Can you specify spring stiffness and damping as a curve instead of a single value ?

[Ionut Cosmin]

I am wondering if it is possible to specify the stiffness and damping coefficients as curves ? I have a gas damper in real life on which the compression force depends on the velocity of the piston rod, so my values for stiffness and damping are variable. Can I model this with a translational spring damper in msc.adams ?

 

[GregLocock]

Assuming you are using View

The answer is yes. Non linear arrays of numbers can be entered directly, that's called a spline. So right click in the textbox by the K in the spring design box, choose parametize/exprsssion builder. Then you can use AKISPLINE to create a function to read your x and f arrays, which you will also need to create.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[Ionut Cosmin]

Hi Greg,

Yes, I am using View. I have tried using what you have mentioned, although I used AKIMA_SPLINE (because I cannot find AKISPLINE in the options, I am using MSC ADAMS 2014), but I get the following error:

I don't think the K coefficient accepts multiple values.

Thanks,
Cosmin

 

[GregLocock]

AKIMA_SPLINE is the right one. So did you create x and F splines and refer to them in your expression?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[Ionut Cosmin]

Yes, now it works, I could not understand the independent variables at first but I have managed to sort it out. I created a measuring function with the following syntax: AKISPL(ABS( .damper_simplu.SPRING_1.deformation),.damper_simplu.SPRING_1.force ,SplineForce, 0) and now the simulation works.

Thanks a lot Greg!

Regards,
Cosmin

 

[johnie134]

it is non-linear. very advanced for skilled enginners ONLY