Question

Two beams, A and B, made with the same material are to be subjected to a three-point bending test. Beam A has a dimension of 1.25 in x 2.5 in x 0.5 in while Beam B has a dimension of 1.5 in x 1.5 in x 0.75 in. Compare the respective fracture loads that will cause the beams to fail.

Answer 1

For beam A we have dimension as L$_A=$ 2.5 inch, B$_A=1.5 , H_A=0.5 inch$

for flexural modulus we know that

$E_F= \frac{L^3 m}{bd^3}= \frac{2.5^3 \times m}{1.5\times 0.5^3}=41.67 m$

Similary, for the beam B which has dimension given as $1.5\times 1.5\times 0.75$

$E_F= \frac{L^3 m}{bd^3}= \frac{1.5^3 \times m}{1.5\times 0.75^3}= 4 m$

So here we are getting different flexural modulus for beam A and beam B

The flexural modulus of A is more than that of B