In-situ elastic-plastic fracture mechanics on the microscale by means of continuous dynamical testing

Abstract

Measuring the local behaviour of a propagating crack in a quantitative manner has always been a challenge in the field of fracture mechanics. In-situ microcantilever testing inside a scanning electron microscope (SEM) is one of the most promising techniques for the investigation thereof. However, quantifying such experiments is fairly challenging. Here, for the first time we utilize a continuous measurement of the dynamic compliance in-situ to permit evaluation of the crack length. Microcantilever experiments have been performed on brittle single crystalline Si and nanocrystalline Fe to assess the stability of the setup, the applicability of the technique inside an SEM and to establish a correlation between stiffness and crack length. Subsequently, micromechanical fracture tests were performed on single crystalline, 〈001〉{001} oriented tungsten as a model material and continuous J-Δa curves were measured. The gathered data was evaluated with close relation to standardized fracture mechanics testing and showed an overall agreement with literature data. This novel possibility to measure J-Δa curve behaviour continuously and locally while also following the crack extension through in-situ imaging inside an SEM is generally applicable and will allow new insights in the crack propagation of modern materials. Keywords: In-situ microcantilever testing, Elastic-plastic fracture mechanics, Dynamic compliance measurement, Tungsten