Which mode of fracture causes catastrophic failure: brittle, or ductile?
The correct answer and explanation is:
The correct answer is brittle fracture.
Explanation:
Brittle fracture occurs when a material breaks suddenly without significant deformation, usually under stress. This type of failure is catastrophic because it happens without warning, leaving no time for the material to redistribute stress or absorb energy. Brittle materials typically fracture at low strain levels, and they do not exhibit much plastic deformation before breaking. Common examples of brittle fractures include the snapping of glass or the failure of some ceramics and certain metals at low temperatures.
The failure mechanism behind brittle fracture is often linked to the propagation of cracks. These cracks can initiate due to stress concentrators such as flaws, notches, or changes in material structure. When a material is subjected to stress, these cracks can rapidly grow and lead to complete failure. In brittle materials, the crack grows in a straight path without any significant plastic deformation around it, which makes the failure quick and often unexpected. Moreover, the material’s ability to deform before failure is minimal, contributing to a lack of warning signs that could indicate impending failure.
On the other hand, ductile fracture is characterized by a significant amount of plastic deformation before failure occurs. Ductile materials, such as mild steel or aluminum, undergo necking, elongation, and deformation, which absorb energy and give visible signs before they break. This makes ductile fractures less catastrophic compared to brittle fractures because they allow for the redistribution of stress and the possibility of repair or precautionary actions.
Thus, brittle fracture is more likely to cause catastrophic failure because of its sudden nature and lack of plastic deformation, making it difficult to detect and manage before the material breaks.