SU1696966A1 - Method for testing thermomechanical fatigue properties of specimens - Google Patents

Abstract

The invention relates to testing equipment, to strength tests. The purpose of the invention is to improve the accuracy by eliminating the effect of the damaged ™ in the material caused by the measurement of the elastic parameters. Two samples were simultaneously tested that were under identical thermal-force exposure conditions. Elastic characteristics were removed from an additional sample to eliminate the error from these measurements in the main sample. As the fatigue characteristic of the main sample, its longitudinal plastic deformation is used, which is determined by the formula Јprod (ERU Ј onU) and –a / E at aa Ot; itЈ0d H & v - ОYOGU "- 0.002 at where ECU is the free temperature deformation of the specimen; Bop - transverse deformation of the main sample; voltage; E is Young's modulus; / g - Poisson's ratio, Yield stress ratio, 2 Cp. f-crystals.

Description

cl

WITH

The invention relates to testing equipment, to strength tests.

The purpose of the invention is to improve the accuracy by eliminating the effect of damage in the material caused by the measurement of elastic parameters.

The method is carried out as follows.

The primary and secondary samples are subjected to identical cyclic thermomechanical effects by installing them in the grippers of one testing machine. The free temperature deformation was preliminarily measured on the samples. After installation in the grips, the samples are subjected to a certain number of thermal cycles with simultaneous mechanical loading. The parameters of the elastic properties are determined on an additional sample. These parameters can be Poisson's ratio, Young's modulus, the yield strength of the material, which is a function of the natural frequency of the sample.

Since these parameters require loading the specimen to the yield point, this introduces damage that is comparable to thermal cycling damage. Therefore, in order to eliminate this error, the parameters are determined on an additional sample.

On the main sample, the transverse strain in the most dangerous section is recorded.

As a fatigue characteristic of the main sample, its longitudinal plastic deformation is used, which is determined from the ratio

but

chz aa aa

Esb-°n ° P About

AND

with -

sowing

- -j at (7 0t,

- 0.002 at a OT.

where Јpr0d- longitudinal plastic deformation:

all free temperature deformation of the sample;

Bop - transverse deformation of the main sample;

a - the voltage of the main sample;

E is Young's modulus;

fi is the Poisson's ratio;

From - the yield strength of the additional sample.

The measurement of the elastic characteristics on the specimen is carried out in at least one cycle, since during the measurements during one cycle, the processes of strengthening, softening, the Bauschinger effect, etc., are realized, which will affect subsequent loads. When measuring at least one cycle, the measurement error is significantly reduced due to the effect of the material forgetting the loading history with several changes in the direction of the loading path.

The determination of the elastic characteristics is carried out by twisting the longitudinal loaded additional sample, since it can be measured without changing the force-temperature effect, i.e. identical to the main sample.

Claims (3)

1. The method of testing samples for thermomechanical fatigue, which consists in placing the sample in the grips of the testing machine, subjecting it to cyclic thermomechanical action, periodically measuring pa0 five 0 The elastic properties measurements and determine the fatigue characteristics at different temperatures, characterized in that, in order to improve accuracy by eliminating the effect of damage in the material caused by measuring the elastic parameters, an additional sample is used that is identical to the main one and is subjected to its cyclic thermomechanical action identical to the main one. , register the free deformation of one of the samples and the transverse deformation of the main sample in the most dangerous section, record the elastic parameters properties on an additional sample, and the fatigue characteristics are used as the longitudinal plastic deformation of the core sample, defined by the ratio of  In ЈI ° P- | pris7 0g; pl tno prod ,, plprod / „-POP sowing s p 0.002 at a From, where Јcb is the free temperature deformation of the sample; Bop - transverse deformation of the main sample; E is the Young's modulus of the additional sample; (l - Poisson's ratio of the additional sample; From - the yield strength of the additional sample. 2. A method according to claim 1, characterized in that the measurement of the parameters of the elastic properties is carried out in one cycle. 3. The method according to claim 1, characterized in that the determination of the parameters of the elastic properties is carried out by torsion.