A cylindrical component will be designed with a circumferential notch to accommodate a small snap ring. If the notch is 1 mm deep and has a radius of 0.5 mm, calculate the theoretical and effective stress concentration factors for this component (i) if it is made of annealed stainless steel alloy 405 with a tensile strength of 415 MPa, or (ii) if it is made with cold rolled stainless steel alloy 17-7PH with a tensile strength of 1380 MPa. What conclusion can you draw about plasticity, stress concentrations, and fatigue 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 cylindrical component will be designed with a
circumferential notch to accommodate a small snap ring. If
the notch is 1 mm deep and has a radius of 0.5 mm, calculate
the theoretical and effective stress concentration factors for
this component (i) if it is made of annealed stainless steel
alloy 405 with a tensile strength of 415 MPa, or (ii) if it is
made with cold rolled stainless steel alloy 17-7PH with a
tensile strength of 1380 MPa. What conclusion can you draw
about plasticity, stress concentrations, and fatigue life?
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