G. Totis

University of Udine | UNIUD · Polytechnic Department of Engineering and Architecture

CoCr alloys are widely used as human implants because of both their superior corrosion resistance and superior mechanical properties (fatigue, wear resistance, etc.) respect to other metal alloys used in biomedical field. In particular, CoCrW alloys are used mainly to produce dental implants. In this study, the effects of thermal treatment on the c...

AISI 316 L stainless steel is widely used as material to produce components by means of additive manufacturing. To increase the circular economy, the powders are collected and re-used after the printing process, thus the effect of powder recycling on microstructure and properties of printed components is of the utmost importance. This work focused...

Measuring the cutting force when milling slender/thin-walled parts is difficult because of the large and long-lasting structural vibrations that cause inertial disturbances in the measured signals. Under these conditions, signal filtering is the only option to significantly extend the dynamic bandwidth of the device above 3 kHz. Non-parametric filt...

The effect of post-processing heat treatment on the corrosion behavior of AISI 316L stainless steel manufactured by laser powder bed fusion (L-PBF) is investigated in this work. Produced stainless steel was heat treated in a broad temperature range (from 200 °C to 1100 °C) in order to evaluate the electrochemical behavior and morphology of corrosio...

The aim of this work is to describe some experiences of additive manufacturing - AM - for nuclear fusion applications. In this paper, a first case study is introduced concerning the realization of a scale prototype of an in-vessel component for tokamak nuclear fusion reactors, a wishbone of the deflector made in Ti-6Al-4V alloy. The 3D model of the...

Background Metal lattice structures obtained through Selective Laser Melting may increase the strength-to-weight ratio of advanced 3D printed parts, as well as their damping properties. Recent experimental results showed that AlSi10Mg and AISI 316L lattices are characterized by higher Rayleigh damping coefficients with respect to the fully dense ma...

The growing interest in additively manufactured metals for structural purposes renders their mechanical characterisation of foremost importance. In that context, low cycle fatigue (LCF) properties are lacking, especially for the AISI 316L stainless steel which is the material studied in this work alongside its elastoplastic response. Corroborating...

In order to characterize cutting mechanics during high-speed milling and micromilling applications, high-end piezoelectric dynamometers with a wide frequency bandwidth are necessary. Nevertheless, when installed into the machine tool their signal bandwidth is limited by the dynamic behaviour of the machining system. Thus, special filters have to be...

Hybrid metal and extrusion bonding (HYB) is an emerging solid-state welding technique that was developed about ten years ago. HYB exploits the fundamental idea of the well-established friction stir welding (FSW) technology, but a filler material is employed to enhance control of the weld microstructure and mechanical properties of the joint. HYB an...

The recently adopted Medical Device Regulation (MDR) has finally entered into force on 26 May 2021. As innovation and especially the advent of customized prostheses has deeply modified many surgical procedures in our discipline, it is imperative for the contemporary surgeon to become aware of the impact that the MDR will have on many aspects, inclu...

Additive manufacturing technology with metal powder has facilitated the production of innovative and even more complex heat sinks. The layer-additive process offers a wide range of geometries that may be exploited for advanced cooling purposes and the final identification of the best heat sink configuration has to deal with other constraints impose...

The feasibility of a pressure vessel shape optimization is here investigated. An analytical procedure based on calculus of variations is used for the shape optimization of a naturally closed pressure vessel aiming at either minimizing the mass or maximizing the volume under structural integrity constraints. The obtained shapes are ellipsoids with v...

Modern additive manufacturing technologies allow the creation of parts characterized by complex geometries that cannot be created using conventional production techniques. Among them the Selective Laser Melting (SLM) technique is very promising. By using SLM it is possible to create lightweight lattice structures that may fill void regions or parti...

Chatter vibrations arising during machining operations are detrimental for cutting process performance, since they may cause poor surface quality of the machined part and severe damages to machine tool elements. Passive approaches for chatter suppression are based on the integration of special mechanical components with high-damping properties with...

Modern additive manufacturing technologies allow the creation of parts characterized by complex geometries that cannot be created using conventional production techniques. Among them the Selective Laser Melting (SLM) technique is very promising. By using SLM it is possible to create lightweight lattice structures that may fill void regions or parti...

Nowadays, advanced metal components with high geometrical complexity can be 3D printed by using the Selective Laser Melting (SLM) technology. Despite SLM resolution and accuracy are generally limited to some tenths of mm, it should be possible to produce finer and more precise details by applying lasers with a small spot diameter. However, to prese...

Advanced piezoelectric dynamometers with a wide frequency bandwidth are required for cutting force measurement in high-speed milling and micromilling applications. In many applications, the signal bandwidth is limited by the dynamic response of the mechanical system, thus compensation techniques are necessary. The most effective compensation techni...

After more that 60 years of investigation, chatter vibrations in metal cutting are still a major cause for poor surface finish and machine tool damage. In order to avoid undesired machining conditions, chatter prediction algorithms may be applied to draw stability charts that allow a preliminary identification of the safe areas. Nevertheless, the s...

AISI 316L is a material that is widely used in several technological applications. This material is also suitable for use in the 3D printing of metal components. In this study, the wear behavior of AISI 316L steel produced using Selective Laser Melting technology was investigated in order to determine its metallurgical evolution under high Hertzian...

Regenerative chatter vibrations arising during machining operations are a severe problem affecting the manufacturing production of high-precision mechanical components. A relatively deep understanding of this phenomenon when the cutting tool has equally spaced cutting teeth without runout has been achieved by now. However, real cutting tools are al...

This work investigates the electrochemical behaviour of an AISI 316L stainless steel produced by selective laser melting (SLM) and compares its behaviour with that of wrought stainless steel with similar chemical composition. The SLM stainless steel specimens are tested in the as‐produced condition without stress relief or recrystallization heat tr...

Lattice structures are of great interest for robotic applications due to their lightweight and their mechanical characteristics such as the stiffness and damping. However, lattice structures require special production processes such as 3D metal printing. In this research, lattice structures obtained by Selective Laser Melting of Aluminum were chara...

In order to increase the material removal rate in milling, advanced cutting tools with complex geometry are typically applied under extreme cutting conditions which may trigger undesired chatter vibrations of the machining system. Recently some dynamic milling models were proposed in the literature which take into account the higher geometrical com...

Self-excited anomalous vibrations called chatter affected milling operations since the beginning of the industrial era. Chatter is responsible for bad surface quality of the machined part and it may severely damage machining system elements. Although the significant advances of recent years, state of the art dynamic models are not yet able to compl...

The problem of undesired self-excited chatter vibrations in milling is very common. However, only in the last two decades some significant achievements for the theoretical understanding of this intricate phenomenon have been accomplished. Nevertheless, state of the art dynamic models are still not able to completely explain milling dynamics and cha...

In the automotive market, there is a strong interest for the production of sidewinder keys made of Nickel-coated Nickel-Silver alloy. The Nickel coating improves wear resistance and brightness of the key, nevertheless it reduces the machinability and the tool life when milling the key groove is short. In this work, several innovative tool coatings...

In this paper an innovative algorithm to reproduce non-uniform, photorealistic, gray-scale images on large surfaces, using an ordinary industrial spray-painting robot is proposed. The algorithm splits the process into a set of iterative steps with decreasing spray-gun stroke diameters. Thus, it can efficiently build up the image starting with large...

Automation of engineering procedures for the development of new manufacturing processes is of great importance in modern competitive conditions. For example, metalworking companies would greatly benefit from the development of methods for automatic generation, testing and optimization of part programs for machining operations. Indeed, the generatio...

Nowadays, high levels of automation, integration and flexibility are required to increase the competitiveness of manufacturing industries. In this perspective, an increasing interest in unmanned, intelligent machining systems has emerged. Ideally, future production systems will be designed to automatically perform complex tasks, such as planning an...

When machining high precision mechanical parts, self-excited chatter vibrations must be absolutely avoided since they cause unacceptable surface finish and dimensional errors. Such unstable vibrational phenomena typically arise when the overall machining system stiffness is relatively low, as in the case of internal turning operations performed wit...

Injection molding is a complex process regulated by many factors (injection speed, injection pressure, melt temperature, mold temperature, and others). Despite, process control and parameter optimization, it is often difficult to replicate thermoplastic components with adequate dimensional accuracy, especially in the case of geometries with high as...

Continuous innovation of products and optimization of manufacturing processes are of fundamental importance for preserving competitiveness. In the last decades, several approaches based on analytic models for optimization of basic machining operations such as cylindrical turning and face milling have been developed. However, the analytic approaches...

In modern industry conditions, it is very important to develop methodologies for reducing costs and achieving the maximum quality of machined parts, especially considering the dimensional accuracy of workpieces. Geometrical and dimensional inaccuracies are due to several factors, such as workpiece and tool deformation during machining, thermal dist...

Tool geometry optimization, workpiece material characterization, process monitoring and optimization are based on the measurement of cutting forces by using machining dynamometers. Commercial dynamometers cover a wide range of machining applications, nevertheless there is a lack of measuring devices suitable for investigating milling and drilling a...

Chatter is a vibrational problem affecting machining operations, which may cause bad surface quality and damages to the machining system. In recent decades, several techniques for avoiding chatter onset were developed. Among other techniques, the continuous modulation of spindle speed during the cutting process (also called Spindle Speed Variation...

Preventive evaluation of costs is strategic for the whole manufacturing industry and especially for companies whose manufacturing technology is based on expensive machinery, tools and fixtures, such as injection moulding of aluminium. Preventive evaluation of production costs and time is even more relevant for the mould producer, in order to quickl...

Molybdenum is a refractory metal which is recommended for advanced engineering applications requiring high mechanical strength and corrosion resistance at extremely high temperatures. However, Molybdenum-based alloys are generally difficult to machine, due to their superior physical and mechanical properties, usually requiring effective refrigerati...

Nowadays, the availability of reliable mathematical models of machining system dynamics is a key issue for achieving high quality standards in precision machining. Dynamic models can indeed be applied for tooling system design, preventive evaluation of cutting process stability and optimization of cutting parameters. This is of particular concern i...

When machining high precision mechanical parts, self-excited chatter vibrations must be absolutely avoided since they cause unacceptable surface finish and dimensional errors. Such unstable vibrational phenomena typically arise when the overall machining system stiffness is relatively low, as in the case of internal turning operations performed wit...

Accurate and reliable measurement of cutting forces in turning is essential for tool geometry, tool trajectory and cutting parameters optimization, as well as for tool condition monitoring and machinabilty testing. In this work, an innovative dynamometer for triaxial cutting force measurement in turning, specifically designed to be applied at a mil...

Cutting force information may be used for several tasks, such as tool design and trajectory optimization, tool condition monitoring, machinability testing and many others. Accordingly, cutting force measuring has become a crucial activity aimed at enhancing process performance. In this work, the development of an innovative rotating dynamometer for...

The development of a chatter detection system based on multiple sensors and suitable for application in industrial conditions was investigated in this paper. The signals obtained from a monitoring system composed of accelerometers mounted on the machine head and an axial force sensor were processed by using advanced signal analysis techniques such...

The reliability of conventional chatter prediction algorithms is limited by the inaccuracy of machining system dynamic models. In this paper, a new probabilistic algorithm for a robust analysis of stability in milling, which performs the stability analysis on an uncertain dynamic milling model, is presented. In this approach, model parameters are c...

Kurzfassung Inwieweit eine dreidimensionale, piezoelektrische Einzelschneidenkraftmessung an einem Messerkopf umsetzbar ist, zeigen die Ergebnisse der Forschungsarbeiten am Werkzeugmaschinenlabor (WZL) der RWTH Aachen. Anhand von Voruntersuchungen, im Analogieprozess Drehen, wird exemplarisch der Aufbau eines Messerkopfdynamometers untersucht. Durc...

In which way a 3D piezoelectric force measurement at each cutting edge can be integrated into a face cutter, is shown by the results of the Laboratory for Machine Tools and Production Engineering (WZL) in RWTH Aachen. In analogy, the setup of one milling dynamometer has been analysed exemplary within turning trials. By reduction of masses and lever...

The development of a chatter detection system for application in industrial conditions was investigated. Several sensors—rotating dynamometer, accelerometers, acoustic emission and electrical power sensors—were compared to determine which signals are most sensitive to chatter onset. The signal characteristics both in time and frequency domain were...

Manufacturers’ main targets (high productivity, high quality and low costs) are found in a complex economic environment demanding flexibility and spirit of adaptability. The achievement of these goals is strongly dependent on the logistic technological architecture making up the planning stage, which regulates the production process. First, the int...