Paris law:da/dN=C(K-Kth)m
Yield stress of high strength steel is over 460 Mpa here.
Kth is threshold stress strength factor.
I can only find that of mild steel in BS7910-2005 and ASTM and JSSC
Hu Lili
Unfortunately, you cannot get ready-made values of the constants you are looking for. You have to conduct the fatigue crack growth rate (FCGR) experiments, plot the crack growth rate (da/dN) vs stress intensity factor range (delK) to get these numbers. The slope of the plot would give you the "m" and the Y intercept will give you the value of C. You may refer to ASTM E647 on how to conduct this test.
If you know the steel specification, you may try your luck with any published literature. Be cautioned that the processing condition may not be the same and the numbers that you pick from the literature need not be accurate. Typically the value of "m" for steels would be in the range of 3-5 and that of "C" in the range of 10^-8 to 10^-10 mm/cycle.
The best way is to conduct the FCGR test to get these numbers.
Material constant m, crack length and the fracture toughness's Delta are also unknown.
Hu Lili
Unfortunately, you cannot get ready-made values of the constants you are looking for. You have to conduct the fatigue crack growth rate (FCGR) experiments, plot the crack growth rate (da/dN) vs stress intensity factor range (delK) to get these numbers. The slope of the plot would give you the "m" and the Y intercept will give you the value of C. You may refer to ASTM E647 on how to conduct this test.
If you know the steel specification, you may try your luck with any published literature. Be cautioned that the processing condition may not be the same and the numbers that you pick from the literature need not be accurate. Typically the value of "m" for steels would be in the range of 3-5 and that of "C" in the range of 10^-8 to 10^-10 mm/cycle.
The best way is to conduct the FCGR test to get these numbers.
You have several unknown parameters.
As said before, If you don't have any values from the literature, you have to do the experiment yourself, then plot log(da/dN) as a function of log K.
log(da/dN)= log C + m log (K-Kth)
to get C, m and Kth
You may see in my paper "Strength testing and analysis of fatigue crack growth in selected aircraft materials."
thank you all. i do not know how to reply to someone, so may i ask a question to Prof. Sylwester Klysz?
what does Specimen 2-05-71 in table 4 of STRENGTH TESTING AND ANALYSIS OF FATIGUE CRACK GROWTH IN SELECTED AIRCRAFT MATERIALS mean? and how can you do so many fatigue tests to get c and m? I believe it cost a lot.
Look at the extensive work by Edward Troiano and his co-workers at the US Army Benet Research Labs. Start by clicking this google scholar link: https://goo.gl/H0hya8
https://www.researchgate.net/publication/301348952_Licensed_Under_Creative_Commons_Attribution_CC_BY_Investigation_on_Mode_-_I_Fracture_Parameters_Using_Steel_Fibers_in_High_Strength_Concrete?ev=prf_pub
Article Licensed Under Creative Commons Attribution CC BY Investigat...
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Mechanics
- Classical Mechanics
- Continuum Mechanics