OLOAD -Transient Analysis

gopal_rathore

Hi,

I am running transient run with sinusoidal loading. I have given table D1 as sinusoidal function of time in the form of values for once cycle. When I am checking the OLOAD i,e applied load.

I am getting a linear curve for some initial time and then curve follows sinusoidal path. Also at t=0. table d1 value is 0.5 but the same in force is zero.

Kindly let me know about this.

 

 

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gopal_rathore

Hi,

@Prakash Pagadala Kindly let me know about the above points?

 

Thank you

Altair Forum User

Hi Gopal,

 

Did you request for a set of nodes or for all?

 

Do you have gravity with MTRAN/DTRAN analysis type? If yes, it is not supported for the same.

 

 

gopal_rathore

Hi,

I have requested for a set of nodes. I am not using gravity with DTRAN analysis

 

Thank you

gopal_rathore

Hi,

@Prakash Pagadala I was not expecting the linear linear line in the Oload input load as my TABLE D1 represents a sinusoidal wave.The objective is to do a repeated cycle fatigue analysis and for the same I making a transient run for one cycle for fatigue calculation.

gopal_rathore

Hi,

I can understand the reason for the linearity in the start as the load is not zero at t=0 thus it takes a time step to reach the initial value. Can you give me a general guideline to for making a relation between no. of time steps , simulation time and time step size.

Altair Forum User

Hi Gopal,

 

Do you mean for fatigue time history?

 

Maybe Load Time History Compression on OptiStruct will guide.

 

 

gopal_rathore

Hi,

No I meant for transient analysis

Altair Forum User

Hi Gopal,

 

Sorry for a late response. I think you can define analysis time step and end time using TSTEP. Where N in TSTEP  is number of time steps and DT is time increment. 

 

gopal_rathore

Hi,

I am clear with TSTEP load card.I wanted to know about how we decide the number of time steps for a particular time run. For eg. we have 1 sec of simulation run, no. of time steps can be any value from low ot high. So is there any general base don load variation and time as parameter.

 

Thank you.

Altair Forum User

Hi Gopal,

 

If it is explicit the element size affects the time step. 

 

But in implicit I need to check with my experts... I shall get back to you after learning /emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20'> 

gopal_rathore

Hi,

Thank you for your response./emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20' />