RU2783820C1 - Test stand for high-intensity shock impact testing of instruments and equipment - Google Patents

Abstract

FIELD: testing.

SUBSTANCE: invention relates to stands for high-intensity shock impact testing of instruments and equipment and can be used in testing aircraft, rocket and space instruments and equipment for shock impact. A stand consisting of a hammer, a hammer suspension, a rotary traverse, a frame, a securing apparatus, vibration-insulating liners, recording sensors, and an anvil is used for testing. Said anvil is made in the form of a box consisting of rigidly interconnected rectangular metal panels with slots and a replaceable bottom with the test object installed on the inner surface thereof, fastened with the box. The replaceable vibration-insulating liners are installed between the box and the bottom, as well as between the box and the power floor, and crashers are installed at different points on the outer surface of the bottom, wherein the anvil in the form of a box with a bottom and the test object is secured to the power floor by means of screw clamps. The recording sensors are installed on the bottom at minimum distance from the points of attachment of the test object, as defined by the technical settings of installation of the recording sensors, both on the inside and on the outside of the bottom, wherein the sensors monitoring the load at the same point of attachment are installed on a single line perpendicular to the bottom.

EFFECT: possibility of more accurate reproduction of shock load.

1 cl, 9 dwg

Description

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

There are quite a few different impact test benches available. Tests are carried out using vibration electrodynamic stands, stands with falling tables, pyrotechnic, pneumatic, etc. (Vibrations in engineering: A reference book in 6 volumes. M.: Mashinostroenie v.5 Measurements and tests, edited by M.D. Genkin, 1981, pp. 476-477). Or a pendulum pile driver, consisting of a hammer, a bed, an anvil on which the equipment under test is installed, a rotary traverse that provides the necessary lifting height of the hammer, which ensures the desired speed of impact of the hammer with the anvil, a pneumatic damper that slows down the anvil after impact with the hammer (G.S. Batuev , YV Golubkov and other Engineering methods for studying shock processes M. Mashinostroenie, 1977, pp. 24-25) (analogues).

The use of specific bench types in each test case depends on the type of load to be reproduced. Currently, systems based on mechanical (copra) stands (ballistic, with falling tables, etc.) find the greatest application in testing apparatus and equipment.

The closest (prototype ) for high intensity impact testing (up to thousands of “g”) is the solution - RF patent No. 2628450 “Test bench for high intensity impact instruments and equipment”. The stand consists of a hammer, a hammer suspension, a rotary traverse, a frame, a fixing device, an anvil for mounting equipment, made in the form of a rectangular replaceable metal panel with cutouts, vibration isolating pads, and recording sensors.

However, this stand has a number of significant drawbacks when used for testing, when it is necessary to create shock effects both in the plane of attachment of the test object and perpendicular to it. Usually, for such tests (perpendicular to the mounting plane), a special tool is used (and the test object is attached to it), which is installed on the anvil. The tooling is used only for fastening the test object, and high requirements are imposed on it in terms of rigidity, weight, etc. Such a test scheme complicates the formation of the required loading regime, since the equipment introduces distortions of the test mode due to its own resonances. In addition, the actual increase in the mass of the test object (due to the mass of the tooling) requires a significant increase in the impact itself, which introduces additional restrictions on reproducible loading modes.

For the claimed invention, the following essential features in common with the prototype have been identified: a test stand for impact testing of instruments and equipment, consisting of a hammer, a hammer suspension, a rotary traverse, a bed, a fixing device, an anvil for mounting equipment, made in the form of a rectangular replaceable metal panel with cutouts , anti-vibration pads, recording sensors.

The technical problem solved by this invention is the partial elimination of these shortcomings for better testing of instruments and equipment for impact.

The technical result of this invention is the possibility of a more accurate reproduction of the shock load.

This result is achieved by the fact that the anvil is made in the form of a box, consisting of rectangular metal panels with cutouts, rigidly connected to each other and a replaceable bottom, with a test object installed on its inner surface and fastened to the box with bolts, moreover, between the box and the bottom, as well as replaceable vibration isolating pads are installed between the box and the power floor, and the crashers are installed on the outer surface of the bottom in different places, while the anvil in the form of a box with the bottom and the test object is fixed to the power floor with clamps, and the recording sensors are installed on the bottom at a minimum distance from the attachment points of the test object, determined by the technical conditions for the installation of recording sensors, both on the inside and on the outside of the bottom, while the sensors that control the loading at the same attachment point are installed on the same line perpendicular to the bottom.

The essence of the claimed solution is illustrated by drawings, where figure 1-4 shows a stand for impact testing. The stand (figure 1) consists of a frame 1 for mounting the suspension with a hammer 2, an anvil in the form of a box, consisting of rectangular metal panels 5 with cutouts 8 and ribs between the cutouts 9, replaceable bottom 3, anti-vibration pads 4, test object 7, installed on the inner surface of the bottom 3. On the inner surface of the bottom 3 at a minimum distance from the attachment points of the test object, determined by the technical conditions for installing the recording sensors, control sensors 6 are installed. The minimum distance from the test object is determined by the dimensions of the sensors, the type of connectors and cables used. The anvil in the form of a box of rectangular metal panels 5 and the bottom 3 is attached to the power floor 16 through insulating gaskets 11 using a clamp consisting of a pressing plate 10 and a fastener 18.

Figure 2 shows a view of the bottom 3 of the anvil from the outside. Figure 2 shows the attachment points of the bottom to rectangular metal panels using bolts 12, the installation location of the control sensors on the outside of the bottom 13. In this case, the sensors 6 and 13, which control the loading at the same attachment point, are installed on the same line perpendicular to the bottom . A set of crashers 14 shows the places where impacts are applied to select the best result and the choice of the position of the crasher for testing 15. The vibration isolating pad 11 separates the anvil from the force floor 16. The dotted lines show the position of the test object 7 on the inner surface of the bottom. Figure 3, 4 shows in more detail the fastening of the anvil to the power floor 16 using a clamp, consisting of a preload plate 10 and a fastener 18, installed in the groove 17 of the power floor 16.

The stand functions as follows.

If it is necessary to create a shock effect in the form of a shock acceleration spectrum (SCA) in three mutually perpendicular directions, a test method is adopted and equipment is developed to locate the test object (for example, a plate with cutouts, which provides the necessary shape of the SCA, primarily the inflection point of the spectrum and uniformity reproducible shock spectrum). At the same time, the impact speed of the hammer and the plate provides the desired amplitude of accelerations, and the free surface of the bottom from the side of the pendulum allows you to strike at any point of the bottom. Table 1 shows one of such acceleration shock spectra as an example. The creation of the necessary USU in the plane of attachment of the test object is easier, because the test object is attached directly to the plate and no additional equipment is required. With impacts perpendicular to the plane of attachment of the test object, the need to use additional equipment leads to a significant distortion of the generated USU.

Table 1 Impact levels

Axis Frequency subrange, Hz Impact acceleration, g (at Q=10) X, Y, Z 20 - 1000 50-1000 1000 - 10,000 1000

The anvil box (Fig.1) consists of panels 5, each of which provides the desired transition frequency (for example, close to 1000 Hz), due to the own resonances of the panels. As a result, on the bottom 3, through the anti-vibration pads 4, a response is transmitted to the impact force created by the hammer 2. Depending on the thickness and material of the anti-vibration pads 4, the amount of impact from the panels 5 on the bottom 3 is adjusted. boxes to the bottom (to the test object) vibration-isolating pads are made of various materials. When installing a vibration isolating pad 4, for example, from soft rubber, high-frequency components of the impact are filtered out, but the possibility of transmitting low-frequency components remains, and when the vibration isolating pad 4 is made of materials with a higher acoustic impedance than the material of the bottom 3 and panel 5 of the anvil box, high-frequency shock effects are transmitted to the test object. Attaching the anvil directly to the power floor makes it possible to exclude as much as possible the influence of elements that distort the formed loading mode in standard stands, including the prototype (frame, tooling, etc.). Vibration-isolating pads 11 between the anvil and force floor 16 must be made of an insulating material (for example, soft rubber), which allows isolating the anvil from impacts transmitted through the force field and providing longitudinal, transverse and torsional vibrations of the anvil that occur after impact. Anti-vibration pad (for example, made of rubber) 11 eliminates the collision of the plate 5 with the power floor 16, while allowing the box of plates 5 with the bottom 3 (anvil) to perform spatial vibrations. This ensures the filling of the low-frequency spectrum (up to 300-500 Hz), and the transverse vibrations of the bottom 3, the longitudinal, transverse vibrations of the panels 5, as well as the torsional vibrations of the box (rigidly connected panels 5) fill the high-frequency components in the shock spectrum. Fastening the anvil to the power floor 16 with clamp 18 (figure 3, 4), holding the anvil, allows it to perform spatial oscillations.

The dimensions and material of the hammer, its speed of impact with the bottom create the necessary duration of exposure to excite natural oscillations of the bottom and anvil panels. reproduce torsional vibrations

In FIG. 2 shows the location of the crashers 14,15. The application of impact through crashers (when working out test modes on a dynamic mock-up) at various points of the bottom allows you to excite various forms of bottom oscillations to form the required shock spectrum of accelerations, and to select the point of impact application that provides the best formation of the required USU. Recording sensors are installed both on the inner 6 and on the outer side of the bottom 13, which makes it possible to control the loading at all attachment points of the test object. When testing, it is not always possible to install recording sensors close to all fixing points. Moreover, the sensors that control the loading of the same attachment point of the test object are installed on the same line perpendicular to the bottom, both from the inside and from the outside of the bottom. This allows making a conclusion about the identity of the loading of the test object during registration by sensors, both from the inside and from the outside of the bottom, according to the sensors located only on the outside of the bottom. As a result of multiple reflections from the boundaries of the plate and cutouts, as well as due to the longitudinal and transverse vibrations of the bottom, a damped non-stationary vibration occurs at the installation site of the test object 7. Accelerations occurring in the plate are measured by registering sensors 6,13 (acceleration measurement results are used to build USS).

The calculation of the required parameters of the box, the bottom and the speed of impact of the hammer with the bottom was carried out using the finite element method in the ANSYS Workbench package. Figures 5-8 show the results of a numerical experiment for the preparation of the anvil (selection of panels 5, bottom 3, etc.). Figure 5 shows a finite element model of the anvil (a box with a bottom) installed on the force field to provide the USU parameters given in table 1. The model (figure 5) consists of 232302 nodes and 94226 elements. The calculations used a nonlinear damping model. In the process of performing numerical experiments, the necessary parameters of the duct panels, bottom thickness, dimensions and location of cutouts were determined. Calculations were performed for various panel configurations: solid slab (without cutouts), with various types of cutout sizes and panel thicknesses, which made it possible to determine the required dimensions of the test bench plate.

As a result of the calculations, the following dimensions of the box and the bottom were obtained for a device weighing 8.9 kg with 4 points of attachment of the test object to the bottom 3 under impact according to Table 1. The box panels and the bottom are aluminum. Panels 530x340 mm, thickness 20mm, bottom 530x530 mm, thickness 15mm. The dimensions of the cutouts on the panel are 70x55mm, the distance between the cutouts is 40mm, the distance from the cutout to the end of the panel is 10mm, the weight of the test object is 8.9 kg, the dimensions are 180x200mm, four attachment points, the thickness of the rubber gaskets 4 between the bottom and the box is 5mm, and between the box and power floor 10 mm.

Table 2 shows the vibration frequencies that have the maximum effective mass (i.e., these frequencies determine the main vibration tones of the panel with the test object). It should be noted that the frequency of 292 Hz (Fig.6) determines the main transverse form of oscillations of the bottom as a whole, 787 Hz (Fig.7) - the form of transverse oscillations of the plates in the cutouts, the frequency of 1986 Hz (Fig.8) determines the joint oscillations of the box plates , the bottom and the test object, and the frequency of 3762 Hz determines the rotational form of vibrations around the X axis. The hammer is made of steel with a spherical bronze striker, the crushers are made of soft aluminum alloy MA2, which ensured the creation of a shock pulse close to a half-sinusoidal shape with a duration of ~ 0.2 ms , and the response of the bottom with the test object at the control point is obtained in the form of non-stationary vibration.

Table 2 . Frequencies with maximum effective masses

Form number Frequency Effective masses fourteen 292Hz 16.6% 46 787Hz 9.5% 60 1986Hz 2.7% 175 3762Hz 1.43%

The occurrence of resonances at these frequencies is associated, first of all, with the duration of impact, determined by the size and shape of the hammer (the duration of the impact pulse is approximately equal to twice the length of the hammer divided by the speed of sound in the hammer material).

Table 3 shows the permissible errors in the reproduction of shock acceleration spectra.

Table 3. Permissible errors during testing

by the method of shock acceleration spectra.

1. At least 50% of the shock acceleration spectrum must be
between -3 dB and +3 dB from nominal test specification 2. At least 80% of the shock acceleration spectrum must be
between -3 dB and +6 dB from nominal test specification 3. All 100% of the shock acceleration spectrum must be
between -6dB and +9dB of nominal test specification.

The procedure for selecting the optimal dimensions of the bottom, panels, the number of cutouts and their dimensions, the shape and weight of the hammer refers to the "know-how" of the invention, and is not considered in the submitted materials.

Example of practical implementation

The stand under consideration was used during qualification shock tests of the control unit (CU) of one of the spacecraft of ISS JSC.

Impact tests were carried out according to the shock acceleration spectrum method in accordance with the requirements given in Table 1, sequentially along each of the three mutually perpendicular axes. As an example, let's consider impact tests of the CU in the direction of the “X-X” axis (perpendicular to the plane of the block attachment).

Previously, the test scheme shown in Fig.3 was adopted. The necessary dimensions and thicknesses of the box and bottom panels were obtained by calculation. As a result of the calculations, the following dimensions of the box and the bottom for the device weighing 8.9 kg were obtained under impact according to Table 1. The box panels and the bottom are aluminum. Panels 530x340 mm in size, 20 mm thick, bottom 530x530 mm, 15 mm thick. The cutout dimensions on the panels are 70x55 mm, the distance between the cutouts is 40mm, the distance from the cutout to the end of the panel is 10 mm, the mass of the test object is 8.9 kg, the dimensions of the seating surface are 180x200 mm, four attachment points, the thickness of the rubber gaskets is 10 mm.

The hammer has a length of 360 mm, a diameter of 120 mm, the material is steel. A replaceable spherical bronze head is threaded into the hammer. Crashers from MA2. Accelerations are recorded using impact accelerometers from GlobalTest AP1020. At first, a simulator of the BU was installed on the bottom, on which the speed of the impact of the hammer and the bottom was specified. During the tests, the equivalence of impact actions between the sensors installed on the inner and outer surfaces of the bottom was confirmed. The point of impact application was also determined. Differences in the readings of the sensors at points 6 and 13 did not exceed 5-7% (with an allowable error of 15%). Crasher 15 is selected as the point of impact application (figure 2). Impact speed of striker with crasher ~ 1.7 m/s. After that, a standard device was installed on the stand, and impact testing of the device was carried out, while the sensors installed on the panel from the inside were removed (the equivalence of their readings with the sensors on the outer surface was demonstrated during mock-up testing).

Figure 9 shows the graphs: “a” is the required USA, “in” is a positive USA, “c” is a negative USA, “d” is the total USA, “e” is the allowable error range (±3 dB). Graphs are presented for point 13 (5) shown in Fig.2.

The calculation of the impact acceleration spectra was carried out at a quality factor Q=10 using the Smallwood algorithm.

As can be seen from Fig.9 on the USU graphs, frequencies close to those shown in Table 2 can be distinguished. These are frequencies up to ~ 300 Hz providing filling of the low-frequency spectrum, frequencies 700-800 Hz, providing a transition frequency of 1000 Hz, frequencies above 2500 Hz, providing high-frequency components of the spectrum . In addition, positive, negative, as well as the total USA correspond to the minimum allowable error in the USA of ±3 dB (Table 3). The creation of a shock effect in the form of non-stationary vibration at the location of the device with symmetrical positive and negative USUs makes it possible to halve the required number of shocks along the “X-X” axis, to create impacts that are closer to real ones, compared to the impact on the device of single acceleration pulses. That is, the stand makes it possible to more accurately reproduce the real shock load.

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)

Stand for testing high-intensity impacts of instruments and equipment, consisting of a hammer, a hammer suspension, a rotary traverse, a bed, a fixing device, an anvil for mounting equipment, made in the form of a rectangular replaceable metal panel With cutouts, vibration isolating pads, recording sensors, characterized in that the anvil is made in the form of a box, consisting of rectangular metal panels with cutouts, rigidly connected to each other, and a replaceable bottom with a test object installed on its inner surface and fastened to the box with bolts, and between the box and the bottom, as well as between the box and the power floor, there are replaceable vibration isolating pads, and the crashers are installed on the outer surface of the bottom in different places, while the anvil in the form of a box with the bottom and the test object is fixed to the power floor with clamps, and the recording sensors are installed on the bottom at the minimum distance from the attachment points of the test object, determined by the technical conditions for the installation of recording sensors, both on the inside and on the outside of the bottom, while the sensors that control the loading at the same attachment point are installed on the same line perpendicular to the bottom.

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