CN108593776B - Device and method for measuring elastic modulus of chopped fiber - Google Patents
Device and method for measuring elastic modulus of chopped fiber Download PDFInfo
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- CN108593776B CN108593776B CN201810589492.0A CN201810589492A CN108593776B CN 108593776 B CN108593776 B CN 108593776B CN 201810589492 A CN201810589492 A CN 201810589492A CN 108593776 B CN108593776 B CN 108593776B
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Abstract
The invention discloses a device and a method for measuring the elasticity modulus of chopped fibers. The device comprises an oscillator, a vibration exciter, a frequency meter, a signal receiver, a wave device and a control calculator. By using the device and the method for measuring the elasticity modulus of the chopped fibers, the elasticity modulus of the chopped fibers can be conveniently measured.
Description
Technical Field
The invention relates to an elastic modulus testing technology, in particular to a device and a method for measuring the elastic modulus of chopped fibers.
Background
The elastic modulus reflects the ability of the material to deform against external forces and is one of the basic mechanical properties of the material. Therefore, the elastic modulus and the strength of the fiber or the filament are the basic mechanical properties, and the elastic modulus of the fiber or the filament is required to be considered in the practical application in the fields of civil engineering, aerospace, biomedical materials and the like so as to achieve the purpose of structural design.
For conventional materials, the currently commonly used methods for measuring the elastic modulus are a stress strain method, a bending method, an acoustic resonance method, an ultrasonic method and the like.
As a class of excellent reinforcing materials, chopped fibers have been increasingly used in concrete in recent years. The mixing of the chopped fibers can effectively enhance the cracking resistance and the impact resistance of the concrete and improve the mechanical property and the durability of the concrete. In addition, the fine synthetic fibers can block capillary channels in the concrete, so that the evaporation of water on the exposed surface of the concrete can be reduced, plastic settlement and bleeding of the concrete are prevented, plastic cracks and shrinkage cracks of the concrete can be greatly reduced, and the durability of the concrete such as freezing resistance, seepage resistance and the like is improved.
Because the chopped fibers are generally short, when the elastic modulus of the chopped fibers is measured by a conventional uniaxial stretching method, clamping of the chopped fibers is difficult, and the length of the displacement of the chopped fibers is short and the order of magnitude of the length is small, so that the measurement accuracy is difficult to ensure by the conventional measuring method, and the error is large.
In the prior art, the elastic modulus values of the chopped fibers given by industrial production are obtained by measuring the fiber filaments. However, whether the elastic modulus measured by the staple fiber and the filament fiber is different is not determined, whether the performance index is accurate or not is determined, the performance of the chopped fiber can be accurately evaluated, and the effect of the fiber in concrete is studied.
Currently, the test method for the elastic modulus of chopped fibers is almost blank. In the measurement method of the related art, the elastic modulus of the chopped fiber is measured only by a precision electron level and a microscope using a stretching method. Although the method solves the problem of short wire measurement, the method is still a traditional static test method, the operation is complex, the data needs to be read manually, and the influence factors of errors are more; the used instruments are complex, are generally only suitable for measurement in a laboratory, are inconvenient to move and transfer, and are not suitable for application in engineering sites.
Disclosure of Invention
In view of the above, the present invention provides an apparatus and a method for measuring the modulus of elasticity of a chopped fiber, so that the modulus of elasticity of the chopped fiber can be conveniently measured.
The technical scheme of the invention is realized specifically as follows:
an apparatus for measuring the modulus of elasticity of chopped fibers, the apparatus comprising: the device comprises an oscillator, a vibration exciter, a frequency meter, a signal receiver, a wave shaper and a control calculator;
the oscillator is used for continuously generating audio sinusoidal electric signals within a preset frequency range according to a preset sequence and outputting the generated audio sinusoidal electric signals to the vibration exciter;
the vibration exciter is fixedly connected with one end of the fiber to be tested; the other end of the fiber to be measured is in a free state;
the vibration exciter is used for converting the received audio sinusoidal electric signal into mechanical vibration so that the fiber to be tested generates forced vibration;
the frequency meter is connected with the vibration exciter and is used for recording the vibration frequency of the mechanical vibration of the vibration exciter and outputting the recorded vibration frequency to the wave shaper and the control calculator;
the signal receivers are arranged at two sides of the free end of the fiber to be measured, and are used for measuring the vibration of the fiber to be measured, generating corresponding pulse signals according to the vibration frequency of the fiber to be measured, and outputting the generated pulse signals to the wave shaper and the control calculator;
the wave shaper is used for forming a Lissajous figure according to the received vibration frequency and pulse signals and outputting the formed Lissajous figure to the control calculator;
the control calculator is used for continuously generating an audio sinusoidal electric signal in a preset frequency range according to a preset sequence by controlling the oscillator, receiving a pulse signal output by the signal receiver and a vibration frequency output by the frequency meter, and acquiring the maximum intersection point number of the received Lissajous figure and the horizontal line and the vertical line in real time; according to the maximum intersection number of the Lissajous graph and the horizontal line and the vertical line when the amplitude of the pulse signal is maximum and the vibration frequency recorded by the corresponding frequency meter, calculating to obtain the self-vibration frequency of the fiber to be measured; and calculating the elastic modulus of the fiber to be measured according to the self-vibration frequency and the physical parameters of the fiber to be measured, which are obtained by measuring in advance.
Wherein the signal receiver comprises: a light emitting diode, a phototransistor, and an amplifier;
the light emitting diode and the phototriode are symmetrically arranged at two sides of the free end of the fiber to be tested,
the light emitting diode and the phototriode are connected with a power supply; the light emitting diode is used for outputting a light beam to the phototriode;
the phototriode is used for receiving the light beam output by the light emitting diode; the output end of the phototriode is connected with the amplifier;
the output end of the amplifier is connected with the wave shaper and the control calculator.
Wherein, the wave shaper is an oscilloscope.
Wherein the apparatus further comprises: a lifter;
the lifter is used for adjusting the distance between the signal receiver and the vibration exciter.
Wherein the lifter is an adjustable telescopic rod;
the bottom of the adjustable telescopic rod is connected with the vibration exciter through a connecting piece, and the top of the adjustable telescopic rod is fixedly connected with a preset fixture.
Wherein, the riser includes: the device comprises a base, a supporting rod and a connecting piece;
the base is fixedly connected with the vibration exciter;
the support rod is vertically arranged above the base, and the bottom of the support rod is connected with the base; the support rod is provided with a chute extending along the vertical direction;
the connecting piece is arranged at the upper part of the supporting rod and is in sliding connection with the sliding groove of the supporting rod; the connecting piece is fixedly connected with the signal receiver.
Wherein the control calculator includes: the control receiving unit, the intercepting unit and the calculating unit;
the control receiving unit is used for continuously generating an audio sinusoidal electric signal in a preset frequency range according to a preset sequence by controlling the oscillator, and receiving a pulse signal output by the signal receiver and a vibration frequency output by the frequency meter;
the intercepting unit is used for receiving the Lissajous figures output by the wave shaper and acquiring the maximum intersection point number of the Lissajous figures, the horizontal lines and the vertical lines in real time;
the calculating unit is used for calculating the self-vibration frequency of the fiber to be measured according to the maximum intersection point number of the Lissajous graph and the horizontal line and the vertical line when the amplitude of the pulse signal is maximum and the vibration frequency recorded by the corresponding frequency meter; and calculating the elastic modulus of the fiber to be measured according to the self-vibration frequency and the physical parameters of the fiber to be measured, which are obtained by measuring in advance.
The invention also provides a device for measuring the self-vibration frequency of chopped fibers, which comprises: the device comprises an oscillator, a vibration exciter, a frequency meter, a signal receiver, a wave shaper and a control calculator;
the oscillator is used for continuously generating audio sinusoidal electric signals within a preset frequency range according to a preset sequence and outputting the generated audio sinusoidal electric signals to the vibration exciter;
the vibration exciter is fixedly connected with one end of the fiber to be tested; the other end of the fiber to be measured is in a free state;
the vibration exciter is used for converting the received audio sinusoidal electric signal into mechanical vibration so that the fiber to be tested generates forced vibration;
the frequency meter is connected with the vibration exciter and is used for recording the vibration frequency of the mechanical vibration of the vibration exciter and outputting the recorded vibration frequency to the wave shaper and the control calculator;
the signal receivers are arranged at two sides of the free end of the fiber to be measured, and are used for measuring the vibration of the fiber to be measured, generating corresponding pulse signals according to the vibration frequency of the fiber to be measured, and outputting the generated pulse signals to the wave shaper and the control calculator;
the wave shaper is used for forming a Lissajous figure according to the received vibration frequency and pulse signals and outputting the formed Lissajous figure to the control calculator;
the control calculator is used for continuously generating an audio sinusoidal electric signal in a preset frequency range according to a preset sequence by controlling the oscillator, receiving a pulse signal output by the signal receiver and a vibration frequency output by the frequency meter, and acquiring the maximum intersection point number of the received Lissajous figure and the horizontal line and the vertical line in real time; and calculating the self-oscillation frequency of the fiber to be measured according to the maximum intersection point number of the Lissajous graph and the horizontal line and the vertical line when the amplitude of the pulse signal is maximum and the vibration frequency recorded by the corresponding frequency meter.
The invention also provides a method for measuring the elastic modulus of the chopped fiber, which comprises the following steps:
measuring the natural vibration frequency of the fiber to be measured by using the device for measuring the natural vibration frequency of the chopped fiber to obtain the natural vibration frequency of the fiber to be measured;
and calculating the elastic modulus of the fiber to be measured according to the self-vibration frequency and the physical parameters of the fiber to be measured, which are obtained by measuring in advance.
Wherein, the physical parameters of the fiber to be measured are as follows: the mass, length and cross-sectional moment of inertia of the chopped fibers.
As can be seen from the above, the device and the method for measuring the elastic modulus of the chopped fiber provided by the invention can enable the fiber to be measured to generate forced vibration through the oscillator and the vibration exciter, generate corresponding pulse signals according to the vibration frequency of the fiber to be measured through the signal receiver, and then send the pulse signals and the vibration frequency of the mechanical vibration of the vibration exciter to the wave shaper, so that a lissajous figure can be formed through the wave shaper, and the self-vibration frequency of the fiber to be measured can be calculated through controlling the maximum intersection point number of the lissajous figure and the horizontal line and the vertical line when the amplitude of the pulse signals is maximum and the vibration frequency recorded by the corresponding frequency meter through the control calculator. And then, calculating the elastic modulus of the fiber to be measured according to the self-vibration frequency and the physical parameters of the fiber to be measured, which are obtained by measuring in advance. Therefore, the device and the method for measuring the elastic modulus of the chopped fibers can conveniently measure the elastic modulus of the chopped fibers. Moreover, the device and the method for measuring the elastic modulus of the chopped fiber are simple to operate, can repeatedly measure the fiber to be measured, have no damage to the fiber to be measured, belong to nondestructive detection, and have wide application range; in addition, the device and the method for measuring the elastic modulus of the chopped fibers have the advantages of simple operation steps and high test precision, and can reduce artificial test errors. In addition, the above-described device for measuring the modulus of elasticity of chopped fibers in the present invention may be integrated into one measuring apparatus. The measuring equipment has the advantages of simple structure, easy carrying, convenience and easy use, and is easy to quickly obtain the performance parameters of the short fibers on the engineering site, and the engineering applicability is strong.
Drawings
Fig. 1 is a schematic structural diagram of an apparatus for measuring the natural frequency of chopped fibers according to an embodiment of the present invention.
Fig. 2 is a schematic view of a simple bending of a chopped fiber in an embodiment of the present invention.
Fig. 3 is a schematic structural diagram of a control calculator according to an embodiment of the invention.
FIG. 4 is a flow chart of a method for measuring the elastic modulus of chopped fibers in an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below by referring to the accompanying drawings and examples.
Fig. 1 is a schematic structural diagram of an apparatus for measuring the natural frequency of chopped fibers according to an embodiment of the present invention. As shown in fig. 1, an apparatus for measuring a self-oscillation frequency of a chopped fiber according to an embodiment of the present invention includes: an oscillator 11, a vibration exciter 12, a frequency meter 13, a signal receiver 14, a wave shaper 15, and a control calculator 16;
the oscillator 11 is configured to continuously generate an audio sinusoidal electrical signal within a preset frequency range in a preset sequence, and output the generated audio sinusoidal electrical signal to the exciter 12;
the vibration exciter 12 is fixedly connected with one end of the fiber 10 to be tested; the other end of the fiber 10 to be measured is in a free state;
the vibration exciter 12 is used for converting the received audio sinusoidal electric signal into mechanical vibration, so that the fiber 10 to be tested generates forced vibration;
the frequency meter 13 is connected with the vibration exciter 12, and is used for recording the vibration frequency of the mechanical vibration of the vibration exciter 12 and outputting the recorded vibration frequency to the wave shaper 15 and the control calculator 16;
the signal receivers 14 are disposed at two sides of the free end of the fiber 10 to be measured, and are configured to measure the vibration of the fiber 10 to be measured, generate corresponding pulse signals according to the vibration frequency of the fiber 10 to be measured, and output the generated pulse signals to the undulator 15 and the control calculator 16;
the wave shaper 15 for forming a lissajous pattern based on the received vibration frequency and pulse signal and outputting the formed lissajous pattern to the control calculator 16;
the control calculator 16 is configured to continuously generate an audio sinusoidal electrical signal within a preset frequency range by controlling the oscillator 11 in a preset sequence, receive a pulse signal output by the signal receiver 14 and a vibration frequency output by the frequency meter, and obtain a maximum intersection number of the received lissajous pattern with the horizontal line and the vertical line in real time; and calculating the self-vibration frequency of the fiber 10 to be measured according to the maximum intersection point number of the Lissajous graph and the horizontal line and the vertical line when the amplitude of the pulse signal is maximum and the vibration frequency recorded by the corresponding frequency meter 13.
After the self-vibration frequency of the fiber to be measured is obtained, the elastic modulus of the fiber to be measured can be obtained by calculating according to the self-vibration frequency of the fiber to be measured and the physical parameters of the fiber to be measured.
In the above-described apparatus for measuring the modulus of elasticity of the chopped fibers, the modulus of elasticity of the chopped fibers is measured essentially using a vibration method, rather than using a stretching method.
The natural vibration characteristic parameters (natural vibration frequency and period) of the chopped fibers are related to their own structure and material properties, and this relationship can be deduced by simple bending of the chopped fibers.
For example, fig. 2 is a schematic view of simple bending of a chopped fiber according to an embodiment of the present invention, and as shown in fig. 2, assuming that the mass of the chopped fiber is m, the length is L, the cross-sectional moment of inertia is I, the elastic modulus of the fiber is E, and when a concentrated load F acts on the end of the chopped fiber, the horizontal displacement w of the chopped fiber due to the concentrated load F is w, the horizontal displacement w of the chopped fiber due to the load F satisfies the following relationship:
stiffness is the counter force caused by unit displacement, so the structural transverse stiffness k can be obtained according to formula (1) as:
and the angular velocity ω is related to the structural transverse stiffness k and the mass m as follows:
substituting formula (3) into formula (2) yields:
the relationship among the angular velocity omega, the period T and the frequency f of the self-vibration of the structure is as follows:
substituting the formula (5) into the formula (4) can obtain the following relation between the self-vibration frequency, the period and the elastic modulus of each structure:
from this, it is understood that the elastic modulus of the chopped fiber is related to parameters such as the mass, cross-sectional geometry, length, cross-sectional moment of inertia, and natural frequency of the chopped fiber. That is, the elastic modulus of the chopped fiber can be calculated given parameters such as the mass m, length L, section moment of inertia I, and self-oscillation frequency f of the chopped fiber. For example, the modulus of elasticity of the chopped fibers can be calculated by the above formula.
Since physical parameters such as the mass m, the length L, the section moment of inertia I and the like of the chopped fiber can be obtained relatively easily in advance, the modulus of elasticity of the chopped fiber can be obtained by calculation only by measuring the natural frequency of the chopped fiber.
In the device for measuring the self-vibration frequency of the chopped fibers, the control calculator can control the oscillator to continuously generate the audio sinusoidal electric signals within a preset frequency range according to a preset sequence through the control signal, then the fiber to be measured generates forced vibration through the oscillator and the vibration exciter (for example, the control calculator can control the oscillator to periodically or continuously generate the audio sinusoidal electric signals from A hertz to B hertz in a certain time period, so that the vibration exciter also generates mechanical vibration with different frequencies, the free end of the fiber to be measured generates forced vibration with different amplitudes), the signal receiver can generate corresponding pulse signals according to the vibration frequency of the fiber to be measured, and then the vibration frequencies of the pulse signals and the mechanical vibration of the vibration exciter are transmitted to the wave shaper and the control calculator, and the wave shaper can form Lissajous figures according to the received vibration frequencies and the pulse signals; when the control calculator receives the Lissajous figure, the Lissajous figure can be intercepted in real time through the horizontal line and the vertical line, and the maximum intersection number of the Lissajous figure and the horizontal line and the vertical line is obtained. When the fiber to be measured vibrates at its natural frequency, the amplitude of the pulse signal output by the signal receiver will be maximum. Therefore, the control calculator can calculate the self-vibration frequency of the fiber to be measured according to the maximum intersection point number of the Lissajous figure and the horizontal line and the vertical line when the amplitude of the pulse signal is maximum and the vibration frequency recorded by the corresponding frequency meter. After the natural vibration frequency of the fiber to be measured is obtained, the elastic modulus of the fiber to be measured can be calculated according to the natural vibration frequency and the physical parameters (for example, physical parameters such as the mass m, the length L, the section moment of inertia I and the like of the chopped fiber) of the fiber to be measured, which are measured in advance.
In addition, in a preferred embodiment of the present invention, the wave shaper may be an oscilloscope for displaying the formed lissajous pattern.
In the technical scheme of the invention, the vibration frequency recorded by the frequency meter can be output to the X-axis input end of the oscilloscope, and the pulse signal generated by the signal receiver is output to the Y-axis input end of the oscilloscope. At this point, a composite graphic will appear on the oscilloscope, which is the lissajous graphic. The lissajous figures differ with the frequency, phase and amplitude of the two input signals, and the waveforms presented are also different. When the phase difference of the two signals is 90 degrees, the synthesized graph is a positive ellipse, and when the amplitudes of the two signals are the same, the synthesized graph is a circle; when the phase difference of the two signals is 0 DEG, the composite graph is a straight line, and when the amplitudes of the two signals are the same, the composite graphIs a 45 deg. line to the x-axis. Therefore, the relationship between the frequencies of the two signals inputted can be known by observing the lissajous pattern. Assuming that the lissajous figure is truncated by horizontal and vertical lines, the maximum number of intersections of the lissajous figure with the horizontal and vertical lines can be obtained. Because the oscillator can continuously generate an audio sinusoidal electric signal from A Hz to B Hz periodically or within a certain time period, the vibration exciter also generates mechanical vibration with different frequencies, so that the free end of the fiber to be tested generates forced vibration with different amplitudes. Moreover, when the fiber to be measured vibrates at its natural frequency, the amplitude of the pulse signal output from the signal receiver will be maximized. At this time, it is assumed that the maximum number of intersections of the lissajous figure and the horizontal line is N x The maximum number of intersections with the vertical line is N y The current vibration frequency recorded by the frequency meter is f x The natural vibration frequency f of the fiber to be measured can be calculated according to the following formula y ：
f y ＝f x *N x /N y 。
It is therefore known that the lissajous pattern displayed on the oscilloscope can be changed accordingly by adjusting the frequency of the audio sinusoidal signal of the oscillator. Therefore, the vibration frequency of the fiber to be measured when the amplitude of the pulse signal generated by the signal receiver is maximum can be calculated by adjusting the frequency of the audio sinusoidal electric signal of the oscillator and according to the Lissajous figure displayed on the oscilloscope. At this time, the vibration frequency is the natural vibration frequency of the fiber to be measured.
After the self-vibration frequency of the fiber to be measured is obtained, the elastic modulus of the fiber to be measured can be obtained by calculating according to the self-vibration frequency of the fiber to be measured and the physical parameters of the fiber to be measured.
Of course, in the technical scheme of the invention, other wave formers can be used, so that the self-oscillation frequency of the fiber to be measured can be obtained by adjusting the frequency of the audio sinusoidal electric signal of the oscillator according to the display information of the wave formers. Specific implementation manner is not described in detail herein.
In addition, in the technical scheme of the invention, various forms of signal receivers can be used. The following describes the technical solution of the present invention by taking a specific implementation manner of the signal receiver as an example.
For example, in a preferred embodiment of the present invention, the signal receiver may include: a light emitting diode 41, a phototransistor 42 and an amplifier 43;
the light emitting diode 41 and the phototransistor 42 are symmetrically arranged on both sides of the free end of the fiber 10 to be measured,
the light emitting diode 41 and the phototransistor 42 are connected to a power supply; the light emitting diode 41 is configured to output a light beam to the phototransistor 42;
the phototransistor 42 is configured to receive the light beam output from the light emitting diode 41; the output end of the phototransistor 42 is connected to the amplifier 43;
the output of the amplifier 43 is connected to the wave shaper 1 and to the control calculator 16.
Therefore, when the free end of the fiber to be measured is stationary, the free end of the fiber to be measured is positioned between the light emitting diode and the phototriode, so that the light beam output by the light emitting diode is blocked by the free end of the fiber to be measured; when the free end of the fiber to be measured leaves the static position due to forced vibration, the light beam output by the light emitting diode irradiates on the phototriode. Therefore, when the fiber to be measured is forced to vibrate, the phototransistor generates a corresponding pulse signal according to the vibration frequency of the fiber to be measured, and outputs the pulse signal to the amplifier. The amplifier amplifies the pulse signal and outputs the amplified pulse signal to the waveform device and the control calculator.
In addition, in a preferred embodiment of the present invention, the apparatus for measuring the natural frequency of the chopped fiber may further include: a lifter (not shown in the drawings);
the lifter is used for adjusting the distance between the signal receiver and the vibration exciter.
The distance between the signal receiver and the vibration exciter is adjusted by using the lifter, so that the device for measuring the self-vibration frequency of the chopped fibers can be suitable for chopped fibers with various lengths.
For example, when the length of the fiber to be measured is short, the distance between the signal receiver and the vibration exciter can be shortened by the lifter; when the length of the fiber to be measured is longer, the distance between the signal receiver and the vibration exciter can be increased through the lifter, so that the signal receiver can be conveniently arranged on two sides of the free end of the fiber to be measured, and the self-vibration frequency of the chopped fibers with various lengths can be measured.
In addition, in the technical scheme of the invention, the lifter can be realized in various modes. The following describes the technical solution of the present invention in detail by taking two specific implementation manners as examples.
For example, preferably, in one embodiment of the invention, the lifter may be an adjustable telescopic rod; the bottom of the adjustable telescopic rod is connected with the vibration exciter through a connecting piece with high rigidity, and the top of the adjustable telescopic rod is fixedly connected with a preset fixture (for example, a fixture such as the inner wall of a test box). Therefore, the distance between the signal receiver and the vibration exciter can be adjusted by adjusting the length of the adjustable telescopic rod.
For example, preferably, in one embodiment of the present invention, the lifter may include: the device comprises a base, a supporting rod and a connecting piece;
the base is fixedly connected with the vibration exciter;
the support rod is vertically arranged above the base, and the bottom of the support rod is connected with the base; the support rod is provided with a chute extending along the vertical direction;
the connecting piece is arranged at the upper part of the supporting rod and is in sliding connection with the sliding groove of the supporting rod (namely, can slide up and down along the sliding groove of the supporting rod); the connecting piece is fixedly connected with the signal receiver.
Therefore, the distance between the signal receiver and the vibration exciter can be adjusted by moving the position of the connecting piece on the sliding groove of the supporting rod.
In the technical scheme of the invention, other specific implementation manners can be used for realizing the lifter, and the detailed description is omitted herein.
In addition, in the technical scheme of the invention, the control calculator can be realized in various modes. The technical scheme of the present invention will be described in detail below by taking one specific implementation manner as an example.
For example, fig. 3 is a schematic structural diagram of a control calculator according to an embodiment of the present invention. As shown in fig. 3, in a specific embodiment of the present invention, the control calculator 16 may include: a control receiving unit 61, an intercepting unit 62, and a calculating unit 63;
the control receiving unit 61 is configured to continuously generate an audio sinusoidal electrical signal within a preset frequency range by controlling the oscillator 11 in a preset sequence, and to receive the pulse signal output from the signal receiver 14 and the vibration frequency output from the frequency meter 13;
the intercepting unit 62 is configured to receive the lissajous pattern output by the wave shaper 15, and acquire the maximum number of intersections of the lissajous pattern with the horizontal line and the vertical line in real time;
the calculating unit 63 is configured to calculate the natural vibration frequency of the fiber 10 to be measured according to the maximum intersection point number of the lissajous pattern and the horizontal line and the vertical line when the amplitude of the pulse signal is maximum and the vibration frequency recorded by the corresponding frequency meter 13.
In addition, in a specific embodiment of the present invention, the control calculator may be further configured to calculate the elastic modulus of the fiber to be measured according to the natural frequency and the physical parameter of the fiber to be measured in advance.
At this time, the device shown in fig. 1 can calculate the elastic modulus of the fiber to be measured, so the device can already directly calculate the elastic modulus of the fiber to be measured, so the device is actually a device for measuring the elastic modulus of the chopped fiber.
In addition, in a specific embodiment of the present invention, in the apparatus for measuring the modulus of elasticity of a chopped fiber, the control calculator may also include a control receiving unit, a capturing unit, and a calculating unit, where the control receiving unit, the capturing unit, and the calculating unit have the same functions as the control receiving unit, the capturing unit, and the calculating unit in fig. 3, and further, the calculating unit may be further configured to calculate the modulus of elasticity of the fiber to be measured according to the self-oscillation frequency and the physical parameter of the fiber to be measured in advance.
In addition, in the technical scheme of the invention, a method for measuring the elastic modulus of the chopped fiber is also provided.
FIG. 4 is a flow chart of a method for measuring the elastic modulus of chopped fibers in an embodiment of the present invention. As shown in fig. 4, the method for measuring the elastic modulus of the chopped fiber according to the embodiment of the present invention mainly includes the following steps:
step 401, measuring the natural vibration frequency of the fiber to be measured to obtain the natural vibration frequency of the fiber to be measured.
For example, in a preferred embodiment of the present invention, the device for measuring the natural frequency of the chopped fiber may be used to measure the natural frequency of the fiber to be measured, so as to obtain the natural frequency of the fiber to be measured.
When the device for measuring the self-oscillation frequency of the chopped fibers is used, the fibers to be measured can be kept vertical, one end of the fibers to be measured is fixed on the vibration exciter, the signal receivers are arranged on two sides of the free end of the fibers to be measured, and the free end of the fibers to be measured is aligned with the center of the signal receiver (for example, the free end of the fibers to be measured can be completely shielded between the light emitting diode and the phototriode). Then the fiber to be measured generates forced vibration through the oscillator and the vibration exciter, and a corresponding pulse signal is generated through the signal receiver according to the vibration frequency of the fiber to be measured. Since the oscillator can continuously generate the audio sinusoidal electrical signals within a preset frequency range in a preset sequence, for example, the oscillator can continuously generate the audio sinusoidal electrical signals near a certain preset frequency range (for example, near the natural vibration frequency range of the long fiber, wherein the natural vibration frequency of the long fiber can be obtained by reversely calculating the elastic modulus of the known long fiber), the free end of the fiber to be tested can generate forced vibration with different amplitudes, and the signal receiver can also generate pulse signals with different amplitudes. When the amplitude of the pulse signal is maximum, the self-oscillation frequency of the fiber to be measured can be calculated according to the maximum intersection point number of the Lissajous figure and the horizontal line and the vertical line and the vibration frequency recorded by the corresponding frequency meter.
In addition, in the embodiment of the present invention, it is preferable that the lissajous pattern and the voltage pointer of the amplifier at the maximum amplitude are observed to determine whether the vibration at this time is a spurious resonance.
For example, when the amplitude of the pulse signal is large, the pointer can be seen from the μV table of the amplifier to reach full scale at one time, and the waveform amplitude on the fluorescent screen of the oscilloscope also reaches full scale at one time, the vibration frequency of the fiber to be measured at the moment is the real self-vibration frequency of the fiber to be measured. If the amplitude of the pulse signal is not very large, then the resonance at this time is a spurious resonance. The vibration frequency of the fiber to be measured at this time is not the true natural vibration frequency of the fiber to be measured.
Step 402, calculating to obtain the elastic modulus of the fiber to be measured according to the natural vibration frequency and the physical parameters of the fiber to be measured, which are measured in advance.
In the technical scheme of the invention, because physical parameters such as the mass m, the length L, the section moment of inertia I and the like of the chopped fibers can be obtained by measurement in advance relatively easily, after the self-vibration frequency of the chopped fibers is obtained by measurement, the elastic modulus of the fibers to be measured can be calculated according to the self-vibration frequency and the physical parameters of the fibers to be measured, which are obtained by measurement in advance.
For example, in a preferred embodiment of the present invention, the elastic modulus of the fiber to be measured can be calculated using the above formula (6).
In summary, according to the device and the method for measuring the elastic modulus of the chopped fiber, the fiber to be measured can generate forced vibration through the oscillator and the vibration exciter, the corresponding pulse signals are generated through the signal receiver according to the vibration frequency of the fiber to be measured, and then the pulse signals and the vibration frequency of the mechanical vibration of the vibration exciter are sent to the wave shaper, so that a Lissajous figure can be formed through the wave shaper, and the self-vibration frequency of the fiber to be measured can be calculated through the control calculator according to the maximum intersection point number of the Lissajous figure and the horizontal line and the vertical line when the amplitude of the pulse signals is maximum and the vibration frequency recorded by the corresponding frequency meter. And then, calculating the elastic modulus of the fiber to be measured according to the self-vibration frequency and the physical parameters of the fiber to be measured, which are obtained by measuring in advance. Therefore, the device and the method for measuring the elastic modulus of the chopped fibers can conveniently measure the elastic modulus of the chopped fibers. Moreover, the device and the method for measuring the elastic modulus of the chopped fiber are simple to operate, can repeatedly measure the fiber to be measured, have no damage to the fiber to be measured, belong to nondestructive detection, and have wide application range; in addition, the device and the method for measuring the elastic modulus of the chopped fibers have the advantages of simple operation steps and high test precision, and can reduce artificial test errors. In addition, the above-described device for measuring the modulus of elasticity of chopped fibers in the present invention may be integrated into one measuring apparatus. The measuring equipment has the advantages of simple structure, easy carrying, convenience and easy use, and is easy to quickly obtain the performance parameters of the short fibers on the engineering site, and the engineering applicability is strong.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather to enable any modification, equivalent replacement, improvement or the like to be made within the spirit and principles of the invention.
Claims (9)
1. An apparatus for measuring the natural frequency of chopped fibers, the apparatus comprising: the device comprises an oscillator, a vibration exciter, a frequency meter, a signal receiver, a wave shaper and a control calculator;
the oscillator is used for continuously generating audio sinusoidal electric signals within a preset frequency range according to a preset sequence and outputting the generated audio sinusoidal electric signals to the vibration exciter;
the vibration exciter is fixedly connected with one end of the fiber to be tested; the other end of the fiber to be measured is in a free state;
the vibration exciter is used for converting the received audio sinusoidal electric signal into mechanical vibration so that the fiber to be tested generates forced vibration;
the frequency meter is connected with the vibration exciter and is used for recording the vibration frequency of the mechanical vibration of the vibration exciter and outputting the recorded vibration frequency to the wave shaper and the control calculator;
the signal receivers are arranged at two sides of the free end of the fiber to be measured, and are used for measuring the vibration of the fiber to be measured, generating corresponding pulse signals according to the vibration frequency of the fiber to be measured, and outputting the generated pulse signals to the wave shaper and the control calculator;
the wave shaper is used for forming a Lissajous figure according to the received vibration frequency and pulse signals and outputting the formed Lissajous figure to the control calculator;
the control calculator is used for continuously generating an audio sinusoidal electric signal in a preset frequency range according to a preset sequence by controlling the oscillator, receiving a pulse signal output by the signal receiver and a vibration frequency output by the frequency meter, and acquiring the maximum intersection point number of the received Lissajous figure and the horizontal line and the vertical line in real time; and calculating the self-oscillation frequency of the fiber to be measured according to the maximum intersection point number of the Lissajous graph and the horizontal line and the vertical line when the amplitude of the pulse signal is maximum and the vibration frequency recorded by the corresponding frequency meter.
2. The apparatus of claim 1, wherein the signal receiver comprises: a light emitting diode, a phototransistor, and an amplifier;
the light emitting diode and the phototriode are symmetrically arranged at two sides of the free end of the fiber to be tested,
the light emitting diode and the phototriode are connected with a power supply; the light emitting diode is used for outputting a light beam to the phototriode;
the phototriode is used for receiving the light beam output by the light emitting diode; the output end of the phototriode is connected with the amplifier;
the output end of the amplifier is connected with the wave shaper and the control calculator.
3. The apparatus according to claim 1, wherein:
the wave shaper is an oscilloscope.
4. The apparatus of claim 1, wherein the apparatus further comprises: a lifter;
the lifter is used for adjusting the distance between the signal receiver and the vibration exciter.
5. The apparatus according to claim 4, wherein:
the lifter is an adjustable telescopic rod;
the bottom of the adjustable telescopic rod is connected with the vibration exciter through a connecting piece, and the top of the adjustable telescopic rod is fixedly connected with a preset fixture.
6. The apparatus of claim 4, wherein the lifter comprises: the device comprises a base, a supporting rod and a connecting piece;
the base is fixedly connected with the vibration exciter;
the support rod is vertically arranged above the base, and the bottom of the support rod is connected with the base; the support rod is provided with a chute extending along the vertical direction;
the connecting piece is arranged at the upper part of the supporting rod and is in sliding connection with the sliding groove of the supporting rod; the connecting piece is fixedly connected with the signal receiver.
7. The apparatus of claim 1, wherein the control calculator comprises: the control receiving unit, the intercepting unit and the calculating unit;
the control receiving unit is used for continuously generating an audio sinusoidal electric signal in a preset frequency range according to a preset sequence by controlling the oscillator, and receiving a pulse signal output by the signal receiver and a vibration frequency output by the frequency meter;
the intercepting unit is used for receiving the Lissajous figures output by the wave shaper and acquiring the maximum intersection point number of the Lissajous figures, the horizontal lines and the vertical lines in real time;
the calculating unit is used for calculating the self-vibration frequency of the fiber to be measured according to the maximum intersection point number of the Lissajous graph and the horizontal line and the vertical line when the amplitude of the pulse signal is maximum and the vibration frequency recorded by the corresponding frequency meter.
8. A method of measuring the modulus of elasticity of a chopped fiber, the method comprising the steps of:
measuring the natural vibration frequency of the fiber to be measured by using the device for measuring the natural vibration frequency of the chopped fiber according to claim 1 to obtain the natural vibration frequency of the fiber to be measured;
and calculating the elastic modulus of the fiber to be measured according to the self-vibration frequency and the physical parameters of the fiber to be measured, which are obtained by measuring in advance.
9. The method according to claim 8, wherein:
the physical parameters of the fiber to be measured are as follows: the mass, length and cross-sectional moment of inertia of the chopped fibers.
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