Simulation of crack induced nonlinear elasticity using the combined finite-discrete element method

Area of Science:

• Solid Mechanics
• Non-Destructive Testing (NDT)
• Computational Materials Science

Background:

• Nonlinear ultrasonic techniques are vital for Non-Destructive Testing (NDT) of solids.
• Understanding crack-induced nonlinear elasticity is key to interpreting NDT data.
• Existing methods struggle to explicitly model the complex interactions within cracked materials.

Purpose of the Study:

• To introduce and validate a two-dimensional finite-discrete element method (FDEM) for simulating nonlinear elastic wave propagation.
• To explicitly model crack-induced nonlinear elasticity in solids with horizontal and inclined cracks.
• To investigate the influence of crack surface contact on nonlinear behavior.

Main Methods:

• Developed a 2D FDEM model combining Finite Element Method (FEM) for wave propagation and Discrete Element Method (DEM) for crack surface interactions.
• Discretized the solid into finite elements to capture bulk wave propagation.
• Modeled crack surfaces as discrete elements to track normal and tangential contact.

Main Results:

• Nonlinear elasticity generation was observed only when excitation amplitude induced crack surface contact.
• Nonlinear behavior demonstrated high sensitivity to the normal and tangential contact between crack surfaces.
• FDEM simulations successfully revealed the causality of nonlinear elasticity in cracked solids.

Conclusions:

• The FDEM approach accurately simulates crack-induced nonlinear elasticity.
• Crack surface contact is the primary mechanism for generating nonlinear elastic responses.
• FDEM offers a powerful tool for advancing NDT by decoding nonlinear phenomena in cracked materials.