Characterization and simulation of the fracture behavior of CBN grain types as a function of crystal structure, grain orientation and dressing parameters

点击翻译按钮获取中文摘要

The grinding process is at the end of a multitude of value-added chains and contributes decisively to the application behavior of components. During the grinding process, the edge zone of these components is influenced by a thermo-mechanical and material-metallurgical stress collective. This determines the components edge zone properties. These properties depend on the contact conditions between the grinding wheel and the workpiece acting in the grinding process. A change in the grinding tools topography therefore has a significant influence on the load collective and thus on the grinding process result. In order to predict topographies, recently developed mathematical-generic grinding tool models exist that depict the spatial arrangement of the components grains, binding and pores in a realistic manner as a function of the volumetric composition of a grinding tool. With the aid of this software-based model, grinding wheel topography will be predicted in the future without having to measure the grinding wheel topographies. Out of this, software-based models allow a prediction of the kinematic contact conditions between the grinding wheel and the workpiece, which determine the application behavior as well as the process result. The kinematic contact ratios depend to a large extent on the used breaking behavior of the grain material. However, the fracture behavior of commercially highly relevant grain materials, such as the cubic boron nitride (CBN), is investigated insufficiently.Therefore, the aim of the present research project is an explanation model for the characterization of the fracture behavior of CBN grain materials taking into account the crystal shape of the grain type, the crystal orientation and the dressing parameters.To this end, a method for the quantitative analysis and description of the fracture behavior of CBN grain materials is developed first. Furthermore, the fracture mechanisms of CBN grain materials are investigated in a single-grain dressing process as a function of the crystal shape and the dressing parameters. Based on the findings of the empirical investigations, a numerical modeling of the stresses during the dressing process in CBN grains is carried out and a transfer of the findings to the existing software-based models for the simulation of the grinding tool topography is done. In the future the empirical findings and simulation results are used to simulate grinding processes depending on the specification of the used grinding tool. This offers the potential to substitute cost-intensive empirical series of experiments by simulations, and thus to determine the effects of the resulting grain-breakage-dependent grinding wheel topography on the process behavior as a function of the volumetric composition of the grinding wheel and the dressing process.