A prismatic bar of circular cross-section is loaded by tensile forces ...
's ratio ν = 0.33. Determine:
a) The normal stress on a plane perpendicular to the axis of the bar.
b) The normal strain on a plane perpendicular to the axis of the bar.
c) The change in length of the bar.
d) The lateral strain on a plane parallel to the axis of the bar.
Solution:
a) The normal stress on a plane perpendicular to the axis of the bar is given by:
σ = P/A
where P is the applied load and A is the cross-sectional area of the bar. Since the bar has a circular cross-section, the area is given by:
A = πd^2/4
Substituting the given values, we have:
A = π(0.03 m)^2/4 = 7.07 × 10^-4 m^2
σ = 90 kN/7.07 × 10^-4 m^2 = 127.3 MPa
Therefore, the normal stress on a plane perpendicular to the axis of the bar is 127.3 MPa.
b) The normal strain on a plane perpendicular to the axis of the bar is given by:
ε = σ/E
Substituting the values obtained in part a) and the given values, we have:
ε = 127.3 MPa/70 GPa = 0.00182
Therefore, the normal strain on a plane perpendicular to the axis of the bar is 0.00182.
c) The change in length of the bar is given by:
ΔL = εL
Substituting the value obtained in part b) and the given values, we have:
ΔL = 0.00182 × 3 m = 0.00546 m
Therefore, the change in length of the bar is 0.00546 m.
d) The lateral strain on a plane parallel to the axis of the bar is given by:
νε = νσ/E
Substituting the values obtained in part a) and b) and the given values, we have:
νε = 0.33 × 127.3 MPa/70 GPa = 0.000603
Therefore, the lateral strain on a plane parallel to the axis of the bar is 0.000603.