STABILIZATION OF THE GENERALIZED RAO-NAKRA BEAM BY PARTIAL VISCOUS DAMPING

In this paper, we consider the stabilization of the generalized Rao-Nakra beam equation, which consists of four wave equations for the longitudinal displacements and the shear angle of the top and bottom layers and one Euler-Bernoulli beam equation for the transversal displacement. Dissipative mechanism are provided through viscous damping for two displacements. The location of the viscous damping are divided into two groups, characterized by whether both of the top and bottom layers are directly damped or otherwise. Each group consists of three cases. We obtain the necessary and sufficient conditions for the cases in group two to be strongly stable. Furthermore, polynomial stability of certain orders are proved. The cases in group one are left for future study.

DECLINE OF LATERAL DISPLACEMENT OF SHIP AFTER A MANEUVER BY THE INPUT OF ADDITIONAL AMENDMENT OF THE COURSE

In work is specified, that navigation safety of sailing to a great extent depends on the errors of the navigation measuring, and also from operating reliability of sensors of navigation information. It is also marked that descriptions of exactness of gyroscopic compass influence on navigation safety. Because sizes of his errors the requirements providing the set exactness of determination of azimuthal directions are produced. At maneuvering of ship there are inertia errors which cause appearance of lateral displacement of ship after his turn, that can lead to the navigation failure of ship. Therefore, there is the problem of decline of lateral relocation bias of ship which appears after his turn, that conduces to the decline of navigation accident rate. The analysis of the last achievements and publications is resulted in work, the decision of the considered problem and selection of parts unsolved before is begun in which. Within the framework of theory endless rapid maneuver, expression for total inertia deviation which depends on character of maneuver and breadth of sailing of ship is resulted in the publication. It is shown that transversal relocation bias of ship is an integral function in relation to the function of deviation and for estimation of its size analytical expression is resulted, which it is visible from, that transversal displacement also depends on speed of ship after a maneuver. It is marked in the publication, that transversal displacement is more complete description of exactness of gyrocompass on the protracted time domains, as it represents the consequences of influencing of maneuvering on a gyrocompass in the «smoothed» kind out. From these positions, obviously, that inertia deviation is the index of instantaneous exactness of gyrocompass. Two methods of decline of transversal displacement of ship are offered, thus for estimation of efficiency of the offered procedure of indemnification of lateral displacement of ship the computer program allowing to produce the calculation of the crooked dependence of total inertia error from time with the subsequent graphic reflection was developed. The program also expects and builds the graphs of dependence of lateral displacement without indemnification, total lateral displacement with partial indemnification and with complete indemnification. The results of computer graphic design are resulted, which it ensues from, that total inertia error and lateral without indemnification is multiplied displacements with growth of breadth, during partial indemnification total lateral displacement diminishes approximately in 5 times, and at the variable additional amendment of course lateral displacement of ship is absent.

Quantitative Evaluation of the Echo Intensity of Paraneural Area and Myofascial Structure around Median Nerve in Carpal Tunnel Syndrome

The aim of this study was to investigate whether the echo intensity (EI) of the paraneural area (PA), the median nerve (MN) at the carpal tunnel, the EI of the myofascial structure (MS) around MN, the ‘PA and MN’ at the mid-forearm, and the MN transversal displacement at both sites differs between persons with carpal tunnel syndrome (CTS) and control subjects. Methods: In total, 16 CTS patients and 16 controls, age- and gender-matched, were recruited. Cross-sectional ultrasound images of MN were obtained to evaluate the EI of the PA, the MN at carpal tunnel, the EI of MS, and the ‘PA and MN’ at the mid-forearm in a natural position, then images were taken after a whole-hand grasp movement, to evaluate MN transversal displacement. Inter-rater and intra-rater reliability in control, and differences in the EI and MN displacement between CTS and control, were analyzed. In addition, the correlations between ultrasound parameters and MN displacement were evaluated. Results: The quantitative EI of PA, MN, EI of MS, ‘PA and MN’ had high inter-rater and intra-rater reliability in the control. The EI of PA, MS and ‘PA and MN’ were significantly higher in CTS subjects (p < 0.01), whilst there was no significant difference in the EI of MN at the carpal tunnel. MN displacement was significantly decreased both at the carpal tunnel and the mid-forearm in CTS subjects (p < 0.01). In addition, there were negative correlations among the EI of PA (rs = −0.484, p = 0.004), EI of MS (rs = −0.479, p = 0.002), EI of ‘PA and MN’ (rs = −0.605, p < 0.001) and MN transversal displacement. Conclusions: The higher EI of PA and MS around MN in CTS may indicate greater fibrosis along the course of MN, reducing fascial adaptability, influencing the synergy and coordination of the MS, and increasing the shear stress between MS and MN, and it may further increase the abnormal pressure on the MN not only at the carpal tunnel, but also at the mid-forearm. These results may partly explain the role of PA and MS in CTS pathogenesis.

Experimental characterization of PCI impact on vibrating fuel rod under axial turbulent flow representative of JHR irradiation device ADELINE: Set-up conception and measurement method

Mechanical loading originating due to Pellet- Cladding Interaction (PCI) in PWR nuclear fuel rod constitutes a first order importance phenomenon when attempting at increasing the flexibility o f n uclear r eactors o peration t o f ollow grid demand. The need to improve the understanding of such complex multi-physics phenomena motivates the realization of particular irradiation sequences carried out in highly instrumented devices located in Material Testing Reactors. Among this kind, ADELINE irradiation device is being developed and will be installed in the future Jules Horowitz Reactor. In the perspective of designing the adapted measurement methodology to detect and characterize PCI phenomenology during irradiation, we present in this paper the experimental bench and its associated measurement program, designed to investigate eventual effects of PCI on the non-linear, flow i nduced v ibrations o fuclear fuel r od. A nalytical and numerical models cannot predictively describe the system due to the complexity of phenomena thus the IMPIGRITIA experimental set-up has been developed to reproduce the mechanical interaction between the pellet and the clad at low pressure, room temperature and out of neutron flux. T he d esigned test bench presents a clamped free single short rod, centred in the test section by mean of four centring elements. Different rod configurations are implemented and localized closure of the gap is remotely realized by means of a dilatation system. Laser Doppler Vibrometry is used to measure the transversal displacement of the sample rod in three different conditions: in air, in stagnant water and under turbulent axial flow r ate. T he experimental program and expected results are presented and discussed

A neutrally stable shell in a Stokes flow: a rotational Taylor's sheet

In a seminal paper published in 1951, Taylor studied the interactions between a viscous fluid and an immersed flat sheet which is subjected to a travelling wave of transversal displacement. The net reaction of the fluid over the sheet turned out to be a force in the direction of the wave phase-speed. This effect is a key mechanism for the swimming of micro-organisms in viscous fluids. Here, we study the interaction between a viscous fluid and a special class of nonlinear morphing shells. We consider pre-stressed shells showing a one-dimensional set of neutrally stable equilibria with almost cylindrical configurations. Their shape can be effectively controlled through embedded active materials, generating a large-amplitude shape-wave associated with precession of the axis of maximal curvature. We show that this shape-wave constitutes the rotational analogue of a Taylor's sheet, where the translational swimming velocity is replaced by an angular velocity. Despite the net force acting on the shell vanishes, the resultant torque does not. A similar mechanism can be used to manoeuver in viscous fluids.

Analytical Modeling of Self-Loosening of Bolted Joints

Self-loosening of bolted joints is a common issue in Pressure Vessel and Piping equipment. This phenomenon can not only cause the industry a lot of losses due to maintenance but can result in catastrophic incidents leading to environment and health issues. This paper presents several improvements and innovations that are brought to the subject of self-loosening of bolted joints through a study involving analytical, numerical and experimental work. A new model to prevent self-loosening of bolted joints is developed. Particular focus is put on the effect of the clamping plate thickness on the self-loosening of the joint. A fully instrumented experimental set-up, in conjunction with an M12-1.75 bolt, is deployed to track the bolt tension decrease with the application of an imposed cyclic transversal displacement. In addition to the measurement of the transverse relative displacement between the two clamping parts, the clamping and transverse loads are also recorded. Finally, the relative rotation between the bolt and the nut is measured by means of a rotation sensor directly installed on the nut. The results show that there is a good agreement between the analytical, numerical and experimental results. The new model is compared with FEM and experimentation for different plate thickness configurations.

Experimental and numerical evaluation of the mechanical behavior of diagonally reinforced plates subjected to the effect of residual thermal stresses

This paper presents an experimental and numerical study of the effect of residual thermal stresses on the mechanical behavior of diagonally reinforced plates. The study focuses on the analysis of carbon/epoxy square plates onto which diagonal reinforcements were glued. These reinforcements were glued using two different methodologies: the first method was to glue the reinforcements at operating temperature (22 °C), while in the second methodology reinforcements were cured in an autoclave at 177 °C. Mechanical behavior assessment was based on the stiffness, free vibration, and buckling tests. For the study of the stiffness of the plates, an optical technique to determine the transversal displacement caused by the presence of a static load was employed. For the vibration tests, the natural frequencies associated with the first four modes of free vibration were determined by using a dynamic signal analyzer. For the linear and non-linear buckling, compression tests on a universal testing machine were performed, determining the displacements produced during the test using the digital image processing method. All experimental results were compared with results obtained from numerical approximations made with commercial software. The results show the effect of residual thermal stresses caused during the manufacturing process on the mechanical performance of diagonally reinforced plates.

The Influence of Modal Geometrical Imperfections on the Nonlinear Vibrations of a Thin-Walled Circular Cylindrical Shell

This work investigates the influence of several modal geometric imperfections on the nonlinear vibration of simply-supported transversally excited cylindrical shells. The Donnell nonlinear shallow shell theory is used to study the nonlinear vibrations of the shell. A general expression for the transversal displacement is obtained by a perturbation procedure which identifies all modes that couple with the linear modes through the quadratic and cubic nonlinearities. The imperfection shape is described by the same modal expansion. So, a particular solution is selected which ensures the convergence of the response up to very large deflections. Substituting the obtained modal expansions into the equations of motions and applying the standard Galerkin method, a discrete system in time domain is obtained. Several numerical strategies are used to study the nonlinear behavior of the imperfect shell. Special attention is given to the influence of the form of the initial geometric imperfections on the natural frequencies, frequency-amplitude relation, resonance curves and bifurcations of simply-supported transversally excited cylindrical shells.