CN102968524A - Modeling method for two-dimensional variable-curvature process model of section bar part - Google Patents

Abstract

The invention belongs to the technical field of aircraft manufacturing and relates to a modeling method for a two-dimensional variable-curvature process model of a section bar part. Through dispersing a contour line, the contour line is dispersed into a plurality of line segments and arc segments. By adopting finite element simulation, the recurrent magnitude of every dispersed segment is calculated; a compensated part contour curve is obtained through multiple iteration compensation; and the part contour curve is used for defining the process model of the part. The modeling method for the two-dimensional variable-curvature process model of the section bar part has the beneficial effects the process model of the section bar part can be rapidly and accurately designed, and a design used for a stretch bending mould is provided to craft personnel.

Description

A kind of modeling method of two-dimentional variable curvature section bar part process model

Technical field

The invention belongs to the aircraft manufacturing technical field, relate to a kind of modeling method of two-dimentional variable curvature section bar part process model, be applied to the modelling of two-dimentional variable curvature section bar part process, the foundation that process modeling is manufactured and designed as stretch bending mold.

Background technology

The section bar part is the main components that consists of airframe, usually is used for frame costal margin bar, the long purlin of fuselage.The appearance profile of section bar part is complicated, is generally asymmetric, variable curvature.The present invention finishes the definition of process modeling mainly for asymmetric, the two-dimentional section bar part of variable curvature.

The section bar part directly affects profile accuracy and the structural-load-carrying capacity of aircraft as the main components of airframe, and it creates the important step that determines the overall aircraft performance.Stretch bending process is the main method of section bar part forming, and it is section bar tangential tensile force in addition in crooked coating mould.Appearance profile after the shaping of section bar part is by technological parameter and the coefficient result of stretch bending mold.Traditionally, stretch bending mold is the interior profile design according to the section bar part, because section bar part unloading resilience if adopt traditional stretch bending mold method for designing, is difficult to guarantee satisfy accuracy requirement behind the section bar part stretch wrap forming.The requirement of accurately making for satisfying digitizing, therefore factory manufactures and designs process modeling as stretch bending mold foundation considers that the process modeling definition of resilience becomes an important step of section bar part stretch wrap forming.

Summary of the invention

The technical matters that solves

For fear of the deficiencies in the prior art part, the present invention proposes a kind of modeling method of two-dimentional variable curvature section bar part process model, and the part forming precision that solution stretch bending unloading resilience causes can not meet the requirements of problem.

Technical scheme

A kind of modeling method of two-dimentional variable curvature section bar part process model is characterized in that step is as follows:

Step 1 is cut apart rear discrete be straight-line segment and arc section with section bar parts profile line: when getting the section bar part forming of T cross sectional shape, L cross sectional shape, U cross sectional shape and Z cross sectional shape and the contacted contour curve C of mould outer edge surface, starting point and the terminal point of C are respectively P ^StartAnd P ^End, the C total length is l; Tie point P ^StartAnd P ^EndObtain straight-line segment L; Upper to the some P of straight line L apart from maximum with contour curve C ^TopContour curve C is divided into two curve C ₁And C ₂, curve C ₁Starting point is P ^Top, terminal point is P ^Start, length is l ₁, curve C ₂Starting point is P ^Top, terminal point is P ^End, length is l ₂

Adopt following step with curve C ₁And C ₂Discrete is straight line and arc section:

Step 1a: with separation delta l equal length discrete curve C ₁, obtain C ₁N on the curve discrete point P _i(i=1,2 ..., N), Δ l=(5 ~ 10) mm wherein,

P ₁Be P ^Top, P _nBe discrete curve C ₁Another end points, discrete point P _iCurvature be K _i, tangential direction is

Step 1b removes P ₁, P ₂..., P _NThe intermediate point that mean curvature is identical: to i circulate (i=2 ..., N-1), if K _I-1=K _i=K _I+1Set up, then remove P _iThe point; If be left N after removing the identical intermediate point of curvature ^ZIndividual, to remaining N ^ZIndividual point renumbers

Discrete point

Curvature be

Tangential direction is

Step 1c is according to discrete point

Curvature

With curve C ₁Be divided into straight-line segment and arc section: to i circulate (i=2 ..., N ^Z), if

Set up, then determine a straight-line segment L, starting point is

Terminal point is

Straight length is

Otherwise approach with a circular arc

Invalid adjacent discrete point

So that approximation accuracy

And approach the adjacent discrete point with circular arc

Precision $\stackrel{\‾}{p_{i-1,i+j+1}}>0.1;$

Described circular arc approximation accuracy

Calculation procedure as follows:

Step a calculates discrete point

To the arithmetic mean that approaches the arc section distance

Computing formula is $\stackrel{\‾}{p_{i,i+j}}=\frac{\underset{k=i}{\overset{i+j}{\mathrm{\Σ}}}|R-|\stackrel{\→}{P_k^{Z}O}\left|\right|}{j+1},$ Wherein the center of circle is O, and the radius calculation formula is $R=\frac{\left|\stackrel{\→}{P_i^Z{P}_{i+j}^Z}\right|}{\sqrt{2\×(1-\cos )}},$ The central angle computing formula

Keep In two end points

With

Deletion

With

Between the point;

Obtain being divided into a ₁Individual discrete segments Seg _1u(u=1,2 ..., a ₁) C ₁Curve is worked as Seg _1uDuring for arc section, circular arc curvature is K _1u, the arc radius size is

Arc angle is θ _1u, arc length l _1uWork as Seg _1uDuring for straight-line segment, curvature is K _1u=0, decide R _1u=0 angle is θ _1u=0, straight length l _1uα ₁+ 1 discrete point

To curve C ₂Repeating step 1a ~ step 1c obtains being a ₂Individual discrete segments Seg _2v(v=1,2 ..., α ₂) C ₂Curve, wherein:

P _nBe discrete curve C ₂Another end points; Work as Seg _2vDuring for arc section, circular arc curvature is K _2v, the arc radius size is

Arc angle is θ _2v, arc length l _2vWork as Seg _2vDuring for straight-line segment, curvature is K _2v=0, decide R _2v=0 angle is θ _2v=0, straight length l _2va ₂+ 1 discrete point

With segmentation result Seg _1u, Seg _2vAs the process modeling master pattern;

Step 2: adopt numerical simulation to determine contour curve C ₁And C ₂Curve after the resilience

With

Equate to determine process modeling rebound data model according to arc length

Step is as follows:

Step 2a stretch bending numerical simulation: according to the part process model, adopt finite element analysis software to set up finite element analysis model, wherein size of mesh opening is less than or equal to 5mm, and the grid cell type adopts shell unit, and C is set ₁, C ₂Technological parameter be respectively (0.3% ~ 0.5%) * l in the prestretching amount ₁, (0.3% ~ 0.5%) * l ₂, mend the amount of drawing and be respectively (1% ~ 4%) * l ₁, (1% ~ 4%) * l ₂, rate of bending is 0.5deg/s ~ 2.5deg/s;

Then adopt explicit method that the stretch bending process is carried out numerical simulation, adopt implicit method that springback process is carried out numerical simulation;

Step 2b process modeling rebound data model is determined: extract resilience rear profile curve C ₁And C ₂Corresponding grid node collection set ₁And set ₂, the match in CAD software of these nodes is formed line transect spline ₁And spline ₂, spline ₁And spline ₂Expression C ₁And C ₂Curve after the resilience

With

Equate according to arc length, determine Seg _1u, Seg _2vAt curve

With

In corresponding segmentation

If Seg _1u, Seg _2vBe an arc section, its arc angle is The while basis,

Approximate arc radius after the calculating resilience Obtain process modeling rebound data model;

Arc radius be

Arc angle is

With

Corresponding discrete point is respectively

With

Step 3 process modeling calculates:

Step 3a is to discrete segments Seg _1uAnd Seg _2vCarry out springback compensation:

As discrete segments Seg _1u, Seg _2vDo not need compensation during for straight-line segment;

Work as Seg _1u, Seg _2vDuring for arc section, the arc radius after the compensation is

$R_{2v}^C=R_{2v}-\mathrm{\λ}\×(R_{2v}^S-R_{2v}),$ λ is penalty coefficient, and value is 1;

According to $R_{1u}{\mathrm{\θ}}_{1u}=R_{1u}^C{\mathrm{\θ}}_{1u}^C,$ $R_{2v}{\mathrm{\θ}}_{2v}=R_{2u}^C{\mathrm{\θ}}_{2u}^C,$ Calculate the rear arc angle of compensation

Obtain Seg _1u, Seg _2vDiscrete segments after the compensation

Its arc radius is

Arc angle is

Corresponding curve after the compensation

With

Discrete point be respectively

With

The compensation of each discrete segments of step 3b: contour curve C ₁And C ₂Compensation with starting point P ₁Be benchmark, make the rear curve of compensation

With

Starting point

With

With P ₁Same point, and at P ₁The tangential direction at some place Identical;

Two discrete segments with arbitrary continuation

At tie point

Place's single order is continuous, and curvature direction is consistent, and being compensated curve is process modeling modeling reference model;

Step 3c process modeling design: use the cross sectional shape of section bar in CAD software, get the process modeling of part take process modeling modeling reference model as the outline line sweeping;

The optimization of step 4 process modeling: with

With

Replace C ₁And C ₂, the step 2a in the repeating step 2 ~ step 2b, dis are that the point on the contour curve C arrives

With

Ultimate range, if dis≤0.5mm then finish, if dis＞0.5mm then repeating step 3 are so that dis≤0.5mm;

Step 5: if behind the repeating step 3 still be dis＞0.5mm, then repeating step 4 is until dis≤0.5mm end.

Described finite element analysis software adopts the ABAQUS finite element analysis software.

Described CAD software adopts CATIA software.

Beneficial effect

The modeling method of a kind of two-dimentional variable curvature section bar part process model that the present invention proposes, discrete by to outline line is a plurality of straight lines and arc section with outline line is discrete.Adopt finite element analogy, calculate the springback capacity of each discrete segments, by the parts profile curve after repeatedly iterative compensation must compensate, be used for the process modeling definition of part.Beneficial effect: the method applied in the present invention can fast, accurately design the process modeling of section bar part, offers the design that the technologist is used for stretch bending mold.

Description of drawings

Fig. 1: section bar cross section type;

Fig. 2: L-type material part and inner outline;

Fig. 3: isolated section bar part inner outline;

Fig. 4: inner outline is two sections from peak punishment;

Fig. 5: the equal length of inner outline is discrete;

Fig. 6: the iso-curvature segmentation of inner outline;

Fig. 7: resilience analog result;

Fig. 8: curve C ₁, C ₂After the resilience

Each section result;

Fig. 9: curve C ₁, C ₂After the compensation Each section result;

Figure 10: the C that obtains after the simulation for the second time ^S

1-different cross section shape section bar inner outline, 2-L section bar cross section inner outline, C-section bar inner outline, P ^Start-outline line starting point, P ^End-outline line terminal point, P ^Top-outline line peak, C ₁, C ₂-by peak P ^TopCut apart two outline lines that C obtains.

Embodiment

Now in conjunction with the embodiments, the invention will be further described for accompanying drawing:

Take part shown in Figure 2 as example, this part is variable curvature, asymmetric L shaped cross section section bar part, designs the process modeling of this part.The specific implementation process of process modeling definition is described by reference to the accompanying drawings.

1. extract the inner outline C of this part, outline line length l=665, two end points of outline line C are respectively P ^StartAnd P ^End, the peak P of outline line ^TopArrive straight line for outline line C is upper The point that distance is maximum, P ^TopOutline line C is divided into two sections C ₁, C ₂, length is respectively l ₁=330, l ₂=335 shown in Fig. 3,4.

2. get Δ l=5mm, to l ₁And l ₂Disperse, discrete counting is respectively

The discrete P that is respectively ₁₁..., P _{1 (67)}And P _2i..., P _{2 (68)}As shown in Figure 5.

According to the step of step 1 2. 3. to outline line and l ₂Carry out segmentation, l ₁Be divided into 3 sections Seg ₁₁, Seg ₁₂And Seg ₁₃Every section arc radius is respectively 370.133,359.157,0, and the arc length size is 97.30,83.90,151.032, l ₄Be divided into 4 sections Seg ₂₁, Seg ₂₂, Seg ₂₃And Seg ₂₄Every section arc radius is respectively 415.943,485.063,575.681,677.328, and the arc length size is respectively 83.992,80.56,83.935,83.782, and segmentation result as shown in Figure 6.

4. according to 1. method of the step of step 2, be respectively 0.3% * l in the prestretching amount ₁, 0.3% * l ₂, mend the amount of drawing and be respectively 1% * l ₁, 1% * l ₂, rate of bending is to set up finite element analysis model under the 1.5deg/s, and carries out stretch bending simulation and resilience simulation.Result such as Fig. 7.

5. extract the node coordinate of resilience analog result outline line, in CATIA, set up resilience trailing wheel profile as shown in the figure.According to segmentation arc length size, in segmentation corresponding to resilience trailing wheel profile intercepting, arc angle and the arc radius of each segmentation after the calculating resilience,

With

Arc radius be respectively 397.133,361.157,0.

With

Arc radius be respectively 430.943,505.063,605.681,717.328, the resilience result is as shown in Figure 8.

6. according to the arc radius of each discrete segments after the resilience, be 1 by penalty coefficient, process modeling is revised, each section after revising

With Arc radius be respectively 343.133,357.157,0.

With

Arc radius be respectively 400.943,465.063,545.681,637.328.Correction result as shown in Figure 9.

7. take process modeling as the modeling benchmark, according to 1. method of step in the step 2, be respectively 0.3% * l in the prestretching amount ₁, 0.3% * l ₂, mend the amount of drawing and be respectively 1% * l ₁, 1% * l ₂, rate of bending is to set up finite element analysis model under the 1.5deg/s, and carries out stretch bending simulation and resilience simulation.Get access to C ₁, C ₂The maximum springback capacity of termination is 0.225, the accuracy requirement less than 0.5, as shown in figure 10.Therefore this curve is the process modeling modeling according to model.

Claims (3)

1. the modeling method of a two-dimentional variable curvature section bar part process model is characterized in that step is as follows:

Step 1 is cut apart rear discrete be straight-line segment and arc section with section bar parts profile line: when getting the section bar part forming of T cross sectional shape, L cross sectional shape, U cross sectional shape and Z cross sectional shape and the contacted contour curve C of mould outer edge surface, starting point and the terminal point of C are respectively P ^StartAnd P ^End, the C total length is l; Tie point P ^StartAnd P ^EndObtain straight-line segment L; Upper to the some P of straight line L apart from maximum with contour curve C ^TopContour curve C is divided into two curve C ₁And C ₂, curve C ₁Starting point is P ^Top, terminal point is P ^Start, length is l ₁, curve C ₂Starting point is P ^Top, terminal point is P ^End, length is l ₂

Adopt following step with curve C ₁And C ₂Discrete is straight line and arc section:

Step 1a: with separation delta l equal length discrete curve C ₁, obtain C ₁N on the curve discrete point P _i(i=1,2 ..., N), Δ l=(5 ~ 10) mm wherein,

P ₁Be P ^Top, P _nBe discrete curve C ₁Another end points, discrete point P _iCurvature be K _i, tangential direction is

Step 1b removes P ₁, P ₂..., P _NThe intermediate point that mean curvature is identical: to i circulate (i=2 ..., N-1), if K _I-1=K _i=K _I+1Set up, then remove P _iThe point; If be left N after removing the identical intermediate point of curvature ^ZIndividual, to remaining N ^ZIndividual point renumbers

Discrete point

Curvature be

Tangential direction is

Step 1c is according to discrete point

Curvature

With curve C ₁Be divided into straight-line segment and arc section: to i circulate (i=2 ..., N ^Z), if

Set up, then determine a straight-line segment L, starting point is

Terminal point is

Straight length is

Otherwise approach with a circular arc

Invalid adjacent discrete point

So that approximation accuracy

And approach the adjacent discrete point with circular arc

Precision $\stackrel{\‾}{p_{i-1,i+j+1}}>0.1;$

Described circular arc approximation accuracy

Calculation procedure as follows:

Step a calculates discrete point

To the arithmetic mean that approaches the arc section distance

Computing formula is $\stackrel{\‾}{p_{i,i+j}}=\frac{\underset{k=i}{\overset{i+j}{\mathrm{\Σ}}}|R-|\stackrel{\→}{P_k^{Z}O}\left|\right|}{j+1},$ Wherein the center of circle is O, and the radius calculation formula is $R=\frac{\left|\stackrel{\→}{P_i^Z{P}_{i+j}^Z}\right|}{\sqrt{2\×(1-\cos )}},$ The central angle computing formula

Keep In two end points

With

Deletion With

Between the point;

Obtain being divided into α ₁Individual discrete segments Seg _1u(u=1,2 ..., a ₁) C ₁Curve is worked as Seg _1uDuring for arc section, circular arc curvature is K _1u, the arc radius size is

Arc angle is θ _1u, arc length l _1uWork as Seg _1uDuring for straight-line segment, curvature is K _1u=0, decide R _1u=0 angle is θ _1u=0, straight length l _1ua ₁+ 1 discrete point

To curve C ₂Repeating step 1a ~ step 1c obtains being a ₂Individual discrete segments Seg _2v(v=1,2 ..., a ₂) C ₂Curve, wherein:

P _nBe discrete curve C ₂Another end points; Work as Seg _2vDuring for arc section, circular arc curvature is K _2v, the arc radius size is

Arc angle is θ _2v, arc length l _2vWork as Seg _2vDuring for straight-line segment, curvature is K _2v=0, decide R _2v=0 angle is θ _2v=0, straight length l _2va ₂+ 1 discrete point

With segmentation result Seg _1u, Seg _2vAs the process modeling master pattern;

Step 2: adopt numerical simulation to determine contour curve C ₁And C ₂Curve after the resilience

With

Equate to determine process modeling rebound data model according to arc length

Step is as follows:

Step 2a stretch bending numerical simulation: according to the part process model, adopt finite element analysis software to set up finite element analysis model, wherein size of mesh opening is less than or equal to 5mm, and the grid cell type adopts shell unit, and C is set ₁, C ₂Technological parameter be respectively (0.3% ~ 0.5%) * l in the prestretching amount ₁, (0.3% ~ 0.5%) * l ₂, mend the amount of drawing and be respectively (1% ~ 4%) * l ₁, (1% ~ 4%) * l ₂, rate of bending is 0.5deg/s ~ 2.5deg/s;

Then adopt explicit method that the stretch bending process is carried out numerical simulation, adopt implicit method that springback process is carried out numerical simulation;

Step 2b process modeling rebound data model is determined: extract resilience rear profile curve C ₁And C ₂Corresponding grid node collection set ₁And set ₂, the match in CAD software of these nodes is formed line transect spline ₁And spline ₂, spline ₁And spline ₂Expression C ₁And C ₂Curve after the resilience

With

Equate according to arc length, determine Seg _1u, Seg _2vAt curve

With

In corresponding segmentation

If Seg _1u, Seg _2vBe an arc section, its arc angle is

The while basis,

Approximate arc radius after the calculating resilience

Obtain process modeling rebound data model;

Arc radius be

Arc angle is

With

Corresponding discrete point is respectively

With

Step 3 process modeling calculates:

Step 3a is to discrete segments Seg _1uAnd Seg _2vCarry out springback compensation:

As discrete segments Seg _1u, Seg _2vDo not need compensation during for straight-line segment;

Work as Seg _1u, Seg _2vDuring for arc section, the arc radius after the compensation is

$R_{2v}^C=R_{2v}-\mathrm{\λ}\×(R_{2v}^S-R_{2v}),$ λ is penalty coefficient, and value is 1;

According to $R_{1u}{\mathrm{\θ}}_{1u}=R_{1u}^C{\mathrm{\θ}}_{1u}^C,$ $R_{2v}{\mathrm{\θ}}_{2v}=R_{2u}^C{\mathrm{\θ}}_{2u}^C,$ Calculate the rear arc angle of compensation

Obtain Seg _1u, Seg _2vDiscrete segments after the compensation

Its arc radius is Arc angle is

Corresponding curve after the compensation

With

Discrete point be respectively

With

The compensation of each discrete segments of step 3b: contour curve C ₁And C ₂Compensation with starting point P ₁Be benchmark, make the rear curve of compensation

With Starting point

With

With P ₁Same point, and at P ₁The tangential direction at some place

Identical;

Two discrete segments with arbitrary continuation

At tie point

Place's single order is continuous, and curvature direction is consistent, and being compensated curve is process modeling modeling reference model;

Step 3c process modeling design: use the cross sectional shape of section bar in CAD software, get the process modeling of part take process modeling modeling reference model as the outline line sweeping;

The optimization of step 4 process modeling: with

With

Replace C ₁And C ₂, the step 2a in the repeating step 2 ~ step 2b, dis are that the point on the contour curve C arrives

With

Ultimate range, if dis≤0.5mm then finish, if dis＞0.5mm then repeating step 3 are so that dis≤0.5mm;

Step 5: if behind the repeating step 3 still be dis＞0.5mm, then repeating step 4 is until dis≤0.5mm end.

2. the modeling method of described two-dimentional variable curvature section bar part process model according to claim 1, it is characterized in that: described finite element analysis software adopts the ABAQUS finite element analysis software.

3. the modeling method of described two-dimentional variable curvature section bar part process model according to claim 1, it is characterized in that: described CAD software adopts CATIA software.

Images