3D Revolute Joint with Clearance in Multibody Systems

International audienceThe aim of this paper is to understand the influence of radial and axial clearance in the revolute joints on the overall performance of a circuit breaker. A circuit breaker mechanism is made of seven links, seven revolute joints with clearance in both radial and axial direction, four unilateral contacts with friction, and it has forty-two degrees of freedom. The Moreau-Jean nonsmooth contact dynamics (NSCD) numerical method is used to perform the simulations. The numerical results are validated by careful comparisons with experimental data

A nonsmooth frictional contact formulation for multibody system dynamics

We present a new node-to-face frictional contact element for the simulation of the nonsmooth dynamics of systems composed of rigid and flexible bodies connected by kinematic joints. The equations of motion are integrated using a nonsmooth generalized-α time integration scheme and the frictional contact problem is formulated using a mixed approach, based on an augmented Lagrangian technique and a Coulomb friction law. The numerical results are independent of any user-defined penalty parameter for the normal or tangential component of the forces and, the bilateral and the unilateral constraints are exactly fulfilled both at position and velocity levels. Finally, the robustness and the performance of the proposed algorithm are demonstrated by solving several numerical examples of nonsmooth mechanical systems involving frictional contact.Fil: Galvez, Javier. Université de Liège; BélgicaFil: Cavalieri, Federico José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; ArgentinaFil: Cosimo, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; Argentina. Université de Liège; BélgicaFil: Brüls, Olivier. Université de Liège; BélgicaFil: Cardona, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; Argentin

Silent polymorphisms in the RYR1 gene do not\ud modify the phenotype of the p.4898 I>T\ud pathogenic mutation in central core disease:\ud a case report

Background: Central core disease is a congenital myopathy, characterized by presence of central core-like areas in\ud muscle fibers. Patients have mild or moderate weakness, hypotonia and motor developmental delay. The disease is\ud caused by mutations in the human ryanodine receptor gene (RYR1), which encodes a calcium-release channel.\ud Since the RYR1 gene is huge, containing 106 exons, mutation screening has been limited to three ‘hot spots’, with\ud particular attention to the C-terminal region. Recent next- generation sequencing methods are now identifying\ud multiple numbers of variants in patients, in which interpretation and phenotype prevision is difficult.\ud Case presentation: In a Brazilian Caucasian family, clinical, histopathological and molecular analysis identified a\ud new case of central core disease in a 48-year female. Sanger sequencing of the C-terminal region of the RYR1\ud gene identified two different missense mutations: c.14256 A > C polymorphism in exon 98 and c.14693 T > C in\ud exon 102, which have already been described as pathogenic. Trans-position of the 2 mutations was confirmed\ud because patient’s daughter, mother and sister carried only the exon 98’s mutation, a synonymous variant that was\ud subsequently found in the frequency of 013–0,05 of alleles. Further next generation sequencing study of the whole\ud RYR1 gene in the patient revealed the presence of additional 5 common silent polymorphisms in homozygosis and\ud 8 polymorphisms in heterozygosis.\ud Conclusions: Considering that patient’s relatives showed no pathologic phenotype, and the phenotype presented\ud by the patient is within the range observed in other central core disease patients with the same mutation, it was\ud concluded that the c.14256 A > C polymorphism alone is not responsible for disease, and the associated additional\ud silent polymorphisms are not acting as modifiers of the primary pathogenic mutation in the affected patient. The\ud case described above illustrates the present reality where new methods for wide genome screening are becoming\ud more accessible and able to identify a great variety of mutations and polymorphisms of unknown function in\ud patients and their families.Fundação de Amparo a Pesquisa do Estado de São Paulo - Centro de Pesquisa, Inovação e Difusão (FAPESP-CEPID)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq-INCT)Associação Brasileira de Distrofia Muscular (ABDIM)CAPES-COFECU

A drifting impact oscillator with periodic impulsive loading: Application to percussive drilling

Peer reviewe

Load assessment and analysis of impacts in multibody systems

The evaluation of contact forces during an impact requires the use of continuous force-based methods. An accurate prediction of the impact force demands the identification of the contact parameters on a case-by-case basis. In this paper, the preimpact effective kinetic energy (Formula presented.) is put forward as an indicator of the intensity of the impact force along the contact normal direction. This represents a part of the total kinetic energy of the system that is associated with the subspace of constrained motion defined by the impact constraints at the moment of contact onset. Its value depends only on the mechanical parameters and the configuration of the system. We illustrate in this paper that this indicator can be used to characterize the impact force intensity. The suitability of this indicator is confirmed by numerical simulations and experimentsPostprint (author's final draft

Currents issues in cardiorespiratory care of patients with post-polio syndrome

Post-polio syndrome (PPS) is a condition that affects polio survivors years after recovery from an initial acute attack of the poliomyelitis virus. Most often, polio survivors experience a gradual new weakening in muscles that were previously affected by the polio infection. The actual incidence of cardiovascular diseases (CVDs) in individuals suffering from PPS is not known. However, there is a reason to suspect that individuals with PPS might be at increased risk. Method: A search for papers was made in the databases Bireme, Scielo and Pubmed with the following keywords: post polio syndrome, cardiorespiratory and rehabilitation in English, French and Spanish languages. Although we targeted only seek current studies on the topic in question, only the relevant (double-blind, randomized-controlled and consensus articles) were considered. Results and Discussion: Certain features of PPS such as generalized fatigue, generalized and specific muscle weakness, joint and/or muscle pain may result in physical inactivity deconditioning obesity and dyslipidemia. Respiratory difficulties are common and may result in hypoxemia. Conclusion: Only when evaluated and treated promptly, somE patients can obtain the full benefits of the use of respiratory muscles aids as far as quality of life is concerned.Ctr Univ Augusto Motta, Programa Posgrad Ciencias Reabilitacao, Rio De Janeiro, RJ, BrazilUniv Severino Sombra, Fac Med, Vassouras, RJ, BrazilUniv Fed Rio de Janeiro, Inst Psiquiatria, Lab Mapeamento Cerebral & EEG, BR-22290140 Rio De Janeiro, RJ, BrazilUniv Fed Fluminense, Hosp Univ Antonio Pedro, Niteroi, RJ, BrazilInst Fed Educ Ciencia & Tecnol Rio de Janeiro, Curso Fisioterapia, Rio De Janeiro, RJ, BrazilUniv Fed Piaui, Parnaiba, PI, BrazilUniv Fed Sao Paulo, Dept Neurol, Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Dept Neurol, Sao Paulo, SP, BrazilWeb of Scienc

On the contact detection for contact-impact analysis in multibody systems

One of the most important and complex parts of the simulation of multibody systems with contact-impact involves the detection of the precise instant of impact. In general, the periods of contact are very small and, therefore, the selection of the time step for the integration of the time derivatives of the state variables plays a crucial role in the dynamics of multibody systems. The conservative approach is to use very small time steps throughout the analysis. However, this solution is not efficient from the computational view point. When variable time step integration algorithms are used and the pre-impact dynamics does not involve high-frequencies the integration algorithms may use larger time steps and the contact between two surfaces may start with initial penetrations that are artificially high. This fact leads either to a stall of the integration algorithm or to contact forces that are physically impossible which, in turn, lead to post-impact dynamics that is unrelated to the physical problem. The main purpose of this work is to present a general and comprehensive approach to automatically adjust the time step, in variable time step integration algorithms, in the vicinity of contact of multibody systems. The proposed methodology ensures that for any impact in a multibody system the time step of the integration is such that any initial penetration is below any prescribed threshold. In the case of the start of contact, and after a time step is complete, the numerical error control of the selected integration algorithm is forced to handle the physical criteria to accept/reject time steps in equal terms with the numerical error control that it normally uses. The main features of this approach are the simplicity of its computational implementation, its good computational efficiency and its ability to deal with the transitions between non contact and contact situations in multibody dynamics. A demonstration case provides the results that support the discussion and show the validity of the proposed methodology.Fundação para a Ciência e a Tecnologia (FCT