TY - GEN

T1 - Effect of orientation of small defects on fatigue limit of steels

AU - Lorenzino, Pablo

AU - Okazaki, Saburo

AU - Matsunaga, Hisao

AU - Murakami, Yukitaka

PY - 2014

Y1 - 2014

N2 - In order to clarify the effect of defect orientation on the fatigue limit of three types of steels; JIS-S15C, JIS-S45C and JIS-SNCM439, a small semi-circular slit was introduced into the surface of a round specimen. The slits were tilted at 0°, 30° or 60° with respect to the plane normal to the loading axis, but all of them had the same defect size, \vec{area} = 188 μm, where the area denotes the area of the domain defined by projecting the defect on a plane normal to the loading axis. In all the combinations of the materials and tilting angles, a non-propagating crack was found at the fatigue limit, i.e. the fatigue limit was determined by the non-propagation condition of crack initiated from the defect. In JIS-S15C and JIS-S45C, the fatigue limit was nearly independent of the tilting angle, which was in good agreement with the predicted value by the \vec{area} parameter model. On the other hand, in JIS-SNCM439, the fatigue limit was also in agreement with the prediction at the tilting angle of 0°, but it increased with an increase in the tilting angle. These results indicated that the \vec{area} parameter model can predict a conservative fatigue limit for the tilted defects. In this paper, the mechanistic reason for the effect of the tilting angle on the fatigue limit will be discussed by paying special attention to the crack path and length of non-propagating crack.

AB - In order to clarify the effect of defect orientation on the fatigue limit of three types of steels; JIS-S15C, JIS-S45C and JIS-SNCM439, a small semi-circular slit was introduced into the surface of a round specimen. The slits were tilted at 0°, 30° or 60° with respect to the plane normal to the loading axis, but all of them had the same defect size, \vec{area} = 188 μm, where the area denotes the area of the domain defined by projecting the defect on a plane normal to the loading axis. In all the combinations of the materials and tilting angles, a non-propagating crack was found at the fatigue limit, i.e. the fatigue limit was determined by the non-propagation condition of crack initiated from the defect. In JIS-S15C and JIS-S45C, the fatigue limit was nearly independent of the tilting angle, which was in good agreement with the predicted value by the \vec{area} parameter model. On the other hand, in JIS-SNCM439, the fatigue limit was also in agreement with the prediction at the tilting angle of 0°, but it increased with an increase in the tilting angle. These results indicated that the \vec{area} parameter model can predict a conservative fatigue limit for the tilted defects. In this paper, the mechanistic reason for the effect of the tilting angle on the fatigue limit will be discussed by paying special attention to the crack path and length of non-propagating crack.

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U2 - 10.1051/matecconf/20141207001

DO - 10.1051/matecconf/20141207001

M3 - Conference contribution

AN - SCOPUS:84903291769

SN - 9782759812745

T3 - MATEC Web of Conferences

BT - FDMD II - JIP 2014 - Fatigue Design and Material Defects

PB - EDP Sciences

T2 - Fatigue Design and Material Defects, FDMD II - JIP 2014

Y2 - 11 June 2014 through 13 June 2014

ER -