RU1793319C - Unit for testing samples for static crack resistance under conditions of out-of-center tension - Google Patents

Description

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The invention relates to a technique for testing materials, in particular, can be used to determine the properties of materials, namely, to determine the static crack resistance of pre-hydrogenated samples under eccentric tension.

A device for testing biconsole specimens for resistance to brittle fracture is known, which comprises support elements for securing the specimens, a screw loading mechanism and a force meter.

A disadvantage of such a device is the impossibility of determining the onset of crack growth if it locally moves along the front inside the specimen, i.e. in the absence of its advancement along the lateral surface of the sample, as well as the large overall dimensions of the device.

Closest to the invention is a device for eccentric tension loading of a specimen with an artificial crack, comprising a screw loading mechanism and pins / with which the test specimen is attached.,,

A disadvantage of the known device c-: l accuracy is not high when tested, because it is impossible to determine the loading force and the moment the crack begins to grow (crack start) if it moves along the front inside the specimen.

The purpose of the invention is to increase the accuracy of the test.

This goal is achieved by the fact that in the device for testing samples containing a loading screw mechanism, rigidly connected to the end face of the screw mechanism, a hollow grip with through radial slots and interacting with the pin grips, designed to be placed in the holes of the sample strain and load meters, one of the pins is made in the form of a threaded part with a nut, a working part, a collar and a waveguide part arranged in series along its axis, the strain gauge is made in the form of an acoustic sensor emission and is located at the end of the waveguide part, and a load meter is placed between the nut of the loading mechanism and the gripper and connected to them by means of spherical supports.

In FIG. 1 presents a diagram of the proposed device, front view; in FIG. 2 - the same side view.

The device comprises a hollow grip 1, inside which a second grip 2 is placed, a load meter 3 in the form of a tensometric dynamo with spherical supports 4, a loading screw mechanism 5, a waveguide part 6, a pin 7, screws 8 are fixed to a load meter 3 and a nut of fastening 9 of the waveguide part strain gauge 10 in the form of an acoustic emission sensor. In capture 2, sample 11 is installed.

The device operates as follows.

The tested hydrogenated compact sample 11 is secured with a pin 7 in the second movable gripper 2, after which

place them in the hollow grip 1 and fix the waveguide part 6 and the fastening nut 9, then put the load meter 3 on the spherical supports (balls) 4, fixing it with screws 8, on the second movable grip 2 the wires are led through the technological holes of the grip 1 (not shown). The loading force is transmitted by a screw mechanism 5 through spherical bearings 4 and a load meter 3 on

the second grip 2 and a pin 7 on the test sample 11, which is rigidly attached through the waveguide part b to the grip 1. On the contact area (not shown) of the waveguide part 6, an AE 10 signal sensor is mounted, which is connected to the AE measuring equipment (not shown) .

The use of the waveguide part b AE as the second pin allows

using AE signals, fix the crack start time in hydrogenated samples in the case of their internal subcritical growth and determine the crack resistance parameters of the material using the load fixed at a given time, which is a very important indicator when choosing the type of material and developing equipment operating in hydrogen-containing environments in conditions x

long-term static loading. .

Tests were carried out on compact specimens made of 9KhF steel, previously hydrogenated for 10 hours in a gaseous hydrogen atmosphere with a pressure of 0.1 MPa

at 293 ° K.

As a measuring device for AE signals, an AVN-3 device with a high-speed recording device of the N-338/4 type was used. Bandwidth

was chosen in the range of 120-360 kHz, the gain is 84 dB, and the discrimination level is 0.3 ... 0.4 V.

The load intensities were recorded using a dynamometer on a LKD-4-002 two-coordinate shear builder, having preliminarily dissected the dynamometer using a standard force meter.

Experimental studies have shown that the appearance of AE signals with amplitudes of 200 ..., 300 V and a counting rate of 20 ... 40 cpm / min indicates the onset of crack growth.

Formula A device for testing specimens for: static crack resistance during eccentric tension, containing a loading screw mechanism, rigidly connected to the end of the screw of the mechanism, first a gripper with through radial passages and interacting with the gripper of an itift designed to accommodate j-holes of the sample strain and load meters, characterized in that

that, in order to improve the accuracy of testing, one of the pins is made in the form of a threaded part with a nut, a working part, a collar of the waveguide part located in series along its axis, the strain gauge is made in the form of an acoustic emission sensor and placed on the end of the waveguide part, and the load meter is placed between the nut of the loading mechanism and the gripper and connected to them by means of spherical bearings.