PhD Candidate, Monash University
This research proposes a modelling approach that combines a discrete numerical method with continuum-based models to characterise damage in quasi-brittle materials. In this approach, Discrete Element Method (DEM) is employed as the numerical framework to simulate material cracking. Together with this, coupled damage-plasticity models based on continuum mechanics are proposed to describe the local responses of contacts between particles in DEM. This continuum-discrete modelling approach takes advantage of the appealing features of DEM in replicating the heterogeneous microstructure of quasi-brittle materials and modelling crack initiation and propagation. In addition, the development and implementation of constitutive models are simpler compared to the continuum methods, as these models only deal with the one-dimensional condition of contacts while the heterogeneous response of materials is directly mimicked by DEM. Numerical simulations show that the proposed modelling approach can capture closely the mechanical behaviour of quasi-brittle materials, evidenced by their good agreements with experimental results in both stress-strain responses and crack configurations. Moreover, the microstructural effects and hysteresis response featured in quasi-brittle materials can be naturally captured by DEM simulations. This demonstrates the effectiveness of the modelling approach for characterising damage behaviour in quasi-brittle materials, and also makes the potential to extend this method to other particle-based materials.
Abstract: •Failure of soft rocks can be effectively captured using a new cohesive model combined with DEM.•The combined damage-plasticity cohesive model can describe well the degradation of cement bridges in soft rocks.•This facilitates the characterisation of soft rock failure for better understanding and design.
Pub.: 01 Nov '17, Pinned: 29 Oct '17
Abstract: In this research, a discrete modelling approach employing a new cohesive model is proposed to investigate the failure response of cemented materials. A cohesive model considering mixed-mode fracture is developed based on a generic thermodynamic framework for coupling damage mechanics and plasticity theory. Discrete Element Method (DEM), a well-known computational method for simulating large deformation and cracking issues, is utilised as a numerical platform to facilitate the implementation of the proposed cohesive model. The nature of discrete modelling is analogous to the internal structure of cemented materials, making it more efficient compared with conventional continuum methods to characterise the failure behaviour of cemented materials. This combined cohesive-discrete modelling approach is then employed to simulate four experimental tests under different boundary conditions. Simulation results show excellent agreements with the experiments in terms of both macro force-displacement responses and cracking patterns, suggesting the effectiveness of the proposed modelling approach for conducting numerical experiments and exploring the failure mechanisms in cemented materials.
Pub.: 27 Mar '17, Pinned: 27 Oct '17