PerspectiveMaterials Science

Predicting Fatigue Failures

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Science  10 Jul 2009:
Vol. 325, Issue 5937, pp. 156-158
DOI: 10.1126/science.1173432

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Engineers who design structures often start at the end: They consider how the materials used will fail. Structures must be overdesigned—a bridge may be able to withstand twice the expected load when it is first built—but over time, repeated cycles of loading and unloading introduce defects in the materials that can ultimately lead to fatigue failure; for example, a paper clip that is bent back and forth until eventually it snaps. Predicting failure is easier for ductile than for brittle materials, and designers can accurately model their response to fatigue loading (1). However, many relatively brittle materials, such as advanced ceramics, intermetallics, and composites of brittle and ductile materials, are seeing increased use due to their favorable low-density or high-temperature properties. New methods are needed to predict when and how these materials will fail due to cyclic fatigue loading.