Predefined temperature field in Stress Analysis

Numerical methods and mathematical models of Elmer
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hm7788
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Predefined temperature field in Stress Analysis

Post by hm7788 »

Hi, does anyone know if Elmer support the predefined field? Specifically, can I use pre-calculated temperature field as the load to calculate the thermal stress? Below is a description of my problem :

I am conducting a thermal-mechanical analysis to predict the distortion in laser additive manufacturing (similar to laser welding process). The heat from laser will cause residual stress and deflection of the components. This is a typical thermal-mechanical coupled problem. Elmer has a similar example regarding the thermal/mechanical analysis as shown in Example 9 of Elmer non-GUI Tutorial. That example firstly calculated the temperature field, and then calculated the thermal stress. The example was performed in steady analysis, so the analysis make sense. But once I converted the example to a transient analysis (this is my case), result doesn't look right then. In my case, I used "Timestep_intervals = 6 ", and expected to obtain 6 vtu files with temperature and stress value at each file. But it turned out I obtained 6 vtu files with temperature result only, and a 7th vtu file with both temperature and stress value. This looks like the Stress Analysis only accounts for the temperature field in the last step (6th) instead of each step.

I was able to conduct a fully coupled analysis by commenting "Exec Solver = After All" line in Stress Analysis Solver, but this takes too much time to complete a simulation. So, I would like to firstly calculate the temperature field in all time steps, then use those temperature field as a load to calculate the stress in each time step. Just wondering if anybody knows how to use this function in Elmer. I'd appreciate if anyone can give me any instruction.

Thanks very much,
Jingfu
raback
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Re: Predefined temperature field in Stress Analysis

Post by raback »

Hi Jingfu

There is really no foreseeable benefit in computing first all temperatures and then all stresses. Elmer does not even save the old temperatures except to files.

What you could study is the different linear solver strategies and telorances for StressSolver. It is difficult to say much beyond this not seeing the full case.

-Peter
hm7788
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Joined: 19 Sep 2017, 20:01
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Re: Predefined temperature field in Stress Analysis

Post by hm7788 »

Hi Peter,

Thanks for the clarification, and thanks for pointing out the different linear solver strategies. After switching the linear system solver from direct method to iterative method, I was able to calculate the temperature and stress at each step much faster. This should meet my current needs.

Thanks very much,
Jingfu
raback wrote:Hi Jingfu

There is really no foreseeable benefit in computing first all temperatures and then all stresses. Elmer does not even save the old temperatures except to files.

What you could study is the different linear solver strategies and telorances for StressSolver. It is difficult to say much beyond this not seeing the full case.

-Peter
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