topic Re: Fixed vs frictionless in Inventor Forum

Fixed vs frictionless

Yashasvi23481 — Thu, 20 Dec 2018 01:15:53 GMT

Hi All,

This might be quick one. I am doing a test to analyse the stability of assembly under wind condition. I have determined 80 kmph = 68.3N. With windspeed everything is movable. In that case, I am not sure to select the base as fixed constraint. It cant be fixed as I need to test if assembly will tip over. When I select just the edge for name sake, it stops the simulation saying not enough constraints.

So now my question is: If I select base surface as frictionless, will it show the movement if it moves in practical ? there is arrow underneath the symbol of frictionless. I have to do as many as 20 to 25 test using same set of constraint so I want to ask in weather condition like wind, can I use frictionless rather than fixed to get correct results?

Thanks for help.

Regards,

Yash

Re: Fixed vs frictionless

Xun.Zhang — Thu, 20 Dec 2018 02:46:31 GMT

Hello Yash,

You probably need below solution -

https://knowledge.autodesk.com/support/cfd/learn-explore/caas/sfdcarticles/sfdcarticles/What-Autodesk-products-do-wind-simulation.html?st=cfd%20wind%20load

Hope it helps!

Re: Fixed vs frictionless

johnsonshiue — Thu, 20 Dec 2018 04:23:23 GMT

Hi Yash,

When the assembly is moving (no matter how slow it is), the analysis would need to be dynamic, not static. In static FEA, something has to be grounded. Otherwise, the geometry would be floating in the space and it will not converge to a solution. The result will be wrong.

Many thanks!

Re: Fixed vs frictionless

Yashasvi23481 — Thu, 20 Dec 2018 04:58:47 GMT

Hi Johnson,

Thanks for suggesting Dynamic Analysis. What is frictionless constrain then used for ? It shows up in static analysis. How to perform Dynamic simulation ? Never done before.

Regards,

Yash

Re: Fixed vs frictionless

johnsonshiue — Thu, 20 Dec 2018 06:25:08 GMT

Hi! Static analysis does not mean all geometry is fixed. Some is allowed to move but the entire system should stay put. Frictionless constrain allows the given geometry to move under stress. Dynamic analysis allows the entire system to move and study the impact and stress during motion.

Many thanks!

Re: Fixed vs frictionless

JDMather — Thu, 20 Dec 2018 13:45:25 GMT

@Yashasvi23481 wrote:

I need to test if assembly will tip over.

I think all of the previous responders got distracted by terms used in stress analysis and missed this part of the problem description. This is not a stress or CFD analysis - this sounds to me like it is a simple motion (mechanical physics) analysis.

Environments>Dynamic Simulation.

Turn on your sound.

Re: Fixed vs frictionless

JDMather — Thu, 20 Dec 2018 13:46:19 GMT

ahhhhh