Creep Strain Power Law

[flaus77]

I am in great need for the coefficients of the Creep Strain Power Law, viz., the C1, C2, and C2 coefficients in the equation,

Creep Strain = C1*((Uniaxial Stress)^ C2))*(time^ C3)

for AISI 1020 steel at 0F and 300F.

Please help and thank you with much appreciation!

 

[metengr]

flaus77
There is no measurable creep deformation at 0 deg F and 300 deg F for structural or low carbon steel. The time dependent properties of creep for low carbon steels is observed at 700 deg F and higher.

 

[flaus77]

ok ... then, what would be the coefficients at lets say 700F and
850F?

 

[metengr]

Why do you need to use the creep strain power law? You most likely would need to perform an extensive search for papers on this subject and hope someone has published the values.

http://www.springerlink.com/content/x226134672258719/

If you are looking to evaluate x% of creep deformation in either 10,000 hours or 100,000 hrs as a function of service temperature, there is data available for carbon steel at or above 700 deg F.

 

[flaus77]

Thank you for your most timely response ... could you please direct me to the data available for carbon steel pertaining to x% of creep deformation as a function of service temperature ...?

I am trying to use the creep strain power law to determine the extent of deformation and strain of a shell material subjected to
creep constant stresses at elevated temperatures using FEA ...

 

[metengr]

flaus77;
I doubt that you have a copy of the ASME B&pv Code, Section II, Part D. I will list some of the allowable stress values that are time dependent, meaning creep deformation would most likely govern-

ASME SA 36 structural steel

700 deg F 15.6 Ksi
750 13.0
800 10.8

The stress above are based on the following

(b) At temperatures in the range where creep and
stress rupture strength govern the selection of stresses,
the maximum allowable stress value for all materials
is established by the Committee not to exceed the
lowest of the following:
(1) 100% of the average stress to produce a creep
rate of 0.01%/1000 hr;
(2) 100Favg% of the average stress to cause rupture
at the end of 100,000 hr;
(3) 80% of the minimum stress to cause rupture
at the end of 100,000 hr.

Most likely, (a) above would govern.

 

[metengr]

Most likely, (a) above would govern.

Sorry, it should be (b)(1), and not (a).

 

[flaus77]

Thank you for the info ...unfortunately, this data does not help me with the coefficients ...