Mechanical fatigue fractures bivalve shells
Mechanical fatigue fractures bivalve shells
复制标题
DOI：
10.1242/jeb.220277
复制
发表时间：
2020-05-01
影响因子：
2.8
通讯作者：
Denny, M. W.
中科院分区：
文献类型：
--
作者：
Crane, R. L.;Denny, M. W.
软体动物贝壳可以抵御各种环境和捕食性物理威胁，从一次性的撞击到慢性的低强度压力。炮弹作为装甲的有效性通常是通过炮弹强度测试来量化的：不断增加的力被施加到灾难性的断裂。这项测试没有捕捉到疲劳的潜在作用，疲劳是一种慢性或重复的、低强度的力量削弱和破坏结构的过程。对加州贻贝(Mytilus Calfornianus)贝壳的强度和抗疲劳性进行了量化。壳体进行疲劳测试，直到灾难性的失效，要么反复加载阀门到设定的力(循环)，要么在恒定的力(静态)下加载阀门。阀门在循环和静态载荷下都会疲劳，也就是说，重复或长时间施加亚临界力会破坏阀门。更坚固、更耐疲劳的瓣膜往往更大、相对更宽，而且是右侧的瓣膜。此外，在考虑瓣膜的预计强度后，循环和静态载荷的疲劳阻力曲线没有差异，这表明贻贝的疲劳断裂更多地依赖于力的持续时间，而不是循环次数。将贻贝通常经历的力量与疲劳抵抗力联系起来，可以澄清疲劳与之相关的威胁范围。一些捕食者可能会依赖疲劳，而像大浪冲击或失败的捕食尝试等间歇性事件可能会在很长一段时间内削弱贝壳。在考虑有壳生物的生态或贝壳形态的演变时，量化贝壳疲劳阻力提供了一种视角，可以解释一生中大大小小的威胁的累积损害。
Mollusk shells protect against diverse environmental and predatory physical threats, from one-time impacts to chronic, low-magnitude stresses. The effectiveness of shells as armor is often quantified with a test of shell strength: increasing force is applied until catastrophic fracture. This test does not capture the potential role of fatigue, a process by which chronic or repeated, low-magnitude forces weaken and break a structure. We quantified the strength and fatigue resistance of California mussel (Mytilus californianus) shells. Shells were fatigue tested until catastrophic failure by either loading a valve repeatedly to a set force (cyclic) or loading a valve under constant force (static). Valves fatigued under both cyclic and static loading, i.e. subcritical forces broke valves when applied repeatedly or for long durations. Stronger and more fatigue-resistant valves tended to be more massive, relatively wider and the right-hand valve. Furthermore, after accounting for the valves' predicted strength, fatigue resistance curves for cyclic and static loading did not differ, suggesting that fatigue fracture of mussels is more dependent on force duration than number of cycles. Contextualizing fatigue resistance with the forces mussels typically experience clarifies the range of threats for which fatigue becomes relevant. Some predators could rely on fatigue, and episodic events like large wave impacts or failed predation attempts could weaken shells across long time scales. Quantifying shell fatigue resistance when considering the ecology of shelled organisms or the evolution of shell form offers a perspective that accounts for the accumulating damage of a lifetime of threats, large and small.