Fatigue limit

About: Fatigue limit is a research topic. Over the lifetime, 20489 publications have been published within this topic receiving 305744 citations. The topic is also known as: endurance limit & fatigue strength.

A stress‐based method to predict lifetime under multiaxial fatigue loadings

Abstract: This paper extends to low/medium-cycle fatigue a stress-based method recently proposed by the same authors for high-cycle multiaxial fatigue assessments. By considering the plane of maximum shear stress amplitude coincident with the microcrack initiation plane, the method requires the calculation both of the maximum shear stress amplitude and the maximum normal stress relative to the same plane. Multiaxial fatigue life estimates are made by means of bi-parametric modified Wohler curves, which take into account the mean stress effect, the influence of the out-of-phase angle and the presence of notches by using a generalization to multiaxial fatigue of the fatigue strength reduction factor K f . Approximately 700 experimental data taken from the literature are used to demonstrate that the method is a useful tool to summarize fatigue strength data of both smooth and notched components, subjected to either in-phase or out-of-phase loads. Finally, a simple practical rule for the calculation of the multiaxial fatigue strength reduction factor is proposed.

Study of fatigue resistance of chemical and radiation crosslinked medical grade ultrahigh molecular weight polyethylene

Abstract: The aim of this work is to understand the role of chemical and radiation induced crosslinking on the fatigue crack propagation resistance of medical grade ultrahigh molecular weight polyethylene (UHMWPE). In recent years, the need to improve the tribological performance of UHMWPE used in total joint replacements has resulted in the widespread utilization of crosslinking as a method to improve wear resistance. Although crosslinking has been shown to drastically improve the wear resistance of the polymer, the potential trade-off in fatigue properties has yet to be addressed. Fatigue crack propagation resistance is a concern in tibial inserts where large cyclic stresses are sufficient to drive the growth of subsurface cracks that potentially contribute to delamination wear mechanisms. For clinical relevance, the combined effects of sterilization and aging are examined in two commercially available crosslinked resins. Nonsterile and unaged resins serve as a control. To evaluate the effect of crosslinking, a comparison is made to uncrosslinked resins. Scanning electron microscopy is used to provide an understanding of fatigue fracture mechanisms in the crosslinked polymers. The results of this study show that the current level of crosslinking used in orthopedic resins for enhanced wear resistance is not beneficial for fatigue crack propagation resistance.

Fatigue fracture of the interlocking nail in the treatment of fractures of the distal part of the femoral shaft.

Abstract: The clinical and mechanical factors predisposing to a fatigue fracture of an interlocking nail were studied in seven patients who were treated for a fracture of the distal part of the femur. In all patients, the fracture of the femur was five centimeters or less from the more proximal of the two distal screw-holes. Finite-element analysis revealed that the stress on the nail exceeded its fatigue endurance limit and that the femur had to regain 50 per cent of its original stiffness through healing to accommodate weight-bearing without the risk of fatigue failure of the nail. The risk of fatigue failure may be minimized by using nails that have a larger diameter and by avoiding early weight-bearing.