دانلود رایگان مقاله روش پردازش تصویر برای ارزیابی توسعه ترک خوردگی در کائوچو و مواد مرکب

Abstract

Strain Hardening Cementitious Composites (SHCC) exhibit tension-hardening behavior accompanied by the formation of multiple cracks. To study the multiple cracking process, cracks are identified from digital images. As conventional image processing technique based on a single threshold of gray intensity cannot accurately determine the width of both fine and wide cracks, a new double-threshold algorithm is developed and its accuracy is verified by comparing with direct measurement under the microscope. Then, an additional algorithm for removing the noises and isolating individual crack regions is introduced. With the improved image processing method applied to a large number of sequential images, detailed information on the development of crack number and width is acquired. The average value and deviation of crack width at a given strain can be calculated to facilitate durability design. Also, with the stress-crack width relation obtained for various cracks, the fiber distribution among cracked sections can be estimated.

5. Conclusions

For strain hardening cementitious composites (SHCC), the multiple cracks often exhibit complex patterns, with high variation in crack width. In this study, a new double-threshold algorithm was first developed to treat large and small cracks separately, so all crack widths can be accurately captured. The approach has been verified by comparing crack width from a processed image to direct measurements under the microscope. Then, another algorithm was developed to automatically eliminate noises in the image and separate cracking regions from one another. By processing sequential images taken from the same specimen, the development of the cracking patterns with increased loading can be tracked and useful information can be obtained. The crack number from image processing is found to show a reasonable trend consistent with theory of stress transfer. At various strain levels, the mean crack width and standard derivation are assessed, so the probability for a crack to exceed a critical width can be determined to facilitate durability design.