90 likes | 222 Views
Mechanics of Materials Lab. Lecture 19 Fatigue Mechanical Behavior of Materials Sec. 9.6-9.8 Jiangyu Li University of Washington. Safety Factor with Mean Stress. Example.
E N D
Mechanics of Materials Lab Lecture 19 Fatigue Mechanical Behavior of Materials Sec. 9.6-9.8 Jiangyu Li University of Washington Jiangyu Li, University of Washington
Safety Factor with Mean Stress Jiangyu Li, University of Washington
Example • Man-Ten steel (sf’=1089MPa, b=-0.115) subject to stress amplitude of 180 Mpa and mean stress of 100PMa for 20000 cycles • What is the safety factor in life and stress? Jiangyu Li, University of Washington
Multiaxial Stress Jiangyu Li, University of Washington
Multiaxial Stress Jiangyu Li, University of Washington
Example • A solid circular shaft of diameter 50mm is made of Ti-6Al-4V. A zero-to-maximum cyclic torque of T=10 kN.m is applied, together with a zero-to-maximum cyclic bending moment of M=7.5 kN.m applied in phase with same frequency. What is the fatigue life? Jiangyu Li, University of Washington
Example • A solid circular shaft is made of AISI 4142 steel with diameter of 50mm, and loaded in cyclic torsion between zero and a torque of 20 kN.m. • What is fatigue life • What shaft diameter is needed if 100000 cycles are expected in life and safety factor must be at least 20 Jiangyu Li, University of Washington
Assignment Mechanical Behavior of Materials 9.30, 9.31,9.33 , 9.35, 9.39 Jiangyu Li, University of Washington