CN103185744A - Detection device for measuring transmission time of ultrasonic waves in sheet material - Google Patents

Abstract

The invention discloses a detection device for measuring the transmission time of ultrasonic waves in a sheet material. The device comprises a test board and two groups of ultrasonic wave measuring modules, wherein the test board consists of a fixed seat and a table top; a board table is arranged in front of the fixed seat; and the two groups of ultrasonic wave measuring modules consist of an ultrasonic wave transmitting module and an ultrasonic wave receiving module, and are connected to a computer in parallel after passing through respective corresponding time measuring modules and respective corresponding single chip microcomputers. As proved by factory practice, the requirement of time detection in nondestructive detection of wood can be met by using ultrasonic waves and other detection means, and the detection device has important significance to nondestructive online detection of the strength of artificial plates, and is an extremely important means for increasing the utilization ratio of the artificial plates.

Description

A detection device for measuring the propagation time of ultrasonic waves in plates

technical field

The invention relates to the field of measurement, in particular to a detection device for measuring the propagation time of ultrasonic waves in a plate.

Background technique

With the increase of timber demand, the use of wood-based panels to replace logs and sawn timber has become one of the effective ways to efficiently utilize timber resources. The advantages of wood-based panels are: large format, good structure, convenient construction; low expansion and contraction rate, stable size, uniform material than sawn timber, not easy to deform and crack; veneer and various scraps used as wood-based panels are easy to impregnate, so It can be used for various functional treatments (such as flame retardant, anti-corrosion, anti-shrinkage, wear-resistant, etc.); it has strong applicability in a wide range of thickness and density levels; its bending and forming performance is better than that of sawn timber. The disadvantage of wood-based panels is that the glue layer will age and the long-term bearing capacity is poor. Therefore, non-destructive online testing of the strength of wood-based panels is of great significance, and it is also an extremely important means to improve the utilization rate of wood-based panels. In the prior art, the detection of wood is inconvenient and the detection efficiency is low. At present, there is no online real-time detection equipment for the mechanical strength of wood in my country.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method and device for non-destructive detection of boards, which can solve the defects of inconvenient wood detection and low detection efficiency in the prior art, and can classify the boards detected.

working principle:

According to the "penetration method" or the transmission method, a transmitting transducer is used to transmit ultrasonic pulse waves, so that the ultrasonic waves propagate in the detected wood and are then received by the receiving transducer. The received ultrasonic signal is converted into an electrical signal, and then sent to the single-chip microcomputer after signal processing by the ultrasonic receiving circuit, and the time of the ultrasonic wave in the plate can be calculated.

V _speed = L/T (1)

In formula (1), L is the length of the plate

T - propagation time of ultrasonic waves in the plate

V _speed —the propagation speed of ultrasonic waves in the plate

Ev=ρV _speed ² , (2)

In the formula (2), Ev is the dynamic modulus of elasticity of the plate

ρ - the average density of the board

ρ = M/V _body (3)

In formula (3), M is the mass of the plate

V- _body -plate volume

V _body = L*W*H (4)

In formula (4), L is the length of the plate

W is the width of the sheet

H - the thickness of the plate

According to (1), (2), (3) and (4), the dynamic elastic modulus of the plate is obtained:

And because of the positive correlation between the elastic modulus and the mechanical strength of the board, different boards are divided into corresponding grades.

In order to achieve the detection of the ultrasonic wave penetrating plate time in the above-mentioned purpose, the present invention realizes through the following technical solutions:

The invention discloses a detection device for measuring the propagation time of an ultrasonic wave in a plate, which comprises:

A test bench consisting of a fixed seat and a table top, the table top is arranged in front of the fixed seat;

Two groups of ultrasonic measuring modules composed of an ultrasonic emitting module and an ultrasonic receiving module are connected to the computer in parallel after passing through respective corresponding time measuring modules and respective corresponding single-chip microcomputers.

In the above device, the ultrasonic transmitting module includes an ultrasonic transmitting sensor and an ultrasonic transmitting circuit;

The ultrasonic receiving module includes an ultrasonic receiving sensor and an ultrasonic receiving circuit composed of a high-pass filter circuit, an amplifying circuit, a resonant filtering and amplifying circuit, a full-wave rectifying circuit, a threshold comparison circuit, and a Darlington tube driving circuit.

In the above device, the ultrasonic transmitting sensor and the ultrasonic receiving sensor in the group are installed on both sides of the plate in the width direction, and are located on the same straight line;

Sensors of the same type between groups are installed on both sides of the sheet in the vertical width direction and are located on the same straight line.

In the above device, the ultrasonic sensor is fixed in a push-pull device driven by an air cylinder and fixed in a fixed seat with a built-in spring.

It can be seen from the above that a detection device for measuring the propagation time of ultrasonic waves in boards in the present invention can realize the requirements for time detection in the non-destructive detection of wood by using ultrasonic waves and other detection means, and perform non-destructive online detection of the strength of wood-based panels It is of great significance and is also an extremely important means to improve the utilization rate of wood-based panels.

Description of drawings

Fig. 1 is a system block diagram of a plate non-destructive testing method in an embodiment of the present invention;

Fig. 2 is a schematic diagram of the sensor installation position of the detection device for measuring the ultrasonic propagation time in the plate in the embodiment of the present invention;

3 is a schematic diagram of a detection device for measuring the propagation time of ultrasonic waves in a plate in an embodiment of the present invention;

Fig. 4 is a diagram of an ultrasonic transmitting circuit and a receiving circuit in an embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

The embodiment of the present invention provides a specific implementation of the device for non-destructive testing of plates. Figure 1 is a system block diagram of the method for non-destructive testing of plates in the embodiment of the present invention, as shown in Figure 1, including the following aspects:

1. A plate thickness detection device 101, used to measure the thickness of the plate. The measurement of thickness is mainly to measure the small variation of thickness. The thickness of each batch of wood in the factory is roughly the same, which can be expressed as (W+Δw). First, set this standard quantity as W, and only need to measure the variation Δw of each piece of wood and the standard value (Δw has positive and negative points). By giving a fixed distance between a pair of displacement sensors, when the thickness changes, the displacement sensor The pressing amount changes, and the signal is collected into the controller through the signal conditioning circuit, so as to calculate the thickness.

2. A device 102 for plate length detection. In the length measurement, the system can drive the movement of the rotary encoder through the friction between the plate and the rotary encoder when the plate moves forward, and obtain the length of the plate by measuring the number of turns of the rotary encoder when the plate moves forward. The output of the pulse output circuit and the phase detection circuit is connected to the counting port and the digital port of the data acquisition card after long-term transmission. The length of the plate can be obtained by multiplying the remembered pulse number by a constant. Among them, the constant=(circumference length of the rotary encoder that is in contact with the sheet material)/code number of the rotary encoder.

3. After the thickness measurement and length measurement are completed, the static measurement platform for width measurement, weight measurement and wave velocity is reached, which includes a quality measurement device 103 , a width measurement device 104 and a time measurement device 105 . The present invention takes into account the objective conditions of the industrial site, the force of the frame part, and the performance of the load cell and other related factors, and adopts a static measurement method. When the plate arrives at the static measurement platform, the photoelectric sensor sends a signal to start Sample weighing signal. Multiple measurements are averaged to improve measurement accuracy. Because the signal collected by the load cell is a current signal, it is directly sent to the data acquisition card connected to the host computer for data acquisition after being transmitted through the long line through the electrorheological voltage conditioning circuit.

4. After the weight measurement is over, start the wave velocity measurement. Wherein, the wave velocity measurement further includes a plate width measuring device 104 and a measuring device 105 for the propagation time of ultrasonic waves in the width direction.

In a similar manner to thickness measurement, width measurement also measures small changes in width. By giving a fixed distance between a pair of displacement sensors, when the width changes, the indentation of the displacement sensors changes. The output signal of the displacement sensor is connected to the single-chip microcomputer after passing through the signal conditioning circuit.

Wherein, the time measurement device includes: a test bench composed of a fixed seat and a table top, and a table top is arranged in front of the fixed seat; two groups of ultrasonic measurement modules composed of an ultrasonic transmitting module and an ultrasonic receiving module, through respective corresponding time measuring modules, and respective After the corresponding microcontroller, connect it to the computer in parallel.

Among them, the ultrasonic transmitting module includes ultrasonic transmitting sensor and ultrasonic transmitting circuit; The tube driving circuit is connected in turn to form an ultrasonic receiving circuit.

Figure 2 is a schematic diagram of the sensor installation position of the detection device for measuring the propagation time of ultrasonic waves in the plate in the embodiment of the present invention. As shown in Figure 2, the ultrasonic transmitting sensors and ultrasonic receiving sensors in the group are installed on both sides of the plate in the width direction , and are located on the same straight line; sensors of the same type between groups are installed on both sides of the plate in the vertical width direction, and are located on the same straight line.

Fig. 3 is the schematic diagram of the detection device of measuring ultrasonic propagation time in the plate in the embodiment of the present invention, as described in Fig. 3, specifically, after the single-chip microcomputer receives the ultrasonic measurement signal sent by the upper computer, it sends to the ultrasonic sending circuit pulse signal, and start the time measurement module to start timing. The sent pulse signal excites the ultrasonic sensor to send ultrasonic wave after passing through the ultrasonic transmitting circuit, and the ultrasonic sensor at the other end receives the signal through the plate, and then the signal is conditioned by the ultrasonic receiving circuit to generate an edge signal, so that the time measurement module stops timing. The single-chip microcomputer reads the time data of the timing chip, and at the same time, according to the previously measured width data, returns the measured data and the calculated speed value to the computer.

5. An evaluation unit 106 comprising a data acquisition unit and a data processing unit. In the present invention, the data acquisition unit is a data acquisition card, and the data processing unit is a host computer. The upper computer performs calculations based on the data collected by the data acquisition card and various data processed. According to the above principles, the elastic modulus of the plate is obtained for grade division.

6. The method in the embodiment of the present invention further includes a display unit 107 for displaying the measurement results of each measuring device, as well as the elastic modulus of the sheet and the grade of the sheet calculated according to the measurement results.

It can be seen from the above that a detection device for measuring the propagation time of ultrasonic waves in boards in the present invention can realize the requirements for time detection in the non-destructive detection of wood by using ultrasonic waves and other detection means, and perform non-destructive online detection of the strength of wood-based panels It is of great significance and is also an extremely important means to improve the utilization rate of wood-based panels.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the present invention. within the scope of protection.

Claims (3)

1. A detection device for measuring ultrasonic wave propagation time in plates, characterized in that the device comprises: A test bench consisting of a fixed seat and a table top, the table top is arranged in front of the fixed seat; Two groups of ultrasonic measuring modules composed of an ultrasonic emitting module and an ultrasonic receiving module are connected to the computer in parallel after passing through respective corresponding time measuring modules and respective corresponding single-chip microcomputers. 2. The device according to claim 1, characterized in that, The ultrasonic transmitting module includes an ultrasonic transmitting sensor and an ultrasonic transmitting circuit; The ultrasonic receiving module includes an ultrasonic receiving sensor and an ultrasonic receiving circuit composed of a high-pass filter circuit, an amplifying circuit, a resonant filtering and amplifying circuit, a full-wave rectifying circuit, a threshold comparison circuit, and a Darlington tube driving circuit. 3. The device according to claim 2, characterized in that, The ultrasonic transmitting sensor and ultrasonic receiving sensor in the group are installed on both sides of the plate in the width direction and are located on the same straight line; Sensors of the same type between groups are installed on both sides of the sheet in the vertical width direction and are located on the same straight line.

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