(d) Show the given stress state and draw the load line. Determine the factors of safety with respect to fatigue and to first-cycle yielding.
Design Against Fluctuating Loads
Machine elements are subjected to varieties of loads, some components are subjected to static loads, while some machine components are subjected to fluctuating loads, whose load magnitude tends to fluctuate. The components of a machine, when rotating at a high speed, are subjected to a high degree of load, which fluctuates from a high value to a low value. For the machine elements under the action of static loads, static failure theories are applied to know the safe and hazardous working conditions and regions. However, most of the machine elements are subjected to variable or fluctuating stresses, due to the nature of load that fluctuates from high magnitude to low magnitude. Also, the nature of the loads is repetitive. For instance, shafts, bearings, cams and followers, and so on.
Design Against Fluctuating Load
Stress is defined as force per unit area. When there is localization of huge stresses in mechanical components, due to irregularities present in components and sudden changes in cross-section is known as stress concentration. For example, groves, keyways, screw threads, oil holes, splines etc. are irregularities.
Fatigue failure of material refer to the failure under the action of cyclic elastic stress. Fatigue generally involves the formation and gradual growth of cracks and ultimately to fracture as a result of reduced load carrying capacity.
First-cycle yielding in a material is directly related to low cycle fatigue in terms of repeated plastic deformation creating structural cracking of the material within the first cycle of stress strain load that propagated quickly to the break failure point.
Trending now
This is a popular solution!
Step by step
Solved in 2 steps with 1 images
