Date of Award
Program or Major
Doctor of Philosophy
This thesis covers topics at two fundamental scales at which plastic deformation is occurring – macroscopic and microscopic.
The first topic is related to the localization of deformation and subsequent necking that happens in metals during deformation, e.g., sheet metal during forming. The open fundamental question is – what happens to the material properties inside of the localized region. The localization process is very challenging to analyze, even using a conventional tension test since several effects such as material hardening as well as effects of strain-rate and temperature are strongly coupled. In this thesis we propose a novel approach that allows to decouple these effects and furthermore to identify the true hardening behavior of material. The solution is based on solving an inverse problem that involves optimization of an expensive black-box function. The methodology developed is presented in detail.
In the second topic we consider the microscopic aspects of deformation, namely grain-scale plasticity. More specifically, we apply a crystal plasticity finite element framework to analyze the deformation-induced surface roughening effect. This task also involves a number of challenges. One such challenge is the accurate calibration of the model, which was tackled here using the black-box optimization procedure developed earlier. The second challenge is the accurate non-destructive reconstruction of a 3D texture based on images of several planar sections. The texture reconstruction problem was solved and presented as a general methodology. Subsequently it was possible to construct a comprehensive model that accounts for all major effects. It is shown that this model is able to capture the physics of deformation-induced surface roughening, however primarily in the average sense.
Knysh, Pavlo, "Study of post-necking hardening identification and deformation-induced surface roughening of metals" (2019). Doctoral Dissertations. 2477.