Edge effects of metal plate in laser forming

To search for the new scanning plan that can reduce the bending angle variation and the bending curvatures of the bending edge, an explanation for the causes of the edge effects was given. Six new scanning strategies were proposed through the change of the scanning length of middle and two ends based on the above analyses. Numerical simulations were carried out to study the edge effects using the six new scanning strategies. The simulation results show that the new scanning strategies can improve effectively the quality of the forming parts.

Magnetoelectric effects in multiferroic laminated plates with imperfect interfaces

Two-dimensional （2D） equations for multiferroic （MF） laminated plates with imperfect interfaces are established in this paper. The interface between two adjacent sublayers, which are not perfectly bonded together, is modeled as a general spring-type layer. The mechanical displacements, and the electric and magnetic potentials of the two adjacent layers are assumed to be discontinuous at the interface. As an example, the influences of imperfect interfaces on the magnetoelectric （ME） coupling effects in an MF sandwich plate are investigated with the established 2D governing equations. Numerical results show that the imperfect interfaces have a significant impact on the ME coupling effects in MF laminated structures.

Static deformation of a multilayered one-dimensional hexagonal quasicrystal plate with piezoelectric effect

Quasicrystals （QCs） are sensitive to the piezoelectric （PE） effect. This paper studies static deformation of a multilayered one-dimensional （1D） hexagonal QC plate with the PE effect. The exact closed-form solutions of the extended displacement and traction for a homogeneous piezoelectric quasicrystal （PQC）plate are derived from an eigensystem. The general solutions for multilayered PQC plates are then obtained using the propagator matrix method when mechanical and electrical loads are applied on the top surface of the plate. Numerical examples for several sandwich plates made up of PQC, PE, and QC materials are provided to show the effect of stacking sequence on phonon, phason, and electric fields under mechanical and electrical loads, which is useful in designing new composites for engineering structures.

Dynamic Stability of Viscoelastic Plates with Finite Deformation and Shear Effects

Based on Reddy's theory of plates with higher order shear deformations and the Boltzmann superposition principles, the governing equations were established for dynamic stability of viscoelastic plates with finite deformations taking account of shear effects. The Galerkin method was applied to simplify the set of equations. The numerical methods in nonlinear dynamics were used to solve the simplified system. It could be seen that there are plenty of dynamic properties for this kind of viscoelastic plates under transverse harmonic loads. The influences of the transverse shear deformations and material parameter on the dynamic behavior of nonlinear viscoelastic plates were investigated.

NUMERICAL-PERTURBATION ANALYSIS OF EDGE EFFECT IN BENDING LAMINATED PLATE

In this paper, we consider a bending laminated plate. At first, the dimensionless variables are used to transform the equilibrium equations of any layer to perturbation differential equations. Secondly, the composite expansion is used and the solution domain is divided into interior and boundary layer regions and the mathematical models for the outer solution and the inner solution are yielded respectively. Then, the inner solution is expressed with the boundary intergral equation.

Geomorphological effects of plate movement during Quaternary in China' s tropics

The eastern and western fronts of plate movement in Taiwan Island and Tibetan Plateau respectively are the two major sources of tectonic force for the morphogensis during Quaternary in China's tropics. Seven examples of geomorphological effects of plate movement are enumerated to discuss the differentiation of tectonic landforms in space and time during Quaternary. The tectonic movement tends to be more active since middle Pleistocene. Some phenomena such as the arc-shape mountain systems, volcanism and crustal deformation imply that the juncture zone of eastern and western tectonic forces is located at about 110 o E.

EFFECT OF DAMAGE ON NONLINEAR DYNAMIC PROPERTIES OF VISCOELASTIC RECTANGULAR PLATES

The nonlinear dynamic behaviors of viscoelastic rectangular plates including the damage effects under the action of a transverse periodic load were studied. Using the von Karman equations, Boltzmann superposition principle and continuum damage mechanics, the nonlinear dynamic equations in terms of the mid_plane displacements for the viscoelastic thin plates with damage effect were derived. By adopting the finite difference method and Newmark method, these equations were solved. The results were compared with the available data. In the numerical calculations, the effects of the external loading parameters and geometric dimensions of the plate on the nonlinear dynamic responses of the plate were discussed. Research results show that the nonlinear dynamic response of the structure will change remarkably when the damage effect is considered.

A two-dimensional fully analytical model with polarization effect for off-state channel potential and electric field distributions of GaN-based field-plated high electron mobility transistor

In this paper, we present a two-dimensional （2D） fully analytical model with consideration of polarization effect for the channel potential and electric field distributions of the gate field-plated high electron mobility transistor （FP-HEMT） on the basis of 2D Poisson＇s solution. The dependences of the channel potential and electric field distributions on drain bias, polarization charge density, FP structure parameters, A1GaN/GaN material parameters, etc. are investigated. A simple and convenient approach to designing high breakdown voltage FP-HEMTs is also proposed. The validity of this model is demonstrated by comparison with the numerical simulations with Silvaco-Atlas. The method in this paper can be extended to the development of other analytical models for different device structures, such as MIS-HEMTs, multiple-FP HETMs, slant-FP HEMTs, etc.

Chemical Reaction and Thermal Diffusion Effects on Mass Transfer Flow through an Inclined Plate

A numerical investigation of boundary layer mass transfer flow through an inclined plate with the effect of chemical reaction and thermal diffusion is presented in this study. The governing partial differential equations (PDE) are transformed to a system of dimensionless non-similar coupled PDEs. The transformed, non-similar conservations equations (momentum balance equation, energy balance equation and concentration balance equation) are then solved using a numerical approach known as explicit finite difference method (EFDM). Basically EFDM introduced for the unsteadiness in the momentum, temperature, and concentration fluid fields is based on the time dependent fluid velocity, temperature and concentration of the boundary surface. During the course of discussion, it is found that the various parameters related to the problem influence the calculated resultant expressions. The computed numerical solution results for the velocity, temperature, and concentration distribution with the effect of various important dimensionless parameters (Grashof number, Modified Grashof number, Prandtl number, Schmidt number, Soret number, Dufour number, chemical reaction parameter and inclination parameter) entering into the problems are critically analyzed and discussed graphically. It can be seen that two physical phenomena chemical reaction and thermal diffusion can greatly effect on the boundary layer fluid flows through an inclined plate.

Scale effects on nonlocal buckling analysis of bilayer composite plates under non-uniform uniaxial loads

Scale effects are studied on the buckling behavior of bilayer composite plates under non-uniform uniaxial compression via the nonlocal theory. Each isotropic plate is composed of a material that is different from others, and the adhesive between the plates is modeled as the Winkler elastic medium. According to the symmetry, effects of the Winkler non-dimensional parameter, the thickness ratio, the ratio of Young＇s moduli, and the aspect ratio are also considered on the buckling problem of bilayer plates, where only the top plate is under the uniaxial compression. Numerical examples show that the Winkler elastic coefficient, the thickness ratio, and the ratio of Young＇s moduli play decisive roles in the buckling behavior. Nonlocal effect is significant when the high-order buckling mode occurs or the aspect ratio is small.

Simulating the Intensifying Effect of Phosphors on Imaging Plate with UV photons

It is assumed from the energy level that ultraviolet (UV) photons may have intensifying effect on BaFBr∶Eu 2+. In this paper, effect of UV photons (220～290 nm) on the PSL intensity of X-ray irradiated BaFBr∶Eu 2+ was measured and compared to that on the PSL intensity of 220 nm photons irradiated BaFBr∶Eu 2+. It was found that after the excitation of UV photons the PSL intensity of X-ray irradiated samples decreases least at 250 nm and that of 220 nm photons irradiated samples increases most at 250 nm. When the irradiation sources are X-rays and 220 nm photons the excited electrons are photoelectron and thermal-electrons, respectively, and they have different possibility of being captured by electron traps or combined with luminescent centers. And the peak at 250 nm can be explained with the model of electrons tunneling. It is assumed that the electrons excited by 250 nm have the most possibility of tunneling.

圆锥-球缺组合药型罩战斗部侵彻双层水间隔靶板

为提升聚能战斗部毁伤性能,基于组合药型罩战斗部的起爆机理,设计一种圆锥-球缺组合药型罩聚能战斗部及双层水间隔靶板结构,建立该战斗部侵彻双层水间隔靶板的物理模型,进行数值模拟计算,根据计算结果加工战斗部及靶板的1∶3缩比模型样机,展开相应试验,为设计全尺寸战斗部样机奠定了基础。试验结果表明:该战斗部侵彻含水夹层目标时具有独特的优势,对目标的破坏效应显著增强。

Size-dependent effect on biaxial and shear nonlinear buckling analysis of nonlocal isotropic and orthotropic micro-plate based on surface stress and modified couple stress theories using differential quadrature method

The size-dependent effect on the biaxial and shear nonlinear buckling analysis of an isotropic and orthotropic micro-plate based on the surface stress, the modified couple stress theory （MCST）, and the nonlocal elasticity theories using the differential quadrature method （DQM） is presented. Main advantages of the MCST over the classical theory （CT） are the inclusion of the asymmetric couple stress tensor and the consideration of only one material length scale parameter. Based on the nonlinear von Karman assumption, the governing equations of equilibrium for the micro-classical plate consid- ering midplane displacements are derived based on the minimum principle of potential energy. Using the DQM, the biaxial and shear critical buckling loads of the micro-plate for various boundary conditions are obtained. Accuracy of the obtained results is validated by comparing the solutions with those reported in the literature. A parametric study is conducted to show the effects of the aspect ratio, the side-to-thickness ratio, Eringen＇s nonlocal parameter, the material length scale parameter, Young＇s modulus of the surface layer, the surface residual stress, the polymer matrix coefficients, and various boundary conditions on the dimensionless uniaxial, biaxial, and shear critical buckling loads. The results indicate that the critical buckling loads are strongly sensitive to Eringen＇s nonlocal parameter, the material length scale parameter, and the surface residual stress effects, while the effect of Young＇s modulus of the surface layer on the critical buckling load is negligible. Also, considering the size dependent effect causes the increase in the stiffness of the orthotropic micro-plate. The results show that the critical biaxial buckling load increases with an increase in G12/E2 and vice versa for E1/E2. It is shown that the nonlinear biaxial buckling ratio decreases as the aspect ratio increases and vice versa for the buckling amplitude. Because of the most lightweight micro-composite materials with high strength/weight and stiffness/weight ratios, it is anticipated that the results of the present work are useful in experimental characterization of the mechanical properties of micro-composite plates in the aircraft industry and other engineering applications.

结构刚塑性动力解的弹性补偿

近年来,我国学者以膜力因子法和饱和分析方法相结合为理论工具,对梁、板等结构件在脉冲载荷作用下的塑性大变形行为作了全面深入的研究,为脉冲加载下结构的最终挠度提供了优于历史上各种刚塑性近似解的最佳刚塑性预测公式。然而,由于实际工程应用中金属结构弹塑性动力响应的复杂性和数值模拟的局限性,与考虑材料弹性效应的结果相比,刚塑性解对脉冲加载下结构所预测的最终挠度的误差有多大,是一个亟待解决的关键问题。对这个问题的首阶段研究成果厘清了材料弹性对脉冲加载下结构塑性动态大变形的影响,定量评估了由最佳刚塑性理论解与弹塑性数值模拟得到的最终挠度预测结果之间的差异。在此基础上,提出了补偿弹性效应的策略和方法,即:在已有的最佳刚塑性解预测的挠度基础上添加一个补偿项,将补偿项表达为脉冲载荷强度的效应与结构自身刚度的效应分离的变量函数,并尽量减少待定系数/指数的数量,以求表达式的简洁;根据这些原则在金属结构的主要工程应用领域内选定结构刚度和外载参数的变化范围,对固支梁和固支方板的案例实施拟合与补偿,最后得到了对梁和板增添补偿项后的简单而实用的最终挠度预测公式,其相对误差在3%的范围之内,很适合工程设计应用。文末列表给出了符号与公式的一览,并对梁和方板的结果作了综合和比较。

数字化导板辅助植入种植体对老年前牙种植修复患者满意度及修复美学效果的影响

目的探究数字化导板辅助植入种植体对老年前牙种植修复患者满意度及修复美学效果的影响。方法回顾性选取2021年1月—2023年12月收治的行前牙种植修复的老年患者临床资料,依据修复方案不同进行分组,采用常规种植修复的42例(67颗种植体)为常规组,采用数字化导板辅助植入种植体修复的56例(84颗种植体)为数字化组。比较2组牙齿修复效果、种植准确度、咬合功能和种植体稳定性,记录修复后并发症与治疗费用,评价美学效果和患者满意度。结果术后第3个月和第6个月,数字化组美学、功能和生物学评分,种植体根部颊舌向与垂直向、颈部颊舌向与垂直向及根尖偏差距离均低于常规组(均P<0.05),咬合功能和种植体稳定性评分均高于常规组(均P<0.05);数字化组治疗费用高于常规组(P<0.05),手术时长少于常规组(P<0.05);数字化组术后3个月内并发症总发生率低于常规组(P<0.05);术后第3、第6个月,数字化组粉色美学指数(PES)、白色美学指数(WES)评分、对修复的满意度均高于常规组(均P<0.05)。结论数字化导板辅助植入种植体在老年患者前牙种植修复中效果良好,可减少并发症与治疗时长,保证精确度与稳定性,改善咬合功能和美观度,患者满意度提高。

波纹钢形状与拱效应对加固盖板涵承载力的影响

为了探索波纹钢形状对加固盖板涵承载力的影响及填充混凝土的拱效应形成机制,采用室内试验与数值分析相结合的研究方法,以一个室内模型试验结果为基准,建立了72个箱形、圆弧及其之间的过渡形状的波纹钢加固盖板涵的数值模型,探明了加固体系承载力随波纹钢形状参数的变化规律;基于合理拱轴的概念,探明了填充混凝土的拱效应形成机理,并采用5个数值模型进行了验证。结果表明:拱腋半径保持不变时,加固体系的承载力随着拱顶、侧墙半径的增加而减小;拱顶、侧墙半径不变时,加固体系的承载力随着拱腋半径的增加而增大;提升加固体系承载力最有效的方式是增加拱腋半径,其次是减小拱顶和侧墙半径;填充混凝土的拱效应与荷载类型有关,当波纹钢的形状能保持拱轴连续并且在素混凝土刚性角以内时,加固体系的承载力最高。在设计波纹钢加固盖板涵结构时,应根据实际工程需要综合考虑波纹钢形状与填充混凝土的拱效应,尽量避免紧贴原盖板涵的加固设计。

洋中脊动力学与俯冲带地震-岩浆-成矿事件远程效应

板块俯冲带和大陆岩浆弧的深部过程与极端地质事件之间存在密切的关系。板块俯冲与造山过程会导致地震、岩浆活动和成矿等事件的发生。这些极端事件的发生与俯冲过程中的壳幔相互作用、地幔楔形成、岩石圈部分熔融、构造-岩浆活动等因素密切相关。然而,人们对洋中脊新生地壳的不均匀性或先天“缺陷”对以上的极端事件的长远影响和远程效应了解甚少。在洋中脊新的地壳形成过程中,由于受到板块扩张、压力降低、软流圈物质上涌等因素的作用,导致新生地壳温度升高、孔隙度和裂缝发育、密度降低、结构复杂的正反馈过程。因此,新生地壳在密度、强度、温度、厚度等方面存在非均质性。这些地壳的差异性将影响和决定板块在扩张和俯冲过程中的行为,并对板块俯冲作用形成的地震、岩浆和成矿等事件产生远程影响。以太平洋俯冲和安第斯造山带为例研究发现,板块运动速度、板块俯冲角度、板片撕裂、岩石圈厚度、Moho面深度等的突变与地震、火山和斑岩矿床的时空分布存在远程关联效应,这些认知对预测板块俯冲-碰撞带发生的极端地质事件的时空分布具有重要意义。

水下爆炸载荷下柔性支撑板架结构防护效能快速预报与优化方法

为实现柔性支撑板架结构在水下爆炸下防护效能的快速评估和设计优化,基于高置信度仿真,建立了水下爆炸作用下柔性支撑板架防护效能的评估方法并开展试验验证。采用验证后的高置信度仿真方法生成样本工况数据,并通过径向基神经网络模型构建能快速评估柔性支撑板架结构防护效能的代理模型。结合多岛遗传算法对建立的代理模型进行防护结构高防护效能和轻量化的多目标优化并获取最优结构参数。建立的快速预报与优化方法可以为相关的结构设计优化提供重要的技术支撑。

基于渐近均匀化的梯度加筋板结构优化设计

梯度加筋板结构以其优异性能广泛应用于航空航天、汽车和交通等领域。针对梯度板的渐变结构导致均匀化及两尺度优化设计计算量过大及效率过低的问题,本文采用机器学习方法搭建以微结构变形参数为输入、等效刚度系数为输出的人工神经网络,实现等效刚度的高效预测。在优化过程中,本文引入表征单胞变形的单元设计变量,实现梯度板局部变形的显式控制,并引入映射函数节点设计变量,保证优化过程中单胞的局部变形与映射函数一致,方便两尺度优化结果解耦。数值算例验证了本文方法的有效性和正确性。

变形铂金板测定表面张力的校正方法

铂金板是平板法测量液体表面张力的关键元件,但频繁经历清洗和灼烧极易使其变形,导致测量结果不准确。更换新板不仅增加实验成本,也影响实验连续性。为此,提出了一种变形铂金板的校正方法。描述了平板法测量液体表面张力的工作原理,分析出影响变形铂金板测量不准确的原因在于其有效润湿长度不再等同于其周长;在此基础上建立了变形铂金板有效润湿长度的求解模型;设计了不同温度、不同试剂条件下使用变形铂金板测定表面张力实验,验证了该校正方法的准确性和有效性。结果表明,校正后变形铂金板所测得的表面张力与参考值的偏差在0.200 mN/m以内,相对偏差在0.50%以内,符合液体表面张力的测量需求。研究结果保证了变形铂金板测量表面张力的准确性,实现了铂金板的重复利用。