Development of a Portable Laser Shearography System for Crack Detection in Bridges

摘要

Laser digital shearography is a nondestructive optical method for detecting fine cracks (<10 microns) which has been applied for field inspection in a number of industries including automotive and aerospace. Under a Phase I SBIR grant from the Department of Transportation, a system for specific use in civil engineering is being developed. The adaptations include a rugged low cost laser and CCD imager and a vacuum system for mounting the instrument on a structure. Automated image analysis is being developed to identify cracks in the shearography image and then to calculate parameters such crack mouth opening displacement (CMOD), crack length and orientation. Calibration of the system involves the use of concrete prisms that have been treated with the Duggan cycle to induce cracking.