A cylindrical metal bar is to be subjected to reversed and rotating-bending stress cycling. Fatigue failure is not to occur for at least 107 cycles when the maximum load is 250 N. Possible materials for this application are the seven alloys having S-N behaviors displayed in Figure 8.20. Rank these alloys from least to most costly for this application. Assume a factor of safety of 2.0 and that the distance between load-bearing points is 80.0 mm (0.0800 m). Use cost data found in Appendix C for these alloys as follows:

Alloy designation ______________________ Alloy designation

(Figure 8.20) ______________ (Cost data to use-Appendix C)

EQ21A-T6 Mg ............................. AZ31B (extruded) Mg

70Cu-30Zn brass ..................................... Alloy C26000

2014-T6 Al ........................................... Alloy 2024-T3

Ductile cast iron ......................... Ductile irons (all grades)

1045 steel....................... Steel alloy 1040 Plate, cold rolled

4340 steel ....................... Steel alloy 4340 Bar, normalized

Ti-5Al-2.5Sn titanium......................... Alloy Ti-5Al-2.5Sn

You may also find useful data that appears in Appendix B?