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Stress analysis on automobile rim

Question asked by Pranav Verma on Sep 5, 2012
Latest reply on Sep 8, 2012 by Pranav Verma

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Hello, I am new to solidworks simulation. I needed some help for my project, that basically aims in finding the stresses developed on a car rim.

What I basically want to know is how to apply a bearing load over an area, as i want to know whether the design of the rim will be able to take the load applied due to the wieght of the car. And how do I go through the simulation. How will a virtual wall help me??

Any other alternatives for finding the stresses, displacements on the rim due to the load acting on it.

I want the rim to be static and the main area of concentration is near the contact surface of the rim with the ground.

I have uploaded the rim I have made for testing.

I look forward for your help!

Thank you in advance.

Anthony Botting Sep 6, 2012 10:38 AM

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I might try just open a sketch and draw two ovals, then project the sketch up to the rim areas and issue command "insert...curve...split line" to split the rim surfaces in two places. Then, just fix those two little surfaces (completely fixed). This will 'hold' the rim and hopefully stop the "large displacement" notice from popping up. However, the notice could still pop-up if the load is so large compared to the stiffness of the rim material/structure, that the deformation does fall out of the "small displacement theory".

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Anthony Botting Sep 5, 2012 11:33 AM
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There is a bearing fixture (in "fixtures"), and there is a bearing load (in "external loads"). You would probably need to review the help files on each of the two functions to see how they might be used.
Perhaps a valid approach is to use the virtual wall as the ground, and apply a bearing load to the hub. I cannot recall if needed, but you may have to install contacts between the rim and the virtual wall.
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- Pranav Verma @ Anthony Botting on Sep 5, 2012 2:56 PM
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  I made the virtual wall considering the target plane as the plane where there will be contact(ground and rim). And I applied 5000N bearing load on the hub. I was not able to figure out where to apply the bearing fixture if it has to be applied. Am i going in the right direction? And what should i do about the fixtures??
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  - Anthony Botting @ Pranav Verma on Sep 5, 2012 3:47 PM
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    Yes I believe you are fine, but you don't need to apply a bearing fixture, just a fixture on the rim somewhere.
    
    The way I understand it, the "bearing load" and "bearing fixture" can be used to formulate the problem in at least two (equivalent) ways.
    1) Bearing Load: pushes on the bearing so you'd need a fixture on a portion of the rim (such as contact with another body, a virtual wall; or just restrain some portion of the rim, such as a small patch, with a fixture.
    2) Bearing Fixture: This holds the bearing area in translation (but not rotation), so you'd need to apply a force on a portion of the rim. I'm fairly certain you'd need to turn-on the "soft spring" option in the properties to prevent rigid body motion.
    I hope that helps.
    
    .
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    - Pranav Verma @ Anthony Botting on Sep 5, 2012 4:03 PM
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      I simulated my model by taking the bearing load applied on the hub and the contact of the virtual wall with the rim. When the iterations were being done it asked me to reieterate it considering larger displacements. After the iterations were done. There was some translation motion of the rim, which I think is because I didnt put any fixtures and the solver considered it for larger displacements. Then I tried simulating it with fixed geometry fixtures, and applied the fixed geometry where the lug nuts are put, in that case my hub was deformed terribly, and I was assured that I was going wrong by applying that fixture. After that I again simulated it by putting a bearing fixture on the hub itself. I figured that even bearing fixture that I applied is wrong. Can't really figure out what type of fixture should I put !
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      - Anthony Botting @ Pranav Verma on Sep 5, 2012 5:10 PM
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        The method where you put a bearing load on the hub, then a contact with a virtual wall, should work OK as long as you use the "small displacement formulation", AND do turn-on the "Soft spring option to stabilize the model". Don't use the "large displacements" option at this point, because what you are experiencing is a phenomenon called "rigid body motion"...this just means there are not enough supports to prevent the body from rotating or translating about or along one of the coordinate axes - thus numerical roundoff inside the calculations will "see" the body as moving, and post a notice that it wants you to switch to "large displacement" - which would not be appropriate for this analysis. The soft spring option will place little springs on every node of the model, effectively preventing rigid body motion.
        The iterations you observe should only be coming from the contacts where the rim touches the virtual wall. Since the contact area would be expected to change size as the load is ramped-up, then it has to iterate to determine which parts of the rim are deforming into the virtual wall. This is actually a nonlinear behavior.
        Just make sure to turn on the Soft Spring option and don't let it fool you into switching over to 'large displacement'.
        
        Option for quick results: To avoid this nonlinearity of contacts - you could split out a small area of the rim that represents a contact patch (i.e., represents what you think would deform "flat" as it presses into a rigid surface, such as a smal oval), and just fix that small area on the rim with a totally fixed "fixture". Suppress the virtual wall and existing contacts. Then, it will run really fast but the contact surface may not be realistic.
        Hope that helps a little.
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        Pranav Verma @ Anthony Botting on Sep 6, 2012 4:19 AM
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        Bearing load - Check
        Virtual wall - Check
        Soft-spriing option - Check
        
        Still I am being asked to switch over to large displacement !
        
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        Anthony Botting @ Pranav Verma on Sep 6, 2012 10:38 AM
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        I might try just open a sketch and draw two ovals, then project the sketch up to the rim areas and issue command "insert...curve...split line" to split the rim surfaces in two places. Then, just fix those two little surfaces (completely fixed). This will 'hold' the rim and hopefully stop the "large displacement" notice from popping up. However, the notice could still pop-up if the load is so large compared to the stiffness of the rim material/structure, that the deformation does fall out of the "small displacement theory".
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        Pranav Verma @ Anthony Botting on Sep 6, 2012 11:13 AM
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        What I tried doing after reading above, I created a sketch of two ovals on the flanges of the rim on the plane in which my virtual wall is. That sketch is already over the areas of the rim about the flange. I am trying to project the curve, but i am not able to do it properly, please guide me through that.
        The plane 2 is my virtual wall plane. The 1st image is the bottom view of the rim and the second image is the left hand side view of the rim.
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        Anthony Botting @ Pranav Verma on Sep 6, 2012 1:49 PM
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        You should be able to run the command and then it will prompt for the surfaces to split. Then just select the rim surfaces that you want to split and click ok. Does it provide the prompt?
        If it does not work, try clicking on the "?" item at the top right of the property manager for that command. I believe there are some pictures and perhaps animations in the help file, showing how to execute the command....
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        Pranav Verma @ Anthony Botting on Sep 8, 2012 5:16 AM
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        That split line fixed geometry gave me some what expected results ! Thank you soo much sir.
        If I have to study the stresses at the flange area on the bottom, then where can I apply the fixtures? I tried reducing the oval dimensions for better results, but is there any other alternative to that?
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        Anthony Botting @ Pranav Verma on Sep 8, 2012 10:39 AM
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        A way to simulate that might be to make a "road" section or block and install contacts between the road and the rim. Assuming the road is asphalt or concrete, it would be super-soft compared to the rim. This falls into nonlinear territory so it might take a good long time to run.
        Perhaps you could make a tire of sorts, and set up contacts between the tire and a virtual wall.
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        Pranav Verma @ Anthony Botting on Sep 8, 2012 11:39 AM
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        If i create a tire then wil i have to consider the air pressure inside the tire?
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        Anthony Botting @ Pranav Verma on Sep 8, 2012 11:49 AM
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        You could do that. It would help to stiffen the rubber side walls so they won't deflect as much. You could run it both ways and see if there's a big difference on the stresses in the rim flanges.
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        Pranav Verma @ Anthony Botting on Sep 8, 2012 11:57 AM
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        applying a pressure of 30psi on the inner faces of the tire will be enough?
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Stress analysis on automobile rim

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