【ANSYS算例】機(jī)翼模型的振動(dòng)模態(tài)分析

一個(gè)簡(jiǎn)化的飛機(jī)機(jī)翼模型如圖7-4所示，該機(jī)翼沿延翼方向?yàn)榈群穸?。有關(guān)的幾何尺寸見圖7-4，機(jī)翼材料的常數(shù)為：彈性模量E=0.26GPa，泊松比“二0.3，密度(a)飛機(jī)機(jī)翼模型B燦見山仍t0)U(U.C175,Q.OLaS.O)p—(a)飛機(jī)機(jī)翼模型B燦見山仍t0)U(U.C175,Q.OLaS.O)(b)翼形的幾何坐標(biāo)點(diǎn)圖7-4振動(dòng)模態(tài)分析計(jì)算模型示意圖解答這里體單元SOLID45進(jìn)行建模，并計(jì)算機(jī)翼模型的振動(dòng)模態(tài)。建模的要點(diǎn)：⑴首先根據(jù)機(jī)翼橫截面的關(guān)鍵點(diǎn)，采用連接直線以及樣條函數(shù)＜BSPLIN＞進(jìn)行連接以形成一個(gè)由封閉線圍成的面；⑵在生成的面上采用自由網(wǎng)格劃分生成面單元(PLANE42)；⑶設(shè)置體單元SOLID45，采用＜EXTOPTxVEXT＞進(jìn)行Z方向的多段擴(kuò)展；⑷設(shè)置模態(tài)分析＜ANTYPE,2＞，采用Lanczos方法進(jìn)行求解VMODOPT,LANB＞；⑸在后處理中，通過VSET＞調(diào)出相關(guān)階次的模態(tài)；⑹顯示變形后的結(jié)構(gòu)圖并進(jìn)行動(dòng)態(tài)演示vPLDI＞vANMODE＞。給出的基于圖形界面的交互式操作(stepbystep)過程如下。(1)進(jìn)入ANSYS(設(shè)定工作目錄和工作文件)程序—ANSYS-——ANSYSInteractive—Workingdirectory(設(shè)置工作目錄)—Initialjobname(設(shè)置工作文件名)：Modal—Run⑵設(shè)置計(jì)算類型ANSYSMainMenu：Preferences”—Structural—OK(3)選擇單元類型ANSYSMainMenu：Preprocessor—ElementType—Add/Edit/Delete—Add???—Structuralsolid：Quad4node42—Apply—solid—Brick8node45—OK—Close定義材料參數(shù)ANSYSMainMenu：Preprocessor—MaterialProps—MaterialModels—Structural—Linear—Elastic—Isotropic:EX:0.26E9(彈性模量),PRXY:03(泊松比)—OK—Density:88^—OK—Material—Exit生成幾何模型ANSYSMainMenu:Preprocessor—Modeling—Create—Keypoints—InActiveCS—X,Y,Zlocation:0j090fApplyfX,Y,Zlocation:0.05y0yOfApplyfX,Y,Zlocation:0.0575j0.005jOfApplyfX,Y,Zlocation:0.0475,0.01?5,0fApplyfX,Y,Zlocation:0.0?5,0.006?5,0—OKANSYSMainMenu：PreprocessorfModelingfCreatefLinesfLinesfStraightLinef依次選擇關(guān)鍵點(diǎn)1,2,5,1fOKANSYSMainMenu：PreprocessorfModelingfCreatefLinesfSplinesfWithOptionsfSplinethruKPsf依次選擇關(guān)鍵點(diǎn)2,3,4,5fOKf輸入以下數(shù)據(jù):XV1:4025,YV1:0,ZV1:0f輸入以下數(shù)據(jù):XV6:4025,YV6沁00625,ZV6:0fOKANSYSMainMenu：PreprocessorfModelingfCreatefAreasfArbitraryfByLinesf選擇所有3條線fOK(6)網(wǎng)格劃分ANSYSMainMenu：PreprocessorfMeshingfMeshToolfglobalfSetfElementedgelength:000625fOKfMeshfPickAllfClosefClose(點(diǎn)擊關(guān)閉MeshTool工具欄)ANSYSMainMenu：PreprocessorfModelingfOperatefExtrudefElemExtOptsfElementtypenumber:2SOLID45fTheNo.ofelementdivisions:10fOKANSYSMainMenu：PreprocessorfModelingfOperatefExtrudefAreasfByXYZOffsetfPickAllfOffsetsforextrusionintheZdirection:090j0.2^fOKfClose模型施加載荷ANSYSUtilityMenu：SelectfEntitiesfElementsfByAttributesfElemtypenumfTheelementtypenumber:1fUnselectfApply模型施加約束ANSYSUtilityMenu：SelectfEntitiesfNodesfByLocationfZcoordinatesfTheZcoordinatelocation:0fFromFUllfApplyANSYSMainMenufPreprocessorfLoadsfDefineLoadsfApplyfStructuralfDisplacementfOnNodesfPickAllfAllDOFfOKfByNum/PickfSelectAllf點(diǎn)擊Cancel(關(guān)閉窗口)(9)分析計(jì)算ANSYSMainMenu：SolutionfAnalysisTypefNewAnalysisfModalfOKANSYSMainMenu：SolutionfAnalysisTypefAnalysisOptionsf點(diǎn)擊BlockLanczosfNo.ofmodestoextract:5fNo.ofmodestoexpand:5fOKfOKANSYSMainMenu：SolutionfSolvefCurrentLSfFilefClosefOKfYesfYesfClose(Solutionisdone!).(10)結(jié)果顯示ANSYSMainMenu：GeneralPostprocfResultsSummaryfClose(各階模態(tài)的頻率見表7-5)。ANSYSMainMenu：GeneralPostprocfReadResultsfFirstSetANSYSUtilityMenu：PlotCtrlsfAnimatefModeShapefOKf在AnimationController中作相應(yīng)設(shè)置(這里不詳細(xì)說明)，然后關(guān)閉當(dāng)前窗口fCloseANSYSMainMenu：GeneralPostprocfReadResultsfNextSetANSYSUtilityMenu：PlotCtrlsfAnimatefModeShapefOK(各階模態(tài)見圖7-5)。(11)退出系統(tǒng)ANSYSUtilityMenu：FiletExit…tSaveEverythingtOK

表7-5機(jī)翼模型的各階模態(tài)頻率階次(SET)12345頻率/Hz14.54164.50991.655137.93261.76(c)第3階振動(dòng)模態(tài)(b)第2階振動(dòng)模態(tài)AN4>?JI.KtLLHHdJ4(d)第(c)第3階振動(dòng)模態(tài)(b)第2階振動(dòng)模態(tài)AN4>?JI.KtLLHHdJ4(d)第4階振動(dòng)模態(tài)圖7-5機(jī)翼模型的各階振動(dòng)模態(tài)【ANSYS【ANSYS算例】7.4(2)機(jī)翼模型的振動(dòng)模態(tài)分析(命令流)針對(duì)【ANSYS算例】7.4(1)的GUI操作，提供完整的命令流。解答給出的命令流如下。!%%%%[ANSYS算例]7.4(2)%%%%%begin%%%%%/PREP7ET,1,PLANE42ET,2,SOLID45MP,EX,1,0.26e9MP,DENS,1,886MP,PRXY1,0.3KK,,0.05,,,K,,0.0575,0.005,,K,,0.0475,0.0125,,K,,0.025,0.00625,,LSTR,1,2LSTR,5,1!進(jìn)入前處理!選取單元類型1(平面單元)!選取單元類型2(空間單元)!定義材料的彈性模量(1號(hào)材料)!定義材料的密度(1號(hào)材料)!定義材料的泊松比(1號(hào)材料)!生成幾何點(diǎn)1,坐標(biāo)(0,0,0)!生成幾何點(diǎn)2,坐標(biāo)(0.05,0,0)!生成幾何點(diǎn)3,坐標(biāo)(0.0575,0.005,0)!生成幾何點(diǎn)4,坐標(biāo)(0.0475,0.0125,0)!生成幾何點(diǎn)5,坐標(biāo)(0.025,0.00625,0)!連接點(diǎn)1和2生成直線1!連接點(diǎn)5和1生成直線2

!采用!采用B樣條，連接點(diǎn)2,3,4,5生成曲線3!由線1,2,3圍成一個(gè)面!在單元?jiǎng)澐智埃x單元的邊的尺度為0.00625!設(shè)置單元?jiǎng)澐值念愋蜑?D四邊形（key=O）!設(shè)置網(wǎng)格的自由劃分（0）!對(duì)所有的面進(jìn)行網(wǎng)格劃分（無(wú)設(shè)置時(shí)，則默認(rèn)為采用第1號(hào)類型單元）!設(shè)置單元類型2（空間單元）!設(shè)置體單元擴(kuò)展為10段!對(duì)所有的面進(jìn)行Z方向的體（包括單元）擴(kuò)展，每次擴(kuò)展的Z方向增量為0.25!除單元類型1外，選擇所有的單元（實(shí)際上就是體單元）!選擇Z=0的節(jié)點(diǎn)!對(duì)所選擇的節(jié)點(diǎn)施加全部的固定約束!選擇所有的節(jié)點(diǎn)!前處理結(jié)束!進(jìn)入求解模塊!設(shè)置模態(tài)分析（2）!設(shè)定LANB方法，提取5階模態(tài)!設(shè)定模態(tài)擴(kuò)展數(shù)為5ESIZE,0.00625MSHAPE,0,2DMSHKEY,0AMESH,allTYPE,2EXTOPT,ESIZE,10,0,VEXT,all,,,0,0,0.25,,,,ESEL,U,TYPE,,1NSEL,S,LOC,Z,0D,all,,,,,,ALL,,,,,NSEL,ALLFINISH/SOLUANTYPE,2/SOLUMODOPT,LANB,5MXPAND,5,,,0M