Study On Cylindricity Error Evaluation And Inner Surface Display Of Pipe Based On Industrial CT

Industrial computerized tomography (Industrial CT) acquires projection data, which the x-ray transmits the cross-section of the tested object without damage to the object. The cross-section images can be obtained with special image reconstruction algorithm. Industrial CT, which has the obvious advantage of non-destructivity, can solve many problems that the traditional methods can not solve. There are many kinds of pipelines in real workpiece. The cylindricity error evaluation and inner surface display of pipe are significant for evaluating performance and service life. Based on industrial CT, this dissertation studied the cylindricity error evaluation and inner surface display of pipeline.Cylindricity error is defined as the changes between measured column and ideal column. Because of the limit of measuring tools, the traditional methods can not evaluate the cylindricity error of internal pipe. This dissertation presents cylindricity error measure according to industrial CT. The inspected area is scanned by industrial CT, which obtains the CT images of the inspected area. The edge is detected with Facet algorithm. Then the mathematical model is established by the least-square method. The cylindricity error can be got by optimization. The results show that this method can get cylindricity error without damage and touch.In industrial CT image analysis and process, it is necessary to display the inner surface of the pipeline for subsequent analysis and defect detection. There are usually section display and virtual endoscope for inner surface display. At first, we get the target with region growing for section display, then use contour extracting and contour tracking to get the target's contour points. Finally, we calculate the distances between the centroid and the contour points and transform the distances to gray for writing to an image. The experimental results show that section display is simple and effective. It can observe the defects on the inner surface.Virtual endoscope display is a kind technology of simulating traditional optical endoscope. It can display inner face of target with three-dimensional quality. At first we use image segmentation to get the target and locate the edge points, then extract the central path of the target. In order to move the virtual camera lens slowly we smooth the path with B-spline. After that we use the shortest diagonal method to complete the contour tiling and render the surface at last. Also we study a special method for the contour tiling of the pipeline. Virtual endoscope display can observe the inner surface of the pipe dynamically and directly.