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1

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

2

Visualization of gas tungsten arc weld pools  

Microsoft Academic Search

Surface flow visualization of gas tungsten arc weld pools for HY-80 steel is presented using a pulsed laser light source and a conventional night vision image-intensifier tube equipped video camera. Visualization of the weld pool free surface is made possible by seeding a flow with alumina particles for both stationary and moving arc welds. These visualizations reveal several new features

Daniel C. Espinosa

1991-01-01

3

Obtaining weld pool vision information during aluminium alloy TIG welding  

Microsoft Academic Search

An image sensing system for the TIG (tungsten inert-gas arc) welding process of aluminium alloy was established. The relationships between the image sensing system and the characteristic of welding current were discussed in detail. Front and back images of the weld pool were obtained with different welding parameters. In order to process the image, the characteristics of an aluminium alloy

J. J. Wang; T. Lin; S. B. Chen

2005-01-01

4

Weld pool solidification and microstructures.  

National Technical Information Service (NTIS)

Solidification behavior controls the size and shape of grains, the rate and extent of segregation, the distribution of inclusions, the extent of defects such as porosity and hot-cracking, and, ultimately, the properties of weld metal. In the past, theorie...

S. A. David J. M. Vitek

1991-01-01

5

Surface height and geometry parameters for describing shape of weld pool during pulsed GTAW  

NASA Astrophysics Data System (ADS)

Weld penetration and fine formation are the major factors for consideration of weld bead quality. The geometry of weld pool contains abundant information about the weld penetration. The weld pool surface is depressed during full- penetration because of arc impulse, and the weld pool surface may be convex during part-penetration or welding with filler. In this paper, we present the surface height and shape parameters for describing the three dimension of weld pool. During pulsed GTAW process, the weld pool image can be obtained through visual sensing system by the illumination of arc light on weld pool. The inverted image of tungsten tip and arc shape can be seen clearly from the weld pool image. The position of inverted tungsten tip varies with the surface height according to the principle of specula reflection. The point of tungsten tip is located to calculate the surface height. The shape of weld pool has been characterized with size and shape parameters, such as pool width, length and a series of rear angles, etc. A simple nonlinear formula with only four parameters is proposed for describing the pool shape, and the regression results are shown with high accuracy. Based on the surface height and geometry parameters of weld pool, the shape of weld pool can be strictly defined, which lays the foundation for further study on process model and weld penetration control.

Zhao, Dongbin; Chen, Shanben; Wu, Lin

1999-08-01

6

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

7

Modeling of inclusion growth and dissolution in the weld pool  

Microsoft Academic Search

The composition, size distribution, and number density of oxide inclusions in weld metal are critical factors in determining\\u000a weldment properties. A computational model has been developed to understand these factors, considering fluid flow and the\\u000a temperature field in the weld pool during submerged are (SA) welding of low-alloy steels. The equations of conservation of\\u000a mass, momentum, and energy are solved

T. Hong; T. Debroy; S. S. Babu; S. A. David

2000-01-01

8

Neural Network Modeling of Weld Pool Shape in Pulsed-Laser Aluminum Welds  

SciTech Connect

A neural network model was developed to predict the weld pool shape for pulsed-laser aluminum welds. Several different network architectures were examined and the optimum architecture was identified. The neural network was then trained and, in spite of the small size of the training data set, the network accurately predicted the weld pool shape profiles. The neural network output was in the form of four weld pool shape parameters (depth, width, half-width, and area) and these were converted into predicted weld pool profiles with the use of the actual experimental poo1 profiles as templates. It was also shown that the neural network model could reliably predict the change from conduction-mode type shapes to keyhole-mode shapes.

Iskander, Y.S.; Oblow, E.M.; Vitek, J.M.

1998-11-16

9

Monitoring of weld joint penetration based on weld pool geometrical appearance  

SciTech Connect

Weld joint penetration monitoring and control are fundamental issues in automated welding. A skilled human operator can determine the weld penetration from the geometrical appearance of the weld pool. To emulate this using machine vision, a high-shutter-speed camera assisted with pulsed laser illumination is used to capture the clear image of the weld pool.d The pool boundary is extracted by the developed real-time image processing algorithm. In order to emphasize the emulation of the human operator, general terms, i.e., size, shape and geometrical appearance, are used for the conceptual discussion, whereas more specific terms such as length, width, and rear angles are used in the detailed analysis. In particular, the size will be specified by the pool width and length, and the shape will be defined using the proposed rear angle of the weld pool. The geometrical appearance is described by a combination of the size and shape parameters. To investigate the relationships, which could be complicated, between the weld penetration and different parameters, neural networks are used because of their capability for modeling complicated nonlinear functions. Extensive experiments have been developed to measure the weld penetration from the captured image in 200 ms using the neural network and real-time image processing.

Kovacevic, R.; Zhang, Y.M.; Li, L. [Univ. of Kentucky, Lexington, KY (United States)

1996-10-01

10

Visualization of gas tungsten arc weld pools  

NASA Astrophysics Data System (ADS)

Surface flow visualization of gas tungsten arc weld pools for HY-80 steel is presented using a pulsed laser light source and a conventional night vision image-intensifier tube equipped video camera. Visualization of the weld pool free surface is made possible by seeding a flow with alumina particles for both stationary and moving arc welds. These visualizations reveal several new features not incorporated in the existing models for stationary welds. A strong clockwise stirring is observed contrary to the axisymmetric computational models. Also, the pool surface shows a bulge near the center. Complex flow patterns are observed for moving arc welding. Interpretations of the observed flows based on the driving forces are provided.

Espinosa, Daniel C.

1991-09-01

11

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

12

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

Microsoft Academic Search

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

R. Kovacevic; Z. N. Cao; Y. M. Zhang

1996-01-01

13

Weld pool flow visualization studies during gas tungsten arc welding of steel and aluminum  

Microsoft Academic Search

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

Peter E. Schupp

1992-01-01

14

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

Microsoft Academic Search

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

Schupp

1992-01-01

15

Numerical simulation of transient development and diminution of weld pool in gas tungsten arc welding  

NASA Astrophysics Data System (ADS)

A mathematical model has been developed to describe the transient heat and fluid flow fields in gas tungsten arc welding (GTAW). The transient development and diminution of the weld pool at two periods after the arc ignites and extinguishes are analysed quantitatively. The data for the weld pool configurations under different welding conditions from the transient state to the quasi-steady state are obtained. The time for the weld pool shape to reach the quasi-steady state and the time for the weld pool to solidify completely are predicted. GTAW experiments show that the predictions of the weld pool shape based on the model are in agreement with the measured values. The numerical results of the dynamic development and diminution of weld pool configurations could be used to correlate the transient characteristics of weld pool behaviour with the occurrence of weld formation defects.

Wu, Chuan Song; Yan, Fengjie

2004-01-01

16

Vision detection of weld pool shape parameters and numerical simulation  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

17

Weld pool flows during initial stages of keyhole formation in laser welding  

NASA Astrophysics Data System (ADS)

Weld pool transport phenomena during the transition from conduction-mode laser spot welding to keyhole laser spot welding of titanium were studied by numerical simulation. A range of laser powers were simulated and temperature dependent evaporation recoil pressure and cooling were applied as boundary conditions on the weld pool surface. Simulation results predicted a complex time-varying flow pattern during weld pool development. The surface-normal flow at the weld pool centre oscillated between upwards and downwards during the simulation time due to interaction of competing effects of evaporation recoil and surface tension pressures and laser heating and evaporation cooling. The results show that the laser weld pool flow dynamics play a key role during the transition from conduction-mode laser welding to keyhole welding.

Cho, Jung-Ho; Farson, Dave F.; Milewski, John O.; Hollis, Kendall J.

2009-09-01

18

3D finite element simulation of TIG weld pool  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

19

Computerized radiographic weld penetration control with feedback on weld pool depression  

SciTech Connect

Welding pool depression depends on plasma pressure and heat input to the pool and therefore is related to weld penetration. On the basis of information on pool depression received from radiographic images in real time during welding, the possibility of using automated weld penetration control to maintain the required weld penetration has been studied. The experimental system developed includes an arc welding unit, a welding manipulator, a real-time x-ray system, an image processing unit, and a system controller. By analyzing the radiographic information together with metallographs of the appropriate weld cross section, the depth of the liquid metal in the pool has been determined at different levels of current and weld penetration.

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

1989-10-01

20

Neural network modeling of pulsed-laser weld pool shapes in aluminum alloy welds.  

National Technical Information Service (NTIS)

A model was developed to predict the weld pool shape in pulsed Nd:YAG laser welds of aluminum alloy 5754. The model utilized neural network analysis to relate the weld process conditions to four pool shape parameters: (1) penetration width, (2) width at h...

J. M. Vitek Y. S. Iskander E. M. Oblow S. S. Babu S. A. David

1998-01-01

21

Weld Pool Flow Visualization Studies during Gas Tungsten Arc Welding of Steel and Aluminum.  

National Technical Information Service (NTIS)

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 pa...

P. E. Schupp

1992-01-01

22

Weld pool flow visualization studies during gas tungsten arc welding of steel and aluminum  

NASA Astrophysics Data System (ADS)

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, Peter E.

1992-03-01

23

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

24

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

25

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

26

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

NASA Astrophysics Data System (ADS)

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

Kang, Namhyun

27

Electrochemical Effects on Weld Pool Chemistry in Submerged Arc and DC Electroslag Welding.  

National Technical Information Service (NTIS)

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(meta...

M. Blander D. L. Olson

1986-01-01

28

Neural network modeling of pulsed-laser weld pool shapes in aluminum alloy welds  

Microsoft Academic Search

A model was developed to predict the weld pool shape in pulsed Nd:YAG laser welds of aluminum alloy 5754. The model utilized neural network analysis to relate the weld process conditions to four pool shape parameters: (1) penetration width, (2) width at half-penetration, and (3) cross-sectional area. The model development involved the identification of the input (process) variables, the desired

J. M. Vitek; Y. S. Iskander; E. M. Oblow; S. S. Babu; S. A. David; P. W. Fuerschbach; H. B. Smartt

1998-01-01

29

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

30

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

Microsoft Academic Search

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 Poâ 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

M. Blander; D. L. Olson

1986-01-01

31

Neural network modeling of pulsed-laser weld pool shapes in aluminum alloy welds  

SciTech Connect

A model was developed to predict the weld pool shape in pulsed Nd:YAG laser welds of aluminum alloy 5754. The model utilized neural network analysis to relate the weld process conditions to four pool shape parameters: (1) penetration width, (2) width at half-penetration, and (3) cross-sectional area. The model development involved the identification of the input (process) variables, the desired output (shape) variables, and the optimal neural network architecture. The latter was influenced by the number of defined inputs and outputs as well as the amount of data that was available for training the network. After appropriate training, die best network was identified and was used to predict the weld shape. A routine to convert the shape parameters into predicted weld profiles was also developed. This routine was based on the actual experimental weld profiles and did not impose an artificial analytical function to describe the weld profile. The neural network model was tested on experimental welds. The model predictions were excellent. It was found that the predicted shapes were within the experimental variations that were found along the length of the welds (due to the pulsed nature of the weld power) and the reproducibility of welds made under nominally identical conditions.

Vitek, J.M.; Iskander, Y.S.; Oblow, E.M.; Babu, S.S.; David, S.A. [Oak Ridge National Lab., TN (United States); Fuerschbach, P.W. [Sandia National Labs., Albuquerque, NM (United States); Smartt, H.B. [Idaho National Engineering and Environmental Lab., Idaho Falls, ID (United States)

1998-09-01

32

Neural network modeling of pulsed-laser weld pool shapes in aluminum alloy welds  

SciTech Connect

A model was developed to predict the weld pool shape in pulsed Nd:YAG laser welds of aluminum alloy 5754. The model utilized neural network analysis to relate the weld process conditions to four pool shape parameters: penetration, width, width at half-penetration, and cross-sectional area. The model development involved the identification of the input (process) variables, the desired output (shape) variables, and the optimal neural network architecture. The latter was influenced by the number of defined inputs and outputs as well as the amount of data that was available for training the network. After appropriate training, the best network was identified and was used to predict the weld shape. A routine to convert the shape parameters into predicted weld profiles was also developed. This routine was based on the actual experimental weld profiles and did not impose an artificial analytical function to describe the weld profile. The neural network model was tested on experimental welds. The model predictions were excellent. It was found that the predicted shapes were within the experimental variations that were found along the length of the welds (due to the pulsed nature of the weld power) and the reproducibility of welds made under nominally identical conditions.

Vitek, J.M.; Iskander, Y.S.; Oblow, E.M.; Babu, S.S.; David, S.A. [Oak Ridge National Lab., TN (United States); Fuerschbach, P.W. [Sandia National Labs., Albuquerque, NM (United States); Smartt, H.B.; Pace, D.P. Tolle, C.R. [Idaho National Engineering and Environmental Lab., Idaho Falls, ID (United States)

1998-11-01

33

Neural Network Modeling of Weld Pool Shape in Pulsed-Laser Aluminum Welds.  

National Technical Information Service (NTIS)

A neural network model was developed to predict the weld pool shape for pulsed-laser aluminum welds. Several different network architectures were examined and the optimum architecture was identified. The neural network was then trained and, in spite of th...

Y. S. Iskander E. M. Oblow J. M. Vitek

1998-01-01

34

Visual sensing of weld pool in variable polarity TIG welding of aluminium alloy  

Microsoft Academic Search

The passive visual sensing method was successfully applied to monitor the weld pool in TIG welding of aluminium alloy. In order to reduce the disturbance from the arc and acquire clear image, two techniques were used: one was the own-developed computer-controlled variable polarity power(VPP), the other was the composite filter technology. The VPP source did not have high-frequency electromagnetic interference

Guang-jun ZHANG; Zhi-hong YAN; Lin WU

2006-01-01

35

Simultaneous vision image sensing of weld pool of pulsed GTAW in multi-orientation in a frame  

NASA Astrophysics Data System (ADS)

Welding arc light spectrum in the range of 600nmí½700nm basically composes of continuous spectrum without metal spectrum and argon spectrum. The radiation strength of this continuous spectrum is low and smooth, which is benefit for reducing process, and the response sensitivity of CCD camera is high at this wavelength range. So, choose a suitable imaging spectrum window, use the continuous spectrum of this window to illuminate the welding pool and use CCD camera to sample the pool image. The reflection of arc light from liquid metal pool surface is specular reflection, the reflection of arc light from the workpiece surface is diffuse reflection, which improves the contrast of the welding pool image. This kind of vision image sensing method takes full advantage of the arc light as a benefit factor, and realizes to acquire the comprehensive information of the pool only from a single sensing source. Based on the above principle, this paper develops a visual image sensing system for weld zone of pulsed GTAW. The system as a part of the control system for weld shape can realize simultaneous image sensing of front topside, back topside and bottom side weld pool in a frame. Both the topside and bottom images concentrate on the same target of the CCD camera through the visual sensing light path system. The composite filter technology with low sampling image current is used to overcome the influence of arc light. The high quality and clear images of weld zones are acquired, which supply plenty information to study the dynamic process of pulsed GTAW. In addition, in order to extract the actual size parameters of weld pool, the image sensing system is calibrated.

Zhang, Guangjun; Chen, Shanben; Liu, Xiaodong; Wu, Lin

2001-09-01

36

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

37

Approaches for High-Speed Melt Pool Detection in Laser Welding Applications  

Microsoft Academic Search

In this paper several approaches for the detection of the melt pool circle (i.e. its position and radius) in laser welding applications are described. In- stead of indirectly examining the evolution of the melt pool via the radiation of plasma that is gen- erated during the welding process, we use a direct view onto the melt pool that is possible

Nicolaj C. Stache; Henrik Zimmer; Jens Gedicke; Boris Regaard; Alexander Olowinsky; Achim Knepper; Til Aach

38

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

NASA Astrophysics Data System (ADS)

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

Song, Hong Sheng; Zhang, Yu Ming

2007-12-01

39

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

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

40

Mathematical modeling of three-dimensional heat and fluid flow in a moving gas metal arc weld pool  

Microsoft Academic Search

Mathematical models capable of accurate prediction of the weld bead and weld pool geometry in gas metal arc (GMA) welding\\u000a processes would be valuable for rapid development of welding procedures and empirical equations for control algorithms in\\u000a automated welding applications. This article introduces a three-dimensional (3-D) model for heat and fluid flow in a moving\\u000a GMA weld pool. The model

M. Ushio; C. S. Wu

1997-01-01

41

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

42

The laser welding of thin metal sheets: an integrated keyhole and weld pool model with supporting experiments  

Microsoft Academic Search

An integrated mathematical model for laser welding of thin metal sheets under a variety of laser material processing conditions has been developed and tested against the results of experiments. Full account is taken in the model of the interaction of the laser-generated keyhole with the weld pool. Results calculated from the model are found to agree well with experiment for

R. Ducharme; K. Williams; P. Kapadia; J. Dowden; B. Steen; M. Glowacki

1994-01-01

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

Experimental measurement of thin plate SS 304 GTAW weld pool surface temperatures  

SciTech Connect

The optical spectral radiometric/laser reflectance method was used to noninvasively measure arc-side GTAW weld pool surface temperatures for 1.5 mm thick plate SS 304. Weld pool surface temperature isothermal contour and topology plots, as well as lengthwise centerline temperature profiles, were generated for welder currents of 38, 50, and 70 A; welder voltages of 7.5, 8.0 and 8.5 V, respectively; and welding speeds of 0.423, 1.270, and 2.540 mm/s (1, 3, and 6 in/min), respectively. Purpose of the work was to investigate the possibility of constitutional supercooling in the tail region of the weld pools. The peak weld pool temperatures in the range of 2000 to 2800/sup 0/K were often found to lead the electrode instead of lag it. These results were compared to those for experimental measurements of electron beam welds and predictions based on vaporization theory. Under most conditions, no two weld pools are alike and that the concept of quasi-steady-state pools does not represent reality. They are instead dynamically (stochastically) varying about mean value representative characteristics. No evidence of tail region constitutional supercooling was found.

Kraus, H.G.

1987-01-01

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

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

47

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

PubMed

Effects of gravitational acceleration were investigated on the weld pool shape and microstructural evolution for 304 stainless steel and Al-4wt% Cu alloy. Effects of welding heat source were investigated by using laser beam welding (LBW) and gas tungsten arc welding (GTAW). As the gravitational level was increased from low gravity (LG approximately 1.2 g) to high gravity (HG approximately 1.8 g) using a NASA KC-135 aircraft, the weld pool shape for 304 stainless steel was influenced considerably during GTAW. However, insignificant change in the microstructure and solute distribution was observed at gravitational levels between LG and HG. The GTAW on Al-4 wt% Cu alloy was used to investigate the effect of gravitational orientation on the weld solidification behavior. Gravitational orientation was manipulated by varying the welding direction with respect to gravity vector; that is, by welding upward opposing gravity ( ||-U) and downward with gravity ( ||-D) on a vertical weld piece and welding perpendicular to gravity (perpendicular) on a horizontal weld piece. Under the same welding conditions, a larger primary dendrite spacing in the ||-U weld was observed near the weld pool surface and the fusion boundary than in the case of perpendicular or ||-D welds. The ||-D weld exhibited different solidification morphology and abnormal S shape of solidification rate curve during its growth. For 304 stainless steel GTAW, significant effects of gravitational orientation were observed on the weld pool shape that was associated with weld surface morphology and convection flow. However, the weld pool shape for LBW was mostly constant with respect to the gravitational orientation. PMID:15644379

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

2004-11-01

48

Numerical study of arc plasmas and weld pools for GTAW with applied axial magnetic fields  

NASA Astrophysics Data System (ADS)

A 3D numerical model containing the welding arc and the weld pool for gas tungsten arc welding (GTAW) with applied axial magnetic fields is established. The model is validated by comparing the calculated arc temperature with the measured ones. The influence of the magnetic field on the welding process is studied by changing the magnetic inductions, from 0 T to 0.06 T. For welding arcs, a radial spread is discovered, and a reverse flow appears over the anode. The distribution of temperature, heat flux, current density and pressure on the anode surface becomes double-peaked, while the voltage distributes in a double-valley type. For weld pools, the fluid flow cycle brings about a wide and shallow pool. In the circumferential direction, the fluid in the centre areas rotates in an opposite direction to that in the outer regions; in the axial direction, the fluid flows upwards at the centre while downwards in the edge area of the weld pool. All the driving forces including the surface tension, the shear stress from the arc plasma, the electromagnetic force and the buoyancy force that influence the fluid flow are analysed to explain these phenomena. The mechanism of how the applied axial magnetic field regulates the GTAW process is thus clarified.

Yin, Xianqing; Gou, Jianjun; Zhang, Jianxun; Sun, Jiangtao

2012-07-01

49

Measurement of nugget size of spot weld by digital shearography  

NASA Astrophysics Data System (ADS)

Resistance spot welding is now widely used in the fabrication of sheet metals, mainly due to the cost and time considerations. Friction stir spot welding is getting more and more acceptance in the automotive industries. Such spot welds are found in nearly all products where sheet metal is joined. Obviously the quality of the spot weld has a direct impact on the quality of the product. The most important quality target of spot welds is the size of the weld nuggets. If the weld nuggets are improperly or incompletely formed, or the area surrounding the nugget is smaller than required, the structural integrity of the entire part may be uncertain. Furthermore these inconsistencies are usually internal and are seldom visible to optical inspection. This study is focused on the quality analysis of the spot welds by using "Digital Shearography". The paper mainly focuses on developing a novel, whole field technique for non-destructive inspecting the size of spot-welds, both for the resistance spot weld and the friction stir spot weld.

Yang, Lianxiang; Samala, Praveen R.; Liu, Sheng; Long, Kah Wah; Lee, Yung-Li

2005-08-01

50

Prediction and Optimization of Pulsed Current Gas Tungsten Arc Welding Process Parameters to Obtain Sound Weld Pool Geometry in Titanium Alloy Using Lexicographic Method  

Microsoft Academic Search

Abstact  In this article the weld pool geometry of pulsed current gas tungsten arc (GTA)-welded titanium alloy was analyzed. Increase\\u000a in use of pulsed current process creates dependancy on the use of mathematical equations to predict the weld pool geometry.\\u000a Hence, the development of mathematical models using four factors, five levels, central composite design was attempted. The\\u000a developed models were checked

M. Balasubramanian; V. Jayabalan; V. Balasubramanian

2009-01-01

51

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

52

Simulation of time-dependent pool shape during laser spot welding: Transient effects  

NASA Astrophysics Data System (ADS)

The shape and depth of the area molten during a welding process is of immense technical importance. This study investigates how the melt pool shape during laser welding is influenced by Marangoni convection and tries to establish general qualitative rules of melt pool dynamics. A parameter study shows how different welding powers lead to extremely different pool shapes. Special attention is paid to transient effects that occur during the melting process as well as after switching off the laser source. It is shown that the final pool shape can depend strongly on the welding duration. The authors use an axisymmetric two-dimensional (2-D) control-volume-method (CVM) code based on the volume-averaged two-phase model of alloy solidification by Ni and Beckermann[1] and the SIMPLER algorithm by Patankar.[2] They calculate the transient distribution of temperatures, phase fractions, flow velocities, pressures, and concentrations of alloying elements in the melt and two solid phases (peritectic solidification) for a stationary laser welding process. Marangoni flow is described using a semiempirical model for the temperature-dependent surface tension gradient. The software was parallelized using the shared memory standard OpenMP.

Ehlen, Georg; Ludwig, Andreas; Sahm, Peter R.

2003-12-01

53

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

NASA Astrophysics Data System (ADS)

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 finite element analysis software ANSYS, distributions of current density and magnetic field as well as fluid flow and heat transfer in three-dimensional moving weld pool were systematically investigated to understand and reveal the effect of external longitudinal magnetic field on liquid metal in moving GTA weld pool and also to supply basis for the application of external longitudinal magnetic field welding technology.

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

2002-11-01

54

Influence of weld size on fatigue crack growth characteristics of flux cored arc welded cruciform joints  

Microsoft Academic Search

The influence of weld size (L\\/Tp) on fatigue crack growth characteristics of flux cored arc welded (FCAW) cruciform joints, containing lack of penetration (LOP) defect, has been studied. Quenched and tempered (Q&T) steel of ASTM 517 ‘F’ grade has been used as the base material. Fatigue crack growth experiments were carried out in a vertical pulsar under constant amplitude loading

V. Balasubramanian; B. Guha

1999-01-01

55

Predicting the backside width of weld pool during pulsed GTAW process based on a neural network model  

NASA Astrophysics Data System (ADS)

Modeling of welding process is the base of process control. Because welding process is a multivariable, strong coupling, time-varying and nonlinear system, traditional modeling methods are not suitable. In this paper, the dynamic neural network model for predicting backside width of pulsed GTAW weld pool by welding parameters and topside shape parameters was constructed. Orthogonal method was applied to design the sampling experiments. Experiments were carried on low carbon steel with 2mm thickness during pulsed gas tungsten arc butt-welding with gap. 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 length, maximum width, gap width and the half-length ratio, and the backside dimension such as area, length and maximum width were calculated. Artificial neural network was applied to establish the model for predicting backside width of weld pool. The inputs of the model were the topside dimension, shape of weld pool and welding parameters such as pulse current, pulse duty ratio, and welding speed. The output of the model was the backside width of weld pool. The algorithm was the extended delta-bar-delta (EDD), and the learning ratio automatically determined by the algorithm. Threshold function was sigmoid function. The training cycle was selected to be 50000. The final EMS error of backside width was 5.2 percent. The simulation experiments were carried out to test the accuracy of the ANN model. From the results of the test, the output of ANN model can predict the backside width precisely.

Zhang, Guangjun; Chen, Shanben; Liu, Xiaodong; Wu, Lin

2001-10-01

56

Melt-pool and keyhole dynamics during thin-plate laser welding of steel  

NASA Astrophysics Data System (ADS)

An investigation is made of the melt-pool formed during keyhole welding with a cw CO2 laser on thin plate mild steel. The aim of the study is to analyze the dynamics of the melt-pool and keyhole in order to provide information on the causes of instabilities found during high speed welding. Such problems found during high speed welding include humping, keyhole failure, and surface tension driven melt-pool instabilities. The effects of varying laser power (2 to 4 kW), traverse speed, shroud gas, gas delivery angle, and plate thickness were studied. The methods used included various high speed camera techniques. Two high speed cameras are used, a high speed video camera at a frame rate of 1,000 frames per second and a high speed gated camera used in conjunction with a frame grabber capable of gate speeds as low as 25 ns and freeze frame multi-imaging. The high speed video system was used to gather information on the gross melt-pool characteristics, e.g., shape, length, width, and any other slow changes present (of the order of 100 Hz). It is hoped by correlating these results with theory that an insight into high speed behavior will be obtained.

Williams, K.; O'Neill, William; Steen, William M.

1993-05-01

57

Influence of simulated high- G on the weld size of aL–lI alloy  

Microsoft Academic Search

Whether welding processes are used on earth or in space, they have the same objective: to obtain defect-free welds. To fully understand the effect of gravity on the weld pool geometry and solidification one should perform experiments within a broad range of gravitational acceleration. High-gravity arc welding experiments were done on Al–Li alloy using the centrifuge called Multi-Gravity Research Welding

Daryush K. Aidun

2001-01-01

58

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

NASA Astrophysics Data System (ADS)

A mathematical formulation has been developed and computed results are presented describing the temperature profiles in gas tungsten arc welding (GTAW) arcs and, hence, the net heat flux from the welding arc to the weld pool. The formulation consists of the statement of Maxwell's equations, coupled to the Navier-Stokes equations and the differential thermal energy balance equation. The theoretical predictions for the heat flux to the workpiece are in good agreement with experimental measurements — for long arcs. The results of this work provide a fundamental basis for predicting the behavior of arc welding systems from first principles.

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

1992-06-01

59

Lin28a regulates germ cell pool size and fertility.  

PubMed

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

2013-05-01

60

Anode behaviour in GTA welding and its effect on fusion of thin plate: Study of effects of anode behaviour on the molten pool in GTA (TIG) welding (4th report)  

Microsoft Academic Search

The configuration of anode spots on the molten pool in GTA welding of thin plate is discussed on the basis of observations of the behaviour of slag particles under varying welding conditions and with regard to the base metal content of minor elements.The positions of slag particles on the molten pool are largely influenced by surface flow on the pool

A. Okada; H. Nakamura

1994-01-01

61

Readily releasable pool size changes associated with long term depression  

PubMed Central

We have estimated, for hippocampal neurons in culture, the size of the autaptic readily releasable pool before and after stimulation of the sort that produces culture long term depression (LTD). This stimulation protocol causes a decrease in the pool size that is proportional to the depression of synaptic currents. To determine if depression in this system is synapse specific rather than general, we have also monitored synaptic transmission between pairs of cultured hippocampal neurons that are autaptically and reciprocally interconnected. We find that the change in synaptic strength is restricted to the synapses on the target neuron that were active during LTD induction. When viewed from the perspective of the presynaptic neuron, however, synapse specificity is partial rather than complete: synapses active during induction that were not on the target neuron were partially depressed.

Goda, Yukiko; Stevens, Charles F.

1998-01-01

62

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

63

Laser-induced plasma as a source for an intensive current to produce electromagnetic forces in the weld pool  

NASA Astrophysics Data System (ADS)

Laser beam welding performed with a CO2 laser by applying a magnetic field perpendicular to the welding direction influences the weld pool dynamics, which changes the seam properties significantly. From these results it was concluded that an intensive current density must exist in the melt. In repeating those welding experiments with a Nd:YAG laser, however, no significant effects could be observed. To explain this discrepancy, detailed trials with both CO2 and Nd:YAG lasers were carried out and led to an explanation which is presented in this paper. Looking at the welding process with radiation of 10.6 ?m and 1.06 ?m, the only significant difference is the presence of a laser-induced plasma plume above the workpiece in the case of the longer wavelength. Therefore, the investigations were concentrated on its possible role in establishing a current flow through the weld pool. This current was directly measured during the welding process (bead on plate): Two aluminum plates separated by an insulated gap of 0.85 mm were moved under the focused beam (3 kW; 5 m/min) and the signal was recorded as function of the gap's position. From these measurements were deduced values of current that amounted to approximately 0.3 A with CO2 and more then one order of magnitude less with Nd:YAG lasers.

Ambrosy, Günter; Avilov, Vjaceslav; Berger, Peter; Hügel, Helmuth

2007-05-01

64

The effect of the cathode tip angle on the GTAW arc and weld pool: I. Mathematical model of the arc  

NASA Astrophysics Data System (ADS)

By developing mathematical models for the arc and the weld pool in the GTAW process, the effect of the electrode tip angle on both arc and weld pool was studied. The present paper is concerned with the model for the arc. By applying a variable cathode surface area, the effect of the electrode tip angle (in the range of 10 to 0022-3727/30/19/013/img1) on the arc properties, especially on the anode current density, heat flux and gas shear stress over the weld pool, was investigated. Comparison of the calculated results with the available experimental data for 200 A arcs of different lengths showed that the model predictions for temperatures higher than 10 000 K are in very good agreement. For temperatures less than 10 000 K, some modifications were necessary to take into account the absorption of heat by the cooler parts of the arc. It was found that by increasing the electrode tip angle, the anode spot at the weld pool surface tended to be more localized. This led to a higher maximum heat flux and anode current density. On the other hand, the gas shear stress increased on decreasing the electrode tip angle.

Goodarzi, Massoud; Choo, Roland; Toguri, James M.

1997-10-01

65

Effects of patch-size on the structure of assemblages in rock pools  

Microsoft Academic Search

Rock pools represent patches or islands of habitat different from the surrounding shore. They contain diverse assemblages of invertebrates and algae. The shape, size, height on the shore and exposure to waves are considered important influences on the abundances of organisms. In studies of natural pools, these factors are confounded because pools are rarely comparable; they differ in size, position

A. J. Underwood; G. A. Skilleter

1996-01-01

66

Controls on the size and occurrence of pools in coarse-grained forest rivers  

Microsoft Academic Search

Controls on pool formation are examined in gravel- and cobble-bed rivers in forest mountain drainage basins of northern California, southern Oregon, and southeastern Alaska. We demonstrate that the majority of pools at our study sites are formed by flow obstructions and that pool geometry and frequency largely depend on obstruction characteristics (size, type, and frequency). However, the effectiveness of obstructions

John M. Buffington; Thomas E. Lisle; Richard D. Woodsmith; Sue Hilton

2002-01-01

67

Metal mesh heating element size effect in resistance welding of thermoplastic composites  

Microsoft Academic Search

The objective of this work is to determine the effects of metal mesh heating element size on resistance welding of thermoplastic composites. The materials to be resistance-welded consisted of carbon fiber\\/poly-ether-ketone-ketone (CF\\/PEKK), carbon fiber\\/poly-ether-imide (CF\\/PEI) and glass fiber\\/PEI (GF\\/PEI). Four different metal mesh sizes were used as heating elements. The samples were welded in a lap shear joint configuration and

Martine Dubé; Pascal Hubert; Jan NAH Gallet; Darko Stavrov; Harald EN Bersee; Ali Yousefpour

2012-01-01

68

Estimating the number and sizes of undiscovered oil and gas pools  

SciTech Connect

This study introduces a new specification of oil and gas exploration as a sampling process, in order to estimate the number and sizes of undiscovered oil and gas pools by statistical inference from discovered pools as a sample. Oil and gas exploration is quite unlike drawing samples at random in that actual sampling is sized-biased, subject to truncation of uneconomic pools, and to censorship of discovered pool sizes. The method of estimating the number and sizes of undiscovered pools proposed in this study specifically accounts for these non-random components of exploration as a sampling process, and can be easily implemented using the Expectation-Maximization algorithm. The method allows for choices between single and multiple point truncation of uneconomic pool sizes, and generalizes quite easily to the bivariate case necessary to analyze plays with pools that contain oil with associated gas. Its usefulness is enhanced by the introduction of powerful tests of fit of the lognormal distribution to the distribution of discovered pool sizes, and of meaningful measures of the uncertainty of estimates of the number and sizes of undiscovered pools. Application of the method to oil and gas plays in the San Juan basin of northwest New Mexico show that it yields quite reasonable and useful results. The method, when applied to data analyzed using other methods of estimating the number and sizes of undiscovered pools, confirms that failure to account for truncation of uneconomic pools will result in an overestimate of the average size of pools in a play. By avoiding this, and other, problems, the proposed estimation procedure should lead to better assessments of a play's potential for future discoveries of economically recoverable oil and gas.

Long, K.R.

1988-01-01

69

Robust High-Speed Melt Pool Measurements for Laser Welding with Sputter Detection Capability  

Microsoft Academic Search

Although lasers are widely used for welding in precision engineering industry, it is still a challenge to achieve high accuracy\\u000a in creating and positioning welding spots at extremely high processing speed.\\u000a \\u000a Towards this end, we propose a system for monitoring the welding process in order to ensure good quality of the welding spots.\\u000a Our technology enables high speed image acquisition

Nicolaj C. Stache; Henrik Zimmer; Jens Gedicke; Alexander Olowinsky; Til Aach

2007-01-01

70

Welding.  

ERIC Educational Resources Information Center

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

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

71

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

2008-08-27

72

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

73

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

PubMed Central

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

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

2012-01-01

74

Welding.  

ERIC Educational Resources Information Center

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

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

75

Effects of heater size and orientation on pool boiling heat transfer from microporous coated surfaces  

Microsoft Academic Search

The present research is an experimental study of pool boiling behavior using flat, microporous-enhanced square heater surfaces immersed in saturated FC-72. Flush-mounted 2cm×2cm and 5cm×5cm copper surfaces were tested and compared to a 1cm×1cm copper surface that was previously investigated. Heater surface orientation and size effects on pool boiling performance were investigated under increasing and decreasing heat-flux conditions for two

K. N. Rainey; S. M. You

2001-01-01

76

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

PubMed

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

Cheng, Lailiang

2003-01-01

77

Effect of species pool size on species occurrence frequencies: Musical chairs on islands  

PubMed Central

If species interactions affect species distributions, then species occurrence frequencies (?i), defined as the fraction of an archipelago's islands that species i inhabits, should vary with species pool size. A “natural experiment” approximating this test is provided by the Bismarck, Solomon, and New Hebrides archipelagoes, whose bird species pools decrease in that order, the species of each archipelago being mostly a subset of those of the next richer archipelago. The average ? for an archipelago's species decreases with archipelago pool size. In the archipelago with the largest pool, most species are on few islands and few species are on most islands, whereas the reverse is true in the archipelago with the smallest pool. For species shared between two or more archipelagoes, ?i decreases with pool size or number of species in the same guild. These interarchipelagal differences in ?i or average ? reflect differences in level of interspecific competition, which reduces ?s in species-rich archipelagoes in two ways: usually, by reducing a species' incidence on small islands and restricting the species to larger islands; less often (for so-called supertramps), by restricting a species to small islands.

Diamond, Jared

1982-01-01

78

The effects of turbulence on molten pool transport during melting and solidification processes in continuous conduction mode laser welding of copper–nickel dissimilar couple  

Microsoft Academic Search

The melting and solidification stages of a continuous copper–nickel dissimilar metal conduction mode laser welding have been simulated numerically in this study. The heat, mass and momentum transports in molten metal pool have been analysed using both laminar and turbulent flow models separately for the same process parameters. The phase change aspects related to solidification and melting are accounted for

Nilanjan Chakraborty

2009-01-01

79

Laser assisted non-consumable arc welding process development  

SciTech Connect

The employment of Laser Beam Welding (LBW) for many traditional arc welding applications is often limited by the inability of LBW to compensate for variations in the weld joint gap. This limitation is associated with fluctuations in the energy transfer efficiency along the weld joint. Since coupling of the laser beam to the workpiece is dependent on the maintenance of a stable absorption keyhole, perturbations to the weld pool can lead to decreased energy transfer and resultant weld defects. Because energy transfer in arc welding does not similarly depend on weld pool geometry, it is expected that combining these two processes together will lead to an enhanced fusion welding process that exhibits the advantages of both arc welding and LBW. Laser assisted non-consumable arc welds have been made on thin section aluminum. The welds combine the advantages of arc welding and laser welding, with enhanced penetration and fusion zone size. The use of a pulsed Nd:YAG laser with the combined process appears to be advantageous since this laser is effective in removing the aluminum oxide and thereby allowing operation with the tungsten electrode negative. The arc appears to increase the size of the weld and also to mitigate hot cracking tendencies that are common with the pulsed Nd:YAG laser.

Fuerschach, P.W.; Hooper, F.M.

1997-09-01

80

Creep behavior of a large full-size welded austenitic steel plate  

SciTech Connect

The high-temperature design codes are presently considering the use of stress reduction factors for designing welded structures submitted to creep. These reduction factors are derived from creep tests which are generally made on small specimens and are not necessarily representative of large-size geometries. These codes are very likely overconservative, consequently uneconomical and need to be improved; an investigation to assess and quantify the supposed size effect is required. This paper presents an experimental and numerical study on creep behavior at 600 C of full-size welded joints taking into account real full-thickness of weldings. The material investigated is the austenitic stainless steel 316L(N) with manual metal arc welds using the 19 Cr 12 Ni 2 Mo electrode grade. The creep laws used in calculations are those obtained from tests using small specimens, but some coefficients of their theoretical formulation have been modified to obtain a better coherence with full-size specimen data. Between small and large full-size specimens, experimental results show no significant difference in time to rupture, and the same location of fracture, at the center of the weldment, is observed. Finite element simulations performed for full-size welded joints provide rupture times that are consistent with measured values. The calculated percentage of the damaged volume in the weld metal as a function of load levels and of creep-time duration is studied; it shows that the creep-rupture times for high stress loading are determined with higher accuracy than for low stress loading.

Koundy, V.; Allais, L. [CEA-CEREM, Gif-sur-Yvette (France). Service de Recherches Metallurgiques Appliquees; Delhaye, M. [INSA-Rennes (France). Dept. Genie Mecanique et Automatique

1998-08-01

81

Prediction of oil or gas pool sizes when discovery record is available  

Microsoft Academic Search

The Upper Devonian Bashaw reef play of the Western Canada Basin was used to demonstrate: (1) estimation of pool size distribution by means of a discovery model, (2) the usefulness of a feedback mechanism in petroleum resources evaluations, and (3) enhancement of reliability by reducing uncertainty associated with estimates. The feedback mechanism presented herein allows us to challenge geological interpretations.

P. J. Lee; P. C. C. Wang

1985-01-01

82

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

83

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

2013-06-11

84

Quality of the log-geometric distribution extrapolation for smaller undiscovered oil and gas pool size  

USGS Publications Warehouse

The U.S. Geological Survey procedure for the estimation of the general form of the parent distribution requires that the parameters of the log-geometric distribution be calculated and analyzed for the sensitivity of these parameters to different conditions. In this study, we derive the shape factor of a log-geometric distribution from the ratio of frequencies between adjacent bins. The shape factor has a log straight-line relationship with the ratio of frequencies. Additionally, the calculation equations of a ratio of the mean size to the lower size-class boundary are deduced. For a specific log-geometric distribution, we find that the ratio of the mean size to the lower size-class boundary is the same. We apply our analysis to simulations based on oil and gas pool distributions from four petroleum systems of Alberta, Canada and four generated distributions. Each petroleum system in Alberta has a different shape factor. Generally, the shape factors in the four petroleum systems stabilize with the increase of discovered pool numbers. For a log-geometric distribution, the shape factor becomes stable when discovered pool numbers exceed 50 and the shape factor is influenced by the exploration efficiency when the exploration efficiency is less than 1. The simulation results show that calculated shape factors increase with those of the parent distributions, and undiscovered oil and gas resources estimated through the log-geometric distribution extrapolation are smaller than the actual values. ?? 2010 International Association for Mathematical Geology.

Chenglin, L.; Charpentier, R. R.

2010-01-01

85

Swimming Pools.  

ERIC Educational Resources Information Center

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

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

86

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

2011-03-27

87

Quantitative Magnetization Transfer Measured Pool Size Ratio Reflects Optic Nerve Myelin Content in ex vivo Mice  

PubMed Central

Optic nerves from mice that have undergone retinal ischemia were examined using a newly implemented quantitative magnetization transfer (qMT) technique. Previously published results indicate that the optic nerve from retinal ischemia mice suffered significant axon degeneration without detectable myelin injury at three days after reperfusion. At this time point, we acquired ex vivo qMT parameters from both shiverer mice (which have nearly no myelin) and control mice that have undergone retinal ischemia, and these qMT measures were compared with diffusion tensor imaging (DTI) results. Our findings suggests that the qMT estimated ratio of the pool sizes of the macromolecular and free water protons reflected the different myelin contents in the optic nerves between the shiverer and control mice. This pool size ratio was specific to myelin content only and was not significantly affected by the presence of axon injury in mouse optic nerve three days after retinal ischemia.

Ou, Xiawei; Sun, Shu-Wei; Liang, Hsiao-Fang; Song, Sheng-Kwei; Gochberg, Daniel F.

2008-01-01

88

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

Microsoft Academic Search

The objective of this study was to determine xanthophyll cycle pool size and composition in response to N status and their relationships to non-photochemical quenching in apple leaves. Bench-grafted Fuji\\/M.26 trees were fertilized with different N concentrations (0-20 mM) in a modified Hoagland's solution for 6 weeks to create a wide range of leaf N status (1-4.4 g m-2). Chlorophyll

Lailiang Cheng

2003-01-01

89

Egfr signaling controls the size of the stem cell precursor pool in the Drosophila ovary.  

PubMed

In many animals, germline progenitors are kept undifferentiated to give rise to germline stem cells (GSCs), enabling continuous production of gametes throughout animal life. In the Drosophila ovary, GSCs arise from a subset of primordial germ cells (PGCs) that stay undifferentiated even after gametogenesis has started. How a certain population of PGCs is protected against differentiation, and the significance of its regulatory mechanisms on GSC establishment remain elusive. Here we show that epidermal growth factor receptor (Egfr) signaling in somatic stromal intermingled cells (ICs), activated by its ligand produced in germ cells, controls the size of the PGC pool at the onset of gametogenesis. Egfr signaling in ICs limits the number of cells that express the heparan sulfate proteoglycan Dally, which is required for the movement and stability of the locally-produced stromal morphogen, Decapentaplegic (Dpp, a BMP2/4 homologue). Dpp is received by PGCs and maintains them in an undifferentiated state. Altering Egfr signaling levels changes the size of the PGC pool and affects the number of GSCs established during development. While excess GSC formation is compensated by the adult stage, insufficient GSC formation can lead to adult ovarioles that completely lack GSCs, suggesting that ensuring an absolute size of the PGC pool is crucial for the GSC system. PMID:23376160

Matsuoka, Shinya; Hiromi, Yasushi; Asaoka, Miho

2013-01-31

90

Light qualities and dose influence ascorbate pool size in detached oat leaves.  

PubMed

In this work, we studied the mechanism of light influence on AsA pool size in Avena sativa L. under the effects of low intensity light at different wavelengths. Exposure to low intensity light of oat leaf segments incubated in water or in l-galactono-1,4-lactone (GL), resulted in an increase in AsA content compared with the dark control. This increase was due to modulation of l-galactono-1,4-lactone dehydrogenase (GLDH; EC 1.3.2.3) light-dependent activity and was dependent on the size of the endogenous GL pool. Both blue and red light were effective in increasing AsA, and this increase depended on both exposure time and light intensity. Protein biosynthesis, photosynthesis and calcium were involved in controlling the level of light-dependent AsA. We suggest that multiple checkpoints correlated to the presence of light underlie the ascorbate pool size. The presence of a light-activated switch for the maintenance of an adequate AsA level seems to be necessary for the various tasks of scavenging reactive oxygen species, in response to the dark-light cycle which plants experience under natural conditions. PMID:22195578

Mastropasqua, Linda; Borraccino, Giuseppe; Bianco, Laura; Paciolla, Costantino

2011-11-18

91

Postillumination isoprene emission: in vivo measurements of dimethylallyldiphosphate pool size and isoprene synthase kinetics in aspen leaves.  

PubMed

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 x 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 CO(2) and O(2) 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, CO(2), and O(2) 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, Ulo

2009-01-07

92

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

Microsoft Academic Search

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

V Balasubramanian; B Guha

1999-01-01

93

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

Microsoft Academic Search

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

Mark W. Eakes

1994-01-01

94

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

95

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

96

Welding.  

ERIC Educational Resources Information Center

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

Baldwin, Harold; Whitney, Gregory

97

Welding.  

ERIC Educational Resources Information Center

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

Cowan, Earl; And Others

98

Erection and welding of large-sized structures in space  

NASA Astrophysics Data System (ADS)

The paper deals with the construction requirements of large structures. It is shown that, depending upon their purpose, different technical solutions concerning architectural appearance, methods of assembly and erection can be found. Description and brief technical characteristics of several types of large-sized truss and shell structures optimized for assembling in space are presented, and the equipment and procedures of assembly and permanent joining of the structures in space are described.

Bulattsev, A. R.; Moreinis, M. M.; Skorobogatov, S. A.; Motry, V. I.; Samilov, V. N.; Beletskii, D. V.

99

Fatigue assessment of large-size welded joints based on the effective notch stress approach  

Microsoft Academic Search

In this paper the applicability of the effective notch stress approach to fatigue assessment of existing large-size specimens for cruciform joints, diaphragm joints and out-of-plane gusset joints has been investigated, by considering fatigue crack initiation points, stress distributions and fatigue strengths. By using the maximum principal stress, it is possible to distinguish whether fatigue cracks will initiate at the weld

Chitoshi Miki

2008-01-01

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

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

102

Modeling, optimization and classification of weld quality in tungsten inert gas welding  

Microsoft Academic Search

In this paper, a neural network is used to construct the relationships between welding process parameters and weld pool geometry in tungsten inert gas (TIG) welding. An optimization algorithm called simulated annealing (SA) is then applied to the network for searching the process parameters with an optimal weld pool geometry. Finally, the quality of aluminum welds based on the weld

Y. S Tarng; H. L Tsai; S. S Yeh

1999-01-01

103

Mathematical modelling of circumferential GTA welding of pipes with single V groove  

Microsoft Academic Search

This paper describes a three-dimensional model for circumferential GTA welding of pipes with a single V groove. It consists of a heat conduction model and a molten pool balance model.In the heat conduction model, the transient temperature distribution on the pipe is numerically analysed to estimate the molten pool size by the finite difference method. In the molten pool balance

T. Yokogawa; T. Ohji; Y. Hirata; F. Miyasaka; T. Masutani

1999-01-01

104

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

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  

Microsoft Academic Search

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

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

2008-01-01

106

Phosphoinositide pool sizes and flux in rabbit aortic rings during normoxia and hypoxia  

SciTech Connect

The authors wanted to determine if various ATP-dependent reactions in the phosphatidylinositol cycle are inhibited during hypoxia-induced relaxations (PO/sub 2/ 10-20 mmHg, 10 min). Rings, so treated, show decreases in Pcr/Cr/sub T/ but no change in tissue ATP. Flux measurements were made after a 30 min incubation of resting rings with /sup 3/H-myoinositol. Rings were frozen under resting conditions and 5 min after the muscle was contracted by 5.5 ..mu..M norepinephrine. Effects on pool sizes (nmoles/100 nmole total PL) (N=5) are presented. Data indicate (a) PI resynthesis in the e.r. is inhibited during hypoxia, but plasma membrane kinase reactions may be unaffected; (b) the PI cycle may be altered during hypoxia-induced relaxations of vascular smooth muscle.

Not Available

1986-03-01

107

10 CFR 905.32 - Resource extensions and resource pool size.  

Code of Federal Regulations, 2013 CFR

...percentages shall be applied to the resource under contract at the time. (d) The additional resource pool increments shall be established...extensions for existing customers and allocations to new customers from the resource pool have been made,...

2013-01-01

108

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

109

Modeling of soil C-dynamics reveals different carbon pool sizes and decomposition rates under varying incubation temperatures  

NASA Astrophysics Data System (ADS)

Soils contain about two thirds of all organic carbon that is stored in terrestrial ecosystems. Annual release of soil carbon (C) to the atmosphere currently exceeds the rate of anthropogenic CO2 emissions by a factor of 10 demonstrating that even small changes in soil C cycling are highly relevant to the global C cycle. Total soil organic matter consists of different C pools with intrinsic turnover rates ranging from less than a year to thousands of years. The objectives of this study were to model soil C-dynamics of a long-term incubation study (336 days, Conant et al. 2008) under two different incubation temperatures (25°C and 35°C) to obtain i) soil CO2-efflux rates, ii) C-dynamics and iii) temperature sensitivities of C-pools with different turnover times. Respiration rates and soil C-dynamics of three different C-pools were modeled by a 1st order differential equation and data assimilation techniques were used to optimize parameter estimation. All C of the most labile pool (fast turnover time) was respired within the first ten days of the incubation study and pool size as well as absolute decline of the labile C-pool did not differ between temperatures. The intermediate C-pool (intermediate turnover time) was initially 70% larger at the higher temperature but as C was respired at a higher rate the intermediate pool was of equal size at both temperatures after 336 days of incubation. The most recalcitrant C-pool (slow turnover time) declined very slowly over time at both temperatures. However, the contribution of the recalcitrant C-pool to the whole CO2-efflux became more important towards the end of the incubation study. A 10K higher incubation temperature resulted in a larger intermediate C-pool and therefore in twice as much C released. This modeling study shows that higher temperatures increase the amount of easily decomposable C and that C-pool sizes vary at different temperatures. These results are of particular interest for high latitude regions as temperatures are predicted to increase more rapidly in arctic ecosystems and strong effects of higher temperatures on permafrost C are to be expected.

Schädel, C.; Luo, Y.; Schuur, E. A.; Zhou, J.

2011-12-01

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

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

112

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

113

Laser Welding Metallography.  

National Technical Information Service (NTIS)

The metallographic preparation of weld samples becomes an absolute necessity when laser welding ultra-small parts as small diameter thin wall tubing or postage stamp-size and smaller machined components. In such welding situations, only a metallographic c...

J. L. Ferreira

1986-01-01

114

Heat and fluid flow in complex joints during gas metal arc welding-Part I: Numerical model of fillet welding  

NASA Astrophysics Data System (ADS)

Gas metal arc (GMA) fillet welding is one of the most important processes for metal joining because of its high productivity and amiability to automation. This welding process is characterized by the complicated V-shaped joint geometry, a deformable weld pool surface, and the additions of hot metal droplets. In the present work, a three-dimensional numerical heat transfer and fluid flow model was developed to examine the temperature profiles, velocity fields, weld pool shape and size, and the nature of the solidified weld bead geometry during GMA fillet welding. The model solved the equations of conservation of mass, momentum, and energy using a boundary fitted curvilinear coordinate system. Apart from the direct transport of heat from the welding arc, additional heat from the metal droplets was modeled considering a volumetric heat source. The deformation of the weld pool surface was calculated by minimizing the total surface energy. Part I of this article is focused on the details of the numerical model such as coordinate transformation and calculation of volumetric heat source and free surface profile. An application of the model to GMA fillet welding of mild steel is described in an accompanying article (W. Zhang, C.-H. Kim and T. DebRoy, J. Appl Phys. 95, 5220 (2004)).

Zhang, W.; Kim, C.-H.; Debroy, T.

2004-05-01

115

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

116

Effect of weld size on fatigue crack growth behaviour of cruciform joints by strain energy density factor approach  

Microsoft Academic Search

The effect of weld size on fatigue crack growth behaviour of cruciform joints containing lack of penetration defect has been analysed by using the strain energy density factor concept. Load carrying cruciform joints were fabricated from ASTM 517`F' grade steel. Fatigue crack growth experiments were carried out in a mechanical resonance vertical pulsator (SCHENCK 200 kN capacity) with a frequency

V. Balasubramanian; B. Guha

1999-01-01

117

Modeling Grain Size and Strain Rate in Linear Friction Welded Waspaloy  

NASA Astrophysics Data System (ADS)

The high-temperature deformation behavior of the Ni-base superalloy, Waspaloy, using uniaxial isothermal compression testing was investigated at temperatures above the ?' solvus, 1333 K, 1373 K, and 1413 K (1060 °C, 1100 °C, and 1140 °C) for constant true strain rates of 0.001, 0.01, 0.1, and 1 s-1 and up to a true strain of 0.83. Flow softening and microstructural investigation indicated that dynamic recrystallization took place during deformation. For the investigated conditions, the strain rate sensitivity factor and the activation energy of hot deformation were 0.199 and 462 kJ/mol, respectively. Constitutive equations relating the dynamic recrystallized grain size to the deformation temperature and strain rate were developed and used to predict the grain size and strain rate in linear friction-welded (LFWed) Waspaloy. The predictions were validated against experimental findings and data reported in the literature. It was found that the equations can reliably predict the grain size of LFWed Waspaloy. Furthermore, the estimated strain rate was in agreement with finite element modeling data reported in the literature.

Chamanfar, Ahmad; Jahazi, Mohammad; Gholipour, Javad; Wanjara, Priti; Yue, Stephen

2013-09-01

118

Liquid metal expulsion during laser spot welding of 304 stainless steel  

NASA Astrophysics Data System (ADS)

During laser spot welding of many metals and alloys, the peak temperatures on the weld pool surface are very high and often exceed the boiling points of materials. In such situations, the equilibrium pressure on the weld pool surface is higher than the atmospheric pressure and the escaping vapour exerts a large recoil force on the weld pool surface. As a consequence, the molten metal may be expelled from the weld pool surface. The liquid metal expulsion has been examined both experimentally and theoretically for the laser spot welding of 304 stainless steel. The ejected metal droplets were collected on the inner surface of an open ended quartz tube which was mounted perpendicular to the sample surface and co-axial with the laser beam. The size range of the ejected particles was determined by examining the interior surface of the tube after the experiments. The temperature distribution, free surface profile of the weld pool and the initiation time for liquid metal expulsion were computed based on a three-dimensional transient heat transfer and fluid flow model. By comparing the vapour recoil force with the surface tension force at the periphery of the liquid pool, the model predicted whether liquid metal expulsion would take place under different welding conditions. Expulsion of the weld metal was also correlated with the depression of the liquid metal in the middle of the weld pool due to the recoil force of the vapourized material. Higher laser power density and longer pulse duration significantly increased liquid metal expulsion during spot welding.

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

2006-02-01

119

Mechanical properties of duplex steel welded joints in large-size constructions  

Microsoft Academic Search

Thick panels measuring 9.5, 14.5, and 18.5 mm made of UNS S31803 duplex steel were tested for welding with the use of powder wire. The target task consisted in determination of the impact of the welding process with an increased root gap on the mechanical properties of joints, as compared with the properties achieved by welding with a 6-mm threshold distance

Jerzy Nowacki; Piotr Zaj?c

2011-01-01

120

Mechanical properties of duplex steel welded joints in large-size constructions  

Microsoft Academic Search

Thick panels measuring 9.5, 14.5, and 18.5 mm made of UNS S31803 duplex steel were tested for welding with the use of powder wire. The target task consisted in determination of the impact of the welding process with an increased root gap on the mechanical properties of joints, as compared with the properties achieved by welding with a 6-mm threshold distance

Jerzy Nowacki; Piotr Zaj?c

2012-01-01

121

Nutrient demand interacts with legume maturity to affect rumen pool sizes in dairy cows.  

PubMed

Effects of legume maturity on dry matter intake (DMI), milk production, ruminal fermentation and pool sizes, and digestion and passage kinetics, and the relationship of these effects with preliminary DMI (pDMI) were evaluated using 16 ruminally and duodenally cannulated Holstein cows in a crossover design with a 14-d preliminary period and two 17-d treatment periods. During the preliminary period, the pDMI of individual cows ranged from 22.9 to 30.0 kg/d (mean=25.9 kg/d) and the 3.5% fat-corrected milk yield ranged from 34.1 to 68.2 kg/d (mean=43.7 kg/d). Experimental treatments were diets containing alfalfa silage harvested either a) early-cut, less mature (EC) or b) late-cut, more mature (LC) as the sole forage. Early- and late-cut alfalfa contained 40.8 and 53.1% neutral detergent fiber (NDF) and 23.7 and 18.1% crude protein, respectively. Forage:concentrate ratios were 53:47 and 42:58 for EC and LC, respectively; both diets contained approximately 22% forage NDF and 27% total NDF. Preliminary DMI, an index of nutrient demand, was determined during the last 4d of the preliminary period when cows were fed a common diet and used as a covariate. Main effects of alfalfa maturity and their interaction with pDMI were tested by ANOVA. Alfalfa maturity and its interaction with pDMI did not affect milk yield but EC increased DMI compared with LC; thus, EC had lower efficiency of milk production than LC. The EC diet decreased milk fat concentration more per kilogram of pDMI increase than the LC diet, but milk fat yield was not affected. The lower concentration and faster passage rate of indigestible NDF for EC resulted in lower rumen pools of indigestible NDF, total NDF, and dry matter than did LC, which EC increased at a slower rate than did LC as pDMI increased. The EC diet decreased starch intake and increased ruminal pH compared with the LC diet. The rate of ruminal starch digestion was related to level of intake, but this did not affect ruminal or postruminal starch digestion. Total-tract digestibility of NDF, organic matter, and dry matter was higher for EC than LC. Microbial efficiency tended to be related to pDMI and the response differed by treatment. When alfalfa silage was the only source of forage in the diet, cows supplemented with additional concentrate to account for decreased protein and increased fiber concentrations associated with LC produced similar fat-corrected milk yields with greater efficiency than cows fed EC. PMID:22541491

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

2012-05-01

122

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

123

Instability of the growth-limiting proteins of the Avena coleoptile and their pool size in relation to auxin  

Microsoft Academic Search

The stability and pool size of the growth-limiting proteins (GLP) of the Avena coleoptile have been studied by measuring the time required for cycloheximide to inhibit the growth of auxin-treated segments. Inhibition of growth follows inhibition of protein synthesis by 20–25 min regardless of the growth rate. This indicates that the growth inhibition is due to inherent instability of the

Robert Cleland

1971-01-01

124

Zinc Absorption and Exchangeable Zinc Pool Sizes in Breast-Fed Infants Fed Meat or Cereal as First Complementary Food  

Microsoft Academic Search

Background: The aims of this study were to compare the absorption efficiency of zinc from rice cereal and meat, with and without human milk, in 7-month-old breast-fed infants and to compare the size of exchangeable zinc pools in the infants according to the assigned complementary food. Methods: Fractional absorption of zinc was measured in male infants using extrinsic labeling with

Sanju Jalla; Jamie Westcott; Marsha Steirn; Leland V. Miller; Melanie Bell; Nancy F. Krebs

2002-01-01

125

Estimating effects of processing conditions and variable properties upon pool shape, cooling rates, and absorption coefficient in laser welding  

Microsoft Academic Search

This paper examines the role of traverse speed, Beer–Lambert absorption coefficient ?, surface reflectivity, and changing liquid thermal conductivity upon the shape of the melt pool and the cooling rates that occur. The dependence of ? upon processing conditions is also examined. A three-dimensional variable property, moving heat source, quasi-steady-state, finite difference model for heat conduction into the substrate during

T. Chande; J. Mazumder

1984-01-01

126

Dynamics of near-alpha titanium welding  

NASA Astrophysics Data System (ADS)

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

Neuberger, Brett William

127

Heat and fluid flow in complex joints during gas metal arc welding-Part II: Application to fillet welding of mild steel  

NASA Astrophysics Data System (ADS)

A numerical model described in part I [W. Zhang, C.-H. Kim, and T. DebRoy, J. Appl. Phys. 95, 5210 (2004)] was used to investigate the heat transfer and free surface flow during gas metal arc fillet welding of mild steel. Dimensional analysis was used to understand the importance of heat transfer by conduction and convection and the role of various driving forces on convection in the liquid weld pool. The calculated shape and size, finger penetration characteristic and solidified surface profile of the fillet welds were in fair agreement with the experimental results for various welding conditions. The calculated cooling rates were also in good agreement with independent experimental data. The effect of welding parameters on important weld bead characteristics was quantitatively studied using the numerical model. The results reported here indicate a significant promise for understanding and control of gas metal arc fillet welding processes based on fundamental principles of transport phenomena.

Zhang, W.; Kim, C.-H.; Debroy, T.

2004-05-01

128

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

129

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

Microsoft Academic Search

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

S. Ohta; H. Kitamura

1994-01-01

130

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

131

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

132

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

PubMed Central

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

Gray, Joshua P.; Alavian, Kambiz N.; Jonas, Elizabeth A.

2012-01-01

133

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

PubMed

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

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

2012-05-01

134

Inhibitors of inflammation and endogenous surfactant pool size as modulators of lung injury with initiation of ventilation in preterm sheep  

PubMed Central

Background Increased pro-inflammatory cytokines in tracheal aspirates correlate with the development of BPD in preterm infants. Ventilation of preterm lambs increases pro-inflammatory cytokines and causes lung inflammation. Objective We tested the hypothesis that selective inhibitors of pro-inflammatory signaling would decrease lung inflammation induced by ventilation in preterm newborn lambs. We also examined if the variability in injury response was explained by variations in the endogenous surfactant pool size. Methods Date-mated preterm lambs (n = 28) were operatively delivered and mechanically ventilated to cause lung injury (tidal volume escalation to 15 mL/kg by 15 min at age). The lambs then were ventilated with 8 mL/kg tidal volume for 1 h 45 min. Groups of animals randomly received specific inhibitors for IL-8, IL-1, or NF-?B. Unventilated lambs (n = 7) were the controls. Bronchoalveolar lavage fluid (BALF) and lung samples were used to quantify inflammation. Saturated phosphatidylcholine (Sat PC) was measured in BALF fluid and the data were stratified based on a level of 5 ?mol/kg (~8 mg/kg surfactant). Results The inhibitors did not decrease the cytokine levels or inflammatory response. The inflammation increased as Sat PC pool size in BALF decreased. Ventilated lambs with a Sat PC level > 5 ?mol/kg had significantly decreased markers of injury and lung inflammation compared with those lambs with < 5 ?mol/kg. Conclusion Lung injury caused by high tidal volumes at birth were decreased when endogenous surfactant pool sizes were larger. Attempts to decrease inflammation by blocking IL-8, IL-1 or NF-?B were unsuccessful.

2010-01-01

135

Regulation of memory CD4 T-cell pool size and function by natural killer T cells in vivo  

PubMed Central

To develop more effective vaccines and strategies to regulate chronic inflammatory diseases, it is important to understand the mechanisms of immunological memory. Factors regulating memory CD4+ T helper (Th)-cell pool size and function remain unclear, however. We show that activation of type I invariant natural killer T (iNKT) cells with glycolipid ligands and activation of type II natural killer T (NKT) cells with the endogenous ligand sulfatide induced dramatic proliferation and expansion of memory, but not naïve, CD4 T cells. NKT cell-induced proliferation of memory Th1 and Th2 cells was dependent largely on the production of IL-2, with Th2-cell proliferation also affected by loss of IL-4. Type II NKT cells were also required for efficient maintenance of memory CD4 T cells in vivo. Activation of iNKT cells resulted in up-regulation of IFN-? expression by memory Th2 cells. These IFN-?–producing memory Th2 cells showed a decreased capability to induce Th2 cytokines and eosinophilic airway inflammation. Thus, activated NKT cells directly regulate memory CD4 T-cell pool size and function via the production of cytokines in vivo.

Iwamura, Chiaki; Shinoda, Kenta; Endo, Yusuke; Watanabe, Yukiko; Tumes, Damon John; Motohashi, Shinichiro; Kawahara, Kazuyoshi; Kinjo, Yuki; Nakayama, Toshinori

2012-01-01

136

Distortion of laser welded titanium plates.  

PubMed

The distortion of laser welded titanium plates was assessed for different operating conditions of the laser welding device, and with different welding parameters (in terms of weld point and prewelding). In this study, Nd : YAG laser welding device was used to join the titanium plates. The results showed that distortion increased stepwise after each welding point along the welding zone (one-side welding), but decreased consecutively as the welding proceeded on the second side of the weld (two-side welding). In the case of one-side welding, the dependence of distortion on current and spot diameter presented maxima--due to changes in the welding pool characteristics. For two-side weld the same parameters exercised little influence on its distortion recovery, due to the effect of solidified weld pools from the first side. Current and spot diameter determined the weld pool, which in turn regulated distortion based on shrinkage. Four-point prewelding significantly decreased the final distortion for both one- and two-side welds. Alternating two-side welding of prewelded assembly showed lower distortion than a classic two-side weld. PMID:15688724

Iwasaki, Keiji; Ohkawa, Shoji; Rosca, Iosif D; Uo, Motohiro; Akasaka, Tsukasa; Watari, Fumio

2004-12-01

137

71st American Welding Society annual meeting  

SciTech Connect

Detailed summaries are given for the 151 Technical and Brazing Conference papers presented at the 71st Annual Convention of the American Welding Society. Some of the topics covered were: computer technology for welding applications, weld testing, microstructure analysis, weld pool studies, electrode performance, welding processes and equipment development, thermal spraying, welding in marine and pipeline construction, weld cracking studies, aluminum welding, brazing, ceramic joining and low alloy steel welding. Also included are abstracts for the 29 poster sessions and 16 education session papers and the names and addresses of all professional program, poster session and education program participants.

Not Available

1990-01-01

138

Presynaptic Calcium Influx Controls Neurotransmitter Release in Part by Regulating the Effective Size of the Readily-Releasable Pool  

PubMed Central

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 contributed. Reducing calcium influx by blocking R-type voltage-gated calcium channels (VGCCs) with Ni2+, 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, this contributes to the calcium dependence of synaptic strength, and it influences the manner in which presynaptic modulation of presynaptic calcium channels affects neurotransmitter release.

Thanawala, Monica S.; Regehr, Wade G.

2013-01-01

139

A computationally efficient model of convective heat transfer and solidification characteristics during keyhole mode laser welding  

NASA Astrophysics Data System (ADS)

Computationally efficient heat transfer models of keyhole mode laser welding ignore fluid flow in the gas, liquid, and the two phase solid-liquid regions. These models cannot be applied to high Peclet number systems where convective heat transfer affects weld pool geometry, cooling rate, and other weld attributes. Here we show that by synthesizing features of an existing model to determine keyhole shape and size with rigorous fluid flow and heat transfer calculations in the liquid and the two phase solid-liquid regions, important features of both high and low Peclet number systems can be satisfactorily simulated. The geometry of the keyhole is calculated by assuming thermal equilibrium at the gas/liquid interface and point by point heat balance at the keyhole wall. The heat transfer outside the vapor cavity is calculated by numerically solving the equations of conservation of mass, momentum, and energy. A vorticity based turbulence model is used to estimate the values of effective viscosity and effective thermal conductivity of the liquid metal in the weld pool. It is shown that the temperature profile and the weld pool shape and size depend strongly on the convective heat transfer for low thermal conductivity alloys like stainless steel. For high thermal conductivity aluminum alloys, on the other hand, convection does not play a significant role in determining the shape and size of the weld pool. The computed solidification parameters indicated that the solidification structure becomes less dendritic and coarser with the decrease in welding velocity. The results demonstrate that a numerically efficient convective heat transfer model of keyhole mode laser welding can significantly improve the current understanding of weld attributes for different materials with widely different thermal properties.

Rai, R.; Roy, G. G.; Debroy, T.

2007-03-01

140

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

141

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

142

In-process monitoring and feedback control for stable production of full-penetration weld in continuous wave fibre laser welding  

NASA Astrophysics Data System (ADS)

Laser micro-welding has been applied for device sealing in electronics and automobile industries. Welding of corners in goods and products is a problem owing to easier formation of a weld with burn-through, shallow penetration or a non-bonded part when a drastic change in the welding speed or laser power occurs. This research was therefore undertaken with the objective of obtaining a fundamental knowledge of in-process monitoring and feedback control for the stable production of a full-penetration weld with a constant bead width on the bottom surface irrespective of the changes in the laser power and the welding speed. Variation in weld penetration geometry was investigated by rapid deceleration and acceleration in the welding speed during lap welding of pure titanium thin sheets with a continuous wave (CW) single-mode fibre laser beam. The rapid deceleration in the welding speed led to a considerable change in the full-penetration weld geometry or a partially penetrated weld (if the power was accordingly reduced), resulting in the difficulty in the stable production of a full-penetration weld bead. The heat radiation intensity measured from the laser-irradiated area was useful as an in-process monitoring signal for detecting the molten pool size on the laser-irradiated surface. However, the utilization of monitoring of heat radiation was difficult for predicting the weld bead width on the bottom surface due to the formation of partial penetration or the change in the penetration shape. The laser power was controlled at a 4 ms interval according to the heat radiation signal in order to adjust the weld bead width on the laser-irradiated surface to the target weld penetration geometry affected by thermal storage. Consequently, the feedback-controlled laser power produced a stable full-penetration weld with the designed bead width on the bottom surface irrespective of the rapid deceleration of the welding speed and the corresponding decrease in laser power. Furthermore, the developed feedback control algorithm was effective in rapid acceleration of the welding speed. From these results, it was confirmed that the consideration of the feedback control algorithm including a thermophysical property such as thermal storage was essential for the suppression of the effect due to rapid deceleration and acceleration of the welding speed and the laser power in lap seam micro-welding with a CW fibre laser.

Kawahito, Yousuke; Ohnishi, Terumasa; Katayama, Seiji

2009-04-01

143

A scanning transmission electron microscopy method for determination of manganese composition in welding fume as a function of primary particle size  

Microsoft Academic Search

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 assessment and health research. Dark field images were collected to

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

2011-01-01

144

Method for enhanced control of welding processes  

DOEpatents

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

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

2000-01-01

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.

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

2011-01-01

146

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

147

Size and Specific Radioactivity of the [3H]Thymidine Triphosphate Pool and DNA Synthesis in the Radicles of Germinating Cotton 1  

PubMed Central

By relating the specific radioactivity, size, and turnover of the labeled thymidine triphosphate pool to DNA synthesis, it was shown that the 32- to 38-hour interval of cotton seedling (Gossypium barbadense L.) germination was the peak period of DNA synthesis within the radicle tip during a total germination time of 48 hours at 35 C.

Katterman, Frank R. H.; Clay, Willard F.

1975-01-01

148

Determination of GTA welding efficiencies  

NASA Astrophysics Data System (ADS)

A method is developed for estimating welding efficiencies for moving arc GTAW processes. Under quasi-conditions, the net heat transfer rate from the weld pool to the work piece is estimated from a 3-D numerical heat transfer conduction model. The dimensions of the weld pool used in the computational model are obtained experimentally using a laser vision system and by metallurgical examination. The welding efficiency is then calculated by dividing the net heat transfer rate by the total power input during the experiments. Efficiencies are measured for a range of power inputs and torch speeds and then compared with those available in the literature.

Franche, Candonino P.

1993-03-01

149

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

PubMed

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

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

2012-05-01

150

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

151

Mechanism and optimization of oxide fluxes for deep penetration in gas tungsten arc welding  

NASA Astrophysics Data System (ADS)

Five single oxide fluxes—Cu2O, NiO, SiO2, CaO, and Al2O3—were used to investigate the effect of active flux on the depth/width ratio in SUS304 stainless steel. The flux quantity, stability, and particlesize effect on the weld-pool shape and oxygen content in the weld after welding was studied systematically. The results showed that the weld depth/width ratio initially increased, followed by a decrease with the increasing flux quantity of the Cu2O, NiO, and SiO2 fluxes. The depth/width ratio is not sensitive to the CaO flux when the quantity is over 80×10-5 mol on the 5×0.1×50 mm slot. The Al2O3 flux has no effect on the penetration. The oxygen content dissolved in the weld plays an important role in altering the liquid-pool surface-tension gradient and the weld penetration. The effective range of oxygen in the weld is between 70 and 300 ppm. A too-high or too-low oxygen content in the weld pool does not increase the depth/width ratio. The decomposition of the flux significantly depends on the flux stability and the particle size. Cu2O has a narrow effective flux-quantity range for the deep penetration, while the Al2O3 flux has no effect. The SiO2 flux with a small particle size (0.8 or 4 µm) is a highly recommended active flux for deep penetration in actual gas tungsten arc welding (GTAW) applications.

Lu, Shanping; Fujii, Hidetoshi; Sugiyama, Hiroyuki; Nogi, Kiyoshi

2003-09-01

152

The influence of operating parameters on number-weighted aerosol size distribution generated from a gas metal arc welding process  

Microsoft Academic Search

In light of recent research on the potential health problems associated with sub-micrometer aerosols, a study was conducted to determine the effect that droplet mass transfer mode, shield gas composition, and welding spatter had upon the aerosols generated from a Gas Metal Arc Welding (GMAW) Operation. The results revealed that the sub-micrometer aerosols produced during spray transfer resulted in markedly

Anthony T Zimmer; Paul A Baron; Pratim Biswas

2002-01-01

153

Welded Kimberlite?  

NASA Astrophysics Data System (ADS)

Welding of pyroclastic deposits generally involves the sintering of hot glassy vesicular particles and requires the presence of a load and/or high temperatures. Welding can occur on various scales as observed in large welded pyroclastic flows, in small-volume agglutinated spatter rims, or as in coalesced clastogenic lava flows. In all these examples welding occurs mainly by reduction or elimination of porosity within the vesicular clasts and/or inter-clast pore space. The end result of welding in pyroclastic deposits is to produce dense, massive, coherent deposits. Here, we present a possible new end-member of the welding process: welding of non- vesicular pyroclasts in intra-crater kimberlite deposits. Kimberlite melt is a low-viscosity liquid carrying abundant crystals. Because of this, kimberlite eruptions generally produce non-vesicular pyroclasts. During welding, these pyroclast cannot deform by volume reduction to form typical fiamme. As a result, welding and compaction in kimberlites proceeds via the reduction of inter-clast pore space alone. The lack of porous pyroclasts limits the maximum amount of volumetric strain within pyroclastic kimberlite deposits to about 30%. This value is substantially lower than the limiting values for welding of more common felsic pyroclastic flows. The lower limit for volumetric strain in welded kimberlite deposits severely restricts the development of a fabric. In addition, pyroclastic kimberlite deposits commonly feature equant-shaped pyroclasts, and equant-shaped crystals. This, in turn, limits the visibility of the results of compaction and pore space reduction, as there are few deformable markers and elongate rigid markers that are able to record the strain during compaction. These features, together with the low viscosity of kimberlite magma and the stratigraphic position of these kimberlite deposits within the upper reaches of the volcanic conduit, call for careful interpretation of coherent-looking rocks in these settings. In this contribution we explore the possible welded origin for dark and competent kimberlite facies from the Victor Northwest pipe (Northern Ontario, Canada). This volumetrically extensive facies superficially resembles a coherent rock. The following observations on the dark and competent facies are suggestive of a pyroclastic, rather than intrusive or extrusive coherent origin: The facies is completely enveloped by pyroclastic facies; has gradational contacts with adjacent pyroclastic facies above and below; contains faint outlines of primary pyroclasts; shows diffuse grain size variations and rare bedding; shows systematic changes in components from the underlying pyroclastic facies to the dark and competent facies to the overlying pyroclastic facies implying a lack of a depositional break in this succession; and shows a faint, generally subhorizontal fabric despite the presence of an equant grain shape population. In addition, we present evidence that the original inter-clast porosity has been reduced or eliminated by syn-depositional welding rather than by precipitation of secondary minerals in the inter-clast pore spaces. We feel that the latter process (i.e., alteration) is highly unlikely because: The kimberlite package contains intervals with well crystallized groundmass similar to coherent kimberlite, this texture simply cannot be produced by alteration; the kimberlite is in fact the freshest rock within the pipe, containing mostly fresh olivines; and the dark and competent kimberlite does not show a patchy or vein-related heterogeneity typical of alteration. In summary, these deposits likely represent a variably welded succession of proximal spatter/fire fountaining kimberlite deposits.

van Straaten, B. I.; Kopylova, M. G.; Russell, J. K.; Scott Smith, B. H.

2009-05-01

154

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

155

Modeling of heat transfer and fluid flow during laser welding of aluminum  

Microsoft Academic Search

This paper presents a two-dimensional model to study the fluid flow and heat transfer phenomena which occur during deep penetration laser welding. Using finite volume method analysis software FLUENT, behavior of temperature field and weld pool shape were analyzed. The results show that the method can be used to predict the shape of the welding pool as function of welding

Nabil Allalou; El Hachemi Amara; N. Mebani; L. Achab; F. Hamadi

2005-01-01

156

Simulation and controlling for weld shape process in P-GMAW based on fuzzy logic  

Microsoft Academic Search

A sensing and controlling system is established for pulsed gas metal arc welding (P-GMAW). The topside weld pool characterizing parameters can be captured in real-time and the back side weld pool width can be predicted from these parameters by a neural network model. A fuzzy controller is established and then the close loop controlling for weld penetration is realized. Based

Zhihong Yan; Guangjun Zhang; Lin Wun

2011-01-01

157

Pulse laser welding of aluminum alloy by combined radiation  

Microsoft Academic Search

The formation features of welded connections of aluminum alloys by combined laser radiation are considered. The mechanism of a molten pool formation is investigated by numerical modeling and experimentally. The attainment criteria of qualitative butt-welded connection are determined.

Alexander V. Fedin; Yevgeny A. Chaschin; Igor V. Shilov; Sergey A. Solokhin; Mikhail N. Ershkov

2007-01-01

158

Pulse laser welding of aluminum alloy by combined radiation  

NASA Astrophysics Data System (ADS)

The formation features of welded connections of aluminum alloys by combined laser radiation are considered. The mechanism of a molten pool formation is investigated by numerical modeling and experimentally. The attainment criteria of qualitative butt-welded connection are determined.

Fedin, Alexander V.; Chaschin, Yevgeny A.; Shilov, Igor V.; Solokhin, Sergey A.; Ershkov, Mikhail N.

2007-08-01

159

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

160

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

SciTech Connect

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

Kim, J.S.; Watanabe, T.; Yoshida, Y. [Chiba Univ. (Japan)

1995-03-01

161

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

PubMed Central

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

2012-01-01

162

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

NASA Astrophysics Data System (ADS)

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

Kim, Taewon; Suga, Yasuo; Koike, Takashi

163

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

164

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

Microsoft Academic Search

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

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

2003-01-01

165

Why to measure a broad range of city sizes? Analysis of globally pooled data of urban GHG measurements for sustainability  

NASA Astrophysics Data System (ADS)

We have assembled a database of urban GHG emissions from various published sources, including about 200 cities globally. Analyzing this CO2 emission inventory from multiple countries we find power-law relations between the emissions and city size, measured in population. The results suggest that in developing countries large cities emit more CO2 per capita compared to small cities, i.e. they tend to comprise super-linear correlations. For developed countries the results suggest the opposite, i.e. linear or sub-linear correlations, implying better efficiency of large cities. We derive how the total emissions of an entire country relate with the power-law correlations and find that the size of the most populated city is dominating in the case of linear and super-linear correlations, while a transition occurs to sub-linear correlations, where the size of the largest city has no influence. It is important to further substantiate an overview of city emission inventories across a broad range of city sizes and types to further clarify the complex relationships between cities and GHG emissions. On the one hand, we propose a minimum set of meta-information to be reported together with the emission inventories, e.g. for determining comparability among inventories. On the other hand, we propose to fill evident gaps with respect to regions (e.g. sub-Saharan African and South American cities) and types of cities (e.g. small medium and low-income country cities) to allow for a better global overview of city sizes, income, and emissions. We conclude that from the climate change mitigation point of view, urbanization is desirable in developed countries and should be avoided in developing countries, if effinciency increasing mechanisms can not be established. More data acquisition is needed to support our empirical findings.

Rybski, Diego; Sterzel, Till; Reusser, Dominik E.; Fichter, Christina; Kropp, Jürgen P.

2013-04-01

166

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…

Alaska State Dept. of Education, Juneau.

167

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.

168

Welding IV.  

ERIC Educational Resources Information Center

|Instructional objectives and performance requirements are outlined in this course guide for Welding IV, a competency-based course in advanced arc welding offered at the Community College of Allegheny County to provide students with proficiency in: (1) single vee groove welding using code specifications established by the American Welding Society…

Allegheny County Community Coll., Pittsburgh, PA.

169

Welding Curriculum.  

ERIC Educational Resources Information Center

|This competency-based curriculum guide is a handbook for the development of welding trade programs. Based on a survey of Alaskan welding employers, it includes all competencies a student should acquire in such a welding program. The handbook stresses the importance of understanding the principles associated with the various elements of welding.…

Alaska State Dept. of Education, Juneau. Div. of Adult and Vocational Education.

170

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

171

Infrared Sensing Techniques for Adaptive Robotic Welding.  

National Technical Information Service (NTIS)

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 o...

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

1986-01-01

172

Heat and fluid flow in complex joints during gas metal arc welding-Part I: Numerical model of fillet welding  

Microsoft Academic Search

Gas metal arc (GMA) fillet welding is one of the most important processes for metal joining because of its high productivity and amiability to automation. This welding process is characterized by the complicated V-shaped joint geometry, a deformable weld pool surface, and the additions of hot metal droplets. In the present work, a three-dimensional numerical heat transfer and fluid flow

W. Zhang; C.-H. Kim; T. Debroy

2004-01-01

173

The paired deuterated retinol dilution technique can be used to estimate the daily vitamin A intake required to maintain a targeted whole body vitamin A pool size in men.  

PubMed

The estimated average requirement (EAR) for vitamin A (VA) of adult males is based on the amount of dietary VA required to maintain adequate function and provide a modest liver VA reserve (0.07 ?mol/g). In the present study, the paired-deuterated retinol dilution technique was used to estimate changes in VA pool size in Bangladeshi men from low-income, urban neighborhoods who had small initial VA pool sizes (0.059 ± 0.032 mmol, or 0.047 ± 0.025 ?mol/g liver; n = 16). The men were supplemented for 60 d with 1 of 8 different levels of dietary VA, ranging from 100 to 2300 ?g/d (2 men/dietary VA level). VA pool size was estimated before and after the supplementation period. The mean change (plus or minus) in VA pool size in the men was plotted against their corresponding levels of daily VA intake and a regression line was fit to the data. The level of intake at which the regression line crossed the x-axis (where estimates of VA pool size remained unchanged) was used as an estimate of the EAR. A VA intake of 254-400 ?g/d was sufficient to maintain a small VA pool size (0.059 ± 0.032 mmol) in the Bangladeshi men, corresponding to a VA intake of 362-571 ?g/d for a 70-kg U.S. man, which is lower than their current EAR of 625 ?g/d. The data suggest that the paired-deuterated retinol dilution technique could be used for estimating the EAR for VA for population subgroups for which there are currently no direct estimates. PMID:21248191

Haskell, Marjorie J; Jamil, Kazi M; Peerson, Janet M; Wahed, Mohammed A; Brown, Kenneth H

2011-01-19

174

Adaptive tracking of weld joints using active contour model in arc-welding processes  

NASA Astrophysics Data System (ADS)

12 This paper presents a vision processing scheme to automatic weld joint tracking in robotic arc welding process. Particular attention is concentrated on its robustness against various optical disturbances, such as arc glares and weld spatters radiating from the melted weld pool. Underlying the developed vision processing is a kind of model-based pattern searching, which is necessarily accompanied by two separate stages of modeling and tracking. In the modeling stage, a syntactic approach is adopted to identify unknown weld joint structure. The joint profile identified in the modeling stage is used as a starting point for successive tracking of variations in the geometry of weld joint during welding, which is automatically achieved by an active contour model technology following feature- based template matching. The performance of the developed scheme is investigated through a series of practical welding experiments.

Kim, Jaeseon; Koh, Kyoungchul; Cho, Hyung S.

2001-02-01

175

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

176

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

177

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

178

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

179

Mechanism governing nitrogen absorption by steel weld metal during laser welding  

Microsoft Academic Search

The existence of monatomic nitrogen in the plasma just over the keyhole during CO2 laser welding was confirmed by the monochromatic image of a specific spectrum line emitted by monatomic nitrogen. The smaller\\u000a reaction area of the molten pool with monatomic nitrogen is considered to lead to less nitrogen absorption during CO2 laser welding than that during arc welding. The

Wei Dong; Hiroyuki Kokawa; Yutaka S. Sato; Susumu Tsukamoto; Makoto Ogawa

2004-01-01

180

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

181

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

182

Grain refinement of aluminum weld metal  

Microsoft Academic Search

The influence of titanium and zirconium microadditions on the grain refinement in aluminum weld metal is investigated. These grain refiners significantly alter the morphology of the solidification structure. The time to nucleate the first grain in the weld metal, the weld metal solidification rate and the columnar grain size are all characterized as a function of the grain refiner content.

H. Yunjia; D. L. Olson; G. R. Edwards

1989-01-01

183

Keyhole Welding: The Solid and Liquid Phases  

NASA Astrophysics Data System (ADS)

Deep penetration laser welding relies on the evaporation of material by a high power laser beam in order to drill a vapour capillary, usually referred to as a keyhole. During continuous welding the keyhole is kept open by the pressure in the vapour which evaporates continuously from its wall; the pressure acts continuously against the surface tension pressure that favours contraction. In contrast to pulsed wave (pw-) laser welding, during continuous wave (cw-) laser welding quasi-steady state conditions of the accompanying temperature field, and thus of the shape of the keyhole and melt pool, are established. Nevertheless, in the keyhole and melt pool complex fluid mechanical mechanisms take place. The most important thermodynamic and melt flow phenomena in keyhole laser welding will be briefly discussed. For some of them mathematical models and calculation results will be presented, complementing a comprehensive survey that was published earlier [1].

Kaplan, Alexander

184

Regulation of biliary cholesterol output in the rat: dissociation from the rate of hepatic cholesterol synthesis, the size of the hepatic cholesteryl ester pool, and the hepatic uptake of chylomicron cholesterol  

Microsoft Academic Search

These studies were designed to determine the importance of the rate of hepatic cholesterol synthesis, the size of the hepatic cholesteryl ester pool, the amount of chylomicron cholesterol reaching the liver, and the rate of bile acid transport into bile as determinants of the rate of biliary cholesterol output. Female rats that had been sub- jected to diurnal light cycling,

Stephen D. Turley; John M. Dietsch

185

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

PubMed

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

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

2004-04-16

186

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

Microsoft Academic Search

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

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

2000-01-01

187

The Optically Determined Size of Exo\\/Endo Cycling Vesicle Pool Correlates with the Quantal Content at the Neuromuscular Junction of Drosophila Larvae  

Microsoft Academic Search

According to the current theory of synaptic transmission, the amplitude of evoked synaptic potentials correlates with the number of synaptic vesicles released at the presynaptic termi- nals. Synaptic vesicles in presynaptic boutons constitute two distinct pools, namely, exo\\/endo cycling and reserve pools (Kuromi and Kidokoro, 1998a). We defined the vesicles that were endocytosed and exocytosed during high K 1 stimulation

Hiroshi Kuromi; Yoshiaki Kidokoro

1999-01-01

188

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

189

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

190

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

191

Laser welding of sheet metals  

NASA Astrophysics Data System (ADS)

Laser welding of sheet metals is an important application of high power lasers, and has many advantages over conventional welding techniques. Laser welding has a great potential to replace other welding technique in the car-body manufacturing because of high laser weld quality and relatively low manufacturing cost associated with the laser technique. However, a few problems related to the laser welding of sheet metals limit its applications in industries. To have a better understanding of the welding process, laser welding experimental studies and theoretical analysis are necessary. Temperature-dependent absorptivities of various metals are obtained theoretically for COsb2, COIL (Chemical Oxygen-Iodine Laser) and Nd:YAG lasers. It is found that the absorptivities for COIL and Nd:YAG lasers are 2.84 and 3.16 times higher than for the COsb2 laser, and the absorptivity increases with increasing temperature of the metals. Surface roughness and oxide films can enhance the absorption significantly. The reflectivity of as-received steel sheets decreases from 65-80% to 30-40% with surface oxide films for COsb2 lasers. Laser welding experiments show that the tensile strengths of the weld metals are higher than the base metals. For samples with surface oxide films, the oxygen concentration in the weld metals is found to be higher than in the specimens without oxidation, and the toughness of the weld metals is degraded. When steel powders are added to bridge the gap between two sheets, the oxygen content in the weld metals decreases and the toughness increases. A mathematical model is developed for the melt depth due to a stationary laser beam. The model results show that the melt depth increases rapidly with time at the beginning of laser irradiation and then increases slowly. Also, the melt depth is found to increase rapidly with laser intensities and then increases slowly for higher intensity. The average rate of melting and the times to reach the melting and boiling temperatures at the substrate surface are obtained by using the model. Another mathematical model is developed for the weld width weld pool shape due to a moving Gaussian laser beam. The model prediction compare well with experimental results.

Xie, Jian

192

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

193

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

194

In-process monitoring and adaptive control for gap in micro butt welding with pulsed YAG laser  

NASA Astrophysics Data System (ADS)

A gap is one of the most important issues to be solved in laser welding of a micro butt joint, because the gap results in welding defects such as underfilling or a non-bonded joint. In-process monitoring and adaptive control has been expected as one of the useful procedures for the stable production of sound laser welds without defects. The objective of this research is to evaluate the availability of in-process monitoring and adaptive control in micro butt welding of pure titanium rods with a pulsed neodymium : yttrium aluminium garnet (Nd : YAG) laser beam of a 150 µm spot diameter. It was revealed that a 45 µm narrow gap was detected by the remarkable jump in a reflected light intensity due to the formation of the molten pool which could bridge the gap. Heat radiation signal levels increased in proportion to the sizes of molten pools or penetration depths for the respective laser powers. As for adaptive control, the laser peak power was controlled on the basis of the reflected light or the heat radiation signals to stably produce a sound deeply penetrated weld reduced underfilling. In the case of a 100 µm gap, the underfilling was greatly reduced by half smaller than those made with a conventional rectangular pulse shape in seam welding as well as spot welding with a pulsed Nd : YAG laser beam. Consequently, the adaptive control of the laser peak power on the basis of in-process monitoring could reduce the harmful effects due to a gap in micro butt laser welding with a pulsed laser beam.

Kawahito, Yousuke; Kito, Masayuki; Katayama, Seiji

2007-05-01

195

Induction-assisted laser welding of IN738 nickel–base superalloy  

Microsoft Academic Search

Induction-assisted laser welding was performed with filler metal additions to weld IN-738, a nickel–base superalloy. IN-738 powder was added through a coaxial nozzle to the weld pool in order to reduce the weld defects, such as underfill and porosity in the welds. This was particularly important for the square-groove butt joints due to the presence and opening of gaps in

M. F. Chiang; C. Chen

2009-01-01

196

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

PubMed

The purpose of this study was to evaluate the efficacy of laser welding and conventional welding on the tensile strength and ultimate tensile strength of the cobalt-chromium alloy. Samples were prepared with two commercially available cobalt-chromium alloys (Wironium plus and Diadur alloy). The samples were sectioned and the broken fragments were joined using Conventional and Laser welding techniques. The welded joints were subjected to tensile and ultimate tensile strength testing; and scanning electron microscope to evaluate the surface characteristics at the welded site. Both on laser welding as well as on conventional welding technique, Diadur alloy samples showed lesser values when tested for tensile and ultimate tensile strength when compared to Wironium alloy samples. Under the scanning electron microscope, the laser welded joints show uniform welding and continuous molt pool all over the surface with less porosity than the conventionally welded joints. Laser welding is an advantageous method of connecting or repairing cast metal prosthetic frameworks. PMID:23858281

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

2012-04-18

197

Real-time ultrasonic sensing of arc welding processes  

SciTech Connect

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

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

1983-01-01

198

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

199

A study on fatigue crack initiation point of load-carrying fillet welded cruciform joints  

Microsoft Academic Search

Load-carrying fillet welded cruciform joints have two fatigue crack initiating points. These are located at the weld toes and weld roots, where high stress concentrations occur. The location of the fatigue crack initiation depends on the weld size, plate thickness and weld penetration. These mechanisms are easily understood. Previous experimental results have indicated that the fatigue crack originating point is

Shigenobu Kainuma; Takeshi Mori

2008-01-01

200

An investigation into welding parameters affecting the tensile properties of titanium welds  

Microsoft Academic Search

Grain size and amount of martensite formation affect the tensile strength of the alloy and these two factors are in turns related to the cooling rate of the welding process. There was found a trend of decreased tensile strength with the increase of welding heat input and a trend of increased tensile strength with the increase of welding cooling rate.

Winco K. C. Yung; B. Ralph; W. B. Lee; R. Fenn

1997-01-01

201

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

Microsoft Academic Search

A three-dimensional mathematical model was developed to simulate the flow patterns and temperature distributions in a moving\\u000a A-TIG weld pool of 304 stainless steels with different oxygen content using PHOENICS software. It is shown that the surface-active\\u000a element, oxygen, is important, because it affects the weld shape by changing the flow patterns in the weld pool. The weld\\u000a bead penetration

Yuzhen Zhao; Yaowu Shi; Yongping Lei

2006-01-01

202

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.

203

Welding Curriculum.  

ERIC Educational Resources Information Center

|The purpose of this welding program is to provide students with skills and techniques to become employed as advanced apprentice welders. The welding program manual includes the following sections: (1) course description; (2) general objectives; (3) competencies; (4) curriculum outline for 13 areas; (5) 13 references; and (6) student progress…

EASTCONN Regional Educational Services Center, North Windham, CT.

204

WELDING METHOD  

DOEpatents

A semi-automatic method is described for the weld joining of pipes and fittings which utilizes the inert gasshielded consumable electrode electric arc welding technique, comprising laying down the root pass at a first peripheral velocity and thereafter laying down the filler passes over the root pass necessary to complete the weld by revolving the pipes and fittings at a second peripheral velocity different from the first peripheral velocity, maintaining the welding head in a fixed position as to the specific direction of revolution, while the longitudinal axis of the welding head is disposed angularly in the direction of revolution at amounts between twenty minutas and about four degrees from the first position.

Cornell, A.A.; Dunbar, J.V.; Ruffner, J.H.

1959-09-29

205

Optical signal oscillations in laser keyhole welding and potential application to lap welding  

NASA Astrophysics Data System (ADS)

We describe an optical sensor for process monitoring of Nd:YAG laser welding. This sensor detects the broadband radiation produced by the welding process, dividing it into broad spectral bands (designated UV/visible and IR). Fourier analysis is used to investigate an oscillatory intensity modulation of the optical signals, which is believed to arise from a combination of keyhole and weld-pool oscillations. The spectral content of the oscillations may be used to detect a fully open welding keyhole and to determine the work-piece thickness under this welding regime. These oscillations have also been utilized in the development of a tracking technique which detects the misalignment from an overlap welding seam and excessive gaps in the lap joint.

Haran, F. M.; Hand, D. P.; Ebrahim, S. M.; Peters, C.; Jones, J. D. C.

1997-06-01

206

Thermal cycles in multiple electrode submerged arc welding  

SciTech Connect

Multiple electrode submerged arc welding (SAW) is often used to increase the deposition rate in high productivity fabrication. However, while the development and application of the process have succeeded, the approach has not been systematic, and there is limited scientific information available regarding the process. This paper is concerned with the thermal cycles and resulting weld bead shape in four-electrode SAW. The experimental data were obtained with embedded thermocouples, by macroscopic examination of sections, and by weld pool ejection. The discussion considers the relationships between the welding conditions, the thermal responses and bead profiles. Data describing the geometry of the solidification boundary during the welding process are included and used to augment the description of the heat flow outside the weld pool. The study concludes that one may anticipate and control many features of the thermal response and bead profile.

Ahmed, N.U.; Jarvis, B.L. [CSIRO, Woodville (Australia)

1996-01-01

207

Application of a dimensionless parameter model for Laser Beam Welding.  

National Technical Information Service (NTIS)

A new dimensionless parameter model for continuous wave laser welding that relates the size of the weld to the energy absorbed by the part is described. The model has been experimentally validated previously through calorimetric determinations of the net ...

P. W. Fuerschbach

1994-01-01

208

Plasma Arc Welding Weld Imaging.  

National Technical Information Service (NTIS)

A welding torch for plasma arc welding apparatus has a transparent shield cup disposed about the constricting nozzle, the cup including a small outwardly extending polished lip. A guide tube extends externally of the torch and has a free end adjacent to t...

D. J. Rybicki W. F. Mcgee

1993-01-01

209

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

210

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

211

Modeling of transport phenomena during laser welding process  

NASA Astrophysics Data System (ADS)

This dissertation, consisting of three papers, presents the results of research investigations on laser welding of zinc-coated steel sheets and three-dimensional laser keyhole welding by numerical analysis. In the first paper, the mathematical model and numerical techniques are developed to simulate the keyhole formation, zinc vapor formation and zinc vapor escaping processes. In the study, the keyhole is used as an effective way to vent the high-pressure zinc vapor generated at the interface between the two zinc-coated metal sheets. The interaction between the weld pool and the escaping zinc vapor is investigated. It is the first comprehensive mathematical model for laser welding of zinc-coated steel sheets. In the second paper, the aforementioned model is employed to study the defect formation mechanisms in laser welding of zinc-coated steel sheets. Welding defects, such as voids at the root of welded metal, the undercut on the top surface and the bubbles trapped in the weld pool are simulated. The reasons causing these welding defects are given through the studies of the zinc vapor-weld pool interaction and the fluid flow and heat transfer during the keyhole collapse and metal solidification processes. In the third paper, the aforementioned stationary 2-D model is extended to modeling a 3-D moving laser keyhole welding process. The heat transfer and fluid flow in the welding pool around the keyhole are calculated. Also, the laser induced plasma inside the keyhole due to the Inverse Bremsstrahlung absorption is considered to calculate the temperature distribution inside the keyhole. Energy distribution inside the keyhole is computed by considering the Fresnel absorption and multiple reflections phenomena.

Zhou, Jun

212

Modeling cast IN738 superalloy gas tungsten arc welds  

Microsoft Academic Search

A three-dimensional finite-element thermal model has been developed to generate weld profiles, and to analyze transient heat flow, thermal gradients and thermal cycles in cast IN-738 superalloy gas tungsten arc welds. Outputs of the model (cooling rates, the thermal gradient G and the growth rate R) were used to describe solidification structures found around the weld pool for three different

E. A. Bonifaz; N. L. Richards

2009-01-01

213

Measurement and modelling of residual stresses in a TIG weld  

Microsoft Academic Search

Residual stresses due to TIG welding have been measured using neutron diffraction and the results compared with a finite element model calculation. Measurements were made on a single-pass, autogenous, bead-on-plate TIG weld made along the centre line of an aluminium alloy rectangular plate of dimensions 172쏦Ƿ mm3. The weld is 150 mm long with the start and end pools centred

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

2002-01-01

214

Virginia Tech - Buffer Pool  

NSDL National Science Digital Library

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

Shaffer, Cliff; Sariaya, Purvi

215

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

216

Swimming pools soak up the sun  

SciTech Connect

Solar pool heaters survived the boom and bust solar years of the 1970s and 1980s. Today they are even popular and cost-effective in parts of the country where many people think solar is impractical. This article discusses the following topics: how solar pool heaters work; types of solar pool heater collectors; collector and pump sizing; collector siting and mounting; systems costs and economics; pool covers. 3 figs.

Cuoghi, D.; Hesse, P.; Schiller, T.

1996-05-01

217

Laser welding of selected aerospace alloys  

NASA Astrophysics Data System (ADS)

The study was aimed at developing an understanding of the microstructural effects of the laser welding process on the alloys, and assessing the structural integrity of the resultant welds. The effect of laser processing parameters such as laser power, laser beam traverse speed, lens focal length, and the manipulation of these parameters on the welding efficiency and weld area integrity was also investigated. Other tasks within the project included a study on the possibility of using an anodic film to enhance the laser weld ability of Al 6061. Finally, attempts were made to identify phases observed in the weld area of the composite materials. Nimonics C263 and PE11 exhibited laser welds free of cracks and porosity. The difference in composition between the two alloys did not result in any significant dissimilarities in their response to the laser welding process. The welds in both alloys exhibited a fine columnar dendritic microstructure, and while carbides were observed in the interdendritic regions of the welds, electron optical analysis did not reveal any gamma' precipitates in this region. It was concluded that for the welding of thin gage materials above a threshold laser power the resultant welding efficiency shows a greater dependence on laser beam mode, and laser spot size, than on laser power, and beam traverse speed. Aluminum 6061 was not easily welded with a laser in its as received form, and the welds showed some degree of porosity. Anodizing was found to improve the welding efficiency in this material. While the presence of an anodic film on the metal surface increased the welding efficiency of the alloy, no relationship was found between the thickness of the anodic film and welding efficiency in the range of film thicknesses investigated. Weld regions were observed to be cellular dendritic in structure, with narrow heat affected zones. No precipitates or low melting point phases could be identified in the weld region. Melt zones were successfully produced in the composite materials, with the main problem encountered being that of porosity adjacent to the weld bead. It was shown that manipulation of the laser welding parameters resulted in a decrease in this porosity.

Ebadan, Gracie E.

218

Laser welding of metals  

Microsoft Academic Search

The physical processes associated with laser welding and the existing laser welding techniques are reviewed. Attention is given to the characteristics of joint formation during the welding by pulsed and continuous-wave lasers; the principal welding parameters and their effect on the melting characteristics and weld quality; and the principal types of equipment used for laser welding. The discussion also covers

Aleksandr G. Grigor'iants; Igor'n. Shiganov

1988-01-01

219

Syllabus in Trade Welding.  

ERIC Educational Resources Information Center

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

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

220

Welding and Weldability of Thorium-Doped Iridium Alloys  

SciTech Connect

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

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

2000-03-12

221

Nd:YAG laser welding: an overview  

Microsoft Academic Search

Laser welding is used when it is essential to limit the size of the heat-affected zone (HAZ), to reduce the roughness of the welded surface and to eliminate mechanical effects. Solid-state lasers operating in a continuous or pulsed mode can function as welding sources. Present-day lasers can provide vey high levels of power per unit area. The application of solid-state

Stefanos Karagiannis; George Chryssolouris

2003-01-01

222

Electrode carrying wire for GTAW welding  

NASA Astrophysics Data System (ADS)

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

Morgan, Gene E.; Dyer, Gerald E.

1990-05-01

223

Seam gap bridging of laser based processes for the welding of aluminium sheets for industrial applications  

Microsoft Academic Search

Laser welding has a large potential for the production of tailor welded blanks in the automotive industry, due to the low\\u000a heat input and deep penetration. However, due to the small laser spot and melt pool, laser-based welding processes in general\\u000a have a low tolerance for seam gaps. In this paper, five laser-based welding techniques are compared for their gap

Bernard Johan Aalderink; B. Pathiraj; R. G. K. M. Aarts

2010-01-01

224

Thermocapillary and arc phenomena in stainless steel welding  

Microsoft Academic Search

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

S. W. Pierce; D. L. Olson; P. Burgardt

1999-01-01

225

Characterizing laser fusion welded aluminum using synchrotron x ray microtomography  

Microsoft Academic Search

Preliminary research into the application of high power Nd-YAG lasers for welding indicate a dependency of the occurrence of weld discontinuities on processing parameters such as pulse duty cycle, travel speed, etc. The size and distribution of weld features have been characterized using synchrotron microtomography, using facilities at the National Synchrotron Light Source. The ability of this technique to image

J. O. Milewski; A. B. Hmelo; K. L. Damico; J. H. Dunsmuir; S. R. Ferguson

1992-01-01

226

PENETRATION AND DEFECT FORMATION IN HIGH CURRENT ARC WELDING  

SciTech Connect

The work performed during the three previous years can be roughly divided into two main categories: (1) development of advanced modeling techniques; and (2) modeling of arc welding process. The work in the first category comprised the development of the Order of Magnitude Scaling (OMS) technique, which is complementary to numerical modeling techniques such as finite elements, but it provides approximate formulas instead of just numerical results. Borrowing concepts from OMS, another modeling technique based on empirical data was also developed. During this stage special software was also developed. The second category comprised the application of OMS to the three main subsystems of arc welding: the weld pool, the arc, and the electrode. For each of these subsystems they found scaling laws and regimes. With this knowledge, they analyzed the generation of weld pool defects during high current arc welding, proposed a mechanistic description of the process, and possible solutions.

MENDEZ,P.F.; EAGAR, T.W.

2003-01-01

227

Pulsed magnetic welding  

SciTech Connect

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

Sheely, W.F.

1986-11-20

228

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

229

Welding Curtains  

NASA Astrophysics Data System (ADS)

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

230

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

231

Variation of laser energy transfer efficiency with well pool depth  

SciTech Connect

A series of CO{sub 2} laser welds were made at a constant beam irradiance of 6 MW/cm{sup 2} on 304 stainless steel with travel speeds selected to produce welds with varying levels of weld penetration. Using a Seebeck envelope calorimeter, the net heat input to the part was measured for each weld. It was found that the energy transfer efficiencies varied from 0.29 to 0.86, and decreased at high travel speeds where the weld penetration depth was as shallow as 0.13 mm. The decrease in beam absorption with decreasing weld pool depth is consistent with an absorption mechanism that requires multiple internal reflections within the weld pool. Equations have been developed which conn -ct the keyhole cavity dimensions with the energy transfer efficiency, and correlations with the experimental data have determined the keyhole cavity radius to be 0.1 mm for a focused laser beam with a spot radius of 0.059 mm.

Fuerschbach, P.W.; MacCallum, D.O.

1995-12-01

232

Numerical models of in-service welding of gas pipelines  

Microsoft Academic Search

It is accepted that numerical methods have a useful role in the assessment of welding conditions for the safe in-service welding of high-pressure gas pipelines. Only limited published work has considered the direct calculation of burn-through using a combination of thermal and stress analysis. Using empirical relationships between welding process parameters, and weld bead size and shape is an appropriate

P. N. Sabapathy; M. A. Wahab; M. J. Painter

2001-01-01

233

Calorimetry of the arc welding process  

SciTech Connect

Minimizing the total heat input in arc welding is not usually a critical consideration when the size of the fusion zone and the weldment are very large. At SNLA, however, most welding can usually be described as microwelding. The depth of penetration is typically only 0.8 mm and hermeticity rather than mechanical strength is the primary joining requirement. For these type welds, minimizing heat input becomes a major process requirement since distortion of small components and damage to heat sensitive parts may result from large increases in the bulk temperature. In conclusion, we have found calorimetry to be a useful technique to determine the effect of arc welding process variables on heat input and melting efficiency and also to better select the required welding process for our weld geometries.

Fuerschbach, P.W.; Knorovsky, G.A.

1986-01-01

234

Correlation spectroscopy as a tool for detecting losses of ligand elements in laser welding of aluminium alloys  

Microsoft Academic Search

The plasma plume induced during laser welding of metals is a mixture of metal vapour, coming from the vaporised weld pool surface and shielding gas. The influence of the shielding gas on the welded joints quality is not yet well understood and very few investigations, to the best of our knowledge, were addressed to study its role in case of

T. Sibillano; A. Ancona; V. Berardi; E. Schingaro; P. Parente; P. M. Lugarà

2006-01-01

235

Structure/property relationships in multipass GMA welding of beryllium.  

SciTech Connect

Beryllium is an interesting metal that has a strength to weight ratio six times that of steel. Because of its unique mechanical properties, beryllium is used in aerospace applications such as satellites. In addition, beryllium is also used in x-ray windows because it is nearly transparent to x-rays. Joining of beryllium has been studied for decades (Ref.l). Typically joining processes include braze-welding (either with gas tungsten arc or gas metal arc), soldering, brazing, and electron beam welding. Cracking which resulted from electron beam welding was recently studied to provide structure/property relationships in autogenous welds (Ref. 2). Braze-welding utilizes a welding arc to melt filler, and only a small amount of base metal is melted and incorporated into the weld pool. Very little has been done to characterize the braze-weld in terms of the structure/property relationships, especially with reference to multipass welding. Thus, this investigation was undertaken to evaluate the effects of multiple passes on microstructure, weld metal composition, and resulting material properties for beryllium welded with aluminum-silicon filler metal.

Hochanadel, P. W. (Patrick W.); Hults, W. L. (William L.); Thoma, D. J. (Dan J.); Dave, V. R. (Vivek R.); Kelly, A. M. (Anna Marie); Pappin, P. A. (Pallas A.); Cola, M. J. (Mark J.); Burgardt, P. (Paul)

2001-01-01

236

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

237

Study on DC Double Pulse Metal Inert Gas (MIG) Welding of Magnesium Alloy  

Microsoft Academic Search

This article gives a preliminary research on direct current (DC) double pulse metal inert gas (MIG) welding of magnesium alloys. It will be an effort for broadening the application of this new MIG welding process. The unique parameters of DC double pulse MIG welding are selected to investigate their effects on weld bead geometry size and appearance of AZ31B Mg

Zhaodong Zhang; Xiangyu Kong

2012-01-01

238

Laser net shape welding  

Microsoft Academic Search

Over the last 40 years of laser welding practice, weld bead geometry always experiences a section of the weld bead slightly above or below the parent material surface. In this paper, a new concept – net shape welding is introduced, whereby the weld joint fusion zone is flat to the parent material surface. Experimental work was carried out to demonstrate

Lin Li; Ramadan Eghlio; Sundar Marimuthu

2011-01-01

239

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

NASA Astrophysics Data System (ADS)

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

Salminen, Antti; Jansson, Anssi; Kujanpää, Veli

2003-06-01

240

The effects of process variables on pulsed Nd:YAG laser spot welds; Part 1: AISI 409 stainless steel  

SciTech Connect

The weldabilities of AA 1,100 aluminum and AISI 409 stainless steel by the pulsed Nd:YAG laser welding process have been examined experimentally and compared. The effects of Nd:YAG laser welding parameters, including laser pulse time and power intensity, and material-dependent variables, such as absorptivity and thermophysical properties, on laser spot-weld characteristics, such as weld diameter, penetration, melt area, melting ratio, porosity, and surface cratering, have been studied experimentally. When welding AISI 409 stainless steel, weld pool shapes were found to be influenced most by the power intensity of the laser beam and to a lesser extent by the pulse duration. Conduction mode welding, keyhole mode welding, and drilling were observed. Conduction mode welds were produced when power intensities between 0.7 and 4 GW/m{sup 2} were used. The initial transient in weld pool development occurred in the first 4 ms of the laser pulse. The initial transient in weld pool development occurred in the first 4 ms of the laser pulse. Following this, steady-state conditions existed and conduction mode welds with aspect ratios (depth/width) of about 0.4 were produced. Keyhole mode welds were observed at power intensities greater than 4 GW/m{sup 2}. Penetration of these keyhole mode welds increased with increases in both power intensity and pulse time. The major weld defects observed in the stainless steel spot welds were cratering and large-occluded gas pores. Significant metal loss due to spatter was measured during the initial 2 ms of keyhole mode welds. With increasing power intensity, there was an increased propensity for occluded gas pores near the bottom of the keyhole mode welds.

Liu, J.T.; Weckman, D.C.; Kerr, H.W. [Univ. of Waterloo, Ontario (Canada). Dept. of Mechanical Engineering

1993-12-01

241

Local properties of undermatched steel weld metal  

NASA Astrophysics Data System (ADS)

Samples from two undermatched, multipass welds on 50.8-mm-thick HY-100 steel were tested using a novel microtensile test machine and the local material properties were investigated using a chemical analysis, metallography, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The microtensile test technique allowed samples from individual weld beads and weldmetal heat-affected zones to be tested in three orthogonal directions. Relationships between local microhardness and tensile properties were established. The filler metals for the two welds were MIL-70S and MIL-100S. The MIL-70S weld formed ferritic microstructures; the weld-metal heat-affected sites were predominantly polygonal ferrite, while the as-deposited regions were a mixture of lath and polygonal ferrite. This weld showed a large variation in properties from the central weld bead to the outer ones. The outermost site exhibited significant anisotropy in strength that was not revealed by microhardness measurements. The yield strength specification was 483 MPa, while the average at the center of the weld was 675 MPa and the outer sites had an average of 445 MPa. Elongation for the samples from the center was significantly lower as well, 5 pct as compared to 18 pct for the outer sites. The yield strength showed a strong correlation with the size of inclusions measured by TEM. Microprobe analysis found no dilution of the base metal alloying additions into the weld metal. The MIL-100S filler formed predominantly fine acicular ferrite throughout the weld. The strength was much more uniform; the yield strength specification was 690 MPa, while the center of the weld was 756 MPa and the outer sites had an average of 616 MPa. The inclusion size did not play an important role in the variation in mechanical properties.

Lavan, David A.; Sharpe, W. N.

2001-04-01

242

Laser Keyhole Welding: The Vapour Phase  

NASA Astrophysics Data System (ADS)

Several aspects of the properties of the keyhole and its relationship to the weld pool in laser keyhole welding are considered. The aspect of most immediate importance is the exchange of energy between the laser beam itself and the molten material of the weld pool. Many mechanisms are involved, but the two considered here are the process of direct absorption at the keyhole wall (Fresnel absorption) and the two-stage process of absorption of energy by inverse bremsstrahlung into the ionised vapour that forms in the case of the longer-wavelength lasers such as the CO2, laser, followed by thermal conduction to the wall. Consideration is given to the role of the Knudsen layer at the boundary. The possibility that the exchange may be influenced by the vapour flow in the keyhole is considered. More generally, the dynamics of the flow is investigated and the balances necessary to keep the keyhole open are investigated. A simple model of the interaction of the vapour with the molten material in the weld pool is proposed which can be used to investigate their interaction. Order of magnitude estimates suggest that it is far from simple but that some simplifying approximations are possible.

Dowden, John

243

Performance Study and Dynamic Optimization Design for Thread Pool Systems.  

National Technical Information Service (NTIS)

Thread pools have been widely used by many multithreaded applications. However, the determination of the pool size according to the application behavior still remains problematic. To automate this process, in this thesis we have developed a set of perform...

D. Xu

2004-01-01

244

FCAW orbital pipe welding technology improves fab shop productivity  

SciTech Connect

Fabricators, like all companies facing increasing competition, are reevaluating and redesigning work flow and plant layout, and implementing new techniques to improve productivity and reduce work-in-process times. Submerged arc welding (SAW) has been widely used for years to produce high-quality mechanized butt joint welds in pipe, but requires workpieces to be rotated under a fixed torch. Submerged arc welding can provide high deposition rates, but requires considerable capital expenditures for turning rolls and positioners, especially if the pipe work consists of larger-diameter pipe, long lengths and heavy assemblies. Spool pieces with complex or asymmetrical configurations (elbows, for example) often cannot be conveniently rotated without special and time-consuming fixturing. Many assemblies may consist of pipe connections that must be made in position. Traditionally, these welds have been made using manual techniques: shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW) or a combination of processes by skilled welders. With the growing shortage of skilled welders worldwide, fabricators are increasingly evaluating different processes and techniques to compensate for less-skilled welders or to improve the productivity of their skilled work force. One technique increasingly being used in mechanized orbital flux cored arc welding (FCAW). FCAW might be thought of as the submerged arc process turned inside out. With SAW, a solid wire electrode is simultaneously fed into the weld pool along with powdered flux. Instead of solid wire, FCAW substitutes a metal tube or sheath, wrapped around a core of flux. The orbital systems on the market today use additional gas shielding of the weld pool. All-position FCAW wires are formulated with fluxing agents that promote rapid pool solidification, which allow welds to be made in all positions.

Emmerson, J.G.

1999-11-01

245

WELDING PROCESS  

DOEpatents

A method of joining metal parts for the preparation of relatively long, thin fuel element cores of uranium or alloys thereof for nuclear reactors is described. The process includes the steps of cleaning the surfaces to be jointed, placing the sunfaces together, and providing between and in contact with them, a layer of a compound in finely divided form that is decomposable to metal by heat. The fuel element members are then heated at the contact zone and maintained under pressure during the heating to decompose the compound to metal and sinter the members and reduced metal together producing a weld. The preferred class of decomposable compounds are the metal hydrides such as uranium hydride, which release hydrogen thus providing a reducing atmosphere in the vicinity of the welding operation.

Zambrow, J.; Hausner, H.

1957-09-24

246

WELDING APPARATUS  

DOEpatents

This patent covers an arrangement for replacing air in a welding chamber with an inert gas. This operation usually is time-consuming because of the tendency of the inert gas to mix with the air being removed from the welding chamber. The chamber is open at the bottom and has at its top a cover and a porous plate a little below the cover. The inert gas is admitted to the chamber through two screened openings in the cover. On passing through the porous plate, the gas acts as a piston extending across the chamber and moving downwardly to expel the air through the lower open end of the chamber, with a minimum of mixing with the air being expelled. (AEC)

Correy, T.B.; DeWitt, D.E.; Nelson, I.V.

1963-04-23

247

Second Phase Precipitation in As-Welded and Solution Annealed Alloy 22 Welds  

SciTech Connect

The precipitation characteristics of tetrahedrally close-packed (TCP) phases during the welding and the subsequent solution annealing process of Alloy 22 1 1/2 inch thick plate double-U prototypical welds are investigated. Electron backscatter diffraction (EBSD) was used to provide large scale microstructural observation of the weld cross section, and scanning electron microscopy (SEM) was used to map the location of the TCP phases. Analysis shows that TCP precipitation occurs congruent to the weld passes, with the solution annealing reducing the sizes of coarser precipitates.

El-Dasher, B S; Torres, S G

2005-01-12

248

ECS DAAC Data Pools  

NASA Astrophysics Data System (ADS)

As part of its Earth Observing System (EOS), NASA supports operations for several satellites including Landsat 7, Terra, and Aqua. ECS (EOSDIS Core System) is a vast archival and distribution system and includes several Distributed Active Archive Centers (DAACs) located around the United States. EOSDIS reached a milestone in February when its data holdings exceeded one petabyte (1,000 terabytes) in size. It has been operational since 1999 and originally was intended to serve a large community of Earth Science researchers studying global climate change. The Synergy Program was initiated in 2000 with the purpose of exploring and expanding the use of remote sensing data beyond the traditional research community to the applications community including natural resource managers, disaster/emergency managers, urban planners and others. This included facilitating data access at the DAACs to enable non-researchers to exploit the data for their specific applications. The combined volume of data archived daily across the DAACs is of the order of three terabytes. These archived data are made available to the research community and to general users of ECS data. Currently, the average data volume distributed daily is two terabytes, which combined with an ever-increasing need for timely access to these data, taxes the ECS processing and archival resources for more real-time use than was previously intended for research purposes. As a result, the delivery of data sets to users was being delayed in many cases, to unacceptable limits. Raytheon, under the auspices of the Synergy Program, investigated methods at making data more accessible at a lower cost of resources (processing and archival) at the DAACs. Large on-line caches (as big as 70 Terabytes) of data were determined to be a solution that would allow users who require contemporary data to access them without having to pull it from the archive. These on-line caches are referred to as "Data Pools." In the Data Pool concept, data is inserted via subscriptions based on ECS events, for example, arrival of data matching a specific spatial context. Upon acquisition, these data are written to the Data Pools as well as to the permanent archive. The data is then accessed via a public Web interface, which provides a drilldown search, using data group, spatial, temporal and other flags. The result set is displayed as a list of ftp links to the data, which the user can click and directly download. Data Pool holdings are continuously renewed as the data is allowed to expire and is replaced by more current insertions. In addition, the Data Pool may also house data sets that though not contemporary, receive significant user attention, i.e. a Chernobyl-type of incident, a flood, or a forest fire. The benefits are that users who require contemporary data can access the data immediately (within 24 hours of acquisition) under a much improved access technique. Users not requiring contemporary data, benefit from the Data Pools by having greater archival and processing resources (and a shorter processing queue) made available to them. All users benefit now from the capability to have standing data orders for data matching a geographic context (spatial subscription), a capability also developed under the Synergy program. The Data Pools are currently being installed and checked at each of the DAACs. Additionally, several improvements to the search capabilities, data manipulation tools and overall storage capacity are being developed and will be installed in the First Quarter of 2003.

Kiebuzinski, A. B.; Bories, C. M.; Kalluri, S.

2002-12-01

249

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

250

Modeling of thermal stresses in welds  

SciTech Connect

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

Zacharia, T.; Aramayo, G.A.

1993-12-31

251

Investigation of Microstructural Features Determining the Toughness of 980 MPa Bainitic Weld Metal  

NASA Astrophysics Data System (ADS)

The microstructural features that control the impact toughness of weld metals of a 980 MPa 8 pct Ni high-strength steel are investigated using instrumented Charpy V tester, optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), electron back-scattered diffraction (EBSD), and finite-element method (FEM) calculation. The results show that the critical event for cleavage fracture in this high-strength steel and weld metals is the propagation of a bainite packet-sized crack across the packet boundary into contiguous packets, and the bainitic packet sizes control the impact toughness. The high-angle misorientation boundaries detected in a bainite packet by EBSD form fine tear ridges on fracture surfaces. However, they are not the decisive factors controlling the cleavage fracture. The effects of Ni content are essential factors for improving the toughness. The extra large cleavage facets seriously deteriorate the toughness, which are formed on the interfaces of large columnar crystals growing in welding pools with high heat input.

Cao, R.; Zhang, X. B.; Wang, Z.; Peng, Y.; Du, W. S.; Tian, Z. L.; Chen, J. H.

2013-10-01

252

The dynamics of droplet formation and detachment in gas metal arc welding  

SciTech Connect

Experimental measurements of gas metal arc welding are required for the development and confirmation of models of the process. This paper reports on two experiments that provide information for models of the arc physics and of the weld pool dynamics. The heat transfer efficiency of the spray transfer mode in gas metal arc welding was measured using a calorimetry technique. The efficiency varied from 75 to 85%. A special fixture was used to measure the droplet contribution, which is determined to be between 35 and 45% of the total input energy. A series of experiments was performed at a variety of conditions ranging from globular to spray to streaming transfer. The transfer was observed by taking high-speed movies at 500 to 5000 frames per second of the backlighted droplets. An automatic image analysis system was used to obtain information about the droplets including time between detachments, droplet size, and droplet acceleration. At the boundary between the globular and spray modes, the droplet size varies between small droplets that melt off faster than average, resulting in a smaller electrode extension, and large droplets that melt off slower than average, resulting in an increase in the electrode extension. 5 refs., 4 figs., 2 tabs.

Johnson, J.A.; Smartt, H.B.; Clark, D.E.; Carlson, N.M.; Watkins, A.D.; Lethcoe, B.J.

1990-01-01

253

Heat transfer from internally heated hemispherical pools  

SciTech Connect

Experiments were conducted on heat transfer from internally heated ZnSO/sub 4/-H/sub 2/O pools to the walls of hemispherical containers. This experimental technique provides data for a heat transfer system that has to date been only theoretically treated. Three different sizes of copper hemispherical containers were used: 240, 280, 320 mm in diameter. The pool container served both as a heat transfer surface and as an electrode. The opposing electrode was a copper disk, 50 mm in diameter located at the top of the pool in the center. The top surface of the pool was open to the atmosphere.

Gabor, J.D.; Ellsion, P.G.; Cassulo, J.C.

1980-01-01

254

Three-dimensional modeling of the plasma arc in arc welding  

SciTech Connect

Most previous three-dimensional modeling on gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) focuses on the weld pool dynamics and assumes the two-dimensional axisymmetric Gaussian distributions for plasma arc pressure and heat flux. In this article, a three-dimensional plasma arc model is developed, and the distributions of velocity, pressure, temperature, current density, and magnetic field of the plasma arc are calculated by solving the conservation equations of mass, momentum, and energy, as well as part of the Maxwell's equations. This three-dimensional model can be used to study the nonaxisymmetric plasma arc caused by external perturbations such as an external magnetic field. It also provides more accurate boundary conditions when modeling the weld pool dynamics. The present work lays a foundation for true three-dimensional comprehensive modeling of GTAW and GMAW including the plasma arc, weld pool, and/or electrode.

Xu, G.; Tsai, H. L. [Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, 1870 Miner Circle, Rolla, Missouri 65409 (United States); Hu, J. [Department of Mechanical Engineering, University of Bridgeport, Bridgeport, Connecticut 06604 (United States)

2008-11-15

255

Three-dimensional modeling of the plasma arc in arc welding  

NASA Astrophysics Data System (ADS)

Most previous three-dimensional modeling on gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) focuses on the weld pool dynamics and assumes the two-dimensional axisymmetric Gaussian distributions for plasma arc pressure and heat flux. In this article, a three-dimensional plasma arc model is developed, and the distributions of velocity, pressure, temperature, current density, and magnetic field of the plasma arc are calculated by solving the conservation equations of mass, momentum, and energy, as well as part of the Maxwell's equations. This three-dimensional model can be used to study the nonaxisymmetric plasma arc caused by external perturbations such as an external magnetic field. It also provides more accurate boundary conditions when modeling the weld pool dynamics. The present work lays a foundation for true three-dimensional comprehensive modeling of GTAW and GMAW including the plasma arc, weld pool, and/or electrode.

Xu, G.; Hu, J.; Tsai, H. L.

2008-11-01

256

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; Zhang, Wei [ORNL; Yu, Zhenzhen [ORNL; Feng, Zhili [ORNL

2012-01-01

257

Introduction to Welding.  

ERIC Educational Resources Information Center

|This curriculum guide provides six units of instruction on basic welding. Addressed in the individual units of instruction are the following topics: employment opportunities for welders, welding safety and first aid, welding tools and equipment, basic metals and metallurgy, basic math and measuring, and procedures for applying for a welding job.…

Fortney, Clarence; Gregory, Mike

258

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

259

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

260

Thin plate gap bridging study for Nd:YAG pulsed laser lap welds.  

SciTech Connect

In an on going study of gap bridging for thin plate Nd:YAG laser lap welds, empirical data, high speed imaging, and computer modeling were utilized to better understand surface physics attributed to the formation and solidification of a weld pool. Experimental data indicates better gap bridging can be achieved through optimized laser parameters such as pulse length, duration, and energy. Long pulse durations at low energies generating low peak powers were found to create the highest percent of gap bridging ability. At constant peak power, gap-bridging ability was further improved by using a smaller spot diameter resulting in higher irradiances. Hence, welding in focus is preferable for bridging gaps. Gas shielding was also found to greatly impact gap-bridging ability. Gapped lap welds that could not be bridged with UHP Argon gas shielding, were easily bridged when left unshielded and exposed to only air. Incident weld angle and joint offset were also investigated for their ability to improve gap bridging. Optical filters and brightlight surface illumination enabled high-speed imaging to capture the fluid dynamics of a forming and solidifying weld pool. The effects of various laser parameters and the weld pool's interaction with the laser beam could also be observed utilizing the high-speed imaging. The work described is used to develop and validate a computer model with improved weld pool physics. Finite element models have been used to derive insight into the physics of gap bridging. The dynamics of the fluid motion within the weld pool in conjunction with the free surface physics have been the primary focus of the modeling efforts. Surface tension has been found to be a more significant factor in determining final weld pool shape than expected.

Roach, Robert Allen; Fuerschbach, Phillip William; Bernal, John E.; Norris, Jerome T.

2006-01-01

261

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

262

Pipeline welding goes mechanized  

Microsoft Academic Search

Spread four has bugs in the cornfield--but not to worry. The bug referred to here is a mechanized welding bug, specifically a single welding head, computer-aided gas metal arc (GMAW) system from CRC-Evans Automatic Welding powered by a Miller Electric XMT{reg{underscore}sign} 304 inverter-based welding machine. The bug operator and owner of 32 inverters is Welded Construction, L.P., of Perrysburgh, Ohio.

Beeson

1999-01-01

263

Alloying element vaporization during laser spot welding of stainless steel.  

SciTech Connect

Alloying element loss from the weld pool during laser spot welding of stainless steel was investigated experimentally and theoretically. The experimental work involved determination of work-piece weight loss and metal vapor composition for various welding conditions. The transient temperature and velocity fields in the weld pool were numerically simulated. The vaporization rates of the alloying elements were modeled using the computed temperature profiles. The fusion zone geometry could be predicted from the transient heat transfer and fluid flow model for various welding conditions. The laser power and the pulse duration were the most important variables in determining the transient temperature profiles. The velocity of the liquid metal in the weld pool increased with time during heating and convection played an increasingly important role in the heat transfer. The peak temperature and velocity increased significantly with laser power density and pulse duration. At very high power densities, the computed temperatures were higher than the boiling point of 304 stainless steel. As a result, evaporation of alloying elements was caused by both the total pressure and the concentration gradients. The calculations showed that the vaporization occurred mainly from a small region under the laser beam where the temperatures were very high. The computed vapor loss was found to be lower than the measured mass loss because of the ejection of tiny metal droplets owing to the recoil force exerted by the metal vapours. The ejection of metal droplets has been predicted by computations and verified by experiments.

Fuerschbach, Phillip William; DebRoy, Tarasankar (Pennsylvania State University); He, Xiuli (Pennsylvania State University)

2004-02-01

264

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 ...

265

Microstructure characteristics and mechanical properties of laser weld bonding of magnesium alloy to aluminum alloy  

Microsoft Academic Search

Weldability of magnesium alloy to aluminum alloy in laser weld bonded (LWB) joints was investigated. Results showed that magnesium\\/aluminum\\u000a could be easily joined by LWB under proper technological parameters. The weld was characterized by complex vortex flow at\\u000a the bottom, and there existed intermetallic compound layer between weld pool and lower sheet metal, which was composed of\\u000a the brittle phases

Liming Liu; Heng Wang; Gang Song; Jia’nan Ye

2007-01-01

266

Possible diagnostic signal for monitoring CO2 laser welding of aluminum alloy sheets  

Microsoft Academic Search

In an effort to look for a diagnostic signals for in-line monitoring during laser welding of aluminum alloy, a pyroelectric detector was used to record the reflected laser radiation from the weld pool when a CO2 laser welds aluminum alloy sheets. The signals were processed with a fast-Fourier transform (FFT). From the FFT spectrum strong components of the reflected laser

Hongping Gu; Walter W. Duley

1995-01-01

267

Electric Welding Equipment and Automation of Welding in Construction.  

National Technical Information Service (NTIS)

The main types of electric welding equipment and systems for automation of welding applied in construction are considered. Diagrams and characteristics of machines, transformers and automata for arc welding, and machines for resistance welding, including ...

S. G. Sarafanov S. M. Taz'ba Y. Y. Terent'ev E. S. Feder

1964-01-01

268

Modeling growth and dissolution of inclusions during fusion welding of steels  

Microsoft Academic Search

The characteristics of inclusions in the weld metals are critical factors to determine the structure, properties and performance of weldments. The research in the present thesis applied computational modeling to study inclusion behavior considering thermodynamics and kinetics of nucleation, growth and dissolution of inclusion along its trajectory calculated from the heat transfer and fluid flow model in the weld pool.

Tao Hong

2003-01-01

269

Thin plate gap bridging study for Nd:YAG pulsed laser lap welds  

Microsoft Academic Search

In an on going study of gap bridging for thin plate Nd:YAG laser lap welds, empirical data, high speed imaging, and computer modeling were utilized to better understand surface physics attributed to the formation and solidification of a weld pool. Experimental data indicates better gap bridging can be achieved through optimized laser parameters such as pulse length, duration, and energy.

Robert Allen Roach; Phillip William Fuerschbach; John E. Bernal; Jerome T. Norris

2006-01-01

270

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

Microsoft Academic Search

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

Z. Tang; M. Gatzen

2010-01-01

271

Verification of temperature distribution in the system for pad welding by means of infrared thermography  

Microsoft Academic Search

The heat transfer in the system for pad welding of plates is considered. Particularly, the presence of air gap between the padded material and technological stand is investigated. The air gap appears due to the extremely high temperatures in the vicinity of the welding pool, which involve a deformation of the padded plate. The heat resistance of the air gap

I. Szczygie?; A. Fic; T. Kruczek; A. Sachajdak

272

Finite volume methods applied to the computational modelling of welding phenomena  

Microsoft Academic Search

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

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

2002-01-01

273

A Study on Analysis of Weld Distortion in Multi-pass Arc Welding  

NASA Astrophysics Data System (ADS)

Since prediction and control of welding deformation are one of an important problems connected with reliability of the manufactured structures, welding deformation should be measured and controlled with quickly and actively. Also, welding variables which have lots of effects on welding deformation such as arc voltage, welding current and welding speed can also be controlled. This study focuses on development of a simple 2D(a two-dimension) FEM(Finite Element Method) to calculate not only the transient thermal histories, but also the sizes of Fusion Zone(HZ) and Heat-Affected Zone (HAZ) in multi-pass arc welding including the butt weld type with dissimilar thickness, and to develop the new model for finding the parameters of Godak's heat source model based on a GA(Genetic Algorithm). The developed model included a GA program using MATLB and GA toolbox, and a batch mode thermal model using ANSYS software. The thermal model was verified by comparison with Goldak's work and the molten zone section from obtained the experimental data. In addition, the developed model could be applied the various welding types in order to employ for the manufacturing industries.

Lee, J. H.; Kim, I. S.; Jang, H. K.; Kim, H. J.; Kwak, S. K.; Ryoo, H. S.; Hong, S. H.; Shim, J. Y.

2011-01-01

274

A Pooled Exploratory Analysis of the Effect of Tumor Size and KRAS Mutations on Survival Benefit from Adjuvant Platinum-Based Chemotherapy in Node Negative Non-Small Cell Lung Cancer  

PubMed Central

Introduction Staging of node negative (N0) non-small cell lung cancer is modified in the 7th edition TNM classification. Here, we pool data from JBR.10 and CALGB-9633 to explore the prognostic and predictive effects of the new T-size descriptors and KRAS mutation status. Methods Node negative patients were reclassified as T2a (>3-?5cm), T2b (>5-?7cm), T3 (>7cm) or T?3 cm (?3cm but other T2 characteristics). Results Of 538 eligible patients, 288 (53.5%) were T2a, 111 (21%) T2b, 62 (11.5%) T3, while 77 (14%) T?3cm were excluded to avoid confounding. KRAS mutations were detected in 104/390 (27%) patients. T-size was prognostic for disease-free survival (DFS; p=0.03), but borderline for overall survival (OS; p=0.10), on multivariable analysis. Significant interaction between the prognostic value of KRAS and tumor size was observed for OS (p=0.01), but not DFS (p=0.10). There was a non-significant trend (p=0.24) for increased chemotherapy effect on OS with advancing T-size (HR T2a 0.90, [0.63-1.30]; T2b 0.69, [0.38-1.24]; and T3 0.57, [0.28-1.17]). The HR for chemotherapy effect on OS in T2a patients with KRAS wild-type tumors was 0.81 (p=0.36), while a trend for detrimental effect was observed in those with mutant tumors (HR 2.11; p=0.09; interaction p=0.05). Similar trends were observed in T2b-T3 patients with wild-type (HR 0.86; p=0.62), and KRAS mutant tumors (HR 1.16; p=0.74; interaction p=0.58). Conclusion Chemotherapy effect appears to increase with tumor size. However, this small study could not identify subgroups of patients who did or did not derive significant benefit from adjuvant chemotherapy based on T-size or KRAS status.

Cuffe, Sinead; Bourredjem, Abderrahmane; Graziano, Stephen; Pignon, Jean-Pierre; Domerg, Caroline; Ezzalfani, Monia; Seymour, Lesley; Strevel, Elizabeth; Burkes, Ronald; Capelletti, Marzia; Janne, Pasi A.; Tsao, Ming-Sound; Shepherd, Frances A.

2012-01-01

275

Analysis of evaporation in laser welding  

NASA Astrophysics Data System (ADS)

The evaporation process in CO2 laser welding was analyzed experimentally on the basis of evaporation and soot deposition rates, light scattering and plasma behavior. Heavier shielding gas results in more soot deposition by carrying the condensed particles to the work surface. At power density, 2-3 x 10(exp 5) W/sq cm), which is just below the critical value for deep penetration welding, the soot deposition becomes heaviest with accompanying violent fluctuation of the light emission of the plasma. A hypothetical mechanism of the soot deposition is proposed; at 2-3 x 10(exp 5) W/sq cm, the molten pool surface is hemispherically depressed by the recoil force of evaporation, and acts like a concave mirror to refocus the reflected laser beam within the plasma plume to heat it up. The adiabatic expansion of the plasma caused by the molten pool motion plays an important role to condense the vapor into the soot.

Miyamoto, Isamu

1995-04-01

276

A theoretical model for gas metal arc welding and gas tungsten arc welding. I.  

NASA Astrophysics Data System (ADS)

A recently developed theory for predicting arc and electrode properties in gas metal arc welding (GMAW) has been generalized to include arc-electrode interfaces, variation of surface tension pressure with temperature, Marangoni forces and handling of weld pool development in stationary gas tungsten arc welding (GTAW). The new theory is a unified treatment of the arc, the anode, and the cathode, and includes a detailed account of sheath effects near the electrodes. The electrodes are included as dynamic entities and the volume of fluid method is used to handle the movement of the free surface of the molten metal at one electrode. Predictions can be made of the formation and shape of the welding droplets as a function of time in GMAW and also of weld pool development in GTAW, accounting for effects of surface tension, inertia, gravity, arc pressure, viscous drag force of the plasma, Marangoni effect and magnetic forces, and also for wire feed rate in GMAW. Calculations are made of current densities, electric potential, temperatures, pressures and velocities in two dimensions, both in the arc and also within the molten metal and solid electrodes. Calculations are presented for GMAW and GTAW for an arc in argon and the results are compared with experimental temperature measurements for the plasma and the electrodes.

Haidar, J.

1998-10-01

277

Effect of vibratory weld conditioning on welded valve properties  

Microsoft Academic Search

The approach to improve the quality of full welded valve by the application of vibratory weld conditioning (VWC) was investigated in this paper. The effect of VWC on the welded joint properties was studied. Cylinders with different thicknesses were welded by submerged arc welding (SAW). The experiment results show that the vibration applied during welding generally reduces the residual deformation

Lu Qinghua; Chen Ligong; Ni Chunzhen

2008-01-01

278

March madness? Strategic behavior in NCAA basketball tournament betting pools  

Microsoft Academic Search

This paper uses data from the natural experiment of NCAA Basketball Tournament “betting pools” in a descriptive study of strategic behavior. The observed behavior in these pools differs from equilibrium behavior in a robust manner; bettors overback the heaviest favorites. The size of this bias falls slightly in larger pools, where the induced profit opportunities are higher than in smaller

Andrew Metrick

1996-01-01

279

poolMC: Smart pooling of mRNA samples in microarray experiments  

PubMed Central

Background Typically, pooling of mRNA samples in microarray experiments implies mixing mRNA from several biological-replicate samples before hybridization onto a microarray chip. Here we describe an alternative smart pooling strategy in which different samples, not necessarily biological replicates, are pooled in an information theoretic efficient way. Further, each sample is tested on multiple chips, but always in pools made up of different samples. The end goal is to exploit the compressibility of microarray data to reduce the number of chips used and increase the robustness to noise in measurements. Results A theoretical framework to perform smart pooling of mRNA samples in microarray experiments was established and the software implementation of the pooling and decoding algorithms was developed in MATLAB. A proof-of-concept smart pooled experiment was performed using validated biological samples on commercially available gene chips. Differential-expression analysis of the smart pooled data was performed and compared against the unpooled control experiment. Conclusions The theoretical developments and experimental demonstration in this paper provide a useful starting point to investigate smart pooling of mRNA samples in microarray experiments. Although the smart pooled experiment did not compare favorably with the control, the experiment highlighted important conditions for the successful implementation of smart pooling - linearity of measurements, sparsity in data, and large experiment size.

2010-01-01

280

Performance Study and Dynamic Optimization Design for Thread Pool Systems  

SciTech Connect

Thread pools have been widely used by many multithreaded applications. However, the determination of the pool size according to the application behavior still remains problematic. To automate this process, in this thesis we have developed a set of performance metrics for quantitatively analyzing thread pool performance. For our experiments, we built a thread pool system which provides a general framework for thread pool research. Based on this simulation environment, we studied the performance impact brought by the thread pool on different multithreaded applications. Additionally, the correlations between internal characterizations of thread pools and their throughput were also examined. We then proposed and evaluated a heuristic algorithm to dynamically determine the optimal thread pool size. The simulation results show that this approach is effective in improving overall application performance.

Dongping Xu

2004-12-19

281

Effect of Welding Consumables on Arc Welding Process Control and Weld Metal Structure and Properties.  

National Technical Information Service (NTIS)

The effect of welding consumables on arc welding process control and weld metal structure and properties was investigated. The first study demonstrated the potential use of exothermically (thermite) assisting steel arc welding consumables for field repair...

D. L. Olson R. H. Frost

1998-01-01

282

Special Welding Technologies in Pipelines  

Microsoft Academic Search

The antigravitational welding processes are defined as the welding processes where the welding molten metal has the natural tendency to flow. The Welding Equipment and Technology researchers of Robotics and Welding Department of DUN?REA DE JOS UNIVERSITY FROM GALA?I- ROMANIA are working from 15 years on the field of antigravitational welding and performed theoretical and experimental activities. Experimental and industrial

Emil Costantin; Mihaela Iord?chescu

283

Laser cladding technique for welding of superthin foil  

NASA Astrophysics Data System (ADS)

It is difficult to get a good welding spot and nearly impossible to weld very thin metal foil (several microns) onto a foreign metal workpiece over 1000 times larger in size. It ls often the case when the foil has been vaporized and sputtered while the bigger piece to be welded is not heated. In this paper we introduce the laser powder-covered welding technique which has a high success rate. The finished welding spots forms a micro-rivet and the laser point welding is the most reliable mutual melting weld. Studies indicate that the laser-cladding technique poses special technical requirements to the melting dynamics of the powder materials. Some useful conclusions are given. The requirements to the parameters of laser pulse are quite different from those of ordinary laser welding. The main points of the technique and the micro-analyses of the welding spot and other features are given. The technique presented is a novel method of welding between tiny piece and workpiece of different size and properties.

Zhang, Qiu'e.; Li, Yongda; Zheng, Yong; Li, Li J.

2002-09-01

284

Laser beam welding of an Oxide Dispersion Strengthened super alloy  

Microsoft Academic Search

Laser beam welding was used successfully to join the Oxide Dispersion Strengthened Super alloy PM1000 for a range of welding\\u000a conditions. A microscopical study revealed a disturbed structure of dendrites and micro sized particles, which were formed\\u000a during the molten state of the weld process. Although the particles are a result of melting and clustering of the yttrium\\u000a oxide particles,

H. J. K. Lemmen; K. J. Sudmeijer; I. M. Richardson; S. van der Zwaag

2007-01-01

285

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

286

Lung surfactant in a cystic fibrosis animal model: increased alveolar phospholipid pool size without altered composition and surface tension function in cftrm1HGU/m1HGU mice  

PubMed Central

BACKGROUND: Progressive pulmonary dysfunction is a characteristic symptom of cystic fibrosis (CF) and is associated with functional impairment and biochemical alterations of surfactant phospholipids in the airways. However, the fundamental question of whether surfactant alterations in the CF lung are secondary to the pulmonary damage or are present before initiation of chronic infection and inflammation has yet to be resolved in patients with cystic fibrosis but can now be addressed in CF mice that exhibit the basic defect in the airways. A study was therefore undertaken to investigate the pool sizes, composition, and function of lung surfactant in the non-infected cftrm1HGU/m1HGU mouse. METHODS: The amount and composition of phospholipid classes and phosphatidylcholine molecular species were determined in bronchoalveolar lavage (BAL) fluid and lavaged lungs by high performance liquid chromatography (HPLC). Surfactant protein A (SP- A) levels in BAL fluid were determined by ELISA and surfactant for functional measurements was isolated from BAL fluid by differential ultracentrifugation. Equilibrium and minimal surface tension of surfactant was assessed by the pulsating bubble surfactometer technique. MF1, BALB/c, C57/BL6, and C3H/He mice served as controls. RESULTS: BAL fluid of cftrm1HGU/m1HGU mice contained 1.02 (95% confidence interval (CI) 0.89 to 1.16) mumol phospholipid and 259 (239 to 279) ng SP-A. BAL fluid of MF1, BALB/c, C57BL/6, and C3H/He mice contained 0.69 (0.63 to 0.75), 0.50 (0.42 to 0.57), 0.52 (0.40 to 0.64), and 0.45 (0.27 to 0.63) mumol phospholipid, respectively. After correction for the different body weights of mouse strains, phospholipid levels in BAL fluid of cftrm1HGU/m1HGU mice were increased by 64 (52 to 76)%, 60 (39 to 89)%, 72 (45 to 113)%, and 92 (49 to 163)%, respectively, compared with controls. The amount of SP-A in BAL fluid and the composition of phospholipid as well as phosphatidylcholine molecular species in BAL fluid and lung tissue was unchanged in cftrm1HGU/m1HGU mice compared with controls. The increase in phospholipids in BAL fluid of cftrm1HGU/m1HGU mice resulted from an increased fraction of large aggregates which exhibited normal surface tension function. CONCLUSION: In cftrm1HGU/m1HGU mice surfactant homeostasis is perturbed by an increased phospholipid pool in the alveolar compartment. ???

Bernhard, W.; Wang, J. Y.; Tschernig, T.; Tummler, B.; Hedrich, H. J.; von der Hardt, H.

1997-01-01

287

Pools, riffles, and channelization  

Microsoft Academic Search

The addition of regularly spaced deeps (pools) and shallows (riffles) that provide a variety of flow conditions, areal sorting\\u000a of stream-bed material, cover for wildlife, and a positive aesthetic experience, may be desirable in many channel projects.\\u000a Such designs will reduce adverse environmental impacts of stream channel modifications.\\u000a \\u000a Analysis of variance for pool-to-pool spacing data suggests that there is no

Edward A. Keller

1978-01-01

288

CO 2 and diode laser welding of AZ31 magnesium alloy  

NASA Astrophysics Data System (ADS)

Magnesium alloys are being increasingly used in automotive and aerospace structures. Laser welding is an important joining method in such applications. There are several kinds of industrial lasers available at present, including the conventional CO 2 and Nd:YAG lasers as well as recently available high power diode lasers. A 1.5 kW diode laser and a 2 kW CO 2 laser are used in the present study for the welding of AZ31 alloys. It is found that different welding modes exist, i.e., keyhole welding with the CO 2 laser and conduction welding with both the CO 2 and the diode lasers. This paper characterizes welds in both welding modes. The effect of beam spot size on the weld quality is analyzed. The laser processing parameters are optimized to obtain welds with minimum defects.

Zhu, Jinhong; Li, Lin; Liu, Zhu

2005-07-01

289

Physicochemical characterisation of different welding aerosols  

Microsoft Academic Search

Physicochemical properties important in exposure characterisation of four different welding aerosols were investigated. Particle\\u000a number size distributions were determined by scanning mobility particle sizer (SMPS), mass size distributions by separation\\u000a and weighing the individual size fractions of an 11-stage cascade impactor. The size distribution of the primary particles\\u000a of agglomerates, chemical composition and morphology of the particles were examined by

B. Berlinger; N. Benker; S. Weinbruch; M. Ebert; W. Koch; D. G. Ellingsen; Y. Thomassen

2011-01-01

290

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

291

Instructional Guidelines. Welding.  

ERIC Educational Resources Information Center

|Using the standards of the American Welding Society and the American Society of Mechanical Engineers, this welding instructional guidelines manual presents a course of study in accordance with the current practices in industry. Intended for use in welding programs now practiced within the Federal Prison System, the phases of the program are…

Fordyce, H. L.; Doshier, Dale

292

Welding Course Curriculum.  

ERIC Educational Resources Information Center

|This guide is intended for use in helping students gain a fundamental background on the major aspects of the welding trade. The course emphasis is on mastery of the manipulative skills necessary to develop successful welding techniques and on acquisition of an understanding of the specialized tools and equipment used in welding. The first part…

Genits, Joseph C.

293

Virtual Training for Welding  

Microsoft Academic Search

A mixed reality system has been created for simulating gas metal arc welding (GMAW) welding. This simulation system is intended for use in training human welders. The system is comprised of a real welding torch attached to a force feedback device, a head-mounted display, a 6 DOF tracking system for both the torch and the user's head, and external audio

Kenneth Fast; Timothy Gifford; Robert Yancey

2004-01-01

294

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

295

Microwave welding of thermoplastics  

Microsoft Academic Search

The aim of this work was to develop a new and versatile method for welding thermoplastics using microwave energy. A multimode cavity applicator was developed including features designed to deliver an even energy density and to apply weld pressure. A review of possible microwave susceptible implant materials was undertaken and results of welding trials using several candidate materials showed that

R. J. Wise; I. D. Froment

2001-01-01

296

On the Variability of Giant Sea-Salt Size Distributions as Observed from Aircraft during the VOCALS Campaign: Relationship to Marine Stratocumulus, Cold Pools and Implications for Drizzle Formation  

NASA Astrophysics Data System (ADS)

This study presents a quantum leap in the observations of marine sea-salt size distributions. The observations are obtained with a new instrument, the Giant Nucleus Impactor (GNI), which consists of polycarbonate slides exposed in the free airstream outside an aircraft, followed by storage in desiccated test tubes. The slides are subsequently analyzed in the laboratory, using a humidified automatic optical digital microscope system. The instrument has been extensively characterized in terms of uncertainty. 450 slides, each with typical sample volumes of 300 liters and ~50,000 particles per slide, were exposed from the NSF/NCAR C-130 research aircraft during the 2008 VOCALS campaign over the Pacific Ocean off the coast of Chile. The observed particle size range is 0.7 ?m - 12 ?m dry radius range for relatively low wind speeds of 1-14 m/s in the marine boundary layer. Figure 1 shows the aerosol mass loading as a function of wind speed for 286 slides that were exposed within a narrow altitude range 120 - 180 m above the sea surface. All slides obtained within a single flight are shown with the same symbol. The figure shows a general trend of higher mass loading with increasing wind speed, but at the same time a clustering of the measurements obtained within a given day. This suggest that wind speed is not the sole determinant of the giant sea salt mass loading, but the action of other factors, possibly cold pools or wave fields that are not in balance with the wind at the time of the slide exposures. The implications for drizzle precipitation formation are considerable. The concentration of the largest of the giant sea-salt particles are related to the observations of drizzle drops in the VOCALS stratocumulus in the vicinity of the exposed slides. In-cloud observations of cloud droplet size spectra as well as drizzle drop spectra shows two important conclusions: In lightly drizzling clouds (low drizzle drop concentrations of a few per litre), the drizzle drop concentrations can be explained if drizzle drops form on all particles larger than about 4 ?m dry radius. In more intense drizzling clouds (drizzle drop concentrations of about 100 per litre), almost all giant sea-salt particles with dry radius > 1 ?m dry radius are needed to explain the observed drizzle drop concentrations. Even so, these intensely precipitating clouds are also characterized by large cloud droplets. The implementation of giant sea-salt particles as nuclei for warm rain in large-scale models is implemented using a "toss-box" model, which includes both condensational and coalescence growth.

Jensen, J.

2012-04-01

297

The effect of weld bead dimensions on the fatigue strength of cruciform joints  

Microsoft Academic Search

The choice of weld bead size in the case of welded cruciform joints can be problematic, especially when the sheets forming the joint are of differing thickness. Technological standards generally recommend a weld bead thickness less than the minimum thickness of the sheets to be joined, whereas structural standards do not envisage any dependency between joint static and fatigue strength

B. Atzori; G. Demelio; B. Rossi

2012-01-01

298

The effect of weld bead dimensions on the fatigue strength of cruciform joints  

Microsoft Academic Search

The choice of weld bead size in the case of welded cruciform joints can be problematic, especially when the sheets forming the joint are of differing thickness. Technological standards generally recommend a weld bead thickness less than the minimum thickness of the sheets to be joined, whereas structural standards do not envisage any dependency between joint static and fatigue strength

B. Atzori; G. Demelio; B. Rossi

2011-01-01

299

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

300

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

301

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

302

A dimensionless parameter model for arc welding processes  

NASA Astrophysics Data System (ADS)

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

Fuerschbach, P. W.

303

A dimensionless parameter model for arc welding processes  

SciTech Connect

A dimensionless parameter model previously developed for C0{sub 2} laser beam welding has been shown to be applicable to GTAW and PAW autogenous arc welding processes. The model facilitates estimates of weld size, power, and speed based on knowledge of the material`s thermal properties. The dimensionless parameters can also be used to estimate the melting efficiency, which eases development of weld schedules with lower heat input to the weldment. The mathematical relationship between the dimensionless parameters in the model has been shown to be dependent on the heat flow geometry in the weldment.

Fuerschbach, P.W.

1994-12-31

304

Prediction of Submerged Arc Welding Yield Parameters through Graphical Technique  

Microsoft Academic Search

In submerged arc welding (SAW), selecting appropriate values for process variables is essential in order to control bead size and quality. Also, condition must be selected that will ensure a predictable weld bead, which is critical for obtaining high quality. In this investigation, mathematical models (based on multi-regression method) have been developed and side by side prediction through artificial neural

Aniruddha Ghosh; Somnath Chattopadhyaya; R. K. Das; P. K. sarkar

2011-01-01

305

Particle-reinforced metal matrix composite as a weld deposit  

Microsoft Academic Search

Weld metal consisting of particulate-reinforced metal matrix composite structure was produced with ceramic or refractory metal powder filled cored wire. Results are presented for both gas tungsten arc and gas metal arc weldments on Type 304 stainless steel. The effect of powder particle density and size distribution on the dispersion of particulates in the weld deposit was investigated. The motion

E. I. Kivineva; D. L. Olson; D. K. Matlock

1995-01-01

306

Real-time control in pulsed laser welding  

NASA Astrophysics Data System (ADS)

The possibilities of pulsed laser welding of aluminium alloys monitoring are investigated. Simple finite element modeling of conduction and keyhole welding has been carried out. A complete instrumentation has been set up, including beam and plasma monitoring and impact shape and size measurements. This set up enables a real time monitoring of the seam and the detection of critical defects.

de Charette, Regis; Coste, Frederic; Sabatier, Lilian; Chevalier, Jean-Pierre

1996-09-01

307

Probing liquation cracking and solidification through modeling of momentum, heat, and solute transport during welding of aluminum alloys  

SciTech Connect

A transport phenomena-based mathematical model is developed to understand liquation cracking in weldments during fusion welding. Equations of conservation of mass, momentum, heat, and solute transport are numerically solved considering nonequilibrium solidification and filler metal addition to determine the solid and liquid phase fractions in the solidifying region and the solute distribution in the weld pool. An effective partition coefficient that considers the local interface velocity and the undercooling is used to simulate solidification during welding. The calculations show that convection plays a dominant role in the solute transport inside the weld pool. The predicted weld-metal solute content agreed well with the independent experimental observations. The liquation cracking susceptibility in Al-Cu alloy weldments could be reliably predicted by the model based on the computed solidifying weld-metal composition and solid fraction considering nonequilibrium solidification.

Mishra, S.; Chakraborty, S.; DebRoy, T. [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802-5005 (United States)

2005-05-01

308

Size effects in the fatigue behavior of welded steel tubular bridge joints Gro¨ßeneffekte beim Ermudungsverhalten von geschweißten kreisformigen Stahl- hohlprofilverbindungen fur den Bruckenbau  

Microsoft Academic Search

Tubular space trusses for bridge applications use thick-walled tubes. The reduction in fatigue resistance due to geometrical size effects is thus an important issue. In order to carry out a thor- ough study, both fatigue tests on large-scale specimens and ad- vanced 3D crack propagation modelling were carried out at ICOM\\/EPFL. The study is limited to circular hollow sections (CHS)

A. Nussbaumer; L. A. Costa Borges

309

Application of Island Biogeography Theory to Temporary Pools  

Microsoft Academic Search

One aspect of island biogeography theory contends that a direct correlation exists between the size of an island and the species richness of an island. We applied this aspect of island biogeography theory to temporary pools. Six temporary pools were randomly selected and placed into three size categories based on the volume of water contained in each. The contents were

Ferrella March; David Bass

1995-01-01

310

Method for welding beryllium  

DOEpatents

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

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

1997-01-01

311

Welding, terms and definitions  

SciTech Connect

This book provides a dictionary of the technical language used in the welding industry. Its purpose is to establish standard terms to aid in the communication of welding information. Since it is intended to be a comprehensive compilation of welding terminology, nonstandard terms used in the welding industry are also included. All terms are either standard or non-standard. They are arranged in the conventional dictionary letter-by-letter alphabetical sequence. A total of 946 terms are defined and the definitions are illustrated by 41 Figures. Also included is the Master Chart of Welding and Allied Processes and the Joining Method Diagram with corollary classification diagrams.

Not Available

1985-01-01

312

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

313

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

314

Influence of saw fluxes on low-carbon steel weld microstructure  

Microsoft Academic Search

The influence of submergedarc flux composition on the inclusion morphology and weld metal microstructures of low carbon steels\\u000a is investigated. Systematic weld oxygen variations and changes in inclusion shape and size are obtained by changing the welding\\u000a flux composition. The influence of inclusion content, morphology, and distribution on achieving specific types of weld metal\\u000a ferrite is described.

J. W. Jang; S. Shah; J. E. Indacochea

1987-01-01

315

Stress corrosion cracking susceptibility of friction stir welded AA7075–AA6056 dissimilar joint  

Microsoft Academic Search

Two aluminium alloys, AA7075 and AA6056, were friction stir welded, with the AA7075 alloy placed on the advancing side of the welding tool. Microstructural observations revealed the development of a recrystallised fine-grained weld nugget, with two different grain sizes, resulting from the two different base materials. Slow strain rate tensile (SSRT) tests in air have shown that the weld nugget

P. Bala Srinivasan; W. Dietzel; R. Zettler; J. F. dos Santos; V. Sivan

2005-01-01

316

Effect of oxide inclusions on the kinetics of the austenite to ferrite transformation in low alloy steel weld metal.  

National Technical Information Service (NTIS)

Isothermal transformation kinetics of austenite to acicular ferrite and allotriomorphic ferrite were measured in reheated low alloy steel weld deposits with similar weld compositions and austenite grain size but different inclusion characteristics. Accele...

S. S. Babu S. A. David J. M. Vitek T. DebRoy

1994-01-01

317

(Welding under extreme conditions)  

SciTech Connect

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

Davis, S.A.

1989-09-29

318

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

319

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

320

Monitoring pool-tail fines  

NASA Astrophysics Data System (ADS)

Fine sediment < 2 and < 6 mm deposited in pool-tail areas of mountain streams is often measured to monitor changes in the supply of fines (e.g., by dam removal, bank erosion, or watershed effects including fires and road building) or to assess the status and trend of aquatic ecosystems. Grid counts, pebble counts, and volumetric bedmaterial samples are typically used to quantify pool-tail fines. Grid-count results exhibit a high degree of variability not only among streams and among operators, but also among crews performing a nearly identical procedure (Roper et al. 2010). Variability is even larger when diverse methods are employed, each of which quantifies fines in a different way: grid counts visually count surface fines on small patches within the pool-tail area, pebble counts pick up and tally surface particles along (riffle) transects, and volumetric samples sieve out fines from small-scale bulk samples; and even when delimited to pool-tail areas, individual methods focus on different sampling locales. Two main questions were analyzed: 1) Do pool-tail fines exhibit patterns of spatial variability and are some grid count schemes more likely to provide accurate results than others. 2) How and why does the percentage of fines vary among grid counts, pebble counts, and volumetric samples. In a field study, grids were placed at 7 locales in two rows across the wetted width of 10 pool tails in a 14-m wide 3rd order coarse gravel-bed mountain stream with <4% sand and <8% < 6 mm. Several pebble count transects were placed across each pool-tail area, and three volumetric samples were collected in each of three pool tails. Pebble and grid counts both indicated a fining trend towards one or both banks, sometimes interrupted by a secondary peak of fines within the central half of the wetted width. Among the five sampling schemes tested, grid counts covering the wetted width with 7 locales produced the highest accuracy and the least variability among the pools of the reach. Pebble counts between the two waterlines indicated 2-3 times more fines than grid counts, likely because grid counts did not extend exactly up to the waterline. However, when confined to the central 50% of the wetted width, grid counts indicated 1.2 and 1.6 times more fines < 2 and < 6 mm than pebble counts, likely because the plexiglass viewer used with grid counts improved the visibility of the bed. Volumetric armor layer samples (particles > 90 mm removed) indicated 1.4 and 1.2 times more fines < 2 and < 6 mm than grid counts at the same locales, while subarmor samples had 8-9 times more fines. In conclusion, methodological differences and the specific sampling locales selected by a method affect comparability of sampling results. Grid count accuracy and precision may be improved by extending both the width coverage and the sample size within a pool tail.

Bunte, K.; Potyondy, J. P.; Abt, S. R.; Swingle, K. W.

2010-12-01

321

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

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

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

322

Laser welding beryllium in a deuterium atmosphere  

Microsoft Academic Search

Methods for laser welding beryllium in high pressure deuterium atmospheres were investigated. The methods included direct fusion welds, braze welds and fusion welds in aluminum coatings on beryllium. Bead-on-plate laser welds were made in deuterium, argon and helium atmospheres. Severe porosity was observed in welds made in deuterium atmospheres. Weld cracking was observed in welds made in inert gas atmospheres.

G. E. Faulkner; T. J. Ramos; J. R. Murchie

1982-01-01

323

Pooling of urine specimens for PCR testing: a cost saving strategy for Chlamydia trachomatis control programmes  

Microsoft Academic Search

OBJECTIVES: To evaluate pooling of first catch urine (FCU) specimens as a cost effective strategy for chlamydia testing. METHODS: Mock specimens were pooled with and without dilution to determine optimal pool size and ease of work flow. The performance of the Amplicor Chlamydia trachomatis PCR assay on pooled specimens was compared with individual testing using 370 FCU specimens from asymptomatic

R. W. Peeling; B. Toye; P. Jessamine; I. Gemmill

1998-01-01

324

Stitch-Bond Parallel-Gap Welding for IC Circuits: Stitch-bonded flatbacks can be superior to soldered dual-in-lines where size, weight, and reliability are important.  

National Technical Information Service (NTIS)

This citation summarizes a one-page announcement of technology available for utilization. Flatback integrated circuits installed by stitch-bond/parallel-gap welding can be considerably more economical for complex circuit boards than conventional solder-in...

1981-01-01

325

Thermostatics and thermodynamics of surface tension in weld pools  

SciTech Connect

Thermostatics (classical or ''global'' thermodynamics) in the form of the Gibbs' adsorption isotherm is used to demonstrate the relationship of surface-active solutes to the temperature coefficient of surface tension. The structure of the surface layer may also be deduced. Thermodynamics (irreversible or ''local'') has been applied to the surface. The analysis provides a thermodynamic basis for the Marangoni effect.

Papazian, H.A.

1986-02-01

326

Elucidation of laser welding phenomena and factors affecting weld penetration and welding defects  

Microsoft Academic Search

The behavior and effect of a plasma plume on the weld penetration are greatly different between CO2 laser welding and YAG, disk or fiber laser welding. The effects of the power and the power density on the weld penetration are elucidated. Spattering leading to the formation of underfilled weld beads is controlled by inclining the laser beam. Porosity is formed

Seiji Katayama; Yousuke Kawahito; Masami Mizutani

2010-01-01

327

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

328

Optimal welding of beta titanium orthodontic wires.  

PubMed

Today the orthodontist is confronted by an array of new orthodontic wire materials that, when applied to appliance design, can vastly increase the flexibility and versatility of therapy. Welded joints, especially for the newer titanium alloy wires, provide a means to extend the useful applications of these materials. The purpose of this study was to determine the optimum settings for electrical resistance welding of various configurations of titanium-molybdenum (TMA) wires. Specimens were of a t-joint configuration and were mechanically tested in torsion to simulate the failure mode most often observed in clinical practice. Variables included wire size, wire orientation, and welding voltage. Results indicated that excellent welds can be obtained with very little loss of strength and ductility in the area of the weld joint. Torsional loads at failure were at least 90% of the unwelded base material. Although a wide range of voltage settings resulted in high-strength welds, typically a narrow range of voltages yielded optimal ductility. PMID:2888304

Nelson, K R; Burstone, C J; Goldberg, A J

1987-09-01

329

Electroslag Welding on Hydraulic Machinery.  

National Technical Information Service (NTIS)

The use of consumable guide electroslag welding process with components for hydraulic machinery having curved and profiled seams is described. Tests were carried out to optimize the welding parameters and the mechanical properties of welding joints with c...

E. Schorer F. J. Edel A. Borontschuk

1983-01-01

330

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

331

Swimming pool cleaner poisoning  

MedlinePLUS

... acids in them, or breathes in their fumes. Chlorine, a chemical in swimming pool cleaners, is more ... Bromine Calcium chloride Calcium hypochlorite Chelated copper ... bisulfate, phosphoric acid, sodium thiosulfate, cyanuric acid)

332

Storage Pool Deficiencies  

MedlinePLUS

... should be performed by a specialist at a hemophilia treatment centre. In people with storage pool deficiencies: The ... Hemophilia How Do You Get Hemophilia? Severity of Hemophilia Symptoms & Diagnosis Treatment Hemophilia in Pictures FAQs Resources Carriers and Women ...

333

An integrated meso-scale numerical model of melting and solidification in laser welding  

NASA Astrophysics Data System (ADS)

The authors present an integrated numerical model for the simulation of laser spot welding of an aluminium alloy at meso-scale in 2D. This model deals with the melting of the parent materials which form the weld pool and the subsequent solidification of the liquid metal in the pool, during the welding process. The melting of the parent materials due to the applied heating power is an important phenomenon, which determines the conditions at the onset of solidification, such as the geometry of the weld pool and the distribution of the temperature field. An enthalpy method is employed to predict the melting during the heating phase of welding. A Gaussian distribution is used to model the heat input from the laser. Once the laser beam is switched off and the melting halts, solidification commences. The UCD front tracking model [1,2] for alloy solidification is applied to predict the advancement of the columnar dendritic front, and a volume-averaging formulation is used to simulate nucleation and growth of equiaxed dendrites. A mechanical blocking criterion is used to define dendrite coherency, and the columnar-to-equiaxed transition within the weld pool is predicted.

Duggan, G.; Tong, M.; Browne, D. J.

2012-01-01

334

Analysis of effect of temperature gradients on surface-tension phenomena in gas-tungsten-arc welds  

SciTech Connect

Fluid motion directed by surface tension is considered as a contributor to heat penetration in a weld pool. The potential phenomena at the gas-liquid interface were analyzed, and the dependence of surface motion on temperature in the gas-tungsten-arc (GTA) welding process was examined. An existing heat-transfer model was used and was able to predict weld size to +- 50% of the actual value. A momentum-transfer equation was derived by considering the contribution of Lorentz force. The momentum boundary condition was developed and was able to predict the Marangoni effect. The magnitude of surface-tension-driven force is comparable to the gravitational force on one gram. An empirical approach was proposed to couple heat-transfer and momentum-transfer phenomena. A dimensional analysis identified the pertinent dimensionless groups as Reynolds, Weber, Froude, Peclet, and Power numbers and a dimensionless velocity. A simplified form of the correction was developed by combining dimensionless groups to yield a correlation with the Bond, Prandtl, and modified power numbers. Future experimental work was proposed to test the functionality of the dimensionless groups.

Lee, H.A.; Chien, P.S.J.

1982-10-01

335

Dye-enhanced laser welding for skin closure.  

PubMed

The use of a laser to weld tissue in combination with a topical photosensitizing dye permits selective delivery of energy to the target tissue. A combination of indocyanine green (IG), absorption peak 780 nm, and the near-infrared (IR) alexandrite laser was studied with albino guinea pig skin. IG was shown to bind to the outer 25 microns of guinea pig dermis and appeared to be bound to collagen. The optical transmittance of full-thickness guinea pig skin in the near IR was 40% indicating that the alexandrite laser should provide adequate tissue penetration. Laser "welding" of skin in vivo was achieved at various concentrations of IG from 0.03 to 3 mg/cc using the alexandrite at 780 nm, 250-microseconds pulse duration, 8 Hz, and a 4-mm spot size. A spectrum of welds was obtained from 1- to 20-W/cm2 average irradiance. Weak welds occurred with no thermal damage obtained at lower irradiances: stronger welds with thermal damage confined to the weld site occurred at higher irradiances. At still higher irradiances, local vaporization occurred with failure to "weld." Thus, there was an optimal range of irradiances for "welding," which varied inversely with dye concentration. Histology confirmed the thermal damage results that were evident clinically. IG dye-enhanced laser welding is possible in skin and with further optimization may have practical application. PMID:1377319

DeCoste, S D; Farinelli, W; Flotte, T; Anderson, R R

1992-01-01

336

WELDED JACKETED URANIUM BODY  

DOEpatents

A fuel element is presented for a neutronic reactor and is comprised of a uranium body, a non-fissionable jacket surrounding sald body, thu jacket including a portion sealed by a weld, and an inclusion in said sealed jacket at said weld of a fiux having a low neutron capture cross-section. The flux is provided by combining chlorine gas and hydrogen in the intense heat of-the arc, in a "Heliarc" welding muthod, to form dry hydrochloric acid gas.

Gurinsky, D.H.

1958-08-26

337

Underwater Stud Welding  

Microsoft Academic Search

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

K. Masubuchi; H. Ozaki; J. Chiba

1978-01-01

338

Dual wire welding torch and method  

DOEpatents

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

339

Role of surface-active elements during keyhole-mode laser welding  

NASA Astrophysics Data System (ADS)

During high power density laser welding of mild steel, the keyhole depth, liquid metal flow, weld geometry and weld integrity are affected by base-metal sulfur content and oxygen (O2) present in the atmosphere or shielding gas. The role of these surface-active elements during keyhole-mode laser welding of steels is not well understood. In order to better understand their effects, welding of mild steel specimens containing various concentrations of oxygen and sulfur are examined. In addition, a numerical model is used to evaluate the influence of the surface-active elements on heat transfer and fluid flow in keyhole-mode laser welding. Increase in base-metal sulfur concentration or O2 content of shielding gas results in decreased weld widths. Sulfur results in a negligible increase in penetration depth whereas the presence of O2 in shielding gas significantly affects the weld penetration. It has earlier been proposed that oxygen, if present in the shielding gas, can get introduced into the weld pool resulting in formation of carbon monoxide (CO) at the keyhole surface and additional pressure from CO can result in increased penetration. Numerical modelling has been used in this work to understand the effects of formation of CO on the keyhole and weld geometries.

Ribic, B.; Tsukamoto, S.; Rai, R.; DebRoy, T.

2011-12-01

340

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

341

Effects of residual stress, weld toe notch and weld defects on fatigue of welded steel structures  

Microsoft Academic Search

In studying the fatigue behavior of fillet welded railroad tank car shell structures, the effects of welding residual stress, weld toe notch, and weld defects on the fatigue of fillet welded A515 steel specimens were evaluated. Both hole-drilling and sectioning measurement techniques were used to obtain residual stress information. Pad-on-plate weld specimens were designed to simulate the tank car structure

Wenyu Shen

1992-01-01

342

Capabilities of Ultrasonic Phased Arrays for Far-Side Examinations of Austenitic Stainless Steel Piping Welds  

SciTech Connect

A study was conducted to assess the ability of advanced ultrasonic techniques to detect and accurately determine the size of flaws from the far-side of wrought austenitic piping welds. Far-side inspections of nuclear system austenitic piping welds are currently performed on a “best effort” basis and do not conform to ASME Code Section XI Appendix VIII performance demonstration requirements for near side inspection. For this study, four circumferential welds in 610mm (24inch) diameter, 36mm (1.42inch) thick ASTM A-358, Grade 304 vintage austenitic stainless steel pipe were examined. The welds were fabricated with varied welding parameters; both horizontal and vertical pipe orientations were used, with air and water backing, to simulate field welding conditions. A series of saw cuts, electro-discharge machined (EDM) notches, and implanted fatigue cracks were placed into the heat affected zones of the welds. The saw cuts and notches ranged in depth from 7.5% to 28.4% through-wall. The implanted cracks ranged in depth from 5% through-wall to 64% through-wall. The welds were examined with phased array technology at 2.0 MHz, and compared to conventional ultrasonic techniques as a baseline. The examinations showed that phased-array methods were able to detect and accurately length-size, but not depth size, the notches and flaws through the welds. The ultrasonic results were insensitive to the different welding techniques used in each weld.

Anderson, Michael T.; Cumblidge, Stephen E.; Doctor, Steven R.

2006-10-01

343

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.

Borenstein, Amy R.; Nelson, Lorene M.

2012-01-01

344

Hybrid laser-arc welding of galvanized high-strength steels in a gap-free lap-joint configuration  

NASA Astrophysics Data System (ADS)

In order to meet the industry demands for increased fuel efficiency and enhanced mechanical and structural performance of vehicles as well as provided excellent corrosion resistance, more and more galvanized advanced high-strength steels (AHSS) have been used to fabricate automobile parts such as panels, bumpers, and front rails. The automotive industry has shown tremendous interest in using laser welding to join galvanized dual phase steels because of lower heat input and higher welding speed. However, the laser welding process tends to become dramatically unstable in the presence of highly pressurized zinc vapor because of the low boiling point of zinc, around 906°C, compared to higher melting point of steel, over 1500°C. A large number of spatters are produced by expelling the liquid metal from the molten pool by the pressurized zinc vapor. Different weld defects such as blowholes and porosities appear in the welds. So far, limited information has been reported on welding of galvanized high strength dual-phase steels in a gap-free lap joint configuration. There is no open literature on the successful attainment of defect-free welds from the laser or hybrid welding of galvanized high-strength steels. To address the significant industry demand, in this study, different welding techniques and monitoring methods are used to study the features of the welding process of galvanized DP steels in a gap-free lap joint configuration. The current research covers: (i) a feasibility study on the welding of galvanized DP 980 steels in a lap joint configuration using gas tungsten arc welding (GTAW), laser welding, hybrid laser/arc welding with the common molten pool, laser welding with the assistance of GTAW preheating source and hybrid laser-variable polarity gas tungsten arc welding (Laser-VPGTAW) techniques (Chapter 2-4); (ii) a welding process monitoring of the welding techniques including the use of machine vision and acoustic emission technique (Chapter 5); (iii) Modeling of hybrid laser-GTAW as a preheating source welding process of galvanized steels in a gap-free lap joint configuration (Chapter 6). Experimental results demonstrated that completely defect-free lap joints in galvanized high strength steels can be obtained in a gap-free configuration by using the laser welding process with the GTAW torch preheating and hybrid laser-VPGTAW welding technique. Effects of the welding parameters on the weld quality are discussed. The mechanical properties of the welded joints are studied. A machine vision system and an acoustic emission (AE) signal acquisition system are employed to acquire the images of the molten pool and the emitted AE signals on-line. Furthermore, image processing and Short Time Fourier Transform (STFT) techniques are employed to analyze the acquired images of the molten pool and the collected AE signals. The acquisition attempts are composed of (1) monitoring the weld defects by machine vision; (2) monitoring the formation of spatters from the AE signals; (3) detecting the weld modes by the induced plume; and (4) monitoring the instability of the welding process by machine vision. In addition, the numerical results have been validated by the experimental data.

Yang, Shanglu

345

A correlation of welding solidification parameters to weld macrostructure  

NASA Astrophysics Data System (ADS)

A 3-D finite difference model simulating single pass autogenous welds was used to predict the temperature fields in HY-80 steel arc weldments at various powers and torch velocities. From the predicted temperature field, two important solidification parameters were calculated at the solid-liquid interface: temperature gradients and crystal growth velocities. These were correlated with the macrostructures observed in actual weldments. For purposes of model validation, the predicted and actual fusion zone sizes were in agreement, as were the predicted time temperature curves compared to those measured with thermocouples embedded in the plate.

Novak, Francis G.

1992-06-01

346

EVALUATION OF CONSTANT CURRENT WELD CONTROL FOR PINCH WELDING  

Microsoft Academic Search

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

P Korinko; H HOWARD

2005-01-01

347

REVIEW ARTICLE: Modelling of thermal plasmas for arc welding: the role of the shielding gas properties and of metal vapour  

NASA Astrophysics Data System (ADS)

The methods used to model thermal plasmas, including treatments of diffusion in arcs in gas mixtures, are reviewed. The influence of thermophysical properties on the parameters of tungsten-inert-gas (TIG) welding arcs, particularly those that affect the weld pool, is investigated using a two-dimensional model in which the arc, anode and cathode are included self-consistently. The effect of changing each of six thermophysical properties on the characteristics of an argon TIG arc is assessed. The influence of the product of specific heat and mass density is found to be particularly important in determining the arc constriction. By examining the influence of the different properties on the heat flux density, current density and shear stress at the anode, it is concluded that the weld pool depth can be increased by using shielding gases with high specific heat, thermal conductivity and viscosity. The effect of metal vapour on the arc and weld pool properties is assessed. The most important effect of the metal vapour is found to be the increased electrical conductivity at low temperatures, which leads to lower heat flux density and current density at the weld pool, implying a shallower weld pool.

Murphy, A. B.; Tanaka, M.; Yamamoto, K.; Tashiro, S.; Sato, T.; Lowke, J. J.

2009-10-01

348

Welding: Scope and Sequence.  

ERIC Educational Resources Information Center

Intended for use by all welding instructors in the Metropolitan Nashville Public Schools, this guide provides a sequential listing of course content and scope. A course description provides a brief overview of the content of the courses offered in the welding program. General course objectives are then listed. Outlines of the course content are…

Nashville - Davidson County Metropolitan Public Schools, TN.

349

1974 Welding Task Analysis.  

ERIC Educational Resources Information Center

The study seeks to provide current empirical data for welding curriculum development and updating and for an occupational ladder. To secure information, a descriptive survey was conducted in Washington, Oregon, and British Columbia. A welder and welding supervisor in each of 58 responding industries filled out an in-depth questionnaire; the…

Bacon, Charles Frederick

350

Vocational Preparation Curriculum: Welding.  

ERIC Educational Resources Information Center

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

Usoro, Hogan

351

Improvements in Keyhole Welding.  

National Technical Information Service (NTIS)

A method of controlling the keyhole welding process is described. The light emission from the efflux plasma is monitored to detect the deviation of the plasma from a plane along the line of the weld containing the direction of the incident beam or plasma ...

J. C. Metcalfe M. B. C. Quigley

1976-01-01

352

Diffusion Weld Test Fixture.  

National Technical Information Service (NTIS)

A weld joint test fixture for testing the strength of a weld joining several members forming a test specimen is provided. The fixture includes a base which supports the test specimen and an attachment for applying a testing force to the test specimen whil...

W. Maciejewski R. Tyron G. Kavarnos E. McLaughlin K. Janecek

1994-01-01

353

Tool for Welding Plastics.  

National Technical Information Service (NTIS)

The invention relates to a device for welding thermoplastics such as polyethylene and Teflon-FEP and for welding material such as silver chloride. The device consists of a resistance wire coiled around the external surface of a tubular insulating member w...

J. S. Ard

1980-01-01

354

Robotic friction stir welding  

Microsoft Academic Search

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

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

2004-01-01

355

Analysis and validation of laser spot weld-induced distortion  

SciTech Connect

Laser spot welding is an ideal process for joining small parts with tight tolerances on weld size, location, and distortion, particularly those with near-by heat sensitive features. It is also key to understanding the overlapping laser spot seam welding process. Rather than attempting to simulate the laser beam-to-part coupling (particularly if a keyhole occurs), it was measured by calorimetry. This data was then used to calculate the thermal and structural response of a laser spot welded SS304 disk using the finite element method. Five combinations of process parameter values were studied. Calculations were compared to experimental data for temperature and distortion profiles measured by thermocouples and surface profiling. Results are discussed in terms of experimental and modeling factors. The authors then suggest appropriate parameters for laser spot welding.

Knorovsky, G.A.; Kanouff, M.P.; Maccallum, D.O.; Fuerschbach, P.W.

1999-12-09

356

An evaluation of consumable inserts for gas tungsten arc welding  

SciTech Connect

This study presents information on the use of consumable inserts to make 100% penetration welds in 304 and modified A286 (designated JBK-75) stainless steels. Current and voltage ranges which produced acceptable welds were found for different combinations of joint preparations and inserts. Three third member insert designs were examined: Type A (AWS Class 1), Type G (AWS Class 3), and Type K (AWS Class 5). One joint design incorporated the configuration of the Type G insert into the root face of the joint (termed an ''integral insert''). Joints welded with and without filler wire addition were made for comparison. Metallurgical and radiographic tests were done on all welds. It was found that the consumable insert root pass was comparable to the wire-fed root pass in weld shape and size using the same parameters; it also had additional advantages in ease of use, cleanliness, inspectability and reduced procedure complexity.

Chavez, A.E.; Marburger, S.J.

1987-03-01

357

Method for welding beryllium  

DOEpatents

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

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

1997-04-01

358

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...

359

Underwater wet welding of steel  

Microsoft Academic Search

Underwater wet welding is conducted directly in water with the shielded metal arc (SMA) and flux cored arc (FCA) welding processes. Underwater wet welding has been demonstrated as an acceptable repair technique down to 100 meters (325 ft.) in depth, but wet welds have been attempted on carbon steel structures down to 200 meters (650 ft.). The primary purpose of

S. Ibarra; S. Liu; D. L. Olson

1995-01-01

360

Rheology of welding: Field constraints  

Microsoft Academic Search

Pyroclastic deposits emplaced at high temperature and having sufficient thickness become welded via sintering, compaction and flattening of hot glassy particles. The welding process is attended by pronounced changes in the physical properties of the deposit and welding intensity can be tracked by measuring the density, porosity, fabric or strength of samples. Ultimately, the intensity of welding reflects the aggregate

K. Russell; S. Quane

2003-01-01

361

Ultrasonic seam welding. Final report  

SciTech Connect

Ultrasonic seam welding has been evaluated for making continuous seam welds on aluminum and copper-foil conductors. A seam welding system has been designed and fabricated, weldable material combinations have been identified, and the process parameters for welding materials applicable to flat cable production have been established.

Darner, G.S.

1980-06-01

362

Welds in thermoplastic composite materials  

NASA Astrophysics Data System (ADS)

Welding methods are reviewed that can be effectively used for joining of thermoplastic composites and continuous-fiber thermoplastics. Attention is given to the use of ultrasonic, vibration, hot-plate, resistance, and induction welding techniques. The welding techniques are shown to provide complementary weld qualities for the range of thermoplastic materials that are of interest to industrial and technological applications.

Taylor, N. S.

363

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\\u000a material in aluminum tailor welded blanks under uniaxial tension conditions. Aluminum tailor welded blanks consist of multiple\\u000a thickness and alloy sheet materials welded together into a single, variable thickness blank. To evaluate the mechanical properties\\u000a of the weld material in these

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

2000-01-01

364

On line sensing of weld penetration using infrared thermography  

SciTech Connect

The objective of this research is to apply new sensing techniques, artificial intelligence, and robotics to improve the welding process through control of penetration depth and width parameters. By producing a constant depth and width of penetration through on line control, the quality and strength of welds may be improved to a new level of reliability previously unobtainable. Experimental data presented in this paper indicate that depth and width of penetration can be monitored by infrared thermography and hence controlled dynamically during the weld process. Infrared thermography is used to monitor surface temperature distributions in the vicinity of the molten metal pool. Characteristics of temperature distributions perpendicular to the direction of arc travel are analyzed and correlated with weld bead width and depth as measured by destructive examination after the weld production. The results show that there is a linear relationship between peak weld plate surface temperature and depth of penetration. Additionally, surface puddle width is found to be directly correlated to measured distance separating solidus temperatures of the molten metal as measured by infrared thermography.

Wang, Y.; Chin, B.A.

1986-01-01

365

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

SciTech Connect

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

Morgan, M.T.

1995-06-01

366

Temperature field and flow field during tungsten inert gas bead welding of copper alloy onto steel  

Microsoft Academic Search

The temperature field in the base metal and bead-on-plate weld during tungsten inert gas bead welding Hs201 copper alloy onto 35CrMnSiA steel was studied and the fluid flow of the partially melted steel in the molten pool was analyzed. The results show that the thermal cycle changes remarkably and the peak temperature and the cooling speed in the fusion interface

Shixiong Lv; Jianling Song; Haitao Wang; Shiqin Yang

2009-01-01

367

Weld overlay coatings for erosion control  

SciTech Connect

A literature review was made. In spite of similarities between abrasive wear and solid particle erosion, weld overlay hardfacing alloys that exhibit high abrasion resistance may not necessarily have good erosion resistance. The performance of weld overlay hardfacing alloys in erosive environments has not been studied in detail. It is believed that primary-solidified hard phases such as carbides and intermetallic compounds have a strong influence on erosion resistance of weld overlay hardfacing alloys. However, relationships between size, shape, and volume fraction of hard phases in a hardfacing alloys and erosion resistance were not established. Almost all hardfacing alloys can be separated into two major groups based upon chemical compositions of the primary solidified hard phases: (a) carbide hardening alloys (Co-base/carbide, WC-Co and some Fe base superalloys); and (b) intermetallic hardening alloys (Ni-base alloys, austenitic steels, iron-aluminides).

Levin, B.; DuPont, J.N.; Marder, A.R.

1993-03-03

368

Capabilities of infrared weld monitor  

SciTech Connect

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

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

1997-11-01

369

Fusion zone grain refinement in aluminum alloy welds through magnetic arc oscillation and its effect on tensile behavior  

Microsoft Academic Search

Grain size reduction in weld fusion zones confers the advantages of an increased resistance to solidification cracking and\\u000a an improvement in mechanical properties. Oscillation of the welding arc through an imposed alternating magnetic field is one\\u000a of several approaches to modify weld solidification structures. In this study, gas tungsten arc welds were produced in two\\u000a high strength, age hardenable aluminum

G. D. Janaki Ram; R. Murugesan; S. Sundaresan

1999-01-01

370

Porosity, underfill and magnesium loss during continuous wave Nd:YAG laser welding of thin plates of aluminum alloys 5182 and 5754  

SciTech Connect

The influence of various welding parameters on porosity and underfill formation and magnesium loss during continuous wave Nd:YAG laser beam welding of thin plates of aluminum-magnesium Alloys 5182 and 5754 was investigated. The porosity within the welds was characterized by radiography, optical microscopy and SEM. The compositional change in the welds was measured by electron microprobe analysis. The experimental results showed that the instability of the keyhole was the dominant cause of macro-porosity formation during laser welding of thin plates of aluminum Alloys 5182 and 5754. Hydrogen did not play a significant role in porosity formation. Although underfill was commonly observed at the root of full-penetration welds, sharp or deep notches, which are harmful to the mechanical properties of the welds, were not present. Reduction in magnesium concentration was more pronounced during conduction mode welding. Welding in keyhole mode resulted in much larger weld pool and less pronounced composition change. The extent of defocusing of the laser beam greatly affected the stability of the keyhole, weld pool geometry, pore formation and composition change.

Pastor, M.; Zhao, H.; Martukanitz, R.P.; Debroy, T. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering

1999-06-01

371

Getting Pool Light Right.  

ERIC Educational Resources Information Center

Examines the use of lighting, both artificial and natural, that can enhance the aesthetic quality and functionality of areas with indoor swimming pools. Discusses glare and shadow-reduction measures that aid competitive events, including lighting above and below water levels, and highlights lighting issues during televised events. Descriptions of…

Hunsaker, Scot

1998-01-01

372

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

PubMed Central

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

Pesch, Beate

2012-01-01

373

Exploring infrared sensoring for real time welding defects monitoring in GTAW.  

PubMed

This paper presents an evaluation of an infrared sensor for monitoring the welding pool temperature in a Gas Tungsten Arc Welding (GTAW) process. The purpose of the study is to develop a real time system control. It is known that the arc welding pool temperature is related to the weld penetration depth; therefore, by monitoring the temperature, the arc pool temperature and penetration depth are also monitored. Various experiments were performed; in some of them the current was varied and the temperature changes were registered, in others, defects were induced throughout the path of the weld bead for a fixed current. These simulated defects resulted in abrupt changes in the average temperature values, thus providing an indication of the presence of a defect. The data has been registered with an acquisition card. To identify defects in the samples under infrared emissions, the timing series were analyzed through graphics and statistic methods. The selection of this technique demonstrates the potential for infrared emission as a welding monitoring parameter sensor. PMID:22219697

Alfaro, Sadek C A; Franco, Fernand Díaz

2010-06-14

374

Numerical simulation of laser keyhole welding processes based on control volume methods  

NASA Astrophysics Data System (ADS)

The control volume method (CVM) is the basic technique of computational fluid dynamics, a mathematical model for the simulation of keyhole and pool formation during deep penetration laser beam welding. Using CVM is different from using the finite element method. A three-dimensional volumetric heat source model consisting of a rotary Gaussian volumetric heat source and a double ellipsoid heat source is developed. Taking into account buoyancy and gravity, SIMPLE solution and first order upwind discretization under-relaxation iteration are used. The modelling is carried out for Ti-6Al-4V in laser keyhole welding using CVM. The local temperature distribution in the fusion zone is simulated separately with regard to dependence on laser power inputs and welding speeds. The results indicate that eddies occur near the top and bottom surfaces and help heat transfer and bulbous weld pool formation. To assess the accuracy of the developed model, the computed and experimentally determined pool shapes of laser keyhole welding are compared for welds on titanium alloys.

Wang, Hong; Shi, Yaowu; Gong, Shuili

2006-11-01

375

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

NASA Astrophysics Data System (ADS)

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

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

2005-02-01

376

Resistance seam welding  

SciTech Connect

Considerable insight and understanding were achieved in regard to the influence of all of the weld parameters on the seam weld processes at Allied-Signal Inc., Kansas City Division (KCD). Several mechanical improvements were made in the seam weld equipment. The electrode design was modified to include glass bead blasting of the periphery. This greatly improved the electrode performance consistency. Also, the new electrode design defined a refurbishing process that allowed the electrodes to be used up to three times. Originally, the electrodes were discarded after one use. A substantial cost savings resulted form this improvement. A O to 1500 ampere current transformer was inserted in the weld circuit to monitor weld current during the weld as an additional process control element. The transformer is also used to calibrate the weld power supply. A monocular microscope with a cross hair reticle was added to allow more precise electrode alignment. Other improvements included increased brush spring force and the addition of a 5 to 1 gear reduction on the electrode drive motor. 5 refs.

Hollar, D.L. Jr.

1992-03-01

377

Reserve Growth of Alberta Oil Pools  

USGS Publications Warehouse

This Open-File Report is based on a presentation delivered at the Fourth U.S. Geological Survey Workshop on Reserve Growth on March 10-11, 2008. It summarizes the results of a study of reserve growth of oil pools in Alberta Province, Canada. The study is part of a larger effort involving similar studies of fields in other important petroleum provinces around the world, with the overall objective of gaining a better understanding of reserve growth in fields with different geologic/reservoir parameters and different operating environments. The goals of the study were to: 1. Evaluate historical oil reserve data and assess reserve growth. 2. Develop reserve growth models/functions to help forecast hydrocarbon volumes. 3. Study reserve growth sensitivity to various parameters ? for example, pool size, porosity, oil gravity, and lithology. 4. Compare reserve growth in oil pools/fields of Alberta provinces with those from other large petroleum provinces.

Verma, Mahendra K.; Cook, Troy

2008-01-01

378

Estimates of array and pool-construction variance for planning efficient DNA-pooling genome wide association studies  

PubMed Central

Background Until recently, genome-wide association studies (GWAS) have been restricted to research groups with the budget necessary to genotype hundreds, if not thousands, of samples. Replacing individual genotyping with genotyping of DNA pools in Phase I of a GWAS has proven successful, and dramatically altered the financial feasibility of this approach. When conducting a pool-based GWAS, how well SNP allele frequency is estimated from a DNA pool will influence a study's power to detect associations. Here we address how to control the variance in allele frequency estimation when DNAs are pooled, and how to plan and conduct the most efficient well-powered pool-based GWAS. Methods By examining the variation in allele frequency estimation on SNP arrays between and within DNA pools we determine how array variance [var(earray)] and pool-construction variance [var(econstruction)] contribute to the total variance of allele frequency estimation. This information is useful in deciding whether replicate arrays or replicate pools are most useful in reducing variance. Our analysis is based on 27 DNA pools ranging in size from 74 to 446 individual samples, genotyped on a collective total of 128 Illumina beadarrays: 24 1M-Single, 32 1M-Duo, and 72 660-Quad. Results For all three Illumina SNP array types our estimates of var(earray) were similar, between 3-4 × 10-4 for normalized data. Var(econstruction) accounted for between 20-40% of pooling variance across 27 pools in normalized data. Conclusions We conclude that relative to var(earray), var(econstruction) is of less importance in reducing the variance in allele frequency estimation from DNA pools; however, our data suggests that on average it may be more important than previously thought. We have prepared a simple online tool, PoolingPlanner (available at http://www.kchew.ca/PoolingPlanner/), which calculates the effective sample size (ESS) of a DNA pool given a range of replicate array values. ESS can be used in a power calculator to perform pool-adjusted calculations. This allows one to quickly calculate the loss of power associated with a pooling experiment to make an informed decision on whether a pool-based GWAS is worth pursuing.

2011-01-01

379

Acoustic microscopy of internal structure of resistance spot welds.  

PubMed

Acoustic microscopy, although relatively new, has many advantages within the industrial quality control process. Its high degree of sensitivity, resolution, and reliability make it ideal for use in resistance spot weld analysis, aiding in visualization of small-scale nugget failures, as well as other defects, at various depths. Acoustic microscopy makes it possible to inspect fine detail of internal structures, providing reliable inspection and characterization of weld joints. Besides weld size measurements, this technique is able to provide high resolution, three-dimensional images of the weld nuggets, revealing possible imperfections within its microstructure that may affect joint quality. The high degree of accuracy allows one to consider the results of acoustic microscopy an authoritative measure of weld size, particularly in the case of high strength steels, dual phase steel, USIBOR steel, etc. Indeed, this technique is effective even when both conventional ultrasound and hammer and chisel methods are not. In this paper, the potential of scanning acoustic microscopy as a means to provide qualitative and quantitative information about the internal microstructure of the resistance spot welds is demonstrated. Thus, acoustic microscopy is shown to be a unique and effective laboratory instrument for the evaluation and calibration of weld quality. PMID:17703655

Chertov, Andrey M; Maev, Roman G; Severin, Fedar M

2007-08-01

380

Some effects of flux physical properties on weld-bead formation, in the SAW process  

SciTech Connect

The study of fundamental arc-welding process characteristics is important for controlling both the formation of and the mechanical properties in weld metals. Automated and semi-automated welding procedures require accurate knowledge of the effects on weld-bead dimensions of changes in process variables, in order to fill joints rapidly without defects. In the SAW process, one such variable is the type of flux used. Two classes of flux properties are important: flux chemistry and reactivity, which affect weld-metal composition and properties; and flux physical properties, which can be intrinsic, e.g., viscosity and surface tension, or extrinsic, e.g., particle size. Physical properties affect (or allegedly affect) bead dimensions, welding speed, and weldingcurrent capabilities. Much recent work on the SAW process has been concerned with the chemical composition and mechanical properties of weld metals.

Patchett, B.M.

1983-12-01

381

Defect detection in partially completed SAW and TIG welds using online radioscopy and image processing  

NASA Astrophysics Data System (ADS)

An application of machine vision applied to the analysis of radioscopic images of incomplete weld geometries is described. The rationale of the work is to identify weld defects as soon as they are produced, thereby reducing the costs of any subsequent repairs. Existing methods of weld and defect identification are compared, leading to the development of filtering and 'window' based variance operator for segmentation of suspect defect areas inside the weld region is described. The software and radioscopic imaging system have been benchmarked through a series of demonstration trials on both 80 mm thick carbon steel submerged arc welded testpieces, and 25mm thick carbon steel tungsten inert gas welded testpieces. The range of intentionally implanted defects, from root cracks to lack of side wall fusion, were detected with an overall accuracy of 87 percent, and classified in terms of defect size, shape, and position within the weld region.

Bonser, Gary R.; Lawson, Shaun W.

1998-03-01

382

New friction welding process for pipeline girth welds—welding time optimisation  

Microsoft Academic Search

A promising new welding method for fully automatic joining of pipelines has been developed. The proposed welding procedure\\u000a is a new variant of the conventional friction welding process. A rotating intermediate ring is used to generate the heat necessary\\u000a to realise the weld. In the first part of this paper, the working principles of the welding process are described. The

Koen Faes; Alfred Dhooge; Patrick De Baets; Paul Afschrift

2009-01-01

383

Surface preparation effects on GTA (gas tungsten arc) weld penetration 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 GTA welds on JBK-75, an austenitic precipitation hardenable stainless steel similar to A286. Minor changes in surface (weld groove) preparation produced substantial changes in the penetration characteristics and welding behavior of this alloy. Increased and more consistent weld penetration (higher d/w ratios) along with improved arc stability and less arc wander result from wire brushing and other abrasive surface preparations, although chemical and machining methods did not produce any improvement in penetration. Abrasive treatments roughen the surface, increase the surface area, and increase the surface oxide thickness. 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. Similar results were observed with changes in filler wire surface oxide thickness, caused by changes in wire production conditions. 15 refs., 14 figs., 4 tabs.

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

1989-01-01

384

Robotics for welding research  

SciTech Connect

The welding metallurgy research and education program at Colorado School of Mines (CSM) is helping industries make the transition toward automation by training students in robotics. Industry's interest is primarily in pick and place operations, although robotics can increase efficiency in areas other than production. Training students to develop fully automated robotic welding systems will usher in new curriculum requirements in the area of computers and microprocessors. The Puma 560 robot is CSM's newest acquisition for welding research 5 references, 2 figures, 1 table.

Braun, G.; Jones, J.

1984-09-01

385

Metabolic pools differ among ecologically diverse Drosophila species.  

PubMed

Studies of the genetic mechanisms underlying metabolic storage have focused on a few model organisms. Although very fruitful, these studies have not allowed for the examination of mechanisms across a phylogenetic spectrum. The exploration of natural patterns of metabolic pool size variation across species will help us to better understand the genetics of metabolic adaptation. We examined the metabolic pools size (triglyceride, glycogen and protein) at two ages in 12 Drosophila species with distinctly different ecologies for which complete genome sequences (for 11 of the 12 species) are known. Overall, there were significant differences across species for all three pools, while age and sex appear to affect some metabolic pools more than others. After correcting for the phylogenetic relatedness of the species used, we observed no association between triglyceride and glycogen content. Although within species these two pools sometimes are correlated, at a larger phylogenetic scale control of triglyceride and glycogen contents may have been shaped independently by natural selection. PMID:19698720

Matzkin, Luciano M; Mutsaka, Kudzaishe; Johnson, Sarah; Markow, Therese A

2009-08-29

386

Application of a dimensionless parameter model for Laser Beam Welding  

SciTech Connect

A new dimensionless parameter model for continuous wave laser welding that relates the size of the weld to the energy absorbed by the part is described. The model has been experimentally validated previously through calorimetric determinations of the net heat input and metallographic measurements of the weld size. It will be shown that both the melting efficiency and energy transfer efficiency for LBW are quite variable and need to be considered when selecting processing conditions. Specific applications will be detailed in order to observe the simplicity and value of the model in laser weld process development. It will be shown that by using certain dimensionless parameters one can determine the energy transfer efficiency and thereby correctly select processing conditions that more fully utilize the available laser output power. In applications where minimizing heat input to the surrounding weldment is paramount, the dimensionless parameters can be used to select conditions that maximize melting efficiency.

Fuerschbach, P.W.

1994-09-01

387

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

388

Measurement of workpiece temperature during welding for welding robot control  

NASA Astrophysics Data System (ADS)

MIG/MAG welding robot seam tracking system based on a symetrically noncontact temperature measurement is presented. Using literature in formation on temperature distribution during welding, a model for the prediction of the behavior of a pyrometer twin is constructed. The temperature difference between the measuring points constitutes the signal for a position control of the twin holding welding torch. As temperature measurement is made impossible by radiation originating from the welding arc, this is done during intermittent welding in time intervals in which the welding arc is switched off.

Illegrams, P. F. A.

389

Underwater wet welding of steel  

SciTech Connect

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

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

1995-05-01

390

Seismic Analysis of Large Pools.  

National Technical Information Service (NTIS)

Large pools for storing spent, nuclear fuel elements are being proposed to augment present storage capacity. To preserve the ability to isolate portions of these pools, a modularization requirement appears desirable. The purpose of this project was to inv...

R. G. Dong F. J. Tokarz

1976-01-01

391

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

392

A new finite element model for welding heat sources  

Microsoft Academic Search

A mathematical model for weld heat sources based on a Gaussian distribution of power density in space is presented. In particular\\u000a a double ellipsoidal geometry is proposed so that the size and shape of the heat source can be easily changed to model both\\u000a the shallow penetration arc welding processes and the deeper penetration laser and electron beam processes. In

John Goldak; Aditya Chakravarti; Malcolm Bibby

1984-01-01

393

Friction stir welding tool  

DOEpatents

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

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

2008-04-15

394

Welding Qualification Sharing  

SciTech Connect

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

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

2002-07-01

395

Totally Confined Explosive Welding.  

National Technical Information Service (NTIS)

A method is described for eliminating the noise and debris of explosive welding techniques by totally enclosing and applying the explosive pressure through the wall of an enclosure. This method eliminates the problem of scattering debris, and personnel ha...

L. J. Bement

1973-01-01

396

Computational Weld Mechanics.  

National Technical Information Service (NTIS)

An overview of the aims and methods of computational weld mechanics is presented. In particular, relevant literature and recent developments in the authors' laboratory are described. The presentation emphasizes an exposition of the computational principle...

J. Goldak B. Patel M. Bibby J. Moore

1986-01-01

397

Weld metal ductility in aluminum tailor welded blanks  

NASA Astrophysics Data System (ADS)

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 tailor welded blanks, a series of tensile specimens containing varying ratios of weld and monolithic material in the gage area of the specimen were tested. These experimental results show that increasing the amount of weld in the cross-sectional area of the specimen decreases the ductility of the specimen and that the weld characteristics have a pronounced impact on ductility. Using the experimental results and classical tensile instability and necking models, a numerical model was developed to describe the ductility of the weld metal. The model involves basic material properties and an initial imperfection level in both the weld and monolithic materials. The specimens studied were produced from 1- to 2-mm AA5182-O aluminum alloy sheet material welded into blanks using an autogenous gas tungsten arc welding process.

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

2000-11-01

398

Telephone pools and economic incentives  

Microsoft Academic Search

We identify the incentive structure for a firm that participates in a pooling arrangement. These pooling arrangements have been common in the telecommunications industry, both in the United States and in Canada. We identify alternative mechanisms, including cost caps, yardstick competition, transfer prices, and fixed revenue allocators. A pooling firm has inferior incentives for cost reducing innovation, truthful reporting of

Dale E. Lehman; Dennis L. Weisman

1996-01-01

399

Weld braze technique  

SciTech Connect

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

Alexander, R.J.; Kanne, W.R.; Kelker, J.W.

1982-04-20

400

Research on Narrow Gap Welding Parameters Optimization  

Microsoft Academic Search

The effects of welding voltage, welding current and weld heat input on the A105 steel weld formation quality using submerged-arc welding (SAW) with small diameter welding wire were experimentally researched. Through lots of experiments of surface overlaying on flat plates, the optimal parameters were obtained sequentially using numerical regression analysis. The calculated results were compared with experimental data to verify

Qinghua Lu; Zhishui Yu; Guoxiang Xu; Jianping He

2009-01-01

401

Welding of aluminium alloy by using filler-added laser-arc hybrid welding process  

Microsoft Academic Search

Laser-arc hybrid welding is considered to be an efficient, practical welding process because its deposited metal from welding wire can increase gap-bridging ability and prevent welding defects such as undercutting or underfilling. The deposition rate from welding wire, however, cannot be adjusted independently on the welding current under the stable welding conditions because it is necessary to maintain a constant

Jing-bo Wang; Hitoshi Nishimura; Seiji Katayama; Masami Mizutani

2011-01-01

402

Effect of Weld Conditions on the Deformation Behaviour of Tailor Welded Blanks (TWB)  

Microsoft Academic Search

The critical issue during finite element analysis of tailor welded blank is the handling of the weld region - either the weld may be treated just as a weld line (without imposing mechanical properties) or as a weld zone (by imposing separate mechanical properties to the weld zone). The formability of TWB will be affected not only by the weld

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

2004-01-01

403

Aluminum laser welding optimization  

NASA Astrophysics Data System (ADS)

Pulsed Nd:YAG laser with maximal power 150 W is used in our laboratory to cut, drill and weld metal and non-metal thin materials to thickness 2 mm. Welding is realized by fixed processing head or movable fiber one with beam diameter 0,6 mm in focus plane. Welding of stainless and low-carbon steel was tested before and results are publicized and used in practice. Now the goal of our experiment was optimization of process parameters for aluminum that has other physical properties than steels, lower density, higher heat conductivity and surface reflexivity. Pure alumina specimen 0,8 mm and Al-Mg-Si alloy 0,5 mm prepared for butt welds. Problem with surface layer of Al2O3 was overcome by sanding and chemical cleaning with grinding paste. Critical parameters for good weld shape are specimen position from beam focus plane, pulse length and energy, pulse frequency and the motion velocity that determines percentage of pulse overlap. Argon as protective gas was used with speed 6 liters per second. Thermal distribution in material can be modeled by numerical simulation. Software tool SYSWELD makes possible to fit laser as surface heat source, define weld geometry, and make meshing of specimen to finite elements and compute heat conduction during process. Color isotherms, vectors, mechanical deformations and others results can be study in post-processing.

Chmelí?ková, Hana; Halenka, Viktor; Lapšanská, Hana; Havelková, Martina

2007-05-01

404

Thermal plasma properties for Ar-Al, Ar-Fe and Ar-Cu mixtures used in welding plasmas processes: I. Net emission coefficients at atmospheric pressure  

NASA Astrophysics Data System (ADS)

This article is devoted to the calculation of the net emission coefficient (NEC) of Ar-Al, Ar-Fe and Ar-Cu mixtures at atmospheric pressure for arc welding processes. The results are given in data tables for temperatures between 3 kK and 30 kK, for five plasma thicknesses (0, 0.5, 1, 2, 5 mm) and ten concentrations of metallic vapours (pure gas, 0.01%, 0.1%, 1%, 5%, 10%, 25%, 50%, 75% and pure metal vapours in mass proportions). The results are in good agreement with most of the works published on the subject for such mixtures. They highlight the influence of three parameters on the radiation of the plasma: the NEC is directly related to temperature and inversely related to plasma radius and is highly sensitive to the presence of metal vapours. Finally, numerical data are supplied in tables in order to develop accurate computational modelling of welding arc and to estimate both qualitatively and quantitatively the influence of each metallic vapour on the size and on the shape of the weld pool.

Cressault, Y.; Gleizes, A.

2013-10-01

405

Pooling of urine specimens for PCR testing: a cost saving strategy for Chlamydia trachomatis control programmes  

PubMed Central

OBJECTIVES: To evaluate pooling of first catch urine (FCU) specimens as a cost effective strategy for chlamydia testing. METHODS: Mock specimens were pooled with and without dilution to determine optimal pool size and ease of work flow. The performance of the Amplicor Chlamydia trachomatis PCR assay on pooled specimens was compared with individual testing using 370 FCU specimens from asymptomatic men presenting to an STD clinic. Cost savings associated with pooling were estimated. RESULTS: Using mock specimens, the sensitivity and specificity of the Amplicor PCR assay were not affected by pool sizes of two and five, but at a pool size of 10 decreased sensitivity due to inhibition was observed in one of five mock pools when the pooling method which involved no dilution was used. Archived FCU specimens from a study of 370 asymptomatic men were combined consecutively into 74 pools of five and tested by PCR. Of the 18 pools that contained positive specimens, 17 were PCR positive. Compared with testing FCU specimens individually, pooling resulted in a sensitivity of 95%, specificity of 100%, and a cost savings of 57% based on reduced number of tests required. CONCLUSION: Depending on the prevalence of infection, pooling of FCU specimens for PCR testing may result in cost savings compared with testing specimens individually. Further evaluations to validate this strategy using fresh FCU specimens are needed. ???

Peeling, R. W.; Toye, B.; Jessamine, P.; Gemmill, I.

1998-01-01

406

Analysis of the integrity of welded pipes of gas mains by the FITNET procedures  

Microsoft Academic Search

We have evaluated the integrity of a rectilinear element of a welded pipe of a gas main after its operation for 40 years with\\u000a the use of the FITNET procedures according to the Failure-Assessment-Diagram approach. We have determined the critical sizes\\u000a of defects in the base (17G1S steel) and weld metal of a longitudinal welded joint of a reserve pipe.

I. R. Dzioba; O. T. Tsyrul’nyk

2009-01-01

407

Investigation of transport phenomena and defect formation in pulsed laser keyhole welding of zinc-coated steels  

NASA Astrophysics Data System (ADS)

Lasers are being used to weld zinc-coated steels due to high welding speed, high aspect ratio, and narrow heat affected zone. However, escape of high-pressure zinc vapour in the welding process can damage the weld pool continuity and cause large voids and serious undercuts in the final welds. In this paper, a mathematical model and the associated numerical techniques have been developed to study the transport phenomena and defect formation mechanisms in pulsed laser keyhole welding of zinc-coated steels. The volume-of-fluid (VOF) method is employed to track free surfaces. The continuum model is used to handle the liquid phase, the solid phase and the mushy zone of the metal. The enthalpy method is employed to account for the latent heat during melting and solidification. The transient heat transfer and melt flow in the weld pool during the keyhole formation and collapse processes are calculated. The escape of zinc vapour through the keyhole and the interaction between zinc vapour and weld pool are studied. Voids in the welds are found to be caused by the combined effects of zinc vapour-melt interactions, keyhole collapse and solidification process. By controlling the laser pulse profile, it is found that the keyhole collapse and solidification process can be delayed, allowing the zinc vapour to escape, which results in the reduction or elimination of voids. The good agreement between the model predictions and the experimental observations indicates that the proposed model lays a solid foundation for future study of laser welding of zinc-coated steels.

Zhou, J.; Tsai, H. L.; Lehnhoff, T. F.

2006-12-01

408

Finite element modeling of multipass GMA welds in steel plates  

SciTech Connect

Distortions from gas metal arc (GMA) multipass welds of thick steel plates were measured in experiments and calculated using finite element analysis. Two- and three-dimensional finite element simulations were compared with the experimentally measured in-plane distortions in a 2-3/4 in. thick steel plate. Thermal analyses were performed using 2D models of the weld cross-section. These temperature histories were used for 2D and 3D mechanical analyses. Data for verification of thermal analyses included weld cross-sections, weld pool crater shape from power-off tests, and embedded and surface thermocouple temperature histories. Mechanical analyses were verified using caliper measurements of shrinkage transverse to the weld and strain gage measurements. Calculated in-plane shrinkage from the 3D model for 4 passes compared well with caliper measurements of a test specimen`s distortion. Two-dimensional mechanical analyses were not capable of predicting the accumulation of shrinkage occurring after the first pass.

NONE

1995-12-01

409

The Swimming Pool  

NSDL National Science Digital Library

This problem provides an opportunity for introducing and raising children's awareness of negative numbers. The first part of the problem is moving up and down a ladder or steps into a swimming pool. Students are counting along a number line, but in this case it is vertical rather than the more usual horizontal orientation. The final part of the activity encourages children to be creative and invent their own way of numbering the steps below the water level. The Teachers' Notes page offers suggestions for implementation and discussion as well as ideas for extension and support.

2008-01-01

410

NEW WELDING TECHOLOGY - THE COLD WELDING ON COGGED SURFACES  

Microsoft Academic Search

Welding by cold pressing on cogged surfaces, produces the joint of a component made from an easy deformable metal by pressing on the cogged surface of a harder metal component. Different welds between aluminium (the easy deformable component) and copper, brass, steel, stainless steel (harder component, cogged on the contact surface) can be obtained. The weld is obtained only by

Bogdan GEORGESCU; Valeriu GEORGESCU

411

Mechanisms that control the geometry of pulsed Nd:YAG laser welds  

SciTech Connect

A two-dimensional conduction laser welding code developed by Russo overpredicted the geometry of pulsed welds for welding parameters typically used in production. At low heat fluxes, however, there was good agreement between the experimental results and the welding code. The limitations of the code appear to result from ignoring some of the important physics of the laser welding processes. Subsequent experimental process research and further efforts have concentrated on beam-plume interactions and weld pool convection. A key experiment that has been used in testing the physical models is one where the role of a surface active element in controlling the geometry of austenitic stainless steels welds was evaluated. This experiment involved a significant range of heat fluxes and addressed the role of the laser plume. In this paper, both experimental and theoretical studies of the laser plume are discussed. Furthermore, the role of surface tension-driven convection (Marangoni flow) is explored. The results of this research are used to explain the geometry of austenitic stainless steel welds from the above experiment. 8 refs., 7 figs.

Jellison, J.L.; Russo, A.J.; Peebles, H.C.; Williamson, R.L.

1988-01-01

412

A theoretical and experimental analysis of variances in weld bead morphologies  

NASA Astrophysics Data System (ADS)

Predictable and reproducible weld bead morphologies and dimensions are a major concern in welding. In bead-on-plate welding, the heat flow is controlled by the heat source parameters (power, speed, and radius) and the physical properties and dimensions of the workpiece, especially its thickness. Complex models that account for weld pool circulation have been developed to quantify welds. However, to some extent, fluctuations in weld dimensions can be explained with conduction models of moving Gaussian heat sources. In early investigations with point and line heat sources, relationships between process parameters and plate thickness were derived to differentiate between two- and three-dimensional heat flow. To date, the heat source radius ( R) has not been taken into account. The dimensionless ratio ( D*) of the plate thickness ( D) to the heat source radius ( R) is actually a variable to consider. With the introduction of additional dimensionless parameters (*)—speed (v*), power (q*)— relationships among governing variables, heat flow dimension, and weld bead dimensional fluctuations can be derived. Weld bead fluctuations are found to depend on dimensionless variables (v*, q*, D* ) and occur when the heat flow dimension is intermediate between two- and three-dimensional. Occasionally, experimental data exhibit trends that differ from predictions. This article presents a dimensionless version of a heat flow model and discusses the discrepancies between experimental and theoretical results.

Marya, M.; Marya, S. K.

1998-08-01

413

Microstructure Refinement After the Addition of Titanium Particles in AZ31 Magnesium Alloy Resistance Spot Welds  

NASA Astrophysics Data System (ADS)

Microstructural evolution of AZ31 magnesium alloy welds without and with the addition of titanium powders during resistance spot welding was studied using optical microscopy, scanning electron microscopy, and transmission electron microscopy (TEM). The fusion zone of AZ31 magnesium alloy welds could be divided into columnar dendritic zone (CDZ) and equiaxed dendritic zone (EDZ). The well-developed CDZ in the vicinity of the fusion boundary was clearly restricted and the coarse EDZ in the central region was efficiently refined by adding titanium powders into the molten pool, compared with the as-received alloy welds. A microstructural analysis showed that these titanium particles of approximately 8 µm diameter acted as inoculants and promoted the nucleation of ?-Mg grains and the formation of equiaxed dendritic grains during resistance spot welding. Tensile-shear testing was applied to evaluate the effect of titanium addition on the mechanical properties of welds. It was found that both strength and ductility of magnesium alloy welds were increased after the titanium addition. A TEM examination showed the existence of an orientation matching relationship between the added Ti particles and Mg matrix, i.e., [ {0 1bar{1}0} ]_{{Mg}} // [ { 1bar{2} 1bar{3}} ]_{{Ti}} {{and}} ( {000 2} )_{{Mg}} // ( 10bar{1}0)_{{Ti}} in some grains of Ti polycrystal particles. This local crystallographic matching could promote heterogeneous nucleation of the Mg matrix during welding. The diameter of the added Ti inoculant should be larger than 1.8 µm to make it a potent inoculant.

Xiao, L.; Liu, L.; Esmaeili, S.; Zhou, Y.

2012-02-01

414

Fractured welds stir not debate  

SciTech Connect

This article reviews the growing discussion regarding the failures of welded joints in a number of beam-to-column connections. In the Northridge Earthquake of 1994, there were a large number of such failures, and weld material E70T-4 was the common element in each failure. This weld material is utilized with FCAW, a semiautomatic welding process that allows a higher deposition rate. The manufacturer of the weld material argues that many of the welds were improperly performed, while others argue that the fracture toughness of the weld material is very low. With a minor defect, this would lead to brittle fracture under the cyclic loading that would occur during a seismic event. Use of the manual SMAW process using weld material E7018 is recommended.

Rosenbaum, D.B.; Stocker, L.J.P.

1996-05-06

415

Microstructural Modification During Laser Welding.  

National Technical Information Service (NTIS)

An investigation was carried out to determine the effect of rapid solidification on the weld metal microstructure of austenitic stainless steels and its implication on the ferrite constitution diagram. A wide variety of stainless steels were laser welded ...

S. A. David J. M. Vitek

1988-01-01

416

Practical analysis of welding processes using finite element analysis.  

SciTech Connect

With advances in commercially available finite element software and computational capability, engineers can now model large-scale problems in mechanics, heat transfer, fluid flow, and electromagnetics as never before. With these enhancements in capability, it is increasingly tempting to include the fundamental process physics to help achieve greater accuracy (Refs. 1-7). While this goal is laudable, it adds complication and drives up cost and computational requirements. Practical analysis of welding relies on simplified user inputs to derive important relativistic trends in desired outputs such as residual stress or distortion due to changes in inputs like voltage, current, and travel speed. Welding is a complex three-dimensional phenomenon. The question becomes how much modeling detail is needed to accurately predict relative trends in distortion, residual stress, or weld cracking? In this work, a HAZ (Heat Affected Zone) weld-cracking problem was analyzed to rank two different welding cycles (weld speed varied) in terms of crack susceptibility. Figure 1 shows an aerospace casting GTA welded to a wrought skirt. The essentials of part geometry, welding process, and tooling were suitably captured lo model the strain excursion in the HAZ over a crack-susceptible temperature range, and the weld cycles were suitably ranked. The main contribution of this work is the demonstration of a practical methodology by which engineering solutions to engineering problems may be obtained through weld modeling when time and resources are extremely limited. Typically, welding analysis suffers with the following unknowns: material properties over entire temperature range, the heat-input source term, and environmental effects. Material properties of interest are conductivity, specific heat, latent heat, modulus, Poisson's ratio, yield strength, ultimate strength, and possible rate dependencies. Boundary conditions are conduction into fixturing, radiation and convection to the environment, and any mechanical constraint. If conductivity, for example, is only known at a few temperatures it can be linearly extrapolated from the highest known temperature to the liquidus temperature. Over the liquidus to solidus temperature the conductivity is linearly increased by a factor of three to account for the enhanced heat transfer due to convection in the weld pool. Above the liquidus it is kept constant. Figure 2 shows an example of this type of approximation. Other thermal and mechanical properties and boundary conditions can be similarly approximated, using known physical material characteristics when possible. Sensitivity analysis can show that many assumptions have a small effect on the final outcome of the analysis. In the example presented in this work, simplified analysis procedures were used to model this process to understand why one set of parameters is superior to the other. From Lin (Ref. 8), mechanical strain is expected to drive HAZ cracking. Figure 3 shows a plot of principal tensile mechanical strain versus temperature during the welding process. By looking at the magnitudes of the tensile mechanical strain in the material's Brittle Temperature Region (BTR), it can be seen that on a relative basis the faster travel speed process that causes cracking results in about three times the strain in the temperature range of the BTR. In this work, a series of simplifying assumptions were used in order to quickly and accurately model a real welding process to respond to an immediate manufacturing need. The analysis showed that the driver for HAZ cracking, the mechanical strain in the BTR, was significantly higher in the process that caused cracking versus the process that did not. The main emphasis of the analysis was to determine whether there was a mechanical reason whether the improved weld parameters would consistently produce an acceptable weld, The prediction of the mechanical strain magnitudes confirms the better process.

Cowles, J. H. (John H.); Dave, V. R. (Vivek R.); Hartman, D. A. (Daniel A.)

2001-01-01

417

In-situ spatially resolved x-ray diffraction mapping of the alpha to beta to alpha transformation in commercially pure titanium arc welds  

SciTech Connect

Spatially Resolved X-Ray Diffraction (SRXRD) is used to map the {alpha}{r_arrow}{beta}{r_arrow}{alpha} phase transformation in the heat affected zone (HAZ) of commercially pure titanium gas tungsten arc welds. In-situ SRXRD experiments were conducted on arc welds using a 200 pm diameter x-ray beam at Stanford Synchrotron Radiation Laboratory (SSRL). A map was created which identifies six HAZ microstructural regions that exist between the liquid weld pool and the base metal during welding. The first region is single phase {beta}-Ti that forms in a 2- to 3-mm band adjacent to the liquid weld pool. The second region is back transformed {alpha}-Ti that forms behind the portion of the HAZ where {beta}-Ti was once present at higher temperatures. The third region is completely recrystallized {alpha}-Ti that forms in a 2- to 3-mm band surrounding the single phase {beta}-Ti region. Recrystallized {alpha}-Ti was observed by itself and also with varying amounts of {beta}-Ti. The fourth region of the weld is the partially transformed zone where {alpha}-Ti and {beta}-Ti coexist during welding. The fifth region is directly behind the partially transformed zone and consists of a mixture of recrystallized and back transformed {alpha}-Ti The sixth region is farthest from the weld pool and consists of {alpha}-Ti that is undergoing annealing and recrystallization. Annealing of the base metal was observed to some degree in all of the SRXRD patterns, showing that annealing exceeded 13 mm from the centerline of the weld. Although the microstructure consisted predominantly of {alpha}-Ti, both prior to the weld and after the weld, the (002) texture of the starting material was altered during welding to produce a predominantly (101) texture within the resulting HAZ.

Elmer, J. W., LLNL

1998-05-15

418

Detection of West Nile virus in large pools of mosquitoes.  

PubMed

We conducted a laboratory evaluation of the ability of commercial antigen-capture assays, the Rapid Analyte Measurement Platform (RAMP) and the VecTest wicking assay, as well as Real Time reverse transcriptase polymerase chain reaction (RT-PCR, Taqman) and Vero cell plaque assay to detect West Nile virus (WNV) in large mosquito pools. Real-Time PCR (Taqman) was the most sensitive, detecting WNV ribonucleic acid (RNA) in 100% of samples containing a single infected mosquito in pool sizes of up to 500 mosquitoes. Mosquito body tissues minimally impacted the ability of Real Time RT-PCR to detect WNV in a pool size of 500, reducing sensitivity by 0.6 log10 plaque-forming units (PFU)/ml. Vero cell plaque assay detected live virus from a single infected mosquito in 100% of pools containing up to 200 mosquitoes, but was unreliable at larger pool sizes. VecTest detected 100% of positive pools containing 50 mosquitoes with 5.8 log10 PFU/ml virus, 100 mosquitoes with 5.9 log10 PFU/ml, and 200 mosquitoes with 5.2 log10 PFU/ ml. The RAMP assay detected 100% of positive pools containing 50 mosquitoes with 3.3 log10 PFU/ml virus, 100 mosquitoes with 3.7 log10 PFU/ml, and 200 mosquitoes with 4.0 log10 PFU/ml. Results indicate that WNV can be reliably detected by all 4 assays in pools of mosquitoes exceeding 50 specimens, though there is some loss of sensitivity with very large pool sizes. PMID:18240515

Sutherland, Genevieve L; Nasci, Roger S

2007-12-01

419

A probabilistic evaluation of alternative weld inspection sampling plans  

Microsoft Academic Search

Presents simple formulas for predicting the effectiveness of sampling plans for inspecting welds in nuclear power plant piping systems. The alternative plans differ in terms of the initial sample size and the strategy used to expand the sample size. This study is concerned with developing formulas that describe the plans as they are actually implemented, particularly variants of the ASME

P. G. Heasler; F. A. Simonen

1990-01-01

420

13 CFR 120.1708 - Pool Certificates.  

Code of Federal Regulations, 2012 CFR

...backing a Pool Certificate, SBA, through the CSA, will make advances to maintain the schedule... (e) Pool Certificate form. The CSA prepares the Pool Certificate. SBA must...Certificate must be registered with the CSA. (g) Face amount of Pool...

2012-01-01

421

13 CFR 120.1706 - Pool Originator's retained interest in Pool.  

Code of Federal Regulations, 2012 CFR

...interest will decline with Loan Interest payments, prepayments, defaults and any other early termination. At Pool formation, the CSA will issue the Pool Originator a Pool Originator Receipt evidencing the Pool Originator's retained interest in the Pool....

2012-01-01

422

Welding. Performance Objectives. Intermediate Course.  

ERIC Educational Resources Information Center

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

Vincent, Kenneth

423

Welding. Performance Objectives. Basic Course.  

ERIC Educational Resources Information Center

|Several intermediate performance objectives and corresponding criterion measures are listed for each of eight terminal objectives for a basic welding course. The materials were developed for a 36-week (2 hours daily) course developed to teach the fundamentals of welding shop work, to become familiar with the operation of the welding shop…

Vincent, Kenneth

424

Friction stir welding and processing  

Microsoft Academic Search

Friction stir welding (FSW) is a relatively new solid-state joining process. This joining technique is energy efficient, environment friendly, and versatile. In particular, it can be used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding. FSW is considered to be the most significant development in metal joining in a

R. S. Mishra; Z. Y. Ma

2005-01-01

425

Pipe weld crown removal device  

Microsoft Academic Search

A device is provided for grinding down the crown of a pipe weld joining aligned pipe sections so that the weld is substantially flush with the pipe sections joined by the weld. The device includes a cage assembly comprising a pair of spaced cage rings adapted to be mounted for rotation on the respective pipe sections on opposite sides of

C. K. Sword; P. J. Sette

1992-01-01

426

Pipe weld crown removal device  

Microsoft Academic Search

This invention is comprised of a device that provides for grinding down the crown of a pipe weld joining aligned pipe sections so that the weld is substantially flush with the pipe sections joined by the weld. The device includes a cage assembly comprising a pair of spaced cage rings adapted to be mounted for rotation on the respective pipe

C. K. Sword; P. J. Sette

1991-01-01

427

Laser welding of aluminum alloys  

Microsoft Academic Search

Recent interest in reducing the weight of automobiles to increase fuel milage has focused attention on the use of aluminum and associated joining technologies. Laser beam welding is one of the more promising methods for high speed welding of aluminum. Consequently, substantial effort has been expended in attempting to develop a robust laser beam welding process. Early results have not

Keng H. Leong; Kenneth R. Sabo; Paul G. Sanders; Walter J. Spawr

1997-01-01

428

Submerged Arc Welding of Titanium.  

National Technical Information Service (NTIS)

Studies of flux shielded welding of titanium indicate that acceptable submerged arc weld bead shape may not be attained with pure CaF2 flux. Addition of chlorides to the CaF2 flux improves the weld bead shape but reduces the deoxidizing potential of the f...

G. Hunter G. B. Kenney M. Ring B. A. Russell T. W. Eagar

1978-01-01

429

Welding. Performance Objectives. Basic Course.  

ERIC Educational Resources Information Center

Several intermediate performance objectives and corresponding criterion measures are listed for each of eight terminal objectives for a basic welding course. The materials were developed for a 36-week (2 hours daily) course developed to teach the fundamentals of welding shop work, to become familiar with the operation of the welding shop…

Vincent, Kenneth

430

[Treatment of thermal pool waters].  

PubMed

No laws currently exist regarding the treatment of spa pool water, since it is not completely logical that these should have the same requirements as normal swimming pools. The problem arises especially with regards to the use of chlorine as a disinfectant, which may actually annulate the therapeutic effects of spring waters by altering their physical-chemical characteristics. Possible choices may be represented by frequent replacement of pool water, which may be easily achievable for small pools but more difficult to implement for larger pools, or by alternative disinfection methods such as ozone or ultraviolet rays. The efficacy of these methods must be shown through frequent chemical and microbiological analyses and future, to be hoped-for laws or guidelines, will need to be aimed at defining safety performance standards rather than prescribing analytical intervention and control methods. Beyond the choice of disinfection method, it is extremely important to highlight some relevant hygienic measures that bathers should take and that play a fundamental role in preventing infectious diseases which may be acquired in pools. The most important of these include: showering before entering the pool, wearing slippers around the pool, not urinating in the pool, not bathing if affected by diarrhea, wearing a bathing cap, avoiding the use of contact lenses while bathing and avoiding exchanging towels. Pool managers have the important role of avoiding overcrowding of the facilities and ensuring that all technological systems function properly. PMID:17206228

Signorelli, Carlo; Pasquarella, Cesira; Saccani, Elisa; Sansebastiano, Giuliano

431

Friction stir welding tool and process for welding dissimilar materials  

DOEpatents

A friction stir welding tool and process for lap welding dissimilar materials are detailed. The invention includes a cutter scribe that penetrates and extrudes a first material of a lap weld stack to a preselected depth and further cuts a second material to provide a beneficial geometry defined by a plurality of mechanically interlocking features. The tool backfills the interlocking features generating a lap weld across the length of the interface between the dissimilar materials that enhances the shear strength of the lap weld.

Hovanski, Yuri; Grant, Glenn J; Jana, Saumyadeep; Mattlin, Karl F

2013-05-07

432

Laser welding of synthetic epikeratoplasty lenticules to the cornea.  

PubMed

We used a milliwatt continuous wave CO2 laser mounted on an operating microscope to study the feasibility of welding synthetic collagen epikeratoplasty lenticules to the cornea. In vitro studies and experimentation in rabbits and monkeys showed no welding effects using direct laser radiation with powers ranging from 17 mW to 1 W. Only tissue shrinkage was observed. Experiments using various adjunctive solders produced a temporary welding effect using 30% bovine serum albumin welded with a power of 35-45 mW, 325 microns spot size, moving the beam 5 mm/sec. The lenticules remained in place until the 4th postoperative day when epithelium grew underneath the lenticule, dislodging it. Histopathologic examination demonstrated epithelial migration over the solder displacing the epikeratoplasty lenticule and anterior stromal denaturization and disruption. PMID:2076420

Gailitis, R P; Thompson, K P; Ren, Q S; Morris, J; Waring, G O

433

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01