RU2845809C1 - Method of determining apparent density in quartz ceramic articles - Google Patents

Abstract

FIELD: measuring.

SUBSTANCE: invention can be used for determination of apparent density in quartz ceramic articles. Ultrasound speed is measured and the controlled parameter is determined from an experimental calibration curve pre-plotted based on the results of measuring the ultrasound speed values in comparison with the results of determining the apparent density according to the results of direct determination of the apparent density of the samples, wherein determination of longitudinal ultrasonic waves velocity is performed using direct piezoelectric transducer with resonance frequency of 1 MHz to 10 MHz with established delay line at ambient air temperature from 15 °C to 35 °C in time interval between signal from workpiece or article material surface and first bottom echo signal, wherein glycerine is used to create an acoustic contact between the piezoelectric transducer and the delay line, and between the delay line and the surface of the ceramic article distilled water, before taking measurements, adjusting the parameters of the ultrasonic thickness gauge using a control sample.

EFFECT: possibility of rapid local determination of apparent density in material of workpieces or articles made from quartz ceramic using ultrasonic waves.

1 cl, 5 dwg

Description

The invention is intended for determining the apparent density of the material of blanks or products made of quartz ceramics using ultrasonic waves and can be used to determine the apparent density of blanks or products used in the aerospace, mechanical engineering, shipbuilding, energy and other industries.

Apparent density is the ratio of the mass of dry material to the total volume [GOST 28874-2004 INTERSTATE STANDARD REFRACTORIES CLASSIFICATION Refractories. Classification].

There are known methods for determining the apparent density of ceramics [GOST 473.4-81 “Chemically resistant and heat-resistant ceramic products. Method for determining apparent density and apparent porosity”] and refractories [GOST 2409-2014 “Refractory products. Method for determining apparent density, open and total porosity, water absorption].

The essence of the methods lies in determining the apparent density, expressed as the ratio of the mass of the dried sample to the volume it occupies, including pores.

The main disadvantages of these methods are the impossibility of local determination of the apparent density of the material of the products, high labor intensity and low efficiency due to the need to make samples from the products, which are significant disadvantages in the conditions of serial production.

An ultrasonic method for monitoring the density during operation of parts made of highly filled composite materials based on octogen is known [RU Patent No. 2473894 C1 RF, IPC G01N 29/07, published 2013 Bulletin No. 3], which consists of exciting ultrasonic waves in a given zone of the part under study with a known initial density (ρ ₀ ), measuring their propagation time, re-exciting ultrasonic waves in the same zone during operation, measuring their propagation time, determining the relative change in propagation time (δt) and calculating the density (ρ) of the part under study using the following equation:

ρ = ρ ₀ × [1 + (a × δt + b)],

where a and b are empirical coefficients.

The main disadvantage of the proposed solution is that it is necessary to know the initial value of the density (ρ ₀ ), the local value of which is unknown for anisotropic quartz ceramics.

The closest in technical essence is the method for monitoring the apparent density of fired shell blanks made of quartz ceramics [RU Patent No. 2813126 C1, IPC G01N 29/07, G01N 9/24, published 2024 Bulletin No. 4], which includes measuring the speed of ultrasound and determining the controlled parameter using a pre-built regression dependence, characterized in that the apparent density of the blank material is determined using a pre-built regression dependence:

ρ _each = ϕ (With _US , δ, τ, T),

where ρ _kazh – apparent density, kg/ ^m3 ;

ϕ – sign of the correlation relationship;

С _УЗ – the speed of propagation of ultrasonic vibrations, m/s;

δ – shrinkage coefficient of the workpiece after firing, %;

τ – time of blank formation during molding, min.;

T – firing temperature of the workpiece, °C,

constructed based on the results of measuring the values of ultrasound speed, the shrinkage coefficient in fired blanks, the time of setting and the firing temperature of the blanks in comparison with the results of determining the apparent density based on the results of direct determination of the apparent density of samples from the technological allowance of blanks and satellite samples.

The main disadvantage of this method is the need to determine a large number of parameters (shrinkage coefficient of the workpiece, set time, firing temperature of the workpiece) at various stages of production, during the molding process of the workpiece, during and after firing of the workpiece, which leads to a decrease in the efficiency of control of determining the apparent density in the material of the workpieces or products, as well as to high labor intensity.

The technical result of the proposed invention is the possibility of local determination of apparent density in the material of blanks or products made of quartz ceramics using ultrasonic waves with high efficiency and low labor intensity.

The technical result is achieved in that a method is proposed for determining the apparent density in quartz ceramic products, including measuring the ultrasound velocity and determining the controlled parameter using an experimental calibration dependence, previously constructed using the results of measuring the ultrasound velocity values, in comparison with the results of determining the apparent density using the results of directly determining the apparent density of the samples, characterized in that the longitudinal ultrasonic wave velocity is determined using a direct piezoelectric transducer with a resonant frequency of 1 MHz to 10 MHz with an installed delay line at an ambient air temperature of 15 °C to 35 °C in the time interval between the signal from the surface of the workpiece or product material and the first bottom echo signal, wherein glycerin is used to create an acoustic contact between the piezoelectric transducer and the delay line, and distilled water is used between the delay line and the surface of the ceramic product, before taking measurements, the parameters of the ultrasonic thickness gauge are adjusted using a control sample.

Determination of the apparent density of blanks and products made of quartz ceramics is carried out using a pre-established experimental calibration relationship between the measured informative parameter – the propagation velocity of longitudinal ultrasonic waves Cl (USW) in quartz ceramics and its apparent density (ρ), determined on the samples.

The choice of the longitudinal ultrasonic wave (USW) velocity as an informative parameter (measured value) is due to the possibility of measuring it with greater accuracy compared to the amplitude or spectral characteristics of ultrasonic waves, since ensuring stable acoustic contact in the conditions of serial production when testing complex-shaped blanks or products made of quartz ceramics with a rough surface is a labor-intensive and difficult task.

To measure the velocity of longitudinal ultrasound waves, an echo-pulse control method is used, which allows for direct piezoelectric transducer (PET) control with one-sided access.

This makes it easier to carry out measurements, since there is no need to access the opposite wall surface of the product being tested, which would be very difficult or even impossible when determining the density in large-sized products or monitoring the density in cramped areas.

In addition, the use of direct transducers allows local determination of the time of passage of the ultrasonic wave (for subsequent calculation of the ultrasonic wave velocity) in blanks or products made of quartz ceramics.

The measurement of the velocity of longitudinal ultrasound waves is carried out at a frequency from 1 MHz to 10 MHz (determined by the resonant frequency of the PEP and the frequency of the probing pulses), since this ensures an optimal ratio between the sensitivity of control, the accuracy of measuring the propagation time of ultrasound waves and their attenuation in quartz ceramics.

The use of longitudinal USW frequencies above 10 MHz is impractical due to a decrease in wavelength and, consequently, an increase in USW attenuation in ceramics, which does not allow measurements to be taken in products or blanks due to the impossibility of identifying the “bottom” (reflected from the opposite wall of the product) echo pulse against the background of structural noise.

The use of a frequency below 1 MHz is also impractical due to the increase in the error in determining the propagation time of the ultrasound wave due to the increase in the width of the ultrasonic pulse, as well as a decrease in sensitivity due to the increase in the length of the ultrasound wave.

When measuring, a delay line made of polymer material (rexolite, organic glass, cross-linked polystyrene, etc.) is used to increase the accuracy of measurements and eliminate mechanical damage to the expensive PE.

The speed of ultrasonic testing in a material (C) depends on its temperature and is determined by the ratio [Non-destructive testing: Handbook: In 7 volumes. General editor V. V. Klyuev. Volume 3: Ultrasonic testing / I. N. Ermolov, Yu. V. Lange. Ultrasonic testing. – 2nd ed., corrected. – Moscow: Mashinostroenie, 2006 – 864 p]:

C = C ₀ + K _C × (T – T ₀ ),

Where C – the speed of the ultrasound at temperature T;

C ₀ – the speed of the ultrasonic wave at the initial temperature T ₀ ;

K _C – temperature coefficient of the RAS speed.

In this regard, in order to ensure an accurate determination of the USV velocity, measurements should be carried out at an ambient air temperature of 15°C to 35°C. In this case, errors associated with the influence of changes in the ambient air temperature (ceramics temperature) are negligible (no more than 0.5%) and do not have a significant effect on the accuracy of the results obtained.

If the ambient temperature changes over a larger range, the measurement error will increase.

An example of the implementation of the proposed method is illustrated in Fig. 1, 2, 3, 4 and 5.

Fig. 1 shows the propagation patterns of the ultrasound wave in the delay line and the walls of the controlled contraction, as well as the resulting oscillogram.

Fig. 2 shows the installation of a PEP with a delay line on a ceramic workpiece.

Fig. 3 shows an oscillogram from the flaw detector screen.

Fig. 4 shows the experimental calibration dependence “density – RAS velocity”.

Fig. 5 shows the installation of a PEP with a delay line on a quartz ceramic product.

The use of a delay line for measuring the velocity of longitudinal USWs is shown in Fig. 1, where 1 is a direct PEP, 2 is a delay line, 3 is the wall of the tested product, 4 are longitudinal USWs propagating in the delay line, 5 are longitudinal USWs propagating in the wall of the tested product, 6 is a probing pulse, 7 is the measured time interval.

Thus, by measuring the time interval 7 between the signal 8 from the surface of the product and the first bottom echo signal 9, the propagation time of longitudinal ultrasonic waves directly in the wall of the monitored product is determined (without taking into account the propagation time of ultrasonic waves in the elements of the PE and the delay line).

To ensure acoustic contact between the PEP and the delay line, glycerin is used, as it is characterized by good surface wettability, low ultrasound attenuation and dries for a long time.

To create an acoustic contact between the delay line and the surface of the workpiece or product, distilled water is used, as it is characterized by low attenuation of longitudinal ultrasound waves, does not have a negative effect on the properties of quartz ceramics and does not require removal from its surface after measurements.

To check the correct operation of the equipment, as well as to take into account the mechanical wear of the delay line, the propagation time of the ultrasonic waves in cables and equipment during measurements, before taking measurements, the parameters (delay time, time sweep, gain, etc.) of the ultrasonic thickness gauge are adjusted using a control sample with a known thickness and the propagation speed of longitudinal ultrasonic waves at a given ambient air temperature.

The implementation of the claimed method is confirmed by the following examples.

Example 1

In the wall of the controlled article 3, using a direct piezoelectric transducer 1 with a resonant frequency of 1 MHz with an installed delay line 2, the velocity of the longitudinal USV Cl was measured (Fig. 2). The measurement of the USV velocity was carried out at an ambient air temperature of plus 30 °C. The time interval was measured7between signal 8 from the surface of the workpiece and the first bottom echo signal 9 (Fig. 3). Glycerin was used to create an acoustic contact between the piezoelectric transducer and the delay line, and distilled water was used between the delay line and the surface of the ceramic product. The measured value of the ultrasonic wave velocity Cl was 4200 m/s. The apparent density (ρ) was determined using a previously constructed experimental calibration dependence (Fig. 4):

ρ = 3E-08×Cl ² - 0.0002×Cl + 2.2195 = 1.956 g/cm ³

Before carrying out measurements, the parameters of the ultrasonic thickness gauge were adjusted using a control sample.

Example 2

The method for determining the apparent density in a quartz ceramic product is performed in a similar manner to that given in Example 1. In this case, a direct PE with a resonant frequency of 5 MHz is used (Fig. 5). The ambient air temperature during the measurements was 25 °C. The measured value of the ultrasonic velocity Cl was 4580 m/s. The determined value of the apparent density of the quartz ceramic product was 1.979 g/cm ³ .

Example 3

The method for determining the apparent density in a quartz ceramic product is performed in a similar manner to that given in Example 1. A direct piezoelectric transducer with a resonant frequency of 10 MHz is used. The ambient air temperature during the measurements was 18 °C. The measured value of the ultrasonic velocity Cl was 5160 m/s. The determined value of the apparent density of the quartz ceramic product was 2.03 g/cm ³ .

The proposed method has the following advantages:

1. It is highly efficient and low labor-intensive (it takes no more than 5 minutes to determine the apparent density of the material of quartz ceramic products and blanks).

2. It is characterized by the accuracy of determining the apparent density of the material of quartz ceramic products (the coefficient of determination of the experimental calibration (regression) dependence R ² = 0.9999).

3. Allows local determination of the density of the material of blanks or products made of quartz ceramics, regardless of their shape and size.

Claims (1)

A method for determining the apparent density in quartz ceramic products, including measuring the ultrasound velocity and determining the controlled parameter using an experimental calibration dependence, previously constructed using the results of measuring the ultrasound velocity values, in comparison with the results of determining the apparent density using the results of directly determining the apparent density of the samples, characterized in that the longitudinal ultrasound wave velocity is determined using a direct piezoelectric transducer with a resonant frequency of 1 MHz to 10 MHz with an installed delay line at an ambient air temperature of 15°C to 35°C in the time interval between the signal from the surface of the workpiece or product material and the first bottom echo signal, wherein glycerin is used to create acoustic contact between the piezoelectric transducer and the delay line, and distilled water is used between the delay line and the surface of the ceramic product; before taking measurements, the ultrasonic thickness gauge parameters are adjusted using a control sample.