RU2269103C1 - Dynamometric device for strength test of aircrafts - Google Patents

Abstract

FIELD: measuring engineering.

SUBSTANCE: device comprises housing, dynamometric gauge with contact plungers of the flexible member and unit for setting two levels of deformation. The unit for setting two level of deformations is made of two calibrated cylinders of different diameters and provided with conical adapters secured to the rotatable axle for permitting movement in the threaded bushing.

EFFECT: expanded functional capabilities.

4 dwg

Description

The invention relates to measuring equipment, in particular to means for measuring forces during structural strength tests of aircraft structures.

Scope - aviation technology, mechanical engineering, nuclear energy, shipbuilding, etc.

When conducting static, thermal, static, resource and climatic tests for the strength of aircraft, force measuring sensors with strain gauge transducers are widely used. Prior to testing, these sensors are graduated on exemplary silos and verified by metrological services. Then, the force sensors together with the measuring channels of the measuring information systems (IMS) or automatic load control systems of the structure (ACS) are graduated again and after that the sensors are installed in the load reproduction systems. Re-calibrating the load cell during testing is a time-consuming and expensive operation. The reasons for their implementation may be changes in the conversion coefficient of the load cell caused by overload, moisture saturation, aging of adhesives used in strain gages, failure of the measurement channels of IMS and ACS, cable communication lines, etc., as well as for periodic metrological verification.

The most time-consuming is the operation of re-calibrating the force sensors installed in complex stands for climatic testing of structures with reproduction of the effects of moisture, temperature, load, solar radiation and other factors. In these stands, load cells are installed either outside the climate chamber, and the connection with the structure is carried out by rods with bellows or in the climate chamber. In the latter case, strain gages glued to the elastic element of the load cell are sealed to protect against moisture. It was experimentally established that absolute sealing cannot be achieved, and the change in the conversion coefficient can vary up to 3-5% of the initial value when exposed to 90-100% moisture during the year. In the event of a breach of sealing, there is a sharp decrease in the conversion coefficient and erroneous test results. Therefore, periodic monitoring of the measuring characteristics of load cells should be carried out.

To do this, when climate testing the structural strength of aircraft, it is most advisable to use force sensors with devices that provide performance monitoring without dismantling them from the test bench.

It is known that a device for measuring force, containing a load sensor, a load-loading system and recording equipment (see Baranov A.N., Belozerov D.G., Ilyin Yu.S., Kutinov V.F. M .: "Engineering", 1974 g., pp. 254-255).

The disadvantage of the device when measuring forces under climatic conditions is the change in the measuring characteristics during long-term operation and the inability to correct them without dismantling the device from the test bench. The device requires additional periodic calibrations on exemplary testing machines, which significantly increases the complexity of the tests and the cost of measurements.

A known device for measuring strength during climatic tests on the strength of aircraft structures (see RF Patent 2085876, TsAGI, authors Ilyin Yu.S. and Perunin OA, 1997), adopted as a prototype.

The device comprises a housing, a load sensor, a node for setting two levels of deformations of a normalized value, made in the form of a wedge with exemplary measuring tiles and a sensor for monitoring the position of the wedge.

The disadvantage of this device is the presence of a wedge position monitoring sensor and a second measuring channel for recording its readings.

The task of the invention is to increase the accuracy of force measurement during long-term climatic tests of aircraft structures for strength and reduce operating costs for their implementation.

The technical result is the provision of the possibility of periodic calibration of force sensors in the process of short-term stopping of the test bench without re-installation of load-bearing and force-measuring devices.

The technical result is achieved in that in a device containing a housing, a force sensor with contact pushers of an elastic element and a unit for setting two levels of deformations of a normalized value, a unit for setting two levels of deformations of a normalized value is made in the form of two calibrated cylinders of different diameters with conical transitions mounted on a rotating axis with the possibility of movement in a threaded sleeve pivotally mounted on the device body, and contact pushers of the elastic element of the sensor are made wedge-shaped appearance,

Figure 1 shows a structural diagram of the proposed device.

In Fig.2 shows a section along aa, bb and bb in Fig.1.

Figure 3 presents the dependence of the output signal of the device during calibration and operation.

Figure 4 shows the dependence of the output signal at control calibrations of the device before and during climatic tests.

The proposed device (figure 1) consists of a housing 1, a load sensor 2, on the elastic element of which tensor resistors 3 are glued in the stretched and compressed zones, connected according to the scheme of the measuring bridge connected to the electrical connector 4. The elastic element is equipped with two attachment points for application of the measured forces that on the inside have contact pushers 5a and 5b of a wedge-shaped form. A power unit 6 is installed on the housing for loading the elastic element into two normalized levels of deformation.

The power unit (see figure 2, section A-A) is made in the form of two calibrated cylinders 7a and 7b of different diameters with conical transitions 8a and 8b, mounted on a rotating axis 9, which has the ability to move in the threaded sleeve 10 (see figure 2, sec. BB). The threaded sleeve is pivotally mounted on the housing 1. At the free end of the axis of the load-bearing unit, a manual drive limb 11 is mounted for rotation and, accordingly, axis movement.

The proposed device operates as follows. The elastic element of the load sensor 2 is loaded during calibration by forces P on a reference force-setting machine. In this case, the surface of the elastic element is deformed in the sticker region of the strain gauges 3, which causes, accordingly, a change in their electrical resistance and leads to a change in the output signal of the measuring bridge. The magnitude of the set forces and the output signal determine the calibration characteristic n ^g = φ (p ^g ) (see Fig. 3) of the load cell and the conversion coefficient K.

и

(см. фиг.4).After calibration in the same normal climatic conditions, the elastic element of the load cell is additionally loaded by rotating and, accordingly, moving the axis 9 of the device together with two calibrated cylinders of different diameters and conical transitions. At the same time, on horizontal sections of the additional characteristic, the control signals of the load sensor are counted

and

(see figure 4).

и

(см. фиг.4) функцию влияния климатических условий на коэффициент преобразования К и нагружают конструкцию до величины силы, определяемой с учетом функции влияния климатических условий по формуле:When carrying out climatic tests of the structure on a test bench, the operation of the load sensor is similar to the calibration, but the sequence of operations changes: first, the elastic element is additionally loaded at two normalized strain levels, determined by the value of the control signals

and

(see figure 4) the function of the influence of climatic conditions on the conversion coefficient K and load the structure to a force value determined taking into account the function of the influence of climatic conditions according to the formula:

where U _o - the initial signal of the load cell during structural testing;

U _i - the output signal of the load cell at the i-th stage of loading direct test design;

K is the conversion coefficient of the calibration characteristic;

и

- контрольные выходные сигналы при дополнительном нагружении упругого элемента на первый и второй нормированные уровни деформации при градуировке;

and

- control output signals with additional loading of the elastic element to the first and second normalized levels of deformation during graduation;

и

- контрольные выходные сигналы при дополнительном нагружении упругого элемента на первый и второй нормированные уровни деформации при климатических условиях.

and

- control output signals with additional loading of the elastic element to the first and second normalized levels of deformation under climatic conditions.

In the device, the reference lines of the wedge pushers 5a and 5b are placed perpendicular to the axis 9 (see Fig. 2 sec. Moreover, the possible presence of backlash in the threaded axis-sleeve pair does not lead to additional measurement errors that would occur if the supports were made in the form of a cone.

The introduction of the device into the practice of experimental research provides:

- improving the accuracy of force measurements during climatic tests on the strength of aircraft structures;

- reduction of operating costs for the preparation and conduct of tests;

- cost reduction for the manufacture of load cells in comparison with the prototype.

Claims (1)

A device for measuring strength during climatic tests on the strength of aircraft structures, comprising a housing, a load cell with contact pushers of an elastic element and a unit for setting two levels of deformations of a normalized value, characterized in that the unit for setting two levels of deformations of a normalized value is made in the form of two calibrated cylinders of different diameters with conical transitions mounted on a rotating axis with the possibility of movement in a threaded sleeve pivotally mounted on the body ce device, and the pushers contact the elastic member force-measuring sensor are made wedge-shaped form.

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