Method of measuring intrinsic stresses in structural components of machines and apparatus and devices for performing such method

Claim 3

A method as claimed in claim 1, wherein the groove cutting increments are of circular shape on the component and on the specimens so that the core surface areas of the component and the specimen are circular.

Claim 4

A method as claimed in claim 2; further comprising the step of attaching electrical wire strain gages, each comprising an elongated rectangular strip, in an arrangement in which the longitudinal and symmetry axes of the strips pass through the center point of the area.

Claim 5

A method as claimed in claim 3, further comprising the steps of attaching the wire strain gages, in the configuration of elongated strips mounted on a gage carrier by cementing the gage carrier face-to-face upon the area of the component member, then covering the gage carrier and the gages attached thereto by a protective layer consisting of a thermally and electrically insulating plastic adhesive mass with the connecting wires of the gages protruding through the mass, placing a perforated solder-spot carrier about the area, and threading the wires through the perforations, pressing the solder-spot carrier into the surface of the protective layer, and soldering the connecting wires to the solder spots of the solder-spot carrier.

Claim 6

A method as claimed in claim 3, further comprising the step of arranging three strain gage strips on the area in star configuration with the strips longitudinally intersecting each other at the center point and extending in three measuring directions (a, b, c), the triple arrangement being mirror symmetrical relative to two symmetry axes passing through the center point.

Claim 7

A method as claimed in claim 3, further comprising the step of arranging three strain gage strips on the area in star configuration with the strips longitudinally intersecting each other at the center point and extending in three measuring directions (a, b, c), the triple arrangement being mirror symmetrical relative to two symmetry axes passing through the center point, covering the attached strain gage strips with a protective layer of a thermally and electrically insulating plastic adhesive mass with the connecting wires of the gages protruding through the mass, placing a perforated solder-spot carrier about the area, and threading the wires through the perforations, pressing the solder spot carrier into the surface of the protective layer, and soldering the connecting wires to the solder spots of the carrier, the solder-spot carrier having four metal plates of which each corresponds approximately to one-quarter section of a Circle, placing the four section plates in a circular arrangment about the strain gage area and leaving between them an insulating space corresponding to a cross of coordinate axes, connecting one of the plates to one wire of each of the gages, and connecting the three other plates to the wires corresponding to the three respective measuring directions (a, b and c).

Claim 8

A method as claimed in claim 2, further comprising the step of giving the component core surface area a diameter of about 14 mm, the gage arrangement a diameter of about 12 mm, and the groove a radial width of about 4 mm.

Claim 9

A method as claimed in claim 2, for measuring inherent stresses in a structural component having a substantially biaxial inherent stress condition, said condition comprising a plural axial inherent stress condition in which a third main stress near free surfaces is approximately perpendicular to the surface while a substantially biaxial condition, substantially unaffected by the third inherent main stress, prevails in planes parallel to the surface in any direction of the first and second inherent main stress, said method further comprising the steps of effecting, after each incremental cutting, the strain measuring operation in those different measuring directions (a, b, c) of which two direction (a, b) are perpendicular to each other, measuring the corresponding three surface strains (one of d epsilon a, d epsilon b and d epsilon c and epsilon a, epsilon b and epsilon c) of the resulting component core surface area, thereby determining the first differential functions (d epsilon a)/(dz), (d epsilon b)/(dz) and (d epsilon c)/(dz) separately testing the calibrating specimen in the same three measuring directions (a, b, c) and in a simulated two axial condition of inherent stress, in which the direction of the specimen inherent stress ( sigma *a) coincides with the direction of an externally applied main stress ( sigma *1), measuring each time of the specimen the surface strains (d epsilon *a, Sigma d epsilon *a) in the first measuring direction a. of the specimen core surface area, the surface strains ( epsilon b*, Sigma epsilon b*) in the second measuring direction b. of the specimen core surface area and measuring the corresponding cutting depth (one of dz and epsilon dz), thereby determining the second differential functions (d epsilon *a)/(dz), (d epsilon *b)/(dz ) and determining from the thus measured specimen data the decay functions K1 f1(z) ((E*)/( sigma *a2- sigma *b2))( sigma *a(d epsilon *a)/(dz) - sigma *b(d epsilon *b)/(dz) )K2 f2 (z) (E*/ Mu * ( sigma *b2- sigma *a2)) - ( sigma *a((d epsilon *b)/(dz))-sigma *b((d epsilon *a)/(dz)) wherein sigma *a, sigma *b are the inherent stresses of the calibrating specimen simulated by external forces and obtaining at the corresponding depth dz of the removed layer of material, Mu * is the Poisson''s ratio number of the calibrating material, and deriving from the thus resulting quantities of K1, K2, (d epsilon a)/(dz), (d epsilon b)/(dz), (d epsilon c)/(dz) the inherent stresses sigma a(z) (E/K12- Mu 2K22)(K1( d epsilon a)/(dz))+ Mu K2 (d epsilon b/dz)) sigma b(z) (E/K12- Mu 2K22)(K1( d epsilon b/dz)+ Mu K2( d epsilon a/dz) sigma c(z) (E/K12- Mu 2K22)( K1(d epsilon c/dz)+ Mu K2((d epsilon a/dz) +( d epsilon b/dz) - ( d epsilon c/dz))) wherein sigma a, sigma b, sigma c are the median inherent stresses released in the three directions (a, b, c) at the groove depth z of the body in the layer of material having the depth dz, Mu is the Poisson''s ratio of the body material.

Claim 10

A method as claimed in claim 8, wherein the second main stress ( sigma *b sigma 2) is zero for the calibrating test, whereby the following decay functions are obtained K1 f1(z) (E*/ sigma *a( d epsilon *a/dz) and K2 f2 (z) (-E*/ Mu * sigma *a)( d epsilon *b/dz).

Claim 11

A method as claimed in claim 8, comprising the step of placing the third measuring direction (c) between the first and second directions (a and b) at an angle of 45* to the first direction, so that the main inherent stress of the component corresponds to sigma 1,2 sigma max,min ( sigma a(z)+ sigma b(z)/2) + or - 1/ Square Root 2 Square Root ( sigma a(z)- sigma c(z))2+( sigma c(z)- sigma b(z))2 and the angle Alpha in counterclockwise direction between the first measuring direction and the main stress axis is determined in accordance with the equation tan 2 Alpha ( 2 sigma c(z) - ( sigma a(z)+ sigma b(z)) /( sigma a(z) - sigma b(z) ))

Claim 12

A method as claimed in claim 1, wherein the specimen material for said calibrating test consists of synthetic plastic having a modulus of elasticity in the order of E* about 3.0 X 104 kp/cm2 and a Poisson''s ratio Mu * about 0.33.

Claim 13

Method according to claim 1, wherein a substantially uniaxial inherent stress condition prevails in a component, the width y'' of which is very small relative to its length x'' and its depth z, the inherent stress sigma z(z) being present only substantially perpendicularly to the z-coordinate, the method comprising determining the decay function Kz (E*/ sigma *z).( d epsilon *z/dz) and determining the inherent stress sigma z(z) (E/Kz).( d epsilon z/dz).