Investigation of Low Temperature Deformation Measurement Problem by the Contact Holographic Interferometers

Abstract

The materials currently used in modern structures do dramatically change their mechanical properties under the influence of low operating temperatures. One of the factors affecting the breakdown of various structural elements at low temperatures, is the placement of the stress concentrations. The existing analytical design schemes cannot always correctly take into account the material mechanical properties changes caused by the temperature decrease. In the present work we consider the method of contact holographic interferometry, which made it possible to efficiently determine surface displacements and strains at the temperature of –50 °C. The contact holographic interferometer is presented as an assembly of the object surface section and holographic plate in an immediate vicinity to the object. This technique is used to determine in-plane and out-of-plane displacements of tested object. If a hologram is recorded at metallized grating surface it restores information peculiar to some optical methods: holographic interferometry, speckle photography, holographic moire and mirror-optical method. For the interpretation of interference patterns new simple analytical equations are obtained. Contact holographic interferometers are used effectively to solve some elasto-plastic deformation measurement problems of isotropic and polycristalline materials. It is specially designed to permit the accurate measurement of the in-plane component of strain in the immediate vicinity of stress concentrators in plates.KeywordsHolographic interferometryTemperature problem