Strength and Durability

Abstract

In his notebooks Leonardo de Vinci recorded experiments demonstrating that short lengths of iron wire were stronger, in tension, than longer ones. Galileo asserted that if one makes geometrically similar structures of different dimensions the larger will be the weaker, see, e.g., Timoshenko [111, pp. 5–7]. This phenomenon is called the size effect. It is well known today that scale models of canal/river locks or dams, not to mention bridges, airplanes, etc., may fail to show defects that appear in the real structure. This may be because neither gravity nor the environment (often too the composition and density of air or water) can be scaled. Moreover, when failure stems from the exceedence of a critical load the conditions producing it may not be invariant with scale.