The failure or fracture of a product or component in a single event is known as mechanical overload. It is a common failure mode

Failure mode

Failure causes are defects in design, process, quality, or part application, which are the underlying cause of a failure or which initiate a process which leads to failure. Where failure depends on the user of the product or process, then human error must be considered.-Component failure:A part...

, and may be contrasted with fatigue

Fatigue (material)

'In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material.Fatigue occurs...

, creep

Creep (deformation)

In materials science, creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses. It occurs as a result of long term exposure to high levels of stress that are below the yield strength of the material....

, rupture, or stress relaxation

Stress relaxation

Stress relaxation describes how polymers relieve stress under constant strain. Because they are viscoelastic, polymers behave in a nonlinear, non-Hookean fashion...

. The terms are used in forensic engineering

Forensic engineering

Forensic engineering is the investigation of materials, products, structures or components that fail or do not operate or function as intended, causing personal injury or damage to property. The consequences of failure are dealt with by the law of product liability. The field also deals with...

 and structural engineering

Structural engineering

Structural engineering is a field of engineering dealing with the analysis and design of structures that support or resist loads. Structural engineering is usually considered a specialty within civil engineering, but it can also be studied in its own right....

 when analysing product failure. Failure may occur because either the product is weaker than expected owing to a stress concentration

Stress concentration

A stress concentration is a location in an object where stress is concentrated. An object is strongest when force is evenly distributed over its area, so a reduction in area, e.g. caused by a crack, results in a localized increase in stress...

, or the applied load is greater than expected and exceeds the normal tensile strength

Tensile strength

Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...

, shear strength

Shear strength

Shear strength in engineering is a term used to describe the strength of a material or component against the type of yield or structural failure where the material or component fails in shear. A shear load is a force that tends to produce a sliding failure on a material along a plane that is...

 or compressive strength

Compressive strength

Compressive strength is the capacity of a material or structure to withstand axially directed pushing forces. When the limit of compressive strength is reached, materials are crushed. Concrete can be made to have high compressive strength, e.g...

 of the product.

Examples

Examples include the many components which fail in car crashes, train crashes, and airplane crashes as a result of impact loading. The problem for the investigator is to determine which failures have been caused by the crash, and which may have caused the crash. It usually involves examining the broken parts for signs of fatigue

Fatigue (material)

'In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material.Fatigue occurs...

 crack growth or other damage to the part which cannot be attributed to the crash itself. For very large structural failure

Structural failure

Structural failure refers to loss of the load-carrying capacity of a component or member within a structure or of the structure itself. Structural failure is initiated when the material is stressed to its strength limit, thus causing fracture or excessive deformations...

s such as the collapse of bridges, it is necessarily a long and tedious process of sifting the broken parts.