Finite Element Analysis (FEA) Background - UK：有限元分析（有限元）背景-英国.ppt

Finite Elements Analysis BasicsAnalysis FoundationIn designing the gear shafts below, what quantities would we examine?–Stress– Strain– Displacement– Rotation– TemperaturesIMc??JTr??L???AEPL??GJTL??)(TT????AP??2222221zTyTxTtT????????????)()1(2yxxE????????Analysis FoundationIn designing a valve, burner, or heat sink, what quantities would we examine?– Pressure drop– Temperatures– Mass flow rate– Velocities– Fluid mixingdtdwzwywxwzPgdtdvzvyvxvyPgdtduzuyuxuxPgzyx????????????????????????????????????????????????????????????????????????2222222222222222222222121122zgVPzgVP???????3/15/?22opDDVAFC????VD?ReAnalysis Foundation?Hand calculations are easily applied to simple geometries.– Cylinders– Blocks– Beam structuresThey are not easily or accurately applied to general (complex) shapes.?To plex shapes we break them into many simple shapes pute bined Analogy: AreaSuppose we want pute the area of a generic Analogy: AreaWhat do we do to improve the accuracy of the area measurement?FEA MeshThe pieces we divide the model into are called ELEMENTS. Equations are generated for each element. These bined into a system of equations for the entire structure. Matrix algebra is used to solve the system of Mesh: Elements? Each element is a simple solid.? Elements are connected together at locations called Mesh: Elements? A BRICK element model often must be created MANUALLY.? A TETRA element can be created elementTetrahedral (Tetra) elementBrick Elements vs. Tetra Elements?Brick Models:+ Usually have many fewer elements than a Tetra model (Quicker Solution).- Time-consuming to generate.- Very difficult to create a brick model plex parts.?Tetra Models:+ Quick to generate the model (with Automatic meshing).+ The same accuracy can be achieved as with Bricks.+ Can mesh plex parts.- Usually have more elements than a Brick model.