CN103868630A - Inverse magnetostrictive effect-based suspender tension sensor and tension measuring method thereof - Google Patents

Abstract

A boom tension sensor based on the inverse magnetostrictive effect, which is composed of two clamps, a connecting rod, two excitation coils and a detection coil; one end of the clamp forms a clamping part, and the other end of the clamp forms a connecting part, and the clamp passes through the clamp The holding part is fixedly connected with the suspender to be tested, and the fixture is connected with the connecting rod through the connecting part; the excitation coil is wound on the position between the connecting part and the clamping part on the fixture, and the detection coil is wound between the two connecting parts on the connecting rod The connecting rod forms a yoke, the clamp forms a magnetic pole, and the yoke, the two magnetic poles and the suspender to be tested between the two magnetic poles form a closed magnetic circuit. The beneficial technical effects of the invention are: greatly simplifying the installation process of the tensile stress sensor based on the inverse magnetostrictive effect, expanding the adaptability of the tensile stress sensor to the environment, and providing a new means for the stress monitoring of the suspender.

Description

Suspender tension sensor and its tension measurement method based on inverse magnetostrictive effect

technical field

The invention relates to an internal stress measurement technology for steel members of cables and rods, in particular to a suspender tension sensor based on an inverse magnetostrictive effect and a tension measurement method thereof.

Background technique

The suspenders in tie-bar arch bridges can generally be made into rigid suspenders or flexible suspenders. Rigid boom applications are as follows:

The boom is an axial tension member. It is easy to crack when it is made of reinforced concrete members, and the cross-sectional size is also large. Therefore, prestressed members are often used. By applying precompressive stress to the boom, it can avoid the boom under load Cracking, so called a rigid boom. The flexible suspender is made of prestressed high-strength steel wire bundle or steel strand, which only bears the action of tension and cannot be compressed. It is more reasonable and convenient to use when the bridge is wide, the distance between the suspenders is large, and the load is also large. Whether it is a rigid boom or a flexible boom, the above requires accurate measurement of its tension.

At present, there are vibration frequency method and electromagnetic measurement method through the installation of sleeve type magnetic elastic sensor that can be initially used for boom tension measurement at home and abroad. The vibration frequency method is to install the acceleration sensor on the boom to measure the natural frequency of the boom vibration, and then use the mechanical parameters of the boom to establish a structural model and perform modal analysis to obtain the relationship between the tension and the vibration frequency, thereby calculating the tension. In addition to the indirect measurement method, it is inconvenient to measure the frequency of the boom through random vibration, and often requires external excitation.

When a ferromagnetic material is subjected to external stress, its geometric parameters such as length and cross-sectional area and internal stress will change. This change in geometric parameters and internal stress will eventually lead to changes in the magnetic characteristic parameters (such as magnetic permeability) of ferromagnetic materials. . When the magnetic characteristic parameter (magnetic permeability) changes due to the change of force, if electromagnetic excitation is applied to the ferromagnetic material, the change of its magnetic characteristic parameter can be measured in an appropriate way to infer its stress state.

At present, the research and application of stress measurement based on inverse magnetostriction for cable-strut steel members is still in its infancy. For the suspender, the common measurement method is: use the suspender to be tested as the iron core, and set the induction coil outside the iron core. and the excitation coil, the tested boom is not only the iron core of the excitation coil but also the iron core of the induction coil. This measurement method needs to connect the coil to the outside of the tested boom, so in the prior art, either in the production or installation of the boom The coil sleeve is put on the boom in advance, or the coil can only be wound on site. The installation of the measuring device is very troublesome, which greatly limits its application and measurement accuracy.

Contents of the invention

Aiming at the problems in the background technology, the present invention proposes a boom tension sensor based on the inverse magnetostrictive effect, the structure of which is: the boom tension sensor consists of two clamps, a connecting rod, two excitation coils and a detection coil Composition; one end of the clamp forms a clamping part, the other end of the clamp forms a connecting part, the clamp is fixedly connected to the suspension rod to be tested through the clamping part, and the clamp is connected to the connecting rod through the connecting part; the excitation coil is wound on the connecting part and the clamp The position between the holding parts, the detection coil is wound at the position between the two connecting parts on the connecting rod; the connecting rod forms a yoke, the clamp forms a magnetic pole, the yoke, the two magnetic poles and the connection between the two magnetic poles The suspenders to be tested form a closed magnetic circuit.

The principle of the above-mentioned boom tension sensor is: after the yoke, the left and right magnetic poles and the suspender to be tested between the two magnetic poles form a closed magnetic circuit, at this time, only the output induced voltage on the detection coil By measuring, we can know the external stress that the suspender to be tested bears under the current situation. Compared with the prior art, the structure proposed by the present invention has the advantages of simple structure and convenient disassembly and assembly. It does not need to pre-set sensors when making or installing suspenders, nor does it need to wind coils on site. The installation of sensors on the booms in operation greatly expands the application environment of sensors based on the inverse magnetostrictive effect in stress measurement.

In order to simplify the structure of the sensor for manufacturing and improve the aesthetics of the sensor, the present invention also makes the following improvement on the basis of the foregoing solution: the axial direction of the connecting rod is parallel to the axial direction of the suspension rod to be tested. Based on the same reason as the aforementioned improvement, the present invention also proposes the following preferred solution for the structure of the connecting rod and the clamp: the axial direction of the connecting rod is perpendicular to the axial direction of the clamp.

The present invention also proposes the following optimal solution for the connecting rod: the connecting rod is in the shape of a cuboid, and the connecting rod is provided with two axially parallel mounting holes, the shape of the mounting holes matches the shape of the connecting part, and the connecting part is plugged into the mounting hole Inside, the connection part and the mounting hole are interference fit.

Preferably, the clamping part is composed of two clamping blocks, one of which is an integral structure with the clamp body; semicircular notches are provided on the two clamping blocks, and the two semicircular notches will be The measuring boom is clamped inside; the two clamping blocks are connected by bolts.

The present invention also proposes a method for measuring the tension of the boom based on the inverse magnetostrictive effect, the hardware device on which the measurement method depends is the aforementioned tension sensor for the boom; the measurement method is:

1) Install the aforementioned boom tension sensor on the boom to be tested;

2) Apply electromagnetic excitation to the boom tension sensor regularly, read the output voltage value of the boom tension sensor under the current electromagnetic excitation conditions, and calculate the pulling force;

3) Compare the calculated pulling force with the set safety threshold: if the calculated pulling force is greater than the safety threshold, an alarm will be issued; if the pulling force is less than the safety threshold, only a record will be made without an alarm, and return to step 2);

In step 2), the pulling force σ(t) is calculated according to the following formula:

Among them, N _induction is the number of _turns of the induction coil; S is the cross-sectional area of the boom to be tested; H _m is the magnetic field amplitude of electromagnetic excitation; V is the output voltage of the boom tension sensor under the current electromagnetic excitation condition; m ₁ is the first-order Taylor expansion coefficient related to the material of the suspender, and m ₁ can be obtained by performing simulation experiments on samples with the same material as the suspender to be tested.

The beneficial technical effects of the invention are: greatly simplifying the installation process of the tensile stress sensor based on the inverse magnetostrictive effect, expanding the adaptability of the tensile stress sensor to the environment, and providing a new means for the stress monitoring of the suspender.

Description of drawings

Fig. 1, structural representation one of the present invention;

Figure 2. Schematic diagram of the fixture structure;

Fig. 3, the structural representation two of the present invention;

The names of the parts corresponding to each mark in the figure are: fixture 1, clamping part 1-1, connecting part 1-2, clamping block 1-3, connecting rod 2, excitation coil 3, detection coil 4, crane to be tested pole 5.

Detailed ways

A boom tension sensor based on the inverse magnetostrictive effect, its structure is: the boom tension sensor is composed of two clamps 1, a connecting rod 2, two excitation coils 3 and a detection coil 4; one end of the clamp 1 A clamping part 1-1 is formed, and the other end of the clamp 1 forms a connecting part 1-2. The clamp 1 is fixedly connected to the suspension rod 5 to be tested through the clamping part 1-1, and the clamp 1 is connected to the connecting rod 2 through the connecting part 1-2. The excitation coil 3 is wound at the position between the connecting part 1-2 and the clamping part 1-1 on the clamp 1, and the detection coil 4 is wound at the position between the two connecting parts 1-2 on the connecting rod 2; The connecting rod 2 forms a yoke, the clamp 1 forms a magnetic pole, and the yoke, the two magnetic poles and the suspension rod 5 to be tested between the two magnetic poles form a closed magnetic circuit.

Further, the axial direction of the connecting rod 2 is parallel to the axial direction of the suspension rod 5 to be tested.

Further, the axial direction of the connecting rod 2 is perpendicular to the axial direction of the fixture 1 .

Further, the connecting rod 2 is in the shape of a cuboid, and the connecting rod 2 is provided with two axially parallel mounting holes, the shape of the mounting holes matches the shape of the connecting part 1-2, and the connecting part 1-2 is inserted into the mounting hole , The connecting part 1-2 is interference fit with the mounting hole.

Further, the clamping part 1-1 is composed of two clamping blocks, one of which is an integral structure with the body of the fixture 1; semicircular notches are arranged on the two clamping blocks, and the two semicircular The suspender 5 to be tested is clamped by the shaped gap; the two clamping blocks are connected by bolts.

A method for measuring the tension of a boom based on the inverse magnetostrictive effect, the hardware involved includes a tension sensor of the boom, and the tension sensor of the boom consists of two clamps 1, a connecting rod 2, two excitation coils 3 and a detection coil 4 Composition; one end of the clamp 1 forms a clamping part 1-1, the other end of the clamp 1 forms a connecting part 1-2, the clamp 1 is fixedly connected to the suspension rod 5 to be tested through the clamping part 1-1, and the clamp 1 passes through the connecting part 1 -2 is connected with the connecting rod 2; the excitation coil 3 is wound on the clamp 1 between the connecting part 1-2 and the clamping part 1-1, and the detection coil 4 is wound on the connecting rod 2 between the two connecting parts 1-2 The connecting rod 2 forms a yoke, the clamp 1 forms a magnetic pole, and the yoke, the two magnetic poles and the suspender 5 to be tested between the two magnetic poles form a closed magnetic circuit;

The monitoring methods are:

1) Install the aforementioned boom tension sensor on the boom 5 to be tested;

2) Apply electromagnetic excitation to the boom tension sensor regularly, read the output voltage value of the boom tension sensor under the current electromagnetic excitation conditions, and calculate the pulling force;

3) Compare the calculated pulling force with the set safety threshold: if the calculated pulling force is greater than the safety threshold, an alarm will be issued; if the pulling force is less than the safety threshold, only a record will be made without an alarm, and return to step 2);

In step 2), the pulling force σ(t) is calculated according to the following formula:

Wherein, N _induction is the number of turns of the induction coil; S is the cross-sectional area of the suspension rod 5 _{to be measured} ; H _m is the magnetic field amplitude of electromagnetic excitation; V is the output voltage of the suspension rod tension sensor under the current electromagnetic excitation condition; m ₁ is the first-order Taylor expansion coefficient related to the material of the suspender, and m ₁ can be obtained by performing a simulation experiment on a sample made of the same material as the suspender 5 to be tested.

The aforementioned formula for calculating the pulling force is derived as follows:

When a certain form of exciting magnetic field is adopted to magnetize the suspender axially, the induced output voltage caused by the external force and the temperature change of the material varies according to the different exciting magnetic fields; the exciting magnetic field can be divided into steady magnetic field excitation, Periodic pulsed magnetic field excitation and alternating magnetic field excitation, etc.;

Due to the electromagnetic induction between the excitation and induction coil of the sensor, according to Faraday's law of electromagnetic induction, the magnetic flux passing through the coil must be changed, so a periodic pulse current with a certain duty cycle and a fixed amplitude is applied to the excitation coil. , so as to generate a periodic pulsed excitation magnetic field, then, without considering the temperature, the relationship between the tension acting on the boom and the sensor output (that is, the integral induced voltage) is shown by the following formula:

表示磁场变化；μ(0,0)为空气在0摄氏度下的磁导率；S_吊为吊杆横截面积；m₁为与吊杆材料相关的一阶泰勒展开实验系数；m₂为与吊杆的材料相关的二阶泰勒展开系数；σ(t)为作用在吊杆上的拉力；Among them, V _induction (t) is the total output induction voltage; N _induction is the number of turns of the induction coil; μ ₀ is the air permeability; S _is the air gap area of the inverse magnetostrictive boom sensor section; H (t) is The magnetic field generated by the exciting coil current;

Indicates the change of the magnetic field; μ(0,0) is the magnetic permeability of air at 0 degrees Celsius; S is _the cross-sectional area _of the boom; m ₁ is the first-order Taylor expansion experimental coefficient related to the material of the boom; Second-order Taylor expansion coefficient related to the material of the suspender; σ(t) is the tension acting on the suspender;

The above formula integrates the time from t ₀ to t:

则有：If H(t)=H _m , then H(t ₀ )=-H _m , let

Then there are:

It can be known from the above formula that the induced integral voltage and the applied external force have a quadratic function relationship. In actual engineering, the above formula can be simplified into a linear function through linear fitting, then the above formula can be simplified as:

为与感应线圈匝数、激励磁场、缆索截面积、材料初始磁导率等有关的电压常数；则传感器的输出灵敏度S_灵敏度可用下式表达：in,

is the voltage constant related to the number of turns of the induction coil, the excitation magnetic field, the cross-sectional area of the cable, the initial permeability of the material, etc.; then the output sensitivity S _sensitivity of the sensor can be expressed by the following formula:

The transformation of the above formula can be obtained

Claims (6)

1. The utility model provides a jib force sensor that pulls based on contrary magnetostrictive effect which characterized in that: the suspender tension sensor consists of two clamps (1), a connecting rod (2), two exciting coils (3) and a detecting coil (4); one end of the clamp (1) forms a clamping part (1-1), the other end of the clamp (1) forms a connecting part (1-2), the clamp (1) is fixedly connected with a to-be-tested suspender (5) through the clamping part (1-1), and the clamp (1) is connected with the connecting rod (2) through the connecting part (1-2); an excitation coil (3) is wound at a position between the connecting part (1-2) and the clamping part (1-1) on the clamp (1), and a detection coil (4) is wound at a position between the two connecting parts (1-2) on the connecting rod (2); the connecting rod (2) forms a yoke, the clamp (1) forms a magnetic pole, and the yoke, the two magnetic poles and the to-be-detected suspender (5) between the two magnetic poles form a closed magnetic loop.

2. The inverse magnetostrictive effect-based boom tension sensor according to claim 1, wherein: the axial direction of the connecting rod (2) is parallel to the axial direction of the suspender (5) to be measured.

3. The inverse magnetostrictive effect-based boom tension sensor according to claim 2, wherein: the axial direction of the connecting rod (2) is vertical to the axial direction of the clamp (1).

4. The inverse magnetostrictive effect-based boom tension sensor according to claim 1, wherein: the connecting rod (2) is cuboid, two axially parallel mounting holes are formed in the connecting rod (2), the shape of each mounting hole is matched with that of the connecting portion (1-2), the connecting portions (1-2) are inserted into the mounting holes, and the connecting portions (1-2) are in interference fit with the mounting holes.

5. The inverse magnetostrictive effect-based boom tension sensor according to claim 1, wherein: the clamping part (1-1) consists of two clamping blocks, wherein one clamping block and the clamp (1) body are of an integral structure; the two clamping blocks are provided with semicircular gaps, and the two semicircular gaps clamp the suspender (5) to be tested; the two clamping blocks are connected through bolts.

6. A suspender tension measuring method based on the inverse magnetostriction effect is characterized in that: the related hardware is provided with a suspender tension sensor, and the suspender tension sensor consists of two clamps (1), a connecting rod (2), two exciting coils (3) and a detecting coil (4); one end of the clamp (1) forms a clamping part (1-1), the other end of the clamp (1) forms a connecting part (1-2), the clamp (1) is fixedly connected with a to-be-tested suspender (5) through the clamping part (1-1), and the clamp (1) is connected with the connecting rod (2) through the connecting part (1-2); an excitation coil (3) is wound at a position between the connecting part (1-2) and the clamping part (1-1) on the clamp (1), and a detection coil (4) is wound at a position between the two connecting parts (1-2) on the connecting rod (2); the connecting rod (2) forms a yoke, the clamp (1) forms a magnetic pole, and the yoke, the two magnetic poles and the to-be-detected suspender (5) between the two magnetic poles form a closed magnetic loop;

the monitoring method comprises the following steps:

1) the suspender tension sensor is arranged on a suspender (5) to be measured;

2) electromagnetic excitation is applied to the suspender tension sensor regularly, the output voltage value of the suspender tension sensor under the current electromagnetic excitation condition is read, and tension is calculated;

3) comparing the calculated tension with a set safety threshold: if the calculated tension is greater than the safety threshold, an alarm is sent; if the tension is smaller than the safety threshold, only recording and not alarming, and returning to the step 2);

in step 2), the pulling force σ (t) is calculated according to the following formula:

wherein N is_InductionThe number of turns of the induction coil; s_{Hanging crane}The cross section area of the suspender (5) to be measured; h_mA magnetic field amplitude that is an electromagnetic excitation; v is the output voltage of the suspender tension sensor under the current electromagnetic excitation condition; m is₁M being the first order Taylor expansion coefficient related to the material of the boom₁Can be obtained by carrying out simulation experiment on a sample which is the same as the material of the suspender (5) to be measured.

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