Numerical modelling of the aluminium extrusion process

The extrusion of aluminium alloys involves the shaping of the product from an homogenised billet into a complex shape. In addition the properties of the extrudate are closely related to the processing parameters (temperature, stain rate, and material morphology). Since all the parameters vary throughout the ram stroke and throughout the billet the prediction of the condition of the extrudate is complex. In this study the analysis is accomplished by the use of finite element analysis coupled with sub-illodelling of the structural features. The study is extended to include the lieat-treatment process necessary for precipitation hardened alloys subsequent to the process. The author has published these results in a number of learned journals and these are given in Appendix. After a concise introduction and crirical literature review chapter3 analyses the basic operation of the finite element package(FEM) discussing the procedures involved, the equilibrium equations and the more practical aspect of the mesh morphology and size. Finite Element analysis and material structural models have been integrated using parallel processing technology and program sub-routines. In this section the external inputs are also defined paying particular attention to the friction conditions and the constitutive equations. The thesis then proceeds to describe and analyse the integrated modelling of the process necessary to introduce the user introduction of the equations necessary to produce a comprehensive analysis of the material structural problems. This includes the cellular automata teclu-iiques. Various complex extrusion geometries are analysed and the effects of scaling considered. Development of the extrudate surface and criteria for ptedicting this important feature are coinprehebsivcly covered in chapter 5 whilst chapter 6 considers some special technologies such as the use of pockets to obtain homogenous structures. Isothermal extrusion is also included in this section

A paradigm to be discarded: Geological and paleoecological data falsify the HAFFER & PRANCE refuge hypothesis of Amazonian speciation

All geological data from Amazonian landforms imply continuous humid weathering throughout late Tertiary and Quaternary times, with all claims for arid land processes shown to be in error. Sand dunes exist only where thick deposits of sand prevent stable vegetative cover. A ground truth survey shows that proposed dune fields in the Pantanal do Mato Grosso do not in fact exist and that dunes in Pantanal Setentrional continue to be active. All available Amazonian pollen data, without exception and including new data, imply biome stability: no pollen data suggest increased coverage of savanna in glacial times, claims to the contrary being demonstrably in error. Amazonian climate is not monolithic, with secular climatic changes across the basin not in phase. New evidence shows that vegetation response to lowered temperatures, lowered CO2, and fluctuating dry seasons produced by MILANKOVITCH forcing resulted only in population changes within plant communities without biome replacements. Diversity between habitats within the forest provides vicariance for alternative evolutionary models. The "aridity with refuges paradigm" now impedes Amazonian research and should be discarded

Space programs summary no. 37-27, volume IV for the period April 1, 1964 to May 31, 1964. Supporting research and advanced development

Space exploration programs - systems analysis - spacecraft power and guidance systems - propellant engineering and communications system

The application of parallel computer technology to the dynamic analysis of suspension bridges

This research is concerned with the application of distributed computer technology to the solution of non-linear structural dynamic problems, in particular the onset of aerodynamic instabilities in long span suspension bridge structures, such as flutter which is a catastrophic aeroelastic phenomena. The thesis is set out in two distinct parts:- Part I, presents the theoretical background of the main forms of aerodynamic instabilities, presenting in detail the main solution techniques used to solve the flutter problem. The previously written analysis package ANSUSP is presented which has been specifically developed to predict numerically the onset of flutter instability. The various solution techniques which were employed to predict the onset of flutter for the Severn Bridge are discussed. All the results presented in Part I were obtained using a 486DX2 66MHz serial personal computer. Part II, examines the main solution techniques in detail and goes on to apply them to a large distributed supercomputer, which allows the solution of the problem to be achieved considerably faster than is possible using the serial computer system. The solutions presented in Part II are represented as Performance Indices (PI) which quote the ratio of time to performing a specific calculation using a serial algorithm compared to a parallel algorithm running on the same computer system

Numerical modelling of the aluminium extrusion process

The extrusion of aluminium alloys involves the shaping of the product from an homogenised billet into a complex shape. In addition the properties of the extrudate are closely related to the processing parameters (temperature, stain rate, and material morphology). Since all the parameters vary throughout the ram stroke and throughout the billet the prediction of the condition of the extrudate is complex. In this study the analysis is accomplished by the use of finite element analysis coupled with sub-illodelling of the structural features. The study is extended to include the lieat-treatment process necessary for precipitation hardened alloys subsequent to the process. The author has published these results in a number of learned journals and these are given in Appendix. After a concise introduction and crirical literature review chapter3 analyses the basic operation of the finite element package(FEM) discussing the procedures involved, the equilibrium equations and the more practical aspect of the mesh morphology and size. Finite Element analysis and material structural models have been integrated using parallel processing technology and program sub-routines. In this section the external inputs are also defined paying particular attention to the friction conditions and the constitutive equations. The thesis then proceeds to describe and analyse the integrated modelling of the process necessary to introduce the user introduction of the equations necessary to produce a comprehensive analysis of the material structural problems. This includes the cellular automata teclu-iiques. Various complex extrusion geometries are analysed and the effects of scaling considered. Development of the extrudate surface and criteria for ptedicting this important feature are coinprehebsivcly covered in chapter 5 whilst chapter 6 considers some special technologies such as the use of pockets to obtain homogenous structures. Isothermal extrusion is also included in this section.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The 1986 Get Away Special Experimenter's Symposium

The 1986 Get Away Special (GAS) Experimenter's Symposium will provide a formal opportunity for GAS Experimenter's to share the results of their projects. The focus of this symposium is on payloads that will be flown in the future

Notes of a military reconnoissance, from Fort Leavenworth, in Missouri, to San Diego, in California, including part of the Arkansas, Del Norte, and Gila Rivers.

Notes from an Expedition; Fort Leavenworth to San Diego, California. 16 Dec. SED 7, 30-1, v3, 416p. [5051 or HED 41,30-1, v4, 614p. (517] Encounters with Indian tribes of the Southwest during 1846-47 (House version includes an expedition to New Mexico)

Camas, Fall 2003

Dust of Snow / John Eider -- Beautiful River, Arms of Cod / Susan Tomlinson -- Low Murmur, Low Song / Danielle Lattuga -- First Person / Katharine Hyzy, John Elder -- Huckleberry Wine -- Perspectives / Wren Farris, Tami Brunk -- Poetry / Ryan Newhouse, Melissa Matthewson, Jeremy Watterson -- Interview/Review / Andrea Peacock by Margot Higgins -- Book Reviews -- Last Words / Jeff Kessle

Discrete Mathematics and Symmetry

Some of the most beautiful studies in Mathematics are related to Symmetry and Geometry. For this reason, we select here some contributions about such aspects and Discrete Geometry. As we know, Symmetry in a system means invariance of its elements under conditions of transformations. When we consider network structures, symmetry means invariance of adjacency of nodes under the permutations of node set. The graph isomorphism is an equivalence relation on the set of graphs. Therefore, it partitions the class of all graphs into equivalence classes. The underlying idea of isomorphism is that some objects have the same structure if we omit the individual character of their components. A set of graphs isomorphic to each other is denominated as an isomorphism class of graphs. The automorphism of a graph will be an isomorphism from G onto itself. The family of all automorphisms of a graph G is a permutation group