In a 32-bit operating system such as Windows 2000 or Windows XP there is a limitation of 232 = 4GB of memory that can be addressed. Windows reserves 2GB for the operating system leaving only 2GB for external programs (such as NEiNastran). With the analyst’s ever increasing demand for more detail and finer mesh sizes, some have reached the limit of the 32-bit platform.   With the release of Windows XP x64, engineers now have a direct upgrade path to a 64- bit platform without having to switch to a Unix/Linux based operating system.

There are many types of behavior that may be referred to as nonlinear. Some examples of nonlinear behavior include materials that change properties as they are loaded, displacements which cause loads to alter their distribution or magnitude, gaps which may open or close. The degree of nonlinearity may be mild or severe.

The need for high performance-to-weight ratio structures coming from the most advanced engineering fields is the main driver of the increasing usage of composite materials for critical applications. In order to design light and safe systems on time to meet the market requirements, accurate and effective analysis tools are necessary. NASA has recently developed LaRC02, a set of first-ply-failure criteria for composites which have been shown to be accurate and physically consistent. The LaRC02 formulation seemed to be particularly well suited for design purposes, due to its optimal trade-off between accuracy, material characterization requirements, computational effort and ease of results interpretation. The present work describes with some insights the LaRC02 criterion features and its implementation into NEiNastran, a commercial finite element software package. The accuracy and usefulness of the method are shown through some application examples, ranging from simple validation cases to a real-world structure.

NEiNastran V9 adds a powerful new feature that allows automatic surface contact generation (ASCG) between discontinuous bodies. This feature is ideally suited for models in which the contact areas are initially touching and where little sliding is expected. The automated surface contact generation works in three phases. First the user defines parameters such as which elements should be considered for each contact pair generated (the default is all solid and shell elements in the model), what the near tolerance is for objects to be considered in contact with each other, and the type of contact to be generated (i.e., general, welded, bi-directional sliding, or rough). Using these user defined parameters, a region of elements is considered. The default would be all solid and shell elements in the model. The first phase consists of identifying the external surfaces of these elements. For shells it would be the entire element. For solids it would be any exterior surface. The second phase then looks for grid points that are positioned on or near and above (within the user defined tolerance) of each surface. The third phase eliminates invalid contact scenarios by considering surface normals. It is important that surfaces that are to be welded are not offset and that shell normals are oriented properly.