CN110781624A - Numerical analysis method based on tensile and compressive unequal elastic modulus of composite material - Google Patents
Numerical analysis method based on tensile and compressive unequal elastic modulus of composite material Download PDFInfo
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Abstract
The invention relates to a numerical analysis method based on unequal tensile and compressive elastic modulus of a composite material, and belongs to the field of finite element analysis of structural strength. The method adopts the constitutive relation of different modulus elasticity theories and judges the first invariant (J) of the stress tensor
1) The positive and negative of the structure are endowed with different elastic moduli of tension and compression for the material, more accurate structural stress strain distribution is obtained after multiple rounds of iterative calculation, and the conflict relationship between the calculation precision and the difficulty in obtaining calculation resources is effectively solved, so that the analysis method is simplified, and the analysis precision is improved.
Description
Technical Field
The invention belongs to the field of structural strength finite element analysis, and particularly relates to a numerical analysis method based on tensile and compression unequal elastic modulus of a composite material.
Background
Compared with the traditional metal material, the fiber reinforced composite material has the characteristics of high specific modulus and high specific strength, and can reduce the structural weight to the maximum extent while meeting the structural performance requirement. In addition, the composite material has comprehensive excellent performances such as fatigue resistance, corrosion resistance, strong designability and the like, and the development direction which tends to be low in cost also enables the composite material to have wider development prospects in application in aerospace structures. The composite materials applied in the current engineering comprise carbon fiber reinforced resin matrix composite materials, C/C composite materials, continuous fiber reinforced ceramic matrix composite materials (C/SiC) and the like, and the high-performance materials have the common characteristics: the anisotropy, tensile and compressive moduli of elasticity vary, and even some materials may have ratios of tensile-to-compressive moduli of elasticity as high as 10 times.
In analyzing the problems of composite materials with different anisotropies and different tensile and compressive moduli, the traditional processing methods are divided into two types: one of the methods is to establish a complete material attribute library according to the anisotropic attributes of the material, assign the complete material attributes to each unit, and solve the complete material attributes, and the method has obvious advantages and disadvantages: the advantage is that the stress strain and displacement result of most components can be accurately output. The method has the disadvantages that stress concentration positions at the corners of the member are limited by grid units, the corresponding directions of material properties of all units are prone to deviation, and further calculation results are seriously influenced, however, the stress concentration positions in engineering practice are prone to being concerned by engineering personnel, and therefore calculation result deviation at key positions is unacceptable; secondly, the analysis method consumes more computing resources, has overlong analysis time, and is difficult to obtain the complete attributes of anisotropic materials in practical engineering application, thereby bringing errors and difficulty to accurate analysis. The other type of analysis method is to neglect the difference of anisotropy, tensile modulus and compressive modulus of the material and endow each unit with isotropic material properties for analysis.
Disclosure of Invention
Objects of the invention
The purpose of the invention is: the numerical analysis method based on the tensile and compression unequal elastic modulus of the composite material is provided, the calculation analysis method is simplified, the calculation precision is improved, and the calculation flow is optimized.
(II) technical scheme
In order to solve the technical problems, the invention provides a numerical analysis method based on the tensile and compression unequal elastic modulus of a composite material, which comprises the following steps:
s1: establishing a complete finite element model based on the analysis object, and setting boundary conditions of the researched problem and initial material properties of each component of the analysis object;
s2: establishing a solving file, solving an integral rigidity equation of an analysis object, and obtaining a first invariant J1 defined as stress tensors of the tension and compression different modulus members;
s3: judging whether the first invariant of the stress tensor of each unit is larger than or equal to 0 or not, and if so, keeping the material attribute of the unit unchanged; if the unit is judged to be not the compression modulus, giving the unit the material property of the compression modulus;
s4: recalculating the first invariant J1 'of the stress tensor according to the method in the step 2, analyzing and comparing the recalculated first invariant J1' with the last output first invariant J1, judging whether the analysis result of the two times of solution meets the convergence condition, and stopping the calculation if the convergence condition is met; the convergence condition is not satisfied, and the steps S3 and S4 are repeatedly performed;
s5: and after the loop calculation is finished, outputting a required result, and finishing the numerical analysis of the structure.
(III) advantageous effects
The invention relates to a structural analysis and calculation method for a material with unequal tensile and compressive elastic modulus, which can reasonably simplify material parameters, effectively improve the calculation precision of the material structure, improve the reliability of the structure and accurately obtain the safety margin of the structure.
Drawings
FIG. 1 is a diagram of a non-linear model in an embodiment of the invention.
FIG. 2 is a flow chart of a method according to an embodiment of the present invention.
Detailed Description
In order to make the objects, contents and advantages of the present invention clearer, the following detailed description of the embodiments of the present invention will be made in conjunction with the accompanying drawings and examples.
The invention reasonably simplifies the parameters of the composite material mainly aiming at the characteristic that the composite material has larger difference of tensile-compression elastic modulus so as to achieve the aim of improving the calculation precision. By adopting the constitutive relation of different modulus elasticity theories, under the action of tensile stress or compressive stress with the same absolute value, the material can generate tensile strain or compressive strain with different absolute values, and under the action of axial stress, the stress-strain relation is nonlinear, namely the material has different tensile modulus E
tAnd compression modulus E
cAs shown in fig. 1, the composite material is computationally analyzed by using 3 independent elastic constants of tensile modulus, compressive modulus and poisson ratio of the material, so that the analysis method is simplified and the analysis accuracy is provided.
The core theory of the analysis of the invention is based on a bilinear constitutive model and based on the first invariant (J) of the stress tensor
1) The composite materials with unequal tensile and compressive moduli of elasticity are analyzed and optimized for decision criteria. First invariant of stress tensor J
1＝σ
1+σ
2+σ
3For a determined stress state, which is univalent, σ
1、σ
2And σ
3Respectively the principal stress at that point. In numerical simulation calculation, J
1When the elastic modulus of the material is more than or equal to 0, the elastic modulus of the material is set as the tensile elastic modulus J
1When the elastic modulus of the material is less than 0, the elastic modulus of the material is set to be the compressive elastic modulus, so that an accurate structural stress strain state can be obtained, and a structural strength analysis result can be reflected more truly.
Referring to fig. 2, the specific calculation flow of the numerical analysis method of the present invention is as follows:
1) based on the analysis object, a complete finite element model is established, and boundary conditions of the problem to be researched and initial material properties of each component of the analysis object are set. Two material properties are defined for components with different moduli in tension and compression, and the element initial material property in all finite element models is the tensile modulus.
2) And establishing a solving file, solving the integral rigidity equation of the analysis object, and obtaining a first invariant J1 defined as the stress tensor of the tension and compression different modulus members.
3) Judging whether the first invariant J1 of the stress tensor of each unit is more than or equal to 0, if so, keeping the material attribute of the unit unchanged; if not, the material property of the compression modulus is given to the unit.
4) Recalculating the first invariant J1 of the stress tensor according to the method in the step 2, analyzing and comparing the recalculated first invariant J1 with the last output first invariant J1, judging whether the analysis result of the two times of solution meets the convergence condition, and stopping the calculation if the convergence condition is met; if the convergence condition is not satisfied, the steps 3 and 4 are repeatedly executed.
5) And after the loop calculation is finished, outputting a required result, and finishing the numerical analysis of the structure.
The analysis method effectively overcomes the defects of two traditional analysis methods, combines the advantages of the analysis methods to make up for the deficiencies, and solves the conflict relationship between the calculation precision and the difficulty in obtaining the calculation resources, thereby simplifying the analysis method and improving the analysis precision; meanwhile, the method is adopted to analyze the data, is widely applied to the actual engineering analysis process, and is used for comparing the calculation analysis result with the test result, so that the coincidence degree of the comparison result is high.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (4)
1. A numerical analysis method based on tensile and compression unequal elastic modulus of a composite material is characterized by comprising the following steps:
s1: establishing a complete finite element model based on the analysis object, and setting boundary conditions of the researched problem and initial material properties of each component of the analysis object;
s2: establishing a solving file, solving an integral rigidity equation of an analysis object, and obtaining a first invariant J1 defined as stress tensors of the tension and compression different modulus members;
s3: judging whether the first invariant of the stress tensor of each unit is larger than or equal to 0 or not, and if so, keeping the material attribute of the unit unchanged; if the unit is judged to be not the compression modulus, giving the unit the material property of the compression modulus;
s4: recalculating the first invariant J1 'of the stress tensor according to the method in the step 2, analyzing and comparing the recalculated first invariant J1' with the last output first invariant J1, judging whether the analysis result of the two times of solution meets the convergence condition, and stopping the calculation if the convergence condition is met; the convergence condition is not satisfied, and the steps S3 and S4 are repeatedly performed;
s5: and after the loop calculation is finished, outputting a required result, and finishing the numerical analysis of the structure.
2. A method for numerical analysis of differential tensile and compressive moduli of elasticity as set forth in claim 1, wherein in said step S1, two material properties are defined for the members having different tensile and compressive moduli, and the element initial material property in all finite element models is the tensile modulus.
3. A method for numerically analyzing a tensile-compressive unequal elastic modulus according to claim 2, wherein in the step S2, the first invariant J of the stress tensor
1＝σ
1+σ
2+σ
3For a determined stress state, which is univalent, σ
1、σ
2And σ
3Respectively the principal stress at that point.
4. A method for numerical analysis of differential tensile and compressive moduli of elasticity according to any one of claims 1 to 3, wherein the entire procedure of the numerical analysis method is performed in ANSYS software, implementing a computational analysis of numerical simulation.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102901673A (en) * | 2012-10-11 | 2013-01-30 | 山东理工大学 | Method for measuring tensile and compression elastic modulus of sheets with inconsistent tensile and compression modulus |
| CN103018112A (en) * | 2012-11-23 | 2013-04-03 | 西南交通大学 | Method for adopting bend test to test tensile elasticity modulus of material |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102901673A (en) * | 2012-10-11 | 2013-01-30 | 山东理工大学 | Method for measuring tensile and compression elastic modulus of sheets with inconsistent tensile and compression modulus |
| CN103018112A (en) * | 2012-11-23 | 2013-04-03 | 西南交通大学 | Method for adopting bend test to test tensile elasticity modulus of material |
Non-Patent Citations (2)
| Title |
|---|
| 姚文娟 等: "拉压不同模量弯压柱的有限元数值解", 《南昌大学学报 工科版》 * |
| 蔡来生 等: "拉压模量不同弹性物质的本构", 《西安科技大学学报》 * |
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