CN113074849A - Concrete surface absolute stress measuring method based on laser ultrasonic technology - Google Patents
Concrete surface absolute stress measuring method based on laser ultrasonic technology Download PDFInfo
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- CN113074849A CN113074849A CN202110327297.2A CN202110327297A CN113074849A CN 113074849 A CN113074849 A CN 113074849A CN 202110327297 A CN202110327297 A CN 202110327297A CN 113074849 A CN113074849 A CN 113074849A
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- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/25—Measuring force or stress, in general using wave or particle radiation, e.g. X-rays, microwaves, neutrons
- G01L1/255—Measuring force or stress, in general using wave or particle radiation, e.g. X-rays, microwaves, neutrons using acoustic waves, or acoustic emission
Abstract
The invention particularly relates to a concrete surface absolute stress measuring method based on a laser ultrasonic technology, which comprises the following steps: arranging a collection point in a to-be-measured area on the surface of the concrete member, and arranging a main compressive stress excitation point on the surface of the concrete member, so that the main compressive stress excitation point can be connected with the collection point to form a main compressive stress measuring line along the main compressive stress direction; emitting laser beams to the main pressure stress excitation point and exciting ultrasonic waves; collecting ultrasonic signals of a main pressure stress excitation point at a collection point, and calculating corresponding ultrasonic signal propagation time; calculating the ultrasonic wave speed on the main pressure stress measuring line according to the length of the main pressure stress measuring line and the corresponding ultrasonic signal propagation time; and then calculating the absolute main compressive stress on the main compressive stress measuring line as the absolute main compressive stress of the region to be measured. The method for measuring the absolute stress of the concrete surface can realize nondestructive measurement of the absolute stress, thereby being used for frequent measurement and ensuring the measurement effect of the absolute stress of the concrete.
Description
Technical Field
The invention relates to the technical field of concrete stress measurement, in particular to a method for measuring absolute stress of a concrete surface based on a laser ultrasonic technology.
Background
The concrete is a main material adopted in civil engineering, and has the advantages of easily available materials, low price, strong plasticity, easy construction and the like. The performance of concrete can be changed due to the service time of the member, the external environment and various loads, so that the concrete member is cracked, the bearing capacity is reduced, even the concrete member is damaged, and serious personal and property losses are caused. In order to ensure the workability of the concrete member, the state of the concrete is evaluated. The existing concrete evaluation mainly comprises concrete mechanical properties, defects, concrete stress and the like, wherein the concrete stress can intuitively reflect the safety of a concrete member.
The absolute stress can indicate the stress level of the structure, the safety reserve of the stress and other indexes, and is one of the important indexes for judging the safety state of the bridge (the absolute stress is also called as working stress or lasting stress, and refers to the sum of actual stresses generated by various loads, deformations and constraint actions on the structure), so the detection of the absolute stress is very important in the strain detection. The existing concrete stress detection technology can be divided into a destructive detection technology and a nondestructive detection technology. For example, chinese patent publication No. CN104864989B discloses "a method for testing absolute stress of existing concrete structure", which includes: measuring the propagation speed of ultrasonic waves of the concrete member in a stress-free state; acquiring the propagation speed of ultrasonic waves in the concrete structure along the stress sigma 1 direction by using an embedded spherical ultrasonic probe and ultrasonic detection equipment; and calculating the absolute stress sigma 1 of the interior of the concrete structure in the sigma 1 direction according to a formula.
The method for testing the absolute stress of the concrete member (structure) in the prior art is also a method for measuring the absolute stress of the concrete, and the method directly measures the internal absolute stress of the concrete member through the acoustic elastic effect. The applicant has found that the absolute stresses include an absolute principal compressive stress and an absolute principal tensile stress perpendicular to each other, which is measured in the above-mentioned prior art solutions. However, when the existing measuring method is used for measuring absolute stress, a hole needs to be drilled in the surface of the concrete member to take out a sample core, an embedded transducer is used for exciting and receiving ultrasonic waves, and a sensor needs to be embedded into a hole drilled in the concrete member, that is, the existing measuring method needs to destroy the structure of the concrete member, is not suitable for frequent detection, and results in poor measuring effect of the absolute stress of the concrete. Therefore, the applicant thought to devise a method of measuring the absolute stress of a concrete surface that enables non-destructive measurement.
Disclosure of Invention
Aiming at the defects of the prior art, the technical problems to be solved by the invention are as follows: how to provide a concrete surface absolute stress measuring method capable of realizing nondestructive measurement of absolute stress, thereby being used for frequent measurement and ensuring the measurement effect of concrete absolute stress.
In order to solve the technical problems, the invention adopts the following technical scheme:
a concrete surface absolute stress measuring method based on a laser ultrasonic technology comprises the following steps:
s01: arranging a collection point in a to-be-measured area on the surface of the concrete member, and arranging a main compressive stress excitation point on the surface of the concrete member, so that the main compressive stress excitation point can be connected with the collection point to form a main compressive stress measuring line along the main compressive stress direction;
s02: emitting laser beams to the main pressure stress excitation point and exciting ultrasonic waves;
s03: collecting ultrasonic signals of a main pressure stress excitation point at a collection point, and calculating corresponding ultrasonic signal propagation time;
s04: calculating the ultrasonic wave speed on the main pressure stress measuring line according to the length of the main pressure stress measuring line and the corresponding ultrasonic signal propagation time; then, calculating the absolute main compressive stress on the main compressive stress measuring line as the absolute main compressive stress of the region to be measured according to the following formula:
Preferably, the absolute principal tensile stress of the region to be measured is calculated by:
s11: arranging a main tensile stress excitation point on the surface of the concrete member, so that the main tensile stress excitation point can be connected with the acquisition point to form a main tensile stress measuring line along the main tensile stress direction;
s12: emitting laser beams to the main tensile stress excitation point and exciting ultrasonic waves;
s13: collecting ultrasonic signals of a main tensile stress excitation point at a collection point, and calculating corresponding ultrasonic signal propagation time;
s14: calculating the ultrasonic wave speed on the main tensile stress measuring line according to the length of the main tensile stress measuring line and the corresponding ultrasonic signal propagation time; then, calculating the absolute main tensile stress on the main tensile stress measuring line as the absolute main tensile stress of the region to be measured according to the following formula:
Preferably, the stress-free ultrasonic wave velocity of the concrete member is calculated by the following steps:
s21: arranging an unstressed excitation point on the surface of the concrete member, so that the unstressed excitation point can be connected with a collection point to form an unstressed measuring line with an included angle of 45 degrees with the main pressure stress direction and the main tensile stress direction;
s22: emitting laser beams to the stress-free excitation points and exciting ultrasonic waves;
s23: collecting ultrasonic signals of the stress-free excitation point at a collection point, and calculating corresponding ultrasonic signal propagation time;
s24: and calculating the ultrasonic wave speed on the stress-free measuring line according to the length of the stress-free measuring line and the corresponding ultrasonic signal propagation time to be used as the stress-free ultrasonic wave speed of the concrete member.
Preferably, the stress distribution of the region to be measured is calculated according to the absolute main compressive stress on the main compressive stress measuring line and the absolute main tensile stress on the main tensile stress measuring line.
Preferably, the acquisition point is arranged at the central position of the area to be measured; the main pressure stress excitation point, the main tensile stress excitation point and the stress-free excitation point are all arranged around the acquisition point.
Preferably, the device comprises two main compressive stress excitation points symmetrically arranged at two sides of the acquisition point, two main tensile stress excitation points symmetrically arranged at two sides of the acquisition point, and four stress-free excitation points arranged between the adjacent main compressive stress excitation points and main tensile stress excitation points.
Preferably, the main compressive stress excitation point, the main tensile stress excitation point and the unstressed excitation point can be sequentially enclosed to form a circular path with the acquisition point as a circle center, and the circular path can enclose the area to be measured.
Preferably, no concrete defect exists on the main pressure stress measuring line, the main tensile stress measuring line and the stress-free measuring line.
Preferably, a laser beam is emitted and an ultrasonic wave is excited in an ablation mechanism, and the excited ultrasonic wave is a rayleigh wave.
Preferably, the ultrasonic signal is collected by a laser vibration pickup at the collection point.
Compared with the prior art, the concrete surface absolute stress measuring method has the following beneficial effects:
1. in the invention, the acquisition point and the excitation point are arranged on the surface of the concrete member, and the ultrasonic wave is excited and the ultrasonic wave signal is acquired on the surface of the concrete member, so that the nondestructive measurement of the absolute stress can be realized without damaging the structure of the concrete member when the absolute stress is measured, and the measurement method can be used for frequent measurement.
2. In the invention, the main pressure stress measuring line parallel to the main pressure stress direction is arranged, and the absolute main pressure stress on the main pressure stress measuring line is calculated as the absolute main pressure stress of the region to be measured according to the ultrasonic wave speed on the main pressure stress measuring line and the 'acoustic elastic effect', so that the measurement accuracy of the absolute main pressure stress of the region to be measured can be improved (because the ultrasonic wave speed is sensitive to the stress when the measuring line is parallel to the absolute main pressure stress), and the measurement effect of the absolute corresponding stress of the concrete can be ensured.
Drawings
For purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made in detail to the present invention as illustrated in the accompanying drawings, in which:
FIG. 1 is a logic diagram of a method for measuring absolute stress of a concrete surface according to an embodiment;
FIG. 2 is a schematic diagram of a concrete surface absolute stress measuring method according to an embodiment;
fig. 3 is a schematic structural diagram of an ultrasonic transceiver according to a second embodiment.
Detailed Description
The following is further detailed by the specific embodiments:
the first embodiment is as follows:
the embodiment discloses a concrete surface absolute stress measuring method based on a laser ultrasonic technology.
As shown in fig. 1 and 2, the method for measuring the absolute stress of the concrete surface based on the laser ultrasonic technology comprises the following steps:
s01: arranging a collection point in a to-be-measured area on the surface of the concrete member, and arranging a main compressive stress excitation point on the surface of the concrete member, so that the main compressive stress excitation point can be connected with the collection point to form a main compressive stress measuring line along the main compressive stress direction;
s02: emitting laser beams to the main pressure stress excitation point and exciting ultrasonic waves;
s03: collecting ultrasonic signals of a main pressure stress excitation point at a collection point, and calculating corresponding ultrasonic signal propagation time;
s04: calculating the ultrasonic wave speed on the main pressure stress measuring line according to the length of the main pressure stress measuring line and the corresponding ultrasonic signal propagation time; then, calculating the absolute main compressive stress on the main compressive stress measuring line as the absolute main compressive stress of the region to be measured according to the following formula:
Specifically, the acoustic elastic coefficient can be selected according to an empirical formula, and when a test block for testing is reserved in the concrete member, the test block is calibrated to obtain the acoustic elastic coefficient. The directions of the main compressive stress and the main tensile stress of the concrete member are perpendicular to each other, and the directions are easy to judge. Because the tensile strength of the concrete member is low, when no crack exists on the surface of the concrete member, the absolute main tensile stress of the surface of the concrete member can be considered to be small, and therefore the concrete member can be considered to be in a one-way stressed state when the absolute main compressive stress is measured. In this embodiment, a pulse laser is excited by a pulse laser, and the single-pulse laser energy reaches mJ level. The ultrasonic waves are excited on the surface of the concrete member through the ablation mechanism, the excited ultrasonic waves are Rayleigh waves, the ultrasonic waves excited by the ablation mechanism have higher energy and higher signal-to-noise ratio, and the detection accuracy of the absolute stress is favorably improved. Gather ultrasonic signal through the laser vibration pickup, the spatial resolution of laser vibration pickup is very high, can reach 0.1mm for the fixed ultrasonic signal who gathers the point that can be fine gathers.
In the invention, the acquisition point and the excitation point are arranged on the surface of the concrete member, and the ultrasonic wave is excited and the ultrasonic wave signal is acquired on the surface of the concrete member, so that the nondestructive measurement of the absolute stress can be realized without damaging the structure of the concrete member when the absolute stress is measured, and the measurement method can be used for frequent measurement. Secondly, the invention sets a main pressure stress measuring line parallel to the main pressure stress direction, and calculates the absolute main pressure stress on the main pressure stress measuring line as the absolute main pressure stress of the region to be measured according to the ultrasonic wave speed on the main pressure stress measuring line and the 'acoustic elastic effect', so that the measurement accuracy of the absolute main pressure stress of the region to be measured can be improved (because the ultrasonic wave speed is sensitive to the stress when the measuring line is parallel to the absolute main pressure stress), and the measurement effect of the absolute corresponding stress of the concrete can be ensured.
In the specific implementation process, the absolute main tensile stress of the region to be measured is calculated through the following steps:
s11: arranging a main tensile stress excitation point on the surface of the concrete member, so that the main tensile stress excitation point can be connected with the acquisition point to form a main tensile stress measuring line along the main tensile stress direction;
s12: emitting laser beams to the main tensile stress excitation point and exciting ultrasonic waves;
s13: collecting ultrasonic signals of a main tensile stress excitation point at a collection point, and calculating corresponding ultrasonic signal propagation time;
s14: calculating the ultrasonic wave speed on the main tensile stress measuring line according to the length of the main tensile stress measuring line and the corresponding ultrasonic signal propagation time; then, calculating the absolute main tensile stress on the main tensile stress measuring line as the absolute main tensile stress of the region to be measured according to the following formula:
In the actual measurement process, when cracks exist on the surface of the concrete member, a large absolute main tensile stress exists on the surface of the concrete member, that is, the absolute main tensile stress can reflect the cracks existing on the surface of the concrete member to a certain extent, so that the measurement of the absolute main tensile stress is very important. Therefore, the invention is provided with the main tensile stress measuring line parallel to the main tensile stress direction, and calculates the absolute main tensile stress on the main tensile stress as the absolute main tensile stress of the region to be measured according to the ultrasonic wave speed on the main tensile stress measuring line and the acoustic elastic effect, so that the measurement accuracy of the absolute main tensile stress of the region to be measured can be improved (because the ultrasonic wave speed is sensitive to the stress when the measuring line is parallel to the absolute main tensile stress), and the measurement effect of the absolute corresponding stress of the concrete can be further ensured.
In the specific implementation process, the unstressed ultrasonic wave speed of the concrete member is calculated through the following steps:
s21: arranging an unstressed excitation point on the surface of the concrete member, so that the unstressed excitation point can be connected with a collection point to form an unstressed measuring line with an included angle of 45 degrees with the main pressure stress direction and the main tensile stress direction;
s22: emitting laser beams to the stress-free excitation points and exciting ultrasonic waves;
s23: collecting ultrasonic signals of the stress-free excitation point at a collection point, and calculating corresponding ultrasonic signal propagation time;
s24: and calculating the ultrasonic wave speed on the stress-free measuring line according to the length of the stress-free measuring line and the corresponding ultrasonic signal propagation time to be used as the stress-free ultrasonic wave speed of the concrete member.
Specifically, according to the theory of acoustic elasticity, when the measurement line is perpendicular or parallel to the absolute main compressive stress or the absolute main tensile stress, the ultrasonic wave velocity is sensitive to the stress, so that the direction of the measurement line and the absolute main compressive stress and the absolute main tensile stress is 45 degrees, and the measured ultrasonic wave velocity is approximate to the unstressed ultrasonic wave velocity. Therefore, the stress-free ultrasonic wave velocity of the concrete member can be well calculated through the steps, and the measurement effect of the concrete absolute force can be assisted and guaranteed.
In the specific implementation process, the stress distribution of the region to be measured is calculated according to the absolute main compressive stress on the main compressive stress measuring line and the absolute main tensile stress on the main tensile stress measuring line. Specifically, each excitation point (corresponding measurement line) can measure an absolute principal tensile stress or an absolute principal compressive stress, so that the stresses of all excitation points are integrated, and each excitation point is used as a pixel point, so that a plane stress distribution diagram of the region to be measured can be made. Therefore, the stress distribution condition of the area to be measured can be visually obtained, and the measurement effect of the concrete absolute stress is favorably improved.
In a specific implementation process, referring to fig. 2, the acquisition point is arranged at the center of the region to be measured; the main pressure stress excitation point, the main tensile stress excitation point and the stress-free excitation point are all arranged around the acquisition point. The device comprises two main compressive stress excitation points symmetrically arranged on two sides of an acquisition point, two main tensile stress excitation points symmetrically arranged on two sides of the acquisition point, and four stress-free excitation points arranged between the adjacent main compressive stress excitation points and the adjacent main tensile stress excitation points. The main pressure stress excitation point, the main tensile stress excitation point and the unstressed excitation point can be sequentially enclosed to form a circular path with the acquisition point as a circle center, and the circular path can surround the area to be measured.
In this embodiment, the number and the arrangement positions of the main compressive stress excitation points, the main tensile stress excitation points and the unstressed excitation points enable a circular path which takes the collection point as a circle center and can surround the region to be measured to be formed in a surrounding manner, so that the measurement effect of the absolute stress of the region to be measured can be ensured. Secondly, the number and the arrangement positions of the main pressure stress excitation points, the main tensile stress excitation points and the stress-free excitation points are more favorable for calculating the stress distribution (diagram) of the area to be measured, namely the stress distribution condition of the area to be measured can be more intuitively obtained, so that the measurement effect of the absolute stress of the concrete is favorably improved.
In the specific implementation process, no concrete defect exists on the main pressure stress measuring line, the main tensile stress measuring line and the stress-free measuring line. Therefore, the influence of the defects on the surface of the concrete on the detection of the absolute stress can be avoided.
Example two:
the present embodiment discloses an ultrasonic wave transmitting and receiving apparatus based on the first embodiment.
As shown in fig. 3, the ultrasonic transceiver includes a laser excitation assembly for emitting a laser beam to an excitation point on the surface of the concrete member and exciting an ultrasonic wave, a signal transmission assembly having a signal acquisition end facing an acquisition point on the surface of the concrete member and capable of acquiring an ultrasonic signal and a signal output end in data transmission connection with a set measurement terminal; the first action platform is used for driving the laser excitation assembly to move or rotate, and the second action platform is used for driving the signal transmission assembly to move or rotate; the first action platform and the second action platform are both controlled by the measuring terminal; the laser excitation assembly is arranged on the action end of the first action platform; the signal transmission assembly is arranged on the action end of the second action platform, and the second action platform is arranged on the action end of the first action platform and is positioned beside the laser excitation assembly. Specifically, the measuring terminal comprises an upper computer and a PC terminal. The upper computer is provided with Labview/Matlab software, can send out control commands, has the function of integrating a plurality of powerful functions such as numerical analysis, matrix calculation, scientific data visualization, modeling and simulation of a nonlinear dynamic system and the like into a window environment which is easy to use, and stores the data collected by the A/D collector into a PC terminal after processing. The PC terminal is connected with the first driving motor, the second driving motor and the A/D collector, controls the laser excitation assembly and the signal transmission assembly to work, analyzes the collected ultrasonic information, and calculates and obtains the absolute stress of the concrete surface.
According to the invention, the laser excitation assembly can emit laser beams to the excitation points on the surface of the concrete member and excite ultrasonic waves through the laser beams, namely the ultrasonic waves can be effectively excited on the surface of the concrete member, and meanwhile, the ultrasonic excitation position of the laser excitation assembly can be adjusted through the first action platform, so that the ultrasonic waves can be generated on different directions of the surface of the concrete member. Secondly, the ultrasonic signal on concrete member surface can be gathered and sent to measurement terminal to signal transmission subassembly, can effectual collection and send the ultrasonic signal on concrete member surface promptly, can adjust the collection position of signal transmission subassembly through the second action platform simultaneously, make its collection ultrasonic signal that can be better, more accurate to can assist the measurement of concrete surface absolute stress. Furthermore, the distance between the excitation point and the collection point can be determined according to the position deviation of the first action platform and the second action platform after moving and rotating, so that the ultrasonic wave speed can be calculated in an auxiliary mode, and the measuring effect of the concrete surface absolute stress is guaranteed.
In a specific implementation process, referring to fig. 2, the laser excitation assembly includes a pulse laser having an emitting end facing the concrete member and capable of emitting a laser beam, a total reflector disposed between the pulse laser and the concrete member and having an incident end facing the emitting end of the pulse laser, and a focusing lens disposed between the total reflector and the concrete member and having an exit end facing the total reflector and an exit end facing the excitation point of the concrete member; the focusing lens can excite ultrasonic waves through an ablation mechanism after receiving the laser beams. Specifically, the pulse laser is pulse type, and the single pulse laser energy can reach mJ magnitude. The total reflection mirror is positioned at a proper position between the pulse laser and the focusing lens and can reflect the laser beam generated by the pulse laser to enable the laser beam to be incident into the focusing lens. The position of the focusing lens is determined by the focal length of the lens and the concrete member, and the laser beam is required to be focused to the position of the excitation point on the surface of the concrete sample.
According to the invention, the laser excitation component emits a laser beam through the pulse laser, the laser beam is emitted into the focusing lens through the holophote, then the focusing lens converges the laser beam and excites ultrasonic waves through an ablation mechanism, so that the ultrasonic waves can be effectively excited on the concrete member to be tested. And the ultrasonic waves excited by the ablation mechanism have higher energy and higher signal-to-noise ratio, and are beneficial to improving the measurement accuracy of the concrete surface absolute stress.
In a specific implementation process, the first action platform comprises a first framework, a first mounting plate and a first driving motor, wherein the first mounting plate is arranged above the first framework at intervals and used for mounting the laser excitation assembly, and the first driving motor is arranged between the first framework and the first mounting plate and used for driving the first mounting plate to move horizontally and rotate vertically on the first framework; the first mounting plate is used as an action end of the first action platform; the first drive motor is controlled by the measuring terminal. Specifically, first action platform still includes the first scale that sets up between first skeleton and first driving motor. The first graduated scale is used for measuring the moving and rotating distances of the first mounting plate; the minimum scale of the first graduated scale is 1mm, so that the adjustment precision of the ultrasonic excitation position of the laser excitation assembly is guaranteed. The small receptacles of the first mounting plate are sufficient and strong enough to support other components. The first framework is made of aluminum alloy or stainless steel materials, can support the first mounting plate and the accessory parts thereof, and can move in three axes within a certain range under the driving of the first driving motor. The first driving motor is a stepping motor and is used for driving the first mounting plate to move in a three-axis mode with millimeter precision and controlled by the PC terminal.
According to the invention, the position of the first mounting plate can be adjusted by controlling the first driving motor, so that the ultrasonic excitation position of the laser excitation assembly can be adjusted, ultrasonic waves can be generated on different directions of the surface of the concrete member, and the measurement of the absolute stress of the surface of the concrete can be effectively assisted.
In a specific implementation process, the second action platform comprises a second framework arranged on the first mounting plate and positioned beside the laser excitation assembly, a second mounting plate arranged above the second framework at intervals and used for mounting the signal transmission assembly, and a second driving motor arranged between the second framework and the second mounting plate and used for driving the second mounting plate to move horizontally and rotate vertically on the second framework; the second mounting plate is used as an action end of the second action platform; the second drive motor is controlled by the measuring terminal. Specifically, the second action platform further comprises a second graduated scale arranged between the second framework and the second driving motor. The second graduated scale is used for measuring the moving distance of the second mounting plate; the minimum scale of the second graduated scale is 1mm, so that the adjustment precision of the acquisition position of the signal transmission assembly is guaranteed. The small receptacles of the second mounting plate are sufficient and strong enough to support other components. The second framework is made of aluminum alloy or stainless steel materials, can support the second mounting plate and the accessory parts thereof, and can move in three axes within a certain range under the driving of the second driving motor. The second driving motor is a stepping motor and is used for driving the second mounting plate to move in a three-axis mode with millimeter precision and controlled by the PC terminal.
According to the invention, the position of the second mounting plate can be adjusted by controlling the second driving motor, so that the acquisition position of the signal transmission assembly can be adjusted, the ultrasonic signal can be acquired better and more accurately, and the measurement of the concrete surface absolute stress can be assisted. Meanwhile, the distance between the excitation point and the collection point can be determined according to the position deviation of the first action platform and the second action platform after moving and rotating, so that the ultrasonic wave speed can be calculated in an auxiliary mode, and the measuring effect of the concrete surface absolute stress is guaranteed.
In the specific implementation process, the signal transmission assembly comprises a laser vibration pickup with a signal acquisition end facing the concrete member to be measured and capable of acquiring ultrasonic signals, and an A/D collector with a signal input end connected with the laser vibration pickup in data transmission and a signal output end connected with the measurement terminal in data transmission. Specifically, the laser vibration pickup is a laser dry vibration pickup, which collects ultrasonic signals corresponding to the collection points and converts the ultrasonic signals into electrical signals, and the spatial resolution of the laser vibration pickup is very high and can reach 0.1 mm. The A/D collector is used for acquiring the electric signal of the laser vibration pickup and sending the electric signal to the detection terminal; the A/D collector is in data transmission connection with the Labview/Matlab upper computer, and the collecting action is controlled by the Labview/Matlab upper computer.
In the invention, the signal transmission component acquires the ultrasonic signals through the laser vibration pickup and converts the ultrasonic signals into electric signals, and the A/D collector acquires the electric signals of the laser dry vibration pickup and sends the electric signals to the measuring terminal, thereby effectively realizing the acquisition and sending of the ultrasonic signals on the surface of the concrete member.
In the specific implementation process, the ultrasonic transceiver further comprises an oscilloscope which is arranged on the action end of the second action platform, and the signal input end of the oscilloscope is connected with the signal input end of the laser vibration pickup; the oscilloscope is controlled by the measuring terminal. Specifically, the oscilloscope, which requires a bandwidth of not less than 50MHz, is connected to the laser pickup and the trigger to convert the electrical signal of the laser pickup into a visual waveform. The trigger is connected with the oscilloscope and used for triggering the oscilloscope to act. According to the invention, the waveform change condition of the ultrasonic signal can be visually displayed through the oscilloscope, and the measurement can be completed in an auxiliary manner.
The foregoing is merely an example of the present invention, and common general knowledge in the field of known specific structures and characteristics is not described herein in any greater extent than that known in the art at the filing date or prior to the priority date of the application, so that those skilled in the art can now appreciate that all of the above-described techniques in this field and have the ability to apply routine experimentation before this date can be combined with one or more of the present teachings to complete and implement the present invention, and that certain typical known structures or known methods do not pose any impediments to the implementation of the present invention by those skilled in the art. It should be noted that, for those skilled in the art, without departing from the structure of the present invention, several changes and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.
Claims (10)
1. A concrete surface absolute stress measuring method based on a laser ultrasonic technology is characterized by comprising the following steps:
s01: arranging a collection point in a to-be-measured area on the surface of the concrete member, and arranging a main compressive stress excitation point on the surface of the concrete member, so that the main compressive stress excitation point can be connected with the collection point to form a main compressive stress measuring line along the main compressive stress direction;
s02: emitting laser beams to the main pressure stress excitation point and exciting ultrasonic waves;
s03: collecting ultrasonic signals of a main pressure stress excitation point at a collection point, and calculating corresponding ultrasonic signal propagation time;
s04: calculating the ultrasonic wave speed on the main pressure stress measuring line according to the length of the main pressure stress measuring line and the corresponding ultrasonic signal propagation time; then, calculating the absolute main compressive stress on the main compressive stress measuring line as the absolute main compressive stress of the region to be measured according to the following formula:
2. The method for measuring the absolute stress of the surface of the concrete based on the laser ultrasonic technology as claimed in claim 1, wherein the absolute principal tensile stress of the area to be measured is calculated by the following steps:
s11: arranging a main tensile stress excitation point on the surface of the concrete member, so that the main tensile stress excitation point can be connected with the acquisition point to form a main tensile stress measuring line along the main tensile stress direction;
s12: emitting laser beams to the main tensile stress excitation point and exciting ultrasonic waves;
s13: collecting ultrasonic signals of a main tensile stress excitation point at a collection point, and calculating corresponding ultrasonic signal propagation time;
s14: calculating the ultrasonic wave speed on the main tensile stress measuring line according to the length of the main tensile stress measuring line and the corresponding ultrasonic signal propagation time; then, calculating the absolute main tensile stress on the main tensile stress measuring line as the absolute main tensile stress of the region to be measured according to the following formula:
3. The method for measuring the absolute stress of the surface of the concrete based on the laser ultrasonic technology as claimed in claim 2, wherein the stress-free ultrasonic wave velocity of the concrete member is calculated by the following steps:
s21: arranging an unstressed excitation point on the surface of the concrete member, so that the unstressed excitation point can be connected with a collection point to form an unstressed measuring line with an included angle of 45 degrees with the main pressure stress direction and the main tensile stress direction;
s22: emitting laser beams to the stress-free excitation points and exciting ultrasonic waves;
s23: collecting ultrasonic signals of the stress-free excitation point at a collection point, and calculating corresponding ultrasonic signal propagation time;
s24: and calculating the ultrasonic wave speed on the stress-free measuring line according to the length of the stress-free measuring line and the corresponding ultrasonic signal propagation time to be used as the stress-free ultrasonic wave speed of the concrete member.
4. The method for measuring the absolute stress of the surface of the concrete based on the laser ultrasonic technology as claimed in claim 2, wherein: and calculating the stress distribution of the region to be measured according to the absolute main compressive stress on the main compressive stress measuring line and the absolute main tensile stress on the main tensile stress measuring line.
5. The method for measuring the absolute stress of the surface of the concrete based on the laser ultrasonic technology as claimed in claim 4, wherein: arranging a collection point at the central position of the area to be measured; the main pressure stress excitation point, the main tensile stress excitation point and the stress-free excitation point are all arranged around the acquisition point.
6. The method for measuring the absolute stress of the surface of the concrete based on the laser ultrasonic technology as claimed in claim 5, wherein: the device comprises two main compressive stress excitation points symmetrically arranged on two sides of an acquisition point, two main tensile stress excitation points symmetrically arranged on two sides of the acquisition point, and four stress-free excitation points arranged between the adjacent main compressive stress excitation points and the adjacent main tensile stress excitation points.
7. The method for measuring the absolute stress of the surface of the concrete based on the laser ultrasonic technology as claimed in claim 6, wherein: the main pressure stress excitation point, the main tensile stress excitation point and the unstressed excitation point can be sequentially enclosed to form a circular path with the acquisition point as a circle center, and the circular path can surround the area to be measured.
8. The method for measuring the absolute stress of the surface of the concrete based on the laser ultrasonic technology as claimed in claim 3, wherein: and no concrete defects exist on the main pressure stress measuring line, the main tensile stress measuring line and the stress-free measuring line.
9. The method for measuring the absolute stress of the surface of the concrete based on the laser ultrasonic technology as claimed in claim 3, wherein: a laser beam is emitted and an ultrasonic wave is excited by an ablation mechanism, and the excited ultrasonic wave is a Rayleigh wave.
10. The method for measuring the absolute stress of the surface of the concrete based on the laser ultrasonic technology as claimed in claim 3, wherein: and collecting ultrasonic signals through a laser vibration pickup at a collecting point.
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