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Question 3 (10 points): A cylindrical 2014-T6 Al alloy (Figure 8.21 shown below) is subjected to axial tension-compression stress testing with reversed-cycling. If the load amplitude is 9,000 N, compute the minimum allowable bar diameter to ensure that fatigue failure will not occur at 10' cycles. Assume a factor of safety of 2.2. Data in the Figure were taken for reversed tension-compression tests, and that is stress amplitude (hint: example problem 8.3) 700 600 T-5A-2/5Sn titanium alloy 4340 Steel 500 400 Maximum Stress S (MPa) 1045 steel 300 Ductilo castron 200 70CU 3Ozn brass 2014.16 Alloy 100 EQ21A 16 Mgo 0 10 10 10 30 TO Cycles of N

700 600 Ti-5A1-25Sn titanium alloy 4340 steel 500 400 Maximum stress, S (MPa) 1045 steel 300 Ductile cast iron 1200 7oCu 3oZn brass 2014-T6 Al alloy 100 EQ21A T6 Mg alloy 0 104 10 10 100 10 100 Cycles to failure, in