Fatigue Life Estimation of Welded Joints considering Statistical Characteristics of Multiple Surface Cracks

복수 표면균열의 확률적 특성을 고려한 용접부 피로수명 평가

  • 한정우 (한국기계연구원 기계시스템신뢰성연구센터) ;
  • 한승호 (한국기계연구원 기계시스템신뢰성연구센터)
  • Published : 2005.11.01


Multiple surface crack distributed randomly along a weld toe influences strongly on the fatigue crack propagation life of welded joint. It is investigated by using statistical approaches based on series of systematic experiments. From the statistical results, initial crack numbers and its locations follow the normal distribution, and the probability of initial crack depths and lengths can be described well by tile Weibull distribution. These characteristics are used to calculate the fatigue crack propagation life, in which the mechanisms of mutual interaction and coalescence of the multiple cracks are considered as well as the Mk-factors obtained from a parametric study on the crack depths and lengths. The automatic calculation is achieved by the NESUSS, where the parameters such as the number, location and size of the cracks are all treated as random variables. The random variables are dealt through the Monte-Carlo simulation with sampling random numbers of 2,000. The simulation results show that the multiple cracks lead to much shorter crack propagation life compared with those in single crack situation. The sum of the simulation and tile fatigue crack initiation life derived by the notch strain approach agrees well with the experiments.


Multiple Surface Crack;Fatigue Crack Propagation Life;M-Fractor;Normal Distribution;Weibull Distribution;Monte-Carlo Simulation


  1. Suh, C., Hwang, N. and Park, M., 1994, 'Fatigue Crack Growth, Coalescence Behavior and Its Simulation on Multi-surface Cracks,' Transactions of KSME, Vol. 18, No. 3, pp. 716-728
  2. Kim, J., Lee, J. and Hong, C., 1996, 'Fatigue Life Prediction for Multiple Surface Cracks in Finite Plates,' Transactions of the Society of Naval Architecture of Korea, Vol. 33, No. 4, pp. 75-86
  3. Han, J., Han, S., Shin, B. and Kim, J., 2004, 'Fatigue Life Estimation of Welded Joints by using Mk-factor under a Propagation Mechanism of Multiple Collinear Surface Cracks,' Journal of KWS, Vol. 22, No. 4, pp. 369-377
  4. Han, J., Han, S., Shin, B. and Kim, J., 2004, 'Fatigue Life Estimation of Cruciform Welded Joint considering Multiple Collinear Surface Cracks,' Transactions of KSME (A), Vol. 28, No. 10, pp. 1549-1557
  5. Bang, H. and Yoon, H., 2000, 'The Probability Distribution of Fatigue Crack Propagation Life considering Effect of Crack Coalescence,' Transactions of KSME (A), Vol. 24, No. 5, pp. 1281-1287
  6. Nilsson, F., Brickstad, B. and Skanberg, L., 1990, 'Failure Probability of Nuclear Piping due to IGSCC,' Int. J. Pres. Ves. & Piping, Vol. 43, pp. 205-217
  7. Xie, L., 1999, 'Multi-crack Growth/Coalescence Simulation and its Role in Passive Component Leak-before-break Concept,' Nuclear Engineering and Design Vol. 194, pp. 113-122
  8. Yamada, K., Makino, T., Baba, C. and Kikuchi Y., 1980, 'Fatigue Analysis Based on Crack Growth from Toe of Gusset End Weld,' Journal of JSCE, Vol. 303, pp. 31-41
  9. Yamada, K., Makino, T. and Kikuchi Y., 1979, 'Fracture Mechanics Analysis of Fatigue Cracks Emanating from Toe of Fillet Weld,' Journal of JSCE, Vol. 292, pp. 1-12
  10. Madox, S., 1975, 'An Analysis of Fatigue Cracks in Fillet Welded Joints,' International Journal of Fracture, Vol. 11, No. 2 pp. 221-243
  11. Bowness, D and Lee, M., 2000, 'Prediction of Weld Toe Magnification Factors for Semi-elliptical Cracks in T-butt joints,' International Journal of Fatigue, Vol. 22, pp. 369-387
  12. Han, J., Han, S., Shin, B. and Kim, J., 2004, 'Fatigue Life Estimation of Welding Details by Using a Notch Strain Approach,' Transactions of KSME (A), Vol. 28, No. 7, pp. 977-985