In order to reduce noise effectively in the welding defect image and preserve the minutiae information, a noise reduction method of welding defect image based on nonsubsampled contourlet transform(NSCT) and anisotropi...In order to reduce noise effectively in the welding defect image and preserve the minutiae information, a noise reduction method of welding defect image based on nonsubsampled contourlet transform(NSCT) and anisotropic diffusion is proposed. Firstly, an X-ray welding defect image is decomposed by NSCT. Then total variation(TV) model and Catte_PM model are used for the obtained low-pass component and band-pass components, respectively. Finally, the denoised image is synthesized by inverse NSCT. Experimental results show that, compared with the hybrid method of wavelet threshold shrinkage with TV diffusion, the method combining NSCT with P_Laplace diffusion, and the method combining contourlet with TV model and adaptive contrast diffusion, the proposed method has a great improvement in the aspects of subjective visual effect, peak signal-to-noise ratio(PSNR) and mean-square error(MSE). Noise is suppressed more effectively and the minutiae information is preserved better in the image.展开更多
Residual stress continues to be important issues in shipbuilding. This paper demonstrates how the heat affected zone that results from welding could be identified nondestructively using MBN （magnetic Barkhausen noise...Residual stress continues to be important issues in shipbuilding. This paper demonstrates how the heat affected zone that results from welding could be identified nondestructively using MBN （magnetic Barkhausen noise） technique. A stress concentration region was created by placing a weld bead on a marine steel plate used in ship construction. MBN measurements were made on the back surface of the welded plate along the weld direction and perpendicular to it in a line that crosses the weld bead. The stress distribution as deduced from the MBN measurements was found to be anisotropic in the material of the heat affected zone. The heat induced anisotropy was completely eliminated by shot peening the HAZ material as revealed by MBN intensity. It was concluded that the directional MBN measurements could be used to characterize the induced anisotropy and hence assess the thermal residual stresses distribution near a localized stresses concentration regions imposed by welding.展开更多
In industrial X-ray inspection, in order to identify weld defects automatically, raise the identification ratio, and avoid processing of complex background, it is an important step for sequent processing to extract we...In industrial X-ray inspection, in order to identify weld defects automatically, raise the identification ratio, and avoid processing of complex background, it is an important step for sequent processing to extract weld from the image. According to the characteristics of weld radiograph image, median filter is adopted to reduce the noise with high frequency, then relative gray-scale of image is chosen as fuzzy characteristic, and image gray-scale fuzzy matrix is constructed and suitable membership function is selected to describe edge characteristic. A fuzzy algorithm is adopted for enhancing radiograph image processing. Based on the intensity distribution characteristic in weld, methodology of weld extraction is then designed. This paper describes the methodology of all the weld extraction, including reducing noise, fuzzy enhancement and weld extraction process. To prove its effectiveness, this methodology was tested with 64 weld negative images available for this study. The experimental results show that this methodology is very effective for extracting linear weld.展开更多
基金Supported by the National Natural Science Foundation of China(No.60872065)Open Foundation of State Key Laboratory of Advanced Welding and Connection,Harbin Institute of Technology(AWPT-M04)Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘In order to reduce noise effectively in the welding defect image and preserve the minutiae information, a noise reduction method of welding defect image based on nonsubsampled contourlet transform(NSCT) and anisotropic diffusion is proposed. Firstly, an X-ray welding defect image is decomposed by NSCT. Then total variation(TV) model and Catte_PM model are used for the obtained low-pass component and band-pass components, respectively. Finally, the denoised image is synthesized by inverse NSCT. Experimental results show that, compared with the hybrid method of wavelet threshold shrinkage with TV diffusion, the method combining NSCT with P_Laplace diffusion, and the method combining contourlet with TV model and adaptive contrast diffusion, the proposed method has a great improvement in the aspects of subjective visual effect, peak signal-to-noise ratio(PSNR) and mean-square error(MSE). Noise is suppressed more effectively and the minutiae information is preserved better in the image.
文摘Residual stress continues to be important issues in shipbuilding. This paper demonstrates how the heat affected zone that results from welding could be identified nondestructively using MBN （magnetic Barkhausen noise） technique. A stress concentration region was created by placing a weld bead on a marine steel plate used in ship construction. MBN measurements were made on the back surface of the welded plate along the weld direction and perpendicular to it in a line that crosses the weld bead. The stress distribution as deduced from the MBN measurements was found to be anisotropic in the material of the heat affected zone. The heat induced anisotropy was completely eliminated by shot peening the HAZ material as revealed by MBN intensity. It was concluded that the directional MBN measurements could be used to characterize the induced anisotropy and hence assess the thermal residual stresses distribution near a localized stresses concentration regions imposed by welding.
文摘In industrial X-ray inspection, in order to identify weld defects automatically, raise the identification ratio, and avoid processing of complex background, it is an important step for sequent processing to extract weld from the image. According to the characteristics of weld radiograph image, median filter is adopted to reduce the noise with high frequency, then relative gray-scale of image is chosen as fuzzy characteristic, and image gray-scale fuzzy matrix is constructed and suitable membership function is selected to describe edge characteristic. A fuzzy algorithm is adopted for enhancing radiograph image processing. Based on the intensity distribution characteristic in weld, methodology of weld extraction is then designed. This paper describes the methodology of all the weld extraction, including reducing noise, fuzzy enhancement and weld extraction process. To prove its effectiveness, this methodology was tested with 64 weld negative images available for this study. The experimental results show that this methodology is very effective for extracting linear weld.
