Question

Question Four (15 marks) A cylindrical steel machine component is dynamically loaded with alternating torque and bending Maximum torque Max. bending moment as follows 40Nm (CW) -38 Nm Minimum torque Min. bending moment 175Nm (CCW), 238 Nm 500 MPa, Se = 280 MPa For the steel, Sut = 700 MPa, Sv = Assuming that o'm/a'a is constant, and that the design factor of safety for fatigue is 2.0 Estimate the diameter of the cylindrical component (a) (10 marks) 16T 32M and r Note that for a cylinder, max min min and o Also, aa same ta, Tm imax 2 Assuming that the diameter of the component is 30mm, estimate the design factor of safety for static plastic yield. (b) (5 marks) S Remember that N, 1/2 may be used for Von Mises 2 +3r max and that o max max max criterion

Answer 1

olutiom T 15 NM Tmin-40NM Mmax 239NA, Mrin -38 NM convertins N.M to NMN 32 K1038 M P 2 32 MMAS 6max 32 X238810 - TTds Wel3 1 32A 108 Tel3 6pin Mfa 16X 10 175 MPa nin:1 16103 40 Mla 138 MPa 6mas +6pin 32K103 100 MPa EPY 16 X10 107.5 MPa 2 32X1O53.5MI Tman-min gLK 1033.75 MPa 16X 1067-5 MPa Ynag+in 2 using lon Mises Now critrion 32X 163 dVI53.753 92Y103 3 .46 Mfa 6a 32X 10 1002+3x33752 M- TId3 Sal 3EX(115.83) Mla esing slerbey Sine nothing ts airer. So an Criterion becuse itis Satest) Se 280M Pa 1 TA Sy N2

32X10 166.46 + 32X 103 115.83 X 038 8415.196 S0O 2 d2.629MM c3 2 cliameter ld) 30MM Caiven Omax - 89.78 MP Tmayo 33 MPa So Using Von mises Cyiterign Oma t3 X 332 = l06.43MPa 4.698 factor ct Satety N) 1 max 06.43