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

• Applicant: Professor Dr.-Ing. Carsten Heinzel
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 435367659

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.

• DFG Programme: Research Grants