The work described in this paper is an evaluation of the contact characteristics of bi-metallic gears forged through a novel bi-metallic gear forging process. Finite element analysis of the contact characteristics of single material gears was first performed to validate the tooth contact and tooth root stresses with empirical American Gear Manufacturers Association and British Standard standards. Having verified the validity of the model, simulations were performed for gears comprising lightweight cores with teeth bounded by steel bands of uniform thicknesses, 1 mm, 2 mm, 4 mm, and 6 mm to evaluate the differences in stress distribution and compare to single material gear teeth. The forged profiles obtained experimentally by utilising 2 mm, 4 mm, and 6 mm thickness bands via the bi-metallic gear forging process are also discussed. The uniform thickness model is subsequently adapted to incorporate the experimental forged profiles in order to estimate the contact stress, root stress, and stress distribution within the teeth to identify performance differences between bi-metallic forged gears and traditional single material gears.
This paper provides a review of the methods developed over the years for reducing working forces for the precision metal forming processes. Precision forging normally involves completely, or near completely closed cavity dies with no or minimal draft, making features on the extremities difficult to fill and requiring high loads. Means to minimise load, in order to enhance tool life, or reduce press capacity are crucial to the success of precision forging processes. The main concentration of this study is on design features which can be incorporated in tooling and/or workpiece in order to assist in minimisation of forging load while achieving complete die filling. The load reduction methods are presented using examples mainly of precision gear forging, which is representative of the precision forging of other axisymmetric components with complex peripheral shape. The methods reviewed are divided into the categories of (i) billet design, (ii) tool design and (iii) process design. Their effects on forging load reduction for precision forging, along with the authors' opinions as to the benefits, drawbacks and applicability of each, are presented.
This paper provides a review of recent developments in the manufacturing of lightweight multi-metal components, and in particular gears. The literature has shown that significant efforts have been made in manufacturing light gears and numerous technical challenges exist when designing for and manufacturing with dissimilar metals including challenges in heating technologies, mechanical performance, processing parameters, metal compatibility and the interface layer between adjacent materials, as well as difficulties in multi-metal simulations. Whilst the scope of multi-metal manufacturing is vast, the main concentration of this study is on the main stages of multi-metal gear production, and specifically on preform production, multi-metal heating, intermetallic bonding, and modelling of essential forming parameters. The effects of each of these methods as well as the numerous approaches studied in the literature are presented, with a recommendation being made as to a processing route that may lead to a robust multi-metal gear with minimal production line modifications to conventional steel gears.
Constitutive equations have been used extensively to accurately describe material properties over a wide range of temperatures and strain rates in numerical simulations. In this paper, an algorithmic method of determining the constants of such constitutive equations is presented. The Genetic Algorithm implementation utilising MATLAB is described, and example fits to experimental data are presented.
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