CN106855539A - A kind of anchor rod nondestructive testing method and equipment based on stress wave - Google Patents

Abstract

The invention discloses a kind of anchor rod nondestructive testing method based on stress wave and equipment, stress wave signal is gathered by acceleration transducer, signal after amplification and filter circuit by being admitted to AD conversion module, digital data transmission is converted analog signals into ARM controller, ARM controller carries out time and frequency domain analysis to signal, according to reflection wave signal in cross correlation algorithm identification stress wave waveform；The present invention can accurately carry out the judgement of the measure and mortar saturation degree of rock-bolt length, and then judge anchor rod anchored quality.The equipment can also be applied carries out anchor pole detection without damage in the side slope using suspension roof support, tunnel, dam body, with wide application value.

Description

A method and device for non-destructive testing of bolts based on stress wave method

technical field

The invention belongs to the technical field of bolt detection in coal mines, in particular to a nondestructive detection method and equipment for bolts based on a stress wave method.

Background technique

Anchor is a very widely used material in coal mine production. The mine bolt is a force-bearing member installed in the rock-soil layer. One end of it is connected to the engineering building, and the other end is anchored in the rock-soil layer. If necessary, pre-gravity is applied to it to effectively To bear structural loads, prevent structural deformation, and maintain the stability of structural buildings. Therefore, the quality of bolt anchorage affects the safety of coal mine production to a large extent.

At present, there are mainly two methods for detecting the anchorage quality of bolts in the engineering field, one is destructive testing, and the other is non-destructive testing. Destructive testing includes coring method and pulling test method. The biggest advantages of these two methods are intuitive and accurate, but they are both destructive testing methods, and the operation is complicated, the workload is heavy, and the cost is huge. Non-destructive testing includes stress wave methods and ultrasonic methods. In practice of ultrasonic method, the signal attenuates seriously during the propagation process in the anchor rod, and the end of the anchor rod needs to be polished and smoothed before the ultrasonic wave can be coupled into the anchor rod body.

Existing testing equipment includes pull-out gauges, force-measuring anchors and GRANIT-type anchor non-destructive testing equipment based on ultrasonic theory. The two force detection methods of pull-out meter and force-measuring bolt produce strong disturbance to the roadway reinforced by bolt, which reduces the reinforcement effect of bolt on surrounding rock, which is only suitable for random inspection, not suitable for large-scale Carry out bolt quality checks. GRANIT non-destructive testing equipment for bolts can carry out non-destructive testing on bolts, but due to the serious attenuation of the ultrasonic signal, it can usually only detect bolts within 3.0m.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a method and equipment for the non-destructive detection of bolts based on the stress wave method. Disadvantages and the problem of serious signal attenuation and short measurement length of ultrasonic method. The equipment is easy to operate, has strong environmental adaptability, good human-computer interaction, high measurement data accuracy, good effect, and fast data processing speed. It can measure bolts over 10m, and the measurement error of bolt length is less than 3%, which is better than ordinary Anchor length detection equipment.

The technical scheme that realizes the object of the present invention is:

A method for the non-destructive testing of bolts based on the stress wave method, specifically comprising the following steps:

(1) Install the acceleration sensor on the end of the free section of the anchor rod;

(2) Connect the acceleration sensor to the signal conditioning module with a cable, turn on the power of the device, set it on the LCD screen, and adjust the device to the state where data is to be collected;

(3) Hit the end of the free section of the bolt with a vibrating hammer to generate a stress wave;

(4) The acceleration sensor collects the stress wave signal, and transmits the collected stress wave signal to the signal conditioning module;

(5) After the signal conditioning module performs signal amplification and filtering on the received signal, the signal is transmitted to the AD conversion module, and the digital signal after the AD conversion is sent to the ARM controller module for data processing;

(6) The data processed by the ARM controller module is displayed in the LCD screen display module, the acquisition of the stress wave signal is completed, and the initial stress waveform is obtained;

(7) Click HHT analysis on the LCD screen to get the Hilbert-Huang transformation diagram of the stress wave waveform.

(8) Analyze the waveform obtained by the Hilbert-Huang transformation to obtain the length of the bolt.

(9) Finally, save the Hilbert-Huang transformation diagram of the stress wave waveform in (7) and the bolt length value in (8) to the SD card storage module.

In the step (3), the vibrating hammer strikes the anchor rod continuously for 4-6 times with the same frequency and strength.

The initial stress waveform diagram obtained in the step (6) is obtained after processing a plurality of stress waveform diagrams by a normalized superposition method.

The HHT analysis in the step (7) is obtained by performing Hilbert-Huang Transform (HHT) analysis on the stress wave waveform.

The calculation of the length of the bolt in the step (8) is based on the waveform obtained by HHT analysis, and the corresponding time t ₁ of the reflection signal of the anchorage section and the corresponding time t ₂ of the reflection signal of the bottom end are obtained. According to the stress wave in the bare bolt Propagation velocity υ ₁ = 5130m/s, using the formula l ₁ = (υ ₁ *t ₁ )/2 to obtain the length l ₁ of the free section of the anchor rod; according to the propagation velocity of the stress wave in the anchorage section υ ₂ = 4700m/s, Use the formula l ₂ =(υ ₂ *(t ₂ -t ₁ ))/2 to obtain the length l ₂ of the anchorage section of the anchor rod, and obtain the total length l of the anchor rod according to the formula l=l ₁ +l ₂ .

A non-destructive testing device for bolts based on the stress wave method, including sequentially connected acceleration sensors, signal conditioning modules, AD conversion modules and ARM controller modules, and also includes an exciting hammer, power supply module, LCD display module and SD card storage module ;The power supply module is connected with the signal conditioning module, the AD conversion module and the ARM controller module respectively, the ARM controller module is also connected with the LCD display module and the SD card storage module, the acceleration sensor is installed on the anchor rod, and the vibration hammer strikes the anchor rod .

The acceleration sensor is installed at the end of the free section of the anchor rod.

The signal conditioning module further includes a sequentially connected signal amplifier circuit and a signal filter circuit, the acceleration sensor is connected to the signal amplifier circuit, the signal filter circuit is connected to the AD conversion module, and the signal filter circuit is a fourth-order Butterworth low-pass filter .

The signal amplifying circuit includes a first operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a Six capacitors and the seventh capacitor; the positive input terminal of the first operational amplifier is respectively connected to one end of the first resistor, the third capacitor, and the fourth capacitor, and the negative input terminal is respectively connected to one end of the second resistor, one end of the fifth capacitor, and the fourth capacitor. The other end of the capacitor is connected; the other end of the first resistor is connected to the positive output end of the acceleration sensor; the other end of the second resistor is connected to the negative output end of the acceleration sensor; the other end of the third capacitor and the other end of the fourth capacitor are grounded ; One end of the first capacitor and the second capacitor are grounded, and the other end is connected to +5V voltage; the first operational amplifier pin 1 is connected to +5V voltage, the second pin is connected to -5V voltage, and the third pin is respectively connected to the third One end of the resistor and the fourth resistor are connected, pins 4 and 5 are grounded; the other end of the fourth resistor is connected to the ground; the other end of the third resistor is connected to the signal output terminal of the first operational amplifier, and the signal output terminal is also connected to the signal filter circuit connection;

_The gain is set by two external resistors _R3 and R4, and the stability is much higher than that of an instrumentation amplifier using a single resistor to set the gain. The gain expression is:

The signal filter circuit includes a second operational amplifier, a third operational amplifier, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, an eighth capacitor, a ninth capacitor, a tenth capacitor and an eleventh capacitor ; One end of the fifth resistor is connected with the signal output end of the first operational amplifier of the signal amplification circuit, and the other end is connected with one end of the sixth resistor and the ninth capacitor respectively; the other end of the sixth resistor is connected with the positive input of the second operational amplifier The positive input terminal of the second operational amplifier is also connected with one end of the eighth capacitor; the other end of the eighth capacitor is grounded; the negative input terminal of the second operational amplifier is connected with the signal output terminal of the second operational amplifier; the second operational amplifier The signal output terminal of the amplifier is also connected to the other end of the ninth capacitor and one end of the seventh resistor; the No. 1 pin of the second operational amplifier is connected to +5V voltage, and the No. 2 pin is connected to -5V voltage; the other end of the seventh resistor Connect with one end of the eighth resistor and the eleventh capacitor respectively; the other end of the eighth resistor is respectively connected with the positive input end of the third operational amplifier; the positive input end of the third operational amplifier is also connected with one end of the tenth capacitor; The other end of the tenth capacitor is grounded; the No. 1 pin of the third operational amplifier is connected to +5V voltage, and the No. 2 pin is connected to -5V voltage; the signal output end of the third operational amplifier is connected to the other end of the eleventh capacitor and the third The negative input terminal of the operational amplifier is connected to the AD conversion module.

A method and equipment for non-destructive testing of bolts based on the stress wave method provided by the present invention have good measurement results. Compared with the coring method, the drawing test method and the ultrasonic method, the present invention has the following advantages:

1. This equipment belongs to non-destructive testing and does not cause damage to the anchor itself; compared with ultrasonic non-destructive testing technology, this equipment avoids the shortcomings of serious ultrasonic signal attenuation and can only measure anchors within 3m;

2. The equipment can measure bolts over 10m, and the measurement error of bolt length is less than 3%, which is better than ordinary bolt length detection equipment;

3. The device has good portability and is suitable for measuring bolts in complex environments. It has the characteristics of early detection of faults, high sensitivity, strong anti-interference ability and high accuracy;

4. The human-computer interaction is good, and it can be input by keyboard to set the detection location, date, anchor number and sampling frequency. It has functions such as one-key waveform storage and upper computer data analysis.

Description of drawings

Fig. 1 is a bolt detection model diagram of the present invention;

Fig. 2 is a structural block diagram of detection equipment of the present invention;

Fig. 3 is a signal amplification circuit diagram;

Figure 4 is a signal filter circuit diagram.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited thereto.

Example:

A method for the non-destructive testing of bolts based on the stress wave method, specifically comprising the following steps:

(1) Install the acceleration sensor on the anchor rod;

(2) Connect the acceleration sensor to the signal conditioning module with a cable, turn on the power of the device, set it on the LCD screen, and adjust the device to the state where data is to be collected;

(3) Hit the end of the free section of the bolt with a vibrating hammer to generate a stress wave;

(4) The acceleration sensor collects the stress wave signal, and transmits the collected stress wave signal to the signal conditioning module;

(5) After the signal conditioning module performs signal amplification and filtering on the received signal, the signal is transmitted to the AD conversion module, and the digital signal after the AD conversion is sent to the ARM controller module for data processing;

(6) The data processed by the ARM controller module is displayed in the LCD screen display module, the acquisition of the stress wave signal is completed, and the initial stress waveform is obtained;

(7) Click HHT analysis on the LCD screen to get the Hilbert-Huang transformation diagram of the stress wave waveform.

(8) Analyze the waveform obtained by the Hilbert-Huang transformation to obtain the length of the bolt.

(9) Finally, save the Hilbert-Huang transformation diagram of the stress wave waveform in (7) and the bolt length value in (8) to the SD card storage module.

The acceleration sensor in the step (1) is installed at the end of the free section of the anchor rod.

In the step (3), the vibrating hammer strikes the anchor rod continuously for 4-6 times with the same frequency and strength.

The initial stress waveform diagram obtained in the step (6) is obtained after processing a plurality of stress waveform diagrams by a normalized superposition method.

The HHT analysis in the step (7) is obtained by performing Hilbert-Huang Transform (HHT) analysis on the stress wave waveform.

The calculation of the length of the bolt in the step (8) is based on the waveform obtained by HHT analysis, and the corresponding time t ₁ of the reflection signal of the anchorage section and the corresponding time t ₂ of the reflection signal of the bottom end are obtained. According to the stress wave in the bare bolt Propagation velocity υ ₁ = 5130m/s, using the formula l ₁ = (υ ₁ *t ₁ )/2 to obtain the length l ₁ of the free section of the anchor rod; according to the propagation velocity of the stress wave in the anchorage section υ ₂ = 4700m/s, Use the formula l ₂ =(υ ₂ *(t ₂ -t ₁ ))/2 to obtain the length l ₂ of the anchorage section of the anchor rod, and obtain the total length l of the anchor rod according to the formula l=l ₁ +l ₂ .

As shown in Figure 1, the bolt includes a free section and an anchor section. The free section refers to the area where the tensile force at the head of the anchor is transmitted to the anchor body, and its function is to apply prestress to the anchor; the anchor section refers to the cement slurry The function of the area where the prestressed tendon is bonded to the soil layer is to increase the bonding friction between the anchor body and the soil layer, increase the pressure bearing effect of the anchor body, and transmit the tensile force of the free section to the depth of the soil; anchoring The interface is the interface between the free section and the anchor section; the bottom end is the end of the anchor section of the anchor; the acceleration sensor is installed at the end of the free section of the anchor; when the measurement is started, an excitation hammer is used to strike the end of the free section of the anchor to generate Stress wave, when the stress wave propagates longitudinally along the anchor rod body to the anchoring interface, part of the stress wave is reflected, while the other part of the stress wave is transmitted into the anchorage section and continues to propagate, and is reflected again when it reaches the bottom of the anchorage. Ideally, The acceleration sensor will receive two reflection signals successively.

As shown in Figure 2, a non-destructive testing equipment for bolts based on the stress wave method includes an acceleration sensor 1, a signal conditioning module, an AD conversion module 4 and an ARM controller module 5 connected in sequence, as well as a vibrating hammer and a power supply module. 7. LCD display module 6 and SD card storage module 8; power supply module 7 is connected with signal conditioning module, AD conversion module 4 and ARM controller module 5 respectively, and ARM controller module 5 is also connected with LCD display module 6 and SD card storage module 8 connection, the acceleration sensor 1 is installed on the anchor rod, and the vibrating hammer strikes the anchor rod.

The acceleration sensor 1 is installed at the end of the free section of the anchor rod.

The signal conditioning module further includes a sequentially connected signal amplifier circuit 2 and a signal filter circuit 3, the acceleration sensor 1 is connected to the signal amplifier circuit 2, the signal filter circuit 3 is connected to the AD conversion module 4, and the signal filter circuit 3 is a fourth-order Butterworth low pass filter.

As shown in Figure 3, the signal amplifying circuit 2 includes a first operational amplifier U1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first capacitor C1, and a second capacitor C2 , the third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, the sixth capacitor C6 and the seventh capacitor C7; the positive input terminal of the first operational amplifier is respectively connected with the first resistor R1, the third capacitor C3, and the fourth capacitor C4 One end of the first resistor R1 is connected to the positive output end of the acceleration sensor; the negative input end is connected to one end of the second resistor R2, one end of the fifth capacitor C5, and the other end of the fourth capacitor C4; The other end of R2 is connected to the negative output end of the acceleration sensor; the other end of the third capacitor C3 and the other end of the fourth capacitor C4 are grounded; one end of the first capacitor C1 and the second capacitor C2 is grounded, and the other end is connected to +5V voltage; Pin 1 of the first operational amplifier U1 is connected to +5V voltage, pin 2 is connected to -5V voltage, pin 3 is respectively connected to one end of the third resistor R3 and fourth resistor R4, and pins 4 and 5 grounding; the other end of the fourth resistor R4 is grounded; the other end of the third resistor R3 is connected to the signal output terminal of the first operational amplifier U1, and the signal output terminal is also connected to the signal filter circuit 3;

_The gain is set by two external resistors _R3 and R4, and the stability is much higher than that of an instrumentation amplifier using a single resistor to set the gain. The gain expression is:

As shown in Figure 4, the signal filtering circuit 3 includes a second operational amplifier U3, a third operational amplifier U4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, and an eighth capacitor C8, the ninth capacitor C9, the tenth capacitor C10 and the eleventh capacitor C11; one end of the fifth resistor R5 is connected to the signal output end of the first operational amplifier U1 of the signal amplifying circuit, and the other end is respectively connected to the sixth resistor R6 and the first operational amplifier U1 One end of nine capacitors C9 is connected; the other end of the sixth resistor R6 is connected with the positive input of the second operational amplifier U2; the positive input of the second operational amplifier U2 is also connected with one end of the eighth capacitor C8; the eighth capacitor C8 The other end is grounded; the negative input end of the second operational amplifier U2 is connected with the signal output end of the second operational amplifier U2; the signal output end of the second operational amplifier U2 is also connected with the other end of the ninth capacitor C9 and one end of the seventh resistor R7 connection; the No. 1 pin of the second operational amplifier U2 is connected to +5V voltage, and the No. 2 pin is connected to -5V voltage; the other end of the seventh resistor R7 is respectively connected to one end of the eighth resistor R8 and the eleventh capacitor C11; The other ends of the eight resistors R8 are respectively connected to the positive input of the third operational amplifier U3; the positive input of the third operational amplifier U3 is also connected to one end of the tenth capacitor C10; the other end of the tenth capacitor C10 is grounded; the third operational The No. 1 pin of the amplifier U3 is connected to +5V voltage, and the No. 2 pin is connected to -5V voltage; the signal output terminal of the third operational amplifier U3 is respectively connected to the other end of the eleventh capacitor C11 and the negative input terminal of the third operational amplifier U3 , and the AD conversion module 4 is connected.

Claims (10)

1. A bolt non-destructive testing method based on stress wave method, is characterized in that, specifically comprises the steps: (1) Install the acceleration sensor on the end of the free section of the anchor rod; (2) Connect the acceleration sensor to the signal conditioning module with a cable, turn on the power of the device, set it on the LCD screen, and adjust the device to the state where data is to be collected; (3) Hit the end of the free section of the bolt with a vibrating hammer to generate a stress wave; (4) The acceleration sensor collects the stress wave signal, and transmits the collected stress wave signal to the signal conditioning module; (5) After the signal conditioning module performs signal amplification and filtering on the received signal, the signal is transmitted to the AD conversion module, and the digital signal after the AD conversion is sent to the ARM controller module for data processing; (6) The data processed by the ARM controller module is displayed in the LCD screen display module, the acquisition of the stress wave signal is completed, and the initial stress waveform is obtained; (7) Click HHT analysis on the LCD screen to get the Hilbert-Huang transformation diagram of the stress wave waveform. (8) Analyze the waveform obtained by the Hilbert-Huang transformation to obtain the length of the bolt. (9) Finally, save the Hilbert-Huang transformation diagram of the stress wave waveform in (7) and the bolt length value in (8) to the SD card storage module. 2. The method according to claim 1, characterized in that, in the step (3), the vibrating hammer strikes the anchor rod continuously for 4-6 times with the same frequency and strength. 3. The method according to claim 1, characterized in that the initial stress waveform obtained in the step (6) is obtained after processing a plurality of stress waveforms using a normalized superposition method. 4. The method according to claim 1, characterized in that the HHT analysis in the step (7) is obtained by performing Hilbert-Huang Transform (HHT) analysis on the stress wave waveform. 5. method according to claim 1, it is characterized in that, ask the length of anchor rod in the described step (8), be the waveform that obtains according to HHT analysis, obtain the corresponding time t ₁ and the bottom end reflection of anchoring segment reflection signal The signal corresponds to time t ₂ , according to the propagation velocity of the stress wave in the bare anchor υ ₁ =5130m/s, use the formula l ₁ =(υ ₁ *t ₁ )/2 to obtain the free section length l ₁ of the anchor; according to The propagation velocity of the stress wave in the anchorage section is υ ₂ =4700m/s, using the formula l ₂ =(υ ₂ *(t ₂ -t ₁ ))/2 to obtain the length l ₂ of the anchorage section of the anchor rod, according to the formula l= l ₁ +l ₂ Calculate the total length l of the anchor rod. 6. A bolt non-destructive testing device based on the stress wave method, characterized in that it includes an acceleration sensor, a signal conditioning module, an AD conversion module and an ARM controller module connected in sequence, and also includes a vibrating hammer, a power supply module, and an LCD display module and SD card storage module; the power supply module is respectively connected with the signal conditioning module, AD conversion module and ARM controller module, and the ARM controller module is also connected with the LCD display module and SD card storage module, and the acceleration sensor is installed on the anchor rod to activate The vibrating hammer strikes the bolt. 7. The device according to claim 6, wherein the acceleration sensor is installed at the end of the free section of the anchor rod. 8. The device according to claim 6, wherein the signal conditioning module further comprises a sequentially connected signal amplifying circuit and a signal filtering circuit, the acceleration sensor is connected to the signal amplifying circuit, and the signal filtering circuit is connected to the AD conversion module Connected, the signal filtering circuit is a fourth-order Butterworth low-pass filter. 9. The device according to claim 8, wherein the signal amplifying circuit comprises a first operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, a second capacitor, the third capacitor, the fourth capacitor, the fifth capacitor, the sixth capacitor and the seventh capacitor; the positive input terminal of the first operational amplifier is respectively connected with one end of the first resistor, the third capacitor and the fourth capacitor, and the negative input terminal Connect to one end of the second resistor, one end of the fifth capacitor, and the other end of the fourth capacitor respectively; the other end of the first resistor is connected to the positive output end of the acceleration sensor; the other end of the second resistor is connected to the negative output end of the acceleration sensor ;The other end of the third capacitor and the other end of the fourth capacitor are grounded; one end of the first capacitor and the second capacitor is grounded, and the other end is connected to +5V voltage; the No. 1 pin of the first operational amplifier is connected to +5V voltage, and the No. 2 The pins are connected to -5V voltage, the No. 3 pin is connected to one end of the third resistor and the fourth resistor respectively, and the No. 4 and No. 5 pins are grounded; the other end of the fourth resistor is grounded; the other end of the third resistor is connected to the first The signal output end of the operational amplifier is connected, and the signal output end is also connected with the signal filter circuit; _The gain is set by two external resistors _R3 and R4, and the stability is much higher than that of an instrumentation amplifier using a single resistor to set the gain. The gain expression is: 10. The device according to claim 8, wherein the signal filtering circuit comprises a second operational amplifier, a third operational amplifier, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a Eight capacitors, the ninth capacitor, the tenth capacitor and the eleventh capacitor; one end of the fifth resistor is connected to the signal output end of the first operational amplifier of the signal amplifying circuit, and the other end is connected to one end of the sixth resistor and the ninth capacitor respectively ; The other end of the sixth resistor is connected to the positive input of the second operational amplifier; the positive input of the second operational amplifier is also connected to one end of the eighth capacitor; the other end of the eighth capacitor is grounded; the negative input of the second operational amplifier terminal is connected with the signal output terminal of the second operational amplifier; the signal output terminal of the second operational amplifier is also connected with the other end of the ninth capacitor and one end of the seventh resistor; the No. 1 pin of the second operational amplifier is connected with +5V voltage, Pin 2 is connected to -5V voltage; the other end of the seventh resistor is connected to one end of the eighth resistor and the eleventh capacitor respectively; the other end of the eighth resistor is respectively connected to the positive input end of the third operational amplifier; the third operational amplifier The positive input terminal of the amplifier is also connected to one end of the tenth capacitor; the other end of the tenth capacitor is grounded; the No. 1 pin of the third operational amplifier is connected to +5V voltage, and the No. 2 pin is connected to -5V voltage; the third operational amplifier’s The signal output end is respectively connected with the other end of the eleventh capacitor, the negative input end of the third operational amplifier, and the AD conversion module.