Spherical Harmonic Based Smoothing And Finite Element Analysis For Cement Particle

The composite of cement, represented by cement mortar, is widely used in the society. Ithas many advantages, such as the wide range of raw materials sources, controlled strength andshape of plastic and inexpensive. But itself has shortcomings, such as its inherent bad crackresistance, brittleness, and so on. To a certain extent, these disadvantages affected its furtherapplication in the field of building materials. So, composite of cement research not only has ahigh theoretical value, but also has important practical significance and application value.In the past few years, due to the gradual application of the CT technique in materialresearch, it was possible to get two-dimensional tomographic image sequences of materials.Three-dimensional model of materials microstructure can be directly reconstructed based onthese sequence images. Nowadays the three-dimensional reconstruction algorithms are quitemature. The real material micro-structure can be obtained. Because material micro-structurehas important influence to the material macroscopic performance, therefore the study ofmaterial micro-structure plays an important role in improving the material properties. Forcomposite of cement, the3D micro-structure of cement model can be built by3D images andgraphics techniques. It will provide a new method and a new approach for the cement materialresearch.The major research contents are as follows:1. Firstly, gain the2D tomographic image sequences through CT technique. We havestudied the method of multi-contour extraction from complex background image. Introducethe knowledge of the active contout model and level set method and use fast globalminimization of active contour model, mathematics morphology and median filter algorithmto extract the cement contours. Combine the characteristic of the cement particles, and splitout the multi-layer contours of cement particles.2. Researched the3D reconstraction technology based on2D continuous tomographyimages. There are mainly two major technologies: surface rendering, volume rendering. Theclassic algorithm based on surface rendering is marching cubes (MC) and the classicalgorithm based on volume rendering is ray casting. Visualization tools kit (VTK)encapsulates the above algorithms. We separately used vtkMarchingCubes class and vtkVolumeRayCastCompositeFunction class provided by VTK, combined with VS2005software platform, reconstruct the cement particles in BMP format. Comparison of resultsfound: surface rendering method is efficient, fast, but the surface of reconstructed cement isjagged; volume rendering algorithm has good render effect, kept many details of the particle,but less efficient than surface rendering algorithm.3. In order to ensure the convergence during the cement microstructure model processing,we use the spherical harmonic function to smooth the reconstructed cement particles. Thispaper describes the properties of spherical harmonic basis functions and its application in3Dsurface smoothing. Use several orders of the spherical harmonic function to reconstructcement particles and successfully get the approximation image of cement particles. The resultshows spherical harmonic function is useful for the cement surface smoothing.4. Import the First Order Ellipsoid of cement particles to the finite element analysissoftware ANSYS and establish the finite elment model of the micro-structure of cement. Getthe reflection of stress and strain of cement materials, and from the quantitative to analysis theimpact on the macro-performance of micro-structure. Finally，we obtained the effective elasticmodulus of finite element model of cement micro-structural.