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1

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

Microsoft Academic Search

This paper describes a method of determining the optimal sensor location to measure weldment surface temperature, which has a close correlation with weld pool size in the gas metal arc (GMA) welding process. Due to the inherent complexity and nonlinearity in the GMA welding process, the relationship between the weldment surface temperature and the weld pool size varies with the

K. S. Boo; H. S. Cho

1994-01-01

2

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

SciTech Connect

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

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

1994-11-01

3

Weld pool phenomena  

SciTech Connect

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

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

1994-09-01

4

Numerical simulation of weld pool geometry in laser beam welding  

NASA Astrophysics Data System (ADS)

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

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

2000-03-01

5

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

NASA Astrophysics Data System (ADS)

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

Zhao, Yuzhen; Zhou, Heping; Shi, Yaowu

2006-04-01

6

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

7

Control of Gas Tungsten Arc welding pool shape by trace element addition to the weld pool  

DOEpatents

An improved process for Gas Tungsten Arc welding maximizes the depth/width ratio of the weld pool by adding a sufficient amount of a surface active element to insure inward fluid flow, resulting in deep, narrow welds. The process is especially useful to eliminate variable weld penetration and shape in GTA welding of steels and stainless steels, particularly by using a sulfur-doped weld wire in a cold wire feed technique.

Heiple, C.R.; Burgardt, P.

1984-03-13

8

Modeling of inclusion growth and dissolution in the weld pool  

SciTech Connect

The composition, size distribution, and number density of oxide inclusions in weld metal are critical factors in determining weldment properties. A computational model has been developed to understand these factors, considering fluid flow and the temperature field in the weld pool during submerged arc (SA) welding of low-alloy steels. The equations of conservation of mass, momentum, and energy are solved in three dimensions to calculate the velocity and temperature fields in the weld pool. The loci and corresponding thermal cycles of thousands of oxide inclusions are numerically calculated in the weld pool. The inclusions undergo considerable recirculatory motion and experience strong temperature gyrations. The temperature-time history and the computed time-temperature-transformation (TTT) behavior of inclusions were then used to understand the growth and dissolution of oxide inclusions in the weld pool. The statistically meaningful characteristics of inclusion behavior in the weld pool, such as the residence time, number of temperature peaks, etc., were calculated for several thousand inclusions. The calculated trends agree with experimental observations and indicate that the inclusion formation can be described by combining thermodynamics and kinetics with the fundamentals of transport phenomena.

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

2000-02-01

9

Weld pool penetration measurement using ultrasound with thermal gradient correction factors  

Microsoft Academic Search

Weld penetration is critical to final weld performance. There are many techniques for determining surface parameters of weld pools but the transient nature of the pools, high temperatures and intense electromagnetic energy make direct measurement of the penetration of weld pools difficult. In order to determine weld pool penetration ultrasonically from below the weld pool it is necessary to compensate

John Martin Anderton

1998-01-01

10

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

E-print Network

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

Paris-Sud XI, Université de

11

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

12

Vision-based weld pool boundary extraction and width measurement during keyhole fiber laser welding  

NASA Astrophysics Data System (ADS)

In keyhole fiber laser welding processes, the weld pool behavior is essential to determining welding quality. To better observe and control the welding process, the accurate extraction of the weld pool boundary as well as the width is required. This work presents a weld pool edge detection technique based on an off axial green illumination laser and a coaxial image capturing system that consists of a CMOS camera and optic filters. According to the difference of image quality, a complete developed edge detection algorithm is proposed based on the local maximum gradient of greyness searching approach and linear interpolation. The extracted weld pool geometry and the width are validated by the actual welding width measurement and predictions by a numerical multi-phase model.

Luo, Masiyang; Shin, Yung C.

2015-01-01

13

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

Microsoft Academic Search

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

S. C Juang; Y. S Tarng

2002-01-01

14

Molten pool characterization of laser lap welded copper and aluminum  

NASA Astrophysics Data System (ADS)

A 3D finite volume simulation model for laser welding of a Cu-Al lap joint was developed using ANSYS FLUENT to predict the weld pool temperature distribution, velocity field, geometry, alloying element distribution and transition layer thickness—all key attributes and performance characteristics for a laser-welded joint. Melting and solidification of the weld pool was simulated with an enthalpy-porosity formulation. Laser welding experiments and metallographic examination by SEM and EDX were performed to investigate the weld pool features and validate the simulated results. A bowl-shaped temperature field and molten pool, and a unique maximum fusion zone width were observed near the Cu-Al interface. Both the numerical simulation and experimental results indicate an arch-shaped intermediate layer of Cu and Al, and a gradual transition of Cu concentration from the aluminum plate to the copper plate with high composition gradient. For the conditions used, welding with Cu on top was found to result in a better weld joint.

Xue, Zhiqing; Hu, Shengsun; Zuo, Di; Cai, Wayne; Lee, Dongkyun; Elijah, Kannatey-Asibu, Jr.

2013-12-01

15

On the calculation of the free surface temperature of gas-tungsten-arc weld pools from first principles: Part II. modeling the weld pool and comparison with experiments  

Microsoft Academic Search

By combining a mathematical model of the welding arc and of the weld pool, calculations are presented to describe the free\\u000a surface temperature of weld pools for spot welding operations. The novel aspects of the treatment include the calculation\\u000a of the heat and current fluxes falling on the free weld pool surface from first principles, a realistic allowance for heat

R. T. C. Choo; J. Szekely; S. A. David

1992-01-01

16

THESIS FOR THE DEGREE OF LICENTIATE OF PHILOSOPHY Weld Pool Simulations  

E-print Network

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

Patriksson, Michael

17

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

E-print Network

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

Eagar, Thomas W.

18

Stability of Full Penetration, Flat Position Weld Pools  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

19

Effect of Welding Parameters on the Size of Heat Affected Zone of Submerged Arc Welding  

Microsoft Academic Search

This paper discusses the effect of welding parameters on the size of the heat affected zone (HAZ) and its relative size as compared to the weld bead of submerged arc welding. It is discovered that the welding parameters influences the size of weld bead and HAZ differently which can be relate to the effect of welding parameters on the various

C. S. Lee; R. S. Chandel; H. P. Seow

2000-01-01

20

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

Microsoft Academic Search

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

Fang Wang

2003-01-01

21

INFLUENCE OF SURFACE DEPRESSION AND CONVECTION ON ARC WELD POOL GEOMETRY  

E-print Network

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

Eagar, Thomas W.

22

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

23

Heat transfer and fluid flow in a partially or fully penetrated weld pool in gas tungsten arc welding  

Microsoft Academic Search

In this study, fluid flow driven by a combination of electromagnetic force, buoyancy force, arc drag force, and surface tension gradient is numerically analyzed for a partially or fully penetrated weld pool in stationary gas tungsten arc welding (GTAW). Irregular shape of the weld pool and the moving liquid–solid interface is handled by a boundary-fitted-coordinates technique. Surface tension on the

H. G. Fan; H. L. Tsai; S. J. Na

2000-01-01

24

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

25

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

Microsoft Academic Search

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

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

2009-01-01

26

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

27

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

28

Experimental characterization of the weld pool flow in a TIG configuration  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

29

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

30

Weld pool penetration measurement using ultrasound with thermal gradient correction factors  

NASA Astrophysics Data System (ADS)

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

Anderton, John Martin

31

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

32

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

33

Computational Analysis of the Effects of Process Parameters on Molten Pool Transport in Cu-Ni Dissimilar Laser Weld Pool  

Microsoft Academic Search

A three-dimensional, transient numerical model is used for analyzing the effects of process parameters such as laser power and the laser scanning speed on turbulent momentum, heat and mass transport in a typical dissimilar metal weld pool of a copper-nickel binary couple. The conservation equations are solved in a coupled manner using a semi-implicit pressure linked algorithm in the framework

Alexandros K. Skouras; Nilanjan Chakraborty; Suman Chakraborty

2010-01-01

34

Modeling the field of laser welding melt pool by RBFNN  

E-print Network

Efficient control of a laser welding process requires the reliable prediction of process behavior. A statistical method of field modeling, based on normalized RBFNN, can be successfully used to predict the spatiotemporal dynamics of surface optical activity in the laser welding process. In this article we demonstrate how to optimize RBFNN to maximize prediction quality. Special attention is paid to the structure of sample vectors, which represent the bridge between the field distributions in the past and future.

Bracic, A Borstnik; Grabec, I

2007-01-01

35

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

NASA Astrophysics Data System (ADS)

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

Xiangdong, Gao; Qian, Wen

2013-12-01

36

Plasma diagnostics approach to welding heat source/molten pool interaction  

SciTech Connect

Plasma diagnostic techniques show that weld fusion zone profile and loss of metal vapors from the molten pool are strongly dependent on both the intensity and distribution of the heat source. These plasma properties, are functions of cathode vertex angle and thermal conductivity of the shielding gas, especially near the anode.

Key, J.F.; McIlwain, M.E.; Isaacson, L.

1980-01-01

37

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

PubMed

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

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

2014-05-01

38

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

39

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

Microsoft Academic Search

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

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

1992-01-01

40

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

E-print Network

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

Towers, Naomi M.

41

Plasma effect on weld pool surface reconstruction by shape-from-polarization analysis  

SciTech Connect

The polarimetric state of the thermal radiations emitted by the weld metal contains geometric information about the emitting surface. Even though the analysed thermal radiation has a wavelength corresponding to a blind spectral window of the arc plasma, the physical presence of the arc plasma itself interferes with the rays radiated by the weld pool surface before attaining the polarimeter, thus modifying the geometric information transported by the ray. In the present work, the effect of the arc plasma-surrounding zone on the polarimetric state and propagation direction of the radiated ray is analyzed. The interaction with the arc plasma zone induces a drop in ray intensity and a refraction of ray optical path.

Coniglio, N.; Mathieu, A., E-mail: alexandre.mathieu@u-bourgogne.fr [Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS/Université de Bourgogne, 12 rue de la Fonderie, 71200 Le Creusot (France); Aubreton, O.; Stolz, C. [Université de Bourgogne Laboratoire Le2i UMR CNRS 6306, allée Alain Savary, 21000 Dijon (France)

2014-03-31

42

Gravitational effects on the development of weld-pool and solidification microstructures  

SciTech Connect

This research effort has as its objective the development of a quantitative understanding of the effects of both low- and high-g environments on the solidification microstructures and morphologies that are produced in alloy single crystals during a variety of melting and solidification processes. The overall goal of the effort is to delineate the nature of the roles played by natural convection, surface-tension-driven convection, and mass transport effects due to interactions associated with various heating methods that are used to form melt pools in practical, commercially important alloy systems. The experimental and theoretical investigations comprising this effort encompass the study of configurations in which stationary heat sources are employed as well as melt pools formed by moving heat sources like those frequently used in fusion-welding processes.

Boatner, L.A.; David, S.A. [Oak Ridge National Lab., TN (United States); Workman, G. [Univ. of Alabama, Huntsville, AL (United States). Johnson Research Center

1994-09-01

43

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

44

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

PubMed

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

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

2013-04-01

45

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

NASA Technical Reports Server (NTRS)

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

Canright, David; Henson, Van Emden

1996-01-01

46

REGULATION OF TRACHEBRONCHIAL TISSUE SPECIFIC STEM CELL POOL SIZE  

PubMed Central

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

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

2013-01-01

47

Adaptive control of seam tracking through progressive HAZ and weld pool penetration using thickness measurement  

Microsoft Academic Search

A mathematical model for predictive\\/adaptive control of weld bead penetration and seam tracking in tungsten inert gas welding as an approach to process control of robotic GTAW has been developed. Weld process parameters such as : base current and time, pulse current and time, electrode tip to workpiece distance, filler traveling speed, torch traveling speed and workpiece thickness have been

Iskandar Baharin; B. H. Mir Sadehgi

1995-01-01

48

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.

49

WELDING RESEARCH -s85WELDING JOURNAL  

E-print Network

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

Zhang, YuMing

50

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

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

51

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. PMID:16578762

Diamond, Jared

1982-01-01

52

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.

53

Active transport of potassium by the Cecropia midgut; tracer kinetic theory and transport pool size.  

PubMed

1. Tracer influx kinetics have been analysed theoretically to determine the size of the transport pool with no assumptions regarding the transport pathway. 2. For a calculation of the size of the transport pool to be made, the following six conditions are required by the theory: tracer steady state attained, tissue steady state attained, Isc measures next flux, small magnitude and constant time-course of efflux, and correction for decay in pumping rate. 3. The size of the pool, SI, is given by the steady state influx, Finfinity, divided by the mixing-time constant, alpha. 4. Some experimental results are analysed by three different graphical methods, and it is shown that these three methods are equivalent. Specifically, alpha is equal to the reciprocal of the 75% mixing time, t75, divided by 1n 4 and is equal to the reciprocal of the lag time, X. 5. The tracer kinetic theory is applied to active potassium transport across the isolated short-circuited midgut: the transport meets the six conditions required by the theory. 6. The size of the transport pool of potassium in one midgut is calculated to be 80.5 muequiv./g wet weight under high-K steady-state conditions. A value as high as this suggests that the pool is intracellular. PMID:1202123

Wood, J L; Harvey, W R

1975-10-01

54

Dynamics of space welding impact and corresponding safety welding study.  

PubMed

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

Fragomeni, James M; Nunes, Arthur C

2004-03-01

55

Detection and Sizing of Fatigue Cracks in Steel Welds with Advanced Eddy Current Techniques  

NASA Astrophysics Data System (ADS)

Butt-welded specimens were fatigued to produce cracks in the weld heat-affected zone. Advanced eddy current (AEC) techniques were used to detect and size the cracks through a coating. AEC results were compared with magnetic particle and phased-array ultrasonic techniques. Validation through destructive crack measurements was also conducted. Factors such as geometry, surface treatment, and crack tightness interfered with depth sizing. AEC inspection techniques have the potential of providing more accurate and complete sizing flaw data for manufacturing and in-service inspections.

Todorov, E. I.; Mohr, W. C.; Lozev, M. G.

2008-02-01

56

Size of Vesicle Pools, Rates of Mobilization, and Recycling at Neuromuscular Synapses of a Drosophila mutant, shibire  

Microsoft Academic Search

Two vesicle pools, readily releasable (RRP) and reserve (RP) pools, are present at Drosophila neuromuscular junctions. Using a temperature-sensitive mutant, shibirets, we studied pool sizes and vesicle mobilization rates. In shibirets, due to lack of endocytosis at nonpermissive temperatures, synaptic currents continuously declined during tetanic stimulation until they ceased as the result of vesicle depletion. By then, ?84,000 quanta were

Ricardo Delgado; Carlos Maureira; Carolina Oliva; Yoshiaki Kidokoro; Pedro Labarca

2000-01-01

57

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

E-print Network

Planktonic phosphorus pool sizes and cycling efficiency in coastal and interior British Columbia long acknowledged the importance of phosphorus (P) in determining the organism biomass and productivity of precise measurements of the dissolved inorganic phosphorus (PO3Ã? 4 ) and (2) accurate or complete

Mazumder, Asit

58

Performance Model for the Pool Size Behavior in Apache HTTP Server Software  

E-print Network

1 Performance Model for the Pool Size Behavior in Apache HTTP Server Software Tien Van Do, Ram Chakka, Thang Le Nhat, Udo Krieger Abstract The operation of the Web server's software architecture a way for a Web server software to organize (process or threading based) itself into more simultaneously

Do, Tien Van

59

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).

60

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

61

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

PubMed

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

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

2013-08-01

62

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. PMID:9448323

Goda, Yukiko; Stevens, Charles F.

1998-01-01

63

Welding  

NSDL National Science Digital Library

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

2010-09-29

64

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

PubMed Central

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

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

2009-01-01

65

Weld width indicates weld strength  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

66

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

67

Modeling of Heat and Mass Transfer in Fusion Welding  

SciTech Connect

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

Zhang, Wei [ORNL

2011-01-01

68

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

69

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

70

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

71

Seed growth rate and carbohydrate pool sizes of the soybean fruit.  

PubMed

The relationships between various carbohydrate pools of the soybean (Glycine max [L.] Merrill) fruit and growth rate of seeds were evaluated. Plants during midpod-fill were subjected to various CO(2) concentrations or light intensities for 7 days to generate different rates of seed growth. Dry matter accumulation rates of seeds and pod wall, along with glucose, sucrose, and starch concentrations in the pod wall, seed coat, and embryo were measured in three-seeded fruits located from nodes six through ten. Seed growth rates ranged from 4 to 37 milligrams.day(-1).fruit(-1). When seed growth rates were greater than 12 milligrams.day(-1).fruit(-1), sucrose concentration remained relatively constant in the pod wall (1.5 milligrams.100 milligrams dry weight(-1)), seed coat (8.5 milligrams.100 milligrams dry weight(-1)), and embryo (5.0 milligrams.100 milligrams dry weight(-1)). However, sucrose concentrations decreased in all three parts of the fruit as growth rate of the seeds fell below 12 milligrams.day(-1).fruit(-1). This relationship suggests that at high seed growth rates, flux of sucrose through the sucrose pools of the fruit was more important than pool size for growth. Starch concentration in the pod wall remained relatively constant (2 milligrams.100 milligrams dry weight(-1)) at higher rates of seed growth but decreased as seed growth rates fell below 12 milligrams.day(-1).fruit(-1). This suggests that pod wall starch may buffer seed growth under conditions of limiting assimilate availability. There was no indication that carbohydrate pools of the fruit were a limitation to transport or growth processes of the soybean fruit. PMID:16664469

Fader, G M; Koller, H R

1985-11-01

72

Treatment of familial hypercholesterolemia by portacaval anastomosis: effect on cholesterol metabolism and pool sizes.  

PubMed Central

Measurements of the key parameters of cholesterol homeostasis and the mass of the body pools of cholesterol were carried out in two patients with familial hypercholesterolemia (FH), one homozygote and one heterozygote, before and 28 and 18 months, respectively, after portacaval anastomosis (PCA). In both patients the procedure significantly reduced the plasma concentrations of total and low density lipoprotein cholesterol and the daily rate of whole body cholesterol and bile acid synthesis. In addition, PCA caused a net efflux of accumulated tissue cholesterol as demonstrated by reductions in the rapidly exchangeable and total exchangeable masses of body cholesterol. Shunt patency was verified by demonstration of increased bile acids in serum from fasting patients and from patients 2 hr after a meal and by increased plasma glucagon before and after arginine infusion. Other than a persistently increased level of serum alkaline phosphatase, liver function tests have fallen within the normal range in both patients; there has been no evidence of hepatic encephalopathy. In the homozygous patient there has also been a striking resolution in xanthoma size and distribution. These multiple effects on cholesterol homeostasis and pool sizes strongly suggest that PCA can reverse the progressive accumulation of cholesterol in body tissues of FH patients. PMID:6572906

McNamara, D J; Ahrens, E H; Kolb, R; Brown, C D; Parker, T S; Davidson, N O; Samuel, P; McVie, R M

1983-01-01

73

Influence of the Diadinoxanthin Pool Size on Photoprotection in the Marine Planktonic Diatom Phaeodactylum tricornutum1  

PubMed Central

The pool size of the xanthophyll cycle pigment diadinoxanthin (DD) in the diatom Phaeodactylum tricornutum depends on illumination conditions during culture. Intermittent light caused a doubling of the DD pool without significant change in other pigment contents and photosynthetic parameters, including the photosystem II (PSII) antenna size. On exposure to high-light intensity, extensive de-epoxidation of DD to diatoxanthin (DT) rapidly caused a very strong quenching of the maximum chlorophyll fluorescence yield (Fm, PSII reaction centers closed), which was fully reversed in the dark. The non-photochemical quenching of the minimum fluorescence yield (Fo, PSII centers open) decreased the quantum efficiency of PSII proportionally. For both Fm and Fo, the non-photochemical quenching expressed as F/F? ? 1 (with F? the quenched level) was proportional to the DT concentration. However, the quenching of Fo relative to that of Fm was much stronger than random quenching in a homogeneous antenna could explain, showing that the rate of photochemical excitation trapping was limited by energy transfer to the reaction center rather than by charge separation. The cells can increase not only the amount of DT they can produce, but also its efficiency in competing with the PSII reaction center for excitation. The combined effect allowed intermittent light grown cells to down-regulate PSII by 90% and virtually eliminated photoinhibition by saturating light. The unusually rapid and effective photoprotection by the xanthophyll cycle in diatoms may help to explain their dominance in turbulent waters. PMID:12114593

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

2002-01-01

74

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

75

Laser spot size and beam profile studies for tissue welding applications  

NASA Astrophysics Data System (ADS)

We evaluated the effect of changes in laser spot size and beam profile on the thermal denaturation zone produced during laser skin welding. Our objective was to limit heating of the tissue surface, while creating enough thermal denaturation in the deeper layers of the dermis to produce full-thickness welds. Two-cm-long, full-thickness incisions were made on the backs of guinea pigs, in vivo. India ink was used as an absorber. Continuous-wave, 1.06-?m, Nd:YAG laser radiation was scanned over the incisions, producing approximately 100 ms pulses. Cooling times of 10.0 s between scans were used. Laser spot diameters of 1, 2, 4, and 6 mm were studied, with powers of 1, 4, 16, and 36 W, respectively. The irradiance remained constant at 127 W/cm2. 1, 2, and 4 mm diameter spots produced thermal denaturation to a depth of 570 +/- 100 ?m, 970 +/- 210 ?m, and 1470 +/- 190 ?m, respectively. The 6-mm- diameter spot produced full-thickness welds (1900 ?m), but also burns due to the high incident power. Monte Carlo simulations were also conducted, varying the laser spot diameter and beam profile. The simulations verified that an increase in laser spot diameter result in an increase in the penetration depth of radiation into the tissue.

Fried, Nathaniel M.; Hung, Vincent C.; Walsh, Joseph T., Jr.

1999-06-01

76

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

77

WELDING RESEARCH -s57WELDING JOURNAL  

E-print Network

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

Zhang, YuMing

78

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

PubMed Central

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

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

2013-01-01

79

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

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

80

Tailoring weld geometry and composition in fusion welding through convective mass transfer calculations  

Microsoft Academic Search

In the past two decades, numerical transport phenomena based models have provided useful information about the thermal cycles and weld pool geometry. However, no effort has been made to apply these concepts to design weld consumables, to study the weld bead shape on welding two plates with different sulfur contents and to tailor weld pool geometry to specified dimensions. The

Saurabh Mishra

2006-01-01

81

Satellite-cell pool size does matter: defining the myogenic potency of aging skeletal muscle  

PubMed Central

The deteriorating in vivo environment is thought to play a major role in reduced stem cell function with age. Stem cell capacity to support tissue maintenance depends not only on their response to cues from the surrounding niche, but also on their abundance. Here we investigate satellite cell (myogenic stem cell) pool size and its potential to participate in muscle maintenance through old age. The numbers and performance of mouse satellite cells have been analyzed using molecular markers that exclusively characterize quiescent satellite cells and their progeny as they transit through proliferation, differentiation and generation of reserve cells. The study establishes that abundance of resident satellite cells declines with age in myofibers from both fast- and slow-twitch muscles. Nevertheless, the inherent myogenic potential of satellite cells does not diminish with age. Furthermore, the aging satellite cell niche retains the capacity to support effective myogenesis upon enrichment of the mitogenic milieu with FGF. Altogether, satellite cell abundance, but not myogenic potential, deteriorates with age. This study suggests that the population of satellite cells that participate in myofiber maintenance during routine muscle utilization is not fully replenished throughout life. PMID:16554047

Shefer, Gabi; Van de Mark, Daniel P.; Richardson, Joshua B.; Yablonka-Reuveni, Zipora

2009-01-01

82

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

83

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

84

Optically controlled welding system  

NASA Technical Reports Server (NTRS)

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

Gordon, Stephen S. (inventor)

1988-01-01

85

Optically controlled welding system  

NASA Technical Reports Server (NTRS)

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

Gordon, Stephen S. (Inventor)

1989-01-01

86

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

87

Active weld control  

NASA Technical Reports Server (NTRS)

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

Powell, Bradley W.; Burroughs, Ivan A.

1994-01-01

88

Acoustic-Emission Weld-Penetration Monitor  

NASA Technical Reports Server (NTRS)

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

Maram, J.; Collins, J.

1986-01-01

89

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

PubMed Central

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

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

2011-01-01

90

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

91

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

E-print Network

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

Boyer, Edmond

92

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

EPA Science Inventory

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

93

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

PubMed

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

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

2014-09-01

94

Fluid Flow Phenomena during Welding  

SciTech Connect

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

Zhang, Wei [ORNL

2011-01-01

95

Predictors of infarct size after primary coronary angioplasty in acute myocardial infarction from pooled analysis from four contemporary trials.  

PubMed

Determinates of infarct size in patients with acute myocardial infarction (AMI) undergoing percutaneous coronary intervention (PCI) have been incompletely characterized, in part because of the limited sample size of previous studies. Databases therefore were pooled from 4 contemporary trials of primary or rescue PCI (EMERALD, COOL-MI, AMIHOT, and ICE-IT), in which the primary end point was infarct size assessed using technetium-99m sestamibi single-photon emission computed tomographic imaging, measured at the same core laboratory. Of 1,355 patients, infarct size was determined using technetium-99m sestamibi imaging in 1,199 patients (88.5%), at a mean time of 23 +/- 15 days. Median infarct size of the study population was 10% (interquartile range 0% to 23%; mean 14.9 +/- 16.1%). Using multiple linear regression analysis of 18 variables, left anterior descending infarct artery, baseline Thrombolysis In Myocardial Infarction grade 0/1 flow, male gender, and prolonged door-to-balloon time were powerful independent predictors of infarct size (all p <0.0001). Other independent correlates of infarct size were final Thrombolysis In Myocardial Infarction grade <3 flow (p = 0.0001), previous AMI (p = 0.005), symptom-onset-to-door time (p = 0.021), and rescue angioplasty (p = 0.026). In conclusion, anterior infarction, time to reperfusion, epicardial infarct artery patency before and after reperfusion, male gender, previous AMI, and failed thrombolytic therapy were important predictors of infarct size after angioplasty in patients with AMI assessed using technetium-99m sestamibi imaging and should be considered when planning future trials of investigational drugs or devices designed to enhance myocardial recovery. PMID:17950792

Stone, Gregg W; Dixon, Simon R; Grines, Cindy L; Cox, David A; Webb, John G; Brodie, Bruce R; Griffin, John J; Martin, Jack L; Fahy, Martin; Mehran, Roxana; Miller, Todd D; Gibbons, Raymond J; O'Neill, William W

2007-11-01

96

EFFECTS OF SURFACE DEPRESSION AND CONVECTION IN GTA WELDING  

E-print Network

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

Eagar, Thomas W.

97

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

PubMed Central

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

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

2014-01-01

98

Grain Refinement by Laser Welding of AA 5083 with Addition of Ti/B  

NASA Astrophysics Data System (ADS)

Grain refinement was reported to improve the mechanical properties and reduce the hot crack susceptibility of aluminum welds. Some of today's filler materials already contain grain refiners. However, their effectiveness will strongly depend on the boundary conditions of welding. The aim of this study is thus to determine the minimum content of Ti/B grain refiner, which is needed to achieve a small grain size with 100% globular grains of the weld metal for different welding conditions, particularly with respect to high welding speed and cooling rate by laser welding. Controlled amounts of TiborTM grain refiner (containing Ti and B in a ratio of 5:1) were introduced into the molten pool of AA 5083 by pre-deposited cast inserts under different welding conditions by laser welding. The results show that, despite the high cooling rate and great melt overheating, the laser weld could be grain refined to a mean grain size at ca. 22 ?m. The minimal required Tibor™ concentration for complete grain refinement increases with welding speed. The WDX analysis has confirmed that the titanium aluminides are the nucleation site for equiaxed grains.

Tang, Z.; Seefeld, T.; Vollertsen, F.

99

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

E-print Network

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

Eagar, Thomas W.

100

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

101

Flow Dynamics in Arc Welding  

SciTech Connect

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

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

2008-02-21

102

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

103

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

PubMed Central

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

Northfield, T C; Hofmann, A F

1975-01-01

104

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

NASA Astrophysics Data System (ADS)

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

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

105

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

PubMed Central

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

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

2013-01-01

106

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

107

Autogeneous Friction Stir Weld Lack-of-Penetration Defect Detection and Sizing Using Directional Conductivity Measurements with MWM Eddy Current Sensor  

NASA Technical Reports Server (NTRS)

Al 2195-T8 plate specimens containing Friction Stir Welds (FSW), provided by Lockheed Martin, were inspected using directional conductivity measurements with the MWM sensor. Sensitivity to lack-of-penetration (LOP) defect size has been demonstrated. The feature used to determine defect size was the normalized longitudinal component of the MWM conductivity measurements. This directional conductivity component was insensitive to the presence of a discrete crack. This permitted correlation of MWM conductivity measurements with the LOP defect size as changes in conductivity were apparently associated with metallurgical features within the first 0.020 in. of the LOP defect zone. Transverse directional conductivity measurements also provided an indication of the presence of discrete cracks. Continued efforts are focussed on inspection of a larger set of welded panels and further refinement of LOP characterization tools.

Goldfine, Neil; Zilberstei, Vladimir; Lawson, Ablode; Kinchen, David; Arbegast, William

2000-01-01

108

Exchangeable zinc pool size at birth is smaller in small-for- gestational-age than in appropriate-for-gestational-age preterm  

Microsoft Academic Search

ABSTRACT Background: Small-for-gestational-age (SGA) infants are suscep- tible to postnatal zinc deficiency, but whether this susceptibility is due to intrauterine factors or to high postnatal growth requirements is unknown. Objective: We hypothesized that the size of the exchangeable,zinc pool (EZP), which reflects metabolically available zinc, would be smaller in SGA than in appropriate-for-gestational-age (AGA) in- fants born prematurely. Design: Intravenous

Nancy F Krebs; Jamie L Westcott; Donna J Rodden; Katharine W Ferguson; Leland V Miller; K Michael Hambidge

109

Thermochemical Analysis of Hydrogen Absorption in Welding  

E-print Network

the amount of hy- drogen initially absorbed by the weld pool. Diffusible hydrogen measurements can Model Sievert's Law Diffusible Hydrogen Diatomic H2 Pressure 1-12 Measuring Weld Hydrogen Terasaki'' .' j I ~l Thermochemical Analysis of Hydrogen Absorption in Welding A new model that addresses

Eagar, Thomas W.

110

Optical penetration sensor for pulsed laser welding  

DOEpatents

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

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

2000-01-01

111

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

112

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

SciTech Connect

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

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

2009-01-01

113

Tailoring weld geometry and composition in fusion welding through convective mass transfer calculations  

NASA Astrophysics Data System (ADS)

In the past two decades, numerical transport phenomena based models have provided useful information about the thermal cycles and weld pool geometry. However, no effort has been made to apply these concepts to design weld consumables, to study the weld bead shape on welding two plates with different sulfur contents and to tailor weld pool geometry to specified dimensions. The present research focuses on these unexplored areas. The research proposed here seeks to develop a quantitative understanding of mass transport during fusion welding, with special emphasis on the role of surface active elements and the effect of solute distribution on weld defects like liquation cracking. A comprehensive model, incorporating numerical three-dimensional calculations of temperature and velocity fields and solute distribution in the weld pool is developed for the proposed quantitative study. The study identifies the factors that affect the weld pool geometry on joining two plates with different sulfur contents, and predicts the susceptibility of an aluminum-copper alloy GMA weld to liquation cracking. The specific contributions of the present thesis research include (i) development of a numerical solute transport model for fusion welding; (ii) improving the reliability of output of the numerical model; (iii) achieving computational efficiency and economy by developing a neural network trained by data generated by the numerical model; (iv) creating a bi-directional methodology where a target weld attribute like weld pool geometry can be attained via multiple combinations of input process parameters like arc current, voltage and welding speed; (v) calculating sulfur distribution during gas tungsten arc welding of stainless steel plates with different sulfur contents and predicting the arc welding of aluminum-copper alloys by incorporating the heat and mass addition from filler metal and a non-equilibrium solidification model, and using the copper content of the mushy zone to predict the occurrence of liquation cracking.

Mishra, Saurabh

114

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

E-print Network

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

Cambridge, University of

115

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

PubMed

The effects of a high level of dietary fibre (DF) either as arabinoxylan (AX) or resistant starch (RS) on digestion processes, SCFA concentration and pool size in various intestinal segments and on the microbial composition in the faeces were studied in a model experiment with pigs. A total of thirty female pigs (body weight 63.1 (sem 4.4) kg) were fed a low-DF, high-fat Western-style control diet (WSD), an AX-rich diet (AXD) or a RS-rich diet (RSD) for 3 weeks. Diet significantly affected the digestibility of DM, protein, fat, NSP and NSP components, and the arabinose:xylose ratio, as well as the disappearance of NSP and AX in the large intestine. RS was mainly digested in the caecum. AX was digested at a slower rate than RS. The digesta from AXD-fed pigs passed from the ileum to the distal colon more than twice as fast as those from WSD-fed pigs, with those from RSD-fed pigs being intermediate (P< 0.001). AXD feeding resulted in a higher number of Faecalibacterium prausnitzii, Roseburia intestinalis, Blautia coccoides-Eubacterium rectale, Bifidobacterium spp. and Lactobacillus spp. in the faeces sampled at week 3 of the experimental period (P< 0.05). In the caecum, proximal and mid colon, AXD feeding resulted in a 3- to 5-fold higher pool size of butyrate compared with WSD feeding, with the RSD being intermediate (P <0.001). In conclusion, the RSD and AXD differently affected digestion processes compared with the WSD, and the AXD most efficiently shifted the microbial composition towards butyrogenic species in the faeces and increased the large-intestinal butyrate pool size. PMID:25327182

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

2014-12-14

116

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

NASA Astrophysics Data System (ADS)

The transport of hydrogen during fusion welding of the titanium alloy Ti-6Al4V is analyzed. A coupled thermodynamic/kinetic treatment is proposed for the mass transport within and around the weld pool. The modeling indicates that hydrogen accumulates in the weld pool as a consequence of the thermodynamic driving forces that arise; a region of hydrogen depletion exists in cooler, surrounding regions in the heat-affected zone and beyond. Coupling with a hydrogen diffusion-controlled bubble growth model is used to simulate bubble growth in the melt and, thus, to make predictions of the hydrogen concentration barrier needed for pore formation. The effects of surface tension of liquid metal and the radius of preexisting microbubble size on the barrier are discussed. The work provides insights into the mechanism of porosity formation in titanium alloys.

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

2012-02-01

117

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

PubMed

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

Hewett, P

1995-02-01

118

Computerized radiographic sensing and control of an arc welding process  

SciTech Connect

This paper summarizes an effort in which real-time radiography was implemented for on-line arc welding process study and control. X-ray penetrating radiation was used for volume observation in the welding pool and the heat-affected zone during the weld process. The advantages of such a technique are online detection and monitoring of defect formation in the weld and capability to study metal fusion and filler metal/base metal interaction and metal transfer in the welding pool. This technique may also be used for postservice, real-time remote testing of weld quality.

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

1990-03-01

119

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

120

Emission spectrometry evaluation in arc welding monitoring system  

Microsoft Academic Search

This work describes exploratory experimental procedures implemented for the development of a non-intrusive and real-time sensor for weld defect tracking which uses emission spectrometry for measuring the electromagnetic content of the plasma-weld pool interface in the GMA welding arc. The welding process monitoring is carried out by calculating the iron (Fe) and the manganese (Mn) electronic temperatures within the welding

Sadek C. A. Alfaro; Diogo de S. Mendonça; Marcelo S. Matos

2006-01-01

121

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

122

Effects of varying subatmospheric pressure on stationary plasma arc welds  

NASA Technical Reports Server (NTRS)

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

Chin, J. J.; Rubinsky, B.

1991-01-01

123

Welding Research  

NASA Technical Reports Server (NTRS)

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

1982-01-01

124

Mathematical Model Of Variable-Polarity Plasma Arc Welding  

NASA Technical Reports Server (NTRS)

Mathematical model of variable-polarity plasma arc (VPPA) welding process developed for use in predicting characteristics of welds and thus serves as guide for selection of process parameters. Parameters include welding electric currents in, and durations of, straight and reverse polarities; rates of flow of plasma and shielding gases; and sizes and relative positions of welding electrode, welding orifice, and workpiece.

Hung, R. J.

1996-01-01

125

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

E-print Network

heater sizes were obtained in low-g (0.01 ± 0.025 g) and high-g (1.7 ± 0.5 g) aboard the KC-135 aircraft transfer remained unaffected. � 2003 Elsevier Inc. All rights reserved. Keywords: Microgravity; Boiling

Kim, Jungho

126

The keyhole region in VPPA welds  

NASA Technical Reports Server (NTRS)

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

Walsh, Daniel W.

1988-01-01

127

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

E-print Network

space or personal protective equipment, therefore, may be exposed to a serious threat to his health. The results of this research underscore the importance of properly designed engineering controls in areas where welding is conducted and highly toxic... that cadmium, chromium, lead, titanium, magnesium, manganese, mercury molybdenum, n1ckel, vanadium, zinc and florides are in the category of pulmonary irritants or toxic inhalants. Studies in many countr1es by many researchers have dealt with the chemical...

Owen, Richard James

2012-06-07

128

Thermocapillary and Magnetohydrodynamic Effects in Modelling the Thermodynamics of Stationary Welding Processes  

E-print Network

Welding Processes Michael HUGHES, Gareth A. TAYLOR and Koulis PERICLEOUS Centre for Numerical Modelliqng transport and solidification in a stationary axisymmetric weld pool. The PHOENICS implementations, the integration of the effects within the fluid dynamics of an axisymmetric weld pool is compared against

Taylor, Gary

129

Daily consumption of orange-fleshed sweet potato for 60 days increased plasma ?-carotene concentration but did not increase total body vitamin A pool size in Bangladeshi women.  

PubMed

We assessed the effect of daily consumption of orange-fleshed sweet potatoes (OFSP), with or without added fat, on the vitamin A (VA) status of Bangladeshi women with low initial VA status. Women (n = 30/group) received one of the following for 6 d/wk over 10 wk: 1) 0 ?g retinol activity equivalents (RAE)/d as boiled white-fleshed sweet potatoes (WFSP) and a corn oil capsule, 2) 600 ?g RAE/d as boiled OFSP and a corn oil capsule, 3) fried OFSP and a corn oil capsule, or 4) boiled WFSP and a retinyl palmitate capsule in addition to their home diets. Plasma concentrations of retinol and ?-carotene and total body VA pool size were assessed before and after the 60-d intervention. Initial and final plasma retinol concentrations (mean ± SD) were 0.75 ± 0.18 ?mol/L and 0.84 ± 0.19 ?mol/L, respectively (P = 0.31); final means did not differ by group. Initial and final plasma ?-carotene concentrations were 0.10 ± 00 ?mol/L and 0.18 ± 0.09 ?mol/L, respectively (P < 0.0001); final mean plasma ?-carotene concentrations were higher in groups that received OFSP (P < 0.0001), and final mean plasma ?-carotene was marginally higher in the group that received fried OFSP compared with boiled OFSP (P = 0.07). Initial and final total body VA pool sizes were 0.060 ± 0.047 mmol and 0.091 ± 0.070 mmol, respectively (P = 0.05, n = 110) and did not differ by group. Despite an increase in plasma ?-carotene concentration, the impact of OFSP on VA status appears to be limited in Bangladeshi women residing in a resource-poor community. PMID:22933750

Jamil, Kazi M; Brown, Kenneth H; Jamil, Maleka; Peerson, Janet M; Keenan, Alison H; Newman, John W; Haskell, Marjorie J

2012-10-01

130

The mechanism of penetration increase in A-TIG welding  

NASA Astrophysics Data System (ADS)

The mechanism of the increasing of A-TIG welding penetration is studied by using the activating flux we developed for stainless steel. The effect of flux on the flow and temperature fields of weld pool is simulated by the PHOENICS software. It shows that without flux, the fluid flow will be outward along the surface of the weld pool and then down, resulting in a flatter weld pool shape. With the flux, the oxygen, which changes the temperature dependence of surface tension grads from a negative value to a positive value, can cause significant changes on the weld penetration. Fluid flow will be inward along the surface of the weld pool toward the center and then down. This fluid flow pattern efficiently transfers heat to the weld root and produces a relatively deep and narrow weld. This change is the main cause of penetration increase. Moreover, arc construction can cause the weld width to become narrower and the penetration to become deeper, but this is not the main cause of penetration increase. The effects of flux on fluid flow of the weld pool surface and arc profiles were observed in conventional TIG welding and in A-TIG welding by using high-speed video camera. The fluid flow behavior was visualized in realtime scale by micro focused X-ray transmission video observation system. The result indicated that stronger inward fluid flow patterns leading to weld beads with narrower width and deeper penetration could be apparently identified in the case of A-TIG welding. The flux could change the direction of fluid flow in welding pool. It has a good agreement with the simulation results.

Zhang, Rui-Hua; Pan, Ji-Luan; Katayama, Seiji

2011-06-01

131

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

E-print Network

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

Zhang, YuMing

132

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

133

Neurofuzzy Model-Based Weld Fusion State Estimation  

E-print Network

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

Zhang, YuMing

134

Variable-Polarity Plasma Arc Welding Of Alloy 2219  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

135

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

SciTech Connect

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

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

2012-12-31

136

Pool Purification  

NASA Technical Reports Server (NTRS)

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

1988-01-01

137

Welding I.  

ERIC Educational Resources Information Center

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

Allegheny County Community Coll., Pittsburgh, PA.

138

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.

139

Friction Stir Welding Development  

NASA Technical Reports Server (NTRS)

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

Romine, Peter L.

1998-01-01

140

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

E-print Network

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

Eagar, Thomas W.

141

The application of nanosecond-pulsed laser welding technology in MEMS packaging with a shadow mask$  

E-print Network

The application of nanosecond-pulsed laser welding technology in MEMS packaging with a shadow mask wiring is not pre- ferred. A comprehensive review on laser welding was given in [6]. The laser welding of laser welding is to create the liquid pool by absorption of incident radiation, allow it to grow

Lin, Liwei

142

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

143

Advanced Welding Concepts  

NASA Technical Reports Server (NTRS)

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

Ding, Robert J.

2010-01-01

144

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

NASA Technical Reports Server (NTRS)

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

Walsh, Daniel W.

1987-01-01

145

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

146

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

147

Welding Introduction  

NSDL National Science Digital Library

The Materials Education Resource Center has provided this module to help students learn the basics of metal welding, including techniques. Students will learn the vocabulary used in welding and see examples of welding processes. This PDF document includes a step by step procedure for the learning module as well as links to supporting videos and online reference tools.

Stoebe, Thomas G.

2012-09-24

148

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

149

Heat transfer and fluid flow during keyhole mode laser welding of tantalum, Ti 6Al 4V, 304L stainless steel and vanadium  

NASA Astrophysics Data System (ADS)

Because of the complexity of several simultaneous physical processes, most heat transfer models of keyhole mode laser welding require some simplifications to make the calculations tractable. The simplifications often limit the applicability of each model to the specific materials systems for which the model is developed. In this work, a rigorous, yet computationally efficient, keyhole model is developed and tested on tantalum, Ti-6Al-4V, 304L stainless steel and vanadium. Unlike previous models, this one combines an existing model to calculate keyhole shape and size with numerical fluid flow and heat transfer calculations in the weld pool. The calculations of the keyhole profile involved a point-by-point heat balance at the keyhole walls considering multiple reflections of the laser beam in the vapour cavity. The equations of conservation of mass, momentum and energy are then solved in three dimensions assuming that the temperatures at the keyhole wall reach the boiling point of the different metals or alloys. A turbulence model based on Prandtl's mixing length hypothesis was used to estimate the effective viscosity and thermal conductivity in the liquid region. The calculated weld cross-sections agreed well with the experimental results for each metal and alloy system examined here. In each case, the weld pool geometry was affected by the thermal diffusivity, absorption coefficient, and the melting and boiling points, among the various physical properties of the alloy. The model was also used to better understand solidification phenomena and calculate the solidification parameters at the trailing edge of the weld pool. These calculations indicate that the solidification structure became less dendritic and coarser with decreasing weld velocities over the range of speeds investigated in this study. Overall, the keyhole weld model provides satisfactory simulations of the weld geometries and solidification sub-structures for diverse engineering metals and alloys.

Rai, R.; Elmer, J. W.; Palmer, T. A.; Roy, T. Deb

2007-09-01

150

Deconvoluting the Friction Stir Weld Process for Optimizing Welds  

NASA Technical Reports Server (NTRS)

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

Schneider, Judy; Nunes, Arthur C.

2008-01-01

151

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

152

Grain refinement control in TIG arc welding  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

153

RIM1 and RIM2 redundantly determine Ca2+ channel density and readily releasable pool size at a large hindbrain synapse.  

PubMed

The localization and density of voltage-gated Ca(2+) channels at active zones are essential for the amount and kinetics of transmitter release at synapses. RIM proteins are scaffolding proteins at the active zone that bind to several other presynaptic proteins, including voltage-gated Ca(2+) channel ?-subunits. The long isoforms of RIM proteins, which contain NH2-terminal Rab3- and Munc13-interacting domains, as well as a central PDZ domain and two COOH-terminal C2 domains, are encoded by two genes, Rim1 and Rim2. Here, we used the ideal accessibility of the large calyx of Held synapse for direct presynaptic electrophysiology to investigate whether the two Rim genes have redundant, or separate, functions in determining the presynaptic Ca(2+) channel density, and the size of a readily releasable vesicle pool (RRP). Quantitative PCR showed that cochlear nucleus neurons, which include calyx of Held generating neurons, express both RIM1 and RIM2. Conditional genetic inactivation of RIM2 at the calyx of Held led to a subtle reduction in presynaptic Ca(2+) current density, whereas deletion of RIM1 was ineffective. The release efficiency of brief presynaptic Ca(2+) "tail" currents and the RRP were unaffected in conditional single RIM1 and RIM2 knockout (KO) mice, whereas both parameters were strongly reduced in RIM1/2 double KO mice. Thus, despite a somewhat more decisive role for RIM2 in determining presynaptic Ca(2+) channel density, RIM1 and RIM2 can overall replace each other's presynaptic functions at a large relay synapse in the hindbrain, the calyx of Held. PMID:25343783

Han, Yunyun; Babai, Norbert; Kaeser, Pascal; Südhof, Thomas C; Schneggenburger, Ralf

2015-01-01

154

Hoisting and Rigging: Visual Structural Weld Inspection Criteria and Form  

E-print Network

Hoisting and Rigging: Visual Structural Weld Inspection Criteria and Form Department: Field Safety ­ specify Carbon steel: specifications, if known All others: alloy, if known Weld filler alloy, if known Yes No Is the weld painted? Is surface corrosion within acceptable limits? Does the weld size match the engineering

Wechsler, Risa H.

155

Effect of rapid solidification on stainless steel weld metal microstructures and its implications on the Schaeffler diagram  

Microsoft Academic Search

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 at different welding speeds and laser power levels. Results indicate that both weld pool cooling rate and the postsolidification solid state cooling

S. A. David; J. M. Vitek; R. W. Reed; T. L. Hebble

1987-01-01

156

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

2012-06-01

157

Tailoring weld geometry during keyhole mode laser welding using a genetic algorithm and a heat transfer model  

NASA Astrophysics Data System (ADS)

Tailoring of weld attributes based on scientific principles remains an important goal in welding research. The current generation of unidirectional laser keyhole models cannot determine sets of welding variables that can lead to a particular weld attribute such as specific weld geometry. Here we show how a computational heat transfer model of keyhole mode laser welding can be restructured for systematic tailoring of weld attributes based on scientific principles. Furthermore, the model presented here can calculate multiple sets of laser welding variables, i.e. laser power, welding speed and beam defocus, with each set leading to the same weld pool geometry. Many sets of welding variables were obtained via a global search using a real number-based genetic algorithm, which was combined with a numerical heat transfer model of keyhole laser welding. The reliability of the numerical heat transfer calculations was significantly improved by optimizing values of the uncertain input parameters from a limited volume of experimental data. The computational procedure was applied to the keyhole mode laser welding of the 5182 Al-Mg alloy to calculate various sets of welding variables to achieve a specified weld geometry. The calculated welding parameter sets showed wide variations of the values of welding parameters, but each set resulted in a similar fusion zone geometry. The effectiveness of the computational procedure was examined by comparing the computed weld geometry for each set of welding parameters with the corresponding experimental geometry. The results provide hope that systematic tailoring of weld attributes via multiple pathways, each representing alternative welding parameter sets, is attainable based on scientific principles.

Rai, R.; Roy, T. Deb

2006-03-01

158

Elements of arc welding  

SciTech Connect

This paper looks at the following arc welding techniques: (1) shielded metal-arc welding; (2) submerged-arc welding; (3) gas metal-arc welding; (4) flux-cored arc welding; (5) electrogas welding; (6) gas tungsten-arc welding; and (7) plasma-arc welding.

Not Available

1993-07-01

159

Cave Pool  

USGS Multimedia Gallery

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

160

The physics of welding  

Microsoft Academic Search

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

J. F. Lancaster

1984-01-01

161

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

Code of Federal Regulations, 2013 CFR

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

2013-10-01

162

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

Code of Federal Regulations, 2010 CFR

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

2010-10-01

163

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

Code of Federal Regulations, 2012 CFR

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

2012-10-01

164

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

Code of Federal Regulations, 2011 CFR

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

2011-10-01

165

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

166

WELDING RESEARCH -s229WELDING JOURNAL  

E-print Network

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

Zhang, YuMing

167

WELDING RESEARCH -s11WELDING JOURNAL  

E-print Network

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

Zhang, YuMing

168

Ultrasound in arc welding: a review.  

PubMed

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

da Cunha, Tiago Vieira; Bohórquez, Carlos Enrique Niño

2015-02-01

169

Laser Beam Oscillation Strategies for Fillet Welds in Lap Joints  

NASA Astrophysics Data System (ADS)

Laser beam oscillation opens up new possibilities of influencing the welding process in terms of compensation of tolerances and reduction of process emissions that occur in industrial applications, such as in body-in-white manufacturing. The approaches are to adapt the melt pool width in order to generate sufficient melt volume or to influence melt pool dynamics, e.g. for a better degassing. Welding results are highly dependent on the natural frequency of the melt pool, the used spot diameter and the oscillation speed of the laser beam. The conducted investigations with an oscillated 300 ?m laser spot show that oscillation strategies, which are adjusted to the joining situation improve welding result for zero-gap welding as well as for bridging gaps to approximately 0.8 mm. However, a complex set of parameters has to be considered in order to generate proper welding results. This work puts emphasize on introducing them.

Müller, Alexander; Goecke, Sven-F.; Sievi, Pravin; Albert, Florian; Rethmeier, Michael

170

Damage Tolerance Assessment of Friction Pull Plug Welds  

NASA Technical Reports Server (NTRS)

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

McGill, Preston; Burkholder, Jonathan

2012-01-01

171

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

172

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

173

Welding II.  

ERIC Educational Resources Information Center

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

Allegheny County Community Coll., Pittsburgh, PA.

174

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.

175

FINITE VOLUME METHODS APPLIED TO THE COMPUTATIONAL MODELLING OF WELDING PHENOMENA  

E-print Network

1 FINITE VOLUME METHODS APPLIED TO THE COMPUTATIONAL MODELLING OF WELDING PHENOMENA Gareth A.Taylor@brunel.ac.uk ABSTRACT This paper presents the computational modelling of welding phenomena within a versatile numerical) and Computational Solid Mechanics (CSM). With regard to the CFD modelling of the weld pool fluid dynamics, heat

Taylor, Gary

176

Internal Wire Guide For Gas/Tungsten-Arc Welding  

NASA Technical Reports Server (NTRS)

Wire kept in shielding gas, preventing oxidation. Guide inside gas cup of gas/tungsten-arc welding torch feeds filler wire to weld pool along line parallel to axis of torch. Eliminates problem of how to place and orient torch to provide clearance for external wire guide.

Morgan, Gene E.; Dyer, Gerald E.

1990-01-01

177

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

NASA Astrophysics Data System (ADS)

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

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

178

Cellular automata modeling of weld solidification structure  

SciTech Connect

The authors explore the use of cellular automata in modeling arc-welding processes. A brief discussion of cellular automata and their previous use in micro-scale solidification simulations is presented. Macro-scale thermal calculations for arc-welding at a thin plate are shown to give good quantitative and qualitative results. Combining the two calculations in a single cellular array provides a realistic simulation of grain growth in a welding process. Results of simulating solidification in a moving melt pool in a poly-crystalline alloy sheet are presented.

Dress, W.B.; Zacharia, T.; Radhakrishnan, B.

1993-12-31

179

Vaccum Gas Tungsten Arc Welding, phase 1  

NASA Technical Reports Server (NTRS)

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.

1995-01-01

180

WELDING RESEARCH -S237WELDING JOURNAL  

E-print Network

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

Cambridge, University of

181

WELDING RESEARCH -s231WELDING JOURNAL  

E-print Network

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

Zhang, YuMing

182

WELDING RESEARCH -s87WELDING JOURNAL  

E-print Network

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

Eagar, Thomas W.

183

Increasing Productivity of Welding  

E-print Network

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

Uhrig, J. J.

1983-01-01

184

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

E-print Network

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

Eagar, Thomas W.

185

Effects of controlled interruption of the enterohepatic circulation of bile salts by biliary diversion and by ileal resection on bile salt secretion, synthesis, and pool size in the rhesus monkey  

PubMed Central

The effects of controlled interruption of the enterohepatic circulation (EHC) of bile salts by biliary diversion on bile volume, bile salt secretion and synthesis rates, bile salt pool size, and the relationship to fecal fat excretion were studied in 16 rhesus monkeys. Bile from a chronic bile fistula was returned to the intestine through an electronic stream-splitter which, by diverting different percentages of bile to a collecting system, provided graded and controlled interruption of the EHC. The increase in hepatic bile salt synthesis in response to interruption of the EHC was limited and reached a maximum rate at 20% interruption of the EHC. Up to this level of biliary diversion, the increased hepatic synthesis compensated for bile salt loss so that bile salt secretion and pool size were maintained at normal levels. With diversion of 33% or more, there was no further increase in hepatic bile salt synthesis to compensate for external loss, and as a result there was diminished bile salt secretion, a reduction in bile salt pool size, and steatorrhea was observed. The effects of interruption of the EHC by the streamsplitter were compared with those produced by resection of the distal one-third or two-thirds of small bowel. While ileal resection appreciably reduced bile salt secretion, the EHC was by no means abolished. Bile salt reabsorption from the residual intestine was greater after one-third than after two-thirds small bowel resection. These observations suggest that jejunal reabsorption of bile salts occurs and may well contribute to the normal EHC. PMID:4983661

Dowling, R. Hermon; Mack, Eberhard; Small, Donald M.

1970-01-01

186

Real-time ultrasonic weld evaluation system  

NASA Astrophysics Data System (ADS)

Ultrasonic testing techniques are currently used as an alternative to radiography for detecting, classifying,and sizing weld defects, and for evaluating weld quality. Typically, ultrasonic weld inspections are performed manually, which require significant operator expertise and time. Thus, in recent years, the emphasis is to develop automated methods to aid or replace operators in critical weld inspections where inspection time, reliability, and operator safety are major issues. During this period, significant advances wee made in the areas of weld defect classification and sizing. Very few of these methods, however have found their way into the market, largely due to the lack of an integrated approach enabling real-time implementation. Also, not much research effort was directed in improving weld acceptance criteria. This paper presents an integrated system utilizing state-of-the-art techniques for a complete automation of the weld inspection procedure. The modules discussed include transducer tracking, classification, sizing, and weld acceptance criteria. Transducer tracking was studied by experimentally evaluating sonic and optical position tracking techniques. Details for this evaluation are presented. Classification is obtained using a multi-layer perceptron. Results from different feature extraction schemes, including a new method based on a combination of time and frequency-domain signal representations are given. Algorithms developed to automate defect registration and sizing are discussed. A fuzzy-logic acceptance criteria for weld acceptance is presented describing how this scheme provides improved robustness compared to the traditional flow-diagram standards.

Katragadda, Gopichand; Nair, Satish; Liu, Harry; Brown, Lawrence M.

1996-11-01

187

Microstructure Improvement in Weld Metal under the Ultrasonic Application  

SciTech Connect

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

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

2007-01-01

188

Welding Supervisor  

NSDL National Science Digital Library

In this video segment adapted from Pennsylvania College of Technology and WVIA, get a behind-the-scenes look at a Toyota manufacturing plant with a manufacturing specialist who oversees robotic welding cells.

WGBH Educational Foundation

2009-12-24

189

Wonder Weld  

SciTech Connect

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

None

2012-01-01

190

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.

191

Oxygen effect on low-alloy steel weld metal properties  

SciTech Connect

It is shown that the weld metal oxygen content in submerged arc low-alloy steel welds, as well as in low-carbon steel welds is dependent on the concentration of oxides decomposed at low temperatures in a weld pool slag phase. The oxygen is mainly in the form of fine dispersed oxide inclusions of less than 0.03 [mu]m. Differentiated evaluation of silicon reduction effects in submerged arc welded low-alloy steels revealed that weld metal brittle fracture strength depends to a considerable degree on total weld metal oxide inclusion content than on silicon increment in the weld. Therefore, the increase of weld metal brittle fracture susceptibility with the growth of weld oxide inclusion content is important to know. Welds with lowered oxygen content [0] [<=] 0.02% also display the tendency to decrease in plasticity because (1) the ferritic-pearlitic matrix of improved purity is likely to generate unbalanced structures on cooling and, (2) when there are no oxide inclusions, the shape of sulfur and phosphor precipitation from the melt changes from globular to film-like. Optimal low-alloy steel weld metal oxygen content is defined in the range of 0.02-0.035.

Potapov, N.N. (Scientific Industrial Corp., of Machinery Technology, Moscow (Russian Federation). Welding Dept.)

1993-08-01

192

Tool For Friction Stir Tack Welding of Aluminum Alloys  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

193

Contrasting styles of welding observed in the proximal Askja 1875 eruption deposits II: Local welding  

NASA Astrophysics Data System (ADS)

As an alternative to classical welding models of fall deposits due to the progressive accumulation of hot tephra which then weld, we describe here welded deposits on the northern 1875 caldera rim of Askja volcano that have welded due to the influence of hot, discrete spatter bombs impacting into and supplying heat to a halo of surrounding tephra. This style of welding we term 'local welding' in contrast to 'regional welding' which is described elsewhere [Carey, R.J., Houghton, B.F., Thordarson, T., 2008. Contrasting styles of welding observed in the proximal Askja 1875 eruption deposits I: Regional welding. J. Volcanol. Geotherm. Res. 171, 1-19. doi:10.1016/j.jvolgeores.2007.11.020]. Locally welded deposits are associated with the rhyolitic Plinian phase of the 1875 eruption of Askja volcano. Two distinct welding units (W1 and W2) are interbedded with Plinian fall on the northern caldera rim, and grade outwards to weakly dispersed non-welded fall. Spatter bombs are found in both welding units but vary in their characteristic sizes and internal features. In the W1 unit simple bombs with homogeneous internal characteristics up to ˜ 60 cm in diameter are found. In the W2 unit, large discrete spatter bombs with complex internal features range up to 9 m in diameter. We describe here two case studies showing the effects of a) single small spatter bombs; b) multiple small spatter bombs and c) large discrete spatter bombs varying in size. Vertical and lateral profiles through welding zones reveal that the primary controls on local welding are the availability of supplied or added heat and the loading capacity of the spatter bomb. Local welding grades are much higher than that of regional welding, as the combined effects of heat, compaction and insulation can provide suitable conditions which lead to dense welding and, proximal to the spatter bomb, rheomorphic flowage. If heating and loading exceed the critical requirement for welding, porosity loss via matrix welding and vesicle collapse occurs to a point where further strain must be accommodated as shearing and ductile flowage. The spatter bombs are found only within the weakly dispersed welding units and are the final erupted products of each fountaining phase. Their low viscosities are evident by their deformation on impact and fluidal forms, and hold some important clues to eruption dynamics in the shallow conduit and vent regions.

Carey, R. J.; Houghton, B. F.; Thordarson, T.

2008-03-01

194

Weld metal composition change during conduction mode laser welding of aluminum alloy 5182  

NASA Astrophysics Data System (ADS)

Selective vaporization of volatile elements during laser welding of automotive aluminum alloys affects weld metal composition and properties. An experimental and theoretical study was carried out to seek a quantitative understanding of the influences of various welding variables on vaporization and composition change during conduction mode laser welding of aluminum alloy 5182. A comprehensive model for the calculation of vaporization rate and weld metal composition change was developed based on the principles of transport phenomena, kinetics, and thermodynamics. The calculations showed that the vaporization was concentrated in a small high-temperature region under the laser beam where the local vapor pressure exceeded the ambient pressure. The convective vapor flux driven by the pressure gradient was much higher than the diffusive vapor flux driven by the concentration gradient. The computed weld pool geometry, vaporization rates, and composition changes for different welding conditions agreed well with the corresponding experimental data. The good agreement demonstrates that the comprehensive model can serve as a basis for the quantitative understanding of the influences of various welding variables on the heat transfer, fluid flow, and vaporization occurring during conduction mode laser welding of automotive aluminum alloys.

Zhao, H.; Debroy, T.

2001-02-01

195

A PARANETRIC STlJDY OF THE ELECTROSLAG WELDING PROCESS  

E-print Network

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

Eagar, Thomas W.

196

Minimization of welding residual stress and distortion in large structures  

E-print Network

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

Michaleris, Panagiotis

197

Characterization of a friction-stir-welded aluminum alloy 6013  

NASA Astrophysics Data System (ADS)

The aluminum alloy 6013 was friction-stir welded in the T4 and the T6 temper, and the microstructure and mechanical properties were studied after welding and after applying a postweld heat treatment (PWHT) to the T4 condition. Optical microscopy (OM), transmission electron microscopy (TEM), and texture measurements revealed that the elongated pancake microstructure of the base material (BM) was transformed into a dynamically recrystallized microstructure of considerably smaller grain size in the weld nugget. Strengthening precipitates, present before welding in the T6 state, were dissolved during welding in the nugget, while an overaged state with much larger precipitate size was established in the heat-affected zone (HAZ). Microhardness measurements and tensile tests showed that the HAZ is the weakest region of the weld. The welded sheet exhibited reduced strength and ductility as compared to the BM. A PWHT restored some of the strength to the as-welded condition.

Heinz, Beate; Skrotzki, Birgit

2002-06-01

198

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

SciTech Connect

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

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

1999-03-01

199

Weld repair method for aluminum lithium seam  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

200

Computational simulation of weld microstructure and distortion by considering process mechanics  

NASA Astrophysics Data System (ADS)

Highly precise fabrication of welded materials is in great demand, and so microstructure and distortion controls are essential. Furthermore, consideration of process mechanics is important for intelligent fabrication. In this study, the microstructure and hardness distribution in multi-pass weld metal are evaluated by computational simulations under the conditions of multiple heat cycles and phase transformation. Because conventional CCT diagrams of weld metal are not available even for single-pass weld metal, new diagrams for multi-pass weld metals are created. The weld microstructure and hardness distribution are precisely predicted when using the created CCT diagram for multi-pass weld metal and calculating the weld thermal cycle. Weld distortion is also investigated by using numerical simulation with a thermal elastic-plastic analysis. In conventional evaluations of weld distortion, the average heat input has been used as the dominant parameter; however, it is difficult to consider the effect of molten pool configurations on weld distortion based only on the heat input. Thus, the effect of welding process conditions on weld distortion is studied by considering molten pool configurations, determined by temperature distribution and history.

Mochizuki, M.; Mikami, Y.; Okano, S.; Itoh, S.

2009-05-01

201

WELDING RESEARCH -s281WELDING JOURNAL  

E-print Network

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

DuPont, John N.

202

WELDING RESEARCH -s77WELDING JOURNAL  

E-print Network

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

DuPont, John N.

203

WELDING RESEARCH -S249WELDING JOURNAL  

E-print Network

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

Zhang, YuMing

204

WELDING RESEARCH -s51WELDING JOURNAL  

E-print Network

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

DuPont, John N.

205

WELDING RESEARCH -S125WELDING JOURNAL  

E-print Network

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

DuPont, John N.

206

WELDING RESEARCH -S59WELDING JOURNAL  

E-print Network

WELDING RESEARCH -S59WELDING JOURNAL ABSTRACT. The fatigue crack propaga- tion behavior of 316L. Consequently, an understanding of the fatigue crack propa- gation behavior of welds is important. Maddox (Ref. 1) and Parry et al. (Ref. 2) have shown that the fatigue crack growth behavior of welds can

DuPont, John N.

207

Multi-physical Simulation of Laser Welding  

NASA Astrophysics Data System (ADS)

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

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

208

Submerged arc flux welding with CaF/sub 2/-CaO-SiO/sub 2/ fluxes: Possible electrochemical effects on weld metal  

SciTech Connect

Compositional changes of weld metal from welds made by submerged arc flux welding of steel using CaF/sub 2/-CaO-SiO/sub 2/ fluxes are consistent with an electrochemical mechanism in which the filler wire is anodically oxidized to form oxides and fluorides, and metals are cathodically deposited at the weld pool-flux interface. This speculative mechanism, if proven by further detailed studies, could make it possible to predict fluxes which will improve the quality of welds. 10 refs., 3 figs., 3 tabs.

Shah, S.; Blander, M.; Indacochea, J.E.

1987-01-01

209

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

PubMed

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

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

2011-03-01

210

Weld-Ed Research, Publications, and Presentations  

NSDL National Science Digital Library

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

2011-10-07

211

Pulsed magnetic welding  

Microsoft Academic Search

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

Sheely

1986-01-01

212

Narrow gap laser welding  

DOEpatents

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

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

1998-01-01

213

Development and application of software packages in welding engineering  

NASA Astrophysics Data System (ADS)

The weldability of some material is analyzed with simple calculating program in this paper, and weldability testing data are shared through database system. The welding procedures are designed with help of expert systems, and the knowledge is shared among welding engineers. Not only the preparing progress of the welding documents is completed with database systems but also the complex decision on the necessity of the qualification test according to the present procedure qualification records (PQRs) and manufacture codes is made. Moreover, the artificial neural network (ANN) technique is proven to be one of the effective ways to predict mechanical properties of welded joints when there are enough tested data to train the models. Finally, the achievements in modeling microstructure of welded joints are introduced, especially in solid transformation and grain growth in both heat-affected zone (HAZ) and welded molten pool.

Wei, Yan-Hong; Zhan, Xiao-Hong; Dong, Zhi-Bo

2011-06-01

214

Welded Scoria  

USGS Multimedia Gallery

Samples of welded scoria. Scoria is another word for the ‘cinders’ that make up volcanic cinder cones. Roza Member, Columbia River Basalt Group. Southeast of Winona, WA. Cinder cones (otherwise known as scoria cones) are the most common type of volcano on Earth. They’re also one o...

215

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

216

Careers in Welding  

NSDL National Science Digital Library

Careers in Welding is a portal jointly produced by the American Welding Society and Weld-Ed, the Nation Center for Welding Education and Training. Here, visitors will find information for educators, students, and welding professionals, in addition to general information about exploring a career in welding. Educators can find teaching tips, curriculum, professional development information, resources and products, events, and networking opportunities. Students can find information about schools with welding programs, scholarships, jobs, and much more. For the welding professional, the site has tips for building a resume, finding a job, and AWS certification information. The site also features videos of technicians and general articles, such as "Why Welding?" and "Welding Fast Facts," that offer information on why to choose a career in welding.

2010-04-15

217

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

218

Fundamentals of the chemical behavior of select welding fluxes  

SciTech Connect

This investigation evaluates the relative effects of thermochemical and electrochemical reactions on the transport of elements, particularly manganese, from the flux to the weld metal in submerged arc welding. The experimental fluxes used were silica-calcium oxide-based, containing 20 wt-% MnO, 15 wt-% CaF[sub 2], and SiO[sub 2] to CaO ratios that varies from 5.50 to 1.16. The slags formed show good detachability, and the welds produced have good bead morphology. The dilution effect was eliminated by drawing the welding wire from the same materials as the base plate. The welding parameters were held constant during weld production and two polarities were used. The arc was found to be stable, but was more so for electrode-positive (reverse) polarity welds. The results of chemical analyses of fluxes, slags and welds are consistent with the following three mechanisms working in parallel that all affect the compositions (and the apparent compositions) of weld metal: (1) the pyrochemical reactions between the slag and the metal; (2) electrochemical reactions at the anodes and cathodes (oxidation and reduction, respectively); and (3) occlusion of slag or solid products of reactions in the weld pool. 22 refs., 6 figs., 1 tab.

Polar, A.; Indacochea, J.E. (Univ. of Illinois, Chicago, IL (United States)); Blander, M. (Argonne National Lab., IL (United States))

1991-01-01

219

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

NASA Astrophysics Data System (ADS)

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

Pang, Shengyong; Chen, Weidong; Wang, Wen

2014-06-01

220

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.

2014-02-01

221

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

222

Macroporosity free aluminum alloy weldments through numerical simulation of keyhole mode laser welding  

NASA Astrophysics Data System (ADS)

A transport phenomena-based numerical model is developed to predict the keyhole geometry and temperature profiles in the weldment during laser welding. The model can be used to prevent macroporosity formation during laser welding of aluminum alloys. The experimental results show that the weld metal contains large pores when the welding mode changes from conduction to keyhole mode or vice versa due to changes in welding variables. Based on this observation, the mathematical model predicts macroporosity formation when welding is conducted under conditions where small changes in welding parameters lead to a change in the welding mode. The model has been used to predict the geometry of the keyhole and the fusion zone, and the weldment temperature field for laser beam welding of aluminum alloys 5182 and 5754. The calculated weld pool depth, width, and shape for different welding speeds agreed well with the experimental results. The calculations showed that the keyhole profiles for high-speed welding were asymmetric. Negative beam defocusing resulted in a deeper keyhole than that obtained with positive beam defocusing. The transition from keyhole to conduction mode was more abrupt for negative beam defocusing. The model could predict the formation of macroporosity during laser welding of aluminum alloys 5182 and 5754. The results provide hope that transport phenomena-based models can be useful to prevent the formation of macroporosity during keyhole mode laser welding of aluminum alloys.

Zhao, H.; DebRoy, T.

2003-06-01

223

Friction Stir Weld System for Welding and Weld Repair  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

224

Effect of Lack of Penetration on the fatigue strength of high strength steel butt weld  

Microsoft Academic Search

Fatigue tests are performed to evaluate the fatigue strength of high strength steel containing partial penetration butt weld\\u000a and full penetration butt weld. The influence of the unwelded ligament (Lack of Penetration) in the partial penetration welds\\u000a on the fatigue life is analyzed for various LOP sizes. For full penetration welds, the fatigue crack initiated at the weld\\u000a toe and

Sungho Kim; Keunchan Jin; Wan Sung; Soowoo Nam

1994-01-01

225

Friction plug welding  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

226

Friction Stir Welding  

NASA Technical Reports Server (NTRS)

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

Nunes, Arthur C., Jr.

2008-01-01

227

Slag Metal Reactions during Submerged Arc Welding of Alloy Steels  

Microsoft Academic Search

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

U. Mitra; T. W. Eagar

1984-01-01

228

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

229

Virtual Tide Pool  

NSDL National Science Digital Library

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

Science NetLinks (PBS; )

2003-04-29

230

Automated Spot Weld Inspection using Infrared Thermography  

SciTech Connect

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

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

2012-01-01

231

Weld-Bead Shaver  

NASA Technical Reports Server (NTRS)

Hand-held power tool shaves excess metal from inside circumference of welded duct. Removes excess metal deposited by penetration of tungsten/inert-gas weld or by spatter from electron-beam weld. Produces smooth transition across joint. Easier to use and not prone to overshaving. Also cuts faster, removing 35 in. (89 cm) of weld bead per hour.

Guirguis, Kamal; Price, Daniel S.

1990-01-01

232

Combinatorial optimization of welding  

E-print Network

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

Sóbester, András

233

The aluminum spot weld  

SciTech Connect

Weld conditions which promote long tip life for aluminum spot welds are not necessarily associated with high weld quality in terms of freedom from defects such as porosity, cracks and expulsion. Schedules which produce good weld nuggets in terms of the peel test and long tip life may not produce a good response in terms of fatigue life. The fatigue life range is optimized by maximizing the weld nugget diameter, i.e., by employing a weld schedule which may lead to expulsion and weld porosity. Weld strength, in both peel and overlap shear configurations, was found to be linearly dependent upon weld diameter. In the peel test, the strength was also dependent upon the base metal thickness, in that for a given thickness, there is a critical diameter for the transition between weld fracture and nugget pull-out. For a given nugget diameter, if pull-out is observed then the strength is greater than if fracture occurs through the weld. In the shear test, the opposite response was observed, the strength for nugget pull-out being less than that for weld shear failure. Weld pull-out was found only for the thinnest base metal thickness tested and the shear load depended only upon the weld diameter over the range of thicknesses tested. Maximum strength in an aluminum spot weld is obtained by maximizing the weld nugget diameter for that thickness of material.

Thornton, P.H.; Krause, A.R.; Davies, R.G. [Ford Motor Co., Dearborn, MI (United States). Scientific Lab.

1996-03-01

234

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. PMID:22588152

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

2012-01-01

235

Heat Flow during the Autogenous GTA Welding of Pipes  

NASA Astrophysics Data System (ADS)

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

Kou, Sindo; Le, Y.

1984-06-01

236

Welding Supervisor  

NSDL National Science Digital Library

Teachers' Domain presents this video as part of a series on advanced technological education. This video features a manufacturing specialist working in an automotive plant. The clip demonstrates what a typical workday is like for someone working in this setting. Skilled supervisors are needed to oversee welding performed by robots. The video may be viewed online or downloaded. To download the clip, users must create a free login for Teachers' Domain. Running time for this QuickTime video is 3:02. Educators will also find a background essay, discussion questions, and standards alignment for the material.

2010-09-30

237

Determining The Weld Quality In Extrusion Welding  

NASA Astrophysics Data System (ADS)

An overview is first given over various methods applied for testing of the bond strength across the extrusion weld obtained in hollow extruded profiles of light metals. A new innovative technique for measurement of weld quality has been developed and the mechanical characteristic of the method is then described. An application of the technique is finally presented where a contaminant film is observed to flow into the extrusion weld so that extrusion weld quality becomes lowered due to the presence of the film. The reduction of the weld quality in this case is quantified by the new technique.

Valberg, Henry; Melkild, Tony; Kandis, Janis

2011-05-01

238

Advanced Welding Applications  

NASA Technical Reports Server (NTRS)

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

Ding, Robert J.

2010-01-01

239

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

E-print Network

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

Triantaphyllou, Evangelos

240

Development of techniques for welding V Cr Ti alloys  

NASA Astrophysics Data System (ADS)

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

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

1998-10-01

241

Weld geometry strength effect in 2219-T87 aluminum  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

242

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

E-print Network

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

Eagar, Thomas W.

243

WELDING RESEARCH SUPPLEMENT TO THE WELDING JOURNAL, JUNE, 1982  

E-print Network

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

Eagar, Thomas W.

244

Welded solar cell interconnection  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

245

Laser weld jig  

DOEpatents

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

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

1982-01-01

246

Virtual Welding Trainers  

NSDL National Science Digital Library

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

2009-09-24

247

Low-temperature friction-stir welding of 2024 aluminum  

SciTech Connect

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

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

1999-09-10

248

Fusion welding process  

DOEpatents

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

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

1983-01-01

249

Reprocessing weld and method  

SciTech Connect

A process is described for improving the fatigue resistance of a small primary structural weld at a joint between structural members of a weldment, the weld having been made with the welding energy input of E[sub 1], the process comprising: applying a reprocessing weld on at least a portion of either one or both toes of the primary structural weld, thereby covering said toe portion, the reprocessing weld containing a filler metal and having a cross-sectional area which is less than the corresponding cross-sectional area of the primary structural weld, the reprocessing weld extending onto the face of the primary structural weld at one side of the toe portion covered and onto the structural member at the other side of the toe portion covered, and the total welding energy input, E[sub 2], used in said reprocessing the primary structural weld being less than the welding energy input E[sub 1] of the primary structural weld.

Killian, M.L.; Lewis, H.E.

1993-08-03

250

Effect of cooling after welding on microstructure and mechanical properties of 12 Pct Cr steel weld metals  

NASA Astrophysics Data System (ADS)

The microstructure of three 12 pct cr steel weld metals with different nickel and nitrogen contents was studied in as-welded condition and after postweld heat treatment with and without intercooling. Tensile strength and impact toughness of the weld metals were investigated in different postweld heat treatment conditions. In weld metals heat treated without intercooling, austenite decomposed by a eutectoid reaction that resulted in M23C6 aggregates around retained ?-ferrite. Two morphologies of M2N and MN precipitates were found in a low-dislocation ?-ferrite. It was concluded that these phases were also transformed from austenite. In weld metals heat treated with intercooling, M23C6 precipitates were smaller and more homogeneously distributed. Different MN precipitates were found in the tempered martensite. The fracture mode of the weld metals at room temperature was mainly transgranular cleavage with some fibrous fracture. Intercooling treatment improved Charpy impact toughness of the 12 pct Cr steel weld metals substantially. It was found that the important microstructural factors affecting the impact toughness of the weld metals which were heat treated without intercooling were the sizes of the ?-ferrite grains, nonmetallic inclusions, and M23C6 aggregates. For the weld metals heat treated with intercooling, the factors which affect the toughness of the weld metals were the sizes of martensite packets and nonmetallic inclusions.

Cai, Guang-Jun; Andrén, Hans-Olof; Svensson, Lars-Erik

1997-07-01

251

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

252

Development of porosity prevention procedures during laser welding  

NASA Astrophysics Data System (ADS)

High power CO2, YAG and LD-pumped solid-state lasers have been developed to produce a deep penetration type of high-quality, high-performance and high-speed weld joints. However, porosity is easily formed in such deep keyhole-type weld beads. The authors have developed microfocused X-ray transmission imaging system, and revealed keyhole behavior and porosity formation mechanism in high power laser welding. This paper will describe a summary of porosity formation mechanism and prevention procedures during cw laser welding of aluminum alloys. Especially, many bubbles were formed by the evaporation of the metals from the bottom tip of the keyhole and flowed upwards according to the liquid flow near the solid-liquid interface inside the molten pool. The majority of them were trapped and captured at the solidifying front of the weld beads, leading to the formation of porosity. Moreover, it was revealed that the shielding gas was chiefly included in the porosity. Main melt flows were observed as a function of welding speed. As the speed was increased, vapor plume was ejected from the keyhole inlet more and more normal to the plate surface, and consequently induced the upward flow of the keyhole-surrounding liquid. On the basis of the above knowledge, full penetration welding, properly pulse-modulated laser welding, vacuum or low pressure welding, welding using the tornado nozzle, very low or high speed welding, and so on were investigated, and it was consequently confirmed that these procedures were beneficial to the reduction in porosity.

Katayama, Seiji; Mizutani, Masami; Matsunawa, Akira

2003-03-01

253

The marginated pool.  

PubMed

The pulmonary circulation harbors a large intravascular reservoir of leukocytes referred to as the Marginated Pool. This marginated pool is balanced by propelling and retaining forces acting on leukocytes during their passage through the pulmonary circulation. The present paper discusses these factors and their underlying mechanisms. PMID:11867908

Kuebler, Wolfgang M; Goetz, Alwin E

2002-01-01

254

Pooling Your Assets.  

ERIC Educational Resources Information Center

For small, private institutions, the real estate pooled income fund can be ideal for constructing new facilities, especially if the facility will produce revenue. Even a public or well-endowed private institution may have a unique project for which a pooled income fund may be a nontraditional funding solution. (MSE)

Hart, Kenneth M.

1990-01-01

255

Fanfares & Fireworks Pool Party  

E-print Network

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

Pilyugin, Sergei S.

256

Fanfares & Fireworks Pool Party  

E-print Network

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

Pilyugin, Sergei S.

257

Hardness, Microstructure, and Residual Stresses in Low Carbon Steel Welding with Post-weld Heat Treatment and Temper Bead Welding  

NASA Astrophysics Data System (ADS)

This paper investigates the effects of post-weld heat treatment (PWHT) and temper bead welding (TBW) on hardness, microstructure and residual stresses in multi-layer welding on low carbon steel specimens made with two different weld geometries, viz. (1) smooth-contoured and (2) U-shaped. It was found that the PWHT technique gave overall lower hardness than the TBW technique, but the hardness values in both techniques were acceptable. Microscopy analysis showed that the TBW technique was more effective in tempering the heat affected zone as the grain size decreased slightly at the fusion line in spite of the higher temperature at the fusion line. Residual stresses measured using the hole-drilling method showed that the residual stress is not reduced below yield stress near the last bead solidified in TBW. Only PWHT gives low residual stress results in this area. High tensile residual stresses may result in sensitivity to fatigue loading.

Aloraier, Abdulkareem S.; Joshi, Suraj; Price, John W. H.; Alawadhi, Khaled

2014-04-01

258

Prediction of residual stresses in butt welded plates using inherent strains  

SciTech Connect

The source of residual stresses in the vicinity of a weld may be expressed in terms of inherent strains. The characteristics of the inherent strain distributions in butt welds are investigated. It is found that the patterns vary little with changes in the welding conditions and sizes of the welded plates. With some assumptions, simple formulas are derived for the distribution and magnitude of inherent strain in a butt weld. A method of predicting the residual stress in a butt-welded plate using the characteristics of inherent strain distributions is presented. The validity of the method is confirmed by thermal elasto-plastic analysis using the finite element method (FEM).

Ueda, Y. (Osaka Univ., Mihogaoka (Japan). Welding Research Inst.); Yuan, M.G. (Daikin Industries, Ltd., Kanaokacho (Japan). Production Engineering Center)

1993-10-01

259

Infrared Thermography For Welding  

NASA Technical Reports Server (NTRS)

Infrared imaging and image-data-processing system shows temperatures of joint during welding and provides data from which rates of heating and cooling determined. Information used to control welding parameters to ensure reliable joints, in materials which microstructures and associated metallurgical and mechanical properties depend strongly on rates of heating and cooling. Applicable to variety of processes, including tungsten/inert-gas welding; plasma, laser, and resistance welding; cutting; and brazing.

Gilbert, Jeffrey L.; Lucky, Brian D.; Spiegel, Lyle B.; Hudyma, Russell M.

1992-01-01

260

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

261

In vitro NIR laser tissue welding of porcine ocular tissues  

NASA Astrophysics Data System (ADS)

In this study, 72 different combinations of laser welding parameters were compared for their effectiveness in welding ocular tissue. The laser employed in the welding system was a near infrared (NIR) erbium fiber laser with a wavelength of 1.455 ?m . The laser system used a motorized translational stage and shutter to control the laser exposure of the tissue being welded. The emission wavelength of the laser in the NIR range corresponds to one of the lesser absorption bands of water. Parameters of the laser welding system that could be changed to allow a more effective distribution of the laser energy and therefore management of thermal energy included: the number and kinds of intricate offset patterns of light on or around the incision, the number of lines per pattern, the power level, the speed of the laser beam movement over the tissues, the spot size, dwell time and the focus plane of the light beam in the tissue. Histopathology was used as an endpoint indication of the effects that the various sets of welding parameters had on the welded tissues. Standard Hematoxylin and Eosin stain and Sirius Red F3B (Direct Red 80) in combination with polarization microscopy were used to stain and visualize the welded ocular tissue. Paradoxically, the best cornea welds quantified using histopathology occurred with fluence of 4,500 mJ/cm2 or less while the corneal welds exhibiting the strongest tensile strengths, but most tissue damage had a delivered fluence above 7,000 mJ/cm2. The best histological representatives of welded corneas had an average delivered fluence of 2,687 mJ/cm2 and an irradiance of 14 W/cm2. Using the properly determined parameters, the NIR erbium fiber welding system provided full thickness welds without the requirement of extrinsic dyes, chromophores, or solders. The NIR laser system with the appropriately developed parameters can be used effectively to weld ocular tissues.

Rosen, Richard B.; Savage, Howard E.; Halder, Rabindra K.; Kartazayeu, Uladzimir; McCormick, Steven A.; Katz, Alvin; Perry, Henry D.; Alfano, Robert R.

2005-04-01

262

Marginated pool of neutrophils in rabbit lungs.  

PubMed

The size and location of the marginated pool of neutrophils (PMNs) in rabbit lungs were evaluated, and the rate of exchange of the PMNs with the circulating pool was determined. 99mTc-labeled erythrocytes (99mTc-RBCs) and 125I-labeled macroaggregated albumin (125I-MAA) were used to determine RBC transit times in the pulmonary circulation. Radiolabeled PMNs were studied on their first passage through the lungs. After 10 min of circulation, the lungs were fixed, gamma counted, and prepared for morphometric and autoradiographic studies; 74 +/- 3% of the PMNs was retained in the lungs on the first passage, and 23 +/- 2% was within the pulmonary marginated pool 10 min later. The regional PMN retention and the rate of exchange between the marginated and circulating PMN pools in the lung were directly related to RBC transit time. The radiolabeled PMNs distributed similarly to the unlabeled cells within the microvasculature and had a similar exchange rate between the marginated and circulating pools (1.4 +/- 0.2%/s using labeled cells and 1.5 +/- 0.5%/s using unlabeled cells). The marginated pool was located primarily within alveolar capillaries and contained two to three times as many PMNs as the total circulating pool. PMID:3693216

Doerschuk, C M; Allard, M F; Martin, B A; MacKenzie, A; Autor, A P; Hogg, J C

1987-11-01

263

Coil Welding Aid  

NASA Technical Reports Server (NTRS)

Positioner holds coil inside cylinder during tack welding. Welding aid spaces turns of coil inside cylinder and applies contact pressure while coil is tack-welded to cylinder. Device facilitates fabrication of heat exchangers and other structures by eliminating hand-positioning and clamping of individual coil turns.

Wiesenbach, W. T.; Clark, M. C.

1983-01-01

264

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

265

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.

266

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

267

Variable polarity arc welding  

NASA Technical Reports Server (NTRS)

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

Bayless, E. O., Jr.

1991-01-01

268

FINITE ELEMENT ANALYSIS OF THERMAL TENSIONING TECHNIQUES MITIGATING WELD BUCKLING DISTORTION  

E-print Network

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

Michaleris, Panagiotis

269

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

270

Welding High Strength Modern Line Pipe Steel  

NASA Astrophysics Data System (ADS)

The effect of modern mechanized girth welding on high strength line pipe has been investigated. The single cycle grain coarsened heat affected zone in three grade 690 line pipe steels and a grade 550 steel has been simulated using a Gleeble thermo-mechanical simulator. The continuous cooling transformation diagrams applicable to the grain coarsened heat affected zone resulting from a range of heat inputs applicable to modern mechanized welding have been established by dilatometry and metallography. The coarse grained heat affected zone was found to transform to lath martensite, bainite, and granular bainite depending on the cooling rate. The impact toughness of the steels was measured using Charpy impact toughness and compared to the toughness of the grain coarsened heat affected zone corresponding to a welding thermal cycle. The ductile to brittle transition temperature was found to be lowest for the steel with the highest hardenability. The toughness resulting from three different thermal cycles including a novel interrupted intercritically reheated grain coarsened (NTR ICR GC HAZ) that can result from dual torch welding at fast travel speed and close torch spacing have been investigated. All of the thermally HAZ regions showed reduced toughness that was attributed to bainitic microstructure and large effective grain sizes. Continuous cooling transformation diagrams for five weld metal chemistries applicable to mechanized pulsed gas metal arc welding of modern high strength pipe steel (SMYS>550 MPa) have been constructed. Welds at heat inputs of 1.5 kJmm-1 and 0.5 kJmm-1 have been created for simulation and analysis. Dilatometric analysis was performed on weld metal specimens cut from single pass 1.5 kJmm-1 as deposited beads. The resulting microstructures were found to range from martensite to polygonal ferrite. There is excellent agreement between the simulated and as deposited weld metal regions. Toughness testing indicates improved energy absorption at -20 °C with increased cooling time.

Goodall, Graeme Robertson

271

Weld-Ed: National Center for Welding Education  

NSDL National Science Digital Library

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

2008-07-21

272

What is a Welding Technician?  

NSDL National Science Digital Library

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

2009-10-06

273

Welding Technician National Core Curriculum  

NSDL National Science Digital Library

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

2011-10-11

274

What is a Welding Engineer?  

NSDL National Science Digital Library

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

2009-10-07

275

WELD—an environment for Web-based electronic design  

Microsoft Academic Search

Increasing size and geographical separation of design data and teams has created a need for a network-based electronic design environment that is scaleable, adaptable, secure, highly available, and cost effective. In the WELD project we are evaluating aspects of the network integration and communication infrastructure needed to enable such a distributed design environment. The architecture of WELD and the components

Francis L. Chan; Mark D. Spiller; A. Richard Newton

1998-01-01

276

Fatigue-reliability analysis of resistance spot-welds  

Microsoft Academic Search

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

Yung-Li Lee; Ming-Wei Lu

1994-01-01

277

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

NASA Astrophysics Data System (ADS)

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

Zhao, Yuzhen; Shi, Yaowu; Lei, Yongping

2006-06-01

278

Study of weld offset in longitudinally welded SSME HPFTP inlet  

NASA Technical Reports Server (NTRS)

Welded joints are an essential part of rocket engine structures such as the Space Shuttle Main Engine (SSME) turbopumps. Defects produced in the welding process can be detrimental to weld performance. Recently, review of the SSME high pressure fuel turbopump (HPFTP) titanium inlet X-rays revealed several weld discrepancies such as penetrameter density issues, film processing discrepancies, weld width discrepancies, porosity, lack of fusion, and weld offsets. Currently, the sensitivity of welded structures to defects is of concern. From a fatigue standpoint, weld offset may have a serious effect since local yielding, in general, aggravates cyclic stress effects. Therefore, the weld offset issue is considered in this report. Using the FEM and beamlike plate approximations, parametric studies were conducted to determine the influence of weld offsets and a variation of weld widths in longitudinally welded cylindrical structures with equal wall thicknesses on both sides of the joint. Following the study, some conclusions are derived for the weld offsets.

Min, J. B.; Spanyer, K. S.; Brunair, R. M.

1992-01-01

279

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

280

Reliability-based optimization of multi-component welded structures  

SciTech Connect

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

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

1994-11-01

281

Welding of 316L Austenitic Stainless Steel with Activated Tungsten Inert Gas Process  

NASA Astrophysics Data System (ADS)

The use of activating flux in TIG welding process is one of the most notable techniques which are developed recently. This technique, known as A-TIG welding, increases the penetration depth and improves the productivity of the TIG welding. In the present study, four oxide fluxes (SiO2, TiO2, Cr2O3, and CaO) were used to investigate the effect of activating flux on the depth/width ratio and mechanical property of 316L austenitic stainless steel. The effect of coating density of activating flux on the weld pool shape and oxygen content in the weld after the welding process was studied systematically. Experimental results indicated that the maximum depth/width ratio of stainless steel activated TIG weld was obtained when the coating density was 2.6, 1.3, 2, and 7.8 mg/cm2 for SiO2, TiO2, Cr2O3, and CaO, respectively. The certain range of oxygen content dissolved in the weld, led to a significant increase in the penetration capability of TIG welds. TIG welding with active fluxes can increase the delta-ferrite content and improves the mechanical strength of the welded joint.

Ahmadi, E.; Ebrahimi, A. R.

2014-12-01

282

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

283

Evaluation of solar cell welds by scanning acoustic microscopy  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

284

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

285

Critical Initial Flaw Size Analysis  

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

286

Swimming pool granuloma  

MedlinePLUS

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

287

Pools for the Handicapped.  

ERIC Educational Resources Information Center

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

American School and University, 1979

1979-01-01

288

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

Code of Federal Regulations, 2013 CFR

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

2013-10-01

289

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

Code of Federal Regulations, 2011 CFR

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

2011-10-01

290

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

Code of Federal Regulations, 2012 CFR

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

2012-10-01

291

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

Code of Federal Regulations, 2010 CFR

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

2010-10-01

292

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

SciTech Connect

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

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

2004-03-15

293

Microstructural Characteristics of a Stainless Steel/Copper Dissimilar Joint Made by Laser Welding  

NASA Astrophysics Data System (ADS)

The microstructures and its formation mechanism of a stainless steel/copper dissimilar joint by laser welding were investigated. It was found that the two modes of joining, i.e., welding-brazing and fusion welding, depend on different processing parameters. In the welding-brazing mode, the interface between copper and the fusion zone has scraggy morphology because the molten pool is frozen by solid copper with high thermal conductivity. The interdiffusion of elements occurs in the neighborhood of the interface, which leads to the metallurgy bond of the mode. In the fusion welding mode, the liquid phase in the fusion zone undergoes not only primary but also secondary liquid separation due to the high cooling rate and high supercooling level of laser welding. Some microcracks generated in the fusion zone by thermal stress mismatch are healed by liquid copper filling.

Chen, Shuhai; Huang, Jihua; Xia, Jun; Zhang, Hua; Zhao, Xingke

2013-08-01

294

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

295

An introduction to mid-Atlantic seasonal pools  

USGS Publications Warehouse

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

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

2005-01-01

296

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

SciTech Connect

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

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

2007-06-06

297

VPPA weld model evaluation  

NASA Astrophysics Data System (ADS)

NASA uses the Variable Polarity Plasma Arc Welding (VPPAW) process extensively for fabrication of Space Shuttle External Tanks. This welding process has been in use at NASA since the late 1970's but the physics of the process have never been satisfactorily modeled and understood. In an attempt to advance the level of understanding of VPPAW, Dr. Arthur C. Nunes, Jr., (NASA) has developed a mathematical model of the process. The work described in this report evaluated and used two versions (level-0 and level-1) of Dr. Nunes' model, and a model derived by the University of Alabama at Huntsville (UAH) from Dr. Nunes' level-1 model. Two series of VPPAW experiments were done, using over 400 different combinations of welding parameters. Observations were made of VPPAW process behavior as a function of specific welding parameter changes. Data from these weld experiments was used to evaluate and suggest improvements to Dr. Nunes' model. Experimental data and correlations with the model were used to develop a multi-variable control algorithm for use with a future VPPAW controller. This algorithm is designed to control weld widths (both on the crown and root of the weld) based upon the weld parameters, base metal properties, and real-time observation of the crown width. The algorithm exhibited accuracy comparable to that of the weld width measurements for both aluminum and mild steel welds.

McCutcheon, Kimble D.; Gordon, Stephen S.; Thompson, Paul A.

1992-07-01

298

VPPA weld model evaluation  

NASA Technical Reports Server (NTRS)

NASA uses the Variable Polarity Plasma Arc Welding (VPPAW) process extensively for fabrication of Space Shuttle External Tanks. This welding process has been in use at NASA since the late 1970's but the physics of the process have never been satisfactorily modeled and understood. In an attempt to advance the level of understanding of VPPAW, Dr. Arthur C. Nunes, Jr., (NASA) has developed a mathematical model of the process. The work described in this report evaluated and used two versions (level-0 and level-1) of Dr. Nunes' model, and a model derived by the University of Alabama at Huntsville (UAH) from Dr. Nunes' level-1 model. Two series of VPPAW experiments were done, using over 400 different combinations of welding parameters. Observations were made of VPPAW process behavior as a function of specific welding parameter changes. Data from these weld experiments was used to evaluate and suggest improvements to Dr. Nunes' model. Experimental data and correlations with the model were used to develop a multi-variable control algorithm for use with a future VPPAW controller. This algorithm is designed to control weld widths (both on the crown and root of the weld) based upon the weld parameters, base metal properties, and real-time observation of the crown width. The algorithm exhibited accuracy comparable to that of the weld width measurements for both aluminum and mild steel welds.

Mccutcheon, Kimble D.; Gordon, Stephen S.; Thompson, Paul A.

1992-01-01

299

Welding arc plasma physics  

NASA Technical Reports Server (NTRS)

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

Cain, Bruce L.

1990-01-01

300

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

SciTech Connect

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

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

1980-05-01

301

Low-Temperature Friction-Stir Welding of 2024 Aluminum  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

302

Automated Weld Characterization Using the Thermoelectric Method  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

303

Vernal Pool Lessons and Activities.  

ERIC Educational Resources Information Center

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

Childs, Nancy; Colburn, Betsy

304

Tidal Pool on Folly Island  

USGS Multimedia Gallery

A tidal pool on Folly Island. Tidal pools are small pools of water that are left when the tide recedes. Because these pools have water more or less permanently, distinct ecosystems can develop separate from the surrounding beach. Folly Island, a preserve owned by the Maine Coast Heritage Trust, is a...

305

Welding and joining: A compilation  

NASA Technical Reports Server (NTRS)

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

1975-01-01

306

Welding skate with computerized controls  

NASA Technical Reports Server (NTRS)

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

Wall, W. A., Jr.

1968-01-01

307

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

308

Three Practical Issues for Modern Adaptive Testing Item Pools.  

ERIC Educational Resources Information Center

As adaptive testing moves toward operational implementation in large scale testing programs, where it is important that adaptive tests be as parallel as possible to existing linear tests, a number of practical issues arise. This paper concerns three such issues. First, optimum item pool size is difficult to determine in advance of pool…

Stocking, Martha L.

309

Friction Stir Welding  

NSDL National Science Digital Library

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

Leske, Cavin.

310

A Compact Gas/Tungsten-Arc Welding Torch  

NASA Technical Reports Server (NTRS)

Compact gas/tungsten-arc welding torch delivers 100-A current, yet used in confined spaces inaccessible to even smallest commercially available torch. Despite its extremely small size, torch contains all usual components and delivers high current.

Morgen, Gene E.

1991-01-01

311

Fluid Flow Characteristics and Porosity Behavior in Full Penetration Laser Welding of a Titanium Alloy  

NASA Astrophysics Data System (ADS)

In this paper, a computational fluid mechanics model is developed for full penetration laser welding of titanium alloy Ti6Al4V. This has been used to analyze possible porosity formation mechanisms, based on predictions of keyhole behavior and fluid flow characteristics in the weld pool. Numerical results show that when laser welding 3 mm thickness titanium alloy sheets with given laser beam focusing optics, keyhole depth oscillates before a full penetration keyhole is formed, but thereafter keyhole collapses are not predicted numerically. For lower power, lower speed welding, the fluid flow behind the keyhole is turbulent and unstable, and vortices are formed. Molten metal is predicted to flow away from the center plane of the weld pool, and leave a gap or void within the weld pool behind the keyhole. For higher power, higher speed welding, fluid flow is less turbulent, and such vortices are not formed. Corresponding experimental results show that porosity was absent in the melt runs made at higher power and higher welding speed. In contrast, large pores were present in melt runs made at lower power and lower welding speed. Based on the combination of experimental results and numerical predictions, it is proposed that porosity formation when keyhole laser welding may result from turbulent fluid flow behind the keyhole, with the larger the value of associated Reynolds number, the higher the possibility of porosity formation. For such fluid flow controlled porosities, measures to decrease Reynolds number of the fluid flow close to the keyhole could prove effective in reducing or avoiding porosity.

Chang, Baohua; Allen, Chris; Blackburn, Jon; Hilton, Paul; Du, Dong

2014-11-01

312

Welding / Materials Joining Career Tree  

NSDL National Science Digital Library

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

2009-10-06

313

Analysis of a fibre laser welding case study, utilising a matrix flow chart  

NASA Astrophysics Data System (ADS)

For fibre laser welding of an eccentric corner joint, the quality of the resulting weld cross section was studied with respect to the dependence on process parameters like lateral laser beam alignment, beam inclination, focal plane position or welding speed. The complex load situation of the support beamer was simplified to bending of one corner. Due to fatigue load, the weld properties causing the peak stress are essential, in particular the top and root shape of the weld cross section. For the parameters varied, the resulting shapes were categorized into different top and root classes, determined by certain key dimensions, considering also welding defects like undercuts. The shapes are boundary conditions for Finite Element Analysis of the joint under load for quantitative comparative analysis of the maximum stress. As two high strength steel grades were joined, the hardness transition across the weld was of interest, too. High speed imaging of the weld pool surface shape provided additional information on the relation between the parameter input and quality output. The different trends identified were discussed and guidelines were derived. As the systematic documentation of results is unsatisfactory in welding, a new method was developed and applied for the first time, called the Matrix Flow Chart. It enables an illustrative view on the resulting welding trends in a combined manner and is extendable by other researchers.

Karlsson, J.; Kaplan, A. F. H.

2011-02-01

314

Enhanced diffusion welding  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

315

Arc Welding Fundamentals  

NSDL National Science Digital Library

This page from SnoCAMP provides an in-depth, technical introduction to the topic of arc welding. Sections covered are basic welding circuit, arc shielding and nature of the arc. The page also provides a number of downloadable resources on the topic, most of which are available as Microsoft Word documents. This page is an excellent reference for students learning the basics of this type of welding technology.

2013-08-02

316

A simulation model for estimating probabilities of defects in welds  

SciTech Connect

In recent work for the US Nuclear Regulatory Commission in collaboration with Battelle Pacific Northwest National Laboratory, Rolls-Royce and Associates, Ltd., has adapted an existing model for piping welds to address welds in reactor pressure vessels. This paper describes the flaw estimation methodology as it applies to flaws in reactor pressure vessel welds (but not flaws in base metal or flaws associated with the cladding process). Details of the associated computer software (RR-PRODIGAL) are provided. The approach uses expert elicitation and mathematical modeling to simulate the steps in manufacturing a weld and the errors that lead to different types of weld defects. The defects that may initiate in weld beads include center cracks, lack of fusion, slag, pores with tails, and cracks in heat affected zones. Various welding processes are addressed including submerged metal arc welding. The model simulates the effects of both radiographic and dye penetrant surface inspections. Output from the simulation gives occurrence frequencies for defects as a function of both flaw size and flaw location (surface connected and buried flaws). Numerical results are presented to show the effects of submerged metal arc versus manual metal arc weld processes.

Chapman, O.J.V. [Rolls-Royce and Associates, Ltd., Derby (United Kingdom); Khaleel, M.A.; Simonen, F.A. [Battelle Memorial Inst., Richland, WA (United States). Pacific Northwest National Lab.

1996-12-01

317

Friction Stir Weld Restart+Reweld Repair Allowables  

NASA Technical Reports Server (NTRS)

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

Clifton, Andrew

2008-01-01

318

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

319

Physics of Fusion Welding  

NASA Technical Reports Server (NTRS)

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

Nunes, A. C., Jr.

1986-01-01

320

Welding Design Project  

NSDL National Science Digital Library

Using the links given, students are to start the design process for their welding project. This project is designed to assess what the students have learned in AgriMetal Fabrication. Oxy Fuel and Welding Safety Go here to review safety when welding and cutting. Design IdeasWelding Discussion Using these two links, think about and start planning what project you want to make. Once you have decided what you would like to build go here: Oxy Fuel Cutting to review the oxy fuel cutting system. Once you are re-familiarized with it, ...

Gibson, Jay

2009-10-27

321

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

322

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

323

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

NASA Astrophysics Data System (ADS)

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

Harooni, Masoud; Carlson, Blair; Kovacevic, Radovan

2014-05-01

324

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

325

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

NASA Astrophysics Data System (ADS)

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

Unt, Anna; Poutiainen, Ilkka; Salminen, Antti

326

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

Microsoft Academic Search

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

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

1981-01-01

327

Development on Methods of Laser Welding of Plastics  

Microsoft Academic Search

First the principle of laser welding of plastics is explained in this paper. Several laser welding methods of plastics are introduced, including contour welding, simultaneous welding, quasi-simultaneous welding, mask welding, diffractive welding, Hybrid welding and Globo welding. Then the main equipments used in laser welding of plastics and the main materials available for laser welding are presented in this paper.

Xuanxuan Shen; Chuanyang Wang

2010-01-01

328

Manually Operated Welding Wire Feeder  

NASA Technical Reports Server (NTRS)

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

Rybicki, Daniel J. (Inventor)

2001-01-01

329

Determination of pool boiling Critical Heat Flux enhancement in nanofluids  

E-print Network

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

Truong, Bao H. (Bao Hoai)

2007-01-01

330

Pooled Screening for Synergistic Interactions Subject to Blocking and Noise  

PubMed Central

The complex molecular networks in the cell can give rise to surprising interactions: gene deletions that are synthetically lethal, gene overexpressions that promote stemness or differentiation, synergistic drug interactions that heighten potency. Yet, the number of actual interactions is dwarfed by the number of potential interactions, and discovering them remains a major problem. Pooled screening, in which multiple factors are simultaneously tested for possible interactions, has the potential to increase the efficiency of searching for interactions among a large set of factors. However, pooling also carries with it the risk of masking genuine interactions due to antagonistic influence from other factors in the pool. Here, we explore several theoretical models of pooled screening, allowing for synergy and antagonism between factors, noisy measurements, and other forms of uncertainty. We investigate randomized sequential designs, deriving formulae for the expected number of tests that need to be performed to discover a synergistic interaction, and the optimal size of pools to test. We find that even in the presence of significant antagonistic interactions and testing noise, randomized pooled designs can significantly outperform exhaustive testing of all possible combinations. We also find that testing noise does not affect optimal pool size, and that mitigating noise by a selective approach to retesting outperforms naive replication of all tests. Finally, we show that a Bayesian approach can be used to handle uncertainty in problem parameters, such as the extent of synergistic and antagonistic interactions, resulting in schedules for adapting pool size during the course of testing. PMID:24454940

Li, Kyle; Precup, Doina; Perkins, Theodore J.

2014-01-01

331

Pooling problems - Optimization Online  

E-print Network

in the petroleum industry, is a type of minimum cost network flow problem with only two sets of nodes: ... appear in many different and important petrochemical optimization problems such as front-end scheduling ..... NP-hardness of the pooling problem. ...... Global optimization for the synthesis of integrated water systems in ...

2013-09-02

332

Cable Pool - Cherryfield  

USGS Multimedia Gallery

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

333

Modeling of heat transfer and fluid flow in keyhole mode welding  

NASA Astrophysics Data System (ADS)

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

Rai, Rohit

334

Design and fabrication of reactor components: welding  

Microsoft Academic Search

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

Vannan

1973-01-01

335

Diffusion weld test fixture  

Microsoft Academic Search

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 while the test specimen is supported by the base. The fixture further includes holding elements attached to

Wendell C. Maciejewski; Kurt J. Janecek; George J. Kavarnos; Elizabeth A. McLaughlin

1995-01-01

336

Diffusion weld test fixture  

Microsoft Academic Search

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 while the test specimen is supported by the base. The fixture further includes holding elements attached to

Wendell Maciejewski; Roger Tyron; George Kavarnos; Elizabeth McLaughlin; Kurt Janecek

1994-01-01

337

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.

338

Unique Cryogenic Welded Structures  

Microsoft Academic Search

For the last few decades, the E. O. Paton Electric Welding Institute has been active in the field of cryogenic materials science. Integrated research on development of new grades of steels and alloys for cryogenic engineering was carried out in collaboration with the leading institutions of Russia, Ukraine, and Georgia. Commercially applied welding technologies and consumables were developed. They include

K. A. Yushchenko; G. G. Monko

2004-01-01

339

Laser Welding in Space  

NASA Technical Reports Server (NTRS)

Solidification type welding process experiments in conditions of microgravity were performed. The role of convection in such phenomena was examined and convective effects in the small volumes obtained in the laser weld zone were observed. Heat transfer within the weld was affected by acceleration level as indicated by the resulting microstructure changes in low gravity. All experiments were performed such that both high and low gravity welds occurred along the same weld beam, allowing the effects of gravity alone to be examined. Results indicate that laser welding in a space environment is feasible and can be safely performed IVA or EVA. Development of the hardware to perform the experiment in a Hitchhiker-g platform is recomended as the next step. This experiment provides NASA with a capable technology for welding needs in space. The resources required to perform this experiment aboard a Shuttle Hitchhiker-pallet are assessed. Over the four year period 1991 to 1994, it is recommended that the task will require 13.6 manyears and $914,900. In addition to demonstrating the technology and ferreting out the problems encountered, it is suggested that NASA will also have a useful laser materials processing facility for working with both the scientific and the engineering aspects of materials processing in space. Several concepts are also included for long-term optimization of available solar power through solar pumping solid state lasers directly for welding power.

Workman, Gary L.; Kaukler, William F.

1989-01-01

340

Welding School Locator  

NSDL National Science Digital Library

This page on the American Welding Society's website provides visitors with the opportunity to search for schools offering a welding program. Visitors can search by school name, city, US state, or country. When locating a school within the United States, an option is also provided to find schools within a certain radius of a location. Lastly, maps are provided that allow browsing for schools.

2011-10-11

341

DC arc weld starter  

DOEpatents

A system for starting an arc for welding uses three DC power supplies, a high voltage supply for initiating the arc, an intermediate voltage supply for sustaining the arc, and a low voltage welding supply directly connected across the gap after the high voltage supply is disconnected.

Campiotti, Richard H. (Tracy, CA); Hopwood, James E. (Oakley, CA)

1990-01-01

342

Fatigue of welded components  

SciTech Connect

Fatigue cracks in engineering structures typically initiate from discontinuities associated with weld joints. Such discontinuities can be volumetric or planar in nature and, in either case, elevate local stresses sufficiently so as to drastically reduce weld joint fatigue strength. In addition, the weld geometry itself can induce stress concentrations higher than those associated with the weld discontinuities. For instance, one of the most fatigue sensitive weld details is a fillet weld termination oriented perpendicular to the applied cyclic stress field. In this case, fatigue cracking initiates from the toe of the fillet weld and propagates through the adjacent base metal in a rather rapid fashion. Although the applied service stresses may be within Code design allowables for ``fatigue rated`` components, welded and bolted connections can sufficiently elevate local stresses to initiate and propagate cracks. Since most fatigue failures occur at weldments, it is reasonable to expect that modern design codes would incorporate the effects of weldments on fatigue life. This paper examines the parameters which most affect the fatigue performance of weldments and the manner in which various codes address fatigue.

Barsom, J.M. [United States Steel, Pittsburgh, PA (United States); Vecchio, R.S. [Lucius Pitkin, Inc., New York, NY (United States)

1995-12-01

343

Welding Project 1  

NSDL National Science Digital Library

In this lesson we will examine MIG welding techniques and equipment. welding logo Open this mig tutorial and go through the outline and complete exersizes 1 and 2. Basic Mig Tutorial SHOP PROJECT: The next link will guide you through the shop project we will create. Read through the steps and procedures and be prepared to discuss them in class. Unit plan, car builder ...

Orr, Mr.

2005-10-29

344

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

345

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

346

Assessment of fatigue and selection of steel on constructions of steel bridges welded according to Eurocode 3  

Microsoft Academic Search

In this study, results of X-ray radiographic examinations in situ of butt welds in 155 steel railway bridges in Poland are presented. In 34 bridges, cracks in 437 joints were found. Distribution and size of stresses in a section of weld weakened with those weld unconformities were determined as well as brittle fractures and fatigue cracks were discussed. Fatigue classes

Bernard Wichtowski

2011-01-01

347

A combined enthalpy / front tracking method for modelling melting and solidification in laser welding  

NASA Astrophysics Data System (ADS)

The authors present an integrated meso-scale 2D numerical model for the simulation of laser spot welding of a Fe-Cr-Ni steel. The melting of the parent materials due to the applied heating power is an important phenomenon, leading to the formation of the weld pool and the subsequent conditions from which solidification proceeds. This model deals with the dynamic formation of the weld pool whereby melting may be occurring at a given location while solidification has already commenced elsewhere throughout the weld pool. Considering both melting and possible simultaneous solidification in this manner ensures a more accurate simulation of temperature distribution. A source based enthalpy method is employed throughout the calculation domain in order to integrate the melting model with the UCD front tracking model for alloy solidification. Melting is tracked via interpolation of the liquidus isotherm, while solidification is treated via both the tracking of the advancing columnar dendritic front, and the nucleation and growth of equiaxed dendrites using a volume-averaging formulation. Heterogeneous nucleation is assumed to take place on TiN grain refiner particles at a grain refiner density of 1000 particles per mm2. A mechanical blocking criterion is used to define dendrite coherency, and the columnar-to-equiaxed transition within the weld pool is predicted.

Duggan, G.; Mirihanage, W. U.; Tong, M.; Browne, D. J.

2012-07-01

348

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

349

Welding Sensor System  

NASA Technical Reports Server (NTRS)

A system originally designed for welding components of the huge Space Shuttle external tank led to a laser-based automated welder for industrial use. A laser sensor tracks the seam where two pieces of metal are to be joined, measures gaps, misfits and automatically corrects welding of torch distance and height. A small industrial computer translates the sensor's information to the weld head and records and displays weld data for control purposes and analysis. The system was modified for commercial use by Marshall Space Flight Center (MSFC), Martin Marietta and Applied Research, Inc., which produces the commercial system. Applications are in industrial welding processes that require repetitive operations and a high degree of reliability.

1993-01-01

350

Method for welding beryllium  

SciTech Connect

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. Beryllium parts made using this method can be used as structural components in aircraft, satellites and space applications.

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

1995-12-31

351

Vacuum Gas Tungsten Arc Welding  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

352

Multihole Arc-Welding Orifice  

NASA Technical Reports Server (NTRS)

Modified orifice for variable-polarity plasma-arc welding directs welding plume so it creates clean, even welds on both Inconel(R) and aluminum alloys. Includes eight holes to relieve back pressure in plasma. Quality of welds on ferrous and nonferrous alloys improved as result.

Swaim, Benji D.

1989-01-01

353

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

354

Argon Welding Inside A Workpiece  

NASA Technical Reports Server (NTRS)

Canopies convert large hollow workpiece into inert-gas welding chamber. Large manifold serves welding chamber for attachment of liner parts in argon atmosphere. Every crevice, opening and passageway provided with argon-rich environment. Weld defects and oxidation dramatically reduced; also welding time reduced.

Morgan, Gene E.

1988-01-01

355

Weld Results SUNY Stony Brook  

E-print Network

Weld Results Yan Zhan SUNY Stony Brook June 13rd, 2013 1 #12;Outline · Studied Parameters · Results Analysis ­ Contours Plots For the Weld Region ­ Axial Velocity Profile at Different Locations Near the Weld ­ Plots of Turbulent Kinetic Energy and Momentum Thickness Near the Weld ­ Line Plot Goes From Inlet

McDonald, Kirk

356

Alternating-Polarity Arc Welding  

NASA Technical Reports Server (NTRS)

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

Schwinghamer, R. J.

1987-01-01

357

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

358

Heat Treatment of Friction-Stir-Welded 7050 Aluminum Plates  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

359

Grinding Parts For Automatic Welding  

NASA Technical Reports Server (NTRS)

Rollers guide grinding tool along prospective welding path. Skatelike fixture holds rotary grinder or file for machining large-diameter rings or ring segments in preparation for welding. Operator grasps handles to push rolling fixture along part. Rollers maintain precise dimensional relationship so grinding wheel cuts precise depth. Fixture-mounted grinder machines surface to quality sufficient for automatic welding; manual welding with attendant variations and distortion not necessary. Developed to enable automatic welding of parts, manual welding of which resulted in weld bead permeated with microscopic fissures.

Burley, Richard K.; Hoult, William S.

1989-01-01

360

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

ERIC Educational Resources Information Center

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

He, Wei; Reckase, Mark D.

2014-01-01

361

Effect of UIT on Fatigue Life in Web-Gusset Welded Joints  

NASA Astrophysics Data System (ADS)

Ultrasonic impact treatment (UIT), which is a peening method, is usually used as a post-weld treatment in order to improve the fatigue strength of welded joints. In this study, fatigue tests were carried out on web-gusset welded joints treated by UIT and the results were compared with the fatigue lives of as-welded joints in order to examine the effects of UIT on the fatigue lives of welded joints. The fatigue lives of web-gusset welded joints treated by UIT increased to more than ten times those of as-welded joints. The introduction of compressive residual stress, relaxation of stress concentration at a weld toe, and refinement of grains under the weld toes were considered as possible reasons for the improvement in fatigue life caused by UIT. Residual stress near weld toes was measured using the X-ray diffraction method. The stress concentration factor at the weld toes was analyzed using the finite element method (FEM). The grain size under the weld toes was measured using electron backscatter diffraction pattern (EBSD) analysis.

Togasaki, Yu; Tsuji, Hirokazu; Honda, Takashi; Sasaki, Tetsuya; Yamaguchi, Atsushi

362

Characterisation of fume from hyperbaric welding operations  

NASA Astrophysics Data System (ADS)

We report preliminary work characterising dust from hyperbaric welding trials carried out at increased pressure in a helium and oxygen atmosphere. Particle size and concentration were measured during welding. Samples for quartz and metal analysis and toxicity assessment were taken from a filter in the local fume extraction system. The residue of dust after metal extraction by nitric acid in hydrogen peroxide predominantly a non-metallic white powder assumed to be dust from welding rod coatings and thermal insulation material. Metallic analysis showed predominantly calcium, from the welding rod coating, and period 4 transition metals such as iron, manganese, magnesium and titanium (inductively coupled mass spectrometry, Agilent 7500c). The presence of zirconium indicated a contribution from grinding. The fume was nanoparticulate in nature with a mean particle diameter of 20-30 nm (MSI Inc WPS 1000XP). It showed an intermediate level of oxidative potential regarding the low-molecular weight respiratory tract lining fluid antioxidants ascorbate and glutathione and caused release of the inflammatory marker IL-8 in a human lung A 549 epithelial cell culture with no indication of cytotoxicity. The study findings have strong implications for the measurement techniques needed to assess fume exposure in hyperbaric welding and the provision of respiratory protection.

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

2009-02-01

363

Robotic weld overlay coatings for erosion control  

NASA Astrophysics Data System (ADS)

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

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

1994-01-01

364

Parameters controlling microstructure and hardness during friction-stir welding of precipitation-hardenable aluminum alloy 6063  

Microsoft Academic Search

The aluminum (Al) alloys 6063-T5 and T4 were friction-stir welded at different tool rotation speeds (R), and then distributions of the microstructure and hardness were examined in these welds. The maximum temperature of the\\u000a welding thermal cycle rose with increasing R values. The recrystallized grain size of the weld increased exponentially with increasing maximum temperature. The relationship\\u000a between the grain

Yutaka S. Sato; Mitsunori Urata; Hiroyuki Kokawa

2002-01-01

365

Analysis of ripple formation in single crystal spot welds  

NASA Technical Reports Server (NTRS)

Stationary spot welds have been made at the (001) surface of Fe-l5%Ni-15%Cr single crystals using a Gas Tungsten Arc (GTA). On the top surface of the spot welds, very regular and concentric ripples were observed after solidification by differential interference color microscopy. Their height (typically 1--5 micrometers and spacing, typically approximately 60 micrometers) decreased with the radius of the pool. These ripples were successfully accounted for in terms of capillary-wave theory using the fundamental mode frequency f(sub 0) given by the first zero of the zero-order Bessel function. The spacing d between the ripples was then equated to v(sub s)/f(sub 0), where v(sub s) is the solidification rate. From the measured ripple spacing, the velocity of the pool was deduced as a function of the radius, and this velocity was in good agreement with the results of a heat-flow simulation.

Rappaz, M.; Corrigan, D.; Boatner, L. A.

1997-01-01

366

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. PMID:22539559

Pesch, Beate

2012-01-01

367

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

PubMed

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

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

2012-07-01

368

Real-time monitoring of the laser hot-wire welding process  

NASA Astrophysics Data System (ADS)

The laser hot-wire welding process was investigated in this work. The dynamics of the molten pool during welding was visualized by using a high-speed charge-coupled device (CCD) camera assisted by a green laser as an illumination source. It was found that the molten pool is formed by the irradiation of the laser beam on the filler wire. The effect of the hot-wire voltage on the stability of the welding process was monitored by using a spectrometer that captured the emission spectrum of the laser-induced plasma plume. The spectroscopic study showed that when the hot-wire voltage is above 9 V a great deal of spatters occur, resulting in the instability of the plasma plume and the welding process. The effect of spatters on the plasma plume was shown by the identified spectral lines of the element Mn I. The correlation between the Fe I electron temperature and the weld-bead shape was studied. It was noted that the electron temperature of the plasma plume can be used to real-time monitor the variation of the weld-bead features and the formation of the weld defects.

Liu, Wei; Liu, Shuang; Ma, Junjie; Kovacevic, Radovan

2014-04-01

369

Contribution to arc plasma modeling for welding TIG application  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

370

Cellular neural networks for welding arc thermograms segmentation  

NASA Astrophysics Data System (ADS)

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

Jamrozik, Wojciech

2014-09-01

371

STUDIES OF THE FATIGUE STRENGTH OF PRESSURE VESSELS. (1) CYCLIC PRESSURE TESTS OF LARGE SIZE PRESSURE VESSELS. (2) EFFECTS OF NOTCHES AND WELD DEFECTS ON PRESSURE VESSEL FATIGUE STRENGHT  

Microsoft Academic Search

The plastic fatigue strength of 36-in. ID pressure vessels is ; investigated. The pressure vessels are fabricated from A-201, A-302, and T-1 ; steels and have a wall thickness of 2 in. Variables investigated are material ; properties, design details, fabrication methods, and inspection techniques. The ; fatigue strength of weld-repaired fatigue cracks is evaluated. Stress ; concentration factors determined

A. G. Pickett; J. D. Michie

1963-01-01

372

Webster Pool Fitness Center  

E-print Network

Archbold/ Flanagan Webster Pool (Archbold) Women's Building Goldstein Fitness Center Marion Fitness Center Brockway Fitness Center Marshall Square Mall Fitness Center Tennity Ice Skating Pavilion Ernie Davis Hall Fitness Center 6:30am- 11:30pm 7:00- 9:30am, 11:30am- 2:30pm 5:00pm- 11:30pm 7:00am- 2:00am

Mather, Patrick T.

373

Allergic to Pool Water  

PubMed Central

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

2012-01-01

374

CO2 laser welding of magnesium alloys  

NASA Astrophysics Data System (ADS)

Metallic alloys with a low mass density can be considered to be basic materials in aeronautic and automotive industry. Magnesium alloys have better properties than aluminum alloys in respect of their low density and high resistance to traction. The main problems of magnesium alloy welding are the inflammability, the crack formation and the appearance of porosity during the solidification. The laser tool is efficient to overcome the difficulties of manufacturing by conventional processing. Besides, the laser processing mainly using shielding gases allows an effective protection of the metal against the action of oxygen and a small heat affected zone. In this paper, we present experimental results about 5 kW CO2 laser welding of 4 mm-thick magnesium alloy plates provided by Eurocopter France. The focused laser beam has about 0.15 mm of diameter. We have investigated the following sample: WE43, alloy recommended in aeronautic and space applications, is constituted with Mg, Y, Zr, rare earth. More ductile, it can be used at high temperatures until 250 degrees Celsius for times longer than 5000 hours without effects on its mechanical properties. A sample of RZ5 (French Norm: GZ4TR, United States Norm ZE41) is composed of Mg, Zn, Zr, La, rare earth. This alloy has excellent properties of foundry and it allows to the realization of components with complex form. Also, it has a good resistance and important properties of tightness. The parameters of the process were optimized in the following fields: laser power: 2 to 5 kW, welding speed: 1 to 4.5 m/min, focal position: -3 mm to +3 mm below or on the top of the metal surface, shielding gas: helium with a flow of 10 to 60 l/min at 4 bars. Metallurgical analyses and mechanical control are made (macroscopic structure, microscopic structure, interpretations of the structures and localization of possible defects, analyse phases, chemical composition, hardness, tensile test etc.) to understand the parameters influence of welding on the obtained beads. For a given laser power, we considered that the welding speed as well as the focal position strongly influence the macroscopic and microscopic welding aspect, whereas the dependence with the flow of the protection gas is weak. For WE43, the bead appears correct in the macroscopic scale for a laser power of 2 kW, a speed of 2 m/min, a focal position on the metal surface or 1 mm under; and an output helium gas of 50 l/min. For RZ5, a correct weld is obtained with a 3 kW laser power, a welding speed of 2 m/min, a focal position of 1.5 mm under the surface and a 50 l/min output helium gas. The microscopic examination showed that the size of the grains has clearly reduced (reduction factor can be up to 35) without formation of porosities, neither cracks nor inclusions; indeed the measured Vickers microhardness of the weld bead is slightly higher than the basic metal. Experiments show that we obtained adequate parameters for high quality welding without using filler material. In future, we plan to weld at higher speed by optimizing the various parameters of the laser welding (power, focal position welding speed and gas flow, ...). Furthermore, we will try to weld samples with a thickness superior than 4 mm.

Dhahri, Mohammed; Masse, Jean Eric; Mathieu, J. F.; Barreau, Gerard; Autric, Michel L.

2000-02-01

375

Aircraft observations of cold pools under marine stratocumulus  

NASA Astrophysics Data System (ADS)

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

Terai, C. R.; Wood, R.

2013-04-01

376

Thermal stir welding apparatus  

NASA Technical Reports Server (NTRS)

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

Ding, R. Jeffrey (Inventor)

2011-01-01

377

Thermal stir welding process  

NASA Technical Reports Server (NTRS)

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

Ding, R. Jeffrey (Inventor)

2012-01-01

378

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

379

Eddy current inspection of weld defects in tubing  

NASA Astrophysics Data System (ADS)

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

Katragadda, G.; Lord, W.

380

Eddy current inspection of weld defects in tubing  

NASA Technical Reports Server (NTRS)

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

Katragadda, G.; Lord, W.

1992-01-01

381

Lasers of All Sizes  

NASA Astrophysics Data System (ADS)

* Introduction * The Laser in All Its Forms * Gas lasers * Dye lasers * Solid-state lasers * Lasers for Every Taste * The rise of lasers * Lasers of all sizes * The colors of the rainbow... and beyond * Shorter and shorter lasers * Increasingly powerful lasers * Lasers: A Universal Tool? * Cutting, welding, and cleaning * Communicating * Treating illnesses * Measuring * Supplying energy? * Entertaining * Understanding * Conclusion

Balcou, Philippe; Forget, Sébastien Robert-Philip, Isabelle

2015-10-01

382

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

383

29 CFR 1910.255 - Resistance welding.  

...welding machines (nonportable) —(1) Voltage. All external weld initiating control circuits shall operate on low voltage, not...multispot welding machines, including 2-post and 4-post weld presses. (8) Safety pins. On large machines,...

2014-07-01

384

29 CFR 1910.255 - Resistance welding.  

Code of Federal Regulations, 2010 CFR

...welding machines (nonportable) —(1) Voltage. All external weld initiating control circuits shall operate on low voltage, not...multispot welding machines, including 2-post and 4-post weld presses. (8) Safety pins. On large machines,...

2010-07-01

385

49 CFR 192.225 - Welding procedures.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 2011-10-01 false Welding procedures. 192.225 Section 192.225...PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.225 Welding procedures. (a) Welding must be...

2011-10-01

386

49 CFR 192.225 - Welding procedures.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 2010-10-01 false Welding procedures. 192.225 Section 192.225...PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.225 Welding procedures. (a) Welding must be...

2010-10-01

387

49 CFR 192.225 - Welding procedures.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 2013-10-01 false Welding procedures. 192.225 Section 192.225...PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.225 Welding procedures. (a) Welding must be...

2013-10-01

388

49 CFR 192.225 - Welding procedures.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 2012-10-01 false Welding procedures. 192.225 Section 192.225...PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Welding of Steel in Pipelines § 192.225 Welding procedures. (a) Welding must be...

2012-10-01

389

Laser weld jig. [Patent application  

DOEpatents

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

Van Blarigan, P.; Haupt, D.L.

1980-12-05

390

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

391

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

392

Weld failure detection  

DOEpatents

Method and apparatus for detecting failure in a welded connection, particrly applicable to not readily accessible welds such as those joining components within the reactor vessel of a nuclear reactor system. A preselected tag gas is sealed within a chamber which extends through selected portions of the base metal and weld deposit. In the event of a failure, such as development of a crack extending from the chamber to an outer surface, the tag gas is released. The environment about the welded area is directed to an analyzer which, in the event of presence of the tag gas, evidences the failure. A trigger gas can be included with the tag gas to actuate the analyzer.

Pennell, William E. (Unity Township, Westmoreland County, PA); Sutton, Jr., Harry G. (Mt. Lebanon, PA)

1981-01-01

393

Online NIR diagnostic of laser welding processes and its potential for quality assuring sensor systems  

NASA Astrophysics Data System (ADS)

We have integrated an imaging thermographic sensor into commercial welding optics for observation of the weld zone. Key element of the sensor is an InGaAs-camera that detects the thermal radiation of the welding process in the wavelength range of 1,200 to 1,700 nm. This is well suited to record images of the keyhole, the melt pool and the thermal trace. The sensor was integrated to the welding heads for on-axis observation to minimize the interfering contour to ensure easy adaption to industrial processes. The welding heads used were established industrial-grade TRUMPF optics: a BEO fixed optics with 280 mm focal length, or a TRUMPF PFO-3D scanner optics with 450 mm focal length. We used a TRUMPF TruDisk 16002 16kW-thin disk laser that transmits its power through a 200 ?m core diameter light cable. The images were recorded and features of the various process zones were evaluated by image processing. It turns out that almost all weld faults can be clearly detected in the NIR images. Quantitative features like the dimension of the melt pool and the thermal trace can be derived from the captured images. They are correlated to process input parameters as well as to process results. In contrast to observation in the visible spectrum the NIR camera records the melt pool without auxiliary illumination. As an unrivaled attribute of the NIR sensor it supports an online heat flow thermography of the seam and allows identifying missing fusion ("false friends") of lap joints virtually during the welding process. Automated weld fault detection and documentation is possible by online image processing which sets the basis for comprehensive data documentation for quality assurance and traceability.

Dorsch, Friedhelm; Braun, Holger; Keβler, Steffen; Pfitzner, Dieter; Rominger, Volker

2014-02-01

394

Friction stir weld tools  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

395

Weld braze technique  

DOEpatents

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.

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

1982-01-01

396

Friction Stir Weld Tools  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

397

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

398

Weld radiograph enigmas  

NASA Technical Reports Server (NTRS)

Weld radiograph enigmas are features observed on X-ray radiographs of welds. Some of these features resemble indications of weld defects, although their origin is different. Since they are not understood, they are a source of concern. There is a need to identify their causes and especially to measure their effect on weld mechanical properties. A method is proposed whereby the enigmas can be evaluated and rated, in relation to the full spectrum of weld radiograph indications. Thie method involves a signature and a magnitude that can be used as a quantitive parameter. The signature is generated as the diference between the microdensitometer trace across the radiograph and the computed film intensity derived from a thickness scan along the corresponding region of the sample. The magnitude is the measured difference in intensity between the peak and base line values of the signature. The procedure is demonstated by comparing traces across radiographs of a weld sample before and after the introduction of a hole and by a system based on a MacIntosh mouse used for surface profiling.

Jemian, Wartan A.

1986-01-01

399

Concurrent ultrasonic weld evaluation system  

DOEpatents

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

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

1987-01-01

400

Concurrent ultrasonic weld evaluation system  

DOEpatents

A system for concurrent, non-destructive evaluation of partially completed welds for use in conjunction with an automated welder is disclosed. The system utilizes real time, automated ultrasonic inspection of a welding operation as the welds are being made by providing a transducer which follows a short distance behind the welding head. Reflected ultrasonic signals are analyzed utilizing computer based digital pattern recognition techniques to discriminate between good and flawed welds on a pass by pass basis. The system also distinguishes between types of weld flaws. 5 figs.

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

1987-12-15

401

Concurrent ultrasonic weld evaluation system  

DOEpatents

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

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

1985-09-04

402

Residual stress and strain in MIG butt welds in 5083-H321 aluminium: As-welded and fatigue cycled  

Microsoft Academic Search

This paper presents single-line residual stress profiles for 8mm 5083-H321 aluminium plates joined by gas metal arc (MIG) welding. The data were obtained by synchrotron diffraction strain scanning. Weld metal stresses (up to ?7mm either side of the centreline) are quite scattered and unreliable because of the large epitaxial grain size in the fusion zone. Peak magnitude of the transverse

M. N. James; D. J. Hughes; D. G. Hattingh; G. Mills; P. J. Webster

2009-01-01

403

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

NASA Technical Reports Server (NTRS)

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

Chen, Po-Shou; Russell, Carolyn

2012-01-01

404

SNP calling by sequencing pooled samples  

PubMed Central

Background Performing high throughput sequencing on samples pooled from different individuals is a strategy to characterize genetic variability at a small fraction of the cost required for individual sequencing. In certain circumstances some variability estimators have even lower variance than those obtained with individual sequencing. SNP calling and estimating the frequency of the minor allele from pooled samples, though, is a subtle exercise for at least three reasons. First, sequencing errors may have a much larger relevance than in individual SNP calling: while their impact in individual sequencing can be reduced by setting a restriction on a minimum number of reads per allele, this would have a strong and undesired effect in pools because it is unlikely that alleles at low frequency in the pool will be read many times. Second, the prior allele frequency for heterozygous sites in individuals is usually 0.5 (assuming one is not analyzing sequences coming from, e.g. cancer tissues), but this is not true in pools: in fact, under the standard neutral model, singletons (i.e. alleles of minimum frequency) are the most common class of variants because P(f) ? 1/f and they occur more often as the sample size increases. Third, an allele appearing only once in the reads from a pool does not necessarily correspond to a singleton in the set of individuals making up the pool, and vice versa, there can be more than one read – or, more likely, none – from a true singleton. Results To improve upon existing theory and software packages, we have developed a Bayesian approach for minor allele frequency (MAF) computation and SNP calling in pools (and implemented it in a program called snape): the approach takes into account sequencing errors and allows users to choose different priors. We also set up a pipeline which can simulate the coalescence process giving rise to the SNPs, the pooling procedure and the sequencing. We used it to compare the performance of snape to that of other packages. Conclusions We present a software which helps in calling SNPs in pooled samples: it has good power while retaining a low false discovery rate (FDR). The method also provides the posterior probability that a SNP is segregating and the full posterior distribution of f for every SNP. In order to test the behaviour of our software, we generated (through simulated coalescence) artificial genomes and computed the effect of a pooled sequencing protocol, followed by SNP calling. In this setting, snape has better power and False Discovery Rate (FDR) than the comparable packages samtools, PoPoolation, Varscan : for N = 50 chromosomes, snape has power ? 35%and FDR ? 2.5%. snape is available at http://code.google.com/p/snape-pooled/ (source code and precompiled binaries). PMID:22992255

2012-01-01

405

Experimental and numerical investigations of hybrid laser arc welding of aluminum alloys in the thick T-joint configuration  

NASA Astrophysics Data System (ADS)

In the present investigation, a numerical finite element model was developed to simulate the hybrid laser arc welding of different aluminum alloys, namely 5××× to 6××× series. The numerical simulation has been considered two double-ellipsoidal heat sources for the gas metal arc welding and laser welding. The offset distance of the metal arc welding and laser showed a significant effect on the molten pool geometry, the heat distribution and penetration depth during the welding process. It was confirmed that when the offset distance is within the critical distance the laser and arc share the molten pool and specific amount of penetration and dilution can be achieved. The models and experiments show that the off-distance between the two heat sources and shoulder width have considerable influence on the penetration depth and appearance of the weld beads. The experiments also indicate that the laser power, arc voltage and type of the filler metal can effectively determine the final properties of the bonds, specifically the bead appearance and microhardness of the joints. The experiments verified the numerical simulation as the thermocouples assist to comprehend the amount of heat distribution on the T-joint coupons. The role of the welding parameters on the mechanism of the hybrid laser welding of the aluminum alloys was also discussed.

Mazar Atabaki, M.; Nikodinovski, M.; Chenier, P.; Ma, J.; Liu, W.; Kovacevic, R.

2014-07-01

406

Nine Ball Pool Model  

NSDL National Science Digital Library

The Nine Ball Pool Model is set up as a game of nine-ball (nine balls in a diamond formation with a cue ball), and the player may hit the balls in any order. With normal play (the player selecting "Nine-Ball"), the goal of the game is to sink all of the balls in as little time as possible, with the least number of possible turns, and with the least possible number of scratches (sinking of the cue ball). The player may see these statistics at the bottom-right corner of the play screen and will get a final report upon sinking the last non-cue ball. (The back arrow is a total reset button for the simulation.) This form of play is essentially a free-for-all. The Nine Ball Pool Model was created using the Easy Java/JavaScript Simulations (EjsS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive.

Kozlowski, Ryan

2014-03-09

407

Evaluation of Allele Frequency Estimation Using Pooled Sequencing Data Simulation  

PubMed Central

Next-generation sequencing (NGS) technology has provided researchers with opportunities to study the genome in unprecedented detail. In particular, NGS is applied to disease association studies. Unlike genotyping chips, NGS is not limited to a fixed set of SNPs. Prices for NGS are now comparable to the SNP chip, although for large studies the cost can be substantial. Pooling techniques are often used to reduce the overall cost of large-scale studies. In this study, we designed a rigorous simulation model to test the practicability of estimating allele frequency from pooled sequencing data. We took crucial factors into consideration, including pool size, overall depth, average depth per sample, pooling variation, and sampling variation. We used real data to demonstrate and measure reference allele preference in DNAseq data and implemented this bias in our simulation model. We found that pooled sequencing data can introduce high levels of relative error rate (defined as error rate divided by targeted allele frequency) and that the error rate is more severe for low minor allele frequency SNPs than for high minor allele frequency SNPs. In order to overcome the error introduced by pooling, we recommend a large pool size and high average depth per sample. PMID:23476151

Guo, Yan; Samuels, David C.; Li, Jiang; Clark, Travis; Li, Chung-I; Shyr, Yu

2013-01-01

408

Relationship between apposition pressure during welding and tensile strength of the acute weld  

NASA Astrophysics Data System (ADS)

Dye-assisted photothermal welding is a technique used to close wounds by thermally cross-linking collagen across apposed tissue edges. For a successful weld, not only do laser parameters have to be optimized, but also apposition of the incision has to be consistent and controlled. The objective of this study was to quantify the relationship between the applied apposition pressure (i.e., the compressive force holding the wound closed during the welding procedure divided by the area of the skin-to-skin interface) and the tensile strength of the wound following the welding procedure. By using a clamping device made of two complementary pieces, each 3 cm wide with a row of 10 equally spaced blunt wire mesh tips, the apposition pressure along a 2-cm-long incision in each albino guinea pig was quantified using a 127-micrometers -thick load cell and varied from 0-1.8 kgf/cm2. A continuous wave, Nd:YAG laser emitting 10.0 W of 1.06-micrometers radiation from a 600-micrometers -diameter fiber irradiating a 5-mm-diameter spot size was scanned across the incision in order to deliver 300 J of total energy. As the apposition pressure of the incisions was increased, the resulting tensile strength of welded skin increased in a sigmoidal manner. For this welding technique, an apposition pressure of at least 1.2 kgf/cm2 is necessary to obtain maximum weld strength of the skin (2.56+/- 0.36 kg/cm2).

Wu, Paul J.; Walsh, Joseph T., Jr.

2001-05-01

409

Stud arc welding in a magnetic field – Investigation of the influences on the arc motion  

NASA Astrophysics Data System (ADS)

Stud arc welding is widely used in the construction industry. For welding of studs with a diameter larger than 14 mm a ceramic ferrule is usually necessary in order to protect the weld pool. Disadvantages of using such a ferrule are that more metal is molten than necessary for a high quality welded joint and that the ferrule is a consumable generally thrown away after the welding operation. Investigations show that the ferrule can be omitted when the welding is carried out in a radially symmetric magnetic field within a shielding gas atmosphere. Due to the Lorentz force the arc is laterally shifted so that a very uniform and controlled melting of the stud contact surface as well as of the work piece can be achieved. In this paper a simplified physical model is presented describing how the parameters welding current, flux density of the magnetic field, radius of the arc and mass density of the shielding gas influence the velocity of the arc motion. The resulting equation is subsequently verified by comparing it to optical measurements of the arc motion. The proposed model can be used to optimize the required field distribution for the magnetic field stud welding process.

Hartz-Behrend, K.; Marqués, J. L.; Forster, G.; Jenicek, A.; Müller, M.; Cramer, H.; Jilg, A.; Soyer, H.; Schein, J.

2014-11-01

410

A study of narrow gap laser welding for thick plates using the multi-layer and multi-pass method  

NASA Astrophysics Data System (ADS)

This paper details a new method that combines laser autogenous welding, laser wire filling welding and hybrid laser-GMAW welding to weld 30 mm thick plate using a multi-layer, multi-pass process. A “Y” shaped groove was used to create the joint. Research was also performed to optimize the groove size and the processing parameters. Laser autogenous welding is first used to create the backing weld. The lower, narrowest part of the groove is then welded using laser wire filling welding. Finally, the upper part of the groove is welded using laser-GMAW hybrid welding. Additionally, the wire feeding and droplet transfer behaviors are observed by high speed photography. The two main conclusions from this work are: the wire is often biased towards the side walls, resulting in a lack of fusion at the joint and the creation of other defects for larger groove sizes. Additionally, this results in the droplet transfer behavior becoming unstable, leading to a poor weld appearance for smaller groove sizes.

Li, Ruoyang; Wang, Tianjiao; Wang, Chunming; Yan, Fei; Shao, Xinyu; Hu, Xiyuan; Li, Jianmin

2014-12-01

411

Pooled Energy Budgets: Resituating Human Energy Allocation Trade-offs  

E-print Network

assume that energy expended in activity (foraging effort) is proportional to body size, and that energyPooled Energy Budgets: Resituating Human Energy Allocation Trade-offs KAREN L. KRAMER AND PETER T. ELLISON Across taxa, many life-history traits vary as a function of differences in body size.1­5 Among

Kramer, Karen L.

412

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

413

Certification of a weld produced by friction stir welding  

SciTech Connect

Methods, devices, and systems for providing certification of friction stir welds are disclosed. A sensor is used to collect information related to a friction stir weld. Data from the sensor is compared to threshold values provided by an extrinsic standard setting organizations using a certification engine. The certification engine subsequently produces a report on the certification status of the weld.

Obaditch, Chris; Grant, Glenn J

2013-10-01

414

Basic Welding Skills. Welding Module 1. Instructor's Guide.  

ERIC Educational Resources Information Center

This guide is intended to assist vocational educators in teaching a six-unit module in basic welding skills. The module is part of a welding curriculum that has been designed to be totally integrated with Missouri's Vocational Instruction Management System. The following topics are covered in the module: the welding profession, personal safety,…

Missouri Univ., Columbia. Instructional Materials Lab.

415

Microstructural evolution of 6063 aluminum during friction-stir welding  

SciTech Connect

The microstructural distribution associated with a hardness profile in a friction-stir-welded, age-hardenable 6063 aluminum alloy has been characterized by transmission electron microscopy (TEM) and orientation imaging microscopy (OIM). The friction-stir process produces a softened region in the 6063 Al weld. Frictional heating and plastic flow during friction-stir welding create fine recrystallized grains in the weld zone and recovered grains in the thermomechanically affected zone. The hardness profile depends greatly on the precipitate distribution and only slightly on the grain size. The softened region is characterized by dissolution and growth of the precipitates during the welding. Simulated weld thermal cycles with different peak temperatures have shown that the precipitates are dissolved at temperatures higher than 675 K and that the density of the strengthening precipitate was reduced by thermal cycles lower than 675 K. A comparison between the thermal cycles and isothermal aging has suggested precipitation sequences in the softened region during friction-stir welding.

Sato, Y.S.; Kokawa, Hiroyuki [Tohoku Univ., Sendai (Japan). Dept. of Materials Processing; Enomoto, Masatoshi [Showa Aluminum Corp., Oyama City, Tochigi (Japan); Jogan, Shigetoshi [Showa Aluminum Corp., Sakai, Osaka (Japan)

1999-09-01

416

Welding arc length control system  

NASA Technical Reports Server (NTRS)

The present invention is a welding arc length control system. The system includes, in its broadest aspects, a power source for providing welding current, a power amplification system, a motorized welding torch assembly connected to the power amplification system, a computer, and current pick up means. The computer is connected to the power amplification system for storing and processing arc weld current parameters and non-linear voltage-ampere characteristics. The current pick up means is connected to the power source and to the welding torch assembly for providing weld current data to the computer. Thus, the desired arc length is maintained as the welding current is varied during operation, maintaining consistent weld penetration.

Iceland, William F. (Inventor)

1993-01-01

417

Homopolar welding development and economics  

SciTech Connect

Homopolar welding (HPW) is a single-shot solid-state resistance forge welding process that is under development as a single-station pipe welding method. Weld quality issues have been addressed by a Joint Industry Program and the process economics favor commercial use. Fielding of a HPW system is dependent on process tooling design, the speed of the process, and the economics of the process. The HPW weld speed of three seconds makes weld advance times of 12 to 20 minutes possible and will result in a large reduction in overall pipeline construction costs. In addition, HPW is an inherently controllable process, so the weld power pulse will be tailorable to meet a variety of weld and material requirements.

Pappas, J.A.; Harville, M.W.; Weldon, J.M. [Parker Kinetic Designs, Inc., Austin, TX (United States); Carnes, R.W.; Hudson, R.S.; Nichols, S.P. [Univ. of Texas, Austin, TX (United States). Center for Electromechanics

1996-09-01

418

Modelling of friction stir welding  

E-print Network

This thesis investigates the modelling of friction stir welding (FSW). FSW is a relatively new welding process where a rotating non-consumable tool is used to join two materials through high temperature deformation. The aim of the thesis...

Colegrove, Paul Andrew

419

Synaptic Vesicle Pools: An Update  

PubMed Central

During the last few decades synaptic vesicles have been assigned to a variety of functional and morphological classes or “pools”. We have argued in the past (Rizzoli and Betz, 2005) that synaptic activity in several preparations is accounted for by the function of three vesicle pools: the readily releasable pool (docked at active zones and ready to go upon stimulation), the recycling pool (scattered throughout the nerve terminals and recycling upon moderate stimulation), and finally the reserve pool (occupying most of the vesicle clusters and only recycling upon strong stimulation). We discuss here the advancements in the vesicle pool field which took place in the ensuing years, focusing on the behavior of different pools under both strong stimulation and physiological activity. Several new findings have enhanced the three-pool model, with, for example, the disparity between recycling and reserve vesicles being underlined by the observation that the former are mobile, while the latter are “fixed”. Finally, a number of altogether new concepts have also evolved such as the current controversy on the identity of the spontaneously recycling vesicle pool. PMID:21423521

Denker, Annette; Rizzoli, Silvio O.

2010-01-01

420

Sharing rules for a Common-Pool Resource with private alternatives  

Microsoft Academic Search

Agents with ex-ante claims over a common pool resource (CPR) of uncertain size face the risk of resource shortage if the sum of the claims they have over the common pool resource is incompatible with the actual resource size. In case of shortage, a sharing rule or bankruptcy rule is required to organize the restrictions and allocate the available resource

Marianne Lefebvre; Sophie Thoyer; Mabel Tidball; Marc Willinger

2011-01-01

421

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

SciTech Connect

Isothermal transformation kinetics of austenite to acicular ferrite and allotriomorphic ferrite were measured in reheated low alloy steel weld deposits with similar weld compositions and austenite grain size but different inclusion characteristics. Accelerated kinetics of transformation to acicular ferrite were observed in weld metal containing coarser and titanium-rich inclusions. In contrast, kinetics of transformation to allotriomorphic ferrite were not influenced by inclusion characteristics, but, rather, by the austenite grain size and carbon concentration.

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

1994-09-01

422

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

Microsoft Academic Search

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

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

2009-01-01

423

Robotic Welding and Inspection System  

SciTech Connect

This paper presents a robotic system for GTA welding of lids on cylindrical vessels. The system consists of an articulated robot arm, a rotating positioner, end effectors for welding, grinding, ultrasonic and eddy current inspection. Features include weld viewing cameras, modular software, and text-based procedural files for process and motion trajectories.

H. B. Smartt; D. P. Pace; E. D. Larsen; T. R. McJunkin; C. I. Nichol; D. E. Clark; K. L. Skinner; M. L. Clark; T. G. Kaser; C. R. Tolle

2008-06-01

424

Orbital Friction Stir Weld System  

NASA Technical Reports Server (NTRS)

This invention is an apparatus for joining the ends of two cylindrical (i.e., pipe-shaped) sections together with a friction stir weld. The apparatus holds the two cylindrical sections together and provides back-side weld support as it makes a friction stir weld around the circumference of the joined ends.

Ding, R. Jeffrey (Inventor); Carter, Robert W. (Inventor)

2001-01-01

425

Orbital friction stir weld system  

NASA Technical Reports Server (NTRS)

This invention is an apparatus for joining the ends of two cylindrical (i.e., pipe-shaped) sections together with a friction stir weld. The apparatus holds the two cylindrical sections together and provides back-side weld support as it makes a friction stir weld around the circumference of the joined ends.

Ding, R. Jeffrey (Inventor); Carter, Robert W. (Inventor)

2001-01-01

426

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

427

Weld-bonded titanium structures  

NASA Technical Reports Server (NTRS)

Structurally stronger titanium articles are produced by a weld-bonding technique comprising fastening at least two plates of titanium together using spotwelding and curing an adhesive interspersed between the spot-weld nuggets. This weld-bonding may be employed to form lap joints or to stiffen titanium metal plates.

Vaughan, R. W.; Creedon, J. F. (inventors)

1976-01-01

428

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

429

Oxy-Fuel Welding & Cutting  

NSDL National Science Digital Library

This page from SnoCAMP provides a few resources on oxy-fuel welding and cutting. Documents cover topics like the oxyacetylene process, health and safety in welding, oxy-fuel safety and cutting and welding math and physics. Documents include a lesson plan, handouts, and a test.

2013-07-31

430

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

431

Self-Reacting Friction Stir Welding for Aluminum Alloy Circumferential Weld Applications  

NASA Technical Reports Server (NTRS)

Friction stir welding is an innovative weld process that continues to grow in use, in the commercial, defense, and space sectors. It produces high quality and high strength welds in aluminum alloys. The process consists of a rotating weld pin tool that plasticizes material through friction. The plasticized material is welded by applying a high weld forge force through the weld pin tool against the material during pin tool rotation. The high weld forge force is reacted against an anvil and a stout tool structure. A variation of friction stir welding currently being evaluated is self-reacting friction stir welding. Self-reacting friction stir welding incorporates two opposing shoulders on the crown and root sides of the weld joint. In self-reacting friction stir welding, the weld forge force is reacted against the crown shoulder portion of the weld pin tool by the root shoulder. This eliminates the need for a stout tooling structure to react the high weld forge force required in the typical friction stir weld process. Therefore, the self-reacting feature reduces tooling requirements and, therefore, process implementation costs. This makes the process attractive for aluminum alloy circumferential weld applications. To evaluate the application of self-reacting friction stir welding for aluminum alloy circumferential welding, a feasibility study was performed. The study consisted of performing a fourteen-foot diameter aluminum alloy circumferential demonstration weld using typical fusion weld tooling. To accomplish the demonstration weld, weld and tack weld development were performed and fourteen-foot diameter rings were fabricated. Weld development consisted of weld pin tool selection and the generation of a process map and envelope. Tack weld development evaluated gas tungsten arc welding and friction stir welding for tack welding rings together for circumferential welding. As a result of the study, a successful circumferential demonstration weld was produced leading the way for future circumferential weld implementation.

Bjorkman, Gerry; Cantrell, Mark; Carter, Robert

2003-01-01

432

Failure Behavior of Three-Steel Sheets Resistance Spot Welds: Effect of Joint Design  

NASA Astrophysics Data System (ADS)

There is a lack of comprehensive understanding concerning failure characteristics of three-steel sheet resistance spot welds. In this article, macro/microstructural characteristics and failure behavior of 1.25/1.25/1.25 mm three-sheet low carbon steel resistance spot welds are investigated. To evaluate the mechanical properties of the joint, the tensile-shear test was performed in three different joint designs. Mechanical performance of the joint was described in terms of peak load, energy absorption, and failure mode. The critical weld nugget size required to insure pullout failure mode was obtained for each joint design. It was found that the joint design significantly affects the mechanical properties and the tendency to fail in the interfacial failure mode. It was also observed that stiffer joint types exhibit higher critical weld size. Fusion zone size along sheet/sheet interface proved to be the most important controlling factor of spot weld peak load and energy absorption.

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

2012-08-01

433

Friction stir welding tool and process for welding dissimilar materials  

SciTech Connect

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

434

Direct laser diode welding system with anti-reflection unit  

NASA Astrophysics Data System (ADS)

A high power laser diode system for welding is widely known. However, the reliability and the reasonability are required by an industrial market. Reliability, especially lifetime, mainly depends on the temperature of laser diode (LD) and it might be rise if LD would receive reflection from welding point. This paper conducted the measurement of the reflection during welding by applying 1/4 wavelength plate and PBS. Results indicated the reflection during welding was inevitable. We developed a prototype high power laser diode system, which equipped an anti-reflection unit, to improve the reliability. The system traveled 3m/min and its bead width was 1.2 mm for 1.5 mm Al (A5052) under the spot size 2.7 x 0.6 mm FWHM. Additionally, we started to develop fast and slow collimation lenses for LD to realize a reasonale price for system The brief evaluation of fast collimation lenses was also reported.

Nagayasu, Doukei; Wang, Jing-bo

2003-11-01

435

Program for Heat Flow in Welding  

NASA Technical Reports Server (NTRS)

Program contains numerical model of temperature distribution in vicinity of weld. Weld model used to produce estimated welding power requirements, welding-power-loss analysis, heat-affected-zone temperature history, and weld-puddle cross-section plots. Applied to gas/tungsten-arc, plasma-arc, electron-beam, and laser-beam welds on wide plates under steady conditions. User predicts power requirements and temperature distributions. Weld model written in BASIC.

Nunes, A. C., Jr.; Graham, M.

1986-01-01

436

Automatic welding comes of age. [Offshore  

Microsoft Academic Search

Automatic pipe welding systems today fall into three main categories: gas metal arc welding, gas-tungsten arc welding, and flash-butt welding. The first automatic welding devices used offshore were the CRC and H.C. Price systems. Both use gas metal arc welding with a consumable steel filler wire. The recently developed McDermott flash-butt welding system is described. (DLC)

D. L. Jr

1981-01-01

437

Thermal Stir Welding: A New Solid State Welding Process  

NASA Technical Reports Server (NTRS)

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

Ding, R. Jeffrey

2003-01-01

438

Thermal Stir Welding: A New Solid State Welding Process  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

439

Welding and properties of welds of TMCP-steel  

SciTech Connect

Thermomechanical control process (TMCP) of steel includes a multiplicity of processing schedules of combined thermal and mechanical working treatments that have been developed to optimize the resulting microstructure and mechanical properties of various steel grades. Weld metal properties of multipass submerged arc welded (SAW) TMCP steel joints were investigated in order to study the influences of different welding wires and heat inputs. Weld metal characterization consisted of tensile, Charpy-V Notch (CVN) and hardness testing, and microstructural examination. Cross-weld tensile specimens were tested principally to examine whether HAZ softening, which might have occurred, causes failure in this region. The tests verified that by using the right welding wire; it is possible to achieve weld joint which fulfills the strength requirements and gives satisfactory toughness at low temperatures.

Brederholm, A.T.; Kotamies, J.M.N.; Haenninen, H. [Helsinki Univ. of Technology, Espoo (Finland). Lab. of Engineering Materials

1995-12-31

440

Capabilities of Ultrasonic Phased Arrays for FarSide Examinations of Austenitic Stainless Steel Piping Welds  

Microsoft Academic Search

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

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

2006-01-01

441

Extravehicular activity welding experiment  

NASA Technical Reports Server (NTRS)

The In-Space Technology Experiments Program (INSTEP) provides an opportunity to explore the many critical questions which can only be answered by experimentation in space. The objective of the Extravehicular Activity Welding Experiment definition project was to define the requirements for a spaceflight experiment to evaluate the feasibility of performing manual welding tasks during EVA. Consideration was given to experiment design, work station design, welding hardware design, payload integration requirements, and human factors (including safety). The results of this effort are presented. Included are the specific objectives of the flight test, details of the tasks which will generate the required data, and a description of the equipment which will be needed to support the tasks. Work station requirements are addressed as are human factors, STS integration procedures and, most importantly, safety considerations. A preliminary estimate of the cost and the schedule for completion of the experiment through flight and postflight analysis are given.

Watson, J. Kevin

1989-01-01

442

Tidal Pools--Miniature Oceans  

ERIC Educational Resources Information Center

A comprehensive discussion of the biological activity in tidal pools is provided. The importance of environmental factors such as oxygen supply, temperature, salinity, and light is detailed. Plants and animals that might be found in a tidal pool are identified and described. (BT)

Plake, Linda Perry

1977-01-01

443

Radiation and annealing response of WWER 440 beltline welding seams  

NASA Astrophysics Data System (ADS)

The focus of this paper is on the irradiation response and the effect of thermal annealing in weld materials extracted from decommissioned WWER 440 reactor pressure vessels of the nuclear power plant Greifswald. The characterisation is based on the measurement of the hardness, the yield stress, the Master Curve reference temperature, T0, and the Charpy-V transition temperature through the thickness of multi-layer beltline welding seams in the irradiated and the thermally annealed condition. Additionally, the weld bead structure was characterised by light microscopic studies. We observed a large variation in the through thickness T0 values in the irradiated as well as in thermally annealed condition. The T0 values measured with the T-S-oriented Charpy size SE(B) specimens cut from different thickness locations of the multilayer welding seams strongly depend on the intrinsic weld bead structure along the crack tip. The Master Curve, T0, and Charpy-V, TT47J, based ductile-to-brittle transition temperature progressions through the thickness of the multi-layer welding seam do not correspond to the forecast according to the Russian code. In general, the fracture toughness values at cleavage failure, KJc, measured on SE(B) specimens from the irradiated and large-scale thermally annealed beltline welding seams follow the Master Curve description, but more than the expected number lie outside the curves for 2% and 98% fracture probability. In this case the test standard ASTM E1921 indicates the investigated multi-layer weld metal as not uniform. The multi modal Master Curve based approach describes the temperature dependence of the specimen size adjusted KJc-1T values well. Thermal annealing at 475 °C for 152 h results in the expected decrease of the hardness and tensile strength and the shift of Master Curve and Charpy-V based ductile-to-brittle transition temperatures to lower values.

Viehrig, Hans-Werner; Houska, Mario; Altstadt, Eberhard

2015-01-01

444

Some issues in life assessment of longitudinal seam welds based on creep tests with cross-weld specimens  

NASA Astrophysics Data System (ADS)

In order to reduce production costs, it is of great interest to use longitudinal seam welds when manufacturing large diameter pipes. The cost reduction can be as high as 30 percent. However, severe in-service accidents, for this type of pipes working in the creep regime, have occurred mainly due to mismatch in weldment creep properties. In the present paper, both full scale seam welded pipes and cross-weld specimens are studied with the damage mechanics concept using finite element technique. The same mechanical model of multiple material zones is used for the two components. Both the influence of differences in creep properties between the weldment constituents and the size effect of the cross-weld specimen, are studied.

Segle, P.; Tu, S. T.; Storesund, J.; Samuelson, L. A.

1995-05-01

445

Model of large pool fires.  

PubMed

A two zone entrainment model of pool fires is proposed to depict the fluid flow and flame properties of the fire. Consisting of combustion and plume zones, it provides a consistent scheme for developing non-dimensional scaling parameters for correlating and extrapolating pool fire visible flame length, flame tilt, surface emissive power, and fuel evaporation rate. The model is extended to include grey gas thermal radiation from soot particles in the flame zone, accounting for emission and absorption in both optically thin and thick regions. A model of convective heat transfer from the combustion zone to the liquid fuel pool, and from a water substrate to cryogenic fuel pools spreading on water, provides evaporation rates for both adiabatic and non-adiabatic fires. The model is tested against field measurements of large scale pool fires, principally of LNG, and is generally in agreement with experimental values of all variables. PMID:16442217

Fay, J A

2006-08-21

446

[Welding-related respiratory diseases].  

PubMed

Welders are exposed to fumes containing different gases, fumes and particles, depending on the composition of the welding electrodes, welded material and the welding method used. Welders are workers at risk of developing various respiratory signs and symptoms. Health effects associated with welding include different lung function abnormalities, including metal fume fever, bronchial asthma, chronic obstructive pulmonary disease, pneumoconiosis and other pulmonary fibrosis (chronic beryllium disease, cobalt lung), and lung cancer. The authors describe some aspects of etiology, pathogenesis, diagnostics, prophylaxis, and medical certification of welding-related respiratory diseases. PMID:19746888

Wittczak, Tomasz; Walusiak, Jolanta; Pa?czy?ski, Cezary

2009-01-01

447

Unique Cryogenic Welded Structures  

SciTech Connect

For the last few decades, the E. O. Paton Electric Welding Institute has been active in the field of cryogenic materials science. Integrated research on development of new grades of steels and alloys for cryogenic engineering was carried out in collaboration with the leading institutions of Russia, Ukraine, and Georgia. Commercially applied welding technologies and consumables were developed. They include large, spherical tanks for storage of liquefied gases (from oxygen to helium) under high pressures; space simulators with a capacity of 10 000 m3 and more; and load-carrying elements of superconducting fusion magnetic systems for the TOKAMAK, MGD, and ITER series.

Yushchenko, K.A.; Monko, G.G. [E.O. Paton Electric Welding Institute, Kiev 03680 (Ukraine)

2004-06-28

448

Unique Cryogenic Welded Structures  

NASA Astrophysics Data System (ADS)

For the last few decades, the E. O. Paton Electric Welding Institute has been active in the field of cryogenic materials science. Integrated research on development of new grades of steels and alloys for cryogenic engineering was carried out in collaboration with the leading institutions of Russia, Ukraine, and Georgia. Commercially applied welding technologies and consumables were developed. They include large, spherical tanks for storage of liquefied gases (from oxygen to helium) under high pressures; space simulators with a capacity of 10 000 m3 and more; and load-carrying elements of superconducting fusion magnetic systems for the TOKAMAK, MGD, and ITER series.

Yushchenko, K. A.; Monko, G. G.

2004-06-01

449

In-Situ Measurement of Metal Drop Temperature in GMA Short-Circuiting Welding  

NASA Astrophysics Data System (ADS)

Temperatures of metal drop in GMA short-circuiting welding process were in-situ measured using newly developed instrument designed on the basis of two-color pyrometry, which consisted of optical lenses, interference filters for two colors and two sets of high sensitive CCD cameras with fast shutter. In order to avoid radiation from arc plasma, temperature measurement was carried out immediately after molten drop at electrode wire tip was contacted with weld pool and arc was extinguished. Welding current in arcing period was adjusted from 50 A to 250 A using experimental power source in Ar + 20%CO2 mixture gas shielded GMA welding with mild steel wire of 1.2 mm in diameter. It is shown through in-situ measurement that average temperature of metal drop ranges from 2200 K to 2700 K, depending on level and period of arc current governing electrode wire melting.

Hirata, Yoshinori; Onda, Masahiko; Nagaki, Hayato; Ohji, Takayoshi

450

Modelling of laser welding of flat parts using the modifying nanopowders  

NASA Astrophysics Data System (ADS)

A mathematical model is formulated to describe thermophysical processes at laser welding of metal plates for the case when the modifying nanoparticles of refractory compounds have been introduced in the weld pool (the nanopowder seed cultrure fermenters — NSCF). Specially prepared nanoparticles of refractory compounds serve the crystallization centers that is they are in fact the exogenous primers, on the surface of which the individual clusters are grouped. Owing to this, one can control the process of the crystallization of the alloy and the formation of its structure and, consequently, the joint weld properties. As an example, we present the results of computing the butt welding of two plates of aluminum alloy and steel. Computed and experimental data are compared.

Cherepanov, A. N.; Shapeev, V. P.

2013-06-01

451

Dual-beam laser welding of AZ31B magnesium alloy in zero-gap lap joint configuration  

NASA Astrophysics Data System (ADS)

Porosity within laser welds of magnesium alloys is one of the main roadblocks to achieving high quality joints. One of the causes of pore formation is the presence of pre-existing coatings on the surface of magnesium alloy such as oxide or chromate layers. In this study, single-beam and dual-beam laser heat sources are investigated in relation to mitigation of pores resulting from the presence of the as-received oxide layer on the surface of AZ31B-H24 magnesium alloy during the laser welding process. A fiber laser with a power of up to 4 kW is used to weld samples in a zero-gap lap joint configuration. The effect of dual-beam laser welding with different beam energy ratios is studied on the quality of the weld bead. The purpose of this paper is to identify the beam ratio that best mitigates pore formation in the weld bead. The laser molten pool and the keyhole condition, as well as laser-induced plasma plume are