Connection force measurement of precision small interference components using ultrasound

Precision small interference components are mainly assembled using the press-fit method. Interface wear is inevitable in the press-fit process, which will reduce the connection strength. Pull-out experiments are the main means of measuring the connection force, but they are not available in the production process for its destructive characteristics. In this study, a nondestructive testing method for connection force based on ultrasound is proposed. An acoustic model was constructed based on the virtual layer model and statistical microcontact theory, which can be used to obtain the R-K-n-P mapping relationship. An ultrasonic measurement device was built manufactured and calibrated to achieve accurate alignment of the ultrasonic transducer with the interference component and accurate measurement of contact stress. The coaxiality error between the fixture and the turntable is less within +/- 5.9 mu m. The parallelism errors between the turntable and Z-axis stage in the xoz- and yoz-plane are 0.0894 degrees and 0.0662 degrees, respectively. The measurement error due to the transducer positioning error is less than 1.5%. The equivalent static friction coefficient was proposed to compensate R-K-n-P calibration error and measurement error. The integral expression of the connection force was given. Finally, the connection force of the interference components was measured and verified by pull-out experiments. The measurement error is within +/- 10%.