Inter-University Research Seminar

Solid Mechanics UTP

Inter-University Research Seminar

Plasticity in aero engine materials – A review of the fundamentals and comments on thermodynamic implications

Dr James Rouse

University of Nottingham

Thom Building LR2 and at Begbroke Site

2pm Wednesday 26^th February 2020

The ability to predict how elastic and plastic phenomena affect the deformation behaviour of materials is vital in almost all engineering applications. Components and structures must be designed such that they can be safely worked over potentially wide ranges of operating conditions. This is particularly true in aero engine applications, where components will be expected to withstand high loads at extreme temperatures for a variety of loading rates. Mechanical simulations of candidate designs are routinely performed in order to establish if some critical criterion (representing some failure mechanism, for example) is or is not satisfied. Central to this process is an underlying description of the material’s deformation behaviour; a relationship between stress and strain. This seminar will introduce and discuss several important features of the many macroscopic material models that are routinely used to describe elasticity and plasticity in metallic aerospace components. In particular, the thermodynamics of material deformation modelling will be discussed and methods to extend the modelling efforts to include less well-known phenomena will be summarised.

Topics covered will include:

• Fundamental experimental observations in elasticity and plasticity.
• Basic hardening mechanisms in simple plasticity descriptions and key terms such as the normality hypothesis and the consistency condition.
• The introduction of time/rate dependency in elastic/plastic models using flow rules and the concept of overstress.
• The concept of “free energy” and its role in a thermodynamic basis for material model development.
• The implications of thermodynamic assumptions in material model formulation.