Research On Computer Processing Of Holograph Of Residual Stress-Strain Field In Welding

Laser holography interferometry is a full-court, non-contact, nondestructive, detection with high precision and a large amount of information. So far there is no systematic, integrated application software which could be used to process the holograph (interference stripe pattern) of residual stress-strain field in welding. Concerning the characteristics of holograph, the required functions of the software are analyzed systematically. With Borland Delphi 5.0 and Object- Oriented Programming technology, the application software that can be used to process the interference stripe pattern of residual stress-strain field in welding is developed. In order to investigate the distribution of residual stress-strain field, digital image processing technology is applied and optimized in the software: medium filtering, hologram equalization, manual or automatic adjustment of gray value, fringe sharpening with Sobel operator, special treatments applied to strength the signal in weak zone by manual operation. Binary value image is gained through the processing method which the threshold is the expectation of the whole image and then the stripe image is thinned by Pavlidis Thinning Algorithm to make sure that the perfect interference stripe pattern could be obtained. Measurement of deformation in normal direction could be simplified greatly because of the reasonable arrangement of optics apparatuses: firstly, measuring zone is selected freely by selecting the measuring reference line through mouse; secondly, the result梔istribution of residual stress-strain field is output through a new form in a coordinate chart which is designed through Delphi 5.0. Integrated application software with completely visual form, easily operation, friendly frame and excellent maintenance is developed through Borland Delphi 5.0 and can meet the requirement. Also, this application software can be used in processing other various interference stripe patterns.