To maintain a leading position within a business area constant development is required, both in the organization and of products. To follow developments in sustainability, the optimization of products has become crucial as the earth’s resources are not infinite. When working with development of metal components exposed for high internal pressure, the method of autofrettage has proven to extend fatigue life. The governing mechanism is that residual stresses, created in the material, counteract with the tensile stresses caused by an operating pressure, thus peak stresses during a load cycle are reduced.
In an effort to identify a methodology for implementation of the autofrettage process on complex geometries a numerical model was established. The numerical model was utilized to investigate if the effective stress according to the von Mises yield criterion, independently is sufficient enough to define a range of autofrettage pressures that has a positive impact on a component. The methodology predicted the optimum autofrettage pressure, as the ambition wasto improve the fatigue life to the fullest extent possible. The numerical results were subsequently used to perform experiments, to compare the change in fatigue life.
The experimental results strongly indicates that the effective stress according to the von Mises yield criterion, are sufficient enough to identify a range of autofrettage pressure that generates increased fatigue life. The optimal autofrettage pressure cannot be determined solely by the effective stress, experiments indicated that knowledge regarding the tensile and compressive stress state of the material is of utmost importance. Compared to the reference specimen, experimental results indicate highly increased fatigue life, up to a factor 12, when exposed for the autofrettage process.