Nobuo OGAWA*, Tomohiro HIRANO*, Kimiharu OHTA*, Kosuke HOSINO** and Koji ARAI** * Department of Mechanical Engineering, Faculty of Science and Technology Science University of Tokyo, Noda City Yamasaki 2641, Chiba, Japan **Nicchu Corporation, Abiko City Aoyama 17, Chiba Japan
Shotpeening is of wide application in manufacturing field, for example on a gear and on a turbine-blade. An estimation of effects of shotpeening is carried out by measurements of an arc height and a coverage using Almen-Strip. The methods can not measure quantitative measurements of the impact number and of the impact load due to the shotpeening to the measuring points. In the present article, the new high quantitative measuring method is presented by using the piezoelectric sensor. The piezoelectric sensor impacting shots generates impulse voltage depend on the impulse load. The degree of the impulse voltage generated by impact of the shots is determined depend on the mass and impact velocity to piezoelectric sensor. Therefore, the impulse load and the impact number can be measured by the measuring of the impulse voltage generated by the impact the shots. Here, the relationship between the impulse load and the impulse voltage is determined by a preparatory experiments depend on type of the sensor. The data measured by the piezoelectric sensor are processed by using the microcomputer through AD converter. The impact of the shots generates impulse voltage following damped wave. In this investigation number and voltage of the first impulse waves are needed. The data under the threshold level determined by a preparatory experiment are omitted. Only number and degree of the first impulse voltage are measured and impulse load is calculated using the relationship between output of the piezoelectric sensor and impulse load measured by a preparatory experiments. The piezoelectric sensor made of ceramics is strong and merely damaged by the impact of the shots. In this study, first, the relationship between the results by the piezoelectric sensor and the residual stress by X-ray methods is discussed in. Second the data taking by piezoelectric sensor mounted on the gear model are analyzed. The distribution of impact number on the gear is measured as the application of new piezoelectric sensor method to industrial fields. The data are given on the surface of Almen-Strip. The residual stress varies with the peening time. profile has the maximum point. The profile shows decreasing of the residual stress depend on the peening time after the maximum point. The residual stresses are released partially with large plastic deformation due to the shotpeening. As a result, the residual stress has small value to the peening time. The piezoelectric sensor clears the distribution of the impulse load on the surface of the work. On the other hand, the distribution of share stress inside the work are given by load on the surface theoretically. Therefore the impulse load measured by piezoelectric sensor can conjecture the maximum point and the value of the share stress in the work. Consequently, effects of the shotpeening are quantified by the new method.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 2, pages 871 - 874 Publisher:Ashgate Publishing Company
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