With the fundamental objective of establishing the universality of the Griffith energy competition to describe the growth of large cracks in solids just under monotonic but under general loading conditions, this paper puts forth a generalization of the classical Griffith energy competition in nominally elastic brittle materials to arbitrary quasistatic loading conditions, which include monotonic and cyclic loadings as special cases. Centered around experimental observations, the idea consists in: () viewing the critical energy release rate as a material constant but rather as a material function of both space and time , () one that decreases in value as the loading progresses, this solely within a small region around crack fronts, with the characteristic size of such a region being material specific, and () with the decrease in value of being dependent on the history of the elastic fields in . By construction, the proposed Griffith formulation is able to describe any Paris-law behavior of the growth of large cracks in nominally elastic brittle materials for the limiting case when the loading is cyclic. For the opposite limiting case when the loading is monotonic, the formulation reduces to the classical Griffith formulation. Additional properties of the proposed formulation are illustrated via a parametric analysis and direct comparisons with representative fatigue fracture experiments on a ceramic, mortar, and PMMA.

中文翻译：

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非单调载荷断裂的格里菲斯描述及其在疲劳中的应用


以建立格里菲斯能量竞争的普遍性来描述单调但一般载荷条件下固体中大裂纹的扩展为基本目标，本文将名义弹性脆性材料中的经典格里菲斯能量竞争推广到任意准静态载荷条件，包括作为特殊情况的单调载荷和循环载荷。以实验观察为中心，该想法在于：（）将临界能量释放率视为材料常数，而不是空间和时间的材料函数，（）随着加载的进行，其值会减小，这仅在裂纹前沿周围的小区域，该区域的特征尺寸因材料而异，并且 () 的值减小取决于 中弹性场的历史。通过构造，所提出的格里菲斯公式能够描述在循环载荷的极限情况下名义弹性脆性材料中大裂纹生长的任何巴黎定律行为。对于相反的极限情况，当载荷是单调的时，公式简化为经典的格里菲斯公式。通过参数分析以及与陶瓷、砂浆和 PMMA 上代表性疲劳断裂实验的直接比较，说明了所提出配方的其他特性。