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simulation of cubesat shock response during launch

    • BÙI HIẾU

      i'm working on simulating cubesat's shock response during its launch. Although I have read many documents, I still do not understand how to make the shock response spectrum in shock response. Or can someone give me the steps to simulate it. I'm working to simulate models and don't know what to do next with them.

    • dlooman
      Ansys Employee

      A Shock Response Spectrum can be created with the APDL command, RESP,  using the transient time-history.  A blog on this topic is pasted below.

      In the input below the POST26 RESP command is used to compute the shock response spectrum for a 20g triangular acceleration of 10 milli-sec duration.  The time-history includes time after the shock load for the lower frequencies to reach their peak displacement value.  The input assumes that a modal analysis has been done and expanded.

      ! After a modal analysis...


      amplitude=20                   ! pulse amplitude (20 g)

      width=0.01                     ! pulse width (10 milli-secs)



      acel(1,0)=0.0, 0.5*width, width, 5.0*width

      acel(1,1)=0.0, amplitude, 0.0, 0.0



      /axlab,y,ACEL (g)

      *vplot,acel(1,0),acel(1,1)     ! verify acceleration input




      The table array, acel, can now be used as input to the RESP command in the time-history post-processor.




      store,alloc,10         ! allocate the number of frequencies to be solved for

      vput,acel(1,0),1,0     ! variable 1 is time values

      vput,acel(1,1),2,0     ! variable 2 is acceleration values

      data,5,1,10,1,Frequncy ! variable 5 is frequency list (I love this old command!) 


      10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0


      ! Use parameters for RESP command input to make more readable

      Spec=6             ! variable to contain spectrum output

      Freq=5             ! variable with frequencies to be solved for

      Inp_Acel=2         ! variable with acceleration input

      Out_Type=3         ! create acceleration spectrum

      Damp=0.05          ! damping (ratio to critical) to be used

      Tinc=0.0005        ! integration time step, 20 pts per cycle at 100 hz

      Inp_Type=1         ! acceleration input, new at 14.0




      /title,Response Spectrum for %amplitude%g, %width*1000% m-sec shock load (5% Damping)

      /axlab,x,Frequency (Hz)

      /axlab,y,Peak Acceleration (g)

      xvar,Freq          ! x axis is frequency

      plvar,Spec         ! plot acceleration spectrum



      So with 15 or 20 lines of APDL input you can create your own shock response spectrum based on any arbitrary shape, peak value or duration of loading.  To provide a complete overview of the spectrum process the commands below retrieve the spectrum values into an array named SRS and input the values in a sample spectrum analysis.



      vget,SRS,Spec         ! retrieve variable 6 (Spec) into array parameter SRS






      sed,1                           ! x direction

      svtype,2,386.4                  ! accel spectrum, factor to convert g values to in/s^2

      freq,10,20,30,40,50,60,70,80,90 ! limit of 9 frequencies per line




      svplot,,Damp                    ! plot spectrum to verify input


      • BÙI HIẾU

        Thank you for your help. I will try it 


    • peteroznewman

      If you have matlab, you can use the Vibrationdata app package to create an SRS from acceleration-time history data.

      If you don't have matlab, you can use the runtime Vibrationdata program to create an SRS from acceleration-time history data.

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