MECH ENGINEERING DESIGN(LL)+ACCESS
MECH ENGINEERING DESIGN(LL)+ACCESS
10th Edition
ISBN: 9781260113952
Author: BUDYNAS
Publisher: MCG
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Textbook Question
Chapter 1, Problem 13P

A fatigue test is performed on rotating beam specimens where, for each rotation cycle, the specimens experience tensile and compressive stresses of equal magnitude. The cycles-to-failure experience with 69 specimens of 5160H steel from 1.25-in hexagonal bar stock was as follows:

L 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210
f 2 1 3 5 8 12 6 10 8 5 2 3 2 1 0 1

where L is the life in thousands of cycles, and f is the class frequency of failures.

  1. (a)   Estimate the mean and standard deviation of the life for the population from which the sample was drawn.
  2. (b)   Presuming the distribution is normal, how many specimens are predicted to fail at less than 115 kcycles?
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