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Deformation measurement by optical field methods in material testing and for verification of numerical simulation

Optical field methods are suitable for deformation measurements of all visible points on a considered object surface. Using the deformation values the strain tensor for the case of plane deformation state of all points can be determined. Applying an adapted strength hypothesis to its components produces a reference strain. In order to dimension an object the reference value has to be smaller than the allowed strain measured by a one-dimensional tensile test. The electronic speckle pattern interferometry and the object grating method are particularly suitable for material testing and for verification of numerical simulation. The electronic speckle pattern interferometry is especially applied, if the two compared deformation states differ from each other only by a small amount and if the expected strain values are small. The application of the object grating method is not limited by the two considered deformation states. The limitation is given more by the accuracy of the digital image processing algorithms or the grating structure. The strain values to be determined have to be greater than 0.1%. Furthermore the object grating method is applicable for the case of very small object surfaces which take only few micrometer squared and at high temperatures up to approximable 1000 degrees Celsius. Several practical examples of the application of these two methods in material testing and for verification of numerical simulation are presented.