Ultrasonic process for measuring stress in a bolt or similar part adapted to this method

Claim 2

Process for the measurement of stress in a structural element by making use of the reflection of an acoustic wave and by measuring a transit time of the latter with the aid of an equipment measuring the time of appearance of an echo coming from an interface, wherein one or a plurality of ends of rectilinear measurement paths, having the material form of an internal artificial reflector, is or are selected in the medium, wherein a beam of acoustic waves is transmitted in such a manner that acoustic rays carrying sufficient energy touch the useful reflectors, wherein the echoes corresponding to the reflectors are selected, wherein the transit times characteristic of the useful acoustic rays as far as the internal artificial reflectors are determined by measurement, and wherein the transit times for each internal reflector considered individually, or the respective differences of transit time of each pair of reflectors, are transposed into a value of external stress or into a value of stress in the zone delimited by each pair of reflectors.

Claim 3

Process as claimed in claim 1, wherein a rectilinear measurement path bounded by two internal artificial reflectors is selected in the medium, wherein a beam of acoustic waves, the axis of which is substantially identical with the selected rectilinear measurement path, is transmitted, wherein the echoes corresponding to the internal artificial reflectors are selected, wherein the transit time characteristic of an acoustic ray between the two reflectors is measured, this time being the difference between the transit times of the coincident or substantially parallel acoustic rays as far as each of the two reflectors, and wherein the values of transit time are transposed into values of stress.

Claim 4

Process as claimed in claim 1, wherein a narrow ultrasonic beam is used.

Claim 5

Process as claimed in claim 1, wherein a focused ultrasonic beam is used.

Claim 6

Process as claimed in claim 1, wherein the measurement is made by continuous transmission and determination of the resonance frequencies of the wave which are due to the two internal reflectors.

Claim 7

Process as claimed in claim 1, wherein transverse ultrasonic waves are used.

Claim 8

Process as claimed in claim 1, wherein longitudinal ultrasonic waves are used.

Claim 9

Process as claimed in claim 1, wherein surface ultrasonic waves are used.

Claim 10

Process as claimed in claim 1, wherein a longitudinal wave and a transverse wave are used in combination, concomitantly or in succession.

Claim 11

Process as claimed in claim 1, wherein the artificial reflectors consist of transverse perforations or bores disposed in parallel planes and forming an angle in relation to one another.

Claim 12

Process as claimed in claim 1, wherein the reflectors consist of two coaxial bores of small diameter, but of different diameters and of different depths.

Claim 13

Process as claimed in claim 1, wherein the positioning of the transmitter/receiver sensor is effected by finding the position in which the amplitudes of the reflection echoes on the internal artificial reflectors are as far as possible simultaneously maximum or attain respective relative heights marked in advance during the calibration.

Claim 14

Process as claimed in claim 1, wherein the measurement is made by utilizing two different frequencies of acoustic waves.

Claim 15

Structural element for performing the process as claimed in claim 1, which has one or more artificial reflectors (8, 9) for the acoustic waves.

Claim 16

Structural element as claimed in claim 14, which consists of a bolt, a threaded rod, or a tie.

Claim 17

Structural element as claimed in claim 14, which is provided with artificial reflectors (8, 9) which consist of transverse perforations or bores disposed in parallel planes and forming an angle in relation to one another.

Claim 18

Structural element as claimed in claim 16, in which the perforations or bores (10, 11) form an angle of 90° between them.

Claim 19

Structural element as claimed in claim 16, in which the perforations or bores (10, 11) form an angle between 0° and 90° in such a direction that this angle increases with the angular torsional deformation on tightening.

Claim 20

Structural element as claimed in claim 14, which is provided with positioning means such as a bush or a socket in the end of the part intended to receive a sensor.

Claim 21

Process for the measurement of stress in a structural element by making use of the reflection of an acoustic wave and by measuring a transit time of the latter with the aid of an equipment measuring the time of appearance of an echo coming from an interface, wherein one or a plurality of ends of rectilinear measurement paths, having the material form of an internal artificial reflector, is or are selected in the medium, wherein a beam of acoustic waves is transmitted in such a manner that acoustic rays carrying sufficient energy touch the useful reflectors, wherein the echoes corresponding to the reflectors are selected, wherein the transit times characteristic of the useful acoustic rays as far as the internal artificial reflectors are determined by measurement, and wherein the transit times for each internal reflector considered individually, or the respective differences of transit time of each pair of reflectors, are transposed into a value of external stress or into a value of stress in the zone delimited by each pair of reflectors; and wherein the artificial reflectors consist of transverse perforations or bores disposed in parallel planes and forming an angle in relation to one another, said perforations or bores forming an angle of 90° between them.

Claim 22

Process for the measurement of stress in a structural element by making use of the reflection of an acoustic wave and by measuring a transit time of the latter with the aid of an equipment measuring the time of appearance of an echo coming from an interface, wherein one or a plurality of ends of rectilinear measurement paths, having the material form of an internal artificial reflector, is or are selected in the medium, wherein a beam of acoustic waves is transmitted in such a manner that acoustic rays carrying sufficient energy touch the useful reflectors, wherein the echoes corresponding to the reflectors are selected, wherein the transit times characteristic of the useful acoustic rays as far as the internal artificial reflectors are determined by measurement, and wherein the transit times for each internal reflector considered individually, or the respective differences of transit time of each pair of reflectors, are transposed into a value of external stress or into a value of stress in the zone delimited by each pair of reflectors; and wherein the artificial reflectors consist of transverse perforations or bores disposed in parallel planes and forming an angle in relation to one another, said perforations or bores forming an angle of 90° between them.

Claim 23

Process for the measurement of stress in a structural element by making use of the reflection of an acoustic wave and by measuring a transit time of the latter with the aid of an equipment measuring the time of appearance of an echo coming from an interface, wherein one or a plurality of ends of rectilinear measurement paths, having the material form of an internal artificial reflector, is or are selected in the medium, wherein a beam of acoustic waves is transmitted in such a manner that acoustic rays carrying sufficient energy touch the useful reflectors, wherein the echoes corresponding to the reflectors are selected, wherein the transit times characteristic of the useful acoustic rays as far as the internal artificial reflectors are determined by measurement, and wherein the transit times for each internal reflector considered individually, or the respective differences of transit time of each pair of reflectors, are transposed into a value of external stress or into a value of stress in the zone delimited by each pair of reflectors; and wherein the artificial reflectors consist of transverse perforations or bores disposed in parallel planes and forming an angle in relation to one another, said perforations or bores forming an angle between 0° and 90° in a direction such that this angle increases with the angular torsional deformation on tightening.

Claim 24

Process for the measurement of stress in a structural element by making use of the reflection of an acoustic wave and by measuring a transit time of the latter with the aid of an equipment measuring the time of appearance of an echo coming from an interface, wherein one or a plurality of ends of rectilinear measurement paths, having the material form of an internal artificial reflector, is or are selected in the medium, wherein a beam of acoustic waves is transmitted in such a manner that acoustic rays carrying sufficient energy touch the useful reflectors, wherein the echoes corresponding to the reflectors are selected, wherein the transit times characteristic of the useful acoustic rays as far as the internal artificial reflectors are determined by measurement, and wherein the transit times for each internal reflector considered individually, or the respective differences of transit time of each pair of reflectors, are transposed into a value of external stress or into a value of stress in the zone delimited by each pair of reflectors; and wherein the artificial reflectors consist of transverse perforations or bores disposed in parallel planes and forming an angle in relation to one another, said perforations or bores forming an angle between 0° and 90° in a direction such that this angle increases with the angular torsional deformation on tightening.