemical composition and morphology of the particles were examined by TEM. There were significant differences in the particle number size distributions of the different welding aerosols according to the SMPS determinations. The particle mass size distributions determined gravimetrically were, however, not really different. The dominant range with respect to mass was between 0.1 and 1 ?m, regardless of the welding technique. Most of the primary particles in all different welding aerosols had diameters between 5 and 40 nm. All types of primary particles had a tendency to form chainlike agglomerates. A clear size dependence of the particle chemical composition was encountered in the case of manual metal arc welding aerosol. Small particles with diameters below 50 nm were mostly metal oxides in contrast to larger particles which also contained more volatile elements (e.g. potassium, fluorine, sodium, sulphur). PMID:20845032

Berlinger, B; Benker, N; Weinbruch, S; L'Vov, B; Ebert, M; Koch, W; Ellingsen, D G; Thomassen, Y

2011-02-01

312

Plunge pools and paleoprecipitation  

Microsoft Academic Search

Sedimentary sequences in the form of ridges or terraces surrounding plunge pools at the base of waterfalls can provide records of past discharge and as a consequence an indirect measure of rainfall variations over many thousands of years. Waves generated by the waterfall deposit sands and pebbles as a beach at the perimeter of the plunge pool. As climatic conditions

Jonathan Nott; David Price

1994-01-01

313

A Data Mining Study of Weld Quality Models Constructed with MLP Neural Networks from Stratified Sampled Data  

E-print Network

A Data Mining Study of Weld Quality Models Constructed with MLP Neural Networks from Stratified method was implemented to sample radiographic welding data. The sample size was varied at different, Stratified sampling, Radiography, Weld quality. 1. Introduction Welded structures, especially those

Triantaphyllou, Evangelos

314

Welding Phenomenon and Removal Mechanism of Aluminum-Oxide Films by Space GHTA Welding Process in Vacuum  

NASA Astrophysics Data System (ADS)

Aluminum alloys have been widely used in constructing various space structures including the ISS (International Space Station) and launch vehicles. In order to apply the welding technology in space, welding experiments on aluminum alloy were performed using by the GHTA (Gas Hollow Tungsten Arc) welding processes using an inverter controlled DC/AC GTA welding machine in vacuum. We observed the removal mechanism of aluminum-oxide films on molten metal in detail during the welding using a high-speed video camera. As a result, it is clarified that the impact arc pressure produced by pulsed current mechanically crushes and removes aluminum-oxide films on the molten pool. This removal mechanism of aluminum-oxide films is completely different from a removal mechanism by cleaning action.

Suita, Yoshikazu; Ekuni, Tomohide; Kamei, Misa; Tsukuda, Yoshiyuki; Terajima, Noboru; Yamashita, Masahiro; Imagawa, Kichiro; Masubuchi, Koichi

315

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

NASA Astrophysics Data System (ADS)

Aluminum alloys have been widely used in the constructing various space structures including the International Space Station (ISS) and launch vehicles. For space application, welding experiments of an aluminum alloy were conducted by the GHTA (Gas Hollow Tungsten Arc) welding processes using a filler wire feeder in vacuum. We investigated the melting phenomena of a base metal and a filler wire, bead formation phenomena and effects of wire feeding speed on melting characteristics. The melting phenomenon of melt-run welding with a filler wire was basically the same as that of without a filler wire. It was clarified that the effects of wire feeding speed on bead sizes and configurations. Furthermore the butt welding joints were welded by the optimum wire feeding speed and the tensile strengths of those joints were evaluated. The mean value of tensile strengths of butt welding joints that were made using d.c.-pulsed GHTA welding with filler wire in vacuum was almost same value as that was welded by GTA (Gas Tungsten Arc) welding in air.

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

316

Weld geometry strength effect in 2219-T87 aluminum  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

317

Development of techniques for welding V Cr Ti alloys  

NASA Astrophysics Data System (ADS)

Welding vanadium alloys is complicated by interstitial impurity introduction and redistribution at elevated temperatures. Gas tungsten arc (GTA) welding, which will probably be required for the fabrication of large tokamak structures, must be done in a glove box environment. Welds were evaluated by Charpy testing. GTA welds could be made with a ductile to brittle transition temperature (DBTT) of 50°C with a post-weld heat treatment (PWHT) or by using a heated Ti getter system on the glove box to reduce interstitial contamination. Titanium-O,N,C precipitates in the fusion zone were found to transform to a more oxygen-rich phase during a PWHT of 950°C/2 h. Hydrogen was found to promote cleavage cracking following welding in cases where the atmosphere was contaminated. Grain size and microstructure also affected weld embrittlement.

Grossbeck, M. L.; King, J. F.; Alexander, D. J.; Rice, P. M.; Goodwin, G. M.

1998-10-01

318

Adaptive Robotic Welding Using Preview Vision Sensing of Joint Geometry  

NASA Astrophysics Data System (ADS)

Conventional robotic welding systems can only be used in applications where parts are highly repeatable and well fixtured. In this paper, vision sensing and processing techniques that permit in-process determination of the position and detailed three-dimensional surface geometry of a weld joint are presented. Structured lighting in the form of a cone of laser light and specialized vision processing schemes are used to obtain three-dimensional geometric surface descriptions from a two-dimensional TV image. This geometric description is used to define joint position, surface orientations, and a variety of cross-sectional measurements such as fill volume, preparation angles, gap size, and presence and dimensions of a previously deposited weld bead or tack weld. The visual feedback is then used for real time control of the torch position relative to the weld joint, and for in-process adjustment of welding process parameters such as welding arc voltage, and wire feed rates.

Agapakis, J. E.; Epstein, G. N.; Friedman, J. M.; Katz, J. M.; Koifman, M.

1987-03-01

319

Repair Welding of Irradiated Materials: Modeling of Helium Bubble Distributions for Determining Crack-Free Welding Procedures  

SciTech Connect

In this paper, a computational simulation study is presented on the prediction of helium bubble evolution during repair welding of irradiated 304 stainless steel. Realistic spatial and temporal temperature and stress evolution during welding were obtained from simulation of the repair welding operation using the finite element model approach. The helium bubble evolution model by Kawano et al. was adopted as a user subroutine in the finite element model to predict the spatial distribution and temporal evolution of the helium bubble size and density in the heat-affected zone (HAZ) of partial penetration welds. Comparisons with experimental results available in open literature show that the predicted average helium bubble sizes were consistent with those observed experimentally under similar conditions. In addition, the computer simulation revealed strong spatial variation of helium bubble size due to the differences in combined thermal and stress conditions experienced in different locations in the HAZ. The predicted location of the maximum helium bubble agreed well with the observed helium-induced cracking site. The effect of welding heat input and welding speed was also investigated numerically. The modeling approach adopted in this study could be used as a cost-effective tool to quantitatively correlate the welding condition, radiation damage, and the likelihood of cracking, under the influence of welding-induced thermal and stress cycles. The model will also be useful in studying the degradation of properties from helium bubble formation of post-welded structures, even if a successful weld is made. (authors)

Feng, Zhili; Wilkowski, Gery [Engineering Mechanics Coporation of Columbus, 3518 Riverside Dr Upper Arlington, OH 43221 (United States)

2002-07-01

320

Welding Many Thin Metal Layers  

NASA Technical Reports Server (NTRS)

Electron-beam welding yields reliable, leakproof joints. Welding bands (also called "doublers") sandwiched between layers welded to increase final weld-section thickness. New technique ensures repeatable leakproof assemblies.

Hartwell, B. O.; Caras, P.; Hobbes, P. H.

1985-01-01

321

Selected Welding Techniques, Part 2.  

National Technical Information Service (NTIS)

Partial contents: CONVENTIONAL WELD JOINTS VERSUS BUTT JOINTS IN 1- INCH ALUMINUM PLATE, SPECIAL WELD JOINT PREPARATION, UPSET METAL EDGES FOR INCREASED WELD JOINT STRENGTH, OUT-OF-POSITION WELDING OF HEAVY GAGE ALUMINUM ALLOY IN SPACE VEHICLE APPLICATION...

1964-01-01

322

Laser weld jig  

DOEpatents

A system is provided for welding a workpiece (10, FIG. 1) along a predetermined weld line (12) that may be of irregular shape, which includes the step of forming a lip (32) on the workpiece to extend parallel to the weld line, and moving the workpiece by engaging the lip between a pair of rotatable members (34, 36). Rotation of one of the members at a constant speed, causes the workpiece to move so that all points on the weld line sequentially pass a fixed point in space (17) at a constant speed, so that a laser welding beam can be directed at that fixed point to form a weld along the weld line. The workpiece can include a reuseable jig (24) forming the lip, and with the jig constructed to detachably hold parts (22, 20) to be welded at a position wherein the weld line of the parts extends parallel to the lip on the jig.

Van Blarigan, Peter (Livermore, CA); Haupt, David L. (Livermore, CA)

1982-01-01

323

Virtual Welding Trainers  

NSDL National Science Digital Library

Weld-Ed, the National Center for Welding Education and Training have provided this Power Point presentation entitled âÂÂVirtual Welding Trainersâ that covers the pros and cons of implementing a virtual welding program in education. Virtual welding programs have gained attention in the past years because of a decrease in the welding workforce and increasing workforce performance. This slide show provides a history and examples of virtual reality simulation. There are lists of benefits, like instant feedback and reduced environmental concerns. Also provided are virtual welding development barriers, such as high start-up costs. Last but not least, there is a list of other institutions that are using virtual welding programs.

2009-09-24

324

Welded solar cell interconnection  

NASA Technical Reports Server (NTRS)

The efficiency of the welding of solar-cell interconnects is compared with the efficiency of soldering such interconnects, and the cases in which welding may be superior are examined. Emphasis is placed on ultrasonic welding; attention is given to the solar-cell welding machine, the application of the welding process to different solar-cell configurations, producibility, and long-life performance of welded interconnects. Much of the present work has been directed toward providing increased confidence in the reliability of welding using conditions approximating those that would occur with large-scale array production. It is concluded that there is as yet insufficient data to determine which of three methods (soldering, parallel gap welding, and ultrasonic welding) provides the longest-duration solar panel life.

Stofel, E. J.; Browne, E. R.; Meese, R. A.; Vendura, G. J.

1982-01-01

325

Linear dimension establishes weld integrity  

NASA Technical Reports Server (NTRS)

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.

Lewis, J. C.

1978-01-01

326

Low-temperature friction-stir welding of 2024 aluminum  

SciTech Connect

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).

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

327

Fusion welding process  

DOEpatents

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

Thomas, Kenneth C. (Export, PA); Jones, Eric D. (Salem, PA); McBride, Marvin A. (Hempfield Township, Westmoreland County, PA)

1983-01-01

328

Intelligent Welding Controller  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

329

In-service Inspection Ultrasonic Testing of Reactor Pressure Vessel Welds for Assessing Flaw Density and Size Distribution per 10 CFR 50.61a, Alternate Fracture Toughness Requirements  

SciTech Connect

Pressurized thermal shock (PTS) events are system transients in a pressurized water reactor (PWR) in which there is a rapid operating temperature cool-down that results in cold vessel temperatures with or without repressurization of the vessel. The rapid cooling of the inside surface of the reactor pressure vessel (RPV) causes thermal stresses that can combine with stresses caused by high pressure. The aggregate effect of these stresses is an increase in the potential for fracture if a pre-existing flaw is present in a material susceptible to brittle failure. The ferritic, low alloy steel of the reactor vessel beltline adjacent to the core, where neutron radiation gradually embrittles the material over the lifetime of the plant, can be susceptible to brittle fracture. The PTS rule, described in the Code of Federal Regulations, Title 10, Section 50.61 (§50.61), “Fracture Toughness Requirements for Protection against Pressurized Thermal Shock Events,” adopted on July 23, 1985, establishes screening criteria to ensure that the potential for a reactor vessel to fail due to a PTS event is deemed to be acceptably low. The U.S. Nuclear Regulatory Commission (NRC) completed a research program that concluded that the risk of through-wall cracking due to a PTS event is much lower than previously estimated. The NRC subsequently developed a rule, §50.61a, published on January 4, 2010, entitled “Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events” (75 FR 13). Use of the new rule by licensees is optional. The §50.61a rule differs from §50.61 in that it requires licensees who choose to follow this alternate method to analyze the results from periodic volumetric examinations required by the ASME Code, Section XI, Rules for Inservice Inspection (ISI) of Nuclear Power Plants. These analyses are intended to determine if the actual flaw density and size distribution in the licensee’s reactor vessel beltline welds are bounded by the flaw density and size distribution values used in the PTS technical basis. Under a contract with the NRC, Pacific Northwest National Laboratory (PNNL) has been working on a program to assess the ability of current inservice inspection (ISI)-ultrasonic testing (UT) techniques, as qualified through ASME Code, Appendix VIII, Supplements 4 and 6, to detect small fabrication or inservice-induced flaws located in RPV welds and adjacent base materials. As part of this effort, the investigators have pursued an evaluation, based on the available information, of the capability of UT to provide flaw density/distribution inputs for making RPV weld assessments in accordance with §50.61a. This paper presents the results of an evaluation of data from the 1993 Browns Ferry Nuclear Plant, Unit 3, Spirit of Appendix VIII reactor vessel examination, a comparison of the flaw density/distribution from this data with the distribution in §50.61a, possible reasons for differences, and plans and recommendations for further work in this area.

Sullivan, Edmund J.; Anderson, Michael T.; Norris, Wallace

2012-09-17

330

Weld controller for automated nuclear service welding  

SciTech Connect

B and W Nuclear Technologies (BWNT) uses many different types of weld heads for automated welding in the commercial nuclear service industry. Some weld heads are purchased as standard items, while others are custom designed and fabricated by BWNT requiring synchronized multiaxis motion control. BWNT recently completed a development program to build a common weld controller that interfaces to all types of weld heads used by BWNT. Their goal was to construct a system that had the flexibility to add different modules to increase the capability of the controller as different application needs become necessary. The benefits from having a common controller are listed. This presentation explains the weld controller system and the types of applications to which it has been applied.

Barfield, K.L.; Strubhar, P.M.; Green, D.I. [B and W Nuclear Technologies, Lynchburg, VA (United States)

1995-12-31

331

How to map your industry's profit pool.  

PubMed

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

Gadiesh, O; Gilbert, J L

1998-01-01

332

Damage Tolerance Behavior of Friction Stir Welds in Aluminum Alloys  

NASA Technical Reports Server (NTRS)

Friction stir welding is a solid state welding process used in the fabrication of various aerospace structures. Self-reacting and conventional friction stir welding are variations of the friction stir weld process employed in the fabrication of cryogenic propellant tanks which are classified as pressurized structure in many spaceflight vehicle architectures. In order to address damage tolerance behavior associated with friction stir welds in these safety critical structures, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size. Test data describing fracture behavior, residual strength capability, and cyclic mission life capability of friction stir welds at ambient and cryogenic temperatures have been generated and will be presented in this paper. Fracture behavior will include fracture toughness and tearing (R-curve) response of the friction stir welds. Residual strength behavior will include an evaluation of the effects of lack of penetration on conventional friction stir welds, the effects of internal defects (wormholes) on self-reacting friction stir welds, and an evaluation of the effects of fatigue cycled surface cracks on both conventional and selfreacting welds. Cyclic mission life capability will demonstrate the effects of surface crack defects on service load cycle capability. The fracture data will be used to evaluate nondestructive inspection and proof test requirements for the welds.

McGill, Preston; Burkholder, Jonathan

2012-01-01

333

Pools for the Handicapped.  

ERIC Educational Resources Information Center

Three institutions in Ohio now stress hydrotherapy and water recreation as important parts of individual educational programs for the handicapped. Specially designed and adapted pools provide freedom of movement and ego building as well as physical education and recreation. (Author)

American School and University, 1979

1979-01-01

334

The Vernal Pool Association  

NSDL National Science Digital Library

This site is based at Reading Memorial High School in Reading, MA. It features general information defining and describing vernal pools as a habitat type, including an illustrated cartoon series. Resources for educators and students include suggestions for classroom and field trip activities, examples of school projects, field guides, and teacher resources such as workshops. While this site contains several references to state-specific resources and regulations, it is relevant and useful outside of Massachusetts wherever vernal pools are found. The teacher responsible for the text on this site spent a sabbatical developing a resource kit for educators, which is available for purchase. Links are provided to scientific researchers conducting vernal pool studies, including their methods and results. There is an extensive page of resources, both digital in print. Educators and students are encouraged to download and use the collection of 78 slides of vernal pools and associated species on this site.

Kenney, Leo

335

Swimming Pool Accessibility.  

National Technical Information Service (NTIS)

This project was conducted for the U.S. Architecture and Transportation Barriers Compliance Board to identify and evaluate methods and standards related to enabling access to swimming pools by peolple with disabilities, It focuses on the appropriateness, ...

E. J. Hamilton, K. Mispagel, R. Bloomer

1996-01-01

336

Plasma transferred arc repair welding of the nickel-base superalloy IN-738LC  

NASA Astrophysics Data System (ADS)

Plasma transferred arc welding (PTA) has been considered a promising process to restore worn areas of land-based gas turbine blades and vanes. The objective of this investigation was to study the effect of PTA welding on the repairing of IN-738LC superalloy components. Tensile tests were conducted on specimens welded with various combinations of parameters. Room temperature, 760 °C, and 980 °C were selected as tensile test temperatures. High-temperature phase transformed, during solidification, were identified by differential thermal analysis (DTA). The weld-pool shapes and microstructures of welded specimens prepared by various welding parameters were evaluated by optical metallography (OM), a scanning electron microscope (SEM) equipped with energy dispersive x-ray spectrometer (EDS), and microhardness testing. Results of this study showed that PTA welded specimens exhibited 96% nominal tensile strength of IN738LC base materials. Specimen failure was observed predominantly in the base materials instead of in the heat-affected zone (HAZ) for gas tungsten arc weld (GTAW) repair weldments. IN-738LC is considered susceptible to weld cracking during fusion welding; however, using a low-input heat repair welding process (PTA), cracking susceptibility could be minimized by the optimized welding parameters.

Su, C. Y.; Chou, C. P.; Wu, B. C.; Lih, W. C.

1997-10-01

337

Plasma transferred arc repair welding of the nickel-base superalloy IN-738LC  

SciTech Connect

Plasma transferred arc welding (PTA) has been considered a promising process to restore worn areas of land-based gas turbine blades and vanes. The objective of this investigation was to study the effect of PTA welding on the repairing of IN-738LC superalloy components. Tensile tests were conducted on specimens welded with various combinations of parameters. Room temperature, 760 C, and 980 C were selected as tensile test temperatures. High-temperature phase transformed, during solidification, were identified by differential thermal analysis (DTA). The weld-pool shapes and microstructures of welded specimens prepared by various welding parameters were evaluated by optical metallography (OM), a scanning electron microscope (SEM) equipped with energy dispersive x-ray spectrometer (EDS), and microhardness testing. Results of this study showed that PTA welded specimens exhibited 96% nominal tensile strength of IN-738LC base materials. Specimen failure was observed predominantly in the base materials instead of in the heat-affected zone (HAZ) for gas tungsten arc weld (GTAW) repair weldments. IN-738LC is considered susceptible to weld cracking during fusion welding; however, using a low-input repair welding process (PTA), cracking susceptibility could be minimized by the optimized welding parameters.

Su, C.Y.; Chou, C.P. [National Chiao Tung Univ., Hsinchu (Taiwan, Province of China). Dept. of Mechanical Engineering; Wu, B.C.; Lih, W.C. [Industrial Technology Research Inst., Hsinchu (Taiwan, Province of China). Materials Research Labs.

1997-10-01

338

The choice of welding parameters and prediction of weld seam dimensions for welding rapid prototyping  

Microsoft Academic Search

The data of welding seam width and height were obtained by TIG welding experiments. Two models were established using BP neural networks: One can predict the weld seam dimensions by inputting the welding parameters, and the other model can perform oppositely. Originally by inputting given welding seam dimensions to the model one, the welding parameters can be predicted. Then change

Jian-ning Xu; Hua Zhang; Guang-yun Zhang; Yu-long Li; Rong-hua Hu

2008-01-01

339

An engineering model to simulate the thermal response of electronic devices during pulsed Nd:YAG laser welding  

SciTech Connect

A model is developed to predict the thermal response of real electronic devices during pulsed Nd:YAG laser welding. Modeling laser-part interaction requires incorporation of weld pool hydrodynamics, and laser-metal vapor and laser-surface interactions. Although important information can be obtained from these models, they are not appropriate for use in design of actual components due to computational limitations. In lieu of solving for these detailed physics, a simple model is constructed. In this model, laser-part interactions are accounted for through an empirically determined energy transfer efficiency which is developed through the use of modeling and experiments. This engineering model is appropriate since part thermal response near the weld pool and weld pool shape is not of interest here. Reasonable agreement between predictions and experimental measurements for welding of real components are indicated.

Gianoulakis, S.E.; Voth, T.E.; Fuerschbach, P.W. [Sandia National Labs., Albuquerque, NM (United States). Engineering Sciences Center; Prinzbach, J.H. [Wilson Greatbatch Ltd., Clarence, NY (United States). Technology Dept.

1996-12-31

340

Critical Initial Flaw Size Analysis  

NASA Technical Reports Server (NTRS)

An independent assessment was conducted to determine the critical initial flaw size (CIFS) for the flange-to-skin weld in the Ares I-X Upper Stage Simulator (USS). The USS consists of several "tuna can" segments that are approximately 216 inches in diameter, 115 inches tall, and 0.5 inches thick. A 6 inch wide by 1 inch thick flange is welded to the skin and is used to fasten adjacent tuna cans. A schematic of a "tuna can" and the location of the flange-to-skin weld are shown in Figure 1. Gussets (shown in yellow in Figure 1) are welded to the skin and flange every 10 degrees around the circumference of the "tuna can". The flange-to-skin weld is a flux core butt weld with a fillet weld on the inside surface, as illustrated in Figure 2. The welding process may create loss of fusion defects in the weld that could develop into fatigue cracks and jeopardize the structural integrity of the Ares I-X vehicle. The CIFS analysis was conducted to determine the largest crack in the weld region that will not grow to failure within 4 lifetimes, as specified by NASA standard 5001 & 5019 [1].

Dawicke, David S.; Raju, Ivatury S.; Cheston, Derrick J.

2008-01-01

341

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

NASA Technical Reports Server (NTRS)

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

McGill, Preston; Burkholder, Jonathan

2012-01-01

342

Welding-Current Indicator  

NASA Technical Reports Server (NTRS)

Light flashes on to indicate high current. Simple, inexpensive display circuit indicates when 3,000-A welding current flows in welding gun. Onset of welding current induces voltage and current in 1,000-turn, 28-gauge copper-wire coil. Single-transistor amplifier amplifies induced current, energizing light-emitting diode (LED) connected to collector of transistor. Light from LED gives simple, direct indication of welding current.

Hensley, Milton C.; Huston, Steven W.; Kroy, Ralph E.

1990-01-01

343

Thermocapillary and arc phenomena in stainless steel welding  

SciTech Connect

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.

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

344

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

NASA Astrophysics Data System (ADS)

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

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

345

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

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

346

Microhardness Testing of Aluminum Alloy Welds  

NASA Technical Reports Server (NTRS)

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.

Bohanon, Catherine

2009-01-01

347

Portable Weld Tester.  

ERIC Educational Resources Information Center

This training manual, which was developed for employees of an automotive plant, is designed to teach trainees to operate a portable weld tester (Miyachi MM-315). In chapter 1, the weld tester's components are illustrated and described, and the procedure for charging its batteries is explained. Chapter 2 illustrates the weld tester's parts,…

Eckert, Douglas

348

Plasmas for Welding  

NSDL National Science Digital Library

To learn about an important plasma used in manufacturing, visit MIT's Plasmas for Welding. The text describes the arc, which is a plasma, and explains how the arc and the metal to be welded are part of an electric circuit. With photos, the site shows how high-power welding machines cut openings in large sheets of metal.

2006-08-05

349

Welding Plutonium Storage Containers  

SciTech Connect

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.

HUDLOW, SL

2004-04-20

350

Variable polarity arc welding  

NASA Technical Reports Server (NTRS)

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.

Bayless, E. O., Jr.

1991-01-01

351

An introduction to mid-Atlantic seasonal pools  

USGS Publications Warehouse

Seasonal pools, also known as vernal ponds, provide important ecological services to the mid-Atlantic region. This publication serves as an introduction to seasonal pool ecology and management; it also provides tools for exploring seasonal pools, including a full-color field guide to wildlife. Seasonal pools are defined as having four distinctive features: surface water isolation, periodic drying, small size and shallow depth, and support of a characteristic biological community. Seasonal pools experience regular drying that excludes populations of predatory fish. Thus, pools in the mid-Atlantic region provide critical breeding habitat for amphibian and invertebrate species (e.g., spotted salamander (Ambystoma maculatum), wood frog (Rana sylvatica), and fairy shrimp (Order Anostraca)) that would be at increased risk of predation in more permanent waters. The distinctive features of seasonal pools also make them vulnerable to human disturbance. In the mid-Atlantic region, land-use changes pose the greatest challenges to seasonal pool conservation. Seasonal pools are threatened by direct loss (e.g., filling or draining of the pool) as well as by destruction and fragmentation of adjoining terrestrial habitat. Many of the species that depend on seasonal pools for breeding spend the majority of their lives in the surrounding lands that extend a radius of 1000 feet or more from the pools; these vital habitats are being transected by roads and converted to other land uses. Other threats to seasonal pools include biological introductions and removals, mosquito control practices, amphibian diseases, atmospheric deposition, and climate change. The authors recommend a three-pronged strategy for seasonal pool conservation and management in the mid-Atlantic region: education and research, inventory and monitoring of seasonal pools, and landscape-level planning and management.

Brown, L.J.; Jung, R.E.

2005-01-01

352

Analysis of Welding Zinc Coated Steel Sheets in Zero Gap Configuration by 3D Simulations and High Speed Imaging  

NASA Astrophysics Data System (ADS)

Welding of zinc coated sheets in zero gap configuration is of eminent interest for the automotive industry. This Laser welding process would enable the automotive industry to build auto bodies with a high durability in a plain manufacturing process. Today good welding results can only be achieved by expensive constructive procedures such as clamping devices to ensure a defined gad. The welding in zero gap configuration is a big challenge because of the vaporised zinc expelled from the interface between the two sheets. To find appropriate welding parameters for influencing the keyhole and melt pool dynamics, a three dimensional simulation and a high speed imaging system for laser keyhole welding have been developed. The obtained results help to understand the process of the melt pool perturbation caused by vaporised zinc.

Koch, Holger; Kägeler, Christian; Otto, Andreas; Schmidt, Michael

353

Gas tungsten arc welding of vanadium alloys with impurity control  

NASA Astrophysics Data System (ADS)

Gas tungsten arc welding in vanadium alloys is controlled by interstitial impurities. Techniques have been developed to weld V-4Cr-4Ti in a high-purity argon atmosphere resulting in a DBTT of -20 °C. The atmosphere was controlled by a Zr-Al getter which is activated at high temperature to obtain a clean surface then cooled and allowed to absorb hydrogen and oxygen impurities. Through the use of low-oxygen base metal and high-purity weld filler wire, a DBTT of -145 °C was obtained. Experiments using electron beam welding have shown that grain size also has an important effect on weld ductility. Introduction of nitrogen and yttrium has been used to study their effect on grain size. Using a combination of atmosphere control, alloy purity control, and grain size control, it is anticipated that V-Cr-Ti alloys will be weldable in field conditions.

Grossbeck, M. L.; King, J. F.; Nagasaka, T.; David, S. A.

2002-12-01

354

Outsourcing, labor market pooling, and labor contracts  

Microsoft Academic Search

This paper considers the interaction between input sharing and labor market pooling in urban areas. In particular, it examines the impact of the size of a city and business risks on the organizational structures of firms located in urban agglomerations, and it also discusses the impact of organizational structure on incentives to insure workers against income risks. It is shown

Pierre M. Picard; David E. Wildasin

2011-01-01

355

Pooling of spare components between airlines  

Microsoft Academic Search

The purpose of providing component availability service is to maximize aircraft utilization by keeping spare units ready to be installed whenever needed. Since the size of the fleet supported by the spare component inventory is the most important driver behind the inventory cost, inventory pooling among a number of airlines is an intuitive way of exploiting the scale economies of

Jani Kilpi; Ari P. J. Vepsäläinen

2004-01-01

356

Weld-Ed: National Center for Welding Education  

NSDL National Science Digital Library

Weld-Ed, in collaboration with business and industry, improves the quality, quantity and availability of welding technicians through advancement of educational curriculum and instructor professional development. To accomplish the mission, the Center's staff and partners work collaboratively on the development of new and improved curricula in all areas of the materials joining industry. As a result of these efforts, faculty and instructors are provided continuing education opportunities throughout the academic year and in the summer months. These new programs are specifically designed to train the next generation of workers for the materials joining industry and to upgrade the skills of existing workers.

2008-07-21

357

FINITE ELEMENT ANALYSIS OF THERMAL TENSIONING TECHNIQUES MITIGATING WELD BUCKLING DISTORTION  

E-print Network

FINITE ELEMENT ANALYSIS OF THERMAL TENSIONING TECHNIQUES MITIGATING WELD BUCKLING DISTORTION #12;ABSTRACT Weld distortion in thin section structures is usually caused by buckling due to the residual stresses. In addition to conventional techniques, such as reduction of weld size and design

Michaleris, Panagiotis

358

Effect of Thickness Ratio on Formability of Tailor Welded Blanks (TWB)  

Microsoft Academic Search

Tailor welded blanks (TWBs) are made by welding same or different materials having same\\/different properties into a single blank. They can be tailored to any specific shape and size. The formability of these blanks depend on material and geometric parameters like strength ratio and thickness ratio. This paper studies the effect of thickness ratio on the formability of tailor welded

V. Vijay Bhaskar; R. Ganesh Narayanan; K. Narasimhan

2004-01-01

359

Regression models for group testing data with pool dilution effects  

PubMed Central

Group testing is widely used to reduce the cost of screening individuals for infectious diseases. There is an extensive literature on group testing, most of which traditionally has focused on estimating the probability of infection in a homogeneous population. More recently, this research area has shifted towards estimating individual-specific probabilities in a regression context. However, existing regression approaches have assumed that the sensitivity and specificity of pooled biospecimens are constant and do not depend on the pool sizes. For those applications, where this assumption may not be realistic, these existing approaches can lead to inaccurate inference, especially when pool sizes are large. Our new approach, which exploits the information readily available from underlying continuous biomarker distributions, provides reliable inference in settings where pooling would be most beneficial and does so even for larger pool sizes. We illustrate our methodology using hepatitis B data from a study involving Irish prisoners. PMID:23197382

McMahan, Christopher S.; Tebbs, Joshua M.; Bilder, Christopher R.

2013-01-01

360

Fundamentals of friction stir spot welding  

NASA Astrophysics Data System (ADS)

The recent spike in energy costs has been a major contributor to propel the use of light weight alloys in the transportation industry. In particular, the automotive industry sees benefit in using light weight alloys to increase fuel efficiency and enhance performance. In this context, light weight design by replacing steel with Al and/or Mg alloys have been considered as promising initiatives. The joining of structures made of light weight alloys is therefore very important and calls for more attention. Friction Stir Spot Welding (FSSW) is an evolving technique that offers several advantages over conventional joining processes. The fundamentals aspects of FSSW are systematically studied in this dissertation. The effects and influence of process inputs (weld parameters and tool geometry) on the process output (weld geometry and static strength) is studied. A Design of Experiments (DoE) is carried out to identify the effect of each process parameter on weld strength. It is found that the tool geometry, and in particular the pin profile has a significant role in determining the weld geometry (hook, stir zone size etc.) which in turn influences the failure mode and weld strength. A novel triangular pin tool geometry is proposed that suppresses the hook formation and produces welds with twice the static strength as those produced with conventional cylindrical pin tools. An experimental and numerical approach is undertaken to understand the effect of pin geometry on the material flow and failure mechanism of spot welds. In addition, key practical issues have been addressed such as quantification of tool life and a methodology to control tool plunge depth during welding. Finally, by implementing the findings of this dissertation, FSSW is successfully performed on a closure panel assembly for an automotive application.

Badarinarayan, Harsha

361

What is a Welding Engineer?  

NSDL National Science Digital Library

This document from Weld-Ed, the National Center for Welding Education and Training, presents the fundamentals of the career path of welding engineer. It lists the typical job responsibilities, educational requirements, recommended areas of knowledge and/or skill, and salary/wage data for welding engineers. It would be an excellent addition to any welding or materials joining classroom, or to recruitment resources for welding two-year or certification programs.

2009-10-07

362

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.

2011-10-11

363

What is a Welding Technician?  

NSDL National Science Digital Library

This document from Weld-Ed, the National Center for Welding Education and Training, presents the fundamentals of the career path of welding technician. It lists the typical job responsibilities, educational requirements, recommended areas of knowledge and/or skill, and salary/wage data for welding technicians. It would be an excellent addition to any welding or materials joining classroom, or to recruitment resources for welding two-year or certification programs.

2009-10-06

364

Microstructure and failure behavior of dissimilar resistance spot welds between low carbon galvanized and austenitic stainless steels  

Microsoft Academic Search

Resistance spot welding was used to join austenitic stainless steel and galvanized low carbon steel. The relationship between failure mode and weld fusion zone characteristics (size and microstructure) was studied. It was found that spot weld strength in the pullout failure mode is controlled by the strength and fusion zone size of the galvanized steel side. The hardness of the

P. Marashi; M. Pouranvari; S. Amirabdollahian; A. Abedi; M. Goodarzi

2008-01-01

365

Fatigue-reliability analysis of resistance spot-welds  

Microsoft Academic Search

The resistance spot welding process has been widely used in the automotive industry for decades. Once the vehicle weight reduction by down-gaging sheet metal and down-sizing reinforcements becomes of importance, the fatigue performance of spot welds will be a critical factor in design and analysis. Since most of the existing analytical approaches are still deterministic and too complicated to use,

Yung-Li Lee; Ming-Wei Lu

1994-01-01

366

Solidification microstructures in single-crystal stainless steel melt pools  

SciTech Connect

Development of microstructure of stationary melt pools of oriented stainless steel single crystals (70%Fe-15%Ni-15%Cr was analyzed. Stationary melt pools were formed by electron-beam and gas-tungsten-arc heating on (001), (011), and (111) oriented planes of the austenitic, fcc-alloy crystals. Characterization and analysis of resulting microstructure was carried out for each crystallographic plane and welding method. Results showed that crystallography which favors ``easy growth`` along the <100> family of directions is a controlling factor in the microstructural formation along with the melt-pool shape. The microstructure was found to depend on the melting method, since each method forms a unique melt-pool shape. These results are used in making a three-dimensional reconstruction of the microstructure for each plane and melting method employed. This investigation also suggests avenues for future research into the microstructural properties of electron-beam welds as well as providing an experimental basis for mathematical models for the prediction of solidification microstructures.

Sipf, J.B.; Boatner, L.A.; David, S.A.

1994-03-01

367

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

SciTech Connect

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.

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

368

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...

369

Reliability-based optimization of multi-component welded structures  

SciTech Connect

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.

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

370

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

371

Weld metal ductility in aluminum tailor welded blanks  

Microsoft Academic Search

The objective of the research described in this article was to characterize and numerically describe the ductility of weld material in aluminum tailor welded blanks under uniaxial tension conditions. Aluminum tailor welded blanks consist of multiple thickness and alloy sheet materials welded together into a single, variable thickness blank. To evaluate the mechanical properties of the weld material in these

R. W. Davies; M. T. Smith; M. A. Khaleel; S. G. Pitman; H. E. Oliver

2000-01-01

372

Experimental research on sunken weld of tailor welded blanks  

Microsoft Academic Search

Sunken weld is one of the common defects of tailor welded blanks (TWB), which seriously affects the strength of weld. The reasons for sunken weld are discussed based on theoretical analyses and experiments. The results show that sunken weld is affected by gaps and offsets. Positive offset (laser spot shifts to the thicker steel sheet) can reduce the harmful effects

Dong Chen; Mingyang Zhao; Tianxu Zhu; Sijun Zhu; Chenyuan Wang

2010-01-01

373

Influence of sulfur and welding conditions on penetration in thin strip stainless steel  

SciTech Connect

Welding trials and surface tension measurements have been carried out on 304 stainless steels with sulfur (S) contents between 20 and 100 ppm. Surface tension measurements, determined by the levitated drop method, indicated that the temperature coefficient of surface tension (d[gamma]/dT) changed from negative to positive values at S contents exceeding approximately 50 ppm. Strips with a thickness of approximately 1 mm were GTA welded on both single-electrode, small-scale and multi-electrode industrial-scale units. Welding speeds of 1 to 2 m min[sup [minus]1] were used on the small-scale unit and up to 5 m min[sup [minus]1] on the industrial unit. The weld penetration was found to increase, for both full and partial penetration welds, with (1) increasing sulfur contents; and (2) increasing linear energy. On the small scale-unit markedly higher penetration was observed in heats with S contents > 60 ppm. But the influence of S contents was only of minor importance for welds obtained on the industrial unit. It was found that the similar weld geometry could be obtained for both low ([<=] 60 ppm) and high (> 60 ppm) sulfur contents by careful adjustment of welding parameters. The observed changes in weld geometry are consistent with the proposition that the fluid flow in the weld pool is dominated by thermo-capillary (Marangoni) forces during the GTA welding of thin strips.

Scheller, P.R. (Krupp Stahl AG, Bochum (Germany)); Brooks, R.F.; Mills, K.C. (National Physical Lab., Middlesex (United Kingdom). Division of Materials Metrology)

1995-02-01

374

Annual report, FY 1979 Spent fuel and fuel pool component integrity.  

SciTech Connect

International meetings under the BEFAST program and under INFCE Working Group No. 6 during 1978 and 1979 continue to indicate that no cases of fuel cladding degradation have developed on pool-stored fuel from water reactors. A section from a spent fuel rack stand, exposed for 1.5 y in the Yankee Rowe (PWR) pool had 0.001- to 0.003-in.-deep (25- to 75-..mu..m) intergranular corrosion in weld heat-affected zones but no evidence of stress corrosion cracking. A section of a 304 stainless steel spent fuel storage rack exposed 6.67 y in the Point Beach reactor (PWR) spent fuel pool showed no significant corrosion. A section of 304 stainless steel 8-in.-dia pipe from the Three Mile Island No. 1 (PWR) spent fuel pool heat exchanger plumbing developed a through-wall crack. The crack was intergranular, initiating from the inside surface in a weld heat-affected zone. The zone where the crack occurred was severely sensitized during field welding. The Kraftwerk Union (Erlangen, GFR) disassembled a stainless-steel fuel-handling machine that operated for 12 y in a PWR (boric acid) spent fuel pool. There was no evidence of deterioration, and the fuel-handling machine was reassembled for further use. A spent fuel pool at a Swedish PWR was decontaminated. The procedure is outlined in this report.

Johnson, A.B. Jr.; Bailey, W.J.; Schreiber, R.E.; Kustas, F.M.

1980-05-01

375

Evaluation of solar cell welds by scanning acoustic microscopy  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

376

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

Microsoft Academic Search

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

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

2006-01-01

377

Development of an intelligent system for cooling rate and fill control in GMAW. [Gas Metal Arc Welding (GMAW)  

SciTech Connect

A control strategy for gas metal arc welding (GMAW) is developed in which the welding system detects certain existing conditions and adjusts the process in accordance to pre-specified rules. This strategy is used to control the reinforcement and weld bead centerline cooling rate during welding. Relationships between heat and mass transfer rates to the base metal and the required electrode speed and welding speed for specific open circuit voltages are taught to a artificial neural network. Control rules are programmed into a fuzzy logic system. TRADITOINAL CONTROL OF THE GMAW PROCESS is based on the use of explicit welding procedures detailing allowable parameter ranges on a pass by pass basis for a given weld. The present work is an exploration of a completely different approach to welding control. In this work the objectives are to produce welds having desired weld bead reinforcements while maintaining the weld bead centerline cooling rate at preselected values. The need for this specific control is related to fabrication requirements for specific types of pressure vessels. The control strategy involves measuring weld joint transverse cross-sectional area ahead of the welding torch and the weld bead centerline cooling rate behind the weld pool, both by means of video (2), calculating the required process parameters necessary to obtain the needed heat and mass transfer rates (in appropriate dimensions) by means of an artificial neural network, and controlling the heat transfer rate by means of a fuzzy logic controller (3). The result is a welding machine that senses the welding conditions and responds to those conditions on the basis of logical rules, as opposed to producing a weld based on a specific procedure.

Einerson, C.J.; Smartt, H.B.; Johnson, J.A.; Taylor, P.L. (EG and G Idaho, Inc., Idaho Falls, ID (United States)); Moore, K.L. (Idaho State Univ., Pocatello, ID (United States))

1992-01-01

378

On-line inspection of weld quality based on dynamic resistance curve in resistance spot welding and weldbonding  

NASA Astrophysics Data System (ADS)

In order to reduce destructive testing of car sub-assemblies, on-line inspection of weld quality has gained more and more concern in terms of both resistance spot welding (RSW) and weldbonding. Dynamic resistance directly determines the amount of heat generated by current flow and consequently reflects nugget formation and growth, which is one of the most effective technologies for quality inspection. Under the measurements of voltage and current at the secondary circuit of a welding transformer, this paper proposes a method for on-line inspection of weld quality based on two indicators from dynamic resistance curve: time to nugget initiation and durable time to nugget expansion. Firstly, during the welding process of RSW and weldbonding, the proper range of time to nugget initiation and durable time to nugget expansion for good welds is set up. Then on-line inspection of weld quality on the basis of the developed proper range of these two indicators is carried out. The experimental results show the following conclusions: it is clearly able to separate accepted welds without expulsion from the welds of unaccepted nugget size in both RSW and weldbonding; the proper range for good welds, independent of electrode wear, is obtained only for a new electrode.

Sun, Haitao; Zhang, Yansong; Lai, Xinmin; Chen, Guanlong

2008-12-01

379

Single crystals for welding research  

SciTech Connect

Most welds last for many years, but a few fail after a relatively short time. Knowing the reasons why welds fail is important because cracks in welds can threaten the safety of people in buildings, airplanes, ships, automobiles, and power plants. Bad welds can lead to costly, extended shutdowns of industrial facilities such as petroleum refineries. Thus, research on this very important fabrication technology is critical to the multibillion-dollar welding industry. Research at ORNL and elsewhere strives to determine the structural features that make some welds strong and others weak. The goals are to find cost-effective ways to characterize the structure and strength of a new weld, correctly predict whether it will last a long time, and determine the welding conditions most likely to produce high-quality welds. There is more to welding than meets the eye. The cracks that make welds fail result from the complexities of microstructures formed during welding. Thus weld microstructure is linked to weld properties such as mechanical strength. As the hot weld material cools from a liquid into a solid, the crystalline grains grow at different speeds and in different directions, forming a new microstructure. By using single crystals rather than polycrystalline alloys to study different weld microstructures, scientists at ORNL have developed a way to predict more accurately the microstructures of various welds. The results could guide welders in providing the right conditions (correct welding speed, heat input, and weld thickness) for producing safer, higher-quality, and longer-lasting welds.

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

1991-01-01

380

Effects of welding wire composition and welding process on the weld metal toughness of submerged arc welded pipeline steel  

Microsoft Academic Search

The effects of alloying elements in welding wires and submerged arc welding process on the microstructures and low-temperature impact toughness of weld metals have been investigated. The results indicate that the optimal contents of alloying elements in welding wires can improve the low-temperature impact toughness of weld metals because the proeutectoid ferrite and bainite formations can be suppressed, and the

De-liang Ren; Fu-ren Xiao; Peng Tian; Xu Wang; Bo Liao

2009-01-01

381

Robotic Welding Of Injector Manifold  

NASA Technical Reports Server (NTRS)

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.

Gilbert, Jeffrey L.; Shelley, D. Mark

1992-01-01

382

Tube-weld inspection tool  

NASA Technical Reports Server (NTRS)

Tool compares weld width with notch width. Weld is considered satisfactory if weld is wider than notch. Fiber optics permit inspection head to be completely rotated around tube for complete inspection of weld. Forty-five degree mirror mounted over notch aids in comparing notch and weld widths.

Stanford, H. B.

1978-01-01

383

Vacuum tube automatic weld station  

Microsoft Academic Search

A microcomputer controlled tube welding station has been developed that significantly improves the productivity of the process by providing fully automatic operation and improved weld quality. In addition, the microcomputer allows easy changing of the process to study and determine the optimum weld cycle parameters. The weld station provides the following significant features: (1) fully automatic flush and weld cycle;

1981-01-01

384

Welding of TZM molybdenum alloy  

Microsoft Academic Search

Molybdenum and TZM alloy are not too difficult to form or weld if the proper procedures are employed. Consistently good welds can be obtained by controlling the area of heating by ensuring full penetration of the welded pieces and by reducing the stresses. A large percentage of the problems incurred in welding TZM can be corrected by good weld joint

Hanks

1970-01-01

385

Characterization of tool wear and weld optimization in the friction-stir welding of cast aluminum 359+20% SiC metal-matrix composite  

SciTech Connect

Tool wear for threaded steel pin tools declines with decreasing rotation speed and increasing traverse or weld speeds for the friction-stir welding (FSW) of Al 359+20% SiC metal-matrix composite (MMC). Less than 10% tool wear occurs when the threaded tool erodes to a self-optimized shape resembling a pseudo-hour glass at weld traverse distances in excess of 3 m. There is only a 7% reduction in the SiC mean particle size in the weld zone for self-optimized pin tools with no threads as compared with a 25% variation for threaded tools wearing significantly at the start of welding. The weld zone becomes more homogeneous for efficient welding with self-optimized tools, and there is a reduction in the weld zone grain size due to dynamic recrystallization, which facilitates the solid-state flow. Transmission electron microscopy shows little difference in the dislocation density from the base material to the weld zone, but there is a propensity of dislocation loops in the weld zone. The weld zone is observed to harden by as much as 30%, in contrast to the base material, as a consequence of the recrystallized grain size reduction and the SiC particles distributed therein.

Fernandez, G.J.; Murr, L.E

2004-03-15

386

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

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Welds and welding inspection: Standards of...PIPELINE Construction § 195.228 Welds and welding inspection: Standards of acceptability. (a) Each weld and welding must be inspected to...

2012-10-01

387

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

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Welds and welding inspection: Standards of...PIPELINE Construction § 195.228 Welds and welding inspection: Standards of acceptability. (a) Each weld and welding must be inspected to...

2013-10-01

388

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

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Welds and welding inspection: Standards of...PIPELINE Construction § 195.228 Welds and welding inspection: Standards of acceptability. (a) Each weld and welding must be inspected to...

2010-10-01

389

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

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Welds and welding inspection: Standards of...PIPELINE Construction § 195.228 Welds and welding inspection: Standards of acceptability. (a) Each weld and welding must be inspected to...

2011-10-01

390

Stochastic pooling networks  

NASA Astrophysics Data System (ADS)

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.

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

2009-01-01

391

Influence on the dilution by laser welding of aluminum with magnetic stirring  

NASA Astrophysics Data System (ADS)

The Aluminum 6xxx alloys are well-known for their high susceptibility to hot cracking. It has been reported that this problem can be effectively resolved by introducing silicon into the molten pool. However, the high welding speed by laser welding process results in an inhomogeneous dilution of the silicon, which may lead to hot cracks in the Sipoor area. The idea of applying a low frequency magnetic field during laser welding process has been already carried out recently in order to make a stir effect inside the molten pool and therefore to improve the element dilution in the weld joint. In this paper, the effects of the magnetic field on the melt flow as well as the element dilution are shown by applying copper as “tracer” inside the molten pool. Several methods were designed with different forms of copper at different positions in the workpieces to visualize the melt flow and the corresponding element dilution in different areas of the molten pool. In addition, laser welding with AlSi18 filler wire was also conducted to realize a real welding process comparing to that with “tracer”. WDX analysis was then carried out to investigate how silicon distributed inside the welds with the help of magnetic stirring. The results demonstrate that a DC magnetic field, with its direction coaxial to the laser, tends to modify the melt flow dynamics at flux density up to 100 mT. The results of laser welding with filler wire showed that by the help of an AC magnetic field with a frequency up to 10 Hz and flux density above 100 mT, the element dilution could be improved in the weld joint. The WDX analysis showed that under the influence of an alternating magnetic field a periodicity of the silicon distribution can be achieved, which depends greatly on the magnetic frequency.

Tang, Z.; Gatzen, M.

392

Effect of changes in testing parameters on the cost-effectiveness of two pooled test methods to classify infection status of animals in a herd  

Microsoft Academic Search

Monte Carlo simulation was used to determine optimal fecal pool sizes for identification of all Mycobacterium avium subsp. paratuberculosis (MAP)-infected cows in a dairy herd. Two pooling protocols were compared: a halving protocol involving a single retest of negative pools followed by halving of positive pools and a simple protocol involving single retest of negative pools but no halving of

Locksley L. Mc V. Messam; Joshua M. O’Brien; Sharon K. Hietala; Ian A. Gardner

2010-01-01

393

Welding arc plasma physics  

NASA Technical Reports Server (NTRS)

The problems of weld quality control and weld process dependability continue to be relevant issues in modern metal welding technology. These become especially important for NASA missions which may require the assembly or repair of larger orbiting platforms using automatic welding techniques. To extend present welding technologies for such applications, NASA/MSFC's Materials and Processes Lab is developing physical models of the arc welding process with the goal of providing both a basis for improved design of weld control systems, and a better understanding of how arc welding variables influence final weld properties. The physics of the plasma arc discharge is reasonably well established in terms of transport processes occurring in the arc column itself, although recourse to sophisticated numerical treatments is normally required to obtain quantitative results. Unfortunately the rigor of these numerical computations often obscures the physics of the underlying model due to its inherent complexity. In contrast, this work has focused on a relatively simple physical model of the arc discharge to describe the gross features observed in welding arcs. Emphasis was placed of deriving analytic expressions for the voltage along the arc axis as a function of known or measurable arc parameters. The model retains the essential physics for a straight polarity, diffusion dominated free burning arc in argon, with major simplifications of collisionless sheaths and simple energy balances at the electrodes.

Cain, Bruce L.

1990-01-01

394

Welding for life  

SciTech Connect

State of the Art Welding Techniques are being utilized to extend the life of major steam turbine components, as well as other traditional types of repairs. The development of a temper bead welding technique has allowed Houston Lighting and Power (HL and P) to perform innovative weld repairs. Nozzle vanes are weld repaired without removing the nozzle blocks from the case; repair life has also been doubled. A new two wire Gas Tungsten ARC Welding (GTAW) machine has produced high deposition rates while maintaining excellent mechanical properties. This results in faster turn-around time and with an improved weld repair. Development of a weld wire specification has also been instrumental in achieving additional component life by increasing the resistance to fatigue, especially in the heat affected zone. All these factors work together to enhance the weld repairs. Tensile strengths of 140,000 PSI with good ductility have been achieved. This paper will discuss their experiences with several repairs and recap the results of some studies and tests performed during the technique development stages. Major repairs include; weld repair of cases, nozzle blocks, nozzle boxes, stationary blade repair, forced draft fan shaft buildup, weld repair of turbine shrouds, blades, tennons and journals.

Stiebler, T.J.; Nugent, R.M.; Wilson, R.P. [Houston Lighting and Power Co., Houston, TX (United States). EDC Central Repair Shop

1994-12-31

395

Determination of pool boiling Critical Heat Flux enhancement in nanofluids  

E-print Network

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 ...

Truong, Bao H. (Bao Hoai)

2007-01-01

396

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

SciTech Connect

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.

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

2007-06-06

397

Assessment of stress-corrosion cracking in a spent-fuel pool pipe  

Microsoft Academic Search

Intergranular stress corrosion cracks found in the weld heat affected zone of pipe in the Spent Fuel Pool piping system at Three Mile Island Unit No. 1 have been evaluated by a series of analytical tests. The intergranular nature of the cracks was identified by optical metallography and scanning electron miroscopy. The presence of Cl⁻ was observed by Energy Dispersive

R. H. Jones; A. B. Jr. Johnson; F. S. Giacobbe

1981-01-01

398

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

399

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

SciTech Connect

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.

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

1994-12-31

400

Influence of the weld conditions on the forming-limit strains of tailor-welded blanks  

Microsoft Academic Search

The main objective of the present work is to study experimentally the influence of just the weld conditions, namely the weld region, weld orientation, and weld location, on the forming-limit strains of steel laser-welded blanks. Transverse and longitudinal weld orient- ations are considered for this study. The weld location includes both centre and offset weld positions in the transverse weld

R Ganesh Narayanan; K Narasimhan

2008-01-01

401

EVALUATION OF CONSTANT CURRENT WELD CONTROL FOR PINCH WELDING  

SciTech Connect

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.

Korinko, P; STANLEY, S; HOWARD, H

2005-10-11

402

Computerized adaptive control weld skate with CCTV weld guidance project  

NASA Technical Reports Server (NTRS)

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

Wall, W. A.

1976-01-01

403

Periscope For Viewing Weld Penetration  

NASA Technical Reports Server (NTRS)

Periscope enables viewing of weld joint from inside cylindrical duct to determine when weld penetration occurs. Supplies steady stream of inert gas to shield joint. Device used to calibrate and evaluate techniques for sensing weld penetration.

Gordon, Stephen S.; Marman, Jonathan M.

1988-01-01

404

Two-Pulse Stitch Welding  

NASA Technical Reports Server (NTRS)

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.

Torborg, C. J.

1985-01-01

405

Welding and joining: A compilation  

NASA Technical Reports Server (NTRS)

A compilation is presented of NASA-developed technology in welding and joining. Topics discussed include welding equipment, techniques in welding, general bonding, joining techniques, and clamps and holding fixtures.

1975-01-01

406

GMA-laser Hybrid Welding of High-strength Fine-grain Structural Steel with an Inductive Preheating  

NASA Astrophysics Data System (ADS)

The industrial useof GMA-laser hybrid welding has increased in the last 10 years, due to the brilliant quality of the laser beam radiation, and higher laser output powers. GMA-laser hybrid welding processes operate in a common molten pool. The combination of the laser beam and the arc results in improved welding speed, penetration depth, heat affected zone and gap bridgeability. Single-layer, GMA-laser hybrid welding processes have been developed for high-strength fine-grain structural steels with a grade of S690QL and a thickness of 15 mm and 20 mm. In addition, the welding process is assisted by an integrated, inductive preheating process to improve the mechanical properties of the welding seam. By using the determined parameters regarding the energy per unit length, and the preheating temperature, welding seams with high quality can be achieved.

Lahdo, Rabi; Seffer, Oliver; Springer, André; Kaierle, Stefan; Overmeyer, Ludger

407

Aircraft observations of cold pools under marine stratocumulus  

NASA Astrophysics Data System (ADS)

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.

Terai, C. R.; Wood, R.

2013-10-01

408

Welding in Space Workshop  

NASA Technical Reports Server (NTRS)

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.

Workman, Gary L.

1990-01-01

409

Associations of welding and manganese exposure with Parkinson disease  

PubMed Central

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

Borenstein, Amy R.; Nelson, Lorene M.

2012-01-01

410

Welding / Materials Joining Career Tree  

NSDL National Science Digital Library

This illustration from Weld-Ed, the National Center for Welding Education and Training, presents a list of possible careers in welding and materials joining. It was developed by Ernest Levert of Lockheed Martin and lists such paths as pipe welder, x-ray technician, shop owner, and high school teacher, among many others. It would be an excellent addition to the wall of any welding or materials joining classroom, or to recruitment resources for welding two-year or certification programs.

2009-10-06

411

Enhanced diffusion welding  

NASA Technical Reports Server (NTRS)

Surfaces of unrecrystallized alloys are sanded and polished. This is followed by a two-step welding process by which the strength of the parent metal is retained at the weld joint. The first step forces the surfaces into intimate contact at a temperature where the metal still has good ductility. The second step causes diffusion, recrystallization, and grain growth across the original weld interface.

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

1973-01-01

412

Acicular ferrite transformation in alloy-steel weld metals  

Microsoft Academic Search

In this paper, the morphology of acicular ferrite in alloy-steel weld metals has been investigated. The effect of the grain\\u000a size of prior austenite on acicular ferrite transformation has also been studied. It is found that acicular ferrite can form\\u000a in reheated weld metals when the austenite grain size is relatively large. On the other hand, classical sheaf-like bainite\\u000a will

J. R. Yang; H. K. D. H. Bhadeshia

1991-01-01

413

Bond formation in ultrasonically welded aluminum sheet metal  

NASA Astrophysics Data System (ADS)

Ultrasonic welding (USW), a solid state joining technology, has been used to bond aluminum alloys commonly used in the automotive industry. Bonding occurs due to USW's high frequency (˜20 kHz) in-plane vibration of sample interfaces while being held under moderate clamp pressure normal to the plane of vibration. Vibration and clamp pressure are transmitted into bond formation via contact with a weld-tip. To better understand how weld-tip geometry affected bond formation, experiments were conducted to quantify how tip geometry influenced plastic deformation characteristics between fully welded coupons of 0.9mm thick AA6111-T4 aluminum alloy. Weld-interface microstructure features were documented by optical microscopy and features quantified in a 19 point matrix. Correlation between microstructure features, such as rolling-wakes, and resulting weld bond strengths of more than 3.0kN is made. Weld zone microstructure features appear to result from deformation at and severe migration of the original weld interface during USW. To confirm this hypothesis, intrinsic and extrinsic markers were employed to monitor weld interface deformation characteristics. Various physical and analytical techniques were used in conjunction with these markers to show that joining of "like" and "dislike" aluminum samples is achieved through mechanical mixing of mating interfaces and not by elemental diffusion. It is also hypothesized that severe deformation of the original interface would result in areas of high residual strain within a formed weld zone. To investigate this and the influence that tip geometry may have on residual strain, fully welded samples were annealed at 500°C for a controlled period of time and recovery, recrystallization and grain growth characteristics were monitored. In all welds, initial recrystallization and grain growth occurred at the outer ends of weld zones and along weld interfaces where the most turbulent mixing and grain size reduction was observed. Similarity in how all welds responded to annealing indicates that the tip geometries investigated had little influence on resulting weld formation. This claim is further supported by lap-shear failure load data for welds made with these tips being within statistical error of each other.

Wilkosz, Daniel Edward

414

Allergic to Pool Water  

PubMed Central

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

2012-01-01

415

COLPEX - Cold Pool Experiment  

Microsoft Academic Search

Planning has started towards designing a new field campaign aimed at studying the behaviour of the boundary layer over complex terrain. Of specific interest is the formation of cold-pools in valleys during stable night-time conditions. The field campaign will run continuously until the end of the winter in 2009\\/10. The experiment will make use of a wide variety of ground-based

H. Wells; J. Price; V. Horlacher; P. F. Sheridan; S. B. Vosper; A. R. Brown; S. D. Mobbs; A. N. Ross

2009-01-01

416

Friction Stir Weld Restart+Reweld Repair Allowables  

NASA Technical Reports Server (NTRS)

A friction stir weld (FSW) repair method has been developed and successfully implemented on Al 2195 plate material for the Space Shuttle External Fuel Tank (ET). The method includes restarting the friction stir weld in the termination hole of the original weld followed by two reweld passes. Room temperature and cryogenic temperature mechanical properties exceeded minimum FSW design strength and compared well with the development data. Simulated service test results also compared closely to historical data for initial FSW, confirming no change to the critical flaw size or inspection requirements for the repaired weld. Testing of VPPA fusion/FSW intersection weld specimens exhibited acceptable strength and exceeded the minimum design value. Porosity, when present at the intersection was on the root side toe of the fusion weld, the "worst case" being 0.7 inch long. While such porosity may be removed by sanding, this "worst case" porosity condition was tested "as is" and demonstrated that porosity did not negatively affect the strength of the intersection weld. Large, 15-inch "wide panels" FSW repair welds were tested to demonstrate strength and evaluate residual stresses using photo stress analysis. All results exceeded design minimums, and photo stress analysis showed no significant stress gradients due to the presence of the restart and multi-pass FSW repair weld.

Clifton, Andrew

2008-01-01

417

Increasing Productivity of Welding  

E-print Network

been solid steel electrode wires, 1/16" and smaller, which is normally used for gas metal arc welding and the flux-cored electrode wire. The chart shows that these are increasing at a fairly steady rate with the small solid electrode wire... the entire operation is manual; "Semiautomatic Welding", wherein the arc is maintained by the machine which also feeds the filler metal, but the travel and direction is done by the welder. The third method is "Machine Welding" or mechanized welding, where...

Uhrig, J. J.

1983-01-01

418

Robot welding process control  

NASA Astrophysics Data System (ADS)

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.

Romine, Peter L.

1991-07-01

419

Robot welding process control  

NASA Technical Reports Server (NTRS)

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.

Romine, Peter L.

1991-01-01

420

Physics of Fusion Welding  

NASA Technical Reports Server (NTRS)

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

Nunes, A. C., Jr.

1986-01-01

421

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

NASA Astrophysics Data System (ADS)

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

Bag, S.; de, A.

2010-09-01

422

Detection of defects in laser welding of AZ31B magnesium alloy in zero-gap lap joint configuration by a real-time spectroscopic analysis  

NASA Astrophysics Data System (ADS)

The effect of surface oxide layer existing at the lap-joint faying surface of magnesium sheets is investigated on the keyhole dynamics of the weld pool and weld bead qualities. It is observed that by removing the oxide layer from the faying surface of the lap joint, a high quality weld can be achieved in the laser welding process. However, the presence of an oxide layer deteriorates the quality of the weld by forming pores at the interface of the two overlapped sheets. The purpose of this paper is to identify the correlation between the integrity of the weld and the interaction between the laser and material. A spectroscopy sensor was applied to detect the spectra emitted from a plasma plume during the laser welding of AZ31B magnesium alloy in a zero-gap lap joint configuration. The electron temperature was calculated by applying a Boltzmann plot method based on the detected spectra, and the correlation between the pore formation and the spectral signals was studied. The laser molten pool and the keyhole condition were monitored in real-time by a high speed charge-coupled device (CCD) camera. A green laser was used as an illumination source in order to detect the influence of the oxide layer on the dynamic behavior of the molten pool. Results revealed that the detected spectrum and weld defects had a meaningful correlation for real-time monitoring of the weld quality during laser welding of magnesium alloys.

Harooni, Masoud; Carlson, Blair; Kovacevic, Radovan

2014-05-01

423

Dual wire welding torch and method  

SciTech Connect

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.

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

424

Gaseous hydrogen embrittlement of T-250 laser welds  

NASA Astrophysics Data System (ADS)

The tensile properties of laser-welded T-250 maraging steel are measured, with attention paid to the influence of strain rate and gaseous hydrogen on the fracture behavior of welded specimens. Post-weld heat treatments are performed on laser-welded specimens to obtain underaged (WU), peak-aged (WP), and overaged (WO) specimens. Hydrogen embrittlement (HE) affects the tensile fracture behavior of the welded specimens; HE changes not only the fracture mode but also the fracture location. Without the influence of hydrogen, the fracture location is at the softest region, the weld metal (WM), and the fracture appearance reveals a ductile dimple fracture. For welds sensitive to HE, the fracture is initiated at the heat-affected zone (HAZ) with coarse grain size, and the associated fracture surface exhibits intergranular and quasi-cleavage fractures that are brittle in nature. In addition, the HAZ with coarse grain size is more prone to HE, as compared to other regions in the welded specimens. The WU specimens are susceptible to HE in air under a low strain rate, while the WP specimens are only susceptible to gaseous hydrogen embrittlement (GHE). However, the WO specimens are immune to GHE and insensitive to strain rate.

Tsay, L. W.; Huang, W. B.; Chen, C.

1997-04-01

425

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

SciTech Connect

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.

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

2006-12-20

426

Manually Operated Welding Wire Feeder  

NASA Technical Reports Server (NTRS)

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.

Rybicki, Daniel J. (Inventor)

2001-01-01

427

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

NASA Astrophysics Data System (ADS)

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.

Unt, Anna; Poutiainen, Ilkka; Salminen, Antti

428

Aircraft observations of cold pools under marine stratocumulus  

NASA Astrophysics Data System (ADS)

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 env