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The influence of cutting forces during the machining of titanium alloys has attained prime attention in selecting the optimal cutting conditions to improve the surface integrity of medical implants and biomedical devices. So far, it has not been easy to explain the chip morphology of Ti6Al4V and the thermo-mechanical interactions involved during the cutting process. This paper investigates the chip configuration of the Ti6Al4V alloy under dry milling conditions at a macro and micro scale by employing the Johnson-Cook material damage model. 2D modeling, numerical milling simulations, and post-processing were conducted using the Abaqus/Explicit commercial software. The uncut chip geometry was modeled with variable thicknesses to accomplish the macro to micro-scale cutting by adapting a trochoidal path. Numerical results, predicted for the cutting reaction forces and shearing zone temperatures, were found in close approximation to experimental ones with minor deviations. Further analyses evaluated the influence of cutting speeds and contact friction coefficients over the chip flow stress, equivalent plastic strain, and chip morphology. The methodology developed can be implemented in resolving the industrial problems in the biomedical sector for predicting the chip morphology of the Ti6Al4V alloy, fracture mechanisms of hard-to-cut materials, and the effects of different cutting parameters on workpiece integrity.

It is widely recognised that subgrain size has significant influence on the strength and ductility of metals. Modelling of subgrain size evolution is essential for the detailed understanding and control of mechanical properties. In the present paper, the evolutions of subgrain size during hot extrusion of various aluminium alloys are first predicted. The microstructural models are then applied to the extrusion of a thin wide semi-closed section using a feeder plate. The feeder plate is investigated by comparing forward extrusion with and without the plate. Results such as temperature, velocity profile, microstructure and pressure distribution are discussed. The influence of the die configuration and the suitability of using several tuning parameters for each alloy are also discussed.

Human and animal footprints found in the Valsequillo Basin were formed on the upper bedding planes surfaces of a volcanic ash (Xalnene Ash) deposited by a subaqueous volcano along the shores of a Pleistocene lake. The footprints were made on lake shorelines and the exposed lake floor during low stands associated, either with water displacement during the volcanic eruption, or due to climatically-driven fluctuations in the water balance. The Xalnene Ash has been dated to at least 40 K BP and consequently the human footprints provide evidence for much earlier colonization of the Americas than is often accepted. The methodology used to record, analyze and conserve these footprints used three-dimensional laser scanning, with sub-millimeter precision. This data were used to reproduce polymer models of individual footprints using the application of rapid-prototyping technology. This technology has wide significance for the study of ichnofacies in general. The characteristics of the human footprints and some pro...

Materials which form the surface and subcutaneous layers of an extrudate experience large deformations when they traverse the die land. This, when added to the inhomogeneity caused by the dead metal zone, leads to considerable modifications to the deformation parameters when compared to the remainder of the extrusion. The distribution of structure is therefore greatly inhomogeneous. Reference to both empirical and physical models of the recrystallisation process indicates that nucleation and growth will differ at these locations in those aluminium alloys that are usually solution treated and aged subsequent to the deformation process. Since static recrystallisation has a significant influence on many of the properties of the extrudate, it is therefore essential to provide the methodology to predict these variations. In the work presented, a physical model, for AA2024, based on dislocation density, subgrain size and misorientation is modified and integrated into the commercial finite element method (FEM) code, FORGE, to study the microstructure changes. Axi-symmetrical and shape extrusion are presented as examples. The evolution of the substructure influencing static recrystallisation is studied. The predicted results show an agreement with the experimental measurement. The distribution of equivalent strain, temperature compensated strain rate and temperatures are also presented to aid interpretation. Importantly the properties of hard alloys improve as the temperature of the extrusion is raised. This phenomenon is discussed and theoretically justified. This paper also presents some innovative work where the physically based models, and the Cellular Automata (CA) method, are combined to simulate the static recrystallisation process. The FEM is adopted to provide the initial morphology and state variables for the structure models, such as the equivalent strain, the temperature and the equivalent strain rate. The subgrain size, and dislocation densities are calculated from physically based models and are transferred to CA models to construct the data required to define the initial state for recrystallisation. Simulation results are compared with experimental measurements. It is demonstrated that CA integrated with the physically based models is effective in predicting the structural changes by selecting a suitable neighbourhood and reasonable transition rules.

The major objective of the present paper is to explore the complicated interactions between die design, forming parameters (i.e. ram speed, container temperature, billet temperature and extrusion ratio) and the product qualities (extrudate shape, surface condition and microstructure) by the use of finite element modelling (FEM). The various models (such as recrystallisation, damage criteria, etc.) have been integrated into the commercial codes, FORGE2® and FORGE3®, through user routines. The physical recrystallisation model proposed by Sellars and Zhu [Mater. Sci. Eng. A280 (2000) 1] and Vatne et al. [Acta Mater. 44 (1996) 4463] have been compared. The predicted distributions of the volume fraction recrystallised were also compared with the experimental results from the literature. The influences of forming parameters on the occurrence of surface cracks were studied by the combination of the Taguchi method with the FEM. It was found that the choked die could significantly reduce the possibility of producing surface cracks. Through simulating a shape extrusion process using two different die structures, it was found that the use of an expansion chamber can significantly reduce the degree of non-uniformity in terms of the extruded product shape and properties. The character of the complex material flow is also identifiable, which is very useful to help improve die design.

The interplay between materials science and sports equipment takes many forms. Certainly a broad cross section of materials is used in sporting equipment to improve performance and safety, and to reduce cost. The new materials used in sports equipment originate from a long history of innovation, drawing from and contributing to other technologies. Amateurs and professionals play sports, so rules on the use of new technology vary immensely. This allows for a short circuit of new technology into the market-place in some cases and restriction or prohibition of opportunities in others. Also materials selection and development for sports equipment must stretch beyond consideration of the object itself to include the human interface and design of a system that best makes use of the materials. Sports after all are about human capability and interaction. The equipment is just a facilitator. Certainly more efficient ways exist of placing a ball into a hole than hitting it with a long metal stick from hundreds of yards away. This is perhaps the most unique element of materials development for sports. The rules governing materials development are not just laws of science and of government but rules put into place just for “sport.” Because of the connection of sports to the lives of so many people, either as participants or spectators, materials science of sporting equipment is also a great platform for educating students about materials selection and behavior.

This paper describes a detailed study of tube extrusion by simulation using finite element method (FEM). The finite element model used one-sixth of symmetry. The extrusion load, temperature evolution and metal flow were predicted. Innovative methods, combining both grid and surface tools, were used to define in detail the flow of material. These showed clearly the inner and outer surface formation mechanisms of the tube extrusion. The seam weld, an important quality indicator, was also evaluated by selecting an appropriate criterion.

This paper presents a design idea for an electric charging device designed to sit underneath the keypad of various mobile devices using piezoelectric and similar effect materials. It discusses the benefits of such a device and the current problems associated with developing one. The basis for the device is that multiple piezoelectric materials placed under the keypad are subjected to repeated loading from activities such as ‘texting’ or ‘menu browsing’. This causes a variable voltage generation which can assist in charging or other suitable function of the device. The paper shows the ways to achieve this goal and examine current piezoelectric generators.Copyright © 2009 by ASME

This paper is based on research carried out as part of the VICARIA project, an interactive tool which was developed from an EC Leonardo grant, to provide distance learning and virtual classrooms in the field of risk management and control. Companies are responsible to provide appropriate training especially in sensitive and critical areas such as risk assessment and management; unfortunately many consider, risk analysis training to be expensive, costly and time consuming. VICARIA allows flexibility in training time, it is cost-effective i.e. reduced travel and subsistence expenses, it enables managers to attend and assist in courses, allowing them to judge the relevancy and quality of training provided and also VICARIA offers specialised and the latest knowledge in the specific field of risk analysis. This system includes accessibility, interoperability, durability and re-usability aspects and uses open standards with respect to platform and content. English, French and Greek are the languages used.

The main objective of the work of this paper is to study the possibility of using a small scale geometrical model in the numerical simulation of aluminium extrusion. The advantages and shortcomings of the application of the\ud geometrically similar model in FEM simulation are discussed. Thermal – mechanical and metallurgical combined\ud simulations are performed within two tests using geometrically similar models and assessment is made in terms of mechanical and material properties. It was found that small scale simulation could not reproduce most of the\ud important forming parameters of the original process, although it could help to bring about significant savings in\ud computation time.

It is widely recognized that subgrain size has significant influence on the strength and ductility of metals. Modelling of subgrain size evolution is essential for the detailed understanding and control of mechanical properties. In the present paper, the evolutions of subgrain size during hot extrusion of various aluminum alloys are first predicted. A nearly constant distribution of subgrain size is pursued by iso‐subgrain extrusion processes. Substructural strengthening coupled with microstructural evolution is also studied in addition to the normal thermal‐mechanical coupled analysis.

In this paper, both direct and indirect extrusions are simulated using a viscoplastic constitutive model. The simulated velocity fields for both direct and indirect extrusions are discussed and com...

In this work the use of the carbon anode dust (CAD), which is solid residue from aluminium production, as a low-cost adsorbent for removal of Cr (VI) ions from aqueous solution was investigated. The influence of pH value on adsorption capacity of carbon anode dust is examined. The adsorption capacity was found to be pH dependent and increased along with an increase in pH value. The equilibrium data for the adsorption of Cr (VI) ions from aqueous solutions on carbon anode dust were tested using the Freundlich and Langmuir isotherms. Langmuir isotherm was found to be more suitable for description of Cr (VI) adsorption.

End milling is commonly used machining process for the manufacturing of dies and molds, as well as numerous very high precision machine components. Flank wear develops due to abrasion of the cutting tool edge against the machined workpiece surface and is measured by the average width of wear land on the primary clearance face. This study presents the prediction of flank wear in end milling process. Machining parameters (cutting speed, vc, feed per tooth, ft, radial depth of cut, ae) and machining time, t, have been used as input variables. Since the flank wear has an influence on surface quality, the surface roughness has also been observed in this study. Regression analysis and radial basis function neural networks have been applied to data experimentally determined by means of the design of experiment and the effective mathematical models have been developed. The results obtained by the models have been compared. Both models have the relative prediction error below 7.66 %. The best prediction of flank wear and surface roughness shows radial basis function neural network model with the average relative prediction error of 4.48 % and 4.47 %, respectively.

In this paper a comparison of some very interesting experimentally obtained data regarding mechanical properties , creep behavior and fracture toughness of two structural steels are presented. Under consideration are high strength low alloy S355Jo steel and 50CrMo4 steel.Mechanical properties as well as creep behavior were determined by uniaxial tests......