Problem 4) A helical compression spring is made of hard drawn carbon A227 ste has a wire diameter of 0.94 mm. The outside diameter of the spring is 11.1Imm. The ends are squared and there are 12.5 total turns. G = 79.3 GPa and use Table 1 in lecture if torsional yield%3D0.45 ultimate stress a) Estimate the torsional yield strength of the wire. b) Estimate the static load corresponding to the yield strength. c) Estimate the scale of the spring (the spring constant). d) Estimate the deflection that would be caused by the load in part b e) Estimate the solid length of the spring f) What length should the spring be to ensure that when it is compressed solid and then released, there will be no permanent change in the free length? g) f), is buckling a possibility? Given the length found in part (h) What is the pit-
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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