Narrow Results

This paper aims at presenting a thermodynamically consistent elastoplastic fractional time-dependent damage model for describing short- and long-term behaviors of rock-like materials. The model utilizes generalized potential theory with a yield criterion, a non-associated flow rule and an isotropic plastic hardening function for describing the evolution of plasticity. A time-dependent Lemaitre-type damage is introduced through fractional derivative considering the short- and long-term evolution of microstructure, which leads to progressive degradation of elastic modulus and failure strength of material. In this context, both instantaneous and delayed deformations shall be well described within the unique constitutive model. For practical application, an efficient and convergent semi-implicit return mapping (SRM) algorithm involving a plasticity-damage decoupling corrector is developed. The proposed model is finally adopted to predict the mechanical and deformation behavior of several types of rocks under different loading conditions in conventional or quasi-static (different loading strain rate) triaxial compression tests, creep tests and relaxation tests. Comparisons between model predictions and experimental data demonstrate that the proposed model has the capability to reproduce main features of short and long-term behaviors of rock-like materials.

This paper discusses material named Polyurethane bonding which can be used in the stabilization of railroad ballast layer. An experimentation of the static and dynamic response of this material is important in designing appropriate solutions for railroad ballast layer, especially for the transition zone. A comprehensive study on the SHPB testing of Polyurethane bonding is presented in the strain rate range of 1000s${}^{-1}$–4000s${}^{-1}$. Variable power law was used to predict the material response at elevated strain rates as high as 10,000s${}^{-1}$. These results are compared with the material’s quasi-static response. The effects of strain rate on material parameters like Young’s Modulus and Yield Strength were investigated under various high strain rate dynamic experiments. It was found that the yield strength as well as Young’s modulus increased with the strain rate and the trend was more evident at higher strain rates. Quasi-Static Uniaxial Compression tests gave the typical stress–strain relationship of the material. A close investigation of the material response indicates that the behavior of this class of Polyurethane has a close resemblance with PMMA at the quasi-static as well as at various high strain rates.