A metal plate is to be exposed to cyclic tensile- compressive loading in which the maximum tensile stress is 131MPa and the maximum compressive stress is 81MPa. If the initial and critical internal crack lengths are 1mm and 6mm, and the values of parameters m and A are 4 and 5*10-36 respectively, estimate the fatigue life (in number of cycles). Provide the value only. If you believe that is not possible to solve the problem because some data is missing, please say UNSOLVABLE
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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