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I need to perform frequency response analysis (sol 111) in Nastran need to Apply unit acceleration I

User: "cheerla3896"
Altair Community Member
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I need to perform frequency response analysis (sol 111) in Nastran need to Apply unit acceleration I have couple of question kindly suggest me execute this problem

1.SPCD IneedtobeConsider1or9810?

2. I need to apply multiple SPCDs since I'm working on the rear twist beam of a suspension system. It has 12 hard points, and I need to excite each hard point in all three directions (X, Y, Z).

While using SPCD, first I will activate SPC=1. Then, I will call RLOAD1 excitation SPCD. In the load step, the support is SPC. However, in the image below, I have two SPCs. One SPC will activate based on the excitation direction I apply. The other SPC needs to be applied in the global case control or neglected?I'm getting an error below.

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    Hello,

    for question 1 it depends on the unit measure system. If the model is in mm and you want to apply 1g you should input 9810 mm/s^2.

    For 2 if you want to apply multiple excitations on the same lc you should add 1 spc for every spcd.

    KR

    User: "cheerla3896"
    Altair Community Member
    OP

    Yeah i have added 1spc and for every SPCD, but i wanted to have multiple load collectors and when i use multiple load collectors I'm getting the below error

    error

    USAGE OF MULTIPLE BOUNDARY CONDITIONS IN FREQUENCY RESPONSE ANALYSIS IS CURRENTLY NOT SUPPORTED FOR SPCD PROBLEMS

    IF THE SPECIFIED ENFORCED MOTION IS NOT THE SAME FOR ALL OF THE BOUNDARY CONDITIONS

    USER INFORMATION:

    NASTRAN CURRENTLY HAS THE RESTRICTION THAT A FREQUENCY RESPONSE JOB WITH MULTIPLE BOUNDARY CONDITIONS INVOLVING SPCD

    ENFORCED MOTION USAGE MUST HAVE THE SAME SPECIFIED ENFORCED MOTION FOR ALL OF THE BOUNDARY CONDITIONS

    This is a community forum for the usage of Altair products, for issues regarding Nastran you should contact their support…. or you can use OptiStruct.