对金属材料内部裂纹愈合的机理、行为和规律进行深入研究，是改善金属材料性能、提高品质和延长使用寿命的重要基础性工作，对丰富材料学理论具有十分重要的意义。本文利用高温显微镜，原位、动态观察了平板撞击铜试样剖分面上孔洞的愈合过程，并对出现明显愈合现象的愈合孔洞进行了扫描电镜下的精细组织观察。观察结果显示，几十μm级孔洞在温度为750℃时开始愈合，在900℃时明显愈合；愈合孔洞的精细结构由μm级团状颗粒与nm级颗粒组成。基于上述实验观察到的现象，提出了孔洞愈合过程的唯象模型，该模型认为，开放式孔洞的愈合过程为孔洞棱边的钝化及形状的规则化，及由孔洞内界面的弓出而导致的孔洞愈合。

The research purpose on the healing of inner crack in metallic materials is to provide an effective approach for improving their properties and prolonging their lifetime. The crack healing process of 20MnMo steel with inner pre-crack was analyzed. It was found that all inner cracks could be healed in different degree. There were very fine ferrite grains in healing region. The micro-crack healing process in single crystal of BBC-Fe was simulated by the molecule dynamics method, which showed that the critical temperature of crack healing in BBC-Fe is 673K There were micro-voids, dislocations and twins left after crack healing.

With the development of technology, metalforming has become a very complex huge engineering system. We divided the problems involved in advanced metalforming processes into four levels, e.g., mechanism analysis, system base, subsystem and system. As it is impossible to do all the requisite tests, it is reasonable to make use of modeling and simulation to investigate the advanced metalforming system. By simulation, we can leam the overall relations of system variables, analyze the full process of system models, and optimize models and system. Now, modeling and simulation have been, widely used in Chinese metalforming engineering. The main reason is that it can decrease development cost, improve working reliability, and increase training safety of engineering system. In the past decade, Chinese scientists and engineers engaged in metalforming engineering have performed creative and fruitful research works, and gain a good profit. In this paper, authors will make a brief review about modeling and simulation done by their research group and other Chinese colleagues.

In order to investigate the flowing behavior of metal in rolling turbine blade steel with asymmetric pass,a FORTRAN program for calculating three-dimensional deformation was prepared.The program based on the principle of rigid-plastic FEM used 20-nodal isoparametric elements. The assumptions about initial velocity field and friction force were put forward, Through calculations,the flow of material and the distribution of velocity,strain and unit draught pressure were obtained.The experiment was performed with plasticine,lead and steel. The result of experiment and calculation are the same in egularity,and can be used in practical rolling process.

通过物理模拟及SAM分析研究，明确了金属材料内部裂纹高温修复的现象，确定了其初步规律，成功地将SAM技术用于对金属材料高温损伤的定量检测。声显微镜扫描图像显示，随着加热温度的升高，试件内裂纹逐渐修复。在内裂纹的修复过程中，原裂纹区域首先被晶粒细小的金属所占据，随修复过程的进行，原裂纹区域的细晶部分逐渐减小并与基体金属相融合，直至完全消失。通过声显微扫描图像对内裂纹的变化情况进行了实际测量，得到了加热温度和保温时间对裂纹修复程度的影响规律。研究结果表明：裂纹的修复主要取决于加热温度，保温时间的影响相对较小。根据实验所得数据，回归整理出了以影响系数表示的高温损伤演化方程。

夹杂性裂纹是大型锻件生产的主要质量问题。为此对大型锻件内部夹杂性裂纹的形成机理进行了模拟研究，发现锻件内部裂纹在高温下自修复的现象及规律。在此基础上提出了可有效控制夹杂性裂纹的大型锻件及针对管板和模块类锻件的锻造工艺。实用这些工艺不仅提高了锻件的成品率，且改善了产品的内在质量，其经济和社会效益十分显著。

通过物理模拟研究，发现了20MnMo钢内裂纹在高温下可修复的现象，并总结了其初步规律，认为这种修复过程主要是由原子的扩散迁移所造成。内裂纹的修复可分为空洞填充和晶粒长大两个阶段。填充物初期由细小晶粒所组成，存在Fe的成分偏析，与基体的分界面清晰。随后的晶粒长大与成分均匀化同时进行，一定的塑性变形，可使内裂纹及空洞等被很好的填充和压合。为保证内裂纹的完全修复，需一定的保温时间，使晶粒充分长大。

In this paper, the background of basic principles and methods of crystal plasticity simulation are reviewed. The newest research developments at home and abroad on computer simulation of polycrystalline materials are summaried. The existing problems and further directions in crystal plasticity simulation research are suggested. On the basis of finite element analysis, crystal plasticity simulation can be used to optimize the metal forming process and improve the quality of products.

The flow stress of ferrite/pearlite steel under uni-axial tension was simulated with finite element method (FEM) by applying commercial software MARC/MENTAT. Flow stress curves of ferrite/pearlite steels were calculated based on unit cell model. The effects of volume fraction, distribution and the aspect ratio of pearlite on tensile properties have been investigated.