SU1499158A1 - Method and apparatus for testing materials for stress relaxation in twisting - Google Patents

Abstract

The invention relates to a test technique and allows studying the process of stress relaxation in various materials during their torsion. The purpose of the invention (method) is to simplify the tests. A sample of the material in the form of a helical spring is used, and the loading is carried out by applying a load in the axial direction. The purpose of the invention (device) is to simplify the tests and improve the accuracy of the determination of stress relaxation. Samples of materials 16 are placed between two parallel plates 3, 4, which at one end abut against the ends of the pushers 8 arranged to move in the holes of the plate 3 and with the possibility of contact with it by the thickened ends along the lines 7. The lateral surface of the unstreaded parts of the pushers and the ends their thickened ends are covered with dielectric. The plates 3 and 4 deform the samples 16 and are rigidly interconnected by stitches 5. The plates 3 and 4, the strings 5 and the pushers 8 are made of electrically conductive material, they together with the elastic element 12, the power source 14 and the signal lamp 15 form a signal circuit 13. The change in the compressive force of the samples 16 materials is periodically determined at the time of breaking the signal circuit 13 along the contact line 7, when the signal lamp 15 is extinguished, by applying the elastic element 12 of the load cell 11 to the ends of the pushers 8, and judging by the changes in the efforts n straight zheny 16 material samples. 1 il.

Description

and

with so

sd

00

with the elastic element 12, the power source 1A and the signal lamp 15 form a signal circuit 13. The variation of the compressive force of the samples is 16 mA; the channels are periodically determined at the moment of breaking the signal circuit 13 through the contact line 7 when it goes out

the signal lamp 15, by acting on the elastic element 12 of the force-measuring device 11 on the ends of the pushers 8, and judging by the changes in the efforts, the stress relaxation process in the samples 16 of materials is judged. 2 sec. f-ly, 1 ill., 1 tab.

The invention relates to a testing technique, and specifically to methods for studying the process of stress relaxation in various materials and devices for their implementation.

The purpose of the invention is to simplify the tests and improve the accuracy of determining the relaxation of stresses.

The method is carried out as follows.

A wire with a circular cross section is made from the material to be tested. A wire is wound around the sample in the form of a helical coil spring. The spring is loaded with axial force and maintained at constant deformation, at which the sample material undergoes torsion.

The change in load over time is measured and is judged by the process. stress relaxation that occurs in the sample of the test material. The sample parameters of the test material are selected as follows: t l ,, 8d, where d is the diameter of the cross section of the prvolvolok; t is the step of the sample turns; D is the average diameter of the sample coils. Such parameters of the sample provide the ability to vary in a wide range the magnitude of the initial tangential stresses during torsion and to virtually eliminate the effect on the relaxation of tangential stresses in the event of a breakdown of stresses due to bending, stretching, and shear of the sample material.

Example. From carbon steel, grade 70, and stainless steel, grade 12X18H10T, wire was manufactured with a diameter of d of 0.8 mm. Samples of materials with the parameters t 1.44 mm and D were wound from wire. 3.84 mm, which made it possible to achieve tangential stresses in torsion up to 1100 MPa

The table shows the relaxation values of tangential stresses at their initial value of 350 MPa.

-25

The samples of materials tested in the environment of freon 22 with oil HF22-24 with,

The drawing shows a diagram of the proposed device.

The device contains a table 1 with a drive. 2, two parallel plates 3 and 4 of electrically conductive material, a stitch 5 for rigidly joining the plates 3 and 4, and limiters 6, the distance between them. Plate 3 has holes, and plate 4 is located on the table 1.

The device also contains passing through holes in the plate 3 with the possibility of moving and contacting with conical thickened ends with it along line 7 pushers 8 of electrically conductive material. The lateral surface of the non-thickened parts of the pushers 8 and the ends of their thickened ends are covered with dielectric 9 and 10, for example boron nitride.

In addition, the device contains a force meter 11 with an elastic element 12, which the end of the rie-thickened part of the pusher 8 touches, and an electrical signal circuit 13 with a power source 14 and a signal

five .

naNmoli 15, closing with ends through plates 3 and 4, pusher 8 along line 7 and tie 5, made of an electrically conductive material.

The device works in the following way.

Materials 16 are positioned between plate 4 and the ends of thickened parts of the pushers 8. Limiters 6 are placed between the plates and the plates are rigidly clamped 5. Materials samples 16 acquire a constant deformation in time and, accordingly, the initial values of tangential torsional stresses.

Deformed samples 16 materials with plates 3 and 4 are placed in a heat chamber (not shown) with a gas or liquid working medium and kept in it.

Periodically, the fixture of plates 3 and 4 with samples 16 is placed on table 1, the actuator 2 is turned on and the end of the non-thickened part of the corresponding pusher 8 is fed to the elastic element 12 before they touch.

In this case, the signal electric circuit 13 closes and the signal lamp 15 lights up.

Further movement of the table 1 leads to an increase in the load acting from the side of the elastic element 12 to the corresponding pusher 8. At some load, the sample 16 deforms and the signal circuit 13 is broken, since the contact on line 7 is broken. The lamp 15 is extinguished, and the magnitude of the corresponding load is recorded by a force measuring device 11.

Similar periodical load measurements make it possible to simply and accurately investigate the process of stress relaxation, which

The latter flows in samples of 16 materials at different levels of initial stresses, at different temperatures and the effect on the samples of working gas or liquid media.

Claims (1)

Invention Formula 10 1. Method of testing materials for stress relaxation in torsion, which consists in the fact that in a sample of a material, tangential stresses are created by mechanical 15 load and measure the change in load over time, characterized in that, in order to simplify testing, a sample is used in the form of a helical cylindrical spring, and the load is carried out by applying a compressive load in the axial direction. 2 o Device for testing stress relaxation materials 25 in torsion, containing two parallel and rigidly interconnected plates of electrically conductive material, one of which has openings, and a passage through them through 30 are capable of moving and contacting with the surface of this plate the pushers of electrically conductive material with thicker ends facing the other plate and designed to interact with their ends with samples of materials, characterized in that, in order to simplify the tests and increase the accuracy of relaxation determination, The stresses in contact with the plate, the surface of the end of the push rod, are tapered, and the lateral surface of the non-thickened parts of the pushers and the ends of their thickened ends are covered with a dielectric. 35