Vehicle barrier crash with lumped masses

[jenkinsja55]

I am using Simulation 2013 (new user) and am trying to set up a simplified vehicle into barrier crash using lumped masses and spring/dampers.  I'm not sure exactly how to set this type of analysis up.  I want to apply an initial velocity to the vehicle and have it move against the spring (representing the vehicle crush stiffness) toward the fixed rigid barrier.  Ultimately I would like to represent the vehicle graphically, but initially I would like to see if I can get Simulation to calculate the velocity changes and displacements to match actual test data.  Any ideas from other users would be greatly appreciated - speak slowly - I'm new here... lol

[AstroJohnPE]

Hi,

I think you can only apply initial velocities to parts. I do not think you can apply it to a lumped mass.

So I suggest making a simply block of known volume and set the mass density to get the desired total mass. Then apply the initial velocity to the part.

[jenkinsja55]

Thank you John - I have created a large heavy barrier block and made the element type rigid.  I then made a 1mx1mx1m cube 1 meter away from the barrier and made the element type brick.  I assigned a custom material with a mass density of 873 Kg/m^3 which should give me the mass of the vehicle at 873 Kg.  I connected a node on the rigid barrier to a node on the vehicle block where all nodes are constrained to x translation only wsith a spring having the k factor I want to use.  When I select the vehicle block part and right click to add the initial velocity - I do not get that as a choice - I only get initial temperature as a choice.  (I am using Naterual Frequency (modal) with load stiffening).

Any idea why it will not give me the initial velocity choice for this part?  Did I set it up correctly otherwise?

Thanks

[AstroJohnPE]

My mistake for assuming that you were using MES (Mechanical Event Simulation) to perform a crash analysis. Initial velocities are a load available in MES only.

Perhaps you should explain what your analysis approach will be: analysis type(s), element types, loads, what results you want, etc. From what I understand of your model, I do not understand how a modal analysis will be helpful, and I think there are no loads that are causing a stiffening effect (so modal with load stiffening seems doubly incorrect).

You may also want to look at the "Getting Started > Online Wiki Help" and read about the different element types. A rigid element in linear analysis is a line; it sounds like you have a solid object (which would be a brick element type).

[jenkinsja55]

Thanks John - I did switch to MES and now have a working model.  It accurately simulates the vhicle crush and the timing of the maximum crush as well.  Kudos to you!

Jeff