SU1176225A1 - Flaw detector - Google Patents

Abstract

A DEFECTOSCOPE containing a heater installed in one corus with a sensitive element connected through a voltage amplifier to a defect indicator, a thermostat connected to a heater, characterized in that, in order to improve resolution, the sensitive element is designed as two thermal resistance elements included in the bridge circuit and separated by interchangeable gaskets, the thickness and thermal characteristics of which are the same, w. as for controlled material. (L

Description

1

The invention relates to defect-scopy and is intended to conduct NIN non-destructive testing of solid sheet materials and products from them.

The aim of the invention is to increase the resolution of detection of defects in materials with a wide range of thermal characteristics.

FIG. 1 shows the flow chart of the flaw detector; in fig. 2 - thermal head, general view; Fig. 3 shows the connection of thermistors included in the sensitive element.

The flaw detector (Fig. 1) consists of a thermal head 1, an electric unit for controlling the temperature difference between the surface of the sensing element and the environment 2, the voltage amplifier 3 and the indicator 4

The heat head (Fig. 2) consists of a metal case 5, made in the form of a glass, to the bottom of which a sensitive element is attached, consisting of thermo-resistive elements 6 and 7 and replaceable gasket 8 between them.

Thermistor 7 forms the working contact surface of the thermal head. It is protected from mechanical damage by a membrane 9, which, to reduce its thermal resistance, is made of a thin, highly heat-conducting material, for example copper foil.

A heater 10 and a thermistor 11 are placed inside the cup, serving as a sensor in the temperature control circuit of the thermal head casing 5, the casing 5 together with the sensing element is placed in a thermally insulating guide sleeve 12. The thermal head membrane 9 contacts with the test sample 13 with defect 14.

FIG. 3 shows the connection circuit of the thermoresistors included in the sensor element, where Rj- and RT are thermistors; R and R are balance resistances of the bridge; E EMF of the power source of the bridge.

The device works as follows.

In the prepared mode, the thermal head is stored by thermal energy generated by the electric heater 10. Temperature level

This energy is determined by thermistor 11, the guide sleeve 12 reduces heat loss to the environment and directs the heat flux from the heater through the sensitive element to the test sample 13. In operating mode, the heat head is brought into contact with the contact surface with the surface of the sample or article under investigation. In this case, a non-stationary process of returning the accumulated thermal energy to the material occurs.

The heat flux rate characteristic of this process is proportional to the temperature difference on the surface of the housing 5 and the specific surface of the sensing element. The temperature difference is created on the replacement gasket 8 when the heat flux passes through it. The voltage unbalance in the diagonal of the bridge circuit for switching on thermistors (Fig. 3) is proportional to the temperature difference on the surface of the interchangeable gasket 8 and characterizes the heat flux through it. This voltage is amplified by a differential voltage amplifier 3 and is applied to the indicator of defect 4. Judging by the magnitude of this voltage, a defect is detected in the controlled material,

The use of two flat thermo resistive elements 6 and 7 (FIG. 2) with identical thermal characteristics to form the sensing element allows one to achieve the goal by substantially reducing the random and eliminating the systematic control errors inherent in the prototype.

In the proposed construction, the measurement error of the heat flux through the Sensors is significantly reduced. The body element associated with the nonidentity of the conversion coefficient of thermopile sensing elements and their uneven sensitivity in the working cavity, as well as the error due to the change in the conversion coefficient of the sensitive element with time due to the electrochemical interaction of thermoelectric materials forming the thermal battery in the bonding medium.

Removable gasket 8 (FIG. 2) allows an increase in sensitivity.

31176225 4

of the flaw detector to the change in the thermophysics of the thermophysical characteristics of the monitored material of the gasket and controlled materials by selecting the optimal surface.

FIG. 2

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FIG. 3

Claims (1)

A DEFECTOSCOPE containing a heater installed in one housing with a sensing element connected via a voltage amplifier to a defect indicator, a temperature regulator connected to a heater, characterized in that, in order to increase the resolution, the sensitive element is made in the form of a system of two thermoresistive elements included in the bridge circuit and separated by interchangeable gaskets, the thicknesses and thermal characteristics of which are selected to be the same as for the controlled material. Figure 1 SU .... 1176225>