Introduction to Engineering-Solid Mechanics 2.Stress and Strain Tension and Compression unstretched (a)Unstretched length and diameter (b)As the force is gradually applied, the rod stretches along its length by the amount 4L.Ad is (a) A=πdP14 the change in diameter AL< (b) Note:Engineers usually calculate the cross-sectional area of round rods,bolts,and shafts in terms of their diameter,rather than radius,because the diameter can be directly measured with a caliper gauge. Introduction to Engineering 7 H.ShaoIntroduction to Engineering Introduction to Engineering —— Solid Mechanics Solid Mechanics Introduction to Engineering Introduction to Engineering H. Shao 7 2. Stress and Strain Tension and Compression (a) Unstretched length and diameter (b) As the force is gradually applied, the rod stretches along its length by the amount ΔL. Δd is the change in diameter Note: Engineers usually calculate the cross-sectional area of round rods, bolts, and shafts in terms of their diameter, rather than radius, because the diameter can be directly measured with a caliper gauge. L Δd ΔL d (a) (b) unstretched A=πd2/4