3. A cantilever beam, made of cold drawn AISI C1025 steel of circular cross section as shown in the figure below, is subjected to a load which varies from –F to 3F. Determine the maximum load that this member can withstand for an indefinite life using factor of safety N=2. A photoelastic model indicates a theoretical stress concentration factor of K=1.42 and the notch sensitivity for a 1/8 in. radius for this material is q=0.9. Analyze at the change of cross section only. 6". 5" Fig. 6-7 3F
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 cantilever beam, made of cold drawn AISI C1025 steel of circular cross section as
shown in the figure below, is subjected to a load which varies from –F to 3F. Determine
the maximum load that this member can withstand for an indefinite life using factor of
safety N=2. A photoelastic model indicates a theoretical stress concentration factor of
Kt=1.42 and the notch sensitivity for a 1/8 in. radius for this material is q=0.9. Analyze at
the change of cross section only
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