Ultrasonic Measurement Of Contact Stress And Evaluation Of Joint Quality In Small Interference Fitting Parts

Precision small interference fitting parts are widely used in aviation,aerospace,transportation and other industrial fields,of which the assembly qualities directly affect the stability and reliability of the system.So,it is important to evaluate the assembly quality of such kind of parts.The connecting quality of the interference fitting parts can be evaluated by analyzing contact stress of the mating surface.Based on the quasi-static spring model of the mating surface and the contact stiffness curve of the components,the theoretical analysis model(R-P-K mathematical model)and the measuring method of the mating surface's contact stress were proposed in the paper.In order to analyze the relation between contact stress and ultrasonic reflection coefficient,a calibration equipment was developed,and the influence of coupling agent,focal length of ultrasonic probe and the diameter of focal point was also researched.According to influence principle,measurement and analysis method of contact stress was set up.In order to evaluate assembly qualities of small interference fitting parts,an ultrasonic measuring device for stress distribution of mating surface was developed,which includes a motion control module and an ultrasonic information acquisition module.The motion module is used to adjust parts position,which is consisted of a three-axis motion stage and precision electric turntables.The ultrasonic information acquisition module can realize the collection of ultrasonic data and transmit it to the computer for the advanced data processing,which is composed of a point-focusing water immersion probe,a pulse transceiver,an oscilloscope.The software system of the device is designed and developed based on LabVIEW software,and the MathScript node is used to collect and process data.In the paper,the stress distribution of three kinds of parts with different interference values(6?m,11?m and 20 ?m)were measured.The connecting forces were calculated according to integral method,and were compared with the press-fit method,of which relative error is less than 16%.Based on pressure-displacement curve method for evaluating assembly qualities,and combined with contract stress distribution map,two new kinds of connection quality assessment methods were proposed.1.The stress concentration area and the wear area of the mating surface can be judged according to the stress map.2.The degree of stress fluctuation can be judged according to the deviation of stress distribution.In general,a new method and a device were proposed to measure the contact stress of the mating surface of small interference fitting parts,which provided technical support for the quality evaluation of component connection.