RU2724993C1 - Method of monitoring force action on ferromagnetic rod element - Google Patents

Abstract

FIELD: measuring equipment.SUBSTANCE: invention relates to measurement instruments. Essence of invention consists in the fact that method of monitoring of force action on ferromagnetic rod element additionally includes stages, on which a ferromagnetic rod element (FRE) with a temperature sensor FRE is placed inside an electromagnetic head (EMH) coil with a temperature sensor EMH, then connecting said electromagnetic pair and said temperature sensors with a monitoring system equipped with its own temperature sensor, previously calibrating the monitoring system, placing it in a special housing, further from the system microcontroller, current pulses are forced to the EMH, amplified by the power unit of the system, with a given frequency and amplitude, and force action on FRE (σ) at a given moment in time is calculated depending on the value of variation of the average value of the measured voltage (Uavg), coil temperature EMH (T1), temperature FRE (T2) and temperature of the monitoring system (T3) based on a given mathematical relationship.EFFECT: providing continuous monitoring of stress-strain state of ferromagnetic structural rod elements, high reliability of measurements.1 cl, 2 dwg

Description

The invention relates to the field of measuring devices, and in particular to methods for continuous monitoring of ferromagnetic rod elements of building structures under the influence of tensile-compression forces, such as cable-stayed and suspension systems, tensile and conventional reinforcement of reinforced concrete structures, bearing cables of movable bridges and lifting mechanisms.

Known methods for determining mechanical stresses using a magnetic circuit to magnetize the product and calculate the complex signal spectrum (RU 2195636, publ. 12/27/2002, RU 2189020, publ. 09/10/2002, RU 2441227, publ. 27.01.2012, RU 2527310, publ. 27.08 .2014, RU 2527666, publ. 09/10/2014). The methods are developed taking into account the relationship of mechanical stresses in a ferromagnetic material with magnetic properties, which manifests itself in the form of the Villari effect (Physical Encyclopedia). Known methods are applicable in cases of periodic checks for defects. However, these methods do not take into account the effects of temperatures that affect the determination of the value of mechanical stress and do not allow high accuracy to continuously monitor the stress-strain state of building structures.

Closest to the claimed one is a method for measuring mechanical stresses in long ferromagnetic structures with a symmetrical section such as rails (RU 2521753, publ. 1.07.2014), according to which the product is pre-magnetized using permanent magnets or by passing current through it. The method is based on the magnetoelastic effect arising under the action of mechanical deformations in a ferromagnetic symmetrical product (Villari effect), and is carried out using movable inductive sensors to scan the rail section.

The known method allows to identify defects and register the presence of mechanical stress in the product, but it does not determine the reliable value of this voltage. The system is not calibrated and does not take into account the effects of temperature. This method is applicable in the case of periodic checks for defects, but for continuous monitoring of metal core elements of building structures, for example, ropes of cable-stayed and hanging systems, cables of hoisting mechanisms, prestressed and ordinary reinforced concrete structures, etc., this method is not applicable.

The technical result is the provision of continuous monitoring of the stress-strain state of ferromagnetic rod structural elements, such as load-bearing cables of cable-stayed and suspension systems, reinforcing elements, etc., and increasing the reliability of the method by taking into account the temperature effect of the environment at each measurement of the magnitude of the force effect, and also pre-calibration of the monitoring system.

The specified technical result is achieved by the fact that the method of monitoring the force on the ferromagnetic rod element includes measuring the force on the rod and is based on the magnetoelastic effect that occurs under the action of mechanical deformations in the ferromagnetic rod element. According to the invention, a ferromagnetic rod element (FSE) is placed inside the coil of the electromagnetic head (EMG) with the EMG temperature sensor and the FSE temperature sensor, then this electromagnetic pair and these temperature sensors are connected to a monitoring system equipped with its own temperature sensor. The monitoring system is pre-calibrated and placed in a special case. Next, from the microcontroller of the system, current pulses are fed to the EMG, amplified by the power unit of the system, with a given frequency and amplitude, and the magnitude of the force effect on the FSE (σ) at a given time is calculated depending on the magnitude of the change in the average value of the measured voltage (U _avg ), temperature coils

EMG (T ₁ ), FSE temperature (T ₂ ) and monitoring system temperature (T ₃ ) according to a given mathematical relationship:

Where

α, β, γ, ε - parameters determined during the calibration of the monitoring system,

i is the summation index;

n is the highest degree with which the variables enter the model,

Next, the value of σ is compared with a given acceptable value and the comparison data is transmitted to the operator console for decision making.

In addition, EMG is performed in the form of a hollow cylinder with a coil, which provides the creation of an alternating magnetic field in the FSE while transmitting current pulses.

The invention is illustrated by the following figures.

In FIG. 1 shows a block diagram of a system for monitoring the force effect on a ferromagnetic core element of a building structure according to the claimed method.

In FIG. 2 is an isometric view of an electromagnetic head with a core ferrimagnetic element (electromagnetic pair) placed inside it.

In FIG. 1 and 2 are shown:

1 - microcontroller (MK);

2 - measuring unit;

3 - power unit;

4 - electromagnetic head (EMG);

5 - EMG temperature sensor;

6 - temperature sensor ferromagnetic rod element (FSE);

7 - power supply of the power unit 3;

8 - operator panel;

9 - power supply monitoring system;

10 - temperature sensor of the monitoring device (inside the cabinet);

11 - FSE in the shell;

12 - cable FSE.

The method is as follows.

Preliminarily, inside the EMG 4 coil, FSE 11 is placed, forming an electromagnetic pair. Temperature sensors 5 and 6 are installed in the EMG 4 in such a way that they measure the temperature of the EMG 4 coil and the temperature of the FSE, respectively. Before installation on the structure, the monitoring system is calibrated, i.e. determine the constant values of α, β, γ, ε, which are the parameters of the mathematical model, depending on the physical characteristics of the FSE 1. The system is placed in a special case (not shown).

A temperature sensor 10 is installed in the housing. When power is supplied from a stabilized power source 7 (the voltage of the power source is stabilized, and the current value is measured), the power unit 3 generates current pulses with a frequency and amplitude set by MK 1 and transmits to EMG 4, the cavity of the coil which is placed FSE 11 (Fig. 2).

In this case, on a low-resistance resistor (not shown) of the measuring unit 2, a drop in the average voltage value is proportional to the current flowing through the EMG coil 4.

According to the Villari effect, when the length (size) of a ferromagnetic rod element changes, its magnetic properties (magnetic permeability) change. Because Since EMG 4 and FSE 11 form an electromagnetic pair, the current pulses flowing through EMG 4 generate an alternating magnetic field in the region of FSE 11. A change in the magnetic properties during deformation of FSE 11 can be detected by measuring the average value of current pulses.

The power unit 3 delivers amplified AC pulses to the EMG 4, in which they change shape and value depending on the magnitude of the force action σ arising at the FSE 11. Then the signal enters the measuring unit 2, which measures the value of the integral voltage (U _avg ) s EMG 4 and then transfers it to MK 1.

MK 1 calculates the load of the force impact σ on the FSE 11 taking into account the temperature readings T ₁ , T ₂ and T ₃ from sensors 5, 6 and 10, as well as taking into account the values of α, β, γ, ε determined during EMG 4 calibration according to the following mathematical dependence :.

For further processing and interpretation of digitized data, information from MK 1 is sent to the operator console 8, for example, to a PC via USB.

The following describes the process of monitoring the force effect on a ferromagnetic (steel) cable with a sheath (strand) of a cable-stayed bridge.

During the installation of the cable-stayed system, a steel cable 12 with a sheath, which is a FSE 11, was placed in the cavity of the EMG 4 coil, installed and secured. Inside the EMG coil 4, temperature sensors 5 and 6 were previously placed. In this form, an electromagnetic pair was installed inside the cable-stayed bridge system.

An external connecting cable was connected to the monitoring system with its own temperature sensor 10 (Fig. 1), which was placed in a separate cabinet.

When power was supplied to the monitoring system from unit 9, MK 1 generated short current pulses, setting a frequency equal to 10 Hz with a pulse duration of 5 ms and a frequency of 1 hour.

The power unit 3, which is a full key bridge circuit with field-effect transistors with drivers and optocouplers, converted the signals into current pulses with similar time characteristics and an amplitude of the order of 7 A and transmitted them to EMG 4.

Temperature sensors 5, 6, and 10, at the request of MK 1, transmitted the following readings to the input of MK 1:

T ₁ = 23 ° C, T ₂ = 27 ° C, T ₃ = 42 ° C.

At the output of the measuring unit 2, the value of the integrated voltage U _{avg of the} secondary current was 2950 mV. As a result of calculations of MK 1, the magnitude of the force impact σ on the cable was 20,000 N. The permissible value of a is not more than 25,000 N.

If the value of σ were above 25000 N, the system would inform the operator of the force σ exceeding the permissible value in the cable. Such an effort would lead to the destruction of the cable.

After 1 hour, the system again polled, generated pulses and recorded the value of U _avg . The survey results: the values of T ₁ , T ₂ , T ₃ remained the same, but the value of U _avg . became equal to 2405 mV. The calculation showed that the value of σ was equal to zero, which indicated an anomaly characteristic of the cable termination. A message about this from MK 1 was received by the operator console.

In addition to the specified technical result, the claimed method has several advantages in comparison with the known, namely:

- the method works in the temperature range from -50 to + 70 ° C, which allows it to be used practically throughout the territory of Russia under any weather conditions without reducing the technical characteristics of the system;

- the ability to install EMG and electromagnetic pairs in reinforced concrete structures at the concreting stage without the risk of damage to the elements of the device;

- the monitoring system implementing the inventive method does not contain moving parts and elements sensitive to mechanical damage, which provides high wear resistance and reliability in operation.

The inventive method can be used to monitor the force effects of the following building structures:

- cable-stayed and hanging systems;

- prestressed and ordinary reinforcement of reinforced concrete structures;

- bearing cables of drawbridges and hoisting mechanisms.

Claims (8)

1. A method for monitoring the force on a ferromagnetic rod element, including measuring the force on the rod and based on the magnetoelastic effect arising from mechanical deformations in the ferromagnetic rod element, characterized in that inside the coil of the electromagnetic head (EMG) with a temperature sensor EMG is placed a ferromagnetic rod element (FSE) with a temperature sensor FSE, then connect this electromagnetic pair and these temperature sensors with a monitoring system equipped with its own temperature sensor, pre-calibrate the monitoring system place it in a special case, then from the microcontroller of the system, current pulses are fed to the EMG, amplified by the power unit of the system, with a given frequency and amplitude, and the magnitude of the force effect on the FSE (σ) at a given time is calculated depending on the magnitude of the change in the average value of the measured voltage (U _avg ), EMG coil temperature (T ₁ ), FSE temperature (T ₂ ) and monitoring system temperature (T ₃ ) according to a given mathematical relationship:

where α, β, γ, ε are the parameters determined during the calibration of the monitoring system, i is the summation index; n is the highest degree with which the variables enter the model,

; then compare the value of σ with a given allowable value and transmit the comparison data to the operator console for decision-making. 2. A method for monitoring the force effect on a ferromagnetic rod element according to claim 1, characterized in that the EMG is performed in the form of a hollow cylinder with a coil, which ensures the creation of an alternating magnetic field in the FSE when current pulses are transmitted.

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