Von mise stress calculation during FRF simulation

Rex_22369

Dear,

I did a sweep calculation for a Degas Bottle, the frequency range is from 15Hz to 100Hz, acceleration level is 3g, when I got the response stress after the model frequency simulation, I outputted the stress tensor of the most critical element, but I found there are 12 stress tensor in the pch file, so how the hyperview use these tensor to get the plot stress? I could not find the way.

Meanwhile, how the Optistruct calculate the damage based on the response stress, I mean how to calculate the cycles at interested frequency, I know the help document, but it doesn't tell too much.

Thanks a lot!

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Rahul Rajan_21763

Please refer attached document for complex results in HyperView.

 

Optistruct supports Fatigue in frequency domain:

• Sine sweep fatigue 
• Random response fatigue

For Sine weep fatigue, stress amplitudes and their no. of cycles are determined by sweeping rate and FRF analysis results.

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Rex_22369

Altair Forum User said:

Please refer attached document for complex results in HyperView.

 

Optistruct supports Fatigue in frequency domain:

• Sine sweep fatigue 
• Random response fatigue

For Sine weep fatigue, stress amplitudes and their no. of cycles are determined by sweeping rate and FRF analysis results.

Hi Rahul,

 

Thanks for your answer, but I did not get your point! you only show me how to calculate the magnitude displacement in time domain, but how the Hyperview uses the 12 stress tensors to find the response Von Mises stress in time domain?

To your 2nd answer, I know what you mean, you need calculate the time to increased to the top frequency, but how the software deal with the bottom frequency? and how will the software use the time to calculate the cycles? I mean the software will count all the time to the top frequency or 50% on the bottom frequency & 50% on the top frequency?

For example:

sweep rate 5Hz/min, bottom frequency is 5Hz, top frequency is 10Hz, so it takes 60 seconds to reach 10Hz.

Then how will the software use this time to count the cycles? 10Hz*60s at 10Hz? or how?

 

Thanks again!

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Rex_22369

I already found the way to calculate the Von Mises Stress by using the Real & Imaginary stress tensor, if anyone is interested on this topic, you can find the attachment below.

I am still working on the cycles counting in Optistruct! 

Rex_22369

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