A pipe with a wall thickness of 6 mm is designed to operate at the hoop stress of 600 MPa and the axial stress of 300 MPa. Evaluate a damage tolerance safety factor SF, associated with the leak-before-break requirement in this design. Assume factor Y = 1 and the most unfavorable orientation of the crack with respect to stresses. Material is a stainless steel with the fracture toughness of 90 MPaym. O1s SF < 1.5 SF 2 3.5
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.
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