Marine metallurgy composite pipe material constitutive model construction method

Abstract

The invention relates to a method for constructing a constitutive model of a marine metallurgy composite pipe material. The method comprises the following steps: S1, acquiring parameters; s2, constructing a model; and S3, outputting the model. The method can avoid dependence on complex finite element simulation or is only suitable for an empirical model of a specific material combination, and is especially suitable for a composite pipe material of which a base layer and a coating layer have no yield platform; the complete stress-strain response of the metallurgical composite pipe under different material combinations and composite proportions can be efficiently and accurately described only by inputting conventional mechanical property parameters, so that a theoretical basis and a practical tool are provided for design, safety evaluation and engineering application of the composite pipe structure.

Description

Technical Field

[0001] This invention belongs to the field of model building technology, specifically relating to a method for constructing a constitutive model of marine metallurgical composite pipe materials. Background Technology

[0002] As modern offshore oil and gas resource development continues to expand into deep and ultra-deep water, subsea pipelines and other equipment not only need to withstand extremely high hydrostatic pressure, complex wave and current loads, and dynamic loads during installation, but also must possess excellent resistance to seawater corrosion and wear. Traditional single-material pipelines cannot simultaneously meet the stringent requirements of the deep-sea environment for both structural strength and ultra-long service life.

[0003] Marine metallurgical composite pipe, as an advanced layered composite material, achieves metallurgical bonding between a high corrosion-resistant alloy cladding (such as duplex stainless steel, nickel-based alloy 625, etc.) and a high-strength and tough base layer (such as high-grade pipeline steels such as X65 and X80) through processes such as hot rolling and explosive bonding. It takes into account the excellent mechanical properties of the base layer and the good corrosion resistance of the cladding, and has become a key technical approach to solve the above contradictions.

[0004] Existing research and experimental results for metallurgical composite pipes used in marine engineering show that the carbon steel material of the outer tube typically does not exhibit a significant yield plateau during uniaxial tension, and the stress-strain curve displays a continuous and smooth elastoplastic transition. This characteristic differs from the base layer conditions of some composite plate materials, which exhibit a significant yield plateau. Therefore, existing constitutive model methods proposed for composite plates are not applicable to the characteristics of the outer tube material of marine metallurgical composite pipes.

[0005] In the field of material constitutive models, the Ramberg-Osgood (RO) model is a commonly used model to describe the elastoplastic stress-strain relationship of metallic materials. Its classic form is as follows: ; in: In response, For stress, For elastic modulus, The yield strength is 0.2% of the plastic strain. The strain hardening index is denoted as .

[0006] To further improve the fitting accuracy, Mirambell et al. proposed a two-stage Ramberg-Osgood model: ; This model uses different hardening indices to fit the yield stage and hardening stage of the material, which can more accurately describe materials such as X65 steel that do not have a clear yield plateau.

[0007] However, there are still significant challenges in constitutive modeling for this type of composite pipe: First, it exhibits multi-stage nonlinear deformation in uniaxial tension, with macroscopic yielding showing continuous transition characteristics; second, existing constitutive models for composite plates are mostly based on the premise that the base layer has a yield plateau, which is difficult to apply to marine metallurgical composite pipes with carbon steel outer tubes that do not have a yield plateau; third, its mechanical properties are affected by the constitutive behavior of the cladding and base layer materials and the composite ratio, while existing methods are either limited to specific material combinations or rely on complex finite element simulations, and there is still a lack of a universal model that can uniformly characterize the mechanical behavior of this type of composite pipe across the entire strain range.

[0008] Therefore, there is an urgent need for a method that can quickly and accurately establish the full range of stress-strain constitutive relationships for marine metallurgical composite pipes based on the basic parameters of materials and the composite ratio, so as to meet the needs of engineering applications. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings and deficiencies of existing technologies by providing a method for constructing a constitutive model of marine metallurgical composite pipe materials. Based on the strain consistency assumption, a set of explicit and unified constitutive relation formulas is constructed by introducing key mechanical parameters and composite ratios of the cladding and base materials.

[0010] The technical problem solved by this invention is achieved through the following technical solution: A method for constructing a constitutive model of marine metallurgical composite pipe materials, the method comprising the following steps: S1. Parameter Acquisition: Obtain the key mechanical parameters of the base material and cladding material of marine metallurgical composite pipe: Composite ratio Elastic modulus of base material Yield stress of base material Stress of base material under 0.01% plastic strain Or the strain hardening index of the first stage of the base material Strain under tensile strength of base material Tensile strength of base material ; Elastic modulus of coating material Yield stress of coating material Stress of coating material under 0.01% plastic strain Or the strain hardening index of the first stage of the coating material Stress of coating material under 2% plastic strain Strain of coating material under 2% plastic strain 2% plastic strain tangential modulus of coating material ; Selectively input the necessary parameters based on the actual stress-strain curve shape of the selected material; S2, Model Building: Substitute the above parameters into the following set of formulas to calculate and construct the key characteristic parameters and mathematical expressions of the constitutive model of the composite pipe material: ; ; ; ; ; ; ; ; ; ; ; ; ; S3, Model Output: The output is the explicit constitutive model and its stress-strain curve established by the above set of formulas, which is used to describe the mechanical behavior of metallurgical composite pipe materials.

[0011] The advantages and beneficial effects of this invention are as follows: 1. This invention avoids relying on complex finite element simulations or empirical models that are only applicable to specific material combinations, and is especially suitable for composite pipe materials where neither the base layer nor the cladding layer has a yield plateau. By simply inputting conventional mechanical property parameters, it can efficiently and accurately describe the complete stress-strain response of metallurgical composite pipes under different material combinations and composite ratios, thereby providing a theoretical basis and practical tools for the design, safety assessment, and engineering application of such composite pipe structures.

[0012] 2. High accuracy: Based on the physical assumption of "strain consistency", the constitutive model constructed by weighted calculation of key parameters can accurately predict the mechanical response of the composite pipe from the elastic to the strengthening stage. The theoretical results are in high agreement with the high-precision simulation, which is far better than the simplified homogeneous model.

[0013] 3. High efficiency and easy operation: No complex modeling is required. Only a set of key parameters that can be obtained through conventional tensile tests need to be input. A high-precision constitutive model can be quickly constructed through explicit calculation formulas, which greatly improves calculation efficiency and facilitates engineering applications.

[0014] 4. Easy to promote: The model construction method has a clear logic and is easy to program into a special tool or integrate into existing software, which facilitates its widespread promotion in the field and provides a practical and efficient solution for composite pipe structure design and safety assessment. Attached Figure Description

[0015] Figure 1 This is a comparison curve of theoretical prediction and simulation verification of the stress-strain curve of the metallurgical composite pipe material of this invention. Detailed Implementation

[0016] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0017] A method for constructing a constitutive model of marine metallurgical composite pipe materials, the innovation of which lies in the following steps: S1. Parameter Acquisition: Obtain the key mechanical parameters of the base material and cladding material of marine metallurgical composite pipe: Composite ratio Elastic modulus of base material Yield stress of base material Stress of base material under 0.01% plastic strain Or the strain hardening index of the first stage of the base material Strain under tensile strength of base material Tensile strength of base material ; Elastic modulus of coating material Yield stress of coating material Stress of coating material under 0.01% plastic strain Or the strain hardening index of the first stage of the coating material Stress of coating material under 2% plastic strain Strain of coating material under 2% plastic strain 2% plastic strain tangential modulus of coating material ; Selectively input the necessary parameters based on the actual stress-strain curve shape of the selected material; S2, Model Building: Substitute the above parameters into the following set of formulas to calculate and construct the key characteristic parameters and mathematical expressions of the constitutive model of the composite pipe material: ; ; ; ; ; ; ; ; ; ; ; ; ; The meanings of the above parameters are shown in Table 1.

[0018] Table 1. Explanation of Constitutive Model Symbols

[0019] S3, Model Output: Output the explicit constitutive model established by the above set of formulas and its stress-strain curve, as follows: Figure 1 The blue curve in the figure describes the mechanical behavior of metallurgical composite pipe materials.

[0020] To verify the accuracy and reliability of the construction method described in this invention, examples and verification processes are given, using base material X65 and cladding material Alloy625 as representative materials. Verification method: A refined numerical model of a uniaxial tensile specimen of a metallurgical composite pipe was established using the finite element simulation software ABAQUS. In the model, the base layer and cladding materials were assigned accurate stress-strain curve data obtained through actual measurements. Through computational simulation, the macroscopic stress-strain response curve of the composite pipe under uniaxial tensile load was directly obtained, as shown below. Figure 1 As shown by the red curve in the figure, this curve is used as the verification benchmark.

[0021] Simultaneously, the key parameters required for the method of this invention (i.e., those required in step S1) are extracted from the measured curves of the base layer and overlay materials used for simulation. , , , ( ), , , , , ( ), , , (etc.) and substitute them into the formula group of the present invention (step S2) for calculation and model construction to obtain the curve predicted by the constitutive model constructed by the method of the present invention.

[0022] Verification results: The baseline curve obtained from finite element simulation and the theoretical curve predicted by the method of this invention are plotted on the same graph for comparison. The results are as follows: Figure 1 As shown, the results indicate that the theoretically predicted curve calculated using the method described in this invention closely matches the baseline curve verified by finite element simulation in the elastic, yield, and strengthening stages. The two curves exhibit similar values ​​at key characteristic points (such as elastic modulus, yield strength, and tensile strength) and show consistent trends throughout the entire strain history. This comparison fully demonstrates that the construction method proposed in this invention, based on key parameters and explicit formula sets, can efficiently and accurately construct constitutive models of metallurgical composite pipe materials, fully meeting the accuracy requirements for engineering design and analysis.

[0023] The set of key parameters described in this invention is the minimum set required for this invention. In practical applications, other parameters (such as tangent modulus under different plastic strains and other relevant mechanical parameters) can be added to describe three or more segments for more refined corrections, thereby constructing a more complex constitutive model. However, this is an equivalent alternative to the present invention. The construction method of the present invention can be programmed into a dedicated system or made into a calculation chart or Excel spreadsheet tool. All of these implementation methods are within the protection scope of the present invention.

[0024] Although embodiments and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A method for constructing a constitutive model of marine metallurgical composite pipe materials, characterized in that: The steps of the method are as follows: S1. Parameter Acquisition: Obtain the key mechanical parameters of the base material and cladding material of marine metallurgical composite pipe: Composite ratio Elastic modulus of base material Yield stress of base material Stress of base material under 0.01% plastic strain Or the strain hardening index of the first stage of the base material Strain under tensile strength of base material Tensile strength of base material ; Elastic modulus of coating material Yield stress of coating material Stress of coating material under 0.01% plastic strain Or the strain hardening index of the first stage of the coating material Stress of coating material under 2% plastic strain Strain of coating material under 2% plastic strain 2% plastic strain tangential modulus of coating material ; Selectively input the necessary parameters based on the actual stress-strain curve shape of the selected material; S2, Model Building: Substitute the above parameters into the following set of formulas to calculate and construct the key characteristic parameters and mathematical expressions of the constitutive model of the composite pipe material: ； ； ； ； ； ； ； ； ； ； ； ； ； S3, Model Output: The output is the explicit constitutive model and its stress-strain curve established by the above set of formulas, which is used to describe the mechanical behavior of metallurgical composite pipe materials.

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