Hi,(adsbygoogle = window.adsbygoogle || []).push({});

I was wondering if some one could help me with my stress calculation problem.

I have designed a front suspension assembly for a locost sports car on pro/e. I would like to validate my design by performing some bending moment calculations of the part and then comparing the stress found in a 3g bump situation to that of the yield stress.

I have performed some of the calculations so far but don't know if i am going in the right direction and what to do next. I'm working in SI units.

I have simplified the v shaped wishbone to one length of tubing.

length = 0.3429m

One end is connected to the chassis and rotates about the bracket.

The other is connected to the lower ball joint that connects to the wheel and upright assembly.

The suspension spring and damper bracket centre is located 0.08407m from the lower balljoint.

The force at the wheel end is the reaction force of half the axle wieght + 3g

weight of axle = 300kg /2 = 150kg x 3g = 4414.5N

In a 3g bump the wishbone will rotate up wards and the damper would compress right up to the bump stops and so effectively would be stationary. therefore if clockwise moments = anti clockwise then..

4414.5N x 0.3429 = A x 0.2588

( 0.2588 is 0.3429 - 0.08407)

therfore A (force at suspension bracket =

5849.03N

I found the second moment of area to be..

I = 2 x10-8 m2

and y = 0.0127m

so if sigma = My/I then i should be able to find sigma and see if is below the yeild stress of the steel

This is how far i got with the calculations

Is the force at the suspension bracket correct?

What is M ?

I wanted the calculations to be for two bars side by side so to get the corect stress do i change the second moment of area to the value for two bars or,

perform the calcs for one bar and then x 2?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Lower wishbone stress calculation problem

**Physics Forums | Science Articles, Homework Help, Discussion**