A probabilistic methodology for evaluating failure risk, assessing service life, and establishing design parameters for structures subject to fatigue failure has been developed. In this methodology, engineering analysis is combined with experience from tests and service to quanti& failure risk. The methodology is particularly valuable when information on which to base design analysis or failure...

An experimental study of the fatigue life of cortical bone screws under conditions which stimulated in vivo usage was performed. The two most important factors influencing fatigue life were axial screw tension (the force normal of the plate to bone) and the cyclic shearing load. All screws failed at the root of the thread in the interface between the plate and the bone. A modified screw design ...

Cyclic stresses are often related to the premature mechanical failure of metallic biomaterials. The complex interaction between fatigue and corrosion in the physiological environment has been subject of many investigations. In this context, microstructure, heat treatments, plastic deformation, surface finishing and coatings have decisive influence on the mechanisms of fatigue crack nucleation a...

Flexural fatigue tests are typically run under displacement or in a straincontrolled mode. In these tests, either the oscillatory displacement amplitude or strain amplitude applied to the bottom of the specimen is kept constant. The evolution of loading required to cause fatigue is then measured. Load amplitude decreases with the number of cycles, and the specimen is considered to have failed w...

This paper presents an overview of Laser Shock Processing and then discusses how the process can be extended to treat fastener holes on aging aircraft. The process is used to treat localized fatigue-critical areas by developing deep residual compressive stresses to inhibit the initiation and propagation of fatigue cracks. This feature can be applied to fastener holes in aircraft structures to d...

The objective of this study was to examine the effects of the hydroxyapatite (HA) reinforcement morphology and content on the fatigue behavior of HA reinforced high density polyethylene (HDPE). To this end, HDPE was reinforced with 20 and 40 vol% of either HA whiskers or an equiaxed HA powder, and tested in four-point bending fatigue under simulated physiological conditions. The fatigue life, m...

INTRODUCTION The purpose of this study was to evaluate the effect of various degrees of cyclic fatigue on torsional failure and torsional preloading on the cyclic fatigue life of heat-treated K3XF nickel-titanium (NiTi) instruments (SybronEndo, Orange, CA). METHODS The mean number of cycles until failure (Nf) of K3XF and K3 NiTi instruments was examined in a 3-point bending apparatus with a 7...

cost—the “cost of caring,” or compassion fatigue.1 fatigue may lead to increased absenteeism, turnover, and worker’s compensation claims; inappropriate behavior with clients; and changes in relationships such as the inability to work well with others, unhealthy competition, lack of flexibility, failure to complete tasks, and spreading rumors and gossip.3 Compassion fatigue can ultimately cause ...

The purpose of this study was to investigate cortical mechanisms upstream to the corticospinal motor neuron that may be associated with central fatigue and sense of effort during and after a fatigue task. We used two different isometric finger abduction protocols to examine the effects of muscle activation and fatigue the right first dorsal interosseous (FDI) of 12 participants. One protocol wa...

BACKGROUND There is currently little information regarding factors associated with specific modes of motion segment failure using a fatigue failure model. METHODS Thirty-six human lumbar motion segments were fatigue tested using spinal compressive and shear loads that simulated lifting a 9 kg weight in three torso flexion angles (0 degrees, 22.5 degrees, and 45 degrees). Twenty-five segments ...