RU2002205C1 - Method for determination of temperature stresses at preset temperatures - Google Patents

Abstract

The invention relates to measuring technique and can be used to reliably determine temperature stresses with a satisfactory accuracy for practical purposes (1% error) in various structural materials and parts representing linear systems in the elastic region of deformation c. loose or pinched form The purpose of the invention is to expand the scope of the method for determining the absolute values and sign of temperature stresses. This is achieved due to the fact that four additional samples are manufactured, the yield strength is measured on them, respectively, at four different temperatures, two of which lie below, and the other two above the region of the assumed characteristic temperature, at which the straight angle changes , characterizing the dependence of the yield strength of the material on temperature. According to the results of measurements on these four samples, the true value of the characteristic temperature of the controlled material is found and accepted this temperature as the base for calculating the thermal stress yl 2 Table 4

Description

The invention relates to measuring technique and can be used to determine temperature stresses (VT) with accuracy satisfactory for practical purposes in various structural materials and parts representing linear systems in the elastic region of deformation, in a free or protected form.

Methods are known when a material is deformed by an elastic VT in proportion to the elastic modulus E, LTEC (a) and temperature change LT.

Moreover, the force and temperature effects in this case obey the principle of superposition.

Its disadvantage is the high dispersion of the VT, which limits the scope.

A method for determining TH is also known. Its essence is that the thermomechanical parameters of a homogeneous stabilized material representing a linear system are determined.

They determine the temperature deformations and VT.

The disadvantage of this method is the large dispersion of thermomechanical parameters, which limits the scope of its application, especially when determining absolute values taking into account the sign of VT,

The purpose of the invention is to expand the scope of the method for determining the absolute values and sign of VT within the range from absolute zero to the minimum temperature at which the controlled material loses its elastic properties.

This is achieved by producing four additional samples, measuring the yield strength on them, respectively, at four different temperatures, two of which are lower and the other two are above the region of the assumed characteristic temperature at which the angle of inclination of the straight line, which characterizes dependence of the yield strength of the material on temperature, according to the results of measurements on these four samples, they find the true value of the characteristic temperature of the controlled material and take this rate a reference for calculating temperature stresses.

In FIG. Figure 1 shows the resulting excess forces between particles (atom) of a solid (P) representing a linear system from the distance between them caused by the action of temperature in the elastic deformation region.

It is known that between particles of a solid body there are both attractive and repulsive forces. The result is an equilibrium of the particle system. At the point r0 (P) is equal to zero. This state of microequilibrium of the particles of the body at the minimum potential energy is used as the base — the reference point in determining the VT.

In FIG. Figure 2 shows a model for the formation of a TN stretch in the section with "-th, i.e. relative to r0 of FIG. 1. When the temperature decreases in a controlled body in the o-pz region under the influence of thermal energy, compressive excess PTC forces arise, which cause particle repulsion reactions and reactive temperature tensile forces of PTr. They form tensile Ths relative to the point of microequilibrium, in the region of decline.

In FIG. Figure 3 shows a model for the formation of compression VTs on a constant section from th to the maximum temperature at which the material retains elastic properties. The solid lines conditionally depict (Fig. 2 and 3) the state at r, and the dash-dot (phi r 2) state is lower than R0; Fig. 3 above r0, i.e. after additional exposure to temperature relative to Go.

on Fig, 4 shows the temperature dependence of the yield strength of homogeneous stabilized steel EP921.

Here, 0-1 defines the stretching TH in the recession area, and 0-2 the compression TH in the constant section relative to the abscissa axis 3-4.

The yield stress is measured after the temperature is equalized over the entire volume of the sample, which is recorded by stopping the increment of the controlled parameter, for example, the natural frequency of the sample.

The measured values of yield strengths for each section at two points are connected by a straight line, since the body is a linear system.

An increase in accuracy and a decrease in the laboriousness of determining TN were achieved by dividing them into compressive and tensile components with: abscissa — characteristic temperature (XT), ordinate — microequilibrium of excess forces caused by temperature.

The invention is illustrated by the following example.

Steel OZH9K14NBMZD (EP921) was used, as well as to determine the TH equation

atr “Wed E Wed AT,

where "cf. Est - the average value of the thermal expansion coefficient and the elastic modulus within the limits of DT;

AT - increment, temperature from controlled, at which the VT is measured to XT;

a is the experimental coefficient, for metals in the constant section, 11 const.

To determine coefficient (a), samples are prepared without the formation of an altered surface layer and plastic internal stresses, and the TEC is measured. modulus of elasticity and yield strength, and the results are summarized in table. 1.

DT 500-20 4800СDate

 Yasr E Wed DT.

Accepted, 11 const.

6 samples No. 17-K GOST 1497-73 are made from the blank in the released condition

Each of them is perforated: m / min, 125 mm / st, 09 mm / rev to limit the altered surface layer.

Then all samples are quenched with T 790 ° C, t-120 min and cooling in air, followed by tempering at T 570 ° C, min. and air cooled.

Three values of the yield strength were measured on the constant section and three values on the decline section after holding until the temperature was completely equalized over the sample volume (120 min.). A third point in each of the sections indicates that the body represents a linear system. zhenii are summarized in table. 2.

(56) Feodosiev V.I. On temperature stresses. Ten Lectures on Material Resistance, Moscow: Nauka, 1969.

USSR copyright certificate No. 1186944. cl. G01 B 17/04,

Table 1

table 2

Claims (1)

The claims A METHOD FOR DETERMINING TEMPERATURE STRESSES AT A TEMPERATURE SETTING, which consists in making samples from a uniform stabilized material by cutting in the finishing mode, corresponding to the mutual compensation of surface structure defects from the force and thermal effects of the cutting process, and the linear expansion temperature is determined on these samples at a base temperature , the elastic modulus and the experimental coupling coefficient, and from these data, taking into account the difference between the set and base temperatures, determine emperaturnye voltage, characterized in that, in order 0 5 To expand the scope of the method for determining the absolute values and sign of temperature stresses, four additional samples are prepared, the yield strength is measured on them, respectively, at four different temperatures, two of which lie below and the other two above the area of the expected characteristic temperature, at which the angle of inclination of the straight line, which characterizes the dependence of the yield strength of the material on temperature, is changed according to the results of measurements on these four samples the muddy value of the characteristic temperature of the material under study and is prone to this temperature as a base for calculating temperature stresses. fae. 1 (rig. 2 Sff, 2 7Olg / h 160 R & 0. 120,700. Ј / / & RPG0 /  IN. Fig.3 & U0SL70 / / T0S / G70 / 1 // S / 770 &