Contact Stiffness In Motion Solve

Sivaprakash_V · 2025-02-03T11:31:24+00:00

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Hi ,

I am performing MBD analysis using Altair Inspire & Motion Solve.

In that, I need to assign the contact between to two parts.

After selecting the parts, In the property browser under properties- there are some parameters like Stiffness, damping, exponent and penetration depth.

In which basis, should enter those values.
For example, I am using Steel as part and aluminium as other parts, by using different materials how can I choose the contact stiffness value, exponent as well damping.
I am new to MBD analysis, Could you explain me the basic things in this?

Thanks & Regards,
sivaprakash V

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Inspire Motion

MotionView/MotionSolve

Accepted answers

Vishvam

You can initially set default or low values for stiffness and run a simulation. In the results, check the contact overview for the maximum penetration seen in the simulation result. If these are higher than expected, increase the stiffness.

Ideally, penetration should be less than 1% of the contact surface dimension (e.g., for a 100 mm diameter sphere, penetration should be <1 mm).

If penetration is very small but simulation becomes unstable, then decrease stiffness slightly.

All comments

Vishvam

@Sivaprakash_V
As the solver is Motionsolve in both the softwares of Inspire Motion and Motionview, contact parameters can be changed in the same way.

The MotionSolve contact settings to be used as baseline values in a problem strongly depend on things such as 1) quality of the geometry at the contact interface (Mesh resolution) 2) component mass (Stiffness), 3) relative velocity (Damping), 4) duration of the event (Units... sec or millisec), 5) if there are external loads applied of large or small values.

There is some good documentation in the Motionsolve Help on Contact best practices that helps explain the theory behind contacts and also it and how to adjust in certain situations: Best Practices for Running 3D Contact Models in MotionSolve

Hope this helps!

Sivaprakash_V

Hi sir,

Yes, I performed the motion analysis with default values and result was not expected.

I think you saw in the previous meet, what was the issue which I faced during run the motion.

So that I want to change those values and I am interested to know how the stiffness value is calculated.
I gone through the link which you shared, The damping values can be 0.1 percentage of Stiffness.

But for stiffness, initially we run the simulation and the increase gradually and If we run the motion with these, then How to know which stiffness value should be enough for the model ?
Can you explain more about stiffness in Motion view / Inspire Motion ?

Thanks & Regards,
Sivaprakash V.

Vishvam

Ideally, penetration should be less than 1% of the contact surface dimension (e.g., for a 100 mm diameter sphere, penetration should be <1 mm).

If penetration is very small but simulation becomes unstable, then decrease stiffness slightly.

GTT Adam

Hi @Sivaprakash_V,

Contact can be defined using 3 different formulations in MotionSolve: Impact, Poisson, and Volume.

The general overview is that these methods behave like a spring, which have parameters for stiffness and damping coefficients. Starting with default values, measure the amount of penetration between the two bodies either visually or with an Output. Steadily increase the stiffness of this Contact until the penetration between two bodies is minimized.

I do recommend that you look into the Help Documentation regarding each formulation to see if one is more suitable for your specific case than another.

You can check out this article on 3D contact best practices using MotionSolve:

https://help.altair.com/hwsolvers/ms/topics/solvers/ms/best_practices_for_modeling_3d_contacts_ms.htm?zoom_highlight=contact

Lastly, Altair offers an introductory course, MotionView/MotionSolve Introduction eLearning, for solving multi-body dynamics (MBD) problems using HyperWorks and illustrates constructing, solving and post-processing MBD problems. This course focuses on general Multibody mechanisms and is a starting point for learning modeling in MotionSolve.
You can find it at the following link:

https://learn.altair.com/enrol/index.php?id=496

Hope this helps!

Adam Reid

Sivaprakash_V

Hi @ GTT Adams & @ Vishvam,

Thanks for your answers.

I will follow the suggestions provided by you.

Thanks & Regards,
Sivaprakash V.