(Micro)-Crack detection using local Radon transform

The detection of cracks and micro-cracks in materials or structures is an important and non-trivial task. A typical method is optical microscopy, providing a 2D image with the crack showing as a line in the material. The use of 3D-visualisationmethods, such as computed tomography (CT), permits the visualisation of materials as complete 3D volumes. In this case, occuring cracks are locally plane-like structures that can be described as 2D surfaces with a 3D topography. To receive the necessary data, the images of the investigated objects are obtained via X-ray computed tomography, providing a 3D-visualisation of materials at micron-range resolutions. In this article, computed tomography is used to investigate cracks in composite materials such as short-fibre reinforced carbon fibre reinforced plastics (CFRP). The goal of this article is to detect all relevant cracks inside an object in a stable way, reducing the effect of noise. The results show the cracks to be smooth and locally connected, resulting in connected components containing a large number of voxels. For this purpose, a mathematical technique based on the local Radon transform is applied. In order to achieve an improvement in speed, the structure tensor is applied to guess the orientation of the local structure. The aim is to determine cracks and to follow crack growth and evolution to increasing loads.