METHOD OF MEASURING SPECIFIC ELECTRICAL RESISTANCE OF A METAL SAMPLE DURING ITS STRETCHING Russian patent published in 2019 - IPC G01N27/02 G01R27/02 

FIELD: test equipment.

SUBSTANCE: invention relates to the field of test equipment and can be used for measurement of specific electric resistance of metal specimens during stretching during mechanical tests. When the specimen is stretched, the distance between its arbitrary points 1 and 2 increases, and cross section S – decreases. Both effects lead to increase in electrical resistance between points 1 and 2, which is considerably greater than change of p. This makes it impossible to determine its value from results of measuring voltage U₁₂ between points 1 and 2 at a given current value without taking into account change in geometry of the sample during its deformation. Complexity of problem consists in small changes S and ρ, making parts of percentage. According to the invention, variation of and S during stretching is compensated by convergence of points 1 and 2 of measurement of electric voltage U₁₂. For this purpose potential electrodes 1 and 2 are made with possibility of movement along axis of sample 4 at maintaining electric contact with it, prior to expansion of sample 4 potential electrode 1 is fixed at a given distance relative to transverse plane of sample 4, passing through initial point of potential electrode 2, and potential electrode 2 – relative to transverse plane of sample 4, passing through initial point of potential electrode 1, relative deformation is determined ε of sample and by recorded voltage Un, taking into account known values of current I, cross section S=S₀ and before stretching, determined value of specific electric resistance of metal sample is determined by formula To determine value ε potential electrode 3 fixed in transverse plane of initial installation of potential electrode 1 and fixation of electrode 2 is used, voltage U₃ between potential electrode 3 and potential electrode 1 and corresponding relative deformation is determined by formula

EFFECT: high accuracy of measurements by eliminating operations associated with determining geometrical dimensions of the sample, which change during its stretching.

1 cl, 2 dwg