RU2651627C1 - Stand for measurement of loads influencing on the object of aviation equipment - Google Patents

Abstract

FIELD: aircraft engineering.

SUBSTANCE: invention relates to devices designed for aerodynamic testing, and can be used in aircraft building. Stand includes a dynamometer platform, designed to fix the object, installed by means of at least four variable hardness plates on a fixed support platform with the possibility of moving the dynamometer platform along three orthogonal axes, each plate being formed with a flexible portion, coupled with hard parts, and is equipped with a load measuring element, and is characterized in that it comprises a sensor, registering the longitudinal movements of the dynamometer platform and designed to measure the longitudinal load, and the load measuring element is made in the form of two pairs of identical strain gage sensors, intended for measuring vertical and lateral loads, installed on at least one flexible section of each plate at the same level relative to the fixed support platform, sensors of each pair are mounted on opposite wide sides of the plate, wherein the vertical symmetry axes of the sensing elements of the sensors of one pair are oriented along the vertical axis of symmetry of the wide side of the plate, and the vertical axis of symmetry of the sensing elements of the sensors of the other pair are parallel to it, sensors are connected in one arm of separate measuring bridges, and the sensors of each pair are connected in series.

EFFECT: technical result consists in the possibility of increasing the accuracy of simulating the conditions of a supersonic flight of an aircraft.

1 cl, 12 dwg

Description

The invention relates to devices intended for aerodynamic testing, and can be used in the aircraft industry for aerodynamic testing of objects of aviation technology.

When testing an object of aviation technology, for example, a supersonic aircraft (LA) or its components (fuselage, wings, stabilizing surfaces, an engine integrated in the aircraft), to determine the total force acting on the aircraft or its parts, determine its components in three orthogonal axes, as well as aerodynamic moments around these axles. All these quantities arise under the influence of the engine’s traction force, as well as pressure pulsations when the air flows around the surfaces of the body and components of the aircraft and are important characteristics of its aerodynamic properties.

Known bench according to patent RU 2276279 for measuring the components of the thrust of a jet engine with a deflected thrust vector. The bench includes a dynamometer platform for mounting the test engine mounted with flexible racks on the support frame with the possibility of horizontal movement along the X and Z axes, three load cells for measuring components ± Rx, ± Ry, ± Rz of the traction force installed on the support frame, lever gears for vertical movement of the dynamometer platform under the action of the component of the traction force ± Ry, as well as additional linkage gears with loads of the estimated weight to ensure backlash-free operation dividing the thrust component values for the reversing operation of the engine.

The equality of the gear ratios of two pairs of parallel power receiving arms, which take the load from the dynamometer platform, and two pairs of force measuring levers interacting with force measuring sensors, ensures the balance of forces on the joints connecting them from the moments relative to the X, Y, Z axes, which eliminates the interaction of forces on measured components of traction forces ± Rx, ± Ry, ± Rz.

The complex design of the stand, the presence of mechanical connections and multiple transmission of forces through the levers reduces the accuracy and reliability of the measurement of traction components. In addition, when conducting high-altitude tests of large-sized aircraft models and their propulsion systems, the test object is placed in a limited-volume aerodynamic nozzle and aft diffuser of a pressure chamber, in which supersonic flight speeds are simulated. The use of various schemes and designs of mechanical-type scales in connection with their large size and complex design is not possible.

The closest analogue of the claimed technical solution is a stand for measuring the vertical load acting on the object of aircraft (patent RU 127464). The bench comprises a dynamometer platform with an object fixed on it, mounted on a fixed support frame by means of four flexible racks, for example, rigidly fixed to the platform and the frame of the plates. Flexible racks provide the ability to move the dynamometer platform along three orthogonal axes. Each rack includes a middle hard section where three-component piezoelectric acceleration sensors with built-in voltage amplifiers are installed. Such a rack can be made in the form of a plate with two flexible sections, each of which is paired with hard sections. One of the three orthogonal measuring axes of each sensor is directed along the flexible strut. The voltage amplifiers are connected to power sources through cables. Power sources are connected via cables to the voltage signal recorder analyzer.

When testing an object of aviation technology, vibration accelerations of lateral vibrations of flexible plates are recorded by vibration acceleration sensors. The natural frequency of transverse vibrations of each flexible plate varies depending on the vertical force applied to it, which coincides with its axis. Before or after the tests, the natural frequencies of the transverse vibrations of the flexible plate are calculated depending on the vertical load applied to it along its axis. For experimentally recorded frequencies of natural transverse vibrations of a flexible plate, the values of the vertical load acting on the flexible rack are determined from the calculated dependencies. The algebraic sum of the vertical loads acting on each flexible rack determines the resultant vertical load (force) acting on the object of aircraft. In addition, by the resultant vertical force, the pitch moment M _(tf) can be calculated relative to the point selected in space, which can be considered the center of mass of an aircraft.

The stand is compact and structurally simple, but it does not allow to measure the forces acting along the axes directed in the longitudinal and transverse directions to the object, and to determine the yaw moment and pitch moment from them.

Among the devices intended for aerodynamic testing of objects of aviation technology, there were no stands with wide functional capabilities, quite simple and compact for use in conditions simulating high-altitude flight, which make it possible to measure the vertical, longitudinal and transverse loads acting on the object, and determine from the results of measurements moments of roll, yaw and pitch.

Thus, the technical problem lies in the fact that when testing the aircraft does not provide simulation of all loads (vertical, longitudinal and transverse, moments of roll, yaw and pitch) acting on the aircraft.

The proposed bench for measuring the loads acting on the object of aircraft, has all the required functional characteristics: in the harsh test conditions associated with simulating high-altitude supersonic flight, including in conditions of spatial limitation, it allows to determine all load components, moments of roll, yaw and pitch .

The technical result consists in the fact that the stand for measuring the loads acting on the object of aviation technology, provides improved accuracy of simulating the conditions of a supersonic flight of an aircraft.

The stand for measuring the loads acting on the object of aviation technology includes a dynamometer platform designed to fix the object, mounted by at least four variable-rigidity plates on a fixed support platform with the possibility of moving the dynamometer platform along three orthogonal axes, each plate having a flexible section, paired with hard sections, and is equipped with a load measuring element, and is characterized in that it further comprises a sensor, a register which measures the longitudinal displacements of the dynamometer platform and is designed to measure the longitudinal load, and the load measuring element is made in the form of two pairs of identical strain gauge sensors designed to measure vertical and lateral loads installed on at least one flexible section of each plate at the same level with respect to the stationary support platform, the sensors of each pair are mounted on opposite wide sides of the plate, with the vertical axis of symmetry of the sensitive elements of the dates the sensors of one pair are oriented along the vertical axis of symmetry of the wide side of the plate, and the vertical axis of symmetry of the sensitive elements of the sensors of the other pair are parallel to it, the sensors are connected to one shoulder of the individual measuring bridges, and the sensors of each pair are connected in series.

The essential features of the invention allow

- determine the moments of pitch, roll, yaw;

- measure the longitudinal load acting on the aircraft object using a sensor that records the longitudinal displacements of the dynamometer platform and is designed to measure the longitudinal load (force sensor) interacting with the dynamometer platform and the fixed support platform;

- measure vertical and lateral loads using the following technical solutions:

- pairwise installation of the same strain gauge sensors at the same level with respect to the fixed base plate, with the pair sensors being connected in series to one shoulder of the measuring bridge eliminates the influence of the longitudinal load on the reading of the measuring bridge;

- the installation of one pair of sensors along the vertical axis of symmetry of the wide side of the plate (neutral axis) with the sequential inclusion of the pair sensors in one shoulder of the measuring bridge eliminates the influence of the transverse load on the reading of the measuring bridge and measures the vertical load acting on the test object;

- installation of the second pair of sensors parallel to the first pair, at the same level, with horizontal shift only, with the pair sensors being connected in series on one shoulder of the measuring bridge, allows you to determine the transverse load from the stresses on the measuring bridges arising under the action of vertical and lateral loads and measured separately voltages on measuring bridges arising under the action of vertical loads.

To describe the possible design of the stand and its operation, FIG. 1-12 where

in FIG. 1 shows a perspective view of a dynamometric platform with an aircraft mounted on it, mounted on a support platform;

in FIG. 2 shows a force sensor connected to a dynamometer platform and a support platform through traction and stops and through lead wires connected to one shoulder of a separate measuring bridge;

in FIG. 3 shows a view of a plate with strain gauge sensors in an undeformed state;

in FIG. 4 is a view of E shown in FIG. 3 (view of the plate on the left);

in FIG. 5 is a left view of a plate in a deformed state under the influence of vertical Fy and horizontal longitudinal Fx loads;

in FIG. 6 is a view of D indicated in FIG. 3 plates (right view);

in FIG. 7 is a view of the plate on the right in a deformed state under the influence of vertical Fy and horizontal longitudinal Fx loads;

in FIG. 8 is a partial view A (FIG. 1) showing internal forces;

in FIG. 9 shows a plate in a deformed state under the action of horizontal lateral load Fz;

in FIG. 10 is a partial view B (FIG. 1) showing internal transverse forces and moments;

in FIG. 11 is a view B (FIG. 1) showing internal lateral forces;

in FIG. 12 shows the signals recorded during the high-altitude tests from the measuring diagonals of individual measuring bridges, each of which is connected to a pair of sensors from each plate located on the axis of symmetry of its larger surface.

The stand for measuring the loads acting on the studied object 1, for example, an object of aviation technology (Fig. 1), contains a movable dynamometer platform 2 with an object 1 fixed on it and a fixed support platform 3. Platforms 2 and 3 are interconnected at the corners by four flexible plates 4, 5, 6, 7, which provide the ability to move the platform 2 along three orthogonal axes, and its surface remains almost parallel to the horizontal plane of the fixed platform 3. Fixed platform 3 is rigidly Knit pressure chamber with the housing (not shown). The object 1 is mounted on the dynamometer platform 2 using a streamlined pylon 8. Flexible plates are fixed on opposite sides of the dynamometer platform and the corresponding sides of the stationary platform in parallel pairs, ensuring the parallelism of the surfaces of the platforms, each pair of plates symmetrically located on the side of the dynamometer platform (in Fig. 1 - in the corners of the platform 2).

Flexible plates are plates of variable stiffness with at least one flexible section conjugated to rigid sections. Flexible sections have parallel flat surfaces on which strain gauge sensors are installed. Preferably, each plate (Fig. 3) is made with two flexible sections 9 and 10, paired with the Central hard section 11 (shown on the plate 4, Fig. 1) and two extreme, by which the plates are attached to the dynamometric and stationary platforms. In FIG. 3-9 plates have rectangular recesses in the upper and lower parts for attachment to platforms. The plates have a longitudinal and preferably transverse plane of symmetry.

An abutment 12 with a force sensor 14 is attached to the fixed platform 3 from the side of the dynamometer platform 2, and an abutment 13 is fixed to the platform 2 from the platform 3 side with a rod 15 rigidly connected with it, whose axis is parallel to the longitudinal axis of symmetry of the dynamometric platform (Fig. 1, 2 ) and coincides with the axis of the force sensor 14. The force sensor 14 detects the longitudinal displacements of the dynamometer platform and is designed to measure the longitudinal load. In the embodiment of the stand shown in FIG. 1, use a strain gauge force sensor.

On at least one flexible section of each plate, strain gauge sensors are designed for measuring vertical and lateral loads, and the same sensors are installed on all plates. In the presented embodiment of the stand (Fig. 1), the sensors are installed on the upper flexible section 9 of each plate. The sensors are placed on parallel wide sides of the flexible portion of the plate in two pairs. On (Fig. 1, 3, 4, 5, 6, 7, 9) sensors 16, 18 are located located on the outside of the plate 5, and sensors 17, 19 located on the inside of the plate 6. The sensor element is made rectangular, has symmetry axes, usually indicated by marks on the sensor housing, which facilitates its installation. The sensors are installed at the same level relative to the surface of the fixed platform 3, that is, the frontal projections of the sensors of each pair of sensors coincide, the profile projections of the sensors 16, 18 and 17, 19 located on one side of the plate also coincide. The vertical axis of symmetry of the sensitive elements of the sensors 16, 17 of one pair are oriented along the vertical axis of symmetry of the wide side of the plate, and the vertical axis of symmetry of the sensitive elements of the sensors 18, 19 of the other pair are parallel to it.

The strain gauge sensors of each pair mounted on the plates through the output conductors 20 are connected in series to one shoulder of a separate measuring bridge (Fig. 5, 7). The strain gauge force sensor 14 through the output conductors 20 is also connected to one shoulder of a separate measuring bridge (Fig. 2). The measuring bridge consists of four resistances (shoulders) and is connected to a separate analog-to-digital measuring converter (ADC) with a built-in power supply and a measuring amplifier of the sensor signal. The supply voltage U is supplied to points A, B of the bridge, and points B and D are connected to the measuring amplifiers of the ADC. All ADCs are included in the multi-channel recorder-analyzer of signals 21, connected by a high-speed communication channel 22 to the station 23 for collecting and processing data (Fig. 1). The object 1 complete with a dynamometric platform 2 and a stationary supporting platform 3 can be installed in a pressure chamber (not shown).

The stand for measuring the loads acting on the object of aircraft, operates as follows. The object 1, mounted on the pylon 8, is surrounded by a stream of air simulating flight conditions, and moves together with the dynamometer platform 2, which is connected to the fixed platform 3 by flexible plates 4, 5, 6, 7 (Fig. 1). Rigid fastening of the flexible plates to the movable platform 2 and the stationary platform 3 allows the movement of the movable platform 2 in the longitudinal, vertical and transverse directions, and its surface remains almost parallel to the horizontal plane of the platform 3 with minor movements that occur during testing.

When the movable dynamometric platform 2 is longitudinally moved to a tensile strain gauge 14, which is fixed to the support 12 on a fixed platform 3, a tensile or compressive load F _x is transmitted rigidly connected to it through the stop 13 and the rod 15. This leads to an increase or decrease in the length of the sensor element of the sensor depending on the direction of movement of the movable platform 2. The strain gauge force sensor 14 is sequentially connected through the lead conductor 20 to one arm of a separate measuring bridge (Fig. 2). When the length of the sensor element of the strain gauge force sensor 14 changes, its resistance R14 and, accordingly, the shoulder resistance in which it is included, change. Therefore, between points B and D of the measuring diagonal of the bridge, a potential difference appears (unbalance voltage of the bridge) recorded by the ADC measuring amplifier. The voltage V recorded between points B and D of the measuring diagonal of the bridge (Fig. 2) at the output of the ADC, which is part of the multi-channel recorder-analyzer of signals 21, is converted into a digital code, which is transmitted via a high-speed communication channel 22 to the data collection and processing station 23 (Fig. 1).

The measurement results are processed according to the program, in which it is assumed that in the stress-strain state, the sensor 14 is within elastic deformations. Then the relationship between the readings of the force sensor 14 and the magnitude of the tensile or compressive horizontal load Fx acting on it will also be linear. The proportionality coefficient Kx, having the dimension [N / B], is preliminarily determined at the stand during calibration loading by tensile or compressive forces. The value of the longitudinal load Fx is determined by the voltage V recorded between the points B and D of the measuring diagonal of the bridge and the proportionality coefficient Kx:

The actual sign of the longitudinal load Fx will be determined by the sign of the measured voltage V between points B and D of the measuring diagonal of the bridge, in which the sensor 14 is included (Fig. 2). The plus sign corresponds to tensile, and the minus sign to compressive longitudinal forces.

Under the action of the load Fx, which causes the longitudinal movement of the dynamometer platform (Figs. 5, 7), due to bending deformations of the plates, changes in the length of the pair sensors will be identical in magnitude but opposite in sign: on the stretch side of the plate — increase in length and decrease on the side of compression of the plate . Therefore, when adding the resistances from the bending components of the deformations of each sensor from a separate pair of R16, R17 and R18, R19, connected in series in one shoulder of a separate measuring bridge, the resistance changes mutually cancel, the voltage on the bridge is not recorded.

Under the action of the load Fy, which causes the vertical movement of the dynamometer platform, the change in the lengths and resistances of all sensors will be the same in magnitude and sign. The resistance of each pair of sensors included in the arm of an individual bridge in series will be equal to twice the resistance of one sensor. Provided that in the stress-strain state the flexible sections of the plates are within elastic deformations, the magnitude of the vertical load acting on each plate will be proportional to the detected bridge unbalance voltage:

where Ku is the coefficient of proportionality, [N / V], V is the voltage between points B and G of the measuring diagonal of the bridge, [V].

The proportionality coefficient Ku is preliminarily determined at the stand during calibration loading. For all plates, the proportionality coefficient Ku is the same, since the plates and the sensors are the same.

The resultant vertical load Fy (equal) is equal to the algebraic sum of the vertical loads acting on each flexible rack:

where F _y1 , F _y2 , F _y3 , F _y4 are the loads determined using sensors 16, 17 installed along the vertical axis of symmetry of the wide sides of the plates (Fig. 1, 3, 5).

The actual signs of the vertical loads acting on each plate will be determined by the signs of the measured voltages V between points B and D of the measuring diagonals of the individual bridges, to which one sensor 16, 17 is connected to one arm (see Fig. 5). The plus sign corresponds to tensile, and the minus sign corresponds to vertical forces compressing the rack.

For a zero measurement value for each plate, the initial voltage V between the points B and D of the measuring diagonal of a separate pair of sensors is taken when the flexible plates are already loaded with the weight of the test object 1 mounted on a movable dynamometer platform 2 using a streamlined pylon 8 (see Fig. 1 ) In this case, there is no need to know the weight of the object in advance and take it into account when processing the measurement results obtained during the test.

When determining the resultant vertical load Fy (rav), only the vertical loads Fy determined using sensors 16, 17 installed along the vertical axis of symmetry of the wide sides of the plates (see Figs. 1, 3, 5) are taken into account, i.e., so that the vertical axes the symmetries of the sensitive elements and the frontal sections of the sensors 16, 17 coincide with the vertical symmetry axes of the wide sides of the plates (Fig. 3). When these sensors deform from bending during transverse movements of the dynamometer platform under the action of a transverse load Fz (see Fig. 9), their length will remain unchanged, since the vertical axis of symmetry of the wide sides of the plates and the axis of symmetry of the front sections of each sensor coincide with their neutral axes. Therefore, the resistances of the sensors do not change with such deformation. Therefore, the voltages recorded on the corresponding measuring bridges change only under the action of the vertical load on the test object.

For each of the pair of strain gauge sensors 18, 19 (Fig. 1, 3) installed parallel to the vertical axis of symmetry of the wide sides of the plates, the change in length and resistance will occur from compression and tensile strains caused by the action of the vertical load, and bending strains caused by the action lateral load during spatial movement of the dynamometric platform (see Fig. 7, 9). Therefore, the total change in length and, accordingly, the change in resistance of each of the pair of sensors will be determined by compression (tension) and bending deformations.

From the values of the moments of internal forces acting relative to the Z axis passing through the center of gravity of the object (CT), the pitch moment M _{(tf) is determined} . An example of such a design scheme is shown in FIG. 8. The internal tensile or compressive vertical forces in the cross sections of the flexible sections of each plate are determined by the measurement results. In the calculation, it is assumed that the internal tensile vertical force R _y1 = F _y1 acts in the cross section A1 of the flexible section of the plate 5, the internal tensile vertical force R _y4 = F _y4 acts in the cross section A4 of the flexible section of the plate 6 (Fig. 1, 8), the internal tensile vertical force R _y2 = F _y2 acts in the cross section A2 (not shown) of the flexible portion of the plate 4 (Fig. 1), and the internal tensile vertical force R _y3 = F _y3 acts in the cross section A3 (not shown) of the flexible portion of the plate 7 (Fig. 1). In the cross section of the rod 15, an internal tensile longitudinal force Rx = Fx acts. The pitch moment is determined by the formula

where P _1z , P _2z , P _3z , P _4z are the distances between the YZ plane passing through the center of gravity and the parallel planes passing through the vertical axis of symmetry of each plate, P _5z is the distance between the XZ plane passing through the center of gravity, and parallel to it by a plane passing through the horizontal axis of symmetry of the thrust; the distance is equal to the length of the segment perpendicular to the indicated planes.

When summing, the plus sign corresponds to the moments acting counterclockwise, and the minus sign corresponds to the moments acting clockwise. The signs of moments in (4) are determined according to the formulated rule in accordance with the directions of the internal vertical forces Ry and the longitudinal force R _x selected in the calculation scheme. The actual signs of the vertical loads Fy acting on each plate 4, 5, 6, 7, and the longitudinal load Fx acting on the link 15 (Fig. 1) will be determined by the signs of the measured voltages V between points B and D of the measuring diagonals of the individual bridges. The plus sign corresponds to tensile, and the minus sign to compressive plates and thrust to 15 loads (formulas 1, 2).

Under the action of the transverse load Fz, causing the lateral movement of the dynamometer platform, as already noted, the length of the sensors 16, 17 does not change. Whereas the change in the lengths and resistances of the sensors 18, 19, located not on the neutral axes of the sides of the plates, caused by bending deformation, will be the same both in magnitude and in sign (Fig. 9). The total change in resistance of each such pair of sensors is equal to twice the change in resistance of one sensor.

Each of the pair of sensors 18, 19 will change the length and resistance to compression deformation (tension) of the plates caused by the vertical movement of the dynamometer platform under the action of the vertical load Fy. In this case, changes in the lengths and resistances of the sensors 18, 19 on each plate will be the same in magnitude and sign, and the total resistance of the sensors 18, 19 connected in series in one shoulder (Fig. 7) will be equal to twice the resistance of one sensor.

The change in the length and resistance of each sensor 18, 19 on all plates from bending under the action of a transverse load Fz (Fig. 9) and from compression (tension) under the action of a vertical load Fy (Fig. 7) will be equal to the sum of the change in length and resistance from each force . In the stress-strain state, all sensors are within elastic deformations, therefore, the voltage V _(sum) between points B and D of the measuring diagonals of each bridge, one pair of sensors 18, 19 is included in one shoulder, will also be equal to the sum of the stresses caused by the change in the resistance of the sensors from bending V ₍ bending ₎ and compression (stretching) V ₍ compress ₎ :

The voltage V _{(s) is the} same for each pair of sensors 16, 17 and 18, 19 on one plate and measured for a pair of sensors 16, 17, so the voltage from the change in the resistance of the sensors 18, 19 from the bend V _(s) will be determined by the difference between the total V _(sum) voltage between points B and G from the measuring diagonal of a separate bridge, one arm of which includes a pair of sensors 18, 19 (Fig. 7), and voltage between points B and G from the measuring diagonal of a separate bridge, one arm of which includes a pair sensors 16, 17 (Fig. 5).

To determine the transverse load Fz, the internal bending moment Mx, acting in the sections of the flexible sections 9 of each plate, where the strain gauge sensors 16, 18 are located (Fig. 9), is calculated in the direction of the X axis relative to the center of gravity of the plate section, according to the ratio:

where J is the moment of inertia of the cross section of the flexible section of the plate relative to the axis parallel to the axis X passing through the center of gravity of the cross section of the plate at the location of the sensors (Fig. 9);

S is the cross-sectional area of the flexible portion of the plate at the location of the sensors;

V _(izg) is the voltage between points B and D of the measuring diagonal of an individual bridge, caused by a change in the resistances of the sensors 18, 19 only from bending under the action of the transverse force Fz;

Lz is the distance between the centers of the frontal sections of the sensors 16 and 18;

Kу is the proportionality coefficient having the dimension [N / V], determined directly on the stand, during calibration loading (see Fig. 1) of the dynamometer platform 2 by tensile or compressive vertical forces Fy.

The plus sign corresponds to the moment acting counterclockwise according to FIG. 9 calculation scheme. The actual signs of the bending moments Mx acting on each plate will be determined by the signs of the stresses V _(arcs) calculated from relations (5 ₎ . The signs V _(sum) and V _(squ) in relation (5) are determined by the signs of the measured voltages (Fig. 5.7).

As noted, the proportionality coefficients Ku, which determine the relationship between the applied vertical forces during calibration and the stresses V _(s) between points B and D of the measuring diagonals of the bridge (see Fig. 5), are the same for the same plates and strain gauge sensors within elastic deformations. Therefore, for the deformations of the plates and sensors under the action of the vertical load Fy and the transverse load Fz, the linearity property is fulfilled, when the total deformation and the change in resistance are equal to the sum of the change in the lengths and resistances of the sensors from each force separately. Therefore, it is assumed that the proportionality coefficients Кz, having the dimension [N / V], which determine the linear dependence between the applied transverse forces Fz and the voltages V _(ar) on the measuring bridges with sensors 18, 19, are the same for all plates and are taken equal to Ku.

In relation (6) for the internal bending moment Mx in the cross sections of the flexible sections 9 of each plate, where the strain gauge sensors 16, 18, V _(ar) are located, the change in the resistance of each of the sensors 18, 19 is doubled, and the coefficient 2 in the denominator takes into account the change in stress at a change in the resistance of only one sensor 18 (Fig. 9) under the action of a transverse load Fz.

With a known value of the internal bending moment Mx, the transverse force Fz is determined by the relation

where Ly is the distance between two planes parallel to the XZ plane, one of which passes through the inflection point, which for the plate of the used construction is located on the middle of the neutral axis of the wide side, the other through the horizontal axis of symmetry of the sensitive elements of the sensors 16, 18 or 17, 19.

The actual signs of the transverse loads Fz acting on each plate will be determined by the actual signs of the internal bending moments Mx, calculated from relations (6).

To determine the resultant lateral load F _{z (rav)} acting on the test object, an algebraic summation of the transverse forces acting on each plate is carried out:

The value of the transverse load Fz, determined by the relations (6, 7), in the proposed installation scheme of strain gauge sensors on each plate does not depend on the distances Lz and Ly, which determine the location of the sensors (Fig. 1, 3, 9). In the direction of the Z axis, only the transverse load Fz acts on each plate. Therefore, when a plate deforms from bending under the action of a transverse load Fz, the magnitude of the bending moment Mx for each plate changes only when the sensors move along the Y axis so that in relation (7) when the distance Ly changes, the value of the transverse load Fz must remain constant. For each cross section of a flexible section of the plate with sensors, characterized by the distance Ly from the inflection point (TP), the moment Mx will have a constant value determined by the integral of the diagram of the stresses arising in this section during bending from the action of the transverse load Fz. Therefore, when the distance Lz changes due to a change in the position of the sensors 19 along the Z axis on the plates (Fig. 9), under the action of the transverse force Fz, their lengths and resistances and, consequently, the stresses V _ar due to bending deformations caused by the transverse force Fz. However, these deformations and the resulting bending stresses in the cross sections of the flexible sections of the plate will be such that the values of bending moments Mx obtained from the results of measurements and processing using relations (6) will not depend on changes in the distances Lz, which determine the relative position of the sensors 16, 18 or 17, 19 on a stand, at a given value of Ly.

The heeling moment M (krn) is determined by the sum of the moments from the internal transverse Rz forces and bending moments Mx acting in cross sections of the flexible sections 9 of all the plates (see Figs. 1, 10) with respect to the X axis passing through the center of gravity of the center of gravity of object 1 (Fig. . 10). An example of a design circuit is shown in FIG. 10. The internal bending forces R _z3 , R _z4 in the cross sections of the upper flexible sections of each plate 6.7 are equal in magnitude to the transverse loads Fz acting on each plate. In the calculation, it is assumed that the internal transverse force R _z3 = F _z3 acts in the cross section A3 of the upper flexible section of the plate 7, and the internal transverse force R _z4 = F _z4 acts in the cross section A4 of the upper flexible plate 6 (Fig. 1, 10). For the calculation, it is assumed that the internal transverse force R _z1 = F _z1 (Fig. 11) acts in the cross section A1 (not shown) of the upper flexible section of the plate 5 (Fig. 1), and the internal transverse force R _z2 = F _z2 (Fig. 11) acts in cross section A2 (not shown) of the upper flexible section of the plate 4 (Fig. 1). It is assumed that the directions of action of the internal transverse forces R _z1 , R _z2 coincide with the directions of action of the internal transverse forces R _z3 , R _z4 .

In the cross sections A3, A4 of the plates 7, 6 (Fig. 1, 10), the internal bending moments M _x3 , M _x4 determined by the measurement results and calculations by the ratios (6, 7). It is also assumed for calculation that in the cross sections A1, A2 of the plates 5, 4 (Fig. 1), the internal bending moments M _x1 , M _x2 (not shown) act in the direction of the X axis with respect to the center of gravity (CT) of object 1; The calculation scheme assumes that the direction of action of the bending moments M _x1 , M _x2 coincides with the direction of action of the bending moments M _x3 , M _x4 .

The roll moment M _(crc) according to FIG. 10 calculation scheme is determined by the ratio

where P1x, P2x, P3x, P4x are the distances between the XZ plane passing through the center of gravity and the parallel planes passing through the cross sections A1, A2, A3, A4 of each plate (Fig. 1, 10). The distances are equal to the lengths of the segments perpendicular to the indicated planes.

When summing, the plus sign corresponds to the moments acting counterclockwise, and the minus sign corresponds to the moments acting clockwise when adopted in FIG. 10 calculation scheme. The actual signs of the moments in (9) will be determined by the signs of the transverse loads Fz acting on each rack, calculated by the relations (7).

The yaw moment M _(rsk) is determined by the sum of the moments of the internal transverse forces Rz acting in the cross sections of the upper flexible sections 9 of all the plates relative to the Y axis passing through the center of gravity of the center of gravity of object 1 (Figs. 1, 10, 11). The internal transverse forces Rz1, Rz2, Rz3, Rz4 are equal in magnitude to the transverse forces Fz acting on each plate, determined by the results of measurements and calculations by relations (6, 7). It is assumed that the directions of action of all internal transverse forces coincide (Fig. 11).

The yaw moment M _(rsk) according to FIG. 11 calculation scheme is determined by the ratio

where P1y, P2y, P3y, P4y are the distances between the YZ plane passing through the center of gravity (CT) and its parallel planes passing through the cross sections A1, A2, A3, A4 of each plate (Fig. 1, 10, 11). The distances are equal to the lengths of the segments perpendicular to the indicated planes.

When summing, the plus sign corresponds to the moments acting counterclockwise, and the minus sign corresponds to the moments acting clockwise. The actual signs of the moments in (10) will be determined by the signs of the transverse loads Fz acting on each plate, calculated by the relations (6, 7).

In FIG. Figure 12 shows the signals of the measured voltages V recorded between the points B and D of the measuring diagonals of individual bridges recorded during high-altitude testing of the object (supersonic aircraft), to one arm of which a pair of sensors 16, 17 (see Fig. 5) are mounted on the outer and inner wide sides of the upper flexible sections of the plates 4, 5, 6, 7 along the vertical axis of symmetry (neutral axes) of these sides (Fig. 1, 3, 4). The time interval ΔT corresponds to the operating mode when the aircraft engine is running. The average values of the measured voltages in this interval are equal to the following values:

plate 5 (line A) - V5 = -0.184 V; plate 4 (line B) - V4 = -0.153 V;

plate 7 (line B) - V7 = + 0.002; plate 6 (line G) - V6 = + 0.106 V.

The value of the proportionality coefficient Ku, determined during calibration loading by the tensile and compressive vertical forces of the movable platform 2 with the object 1 installed on it using the streamlined pylon 8 (Fig. 1), was Ku = 13800 [N / V]. The vertical loads Fy acting on each plate, according to (2), take the following values:

F _y5 ≈-2539 N, F _y4 ≈-2111 N, F _y5 ≈ + 28 N, F _y6 ≈ + 1463 N.

The resultant vertical load F _{y (rav)} acting on the aircraft, according to (3), is equal to the algebraic sum of all vertical loads:

F _{y (equal)} = Fy1 + Fy2 + Fy3 + Fy4 = -3159 H.

This means that when the propulsion system is running, the bow of the supersonic aircraft will be tilted down, and the aft of the aircraft will be raised up (Fig. 1, 8). During bench tests with respect to the horizontal plane, the aircraft is inverted with respect to its position during flight. Therefore, for flight conditions, the result obtained at the stand means that, with the engine running, the aircraft has a positive lift force Fпод = 3159 N.

The proposed technical solution provides the definition of the longitudinal, vertical and lateral loads acting on the aircraft object according to the proposed measurement scheme when it is blown by an air stream at a stand in a pressure chamber simulating altitude flight conditions, and also allows you to determine the moments of roll, yaw and pitch.

Claims (1)

A stand for measuring the loads acting on an object of aviation technology, including a dynamometer platform designed to fix the object, installed by means of at least four variable-rigidity plates on a fixed support platform with the possibility of moving the dynamometer platform along three orthogonal axes, each plate made with a flexible section coupled to hard sections, and provided with a load measuring element, characterized in that it contains a sensor that records pr longitudinal displacements of the dynamometer platform and designed to measure longitudinal load, and the load measuring element is made in the form of two pairs of identical strain gauge sensors designed to measure vertical and lateral loads installed on at least one flexible section of each plate at the same level with respect to the stationary support platform, sensors each pair are mounted on opposite wide sides of the plate, with the vertical axis of symmetry of the sensitive elements of the sensors of one the pairs are oriented along the vertical axis of symmetry of the wide side of the plate, and the vertical axis of symmetry of the sensitive elements of the sensors of the other pair are parallel to it, the sensors are connected to one shoulder of the individual measuring bridges, and the sensors of each pair are connected in series.

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