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1、wordIntroduction这篇文章我本人在学习 patran/natran 过程中遇到的问题，与后来找到的解决方法，这篇文章 也在逐步更新中，希望这篇文档能给那些学习用 patran/nastran 的一点帮助。Yuanchongxin Delft2011/10/3111. THE SOLUTION FOR THE RESIDUAL STRUCTURE AND THE APPLIED LOADS FOR THE CURRENT SUBCASE ARE ZERO.后来将边界条件由改为，即将位移约束变成 simplified supported，就没 有此问题了。2. USER WARNIN
2、G MESSAGE 4124 (IFS3P)THE SPCADD OR MPCADD UNION CONSISTS OF A SINGLE SET 在图中用了 RB3 的 MPC，其中 dependent node (ux,uy,uz), independent(ux,uy,uz,rx,ry,rz),有可 能是这里的问题。不过这个倒不影响计算结果。3. 建立夹层结构的有限元网络对于 meshing, sweep can produce the solid element on the basis of the shell element. 另外 sweep 下的 loft，可以在两个 shel
3、l mesh 之间，创建 solid element. 对于夹层结构的 modeling, shell and solid element should share mon node. 否如此算出来的 结果，solid stress 为零。至于如何共用节点，如此需用到 element 下的 sweep 命令。4. No PARAM values were set in the Control File不管失败还是成功的 f06 文件中，都会出现这句话。这句话是正常的。 如果出现结果为，并且还没有 fatal，另一种可能是因为 mpc 没有包括全部边界节点，在 对夹层结构圆柱进展分析时，发现由于
4、没有完全把边界节点进展 displacement 界定，以与没 有完全进展 mpc 限制，f06 文件中为，后来改正一下，就好了。5. RBE3 加载与使用可以用 RBE进展 axial load 的加载，但不能用于 bending moment 的加载，曾尝试过，发现 f06 文件中全部为零。 后改成直接对边界曲线进展加载， 问题解决。 比照下将 bending moment 加载到曲线和加载到节点上的区别： 曲线：bending moment 为 40, EIGENVALUE = 2.187715E-02 节点：bending moment 为 40, EIGENVALUE = 2.187
5、715E-02 结果完全一样，这说明将载荷加到曲线或曲线上的节点上，得到的结果完全一样。 Axial load 加载到 RBE点上和加载到节点上的区别： RBE3：axial load=30, EIGENVALUE = -2.379083E+00 节点：USER FATAL MESSAGE 4683 (LNNRIGL) KDIF MATRIX NEEDED FOR EIGENVALUE ANALYSIS 由此可以看出，对于圆柱体来说，轴向载荷只能依靠 rbe来加载，而弯曲载荷如此靠 RBE2 加载。 出现此问题，还有可能没有载荷加载。 另外，奇怪的事，当弯曲载荷施加于平板时，用 linear
6、static 分析可以成功，但是用 105 计算时却出现 4683 的错误。后来将载荷改为轴向压力时，可使上述错误消失。这说明 载荷方向不对，也会出现类似错误。那至于圆柱应该如何呢？2RBE3 的加载，dependent 的 dof 应该是 123, indepdendent 应该是 123456. 不然造成无解。不 过有个参考书上正好相反，但用 nastran 计算有误。不知为何，这里需要提到的是计算结果 与参考书相差为 2，现在尚未找出原因。6. USERFATALMESSAGE 9050 (SEKRRS) RUN TERMINATED DUE TO EXCESSIVE PIVOT RAT
7、IOS IN MATRIX KLL. USER ACTION: CONSTRAIN MECHANISMS WITH SPCI OR SUPORTI ENTRIES OR SPECIFY PARAM,BAILOUT,-1 TO CONTINUE THE RUN WITH MECHANISMS. 以前也遇到这种情况，这次遇到后，又在一节点加载了位移约束，就解决了。看来这 种错误主要是由于约束不够，线性方程组无解造成的。 还有可能是没有 equivalence，This should solve your problem or reduce the number of failed ratios.有
8、一次就遇到此情况。7. 常用材料定义比照表MAT1 MAT2 MAT3 MAT8 MAT9isotropic anisotropic(2) orthotropic(3) orthotropic(2) anisotropic(3) ? Use a FORCE entry if you want to define a static, concentrated force at a grid point by 一个点的力 specifying a vector. ? Use a FORCE1 entry if the direction is determined by a vector conn
9、ecting two grid points. 两个点的力 ? Use a FORCE2 entry if the direction is specified by the cross product of two such vectors. 以上的乘积SPC1,42,123456,1,2,3,4,6,7,8,9 42为SID。SID: load set identification number 载荷序号 G: Grid point 加载点 CID：Coordinate system identification number 坐标序号 F：Scale factor 放大因子 Ni：三维方
10、向的微量，由 CID 决定 例子： FORCE 3 8 0 2000. 1. 0. 0. 加载在节点 8 上的力，大小为 2000N.向量为，分析坐标为 coord 0. SID=3。 Force1 和 force2 的例子在nastran user goodP142.38. MPCThe displacement constrain can affect the output result sharply. When analysis the buckling of the cylinder, I set the top end as , which means that it can mo
11、ve at z direction. While the bottom is set as 123456, which means fixed. The result is equal to the reference, but the deformation doesnt resemble much. I dont know why. 1. The mpc is set as RBE3 Dependent 123456 Independent 123 If the RBE3 is changed as Dependent 123 Independent 123456 The obtained
12、 Eigenvalue doesnt alter much. The former is 0.337, the latter is 0.332. 2. The load can add on one side, and the other side is fixed. It is not good to set pressive load at both end, in this case, the patran is prone to fail. 3. Under pressive load for cylinder, The deformation is not very symmetry
13、, and some part have abnormal large deformation, I dont know why now.9. 关于几个应力的计算方法von Mises Stress：Good question. Von Mises Stress is actually a misnomer. It refers to a theory called the Von Mises - Hencky criterion for ductile failure. In an elastic body that is subject to a system of loads in 3
14、dimensions, a plex 3 dimensional system of stresses is developed (as you might imagine). That is, at any point within the body there are stresses acting in different directions, and the direction and magnitude of stresses changes from point to point. The Von Mises criterion is a formula for calculat
15、ing whether the stress bination at a given point will cause failure. There are three Principal Stresses that can be calculated at any point, acting in the x, y, and z directions. (The x,y, and z directions are the principal axes for the point and their orientation changes from point to point, but th
16、at is a technical issue.)4Von Mises found that, even though none of the principal stresses exceeds the yield stress of the material, it is possible for yielding to result from the bination of stresses. The Von Mises criteria is a formula for bining these 3 stresses into an equivalent stress, which is then pared to the yield stress of the material. (The yield stress is a known property of the material, and is usually considered to be the failure st
