Behavioral Characteristics of Fatigue Cracks in Small Hole Defects Located on Opposite Sides of the Shaft Cross Section

  • Sam-Hong (Department of Mechanical Engineering, Korea University) ;
  • Il-Hyuk (Department of Mechanical Engineering, Graduate School, Korea University) ;
  • Jeong-Moo (Research Institute of Engineering & Technology, Korea University)
  • Published : 2004.10.01

Abstract

The shaft with the circular cross section has symmetric structural combination parts to keep the rotating balance. Hence the crack usually initiates from symmetric combination parts due to the stress concentration of these parts. In this study to estimate the fatigue behavior of symmetric cracks, the fatigue test was performed by using a rotary bending tester and the specimen with symmetric defects in circular cross section. The characteristics of crack initiation and propagation on the symmetric surface cracks in circular cross section were examined. We also observed the internal crack using the oxidation coloring method and investigated the fatigue behavior using the relationship between the surface crack and the internal crack. As a result, the fatigue life of symmetric cracks was reduced by 35% compared to that of a single crack. We examined the characteristics of fatigue behavior of elements with symmetric cracks using internal crack propagation rate and maximum stress intensity factor range that were obtained from an approximation method.

Keywords

References

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