Measurement And Evaluation For Surface Topography Of Laser Roughen Steel Rolls

A large number of metal sheets have been used for decorating and improving the living environment in many applications, such as automotive, aerospace, appliances, construction, decoration and other industries. Surface texturing of cold roll is a surface pretreatment technique for the production of high-quality sheet. By textured on the cold roll surface, the surface morphology of a sheet surface which meets the requirements of the following processes can be produced. The numbers of high quality sheets are growing with the people's living condition. Formability of stamping, distinctness of image, abrasion resistance and other performance requirements are also rising. With its high efficiency, economy, pollution-free, computer-controlled, and other unique advantages, laser texturing technology can be used to meet the design requirements of the metal sheets. So it has the potential to be developed into a mainstream cold-roll texturing technology. However, since the assessments of roll and sheet surface properties are often based on two-dimensional roughness of the surface profile curve, which makes it difficult to analysis and evaluation of laser texturing sheet surface. It also makes it can not feedback for laser texturing process, thus largely restrict the application and development of laser texturing technology.Firstly, as for the lack of surface topography detecting method of textured cold rollers and metal sheets, a three-dimensional micro-topography measuing system is achieved in this thesis which is based on the light-sectioning method. This system consists of a light sectioning microscope optical subsystem, a CCD image acquisition subsystem, a three-axis fine adjusting device and computer data processing subsystem. Measuring principles and methods of light-sectionging measuring system are analyzed, as well as the applicability of this system in measuring the surface micro-topography made by laser texturing technology. Theoretical analysis and numerical simulation of the light-sectionging microscope are practiced, and a muti-parameter model of image position versus topography height is derived. An optimizing model of sampling space in this system is verified by measuring and sampling on regular simulation surface. A threshold segmentation algorithm based on normal distribution of light intensity is used to extract the image edges. A two-dimensional bilinear interpolation algorithm is used to reconstructe the surface topography, and a sparse matrix method is adopted to solve the matrix of interpolation equation. Secondly, after the textured 3D surface topography has been reconstructed, many 3D topography parameters are calculated and investigated following with three-dimensional morphology parameters of the ISO 21578-2 specification. For analyzing and evaluating a non-Gaussian surface morphology reasonably, the Abbott-Fireston curve is obtained after the surface morphology is decomposed by a multi-gaussian decomposition method. Finally, the parameters are analyzed and summarized according to the surface major performance and applications of textured metal sheet and cold roller.By introducting a computer to the light-sectioning method measuring system, an automatic instrument of three-dimensional micro-topography measurement is realized. It can be used to measure on laser textured cold rollers and metal sheets under the shop floor conditions, and the 3D topography parameter set can be calculated after the surface has been reconstructed. The accuracy of this measuring instrument in horizontal and vertical is about 0.5μm and 0.3μm respectively. It is suitable for measuring the topography of surface texture with a height between -10～10μm. So it is can be used for measuring the surfaces of laser textured cold roller and metal sheet. A standard roughness block is used for calibration of the surface microtopography measuring system. It shows that the reconstructing topography is good agreement with the actual asperity of the surface. Using this mearsing the surface of laser textured cold rollers and metal sheets, the actual surface topography can be reconstructed effectively. A set of parameters of the surface three-dimensional topography provide a quantitative insight into functions and performance of textured surface. It is necessary for supporting the digital management of textured surfaces, and feedback tu the development of the laser texturing technology.The forword researchs about this measuring system are to improve the flexibility and reliability of the optical subsystem. The relational model between different surface topography and performance should be found. A software system should be built to feedback and control the quality of laser texturing process.