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Nickel-based super alloys are widely employed in critical applications, mainly in aerospace, marine, and chemical industries, concerning the production of highperformance artifacts. These alloys are considered as hardto- cut materials, because of their modest machinability, so it is very difficult to implement in an industrial context highspeed machining processes that can lead to higher quality products, with improved mechanical characteristics and higher dimensional accuracy, and increase productivity. Among these alloys stands out Waspaloy, thanks to its very high mechanical properties, such as stiffness and strength to weight ratio. In order to implement effective machining processes, it is important to analyze the behavior of the material during machining in terms of variables of industrial interest (forces, tool wear, etc.). The aim of this paper is to disclose the results of an experimental investigation aimed to determine the effects of different cutting parameters on cutting forces, chip morphology, tool wear, and temperature at tool-chip interface, during orthogonal machining ofWaspaloy (45 HRC). Experiments were performed in different lubri-cooling conditions (dry, wet, and cryogenic) and at varying cutting conditions (cutting speed and feed rate). [ABSTRACT FROM AUTHOR]

The finite element method is the reference technique in the simulation of metal forming and provides excellent results with both Eulerian and Lagrangian implementations. The latter approach is more natural and direct but the large deformations involved in such processes require remeshing-rezoning algorithms that increase the computational times and reduce the quality of the results. Meshfree methods can better handle large deformations and have shown encouraging results. However, viscoplastic flows are nearly incompressible, which poses a challenge to meshfree methods. In this paper we propose a simple model of viscoplasticity, where both the pressure and velocity fields are discretized with maximum entropy approximants. The inf-sup condition is circumvented with a numerically consistent stabilized formulation that involves the gradient of the pressure. The performance of the method is studied in some benchmark problems including metal forming and orthogonal cutting. [ABSTRACT FROM AUTHOR]

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Residual stresses are normally generated in any cutting operation. However, while compressive residual stresses are sometimes suitable as they may even enhance and improve the piece life, tensile residual stresses can be very detrimental representing a negative feature for fatigue life, corrosion, strength and other functional aspects. Thus, a proper set-up of the process parameters in machining operations has a dramatic importance. Currently, optimization methodologies do not seem to be very effective for industrial needs, for which the optimal setup being a desired residual stresses profile becomes a relevant issue. On the basis of the previous considerations, this work proposes a data mining technique, which has proven to be reliable to identify the analytical relationship between residual stresses and the proper process parameters. In order to ensure the use of the developed technique in practice, it has been integrated in the user-friendly software, Predators. [ABSTRACT FROM AUTHOR]

Although the competitiveness of the Incremental Sheet Forming process is deeply assessed, some specific aspects penalise its industrial application. In particular, the idea to take advantage of the bigger formability appears of a great interest but the non homogeneous thickness distribution reduces the industrial applicability. It is well known that the process allows to work in the critical “necking-to-tearing” space which results in a strong thinning before failure. However, a significant improvement in the thickness distribution can be obtained by using a modified tool trajectory. In fact, previous experimental investigations carried out by the authors showed that it is possible to influence the thinning phenomenon by applying a proper tool trajectory. Rather than the conventional tool path, which describes the tangent profile to the desired shape, the imposed wall angle can be modified in order to compensate the localised thinning. Unfortunately, this approach increases the process design complexity and suggests to consider the tool trajectory as a decision variable to be optimised in the process design. For this reason, an optimisation model is required in order to simplify the choice among all the possible alternatives. In this paper, a promising analytical model is highlighted and a user friendly procedure is set up to simplify the approach. Satisfactory experimental results which validate the proposed technique are also presented. [ABSTRACT FROM AUTHOR]

Residual stresses play an important role in the service quality of a component. Therefore, it is essential to predict and control residual stresses on the machined surface and subsurface. The paper is focused on the numerical prediction of residual stresses in the orthogonal cutting process of a mild steel. An advanced approach to model heat transfer phenomena at the tool-chip interface was included in the numerical simulation. The FEM results were compared with some experimental data obtained turning AISI 1045 steel using uncoated WC tool. [ABSTRACT FROM AUTHOR]

Titanium and its alloys have rapidly become a strategic material in aerospace industry due, for example, to high strength vs. weight ratio, excellent mechanical proprieties, corrosion resistance and galvanic compatibility with fiber reinforced composite materials. A big problem that has to be considered is, however, the higher cost of components as compared to other alloys. In fact, the market price of the base metal has to be added to manufacturing ones. To reduce production costs, Titanium net shape technologies have been continuously developed. Superplastic forming (SPF) technology can be considered in this frame. Through the SPF some alloys can be slowly formed well beyond their normal limitations at elevated temperatures, allowing very deep forming sequences. In this study, the SPF process to produce aircraft parts was investigated. The well-known Titanium alloy Ti6Al4V was chosen as workpiece material. The investigation was carried out by numerical analysis to check the predicting capability of these simulation tools. In detail, FE analyses were developed using two different codes, namely Marc and Ls-Dyna. The aim was the optimization of pressure trend to obtain the desired shape with a reasonable accuracy and without material breaking. Finally, some considerations on the experimental manufacturing of the components are reported. [ABSTRACT FROM AUTHOR]

In this paper, the Natural Element Method (NEM) together with the alpha shapes and some extra numerical procedures are used in the simulation of hollow profiles, emphasizing on the simulation of the welding lines. Numerical results are compared with experimental ones, checking the accuracy of the method. [ABSTRACT FROM AUTHOR]

Incremental Forming is a flexible and innovative sheet metal forming process able to form complex shapes without the need of any expensive die. In this way, expensive fixtures are avoided obtaining a cheaper production, more advantageous for small production batches. Anyway, more than the process slowness, the geometrical accuracy represents the most important drawback today. In particular, two kinds of geometrical errors can be observed on a sheet component incrementally formed: the presence of elastic springback that modifies the imposed final depth, that “moves away” from the designed one, and the undesired bending effect of the sheet, which undergoes to the punch action. Several studies which tend to optimise the equipment and/or the tool path, in order to reduce the profile diverting, were executed. In this paper, an experimental investigation was carried out in order to test and introduce a new approach able to solve the above problem. More in detail, the test were executed applying an additional back- drawing phase, after the conventional negative deformation. Different testing conditions were evaluated during the experimental campaign and critically compared in the analysis. [ABSTRACT FROM AUTHOR]

A number of scientists are currently involved in Incremental Forming investigation, in order to better understand the process and to extend its applicability to industrial practice. If flexibility is probably the main advantage deriving from Incremental Forming use, today a new point of view is given by the possibility to use the process instead of a sequence of operations, allowing also a better sustainability. Formability enhancing is one of the keyfactors of this success and for this reason it is widely investigated, also on lightweight materials, for which the use of a preliminary heating is required. In the paper the formability of Magnesium AZ31 is investigated in warm Incremental Forming, focusing the attention on the tools currently utilised for describing material formability. It is shown that Forming Limit Curves fail in this goal while a study of fracture, exploiting results of conventional tensile tests, supplies more appreciable results. [ABSTRACT FROM AUTHOR]

For three dimensional tube hydroforming operations (i.e. T or Y shaped tubes) the calibration of both material feeding history and internal pressure path during the process is crucial and many approaches to such optimization were presented; the authors developed some procedures to optimize pressure paths and punch velocity histories with the application of an integrated method FEM - Gradient based optimization tools. In this paper, an experimental validation campaign of the utilized optimization strategies is presented with the aim to assess the effectiveness of the developed procedures. An optimization procedure (gradient based techniques) was applied on the process parameters leading to the determination of an optimal pressure path. Finally, a testing machine was set up to carry out hydroforming operations on T-shaped tubes. The developed equipment allows a computer assisted control of both the internal fluid pressure paths and the punches actions (material feeding paths). The experimental evidences validated the results obtained by the optimization strategies utilized to design the process parameters. [ABSTRACT FROM AUTHOR]

In this paper the prediction of tool wear on carbide uncoated tools was taken into account. In particular, two different tool wear models based on the diffusion mechanism and on the abrasion mechanism were considered. The calibration of the utilized models was done using the results obtained by experimental analysis performed on an orthogonally machined AISI 1020 tube. Once the calibration was executed, numerical simulations, for both the utilized tool wear models, were simultaneously performed with the aim to test the capability of the proposed numerical procedure. The comparison between the two tool wear mechanisms for predicting the flank tool wear is discussed in the paper. [ABSTRACT FROM AUTHOR]

New research trends on Incremental Forming processes are strongly based on the development of more efficient control tools or design procedures, able to reduce the time associated to the preliminary setup phase. The latter, in fact, still penalises the industrial application of the above process. If adequate knowledge has been reached nowadays, thanks to the activity of several researchers all over the World, the process feasibility of complex or irregular geometries is still related to the execution of some preliminary “trial & errors” experimental tests. It seems quite obvious that more efforts have to be spent to increase the process control capability by means of innovative and generalised solutions, such as artificial intelligence techniques, neural networks, numerical simulations and so on. With this perspective, the present paper aims to improve the IF control capability for complex shapes by means of an optimised FE model. [ABSTRACT FROM AUTHOR]

The accuracy of the results obtained from FEM simulation of machining operations depends on the accuracy of input data. Among these, the flow stress data of the workpiece are extremely important together with the friction along the tool-chip interface. In this study, an identification procedure for the determination of material parameters that are used for the FEM simulation of machining processes is proposed. The procedure is based on the coupling of a numerical identification procedure and Arbitrarian Lagrangian Eulerian (ALE) Finite Element simulations of turning operations. An experimental campaign was developed in order to calibrate the model and to validate the procedure. The basic idea is to utilize only machining tests to properly define the material behaviour of the workpiece material, taking also into account the thermal phenomena involved in the process. The preliminary results of this analysis are discussed in the paper. [ABSTRACT FROM AUTHOR]

This paper deals with the simulation of cutting processes. In particular, 3D FE simulations were carried out in order to estimate tool wear development during turning operations. An analytical model taking into account diffusive wear mechanism has been implemented in a proper software subroutine for the tool wear evaluation. Preliminarily conducted experimental tests allowed the analytical expression coefficients evaluation. The adopted wear model gave the possibility of correctly defining the tool wear during both the (initial) transient phase and the steady-state of the analyzed turning operation. A comparison between experimental and simulative results showed a general good agreement. The final goal of the research is to identify a FE based strategy to be reliably used to forecast tool geometry and cutting parameters influences on tool wear. [ABSTRACT FROM AUTHOR]

Nowadays, magnesium alloys materials are more and more utilised in transportation industry in order to reduce the vehicles mass, and thus to minimize air pollution and fuel consumption. Since they present a quite low formability at room temperature, promising applications are developing in the area of sheet metal working in warm temperature conditions. The paper presents a complete characterisation of the magnesium alloy AZ31B formability at elevated temperature. Both uniaxial tensile and hemispherical punch tests are utilised to determine the material formability sensitivity to temperature, strain, rate, and rolling directions. [ABSTRACT FROM AUTHOR]

In machining of parts, surface quality is one of the most impellent customer requirements. The most relevant issues are surface roughness and residual stresses. In particular, the latter are affected by tool geometry, material characteristics and process conditions. Residual stresses can have a significant effect on the service quality and the component life. Residual stresses can be determined by both empirical and numerical investigations for selected configurations, however, these are expensive procedures. This paper presents a hybrid model based on the artificial neural networks (ANNs) and finite element method (FEM) that can be used to predict the residual stress profile. A three layer neural network has been trained and tested on the data obtained by numerical investigations of hard machining of 52100 bearing steel. The numerical results are consistent with experimental data. [ABSTRACT FROM AUTHOR]