SU1305587A1 - Method of checking residual mechanical stresses in members - Google Patents

Abstract

The invention relates to non-destructive quality control of materials and products. The aim of the invention is to improve the accuracy of monitoring residual / exact mechanical stresses when the transducer is scanning the surface of a structural member. To do this, before measuring the monitored parameter, the converter scanning the surface of the control object corrects the air gap between the test object and the primary transducer, each time to achieve the equality of the total magnetic resistances caused by the converter, the test object, the air gap and the scattering fields. As a criterion of the accepted equality of the induced emf of the measuring winding of the converter in the saturation mode at each new position. 2 Il. C /) CO sd ate CX) |

Description

The invention relates to non-destruction maxirnet quality control of materials and products and can be used to control residual mechanical stresses in flat extended structural elements. ,

The purpose of the invention is to increase the control accuracy when a transducer is scanning the surface of a structural element by creating control conditions independent of the position of the transducer.

FIG. I presents the total weber-ampere characteristic at

different transducer positions relative to the surface to be controlled; in fig. 2 shows a replacement circuit for a converter interacting with a control object.

The procedure is as follows.

It is known that the EMF of the converter, determined in the saturation mode, is not sensitive to mechanical stresses. This feature of the magnetoelastic effect is the basis of the method of co-control of residual stresses under conditions of a change in the air gap between the transducer controlled surface of the structural element. The indicated changes in the air gap lead to deformation of the total weber-ampere characteristic (Fig. 1), and therefore the measurement of the maternal parameter, such as induction, at a certain point in the magnetization curve will not correspond to the condition that the control mode remains unchanged. The surface of the structural member is scanned by a transducer. At the initial position of the converter, to which some initial air gap 8 corresponds, the controlled section of the structural element is magnetised before the induction Hacbfflie Wi (saturation mode), which will correspond to a certain magnetizing current IH

R. Qf 7 4-7 .1

)

J-u

W

 where,, Zg and Zi, s are the magnetic resistances of the converter, the structural element, the air gap and the magnetic resistance caused by the scattering fluxes, respectively; W is the number of turns of the magnetizing winding of the converter.

five

0

five

0

j

five

0

Since the EMF in the measuring ob-, the coil of the converter is proportional to. on the rate of change of magnetic induction, it is reasonable to monitor the value of induction in the saturation ratio by the value of the emf. Then, without changing the position of the converter, its EMF is measured for a given value of the magnetic field strength or, equivalently, for a given value of the current in the magnetizing winding 1 | "At subsequent positions of the converter, before measuring on the magnetizing winding of the converter, a current of a given magnitude is passed... And changing the distance from the converter to the test surface to obtain a measuring winding emf of the same value as in the initial position of the converter, which means that total magnetic resistances of the considered replacement circuit (FIG. 2) for different transducer positions, since

M |, 5..eonst.

The correction of the air gap for the new position of the converter is equivalent to the artificial deformation of the total weber-ampere characteristic to a certain fixed value, which makes it possible to control the mechanical stresses at the same magnetizing current ii for all the positions, i.e. to create conditions independent of the converter transducer conditions, 1 tons of residual mechanical stresses over the entire surface of the structural element.

pr - eq

Analyzing the 45 EMF measured at a certain intensity of the magnetic field from the measuring winding of the converter, the magnitude of the residual stresses is judged.

Claims (1)

Invention Formula The method of controlling the residual mechanical stresses in the structural elements, in which the electroinductive transducer is brought into interaction with the controlled section of the structural element, changes the distance from the transducer. T1 to the surface of the monitored section, for a fixed value 3I the specified distance is measured by the emf of the converter and, by its value, the magnitude of the residual mechanical stresses is determined, differing from the fact that, in order to increase the accuracy of control when the converter is scanning the surface of the structural element, 305587.4  the converter is produced many times each time in the saturation mode and at a fixed value of the magnetic field strength, and - 5 oi converter to surface the controlled area is chosen from the condition of constant EMF of the converter in the saturation mode. Compiled by I. Rekunov Editor A. Kozoriz Tehred M. Khodanich Proofreader T. Kolb Order 1423/42 Circulation 777 Subscription VNIIPI State Committee CCCF for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4 fuz 2