AN ANALYTICAL PROCEDURE FOR PREDICTING OPENING LOADS OF CRACKS AT NOTCHES

— An analytical procedure for the prediction of opening load levels for cracks growing from notches is presented, and estimates are made using experimental crack opening load data. The procedure is based on McClung's original procedure for estimating the local elastic-plastic stress—strain situation at the point of a hypothetical crack tip in a notched but uncracked body. A crack opening stress value for a crack in an urmotched body under the same stress—strain condition is then predicted. The corresponding opening load level for the crack stress-strain configuration in the notched but uncracked body is then predicted with a simple backward calculation. For the evaluation of the elastic-plastic stress distribution, simple analytical relationships, such as Neuber's rule, are used. Estimation of the crack opening stress level is performed using various crack opening stress formulae reported in the literature for cracks in unnotched specimens under a uniform stress distribution. The accuracy of all the investigated crack opening stress formulae within the scope of the presented procedure is checked, and discussed in detail using experimental data sets for opening load levels of comer cracks and through-thickness cracks in notched specimens of FeE460 and A15086. The predicted results using Newman's crack opening stress formulae, simply modified in respect to the definition of the flow stress, have been identified to be qualitatively and quantitatively consistent with the trends observed in experimental crack opening data.

[1]  W A Matejka,et al.  A High Purity Approach to High Chromium Ferritic Stainless Steels , 1975 .

[2]  J. Schijve,et al.  Some formulas for the crack opening stress level , 1980 .

[3]  A. U. De Koning,et al.  A Simple Crack Closure Model for Prediction of Fatigue Crack Growth Rates Under Variable-Amplitude Loading , 1981 .

[4]  R. C. McClung,et al.  A Simple Model for Fatigue Crack Growth Near Stress Concentrations , 1991 .

[5]  T. Seeger,et al.  THE CONSEQUENCES OF SHORT CRACK CLOSURE ON FATIGUE CRACK GROWTH UNDER VARIABLE AMPLITUDE LOADING , 1991 .

[6]  James C. Newman,et al.  Recent developments in analysis of crack propagation and fracture of practical materials. [stress analysis in aircraft structures] , 1978 .

[7]  Tim Topper,et al.  The effective stress range as a mean stress parameter , 1992 .

[8]  S. Mall,et al.  Dugdale plastic zone size and CTOD equations for the compact specimen , 1984 .

[9]  J. Schijve.  Fatigue Crack Closure: Observations and Technical Significance , 1986 .

[10]  Abul K. Azad,et al.  FRACTURE ENERGY OF WEAKLY REINFORCED CONCRETE BEAMS , 1989 .

[11]  W. Elber.  The Significance of Fatigue Crack Closure , 1971 .

[12]  G. Masing,et al.  Eigenspannungen und Verfestigung beim Messing , 1926 .

[13]  R. C. McClung,et al.  Closure and Growth of Fatigue Cracks at Notches , 1992 .

[14]  H. Neuber.  Theory of Stress Concentration for Shear-Strained Prismatical Bodies With Arbitrary Nonlinear Stress-Strain Law , 1961 .

[15]  Kumar,et al.  Engineering approach for elastic-plastic fracture analysis , 1981 .

[16]  T. Topper,et al.  A study of the effect of mechanical variables on fatigue crack closure and propagation , 1986 .