RU2666964C1 - Method for protecting electronic blocks from inertial shock and vibration impacts - Google Patents

Abstract

FIELD: electronic equipment.SUBSTANCE: use to protect electronic unit. Essence of invention lies in fact that electronic unit housing in form of base with walls is filled with damping material, and as damping material, composition of high strength composite is used comprising polymer matrices with small percentage addition of vertically oriented multilayer carbon nanotubes and binder that ensures homogeneity of composite selected so that in zone of inertial action due to proposed damping material, natural frequency of electronic unit is shifted to high frequency region.EFFECT: providing possibility of increasing efficiency of protection of electronic unit from shock and vibration effects.1 cl, 4 dwg

Description

The invention relates to methods of protection against inertial shock and vibration effects of electronic units, and more specifically, to methods of protection against inertial shock and vibration effects of electronic units operated under inertial loads, which primarily include electronic units of aviation, missile and transported technicians.

The known device "Radio electronic block" (see AS No. 1594714 dated 05/06/88, published in the "Inventions" No. 35 dated 09/23/90), containing a case in the form of a base with walls, in which printed circuit boards and gaskets made of vibration-absorbing material. The boards are installed in such a way that the ratio of the natural frequencies of adjacent boards, as well as the extreme board and base, is greater than or equal to two.

A disadvantage of the known method implemented in the known device is that this method protects the device only from exposure to vibrational loads.

Of the known closest in technical essence is a method of protecting equipment from shock, implemented in a device for protection against mechanical stress (see patent RU 2302091 from 08/15/2005, published in BI No. 18, 06/27/2007), according to to which a package of printed circuit boards is installed on shock-absorbing gaskets inside one housing, which is filled with discrete working media (DLS). The body is made deformable and placed in another rigid body, the space between the bodies is filled with a damping material - a polymer compound.

However, this method does not provide effective protection of the electronic unit from shock and vibration, causing forced vibrations, adversely affecting the operation of the electronic unit, since the damping material of the prototype has a low strength. The use of the damping material of the prototype leads to the fact that in the zone of inertial load, the natural frequencies of the oscillations of the electronic unit become close to the low-frequency component of the energy spectrum of the impact.

This drawback leads, in turn, to the appearance of forced oscillations close enough to resonant oscillations and, as a consequence, to an increase in the probability of destruction of electronic components.

The technical result of the proposed method is to increase the efficiency of protecting the electronic unit from shock and vibration.

The essence of the proposed method lies in the fact that the elements of the electronic unit are placed in the cavity of the housing, the internal volume of which is filled with damping material.

According to the invention, the composition of the composite with high strength, rigidity and hardness is used as a damping material, including polymer matrices with a small percentage of vertically oriented multilayer carbon nanotubes and a substance providing uniformity of the composite, selected so that in the zone of inertial action due to the proposed damping the material provides a shift in the natural frequency of oscillations of the electronic unit in the region of high .

Moreover, the addition of vertically oriented multilayer carbon nanotubes and a substance ensuring the uniformity of the composite is 3-7% of the mass of the polymer matrix of the damping material, increasing the Young's modulus E of the nanocomposite to a value selected from a condition that takes into account the maximum value of axial acceleration a _max acting under extreme conditions of use, and the normalized value of axial acceleration a _n

E = 350 - (a_max - but_n) / but_max, MPa

The angle of deviation of carbon nanotubes from the longitudinal axis of the polymer matrix is from 0 to 8 °.

This combination of new features with the known ones makes it possible to increase the efficiency of protecting the electronic unit from shock and vibration influences characteristic of control systems for aircraft, rocket and transport equipment

The use of a nanostructured material with high stiffness, strength, and hardness as a damping material makes it possible to increase the elastic modulus E.

Therefore, by increasing the elastic modulus E, the natural frequencies of the electronic unit oscillations are shifted to the high frequency region, which leads to a decrease in the amplitude of the forced oscillations, a rapid attenuation of the oscillatory process and, as a result, to a decrease in the probability of destruction of the electronic unit elements.

The shift of the natural frequencies of oscillations of the electronic unit to the high-frequency region, simultaneously leads to a phase shift between forced and natural frequencies of oscillations.

The proposed method of protecting electronic components from inertial shock and vibration is illustrated by drawings.

Figure 1, shows a diagram of a device that implements the inventive method of protecting electronic components from inertial shock and vibration effects of its implementation.

The device contains (figure 1):

1 - housing;

2 - electronic unit;

3 - damping material;

4 - polymer matrix;

5 - multilayer carbon nanotubes;

6 - a binder.

It is known to use a damping material from a nanocomposite, for example, see Mikhailin Yu.L. Structural polymer composite materials. 2nd ed. SPb .: Scientific foundations and technologies, 2010. p. 344. and also, Tarasov V.A., Stepanishchev N.A. The use of nanotechnology for hardening the polyester matrix of a composite material. Bulletin of MSTU. N.E. Bauman. Ser. Engineering. Specialist. issue Actual problems of the development of rocket and space technology and weapons systems, 2010, p. 207–216.

известного демпфирующего материала, например, на основе компаунда и при использовании

демпфирующего наноструктурируемого материала, по заявляемому способу, соответственно, для длительности инерционного ударного воздействия: 1 – 0,2 мс; 2 – 0,3 мс; 3 – 0,5 мс; 4 – 0,8 мс.The graph (figure 2) shows the dependence of the spectral density of the inertial shock, typical for control systems of aviation, rocket and transport equipment and the spectrum of natural frequencies of oscillations of the electronic unit: - when using

known damping material, for example, based on a compound and when using

damping nanostructured material, according to the claimed method, respectively, for the duration of the inertial shock: 1 - 0.2 ms; 2 - 0.3 ms; 3 - 0.5 ms; 4 - 0.8 ms.

The graph (figure 3) shows the dependence of the relative voltage at the output of the acceleration sensor characterizing the oscillatory process of the electronic unit, 1 - when using a known damping material, for example, based on a compound; 2 - when using nanostructured damping material according to the claimed method, respectively, for the duration of the inertial shock, equal to 0.2 ms and 0.3 ms.

The photographs (Fig. 4) show: 4a - waveform of inertial shock action on electronic blocks with the existing protection method; 4b is an oscillogram of impact on an electronic unit when using the proposed method for protecting electronic units from inertial shock and vibration.

The method is as follows.

First, in the body of the electronic unit in the form of a base with walls, in which the elements of the electronic unit are installed, fill the internal volume with damping material.

As a damping material, a composite composition with high strength is used including polymer matrices with a small percentage addition of vertically multilayer carbon nanotubes and a binder to ensure uniformity of the composite.

Then, multilayer carbon nanotubes are oriented vertically so that the angle of deviation of the carbon nanotubes from the longitudinal axis of the polymer matrix is from 0 to 8 °.

Next, the composition of the composite is selected in such a way that in the zone of inertial impact due to the proposed damping material, the natural frequency of the electronic unit is shifted to the high frequency region.

Moreover, the addition of vertically oriented multilayer carbon nanotubes and a binder that ensures uniformity of the composite is 3-7% of the mass of the polymer matrix of the damping material, increasing the Young's modulus E of the nanocomposite to a value chosen from a condition that takes into account the maximum axial acceleration a _max acting under extreme conditions application and normable axial acceleration value and _n

E = 350 - (a _max - a _n ) / a _max , MPa.

The resistance of electronic components to inertial shock and vibration is determined by the coefficient of dynamism and damping coefficient.

The dynamic coefficient with kinematic perturbation and low damping is (see Karpushin VB Vibrations and shocks in radio equipment. Publishing House: “Soviet Radio”, Moscow, 1971, p. 327)

μ = x ₁ / x ₀ ,

where x ₁ and x ₀ are the vibration amplitude of the block and the base, respectively (in this case, the case).

.With inertial perturbations, the amplitude is compared under static and dynamic inertial perturbations. Under dynamic inertial disturbance, the amplitude of the forced oscillations to a certain extent characterizes the degree of dynamism of the oscillatory system. Under static conditions, the ratio F / k = F _article / k = x _article represents a static deflection. While A = F / k, the amplitude of the force of exciting oscillations in dynamic conditions. With a sinusoidal dynamic inertial perturbation, the perturbing force equal to F = ma is represented as

.

), возбуждающих динамические колебания. Коэффициент динамичности μ (см. Карпушин В.Б. Вибрации и удары в радиоаппаратуре. Изд-во: “Советское радио”, Москва, 1971 г., стр.354) The dynamic coefficient of the system μ is the ratio of the amplitude of the excited vibrations A = F / k to the static deflection x _st under the action of the force F _st numerically equal to F (

) exciting dynamic vibrations. The dynamic factor μ (see Karpushin VB Vibrations and shocks in radio equipment. Publishing House: “Soviet Radio”, Moscow, 1971, p. 354)

,

,

where α = f / f ₀ is the detuning coefficient is the ratio of the frequency f of the disturbing vibrations to the natural frequency f _{0 of the} electronic unit.

In a number of literary sources, the detuning coefficient is denoted by γ, and the dynamic coefficient of the system is η.

In the presence of damping in electronic units, the influence of damping is estimated by the damping coefficient β (see Karpushin VB Vibrations and shocks in radio equipment. Publishing House: Sovetskoe Radio, Moscow, 1971, p. 7). In a number of literary sources, the damping coefficient is denoted by h (see AP Nenashev, Design of Radio-Electronic Means. Moscow: Vyssh. Shk., 1990, p. 327). The damping coefficient characterizes the force of viscous friction F = β v, which is proportional to the instantaneous displacement velocity v and is directed against the direction of motion.

The dynamic coefficient in this case is determined

или

,

or

,

.Where

.

Forced vibrations of the electronic unit accompany the action of an external force, while free vibrations quickly disappear due to attenuation.

The amplitude of the forced oscillations is determined by the dependence

.

.

Thus, an increase in the coefficient of dynamism and a decrease in the amplitude of forced oscillations is achieved by increasing the coefficient of detuning γ and increasing the damping coefficient h.

It is known that the frequency of free oscillations is determined

,

,

where k is the coefficient of elasticity,

m is the mass.

The coefficient of elasticity k or stiffness, for example, of the rod is proportional to Young's modulus E, the cross-sectional area S and inversely proportional to the length of the rod l ₀ : k = E / Sl ₀ (see Physics for in-depth study (in 3 books) / Butikov E. I., Kondratiev A.S., Volume 1. Mechanics Textbook M., Fizmatlit, 2001, 2004, p.142).

Consequently, increasing the Young's modulus E causes an increase in the detuning coefficient γ.

The damping coefficient h characterizes the damping of forced oscillations. The process of damping of forced oscillations is determined by the relative attenuation coefficient

D = h / h _cr

Where

- коэффициент критического демпфирования.

- coefficient of critical damping.

For D> l, the oscillation is completely absent, and the so-called non-periodic motion occurs, in which, if the system is deviated from its equilibrium position, it tends to gradually return to its original position.

In some cases, along with the relative attenuation coefficient D = h / h _cr , the notion of attenuation coefficient ε is used, the value of which is numerically equal to ε = 2 D (see A. Nenashev, Design of Radio-Electronic Means. M .: Higher school, 1990 , p. 327).

The increase in the efficiency of protection of electronic components from vibration is achieved by increasing the Young's modulus E, the value of which is chosen equal to E = 350 MPa

At the same time, increasing the efficiency of protecting electronic components from shock and vibration is achieved by increasing Young's modulus, the value of which is selected from a condition that takes into account the maximum value of axial shock acceleration.

Under the influence of short shock accelerations, an increase in the protection efficiency of electronic blocks is achieved by increasing the Young's modulus and simultaneously increasing the damping coefficient h.

The value of the damping coefficient h depends on a number of factors, including the value of Young's modulus E and increases with decreasing value of Young's modulus E.

Therefore, increasing the efficiency of protecting electronic components from inertial shock and vibration is achieved by increasing Young's modulus, the value of which is selected from a condition that takes into account the maximum value of axial shock acceleration a _max acting in extreme conditions of use, and the normalized value of axial acceleration a _n

E = 350 - (a_max- but_n) / but_max, MPa

The value of the damping coefficient h, in mathematical modeling of the processes of inertial shock and vibration effects and the assessment of the stability of electronic units to these effects, I choose based on the normalized value of axial acceleration a _n . The normalized value of axial acceleration, in which during the mathematical modeling of inertial shock effects, the process of damping of forced vibrations insignificantly affects the value of the dynamic coefficient, changes by no more than 5% when the damping coefficient h changes by 20 ... 25%.

Claims (3)

A method of protection against inertial shock and vibration effects of electronic blocks, which consists in the fact that the elements of the electronic block are placed in the cavity of the housing, the internal volume of which is filled with damping material, characterized in that the composition of the composite with high strength, including polymer matrices, is used as a damping material with a small percentage addition of vertically oriented multilayer carbon nanotubes and a binder to ensure the uniformity of the composite, selected so that in the zone of inertial action due to the proposed damping material, the natural frequency of the electronic unit is shifted to the high frequency region, and the addition of vertically oriented multilayer carbon nanotubes and a binder that ensures the uniformity of the composite is 3-7% of the matrix weight of the polymer damping material increasing the Young's modulus E of the nanocomposite to a value selected from a condition that takes into account the maximum value of axial acceleration a _max , d Procedure in extreme conditions of use, and the rated value of the axial acceleration a _n E = 350 - (a _max - a _n ) / a _max , MPa. and the angle of deviation of carbon nanotubes from the longitudinal axis of the polymer matrix is from 0 to 8 °.

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