A component is subjected to a maximum cyclic stress of 750 MPa and a minimum of 70 MPa. The steel from which it is manufactured has an ultimate tensile strength, σu, of 1050 MPa and a measured endurance limit, σe, of 400 MPa. The fully reversed stress at 1000 cycles is 750 MPa. Using both the Goodman and Gerber mean stress correction procedures, calculate the component life.
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.
A component is subjected to a maximum cyclic stress of 750 MPa and a minimum of 70 MPa. The steel
from which it is manufactured has an ultimate tensile strength, σu, of 1050 MPa and a measured endurance
limit, σe, of 400 MPa. The fully reversed stress at 1000 cycles is 750 MPa. Using both the Goodman and Gerber
mean stress correction procedures, calculate the component life.
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