Week 12:Project-1-Meshing of Door Inner Panel Challenge
Aim : To create the shell (2-D) meshing for the car side door panel by eliminating geometric errors and considering the given elements quality criteria using hypermesh.
Introduction:
1. Car side Door panel
The side door panel is the palstic part. material used for the door panel are acrylonitrile-butadine-styyrene(ABS), ABS/polycarbonnate alloys, polypropylene(PP)
properties
1. Hogh weathering resistance
2. High strength and toughness up to 140deg c
3. Very good heat resistance
4. Good processing characteristics
5. Remail flexible down to 150degree
6. High rigidity
7. Good impact resistance
In the fig0.2 shown the example for side door panel.
Fig.0.1:side door panel
2. Finite Element Analysis
The finite element method is a numerical technique for obtainig an approximate soluction to a wide variety of engineering problem. FEA is done by three phases.
1. pre-processing
2. Solution
3. Post-processing
this project comes under pre-processing. the goals of pre-processing are to develop an appropriate finite element mesh, assign suitable material ID and Hyper-mesh are the example tools and in this project Hypermesh is used. Hypermesh interface is shown in the fig 0.2:
Hypermesh Interface
Above all types of element are done under user-define quality criteria for example, refer tables 1.1
Table 1.1:
Element quality criteria
procedure
The meshing is done by following steps
1. Import side_panel.hm in to hypermesh
2. CAD geometry clean up and topology
3. Mid-surface extraction
4. Defeature
5. Shell meshing
6. Creating properties and thickness assiging.
1. Import side_door.hm in to hypermesh :file>open>model, browse the file and open. in the figure 1,1 shown the model.
file.
From the imported file we can see so many feature such as Ribs, Locators etc. so that this component has different thickness on each feature.
2. CAD geometry clean up and topology: In this steps the given model undergoes check. where all the defect such as collapsed faces, cracks, free edges, T-edges are clear, in the figure 2.1 show description on surface.
on surface
Tool used in topology
Tool>EDge EDit Panel
A. Equivalence(multiple edges at a time) search surface for pairs og free edges and combine into sherad edges
B. Toggle (edge pair at a time) select an edge. equivalences with other free edges found within a user specified tolerance
C. Replace(1 edges pair at a time) select
2. edge to equivalence togethe. control which edges to reain and which to move
D. Geom>surface>Ruled or Geom>Quick edit > filler surface or 2D> spline >surface only (to create missing surface).
In the given model there are so many defects fillets which are very small and should be defeated. in the fig 2.2 shown some defects
Fig.2.2:defects
Defeature all small fillets by using steps
a. Geom>Defeature>surface fillets.
b. Use the surface fillets subpanels to identify and remove surface fillets (curved surface that create a smooth transition between relatively perpendicular geometric relatively perpendicular geometric entities). you can identify fillet based on the radius becasue fillet are always uniform arcs you can also select a fillet by picking on the edge that it connects. once found fillets can be remove using tools that display automatically after the find process.
C. By clicking on remove alll selected fillet will be removes in the fig 2.3 shown the fillets removed by surface fillets.
fillets
Fill missing surafec using line drag: use the drag along line subpanel to create surface by dragging lines or a node list along another line, called the ''drag line''
Steps
a. Select the lines or node list to drag.
b. Select the line that the drag will follow. this can also be a series of connected lines.
c. Merge the input lines into smooth lines when possible, and create a surafe for each group that froms a tangentially continous line. clear this chechbox to crate a surface for each input line, with sheard edges connects surface where relevant
D. Choose where to organize the resulting surafce component shown in the figure 3.4
3. Mid-surface extraction: the given model; is a door panel and before going to the mid-surface extraction check for thickness of entity and measure(Geom.distace). we founddifferent thickness on each feature. for the parent we have T 2.8 units. to simple extraction of mid surafce. model divided in to two component shown in the figure 3.1
comp.
Mid surface is done by manually using offset (Geom>surface edit>offset).offset panel shown in the fig bellow
steps
A. select offset
B. offset moves the selected surface without retaining their connecting to surrounding geometry.
C. select the suraface and make a duplicate the same surface.
D. Input the value which is half of the thickness
E. to check the direaction click on vector normal so that we acn see that offset direaction, also one can change thge diraction by reserve normal shown in figure 3.2
fig.3.3: check offset
Direction of offset
for the all ribs extraction of mid one file final edit tool from midsurface. ( Geom>midsurface>final edit tool) show panel below
select a surface that reperesnts one side of the solid.
select a surface that reperesent the second side of the solid
select extraction options accordingly to define accordingly ti define which surface to take into account when contructing midsurface.
By default , only two surafce that are selected with the side 1 and side 2 surf selectors are considered.
To take into account offset direction of the adjacent midsurface cheeckbox
To to allow modifying pre-existing adjacent midsurafce, select the combine with adjacent midsurafce checkbox. in the fig3.4 shown the mid for rib
Tool
Extend all the ribs to the base surface using extend.
Select the line of extend a surface over edges to another surafe.
select the target surface.
in the fig 3.5 shown the mid surface for the model.
4. Defeaturing : Update the criteria length as per gi8ven element quality criteria which is target/average length 5. Removeing all unnecessary edges, fillet radius etc. also maintain distance between two edges or nodes not less than minimum length of 2.
tools to Defeaturing
A. Toggle edge
Left-click a free edges (red) or a sheared edges to make it supposed(blue).
in either case, the edge must meet the criteria for the type of edge yoe wish to change it to
B. Replace ( 1 edge pair at a time ) 2 edge to equivalence together.
control which edge to retain and which to move
5. Shell meshing:- before meshing assign given element quality criteria in to hypermesh by preferance>criteria file setting shown in fig 5.1
fig 5.1: quality criteria
start meshing process by automesh (2D>automesh) step to mesh
step to mesh
a. select surface for initial mesh and for remash select elements.
b. select size and bias abd select mesh size which is target/average length 5. use the size and bias subpanel to perform size and bias meshing, a flesxible and poerfull meshing method a minimum of inputs are required for the element criteria setting c. select the types of meshing as mixed (quad, tria, mixed, r tria ) and clock on alin and size in order to get proper mesh near feature.
clock on mesh or middle mouse button
modify mesh flow by changing surafce to element and select the element. make sure that while doing mesh all the element quality criteria mush be satisfied. avoid maxim opposite traits and. in fig.5.2 show the mesh flow
fig.5.2: mesh flow
In the fig 5.3 shown the starting point and end point for component to achive better flow.
fig.5.3:mesh start and end point
Remove all quality failing elements by smoothing, by changing distance, angle b/w the nodes of failing element we can see o element are failed
6. Creating properties and thickness assigning: Not only property we can create component, amterial, cross sectionetc by right click on right tab area and select requirement shown in the fig 6.1
Before creating properties we need to create component as per different thickness. right click on the tab area and select component and create component in the figure 6.2
the component as per the thickness if we have verify thickness (taper) then devide the region with respect to mesh flow and design thickness value fro maximum to minimum with equal intervals.
Fig.6.2:components
create property as per the compoent thickness. to createe right click on the tab area and select propert and create properaty
A. select property, we can see that property in the tab area.
B. click on the property and rename, change the thickness, select material, card imange and etc. for each component we mneed to create property shown in the fig6.3
fig.6.3 properties
Each property card has following properties
slover keyword
Id
color
card image
thickness T etc shown in the figure.6.4
fig.6.4.properties
Card
Assign properties to each component by right click on comp>assign>select property. in the graphics areas we can see the model after applying properties shown in the figure.6.5
Fig.6.5:After Applying
Properties
In the fig.6.5 2D detailed elements representation as result
elements reperentation as result
find free edges: Use the edges panel to find the free edges in a group of shell elements, find''T'' connection in a group of shell elements free edges are find as pair of node.
identify an elements edges that is not sheared with another element free edges are normally found the outer perimeter of a part or round opening within the part.
free edges found in your model are display as red plot elements in their own component called^edges. free edges within a filed of elements typically indicate a discontinuties may be intentional, such unintentional, due to geometery discontinuities, meshing methods or components boundary, incase where the mesh has discontinuity there will typically we more then one node at approximately the same location in space such node as called ''coincident'' you can use equivalence to remove the coincident nodes, based on a search tolerance that you specify
steps
1. Go to tools>edge
2. select the elements whose associateed edges you wish to find
3. specify a spherical search radious around each node in the select components. or group of elements. if multiple node are found within this search tolerance they are consider coincide and can be resolved with the equivalent function. tolerance is approximately 60 to 70 % of the thickness
4. click on preview equivalence. and equivalence to join nodes.
5. click on find edges to see the free edges in red color for mesh shown in fig 6.6.1
Edges
check for normals: use the normals panel to display and reverse the normals of element or surface. the orientation of elemet normal can also we adjusted. the normal of an element is determineed by following the order of nodes of element using the right-hand rule.
step
a. use the elements subpanel to display and reverse the normals of elements indirectly by component or directly by elemet or elect to have all of the display 2D element selected automatically. click display to review the current normal orientation of the select element
b. adjust normal based on the orientation method you specified
d. flip all of the normal of the select element shown in the figure 6.6.2
result
shell (2-D) mesh is done successfully for side door panel model by elimibating geometerical errors and considering the given element quality criteria also assigning thickness using Hypermesh.
in the fig 6.7 shown the final FE model.
