Materials Science Forum Vols. 580-582

Abstract: Welding tasks in shipbuilding create great problems for a manual welder since welding takes place in closed area with associated work environmental problems. This paper addresses the problems involved in the welding robot with control algorithm and system. The control system may similarly be modified as a tracking simulation test. The performance of the control system is assessed through the use of field data. The aim of this paper is to determine feasible parameters for a welding procedure with simulation for seam tracking of welding robot system. The main advantage of tracking simulation is its flexibility in that as the welding parameters are modified at a sufficiently high rate. Tracking simulation showed that the development of robot control algorithms should be performed by simulation, since it saves time, expenses and efforts. This paper will contribute to an increased use of automated welding technology with tracking simulation methods. Also, this paper’s results can be used for the optimization of welding process using simulation method with LabVIEW.

Abstract: High integration, density and complexity are essential in electronic products such as compact and light mobile phone recently. A new type of development for component and material is also needed. In the PCB design aspect, a technique such as pad on via, trying to keep up with the demand for compact and slim products, is commonly used. In a response to increased pressure from these situations, an enhanced ability on reliability of electronic products is gradually needed. The high cost and risk, however, are higher and higher for the assurance in the reliability. We made a procedure which can evaluate a solder joint reliability on the product development phase. Furthermore, we've pursued a development process for preventing failure as we analyzed the failure mode from predicting the causes of the failure more precisely. In this study, focusing on the joint reliability of the solder interconnection between CSP and pad on via, we have passed through a test procedure as follows. First, making samples applied with high integrated circuit (CSP: 0.65 pitch, via hole size: 165um, solder: Sn-3.0Ag-0.5Cu). Second, operating the thermal cycling experiment (- 45°C~+125°C, 30min/cycle) to find a failure of the test specimen with an electrical method. Third, observation the non-destructive X-ray microscopy and the metallographic cross-sectioning. Fourth, simulation of the finite element model and deformation analysis. Fifth, completion the modeling of the failure mode. Lastly, prediction a lifetime of the solder joint.

Abstract: Friction stir welding (FSW) is a solid-state joining technique which can produce high-quality joints efficiently. The residual stresses in FSW are generated due to the effect of both the uneven temperature field and of the tool force, which is different from that in fusion welding. In this study the residual stresses of 3mm-thick 2024-T4 aluminum alloy FSW joints have been investigated by using the Hole-drilling method. To reduce the influence of drilling upon the experimental results, annealed stress-free 2024 aluminum alloy plates were drilled; the relieved strains were measured and were subtracted from the total strains measured from the joints. The results showed that the longitudinal residual stresses in the joint were much larger than the transverse residual stresses; high longitudinal tensile residual stresses were concentrated near the tool shoulder direct affected zone and asymmetrically distributed at the different sides of the weld line; i-e, high at the advancing side and relatively low at the retreating side. Outside the tool shoulder direct affected zone, the longitudinal residual stresses decreased rapidly and became compressive residual stresses away from the weld line; the peak of the longitudinal residual stresses was 164.5MPa.The mechanism of the generation of the residual stresses was analyzed preliminarily.

Abstract: Heat generation is a dynamic process under solid state joining conditions during friction stir welding (FSW). In this article, a new heat source model in which heat generation, depending on yield stress and tool rotation speed, was established and was applied to simulate thermal field of FSW welded 2024-T3 panels. Results showed that for 2mm/s welding speed and 400rpm rotation speed, the simulated temperature-time curves on different positions corresponded well with measured results. With the increasing of rotation speed, temperature increased steadily but tended to a saturation state at high rotation speeds, which is consistent with the fundamentals of solid state joining.

Abstract: The wetting and flowing behaviors of the filler metal during laser brazing process were analyzed by the computer simulation. Two situations of the wetting and flowing during laser brazing were modelled, i.e., the metled Au-18%Ni and Ag-10%Pd filler metals on the butt joint of Inconel 600, and the melted Cu-8%Sn filler metal on the dissimilar butt joint of type 304 stainless steel to Cu. The filler metal droplet wetted and spread on the base metals and simultaneously infiltrated into the joint gap with the lapse of time. The Au-Ni and Ag-Pd filler metal infiltrated into the 0.3mm wide joint gap at the completion of brazing even in the single beam brazing. The Au-Ni filler metal did not infiltrate into the joint gap completely at the brazing clearances of 0.1-0.2mm in the single beam brazing, however, it could be filled up in the joint gap in the tandem beam brazing. The Cu-Sn filler metal wetted on the both base metals of stainless steel and Cu and filled up the 0.3mm wide joint gap when the location of preheating beam deviated in 0.5mm to Cu substrate, however, it did not infiltrate into the joint gap completely at the deviation distance of preheating beam to Cu substrate being 1.0mm. It followed that the wetting and flowing behaviors of the filler metal during laser brazing process could be predicted by the computer simulation.

Abstract: A finite element analysis was conducted to study the roles of temperature and pressure in the formation of electrode pitting in resistance spot welding of an aluminum alloy. The distributions of pressure and temperature were computed at the electrode tip surface. Results showed that the highest temperature is always located at the center of electrode tip surface, while electrode pressure is concentrated mainly at the edge of contact region. The location of the concentrated electrode pressure coincides with that of electrode pitting, which indicates that the pressure concentration plays a more significant role than the temperature in the formation of pitting.

Abstract: A three dimensional heat transfer model on laser-plasma hybrid welding has been proposed, that takes into account the interaction between laser beam and plasma arc. Through FEM computation, the temperature fields were computed and analyzed for an Al-Li alloy during laserplasma hybrid welding with different distances between the two heat sources. The simulation results are in agreement with the experimental results.

Abstract: A three-dimensional model which takes into account Marangoni shear stress, buoyancy force, and electromagnetic force in the laser-plasma hybrid welding pool is presented. Distribution of velocity and temperature in welding pool are calculated by finite volume method (FVM). Numerical analysis shows that the Marangoni shear stress determines flow pattern and the electromagnetic force can widen bottom surface of welding pool. The simulation results agree well with corresponding experimental results.

Abstract: Hybrid Rotary Friction Welding is a modified type of common rotary friction welding processes. In this welding method, parameters such as pressure, angular velocity and time of welding control temperature, stress, strain and their variations which play an important rule in defining optimum process parameter combinations in order to improve the design and manufacturing of welding machines and quality of welded parts. Thermo-mechanical simulation of friction welding has been carried out. It has been shown that simulation is an important tool for prediction of generated heat and strain at the weld interface and can be used for prediction of microstructure and evaluation of quality of welds. For simulation of Hybrid Rotary Friction Welding a commercial finite element program has been used and the effects of pressure on temperature and strain variations have been investigated.

Abstract: For many years, rivet joint technology has been applied in the automotive and aerospace industry. Recently, it began to apply laser welding technology to lap joints instead of rivet joining. Laser spot welding has some potential advantages including time saving, cost reduction, material saving and weight reducing. A lap joint of aluminum alloy LY12 with different plate thickness, namely 2mm and 1mm, was spot-welded by CO2 laser. For the welding, laser power in pulse form with ramping-up and cooling-down shape was used, and pure helium gas served as shielding gas to fill around welding area. In this study transient three-dimensional non-linear finite element modeling was used to analyze heat flow and residual stress of the laser spot welding of aluminum alloy LY12. In modeling the temperature dependence of material properties, influence of contact surfaces are taken into account. To analyze, Gaussian distributed heat source model and thermo-elasto-plastic behavior were applied. Weld dimensions and residual stress at the weld surface were calculated numerically and compared with the experimental results.