关于有限元分析教程

维分子

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[ 本帖最后由 维分子 于 2008-3-28 09:08 编辑 ]

维分子

有限元分析的主要步骤
前处理
: V3 f5 V5 O1 L/ S4 P- p4 m. V" r2 i$ H建立分析对象的有限元模型
. N0 h8 y  j& `! Z求解
对有限元模型的计算工况进行求解
后处理
观察分析结果，评估设计是否符合要求

维分子

Cosmos/Works有限元分析的步骤
9 }+ V4 h& d$ J2 k  `) M- n# M建立几何模型
0 |- {" @/ u5 m, _/ ~定义材料属性
定义边界条件(约束和载荷)
划分网格
求解
6 J  T5 Z$ P! u8 R! L8 i查看和评估结果

维分子

企业需求与有限元分析
4 g$ p) a2 f2 e0 R更少的样机：省钱
更短的周期：省时
* U* D( `  m# }3 r+ _) R更好的质量：品质

维分子

线性静力分析：定义专题
Displacement in the radial direction:
" L/ V2 M+ |: v% sSelect “Axis1” and then define displacement plot in X-direction (radial to the axis). Select deformation scale=1
Right-click on the displacement plot icon “plot2” and then select”List selected”
8 R$ t  i3 \) |  p: _8 S9 SAverage displacement of “pole piece lower” = -0.0019504” (decrease in radius)
# c! ~0 g6 R  f; CAverage displacement of “pole piece upper” = 0.007896 “ (increase in radius)
( `6 U& z' g1 C4 ?( gSum of these 2 displacement = 0.009846” ~Initial interfernce of 0.01”
5 f8 {* l4 s9 FHoop Stress (tangential):
Select “Axis1” and then define stress plot in Y-direction (radial to the axis). Select deformation scale=1
Right-click on the stress plot icon “plot2” and then select”List selected”
1 B0 T' {) E* Y* O5 @Negative stress on “pole piece lower” (compression)
1 ?' f# B# `8 r2 ]; r2 ?% _6 kPositive stress on “pole piece upper” (tension)
6 u: [. d0 x7 P+ }线性静力分析：定义材料属性
2 }* Q& K5 S9 s/ aSimulate parts which are separated by large gaps
6 j3 R# H/ [$ nFirst run the model with small displacement option and look at the results
If you see that there is a change in the orientation of the contact surfaces during loading or if the results doesn’t look realistic, use large deflection option

% a. P/ J. M( ^9 e1 `# e* ~线性静力分析：网格划分
: a/ [# Z, t% J; ?Open “RectangleGap.sldasm”
Define a static study “smallcontact”
Apply material “Alloy steel” to both parts
Apply a pressure of 725 psi on the top face
3 \  u4 h: [+ q0 w# uSelect the two front faces and then apply restraint. Select Flat face option and then select “Normal to face”
Fix the left semi-circular face
$ _2 ^% X1 b' m3 l6 B8 Z1 cHide the loads/bc symbols
Define “Surface” contact between the top face of the bottom leg and the perpendicular face
( \4 T6 Z- j% KCreate mesh and run
Define a stress plot with scale factor = 1. Look at the contact surface.
6 V, i4 m. c/ i4 l) ?线性静力分析：定义约束
; P) {% t' `: g7 y) h9 [6 ~- CDefine a new static study “LargeDisp”
& g/ w( l' m$ S; q" DDrag’n drop the material and loads/bc folders from “small contact” study
Right-click on the study name and click on properties. Select “Large displacement contact” option.
Run the analysis
% \6 K, `$ B! f6 \Define a stress plot with scale factor = 1. Look at the contact area.
% C- e; R' E) @# L/ C; X2 H  I线性静力分析：定义载荷
/ p2 v3 Q# ~! u# S" w) M. n  P8 E/ g; DSimulate heat resistance between parts for thermal analysis
1 p3 Y3 F' m6 n. z4 P, @8 L: V Account for heat resistance of thin parts without actually modeling them!

* _. l! X/ z. ?  L* f线性静力分析：求解
: a4 R2 n* @' o# a% g# q0 YOpen “Thermal contact resistance_transistor.sldasm”
Explode the model and set preferred units to “SI” and temperature units to “Kelvin”
Define a thermal study “NoRes”
Apply material “AISI 304” for “Voltage regulator” and “Copper” for Heat sink
Define “Surface” contact with No resistance between the contact faces
9 `4 I" x, ?0 j: n. t' JApply convection to all the faces of the model except the contact faces
9 c3 T1 i& r# N' c% ]- Y5 fFilm coefficient = 250 W/(m^2.K)
$ E/ v% n6 B, r- q. E' |9 kBulk temperature = 298 K
$ {% V8 v+ J% P5 h线性静力分析：观察结果
Apply Heat power = 25 W for “Voltage regulator”
Mesh with default settings and run the analysis
Notice the temperature distribution of the heat sink
3 S" U8 s7 N+ E  R6 eDistributed Resistance:
: \- g7 t) K* g# E+ CDefine a new thermal study “DistRes”
Drag’n drop “Material” folder and Loads/Bc folder from NoRes study to DistRes study
Edit contact pair definition and define distributed resistance = 0.005 K.m^2/W
Total resistance = Distributed resistance X Contact area                           = 0.005 X 0.0003392 = 14.7 K/W
. B" n# r! h5 P3 J; w& cRun the study “DistRes”
3 T% l" z; I- A$ h: v3 BNotice the temperature distribution of the heat sink
Thermal Contact Example (Cont’d)
Probe the temperature value
Define a thermal plot with mesh
Right-click the plot icon and select Probe
! S3 a0 ^6 N2 FPick all the nodes on the edge of both the parts
# d. T* P1 ?: F+ n1 e* R3 C( \Click on the Plot icon to view the temperature variation from the top face of the voltage regulator to the bottom of the heat sink

Thermal Contact Example (Cont’d)
Total Resistance:
Define a new thermal study “TotalRes”
Drag’n drop “Material” folder and Loads/Bc folder from NoRes study to TotalRes study
; L7 \5 R' B9 m0 EEdit contact pair definition and define Total resistance = 25 K/W
' \) `  ^, \' O" @) c' sRun the study “TotalRes”
8 |6 V2 [& R" N4 `1 |" }3 vNotice the temperature distribution of the heat sink

Load Simulation: Remote Loads
8 h- v- l* o3 Z7 x/ qRemote Loads
- }/ [+ F2 p- r8 X4 x0 xDirect Transfer
) X  E7 Y0 F$ B; N; MFlexible surface
  c8 G& Z3 O* \; r1 {' X. }Applied as equivalent force & moment
Rigid Beam
Rigid surface
Remote Restraint
, j$ Q! V$ x" a" s, I9 cRigid connection
Model effect of a rigid virtual part between two faces


4 q( j% H/ I( H) I( r% w0 Y) ORemote Load Example
3 r( q1 {3 c* A7 VOpen “RemoteLoadExample.sldasm”
" a+ l& Q3 @$ J' q! S. _Define a static study “Remote”
Apply material “Alloy steel”
2 g9 J$ M5 K. `- z$ c% G1 ]Fix the flat face
4 P1 h* d) ]2 O8 g4 TSelect “Coordinate system1” and the end face of the cantilever. Define remote load of 10N in the X direction.
Create mesh and run.
" M5 D. T( t0 h* vDouble-click on “Plot1” under the stress folder
Animate the results
/ i' V# d1 J4 Y& z2 k, x: M6 CCompare the plot results of “Remote” study with “Axial Tension” study
" W1 Q5 `( [" Z/ Q6 F; f
Motion Load Transfer Using Remote Loads
Go to SW Add-in and click “COSMOS/Motion”
Open “LoadTransferModel_With_Result.sldasm”
Play the animation and save the load file for frame # 300
Delete the motion results
Go to CW menu, Import Motion Load and open this load file from “MotionLoadTransfer” directory
% u) X6 z1 }2 k' Y  ^Select all the loads related to crank-1 and then click OK.
5 [; r+ ~4 e' A$ T" E5 }; oOpen the part “crank”
You’ll see that there is a new study “Frame-300” with motion loads transferred as remote loads
  {  ]" `* B$ rApply material “Plain carbon steel”
Go to study properties and select “FFEPlus” solver and “Inertia relief option”
Run the analysis
" P2 r  h0 E( l, @9 ~2 JPostprocessing: Results in local CS
Plotting
  ]! f6 b$ U- M$ j! m8 l# l$ rListings
: l3 ~& x+ k4 \- ]6 V' M% UReaction forces
  Q+ h$ `& x3 p. d4 MPostprocessing: Exploded views
Plot results on SolidWorks exploded views
& f4 M* r7 ~5 E0 Z: A" `
( |3 T! S) ^( w' d( t" ?& fPostprocessing: New tools
Improved probing with graphing option
List results by Entity
% p' Q$ y0 B7 L$ U8 b4 vWeb Reports
' S5 L4 n2 O) R# iInclusion of report templates in the feature tree
Saving of report setting
$ _7 A+ {) G: Q$ J/ b; ]: FAutomatic creation of all plots
( u% x3 K# \5 y4 {% PReport Example
Open “ReportExample.sldasm”
' a3 k2 C  E2 @/ c" f- hNew option save JPEG files (Right-click on the Study name)
' g& m2 n+ S; A4 `% L* @( \& x$ CRight-click on Report and click define
Point to the logo file “ReportLogo.bmp”
Point to the right stress AVI and VRML files
8 C# g: k4 {/ S. U: oSelect option “Automatically update all plots in JPEG files”. Click OK.
3 I" f8 h6 b/ m! kYou can also get a print version
Material
Supports orthotropic material properties for solids and shells
. g5 N: |& F3 ~- c! O2 l3 b8 YOption to use different Material library files
New redesigned material browser utility
- E/ G) m8 r' w
# n) j! U  v3 \9 R, gLicensing
Single license file for hardware lock & FlexLM security
New License Administrator to manage the license
' U3 R- X4 h" X0 N5 P6 oSupport USB port hardware lock
Support redundant servers
) M" l5 ?/ q- ^* i4 Q
/ R; N9 r- b2 UOther customer enhancements
4 w% Q5 o' O9 F, m* eAutomatically run analysis after meshing
Edge pressure for shells
Apply uniform temperature to components
Automatic adjustments of Max & min in plots on update
FFEPlus solver for thermal analysis
Increase the limit on number of modes for frequency analysis from 20 to 100
8 G2 M0 g. C' a+ [$ W) qAdd symbol for gravity loads
Improve section clipping
; r  Z/ r/ g* e' k  w2 X' KSave plots in JPEG format
Improve transient thermal animations
! `7 E0 h: L: j% M& a6 V. w4 n! E6 gOption to switch between different languages
- `  d$ f- Z/ v) kOthers…
1 x: C, K! l5 o& F
Thank You!