RU2794872C1 - Method for testing tools and equipment for high-intensity shocks - Google Patents

Abstract

FIELD: aviation; rocket and space technology.

SUBSTANCE: methods for testing tools and equipment for high-intensity shock. Invention can be used for testing tools and equipment in aviation and rocket and space technology. The method consists in creating a shock effect in form of non-stationary vibration, registering accelerations and obtaining the same shock spectrum of accelerations at the attachment points of the test object for positive and negative values of the shock spectrum of accelerations. It differs from the background methods in that prior to the start of impact tests, tests are carried out to determine the resonant frequencies of the tooling with a dynamic layout of the test object along three mutually perpendicular axes, the results of which preliminarily determine the number and installation locations of pyro devices on the tooling at points that provide maximum response at the points of loading control dynamic layout at frequencies corresponding to the transition frequency of the given shock acceleration spectrum. Then, shock tests are carried out by simultaneous detonation of pyrotechnic devices, accelerations are recorded at the control points of the dynamic layout in form of non-stationary vibration, total, positive and negative shock acceleration spectra are obtained. Next, the resulting acceleration shock spectra are compared with the required acceleration shock spectra at each control point of the dynamic layout in three mutually perpendicular directions, and if they differ by an amount greater than the allowable error, the number, power and installation locations of the pyro devices are specified. After that, impact tests are repeated, and the required impact action in form of impact acceleration spectra is formed simultaneously at the points of control of loading of the dynamic layout along three mutually perpendicular axes.

EFFECT: creating impacts that correspond to the actual operating conditions of the equipment and ensure, during testing, simultaneous loading of the test object along three mutually perpendicular axes in two opposite directions (positive and negative) at various attachment points of the test object in order to reduce the number of impacts on the test object.

1 cl, 8 dwg

Description

This invention relates to impact testing methods and can be used in impact testing of various instruments and equipment.

There are various ways to carry out impact testing. Their main difference lies in the creation of either a single pulse of various shapes (as an external influence), or in the formation of a shock acceleration spectrum (SAS). Tests according to the method of shock acceleration spectra using vibration electrodynamic stands (synthesizing a shock excitation signal using elementary signals), stands with falling tables (the simplest signals are reproduced, which provide the necessary USU). Tests according to the method of shock acceleration spectra are carried out when the impact itself is not important, but the reaction that this impact causes in the structure is important (kn. The use of electrodynamic stands is limited both by the amplitude of the reproducible effects (usually 200-300 g) and by the frequency (the frequency range of the reproducible effects does not exceed 2.5-3 kHz).

To create shock effects, in addition to electrodynamic stands, there is a fairly diverse set of tools, for example, all kinds of hydraulic, mechanical stands.

These devices make it possible to reproduce various ways of loading the test object (with exposure levels up to tens of thousands of “g”), for example, by dropping the frame from a certain height. Impact is created by hitting a heavy pendulum on a table on which the test object is fixed. (Vibrations in engineering, a reference book in 6 volumes. Volume 5. Measurements and tests, edited by M.D. Genkin M. Mashinostroenie 1981. pp. 476 - 477). Or a solution (G.S. Batuev, Yu.V. Golubkov and others. Engineering methods for studying shock processes M. Mashinostroenie, 1977, pp. 24-25), where the simplest signals are reproduced on a pendulum impactor, but they significantly increase the amplitude of accelerations , are also focused on creating a “clean” impulse by suppressing secondary vibration. Like a single impulse, the shock spectrum of accelerations (from a single impulse) is realized in one direction . Or a solution (Kruglov Yu.A., Tumanov Yu.A. Shock and vibration protection of machines, equipment and apparatus. - L. Mashinostroyeniye. 1986. p. 151), when the shock effect of the pendulum striker is created in a spring-loaded platform on which the test object is installed, in in the form of a single impulse, from which the shock spectrum of accelerations is calculated - analogs.

The main disadvantage of the above test methods is that

when using electrodynamic stands to create shock effects, there are restrictions on the amplitude-frequency range of reproducible loads, i.e. they are not suitable for reproducing impacts of high intensity and are focused on creating a superposition of impact impulses in one direction.

Typical mechanical stands (for example, impact test benches with falling tables) are focused on creating a shock effect in the form of a single impulse that acts on all elements of the test object, and not just at its attachment points. In addition, shock tests on such equipment violate the “physics” of loading on-board equipment (BA), since In real operation, the BA is loaded by a passing deformation wave in the structure, and the response to impact has a complex shape in the form of non-stationary vibration.

In addition, when performing impact tests of spatial structures, loading along one axis, as a rule, leads to a response in all three. And the successive reproduction of impacts on three axes leads to additional (and unjustified) loading on the remaining axes, especially when it is necessary to carry out loading in the positive and negative directions of the axes

The closest to the claimed invention is the solution according to the patent of the Russian Federation No. 2745342. This is a method of testing for high-intensity shocks using the method of shock acceleration spectra, which consists in creating non-stationary vibration sequentially along each of three mutually perpendicular axes using a shock stand. Obtaining a shock spectrum of accelerations at the attachment points of the test object for positive and negative values of accelerations of non-stationary vibration, and the number of shocks generated on the test object is halved relative to the required number of shocks along each of the axes - "prototype".

The disadvantages of this solution for the formation of impact is, first of all, the creation of impact on the test object sequentially along each of the three mutually perpendicular axes, which do not exist in real operation. This is especially important when testing spatial structures that have several attachment points, often not even lying in the same plane. This entails an increase in the number of shocks along the axes: the creation of the required shock spectrum even in two directions along one of the axes creates additional shocks along the other two axes. It is practically impossible to create the required shock spectrum in two directions of the axis in three mutually perpendicular directions by a single source of shock effects (both mechanical and pyrotechnic) for large-sized structures.

For the claimed method, the following essential features common with the prototype have been identified: a method for testing high-intensity shock effects of instruments and equipment using the method of shock acceleration spectra, which consists in creating a shock in the form of non-stationary vibration, recording accelerations and obtaining the same shock spectrum of accelerations at the attachment points of the test object for positive and negative values of accelerations of non-stationary vibration sequentially along each of the three mutually perpendicular axes, halving relative to the required number of impact actions along each of the axes, for which positive and negative shock acceleration spectra are formed.

The technical problem of the present invention is the creation of impacts that correspond to the actual operating conditions of the equipment and ensure, during testing, simultaneous loading of the test object along three mutually perpendicular axes in two opposite directions (positive and negative) at different points of attachment of the test object in order to reduce the number of impacts on the test object .

The specified technical problem is solved due to the fact that before the start of impact tests, tests are carried out to determine the resonant frequencies of the equipment with a dynamic layout of the test object along three mutually perpendicular axes, the results of which preliminarily determine the number and installation locations of pyrodevices on the equipment at points that provide maximum response in loading control points of the dynamic layout at frequencies corresponding to the transition frequency of the specified shock acceleration spectrum, then impact tests are carried out, simultaneous detonation of pyrotechnic devices, accelerations are recorded at the control points of the dynamic layout in the form of non-stationary vibration, total, positive and negative shock acceleration spectra are obtained, the obtained acceleration shock spectra with the required acceleration shock spectra at each control point of the dynamic layout in three mutually perpendicular directions, and if they differ by a value greater than the permissible error, the number, power and installation locations of the pyrodevices are specified, the impact tests are repeated, and the required impact action in in the form of shock acceleration spectra, they are formed simultaneously at the points of control of loading of a dynamic layout along three mutually perpendicular axes by simultaneous detonation of pyrotechnic devices, and the number, power and installation locations of pyrodevices are changed, shock tests are repeated until a dynamic layout is obtained at points of control of loading of a dynamic layout in three mutually perpendicular directions throughout in a given frequency range of acceleration shock spectra that differ from the required acceleration shock spectra by an amount less than the permissible error, the dynamic layout is replaced with a standard test object, its impact tests are carried out in the generated mode, while the total number of impact actions during impact tests is reduced by six times.

The essence of the claimed solution is illustrated by drawings, where figure 1 shows the equipment 1 installed in it with the help of lugs 2 spatial antenna system (AS) 3 developed by JSC "ISS". Shock effects on the antenna system are carried out using pyrotechnic devices (PU) 4 rigidly attached to equipment 1. During vibration tests, AC 3 with equipment 1 is installed on a vibration stand and its vibration loading is carried out. Vibration and shock loading is controlled, for example, using three-axis accelerometers AR1020 5. Accelerometers (acceleration sensors) are used to register vibration accelerations during frequency tests, when the impact is specified in the form of vibration acceleration power spectral density (SPD) and the response is also obtained in the form of SPD. Figure 2 as an example shows the responses in the form of PSD at a point on one of the lugs 2 in three mutually perpendicular directions X,Y,Z (A2X, A2Y, A2Z). At other control points, the results are similar. This allows, as in tests for harmonic vibration, to obtain the resonant frequencies of the test object (resonant frequencies do not depend on the method of excitation). The frequency range with the maximum response along three mutually perpendicular axes is determined by the response at the attachment points of the lugs. Figure 3 in table 1 shows the requirements for shock loading of the AU. Table 1 shows that the transition frequency for the USU is 1000Hz. In all directions (figure 2) at a frequency of 1000 Hz there are resonances with a quality factor from 3 (A2X) to 5-6 (A2Y, A2Z). The quality factor is obtained from the SPM ratio according to the formula

,Q=

,

Where:

Q - quality factor at a frequency of 1000 Hz;

S ₁ - power spectral density at the control point at a frequency of 1000 Hz;

S ₂ - given power spectral density at the control point at a frequency of 1000 Hz

(during these tests, the PSD was equal to 0.001 g ² /Hz in the frequency range from 20Hz to 2000Hz).

Based on the results of the analysis of the SPM graphs (figure 2), as well as the design of the tooling and the AU, a decision is made on the points of application of impacts. Since the AU and equipment in the plane of attachment of the AU are symmetrical, the PU is installed on the equipment at four points in the middle between the lugs (figure 1), which ensures maximum response at the impact control points.

During shock tests with the help of PU 4 in the test object (AS) at control points 5 after the PU is triggered, non-stationary vibration is excited, based on the measurement results of which, shock acceleration spectra are built. Shock acceleration spectra are formed with the allowable errors given in table 2 shown in Fig.4. Graphs of non-stationary vibration for a point on one of the lugs 2 are shown in Fig.5, and USU for different directions of the axes in Fig.6 (X-X), Fig.7 (Y-Y), Fig.8 (Z-Z).

Figures 6-8 show the required USU 6, USU obtained under impact: positive 7, negative 8, total 9. Also, the graphs show the permissible errors: plus 3dB pos.10, minus 3dB pos.11, plus 6dB pos. 12, plus 9dB pos.13.

As can be seen from the graphs of Fig.6-8, the obtained USU meet the requirements of table 2, Fig.4.

The essence of the proposed solution can be explained as follows.

Currently, the requirements for instruments and equipment are set, as a rule, in the form of USU with an indication of the number of impacts. For example, typical requirements for on-board equipment are formulated as follows: “Impact loads are specified in the form of three impacts in each direction along each of three mutually perpendicular axes.” The requirement to create impacts along one axis in two directions is due to the fact that some of the equipment components respond differently to loading in different directions (for example, microswitches). At the same time, most of the impact test benches are focused on creating classical single acceleration pulses, especially when it is necessary to create shock effects of increased intensity (up to tens of thousands of “g”), when the use of electrodynamic test benches for the formation of USA is impossible. When obtaining the required USA using a single pulse, the amplitude of accelerations increases significantly in comparison with non-stationary vibration, which has a close USA (3-4 times). Moreover, non-stationary vibration can be considered as a set of positive and negative pulses that decay in time (their amplitude decreases) and provide the required USA at a much lower amplitude. In addition, the non-stationary vibration created at the installation site of the test object is more consistent with the “physics” of loading real equipment, for example, as part of spacecraft (after the pyrotechnic devices are triggered, the responses at the equipment installation sites are recorded in the form of non-stationary vibration). It should also be noted that the impact from one pyrodevice on a spacecraft simultaneously causes a response in three mutually perpendicular directions. It is possible to create such an impact only by full-scale operation of a standard pyrodevice on a real spacecraft (SC). But the equipment is created in parallel with the creation of the spacecraft itself. In addition, any external influences (including impact ones) during autonomous testing must be reproduced taking into account the safety factor (for USU it is equal to two). Under sequential loading, the equipment experiences excessive impacts (even when it is possible to load the positive and negative directions of the impact axis with one impact), because under shock loading, it is impossible to ensure the response of the test object only along one axis.

When testing large-sized spatial structures (for example, spacecraft antennas), the creation of shock even in two directions often becomes impossible due to the complexity of the equipment, the size of shock stands, etc. It is even more difficult to create actions that simulate the simultaneous loading of equipment in three mutually perpendicular directions. In this case, the shock loading of the test object is possible only by the shock effects created by the small-sized launcher according to the procedure discussed above.

Since, by definition, “the shock spectrum of accelerations is the dependence of the maximum response to the impact action of an ensemble of oscillatory systems with the same degree of freedom and the same damping on the natural frequencies of these systems,” positive and negative USA values show the maximum response in these directions. That is, in other tests with a given USU, there will be no greater response, and additional tests are not required (the necessary loading conditions have already been implemented). Thus, the number of impacts along one axis can be halved, and since the required USU is created immediately in three directions, the total number of impacts is reduced by six times. Smallwood's algorithm (D.O. Smallwood, "An Improved Recursive Formula for Calculating Shock Response Spectra", Sandia National Laboratories, Albuquerque, New Mexico) is most widely used to calculate shock acceleration spectra. The formation of the USU during impact tests is carried out with a predetermined error. This error may be different for different frequency ranges. Typical requirements for errors are given in table 2 (figure 4).

It should also be noted that the formation of the required USU for testing is carried out in several stages, since, as a rule, it is not possible to immediately obtain the necessary USU. At the first stage, according to the results of vibration tests, responses are obtained at the attachment points of the test object. Since the tooling for vibration and shock testing is prefabricated, during its design it is possible to choose such stiffnesses that one of the possible resonances will be in the region of the transition frequency. For the loading mode shown in table 1 in figure 4, the transition frequency is 1000 Hz.

The use of an adjustable source of impacts, changing the points of application of these impacts, various crashers, and so on, allows you to select the desired impact. Therefore, the development of the desired test mode is carried out on a dynamic layout of the device, and only after the formation of the required test mode, they proceed to testing the standard device.

An example of practical implementation.

As an example, consider the creation of the required USA for the antenna system shown in Fig.1. The results of the formation of the required USU shown in Fig.6-8 for control point 2 in accordance with the requirements given in table 1 (figure 3), with the errors shown in table 2 (figure 4). For the rest of the control points in the places where the speakers are attached, the results are similar.

In Fig.1, shows the equipment 1 installed in it with the help of lugs 2 spatial antenna system (AS) 3 developed by JSC "ISS". Impact on the antenna system is carried out with the help of adjustable pyrotechnic devices 4 rigidly attached to the equipment 1. The control parameters of the PU are the power of the pyrocomposition used, the shape, weight of the striker, the distance from the striker to the point of application of the impact. The used PU allows you to create shock effects from tens of “g” to tens of thousands of “g”. Due to the holes in the PU flanges, they can be mounted almost anywhere in the tooling.

First, vibration tests were carried out using the method of broadband random vibration. When carrying out vibration tests, AC 3 with equipment 1 is installed on a vibration stand and its vibration loading is carried out. Vibration and shock loading is controlled using three-axis accelerometers AR1020 5. Accelerometers (acceleration sensors) are used to register vibration accelerations during frequency tests, when the impact is specified in the form of vibration acceleration power spectral density (SPD) and the response is also obtained in the form of SPD. Figure 2 as an example shows the responses in the form of PSD at a point on one of the lugs 2 in three mutually perpendicular directions X,Y,Z (A2X, A2Y, A2Z). At other control points, the results are similar. This allows, as in tests for harmonic vibration, to obtain the resonant frequencies of the test object (resonant frequencies do not depend on the method of excitation). The frequency range with the maximum response along three mutually perpendicular axes is determined by the response at the attachment points of the lugs. Figure 3 in table 1 shows the requirements for shock loading of the AU. Table 1 shows that the transition frequency for the USU is 1000Hz. In all directions (figure 2) at a frequency of 1000 Hz there are resonances with a quality factor from 3 (A2X) to 5-6 (A2Y, A2Z). The quality factor is obtained from the SPM ratio according to the formula

,Q=

,

Where:

Q - quality factor at a frequency of 1000 Hz;

S ₁ - power spectral density at the control point at a frequency of 1000 Hz;

S ₂ - given power spectral density at the control point at a frequency of 1000 Hz

(during these tests, the PSD was equal to 0.001 g ² /Hz in the frequency range from 20Hz to 2000Hz).

Based on the results of the analysis of the SPM graphs (figure 2), as well as the design of the tooling and the AU, a decision is made on the points of application of impacts. Since the AU and equipment in the plane of attachment of the AU are symmetrical, the PU is installed on the equipment at four points in the middle between the lugs (figure 1), which ensures maximum response at the impact control points.

During shock tests with the help of PU 4 in the test object (AS) at control points 5 after the PU is triggered, non-stationary vibration is excited, based on the measurement results of which, shock acceleration spectra are built. Shock acceleration spectra are formed with the allowable errors given in table 2 shown in Fig.4. Graphs of non-stationary vibration for point 2 are shown in Fig.5, and USU for different directions of the axes in Fig.6 (X-X), Fig.7 (Y-Y), Fig.8 (Z-Z).

Figures 6-8 show the required USU 6, USU obtained under impact: positive 7, negative 8, total 9. Also, the graphs show the permissible errors: plus 3dB pos.10, minus 3dB pos.11, plus 6dB pos. 12, plus 9dB pos.13.

As can be seen from the graphs of Fig.6-8, the obtained USU meet the requirements of table 2, Fig.4.

Thus, when implementing the claimed invention, the following technical result is achieved: the non-stationary vibration created at the installation site of the test object is more consistent with the “physics” of loading real equipment. As a result, during autonomous testing of the AU, due to the created non-stationary vibration, the required shock acceleration spectra were reproduced simultaneously in positive and negative directions in three mutually perpendicular directions, due to which the number of shocks was reduced by 6 times (from the required 18 to 3)

From the sources of information and patent materials known to the authors, no set of features similar to the set of features of the claimed objects is known.

Claims (1)

A method for testing high-intensity shock effects of instruments and equipment using the method of shock acceleration spectra, which consists in creating a shock effect in the form of non-stationary vibration, recording accelerations and obtaining the same shock acceleration spectrum at the attachment points of the test object for positive and negative values of accelerations of non-stationary vibration sequentially for each of three mutually perpendicular axes, halving the required number of shocks along each of the axes, for which the same positive and negative shock acceleration spectra are formed, characterized in that before the start of shock tests, tests are carried out to determine the resonant frequencies of the tooling with a dynamic layout of the test object in three mutually perpendicular axes, based on the results of which the number and installation locations of pyrotechnic devices on the tooling are preliminarily determined at points that provide the maximum response at the loading control points of the dynamic layout at frequencies corresponding to the transition frequency of the specified shock acceleration spectrum, then impact tests are carried out by simultaneous detonation of pyrotechnic devices, recorded in points of control of the dynamic layout of accelerations in the form of non-stationary vibration, receive total, positive and negative shock acceleration spectra, compare the received shock acceleration spectra with the required shock acceleration spectra at each control point of the dynamic layout in three mutually perpendicular directions, and if they differ by a value greater than than the permissible error, specify the number, power and installation locations of pyrotechnic devices, repeat impact tests, and the required impact action in the form of shock acceleration spectra is formed simultaneously at the points of control of loading of the dynamic layout along three mutually perpendicular axes by simultaneous detonation of pyrotechnic devices, and the number and power are changed and installation sites of pyrodevices, repeat impact tests until a dynamic mock-up is obtained at the loading control points in three mutually perpendicular directions in the entire specified frequency range of shock acceleration spectra that differ from the required shock acceleration spectra by an amount less than the permissible error, replace the dynamic mock-up with a standard object tests, its impact tests are carried out in the generated mode, while the total number of impacts during impact tests is reduced by six times.

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