Question

The mechanical component shown in the figure is subjected to variable loading conditions that cause the axial stresses to fluctuate as indicated in the stress-time history. The material of the part is AISI 1045 HR steel with an ultimate static strength of 570 MPa. The part has been tested in the laboratory under different completely reversed stress amplitudes, the fatigue life results of these tests are shown in the table a) The S-N diagram of the part based on the experimental data provided in the table. Use a linear regression to estimate the model constants. Set a logarithmic scale of the number of cycles and a linear scale for the fatigue strength. b) The number of repetition of the stress cycles shown in the stress-time history that the part is able to sustain before fatigue failure. Use Miner's law to model the level of fatigue damage accumulated after one repetition c) Whether the sequence of the applied stress cycles affect the fatigue life of the mechanical component Stress (MPa) 280 cycles 100 cycles 550 cycles 350 cycles 530 340 240 -240 one repetition Stress (MPa) N (Cycles) 524 459 410 257 1,494 6,749 315 270 250 36930 321,500 1,000,000

Answer 1

a) we daw S-N cusve in encel. The oqustiom we hntan are -34.398, To.y) mine s Law sustain 5 30 m N 163.8 3 to0 S36 3 56 S147

2 take ato atca their ovd not ocuhance.. ttence术eleguenle doer no the taitne r of th e machani cal cennybne

Stress (MPa) N S-N Curve у#-34.398х + 705.4 459 410 352 315 270 250 257 5.549076 1494 7.309212 67498.81715 19090 9.85692 3693010.51678 32150012.68075 1000000 13.81551 600 500 400 300 200 100 10 12 14 16 Ln (N)