CN114371075B - Evaluation method of constraint stress of titanium alloy thin-wall component under complex load - Google Patents
Evaluation method of constraint stress of titanium alloy thin-wall component under complex load Download PDFInfo
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Abstract
The invention discloses an evaluation method of constraint stress of a titanium alloy thin-wall component under complex load, which comprises the following steps: simplifying the actual service working condition of a preset titanium alloy thin-wall component into a biaxial deformation experiment to obtain an experimental stress strain curve in the main bearing direction; cutting a sample on a component to perform a uniaxial tension experiment to obtain a uniaxial stress strain curve of the material; obtaining a reference value of a crystal plasticity constitutive parameter, and performing crystal plasticity simulation trial calculation to obtain a simulated stress-strain curve of uniaxial stretching; adjusting the reference value to enable the experiment and simulation stress-strain curves of uniaxial stretching to be basically consistent; modifying boundary conditions of crystal plasticity simulation trial calculation according to the actual service conditions, and calculating again to obtain a simulated stress strain curve of the main bearing direction; and (3) simulating the main bearing direction, comparing experimental stress-strain curves to obtain constraint stress, and further evaluating the early cracking reason of the preset titanium alloy thin-wall component. The method clarifies the influence of different component structures on the representation of the mechanical properties of the main bearing direction.
Description
Technical Field
The invention relates to the technical field of mechanical properties of metal materials, in particular to an evaluation method of constraint stress of a titanium alloy thin-wall member under complex load.
Background
The titanium alloy has high specific strength, good toughness and excellent high-temperature performance, and has wide application prospect in the fields of aerospace, ships, chemical industry and the like. Titanium alloy components are often subjected to complex loads, i.e., multiaxial stresses, during actual service. However, early cracking of titanium alloy components under multiaxial stress may occur. The reliability design and the service life prediction of the component are not accurate enough based on the mechanical properties of the titanium alloy obtained by the unidirectional stretching experiment. The mechanical behavior of the titanium alloy component (particularly the titanium alloy thin-wall component) under the action of complex load is effectively simplified by adopting a biaxial stretching experiment, namely, the material in the central area is in different stress states by changing the load ratio or displacement ratio of two axial directions. However, because of the large number of cross-shaped specimen structures used in biaxial stretching experiments, cross-shaped specimens of different structures often yield different stress-strain curves. The main reason is that the deformation of a sample in one direction (the main bearing direction is denoted by the X direction) is constrained by the deformation in the other direction (the non-main bearing direction is denoted by the Y direction), and the difference between the stress strain curve in the X direction under the simulated biaxial stress action and the stress strain curve in the X direction obtained by the biaxial stretching experiment is the "constraint stress" in the X direction caused by the structure (the width and the like) of the sample in the Y direction, and the constraint stress is related to the structure and the plastic deformation amount of the cross-shaped sample.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the related art to some extent.
Therefore, one purpose of the invention is to provide an evaluation method of constraint stress of a titanium alloy thin-wall member under complex load, which is helpful for clearing the influence of different member structures on the representation of mechanical properties in the main bearing direction.
In order to achieve the above purpose, the embodiment of the invention provides an evaluation method of constraint stress of a titanium alloy thin-wall member under complex load, which comprises the following steps: step S1, simplifying the actual service condition of a preset titanium alloy thin-wall component into a biaxial deformation experiment of a cross-shaped sample, and carrying out the biaxial deformation experiment to obtain an experimental stress strain curve in a main bearing direction; s2, cutting a uniaxially stretched dog-bone sample from a material used in the preset titanium alloy thin-wall member, and carrying out a uniaxial stretching experiment on the uniaxially stretched dog-bone sample to obtain an experimental stress strain curve of the uniaxial stretching of the dog-bone sample; step S3, obtaining a reference value of a crystal plasticity constitutive parameter of the titanium alloy in the preset titanium alloy thin-wall component, and performing crystal plasticity simulation trial calculation to obtain a simulated stress-strain curve of uniaxial stretching; s4, adjusting a reference value of the crystal plasticity constitutive parameter to enable the uniaxial stretching simulated stress strain curve to be basically matched with the uniaxial stretching experimental stress strain curve of the dog-bone sample, and obtaining an actual value of the crystal plasticity constitutive parameter; step S5, based on the actual value of the crystal plasticity constitutive parameter, modifying the boundary condition of the crystal plasticity simulation trial calculation to enable the boundary condition to be consistent with the actual service working condition determined in the step S1, and then performing crystal plasticity simulation trial calculation to obtain a simulated stress-strain curve of the main bearing direction; s6, comparing the simulated stress-strain curve of the main bearing direction with the experimental stress-strain curve of the main bearing direction, wherein the difference value is used as constraint stress which is the influence of a sample structure in a non-main bearing direction on the mechanical property of the main bearing direction; and S7, evaluating the early cracking reason of the preset titanium alloy thin-wall component according to the constraint stress.
The evaluation method of the constraint stress of the titanium alloy thin-wall component under the complex load solves the problems that the strength of the main bearing direction is difficult to accurately represent due to the influence of the constraint stress of the titanium alloy thin-wall component under the complex load by the component structure and the plastic strain amount, so that early cracking reasons of the titanium alloy component cannot be clarified, and the like, and further helps to clear the influence of different component structures on the mechanical property representation of the main bearing direction, and has important significance in finding out the early cracking reasons of the titanium alloy component under the complex load.
In addition, the method for evaluating the constraint stress of the titanium alloy thin-wall component under the complex load according to the embodiment of the invention can also have the following additional technical characteristics:
further, in one embodiment of the invention, the two mutually perpendicular arms in the cross-shaped specimen are dimensionally consistent.
Further, in one embodiment of the invention, any direction of the cross-shaped sample is simplified into stretching or compressing according to the actual service condition of the preset titanium alloy thin-wall component, and any direction is controlled by monotonic load or displacement, and the loading process in any direction is synchronous or asynchronous with the loading process in the other direction.
Alternatively, in one embodiment of the present invention, the strain rate at which plastic deformation occurs in either direction is maintained at 0.0001 to 0.01s when either direction of the cross-shaped specimen is subjected to monotonic load or displacement control -1 Within the range.
Further, in one embodiment of the present invention, the titanium alloy in the preset titanium alloy thin-walled member comprises alpha titanium and near alpha titanium and a portion of alpha+beta titanium alloy.
Further, in one embodiment of the present invention, the crystal plastic model is a sliding system and twin system resistance evolution model, specifically:
wherein alpha refers to a sliding system, beta refers to a twin crystal system,for the slip-slip interaction +.>c 1 、c 2 、c 3 、c 4 Fitting parameters for the model>As the volume fraction of twin crystal, N s For the number of slip systems, +.>Shear rate of slip system, ζ α′ For the critical value of the slip resistance, +.>Saturation value of slip resistance, N tw For the number of twinning systems>Shear rate for twin system, +.>Between slipping and twinningInteraction(s) (i.e. the person is at risk)>Is a twinning-twinning interaction.
Further, in one embodiment of the present invention, the crystal plastic constitutive parameters include, but are not limited to, the cutting stress threshold τ of each slip system of the titanium alloy alpha phase 0 Saturation value τ ∞ Interactions between slip-slipInteractions between slip-twins>Interaction between twin-twin +.>Model fitting parameter c 1 、c 2 、c 3 、c 4 。
Further, in one embodiment of the present invention, the boundary conditions of the crystal plasticity simulation trial after modification are:
wherein F is deformation gradient, a and b are variables, and p is stress.
Further, in an embodiment of the present invention, the constraint stress evolution rule is:
Δσ＝f(b,t,ε x )
wherein delta sigma is constraint stress, b is arm width of a cross sample, t is thickness of the preset titanium alloy thin-wall component, epsilon x Is the amount of strain of plastic deformation in the primary load-bearing direction.
Optionally, in one embodiment of the present invention, if Δσ is a positive value and Δσ is positively related to a variable, an experimental value of mechanical properties in a main bearing direction is lower than an analog value, and early cracking of the preset titanium alloy thin-walled member is caused by stress concentration at a local position; if delta sigma approaches 0, the experimental value of the mechanical property of the main bearing direction approaches to the simulation value, and the design of the preset titanium alloy thin-wall component and the simplified double-shaft deformation working condition thereof are reasonable in structure.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
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The foregoing and/or additional aspects and advantages of the invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a flow chart of a method of evaluating constraint stress of a titanium alloy thin-walled member under a complex load in accordance with one embodiment of the present invention;
FIG. 2 is a simplified dual axis deformed sample structure diagram of one embodiment of the present invention;
FIG. 3 is a simulation result after checking the plastic constitutive parameters of the crystal and a reference experimental result according to an embodiment of the present invention;
figure 4 is a schematic representation of the RVE model structure employed in the crystal plasticity simulation of one embodiment of the present invention;
fig. 5 is a schematic diagram showing a comparison between a mechanical behavior of a main bearing direction under simulated biaxial stress and a mechanical behavior of the main bearing direction obtained by a simplified biaxial deformation experiment (wherein the difference between the two is the effect of constraint stress, i.e. a gradient color portion) according to an embodiment of the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
The following describes an evaluation method of constraint stress of a titanium alloy thin-wall component under a complex load according to an embodiment of the present invention with reference to the accompanying drawings.
FIG. 1 is a flow chart of a method of evaluating the constraint stress of a titanium alloy thin-walled member under a complex load in accordance with one embodiment of the present invention.
As shown in fig. 1, the method for evaluating the constraint stress of the titanium alloy thin-wall component under the complex load comprises the following steps:
in step S1, the actual service condition of the preset titanium alloy thin-wall member is simplified into a biaxial deformation experiment of a cross-shaped sample, and the biaxial deformation experiment is performed to obtain an experimental stress strain curve in the main bearing direction, wherein the titanium alloy in the preset titanium alloy thin-wall member comprises alpha titanium and near alpha titanium, near alpha titanium and part of alpha+beta titanium alloy.
In some embodiments, the actual service working condition of the preset titanium alloy thin-wall component is simplified into a biaxial deformation (stretching or compression) working condition of a cross-shaped sample, the simplified biaxial load ratio or displacement ratio is determined, and then a simplified biaxial deformation experiment is carried out to obtain an experimental stress strain curve of the main bearing direction.
Further, the two mutually perpendicular arm structures in the cross-shaped sample are consistent.
Further, any direction of the cross-shaped sample can be simplified into stretching or compressing according to the actual service condition of the preset titanium alloy thin-wall component, any direction is controlled by monotonic load or displacement, and the loading process of any direction and the loading process of the other direction can be synchronous or asynchronous; when any direction of the cross-shaped sample is controlled by monotonic load or displacement, the strain rate of plastic deformation in any direction is kept between 0.0001 and 0.01s -1 Within the range.
In step S2, a uniaxially stretched dog-bone specimen is cut from a material used in the preset titanium alloy thin-wall member, and a uniaxial stretching experiment is performed on the uniaxially stretched dog-bone specimen, so as to obtain an experimental stress strain curve of the uniaxial stretching of the dog-bone specimen.
In some embodiments, after the biaxial deformation test is completed, the preset titanium alloy thin-walled member is sampled to obtain a uniaxially stretched dog-bone specimen, and then the uniaxially stretched dog-bone specimen is subjected to a uniaxial stretching test (dog-bone specimen) to obtain an experimental stress strain curve of the material under uniaxial stress.
In step S3, a reference value of a crystal plasticity constitutive parameter of the titanium alloy in the preset titanium alloy thin-wall component is obtained, and crystal plasticity simulation trial calculation is carried out, so that a simulated stress-strain curve of uniaxial tension is obtained.
In some embodiments, after the step S2 is completed, a crystal plastic model of the titanium alloy is established, reference literature data is referred to obtain reference crystal plastic constitutive parameters of the titanium alloy and original boundary conditions of crystal plastic simulation trial calculation according to chemical components of the titanium alloy, and the crystal plastic simulation trial calculation is performed to obtain a simulated stress strain curve of uniaxial stretching.
The crystal plastic model adopts a unique crystal plastic model, namely a sliding system and a twin crystal system resistance evolution model are respectively as follows:
wherein alpha refers to a sliding system, beta refers to a twin crystal system,for the slip-slip interaction +.>c 1 、c 2 、c 3 、c 4 Fitting parameters for the model>As the volume fraction of twin crystal, N s Is a slip systemNumber of systems->Shear rate of slip system, ζ α′ For the critical value of the slip resistance, +.>Saturation value of slip resistance, N tw For the number of twinning systems>Shear rate for twin system, +.>For the glide-twinning interaction, +.>Is a twinning-twinning interaction.
In some embodiments, the crystal plasticity constitutive parameters include, but are not limited to, the shear stress threshold τ for each slip system of the titanium alloy alpha phase 0 Saturation value τ ∞ Interactions between slip-slipInteractions between slip-twinsInteraction between twin-twin +.>Model fitting parameter c 1 、c 2 、c 3 、c 4 。
The original boundary conditions of the crystal plasticity simulation trial calculation are as follows:
in step S4, a reference value of the intrinsic crystal plastic parameter is adjusted, so that the uniaxial tensile simulated stress-strain curve is substantially identical to the uniaxial tensile experimental stress-strain curve of the dog-bone sample, and an actual value of the intrinsic crystal plastic parameter is obtained.
In some embodiments, the uniaxial tensile simulated stress-strain curve is compared with the uniaxial tensile experimental stress-strain curve of the dog-bone sample, and the reference value of the intrinsic crystal plastic parameter is adjusted to make the uniaxial tensile simulated stress-strain curve consistent with the uniaxial tensile experimental stress-strain curve of the dog-bone sample, so that the simulated value of the intrinsic crystal plastic parameter obtained in the literature is modified and checked to obtain the actual value of the intrinsic crystal plastic parameter.
In step S5, based on the actual value of the crystal plasticity constitutive parameter, modifying the boundary condition of the crystal plasticity simulation trial calculation to make the boundary condition consistent with the actual service condition determined in step S1, and performing the crystal plasticity simulation trial calculation to obtain the simulated stress-strain curve of the main bearing direction.
In some embodiments, the boundary conditions of the crystal plastic simulation are modified to conform to the simplified biaxial deformation regime of step one based on the actual values of the crystal plastic constitutive parameters, asF is a deformation gradient, a and b are variables, p is stress, and then the simulation of crystal plasticity is carried out to obtain a simulated stress-strain Curve Curve X of the main bearing direction under the boundary condition.
In step S6, the simulated stress-strain curve in the main bearing direction is compared with the experimental stress-strain curve in the main bearing direction, and the difference is used as the constraint stress which is the influence of the sample structure in the non-main bearing direction on the mechanical property in the main bearing direction.
In some embodiments, subtracting the experimental stress-strain Curve of the main bearing direction in step S1 from the simulated stress-strain Curve Curve X of the main bearing direction to obtain the influence (i.e. constraint stress evolution rule) Δσ=f (b, t, ε) of the non-main bearing direction sample structure on the mechanical properties (simulated values) of the main bearing direction x ) Wherein delta sigma is constraint stress, b is cross-shapedThe arm width of the sample, t is the thickness of the preset titanium alloy thin-wall component epsilon x Is the amount of strain of plastic deformation in the primary load-bearing direction.
In step S7, the early cracking reason of the preset titanium alloy thin-wall component is evaluated according to the constraint stress.
Specifically, in the embodiment of the present invention, the constraint stress Δσ=f (b, t, ε) obtained based on step S6 x ) Evaluating the cause of early cracking of the titanium alloy thin-wall component, wherein if delta sigma is a positive value and delta sigma is obviously increased along with the increase of the strain quantity, the experimental value of the mechanical property of the main bearing direction is lower than the simulation value, and the early cracking of the preset titanium alloy thin-wall component is caused by stress concentration at a local position; if delta sigma approaches 0, the experimental value of the mechanical property of the main bearing direction approaches to the simulation value, and at the moment, the design of the preset titanium alloy thin-wall component and the structure of the biaxial stretching sample simplified by the component are reasonable.
Further, the method for evaluating the constraint stress of the titanium alloy thin-wall component under the complex load provided by the embodiment of the invention is described in detail below with reference to a specific embodiment.
The selected material of the preset titanium alloy thin-wall component is commercial pure titanium (or Ti-6 Al-4V), and the thickness of the component is 2mm.
Step one, according to the actual service working condition of a preset titanium alloy thin-wall component, the service load of the thin-wall component can be simplified into a tensile biaxial stress with the stress ratio of the main bearing direction to the non-main bearing direction of 2:1, a cross-shaped sample (shown in figure 2) with the same plate thickness as the component is adopted to carry out a biaxial deformation experiment, and an experimental stress strain curve of the main bearing direction is obtained;
step two, cutting a uniaxially stretched dog-bone-shaped sample from a material for a preset titanium alloy thin-wall component, and carrying out a uniaxial stretching experiment to obtain an experimental stress strain curve of the material under uniaxial stress, wherein the result is shown in figure 3;
step three, according to the chemical composition of commercial pure titanium (or Ti-6 Al-4V), consulting literature data to determine the cutting stress critical value tau of each sliding system of titanium alloy alpha phase 0 Saturation value τ ∞ Interactions between slip-slipInteractions between slip-twins>Interaction between twin-twin +.>Model fitting parameter c 1 、c 2 、c 3 、c 4 And the material constitutive parameters. Based on a sliding system and a twin crystal system resistance evolution model, carrying out crystal plasticity simulation trial calculation, comparing a calculation result with the dog-bone-shaped sample experiment obtained in the step two (even if the calculation result is basically consistent with the experimental stress-strain curve obtained in the step two), and modifying and checking the simulation value of the crystal plasticity constitutive parameter obtained in the literature to obtain the actual value of the crystal plasticity constitutive parameter;
step four, based on the actual value of the crystal plasticity constitutive parameter obtained in the step three, modifying the boundary condition of the crystal plasticity simulation to be consistent with the simplified biaxial deformation working condition in the step one, namely, the ratio of the stretching stress in the main bearing direction to the stretching stress in the non-main bearing direction is 2:1,performing crystal plasticity simulation to obtain a simulated stress-strain Curve Curve X (shown in FIG. 5) of the main bearing direction under the boundary condition;
step five, the simulated stress-strain Curve Curve X of the main bearing direction obtained by means of crystal plasticity simulation in step four is subjected to difference value with the experimental stress-strain Curve of the main bearing direction obtained in step one, so that the influence delta sigma (namely constraint stress evolution law, shown as a long Curve in fig. 4) of the non-main bearing direction sample structure on the mechanical property (simulated value) of the main bearing direction is obtained, and delta sigma=f (b, t, epsilon x )；
Step six, based on the evolution law delta sigma=f (b, t, epsilon) of the constraint stress obtained in the step five x ) Evaluating the cause of early cracking of the titanium alloy thin-wall component: since the constraint stress delta sigma is a positive value,and delta sigma is obviously increased along with the increase of the strain quantity, which shows that the experimental value of the mechanical property of the main bearing direction is lower than the simulation value, and the early cracking of the component at the moment is often caused by stress concentration at the local position of the component, so that the design of the titanium alloy component needs to be optimized to avoid the stress concentration of the structure.
In summary, the evaluation method for the constraint stress of the titanium alloy thin-wall component under the complex load provided by the embodiment of the invention can be used for checking the stress strain curve of the main bearing direction of the titanium alloy under the simulated biaxial stress by the crystal plastic model after parameters are checked, determining the mechanical behavior of the titanium alloy under the simulated biaxial stress, comparing the stress strain curve of the main bearing direction of the thin-wall component under the simulated multiaxial stress with the experimental result of an actual component or a structure simplified sample thereof to obtain a difference value, evaluating the constraint stress of the titanium alloy thin-wall component under the complex load, establishing an evolution model of the constraint stress, accurately evaluating the design reliability of the titanium alloy thin-wall component and the possible early cracking reason of the titanium alloy thin-wall component, so as to be convenient for optimizing the design of the titanium alloy component, solving the early cracking problem caused by structural factors and the problem that the mechanical property of the titanium alloy thin-wall component in the main bearing direction is difficult to accurately represent, and further being beneficial to clear the influence of different component structures on the mechanical property representation of the main bearing direction and having important significance for searching the early cracking reason of the titanium alloy component under the complex load.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.
Claims (6)
1. The method for evaluating the constraint stress of the titanium alloy thin-wall component under the complex load is characterized by comprising the following steps of:
step S1, simplifying the actual service condition of a preset titanium alloy thin-wall component into a biaxial deformation experiment of a cross-shaped sample, and carrying out the biaxial deformation experiment to obtain an experimental stress strain curve in a main bearing direction;
s2, cutting a uniaxially stretched dog-bone sample from a material used in the preset titanium alloy thin-wall member, and carrying out a uniaxial stretching experiment on the uniaxially stretched dog-bone sample to obtain an experimental stress strain curve of the uniaxial stretching of the dog-bone sample;
s3, constructing a crystal plastic model of the titanium alloy, acquiring a reference value of a crystal plastic constitutive parameter of the titanium alloy in the preset titanium alloy thin-wall component, and performing crystal plastic simulation trial calculation to obtain a simulation stress strain curve of uniaxial tension;
s4, adjusting a reference value of the crystal plasticity constitutive parameter to enable the uniaxial stretching simulated stress strain curve to be basically matched with the uniaxial stretching experimental stress strain curve of the dog-bone sample, and obtaining an actual value of the crystal plasticity constitutive parameter;
step S5, based on the actual value of the crystal plasticity constitutive parameter, modifying the boundary condition of the crystal plasticity simulation trial calculation to enable the boundary condition to be consistent with the actual service working condition determined in the step S1, and then performing crystal plasticity simulation trial calculation to obtain a simulated stress-strain curve of the main bearing direction;
s6, comparing the simulated stress-strain curve of the main bearing direction with the experimental stress-strain curve of the main bearing direction, wherein the difference value is used as constraint stress which is the influence of a sample structure in a non-main bearing direction on the mechanical property of the main bearing direction;
step S7, evaluating early cracking reasons of the preset titanium alloy thin-wall component according to the constraint stress, wherein the constraint stress evolution rule is as follows:
Δσ＝f(b,t,ε x )
wherein delta sigma is constraint stress, b is arm width of a cross sample, t is thickness of the preset titanium alloy thin-wall component, epsilon x Is the strain amount of plastic deformation in the main bearing direction;
if delta sigma is positive and delta sigma is positively correlated with a variable, the experimental value of the mechanical property of the main bearing direction is lower than the simulation value, and the early cracking of the preset titanium alloy thin-wall component is caused by stress concentration at a local position;
if delta sigma approaches 0, the experimental value of the mechanical property of the main bearing direction approaches to the simulation value, and the design of the preset titanium alloy thin-wall component and the simplified double-shaft deformation working condition thereof are reasonable in structure.
2. The method for evaluating the constraint stress of a titanium alloy thin-walled member under a complex load according to claim 1, wherein the two mutually perpendicular arms in the cross-shaped specimen are maintained to be uniform in structural dimension.
3. The method for evaluating the constraint stress of the titanium alloy thin-wall member under the complex load according to claim 2, wherein any direction of the cross-shaped sample is simplified into stretching or compressing according to the actual service condition of the preset titanium alloy thin-wall member, any direction is controlled by monotonic load or displacement, and the loading process in any direction is synchronous or asynchronous with the loading process in the other direction.
4. The method for evaluating constraint stress of a thin-walled titanium alloy member under a complex load according to claim 3, wherein the strain rate at which plastic deformation occurs in any direction is maintained at 0.0001 to 0.01s when any direction of the cross-shaped specimen is subjected to monotonous load or displacement control -1 Within the range.
5. The method for evaluating constraint stress of a titanium alloy thin-wall component under complex load according to claim 1, wherein the crystal plastic model is a sliding system and twin crystal system resistance evolution model, specifically comprising:
wherein alpha refers to a sliding system, beta refers to a twin crystal system,for the slip-slip interaction +.>c 1 、c 2 、c 3 、c 4 Fitting parameters for the model>As the volume fraction of twin crystal, N s For the number of slip systems, +.>Shear rate of slip system, ζ α′ For the critical value of the slip resistance, +.>Saturation value of slip resistance, N tw For the number of twinning systems>Shear rate for twin system, +.>For the glide-twinning interaction, +.>Is a twinning-twinning interaction.
6. The method for evaluating the constraint stress of a titanium alloy thin-walled member under a complex load according to claim 1 wherein the crystal plasticity constitutive parameters include, but are not limited to, the critical value τ of the shear stress of each sliding system of the titanium alloy alpha phase 0 Saturation value τ ∞ Interactions between slip-slipInteractions between slip-twins>Interaction between twin-twin +.>Model fitting parameter c 1 、c 2 、c 3 、c 4 。
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