BEAM188單元中文說明

1、精選優(yōu)質(zhì)文檔-傾情為你奉上精選優(yōu)質(zhì)文檔-傾情為你奉上專心-專注-專業(yè)專心-專注-專業(yè)精選優(yōu)質(zhì)文檔-傾情為你奉上專心-專注-專業(yè)Release 10.0 Documentation for ANSYSBEAM1883-D Linear Finite Strain Beam三維線性有限應(yīng)變梁單元BEAM188 Element DescriptionBEAM188單元描述BEAM188 is suitable for analyzing slender to moderately stubby/thick beam structures. This element is based on Timos

2、henko beam theory. Shear deformation effects are included.Beam188 單元適合于分析從細長到中等粗短的梁結(jié)構(gòu)，該單元基于鐵木辛哥梁結(jié)構(gòu)理論，并考慮了剪切變形的影響。BEAM188 is a linear (2-node) or a quadratic beam element in 3-D. BEAM188 has six or seven degrees of freedom at each node, with the number of degrees of freedom depending on the value of

3、KEYOPT(1). When KEYOPT(1) = 0 (the default), six degrees of freedom occur at each node. These include translations in the x, y, and z directions and rotations about the x, y, and z directions. When KEYOPT(1) = 1, a seventh degree of freedom (warping magnitude) is also considered. This element is wel

4、l-suited for linear, large rotation, and/or large strain nonlinear applications. Beam188 是三維線性（2 節(jié)點）或者二次梁單元。每個節(jié)點有六個或者七個自由度，自由度的個數(shù)取決于KEYOPT(1)的值。當(dāng)KEYOPT(1)0（缺?。r，每個節(jié)點有六個自由度；包括節(jié)點坐標(biāo)系的x、y、z 方向的平動和繞x、y、z 軸的轉(zhuǎn)動。當(dāng)KEYOPT(1)=1 時，每個節(jié)點有七個自由度，這時引入了第七個自由度（橫截面的翹曲）。這個單元非常適合線性、大角度轉(zhuǎn)動以及大應(yīng)變等非線性問題。BEAM188 includes stres

5、s stiffness terms, by default, in any analysis with ,ON. The provided stress stiffness terms enable the elements to analyze flexural, lateral, and torsional stability problems (using eigenvalue buckling or collapse studies with arc length methods).當(dāng)NLGEOM 選項打開的時候，beam188 的應(yīng)力剛化，在任何分析中都是缺省項。應(yīng)力剛化選項使本單元

6、能分析彎曲、橫向及扭轉(zhuǎn)穩(wěn)定問題（用弧長法分析特征值屈曲和塌陷）。BEAM188 can be used with any beam cross-section defined via , , , , and . The cross-section associated with the beam may be linearly tapered. Elasticity, creep, and plasticity models are supported (irrespective of cross-section subtype). A cross-section associated wit

7、h this element type can be a built-up section referencing more than one material.Beam188可以采用sectype、secdata、secoffset、secwrite 及secread 命令定義橫截面。本單元支持彈性、蠕變及塑性模型（不考慮橫截面子模型）。這種單元類型的截面可以由不同材料組成。BEAM188 ignores any real constant data beginning with Release 6.0. See the command for defining the transverse

8、 shear stiffness, and added mass.Beam188 從6.0 版本開始忽略任何實常數(shù)，參考seccontrols 命令來定義橫向剪切剛度和附加質(zhì)量。For BEAM188, the element coordinate system (,ESYS) is not relevant.單元坐標(biāo)系統(tǒng)（/psymb，esys）與beam188 單元無關(guān)。Figure188.1:BEAM188 Geometry圖188.1：Beam188 單元幾何示意圖BEAM188 Input DataBEAM188 輸入數(shù)據(jù)The geometry, node locations, a

9、nd coordinate system for this element are shown in . BEAM188 is defined by nodes I and J in the global coordinate system. 該單元的幾何形狀、節(jié)點位置、坐標(biāo)體系如圖188.1 “Beam188 單元幾何示意圖”所示，beam188 由整體坐標(biāo)系的節(jié)點I 和J 定義。Node K is a preferred way to define the orientation of the element. For information about orientation nodes

10、 and beam meshing, see in the . See the and command descriptions for details on generating the K node automatically.節(jié)點K 是定義單元方向的首選方式，有關(guān)方向節(jié)點和梁的網(wǎng)格劃分的信息可以參見ANSYS Modeling and Meshing Guide中的Generating a Beam Mesh With Orientation Nodes。參考和命令描述可以得到k 節(jié)點自動生成的詳細資料。BEAM188 may also be defined without the or

11、ientation node. In this case, the element x-axis is oriented from node I (end 1) toward node J (end 2). For the two-node option, the default orientation of the element y-axis is automatically calculated to be parallel to the global X-Y plane. For the case where the element is parallel to the global

12、Z-axis (or within a 0.01 percent slope of it), the element y-axis is oriented parallel to the global Y-axis (as shown). For user control of the element orientation about the element x-axis, use the third node option. If both are defined, the third node option takes precedence. The third node (K), if

13、 used, defines a plane (with I and J) containing the element x and z-axes (as shown). If this element is used in a large deflection analysis, it should be noted that the location of the third node (K) is used only to initially orient the element.Beam188 也以在沒有方向節(jié)點的情況下被定義。在這種情況下，單元的x 軸方向為I 節(jié)點指向J節(jié)點。對于兩

14、節(jié)點的情況，默認的y 軸方向按平行xy 平面自動計算。對于單元平行與z 軸的情況（或者斜度在0.01以內(nèi)），單元的y 軸的方向平行與整體坐標(biāo)的y 軸（如圖188.1）。用第三個節(jié)點的選項，用戶可以定義單元的x 軸方向。如果兩者都定義了，那么第三節(jié)點的選項優(yōu)先考慮。第三個節(jié)點（K）如果采用的話，將和I、J 節(jié)點一起定義包含單元x 軸和z 軸的平面(如圖188.1)。如果該單元采用大變形分析，需要注意這個第三號節(jié)點僅僅在定義初始單元方向的時候有效。The beam elements are one-dimensional line elements in space. The cross-sect

15、ion details are provided separately using the and commands (see in the for details). A section is associated with the beam elements by specifying the section ID number (). A section number is an independent element attribute. In addition to a constant cross-section, you can also define a tapered cro

16、ss-section by using the TAPER option on the command (see ).梁單元是一維空間線單元。橫截面資料用sectype和secdata 命令分別提供，參見ANSYS Structural Analysis Guide 的Beam Analysis and Cross Sections 看詳細資料。截面與單元用截面ID 號（SECNUM）來關(guān)聯(lián)，截面號是獨立的單元屬性。除了等截面，還可以用sectype 命令中的錐形選項來定義楔形截面（參考Defining a Tapered Beam）。The beam elements are based o

17、n Timoshenko beam theory, which is a first order shear deformation theory: transverse shear strain is constant through the cross-section; that is, cross-sections remain plane and undistorted after deformation. BEAM188 is a first order Timoshenko beam element which uses one point of integration along

18、 the length with default KEYOPT(3) setting. Therefore, when SMISC quantities are requested at nodes I and J, the centroidal values are reported for both end nodes. With KEYOPT(3) set to 2, two points of integration are used resulting in linear variation along the length.單元基于鐵木辛哥梁理論，這個理論是一階剪切變形理論；橫向剪

19、切應(yīng)力在橫截面是不變的，也就是說變形后橫截面保持平面不發(fā)生扭曲。Beam188 是一階鐵木辛哥梁單元，沿著長度用了一個積分點，用默認的KEYOPT(3)設(shè)置。因此，在I 和J 節(jié)點要求SMISC 數(shù)值的時候，中間數(shù)值在兩端節(jié)點均輸出。當(dāng)KEYOPT（1） 設(shè)置為2，兩個積分點作為延長的線性變量被運用。BEAM188 lements can be used for slender or stout beams. Due to the limitations of first order shear deformation theory, only moderately thick beams m

20、ay be analyzed. The slenderness ratio of a beam structure (GAL2/(EI) may be used in judging the applicability of the element, where: Beam188單元可以用在細長或者短粗的梁。由于一階剪切變形的限制，只有適度的“粗”梁可以分析。梁的長細比（GAL2/(EI)可以用來判定單元的適用性，式中：G Shear modulus 剪切模量A Area of the cross section 截面積L Length of the member 構(gòu)件長度EI Flexura

21、l rigidity 抗彎剛度It is important to note that this ratio should be calculated using some global distance measures, and not based on individual element dimensions. The following graphic provides an estimate of transverse shear deformation in a cantilever beam subjected to a tip load. Although the resul

22、ts cannot be extrapolated to any other application, the example serves well as a general guideline. We recommend that the slenderness ratio should be greater than 30. 需要注意的是這個比例的計算需要用一些全局距離尺寸，不是基于獨立的單元尺度。下面這個圖提供了受端部集中荷載的懸臂梁的橫向剪切變形的例子，這個例子可以作為一個很好的大致的指導(dǎo)。我們推薦長細比要大于30。Figure188.2:Transverse-Shear Defor

23、mation Estimation圖188.2：橫向剪切變形的評估示意Slenderness Ratio (GAL2/(EI)長細比 Timoshenko / Euler-Bernoulli位移：鐵木辛哥/歐拉伯努力251.120501.0601001.03010001.003These elements support an elastic relationship between transverse shear forces and transverse shear strains. You can override default values of transverse shear

24、stiffnesses using the command.這些單元支持橫向剪切力和橫向剪切變應(yīng)力的彈性關(guān)系。你可以用seccontrols 命令重新定義默認的橫向剪切剛度值。The St. Venant warping functions for torsional behavior are determined in the undeformed state, and are used to define shear strain even after yielding. ANSYS does not provide options to recalculate in deformed c

25、onfiguration the torsional shear distribution on cross-sections during the analysis and possible partial plastic yielding of cross-sections. As such, large inelastic deformation due to torsional loading should be treated and verified with caution. Under such circumstances, alternative modeling using

26、 solid or shell elements is recommended.無形變的狀態(tài)決定了扭轉(zhuǎn)作用引起的圣維南翹曲變形，可以用來定義屈服后的剪應(yīng)力。Ansys 沒有提供選項使不成型的結(jié)構(gòu)重新計算，這種結(jié)構(gòu)是由分析過程中的扭轉(zhuǎn)剪切對橫截面的作用以及部分截面塑性屈服引起的。正因為此，由扭轉(zhuǎn)作用引起的非彈性大變形需要小心的來處理和校核。在這樣的情況下，推薦使用solid 或者shell 單元來替換。BEAM188 elements support “restrained warping” analysis by making available a seventh degree of fre

27、edom at each beam node. By default, BEAM188 elements assume that the warping of a cross-section is small enough that it may be neglected (KEYOPT(1) = 0). You can activate the warping degree of freedom by using KEYOPT(1) = 1. With the warping degree of freedom activated, each node has seven degrees o

28、f freedom: UX, UY, UZ, ROTX, ROTY, ROTZ, and WARP. With KEYOPT(1) = 1, bimoment and bicurvature are output.Beam188單元支持“約束扭轉(zhuǎn)”分析，通過定義梁節(jié)點的第七個自由度來實現(xiàn)。Beam188 單元默認的假設(shè)是截面的扭轉(zhuǎn)是足夠小的以至于可以忽略（KEYOPT（1）0）。你可以激活它的扭轉(zhuǎn)自由度通過定義KEYOPT（1）1。當(dāng)激活節(jié)點的扭轉(zhuǎn)自由度的時候，每個節(jié)點有七個自由度：UX，UY，UZ，ROTX, ROTY, ROTZ, 和WARP。當(dāng)KEYOPT(1) = 1，雙力矩和雙弧線將

29、被輸出。In practice, when two elements with “restrained warping” come together at a sharp angle, you need to couple the displacements and rotations, but leave the out-of-plane warping decoupled. This is normally accomplished by having two nodes at a physical location and using appropriate constraints. T

30、his process is made easier (or automated) by the command, which decouples the out-of plane warping for any adjacent elements with cross-sections intersecting at an angle greater than 20 degrees.實際上，當(dāng)兩個“約束扭轉(zhuǎn)”的單元以一個銳角組合在一起的時候，你需要耦合他們的唯一合轉(zhuǎn)角，使它們平面外的自由度解藕。一般通過用兩個節(jié)點在物理位置和運用合適的約束可以實現(xiàn)。這個過程通過ENDRELEASE命令很容易的

31、（自動的）實現(xiàn)，命令將兩個臨近橫截面相交角度大于20度的單元的平面外扭轉(zhuǎn)解耦。BEAM188 allows change in cross-sectional inertia properties as a function of axial elongation. By default, the cross-sectional area changes such that the volume of the element is preserved after deformation. The default is suitable for elastoplastic application

32、s. By using KEYOPT(2), you can choose to keep the cross-section constant or rigid. Scaling is not an option for (,GENB).Beam188 允許改變橫截面慣性屬性來實現(xiàn)軸向伸長的功能。默認的，截面面積改變而使得單元的體積變形后不變化。這種默認的值對于彈塑性應(yīng)用是適用的。通過運用KEYOPT（2）選項,你可以選擇橫截面是恒定的或者剛性的。Scaling命令不適用于一般的非線性梁截面。Element output is available at element integration

33、 stations and at section integration points.單元的輸出在單元積分位置和截面的積分點可以使用。Integration stations (Gauss points) along the length of the beam are shown in .沿著梁長度的積分點（高斯點）如圖Figure 188.3所示：Figure188.3BEAM188 Element Integration Stations圖188.3：Beam188單元積分點The section strains and forces (including bending moment

34、s) may be obtained at these integration stations. The element supports output options to extrapolate such quantities to the nodes of the element.截面的應(yīng)變和力（包括彎距）可以在這些積分點上得到。單元支持輸出選項來外推這些數(shù)值到單元的節(jié)點。BEAM188 can be associated with either of these cross section types:Beam188可以設(shè)置各種截面形式：Generalized beam cross

35、sections (,GENB), where the relationships of generalized stresses to generalized strains are input directly. 可直接輸入材料廣義應(yīng)力應(yīng)變關(guān)系生成廣義梁截面(,GENB)。Standard library section types or user meshes which define the geometry of the beam cross section (,BEAM). The material of the beam is defined either as an eleme

36、nt attribute (MAT), or as part of section buildup (for multi-material cross sections).可生成既有的或者用戶指定的截面形式(,BEAM)，梁元材料可以由MAT命令生成，也可以由多種材料的截面形式組成。Generalized Beam Cross Sections廣義的梁橫截面When using nonlinear general beam sections, neither the geometric properties nor the material is explicitly specified. G

37、eneralized stress implies the axial force, bending moments, torque, and transverse shear forces. Similarly, generalized strain implies the axial strain, bending curvatures, twisting curvature, and transverse shear strains. (For more information, see .) This is an abstract method for representing cro

38、ss section behavior; therefore, input often consists of experimental data or the results of other analyses. 當(dāng)使用非線性梁截面時，幾何特征和材料屬性均明確指定。廣義應(yīng)力包括軸力，彎矩，扭矩以及橫向切應(yīng)力。同樣，廣義應(yīng)變包括軸向應(yīng)變，彎曲應(yīng)變，扭轉(zhuǎn)應(yīng)變以及橫向剪切應(yīng)變（更多信息詳見.）這是一個抽象方法反映截面的行為，因此輸入的數(shù)據(jù)常常由試驗或者其他分析構(gòu)成。The BEAM188 elements, in general, support an elastic relationship b

39、etween transverse shear forces and transverse shear strains. You can override default values of transverse shear stiffnesses via the command. Beam188一般支持橫向切應(yīng)力和橫向切應(yīng)變之間的彈性關(guān)系，可通過 命令改寫默認的應(yīng)力應(yīng)變關(guān)系。When the beam element is associated with a generalized beam (,GENB) cross section type, the relationship of tr

40、ansverse shear force to the transverse shear strain can be nonlinear elastic or plastic, an especially useful capability when flexible spot welds are modeled. In such a case, the command does not apply. 當(dāng)梁單元采用廣義梁截面時，橫向切應(yīng)力和橫向切應(yīng)變之間的關(guān)系為非彈性或者塑性，會生成一個可用的屈服點。這種情況下，命令不再適用。Standard Library Sections標(biāo)準截面形式：BE

41、AM188 are provided with section-relevant quantities (area of integration, position, Poisson function, function derivatives, etc.) automatically at a number of section points using and . Each section is assumed to be an assembly of a predetermined number of 9-node cells. The following graphic illustr

42、ates models using the rectangular section subtype and the channel section subtype. Each cross-section cell has 4 integration points and each may be associated with an independent material type.Beam188提供了截面相關(guān)參數(shù)（面積，位置，分布函數(shù)，導(dǎo)數(shù)等等）可以通過 and 命令使用于定義截面。每個截面假定由預(yù)定的9個節(jié)點單位組成。下圖列舉了通過矩形子項和通道子項建立模型，每個截面單元有4個積分點，每個

43、積分點可設(shè)置獨立的材料屬性。Figure188.4Cross-Section Cells圖188.4：Beam188截面單元格BEAM188 provide options for output at the section integration points and/or section nodes. You can request output only on the exterior boundary of the cross-section. ( prints the section nodal and section integration point results. Stres

44、ses and strains are printed at section nodes, and plastic strains, plastic work, and creep strains are printed at section integration points.)Beam188提供在積分點和界面節(jié)點輸出的選項。你可以要求僅在截面的外表面輸出。（PRSSOL 打印截面節(jié)點和截面積分點結(jié)果。應(yīng)力和應(yīng)變在截面的截面打印，塑性應(yīng)變，塑性作用，蠕變應(yīng)力在截面的積分點輸出）。When the material associated with the elements has inela

45、stic behavior or when the temperature varies across the section, constitutive calculations are performed at the section integration points. For more common elastic applications, the element uses precalculated properties of the section at the element integration points. However, the stresses and stra

46、ins are calculated in the output pass at the section integration points.當(dāng)與單元相關(guān)的材料有非彈性的行為或者當(dāng)截面的溫度有變化，基本計算在截面的積分點上運行。對于更多的常見的彈性的運用，單元運用預(yù)先計算好的單元積分點上的截面屬性。無論如何，應(yīng)力和應(yīng)變通過截面的積分點輸出來計算。If the section is assigned the subtype ASEC, only the generalized stresses and strains (axial force, bending moments, transve

47、rse shears, curvatures, and shear strains) are available for output. 3-D contour plots and deformed shapes are not available. The ASEC subtype can be displayed only as a thin rectangle to verify beam orientation.如果截面指定為ASEC 子項，僅僅廣義的應(yīng)力和應(yīng)變（軸力、彎距、橫向剪切、彎曲、剪應(yīng)力）能夠輸出。3D 輪廓線和變形形狀不能輸出。ASEC 子項僅僅可以作為薄矩形來認定梁的方向

48、。BEAM188 allow for the analysis of built-up beams, (i.e., those fabricated of two or more pieces of material joined together to form a single, solid beam). The pieces are assumed to be perfectly bonded together. Therefore, the beam behaves as a single member. Beam188 能夠?qū)M合梁進行分析，（例如，那些由兩種或者兩個以上材料復(fù)合而成

49、的簡單的實體梁）。這些組件被假設(shè)為完全固接在一起的。因此，該梁表現(xiàn)為單一的構(gòu)件。The multi-material cross-section capability is applicable only where the assumptions of a beam behavior (Timoshenko or Bernoulli-Euler beam theory) holds. 多材料截面能力僅僅在梁的行為假定（鐵木辛哥或者伯努力歐拉梁理論）成立的時候能運用。In other words, what is supported is a simple extension of a con

50、ventional Timoshenko beam theory. It may be used in applications such as: 換言之，支持簡單的傳統(tǒng)鐵木辛哥梁理論的擴展?？蓱?yīng)用于以下方面：bimetallic strips雙層金屬帶beams with metallic reinforcement帶金屬加固的梁sensors where layers of a different material has been deposited位于不同材料組成的層上的傳感器BEAM188 do not account for coupling of bending and twis

51、ting at the section stiffness level. The transverse shears are also treated in an uncoupled manner. This may have a significant effect on layered composite and sandwich beams if the layup is unbalanced.Beam188不會計算在截面剛度水平上的彎距和扭距的耦合。橫向的剪切也作為一個獨立的量來計算。這對于分層的組合物和夾層量可能會有很大的影響，如果接頭處不平衡。BEAM188 do not use

52、higher order theories to account for variation in distribution of shear stresses. Use ANSYS solid elements if such effects must be considered.Beam188沒有用高階理論來計算剪切應(yīng)力的變化，如果這些作用必須考慮的話，就需要運用ANSYS 實體單元。Always validate the application of BEAM188 for particular applications, either with experiments or other

53、 numerical analysis. Use the restrained warping option with built-up sections after due verification.要使beam188用于特殊的應(yīng)用，做試驗或者其他的數(shù)值分析，合適驗證后使用組合截面的約束扭曲的選項。For the mass matrix and evaluation of consistent load vectors, a higher order integration rule than that used for stiffness matrix is employed. The e

54、lements support both consistent and lumped mass matrices. Use ,ON to activate lumped mass matrix. Consistent mass matrix is used by default. An added mass per unit length may be input with the ADDMAS section controls. See .對于質(zhì)量矩陣和一致荷載向量的賦值，將使用到比剛度矩陣使用的規(guī)則更高階的積分規(guī)則。單元支持一致質(zhì)量矩陣和集中質(zhì)量矩陣。用LUMPM，ON 命令來激活集中質(zhì)量

55、矩陣。一致質(zhì)量矩陣是默認使用的。每單位長度的附加質(zhì)量將用ADDMAS 截面控制來輸入，詳見BEAM188 Input Summary。Forces are applied at the nodes (which also define the element x-axis). If the centroidal axis is not colinear with the element x-axis, applied axial forces will cause bending. Applied shear forces will cause torsional strains and mo

56、ment if the centroid and shear center of the cross-section are different. The nodes should therefore be located at the desired points where you want to apply the forces. Use the OFFSETY and OFFSETZ arguments of the command appropriately. By default, ANSYS uses the centroid as the reference axis for

57、the beam elements.在節(jié)點（這些截面定義了單元的x 軸）上施加力，如果重心軸和單元的x 軸不是共線的，施加的軸力將產(chǎn)生彎距。如果質(zhì)心和剪切中心不是重合的，施加的剪切力將導(dǎo)致扭轉(zhuǎn)應(yīng)力和彎曲。因而需要在那些你需要施加力的位置設(shè)置節(jié)點，可以使用secoffset 命令中的offsety 和offsetz 自變量。默認的，ansys 會使用梁單元的質(zhì)心作為參考軸。Element loads are described in . Pressures may be input as surface loads on the element faces as shown by the cir

58、cled numbers on . Positive normal pressures act into the element. Lateral pressures are input as force per unit length. End pressures are input as forces.單元荷載在Node and Element Loads 被描述。壓力可能被作為單元表面力被輸入，就像圖188.1中帶圈的數(shù)字所示。正的壓力指向單元內(nèi)部。水平壓力作為單元長度的力來輸入。端部的壓力作為力輸入。When KEYOPT(3) = 0 (default), BEAM188 is ba

59、sed on linear polynomials, unlike other Hermitian polynomial-based elements (for example, ). Refinement of the mesh is recommended in general.當(dāng)keyopt（3）0 的時候（默認），beam188 基于線性多項式，和其他的基于厄密多項式的單元（例如beam4）不同，一般來說要求網(wǎng)格劃分要細化。When KEYOPT(3) = 2, ANSYS adds an internal node in the interpolation scheme, effec

60、tively making this a Timoshenko beam element based on quadratic shape functions. This option is highly recommended unless this element is used as a stiffener and you must maintain compatibility with a first order shell element. Linearly varying bending moments are represented exactly. The quadratic