Time-history Measurement of Welding Deformation Using Digital Image Correlation Technique

摘要

Recently, image processing techniques such as digital image correlationrn(DIC) have been actively introduced to the measurement ofrndeformation and strain of structures due to the rapid improvement ofrndigital cameras, especially pixel resolution. The DIC technique is anrneasy and instant method for obtaining a lot of information ofrndeformation. In photos taken with a digital camera, all the informationrninvolves the points in the pixels. Due to the range of accuracy ofrndeformation that can be obtained, this method is considered to be veryrnuseful.rnThe measurement method using DIC can measure with high accuracyrnonly when the out-of-plane displacement is small. However, the errorrnof displacement becomes large when the out-of-plane displacement isrnlarge. In this situation, the measured size is not the same as the real sizernof the object. To overcome the problem, a measurement method basedrnon the stereo imaging technique using two digital cameras is proposedrnhere. The proposed method can measure not only in-plane deformationrnbut also out-of-plane deformation with high accuracy withoutrncalibration of the errors caused by out-of-plane displacement.rnIn this study, the measurement accuracy of the proposed method for inplanernand out-of-plane deformation is discussed through the applicationrnof bead-on-plate welding. It is found that the proposed method canrnmeasure transverse shrinkage and angular distortion with high accuracyrnin comparison with measurements using a vernier caliper or laserrndistance meter. The methods using a vernier caliper and laser distancernmeter can measure only a few points at a time, but the proposed twodigital-rncamera method can measure the full field in a short time. Thisrnshows that the proposed method has many important advantages.