Proper Material Selection method on designed chassis

[COLOR=#444444][FONT=Helvetica Neue]Hi, I am doing [/FONT][/COLOR][B]material selection[/B][COLOR=#444444][FONT=Helvetica Neue] for designed chassis. How to justify which material is suitable for our design? Normally by young modulus needed but in case of chassis complex design how to determine the young modulus needed?

I has been thinking is there a way to calculate or generate the young modulus or yield strength needed according to our chassis design for hand truck or trolley in order to select the suitable material for the metal tube.

Or there is another way to perform material selection on complex structure? [/FONT][/COLOR]
[COLOR=#444444][FONT=Helvetica Neue]Thanks for helping.[/FONT][/COLOR]