On Generating Fatigue Crack Growth Thresholds

Abstract The fatigue crack growth threshold, defining crack growth as either very slow or nonexistent, has been traditionally determined with standardized load reduction methodologies. These experimental procedures can induce load history effects that result in crack closure. This history can affect the crack driving force, i.e. during the unloading process the crack will close first at some point along the wake or blunt at the crack tip, reducing the effective load at the crack tip. One way to reduce the effects of load history is to propagate a crack under constant amplitude loading. As a crack propagates under constant amplitude loading, the stress intensity factor range, ΔK, will increase, as will the crack growth rate, da/dN. A fatigue crack growth threshold test procedure is experimentally validated that does not produce load history effects and can be conducted at a specified stress ratio, R. The authors have chosen to study a ductile aluminum alloy where the plastic deformations generated during testing may be of the magnitude to impact the crack opening.

[1]  S. Suresh,et al.  Crack initiation under far-field cyclic compression and the study of short fatigue cracks , 1986 .

[2]  J. Newman.  Stress analysis of the compact specimen including the effects of pin loading , 1974 .

[3]  A. Ohta,et al.  Fatigue crack closure over the range of stress ratios from −1 to 0.8 down to stress intensity threshold level in HT80 steel and SUS304 stainless steel , 1978, International Journal of Fracture.

[4]  Tim Topper,et al.  Evaluation of small cycle omission criteria for shortening of fatigue service histories , 1979 .

[5]  K. Minakawa,et al.  On crack closure in the near-threshold region , 1981 .

[6]  G. Marcì.  Fatigue Crack Propagation Threshold: What is it and how is it measured? , 1998 .

[7]  R. Piascik,et al.  An Indirect Technique for Determining Closure-Free Fatigue Crack Growth Behavior , 2000 .

[8]  William A. Herman,et al.  A SIMPLIFIED LABORATORY APPROACH FOR THE PREDICTION OF SHORT CRACK BEHAVIOR IN ENGINEERING STRUCTURES , 1988 .

[9]  W. Elber.  Crack-closure and crack-growth measurements in surface-flawed titanium alloy Ti6Al-4V , 1975 .

[10]  S. Suresh,et al.  Influence of corrosion deposits on near-threshold fatigue crack growth behavior in 2xxx and 7xxx series aluminum alloys , 1982 .

[11]  James Lankford,et al.  THE GROWTH OF SMALL FATIGUE CRACKS IN 7075–T6 ALUMINUM , 1982 .

[12]  Rj Bucci,et al.  Pitfalls to Avoid in Threshold Testing and its Interpretation , 2000 .

[13]  Paul C. Paris,et al.  An evaluation of ΔKeff estimation procedures on 6061-T6 and 2024-T3 aluminum alloys , 1999 .

[14]  D. L. Chen,et al.  Effect of stress ratio and loading condition on the fatigue threshold , 1992 .

[15]  J. Barsom,et al.  Fatigue-Crack Propagation in Steels of Various Yield Strengths , 1971 .

[16]  Rj Bucci,et al.  Fatigue Crack Growth Measurement and Data Analysis , 1981 .

[17]  R. Bucci.  Development of a Proposed ASTM Standard Test Method for Near-Threshold Fatigue Crack Growth Rate Measurement , 1981 .

[18]  C. J. Beevers,et al.  A FATIGUE CRACK CLOSURE MECHANISM IN TITANIUM , 1979 .

[19]  James C. Newman,et al.  Fatigue crack growth thresholds, endurance limits, and design , 2000 .

[20]  J. Newman.  A crack-closure model for predicting fatigue crack growth under aircraft spectrum loading , 1981 .

[21]  R. Ritchie,et al.  Use of a constant Kmax test procedure to predict small crack growth behavior in 2090-T8E41 aluminum-lithium alloy , 1987 .

[22]  James C. Newman,et al.  An Evaluation of the Plasticity-Induced Crack-Closure Concept and Measurement Methods , 1998 .

[23]  Subra Suresh,et al.  Crack initiation in cyclic compression and its applications , 1985 .

[24]  James C. Newman,et al.  A nonlinear fracture mechanics approach to the growth of small cracks , 1983 .

[25]  M. H. Aliabadi.  Localized Damage, Computer-Aided Assessment and Control , 1990 .

[26]  D. S. Dugdale.  Yielding of steel sheets containing slits , 1960 .

[27]  R. Pippan,et al.  The use of fatigue specimens precracked in compression for measuring threshold values and crack growth , 1994 .

[28]  J. B. Chang,et al.  Methods and models for predicting fatigue crack growth under random loading , 1981 .

[29]  David Taylor,et al.  FATIGUE CRACK PROPAGATION BEHAVIOUR OF SHORT CRACKS; THE EFFECT OF MICROSTRUCTURE , 1981 .

[30]  James C. Newman,et al.  A CRITICAL STUDY OF THE CRACK CLOSURE EFFECT ON NEAR‐THRESHOLD FATIGUE CRACK GROWTH , 1983 .

[31]  R. P. Hubbard.  Crack Growth Under Cyclic Compression , 1969 .

[32]  P. C. Paris,et al.  A Critical Analysis of Crack Propagation Laws , 1963 .

[33]  S. Pearson.  Initiation of fatigue cracks in commercial aluminium alloys and the subsequent propagation of very short cracks , 1975 .