CN111795661A - Method and system for detecting 3D geometry of underwater acoustic materials - Google Patents

Abstract

The invention discloses a method and a system for detecting the three-dimensional geometry of underwater acoustic materials in a simulated environment of underwater variable temperature and pressure. The tomography detection, and then the three-dimensional geometric reconstruction of the CT tomographic image of the sample can accurately obtain the three-dimensional geometric shape of the underwater acoustic material sample under the corresponding working conditions. The detection method based on the present invention also realizes a detection method for the static bulk compressive modulus of the underwater acoustic material, which can accurately measure the static bulk modulus of the material under corresponding working conditions. The detection method proposed by the invention realizes the direct detection of the three-dimensional geometrical appearance of the apparent shape, the three-dimensional geometrical appearance of the internal cavity, and the three-dimensional geometrical appearance of the internal microstructure/doping material of the underwater acoustic material under the simulated environment of underwater variable temperature and pressure. The measurement can provide a very important reference for the design and performance evaluation of underwater acoustic materials.

Description

Method and system for detecting 3D geometry of underwater acoustic materials

technical field

The invention belongs to the field of detection and design of underwater acoustic materials, and in particular relates to a detection method and a detection system for simulating the three-dimensional geometry of underwater acoustic materials in a simulated environment of underwater temperature and pressure variation, and a detection method based on the three-dimensional geometry of underwater acoustic materials. Method for the detection of static bulk compressive modulus.

Background technique

Underwater acoustic materials are mainly used for the vibration and acoustic treatment of underwater vehicles, such as the sound-absorbing coating laid on the surface of the vehicle hull to reduce sonar echoes and the sound insulation to reduce the hull's own vibration radiating noise into the water. Decoupling covering layers, etc., have been widely used.

Traditional underwater acoustic materials are mainly viscoelastic materials, and the main substrates are rubber materials and polyurethane materials. In order to meet various practical applications, its interior is often embedded with a cavity structure (as shown in Figure 1) or a structure containing foam (as shown in Figure 2), which is used to enhance the internal scattering, resonance and other effects, and further increase the The loss inside the material is large, and the damping and absorption performance of the vibration and sound of the material layer is improved.

In order to design and prepare underwater acoustic materials that meet practical application conditions, the basic physical parameters and geometric parameters of the materials are required first, and then the corresponding underwater acoustic materials are predicted and optimized by means of finite element methods. The acoustic parameters of the material mainly include density, dynamic modulus and loss factor, etc., and corresponding commercial equipment and experimental devices have been tested; the geometric parameters of the material mainly include the thickness of the material layer, the structure of the cavity or scatterer, etc. geometry.

Because actual hydroacoustic materials often work in different underwater temperatures (depending on factors such as water area, water depth and season time, the variation range is usually 4-40°C) and hydrostatic pressure (depending on the working water depth, the variation range is usually 0-40°C). 3MPa) environment, its physical parameters and geometric parameters will change correspondingly with temperature and pressure, especially for hydroacoustic materials such as cavity-containing structure and bubble-containing type, the internal geometric structure often changes significantly with the change of hydrostatic pressure. At present, the physical parameters under different pressures have been measured through experiments, but the geometric changes have not been measured directly, and can only be predicted by numerical simulation through static analysis. The static modulus and Poisson's ratio of the materials required in these simulation calculations are generally obtained by testing or empirical estimation by the universal material testing machine, while the modulus measured by the material testing machine is not the corresponding temperature and hydrostatic pressure (or called In addition, since the actual viscoelastic hydroacoustic material may have nonlinearity under large hydrostatic pressure, nonlinear parameters are added to the accurate simulation of direct static deformation (to be test) and bring additional difficulties. At the same time, some over-simplified boundary conditions are often introduced in the numerical prediction of statics. The three-dimensional geometry of the material layer under the corresponding working conditions obtained through numerical simulation analysis is often very different from the results under real conditions. The lack of direct test results to verify the accuracy of the simulation results will greatly affect the reliability of the final design results. In addition, for some cavity-containing structures, the internal cavity is significantly deformed under the actual hydrostatic pressure condition, which in turn leads to an increase in the apparent equivalent density of the entire material layer. If the three-dimensional geometric deformation of underwater acoustics under corresponding working conditions cannot be detected in advance, it may even bring hidden dangers to the safety of the aircraft. At present, due to the lack of direct and accurate detection methods and devices for the three-dimensional geometry of underwater acoustic materials in a simulated environment of underwater temperature and pressure, the design and development of underwater acoustic materials are seriously restricted.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a direct and accurate detection method for the three-dimensional geometry of underwater acoustic materials in a simulated environment of underwater temperature and pressure variation; and based on this method, to provide a material under corresponding reference temperature and reference pressure. A detection method for static bulk compressive modulus; meanwhile, a three-dimensional geometry detection system for underwater acoustic materials in a simulated environment of underwater temperature and pressure variation required for the detection is provided, so as to solve the deficiencies of the current detection technology mentioned in the background art.

In order to solve the above technical problems, the present invention provides a three-dimensional geometry detection system for underwater acoustic materials, which is characterized in that it includes an underwater environment simulation device, a CT scanning system and a detection control system; the underwater environment simulation device includes an underwater environment simulation device. and a sample cavity for fixing the underwater acoustic material sample, which is used to provide an underwater temperature-variable pressure-variable simulation environment for the underwater acoustic material sample; the CT scanning system includes a sample stage for fixing the underwater environment simulation device, which is used for The underwater acoustic material sample in the underwater environment simulation device is subjected to CT scanning to obtain a tomographic image of the underwater acoustic material sample corresponding to the measured temperature and pressure. The three-dimensional geometry of the underwater acoustic material sample; the detection control system, firstly, provides a human-computer interaction interface, inputs the detection scheme, and outputs the detection results; The temperature and pressure are controlled and displayed; the third is to control the CT scanning system to scan according to the input detection scheme and obtain the three-dimensional geometry of the underwater acoustic material sample corresponding to the measured temperature and pressure.

Further, the underwater environment simulation device includes a temperature-variable and pressure-variable container, a temperature-variable and pressure-variable environmental medium, a pressure-variable system, a temperature-variable system, and a temperature and pressure control system. In the cavity, the variable temperature and pressure vessel can be penetrated by X-rays, so as to scan the hydroacoustic material sample in the underwater simulated environment of variable temperature and pressure; The sample cavity is used to realize the simulated environment of underwater temperature and pressure change in the sample cavity, and the boundary in contact with the underwater acoustic material sample has sufficient contrast to ensure the reconstruction accuracy of the outer boundary of the underwater acoustic material sample; the pressure changing system , used to pressurize, depressurize and maintain the pressure of the variable temperature and pressure variable environmental medium; the temperature variable system is used to heat up, cool down and keep warm the variable temperature and pressure variable environmental medium; the temperature and pressure control system, in the detection control Under the control of the system, the temperature in the sample chamber is obtained through the temperature sensor, the pressure in the sample chamber is obtained through the pressure sensor, the pressure-variable system and the temperature-variable system are controlled, and then the temperature and pressure inside the sample chamber are controlled.

Further, the sample cavity of the temperature-changing and pressure-changing container is enclosed by a pressure-resistant wall, an upper cover and a bottom plate, and a sealing ring is used to seal between the upper cover, the bottom plate and the pressure-resistant wall; the temperature-changing and pressure-changing environmental medium, Use gas medium, or use seawater with tracer added or artificially simulated seawater medium; the pressure transformation system includes a booster device, a pressure relief device, a pressure regulating valve and a pressure regulating valve controller; the booster device adopts a compressed gas cylinder or a The hydraulic pump and the booster device are connected to the sample chamber through pipelines. The outlet of the booster device is equipped with a pressure regulating valve and a pressure regulating valve controller. The temperature and pressure control system controls the pressure regulating valve through the pressure regulating valve controller to adjust the boosting. The outlet pressure of the device is used to control the pressure in the sample chamber; the pressure relief device is connected to the sample chamber through a pipeline, and the sample chamber is depressurized under the control of the temperature and pressure control system; the temperature changing system adopts an internal circulation method or an external circulation method; When the internal circulation mode is adopted, the heated or cooled variable temperature and pressure variable environment medium is driven by the circulating pump to circulate in the sample chamber and the circulating pipeline in the variable temperature and pressure variable container, and the heat exchange part of the heat exchange tube in the circulating pipeline is exchanged. , and finally achieve cyclic heat exchange to realize the temperature change in the sample chamber; when the external circulation method is adopted, the temperature and pressure change environment container is placed in the insulation jacket, and there is a heat exchange medium in the gap between the temperature change pressure environment container and the insulation jacket. The heat medium exchanges heat with the variable pressure and temperature environment medium in the sample chamber through the temperature and pressure change container, and the heat exchange medium is driven by the circulating pump to circulate in the gap between the temperature and pressure change environment container and the insulation jacket and the circulation pipeline. Heat is exchanged in the heat exchange tube part in the circulation pipeline; the affiliated circulation pump is controlled by a temperature and pressure control system; the temperature and pressure control system includes an acquisition card and a controller, and the acquisition card is used to collect the data of the pressure sensor and the temperature sensor. Signal; the controller is used to control the variable voltage system and the variable temperature system.

Further, the hydroacoustic material is a viscoelastic material, and the hydroacoustic material sample has an embedded cavity structure or a foamed structure.

The present invention also provides a method for detecting the three-dimensional geometry of an underwater acoustic material based on the above system, which is characterized in that the underwater acoustic material sample is fixed in an underwater environment simulation device, and the underwater environment simulation device provides underwater temperature and pressure changes. Simulate the environment, and then perform tomographic CT scanning on the underwater acoustic material sample fixed in the underwater environment simulation device, and finally perform three-dimensional reconstruction processing on the tomographic image of the underwater acoustic material sample to obtain the underwater temperature and pressure variable pressure simulation environment. 3D geometry of acoustic material samples.

Further, the method for detecting the three-dimensional geometry of the underwater acoustic material includes the steps of:

Step 1, the step of sample installation and fixation: fix the underwater acoustic material sample in the sample cavity of the underwater environment simulation device, and then install and fix the underwater environment simulation device on the sample stage of the CT scanning system;

Step 2, the step of temperature-variable control of the sample chamber: performing temperature-variable control on the underwater environment simulation device until the temperature in the sample chamber reaches the set temperature state;

Step 3, the step of variable pressure control in the sample chamber: after the temperature in the sample chamber is stabilized, perform variable pressure control on the underwater environment simulation device until the pressure in the sample chamber reaches the set pressure state;

Step 4, the step of controlling the temperature and pressure in the sample chamber: when the temperature and pressure in the sample chamber reach the set value, the temperature and pressure in the sample chamber must be stable for a long enough time to ensure that the sample of the hydroacoustic material is stable. The overall temperature is stable and consistent and the deformation is stable;

Step 5, the step of sample CT scanning and three-dimensional reconstruction: the CT scanning system is used to perform CT scanning on the underwater environment simulation device containing the underwater acoustic material sample. During the entire CT scanning period, the temperature-variable pressure-variable environment simulation device is in a state of heat preservation and pressure preservation , obtain the tomographic image of the hydroacoustic material sample corresponding to the set temperature and pressure through CT scanning, store the tomographic image results and perform three-dimensional reconstruction, and obtain the hydroacoustic material sample corresponding to the set temperature and pressure. 3D geometry.

Further, the method for detecting the three-dimensional geometry of the underwater acoustic material also includes:

Step 6, the step of changing the underwater temperature and pressure variation simulation environment for multiple measurements: change the underwater temperature and pressure variation simulation environment, and repeat steps 1 to 5 until the underwater acoustic material samples are completed in multiple underwater temperature and pressure variation simulation environments. The changing of the underwater temperature and pressure simulation environment refers to changing the pressure of the underwater temperature and pressure simulation, or changing the temperature of the underwater temperature and pressure simulation, or changing the underwater temperature and pressure simulation. pressure and temperature.

Further, the method for detecting the three-dimensional geometry of the underwater acoustic material further includes:

Step 7, the step of repeating the measurement by replacing the sample: repeating the measurement by replacing the underwater acoustic material sample, until the CT scanning and three-dimensional reconstruction of all the underwater acoustic material samples are completed.

The present invention also provides a method for detecting the static bulk compressive modulus of underwater acoustic materials, which is characterized in that: based on the above-mentioned three-dimensional geometric shape detection method of underwater acoustic materials, on the basis of a reference pressure and a reference temperature, a set pressure increase Measure the total volume change of the material before and after pressurization, and then calculate the static bulk compressive modulus of the underwater acoustic material, including the following steps:

Step 1, the step of CT scanning of the sample under the reference pressure and the reference temperature: according to the above-mentioned three-dimensional geometric shape detection method of the underwater acoustic material, firstly perform the three-dimensional geometric shape detection of the underwater acoustic material sample under the reference pressure and the reference temperature;

Step 2, the step of CT scanning of the sample after pressurization: on the basis of the above-mentioned reference pressure and reference temperature, a pressure increment ΔP is set, and then the heat preservation and pressure keeping control is performed, and after stabilization, the three-dimensional geometry of the underwater acoustic material sample is carried out. Detection method;

Step 3, the step of obtaining the volume of the sample before and after pressurization: according to the obtained three-dimensional geometry of the underwater acoustic material sample before and after the pressurization, respectively obtain the total volume V1 and V2 of the underwater acoustic material sample before and after the pressurization;

计算得到水声材料静态体积压缩模量；Step 4, the step of calculating the static bulk compressive modulus of the sample: obtain the total volume change ΔV=V1-V2 of the underwater acoustic material sample before and after pressurization, through the definition formula

Calculate the static bulk compressive modulus of the underwater acoustic material;

Step 5, the step of detecting the static bulk compressive modulus under different reference pressures and reference temperatures: change the temperature and pressure, repeat steps 1 to 4 at different reference pressures and reference temperatures, and obtain the static volume of the underwater acoustic material under different reference pressures and reference temperatures Compression modulus.

beneficial effect

The detection method and system of the present invention can detect the three-dimensional geometry of the hydroacoustic material under the simulated environment of underwater temperature and pressure variation, and obtain the apparent geometry and internal cavity geometry of the hydroacoustic material under different temperatures and static pressures. It can be directly used in the finite element analysis and design of acoustic and vibration aspects of underwater acoustic materials, providing accurate geometric models under corresponding working conditions for numerical simulation; the directly detected The three-dimensional geometry of the material can also be used to verify the deformation results of the hydroacoustic material statics simulation to improve the reliability of the hydroacoustic material statics design. At the same time, the directly measured static bulk compressive modulus of the material can provide basic material parameters for relevant static analysis.

The detection method proposed by the present invention breaks through the limitation that traditional methods cannot directly test the three-dimensional geometry of underwater acoustic materials in the simulated environment of underwater temperature and pressure variation, especially the cavity geometry and microstructure deformation inside the material. Morphology and structural deformation are very important references for the design and performance evaluation of underwater acoustic materials. The detection method of the present invention is based on three-dimensional CT scanning and reconstruction technology, and the measured material geometry can achieve high precision (mainly depends on the size of the CT machine and the sample, for industrial CT size, the sample diameter is 10 cm, and the reconstructed three-dimensional geometric size is The accuracy can reach the order of 50um or even higher).

The detection method for the static bulk compressive modulus of materials proposed based on the detection method of the present invention is a new method for directly obtaining the static bulk compressive modulus of materials, with simple operation and calculation process, and high test accuracy; Static bulk compressive modulus at base pressure and temperature, which provides a series of basic material parameters for related research.

The three-dimensional geometric shape detection system of underwater acoustic materials in the simulated environment of underwater variable temperature and pressure can meet the requirements of three-dimensional CT scanning of underwater acoustic materials and simulated actual working conditions of underwater acoustic materials at the same time, and can adopt a highly integrated The automatic control equipment performs functions such as data acquisition, control and monitoring, and is easy to operate, safe and efficient.

Description of drawings

Fig. 1 is a schematic diagram of an underwater acoustic material containing a cavity structure;

Figure 2 is a schematic diagram of a foamed polymer hydroacoustic material;

Figure 3 is a schematic diagram of the principle of an underwater environment simulation device for simulating the actual working conditions of underwater acoustic materials;

Figure 4 is a schematic diagram of a three-dimensional geometry detection system for underwater acoustic materials in a simulated environment of underwater temperature and pressure variation;

Figure 5 is a flow chart of the detection of the three-dimensional geometry of underwater acoustic materials in a simulated environment of underwater temperature and pressure variation;

Figure 6 is a flow chart of the detection of static bulk compressive modulus of underwater acoustic materials in a simulated environment of underwater temperature and pressure variation.

Reference number:

1. Underwater environment simulation device 2. Underwater acoustic material samples

3. CT detector plane 4. CT sample stage

5. CT X-ray light source

101, thermocouple 102, sample cavity

103. Pressure-resistant wall 104. Control and monitoring system

105, heat exchange bottom plate 106, bottom cover

107, circulating pump 108, constant temperature water tank

109. Compressed gas cylinder (pressurizing device) 110. Pressure regulating valve

111. Controller 112. Pressure sensor

113. Insulation jacket

Detailed ways

The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The underwater environment simulation device in the specific embodiment of the present invention is shown in FIG. 3 . The variable temperature and pressure environment simulation device is used to simulate the actual working conditions of underwater acoustic materials, and provides an underwater simulation environment, including variable temperature and pressure vessels, variable temperature and pressure environmental media, variable pressure systems, variable temperature systems, and temperature and pressure control systems.

Variable temperature and pressure vessel: used to place hydroacoustic material samples and provide a chamber that can simulate actual working conditions, namely the sample chamber. The size of the sample cavity is determined according to the maximum size of the sample, and it is necessary to ensure that during the CT scanning process, the tomography can penetrate all parts of the sample without obstruction. The sample cavity is enclosed by a pressure-resistant wall, an upper cover, and a bottom plate. In order to ensure air tightness, the connection between the upper cover and the pressure-resistant wall, the bottom plate and the pressure-resistant wall must be sealed with a sealing ring. There are openings on the pressure-resistant wall or upper cover to facilitate the entry and exit of the variable temperature and pressure environment medium into the sample cavity. The temperature sensor adopts a thermocouple, which is inserted into the sample chamber through the opening on the upper cover to test the internal temperature. The pressure-resistant wall of the sample chamber must not only meet the requirements of being able to withstand the maximum hydrostatic pressure of the corresponding working conditions, but also ensure that the X-rays emitted by the CT scanning system can penetrate. carbon fiber composite material), and its wall thickness and outer dimensions must also be determined in consideration of X-ray penetration and scanning field of view; if a metal material (such as duralumin, etc.) is used, it must be A thin-walled structure may be used to ensure X-ray penetration. The outside of the pressure-resistant wall is designed with a thermal insulation jacket, and the thermal insulation material with good thermal insulation performance is used to improve the thermal insulation performance of the internal sample cavity. The pressure-resistant wall of the sample chamber and the cavity between the thermal insulation jacket are used for circulating water to exchange heat. There is a bottom cover under the bottom plate, and the bottom plate and the bottom cover are sealed by a sealing ring to form a heat exchange cavity, so that the external circulating medium can flow and exchange heat, and the bottom cover is open to facilitate the inflow and outflow of the heat exchange medium. The variable temperature and pressure vessel is held up by a bracket, and the bracket needs to be designed with corresponding bolt holes, so that the entire variable temperature and pressure vessel can be fixed on the CT sample stage during CT scanning. During the test, the total weight of the underwater environment simulation container cannot exceed the maximum load-bearing capacity of the CT sample stage.

Variable temperature and pressure variable environment medium: that is, the environmental medium used for variable temperature and pressure change around the sample in the sample chamber. If the mechanical and thermophysical properties of the hydroacoustic material sample itself are not sensitive to the actual application of the environmental medium, such as seawater, a gas medium is preferred to improve the penetration force of CT, such as air or helium, etc., and the environmental medium and material samples can also be improved. The density contrast, or the density difference, can improve the imaging contrast at the outer boundary of the sample and improve the reconstruction accuracy at the boundary. If the mechanical and thermophysical properties of the hydroacoustic material sample are sensitive to the actual application environmental medium, the corresponding environmental medium must be selected, such as seawater or artificial simulated seawater medium. At this time, in order to improve the imaging contrast at the interface between the environmental medium and the material sample, a tracer needs to be added to the environmental medium liquid.

Variable pressure system: a system for pressurizing, depressurizing and maintaining pressure of the ambient medium in the sample chamber. Based on the above-selected variable temperature and variable pressure environment medium, the corresponding pneumatic or hydraulic control system is adopted. The pressure transformation system includes a booster device, a pressure relief device, and the booster device adopts a compressed gas cylinder or a hydraulic pump. A pressure regulating valve is installed on the outlet pipeline of the booster device, and a corresponding controller is preferably configured to facilitate accurate pressure regulation, adjust the outlet pressure of the booster device, and then control the pressure in the sample chamber. A corresponding pressure sensor is installed in the sample chamber or in the inlet pipeline connected to the underwater environment simulation device to detect the ambient medium pressure in the sample chamber, preferably a sensor with a pressure transmitter is used to facilitate the detection of The pressure signal is converted into an electrical signal or a digital signal and sent to the control computer. The control adopts industrial general pressure control methods such as PID to accurately control the outlet pressure of the pressure regulating valve. In Figure 3, the temperature and pressure control system is connected to the controller of the pressure reducing valve at the outlet of the booster device through the control line, and the pressure sensor is connected to the corresponding port of the temperature and pressure control system through the data line to control the solenoid valve of the air relief device (air relief valve). Connect the corresponding port of the control system through the control line. The high pressure port of the pressure regulating valve is installed at the outlet of the booster system, the low pressure port is connected to one end of the pipeline leading to the sample chamber, and the other end of the pipeline is connected to the inlet end of the variable temperature and pressure variable environment medium entering the sample chamber. The outlet end is connected to the air release device, and the external temperature-variable pressure-variable environmental medium supply device supplies the temperature-variable pressure-variable environmental medium in the sample chamber through the inlet end and the outlet end of the sample chamber.

Variable temperature system: a system used to heat up, cool down and keep warm for the variable temperature and pressure environment medium. The variable temperature system has two options of inner circulation and outer circulation. 1) Internal circulation mode: The circulating pump drives the variable temperature and pressure variable environmental medium to circulate in the sample chamber and the circulating pipeline. The heat exchange tube part in the circulation pipeline is placed in the corresponding heat exchange box. The heat exchange tube can be designed in the form of a coil to enhance the heat exchange efficiency. The heat exchange tank can be a circulating water exchange tank, and its temperature control range covers the temperature range of the simulated working conditions. All external circulation pipes need to be covered with thermal insulation material to reduce the heat exchange between the intermediate pipes and the surrounding atmosphere. The heated or cooled environment medium with variable temperature and pressure performs circulating flow heat exchange to realize the temperature change in the sample chamber. Using the internal circulation method, the pressure regulating valve and the exhaust valve should be closed during the temperature change process to reduce the impact of changes in the external environment. The internal circulation heat exchange efficiency is high, but the system is relatively complex. 2) External circulation mode, there is a heat exchange cavity in the outer shell of the variable temperature and pressure environment container (the pressure-resistant wall and bottom plate shown in Figure 3) and the interlayer between the external insulation jacket. Variation in the internal sample chamber. The heat exchange medium is liquid such as water or antifreeze. The heat exchange medium adopts methods such as constant temperature water tank to realize heat exchange, and then flows and circulates through the circulating pump to achieve the circulating heat exchange of the sample cavity. The constant temperature water tank is a circulating water tank, and the temperature control range covers the temperature range of the simulated working conditions. At the bottom of the sample chamber, a metal base plate with high thermal conductivity, such as a copper plate, is used for heat exchange, and the lower part is designed with a heat exchange fin structure. A bottom cover is used for sealing under the bottom plate, and the heat exchange medium can exchange heat with the ambient medium in the sample chamber through the heat exchange cavity between the bottom plate and the bottom cover. The external circulation system is relatively simple, but the heat exchange efficiency is relatively low. The choice of inner loop and outer loop should be weighed according to the actual application. A thermocouple is installed in the sample chamber, which transmits the measured temperature value to the corresponding control system in real time. The temperature control adopts industrial general temperature control methods such as PID to accurately control the temperature and circulating flow rate of the heat exchange box and the constant temperature water tank. In Figure 3, the temperature change system adopts the external circulation mode, the temperature and pressure control system is connected to the thermocouple through the data line, and the control port of the constant temperature water tank and the control line of the circulating pump are connected through the control line. The circulating pump drives the circulation of the heat exchange medium, the heat exchange medium circulates in the heat exchange chamber, the constant temperature water tank and the circulation pipeline, and the heat exchange medium exchanges heat in the constant temperature water tank.

Temperature and pressure control system: It is mainly used for real-time monitoring of temperature and pressure inside the sample chamber, including acquisition card and controller. The acquisition card is used to collect signals from pressure sensors and temperature sensors; All kinds of valves, heaters, refrigerators, etc. in the control pipeline work normally.

Based on the underwater environment simulation device, the present invention provides a three-dimensional geometry detection system for underwater acoustic materials, which includes an underwater environment simulation device, a CT scanning system and a detection control system, as shown in FIG. 4 .

The CT scanning system includes a sample stage for fixing the underwater environment simulation device, and is used to perform CT scanning on the underwater acoustic material sample fixed in the underwater environment simulation device to obtain the underwater acoustic material corresponding to the measured temperature and pressure. a tomographic image of the sample, using the tomographic image for three-dimensional reconstruction to obtain the three-dimensional geometry of the hydroacoustic material sample corresponding to the measured temperature and pressure;

The detection control system, firstly, provides a human-computer interaction interface, inputs the detection scheme, and outputs the detection result; secondly, controls the underwater environment simulation device according to the inputted detection scheme, and controls and displays the temperature and pressure inside the sample chamber; It is to control the CT scanning system to scan according to the input detection scheme and obtain the three-dimensional geometry of the underwater acoustic material sample corresponding to the measured temperature and pressure.

In order to facilitate the corresponding operation of the operator, the temperature and pressure control system can be integrated with the detection control system for centralized control and real-time monitoring.

The method for detecting the three-dimensional geometry of an underwater acoustic material in the specific embodiment of the present invention, the working flow chart is shown in Figure 5, and includes the following steps:

(1) Selection of CT scanning system: According to the material and size of the underwater acoustic material sample, select or customize a CT scanning system with corresponding functions and performance. At the same time, the maximum working voltage of the light source should ensure that the X-ray emitted under the corresponding conditions can penetrate the entire holder containing the material sample;

(2) Design and manufacture of underwater environment simulation device: On the basis of step (1), the actual working conditions (such as: temperature range of 4-40°C, pressure range of 0-3MPa) and CT scanning system are comprehensively considered. performance, design and manufacture a corresponding underwater environment simulation device that simulates the actual working conditions of underwater acoustic materials. The temperature and pressure control accuracy of the sample chamber of the underwater environment simulation device must meet the corresponding requirements, such as: the temperature fluctuation is less than ±1℃, and the pressure fluctuation is less than ±0.1MPa;

(3) Installation and fixation of underwater acoustic material samples: Install and fix the underwater environment simulation device used to simulate the actual working conditions of underwater acoustic materials on the sample stage of the CT scanning system, and place the prepared underwater acoustic material samples in the water. In the sample chamber of the lower environmental simulation device, close the sealing cover to ensure the airtightness of the sample chamber;

(4) Variable temperature control in the sample chamber: start to heat up or cool down the variable temperature and variable pressure environment medium in the sample chamber, and keep the temperature after the chamber reaches the set temperature. If you need to test at ambient temperature (ie room temperature), this step can be omitted;

(5) Variable pressure control in the sample chamber: After the temperature in the sample chamber is stable, start to pressurize the ambient medium in the sample chamber, and hold the pressure after the pressure reaches the set pressure. If it is necessary to test under ambient pressure (ie atmospheric pressure) , this step can be omitted;

(6) Control of heat preservation and pressure in the sample chamber: During the pressurization process in the above step (5), the temperature of the ambient medium in the sample chamber will fluctuate. At this time, a temperature and pressure control system must be used to control the temperature and pressure in the sample chamber. Precise control, monitor the temperature and pressure in the sample chamber through the pressure and temperature monitoring software, when the temperature and pressure are stable at the set value (the temperature fluctuation is less than ±1℃, the pressure fluctuation is less than ±0.1MPa), wait for at least half an hour or more , to ensure that the overall temperature of the underwater acoustic material sample is stable and consistent and the deformation is stable;

(7) CT scanning of material samples: CT scanning system was used to conduct CT scanning tests on variable temperature and pressure-variable containers containing samples, and the results of tomographic test images were stored in a computer. During the entire scanning test, the sample chamber was kept in a state of heat preservation and pressure, and the temperature and pressure in the holder were monitored in real time. If the fluctuation of the internal temperature and pressure exceeds the specified allowable fluctuation range, the test needs to be stopped. The data during the test is invalid, and the heat preservation and pressure preservation process is re-executed, and then the scanning test is started after stabilization;

(8) CT scan of samples under different working conditions: Continue to repeat the above (3)-(7) process, and perform preset simulation working conditions for the sample at different temperatures (such as 6 temperatures equally divided in the range of 4-40°C) and pressure ( CT tomography test under 4 pressures equally divided in the range of 0~3MPa), close the CT system after the test, and open the pressure relief valve;

(9) CT scan of different samples: turn off the CT system, open the pressure relief valve, and release the pressure in the holder. Open the holder, replace the sample, repeat the process (3)-(8), complete the CT tomography test of all samples to be tested under different preset simulation conditions, close the CT system after the test, open the pressure relief valve, and close all Control System;

(10) Three-dimensional geometric reconstruction of material samples: The CT scan test results are post-processed by a three-dimensional reconstruction program, and the three-dimensional geometric shapes of the underwater acoustic material samples under the corresponding working conditions are obtained by reconstruction, and the output is the corresponding data containing geometric data. The files (such as STL files in 3D patch format) can be further converted into general CAD format files such as igs containing 3D solid geometric data, and provide input material solid models for 3D geometric analysis and related finite element analysis required for subsequent design. This step can be performed after a single scan is completed, or after a certain amount of data is accumulated after part of the scan is completed, or after all scans are completed to obtain all data.

Based on the detection method of the three-dimensional geometry of the underwater acoustic material, a detection method of the static bulk compressive modulus of the underwater acoustic material at the corresponding reference temperature and reference pressure can also be realized. The working flow chart is shown in Figure 6, including the following steps :

(a) Three-dimensional CT scan of the sample under the reference pressure and temperature: according to the above steps (3)-(7), first carry out the CT scan test of the sample under the reference pressure and reference temperature, such as the reference pressure 2MPa and the reference temperature 25°C;

(b) CT scan of the sample after pressurization: On the basis of the above reference pressure and reference temperature, set a pressure increment ΔP (a small amount relative to the reference pressure, which can be a negative value, such as -0.1MPa), and then Carry out heat preservation and pressure control, and conduct CT scanning test of the sample after stabilization;

(c) Three-dimensional geometric reconstruction of samples before and after pressurization: 3D reconstruction of the scan results before and after pressurization, and analysis with CAD tools, the total volumes V1 and V2 of the samples before and after pressurization can be obtained respectively;

计算得到；(d) Calculation of the static bulk compressive modulus of the sample: the total volume change ΔV=V1-V2 of the material before and after pressurization can be obtained, and the static bulk compressive modulus can be determined by the formula

calculated;

(e) Detection at different reference temperatures and pressures: Repeat the steps (a)-(d) above under different reference temperature and pressure conditions to obtain the static bulk compressive modulus of the material at different temperatures and pressures.

The above 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 principles of the present invention should be included within the protection scope of the present invention.

Claims (9)

1. A three-dimensional geometric morphology detection system for an underwater acoustic material is characterized by comprising an underwater environment simulation device, a CT scanning system and a detection control system;

the underwater environment simulation device comprises a sample cavity for accommodating and fixing an underwater acoustic material sample and is used for providing an underwater temperature and pressure changing simulation environment for the underwater acoustic material sample;

the CT scanning system comprises a sample table for fixing the underwater environment simulation device, and is used for carrying out CT scanning on an underwater acoustic material sample fixed in the underwater environment simulation device to obtain an underwater acoustic material sample tomography image corresponding to the measured temperature and pressure, and carrying out three-dimensional reconstruction by adopting the tomography image to obtain the three-dimensional geometric morphology of the underwater acoustic material sample corresponding to the measured temperature and pressure;

the detection control system provides a human-computer interaction interface, inputs a detection scheme and outputs a detection result; secondly, controlling the underwater environment simulation device according to the input detection scheme, and controlling and displaying the temperature and the pressure in the sample cavity; and thirdly, controlling a CT scanning system to scan according to the input detection scheme and acquiring the three-dimensional geometric morphology of the underwater acoustic material sample corresponding to the measured temperature and pressure.

2. The detection system for the three-dimensional geometric morphology of the underwater acoustic material as claimed in claim 1, wherein the underwater environment simulation device comprises a temperature and pressure variable container, a temperature and pressure variable environment medium, a pressure variable system, a temperature variable system and a temperature and pressure control system,

the temperature and pressure changing container comprises a sample cavity, an underwater acoustic material sample is fixed in the sample cavity, and the temperature and pressure changing container can be penetrated by X rays so as to scan the underwater acoustic material sample in the underwater temperature and pressure changing simulation environment;

the temperature and pressure changing environment medium enters and exits the sample cavity through the opening on the temperature and pressure changing container, is used for realizing the underwater temperature and pressure changing simulation environment in the sample cavity, and has enough contrast on the boundary contacted with the underwater sound material sample so as to ensure the reconstruction precision of the outer boundary of the underwater sound material sample;

the variable pressure system is used for pressurizing, decompressing and maintaining the medium in the variable temperature and variable pressure environment;

the temperature-changing system is used for heating, cooling and preserving the temperature of the temperature-changing and pressure-changing environment medium;

the temperature and pressure control system acquires the temperature in the sample cavity through the temperature sensor under the control of the detection control system, acquires the pressure in the sample cavity through the pressure sensor, and controls the variable pressure system and the variable temperature system so as to control the temperature and the pressure in the sample cavity.

3. The detection system for the three-dimensional geometrical morphology of the underwater acoustic material according to claim 2,

the sample cavity of the temperature and pressure changing container is enclosed by a pressure resistant wall, an upper cover and a bottom plate, and the upper cover, the bottom plate and the pressure resistant wall are sealed by sealing rings;

the temperature and pressure changing environment medium adopts a gas medium, or adopts seawater added with a tracer or an artificial simulated seawater medium;

the pressure varying system comprises a pressurizing device, a pressure relief device, a pressure regulating valve and a pressure regulating valve controller; the pressure control system comprises a pressure regulating valve, a pressure regulating valve controller, a temperature and pressure control system, a pressure regulating valve controller, a pressure regulating valve controller and a pressure regulating valve controller, wherein the pressure regulating valve controller is connected with the sample cavity; the pressure relief device is connected with the sample cavity through a pipeline and is used for relieving the pressure of the sample cavity under the control of a temperature and pressure control system;

the temperature changing system adopts an internal circulation mode or an external circulation mode; when an internal circulation mode is adopted, the heated or cooled temperature and pressure changing environment medium is driven by a circulating pump to circularly flow in a sample cavity and a circulating pipeline in a temperature and pressure changing container, and heat exchange is carried out on a heat exchange pipe part in the circulating pipeline to finally realize circulating heat exchange, so that the temperature change in the sample cavity is realized; when an external circulation mode is adopted, the temperature and pressure changing environment container is arranged in the heat insulation sleeve, a heat exchange medium is arranged in a gap between the temperature and pressure changing environment container and the heat insulation sleeve, the heat exchange medium exchanges heat with the temperature and pressure changing environment medium in the sample cavity through the temperature and pressure changing container, the heat exchange medium is driven by the circulating pump to circularly flow in the gap between the temperature and pressure changing environment container and the heat insulation sleeve and the circulating pipeline, and the heat exchange of a heat exchange pipe part in the circulating pipeline is carried out; the circulating pump is controlled by a temperature and pressure control system;

the temperature and pressure control system comprises an acquisition card and a controller, wherein the acquisition card is used for acquiring signals of the pressure sensor and the temperature sensor; the controller is used for controlling the variable pressure system and the variable temperature system.

4. A system for detecting the three-dimensional geometry of an underwater acoustic material according to claims 1-3, wherein the underwater acoustic material is a viscoelastic material, and the sample of the underwater acoustic material has an embedded cavity structure or a foam structure.

5. The underwater acoustic material three-dimensional geometric shape detection method based on the system of any one of claims 1 to 4 is characterized in that an underwater acoustic material sample is fixed in an underwater environment simulation device, the underwater environment simulation device provides an underwater temperature and pressure changing simulation environment, then the underwater acoustic material sample fixed in the underwater environment simulation device is subjected to tomography CT scanning, and finally, a tomography image of the underwater acoustic material sample is subjected to three-dimensional reconstruction processing to obtain the three-dimensional geometric shape of the underwater acoustic material sample in the underwater temperature and pressure changing simulation environment.

6. The method for detecting the three-dimensional geometric morphology of the underwater acoustic material as claimed in claim 5, characterized by comprising the steps of:

step 1, sample installation and fixation: fixing an underwater acoustic material sample in a sample cavity of an underwater environment simulation device, and then installing and fixing the underwater environment simulation device on a sample table of a CT scanning system;

step 2, controlling the temperature change of the sample cavity: carrying out variable temperature control on the underwater environment simulation device until the temperature in the sample cavity reaches a set temperature state;

step 3, controlling the variable pressure in the sample cavity: after the temperature in the sample cavity is stable, carrying out variable pressure control on the underwater environment simulation device until the pressure in the sample cavity reaches a set pressure state;

step 4, controlling the heat preservation and pressure maintaining in the sample cavity: when the temperature and the pressure in the sample cavity reach set values, heat preservation and pressure maintaining control is carried out, and the temperature and the pressure in the sample cavity need to be stable for a long time to ensure that the integral temperature of the underwater acoustic material sample is stable and consistent and the deformation is stable;

step 5, CT scanning and three-dimensional reconstruction of the sample: and carrying out CT scanning on the underwater environment simulation device containing the underwater acoustic material sample by adopting a CT scanning system, wherein the temperature and pressure changing environment simulation device is in a heat preservation and pressure maintaining state during the whole CT scanning period, acquiring an underwater acoustic material sample tomography image corresponding to the set temperature and pressure through CT scanning, storing the tomography image result and carrying out three-dimensional reconstruction to obtain the three-dimensional geometric morphology of the underwater acoustic material sample corresponding to the set temperature and pressure.

7. The method for detecting the three-dimensional geometrical morphology of the underwater acoustic material as claimed in claim 6, further comprising:

step 6, changing the underwater variable temperature and pressure simulation environment for multiple measurements: changing an underwater temperature and pressure changing simulation environment, and repeating the steps 1 to 5 until CT scanning and three-dimensional reconstruction of the underwater acoustic material sample in a plurality of underwater temperature and pressure changing simulation environments are completed; the changing of the underwater temperature and pressure varying simulation environment refers to changing of the pressure of the underwater temperature and pressure varying simulation, or changing of the temperature of the underwater temperature and pressure varying simulation, or changing of the pressure and the temperature of the underwater temperature and pressure varying simulation.

8. The method for detecting the three-dimensional geometric morphology of the underwater acoustic material in the underwater temperature and pressure varying simulation environment as claimed in claim 6 or 7, further comprising:

and 7, replacing the sample to repeat the measurement: and replacing the underwater sound material samples to repeatedly measure until the CT scanning and the three-dimensional reconstruction of all the underwater sound material samples are completed.

9. A method for detecting the static volume compression modulus of an underwater acoustic material is characterized by comprising the following steps: the method for detecting the three-dimensional geometric morphology of the underwater acoustic material according to claim 6, wherein a pressure increment is set on the basis of a reference pressure and a reference temperature, the total volume change of the material before and after pressurization is measured, and the static volume compression modulus of the underwater acoustic material is calculated and obtained, and the method comprises the following steps:

step one, CT scanning of a sample under a reference pressure and a reference temperature: the method for detecting the three-dimensional geometrical morphology of the underwater acoustic material as claimed in claim 6, wherein the method comprises the steps of firstly detecting the three-dimensional geometrical morphology of an underwater acoustic material sample under a reference pressure and a reference temperature;

step two, the step of pressurized sample CT scanning: setting a pressure increment delta P on the basis of the reference pressure and the reference temperature, then carrying out heat preservation and pressure maintaining control, and carrying out a three-dimensional geometric shape detection method of the underwater acoustic material sample after stabilization;

step three, acquiring the volume of the sample before and after pressurization: respectively obtaining the total volumes V1 and V2 of the underwater sound material sample before and after pressurization according to the obtained three-dimensional geometric shapes of the underwater sound material sample before and after pressurization;

step four, calculating the static volume compression modulus of the sample: obtaining the total volume change DeltaV of the underwater acoustic material sample before and after pressurization as V1-V2 by defining the formula

Calculating to obtain the static volume compression modulus of the underwater acoustic material;

step five, detecting the static volume compression modulus under different reference pressures and reference temperatures: and changing the temperature and the pressure, and repeating the first step to the fourth step at different reference pressures and reference temperatures to obtain the static volume compression modulus of the underwater acoustic material at different reference pressures and reference temperatures.

Images