hi!
i am interested in the fatigue crack growth of a cracked body.Recently,i am stucked by a problem of how is the stree-strain relationship near the crack tip under cyclic loading.As we know,the HRR field near a crack tip under monotanic loading is well solved.So,i doublt that if the type of the HRR formulation can still be used under cyclic loading.If not,why?And how to solve this problem?if there is any suggestions or references ,i would be appreciated!
R: stress-strain field near the crack tip under cyclic loading
Once you prescribe a stress-strain model, such as the J2 flow theory, you should be able to solve the boundary-value problem, possibly by using a numerical method. Such a boundary-value problem should have been atempted. I recall hearing about it. However, solutions of this kind have not been useful in addressing the engineering problem of fatigue.
The widely used approach to crack growth under cyclic loading is that due to Paul Paris. The best introduction to the approach is Paris's original paper published in 1961.
In reply to R: stress-strain field near the crack tip under cyclic loading by Zhigang Suo
Dear sir： Thanks for
Dear sir：
Thanks for your reference.Yesterday,i have seen your discussion with Mike。Though i do not understand very well, i still learn too much from your attitude to science!Now ,i want to explain my problem more clearly. The HRR field near the crack tip has been accepted for years under monotonic loading, so i want to find a way to represent the stress-strain relationship near a crak-tip under cylic loading.Maybe ,it is more or less the same formulation as HRR form.If not ,may i get an empirical one by FEA result? I want to try the following tow ways:
one,the crack model was solved with the cyclic constitutive law ;
two, the crack model was solved with the monotonic constitutive law.
i doubt that whether they are practicable? i am looking forword to your suggestion!thanks!
yours sincerely !
cohesive zone model may work
Dear Chen:
The cohesive zone model may work for elastoplastic materials as well as quasibrittle materials. It can conveniently take care of cumulative damage over cycling. Thousands and even tens of thousands of cycles can be simulated on a regular PC nowadays. If you look into the recent literature, you may find quite many pulications applying it to simulating fatigue crack growth. One early reference of mine is given below FYI (though my interest has shifted). Good luck.
Yang, B., Mall, S., and Ravi-Chandar, K. (2001). IJSS 38, 3927-3944. (Please let me know if you need a copy of the reprint.)
Bo
In reply to cohesive zone model may work by Bo Yang
Cohesive zone model
Dear sir:
thanks for help!I have downloaded some papers linked to this usefull model ! By scanning them ,i have some questions as follows:
first, whether it can solve the cyclic stress-strain ralationship near the fatigue crack tip;
second,by this method when the crack starts growing and how much the length per each cycle is.
i would be appreciated for your reply!