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Sandwich structures with a soft core typically exhibit multiple deformation modes such as bending, twisting and compression when subjected to transverse loads. Compressive behavior of soft core significantly affects the structural response, which is usually neglected in conventional plate theories. Additionally, conventional plate theories do not take into account transverse shear stress continuity. In order to address this concern and precisely characterize the characteristics of arbitrary multilayer laminated structures, a novel electromechanical coupled finite element model is developed. This model is based on a compressible layerwise third-order shear deformation theory with a soft core. Notably, the proposed model theory requires only twelve degrees of freedom for each quadratic element node. The accuracy of the model is validated first. Afterwards, several numerical investigations are carried out for piezolaminated sandwich structures with different width-to-thickness ratios, reinforcement angle and skew angle. The results demonstrate the applicability of the current model in predicting the behavior of laminated sandwich plates. [ABSTRACT FROM AUTHOR]

Sandwich structures with thick soft cores subjected to transverse loads are usually resulting in deformations with various modes, including bending, twisting and compressing. In addition, the compression of the core results in a significant influence of the structural response. All classical plate theories are inadequate in predicting the behavior sandwich structures with thick soft core due to the assumption of no thickness change during deformation. To overcome this issue, a hybrid first/third-order shear deformation hypothesis with consideration of compressive effect is proposed for sandwich structures with thick soft cores. The first-order shear deformation theory is applied to both the top and bottom layers, while a refined third-order shear deformation theory that releases the assumption of no thickness change is developed for the thick soft cores. An eight-node quadrilateral plate element with twelve degrees of freedom including compressible displacements is created for finite element modeling. Based on the proposed refined hybrid first/third-order theory, a finite element model is developed using the Hamilton's principle. The numerical model is first validated by the computational results of sandwich structures using commercial software. Then, the influences of various parameters on static displacements, vibrations and compressive deformations are systematically investigated, including e.g. boundary conditions, thickness of the core and face layers, elastic modulus of the core layer and the plate size. The present finite element modeling approach provides a powerful tool to accurately investigate the mechanical response of sandwich structures. [ABSTRACT FROM AUTHOR]

A finite element formulation using zig-zag hypothesis is developed for sandwich smart structures with partially smart constrained layer damping (SCLD) treatment. In order to achieve higher accuracy, both of the viscoelastic and elastic layers of the sandwich structures are based on the Reissner–Mindlin theory. An eight-node quadrilateral element with seven mechanical degrees of freedom (DOFs) is considered for the finite element (FE) analysis. Using Hamilton's principle, a piezoelectric coupled dynamic FE model is obtained. This FE model is validated by frequency and loss factor analysis of an elastic–viscoelastic–elastic plate. Furthermore, the effects of various parameters on the damping characteristics of the cantilever sandwich smart structures are carried out, e.g. coverage percentage and position of SCLD, thickness of the viscoelastic or piezoelectric layer, curvature of structures, and shear modulus and loss factor of the viscoelastic layer. [ABSTRACT FROM AUTHOR]

Regarding to viscoelastic laminated piezo smart plates and shells, electro-mechanically coupled finite element (FE) formations are derived based on zig-zag hypothesis for vibration and damping analyses. Three lamination configurations are considered in the model, where both elastic layers and viscoelastic layers are assumed to be Reissner–Mindlin plate. The quadratic element is adopted for FE modeling, each node has seven mechanical degrees of freedom (DOFs), which considers the complex shear modulus of viscoelastic materials. The analytical model is first validated by FE simulation of viscoelastic sandwich plates. Later, the effects of various parameters on the damping performance of piezo-viscoelastic laminated cylindrical structures are carried out, e.g. boundary conditions, reinforcement orientation angle, thickness of the viscoelastic core and structural curvature. The present FE modeling and analyses provide a powerful tool to accurately investigate the behaviors of viscoelastic laminated structures. [ABSTRACT FROM AUTHOR]

The paper develops a geometrically nonlinear finite element model with large rotation based on the first-order shear deformation (FOSD) hypothesis for static and dynamic analyses of piezoelectric integrated carbon nanotube reinforced functionally graded (P-CNT-FG) composite structures. A constant electric field distribution through the thickness of plate is considered. An eight-node quadrilateral plate element with five mechanical degrees of freedom (DOFs) and one electric degree of freedom is developed for finite element analysis. Four typical forms of CNT distributions are included in the model, namely uniform, V-shaped, O-shaped, and X-shaped distributions. The nonlinear model considers fully geometrically nonlinear strain-displacement relations and large rotations of the shell direction of plate. Using the Hamilton's principle, a nonlinear dynamic model including dynamic and sensory equations is obtained. The proposed nonlinear model is validated by a frequency analysis of a simply supported P-CNT-FG composite plate. Furthermore, the effects of various parameters on the static and dynamic behavior are investigated, e.g. CNT-reinforcement orientation, CNT distribution, the number of laminate layers and volume fraction. [ABSTRACT FROM AUTHOR]

Oceanographic observations and models show that the heat brought by the warm modified Circumpolar Deep Water (mCDW) intrusion accelerates the melting of the Antarctic ice shelf and the loss of sea ice. Limited by the time scale of instrument recording, there are few records of mCDW intrusion into the East Antarctic continental shelf in the historical period. Here, we present a novel proxy of cadmium (Cd) concentrations in Adélie penguin feathers in an ornithogenic sediment profile to reconstruct the variability in mCDW intrusion into the continental shelf in Prydz Bay, East Antarctica, over the past 2500 years. Our reconstruction revealed that the intrusion of mCDW was enhanced from ∼1500 to 300 yr BP, stimulating the regional increase in glacier discharge and decrease in sea ice; at approximately 200 yr BP, mCDW intrusion weakened and then continued to enhance again during approximately the last 150 years. Furthermore, the enhancement of mCDW intrusion into Prydz Bay appeared to be driven by the southward shift and strengthening of the Southern Hemisphere Westerlies (SWW). The results implied that since this trend in SWW is forecasted for persisting into the 21st century, mCDW intrusion into Prydz Bay may increase continuously, threatening the stability of ice shelf and sea ice, and even the Antarctic Bottom Water formation in the future. [ABSTRACT FROM AUTHOR]

In order to implement the cost-effective machining of granite materials with diamond impregnated tools, one should realize low tool wear, low energy consumption, and high cutting efficiency, while the accuracy of the workpiece surfaces are maintained to be satisfactory. It is understood that the main factors affecting the tool wear, the energy, and the efficiency during the machining process are related to the tribological interactions that occur at the interface between the diamond tool surface and the workpiece. Based on this consideration, the authors propose a new machining method to machine granite materials to achieve improved cost effectiveness. In the proposed method, the tribological interactions are maintained to a minimum. [Copyright &y& Elsevier]

To meet the increasing demand on the quality and cost of precision components for the semiconductor industries, extensive studies on high efficiency and precision machining of ceramic materials have been conducted over the past few years. It is found that the effects of grinding pressure and the rotational speed of the spindle in the machining of ceramic materials are very significant on the quality of the grinding process. In order to achieve stable grinding conditions for improved performance, a new grinding control scheme in which the grinding pressure is maintained constant throughout the grinding process was explored in the present study. Based on the experimental results, the microanalysis of the ground surfaces, and the comparison of the analytic and measured temperature profiles, the material removal mechanisms for constant pressure grinding were discussed. [Copyright &y& Elsevier]