scholarly journals Defect detection in plates using dynamic response signals and discrete wavelet transform

2018 ◽  
Author(s):  
Anna Knitter-Piątkowska ◽  
Michał Guminiak
Keyword(s):  
Wavelet Transform ◽  
Dynamic Response ◽  
Discrete Wavelet Transform ◽  
Defect Detection ◽  
Discrete Wavelet

Detection of Defects in Welded Structures With Complex Geometry Using Statistical Method Based on Discrete Wavelet Transform

2009 ◽  
Author(s):  
Tsun-Yen Wu ◽  
I. Charles Ume ◽  
Matthew D. Rogge
Keyword(s):  
Wavelet Transform ◽  
Energy Distribution ◽  
Discrete Wavelet Transform ◽  
Statistical Method ◽  
Defect Detection ◽  
Complex Geometry ◽  
Inspection System ◽  
Discrete Wavelet ◽  
Electromagnetic Acoustic Transducer ◽  
The Difference

In this paper, an inspection system and a defect detection method are presented. A welded sample with complex geometry was placed on an inspection system and inspected by generating ultrasound on one side of the weld and receiving on the other with an electromagnetic acoustic transducer (EMAT) sensor. Ultrasonic signals along the weld were acquired at locations with 1 mm distance between inspections. In order to detect the presence of defects, a statistical method based on Discrete Wavelet Transform (DWT) is implemented. Energy of each location along the weld is calculated and useful information indicating presence of defects is extracted by DWT using different mother wavelets. By comparing the energy distribution obtained from a particular sample, or a target, with a baseline energy distribution, defect locations are predicted. The baseline energy distribution is obtained by averaging energy distributions calculated for all inspected samples. The difference between a target and the reference is viewed as an indication of presence of defects. The results showed that the method can isolate signal changes that were caused by defects. Comparison to destructive cut-checks shows the accuracy of defect detection is high.

Improving Space Localization Properties of the Discrete Wavelet Transform

Informatica ◽  
2013 ◽  
Vol 24 (4) ◽  
pp. 657-675
Author(s):  
Jonas Valantinas ◽  
Deividas Kančelkis ◽  
Rokas Valantinas ◽  
Gintarė Viščiūtė
Keyword(s):  
Wavelet Transform ◽  
Discrete Wavelet Transform ◽  
Discrete Wavelet ◽  
Space Localization

An Adaptive Binarization Method for Cost-efficient Document Image System in Wavelet Domain

2020 ◽  
Vol 64 (3) ◽  
pp. 30401-1-30401-14 ◽  
Author(s):  
Chih-Hsien Hsia ◽  
Ting-Yu Lin ◽  
Jen-Shiun Chiang
Keyword(s):  
Wavelet Transform ◽  
Discrete Wavelet Transform ◽  
Document Image ◽  
Background Information ◽  
Raspberry Pi ◽  
Discrete Wavelet ◽  
Image System ◽  
Low Frequencies ◽  
Cost Efficient ◽  
Binarization Method

Abstract In recent years, the preservation of handwritten historical documents and scripts archived by digitized images has been gradually emphasized. However, the selection of different thicknesses of the paper for printing or writing is likely to make the content of the back page seep into the front page. In order to solve this, a cost-efficient document image system is proposed. In this system, the authors use Adaptive Directional Lifting-Based Discrete Wavelet Transform to transform image data from spatial domain to frequency domain and perform on high and low frequencies, respectively. For low frequencies, the authors use local threshold to remove most background information. For high frequencies, they use modified Least Mean Square training algorithm to produce a unique weighted mask and perform convolution on original frequency, respectively. Afterward, Inverse Adaptive Directional Lifting-Based Discrete Wavelet Transform is performed to reconstruct the four subband images to a resulting image with original size. Finally, a global binarization method, Otsu’s method, is applied to transform a gray scale image to a binary image as the output result. The results show that the difference in operation time of this work between a personal computer (PC) and Raspberry Pi is little. Therefore, the proposed cost-efficient document image system which performed on Raspberry Pi embedded platform has the same performance and obtains the same results as those performed on a PC.

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