Töjbarheten

Töjbarheten, often translated as ductility or stretchability in materials science, is the property of a material to undergo significant plastic deformation under tensile stress before it fractures. It indicates how much a specimen can be elongated or reshaped without breaking, and it is closely related to how a material behaves under forming processes and in service where large strains may occur.

Two common quantitative measures are elongation at fracture and reduction of area. Elongation at fracture expresses how much the original length increases at failure, usually given as a percentage. Reduction of area describes the decrease in cross-sectional area at the fracture point. Together with yield strength and ultimate tensile strength, these measures provide a picture of a material’s ability to deform plastically before failure. In practice, ductile materials can neck and stretch considerably under load, while brittle materials fail with little or no plastic deformation.

Factors influencing töjbarheten include temperature, strain rate, and microstructure. Higher temperatures generally increase ductility for many metals, whereas rapid loading can reduce it. Alloying, grain size, phase distribution, and impurities also play important roles. Different materials show wide variation: many metals (such as copper and aluminum) display high ductility, whereas ceramics and some high-strength steels exhibit low töjbarhet.

In engineering, töjbarheten is crucial for safety and performance, affecting crash energy absorption, forming efficiency, and durability under fluctuating loads. Testing standards like tension tests (for example, ASTM E8 / ISO 6892) quantify ductility to guide material selection and design.