SU765713A1 - Method of detecting and determining fatigue crack coordinate - Google Patents

Description

The invention relates to a measurement technique and can be used in testing the strength of materials and structures. A known method of detecting and determining the coordinates of the fatigue footpins is that strips of an electrically conductive material are glued to the surface of the sample of the material before testing it. If the sample is conductive, an insulating sludge is inserted between the nsl and the strip. An electric current is passed through the strips. The strips burn out at the place where the fatigue crack occurs, where the heat created by the current cannot be dissipated. The arc discharge that occurs at the point of burnout of the strip visually determines the location of fracture i, however, the visual determination of the location of the occurrence of a crack can lead to subjective errors in the control. Visual inspection is unproductive. And before a fatigue crack is detected, sample failure can occur. In addition, the arc discharge may be located in a place difficult to access for visual inspection. The closest technical solution to the invention is a test at the site of the possible occurrence of a crack of the strength L2J Sensor. A method for detecting fatigue tr & s using a sensor located on the strength test object at the place where the crack is likely to occur. When a crack arises and grows, the substrate and the tooth of the sensor comb are broken, which leads to an abrupt decrease in the capacitance between the lining and the test piece. The length of the crack is judged by the number of jumps or the total value of the change in the capacitance of the spring. Since the capacitance of the sensor is proportional to its length, the length L of the shortened sensor is coordinate 3.

dinate cracks can be found from the relation: L.O, Us.

So Shx

where is LO and Co

- the known length and capacity of the sensor until it breaks with a crack, Cx - the capacity of the sensor shortened by a crack, measured after the occurrence of a crack. The disadvantage of this method, based on the measurement of the capacitance between the sensor and the electrically conductive object of strength testing, is that its scope is limited to electrically conductive objects.

The chain of the invention is an extension of the field of application.

The goal is achieved by attaching a sensor consisting of an insulating substrate and an electrically conductive lining in the form of a strip having an electrical lead at one end to the object of the test where a fatigue crack is likely to occur.

In the space surrounding the test object, a magnetic radiation is generated, which induces an electrical signal in the sensor, the value of which is proportional to the length of the sensor. With

the occurrence of a crack that breaks the sensor and reduces its length; the magnitude of the signal induced in the sensor is also reduced. Based on the value of the reduced signal, the coordinate of the crack is judged, since this value of the signal is pre-horizontal to the crack length.

The drawing shows a block diagram of a single device that implements

the proposed method.

The device consists of an electromagnetic radiation generator 1, a sensor 2 placed on the object 3 of the strength test, an electronic key 4

and the rhythm of the stratora

Generator 1 generates, in the space surrounding the test object 3, electromagnetic radiation. Sensor 2, made in the form of electromotive

The strip located on the insulating substrate is an electrical antenna that receives electromagnetic radiation. Under the influence of radiation in the sensor 2 is induced electric

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This value is proportional to the length of the sensor 2. The signal from the sensor 2 is fed to the input of the electronic key 4 An open or closed key state

4 is determined by the magnitude of the signal from sensor 2 to control input 4. Until a crack is formed

and rupture of sensor 2, the magnitude of the induced signal is such that the key 4 is closed and does not pass the signal to the recorder 5

In the event of cracks and rupture of the sensor 2, its length becomes less than the original, due to which the value of the electrical signal induced in the sensor 2 decreases. Reducing the signal size causes key 4 to open, and it passes the signal from sensor 2 for the recorder 5. Recorder

5 fixes the value of the electrical signal proportional to the length of the sensor 2 to the crack. Based on the fixed signal value, the crack coordinate is judged, since this value is proportional to the length of sensor 2 to cracks,

The detection and determination of the crack coordinate by the magnitude of the electrical signal induced in the sensor allows one to apply this method both for testing the strength of electrically conductive and non-electrically conductive objects, which expands the scope of application of the method.

Claims (2)

1.Patent UK No. 970403 cl. (IN, 1964. 2. Finkel VM Physics of Destruction, Metallurgi Publishing House, Moscow, 1970, p. 72 (prototype). /,