Viscoelasticity parameter detection method and system
By applying a tangential load to a viscoelastic material and recording the response curve, the problem of sample shape and size requirements in the prior art is solved, and high-precision viscoelastic parameter detection on the original sample is achieved.
Patent Information
- Application Number
- CN202511127847.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-12
- Publication Date
- 2025-11-11
AI Technical Summary
Existing methods for testing viscoelastic materials have specific requirements for sample shape and size, making it impossible to perform tests directly on the original sample. Furthermore, they can lead to errors in the test results for thin samples such as rubber, hydrogels, and biological soft tissues.
The sample is pressed in with an indenter and a tangential load, including shear force or shear displacement, is applied. The relationship curve between the tangential response of the sample and time is recorded, and the viscoelastic parameters are determined by fitting the constitutive equation.
This method enables direct detection on the original sample, reduces sensitivity to Poisson's ratio, improves the accuracy and efficiency of viscoelastic parameter detection, and simplifies the operation process.
Smart Images
Figure CN120927441A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of materials mechanics, and in particular to a method and system for detecting viscoelastic parameters. Background Technology
[0002] In the fields of advanced manufacturing and engineering technology, viscoelastic materials, as a special material system that combines the energy dissipation characteristics of viscous fluids with the deformation memory capabilities of elastic solids, have been widely used in many cutting-edge fields. Specifically, in the field of flexible electronic devices, viscoelastic materials can serve as key components, ensuring the stable operation of devices in complex environments thanks to their flexibility and energy dissipation capabilities; in intelligent vibration damping systems, they can effectively absorb and disperse vibration energy, improving the system's vibration damping performance, playing an important role in industries with stringent vibration damping requirements such as aerospace and automotive manufacturing; in the field of biomedical devices, the excellent biocompatibility and unique mechanical properties of viscoelastic materials provide strong support for the research and development of devices such as artificial organs and tissue engineering scaffolds.
[0003] Viscoelastic materials come in many varieties, including common types such as polymer adhesives, hydrogels, rubber composites, and biomimetic materials. It is noteworthy that the dynamic mechanical behavior of viscoelastic materials—that is, their mechanical response under alternating or dynamic loads—plays a decisive role in the performance of engineering structures under dynamic and complex loading conditions. It directly determines the energy buffering efficiency of the engineering structure; efficient energy buffering can significantly reduce external impact loads, thereby reducing the risk of structural damage. Its deformation recovery characteristics are directly related to the functional maintenance ability of the engineering structure under repeated stress; excellent deformation recovery performance ensures the continuous and stable operation of the structure. Furthermore, material properties profoundly affect the long-term service reliability of engineering structures; stable material properties can not only effectively extend the service life of the structure but also significantly reduce the total life cycle cost by reducing maintenance frequency and replacement needs.
[0004] Common methods for viscoelasticity testing include dynamic mechanical testing, uniaxial stress relaxation or creep testing, and normal indentation. Dynamic mechanical testing uses dynamic thermomechanical analysis (DMA) to measure the material's mechanical response by applying periodic loads and adjusting the temperature or loading frequency, obtaining the stored energy and loss modulus, and then deriving the material's viscoelastic parameters. Uniaxial stress relaxation or creep testing applies a uniaxial load to the material and obtains the change curve of the material's relaxation modulus or creep compliance over time, which is then fitted to obtain the material's viscoelastic parameters. Both of these methods have specific requirements for sample shape and size, requiring separate sample preparation and making it impossible to test existing samples. Normal indentation uses an indenter to press into the material and performs stress relaxation or creep testing to infer the material's viscoelastic parameters. Normal indentation can be performed directly on the original sample. However, for thin samples that are close to incompressible materials (such as most rubbers, hydrogels, and biological soft tissues), the mechanical response generated during normal indentation is highly sensitive to the material's Poisson's ratio, which leads to a large error in the inversion results of viscoelastic material parameters. Summary of the Invention
[0005] In view of this, this disclosure proposes a viscoelastic parameter detection scheme.
[0006] According to one aspect of this disclosure, a method for detecting viscoelastic parameters is provided, comprising:
[0007] The sample to be tested is fixed on a substrate, and an indenter is pressed into the sample and held therein; wherein the sample is a viscoelastic material, and the effective working area of the indenter is smaller than the in-plane dimension of the sample; a tangential load is applied to the indenter at a preset rate until a preset loading amount is reached, the tangential load including shear force or shear displacement; the preset loading amount is held for a preset time to obtain the relationship curve of the tangential response of the sample versus time; the relationship curve is converted into parameters in the constitutive equation, and the viscoelastic parameters of the sample are determined according to the parameters in the constitutive equation.
[0008] In one possible implementation, when the tangential load is a shear force, the step of applying a tangential load to the indenter at a preset rate until a preset loading amount is reached, maintaining the preset loading amount for a preset time, and obtaining the relationship curve of the tangential response of the sample versus time includes: applying a shear force to the indenter at a preset rate until the shear force reaches a preset shear force, maintaining the preset shear force for a preset time, and obtaining the relationship curve of the shear displacement of the sample versus time.
[0009] In one possible implementation, when the tangential load is a shear displacement, the step of applying a tangential load to the indenter at a preset rate until a preset loading amount is reached, maintaining the preset loading amount for a preset time, and obtaining the relationship curve of the tangential response versus time of the sample includes: applying a shear displacement to the indenter at a preset rate until the shear displacement reaches a preset shear displacement value, maintaining the preset shear displacement value for a preset time, and obtaining the relationship curve of the shear force versus time of the sample.
[0010] In one possible implementation, the time range in the relationship curve includes: from the start of applying a tangential load to the pressure head to the end of maintaining the preset load for a preset time, or from the arrival of the preset load to the end of maintaining the preset load for a preset time.
[0011] In one possible implementation, the relationship curve is transformed into parameters in the constitutive equation, and the viscoelastic parameters of the sample are determined based on the parameters in the constitutive equation. This includes: selecting a constitutive equation; fitting the relationship curve to the constitutive equation; inverting the parameters in the constitutive equation; and determining the viscoelastic parameters of the sample based on the parameters in the constitutive equation.
[0012] According to another aspect of this disclosure, a viscoelastic parameter detection system is provided, comprising: experimental equipment and a viscoelastic parameter acquisition module, wherein the experimental equipment includes an indenter, wherein:
[0013] The sample to be tested is a viscoelastic material, which is fixed on the base of the experimental device. The experimental device is used to control the indenter to press into and hold the sample, and the effective working area of the indenter is smaller than the in-plane dimension of the sample. The experimental device is used to apply a tangential load to the indenter at a preset rate until a preset loading amount is reached, where the tangential load includes shear force or shear displacement. The preset loading amount is held for a preset time to obtain the relationship curve of the tangential response of the sample versus time. The viscoelastic parameter acquisition module is used to convert the relationship curve into parameters in the constitutive equation, and determine the viscoelastic parameters of the sample based on the parameters in the constitutive equation.
[0014] In one possible implementation, when the tangential load is a shear force, the experimental apparatus is used to apply a shear force to the indenter at a preset rate until the shear force reaches a preset shear force, maintain the preset shear force for a preset time, and obtain the shear displacement versus time curve of the sample.
[0015] In one possible implementation, when the tangential load is a shear displacement, the experimental apparatus is used to apply a shear displacement to the indenter at a preset rate until the shear displacement reaches a preset shear displacement value, maintain the preset shear displacement value for a preset time, and obtain the relationship curve between the shear force and time of the sample.
[0016] In one possible implementation, the time range in the relationship curve includes: from the start of applying a tangential load to the pressure head to the end of maintaining the preset load for a preset time, or from the arrival of the preset load to the end of maintaining the preset load for a preset time.
[0017] In one possible implementation, the viscoelastic parameter acquisition module is configured to: select a constitutive equation; fit the relationship curve to the constitutive equation, invert the parameters in the constitutive equation, and determine the viscoelastic parameters of the sample based on the parameters in the constitutive equation.
[0018] In this embodiment, the sample to be tested is fixed on a substrate, and an indenter is pressed into and held within the sample. The sample is a viscoelastic material, and the effective working area of the indenter is smaller than the in-plane dimension of the sample. A tangential load is applied to the indenter at a preset rate until a preset loading amount is reached; the tangential load includes shear force or shear displacement. The preset loading amount is held for a preset time, resulting in a curve showing the relationship between the tangential response of the sample and time. This curve is then converted into parameters in the constitutive equation, and the viscoelastic parameters of the sample are determined based on these parameters. Therefore, testing can be performed directly on the original sample, avoiding the additional sample preparation step, and significantly reducing the sensitivity to Poisson's ratio, thus improving the accuracy of viscoelastic parameter detection.
[0019] Other features and aspects of this disclosure will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description
[0020] The accompanying drawings, which are included in and form part of this specification, illustrate exemplary embodiments, features, and aspects of this disclosure together with the specification and serve to explain the principles of this disclosure.
[0021] Figure 1 A flowchart illustrating a viscoelastic parameter detection method according to an embodiment of the present disclosure is shown.
[0022] Figure 2 A schematic diagram is shown of a cylindrical indenter pressing into a sample and applying shear displacement according to an embodiment of the present disclosure.
[0023] Figure 3 A schematic diagram showing the relationship between shear force and time for a pressure head according to an embodiment of the present disclosure is provided.
[0024] Figure 4 A schematic diagram of a generalized Maxwell model according to an embodiment of the present disclosure is shown.
[0025] Figure 5 A schematic diagram showing the finite element simulation results of the shear stiffness of a cylindrical indenter pressed into a sample according to an embodiment of the present disclosure.
[0026] Figure 6 A block diagram of a viscoelastic parameter detection system according to an embodiment of the present disclosure is shown. Detailed Implementation
[0027] Various exemplary embodiments, features, and aspects of this disclosure will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.
[0028] As used herein, the terms “comprising,” “including,” “having,” or variations thereof are open-ended and include one or more of the stated features, integrals, elements, steps, components, or functions, but do not exclude the presence or addition of one or more other features, integrals, elements, steps, components, functions, or groups thereof.
[0029] When an element is referred to as “connected,” “coupled,” “responding,” or a variation thereof relative to another element, it may be directly connected, coupled, or responding to another element, or there may be an intermediate element present.
[0030] Although the terms first, second, third, etc., may be used herein to describe various elements / operations, these elements / operations should not be limited by these terms. These terms are only used to distinguish one element / operation from another. Therefore, without departing from the teachings of the inventive concept, a first element / operation in some embodiments may be referred to as a second element / operation in other embodiments.
[0031] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.
[0032] Furthermore, to better illustrate this disclosure, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that this disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art have not been described in detail in order to highlight the main points of this disclosure.
[0033] Figure 1A flowchart illustrating a viscoelastic parameter detection method according to an embodiment of the present disclosure is shown. Figure 1 As shown, the viscoelastic parameter detection method of this disclosure embodiment may include:
[0034] S11. Fix the sample to be tested on the substrate, and press the indenter into the sample and hold it therein; wherein the sample is a viscoelastic material, and the effective working area of the indenter is smaller than the in-plane dimension of the sample;
[0035] In this embodiment of the disclosure, the sample to be tested is a viscoelastic material. Viscoelastic materials are a class of substances that combine the properties of elastic solids and viscous fluids. When subjected to force, they can undergo recoverable deformation due to elasticity like a spring, and energy can be dissipated due to intermolecular friction, etc. Like a viscous fluid, the strain develops over time and cannot be completely restored instantaneously after unloading.
[0036] Viscoelastic parameters are physical quantities used to describe the properties of viscoelastic materials, reflecting the deformation characteristics of the material under different time and stress / strain conditions. Specifically, viscoelastic parameters include storage modulus, loss modulus, and loss factor.
[0037] The substrate can be a carrier used to support and fix the sample, possessing stable mechanical properties. Substrates include metal substrates, ceramic substrates, polymer substrates, and biomaterial substrates. In one possible implementation, the sample can be fixed on the substrate of the experimental device. The experimental device can be a device that applies a controllable load to the indenter and simultaneously records the mechanical response in directions perpendicular (normal) and parallel (tangential) to the surface of the sample to be tested, such as a universal testing machine or an atomic force microscope. This disclosure does not limit this aspect.
[0038] An indenter is a component or tool used to apply pressure or load. Its core function is to concentrate and transfer external force to the sample to be tested in order to achieve a specific physical effect or measurement purpose. In the embodiments of this disclosure, the dimensions of the indenter are known. The indenter can be a hard indenter, which can be a tool or component made of a material with high hardness and wear resistance. When the hard indenter is pressed into the sample to be tested, the shape of the indenter remains unchanged, such as metal, ceramic, diamond, etc.
[0039] The shape of the indenter can be selected according to actual needs. For example, it can be selected according to the type of viscoelastic material. A spherical indenter can be selected for rubber or hydrogel, and a cylindrical indenter can be selected for biological soft tissue or thin-layer gel, etc. This disclosure does not limit this.
[0040] In one possible implementation, the indenter can be mounted on experimental equipment. A preset normal pressure is applied to the indenter, pressing it into the sample and maintaining this pressed-in state for a period of time to ensure sufficient contact between the sample and the indenter. The specific time can be determined based on the material dimensions and properties of the indenter and sample, ranging from milliseconds to seconds; this disclosure does not limit this time. This method ensures that the interaction between the sample and the indenter reaches a stable state. In subsequent steps, when a tangential load is applied, the sample and indenter can move together through adhesion or friction, thereby improving the accuracy and reliability of the measurement results.
[0041] When the indenter is pressed into the sample to be tested, the pressing position can be any non-edge area on the sample surface. The edge area is a specific area of the sample boundary and its surroundings that may significantly interfere with the test results or cause sample failure due to factors such as geometric boundary effects and abnormal stress distribution. The edge area can be a region extending into the sample from the sample geometric boundary to the characteristic size (such as sample thickness, diameter, or side length). The specific range can be determined according to the sample shape and size, and this disclosure does not limit this.
[0042] The effective working area of the indenter can be the area of the region where the indenter actually contacts the sample and can transmit pressure, while the in-plane dimension of the sample can be the area of the region on the sample that can actually withstand the pressure applied by the indenter. In this embodiment, the effective working area of the indenter is smaller than the in-plane dimension of the sample. This ensures that the pressure applied by the indenter can be stably borne by the sample, improving the reliability of the detection process and reducing potential damage to the sample.
[0043] S12. Apply a tangential load to the pressure head at a preset rate until a preset loading amount is reached, wherein the tangential load includes shear force or shear displacement;
[0044] After a preset pressure is applied to the pressure head and the pressing state is maintained for a preset time, a tangential load can be applied to the pressure head at a preset rate until a preset loading amount is reached. The tangential load can be a shear force or a shear displacement, and the corresponding preset loading amount can be a preset shear force or a preset shear displacement value.
[0045] In one possible implementation, a tangential load can be applied to the indenter at a preset rate using experimental equipment until the preset loading amount is reached. This method allows for precise control of the loading process, thereby obtaining more accurate and reliable experimental data.
[0046] For example, when the tangential load is a shear force, a shear force can be applied to the pressure head at a preset rate until the shear force reaches the preset shear force, indicating that the shear force has reached the preset loading amount. When the tangential load is a shear displacement, a shear displacement can be applied to the pressure head at a preset rate until the shear displacement reaches the preset shear displacement value, indicating that the shear displacement has reached the preset loading amount.
[0047] For example, Figure 2 A schematic diagram is shown illustrating how a cylindrical indenter, according to an embodiment of the present disclosure, presses into a sample and applies shear displacement. See also... Figure 2 , Figure 2 The indenter is a cylindrical indenter, which is pressed into the sample to be tested. The sample is fixed on the substrate, where h is the thickness of the sample. It can be seen that... Figure 2 The sample to be tested is a thin sample, and the arrow indicates the direction of the shear displacement applied to the indenter.
[0048] S13. Maintain the preset loading amount for a preset time to obtain the relationship curve between the tangential response of the sample and time;
[0049] After applying a tangential load to the preset loading amount, this force or displacement can be maintained for a preset time, while recording the change of the mechanical response of the sample over time during this process, and finally forming a relationship curve to observe the dynamic mechanical behavior of the sample under stable load.
[0050] This relationship curve reflects the change of the sample's response to applied force or displacement over time, and can reflect the viscoelasticity of the sample, providing experimental data support for the subsequent determination of viscoelastic parameters.
[0051] S14. Convert the relationship curve into parameters in the constitutive equation, and determine the viscoelastic parameters of the sample based on the parameters in the constitutive equation.
[0052] After obtaining the relationship curve through experimental equipment, the data of the relationship curve measured by the experimental equipment can be combined with the theoretical model. Through parameter fitting, specific parameters that can describe the viscoelastic behavior of the material can be obtained.
[0053] The process involves fitting experimentally measured data with theoretical models to obtain parameter data. Experimental data consists of applying a tangential load using experimental equipment and recording the change in the mechanical response of the sample over time to obtain a relationship curve. The theoretical model is the constitutive equation, which describes the behavior of viscoelastic materials. This equation contains a series of unknown parameters related to the viscoelastic properties of the material.
[0054] When performing parameter fitting, the experimental relationship curve is fitted to the constitutive equation. The parameters in the constitutive equation are adjusted by an optimization algorithm so that the prediction result of the constitutive equation is as consistent as possible with the experimental curve, thus completing the fitting.
[0055] Once the fitting is complete, the parameters in the constitutive equation are determined, and these parameters can reflect the viscoelastic properties of the sample.
[0056] In this embodiment, the sample to be tested is fixed on a substrate, and an indenter is pressed into the sample and held in place. The effective working area of the indenter is smaller than the in-plane dimension of the sample, ensuring that the pressure applied by the indenter can be stably borne by the sample and reducing potential damage to the sample. A tangential load is applied to the indenter at a preset rate until a preset loading amount is reached. This process allows for precise control of the loading conditions and obtains accurate experimental data. The preset loading amount is maintained for a period of time, and the relationship curve between the tangential response and time of the sample is recorded. This not only provides information on the dynamic mechanical behavior of the sample under stable load but also provides crucial data for subsequent analysis of its viscoelastic properties. Finally, the relationship curve is converted into parameters in the structural equation, and the viscoelastic parameters of the sample are determined, achieving a precise quantitative description from experimental data to material properties. This process significantly improves the accuracy of viscoelastic parameter detection and reduces the sensitivity to Poisson's ratio. Simultaneously, it eliminates the need for special sample preparation, enabling in-situ detection, simplifying the operation process, reducing costs and time investment, and possessing wide applicability. It provides strong support for the design, performance prediction, and engineering applications of viscoelastic materials.
[0057] In one possible implementation, when the tangential load is a shear force, the step of applying a tangential load to the indenter at a preset rate until a preset loading amount is reached, maintaining the preset loading amount for a preset time, and obtaining the relationship curve of the tangential response of the sample versus time includes: applying a shear force to the indenter at a preset rate until the shear force reaches a preset shear force, maintaining the preset shear force for a preset time, and obtaining the relationship curve of the shear displacement of the sample versus time.
[0058] In one possible implementation, when the tangential load is a shear displacement, the step of applying a tangential load to the indenter at a preset rate until a preset loading amount is reached, maintaining the preset loading amount for a preset time, and obtaining the relationship curve of the tangential response versus time of the sample includes: applying a shear displacement to the indenter at a preset rate until the shear displacement reaches a preset shear displacement value, maintaining the preset shear displacement value for a preset time, and obtaining the relationship curve of the shear force versus time of the sample.
[0059] It should be noted that the preset shear force, preset shear displacement, and preset time can be any value. However, in practical applications, the resolution of the actual experimental equipment, the pressure head, and the slippage of the sample need to be considered. This refers to the phenomenon of relative displacement on the surface or inside of the material due to external loads or changes in the internal structure.
[0060] Therefore, in practical applications, experimental equipment can be used to observe whether preset shear force, preset shear displacement, and preset time can induce observable changes in the mechanical behavior of the sample. These changes can be reflected by relationship curves; for example, the change in the relationship curve can be similar to the trend of previously experienced stress-time or strain-time relationship curves. In other words, the magnitudes of the preset shear force, preset shear displacement, and preset time can be the minimum threshold required to induce observable changes in the mechanical behavior of the sample.
[0061] In this embodiment, when the tangential load is a shear force, a shear force is applied to the indenter at a preset rate until the preset shear force is reached, and this preset shear force is maintained for a preset time, thus obtaining the shear displacement versus time curve of the sample. This achieves precise measurement of the sample's displacement response during the stress process. By recording the change in shear displacement over time, the deformation behavior of the sample under shear force can be observed in detail. This measurement method directly reflects the mechanical properties of the sample under actual stress conditions, providing an accurate data basis for subsequent constitutive equation fitting and viscoelastic parameter determination. Simultaneously, by controlling the shear force loading rate and holding time, the mechanical response of the sample at different time scales can be effectively captured, helping to improve the accuracy and reliability of parameter determination, thereby more accurately describing and predicting the performance of viscoelastic materials in practical applications.
[0062] Furthermore, when the tangential load is shear displacement, by applying shear displacement to the indenter at a preset rate until a preset shear displacement value is reached, and holding this preset shear displacement value for a preset time, the relationship curve of shear force versus time of the sample is obtained. This enables precise measurement of the mechanical response of the sample under controlled deformation conditions. By recording the change of shear force over time, the stress relaxation behavior of the sample under shear displacement can be observed in detail. This measurement method directly reflects the mechanical properties of the sample under actual deformation conditions, providing an accurate data foundation for subsequent constitutive equation fitting and viscoelastic parameter determination. Simultaneously, by controlling the loading rate and holding time of the shear displacement, the mechanical response of the sample at different time scales can be effectively captured, helping to improve the accuracy and reliability of parameter determination, thereby more accurately describing and predicting the performance of viscoelastic materials in practical applications.
[0063] In one possible implementation, the time range in the relationship curve includes: from the start of applying a tangential load to the pressure head to the end of maintaining the preset load for a preset time, or from the arrival of the preset load to the end of maintaining the preset load for a preset time.
[0064] When a tangential load is applied to the indenter at a preset rate, if the tangential load is a shear force, the indenter will move together with the sample; if the tangential load is a shear displacement, the indenter will be subjected to the reaction force of the sample. The indenter can be mounted on experimental equipment, which may have a sensor module to monitor and record the dynamic changes of the load (force or displacement) in real time.
[0065] Therefore, the experimental equipment can record the displacement of the indenter and the sample moving together, or the reaction force of the sample on the indenter, i.e., the tangential response of the sample, from the initial application of the tangential load to the end of the preset time, after maintaining the preset load for a preset time, thus obtaining the relationship curve between the tangential response of the sample from the initial application of the tangential load to the end of the preset time and time. In this way, the dynamic response characteristics of the sample under tangential load can be measured more accurately.
[0066] The experimental equipment can also start recording the displacement of the indenter and the sample or the reaction force of the sample on the indenter when the tangential load reaches the preset loading amount, i.e. the tangential response of the sample. After the preset loading amount and preset time are completed, the relationship curve between the tangential response of the sample and time can also be obtained. In this way, the dynamic response characteristics of the sample under tangential action can be measured more conveniently.
[0067] For example, Figure 3 A schematic diagram showing the relationship between shear force and time for a pressure head according to an embodiment of the present disclosure is provided. (See also...) Figure 3 , Figure 3 The x-axis represents time t (s), and the y-axis represents the shear force F exerted on the indenter by the sample. x (N), where the horizontal axis time t starts from when the shear displacement is applied to the pressure head and ends after 8s. The first 2s is the change of shear force on the pressure head when the tangential displacement is applied to the pressure head until the preset shear displacement is reached. The 2nd to 10ths is the change of shear force on the pressure head after the preset time (8s) is maintained.
[0068] In this embodiment, the time range of the relationship curve covers the entire time from the initial application of the tangential load to the end of maintaining the preset loading amount, or the time period from reaching the preset loading amount to the end of maintaining the preset loading amount. This ensures a complete record of the sample's mechanical response, capturing both the initial transient response and the subsequent steady-state response in detail. This comprehensive data acquisition method allows for more accurate analysis of the properties of viscoelastic materials, thereby improving the reliability of experimental results. Furthermore, this complete time-range data acquisition provides a more accurate basis for converting the relationship curve into parameters in the structural equation, thus enabling a more precise determination of the sample's viscoelastic parameters.
[0069] In one possible implementation, the relationship curve is transformed into parameters in the constitutive equation, and the viscoelastic parameters of the sample are determined based on the parameters in the constitutive equation. This includes: selecting a constitutive equation; fitting the relationship curve to the constitutive equation; inverting the parameters in the constitutive equation; and determining the viscoelastic parameters of the sample based on the parameters in the constitutive equation.
[0070] After obtaining the relationship curve, to further determine the viscoelastic parameters of the sample, it is necessary to fit the curve and then invert it to obtain the viscoelastic parameters of the sample. Specifically, firstly, it is necessary to select a constitutive equation. The constitutive equation can be a generalized Maxwell model, a Kelvin-Voigt model, etc., or it can be selected according to the characteristics of the curve. For example, if the curve characteristics show exponential decay, a generalized Maxwell model can be selected; if the curve characteristics show stepwise relaxation, a Kelvin-Voigt model can be selected. This disclosure does not limit this.
[0071] For example, Figure 4 The diagram illustrates a generalized Maxwell model according to an embodiment of the present disclosure. The generalized Maxwell model is a model used to describe the viscoelastic behavior of materials. (See also...) Figure 4 ,in:
[0072] E ∞ The long-term elastic modulus of a material, also known as the residual modulus or the modulus at infinite relaxation time, reflects the stiffness characteristic of a material that can elastically recover after undergoing long-term or instantaneous deformation. When a material is subjected to stress and time approaches infinity, the elastic modulus exhibited by the material is E. ∞ .
[0073] E i (i = 1, 2, ..., n) represents the elastic modulus of the spring in the i-th Maxwell element (composed of a spring and a damper connected in parallel). Each E iCorresponding to the elastic properties of materials within different relaxation time ranges, multiple such units connected in parallel can simulate the complex elastic behavior of materials at different time scales.
[0074] η i (i = 1, 2, ..., n) represents the viscosity coefficient of the damper in the i-th Maxwell element. The viscosity coefficient measures the viscous property of a material, that is, how easily a material deforms under stress and its ability to dissipate energy. A larger viscosity coefficient means that the material is more viscous, deforms relatively slowly under stress, and loses more energy as heat.
[0075] These symbols together constitute the generalized Maxwell model, which is used to describe the mechanical response behavior of materials at different time scales, including elastic recovery, viscous flow, and the coupling effect between the two. It can be used to fit and predict experimental curves of stress relaxation, creep, etc. of materials.
[0076] After selecting the constitutive equation, the relationship curve can be fitted to the constitutive equation to obtain the parameters related to the viscoelasticity of the sample. Specifically, the mapping relationship between the response of the viscoelastic material and the parameters can be established through finite element simulation, and the constitutive parameters of the viscoelastic material can be efficiently inverted by combining fitting techniques. Constitutive parameters are the parameters in the constitutive equation (such as elastic modulus, relaxation time, etc.).
[0077] For example, assuming the indenter is a cylindrical indenter, and assuming that the previous steps yielded a curve showing the relationship between the shear force and time of the sample (e.g. Figure 3 The relationship curve shown is assumed to be selected from the constitutive equation. Figure 4 The generalized Maxwell model shown can be used to obtain the shear force F. x The formula (1) for the change with time t is:
[0078]
[0079] Where h is the sample thickness, ν is Poisson's ratio, a is the radius of the cylindrical indenter, e is the natural constant, V is the shear rate (i.e., the preset rate), t0 is the shear time (i.e., the time from the application of tangential displacement to the indenter until the preset shear displacement is reached), and E ∞ E i (i = 1, 2, ..., n) and η i (i = 1, 2, ..., n) As mentioned above, H(x) is the Heaviside step function, τ i (i = 1, 2, ..., n) represents the relaxation time in the i-th Maxwell element, τ i =η i / E i .
[0080] Therefore, after obtaining the curve of the relationship between shear force and time of the sample, the parameters in the constitutive equation can be obtained by fitting the curve of the relationship between shear force or shear displacement and time (such as formula (1)). Specifically, this can be achieved by a viscoelastic parameter acquisition module in a computer. This module can be a computer program written by a programming tool. Fitting is performed through this module. The embodiments disclosed herein will not be elaborated here.
[0081] After fitting the parameters in the constitutive equation, these parameters can be converted into specific viscoelastic parameters of the sample (such as storage modulus, loss modulus, and loss factor). Similarly, this process can also be implemented by a viscoelastic parameter acquisition module in a computer, which will not be elaborated here in the embodiments of this disclosure.
[0082] In this embodiment, the viscoelastic parameters of the sample are determined by converting the relationship curve into parameters in the constitutive equation. Then, the experimentally obtained relationship curve is fitted to the constitutive equation, and an optimization algorithm is used to adjust the unknown parameters in the equation, making the predicted results as consistent as possible with the experimental data. This allows for the inversion of key parameters in the constitutive equation, and the specific viscoelastic parameters of the sample are then determined based on these parameters. This achieves a precise quantitative description of material properties from experimental data, improving the accuracy and reliability of parameter determination. Simultaneously, fitting and inversion effectively filter out the influence of experimental noise and errors, further enhancing parameter accuracy. Furthermore, this method provides a general and systematic approach for determining the parameters of different viscoelastic materials, helping to better predict and utilize the mechanical properties of materials in engineering applications, and providing strong support for material design, optimization, and selection.
[0083] In this embodiment, the sample to be tested is fixed on a substrate, and an indenter is pressed into and held within the sample. The sample is a viscoelastic material, and the effective working area of the indenter is smaller than the in-plane dimension of the sample. A tangential load is applied to the indenter at a preset rate until a preset loading amount is reached; the tangential load includes shear force or shear displacement. The preset loading amount is held for a preset time, resulting in a curve showing the relationship between the tangential response of the sample and time. This curve is then converted into parameters in the constitutive equation, and the viscoelastic parameters of the sample are determined based on these parameters. This method not only allows for direct testing on the original sample, avoiding the additional sample preparation step, but also significantly reduces the sensitivity to Poisson's ratio and improves the accuracy of viscoelastic parameter detection.
[0084] Poisson's ratio describes the relationship between the lateral and longitudinal deformation of a material under stress. Viscoelastic materials with a Poisson's ratio close to 0.5 are called "incompressible materials," and their volume remains essentially unchanged under stress. For traditional elastic and linear elastic materials, the range of Poisson's ratio is generally [-1, 0.5], while for viscoelastic materials it is generally [0, 0.5]. Therefore, the value of ν in expression (1) can be [0, 0.5].
[0085] In existing normal indentation methods, the deformation mode of thin samples is strongly dependent on Poisson's ratio, and in instrumented indentation data analysis, Poisson's ratio errors are amplified in the final viscoelastic parameter detection results. Therefore, for thin samples of incompressible materials, normal indentation is highly sensitive to Poisson's ratio.
[0086] In this embodiment, a shear-indentation method is used to apply a tangential load to the indenter. The tangential load reduces the sensitivity of the data analysis results to Poisson's ratio, thereby improving the accuracy of viscoelastic parameter detection.
[0087] For example, Figure 5 The diagram shows data from a finite element simulation of the shear stiffness of a cylindrical indenter pressed into a shear sample according to an embodiment of the present disclosure.
[0088] See Figure 5 In this context, K on the ordinate represents the effective stiffness, which can be obtained from the shear force / shear displacement experienced by the indenter. K0 represents the stiffness of the viscoelastic material assuming infinite thickness. K / K0 is a correction factor for finite thickness. On the abscissa, a represents the indenter radius, and h represents the sample thickness. Figure 5 In the figure, the indenter radius is constant. Therefore, the horizontal axis from left to right represents the sample thickness from thick to thin (i.e., thick substrate and thin substrate in the figure, which correspond to thick sample and thin sample here). The three curves represent samples with different Poisson ratios. FEM is the correction coefficient at the node of the horizontal axis, and Fit is the continuous curve obtained by fitting FEM.
[0089] from Figure 5 As can be seen, even when the sample is very thin (i.e., the abscissa is very large), different Poisson ratios show low sensitivity to changes in the correction coefficient, and do not cause significant fluctuations (large increases or decreases) in the correction coefficient.
[0090] In this embodiment, an indentation-based experimental method is used instead of a uniaxial experiment. This allows viscoelasticity testing to be performed directly on the original sample, avoiding the need for additional sample preparation steps, thereby improving testing efficiency, simplifying the process, and significantly reducing testing costs.
[0091] In this embodiment of the disclosure, indentation shearing is used instead of normal indentation. Shearing can be performed using relaxation or creep methods. For thin samples that are nearly incompressible, shear loading reduces the sensitivity to Poisson's ratio compared to normal loading, thereby improving the accuracy of viscoelastic parameter testing.
[0092] Figure 6 A block diagram of a viscoelastic parameter detection system according to an embodiment of the present disclosure is shown. Figure 6 As shown, the system includes: experimental equipment 22 and a viscoelastic parameter acquisition module 23. The experimental equipment includes an indenter 21.
[0093] The sample to be tested is a viscoelastic material, and the sample is fixed on the substrate of the experimental device 22.
[0094] The experimental device 22 is used to control the indenter to press into the sample and hold it therein, wherein the effective working area of the indenter is smaller than the in-plane dimension of the sample;
[0095] The experimental device 22 is used to apply a tangential load to the indenter at a preset rate until a preset loading amount is reached, wherein the tangential load includes shear force or shear displacement; and to maintain the preset loading amount for a preset time to obtain the relationship curve between the tangential response of the sample and time.
[0096] The viscoelastic parameter acquisition module 23 is used to convert the relationship curve into parameters in the constitutive equation, and determine the viscoelastic parameters of the sample based on the parameters in the constitutive equation.
[0097] The experimental equipment is described above.
[0098] In one possible implementation, when the tangential load is a shear force, the experimental device 22 is used to apply a shear force to the indenter at a preset rate until the shear force reaches a preset shear force, maintain the preset shear force for a preset time, and obtain the relationship curve of the shear displacement of the sample versus time.
[0099] In one possible implementation, when the tangential load is a shear displacement, the experimental device 22 is used to apply a shear displacement to the indenter at a preset rate until the shear displacement reaches a preset shear displacement value, maintain the preset shear displacement value for a preset time, and obtain the relationship curve between the shear force and time of the sample.
[0100] In one possible implementation, the time range in the relationship curve includes: from the start of applying a tangential load to the pressure head to the end of maintaining the preset load for a preset time, or from the arrival of the preset load to the end of maintaining the preset load for a preset time.
[0101] In one possible implementation, the viscoelastic parameter acquisition module 23 is used to select a constitutive equation; fit the relationship curve to the constitutive equation, invert the parameters in the constitutive equation, and determine the viscoelastic parameters of the sample based on the parameters in the constitutive equation.
[0102] In some embodiments, the system provided in this disclosure may have functions or include modules that can be used to execute the methods described in the above method embodiments. The specific implementation of these methods can be referred to the description in the above method embodiments, and for the sake of brevity, they will not be repeated here.
[0103] According to one aspect of this disclosure, an apparatus is provided that includes the aforementioned viscoelastic parameter detection system. The apparatus may include electronic equipment, for example, the electronic equipment may be provided as a server or terminal device.
[0104] The above description is merely an exemplary embodiment of the present invention and is not intended to limit the scope of protection of the present invention, which is determined by the appended claims.
[0105] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.
[0106] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0107] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those shown in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.
[0108] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.
Claims
1. A method for detecting viscoelastic parameters, characterized in that, include: The sample to be tested is fixed on a substrate, and an indenter is pressed into the sample and held therein; wherein the sample is a viscoelastic material, and the effective working area of the indenter is smaller than the in-plane dimension of the sample; A tangential load is applied to the pressure head at a preset rate until a preset loading amount is reached, wherein the tangential load includes shear force or shear displacement; By maintaining the preset loading amount for a preset time, the relationship curve between the tangential response and time of the sample is obtained; The relationship curve is converted into parameters in the constitutive equation, and the viscoelastic parameters of the sample are determined based on the parameters in the constitutive equation.
2. The method according to claim 1, characterized in that, When the tangential load is a shear force, the process of applying the tangential load to the indenter at a preset rate until a preset loading amount is reached, maintaining the preset loading amount for a preset time, and obtaining the relationship curve between the tangential response and time of the sample includes: A shear force is applied to the indenter at a preset rate until the shear force reaches the preset shear force, and the preset shear force is maintained for a preset time to obtain the shear displacement versus time curve of the sample.
3. The method according to claim 1, characterized in that, When the tangential load is a shear displacement, the tangential load is applied to the indenter at a preset rate until a preset loading amount is reached, and the preset loading amount is maintained for a preset time to obtain the relationship curve of the tangential response of the sample versus time, including: A shear displacement is applied to the indenter at a preset rate until the shear displacement reaches a preset shear displacement value. The preset shear displacement value is maintained for a preset time to obtain the relationship curve between the shear force and time of the sample.
4. The method according to any one of claims 1-3, characterized in that, In the relationship curve, the range of time variation includes: from the start of applying a tangential load to the pressure head to the end of maintaining the preset load amount for a preset time, or from the time the preset load amount is reached to the end of maintaining the preset load amount for a preset time.
5. The method according to claim 1, characterized in that, The relationship curve is converted into parameters in the constitutive equation, and the viscoelastic parameters of the sample are determined based on the parameters in the constitutive equation, including: Choose the constitutive equation; The relationship curve is fitted to the constitutive equation, and the parameters in the constitutive equation are obtained by inversion. Based on the parameters in the constitutive equation, the viscoelastic parameters of the sample are determined.
6. A viscoelastic parameter detection system, characterized in that, include: Experimental equipment and a viscoelastic parameter acquisition module, wherein the experimental equipment includes an indenter, wherein: The sample to be tested is a viscoelastic material, and the sample is fixed on the substrate of the experimental equipment; The experimental apparatus is used to control the indenter to press into and hold the sample, wherein the effective working area of the indenter is smaller than the in-plane dimension of the sample; The experimental apparatus is used to apply a tangential load to the indenter at a preset rate until a preset loading amount is reached, wherein the tangential load includes shear force or shear displacement; and to maintain the preset loading amount for a preset time to obtain the relationship curve between the tangential response of the sample and time. The viscoelastic parameter acquisition module is used to convert the relationship curve into parameters in the constitutive equation, and determine the viscoelastic parameters of the sample based on the parameters in the constitutive equation.
7. The system according to claim 6, characterized in that, When the tangential load is a shear force The experimental apparatus is used to apply shear force to the indenter at a preset rate until the shear force reaches the preset shear force, maintain the preset shear force for a preset time, and obtain the relationship curve of shear displacement versus time for the sample.
8. The system according to claim 6, characterized in that, When the tangential load is a shear displacement The experimental apparatus is used to apply shear displacement to the indenter at a preset rate until the shear displacement reaches a preset shear displacement value, maintain the preset shear displacement value for a preset time, and obtain the relationship curve between the shear force and time of the sample.
9. The system according to any one of claims 6-8, characterized in that, In the relationship curve, the range of time variation includes: from the start of applying a tangential load to the pressure head to the end of maintaining the preset load amount for a preset time, or from the time the preset load amount is reached to the end of maintaining the preset load amount for a preset time.
10. The system according to claim 6, characterized in that, The viscoelastic parameter acquisition module is used to select a constitutive equation; fit the relationship curve to the constitutive equation, invert the parameters in the constitutive equation, and determine the viscoelastic parameters of the sample based on the parameters in the constitutive equation.