A Modified Elasto-Plastic Pressure Dependent Numerical Combined Hardening Model for Characterizing Permanent Deformation under Cyclic Loading
Abstract
Rutting is an extremely important load related distress in flexible pavements and is attributed to frequent passes of tire load, resulting in formation of longitudinal depression in the wheel track. This research developed a numerical model to capture the rutting in base layer, which is a critical aspect.
The isotropic Drucker-Prager model does not capture the evolution of yield surface beyond first few load cycles in the case of cyclic loading simulating frequent passes of aircraft tires. An elasto-plastic model having a progressively evolving yield surface with the introduction of a new parameter, $\gamma$, has been introduced in this dissertation. The mechanism allows yield surface to progressively evolve and reduce in size, even in the case of cyclic loading with constant load amplitudes such as a typical aircraft wheel.
It was reasoned that permanent deformation in elasto-plasticity occurs due to irreversible plastic strain. However, as the material is unloaded, the stress state returns to the elastic region. The proposed model results in further plastic deformation because the yield surface reduces in size; due to which the stress state in the next loading cycle lies outside the reduced yield surface.
Addition of the combined hardening model along with incorporation of $\gamma$ parameter resulted in increased equivalent plastic strain and vertical plastic strain; thereby resulting in increased rutting.
Finally, refinements to the parameter $\gamma$ were recommended in order to make the proposed model more realistic. These refinement are sought by researching through the fundamentals of the granular base material's micro-mechanics and conducting study on reverse-mapping the monotonic test stress-strain curve from cyclic tests.
Citation
Nadkarni, Atish Anil (2020). A Modified Elasto-Plastic Pressure Dependent Numerical Combined Hardening Model for Characterizing Permanent Deformation under Cyclic Loading. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /193036.