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In this paper an experimental investigation was conducted to determine the effects of the tool cutting-edge geometry, workpiece hardness, cutting speed, and microstructural changes (white and dark layers) on the residual stresses in dry orthogonal hard machining of AISI 52100 steel. X-ray diffraction technique was used to obtain in-depth residual stresses profiles in both axial and circumferential directions. The results show that tool geometry, workpiece hardness and cutting parameters significantly affect the surface residual stress, maximum compressive residual stress below the machined surface and its location. Moreover, microstructural analysis shows that thermally-induced phase transformations have a significant impact on the magnitude and location of this maximum compressive residual stress peak. [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]

Aluminum foams are new materials mainly produced by expansion in proper chambers. A relevant quantity of voids is generated in the metallic matrix during manufacturing, resulting in a low material density. However, these voids are not homogeneously distributed in the volume and strongly affect the loading behavior and damage. Simple models based on the apparent density were published in literature. Recently, more accurate formulations based on a statistical distribution of the voids along the thickness were presented. This strategy surely represents a great improvement in respect to the previous modeling but does not help the researchers when large deformations occur. Moreover, the introduction of porous materials shows a high limitation since actual voids distribution cannot be well implemented. In this paper, a new modeling is presented in order to obtain better predictions when material deformation in secondary operations is investigated. Material is modeled by the introduction of a number of voids according to the observation of foamed billets. In this way, a more reliable prediction is obtained as highlighted comparing load curves and material collapse in some critical zones. [ABSTRACT FROM AUTHOR]

Abstract: In machining of hard parts, surface integrity is one of the most specified customer requirements. Often, the major indications of surface integrity are surface roughness and residual stresses. However, the material microstructure also changes in machined-hardened steels, and it must be taken into account for improving product performance. In this paper, a hardness-based flow stress and an empirical model for describing the white and dark layers formation were developed and implemented in a FE code. The proposed model was validated by comparing the predicted results with the experimental evidences. [Copyright &y& Elsevier]

Abstract: In this study an analysis of the forging process of a simple-shaped metallic foam billet was carried out using both experimental trials and mathematical models in order to obtain a 3D geometry of the complex form. In particular, the deforming behaviour of a metallic foam and the development of density gradients were investigated through a series of experimental forging tests in order to produce a selected portion of a hip prosthesis. This type of replacement for human bone was chosen as object of study due to its elevated commercial demand and its particularly complex 3D shape. A commercial finite element code (Deform 3D®), with an accurate rheology of the material, was utilized to model the foam behaviour during the forging process. The code for the rheology of the material is considered using a model valid for porous materials which also includes a measure of local density. The usefulness of the model used was verified by the comparison of the predicted results (the force necessary for the completion of the forging process and the final shape obtained) and the experimental evidence. [Copyright &y& Elsevier]

Abstract: Industrial application of magnesium alloy AZ31 is dramatically increasing due to the very competitive mechanical strength vs. weight ratio. On the other hand, AZ31 is very difficult to be formed at room temperature. In this study incremental forming of the above material is taken into account, with particular reference to formability limits. The role of the main process parameters on material formability was investigated through a wide experimental campaign and a rigorous statistical analysis. [Copyright &y& Elsevier]

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]

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]