跌落過程分析.

1、Drop Test of a Container 學(xué)科學(xué)科: LS-DYNA 分析類型分析類型: 顯式動(dòng)力學(xué)分析顯式動(dòng)力學(xué)分析 使用的單元類型使用的單元類型: SHELL163 Problem Specification Problem Description Define Analysis Type Input Geometry Define Element Type, Real Constants, Material Model Properties Generate Mesh Apply Loads Obtain Solution Review Results 問題描述 這是一個(gè)鋁盒跌落

2、到鋼板平面的動(dòng)力學(xué)分析，如下所述，盒子是一個(gè)五邊正方體，每邊為20inch長和0.1inch厚。它已在X，Y，Z的每個(gè)軸向轉(zhuǎn)動(dòng)了450，板上部是邊長100inch，厚度為0.1inch的方鋼板。作用在盒子上的力僅為其只身重量。它從72inch 高處落下。這是一個(gè)典型的跌落試驗(yàn)。問題的目的是驗(yàn)證ANSYS/LS-DYNA的顯式動(dòng)力學(xué)的能力為大變形和復(fù)雜接觸動(dòng)力學(xué)問題?；緟?shù)容器和板上部的尺寸如上所述. 鋁合金容器的參數(shù)：鋁合金容器的參數(shù)： Youngs modulus of 10.3E6 psi, density of 2.5E-4 lbf-sec2/in4, Poissons ratio o

3、f 0.334, Yield Stress of 5,000 psi, Tangent modulus of 20,000 psi. 板是由碳鋼制成：板是由碳鋼制成： Youngs modulus of 30.0E6 psi, Density of 7.3E-4 lbf-sec2/in4, Poissons ratio of 0.292.方法和假設(shè) (Approach and Assumptions) 在自由降落階段，容器由于重力作用進(jìn)行簡單加速。為節(jié)省CPU時(shí)間，在板上方20inch處開始模擬分析，并施加200inch/s的初始速度以模擬最初52inch的自由降落. 200 inch/s的速

4、度大致由公式 Vf = SQRT (2*a*s) 推導(dǎo)而來，其中 Vf 是最終速度(final velocity), a 是重力加速度, 而 s 位移?？諝獾哪Σ帘缓雎粤? 假定板上部具有剛性力學(xué)行為，而容器具有雙線性運(yùn)動(dòng)硬化Von mises塑性行為(bilinear kinematic hardening von Mises plasticity). 固體建模用于生成容器的3D模型, 然后對其劃分網(wǎng)格。節(jié)點(diǎn)和單元的直接生成(Direct generation)用于table top的建模。板上部為劃分成剛性單元，并僅用一個(gè)單元來表示.操作步驟 用問題描述中的信息和如下用問題描述中的信息和如

5、下劃線上劃線上的步驟自己來求解問題的步驟自己來求解問題.或者，通過或者，通過選擇選擇step1的連接用詳細(xì)的交互式單步求解完成的連接用詳細(xì)的交互式單步求解完成。定義分析類型定義分析類型 Define Analysis Type 1. Set preferences.輸入幾何模型輸入幾何模型 Input Geometry2. Read in geometry of the container.材料參數(shù)材料參數(shù)Define Element Type, Real Constants, Material Model Properties3. Define element type.4. Define

6、real constants.5. Specify material models.生成網(wǎng)格生成網(wǎng)格 Generate Mesh6. Mesh the container.7. Generate table top elements.8. Create container component.9. Create table top component.10. Specify contact parameters. 施加載荷施加載荷Apply Loads11. Apply initial Velocity to the container12. Apply acceleration to the

7、 container. 獲得解獲得解Obtain Solution13. Specify Output Controls14. Solve.查看結(jié)果查看結(jié)果Review Results15. Animate stress contours16. Animate deformed shape17. Exit the ANSYS program操作步驟 1. 定義preferences 首先設(shè)定Preferences in order to filter quantities that pertain to this discipline only.1. Main Menu Preferences

8、2, (check) “Individual discipline(s) to show in the GUI” = Structural3, (check) “Discipline options” = LS-DYNA Explicit4, OK（續(xù)）1.4. 輸入幾何模型輸入幾何模型1.4.1. Step 2: 讀入容器的幾何結(jié)構(gòu)讀入容器的幾何結(jié)構(gòu)通過讀入包括容器模型的文件來開始模擬。1, Utility Menu File Read Input from .2, File name: container.inp UNIX version: /ansys_inc/v90/ansys/dat

9、a/models/container.inp PC version: Program FilesAnsys IncV90ANSYSdatamodelscontainer.inp3,OK2. 定義材料性能1.5. 定義單元類型，實(shí)常數(shù)和材料模型性能定義單元類型，實(shí)常數(shù)和材料模型性能1.5.1. Step 3: 定義單元類型定義單元類型 因?yàn)槟Ｐ褪蔷邌驯”诤竦娜萜髯矒舭宓?選用殼(shell)單元模擬物理模型。為更精確的結(jié)果，顯式的薄壁結(jié)構(gòu)殼元SHELL163 用于選擇的單元。這種4節(jié)點(diǎn)單元用于平面和常規(guī)載荷。1，Main Menu Preprocessor Element Type Add/Ed

10、it/Delete2, Add.3, “LS-DYNA Explicit” (left column)4, “Thin Shell 163” (right column)5, OK現(xiàn)在, 設(shè)定 S/R corotational Hughes-Liu 單元公式以減少模型沙漏模型 (hourglass).6, Options.7, (drop down) “Element Formulation” = S/R corotation8, OK9, Close(續(xù))1.5.2. Step 4: 定義實(shí)常數(shù)定義實(shí)常數(shù)下一步下一步, 通過定義恰當(dāng)?shù)膶?shí)常數(shù)來定義殼單元的厚度通過定義恰當(dāng)?shù)膶?shí)常數(shù)來定義殼單元的

11、厚度.1, Main Menu Preprocessor Real Constants2, Add.3, OK to define real constant set for SHELL163.注意注意: 因?yàn)闆]有給定積分點(diǎn)的輸入位置因?yàn)闆]有給定積分點(diǎn)的輸入位置(No. of integration pts), 使用的缺省值為使用的缺省值為2. 為本教程的驗(yàn)證目的，缺省值為本教程的驗(yàn)證目的，缺省值2已已經(jīng)足夠。然而，對于大多數(shù)的非線性分析，經(jīng)足夠。然而，對于大多數(shù)的非線性分析，NIP 值應(yīng)當(dāng)大值應(yīng)當(dāng)大于于2.4, 如果單元是均勻厚度，只需定義節(jié)點(diǎn)如果單元是均勻厚度，只需定義節(jié)點(diǎn)1處的厚度，在本

12、例中，處的厚度，在本例中，設(shè)定設(shè)定 “Thickness at node 1” = 0.1. 5, OK6, Close（續(xù)）1.5.3. Step 5: 設(shè)定材料模型設(shè)定材料模型現(xiàn)在為接觸和目標(biāo)表面設(shè)定材料模型現(xiàn)在為接觸和目標(biāo)表面設(shè)定材料模型.1, Main Menu Preprocessor Material Props Material Models2, (雙擊雙擊) “LS-DYNA”, 然后然后 “Rigid Material” 來設(shè)定來設(shè)定Table Top, 并設(shè)為并設(shè)為 “Material Model Number 1”.3, “DENS” = 7.3e-44, “EX” =

13、30e65, “NUXY” = 0.2926, (下拉下拉) “Translational Constraint Parameter” = All disps.7, (下拉下拉) “Rotational Constraint Parameter” = All rotations8, OK9, Material New Model 來為容器設(shè)定材料模型, 并指定為 “Material Model Number 2”.10, “Define Material ID” = 211, OK12, (雙擊) “Nonlinear”, then “Inelastic”, then “Kinematic H

14、ardening”, then “Bilinear Kinematic”13, “DENS” = 2.5e-414, “EX” = 10.3e615, “NUXY” = 0.33416, “Yield Stress” = 500017, “Tangent Modulus” = 2000018,OK19, Material Exit20, Toolbar: SAVE_DB劃分網(wǎng)格1.6. 生成網(wǎng)格生成網(wǎng)格1.6.1. Step 6: Mesh the container.在顯式求解中，例如ANSYS LS-DYNA, 分析時(shí)間高度依賴于模型中的最小單元. 因此, 為得到精確的結(jié)果, 應(yīng)采用均勻尺

15、寸的單元.在本例中，采用缺省的單元尺寸。這里在容器的每個(gè)面上給出3x3的網(wǎng)格。1, Main Menu Preprocessor Meshing Mesh Tool2, (drop down) “Element Attributes” = Global; then Set3, (drop down) “Material number” = 24, OK5, (drop down) “Mesh” = Areas6, (check) “Mapped”7, Mesh8, Pick All 9, Toolbar: SAVE_DB（續(xù)） 1.6.2. Step 7: 生成板面單元生成板面單元現(xiàn)在通過現(xiàn)在

16、通過“Direction Element Generation”劃分劃分table top 的網(wǎng)格的網(wǎng)格. table top被定義成剛性表面，因此在該表面僅需定義一個(gè)單元被定義成剛性表面，因此在該表面僅需定義一個(gè)單元. 通過定義其通過定義其四個(gè)角部節(jié)點(diǎn)生成該模型，然后從這些節(jié)點(diǎn)建立單元四個(gè)角部節(jié)點(diǎn)生成該模型，然后從這些節(jié)點(diǎn)建立單元.1, Utility Menu PlotCtrls Pan, Zoom, Rotate2, Obliq3, Close4, Utility Menu PlotCtrls Numbering5, (check) “Node numbers” = On6, OK 7,

17、 (drop down in MeshTool) “Element Attributes” = Global; then Set8, (drop down) “Material number” = 19, OK10, Close MeshTool( (續(xù)續(xù)) )11, Main Menu Preprocessor Modeling Create Nodes In Active CS12, “Node number” = Leave blank so it defaults to the next available node number.13, “X Y Z Location in acti

18、ve CS” = -50, -20, -5014, Apply 生成遠(yuǎn)方左角點(diǎn)的節(jié)點(diǎn)生成遠(yuǎn)方左角點(diǎn)的節(jié)點(diǎn).15, “X Y Z Location in active CS” = -50, -20, 5016, Apply生成近處左角點(diǎn)的節(jié)點(diǎn)生成近處左角點(diǎn)的節(jié)點(diǎn).17, “X Y Z Location in active CS” = 50, -20, 5018, Apply生成遠(yuǎn)方右角點(diǎn)的節(jié)點(diǎn)生成遠(yuǎn)方右角點(diǎn)的節(jié)點(diǎn).19, “X Y Z Location in active CS” = 50, -20, -5020, OK生成遠(yuǎn)方右角點(diǎn)的節(jié)點(diǎn)生成遠(yuǎn)方右角點(diǎn)的節(jié)點(diǎn).現(xiàn)在生成單元現(xiàn)在生成單元.21,

19、Main Menu Preprocessor Modeling Create Elements Auto Numbered Thru Nodes22, 按反時(shí)針方向，點(diǎn)取剛剛生成的四個(gè)節(jié)點(diǎn)按反時(shí)針方向，點(diǎn)取剛剛生成的四個(gè)節(jié)點(diǎn).23, OK24, Utility Menu Plot Elements 生成容器部件1.6.3. Step 8: Create container component.大多數(shù)的接觸算法要求接觸參數(shù)，它們可以是大多數(shù)的接觸算法要求接觸參數(shù)，它們可以是 components, part IDs, 或或 part assembly IDs. 在本例中，由容器的節(jié)點(diǎn)產(chǎn)生在本例中

20、，由容器的節(jié)點(diǎn)產(chǎn)生 component.1,Utility Menu Select Entities2,(first drop down) “Elements”3,(second drop down) “By Attributes”4,(check) “Material num”5,“Min,Max,Inc.” = 26,Apply7,(first drop down) “Nodes”8,(second drop down) “Attached to”9,(check) “Elements”10,OK定義部件定義部件11, Utility Menu Select Comp/Assembly C

21、reate Component12, “Component name” = BOX13, (drop down) “Component is made of” = Nodes14, OK15, Utility Menu Plot Nodes 16, Utility Menu Select Everything 生成生成Table Top Table Top 組件組件1.6.4. Step 9: 生成生成table top component. 現(xiàn)在現(xiàn)在, 生成由生成由table top 的節(jié)點(diǎn)組成的組件的節(jié)點(diǎn)組成的組件.1, Utility Menu Select Entities2, (fi

22、rst drop down) “Elements”3, (second drop down) “By Attributes”4, (check) “Material num”5, “Min,Max,Inc” = 16, Apply7, (first drop down) “Nodes”8, (second drop down) “Attached to”9, (check) “Elements”10, OK（續(xù)）11, Utility Menu Select Comp/Assembly Create Component12, “Component name” = TABLE13, (drop

23、down) “Component is made of” = Nodes14, OK15, Utility Menu Plot Nodes 16, Utility Menu Select Everything17, Toolbar: SAVE_DB定義接觸參數(shù)1.6.5. Step 10: Specify contact parameters.在已知接觸行為的分析中，為得到最好的結(jié)果應(yīng)選擇恰當(dāng)?shù)慕佑|算法。然而這方面問題的本質(zhì)，接觸條件可能是無法預(yù)測的。為此，通過選擇自動(dòng)面-面接觸，程序能自動(dòng)地調(diào)整以適應(yīng)模擬中的變化。1, Main Menu Preprocessor LS-DYNA Optio

24、ns Contact Define Contact2, “Contact Type” = “Surface to Surf” (left column); “Automatic (ASTS)” (right column)3, OK4, (drop down) “Contact Component or Part no.” = BOX5, (drop down) “Target Component or Part no.” = TABLE6, OK7, Toolbar: SAVE_DB 施加載荷1.7. 施加載荷施加載荷1.7.1. Step 11: 在容器上給出初始速度在容器上給出初始速度1

25、, Main Menu Solution Initial Velocity On Nodes w/Nodal Rotate2, (drop down) “Input velocity on component” = BOX3, “Global Y-component” = -2004, OK 在瞬態(tài)動(dòng)力學(xué)分析中，載荷必須定義為分析的過程( duration of the analysis)，為此生成包括這個(gè)數(shù)據(jù)的列陣(Array)5, Utility Menu Parameters Array Parameters Define/Edit6, Add.7, “Parameter name” =

26、 TIME8, OK9, Edit.10, “1” = 011, “2” = 112, File Apply/Quit13，Add.14, “Parameter name” = ACCG15, OK16, (highlight) “ACCG”17, Edit.18, “1” = 386.419, “2” = 386.420, File Apply/Quit21, Close施加加速度于容器施加加速度于容器1.7.2. Step 12: Apply acceleration to the container.1, Main Menu Solution Loading Options Specif

27、y Loads2, “Load Labels” = ACLY3, (drop down) “Component name or PART number:” = BOX4, (drop down) “Parameter name for time values:” = TIME5, (drop down) “Parameter name for data values:” = ACCG6, OK 求解控制求解控制1.8. Obtain Solution1.8.1. Step 13: 設(shè)定輸出控制設(shè)定輸出控制.1,Main Menu Solution Time Controls Solution

28、Time2,“Terminate at Time:” = 1.03，OK4, Main Menu Solution Output Controls File Output Freq Number of Steps 5,“Specify Results File Output Interval” = 506,“Specify Time History Output Interval” = 507,OK8,Main Menu Solution Analysis Options Energy Options9,OK to turn on all energy options10,Toolbar: S

29、AVE_DB1.8.2. Step 14: Solve.1, Main Menu Solution Solve2,查看狀態(tài)窗口的信息，然后選擇: File Close (Windows) or Close (X11/Motif), to close the window. 3,OK 進(jìn)行初始求解.注意: A verification window will appear to notify you of a warning message. This warning was generated due to constraining the table top by defining it a

30、s a rigid element rather than using degrees of freedom constraints. Therefore the warning can be ignored.4,Yes5,Close求解求解查看結(jié)果1.9. Review Results1.9.1. Step 15: Animate stress contours.1, Utility Menu Plot Elements2, Utility Menu PlotCtrls Pan, Zoom, Rotate3,Front4,Close5,Utility Menu PlotCtrls Numbering6,(check) “Node numbers” = Off7,OK8,Main Menu General Postproc Read Results First set9,Utility Menu PlotCtrls Animate Over Results10,(c