RU1837197C - Method of testing rod specimens at axially-symmetric loading - Google Patents

Description

| The invention relates to test equipment.

| The purpose of the invention is to improve the accuracy of ciii when testing specimens rigidly fixed in grips by taking into account the effect of concomitant bending.

In FIG. 1 is a diagram of an apparatus for implementing the method; in FIG. 2 is a diagram of an implementation of the described method; in FIG. 3 indicates the placement of the elastic elements of the sensor.

A device for testing rod samples under axisymmetric loading and contains a frame 1 with active 2 and passive 3 grippers placed on it and a measuring device including dynamometers 4, 5, automatic measurement unit b and terminal 7. In addition, a device 8 is located

to fix the initial relative position of the dynamometers 4, 5. In this case, the elastic elements 9, 10, 11 of each of the dynamometers are fixed on each of the corresponding grippers 2 and 3, so that the centers of the elastic elements 9,10,11 lie in the same plane perpendicular to the axis of the subject Sample 12.

The method is implemented as follows.

Sample 12 is fixed in grippers 2, 3. Then, elastic elements 9-11 of dynamometers 4, 5 are fixed on the latter so that the centers of elements 9-11 lie in one plane perpendicular to the axis of sample 12.

To correctly determine the parameters of the accompanying bend, it is necessary to have data on the relative initial position of the dynamometers in the axial and

with xi

yu xi

direction relative to each other. x orientation may vary when samples are inserted into the testing machine. To fix the initial relative position of the dynamometers in the axial and angular directions, use the device 8. As the indicated device, for example, an optical catheter can be used, while on the side surface of the body of each dynamometer made in the form of a cylinder, a degree grid in metrology should be applied load cell plane,

Let us consider the power circuit, consisting of sample 12, grippers 2,3, and dynamometers 4, 5 as a whole, and suppose that bending deformation occurs in the power circuit due to imperfections in the test system. Possible diagrams of components of the bending moment (bending in the general case may have a spatial character) are shown in Figs. 2. In this case, bending parameters can be determined not on the sample itself, but outside it, for example, in fixed sections D and F, by dynamometers 4, 5 capable of determining the axial force and the vector of bending moment.

According to the calculation scheme, from the known values of the bending moments MYD, MZD, MYF, MZF in fixed sections D and F, it becomes possible to determine the bending stresses at any point in the sample. We show this by the example of section K for a bar sample of circular cross-section. The maximum bending stresses in section K are determined by the well-known expression:

Omax -

Mk

Wv

where WY is the axial moment of resistance of the cross section; MK - the resulting bending moment in section K:

MK VMfiT + Mik where MYK MYD + (MYF - MYD)

MZK - MZD + (MZF - MZD)

components of the moment in section K.

Bending strains in the elastic elements 9-11 of dynamometers 4.5 are expressed as follows:

M R

EA -gy- cos p

EB - - p-g cos (p cos "1 -I- sin p sin" 1 j.

Јс-р-р cos p cos a.1 + sin у sin с,

0)

where E is Young's modulus; I IY Iz is the axial moment of inertia of the cross section. From the joint solution of the equations of system (1) we obtain

fifteen

1

yaarctg (slnai- + siriaa) ev -EC

+ cos od -cos cn). (2)

twenty

With "1 a.2-aza 120 °, expression (2) is simplified:

 - arctg

1

2 cos 30 °

In the case under consideration, the angle p, determined by the expression (2) or (2), is plotted off the Z axis (i.e., sensor A) according to the usual sign rule for corners.

Having determined the angle (p, by any of the equations (1), we can calculate the value of the bending moment M.

It should be noted that all of the above applies to the case where the sensors

only bending deformations are recorded. Deformations from the central extension or compression of the rod must be isolated and subtracted from the readings of the sensors 9, 10, 11.

Thus, the placement of the elastic elements of the load sensors on each of the grips of the testing machine so that their centers lie in the same plane perpendicular to the axis of the tested rigidly fixed bar specimen under axisymmetric loading, makes it possible to take into account the effect of concomitant bending, which in turn increases the accuracy testing.

Claims (1)

Reten formula and goiter A method of testing rod samples under axisymmetric loading, according to which the sample is fixed in grippers, load sensors are installed in two non-parallel planes axis of the sample, the sample is subjected to axisymmetric loading and the process characteristics are measured, according to which the stress-strain state of the sample material is measured characterized in that. with the aim of improved accuracy when testing the sensors are fixed on the grippers, and Rigidly fixed in captures on each capture so. that their centers lie sample by taking into account the effect of soputst in one plane perpendicular to the axis bending, elastic elements of the sample. t fieL pv & 3 „/