A few questions regarding solidworks simulation.

[andrewkeisler]

Running a static simulation, using a force, and showing von mises results (or any other kind that I have tried) the von mises PSI barely changes when selecting different materials. Say 6061t6 and then running 7075t6 the PSI difference is a few percent at best. In my mind, the difference should around 100 percent since then yeild and ultimate strength or 7075t6 is is almost double that of 6061t6.

Second question. I am simulating a spindle that consists of 4 peices that all have a press fit and bolt together through the back sides. When adding bolt connectors to the spindle assembly and selecting no penetration, the results are not very accurate. The "RED" stress area is on the edge of where the bolts enter the threads. The press fit bosses should lessen the stresses on the threads but I havent found a way for the bolts to work in hand with a press fit application. Running the test without connectors and bonded is not 100 percent accurate either. Is there a way to show a ultimate strength simulation? That would be very beneficial and would possibly allow me to keep using the bolt connectors.

Thanks in advance guys!

Andrew

 

[JMirisola]

I'd suggest posting your question in the Simulation Forum.

Jeff Mirisola
My Blog

 

[rollupswx]

Attach your files here.
Changing material does not necessarily have a significant effect on the calculated stress - you should be ckecking the Factor of Safety (cal stress/yield stress).
In any case, attach your files so that others can take a look.

 

[NickE]

You're missing one of the fundamental parts of materials science, that Stiffness, controls how much stress the material sees due to the strain present as a result of the loading condition. Additionally this Stiffness is known as Young's Modulus, a property of the material that is almost completely independent of the alloying or heat treatment condition of the material.

If you look at the stress-strain curve for a material you will observe a linear region of the curve, the slope of this linear region is the Modulus of the material, or stiffness. This is used with the strain matrix in the FEM to create a stress analysis. See the attached document.

http://www.clear.rice.edu/mech403/HelpFiles/FEM_stress_concepts.pdf

Since the modulus is relatively insensitive to changes in alloy composition and heat treatment, (see note 1) changing from 6061t6 to 7075t6 results in almost no change in modulus and hence no change in stress. In order to see a stress change you are going to have to move from the aluminium alloy systems into an alternate material. Steel/Ti/Be will all show you a change in the magnitude of the stresses in your analysis. Note that the geometry of the stress field, and the relative magnitude of the stresses will not change. These two results are only related to the loading condition and the geometry of the assembly or structure.

Note 1:
thread discussion of Modulus and it's insensitivities.

http://www.eng-tips.com/viewthread.cfm?qid=87802

Nick

 

[andrewkeisler]

Thanks for the replies! Sorry it has taken me awhile to get on here and attach my model, I have been finalizing a few things on it. If you wouldn't mind checking it out and giving some insite on the best possible way to simulate with yeild/ultimate strength in mind. All the peices press and bolt together. I haven't figured out how to apply force to a cyclindrical object yet, so that explains the "pusher". Fixtures are applied to the 3 holes, 2 of which are ball joints and the other is a tie rod attachment. Force is applied to the "pusher".

Thanks guys!