L.K. Bhaskar; D. Sonawane; H. Holz; J. Paeng; P. Schweizer; J. Rao; B. Bellón; D. Frey; A. Lambai; L. Petho; J. Michler
arXiv preprint arXiv:2502.06668 (2025)
Understanding the dynamic behaviour of materials has long been a key focus in the field of high strain rate testing, and a critical yet unresolved question is whether flow stresses exhibit a significant strength upturn at strain rates ranging between 103 and 104s−1, and, if so, why. Current macro- and microscale mechanical testing is limited, as no single experimental method spans the entire strain rate range of 102 to 105s−1, where such an upturn is expected. In this study, we address these limitations using a highly customized piezoelectric in situ nanomechanical test setup, which enables, for the first time, constant indentation strain rates up to 105s−1. This system was employed to investigate the rate-dependent hardness in single-crystalline molybdenum, nanocrystalline nickel, and amorphous fused silica across strain rates of 101 to 105s−1, remarkably revealing an upturn in hardness in all three materials. The constancy of strain rate allowed, post-deformation microstructural analysis specific to the tested strain rates, shedding light on the potential mechanisms causing the hardness upturn.