Papers by Maria Cristina Valigi
The paper represents an extension of a previous work where the problem of chatter in a rolling mi... more The paper represents an extension of a previous work where the problem of chatter in a rolling mill producing advanced high-strength steels (AHSS) was investigated by a combination of a linear lumped parameter model and the slab analysis. In this paper the authors show the detailed experimental study of the problem with a complete description of all the phases related to the vibrational investigation that lead to the solution of the problem. Furthermore, a different model based on the Orowan’s method together with a nonlinear model of the rolling mill is presented and simulations are performed.
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Chatter in rolling mills is the undesirable vibration observed in most of the rolling mills opera... more Chatter in rolling mills is the undesirable vibration observed in most of the rolling mills operating at high speed and rolling thin strip. In this work the authors discuss some problems relative to the vibrations occurring in a S6-high cold rolling mill. It can result in not good surface finish for some applications and, rare cases, in gauge variations in the rolled strip and it is considered to be the result of interaction between rolling mill structure and rolling-process. Three basic types of chatter can be classified in rolling mills: torsional, third-octave mode, and fifth-octave-mode chatter. S6-high rolling mill is an innovative mode to work the steel: it allows the use of very small work rolls laterally guided by individually adjustable side support rolls, which are supported by two rows of roller bearings mounted in cassettes. It has six rolls able to roll steel strip coming directly from hot rolling mill train. A proposed solution based on empirical observations, vibratio...
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Augmenting the human body with supernumerary robotic extra limbs is a cutting-edge research topic... more Augmenting the human body with supernumerary robotic extra limbs is a cutting-edge research topic with many potential applications. In this paper we focus on human hand augmentation with robotic extra fingers, used in particular as compensatory and rehabilitation tool for people with upper limb impairments. We designed and developed devices composed of single or multiple extra fingers. Underactuation and compliance are design choices that can reduce the device complexity and weight, maintaining the adaptability to different grasped objects. Each finger is composed of modular phalanges and is actuated with a single tendon. Interphalangeal joints include a passive elastic element that allows restoring the initial reference configuration when the tendon is released. The stiffness of each passive element can be customized in the manufacturing process and can be chosen according to a desired closure movement of the fingers. This paper summarizes the main design principles and the main ap...
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Chatter in rolling mills is the undesirable vibration observed in most of the rolling mills opera... more Chatter in rolling mills is the undesirable vibration observed in most of the rolling mills operating at high speed and rolling thin strip. In this work the authors discuss some problems relative to the vibrations occurring in a S6-high cold rolling mill. It can result in not good surface finish for some applications and, rare cases, in gauge variations in the rolled strip and it is considered to be the result of interaction between rolling mill structure and rolling-process. Three basic types of chatter can be classified in rolling mills: torsional, third-octave mode, and fifth-octave-mode chatter. S6-high rolling mill is an innovative mode to work the steel: it allows the use of very small work rolls laterally guided by individually adjustable side support rolls, which are supported by two rows of roller bearings mounted in cassettes. It has six rolls able to roll steel strip coming directly from hot rolling mill train. A proposed solution based on empirical observations, vibratio...
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Sensors
This paper focuses on new instrumented trolleys, allowing automated 3D inspection of railway infr... more This paper focuses on new instrumented trolleys, allowing automated 3D inspection of railway infrastructures, using optical scanning principles and devices for defects and damage evaluation. Inspection of rolling components is crucial for wear evaluation and to schedule maintenance interventions to assure safety. Currently, inspection trolleys are mainly instrumented with 2D contact or optical sensors. The application of 3D non-contact digitizers proposed in this paper allows for a quick and more complete monitoring of the health conditions of railways, also in combination with a proper procedure for automatic 3D inspection. The results of the experimental tests using 3D portable optical scanners on railways are compared with results obtained by a trolley instrumented with 2D contact sensors. The results demonstrate the effectiveness of the trolleys mounting 3D handheld optical digitizers with proper automated software inspection procedures.
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Lubricants
In this paper, a numerical model for predicting the working parameters of the cold rolling mill p... more In this paper, a numerical model for predicting the working parameters of the cold rolling mill process in full film lubrication is presented. The model is useful from an industrial point of view, because it can forecast the thickness reduction of the metal sheet and the pressure trend, so that the rolling mill process parameters can be regulated to obtain a specific output thickness. Experimental tests were performed, and results are compared to the theoretical ones resulting from the model. The novelty of the proposed model is that it combines Orowan’s theory for the plastic deformation analysis with the Reynolds equation in full film lubrication and the continuity conditions. The lubricant flow and viscosity are studied, taking in account their dependence on pressure and temperature. The proposed model describing the full film regime is also compared to another one, previously proposed by the authors, based on the well-known slab analysis and sharing with it the representation of...
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Tribology International, 2016
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Robotics
Augmenting the human hand with robotic extra fingers is a cutting-edge research topic and has man... more Augmenting the human hand with robotic extra fingers is a cutting-edge research topic and has many potential applications, in particular as a compensatory and rehabilitation tool for patients with upper limb impairments. Devices composed of two extra fingers are preferred with respect to single finger devices when reliable grasps, resistance to external disturbances, and higher payloads are required. Underactuation and compliance are design choices that can reduce the device complexity and weight, maintaining the adaptability to different grasped objects. When only one motor is adopted to actuate multiple fingers, a differential mechanism is necessary to decouple finger movements and distribute forces. In this paper, the main features of a wearable device composed of two robotic extra fingers are described and analyzed in terms of kinematics, statics, and mechanical resistance. Each finger is composed of modular phalanges and is actuated with a single tendon. Interphalangeal joints ...
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Materials
It is well known that wear occurring in polyethylene menisci is a significant clinical problem. A... more It is well known that wear occurring in polyethylene menisci is a significant clinical problem. At this regard, wear tests on biomaterials medical devices are performed in order to assess their pre-clinical performance in terms of wear, durability, resistance to fatigue, etc. The objective of this study was to assess the wear of mobile total knee polyethylene inserts after an in vitro wear test. In particular, the wear behavior of mobile bearing polyethylene knee configurations was investigated using a knee joint wear simulator. After the completion of the wear test, the polyethylene mobile menisci were analyzed through a consolidated procedure by using 3D optical scanners, in order to evaluate the 3D wear distribution on the prosthesis surface, wear depths, wear rates, amount of material loss and contact areas. The results in terms of wear rates and wear volumes were compared with results of gravimetric tests, finding equivalent achievements.
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Photonics
3D vision systems are more and more required in a large variety of applications and mostly for me... more 3D vision systems are more and more required in a large variety of applications and mostly for mechanical and medical purposes. This paper presents the study and realization of a prototype of a structured light automated tilt-rotational 3D vision system for high-quality reconstructions of components of various sizes and in cases of freeform and complex surfaces. The main goal of this research work was to develop an instrument with the following main novelties: configurability for different object sizes, high precision and resolution levels and ability to automatically generate the mesh representing the full scanned objects without any intervention of the operator by means of a 2 degrees of freedom automated tilt-rotational mechanical positioning system. A detailed analysis of the instrument and the procedures and results of the performance tests are presented, together with the examination of possible strategies to obtain a better performance, especially by the calibration and the s...
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Materials
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A simulation environment for the dynamics of planetary concrete mixers has been developed, it is ... more A simulation environment for the dynamics of planetary concrete mixers has been developed, it is a model based method using the lumped parameters analysis and integrating the theory of classical mechanics and life analysis. The aim of this work is to give a fast and easy to use tool capable of predicting the behaviour and the useful life of concrete mixers through geometrical and physical parameters. Simulations were conducted in steady states and in perturbed conditions. The gear reduction unit is the part of the mixer under most stress. Results were compared with data obtained from costumers on building sites.
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Proceedings of the ASME 2015 International Mechanical Engineering Congress & Exposition, Nov 2015
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Tribology International, 2016
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. A mechanical face seal for automotive applications that under particular conditions generates u... more . A mechanical face seal for automotive applications that under particular conditions generates undesired acoustic emissions is studied. The work has the aim to demonstrate the reason of this noise.
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. Performance optimization of a mixer is an issue of great significance in many industrial techno... more . Performance optimization of a mixer is an issue of great significance in many industrial technologies: the wear is one of the main phenomena to forecast and test during the design and working of mechanical components, because, if mal-designed, they could be breakage and the machine working compromised. In this paper the authors present the wear problem of the planetary vertical concrete mixer in which the mixer components more suffering wear are the blades. In order to study the wear problem some mixing process models existing in literature are described [1],[2],[3]. The factors influencing mainly blades wear are: kinematics, friction between slurry and blades, friction due to the leakage between vessel and blades and also an inadequate use of machine. In addiction the authors study the movement impressed to the mixer by the epicicloydal gear and the kinematics analysis of blades and arms. As consequence of the kinematics analysis a new shape of blade is proposed.
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Lecture Notes in Mechanical Engineering, 2013
ABSTRACT S6-high rolling mill is an advanced mode to work the steel: it allows the use of very sm... more ABSTRACT S6-high rolling mill is an advanced mode to work the steel: it allows the use of very small work rolls laterally guided by individually adjustable side support rolls, which are supported by two rows of roller bearings mounted in cassettes. In this paper the vibrations generated in a S6-high cold rolling mill are analyzed with the aim to investigate the problem of skid marks generation. Such marks are regular, parallel marking across the width of strip metal that not only significantly affects the mill performance, but also reduces surface quality of the strip steel. The defects of the strip are the consequence of insurgence of vibrations, generically denominated ‘chatter’. The analyzed rolling mill has six rolls able to roll steel strip coming directly from hot rolling mill train. The purpose of the present work is to identify the reason of the excitation in order to limit the problem. A solution based on empirical observations, vibration analysis and considerations of a model is proposed.
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Tribology International, 2014
ABSTRACT Mechanical face seals are used with most types of mechanical equipment, thus understandi... more ABSTRACT Mechanical face seals are used with most types of mechanical equipment, thus understanding the behavior of sealing systems is required for improved performance. The present paper investigates a type of seal utilized in automotive cooling water pumps, which, under particular service conditions, generates undesired acoustic emissions and manifests malfunctioning. The problem is examined through a lumped parameter model together with a mixed friction tribological model. Numerical simulations demonstrate that the phenomenon is caused by the insurgence of stick-slip vibrations during shaft deceleration. In addition, the stability threshold is investigated and the influences of some design parameters are evaluated.
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Simulation Modelling Practice and Theory, 2007
A simulation environment for the dynamics of planetary concrete mixers has been developed, it is ... more A simulation environment for the dynamics of planetary concrete mixers has been developed, it is a model-based method using the lumped parameters analysis and integrating the theory of classical mechanics and life analysis.The aim of this work is to give a fast and easy to use tool capable of predicting the behaviour and the useful life of concrete mixers through
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Papers by Maria Cristina Valigi