Industrial and engineering progress increasingly involves operating many kinds of mechanisms under more onerous conditions than they were previously operated, whether it be in terms of speed, size, load, temperature range, or environmental conditions. Structures and engineering components fail by instability, fatigue, creep, corrosion, or brittle fracture, possibly aggravated by excessive wear. Such failures lead to accidents, breakdown, or more usually to the need to maintain and replace individual parts in machinery and structures.
Steel and concrete, for example, are universally used materials. The failure of the former can cause immediately fatalities when occurring in airplanes, spacecraft and in vehicles operated at high speeds. The failure of concrete has caused structural collapse; excessive loading and stresses due to vibrations or earth tremors being critical factors. Failure of materials in containers or equipment used for hazardous toxic or explosive substances occurs with some regularity and safety specifications may be lacking or inadequate.