Advanced Materials Research Vols. 139-141

Abstract: The influence of forming condition on crash performance of thin-walled structures is investigated, in which high strength low alloy steel HSLA340 and dual phase steel DP590 are considered. Stamping and knife-edge-bending process were carried out respectively to form hat channels, and then, impact tests were performed on the spot-welded top-hat sections subjected to quasi-static and dynamic axial loading conditions to identify the forming effect on the crashworthiness. Regular progressive buckling (quasi-inextensional mode) was observed for knife-edge-bent specimens, while the stamped specimens showed peculiar collapse mode, especially, global instability existed for all the specimens under dynamic impacting and their energy absorption capacity was significantly reduced. The result demonstrates that for accurate assessing the structural performance detailed stamping history of sheet metal components should be taken into consideration.

Abstract: The V-method foundry is an advanced casting technology compared with traditional sand casting. The Pro/E software was used to generate three-dimensional model of cast parts. The solidification process of the automotive axle casting with V-method foundry was simulated by the numerical simulation software, ViewCast. The location and scale of the shrinkage defects caused by the original process were predicted. According to the simulation results, the position of the flange round cooled too fast, which blocked the feeding passage of the round near sprue. The reason was that solidifying sequence was unperfected. The casting process was optimized by means of adding runner and chill. Progressive solidification can be obtained and the shrinkage defects can be eliminated or transferred by the improved technology. The reasonable casting process was obtained and the process has been proofed by the productive practice.

Abstract: Comparing with traditional welding technology, there are many advantages of magnesium laser welding, for example, high welding speed, low line energy, small welding distortion, easy to achieve automate production et al. It is widely used in the area of magnesium welding. Fine microstructure and excellent weld shape can be obtained by choosing reasonable technology parameters and the mechanical properties of welding joint can also be promoted. But there are some defects in the process of welding magnesium alloys with laser, such as, stomas, cracks, impurities and so on. Some actions can be taken to improve or prevent those defects. For example, choosing the appropriate process parameters can solve the problem of cracks, impurities. In this paper, the status of laser welding magnesium alloy is reviewed in recent years, and some problems in magnesium laser welding were analyzed and some suggestions of solving the problems were put forward.

Abstract: According to the characteristic of plate rolling process and the on-line applications, the non-homogeneous wear and thermal expansion of rollers, the elastic recovery and thermal expansion of work pieces, the variation of oil film thickness and the zero point deviation, which influence the precision of gap setting model, are analyzed. Based on the results of analysis, a high-precision gap setting model is proposed, and a zero point correction method is developed, in order to avoid overshoot, damp coefficient, which is affected by the thickness of work piece and zero point deviation are considered, is introduced. On-line applications indicate that the gap setting model improves the precision of gap setting and laid a good foundation of further improvement of thickness accuracy.

Abstract: The track template is a crucial part of the high-speed railway’s track constructing, and the manufacture experiences are still lacked in China. In this paper, the two times drawing process scheme is based on FEA of Dynaform. The pre-forming is the key step of the whole process. The performing scheme was established by simulation and experiment. The pre-formation’s experimental results and simulation results are well coincided. The max relative error of width reaches 1.22%, and the max relative error of length is less than 4.86%. The eligible parts were formed by the drawing process and pilot production has applied to engineering practice.

Abstract: The spring steel strip 50CrVA which is cold rolled was applied to manufacture the diaphragm of the automotive horn by means of sheet metal forming. The combination of the experiments with back-propagation artificial neural network (BPANN) is used to solve the springback problem of the diaphragm. Experiments have shown that a 4-8-1 BPANN is able to predict the springback of the diaphragm successfully, and the network is able to model the relationship between the springback of the diaphragm and the process parameters rationally. BPANN simulation results and experimental ones have shown that the springback of the diaphragm is particularly influenced by such parameters as blank thickness, Young’s modulus, punch radius and yield ratio. Furthermore, the springback of the diaphragm decreases with the increase of blank thickness and Young’s modulus, but increases with the increase of punch radius and yield ratio.

Abstract: Single point incremental forming (SPIF) is a novel sheet metal forming process. Owing to unique deformation mechanism, this process improves the sheet formability as compared to the conventional stamping process. In the current paper, the mechanical properties and spifability (i.e. formability in SPIF) of a wide range of materials were tested. The mechanical properties were mainly determined through tensile testing and the spifability was evaluated using Varying Wall Angle Conical Frustum (VWACF) test. Each mechanical property was drawn against the improvement in sheet formability (i.e. difference of spifability and stampability) and the sole most influential property was identified. It was found that the improvement in formability increases with the increasing of true thickness strain at tensile fracture.

Abstract: Thermal deformation flow stress equation of 1Cr12Ni3Mo2VNbN in the temperature range of 980 °C~1180 °C is established by means of hot simulation test and the regression analysis. The results show that the data obtained accords with hyperbolic sine function and the equation will also enrich the material performance database. The established equation is used in the blade forging production based on numerical simulation technology, and the numerical simulation results show that utilizing flat head billet can solve the problem of filling dissatisfaction at the root of the blade. Adopting water-based graphite lubricant provides better lubrication condition for blade forging. The equipment wear and energy consumption can be reduced by applying initial forging temperature of 1130°C in the blade forging process. The application of thermal deformation flow stress equation and numerical simulation technology can reduce the number of trial production, shorten the process design cycle and improve production efficiency in a large extent.

Abstract: Effects of steel coatings on weldability in resistance spot welding of galvannealed steel sheets were investigated. The steels with different coatings, where Fe content changed from 7.0 wt% to 11.4 wt%, were welded by alternating current (AC) welding machine. The results showed that the weldability in RSW of the GA steel with 11.4 wt% Fe was the best in three researched steels. Higher Fe content in the coating resulted in increased contact resistance and hence reduced welding current needed and increased the range of weld current in RSW.

Abstract: The service life of open-die cold extrusion is the most important factor in economic efficiency. To prolong its service life, the design of the die needs a rational structure. Studying the stress of the die wall and its distribution rule is the precondition in cavity die optimization design. Numerical simulation for tube open-die cold extrusion process using finite element software Deform-3D, the distribution of the stress of die wall, the influence rule of the stress of cavity die wall under various kinds of the processing parameter and the optimum range of stress of cavity die wall. The analysis result can take some effective measures to rational design for the die to decrease the die defect, prolong the service life of the die and increase economic efficiency. It can also offer references for optimization design of cavity die.