A novel experimental device with modified laser shadow spot and optical strain gauge set-up

A new device, which combines the technologies of laser shadow spot and optical strain gauge with image processing, computer voice, and WWW software for detecting the broken procedure of different materials, has been presented in this paper. The whole testing experiments are monitored by an imaging system and guided by the computer voice to predict the crack step by step. The system generates a laser shadow spot or diffraction image on a screen when the laser beam passes through a lens as well as the crack gap of a specimen. The mechanical shelf changed the strength of the specimen and a CCD camera grabbed the variant images of the specimen under strength. The computer calculated each image for guiding the operator how to install the specimen and added the proper strength. Our proposed algorithm calculated the radius of the crash gap, the factors of the strength intensity and the strain value. In the experiment of optical strain gauge, the change in diffraction pattern and strain is caused by the applied force change. In the laser shadow spot experiment, the more the stress on the specimen causes the more the strain intensity factor and the later turns to saturation gradually, which means the specimen will be broken.