diving and squatting forces

[clark]

after conducting torsional stiffness on ansys i want to do FEA for forces in braking and acc. IS the assumption of fixing rear wheels and applying upward force on front wheels allowable in case of diving(opposite in case of squatting)

[Sormaz]

Correct me if I'm wrong, but you are going to want an upward force on both the front and rear wheels. It is the ratio of the two that is important, and can be calculated using your max torque for squat and max clamping forces (and implied torques) for braking (dive)

[clark]

no doubt that force will be upwards on all wheels but,In FEA you need to fix something and apply force on other.. that is why i have written is my assumption tolerable

[Bobby Doyle]

Should you be primarily concerned about the upward forces (FZ)? What other forces are being produced at the contact patch?

[clark]

good take bobby. of course there will be other longitudinal forces in both cases. But why is everyone so silent about the assumption question of mine.....????

[Crispy]

I'm not exactly sure what you are trying to accomplish, but if you want to figure out the loads in suspension components it would make sense to me to apply lateral and longitudinal loads at the contact patches and the equal and opposite "load" at the CG (adding in gravity as well). Then constrain the contact patches from moving vertically. You might also need to add a few other constraints to keep the simulation stable, but you need to be clever about how they are applied so they don't significantly effect the results.

If you want to see how the loads are moving through the chassis you will have to more accurately represent how the various masses pull on the chassis while accelerating, which would be a bit more work.

[flavorPacket]

An alternative analysis approach used for free-free conditions in vehicle engineering is called inertia relief, where the inertia of the object is increased until the system balances out.

[Crispy]

Originally posted by flavorPacket:
An alternative analysis approach used for free-free conditions in vehicle engineering is called inertia relief, where the inertia of the object is increased until the system balances out.

That sounds slick. Do you know how it distributes the inertia?

[flavorPacket]

It depends on the code. Check these out for a brief overview.

http://www.kxcad.net/ansys/ANS...help/thy_tool2.html] ( [url="http://www.kxcad.net/ansys/ANSYS/ansyshelp/thy_tool2.html%5D") http://www.kxcad.net/ansys/ANS...thy_tool2.html (http://www.kxcad.net/ansys/ANSYS/ansyshelp/thy_tool2.html%5B/URL%5D)[/url]

http://www.mscsoftware.com/sup...s105/workshop_17.pdf (http://www.mscsoftware.com/support/online_ex/previous_Nastran/Nas105/workshop_17.pdf)