Types of Idealizations. Idealizations. Cylindrical Shaped Part. Cyclic Symmetry. 3D Shell Model. Axisymmetric

Transcription

1 Types of Idealizations Idealizations Selecting the model type 3D Solid Plane Stress Plane Strain 3D Shell Beam Cyclic Symmetry Cylindrical Shaped Part Interior Pressure Load 3D model can be used to model the entire part. A full 3D model provides a good check for all of the idealized models run previously. Cyclic Symmetry We can eliminate either the upper or lower holed for cyclic symmetry Axisymmetric 3D Shell Model Interior Pressure Load 2D Axisymmetric model All holes and ribs removed All holes removed 1

2 Plane Strain Interior Pressure Load Start With Simple Analysis 3D Shell Simple geometry early in the design All holes and ribs removed Plane Strain Next New Add Features Axisymmetric Add More Features Fix problems if any are found Add some features Do a 3D analysis Fix problems if any are found Add more features Compare results with last step Reduce the problem size with symmetry Eliminate Reentrant Corners Add fillets to eliminate reentrant corners Start With 3D Shell Model Load Load 2

3 Load Cannot Use Axisymmetric Plane Strain Cyclic Symmetry Plane Stress Model as 3D Solid Load Tubular Construction Plane Stress / 3D Solid Idealization Beams 3D Shells 3D Solid Loads in Plane 3D Shell / 3D Solid Idealization 3D Solid Only Solid Too Thick Loads out of Plane 3

4 Use of Symmetry Symmetry Use of symmetry to reduce the size of the model and to constrain it against translation Full featured part De-featured part Part size reduced with symmetrical boundary conditions Part size reduced with asymmetrical boundary conditions Part size reduced with both symmetrical and asymmetrical boundary conditions Part to Analyze Back in,, and lbs 3.44x10-14,00 Full Part Part De-featured Back in,, and 4000 lbs 4

5 De-featured Full Part x10-13,300 Symmetrical Boundary Conditions Symmetrical Half Part Trans Trans Plane Plane Plane Back in,, and Trans Rotate Rotate Rotate in 2000 lbs Half Symmetrical Part x10-14,200

6 Asymmetrical Boundary Conditions Asymmetrical Part Trans Plane Plane Plane Back in,, and Trans Trans Rotate Rotate Rotate 2000 lbs Bottom fixed in and Asymmetrical Boundary Condition x10-13,300 Symmetrical and Asymmetrical boundary conditions Back in,, and x10 - Side fixed in 1000 lbs Bottom fixed in and 13,400

7 Symmetrical and Asymmetrical BC Bracket Results Element Passes CPU Disp VM Stress Full x10-14,00 Defea 94 3, x10-13,300 Sym x10-14,200 Asym x10-13,300 Asym- Sym x10-13,400 Constraining Translation Fully constrained face Partially restrained face with a constrained point Symmetrical boundary condition with small constrained region Symmetry used to constrain translation 000 lbs Chain Link 000 lbs De-featured Part Half Symmetry Fix in,, and 000 lbs 7

8 Half Part Symmetry x10-32,700 Point Fix in and x10 - Point in 000 lbs 30,000 Half Part Point Region Boundary Condition in in,, and 000 lbs 8

9 Region x10-30,000 Constrained with Symmetry in Bottom fixed in in 3.3x10-31, lbs Symmetrical Boundary Conditions Link Results Elements Passes CPU Displace VM Stress Half Part x10-32,700 Point x10-30,000 Region x10-30,000 Symmetry x10-31,200 9

10 Half Part Symmetry Half Part Point Region Symmetrical Boundary Conditions 10