Stress and Strain
Stress is the internal resistance of a material to an applied load, defined as force per unit area (σ = F/A). Strain is the deformation of a material relative to its original dimensions (ε = ΔL/L). Normal stress acts perpendicular to the cross-section, while shear stress acts parallel. The relationship between stress and strain in the elastic region is governed by Hooke's Law (σ = E × ε).
Knowledge Check
1.A steel bar with a cross-sectional area of 200 mm² is subjected to a tensile force of 40 kN. What is the normal stress in the bar?
2.A 3-meter long rod elongates by 6 mm under load. What is the average normal strain?
3.What is the SI unit of stress?
4.A material has a Young's Modulus of 70 GPa and is subjected to a strain of 0.0005. What is the stress?
5.Which type of strain is defined as the change in length divided by the original length?
6.A cylindrical specimen with diameter 10 mm is subjected to a 15 kN tensile load. What is the stress? (π ≈ 3.14)
7.True strain differs from engineering strain in that it uses:
8.A material with Poisson's ratio of 0.3 experiences a longitudinal strain of 0.002. What is the lateral strain?
9.What is the stress at the proportional limit of a material?
10.A 500 mm long bar has a strain of 0.0015. What is the total elongation?