1、BEAM188单元中文说明Release 10.0 Documentation for ANSYSBEAM1883D Linear Finite Strain Beam三维线性有限应变梁单元BEAM188 Element DescriptionBEAM188单元描述BEAM188 is suitable for analyzing slender to moderately stubby/thick beam structures. This element is based on Timoshenko beam theory。 Shear deformation effects are in
2、cluded。Beam188 单元适合于分析从细长到中等粗短的梁结构,该单元基于铁木辛哥梁结构理论，并考虑了剪切变形的影响。BEAM188 is a linear （2node) or a quadratic beam element in 3D。 BEAM188 has six or seven degrees of freedom at each node, with the number of degrees of freedom depending on the value of KEYOPT(1）. When KEYOPT(1) = 0 (the default)， six degr
3、ees 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 well-suited for linear, large rotation， and/or large str
4、ain nonlinear applications。 Beam188 是三维线性(2 节点）或者二次梁单元.每个节点有六个或者七个自由度，自由度的个数取决于KEYOPT(1)的值。当KEYOPT（1）0（缺省）时，每个节点有六个自由度；包括节点坐标系的x、y、z 方向的平动和绕x、y、z 轴的转动.当KEYOPT（1）=1 时，每个节点有七个自由度，这时引入了第七个自由度（横截面的翘曲）.这个单元非常适合线性、大角度转动以及大应变等非线性问题。BEAM188 includes stress stiffness terms, by default， in any analysis with N
5、LGEOM，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）.当NLGEOM 选项打开的时候，beam188 的应力刚化，在任何分析中都是缺省项。应力刚化选项使本单元能分析弯曲、横向及扭转稳定问题(用弧长法分析特征值屈曲和塌陷）。BEAM188 can be
6、used with any beam cross-section defined via SECTYPE, SECDATA， SECOFFSET， SECWRITE， and SECREAD. 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 with this el
7、ement type can be a built-up section referencing more than one material.Beam188可以采用sectype、secdata、secoffset、secwrite 及secread 命令定义横截面。本单元支持弹性、蠕变及塑性模型（不考虑横截面子模型）。这种单元类型的截面可以由不同材料组成。BEAM188 ignores any real constant data beginning with Release 6.0。 See the SECCONTROLS command for defining the transve
8、rse shear stiffness, and added mass。Beam188 从6。0 版本开始忽略任何实常数，参考seccontrols 命令来定义横向剪切刚度和附加质量。For BEAM188， the element coordinate system （/PSYMB，ESYS) is not relevant.单元坐标系统（/psymb，esys）与beam188 单元无关。Figure188.1：BEAM188 Geometry图188.1：Beam188 单元几何示意图BEAM188 Input DataBEAM188 输入数据The geometry, node loc
9、ations, and coordinate system for this element are shown in Figure 188。1： ”BEAM188 Geometry. BEAM188 is defined by nodes I and J in the global coordinate system。 该单元的几何形状、节点位置、坐标体系如图188.1 “Beam188 单元几何示意图所示，beam188 由整体坐标系的节点I 和J 定义.Node K is a preferred way to define the orientation of the element.
10、For information about orientation nodes and beam meshing， see Generating a Beam Mesh With Orientation Nodes in the ANSYS Modeling and Meshing Guide. See the LMESH and LATT command descriptions for details on generating the K node automatically.节点K 是定义单元方向的首选方式，有关方向节点和梁的网格划分的信息可以参见ANSYS Modeling and
11、Meshing Guide中的Generating a Beam Mesh With Orientation Nodes。参考LMESH和LATT命令描述可以得到k 节点自动生成的详细资料。BEAM188 may also be defined without the orientation node。 In this case， the element xaxis is oriented from node I （end 1） toward node J (end 2）。 For the twonode option, the default orientation of the eleme
12、nt yaxis is automatically calculated to be parallel to the global XY plane. For the case where the element is parallel to the global 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 abo
13、ut the element xaxis， use the third node option. If both are defined, the third node option takes precedence。 The third node （K）， if 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 th
14、e location of the third node (K） is used only to initially orient the element.Beam188 也以在没有方向节点的情况下被定义。在这种情况下，单元的x 轴方向为I 节点指向J节点。对于两节点的情况，默认的y 轴方向按平行xy 平面自动计算.对于单元平行与z 轴的情况（或者斜度在0。01以内),单元的y 轴的方向平行与整体坐标的y 轴（如图188.1）。用第三个节点的选项,用户可以定义单元的x 轴方向.如果两者都定义了,那么第三节点的选项优先考虑。第三个节点（K）如果采用的话,将和I、J 节点一起定义包含单元x 轴和z
15、 轴的平面(如图188.1）.如果该单元采用大变形分析,需要注意这个第三号节点仅仅在定义初始单元方向的时候有效。The beam elements are one-dimensional line elements in space。 The crosssection details are provided separately using the SECTYPE and SECDATA commands (see Beam Analysis and Cross Sections in the ANSYS Structural Analysis Guide for details). A s
16、ection is associated with the beam elements by specifying the section ID number （SECNUM). A section number is an independent element attribute. In addition to a constant cross-section， you can also define a tapered crosssection by using the TAPER option on the SECTYPE command (see Defining a Tapered
17、 Beam).梁单元是一维空间线单元。横截面资料用sectype和secdata 命令分别提供，参见ANSYS Structural Analysis Guide 的Beam Analysis and Cross Sections 看详细资料。截面与单元用截面ID 号（SECNUM）来关联，截面号是独立的单元属性。除了等截面，还可以用sectype 命令中的锥形选项来定义楔形截面（参考Defining a Tapered Beam）.The beam elements are based on Timoshenko beam theory， which is a first order she
18、ar deformation theory: transverse shear strain is constant through the cross-section; that is， crosssections remain plane and undistorted after deformation. BEAM188 is a first order Timoshenko beam element which uses one point of integration along the length with default KEYOPT(3) setting。 Therefore
19、， 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。单元基于铁木辛哥梁理论，这个理论是一阶剪切变形理论；横向剪切应力在横截面是不变的，也就是说变形后横截面保持平面不发生扭曲。Beam188 是一阶铁木辛哥梁单元，沿着
20、长度用了一个积分点，用默认的KEYOPT（3）设置。因此，在I 和J 节点要求SMISC 数值的时候，中间数值在两端节点均输出。当KEYOPT（1） 设置为2，两个积分点作为延长的线性变量被运用。BEAM188 lements can be used for slender or stout beams. Due to the limitations of first order shear deformation theory， only moderately ”thick” beams may be analyzed。 The slenderness ratio of a beam str
21、ucture （GAL2/（EI) may be used in judging the applicability of the element， where: Beam188单元可以用在细长或者短粗的梁。由于一阶剪切变形的限制,只有适度的“粗”梁可以分析。梁的长细比（GAL2/（EI)）可以用来判定单元的适用性，式中:G Shear modulus 剪切模量A Area of the cross section 截面积L Length of the member 构件长度EI Flexural rigidity 抗弯刚度It is important to note that this r
22、atio 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 results cannot be extrapolated to any other application
23、, the example serves well as a general guideline. We recommend that the slenderness ratio should be greater than 30。 需要注意的是这个比例的计算需要用一些全局距离尺寸，不是基于独立的单元尺度。下面这个图提供了受端部集中荷载的悬臂梁的横向剪切变形的例子，这个例子可以作为一个很好的大致的指导。我们推荐长细比要大于30。Figure188.2：TransverseShear Deformation Estimation图188。2：横向剪切变形的评估示意Slenderness Rati
24、o （GAL2/（EI）长细比 Timoshenko / Euler-Bernoulli位移：铁木辛哥/欧拉伯努力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 stiffnesses using the SECCONTROLS command.这些单元支持横向剪
25、切力和横向剪切变应力的弹性关系.你可以用seccontrols 命令重新定义默认的横向剪切刚度值。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 configuration the torsional shear distri
26、bution on crosssections 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 solid or shell elements is recommended。
27、无形变的状态决定了扭转作用引起的圣维南翘曲变形，可以用来定义屈服后的剪应力。Ansys 没有提供选项使不成型的结构重新计算，这种结构是由分析过程中的扭转剪切对横截面的作用以及部分截面塑性屈服引起的.正因为此，由扭转作用引起的非弹性大变形需要小心的来处理和校核。在这样的情况下，推荐使用solid 或者shell 单元来替换。BEAM188 elements support “restrained warping” analysis by making available a seventh degree of freedom at each beam node。 By default, BEAM
28、188 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 of freedom: UX, UY， UZ， ROTX, ROTY， ROTZ，
29、 and WARP. With KEYOPT（1) = 1， bimoment and bicurvature are output.Beam188单元支持“约束扭转”分析，通过定义梁节点的第七个自由度来实现。Beam188 单元默认的假设是截面的扭转是足够小的以至于可以忽略(KEYOPT(1）0）。你可以激活它的扭转自由度通过定义KEYOPT（1）1。当激活节点的扭转自由度的时候，每个节点有七个自由度：UX，UY，UZ，ROTX, ROTY， ROTZ, 和WARP。当KEYOPT(1) = 1,双力矩和双弧线将被输出。In practice， when two elements with
30、“restrained warping” come together at a sharp angle, you need to couple the displacements and rotations, but leave the outofplane warping decoupled. This is normally accomplished by having two nodes at a physical location and using appropriate constraints。 This process is made easier （or automated)
31、by the ENDRELEASE command, which decouples the out-of plane warping for any adjacent elements with crosssections intersecting at an angle greater than 20 degrees.实际上，当两个“约束扭转的单元以一个锐角组合在一起的时候，你需要耦合他们的唯一合转角，使它们平面外的自由度解藕。一般通过用两个节点在物理位置和运用合适的约束可以实现。这个过程通过ENDRELEASE命令很容易的（自动的)实现，命令将两个临近横截面相交角度大于20度的单元的平面
32、外扭转解耦。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 applications. By using KEYOPT（2）， you can choose to keep the cross-section constant or rigid. Scaling is not an option for nonlinear general beam sections (SECTYPE,，GENB).Beam188 允许改变横截面惯性属性来实现轴向伸长的功能。默认的，截面面积改变而使得单元的体积变形后不变化。这种默认的值对于弹塑性应用是适用的。通过运用KEYOPT（2）选项，你可
