The method for determining the deformation of structures under test conditions alternating thermal stresses, and a sensor for detecting the deformation

 

(57) Abstract:

The invention relates to measurement techniques, in particular to methods and devices for determining the deformation of the airframe. The aim of the invention is to improve the accuracy of determining the deformation of structures under test conditions alternating thermal stresses. The strain sensor includes testcustomer element 3, the heating element 6 and the sensing element 7 connected to the switch 11 and a transmitter 12 of the measuring path. When implementing the method of the strain sensor mounted on the test structure, connects the measuring instrument, perform functional calibration and calibration of the measuring path. The sensor is subjected to thermo effect, feeding from the transducer 12, the current pulse given power to heating element 6, measure the resistance of the sensor signal of the strain-sensing element 3. Subjected to the test design disposable force loads and additionally measure the resistance of the sensor. The deformation of the structure is determined by the dependence of weather resistance is Z. p. f-crystals, 2 Il.

The invention relates to measurement devices, and in particular to methods of determining the mechanical deformation of structures, structures strain of the strain gauges, as well as methods of monitoring their health, and can be used to determine the deformations of objects, work under alternating thermal stresses in a long time operation.

Known [1] a method for determining deformation of structures under alternating thermal stresses, namely, that connected in the bridge circuit of the strain gages installed on the structure, with one or two load cells measure the deformation, as workers, and three or two not perceive deformations from ekspluatatsionnykh loads, but are subject to deformations alternating temperature stresses, as compensation. At the output of the Normalizer connected to tanzamomo, remove the signal which is proportional to the deformation of operating loads.

The disadvantage of this method is inaccurate determination of transfer function of tentmate for an extended period of research or the operation of the object, t is the quality of the strain gauge, which vary with time and operating conditions of the object.

A known method of controlling the quality of the bonding of the strain gauge [2], based on the supply of the pulse current in the wire strain gauge (DMS, measuring changes in the resistance and compare it with the change of the reference resistance of the strain gauge pasted.

Known [3] the method of controlling the quality of the bonding of strain gages by filing a current pulse of a selected duration considering the fact that the heat flow does not have time to come and spread to the surface of the object.

The disadvantages of the known methods of control are;

supply current pulse of increased amplitude in testcustomer grating sensor that can lead to device failure and achieved little effect its linear expansion due to thermal stabilization of grating material;

comparison of measurement results with indications of control sensors during operation still need somewhere to install and connect;

the lack of availability of functional calibration of the whole path of the measurement (sensor measuring track-measuring transducer-recorder).

The most effective is the governance of deformation.

The strain gauge includes two blade supports, the meter movement in the form of a bracket mounted on it testcustomer and thermosensitive elements, thermostable rod with insulating spacers at the ends connected to the free end of the bracket, the temperature compensating rod with a fixed heating element. The temperature compensating rod at one end through a lining connected with thermostable pivot and at the other end through the strip - blade prop.

The strain sensor mounted on the structure by means of knife supports, mounted on the bracket. Connects the measuring instrument. Before determining deformations produce functional calibration or calibration of the entire measuring path, which provides high accuracy measurements. The calibration carried out by thermo-impact, connecting the voltage to the heating element of the sensor, which causes to increase the temperature compensating rod, thus providing a given deformation of the bracket and accordingly placed the strain gauge.

After achieving equal stages increment predetermined temperature, measure the resistance datti its resistance against thermo effects, made in the calibration.

The proposed method of measurement and sensor deformations can improve the measurement accuracy by eliminating systematic errors in the measuring path.

However, the sensor due to the complicated and cumbersome mechanical structure, its thermal and mechanical inertia, the unreliability of its mounting supports cannot provide with long-term quasi-static loads under alternating thermal stresses required accuracy of strain measurement.

The disadvantage of this method of strain measurement is the low accuracy of determination of the relationship between calibration characteristics obtained when the power and thermo loading.

The aim of the invention is to improve the accuracy of determining the deformation of structures under test conditions alternating thermal stresses.

The goal for the method is achieved in that in the method of determining the deformation of the structure during the tests under alternating thermal stresses, namely, that on the test design set, a strain sensor strain, ovcu just measuring path, a strain sensor is subjected to thermo effect by connecting voltage to its heating element, measure the resistance of the sensor and determine the deformation of the structural dependence of the sensor resistance values of thermo effects, additionally subjected to the design of the disposable force loads and additionally measure the resistance of the sensor and the deformation of the structure is determined taking into account the dependence of the sensor resistance values of force operational loads.

The goal is for the device is achieved in that the sensor for detecting the strain containing testcustomer element with an insulating substrate for mounting to the test structure and the heating element, provided with a heat-conducting plate and a thermosensitive element, the plate is installed in contact with testcustomer element, and thermosensitive heating elements are installed on the plate.

When applying pulses of current to the heating element, mounted on the plate, testcustomermap grating sensor is experiencing stress arising from complex Hermosillo the Oia, moreover, thermo effect is determined by the linear extension plate and heat flow in the structural elements of the sensor, this causes deformation equal to deformation from forces acting on the structure during operation.

Identifying the measurement results from thermo effects with once carried out by the measurement results in a stepwise calibration loading design and making a correction for the temperature increment receive a calibration and functional characterization of the entire measuring system path.

In Fig. 1 shows a strain gauge, a General view of Fig.2 - scheme of the measuring path by using a strain gauge.

The strain gauge (Fig.1) contains wire strain gauge (DMS installed on parts 1 and manufactured by winding with a toner to the substrate 2 of the strain-sensing element 3 from Terzopoulos and closing its shell 4 from that of the binder.

On comisariada the gasket 5 is installed, the heater element 6 a lattice-type and temperature-sensitive element 7 is also a lattice-type, which are located outside vivogenerated extensions as experience design. For example: the heating element 6 can be produced by etching of Constantan foil and the sensing element 7 by etching of the copper foil deposited on a substrate of glue VL-6 and then pasted on the plate 9.

Measuring the tract containing the strain sensor includes a temperature sensitive element of the sensor 7, two conclusions which on the one hand through the measuring route 10 go to the switch 11, and on the other hand is on the switch and on sensorised 3, the second terminal through which the measuring track 10 goes to the switch 11 and to the first input of the heating element 6, the second output of which is connected to the measuring track with the switch, the output of which is connected with the measuring transducer 12, one output of which is connected with the recorder 13, and the other with the switch.

The transmitter 12, the feeding current pulse of a given power to the heater 6, measures the signals from the strain gauge 3 about the change in its resistance when heated for further calculations on the basis of the calibration characteristics with temperature correction.

The duration of heating of the strain gauge, the magnitude of the heating current is the value with the magnitude of the deformation of the structure during its power loading.

In this case, when the wire strain gauge (DMS made of Constantan wire with a thickness of 0.03 mm, substrate binding and membrane from the glue VL-6, a plate made of aluminum foil DM, heating elements made of Constantan foil, heat-sensitive element of the copper foil, a current pulse is equal to I=200 mA and has a duration of not more than 1 sec.

The method of determining the deformation of the structure during testing or operation under alternating thermal stresses is implemented by the following sequence of operations:

on the test design set, a strain sensor strain; connects the measuring instrument, perform functional calibration or calibration of the entire tract, with a strain sensor is subjected to thermo effect by connecting voltage to its heating element and measure the resistance of the sensor. Put the design disposable force loads and additionally measure the resistance of the sensor. The deformation of the structure is determined by the dependence of the sensor resistance values of thermal and force of impact and the force impact of operational nagrazhdennyh VOLTAGES AND the SENSOR FOR detecting the DEFORMATION.

1. The method for determining the deformation of structures under test conditions alternating temperature stresses, namely, that on the testing set design, a strain sensor strain, hook up equipment, prior to testing, perform functional calibration of the entire measuring path, a strain sensor is subjected to thermo effect by connecting voltage to its heating element, measure the resistance of the sensor and determine the deformation of the structure by the dependence of sensor resistance values of thermo effects, characterized in that, to improve accuracy, optionally subjected to the design of the disposable force loads and additionally measure the resistance of the sensor, and deformation of the structure is determined taking into account the dependence of the sensor resistance values of force operational loads.

2. A sensor for detecting the deformation of structures under test conditions alternating temperature stresses containing testcustomer element with an insulating substrate for mounting to ispycoupons plate and a thermosensitive element, plate set in contact with testcustomer element, and thermosensitive heating elements are installed on the plate.

3. The sensor under item 2, characterized in that the heating element is designed as a grid of high-resistance material.

4. The sensor under item 2, characterized in that the sensing element is made in the form of a lattice of heat-sensitive wire.

 

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