4,279 research outputs found
Synovial Lubrication Modeling of Total Hip Replacements Using Musculoskeletal Multibody Dynamics
No full textNowadays the biotribology of the human articulations is a challenging topic in the framework of biomechanics research. A human synovial joint is a complex tribological system which is able to minimize friction and wear of the articulated cartilage surfaces, thanks to the mix of particular natural lubrication regimes which are established within the synovial membrane. Mainly due to the aging process, the cartilage covering the bones linked by the synovial joint tends to deteriorate, causing direct bone-to-bone contact and joint wear: the synovial joint diseases are responsible for loss of mobility, pain and tissues’ inflammation. The replacement of the worn natural joint with a prosthesis is actually needed, so a detailed tribological analysis of the artificial implant has to be conducted in order to predict the artificial joint wear and to maximize its duration.
While the in vitro approach is obviously reliable because it is based on experimental tests, the in-silico analysis is surely cheaper but it needs a deep and detailed mathematical and physical description of the analysed phenomena.
In this chapter the works produced by the authors are presented and the biotribology of the total hip replacements is discussed. In particular, once the numerical modelling of the synovial mixed elasto-hydrodynamic lubrication referred to the artificial hip joint is analysed, the influence of the joint configuration in terms of load and relative motion on its tribological state is introduced as the output of a pure mechanical problem associated with the human musculoskeletal system. The kinematics of the musculoskeletal system plays a key role within the joint tribological analysis, because it defines its dynamical behaviour and, in dependence on the muscular actions, generates the joint reactions which couple the articulations and affect its lubrication/contact state.
A multibody model of the human lower limb is shown and the inverse dynamics of the system subjected to a particular kinematics is described and solved. The aim of this chapter is to propose an algorithm characterised by a direct workflow which starts from the musculoskeletal kinematics and, coupling the multibody and the lubrication models, leads to the calculation of interesting tribological quantities. The proposed approach can be established as a powerful in silico tool adaptable to a particular subject and to several kinematics, in order to analyse the artificial joint tribology of customized implants
Preface Proceedings of ITS-IFToMM 2024 5th International Tribology Symposium of IFToMM
No full textThis book presents the proceedings of the 5th International Tribology Symposium of IFToMM (ITS-IFToMM 2024), held in Salerno, Italy, on May 6th-8th, 2024, jointly with the 9th AIT (Italian Tribology Association) Workshop “Tribology and Industry”. It includes peer-reviewed papers on the latest advances in tribology, discussing topics such as friction, wear, lubrication, lubricants, biotribology, tribomaterials, solid lubricants, surface engineering, tribotesting, tribological design and optimization of machine components, modeling in tribology, contact mechanics, micro/nanotribology, tribology in power generating systems, metal working tribology, tribology in road transport and tribology in medicine. A valuable, up-to-date resource, it offers an essential overview of the subject for scientists and practitioners alike and inspires further investigations and research
Real contact area and friction: an overview of different approaches
No full textThe aim of this chapter is to show and analyze and discuss the results obtained by the Finite Element Model (FEM) in the calculation of the Real Contact Area (RCA) of rough contacts with the presence of friction which plays a key role in mechanical contacts, for its relationship with other variables such as adhesion, wear, etc. The results of the simulations were compared with the outcomes obtained from three consolidated statistical approaches found in scientific literature: the Kogut and Etsion; Cohen, Kligerman and Etsion; and Li, Etsion and Talke models. The investigated conformal coupling consists of rigid smooth plane against a rough deformable plane shaped by a series of hemispheres which represent the surface asperities. A total of 15 samples with different mechanical properties and arithmetical roughness values were considered. The results of the FEM model, obtained in hypothesis of absence of asperities interaction, were achieved in terms of RCA, contact pressure, asperities deformation
I promessi sposi
No full textdi Alessandro Manzoni nelle due edizioni del 1840 e del 1825 raffrontate tra loro dal Prof. Riccardo Folli ; precede una lettera di Ruggiero BonghiVol. 2: quarta edizioneXXXII, 369 S., [3] Bl., 364 S., [1] Bl
Inexact Bregman iteration with an application to Poisson data reconstruction
No full textThis work deals with the solution of image restoration problems by an
iterative regularization method based on the Bregman iteration. Any iteration of this
scheme requires to exactly compute the minimizer of a function. However, in some
image reconstruction applications, it is either impossible or extremely expensive to
obtain exact solutions of these subproblems. In this paper, we propose an inexact
version of the iterative procedure, where the inexactness in the inner subproblem
solution is controlled by a criterion that preserves the convergence of the Bregman
iteration and its features in image restoration problems. In particular, the method
allows to obtain accurate reconstructions also when only an overestimation of the
regularization parameter is known. The introduction of the inexactness in the iterative
scheme allows to address image reconstruction problems from data corrupted by
Poisson noise, exploiting the recent advances about specialized algorithms for the
numerical minimization of the generalized Kullback–Leibler divergence combined with
a regularization term. The results of several numerical experiments enable to evaluat
The Importance of Uncertainty in the Noise Pollution Measurements
No full textThe commentary aims to discuss the importance of uncertainties determination in the measurement of noise pollution focusing the attention on the variability of the measure and as a source of uncertainty and offers an overview of the actual research results trends
Keynote Speech: "Predicting total hip replacement wear: recent in-silico developments combining synovial lubrication and multibody dynamics
No full textThe aim of this keynote was to show the latest research achievements obtained at the Department of Industrial Engineering of the University of Salerno by the research group leading by the Author, in the framework of the computational (bio) tribology and biomechanics applied to artificial human synovial joints.
Main aim of the research was to accurately predict the in-silico wear of artificial implants, modelling the complex tribological phenomena acting in the joints due to the synovial lubrication considering unsteady loading of the joint.
With reference to the Total Hip Replacements (THR), in this lecture were underlined recent computational approaches obtained by merging multibody models, solving the inverse dynamics of musculoskeletal systems, and synovial mixed elasto-hydrodynamic lubrication models. The effectiveness of the proposed analysis consists in the possibility of examining many physical activities, characterized by cyclic kinematic and loading joint conditions like running, swimming and sport in general, in order to predict the implant duration overcoming excessive time and money consumption due to the experimental set-up and investigation, moreover taking into account the complexity of a mixed lubrication model adaptable to several synovial fluid lubrication properties and that considers the surfaces’ contact. The achieved results, mainly in terms of wear volume prediction, were compared with respect to the in-vitro experiments developed by considering standardized (ISO 14242-3) joint loading. The obtained results were very promising, encouraging the research team toward the investigation and the development of more and more accurate models
Noise Pollution: What the Scientific Community Can Do?
No full textral environmental dif culties such as waste management, greenhouse gas emissions, wastewater and environmental noise pollution.
A study made by the World Health Organization (WHO) underlines that noise pollution is second among a series of environmental “stressors” for their public health effects, having it auditory and non-auditory high health impacts.
The question is: what the scientic community can do to control of noise exposure
Key Note Speech: A SURVEY OF RECENT COMPUTATIONAL APPROACHES FOR THE IN-SILICO WEAR DETERMINATION IN TOTAL HIP REPLACEMENTS CONSIDERING SYNOVIAL LUBRICATION EFFECTS AND MUSCULOSKELETAL DYNAMICS
No full textThe aim of this survey was to briefly describe the latest research achievements obtained at the Department of Industrial Engineering of the University of Salerno by the research group leading by the Author, in the framework of the computational (bio) tribology and biomechanics, applied to artificial human synovial joints.
In the framework of biotribology a challenging and interesting topic is represented by the possibility to predict in-silico the wear of the artificial implants, considering and modelling also the complex phenomena acting in the joints due to the synovial lubrication.
With reference to the Total Hip Replacements (THR), in this manuscript were underlined recent computational approaches obtained by merging multibody models, solving the inverse dynamics of musculoskeletal systems, and synovial mixed elasto-hydrodynamic lubrication models. The achieved results, mainly in terms of wear volume prediction, were validated respect to in-vitro experiments considering standardized joint loading and are very promising, encouraging the research team toward the investigation and the development of more and more accurate models
Squeaking in Total Hip Arthroplasty: a Scoping Review on a Biotribological Issue
No full textCeramic-on-ceramic bearings for total hip arthroplasty (THA) are considered to be the best choice to avoid problems such as osteolysis and wear, which are mainly caused by soft bearings. Recent concerns have been raised because of some clinical reports on the presence of audible noise (squeaking) in some ceramic-on-ceramic total hip replacements. The occurrence of squeaking in some patients is related to a complex of tribological and dynamical interactions in the prosthesis components. Such mechanisms include edge loading, stripe wear, impingement, synovial lubrication film ruptures, third body particles, ceramic fracture, and vibrational modes of the entire structure. The resonance of metallic parts can produce noise in the human audible frequencies range, hence the implant metallurgic composition, the design and the tribological behavior play a key role. The aim of this scoping review is to map and summarize the available scientific evidence on hip squeaking, highlighting the theoretical fundamentals on the genesis of the phenomenon with its causes and effects, the adopted numerical approaches together with in-situ experiments, results about squeaking analysis of total hip replacements listed in order of time so that it is easier follow the progress of science and the research future directions. Hence the scope is to provide a comprehensive but at the same time exhaustive document that could help researchers, students, etc. to study more deeply this field
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