Review of Hygrothermal and Mechanical Mechanisms for Kernel Fissuring in Paddy Rice During Rapid Drying

Rapid hot-air drying is indispensable, but kernel fissuring remains a major barrier to its broader adoption. This review critically collates and compares studies on empirical tests and numerical simulation, covering hygrothermal-induced stress, the role of glass transition temperature in grain strength, mechanical impact loading, multi-field simulation methods, and in situ imaging-based validation. Achieving effective rapid drying requires a clear understanding of the grain’s coupled hygrothermal and mechanical behavior. This remains a persistent challenge due to the grain’s heterogeneous structure and oversimplified modeling assumptions. Broadly speaking, research follows two distinct paths: one rooted in empirical experiments, the other in multi-field numerical simulation. The two approaches differ substantially in their explanatory frameworks, predictive capabilities, and ability to adapt to real processing conditions. A key point emphasized in this review is that in situ micro-CT imaging is the bridge between the two approaches: it delivers real-time structural data for model calibration and validation, enabling closed-loop integration of experimental observations and numerical predictions. The integrated technical framework proposed here provides a theoretical basis for reducing grain breakage loss and optimizing drying and conveying equipment.