The finite element analysis of post --

The finite element analysis of post -- The following four series of articles in a newsletter of the American Society of Mechanical Engineers (ASME). It serves as an introduction to the recent analysis discipline known as the finite element method. The author is an engineering and consulting with the analysis of finite element. Finite Element Analysis: Post-processing by Steve Roensch, President, Roensch & Associates latest in a series of four after a finite element model was created and controlled conditions have been applied, and the model was solved, it's time for examine the results of the analysis. This activity is known as post-processing of finite element method. Post-treatment begins with a thorough check of the problems, probably at the solution. Most of the solver a log file that should be searched for waings or errors, and will also provide a quantitative measure of how well-behaved numerical procedures were during the solution. Then, the reaction loads to the seat of the nodes should be combined and referred to as "common sense check." Loads of reaction that are not strictly balance the resulting burden on the application of a linear static analysis should cast doubt on the validity other results. Error norms such as strain energy density and stress deviation among adjacent elements may be the next, but for the H-code analysis of these quantities are better for the eventual goal of adaptive remeshing. Once the solution is revised to numerical problems, the quantities of interest can be examined. Many display options are available, the choice depends on where the mathematical form of quantity and the physical meaning. For example, the movement of a solid linear brick element node is a 3-space-vector component, and the model of global change is often characterized by the superposition of deformed shape of form Undeformed. Dynamic display and animation capabilities to help achieve a strong understanding of the model deformation. Stresses that tensor quantities, currently no single good display technology, and therefore the amount of stress are extracted and displayed. Principal stress vectors can be used as a color arrows in both direction and magnitude. The magnitude of the principal stresses or failure of a scalar stress, such as the Von Mises stress can be the model of colored bands. If this type of presentation is as an object in 3D light sources, the resulting image is an image in the shadow of stress action. Displacement magnitude may also be displayed by colored bands, but this can lead to misinterpretation as a stress plot. An area of post-processing, fast gaining popularity, the adaptive remeshing. Error norms such as strain energy density are used for the model remesh, a dense network of areas that need improvement and a coarser mesh in areas of Overkill. Adaptivity is an associative connection between the CAD model and the geometry of the base, and works best when the boundary conditions can be printed directly on the geometry, as well. Adaptive remeshing is a new demonstration of the iterative nature of the H-code analysis. Optimization is another area enjoying recent advancement. Based on the values of individual results, the model is modified automatically in an attempt to meet certain performance criteria, and again has been resolved. The process is repeated until a certain convergence criterion is met. In its scalar form, optimization of the beam changes the properties of the cross-section of thin-shell and / or material properties in an attempt to maximum stress constraints, maximum deflection constraints, and / or frequency of vibration constraints . Shape optimization is more complex, with the 3D model boundaries changed. This is the best guide to the optimization of parameters such as size, but mesh quality at each iteration can be a conce. Another direction clearly visible in the area of finite element is the integration of FEA packages with so-called "mechanism" packages, the analysis of the movement of forces and movements of large multi-body systems. A long-term goal would be in real-time calculation and display of displacements and stresses in a multi-organ system, the great movement of displacement, with the effects of friction and flow to be considered, if necessary. It is difficult to estimate the increase in computing power needed to do this show, but 2 or 3 orders of magnitude is probably close. Algorithms to this area of analysis can be expected to follow the computing power increases. To summarize, the finite element method is a relatively new discipline, which can quickly become a mature method, especially for structural and thermal analysis. The cost for the application of this technology in everyday life design activities have been dropped, while the ability to expand the method consistently. With training in technology and commercial software packages are increasingly available, the question has shifted from "Why apply FEA?" A "Why not?". The method is able to improve our products in a short design cycle, reducing the probability of field failure, provided it is supported by a capable analyst. There is also a valid indication of the practices detailed in the event of unforeseen litigation until harvest. The time is now for the industry to make greater use of these and other techniques. Copyright 2005 Roensch & Associates. All rights reserved.