Answer Happy

The given steel shaft sees 8.0 kN and 12 kN maximum loads as shown acting along the x and z axes respectively. The bearings at A and B exert only x and z components of force on the shaft and do not resist torque. The gears are also made of steel and are 1.0 cm thick. Assumptions: (cite others in your design as required) 1. max material temperature = 350 deg F 150 mm 2. machined shaft and gear surfaces 3. there are people in vicinity of the shaft/gear assembly 350 mm 4. shaft shoulder fillets at gears have a radius of 3.5 mm F: 12 kN 5. periodic inspections utilize dye penetrant to reveal flaws as small as 0.5 mm. 250 mm 6. Assume bending stress is steady 7. The torsional stress is fluctuating from Tmax to 0.4 Tmax 8. Use your engineering judgement on other required assumptions (safety factor, etc.) A. Determine the shaft's minimum diameter using a suitable Static failure criteria (from text/class) for safe operation to the nearest mm. Show all required torque, shear, and moment diagrams in your analysis. Choose an initial reasonable steel alloy using your text or CES Granta to do this analysis based on materials concepts learned in class. B. Estimate the RR Moore endurance limit S'e and fully corrected Se for this shaft based on initial steel alloy above. C. Determine the shaft's minimum diameter using a suitable Fatigue failure criteria (from text/class) for safe operation to the nearest mm. Determine if infinite life or if possess finite cycles to failure (and cite). (Be sure to include a check for localized yielding due to fluctuating stress-equation 6-49.) D. Based on the fatigue analysis used above and safety factor, use the Granta CES software to further optimize your selection of a specific steel alloy for this shaft by picking at least 2 optimization performance indices. Cite the elemental composition of this steel. Show Granta list of materials, charts, etc. E. Perform a fracture analysis on your fatigue-designed shaft to determine critical crack size, decide if you should pick another steel alloy or keep the one found above. Show chart(s) used-make assumptions/simplifications as required. *BONUS: Calculate the maximum speed this shaft can rotate so as to stay 15% below the critical speed of the shaft. Do the calculation without the gear masses but assume that these masses reduce the shaft-alone critical speed by 40%. Discussion Questions 1. Comment on static and fatigue-based diameters found in A & C, why the difference? Discuss which should be used. 2. Justify your selection of steel alloy and final diameter chosen 3. Discuss your fracture and fatigue analysis results-do these seem reasonable? 4. This is a first iteration design, what further analysis would you do to hone this design? 5. What are 3 steps that can be taken to improve the fatigue life of your shaft that you have designed? A Fx 8 KN -75 mm - 50 mm B