On 7 June, Torsten Sjögren held his docent lecture Seeing is believing - Using digital image correlation in applied research.
In his lecture Torsten Sjögren talked about the benefits of digital image correlation, DIC, a technology which has been available for several decades but is becoming more widely used, as computers' capacity increases and hardware becomes cheaper.
DIC is an optical method to measure strains and displacements in different materials. For example, one can see how electronics are affected by heat or cold, and how concrete and other materials behave at different loads.
With DIC technology, the material is photographed while being subjected to load. A computer program can track the displacements in the pattern in the images, where the pattern may be natural or sprayed on the surface. The displacements can be used to calculate different strain measures and the result is an image where different colours show how different parts of the material stretches.
The technique can be used together with FEM, Finite Element Method, a tool for simulations that also provides a color-coded image where the colours correspond to different stress and strain levels. With the help of DIC one can get different material parameters to use in a FEM simulation, and conversely, DIC can be used to verify a simulation made with FEM.
In his lecture Torsten Sjögren talked about how DIC can be used in materials research and showed examples of how the technology has been used on various materials and also on different scales. To see how a material's different phases accommodate strain at micro level, provides a better understanding of how it will react at macro level.
Torsten Sjögren defended his PhD thesis in Linköping in 2007, but his thesis work was supervised at School of Engineering, Jönköping University. Since then he has worked at SP Technical Research Institute of Sweden.