5. An application calls for an unnotched, 1-cm-diameter polystyrene cylinder to be subject to a sinusoidal tensile-tensi

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5 An Application Calls For An Unnotched 1 Cm Diameter Polystyrene Cylinder To Be Subject To A Sinusoidal Tensile Tensi 1 (40.23 KiB) Viewed 39 times

5. An application calls for an unnotched, 1-cm-diameter polystyrene cylinder to be subject to a sinusoidal tensile-tensile loading with the following characteristics: Fm = 1200 N (mean force) AF = 800 N (force range) frequency = 0.1 Hz (0.1 cycles per second) A) Illustrate the stress-time curve for 1 cycle of loading. Plot stress on the Y axis (units of MPa) and time on the X axis (units of seconds), and be sure to include scale numbers on the X and Y axes. B) Using the fatigue data below, estimate the minimum molecular weight required if the cylinder must support the load given in Part A for at least 4 months (120 days). Assume the fatigue data was collected for the same stress range, frequency, and sample dimensions as above. You can interpolate between the lines given on the graph below if needed. Mean stress (MPa) 20 103 16x105 10* 33.105 86105 10⁰ *10€ Molecular weight (g/mol) FATIGUE LIFE, N Fig. 2.23 Effect of molecular weight on fatigue life in polystyrene (Sauer, Foden, and Morrow (58)].