RU1803781C - Bending resistance testing device for sheets - Google Patents

Abstract

The invention relates to techniques for testing materials, in particular to devices for testing plates for flexural strength. The purpose of the invention is to increase the accuracy of determining the stress-strain state of the plate by providing conditions of free support on its contour. A hollow piston 2 is placed in the housing 1, over the cavity of which a plate 3 is placed with a supporting contour 4 having a cylindrical cross-section 7 and coinciding in plan with the sealing element 5 on the surface of the piston 3. The housing 1 and the plate 3 are connected by a shutter 6, through the holes of which, as well as the holes of the plate 3, the housing 1 and the piston 2, coaxial with it, are guided by locks 7, which are mounted with the possibility of fixing relative to the piston 2. The cavities of the housing 1 and the piston 2 are in communication with the pressure line 9 and hydraulic control oror 8, made in the form of a valve with two spool pairs, the ratio of the working areas of which is proportional to the ratio of the areas of working sections of the cavities of the housing 1 and piston 2. When the working fluid is supplied to the cavities of the housing 1 and piston 2, the plate is loaded with uniform hydrostatic pressure. In this case, due to the regulator 8, the force of pressing the plate against the supporting structure 4 does not introduce errors into the theoretical loading scheme. 1 ill.

Description

The invention relates to techniques for testing structural materials for strength, in particular to devices for testing the strength of composite materials,

The purpose of the invention is to increase the accuracy of determining the stress-strain state of the plate by providing conditions of free support on the circuit.

The drawing shows a diagram of the device.

The device comprises a housing 1. a hollow piston 2 mounted axially in the housing 1 with the possibility of axial movement, a plate 3 with a sealing circuit 4 facing the piston cavity 2, a sealing element 5 for the test plate, located on the end surface of the piston 2, a shutter 6, mechanically linking the plate 3 to the housing 2, the guides - the clamps 7 and the hydraulic regulator 8, in communication with the cavities of the housing 1 and the piston 2 and the pressure line 9.

In the shutter 6, plate 3, housing 1 and piston 2, coaxial holes 10 are made, in which guides 7 are mounted with the possibility of rigid fastening relative to the piston 2 by means of pins 11, and the supporting contour 4 has a cylindrical surface in cross section and coincides in plan with a sealing element 5, while the hydraulic regulator 8 is made in the form of a valve with two spool pairs 12, 13, the ratio of the working areas of which is directly proportional to the ratio of the area of the end surface located in the body cavity the piston 2 and the area of the plate 3, limited by the reference contour 4.

The device operates as follows. ..

L By supplying the working fluid from the pressure line 9 to the cavity of the housing B, the piston 2 together with the test plate laid on the sealing element 5 and guides 10 rises up and presses the plate against the supporting circuit 4, mounted on the upper plate 3. The magnitude of the force the preliminary pressing of the plate to the support is determined from the condition of creating the initial seal of the piston cavity. Quince does not matter when testing the plate. This position can be fixed, for example, by closing the valve connecting the pressure line 9 and cavity B. Then, a working line is supplied from the pressure line 9

fluid into cavity A and a uniform load is created on the test plate. When the regulator 8 is operating, the force P is pressed by the piston 2 of the plate to the support 4 is determined

,,.

(1)

where Qnp, Chm are the pressures inside the cavities B and A, respectively;

.fnp and fnn the area of the end surface of the piston 2 and plate 3, limited by the reference contour, respectively.

During loading, the ratio

RPG

RPL

by means of the regulator 8, it is maintained constant and directly proportional to the ratio of the working areas of the spools. If

f 1 1 / fn / i

- IN 7--

h

Inp

Where

Ttsl

fi and f are the working areas of the spool pairs 13 and 12:

P is the perimeter of the support loop 4: c is the contact width of the sealing element 5 with the test plate, then the compressive force of the sealing element will be sufficient to seal cavity A and will not introduce an error into the theoretical loading scheme corresponding to the uniformly distributed load of the freely supported plate.

This makes it possible to reliably determine the stress-strain state of the plate and. therefore, the elastic and strength characteristics of the test material, which is a prerequisite for creating structures of composite materials of minimum weight / minimum thickness, with minimally sufficient margins of strength and stability.

Claims (1)

SUMMARY OF THE INVENTION bending strength plates, comprising a housing, a hollow piston mounted axially displaceable in the plane of the housing, a plate with a support contour facing the piston cavity, a sealing element for the test plate located on the end face of the piston, a shutter, mechanically. a plate with a housing, and a pressure line with valves, in communication with the cavities of the housing and the piston, characterized in that, in order to increase the accuracy of determining the stress-strain state of the plate due to the conditions of free support on its circuit, it is equipped with guides and a hydraulic regulator in communication with the cavities of the housing and piston, the valve, plate, housing and piston are made coaxial - holes in which guide clips are mounted with the possibility of rigid fixing relative to the piston n by means of pins, and the support contour of the plate has a cylindrical surface in cross section and coincides in plan with the sealing element, while the hydraulic regulator is made in the form of a valve with two spool pairs, the ratio of the working areas of which is directly proportional to the ratio of the area located in the cavity body end surface of the piston and the area of the plate, limited by the reference contour.