Search results for "structural"
showing 10 items of 5047 documents
Reconfigurable waveguides defined by selective fluid filling in two-dimensional phononic metaplates
2022
Abstract We investigate two-dimensional phononic metaplates consisting of a periodic array of cups on a thin epoxy plate that is perforated with periodic cross holes. The cups are individually filled with water or remain empty, in view of creating reconfigurable phononic waveguides. Phononic band gaps exist for empty or filled epoxy cups, leading to waveguides defined with either positive or negative contrast. Straight and 90° bent waveguides are considered experimentally. Lamb waves are excited by a piezoelectric patch glued onto the metaplate and are imaged using a scanning laser vibrometer. Experimental results are compared to a three-dimensional finite element model of fluid–structure i…
The polar method as a tool for solving inverse problems of the classical laminated plate theory
2000
Publisher Summary Fiber reinforced laminates are widely used in modem applications. For these kinds of structures, the Classical Laminated Plate Theory and its various extensions provide efficient methods for theoretical analysis, that is, when the stacking sequence, the orientations, and the properties of the individual laminas are known. For design of laminates, a very limited number of rules are available. For stiffriess design, two are currently known and used in practical applications: the Werren and Norris rule to get membrane isotropy, and the symmetrical sequence rule to suppress stretching/bending coupling. This chapter deals with the resolution of inverse problems of the Classical…
An equivalent single-layer approach for free vibrations analysis of smart laminated thick composite plates
2012
An equivalent single-layer model for the free vibration analysis of smart laminated plates is presented. The electric and magnetic fields are assumed to be quasi-static and third-order in-plane kinematics is employed to adequately take the shear influence into account when the plate thickness increases. The model governing equations are the plate equations of motion written in terms of mechanical primary variables and effective stiffness coefficients, which take the multifield coupling effects into account. The model shows that the surfaces magneto-electric boundary conditions enter the definitions of the laminate forces and moments resultants. Moreover, it reveals that new stiffness terms,…
Fatigue crack growth through particulate clusters in polycarbonate material
2011
The interaction of a crack with a perfectly bonded inclusion or a cluster of inclusions in polycarbonate matrix was investigated through both numerical simulations and fatigue tests. Stress intensity factors (K(I)) were evaluated by boundary element method for several particle sizes, position and finally for inclusion cluster as a precursor study for the experiments. The numerical simulation has shown the crack tendency to circumvent the inclusions with consequential reduction of the growth rate. Fatigue crack growth tests were carried out on several particle-filled specimens at constant value of the applied stress intensity factor range (Delta K(Iapp)) highlighting the crack delay due to t…
Thermo-Elasto-Hydrodynamic Analysis of a Crankshaft Journal Bearing
2006
This paper summarizes the essential parts of a numerical analysis activity in which the application of the Thermo-Elasto-Hydro-Dynamic (TEHD) lubrication theory to a crankshaft journal bearing is examined. The study is carried out through numerical computations performed by a commercial flexible-multibody code which simulates the lubricated contact between elastic bodies in large displacement motion. A multibody model has been created and its thermal behaviour has been validated by comparison with experimental temperatures. The validated model is used to perform two comparative analyses between the TEHD modelling and the Elasto-Hydro-Dynamic (EHD) modelling for max torque and max power cond…
How Do Institutions Affect Structural Unemployment in Times of Crises?
2012
This paper examines the effect of economic crises on structural unemployment using an Autoregressive Distributed Lags model and accounting for the role of institutional settings on an unbalanced panel of 30 OECD economies from 1960 to 2006. We found that downturns have, on average, a significant positive impact on the level of structural unemployment rate. The maximum impact varies with the severity of the downturn. Institutions (such as employment protection legislation, average replacement ratio and product market regulation) influence both the extent of the initial shock and the adjustment pattern in the aftermath of an economic downturn.
Moment-Axial Domain of Corroded R.C. Columns
2018
In the present paper, a simplified model to determine the moment-axial force domain of the cross-section of reinforced concrete columns subjected to corrosion process is presented. The model considers members with square and rectangular cross-sections and it accounts for cover spalling, buckling of longitudinal reinforcing bars, loss of bond of bar in tension, reduction of confinement pressures (due to the reduction of the area of stirrups and cracking of concrete induced by rust formation). The analytical expressions for prediction of the area reduction of steel, bond strength and critical load of longitudinal bars utilized were verified against experimental data available literature.
Reliability Estimation of Optimal Viscoelastic Composite Shells in Critical-Time Calculations
2003
The problem of reliability estimation for optimal viscoelastic composite shells in critical-time calculations is considered. The weight minimization of a viscoelastic composite shell, with constraints on deflections at the critical time, leads to a system deforming unstably, whose deflections grow in time with an increasing rate. A method for estimating the reliability of such shells in calculating the critical time is discussed. This time is regarded as a random variable depending on many, roughly equivalent, factors. An analysis of the reliability is carried out for different values of coefficients of variation, occurring in practice.
Population response during an Oceanic Anoxic Event: The case of Posidonotis (Bivalvia) from the Lower Jurassic of the Neuquén Basin, Argentina
2019
Benthonic marine species show a wide range of biological reactions to seawater chemical changes through time, from subtle adjustments to extinction. The Early Toarcian Oceanic Anoxic Event (T-OAE) was recently recognized in the Neuquén Basin, Argentina, confirming its global scope. The event was identified chemostratigraphically on the basis of a relative increase in marine organic carbon and a characteristic negative carbon-isotope excursion (δ13Corg) in bulk rock and fossil wood in the upper Pliensbachian–lower Toarcian interval in the Arroyo Lapa section (Neuquén). Simultaneously with collection of lithological samples, a high-resolution biostratigraphical survey was carried out, and the…
Dynamic architecture and regulatory implications of the miRNA network underlying the response to stress in melon
2019
miRNAs are small RNAs that regulate mRNAs at both transcriptional and posttranscriptional level. In plants, miRNAs are involved in the regulation of different processes including development and stress-response. Elucidating how stress-responsive miRNAs are regulated is key to understand the global response to stress but also to develop efficient biotechnological tools that could help to cope with stress. Here, we describe a computational approach based on sRNA sequencing, transcript quantification and degradome data to analyse the accumulation, function and structural organization of melon miRNAs reactivated under seven biotic and abiotic stress conditions at two and four days post-treatmen…