Showing papers on "Electric resistance welding published in 2005"

Resistance welding : fundamentals and applications

Abstract: WELDING METALLURGY Solidification in Resistance Spot Welding Phase Transformations in RSW Cracking References ELECTROTHERMAL PROCESSES OF WELDING Introduction Electrical Characteristics of Resistance Welding Thermal Characteristics of Resistance Welding Heat Balance Electrode Life Lobe Diagrams References WELD DISCONTINUITIES Classification of Discontinuities Void Formation in Weld Nuggets Cracking in Welding AA6111 Alloys Cracking in Welding AA5754 Alloys References MECHANICAL TESTING Introduction Shop Floor Practices Instrumented Tests References RESISTANCE WELDING PROCESS MONITORING AND CONTROL Introduction Data Acquisition Process Monitoring References WELD QUALITY AND INSPECTION Weld Quality Attributes Destructive Evaluation Nondestructive Evaluation References EXPULSION IN RESISTANCE SPOT WELDING Influence of Expulsion on Spot Weld Quality Expulsion Process and Detection Expulsion Prediction and Prevention Examples References INFLUENCE OF MECHANICAL CHARACTERISTICS OF WELDING MACHINES Introduction Mechanical Characteristics of Typical Spot Welders Influence of Machine Stiffness Influence of Friction Influence of Moving Mass Follow-Up in a Welding Cycle Squeeze Time and Hold Time Measurement Other Factors References NUMERICAL SIMULATION IN RESISTANCE SPOT WELDING Introduction Coupled Electrical-Thermal-Mechanical Analysis Simulation of Contact Properties and Contact Area Simulation of Other Factors Modeling of Microstructure Evolution Examples of Numerical Simulation of RSW Processes References STATISTICAL DESIGN, ANALYSIS, AND INFERENCE IN RESISTANCE WELDING RESEARCH Introduction Basic Concepts and Procedures Experiments with Continuous Response Experiments with Categorical Responses Computer Simulation Experiments Summary References INDEX

Review of laser hybrid welding

Abstract: In this article, an overview of the hybrid welding process is given. After a short historic overview, a review of the fundamental phenomenon taking place when a laser (CO2 or Nd:YAG) interacts in the same molten pool as a more conventional source of energy, e.g. tungsten in-active gas, plasma, or metal inactive gas/metal active gas. This is followed by reports of how the many process parameters governing the hybrid welding process can be set and how the choice of secondary energy source, shielding gas, etc. can affect the overall welding process. An overview of the benefits and drawbacks of hybrid welding is presented, including reports on gap bridging ability, changes in welding speed and weld penetration, overall weld quality, and changes in heat input to the material being welded. This overview is followed by a few examples of industrial applications of hybrid welding. Finally, a section is devoted to explain about further work required in order to understand and tackle the hybrid welding process more efficiently in the future.In this article, an overview of the hybrid welding process is given. After a short historic overview, a review of the fundamental phenomenon taking place when a laser (CO2 or Nd:YAG) interacts in the same molten pool as a more conventional source of energy, e.g. tungsten in-active gas, plasma, or metal inactive gas/metal active gas. This is followed by reports of how the many process parameters governing the hybrid welding process can be set and how the choice of secondary energy source, shielding gas, etc. can affect the overall welding process. An overview of the benefits and drawbacks of hybrid welding is presented, including reports on gap bridging ability, changes in welding speed and weld penetration, overall weld quality, and changes in heat input to the material being welded. This overview is followed by a few examples of industrial applications of hybrid welding. Finally, a section is devoted to explain about further work required in order to understand and tackle the hybrid welding process more ...

Resistance welding of thermoplastic composites - an overview

Abstract: This paper presents an extensive overview of resistance welding of thermoplastic composites. The objective is to provide a deeper insight into the nature of the resistance welding process and a summary of the vast experimental investigative effort put into it over the years. The main focus is set on the parameters that govern the welding process and the principal phenomena that affect the quality of the joint. The standard experimental procedure, the experimental set-up and the main evaluation methods are also looked at in detail. Finally, several alternative resistance welding methods that involve non-thermoplastic materials and offer possibilities for future applications are briefly reviewed.

Characterization of aluminum/steel lap joint by friction stir welding

Abstract: The welding of a lap joint of a commercially pure aluminum plate to a low carbon steel plate (i.e., Al plate top, and steel plate bottom) was produced by friction stir welding using various rotations and traveling speeds of the tool to investigate the effects of the welding parameters on the joint strength. The joint strength depended strongly on the depth of the pin tip relative to the steel surface; when the pin depth did not reach the steel surface, the joint failed under low applied loads. Meanwhile, slight penetration of the pin tip to the steel surface significantly increased the joint strength. The joint strength tended to increase with rotationspeed and slightly decrease with the increase in the traveling speed, although the results were quite scattered. The effects of the welding parameters were discussed metallographically based on observations with optical and scanning electron microscopes.

Advancements in pulse gas metal arc welding

Abstract: Environmental concerns have driven manufactures to look for alternative materials like aluminium that are lighter in weight and possess good thermal and electrical conductivity. However, fabrication of alternative materials presents a considerable challenge for fabrication in volume production. Welding is one of the most common fabrication processes. Good thermal and electrical conductivity act as a drawback for welding and generally results in excessive heating of base material. Pulse gas metal arc welding (GMAW-P) overcomes this drawback by producing spray transfer at lower mean currents. Modern welding has become complex due to need for setting up of combination of large number of welding parameters to achieve best quality of weld. Trial and error methods are impractical. In addition, there are many facets of disturbances and each has its own source and mitigation techniques. This need has resulted in several advancements in GMAW-P technology. This paper reviews progress in performance of GMAW-P technology.

Friction Stir Spot Welding of Advanced High-Strength Steels - A Feasibility Study

Abstract: An exploratory study was conducted to investigate the feasibility of friction stir spot welding advanced high-strength steel sheet metals. The fixed pin approach was used to weld 600MPa dual phase steel and 1310MPa martensitic steel. A single tool, made of polycrystalline cubic boron nitride, survived over one hundred welding trials without noticeable degradation and wear. Solid-state metallurgical bonding was produced with welding time in the range of 2 to 3 seconds, although the bonding ligament width was relatively small. The microstructures and hardness variations in the weld regions are discussed. The results from tensile-shear and cross-tensile tests are also presented.

The humping phenomenon during high speed gas metal arc welding

Abstract: A commonly observed welding defect that characteristically occurs at high welding speeds is the periodic undulation of the weld bead profile, also known as humping. The occurrence of humping limits the range of usable welding speeds in most fusion welding processes and prevents further increases in productivity in a welding operation. At the present time, the physical mechanisms responsible for humping are not well understood. Thus, it is difficult to know how to suppress humping in order to achieve higher welding speeds. The objectives of this study were to identify and experimentally validate the physical mechanisms responsible for the humping phenomenon during high speed gas metal arc (GMA) welding of plain carbon steel. A LaserStrobe video imaging system was used to obtain video images of typical sequences of events during the formation of a hump. Based on these recorded video images, the strong momentum of the backward flow of molten metal in the weld pool that typically occurred during high speed welding was identified as the major factor responsible for the initiation of humping. Experiments with different process variables affecting the backward flow of molten weld metal were used to validate this hypothesis. These process variables included welding speed, welding position and shielding gas composition. The use of downhill welding positions and reactive shielding gases was found to suppress humping and to allow higher welding speeds by reducing the momentum of the backward flow of molten metal in the weld pool. This would suggest that any process variables or welding techniques that can dissipate or reduce the momentum of the backward flow of molten metal in the weld pool will facilitate higher welding speeds and productivity.

Effects of torch configuration and welding current on weld bead formation in high speed tandem pulsed gas metal arc welding of steel sheets

Abstract: Undercut and humping bead are the common defects that limit the maximum welding speed of tandem pulsed gas metal arc (GMA) welding. In order to increase the maximum welding speed, effects of the inclination angle, interwire distance and welding current ratio between the leading wire and trailing wire on bead formation in high speed welding are investigated. The undercut and humping bead is attributed to the irregular flow of molten metal towards the rear part of the weld pool. This irregular flow can be prevented by the trailing wire with a push angle from 5° to 13° , which provides an appropriate component of arc force in the welding direction. The irregular flow is also related to the distance between the leading wire and the trailing wire, and the flow becomes regular when the distance is in the range 9–12 mm. Moreover, the stabilisation of the bulge of the weld pool between the two wires, the presence of enough molten metal below the trailing arc, and the reduced velocity of molten metal flow ...

Hot cracking in Al–Mg–Si alloy laser welding – operating parameters and their effects

Abstract: Hot cracking is a phenomenon that frequently occurs in the laser welding of some “special” alloys, such as the aluminium–magnesium–silicon type. Each occurrence of this phenomenon needs to be studied in itself, taking into account not only the individual, but also the interactive, influences of the various parameters. The advantage of using laser beams in welding processes lies in the speeds that can be reached. The disadvantage, however, is that, owing to the high cooling rates characteristic of the interaction between the laser beam and the material, the welding speed itself becomes a cause of hot cracking. The aim of this paper is to see how this disadvantage may be eliminated. We consider what the most important parameters may be, relating to tensile strength and the quantity of cracks produced, that might influence the presence or absence of hot cracking. The most influential factors in avoiding hot cracking are the welding speed and wire parameters. Also important is welding stability, as instability generates cracks. We can then determine a technological window, useful for industrial applications, which takes into account the values of these influential factors and stability.

Application of Magnetic Pulse Welding for Aluminum Alloys and SPCC Steel Sheets Joint

Abstract: The magnetic pulse welding (MPW) is a cold weld process of conductive metals to the similar or dissimilar material. MPW uses magnetic pressure to drive the primary metal against the target metal sweeping away surface contaminants while forcing intimate metal-tometal contact, thereby producing a solid-state weld. In this paper the MPW method and its application for several aluminium alloy (A1050, A2017, A3004, A5182, A5052, A6016, and A7075) and steel (SPCC) sheets joint were investigated and the process parameters and welding characteristics are reported.

An experimental study determines the electrical contact resistance in resistance welding

Abstract: Electrical contact resistance is of critical importance in resistance welding. In this article, the contact resistance is experimentally investigated for welding mild steel, stainless steel, and aluminum to themselves. A parametric study was carried out on a Gleeble® machine, investigating the influence on the contact resistance of interface normal pressure, temperature, and base metal.

Joining wood by friction welding

Abstract: At the Chair of Timber Constructions of the Swiss Federal Institute of Technology in Lausanne (EPFL) tests were carried out to join wooden work pieces by friction welding without any additional welding deposit. It could be determined that this kind of technology, which is mainly used for thermoplastics and metal, can also be applied to wood. Tests were carried out to determine the influence of the processing parameters like welding pressure, frequency and amplitude of the circular movement on the welding process and the input of energy at the interface. In addition, the resistance of the joint was examined. The development of the shear strength during solidification of the interface as well as the shear strength achievable after a complete solidification of the interface was the objective of the examinations. Furthermore, the microstructure of the welded joint was studied to reveal the manner in which the thermally decomposed wood forms the connection between the welded pieces.

Method for operation of a welding unit welding unit and welding torch for such a welding unit

Abstract: The invention relates to a method for operation of a welding unit (1), for the execution of welding processes with a welding device (2) and a welding torch (10), whereby operational states for the welding processes are recorded and, depending on the operational state, vibrations which may be felt are generated and a welding unit (1) and a welding torch (10), for carrying out said method. According to the invention, the possibility of providing feedback about particular operational states to people involved in the welding process, in particular, the welder, without the same having to look away from the welding spot or the arc (15) may be achieved, whereby, in particular, the welding current (I) or the welding voltage (V) are modulated, depending on the operational state, to generate acoustic vibrations in the arc occurring during welding, or, depending on the operational state, mechanical vibrations are generated. The vibrations can also be felt by the welder without looking away from welding spot or the arc (15).

A comparative study of single-phase AC and multiphase DC resistance spot welding

Abstract: This paper presents a comparative study of the AC and MFDC resistance spot welding process. Both experiments and finite element simulation were conducted to compare the weld size and energy consumption. The experiments were performed on two identical spot welding machines, one with a single phase ac and the other with a mid-frequency DC weld control. The machines were instrumented such that both the primary and secondary voltage and current signals could be collected for energy calculation. The finite element simulation model was developed to understand the underlying mechanisms of the difference between the ac and MFDC processes. The effect of the current waveform was investigated by using the actual process measurements as an input to the simulation model. It is shown that the MFDC process generally produces larger welds than the AC process with the same root-mean-square welding current. However, this difference is more prominent when the welding current is relatively low. Overall, the AC welding process consumes more energy to make a same sized weld than the MFDC process. The larger the welding current is used, the less efficient the AC welding process will become. The differences between the two welding processes are caused by the contact resistance behavior and the electrical inductance in the AC welding process.

Engineering Design with Polymers and Composites

Abstract: Introduction Introduction History of Polymers History of Composites Examples of Polymers and Composites in Use Definitions and Classifications Identification of Plastics Raw Materials and Production of Polymers Chemical Structures Glass Transition and Melting Temperatures Mechanical Properties of Polymers Introduction Tensile Properties Static Failure Theories Creep Properties Relaxation Properties Dynamic Properties Large Strain Definitions Analysis of Damping Time Hardening Creep Isochronous Creep Curves Viscoelastic Behavior of Polymers Mechanical Models Mathematical Models The Maxwell Fluid The Kelvin Solid The Four-Parameter Model The Boltzmann Superposition Principle Advanced Viscoelastic Models The Viscoelastic Correspondence Principle The Time-Temperature Equivalence Principle Creep and Fatigue Failure Creep Failure under Tension Creep Failure under Compression Fatigue of Polymers Notch Sensitivity under Fatigue Creep Buckling of Shells Impact Strength and Fracture Toughness Impact Strength Fracture Toughness Analysis of the Charpy and Izod Impact Tests using Fracture Mechanics Analysis of Impact Specimens at the Nanoscale Selection of Polymers for Design Applications Introduction Basic Material Properties Performance Parameters Loading Conditions and Geometrical Configurations Availability of Materials A Rectangular Beam in Bending Weighting-Factor Analysis Thermal Gradient through a Beam Rating Factors for Various Loading Requirements Design Optimization Computer Database Design Selection Procedure Design Applications of Some Polymers Phenolic Resins with Fillers Polycarbonate Example Design with PC: Fan Impeller Blade Example Design with PC: Snap/Fit Design Example Design of PVC Pipe Design with Fluorocarbon Resins Composite Material Mechanics Introduction Composite Material Nomenclature and Definitions Analysis of Composite Structures Experimental Determination of Engineering Elastic Constants Composite Laminate Failure Strength Properties and Failure Theories Stiffness of Laminated Composites Thermal Stresses Summary Polymer Processing Extrusion Manufacture of PVC Pipe by Extrusion Injection Molding Thermoforming Blow Molding Adhesion of Polymers and Composites Introduction Fundamentals of Adhesion Adhesives Enhancement of Adhesion in Composites Curing of Adhesives Summary Polymer Fusing and Other Assembly Techniques Introduction Heated Tool Welding Ultrasonic Welding Friction Welding Laser Welding Hot Gas Resistance Welding Induction Welding Mechanical Fastener Connections Tribology of Polymers and Composites Introduction Contact Mechanics Surface Topography Friction Wear PV Limit Rolling and Sliding Modification of Polymers for Friction and Wear Performance Composites Wear of Composites Heat Generation in Sliding Polymer Systems Special Considerations Simulative Laboratory Testing Damping and Isolation with Polymers and Composites Introduction Relevance of the Thermomechanical Spectrum Damping Methods of Material Modification Materials for Damping and Isolation Fundamentals of Vibration Damping and Isolation Role of Dampers Damping Layers Rapid Prototyping with Polymers Introduction Rapid Product Development, Tooling, and Manufacture RP Techniques RP Materials Applications Piezoelectric Polymers Introduction Piezoelectric Strain Behavior Piezoelectric Material Properties Hysteresis Composites Appendix A: Conversion Factors Appendix B: Area Moments of Inertia Appendix C: Beam Reactions and Displacements Appendix D: Laminate MATLAB(R) or Octave Code Appendix E: Sample Input/Output for Laminate Program Appendix F: Composite Materials Properties Appendix G: Thermal and Electrical Properties Index Homework Problems and References appear at the end of each chapter.

Optimization of welding parameters for resistance spot welding of TRIP steel with response surface methodology

Abstract: Many automotive companies are endeavouring to reduce the weight of the car body in response to various environmental issues. One initiative is the development of TRIP (Transformation Induced Plasticity) steels with a high strength and ductility. Resistance spot welding is a complex process, which requires specific optimal welding conditions based on experimental data. However, the trial-and-error method to determine the optimal conditions requires a large number of experiments, and so response surface methodology has been employed to overcome this problem. The second-order model was used here. This has been used in the resistance spot welding process of the TRIP steel and galvanized TRIP steel with a zinc-coated layer to optimize the welding parameters. The welding current, welding time, and welding force were selected as input variables, and the shear strength and indentation were selected as output variables.

CO2 Laser Welding Characteristics of 800 MPa Class TRIP Steel

Abstract: Basic characteristics of CO2 laser welded 800 MPa class TRIP steel such as defects, microstructure, mechanical properties and formability was investigated. Bead-on-plate welding was carried out under various power, welding speed and shield gas. Porosity fraction reduced with increasing the welding speed and using Ar-He mixed shield gas compared to Ar gas. The maximum hardness was obtained at the weld metal as well as HAZ near the weld metal. The value was the same regardless of welding speed and was nearly equal to that of water quenched raw metal. In the perpendicular tensile test to the weld axis, the joints produced at optimum condition were fractured at the base metal and the tensile property was nearly equal to the raw metal. In a parallel tensile test, the strength of the joints was higher than that of the base metal, but elongation was found to be lower than that of the raw metal because a crack was initiated in the bead at the strength levels corresponding to the tensile strength of the base metal and was propagated perpendicular to tensile direction. Elongation and formability were further improved using low power or Ar+He mixed gas compared to high power or Ar gas.

Trends in aluminum resistance spot welding for the auto industry

Abstract: Recent advances in resistance welding technology, alloys, and NDE techniques have helped to reduce manufacturing costs for aluminum sheet structures.

Modelling of electrically enhanced friction stir welding process using finite element method

Abstract: Conventional friction stir welding (FSW) of high strength and high melting point materials, such as steel and titanium, has the disadvantages of a serious tool wear problem and slow welding speed. A new friction stir welding process for such materials called 'electrically enhanced friction stir welding process (EHFSW)' has been suggested and analysed using finite element modelling. The basic idea of EHFSW is that electric current passes from the welding tool into the workpiece through the contact area in the welding region. Thus it results in more localised heating while welding is in progress and is not simply a preheating process. The temperature distribution in the workpiece during the pin plunge stage and the welding stage of the EHFSW process has been determined. The results show that EHFSW can reduce the plunge force significantly with the help of localised electrical heating during the pin plunge stage, which may imply lower tool wear when compared with conventional FSW. At the same time, i...