Question

What Maximum Shear Stress tell you about the failure of material?

Answer 1

If Maximum shear stress value provided to you, then it represents that limit, after which the material will definetly going to fail under shear loading. So it is the Maximum limit of shear stress that material can sustain under operation or loading condition.

But it is not true that every time it will fail by shear alone. It can be tensile, compressive, shear, fatigue etc. Depending upon the operating condition under which they are subjected. Every material has some limit of stress after which it will fail. Whichever will reach before at that point given material will fail. If material reach at maximum shear stress condition first, then it will fail by shear.