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The aim of this paper was to investigate the effects of a post-deposition laser treatment on the titanium cold-sprayed coatings. Commercially pure grade 2 titanium powders were deposited onto an aluminum alloys AA2020-T3 substrate, using a commercial cold spray system. Pre-heated helium was employed as powder carrier gas. Coatings were heat treated using a 220 W diode laser, in order to improve the cohesion between titanium particles, reduce the porosity percentage and promote a homogeneous microstructure. Several samples were realized varying the thickness ratio between the two layers and the scan rate of laser source, to reproduce and investigate the effect of different temperature distributions. Geometry features and microstructure of treated zone were assessed by means of conventional optical microscopy and scanning electron microscopy. Microhardness measurements were carried out to evaluate the mechanical properties of the coating layer. A numerical model of the laser treatment was also implemented to discuss the experimental outcomes.

Incremental forming process, in all its variants, results to be ideal when flexibility is required, especially for small-batch and customized production. Two point incremental forming with partial die (TPIF) presents notable advantages compared to single point incremental forming (SPIF) for obtaining components that present both concave and convex zones; on the other hand, these advantages are not so evident in the case of simple geometries. The following study compares the two techniques by geometrical considerations, FEM analyses and experimental evaluations. Cone frusta are obtained starting from aluminum alloy sheets and features like geometric accuracy, forming and setup times, forming forces and deformative states are investigated, in order to highlight differences and similarities between the two techniques. In particular, TPIF allows to obtain geometries very similar to the designed ones, but requires higher setup and forming times.

Cemented carbides present some characteristics that ensure high performances for cutting and wear-resistant tools. The aim of the work is to evaluate the influence of Chromium Carbide and Nickel on the properties (wear and friction) of a cemented carbide constituted by a hard phase of tungsten carbide and a binder phase of cobalt. Different tests were carried out by varying the percentage of Cr3C2 and, for one only case, also Nickel was added. The tests were carried out by a pin-on-disk apparatus and diamond abrasive sheet. The experimental campaign provided tests for different values of load and relative velocity. Friction coefficient was directly evaluated by the apparatus and data on the wear were obtained by measuring the loss of weight of the samples (parallelepipeds with hemispherical head). The tests allowed to determine the percentage of Cr3C2 that ensure an improvement of the aforementioned properties and to highlight the irrelevance of Nickel.

La profilatura a freddo (cold roll forming) è una lavorazione per deformazione plastica che consente di realizzare profilati, di una definita sezione e lunghezza, dalla deformazione plastica di una lamiera. Questa è indotta ad attraversare diverse stazioni di rulli deformatori, disposti sullo stesso asse di avanzamento. I banchi di rulli, assemblati in maniera folle nella singola stazione, inducono la deformazione plastica nella lamiera e quindi portano alla configurazione desiderata. Al fine di controllare i parametri geometrici della lamiera deformata durante la profilatura, è stata simulata in ambiente FE la fase finale del processo messo a punto dalla Imi Sud S.r.l. mediante il codice di calcolo non lineare LS-Dyna 971, che ha permesso di analizzare le grandezze di interesse nei differenti step di avanzamento. I risultati ottenuti numericamente sono stati confrontati con quelli sperimentali mediante la misurazione di 5 campioni ottenuti direttamente dal processo tecnologico.

Dalla crescente consapevolezza ambientale, dalle preoccupazione per la sostenibilità ambientale e dal crescente problema dello spreco globale, negli ultimi decenni è derivata una notevole tendenza verso l'utilizzo di fibre naturali, piuttosto che di fibre tradizionali, come rinforzi nei materiali compositi. Le fibre naturali sono state utilizzate per rinforzare termoplastici per i loro vantaggi relativi al basso costo, alla bassa densità, alla resistenza specifica accettabile, alle buone proprietà di isolamento termico, alla biodegradabilità e alla rinnovabilità. Tra i polimeri biodegradabili, l'acido polilattico (PLA) si è mostrato essere molto interessante per il suo uso come matrice nei compositi in fibra naturale per molteplici ragioni. L'obiettivo di questo lavoro è la valutazione delle proprietà meccaniche di compositi bio canapa/PLA realizzati con tessuti di fibre naturali al variare della percentuale volumetrica di fibra e della tipologia di tessuto utilizzato come rinforzo.

In the manufacturing of metal components both wear and corrosion have to be considered. In particular corrosion is a very important problem in the aeronautic field, were the aluminum alloys are widespread used, but are affected by several corrosion typologies. Furthermore nowadays carbon fiber reinforced plastics (CFRP) are finding an increasing use, but they can induce galvanic corrosion phenomena when coupled with aluminum alloys. To overcome this problem corrosion resistant coating are used on aluminum components. Otherwise titanium alloys have a very high corrosion resistance and furthermore no galvanic corrosion phenomena arise when coupled with CFRP. On these premises the realization of a titanium coating on aluminum components could allow the use of aluminum alloys coupled with CFRP and improve the corrosion resistance of the above mentioned alloys. The aim of this paper is to study a titanium coating builded on an aluminum substrate by means of the cold spray technique. This technique allows to produce near fully dense coatings. Despite the promise this technique has shown, questions remain about the quality of the material deposited in terms of adhesion strength of coating to substrate, and cohesion strength between cold sprayed particles that make up the coating. In this paper titanium coatings on AA 6082 substrate were carried out and tested. In particular pure titanium powder were used to build up the coating. An experimental campaign was carried out including mechanical, microstructural and electrochemical tests. Furthermore sliding tests, by means of a pin-on-disk apparatus, were carried out in order to study the wear properties of the coating. The results obtained showed a quite compact coating with few porosity, moreover the coating showed a good internal cohesion and a good adhesion with the aluminum substrate, also the electrochemical properties were interesting.

Tool wear monitoring is a fundamental aspect in the evolution of modern machining operations. As the quality of the tool is directly related to the quality of the product, automatic tool wear evaluation is vital to ensure smooth automatic control of machining processes [1]. In this paper, an automatic tool wear detection procedure is presented, where real time collected sequence images of the cutting tool during turning tests are subjected to image processing. The procedure can be divided into four steps: (1) Standardization of tool images; (2) Adjustment of pixel color density to obtain clear edges of the tool wear region; (3) Drawing of the projection line to find out the coordinates of the edge lines; (4) Calculation of tool wear development characteristics. The tool wear characteristics and extension area are evaluated on the basis of the processed edge. One by one, sequence images are processed to automatically provide the growth of tool wear characteristics. In order to verify the procedure accuracy, the tool wear characteristics and extension area are also evaluated manually using a grid number counting technique on paper images. The comparison of the results confirmed that the automatic evaluations achieve a high degree of accuracy. The experimental results indicate that the proposed procedure can be a viable technique to assess the tool wear development characteristics on an on-line basis.

Chemical etching is a non-traditional machining process where a chemical solution is used to remove unwanted material by dissolution. To shape the etched area, before the process, a chemical inert paint (maskant) is applied on the surface. Then the maskant is trimmed away and the uncovered area is subject to the etching. The maskant cut could be obtained mechanically or by laser ablation. In this work, the effect of process parameters, cutting speed and beam power, on interaction phenomena and defect formation in laser cutting of polymeric maskant is studied, using a 30W CO2 laser source.

Roll drawing is a technological process that allows to obtain a notable reduction of the drawing force in comparison with the traditional drawing process with converging dies. Consequently, no thermal or chemical treatment of the wire is required and no lubricant is employed, with significant environmental advantages. The drawing force and the geometrical dimensions of the wire are critical parameters for optimal process design. They have been evaluated by analytical models but, owing to the complexity of the process, a three-dimensional FE model has been developed to obtain a more precise method able to control the process.

Backdrawing incremental forming is a multistep sheet metal forming process for manufacturing components with both concave and convex features, without using patterns; this process preserves the characteristic of flexibility typical of incremental forming. The creation of a component with concave-convex shape using this process is described in the present study. In particular, observations on the choice of tools shape and on the influence of the forming steps sequence are highlighted, in order to evaluate the importance of these parameters in terms of certain geometric features, compared with the design specifications. Moreover, the thickness distribution, nowadays used as forming limit parameter, is evaluated.

Incremental forming is a process that can satisfy the most disparate requirements in terms of feasible geometries; in other words it is possible to affirm that it is a very flexible process. Moreover, the high formability of sheets for the process under examination, allows to get considerable drawability levels. The aim of the present paper has been the evaluation of the formability of steel sheets and the achievement of complex geometries by means of incremental forming process. The paper shows how it is possible to use a FE code, previously validated for forming processes, to evaluate the forming limit curves of the steels. The same code has preliminarily been used in order to simulate the formability of a complex geometry component. The experimental phase,consisting in the realization of the component with the complex geometry, has been carried out and it has confirmed the results of the numerical analysis.

The use of laser technology for the welding of automotive drive shafts subject to the action of residual magnetic field

On the numerical modelling of a milling operation: data recovering and interpolation

On the welding of different materials by a diode laser

Hybrid neural network model for the evaluation of the free surface of rolled bar

Application of Taguchi method to high power diode laser welding of Ti6Al4V

A correlation between the friction coefficient and the roughness of rolls in a hot flat rolling

Finite element model for wire filler and autogeneous laser welding heat sources

CLASSIFICATION OF SOUNDNESS OF TITANIUM ALLOYS WELD ON THE BASIS OF FUSED ZONE LEVELS FOR IMPERFECTIONS

NEURAL-NETWORK AIDED DOE: AN APPLICATION IN CO2 LASER WELDING OF TI6AL4V

EVALUATION OF THE CO2 LASER BEAM WELDING PROCESS EFFICIENCY FOR THE TI6AL4V ALLOY

STUDY OF TITANIUM SHEETS HPDL WELDING PHENOMENON

A BASIC STUDY ON THE HIGH POWER DIODE LASER WELDING

HIGH SPEED JOINING OF POLYMERIC PLASTICS USING DIFFERENT LASER SOURCES (CO2, ND-YAG AND HPDL)

FUZZY METHODS FOR MECHANICAL PREDICTION OF TI6AL4V CO2 LASER WELDED SHEETS