Full‐Field Displacement Measurement of a Speckle Grid by using a Mesh‐Free Deformation Function

  In the present study, a combined experimental–numerical technique for the determination of the displacement and strain fields in the surface of a deformable body is described. The experimental part of this technique is based on the recording of the pair of images of the surface before and after deformation of the body, by means of a digital camera. This is done after spraying the surface with a random field of speckles (dots). Then the dots (having finite dimensions) of the second image are identified and uniquely paired with the dots of the first image. This permits the experimental determination of the deformation field in the surface. Then, by means of a mesh‐free numerical method, a smoothed deformation field can be constructed. For that, the moving least square method is applied. The deformation field being available, the corresponding strain field can easily be obtained. Numerical simulation of this technique in three simple examples indicates that promising applications are expected.