Film impact test equipment and test methods

Abstract

The present application relates to a film impact testing device and a testing method, which belongs to the field of material testing technology. Different from the quasi-static off-plane loading of a traditional bubbler, the compressed gas can be precisely controlled by a valve, and the off-plane impact loading of the film at different loading rates is achieved by instantaneously releasing the compressed gas under different pressure conditions. The mechanical parameters of the material under different loading rates are obtained through a pressure gauge and a deformation measurement system, and a dynamic stress test is performed on the film material to characterize the deformation behavior of the material in the dynamic nonlinear stage and obtain accurate film material parameters.

Description

Technical Field

[0001] The present application relates to the technical field of material testing, and in particular to a thin film impact testing device and a testing method. Background Art

[0002] In order to obtain the mechanical properties parameters of the material, it is first necessary to conduct material mechanical testing, and then obtain the required parameters through necessary calculation and analysis. For the determination of the mechanical properties parameters of flexible film materials, the bubbling test method can be used to carry out mechanical properties testing of film materials. The bubbling method can more accurately reflect the actual service conditions of flexible membrane materials. In related technologies, when conducting a bubbling experiment, the sample is installed on a test bench with holes, and uniform pressure is gradually increased on one side of the membrane. The deflection of the center point of the membrane is measured using a sensor (such as a laser displacement meter, etc.), thereby obtaining the change curve of the membrane deflection and the pressure in the inner cavity of the bubbling device. Combined with an appropriate theoretical model, the stress-strain curve and residual stress and other parameters of the membrane material can be obtained.

[0003] Although the bubbling method can more realistically reflect the stress conditions of flexible membrane materials during service, this experimental method still has some obvious shortcomings, mainly including: the current bubbling test method needs to be based on some assumptions, not the actual morphology of the film sample; most bubbling test methods are aimed at quasi-static mechanical property tests of film materials, which mainly focus on the measurement of elastic modulus and yield strength; and the actual morphology of film samples will undergo nonlinear deformation, and it is difficult to characterize the deformation behavior of the material in the nonlinear stage through quasi-static mechanical property tests. Summary of the Invention

[0004] Based on this, it is necessary to provide a film impact testing device, test method, readable storage medium and computer device to address the problem that traditional film impact loading test is difficult to characterize the deformation behavior of the material in the nonlinear stage through quasi-static mechanical property test.

[0005] In a first aspect, the present application provides a thin film impact testing device, comprising a first pressure gauge, a deformation measurement system, and an air storage chamber, a first valve, and a pressure cavity connected in sequence; wherein the first pressure gauge is connected to the pressure cavity;

[0006] The gas storage chamber is used to store compressed gas;

[0007] The first valve is used to control the instantaneous release of compressed gas in the gas storage chamber into the pressure cavity, thereby impact loading the membrane of the pressure cavity, wherein the membrane seal is provided at the opening of the pressure cavity;

[0008] The first pressure gauge is used to detect the air pressure in the pressure cavity;

[0009] Deformation measurement systems are used for impact measurements on thin films.

[0010] In one embodiment, the film impact testing device further includes a gas compressor connected to the gas storage chamber. The gas compressor is used to compress gas in the device and transfer the compressed gas into the gas storage chamber.

[0011] In one embodiment, the gas storage chamber includes a gas cylinder, a second valve and a three-way valve:

[0012] The second valve is connected between the gas outlet of the gas compressor and the first interface of the tee, the second interface of the tee is connected to the bottle mouth of the gas cylinder, the third interface of the tee is connected to the first valve, and the second valve is used to control the transfer of compressed gas into the gas cylinder.

[0013] In one embodiment, the gas storage chamber further includes a pressure regulator connected between the gas compressor and the second valve, and a second pressure gauge connected to the first interface;

[0014] The pressure regulator is used to regulate the gas flow of compressed gas;

[0015] The second pressure gauge is used to detect the gas pressure of the gas cylinder.

[0016] In one embodiment, the gas storage chamber further includes a regulating pressure reducer connected between the third interface and the first valve;

[0017] The regulating pressure reducer is used to discharge gas from the gas cylinder and reduce the pressure of the cylinder.

[0018] In one embodiment, the device further includes a control terminal, which is connected to the first valve, the second valve, the first pressure gauge, and the second pressure gauge respectively;

[0019] The control terminal is used to control the opening and closing of the first valve and the second valve, and to obtain the pressure values ​​of the first pressure gauge and the second pressure gauge.

[0020] In one embodiment, the control terminal is further connected to the deformation measurement system for controlling the deformation measurement system to perform impact measurement on the film.

[0021] In one embodiment, the control terminal is further configured to obtain constitutive parameters of the film according to the deformation measurement results and the air pressure of the pressure cavity using a virtual field method.

[0022] In a second aspect, the present application provides a film impact testing method, comprising the following steps:

[0023] storing compressed gas in a gas storage chamber;

[0024] placing a film seal at the opening of the pressure chamber;

[0025] The compressed gas in the gas storage chamber is released instantaneously into the pressure cavity to impact load the film;

[0026] Obtain the air pressure of the pressure cavity during the impact loading process, and obtain the deformation measurement results of the film through the deformation measurement system;

[0027] The constitutive parameters of the film are determined based on the air pressure in the pressure chamber and the deformation measurement results of the film.

[0028] In one embodiment, the step of storing compressed gas in the gas storage chamber comprises the following steps:

[0029] Compressed gas is prepared by a gas compressor and transferred to a gas storage chamber so that the gas pressure in the gas storage chamber reaches a preset value.

[0030] In one embodiment, the gas storage chamber includes a gas cylinder, a second valve, and a tee: the second valve is connected between the gas outlet of the gas compressor and the first interface of the tee, the second interface of the tee is connected to the bottle mouth of the gas cylinder, and the third interface of the tee is connected to the first valve;

[0031] The steps of transferring compressed gas into the gas storage chamber include the following steps:

[0032] Close the first valve, open the second valve, and transfer the compressed gas into the gas cylinder through the second valve and the three-way device; when the gas pressure reaches the preset value, close the second valve;

[0033] The step of instantaneously releasing the compressed gas in the gas storage chamber into the pressure cavity comprises the following steps:

[0034] Open the first valve and release the compressed gas instantaneously into the pressure chamber through the three-way device and the first valve.

[0035] In one embodiment, the gas storage chamber further includes a pressure regulator connected between the gas compressor and the second valve, and a second pressure gauge connected to the first interface; the method further includes the following steps:

[0036] Regulating the gas flow of the compressed gas by a pressure regulator;

[0037] The second pressure gauge is used to detect the gas pressure in the gas cylinder.

[0038] In one embodiment, the gas storage chamber further includes a regulating pressure reducer connected between the third interface and the first valve, and the method further includes the following steps:

[0039] When the air pressure exceeds a preset value, the gas in the gas cylinder is discharged by adjusting the pressure reducer to make the air pressure lower than the preset value, and the step of transferring the compressed gas into the gas storage chamber is performed until the air pressure reaches the preset value.

[0040] In one embodiment, the step of determining the constitutive parameters of the film according to the air pressure of the pressure chamber and the deformation measurement results of the film comprises the following steps:

[0041] The virtual field method is used to obtain the constitutive parameters of the film based on the deformation measurement results and the air pressure in the pressure cavity.

[0042] In one embodiment, the step of obtaining the constitutive parameters of the film according to the deformation measurement results and the air pressure of the pressure cavity using the virtual field method includes the following steps:

[0043] Obtain dynamic strain field and acceleration field based on deformation measurement results;

[0044] Obtain the virtual displacement field of the film, and obtain the acceleration virtual work according to the virtual displacement field, dynamic strain field and acceleration field;

[0045] Obtain the prior constitutive model and initial parameters, substitute the dynamic strain field, acceleration field and air pressure of the pressure cavity into the constitutive model, obtain the corresponding stress field, and obtain the internal force virtual work based on the stress field;

[0046] An objective function is constructed based on the residual squares of acceleration virtual work and internal force virtual work. The objective function is optimized and the initial parameters are updated. When the objective function is minimized, the updated parameters are used as the constitutive parameters of the film.

[0047] In a third aspect, the present application provides a readable storage medium having an executable program stored thereon, characterized in that when the executable program is executed by a processor, the steps of any of the above-mentioned film impact testing methods are implemented.

[0048] In a fourth aspect, the present application provides a computer device comprising a memory and a processor, wherein the memory stores an executable program, and wherein the processor implements the steps of any of the above-mentioned confidential data transmission methods when executing the executable program.

[0049] Compared with related technologies, the film impact testing equipment, method, readable storage medium and computer equipment provided by this application are different from the quasi-static off-plane loading of traditional bubblers. The compressed gas can be precisely controlled through a valve, and the off-plane impact loading of the film at different loading rates can be achieved by instantaneously releasing compressed gas under different pressure conditions. The material mechanical parameters under different loading rate conditions are obtained through a pressure gauge and a deformation measurement system. Dynamic stress testing is performed on the film material to characterize the deformation behavior of the material in the dynamic nonlinear stage and obtain accurate film material parameters.

[0050] The details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0052] Figure 1 is a schematic structural diagram of a film impact testing device in one embodiment;

[0053] Figure 2 Schematic diagram of the structure of a film impact testing device (including a gas compressor) in one embodiment;

[0054] Figure 3 is a schematic structural diagram of a film impact testing device in another embodiment;

[0055] Figure 4 is a structural schematic diagram of a film impact testing device in yet another embodiment;

[0056] Figure 5 is a structural schematic diagram of a film impact testing device in yet another embodiment;

[0057] Figure 6 is a schematic structural diagram of a film impact testing device in one embodiment;

[0058] Figure 7 1 is a flow chart of a film impact testing method in one embodiment;

[0059] Figure 8 A schematic diagram illustrating the plane stress assumption in the deformation of a thin film structure in one embodiment;

[0060] Figure 9 Schematic diagram of boundary conditions of a thin film material under off-surface loading conditions in one embodiment;

[0061] Figure 10 Schematic diagram of a virtual displacement field in thin film structure parameter identification in one embodiment;

[0062] Figure 11 A schematic diagram of a thin film structure parameter identification process in one embodiment;

[0063] Figure 12 is a simplified diagram of a thin film material impact testing system in one embodiment;

[0064] Figure 13 is a schematic diagram of the principle of an impact loading system in one embodiment;

[0065] Figure 14(a) 、 14(b) , 14 (c) is a schematic diagram of a bubbling cavity in one embodiment;

[0066] Figure 15 A schematic diagram of changes in pressure gauge output values ​​of the bubbling cavity and the gas storage tank during the loading process in one embodiment;

[0067] Figure 16 1. Images of a film sample before and after loading when the impact pressure is 1.5 MPa in one embodiment;

[0068] Figure 17 A schematic diagram of an off-plane loading test of a membrane material sample in one embodiment;

[0069] Figure 18 Schematic diagram of the strain field of a thin film sample measured by 3D-DIC in one embodiment;

[0070] Figure 19 Schematic diagram of the trend of internal and external virtual work changing with pressure in one embodiment. DETAILED DESCRIPTION

[0071] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and do not limit the scope of protection of this application.

[0072] As used in this application and the claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not intended to refer to the singular and may include the plural. Generally speaking, the terms "comprises" and "include" only indicate the inclusion of the steps and elements specifically identified, and these steps and elements do not constitute an exclusive list. A method or apparatus may also include additional steps or elements.

[0073] Although this application makes various references to certain modules in the system according to embodiments of the present application, any number of different modules may be used and run on the imaging system and / or processor. The modules are merely illustrative, and different aspects of the system and method may use different modules.

[0074] Flowcharts are used in this application to illustrate the operations performed by systems according to embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the various steps may be processed in reverse order or simultaneously. Furthermore, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0075] In practical applications, lightweight materials are widely used in various spacecraft equipment, particularly large-scale deployable antennas, to reduce launch costs and increase payload. The signal receiving surface of these antennas is made of flexible film. Deployable antennas are primarily categorized into three types based on the structural properties of the reflective surface: fixed-surface deployable antennas, inflatable deployable antennas, and mesh deployable antennas. Within the mesh deployable type, the rib-wrapped deployable antennas wrap the radiating ribs around a central sleeve and tie them with ropes before launch. After launch into orbit, the ropes are severed, and the radiating ribs, thanks to their elasticity, straighten from their bent state wrapped around the central sleeve, assisting in the deployment of the flexible antenna. The flexible antenna is subjected to dynamic loading during deployment, and the flexible film of the antenna is in a biaxially stretched state during service.

[0076] To ensure the smooth deployment and safe and reliable operation of large-scale space-deployable antennas after launch, extensive experimental testing and simulation analysis are required during antenna design to simulate the deployment process. Providing accurate material constitutive models and parameters is essential for dynamic structural simulation analysis. However, a comprehensive understanding of the mechanical behavior of flexible membrane materials is currently lacking. For example, in theoretical research and design applications of membrane structures, membranes are generally considered to be isotropic linear elastic materials. This differs significantly from the actual structure and mechanical properties of some membranes. For one thing, some membrane materials are anisotropic composite materials, which exhibit significant variations in mechanical properties in the warp and weft directions. Furthermore, like most flexible materials, membrane materials exhibit significant geometric nonlinearity and large creep when subjected to load. Using linear elastic models to describe the complex mechanical behavior of flexible membranes can pose serious safety risks. Therefore, in-depth research on the mechanical properties of flexible membranes in complex environments is crucial for dynamic simulation analysis and reliability design of related structures. However, conducting relevant measurements is currently difficult.

[0077] See also Figure 1 FIG2 is a schematic diagram of the structure of a thin film impact testing device according to an embodiment of the present application. The thin film impact testing device in this embodiment includes an air storage chamber 110, a first valve 120, and a pressure chamber 130, which are connected in sequence, as well as a first pressure gauge 140 and a deformation measurement system 150. The first pressure gauge 140 is connected to the pressure chamber 130.

[0078] The gas storage chamber 110 is used to store compressed gas;

[0079] The first valve 120 is used to control the instantaneous release of compressed gas in the gas storage chamber 110 into the pressure chamber 130, impact loading the film of the pressure chamber 130, wherein the film seal is provided at the opening of the pressure chamber 130;

[0080] The first pressure gauge 140 is used to detect the air pressure of the pressure chamber 130;

[0081] The deformation measurement system 150 is used to perform impact measurement on the film.

[0082] The gas storage chamber 110 is mainly used to store compressed gas and can also adjust the pressure of the compressed gas to obtain compressed gas of different pressures. The specific pressure value can be detected to achieve pressure control of the compressed gas in the gas storage chamber.

[0083] The first valve 120 is mainly used to control the gas flow between the gas storage chamber 110 and the pressure chamber 130. The first valve 120 can be various types of flow valves, including mechanical valves and solenoid valves, etc. The solenoid valves can include direct-acting solenoid valves, step-by-step direct-acting solenoid valves, pilot-operated solenoid valves, strobe-type switch solenoid valves, etc., which can be controlled to open and close by electrical signals.

[0084] The pressure chamber 130 is connected to the first valve 120 via a quick-connect connector. The pressure chamber 130 has an opening, and the film to be tested is sealed at the opening. When the first valve 120 is opened, compressed gas forms an impact airflow, which can perform an impact test on the film in the pressure chamber 130. The first pressure gauge 140 can continuously monitor the air pressure in the pressure chamber 130, providing feedback on the dynamic changes in air pressure during the impact test, and providing pressure data for the impact test of the film. If used in a bubble test method, the pressure chamber 130 can be the bubble chamber in the bubble device; if used in other types of testing methods, it can be a corresponding cavity for containing compressed gas.

[0085] In this embodiment, unlike the quasi-static off-plane loading of the traditional bubbler, the compressed gas can be precisely controlled by the valve, and the off-plane impact loading of the film at different loading rates is achieved by instantaneously releasing the compressed gas under different pressure conditions. The material mechanical parameters under different loading rate conditions are obtained through the pressure gauge and deformation measurement system, and the film material is subjected to dynamic stress testing to characterize the deformation behavior of the material in the dynamic nonlinear stage and obtain accurate film material parameters.

[0086] In one embodiment, Figure 2 As shown, the film impact testing device further includes a gas compressor 160, which is connected to the gas storage chamber 110. The gas compressor 160 is used to prepare compressed gas and transfer the compressed gas to the gas storage chamber 110.

[0087] In this embodiment, the above-mentioned gas compressor 160 is mainly used to compress the gas to obtain compressed gas with a pressure higher than the general atmospheric pressure, wherein the gas medium can be air or other specific gases. If air medium is used, an air compressor (such as an air pump, etc.) can be used. If it is necessary to detect the characteristic parameters of the film under a specific environment, the corresponding gas medium can be used, such as carbon dioxide, nitrogen, etc.; in addition, the air pressure value of the compressed gas prepared by the gas compressor 160 can be set according to the test requirements, such as greater than 10MPa.

[0088] In one embodiment, Figure 3 As shown, the gas storage chamber 110 includes a gas cylinder 111, a second valve 112 and a three-way valve 113:

[0089] The second valve 112 is connected between the gas outlet of the gas compressor 160 and the first interface of the tee 113, the second interface of the tee 113 is connected to the bottle mouth of the gas cylinder 111, and the third interface of the tee 113 is connected to the first valve 120. The second valve 112 is used to control the transfer of compressed gas into the gas cylinder 111.

[0090] In this embodiment, the gas storage chamber 110 may include a gas cylinder 111, a second valve 112 and a three-way valve 113. The second valve 112 controls the compressed gas to be transferred into the gas cylinder 111 through the three-way valve 113. The first valve 120 controls the gas in the gas cylinder 111 to flow into the pressure chamber 130 through the three-way valve 113. By storing the compressed gas using the gas cylinder 111, the amount and pressure of the compressed gas can be precisely controlled. Moreover, the use of the three-way valve 113, the first valve 120 and the second valve 112 can separate the inflation and deflation processes of the gas cylinder 111 without affecting each other.

[0091] It should be noted that the second valve 112 is mainly used to control the gas flow between the gas compressor 160 and the gas cylinder 111. The second valve 112 can be various types of flow valves, including mechanical valves and solenoid valves, etc. The solenoid valves can include direct-acting solenoid valves, step-by-step direct-acting solenoid valves, pilot solenoid valves, strobe switch solenoid valves, etc., which can be controlled to open and close by electrical signals.

[0092] In one embodiment, Figure 4 As shown, the gas storage chamber 110 further includes a pressure regulator 114 connected between the gas compressor 160 and the second valve 112 , and a second pressure gauge 115 connected to the first interface of the tee 113 ;

[0093] The pressure regulator 114 is used to adjust the gas flow of the compressed gas.

[0094] The second pressure gauge 115 is used to detect the gas pressure of the gas cylinder 111 .

[0095] In this embodiment, the pressure regulator 114 is connected between the gas compressor 160 and the second valve 112, and is used to adjust the gas flow rate of the compressed air generated by the gas compressor 160 into the gas cylinder 111. By adjusting the gas flow rate, the air pressure accuracy can be precisely controlled; the air pressure of the compressed gas in the gas cylinder 111 can be detected by the second pressure gauge 115 to obtain compressed gas of different pressures, thereby realizing the air pressure control of the compressed gas in the gas cylinder.

[0096] In one embodiment, Figure 5 As shown, the air storage chamber 110 further includes a regulating pressure reducer 116 connected between the third interface of the tee 113 and the first valve 120;

[0097] The regulating pressure reducer 116 is used to discharge the gas in the gas cylinder 111 and reduce the pressure of the gas cylinder 111 .

[0098] In this embodiment, during actual application, the air pressure of the compressed gas in the gas cylinder 111 is difficult to accurately reach the preset air pressure value. If it exceeds the preset air pressure value, it indicates that the air pressure is too high at this time. The gas cylinder 111 can be exhausted and decompressed by adjusting the pressure reducer 116 so that the air pressure of the compressed gas in the gas cylinder 111 reaches or is lower than the preset air pressure value. If the air pressure is lower than the preset air pressure value, it can be inflated again to make the air pressure value reach the preset air pressure value. In this way, the air pressure in the gas cylinder 111 can be adjusted to avoid the air pressure in the gas cylinder 111 being too high.

[0099] In one embodiment, Figure 6 As shown, the film impact testing device further includes a control terminal 170, which is connected to the first valve 120, the second valve 112, the first pressure gauge 140, and the second pressure gauge 115 respectively;

[0100] The control terminal 170 is used to control the opening and closing of the first valve 120 and the second valve 112 , and to obtain the pressure values ​​of the first pressure gauge 140 and the second pressure gauge 115 .

[0101] In this embodiment, a control terminal 170 can be set up to control the opening and closing of the first valve 120 and the second valve 112, and obtain the pressure values ​​of the first pressure gauge 140 and the second pressure gauge 115, so as to perform timely overall regulation of the film impact test and monitor the pressure of the compressed gas in real time to provide test data for the film impact test.

[0102] Furthermore, the control terminal 170 may also be connected to the gas compressor 160 to control the operation of the gas compressor 160 .

[0103] In one embodiment, the control terminal 170 is further connected to the deformation measurement system 150 to control the deformation measurement system 150 to perform impact measurement on the film.

[0104] In this embodiment, the control terminal 170 can control the deformation measurement system 150 to perform impact measurement on the film. The morphology of the film material during the impact loading process is not necessarily a standard spherical crown shape. The use of a general bubble analysis method will lead to large errors. However, the use of the deformation measurement system 150 can obtain the true morphology of the film after impact loading for subsequent material parameter analysis.

[0105] It should be noted that the control terminal 170 may be shared with the control center of the deformation measurement system 150 , or the control center of the deformation measurement system 150 may exist independently to control the deformation measurement system 150 .

[0106] Furthermore, the deformation measurement system 150 may include a full-field deformation measurement system, such as a 3D-DIC test system, which generally includes two image collectors to capture and shoot the object to be measured from different angles, and transmit the collected data to a control center (such as a computing device connected to the image collector, etc.), and obtain 3D full-field deformation data through algorithm calculation.

[0107] In one embodiment, the control terminal 170 is further configured to obtain the constitutive parameters of the film according to the deformation measurement results using a virtual field method.

[0108] In this embodiment, under impact loading conditions, due to the inertia effect, the impact load information applied to the film cannot be accurately measured. However, the deformation measurement system can be used to obtain the dynamic deformation and acceleration field of the film without measuring the external impact load applied to the sample. With the help of the principle of virtual work, the virtual work done by the unknown external impact force can be eliminated, and the acceleration field can be equivalent to the load information in the force balance equation based on the principle of virtual work, which is used to identify the constitutive parameters of the film.

[0109] According to the above-mentioned film impact testing device, an embodiment of the present application further provides a film impact testing method. An embodiment of the film impact testing method is described in detail below.

[0110] See also Figure 7 FIG. 1 is a flow chart of a film impact test method according to an embodiment. The film impact test method according to this embodiment includes:

[0111] Step S210: storing compressed gas in the gas storage chamber;

[0112] Step S220: sealing the film at the opening of the pressure chamber;

[0113] Step S230: releasing the compressed gas in the gas storage chamber instantaneously into the pressure cavity to perform impact loading on the film;

[0114] Step S240: obtaining the air pressure of the pressure cavity during the impact loading process, and obtaining the deformation measurement result of the film through the deformation measurement system;

[0115] Step S250: determining the constitutive parameters of the film according to the air pressure of the pressure chamber and the deformation measurement results of the film.

[0116] In this embodiment, unlike the quasi-static off-surface loading of traditional bubblers, the compressed gas can be precisely controlled by a valve, and the off-surface impact loading of the film at different loading rates is achieved by instantaneously releasing the compressed gas under different pressure conditions. The material mechanical parameters under different loading rate conditions are obtained through the pressure gauge and deformation measurement system, and dynamic stress testing is performed on the film material to characterize the deformation behavior of the material in the dynamic nonlinear stage and obtain accurate film material parameters.

[0117] In one embodiment, the step of storing compressed gas in the gas storage chamber comprises the following steps:

[0118] Compressed gas is prepared by a gas compressor and transferred to a gas storage chamber so that the gas pressure in the gas storage chamber reaches a preset value.

[0119] In one embodiment, the gas storage chamber includes a gas cylinder, a second valve, and a tee: the second valve is connected between the gas outlet of the gas compressor and the first interface of the tee, the second interface of the tee is connected to the bottle mouth of the gas cylinder, and the third interface of the tee is connected to the first valve;

[0120] The steps of transferring compressed gas into the gas storage chamber include the following steps:

[0121] Close the first valve, open the second valve, and transfer the compressed gas into the gas cylinder through the second valve and the three-way device; when the gas pressure reaches the preset value, close the second valve;

[0122] The step of instantaneously releasing the compressed gas in the gas storage chamber into the pressure cavity comprises the following steps:

[0123] Open the first valve and release the compressed gas instantaneously into the pressure chamber through the three-way device and the first valve.

[0124] In this embodiment, the gas storage chamber may include a gas cylinder, a second valve and a tee. The second valve controls the compressed gas to be transferred into the gas cylinder through the tee. The first valve controls the gas in the gas cylinder to flow into the pressure chamber through the tee. By using the gas cylinder to store the compressed gas, the amount and pressure of the compressed gas can be precisely controlled. Moreover, the use of the tee, the first valve and the second valve can separate the inflation and exhaust processes of the gas cylinder without affecting each other.

[0125] In one embodiment, the gas storage chamber further includes a pressure regulator connected between the gas compressor and the second valve, and a second pressure gauge connected to the first interface of the tee; the method further includes the following steps:

[0126] Regulating the gas flow of the compressed gas by a pressure regulator;

[0127] The gas pressure of the gas cylinder is detected by a second pressure gauge.

[0128] In this embodiment, a pressure regulator is connected between the gas compressor and the second valve to regulate the flow rate of compressed air generated by the gas compressor into the gas cylinder. By regulating the gas flow rate, the air pressure can be precisely controlled. For example, if a volume of 5 ml of compressed gas is flowing per second, controlling the gas flow rate allows for more precise pressure control within a smaller range. A second pressure gauge can be used to monitor the pressure of the compressed gas in the gas cylinder, providing different compressed gas pressures and enabling pressure control within the cylinder.

[0129] It should be noted that the second pressure gauge detects the air pressure in the gas cylinder. By presetting the air pressure value, different air pressure values ​​in the gas cylinder can be obtained, and the film can be impact tested under different air pressures.

[0130] In one embodiment, the gas storage chamber further includes a regulating pressure reducer connected between the third interface of the tee and the first valve, and the method further includes the following steps:

[0131] When the air pressure exceeds the preset value, the gas in the gas cylinder is discharged by adjusting the pressure reducer to make the air pressure lower than the preset value, and the step of transferring the compressed gas into the air storage chamber is performed again until the air pressure reaches the preset value.

[0132] In this embodiment, during actual application, the air pressure of the compressed gas in the gas cylinder is difficult to accurately reach the preset air pressure value. If it exceeds the preset air pressure value, it indicates that the air pressure is too high at this time. The gas cylinder can be exhausted and decompressed by adjusting the pressure reducer so that the air pressure of the compressed gas in the gas cylinder reaches or is lower than the preset air pressure value. If the air pressure is lower than the preset air pressure value, it can be inflated again to make the air pressure value reach the preset air pressure value. In this way, the air pressure in the gas cylinder can be adjusted to avoid the air pressure in the gas cylinder being too high.

[0133] In one embodiment, the step of determining the constitutive parameters of the film according to the air pressure of the pressure chamber and the deformation measurement results of the film includes the following steps:

[0134] The virtual field method is used to obtain the constitutive parameters of the film based on the deformation measurement results and the air pressure in the pressure cavity.

[0135] In this embodiment, a deformation measurement system is used to perform impact measurement on the film. The morphology of the film material during impact loading is not necessarily a standard spherical crown shape. The use of a general bubble analysis method will lead to large errors. The use of a deformation measurement system can obtain the true morphology of the film after impact loading for subsequent material parameter analysis. Under impact loading conditions, due to the inertia effect, the impact load information of the film cannot be accurately measured, but the use of a deformation measurement system can obtain the dynamic deformation and acceleration field of the film without measuring the external impact load on the sample. With the help of the principle of virtual work, the virtual work done by the unknown external impact force can be eliminated, and the acceleration field can be equivalent to the load information in the force balance equation based on the principle of virtual work, which is used to identify the constitutive parameters of the film.

[0136] Furthermore, the deformation measurement system can adopt full-field testing technology, such as digital image correlation method, grid method, etc.

[0137] In one embodiment, the step of obtaining the constitutive parameters of the film according to the deformation measurement results and the air pressure of the pressure cavity using the virtual field method includes the following steps:

[0138] Obtain dynamic strain field and acceleration field based on deformation measurement results;

[0139] Obtain the virtual displacement field of the film, and obtain the acceleration virtual work according to the virtual displacement field, dynamic strain field and acceleration field;

[0140] Obtain the prior constitutive model and initial parameters, substitute the dynamic strain field, acceleration field and air pressure of the pressure cavity into the constitutive model, obtain the corresponding stress field, and obtain the internal force virtual work based on the stress field;

[0141] An objective function is constructed based on the residual squares of acceleration virtual work and internal force virtual work. The objective function is optimized and the initial parameters are updated. When the objective function is minimized, the updated parameters are used as the constitutive parameters of the film.

[0142] In this embodiment, for the inversion and identification of material constitutive parameters, this application proposes to employ a virtual field method to identify the material's constitutive parameters from full-field deformation. Under impact loading conditions, the impact load applied to the specimen cannot be accurately measured due to inertial effects. However, the full-field measurement system can be used to obtain the specimen's dynamic deformation and acceleration field, eliminating the need to measure the external impact load. The principle of virtual work can be used to eliminate the virtual work performed by the unknown external impact force, and the acceleration field can be equated with load information in the force balance equation based on the principle of virtual work, which can be used to identify the material's constitutive parameters.

[0143] The virtual field method is used to identify the constitutive parameters of thin film materials. It should be emphasized here that the idea of ​​using the virtual field method to identify material parameters is based on the plane stress assumption. Due to the off-plane load, the deformation in the global coordinate system cannot meet this assumption. However, a careful analysis shows that the deformation still meets the plane stress assumption in the local coordinate system. Figure 8 Therefore, before parameter identification, the strain field information obtained in the global coordinate system needs to be converted to the local coordinate system. In addition, when the film material is subjected to an off-plane load, an external force will be applied along the edge of the sealing ring, but the direction and magnitude of this external force cannot be measured (it can be decomposed into tangential and normal loads), as shown in Figure 2. Figure 9 Therefore, in actual operation, it is necessary to define a set of virtual displacement fields, whose virtual displacements in both directions along the boundary are zero, so as to eliminate the virtual work done by the external force along the boundary, as shown in Figure 2. Figure 10 Therefore, the virtual displacement field in the parameter identification process can be defined as:

[0144]

[0145] where u x *,u y *,u z * is the virtual displacement in three directions, x, y, z are the three-dimensional coordinates of the measuring point, and R is the radius of the film sample.

[0146] When using this method to identify the constitutive parameters of a material, a priori constitutive models and initial parameters are required. This application can characterize the constitutive relationship of the material with a high-order polynomial, and derive the expression of the internal force virtual work and acceleration virtual work of the flexible film specimen under off-surface impact loading based on the observed dynamic displacement field and the strain field and acceleration field obtained therefrom. The square of the residual between the internal virtual work and the acceleration virtual work (the unknown external force virtual work term has been eliminated) in the force balance equation is used to establish an appropriate objective function, and then the initial parameters are updated using the optimization calculation method (the initial parameter is X, and a proportional coefficient δ can be set and updated using the formula X=X+δX). When a certain set of parameters minimizes the objective function (such as the square of the virtual work residual is less than the preset value β), the corresponding parameters are considered to be the constitutive parameters of the material. The parameter identification process is as follows Figure 11 The optimization model is implemented using MATLAB, and the identification method is verified through finite element simulation and real tests.

[0147] The film impact testing method of the embodiment of the present application corresponds to the above-mentioned film impact testing equipment, and the technical features and beneficial effects described in the embodiment of the above-mentioned film impact testing equipment are applicable to the embodiment of the film impact testing equipment.

[0148] In response to the testing requirements of the dynamic mechanical properties of thin film materials, this application mainly includes two modules: dynamic loading and deformation measurement and material parameter identification. For the off-surface impact loading system of thin film materials, this application can belong to a micro-fluid bubbling flexible thin film material impact testing system. The thin film material impact testing system can mainly include an air compressor, an air storage chamber, a control terminal, a bubbling device and a full-field deformation measurement system, as shown in the schematic diagram. Figure 12 shown.

[0149] The schematic diagram of the impact loading part is as follows Figure 13 The impact loading system is designed for quasi-dynamic experiments of thin film bubbling using a high-speed camera system as an observation method. The pressure medium is ordinary air, and the preliminary design of the maximum gas impact pressure is 4MPa. Its working principle is as follows:

[0150] 1) Preparation of the initial state of the experiment

[0151] Turn on the air compressor and reach the set pressure. Open the control software on the control terminal and enter the pressurization mode. Close the regulator.

[0152] 2) Gas pressurization process

[0153] The air compressor produces compressed air (pressure greater than 10 MPa). A manually controlled pressure regulator controls the gas flow to the desired accuracy (testing and experience are required). The control terminal controls a second valve, gradually transferring the compressed air into the cylinder. Based on the user-set test pressure, a second pressure gauge is used to monitor whether the cylinder pressure reaches the desired target. Once the target is reached, the second valve is closed. If the cylinder pressure is higher than expected, the user can manually adjust the pressure reducer to release the appropriate amount of air, then repeat the pressurization process until the desired pressure is reached.

[0154] 3) Experimental process

[0155] Once the desired pressure is reached, the control software on the control terminal is transferred to the experimental module. The first valve is opened, and compressed air is instantly released into the bubbling chamber to load the membrane. The pressure changes within the bubbling chamber during this dynamic process are sensed and recorded by the first pressure gauge.

[0156] 4) Deformation measurement

[0157] This application uses a full-field deformation measurement system and a high-precision digital pressure gauge (i.e. Figure 13The first pressure gauge in the center of the instrument measures the deformation response of thin film materials to off-plane impact. This application uses a full-field deformation measurement system because the morphology of thin film materials during impact loading does not necessarily maintain a standard spherical cap shape. Using the bubble analysis method would result in significant errors. Therefore, this application uses a full-field deformation measurement system to obtain the true 3D morphology of thin film specimens after impact loading for subsequent material parameter analysis.

[0158] For the inversion and identification of material constitutive parameters, this application proposes to employ a virtual field method to identify material constitutive parameters from full-field deformation. Under impact loading conditions, the impact load applied to the specimen cannot be accurately measured due to inertial effects. However, a full-field measurement system can be used to obtain the specimen's dynamic deformation and acceleration field, eliminating the need to measure the external impact load. The principle of virtual work can be used to eliminate the virtual work performed by the unknown external impact force, and the acceleration field can be equated with load information in the force balance equation based on the principle of virtual work, which can be used to identify material constitutive parameters.

[0159] This application is different from the quasi-static off-plane loading of traditional bubblers. This application uses a valve device to accurately control the compressed gas pressure, and realizes off-plane impact loading of thin film material samples at different loading rates by instantly releasing compressed gas under different pressure conditions; combining full-field deformation measurement technology and virtual field method to identify the material mechanical parameters under different loading rate conditions, providing a new experimental means for dynamic stress testing of thin film materials, and ultimately providing necessary reference basis for the safety and reliability design of related structures.

[0160] This application proposes to measure the off-surface strain field and acceleration field of the thin film through a full-field deformation measurement system. Based on the principle of the virtual field method, the strain field and acceleration field (inertial force) are used to invert the constitutive parameters of the thin film material without the need for additional measurement of the pressure on the film surface, effectively solving the problem of being unable to accurately and effectively measure the surface pressure of the film under high-pressure conditions.

[0161] This application uses a full-field deformation measurement system to measure the true morphology of thin film materials under impact. Compared with the traditional bubble analysis method, it does not require the assumption that the film is deformed into a sphere due to the expansion effect, and is more in line with the actual deformation situation.

[0162] In order to verify the feasibility of this application, this application has been preliminarily verified. Figure 13 A high-speed impact loading system for thin film materials was designed and manufactured, and the schematic diagram and actual picture of the bubbling cavity are shown in Figure 14. Figure 14a This is a schematic diagram of the bubbling chamber flange. Figure 14b 14c and 14d are the actual pictures of the bubbling cavity without sample and with sample, respectively. Figure 15 is the pressure gauge output value of the bubbling chamber and gas cylinder during loading, Figure 15 The right picture is a partial enlarged picture of the peak part in the left picture. Figure 16 The images of the film sample before and after loading at an impact pressure of 1.5 MPa are shown. This demonstrates that the experimental system provided by the present application can achieve off-plane impact loading of the film sample and obtain three-dimensional morphology information under high-speed impact.

[0163] This application also validates a framework for identifying material parameters. Using existing experimental conditions, low-pressure (0.15 MPa impact loading) off-plane loading tests were conducted on a thermoplastic flexible polyurethane membrane, identifying the material's nonlinear elastic parameters under quasi-static conditions. The load information used for material parameter identification during the loading process was measured by a pressure gauge. Figure 17 Figure 18 is a simplified diagram of the off-surface loading test of a membrane material sample. Figure 19 is the strain field of the thin film sample using the full-field measurement system. Figure 18 To identify the trend of the internal and external virtual work of the system with pressure when the parameters are elastic modulus E = 3.0 GPa, Poisson's ratio = 0.38, yield strength 11.53 MPa and tangent modulus H = 570.23 MPa. Figure 19 The consistency of the internal and external virtual work indicates that the virtual field method can be used to identify the hardening modulus of thin film materials from the out-of-plane deformation. The above experimental verification shows that the impact loading system and material parameter inversion identification process proposed in this application can be used to carry out dynamic impact testing of thin film materials.

[0164] According to the above-mentioned film impact testing device, an embodiment of the present application also provides a readable storage medium and a computer device.

[0165] A readable storage medium stores an executable program, which implements the steps of the above-mentioned film impact testing method when executed by a processor.

[0166] The above-mentioned readable storage medium, through the executable program stored therein, can achieve quasi-static off-plane loading different from traditional bubblers. The compressed gas pressure can be precisely controlled through the valve, and the off-plane impact loading of the film under different loading rates can be achieved by instantaneously releasing compressed gas under different pressure conditions. The material mechanical parameters under different loading rate conditions are obtained through the pressure gauge and deformation measurement system, and dynamic stress testing is performed on the film material to characterize the deformation behavior of the material in the dynamic nonlinear stage and obtain accurate film material parameters.

[0167] A computer device includes a memory and a processor. The memory stores an executable program. When the processor executes the executable program, the steps of the above-mentioned film impact testing method are implemented.

[0168] The above-mentioned computer equipment can achieve quasi-static off-plane loading different from traditional bubblers by running an executable program on the processor. The compressed gas pressure can be precisely controlled through the valve, and the off-plane impact loading of the film under different loading rates can be achieved by instantaneously releasing compressed gas under different pressure conditions. The material mechanical parameters under different loading rate conditions can be obtained through the pressure gauge and deformation measurement system, and dynamic stress testing can be performed on the film material to characterize the deformation behavior of the material in the dynamic nonlinear stage and obtain accurate film material parameters.

[0169] Those skilled in the art will appreciate that all or part of the processes in the above-described embodiments of the thin film impact testing method can be implemented by instructing related hardware through a computer program. The program can be stored in a non-volatile computer-readable storage medium. For example, in the embodiment, the program can be stored in a storage medium of a computer system and executed by at least one processor in the computer system to implement the processes including the above-described embodiments of the thin film impact testing method. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM).

[0170] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0171] Those skilled in the art will appreciate that all or part of the steps in the above-described method embodiments can be performed by instructing related hardware through a program. The program can be stored in a readable storage medium. When executed, the program includes the steps described in the above-described method. The storage medium includes ROM / RAM, a magnetic disk, an optical disk, and the like.

[0172] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that variations and improvements are possible within the scope of the present application, and such variations and improvements are within the scope of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A film impact testing device, characterized in that: The device comprises a first pressure gauge, a deformation measurement system, and an air storage chamber, a first valve, and a pressure cavity connected in sequence; wherein the first pressure gauge is connected to the pressure cavity; The gas storage chamber is used to store compressed gas; The first valve is used to control the instantaneous release of compressed gas in the gas storage chamber into the pressure cavity, thereby impact loading the film of the pressure cavity, wherein the film seal is provided at the opening of the pressure cavity; The first pressure gauge is used to detect the air pressure of the pressure cavity; The deformation measurement system is used to perform impact measurement on the film; The device further comprises a gas compressor connected to the gas storage chamber, the gas compressor being used to prepare compressed gas and transfer the compressed gas into the gas storage chamber; The gas storage chamber includes a gas cylinder, a second valve and a three-way device: The second valve is connected between the gas outlet of the gas compressor and the first interface of the tee, the second interface of the tee is connected to the bottle mouth of the gas cylinder, and the third interface of the tee is connected to the first valve; The second valve is used to control the transfer of the compressed gas into the gas cylinder; The gas storage chamber further includes a pressure regulator connected between the gas compressor and the second valve, and a second pressure gauge connected to the first interface; The pressure regulator is used to adjust the gas flow of the compressed gas; The second pressure gauge is used to detect the gas pressure of the gas cylinder; The device further includes a control terminal, wherein the control terminal is connected to the first valve, the second valve, the first pressure gauge, and the second pressure gauge respectively; The control terminal is used to control the opening and closing of the first valve and the second valve, and to obtain the pressure values ​​of the first pressure gauge and the second pressure gauge; The control terminal is also connected to the deformation measurement system, and is used to control the deformation measurement system to perform impact measurement on the film; The control terminal is further configured to obtain the constitutive parameters of the film according to the deformation measurement results and the air pressure of the pressure cavity using a virtual field method; wherein the virtual displacement field of the film is defined as: where u x *,u y *,u z * is the virtual displacement in three directions, x, y, z are the three-dimensional coordinates of the measuring point, and R is the radius of the film.

2. The film impact testing device according to claim 1, characterized in that: The air storage chamber further includes a regulating pressure reducer connected between the third interface and the first valve; The regulating pressure reducer is used to discharge the gas from the gas cylinder and reduce the pressure of the gas cylinder.

3. A film impact testing method, characterized in that: The method comprises the following steps: storing compressed gas in a gas storage chamber; Disposing a film seal at the opening of the pressure chamber; Instantly releasing the compressed gas in the gas storage chamber into the pressure cavity to perform impact loading on the film; obtaining the air pressure of the pressure cavity during the impact loading process, and obtaining a deformation measurement result of the film through a deformation measurement system; determining constitutive parameters of the film according to the air pressure of the pressure cavity and the deformation measurement results of the film; The step of storing compressed gas in the gas storage chamber comprises the following steps: preparing the compressed gas by a gas compressor and transferring the compressed gas into the gas storage chamber so that the gas pressure in the gas storage chamber reaches a preset value; The gas storage chamber includes a gas cylinder, a second valve and a three-way device: The second valve is connected between the gas outlet of the gas compressor and the first interface of the tee, the second interface of the tee is connected to the bottle mouth of the gas cylinder, and the third interface of the tee is connected to the first valve; the first valve is used to control the instantaneous release of compressed gas in the gas storage chamber into the pressure chamber; The step of transferring the compressed gas into the gas storage chamber comprises the following steps: Close the first valve, open the second valve, and transfer the compressed gas into the gas cylinder through the second valve and the three-way valve; when the gas pressure reaches the preset value, close the second valve; The step of instantaneously releasing the compressed gas in the gas storage chamber into the pressure cavity comprises the following steps: Opening the first valve to instantly release the compressed gas into the pressure chamber through the three-way device and the first valve; The step of determining the constitutive parameters of the film according to the air pressure of the pressure cavity and the deformation measurement result of the film comprises the following steps: The constitutive parameters of the film are obtained according to the deformation measurement results and the air pressure of the pressure cavity using a virtual field method; wherein the virtual displacement field of the film is defined as: where u x *,u y *,u z * is the virtual displacement in three directions, x, y, z are the three-dimensional coordinates of the measuring point, and R is the radius of the film.

4. The film impact testing method according to claim 3, characterized in that: The step of obtaining the constitutive parameters of the film according to the deformation measurement result and the air pressure of the pressure cavity by using the virtual field method comprises the following steps: Acquiring a dynamic strain field and an acceleration field according to the deformation measurement results; Acquire a virtual displacement field of the film, and acquire acceleration virtual work according to the virtual displacement field, the dynamic strain field, and the acceleration field; Obtaining a priori constitutive model and initial parameters, substituting the dynamic strain field, the acceleration field, and the air pressure of the pressure cavity into the constitutive model to obtain a corresponding stress field, and obtaining internal force virtual work based on the stress field; An objective function is constructed according to the residual square of the acceleration virtual work and the internal force virtual work, the objective function is optimized and the initial parameters are updated, and when the objective function is minimized, the updated parameters are used as the constitutive parameters of the film.

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