Abstract: Holographic interferometry can be used to examine minute changes in the surface of components as they undergo stress, thermal expansion, erosion, growth, and vibration. Such changes often can be used to identify the presence of a defect beneath the surface, because of the anomalous microscopic behavior of the surface. In addition, the mechanical characteristics of the component, such as vibrational modes, expansion, and residual stress can be identified through holographic inspection. Over the past 30 years a wide range of methods have evolved as new hardware and technology becomes available. The wide range of procedures, including electronic holography, multiwavelength recording thermoplastic recording, time-averaged holography, real-time holographic interferometry, cineholography, and other methods can be revisited each time a new development is made in lasers, computers, and recording materials. Methods that once held only academic interest often become practical with newly available hardware and software. !27
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