Forging

Abstract: How was Great Britain made? And what does it mean to be British? In this prize-winning book, Linda Colley explains how a new British nation was invented in the wake of the 1707 Act of Union, and how this new national identity was nurtured through war, religion, trade and imperial expansion. Here too are numerous individual Britons - heroes and politicians like Nelson and Pitt; bourgeois patriots like Thomas Coram and John Wilkes; artists, writers and musicians who helped to forge our image of Britishness; as well as many ordinary men and women whose stories have never previously been told. Powerful and timely, this lavishly illustrated book is a major contribution to our understanding of Britain's past and to the growing debate about the shape and survival of Britain and its institutions in the future. \"The most dazzling and comprehensive study of a national identity yet to appear in any language.\" Tom Nairn, Scotsman \"A very fine book ...challenging, fascinating, enormously well-informed.\" John Barrell, London Review of Books \"Wise and bracing history ...which provides an historical context for debate about British citizenship barely begun.\" Michael Ratcliffe, Observer \"Controversial, entertaining and alarmingly topical ...a delight to read.\"Philip Ziegler, Daily Telegraph \"Uniting sharp analysis, pungent prose and choice examples, Colley probes beneath the skin and lays bare the anatomy of nationhood.\" Roy Porter, New Statesman & Society

Abstract: Introduction Metal forming process Analysis and technology in metal forming Plasticity and viscoplasticity Methods of analysis The finite element method (1) The finite element method (2) Plane-strain problems Axisymmetric isothermal forging Steady state processes of extrusion and drawing Sheet metal forming Thermo-viscoplastic analysis Compaction and forging of porous metals Three dimensional problems Preform design in metal forming Solid formulation, comparison of two formulations, and concluding remarks Index.

Abstract: A new method of modeling material behavior which accounts for the dynamic metallurgical processes occurring during hot deformation is presented. The approach in this method is to consider the workpiece as a dissipator of power in the total processing system and to evaluate the dissipated power co-contentJ = ∫o σ e ⋅dσ from the constitutive equation relating the strain rate (e) to the flow stress (σ). The optimum processing conditions of temperature and strain rate are those corresponding to the maximum or peak inJ. It is shown thatJ is related to the strain-rate sensitivity (m) of the material and reaches a maximum value(J max) whenm = 1. The efficiency of the power dissipation(J/J max) through metallurgical processes is shown to be an index of the dynamic behavior of the material and is useful in obtaining a unique combination of temperature and strain rate for processing and also in delineating the regions of internal fracture. In this method of modeling, noa priori knowledge or evaluation of the atomistic mechanisms is required, and the method is effective even when more than one dissipation process occurs, which is particularly advantageous in the hot processing of commercial alloys having complex microstructures. This method has been applied to modeling of the behavior of Ti-6242 during hot forging. The behavior of α+ β andβ preform microstructures has been exam-ined, and the results show that the optimum condition for hot forging of these preforms is obtained at 927 °C (1200 K) and a strain rate of 1CT•3 s•1. Variations in the efficiency of dissipation with temperature and strain rate are correlated with the dynamic microstructural changes occurring in the material.

Abstract: Depositing large components (>10 kg) in titanium, aluminium, steel and other metals is possible using Wire + Arc Additive Manufacturing. This technology adopts arc welding tools and wire as feedstock for additive manufacturing purposes. High deposition rates, low material and equipment costs, and good structural integrity make Wire+Arc Additive Manufacturing a suitable candidate for replacing the current method of manufacturing from solid billets or large forgings, especially with regards to low and medium complexity parts. A variety of components have been successfully manufactured with this process, including Ti–6Al–4V spars and landing gear assemblies, aluminium wing ribs, steel wind tunnel models and cones. Strategies on how to manage residual stress, improve mechanical properties and eliminate defects such as porosity are suggested. Finally, the benefits of non-destructive testing, online monitoring and in situ machining are discussed.

Abstract: : Friction stir welding (FSW) is a solid state joining process 1,2,3 that uses a rapidly-rotating, non-consumable high strength tool-steel pin that extends from a cylindrical shoulder (Figure 1). The workpieces to be joined are firmly clamped to a worktable; the rotating pin is forced with a pre-determined load into them and moved along the desired bond line. Frictional heating is produced from the rubbing of the rotating shoulder with the workpieces, while the rotating pin deforms (i.e. 'stirs') the locally-heated material. To produce a high integrity defect-free weld, process variables (RPM of the shoulder-pin assembly, traverse speed, the downward forging force) and tool pin design must be chosen carefully. FSW can be considered as a hot-working process in which a large amount of deformation is imparted to the workpiece through the rotating pin and the shoulder. Such deformation gives rise to a weld nugget (whose extent is comparable to the diameter of the pin), a thermomechanically-affected region (TMAZ) and a heat-affected zone (HAZ). Frequently, the weld nugget appears to comprise equiaxed, fine, dynamically recrystallized grains whose size is substantially less than that in the parent material. The objective of the present research was to develop a basic understanding of the evolution of microstructure in the dynamically recrystallized region and to relate it to the deformation process variables of strain, strain rate, and temperature. Such a correlation has not been attempted before perhaps because of the difficulty in quantifying the process variables. To overcome such difficulties, recent work 4 to measure and model the local temperature transients during FSW was utilized, and an approximate method was employed to estimate the strain and strain rate in the weld nugget.