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[BALAMUGESH M]

hi,
i am working on creep analysis project. in that i need to benchmark primary and secondary creep strain values with ANSYS creep results. i have inputs like time dependent creep strain values, deflection and constant stress and temperature. so how can i proceed with this and how can i benchmark the data.

(Kind note: Actually, i tried modified time hardening and generalized exponential models for primary creep data in ANSYS. where in these models the deformation is less comparative to experimental value. and result is not converging. what should i change what should i include any recommendations
the input data are only for one experiment result, after this benchmark i need to fins creep failure stress and time i,e tertiary creep(if anyone know that kindly give some info))

[Aniket]

Can you please post your question again?

-Aniket

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[BALAMUGESH M]

hi,
i am working on creep analysis project. in that i need to benchmark primary and secondary creep strain values with ANSYS creep results. i have inputs like time dependent creep strain values, deflection and constant stress and temperature. so how can i proceed with this and how can i benchmark the data.

(Kind note: Actually, i tried modified time hardening and generalized exponential models for primary creep data in ANSYS. where in these models the deformation is less comparative to experimental value. and result is not converging. what should i change what should i include any recommendations
the input data are only for one experiment result, after this benchmark i need to fins creep failure stress and time i,e tertiary creep(if anyone know that kindly give some info))

[John Doyle]

If I understand your statement, you "have inputs like time dependent creep strain values, deflection and constant stress and temperature".  Did you use this data to curve fit time hardening creep?  If not, then I would recommend you follow curve fitting procedures documented in Section 6.4 of MAPDL reference Guide.  6.4. Creep Material Curve-Fitting (ansys.com)

If you have already curve fitted a creep model and you are trying to validate what you have, I would recommend going back to the source of your original input and try to reproduce (for comparison and validation) the same experiment that generated the input.

[BALAMUGESH M]

hi, 
yes i have done curve fitting using modified time hardening and Generalized exponential form. if i use those constants and run the simulation i didnt get the exact deformation as from experimental value. so what are the changes need to change or modify. and can you recommend how to do tertiary creep analysis(using APDL or any other software) with this inputs. and what are ways to benchmark and tertiary analysis method

[John Doyle]

The standard creep options listed in Table 4.2 of the MAPDL Material Reference Guide are limited to primary and secondary creep and do not capture the higher rate of creep strain development that occurs at the onset of tertiary creep.  

Having said that, if you are certain that you are observing tertiary creep in your application, there are other options that might be helpful.  

You can try to combine creep with metal plasticity and possibly a generalized damage model.  See Section 7.1, of MAPDL Material Reference Guide, for a list of valid material combinations.  There is also an APDL example input documented in Section 7.2 of the combination of plasticity, creep and damage.  There are no curve fitting tools available in MAPDL for the damage model options. 

If material combinations is not helpful, it is also possible to write your own user creep routine and link it into the standard MAPDL code.  Please refer to the MAPDL Programmer Reference Guide for more details.

[BALAMUGESH M]

hi,

i need to know, in experimental test analysis 0.143mpa load is applied in the top surface of the model, same i need to do analysis, instead of force i will apply 0.143mpa pressure in the top surface, so my question is if i cut my model into four symmerty part and apply the pressure, what will be the value need to be applied..?? will it be increased by 4 times are remain same??

[BALAMUGESH M]

all material models all the things i cross checked nothing varies, tell me what simulating settings need to adjust or focus. and can you tell me how i proceed fruther to tertiary creep analysis and finding the rupture time and failure stress??