Venymäkäyrät

Venymäkäyrät, also known as strain curves, are graphical representations used in materials science and engineering to illustrate the relationship between stress and strain for a material under tensile or compressive load. These curves are fundamental for understanding a material's mechanical properties. The horizontal axis typically represents strain, which is a measure of deformation (change in length divided by original length), while the vertical axis represents stress, which is force applied per unit area.

The initial part of a typical venymäkäyrä for many ductile materials shows a linear elastic region. In this phase, stress is directly proportional to strain, and the material will return to its original shape if the load is removed. The slope of this linear section is known as the Young's modulus or modulus of elasticity, a key indicator of stiffness. Beyond the elastic limit, the material enters the plastic deformation region. Here, permanent changes occur, and the material will not recover its original shape.

Within the plastic region, the curve may exhibit a yield point, where the material begins to deform significantly with little increase in stress. For some materials, there is an upper and lower yield point. Following yielding, the stress often increases again due to strain hardening, where the material becomes stronger as it deforms. Eventually, the curve reaches its ultimate tensile strength, the maximum stress the material can withstand. Finally, the curve descends towards the fracture point, where the material breaks. The area under the curve can represent the toughness or energy absorbed by the material before fracture.