Probabilistic analysis of the uncertainty in the fatigue capacity of welded joints

Abstract This paper presents the results of a study of the uncertainty in the fatigue capacity (constant amplitude fatigue life) of welded steel joints, due to uncertainties related to geometrical and material parameters. An efficient method of probabilistic fracture mechanics analysis is described and applied. A linearelastic fracture mechanics model and the Paris-Erdogan law of crack propagation were adopted. Stressintensity factors were evaluated by employing an influence function method, which is very cost-effective. The main parameters were treated as stochastic variables. Data for weld and crack geometry of the non-load carrying fillet weld cruciform joint selected as the example joint in the study, were recorded from specimens. Other data were compiled from the literature. The uncertainties associated with the basic variables were transformed into a measure of uncertainty of the fatigue capacity by employing the Monte Carlo simulation technique. The relative contributions to the uncertainty in the fatigue capacity from the various factors were also compared. The S-N data established analytically compared fairly well with test data obtained with 42 specimens. The probabilistic fracture mechanics analysis provided a sufficient sample of data to allow a test of analytical probability distributions to the fatigue life. The fit of two- and three-parameter lognormal and Weibull distributions was examined. Only the three-parameter lognormal pdf passed the chi-square test on the 5% confidence level.

[1]  S J Maddox,et al.  FATIGUE CRACK PROPAGATION DATA OBTAINED FROM PARENT PLATE, WELD METAL AND HAZ IN STRUCTURAL STEELS , 1974 .

[2]  A. Huitson,et al.  Statistical Models in Applied Science. , 1976 .

[3]  C. E. Richards,et al.  Fatigue crack propagation through weld heat affected zones , 1971 .

[4]  R. W. Thresher,et al.  Stress-Intensity Factors for a Surface Crack in a Finite Solid , 1972 .

[5]  G. Irwin.  Crack-Extension Force for a Part-Through Crack in a Plate , 1962 .

[6]  Masanori Kawahara,et al.  A Proposed Design Basis with Special Reference to Fatigue Crack Propagation , 1973 .

[7]  E Haibach.  CUMULATIVE DAMAGE IN MARINE WELDED STRUCTURES , 1976 .

[8]  T Bokalrud.  FINITE ELEMENT ANALYSIS OF BUTT WELD AND CRUCIFORM JOINTS TO DETERMINE THE SIGNIFICANCE OF INTERNAL CRACK-LIKE DEFECTS , 1978 .

[9]  R. W. Finger,et al.  Investigation of deep flaws in thin walled tanks , 1969 .

[10]  John W. Fisher,et al.  FATIGUE STRENGTH OF STEEL BEAMS WITH WELDED STIFFENERS AND ATTACHMENTS , 1974 .

[11]  S. J. Maddox,et al.  An analysis of fatigue cracks in fillet welded joints , 1975 .

[12]  Pedro Albrecht,et al.  RAPID CALCULATION OF STRESS INTENSITY FACTORS , 1977 .

[13]  Pedro Albrecht,et al.  FATIGUE OF PERIODICALLY OVERLOADED STIFFENER DETAIL , 1976 .

[14]  Lawrence L. Kupper,et al.  Probability, statistics, and decision for civil engineers , 1970 .

[15]  A. Wald,et al.  On the Choice of the Number of Class Intervals in the Application of the Chi Square Test , 1942 .

[16]  Stephen John Maddox.  A fracture mechanics analysis of the fatigue strength of welded joints , 1972 .

[17]  A. M. Freudenthal,et al.  On the statistical interpretation of fatigue tests , 1953, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[18]  A. Freudenthal,et al.  Planning and Interpretation of Fatigue Tests , 1952 .