Hi Everybody,

I need to conduct Creep Analysis of plastic components 33% glass fiber with nylon 6/66. The material is from the DuPont.

The component needs Creep Analysis check, as these are tested from -40 degree Celsius to 150 Degree Celsius. It has an internal operating pressure of 120 psi.

Kindly let me know how to go with it and what all material data do I require. Also how to find/calculate creep constants for the analysis.

Presently I am having material data which gives me tensile stress from -40C to 150C at different strain levels (0.1% to 3%). Can I calculate C1, C2 and C3 from this data.

Please let me know what more data I require.

Best Regards

Akash A Vandakudri

I rather doubt that the stress-strain curves you have provide time dependent information. At least you did not so state.

One way to proceed is to perform a DMA test.(1) This test can be used to develop master creep curve data for your material for any reference temperature.

I have the older Cosmos/M which provides two possible creep laws, Bailey-Norton and Exponential. Simulation has been incorporating Cosmos/M functionality over the years, but you will need to verify with SW that they are using this law.

Bailey-Norton has four parameters, C

_{0}, C_{1}, C_{2}and C_{T}. The exponential law has six paramaters. So, subject to verification I would say you are provided with Bailey-Norton. Bailey-Norton is of the formε

^{c}= C_{0}σ^{(C1)}t^{(C2)}e^{(-CT/T)}C

_{1}>1 and 0<C_{2}≤1You would have to find the C

_{i}that match the master curve at the reference temperature for which you are doing your creep study. Note that the master curve in DMA is the log of the apparent modulus versus time.(1) Dynamic Mechanical Analysis, Sepe, Michael P., Plastics Design Library, Norwitch NY, 1998, Chapter 4

ISBN 1-884207-64-2