An expansion device and method for viscoelastic damage and fracture testing of soft materials

Abstract

The present invention belongs to the technical field of biomaterial mechanical property testing instruments, and relates to an expansion device and method for viscoelastic damage and fracture testing of soft materials, the device comprising: a control module, a pressure module, and a fixture module; wherein the control module is used to output the driving signal required for the viscoelastic damage and fracture testing 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 forward and backward through a motor under the action of the driving signal, and apply an equibiaxial, variable rate expansion load to the soft material to be tested in the fixture module to achieve viscoelastic damage and fracture testing; the fixture module includes a front seat and a rear seat, which clamp the soft material to be tested through a gasket. The device and method of the present invention can meet the requirements of viscoelastic damage and fracture testing by controlling the pressure change on the basis of meeting the equibiaxial mechanical loading conditions of the soft material.

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, the two main in vitro mechanical testing methods commonly used for soft materials such as blood vessels and skin are uniaxial stretching and biaxial stretching. In uniaxial stretching, the soft material is cut into rectangular strips, placed in a uniaxial stretching machine, clamped with a clamp, and stretched 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. Specific clamps and specimens need to be designed to conduct damage and fracture experiments. In addition, because the preset biaxial loading conditions cannot be met point by point on the specimen, describing the damage and fracture characteristics of biaxial stretching is more complicated.

[0003] Chinese patent application publication number CN110501226A discloses a biaxial tensile testing machine for biomaterials. This device uses two perpendicular clamps to clamp the biomaterial. This device can only apply perpendicular tensile forces on a plane. The forces acting on the specimen in this plane are irregular and uneven, increasing the difficulty of subsequent stress analysis. Furthermore, the device can only be used on larger specimens. 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 and 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 drive the lead screw forward and backward through the motor under the action of the drive signal, compressing the gas and / or liquid in the cylinder at a variable rate, applying an equibiaxial, variable rate expansion load to the soft material to be tested in the fixture module, and realizing viscoelastic damage fracture testing;

[0008] The fixture module includes 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 220V mains electricity into working voltage and provide it to the controller and 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 to fix the screw and the cylinder axially. When the motor rotates, the rotation inside the motor is converted into the forward and backward movement of the screw, which drives the cylinder to move forward and backward.

[0015] The cylinder is fixed on the cylinder frame, and the cylinder frame is fixed on the 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, which is connected to one end of a pressure gauge after passing through a first pagoda connector. The pressure gauge is used to monitor the pressure applied to the fixture module. A second pagoda connector is installed at the other end of the pressure gauge, and the second pagoda connector 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, thereby providing an equal biaxial expansion load to the soft material to be tested in the fixture module.

[0016] Preferably,

[0017] The controller generates a programmed drive signal based on the set motor rotation speed and rotation direction, acts on the driver, 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 accurately controls 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] Where f is the frequency of the pulse signal in Hz, n is the number of pulses per revolution, i.e. the number of steps of the stepper motor, and s is the step angle of the stepper motor in degrees.

[0020] Preferably, the front seat of the fixture module is fixed on the table, a front seat hole is provided in the center of the front seat, and 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 on 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 provides a viscoelastic damage and fracture testing method for soft materials, which is implemented based on the above-mentioned expansion device and includes:

[0024] (1) Expansion at different rates: The motor is driven to rotate at different speeds according to the control module. The distance the lead screw advances is obtained according to the number of revolutions of the motor. The lead screw compresses the gas and / or liquid in the cylinder and the first and second silicone tubes, and applies an equal biaxial expansion load to the soft material to be tested in the fixture module, thereby achieving 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 according to the 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 equal biaxial expansion load in the opposite direction to the soft material to be tested in the fixture module. After the soft material expands to a smaller deformation, the motor is controlled to stop rotating, thereby achieving pressurization, 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 fixture module is designed to meet the mechanical conditions of biaxial expansion of soft materials, preventing air or water leakage and capable of breaking the soft material. This design not only provides a mechanical environment for biaxial expansion of the soft material, but also applies a very large expansion force, capable of damaging and fracturing 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 using DIC equipment to obtain the real-time deformation field of the expansion. Stress information is calculated using methods such as virtual field method and membrane-like static equilibrium. The point-by-point stress-strain response of the material under biaxial conditions can be obtained, which helps 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 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;

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

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

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

[0038] Figure 5(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 be divided into two stages: elastic stage and damage fracture stage. According to the mechanical conditions of biaxial damage fracture test of soft materials, Example 1 of the present invention proposes an expansion device and method for viscoelastic damage fracture test of soft materials. This device is applicable to common soft materials: biological tissues such as blood vessels, skin, and muscles, as well as hydrogels, rubbers, etc. with elastic modulus between 10 and 20. 6 -10 9Pa. The following will be explained using blood vessels as an example. There are relatively mature methods to simulate the mechanical behavior of blood vessels under in vivo physiological pressure, but simulating the mechanical behavior of blood vessels under super-physiological 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 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 mechanical characteristics of damage and fracture.

[0044] In addition, this 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 device's power source is 220V household AC power. A DC switching power supply with a rated voltage of 12V, a rated current of 5A, and a rated power of 60W connects the mains power to the controller and driver. The stepper servo motor controller outputs signals to the driver, which drives the 42-pivot stepper motor.

[0047] like Figure 1 As shown in the figure, the device mainly consists 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. Under the action of the driving signal, the pressure module is used to drive the screw rod back and forth through the motor, compressing the gas and / or liquid in the cylinder, and applying 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, which clamp 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 base, and pressure gauge.

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

[0052] FIG5( a ) is a front view of the fixture module; FIG5( 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 the soft materials such as blood vessels are laid flat, they are directly clamped and fixed by gaskets in the front and back seats to ensure that there is no air leakage.

[0054] Connections of each module:

[0055] Control module → Pressure module → Fixture module.

[0056] The control module is powered by a 220V power supply. The power supply is connected to the 220V mains, converting the power to a lower voltage and supplying it to the controller and driver. The controller includes a user interface (GUI) that allows programming of motor speed, direction, and other parameters. The controller then outputs programmed drive signals to the driver. The driver's output signals drive the motor.

[0057] The output cable of the driver is connected to the motor, which is fixed to the motor base. The motor base is fixed to the white base, which is bolted to the table. A 50cm long T-shaped threaded screw is inserted into the motor. When the motor rotates, the internal rotation of the motor is converted into the displacement of the screw. A coupling is installed on the right end of the screw, axially fixing the right end of the screw to the left end of the cylinder, so that the back and forth movement of the screw drives the back and forth movement of the cylinder.

[0058] In one embodiment, the cylinder is approximately 50 cm long and is secured to a cylinder frame, which is in turn secured to a base. The forward and backward movement of the cylinder rod compresses and decompresses the air and / or liquid within the cylinder. Air exits through the rightmost outlet of the cylinder, which is fitted with a quick-connect connector. A silicone tube is attached to the other end of the quick-connect 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, providing an equal biaxial expansion load 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. A front seat hole is provided in the center of the front seat, and a circular gasket is provided between the front seat hole and the rear seat to ensure watertightness. After 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; the rear seat is provided with a reducer in front of the gasket 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 based on the set motor rotation speed, controlling the driver to output a pulse signal of a certain frequency. The forward or reverse rotation of the stepper motor is controlled by setting the direction signal. The speed of the stepper motor is controlled by adjusting the frequency of the pulse signal. The number of revolutions of the stepper motor is precisely controlled 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. The speed of the stepper motor is measured in rpm, which satisfies the following formula:

[0061]

[0062] Where f is the frequency of the pulse signal in Hz, n is the number of pulses per revolution, i.e. the number of steps of the stepper motor, and s is the step angle of the stepper motor in degrees.

[0063] Some biological tissue tests require specific solutions, as otherwise the tissue will dehydrate and become inactivated. For example, when testing blood vessels, they must be in contact with saline solution, not air, to maintain their viability. First, use a syringe to inject saline solution into the end of the silicone tubing and into the reducer, ensuring direct contact between the specimen and the saline solution during expansion. The pressure gauge and cylinder should remain filled with air.

[0064] Example 2

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

[0066] At the start of the test, the control module outputs electrical energy and signals, causing the motor to rotate. This rotating motor drives the screw back and forth. The screw compresses the cylinder, which in turn compresses the gas in the silicone tube. The gas acts on the soft material, continuously stretching it, causing it to expand and fracture under high pressure.

[0067] To test the viscoelastic properties of a soft material, a program is set in the controller: the motor rotates a certain number of times, which means the cylinder screw advances a certain distance. After the soft material has expanded to a certain deformation, the motor stops and then reverses by the recorded number of revolutions until the soft material reaches its initial unstressed state. The motor is then restarted to expand the soft material to another deformation, and then reversed again until the material reaches its unstressed state. The speed of the pressurization can also be adjusted by the controller. This process allows the viscoelastic properties of the soft material to be observed.

[0068] Specifically, the testing methods include:

[0069] (1) Expansion at different rates: The motor is driven to rotate at different speeds according to the control module. The distance the lead screw advances is obtained according to the number of revolutions of the motor. The lead screw compresses the gas and / or liquid in the cylinder and the first and second silicone tubes, and applies an equal biaxial expansion load to the soft material to be tested in the fixture module, thereby achieving 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 according to the 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 equal biaxial expansion load in the opposite direction to the soft material to be tested in the fixture module. After the soft material expands to a smaller deformation, the motor is controlled to stop rotating, thereby achieving pressurization, 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 intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and are intended to be encompassed by the claims of the present invention.

Claims

1. An expansion device for viscoelastic damage and 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 drive the lead screw forward and backward through the motor under the action of the drive signal, compressing the gas and / or liquid in the cylinder at a variable rate, applying an equibiaxial, variable rate expansion load to the soft material to be tested in the fixture module, and realizing viscoelastic damage fracture testing; The fixture module includes a front seat and a rear seat, which clamp the soft material to be tested through a gasket; The control module includes: a power supply, a controller and a driver; The power supply is used to convert 220V mains electricity into working voltage and provide it to the controller and 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; 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 to fix the screw to the cylinder shaft. When the motor rotates, the rotation inside the motor is converted into the forward and backward movement of the screw, which drives the cylinder shaft to move forward and backward. The cylinder is fixed on the cylinder frame, the cylinder frame is fixed on the base, the base and the table are fixed 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, which is connected to one end of a pressure gauge after passing through a first pagoda connector, and the pressure gauge is used to monitor the pressure applied to the fixture module, a second pagoda connector is installed at the other end of the pressure gauge, the second pagoda connector is connected to a second silicone tube, and the second silicone tube is connected to a reducer on the fixture module, and 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 controller generates a programmed drive signal based on the set motor rotation speed and rotation direction, acts on the driver, 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 accurately controls 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: Where f is the frequency of the pulse signal in Hz, n is the number of pulses per revolution, i.e. the number of steps of the stepper motor, and s is the step angle of the stepper motor in degrees. The front seat of the fixture module is fixed on the table, and a front seat hole is set in the center of the front seat. A circular gasket is set 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 set in front of the circular gasket of the rear seat for connecting the second silicone tube.

2. The expansion device for viscoelastic damage and fracture testing of soft materials according to claim 1, characterized in that: The diameter of the soft material to be tested is larger than the diameters of the circular washer and the front seat hole.

3. The expansion device for viscoelastic damage and fracture testing of soft materials according to claim 1, 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.

4. A method for viscoelastic damage and fracture testing of soft materials, implemented based on the expansion device according to any one of claims 1 to 3, comprising: (1) Expansion at different rates: The motor is driven to rotate at different speeds according to the control module. The distance the lead screw advances is obtained according to the number of revolutions of the motor. The lead screw compresses the gas and / or liquid in the cylinder and the first and second silicone tubes, and applies an equal biaxial expansion load to the soft material to be tested in the fixture module, thereby achieving 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 according to the 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 equal biaxial expansion load in the opposite direction to the soft material to be tested in the fixture module. After the soft material expands to a smaller deformation, the motor is controlled to stop rotating, thereby achieving pressurization, 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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