How to export all non linear implicit load increments solutions ?

Guilain Lang

Hello,

I have setup a NL simulation using Hypermesh 2021.2 and I have some issues exporting the results. 

I am interested into recording intermediate steps of the computation. In particular, I must record the displacement of 3 RBE elements to compute a rigidity matrix in function of the load.

To do so, I have created options NLPARM and NLOUT. I have set up in both load step inputs NINT to 10 (and applied them to my NL load step).

Then, I have checked the displacement output in the load step. I defined two outputs, one as default for all elements, and the second that I have limited to the 3 RBE. The second format is setup as PUNCH (to export it in excel afterwards). 

However, I have seen two issues I couldn't solve:

1. The number of implicit load increments (in the default output) is not 10 has defined in NINT. Indeed, in Hyperview, I can only display 6 load factor's values.
2. The .pch file only displays the last increment (even when I specify NINT in the output options.

Could you help me with extracting all 10 load increments ?

Best, Guilain

 

PaulAltair

Hi, the NINT value determines only the starting increment size, it may be that your load increment is changing during the run if convergence is achieved relatively easily, so you are starting at a nominal 10 increments, but you don't get that many.

You can set the output frequency (NINT) higher in the NLOUT to make sure you get everything, or set an NLADAPT parameter to force the increment to not increase.

NLOUT is only supported for h3d output, so in pch you will only get final step

Explanation below:

from the NLOUT documentation:

If the difference in load increment from previous load level to the current load level that has been already output to the current load increment is greater than 1/NINT, then the intermediate result corresponding to current load level is saved for output; otherwise, it is not saved. This parameter has no control on the adaptive load size selection. Additionally, it is important to note that the difference from the current load increment to the previous output load increment is calculated based on the previous “output” load increment. Which implies that for the purposes of calculating the difference, the previously output increment is considered, and not just the previous analysis increment.

The following example illustrates the handling of intermediate output when NINT=10 is specified.

Since NINT=10, the value of 1/NINT is 0.1. Therefore, if the difference in load increment from the previous load level that has already been output to the current load increment is greater than 0.1, then the current load increment is selected for output. For NLOUT, the first and last increments are always output by default. In the following case, the first load step is 0.0 and the final load step is 1.0.

Figure 1.

Since the last output frame was 0.0 (last load increment selected for output), the difference between the next load increment and 0.0 should be greater than 0.1 (1/NINT) for it to be selected for output. As indicated in the .monitor file, printing in Figure 1, the first load increment for H3D NLOUT output after 0.0 is 0.142, since 0.0 subtracted from 0.142 is 0.142; which is greater than 0.1. For all other load increments prior to 0.142, the difference is less than 0.1, leading to them not being selected for output.

This is clearly evident in Figure 2 from the corresponding H3D file, as the second increment to be output is 0.142, instead of 0.02 as seen in the .monitor file output in Figure 1.

PaulAltair

Hi, the NINT value determines only the starting increment size, it may be that your load increment is changing during the run if convergence is achieved relatively easily, so you are starting at a nominal 10 increments, but you don't get that many.

You can set the output frequency (NINT) higher in the NLOUT to make sure you get everything, or set an NLADAPT parameter to force the increment to not increase.

NLOUT is only supported for h3d output, so in pch you will only get final step

Explanation below:

from the NLOUT documentation:

If the difference in load increment from previous load level to the current load level that has been already output to the current load increment is greater than 1/NINT, then the intermediate result corresponding to current load level is saved for output; otherwise, it is not saved. This parameter has no control on the adaptive load size selection. Additionally, it is important to note that the difference from the current load increment to the previous output load increment is calculated based on the previous “output” load increment. Which implies that for the purposes of calculating the difference, the previously output increment is considered, and not just the previous analysis increment.

The following example illustrates the handling of intermediate output when NINT=10 is specified.

Since NINT=10, the value of 1/NINT is 0.1. Therefore, if the difference in load increment from the previous load level that has already been output to the current load increment is greater than 0.1, then the current load increment is selected for output. For NLOUT, the first and last increments are always output by default. In the following case, the first load step is 0.0 and the final load step is 1.0.

Figure 1.

Since the last output frame was 0.0 (last load increment selected for output), the difference between the next load increment and 0.0 should be greater than 0.1 (1/NINT) for it to be selected for output. As indicated in the .monitor file, printing in Figure 1, the first load increment for H3D NLOUT output after 0.0 is 0.142, since 0.0 subtracted from 0.142 is 0.142; which is greater than 0.1. For all other load increments prior to 0.142, the difference is less than 0.1, leading to them not being selected for output.

This is clearly evident in Figure 2 from the corresponding H3D file, as the second increment to be output is 0.142, instead of 0.02 as seen in the .monitor file output in Figure 1.

Guilain Lang

Hi Paul,

Thank you for your answer, that's really helpful.

I need to export these steps in a Excel file for post treatment. I understand that it is not possible to extract intermediate results in a .pch file. Do you know any alternative solution ? (to prevent using 10 different loadsteps)

Best, Guilain