Case Study Determine Properties from Tensile Test Data A cylindrical specimen of stainless steel having an initial diameter of 12.8mm and initial length of 50.8mm is pulled in tension. Use the data provided below to a) Plot the data as engineering stress versus engineering strain using excel or similar software. b) Compute the modulus of elasticity. c) Determine the yield strength at a strain offset of 0.002. d) Determine the tensile strength of this alloy. e) What is the approximate ductility, in percent elongation? f) Compute the modulus of resilience. Load (N) Length (mm) 50.800 12,700 25,400 50.825 50.851 38,100 50,800 76,200 89,100 92,700 102,500 107,800 50.876 50.902 50.952 51.003 51.054 51.181 51.308 119,400 128,300 149,700 51.562 51.816 52.832 159,000 53.848 160,400 159,500 151,500 124,700 54.356 54.864 55.880 56.642 Fracture
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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