Abstract
The increasing demand for new, more reliable materials, which are often used in hostile environments, has led to the necessity of establishing equally reliable, quantitative techniques for the non-destructive evaluation (NDE) and characterisation of such materials. Non-destructive evaluation methods are commonly used in applications ranging from materials processing and control to monitoring the effects of environmental degradation and the estimation of remaining useful life of materials. Although linear ultrasonic methods have long been among the most popular and useful of NDE methodologies, this review is concerned with the considerable effort that has been expended recently on understanding, developing, and applying non-linear acoustoelastic techniques. Although applications to complex materials are usually correlative, recent progress in the quantitative modelling of the acoustoelastic properties of multiphase alloys in terms of material composition is also reviewed. Considerable emphasis is placed on understanding the relationship between non-linear acoustoelastic properties and the fundamental atomic structure of simple materials. Such considerations lead to an enhanced understanding of the effect of residual and applied stresses on the acoustoelastic and thermoelastic measurements of metallic alloys. Similar considerations of magnetic domain structure provide an explanation of the effect of stress on the magnetoelastic properties of ferromagnetic materials. Implications of these advances to the non-destructive characterisation and evaluation of materials are discussed.
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