有限元實(shí)例分析

鋼軌道靜力分析一、問題描述如下圖為一剛軌道，建立該剛軌道的三維實(shí)體模型，并對(duì)其進(jìn)行結(jié)構(gòu)靜力分析。鋼軌道結(jié)構(gòu)示意圖彈性模量〔也稱楊式模量〕E=200GPa；泊松比；載荷F=5000N/m選擇單元類型Solid45單元用于建立三維實(shí)體結(jié)構(gòu)的有限元分析模型，本實(shí)例是研究平面應(yīng)力問題，選用8節(jié)點(diǎn)的平面應(yīng)力單元，每個(gè)節(jié)點(diǎn)具有X、Y、Z方向的三個(gè)移動(dòng)自由度。具體操作如下：MainMenu>Preprocessor>ElementType>Add/Edit/Delete“StructuralSolid〞→“Brick8node45〞→ok單元類型庫對(duì)話框三、設(shè)置材料屬性材料特性對(duì)話框點(diǎn)擊主菜單中的“Preprocessor>MaterialProps>MaterialModels〞，彈出窗口如下圖，逐級(jí)雙擊右框中“Structural\Linear\Elastic\Isotropic〞前圖標(biāo)，彈出下一級(jí)對(duì)話框，在“彈性模量〞〔EX〕文本框中輸入：2e11，在“泊松比〞〔PRXY〕文本框中輸入：0.3材料特性對(duì)話框如下圖，再點(diǎn)擊“OK〞按鈕關(guān)閉對(duì)話框。四、實(shí)體建模對(duì)于本實(shí)例的有限元模型，首先需要建立軌道截面幾何模型，然后對(duì)其進(jìn)行三維建造。具體的操作過程如下：1.創(chuàng)立關(guān)鍵點(diǎn)操作：MainMenu>Preprocessor>Modeling>Create>Keypoints>InActiveCS軌道的橫截面由8個(gè)關(guān)鍵點(diǎn)連線而成，其各點(diǎn)坐標(biāo)分別為：1〔0,0,0〕、2〔25,0,0〕、3〔25,15,0〕、4〔17,15,0〕、5〔21,8,0〕、6〔4,8,0〕、7〔8,15,0〕、8〔0,15,0〕。點(diǎn)擊主菜單中的“Preprocessor>Modeling>Create>Keypoints>InActiveCS〞，彈出對(duì)話框。在“Keypointnumber〞一欄中輸入關(guān)鍵點(diǎn)號(hào)1，在“XYZLocation〞一欄中輸入關(guān)鍵點(diǎn)1的坐標(biāo)〔-0.08，0，0〕，點(diǎn)擊“Apply〞按鈕，同理將2~8點(diǎn)的坐標(biāo)輸入，此時(shí)，在顯示窗口上顯示所生成的8個(gè)關(guān)鍵點(diǎn)的位置。2.由關(guān)鍵點(diǎn)生成線的操作：MainMenu>Preprocessor>Modeling>Create>Lines>Lines>InActiveCoord依次選擇各點(diǎn)，即可生成直線。生成后的組成軌道橫截面的直線如下圖。生成面：MainMenu>Preprocessor>Modeling>Create>Areas>Arbitrary>ByLines〔逆時(shí)針選線〕，依次選擇每條線，單擊OK，即可生成平面圖：生成三維實(shí)體點(diǎn)擊主菜單中的“Preprocessor>Modeling>>Operate>Extrude>Areas>AlongNormal〞，彈出平面選擇對(duì)話框，點(diǎn)選上一步驟生成的平面，點(diǎn)擊“OK〞按鈕。之后彈出另一對(duì)話框，在“DIST〞一欄中輸入：50〔軌道的長度〕，其他保存缺省設(shè)置，點(diǎn)擊OK按鈕關(guān)閉對(duì)話框，即可生成工字鋼梁的三維實(shí)體模型。如圖：五、網(wǎng)絡(luò)劃分1．設(shè)定單元大小?？紤]到實(shí)體的邊長為4-50，所以網(wǎng)格尺寸設(shè)置為2。點(diǎn)擊主菜單中的“Preprocessor>Meshing>MeshTool〞,彈出對(duì)話框，在“SizeControl〞標(biāo)簽中的Global一欄點(diǎn)擊Set按鈕，彈出“網(wǎng)格尺寸設(shè)置〞對(duì)話框，在SIZE一欄中輸入：2，其他保存缺省設(shè)置，點(diǎn)擊OK按鈕關(guān)閉對(duì)話框。2．接著上一步，在圖的劃分網(wǎng)格的對(duì)話框中，選中單項(xiàng)選擇框“Mesh〞和“Volumes〞，其他保存缺省設(shè)置，然后點(diǎn)擊“Mesh〞按鈕，彈出體選擇對(duì)話框，點(diǎn)選鋼軌道實(shí)體，并點(diǎn)擊OK按鈕，即可完成對(duì)整個(gè)實(shí)體結(jié)構(gòu)的網(wǎng)格劃分，其結(jié)果所示。六、施加位移約束點(diǎn)擊主菜單的“Preprecessor>Loads>DefineLoads>Apply>Structuaral>Displacemengt>OnAreas〞，彈出面選擇對(duì)話框，點(diǎn)擊軌道的左端面，點(diǎn)擊“OK〞按鈕，彈出對(duì)話框，選擇右上列表框中的“AllDOF〞，并點(diǎn)擊“OK〞按鈕，即可完成對(duì)左端面的位移約束，相當(dāng)于梁的固定端。同理，對(duì)軌道的右端面進(jìn)行固定端約束。七、施加外載荷點(diǎn)擊主菜單中的“Solution>DefineLoads>Apply>Structural>Pressure>OnAreas〞，彈出“選擇〞對(duì)話框，點(diǎn)選受力的兩個(gè)平面，單擊OK按鈕，彈出對(duì)話框。在【VALUELoadPRESvalue】文本框中輸入壓力值5000，單擊OK按鈕。八、求解點(diǎn)擊主菜單中的“Solution>Solve>CurrentLS〞，在彈出對(duì)話框中點(diǎn)擊“OK〞按鈕，開始進(jìn)行分析求解。分析完成后，又彈出一信息窗口提示用戶已完成求解，點(diǎn)擊“Close〞按鈕關(guān)閉對(duì)話框即可。至于在求解時(shí)產(chǎn)生的STATUSCommand窗口，點(diǎn)擊“File>Close〞關(guān)閉即可。九、查看結(jié)果1．查看變形：點(diǎn)擊主菜單中的“GeneralPostproc>PlotResults>DeformedShape，彈出【PlotDeformedShape】對(duì)話框，選擇Def+undefedge〔顯示變形后的結(jié)構(gòu)和未變形輪廓線〕單項(xiàng)選擇按鈕，在圖形窗口中顯示出變形圖及變形前的輪廓線，如下圖：查看節(jié)點(diǎn)等效應(yīng)力：選擇MainMenu>GeneralPostproc>PlotResults>ContourPlot>NodalSolu命令，翻開【ContourNodalSolutionData】等值線顯示節(jié)點(diǎn)解數(shù)據(jù)對(duì)話框，單擊Stree〔應(yīng)力〕>vonMisesstree選項(xiàng)，選擇Defshapeonly(僅顯示變形后模型〕按鈕,單擊OK按鈕，圖形窗口中顯示出等效應(yīng)力分布圖：顯示變形動(dòng)畫：點(diǎn)擊應(yīng)用菜單(Utility>Menu)中的“PlotCtrls>Animate>DeformedResults...)點(diǎn)擊“OK〞按鈕關(guān)閉對(duì)話框，即可顯示本軌道的變形動(dòng)畫〔見附件視頻文件〕。十、解讀后處理結(jié)果本實(shí)例主要是研究軌道的靜態(tài)受力情況，采用的是一般的剛性材料，當(dāng)然，由于本人經(jīng)驗(yàn)缺乏以及資料有限，所以無論是模型的尺寸還是模型的材料、參數(shù)設(shè)計(jì)上可能存在一定的局限性。考慮到實(shí)際應(yīng)用問題，所以將位移約束設(shè)置在軌道的兩邊，可能由于本次施加的載荷較大，所以模型的變形相對(duì)也比擬大。從等效應(yīng)力的分布圖可以看出，底座受力較小，應(yīng)力主要集中在上局部的兩個(gè)受力端，而應(yīng)力最大處是受力面與約束面的接觸處。從應(yīng)力分析和形變分析來看本實(shí)例的網(wǎng)格設(shè)計(jì)精度合理，適合本例子。命令流/BATCH/COM,ANSYSRELEASE10.0UP2005071811:14:4911/19/2021RESUME,'AP1008221','db','.'/COM,ANSYSRELEASE10.0UP2005071811:14:4911/19/2021/PREP7!*VOFFST,1,50,,/DIST,1,0.924021086472,1/REP,FAST/DIST,1,1.08222638492,1/REP,FAST/ZOOM,1,RECT,0.126171,-0.0951754,0.0954618797553,-0.113596486069/DIST,1,1.08222638492,1/REP,FAST/VIEW,1,,,1/ANG,1/REP,FAST/VIEW,1,,,1/ANG,1/REP,FAST/VIEW,1,1,1,1/ANG,1/REP,FAST/DIST,1,0.924021086472,1/REP,FAST/REPLOT,RESIZEESIZE,1,0,ESIZE,1,0,SAVEMSHAPE,1,3DMSHKEY,0!*CM,_Y,VOLUVSEL,,,,1CM,_Y1,VOLUCHKMSH,'VOLU'CMSEL,S,_Y!*VMESH,_Y1!*CMDELE,_YCMDELE,_Y1CMDELE,_Y2!*/DIST,1,1.08222638492,1/REP,FASTFINISH!/EXIT,NOSAV/BATCH/COM,ANSYSRELEASE10.0UP2005071811:26:1311/19/2021RESUME,'AP1008221','db','.'/COM,ANSYSRELEASE10.0UP2005071811:26:1311/19/2021/REPLOT,RESIZE/PREP7ESIZE,2,0,MSHAPE,1,3DMSHKEY,0!*CM,_Y,VOLUVSEL,,,,1CM,_Y1,VOLUCHKMSH,'VOLU'CMSEL,S,_Y!*VMESH,_Y1!*CMDELE,_YCMDELE,_Y1CMDELE,_Y2!*SAVE/DIST,1,1.08222638492,1/REP,FAST/VIEW,1,1,2,3/ANG,1/REP,FAST/VIEW,1,,,1/ANG,1/REP,FAST/VIEW,1,1/ANG,1/REP,FAST/VIEW,1,1,1,1/ANG,1/REP,FASTFLST,2,1,5,ORDE,1FITEM,2,9!*/GODA,P51X,ALL,/UI,MESH,OFF/VIEW,1,,-1/ANG,1/REP,FAST/VIEW,1,-1/ANG,1/REP,FAST/VIEW,1,,1/ANG,1/REP,FAST/VIEW,1,,,1/ANG,1/REP,FAST/VIEW,1,1,2,3/ANG,1/REP,FAST/VIEW,1,1,1,1/ANG,1/REP,FAST/DIST,1,1.08222638492,1/REP,FAST/ZOOM,1,RECT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