The ratio of maximum bending stress to maximum shear stress for a rectangular cantilever beam of depth ‘d’ loaded with a point load at free end is:

Explanation

For a rectangular section beam of width b and depth d under point load P: max bending stress sigma = 6 P L / (b d^2); max shear stress tau_max = 1.5 P / (b d). The ratio sigma / tau_max = (6 P L / b d^2) / (1.5 P / b d) = 4 L / d.