u/Homeboi-Jesus

Solving Kinematic Systems?

Solving Kinematic Systems?

I'll be the first to admit, in my degree program, our dynamics/kinematics course was the weakest course in the entire program. It didn't really prepare us for solving really any kinematic system; but regardless I want to be able to solve these systems.

The above is a system I am looking to analysis and refine for it's function. I'll describe it here what is happening: We have a block with 2 6mm pins that are 48mm apart. This block sees a non-uniform force with a dF loading with an Impulse and free Energy known, along with the dF/dT curve. There are 2 tracks that this block is connected to. It is connected to Track A (forgot to label, but it is the long track) where both pins are inside the track. Then there is Track B, where only the rear pin of the block is connected to it. Track be can be described as a slot on loading block with a spring acting int he same angle of Track A. This spring has a preload value, which is unknown but should be treated as a given for iterative design. As the force acts on the pin block, it depresses the loading block via Track B, compressing the spring. Towards the end of Track B, we would start to see the pin block to pivot as it starts to move down Track A.

What I am trying to solve for is the dT of the entire cycle (i.e loading + recovery) and how far along Track A does the pin block move.

Anyone know of a good starting point on how to begin to solve it, or resources to dig through to get me up to speed on solving these type of systems?

https://imgur.com/a/OvbtUsw

u/Homeboi-Jesus — 8 days ago
▲ 5 r/LSDYNA

Alright guys, this issue has been plaguing me for a long time now. This issue re-appears randomly under certain conditions, I think it is related to penetrator diameter vs armor laminate thickness.

As you can see, our energy becomes insanely negative for contact energy and then everything loses control from there. The elements of the laminate deteriorate and erode themselves far away from the impact area.

The laminate ELFORM = 2, Hourglass ID 2 and 6 were tried, same issue, Element size at center is ~0.0001m, material is a UHMWPE using MAT_003 and *CONTACT_AUTOMATIC_SURFACE_TO_SURFACE_TIEBREAK as the epoxy between the 1mm layers.

The strangest thing is, everything works on most models and I have calibrated the numerical model of it. Yet something is going wrong, and I am not sure what.

Anyone ever see this before?

u/Homeboi-Jesus — 1 month ago