Table Q4 below indicates results on a tensile test of a mild steel specimen. 95 kN Proportional Limit load 30 mm Original diameter Original gauge length Yield Point Load 50 mm 100 kN 0.050 mm Extension at proportional limit Maximum recorded load 160 kN Final length between ga uge points 58.8 mm Final minimum diameter 17.9 mm Table Q4 Calculate the following: a. Modulus of Elasticity for the mild steel. b The proportional limit stress. C. The ultimate tensile strength. d. The percentage elongation. e. The percentage reduction in area,
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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