阅读说明：本技术 一种基于超声检测的聚氨酯粘接剂缺陷测量方法及系统 (Polyurethane adhesive defect measuring method and system based on ultrasonic detection ) 是由 魏培欣 宗艳 梁雯雯 张国旺 王国平 杨晓云 丁柏妍 吴金洋 张煜超 郑云昊 王 于 2021-07-31 设计创作，主要内容包括：本发明公开一种基于超声检测的聚氨酯粘接剂缺陷测量方法及系统,方法包括：S1：选取检测用纵波直探头,根据超声波参数计算近场区长度；S2：采集近场区外待测聚氨酯粘接剂多个不同位置处的超声信号,其中,待测聚氨酯粘结剂表面涂刷有超声波耦合剂；S3：判断超声回波信号是否存在缺陷；S4：获取有缺陷的超声回波信号对应的缺陷回波和缺陷底波的到达时间,以及无缺陷的超声回波信号对应的始波和底波的到达时间；S5：根据各位置处待测聚氨酯粘接剂的厚度,以及到达时间和到达时间,计算聚氨酯粘接剂的缺陷部位距离上表面的距离T。本发明能够实现超声无损检测,深入分析聚氨酯材料中的缺陷信号,从而准确地检测出聚氨酯材料中的缺陷位置。(The invention discloses a polyurethane adhesive defect measuring method and system based on ultrasonic detection, wherein the method comprises the following steps: s1: selecting a longitudinal wave straight probe for detection, and calculating the length of a near field region according to ultrasonic parameters; s2: collecting ultrasonic signals of a plurality of different positions of the polyurethane adhesive to be detected outside the near field region, wherein the surface of the polyurethane adhesive to be detected is coated with an ultrasonic coupling agent; s3: judging whether the ultrasonic echo signal has defects; s4: acquiring the arrival time of a defect echo and a defect bottom wave corresponding to the defective ultrasonic echo signal and the arrival time of a start wave and a bottom wave corresponding to the non-defective ultrasonic echo signal; s5: and calculating the distance T from the defect part of the polyurethane adhesive to the upper surface according to the thickness, the arrival time and the arrival time of the polyurethane adhesive to be detected at each position. The invention can realize ultrasonic nondestructive detection and deeply analyze the defect signal in the polyurethane material, thereby accurately detecting the defect position in the polyurethane material.)

1. A polyurethane adhesive defect measuring method based on ultrasonic detection is characterized by comprising the following steps:

s1: selecting a longitudinal wave straight probe for detection and ultrasonic parameters, and calculating the length of a near field region according to the ultrasonic parameters;

s2: collecting ultrasonic signals of a plurality of different positions of the polyurethane adhesive to be measured outside a near field region by using a longitudinal wave straight probe, wherein the surface of the polyurethane adhesive to be measured is coated with an ultrasonic wave coupling agent;

s3: judging whether the ultrasonic echo signals acquired at each position have defects or not;

s4: acquiring the arrival time t of the defect echo and the defect bottom wave corresponding to the defect ultrasonic echo signal₁And t₂And ultrasound without defectsArrival time t of initial wave and bottom wave corresponding to echo signal₁' and t₂'；

S5: obtaining the thickness of the polyurethane adhesive to be measured at each position, and obtaining the arrival time t according to the thickness₁、t₂And time of arrival t₁'、t₂' calculating the distance T of the defect position of the polyurethane adhesive from the upper surface.

2. The polyurethane adhesive defect measuring method of claim 1, wherein S1 further comprises:

setting initialization parameters of an ultrasonic signal acquisition device, wherein the initialization parameters comprise an oscillography channel, a detection mode, an output pulse width, an initial gain, a sound path and a working mode;

and selecting a standard echo test block for adjustment and adjustment, and adjusting the gain.

3. The polyurethane adhesive defect measuring method of claim 2, wherein the operation mode is set as a single probe for both self-emission and self-reception, and the ultrasonic signal is acquired in a one-emission and one-reception manner.

4. The method of claim 2, wherein when the standard echo test block is used for calibration, the start wave signal and the bottom wave signal of the standard echo test block are respectively overlapped with the 0 th grid and the 8 th grid of the horizontal scale on the screen of the ultrasonic detector, and the gain is adjusted to make the amplitude of the echo signal reach 60% of the longitudinal degree.

5. The polyurethane adhesive defect measuring method of claim 1, wherein S1 further comprises determining a wedge thickness of the longitudinal wave straight probe according to the length of the near field region;

s2, acquiring ultrasonic signals by adopting a longitudinal wave straight probe with the corresponding wedge thickness.

6. The polyurethane adhesive defect measuring method of claim 1, wherein the ultrasonic parameters include a source radius and an ultrasonic wavelength, and the near field region length is calculated by the formula:

in the formula, N is the length of a near field region, Rs is the radius of a wave source, and lambda is the wavelength of ultrasonic waves;

wherein:

wherein C is the preset wave velocity and f is the frequency of the longitudinal wave straight probe.

7. The polyurethane adhesive defect measuring method of claim 1, wherein the surface of the polyurethane adhesive is uniformly coated with CG-98 type ultrasonic coupling agent.

8. The method for measuring defects of a polyurethane adhesive according to claim 1, wherein in step S3, the determining whether the ultrasonic echo signals collected at each position have defects includes:

if the initial wave echo and the bottom wave echo in the acquired ultrasonic echo signal are clearly visible and no obvious defect echo signal exists, the ultrasonic echo signal is free of defects; if the acquired ultrasonic echo signal obviously has a defect echo signal between the initial wave and the bottom wave signal is attenuated, the ultrasonic echo signal has defects.

9. The polyurethane adhesive defect measuring method of claim 1, wherein in step S5, the thickness of the polyurethane adhesive to be measured at the position of ultrasonic echo signal collection and the arrival time t are measured₁、t₂And time of arrival t₁'、t₂' calculating the distance T from the defect site of the polyurethane adhesive to the upper surface, comprising:

calculating the ultrasonic wave in the polyurethane adhesive to be testedSpeed of sound C_LThe formula is as follows:

in the formula, D is the thickness of the polyurethane adhesive to be measured at the ultrasonic echo signal acquisition part;

calculating the distance T between the defective part of the polyurethane adhesive and the upper surface, wherein the formula is as follows:

10. a polyurethane adhesive defect measuring system based on the polyurethane adhesive defect measuring method according to any one of claims 1 to 9, wherein: the device comprises a digital ultrasonic flaw detector, a longitudinal wave straight probe, a polyurethane adhesive to be detected and a PC end; the longitudinal wave straight probe is connected with a wedge block with the thickness matched with the length of the near field region and is connected with the digital ultrasonic flaw detector through a channel line; and the digital ultrasonic flaw detector is connected with a PC end provided with a display unit.

Technical Field

The invention relates to a polyurethane adhesive defect measuring method and system based on ultrasonic detection, and belongs to the technical field of nondestructive detection.

Background

The adhesive connection has the advantages of simple structure, light weight, small size, good manufacturability and the like, and is widely applied to industrial production and life. Polyurethane adhesives are one of the most commonly used adhesives due to their characteristics of high strength, high wear resistance, low temperature resistance, oil resistance, chemical corrosion resistance, and the like.

The defects of glue shortage, bonding surface pollution, incomplete curing, partial bonding and the like can occur in the production process of the bonding structure; aging, cracking, adhesive and cohesive failure, etc. occur during service, thereby destroying the integrity of the bonded structure. In the glued joint structure, the hidden danger of the interface debonding defect is the largest, the bonding strength can be seriously reduced due to the defects in the glued joint structure, under the action of external force, residual stress and the influence of the use environment exist in the interface, the bonding structure has the mechanical property deterioration, and finally the whole failure can be caused. If the defects cannot be found in time and the harmfulness of the defects cannot be judged accurately, huge loss is brought.

Currently, the nondestructive testing methods commonly used for testing the bonding structure include: infrared thermal imaging, radiography, and infiltration. The infrared thermal imaging method is sensitive to external environmental factors such as temperature due to high application cost, and is limited by strict environmental factors in practical application. The radiographic method has high detection cost and slow detection speed, and is harmful to human bodies, and protective measures need to be taken. The infiltration method can only be used for detecting the defects of the openings exposed on the surface of the workpiece, and can not detect the hidden defects inside. Compared with the detection method, the ultrasonic detection method has the advantages of light equipment, low detection cost, high speed, strong penetrating power, accurate defect positioning, high sensitivity, no harm to human bodies and environment, wide range of detected objects, convenience in field use and the like, and is widely applied.

The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a polyurethane adhesive defect measuring method and system based on ultrasonic detection, which deeply analyze defect signals in a polyurethane material through ultrasonic nondestructive detection so as to accurately detect the defect position in the polyurethane material.

In order to achieve the purpose, the invention is realized by adopting the following technical scheme:

in one aspect, the invention provides a polyurethane adhesive defect measuring method based on ultrasonic detection, which comprises the following steps:

s1: selecting a longitudinal wave straight probe for detection and ultrasonic parameters, and calculating the length of a near field region according to the ultrasonic parameters;

s2: collecting ultrasonic signals of a plurality of different positions of the polyurethane adhesive to be measured outside a near field region by using a longitudinal wave straight probe, wherein the surface of the polyurethane adhesive to be measured is coated with an ultrasonic wave coupling agent;

s3: judging whether the ultrasonic echo signals acquired at each position have defects or not;

s4: acquiring the arrival time t of the defect echo and the defect bottom wave corresponding to the defect ultrasonic echo signal₁And t₂And arrival times t of the start wave and the bottom wave corresponding to the ultrasonic echo signal without defects₁' and t₂'；

S5: obtaining the thickness of the polyurethane adhesive to be measured at each position, and obtaining the arrival time t according to the thickness₁、t₂And time of arrival t₁'、t₂' calculating the distance T of the defect position of the polyurethane adhesive from the upper surface.

Further, step S1 includes, before the start of the detection, performing initialization parameter setting on the ultrasound signal acquisition device, where the initialization parameters include an oscillometric channel, a detection mode, an output pulse width, an initial gain, a sound path, and a working mode; and selecting a standard echo test block for adjustment and adjustment, and adjusting the gain. So that the detection process can better distinguish the defect signals.

Furthermore, the working mode is that the single probe is selected to be self-transmitting and self-receiving, and the ultrasonic signals are collected in a transmitting-receiving mode.

Furthermore, when the standard echo test block is used for adjustment, the initial wave signal and the bottom wave signal of the standard echo test block are respectively coincided with the 0 th grid and the 8 th grid of the transverse scale of the screen of the ultrasonic detector, and the gain is adjusted to enable the amplitude of the echo signal to reach 60% of the longitudinal degree. The arrangement can make the scale of the signal appear on the screen as much as possible, and the waveform displayed on the screen at the same time is as complete as possible.

For a disc wave source radiating a longitudinal wave sound field, a series of regions with extremely small sound pressure values appear near the wave source due to wave interference, and the regions are called near-field regions of an ultrasonic field and also called Fresnel regions.

Considering that when measuring in the near field region, the larger defect echo at the sound pressure minimum value may be lower, and the smaller defect echo at the sound pressure maximum value may be higher, which may cause misjudgment and even missing detection, the wedge thickness of the longitudinal wave straight probe is designed by the invention, so that the measurement in the near field region should be avoided in the detection process.

Therefore, in the method of the present invention, S1 further includes determining a wedge thickness of the longitudinal wave straight probe according to the length of the near field region; s2, acquiring ultrasonic signals by adopting a longitudinal wave straight probe with the corresponding wedge thickness.

Further, the ultrasonic parameters include a source radius and an ultrasonic wavelength, and the calculation formula of the length of the near field region is as follows:

in the formula, N is the length of a near field region, Rs is the radius of a wave source, and lambda is the wavelength of ultrasonic waves;

wherein:

wherein C is the preset wave velocity and f is the frequency of the longitudinal wave straight probe.

Furthermore, before detection, the CG-98 type ultrasonic coupling agent is uniformly coated on the surface of the polyurethane adhesive to be detected. . The coupling agent has good coupling performance, can effectively reduce ultrasonic sound energy loss, is easy to clean, is harmless to human bodies and has no pollution to the environment.

Further, in step S3, in step S3, the determining whether the ultrasound echo signal acquired at each position has a defect includes:

if the initial wave echo and the bottom wave echo in the acquired ultrasonic echo signal are clearly visible and no obvious defect echo signal exists, the ultrasonic echo signal is free of defects; if the acquired ultrasonic echo signal obviously has a defect echo signal between the initial wave and the bottom wave signal is attenuated, the ultrasonic echo signal has defects.

Further, in step S5, the thickness of the polyurethane adhesive to be measured at the position where the ultrasonic echo signal is collected, and the arrival time t₁、t₂And time of arrival t₁'、t₂' calculating the distance T from the defect site of the polyurethane adhesive to the upper surface, comprising:

calculating the sound velocity C of ultrasonic waves in the polyurethane adhesive to be measured_LThe formula is as follows:

in the formula, D is the thickness of the polyurethane adhesive to be measured at the ultrasonic echo signal acquisition part;

calculating the distance T between the defective part of the polyurethane adhesive and the upper surface, wherein the formula is as follows:

on the other hand, the invention provides a polyurethane adhesive defect measuring system based on the polyurethane adhesive defect measuring method, which comprises a digital ultrasonic flaw detector, a longitudinal wave straight probe, a polyurethane adhesive to be measured and a PC end; the longitudinal wave straight probe is connected with a wedge block with the thickness matched with the length of the near field region and is connected with the digital ultrasonic flaw detector through a channel line; and the digital ultrasonic flaw detector is connected with a PC end provided with a display unit.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention researches the sound velocity characteristic of the polyurethane material adhesive, and can accurately and quickly detect the defect position in the polyurethane material by analyzing the ultrasonic signal of the polyurethane adhesive;

2. the ultrasonic detection method adopted by the invention has the advantages of light equipment, low detection cost, accurate defect positioning, high sensitivity and wide range of detected objects.

Drawings

FIG. 1 is a schematic flow chart of an embodiment of a measurement method of the present invention;

FIG. 2 is a simulated specimen layout;

FIG. 3 is a schematic view of a measured waveform of a defect-free ultrasonic signal;

fig. 4 is a schematic view of a waveform obtained by measurement of a defective ultrasonic signal.

Detailed Description

The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

Example 1

This embodiment describes a method for measuring defects of a polyurethane adhesive based on ultrasonic detection, and with reference to fig. 1, the method includes the following steps:

s1: selecting a longitudinal wave straight probe for detection and ultrasonic parameters, and calculating the length of a near field region according to the ultrasonic parameters;

s2: collecting ultrasonic signals of a plurality of different positions of the polyurethane adhesive to be measured outside a near field region by using a longitudinal wave straight probe, wherein the surface of the polyurethane adhesive to be measured is coated with an ultrasonic wave coupling agent;

s3: judging whether the ultrasonic echo signals acquired at each position have defects or not;

s4: acquiring the arrival time t of the defect echo and the defect bottom wave corresponding to the defect ultrasonic echo signal₁And t₂And arrival times t of the start wave and the bottom wave corresponding to the ultrasonic echo signal without defects₁' and t₂'；

S5: obtaining the thickness of the polyurethane adhesive to be measured at each position, and obtaining the arrival time t according to the thickness₁、t₂And time of arrival t₁'、t₂' calculating the distance T of the defect position of the polyurethane adhesive from the upper surface.

By using the method, the defect position of the polyurethane adhesive can be rapidly and accurately measured.

Example 2

This example specifically describes a method for measuring defects of a polyurethane adhesive based on ultrasonic testing, which is based on the same inventive concept as that of example 1, and specifically relates to the following.

S1, preparation before detection

1.1, setting initialization parameters of an ultrasonic signal acquisition device, wherein the initialization parameters comprise an oscillography channel, a detection mode, an output pulse width, an initial gain, a sound path and a working mode; and selecting a standard echo test block for adjustment and adjustment, and adjusting the gain. So that the detection process can better distinguish the defect signals. The working mode can be selected as a single-probe self-transmitting and self-receiving mode, and a transmitting-receiving mode is adopted to collect ultrasonic signals.

When the standard echo test block is used for adjustment, the initial wave signal and the bottom wave signal of the standard echo test block are respectively coincided with the 0 th grid and the 8 th grid of the transverse scale of the screen of the ultrasonic detector, and the gain is adjusted to enable the amplitude of the echo signal to reach 60% of the longitudinal degree. The arrangement can make the scale of the signal appear on the screen as much as possible, and the waveform displayed on the screen at the same time is as complete as possible.

1.2 near field region determination

Considering that when measuring in the near field, the larger defect echo at the sound pressure minimum value may be lower, and the smaller defect echo at the sound pressure maximum value may be higher, which may cause misjudgment and even missing detection, the present embodiment designs the wedge thickness of the longitudinal wave straight probe so as to avoid measuring in the near field during the detection process.

The length of the near field region is determined according to the source radius of the ultrasonic wave and the wavelength of the ultrasonic wave, and the calculation formula is as follows:

in the formula, N is the length of a near field region, Rs is the radius of a wave source, and lambda is the wavelength of ultrasonic waves;

wherein:

wherein C is the preset wave velocity and f is the frequency of the longitudinal wave straight probe.

The thickness of the longitudinal wave straight probe wedge can be set to be the length N of the near field region.

1.3 surface treatment of the polyurethane to be tested

Before detection, the CG-98 type ultrasonic coupling agent is uniformly coated on the surface of the polyurethane adhesive to be detected. The coupling agent has good coupling performance, can effectively reduce ultrasonic sound energy loss, is easy to clean, is harmless to human bodies and has no pollution to the environment.

S2, ultrasonic flaw detection and signal acquisition: and acquiring ultrasonic signals of the polyurethane adhesive to be measured at a plurality of different positions outside the near field region by using a longitudinal wave straight probe with a wedge block.

S3, judging whether the ultrasonic echo signals collected at each position have defects: if the initial wave echo and the bottom wave echo in the acquired ultrasonic echo signal are clearly visible and no obvious defect echo signal exists, the ultrasonic echo signal is free of defects, as shown in fig. 3; if the acquired ultrasonic echo signal obviously has a defect echo signal between the initial wave and the bottom wave, and the bottom wave signal is attenuated, the ultrasonic echo signal has a defect, as shown in fig. 4.

S4, acquiring waveform parameters: acquiring the arrival time t of the defect echo and the defect bottom wave corresponding to the defect ultrasonic echo signal₁And t₂And arrival times t of the start wave and the bottom wave corresponding to the ultrasonic echo signal without defects₁' and t₂'. The waveform parameters can be obtained through manual observation, or can be automatically obtained by a PC after a digital ultrasonic flaw detector is connected with the PC.

S5, defect position calculation

Obtaining the thickness of the polyurethane adhesive to be measured at each position, and obtaining the arrival time t according to the thickness₁、t₂And time of arrival t₁'、t₂' calculating the distance T between the defect part of the polyurethane adhesive and the upper surface, and specifically comprising the following steps:

calculating the sound velocity C of ultrasonic waves in the polyurethane adhesive to be measured_LThe formula is as follows:

in the formula, D is the thickness of the polyurethane adhesive to be measured at the ultrasonic echo signal acquisition part;

calculating the distance T between the defective part of the polyurethane adhesive and the upper surface, wherein the formula is as follows:

example 3

This embodiment introduces a polyurethane adhesive defect measurement system based on the polyurethane adhesive defect measurement method described in embodiment 1 or 2, which includes a digital ultrasonic flaw detector, a longitudinal wave straight probe, a polyurethane adhesive to be measured, and a PC terminal; the longitudinal wave straight probe is connected with a wedge block with the thickness matched with the length of the near field region and is connected with the digital ultrasonic flaw detector through a channel line; and the digital ultrasonic flaw detector is connected with a PC end provided with a display unit.

The digital ultrasonic flaw detector is connected with the PC end, transmits the waveform data to the PC end and displays the waveform data on the display unit, and meanwhile, the PC end can automatically acquire the waveform parameter data, calculate the defect position and display and output the defect position.

To investigate the effectiveness of the measurement method of the present invention, the following is illustrated by a self-made polyurethane test block.

The self-made polyurethane material simulation test block is shown in fig. 2, the size of the polyurethane test block is designed to be 90mm multiplied by 6mm multiplied by 25mm in length multiplied by width multiplied by height, a detection area is the inside of polyurethane, meanwhile, a rectangular debonding defect is arranged in the polyurethane, glue injection is performed three times, as shown in fig. 1 from left to right, the rectangular defect is placed in each glue injection, the defect placement depth h is set to be 21mm, 10mm and 4mm, defects of different sizes are set for further verification, the size of the defect is designed to be 1mm multiplied by 2mm in length multiplied by width multiplied by height, 2mm multiplied by 2mm and 3mm multiplied by 2 mm.

With the ultrasonic testing system of example 3, the testing procedure was:

the method comprises the following steps: ultrasonic detector selection and setup

A multichannel digital ultrasonic flaw detector SF580 pulse reflection ultrasonic detector of Sanfeng corporation is selected to generate pulse ultrasonic waves and real-time echo signals.

Setting the parameters of the ultrasonic detector as follows according to the parameters of the test block:

selecting a channel: 2, detection mode: full wave detection

Pulse width: initial gain of 40 ns: 60dB

The sound path: 30mm working mode: single probe self-generating and self-receiving

Step two: standard echo test block calibration

After the setting is finished, the probe is placed at the position where the test block is not defective, the ultrasonic detector is adjusted to enable the initial wave signal and the bottom wave signal of the standard echo to coincide with the 0 th grid and the 8 th grid of the transverse scale of the screen of the ultrasonic detector respectively, and the gain is adjusted to enable the amplitude of the echo signal to reach 60% of the longitudinal degree, wherein the gain is 65dB at the moment.

Step three: straight probe selection

According to a calculation formula of the length of the near field region, a longitudinal wave straight probe with the frequency of 5MHz and the diameter of 10mm is selected and connected with an ultrasonic detector.

Step four: coupling of

Uniformly brushing CG-98 type ultrasonic coupling agent on polyurethane interface

Step five: flaw detection and discrimination

And adopting a conventional mode to acquire ultrasonic signals in a transmitting-receiving mode by using a longitudinal wave straight probe on a polyurethane interface coated with CG-98 type ultrasonic coupling agent. The ultrasonic signals shown in fig. 3 are collected in a defect-free simulation test block, and the initial wave and bottom wave echo signals can be clearly seen. Meanwhile, the probe is placed on the surface of the known pre-buried defect test block, and a defect ultrasonic signal shown in figure 4 is obtained. The defect echo signal can be clearly seen between the initial wave signal and the bottom wave signal, and the bottom wave signal has attenuation.

According to the obtained defect-free ultrasonic signal and the defect ultrasonic signal, combining the formula:

the ultrasonic longitudinal wave velocity in the polyurethane adhesive can be calculated, the embedded defect condition in polyurethane can be analyzed, and the actual calculation result is basically consistent with the defect injection position.

In conclusion, the method combines nondestructive testing and ultrasonic testing methods, can better analyze the propagation condition and the propagation speed of the ultrasonic wave in the polyurethane adhesive, and lays a foundation for actually detecting the debonding defect of the glued part of the car window.

While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.