Research On Ultrasonic Testing Method For Contact Distribution Characteristics Of Mechanical Joints

Machine tool manufacturing industry as an important part of the manufacturing sector,the development of its technical level represents the advanced level of national manufacturing,especially all kinds of precision and ultra-precision machine tools and advanced CNC machine tools.The mechanical joints of the machine tool had a large scale and a large number of types,the precision and performance of the machine was affectcd by the imperfect contact state of the joint surfaces.Therefore,to master the contact state of the joint surfaces under different working conditions is an important breakthrough to evaluate and improve the performance of the machine tool.The various of factors that affect the contact of the joint and the related detection method of joint surfaces were analyzed,the principle of rough joint surfaces was learned.The contact state of the joint surfaces is similar to the internal defects of material,according to the characteristic ultrasonic nondestructive testing principle on joint surfaces was analyzed,the programme that ultrasonic scanning detection on flat-type joint surfaces was determined.The adjustable three-dimensional platform and the drive device were designed,a platform for joint surface detecting system was built,the purpose of automatic ultrasonic detection of the joint surfaces was achieved.Finally the ultrasonic image output by the ultrasonic detection system realized the function of describing the contact distribution characteristics of the joint surfaces.The image deconvolution method is used to improve the resolution of ultrasonic image.The methods of wiener filter was studied,and the best estimate of the point spread function were obtained by using the observed image edge estimation method combined with the parameter-error estimation method.The effectiveness of the deconvolution was illustrated by the algorithm simulation and the deconvolution experiment of ultrasonic image.The stability and accuracy of the detection system were verified by a set of repetitive experiments.According to the principle of the linear relationship between the contact area and the pressure in the small pressure range,the self-calibration method of pressure-reflectance of ultrasonic detecting system was proposed,the purpose is to achieve the description of the pressure distribution characteristics of the joint surfaces.Through a series of ultrasonic testing experiments and ultrasonic signal processing methods,the macro shape error and micro contact distribution of joint surfaces were described.