bicycle fork

[mainagioia]

Good morning.
Somo a mechanical engineering student. I saw an exercise on the ashby book for the choice of materials and I have a doubt. says to choose a material for a fork of a bicycle, and draws the material index (i.e. the coefficient that contains all the parameters that depend on the material to choose). However, it does not explain how it proceeds. I have speculated that the fork is the ab segment, and that it is loaded with the f force as represented in photo. I therefore assumed to see it as a supported beam and tried to obtain the total sigma by adding the contribution of bending and compression (I ask if it is right). At this point I should get the section area to which it is a free parameter as fi to insert it in the performance equation and find the material index, but I can not express to. if there was no normal effort, I would do it quietly and the result would come out also, but with that no, so I don't know if you can give me some disappointment about it. Do I have to put hinge in b? in that case n=0? Thank you.

 

[biz]

♪
fn= normal force
a = section
ff = bending force
a=brain
in fact the product ff*a is the moment of
wf=module of bending resistance
to get the area you need to know what type of section you use: circular, rectangular,piena,cava, etc.

 

[mainagioia]

as I said and as it is also written in the photos,the section is a free parameter. So I don't know what section is optimal, optimization is based on making it as light as possible not knowing area, shape and material. therefore remains the problem of how to obtain and put it in the formula of the mass.

 

[meccanicamg]

I think it's all clear from the fem you're going to use.
if you do a structural analysis in general you will have the formulas of balance to forces and moments to get the reactions.
push-ups and tensions will be dependent on section geometry.
If you stack different sections you can evaluate different tensions and flexions.
If this applies to a "trave" structure of a fem you must set these parameters otherwise you are obliged to geometrically model the whole frame and treat it as "solid" and then you will have to apply very fine mesh in the joints and evaluate every geometric singularity.
the beam model is used to have general indication of the structure quickly. the solid method is used to study in ten joke geometry in the specific.

So if you don't impose an area, you don't go anywhere, either by hand or by fem.

 

[biz]

formula della massa

What do you mean, mass form?

the section is a free parameter

So what's the problem? you have everything you need to do to proceed. in the bending resistance module you have variables concerning the beam section.

 

[mainagioia]

The problem is that I should look for a non-numerical solution. to make it short without numerically explicit nothing and knowing that my unknown is to, that you do not know and all the rest is known, ready to express to? I can't isolate it, I also tried to hypothesize the known values, but it came out 0. If there is a way to explain it my problem is solved. The equation is the one attached. Thank you.

 

[biz]

esempio:[math]\sigma_{max}=\frac{n}{a}±\frac{m_{f}}{w_{f}}[/math][math]=\frac{n}{a}±\frac{8\cdot4m_{f}}{\phi^2\phi\pi}=\frac{n}{a}±\frac{8m_{f}}{a\phi}[/math][math]a=\frac{1}{\sigma_{adm}}\left ( n±\frac{8m_{f}}{\phi} \right )[/math]supposes phi and revenues to