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首页> 外文期刊>Journal of Materials Research >Competing fracture modes in brittle materials subject to concentrated cyclic loading in liquid environments: Monoliths
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Competing fracture modes in brittle materials subject to concentrated cyclic loading in liquid environments: Monoliths

机译：脆性材料在液体环境中承受集中循环载荷的竞争断裂模式：整体

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摘要

The competition between fracture modes in monolithic brittle materials loaded in cyclic contact in aqueous environments with curved indenters is examined. Three main modes are identified: conventional outer cone cracks, which form outside the maximum contact; inner cone cracks, which form within the contact; and median-radial cracking, which form below the contact. Relations describing short-crack initiation and long-crack propagation stages as a function of number of cycles, based on slow crack growth within the Hertzian field, are presented. Superposed mechanical driving forces-hydraulic pumping in the case of inner cone cracks and quasiplasticity in the case of median-radials-are recognized as critically important modifying elements in the initial and intermediate crack growth. Ultimately, at large numbers of cycles, the cracks enter the far field and tend asymptotically to a simple, common relation for center-loaded pennylike configurations driven by slow crack growth. Crack growth data illustrating each mode are obtained for thick soda-lime glass plates indented with tungsten carbide spheres in cyclic loading in water, for a range of maximum contact loads and sphere radii. Generally in the glass, outer cone cracks form first but are subsequently outgrown in depth as cycling proceeds by inner cones and, especially, radial cracks. The latter two crack types are considered especially dangerous in biomechanical applications (dental crowns, hip replacements) where ceramic layers of finite thickness are used as load-bearing components. The roles of test variables (contact load, sphere radius) and material properties (hardness, modulus, toughness) in determining the relative importance of each fracture mode are discussed.
机译：研究了在含水环境中使用弯曲压头循环接触的整体脆性材料中断裂模式之间的竞争。确定了三种主要模式：常规的外锥裂纹，它在最大接触之外形成；内锥裂纹，在接触内形成；以及在接触下方形成的中值径向裂纹。提出了基于赫兹场内缓慢的裂纹扩展来描述短裂纹萌生阶段和长裂纹扩展阶段随循环次数变化的关系。叠加的机械驱动力-在内锥裂纹的情况下是液压泵送，而在正中径的情况下是准塑性-被认为是初始和中间裂纹扩展中至关重要的改性元素。最终，在大量的循环中，裂纹进入远场，并渐渐趋向于由缓慢的裂纹扩展所驱动的中心加载的似硬币状构型的简单通用关系。对于在最大循环载荷和球体半径范围内的循环载荷，在水中循环压入碳化钨球的厚钠钙玻璃板，可获得说明每种模式的裂纹扩展数据。通常在玻璃中，首先形成外部圆锥形裂纹，但随后随着深度的增加，随着内部圆锥形尤其是径向裂纹的产生，圆锥形裂纹逐渐消失。在生物力学应用（牙冠，髋关节置换术）中，后两种裂缝类型被认为特别危险，在该应用中，有限厚度的陶瓷层用作承重组件。讨论了测试变量（接触载荷，球体半径）和材料特性（硬度，模量，韧性）在确定每种断裂模式的相对重要性中的作用。

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