CAESARII官方培训讲义ppt课件

1、CAESAR II 管道应力分析培训王大辉北京艾思弗软件公司2022/7/20.aecsoft2022/7/20.介 绍培训的目的在于让您了解和掌握应力分析的根底概念模型和边境条件的建立结果的分析和评判往复紧缩机的分析专题日常遇到的问题和处理方法2022/7/20.介 绍3D梁单元的特征无限细的杆单元全部行为靠端点位移决议弯曲变形是主要的2022/7/20.介 绍3D Beam Element Characteristics3D梁单元的特征仅阐明整体行为无部分作用外表没有碰撞忽略二次影响小转动遵照胡克定律2022/7/20.Stress Basics应力根底部分坐标系下管道应力分类引发应力的载

2、荷轴向应力Longitudinal Stress - SL环向应力Hoop Stress - SH径向应力Radial Stress - SR剪切应力Shear Stress - 2022/7/20.轴向应力沿管道轴向Along axis of pipe轴向力引起Axial Force轴向力/面积 (F/A)内压引起PressurePd / 4t or P*di / ( do2 - di2 )弯矩引起Bending MomentMc/I最大应力环向的外外表某点处 I/radius Z (截面模量); use M/Z2022/7/20.压力引起的环向应力环向垂直于半径 Pd / 2t和壁厚严密相

3、关环向应力非常重要，但规范应力不思索它。Hoop is very important, its just not part of the “code stress环向应力用来确定壁厚：根据直径、许用应力、腐蚀裕量、加工偏向、压力确定管道壁厚。2022/7/20.压力引发的径向应力沿半径方向向内内壁的径向应力大小是： -P外壁的径向应力大小为 0最大弯曲应力发生在管道的外外表，故该项忽略2022/7/20.剪切应力Shear Stresses平面内垂直半径Shear Force剪力在外外表剪力很小，应力计算忽略支架设计有时需求思索Torque扭矩最大应力在外外表 MT/2Z2022/7/20.3

4、-D 应力评定A loaded, 3-D pipe contains a representative infinitesimal stress cubeadd graphic (Fig 1-13)This stress cube is in equilibrium and can be rotated in spaceadd graphic (rotated cube with loads)This cube can be rotated so that shear stresses are zero. This results in the Principal Stresses.2022/

5、7/20.Simplifying to a 2-D StressThis plane can be rotated to either eliminate or maximize shear stress by using Mohrs Circle:Since we use the outside surface where radial stress is zero; lets move to a plane element:2022/7/20.Using Mohrs CircleCut the square at to calculate S1Cut the square at +90 t

6、o calculate S2Cut the square at +45 to calculate max2022/7/20.Using Mohrs CircleBrittle material (failure by fracture) - max principal stressDuctile material (failure by general yielding) - max principal stress is used to set wall thicknessMaximum shear stress is a good prediction and errs on the co

7、nservative sidesee p84&85 of Adv. Mech. Of Matls2022/7/20.根本应力 “Code Stress规范应力应力评定Evaluating a 3-D StressS = F / A + Pd / 4t + M / Z 轴向力、轴向压力，轴向弯矩一同的分量加和规范不同，上面的算式也不同那些应力没有包含进来？2022/7/20.根本应力 “Code Stress规范应力几个实效实际A Few Failure Theories变形能或八面体剪切应力 (根据米赛斯实际和其它的实际。最大剪应力实际 Columb实际 。大多数实际都根据这个实际。由于剪切影

8、响而限制最大主应力 (Rankine实际) 。CAESAR II 132列输出应力报告中显示了米赛斯或最大剪应力强度实际。应力报告由configuration设置来决议。2022/7/20.根本应力 “Code Stress规范应力基于最大剪应力实效实际，ASME规范委员会公布了规范应力方程Based on the maximum shear failure theory, the Code Committee developed the “code equations 目的在于防止管道系统实效Purpose was to reduce system failures这种处理方法很适用，但依然

9、有问题存在This approach worked well, but there were still problems, even as late as post World War II.研讨阐明直管道比较符合实际Studies showed systems of straight pipe matched theory研讨阐明元件失效比实际发生的早Studies showed systems with fittings failed earlier than theory predicted.ASME规范委员会委托Markl来研讨这个问题Code Committee commissio

10、ned Markl to study this .2022/7/20.根本应力 “Code Stress规范应力Markls 实验和结果将实验用的管道充溢水，按某个方向和位移反复摇摆管道。Test configurations filled with water and cycled through a predetermined displacement预测失效循环次数Theory should be able to predict “cycles to failure发现最先失效的管件及其缘由Fittings caused early failure because 对管件引入应力集中St

11、resses concentrations are introduced by fittings分析实验数据，修正轴向应力弯曲项Test data analyzed and a modification to the bending term of the code stress equation was introduced:Sbending = i M / z2022/7/20.根本应力 “Code Stress规范应力Markls 实验和结果应力加强系数i 和元件的方式有关对于弯头 “i 的计算需求如下:我们需求弯头的几何参数计算弯头柔性“h计算应力增大系数Stress Intensif

12、ication Factor “i, 石化规范对平面内、外的SIF取值不同，电力取一样的sif2022/7/20.根本应力 “Code Stress规范应力Markls 实验和结果A load “in the plane of the fitting causes “in-plane bending平面内A load “out of the plane of the fitting causes “out-of-plane bending平面外2022/7/20.根本应力 “Code Stress规范应力Markls 实验和结果规范上的附注非常重要PetroChem codes modify

13、SIF (and flexibility factor) based on pressure stiffening in a note石化规范规定压力硬化影响和柔性系数应力算式变化如下S = F / A + Pd / 4t + i M / z 应力增大系数不能小于2022/7/20.Basis for “Code Stress EquationsMarkls 实验和结果The SIF is a “fudge factorSIF 是个近似的参数The SIF attempts to increase the bending stress computed at the node point, t

14、o match the actual higher stress due to the stress concentration caused by the fitting.引入SIF 在于改动特殊管件应力集中，让他们的应力根实践大小更接近。Markl only tested 4x4 Std fittings !但Markl 仅测试了Additional work is still being done today in the field of SIFs. Results are published in: PVP, WRC, Journal of Pressure Vessel Techn

15、ology.其他的任务人们依然在继续进展。2022/7/20.规范效验的工况两种失效：Primary failure一次失效Secondary failure二次失效(A third failure mode addressed is Occasional, which is similar to Primary.)2022/7/20.规范效验的工况Primary Failure Case一次失效力的作用Force Driven非自限性Not Self-Limiting分量、压力、集中力Weight, Pressure, Concentrated Forces2022/7/20.规范效验的工况

16、Primary Failure Case一次失效力的作用Force Driven非自限性Not Self-Limiting分量、压力、集中力, Weight、Pressure, Concentrated Forces2022/7/20.规范效验的工况Secondary Failure Case二次失效位移作用Displacement Driven自限性Is Self-Limiting温度、位移和其他变化载荷引起的Temperature, Displacement, plus other varying loads - i.e. weight2022/7/20.规范效验的工况 (1) = W +

17、 T1 + P1 (OPE) (2) = W + P1 (SUS) (3) = DS1 - DS2 (EXP)Operating case, used for:热态restraint & equipment loads推力和弯矩maximum displacements最大位移computation of EXP case计算二次应力Sustained case for PRIMARY loads and stress compliance计算一次应力Expansion case for “extreme displacement stress range膨胀工况，计算二次应力displace

18、ments for case 3 are displacements from case 1 minus displacements from case 22022/7/20.规范效验的工况膨胀工况的解释Expansion Case ExplainedWhat does “DS1 - DS2 (EXP) mean?Is a load case with “T1 (EXP) the same thing?2022/7/20.Load Cases for Code Compliance膨胀工况的解释Expansion Case ExplainedThe code states that the e

19、xpansion stresses are to be computed from the extreme displacement stress range. These are all very important words. Consider their meaning EXTREME极端: In this sense it means the most, or the largest.RANGE范围: Typically a difference. What difference? The difference between the extremes. What extremes?

20、DISPLACEMENT位移: This defines what extremes to take the difference of.STRESS应力: What we are eventually after.2022/7/20.Load Cases for Code Compliance膨胀工况的解释Expansion Case ExplainedPutting everything back together, we are told to compute stresses from the extreme displacement range. How can we do this

21、?计算最大位移范围的应力Consider the equation being solved; K x = f.In this equation, we know K and f, and we are solving for x, the displacement vector.In CAESAR II, when we setup an expansion case, we define it as DS1 - DS2, where the 1 and 2 refer to the displacement vector (x) of load cases 1 and 2 respecti

22、vely.2022/7/20.Load Cases for Code Compliance膨胀工况的解释Expansion Case Explained(Obviously the load case numbers are subject to change on a job by job basis.)What do you get when you take DS1 - DS2?Well x1 - x2 yields x, a pseudo displacement vector.x is not a real set of displacements that you can go o

23、ut and measure with a ruler, rather it is the difference between two positions of the pipe.Once we have x, we can use the same routines used in the OPE or SUS cases to compute element forces, and finally element stresses.2022/7/20.Load Cases for Code Compliance膨胀工况的解释Expansion Case ExplainedHowever,

24、 these element forces are also pseudo forces, i.e the difference in forces between two positions of the pipe.力的大小是两个工况力的差值Similarly, the stresses computed are not real stresses, but stress differences.应力不是真实应力，是应力的差值This is exactly what the code wants, the stress difference, which was computed from

25、a displacement range.二次应力是位移变化量导致的As to whether or not this stress difference is the extreme, well that depends on the job.2022/7/20.Load Cases for Code Compliance膨胀工况的解释Expansion Case ExplainedDS1-DS2 和 T1“一样吗？. 有能够.假设是线性系统，答案是一样的。假设是非线性系统 (如他有 +Ys, or gaps, or friction), 答案是不一样的。缘由是两个工况运用K x = f。

26、The reason for this can be found by examining the equation K x = f for the two different methods.2022/7/20.Load Cases for Code ComplianceExpansion Case ExplainedFor this discussion, rearrange the equation to x = f / K, where we know we dont really divide by K, we multiply by its inverse.OPE: xope =

27、fope / Kope = W + T1 + P1 / KopeSUS: xsus = fsus / Ksus = W + P1 / KsusEXP: xexp = xope - xsus = W + T1 + P1 / Kope - W + P1 / KsusCan we simplify the above equation as follows? EXP: xexp = W + T1 + P1 / K - W + P1 / K2022/7/20.Load Cases for Code Compliance膨胀工况解释Expansion Case ExplainedCan we simpl

28、ify the above equation as follows? EXP: xexp = W + T1 + P1 / K - W + P1 / KCanceling like terms (the ones in red) yields: xexp = T1 / K问题在于Kope 和 Ksus能否相等.线性系统相等.非线性系统不相等2022/7/20.Load Cases for Code Compliance膨胀工况解释Expansion Case Explained假设一个系统有两个操作温度。Another proof that the DS1-DS2 method is the c

29、orrect way to go is to consider a job with two operating temperatures, one above ambient and one below ambient.如 T1 = +300, and T2 = -50. CAESAR II 软件自动建立如下工况:(1) W + T1 + P1 (OPE)(2) W + T2 + P1 (OPE)(3) W + P1 (SUS)(4) DS1 - DS3 (EXP)(5) DS2 - DS3 (EXP)2022/7/20.Load Cases for Code Compliance膨胀工况解

30、释Expansion Case Explained上述工况正确，但没能阐明规范要求的最大应力范围由于CII并不能判别荷载所代表的详细含义为满足规范的要求，用户必需本人定义:(6) DS1 - DS2 (EXP)这个工况是最大位移膨胀应力，正是规范所要求的。您根本不能思索运用T1来计算膨胀应力.2022/7/20.Load Cases for Code ComplianceExpansion Case Explained膨胀工况的解释To summarize:概括如下We take the difference between two load cases to determine a disp

31、lacement range.两个工况确定位移范围From this range we compute a force range and then a stress range.由此我们确定力的范围和应力范围The code requires the extreme displacement stress range.规范要求极端的应力范围The user only has to worry about whether or not the “extreme case has been addressed.用户仅思索最大应力范围即可2022/7/20.Linear vs Non-Linear

32、线性和非线性Terminology applies to boundary conditions.边境条件的类型Recall the equation being solved: Kx = fThis is the equation of a spring.The piping system boundary conditions (i.e. the restraints) are represented as stiffnesses, or springs.管道边境条件代表刚度或弹簧More complex boundary conditions can be defined, invali

33、dating the “linear spring assumption.2022/7/20.Linear vs Non-Linear线性和非线性线性约束 boundary condition is a double acting restraint, such as a “Y support.一种是上下约束Another example of a linear boundary condition is a spring hanger.一种是弹簧The force versus displacement curve for these restraints is a straight lin

34、e 力和位移是线性关系Therefore these restraints are linear.约束是线性的The slope of the line is the stiffness.斜率是刚度2022/7/20.Linear vs Non-Linear线性和非线性非线性约束A “+Y support is a non-linear support.支架Its force vs displacement curve is not a straight line.力和位移不是直线关系Stiffness only exists for negative displacements.向下的位移是

35、刚度是存在的For positive displacements, the stiffness is zero.向上的位移，刚度变为2022/7/20.Linear vs Non-Linear线性和非线性A “gap is also a non-linear support.间隙的引进The force vs displacement curve is not a straight line.力和位移不是线性关系There is no stiffness in the gap.间隙部分没有刚度2022/7/20.Linear vs Non-Linear线性和非线性Friction makes

36、a restraint non-linear摩擦让约束非线性Large rotation rods are also non-linear restraints大的转动吊杆让约束非线性Non-linear restraints in a job mean that Kope is not equal to Ksus. 非线性后，热态管道刚度和冷态刚度不一致(EXP) and (OCC) load cases must be constructed using the difference between two other load cases to account for non-linea

37、r restraints.2022/7/20.偶尔工况的建立Occasional loads are considered “primary, since they are force driven.偶尔荷载是主要载荷，力引起的。Occasional loads occur infrequently.不经常发生The codes employ an “allowable increase factor based on the frequency of occurrence in the determination of the allowable, i.e. k * Sh.基于发生的频率，确

38、定值的大小Examples of occasional loads are wind and earthquake.偶尔载荷是风载荷和地震载荷2022/7/20.偶尔工况的建立The code equation for the OCCasional load case is:MA / Z + MB / Z kShHere, MA is the moment term from the SUStained loads,冷态荷载引发力矩and MB is the moment from the OCCasional loads.偶尔荷载引发力矩This equation states that t

39、he OCCasional case is the sum of the SUStained stresses and the OCCasional stresses.偶尔工况是冷态和偶尔的叠加So we cant run a load case with just a “WIND load and satisfy this code requirement.What about “W + P1 + WIND as a load case?2022/7/20.Occasional Load Case SetupThe “W + P1 + WIND case will work for “lin

40、ear systems only. For “non-linear systems, this is not sufficient, for the same reason “T1 is not sufficient for the EXPansion load case.The best way to setup OCCasional load cases is:(1) W + P1 + T1 (OPE)(2) W + P1 + T1 + WIND (OPE)(3) W + P1 (SUS)(4) DS1 - DS3 (EXP)(5) DS2 - DS1 (OPE)(6) ST5 + ST3

41、 (OCC)2022/7/20.Occasional Load Case Setup(1) W + P1 + T1 (OPE)(2) W + P1 + T1 + WIND (OPE)(3) W + P1 (SUS)(4) DS1 - DS3 (EXP)(5) DS2 - DS1 (OPE)(6) ST5 + ST3 (OCC)This is the normal OPErating caseThis is a combined OPErating case which includes the OCC loadsThis is the standard SUStained caseThis i

42、s the standard EXPansion caseThis difference yields the effects of the OCCasional load on the system. This is not a code case, only a construction case, therefore (OPE). This handles non-linearities.This is our OCCasional code compliance case, stresses from Primary plus Occasional loads.2022/7/20.工况

43、的定义和维护CAESAR II will recommend load cases for “new jobs.By “new jobs, we mean jobs that do not have a “._J file.For “old jobs, having a “._J file, CAESAR II reads in the defined load cases and presents them to the user.The load case editing screen is shown at the right.2022/7/20.工况的定义和维护On this dial

44、og, available load types are listed in the upper left list box.载荷类型Available load case types are listed in the lower left list box.工况类型Load cases (recommended or previously defined) are shown in the grid at the right.引荐生成的工况Recommended load cases can always be obtained by clicking on the Recommend b

45、utton.The analysis commences by clicking on “the running man.2022/7/20.Load Case Generation & MaintenanceSay for a “new job, the load cases at the right are recommended.Say you accept and run these load cases.Upon reviewing the output you discover that pre-defined displacements at node 5 were omitte

46、d.You return to input, add the displacements, and start the Static Analysis processor again.2022/7/20.Load Case Generation & MaintenanceCAESAR II reads these existing load cases and presents them.What will your results be if you run these load cases?Exactly the same as before, because these load cas

47、es dont include the predefined displacements.You must manually add “D1 to the OPE load case, or ask CAESAR II to re-recommend the load cases.2022/7/20.Load Case Generation & MaintenanceNotice the load type list in the upper left contains “D1 now.The corrected load cases are shown at the right.2022/7

48、/20.Load Case Generation & MaintenanceNotice the load type list in the upper left contains “D1 now.The corrected load cases are shown at the right.2022/7/20.Load Case Generation & MaintenanceNotice the load type list in the upper left contains “D1 now.The corrected load cases are shown at the right.

49、Any time you add or remove a complete load type, the load cases are insufficient.If you added displacements to node 110, would the load cases be sufficient?2022/7/20.确保您分析对象的正确性Remember CAESAR II is a finite element program.有限元Remember CAESAR II uses a 3D beam element.3D 梁单元Remember you must have eq

50、uilibrium:坚持平衡Resultant loads should equal applied loads作用力等于反作用力Gravity (weight only) load case should equal the weight of the system重力等于整个系统的总分量Other basic checksVerify nodal 3D coordinates尺寸输入能否正确Check for extreme displacements and/or loads最大位移和推力(see handout)2022/7/20.Problem Solving问题的处置What do

51、 you do when you dont like the results?Recall the equation being solved:Kx = fwhere we solve for x, the displacementsFrom these displacements, we compute element forces & momentsFrom these forces & moments, the Code equations are applied and we compute stresses.2022/7/20.Problem SolvingWhat do you d

52、o when you dont like the results?So if you have a stress problem, it can only be caused by two things: A Code related issue (SIFs, code equation, etc.)Extreme forces and/or momentsIf you have a force/moment problem, they can be caused by only two things:Improper element characteristicsExtreme displa

53、cements2022/7/20.Problem SolvingWhat do you do when you dont like the results?If you have a displacement problem, it can only be caused by two things: Improper input (density, elastic modulus, applied loads)Improper boundary conditionsDont forget to check and recheck the input.Remember that in 3D sy

54、stems, a load in one location can cause pivoting somewhere else downstream, resulting in excessive forces and moments.Try to isolate the load causing the problem, and trace its origin.2022/7/20.Problem Solving设计和分析过程Design by Analysis - The Design Cycle搜集数据Gather all the data, with assumptions建立分析模型和工况Generate the model and load sets分析计算Perform the analysis检查结果Check the result