Dynamic Behaviors of Axially Moving Viscoelastic Plate with Varying Thickness

Structural components of varying thickness draw increasing attention these days due to economy and light-weight considerations. In view of the absence of research in vibration analysis of viscoelastic plate with varying thickness, this study devotes to investigate the dynamic behaviors of axially moving viscoelastic plate with varying thickness. Based on the thin plate theory and the two-dimensional viscoelastic differential constitutive relation, the differential equation of motion of the axially moving viscoelastic rectangular plate is derived, the plate constituted by Kelvin-Voigt model has linearly varying thickness in the y-direction. The dimensionless complex frequencies of axially moving viscoelastic plate with four edges simply supported are calculated by the differential quadrature method, curves of real parts and imaginary parts of the first three-order dimensionless complex frequencies versus dimensionless moving speed are obtained, the effects of the aspect ratio, thickness ratio, the dimensionless moving speed and delay time on the dynamic behaviors of the axially moving viscoelastic rectangular plate with varying thickness are analyzed. When other parameters keep constant, with the decrease of thickness ratio, the real parts of the first three-order natural frequencies decrease, and the critical divergence speeds of various modes decrease too, moreover, whether the delay time is large or small, the frequencies are all complex numbers.

Free vibrations of simply supported nonhomogeneous isotropic rectangular plates of bilinearly varying thickness and elastically restrained edges against rotation using Rayleigh-Ritz method

This paper addresses the free transverse vibrations of thin simply supported nonhomogeneous isotropic rectangular plates of bilinearly varying thickness with elastically restrained edges against rotation. The Gram-Schmidt process has been used to generate two-dimensional boundary characteristic orthogonal polynomials, which have been used in the Rayleigh-Ritz method to study the problem. The lowest three frequencies have been computed for various values of nonhomogeneous parameters, thickness parameters, aspect ratio and flexibility parameters. A comparison of the results with those available in the literature has been made. Three-dimensional mode shapes for the specified plate have been presented.

NON-LINEAR DYNAMIC BEHAVIOR OF THERMOELASTIC CIRCULAR PLATE WITH VARYING THICKNESS SUBJECTED TO NONCONSERVATIVE LOADING

The non-linear dynamic behaviors of thermoelastic circular plate with varying thickness subjected to radially uniformly distributed follower forces are considered. Two coupled non-linear differential equations of motion for this problem are derived in terms of the transverse deflection and radial displacement component of the mid-plane of the plate. Using the Kantorovich averaging method, the differential equation of mode shape of the plate is derived, and the eigenvalue problem is solved by using shooting method. The eigencurves for frequencies and critical loads of the circular plate with unmovable simply supported edge and clamped edge are obtained. The effects of the variation of thickness and temperature on the frequencies and critical loads of the thermoelastic circular plate subjected to radially uniformly distributed follower forces are then discussed.

Part Thickness Variation during the Vacuum Assisted Resin Infusion Process

An experimental procedure was designed to monitor the preform thickness change real-time throughout the vacuum assisted resin infusion( VARI) process. Two kinds of liquid with different viscosity were infused with different post-filling time. The variation of the part thickness during the VARI process was studied. And the effect of the post-filling time on the part thickness was investigated.The results indicate that the compaction behavior of the preform can be divided into three stages,and the fiber volume fraction varies with the post-filling time in a similar sinusoid form. In addition,the post-filling should be overtime for the greatest fiber volume fraction,and when the resin is infused with higher viscosity,the greatest fiber volume fraction is higher.

GENERALIZED VARIATIONAL PRINCIPLES FOR VISCOELASTIC THIN AND THICK PLATES WITH DAMAGE

From the constitutive model with generalized force fields for a viscoelastic body with damage, the differential equations of motion for thin and thick plates with damage are derived under arbitrary boundary conditions. The convolution-type functionals for the bending of viscoelastic thin and thick plates with damage are presented, and the corresponding generalized variational principles are given. From these generalized principles, all the basic equations of the displacement and damage variables and initial and boundary conditions can be deduced. As an example, we compare the difference between the dynamical properties of plates with and without damage and consider the effect of damage on the dynamical properties of plates.

High-yield production of non-layered 2D carbon complexes:Thickness manipulation and carbon nanotube branches for enhanced lithium storage properties

Non-layered two-dimensional(2 D)carbon complexes manifest great potential in energy-related applications owing to their exotic electronic structures,large electrochemically active surface,and intriguing synergistic effects.However,reliable method for mass production and thickness manipulation of 2 D carbon complexes remains great challenges.Here,inspired by blowing chewing gum into bubbles,a“tailored gel expanding"strategy is proposed for high-yield synthesis of non-layered 2 D carbon complexes with tailored thickness from~12 nm to~1 lm,by controllable pyrolysis of metal-polymeric gel with adequate crosslinking degree.The key feature for thickness manipulation is introducing NH4 NO3 in sol-gel process,which tailors the expansion behavior of gel precursor during subsequent pyrolysis.Various of 2 D sheets with intimately coupled N,O-doped carbon(NOC)and Ni Co-based(Ni Co,(Ni Co)S_(2),(Ni Co)Se_(2),Ni Co_(2)O_(4),(Ni Co)(PO_(3))_(2))nanocrystals are obtained on a large scale and without any impurities.Moreover,these 2 D products are branched with in-situ grown CNTs on the surface,accelerating electrons transfer and preventing the nanosheets from stacking.As a demonstration,the 2 D(Ni Co)S_(2)/NOC with optimized thickness manifests excellent lithium storage properties in both half and full cells.This method paves a new path for massive and controlled production of non-layered 2 D materials with tailored thickness and robust structure stability for energy-related applications.

NUMERICAL SIMULATION OF FLOW OF HIGHLY VISCOELASTIC FLOW IN THREE－DIMENSIONAL VARYING THICK SLIT CHANNEL

The distributive law of flow rate is studiedfor highly viscoelastic flow in threedimensional slit channel with varying thickness by using Finite Block Element Method(FBM).As an example.the influence of restrictive block on.flow rate is obtained in fish channel of the plate extruding die and the results of numerical simulation are in concordance withthe approximatical analytical solution.It is proved that FBM can be considered as an important toolfor CAD/CAM.

Deep learning in two-dimensional materials:Characterization,prediction,and design

Since the isolation of graphene,two-dimensional(2D)materials have attracted increasing interest because of their excellent chemical and physical properties,as well as promising applications.Nonetheless,particular challenges persist in their further development,particularly in the effective identification of diverse 2D materials,the domains of large-scale and highprecision characterization,also intelligent function prediction and design.These issues are mainly solved by computational techniques,such as density function theory and molecular dynamic simulation,which require powerful computational resources and high time consumption.The booming deep learning methods in recent years offer innovative insights and tools to address these challenges.This review comprehensively outlines the current progress of deep learning within the realm of 2D materials.Firstly,we will briefly introduce the basic concepts of deep learning and commonly used architectures,including convolutional neural and generative adversarial networks,as well as U-net models.Then,the characterization of 2D materials by deep learning methods will be discussed,including defects and materials identification,as well as automatic thickness characterization.Thirdly,the research progress for predicting the unique properties of 2D materials,involving electronic,mechanical,and thermodynamic features,will be evaluated succinctly.Lately,the current works on the inverse design of functional 2D materials will be presented.At last,we will look forward to the application prospects and opportunities of deep learning in other aspects of 2D materials.This review may offer some guidance to boost the understanding and employing novel 2D materials.

VARI成型厚度稳定与抽真空时间的研究

采用无接触式电涡流位移传感系统,对复合材料真空辅助成型过程中的厚度变化进行了实时监测。研究了在其他条件相同情况下,树脂粘度、充模距离、铺层厚度、铺覆导流网等对厚度稳定需要的最短抽真空时间的影响。结果表明,树脂注满并关闭树脂管以后,持续抽真空可有效提高真空辅助工艺成型纤维体积含量,且有利于减小沿树脂流动方向的厚度梯度;树脂粘度对厚度稳定所需要的最短抽真空时间影响最为明显,粘度越高需抽真空时间越长,充模距离、铺层厚度以及导流网对需要最短的抽真空时间影响相对较小。

The influence of two-dimensional organic adlayer thickness on the ultralow frequency Raman spectra of transition metal dichalcogenide nanosheets

Recently, it has been reported that physisorbed adsorbates can be trapped between the bottom surface of twodimensional(2D) materials and supported substrate to form2 D confined films. However, the influence of such 2D confined adsorbates on the properties of 2D materials is rarely explored. Herein, we combined atomic force microscopy(AFM), Kelvin probe force microscopy(KPFM) and Raman spectroscopy especially the ultralow frequency(ULF) Raman spectroscopy to explore the influence of 2D confined organic adlayer thickness on the ULF breathing modes of few-layer MoS2 and WSe2nanosheets. As the thickness of organic adlayers increased, red shift, coexistence of blue and red shifts as well as blue shift of ULF breathing mode was observed. KPFM measurement confirmed the enhanced n-doping and p-doping behaviors of organic adlayers as their thickness increased,respectively. Our results will provide new insights into the interaction between 2D confined adsorbates and bottom surface of 2D nanosheets, which could be useful for modulating properties of 2D materials.

Independent thickness and lateral size sorting of two-dimensional materials

Two-dimensional(2D)materials possess unique thickness-and lateral-size-dependent properties.Many efforts have been devoted to obtaining 2D materials with narrow structure heterogeneity while it is still challenging to independently control their thickness and lateral size,limiting their widespread applications.Here,we develop a three-step method which achieves independent thickness and lateral size sorting of 2D materials.Taking 2D h-BN flakes as an example,their thickness and lateral size are independently sorted to different fractions with thicknesses smaller than 6 nm.In addition,the 2D h-BN flakes possess narrow distributions of both thickness and lateral size.We further develop a force field extraction method and achieve scalable size sorting of 2D h-BN,which is universal for sorting other 2D materials including MoS2 and graphene oxide.This work reports an effective method to produce structure homogenous 2D materials and will help fundamental studies and applications of 2D materials where thickness and lateral size are of concern.

热压辅助预成型的超大厚度制件VARI成型工艺研究

以VARI工艺为代表的复合材料低成本液体成型技术愈发受到研究关注。针对超大厚度制件的VARI成型,创造性地引入热压辅助预成型技术,以100层的超大厚度层板的VARI成型为例,在制备预成型体的过程中,采用热压辅助预成型,并分析热压辅助预成型引入后,预成型体的厚度变化、进出胶口设置方式以及对最终制件质量的影响。该研究对于提升VARI工艺制件纤维体积含量和制件性能,进一步拓展VARI工艺在民机结构中的应用都具有积极意义,研究结果可以为VARI成型工艺制备的大厚度制件在飞机结构中的设计与应用提供参考。

大齿数裂纹直齿轮时变啮合刚度算法研究

针对齿数大于41的直齿轮,基于切齿几何和齿轮啮合原理,明确渐开线齿廓起点和渐开线与基圆交点的区别,引入过渡曲线参数方程,对基于能量法的时变啮合刚度计算公式进行改进,全面建立了不同裂纹水平的故障轮齿模型。在此基础上,以斜线作为有效齿厚削减限制线,使得裂纹轮齿模型更严格、考虑因素更全面。参考有限元法计算结果,分别讨论了模型修正、裂纹程度、有效齿厚削减限制线具体形式等因素对时变啮合刚度的影响。计算结果表明,未修正轮齿模型会导致大齿数裂纹齿轮时变啮合刚度计算结果偏小;啮合刚度降低程度随裂纹水平的增大而不断增加。根据裂纹水平给出了有效齿厚削减限制线的建模建议:当裂纹水平较低时,有效齿厚削减限制线宜采用直线;当裂纹水平较高时,采用直线会产生较大误差;采用斜线不仅便于计算,同时能够满足计算精度需求,具有更强的实用性。

Optimization of a guided-mode resonance filter by varying the thickness of the buffer layer

In this Letter, we demonstrate that by adjusting the thickness of the buffer layer, the optical responses of a guided-mode resonance filter （GMRF） can be improved for sensor applications. The GMRF is fabricated using a replica molding with a plastic substrate and a UV-curable polymer. SiO2 buffer layers of different thicknesses are deposited before the waveguide-layer deposition. The sensitivity of the GMRFs decreases slightly with in- creasing SiO2 layer thickness. By contrast, the full width at half-maximum reduces substantially with increasing SiO2 layer thickness, resulting in the improvement of the overall figure of merit.

单向变厚度Levy型薄板的自由振动分析

针对单向变厚度Levy型薄板的自由振动问题,基于薄板振动理论,将设定的挠度函数代入关于挠度的变系数四阶偏微分的振动控制方程,把变系数四阶偏微分方程求解挠度的问题转化为第二类Volterra积分方程的求解,并采用二次样条函数近似求解积分方程,建立单向变厚度Levy型薄板自由振动固有频率的求解方法。对3种不同边界条件的Levy型薄板最低固有频率的算例进行验证。研究结果表明:该方法合理可靠、计算简便,满足精度要求;该方法还可进一步推广到求解任意单向变刚度Levy型薄板自由振动的最低固有频率。

基于时变模型的齿轮啮合过程润滑状态研究

基于Dowson提出的最小油膜厚度方程,利用Matlab/Simulink仿真平台,建立齿轮啮合过程润滑状态的实时仿真系统。分析了齿轮啮合过程最小油膜厚度的时域变化情况,研究了齿轮润滑状态随转速、输入扭矩的变化关系,计算结果表明:随着啮合点向主动齿轮齿顶移动,其最小油膜厚度逐渐增大;齿轮点蚀经常发生在节圆附近。对节圆处的润滑状态进行了研究,发现随着输入转速的增加,轮齿节圆处的最小油膜厚度逐渐增加;随着输入扭矩的增加,轮齿节圆处的最小油膜厚度减小。

线性变厚度矩形薄板自由振动的精确解

基于小挠度薄板理论，采用Ｌｅｒｙ法结合Ｆｒｏｂｅｎｉｕｓ法构造的幂级数解，得到了两对边简支另两对边为ＳＳ、ＣＳ、ＦＦ支承的三种线性变厚度矩形薄板的自振频率随板的边长比及厚度比变化的精确解及其振型函数的解析表达式。

路面不等厚排水层设计

基于饱和渗流理论,结合高速公路排水实际情况,提出一种提高排水层排水能力的设计方法。该设计方法建立面层与等厚排水层,面层与不等厚排水层之间的水量交换计算模型,获得等厚排水层不同横向位置断面处的流量计算公式和不等厚排水层不同横向位置断面处的流量计算公式,对比分析等厚和不等厚排水层的排水能力。结果表明:在排水层横向截面积相等的情况下,不等厚排水层的排水能力大于等厚排水层的排水能力。不等厚排水层的厚度渐变坡度对排水层的排水能力的提高有显著作用,其厚度对排水能力影响不显著。因此,排水材料的渗透系数以及不等厚排水层厚度渐变坡度应为不等厚排水层设计的主要控制参数。

线性变厚度粘弹性矩形板在随从力作用下的动力稳定性

利用粘弹性微分型本构关系和薄板理论,对线性变厚度粘弹性矩形薄板建立了在切向均布随从力作用下的运动微分方程,采用微分求积法研究了在随从力作用下线性变厚度粘弹性矩形薄板的稳定性问题,具体对对边简支对边固支和三边简支一边固支条件下体变为弹性、畸变服从Kelvin-Voigt模型的变厚度粘弹性矩形板在随从力下的广义特征值问题进行了求解,分析了薄板的长宽比、厚度比及材料的无量纲延滞时间的变化对随从力作用下矩形薄板的失稳形式及相应的临界荷载的影响.

变厚度多层介质结构的一种三维数值半解析方法

应用复合材料层合结构分层理论思维，建立起以样条函数、级数及插值相结合的新型三维数值半解析算法，以期解决复材层合变厚度结构的变形及内力分析，并作为该类型结构优化设计的高精度内核计算工具。本文方法克服了一般半解析方法对解析函数类型的过分依赖性；在原始数据准备、计算规模、数值精度、收敛特性及稳定性诸方面都较有限元方法有显著改善；特别对复材层合结构的变厚度区段，无需引入任何理论假设。