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Purpose: This paper aims to provide a flexible solution to include additive manufacturing into a process chain complying with Industry 4.0 pillars, overcoming major drawbacks in terms of reliability and experimental effort. Design/methodology/approach: The study is based on the combination of real experimental activities and simulated ones. Findings: The main findings of this work consist into validation of the proposed process chain, which proves to be effective in terms of process flexibility (additive manufacturing, burnishing and process simulation acting synergistically), cost and time reduction and final output quality, encouraging customer involvement towards customization. Originality/value: This paper contributes to current research on the application of burnishing process, an easy to implement and environmentally friendly post-processing method to improve the performance of AM products, by providing a unique perspective integrating a reliable simulation model. Other researchers can employ these outcomes towards manufacturing of the future. A reduced version of this work has been previously published in Procedia Computer Science (Sanguedolce, Rotella, Saffioti & Filice, 2021)

Aerosol Jet® Printing (AJ®P) is a relatively novel additive manufacturing technique, of the type direct writing, principally applied for printed electronics. Particularly, AJ®P has the ability to print various functional inks (conductive, dielectrics, biological solutions) at micro-scale resolution and on free-from substrates. This work investigates AJ®P to fabricate conductive patterns on stereolithography (SLA) samples towards the development of an innovative bioelectrical device for in-vitro dual bioreactor sensing. Silver nanoparticle (AgNPs) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) inks were both tested. Preliminary results show a low metal-polymer AgNPs-SLA interaction, revealing the presence of pores and cracks along with the printed pattern after thermal sintering, with no electrical resistance (R) detected. In contrast, the PEDOT:PSS ink reveals a good covering of the SLA samples, with R decreasing with the number of printed layers (from ~700 KΩ to ~60 Ω for 15 and 40 layers, respectively, on lines 1 cm long). However, using the PEDOT:PSS ink, the total printing time was ~45 minutes, hence not ideal for an industry-oriented vision. Therefore, a study on the optimization of the AgNPs-SLA sample interaction was carried out. SLA samples were coated with Parylene-C (ParC), and further treated with a low pressure plasma. The final results show excellent conductivity (R~2.40 Ω), with a printing time of ~5.5 minutes (7 layers), demonstrating the possibility to obtain a functional circuit. Eventually, the circuit was encapsulated with polydimethylsiloxane (PDMS) in order to avoid a release of Ag+ ions, potentially toxic in the medium culture. ispartof: pages:174-179 ispartof: Procedia CIRP vol:110 pages:174-179 ispartof: V Cirp Biomanufacturing location:Calabria, Italy date:22 Jun - 24 Jun 2022 status: Published online

5. CIRP Conference on BioManufacturing, CirpBioM 2022, Maierato, Italy, 22 Jun 2022 - 24 Jun 2022; Procedia CIRP 110, 32-35 (2022). doi:10.1016/j.procir.2022.06.008 special issue: "V CIRP Conference on BioManufacturing / edited by Elisabetta Ceretti, Luigino Filice", Published by Elsevier, Amsterdam [u.a.]

ispartof: pages:99-104 ispartof: V CIRP CONFERENCE ON BIOMANUFACTURING vol:110 pages:99-104 ispartof: 5th CIRP Conference on BioManufacturing (BioM) location:ITALY, Calabria date:22 Jun - 24 Jun 2022 status: published

The paper presents a deep analysis of surface modifications induced by roller burnishing process of Ti6Al4V titanium alloy. The extensive experimental campaign has been performed based on a Design of Experiments at varying lubrication/cooling strategies (dry, cryogenic and MQL), roller radius, burnishing speed and burnishing depth. The resulting surface integrity has been analyzed in terms of surface roughness, micro hard-ness, microstructural changes and tribological performance. In particular, the wear rate of the burnished sample has been evaluated as a quality indicator of the process. The overall results show the influence of burnishing process parameters on surface quality and wear resistance of Ti6Al4V highlighting the capability of the process to significantly improve the above performance especially when cryogenic cooling is applied. Finally, the extensive experimental activity allowed to find a combination of processing parameters and lubrication conditions able to significantly improve the surface quality of the final component.

Burnishing is considered a super finishing process able to drastically increase surface quality in terms of hardness and roughness of the manufactured parts. Consequently, it is considered appealing for the performance enhancement of products where the surface quality plays a crucial role. However, when burnishing grade 5 titanium alloy, a quantitative relationship between process parameters and surface integrity is still missing. This work provides a deep analysis of the burnishing parameters and their influence on the surface integrity of Ti-6Al-4V. In particular, starting from a large experimental campaign, statistical analysis of the results is performed and models able to describe the surface integrity response based on different burnishing parameters are presented. The overall results allow us to clearly define the relationship within the input and output variables identifying, by the proposed models, different operational windows for surface integrity improvement.

Nickel-based super alloys are widely employed in critical applications, mainly in aerospace, marine, and chemical industries, concerning the production of high-performance artifacts. These alloys are considered as hard-to-cut materials, because of their modest machinability, so it is very difficult to implement in an industrial context high-speed 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 of Waspaloy (45 HRC). Experiments were performed in different lubri-cooling conditions (dry, wet, and cryogenic) and at varying cutting conditions (cutting speed and feed rate).

The phenomenological models for material flow stress and fracture, typically used in the Finite Element simulations of machining Nickel-based alloys, are often deemed to represent only certain metallurgical material states. In contrast, these models are not suitable to describe the constitutive behavior of the workpiece for different metallurgical states (i.e., annealed, aged, etc.) and, consequently, different hardness values. Since the description of the material behavior requires correct formulation of the constitutive law, new flow stress models which include also the hardness effect should be developed and used, for computer simulation of machining Nickel-based alloys. This paper describes the development of a hardness-based flow stress and fracture models for machining Inconel 718 alloy which can be applied for a wide range of work material hardness. These models have been implemented in a non-isothermal viscoplastic numerical model to simulate the influence of work material hardness on the chip formation process. The predicted results are being validated with experimental results properly carried out for this research. They are found to satisfactory predict the cutting forces, the temperature and the chip morphology from continuous to segmented chip as the hardness values change. Copyright © 2013 Elsevier B.V.

In this paper the extrusion process of a cross-shaped profile was investigated. In particular, the study was focused on the distortion of extruding profiles when the workpiece and die axis are not aligned. The process was simulated using the finite element method (FEM) and the natural element method (NEM), both implemented in an updated-Lagrangian formulation, in order to avoid the burden associated with the description of free surfaces in ALE or Eulerian formulations. Furthermore, an experimental equipment was developed in order to obtain reliable data in terms of deformed entity, required process load and calculated pressure. At the end, a comparison between the numerical predictions and the experimentally measured data was carried out. The main results are presented in the paper.

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.

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.

In the modern manufacturing scenario and, in particular, in sheet metal forming, the requirement of customised production is still growing. The introduction of incremental forming enables the production of customised components in small lots. In particular, single point incremental forming is characterised by the simplest equipment; any die, in fact, is avoided reducing the necessary tooling to a simple frame, able to clamp the sheet, and a hemispherical punch that imposes the required deformation. This tooling simplicity and the associated process mechanics, in turn, determine a sometimes relevant lack of accuracy. The paper is focused on the investigation of the influence of the process parameters on accuracy through a reliable statistical analysis. The obtained models permit to implement some effective actions to improve the accuracy taking into account a simple case study.

Finite Element simulation of orthogonal cutting is nowadays assuming a large relevance; in fact a very large number of papers may be found out in technical literature on this topic. In recent years, numerical simulation was performed to investigate various phenomena such as chip segmentation, force prediction and tool wear. On the other hand, some drawbacks have to be highlighted; due to the geometrical and computational complexity of the updated-Lagrangian formulation mostly used in FE codes, a cutting time of only a few milliseconds can be effectively simulated. Therefore, steady-state thermal conditions are not reached and the simulation of the thermal phenomenon may be ineffective. In order to overcome such problem two different approaches are proposed in this paper. The former is based on a pure thermal simulation once the thermal flow on the tool is properly calculated. The latter, on the contrary, is based on an artificial modification of the heat transfer coefficient at the interface between the chip and the tool in the thermo-mechanical simulation. Both of the proposed methodologies are discussed in the paper, highlighting the advantages and the drawbacks of each of them.

Wear prediction in machining has been recently studied by FEM although the use of numerical methods for such applications is still a very challenging research issue. In fact, wear phenomenon involves many aspects related to process mechanics which require a very accurate modelling. In other words, only a very punctual code set-up can help the researchers in order to obtain consistent results in FE analysis. The high relative velocity between chip and tool requires effective material models as well as friction modelling at the interface. Moreover the prediction of temperature distribution is another critical task; in the paper some different procedures are discussed. Subsequently a wear model is presented and calibrated in order to obtain a suitable tool to be implemented in a FE code with the aim to describe the wear evolution during the simulation process. A proper designed experimental campaign supplied some reference data for model set-up and verify in the practical application. All these aspects are carefully discussed in the paper.

This paper presents a new procedure to evaluate the global heat transfer coefficient in orthogonal cutting. The knowledge of the actual heat transfer conditions is a fundamental issue as far as the life, tool wear and tool substitution interval are regarded. More in detail, an Arbitrary Lagrangian-Eulerian approach was utilised to model orthogonal cutting process and the numerical simulations were validated by making experimental tests for identifying cutting forces and internal tool temperatures. A mild steel was cut utilising both an uncoated (WC) and a coated (TiN) tool. On the basis of both experimental and simulative data, a consistent model of the global heat transfer coefficient as function of the local pressure and temperature at the tool-workpiece interface was developed.

Among the innovative sheet metal forming processes, Single Point Incremental Forming (SPIF) represents the simplest and the cheapest one. Despite its relevant advantages, up to now no specific CAE tools for SPIF were developed and the tool trajectory is generally defined utilizing CAD/CAM software developed for machining applications. In the paper an innovative monitoring and control approach, aimed to define and in-process update the most relevant process parameters during an industrial SPIF operation, is proposed. The strategy utilizes as monitoring variable the punch force trend: a set of preliminary tests demonstrated, in fact, its suitability as “spy variable” of the process mechanics and, in particular, of excessive sheet thinning and material failure approaching.

New research trends for Friction Stir Welding include the use of highly resistant materials as steels and titanium alloys. In the paper a continuum based FEM model for Friction Stir Welding of lap joint made out of thin stainless steel sheets is proposed, that is 3D Lagrangian implicit, coupled, rigid-viscoplastic. The model, whose potential has been analyzed though temperature distribution comparisons, is able to predict temperature, strain and strain rate distributions, with varying process variables. In this way the FEM model can be applied for effective process and tool design.

This paper reports the results of an experimental study of the tool wear and cutting forces in turning of Inconel 718 with coated carbide inserts. Inconel 718 is a difficult-to-cut nickel-based super-alloy commonly used in aerospace industry. The effects of cutting speed, feed rate and cutting tool geometry on tool wear have been widely analyzed in literature. Turning operations on complex components such as aircraft engines casings require the insert replacement at the end of each geometric feature manufacturing, independently from the actual tool wear level. For this reason, it is important to preserve tool integrity mainly in the most critical phase of operation (i.e., when the tool engages the workpiece). In fact, if the tool is damaged in this stage the quality of the whole operation is compromised. The attention has been focused on engage cutting conditions because the phenomenon that appears in this critical step plays a wide influence on tool integrity and, consequently, on the quality of the operation. For this purpose a nickel-based super alloy ring-workpiece, (Inconel 718), has been machined in lubricated cutting conditions by using a CNC lathe with carbide coated tools. Two variables have been investigated in this study: the Depth Of Cut (DOC) and the approaching Engage angle (En). In the studied working conditions Speed (S), Feed-rate (F) and removed volume (Vrim) were kept constant. Both tool wear and cutting forces evolution during cutting have been analyzed.

The use of numerical simulations for investigating machining processes is remarkably increasing because of the simulation cost is lower than the experiments and the possibility to analyze local variables such as pressures, strains, and temperatures is allowable. Process simulation is very hard from a computational point of view, since it frequently requires remeshing phases and very small time steps. As a consequence, the simulated cutting time is usually of the order of few milliseconds and no steady cutting conditions are generally achieved, at least as far as thermal conditions are concerned. Therefore, nowadays numerical prediction of cutting temperatures cannot be considered fully reliable. In the paper this issue was taken into account: a mixed Lagrangian-Eulerian numerical approach was utilized and the global heat transfer (film) coefficient at the tool-chip interface was derived through an inverse approach. Finally, the dependence of the film coefficient on pressure and temperature on the rake face was investigated.

Numerical simulation of cutting process is today moving towards two different directions. The former concerns the development of high performance codes able to approach the 3D phenomena, the latter is already focused on the study of some fundamental aspects whose full understanding may be strategic for the knowledge enhancing in this very complex field. In the paper this second way was pursued and a wide analysis on the numerical robustness of the 2D orthogonal cutting process is presented. In particular, the role played by the friction modeling is discussed taking into account a wide integrated numerical and experimental campaign.

Despite the development of high performance finite element-based codes, the simulation of machining still represents a very hard task due to the geometric complexity of the real chip-tool systems and the high cutting speed that requires very long simulation times. For these reasons, many aspects related to machining are not very clear and so easy to simulate. In this paper a rigorous investigation on the role played by the implemented friction model within a 2D simulation of orthogonal cutting was carried out, taking into account different models proposed by the researchers in the last years. The main simulation results were compared with experimental measurements in order to verify if it is possible to identify the best model. Once the comparison with mechanical variables was completed, a subsequent study on temperature predictions utilizing the above friction models was executed as well. The results of this integrated numerical and experimental work are carefully reported in the paper.

Formability is a relevant issue in Single Point Incremental Forming (SPIF) process since it is one of the main point of strength together to the possibility to avoid any dedicated die. Several researches agree that, depending on working material and process parameters, in SPIF operations there is a threshold slope of the wall that cannot be overcame without material breaking. If deep Incremental Forming is taken into account, despite the previous statement it is possible to demonstrate that, when the threshold angle is imposed, there is a relation between the actual workpiece depth and the material breaking approaching. In this paper, the latter relationship was investigated and formally derived by using a proper statistical regression.

Incremental forming processes show a number of advantages compared to the traditional processes but, at the same time, some drawbacks are clearly known. Current problems, include the slowness of the process, low accuracy and a lack of knowledge in the field of material formability. This paper is focused on the latter issue: an industrially oriented methodology for detecting the approach of failure in incremental forming is proposed. The approach is based on the analysis of the trend of the forming force in order to assess whether the process can be run safely. If not, a proper strategy, to avoid material failure, is proposed and experimentally validated.

New trends in sheet metal forming are rapidly developing and several new forming processes have been proposed to accomplish the goals of flexibility and cost reduction. Among them single point incremental forming operations, in which the final shape of the component is obtained by the relative movement of a simple and small punch with respect to the blank, appear quite promising. In the paper, material formability issues in incremental forming were studied. Some relevant correlations among material formability and other mechanical properties of the material were analysed. The FLD 0 value, i.e. the major strain at fracture in plane strain conditions, was determined for different materials and the influence of the main material parameters on formability was accurately investigated through a statistical analysis.

Publisher Summary One of the strategic topics in manufacturing engineering is represented by the reduction of components weight. This aim is pursued by utilizing accurate and effective design tools and using lightweight metals such as aluminum, magnesium, and titanium alloys. Unfortunately, such materials often show a poor ductility, and thus enhancing formability is nowadays one of the most relevant research focus, as well as the development of effective and reliable predictive models of defects insurgence during forming processes. In this scenario, forming by means of superimposed hydrostatic pressure represents a promising alternative manufacturing technique. The chapter discusses the simple upsetting process of AA6082-T6 cylindrical specimens under sticking conditions at the punch-specimen interface. The process is simulated and experimentally carried out both with and without a superimposed hydrostatic pressure. The experimental equipment is designed with the aim to achieve an assigned fluid pressure value inside the chamber during the upsetting process.

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.

The applications of numerical simulation to machining processes have been more and more growing in the last years: today a quite effective predictive capability has been reached, at least as far as global cutting variables (for instance cutting forces) are concerned. On the other hand, the capability to predict local cutting variables (i.e. pressure on the tool, temperature distribution, residual stresses in the machined surface) has to be heavily improved and verified. At the same time, effective experimental procedures for validating numerical results have to be developed. In this work two different approaches were implemented for temperature measuring: a thermocouple based approach and a thermographic analysis were developed. As well the effectiveness of a couple of typologies of numerical simulation was investigated; the former was a 2D fully thermo-mechanical analysis, the latter a 3D pure thermal one. The results of the study permit to assess that a thermo-mechanical simulation does not permit a satisfactory temperature prediction, while an integrated approach including analytical models and pure thermal FE simulations promises relevant advantages.