Fractures are often considered the most serious of all mechanical failures because of their ability to occur quickly and without warning. Generally speaking, most fractures can be classified as either ductile or brittle in nature. A ductile fracture is usually characterized by significant deformation or yielding. With this type of fracture, the crack is usually classified as stable. This means that the crack will not continue to grow without the application of additional loading. On the other hand, brittle fractures typically show little or no deformation prior to fracture. These fractures are considered unstable. This means that the crack will continue to propagate rapidly even without the application of additional loading.

Ductile fractures often result in the formation of a cup and cone appearance as the result of micro-void formation, growth, and coalescence within the material prior to final fracture. The orientation of micro-voids is can often be used by an experienced failure analyst to determine the loading conditions of the component prior to failure.

Brittle fracture are often more serious that ductile fractures because they typically do not provide any warning prior to initiation and will usually fracture across the entire material without additional loading. This means that supported components can suddenly fall and cause injury to bystanders. Brittle fractures are typically identified by a lack of deformation or yielding prior to fracture. Examination of the fracture surface can often reveal the direction of crack propagation and conditions of loading prior to failure.

People often imagine cracked or fractured materials when they think of a mechanical failure. However, a mechanical failure is simply the inability of a component to perform its desired or intended function. Therefore, it is possible for a component to fail long before the problem becomes catastrophic or, in some cases, even recognized. There are several different types of material failures that may result from one or more different modes. Some of these recognized failure modes include:

Creep
Yielding
Fatigue
Fracture
Overload
Buckling
Corrosion
Impact
Wear

To read more about each of the above failure modes, please click on the individual link.