Vibration analysis of rotating Timoshenko beams by means of the differential quadrature method

Vibration analysis of rotating beams is a topic of constant interest in mechanical engineering. The differential quadrature method (DQM) is used to obtain the natural frequencies of free transverse vibration of rotating beams. As it is known the DQM offers an accurate and useful method for solution of differential equations. And it is an effective technique for solving this kind of problems as it is shown comparing the obtained results with those available in the open literature and with those obtained by an independent solution using the finite element method. The beam model is based on the Timoshenko beam theory.Fil: Bambill, Diana Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Felix, Daniel Horacio. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Rossi, Raul Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; Argentin

Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome : Insights from the LUNG SAFE study

Publisher Copyright: © 2020 The Author(s). Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. Methods: In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO2 > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO2 ≥ 0.60 during hyperoxemia). Results: Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO2 < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO2 use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO2 use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO2. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO2 use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO2 use, compared to 39% in a propensity-matched sample of normoxemic (PaO2 55-100 mmHg) patients (P = 0.47). Conclusions: Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort. Trial registration: LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073publishersversionPeer reviewe

Comments on "Free vibration of super elliptical plates with constant and variable thickness by Ritz method"

Free vibration of super elliptical plates with constant and variable thickness by Ritz method has been reported. the shape of the plate in the x y plane can be defined by the super elliptical function. Calculating the area and perimeter of the region may give an idea about the convergence of the integration. the discussers also obtained the area sand perimeters using a finite element code, to be sure about the good precision of their values. The re-calculated values are in excellent agreement with Wang's results. The calculations have been performed for simply supported and clamped super elliptical plates with aspect ratio a/b=1, 1.2, 2, 3; with n=8 and n=10.Fil: Bambill, Diana Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Maiz, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Rossi, Raul Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; Argentin

Free vibration of a rectangular plate with an attached three-degree-of-freedom spring-mass system

The present paper studies the variation of the natural frequencies and mode shapes of rectangular plates carrying a three degree-of-freedom spring-mass system (subsystem), when the subsystem changes (stiffness, mass, moment of inertia, location). An analytical approach based on Lagrange multipliers as well as a finite element formulation are employed and compared. Numerically reliable results are presented for the first time, illustrating the convenience of using the present analytical method which requires only the solution of a linear eigenvalue problem. Results obtained through the variation of the mass, stiffness and moment of inertia of the 3-DOF system can be understood under the effective mass concept or Rayleigh’s statement. The analysis of frequency values of the whole system, when the 3-DOF system approaches or moves away from the center, shows that the variations depend on each particular mode of vibration. When the 3-DOF system is placed in the center of the plate, “new” modes are found to be a combination of the subsystem’s modes (two rotations, traslation) and the bare plate’s modes that possess the same symmetry. This situation no longer exists as the 3-DOF system moves away from the center of the plate, since different bare plate’s modes enable distinct motions of the 3-DOF system contributing differently to the “new’ modes as its location is modified. Also the natural frequencies of the compound system are nearly uncoupled have been calculated by means of a first order eigenvalue perturbation analysis.Fil: Febbo, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Bambill, Diana Virginia. Universidad Nacional del Sur; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rossi, Raul Edgardo. Universidad Nacional del Sur; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Vibrations of simply supported rectangular plates with varying thickness and same aspect ratio cutouts

Vibrations of simply supported rectangular plates with varying thickness and same aspect ratio cutouts were studied. Results obtained were compared with data available. Frequency coefficients were calculated using finite element method and were found to be in good agreement. No dynamic stiffening effect was noticed. Complete set of eigenfunctions can be used for rectangular plates of general anisotropy.Fil: Larrondo, Hilda Angela. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Avalos, Daniel Reynaldo. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Laura, Patricio Adolfo Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Rossi, Raul Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; Argentin

Out-of-plane vibrations of shear deformable continuous horizontally curved thin-walled beams

This paper presents numerical study about the influence of the shear flexibility, due to either bending and warping, on the out-of-plane free vibration of continuous horizontally curved thin-walled beams with both open and closed sections. This study was made by means of a recently developed finite element formulation for shear deformable curved thin-walled beams. The model is briefly reviewed and is used to obtain natural frequencies of continuous I-beams and box beams. A parametric study was performed in order to elucidate the influence of shear deformability, on the dynamic behavior of continuous thin-walled curved beams, for different slenderness ratios, cross-sectional characteristics and boundary conditions.Fil: Piovan, Marcelo Tulio. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca. Grupo de Análisis de Sistemas Mecánicos; ArgentinaFil: Cortínez, Víctor Hugo. Universidad Tecnológica Nacional. Facultad Regional Bahía Blanca. Grupo de Análisis de Sistemas Mecánicos; ArgentinaFil: Rossi, Raul Edgardo. Universidad Nacional del Sur. Departamento de Ingeniería; Argentin

Free vibration analysis of a centrifugally stiffened Timoshenkonon-uniform beam using the differential quadrature method

Este artıculo trata sobre las vibraciones transversales de una viga rotante de seccion no uniforme, utilizando el metodo de cuadratura diferencial (MCD).La formulacion se basa en la teorıa de Timoshenko, que considera las fuerzas de inercia debidas a la traslacion lateral junto con las contribuciones de la deformacion por corte y de la inercia rotatoria. En este trabajo el metodo de cuadratura diferencial se aplica al calculo de las frecuencias naturales. Los resultados obtenidosson comparados con resultados publicados en la literatura abierta y con valores calculados por los autorescon un codigo de elementos finitos. El metodo propuesto ofrece un procedimiento directo y eficiente para analizar con muy buena precision las vibraciones naturales de vigas rotantes de seccion no uniforme.This paper deals with the transverse vibration of non-uniform rotating beams, by means of the differentialquadrature method (DQM).The formulation is based on the Timoshenko beam theory, which takes into account the inertia forces dueto the transverse translation together with the contributions of shear deformation and rotatory inertia. Theapplication of the differential quadrature method is demonstrated by investigating the natural frequencies.The results are compared with published results given in the open literature and with values obtained by theauthors using a finite element code. The proposed method offers a direct and efficient procedure to analyzethe natural vibration of non-uniform rotating beams with very good accuracy.Fil: Felix, Daniel Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Rossi, Raul Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Bambill, Diana Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; Argentin

Transverse vibrations of an orthotropic rectangular plate of linearly varying thickness and with a free edge

This study addresses the determination of the fundamental frequency of the plate or slab when the edge x=a is free and the other three are subjected to all possible supported combinations. Eigenvalues are determined by using the optimized Rayleigh-Ritz and the finite element methods.Fil: Bambill, Diana Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Rossit, Carlos Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Laura, Patricio Adolfo Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Rossi, Raul Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; Argentin

Transverse vibrations of a clamped rectangular plate or slab with an orthotropic patch

This study deals with a clamped, rectangular isotropic plate with a centrally located circular and rectangular patch. The optimized Rayleigh-Ritz method is used to determine the fundamental frequency coefficient. An independent solution is derived by means of the finite element technique.Fil: Laura, Patricio Adolfo Antonio. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Gutierrez, Ruben Hector. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Rossi, Raul Edgardo. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Rossit, Carlos Adolfo. Universidad Nacional del Sur. Departamento de Ingeniería; Argentin

Transverse free vibration of non uniform rotating Timoshenko beams with elastically clamped boundary conditions

In the present paper the Differential Quadrature Method, DQM, and the domain decomposition are used to carry out the free transverse vibration analysis of non-uniform multi-span rotating Timoshenko beams with perfect and not perfect boundary conditions. The cross section could vary in a continuous or discontinuous fashion along the beam length. The material of the beam could be different in each beam span. The influence of elastically clamped boundary conditions at hub end are studied and discussed. The effect of an arbitrary hub radius is considered. The governing differential equations of motion for rotating Timoshenko beams come from the derivation of Hamilton's principle. The first six natural frequencies of vibration are obtained for many particular situations and for some of them the mode shapes are also available. The examples of applications of the method indicated its effectiveness. The results for particular cases are in excellent agreement with published results and results obtained by means of the finite element method.Fil: Bambill, Diana Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Rossit, Carlos Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Rossi, Raul Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Felix, Daniel Horacio. Universidad Nacional del Sur. Departamento de Ingeniería; ArgentinaFil: Ratazzi, Alejandro Ruben. Universidad Nacional del Sur. Departamento de Ingeniería; Argentin