# 쇼트피닝 가공한 스프링강의 고온 피로 파괴 특성에 관한 연구

• Park, Keyung-Dong (Department of Mechanical Engineering, Pukyong National University) ;
• Shin, Yeong-Jin (Department of Mechanical Engineering, Pukyong National University)
• 박경동 (부경대학교 기계공학부) ;
• 신영진 (부경대학교 기계공학부)
• Published : 2006.08.31

#### Abstract

The lightness of components that was required in automobile and machinery industry requires high strength of components. In particular, manufacturing process and new materials development for solving the fatigue facture problem attendant upon high strength of suspension of automobile are actively advanced. In this paper, the effect of compressive residual stress of spring steel(JISG SUP-9)by shot-peening on fatigue crack growth characteristics in high temperature($100^{\circ}C,\;150^{\circ}C,\;180^{\circ}C$)was investigated with considering fracture mechanics. So, we can obtaint the followings. (1) Compressive residual stress is decreased with increasing the test temperature. (2) The effect of compressive residual stress on fatigue crack growth behavior in high temperature is increased below ${\Delta}K=17{\sim}19MPa{\sqrt{m}}$. (3) It was investigated by SEM that the constraint of compress residual stress for plastic zone of fatigue crack tip was decreased in high temperature as compared with room temperature.

#### References

1. R. D. Gillespie, 'Its Effect on Process Consistency and Resultant Improvement in Fatigue Characteristics', Proc. of the 5th International Conference on Shot Peening, Vol. 1, Oxford, pp. 81-90, 1993
2. A. Tange, N. Takamura, 'Relation Between Shotpeening Residual Stress Distribution and Fatigue Crack Propagation Life in Spring Steel', Proc, of the 4th International Conference on Shot-Peening, Vol. 1, Tokyo, pp. 243-253, 1990
3. K. D. Park, 'A Study of Crack tip Characteristics and Fatigue crack transition in High temperature in Low alloy steel for atomic reactor', Dong-a Uni. Thesis of doctorate, pp. 24-28, 1983
4. O. Murakami, A Guide of Fracture Mechanics, pp. 121-127, O-Mu Company, 1979
5. S. G. Jung, S. H. Lee, A guide of Shot peening Processing, pp. 6 -12, Se-Hwa Pub., 2001
6. H. Wohlfahrt, 'The Influence of Peening Conditions on the Resulting Distribution of Residual Stress', Proc, of the 2nd International Conference on Shot Peening, Vol. 1, Chicago, pp. 316-331, 1984
7. J. Willenborg, R. M. Engle and H. A. Wood, 'A Crack Growth Retardation Model Using and Effective Stress Concept', AFFDL-TM-71-1-FBR, 1971