I am carrying out a simulation to find out the axial forces in a nylon rope when a load is applied.
I am using non linear MES with truss elements (sub-divided) to define the rope and the analysis with large deformation switched on.
I need to find out the force which results in the rope when the weight is applied. One load case is when the rope is vertical and held by a pin constraint at the top, the other is when the load is applied to the midpoint of the rope with two pinned constraints at either end.
My question is how do I relate the Youngs modulus of the rope to specify the dashpot coefficient for the element and how does the dashpot coefficient affect the stiffness of the rope?
Also how do I specify the damping in the material definition when specifying curved elements?
Many thanks in advance and any help is greatly appreciated.
Niall
Hi Niall,
This sounds like a homework assignment, so I hope these answers are not directly related to the grading.
There is no correlation between the Youngs modulus and any type of damping, whether it is the dashpot coefficient or the material damping. Unless some other information was given from which the damping can be determined, you can leave the values at 0.
Regardless of what values you choose for damping (0 or anything else), damping does not affect the force in the rope once it reaches its static equilibrium. Once the motion stops, there is no damping. (damping * velocity = force = 0 when velocity = 0)
From what I understand, because it is dificult to calculate the stiffness of most systems, it's not very accurate to calculate the impact force and apply it as a static load (since the impact force is dependant on the impulse which is dependant on the stiffness). I've been adviced to always model the entire impact scenario where possible and use MES.
Can I ask what you did with your model in the end? Were you able to calculate the stress in the truss elements during your chosen loading scenario?
Cheers,
John
Hi if I understand correctly you want to simulate the behavior of the rope under tension when a mass at the end is dropped.
I saw a few years ago a similar simulation If I am right they add two elements a beam and a damping element . The combination of this two elements get them the respective behavior. You can try to simulate with this elements. You can try a search in google scholar for similar simulations.