Studies on the Improvement and the practical application of Contact Pressure Measurement by Means of Ultrasonic Waves

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In the design of joint parts of machines and apparatus, it is very important to have exact information about the contact pressure. In this paper, a quantitative measurement of contact pressure by means of ultrasonic waves using a normal probe has been proposed to measure the contact pressure at a state in which two laminated plates or two laminated cylinders were connected. The experiment was done and the following experimental results are obtained.1. In order to measure the contact pressure quantitatively, the relations between contact pressure and sound pressures of reflected waves from the contact surface and the base were investigated by compressing calibration blocks under various surface roughnesses, in which the contact surface was flat or curved. Each change in the sound pressure of reflected waves becomes smaller as the roughness increases, and then these calibration curves are almost linear.2. Two rectangular plates, a bolted joint and two cylinders composed of boss and bush were compressed under a fixed load, and the sound pressures of reflected waves from the contact surface and the base were measured by the normal probe set on one side of measuring bodies. From the relation between measured curve and caribration curve, the contact pressure was obtained quantitatively. The experimental results were compared with the analytical one. Both results in the two rectangular plates and the bolted joint agree approximately, but both results in the two cylinders are not yet obtained adequate values.3. The cause of the measured error in the two cylinders is found that the curve and the surface roughness between boss and bush are not necessarily uniform.4. From the results destribed above, it is seen that the proposed ultrasonic method is practically for measuring the contact pressure between two laminated plates. Furthermore, the measuring method of the two laminated cylinders will be clarified.