Three-Dimensional Finite Element Analysis of Creep Evolution and Damage at Grain Boundary Level

In many high-temperature structural components, creep damage is a non-negligible factor limiting its lifetime. For most alloys, the main reason for the creep damage is due to the cavitation that occurs at grain boundaries, hence it is meaningful to analyze and simulate this phenomenon. In this project, unlike the traditional approach which treats materials as isotropic, the grain and grain boundary is modeled and analyzed separately. Based on this idea, an in-house numerical procedure is developed for the Finite element simulation of creep evolution at the grain boundary level.

The development is under the Continuum Damage Mechanics theoretical framework, through this procedure the traditional solid element with simple power-law adopts to describe the creep deformation evolution of the grain part. The grain boundary part has been modeled by the Goodman element with Markus’s cavitation model and Newtonian flow model

The in-house procedure was developed from a Smith’s visco-plastic program P61 to solve the creep problem at grain boundary level. The theory and coding implementation of Goodman element (2D/3D) and local-global co-ordinate transformation techniques are summarized in detail.
This research contributes to the development of the Finite Element procedure for simulating creep evolution at the grain boundary level and provides a new understanding regarding the intrinsic relationship between stress redistribution and creep evolution.