Answer to Question #281386 in Mechanical Engineering for ravi

Question

A cantilever beam of cross-section 90 mm. width 120 mm deep carries a UDL of 12 KN/m. over the entire length and a concentrated load of 15 KN at the right end. Find the bending stress in the beam, when the length of beam is 10 m.

Answer 1

Length of beam = 2000 mm

Load at failure = 2 kN

Section dimensions = 40 mm x 60 mm

Moment if inertia

I = bd³/12 = (40) (60³) / 12 = 7.2 x 10⁵ mm⁴

Bending moment about fixed end

M = WL = (2) (2) = 4 kN/m

Bending stress

M / l = $\sigma$ / y

y = depth / 2 = 60 / 2 = 30 mm

$\sigma$ = 166.67 N/mm²