ringo wrote:Holm86 wrote:Is steel pistons necessary?? I thought they would just use some sort of aluminium alloy with a ceramic heat barrier coating on top and low friction coatings on the skirts.
And Mahle delivers pistons to Mercedes right??
I think when it comes to longevity and overall strength, steel is the best choice.
Aluminum will always be lighter, however it's specific modulus is not as high as steel ( stiffness per mass of material).
Another way of looking at it is the young's modulus per density. Steel is about 3 times greater in that regard.
Young's modulus of Aluminium is ~70GPa. Density ~2700kg/m^3
Young's modulus of Steel is ~200GPa. Density ~7800kg/m^3
70/2700 = 0.02592
200/7800 = 0.02564
In other words, about the same.
There goes that argument. Basically for the same weight you can have more material with aluminium, which can help with stiffness (where section properties play a big part).
You could talk in terms of tensile strength, but there is a wide variety of grades of steel and aluminium, and thus a wide variety in tensile strengths.