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This research is aimed at testing the ability of high-end 3D printers to reproduce complex structures having some acoustic performances in terms of sound absorption and sound transmission loss. Specifically, some experiments were made on four different types of geometries to compare their acoustic behaviour. The sound absorption and sound insulation of the samples have been evaluated by means of a four-microphone impedance tube. The adopted technique allows to retrieve the transfer matrix of each specimen and then, through a composition of the matrices, to virtually determine the acoustic performances of any arrangement of the different samples. The experiments revealed promising results in terms of quality, finishing and precision of the jetting process, highlighting benefits and critical issues related to the acoustic performances.

Additive manufacturing is an advanced technology able to produce parts with different grades of complexity, including its shape, microstructure, functionality and material. Regarding material complexity nowadays, it is possible to produce polymer parts with customized reinforced fibre filling such as carbon, Kevlar or glass. These new techno polymers could guarantee good mechanical properties with low cost production, and so different industrial sectors started to implement them in parts design. However, their mechanical behaviour is still under investigation, and many about their mechanical behaviour are still unknown. In this article the authors present the experimental characterization of polymer filled with Kevlar to pin bearing test. Samples have been designed as a function of filling and geometry parameters. Results have been analyzed with statistical methods. Finding highlight similar and different behaviour regarding samples produced with conventional process.

Antiproton annihilations on matter nuclei are usually detected by tracking the charged pions emitted in the process. A detector made of plastic scintillating bars have been built and used in the ASACUSA experiment for the last 10 years. Ageing, movements and transports caused stress on the internal mechanical structure and impacted mostly on the optical readout system which was eventually upgraded: the so far used multi-anode photo-multiplier tubes (PMTs) have been replaced by silicon photomultipliers (SiPM) and the front-end electronics had to be adapted to cope with the new signal formation. This work describes the design and operations of the upgrade, as well as the validation tests with cosmic rays.

Purpose The purpose of present paper is to enlarge the knowledge about the performance of gypsum powder to realize complex molds or cores for aluminum casting. Design/methodology/approach The research was divided into two activities: simple; and complex-part production capability. In the simple-part step, the performance of gypsum powder and the minimum mold thickness that would withstand the casting process. In the complex-part step, the authors first investigated the powder removability as a function of geometry complexity and then binder jetting performance was evaluated for the case of lattice-structure fabrication. Findings All the geometries tested withstand the casting process demonstrating the benefits in terms of complexity part design; however, the process suffers of all the typical defect of casting as misrun, porosity and cold shut. Originality/value The results found in this research improve the benefits related to additive manufacturing application in industrial environment and in particular to the binder jetting technology and the rapid casting approach.

In the present study, laser surface texturing was tested with the aim of improving the tribological properties of a diamond-like carbon (DLC) coating. Two experimental campaigns were designed to realize different micro-grids, and to study the effect of marking speed, laser power, and loop cycle. The grid profiles obtained were analyzed using a digital microscope and a laser probe system to measure the track cross section. At the end of the experiments, the authors identified a good-quality track obtained by imposing a marking speed of 300 mm/s, a power of 0.5 W, and one loop cycle. For the identified condition, the presence of defects (such as cracks) on both the coated surface and at the substrate/coating interface was analyzed. Furthermore, the coating nanohardness, adhesion to the substrate, and wear behavior in dry condition were investigated. The results underline how laser texturing can improve the DLC wear behavior (wear tracks lower than 30%) without considerably affecting the other tested coating properties.

The high-velocity oxy-fuel (HVOF) technique has been extensively used for the deposition of hard metal coatings. The main advantage of HVOF, compared to other thermal spray techniques, is its ability to accelerate the melted powder particles of the feedstock material to a relatively high velocity, leading to good adhesion and low porosity. To further improve the surface properties, a mechanical machining process is often needed; however, a key problem is that the high hardness of the coating makes the polishing process expensive (in terms of time and tool wear). Another approach to achieving surface modification is through interaction with a thermal source, such as a laser beam. In this research, the effects of laser scanning rate, scanning strategy, and number of loop cycles were investigated on an HVOF-coated surface. Cr3C2-25(Ni20Cr) was selected as the coating and Nd:YVO4 as the laser source. The results demonstrate the significance of the starting coating morphology and how the laser process parameters can be tuned to generate different types of modifications, ranging from polishing to texturing.

The cooling system of thermoplastic mold plays a critical role during the production process because it not only affects part quality but also its cycle time. Traditionally, due to the limitations of conventional drilling methods, the cooling system of the thermoforming mold usually consists of simple paralleled straight channels that results in a lack of performance to cool complex shapes. Nowadays thanks to the evolution of additive manufacturing technique (AM) characterized by an increase of shape complexity it is possible to design a complex cooling system conformal to the mold geometry (conformal cooling). However conformal cooling respect to others AM design improvements, as topology optimization, is still under development and specific rules that define how to better design cooling channels still do not exist. In this paper, to enlarge the knowledge about this methodology, the authors simulated the performance of three different conformal geometries (serpentine, rectangular and tank) and compared the results with the traditional geometry in terms of cooling performance. Results highlight how serpentine geometry is able to improve process performance imposing a cooling curve characterized by a higher slope respect to the traditional shape.

In milling operations, the weight of the milling tool greatly affects the motion speed of the mandrel, especially when a complex tool path must be performed. Thus, it is essential to realize more lightweight tools, without a significant decrease in the mechanical and production performance. Traditionally, due to the limitation of the conventional manufacturing processes, the design of a new milling tool cannot be too much complex and thus cannot fully satisfy the mentioned goals. Nowadays, thanks to the topology optimization technique and the additive manufacturing (AM) technologies, such as the selective laser melting (SLM), it is possible to realize more complex part geometries to obtain more lightweight and high-performance tools. In this paper, a new design of a milling tool with a weight reduced by 30% is presented; SLM process has been selected to realize the milling tool. In order to minimize the use of support structures, required by the SLM process to correctly realize the desired part, the new geometry has been little modified. A more lightweight milling tool has been produced and every support structure has been successfully removed from the component.

With the advent of 3D printing, it is now possible to produce any part or system with an approach than makes design much deeply interlaced with production. In this scenario, CAE has gained power thanks to the possibility of thinking and then manufacture ideas that go well beyond what was possible in the past. This design approach is perfectly suitable to push forward mould conformal cooling performance. In this work, a coupling of CAD, CFD and 3D printing supported by experimental tests was applied to define a design procedure for conformal cooling channels. In particular, cooling channels for a mould were engineered via CAD, then tested via CFD and, after an initial optimization procedure, the chosen design was 3D printed in specimens suitable to be mounted on a heat exchanger (HX) experimental test rig that was especially adapted for the scope. Fluids temperature, volume flow rates and heat transfer performance were measured. A feedback loop was considered to link measurements and channels redesign. Results together with design and testing procedures are reported and commented.

In this paper Cobalt-Chromium-Molybdenum (Co-Cr-Mo) specimens produced by Selective Laser Melting (SLM) for biomedical field were studied. In particular, fatigue tests were carried out comparing as-built condition with Hot Isostatic Pressing (HIP) and a heat treatment under vacuum condition. The influence on microstructure and fatigue properties was investigated on plain specimens and with a V-notched geometry. Both vacuum heat treatment and HIP had effects on the microstructure and internal defects, which resulted in an enhancement of quasi-static and fatigue properties. Lastly, notch sensitivity and applicability of ASED failure criterion for fatigue life prediction notched specimens were evaluated.

A technique to reduce burr height in titanium micro-drilling is presented: a poly (methyl methacrylate) coating was applied before machining on the upper and lower surfaces of a titanium specimen (0.5-mm thick). After drilling, a cleaning process (acetone bath) was executed to eliminate the coating, and holes with less burr were obtained. The coating process was executed with a spin-coating machine. To test the efficacy of the technique, two different coating thicknesses (7.9 and 5.4 &mu, m) and two drill bits (0.25- and 0.5-mm diameter) were evaluated. Qualitative and quantitative analyses of the holes obtained were performed with scanning electron microscopy and three-dimensional microscopy, respectively. The results highlight the efficacy of the technique to reduce the burr height by 70% in coated titanium relative to that in an uncoated titanium sheet.

The surface of structural components is usually subjected to higher stresses, greater wear or fatigue damage, and more direct environmental exposure than the inner parts. For this reason, the interest to improve superficial properties of items is constantly increasing in different fields as automotive, electronic, biomedical, etc.Different approaches can be used to achieve this goal: case hardening by means of superficial heat treatments like carburizing or nitriding, deposition of thin or thick coatings, roughness modification, etc. Between the available technologies to modify components surface, Laser Surface Texturing (LST) has already been recognized in the last decade as a process, which improves the tribological properties of various parts.Based on these considerations the aim of the present research work was to realize a controlled laser texture on a Diamond-like Carbon (DLC) thin coating (about 3 µm thick) without damaging both the coating itself and the substrate. In particular, the effect of laser process parameters as marking speed and loop cycle were investigated in terms of texture features modifications. Both qualitative and quantitative analyses of the texture were executed by using a scanning electron microscope and a laser probe system to select the proper laser parameters. Moreover, the effect of the selected texture on the DLC nanohardness, adhesion and wear behavior was pointed out.

Ring Rolling is an advanced local incremental forming technology to fabricate directly precise seamless ring-shape parts with various dimensions and materials. In this process two different deformations occur in order to reduce the width and the height of a preform hollow ring; as results a diameter expansion is obtained. In order to guarantee a uniform deformation, the preform is forced toward the Driver Roll whose aim is to transmit the rotation to the ring. The ring rotational speed selection is fundamental because the higher is the speed the higher will be the axial symmetry of the deformation process. However, it is important to underline that the rotational speed will affect not only the final ring geometry but also the loads and energy needed to produce it. Despite this importance in industrial environment, usually, a constant value for the Driver Roll angular velocity is set so to result in a decreasing trend law for the ring rotational speed. The main risk due to this approach is not fulfilling the axial symmetric constrain (due to the diameter expansion) and to generate a high localized ring section deformation. In order to improve the knowledge about this topic in the present paper three different ring rotational speed trends (constant, linearly increasing and linearly decreasing) were investigated by FEM approach. Results were compared in terms of geometrical and dimensional analysis, loads and energies required.

Laser polishing is a process by which the surface roughness of machined parts can be reduced avoiding ablation phenomena. In this process the laser spot irradiates the sample surface with short laser pulses at a power density that causes a surface melting of the order of few nanometers. Compared to conventional polishing process (as grinding) it ensures the possibility of avoiding any surface orientation, no tool wear, no abrasive or liquids, no debris and less machining time; moreover coupled with a galvo system it results to be more suitable in case of 3D complex workpieces. Nowadays, on this process, several authors are focusing their attention on the wavelength and pulse length effect but a lack of knowledge concerning the effect of other process parameters still exists. In this work the effects of laser path and assist gas were tested by the authors. Nd:YVO4 laser source, characterized by a wavelength equal to 532 nm, was used in the experiments and Ti grade 2 samples were selected. A full experimental plan was designed to investigate the influence of process parameters in terms of average roughness reduction achieved.

Ring Rolling is a complex hot forming process used for the production of shaped rings, seamless and axis symmetrical workpieces. The main advantage of workpieces produced by ring rolling, compared to other technological processes, is given by the size and orientation of grains, especially on the worked surface which give to the final product excellent mechanical properties. In this process different rolls (Idle, Axial, Guide and Driver) are involved in generating the desired ring shape. Since each roll is characterized by a speed law that can be set independently by the speed law imposed to the other rolls, an optimization is more critical compared with other deformation processes. Usually, in industrial environment, a milling curve is introduced in order to correlate the Idle and Axial roll displacement, however it must be underlined that different milling curves lead to different loads and energy for ring realization. In this work an industrial case study was modeled by a numerical approach: different milling curves characterized by different Idle and Axial roll speed laws (linearly decreasing, constant, linearly increasing) were designed and simulated. The results were compared in order to identify the best milling curve that guarantees a good quality ring (higher diameter, lower fishtail) with lower loads and energy required for manufacturing.

Ring Rolling is a very high energy consuming hot forming process used for the production of shaped ring, seamless and axis symmetrical workpieces. Different production steps (Upsetting, Piercing, Ring Rolling) are involved in generating the desired ring shape. In particular the Upsetting and Piercing steps generate a hollow circular preform that will be subsequently enlarged by the rolling mills (Driver, Idle and Axial Rolls) during the Ring Rolling step. In order to reduce the energy and the force needed to produce the workpiece it must be observed that they are strictly affected by the speed laws imposed to the rolling mills which depend on the preform and the final ring geometry. As a consequence the setup of the Upsetting and Piercing steps became fundamental because they impose the preform geometry of the workpiece. Starting from this assumption, in the present work different preforms geometries, characterized by different initial heights, are considered to simulate the Ring Rolling process focusing the results analysis not only on the part feasibility, but also on the energy and force required which affect the equipment dimensioning. An industrial case was considered to validate the FE model. The maximum load and the energy needed for the ring production are considered as main figures for optimizing the process.

WC/Co coatings are widely applied to different types of components due to their extraordinary performance properties including high hardness and wear properties. In industrial applications High Velocity Oxy-Fuel (HVOF) technique is extensively used to deposit hard metal coatings. The main advantage of HVOF compared to other thermal spray techniques is the ability to accelerate the melted powder particles of the feedstock material at a relatively high velocity, leading to obtain good adhesion and low porosity level. However, despite the mentioned benefits, the surface finish quality of WC-Co HVOF coatings results to be poor (Ra higher than 5 µm) thus a mechanical polishing process is often needed. The main problem is that the high hardness of coating leads the polishing process expensive in terms of time and tool wear; moreover polishing becomes difficult and not always possible in case of limited accessibility of a part, micro dimensions or undercuts. Nowadays a different technique available to improve surface roughness is the laser polishing process. The polishing principle is based on focused radiation of a laser beam that melts a microscopic layer of surface material. Compared to conventional polishing process (as grinding) it ensures the possibility of avoiding tool wear, less pollution (no abrasive or liquids), no debris, less machining time and coupled with a galvo system it results to be more suitable in case of 3D complex workpieces. In this paper laser polishing process executed with a Nd:YOV4 Laser was investigated: the effect of different process parameters as initial coating morphology, laser scan speed and loop cycles were tested. Results were compared by a statistical approach in terms of average roughness along with a morphological analysis carried out by Scanning Electron Microscope (SEM) investigation coupled with EDS spectra.

Ring Rolling is an advanced local incremental forming technology to fabricate directly precise seamless ring-shape parts with various dimensions and materials. To produce a high-quality ring different speed laws should be defined: the speed laws of the Idle and Axial rolls must be set to control the ring cross section and the Driver roll angular velocity must be chosen to avoid too high localized deformation on the ring cross section. Usually, in industrial environment, a constant rotation is set for the Driver roll, but this approach does not guarantee a constant ring angular velocity because of its diameter expansion. In particular, the higher is the ring diameter the lower is its angular velocity. The main risk due to this constrain is the generation of a non-uniform ring geometry. An innovative approach is to design a Driver Roll speed law to obtain a constant ring angular velocity. In this paper a FEM approach was followed to investigate the Driver roll speed influence on the Ring Rolling process. Different Driver roll speed laws were tested starting from a model defined in an industrial plant. Results will be analyzed by a geometrical and physical point of view.

Damaged DLC coatings usually require remanufacturing of the entire coated components starting from an industrial chemical de-coating step. Alternatively, a complete or local coating repair can be considered. To pursue this approach, however, a local coating removal is needed as first operation. In this context, controlled decoating based on laser sources can be a suitable and clean alternative to achieve a pre-fixed decoating depth with high accuracy. In the present study, we investigated a laser-based decoating process executed on multilayered DLC films for advanced tribological applications (deposited via a hybrid PVD/PE-CVD technique). The results were acquired via multifocal optical digital microscopy (MF-ODM), which allowed high-resolution 3D surface reconstruction as well as digital profilometry of the lasered and unlasered surface. The study identifies the most critical process parameters which influence the effective decoating depth and the post-decoating surface roughness. In particular, the role of pulse overlap (decomposed along orthogonal directions), laser fluence, number of lasing passes and assist gas is discussed in text. A first experimental campaign was designed to identify the best conditions to obtain full decoating of the DLC + DLC:Cr layers. It was observed that decreasing the marking speed to 200 mm/s was necessary to obtain a sufficient pulse overlap and a nearly planar ablation profile. By operating with microsecond pulses and 1 J/cm2 (fairly above the ablation threshold), less than 10 passes were needed to obtain full decoating of the lasered area with an etching rate of 1.1 μm/loop. Further experiments were then executed in order to minimise the roughness of the rest surface with the best value found at around 0.2 μm. Limited oxidation but higher R a values were observed in Ar atmosphere.

The study of the mechanical behavior of the muscles constituting the pelvic floor is a challenge that demands multidisciplinary efforts. To achieve biomechanical simulation a representative geometric model of the related anatomy and hypotheses for a simplified study involving in a natural delivery process are demanded. There are many muscles included in the pelvic floor region and one of the first simplifications is the choice of the most affected muscle due to delivery. This selection was made based in MRI (Magnetic Resonance Imaging) examination data of a female volunteer with normal anatomy. The MRI images were segmented using InVesalius in order to achieve a 3D surface model. This file represents a very noisy image, with excessive detail, which can be simplified in a controlled way using BioCAD approach, developed at DT3D/CTI Brazil. Starting from it, a computational simulation can be carried out in order to represent virtually the mechanical phenomena related to the child natural delivery, providing information for the understanding of post pregnancy and even natural changes related to it. Despite the fact that the main information to obtain such model is usually available from three dimensional medical examination data, it is not simple to use these data and even more difficult to hold all the information together inside an engineering useful model. Much of the heavy work to achieve a very good representation of an anatomical structure is related to image processing applications, which are responsible for providing filters and features to separate, in the front, signal from noise on the raw image. One of the main parts of this work lies on the achievement of such 3D geometrical model, in order to have a reliable reference from where the virtual modeling and biomechanical simulations starts. Once the appropriated 3D geometrical model of the pelvic floor was available, it was started the 3D finite elements model, in order to simulate a study case related to the child natural delivery, considering the head of the child as a perfect sphere and all the material properties found in literature. The final result showed the predicted displacement of the sphere considered as the child head and the related deformation of the pelvic floor muscle, showing the main stressed regions.

In micro drilling, one of the most important aspects is the quality and homogeneity of the tool surface; because of its dimension, standard coating techniques, such as PVD and CVD, seem to be not enough performing. In the last few years, the development of novel coating techniques, such as Atomic Layer Deposition (ALD), opened new areas for thin layer deposition. In this work the application of ALD coated tools in micro drilling of Ti sheets was tested and characterized. Different analyses were realized in order to measure the homogeneity and the adhesion of coating to the substrate, the tool life, the hole roundness error and the tool wear.

In Ring Rolling process, to generate a seamless and axis symmetrical ring, two independent deformation processes simultaneously occur to reduce the starting ring cross section shape (width and height) in order to increase the diameter. How this shape changes during the whole deformation process greatly affects the produced ring quality and the loads and energy needed. The main problem is that the shape change is due to two deformation processes that occur in two different ring sections. The ring width reduction is realized in the cross section between the Idle and the Driver roll while the cross section deformed by the Axial rolls movement regulates the ring height. The main problem is that each roll speed law could be set independently from the others. In the industrial environment, a milling curve is introduced to correlate them to the ring section shape. In order to enhance the knowledge on how the Idle and Axial roll speed laws affect the Ring Rolling process, in this work an industrial case study was modeled by a numerical approach. Different Idle and Axial roll speed laws (linearly decreasing, constant, linearly increasing), were designed and simulated. The results were analyzed in order to understand how each speed law trend affects the produced ring quality (higher diameter, lower fishtail) and the process performance (lower loads and energy required for manufacturing).

Laser machining is commonly used for fabrication of medical devices with microscale features, including vascular stents, drug delivery devices, and scaffolds for tissue engineering with controlled pore size and porosity. The process can also be used to produce structured scaffolds for controlling cell growth, orientation, and location. Moreover, lasers may be used to fabricate complex channel nets in which cells are subsequently seeded or to pattern channels for microfluidic devices. Traditionally, these micro devices were fabricated using silicon substrates, but recently the use of titanium allowed to produce more robust devices at a reasonable cost. In particular, the high quality surfaces that can be obtained with laser machining reduce the liquid flow turbulence and avoid micro cavities formation, critical for bacteria proliferation. The present research reports the results of an investigation on the process capability of laser ablation to produce micro pockets fabricated on titanium sheet (0.5 mm thick). A first experimental campaign was designed for identifying a set of laser ablation cycles able to realize the micro pockets by changing the process parameters as scanning speed, laser power, q-switch frequency, loop number, and duty cycle. Moreover, a process optimization was executed in order to produce the pockets with a highly flat surface. The results were acquired by a confocal laser scanning microscope (CLSM) to obtain high-resolution images with depth selectivity and were analyzed with statistic methods for the identification of the best parameter configuration.

The development of Hot Stretch Forming (HSF) by the Cyril Bath Company was in response to airframe designers needing to use Titanium airframe components in new commercial aircraft. Many of the airframe component structures are designed to fit against the inside radius of the fuselage curvature. By combining traditional stretch forming technology with hot titanium forming techniques, the HSF guarantees a saving in material and machining time, which are two serious cost issues for today’s aircraft manufacturers. In addition, the process allows for consistent quality in a productively efficient manner, assuring the sustainable attainment of delivery and build schedules. The HSF is an innovative process on the cutting edge of the technologies, so focused research is needed in order to better understand this technology and develop new applications for this process. in this paper the HSF process is investigated: the machine and the different steps that characterized the process were described and the results of a preliminary experimental campaign was discussed focusing the attention on the metallurgical aspect. Moreover a modeling of the process was executed in order to study the stresses and strains undergone by the material among the deformation.

The aim of the present experimental study is to gain information about limits in detection of defects in composites by infraredthermography. Specimens are manufactured of either carbon/epoxy, or glass/epoxy, and withinclusions of foreign materials to simulate defects of different size and positioned at different depths. Tests are carried out by using both pulse and lockin techniques. Results are presented in terms of difference of temperature (pulse), or difference of phase angle (lockin), between damaged zones and sound material. It seems that, apart from diameter and depth, thethickness is very crucial for defects visibility.

Lock-in thermography is employed for non-destructive evaluation of several types of bonded structures, which are commonly encountered in industrial applications. Specimens were fabricated to simulate: adhesively bonded aluminium joints, which are commonly used in aeronautical and automotive fields; bonds between pipes of poly(vinyl chloride) (PVC) employed in the transport of liquids (sewage systems); and bonds between plates of Plexiglas which are widely used in the manufacturing of aquaria. Amongst bonded structures, the composite materials are very important, which are generally made of carbon, glass, or Kevlar™ aramid fibers and epoxy resin, and which find application in many industrial fields, especially the aeronautical industry, because of their higher strength and lower weight as compared to metallic materials. It is known that surface plasma treatment of a material improves its adhesion, but it is also known that this treatment will degrade over time if the material is not bonded immediately. Thu...

Ring Rolling is a complex hot forming process where different rolls are involved in the production of seamless rings characterized by extreme dimensions (i.e. external diameter higher more than 1m). Because each roll can be independently controlled from the other ones different speed laws must be set; usually, in the industrial environment, a milling curve is introduced to monitor the shape of the workpiece during the deformation in order to ensure a correct ring production. In former works the authors focused their attention on the influence of different milling curves for an industrial case and the results underlined that a ring produced with a good quality and lower loads and energy could be obtained imposing a linearly descending trend to the Idle roll speed law. However different approaches could be used in order to evaluate the mentioned speed law.In this work the authors enhanced the knowledge about the optimization of the Idle roll speed law: different Idle roll speed laws were designed and simulated and the results were compared in order to identify the best speed law that guarantees a good quality ring with lower loads and energy required for manufacturing.

Il presente documento, redatto dal gruppo roadmapping di AFIL - Associazione Fabbrica Intelligente Lombardia, indica le macro-­-tematiche di ricerca e innovazione strategiche per il Manifatturiero Avanzato lombardo ed i temi di sviluppo necessari ad affrontare le diverse macro-­-tematiche (tecnologie, metodi e materiali abilitanti). Esso è il risultato di un percorso, finalizzato a coniugare le specificità del Manifatturiero lombardo con le priorità di ricerca e innovazione indicate in sede Europea e Nazionale onde accrescere la competitività futura delle imprese lombarde nell'ottica di "smart specialization" e di collaborazione con altre Regioni Europee e Nazionali. In accordo con la missione di AFIL-­-Associazione Fabbrica Intelligente Lombardia, il Cluster Tecnologico Regionale voluto dalla Regione per rappresentare le necessità di ricerca e sviluppo delle imprese manifatturiere regionali, il documento vuole essere un input per Regione Lombardia per la definizione delle prossime politiche di ricerca a livello regionale.

Titanium alloys, due to their high mechanical properties coupled with light weight and high corrosion resistance, are finding a widespread use in the aeronautic industry. The use of titanium in replacing the conventional alloys, such as aluminum alloys and steel, is reduced by both the high cost of the raw material (it costs anywhere from 3 to 10 times as much as steel or aluminium) and the machining costs (at least 10 times that to machine aluminium). For such a reason new technologies have been studied and developed. In particular many researchers are searching for technologies, such as the precision hot forming, that allows to obtain components with a low buy to fly ratio. Many of the airframe component structures are designed to fit against the inside radius of the fuselage curvature. By combining traditional stretch forming technology with hot titanium forming techniques, the HSF guarantees a saving in material and machining time, which are two serious cost issues for today's aircraft manufacturers. In addition, the process allows for consistent quality in a productively efficient manner, assuring the sustainable attainment of delivery and build schedules. In order to develop and improve the HSF process a modeling of the process itself was executed in order to study the stresses and strains undergone by the material among the deformation. The FEM model was validated through the residual stresses, and in particular the residual stresses provided by the model were compared with the ones experimentally measured using the hole drilling technique. Good agreement, in terms of stress range, was recorded both for the maximum and the minimum stress.. �� 2014 Trans Tech Publications, Switzerland.

Circular laser hardening is the laser surface treatment used in the case of cylindrical workpieces. The single-track treatment is a particular case of circular laser hardening used when only one revolution of the workpiece is executed since the treatment of a narrow surface is required. As a result, an annular narrow hardening track is obtained. During the laser hardening, the initial and final parts of the workpiece are overlapped and treated twice. The main drawback of this treatment is the back-tempering effect focused on the overlapping zone. This phenomenon leads to a hardness decrease in the overlapping zone. To avoid this problem, a new technique called apparent spot (AS) was introduced by the authors. The aim of the AS technique is to increase in a fictitious way the dimensions of the laser spot. In the case of circular laser hardening, this technique results into a high-speed rotation (up to 1,000 rpm) of the cylindrical workpiece instead of the traditional low speed. So, a uniform hardening zone without overlapping and back tempering is obtained. However, despite these benefits, there is still a lack of knowledge about the physics of this treatment in particular referring to the thermal cycle that affects the workpiece. In order to enhance the knowledge of this technique in this work, the AS was modeled via the FE approach. DEFORM software was used to model the circular laser hardening process. The software was firstly validated by a comparison with experimental results. Once the software reliability was tested, a regression model was estimated to predict the surface temperature within the treatments. Good agreement was found between the prediction model and the numerical results.

Ring rolling is a hot forming process used in the production of railway tyres, anti friction bearing races and different ring shaped work pieces for automotive energy production and aerospace applications. The advantages of ring rolling process include short production time, uniform quality, closed tolerances, good material quality and considerable saving in material cost. Despite the benefits some problems still exist according to a correct selection of the process parameters. Due to the nature of the process different rolling mills (driving, idle and axial rolls) are involved and the correct selection of the process parameters is not so feasible. Moreover an experimental approach to solve this problem risks to be more expensive. Actually FE codes are available to simulate the non linear problem that characterizes a ring rolling process. In this work a FE model, based on Deform 3D software, was tested versus experimental results acquired from an industrial plant. The accuracy of the FE model was analyzed through a dual comparison: by geometrical and by physical aspects. A good agreement was found between experimental and numerical results for both comparisons and, as a consequence, this code could be used in order to investigate and optimize the process parameters that characterize the ring rolling process in a virtual not expensive environment. The validated model will allow the studies of more environment-friend process configurations.

Ring Rolling is a complex hot forming process used for the production of shaped rings, seamless and axis symmetrical workpieces. The main advantage of workpieces produced by ring rolling, compared to other technological processes, is given by the size and orientation of grains, especially on the worked surface which give to the final product excellent mechanical properties. In this process different rolls (Idle, Axial, Guide and Driver) are involved in generating the desired ring shape. Because each roll is characterized by a speed law that could be set independently by the speed law imposed to the other rolls an optimization is more critical compared with other deformation processes. Usually in industrial environment a milling curve is introduced in order to correlate the Idle and Axial roll displacement, however it must be underlined that different milling curves lead to different loads and energy for ring realization.In this work an industrial case study was modeled by a numerical approach: different milling curves characterized by different Idle and Axial roll speeds laws (constant, linear and quadratic) were designed and simulated. The results were compared in order to identify the best set of Idle and Axial roll speed laws that guarantee a good quality produced ring (lower fishtail) with lower manufacturing loads and energy.

In these last years, the demand of shaped aluminium bottles and cans was continuously growing. The main problem is related to the fact that normally these objects have very thin thickness and a high strain-hardened material due to the deforming production steps (deep drawing and ironing). In the present paper, a study about the residual formability of cylindrical can is reported. In particular, a first characterization of the flow stress of the ironed component and the identification of the maximum deformation reachable with the hydroforming process were carried out. On the base of these preliminary results, the feasibility of hydroforming aluminium can, namely a small bottle for soft drink, has been investigated. The process is similar to tube hydroforming, even if the bottom part of the can is closed and air is used instead of liquid. The main problems to be solved were related with the possible breakages of the cylindrical body during hydroforming. The process success depends on the material characteristics, the diameter and thickness of the preformed cylindrical body, the shape, the geometry and the dimensions of the final part and the media pressure. The research aims to study the process feasibility and to prove the ability of the simulation software in forecasting the material behaviour. All the simulation phases are supported by experimental tests aiming at validating the finite element method model and to realize sound prototypes of Al soft drink bottles. In such a way, it is possible to have a reliable tool to help the designer in optimizing the process and in identifying new feasible shapes.

Back tempering is one of the most critical problems in laser hardening of extended surfaces. In this type of treatment, several laser tracks are slightly overlapped to obtain a uniform hardened surface. Due to the overlapping, tempered zones are generated on the treated surface with the consequent lack of uniformity in the surface hardness. In this work, a regression model was developed to estimate the loss of hardness due to the tempering effect as a function of the thermal cycle. A specific test, named laser surface treatment test, was designed and executed to reproduce the hardness reduction due to the tempering effect. An analytical thermal model was developed to evaluate the thermal cycle undergone by the material during this test. By the results of the laser surface treatment test combined with the analytical model, a prediction model was estimated. Good agreement was found between predicted and measured hardness decrease, and the identified model could be integrated in a numerical code to evaluate the optimal process parameters.

Laser hardening, compared to other surface hardening processes, presents several advantages: it can be extremely selective and almost without distortion, it achieves higher levels of hardness and thanks to the rapidity of the heating phase it does not require a quenching medium as the material surrounding the heated layer acts as a heat sink. Nevertheless, in case of workpiece with slim geometry, the thermal stress after the treatment induces a sensible deformation on the treatment direction; this deformation can deeply affect the part ability to fulfil its function and/or its reliability. In this paper a solution to recover the workpiece function ability is presented: a second laser treatment (called counter treatment) was executed on the opposite surface of the treated one to reduce the deformation induced by the first treatment. A numerical model was firstly tested and then used to simulate the counter treatment process and to evaluate the optimum process parameters. Based on the numerical analysis, experimental results show that thanks to this technique it is possible to recover up to 80% of the induced deformation.

Ring rolling is a hot forming process used in the production of railway tyres, anti friction bearing races and different ring shaped workpieces for automotive and aerospace applications. The advantages of ring rolling process include short production time, uniform quality, closed tolerances, good material quality and considerable saving in material cost. Despite the benefits some problems still exist according to a correct selection of the process parameters. Due to the nature of the process different rolling mills (driving roll, mandrel and axial rolls) are involved and the correct selection of the process parameters is not so feasible. Moreover an experimental approach to solve this problem risks to be more expensive. Actually FE codes are available to simulate the non linear problem that characterizes a ring rolling process. In this work a FE model, based on Deform 3D software, was tested versus experimental results acquired from an industrial plant. The accuracy of the FE model was analyzed through a dual comparison: by geometrical and by physical aspects. A good agreement was found between the experimental and the numerical results for both comparisons and, as a consequence, this code could be used in order to investigate and optimize the process parameters that characterize the ring rolling process in a virtual not expensive environment.

Back tempering, a well known problem in laser hardening of steels, occurs when a large area is hardened by multiple overlapping passes. The overlapping passes partially temper the previous hardened material in the overlapped zone. Back tempering also occurs in circular laser hardening, a typical laser surface treatment used in case of cylindrical workpieces, since the treated starting/ending surfaces are slightly overlapped. In order to avoid the back tempering phenomenon the apparent spot (AS) technique is addressed and investigated. In case of circular laser hardening the AS technique is based on imposing a high rotational speed to the workpiece, since an apparent circular spot is generated, which contemporaneously heats all the annular surface of the workpiece. As a consequence, back-tempering is avoided. In this paper an experimental campaign is deigned to analyze the effects of the process parameters (laser power, workpiece rotational speed and workpiece diameter) on the hardened tracks in terms of width, thickness and hardness values, when the AS is applied to the circular laser hardening.

In order to improve the wear resistance of parts without affecting the softer, tough interior of the part, laser hardening offers many advantages. Compared to conventional processes, only a shallow layer of the metal part is heated by laser irradiation to just below the melting temperature, while the surrounding material remains at ambient temperature. Due to heat conduction into the bulk material, the surface will cool down as soon as the laser beam moves away. This self‐quenching creates a particularly fine‐grained martensitic micro structure with high hardness without causing fragileness of the base material. Notably lower distortions of parts avoiding costly rework are produced due to laser beam follows the contours precisely. Nevertheless, when part is thin and slim even the low distortion caused by the laser hardening can deeply affects the part ability to function fairly. In this paper a double treatment is proposed in order to recover the bending and bulging deformation induced by the thermal cycl...