Materials Science Forum Vols. 704-705

Abstract: Casting properties and process improvement of A356 aluminium alloy which is used to cast automobile engine cylinder is investigated in the present paper. The effects of flow field and temperature field on the microstructure and defects distribution of A356 is analyzed by ProCAST software. Simutaneously, the mold filling and solidification of the bottom gating and rotated solidification technology is simulated. Thus, the optimize process parameters obtained by calculating is pouring temperature 725°C, pouring times 21s, and preheating temperature of cylinder sleeve 450°C. Then, the cylinder is made under the condition of above parameters and the microstructure of the cylinder was observed. The results show that the microstructure and defects distribution which is simulated by ProCAST software are good agree with the experiments. Keywords：ProCAST; Aluminium alloy cylinder; Flow field; Temperature field;

Abstract: Based on the analyses of aluminum melt solidification and heat transfer during the process of twin-roll casting, a coupling mathematical model of thin-gauge high-speed casting was developed, which included the casting roller shell. At the same time, FEM was adopted to solve the coupling model. The temperature field, thermal stress field and strain field of aluminum melt in casting zone were simulated by this model. When the casting velocity is 7m/min, and the thickness of strip is 2 mm, in the melt zone, the temperature of melt decreases rapidly as it approaches the rollers; the surface stress of strip is larger than the central stress; In the liquid zone and mushy zone, thermal stress is relatively small; in rolling zone, thermal stress is much larger than in the former two zones, and gradually increases along exports, then gradually decreases after the peak; the outsurface strain of the casting strip is larger than the inner strain, and the thermal stress gradually increases along exports.

Abstract: The present contribution focuses on a recently developed model of microstructure evolution. The model is based on a phase field approach, which takes account of kinetic effects in solidification of alloys and intermetallic compounds. It further incorporates crystal orientation as an additional field variable, which evolves through a Monte-Carlo algorithm. Combination of the phase field approach with Monte-Carlo algorithm allows for physically meaningful and computationally effective simulation of microstructure in polycrystalline and intermetallic forming systems. The paper includes various examples of simulated microstructures in different thermal processes.

Abstract: The flow field, temperature field and stress field on the melt-cast explosive process have been studied by using software of Procast combined with experimental method，from which the thermodynamic characteristics of the explosives melt-casting process has been researched. The simulation results show that the charge shrinkage, cracks and pore formation could be effectively reduced by adjusting the temperature and pressure. The simulation results could be used for the optimization of casting processes, thereby improved the safety performance of Melt-cast explosive. Keywords: explosive; casting; simulation; shrinkage defects; cracks;

Abstract: In this paper, we introduce the squeeze casting process to produce flange. This article also introduces the optimized roughcast of flange, the cruces of the die design, the main structure parameters and the working traits of the die. The result shows that using squeeze casting method to produce flange not only can get the qualified part, which also greatly increase the material utilization together with enormously save processing time and processing costs at the same time.

Abstract: Brake hydro cylinder is the key part of automobile hydraulic braking system, which usually works under high pressure condition. So, high safety factor of it is required to avoid accident. There are many kinds of casting defects such as shrinkage cavity, gas entrapment and slag enclosure are formed in the mold filling and solidification processes, which contribute to final casting performance. Based on the mathematical models of molding filling and solidification processes, the numerical simulation has been done. In the meanwhile, the defects forming reasons have been analyzed. According to the simulation results, two types of improved schemes have been analyzed and practiced respectively, and its work piece defects were reduced largely. It is an effective way to improve the casting quality by advanced computer technology.

Abstract: The numerical solidification simulation for gear ring steel casting has been made, and the location and reasons forming casting defects have been predicted by HUAZHU CAE software. Simulating result shows that the directional solidification and efficient feeding were maintained and the casting perfects can be realized by means of the computer simulation optimizing technological and rationally design of gating system, insulated risers, iron chill and compensating efficiently. After magnetic particle detection and ultrasonic inspection, the properties and microstructure of the Gear ring steel casting are in accord with the international standard.

Abstract: Solution polymerization method was used to prepare hydrophilic antifogging acrylate resin. By means of comparison, the optimum synthesis technology conditions was obtained that ethyl acrylate was used as soft monomer , methylcrylate was used as hard monomer. The best functional monomers was acrylic acid and methyl acrylic acid. The accessory functional monoer was β-hydroxyl ethyl acrylate. Cross-linking agent methylol acrylamide belongs to self-cross-linking system. Crosslinker was N-hydroxymethyl acrylamide.The quality rate of cross-linking agent and carboxylic acid is 4 to 1 .The resin can be cured perfectly at the temperature of 100°C in 40 min. The prepared acrylate resin had excellent water-solubility and antifogging.

Abstract: Multi-point forming (MPF) is an advanced flexible manufacturing technology for three-dimensional sheet metal forming. The substance of MPF is replacing the conventional solid dies by a set of discrete punches called ‘‘punch group’’. Because the reconfigurable discrete punches are used, part manufacturing costs are reduced and manufacturing time is shortened. However due to the discrete contacts between the workpiece and punches, the dimple defects occurred, which are inevitable and particular for MPF. For thick plate, the surface defect is the mainly dimple defect during its MPF process. In this study, elastic cushion was proposed to prevent these surface defects. The dynamic explicit finite element method was chosen to implement the simulation of MPF process. The Hill’s anisotropic yield criterion was used to describe the workpiece material behavior, and the elastic cushion was described with using the hyperelastic material model. The method to determine each punch position to construct forming surface was introduced. The MPF process with and without using elastic cushion was simulated to study the effect of the elastic cushion on preventing the surface defects. The relevant experiment was implemented, and it verified that the elastic cushion is effective method to suppress the surface defects during the thick plate MPF process. Keyword: flexible forming process (FFP), elastic cushion, surface defects, multi-point forming (MPF), thick plate, numerical simulation

Abstract: Raising processes of titanium alloy sheets TC1Mδ1.45 were simulated based on ADINA FEA software. The shape distortions induced by plastic anisotropy during forming and springback processes were described. A series of forming tests were conducted for the comparison of simulation prediction and test measurements. Reasonable agreement was obtained between the predicted and measured profiles of formed parts，It shows that the ADINA software is suitable for the analysis of the forming and springback processes of anisotropic titanium alloy sheets. Two sorts of shape distortion phenomena exhibit in the raised workpieces fabricated in room temperature after springback or elastic recovery process: Firstly, the bottom of the flange in the specimen distorts to be a wavy surface and not a plane. There two high points and two low points, and the high points locate in the flange periphery along the transverse direction (TD), and the low points locate in the periphery along the rolling direction (RD); Secondly, the top surface of the raising specimen distorts to be a wavy surface too, and the distortion shape is similar to that in the flange. During thermoforming at 600°C, the elastic recovery can be suppressed effectively and the shape distortion resulted from springback processes can be eliminated, but the anisotropy characteristics of the titanium alloy sheets can not be changed, so forming at high temperature can not solve all the shape distortion problems except the distortion occurred for the reason of springback, unhomogeneous deformation in thickness still exists. Keywords: Titanium Alloy Sheet; Raising; Springback; Shape Distortion; Adina