Prediction of the grinding wheel specification influence on thermal defects in dry grinding through a hierarchical FEM model

Grinding represents an indispensable phase in a manufacturing route because it allows to obtain the final required features in terms of dimensions and roughness. Although the grinding technology has always been applied with lubricants, nowadays, oil application becomes more and more limited to reduce the environmental pollution. In dry finishing technologies, heat control represents the main problematic of the process; indeed, grinding usually reaches relevant temperatures causing thermal defects. Therefore, process temperature prediction represents a challenge allowing to prevent thermal defects on the working material. But the final results are influenced by the kinematics parameters and also by the grinding wheel specifications. This paper aims to predict thermal defects in the material also considering the wheel specification. A hierarchical FEM model which considers both the microscopic and macroscopic aspects of the grinding process was developed. Starting from the mechanical action of a single grain on the material, a moving heat source was built to represent the interaction of the grinding wheel with the workpiece. A single grain grinding model is followed by a thermal model which considers the process parameters and the grinding wheel specification. Tangential grinding tests were developed to validate the model by adopting embedded thermocouples and grinding wheels with different structures were used. To further validate the model, metallographic and micro-hardness analyses were developed to verify the microstructural change due to the grinding cycle. A maximum average percentage difference of 10.8% was detected between calculated and measured temperatures and good agreement with the microstructural analysis was found.