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Ti–6Al–4V is an alloy increasingly used in aeronautics due to its high mechanical properties coupled with lightness. An effective technology used to manufacture titanium components with a reduced buy-to-fly ratio is laser beam welding. Previous studies showed that the key factor that rules the mechanical properties and the fatigue life of the joint is its morphology. The aims of this paper were to investigate the influence of the geometrical features of the joints (height of the top and root reinforcement, depth and radius of the underfill, and the valley–valley underfill distance) on their mechanical properties and also to conduct a finite element (FE) analysis on the real geometry of the welded joints. Ti–6Al–4V rolled sheets 3.2 mm thick were welded in butt joint configuration using a laser source and their performance was studied in terms of weld morphology, microstructure, Vickers microhardness and fatigue life. A full factorial plan, designed varying the welding speed and laser power, was carried out. The real geometry and then the joint morphology were studied through an innovative approach: for each specimen, both the total weld face and the total root surface were acquired using a confocal microscope. Finally, through these acquisitions, the clouds of points of the scanned surfaces were used in order to carry out a FE analysis capable of providing a stress concentration factor, K t , value for each detected joint. The main results are the realization of a reliable FE model by an experimental agreement and the relationship found amongst the fatigue performances and some noticeable metallurgical and geometrical features, such as the underfill depth and the aspect ratio defined as the ratio between the maximum height of the joint and the valley–valley underfill distance.

The aim of the present work is to investigate the feasibility and effects of a selective post-deposition laser treatment on titanium coatings. Commercially pure titanium grade 2 powders were deposited by means of a cold spray process on aluminum alloy AA2024-T3 sheets. The surface treatment of the coating was realized using a 220 W diode laser. The influence of heat input and dimensional features of coating layer and substrate was assessed by an experimental campaign conducted following a design of experiments approach. Optical and scanning electron microscopy analysis of the microstructure of the deposited and treated material as well as micro hardness measurements showed the formation of a compact layer of titanium oxide on the coating surface and the preservation of the temper state of the aluminum substrate.

The incremental forming of titanium alloy sheets combines the advantages of this advanced flexible manufacturing process, that allows to produce complex components without using dedicated tools, with the interesting properties of the material under consideration. In this study, thin sheets of grade 1 titanium were incrementally formed to evaluate their formability and surface quality by varying the tool-sheet contact conditions. Experimental tests and surface analyses highlight dependence on the contact conditions of the surface quality rather than of the formability. Moreover, they emphasize that the tool-sheet contact conditions mainly affect the repeatability of the process due to the occurrence of galling.

This study compares negative incremental forming (NIF) and positive incremental forming (PIF) processes by geometrical considerations, finite element method (FEM) analyses, and experimental evaluations. Conical frusta were manufactured starting from AA5052H19 aluminum alloy sheets using both techniques. The processes were also simulated with LS-DYNA software and a close correlation between the experimental and numerical results was observed. The analysis of forming forces, forming limit diagrams (FLDs), and sheets thinning highlights that the PIF technique allows one to reach higher formability and geometrical accuracy. Finally, the differences in terms of surface quality were also discussed.

Cemented carbides, also known as Widia, are hard metals produced by sintering process and widely used in mechanical machining. They show high cutting capacity and good wear resistance; consequently, they result to be excellent materials for manufacturing cutting tools and sandblast nozzles. In this work, the wear resistance of WC-Co carbides containing Eta-phase, a secondary phase present in the hard metals when a carbon content deficiency occurs, is analyzed. Different mixtures of carbide are prepared and sintered, with different weight percentages of carbon, in order to form Eta-phase and then analyze how the carbon content influences the wear resistance of the material. This characterization is carried out by abrasive wear tests. The test parameters are chosen considering the working conditions of sandblast nozzles. Additional information is gathered through microscopic observations and the evaluation of hardness and microhardness of the different mixtures. The analyses highlight that there is a limit of carbon content below which bad sintering occurs. Considering the mixtures without these sintering problems, they show a wear resistance depending on the size and distribution of the Eta-phase; moreover, the one with high carbon content deficiency shows the best performance.

Nowadays, the need of developing high flexible forming processes matches with the need of weight reduction. In this light, the incremental forming of titanium alloys sheets can guarantee both these aspects by combining the flexibility of the process, particularly suggested for small batches and customized parts, with the good properties of titanium alloys, in particular for aerospace applications.The aim of this work was to obtain information useful to enhance the general knowledge of the hot incremental forming processes of grade 1 titanium sheets at different temperatures.First, both tensile and straight groove tests were carried out by varying the test temperature; in this phase, information regarding both the forming forces and the wear phenomena due to the tool-sheet contact was acquired.Successively, on the basis of the mechanical characterization of the sheets previously carried out, explicit analyses, effectuated by a non-linear FE code, allowed to determine the formability curves of the sheets for the different temperatures.

The interest for natural fibers as reinforcement in composites is growing for a large number of products also for aeronautic applications, where the flame retardant requirement is fundamental. In this research, ammonium polyphosphate was incorporated as flame retardant into hemp/epoxy biocomposites produced by infusion technology. Cone calorimeter, vertical burning, dynamic mechanical analysis and bending tests were performed in order to study fire and mechanical behavior of the produced biocomposites with different percentage of ammonium polyphosphate. The results showed a decisive improvement of the flame properties; no-effect on their mechanical properties and on the technological feasibility of the process were observed. Therefore, the addition of ammonium polyphosphate enhanced flame retardancy of hemp/epoxy-resin biocomposites without sacrificing their mechanical properties.

Sequence design for shape-rolling processes consists of roll pass and profile design, i.e., transforming the billet into a final shape. For the prediction of the mean effective strain of the workpiece during rod rolling, an analytical model by Shinokura and Takai was used. They verified the formula by applying it to a variety of rod-rolling geometries (oval-square, oval-round, square diamond, and diamond-diamond). Today, on the other hand, the finite element (FE) techniques allow analysis of rolling processes in such a way as to simplify the work of design engineers. In this study, a round-oval pass and a round-flat oval pass are analyzed for steel rod rolling. In particular, the analysis of the spread, the surface profile, and cross-sectional area of the workpiece were conducted during rolling. Experimental data such as the maximum spread and the radius are compared with the results of the analytical model and FE analysis.

Cold roll forming is a process for plastic deformation, which allows realizing profiles, with a defined section and established length, from the plastic deformation of a metal sheet. The sheet is induced to cross several stands of rolls, arranged along the same axis of advancing. The rolls induce plastic deformation in the sheet and then lead it to the desired geometric configuration. In order to control the geometric parameters of the plate during the profiling, it was created a FEM model to simulate the final stage of the technological process, developed by an industrial production line of a company located in Naples (Italy), that sells tubes with several cross sections. In this phase, the semi-finished product, having a circular cross section, is forced to cross through four stands of rolls. In this way, it changes the geometric condition of the cross section from circular to square. The model was carried out using a non-linear calculation code, which allows analyzing the parameters of interest in the different process steps. The results, obtained numerically, were compared with the experimental ones through the measurement of five specimens, obtained directly from technological process. The values of percentage deviation, regarding the external dimension and the thickness, for each step of advancement, do not exceed the 3% of error. Then, the analysis results denote the capability to simulate the cold roll forming process using finite element method.

In the manufacturing of metal components both wear and corrosion have to be considered. In particular, corrosion is a primary problem in the aeronautic field, where the aluminium alloys are affected by several corrosion typologies. Furthermore, nowadays carbon fibre reinforced plastics (CFRP) are finding an increasing use, but they can induce galvanic corrosion phenomena when coupled with aluminium alloys. To overcome this problem, corrosion resistant coatings are used on aluminium components. On these premises, the realization of a titanium coating on aluminium components could allow the coupling of CFRP and aluminium alloys, improving the corrosion resistance. Cold Spray Deposition is a recent technology to realize these coatings. This technology allows the production of near fully dense coatings on metallic surfaces. In many applications the coated aluminium sheets have to be machined (cut or drilled). Machining with conventional cutting methods leads to both tool wear and damages in the coating. Laser cutting represents a promising alternative: it does not involve any mechanical cutting force or tool wear and, thanks to the small laser beam spot, it allows to realize complex shapes. In this paper, laser cutting of an Al alloy sheet (0.6 mm thick) coated with Ti Alloy, was studied. The adopted laser source was a 150 W, lamp pumped Nd:YAG, specifically developed for micro-machining operations on metals. During the tests, the process parameters (cutting speed, pulse duration and entrance side) were changed and the kerf geometry was analysed as a function of the process parameters.

Superficial coatings are widely used in industrial applications in order to improve the superficial properties of metallic components. In particular, in the aeronautic field, all the components are coated in order to prevent both corrosion and wear. In this field, heat treatable aluminum alloys, in age hardened condition, are used; consequently, superficial coatings must be carried out through “cold” processes, i.e. coating processes in which the component to be coated remains at low temperatures, below 100°C. Cold gas dynamic spray technique (CGDS) is a process of deposition that consists in the realization of surface coatings with high-velocity metal particles sprayed on the substrate at temperature significantly lower than the melting one of the substrate itself and at relatively low temperatures if compared to other spray techniques. When processing conditions are optimized, the process can produce near fully dense coatings. This technique could be particularly useful in the coating of rolled sheets, needing of successive cold plastic deformations. One of the cold plastic processes is incremental forming, a high flexible process for rapid manufacturing of complex sheet metal part shapes; it presents the potential to be easy to automate and particularly attractive for small batches and customized parts. In this process, a simple tool describes a path that allows to locally deform the sheet clamped along its periphery. The aim of this paper is to study the evolution and behaviour of aluminum coating deposed by CGDS on AA 2024-T3 sheets carried out by an incremental forming process. This evaluation is carried out by characterizing the cold sprayed coating after the forming process for different wall angles of simples geometries.

Reinforced concrete rod produced by European Community countries must comply with standards that establish minimum strength and tensile properties along with other technological and geometrical characteristics; however, possible variability within the assigned limits is not specified. Consequently, a number of manufacturing methods are now used, with the result that over time the mechanical properties of these products vary widely. Increased competition has led to the development of new procedures incorporating both process and quality control. One example is a process based on the heat treatment undergone by the metal bars leaving the final stand of the rolling mill train. In this way, the mechanical and technological properties can be graduated, thereby enhancing strength (particularly yield point) without altering the deformability of the material. This procedure does away with the need to alter the chemical composition of the steel used to manufacture the rods. Process adjustment still relies on the experience of the production manager, however. This paper examines the possibility of applying fuzzy logic computer techniques to the heat treatment process in order to render it more rational and independent of operator unreliability.

Titanium and its alloys are nowadays widely used in many sectors: in the medical field (orthopedic and dental ones), in the architectural field, in the chemical plants field and in aeronautic [1]. In this last field it is more and more used both for its contribution to make lightweight and time durable structures and for its compatibility with new materials, first of all Carbon Fiber Reinforced Plastics (CFRP). Cutting of titanium sheets is one of the primary requirements in the fabrication of most of the components. Laser cutting offers several advantages over conventional cutting methods. It includes narrow kerf width (minimum material lost), straight cut edges, low roughness of cut surfaces, minimum metallurgical and surface distortions, easy integration with computer numerically controlled (CNC) machines for cutting complex profiles and importantly non-contact nature of the process (suitable for cutting in hostile environments and in areas with limited access) [2]. However, due to very limited literature available on laser cutting of titanium, it is very difficult to predict the cut surface quality and optimum process parameters for laser cutting, especially when dross-free cuts are required. Laser cutting of titanium and titanium alloys needs to be carried out with an inert gas, this due to the high reactivity of the titanium with the oxygen at high temperatures [3]. However when the available power is limited, as in the present case, the use of a reactive gas (air) can help to achieve cutting speed value reasonable for industrial applications. The aim of this work is to study the cutting of Ti-6Al-4V rolled sheets 1 mm in thickness, by means of a 100 W fibre laser, (SPI-Red Power) working at wavelength  = 1090 nm. The maximum cutting speed were measured in both CW and pulsed regime at different mean power and different duration. Furthermore, the kerf geometry and the heat affected zone (HAZ) were studied decreasing the cutting speed from the maximum to the 80 % of this values. The results obtained showed that both the power and the cutting speed influence the cutting kerf geometry and HAZ. In particular the synergy of power and speed, resulting roughly into the heat input, seems to rule the whole cutting process.

Incremental forming is a sheet metal forming process characterized by high flexibility; for this reason, it is suggested for rapid prototyping and customised products. On the other hand, this process is slower than traditional ones and requires in-depth studies to know the influence of certain process parameters. The purpose of this study is to investigate the influence of tool rotation on an incremental forming process. Pyramid frusta are created for different speeds and both directions of tool rotation, starting with aluminium alloy sheets; a punch with hemispherical head is used as tool. The variation of speed of tool rotation puts into the variation of friction coefficients, so these ones are preliminarily evaluated for different speeds, in order to explain the influence of tool rotation in terms of forming forces, temperatures reached and surface roughness. The evaluation of these quantities highlights the influence of tool rotation, both in terms of speed and direction of rotation, on the components of the forming forces in the sheet plane, whereas neither the heating of the sheet caused by the friction nor the surface finishing feel the effects of this parameter significantly.

Publisher Summary Hydroforming process is an effective method for manufacturing complicated parts. Hydroforming allows overcoming some of the limitations of conventional deep drawing, increasing the draw ratio and minimizing the thickness reduction of the formed parts. Among the advantages introduced by hydroforming, there are a great flexibility and a remarkable reduction of tooling costs. This process is quite sensitive to the characteristics of the pressure growth laws and the friction between the sheet and the elements of the tooling. This chapter discusses a numerical simulation that has been carried out using the explicit finite element code LS-DYNA with the purpose to optimize a hydroforming process related to the achievement of an asymmetrical aeronautical component. In particular, the number of the steps of the manufacturing cycle actually used to produce the component has been reduced considering the FEM results.

Ti6Al4V is presently one of the most widely used titanium alloys, accounting for more than 50% of all titanium tonnage in the world, and to date no other titanium alloy has been a threat to its dominant position. Laser welding of Ti6Al4V is a major issue in the automotive and aerospace industries. In this paper, both CO2 and diode laser welding processes were investigated for Ti6Al4V alloy sheet joining using either lap or butt configurations. Artificial neural networks (ANN) processed the data coming from the experimental trials. The aim was to interpolate the database in order to form a suitable database for the analysis of the variance (ANOVA) and the Taguchi analysis of the means. The ANOVA has the merit of being able to be validated on a statistical basis while the Taguchi engineering approach has the ability of maximizing the information coming from a small database of data. Therefore, reliable and valuable information over the ranges of the processes investigated was individuated from a limited number of trials.

In the design of roll stands for use in grooved steel rod rolling, the contact pressure between the rolls and the incoming workpiece is very important. This value can be estimated with the help of a number of analytical and seiniempirical models described in the published scientific and technical literature. In this study, the possibility of using numerical simulation in determining the contact pressure during the rolling of a round bar with oval grooves is analyzed. The results of the numerical analyses are then compared with those of two other modified analytical models.

The employment of laser systems for completely automated welding processes needs an analysis of physical mechanisms by means of mathematical models to correlate the characteristic quality indexes of welding to working parameters. In this paper we describe the application of neural networks method in order to correlate, for different kinds of stainless steel, the melting area and the welding efficiency to working parameters, leaving out of account the knowledge of the chemical and thermo-physical properties of working materials. The results are quite satisfactory even if a direct search of the optimal process conditions is not possible.