Device for measuring crack propagation parameters during mechanical tests
The device accurately determines crack initiation by employing additional potential electrodes aligned with the tensile force direction, resolving the challenge of plastic deformation interference in crack formation detection.
Patent Information
- Authority / Receiving Office
- RU · RU
- Patent Type
- Patents
- Current Assignee / Owner
- OBSHCHESTVO S OGRANICHENNOJ OTVETSTVENNOSTYU GTLAB
- Filing Date
- 2026-02-02
- Publication Date
- 2026-07-07
Smart Images
Figure 00000001_ABST
Abstract
Description
[0001] The invention relates to non-destructive testing and can be used to record the length and growth rate of cracks during mechanical testing of metal samples.
[0002] The prior art discloses a “Device for measuring the difference in electrical potentials (see Operating Manual UIRP-20.000.000 RE 2015 of Testsystems LLC)”, comprising a power source, a two-channel recorder, a rectangular metal test sample in which a notch is made on the side of crack development, a pair of current electrodes connected to a power source and a pair of potential electrodes connected to one channel of the two-channel recorder are mounted on the surface of the test sample, wherein the pairs of electrodes are located symmetrically relative to the notch and to each other, and the potential electrodes are located near the notch.
[0003] The above device is the closest to the claimed device in technical essence and is therefore chosen as a prototype.
[0004] The disadvantages of the prototype include limited functionality for accurately determining the onset of crack formation in the test specimen due to plastic deformation of the specimen prior to crack initiation. When a power source is connected to the current electrodes, a potential proportional to the supply current appears on a pair of potential electrodes located symmetrically relative to the notch and remains constant until deformation of the test specimen begins. When a tensile force perpendicular to the notch is applied to the specimen, the test specimen begins to experience mechanical stress, leading to deformation—a change in its geometric dimensions. The onset of a change in geometric dimensions leads to a change in the recorded potential; however, due to plastic deformation of the test specimen, a crack only appears after a certain time.As a crack develops, the recorded potential continues to change until its growth ceases. Changes in the recorded potential during plastic deformation make it impossible to accurately determine the onset of crack development.
[0005] The technical problem to be solved is the creation of a device for measuring crack development parameters during mechanical testing with expanded functionality.
[0006] The technical result achieved is to determine the beginning of the crack development moment.
[0007] In order to achieve the technical result in a device for measuring crack development parameters during mechanical testing, comprising a power source, a two-channel recorder, a rectangular metal test sample in which a notch is made on the side of crack development, on the surface of the test sample, first and second current electrodes are mounted symmetrically relative to the notch, connected to a power source and first and second potential electrodes, located symmetrically and closer than the current electrodes in relation to the notch and connected to the first channel of the two-channel recorder, characterized in that,that, in addition, a third potential electrode is installed on the surface of the test sample between the first potential and first current electrodes and is connected to the second channel of the recorder together with the first potential electrode, or a third potential electrode is installed between the second potential and second current electrodes and is connected to the second channel of the recorder together with the second potential electrode, wherein all electrodes and the end of the notch are located along a straight line running parallel to the side of the test sample from which the notch is made and which is the line of action of the tensile force in different directions relative to the notch.
[0008] Figures 1 and 2 show two possible design options for the claimed device.
[0009] In Figure 1, a device for measuring crack development parameters during mechanical testing comprises a power source 1, a two-channel recorder 2, a rectangular metal test specimen 5 in which a notch 6 is made on the side of crack development. On the surface of the test specimen 5, first 7 and second 8 current electrodes are mounted symmetrically relative to the notch, connected to the power source 1, and first 9 and second 10 potential electrodes are located symmetrically and closer than the current electrodes with respect to the notch 6 and connected to the first channel 3 of the two-channel recorder 2. On the surface of the test specimen 5, a third potential electrode 11 is mounted between the first potential 9 and first current 7 electrodes and is connected to the second channel 4 of the recorder 2 together with the first potential electrode 9.All electrodes 7, 8, 9, 10, 11 and the end of the notch 6 are located along a straight line running parallel to the side of the test sample 5 from which the notch 6 is made and which is the line of action of the tensile force F in different directions relative to the notch 6.
[0010] In Figure 2, the device for measuring crack development parameters during mechanical testing comprises a power source 1, a two-channel recorder 2, a rectangular metal test specimen 5 in which a notch 6 is made on the side of crack development. On the surface of the test specimen 5, the first 7 and second 8 current electrodes are mounted symmetrically relative to the notch, connected to the power source 1, and the first 9 and second 10 potential electrodes are located symmetrically and closer than the current electrodes with respect to the notch 6 and connected to the first channel 3 of the two-channel recorder 2. On the surface of the test specimen 5, the third potential electrode 11 is mounted between the second potential 10 and the second current 8 electrodes and is connected to the second channel 4 of the recorder 2 together with the second potential electrode 10.All electrodes 7, 8, 9, 10, 11 and the end of the notch 6 are located along a straight line running parallel to the side of the test sample 5 from which the notch 6 is made and which is the line of action of the tensile force F in different directions relative to the notch 6.
[0011] A new set of essential features in the claimed device enables the second channel of the recorder to measure the change in electrical potential proportional to the elastic and plastic deformation of the test specimen until crack formation. When a crack appears, plastic deformation in the test specimen ceases, and consequently, the change in potential in the second channel of the recorder also ceases, allowing the precise moment of crack initiation to be determined. The elastic and plastic deformation of the test specimen will have maximum values along the straight line of action of the tensile force, and accordingly, the changes in the measured potentials will be greatest at the electrodes installed along this line. Positioning the end of the notch on the line of maximum deformation ensures that the onset of crack formation coincides with the cessation of the increase in potential measured by the second channel of the recorder.
[0012] The device operates as follows. When the test specimen 5 is subjected to a force F stretching in different directions relative to the notch 6 along a straight line parallel to the side of the test specimen on which the notch 6 is made and intersecting all the electrodes and the end of the notch 6, the test specimen 5 begins to experience mechanical stresses leading to its deformation - a change in geometric dimensions, which leads to the beginning of a change in the potentials recorded by the first 3 and second 4 channels of the recorder 2. When a crack begins to appear, the potential measured by channel 3 of the recorder 2 will continue to grow proportionally to the crack growth, and the increase in the potential recorded by channel 4 of the recorder will stop. The moment the potential recorded by channel 4 of the recorder 2 stops growing will be the exact moment the crack begins to appear, and the moment the potential recorded by channel 3 of the recorder 2 stops growing will be the moment the crack ends growing.In PC 12, the signals from recorder 2 are processed and presented in the form of crack development parameters from the moment of its appearance until the moment of its growth completion.
[0013] A prototype of the device was manufactured, which confirmed its functionality.
Claims
A device for measuring crack development parameters during mechanical testing, comprising a power source, a two-channel recorder, a rectangular metal test specimen in which a notch is made on the side of crack development, first and second current electrodes connected to a power source and first and second potential electrodes located symmetrically and closer than the current electrodes in relation to the notch and connected to the first channel of the two-channel recorder are mounted on the surface of the test specimen, symmetrically relative to the notch, characterized in thatthat, in addition, a third potential electrode is installed on the surface of the test sample between the first potential and first current electrodes and is connected to the second channel of the recorder together with the first potential electrode, or a third potential electrode is installed between the second potential and second current electrodes and is connected to the second channel of the recorder together with the second potential electrode, wherein all electrodes and the end of the notch are located along a straight line running parallel to the side of the test sample from which the notch is made and which is the line of action of the tensile force in different directions relative to the notch.