METHOD TO MEASURE RELATIVE LONGITUDINAL DEFORMATION OF SURFACE AND EXTENSOMETER FOR ITS REALISATION Russian patent published in 2016 - IPC G01B11/16 G01N3/08 

FIELD: instrumentation.

SUBSTANCE: extensometer comprises two reference bodies in the form of sharpened indenters, at the same time one indenter is rigidly connected to the instrument body, and other one is installed as capable of movement, and also a system of transmission of these movements. In the instrument body there is additionally a laser with an optical system of radiation collimation, a focusing lens, the focus of which matches the controlled surface, a light-dividing mirror, a lens, a coordinate-sensitive photoelectric converter and an arreter for a pendulum. The movable indenter is made with an optical reference element, the centre of curvature of which is matched with the tip of the indenter and with the controlled surface, and is rigidly installed on the pendulum hingedly suspended in the upper part of the body. An electromagnet is suspended between the movable and fixed indenters. Substance: the distance "A" between sharp edges of two indenters is measured before installation onto the surface. The pendulum is stopped, a source of light is connected, the perceived focus of beam of which is matched with the tip of the movable indenter, at the same time the image of the focal point of the laser beam reflected from the spherical mirror, with the optical magnification "K" is focused in the position corresponding to the medium position of the light spot on the coordinate-sensitive photoelectric transducer, and they record the conventionally zero coordinate "B" of the energy centre of the light spot. In the stopped position they install an extensometer onto the deformed surface, and the pendulum is uncaged, then the pendulum is pressed with the movable indenter and spherical mirror to the deformed surface by means of the electromagnet. The coordinate of the energy centre of the light spot "C" is recorded, the deformable beam is loaded, and the coordinate of the energy centre of the light spot "D" is recorded. The relative longitudinal deformation is calculated using the formula.

EFFECT: increased extent of accuracy of detection of coordinates of selected base points, accuracy of measurement of distance between sharp edges of indenters and their mutual movements due to deformation of surface, also with account of structural non-uniformity of the deformed material.

2 cl, 3 dwg