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Презентация была опубликована 3 года назад пользователемИнга Веденеева

1 S10-1 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation SECTION 10 PLIES OVER DOUBLY CURVED SURFACES

2 S10-2 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation

3 S10-3 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation APPLYING PLIES TO CURVED SURFACES n How the ply material is to shear when drawn over a curved surface must be specified. There are two different shear (local) draping algorithms u Scissor, or slide u These are material-specific behavior n How the plies are forced globally into contact with the surfaces must be indicated. This is called (global) draping. Methods are u Geodesic, planar, energy, or maximum u These are manufacturing methods n A starting point of fiber application on the surface, and the initial fiber direction at this point must be specified.

4 S10-4 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation n Local draping is concerned with fitting a small section of fabric material to a generally curved surface n If the surface has nonzero Gaussian Curvature the material must shear in its plane to conform to the surface n This deformation is highly dependent on the microstructure of the material. Thus, local shearing can be regarded as a ply material property. n The two shearing methods are u Scissor draping u Slide draping LOCAL DRAPING BY SHEARING

5 S10-5 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation n An originally square piece of material shears in a trellis-like mode about its vertices to form a rhombus n This simulates how woven fabric behaves SCISSOR SHEAR ALGORITHM a a

6 S10-6 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation n An originally square piece of material shears (top and bottom edges remain parallel) with vertical separation remaining constant n This simulates how unidirectional materials behave a a SLIDE SHEAR ALGORITHM

7 S10-7 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation SHEAR ALGORITHM n The shear algorithm is specified when creating the material in MSC.Laminate Modeler. This is because shearing behavior is a ply material property. n For draping select either Scissor or Slide from the pull-down menu n Shear builds up more rapidly using the slide draping algorithm. This reflects actual manufacturing experience that woven fabrics(scissor shear) are more drapable than unidirectional materials(slide shear). Therefore the scissor draping method is the default. For small deformations, predictions using the two shear algorithms are identical.

8 S10-8 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation GLOBAL DRAPING ALGORITHMS n Specifies the way that material is draped on a surface at a macroscopic/global level n Different algorithms used for a doubly curved surface give different draping results n Remember there is no unique drape for a ply!

9 S10-9 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation n Draping starts by defining two perpendicular axes (principle axes), with the origin at the start point, and zero shear there. The types of axes are u None (no axis type specified) u Geodesic u Planar n If draping leaves the region, in the neighborhood of the origin where the draping pattern is unique, the draping proceeds by extension instead of axis. The types of extension are u Geodesic u Energy u Maximum GLOBAL DRAPING ALGORITHMS (Cont.)

10 S10-10 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation GEODESIC AXES Application direction (view direction) Geodesic principal axes Fiber direction ** Reference angle ** * * Reference direction n Geodesic principal axes are created beginning at the starting point and going out along geodesic paths/lines (shortest paths) of the surface. Once these principal axes are defined a unique solution can be found for draping the surface in a neighborhood of the starting point/origin.

11 S10-11 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation n This may be the most natural method for draping, and appropriate for conventional laminating methods n This method can be unsuitable for highly curved surfaces and corners GEODESIC AXES (Cont.)

12 S10-12 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation n Planar principal axes are defined by the intersection of two orthogonal planes and the surface. The planes are defined by the application direction(view direction) vector and a vector created by rotating the reference direction vector through the reference angle n This method is appropriate for symmetrical surfaces PLANAR AXES Application direction (view direction) Principal planes Vector from rotating; fiber direction ** Reference angle ** * * Reference direction

13 S10-13 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation n If no axes are specified(Axis Type: None) no principal axes are defined, and global draping proceeds using only extension, as specified, e.g. Energy. The fabric is extended outwards, beginning at the starting point. NO AXES

14 S10-14 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation GLOBAL DRAPING BY EXTENSION n When either the Geodesic or Planar axis type is selected there is a domain around the start point where the global draping pattern is unique n If draping extends beyond this domain the fabric pattern will not be unique n When draping occurs outside a domain it is done using an extension type instead of an axis type Domain of Unique Global Draping Extend Beyond Domain of Unique Global Draping Start point Domain Extend beyond domain

15 S10-15 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation GLOBAL DRAPING BY EXTENSION (Cont.) n The extension types are u Geodesic u Energy u Maximum

16 S10-16 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation GEODESIC EXTENSION n The fiber closest to a principal axis(*) is identified, then extended along the geodesic path(**) of the surface at the fiber n Note that if geodesic extension is done inside of the domain of unique global draping the result obtained is identical to that obtained for the geodesic axes method * ** Start point Domain

17 S10-17 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation n The fabric is extended from the perimeter edges of the domain in a direction which minimizes the instantaneous shear strain deformation energy. This involves rotating the free edges of the fabric. n This method is suited for highly-curved, deep-drawn surfaces, but draping is less well controlled than previous methods ENERGY EXTENSION

18 S10-18 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation MAXIMUM EXTENSION n The fabric is extended from the perimeter edges of the domain in a direction which minimizes the instantaneous shear angle. This involves rotating the free edges of the fabric.

19 S10-19 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation PROJECTING OR PAINTING PLIES n Can project or paint plies onto a surface n This is totally different from the approaches using draping n Projecting plies is done in one of two ways u Axis method u Plane method u It is not true draping, and is similar to the method used in MSC.Patran n Painting is only valid for isotropic materials. Composites might be modeled as honeycomb or using painting.

20 S10-20 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation n A global axis(e.g. X-axis), corresponding to a fiber direction, is projected normally onto an element at its first node. The axis, created by projecting, is then rotated an angle in the counter-clockwise direction (as viewed from the viewing point). Note that is generally not equal to the element material angle,. n Select an axis u Projected X-axis, Projected Y-axis, or Projected Z-axis u Or, Projected for input of Projection Vector, e.g. AXIS PROJECTING ALGORITHM X Z Y Projected X-axis Parallel to X-axis

21 S10-21 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation n The element material angle is the angle between the intersection of a plane, or one parallel to it, with the element(*) and the first edge of the element(**). The plane is defined in several ways. n The plane is defined by u Plane XZ: X-Z plane rotated by angle about Z-axis from X-axis u Plane YX: Y-X plane rotated by angle about X-axis from Y-axis u Plane ZY: Z-Y plane rotated by angle about Y-axis from Z-axis u Plane: specified by Reference Direction vector, e.g., and rotation about application direction PLANE PROJECTING ALGORITHM x z * **

22 S10-22 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation Place in GUI TypeScissor (drape) Slide (drape) ProjectionLM_Material menu Additional Controls…/ Method Axis: None, Geodesic, Planar Extension: Geodesic, Energy, Maximum Axis Plane LM_Ply menu OVERVIEW OF PLIES

23 S10-23 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation CASE STUDY: VISUALIZATION OF PLY PATTERN n Start using MSC.Laminate Modeler interactively to figure out how to drape a model, obtaining the best possible result n The resulting ply pattern is viewed on-screen with color coding for the degree of shear angle. Prior to V2001 the shear angle spectrum values are default red for 0-5, green for 5-10, and so on. (The values are really just fractions of the Maximum Strain (Degrees) value defined for the material). For V2001 blue is below 50% allowable shear, yellow is up to 100% and red is over 100% allowable shear. n If shear is excessive, try u Reducing the coverage area u Changing the location of the starting point

24 S10-24 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation The numeric extremes are shown in the upper left corner The resulting shear in the ply is color coded on the model CASE STUDY: VISUALIZATION OF PLY PATTERN

25 S10-25 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation PLY MENU TOGGLE ON/OFF DISPLAY ICONS Reference and Application Direction vectors Boundary Visualization (explained later) Outline (debugging tool, not intended for customer use) Draped Pattern Flat Pattern Maximum strain and shear values etc in number form Visualisation of the element by element fibre directions Materials Close Draped Pattern

26 S10-26 PAT325, Section 10, February 2004 Copyright 2004 MSC.Software Corporation n Perform Workshop 5 Draping a Doubly Curved Surface in your exercise workbook n Be sure to ask for help on anything you dont understand EXERCISE

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