Search results for "Layered structure"
showing 10 items of 19 documents
Generalised bisection method for optimum ultrasonic ray tracing and focusing in multi-layered structures
2021
Ultrasonic testing has been used for many decades, proving itself very efficient for detecting defects in many industrial sectors. The desire to apply ultrasonic testing to geometrically complex structures, and to anisotropic, inhomogeneous materials, together with the advent of more powerful electronics and software, is constantly pushing the applicability of ultrasonic waves to their limits. General ray tracing models, suitable for calculating the proper incident angle of single element probes and the proper time delay of phased array, are currently required. They can support the development of new imaging techniques, as Full Matrix Capture and Total Focusing Method, and the execution of …
Poly[bis(μ-pentafluorobenzenethiolato)lead(II)]
2006
The title compound, [Pb(SC6F5)2]n, exhibits a layered structure containing two differently hexacoordinated PbII atoms. One is situated on a centre of inversion and is coordinated by six S atoms, its valence lone pair of electrons being consequently stereochemically inactive. The other Pb atom is pyramidally coordinated by three S atoms and forms three contacts to adjacent F atoms, the stereochemically active lone pair pointing towards the F3 plane.
Pressure effect on superconductivity in FeSe0.5Te0.5
2016
Due to the simple layered structure, isostructural FeSe and FeSe0.5Te0.5 are clue compounds for understanding the principal mechanisms of superconductivity in the family of Fe-based superconductors. High-pressure magnetic, structural and Mossbauer studies have been performed on single-crystalline samples of superconducting FeSe0.5Te0.5 with Tc = 13.5 K. Susceptibility data have revealed a strong increase of Tc up to 19.5 K for pressures up to 1.3 GPa, followed by a plateau in the Tc(p) dependence up to 5.0 GPa. Further pressure increase leads to a disappearance of the superconducting state around 7.0 GPa. X-ray diffraction and Mossbauer studies explain this fact by a tetragonal-to-hexagonal…
Finite deformation analysis of laminated shell via the discontinuous Galerkin method
2022
In this work, we propose a novel formulation for the large displacements and post-buckling response analysis of laminated composite shell structures. In order to accurately recover the solution in the case of multilayered shells, the covariant components of the displacement field are approximated through the thickness using high-order structural theories. The non-linear two-dimensional total Lagrangian formulation is obtained starting from the Principle of Virtual Displacements for the three-dimensional elasticity assuming a linear constitutive relationship between the second Piola–Kirchhoff stress tensor and the Green-Lagrange strain tensor. The discontinuous Galerkin method is used in com…
Buckling analysis of multilayered structures using high-order theories and the implicit-mesh discontinuous Galerkin method
2022
This work presents a novel formulation for the linear buckling analysis of multilayered shells. The formulation employs high-order Equivalent-Single-Layer (ESL) shell theories based on the through-the-thickness expansion of the covariant components of the displacement field, whilst the corresponding buckling problem is derived using the Euler’s method. The novelty of the formulation regards the solution of the governing equations, which is obtained via implicit-mesh discontinuous Galerkin (DG) schemes. The DG method is a high-order accurate numerical technique based on a discontinuous representation of the solution among the mesh elements and on the use of suitably defined boundary integral…
3D simulations and experiments of guided wave propagation in adhesively bonded multi-layered structures
2010
Understanding guided wave propagation in multi-layered plates and interaction with discontinuities can be difficult, as well as the interpretation of the ultrasonic signals. Propagation of guided waves can be studied analytically solving the equations of motion with the proper boundary conditions; nevertheless analytical models can be difficult to solve for complex multi-layered structures or having inner discontinuities. The problem can be efficiently studied using numerical techniques. Simulation of guided wave propagation in multi-layered structures, for ultrasonic waves in the MHz range, is solved here with the finite element analysis based on an explicit integration rule to solve the e…
Finite elements for nonlinear free vibrations analysis of smart laminates subjected to in-plane loadings
2015
Advanced composites, able to provide multi-functional capabilities besides the traditional structural functions, has been gaining attention in many technological fields. This inherent coupling of different physical fields can be exploited in transducer applications, structural health monitoring, vibration control, energy harvesting and other applications. Magneto-electro-elastic (MEE) composite materials are attracting increasing consideration as they couple mechanical, electrical and magnetic fields and this makes them particularly suitable for smart applications. Generally, single-phase materials exhibit either piezoelectric or piezomagnetic behavior and no direct magneto-electric couplin…
Synthesis, Structure, and Properties of BaVO2(AsO4): a New Vanadium Arsenate Containing the V2O42+ Core
1997
The new vanadium arsenate BaAsVO6 has been synthesized hydrothermally and structurally characterized by single-crystal X-ray diffraction, IR spectroscopy, and magnetic susceptibility measurements. It crystallizes in the monoclinic system, space group P21/c with unit cell parameters a = 5.645(1) A, b = 10.243(1) A, c = 8.945(1) A, β = 90.60(1)°, and Z = 2. The layered structure is built up from V2O42+ units and AsO43- anions, the AsO43- ligands being coordinated to two (V2O4)2+ units in both, terminal and bridging μ2-AsO43- fashion. The [VO2(AsO4)]2- layers are separated by Ba2+ cations. The V2O42+ unit has no precedence in oxo-vanadium chemistry.
Melt development of biphasic functionally graded scaffold
2016
Interface tissue engineering requires scaffolds that temporary replace the mechanical function of transition regions between two adjacent tissues. The presence of multi-phasic bio-structures that gradually change are typical features of interface tissues such as ligament-to-bone, tendon-to-bone and cartilage-to-bone. In this work, bi-layered scaffolds (BLS) composed by PLA with pores in the range of 90-110 µm and PCL with pores ranging from 5 to 40 µm were prepared by combining melt mixing, compression molding and particulate leaching. The principal advantages of this method lay in the absence of organic solvent during the preparation and in the easy control and high predictability of poros…
Mechanical behavior of polylactic acid/polycaprolactone porous layered functional composites
2016
Abstract Biopolymeric porous devices exhibiting graded properties can play a crucial role in several fields, such as tissue engineering or controlled drugs release. In this context, the gradient of a specific property can be achieved by developing porous laminates composed by different types of materials. This work presents for the first time a multi-phasic porous laminate based on polycaprolactone (PCL) and polylactic acid (PLA) prepared by combining melt mixing, compression molding and particle leaching. All the materials were characterized from a morphological and a mechanical point of view. The results put into evidence the possibility to tune and to predict the mechanical properties by…