Work out elongation of a bar instantly with clear inputs, formula shown and shareable results.
Combining Hooke's law with the definitions of stress and strain gives the extension directly: delta = FL/(AE). A 3 m steel bar of 400 mm2 section under 40 kN stretches 1.5 mm at 100 MPa stress. Longer bars stretch proportionally more, and stiffer or fatter ones proportionally less.
Elongation
delta = F L / (A E)
Underlying relations
sigma = F/A, epsilon = sigma/E, delta = epsilon L
No. Beyond the elastic limit the extension grows far faster and part of it is permanent, so the linear formula stops applying.
Work out each section separately and add the extensions - stress differs in each because the area does.