Micro-Drilling of ZTA and ATZ Ceramic Composit: Effect of Cutting Parameters on Surface Roughness

Ceramics are a class of materials widely used during last fifteen years for orthopaedic applications. It is well known that they are characterized by low wear rate, and friction coefficient. However, these materials are very difficult to machine into complex shapes because of their brittleness and high hardness. The most effective method to increase the crack resistance is the formation of a composite structure. This class of materials, composed by two or more different ceramics, can present higher characteristic respect to the single component, like fracture toughness and flexural strength. This paper presents a study of the influence of cutting parameters (cutting speed, feed rate and step number) onto the hole surface roughness and deformation due to the drill operation. The ceramic composite materials AZT (alumina toughened zirconia) and ZTA (zirconia toughened alumina) were first characterized in terms of hardness and roughness. After the drilling test, the holes were analyzed using scanning electron microscope (SEM) and an advanced 3-dimensional non-contact optical profilomete

Quando l'idea acquista spessore: tecnologie additive a confronto

"Le “nuove” tecnologie additive [1] stanno cambiando il mondo del manufacturing sia in termini di progettazione sia di modalità di produzione; tale rinnovamento si traduce, di fatto, nella realizzazione secondo una nuova modalità di oggetti dalle caratteristiche più svariate. Il miglioramento più evidente si è avuto grazie al superamento dei tradizionali vincoli che, per esempio, la produzione con stampi comporta; il principale vantaggio ottenuto è l’enorme fl essibilità che le nuove tecnologie additive garantiscono, fl essibilità da intendersi sia in termini di forme e materiali, sia in relazione alla grande varietà di pezzi differenti che è possibile realizzare contemporaneamente

Characterisation of the Thermal Damage in a Martensitic Steel Substrate Consequent to Laser Cladding Process

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A tunable, dual mode field-effect or single electron transistor

A dual mode device behaving either as a field-effect transistor or a single electron transistor (SET) has been fabricated using silicon-on-insulator metal oxide semiconductor technology. Depending on the back gate polarisation, an electron island is accumulated under the front gate of the device (SET regime), or a field-effect transistor is obtained by pinching off a bottom channel with a negative front gate voltage. The gradual transition between these two cases is observed. This dual function uses both vertical and horizontal tunable potential gradients in non-overlapped silicon-on-insulator channel

Effect of in-source beam shaping and laser beam oscillation on the electromechanical properties of Ni-plated steel joints for e-vehicle battery manufacturing

Laser welding is a key enabling technology that transitions toward electric mobility, producing joints with elevated electrical and mechanical properties. In the production of battery packs, cells to busbar connections are challenging due to strict tolerances and zero-fault policy. Hence, it is of great interest to investigate how beam shaping techniques may be exploited to enhance the electromechanical properties as well as to improve material processability. Industrial laser systems often provide the possibility to oscillate dynamically the beam or redistribute the power in multicore fibers. Although contemporary equipment enables elevated flexibility in terms of power redistribution, further studies are required to indicate the most adequate solution for the production of high performance batteries. Within the present investigation, both in-source beam shaping and beam oscillation techniques have been exploited to perform 0.2-0.2 mm Ni-plated steel welds in lap joint configuration, representative of typical cell to busbar connections. An experimental campaign allowed us to define process feasibility conditions where partial penetration welds could be achieved by means of in-source beam shaping. Hence, beam oscillation was explored to perform the connections. In the subset of feasible conditions, the mechanical strength was determined via tensile tests alongside electrical resistance measurements. Linear welds with a Gaussian beam profile enabled joints with the highest productivity at constant electromechanical properties. Spatter formation due to keyhole instabilities could be avoided by redistributing the emission power via multicore fibers, while dynamic oscillation did not provide significant benefits

Texturizzazione laser della lega di magnesio AZ31 per migliorare l’adesione nelle applicazioni biomedicali

"Laser surface texturing of AZ31 Magnesium Alloy to improve adhesion in biomedical application Cardiovascular stent have assumed a primary role to solve heart problems related to constraints that lead to the malfunctioning of a hollow organ. The research is shifting more and more towards the creations of less invasive stent having biocompatibility and biodegradability as primary requirements. Metal that best meets both these requirements and also the structural ones is Magnesium and its alloys. The greatest limit to the use of this material comes from its low corrosion resistance that it is manifested at the body pH. The idea at the basis of this work is to cover the Magnesium stent with a biodegradable polymer to increase its resistance to corrosion. The following paper focuses the study on the texturing surface treatments, achievable by a laser beam, in order to optimize the adhesion between the substrate and the polymer. The Magnesium alloy used is AZ31. Studies of surface modification through the mechanisms of the remelting and microdrilling by laser have been performed on the AZ31 surface. The characterization of the selected surfaces in terms of roughness variations, changes in wettability, oxides formation and geometry of the obtained structures, led to the identification of a limited number of conditions that will be further investigated.

Development of an acquisition system for high deformation barriers using low-cost IMU sensors and Image Analysis

Meso and full-scale impact tests have historically been used to assess the capacity of high-deformation barriers used against natural hazards and to validate numerical models. However, the data acquired from such experiments is typically limited to peak barrier elongation and occasionally force-time-displacement curves acting on specific structural elements. In rare occasions, complex and expensive procedures such as 4D photogrammetry are employed. Herein, a procedure is developed to obtain a barrier deformation data in three dimensions using low-cost MEMS sensors and consumer-grade cameras. The procedure is validated against LIDAR data for both quasi-static and dynamic conditions