Modern finite element analysis can easily achieve accurate results

From finite element analysis （FEA） Obtaining reliable results can be time consuming . Structural analysis usually involves thin-walled structures that can be simulated using shell elements .

This usually means from CAD The solid body of the part file creates the surface . If there is a thick area , The sheet will form at the joint Ts Or radius , You may need to blend the mesh . Creating a hybrid mesh means cutting the part to be meshed into shells , Create surface , Then manage contact sets when connecting solid and shell elements . It takes a lot of time .

For people without a background in stress analysis , You might want to simply use automatic solid meshes . This requires very little preprocessing , Maybe just delete some small features . With the help of modern mesh generation algorithm and FEA solver , For many parts , The problem that simulation leads to increased computing time is not the main contradiction . Saving only two minutes of solution time hardly proves that there is a gain for a complex hybrid mesh that takes hours or days to create .

The result is not reliable

however , The results of solid meshes of thin-walled components may not be reliable . The traditional view is that , To get reliable results , You need several entity elements that pass through the thickness of the entity . If the mesh is fine enough to simulate thin-walled parts , It may take a long time to solve .

In fact, the requirements for multiple solid elements through the thickness of the solid only apply to the first-order elements . These elements have only nodes at their vertices , And the stress and strain are linearly inserted between them .

modern FEA Software usually does not use first-order elements . Now? , Second order elements have become the standard . They have intermediate nodes , The first order polynomial is used to interpolate the stress and strain . Using second-order elements, you can get very good results by using a single element through the thickness of the thin-walled structure . Two or three aspect ratios are usually acceptable , This means that for 1mm Wall thickness of , Generally acceptable 2-3mm Mesh size of .

The accuracy of thin shell high-order element can be proved by modeling a simple plate , Both ends of the plate are provided with elastic supports , And the load uniformly causes bending .

When using first-order entity elements , There will be major mistakes . however , When single-layer second-order solid elements are used , The result is almost the same as using four elements in the entire thickness or using shell elements . For second-order entity elements , As the aspect ratio begins to increase , Good results can still be seen , So there is only one element in the whole thickness , But its plane dimension is the thickness of the plate 2 to 3 times . For a coarse mesh with elements much larger than the plate thickness , Shell elements only show significantly improved accuracy .

by comparison , Even if there are four elements in the whole plate thickness , The accuracy of first-order entity elements is also much lower .

Complex geometry

For more complex shell geometries , Similar results can be obtained . The element size is more important than the radius of the tight bend feature , The value of mesh generation algorithm based on curvature is highlighted , The algorithm will automatically reduce the size of the elements in these areas .

Use second-order entity elements , General advice on using shell elements can be ignored , Unless the solid mesh can realize multiple elements through wall thickness . This means that the time-consuming task of preparing geometry for shell engagement can usually be avoided . The combination of high-order solid elements and curvature based automatic mesh generation makes modern FEA Software can usually get accurate results without effort .