An energy-driven micro breakage approach for aggregates by coupling ball kinematics with shape-based contact correction

Abstract

Micro breakage, characterized by continuous spalling at the corners and edges of aggregates, leads to fines generation, progressive particle rounding, and degradation of the load-bearing skeleton. Nevertheless, conventional discrete element methods (DEM) still face difficulty in representing micro breakage and the associated shape evolution under repeated loading. To address this limitation, an energy-driven micro breakage approach for aggregates is proposed. Specifically, Ball elements are used as kinematic carriers for particle motion, whereas particle-specific spherical-harmonic radial functions r ( θ , φ ) are used to represent irregular particle morphology. The breakage criterion is established by relating the contact elastic energy accumulated in local high-curvature regions to the fracture energy required to create equivalent new free surfaces. When the instantaneous or cumulative energy condition is satisfied, the particle radial function is updated according to the breakage volume. This update modifies the contact curvature and contact-scale geometric information, which are then fed back to the rolling-resistance Hertz contact model, thereby enabling continuous coupling among contact response, shape evolution, and micro breakage. The proposed approach is examined through numerical examples and compared with available laboratory results at the single-particle, multi-particle abrasion, and assembly scales. The results show that it can reasonably reproduce the multi-peak force-displacement response induced by micro breakage, together with the coupled evolution of abrasion ratio, particle shape, energy, and assembly degradation. The proposed approach provides a particle-scale framework for analyzing contact-induced micro breakage, particle rounding, and load-bearing skeleton degradation of graded aggregates under compression-dominated repeated loading.