Question

The results of a tensile test are: Diameter of specimen 15 mm; gauge length 40 mm; load at limit of proportionality 85 kN; extension at limit of proportionality 0.075 mm; maximum load 120 kN;final length at point of fracture 55 mm. Determine

(a) Young’* modulus of elasticity,

(b) the ultimate tensile strength,

(c) the stress at the limit of proportionality,

(d) the percentage elongation.

Answer 1

(a) Young’* modulus of elasticity is given by:

where the load at the limit of proportionality

F = 85 kN = 85000 N,

L = gauge length = 40 mm = 0.040 m,

A = cross-sectional area = πd2/4

= π(0.015)2/4

0.0001767 m2, and

x = extension = 0.075 mm = 0.000075 m

Hence, Young’* modulus of elasticity

= 256.6 × 109 Pa = 256.6 GPa

(b) Ultimate tensile strength

(c) Stress at limit of proportionality

= load at limit of proportionality/cross-sectional area

= 85000/0.0001767 = 481 × 106 Pa = 481 MPa

(d) Percentage elongation