Notation xix Quantity Symbol SI Unit 'Operator'for Airy stress function biharmonic equation Strain rate s-1 Coefficient of viscosity 少 Retardation time (creep strain recovery) Relaxation time (creep stress relaxation)t" Creep contraction or lateral strain ratio J(t) Maximum contact pressure (Hertz) Po N/m2 Contact formulae constant △ N/m2)-1 Contact area semi-axes a,b m Maximum contact stress 0e=-P0 N/m2 Spur gear contact formula constant K N/m2 Helical gear profile contact ratio mp Elastic stress concentration factor K Fatigue stress concentration factor K Plastic flow stress concentration factor Kp Shear stress concentration factor Kts 二 Endurance limit for n cycles of load Sn N/m2 Notch sensitivity factor 9 Fatigue notch factor Kf Strain concentration factor Ke Griffith's critical strain energy release Ge Surface energy of crack face Nm Plate thickness B m Strain energy U Nm Compliance C mN-1 Fracture stress N/m2 Stress Intensity Factor K or K N/m3/2 Compliance function Y Plastic zone dimension m Critical stress intensity factor N/m3/2 “J”Integral Fatigue crack dimension 0 m Coefficients of Paris Erdogan law C,m Fatigue stress range O, N/m2 Fatigue mean stress Om N/m2 Fatigue stress amplitude Ga N/m2 Fatigue stress ratio R, Cycles to failure N 二 Fatigue strength for N cycles GN N/m2 Tensile strength S N/m2 Factor of safety FNotation xix Quantity ‘Operator’ for Airy stress function biharmonic equation Strain rate Coefficient of viscosity Retardation time (creep strain recovery) Relaxation time (creep stress relaxation) Creep contraction or lateral strain ratio Maximum contact pressure (Hertz) Contact formulae constant Contact area semi-axes Maximum contact stress Spur gear contact formula constant Helical gear profile contact ratio Elastic stress concentration factor Fatigue stress concentration factor Plastic flow stress concentration factor Shear stress concentration factor Endurance limit for n cycles of load Notch sensitivity factor Fatigue notch factor Strain concentration factor Griffith‘s critical strain energy release Surface energy of crack face Plate thickness Strain energy Compliance Fracture stress Stress Intensity Factor Compliance function Plastic zone dimension Critical stress intensity factor “J” Integral Fatigue crack dimension Coefficients of Paris Erdogan law Fatigue stress range Fatigue mean stress Fatigue stress amplitude Fatigue stress ratio Cycles to failure Fatigue strength for N cycles Tensile strength Factor of safety SI Unit S S - N/mz (N/m2)- m N/mZ N/mZ Nm m Nm mN-’ N/m2 N/m3I2 m N/m3I2 m N/m2 N/m2 N/m2 - - N/m2 N/m2 -