RU1820302C - Method of determining apparent density of porous articles - Google Patents

Abstract

The invention relates to a test technique. The method includes preliminary physical impact on standard samples with known apparent density, determination of the corresponding parameter, finding the relationship between this parameter and apparent density of standard samples, subsequent physical impact on the test product, determination of the corresponding parameter and finding apparent density from the dependence of apparent density on this parameter. What is new is that the indenter penetration into the surface of the test article at the selected load is used as a physical effect, microhardness is determined as the corresponding parameter: 1 table, 2 silt.

Description

The invention relates to a testing technique, namely, determination of the apparent density of porous products, and can be used for non-destructive testing of products from porous materials.

The aim of the invention is to increase the accuracy of determining the apparent density of porous products.

The goal is achieved by the fact that in the method consisting in that they have a physical effect on the product and determine the parameter, taking into account which the apparent density is determined from the calibration plots, according to the invention, the physical effect is used. They call for the introduction of an indenter into the product at a given load, and microhardness is used as a parameter.

A PMT-3 microhardness meter was used to carry out the method. modernized by automatic loading system. A Vickers pyramid was used to determine the microhardness. Standard samples were made of expanded graphite and highly dispersed fumed silica grade A-300 (GOST 14922-77). Standard samples were prepared by compression in a cylindrical mold. The dimensions of the samples were: diameter 5 mm, thickness 10 mm. To construct a calibration graph or to obtain an analytical relationship between the apparent density and microhardness, 8 standard samples were taken from expanded graphite or A-300 fine dispersed fumed silica. For each sample, apparent density was determined by the well-known method of weighing a sample with a known volume. Then, samples of the test materials were fixed in holders on the object stage of the PMT-3 device. The determination of microhardness was based on the use of the known method of assessment

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kinetic hardness. In the process of introducing the indenter into the test material, holding it under load and unloading, the penetration depth of the ndentor h and the load P were recorded using the H-307 two-coordinate recorder. As a result of the tests, the dependence P f (h) was recorded in the form of a two-coordinate diagram. From the obtained diagram, for a given even load, gyp was determined. (true penetration depth) and the value was calculated

T7 8P microhardness HVh according to the formula HVh.

h2 Then select a new surface area

sample by horizontal movement of the stage of the AMT-3 device and the test process was repeated in the same order. After 30 measurements, the average microhardness for a given density sample was calculated. Then a new load level was selected and the test process was repeated.

In FIG. Figure 1 shows plots of apparent density versus microhardness for expanded graphite samples at various indenter loads; Fig. 2 shows plots of apparent density versus microhardness for samples of A-300 grade high-disperse pyrogenic silica under various indenter loads.

The invention is illustrated by examples of specific performance,

PRI me R 1. From natural graphite grade GOK received expanded graphite by a known method. A 0.194 g sample was taken from the obtained material. Then expanded graphite was pressed in a cylindrical mold with a diameter of 5 mm to a volume equal to 0.196 volume. The resulting sample was weighed on an analytical balance with an accuracy of 0.0001 g and its geometric dimensions were measured with micrometers with an accuracy of 0.01 mm. The apparent density was 990 kg / m3. The microhardness was then determined at different loads (P 1 g, 2 g, 4 g) and in different places. From the calibration plots shown in Fig. 1, the apparent density was determined. The same measurements were carried out for a sample of expanded graphite, which had an apparent density of 410 kg / m. The results are shown in Example 1 of the table.

Example 2. They did as described in Example 1, except that highly dispersed fumed silica of the A-3QO grade was taken to produce porous samples. The results are shown in example 2 of the table.

Example 3 (prototype). For testing, a US-13I device was used. From expanded graphite by pressing in a cylindrical mold with a diameter of 25

mm, standard samples were made with a thickness of 10 mm with different apparent densities. For each sample, the apparent density was determined by a well-known method of weighing a sample with a known

volume. The surface of the samples was repeatedly impregnated with BF-6 glue. Then the samples were sequentially installed in the mandrel. Moreover, one side of the sample was lowered into the liquid, and an acoustic sensor was attached to the other side of the sample. As liquids used water and transformer oil. Then, the operating frequency of the US-13I device was selected. During the tests, the following were recorded: the propagation velocity of the ultrasonic wave, the attenuation coefficient of the ultrasonic wave, the ratio of the amplitudes of the two pulses at the input of the device. The specific acoustic impedance value was determined. Mathematical processing of the results made it possible to determine the dependence of the apparent density on the specific acoustic impedance: p 24.66 L-2.48 Z, where Z is the specific acoustic impedance.

A control determination of apparent density was carried out for graphite products with a known apparent density of 580, 550, 500 kg / m3. The results of measurements and calculations are presented in Example 3 of the table. The error in determining the apparent density of the porous products of the prototype ranged from 9 to 13%. The data given in the examples confirm the achievement of the goal:

the error in determining the apparent density of the claimed method is significantly less than that of the prototype,

In addition to the three, the claimed method makes it possible to determine the local apparent

the density of the products is practically at a given point, since the contact area of the indenter with the test surface is insignificant (25-900 mm). The claimed method allows to determine the apparent density

porous products of complex shape.

Claims (1)

The claims A method for determining the apparent density of porous products, which is that they have a physical effect on the product and determine the parameter, taking into account which the apparent density is determined from the calibration plots, characterized in that, in order to increase accuracy, the quality of the physical impact using the indenter for a given load, and microhardness is used as a parameter. 4OO 8 w; V , 600 L