• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.421-424
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• 2000

Valve springs with high fatigue strength corresponding to the incresement of working stresses, are required for the higher generating power and the better fuel economy of automobile engines. For this purpose, high strength oil tempered wires are being used. By a method of the high strength for the valve spring, modification of manufacturing processes is being applied. In this case, the cause and effect for the improvement of the fatigue strength has not yet been explained obviously. Therefore, in this report, comparison of fatigue life between valve springs of conventional processes with oil tempered wires and new manufacturing processes was made. As a result of the fatigue test, the fatigue life of the latter was attained maximum 7 times than that of the former. It was cleared that the improvement of the fatigue life was caused by difference of compressive residual stresses at depth of 0.2mm below the inner side surface of both valve springs.