When a component subjected to variable load fails at 104 cycles, then such a failure is called as high fatigue cycle failure.  Select one: True False

Q1/ The table below shows the values of stress amplitude and life cycles : Fatigue strength Sf (Mpa) Number of cycles (Nf) 474 111 417 496 352 3002 316 7065 290 21930 262 66075 The test were done, to estimate the failure, on un-notched axially load specimens under zero mean stress. Calculate a and b using the stress -life equation.

Part A and B circle final answers The next 2 question relate to the modified Goodman diagram with the following baseline data. A part is made from steel with the following properties: Ultimate tensile strength is 450 MPa Yields stength is 260 MPa Fully-corrected endurance limit is 180 MPa The part is subjected to a time-varying load with σmax = 150 MPa and σmin = 90 MPa . Part A The safety factor with respect to fatigue is?? Part B - the safety factor with respect to yielding is?

Q) A helical compression spring of a mechanism is subjected to Pas =120 N 19ad cycle. The diameter if the wire is 3 mm, with a spring index of € = 7 P, =4N and .The spring is made of oil-hardened and tempered steel, with”« ~ L0t dm Determine the factor of safety in fatigue loading.

True or False a) If an accurate value for the notch sensitivity is hard to find, I should consider the fatigue stress concentration factor higher than the stress concentration factor under static loading condition in design.  b) It is easier to find the asymptotic value of fatigue strength as the endurance limit on the S-N curve for a brass alloy (Cu70Zn30) than that of endurance limit on the S-N curve for an AISI 1045 steel.   a good fatigue design should keep the fatigue design factor of safety at a minimum value of______________

creep is testing under fluctuating cyclic stresses Select one: True False

Assume any value if it is not available

T or F Ductile materials have long stress-strain diagrams so they fail suddenly without warning. T or F Connections have 3 modes of failure: shearing of bolts, bearing in plate holes, and tension in plates. T or F Brittle materials are often weak in tension. T or F If a beam fails with vertical cracks (perpendicular to the length), then it is due to shear. T or F The maximum normal stress always occurs on a section plane that is normal to the longitudinal axis.

2. The rotating shaft shown in the figure is machined from AISI 1020 CD steel. It is subjected to a force of F = 6 kN. Find the minimum factor of safety for fatigue based on infinite life. If the life is not infinite, estimate the number of cycles. Be sure to check for yielding. ent Design 25 D. 20 +20 35 D. -180- Mechanical Engineering 12200 10sm 3RD Class -3 R. -500 F -280 -175- -50 D. 25 D. 20 20

Question 1 1 pts The drive shaft of a car is subjected to both bending and torsion. The torque, T, is constant at 400 Nm and the bending moment has the following cycle parameters: mean moment of Mm = 250 Nm and alternating moment of Ma = 800 Nm. The shaft is forged from high-carbon steel with an ultimate strength Sut = 615 MPa and endurance limit Se' = 307.5 MPa. The reliability must be 90% and the safety factor is nf = 2.7. For the analysis of the stress concentration, assume the proportions shown in the figure and a size factor kb = 0.9. To evaluate the factors kt, kts, q and qs, it is recommended to use Excel spreadsheets. Calculate the first estimate of the minimum shaft diameter (d) in millimeters using the Goodman criterion. 1≥4 D Id D/d = 1.33 r/d = 0.25 r≥ 4 mm (To evaluate q and qs, it is initially recommended r = 4 mm)