Advanced Materials Research Vols. 418-420

Abstract: The copper specimen was fabricated through liquid die forging under different preheating temperature of mold condition. The effect of preheating temperature of mold on the microstructure, density, hardness, tensile strength and electrical conductivity were investigated. The results show that the crystal grain size was deceased firstly and then increased with the increasing of preheating temperature. Crystal grain was uniform and fine when the preheating temperature was 250 °C. The density of copper fabricated through liquid die forging was improved by about 5% comparing with that through static casting in metal mold. The hardness of copper fabricated through liquid die forging was HBS 85.2 when the preheating temperature was 250°C, which was higher than that at the rest preheating temperature conditions. The tensile strength was 288 MPa when the preheating temperature was 250°C. There was no obvious effect on the electrical conductivity under different preheating temperature.

Abstract: The paper proposes the method of optimization of the fish-tail, which include optimizing the height of cross section, optimizing diffusion angle. A development system of parametrical design is formed by using SolidWorks as platform and using its secondary development as tool. The parametric design system for fish-tail die channel can fully realized the parameterization and the automation; it not only advances efficiency of design, but also provides some useful referenced experience to parametrical system design of other parts.

Abstract: The tensile tests of DP590 dual-phase steel tailor-welded blanks were carried out at different temperatures and strain rates. Quantitative analysis of metallographic was utilized to study the microstructure evolution of the base metal area and the weld zone of the tensile fracture. By combining the microstructure evolution model with the secondary development technologies of ABAQUS, the microstructure evolution of dual-phase steel tailor-welded blanks was simulated during warm tensile tests. The results show that, with the temperature increasing and strain rate decreasing, the dynamic recrystallization volume fraction of ferrite increases, and the martensite transform into equiaxed ferrite gradually. The results of microstructure simulation are in good agreement with experimental results.

Abstract: Surface roughness is one of the most important product quality characteristics. In this paper, experimental investigation of surface roughness was performed in high speed turning of hardened AISI P20 steel with CBN tool based on design of experiment. The influence of cutting speed, feed rate, depth of cut and nose radius on surface roughness were assessed using analysis of variance (ANOVA). Optimal cutting parameters were found to improve the machining performance. Due to the complexity of machining process, artificial neural network (ANN) was employed to develop the predictive model of surface roughness. Simulations were done to study the relationship between surface roughness and cutting parameters based on the proposed model.

Abstract: The production of materials saving products such as Longitude Profile plates (LP plate) and Tailor Rolled Blanks (TRB) needs to solve the problem of the calculation of variable gauge rolling (VGR) parameters. It has been proved that Karman differential equation of force equilibrium for simple rolling is a special case of VGR equations when v_y＝0. Differential equations of force equilibrium for both upwards rolling and downwards rolling were solved and the rolling pressure distribution function for VGR was got in this paper. Finally, details of a set of experiments were presented and the theoretical model of rolling force was proved to be reasonable.

Abstract: Surface finish and dimensional accuracy are two of the most important requirements in machining process. High speed machining (HSM) is capable of producing parts that require little or no grinding/lapping operations within the required machining tolerances. In HSM determination of the optimum combination of cutting parameters for achieving the required level of quality, such as, minimum possible surface roughness and maximum tool life is a very important task. Silicon is conventionally finished using grinding followed by polishing and lapping to achieve required surface finish and surface integrity. In this study small diameter tools are used to achieve high rpm to facilitate the application of low values of feed and depths of cut to ensure high surface roughness values through achievement of ductile mode machining of silicon. Investigations on the effect cutting parameters of high speed end milling on surface finish and integrity of silicon has been conducted to minimizing the amount of finishing requirement in machining of silicon, with the objective of reducing cost and increasing effectiveness of silicon manufacturing process. In this work statistical models were developed using the capabilities of Response Surface Methodology (RSM) to predict the surface roughness in high speed flat end milling of silicon under dry cutting conditions.

Abstract: Vacuum brazing of 316L stainless steel with BNi-2 brazing filler metal.The effects of brazing temperature and brazing clearance on microstructure and mechanical properties of vacuum brazed joints of 316L stainless steel were studied. The results show that: As brazing temperature being 1 070 °C, with the increasing of the brazing clearance, the joint shear strength value become lower and lower. Brazing clearance compounds mainly contain intermetallic and solid solutions.

Abstract: This paper present exploration of polymer extrusion under melted temperature by conform process. The stress distribution of the process is described based on plastic mechanics. Solutions are presented and detailed comparisons are made between theoretical predictions and simulation results.

Abstract: In multi-wire flat rolling process, the error of the rolled wires in thickness was due to the roller deflection and the spring back of the rolled wire. In order to control the dimension accuracy, to know the quantity of thickness error precisely is very important. In this study, the DEFORM-3D finite element analysis software was used to simulate the multi-wire flat rolling process with the elastic-plastic deformation model, supposed the rollers as elastic body and the wires as elastic-plastic body through the rolling process. From the computer simulation results, it can be found that, the deflection of roller has the biggest effect on the dimension accuracy of wire. To control the deflection value of roller, besides roller material and the roller length, the choice of roller diameter is also very important.

Abstract: In this study, we present an experimental/numerical methodology which aims to improve 3D thin sheet hydroforming considering coupled constitutive equations formulated in the framework of of irreversible processes accounting for isotropic hardening as well as isotropic ductile damage. The experimental study is dedicated to the identification of stress-strain flow from the global measure of pole displacement, thickness evolution and internal pressure expansion. Or during the hydroforming processes severe mesh distortion of element occur after a few incremental steps. Hence an automatic mesh generation with remeshing capabilities is essential to carry out the FEA. The proposed technique based on geometrical criteria includes adaptive refinement and coarsening procedure is integrated in a computational environment.