Investigations into the occurrence of microstructures by means of in-situ depth measurements during percussion drilling with ultrashort laser pulses

A model-based data analysis of the depth measurements performed during percussion drilling in stainless steel reveals the occurrence of microstructures by observed deviations from model expectations. For the data analysis, an adaptive correction factor cA was introduced into an analytical drilling model to account for changes in the absorptance caused by the microstructures. The analysis of the temporal evolution of cA during drilling shows that the presence of microstructures coincides with an increased absorption, while the formation of a single borehole tip is associated with a reduced absorption.