MACHINE DESIGN 1 ELEMENT 2" dia 20 150 PROBLEM: The shaft in the figure is rigidly attached to the wall and is made of class 25 cast iron. Stress concentration at the wall for bending and torsion is equal to 2. Sut = 25,000 psi and Suc = 100,000 psi.Find the value of the factor of safety by the Modified Mohr Theory of Failure. Page 1 of 2 Brittle coulomb-Mohr Theory of Failure COMBINED STRESSES, DUCTILE MATERIAL If the material is ductile Material of Cold-drawn 1020 with S = 78,000 psi, S, = 66,000 psi, ɛ, = 15 %, Determine the Factor of safety by the P: The maximum Shear Theory of Failure The Maximum Distortion Energy Theory of Failure.
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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