4

4.11 PLANE STRESS ELEMENT NO.11 WITH 12 NODES

This is a curvilinear Serendipity plane stress element with cubic shape functions. The transformation is isoparametric. The integration is carried out numerically in both axises according to Gauss- Legendre. Thus, the integration order can be selected in Z88I1.TXT in the material information lines. The order 3 is mostly the best choice. This element calculates both displacements and stresses with outstanding precision. The integration order can be chosen again for the stress calculation. The stresses are calculated in the corner nodes (good for an overview) or calculated in the Gauss points (substantially more exactly). Because of its 24*24 element stiffness matrices the element No.11 needs a lot of memory and computing power. Pay attention to edge loads, cf. chapter 3.4.

Plane Stress Elements No.7 can be generated by the net generator Z88N from super elements Plane Stress Elements No.11. Thus, the Plane Stress Element No.11 is well suited as super element. But Plane Stress Elements No.11 cannot be generated by the net generator Z88N from super elements Plane Stress Elements No.11.

Input:

CAD (see chapter 2.7.2): 1-5-6-2-7-8-3-9-10-4-11-12-1

Z88I1.TXT

> KFLAG for cartesian (0) or polar coordinates (1)

> 2 degrees of freedom for each node

> Element type is 11

> 12 nodes per element

> Cross-section parameter QPARA is the element thickness

> Integration order INTORD per each mat info line. 3 is usually good.

Z88I3.TXT

> Integration order INTORD: Basically, it is a good idea to use the same value as chosen in Z88I1.TXT , but different values are permitted

0 = Calculation of the stresses in the corner nodes

1,2,3,4 = Calculation of the stresses in the Gauss points

> KFLAG = 0: Calculation of SIGXX, SIGYY and TAUXY

> KFLAG = 1: Additional calculation of SIGRR, SIGTT and TAURT

> Reduced stress flag ISFLAG:

0 = no calculation of reduced stresses

1 = von Mises stresses computed for the Gauss points (INTORD not 0 !)

Results:

Displacements ino X and Y.

Stresses: The stresses are calculated in the corner nodes or Gauss points and printed along with their locations. For KFLAG = 1 the radial stresses SIGRR, the tangential stresses SIGTT and the accompanying shear stresses SIGRT are computed additionally (makes only sense if a rotational-symmetric structure is available). For easier orientation the respective radiuses and angles of the nodes/points are printed. Optional von Mises stresses

Nodal forces in X and Y for each elementand each node.