The optical method of caustics is an experimental technique which, particularly when used in reflection, has recently found increasing applicability to the fracture mechanics of engineering materials. Having been widely applied to stress intensity factor measurement, it has found a niche in areas where an analytical prediction has been impossible or in need of experimental verification, such as in dynamic fracture. This paper provides an accessible introduction to the method, covering its historical background and theoretical basis, together with a comprehensive guide to, and review of, its practical application to materials such as aluminium and steel.
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