RU2669163C2 - Method of excitation of vibrations and device therefor - Google Patents

Abstract

FIELD: machine building.SUBSTANCE: invention relates to a vibration technique. Method of excitation of oscillations is that they excite resonance oscillations, determine the rigidity of the elastic suspensions of the oscillatory system formed by the working organ and the exciter. On the exciter, a harmonious force is created, resulting in vertical oscillations. Vibrations are transferred to the working system formed by the working member, the disk and the platform for vibration processing of the parts. At the ends, two rods and a compensator are installed at the exciter, which eliminate the longitudinal oscillations of the working system. Amplitude of the oscillations of the working system is regulated by means of a tensioning device and the values of the spring stiffness and the position of the center of gravity and the moment of inertia of the working system are changed in such a way that vibrations close to zero and the necessary amplitude of the oscillations are obtained on a vibration exciter by vertical movements.EFFECT: reduced adverse effects on the elements of the vibrating table.2 cl, 7 dwg

Description

The invention relates to vibration technology and can be used in mechanical engineering for mechanical testing and implementation of vibration technologies for vibration hardening of aircraft parts, as well as in other areas of modern technology operating in conditions of intense dynamic loading. In this regard, it is important to create vibratory technological machines that contribute to the improvement of the characteristics of parts at the stage of their manufacture.

In particular, a number of structural and technical solutions are proposed.

1. There is a method of solving the problems of excitation of stable resonant oscillations based on inertial excitation, which creates the conditions for self-organization of processes of stable oscillations occurring in complex systems of dynamic equilibrium [Antipov V.I. Using Raman parametric resonance to improve vibrating machines // Problems of mechanical engineering and machine reliability. 1998. No. 4, p. 16-21].

In this method, the maximum productivity and energy efficiency of vibrating machines is achieved by creating resonant oscillating systems with technical intelligence, that is, the ability to automatically adapt the machine to constantly acting disturbances during the process without interference from outside. The invention solves the problem of exciting stable resonant oscillations with running-in bodies of revolution based on the use of self-organization processes occurring in complex systems far from equilibrium.

The disadvantage of this invention is that for the self-excitation of the break-in bodies of revolution, it is required to inform the supporting body circular oscillations of a sufficiently large amplitude and high frequency, which is associated with an increase in unbalanced masses of the vibration exciter. Large centrifugal forces created by the rotation of the unbalances load the bearings. This reduces their resource and entails a large unproductive energy consumption to overcome the resistance of rotation of the shaft.

2. A known method of excitation of mechanical vibrations and rotational motions of a system of solids, a diagram of which is given in [Blekhman II. What can vibration do? About Vibration Mechanics and Vibration Technique. M: Science, 1988, p. 134, fig. 12.2, c]. The system consists of one inertial unbalanced vibration exciter, mounted on a softly vibration-proof solid (carrier body), in which two rotation bodies (roller and ring) are placed. Under the influence of vibration, the roller is rolled around on the inner surface of the cylindrical cavity, and the ring is rolled around the outer surface of the axis fixed to the supporting body with its inner surface. In this case, the system operates in a far-resonant mode of oscillation. Here the effect of vibrational rotation support is realized. Bodies of revolution (roller, ring) make complex movements: rotation around its own axis and planetary movement around the center of a cylindrical cavity or axis. The gear ratio of the angular speed of running in to the angular speed of its own rotation is determined by the expression i = r / (r-R), where R is the radius of the treadmill, r is the radius of the body of rotation. It is negative when running outside.

The main disadvantage is the fact that in the case of resonance tuning, in order to overcome the region of intense resonant oscillations, it is necessary to have an engine whose power is 5-6 times higher than the power needed to operate in the resonance mode.

3. A device is known in which, when the body is run in, rotations have an effect on the supporting body, similar to the action of an inertial unbalanced vibration exciter. In vibroengineering, bodies of rotation are used not as causative agents of vibrations, but as working bodies of a machine. For example, in the cone crushers "Mekhanobr-Tekhnika" the working body is a cone-shaped body, which, under the influence of vibrations, is rolled around a cone-shaped cavity in the machine body [I. Blekhman What can vibration do? O “Vibration Mechanics” and vibration technology. M .: Nauka, 1988, p. 128-129, fig. 11.3, a].

The disadvantages include: in the resonant mode of operation of the machine, the energy of the vibration exciter is spent not only on overcoming the friction forces and maintaining the break-in, but also on overcoming the inertial forces of the masses of the system, while in the resonant state the elastic and inertial forces are mutually balanced.

As a prototype adopted a method of exciting resonant mechanical vibrations and a device for its implementation [Antipov V.I., Antipova R.I., Ruin A.A. "A method of exciting resonant mechanical vibrations and a device for its implementation", RF patent No. 2486017, 1/16, 1/06/2011, priority 29.12.2011]. The method consists in the fact that resonant vibrations excite due to periodic forced changes inertial parameters of the oscillatory system formed by the working body with a total mass of elastic suspension and parametric vibration exciter, including a rotor with treadmills in it and rolling bodies in them, carry out elastic suspension of the working body in two mutually perpendicular directions along two axes and adjust the oscillatory system, setting the stiffness of the elastic suspension and rotor speed . In addition, a reactive mass is introduced, connected to the total mass using an elastic system, and translational resonant antiphase vibrations of both masses are excited with the realization of the synergistic effect of the system as a whole. The vibrational system is tuned by setting the stiffness of the elastic system between both masses, the angular velocities of the rotor of the vibration exciter and the run-in, and the natural frequency of oscillation of the rolling bodies. The device contains an oscillating system in the form of a working body connected to the base by elastic bonds with a total mass and a parametric vibration exciter installed on it, in which a balanced rotor with a pair of open circular treadmills arranged symmetrically relative to its two mutually perpendicular diameters is mounted on the motor shaft, their centers are offset from the axis of rotation of the rotor at equal distances towards the treadmill, and in the treadmills the same balanced bodies are placed. Nia.

The rotor is made of a set of identical disks, in adjacent disks, the axes of rolling of the rolling bodies are rotated around the axis of rotation of the rotor by the same angle, and the oscillating system is made with the possibility of moving the working body along two axes. Additionally, it contains a reactive mass connected to the working body and the base by elastic bonds. The working body is equipped with at least two hollow cylinders, which are placed on it symmetrically with respect to the axis of rotation of the rotor, and cylindrical rollers are freely embedded in the cylinder cavity with the possibility of rolling inside the cavities.

The present invention has the following disadvantages:

- the complexity of the design (namely, a two-level system of elastic suspensions and a working body), as a result of which it is necessary to spend a significant amount of time and material on its manufacture;

- vibration is transmitted not only to the working body, but also to the vibration exciter, which leads to its faster wear and shorter operating life.

The aim of the invention is to simplify the method of exciting resonant vibrations, while reducing adverse effects on the elements of the vibration stand.

The method of exciting oscillations, which consists in setting the stiffness of the elastic elements of the oscillatory system depending on a given frequency and amplitude of the oscillations of the working table, exciting the vibrations of the vibration exciter system and transmitting the vibrations to the working table, characterized in that the stiffness of the oscillating system is controlled using a compensator installed on the rigid element of the tensioning device, by changing the length of the rigid element connecting the desktop to the vibration exciter, and the resonant vibrations in is excited by means of the exciter, operating in a determined mode according to the formula:

М - суммарная масса обеих парциальных систем; m₀ - масса дебалансов, которые устанавливают на вибровозбудителе;where p = jω (j is the complex variable, ω is the frequency of the external disturbance), ω is the angular velocity of rotation of the imbalance, the parameters a, b, and c are denoted

M is the total mass of both partial systems; m ₀ - the mass of unbalances that are installed on the exciter;

эксцентриситет вибровозбудителя (R - радиус эксцентрика).

exciter eccentricity (R - radius of the eccentric).

A device for exciting vibrations, consisting of a desktop, vibration exciter and elastic elements, characterized in that the desktop and vibration exciter are connected by a compensator and a rigid element with the possibility of changing length, and are also connected by elastic elements with a base and flexible elements with vertical walls, moreover, a flexible element connecting the exciter with a vertical wall has a tension device.

In FIG. 1 shows a diagram for setting the operating modes of the shaker.

In FIG. Figure 2 shows the dependences of the oscillation amplitudes and the ratio of the oscillation amplitudes of the working parts of the vibrating stand on the frequency of external influences and changes in the inertial parameters of the system.

In FIG. Figure 3 shows the dependences of the frequencies of natural vibrations of partial systems on the stiffnesses of elastic supports and inertial parameters of the system.

In FIG. 1 shows: flexible member 1; supporting disk 2 and platform 3, combined into a desktop for installing a container in which the vibration processing of parts combined into a desktop; hard element 4; vibration exciter 5; tensioner 6; flexible element 7; longitudinal vibration compensator 8; elastic elements 9, 10; base 11.

The following designations are accepted: t. A - the point of hinging of the flexible element 1 with the base 11; l ₀₁ - the length of the flexible element 1; ₁ - the amplitude of the oscillations of the desktop; t. In - the attachment point of the desktop to the elastic element 9; m ₁ is the mass of the desktop; k ₁ - the stiffness of the elastic element 9; k ₂ - the stiffness of the elastic element 10; t. O is the center of gravity of the rigid element; l ₁ - the distance from the center of gravity of the rigid element 4 to t. In the support disk 2; ϕ is the angle of rotation of the working body 4; J, M - moment of inertia and mass of the rigid element 4; t. With - the attachment point of the rigid element 4 to the exciter 5; l ₂ is the distance from the center of gravity of the rigid element 4 to the attachment point with the vibration exciter 5; Q is the harmonic force of the vibration exciter 5; m ₂ - mass of vibration exciter 5; k ₂ - the stiffness of the elastic element 10; t. With ₁ - the attachment point of the flexible element 7 to the exciter 5; y ₂ - the amplitude of the vibration exciter 5; l ₀₂ - the length of the flexible element 7; T. D-point hinged flexible element 7 to the base 11.

The method is as follows. Two partial systems are distinguished: the first consists of a disk and a working platform, combined into a desktop, and the second is an inertial pathogen, which are connected using a rigid element. When a harmonic force Q arises on the vibration exciter, vertical vibrations of the rigid element and the working table are created, the amplitude of which is determined by the ratio:

,

,

эксцентриситет вибровозбудителя (R - радиус эксцентрика); k₁, k₂ - жесткости упругих элементов; ω - частота внешнего возмущения; М- суммарная масса парциальных систем; J- момент инерции;

, l₁ - расстояние от центра тяжести жесткого элемента до рабочего стола; l₂ - расстояние от центра тяжести жесткого элемента до точки крепления с вибровозбудителем; р=jω,

- комплексная переменная.where y - vibration excitation; m ₀ - the mass of unbalances that are installed on the exciter;

exciter eccentricity (R - radius of the eccentric); k ₁ , k ₂ - stiffness of the elastic elements; ω is the frequency of the external disturbance; M is the total mass of partial systems; J is the moment of inertia;

, l ₁ is the distance from the center of gravity of the rigid element to the desktop; l ₂ - the distance from the center of gravity of the rigid element to the attachment point with a vibration exciter; p = jω,

is a complex variable.

At the same time, vibrations with an amplitude of ₂ , determined by

Performing the transformation p = jω, we obtain the following expressions of the amplitudes y ₁ and y ₂ :

The oscillatory system is adjusted by setting the stiffness of the elastic supports k ₁ and k ₂ , adjusting the tension force of the flexible element, changing the position of the center of gravity of the rigid element, as well as the partial frequencies of the systems, defined as:

When creating phenomena that are close to resonance in partial systems, the stiffness of the elastic supports k ₁ and k ₂ , as well as the position of the center of gravity of the rigid element, are set so that inside the frequency range of natural vibrations:

partial frequencies were located.

соотношение амплитуд колебаний

, что свидетельствует о работе рабочего органа как рычага второго рода, а при частоте

- как рычага первого рода.In this vibration stand, linkages are also manifested. The essence of the phenomena is that the stiffness of the elastic supports k ₁ and k ₂ , as well as the position of the center of gravity of the working body is set in such a way that at a frequency

ratio of oscillation amplitudes

, which indicates the work of the working body as a lever of the second kind, and at a frequency

- as a lever of the first kind.

The vibration device operates as follows.

When a harmonic force Q arises on the vibration exciter 5 mounted on an elastic support 10 fixed to the base 11, vertical vibrations are created that are transmitted through the rigid element 4 to the platform for vibration processing 3 and the disk 2 combined into a working table located on the elastic support 9, fixed on the basis of 11; to eliminate longitudinal vibrations, a flexible element 1 is used, fixed by a fixed hinge at point A, a compensator 8, as well as a limiter in the form of a flexible element 7; the tension force of the flexible element 7 and the value of the static load on the rigid element 4 are carried out using the adjusting device 6. In this case, during the operation of the vibration stand on the support disk 2 and the platform for vibration processing 3, combined into a desktop, there are phenomena close to resonance , and on the vibration exciter 5, the amplitude of vibrations at ₂ tends to zero.

The proposed method for exciting vibrations in a vibration test bench with linkages, in comparison with known methods, allows the vibration energy to be transmitted almost completely to the working body, rather than distributing it to the vibration exciter, which allows it to provide dynamic damping of vibrations and its reliable operation.

Based on the results of mathematical modeling, the oscillation amplitudes of ₁ and ₂ were calculated, the ratio of the oscillation amplitudes depending on the frequency of the external influence, presented in the graphs of FIG. 2, as well as the dependence of the natural frequencies of the partial systems on the stiffnesses of the elastic supports shown in FIG. 3. In the graphs of figure 2, two cases were considered. In the first - the ratio R = Jc ² - Mab = 4 kg⋅m ² , a = 0.1 m, b = 0.9 m, s = 0.25 m, M = 150 kg, m ₀ = 3.5 kg; r = 23.343 cm; k ₁ = 4⋅10 ⁵ N / m; k ₂ = 12⋅10 ⁵ N / m. In the second - R = Jc ² -Mab = -6.4 kg⋅m ² , a = 0.2 m, b = 0.8 m, s = 0.25 m M = 150 kg, m ₀ = 3.5 kg; r = 23.343 cm; k ₁ = 12⋅10 ⁵ N / m; k ₂ = 16⋅10 ⁵ N / m, which corresponds to the parameters of real constructive solutions implemented during vibration strengthening of the helicopter blades. The following was established:

1) the partial frequencies of the systems are close to their own frequencies, but do not go beyond them;

2) at the partial frequency n ₂ there is a value of the amplitude of oscillations at ₂ = 0, i.e. dynamic quenching mode is provided on the vibration exciter;

3) depending on the ratio of parameters a, b, and J, the positions of the frequencies change at which the working body acts as levers of the first and second kinds: for R> 0, the working body behaves like a lever of the first kind in the resonance region, and as a lever of the second kind - in the interresonant region; when R <0, the working body behaves as a lever of the first kind in the interresonant region, and as a lever of the second kind in the transresonant region;

In FIG. 3, we also considered the dependences of the eigenfrequencies of partial systems on the stiffnesses and inertial parameters of the working body for two cases. Based on mathematical calculations, the following conclusions can be drawn:

1) as the stiffnesses of the elastic supports k ₁ and k ₂ increase, the natural and partial frequencies increase according to a quadratic dependence;

2) when setting the vibration stand, the stiffness k ₁ determines the values of the upper boundaries of the partial and natural frequencies of the working parts, and the stiffness k ₂ determines the lower boundaries of the partial and natural frequencies;

3) when the inertial parameter R changes to a smaller side, the values of the eigen and partial frequencies decrease;

4) the asymptotic approximation of the curves in some graphs is explained by the proximity of the eigen and partial frequencies;

5) the straightness of the dependence ω _sob.2 (k ₂ ) for each of the cases R is explained by the obtained values of the natural frequencies and the location of the curves on the same graph.

List of references

1. Antipov V.I. Using Raman parametric resonance to improve vibrating machines // Problems of mechanical engineering and machine reliability. 1998. No. 4, p. 16-21

2. Blekhman I.I. What can vibration do? About Vibration Mechanics and Vibration Technique. M .: Nauka, 1988, - 208 p.

Claims (5)

1. The method of excitation of oscillations, which consists in the fact that the stiffness of the elastic elements of the oscillatory system is set depending on a given frequency and the amplitude of the oscillations of the desktop, excite the vibrations of the vibration exciter system and transmit the vibrations to the desktop, characterized in that the rigidity of the oscillatory system is regulated using a compensator mounted on the rigid element of the tensioning device by changing the length of the rigid element connecting the worktable to the vibration exciter, and the resonance vibrations in excite with the help of a vibration exciter operating in the mode determined by the formula:

where y - vibration excitation; m ₀ - the mass of unbalances that are installed on the exciter;

exciter eccentricity (R - radius of the eccentric); k ₁ , k ₂ - stiffness of the elastic elements; ω is the frequency of the external disturbance; M is the total mass of partial systems; J is the moment of inertia;

_, l ₁ is the distance from the center of gravity of the rigid element to the desktop; l ₂ - the distance from the center of gravity of the rigid element to the attachment point with a vibration exciter; p = jω,

is a complex variable. 2. A device for exciting vibrations, consisting of a desktop, vibration exciter and elastic elements, characterized in that the desktop and vibration exciter are connected by a compensator and a rigid element with the possibility of changing length, and are also connected by elastic elements to the base and flexible elements with vertical walls, the flexible element connecting the vibration exciter with a vertical wall has a tensioning device.

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