Influence of undeformed chip parameters on material load and resulting subsurface damage when ultra-precision grinding of hard and brittle materials with coarse-grained diamond grinding wheels

粗粒金刚石砂轮超精磨削硬脆材料时未变形切屑参数对材料载荷及亚表面损伤的影响

• 批准号: 435367659
• 负责人: Professor Dr.-Ing. Carsten Heinzel
• 金额: --
• 依托单位: Fachgebiet Fertigungsverfahren
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/435367659?language=en
• 关键词: Influence; undeformed; chip; parameters; material

The determination of normal and shear stresses in the contact zone while ductile grinding of brittle materials with coarse-grained diamond grinding wheels (dG > 301 µm) is the main focus of this research project. The determined stresses will be correlated with the surface layer after grinding for describing the material separation mechanism by physical quantities. The surface layer is meant to be investigated by measuring the subsurface damages, which can be determined by the depth, the amount and the morphology of cracks.Conventionally, the calculation of chip thickness, which determines if the material separation mechanism is ductile or brittle, is based on phenomenological concepts, but these are limited according to the prediction of the separation mechanism. This is due to the inclusion of the grinding tool topography, which has a statistical nature within the formulas for maximum uncut chip thickness. When applying coarse-grained diamond grinding wheels, the number of active grains and their shape is not statistical, but more like only a few active cutting edges, comparable to a milling process. Consequently, the whole topography of the grinding tool has to be described, which is performed by structured light projection measurements in this research project. A software-based analysis of the measured topographies by linear scattering into grinding direction enables the determination of normal and tangential areas which are in contact with the workpiece during the grinding process. In combination with in-situ measured process forces, normal and shear stresses in the contact zone can be calculated. Their influence on the surface layer are investigated by measuring subsurface damages. The determined load stresses and subsurface damages are meant to be transferred into a generally comprehensive process model, re-defining the calculation basis for the maximum uncut chip thickness. In this process model, physical quantities (in this case normal and shear stresses) should replace the process or system variables.In the proposed research project, reverse plated, single-layered non-dressable diamond grinding wheels with envelope curves with a precision of less than two micrometers are used for grinding, as the dressing of this type of grinding wheels would not lead to a comparable required high precision.

用粗颗粒金刚石砂轮(DG&GT；301µm)延性磨削脆性材料时，接触区的法向应力和剪应力的测定是本研究项目的主要重点。确定的应力将与磨削后的表面层相关联，以物理量描述材料的分离机理。表面层是通过测量亚表面损伤来研究的，亚表面损伤可以由裂纹的深度、数量和形貌来确定。传统上，决定材料分离机制是延性的还是脆性的切屑厚度的计算基于现象学概念，但这些计算受到分离机制预测的限制。这是因为在最大未切割切屑厚度公式中包含了磨具地形，它具有统计性质。在应用粗粒金刚石砂轮时，活跃颗粒的数量及其形状并不是统计的，而更像是只有几个活跃的刀具刃口，堪比一次铣削过程。因此，在本研究项目中，必须描述磨具的整个形貌，这是通过结构光投影测量来执行的。通过对磨削方向的线性散射对测量的形貌进行基于软件的分析，可以确定磨削过程中与工件接触的法向和切向区域。结合现场测量的过程力，可以计算接触区的法向应力和剪应力。通过测量亚表面损伤来研究它们对表层的影响。确定的载荷应力和亚表面损伤将被转移到一般的综合工艺模型中，重新定义最大未切割切屑厚度的计算基础。在这个过程模型中，物理量(在这种情况下是法向应力和剪应力)应该代替过程变量或系统变量。在拟议的研究项目中，使用包络曲线精度小于2微米的单层非可修整金刚石砂轮进行磨削，因为这种砂轮的修整不会产生类似的高精度要求。