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- Title
An experimental and theoretical approach for an estimation of ΔK[sub th].
- Authors
Herold, H.; Streitenberger, M.; Zinke, M.; Orazi, L.; Cammarota, G. P.
- Abstract
The existence of a fatigue threshold value may affect the design process when a damage-tolerant design is considered that uses non-destructive techniques for evaluating the shape and dimensions of the defects inside materials. Obviously it should be possible to estimate the stress field surrounding these defects and this is not generally a problem with modern numerical methods. Many factors are involved in determining the growth rate of a fatigue crack. Some of these are highly significant and it is possible to obtain the coefficients of a correlation function. Some others are not well defined and the only effect is to expand the scatter of experimental data. Consider the sigmoidal curve we obtain when plotting the crack growth rate versus the applied ΔK[sub I] . A very difficult parameter to measure but very useful for fatigue design is the ΔK[sub Ith] value, because below this value a crack may be forming, hence, here ΔK[sub Ith] is defined by the transition between a normal (e.g. 10[sup -10] m/cycle) and a very low range of crack growth rate (<10[sup -10] m/cycle). The ΔK[sub Ith] value is very difficult to obtain by experimental methods because the growth rate is of the order or less than the atomic lattice span (3 × 10[sup -10] m/cycle), but we can correlate the transition value with the cyclic crack tip plastic zone size and other structural parameters of metallic materials. The aim of this work is to offer a contribution about the parameters which influence ΔK[sub Ith] in stainless steels and welded joints based on the crack tip plastic zone radius.
- Subjects
FRACTURE mechanics; MATERIAL fatigue; STAINLESS steel fatigue; WELDED joint fatigue
- Publication
Fatigue & Fracture of Engineering Materials & Structures, 2000, Vol 23, Issue 9, p805
- ISSN
8756-758X
- Publication type
Article
- DOI
10.1046/j.1460-2695.2000.00314.x