Concentrators and waveguides of ultrasonic vibrations. Calculation of concentrators for installations of ultrasonic microwelding. Calculation of artificial light

WORK #3

Objective:

determination of the optimal shape and calculation of the parameters and geometric dimensions of waveguides - concentrators for ultrasonic processing of materials.

Theoretical Provisions

Material Grade	Waveguide input end diameter D (mm)	Waveguide output end diameter d (mm)	Resonance length L	Nodal plane X 0	Gain K y	Resonance frequency (KHz)

Practical part:

Step waveguide calculation:

f is the resonant frequency.

V is the speed of sound.

X 0 \u003d L / 2; X 0 - position of the nodal plane - the place of attachment of the waveguide

K y \u003d N 2 \u003d (D / d) 2, where D and d are the diameters of the input and output ends of the waveguide

Steel: V= 5100

Titanium: V= 5072

Solution:

L 1 \u003d 5200/2 * 27 \u003d 5100 / 54 \u003d 94.4 (mm)

L 2 \u003d 5200 / 54 \u003d 96.2 (mm)

L 3 \u003d 5072 / 54 \u003d 93.9 (mm)

X 01 =94.4/2 =47.2 (mm)

X 02=96.2/2=48.1 (mm)

X 03 =93.9/2=46.9 (mm)

K y \u003d (1.2) 2 \u003d 1.4

Conclusion:

In this work, we got acquainted with an ultrasonic concentrator with a stepped waveguide. The waveguide was calculated by solving a differential equation that describes the oscillatory process, provided that the oscillations are harmonic in nature. In the process of work, the diameters of the input and output ends of the waveguide were found. The signal amplification coefficient depends on its diameters.

Job #4

Waveguides - concentrators - transmitters of mechanical energy of ultrasonic frequency to the material processing zone

Objective:

determination of the optimal shape and calculation of the parameters and geometric dimensions of waveguides-concentrators for ultrasonic processing of materials.

Theoretical Provisions

The input of the energy of ultrasonic vibrations into the material being processed is carried out by a waveguide-instrument complex. The mechanisms of interaction with the material are discussed below, in the next section. This section discusses typical methods for calculating the most common waveguide shapes and the types of tools used in the processing of welded joints.

From a number of parameters characterizing the properties of waveguides, the most important are the vibrational speed, voltage and power that the tool is able to transfer to the processing zone. According to a simplified scheme, for a given value of the amplitude of the vibrational velocity, the calculation of the waveguide is reduced to determining its resonant length, the input and output areas, and the place of its attachment.

The formula for calculating waveguides from solutions of a differential equation describing the oscillatory process, provided that the oscillations are harmonic in nature, the wave front is flat, and the wave propagates only along the axis of the waveguide without loss.

Laboratory equipment and instruments

When performing a laboratory workshop to familiarize students with the equipment and better understand the principle of operation of the ultrasonic kit by students, the laboratory stands have a wide selection of various waveguides (hubs) used with transducers of various shapes and powers.

Available waveguides represent a group of 4 most common shapes and are made of materials that are acoustically transparent and have the necessary strength characteristics.

For ease of perception of the material, the waveguides are made with a working tool fixed on it - a tip and without it.

Practical part:

Calculation of a conical waveguide

L= λ /2 * kl/ , where kl are the roots of the equation

tgkl = kl/1 + (kl) 2 N(1-N) 2

2П / λ = k – wave number

X 0 \u003d 1 / k * arctg (kl / a), where a \u003d 1 / N-1

K y \u003d √1+ (2P * 1 / λ) 2

Solution:

l = 94.4; λ = 94, 4 * 2= 188, 8

K=2*3.14/188.8=0.03

Kl = 0.03 * 94.4 = 2.8

tgkl = 2.8 / 1+ (2.8) 2 * 1.2(1-1.2) 2 = 2

a \u003d 1 / 1.2-1 \u003d 5

X 0 \u003d 1 / 0.03 * arctg (2.8 / 5) \u003d 0.3

K y \u003d √1 + (2 * 3.14 * 1 / 188.8) 2 \u003d 1

Conclusion:

In this work, we got acquainted with an ultrasonic concentrator with a conical waveguide. The waveguide was calculated by solving a differential equation describing the oscillatory process, provided that the oscillations are harmonic in nature. In the process of work, the diameters of the input and output ends of the waveguide were found. The signal amplification coefficient depends on its diameters.

These waveguides are widely used for processing metal structures in places of welded joints, so it is very important to correctly calculate the parameters of the tool to transmit the desired signal frequency.

To transmit ultrasonic vibrations from the transducer to the working tool or to the working environment in ultrasonic installations, concentrators and waveguides are used; the latter have a constant cross-sectional area and a cylindrical shape.

Waveguides are used when there is no need to amplify the amplitude of the transducer oscillations. Hubs are speed transformers; they have a variable cross-sectional area more often cylindrical. Due to this cross section, they convert low-amplitude ultrasonic vibrations reported by the transducer and concentrated at its input end into vibrations of a larger amplitude at the output end. The latter are reported to the working body (instrument) of the ultrasonic unit. Amplification of the amplitude occurs due to the difference in the areas of the input and output ends of the concentrator - the area of ​​the first (input) end of the concentrator is always more area second.

Waveguides and concentrators must be resonant, i.e. their length must be a multiple of an integer number of half-waves (λ/2). Under this condition, the best opportunities are created for matching them with the power source, the oscillatory system as a whole and the mass attached to them (working tool).

Rice. 14. Half-wavelength concentrators

In ultrasonic technological installations exponential (Fig. 14, a), conical (Fig. 14, b) and stepped concentrators are most widely used. The latter are performed with a flange (Fig. 14, c) or without it (Fig. 14, d). There are also conical concentrators with a flange (for example, in the PMS-15A-18 type converter), as well as combined concentrators, in which the steps are of different shapes.

Concentrators and waveguides can be an integral part of the oscillatory system or its replaceable element. In the first case, they are soldered directly to the converter. Replaceable hubs are connected to the oscillatory system (for example, with an adapter flange) by means of a thread.

For concentrators, the cross-sectional area changes according to a certain pattern. Their main characteristic is the theoretical gain K, showing how many times the oscillation amplitude of its output end is greater than the amplitude at the input end. This coefficient depends on the ratio N of the diameters of the inlet D1 and outlet D2 ends of the concentrator: N=D1/D2.

The highest amplitude gain for the same value of N is provided by a stepped concentrator. He has K=N2. This explains the widespread use of step-type concentrators in various ultrasonic devices. In addition, these concentrators are easier to manufacture than others, which is sometimes the most important condition for the successful application of ultrasonic processing. The calculation of a stepped concentrator is much simpler than other types of concentrators.

The value of the amplitude amplification factor of the stepped concentrator is taken taking into account the prevention of the possibility of lateral vibrations, which is observed at high amplification factors (K> 8...10), as well as its strength data. In practice, the gain of a stepped hub is assumed to be from four to six.

The resonant length of the stepped concentrator lp is determined from the expression lp=a/2=C/2f, where X is the wavelength in the rod of constant cross section, cm; С - longitudinal wave velocity (for steel С=5100 m/s); f - resonant frequency, Hz.

In the installation of wire leads in SPP for power electronics, UZS is mainly used. The main parameters of the process with this method of microwelding are: the amplitude of oscillations of the working end of the tool, which depends on the electric power of the converter and the design of the oscillatory system; compression force of welded elements; the duration of the inclusion of ultrasonic vibrations (welding time).

The essence of the USS method lies in the occurrence of friction on the interface between the elements to be joined, resulting in the destruction of oxide and adsorbed films, the formation of physical contact and the development of seizure centers between the parts to be joined.

The ultrasonic concentrator is one of the main elements of the oscillatory systems of microwelding installations. The concentrators are made in the form of rod systems with a smoothly changing cross section, since the radiation area of ​​the transducer is always much larger than the area welded joint. The concentrator is connected to the transducer with a large input cross section, and an ultrasonic instrument is attached to the smaller output cross section. The purpose of the concentrator is the transmission of ultrasonic vibrations from the transducer to an ultrasonic instrument with least loss and the most efficient.

Known in ultrasonic technology a large number of concentrator types. The most widely used are the following: stepped, exponential, conical, catenoid and concentrator of the “cylinder-catenoid” type. In the oscillatory systems of installations, conical concentrators are often used. This is due to the fact that they are easy to calculate and manufacture. However, of the five hubs listed above, the conical one has the highest losses due to internal friction, dissipates the most power, and therefore heats up more. The concentrators with the smallest value of the ratio of the inlet and outlet diameters for the same gain K y have the best stability. It is also desirable that its "half-wavelength" length be the smallest. For the purposes of microwelding, concentrators with 2

The concentrator material should have high fatigue strength, low losses, good brazed solderability, easy processing, and be relatively inexpensive.

The calculation of an ultrasonic concentrator is reduced to determining its length, inlet and outlet sections, and the shape of the profile of its side surfaces. When calculating, the following assumptions are introduced: a) a plane wave propagates along the concentrator; b) oscillations are harmonic in nature; c) the hub oscillates only along the center line; d) mechanical losses in the concentrator are small and linearly depend on the oscillation amplitude (deformation).

Theoretical Gain K y the amplitude of oscillations of the exponential concentrator is determined from the expression

where D0 and D1 are the diameters of the inlet and outlet sections of the concentrator, respectively, mm; N- the ratio of the diameter of the inlet section of the concentrator to the outlet.

The length of the concentrator is calculated by the formula

(2)

where With is the propagation velocity of ultrasonic vibrations in the concentrator material, mm/s; f– operating frequency, Hz.

Nodal plane position x 0(where the waveguide is attached) is expressed by the relation

(3)

The profile generatrix of the catenoidal part of the concentrator is calculated by the equation

(4)

where is the shape factor of the generatrix; X– current coordinate along the concentrator length, mm.

In this work, a computer program was developed for calculating the parameters of five types of ultrasonic concentrators: exponential, stepped, conical, catenoidal, and “cylinder-cathenoid” concentrator, implemented in Pascal (Turbo-Pascal-8.0 compiler). The initial data for calculations are: diameters of the inlet and outlet sections ( D0 and D1), operating frequency ( f) and the propagation velocity of ultrasonic vibrations in the concentrator material (c). The program allows you to calculate the length, position of the nodal plane, the gain, as well as for the exponential, catenoid and concentrator "cylinder-catenoid" the shape of the generatrix with a given step. The block diagram of the algorithm for calculating the exponential concentrator is shown in fig. 6.9.

Calculation example. Calculate the parameters of a half-wave exponential concentrator if the operating frequency is given f= 66 kHz; inlet diameter D0= 18 mm, output D1=6 mm; concentrator material - steel 30KhGSA (ultrasound velocity in the material With= 5.2 10 6 mm/s).

According to formula (1), we determine the gain of the concentrator .

Rice. 6.9. Structural diagram of the algorithm for calculating the exponential concentrator

In accordance with expressions (2) and (3), the length of the concentrator , position of the nodal plane mm.

Equation (4) for calculating the shape of the concentrator profile takes the following form after substitutions:

Calculations using a computer program of the generatrix profile of an exponential concentrator with a step in a parameter X, equal to 5 mm, are given in table. 6.1. According to Table. 6.1, a hub profile is constructed.

Tab. 6.1. Concentrator Profile Calculation Data

x, mm
D x, mm		15,7	13,8		10,6	9,3	8,2	7,2	6,3

In table. 6.2 shows the results of calculating the parameters of various types of ultrasonic concentrators made of steel 30KhGSA (with D0= 18 mm; D1= 6 mm; f= 66 kHz).

Tab. 6.2. Parameters of ultrasonic concentrators

* l 1 and l 2 are the lengths of the cylindrical and catenoidal parts of the concentrator, respectively.

The invention relates to ultrasonic technology, namely to the structures of ultrasonic vibrating systems. The technical result of the invention is to increase the amplitude of oscillations while reducing energy consumption, reducing overall dimensions and weight. The ultrasonic oscillatory system is made of packages of piezoelectric elements located on the concentrator surface forming vibrations. On the packages of piezoelectric elements there are reflective pads, the surface of which, opposite to the piezoelectric elements, is made flat or stepwise variable in diameter. The concentrator has an attachment point and ends with a surface with a working tool. The forming and radiating surfaces of the concentrator have a rectangular shape of the same length in cross section, and the ratio of their transverse dimensions is selected from the condition of ensuring a given gain factor of the concentrator. The total length of the reflective lining, the package of piezoelectric elements and the section of the concentrator to the attachment point is equal to one sixth of the wavelength of ultrasonic vibrations. The length of the concentrator section, on which a smooth radial transition is carried out, and the section with a transverse size corresponding to the radiating surface, are equal to one sixth of the wavelength of ultrasonic vibrations. 2 ill.

Drawings to the RF patent 2284228

The invention relates to ultrasonic technology, namely the design of ultrasonic oscillatory systems, and can be used in technological devices designed to process large volumes of liquid and liquid-dispersed media, to ensure that a large surface is exposed to high-amplitude ultrasonic vibrations, for example, in flow devices or in the implementation press seam-step welding (formation of sealing seams of great length).

Any ultrasonic technological apparatus includes a source of high-frequency electrical oscillations (electronic generator) and an ultrasonic oscillatory system.

The ultrasonic oscillatory system consists of a piezoelectric transducer and a concentrator with a working tool. In the ultrasonic transducer of the oscillatory system, the energy of electrical vibrations is converted into the energy of elastic vibrations of ultrasonic frequency. The concentrator is made in the form of a three-dimensional figure of variable cross section made of metal, in which the ratio of the areas of the surfaces in contact with the transducer and ending with the working tool (radiating ultrasonic vibrations) determines the required amplification factor.

Known ultrasonic oscillatory systems with large areas of the radiating surface. All known oscillatory systems are made according to a constructive scheme that combines piezoelectric or magnetostrictive half-wave transducers and resonant (multiples of half the wavelength of ultrasonic vibrations) concentrators of ultrasonic vibrations. Their longitudinal size corresponds to the wavelength of ultrasonic vibrations, and the transverse size exceeds half the length of ultrasonic vibrations in the concentrator material.

The disadvantage of analogues is the complex distribution of the oscillation amplitude on the radiating surface due to the Poisson's ratio of the concentrator material, which does not allow for the same ultrasonic action along the entire radiating surface, for example, when obtaining a high-quality extended seam.

The closest, in terms of technical essence, to the proposed technical solution is an ultrasonic vibrating system according to US patent 4363992 adopted as a prototype.

An ultrasonic oscillatory system consists of several half-wave piezoelectric transducers installed on one of the surfaces (forming ultrasonic vibrations) of a concentrator, ending with a working end (tool) of a certain shape and size. The transducers are made in the form of series-mounted and acoustically interconnected rear frequency-reducing overlay, a package of an even number of ring piezoelectric elements and a frequency-reducing radiating overlay. The radiating surface of the transducer is acoustically connected to the surface of the concentrator that forms the ultrasonic vibrations. The longitudinal size of the concentrator corresponds to half the wavelength of ultrasonic vibrations in the material of the concentrator. The concentrator is made in the form of a three-dimensional figure of variable cross section made of metal, in which the ratio of the areas of the surfaces in contact with the transducers (forming ultrasonic vibrations) and ending with a working tool (radiating ultrasonic vibrations) determines the required gain.

The concentrator has through grooves, which make it possible to eliminate the uneven distribution of the oscillation amplitude along the radiating surface of the concentrator (i.e., to exclude the deformation of the concentrator perpendicular to the direction of the force). This makes it possible to provide the same ultrasonic effect along the entire radiating surface.

The prototype allows you to partially eliminate the shortcomings of the known oscillatory systems, but has the following common significant disadvantages.

1. The well-known ultrasonic oscillatory system, consisting of ultrasonic transducers and a concentrator, is a resonant system. When the resonant frequencies of the transducers and the concentrator coincide, the maximum amplitude of the ultrasonic vibrations of the working tool and, accordingly, the maximum input of energy into the processed media are ensured. When implementing technological processes, the working tool and part of the concentrator are immersed in various technological media or subjected to static pressure on the radiating surface. The influence of various technological media or external pressure is equivalent to the appearance of an additional attached mass to the radiating surface of the concentrator and leads to a change in the natural resonant frequency of the concentrator and the entire oscillatory system as a whole. In this case, the optimal frequency matching of the converter and the concentrator is violated. The mismatch between the ultrasonic transducer and the concentrator leads to a decrease in the amplitude of oscillations of the radiating surface (working tool) and a decrease in the energy introduced into the media.

To eliminate this shortcoming, in the design and manufacture of oscillatory systems, a preliminary mismatch of the converter and concentrator in terms of resonant frequency is carried out so that when a load appears and the natural frequency of the concentrator decreases, it corresponds to the natural frequency of the converter and ensures maximum energy input. This significantly limits the scope of such an ultrasonic oscillatory system and is insufficient, since in most of the implemented technological processes the value of the added mass changes (for example, the transition from water or oil media to their emulsion, the emergence and development of a cavitation process leading to the formation of a cloud of gas-vapor bubbles and reducing the added mass in any liquid medium) during the implementation of the process itself, which leads to a decrease in the efficiency of input of ultrasonic vibrations.

2. The problem of optimal matching of the transducer and concentrator in frequency is exacerbated by the need to match the wave impedances of liquid and liquid-dispersed media with solid piezoceramic materials of the transducers. For optimal matching, the gain of the concentrator should be 10-15. Such high gains can only be obtained with stepped concentrators, but, at such gains, they exacerbate the dependence of the natural resonant frequency on the load, require a small output section with a significant length (corresponding to a quarter of the wavelength of ultrasonic vibrations in the concentrator material), which leads to reduction of the radiating surface, loss of dynamic stability and the appearance of bending vibrations. For this reason, the oscillatory systems used in practice have a gain of no more than 3...5, which makes them unsuitable for providing high-intensity ultrasonic effects on various technological media.

In addition to the main disadvantages due to the applied design scheme for constructing oscillatory systems, the prototype has several disadvantages due to the technological and operational features of their manufacture and use.

1. An ultrasonic vibrating system with two or more piezoelectric transducers (up to 40...50 mm in diameter) can have a radiating surface length of more than 200...250 mm and a width of more than 5 mm. In this case, the natural resonant frequencies of the piezoelectric transducers differ, which is due to the differences in the electrical and geometric parameters of the piezoelectric elements, frequency-lowering overlays, differences in the compression forces during the transducer assembly, etc., which are permissible according to the regulatory and design documentation. In this case, the excitation of mechanical vibrations of the resonant concentrator is carried out by converters with different operating frequencies, some of which do not coincide with the resonant frequency of the concentrator. It is especially difficult to carry out coordination in an oscillatory system with several converters of different frequencies and a stepped concentrator with a maximum gain. Since this reduces the efficiency of ultrasonic treatment, even compared to an oscillatory system of the same size, but with one transducer.

2. The impossibility of making a complex-profile radiating surface (for example, for the simultaneous formation of two welds and cutting the material between them), since in this case each longitudinal dimension determines its own resonant frequency of the concentrator, which does not correspond to the resonant frequency of the transducers (only one of the operations is effectively performed - forming a seam or cutting material).

3. The impossibility of creating ultrasonic oscillatory systems with an extended bandwidth, in comparison with resonant systems.

4. A two-half-wave oscillatory system with an operating frequency of 22 kHz has a longitudinal dimension of at least 250 mm and, with a radiating surface length of 350 mm, weighs at least 10 kg. In this case, the mounting of the oscillatory system is carried out in the area of ​​minimum vibrations: either in the center of the converter, or in the center of the concentrator. This fastening leads to low mechanical stability and the impossibility of ensuring the accuracy of the impact. Optimal fastening in the center of mass cannot be ensured due to the large amplitudes of mechanical oscillations and the inevitable damping of the oscillatory system.

The revealed shortcomings of the prototype cause its insufficient efficiency, limit functionality, which makes it unsuitable for use in high-performance, automated production.

The proposed technical solution is aimed at eliminating the shortcomings of existing oscillatory systems and creating a new oscillatory system capable of providing the radiation of ultrasonic vibrations with a uniform amplitude distribution along the radiating surface of the concentrator (working tool) with maximum efficiency for all possible loads and changes in the properties of the processed media and the parameters of the oscillatory system, i.e., ultimately, provide an increase in the productivity of processes associated with ultrasonic exposure while reducing energy consumption.

The essence of the proposed technical solution lies in the fact that the ultrasonic oscillatory system containing piezoelectric elements and a concentrator is made of concentrator and packages of an even number of series-installed piezoelectric elements arranged in parallel on the surface of the concentrator and acoustically connected to it. On the packages of piezoelectric elements there are reflective pads acoustically connected with the piezoelectric elements. The opposite surface contacting with the piezoelectric elements is made flat or stepwise variable in diameter, and the dimensions and number of steps are selected from the condition for obtaining a given bandwidth. The concentrator has a fastening unit and ends with a surface emitting ultrasonic vibrations with a working tool. The forming and radiating surfaces of the concentrator have a rectangular shape of the same length in cross section, and the ratio of their transverse dimensions is selected from the condition of ensuring a given gain factor of the concentrator. The total length of the reflective lining, the package of piezoelectric elements and the concentrator section up to the attachment point is equal to one sixth of the wavelength of ultrasonic vibrations in the concentrator material. The dimensions of the concentrator section, on which a smooth transition is made, and the section with a transverse dimension corresponding to the radiating surface, are equal to one sixth of the wavelength of ultrasonic vibrations in the concentrator material, and the smooth transition is made radial, and its dimensions are selected from the condition:

The analysis of possible structural schemes for constructing oscillatory systems made it possible to establish that most of the fundamental limitations inherent in a two-half-wave structural scheme of an oscillatory system can be eliminated by using oscillatory systems that combine a piezoelectric transducer and a concentrator with a high gain factor and any size working tool in a half-wave structural scheme. .

An oscillatory system made according to a half-wave constructive scheme is a single resonant oscillatory system and all changes in its parameters lead only to a mismatch with an electronic generator. The absence of practical designs of such oscillatory systems is due to the impossibility of their implementation on the basis of the magnetostrictive transducers used, until recently, and the complexity of practical implementation based on modern piezoceramic elements due to the need to place them in the maximum mechanical stress, and also due to the lack of electronic generators capable of provide optimal power supply modes for such an oscillatory system with all possible changes in its resonant frequency (up to 3...5 kHz).

The proposed technical solution is illustrated in Fig.1, which schematically shows an ultrasonic oscillatory system containing piezoelectric elements 1, reflective resonant pads 2 and a concentrator 3. Structurally, the oscillatory system is made of concentrator 3 located in parallel on the surface 4 forming ultrasonic vibrations, and acoustically associated with it packages of an even number of series-installed piezoelectric elements 1 (figure 1 shows an oscillatory system with two packages of piezoelectric elements). On each of the packages, consisting of an even number of piezoelectric elements (usually two or four), there are reflective pads 2 acoustically associated with them, the opposite surface of which is in contact with the piezoelectric elements is made flat 5 or stepwise variable in length 6, and the dimensions and number of steps 7 are selected from conditions for obtaining a given bandwidth. The concentrator 3 has a fastening unit 8 and ends with a surface 9 emitting ultrasonic vibrations with a working tool 10. The forming 4 and emitting 9 surfaces of the concentrator have a rectangular shape of the same length L, and the ratio of their transverse dimensions D 1 , D 2 is selected from the condition of ensuring a given gain factor of the concentrator . The total length of the reflective lining 2, the package of piezoelectric elements 1 and the section of the concentrator to the attachment point is equal to one sixth of the wavelength of ultrasonic vibrations in the material of the concentrator. The dimensions of the concentrator section on which the smooth transition takes place, and the section with a transverse dimension corresponding to the radiating surface, correspond to one sixth of the wavelength of ultrasonic vibrations in the concentrator material, and the smooth transition is made radial, and its dimensions are selected from the condition:

where L z is the length of the smooth transition; D 1 , D 2 - transverse dimensions of the forming and radiating surface of the concentrator.

Ultrasonic oscillatory system operates as follows.

When an electrical supply voltage is supplied from the generator of electrical oscillations of ultrasonic frequency (not shown in figure 1), corresponding to the natural frequency of the oscillatory system, to the electrodes of the piezoelectric elements 1, the energy of electrical oscillations is converted into ultrasonic mechanical oscillations due to the piezoelectric effect. These vibrations propagate in opposite directions and are reflected from the boundary surfaces of the reflective lining and the concentrator (working tool). Since the entire length of the oscillatory system corresponds to the resonant size (half the wavelength of ultrasonic vibrations), mechanical vibrations are released at the natural resonant frequency of the oscillatory system. The presence of a stepped-radial concentrator makes it possible to increase the amplitude of oscillations of the radiating surface, in comparison with the amplitude of oscillations, on the opposite surface of the reflective lining in contact with the piezoelectric elements. The magnitude of the oscillation amplitude on the radiating surface depends on the concentrator gain, which is defined as the square of the ratio of the areas of the forming and radiating surfaces of the concentrator, which have a rectangular cross section of the same length.

Attachment 8 hub 3 (figure 1) is located in the area close to the node of the minimum mechanical ultrasonic vibrations, which ensures minimal damping of the ultrasonic oscillating system, i.e. the maximum amplitude of oscillations of the radiating surface and the absence of oscillations at the attachment points of the oscillatory system in production lines.

Due to the fact that obtaining analytical ratios of geometric dimensions for practical calculations in the design of oscillatory systems is difficult due to the lack of a number of accurate data on the propagation of ultrasonic vibrations in bodies of variable cross section from alternating different materials, when choosing the parameters of an oscillatory system, the results of numerical simulation were used, together with graphic dependences of practical study of oscillatory systems with different ratios of the transverse dimensions of the forming and radiating surfaces of the concentrator D 1 , D 2 and sections of the oscillatory system with different lengths . Experimental studies have made it possible to establish that the maximum coefficient of electromechanical transformation is provided under the condition that the piezoelectric elements are displaced from the area of ​​minimum oscillations (maximum mechanical stresses) in such a way that the total length of the reflective lining, the package of piezoelements and the concentrator section to the attachment point is equal to one sixth of the wavelength of ultrasonic vibrations in concentrator material. The choice of the size of the concentrator section, on which a smooth transition is made equal to one sixth of the wavelength of ultrasonic vibrations in the material of the concentrator and its shape, according to the above formula, provides the necessary gain and minimum mechanical stresses at the transition boundary between the smooth transition section and the section with a transverse size corresponding to emitting surface. The results of experimental studies of oscillatory systems with different ratios of the transverse dimensions of the forming and radiating surfaces of the concentrator D 1 , D 2 are presented in Fig.2 a, 6, c, which shows the graphs of the main parameters of the oscillatory system: change in the natural resonant frequency f(a), coefficient gain M p (b), and maximum mechanical stresses max (c) from the radius of the smooth transition. From the dependences obtained, it was found that for any ratio of the transverse dimensions of the forming and radiating surfaces of the concentrator D 1 , D 2 , the minimum effect on the natural resonant frequency occurs at

In this case, the gain approaches the maximum possible, and a significant reduction in mechanical stresses in the area of ​​the piezoelectric elements is provided.

The conducted experimental studies allowed us to confirm the correctness of the results obtained and to develop practical designs of oscillatory systems for various ratios of the transverse dimensions of the forming and radiating surfaces of the concentrator D 1 , D 2 .

Thus, in an oscillatory system with a transverse dimension of the radiating surface equal to D 2 =10 mm and with a transverse dimension of the vibration-forming surface D 1 equal to 38 mm (i.e., when using the most widely used ring piezoelectric elements with an outer diameter of 38 mm), the developed oscillatory system will provide amplification of the ultrasonic vibrations generated by the piezoelectric elements, not less than 11 times (see figure 2).

Similar results were also obtained for other values ​​of D 2 .

So, when using ring piezoelectric elements with an outer diameter of 50 mm in the proposed oscillatory system and providing a gain of 10...15, the transverse size of the radiating surface of the concentrator D 2 can be equal to 16 mm.

To obtain a gain equal to 10 ... 15 in the created oscillatory system with a size D 2 \u003d 20 mm, D 1 will be equal to only 70 mm, which is also easily implemented in practice (piezoelectric elements with a diameter of 70 mm are mass-produced).

Thus, while providing the oscillation amplitude of a package of two piezoelectric elements equal to 5 μm (supply voltage not more than 500 ... 700 V), the oscillation amplitude of the radiating surface of the oscillatory system will be 50 ... mode of developed cavitation in the processing of liquid and liquid-dispersed media, the implementation of welding of polymeric materials and dimensional processing of solid materials.

The developed ultrasonic oscillatory system provided an efficiency (electroacoustic conversion factor) of at least 75% (when radiating into water).

The implementation of the reflective lining with a stepwise changing longitudinal size (ie, the implementation of the opposite surface in contact with the piezoelectric elements is stepwise variable in diameter), allows you to create several different resonant sizes along the length of the oscillatory system. Each of these resonant sizes corresponds to its own resonant frequency of mechanical vibrations. The choice of the number and size of the steps makes it possible to obtain the necessary bandwidth (ie, to ensure the operation of the oscillatory system in the frequency range determined by the maximum and minimum longitudinal dimensions of the reflective lining).

The technical result of the invention is expressed in increasing the efficiency of the ultrasonic oscillatory system (increasing the amplitude of oscillations introduced into various media) by ensuring optimal coordination with the media and the electronic generator. The longitudinal overall dimension of the oscillatory system is reduced by 2 times, and the weight by 4 times compared with the prototype.

The ultrasonic oscillatory system developed in the laboratory of acoustic processes and apparatuses of the Biysk Technological Institute of the Altai State Technical University passed laboratory and technical tests and was practically implemented as part of an installation for making a longitudinal seam 360 mm long when sealing bags for packaging bulk products.

Serial production of the created oscillatory systems is planned for 2005.

Sources of information

1. US patent No. 3113225, 1963

2. US patent No. 4607185, 1986

3. US patent No. 4651043, 1987

4. US patent No. 4363992 (prototype), 1982

5. Ultrasonic technology. Ed. B.A. Agranat. - M.: Metallurgy, 1974.

6. Khmelev V.N., Popova O.V. Multifunctional ultrasonic devices and their application in small-scale production, agriculture and households. Barnaul, AltGTU Publishing House, 1997, 160 p.

CLAIM

An ultrasonic oscillatory system containing piezoelectric elements and a concentrator, characterized in that it is made of concentrator parallel to the surface forming ultrasonic vibrations and acoustically connected to it packages of an even number of piezoelectric elements installed in series, on which reflective plates acoustically connected to them are located, opposite to the contacting one. with piezoelectric elements, the surface of which is made flat or stepped-variable in diameter, and the dimensions and number of steps are selected from the condition for obtaining a given bandwidth, the concentrator has an attachment point and ends with a surface emitting ultrasonic vibrations with a working tool, the forming and radiating surfaces of the concentrator are rectangular in cross section of the same length, and the ratio of their transverse dimensions is selected from the condition of providing a given gain factor of the concentrator, the total length of the reflecting n lining, a package of piezoelectric elements and a section of the concentrator to the attachment point is equal to one sixth of the wavelength of ultrasonic vibrations in the material of the concentrator, the dimensions of the concentrator section on which a smooth transition is made, and the section with a transverse dimension corresponding to the radiating surface, correspond to a sixth of the wavelength of ultrasonic vibrations in the material concentrator, and the smooth transition is made radial, and its dimensions are selected from the condition

where L z is the length of the smooth transition;

D1, D2 - transverse dimensions of the forming and radiating surfaces of the concentrator.

To calculate the ultrasonic speed transformer, the role of which in the scheme under consideration is played by a stepped concentrator, we will use the general form of the equation of longitudinal vibrations (2.1). Since the assumption that the concentrator has its own frequency and carries out harmonic oscillations is also valid in this case, the solution of equation (2.1) can be represented as

Similarly, for a cylinder equivalent in mass to a diamond polishing head with attachment elements to the vibration concentrator, we can write

, (2.18)

where from 4- the speed of sound in the material of the cylinder, equivalent in mass to the smoothing tool with fasteners.

Boundary conditions for an oscillatory system with the origin at a point O 2 can be written as

At ; (2.19)

at ; (2.20)

for , (2.21)

where E 4 - tensile modulus of the material of the structural element of the smoothing head; S 3 and S 4 are the cross-sectional areas of the concentrator foot, small in diameter, and the equivalent cylinder, respectively; a 2- length of the concentrator small diameter stage; b is the height of the equivalent cylinder.

Under condition (2.19), from equation (2.17) we obtain

;

. (2.22)

Taking into account the first part of condition (2.20), from equations (2.17) and (2.18) we obtain

The second part of condition (2.20) can be transformed into the form

. (2.24)

The length of a step of a larger diameter of the concentrator is determined from expression (2.27), taking into account that, due to the absence of a load in the form of a diamond polishing head with fasteners at the end of the stepped concentrator, and :

. (2.28)

For a speed transformer with a 1/2 - wave acoustic system, when the length of one step is 1/4 and , we have

For a cylinder equivalent in mass to a smoothing head with fasteners, we can write

. (2.30)

. (2.31)

b) 3/4 - wave ultrasonic vibration drive

The oscillatory system of such a drive has one possible attachment point, which makes it possible to reduce the length of the drive by 1/4 of the acoustic wave. For the possibility of rigid fastening, the piezoelectric composite transducer in such a circuit is usually made asymmetrical (Fig. 2.3). In this case, a stage of a smaller diameter of the speed transformer with a burnishing tool is connected directly to the oscillation antinode, which is located at the end of the composite converter. Therefore, this step should be considered as a load of the piezoelectric transducer, which accordingly imposes features on the calculation of one of its frequency-reducing overlays.

For the case of harmonic oscillations of the drive, in accordance with the design scheme (Fig. 2.3), the solution of the general equation (2.1) of longitudinal oscillations can be written as

, (2.32)

. (2.33)

Boundary conditions in accordance with the design scheme can be represented as