| On the civil engineering, the crack is always produced due to many ways, such as: design, construction, use, etc. The crack width on the surface obviously affects not only the appearance of the reinforced concrete structure, but also the durability of construction. If the crack width overed a certain numerical value, it may endanger the security of construction. Therefore, the crack is universally attentioned by people. Large number of scientific research proved that the crack is unavoidable. It reflects the characteristics of material which can be accepted by people. The problem is how to control the harmful extent in a certain boundance. In addition, the crack position and configuration reflect the direction and centralized position of the pull stress in concrete, which is certainly corresponding with the reason of the way producting pull stress. Accordingly, we can just use the characteristic to estimate the cause for the appearance of crack on the structure and judge the harm of the crack in order to take corresponding reinforce means.It can be obversed above that accurately obtaining the shape, length, width, depth and other feature of crack takes great effect on estimating the state of concrete component accurately and appling reasonable disposing scheme scientificly. The crack of concrete component must be detected when disposing accident, checking out the construction, checking up the security of dated building, maintaining and repairing design. Therefore, estimating the crack of concrete structure accurately is very important for the evaluation, appraisal and mainteinance of the structure.Alonging with the advancement of detecting technique, the traditional way of determing the length and width by people is gradually replaced by new methods due to its limitations such as subjectivity, low precision, low efficiency, etc. Other methods such as sound, launch way are also gradually showing their limitations. With the development of the mainipulation of images by computer, it has embedded the quantification estimating of the crack on concrete material, exerting great superiority, such as uncontact, relatively convenient, accurate, etc.The digital image processing that based on the optical method is just used to quantificatly analyse the crack feature of structure material. Firstly, collect the crack image by a certain image collecting system. The crack also can be subsectionly collected if it is large. Then the image is processed by a seriels of ways such as filtration, sharping, contrast enhancement, etc. Here, a new method of image enhancement called SFC(Sharp Filter Contrast) combination way is rasied, it provids a high quality image for the following image process, placing an important role. Then, the edge of the crack is orientated by the improved grads threshold way. The edge'sprecision is gone to a pixel by this way. In the following, traditional sub-pixel technique of bary center operaters is improved and used in this paper to obtain the real coordinates of the edge, so the edge's precision is gone to sub-pixel. In the end, the crack feature of width is calculated based on the edge obtained above. Here, two effective ways of measuring the crack feature are rasied, hori-scale way and min-distance way. Their precisions are validated by experiments respectivly. At last, on basis of Visual C++6.0 developing environment, the software of crack feature measurement is realized on C++ and MFC with objected programming method. This makes the crack detection more observely. The software interface is well designed. It has great communication condition bewteen people and computer, greatly visual and reasonable structure system. If cooperated with certain hardware collecting system, it can realize the automatization of the whole process, settling the limitations of the traditional way by people. It shows the great superiority of digital image processing. This technique of crack detecting can also be used in national defence, aerohautis, mechanism fabricate, etc.
|
PDF Full Text Request