Learning Forum

[bhanu34]

Hi Guys,

How to assess the fatigue failure of the Plastic materials specifically Thermoplastics in which the Fatigue failure occurs due to increase in temperature rather than crack propagation at high frequency?

[peteroznewman]

Do you mean that the internal temperature of the plastic increases due to the high frequency vibration of a load?

[bhanu34]

Hi

Yes, The increase in the temperature is due to the damping capacity of polymer (measure of the absorption of energy by the polymer and dissipation as heat during each cycle). the failure in such materials is due to the drastic increase in temperature rather than the crack propagation

To my understanding, nCode and ANSYS Fatigue tool softwares calculate Fatigue life based on the crack propagation principle

I need to know whether we can identify the Fatigue life of such polymers in which the failure occurs due to the increase in temperature rather than the crack propagation?

Thanks

Bhanu

[bhanu34]

When I mentioned high frequency, I mean to say the cycle frequency in the Fatigue testing (It is the number of cycles per unit time)

[peteroznewman]

Is the load a constant displacement or a constant force?

Is the stress above or below the yield strength of the material?

Can you do a hand calculation of the thermal energy created on each cycle?

The ANSYS Fatigue Tool can use experimentally measured SN curve for Stress-Life calculations or coefficients for Strain-Life calculations. The curve or coefficients do not depend on temperature.

Here is a relevant article.