Binocular Measurement Study In Measuring The Closed Impellers’ Size By FPT

A certain type of aero-engine closed impellers formed by precision casting.Because of the impellers which are components of high temperature rotation,the control of internal and surface defects is related to the reliability and the service life of aero-engine.The impeller is made of high temperature alloy by casting,and the best way of surface defect detection is High Sensitivity Fluorescence Penetrant Detection.However,the impeller structure is complex and there are many nearly completely closed space,it is too difficult to observe the presence of defects in fluorescence detection in closed space surfaces,and measure the defect size.This paper attempts to measure the inner surface of the impeller by binocular measurement method.Got images of the sensitivity test piece of fluorescent penetrate detection in this environment.Under UV,these images showed an uneven distribution of light intensity and low contrast.Obtained the standard images of defects by homogenization the light intensity of light field,noise reduction,image segmentation and edge extraction,and measured the scale of these defects.Built a Binocular measurement platform,set the standard test piece in closed space to simulate the environment of enclosed space for impellers,and made a Flexible New Technique for Camera Calibration for binocular measurement system.After comparing NCC algorithm with SIFT algorithm,used NCC algorithm with constraint conditions which matched images and improved matching efficiency and matching accuracy.Realized the accurate measurement of the defect size on the standard test piece,and then used the platform to measure the actual defects on the inner surfaces of impellers,relative difference of measurements of defects’ scales is litter than 5.5 %.In this paper,the binocular stereo measurement platform which was built can effectively solve the problem of obtaining the fluorescence images of the inner surface of impellers.Homogenization of the light intensity of light field,noise reduction,image segmentation and edge extraction are all effective and calibration methods from this research are all simple and accurate to apply to defect detection of inner surface of closed impellers of aero-engine.