CN113343529B - Global control method and device for damage and fracture of integral wallboard structure - Google Patents
Global control method and device for damage and fracture of integral wallboard structure Download PDFInfo
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Abstract
The invention discloses a global control method and a device for damage and fracture of an integral wallboard structure, and relates to the field of design of damage tolerance of an aircraft structure, wherein the method comprises the following steps: establishing a global damage parameter matrix of the integral wall plate structure; determining a control constraint; selecting a first group of parameters, and establishing a three-dimensional shell finite element model of an integral wall plate structure at least comprising three ribs according to the first group of parameters; simulating a crack propagation track by using a finite element method based on the reinforced area and the reinforced unit, and acquiring a change curve of the stress intensity factor along with the crack length; calculating the crack propagation life, the residual strength value and the weight under the first group of parameters according to the change curve; judging whether the crack propagation life, the residual strength value and the weight meet preset conditions or not; if any one of the conditions does not meet the preset condition, returning to the step: a second set of parameters is selected. The invention can maximally delay the crack propagation speed, improve the damage tolerance performance of the whole wallboard and ensure the quick iteration of the optimized design.
Description
Technical Field
The invention relates to the field of design of damage tolerance of an aircraft structure, in particular to a global control method and a global control device for damage and fracture of an integral wall plate structure.
Background
Monolithic panels have found use in a variety of medium and large aircraft structures due to their advantages of good fatigue performance, simplicity of manufacture, and light weight construction. However, compared with the traditional riveted wallboard, the integral wallboard lacks a natural crack arrest original piece, namely a rivet for connecting the stringer and the skin, so that the damage tolerance performance is poorer.
The main problems in the damage and fracture research and design of the integral wallboard at present are as follows: only considering detail control, namely, only carrying out optimization analysis on the shape and the size of the ribs under the condition that global parameters are assumed to be unchanged, the method is only one aspect of designing the damage tolerance of the whole wall plate, and more design and iteration cycles are easily spent without a global angle.
Disclosure of Invention
In view of the above problems, the present invention provides a global control method and apparatus for damage and fracture of an integral wall panel structure, which aims at solving the above problems.
The embodiment of the invention provides a global control method for damage and fracture of an integral wallboard structure, which comprises the following steps:
step S1: establishing a global damage parameter matrix of the integral wall plate structure;
step S2: determining a control constraint for damage fracture of the monolithic wallboard structure;
step S3: selecting a first group of parameters in the global damage parameter matrix, and establishing a three-dimensional shell finite element model of an integral wall plate structure at least comprising three ribs according to the first group of parameters;
step S4: simulating a crack propagation track by using a finite element method based on the reinforced area and the reinforced unit, and acquiring a change curve of the stress intensity factor along with the crack length;
step S5: calculating the crack propagation life under the first set of parameters according to the change curve;
step S6: acquiring a stress intensity factor when a crack expands to the span of the two stringers from the change curve, and calculating a residual intensity value of the integral wallboard structure;
step S7: calculating a weight of the unitary panel structure corresponding to the first set of parameters;
step S8: judging whether the crack propagation life, the residual strength value and the weight meet preset conditions or not;
step S9: and if any one of the crack propagation life, the residual strength value and the weight does not meet the preset condition, returning to the step S3, selecting a second group of parameters in the global damage parameter matrix, and establishing a three-dimensional shell finite element model of the integral wall plate structure at least comprising three ribs according to the second group of parameters.
Optionally, establishing a global damage parameter matrix of the monolithic wallboard structure includes:
determining the area of the ribs;
determining the space between the ribs;
determining the thickness of the skin;
and establishing a global damage parameter matrix of the integral wallboard structure by taking the area of the ribs, the distance between the ribs and the thickness of the skin as parameters.
Optionally, the control constraint includes:
crack propagation life index on the integral wall plate structure, weight index of the integral wall plate structure and residual strength index of the integral wall plate structure.
Optionally, based on the reinforced region and the reinforced unit, simulating a crack propagation trajectory by using a finite element method, and acquiring a change curve of the stress intensity factor along with the crack length, including:
based on the reinforced area and the reinforced unit, simulating the crack propagation track by using a finite element method, and combining a gridding method and a stress intensity factor formula to obtain a change curve of the stress intensity factor along with the crack length.
Optionally, calculating the crack propagation life under the first set of parameters according to the variation curve includes:
calculating the crack propagation life under the first set of parameters by adopting a Paris formula according to the change curve, wherein the Paris formula is as follows:
wherein C, N is the material constant, N1 is the crack propagation life, and Δ K is the stress intensity factor amplitude.
Optionally, the formula of the stress intensity factor is as follows:
wherein K is the stress intensity factor, betaJIs a geometric form factor, betaCFor load redistribution factor, for integral panel betaCσ is the reference stress and a is the crack length, 1.
Optionally, the expression for calculating the residual strength value of the integral panel structure is as follows:
wherein [ sigma ]]rsThe residual intensity value is obtained; μ is a transition breakdown shape factor, with a value of 0.63; η is 0.558; a is ayFor the transitional crack length, it is calculated by:
wherein [ sigma ]]nIs a reference stress, KcIs the fracture toughness of the material in a plane stress state.
Optionally, the expression for calculating the weight of the integral panel structure corresponding to the first set of parameters is:
wherein G1 is weight, L is wallboard length, ρ is density, n is rib number, Si is rib area, Wi is rib spacing, and t is skin thickness.
Optionally, the preset conditions are:
N1≥N
G1≤G
wherein P is an external load, S is a sectional area of the panel, N is a crack propagation life index on the monolithic panel structure, G is a weight index of the monolithic panel structure, and G1 is a weight.
The embodiment of the invention also provides a global control device for damage and fracture of the integral wallboard structure, which comprises:
a matrix building module for building a global damage parameter matrix of the integral panel structure;
determining a constraint module for determining a control constraint for damage and fracture of the integral panel structure;
the parameter establishing model module is used for selecting a first group of parameters in the global damage parameter matrix and establishing a three-dimensional shell finite element model of an integral wall plate structure at least comprising three ribs according to the first group of parameters;
the curve obtaining module is used for simulating a crack propagation track by using a finite element method based on the reinforced area and the reinforced unit, and obtaining a change curve of the stress intensity factor along with the crack length;
the extended life calculating module is used for calculating the crack extended life under the first group of parameters according to the change curve;
the strength factor obtaining module is used for obtaining a stress strength factor when the crack expands to the span of the two stringers from the change curve and calculating the residual strength value of the integral wallboard structure;
a calculate weight module for calculating a weight of the unitary wallboard structure corresponding to the first set of parameters;
the judging module is used for judging whether the crack propagation life, the residual strength value and the weight meet preset conditions or not;
and if any one of the crack propagation life, the residual strength value and the weight does not meet the preset condition, selecting a second group of parameters in the global damage parameter matrix by the parameter building model module, and building a three-dimensional shell finite element model of the integral wall plate structure at least comprising three ribs according to the second group of parameters.
Optionally, the matrix establishing module is specifically configured to:
determining the area of the rib;
determining the space between ribs;
determining the thickness of the skin;
and establishing a global damage parameter matrix of the whole wallboard structure by taking the area of the ribs, the interval of the ribs and the thickness of the skin as parameters.
Optionally, the curve obtaining module is specifically configured to:
based on the reinforced area and the reinforced unit, simulating the crack propagation track by using a finite element method, and combining a gridding method and a stress intensity factor formula to obtain a change curve of the stress intensity factor along with the crack length.
Optionally, the extended lifetime calculation module is specifically configured to:
calculating the crack propagation life under the first set of parameters by adopting a Paris formula according to the change curve, wherein the Paris formula is as follows:
wherein C, N is the material constant, N1 is the crack propagation life, and Δ K is the stress intensity factor amplitude.
The invention provides a global control method for damage and fracture of an integral wallboard structure, which comprises the steps of firstly establishing a global damage parameter matrix of the integral wallboard structure; determining control constraints of damage and fracture of the integral wall plate structure; selecting any one group of parameters in the global damage parameter matrix as a first group of parameters, and establishing a three-dimensional shell finite element model of an integral wall plate structure at least comprising three ribs according to the first group of parameters; simulating a crack propagation track by using a finite element method based on the reinforced area and the reinforced unit, and acquiring a change curve of the stress intensity factor along with the crack length; from the variation curve, the crack propagation life is calculated for a first set of parameters.
In addition, the stress intensity factor when the crack expands to the span of the two stringers is obtained from the change curve of the stress intensity factor along with the length of the crack, and the residual intensity value of the integral wallboard structure is calculated; calculating, from the first set of parameters, a weight of the unitary panel structure corresponding to the first set of parameters; judging whether the crack propagation life, the residual strength value and the weight meet preset conditions or not; if any one of the crack propagation life, the residual strength value and the weight does not meet the preset condition, selecting a second group of parameters from the global damage parameter matrix, establishing a three-dimensional shell finite element model of the whole wallboard structure at least comprising three ribs according to the second group of parameters, repeating the method, obtaining the new crack propagation life, the residual strength value and the weight of the whole wallboard structure based on the second group of parameters, and judging again. The method is repeated until the crack propagation life, the residual strength value and the weight all meet preset conditions.
The integral wallboard structure designed by the method is designed from the global perspective, can maximally delay the crack propagation speed and improve the damage tolerance performance of the integral wallboard under the condition of meeting the design requirement of the damage tolerance and the weight index, thereby further ensuring the safe use of the integral wallboard in the aircraft structure. Meanwhile, the fracture parameters can be rapidly and accurately acquired, rapid iteration of optimization design is guaranteed, and the method has high practicability.
Drawings
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 drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
FIG. 1 is a flow chart of a method for global control of damage and fracture of an integral panel structure according to an embodiment of the present invention;
fig. 2 is a block diagram of a global control device for damage and fracture of a monolithic wallboard structure according to an embodiment of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention, but do not limit the invention to only some, but not all embodiments.
Referring to fig. 1, a flow chart of a global control method for damage and fracture of an integral wall plate structure according to an embodiment of the present invention is shown, where the method includes:
step S1: a global damage parameter matrix for the monolithic wallboard structure is established.
In the embodiment of the invention, the overall loss parameter matrix of the integral wallboard structure needs to be established by comprehensively considering the overall situation of the integral wallboard. The selection of the parameters in the parameter matrix is carried out based on three key factors influencing the damage and fracture of the whole wallboard structure.
The three key factors are: the area of the ribs, the space between the ribs and the thickness of the skin are determined, so that the area of the ribs, the space between the ribs and the thickness of the skin are determined. The specific determination method of the three parameters can be performed according to the existing technology, and the embodiment of the present invention is not particularly limited.
And after the three parameters are determined, establishing a global damage parameter matrix of the whole wallboard structure by taking the area of the ribs, the space between the ribs and the thickness of the skin as parameters.
Step S2: determining a control constraint for damage to the failure of the unitary panel structure.
In the embodiment of the invention, the damage and fracture of the integral wallboard structure have specified indexes in design, and the indexes can be used as control constraints of the damage and fracture of the integral wallboard structure so as to ensure that the final integral wallboard structure meets the design specified requirements. The control constraints include: crack propagation life index on the whole wallboard structure, weight index of the whole wallboard structure and residual strength index of the whole wallboard structure. Naturally, when other indexes are used as control constraint conditions, parameters in the parameter matrix are also changed correspondingly.
Step S3: and selecting a first group of parameters in the global damage parameter matrix, and establishing a three-dimensional shell finite element model of the integral wall plate structure at least comprising three ribs according to the first group of parameters.
In the embodiment of the invention, after the parameter matrix is established and the control restriction is determined, a group of parameters are randomly selected from the overall damage parameter matrix, the parameters are used as a first group of parameters, and the three-dimensional shell finite element model at least comprising the three-rib integral wall plate structure is established according to the first group of parameters.
The finite element model created needs to contain at least three ribs because it is necessary to ensure that the crack has a length of two spans and a ligament width of at least 1/3 board widths when performing the bulk panel residual strength analysis.
Step S4: and simulating a crack propagation track by using a finite element method based on the reinforced area and the reinforced unit, and acquiring a change curve of the stress intensity factor along with the crack length.
In the embodiment of the invention, after the three-dimensional shell finite element model of the integral wall plate structure at least comprising three ribs is established, based on the reinforced area and the reinforced unit, the crack propagation track on the integral wall plate structure can be simulated by using a finite element method, and the change curve of the stress intensity factor along with the crack length can be obtained.
The change curve of the stress intensity factor along with the crack length needs to be obtained by combining a gridding method and a stress intensity factor formula, wherein the stress intensity factor formula is as follows:
wherein K is the stress intensity factor, betaJIs a geometric form factor, betaCFor load redistribution factor, for integral panel betaCσ is the reference stress and a is the crack length, 1.
Step S5: from the variation curve, the crack propagation life is calculated for a first set of parameters.
In the embodiment of the invention, after the change curve of the stress intensity factor along with the crack length is obtained, the crack propagation life under the first group of parameters is calculated according to the change curve. It can calculate the crack propagation life under the first set of parameters using the paris formula:
wherein C, N is the material constant, N1 is the crack propagation life, and Δ K is the stress intensity factor amplitude.
At present, the optimization design of the integral wallboard generally determines a group of global parameters directly according to experience, then focuses on the optimization of the detail parameters of the ribs, and if the global parameters are not optimal values, the efficiency of detail optimization is low or the optimization convergence is poor. Meanwhile, the calculation period of the stress intensity factor strongly related to damage tolerance analysis in the past is complex, and the manual or semi-automatic grid reconstruction method is basically adopted, so that the speed is low, the workload is large, and the effect of optimization design is limited. The method combining global parameter control and XFEM can perform global control and rapid iterative analysis from the initial to the whole optimization design process of whole wallboard damage tolerance design, and can obtain the optimal solution and implementation effect of structural parameters more easily.
Step S6: and (4) acquiring a stress intensity factor when the crack is expanded to the span of the two stringers from the change curve, and calculating the residual intensity value of the integral wallboard structure.
In the embodiment of the invention, in addition to the crack propagation life, the residual strength value and the weight of the whole wallboard structure are calculated, wherein the residual strength value is obtained by acquiring a stress strength factor when the crack propagates to the two stringer spans from the change curve and calculating based on the stress strength factor. The calculation expression is as follows:
wherein [ sigma ]]rsIs the residual intensity value; μ is a transition breakdown shape factor, with a value of 0.63; η is 0.558; a isyFor the transitional crack length, it is calculated by:
wherein [ sigma ]]nIs a reference stress, KcIs the fracture toughness of the material in a plane stress state.
Step S7: the weight of the unitary panel structure corresponding to the first set of parameters is calculated.
In the embodiment of the invention, the weight of the integral wallboard structure can be calculated according to the selected first group of parameters, and the calculation expression is as follows:
wherein G1 is weight, L is wallboard length, ρ is density, n is rib number, Si is rib area, Wi is rib spacing, and t is skin thickness.
Step S8: and judging whether the crack propagation life, the residual strength value and the weight meet preset conditions.
In the embodiment of the present invention, after obtaining the crack propagation life, the residual strength value, and the weight of the integral wall plate, a judgment is performed to judge whether the crack propagation life, the residual strength value, and the weight satisfy a preset condition, where the preset condition is:
N1≥N
G1≤G
wherein P is an external load, S is a sectional area of the panel, N is a crack propagation life index on the monolithic panel structure, G is a weight index of the monolithic panel structure, and G1 is a weight.
Step S9: and if any one of the crack propagation life, the residual strength value and the weight does not meet the preset condition, returning to the step S3, selecting a second group of parameters in the global damage parameter matrix, and establishing a three-dimensional shell finite element model of the integral wall plate structure at least comprising three ribs according to the second group of parameters.
In the embodiment of the invention, after the judgment, if any one of the residual strength value and the weight does not meet the preset condition, i.e., the crack propagation life on the integral panel structure is less than the crack propagation life index on the integral panel structure, or the residual strength value of the integral wall plate structure is smaller than the ratio of the external load to the wall plate sectional area, or the weight of the integral wall plate structure is smaller than the weight index of the integral wall plate structure, the step S3 is required to be returned, any one group of parameters except the first group of parameters is selected from the global damage parameter matrix to serve as a second group of parameters, a three-dimensional shell finite element model of the integral wall plate structure at least comprising three ribs is established according to the second group of parameters, and then the crack propagation life, the residual strength value and the weight of the integral wall plate calculated based on the second group of parameters are obtained according to the steps S4-S7.
And judging the crack propagation life, the residual strength value and the weight of the integral wall plate calculated based on the second group of parameters, if any one of the judgment results does not meet the preset conditions as before, repeating the steps again until the crack propagation life, the residual strength value and the weight both meet the preset conditions, and ending the overall control method for the structural damage and fracture of the integral wall plate.
In the steps of the method, the fracture parameters can be quickly and accurately obtained, and the quick iteration of the optimization design is ensured. The existing method for solving fracture mechanics parameters is mainly based on linear elastic fracture mechanics, has high requirements on finite element model precision, has high difficulty in grid self-adaption technology, and takes a large amount of time, thereby influencing the efficiency and effect of the optimal design of the damage tolerance of the whole wallboard. Because XFEM does not need to acquire fracture mechanical parameters through grid reconstruction, self-adaptive processing and the like, and the requirement on grid precision is not high, the calculation efficiency and precision can be far higher than those of the traditional method, and the quick iteration of the optimization design is ensured.
Based on the global control method for damage and fracture of the integral wallboard structure, an embodiment of the present invention further provides a global control apparatus for damage and fracture of the integral wallboard structure, and referring to fig. 2, a block diagram of the apparatus is shown, and the apparatus includes:
a build matrix module 210 for building a global damage parameter matrix for the monolithic wallboard structure;
determining a constraint module 220 for determining a control constraint for damage fracture of the unitary panel structure;
a parameter establishing model module 230, configured to select a first group of parameters in the global damage parameter matrix, and establish a three-dimensional shell finite element model of an integral wall plate structure including at least three ribs according to the first group of parameters;
an obtaining curve module 240, configured to simulate a crack propagation trajectory by using a finite element method based on the reinforced region and the reinforced element, and obtain a change curve of the stress intensity factor along with the crack length;
a life span calculation module 250, configured to calculate a crack life span under the first set of parameters according to the variation curve;
the strength factor obtaining module 260 is used for obtaining a stress strength factor when the crack propagates to the two stringer spans from the change curve, and calculating a residual strength value of the integral wallboard structure;
a calculate weight module 270 for calculating a weight of the unitary panel structure corresponding to the first set of parameters;
a determining module 280 configured to determine whether the crack propagation life, the residual strength value, and the weight satisfy a preset condition;
if any one of the crack propagation life, the residual strength value and the weight does not meet the preset conditions, the parameter establishing model module selects a second group of parameters in the global damage parameter matrix, and establishes a three-dimensional shell finite element model of the integral wall plate structure at least comprising three ribs according to the second group of parameters.
Optionally, the matrix establishing module 210 is specifically configured to:
determining the area of the ribs;
determining the space between the ribs;
determining the thickness of the skin;
and establishing a global damage parameter matrix of the whole wallboard structure by taking the area of the ribs, the interval of the ribs and the thickness of the skin as parameters.
Optionally, the curve obtaining module 240 is specifically configured to:
based on the reinforced area and the reinforced unit, simulating the crack propagation track by using a finite element method, and combining a gridding method and a stress intensity factor formula to obtain a change curve of the stress intensity factor along with the crack length.
Optionally, the extended lifetime calculating module 250 is specifically configured to:
calculating the crack propagation life under the first set of parameters by adopting a Paris formula according to the change curve, wherein the Paris formula is as follows:
wherein C, N is the material constant, N1 is the crack propagation life, and Δ K is the stress intensity factor amplitude.
In summary, in the global control method for damage and fracture of the integral wall plate structure according to the embodiment of the present invention, a global damage parameter matrix of the integral wall plate structure is first established; determining the control constraint of damage and fracture of the integral wall plate structure; selecting any one group of parameters in the global damage parameter matrix as a first group of parameters, and establishing a three-dimensional shell finite element model of an integral wall plate structure at least comprising three ribs according to the first group of parameters; simulating a crack propagation track by using a finite element method based on the reinforced area and the reinforced unit, and acquiring a change curve of the stress intensity factor along with the crack length; from the variation curve, the crack propagation life is calculated for a first set of parameters.
In addition, the stress intensity factor when the crack expands to the span of the two stringers is obtained from the change curve of the stress intensity factor along with the length of the crack, and the residual intensity value of the whole wallboard structure is calculated; calculating, from the first set of parameters, a weight of the unitary panel structure corresponding to the first set of parameters; judging whether the crack propagation life, the residual strength value and the weight meet preset conditions or not; if any one of the crack propagation life, the residual strength value and the weight does not meet the preset condition, selecting a second group of parameters from the global damage parameter matrix, establishing a three-dimensional shell finite element model of the whole wallboard structure at least comprising three ribs according to the second group of parameters, repeating the method, obtaining the new crack propagation life, the residual strength value and the weight of the whole wallboard structure based on the second group of parameters, and judging again. The method is repeated until the crack propagation life, the residual strength value and the weight all meet the preset conditions.
The integral wallboard structure designed by the method is designed from the global perspective, can maximally delay the crack propagation speed and improve the damage tolerance performance of the integral wallboard under the condition of meeting the design requirement of the damage tolerance and the weight index, thereby further ensuring the safe use of the integral wallboard in the aircraft structure. Meanwhile, the fracture parameters can be rapidly and accurately acquired, rapid iteration of optimization design is guaranteed, and the method has high practicability.
It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, or article that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, or article.
The embodiments of the present invention have been described in conjunction with the accompanying drawings, and the principle and the embodiments of the present invention are explained in detail herein by using specific embodiments, and the above description of the embodiments is only used to help understanding the method of the present invention and the core idea thereof; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (8)
1. A method for global control of damage to and failure of a monolithic panel structure, said method comprising the steps of:
step S1: establishing a global damage parameter matrix of the integral wall plate structure;
step S2: determining a control constraint for damage fracture of the monolithic wallboard structure;
step S3: selecting a first group of parameters in the global damage parameter matrix, and establishing a three-dimensional shell finite element model of an integral wall plate structure at least comprising three ribs according to the first group of parameters;
step S4: simulating a crack propagation track by using a finite element method based on the reinforced area and the reinforced unit, and acquiring a change curve of a stress intensity factor along with the crack length by combining a gridding method and a stress intensity factor formula;
step S5: calculating the crack propagation life under the first set of parameters according to the change curve;
step S6: acquiring a stress intensity factor when a crack expands to the span of the two stringers from the change curve, and calculating a residual intensity value of the integral wallboard structure;
step S7: calculating a weight of the unitary panel structure corresponding to the first set of parameters;
step S8: judging whether the crack propagation life, the residual strength value and the weight meet preset conditions or not;
step S9: if any one of the crack propagation life, the residual strength value and the weight does not meet the preset condition, returning to the step S3, selecting a second group of parameters in the global damage parameter matrix, and establishing a three-dimensional shell finite element model of the integral wall plate structure at least comprising three ribs according to the second group of parameters;
wherein the stress intensity factor formula is as follows:
wherein K is the stress intensity factor, betaJIs a geometric form factor, betaCFor load redistribution factor, for integral panel betaCσ is the reference stress, and a is the crack length.
2. The method of claim 1, wherein establishing a global damage parameter matrix for the monolithic wallboard structure comprises:
determining the area of the rib;
determining the space between ribs;
determining the thickness of the skin;
and establishing a global damage parameter matrix of the whole wallboard structure by taking the area of the ribs, the interval of the ribs and the thickness of the skin as parameters.
3. The method of claim 1, wherein the control constraints comprise:
crack propagation life index on the integral wall plate structure, weight index of the integral wall plate structure and residual strength index of the integral wall plate structure.
4. The method of claim 3, wherein calculating the crack propagation life at the first set of parameters from the variation profile comprises:
calculating the crack propagation life under the first set of parameters by adopting a Paris formula according to the change curve, wherein the Paris formula is as follows:
wherein C, N is the material constant, N1 is the crack propagation life, and Δ K is the stress intensity factor amplitude.
5. The method of claim 4, wherein the expression for calculating the residual strength value of the unitary panel structure is:
wherein [ sigma ]]rsThe residual intensity value is obtained; μ is a transition breakdown shape factor, with a value of 0.63; η is 0.558; a isyFor the transitional crack length, it is calculated by:
wherein [ sigma ]]nIs the reference stress, KcIs the fracture toughness of the material in a plane stress state.
6. The method of claim 1, wherein calculating the weight of the unitary panel structure corresponding to the first set of parameters is expressed as:
wherein G1 is weight, L is wallboard length, ρ is density, n is rib number, Si is rib area, Wi is rib spacing, and t is skin thickness.
7. The method according to claim 5, wherein the preset condition is:
N1≥N
G1≤G
wherein P is an external load, S is a sectional area of the panel, N is a crack propagation life index on the monolithic panel structure, G is a weight index of the monolithic panel structure, and G1 is a weight.
8. A global control for damage fracture of a unitary panel structure, said global control comprising:
a matrix building module for building a global damage parameter matrix of the integral panel structure;
determining a constraint module for determining a control constraint for damage and fracture of the integral panel structure;
the parameter establishing model module is used for selecting a first group of parameters in the global damage parameter matrix and establishing a three-dimensional shell finite element model of an integral wall plate structure at least comprising three ribs according to the first group of parameters;
the curve obtaining module is used for simulating a crack propagation track by using a finite element method based on the reinforced area and the reinforced unit, and obtaining a change curve of the stress intensity factor along with the crack length;
the extended life calculating module is used for calculating the crack extended life under the first set of parameters according to the change curve;
the strength factor obtaining module is used for obtaining a stress strength factor when the crack expands to the span of the two stringers from the change curve and calculating the residual strength value of the integral wallboard structure;
a weight calculation module for calculating a weight of the unitary panel structure corresponding to the first set of parameters;
the judging module is used for judging whether the crack propagation life, the residual strength value and the weight meet preset conditions or not;
if any one of the crack propagation life, the residual strength value and the weight does not meet the preset condition, selecting a second group of parameters in the global damage parameter matrix by the parameter building model module, and building a three-dimensional shell finite element model of an integral wall plate structure at least comprising three ribs according to the second group of parameters;
wherein the stress intensity factor formula is as follows:
wherein K is the stress intensity factor, betaJIs a geometric form factor, betaCFor load redistribution factor, for integral panel betaCσ is the reference stress and a is the crack length, 1.
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| CN101561365A (en) * | 2009-06-04 | 2009-10-21 | 中国航空工业集团公司西安飞机设计研究所 | Damage-tolerance testing method for whole wing spar of airplane |
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| CN112417606A (en) * | 2020-12-08 | 2021-02-26 | 江苏科技大学 | Method for calculating three-dimensional crack propagation fatigue life of spherical shell surface |
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