PSI - Issue 68

Nhan T. Nguyen et al. / Procedia Structural Integrity 68 (2025) 91–98 N.T. Nguyen et al. / Structural Integrity Procedia 00 (2025) 000–000

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the Perzyna-enhanced model exhibited an increase in peak load with higher loading rates, aligning with common findings in existing literature (Fig. 3b). However, very minor difference was observed between the rate-dependent and rate-independent simulations concerning the strain rate inside the FPZ (Fig. 3d), raising the need for experimental study to correlate the macro response and strain rates within the FPZ.

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Fig. 3. The three-point bending response driven with (a) rate-independent model; (b) rate-dependent model; (c) Strain rate inside the FPZ under different macro loading velocities; (d) Strain rates inside the FPZ produced by rate-independent and rate-dependent model. 4. Conclusion In conclusion, this study investigates the strain rate effects inside the Fracture Process Zone (FPZ) on the macro response. Through Smoothed Particle Hydrodynamics (SPH) simulations on a three-point bending test, enhanced by a coupled damage-plasticity model with a Perzyna-type rate-dependent formulation, the study captures the distinct contributions of fracture opening and frictional sliding to energy dissipation and their impact on material response. Our results confirm that strain rates within the FPZ can significantly exceed the quasi-static range, even under relatively slow (or quasi-static) macro-loading conditions. This elevated strain rate in the FPZ impacts the peak strength and fracture resistance of quasi-brittle materials, revealing the influence of fracture opening rates on macro scale properties. These findings emphasise the necessity for rate-dependent modelling in simulating quasi-brittle materials under varying loading conditions, including macro quasi-static ones, as conventional rate-independent models may fail to capture the dynamic interactions within the FPZ. Moreover, the outcomes underscore a gap in experimental data that could validate the influence of strain rate on fracture propagation and material response. Addressing this through future experimental studies would provide crucial insights into the connection between FPZ strain rate and energy dissipation dynamics, ultimately improving the predictive accuracy of numerical models for geotechnical and structural applications involving rock and concrete materials.