Residuaalijännityksiä

Residuaalijännityksiä, known in English as residual stresses, are stresses that exist within a solid material or object in the absence of external forces or loads. These internal stresses arise from various manufacturing processes, such as welding, casting, machining, heat treatment, and plastic deformation. They can also be induced by environmental factors like temperature changes or irradiation.

Residual stresses can be either tensile, pulling the material apart, or compressive, pushing it together. The distribution of these stresses within the material is often complex, with varying magnitudes and directions. They can exist on both macroscopic and microscopic levels.

The presence of residual stresses can significantly affect the mechanical properties and performance of a material. Compressive residual stresses are generally beneficial, as they can improve resistance to fatigue, stress corrosion cracking, and wear by counteracting applied tensile stresses. Conversely, tensile residual stresses can be detrimental, increasing the susceptibility to fracture and reducing the service life of components.

Understanding and controlling residual stresses is crucial in many engineering applications. Various techniques are employed to measure residual stresses, including X-ray diffraction, neutron diffraction, and ultrasonic methods. Furthermore, methods exist to modify residual stress states, such as shot peening or laser peening, to enhance material durability and reliability.