Constitutive sensitivity of the oscillatory behaviour of hyperelastic cylindrical shells

Free and forced nonlinear radial oscillations of a thick-walled cylindrical shell are investigated. The shell material is taken to be incompressible and isotropic within the framework of finite nonlinear elasticity. In comparison with previous seminal works dealing with the dynamic behaviour of hyperelastic cylindrical tubes, in this paper we have developed a broader analysis on the constitutive sensitivity of the oscillatory response of the shell. In this regard, our investigation is inspired by the recent works of Bucchi and Hearn (2013) [28,291, who carried out a constitutive sensitivity analysis of similar problem with hyperelastic cylindrical membranes subjected to static inflation. In the present paper we consider two different Helmholtz free-energy functions to describe the material behaviour: Mooney-Rivlin and Yeoh constitutive models. We carry out a systematic comparison of the results obtained by application of both constitutive models, paying specific attention to the critical initial and loading conditions which preclude the oscillatory response of the cylindrical tube. It has been found that these critical conditions are strongly dependent on the specific constitutive model selected, even though both Helmholtz free-energy functions were calibrated using the same experimental data.The authors are indebted to the Ministerio de Economía y Competitividad de España (Project DPI2014–57989–P) for the financial support which permitted to conduct this work

Corrigendum to "Constitutive sensitivity of the oscillatory behaviour of hyperelastic cylindrical shells" [J. Sound Vib. 358 (2015) 199–216].

An error has been found in Eq. (25) of the recently published paper (https://doi.org/10.1016/j.jsv.2015.07.031) and the authors wish to correct the record by means of this corrigendum. In summary, the error in Eq. (25) of yielded results in which the shell modelled with the Yeoh material showed a non-oscillatory response for some specific loading conditions. This is not the case, as demonstrated in this brief note. We would like to apologize to the readers of the Journal of Sound and Vibration for any inconvenience this error may have caused

Kinetic study of the gas-phase reaction of atomic chlorine with a series of aldehydes

The reactions of Cl atoms with a series of unsaturated aldehydes have been investigated for the first time using a relative method. In order to obtain additional information for a qualitative structure versus reactivity discussion, we have also determined the rate coefficients for the reactions of atomic chlorine with their respective saturated aldehydes. These relative measurements were performed at room temperature and atmospheric pressure of air and N₂, by using ethane, propene and 1-butene as reference compounds. The weighted average relative rate constants obtained, k_Cl&plusmn;2&sigma; (in units of cm³ molecule^&minus;1 s^&minus;1) were: trans-2-pentenal (1.31&plusmn;0.19)&times;10^&minus;10; trans-2-hexenal (1.92&plusmn;0.22)&times;10^&minus;10; trans-2-heptenal (2.40&plusmn;0.29)&times;10^&minus;10; n-pentanal (2.56&plusmn;0.27)&times;10^&minus;10; n-hexanal (2.88&plusmn;0.37)&times;10^&minus;10; n-heptanal (3.00&plusmn;0.34)&times;10^&minus;10. <P style='line-height: 20px;'> Finally, results and atmospheric implications are discussed and compared with the reactivity with OH and NO₃ radicals

Nonlinear resonances of an idealized saccular aneurysm

This paper investigates the occurrence of dynamic instabilities in idealized intracranial saccular aneurysms subjected to pulsatile blood flow and surrounded by cerebral spinal fluid. The problem has been approached extending the original 2D model of Shah and Humphrey (1999) to a 3D framework. The justification for using a 3D formulation arises from the works of Suzuki and Ohara (1978), MacDonald et al. (2000) and Costalat et al. (2011) who showed experimental evidences of intracranial aneurysms with a ratio between wall thickness and inner radius larger that 0.1. Two different material models have been used to describe the mechanical behaviour of the aneurysmal wall: Neo-Hookean and Mooney-Rivlin. To the authors' knowledge, for the first time in literature, the dynamic response of the aneurysm has been analysed using complete nonlinear resonance diagrams that have been obtained from a numerical procedure specifically designed for that purpose. Our numerical results show that, for a wide range of wall thicknesses and both constitutive models considered, the saccular aneurysms are dynamically stable within the range of frequencies associated to the normal heart rates, which confirms previous results of Shah and Humphrey (1999). On the other hand, our results also show that the geometric and material nonlinearities of the problem could bring closer than expected the resonance frequencies of the aneurysm to the frequencies of the pulsatile blood flow.The authors are indebted to the Spanish Ministry of Economy and Competitiveness (Project EUIN2015-62556) for the financial support received which allowed conducting part of this work

2D experiments and numerical simulation of the oscillatory shallow flow in an open channel lateral cavity

Steady shallow flows past an open channel lateral cavity can induce the excitation of an eigenmode of a gravity standing wave inside the cavity, called seiche, which may be coupled with the shedding of vortices at the opening of the cavity. The presence of the seiche is of fundamental interest as it enhances the mass exchange between the main channel and the cavity. Measurements of the time evolution of the water surface are not often found in the literature for this type of flows. In this work, an experimental and numerical study of a shallow flow past a channel lateral cavity is carried out. The main novelty is the use of a pioneering non-intrusive experimental technique to measure the water surface at the channel-cavity region. This optical technique offers high resolution 2D data in time and space of the water surface evolution, allowing to determine the relevant features of the seiche oscillation. Such data are supplemented with Particle Image Velocimetry measurements. Furthermore, the experiments are numerically reproduced using a high-resolution depth-averaged URANS shallow water model, under the assumption that shallow water turbulence is mainly horizontal. The experimental and numerical results are analyzed in the frequency domain. High-resolution two-dimensional amplitude oscillation maps of the seiche phenomenon, as well as velocity fields, are presented. The high quality of the experimental data reported in this work makes this data set a suitable benchmark for numerical simulation models in order to evaluate their performance in the resolution of turbulent resonant shallow flows

Modeling deformation and failure of elastomers at high strain rates

In this paper we develop a new constitutive model to describe the viscoelastic response of elastomers subjected to high strain rates. The key and original feature of the model is that it takes into account the failure of the material using an energy limiter. We calibrate the constitutive model for various strain rates using the experimental data reported by Hoo Fatt and Ouyang (2008) and show the capacity of the proposed formulation to describe the rate-dependent behavior of styrene butadiene rubber. In addition, we implement the model into ABAQUS/Explicit using a simple scheme for the temporal integration of the constitutive equations. Finally, we show sample numerical simulations to illustrate the joint performance of the constitutive model and the integration algorithm.DAI, GV and JARM are indebted to the Spanish Ministry of Economy and Competitiveness (Projects EUIN2015-62556 and DPI2014-57989-P) for the financial support received which allowed conducting part of this work. KYV acknowledges support from the Israel Science Foundation, grant No. ISF-198/15.Publicad

Ergogenic effects of quercetin supplementation in trained rats

[Background] Quercetin is a natural polyphenolic compound currently under study for its ergogenic capacity to improve mitochondrial biogenesis. Sedentary mice have exhibited increased endurance performance, but results are contradictory in human models. [Methods] We examined the effects of six weeks of endurance training and quercetin supplementation on markers of endurance performance and training in a rodent model. Rats were randomly assigned to one of the following groups: placebo+sedentary (PS), quercetin+sedentary (QS), placebo+endurance training (PT) and quercetin+endurance training (QT). Quercetin was administered at a dose of 25 mg/kg on alternate days. During six weeks of treatment volume parameters of training were recorded, and after six weeks all groups performed a maximal graded VO2 max test and a low-intensity endurance run-to-fatigue test. [Results] No effects were found in VO2 peak (p>0.999), nor in distance run during low-intensity test, although it was 14% greater in QT when compared with PT (P = 0.097). Post-exercise blood lactate was increased in QT when compared with PT (p=0.023) and also in QS compared with PS (p=0.024). [Conclusions] This study showed no effects in VO2 peak, speed at VO2 peak or endurance time to exhaustion after six weeks of quercetin supplementation compared with placebo in trained rats. Quercetin was show to increase blood lactate production after high-intensity exercise

A new methodology for the in vivo estimation of the elastic constants that characterize the patient-specific biomechanical behavior of the human cornea

This work presents a methodology for the in vivo characterization of the complete biomechanical behavior of the human cornea of each patient. Specifically, the elastic constants of a hyperelastic, second-order Ogden model were estimated for 24 corneas corresponding to 12 patients. The finite element method was applied to simulate the deformation of human corneas due to non-contact tonometry, and an iterative search controlled by a genetic heuristic was used to estimate the elastic parameters that most closely approximates the simulated deformation to the real one. The results from a synthetic experiment showed that these parameters can be estimated with an error of about 5%. The results of 24 in vivo corneas showed an overlap of about 90% between simulation and real deformed cornea and a modified Hausdorff distance of 25 mu m, which indicates the great accuracy of the proposed methodology. (C) 2014 Elsevier Ltd. All rights reserved.This project has been partially funded by MECD (reference AP2009-2414) and MINECO (INNPACTO, IPT-2012-0495-300000).Lago, MA.; Rupérez Moreno, MJ.; Martínez Martínez, F.; Monserrat Aranda, C.; Larra, E.; Gueell, JL.; Peris-Martinez, C. (2015). A new methodology for the in vivo estimation of the elastic constants that characterize the patient-specific biomechanical behavior of the human cornea. Journal of Biomechanics. 48(1):38-43. https://doi.org/10.1016/j.jbiomech.2014.11.009S384348

NaRALap: augmented reality system for navigation in laparoscopic surgery

The final publication is available at Springer via http://dx.doi.org/10.1007/s11548-011-0579-z.The AR system has a good resolution and currently is used for the placement of the trocars. Possible improvements will be performed to make the system independent of the camera position or to use natural marks. The biomechanical model and the AR algorithms will be combined with a tracker, for tracking the surgical instruments, in order to implement a valid system for liver biopsies. It will take into account the deformation due to the pneumoperitoneum and due to the breath of the patient. To develop the navigator that will guide the laparoscopic interventions, both AR system and biomechanical model will be combined with the laparoscopic camera in order to make an easier environment with only one vision in a 2D monitor.This work has been supported by the project MITYC (ref. TSI020100-2009-189). We would like to express our deep gratitude to the Hospital Clínica Benidorm for its participation in this project.López-Mir, F.; Martínez Martínez, F.; Fuertes Cebrián, JJ.; Lago, MA.; Rupérez Moreno, MJ.; Naranjo Ornedo, V.; Monserrat Aranda, C. (2011). NaRALap: augmented reality system for navigation in laparoscopic surgery. International Journal of Computer Assisted Radiology and Surgery. 6:98-99. https://doi.org/10.0.3.239/s11548-011-0579-zS9899