Defect structure of gold introduced by high-speed deformation

The effect of deformation speed on defect structures introduced into bulk gold specimens at 298 K has been investigated systematically over a wide range of strain rate from ′=10⁻² to 10⁶ s⁻¹. As strain rate increased, dislocation structure changed from heterogeneous distribution, so-called cell structure, to random distribution. Also, stacking fault tetrahedra (SFTs) were produced at anomalously high density by deformation at high strain rate. The anomalous production of SFTs observed at high strain rate is consistent with the characteristic microstructure induced by dislocation-free plastic deformation, which has been recently reported in deformation of gold thin foils. Thus, the results of the present study indicate that high-speed deformation induces an abnormal mechanism of plastic deformation, which falls beyond the scope of dislocation theory. Numerical analysis of dislocation structure and SFTs revealed that the transition point of variation of deformation mode is around the strain rate of 10³ s⁻¹.     

紧凑式轧机变形规程优化设计

本文从紧凑式轧机的轧制变形特点出发,分析了其变形规程设计的主要特点和方法,讨论了限制其道次变形量的基本因素,给出了优化设计的目标函数和约束条件。指出,类似这种具有复杂约束的轧制变形问题采用混合罚函数法处理更为有效,并成功地采用该方法进行了变形规程的试设定。     

Q195冷轧板材轧制困难原因分析

针对部分Q195冷轧板材存在轧制困难的现象，进行了现场检验与分析。带状组织、混晶现象严重导致变形强化系数偏高是造成轧制困难的主要原因。     

橡胶Mooney—Rivlin模型材料系数对轴向刚度影响分析

在橡胶小变形范围内，采用理论推断的方法，得到在相同硬度下橡胶Mooney—Rivlin模型材料系数由C2／C1决定的关系式。并采用ABAQUS有限元软件分析的方法，结合橡胶轴向刚度常规解，分析了C2／C1不同值对橡胶轴向刚度的影响进行，结果显示其影响呈现一定规律性。     

垂直定向液晶光阀及光电特性的研究

系统地讨论了排列相畸变模式液晶光阀结构，原理和制作，结合实际测试对其等效电路和电学匹配进行了分析，详细讨论了它的光电特性及相互关系，实测的液晶垂直排列方式工作的液晶光阀性能指标为，分辨率大于５０ｌｐ／ｍｍ，白光输入灵敏度为６．７７μＷ／ｃｍ＾２，响应时间为２００ｍｓ／３００ｍｓ，白光输出对比度为２００：１。     

冷弯型钢纵向变形的理论分析及计算

对冷弯型钢的纵向变形过程进行了力学分析，得到了变形微分方程，求得了转动角的理论公式，并对其变形形状进行了分析计算。     

34CrMoV结构钢动态再结晶行为研究

应用Gleeble-1500热模拟实验机进行等温压缩试验,研究了变形工艺参数对34CrMoV结构钢动态再结晶行为的影响.结果表明,其流变应力随变形温度升高而降低,随应变速率提高而增大;随着应变速率的降低,应变量的增加和变形温度的升高,动态再结晶速度加快且奥氏体晶粒得到细化.     

A Study of Surface Deformation during Wire‐Rod Rolling of High Speed Steels using Experimental and Computational Techniques

The evolution of surface defects during shape rolling of high‐speed steel billets is studied using longitudinal surface defects prepared by machining and welding. The reduction of the defects during rolling in a production mill is compared to the total area reduction of the billets. Samples are collected after pass 4, 6, 8, 14, 19 and the final pass, 28, representing the finished 5.5mm wire. By inspecting the cross sections, the rotation of the billets from pass to pass is evaluated. Results from FE simulations on solid billets are compared to the experimental results. Generally, simulations predict less reduction than observed experimentally. In most cases cracks reduce most effectively followed by carbon steel welds and stainless steel welds.     

Cyclic X-Y mechanical tests: A new method to perform in situ reversed-deformation experiments in the high-voltage electron microscope

There has been, in the past, only limited success with in situ cyclic or reversed plastic deformation tests in the transmission electron microscope (TEM). This is probably partly due to problems associated with buckling of the foil when an applied tensile or shear stress is reversed. Mechanical analysis shows that dislocation movement can be reversed by tensile stressing in alternating perpendicular directions (i.e., 90° rotations of a tensile stress); thus buckling of the foil can be avoided. A design for performing such X-Y in situ TEM tests is presented, with observations that demonstrate its feasibility.