CN103559390A - Composite material Pi-shaped gluing connection structure tensile strength prediction method based on average invalidation index - Google Patents

Abstract

The invention relates to a composite material Pi-shaped gluing connection structure tensile strength prediction method based on an average invalidation index. The method includes the following steps: (1) a Pi connector geometrical model is built according to geometrical parameters of a composite material Pi-shaped gluing connection structure; (2) determining tensile load and boundary condition of the composite material Pi-shaped connector geometrical model according to the stress condition of the integrated composite material structure; (3) acquiring an accurate Pi connector three-dimensional finite element model through grid encryption based on the Pi connector geometrical model, meanwhile ensuring that grids on key connection faces L, U and B are even and calculating stress distribution of the three-dimensional finite element model under tensile load; (4) extracting positive axis stress component value of nodes on the Pi connector key connection faces L, U and B and calculating the invalidation index Rij on the key connection face; (5) respectively calculating the average invalidation indexes based on the key connection faces L, U and B of the Pi connector; (6) conducting calculation according to the tensile load P0 and the maximum value of the average invalidation indexes to obtain the invalidation strength value P of the obtained connector. The method is applicable to engineering application, can remarkably shorten the developing period of the Pi connector and reduces test cost.

Description

A kind of compound substance π shape based on average inefficacy index is gluedd joint syndeton pulling strengrth Forecasting Methodology

Technical field

The present invention relates to the pulling strengrth prediction of the typical π shape splicing syndeton in integration composite structure, be applicable to widely used compound substance typical case π shape in aerospace flight vehicle and glued joint syndeton.

Background technology

Lightweight, efficient, low-cost composite structure application technology are the gordian techniquies that the developed country of aviation in recent years drops into the aircraft composite structure Design and manufacture of huge fund research.Realize lightweight, important channel efficient, low-cost composite structure is the integration of structure.The version of integration can significantly reduce all kinds of securing members and the work that is linked and packed accordingly, improves the loss of weight efficiency of structure, and significantly reduces manufacturing cost.Meanwhile, integrated structure also has the features such as good static(al), fatigue, permanance/damage tolerance and reliability.

How two or more structural details are linked and are integrated, and guarantee that syndeton can bear and transmit the Focal point and difficult point that certain load is integrated structure.Adopt co-curing and be total to the technology such as splicing, on-plane surface glueds joint and connects and the composite structure element with certain angle can be linked together, effectively reduce securing member quantity and assembly cost, and can transfer surface external applied load, good mechanical property is provided, and is the effective type of attachment that realizes integration composite structure.With respect to common T shape, L shaped, Y shape and hat type of attachment, π shape is gluedd joint and connected is a kind of brand-new on-plane surface type of attachment, and its version is more complicated, and load-bearing capacity is higher.Compound substance π shape is gluedd joint and is connected by web, and covering and π reinforcement form.π reinforcement is by L shaped layer, U-shaped layer, and shape layer and a media assemblage, as shown in Figure 1, can connect the covering and the web that intersect vertically.Existing research fillers is the key position that load is transmitted, also be the weak part of whole joint design, external applied load is delivered to its interface being connected with a shape layer (crucial joint face B) by it with the interface (crucial joint face L & U) that L shaped layer and U-shaped layer are connected, and is finally delivered on covering.Because compound substance syndeton is complicated, influence factor is numerous, and its prediction of strength is extremely difficult.

Due to nonuniformity and the anisotropy of compound substance, the failure procedure of compound substance π shape cementing structure is very complicated, and the main test method that adopts is determined the ultimate strength connecting at present, but adopts the laboratory facilities lead time long, and cost is expensive.Although correlative study at present shows: adopt advanced finite element simulation and numerical analysis method, can follow the trail of composite structure initial damage to the overall process of ultimate failure.But these methods, comprise the progressive damage method based on damage mechanics, virtual crack closure techniques based on fracturing mechanics and the methods such as cohesive zone model based on damage and fracturing mechanics, all need constantly to detect syndeton damage or state of crack growth, and re-start non linear finite element analysis to obtain the load/stress level of redistribution according to the current state of syndeton, and the evaluation of losing efficacy, need the repeatedly iterative computation of stress analysis.This process not only needs to be grasped deep professional knowledge, and calculating scale is large, and computation period is long, is not suitable for engineering application.Therefore, need a kind of simple prediction of strength method badly, with in engineering application effectively prediction on-plane surface π shape glued joint the failure intensity connecting, for the design of integration composite structure provides support.

Summary of the invention

The technical problem to be solved in the present invention is: overcome the deficiencies in the prior art, finite element analysis technology based on detailed, provide a kind of compound substance π shape based on average inefficacy index to glued joint syndeton pulling strengrth Forecasting Methodology, be applicable to engineering application, can significantly shorten the π joint lead time, reduce experimentation cost.

The technical scheme that the present invention solves the problems of the technologies described above employing is: a kind of compound substance π shape based on average inefficacy index is gluedd joint syndeton pulling strengrth Forecasting Methodology, and performing step is as follows:

Steps A, based on finite element analysis software ABAQUS, glueds joint syndeton geometric parameter according to compound substance π shape and sets up π joint geometric model;

Step B, determines tensile load and the boundary condition of compound substance π joint geometric model according to the stressing conditions of integration composite structure;

Step C, based on π joint geometric model, obtains π joint three-dimensional finite element model and the stress distribution under tensile load thereof accurately by mesh refinement;

Step D, extracts the positive axis components of stress value of the crucial joint face L & U of π joint and upper each node of B, and calculates the inefficacy index R on crucial joint face _ij, its expression formula is:

$R_{\mathrm{ij}}=\frac{{\mathrm{\σ}}_{\mathrm{ij}}}{S_{\mathrm{ij}}}(1\≤i\≤j\≤3)$

Wherein, σ _ijand S _ijbe respectively the positive axis components of stress and the allowable value thereof of compound substance;

Step e, based on the crucial joint face L & U of π joint and B, calculates respectively its average inefficacy index

its expression formula is:

${\stackrel{\‾}{R}}_{\mathrm{ij},A}=\frac{\underset{A}{\∫}{R}_{\mathrm{ij}}\mathrm{da}}{\underset{A}{\∫}1\mathrm{da}}(1\≤i\≤j\≤3)$

Wherein A is crucial joint face L & U or B, R _ijfor the inefficacy index on crucial joint face;

Step F, according to tensile load P ₀and the index that on average lost efficacy

maximal value, can be calculated the failure intensity value P of joint, its expression formula is:

$P=P_0/\left(\underset{1\≤i\≤j\≤3}{\max }{\stackrel{\‾}{R}}_{\mathrm{ij},A}\right)$

P wherein ₀for being applied to the tensile load on π joint web,

for the average inefficacy index on crucial joint face, A is crucial joint face L & U or B, by two groups of crucial joint face L & U and B, can predict respectively π joint tensile failure intensity.

In described steps A, according to compound substance π shape splicing syndeton geometric parameter, setting up π joint geometric model implementation procedure is:

(A1), according to compound substance π joint design geometric parameter, utilize finite element analysis software ABAQUS model π joint 3-D geometric model;

(A2) definition material properties and local material direction, and divide geometric model by each laying one-tenth-value thickness 1/10, create compound substance laying and define laying angle, when definition laying angle, need to set up as the case may be corresponding local coordinate system.

Described step B determines that according to the stressing conditions of integration composite structure tensile load and the boundary condition implementation procedure of compound substance π joint geometric model are:

(B1) integration composite structure is carried out to force analysis, determine that π shape is gluedd joint restraint condition and the suffered tensile load of syndeton;

(B2) using restraint condition above as boundary condition, put on π joint geometric model the resulting tensile load of force analysis above applying simultaneously on π joint geometric model.

Described step C is based on π joint geometric model, obtains π joint three-dimensional finite element model and the stress distribution implementation procedure of π joint under tensile load to be accurately by mesh refinement:

(C1) based on above-mentioned π joint 3-D geometric model, divide the grid of local uniform, and guarantee that the grid on crucial joint face L & U and B is even;

(C2) calculate the stress distribution of π joint design, can obtain the maximal value of the integrally-built positive axis components of stress;

(C3) encrypt packing area grid, repeating step (C2), until the maximal value of the positive axis components of stress converges on a certain particular value, and relative error is not more than 1%.

The present invention's advantage is compared with prior art:

(1) the compound substance π shape that the present invention is based on average inefficacy index is gluedd joint syndeton pulling strengrth Forecasting Methodology, summing up on the basis of lot of research and theoretical analysis, average inefficacy index method based on crucial joint face has been proposed, and for predicting the pulling strengrth of compound substance π joint.

(2) the compound substance π shape that the present invention is based on average inefficacy index is gluedd joint syndeton pulling strengrth Forecasting Methodology, it is a kind of method based on experience, for existing prediction of strength method, simplified the computation process of finite element analysis, greatly saved and assessed the cost and the time.

(3) the compound substance π shape that the present invention is based on average inefficacy index is gluedd joint syndeton pulling strengrth Forecasting Methodology, is applicable to the π joint tensile strength prediction in engineering application, can significantly shorten the π joint lead time, reduces experimentation cost.

Accompanying drawing explanation

Fig. 1 (a) is that exemplary complex material π shape is gluedd joint johning knot composition, Fig. 1 (b) is crucial joint face partial enlarged drawing, wherein 1 is web, and 2 is U-shaped layer, and 3 is L shaped layer, 4 is a shape layer, 5 is filler, and 6 is π reinforcement, and 7 is covering, 8 is crucial joint face L & U, and 9 is crucial joint face B;

Fig. 2 is realization flow figure of the present invention.

Embodiment

As shown in Figure 2, the specific implementation of the inventive method is:

1. based on finite element analysis software ABAQUS, according to compound substance π shape, glued joint syndeton geometric parameter and set up π joint geometric model.

According to compound substance π joint design geometric parameter, utilize finite element analysis software ABAQUS model π joint 3-D geometric model; Definition material properties and local material direction, and divide geometric model by each laying one-tenth-value thickness 1/10, create compound substance laying and define laying angle, when definition laying angle, need to set up as the case may be corresponding local coordinate system.

2. according to the stressing conditions of integration composite structure, determine tensile load and the boundary condition of compound substance π joint geometric model.

Integration composite structure is carried out to force analysis, determine that π shape is gluedd joint restraint condition and the suffered tensile load of syndeton; Using restraint condition above as boundary condition, put on π joint geometric model the resulting tensile load of force analysis above applying simultaneously on π joint geometric model.

3. based on π joint geometric model, by mesh refinement, obtain π joint three-dimensional finite element model and the stress distribution under tensile load thereof accurately.

Based on above-mentioned π joint 3-D geometric model, divide the grid of local uniform, and guarantee that the grid on crucial joint face L & U and B is even; Calculate the stress distribution of π joint design, can obtain the maximal value of the integrally-built positive axis components of stress; Encrypt packing area grid, calculated stress distributes again, until the maximal value of the positive axis components of stress converges on a certain particular value, and relative error is not more than 1%.

4. extract the positive axis components of stress value of the crucial joint face L & U of π joint and upper each node of B, and calculate the inefficacy index R on crucial joint face _ij, its expression formula is:

$R_{\mathrm{ij}}=\frac{{\mathrm{\σ}}_{\mathrm{ij}}}{S_{\mathrm{ij}}}(1\≤i\≤j\≤3)$

Wherein, σ _ijand S _ijbe respectively the positive axis components of stress and the allowable value thereof of compound substance.

5. based on the crucial joint face L & U of π joint and B, calculate respectively its average inefficacy index

its expression formula is:

${\stackrel{\‾}{R}}_{\mathrm{ij},A}=\frac{\underset{A}{\∫}{R}_{\mathrm{ij}}\mathrm{da}}{\underset{A}{\∫}1\mathrm{da}}(1\≤i\≤j\≤3)$

Wherein A is crucial joint face L & U or B, R _ijfor the inefficacy index on crucial joint face.

6. according to tensile load P ₀and the index that on average lost efficacy

maximal value, can be calculated the failure intensity value P of joint, its expression formula is:

$P=P_0/\left(\underset{1\≤i\≤j\≤3}{\max }{\stackrel{\‾}{R}}_{\mathrm{ij},A}\right)$

P wherein ₀for being applied to the tensile load on π joint web,

for the average inefficacy index on crucial joint face, A is crucial joint face L & U or B, by two groups of crucial joint face L & U and B, can predict respectively π joint tensile failure intensity.

Non-elaborated part of the present invention belongs to those skilled in the art's known technology.

Claims (4)

1. the compound substance π shape based on average inefficacy index is gluedd joint a syndeton pulling strengrth Forecasting Methodology, it is characterized in that comprising the following steps:

Steps A, based on finite element analysis software ABAQUS, glueds joint syndeton geometric parameter according to compound substance π shape and sets up π joint geometric model;

Step B, determines tensile load and the boundary condition of compound substance π joint geometric model according to the stressing conditions of integration composite structure;

Step C, based on π joint geometric model, obtains π joint three-dimensional finite element model and the stress distribution under tensile load thereof accurately by mesh refinement;

Step D, extracts the positive axis components of stress value of the crucial joint face L & U of π joint and upper each node of B, and calculates the inefficacy index R on crucial joint face _ij, its expression formula is:

$R_{\mathrm{ij}}=\frac{{\mathrm{\σ}}_{\mathrm{ij}}}{S_{\mathrm{ij}}}(1\≤i\≤j\≤3)$

Wherein, σ _ijand S _ijbe respectively the positive axis components of stress and the allowable value thereof of compound substance;

Step e, based on the crucial joint face L & U of π joint and B, calculates respectively its average inefficacy index

its expression formula is:

${\stackrel{\‾}{R}}_{\mathrm{ij},A}=\frac{\underset{A}{\∫}{R}_{\mathrm{ij}}\mathrm{da}}{\underset{A}{\∫}1\mathrm{da}}(1\≤i\≤j\≤3)$

Wherein A is crucial joint face L & U or B, R _ijfor the inefficacy index on crucial joint face;

Step F, according to tensile load P ₀and the index that on average lost efficacy maximal value, can be calculated the failure intensity value P of joint, its expression formula is:

$P=P_0/\left(\underset{1\≤i\≤j\≤3}{\max }{\stackrel{\‾}{R}}_{\mathrm{ij},A}\right)$

P wherein ₀for being applied to the tensile load on π joint web,

for the average inefficacy index on crucial joint face, A is crucial joint face L & U or B, by two groups of crucial joint face L & U and B, can predict respectively π joint tensile failure intensity.

2. a kind of compound substance π shape based on average inefficacy index according to claim 1 is gluedd joint syndeton pulling strengrth Forecasting Methodology, it is characterized in that: in described steps A, according to compound substance π shape splicing syndeton geometric parameter, setting up π joint geometric model implementation procedure is:

(A1), according to compound substance π joint design geometric parameter, utilize finite element analysis software ABAQUS model π joint 3-D geometric model;

(A2) definition material properties and local material direction, and divide geometric model by each laying one-tenth-value thickness 1/10, create compound substance laying and define laying angle, when definition laying angle, need to set up as the case may be corresponding local coordinate system.

3. a kind of compound substance π shape based on average inefficacy index according to claim 1 is gluedd joint syndeton pulling strengrth Forecasting Methodology, it is characterized in that: described step B determines that according to the stressing conditions of integration composite structure tensile load and the boundary condition implementation procedure of compound substance π joint geometric model are:

(B1) integration composite structure is carried out to force analysis, determine that π shape is gluedd joint restraint condition and the suffered tensile load of syndeton;

(B2) using restraint condition above as boundary condition, put on π joint geometric model the resulting tensile load of force analysis above applying simultaneously on π joint geometric model.

4. a kind of compound substance π shape based on average inefficacy index according to claim 1 is gluedd joint syndeton pulling strengrth Forecasting Methodology, it is characterized in that: described step C is based on π joint geometric model, by mesh refinement, obtain π joint three-dimensional finite element model and the stress distribution implementation procedure of π joint under tensile load accurately and be:

(C1) based on above-mentioned π joint 3-D geometric model, divide the grid of local uniform, and guarantee that the grid on crucial joint face L & U and B is even;

(C2) calculate the stress distribution of π joint design, can obtain the maximal value of the integrally-built positive axis components of stress;

(C3) encrypt packing area grid, repeating step (C2), until the maximal value of the positive axis components of stress converges on a certain particular value, and relative error is not more than 1%.

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