Hi, I'm working in a design team for the first time and I'm in charge of choosing a material for an application. I have the constraints, support a tensile load of 50 kg , and the objective which is minimize the weight. I'm using the concept of material indexes to find the best material for the application: The equation that I want to minimize, regarding that the following constraint is maintained: If we substitute A in the first equation we get: The problem i have now understanding is that the method tells me that i should only carry in minimizing (density/ failure strength), if i find the material that in fact minimizes this, how do i now the first constraint: is maintained, in literature i'm recurring to they never check this, should i check this for the material i end up choosing , or is this step unnecessary ? Thank you very much !!