| Metals - Application and properties Metallic materials - metals and metal alloys - have a very large spectrum of properties. In addition to the two characteristic features of structure and function, a difference is also made between structural and constructional materials (e.g. materials for mechanical engineering and terotechnology, precision mechanics and engineering) and functional materials (e.g. materials for electrical engineering, electronics and communication media engineering). Decisive for constructional materials are the mechanical properties strength, ridigity (elasticity) and deformability (plasticity) at a given temperature. These properties define the configuration (e.g. max. test force required for load frame and industrial load cells) and the equipment (e.g. high-resolution extensometers for the determination of the Young's modulus of elasticity) of the industrial testing machines. In case of a mechanical stress e.g. of steel, first - as opposed to rubber for example - the high rigidity immediately takes effect. This means considerable force increases with very little deformations, often less than the thickness of a hair, and an elastic resilience during the reduction in force. Only if the force continues to increase, then a plastic, i.e. permanent deformation is overruling the elastic deformation. Specimens made of very brittle materials (e.g. cast iron) or soft steel subject to low temperatures break all of a sudden and nearly without any plastic deformation once having reached the tensile strength (i.e. without prior necking). |