Asymmetric Plates Research Articles

Resonant magnetic sensor using concentration of magnetic field gradient by asymmetric permalloy plates

This paper demonstrates a novel resonant magnetic sensor that utilizes a concentrator to obtain a large magnetic-field gradient. A silicon-cantilevered resonator, with a 10-µm-diameter magnetic particle on the tip, is placed between two asymmetric permalloy plates, which function as the concentrator; one of the plates has a narrow tip, whereas the other has a wide one. This asymmetric-plate pair generates a large magnetic gradient, which generates considerable force on the magnetic particle. The resonant-frequency varies, depending on the force applied on the particle. The extremal magnetic field can be determined by monitoring the changes in the resonant frequency. The magnetic gradient generated by the concentrator is theoretically calculated using the finite element method, obtaining a gradient of 5.4 × 104 T/m for a magnetic field of 1 T. A resonant magnetic sensor is fabricated using conventional microfabrication techniques, and the magnetic force-dependent resonant-frequency change is observed. The experimental magnetic sensitivity is estimated to be 5.1 × 10−7 T, considering the minimum noise level (3.29 ppm).

Water wave interaction with dual asymmetric non-uniform permeable plates using integral equations

In this study, we analyse the effect of two submerged unequal permeable plates in the propagation of water waves under the assumptions of linear water wave theory. The permeability of the plates varies along the depth of submergence of the plates. The plates are submerged in water of uniform depth. The velocity potential is expanded by using Havelock’s expansion of water wave potential. The associated boundary value problem is transformed into two coupled Fredholm type integral equations with the help of the Havelock’s inversion theorem and the porous plate condition. A multi-term Galerkin approximation in terms of Chebyshev polynomials is used to solve the vector integral equations and to obtain the numerical estimates for the reflection and the transmission coefficients. The computed numerical results for the reflection coefficient are depicted graphically for various values of several parameters. The present results are validated against the known results for the case of two identical impermeable plates and a single permeable plate submerged in water of finite depth.

An analytical approach for free vibrations analysis of viscoelastic circular and annular plates using FSDT

ABSTRACTIn this paper, free vibrations analysis of asymmetric viscoelastic annular and circular plates are studied using the first order shear deformation theory. The viscoelastic behavior is assumed standard linear solid in shear and elastic in bulk. Hamilton's principle is employed to derive governing equations which are five coupled partial differential equations with variable coefficients. Using the perturbation technique and the Fourier series, the equations of motion are solved analytically. Determination of the natural frequencies of the plate with different combinations of boundary conditions including simply supported, clamped, and free are considered. In addition, the sensitivity of the results to the geometrical and mechanical parameters is investigated. The results are compared with those obtained from the literature, classical plate theory, and finite elements package.

Numerical analysis of viscoelastic process-induced residual distortions during manufacturing and post-curing

Degree of cure- and temperature-dependent elastic and viscoelastic models were implemented into ABAQUS to compute the geometrical distortion developed during the RTM manufacturing and post-curing of asymmetric plates and corner shaped parts. Comparisons between the predicted and experimental geometrical distortion for an asymmetric plate reinforced with 3D interlock woven fabric are presented. The results showed that the parts can experience creep behavior when submitted to free-standing post-curing, increasing the total geometrical distortion up to 30%, depending on post-curing cycle and part geometry. The numerical results of this work demonstrate that a temperature-dependent viscoelastic model is needed to accurately predict the geometrical distortion evolution developed during cure cycles where post-curing processes are involved.

Viscoelastic distortion in asymmetric plates during post curing

This study aims at understanding the geometrical instability triggered by the residual stresses generated during the manufacturing and post-curing of composites plates. Asymmetric plates with a [0/90] configuration were manufactured by Resin Transfer Molding (RTM). Manufactured plates were reheated free standing in an convection oven to study their behavior at high temperatures. Digital image analysis was used to monitor the plates curvature evolution with time and temperature. The experimental results of this work demonstrates the impact of the resin’s viscoelastic behavior on the geometrical distortion generated by residual stresses in asymmetric plates at high temperatures.

The IMLS-Ritz analysis of laminated CNT-reinforced composite quadrilateral plates subjected to a sudden transverse dynamic load

A first known study on the mechanical behavior of laminated CNT-reinforced quadrilateral composite plates due to a sudden transverse dynamic load is performed. In this study, a moderately thick plate is considered; therefore, the first-order shear deformation theory (FSDT) is employed in the formulation. The numerical analysis of the problem is carried out using the IMLS-Ritz method. The Newmark-β method is employed for the numerical time integration of the dynamic problem. The Mori-Tanaka approach is adopted for predicting the properties of CNT-composites. The numerical stabilities and accuracies of the IMLS-Ritz method are examined. The convergence properties are illustrated through solving an isotropic square plate and a laminated CNT-composite quadrilateral plate by varying their node numbers and support sizes. A comprehensive parametric study has been carried out to examine the dynamic behavior of symmetric and asymmetric CNT-composite plates.

On physically asymmetric sandwich plates with metal foam core subjected to blast loading: dynamic response and optimal design

The dynamic response of physically asymmetric rectangular sandwich plates with metal foam core subjected to blast loading is investigated analytically and numerically. The so-called ‘bounds’ of analytical solutions for the maximum central deflection of back face-sheets and the structural response time are obtained, respectively, by employing the yield criteria for an asymmetric sandwich structure including core compression. Furthermore, an improved membrane mode analysis considering the ‘residual’ bending moment for asymmetric sandwich plates is presented and the membrane mode solutions are given. It is shown that there is a good agreement between the theoretical predictions and the numerical results. Based on the analytical formulae, optimal design charts are constructed to maximize the impulsive resistance of physically asymmetric sandwich plates for a given mass. Finally, the performances of optimally designed sandwich plates with various face-sheet material combinations are discussed.

Tibial Base Plate for Total Knee Arthroplasty: Symmetric or Asymmetric?

BackgroundIdeal positioning and best coverage of the tibial base plate are essential in total knee arthroplasty. There are 2 types of tibial base plates: symmetric and asymmetric. The superiority of one to the other is still controversial. The aim of this study was to compare symmetric and asymmetric tibial base plates for total knee arthroplasty in terms of rotational alignment and coverage.MethodsThe study was conducted on a total of 80 cadaveric tibial bones. Two surgeons were asked to place 20 symmetric (group 1) and 20 asymmetric (group 2) tibial base plates taking care to ensure the best coverage that they were able to determine. Afterwards, the rotational errors and coverage were assessed with reference to the posterior tibial margin and posterior condylar axis on the three-dimensional computed tomography (3D CT) scan. In the second part of the study, the surgeons were asked to place 20 symmetric (group 3) and 20 asymmetric (group 4) base plates taking care to ensure the best rotational alignment. The rotational errors and the areas uncovered or overstuffed after the application were measured on the 3D CT scan.ResultsOn the comparison of rotational errors, while there was no significant difference between group 1 and group 2 in terms of coverage (p = 0.624), the mean external rotation error was significantly greater in group 2 (p = 0.034). On the comparison of coverage, while there was no significant difference between group 3 and group 4 in terms of rotation (p = 0.36), the mean ratios of the uncovered tibial surface to the total tibial surface (p = 0.041) and also the overstuffed area to the total base plate surface (p = 0.029) were significantly greater in group 4.ConclusionsThe determination of correct size and rotation of the tibial component is essential for favorable outcomes of total knee arthroplasty. In this study, the symmetric tibial base plate design was more effective than the asymmetric design in providing the ideal tibial rotation and coverage.

Blast response of geometrically asymmetric metal honeycomb sandwich plate: Experimental and theoretical investigations

Dynamic response of geometrically asymmetric sandwich plates with aluminum hexagonal honeycomb core subjected to blast loading is investigated experimentally and theoretically. Specimens of various face sheet thicknesses are tested for three blast intensities which are varied by changing the weights of cyclotrimethylene trinitramine (RDX) explosive charges at a constant standoff distance. Four edges of sandwich plates are fully clamped. The deformation and damage modes of sandwich plates are obtained. The influences of the blast loading and the core density on the dynamic response of sandwich plates are analyzed. The analytical model is developed to predict the blast response of the geometrically asymmetric sandwich plate subjected to blast loading. It is shown that the theoretical predictions of the deflection of the center point at the rear face sheet is in good agreement with the experimental results. The geometrical asymmetry due to the thicknesses of the face sheets has a significant effect on the deformation and damage of sandwich plates.

A proposed experimental search for chameleons using asymmetric parallel plates

Light scalar fields coupled to matter are a common consequence of theories of dark energy and attempts to solve the cosmological constant problem. The chameleon screening mechanism is commonly invoked in order to suppress the fifth forces mediated by these scalars, sufficiently to avoid current experimental constraints, without fine tuning. The force is suppressed dynamically by allowing the mass of the scalar to vary with the local density. Recently it has been shown that near future cold atoms experiments using atom-interferometry have the ability to access a large proportion of the chameleon parameter space. In this work we demonstrate how experiments utilising asymmetric parallel plates can push deeper into the remaining parameter space available to the chameleon.

Retrospective study of asymmetric vs symmetric tibial plates and ultracongruent vs posterior stabilized inserts in Indian population: An Indian experience of Natural Knee II.

Results of asymmetric tibial base plates vs symmetric tibial base plates and ultracongruent insert vs posterior stabilized insert in Indian population. A total of 47 knee replacements with mean age of 65.2 years in 38 patients (16 males and 22 females) between 2007-2011 were included. Natural Knee II (21 models) were compared with 26 models of other knees (12 PFC-Sigma, one PFC-RPF, 10 Nexgen and three Vanguard). The ultracongruent insert of NK II lead to creation of greater post-op mean flexion deformity of 18° (range 15-20°) as compared to 5.8° (range 5-8°) in other knees with PS insert (P<0.001, confidence limit of 24.2-0.1). After 3 months NK II patients had a lower mean post-operative knee score of 87 as compared to mean post-operative knee score of 96 (P<0.001, confidence limit of 17.9-0.1) in the non-NK II patients because of greater points deductions due to the creation of greater mean flexion deformity. When NO implant overhang is accepted on medial side, asymmetric tibial base plates leaves large portions of peripheral lateral tibial plateau uncovered by implant; decreasing the implant bone surface area ratio of Knee Society Radiographic Assessment Criteria. Similar problem is not encountered with symmetric tibial base plates. Symmetric and not asymmetric tibial base plates provide greater bone coverage in Indian (ethnic Punjabi) population when no implant overhang is accepted. Further use of NK II was discontinued after just 21 cases in the interest of the patients.

Advanced divertor concept design and analysis for HL-2M

HL-2M is a tokamak device that is under construction and will be put into operation in the near future. Based on the magnetic coil design of HL-2M, standard divertor, snowflake divertor and tripod divertor configurations have been designed. The potential properties of snowflake divertor configurations have been analyzed, such as the low poloidal field (Bp) area around the X-point, the connection length, target plate and magnetic field shear. The linear peeling-ballooning (P-B) mode is studied by BOUT++ code for snowflake divertor configurations. According to the divertor configuration properties of HL-2M, asymmetric target plates have been concept designed to be compatible with the intended single null (SN) divertor configurations as well as double null (DN) divertor configurations. The SOLPS5.0 code is used to predict the details of the divertor plasma under the conditions of the divertor configurations noted above without impurities. This result shows that the peak heat load on an outer target plate of the advanced divertor is about 40% of that of the standard divertor. But more power will be transported to the inner target plate of advanced divertor, and this will cause a higher peak heat load on the inner target plate. The advanced divertor will also have to work under low plasma recycling conditions with high particle temperature and low density in an open divertor target geometry. When the SN configuration changes to a DN tripod divertor configuration, most of the power exhaust is handled by the outer divertor target plates and the peak heat load on these is about 4.1MW/m2 (with a power exhaust of 20MW). This range of optimized divertor configurations and target geometry will enable the study of advanced divertor physics and high performance plasmas in HL-2M tokamak.

Experimental and numerical study on hydrodynamic performance of a wave energy converter using wave-induced motion of floating body

This paper presents results from experimental and numerical investigations on the wave potential extraction of an energy conversion device subjected to regular waves in intermediate water depth. The device is based on a pontoon-type floating breakwater with asymmetric mooring plates. The numerical model is built based on the Navier-Stokes solver coupled with immersed boundary method, volume of fluid method and the mechanics model of energy device. The data obtained in the laboratory investigation suggest that reactive control methods must be employed to optimize the load of the power take off system and maintain the wave energy converter near resonance, which plays an important role in capturing higher wave power. The energy conversion efficiency can reach 14% during experimental runs with only one dynamo installed. Furthermore, by comparing with the experimental results, the applicability of the developed numerical model is demonstrated in predicting the interactions between water waves and the wave power device. With the help of snapshots of water particle velocity field and the wave pressure field from numerical calculation, the flow pattern and external forces from the fluid field can also be estimated. Finally, the effects of mooring angle and the length of floating body on the performance of the energy device are highlighted.

Evaluation of mixed theories for laminated plates through the axiomatic/asymptotic method

This paper proposes variable kinematic, mixed theories for laminated plates built via the asymptotic/axiomatic method (AAM). This method has been recently developed and successfully applied to develop refined theories for multilayered plates and shells. The AAM evaluates the accuracy of each unknown variables of a structural model. The present paper extends the AAM to mixed theories based on the Reissner Mixed Variational Theorem (RMVT). The displacement and transverse stress fields are modeled by means of the Carrera Unified Formulation (CUF), and expansions up to the fourth-order are employed. Equivalent Single Layer (ESL) and Layer Wise (LW) schemes are adopted, and closed-form Navier-type solutions are considered.The AAM is exploited to determine the set of active terms of a refined plate model. The inactive terms are then discarded. The effectiveness of each variable is evaluated with respect to an LW, fourth-order mixed model. Reduced models are built for different thickness ratios, stacking sequences and displacement/stress variables.The results suggest that reduced models with significantly less unknown variables than full models can be built with no accuracies penalties. Such models are problem dependent, and full models should be preferred in the case of thick, asymmetric plates.

Three-dimensional magneto-elastic analysis of asymmetric variable thickness porous FGM circular plates with non-uniform tractions and Kerr elastic foundations

In the present paper, a complicated and general problem of a functionally graded porous variable thickness circular plate subjected to non-axisymmetric and non-uniform shear and normal tractions and a magnetic actuation, and supported by a non-uniform Kerr elastic foundation is analyzed. Although such a combination of complexities may rarely be observed in the practical applications, the developed solution may identically be employed for many practical problems, as special cases. The governing equations are derived based on the three-dimensional theory of elasticity instead of using the approximate plate theories. The solution is proposed based on the differential quadrature and state space vector techniques in the radial and thickness directions, respectively. A comprehensive parametric study is presented to evaluate effects of the material, loading, boundary, and elastic foundation specifications on the resulting displacement, stress, Lorentz force, electromagnetic stress, and magnetic perturbation quantities.

Granular transport in driven granular gas.

We numerically and theoretically investigate the behavior of a granular gas driven by asymmetric plates. The injection of energy in the dissipative system differs from one side to the opposite one. We prove that the dynamical clustering which is expected for such a system is affected by the asymmetry. As a consequence, the cluster position can be fully controlled. This property could lead to various applications in the handling of granular materials in low-gravity environment. Moreover, the dynamical cluster is characterized by natural oscillations which are also captured by a model. These oscillations are mainly related to the cluster size, thus providing an original way to probe the clustering behavior.

Vibration and sound radiation of an asymmetric laminated plate in thermal environments

Analytical studies on the vibration and sound radiation characteristics of an asymmetric laminated rectangular plate are carried out in this paper. Theoretical formulations, in which the effects of thermal environments are taken into account, are derived for the vibration and sound radiation based on both first-order shear deformation plate theory and Rayleigh integral. It is found that the natural frequencies, the resonant amplitudes of vibration response and the sound pressure level decrease with the temperature rising. The natural frequencies of asymmetric plates are smaller than those of symmetric plates and the velocity responses of asymmetric plates are larger than those of symmetric plates.

A global–local theory with stress recovery and a new post-processing technique for stress analysis of asymmetric orthotropic sandwich plates with single/dual cores

While the 3D elasticity and the available local and zigzag theories encounter inaccuracies for very thin plates, results of the global theories become unreliable for thick plates with severe transverse variations in the material properties. In the present research, a quadratic finite element global–local sandwich plate theory with elasticity correction (stress recovery) is proposed for static stress and displacement analysis of sandwich plates with orthotropic face sheets and single or dual cores. Since the transverse shear stresses are derived based on the three-dimensional theory of elasticity, the continuity condition of the transverse shear stresses is satisfied at the interfaces between the layers, a priori. The presented theory not only leads to higher accuracies in comparison to the available high-order zigzag theories in some cases (especially, for soft or dual cores) but also it is computationally more economic. Results show that the results of the available zigzag and global–local theories may encounter inaccuracy problems not only for huge numbers of the sub-layers, but also for small numbers of the orthotropic layers.

Effect of velocity boundary conditions on the heat transfer and flow topology in two-dimensional Rayleigh-Bénard convection.

The effect of various velocity boundary condition is studied in two-dimensional Rayleigh-Bénard convection. Combinations of no-slip, stress-free, and periodic boundary conditions are used on both the sidewalls and the horizontal plates. For the studied Rayleigh numbers Ra between 10(8) and 10(11) the heat transport is lower for Γ=0.33 than for Γ=1 in case of no-slip sidewalls. This is, surprisingly, the opposite for stress-free sidewalls, where the heat transport increases for a lower aspect ratio. In wider cells the aspect-ratio dependence is observed to disappear for Ra ≥ 10(10). Two distinct flow types with very different dynamics can be seen, mostly dependent on the plate velocity boundary condition, namely roll-like flow and zonal flow, which have a substantial effect on the dynamics and heat transport in the system. The predominantly horizontal zonal flow suppresses heat flux and is observed for stress-free and asymmetric plates. Low aspect-ratio periodic sidewall simulations with a no-slip boundary condition on the plates also exhibit zonal flow. In all the other cases, the flow is roll like. In two-dimensional Rayleigh-Bénard convection, the velocity boundary conditions thus have large implications on both roll-like and zonal flow that have to be taken into consideration before the boundary conditions are imposed.

Modular design of the LED vehicle projector headlamp system

A well designed headlamp for a vehicle lighting system is very important as it provides drivers with safe and comfortable driving conditions at night or in dark places. With the advances of the semiconductor technology, the LED has become the fourth generation lighting source in the auto industry. In this study, we will propose a LED vehicle projector headlamp system. This headlamp system contains several LED headlamp modules, and every module of it includes four components: focused LEDs, asymmetric metal-based plates, freeform surfaces, and condenser lenses. By optimizing the number of LED headlamp modules, the proposed LED vehicle projector headlamp system has only five LED headlamp modules. It not only provides the low-beam cutoff without a shield, but also meets the requirements of the ECE R112 regulation. Finally, a prototype of the LED vehicle projector headlamp system was assembled and fabricated to create the correct light pattern.