Fatigue Curves in Bolted Connections

For determining the fatigue strength of bolted connection the method of virtual mean stress can be used.

where:

	σ _a, τ_a	amplitude of normal (shear) stress [MPa, psi].
	σ _e, τ_e	endurance limit at the constant strength [MPa, psi]
	σ _m, τ_m	mean cycle stress [MPa, psi].
	σ _F, τ_F	virtual mean stress [MPa, psi]
	Ψ	factor of Haigh diagram narrowing [-]
		depends on the joint material - recommended values - for traction and bending Ψ <0.15...0.3>
		- for shear Ψ <0.1...0.25>.