Materials Performance: Toughness

Understanding Toughness in Materials

The toughness of a material refers to its ability to absorb energy and plastically deform without fracturing.
It provides an indication of a material’s resistance to mechanical impact, shock or sudden application of load.
In essence, toughness reveals how much deformation a material can endure before breaking.
Materials that are tough are said to have strong mechanical resistance, and can decrease the risk of unexpected or sudden failures.

Deformation is the alteration of the shape of an object when an external force is applied.
Plastic deformation refers to the permanent deformation that remains after releasing the applied load.
Fracture is the separation of an object or material into two or more pieces under the action of stress.
Impact strength is an essential attribute of toughness, measuring the material’s capacity to withstand high force or shock applied rapidly.

Metals, such as steel and titanium, are typically very tough materials. They can undergo considerable deformation before breaking.
Polyethylene and polypropylene, types of plastics, have high impact strength, thus exhibiting good toughness.
Rubber is also known for its toughness due to its high elasticity and resistance to deformation and breakage.

Generally, materials become less tough and more brittle at low temperatures, and more ductile at high temperatures.
Ductile to brittle transition temperature (DBTT) is a crucial property in materials science, describing the temperature at which the mechanical behaviour changes from ductile, with significant plastic deformation, to brittle, where fracture occurs with little or no signs of plastic deformation.

Material toughness is a critical factor in the design and manufacture of items exposed to impact or sudden loads, such as machinery parts, vehicle components and safety equipment.
Structural engineering applications like bridges and buildings also require materials with high toughness to withstand various loads without fracturing.
In many sports equipment, toughness is crucial as the instruments must withstand shock and impact forces.