What is the difference between RBE2 and RBE 3 Elements?

RBE2 and RBE3 are multi point constraint elements, but Rigid and RBE2 elements add stiffness to original structure while RBE3 does not.

RBE2 elements also distribute the force and moment equally among all connected nodes, irrespective of position of force or moment. RBE3 element is constraint equation to distribute force and moment as per the distance (least square weighted function).

What is Hourglass energy? IQ3

1st order reduced-integration elements (which happen to be the very type of elements generally used in explicit solvers) suffer from hourglassing. These elements only have one integration point; because of this the elements can shear without introducing any energies. FEA codes which rely on 1st order reduced integration elements counter this by introducing hourglass energy. In situations where these elements would otherwise shear, this augmented energy keeps this from happening. This is reflected in your reported hourglass energy values. High hourglassing energy is often a sign that mesh issues may need to be addressed.

What is NIP? IQ2

Number of through thickness points for integration.

What are the kind of materials you have used - IQ 1 - LS-Dyna

What are the kind of materials you have used?

MATL1 -This is an isotropic elastic material, also allows modelling of fluids.
MAT 20 - Parts made from this material areconsidered to belong to a rigid body.
MATL 24 - Elasto plastic mat with arbitrary Stress Vs Strain curve and arbritary strain rate dependancy. Also failure based on plastic strain or minimum time step can be dfeined.
MATL57 - for highly compressible low density foam.
MATL 83 - Rate effects can be modelled in low and med density foams. Hysteric unloading behaviour in this model is a function of rate sensitivity with the most rate sensitivity foams providing the largest hysterisis and vice versa.




IQ Stands for interview questions

I have mentioned it in terms of Ls-Dyna, if you can explain the same in terms of Abacus/Ansys, please do post in comments

How to start preparing for the interview - II

Next about the performance requirements.

Well here I'm speaking more in terms of LS dyna as that is my tool of experience.

Global energy, Understand how the energy curves vary for each load case. For example how would the energy curve look for a quasi static load like SBA and how it would vary for a dynamic case like pendulum crash. Why does it differ?

Learn to draw a schematic diagram of the vehicle in terms of the load path.
For example from the bumper beam, towards the crush cans and then the rails etc, or for the same load case (full frontal) if we look at it from a slighter higher position, the load path is from the radiator, then the shotgun, hinge pillars etc.

If the frontal impact starts of with a force of 200 kN how does it get transferred towards the end of the vehicle.

How to start preparing for the interview - I

I will answer it more in terms of an automotive engineer, you may adapt it as per your need.

Identify the load cases in which you have expertise. By load caes i mean as an example - SBS (seat belt anchorage test or Roof crush, SDI (side door intrusion or Full frontal etc.

Next identify the Regulation applicability.

Example full frontal load cases are used for M1 configuration of vehicles or maybe Roll over are used for vehicles with passenger capacity less than 21 for instance.
Maybe you could dwell on which market (European, American, Canadia, Gulf, Asisan) an SBA, SDI is important.
Next study the test setup.
By test setup, I mean the loads, the boundary conditions, be ready to draw a small picture of the test set up as this gives the interviewer more confidence in your capabilities.

Next study the performance requirements.