Question

3. (20 pts) Consider a member made of 2024-T4 aluminum (yield strength 325 MPa, ultimate Ơa-839N,0.102 [MPa] strength 470 MPa) if the fully-reversed S-N diagram is represented as At a location of interest the material is repeatedly subjected to the uniaxial stress history shown in the figure below. Estimate the number of repetitions of this loading history necessary to cause fatigue failure using the Palmgren-Miner rule Think carefully how the cycles in the "repetition" should be counted. Tabulate the mean stress, stress amplitude, number of cycles for each cycle type, and number of cycles to failure Nf for each type of cycle contained in the operational cycle Analyze your results and comment. Which portions of the loading history most contribute to the fatigue failure of the part? . * 275 200 2 999(,oo lo0 END me -lo0 1 23* 9Io PE RATIONAL CYCLE ONE

Answer 1

Minen'sRhe 2. 2 72SM). 2 luri 04-639

o.502 e2. 計300 2 300 : lo) 339 o.204 los alf 124h. mex 200 2 N) 50: ς39 (2N) ο.to2.

0.l0 2 )·69: 291 40-102 losny 6- 2 てyieldstush 1- 32S a-22 5 32 S