crack growth parameters for carbon and alloy steel 2

[alisari61]

Does anyone know crack growth parameters (C and m) values for Carbon steels and alloy steels?

Both Carbon and alloy steels have high strength, over 70 ksi yield and over 90 ksi tensile strength

Thank you

 

[CoryPad]

You mean the Paris equation?

da/dN = C ([Δ]K)^m

Some worst-case numbers according to Barsom and Rolfe:

Microstructure C m
Ferritic-pearlitic 6.89 x 10^-9 3.0
Martensitic 1.36 x 10^-7 2.25
Austenitic 5.61 x 10^-9 3.25

R = 0
Units for C: (mm/cycle)/(MPa[√]m)^m

Reference: Barson and Rolfe, Fracture and Fatigue Control in Structures, 1987, Prentice-Hall

 

[alisari61]

Thank you so much.

Since I am only a structural engineer, I do not have too much info regarding the types of steels (ferritic, austentic, martensitic etc). How should I find out the type of carbon and alloy steels? Can we say they are martensitic since their yield strength is higher than 70 ksi?

Thank you again.

 

[CoryPad]

No you can't say that. You need to look at the material specification or test a part.

 

[alisari61]

I have test results below for carbon and alloy steel. Do they tell type of microstructure?


Alloy - Material Test Report - 1

Grade: 4130R

Normalization Temperature: 1650 F (899 C)
Quench Temperature: 1600 F (871C)
Chemical Analysis:
C: 0.31
Mn: 0.55
P: 0.009
S: 0.011
Si: 0.25
Cu: 0.22
Ni: 0.07
Cr: 0.92
Mo: 0.178
Sn: 0.007
V: 0.002

Carbon - Material Test Report - 1

Grade: 1035R

Chemical Analysis:
C: 0.34
Mn: 0.81
P: 0.006
S: 0.014
Si: 0.24
Cu: 0.22
Ni: 0.08
Cr: 0.13
Mo: 0.024
Sn: 0.007
V: 0.001

Grain size: Fine grain (Meets or exceeds grain size 5)

 

[metengr]

If you are interested in ball park fatigue crack growth information, I would start here, at least for the 1035 steel being in a normalized heat treatment condition, based on what you provided above, look at data for the 1045 normalized in this database;

https://efatigue.com/constantamplitude/crackgrowth/materials/?from_cacrackgrowth=1

For the low alloy, you could try to conduct an internet search for starters.