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Define the Motion of a Plane of Nodes which is NOT Uniform

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My name is Bradley Zentgraf. I work creating FE models of traumatic brain injury.

I am currently trying to take a deformation seen in an element on the macroscale and apply this same deformation to an entire plane of elements on the microscale. I use Hypermesh as my preprocessor and run my simulations with LS Dyna

The main issue I am facing is that I would like to tell an entire plane of nodes on the outer surface of my model to deform in a manner in which the nodal motion is not uniform throughout the plane. (i.e. the top nodes will deform proportionally more than the bottom nodes - this can be seen in the attached jpeg image). Also it should be noted that the material I am deforming is viscoelastic.

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I know how to create sets of nodes, create motion curves, and apply these curves to sets of nodes such that they deform in a particular manner. But I wish to control the motion of each node (on a particular plane) not just a subset of nodes on the plane. However, the deformation of the nodes at the top of the plane is more severe than the nodes at the bottom of the plane. This would mean that each node would have to be given it's own motion curve. There are hundreds of nodes on a plane so it is not practical to create and assign curves for each node.

I have researched some possible solutions to this matter, but I am unsure if these are feasible solutions. It seems that I should be able to tell the plane to act as a rigid body and then prescribe some motion to the top nodes which would then be evenly distributed throughout the plane. But I do not know how this is to be done. Some of the cards that I thought might be useful included the CONSTRAINED_LINEAR and CONSTRAINED_NODAL_RIGID_BODY, which could perhaps tell the nodes on the plane to deform proportionally to one another. Then this could possibly be used in conjunction with the BOUNDARY_PRESCRIBED_MOTION_NODE(DISP) card to tell the top nodes how to deform letting the rest of the nodes "proportionally deform".

Any help you could provide me would be greatly appreciated.

Bradley Zentgraf

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