A linear stress combination ductile fracture identification method, device, computer storage medium and equipment considering hydrostatic stress strengthening are provided

Abstract

The application discloses a linear stress combination ductile fracture identification method considering hydrostatic stress strengthening, comprising the following steps: calculating local principal stresses of a to-be-predicted ductile fracture body; calculating stress invariants and Mises equivalent stresses of the to-be-predicted ductile fracture body based on the local principal stresses; calculating a stress state parameter of the to-be-predicted ductile fracture body based on the stress invariants; converting the local principal stresses to the stress state parameter space based on the Mises equivalent stresses and the stress state parameter; adding a hydrostatic stress strengthening term to a Mohr-Coulomb model; converting the Mohr-Coulomb model with the hydrostatic stress strengthening to a stress-stress state parameter space to obtain a linear stress combination ductile fracture identification model considering the hydrostatic stress strengthening. The application expands the application range of the Mohr-Coulomb model, and can more accurately and stably predict alloy ductile fracture than the Mohr-Coulomb model.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ductile fracture identification, in particular, and especially relates to a stress linear combination ductile fracture identification method considering hydrostatic stress strengthening, a device, a computer storage medium and equipment. BACKGROUND

[0002] Ductile alloy materials are widely used in civil engineering, aerospace and nuclear power fields, and the accurate prediction of ductile fracture of alloy materials is a key problem related to the ultimate state of components and structures. For brittle alloy materials, the Mohr-Coulomb model is widely used, and for some ductile alloy materials, the Mohr-Coulomb model has certain efficacy. The Mohr-Coulomb model assumes that the material fails when the linear combination of the maximum shear stress and the normal stress on its shear stress plane reaches a critical value, and in the principal stress space, it has the following mathematical form:

[0003] (σ1-σ3)+c(σ1+σ3)=b

[0004] In the formula, σ1 and σ3 are the first and third principal stresses; c and b are material parameters.

[0005] However, studies have shown that the Mohr-Coulomb model has a large error in predicting ductile fracture in the high stress triaxiality interval. SUMMARY

[0006] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a linear stress combination ductile fracture identification method considering hydrostatic stress strengthening, aiming to improve the adaptability range of the Mohr-Coulomb model and solve the problem of large error in predicting ductile fracture in the high stress triaxiality interval of the Mohr-Coulomb model.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a linear stress combination ductile fracture identification method considering hydrostatic stress strengthening, comprising the following steps:

[0009] Calculate the local principal stress of the ductile fracture body to be predicted;

[0010] Based on the local principal stress of the ductile fracture body to be predicted, calculate the stress invariant of the ductile fracture body to be predicted;

[0011] Based on the local principal stress of the ductile fracture body to be predicted, calculate the Mises equivalent stress of the ductile fracture body to be predicted:

[0012] calculating a stress state parameter of the ductile fracture body to be predicted based on a stress invariant of the ductile fracture body to be predicted;

[0013] converting local principal stresses of the ductile fracture body to be predicted to a stress state parameter space based on a Mises equivalent stress and the stress state parameter of the ductile fracture body to be predicted;

[0014] adding a hydrostatic stress strengthening term to a Mohr-Coulomb model to establish a hydrostatic stress strengthened Mohr-Coulomb model;

[0015] converting the hydrostatic stress strengthened Mohr-Coulomb model to a stress-stress state parameter space based on the local principal stresses of the ductile fracture body to be predicted converted to the stress state parameter space, to obtain a linear stress combination ductile fracture identification model considering hydrostatic stress strengthening, i.e. to predict a fracture trajectory of the ductile fracture body to be predicted.

[0016] As preferred: the stress invariant of the ductile fracture body to be predicted is calculated by the following formula:

[0017] I1=σ1+σ2+σ3

[0018]

[0019] In the formula, I1, J2 and J3 are respectively the first, second and third stress invariants of the ductile fracture body to be predicted; σ1, σ2 and σ3 are respectively the first, second and third local principal stresses of the ductile fracture body to be predicted.

[0020] As preferred: the Mises equivalent stress of the ductile fracture body to be predicted is calculated by the following formula:

[0021]

[0022] In the formula, σ eq is the Mises equivalent stress of the ductile fracture body to be predicted.

[0023] As preferred: the stress state parameter of the ductile fracture body to be predicted includes a stress triaxiality and a Lode angle parameter, and is calculated by the following formula:

[0024]

[0025] In the formula, η is the stress triaxiality; ξ is the Lode angle parameter.

[0026] As preferred: the expression of the local principal stresses of the ductile fracture body to be predicted converted to the stress state parameter space is as follows:

[0027] σ1=σ eq (η+f1)

[0028] σ2 = σ eq (η + f2)

[0029] σ3 = σ eq (η + f3)

[0030] wherein,

[0031]

[0032] wherein, f1, f2 and f3 are intermediate parameters.

[0033] As a preferred: the hydrostatic stress enhanced Mohr-Coulomb model:

[0034] (σ1-σ3) + c1(σ1+σ3) + c2<η-η0> = c3

[0035] wherein, c1, c2 and c3 are material constants; η0 is a reference stress triaxiality; <x>For the piecewise function, when x > 0, <x>= x, else <x>= 0.

[0036] As preferred: the expression of the linear stress combination ductile fracture identification model considering hydrostatic stress strengthening is as follows:

[0037]

[0038] In the formula, σ eq is the Mises equivalent stress of the body to be predicted for ductile fracture.

[0039] In a second aspect, the application provides a linear stress combination ductile fracture identification device considering hydrostatic stress strengthening, comprising:

[0040] A first processing unit is configured to calculate the local principal stress of the body to be predicted for ductile fracture.

[0041] A second processing unit is configured to calculate the stress invariant of the body to be predicted for ductile fracture based on the local principal stress of the body to be predicted for ductile fracture.

[0042] A third processing unit is configured to calculate the Mises equivalent stress of the body to be predicted for ductile fracture based on the local principal stress of the body to be predicted for ductile fracture.

[0043] A fourth processing unit is configured to calculate the stress state parameter of the body to be predicted for ductile fracture based on the stress invariant of the body to be predicted for ductile fracture.

[0044] A fifth processing unit is configured to convert the local principal stress of the body to be predicted for ductile fracture to the stress state parameter space based on the Mises equivalent stress and the stress state parameter of the body to be predicted for ductile fracture.

[0045] A sixth processing unit is configured to add a hydrostatic stress strengthening term to the Mohr-Coulomb model to establish a hydrostatic stress strengthened Mohr-Coulomb model.

[0046] A seventh processing unit is configured to convert the hydrostatic stress strengthened Mohr-Coulomb model to the stress-stress state parameter space based on the local principal stress of the body to be predicted for ductile fracture converted to the stress state parameter space, to obtain a linear stress combination ductile fracture identification model considering hydrostatic stress strengthening, so as to predict the fracture trajectory of the body to be predicted for ductile fracture.

[0047] In a third aspect, the application provides a computer readable storage medium storing a computer program, wherein the computer program is executed by a processor to control the device where the processor is located to implement the steps of the linear stress combination ductile fracture identification method of the first aspect of the application.

[0048] In a fourth aspect, the present application provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, wherein the processor implements the steps of the linear stress combination ductile fracture identification method according to the first aspect of the present application when executing the computer program.

[0049] The present application has the following advantages due to the above technical solutions:

[0050] The average value of the absolute value of the relative error of the ductile fracture identification model is reduced by 3% compared with the Mohr-Coulomb model. Moreover, the absolute value of the maximum relative error of the present application is reduced by not less than 5% compared with the Mohr-Coulomb model, which can effectively reduce the fracture prediction error of the high stress triaxial stress state.

[0051] In summary, the ductile fracture identification model of the present application expands the application range of the Mohr-Coulomb model, and can more accurately and stably predict the ductile fracture of the alloy than the Mohr-Coulomb model. BRIEF DESCRIPTION OF DRAWINGS

[0052] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not intended to limit the scope of the present application. Throughout the drawings, like reference numerals will be used to refer to like components. In the drawings:

[0053] Figure 1 A flowchart of the stress linear combination ductile fracture identification method according to the embodiments of the present application. DETAILED DESCRIPTION

[0054] In order to make the objectives, technical solutions and advantages of the present application clearer, the specific embodiments of the present application will be further described below with reference to the accompanying drawings. Although the exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0055] The application provides a linear stress combination ductile fracture identification method considering hydrostatic stress strengthening, which comprises the following steps: calculating local principal stresses of a body to be predicted for ductile fracture; calculating stress invariants and Mises equivalent stresses of the body to be predicted for ductile fracture based on the local principal stresses; calculating stress state parameters of the body to be predicted for ductile fracture based on the stress invariants; converting the local principal stresses to the stress state parameter space based on the Mises equivalent stresses and the stress state parameters; adding a hydrostatic stress strengthening term to a Mohr-Coulomb model; converting the Mohr-Coulomb model considering hydrostatic stress strengthening to a stress-stress state parameter space to obtain a linear stress combination ductile fracture identification model considering hydrostatic stress strengthening. The application expands the application range of the Mohr-Coulomb model and can more accurately and stably predict alloy ductile fracture than the Mohr-Coulomb model.

[0056] The linear stress combination ductile fracture identification method and device considering hydrostatic stress strengthening provided by the embodiments of the application are described in detail below with reference to the drawings.

[0057] Please refer to Figure 1 The linear stress combination ductile fracture identification method considering hydrostatic stress strengthening provided by the embodiments of the application comprises the following steps:

[0058] S1, calculating local principal stresses of a body to be predicted for ductile fracture, wherein the local principal stresses of the body to be predicted for ductile fracture of a simple component and structure can be solved by an analytical method, and the local principal stresses of the body to be predicted for ductile fracture of a complex component and structure can be solved by a finite element method. Since both belong to the common knowledge of those skilled in the art, they are not described in detail.

[0059] S2, calculating stress invariants of the body to be predicted for ductile fracture according to the local principal stresses of the body to be predicted for ductile fracture obtained in step S1 by the following formula:

[0060] I1=σ1+σ2+σ3

[0061]

[0062] In the formula, I1, J2 and J3 are respectively the first, second and third stress invariants of the body to be predicted for ductile fracture; and σ1, σ2 and σ3 are respectively the first, second and third local principal stresses of the body to be predicted for ductile fracture.

[0063] S3, calculating Mises equivalent stresses of the body to be predicted for ductile fracture according to the local principal stresses of the body to be predicted for ductile fracture by the following formula:

[0064]

[0065] In the formula, σ eq Mises equivalent stress of the ductile fracture body to be predicted.

[0066] S4, calculating stress state parameters of the ductile fracture body to be predicted, including stress triaxiality and Lode angle parameter, by the following formula according to the stress invariant of the ductile fracture body to be predicted:

[0067]

[0068] In the formula, η is stress triaxiality; ξ is Lode angle parameter.

[0069] S5, converting local principal stresses of the ductile fracture body to be predicted to stress state parameter space based on the Mises equivalent stress of the ductile fracture body to be predicted obtained in step S3 and the stress state parameters obtained in step S4:

[0070] σ1=σ eq (η+f1)

[0071] σ2=σ eq (η+f2)

[0072] σ3=σ eq (η+f3)

[0073] wherein,

[0074]

[0075]

[0076] S6, adding a hydrostatic stress strengthening term to the Mohr-Coulomb model to establish a hydrostatic stress strengthened Mohr-Coulomb model as follows:

[0077] (σ1-σ3)+c1(σ1+σ3)+c2<η-η0>=c3

[0078] In the formula, c1, c2 and c3 are material constants; η0 is a reference stress triaxiality, which is also a material constant; <x>For the piecewise function, when x > 0, <x>= x, else <x>= 0.

[0079] S7, based on the local principal stress of the ductile fracture body to be predicted converted to the stress state parameter space, the hydrostatic stress enhanced Mohr-Coulomb model is converted to the stress-stress state parameter space, and a linear stress combination ductile fracture identification model considering hydrostatic stress enhancement is obtained, that is, the fracture trajectory of the ductile fracture body to be predicted can be predicted, wherein the expression of the linear stress combination ductile fracture identification model is as follows:

[0080]

[0081] Next, in order to embody the effect of the method of the present application, the present application verifies the effectiveness of the ductile fracture criterion by using the fracture test data of Al 2024-T351 aluminum alloy and X80 pipeline steel, and the data are listed in Table 1 and Table 2. Since the number of test data is relatively sufficient, the least square method is used to minimize the average value of the absolute value of the relative error, and the model calibration results are shown in Table 3. The absolute value of the relative error is defined as follows:

[0082]

[0083] In the formula, and are the predicted and experimental Mises equivalent stress respectively; N is the number of experimental samples.

[0084] Table 1 Fracture test data of Al 2024-T351 aluminum alloy

[0085]

[0086]

[0087] Table 2 Ductile fracture test data of X80 pipeline steel

[0088]

[0089] Table 3 Model parameters and maximum relative error

[0090]

[0091] From the comparison results, it can be seen that the average value of the absolute value of the relative error of the ductile fracture identification model is reduced by 3% compared with the Mohr-Coulomb model. Moreover, the absolute value of the maximum relative error of the ductile fracture identification model is reduced by not less than 5% compared with the Mohr-Coulomb model. Most importantly, from Tables 1 and 2, it can be seen that the ductile fracture prediction error of the high stress triaxial stress state can be effectively reduced by the ductile fracture identification model. In summary, the ductile fracture identification model expands the application range of the Mohr-Coulomb model, and can more accurately and stably predict the ductile fracture of the alloy compared with the Mohr-Coulomb model.

[0092] Embodiment 2:

[0093] The above embodiment 1 provides a linear stress combination ductile fracture identification method, and correspondingly, the present embodiment provides a linear stress combination ductile fracture identification device. The linear stress combination ductile fracture identification device provided by the present embodiment can implement the linear stress combination ductile fracture identification method of embodiment 1. The linear stress combination ductile fracture identification device can be realized by software, hardware or a combination of software and hardware. For example, the linear stress combination ductile fracture identification device can include integrated or separate functional modules or functional units to perform the corresponding steps in the methods of embodiment 1. Since the linear stress combination ductile fracture identification device of the present embodiment is basically similar to the method embodiment, the description process of the present embodiment is relatively simple, and the related parts can be referred to the part of the description of embodiment 1. The linear stress combination ductile fracture identification device of the present embodiment is only schematic.

[0094] The linear stress combination ductile fracture identification device provided by the present embodiment comprises:

[0095] The first processing unit is configured to calculate the local principal stress of the ductile fracture body to be predicted;

[0096] The second processing unit is configured to calculate the stress invariant of the ductile fracture body to be predicted based on the local principal stress of the ductile fracture body to be predicted.

[0097] The third processing unit is configured to calculate the Mises equivalent stress of the ductile fracture body to be predicted based on the stress invariant of the ductile fracture body to be predicted.

[0098] The fourth processing unit is configured to calculate the stress state parameter based on the local principal stress of the ductile fracture body to be predicted.

[0099] The fifth processing unit is configured to convert the local principal stress of the ductile fracture body to be predicted to the stress state parameter space based on the Mises equivalent stress and the stress state parameter of the ductile fracture body to be predicted.

[0100] A sixth processing unit is configured to add a hydrostatic stress strengthening term to the Mohr-Coulomb model to establish a hydrostatic stress strengthened Mohr-Coulomb model.

[0101] A seventh processing unit is configured to convert the hydrostatic stress strengthened Mohr-Coulomb model to a stress-stress state parameter space based on the hydrostatic stress strengthened Mohr-Coulomb model to obtain a linear stress combination ductile fracture identification model considering hydrostatic stress strengthening.

[0102] Embodiment 3

[0103] The embodiment provides a processing device for implementing the linear stress combination ductile fracture identification method provided in Embodiment 1. The processing device can be a processing device for a client, such as a mobile phone, a notebook computer, a tablet computer, a desktop computer, etc., to execute the method of Embodiment 1.

[0104] The processing device includes a processor, a memory, a communication interface and a bus. The processor, the memory and the communication interface are connected through the bus to complete the communication among each other. The memory stores a computer program that can run on the processor. When the processor runs the computer program, the linear stress combination ductile fracture identification method provided in Embodiment 1 is executed.

[0105] Preferably, the memory can be a high-speed random access memory (RAM) and can also include a non-volatile memory, such as at least one disk memory.

[0106] Preferably, the processor can be a central processing unit (CPU), a digital signal processor (DSP) or various types of general-purpose processors, which are not limited herein.

[0107] Embodiment 4

[0108] The linear stress combination ductile fracture identification method of Embodiment 1 can be specifically implemented as a computer program product. The computer program product can include a computer readable storage medium on which is loaded a computer readable program instruction for executing the method described in Embodiment 1.

[0109] The computer readable storage medium can be a tangible device that maintains and stores instructions for use by an instruction execution device. The computer readable storage medium can be, for example but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination of the above.

[0110] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced equivalently. Such modifications or replacements do not change the essence of the corresponding technical solutions, which should be covered in the scope of the claims and the specification of the present application. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.< / x> < / x> < / x> < / x> < / x> < / x>

Claims

1. A linear stress combination ductile fracture identification method considering hydrostatic stress intensification, characterized by, The method comprises the following steps: calculating local principal stress of a ductile fracture body to be predicted; calculating stress invariant of the ductile fracture body to be predicted based on the local principal stress of the ductile fracture body to be predicted; calculating Mises equivalent stress of the ductile fracture body to be predicted based on the local principal stress of the ductile fracture body to be predicted: calculating stress state parameter of the ductile fracture body to be predicted based on the stress invariant of the ductile fracture body to be predicted; converting the local principal stress of the ductile fracture body to be predicted to a stress state parameter space based on the Mises equivalent stress and the stress state parameter of the ductile fracture body to be predicted; adding a hydrostatic stress strengthening term to a Mohr-Coulomb model to establish a hydrostatic stress strengthened Mohr-Coulomb model; converting the hydrostatic stress strengthened Mohr-Coulomb model to a stress-stress state parameter space based on the local principal stress of the ductile fracture body to be predicted converted to the stress state parameter space, to obtain a linear stress combination ductile fracture identification model considering hydrostatic stress strengthening, so as to predict a fracture trajectory of the ductile fracture body to be predicted; an expression of the local principal stress of the ductile fracture body to be predicted converted to the stress state parameter space is as follows: wherein, wherein respectively the first, second and third local principal stress of the ductile rupture body to be predicted; is the Mises equivalent stress of the ductile rupture body to be predicted; is the stress triaxiality; is the Lode angle parameter; f 1, f 2 and f 3 are all intermediate parameters; the hydrostatic stress strengthened Mohr-Coulomb model is as follows: wherein , and are material constants; is the reference stress triaxiality; is a piecewise function, when , , otherwise ; an expression of the linear stress combination ductile fracture identification model considering hydrostatic stress strengthening is as follows: In the formula, is the Mises equivalent stress of the ductile fracture body to be predicted.

2. The linear stress combination ductility fracture identification method according to claim 1, characterized by, the stress invariant of the ductile fracture body to be predicted is calculated by the following formula: wherein , and are the first, second and third stress invariants of the ductile rupture body to be predicted, respectively; are the first, second and third local principal stresses of the ductile rupture body to be predicted, respectively.

3. The linear stress combination ductility fracture identification method according to claim 2, characterized by, the Mises equivalent stress of the ductile fracture body to be predicted is calculated by the following formula: wherein is the Mises equivalent stress of the ductile fracture body to be predicted.

4. The linear stress combination ductility fracture identification method according to claim 3, characterized by, the stress state parameter of the ductile fracture body to be predicted includes stress triaxiality and Lode angle parameter, and is calculated by the following formula: wherein is the stress triaxiality; is the Lode angle parameter.

5. A device for identifying linear stress combination ductile fracture taking into account hydrostatic stress enhancement, for implementing the linear stress combination ductile fracture identification method according to any one of claims 1 to 4, characterized in that, The device comprises: a first processing unit configured to calculate local principal stress of a ductile fracture body to be predicted; a second processing unit configured to calculate stress invariant of the ductile fracture body to be predicted based on the local principal stress of the ductile fracture body to be predicted; a third processing unit configured to calculate Mises equivalent stress of the ductile fracture body to be predicted based on the local principal stress of the ductile fracture body to be predicted: a fourth processing unit configured to calculate stress state parameter of the ductile fracture body to be predicted based on the stress invariant of the ductile fracture body to be predicted; a fifth processing unit configured to convert the local principal stress of the ductile fracture body to be predicted to a stress state parameter space based on the Mises equivalent stress and the stress state parameter of the ductile fracture body to be predicted; a sixth processing unit configured to add a hydrostatic stress strengthening term to a Mohr-Coulomb model to establish a hydrostatic stress strengthened Mohr-Coulomb model; a seventh processing unit configured to convert the hydrostatic stress strengthened Mohr-Coulomb model to a stress-stress state parameter space based on the local principal stress of the ductile fracture body to be predicted converted to the stress state parameter space, to obtain a linear stress combination ductile fracture identification model considering hydrostatic stress strengthening, so as to predict a fracture trajectory of the ductile fracture body to be predicted.

6. A computer-readable storage medium, characterized in that, A computer program is stored, and the computer program is executed by a processor to control a device where the processor is located to implement steps of the linear stress combination ductile fracture identification method according to any one of claims 1 to 4.

7. A computer device, characterized by A device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor executes the computer program to implement steps of the linear stress combination ductile fracture identification method according to any one of claims 1 to 4.

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