Method for measuring stress on steel by determining the reverse magnetic permeability under a magnetic bias field

Claim 1

A method for the determination of a stress in a steel material which comprises the steps of: (a) determining the reversible magnetic permeability μ by using a stress detector of steel materials utilizing the phenomenon of magnetostriction under a magnetic bias field H 0 within the range of approach to the saturation magnetization; (b) calculating the value of M, which is the first-order factor on 1/H 0 3 for the reversible magnetic permeability μ of the steel material in the equation μ=1+M/H 0 3 , utilizing the values of μ; and (c) calculating the values of a principal stress σ 1 in the steel material, the other principal stress σ 2 in the steel material which is in the direction perpendicular to the direction of σ 1 and the angle θ between the direction of σ 1 and the direction at which the reversible magnetic permeability μ is determined, from the equation ##EQU5## in which a is the value of the square root of M in a stress-free state and b is the stress sensitivity.

Claim 2

A method for the determination of a stress in a steel material which comprises the steps of: (a) determining the reversible magnetic permeability μ by using a stress detector of steel materials utilizing the phenomenon of magnetostriction under a magnetic bias field H 0 within the range of approach to the saturation magnetization; (b) calculating the value of M, which is the first-order factor on 1/H 0 3 for the reversible magnetic permeability μ of the steel material in the equation μ=1+M/H 0 3 , utilizing the values of μ; and (c) calculating the values of a principal stress σ 1 in the steel material, the other principal stress σ 2 in the steel material which is in the direction perpendicular to the direction of σ 1 and the angle θ between the direction of σ 1 and the direction at which the reversible magnetic permeability μ is determined, from the equation ##EQU5## in which a is the value of the square root of M in a stress-free state and b is the stress sensitivity.

Claim 3

A method for the determination of a stress in a steel material which comprises the steps of: (a) determining the reversible magnetic permeability μ by using a stress detector of steel materials utilizing the phenomenon of magnetostriction under a magnetic bias field H 0 within the range of approach to the saturation magnetization in at least three directions not parallel to each other; (b) calculating the values of M, which is the first-order factor on 1/H 0 3 for the reversible magnetic permeability μ of the steel material in the equation μ=1+M/H 0 3 , utilizing the three values of μ obtained in step (a); and (c) calculating the values of a principal stress σ 1 in the steel material, the other principal stress σ 2 in the steel material which is in the direction perpendicular to the direction of σ 1 and the angle θ between the direction of σ 1 and the direction at which the reversible magnetic permeability μ is determined, by solving a set of at least three simultaneous equations obtained by substituting the three values of M obtained in step (b) in the equation ##EQU6## in which a is the value of the square root of M in a stress-free state and b is the stress sensitivity.

Claim 4

A method for the determination of a stress in a steel material which comprises the steps of: (a) determining the reversible magnetic permeability μ by using a stress detector of steel materials utilizing the phenomenon of magnetostriction under a magnetic bias field H 0 within the range of approach to the saturation magnetization in at least three directions not parallel to each other; (b) calculating the values of M, which is the first-order factor on 1/H 0 3 for the reversible magnetic permeability μ of the steel material in the equation μ=1+M/H 0 3 , utilizing the three values of μ obtained in step (a); and (c) calculating the values of a principal stress σ 1 in the steel material, the other principal stress σ 2 in the steel material which is in the direction perpendicular to the direction of σ 1 and the angle θ between the direction of σ 1 and the direction at which the reversible magnetic permeability μ is determined, by solving a set of at least three simultaneous equations obtained by substituting the three values of M obtained in step (b) in the equation ##EQU6## in which a is the value of the square root of M in a stress-free state and b is the stress sensitivity.