CN113405752B - Ultrasonic detection method for interface rigidity based on microwave network analysis - Google Patents

Abstract

The invention discloses an ultrasonic detection method for interface rigidity based on microwave network analysis, which comprises the following steps: the method comprises the steps of building an experiment system, searching proper detection frequency, searching proper loading range, applying load, reading S parameters and analyzing experiment data. The invention establishes an ultrasonic detection theoretical model of the interface rigidity by applying the S parameter of the microwave network, transfers the microwave network analysis from the electromagnetic wave field to the ultrasonic wave field, and proposes to represent the interface rigidity by detecting the S parameter of a microwave network analyzer. The detection method disclosed by the invention has an important application prospect in the contact condition test of the key assembly interface of the important equipment.

Description

An Ultrasonic Detection Method of Interface Stiffness Based on Microwave Network Analysis

technical field

The invention relates to a nondestructive testing method, in particular to an ultrasonic testing method of interface stiffness based on microwave network analysis.

Background technique

Contact interfaces widely exist in engineering structures and have a significant impact on the macroscopic properties of structures. The interface stiffness is an important parameter to characterize the interface contact, and its detection and evaluation are directly related to the reliability and safety of the engineering structure.

At present, the stiffness detection methods of the pressure-bearing interface are mainly divided into direct detection methods and ultrasonic detection methods. The direct detection method refers to directly measuring the interface stiffness by definition by detecting the interface force and interface displacement. Although the definition method is simple and easy to use, it is difficult to directly measure the contact interface displacement due to the complexity of the actual engineering structure; the ultrasonic detection method is The interface stiffness is characterized by detecting the reflection/transmission coefficient of ultrasonic waves propagating to the contact interface, without the need to directly measure the interface pressure and displacement, and has been widely used in engineering practice.

However, the existing ultrasonic testing technology needs to detect the incident wave and the transmitted wave separately, the experimental procedure is complicated, and the experimental error is large; and the ultrasonic testing result of the interface stiffness is obviously higher than the direct measurement value of the interface stiffness. Therefore, it is necessary to improve the existing ultrasonic testing methods.

Microwave network technology is a key test technology necessary for modern electronic equipment. This technology refers to measuring the impedance characteristics and transmission characteristics of the network under test through the time domain or frequency domain. The relationship between voltage and reflected/transmitted wave voltage can characterize the transmission characteristics of the device under test.

SUMMARY OF THE INVENTION

Aiming at the problems of complicated experimental steps and large error of detection results in the existing interface stiffness detection method, the present invention provides an interface stiffness detection method based on microwave network S-parameters. The detection method simplifies the experimental procedure, reduces the experimental error and conforms to the actual interface contact.

Technical scheme of the present invention:

A method for ultrasonic testing of interface stiffness based on microwave network analysis, the steps are as follows:

1. The theoretical model of interface stiffness detection using microwave network S-parameters is established:

The interface stiffness is characterized by detecting the S-parameters of the microwave network (the S-parameters can be directly read by a microwave network analyzer). The interface stiffness detection model is derived theoretically, such as formula (1):

where K is the interface stiffness, ρ is the density of the structural material, c is the ultrasonic longitudinal wave velocity, ω is the angular frequency, and S is the S parameter of the microwave network. It can be seen from the above formula that when the materials on both sides of the interface remain unchanged, the interface stiffness value can be obtained by detecting the S-parameters of the microwave network, thereby realizing the real-time monitoring of the interface contact state.

2. The technical scheme of S-parameter detection of interface stiffness by microwave network:

Step 1. Build the experimental system

The experimental system is divided into two parts: loading and detection. The loading part is responsible for providing the experimental loading and simultaneously transmitting and receiving ultrasonic signals to the DUT. The detection part is responsible for real-time detection of the S-parameters of the microwave network and recording the experimental data.

(1) Build the loading part of the experimental system

The loading part of the experimental system includes a loading device, a bearing device, a limit block and an ultrasonic probe; the two test pieces are attached to form a contact interface; the two ultrasonic probes are respectively placed in the limit block, and the ultrasonic probe realizes ultrasonic signals and electromagnetic signals. The two limit blocks are placed on the upper and lower surfaces of the test piece respectively, and the limit blocks are used to fix the ultrasonic probe and transmit the loading load to the test piece; the contact part between the ultrasonic probe surface and the test piece uses glycerin as a coupling medium; the loading device and The bearing devices are respectively fixed on the limit blocks, and the loading devices are used to apply loads to the contact interface. The bearing devices contain a pressure sensor, which can feedback the loading force value in real time;

(2) Build the testing part of the experimental system

The detection part of the experimental system includes a computer system and a microwave network analyzer; the computer system is connected to the microwave network analyzer through a network cable, and is responsible for recording experimental data; the microwave network analyzer is used to generate a sine wave sweep frequency signal, and at the same time detect the S parameters of the microwave network in real time; The ultrasonic transmitting probe and the ultrasonic receiving probe are respectively connected with the 1 port and the 2 port of the microwave network analyzer;

Step 2. Find a suitable detection frequency

Appropriately load the load to make the contact interface of the test piece in a compressed state, adjust the microwave network analyzer to display the frequency domain detection interface, select the appropriate frequency band according to the center frequency of the ultrasonic probe, perform a uniform frequency sweep from low to high, and record the highest amplitude frequency value.

Step 3. Find a suitable loading range

In order to ensure that the two test pieces are still in contact when unloading, the minimum loading force value is set according to the material of the test piece; gradually increase the load, the S parameter of the microwave network analyzer gradually increases with the increase of the load, when the load increases to a certain extent When , the change of interface stiffness gradually tends to be gentle, and the increase rate of interface stiffness gradually decreases with the increase of load. Record the load at this time as the maximum loading force value, and select the appropriate loading force interval according to the maximum loading force value.

Step 4. Apply the load and read the S-parameters

Before the experiment, perform multiple loading-unloading operations on the test piece in the range of the minimum to maximum loading force value, in order to eliminate the interference of the plastic deformation of the test piece on the measurement results, set the frequency of the microwave network analyzer to the detection value in step 3, and adjust the load of the loading device For the minimum loading force value, read the S-parameters of the microwave network analyzer, then gradually increase the load of the loading device, and read the corresponding S-parameters of the microwave network analyzer for each increase of the loading force value.

Step 5. Experimental data analysis

By substituting the experimentally measured S parameters under different load conditions into the interface stiffness detection model, and calculating the interface stiffness value under the corresponding load, the change of the contact interface stiffness of the structure to be measured with the load can be monitored in real time, and the indirect detection of the contact interface stiffness can be realized.

The beneficial effects of the invention: the method of the invention only needs to detect the ultrasonic signal once, and does not need to detect the incident wave and the transmitted wave twice, which effectively simplifies the experimental process; and the microwave network analysis method detects the experimental results more in line with the actual interface contact situation , which provides a new microwave network analysis and detection method for the detection of contact interface stiffness.

Description of drawings

Figure 1 is a schematic diagram of an ultrasonic testing device for interface stiffness using microwave network analysis.

Figure 2 is a diagram of the assembly position of the limit block and the ultrasonic probe.

Fig. 3 is a flow chart of ultrasonic testing of interface stiffness using microwave network analysis.

FIG. 4 is a graph showing the interface stiffness detection results of the experimental example.

In the figure: 1 computer system; 2 microwave network analyzer; 3 loading device; 4 limit block; 5 test piece; 6 ultrasonic probe; 7 load device.

Detailed ways

The specific embodiment of the present invention is further described below by taking a certain type of 45 steel square specimen as an example.

Step 1. Build the experimental system

Match the ultrasonic receiving probe with the limit block and place it on the surface of the bearing device. As shown in Figure 2, the ultrasonic receiving probe is connected to the 2 port of the microwave network analyzer, and the test piece is matched to form a contact interface as a whole and placed on the limit block. , place the ultrasonic transmitting probe and the limit block on the overall upper surface of the test piece, the ultrasonic transmitting probe is connected to port 1 of the microwave network analyzer, and the network analyzer and the computer system are connected by a network cable.

Step 2. Find a suitable detection frequency

Apply 100N load to the test piece to make its contact interface in a pressed state, adjust the network analyzer to display the frequency domain detection interface, the center frequency of the ultrasonic probe is 5MHz, set the network analyzer to sweep the frequency band of 2-8MHz, and record the frequency The frequency of 6.2MHz at the highest amplitude in the domain diagram is the detection frequency.

Step 3. Find a suitable loading range

The material to be tested is 45 steel, and the estimated structural stiffness is large. The minimum loading load is set to 1kN, and the load is gradually increased. The S parameter of the microwave network analyzer increases with the increase of the load. When the load increases to a certain extent, The S parameter tends to be stable, which can reflect that the interface stiffness reaches the limit at this time, and the loading load at this time is recorded as 10kN.

Step 4. Carry out the experiment and obtain the interface stiffness test results

Before the experiment, perform multiple loading-unloading operations in the force range of 1kN to 10kN to eliminate the interference of plastic deformation on the test results. Set the frequency of the microwave network analyzer to 6.2MHz, adjust the loading load to 1kN, and read the microwave network. The S-parameter of the analyzer is then gradually increased, and the corresponding S-parameter is read for every 1kN increase. The load and S-parameter are collected by the computer, and the S-parameter is substituted into Equation 1, and the interface stiffness under the corresponding load condition can be calculated. The calculation results are shown in Table 1, and the test results of the interface stiffness of the test piece are shown in Figure 4.

Table 1 S-parameters measured experimentally and interface stiffness data obtained by calculation under corresponding loads

Claims (1)

1. An ultrasonic detection method for interface rigidity based on microwave network analysis is characterized by comprising the following steps:

(1) theoretical model establishment for interface rigidity detection by applying microwave network S parameters

The method comprises the following steps of representing the interface rigidity condition by detecting S parameters of a microwave network, and deducing an interface rigidity detection model by theory, wherein the formula is as follows (1):

in the formula, K is interface rigidity, rho is structural material density, c is ultrasonic longitudinal wave velocity, omega is angular frequency, and S is microwave network S parameter; from the above formula, under the condition that the materials on the two sides of the interface are not changed, the S parameter of the microwave network is detected, namely the interface rigidity value is obtained, so that the real-time monitoring of the interface contact state is realized;

(2) microwave network S parameter detection interface rigidity

Step 1, building an experiment system

The experimental system is divided into a loading part and a detecting part, wherein the loading part is responsible for providing an experimental loading load and simultaneously transmitting and receiving ultrasonic signals to a to-be-tested part, and the detecting part is responsible for detecting the microwave network S parameters in real time and recording experimental data;

1) setting up loading part of experiment system

The experimental system loading part comprises a loading device, a bearing device, a limiting block and two ultrasonic probes; the two ultrasonic probes are respectively an ultrasonic transmitting probe and an ultrasonic receiving probe; attaching the two to-be-tested parts to form a contact interface; respectively placing the two ultrasonic probes into a limiting block, wherein the ultrasonic probes realize the conversion between ultrasonic signals and electromagnetic signals; the two limiting blocks are respectively arranged on the upper surface and the lower surface of the test piece and are used for fixing the ultrasonic probe and transmitting a loading load to the test piece to be tested; glycerol is used as a coupling medium at the contact part of the surface of the ultrasonic probe and the test piece; the loading device and the bearing device are respectively fixed on the limiting block, the loading device is used for applying load to the contact interface, and the bearing device is internally provided with a pressure sensor and can feed back a loading force value in real time;

2) building detection part of experiment system

The test system detection part comprises a computer system and a microwave network analyzer; the computer system is connected with the microwave network analyzer through a network cable and is responsible for recording experimental data; the microwave network analyzer is used for generating sine wave frequency sweeping signals and detecting S parameters of the microwave network in real time; the ultrasonic transmitting probe and the ultrasonic receiving probe are respectively connected with a port 1 and a port 2 of the microwave network analyzer;

step 2, searching for proper detection frequency

Loading a load to enable a contact interface of a to-be-tested piece to be in a compression state, adjusting a microwave network analyzer to display a frequency domain detection interface, selecting a frequency band according to the center frequency of an ultrasonic probe, uniformly sweeping the frequency from low to high, and recording the frequency value at the highest position of the amplitude;

step 3, searching a proper loading range

In order to ensure that two pieces to be tested still keep a contact state during unloading, a minimum loading force value is set according to the material of the pieces to be tested; gradually increasing the load, wherein the S parameter of the microwave network analyzer gradually increases along with the increase of the load, when the load increases to a certain degree, the change of the interface rigidity gradually tends to be smooth, and the increase rate of the interface rigidity gradually decreases along with the increase of the load; recording the load as the maximum loading force value at the moment, and selecting a loading force interval according to the maximum loading force value;

step 4, applying load and reading S parameter

Before the experiment, multiple loading-unloading operations are carried out on a piece to be tested in a range from the minimum loading force value to the maximum loading force value so as to eliminate the interference of the plastic deformation of the test piece on the measurement result, the frequency of the microwave network analyzer is set as the frequency value of the step 2, the load of the loading device is adjusted to be the minimum loading force value, S parameters of the microwave network analyzer are read, then the load of the loading device is gradually increased, and the S parameters of the corresponding microwave network analyzer are read when the loading force value is increased once;

step 5, analyzing experimental data

Substituting S parameters measured by experiments under different load conditions into the formula (1), and calculating the interface rigidity value under the corresponding load, namely monitoring the change condition of the contact interface rigidity of the piece to be measured along with the load in real time, so as to realize indirect detection of the contact interface rigidity.

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