Rolspanningen

Rolspanningen, also known as rolling stresses, are stresses that develop in a material due to the rolling process itself. They are distinct from the stresses induced by external loads. During rolling, a material is passed between two or more rollers, which apply compressive forces to reduce its thickness and/or change its shape. These forces cause plastic deformation within the material.

The rolling process creates a complex stress state. Primarily, there are compressive stresses in the direction of rolling and perpendicular to the rolling direction, which are responsible for the material's deformation. However, tensile stresses can also arise, particularly at the entry and exit points of the rolls. These tensile stresses are often referred to as "tensile residual stresses" after the rolling operation is complete, as they remain in the material even when external forces are removed.

The magnitude and distribution of these residual stresses are influenced by various factors, including the material properties, the rolling parameters (such as reduction per pass, roll diameter, and rolling speed), and cooling conditions. Different rolling techniques, like hot rolling and cold rolling, produce significantly different residual stress patterns. Cold rolling, for example, typically leads to higher residual stresses due to the greater amount of plastic deformation at lower temperatures.

Understanding and controlling rolspanningen is crucial in many manufacturing applications. They can significantly affect the subsequent behavior of the material, influencing its fatigue life, susceptibility to cracking, and dimensional stability. In some cases, residual stresses can be beneficial, for instance, by inducing compressive stresses on the surface to improve wear resistance. Conversely, unfavorable tensile residual stresses can lead to premature failure. Therefore, techniques are often employed to modify or relieve these stresses, such as annealing or shot peening, depending on the desired outcome for the final product.