Prob. 2.9-10. At room temperature (70°F) and with no axial

load (P = 0) the extensional strain of the prismatic bar (Fig.

P2.9-10) in the axial direction is zero, that is, x = 0.

Subsequently, the bar is heated to 120°F and a tensile load

P is applied. The material properties for the bar are: E =

10 x 10³ ksi and a = 13 x 10-6/°F, and the cross-sectional

area of the bar is 1.8 in². For the latter load-temperature condi-

tion, the extensional strain is found to be ex = 900 × 10¯6 in..

(a) Determine the value of the axial tensile load P. (b) De-

termine the normal stress and the shear stress on the oblique

plane NN'. (Note: The total strain is the sum of strain asso-

ciated with normal stress o, (Eq. 2.14) and the strain due to

change of temperature AT (Eq. 2.8).)

Gage measures

extensional

strain €x

N

N'

25°

P2.9-10

P

·x