Search

For a relatively new class of linearization of implicit constitutive relations, wherein the linearized strain tensor is assumed to be a function of the Cauchy stress tensor, we write the balance of linear momentum and the time differentiated constitutive relation as a first order system, and we examine conditions for the hyperbolicity of such a system; this procedure is carried out for one and three dimensions. For the one dimensional case we use the characteristic polynomial and find conditions so that our system is hyperbolic. For three dimensions we find conditions so that our system can be put in a symmetric hyperbolic form. • We write the equations as a first order system. • For the one dimensional case we use the characteristic polynomial and find conditions so that our system is hyperbolic. • For three dimensions we find conditions so that our system can be put in a symmetric hyperbolic form. [ABSTRACT FROM AUTHOR]

In this communication a generalized strain approach is proposed to model constitutive equations for nonlinear residually stressed magneto-electric coupled viscoelastic solids with short term memory. This approach is a change with respect to the work that has been done, in the last decades, on the mechanics of nonlinear solids. The generalized strain model uses spectral invariants, where they have a clear physical meaning and hence are attractive for use in experiments. A specific form for a constitutive equation containing single-variable functions is presented, which are easy to deal with, if compared to multivariable functions. The effects of viscosity, residual stress and magneto-electric fields are studied via the results of boundary value problems, and some of these results are compared with experimental data. • A generalized strain approach is proposed to obtain constitutive equations. • A nonlinear residually stressed magneto-electric coupled viscoelastic solid is built. • The generalized strain model uses spectral invariants, all with physical meaning. • The effects of viscosity, residual stress and magneto-electric fields are studied. [ABSTRACT FROM AUTHOR]

In this prospective, randomised, blinded clinical study, we compared the sedative, antinociceptive and cardiorespiratory effects of intranasal (IN) dexmedetomidine at 5 μg/kg (diluted with 0.03 mL/kg NaCl 0.9%, DEX) with or without methadone (0.3 mg/kg; DEXMET), through a mucosal atomization device to one nostril in twenty healthy client-owned dogs. At 5-min intervals over 45 min, sedation score, onset, cardiopulmonary variables, mechanical nociceptive thresholds (MNTs) were assessed, also ease of administration, adverse effects, and response to IV catheterization. Statistical analysis employed t-test, the Mann-Whitney U, repeated measures ANOVA and Chi-square tests as appropriate (P < 0.05). Higher sedation ocurred in DEXMET (7 [5–10]) compared to DEX (5 [2–7]) from 15 to 30 min (P < 0.01, median [interquartile range]). Heart rate was lower in DEXMET (P < 0.01; 65% reduction vs. 41% in DEX, P = 0.001). The MNTs were higher in DEXMET than DEX from 15 to 45 min (P < 0.01), peaking at T30 (17.1 ± 3.8, DEXMET and 8.5 ± 5.4 N, DEX). No differences were observed in mean arterial blood pressure and respiratory rate. Intranasal administration was considered easy for 8 dogs per group. Reverse sneezing (8 dogs; P < 0.001), sialorrhea and retching (4 and 2 dogs, respectively) occurred in DEXMET. Response to catheterisation was lower in DEXMET than DEX (P = 0.039; 2 and 7 dogs, respectively). In conclusion, intranasal methadone (0.3 mg/kg) increased the sedative and antinociceptive effects produced by dexmedetomidine (5 μg/kg) in healthy dogs and resulted in lower heart rate. • Methadone potentiated sedative effect of intranasal (IN) dexmedetomidine. • Methadone IN produced greater antinociceptive effects than dexmedetomidine alone. • Lower heart rate was observed when both drugs were administered IN. [ABSTRACT FROM AUTHOR]

A new constitutive equation is proposed for rubber, based on expressing the Cauchy stress as a function of the Hencky strain tensor. The model is used for isotropic bodies considering the classical invariants of Rivlin and Spencer. The predictions for the extension and compression of a cylinder, and the inflation of a hollow sphere, are compared with the predictions of the constitutive equation for rubber by Ogden. • A new model is presented for rubber. • A comparison with the Ogden's model is provided. • The behaviour of a hollow sphere is studied. obtained. [ABSTRACT FROM AUTHOR]

Residual stresses may exist in different finitely deformed soft multifunctional materials such as in electro-active and magneto-active polymers. In order to develop accurate constitutive frameworks of these smart materials experiencing electro-magneto-mechanically coupled loads, the presence of residual stresses needs to be considered on the onset of the model development. In this contribution, a spectral constitutive equation for finite strain magneto-electric soft material bodies with residual stresses is developed using spectral invariants, where each spectral invariant has a clear physical meaning. A prototype total energy function comprising of single-variable functions is proposed; a single-variable function that depends on an invariant with a direct meaning is easily handled and is experimentally attractive. Results of some boundary value problems are given. • A electro-magneto-mechanically coupled framework is proposed to model residual stress. • The entire framework is based on the physically motivated spectral invariant. • A prototype total energy function comprising of single-variable functions is propose. • Relevant numerical examples demonstrated significant influence of the stress residual on the electro-magneto-mechanically problems. [ABSTRACT FROM AUTHOR]