Ding Fan

Analysis and Improvement of Metal Transfer Behaviors in Consumable Double-Electrode GMAW Process

Consumable double-electrode gas metal arc welding (consumable DE-GMAW) is the efficient improvement of DE-GMAW. Due to the variety of coupled arc and metal transfer behaviors, this paper applies static force balance theory to analyze the changes in the forces acting on the main and bypass droplets separately. For main torch, the bypass arc changes the forces affecting on the main droplet, and the main metal transfer becomes more desirable. For bypass torch, with direct current electrode negative (DCEN) polarity, the volume of droplet is big and not easily transfers to the weld pool. In order to improve the bypass metal transfer, a method has been proposed which adds CO2 to pure argon shielding gas to change the forces affecting on the bypass droplet. Then, the welding experiment is carried out to test the effectiveness of this method. It is found that bypass droplet transfers easily and the diameter of bypass droplet is decreased significantly. Also a good weld appearance is acquired.

Study on BPNN based welding joint properties soft sensing method

It is found that the mechanical properties of welded joints is mainly related to the welding heating input and complicated mutual effects in multi composition welding material. According to this principle, a soft sensor model based on the BP neural network (BPNN) is designed. The soft sensing BPNN has been constructed by use of the BP network toolkit of the Matlab software. The dates of five kinds of Low-Ally steels mechanical properties under different welding thermal cycle which used to train and test the BPNN have been obtained by welding thermal simulator. In this way, the soft sensing model for welding joint mechanical properties testing has been established. The BPNN has been tested by use of testing samples from the obtained data. By comparing the predicting date and the actual date, it shows that the soft sensing model has acceptable precision. The soft sensing method provides a new way for predication of mechanical properties of welding joints.

Fuzzy PID control of wire extension in pulsed MIG welding for aluminum alloy

Aiming at the problem of wire extension stability in aluminum alloy pulsed MIG welding process, the influence of wire feed speed on wire extension is identified and the mathematic model has been set by the step response experimentation. According to the actuality problem of routine PID control, a self-tuning fuzzy PID system in a dynamic process was designed to improve the adaptability and the control accuracy,and system simulation was conducted by using the Simulink toolbox of MATLAB, and the optimum control parameters was obtained, then the real-time control for wire extension was carried out based on xPC target real-time environment. The results show that the obtained identification model can reflect the change law of wire extension well and the designed self-tuning fuzzy PID system can control the wire extension effectively in aluminum alloy pulsed MIG welding and also have fast response and good robustness.

High Speed Weld Control System of Dual-Bypass MIG Based on LabVIEW

Dual-bypass MIG welding (DB-GMAW) is a new kind of high speed MIG welding with three arcs. In order to monitor the weld process and control it, a high speed weld system of DB-GMAW was built. The system was run by LabVIEW programs, including getting data of system and control output signals. The test result of system showed that all equipments could be used in the same time. Beside images of weld pool and arc, the weld voltages and currents of every part had been acquired. The signals of bypass current and weld speed also had been input TIG welding sources and worktable motor successfully. Meanwhile, the high speed weld formation had a good quality, and all of these established the closed-loop control of high speed DB-GMAW.

Laser beam welding of dissimilar metals of aluminum alloy and galvanized steel sheet

Using CO2 laser, Laser Lap Welding for dissimilar metals of 5A05 aluminum alloy (upper side) and ST04Z galvanized steel sheet (lower side) that both of 1mm thickness was experimented. Moreover, the microscopic structure, mechanical performance of weld joints were also analyzed and tested. The experimental results indicated that: typical melt-brazed lap joints were fused by melted 5A05 and un-melted ST04Z sheet. Fractures basically occurred in heat-affected zone (HAZ) of 5A05. Its density was 94MPa, acknowledged as gliding fracture.

Wire extension with Dual freedom PID control in pulsed MIG welding process of aluminum alloy

Research work of wire extension control with Dual freedom PID controller in pulsed MIG welding process of aluminum alloy. In the condition of optimum parameters, the simulations were firstly completed by separately using Routine PID control and Dual freedom PID control, based on designing the wire speed of wire extension step response and gaining identification model. Based on the results of simulation using Matlab/Simulink, the experimental research on aluminum alloy pulsed MIG welding by using Dual freedom PID control was carried out in the real-time target environment with XPC Target. In the pulsed MIG welding process of aluminum alloy, the results prove that the Dual freedom PID control can bring higher precision and quicker response speed, efficiently control the stability of wire extension, and satisfy the stability of welding process.

High-speed welding based on consumable DE-GMAW

A new efficient welding method, Consumable DE-GMAW was proposed. According to the many problems occurred when the welding process is open-loop, such as instability of the welding process and a large welding spatter, etc. A real-time target hardware platform was built for consumable DE-GMAW based on xPC, and a rapid prototyping control system was also developed for consumable DE-GMAW with the Matlab/Simulink. The high-speed welding based on consumable DE-GMAW was realized under close loop control, and good weld shaping was acquired at high welding speed. Then the reasons realized high-speed welding through consumable DE-GMAW was analyzed briefly according to humping weld induced by arc pressure theory. The theory analysis and experiments results show that consumable DE-GMAW provides a new method for high-speed welding.

Residual stress field analysis of Al/steel butt joint using laser welding–brazing

ABSTRACT The objective of this study is to analyse residual stress of the Al/steel butt joint using the laser welding–brazing. The welding parameters were a laser power of 1200u2009W, a welding speed of 600u2009mm min−1, thickness of 150×150×2u2009mm and 150×150×1u2009mm, respectively. The residual stress was measured by the hole-drilling methods. Then, a finite-element model of the welding process was established, and it was verified by experiments. The results show that the calculated results are in conformity with the experimental results. The longitudinal residual stress on the galvanised steel (329u2009MPa) is larger than that on the aluminium alloy (293u2009MPa). At the location of the fixture, the longitudinal residual stress is substantially zero.

Mechanical Characterization of Tatanium-Based Gradient Bioceramic Composite by Laser Cladding

The gradient calcium phosphate bioceramic coating was produced on titanium alloy substrate by laser cladding. The microstructure, microhardness, fracture toughness, and residual stress of the tatanium-based gradient bioceramic composite coating were investigated. The results show that the microhardness gradually decreases with further depth increasing cross-section. The highest microhardness of the coating and the transition layer is 1544HV and 1160HV, respectively. The fracture toughness KIC is 3.72±0.03 MPa·m1/2 of bioceramic coating and 4.55±0.02 MPa·m1/2 of the transition layer, which is closely resembles the human compact bone. Furthermore, the residual stress gradually decreases from the coating to substrate, which is 221MPa between ceramic layer and the transition layer and 108MPa between the transition layer and substrate. This distribution is conforms to gradient composition design, which reducing harm of the specimen deformation and cracking.

Metal Transfer Behavior of Consumable DE-GMAW

Consumable double-electrode gas metal arc welding (consumable DE-GMAW) is a novel and high efficient welding method. According to the different polarity of two electrodes in consumable DE-GMAW, the metal transfer behaviors are analyzed by using the state force balance theory. For main torch with direct current electrode positive polarity, the arc root area is enlarged by bypass arc and increased electromagnetic force promotes main metal transfer. For bypass torch with direct current electrode negative polarity, the electromagnetic force does not work on the melting area. Only gravity force is major detaching force. The volume of bypass droplet is large and not easily detache to the weld pool.