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## Simulation Mechanical and Multiphysics

Member
Posts: 5
Registered: ‎11-10-2012

# Vehicle barrier crash with lumped masses

284 Views, 4 Replies
12-11-2012 05:58 AM

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

Valued Mentor
Posts: 503
Registered: ‎08-30-2012

# Re: Vehicle barrier crash with lumped masses

12-11-2012 09:39 AM in reply to: jenkinsja55

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.

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16 years experience with Simulation Mechanical
Member
Posts: 5
Registered: ‎11-10-2012

# Re: Vehicle barrier crash with lumped masses

12-11-2012 10:41 AM in reply to: AstroJohnPE

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

Valued Mentor
Posts: 503
Registered: ‎08-30-2012

# Re: Vehicle barrier crash with lumped masses

12-11-2012 05:06 PM in reply to: jenkinsja55

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).

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16 years experience with Simulation Mechanical
Member
Posts: 5
Registered: ‎11-10-2012

# Re: Vehicle barrier crash with lumped masses

12-12-2012 01:30 PM in reply to: AstroJohnPE

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