Optical deformation field measurements

In electronics, thermal fatigue is the most common cause of failure. For a well-founded evaluation of the reliability of a structure, experimental tests are necessary to analyze and determine the physics of failure.

Due to ever shorter product development cycles and the resulting time pressure, supplementary simulations based on finite element models offer a considerable advantage for understanding structural behavior. The scope of experimental tests can thus be considerably reduced. The virtual environment allows both a reliability prediction based on the calculation results and a reliability assessment in a reasonable time.

The Optical Deformation Unit (ODU) was developed at Fraunhofer IKTS to confirm the credibility of the results of the FEM calculations. This can be used to carry out deformation experiments that enable FEM model calibration and verification.

There are few measurement methods that can analyze thermomechanical deformations with high resolution. Digital image correlation makes this possible. It is a powerful tool in conjunction with simulation. The measuring principle is based on the repetition of the following steps:

1. Registration of features in an evaluation area of the reference state (reference image).
2. Recognition of these characteristic features in the measurement state (measurement image).
3. Quantification of the position of the relevant image sections in relation to each other using correlation algorithms.
4. Determination of the relative displacement of the corresponding points and their surroundings and deformation field visualization.