Calculation Formulas for Loaded Tube Joined by Peripheral Butt Welds

Peripheral butt weld loaded with normal stress

Normal stress

where:

	F z	axial force [N, lb]
	A	throat area of the weld [mm 2 , in 2 ]

Comparative stress

where:

	σ	normal stress [MPa, psi]
	α 1	shear stress [MPa, psi]

Peripheral butt weld loaded with torque

Shear stress

where:

	u	constant
		- for calculation in metric units u = 1000
		- for calculation in English units u = 12
	T	torque [Nm, lb ft]
	W	section modulus of throat area of the weld [mm 3 , in 3 ]

Comparative stress

where:

	τ	shear stress [MPa, psi]
	α 2	conversion factor of the weld joint [-]

Peripheral butt weld loaded with combined loading

Resultant reduced stress

where:

	σ	normal stress [MPa, psi]
	τ	shear stress [MPa, psi]

Comparative stress

where:

	σ	normal stress [MPa, psi]
	τ	shear stress [MPa, psi]
	α 1 , α 2	conversion factors of the weld joint [-]

Meaning of used variables:

F z	axial force [N, lb]
F n	normal force [N, lb]
F t	shear force [N, lb]
A	throat area of the weld [mm 2 , in 2 ]
T	torque [Nm, lb ft]
M 1 , M 2	bending moments [Nm, lb ft]
s	plate thickness [mm, in]
W	section modulus of throat area of the weld [mm 3 , in 3 ]
α 1 , α 2	conversion factors of the weld joint [-]