KDP晶体三倍频晶面微观力学行为及加工性能

为了揭示磷酸二氢钾(KDP)晶体三倍频晶面微观弹塑性力学行为及加工性能,开展了纳米压痕研究。建立了KDP晶体三倍频晶面各向异性力学模型,基于光滑粒子流体动力学(SPH)方法对纳米压痕进行了数值仿真并完成了纳米压痕测试实验。实验结果表明:实验与仿真计算的载荷-压入深度关系曲线的相关系数为0.996 328,吻合度较高,验证了力学模型的正确性,得出KDP晶体三倍频晶面的屈服强度为240MPa。数值仿真结果显示:由于材料的各向异性,工件内部应力呈不规则圆弧状分布;载荷大小与等效应力影响深度呈近似线性递增关系;材料表面等效塑性应变分布形状与压头投影面几何形状相类似,存在复映效果。当载荷小于2mN时,各压头的残余应力深度差异性较小(小于0.2μm);随着载荷逐渐增大,这种差异不断扩大。得到的结果为实现KDP晶体三倍频晶面的高效低损伤加工提供了理论支撑。     

J-C本构模型参数对ZL109硅铝合金切削仿真的影响规律

在进行有限元仿真过程中,材料的J-C本构模型发挥着重要的作用。通过力学实验得出的J-C本构模型,往往需要修正才能更好地描述材料的物理力学性能。在对ZL109硅铝合金进行的有限元仿真的基础上,研究J-C本构模型参数的变化对于仿真结果的影响规律,从而为本构模型的研究提供参考性建议。仿真中所用ZL109硅铝合金采用随温度变化的物理力学性能参数,刀具选用目前应用广泛的PCD刀具。通过仿真数据发现:切削力、切削温度主要受J-C本构模型参数中温度软化系数m和应变强化系数B的影响;切屑形态和工件表面残余应力主要受J-C本构模型参数中屈服强度A、应变强化系数B和n的影响。     

一种难加工材料的车削力模型的实验研究

采用了多因素回归正交设计的方法进行了一种难加工材料的车削实验，在给出实验模型和数学推导的基础上，借助于作者设计的计算机软件，高效完成了上述有关工作并建立了该材料切削力的数学模型，为今后的切削加工过程数值模拟以优化切削用量和刀具的结构设计和几伺参数的选择奠定了基础。     

A new model of grit cutting depth in wafer rotational grinding considering the effect of the grinding wheel,workpiece characteristics,and grinding parameters

Wafer rotational grinding is widely employed for back-thinning and flattening of semiconducting wafers during the manufacturing process of integrated circuits. Grit cutting depth is a comprehensive indicator that characterizes overall grinding conditions, such as the wheel structure, geometry, abrasive grit size, and grinding parameters. Furthermore, grit cutting depth directly affects wafer surface/subsurface quality, grinding force, and wheel performance. The existing grit cutting depth models for wafer rotational grinding cannot provide reasonable results due to the complex grinding process under extremely small grit cutting depth. In this paper, a new grit cutting depth model for wafer rotational grinding is proposed which considers machining parameters, wheel grit shape, wheel surface topography, effective grit number, and elastic deformation of the wheel grit and the workpiece during the grinding process. In addition, based on grit cutting depth and ground surface roughness relationship, a series of grinding experiments under various grit cutting depths are conducted to produce silicon wafers with various surface roughness values and compare the predictive accuracy of the proposed model and the existing models. The results indicate that predictions obtained by the proposed model are in better agreement with the experimental results, while accuracy is improved by 40%–60% compared to the previous models.     

基于oldroyd-B本构模型的磨料流加工壁面滑移仿真分析

基于oldroyd-B粘弹性本构模型,应用POLYFLOW软件对流体磨料在圆管中的壁面滑移状态进行了模拟仿真。将得到的圆管中流体磨料的压力值与磨料流加工机床上测试点的压力值进行比较,得到二者的相对误差不超过5%,验证了模拟仿真的可行性。通过仿真可知,流体磨料在工件壁面上的滑移存在速度临界点。通过比较不同管道入口流量、流体磨料黏度和壁面滑移系数对壁面滑移速度的影响可知,当管道入口流量越大、流体磨料的黏度越高,以及壁面滑移系数越小时,加工过程中的壁面滑移速度越大。     

Simulation of the tribological behaviour of components and cutting tools by means of model wear testing

Modelling the wear test process can initiate real-life friction and wear of components and cutting tools. In this paper we describe model wear tests that were developed to discover (a) whether or not simulation of the wear processes that occur during cutting is possible, and (b) how the wear of indexable inserts can be reduced by using thin hard coatings, e.g. TiN, (Ti,Al)N, Ti(C,N) when milling metallic materials. The real-life wear of the track groups of various tracked vehicles was also investigated, in order to evaluate the wear resistance of certain materials.