A high speed tensile assisted testing device for soft materials

Abstract

The application belongs to the technical field of material dynamic mechanical property testing equipment, and discloses a high-speed tensile auxiliary testing device for soft materials, which comprises an upper clamp of the auxiliary testing device, a lower clamp of the auxiliary testing device, a small-range piezoelectric dynamic force sensor, a small-range strain static force sensor and a liftable auxiliary support mechanism. The upper clamp is detachably connected with a conical block of a high-speed tensile testing machine, the lower clamp is installed on a lower end clamp through a piezoelectric sensor and a strain sensor connected in series, and the auxiliary support mechanism is arranged between the upper and lower end clamps of the high-speed tensile testing machine. During testing, the piezoelectric sensor is used to collect dynamic force signals at a high speed, and the stress-strain relationship under a high strain rate is obtained in combination with strain measurement. The application takes into account static prestress regulation and control and dynamic force accurate collection, effectively prevents deformation of a soft sample, does not need to modify a host machine, has strong adaptability, is easy to operate, and can significantly improve the precision and repeatability of high-speed tensile testing of soft materials.

Description

Technical Field

[0001] This invention belongs to the technical field of dynamic mechanical property testing equipment for materials, and in particular relates to a high-speed tensile auxiliary testing device for soft materials. Background Technology

[0002] A high-speed tensile testing machine is a hydraulically driven specialized device with a maximum loading speed of 20 m / s. It is primarily used to test the dynamic mechanical properties of metallic materials, composite materials, and engineering plastics under instantaneous high strain rate loads. It has wide applications in automotive crash safety and lightweighting, aerospace extreme condition verification, and new material research and verification. However, for soft materials such as gels, rubber, and biological tissues, whose strength is relatively low and whose breaking load is very small (possibly only a few Newtons or less), the main high-speed tensile testing machines on the market, such as Instron's VHS series, ZwickRoell's HTM series, and SHIMADZU's HITS-X series, have a minimum load range of no less than 10 kN, making them unsuitable for directly testing these soft materials.

[0003] Meanwhile, conventional high-speed tensile testing machines have a cage-like structure with a free-collision clamping structure with conical blocks at the top. Soft materials have extremely low stiffness and poor load-bearing capacity, which cannot support the weight of the upper conical blocks. During the sample installation process, the samples are prone to bending and deformation, which seriously affects the test accuracy.

[0004] Currently, the industry commonly uses a single dynamic force sensor for data acquisition, which has significant technical limitations. Piezoelectric dynamic force sensors offer excellent high-frequency response and are suitable for high-speed applications, but under static conditions, charge leakage is common, leading to continuous force drift and making it difficult to meet the requirements for precise adjustment of minute prestresses during sample assembly. Strain gauge static force sensors offer high static measurement accuracy and numerical stability, but their slow dynamic response makes it difficult to capture instantaneous minute load changes during high-speed tensile processes. Existing technologies cannot simultaneously meet the dual requirements of static prestress adjustment and dynamic force signal acquisition, significantly hindering the advancement of research on the dynamic mechanical properties of soft materials, new material development, and industrial testing. Summary of the Invention

[0005] The purpose of this invention is to provide a high-speed tensile auxiliary testing device for soft materials, so as to solve the problems existing in the prior art.

[0006] To achieve the above objectives, this invention provides a high-speed tensile auxiliary testing device for soft materials, applicable to the high strain rate tensile mechanical property testing of soft materials with small loads such as gels, rubber, biological tissues, and flexible polymers. The specific structure includes:

[0007] A high-speed tensile testing machine includes an upper clamp and a lower clamp. The upper clamp includes a conical block and a cage structure, with the conical block disposed inside the cage structure.

[0008] The auxiliary testing device has a clamp for holding the upper end of the soft material sample and is detachably connected to the conical block.

[0009] The lower clamp of the auxiliary testing device is used to hold the lower end of the soft material sample;

[0010] A dual series force sensor is mounted on the lower fixture of the auxiliary testing device. It includes a small-range piezoelectric dynamic force sensor and a small-range strain static force sensor. The lower fixture of the auxiliary testing device, the small-range piezoelectric dynamic force sensor and the small-range strain static force sensor are coaxially connected in series from top to bottom and mounted on the lower fixture.

[0011] An auxiliary support mechanism is disposed between the upper clamp and the lower clamp to support the conical block in a height-adjustable manner.

[0012] Optionally, the auxiliary support mechanism includes a support column, a top support ring, a fixed cylinder, a drive ring, and a bottom support ring; the support column is installed inside the fixed cylinder, the top support ring is integrally formed on the top of the support column, and the bottom support ring is installed on the bottom of the support column; the support column has an external thread, and the inner wall of the drive ring has an internal thread that mates with the external thread, forming a threaded transmission pair; the inner wall of the fixed cylinder has an axial guide groove to restrict the circumferential rotation of the support column; when the drive ring is rotated, the support column is driven to rise and fall along the axial guide groove through the threaded transmission pair.

[0013] Optionally, the support columns are multiple, formed by circumferential cutting of a cylindrical body with external threads. Each support column is evenly distributed circumferentially and is fixedly connected by the bottom support ring to achieve synchronous lifting.

[0014] Optionally, the bottom of the side wall of the fixed cylinder is provided with a through hole for the sensor signal line to pass through.

[0015] This invention also provides a method for high-speed tensile auxiliary testing of soft materials, applied to the aforementioned high-speed tensile auxiliary testing device, comprising:

[0016] S1: Place the conical block in the cage structure, connect the upper fixture of the auxiliary testing device to the conical block, and install the lower fixture of the auxiliary testing device on the lower fixture of the high-speed tensile testing machine after connecting it in series with a small-range piezoelectric dynamic force sensor and a small-range strain static force sensor.

[0017] S2: Install the lower end of the soft material sample into the lower fixture of the auxiliary testing device, place the auxiliary support mechanism, and adjust the support column to the initial position before contacting the cone block;

[0018] S3: Adjust the height of the cage structure of the high-speed tensile testing machine, install the upper end of the soft material sample onto the fixture of the auxiliary testing device, and set the small-range strain static force sensor to zero.

[0019] S4: Adjust the height of the cage structure, and by observing the reading of the small-range strain static force sensor, adjust the prestress of the soft material sample to the set value and fix the position of the cage structure; at the same time, rotate the drive ring to move the support column upward until it just supports the conical block.

[0020] S5: Start the high-speed tensile testing machine, and after the cage structure moves downward for a certain distance, accelerate upward according to the set parameters;

[0021] S6: After the cage structure is accelerated to the set speed, it fits with the conical block, which drives the fixture on the auxiliary testing device to move upward and complete the stretching of the soft material sample; at the same time, the dynamic force data is collected by the small-range piezoelectric dynamic force sensor, the deformation image of the soft material sample is captured by the high-speed camera, and the strain data is obtained by the DIC method.

[0022] S7: By combining strain data and dynamic force data, the stress-strain relationship of soft material specimens at high strain rates can be obtained.

[0023] The technical effects of this invention are as follows:

[0024] (1) Balancing static and dynamic measurements, significantly improving test accuracy: This invention adopts a dual-sensor series combination structure, using strain gauge sensors to compensate for the static drift defects of piezoelectric sensors, and precisely controlling the small prestress of the sample, avoiding initial overload and eliminating the interference of sample bending on optical strain measurement; the piezoelectric sensor collects dynamic force signals at close range, and the high-frequency response can accurately capture the instantaneous load changes during high-speed tensile testing, solving the problem that a single sensor cannot adapt to the static and dynamic measurement of soft materials, and significantly improving the accuracy and stability of test data.

[0025] (2) Solving the problem of soft material bearing capacity and strong test stability: The integrated liftable rigid auxiliary support mechanism relies on threaded transmission and axial guide structure to realize the synchronous and stable lifting of four columns, always keeping them horizontally supporting the upper conical block of the testing machine, avoiding the bending and collapse of soft materials due to their inability to bear the weight of the fixture, ensuring that the tensile posture of the specimen is always regular and reducing the test failure rate. The mechanism is manually adjustable, simple in structure, and runs without jamming.

[0026] (3) Standardized process and good test repeatability: The standardized operating process is matched, the steps of prestressing application, sample clamping and equipment operation are unified, the human operation error is small, the data of multiple parallel tests are highly consistent, and it meets the standard requirements of material testing and scientific research. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0029] Figure 1 This is a schematic diagram of the overall structure of the high-speed tensile auxiliary testing device for soft materials in an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the auxiliary support mechanism in an embodiment of the present invention;

[0031] Figure 3 This is a test flowchart in an embodiment of the present invention.

[0032] Labeling Explanation: 1. Auxiliary support mechanism; 2. Upper clamp of auxiliary testing device; 3. Lower clamp of auxiliary testing device; 4. Small-range piezoelectric dynamic force sensor; 5. Small-range strain-type static force sensor; 6. Soft material sample; 7. Base; 8. Cage structure; 9. Conical block; 10. Lower clamp; 11. Top support ring; 12. Support column; 13. Axial guide groove; 14. Drive ring; 15. Fixed cylinder; 16. Bottom support ring; 17. Through hole. Detailed Implementation

[0033] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0034] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] Example 1

[0037] like Figure 1 - Figure 3 As shown, this embodiment provides a high-speed tensile auxiliary testing device for soft materials, including an auxiliary support mechanism 1, an upper clamp 2, a lower clamp 3, a small-range piezoelectric dynamic force sensor 4, and a small-range strain-type static force sensor 5. The overall structure is a vertical tensile structure. All components are assembled using the existing high-speed tensile testing machine base 7, lower clamp 10, cage structure 8, and conical block 9, without requiring modification to the main body. The specific structure is as follows:

[0038] (1) Auxiliary testing device upper clamp 2: This clamp is used to hold the upper end of the soft material sample 6, and is connected to the conical block 9 of the upper clamp of the high-speed tensile testing machine with a detachable threaded structure. The conical block 9 is placed inside the cage structure 8 at the upper end of the testing machine, and the cage structure 8 is connected to the actuator of the testing machine. The threaded connection method allows for quick assembly and disassembly, and is compatible with conical blocks 9 of different specifications.

[0039] (2) Auxiliary support mechanism 1: The auxiliary support mechanism 1 is a liftable rigid support assembly set between the upper and lower clamps 10 of the high-speed tensile testing machine. It mainly consists of four support columns 12 with external threads, a top support ring 11, a fixed cylinder 15, a drive ring 14 with internal threads, an axial guide groove 13, a bottom support ring 16, and a side wall through hole 17.

[0040] In practice, the support columns 12 are integrally machined from a cylindrical body with external threads through circumferential cutting. The four support columns 12 are evenly distributed circumferentially. The top of the columns is integrally formed with a top support ring 11 to increase the support contact area. An axial guide groove 13 is opened on the inner wall of the fixed cylinder 15 to restrict the circumferential rotation of the support columns 12 and only allow them to rise and fall axially. The inner wall of the drive ring 14 and the external threads of the support columns 12 form a threaded transmission pair. The outer wall of the drive ring 14 is provided with a knurled anti-slip structure to facilitate manual rotation operation. The lower ends of the four columns are fixedly connected by a bottom support ring 16 to ensure the synchronization of lifting and lowering and the stability of the structure. A through hole 17 is opened at the bottom of the side wall of the fixed cylinder 15 for the force sensor signal line to pass through.

[0041] During operation, rotating the drive ring 14 can drive the four columns to rise and fall synchronously, providing stable support for the conical block 9 during the acceleration phase of the testing machine, thus preventing the soft sample material from being deformed by pressure.

[0042] In this embodiment, the auxiliary support mechanism 1 can be manually raised and lowered synchronously to stably support the upper conical block 9 of the testing machine, solving the problem that soft sample materials cannot bear the weight of the fixture and the sample is easy to bend and deform, thus ensuring the stability of the sample posture.

[0043] (3) Lower clamp 3 of auxiliary testing device: The lower clamp 3 of auxiliary testing device is installed on the lower clamp 10 of high-speed tensile testing machine after being connected in series with the small-range piezoelectric dynamic force sensor 4 and the small-range strain static force sensor 5. The lower clamp 10 of high-speed tensile testing machine is fixed to the base 7 of high-speed tensile testing machine. The two ends of the tensile specimen of soft specimen material are clamped by the upper clamp 2 and the lower clamp 3 of auxiliary testing device, respectively, forming a vertical tensile structure.

[0044] In this embodiment, the upper clamp 2 and lower clamp 3 of the auxiliary testing device are designed to be detachable and can be directly installed onto the original upper and lower clamps 10 of the high-speed tensile testing machine without modifying the original high-speed tensile testing machine. This design is compatible with mainstream models on the market. The auxiliary support mechanism 1 has reserved signal line through holes 17, which facilitates wiring and disassembly, reducing equipment modification costs.

[0045] Meanwhile, the external components in this embodiment adopt threaded detachable connections, eliminating the need for mechanical modifications to the original high-speed tensile testing machine. They can be directly adapted to high-speed tensile equipment of different models from mainstream domestic and international brands. The disassembly and assembly process is simple, and ordinary testing personnel can operate it. The equipment upgrade and modification costs are low, and the implementation is easy.

[0046] (4) Dual series force sensors: a small-range piezoelectric dynamic force sensor 4 and a small-range strain static force sensor 5 are connected in series, with the small-range piezoelectric sensor arranged on the side closer to the sample.

[0047] The small-range piezoelectric dynamic force sensor 4 is a high-frequency response sensor with a high resonant frequency, capable of capturing minute instantaneous dynamic load changes during high-speed tensile testing, making it suitable for high strain rate testing conditions of soft materials. The small-range strain static force sensor 5 is a high-precision micro-range sensor with stable static measurement values, specifically designed for detecting and adjusting minute prestresses during specimen assembly. By applying minute prestresses through static sensors, bending defects in the specimen can be eliminated without causing deformation. Furthermore, combined with a high-speed camera and DIC technology, it accurately acquires strain data, improving the overall accuracy and repeatability of the test.

[0048] In this embodiment, a small-range piezoelectric dynamic force sensor 4 and a small-range strain-type static force sensor 5 are arranged in series for coordinated operation. The strain-type sensor is responsible for the precise adjustment of minute prestress during the sample assembly stage, solving the problem of static force value drift of the piezoelectric sensor; the piezoelectric sensor is placed close to the sample and, relying on its high-frequency response characteristics, accurately collects the instantaneous dynamic load of high-speed tensile stress, realizing synchronous and accurate measurement of static and dynamic forces.

[0049] Based on the above-described apparatus, this embodiment provides a method for high-speed tensile testing of soft materials, specifically including:

[0050] S1: Connect the upper clamp 2 of the auxiliary testing device to the conical block 9 of the high-speed tensile testing machine, and place the conical block 9 in the cage structure 8. The lower clamp 3 of the auxiliary testing device is installed on the lower clamp 10 of the high-speed tensile testing machine after being connected in series with the small-range piezoelectric dynamic force sensor 4 and the small-range strain static force sensor 5.

[0051] S2: After installing one end of the soft material tensile specimen into the lower clamp 3 of the auxiliary testing device, place the auxiliary support mechanism 1, rotate the drive ring 14 of the auxiliary support mechanism 1 to move the four columns downward, temporarily without supporting the conical block 9, leaving operating space for the upper end of the specimen to be installed.

[0052] S3: Adjust the height of the cage structure 8 so that the sample can be loosely installed on the fixture 2 of the auxiliary testing device. Then place the zero-range strain static force sensor 5 and fix the sample on the fixture 2 of the auxiliary testing device.

[0053] S4: Slowly adjust the height of the cage structure 8 upwards, and observe the reading of the small-range strain static force sensor 5 until the prestress of the sample reaches the set value, then fix the position of the cage structure 8. At the same time, rotate the drive ring 14 of the auxiliary support mechanism 1 to move the four columns upwards until they just support the conical block 9;

[0054] S5: Start the high-speed tensile testing machine. The cage structure 8 first moves downward for a certain distance, and then accelerates upward according to the set parameters.

[0055] S6: When the cage structure 8 accelerates to the set speed, it comes into close contact with the cone block 9, causing the clamp 2 on the auxiliary testing device to move upward, completing the high-speed tensile test of the soft material sample 6 and causing it to break. During this process, the small-range piezoelectric dynamic force sensor 4 continuously collects force signals at a high sampling rate, the high-speed camera captures images of the sample deformation, and the strain value is calculated using the DIC method.

[0056] S7: By combining strain values ​​and dynamic force data, the stress-strain relationship of soft materials under high strain rates (stress deformation of materials under instantaneous high-speed loads) can be obtained.

[0057] Example 2

[0058] This embodiment provides a high-speed tensile testing procedure for rubber materials at room temperature, specifically including:

[0059] Test equipment: The ZwickRoell HTM16020 series high-speed tensile testing machine was used, along with the auxiliary testing device of this invention, a high-speed camera, and the DIC strain analysis system.

[0060] Sample selection: Select conventional elastic rubber rectangular tensile specimens with a thickness of 2 mm, a width of 4 mm, and a gauge length of 20 mm.

[0061] Device assembly: Complete the assembly of the entire device according to the structural setup of Example 1, confirm that the dual sensor signal lines pass through the through holes on the side wall of the support mechanism and are connected to the data acquisition terminal, and check that the threaded connections are tight and the support mechanism moves smoothly.

[0062] Test procedure: The test was performed strictly according to steps S1-S7 shown in Example 1. The tensile speed of the testing machine was set to 10 m / s. The prestress of the specimen was adjusted to 0.05 N using a strain gauge static force sensor. The equipment was started to complete the high-speed tensile test. The sampling frequency of the piezoelectric dynamic force sensor was set to 500 kHz. The deformation of the specimen was photographed simultaneously using a high-speed camera.

[0063] Test results: The high-speed tensile test of the rubber specimen was successfully completed without any specimen bending or slippage. Complete dynamic force and strain data were obtained, and the stress-strain curve of the rubber material under high strain rate was plotted. The test process was stable and the data were continuous and without any missing data.

[0064] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A high-speed tensile auxiliary testing device for soft materials, characterized in that, include: A high-speed tensile testing machine includes an upper clamp and a lower clamp (10). The upper clamp includes a conical block (9) and a cage structure (8). The conical block (9) is disposed inside the cage structure (8). The auxiliary testing device has a clamp (2) for holding the upper end of the soft material sample (6) and is detachably connected to the conical block (9); The auxiliary testing device has a lower clamp (3) for holding the lower end of the soft material sample (6); The dual series force sensors are installed on the lower fixture (3) of the auxiliary testing device. They include a small-range piezoelectric dynamic force sensor (4) and a small-range strain static force sensor (5). The lower fixture (3), the small-range piezoelectric dynamic force sensor (4), and the small-range strain static force sensor (5) are coaxially connected from top to bottom and installed on the lower fixture (10). An auxiliary support mechanism (1) is provided between the upper clamp and the lower clamp (10) for lifting and lowering the conical block (9).

2. The high-speed tensile auxiliary testing device for soft materials according to claim 1, characterized in that, The auxiliary support mechanism (1) includes a support column (12), a top support ring (11), a fixed cylinder (15), a drive ring (14), and a bottom support ring (16). The support column (12) is installed inside the fixed cylinder (15). The top support ring (11) is integrally formed on the top of the support column (12), and the bottom support ring (16) is installed on the bottom of the support column (12). The support column (12) is provided with an external thread, and the inner wall of the drive ring (14) is provided with an internal thread that mates with the external thread, forming a threaded transmission pair. The inner wall of the fixed cylinder (15) is provided with an axial guide groove (13) to restrict the circumferential rotation of the support column (12). When the drive ring (14) is rotated, the support column (12) is driven to rise and fall along the axial guide groove (13) through the threaded transmission pair.

3. The high-speed tensile auxiliary testing device for soft materials according to claim 2, characterized in that, The support columns (12) are multiple, formed by circumferential cutting of a cylindrical tube with external threads. Each support column (12) is evenly distributed circumferentially and is fixedly connected by the bottom support ring (16) to achieve synchronous lifting.

4. The high-speed tensile auxiliary testing device for soft materials according to claim 2, characterized in that, The bottom of the side wall of the fixed cylinder (15) is provided with a through hole (17), which is used for the sensor signal line to pass through.

5. A method for high-speed tensile auxiliary testing of soft materials, applied to the high-speed tensile auxiliary testing device for soft materials according to any one of claims 1-4, characterized in that, include: S1: Place the cone block (9) in the cage structure (8), connect the upper clamp (2) of the auxiliary testing device to the cone block (9), and install the lower clamp (3) of the auxiliary testing device on the lower clamp (10) of the high-speed tensile testing machine after connecting it in series with the small-range piezoelectric dynamic force sensor (4) and the small-range strain static force sensor (5). S2: Install the lower end of the soft material sample (6) into the lower clamp (3) of the auxiliary testing device, place the auxiliary support mechanism (1), and adjust the support column (12) to the initial position where it does not contact the cone block (9); S3: Adjust the height of the cage structure (8) of the high-speed tensile testing machine, install the upper end of the soft material sample (6) onto the clamp (2) of the auxiliary testing device, and set the small-range strain static force sensor (5) to zero. S4: Adjust the height of the cage structure (8), and by observing the reading of the small-range strain static force sensor (5), adjust the prestress of the soft material sample (6) to the set value, and fix the position of the cage structure (8); at the same time, rotate the drive ring (14) to move the support column (12) upward until it just supports the cone block (9). S5: Start the high-speed tensile testing machine, so that the cage structure (8) moves downward for a certain distance and then accelerates upward according to the set parameters; S6: After the cage structure (8) is accelerated to the set speed, it fits with the cone block (9), which drives the clamp (2) on the auxiliary testing device to move upward and complete the stretching of the soft material sample (6); at the same time, the dynamic force data is collected by the small-range piezoelectric dynamic force sensor (4), the deformation image of the soft material sample (6) is captured by the high-speed camera, and the strain data is obtained by the DIC method. S7: By combining strain data and dynamic force data, the stress-strain relationship of the soft material specimen (6) at high strain rate is obtained.

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