Creep of Metallic Materials in Bending

The creep behavior of metallic materials in bending has received limited attention because of the complexity of the stress state and the nontrivial correlation with an equivalent uniaxially deformed state. Furthermore, conventional creep testing methods, i.e., under uniaxial tension and compression, which have a constant stress state during creep and well-established data interpretation protocols, are adequate for studying the creep properties of most materials. Hence, the creep properties of metallic systems have rarely been evaluated in bending. Currently, there is an increase in the demand for testing in-service components and materials having microstructures on small length scales (e.g., a few tens to hundreds of micrometers). In this situation, the material for testing is often in short supply and the dimensions of the relevant samples are very small, thus limiting the feasibility of uniaxial tests. This warrants development of alternate testing techniques, such as indentation and bending, that are ideally suited for testing small-volume samples. In particular, cantilever bending is quite attractive given the possibility of obtaining multiple data points covering a range of stresses from a single sample and the ease of sample fabrication, alignment, and gripping while testing at a small length scale. In addition, the mechanics of power-law creep in bending is well understood and developed. We present herein a review of seminal literature on power-law creep in bending, a topic which has been investigated for almost 90 years now, and an outlook on adopting bending of cantilevers as a mainstream methodology for characterizing the creep behavior of metallic systems