62,950 research outputs found
Wear Assessment and Reduction for Sustainability: Some Applications
No full textWear assessment and reduction are topics of great significance in green tribology as part of the Sustainable Development Goals. In fact, minimization of wear plays a fundamental role in tribology and sustainability, because it promotes enhancement of useful life of components, limitation of waste material and dangerous debris and energy saving. When these goals are achieved in biomechanical applications, they result in improvements of health and life quality of human beings (SDG3). In the industrial field the main result of wear assessment and optimized design of components and processes is the reduction of pollution and minimization of energy dissipation and costs (SDG9, SDG12). In this paper the analysis of different wear assessment workflows and techniques is presented, and advantages in terms of sustainability are discussed. Some case studies are presented to demonstrate how wear assessment helped achieving sustainable products and applications. An example of redesign of mixing blades, based on digital wear evaluation techniques and application of a power consumption prediction model is presented. Experimental results show that the new design results in a longer durability of the blades and in a lower power consumption. Another case study regarding the evaluation of damage of teeth due to friction is presented. Results were used to make a diagnosis and treat the patient to prevent further teeth damages
GREEN TRIBOLOGY: WEAR EVALUATION METHODS FOR SUSTAINABILITY PURPOSES
No full textA sustainable development of machines, mechanisms and processes is one of the main goals of the 2030 agenda for Sustainable Development Goals (SDG). Currently, approximately 23% of the global energy consumption depends on inefficient performance of the tribological contacts. Particularly, about 20% of the energy loss is due to friction issues, and the remaining part is employed to remake and replace worn parts or to fix other wear-related failures. Green tribology is a crucial discipline for enhancing sustainability, because it is oriented at minimizing friction and wear phenomena. Therefore, wear evaluation is a fundamental starting point for designing new production or diagnostic techniques oriented to sustainability. In the industrial field this allows the optimization of design and processes, leading to reduction of pollution, minimization of energy dissipation and costs (SDG9, SDG12). In the field of human life, this can give a strong contribution to prevent damages, extending resistance and useful life of natural or prosthetic biocomponents, with an improvement of health and better life generation (SDG3). This paper presents and discusses various wear evaluation methods and related workflows with different purposes and benefits for sustainability. Some case studies demonstrate that wear evaluation substantially contributes at creating sustainable products and applications
Do Exostoses Correlate with Contact Disfunctions? A Case Study of a Maxillary Exostosis
No full textA maxillary exostosis is a benign overgrowth of bone that occurs on the outer or facial surface of the maxilla and is usually located near the premolar or molar teeth. This paper investigates the correlation between the presence and growth of jaw exostoses and the oral mechanics of contact. For this purpose, a case study of an upper jawbone exostosis of a female patient was considered. 3D models of the patient’s cranial bones were extracted from 2D computerized tomography (CT) data and were analyzed by proper software. A contact congruence evaluation based on the Winkler contact model was performed, and results were presented in terms of indentation maps and load distributions. Results were correlated with the theory of bone remodelling by Wolff
A numerical procedure based on orowan's theory for predicting the behavior of the cold rolling mill process in full film lubrication
No full textIn 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 the lubrication regime, the mathematical procedure, and the boundary conditions.
The results show that the proposed model provides a better prediction of the working parameters
with respect to the model based on the slab analysi
Sustainable Design of Machine Guards
No full textPromoting sustainable industrialization by fostering safety of machinery is a fundamental and ethical approach. Working in safe conditions is essential to comply with the UN’s Sustainable Development Goals (SDG) and, in particular, with SDG3 and SDG8, therefore making machines safer during their operation becomes a basic aim for a more sustainable society. From this perspective, the influence of certain design or/and physical parameters on machine safety must be necessarily analyzed even if standards do not consider them, with obvious advantages also in terms of industrial innovation, complying with SDG9. The present work refers to the study of machine protection panels to characterize their ability to resist ballistic penetration. In ISO 14120-Annex B, the methodologies and standards for the design and validation of machine guards are described, but the influence of many characteristics and parameters has not been considered to characterize the protection performance. This paper presents some results in the terms of withstanding capacity of polycarbonate panels to ballistic penetration considering the size of the guards and their ageing condition due to solar radiation. The analyses for the inspection of the through-hole cracks and deformation of the panels have been performed with an innovative method by using a metrology grade 3D optical scanner and 3D inspection techniques
X-Ray, Thermogravimetric and Electron Spin Resonance Study of the ReOx-TiO2 System M. Valigi, D. Cordischi, D. Gazzoli, C.P. Keijzers and A.A.K. Klaassen J. Chem. Soc., Faraday Trans. I, 77, 1871, 1981
No full textDesign of soft grippers with modular actuated embedded constraints
No full textUnderactuated, modular and compliant hands and grippers are interesting solutions in grasping and manipulation tasks due to their robustness, versatility, and adaptability to uncertainties. However, this type of robotic hand does not usually have enough dexterity in grasping. The implementation of some specific features that can be represented as “embedded constraints” allows to reduce uncertainty and to exploit the role of the environment during the grasp. An example that has these characteristics is the Soft ScoopGripper a gripper that has a rigid flat surface in addition to a pair of modular fingers. In this paper, we propose an upgraded version of the Soft ScoopGripper, developed starting from the limits shown by the starting device. The new design exploits a modular structure to increase the adaptability to the shape of the objects that have to be grasped. In the proposed device the embedded constraint is no rigid neither unactuated and is composed of an alternation of rigid and soft modules, which increase versatility. Moreover, the use of soft material such as thermoplastic polyurethane (TPU) reduces the risk of damage to the object being grasped. In the paper, the main design choices have been exploited and a finite element method (FEM) analysis through static simulation supports a characterization of the proposed solution. A complete prototype and some preliminary tests have been presented
Contact mechanics analysis of a soft robotic fingerpad
No full textThe precision grasping capabilities of robotic hands is a key feature which is more and more required in the manipulation of objects in several unstructured fields, as for instance industrial, medical, agriculture and food industry. For this purpose, the realization of soft robotic fingers is crucial to reproduce the human finger skills. From this point of view the fingerpad is the part which is mostly involved in the contact. Particular attention must be paid to the knowledge of the mechanical contact behavior of soft artificial fingerpads. In this paper, artificial silicone fingerpads are applied to the last phalanx of robotic fingers actuated by tendons. The mechanical interaction between the fingerpad and a flat surface is analyzed in terms of deformations, contact areas and indentations. A reliable model of fingertip deformation properties provides important information for understanding robotic hand performance, that can be useful both in the design phase and for defining control strategies. The approach is based on theoretical, experimental, and numerical methods. The results will be exploited for the design of more effective robotic fingers for precision grasping of soft or fragile objects avoiding damages
Knee Wear Assessment: 3D Scanners Used as a Consolidated Procedure
No full textIt 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
An Educational Test Rig for Kinesthetic Learning of Mechanisms for Underactuated Robotic Hands
No full textTeaching robotics requires interdisciplinary skills and a good creativity, providing instructions and hands-on experiences, exploiting different kinds of learning. Two kinds of learning methods are commonly used: the ‘visual learning’ and the ‘auditory learning’, recognizable by the preference of an approach for images, rather than for texts, or oral explanations. A third possible learning style is the ‘kinesthetic learning’, based on tactile activities, which is generally least exploited, both by teachers in the classroom and by students during individual study. In this perspective, the use of educational test rigs is a good practice and adds an opportunity to share a passion for robotics. The paper focuses on the realization and application of an educational test rig aimed at explaining how a differential mechanism works and how it can be applied to robotic underactuated soft grippers to move multiple robotic fingers independently of each other using just a single actuator. The differential test bench was realized by 3D printing and mounted with the help of students in high school seminaries oriented to encourage students towards robotic or mechatronic studies. This activity was very thrilling for the students and helped them to approach robotics in a natural way, exploiting kinesthetic learning as it is demonstrated by test results
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