Consider two different types of motors. motor a has a characteristic life of 4100 hours (based on a mttf of 4650 hours) and a shape parameter b = 0.8. motor b has a characteristic life of 336 hours (based on a mttf of 300 hours) with a shape parameter b = 3.0. which of these offers better reliability for 100 hours? which of these offers better reliability for 750 hours?

Aturning operation is performed with following conditions: rake angle of 12°, a feed of 0.35 mm/rev, and a depth of cut of 1.1 mm. the work piece is aluminum alloy 6061 with t6 heat treatment (a16061-t6). the resultant chip thickness was measured to be 1.0 mm. estimate the cutting force, fc. use shear stress of 207 mpa and coefficient of friction on the tool face of 0.6.