Materials Science Forum Vols. 561-565

Abstract: The mathematical models of compacting process in green sand molding were built up based on the experiment results of molding sand property testing, in which the nonlinearity problems involved in the molding sand material, the pattern geometry and the contact between sand and flask were considered. These models were then used to numerically simulate the compacting process of green sand and predict the hardness distribution of green sand mold. The effect of sand filling on the initial sand density distribution was taken into account, which was obtained through the two phase flow simulation of sand filling. The predicted results were compared with the measured ones and good agreement was obtained.

Abstract: Rolling force is the most important technical parameter for the tandem cold mill. In this paper, the precise models and calculation process for the rolling force are introduced. The rolling force model is based on the Bland-Ford and Hill theory, and the roll flatten radius is calculated with the Hitchcok’s formula. The deformation resistance of the strip is calculated with the model, whose parameters are decided according to the steel grade. The friction coefficient model is built according to rolling speed and rolled length of the roll. The rolling force and the roll flatten radius are calculated with the iterative method. These models are used for online process control of one five-stand tandem cold mill. Comparing the calculation result and the actual data, the precision of the rolling force calculation is high.

Abstract: For properly choosing grinding parameters, predicting probable faults and processing quality, simulation of grinding based on virtual reality technology was study. Physiognomy forming mechanism of grinding wheel was analyzed and a 3D virtual grinding wheel models was built. Effects to grinding wheel physiognomy by grain size and organization number were analyzed and grain distribution was visually represented. Effect to processing quality by grinding wheel granularity, dressing parameters, grinding wheel speed, feed speed and grinding depth was simulated. And experiments were carried out for comparative analyzing. Experiments result proved the reliability and practicality of the virtual grinding wheel model.

Abstract: The aim of equal channel angular extrusion is to get ultrafine grained bulk materials. The practice process is not under isothermal conditions. It is important to understand the details of the deformation and temperature transient within the shear zone. The temperature rise and temperature distribution in the billet and die during equal channel angular extrusion at different pressing temperatures were investigated by using 3D FEM.

Abstract: Using Oyane ductile fracture criterion, a 2-D coupled thermo-mechanical simulation of center crack occurrence in round billet during 2-roll rotary rolling process is presented with the aid of FE code MSC.Superform. Based on an existing flat-die-model, an improved FE model is advanced, in which not only the influence of roll feed angle and entry cone angle but also the diameter of the piercing roll on the process are taken into account. By adopting the parameters of the Diescher piercer in 140mm Mandrel Mill of Bao Steel in China, the distribution and development of strain/stress in tube rounds are analyzed, and the eigenvalue of ductile fracture as well. The critical percentage of diameter reduction is obtained from the simulation. The result shows a good agreement with the experimental value, and therefore is of widely guiding significance to practical process for rationally formulating deformation parameters of steel tube piercing.

Abstract: A thermodynamic analysis of the Fe-Mn-P ternary system has been carried out using the CALPHAD method. Among the three binary systems relevant to this ternary phase diagram, the thermodynamic parameters of the Mn-P binary system were evaluated in this study. The enthalpy of formation of the binary phosphides obtained from our first-principles calculations was utilized in the present analysis to compensate for the lack of available experimental data. The thermodynamic descriptions of the Fe-Mn and Fe-P binary systems were taken from previous studies. The phase equilibria in the Fe-Mn-P ternary system were analysed based on the experimental data on the phase boundaries. The calculated phase diagrams are in agreement with the experimental results.

Abstract: An effective method was proposed to simulate and control the motion track of guide roller during radial-axial ring rolling in FE simulation. The 3-D finite element model was constructed according to the principle and feature of rolling technology. The rolling process was simulated and analyzed by using dynamic explicit finite element technology. The different rolling processes with different technology parameter were simulated. The width spreads and rolling forces under different parameters are compared and analyzed. The results indicated that high quality ring product could be obtained when rational parameters in radial and axial were assigned.

Abstract: The lattice dynamics and thermodynamic properties of MgS and related II-VI compounds are studied by the first-principles linear-response function calculation in the framework of densityfunctional perturbation theory. The ab initio structural, mechanic and dielectric parameters of these phases are presented. From the theoretical phonon dispersion relations, the linear thermal expansion coefficient and its temperature dependence are calculated. The differences in structural and thermodynamic behaviors of these compounds are explained from their phonon dispersion characters.

Abstract: This paper focuses on a rapid simulation methodology for sheet metal forming, using AutoForm™ software, for an auto-body panel. An engine hood is selected as a sample part. Simulation of the whole process cycle, including drawing, cutting and flanging is presented generally. According to the required outer surface forming quality, the dominant parameter is determined firstly from various parameters using AutoForm™ sigma module. The optimisation of the dominant parameters is then performed to obtain the best result. This methodology can decrease the optimisation time and predict the most crucial parameter in the forming process for design engineers, which can dramatically reduce the lead time of automobile industries.

Abstract: The segregation energy of solute Ga in the staking fault in Cu-Ga alloy was calculated from the first principles. Then, we presented numerical results of the stacking fault energy for Cu-Ga alloy using the value of the segregation energy as a input parameter to a expression in the equilibrium state. The numerical results of the stacking fault energy were in good agreement with the experimental values.