Impact Toughness
Impact toughness is the inherent ability of a material to absorb energy when subjected to a sudden dynamic load. It is extremely important in applications which involve dynamic stresses and sudden shocks. The toughness of a material is a measure of its ability to absorb energy before fracturing.
Impact toughness of materials is primarily determined by the strength of the material and the rate at which it can adopt its new shape afterwards (“deformation”). Materials with good impact toughness tend to be resilient and can deform prior to fracture. Such materials can absorb and dissipate energy from sudden dynamic loads, thereby preventing the fracture from occurring.
Impact toughness is typically measured in terms of an ‘impact energy’, which is a measure of the energy needed to cause a certain amount of deformation or fracture in the material. Impact energies are usually expressed in units such as J/m2 (Joules per square metre) or kJ/m2 (kilojoules per square metre). Materials with higher impact energy values tend to be significantly tougher than materials with lower values.
The impact toughness of a material can vary significantly depending on the type of loading it is subjected to. For example, some materials may have excellent impact toughness with regards to impacts made with a higher velocity (such as a falling weight) but may experience a significant loss to their impact toughness when tested with a lower velocity impact. As such, it is important to understand the type of impacts which a material may face in its service environment before selecting a material for a particular application.
Impact toughness is an important factor in the selection of materials for a variety of application, including those found in automotive, aerospace and industrial applications. For example, rapidly moving parts require a certain level of impact toughness in order to prevent fatigue failure. Likewise, materials which are used in safety applications must have an adequate level of impact toughness to prevent catastrophic failure.
In addition to the type of loading, the initial condition of the material can also affect its impact toughness. For example, materials which have been cold-worked can generally have higher impact energy values than those which have been subjected to a hot-working procedure.
In conclusion, impact toughness is an important property of materials and is typically used as an indicator of their ability to effectively absorb and dissipate energy from sudden dynamic loads before fracturing. The impact toughness of a material can vary significantly depending on the type of loading and the initial condition of the material. As such, it is important to consider metrics such as impact energy and deformation when selecting a material for an application where impact stresses may be a factor.
