SU1236362A1 - Device for measuring restraint of rod in construction - Google Patents

Abstract

The invention relates to the field of methods for experimental study of the mechanical parameters of core structures in construction, engineering, energy, improves the accuracy of measurement of the stability of rods, includes sensors 5, 6 and 7 of the oscillation amplitude installed at the ends of the rods and in the center, the constant resistor 10 , adjusting resistor 11, potential zero-indicator 13 with feedback 14. The movable contact of adjusting resistor 11 is connected back to the potential-zero indicator 13, connected nym terminals to the common point of the compound 10 and the constant adjusting resistor 11. 3 il. about ". (L of fig. 2

Description

The invention relates to the field of experimental studies of the mechanical parameters of core structures and can be used in the examination of core structures in construction, engineering, energy, as well as for non-destructive production control of such structures.

A rod in a known construction, regardless of the design scheme used (truss, frame), has fastening points at the ends that prevent its end sections from turning. The magnitude of the stiffness of these fixtures depends on the quality of manufacture and assembly of structures, and then on its condition under operating conditions, and it also determines the degree of pinching of the rod in the structure, affecting the behavior of the rod under load and its bearing capacity during longitudinal and transverse bending . Thus, the actual clamping of the rods, expressed by any quantitative characteristic, can be judged on the quality of the fabrication of the structure and its actual carrying capacity.

The purpose of the invention is to improve the accuracy of measurement of jamming.

Figure 1 is a diagram illustrating the principle of pinching; figure 2 - diagram of the device; in FIG. 3, the electrical circuit of the device is equivalent, which explains its operation.

EA of FIG. shows curve 1 of the natural transverse oscillations of the pitch of the rod, which has at the end of the elastic rotational laziness. It is similar to the buckling curve of such a rod under axial loading. Here, for comparison, there is a curve 2 of transverse oscillations of the rod hinged at the ends, i.e. pr zero clamped.

The amplitude of oscillations of the rod Y is counted from its undeformed axis X with the origin of reference O in the middle of the vibro span of the rod f. The position of the ends of the vibro-span of the rod ± f / 2 is determined by the condition Yg. The distance between the inflection points 4 of the curved axis of the rod, where its curvature vanishes, is called the free or calculated length of the rod i.

The amplitude of oscillations in the middle section of the rod Yj. In the sections x – a and –a, the amplitudes of the oscillations, respectively, Y Curve, 2 oscillations of the rod with no pinching at the end, is described by the equation

uo v

   - | -.

i a

l

v v ° Ua ° Y

% ji- 2 cos -t§-. (one)

Sensors 5-7 are connected with cross sections 0, + a, - a, which convert the amplitude of oscillations into a proportional electrical signal of the EMF. The transform coefficients of the peripheral sensors k are equal to each other, but may differ from the transform coefficient of the average sensor k. . Wherein

F k V F kY V o- o Q -oi -m Q Ua

(2)

The primary electrical signals of the sensors Un, E, d, E.q are converted by the transducer 8 into a single output signal d, linearly related to the value A :. d oiA + / i,

Where

- (Y.-Y.J / X.

(3)

..

,

The electrical circuit of the device (Fig. 2) is a measuring circuit of series-connected elements, grounded at the ends.

The circuit is conditionally divided into two sections I and II, mating in node 9. Section I contains a fixed resistor 10, having a resistance R and a sensor 5 with an internal resistance Gd, B1 1, the operating EMF E ,. Section II contains sensors 6 and 7 with internal resistance g, g, producing an emf and respectively 5 as well as a control resistor 11 with a moving contact (not shown) with a current resistance R. The value of this resistance is measured on a linear scale 12, and

ak Rj (d - d) aAd, (4) where is the division price. Ohm;

corresponding to R, R and d values,

Zero-clamped

The junction 9 of the sections I and I of the measuring circuit is provided with a null potential indicator 13 and is connected to the moving contact of the adjusting resistor 11 by feedback 14, which adjusts the position of the moving contact so that the zero indicator remains in balance.

The introduction of feedback 14 is equivalent to the condition and O, or the introduction of jumper 15, shown by a dotted line. In the equivalent circuit, it is possible to arbitrarily select two circuits with the current of rear and Iq, and from the condition of the actual non-branching of the measuring circuit DO °

Proceeding from the law (2) of proportional conversion of the amplitudes of oscillations into the EMF of the sensors, the clamping parameter of the rod A is converted into the ratio of the EMF B as follows:

Where

ot 9

h

Thus, the first stage is implemented - the conversion of sensor signals into a single output signal d, linearly related to the parameter of the oscillation curve A. Then the second stage is the implementation of this conversion on a doparcally fixed rod with zero pinch. At the same time, d d, Л А, that when substituted into equality

(6)

gives

B

qAo

(7)

and, accordingly, a dependency is established.

 AB - -5

about

9A

The third, final stage - obtaining - characteristics of the level of the rod h A - A

The device implements the form of communication of the characteristic with the output signal

.five

R

 (d d °).

cos

0

five

0

five

0

in the device implementation example, the pinching characteristic is measured to determine the longitudinal force acting in the rod. Electrodynamic transducers are used as sensors, producing an emf proportional to the amplitude and oscillation frequency E kfV, and the frequency lies in the range of 20 - 55 Hz.

Because all three controlled rod sections; (O, + d, -d) oscillate with one frequency and in-phase, the conversion of the characteristic A to the relation of the EMF B preserves the form of equality (5). The internal resistance of all sensors is 500 Ω, the ratio of the conversion factors q is 1, and condition k is fulfilled by selecting sensors with an error of no more than 0.1%. The sensors are located in the quarter of the span of the rod (a 2/4), therefore the basic value is -1 - w.

A 2 C0S

35

oh, 40

45

50

55

As the adjusting resistor 11, a precision wire potentiometer is used, which has an error of linear conversion resistance - angle not more than 0.3%. It is equipped with a circular reading scale 12 with a division of 55 cm / / div. The impedance of the variable resistor in the base state is R 45.1 kΩ. Accordingly, Rg R + 2G 46.1 kΩ.

According to equation (7), the resistance of a kΩ resistor is calculated and selected. It corresponds to R g 32 kOhm. Known resistors are used as constant resistances in the measuring circuit.

An analog-to-digital converter with a four-bit indication of the potential level of the node 9 was used as a null indicator. Feedback is carried out by an operator who has 32.5

: R -

The second one selects the position of the potentiometer slider from the condition of minimum reading of the null indicator.

The mechanical communication of the reference scale with the movable contact of the potentiometer is made adjustable so that in the basic state the zero reading can be set on the scale d 0. Due to this, the determination of the characteristic of the rod pinch level simplifies:

 (2 cos - | 5)

1,414

55

- | about d

0

d 0,0169. (ten)

, 46100

As can be seen from equations (9) and (10), the conversion factor of the output signal d to the desired characteristic h is completely independent of the conversion factors of the sensors k and their ratio q. In addition, there are no inaccuracies associated with the operations of amplification and signal acquisition, as well as with the interpretation of waveforms. As a result, pinch measurement error is reduced tenfold.

ten

fS

,

20

25

Claims (1)

The invention The device for measuring the clamping of a rod in a construction, including vibration amplitude sensors installed in the center and at the ends of the rod, characterized in that, in order to improve the measurement accuracy, it is equipped with a constant resistor, an adjustment resistor with a reference device resistance, zero-potential indicator with feedback, and one output of the sensor installed in the center of the rod, grounded, and the other output through serially interconnected fixed resistor, A cable resistor and one of the sensors mounted on one end of the rod are connected to one of the terminals of the sensor mounted on the other end of the rod, the other terminal of which is grounded, and the moving contact of the adjusting resistor is feedback connected to the zero potential indicator, connected to the common connection point of the DC and control resistor. .. ., j3 ffi .m y) yaCOsf-. y a -ySco $ 4}. fig.Z