Titanium alloy high-temperature flow stress prediction method considering plastic damage

Abstract

The invention belongs to the technical field of titanium alloy hot working stress analysis, and discloses a method and system for predicting high-temperature flow stress and plastic damage behavior of a titanium alloy, and the method comprises the following steps: obtaining true stress-true strain data of the titanium alloy through a high-temperature tensile experiment; establishing a unified constitutive model for predicting the high-temperature flow stress and the plastic damage behavior of the titanium alloy; and determining material parameters of the unified constitutive model for predicting the high-temperature flow stress and the plastic damage evolution behavior of the titanium alloy by utilizing a numerical difference principle and combining true stress-true strain data of the titanium alloy, and predicting the high-temperature flow stress and the plastic damage behavior of the titanium alloy under the conditions of constant temperature and constant strain rate. According to the method, through a titanium alloy high-temperature tensile experiment, a mathematical model for predicting the titanium alloy high-temperature flow stress and the plastic damage behavior is provided based on a dislocation density theory and a damage evolution mechanism, and the influence of plastic damage on the titanium alloy thermal deformation behavior is considered; and rapid and accurate prediction of the high-temperature flow stress and the plastic damage behavior of the titanium alloy under the high-temperature deformation condition is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of titanium alloy hot working stress analysis, and particularly relates to a titanium alloy high-temperature flow stress prediction method considering plastic damage. BACKGROUND

[0002] Currently, in the process of titanium alloy hot working, the hot deformation process of titanium alloy can be generally divided into two stages of elastic deformation and plastic deformation. The elastic deformation stage of titanium alloy can be accurately described by Hooke's law. When the external load exceeds the yield stress of titanium alloy, plastic deformation of titanium alloy begins to occur on a macro scale, and dislocation movement in the interior of titanium alloy occurs on a micro scale. Due to the work hardening behavior caused by the generation and proliferation of dislocations, the true stress of titanium alloy is further increased; with the increase of the degree of deformation, the dynamic recovery process of dislocation annihilation and dislocation rearrangement caused by vacancy diffusion, dislocation slip and climbing begins to occur, and the growth rate of the true stress of titanium alloy slows down. As a typical low stacking fault energy metal, the dynamic recovery mechanisms such as dislocation climbing and cross-slip of titanium alloy occur slowly, and it is difficult to balance with work hardening. With the increase of strain, the dislocation density gradually rises, and when the critical dislocation density for dynamic recrystallization is reached, dynamic recrystallization begins to occur, the dislocation annihilation rate rises significantly, and the flow softening phenomenon is obvious. Finally, the dislocation annihilation rate and the proliferation rate reach a balance, and the true stress of titanium alloy reaches a peak. In the subsequent deformation process, due to the difference in mechanical properties between the beta phase and the alpha phase, the deformation of the alpha phase and the beta phase interface is not coordinated, micro pores and micro cracks are formed, i.e. plastic damage. Studies have shown that the hot deformation behavior of titanium alloy is extremely complex, and is significantly affected by the comprehensive influence of macro hot deformation conditions such as deformation temperature, strain rate and strain, and the influence of micro deformation mechanisms such as work hardening and dynamic recovery. A large number of experimental and theoretical researches have been carried out by many scholars, and a variety of methods for predicting the high-temperature flow stress and plastic damage behavior of titanium alloy have been invented. Among them, the Arrhenius model, the Cingara model and the related modified models can accurately predict the high-temperature flow stress of titanium alloy under ideal hot deformation conditions such as constant temperature and constant strain rate, the Johnson-Cook model, the Gurson-Tvergaard-Needleman model and the related modified models can accurately predict the plastic damage behavior of titanium alloy under ideal hot deformation conditions such as constant temperature and constant strain rate, however, few people have studied the influence of microstructure evolution on damage and fracture behavior, and there is no method based on the physical mechanism of dislocation density to predict the high-temperature flow stress and plastic damage behavior of titanium alloy under the condition of constant temperature and constant strain rate.

[0003] Through the above analysis, the problems and defects of the prior art are that:

[0004] (1) Existing methods for predicting high-temperature flow stress and plastic damage behavior of titanium alloys do not consider the microstructural evolution and its influence on damage evolution, making it difficult to provide guidance for optimizing the process parameters of high-temperature plastic forming of titanium alloys.

[0005] (2) There has been no physical mechanism based on dislocation density at home or abroad that can predict the high-temperature flow stress and plastic damage behavior of titanium alloys under constant temperature and constant strain rate conditions. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a method for predicting the high-temperature flow stress of titanium alloy taking plastic damage into consideration.

[0007] The present invention is achieved as follows: a method for predicting the high-temperature flow stress of titanium alloy taking plastic damage into consideration, the method for predicting the high-temperature flow stress and plastic damage behavior of titanium alloy comprising: performing a high-temperature tensile test on the titanium alloy at a certain deformation temperature and strain rate to obtain true stress-true strain data of the titanium alloy; establishing a functional relationship between titanium alloy parameters and a high-temperature flow stress equation corrected after damage, and constructing a mathematical model for predicting the high-temperature flow stress and plastic damage behavior of titanium alloy; optimizing and solving material parameters using the numerical difference principle to determine the specific values ​​of the material parameters in the mathematical model for predicting the high-temperature flow stress and plastic damage behavior of titanium alloy; updating the thermal deformation parameters and the material parameters affected by the thermal deformation parameters at any iterative step to predict the high-temperature flow stress and plastic damage behavior of the titanium alloy under constant temperature and constant strain rate conditions.

[0008] Furthermore, the method for predicting high temperature flow stress and plastic damage behavior of titanium alloy includes the following steps:

[0009] Step 1: obtain true stress-true strain data of titanium alloy through high temperature tensile test;

[0010] Step 2: Establish a unified constitutive model to predict the high-temperature flow stress and plastic damage behavior of titanium alloys;

[0011] Step 3: Using the numerical difference principle and combining the true stress-true strain data of titanium alloy, determine the material parameters of the unified constitutive model for predicting the high-temperature flow stress and plastic damage evolution behavior of titanium alloy;

[0012] Step 4: Predict the high-temperature flow stress and plastic damage behavior of titanium alloy under constant temperature and constant strain rate conditions.

[0013] Furthermore, in step 1, the deformation temperature is 780℃~900℃ and the strain rate is 0.001s -1 ~1s -1 High temperature tensile test was carried out on titanium alloy under the condition of thermal deformation to obtain the true stress-true strain data of titanium alloy.

[0014] Furthermore, the establishment of a unified constitutive model for predicting high-temperature flow stress and plastic damage behavior of titanium alloys in step 2 includes:

[0015] σ=σ y +σ p +H;

[0016] Where σ is the high temperature flow stress, σ y is the yield stress, σ p represents the plastic stress associated with dislocations, and H is the isotropic hardening stress;

[0017] Establish the yield stress σ of titanium alloy y Deformation temperature T, strain rate The functional relationship between them is:

[0018]

[0019] Among them, A y , Q y and n y are all material constants; R is the universal gas constant, which is 8.314 J / (mol·K); is the strain rate, T is the deformation temperature; according to the deformation conditions of the high temperature tensile test and the true stress-true strain data of the titanium alloy, the yield stress σ of the titanium alloy is established y and temperature T, strain rate The relationship between and lnσ y -1 / T relationship diagram, and determine the material parameter A by linear fitting method y , Q y and n y Specific value of .

[0020] Establish the relationship between dislocation density and induced stress σ in titanium alloys p Functional relationship:

[0021]

[0022] Among them, ρ i is the dislocation density, is the dislocation density evolution rate, M is the Taylor coefficient, α is the dislocation interaction constant, μ is the material shear modulus, and b is the Burgers vector; the dislocation multiplication rate

[0023] f w is the work hardening coefficient, Dislocation annihilation rate due to dynamic recovery f drv is the dynamic restitution coefficient, Dislocation annihilation rate caused by plastic damage f dm is the damage coefficient, A w , A drv , A dm , n sh , n drv , n dm , m dm , Q sh , Q drv and Q dm are material constants.

[0024] The function relationship between the dislocation density of titanium alloy and the hardening stress H caused by evolution is established:

[0025]

[0026] wherein B is a material constant, B=B0exp(Q B / RT), is the equivalent dislocation density,

[0027] ρ0 is the initial dislocation density, and ρ is the dislocation density of the material in the deformation process.

[0028] The function relationship between the volume fraction of β phase of titanium alloy and temperature T is established:

[0029]

[0030] wherein, and are material constants, T β is the β phase transition temperature, and T is the deformation temperature; according to the deformation conditions of high temperature tensile test and the data of the volume fraction of β phase of titanium alloy, the relationship between the volume fraction of β phase f β of titanium alloy and the temperature T is established, the lnf β -(T β -T) relationship diagram is obtained, and the specific values of the material parameters and are determined by the linear fitting method.

[0031] The high temperature flow stress equation considering the damage correction is established:

[0032]

[0033] wherein D is a damage factor, is the damage evolution rate, is the strain rate, ε p is the plastic strain, η1 and d1 are void growth coefficients, η2, η3 and d2 are void nucleation coefficients, η4 is damage self-healing coefficient, η 10 , η 20 , η 30 , η 40 , d 10 , d 20 , m dm , and γ are material constants.

[0034] Further, in step three, the dislocation density increment Δρ i and the stress increment Δσ caused by any small strain increment Δε are respectively expressed as and Δσ = (Mαμbρ i -1 / 2 +Bρ i -1 / 2 )Δρ i / (2(1-D)), an iterative accumulation algorithm program is written, embedded in numerical simulation software, combined with the true stress-true strain data of titanium alloy, and the material parameters A w , A drv , A dm , n sh , n drv , n dm , m dm , Q sh , Q drv , Q dm , η 10 , η 20 , η 30 , η 40 , d 10 , d 20 , m dm , and γ in the mathematical model for predicting the high-temperature rheological stress and plastic damage behavior of titanium alloy are optimized and solved to determine the specific values of the material parameters in the mathematical model.

[0035] Further, in step four, an iterative accumulation algorithm program is written, embedded in numerical simulation software, to realize the update of the thermal deformation parameters and the material parameters affected by the thermal deformation parameters at any iteration step, and further to predict the high-temperature rheological stress and plastic damage behavior of titanium alloy under constant temperature and constant strain rate conditions; wherein the thermal deformation parameters include deformation temperature and strain rate, and the material parameters affected by the thermal deformation parameters include yield stress σ y , work hardening coefficient f w , dynamic recovery coefficient f drv , damage coefficient fdm a cavity growth coefficient η1, d1, a cavity nucleation coefficient η2, η3 and d2, and a damage self-healing coefficient η4.

[0036] Another object of the present application is to provide a system for predicting high-temperature rheological stress and plastic damage behavior of a titanium alloy, which applies the method for predicting high-temperature rheological stress and plastic damage behavior of a titanium alloy.

[0037] A data acquisition module is configured to obtain true stress-true strain data of the titanium alloy through a high-temperature tensile experiment.

[0038] A model construction module is configured to establish a functional relationship between parameters of the titanium alloy and a modified high-temperature flow stress equation after damage, and to construct a mathematical model for predicting high-temperature rheological stress and plastic damage behavior of the titanium alloy.

[0039] A material parameter determination module is configured to optimize and solve material parameters by using a numerical difference principle, and to determine the material parameters in the mathematical model for predicting high-temperature rheological stress and plastic damage behavior of the titanium alloy.

[0040] An iterative updating module is configured to update material parameters affected by hot deformation and hot deformation parameters at any iteration step, and to predict high-temperature rheological stress and plastic damage behavior of the titanium alloy at a constant temperature and a constant strain rate.

[0041] Another object of the present application is to provide a computer device, which comprises a memory and a processor, and the memory stores a computer program.

[0042] Another object of the present application is to provide a computer readable storage medium, which stores a computer program.

[0043] Another object of the present application is to provide an information data processing terminal for implementing the system for predicting high-temperature rheological stress and plastic damage behavior of a titanium alloy.

[0044] In combination with the above technical solutions and solved technical problems, the technical solution to be protected by the present application has the following advantages and positive effects:

[0045] First, in view of the technical problems existing in the prior art and the difficulty in solving the problems, the technical scheme to be protected by the application and the results and data in the research and development process are closely combined, and the technical problems solved by the technical scheme of the application and some creative technical effects brought after the problems are solved are analyzed in detail and profoundly.

[0046] The application provides a method for quickly and accurately predicting high-temperature rheological stress and plastic damage behavior of titanium alloy under constant temperature and constant strain rate, based on the physical mechanism of hot deformation of titanium alloy.

[0047] Second, the technical scheme is regarded as a whole or from the perspective of the product, the technical effects and advantages of the technical scheme to be protected by the application are described in detail as follows:

[0048] The application provides a mathematical model for predicting high-temperature rheological stress and plastic damage behavior of titanium alloy, based on dislocation density theory and damage evolution mechanism, through high-temperature tensile experiments of titanium alloy.

[0049] Third, as the auxiliary evidence for the creativity of the claims of the application, the following important aspects are also embodied:

[0050] The technical scheme of the application overcomes the technical bias: there are complex microstructure evolutions in the hot deformation process of titanium alloy, such as dislocation evolution, DRX and alpha / beta phase transformation, which have a great influence on the damage and flow behavior. Few people study the influence of microstructure evolution on damage behavior, and there is no physical mechanism based on dislocation density at home and abroad. A model combining the damage and microstructure evolution mechanism in the hot tensile process is established. The application establishes a unified constitutive model for predicting the high-temperature rheological stress and plastic damage behavior of titanium alloy. BRIEF DESCRIPTION OF DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0052] Figure 1 is a flow chart of a method for predicting high-temperature flow stress and plastic damage behavior of a titanium alloy provided by the embodiments of the present application;

[0053] Figure 2 is a schematic diagram of a constitutive model optimization process provided by the embodiments of the present application;

[0054] Figure 3A is a linear relationship 1 between a yield stress and a deformation parameter provided by the embodiments of the present application;

[0055] Figure 3B is a linear relationship 2 between a yield stress and a deformation parameter provided by the embodiments of the present application;

[0056] Figure 4A is a comparison diagram of experimental values and calculated values of deformation temperature at 780℃ provided by the embodiments of the present application;

[0057] Figure 4B is a comparison diagram of experimental values and calculated values of deformation temperature at 820℃ provided by the embodiments of the present application;

[0058] Figure 4C is a comparison diagram of experimental values and calculated values of deformation temperature at 860℃ provided by the embodiments of the present application;

[0059] Figure 4D is a comparison diagram of experimental values and calculated values of deformation temperature at 900℃ provided by the embodiments of the present application;

[0060] Figure 5 is a comparison diagram of predicted values and experimental values of a beta phase volume fraction provided by the embodiments of the present application;

[0061] Figure 6A is a damage evolution diagram when deformed at 780℃ at different strain rates provided by the embodiments of the present application;

[0062] Figure 6B is a damage evolution diagram when deformed at 0.1s -1 at different temperatures and different strain rates provided by the embodiments of the present application. DETAILED DESCRIPTION

[0063] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0064] In view of the problems in the prior art, the present application provides a titanium alloy high-temperature rheological stress prediction method considering plastic damage, which is described in detail below with reference to the drawings.

[0065] In order to enable those skilled in the art to have a full understanding of how the present application is specifically implemented, this part is an explanatory description of the embodiments of the technical solutions claimed in the claims.

[0066] As shown in Figure 1 , the method for predicting the high-temperature rheological stress and plastic damage behavior of titanium alloy provided by the embodiments of the present application comprises the following steps:

[0067] S101, performing high-temperature tensile experiments on the titanium alloy at a certain deformation temperature and strain rate to obtain true stress-true strain data of the titanium alloy;

[0068] S102, establishing a functional relationship between titanium alloy parameters and a high-temperature flow stress equation after damage correction, and constructing a mathematical model for predicting the high-temperature rheological stress and plastic damage behavior of titanium alloy;

[0069] S103, using the numerical difference principle to optimize and solve the material parameters to determine the specific values of the material parameters in the mathematical model for predicting the high-temperature rheological stress and plastic damage behavior of titanium alloy;

[0070] S104, updating the thermal deformation parameters and the material parameters affected by the thermal deformation parameters at any iteration step to predict the high-temperature rheological stress and plastic damage behavior of titanium alloy at a constant temperature and strain rate.

[0071] As a preferred embodiment, the method for predicting the high-temperature rheological stress and plastic damage behavior of titanium alloy provided by the embodiments of the present application specifically comprises the following steps:

[0072] Step 1: performing high-temperature tensile experiments on the titanium alloy under thermal deformation conditions of a deformation temperature of 780℃-900℃ and a strain rate of 0.001s -1 -1s -1 to obtain true stress-true strain data of the titanium alloy.

[0073] Step 2: establishing a unified constitutive model for predicting the high-temperature rheological stress and plastic damage behavior of titanium alloy:

[0074] σ=σ y +σ p +H(1)

[0075] where σ is the high-temperature rheological stress, σ y is the yield stress, σ p represents the plastic stress associated with dislocations, H is the isotropic hardening stress.

[0076] The yield stress σ y of the titanium alloy is established as a function of the deformation temperature T and the strain rate :

[0077]

[0078] where A y , Q y and n y are material constants, R is the universal gas constant (8.314 J / (mol·K)), is the strain rate, and T is the deformation temperature; the yield stress σ y of the titanium alloy is established as a function of the deformation temperature T and the strain rate , i.e. and lnσ y -1 / T, and the specific values of the material parameters A y , Q y and n y are determined by linear fitting.

[0079] The function relationship between the dislocation density and the stress σ p caused by the dislocation density is established as follows:

[0080]

[0081] where ρ i is the dislocation density, is the dislocation density evolution rate, M is the Taylor coefficient, α is the dislocation interaction constant, μ is the material shear modulus, and b is the Burgers vector; the dislocation multiplication rate

[0082] f w is the work hardening coefficient, the dislocation annihilation rate caused by dynamic recovery f drv is the dynamic recovery coefficient, the dislocation annihilation rate caused by plastic damage f dm is the damage coefficient, A w , A drv , A dm , n sh , n drv, n dm , m dm , Q sh , Q drv and Q dm are material constants.

[0083] The function relationship between the dislocation density of titanium alloy and the hardening stress H caused by its evolution is established:

[0084]

[0085] wherein B is a material constant, B=B0exp(Q B / RT), is the equivalent dislocation density,

[0086] ρ0 is the initial dislocation density, and ρ is the dislocation density of the material in the deformation process.

[0087] The function relationship between the volume fraction of β phase of titanium alloy and temperature T is established:

[0088]

[0089] wherein, and are material constants, T β is the β phase transition temperature, and T is the deformation temperature; according to the deformation conditions of high temperature tensile test and the data of the volume fraction of β phase of titanium alloy, the relationship between the volume fraction f β of β phase of titanium alloy and the temperature T is established, that is, the lnf β -(T β -T) relationship diagram, and the specific values of the material parameters and are determined by the linear fitting method.

[0090] The high temperature flow stress equation considering the damage post-modification is established:

[0091]

[0092] wherein D is a damage factor, is the damage evolution rate, is the strain rate, ε p is the plastic strain, η1 and d1 are cavity growth coefficients, η2, η3 and d2 are cavity nucleation coefficients, η4 is a damage self-healing coefficient, η 10 , η 20 , η 30 , η 40 , d 10 , d20 , m dm , and γ are material constants.

[0093] Step 3: Using the numerical difference principle, the dislocation density increment Δρ caused by any small strain increment Δε is converted to i and stress Δσ are expressed as and Δσ=(Mαμbρ i -1 / 2 +Bρ i -1 / 2 )Δρ i / (2(1-D)), write an iterative accumulation algorithm program, embed it into the numerical simulation software, combine the true stress-true strain data of titanium alloy, and calculate the material parameter A of the unified constitutive model for predicting the high-temperature flow stress and plastic damage behavior of titanium alloy. w , A drv , A dm , n sh , n drv , n dm , m dm , Q sh , Q drv , Q dm , η 10 , η 20 , η 30 , η 40 , d 10 , d 20 , m dm , The specific values ​​of the material parameters in the mathematical model for predicting the high-temperature flow stress and plastic damage behavior of titanium alloys are determined by optimizing γ.

[0094] Step 4: Using the numerical difference principle, write an iterative accumulation algorithm program and embed it into the numerical simulation software to update the thermal deformation parameters and the material parameters affected by the thermal deformation parameters at any iteration step, and then predict the high-temperature flow stress and plastic damage behavior of titanium alloy under constant temperature and constant strain rate conditions. The thermal deformation parameters include deformation temperature and strain rate, and the material parameters affected by the thermal deformation parameters include yield stress σ y , work hardening coefficient f w , dynamic recovery coefficient f drv , damage coefficient f dm , void growth coefficient η1, d1, void nucleation coefficient η2, η3 and d2, damage self-healing coefficient η4.

[0095] The system for predicting high-temperature flow stress and plastic damage behavior of titanium alloy provided by an embodiment of the present invention includes:

[0096] The data acquisition module is configured to obtain true stress-true strain data of the titanium alloy through a high-temperature tensile experiment.

[0097] The model construction module is configured to establish a functional relationship between titanium alloy parameters and a modified high-temperature flow stress equation after damage, and to construct a mathematical model for predicting high-temperature flow stress and plastic damage behavior of the titanium alloy.

[0098] The material parameter determination module is configured to optimize and solve the material parameters by using a numerical difference principle, and to determine the material parameters in the mathematical model for predicting high-temperature flow stress and plastic damage behavior of the titanium alloy.

[0099] The iterative updating module is configured to update the material parameters affected by the hot deformation and the heated deformation parameters at any iteration step, and to predict high-temperature flow stress and plastic damage behavior of the titanium alloy at a constant temperature and a constant strain rate.

[0100] The present application proposes a mathematical model for predicting high-temperature flow stress and plastic damage behavior of the titanium alloy by means of a high-temperature tensile experiment of the titanium alloy, based on dislocation density theory and damage evolution mechanism, fully considers the influence of plastic damage on the hot deformation behavior of the titanium alloy, and realizes rapid and accurate prediction of high-temperature flow stress and plastic damage behavior of the titanium alloy under high-temperature deformation conditions.

[0101] The method for predicting high-temperature flow stress and plastic damage behavior of the titanium alloy fully considers the influence of plastic damage on the hot deformation behavior of the titanium alloy, realizes rapid and accurate prediction of high-temperature flow stress and plastic damage behavior of the titanium alloy under high-temperature deformation conditions, can be applied to industrial actual hot working processes under high-temperature deformation conditions, and solves the drawbacks of narrow application range and difficulty in engineering application of the existing prediction methods. The invention and popularization of the method have important significance for reasonably formulating the hot working process of the titanium alloy.

[0102] In order to prove the creativity and technical value of the technical scheme of the present application, this part is an application embodiment of the technical scheme of the claim on a specific product or related technology.

[0103] The unified constitutive model for predicting high-temperature flow stress and plastic damage behavior of the titanium alloy established by the present application establishes a finite element model based on the unified constitutive model of the dislocation density, which is used to predict deformation and damage evolution in the hot tensile test process. The accuracy of the constitutive model is verified by comparing the experimental results with the predicted results. The established constitutive model can accurately predict the softening mechanism and damage evolution process of the material, and provides a theoretical basis for numerical simulation of the hot forming process. Especially, it provides a theoretical basis for the coordinated control of titanium alloy hot forming deformation and performance. On this basis, the hot forming process parameter optimization method is studied, the optimized process window is established, and the temperature and strain rate collaborative control method is created. Finally, the corresponding theoretical and method system is preliminarily established through actual part application verification.

[0104] The present application has achieved some positive effects in research and development or use, and has great advantages compared with the prior art, which will be described below in combination with data and graphs of the test process.

[0105] The present application is a method for predicting high-temperature flow stress and plastic damage behavior of titanium alloy, and the following will take the prediction of high-temperature flow stress and plastic damage behavior of TC4 titanium alloy (typical titanium alloy) as an example to introduce the specific implementation details of the prediction method involved in the present application, and the method comprises:

[0106] Step 1: high-temperature tensile test is performed on the TC4 titanium alloy, the deformation temperature is 780℃, 820℃, 860℃ and 900℃ respectively, and the strain rate is 0.001s -1 , 0.01s -1 , 0.1s -1 and 1s -1 .

[0107] Step 2: a unified constitutive model for predicting high-temperature flow stress and plastic damage behavior of titanium alloy is established: σ = σ y + σ p + H; wherein σ is the high-temperature flow stress, σ y is the yield stress, σ p represents the plastic stress related to dislocation, and H is the isotropic hardening stress. The linear relationship between the yield stress and the deformation parameters provided by the embodiment of the present application is shown in Figures 3A-3B .

[0108] The function relationship between the yield stress σ y of the titanium alloy and the deformation temperature T and the strain rate is established:

[0109]

[0110] wherein A y , Q y and n y are all material constants, R is the universal gas constant (8.314 J / (mol·K)), is the strain rate, and T is the deformation temperature; the yield stress of the TC4 titanium alloy can be measured by the 0.2% strain compensation method using the deformation conditions of the high-temperature tensile test and the true stress-true strain data of the titanium alloy. According to the true stress-true strain data of the TC4 titanium alloy, the relationship graph between the yield stress σ y and the deformation temperature T and the strain rate is drawn, that is, the graph of σ y -1 / T. By the linear fitting method, the linear relationship between the yield stress σ y and the deformation temperature T and the strain rate and lnσ y Regression of data in 1 / T plot to determine material parameter A y , Q y and n y The specific values of A, Q and n are 0.0884, 1.821x10 5 J / mol and 0.405, respectively. Thus the relationship between yield stress σ y and temperature T, strain rate can be expressed as:

[0111]

[0112] The function relationship between dislocation density and stress σ p induced by dislocation density is established:

[0113]

[0114] where ρ i is dislocation density, the initial dislocation density is set as 1x10 12 m -2 , is the evolution rate of dislocation density, M is Taylor coefficient, equal to 3.06, α is dislocation interaction constant, equal to 0.3; μ is material shear modulus, which is significantly related to temperature, the relationship with temperature T can be expressed as μ(T) = 49.02-5.821 / (exp(181 / T)-1); b is Burgers vector (2.95x10 -10 m -1 for α phase, 2.86x10 -10 m -1 for β phase); dislocation proliferation rate f w is work hardening coefficient, dislocation annihilation rate caused by dynamic recovery f drv is dynamic recovery coefficient, dislocation annihilation rate caused by plastic damage f dm is damage coefficient, A w , A drv , A dm , n sh , n drv , n dm , m dm , Q sh , Q drv and Q dm are all material constants.

[0115] The function relationship between the dislocation density of titanium alloy and the hardening stress H caused by its evolution is established:

[0116]

[0117] wherein B is a material constant, B=B0exp(Q B / RT), is the equivalent dislocation density,

[0118] ρ0 is the initial dislocation density, and the initial dislocation density is set to 1×10 12 m -2 ; ρ is the dislocation density of the material in the deformation process.

[0119] The function relationship between the volume fraction of β phase of titanium alloy and temperature T is established:

[0120]

[0121] wherein and are material constants, T β is the β phase transition temperature, about 1263K; T is the deformation temperature; the image processing software Image-ProPlus is used to mark the β phase and measure the volume fraction of TC4 titanium alloy. According to the β phase volume fraction data of TC4 titanium alloy, the relationship diagram between the β phase volume fraction f β and the temperature T is drawn, that is, the lnf β -(T β -T) relationship diagram. Through the linear fitting method, the data in the lnf β -(T β -T) relationship diagram is linearly regressed to determine the specific values of the material parameters and , which are 0.9348 and 9.39×10 -3 respectively. Therefore, the relationship between the β phase volume fraction and the temperature T can be expressed as f β =0.9348exp(-9.39×10 -3 (T β -T)).

[0122] The high-temperature flow stress equation considering the damage correction is established:

[0123]

[0124] wherein D is a damage factor, is a damage evolution rate, is a strain rate, ε p is a plastic strain, η1 and d1 are cavity growth coefficients, η2, η3 and d2 are void nucleation coefficients, η4 is damage self-healing coefficient, η 10 , η 20 , η 30 , η 40 , d 10 , d 20 , m dm , and γ are material constants.

[0125] Step 3: Using the numerical difference principle, the dislocation density increment Δρ i and the stress increment Δσ caused by any small strain increment Δε are respectively expressed as and Δσ = (Mαμbρ i -1 / 2 +Bρ i -1 / 2 )Δρ i / (2(1-D)), an iterative accumulation algorithm program is written, embedded in the numerical simulation software, combined with the true stress-true strain data of TC4 titanium alloy, and optimized to determine the material parameters A w , A drv , A dm , n sh , n drv , n dm , m dm , Q sh , Q drv , Q dm , η 10 , η 20 , η 30 , η 40 , d 10 , d 20 , m dm , and γ, as shown in Table 1. The optimization process is shown in Figure 2 .

[0126] Table 1 The optimized TC4 titanium alloy constitutive model parameter values

[0127]

[0128] Step 4: An iterative accumulation algorithm program is written by using the numerical difference principle, embedded in the numerical simulation software, to realize the update of the hot deformation parameters including the deformation temperature and the strain rate and the material parameters affected by the hot deformation parameters including the yield stress σ y , the work hardening coefficient f w , the dynamic recovery coefficient f drv , the damage coefficient f dm , the void growth coefficient η1, d1, the void nucleation coefficient η2, η3 and d2, and the damage self-healing coefficient η4 at any iteration step, and then the high-temperature flow stress and plastic damage behavior of the titanium alloy at constant temperature and constant strain rate are predicted.

[0129] Figures 4A-4D The prediction results of the high-temperature flow stress and plastic damage behavior of the TC4 titanium alloy at constant temperature and constant strain rate are shown in the figure; Figure 5 The prediction results of the β phase volume fraction at different temperatures are shown in the figure; Figures 6A-6B The prediction results of the damage factor are shown in the figure. It can be found from the figure that the predicted values of the true stress-true strain and the predicted values of the β phase volume fraction at different temperatures are in good agreement with the experimental values, which indicates that the method of the application can accurately predict the high-temperature flow stress and plastic damage behavior of the TC4 titanium alloy.

[0130] It should be noted that the embodiments of the application can be realized by hardware, software or a combination of software and hardware. The hardware part can be realized by special logic; the software part can be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or a specially designed hardware. Those skilled in the art can understand that the above-mentioned devices and methods can be realized by computer executable instructions and / or included in processor control code, such as provided on a carrier medium, such as a magnetic disk, CD or DVD-ROM, a programmable memory, such as a read-only memory (firmware), or a data carrier, such as an optical or electronic signal carrier. The devices of the application and their modules can be realized by hardware circuits, such as very large scale integrated circuits or gate arrays, semiconductors, such as logic chips, transistors, or programmable hardware devices, such as field programmable gate arrays, programmable logic devices, etc. They can also be realized by software executed by various types of processors, or by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0131] The above is only a specific embodiment of the application, but the protection scope of the application is not limited thereto, and any modification, equivalent replacement and improvement made by those skilled in the art within the technical range disclosed by the application, as long as it is within the spirit and principles of the application, should be covered within the protection scope of the application.

Claims

1. A method for predicting high-temperature flow stress and plastic damage behavior of titanium alloy, characterized in that: High-temperature tensile tests were conducted on titanium alloys at certain deformation temperatures and strain rates to obtain true stress-true strain data. Functional relationships between titanium alloy parameters and a post-damage corrected high-temperature flow stress equation were established to construct a mathematical model for predicting high-temperature flow stress and plastic damage behavior of titanium alloys. The material parameters are optimized and solved using the numerical difference principle to determine the specific values ​​of the material parameters in the mathematical model for predicting the high-temperature flow stress and plastic damage behavior of titanium alloys. The thermal deformation parameters and material parameters affected by the thermal deformation parameters are updated at any iteration step to predict the high-temperature flow stress and plastic damage behavior of titanium alloys at constant temperature and constant strain rate. The method for predicting high-temperature flow stress and plastic damage behavior of titanium alloys includes the following steps: Step 1: obtain the true stress-true strain data of titanium alloy through high temperature tensile test; at deformation temperature of 780℃~900℃ and strain rate of 0.001s -1 ~1s -1 High temperature tensile test was carried out on titanium alloy under the condition of thermal deformation to obtain true stress-true strain data of titanium alloy; Step 2: Establish a unified constitutive model to predict the high-temperature flow stress and plastic damage behavior of titanium alloys; Step 3: Using the numerical difference principle and combining the true stress-true strain data of titanium alloy, determine the material parameters of the unified constitutive model for predicting the high-temperature flow stress and plastic damage evolution behavior of titanium alloy; Step 4: Predict the high-temperature flow stress and plastic damage behavior of titanium alloy under constant temperature and constant strain rate conditions.

2. The method for predicting high-temperature flow stress and plastic damage behavior of titanium alloy according to claim 1, characterized in that: The establishment of a unified constitutive model for predicting high-temperature flow stress and plastic damage behavior of titanium alloys in step 2 includes: s = s y +s p +H; Where σ is the high temperature flow stress, σ y is the yield stress, σ p represents the plastic stress associated with dislocations, and H is the isotropic hardening stress.

3. The method for predicting high-temperature flow stress and plastic damage behavior of titanium alloy according to claim 2, characterized in that: Establish the yield stress σ of titanium alloy y Deformation temperature T, strain rate The functional relationship between them is: Among them, A y , Q y and n y are all material constants; R is the universal gas constant, which is 8.314 J / (mol·K); is the strain rate, T is the deformation temperature; according to the deformation conditions of the high temperature tensile test and the true stress-true strain data of the titanium alloy, the yield stress σ of the titanium alloy is established y and temperature T, strain rate The relationship between and lnσ y -1 / T relationship diagram, and determine the material parameter A by linear fitting method y , Q y and n y Specific value of Establish the relationship between dislocation density and induced stress σ in titanium alloys p Functional relationship: Among them, ρ i is the dislocation density, is the dislocation density evolution rate, M is the Taylor coefficient, α is the dislocation interaction constant, μ is the material shear modulus, and b is the Burgers vector; the dislocation multiplication rate f w is the work hardening coefficient, Dislocation annihilation rate due to dynamic recovery f drv is the dynamic restitution coefficient, Dislocation annihilation rate caused by plastic damage f dm is the damage coefficient, A w , A drv , A dm , n sh , n drv , n dm , m dm , Q sh , Q drv and Q dm is the material constant; The functional relationship between the dislocation density of titanium alloy and the hardening stress H caused by evolution is established: Where B is the material constant, B=B0exp(Q B / RT), is the equivalent dislocation density, ρ0 is the initial dislocation density, and ρ is the dislocation density of the material during deformation.

4. The method for predicting high-temperature flow stress and plastic damage behavior of titanium alloy according to claim 3, characterized in that: The functional relationship between the volume fraction of β phase in titanium alloy and temperature T is established: in, and are all material constants, T β is the β phase transformation temperature, T is the deformation temperature; according to the deformation conditions of the high temperature tensile test and the β phase volume fraction data of titanium alloy, the β phase volume fraction f of titanium alloy is established. β and the relationship between the variable temperature T, we can get lnf β -(T β -T) relationship diagram, and determine the material parameters by linear fitting method and Specific value of Establish the high temperature flow stress equation after considering the correction of damage: Where D is the damage factor, is the damage evolution rate, is the strain rate, ε p is the plastic strain, η1 and d1 are the void growth coefficients, η2, η3 and d2 are the void nucleation coefficients, η4 is the damage self-healing coefficient, η 10 , η 20 , η 30 , η 40 , d 10 , d 20 , m dm , and γ are material constants.

5. The method for predicting high-temperature flow stress and plastic damage behavior of titanium alloy according to claim 2, characterized in that: In step 3, the numerical difference principle is used to convert the dislocation density increment Δρ caused by any small strain increment Δε into i and stress Δσ are expressed as and Δσ=(Mαμbρ i -1 / 2 +Bρ i -1 / 2 )Δρ i / (2(1-D)), write an iterative accumulation algorithm program, embed it into the numerical simulation software, combine the true stress-true strain data of titanium alloy, and calculate the material parameter A of the unified constitutive model for predicting the high-temperature flow stress and plastic damage behavior of titanium alloy. w 、A drv 、A dm 、n sh 、n drv 、n dm 、m dm , Q sh , Q drv , Q dm ,η 10 ,η 20 ,η 30 ,η 40 d 10 d 20 、m dm 、 The specific values ​​of the material parameters in the mathematical model for predicting the high-temperature flow stress and plastic damage behavior of titanium alloys are determined by optimizing γ.

6. The method for predicting high-temperature flow stress and plastic damage behavior of titanium alloy according to claim 2, characterized in that: In step 4, the numerical difference principle is used to write an iterative accumulation algorithm program, which is embedded in the numerical simulation software to update the thermal deformation parameters and the material parameters affected by the thermal deformation parameters at any iteration step, and then predict the high-temperature flow stress and plastic damage behavior of the constant temperature and constant strain rate titanium alloy; among them, the thermal deformation parameters include deformation temperature and strain rate, and the material parameters affected by the thermal deformation parameters include yield stress σ y , work hardening coefficient f w , dynamic recovery coefficient f drv , damage coefficient f dm , void growth coefficient η1, d1, void nucleation coefficient η2, η3 and d2, damage self-healing coefficient η4.

7. A system for predicting high-temperature flow stress and plastic damage behavior of titanium alloys using the method for predicting high-temperature flow stress and plastic damage behavior of titanium alloys according to any one of claims 1 to 6, characterized in that: The system for predicting high temperature flow stress and plastic damage behavior of titanium alloys includes: Data acquisition module, used to obtain true stress-true strain data of titanium alloy through high temperature tensile test; Model building module, used to establish the functional relationship between titanium alloy parameters and the high-temperature flow stress equation corrected after damage, and to build a mathematical model for predicting the high-temperature flow stress and plastic damage behavior of titanium alloys; The material parameter determination module is used to optimize and solve the material parameters using the numerical difference principle to determine the material parameters in the mathematical model for predicting the high-temperature flow stress and plastic damage behavior of titanium alloys; The iterative update module is used to update the thermal deformation and material parameters affected by the thermal deformation parameters at any iteration step, and predict the high-temperature flow stress and plastic damage behavior of the constant temperature and constant strain rate titanium alloy.

8. A computer device, characterized in that: The computer device includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method for predicting high-temperature flow stress and plastic damage behavior of titanium alloy as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method for predicting high-temperature flow stress and plastic damage behavior of titanium alloy according to any one of claims 1 to 6.

10. An information data processing terminal, characterized in that: The information data processing terminal is used to implement the system for predicting high-temperature flow stress and plastic damage behavior of titanium alloy as described in claim 7.

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