顶头形状对穿孔毛管壁厚均匀性及能耗影响的研究

针对目前穿孔顶头形状研究所存在的问题,在实验室内就提高一次穿孔毛管的壁厚均匀性及降低能耗进行了系统的试验研究,初步研制成功一种新型的平头对心顶头。     

不同模数下圆柱直齿轮成形的数值模拟及分析

论述了在直齿轮分度圆直径为定值时，变形程度与模数的关系。通过对三种不同模数的齿轮在特定的条件下温挤压成形数值模拟，结果及分析表明，随着齿轮模数的增大，变形程度也增大，金属向齿顶及周围流动就相对较多，齿形就容易充满，但齿轮头部内凹与头的齿部凸肚现象就越厉害。     

Molecular Dynamics Simulation of Micro Mechanisms in Slip Deformation Theory of Crystals

Based on the discussion that there should be a micromechanism that causes a macroscopic slip of mono-crystal copper, molecular dynamics simulations with the analytical displacement feld around a crack tip have been carried out. The result of the simulation shows that macroscopic shear slip in an f.c.c. mono-crystal copper occurs as discrete time events. This is because cross-slips occur in many places in a material such that a macroscopic shear slip is blocked until some critical state of deformation. A macroscopic shear slip then occurs suddenly at the critical state in which the area of disordered atomic arrangement has stretched from one end of a crystal to the other end. The reason why macroscopic shear slips occur in the directions of the slip planes of a crystal is attributed to the fact that the areas of disordered atomic arrangement develop only along those directions.     

单道自动对接焊应变应力场分析

通过给出模拟单道自动对接焊过程的数学模型，用有元法计算瞬时应变场和应力场并与实测值进行比较，结果证实计算值与实测值基本吻合，表明用数学模拟自动对接焊过程是可行的。     

仿真转台用新型连续回转电液伺服马达研究

本文介绍了一种新型仿真转台用叶片式无脉动连续回转电液伺服马达的工作原理，并提出为验证马达性能的非线性PI和微分前馈的复合控制策略，并通过试验对马达的性能进行了验证。     

测定金属凝固温度场的实验教学

介绍材料成型与控制专业材料成形原理中测定金属凝固温度场实验的教学案例。从建立Fe-C状态图的实验方法讲起，较为清晰地说明各种成分金属液的冷却曲线对了解合金性质，了解合金动态凝固行为的作用，并进一步引伸到近代利用所测定的金属凝固温度场的数据对相应温度场所开展的数学模拟和计算机仿真的结果进行评估，从而为用遗传算法、人工神经网络依据试验设计所取得的凝固温度数据，进行高精度建模、优化和预测服务。     

铁矿石冶金性能实验方法的改进

在不影响实验结果的前提下，对铁矿石的还原度实验方法进行改进。改进后每个实验时间缩短3～4．5h，且大大降低了实验成本。     

A computational study of austenite formation kinetics in rapidly heated steels

Surface hardening of steels involves rapid austenitization and subsequent quenching of the surface. The resulting extent of hardening largely depends on the rate of austenitization of the surface under the applied high heating rates. In the present work the kinetics of austenite formation in Fe-C alloys during rapid, non-isothermal heating conditions, characterized by high heating rates and short austenitization periods, were studied by means of computational simulation. Austenitization of lamellar pearlite/proeutectoid ferrite microstructures was simulated by assuming two kinetically distinct stages: i) dissolution of lamellar pearlite followed by ii) dissolution of proeutectoid ferrite. The two stages were simulated by two corresponding 1-D diffusion models employed in series. Numerical solution of the resultant moving-boundary diffusion problems provide calculated results regarding the dependency of vol. fraction austenite on thermal cycle parameters and on initial microstructural features of the steel. Analysis of calculated results showed that the vol. fraction of pearlite transforming to austenite during pearlite dissolution depended on maximum temperature, dwell time and pearlite interlamellar spacing. A functional relationship between these variables, consisting of a thermodynamic and a kinetic term, was established. On the other hand, the total vol. fraction of austenite forming in the steel, after both stages of austenitization, was found to follow a typical sigmoidal kinetic behaviour.     

Advances in Modeling and Simulation of Grinding Processes

In the last decade the relevance of modeling and simulation of grinding processes has significantly risen which is caused by industrial needs and is indicated by the number of publications and research activities in this area. This keynote paper results from a collaborative work within the STC G and gives an overview of the current state of the art in modeling and simulation of grinding processes: Physical process models (analytical and numerical models) and empirical process models (regression analysis, artificial neural net models) as well as heuristic process models (rule based models) are taken into account, and outlined with respect to their achievements in this paper. The models are characterized by the process parameters such as grinding force, grinding temperature, etc. as well as work results including surface topography and surface integrity. Furthermore, the capabilities and the limitations of the presented model types and simulation approaches will be exemplified.     

An improved cutting force and surface topography prediction model in end milling

During the milling operation, the cutting forces will induce vibration on the cutting tool, the workpiece, and the fixtures, which will affect the surface integrity of the final part and consequently the product's quality. In this paper, a generic and improved model is introduced to simultaneously predict the conventional cutting forces along with 3D surface topography during side milling operation. The model incorporates the effects of tool runout, tool deflection, system dynamics, flank face wear, and the tool tilting on the surface roughness. An improved technique to calculate the instantaneous chip thickness is also presented. The model predictions on cutting forces and surface roughness and topography agreed well with experimental results.