Door Slam Simulation

LOKESH KATARI

I am trying to replicate the same locking mechanism to my model which was done for the Tailgate in MV Door Closure Training Document.  I am really confused how to apply to my model. If I am going with the same parameters as in Demo model, My door is not locking. I tried to change the values but the door is not locking.

 

Can anyone please help me with this,

1. How to decide the 3D contact parameters for the door closing mechanism?

2. How to define the latch spring stiffness?

3. After creating 3D contact, After Highlighting the contact, what should I do, If one component is red and other is blue?

 

Please Help me with this

 

Chris Coker_21312

1. Start off with the default parameters.  If you find the penetration is high, you may need to increase the contact stiffness

2. If you have a known spring, the stiffness and preload values are usually available on an engineering drawing.  Also if you know the wire diameter, number of coils, etc. (the physical properties of the spring), the rate and preload can be calculated.  There are a number of calculators online for doing just this.

3. Are you using Inspire, or MotionView?

 

FYI, there are a number of good tutorials in our help for creating contacts, and a very complete section in the MotionSolve help for tuning 3D contacts.  That may also serve you as a good reference.

LOKESH KATARI

Hi, 

Thank you for explaining

 

I am using MotionView.

 

I got one more error. Initially when I run the analysis with Rigid body, it fine but if I am running with Flexbody. I am getting this error

Please help me with this

 

Unable to find an attachment - read this blog

Chris Coker_21312

First an unrelated suggestion:  you should read up on the differences between print interval and max step size for the integrator.  Your output step size is smaller than your integrator step size, which is impossible, so motionsolve takes the print interval values and uses that for the max step size.  This is not a good modeling practice.

 

The error is likely due to some issue with your flexbody.  Make sure you do not have alignment issues with your attachment nodes.  Also check the mass of the flexbody and make sure the mass is reasonable.  A common mistake is to not use the correct units when using flexprep, and you wind up with a flexbody that much too heavy (or light) to be physically realistic.

 

If you have not yet attended one of our online motionview training classes, I think it would be very valuable for you to attend.  In the meantime tutorial MV-2021 would be a good one to check out.  We also have a couple of door closure models in our examples library.

LOKESH KATARI

Hi Chris,

Thank you so much for your suggestion,

 

Can you please be more specific  about the first point or can you provide any material for the print interval and time step

 

Thanks

Chris Coker_21312

quite simply:

Print interval = output time step, or how often you want data to be generated during the simulation.

Integrator time step, the 'max step size' is the maximum allowable step size you want the integrator to take from one step to the next.  Typically, for an accurate answer, you want the integrator to take smaller steps than your output step size.  This applies no matter what tool or solver you are using, it's just basic computational numerics.

So, if you are setting your print interval to be less than the max integrator step size, you are forcing the integrator to use the print interval.  Practically speaking, for most problems, it doesn't really affect the results, but it is considered poor modeling practice, as you typically are going to want to solve the equations of motion at a smaller step than you report results.

LOKESH KATARI

Hi Chris,
Thank you so much for the explanation.

I am doing side door slam simulation, Initially i was doing rigid body analysis with Top hinge(Ball Joint) and Bottom Hinge(Inline Joint) to avoid over constraint.  But for flex body If i am changing to both hinges to revolute joint.  I am getting the same error is coming as above.

Can you please help me with this?

 

LOKESH KATARI

Altair Forum User said:

1. Start off with the default parameters.  If you find the penetration is high, you may need to increase the contact stiffness

2. If you have a known spring, the stiffness and preload values are usually available on an engineering drawing.  Also if you know the wire diameter, number of coils, etc. (the physical properties of the spring), the rate and preload can be calculated.  There are a number of calculators online for doing just this.

3. Are you using Inspire, or MotionView?

 

FYI, there are a number of good tutorials in our help for creating contacts, and a very complete section in the MotionSolve help for tuning 3D contacts.  That may also serve you as a good reference.

Hi Chris, 

I started of with default values but and then increased the stiffness but the door is not locking, 
Can you please be more specific and help me 

Thanks

Chris Coker_21312

If you can share the model, then I can take a quick look at you model.  Without being able to see specific details, it's really impossible to be more specific.

 

In very general terms, for complicated models like this, you should start off with a very small part of the mechanism, and get that working first.  Maybe just two parts that contact each other, etc.  Then, once you have confidence that part of the model is working correctly, you add more complexity, little by little, until you wind up with the complete model that captures the physics you are interested in studying.