Weld Imperfection Inspection Based On Adaptive Optimization Wavelet Transform Algorithm

Welded structure was widely applied to industrial fields. Nowadays, the quality of welding was assessed by the experienced inspection personnel according to relevant standards at present, which might lead to misjudgment and judgment leakage. Therefore, the computer image processing technology should be used to analyze and recognize the X-ray detection result for satisfy the objectivity, scientific and normative demand of the weld quality assessment. As a new subject, wavelet analysis which was characterized by multi-resolution and time-frequency localization, was a good tool to detect abrupt signals and was widely-used in image processing area. Making good use of this, the wavelet image processing technology was applied to X-ray weld image detection and recognition in the paper. The X-ray weld imperfection detection and recognition were implemented by computer.Aiming at the limitation of the traditional dyadic wavelet transform, which can only dispose the data whose length is 2 of integer power, but has to do plenty of boundary treatment when the data length isn't, a new adaptive optimization wavelet transform algorithm was proposed. The core idea are to achieving the optimization of boundary treatment by obtaining the optimal approximate length via length analysis of pending data, and actualize the adaptive selection of wavelet transform base by analyzing the optimal approximate length. The character of no neglecting boundary data of the new algorithm guaranteed the accuracy and reliability of weld imperfection detection, which eliminated the situation that some marginal weld imperfection might be neglected.The theory of wavelet singularity detection, and the different Lipschitz exponent characteristics of noise and signal under wavelet transform domain were investigated. The noise was removed effectively by means of a kind of threshold function which had the same characteristics. Analyzing pros and cons of the traditional multi-resolution edge detection method, a new weld imperfection inspection method based on wavelet multi-resolution image reconstruction was proposed from another point of view, which could detect more rapidly and accurately than the traditional multi-resolution edge detection method. The process of the coarse-to-fine information collecting and processing of the human vision system was simulated successfully. The region model of welding image was constructed based on the characteristic analysis of weld image, and the weld region was extracted effectively. The characters of different weld imperfection are investigated, and the correlative principles and standards of weld defect recognition are introduced amply.In the research for introducing wavelet multi-resolution analysis theory into X-ray weld imperfection detection, the weld imperfection inspection system based on the adaptive optimization wavelet transform was researched and developed according to the new methods proposed in the paper. The main function modules of the system are described in detail. Finally, compared with several traditional edge detection algorithm, the system was applied to practical weld imperfection inspection, and the detection results show that the new method proposed in the paper was correct and effective, and was of a certain practical value.