Separation method and device for material deformation, electronic equipment and storage medium
By collecting the stress and strain data of the polyimide film under different loading conditions, the linear elasticity, viscoelasticity and creep characteristics are determined, which solves the problem of material deformation separation, and improves the accuracy of experiments and the reliability of product design.
Patent Information
- Application Number
- CN202411536929.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-31
- Publication Date
- 2025-02-25
AI Technical Summary
The prior art is difficult to accurately separate and quantify the viscoelastic deformation and creep deformation caused by the polyimide film layer during repeated bending, resulting in uncertainty in crease experiments.
By collecting stress and strain data of the target material under uniaxial tensile, constant strain and constant stress, the linear elastic modulus, viscoelastic modulus and creep characteristics of the material are determined respectively, thereby achieving accurate separation of deformation.
Accurate separation of the deformation of the polyimide film layer is achieved, improving the accuracy of material performance optimization and product design, and reducing the uncertainty of crease experiments.
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Abstract
Description
Technical Field
[0001] The present application relates to the field of material properties, and more specifically, to a material deformation separation method, device, electronic device and storage medium. Background Art
[0002] Colorless Polyimide (CPI) film is a high-performance material that is favored for its excellent transparency, weather resistance, mechanical strength and chemical stability, and is widely used in folding screens. Repeated bending will cause CPI to produce complex mechanical behaviors, the most notable of which is the coexistence of its viscoelastic deformation and creep deformation, which ultimately causes creases on the folding screen. Viscoelastic deformation refers to the instant recoverable elasticity and the viscosity that slowly recovers over time produced by the screen under repeated opening and closing. Creep deformation is a more persistent and irreversible deformation mode that usually occurs when the screen is closed for a long time.
[0003] When calibrating creep model parameters through experimental data, the interference of viscoelastic components can easily lead to larger calibrated creep parameters, which brings uncertainty to the optimization of material properties and product design. Therefore, a major challenge faced in the crease experiment of CPI film layers is how to accurately separate and quantify viscoelastic deformation and creep deformation. Summary of the invention
[0004] The purpose of the embodiments of the present application is to provide a material deformation separation method, device, electronic device and storage medium, so as to separate and quantify elastic deformation and creep from material deformation.
[0005] In a first aspect, an embodiment of the present application provides a material deformation separation method, comprising: collecting first stress data and first strain data when a target material is subjected to uniaxial stretching, and determining a first elastic modulus of the target material based on the first stress data and the first strain data, wherein the first elastic modulus is a characteristic parameter in a linear elastic constitutive equation corresponding to the target material; collecting second stress data at different times when a constant strain is applied to the target material, and determining a second elastic modulus and a first viscosity coefficient of the target material based on the second stress data, wherein the second elastic modulus and the first viscosity coefficient are characteristic parameters in a viscoelastic constitutive equation corresponding to the target material; collecting second strain data at different times when a constant stress is applied to the target material, and determining a second viscosity coefficient and a third viscosity coefficient of the target material based on the second strain data, wherein the second viscosity coefficient and the third viscosity coefficient are characteristic parameters in a creep constitutive equation corresponding to the target material.
[0006] In the above scheme, the characteristic parameters of the linear elastic constitutive equation can be determined by uniaxial stretching the target material, the characteristic parameters of the viscoelastic constitutive equation can be determined by applying a constant strain to the target material, and the characteristic parameters of the creep constitutive equation can be determined by applying a constant stress to the target material. Among them, since the linear elastic constitutive equation, the viscoelastic constitutive equation, and the creep constitutive equation can be independently used to characterize and quantify the linear elastic deformation, viscoelastic deformation, and creep deformation of the target material, after respectively determining the corresponding constitutive equations, the precise separation between the linear elastic deformation, viscoelastic deformation, and creep deformation of the target material is achieved.
[0007] As an optional method, the first elastic modulus of the target material is determined according to the first stress data and the first strain data, including: determining a first relationship curve between stress and strain of the target material within a linear elastic range according to the first stress data and the first strain data; and determining the slope of the first relationship curve as the first elastic modulus. In the above scheme, the target material is subjected to uniaxial stretching within the linear elastic range, and the first stress data and the first strain data collected follow Hooke's law. Therefore, the first elastic modulus can be determined by the slope of the first relationship curve, so that the linear elastic deformation can be separated from the deformation of the target material.
[0008] As an optional manner, determining the second elastic modulus and the first viscosity coefficient of the target material according to the second stress data includes: calculating the linear elastic recoverable stress of the target material according to the first elastic modulus, the constant strain and the linear elastic constitutive equation; determining a second relationship curve between the second stress data and time of the target material under the constant strain according to the second stress data, and determining the total stress reduction in the process of applying the constant strain to the target material; calculating the difference between the total stress reduction and the linear elastic recoverable stress as the viscoelastic recoverable stress of the target material; and fitting the first viscosity coefficient and the second elastic modulus according to the viscoelastic recoverable stress, the second relationship curve and the viscoelastic constitutive equation.
[0009] In the above scheme, since linear elastic and viscoelastic deformations are recoverable, and creep deformation is irrecoverable, the stress required when applying constant strain to the target material for a long time will gradually decrease until it stabilizes. Among them, since the gradual stabilization of stress is a creep phenomenon, the total stress reduction can be regarded as the reduction of linear elastic recoverable stress and viscoelastic recoverable stress. Combined with the determined linear elastic constitutive equation, the linear elastic deformation and viscoelastic deformation can be separated from the total stress reduction, so that the characteristic parameters of the viscoelastic constitutive equation can be determined, and the viscoelastic deformation can be separated from the deformation of the target material.
[0010] As an optional manner, determining the second viscosity coefficient and the third viscosity coefficient of the target material according to the second strain data includes: calculating the linear elastic recoverable strain of the target material based on the first elastic modulus, the constant stress and the linear elastic constitutive equation based on stress consistency; calculating the viscoelastic recoverable strain of the target material according to the first viscosity coefficient, the second elastic modulus, the constant stress and the viscoelastic constitutive equation; determining a third relationship curve between the second strain data and time of the target material under the constant stress according to the second strain data, and determining the total strain increase in the process of applying the constant stress to the target material; calculating the difference between the total strain increase and the elastic strain as the creep irrecoverable strain of the target material, wherein the elastic strain is equal to the sum of the linear elastic recoverable strain and the viscoelastic recoverable strain; fitting the second viscosity coefficient and the third viscosity coefficient according to the creep irrecoverable strain, the third relationship curve and the creep constitutive equation.
[0011] In the above scheme, after a constant stress is applied to the target material for a long time until the strain tends to stabilize, the total strain increase is equal to the superposition of the partial strains caused by linear elasticity, viscoelasticity, and creep, and the stress borne by each partial deformation is the same. Combined with the already determined linear elastic constitutive equation and viscoelastic constitutive equation, the linear elastic deformation, viscoelastic deformation, and creep deformation can be separated from the total strain increase, so that the characteristic parameters of the creep constitutive equation can be determined, thereby realizing the separation of creep deformation from the deformation of the target material.
[0012] As an optional method, the linear elastic constitutive equation, the viscoelastic constitutive equation, and the creep constitutive equation are used to characterize the viscoelastic-creep unified model of the target material, wherein the viscoelastic-creep unified model includes a first spring for characterizing linear elasticity, a first viscoelastic pot and a second spring for characterizing viscoelasticity, and a second viscoelastic pot for characterizing creep. In the above scheme, the viscoelastic-creep unified model divides the mechanical behavior of the target material deformation into three parts, namely, the linear elastic part, the viscoelastic part, and the creep part, and the three parts can be described by the physical model of the spring and the viscoelastic pot, so that the linear elastic constitutive equation, the viscoelastic constitutive equation, and the creep constitutive equation have a projectable model in the specific deformation behavior of the target material and give it a vivid and intuitive meaning. Therefore, the viscoelastic-creep unified model provides a more accurate and practical constitutive equation for the deformation behavior of the target material, improves the calculation efficiency and accuracy, provides a reliable basis for the evaluation of the performance of the target material, and provides strong support for the design, modification and application of the target material.
[0013] As an optional method, one end of the first viscosity pot connected in parallel with the second spring is connected in series with the first spring, and the other end is connected in series with the second viscosity pot. In the above scheme, the viscoelasticity-creep unified model is formed by the first spring, the first viscosity pot and the second spring connected in parallel, and the second viscosity pot connected in series, so that the viscoelasticity-creep unified model can simultaneously describe the linear elasticity, viscoelasticity and creep characteristics of the target material.
[0014] As an optional method, the target material is a CPI film layer. In the above scheme, the CPI film layer is widely used in folding screens as a high-performance material. The deformation separation of the CPI film layer according to the above method is beneficial to the performance optimization and product design of related products.
[0015] In a second aspect, the present application provides a material deformation separation device, comprising: a first determination module, used to collect first stress data and first strain data when a target material is subjected to uniaxial stretching, and determine the first elastic modulus of the target material based on the first stress data and the first strain data, wherein the first elastic modulus is a characteristic parameter in a linear elastic constitutive equation corresponding to the target material; a second determination module, used to collect second stress data at different times when a constant strain is applied to the target material, and determine the second elastic modulus and first viscosity coefficient of the target material based on the second stress data, wherein the second elastic modulus and the first viscosity coefficient are characteristic parameters in a viscoelastic constitutive equation corresponding to the target material; a third determination module, used to collect second strain data at different times when a constant stress is applied to the target material, and determine the second viscosity coefficient and the third viscosity coefficient of the target material based on the second strain data, wherein the second viscosity coefficient and the third viscosity coefficient are characteristic parameters in a creep constitutive equation corresponding to the target material.
[0016] In a third aspect, the present application provides an electronic device, comprising: a processor and a memory, wherein the memory stores machine-readable instructions executable by the processor, and when the machine-readable instructions are executed by the processor, the method steps of the first aspect are performed.
[0017] In a fourth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the method steps of the first aspect are executed.
[0018] Other features and advantages of the present application will be described in the subsequent description, and in part will become apparent from the description, or will be understood by implementing the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.
[0020] Figure 1 A schematic diagram of a process flow of a material deformation separation method provided in an embodiment of the present application;
[0021] Figure 2 A schematic diagram of a first relationship curve provided in an embodiment of the present application;
[0022] Figure 3 A schematic diagram of a second relationship curve provided in an embodiment of the present application;
[0023] Figure 4 A schematic diagram of a third relationship curve provided in an embodiment of the present application;
[0024] Figure 5 A schematic diagram of the result of separating the deformation of a target material provided in an embodiment of the present application;
[0025] Figure 6 A structural schematic diagram of a viscoelasticity-creep unified model provided in an embodiment of the present application;
[0026] Figure 7 A program operation idea diagram of a material deformation separation method based on UMAT simulation provided in this application;
[0027] Figure 8 A structural schematic diagram of a material deformation separation device is provided for this application;
[0028] Fig. 9 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION
[0029] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.
[0030] It should be noted that all technical and scientific terms used in this document have the same meanings as those generally understood by technicians in the technical field to which this application belongs; the terms used in this document are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.
[0031] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.
[0032] It can be understood that the material deformation separation method provided in the embodiment of the present application can be applied to terminal devices (also referred to as electronic devices) and servers; the terminal devices can specifically be smart phones, tablet computers, computers, personal digital assistants (PDA), etc.; the servers can specifically be application servers or Web servers.
[0033] To facilitate understanding of the technical solution provided in the embodiment of the present application, an application scenario of a material deformation separation method provided in the embodiment of the present application is introduced below, taking a server as an execution subject as an example.
[0034] Reference Figure 1 , Figure 1 A schematic flow chart of a material deformation separation method provided in an embodiment of the present application, the method comprising the following steps:
[0035] Step S10: collecting first stress data and first strain data when the target material is subjected to uniaxial stretching, and determining a first elastic modulus of the target material based on the first stress data and the first strain data, wherein the first elastic modulus is a characteristic parameter in a linear elastic constitutive equation corresponding to the target material.
[0036] Uniaxial stretching is a stretching method used in material testing. It is used to apply a force in a single direction to the target material, causing it to deform in this direction, while other directions remain unchanged or change slightly. By uniaxially stretching the target material and controlling the uniaxial stretching amplitude within an appropriate range, the target material can always be in the linear elastic deformation stage, that is, transient elastic response. The above-mentioned linear elastic deformation refers to the deformation of the target material when it is subjected to an external force, and when the external force is removed, the target material can completely recover to its original shape and size.
[0037] In an embodiment of the present application, the elongation (ie, deformation) of the target material during uniaxial stretching may be collected as first strain data, and the force applied to the target material may be collected as first stress data.
[0038] The present application does not specifically limit the uniaxial stretching amplitude of the target material, and those skilled in the art can adjust it according to actual conditions. As an implementation method, the uniaxial stretching amplitude of the target material is controlled to be between 0.1% and 0.4% of the normal strain, and a sensor is used to measure the normal strain and the corresponding normal stress to obtain the first strain data and the corresponding first stress data.
[0039] The linear elastic constitutive equation is a mathematical expression used to describe the relationship between stress and strain of a material within the linear elastic range. In the linear elastic theory, the stress and strain of a material can be considered to be a linear relationship, that is, stress is a linear function of strain. This relationship can be described by Hooke's Law, so the first elastic modulus can be determined by collecting the first stress data and the first strain data. The expression of the linear elastic constitutive equation is:
[0040] σ=E1ε;
[0041] Among them, σ is stress, E1 is the first elastic modulus, and ε is strain.
[0042] Step S20: collecting second stress data at different times when a constant strain is applied to the target material, and determining a second elastic modulus and a first viscosity coefficient of the target material based on the second stress data, wherein the second elastic modulus and the first viscosity coefficient are characteristic parameters in the viscoelastic constitutive equation corresponding to the target material.
[0043] As an implementation method, a stress relaxation experiment can be performed to collect the second stress data at different times when a constant strain is applied to the target material. The stress relaxation experiment is used to measure the change of stress of the target material over time under a constant strain (or displacement) condition, and to collect the stress data as the second stress data.
[0044] Under continuous constant strain, the internal stress of the target material will gradually decrease over time and reach a relatively stable value; in this process, the target material will immediately produce a transient elastic response when the strain is applied, and gradually produce additional deformation after the transient elastic response - viscoelastic deformation. Among them, the above viscoelastic deformation is still recoverable, but unlike linear elastic deformation, viscoelastic deformation has a significant time hysteresis effect, that is, the time for deformation to occur and the time for deformation to recover are very long.
[0045] The present application does not specifically limit the magnitude of the constant strain applied to the target material, and those skilled in the art can adjust it according to actual conditions. As an implementation method, the target material is subjected to a constant strain load of ε0=0.2%, and the stress continues to decrease with time until the stress reaches a stable value, and the acquisition is completed.
[0046] The viscoelastic constitutive equation is a mathematical expression that describes the relationship between stress, strain and time of the target material under force. Viscoelastic materials have the characteristics of both elastic bodies and viscous fluids. When subjected to external forces, they exhibit both elastic deformation and viscous flow. Considering linear elastic deformation, the second elastic modulus and the first viscosity coefficient can be determined by fitting by collecting the second stress data at different times. The expression of the viscoelastic constitutive equation is:
[0047]
[0048] Among them, σ is stress, ε is strain, E2 is the second elastic modulus, η is the first viscosity coefficient, and t is time.
[0049] Step S30: collecting second strain data at different times when a constant stress is applied to the target material, and determining a second viscosity coefficient and a third viscosity coefficient of the target material according to the second strain data, wherein the second viscosity coefficient and the third viscosity coefficient are characteristic parameters in a creep constitutive equation corresponding to the target material.
[0050] As an implementation method, a creep experiment can be used to collect the second strain data at different times when a constant stress is applied to the target material. The creep experiment is used to measure the slow creep deformation of the target material under the constant stress, and collect the strain data as the second strain data.
[0051] Under continuous constant stress, the target material's strain will gradually increase over time and reach a relatively stable value; in this process, the target material will produce irreversible creep deformation, i.e., viscous flow. Among them, the above creep deformation also has a significant time hysteresis effect and cannot be recovered after stress unloading.
[0052] The present application does not specifically limit the magnitude of the constant stress applied to the target material, and those skilled in the art can adjust it according to actual conditions. As an implementation method, the target material is subjected to a constant stress of σ0=40MPa, and the strain continues to increase with time until the strain accumulates to a stable state, and the collection is completed.
[0053] The creep constitutive equation is a mathematical expression used to describe the creep behavior of a material under long-term constant stress. Considering linear elastic deformation and viscoelastic deformation, the second viscosity coefficient and the third viscosity coefficient can be determined by fitting by collecting the second strain data at different times. The expression of the creep constitutive equation is:
[0054]
[0055] Wherein, σ is stress, ε is strain, A is the second viscosity coefficient, B is the third viscosity coefficient, and t is time.
[0056] In the above scheme, the characteristic parameters of the linear elastic constitutive equation are determined by performing uniaxial stretching on the target material, the characteristic parameters of the viscoelastic constitutive equation are determined by applying a constant strain to the target material, and the characteristic parameters of the creep constitutive equation are determined by applying a constant stress to the target material. Since the linear elastic constitutive equation, the viscoelastic constitutive equation, and the creep constitutive equation can be independently used to characterize and quantify the linear elastic deformation, viscoelastic deformation, and creep deformation of the target material, after determining the corresponding constitutive equations respectively, the precise separation between the linear elastic deformation, viscoelastic deformation, and creep deformation of the target material is achieved.
[0057] In some embodiments, determining the first elastic modulus of the target material according to the first stress data and the first strain data in step S10 includes:
[0058] S101: Determine a first relationship curve between stress and strain of a target material within a linear elastic range according to first stress data and first strain data.
[0059] S102: Determine the slope of the first relationship curve as a first elastic modulus.
[0060] The first stress data and the first strain data are plotted one by one in a plane rectangular coordinate system, and each point is smoothly connected to obtain a first relationship curve. Since there is a linear relationship between stress and strain within the linear elastic range, the slope of the first relationship curve is the first elastic modulus, and therefore the slope of the first relationship curve is determined as the first elastic modulus.
[0061] Reference Figure 2 , Figure 2 A schematic diagram of a first relationship curve provided in an embodiment of the present application. Figure 2 In the embodiment shown, the normal stress σ s Corresponding normal strain ε s , in (ε s , σ s ) corresponds to the linear elastic range of the target material, and the slope is the first elastic modulus.
[0062] In the above scheme, the target material is uniaxially stretched within the linear elastic range, and the collected first stress data and first strain data follow Hooke's law. Therefore, the first elastic modulus can be determined by the slope of the first relationship curve, thereby separating the linear elastic deformation from the deformation of the target material.
[0063] In some embodiments, determining the second elastic modulus and the first viscosity coefficient of the target material according to the second stress data in step S20 includes:
[0064] S201: Calculate the linear elastic recoverable stress of the target material according to the first elastic modulus, the constant strain and the linear elastic constitutive equation.
[0065] According to the linear elastic constitutive equation σ = E1ε, by substituting the values of the first elastic modulus E1 and the constant strain ε, the corresponding linear elastic recoverable stress σ value σ1 can be calculated. Since linear elastic deformation is a transient response, while viscoelastic deformation and creep deformation have obvious time hysteresis effects and the deformation time is very long, at the moment when a constant strain is applied to the target material, the constant strain is the linear elastic recoverable strain, and the linear elastic recoverable stress can be obtained by substituting it into the linear elastic constitutive equation.
[0066] S202: Determine a second relationship curve between the second stress data and time of the target material under constant strain according to the second stress data, and determine a total stress reduction amount in a process of applying the constant strain to the target material.
[0067] The second stress data and time are plotted one by one in a plane rectangular coordinate system, and each point is smoothly connected to obtain a second relationship curve.
[0068] Reference Figure 3 , Figure 3 A schematic diagram of a second relationship curve provided in an embodiment of the present application. Figure 3 It can be seen that the stress σ continues to decrease with time until the stress reaches a stable value.
[0069] S203: Calculate the difference between the total stress reduction and the linear elastic recoverable stress as the viscoelastic recoverable stress of the target material.
[0070] exist Figure 3 In the embodiment shown, since creep deformation is an irreversible deformation, the total stress reduction includes two parts: linear elastic recoverable stress σ1 and viscoelastic recoverable stress σ2, and the stress value that tends to be stable is the creep stress. By measuring the total stress reduction, the linear elastic recoverable stress σ1 is known according to step S201, so the viscoelastic recoverable stress σ2 can be calculated, that is, σ2 = total stress reduction - σ1.
[0071] S204: According to the viscoelastic recoverable stress, the second relationship curve and the viscoelastic constitutive equation, a first viscosity coefficient η and a second elastic modulus E2 are obtained by fitting.
[0072] exist Figure 3 In the second relationship curve diagram shown, the curve segments corresponding to the linear elastic recoverable stress σ1 and the viscoelastic recoverable stress σ2 are calibrated according to the order of time response. Given the expression of the viscoelastic constitutive equation and the curve segment corresponding to the viscoelastic recoverable stress σ2 in the second relationship curve, the first viscosity coefficient and the second elastic modulus can be fitted.
[0073] In the above scheme, the linear elastic and viscoelastic deformations are recoverable, while the creep deformation is irrecoverable. When a constant strain is applied to the target material for a long time, the required stress gradually decreases until it stabilizes. The gradual stabilization of stress is a creep phenomenon. Therefore, the total stress reduction can be regarded as the reduction of linear elastic recoverable stress and viscoelastic recoverable stress. Combined with the determined linear elastic constitutive equation, the linear elastic deformation and viscoelastic deformation can be separated from the total stress reduction, so that the characteristic parameters of the viscoelastic constitutive equation can be determined, thereby realizing the separation of viscoelastic deformation from the deformation of the target material.
[0074] In some embodiments, determining the second viscosity coefficient and the third viscosity coefficient of the target material according to the second strain data in step S30 includes:
[0075] S301: Based on stress consistency, the linear elastic recoverable strain of the target material is calculated according to the first elastic modulus, the constant stress and the linear elastic constitutive equation.
[0076] Stress consistency means that the stresses borne by the linear elastic deformation, viscoelastic deformation and creep deformation of the target material are the same, and the total strain produced by the target material is equal to the sum of the partial strains produced by the three deformations.
[0077] Similarly, according to the linear elastic constitutive equation σ=E1ε, by substituting the values of the first elastic modulus E1 and the constant stress σ, the corresponding linear elastic recoverable strain ε1 can be calculated.
[0078] S302: Calculate the viscoelastic recoverable strain of the target material according to the first viscosity coefficient, the second elastic modulus, the constant stress and the viscoelastic constitutive equation.
[0079] According to the viscoelastic constitutive equation By substituting the values of the first viscosity coefficient η, the second elastic modulus E2 and the constant stress σ, the value ε2 of the corresponding viscoelastic recoverable strain ε can be calculated.
[0080] S303: determining a third relationship curve between the second strain data and time of the target material under constant stress according to the second strain data, and determining a total strain increase in a process of applying the constant stress to the target material.
[0081] The second strain data and time are plotted one by one in a plane rectangular coordinate system, and each point is smoothly connected to obtain a third relationship curve.
[0082] Reference Figure 4 , Figure 4 A schematic diagram of a third relationship curve provided in an embodiment of the present application. Figure 4 It can be seen that the strain ε continues to increase with time, and the strain accumulates to a stable state. The total strain increase is equal to the sum of the linear elastic recoverable strain ε1, the viscoelastic recoverable strain ε2, and the creep irrecoverable strain ε3.
[0083] S304: Calculate the difference between the total strain increase and the elastic strain as the creep irrecoverable strain of the target material, wherein the elastic strain is equal to the sum of the linear elastic recoverable strain and the viscoelastic recoverable strain.
[0084] According to the total strain increase εtotal=ε1+ε2+ε3, ε3=εtotal-(ε1+ε2) can be calculated. Among them, ε1+ε2 is the elastic strain, which is equal to the sum of the linear elastic recoverable strain and the viscoelastic recoverable strain.
[0085] S305: According to the creep irrecoverable strain, the third relationship curve and the creep constitutive equation, a second viscosity coefficient and a third viscosity coefficient are obtained by fitting.
[0086] exist Figure 4 In the third relationship curve shown in FIG. 1 , the elastic recoverable strain of the output line is calibrated according to the order of time response. Viscoelastic recoverable strain The curve segment corresponding to the creep irrecoverable strain ε3, given the expression of the creep constitutive equation and the curve segment corresponding to the creep irrecoverable strain ε3 in the third relationship curve, can be fitted to obtain the second viscosity coefficient and the third viscosity coefficient. Figure 5 , Figure 5 A schematic diagram of the result of separating the deformation of a target material provided in an embodiment of the present application, wherein: It can be seen that the method provided in the embodiment of the present application realizes the quantitative separation of linear elasticity, viscoelasticity and creep. After that, for the same target material, the characteristic parameters of the constitutive equation determined according to the method of the above embodiment can be directly used for the separation of linear elasticity, viscoelasticity and creep without solving the characteristic parameters again, which is convenient for the performance analysis and optimization of the target material.
[0087] In the above scheme, after a constant stress is applied to the target material for a long time until the strain tends to stabilize, the total strain increase is equal to the superposition of the partial strains caused by linear elasticity, viscoelasticity, and creep, and the stress borne by each partial deformation is the same. Combined with the already determined linear elastic constitutive equation and viscoelastic constitutive equation, the linear elastic deformation, viscoelastic deformation, and creep deformation can be separated from the total strain increase, so that the characteristic parameters of the creep constitutive equation can be determined, thereby realizing the separation of creep deformation from the deformation of the target material.
[0088] In some embodiments, a linear elastic constitutive equation, a viscoelastic constitutive equation, and a creep constitutive equation are used to characterize a viscoelasticity-creep unified model of a target material, wherein the viscoelasticity-creep unified model includes a first spring for characterizing linear elasticity, a first viscoelasticity pot and a second spring for characterizing viscoelasticity, and a second viscoelasticity pot for characterizing creep.
[0089] In the above embodiment, a unified viscoelastic-creep model based on springs and viscoelastic pots is established for the deformation behavior of the target material. In this model, the linear elastic deformation of the target material is controlled by the first spring, the viscoelastic deformation is controlled by the first viscoelastic pot and the second spring, and the creep deformation is controlled by the second viscoelastic pot.
[0090] In the above scheme, the unified viscoelastic-creep model divides the mechanical behavior of the target material deformation into three parts, namely the linear elastic part, the viscoelastic part and the creep part, and the three parts can be described by the physical models of springs and viscoelastic pots, which provides a projectable model for the linear elastic constitutive equation, the viscoelastic constitutive equation and the creep constitutive equation in the specific deformation behavior of the target material and gives them a vivid and intuitive meaning. In short, the unified viscoelastic-creep model provides a more accurate and practical constitutive equation for the deformation behavior of the target material, improves the calculation efficiency and accuracy, provides a reliable basis for the evaluation of the target material performance, and provides strong support for the design, modification and application of the target material.
[0091] In some embodiments, one end of the first viscosity pot after being connected in parallel with the second spring is connected in series with the first spring, and the other end is connected in series with the second viscosity pot.
[0092] Reference Figure 6 , Figure 6 A structural schematic diagram of a viscoelastic-creep unified model provided in an embodiment of the present application. The first spring used to describe the linear elasticity satisfies the linear elastic constitutive equation σ=E1ε, and the first viscoelastic spring used to describe the viscoelasticity is connected in parallel with the second spring to form a Zener model (or Kelvin-Voigt model) and satisfies the viscoelastic constitutive equation The second viscosity pot used to describe creep satisfies the creep constitutive equation
[0093]
[0094] When the viscoelastic-creep unified model is subjected to an external force, the first spring will respond first. The model immediately produces a linear elastic deformation, which is a transient elastic response. This deformation does not increase or decrease over time, but remains constant until it is fully recovered during the unloading phase. After the transient elastic response, the viscoelastic-creep unified model will gradually produce additional deformation over time - viscoelastic deformation. This deformation is still recoverable and has a significant time hysteresis effect. Under the action of external forces for a long time, the viscoelastic-creep unified model will produce irreversible permanent deformation, which is viscous flow. This deformation corresponds to the creep part of the viscoelastic-creep unified model, which also has a significant time hysteresis effect and is irreversible after unloading.
[0095] Stress consistency in the viscoelastic-creep unified model is manifested as the same stress on the three parts, and the total strain generated by the model is equal to the sum of the partial strains generated by the three parts. The viscoelastic-creep unified model generally satisfies the constitutive equation as follows:
[0096]
[0097] Among them, εtotal is the total strain generated by the unified viscoelastic-creep model, the first term ε1 represents the linear elastic recoverable strain generated by the first spring, the second term ε2 represents the viscoelastic recoverable strain generated by the parallel system of the second spring and the first viscoelastic pot, and the third term ε3 represents the creep irrecoverable strain generated by the second viscoelastic pot.
[0098] In the above scheme, the unified viscoelasticity-creep model is composed of a first spring, a first viscoelasticity pot and a second spring in parallel, and a second viscoelasticity pot in series, so that the unified viscoelasticity-creep model can simultaneously describe the linear elasticity, viscoelasticity and creep properties of the target material.
[0099] As an optional manner, the target material is a CPI film layer.
[0100] As a high-performance material, CPI film is favored for its excellent transparency, weather resistance, mechanical strength and chemical stability, and is widely used in folding screens. The method provided in the embodiment of the present application is applied to the CPI film, and based on the viscoelastic-creep unified model, the separation of the two deformation mechanisms of viscoelasticity and creep can be achieved according to the stress consistency theory.
[0101] In the above scheme, the CPI film layer is widely used in folding screens as a high-performance material. The deformation separation of the CPI film layer according to the above method is beneficial to the performance optimization and product design of related products.
[0102] Reference Figure 7 , Figure 7 A program operation idea diagram of a material deformation separation method based on UMAT simulation provided in this application includes the following steps:
[0103] ① Define user material parameters in ABAQUS software: Create Material→General→UserMaterial→Enter user material parameter values. Define the number of state variables: Create Material→General→Depvar→Enter the number of state variables. In the UMAT subroutine, the number of state variables is defined as 7, 1-6 are creep strains in 6 directions, and 7 is the equivalent creep strain.
[0104] ②Set the static analysis step to simulate the loading and unloading process of the membrane material in the creep relaxation experiment. During the analysis process, extract the stress, strain and total strain increment of the current state of the ABAQUS main program and input them into the UMAT subroutine as state variables.
[0105] ③ If only viscoelastic analysis is considered in the simulation, the strain increment is all elastic strain increment. The stress increment value is calculated by the constitutive equation, the normal stress, shear stress and the corresponding Jacobian matrix are updated, and they are passed to the state variables of the current increment step to facilitate the next step of calculation.
[0106] ④ If viscoelasticity and creep need to be considered simultaneously in the simulation, the strain increment includes elastic strain increment and creep strain increment. The initial creep strain is obtained from the creep constitutive relation, and the creep strain increment value is determined through multiple nonlinear iterations. The elastic strain increment value is obtained by subtracting the creep strain increment from the overall strain increment. The creep stress and viscoelastic stress are updated, and the Jacobian matrix is updated after the two are added, and it is passed to the state variable of the current increment step for the next step of calculation.
[0107] Reference Figure 8 , Figure 8 A structural schematic diagram of a material deformation separation device is provided for this application, including:
[0108] The first determination module is used to collect first stress data and first strain data when the target material is subjected to uniaxial stretching, and determine a first elastic modulus of the target material based on the first stress data and the first strain data, wherein the first elastic modulus is a characteristic parameter in a linear elastic constitutive equation corresponding to the target material.
[0109] The second determination module is used to collect second stress data at different times when a constant strain is applied to the target material, and determine the second elastic modulus and the first viscosity coefficient of the target material according to the second stress data, wherein the second elastic modulus and the first viscosity coefficient are characteristic parameters in the viscoelastic constitutive equation corresponding to the target material.
[0110] The third determination module is used to collect second strain data at different times when a constant stress is applied to the target material, and determine the second viscosity coefficient and the third viscosity coefficient of the target material according to the second strain data, wherein the second viscosity coefficient and the third viscosity coefficient are characteristic parameters in the creep constitutive equation corresponding to the target material.
[0111] In some embodiments, the first determination module further includes: determining a first relationship curve between stress and strain of the target material within a linear elastic range according to the first stress data and the first strain data; and determining the slope of the first relationship curve as the first elastic modulus.
[0112] In some embodiments, the second determination module also includes: calculating the linear elastic recoverable stress of the target material according to the first elastic modulus, the constant strain and the linear elastic constitutive equation; determining the second relationship curve between the second stress data and time of the target material under the constant strain according to the second stress data, and determining the total stress reduction in the process of applying the constant strain to the target material; calculating the difference between the total stress reduction and the linear elastic recoverable stress as the viscoelastic recoverable stress of the target material; fitting the first viscosity coefficient and the second elastic modulus according to the viscoelastic recoverable stress, the second relationship curve and the viscoelastic constitutive equation.
[0113] In some embodiments, the third determination module also includes: calculating the linear elastic recoverable strain of the target material based on stress consistency, according to the first elastic modulus, constant stress and linear elastic constitutive equation; calculating the viscoelastic recoverable strain of the target material according to the first viscosity coefficient, the second elastic modulus, the constant stress and the viscoelastic constitutive equation; determining the third relationship curve between the second strain data and time of the target material under constant stress according to the second strain data, and determining the total strain increase in the process of applying constant stress to the target material; calculating the difference between the total strain increase and the elastic strain as the creep irrecoverable strain of the target material, wherein the elastic strain is equal to the sum of the linear elastic recoverable strain and the viscoelastic recoverable strain; fitting the second viscosity coefficient and the third viscosity coefficient according to the creep irrecoverable strain, the third relationship curve and the creep constitutive equation.
[0114] It should be understood that the device corresponds to the above-mentioned material deformation separation method embodiment and can perform the various steps involved in the above-mentioned method embodiment. The specific functions of the device can be found in the above description. To avoid repetition, the detailed description is appropriately omitted here. The device includes at least one software function module that can be stored in a memory in the form of software or firmware or solidified in the operating system (OS) of the device.
[0115] Reference Fig. 9 , Fig. 9 The electronic device structure diagram provided for the embodiment of the present application includes: a processor 901 and a memory 902, wherein the memory 902 stores machine-readable instructions executable by the processor 901, and when the machine-readable instructions are executed by the processor 901, the methods provided by the above-mentioned method embodiments are executed.
[0116] The present application provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the method steps of the first aspect are executed.
[0117] The processor 901 can be an integrated circuit chip with signal processing capabilities. The above-mentioned processor 901 can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. It can implement or execute various methods, steps and logic block diagrams disclosed in the embodiments of the present application. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc.
[0118] The memory 902 may include but is not limited to random access memory (RAM), read only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable read-only memory (EEPROM), etc.
[0119] This embodiment discloses a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions. When the program instructions are executed by a computer, the computer can execute the methods provided by the above-mentioned method embodiments.
[0120] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.
[0121] In addition, the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
[0122] Furthermore, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.
[0123] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A material deformation separation method, characterized in that: include: Collecting first stress data and first strain data when a target material is subjected to uniaxial stretching, and determining a first elastic modulus of the target material according to the first stress data and the first strain data, wherein the first elastic modulus is a characteristic parameter in a linear elastic constitutive equation corresponding to the target material; collecting second stress data at different times when a constant strain is applied to the target material, and determining a second elastic modulus and a first viscosity coefficient of the target material according to the second stress data, wherein the second elastic modulus and the first viscosity coefficient are characteristic parameters in a viscoelastic constitutive equation corresponding to the target material; The second strain data at different times when a constant stress is applied to the target material is collected, and the second viscosity coefficient and the third viscosity coefficient of the target material are determined according to the second strain data, wherein the second viscosity coefficient and the third viscosity coefficient are characteristic parameters in the creep constitutive equation corresponding to the target material.
2. The method according to claim 1, characterized in that: The determining the first elastic modulus of the target material according to the first stress data and the first strain data includes: Determine a first relationship curve between stress and strain within a linear elastic range of the target material according to the first stress data and the first strain data; The slope of the first relationship curve is determined as the first elastic modulus.
3. The method according to claim 1, characterized in that: The determining the second elastic modulus and the first viscosity coefficient of the target material according to the second stress data comprises: Calculating the linear elastic recoverable stress of the target material according to the first elastic modulus, the constant strain and the linear elastic constitutive equation; Determine a second relationship curve between the second stress data and time of the target material under the constant strain according to the second stress data, and determine a total stress reduction amount in a process of applying the constant strain to the target material; Calculating the difference between the total stress reduction and the linear elastic recoverable stress as the viscoelastic recoverable stress of the target material; The first viscosity coefficient and the second elastic modulus are obtained by fitting according to the viscoelastic recoverable stress, the second relationship curve, and the viscoelastic constitutive equation.
4. The method according to claim 3, characterized in that The determining the second viscosity coefficient and the third viscosity coefficient of the target material according to the second strain data comprises: Based on stress consistency, calculating the linear elastic recoverable strain of the target material according to the first elastic modulus, the constant stress and the linear elastic constitutive equation; Calculating the viscoelastic recoverable strain of the target material according to the first viscosity coefficient, the second elastic modulus, the constant stress and the viscoelastic constitutive equation; determining a third relationship curve between the second strain data and time of the target material under the constant stress according to the second strain data, and determining a total strain increase in a process of applying the constant stress to the target material; Calculating the difference between the total strain increase and the elastic strain as the creep irrecoverable strain of the target material, wherein the elastic strain is equal to the sum of the linear elastic recoverable strain and the viscoelastic recoverable strain; The second viscosity coefficient and the third viscosity coefficient are obtained by fitting according to the creep irrecoverable strain, the third relationship curve and the creep constitutive equation.
5. The method according to claim 1, characterized in that The linear elastic constitutive equation, the viscoelastic constitutive equation, and the creep constitutive equation are used to characterize a unified viscoelasticity-creep model of the target material, wherein the unified viscoelasticity-creep model includes a first spring for characterizing linear elasticity, a first viscoelastic pot and a second spring for characterizing viscoelasticity, and a second viscoelastic pot for characterizing creep.
6. The method according to claim 5, characterized in that One end of the first viscosity pot after being connected in parallel with the second spring is connected in series with the first spring, and the other end is connected in series with the second viscosity pot.
7. The method according to claims 1-6, characterized in that: The target material is a CPI film layer.
8. A material deformation separation device, characterized in that: include: a first determination module, configured to collect first stress data and first strain data when a target material is subjected to uniaxial stretching, and determine a first elastic modulus of the target material according to the first stress data and the first strain data, wherein the first elastic modulus is a characteristic parameter in a linear elastic constitutive equation corresponding to the target material; a second determination module, configured to collect second stress data at different times when a constant strain is applied to the target material, and determine a second elastic modulus and a first viscosity coefficient of the target material according to the second stress data, wherein the second elastic modulus and the first viscosity coefficient are characteristic parameters in a viscoelastic constitutive equation corresponding to the target material; The third determination module is used to collect second strain data at different times when a constant stress is applied to the target material, and determine the second viscosity coefficient and the third viscosity coefficient of the target material according to the second strain data, wherein the second viscosity coefficient and the third viscosity coefficient are characteristic parameters in the creep constitutive equation corresponding to the target material.
9. An electronic device, characterized in that: include: A processor and a memory, wherein the memory stores machine-readable instructions executable by the processor, and when the machine-readable instructions are executed by the processor, the method according to any one of claims 1 to 7 is performed.
10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 7 is executed.