Undamped Response with Variable Springrate
Undamped Response with Variable Springrate
(OP)
I'm trying to solve for the displacement of a mass with an applied constant load. Initially, there is a gap between the mass and spring, that is quickly overcome due to the applied force. The spring has a variable springrate. I have searched through multiple books and internet sites to find an example problem with a variable springrate and have had no luck. Again, this is an undamped case single degree of freedom case. Any suggestions?





RE: Undamped Response with Variable Springrate
Start by writing the force equations with a non-linear spring, it ha been dealth with from the mid 1800's on!
RE: Undamped Response with Variable Springrate
What software packages are you familiar with? Matlab, C-sharp?
I would solve this in Simulink.
Cheers,
RE: Undamped Response with Variable Springrate
Cheers
Greg Locock
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RE: Undamped Response with Variable Springrate
Appreciate the help!
RE: Undamped Response with Variable Springrate
That is rather inelegant and relies on very short dts but it will work.
Cheers
Greg Locock
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RE: Undamped Response with Variable Springrate
has a natural frequency of slightly more than 4 Hz and compresses the spring by about 35 mm.
Cheers
Greg Locock
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RE: Undamped Response with Variable Springrate
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Undamped Response with Variable Springrate
The method you described you used is essentially the Euler numerical method.
I have also used it before with success and would recommend it.
Though, I have never used it to solve a DE that is discontinuous like this one is. When the mass is in the air it is governed by only gravity and we should expect there to be a clear discontinuity when it contacts the spring.
It would be most evident by plotting the force as a function of time.
This problem has intrigued me to an extent because I have in the past used the coefficient of restitution(COR) to model rigid body impact, and I am interested in the correlation of using COR vs. modeling a contact stiffness between the 2 bodies as they impact.
RE: Undamped Response with Variable Springrate
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?