Stiffness Change with Temperature while under compression
Stiffness Change with Temperature while under compression
(OP)
I am modeling a gasket that is initially being compressed in a threaded joint at room temperature and then undergoes a thermal change to -40 deg C. I have created an FEA model to simulate this and extract the reaction forces and contact pressures generated by the gasket at the two temps. I am also accounting for some gasket shrinkage during the thermal change with a thermal expansion/contraction coefficient. In the model, the reaction forces increase dramatically after the step change to -40 deg C. The thermal contraction effect seems to be minor and completely dwarfed by the increase in stiffness at -40 C. I understand the model is predicting these results because I am telling it to use stiffer material properties at -40 C, but what I'm struggling with is if this phenomenon is really physical. Does it make sense that the reaction force would increase in a compressed gland 2-3X just due to temperature change?
Thanks
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RE: Stiffness Change with Temperature while under compression
RE: Stiffness Change with Temperature while under compression
RE: Stiffness Change with Temperature while under compression
RE: Stiffness Change with Temperature while under compression
Be careful of the material glass transition temperature. As you are mostlikely aware FEA can not model material phase transitions. Most rubber formulations transistion to a glass prior to -40. Even if the Tg listed for the rubber is below -40, the transition from a rubber (very viscous solid) to a glass occurs over a temperature range. Therefore the modulus is going to start increasing prior to Tg.
I agree with Compositepro, especially when you consider that in reality a rubber gasket is going to leak at cold temperatures not hot temperatures due to the coefficient of thermal expansions involved in the assembly, therefore contact pressure is not increasing.
Good luck.