Expansion device and method for viscoelastic damage fracture test of soft material

Abstract

The invention belongs to the technical field of biological material mechanical property testing instruments, and relates to an expansion device and method for a soft material viscoelastic damage fracture test, and the device comprises a control module, a pressure module and a clamp module; wherein the control module is used for outputting a driving signal required by a viscoelastic damage fracture test to the pressure module; the pressure module is used for driving a screw rod to move back and forth through a motor under the action of a driving signal, compressing gas and / or liquid in an air cylinder at a variable rate, and applying an equal-biaxial variable-rate expansion load to the to-be-tested soft material in the clamp module, so as to realize a viscoelastic damage fracture test; and the clamp module comprises a front seat and a rear seat, and clamps the soft material to be tested through a gasket. According to the device and the method disclosed by the invention, on the basis of meeting biaxial mechanical loading conditions of soft materials and the like, the requirements of viscoelastic damage fracture testing can be met through controllable pressure change.

Description

Technical Field

[0001] The invention belongs to the technical field of biomaterial mechanical property testing instruments, and in particular relates to an expansion device and method for viscoelastic damage and fracture testing of soft materials. Background Art

[0002] Currently, there are two main in vitro mechanical testing methods for soft materials such as blood vessels and skin: uniaxial stretching and biaxial stretching. Uniaxial stretching is to cut the soft material into rectangular strips, place it in a uniaxial stretching machine, clamp it with a clamp, and stretch it in a certain direction to obtain the fracture characteristics of the soft material along that direction. However, common soft materials are anisotropic, and uniaxial stretching tests cannot describe the damage and fracture characteristics in directions other than the stretching direction. Although biaxial stretching provides biaxial tension, because it uses a hook to hook the tissue, the tissue often breaks at the hook when the tension is too large. It is necessary to design a specific fixture and a specific specimen to conduct damage and fracture experiments. In addition, because the preset biaxial loading conditions cannot be met point by point on the specimen, it is more complicated to describe the damage and fracture characteristics of biaxial stretching.

[0003] The Chinese patent application with publication number CN110501226A provides a biaxial tensile testing machine for biomaterials. The device clamps the biomaterial with two mutually perpendicular clamps, and can only apply mutually perpendicular tensile forces on a plane. The force on the sample on the plane is irregular and uneven, which increases the difficulty of subsequent stress analysis, and can only be used for larger samples. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art, disclose an expansion device for viscoelastic damage and fracture testing of soft materials, and propose a viscoelastic damage and fracture testing method for soft materials.

[0005] In view of this, the present invention discloses an expansion device for viscoelastic damage fracture testing of soft materials, comprising: a control module, a pressure module and a fixture module; wherein,

[0006] The control module is used to output the driving signal required for the viscoelastic damage fracture test to the pressure module;

[0007] The pressure module is used to compress the gas and / or liquid in the cylinder at a variable rate by driving the lead screw to move forward and backward through a motor under the action of a driving signal, and to apply an equibiaxial, variable rate expansion load to the soft material to be tested in the fixture module to achieve viscoelastic damage fracture testing;

[0008] The fixture module comprises a front seat and a rear seat, and clamps the soft material to be tested through a gasket.

[0009] Preferably, the control module includes: a power supply, a controller and a driver;

[0010] The power supply is used to convert the 220V mains power into a working voltage and provide it to the controller and the driver;

[0011] The controller is used to generate a programmed drive signal to act on the driver according to the set motor rotation speed and rotation direction;

[0012] The driver is used to output a signal to drive the motor to rotate.

[0013] Preferably, the pressure module comprises: a motor, a screw rod, a cylinder and a pressure gauge;

[0014] The motor is a stepper motor, the output line of the driver is connected to the motor, a T-shaped threaded screw is sleeved in the motor, a coupling is installed at the end of the screw away from the motor, the screw and the cylinder are axially fixed, when the motor rotates, the rotation inside the motor is converted into the forward and backward movement of the screw, driving the cylinder to move forward and backward;

[0015] The cylinder is fixed on a cylinder frame, and the cylinder frame is fixed on a base. An outlet hole is provided at one end of the cylinder away from the cylinder rod, and a quick connector is installed at the outlet hole. A first silicone tube is installed at the other end of the quick connector, and is connected to one end of a pressure gauge after passing through a first pagoda joint. The pressure gauge is used to monitor the pressure applied to the fixture module. A second pagoda joint is installed at the other end of the pressure gauge, and the second pagoda joint is connected to a second silicone tube. The second silicone tube is connected to a reducer on the fixture module. The air and / or liquid in the cylinder is compressed or decompressed by the forward and backward movement of the cylinder rod, so as to provide an equibiaxial expansion load to the soft material to be tested in the fixture module.

[0016] Preferably,

[0017] The controller generates a programmed drive signal to act on the driver according to the set motor rotation speed and rotation direction, controls the driver to output a pulse signal of a certain frequency, controls the forward or reverse rotation of the stepper motor by setting the direction signal, controls the speed of the stepper motor by adjusting the frequency of the pulse signal, and realizes precise control of the number of rotations of the stepper motor by calculating the number of pulse signals. The stepper motor converts the input electrical pulse signal into the angular displacement of the rotor in the motor, so that the angular velocity of the rotor rotation is proportional to the frequency of the pulse signal; wherein, the unit of the speed of the stepper motor is rpm, which satisfies the following formula:

[0018]

[0019] Among them, f is the frequency of the pulse signal, the unit is Hz, n is the number of pulses per revolution, that is, the number of steps of the stepper motor, and s is the step angle of the stepper motor, the unit is °.

[0020] Preferably, the front seat of the fixture module is fixed on the table top, a front seat hole is provided in the center of the front seat, a circular gasket is provided between the front seat hole and the rear seat, when the soft material to be tested is placed between the circular gasket and the front seat hole, the rear seat is pressed forward to fit the circular gasket, the soft material to be tested and the front seat, and fixed with bolts; a reducing joint is provided in front of the circular gasket of the rear seat for connecting the second silicone tube.

[0021] Preferably, the diameter of the soft material to be tested is larger than the diameters of the circular washer and the front seat hole.

[0022] Preferably, the rear seat of the clamp module is fixed to the front seat via nuts, and the front seat is fixed to the table via nuts.

[0023] On the other hand, the present invention proposes a viscoelastic damage fracture test method for soft materials, which is implemented based on the above expansion device and includes:

[0024] (1) Expansion at different rates: The motor is driven to rotate according to different speeds of the motor set by the control module, and the distance the screw rod advances is obtained according to the number of turns of the motor. The screw rod compresses the gas and / or liquid in the cylinder and the first silicone tube and the second silicone tube, and applies an equibiaxial expansion load to the soft material to be tested in the fixture module, thereby realizing expansion tests at different rates;

[0025] (2) Pressurization, Pause and Pressure Release: The control module outputs a positive pulse signal, and the motor drives the screw rod to expand the soft material at a certain rate. After the expansion reaches a certain deformation, the motor stops rotating and the soft material stops expanding. After the motor stops rotating for a period of time, the control module outputs a negative pulse signal to the pressure module, causing the motor to reverse at a set speed. The rotating motor drives the screw rod to retreat at a certain rate, and the screw rod releases the gas and / or liquid in the cylinder and the first silicone tube and the second silicone tube, and applies an equibiaxial expansion load to the soft material to be tested in the fixture module in the opposite direction. After the soft material expands to a smaller deformation, the motor is controlled to stop rotating, thereby achieving pressure application, pause and pressure release;

[0026] (3) Damage and fracture test: The motor drives the screw to expand the soft material at a certain rate until the soft material breaks.

[0027] Compared with the prior art, the advantages of the present invention are:

[0028] 1. The design of the fixture module meets the mechanical conditions of biaxial loading of the soft material under expansion, does not leak air or water, and can break the soft material. This design not only provides a mechanical environment for biaxial expansion of the soft material, but also the expansion force applied by the device is very large, which can damage and break the soft material.

[0029] 2. The electric drive cylinder converts electricity into gas or liquid pressure, which can provide gas / liquid pressure to break soft materials.

[0030] 3. The application of expansion force can be controlled by a program to achieve operations such as rate change, pressure application, pause and pressure release, meeting the needs of various mechanical research such as viscoelastic damage and fracture.

[0031] 4. Application: When soft materials expand, they are monitored by DIC equipment to obtain the real-time deformation field of the expansion. The stress information is calculated by virtual field method, membrane-like static equilibrium and other methods. The point-by-point stress-strain response of the material under biaxial conditions can be obtained, which helps to analyze the physiological response or damage and fracture behavior of soft materials in vivo.

[0032] 5. The device of the present application can meet the requirements of soft tissue viscoelastic damage and fracture testing through controllable pressure changes on the basis of meeting the biaxial mechanical loading conditions of soft materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the expansion device used for viscoelastic damage and fracture testing of soft materials according to the present invention;

[0034] Figure 2 It is a schematic diagram of the control module composition;

[0035] Figure 3 It is a schematic diagram of the pressure module composition;

[0036] Figure 4 It is a schematic diagram of the fixture module composition;

[0037] FIG5( a ) is a front view of the fixture module;

[0038] FIG5( b ) is a rear view of the fixture module;

[0039] Figure 6 It is a partial enlarged view of the fixture module;

[0040] Figure 7 This is a partial enlarged view of the fixture module from another perspective. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0042] Example 1

[0043] The mechanical response of soft materials can often be divided into two stages: elastic stage and damage fracture stage. Example 1 of the present invention proposes an expansion device and method for viscoelastic damage fracture test of soft materials based on the mechanical conditions of biaxial damage fracture test of soft materials. This device is applicable to common soft materials: biological tissues such as blood vessels, skin, and muscles, and hydrogels, rubbers, etc. with elastic modulus between 10 6 -10 9Pa. The following article uses blood vessels as an example to explain. There are relatively mature methods to simulate the mechanical behavior of blood vessels under in vivo physiological pressure, but simulating supraphysiological pressure, that is, the mechanical behavior when the blood vessels may be damaged and fractured, requires special devices. The biaxial expansion of soft materials by this device is a method to simulate in vivo pressure. It is particularly suitable for soft materials such as blood vessels. It can expand the flattened soft materials according to the condition of a biaxial ratio of 1:1. In mechanics, physical quantities such as the ultimate strength, ultimate elongation, and critical strain energy of the material characterize the damage and fracture characteristics of the material. This device can expand the soft material to the damage and fracture stage, which provides convenience for describing the damage and fracture mechanical properties.

[0044] In addition, the device can also study the viscoelastic damage characteristics of soft materials by controlling the loading rate and repeating the pressure-pause-release cycle.

[0045] The following describes the structure of the device in detail according to the module division of the device.

[0046] The energy source of the device is 220V household AC power. The mains power is connected to the controller and driver through a DC switching power supply with a rated voltage of 12V, a rated current of 5A, and a rated power of 60W. The stepper servo motor controller outputs a signal to the driver, and the driver drives the 42 through-type stepper motor.

[0047] like Figure 1 As shown, the device is mainly composed of a control module, a pressure module, and a fixture module. The control module is used to provide a driving signal to the pressure module; the pressure module is used to drive the screw rod to move forward and backward through the motor under the action of the driving signal, compress the gas and / or liquid in the cylinder, and apply an equibiaxial expansion load to the soft material to be tested in the fixture module; the fixture module includes a front seat and a rear seat, and clamps the soft material to be tested through a gasket.

[0048] The control module controls the pressure module to provide gas or liquid pressure to expand soft materials such as blood vessels installed in the fixture module.

[0049] Control modules such as Figure 2 Shown: includes power supply, controller and driver.

[0050] Pressure modules, such as Figure 3 Shown: includes motor, cylinder, motor and cylinder seat, and pressure gauge.

[0051] Fixture modules, such as Figure 4 Shown: includes base, rear seat and front seat.

[0052] FIG. 5( a ) is a front view of the fixture module; FIG. 5( b ) is a rear view of the fixture module; Figure 6 It is a partial enlarged view of the fixture module; Figure 7 This is a partial enlarged view of the fixture module from another perspective.

[0053] After soft materials such as blood vessels are laid flat, they are directly clamped and fixed by gaskets in the front and rear seats to ensure that there is no air leakage.

[0054] Connection of each module:

[0055] Control module → pressure module → fixture module.

[0056] The control module is powered by 220V voltage. The power supply is connected to the 220V mains electricity, which converts the electricity into a smaller voltage and supplies it to the controller and driver. The controller has a GUI page, which is based on programming to manually set the motor rotation speed, rotation direction and other information, and output the programmed drive signal to act on the driver. The driver outputs the signal to drive the motor to rotate.

[0057] The output line of the driver is connected to the motor, which is fixed on the motor seat, which is fixed on the white base. The base is fixed to the table by bolts. A 50cm long T-shaped threaded screw is sleeved in the motor. When the motor rotates, the rotation inside the motor is converted into the displacement of the screw rod moving forward and backward. A coupling is installed on the right end of the screw rod, which axially fixes the right end of the screw rod and the left end of the cylinder, so that the forward and backward movement of the screw rod drives the forward and backward movement of the cylinder.

[0058] In one embodiment, the cylinder is about 50 cm long and fixed on a cylinder frame, which is fixed on a base. The forward and backward movement of the cylinder rod can compress / decompress the air and / or liquid in the cylinder, and the air comes out from the rightmost outlet of the cylinder. The outlet is equipped with a quick connector, and a silicone tube is installed at the other end of the quick connector.

[0059] The first silicone tube is connected to the cylinder outlet joint on the left and to the left pagoda joint of the pressure gauge on the right. Similarly, the second silicone tube is connected to the right pagoda joint of the pressure gauge on the left and to a reducer on the right. The air and / or liquid in the cylinder is compressed or decompressed by the forward and backward movement of the cylinder rod, and an equal biaxial expansion load is applied to the soft material to be tested in the fixture module. The front seat of the fixture module is fixed to the table by bolts, and a front seat hole is provided in the center of the front seat. A circular gasket is provided between the front seat hole and the rear seat to ensure that there is no water leakage. When the soft material to be tested is placed between the gasket and the front seat hole, the rear seat is pressed forward to fit the gasket, the soft material to be tested and the front seat, and fixed with bolts; a reducer is provided in front of the gasket on the rear seat for connecting the second silicone tube. The diameter of the soft material to be tested is larger than the diameter of the gasket and the front seat hole.

[0060] The controller outputs a control signal to the driver according to the set motor rotation speed, controls the driver to output a pulse signal of a certain frequency, controls the forward or reverse rotation of the stepper motor by setting the direction signal, controls the speed of the stepper motor by adjusting the frequency of the pulse signal, and realizes precise control of the number of rotations of the stepper motor by calculating the number of pulses. The stepper motor converts the input electrical pulse signal into the angular displacement of the rotor in the motor, so that the angular velocity of the rotor rotation is proportional to the pulse frequency; wherein, the unit of the speed of the stepper motor is rpm, which satisfies the following formula:

[0061]

[0062] Among them, f is the frequency of the pulse signal, the unit is Hz, n is the number of pulses per revolution, that is, the number of steps of the stepper motor, and s is the step angle of the stepper motor, the unit is °.

[0063] The test of some biological tissues needs to be carried out in a specific solution, otherwise the tissue is prone to dehydration and inactivation. For example, when testing blood vessels, they need to be in contact with saline to ensure activity, not air. First, use a syringe to inject some saline at the end of the silicone tube and inside the reducer so that the sample and saline are in direct contact during expansion. There is still air in the pressure gauge and cylinder.

[0064] Example 2

[0065] Embodiment 2 of the present invention proposes a viscoelastic damage fracture test method for soft materials, which is implemented based on the above-mentioned expansion device.

[0066] At the beginning of the test, the control module outputs electrical energy and signals to rotate the motor. The rotating motor drives the screw rod to move forward and backward. The screw rod compresses the cylinder to compress the gas in the silicone tube. The gas acts on the soft material, continuously stretching the soft material, causing it to expand and break under high pressure.

[0067] If you need to test the viscoelastic properties of soft materials, you need to set a program in the controller: set the motor to rotate to a certain number of turns, that is, the cylinder screw moves forward a certain distance, and after the soft material is expanded to a certain deformation, the motor stops rotating, and then the motor reverses according to the recorded number of turns until the soft material reaches the initial unpressurized state. After that, start the motor again, expand the soft material to another deformation, and then reverse it until the soft material reaches the unpressurized state. The pressurization speed can also be adjusted by the controller. In this process, the viscoelastic properties of the soft material can be observed.

[0068] Specifically, the testing methods include:

[0069] (1) Expansion at different rates: The motor is driven to rotate according to different speeds of the motor set by the control module, and the distance the screw rod advances is obtained according to the number of turns of the motor. The screw rod compresses the gas and / or liquid in the cylinder and the first silicone tube and the second silicone tube, and applies an equibiaxial expansion load to the soft material to be tested in the fixture module, thereby realizing expansion tests at different rates;

[0070] (2) Pressurization, Pause and Pressure Release: The control module outputs a positive pulse signal, and the motor drives the screw rod to expand the soft material at a certain rate. After the expansion reaches a certain deformation, the motor stops rotating and the soft material stops expanding. After the motor stops rotating for a period of time, the control module outputs a negative pulse signal to the pressure module, causing the motor to reverse at a set speed. The rotating motor drives the screw rod to retreat at a certain rate, and the screw rod releases the gas and / or liquid in the cylinder and the first silicone tube and the second silicone tube, and applies an equibiaxial expansion load to the soft material to be tested in the fixture module in the opposite direction. After the soft material expands to a smaller deformation, the motor is controlled to stop rotating, thereby achieving pressure application, pause and pressure release;

[0071] (3) Damage and fracture test: The motor drives the screw to expand the soft material at a certain rate until the soft material breaks.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. An expansion device for viscoelastic damage fracture testing of soft materials, characterized in that: include: control module, pressure module and fixture module; wherein, The control module is used to output the driving signal required for the viscoelastic damage fracture test to the pressure module; The pressure module is used to compress the gas and / or liquid in the cylinder at a variable rate by driving the lead screw to move forward and backward through a motor under the action of a driving signal, and to apply an equibiaxial, variable rate expansion load to the soft material to be tested in the fixture module to achieve viscoelastic damage fracture testing; The fixture module comprises a front seat and a rear seat, and clamps the soft material to be tested through a gasket.

2. The expansion device for viscoelastic damage fracture testing of soft materials according to claim 1, characterized in that: The control module includes: a power supply, a controller and a driver; The power supply is used to convert the 220V mains power into a working voltage and provide it to the controller and the driver; The controller is used to generate a programmed drive signal to act on the driver according to the set motor rotation speed and rotation direction; The driver is used to output a signal to drive the motor to rotate.

3. The expansion device for viscoelastic damage fracture testing of soft materials according to claim 2, characterized in that: The pressure module includes: a motor, a screw rod, a cylinder and a pressure gauge; The motor is a stepper motor, the output line of the driver is connected to the motor, a T-shaped threaded screw is sleeved in the motor, a coupling is installed at the end of the screw away from the motor, the screw is fixed to the cylinder shaft, and when the motor rotates, the rotation inside the motor is converted into forward and backward movement of the screw, driving the cylinder shaft to move forward and backward; The cylinder is fixed on a cylinder frame, and the cylinder frame is fixed on a base. The base is fixed to the table top by bolts. An outlet hole is provided at one end of the cylinder away from the cylinder rod. A quick connector is installed at the other end of the quick connector. A first silicone tube is installed at the other end of the quick connector. The tube is connected to one end of a pressure gauge after passing through a first pagoda joint. The pressure gauge is used to monitor the pressure applied to the fixture module. A second pagoda joint is installed at the other end of the pressure gauge. The second pagoda joint is connected to a second silicone tube. The second silicone tube is connected to a reducer on the fixture module. The air and / or liquid in the cylinder is compressed or decompressed by the forward and backward movement of the cylinder rod, and an equibiaxial expansion load is applied to the soft material to be tested in the fixture module.

4. The expansion device for viscoelastic damage fracture testing of soft materials according to claim 3, characterized in that: The controller generates a programmed drive signal to act on the driver according to the set motor rotation speed and rotation direction, controls the driver to output a pulse signal of a certain frequency, controls the forward or reverse rotation of the stepper motor by setting the direction signal, controls the speed of the stepper motor by adjusting the frequency of the pulse signal, and realizes precise control of the number of rotations of the stepper motor by calculating the number of pulse signals. The stepper motor converts the input electrical pulse signal into the angular displacement of the rotor in the motor, so that the angular velocity of the rotor rotation is proportional to the frequency of the pulse signal; wherein, the unit of the speed of the stepper motor is rpm, which satisfies the following formula: Among them, f is the frequency of the pulse signal, the unit is Hz, n is the number of pulses per revolution, that is, the number of steps of the stepper motor, and s is the step angle of the stepper motor, the unit is °.

5. The expansion device for viscoelastic damage fracture testing of soft materials according to claim 3, characterized in that: The front seat of the fixture module is fixed on the table top, a front seat hole is arranged in the center of the front seat, a circular washer is arranged between the front seat hole and the rear seat, when the soft material to be tested is placed between the circular washer and the front seat hole, the rear seat is pressed forward to fit the circular washer, the soft material to be tested and the front seat, and fixed with bolts; a reducing joint is arranged in front of the circular washer on the rear seat for connecting the second silicone tube.

6. The expansion device for viscoelastic damage fracture testing of soft materials according to claim 5, characterized in that: The diameter of the soft material to be tested is greater than the diameters of the circular washer and the front seat hole at the same time.

7. The expansion device for viscoelastic damage fracture testing of soft materials according to claim 5, characterized in that: The rear seat of the clamp module is fixed to the front seat through nuts, and the front seat is fixed to the table through nuts.

8. A viscoelastic damage fracture test method for soft materials, implemented based on the expansion device described in any one of claims 3 to 7, comprising: (1) Expansion at different rates: The motor is driven to rotate according to different speeds of the motor set by the control module, and the distance the screw rod advances is obtained according to the number of turns of the motor. The screw rod compresses the gas and / or liquid in the cylinder and the first silicone tube and the second silicone tube, and applies an equibiaxial expansion load to the soft material to be tested in the fixture module, thereby realizing expansion tests at different rates; (2) Pressurization, Pause and Pressure Release: The control module outputs a positive pulse signal, and the motor drives the screw rod to expand the soft material at a certain rate. After the expansion reaches a certain deformation, the motor stops rotating and the soft material stops expanding. After the motor stops rotating for a period of time, the control module outputs a negative pulse signal to the pressure module, causing the motor to reverse at a set speed. The rotating motor drives the screw rod to retreat at a certain rate, and the screw rod releases the gas and / or liquid in the cylinder and the first silicone tube and the second silicone tube, and applies an equibiaxial expansion load to the soft material to be tested in the fixture module in the opposite direction. After the soft material expands to a smaller deformation, the motor is controlled to stop rotating, thereby achieving pressure application, pause and pressure release; (3) Damage and fracture test: The motor drives the screw to expand the soft material at a certain rate until the soft material breaks.

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