JP4691277B2 - Stress measuring apparatus and stress measuring method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a stress measuring apparatus and a stress measuring method for measuring on the site how much stress is acting on steel materials or the like constituting an already constructed structure.
[0002]
[Prior art]
For example, it is necessary to quantitatively measure how much internal stress is acting on a steel material constituting a structure such as a bridge in order to evaluate the safety of the structure. That is.
[0003]
One of the methods for measuring the internal stress of a steel material as a stress measurement object is a magnetostrictive stress measurement method. In this magnetostrictive stress measurement method, as disclosed in, for example, Japanese Patent Application Laid-Open No. 5-231961, when a load is applied to a steel material that is a ferromagnetic material, anisotropy occurs in the magnetization characteristics (easily magnetized in the load acting direction). The difference between the magnetization characteristics in both directions is measured with a measuring probe, and the direction and magnitude of the internal stress acting on the steel material are measured. It is to measure. That is, the main stress difference corresponding to the obtained voltage signal is measured. The main stress difference is a difference (σ1−σ2) between the main stress (σ1) in the load application direction and the main stress (σ2) in the direction perpendicular to the load application direction.
[0004]
In such a magnetostrictive stress measurement method, demagnetization before stress measurement is an important requirement. FIG. 8 shows a comparison of sensitivity characteristics between the case where measurement is performed without demagnetization (without demagnetization) and the case where measurement is performed after demagnetization (with demagnetization). As is apparent from this figure, there is a large difference in measurement accuracy between when demagnetization is performed and when demagnetization is not performed. For this reason, stress measuring apparatuses having means for degaussing the object to be stressed are widely used.
[0005]
FIG. 5 shows a conventional example of a stress measuring apparatus provided with such a demagnetizing means. The stress measuring apparatus 100 includes an apparatus main body 101, a measurement probe 102 connected to the apparatus main body 101 with a cord 102a, and a demagnetizing head 103 connected to the apparatus main body 101 with a code 103a.
[0006]
The circuit configuration of the stress measuring apparatus 100 is shown in FIGS. As shown in these drawings, the stress measurement apparatus 100 includes a measurement circuit unit 110 and a demagnetization circuit unit 120.
The measurement circuit unit 110 includes a signal generator 111, a measurement amplifier 112, and a synchronous rectifier 115 provided in the apparatus main body 101, and an excitation coil 113 and a detection coil 114 provided in the measurement probe 102. It has a configuration.
The degaussing circuit unit 120 includes a two-phase signal generator 121 and a pair of demagnetizing amplifiers 122a and 122b provided in the apparatus main body 101, and a pair of demagnetizing coils 123a and 123b provided in the degaussing head 103. It has a configuration with.
[0007]
In the stress measuring method using the stress measuring apparatus 100, first, as a degaussing step, the degaussing head 103 is brought close to the steel material S as the object to be measured, and the steel material S is demagnetized. That is, as shown in FIG. 6, the two-phase signal generator 121 generates two types of alternating current signals whose phases are different from each other by 90 °, and amplifies the signals by flowing them through demagnetizing amplifiers 122a and 122b, respectively. These signals are passed through the degaussing coils 123a and 123b, respectively. By doing so, magnetic fields having a phase difference of 90 ° are generated in the degaussing coils 123a and 123b, and the steel material S is excited while the direction of magnetization is agitated.
[0008]
When the demagnetization is completed, in the subsequent measurement process, the measurement probe 102 is brought close to the demagnetized portion of the steel material S, and the stress measurement is performed. That is, an alternating current is generated by the signal generator 111, amplified by the measurement amplifier 112, and passed through the excitation coil 113. By doing so, the steel material S is excited, and an output voltage is induced in the detection coil 114 by this excitation. This output voltage flows to the synchronous rectifier 115 and is detected and synchronized / rectified with the alternating current from the signal generator 111, and is output to the output signal processing unit P provided outside the stress measuring device 100. The main stress difference is obtained through flow and calculation processing.
[0009]
[Problems to be solved by the invention]
Such a stress measurement apparatus 100 has a degaussing head that is independent from the measurement probe, and the circuit portions are also independent of each other. This complicates the device configuration and circuit configuration, increases the number of parts, and increases the size and weight of the device.
Further, the measurer had to change the degaussing head and the measurement probe, and the workability at the measurement site was never good.
[0010]
The present invention has been made in view of the above circumstances, and can reduce the number of parts, improve the reliability and durability of the apparatus, simplify the stress measurement work, and improve the measurement efficiency and measurement accuracy. An object of the present invention is to provide a stress measuring apparatus and a stress measuring method that can be used.
[0011]
[Means for Solving the Problems]
The present invention includes an excitation coil and a detection coil that are brought close to the object to be stressed, and an excitation current is passed through the excitation coil to excite the object to be stressed and output to the detection coil by the excitation. A stress measurement device for inducing a voltage and detecting the output voltage to measure a stress acting on the stressed object to be measured, and two types of phases generated by a two-phase signal generator and having a phase difference of 90 ° Current generating means for flowing the AC current to the excitation coil and the detection coil as a degaussing current for degaussing the stress measurement object.
The present invention is also characterized in that the exciting coil and the detecting coil have the same wire thickness and number of turns.
[0012]
As described above, the excitation coil and the detection coil for measuring the stress also have a function for demagnetizing the object to be stressed, so it is necessary to provide a degaussing head separately from the measurement probe. Therefore, the number of parts can be reduced and the device configuration or circuit configuration can be simplified.
[0014]
As described above, since two types of alternating currents are generated by the two-phase signal generator, one signal generator can be installed in the stress measuring device, and the circuit configuration can be simplified. . Moreover, since two types of alternating currents are generated by the same component, distortion of the alternating current waveform and phase shift can be suppressed, and the alternating current can be generated more accurately.
[0015]
Further, the present invention is the above-described stress measuring apparatus, wherein the first core includes a pair of shaft portions, and the first core portion includes the same pair of shaft portions arranged orthogonal to the arrangement direction of the first cores. A core member integrated with two cores, winding the conductive wire around the first core to constitute the exciting coil, and winding the conductive wire around the second core to constitute the detecting coil. It is characterized by that.
[0016]
As described above, since the excitation coil and the detection coil are integrated, demagnetization and stress measurement can be performed while the distance between the coils is always kept constant.
[0017]
Further, the present invention is a stress measurement method using the above-described stress measuring device, wherein a demagnetizing step of flowing a demagnetizing current from the current generating means to each of the exciting coil and the detecting coil, and the current generation A measuring step of passing an exciting current from the means to the exciting coil, inducing an output voltage in the detecting coil, detecting the output voltage, and measuring a stress acting on the stress measurement object. It is characterized by including.
[0018]
As described above, since the stress is measured after degaussing the object to be stressed, the stress can be measured with very high accuracy.
[0019]
Further, the present invention is the stress measurement method described above , wherein the excitation coil and the detection coil are set in a state where the current value of the demagnetizing current flowing through the excitation coil and the detection coil is a peak value. The demagnetization process is started in proximity to the object to be stressed, the current value is gradually decreased from the peak value, and the demagnetization process is terminated when the current value becomes zero. .
[0020]
In this way, the stress measurement object can be degaussed almost certainly in a short time.
[0021]
Further, the present invention is the stress measurement method described above , wherein the excitation coil and the detection coil are set in the state where the current value of the demagnetization current flowing through the excitation coil and the detection coil is 0. The demagnetization step is started in the vicinity of the object to be stressed, the current value is gradually increased from 0 to the peak value, and then gradually decreased from the peak value, and when the current value becomes 0 again, The degaussing step is terminated.
[0022]
In this way, if the excitation coil and the detection coil are brought close to the object to be measured in a state where the current value is 0, a strong magnetic force is generated, so that the stress measuring device can rapidly measure the stress. It is possible to prevent a situation where the object is sucked into the object.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a stress measuring apparatus and a stress measuring method according to the present invention will be described with reference to FIGS. 1 to 4.
[0024]
As shown in FIG. 1, the stress measuring apparatus 1 includes an apparatus main body 2 and a probe 3 connected to the apparatus main body 2 by a cord 3a.
[0025]
The circuit configuration of the stress measuring device 1 is shown in FIGS. This circuit includes a two-phase signal generator 21, a first amplifier 22a, a second amplifier 22b and a synchronous rectifier 25 provided in the apparatus body 2, an excitation coil 24a and a detection coil 24b provided in the probe 3, And a switch 23 for turning on / off the conduction between the second amplifier 22b and the detection coil 24b. Among these, the two-phase signal generator 21, the first amplifier 22 a, and the second amplifier 22 b constitute power generation means 20. The synchronous rectifier 25 is connected to an output arithmetic processing unit P provided outside the stress measuring device 1.
[0026]
The two-phase signal generator 21 generates two types of alternating currents whose phases are different from each other by 90 °, and passes one of the alternating currents to the first amplifier 22a and the other to the second amplifier 22b. . These two types of alternating currents are amplified by the first amplifier 22a and the second amplifier 22b, respectively, and then flow to both the excitation coil 24a and the detection coil 24b if the switch 23 is in an on state. it can. If the switch 23 is in an OFF state, no alternating current can flow from the second amplifier 22b to the detection coil 24b.
3 and 4, the switch 23 is provided between the apparatus main body 2 and the probe 3, that is, in the cord 3 a, but the position provided is from the second amplifier 22 b to the detection coil. The position is not particularly limited as long as it is a position where conduction to 24b can be turned on / off.
[0027]
The probe 3 is provided with a core member 30 as shown in FIG. The core member 30 includes a substantially cylindrical base 31 having a central axis O, and four cores that project from the one end surface side of the base 31 toward the central axis O and are disposed so as to surround the central axis O, that is, a pair of core members 30. The first cores 32a and 32b made up of the shaft parts and the second cores 33a and 33b made up of a pair of shaft parts are integrated. The first cores 32a and 32b that form a pair and the second cores 33a and 33b that also form a pair are orthogonal to each other. The four cores have substantially the same length, volume, and shape.
[0028]
A conductive wire is wound around each of the first cores 32a and 32b and the second cores 33a and 33b to form first coils 41a and 41b and second coils 42a and 42b, respectively. The first coil 41a and the first coil 41b are opposed to each other with the central axis O interposed therebetween, and constitute an exciting coil 24a. The second coil 42a and the second coil 42b are also opposed to each other with the central axis O interposed therebetween, and constitute a detection coil 24b.
[0029]
A stress measurement method using this stress measurement apparatus 1 will be described. This stress measurement method includes a demagnetization step and a measurement step.
First, in the demagnetization step, as shown in FIG. 3, the switch 23 is turned on, and two types of alternating currents as demagnetizing currents are supplied from the current generating means 20 to the exciting coil 24a and the detecting coil 24b. Shed. That is, the two-phase signal generator 21 generates two types of alternating currents whose phases are different from each other by 90 °. The alternating currents are amplified by the first amplifier 22a and the second amplifier 22b, respectively, and flow through the probe 3. Thus, in this degaussing step, the excitation coil 24a and the detection coil 24b perform the same operation as the degaussing coil shown in the conventional example.
In FIG. 3 and the next FIG. 4, the conductive part is indicated by a thick line, and the non-conductive part is indicated by a thin line. Although the alternating current from the two-phase signal generator 21 also flows through the synchronous rectifier 25, the synchronous rectifier 25 does not operate in this demagnetization process.
[0030]
Due to these two types of alternating currents, a magnetic field rotating around the central axis O shown in FIG. 2 is generated in the exciting coil 24a and the detecting coil 24b. As a result, the steel material S is excited while the direction of magnetization is agitated, and the directionality of the magnetization is almost lost and demagnetized.
[0031]
FIG. 3 shows a state in which the probe 3 is close to the steel material (stressed object) S, but there are two types of demagnetization processes.
In the first method, the demagnetizing current is caused to flow in the excitation coil 24 a and the detection coil 24 b in advance as peak values, and the probe 3 is brought close to the steel material S. This state is the starting point of the degaussing process. After starting the demagnetization process, the current value is gradually decreased while maintaining the distance between the steel material S and the probe 3, and the demagnetization process is terminated when the current value becomes zero.
According to the study by the present inventors, the demagnetization of the steel material S can be performed almost certainly in a short time.
[0032]
On the other hand, in the second method, the probe 3 is brought close to the steel material S with the current value of the demagnetizing current flowing through the exciting coil 24a and the detecting coil 24b being 0, that is, without flowing the current. This state is the starting point of the degaussing process. After starting the demagnetization process, the current value is gradually increased from 0 to the peak value while maintaining the distance between the steel material S and the probe 3. Then, the demagnetization process is terminated when the current value becomes 0 again, gradually decreasing from the peak value.
In this way, since no magnetic field is generated in the excitation coil 24a and the detection coil 24b at the start of the demagnetization process, it is possible to prevent a situation in which the probe 3 is suddenly attracted to the steel material S. The workability is very good.
[0033]
In the next measurement step, as shown in FIG. 4, the switch 23 is turned off, and only one of the alternating currents from the current generating means 20 is passed through the exciting coil 24a as the exciting current. That is, the two-phase signal generator 21 generates two types of alternating currents, and these alternating currents flow through the first amplifier 22a and the second amplifier 22b. The current from the second amplifier 22b to the detection coil 24b is Be blocked. By doing so, the excitation coil 24a and the detection coil 24b perform the same operations as the excitation coil and the detection coil shown in the conventional example.
[0034]
One of the two types of alternating current generated by the two-phase signal generator 21 is amplified by the first amplifier 22a and passed through the exciting coil 24a. By doing so, the steel material S is excited, and an output voltage is induced in the detection coil 24b by this excitation. This output voltage flows to the synchronous rectifier 25, is detected here, and is synchronized and rectified with the alternating current from the two-phase signal generator 21, and an output signal processing unit provided outside the stress measuring device 1 The main stress difference is obtained by flowing to P and being processed.
[0035]
In the stress measuring apparatus 1 according to the present embodiment, the excitation coil 24a and the detection coil 24b for measuring stress are also used as a function for demagnetizing the steel material S. It is not necessary to provide a degaussing head separately from the measurement probe, and the number of parts can be reduced to simplify the device configuration or circuit configuration. As a result, the stress measuring device 1 can be reduced in size and weight, and the reliability and durability of the device can be improved.
[0036]
Further, the current generating means 20 generates two types of alternating currents whose phases are different from each other by 90 °, and a two-phase signal generator that passes these alternating currents to the exciting coil 24a and the detecting coil 24b as demagnetizing currents. 21 is included. For this reason, the signal generator mounted in the stress measuring apparatus 1 can be made into one, a circuit structure can be made simpler, and it can contribute further to size reduction and weight reduction of the stress measuring apparatus 1. In addition, since two types of alternating current are generated by the same component, distortion of the alternating current waveform and phase shift can be suppressed, the alternating current can be generated more accurately, and measurement accuracy can be improved. .
[0037]
Further, the probe 3 includes a core member 30 in which the first cores 32a and 32b and the second cores 33a and 33b arranged orthogonal to the arrangement direction of the first cores 32a and 32b are integrated. The exciting coil 24a is constituted by winding a conducting wire around the first cores 32a and 32b, and the detecting coil 24b is constituted by winding a conducting wire around the second cores 33a and 33b. As described above, since the exciting coil 24a and the detecting coil 24b are integrated, the demagnetization and stress measurement can be performed while the distance between the coils is always kept constant, thereby improving the reliability and durability of the apparatus. It is possible to further increase the measurement accuracy as well as increase the measurement accuracy.
[0038]
In the stress measuring method using the stress measuring apparatus 1, as a first method of the degaussing step, the probe 3 is set in a state where the current value of the demagnetizing current flowing through the exciting coil 24a and the detecting coil 24b is set to the peak value. Is brought close to the steel material S, the demagnetization process is started, the current value is gradually decreased from the peak value, and the demagnetization process is terminated when it becomes zero. For this reason, the stress measurement object can be degaussed almost certainly in a short time, and the measurement efficiency can be improved.
[0039]
Further, as a second method of the demagnetization process, the demagnetization process is started by bringing the probe 3 close to the steel material S in a state where the current value of the demagnetization current flowing through the excitation coil 24a and the detection coil 24b is zero. The value is gradually increased from 0 to the peak value and then gradually decreased from the peak value, and the demagnetization process is terminated when the value becomes 0 again. For this reason, since no magnetic field is generated in the exciting coil 24a and the detecting coil 24b at the start of the demagnetization process, it is possible to prevent a situation in which the probe 3 is suddenly attracted to the steel material S by a strong magnetic force. Thus, the efficiency of the stress measurement work can be improved and the burden on the worker can be remarkably reduced.
[0040]
【The invention's effect】
As described above, in the present invention, the configuration as described above is adopted. Therefore, the number of parts is reduced to improve the reliability and durability of the apparatus, and the stress measurement work is simplified to improve the measurement efficiency and It is possible to provide a stress measuring device and a stress measuring method capable of improving measurement accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a stress measuring apparatus according to the present invention.
2 is a perspective view showing an excitation coil and a detection coil provided in the stress measuring apparatus shown in FIG. 1; FIG.
FIG. 3 is a diagram showing a circuit configuration of the stress measuring device shown in FIG. 1;
4 is a diagram showing a circuit configuration of the stress measuring device shown in FIG. 1. FIG.
FIG. 5 is a schematic configuration diagram showing an example of a conventional stress measurement apparatus.
6 is a diagram showing a circuit configuration of the stress measuring apparatus shown in FIG. 5. FIG.
7 is a diagram showing a circuit configuration of the stress measuring device shown in FIG. 5. FIG.
FIG. 8 is a graph showing an example of a difference in sensitivity characteristics depending on the presence or absence of demagnetization.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Stress measuring apparatus 2 Apparatus main body 3 Probe 20 Current generation means 21 Two-phase signal generator 23 Switch 24a Excitation coil 24b Detection coil 25 Synchronous rectifier 30 Core member 31 Base part 32a, 32b 1st core 33a, 33b 2nd Core 41a, 41b 1st coil 42a, 42b 2nd coil P Output signal processing part S Steel material (stressed object to be measured)

Claims (6)

An excitation coil and a detection coil that are close to the object to be stressed are provided. An excitation current is passed through the excitation coil to excite the object to be stressed, and the excitation induces an output voltage in the detection coil. A stress measuring device that detects the output voltage and measures the stress acting on the stress measurement object,
Current generating means for causing two types of alternating currents generated by a two-phase signal generator to have a phase difference of 90 ° to flow through the exciting coil and the detecting coil as a demagnetizing current for demagnetizing the object to be stressed. A stress measuring device comprising: The stress measuring apparatus according to claim 1, wherein the exciting coil and the detecting coil have the same wire thickness and the same number of turns.   A first core composed of a pair of shaft portions, and a core member formed by integrating a second core composed of the same pair of shaft portions arranged orthogonal to the direction of arrangement of the first cores, 3. The detection coil according to claim 1, wherein the exciting coil is configured by winding a conducting wire around one core, and the detecting coil is configured by winding a conducting wire around the second core. Stress measuring device.   A stress measuring method using the stress measuring device according to any one of claims 1 to 3, wherein a degaussing step of flowing a degaussing current from the current generating means to each of the exciting coil and the detecting coil, A measuring step of passing an exciting current from the current generating means to the exciting coil, inducing an output voltage in the detecting coil, and detecting the output voltage to measure a stress acting on the stressed object. And a stress measuring method characterized by comprising:   With the current value of the demagnetizing current flowing through the excitation coil and the detection coil set to a peak value, the demagnetization step is started by bringing the excitation coil and the detection coil close to the object to be stressed. 5. The stress measuring method according to claim 4, wherein the current value is gradually decreased from the peak value, and the degaussing step is terminated when the current value becomes zero.   With the current value of the degaussing current flowing through the excitation coil and the detection coil set to 0, the excitation coil and the detection coil are brought close to the object to be stressed to start the demagnetization step, 5. The demagnetization step is terminated when the current value is gradually increased from 0 to a peak value and then gradually decreased from the peak value, and the current value becomes 0 again. Stress measurement method.

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