ansys工程分析15.ppt

1、Chapter 15結構動力分析Structural Dynamic AnalysisContents15.1何謂動力分析？What Are Dynamic Analyses?15.2解題方法 Solution Methods 15.3質量與阻尼 Mass and Damping 15.4實例：圓柱形子彈的撞擊模擬 Example:Copper Cylinder Impacting on a Rigid Wall 15.5動態負載 Dynamic Loads 15.6初始條件 Initial Conditions 15.7積分時間間隔 Integration Time Steps 15.8練習

2、題：火箭的飛行 Exercise:Rocket Flight 2第15.1節何謂動力分析？What Are Dynamic Analyses?3Dynamic EffectsInertia forceDamping forceElastic ForceExternal forceDynamic Effects415.1.1 Transient Dynamic Analysis515.1.2 Modal Analysis(1/3)615.1.2 Modal Analysis(2/3)715.1.2 Modal Analysis(3/3)Avoid resonanceExploit resonan

3、ceAssess structural stiffnessStructural modal degrees of freedomFurther dynamic analysesetc.815.1.3 Harmonic Response Analysis9第15.2節解題方法Solution Methods10Solution MethodsSolution Methods for Equation of MotionDirect IntegrationMode SuperpositionImplicitExplicitReduceFullFullReduce1115.2.1 Direct In

4、tegrationImplicit method(ANSYS)Explicit method(LS-DYNA)1215.2.2 Implicit vs.Explicit MethodsImplicit methodExplicit method1315.2.3 Mode Superposition Method1415.2.4 Reduced Methodwhere1515.2.5 Methods for Nonlinear Dynamic AnalysisFor nonlinear analysis,the only methods applicable is DIRECT INTEGRAT

5、ION method.Reduced method can not be used for nonlinear analysis.Either implicit or explicit methods can be used.16第15.3節質量與阻尼Mass and Damping1715.3.1 Consistent vs.Lumped Mass MatricesConsistent mass matrixLumped mass matrix1815.3.2 DampingDamping effects is the total of all energy dissipation mech

6、anismsHysteresis(solid damping)Viscous dampingDry-friction(Coulomb damping)1915.3.3 Idealization of Structural DampingStructural dampings are usually small(2%-7%).Equivalent viscous damping is assumed in ANSYS,i.e.,2015.3.4 How ANSYS Forms Damping Matrix?Alpha dampingBeta dampingMaterial dependent b

7、eta dampingElement damping matricesFrequency-dependent damping matrix21第15.4節實例:圓柱型子彈的撞擊模擬Copper Cylinder Impacting on a Rigid Wall2215.4.1 Problem DescriptionxyLDInitial Velocity Vo2315.4.2 Modeling ConsiderationMaterial:bilinear plastic model.VISCO106(2D viscoplastic solid)is used.Use axisymmetric

8、 model.2415.4.3 ANSYS Procedure(1/4)010203040506070809101112131415161718192021FINISH/CLEAR/TITLE,UNITS:SI/PREP7ET,1,VISCO106,1MP,EX,1,117E9MP,NUXY,1,0.35MP,DENS,1,8930TB,BISO,1TBDATA,400E6,100E6TBPLOT,BISO,1RECTNG,0,0.0032,0,0.0324LESIZE,1,4LESIZE,2,20MSHAPE,0,2DMSHKEY,1AMESH,ALLFINISH2515.4.3 ANSYS

9、 Procedure(2/4)2324252627282930313233343536373839404142/SOLUANTYPE,TRANSTRNOPT,FULLNLGEOM,ONIC,ALL,UY,0,-227NSEL,S,LOC,X,0D,ALL,UX,0NSEL,S,LOC,Y,0D,ALL,UY,0NSEL,ALL/PBC,U,ONEPLOTTIME,80E-6DELTIM,0.4E-6KBC,1OUTRES,ALL,4SOLVEFINISH2615.4.3 ANSYS Procedure(3/4)4445464748495051525354555657/POST26TOPNODE

10、=NODE(0,0.0324,0)NSOL,2,TOPNODE,U,Y,DISPDERIV,3,2,1,VELO/GRID,1/AXLAB,X,TIMEs/AXLAB,Y,DISPLACEMENTmPLVAR,2/AXLAB,Y,VELOCITYm/sPLVAR,3FINISH2715.4.3 ANSYS Procedure(4/4)59606162636465/POST1SET,LASTPLDISP,2PLNSOL,EPTO,EQVANTIME,3028第15.5節動態負載Dynamic Loads29Dynamic Loads:An Example010203040506070809101

11、112131415161718/SOLU.F,.!22.5atthenodesTIME,0.5!EndingtimeDELTIM,.!IntegrationstepKBC,0!RampedloadingAUTOTS,ON!OptionOUTRES,.!OptionSOLVE!Loadstep1F,.!10atthenodesTIME,1!EndingtimeSOLVE!Loadstep2FDELE,.!ZerotheforceTIME,1.5!EndingtimeKBC,1!SteppedloadingSOLVE!Loadstep300.51.01.5Time(s)Force(N)22.510

12、30第15.6節初始條件Initial Conditions3115.6.1 Example:An Stationary Plate Subjected to an Impulse LoadThis is the default initial condition.No input is needed.3215.6.2 Example:Initial Velocity on a Golf Club HeadThis simple initial condition can be specified by using IC command.NSEL,ALLIC,ALL,UY,0,V03315.6

13、.3 Example:Plucking a Cantilever Beam0102030405060708091011121314/SOLUANTYPE,TRANS.TIMINT,OFF!TransienteffectsoffTIME,0.001!SmalltimeintervalD,.!ApplydisplacementatdesirednodesKBC,1!SteppedloadsNSUBST,2!Toavoidnon-zerovelocitySOLVETIMINT,ON!TransienteffectsonTIME,.!ActualtimeatendofloadDDELE,.!Delet

14、etheapplieddisplacementSOLVE3415.6.4 Example:Dropping an Object from Rest0102030405060708091011121314151617/SOLUTIMINT,OFF!TransienteffectsoffTIME,0.001!SmalltimeintervalNSEL,.!SelectallnodesontheobjectD,ALL,ALL,0!TemporarilyfixthemNSEL,ALLACEL,.!ApplyaccelerationKBC,1!SteppedloadsNSUBST,2!Toavoidno

15、n-zerovelocitySOLVE!Loadstep1TIMINT,ON!TransienteffectsonTIME,.!ActualtimeatendofloadNSEL,.!SelectallnodesontheobjectDDELE,ALL,ALL!ReleasethemNSEL,ALLSOLVE!Loadstep235第15.7節積分時間間隔Integration time Steps3615.7.1 Response FrequencyResponseTimeMinimumresponsetime3715.7.2 Abrupt Changes in Loading00.51.01.5Time(s)Force(N)22.5103815.7.3 Contact Frequency3915.7.4 Wave Propagation4015.8 Exercise:Rocket Flighty140 in.ThrustTime100 lb1 sec.12341