The hypothesis of contact maturing advocates static fatigue at contacts between sand grains as the key cause contributing to time effects in sand. The focus of the paper is on a model of an individual grain subjected to a sustained load applied through two steel plates. The grain is characterized by the roughness of its surface. The distinct element method is used to construct a model on two scales: the grain scale and the contact scale. Assemblies of bonded sub-particles are used to model both the grain and the contact region. The bond model includes the stress corrosion process, which simulates decaying strength of bonds and fracture. Two components of the time-dependent grain deflection under sustained loads are the displacement owed to sub-critical fracturing of asperities on the grain surface at the contacts and the creep of the core mineral in the grain. The model demonstrates what may be difficult capturing in physical testing. The simulated nominal contact evolves as the number of contact points increases due to sub-critical fracturing of asperities, leaving the contact firmer. The contact evolution process, as observed in simulations, is consistent with the contact maturing hypothesis.

中文翻译：

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持续载荷下包括接触成熟的砂粒挠度的时变模型

接触成熟的假设提倡在沙粒之间的接触处产生静态疲劳，这是造成沙粒时间效应的主要原因。本文的重点是通过两个钢板施加持续载荷的单个谷物的模型。谷物的特征在于其表面的粗糙度。独特元素法用于在两个尺度上构建模型：晶粒尺度和接触尺度。结合的子粒子的集合用于对晶粒和接触区域进行建模。粘结模型包括应力腐蚀过程，该过程模拟了粘结的衰减强度和断裂。在持续载荷下，随时间变化的晶粒挠曲的两个组成部分是由于接触点处的晶粒表面上的亚细裂纹的亚临界断裂和晶粒中核心矿物的蠕变而引起的位移。该模型演示了在物理测试中可能难以捕获的内容。由于粗糙的亚临界破裂，随着接触点数量的增加，模拟的名义接触也随之发展，从而使接触更加牢固。在仿真中观察到的接触演化过程与接触成熟假设是一致的。