A new higher-order shear deformation theory and refined beam element of composite laminates

A new higher-order shear deformation theory based on global-local superposition technique is developed. The theory satisfies the free surface conditions and the geometric and stress continuity conditions at interfaces. The global displacement components are of the Reddy theory and local components are of the internal first to third-order terms in each layer. A two-node beam element based on this theory is proposed. The solutions are compared with 3D-elasticity solutions. Numerical results show that present beam element has higher computational efficiency and higher accuracy.

On well-posedness of two-phase nonlocal integral models for higher-order refined shear deformation beams

Due to the conflict between equilibrium and constitutive requirements,Eringen’s strain-driven nonlocal integral model is not applicable to nanostructures of engineering interest.As an alternative,the stress-driven model has been recently developed.In this paper,for higher-order shear deformation beams,the ill-posed issue(i.e.,excessive mandatory boundary conditions(BCs)cannot be met simultaneously)exists not only in strain-driven nonlocal models but also in stress-driven ones.The well-posedness of both the strain-and stress-driven two-phase nonlocal(TPN-Strain D and TPN-Stress D)models is pertinently evidenced by formulating the static bending of curved beams made of functionally graded(FG)materials.The two-phase nonlocal integral constitutive relation is equivalent to a differential law equipped with two restriction conditions.By using the generalized differential quadrature method(GDQM),the coupling governing equations are solved numerically.The results show that the two-phase models can predict consistent scale-effects under different supported and loading conditions.

A two variable refined plate theory for the bending analysis of functionally graded plates

Bending analysis of functionally graded plates using the two variable refined plate theory is presented in this paper.The number of unknown functions involved is reduced to merely four,as against five in other shear deformation theories. The variationally consistent theory presented here has, in many respects,strong similarity to the classical plate theory. It does not require shear correction factors,and gives rise to such transverse shear stress variation that the transverse shear stresses vary parabolically across the thickness and satisfy shear stress free surface conditions.Material properties of the plate are assumed to be graded in the thickness direction with their distributions following a simple power-law in terms of the volume fractions of the constituents.Governing equations are derived from the principle of virtual displacements, and a closed-form solution is found for a simply supported rectangular plate subjected to sinusoidal loading by using the Navier method.Numerical results obtained by the present theory are compared with available solutions,from which it can be concluded that the proposed theory is accurate and simple in analyzing the static bending behavior of functionally graded plates.

Nonlocal buckling of embedded magnetoelectroelastic sandwich nanoplate using refined zigzag theory

This paper is concerned with a buckling analysis of an embedded nanoplate integrated with magnetoelectroelastic(MEE) layers based on a nonlocal magnetoelectroelasticity theory. A surrounding elastic medium is simulated by the Pasternak foundation that considers both shear and normal loads. The sandwich nanoplate(SNP) consists of a core that is made of metal and two MEE layers on the upper and lower surfaces of the core made of Ba Ti O3/Co Fe2 O4. The refined zigzag theory(RZT) is used to model the SNP subject to both external electric and magnetic potentials. Using an energy method and Hamilton’s principle, the governing motion equations are obtained, and then solved analytically. A detailed parametric study is conducted, concentrating on the combined effects of the small scale parameter, external electric and magnetic loads, thicknesses of MEE layers, mode numbers, and surrounding elastic medium. It is concluded that increasing the small scale parameter decreases the critical buckling loads.

EQUIVALENCE OF REFINED THEORY AND DECOMPOSED THEOREM OF AN ELASTIC PLATE

A connection between Cheng's refined theory and Gregory's decomposed theorem is analyzed. The equivalence of the refined theory and the decomposed theorem is given. Using operator matrix determinant of partial differential equation, Cheng gained one equation, and he substituted the sum of the general integrals of three differential equations for the solution of the equation. But he did not prove the rationality of substitute. There, a whole proof for the refined theory from Papkovich?_Neuber solution was given. At first expressions were obtained for all the displacements and stress components in term of the mid_plane displacement and its derivatives. Using Lur'e method and the theorem of appendix, the refined theory was given. At last, using basic mathematic method, the equivalence between Cheng's refined theory and Gregory's decomposed theorem was proved, i.e., Cheng's bi_harmonic equation, shear equation and transcendental equation are equivalent to Gregory's interior state, shear state and Papkovich_Fadle state, respectively.

KRMN-TYPE EQUATIONS FOR A HIGHER-ORDER SHEARDEFORMATION PLATE THEORY AND ITS USE IN THE THERMAL POSTBUCKLING ANALYSIS

arman-type nonlinear large deflection equations are derived occnrding to theReddy's higher-order shear deformation plate theory and used in the thermal postbuckling analysis The effects of initial geometric imperfections of the plate areincluded in the present study which also includes th thermal effects.Simply supported,symmetric cross-ply laminated plates subjected to uniform or nomuniform parabolictemperature distribution are considered. The analysis uses a mixed GalerkinGolerkinperlurbation technique to determine thermal buckling louds and postbucklingequilibrium paths.The effects played by transverse shear deformation plate aspeclraio, total number of plies thermal load ratio and initial geometric imperfections arealso studied.

AN ANALYTICAL SOLUTION OF RECTANGULAR LAMINATEDPLATES BY HIGHER-ORDER THEORY

On the basis of the Reddy's higher-order theory of composites, this paper introduces a displacement function Phi into it and transforms its three differential equations for symmetric cross-ply composites into only one eight-order differential equation generated by the displacement-function. When a proper Phi is chosen, both solutions are obtained, namely, the Navier-type solution of simply supported rectangular laminated plates and the Levy-type solution with the boundary condition where two opposite edges are simply supported and remains are arbitrary. The numerical examples show that the present results coincide well with the existing results in the references, thus validating that the present solving method is reliable. The higher-order theory of Reddy is simpler in calculation but has higher precision than the first-order shear deformation theory because the former has fewer unknows than the latter and requires no shear coefficients.

Merger estimates for a disformal Kerr black hole in quadratic degenerate higher-order scalar-tensor theories

We investigate the main features of a disformal Kerr black hole merger in quadratic degenerate higher-order scalar-tensor theories.In the ringdown stage of the black hole merger,for the prograde orbit,the real part of the quasinormal modes decreases with an increase in the disformal parameter,and the imaginary part also decreases,except in the Kerr case for a large spin parameter.However,for the retrograde orbit,the real part increases with an increase in the disformal parameter,and the imaginary part always decreases with it.For the approximate final spin,regardless of an equal spin,unequal spin,or generic spin configuration merger,the final black hole spin always increases with an increase in the disformal parameter.Our results show that the disformal parameter in the disformal Kerr solution and the MOG parameter in the Kerr-MOG case have obviously different effects on the black hole merger,which suggests the differences between these two spacetime structures.

A refined finite element method for bending analysis of laminated plates integrated with piezoelectric fiber-reinforced composite actuators

This research presents a finite element formulation based on four-variable refined plate theory for bending analysis of cross-ply and angle-ply laminated composite plates integrated with a piezoelectric fiber-reinforced composite actuator under electromechanical loading. The four-variable refined plate theory is a simple and efficient higher-order shear deformation theory, which predicts parabolic variation of transverse shear stresses across the plate thickness and satisfies zero traction conditions on the plate free surfaces. The weak form of governing equations is derived using the principle of minimum potential energy, and a 4-node non-conforming rectangular plate element with 8 degrees of freedom per node is introduced for discretizing the domain. Several benchmark problems are solved by the developed MATLAB code and the obtained results are compared with those from exact and other numerical solutions, showing good agreement.

Differences of grain-refining effect of Sc and Ti additions in aluminum by empirical electron theory analysis

The differences of grain-refining effect between Sc and Ti additions in aluminum,which cannot be substantially explained by traditional theories,were carefully studied.The empirical electron theory(EET) of solids and molecules was employed to calculate the valence electron structures(VES) of Al3Ti and Al3Sc.The conclusions can be drawn that,in the two alloys Al-Ti and Al-Sc,the different valence electron structures of Al3Ti and Al3Sc and the consequent differences of growth habit of the two particles,and the different interfacial electron density between particles and matrix fundamentally lead to the differences of grain-refining effect between Sc and Ti additions on aluminum and make Sr the better grain-refiner of aluminum.

Higher-order electroelastic modelling of piezoelectric cylindrical nanoshell on elastic matrix

This paper develops electro-elastic relations of functionally graded cylindrical nanoshell integrated with intelligent layers subjected to multi-physics loads resting on elastic foundation.The piezoelectric layers are actuated with external applied voltage.The nanocore is assumed in-homogeneous in which the material properties are changed continuously and gradually along radial direction.Third-order shear deformation theory is used for the description of kinematic relations and electric potential distribution is assumed as combination of a linear function along thickness direction to show applied voltage and a longitudinal distribution.Electro-elastic size-dependent constitutive relations are developed based on nonlocal elasticity theory and generalized Hooke’s law.The principle of virtual work is used to derive governing equations in terms of four functions along the axial and the radial directions and longitudinal electric potential function.The numerical results including radial and longitudinal displacements are presented in terms of basic input parameters of the integrated cylindrical nanoshell such as initial electric potential,small scale parameter,length to radius ratio and two parameters of foundation.It is concluded that both displacements are increased with an increase in small-scale parameter and a decrease in applied electric potential.

优化:人工智能时代的文论问题

日常用语中的“优化”指采取一定措施使事物变得优异。作为计算科学和运筹学中的重要内容,优化是指在一定限制条件下,选取某种方案以获得“最优化”的目标。将优化引入文论,可以与美化相关联,彼此之间有同有异。生成式AI中,优化有模型训练、创意提示、调试迭代三种方式。文艺作品之所以能够被优化,与其作为物质基础的艺术媒介及其作品的“可修正性”有关。在优化的技术演进中,先后经历了手工加工时代的优化、机械复制时代的优化、数字创生时代的优化三个阶段。手工加工时代出现了诸如对“手稿”的“润色、修改”,对“乐器”的“调音”,对“原作”的“临摹、誊写甚至重写”,对“文物、遗迹”的“修复”等不同的“类优化”类型;机械复制时代出现了“参数优化”“剪辑优化”“表演优化”等类型;数字创生时代出现了以算法优化为核心的智能优化。将优化引入文论,需要警惕“最优化”的结果不是“奇异性”,而是“普通性”的算法悖论、数据和变量中的偏差不易被纠偏;相反,易强化成偏见的偏差悖论以及随机并不意味着不同,而只是相似,是风格的重复的生成悖论。

医保DRG精细化监管与精准治理体系构建——以南京“医保高铁”为例

以按疾病诊断相关分组(DRG)支付方式改革为背景,探讨医保部门如何利用信息技术实现对医疗机构的精细化监测和管理,以提高医疗服务质量和效率,控制医疗费用的不合理增长。提出了以“精细化理论”为基础的医保DRG“精密监测—精细化监管—精准治理”三阶段;以南京“医保高铁”为例,构建DRG精细化监管与治理模型框架,分析其监测要素和治理要素,最后提出了落地建议,包括医保牵头横向协同、建立内外结合的服务与费用评估机制等。

感恩拓延-建构理论在体外冲击波碎石术患者精细化护理中的临床实践

目的:探讨感恩拓延-建构理论在体外冲击波碎石术患者精细化护理中的临床应用效果。方法:选取2019年7月—2021年8月郑州人民医院泌尿外科接受体外冲击波碎石术治疗的116例患者作为研究对象,随机数表法将其分为干预组(58例)和对照组(58例)。对照组患者采取常规护理,干预组患者采取基于感恩拓延-建构理论的精细化护理。比较两组患者的术后康复情况(拔除尿管、下床活动及住院时间)、并发症发生情况、术后疼痛情况、随访1个月结石清除率、护理前后负性情绪及护理满意度。结果:干预组患者的术后康复情况均优于对照组,差异有统计学意义(t=9.218、6.898、7.021,P<0.05);两组患者结石清除率、护理满意度,差异有统计学意义(χ^(2)=4.209、4.921,P<0.05)干预组患者术后各时间点VAS评分均显著减小,差异有统计学意义(t=2.379、4.277、11.069、11.921,P<0.05);干预后均明显降低,且干预组比对照组更低,差异有统计学意义(t=9.004、7.045,P<0.05)。结论:基于感恩拓延-建构理论的精细化护理干预应用于体外冲击波碎石术患者中可提高结石清除率,减小术后疼痛,降低术后并发症发生率,促进术后尽快恢复,有利于提高患者对护理工作的满意度。

Exact solution for thermal vibration of multi-directional functionally graded porous plates submerged in fluid medium

An analytical method for analyzing the thermal vibration of multi-directional functionally graded porous rectangular plates in fluid media with novel porosity patterns is developed in this study.Mechanical properties of MFG porous plates change according to the length,width,and thickness directions for various materials and the porosity distribution which can be widely applied in many fields of engineering and defence technology.Especially,new porous rules that depend on spatial coordinates and grading indexes are proposed in the present work.Applying Hamilton's principle and the refined higher-order shear deformation plate theory,the governing equation of motion of an MFG porous rectangular plate in a fluid medium(the fluid-plate system)is obtained.The fluid velocity potential is derived from the boundary conditions of the fluid-plate system and is used to compute the extra mass.The GalerkinVlasov solution is used to solve and give natural frequencies of MFG porous plates with various boundary conditions in a fluid medium.The validity and reliability of the suggested method are confirmed by comparing numerical results of the present work with those from available works in the literature.The effects of different parameters on the thermal vibration response of MFG porous rectangular plates are studied in detail.These findings demonstrate that the behavior of the structure within a liquid medium differs significantly from that within a vacuum medium.Thereby,they offer appropriate operational approaches for the structure when employed in various mediums.

基于高阶剪切变形理论的功能梯度板自由振动分析简化模型

基于高阶剪切变形理论提出了一种功能梯度板自由振动分析的简化模型,该简化模型最显著的特点是适用于功能梯度板的振动分析,且不需要剪切修正。相比于其他具有更多未知变量的剪切变形理论,本文提出的简化模型只包含一个控制方程,极大地减少了计算量。基于该简化模型研究了功能梯度矩形板在简支边界条件下的自由振动,并与其他已有文献进行了比较。结果表明,本文提出的简化模型在分析功能梯度板的自由振动行为时简单且精确。此外,文中还通过多个数值算例分析讨论了不同的梯度指数、长宽比和边厚比对功能梯度板自由振动行为的影响。

Chebyshev polynomial-based Ritz method for thermal buckling and free vibration behaviors of metal foam beams

This study presents the Chebyshev polynomials-based Ritz method to examine the thermal buckling and free vibration characteristics of metal foam beams.The analyses include three models for porosity distribution and two scenarios for thermal distribution.The material properties are assessed under two conditions,i.e.,temperature dependence and temperature independence.The theoretical framework for the beams is based on the higher-order shear deformation theory,which incorporates shear deformations with higher-order polynomials.The governing equations are established from the Lagrange equations,and the beam displacement fields are approximated by the Chebyshev polynomials.Numerical simulations are performed to evaluate the effects of thermal load,slenderness,boundary condition(BC),and porosity distribution on the buckling and vibration behaviors of metal foam beams.The findings highlight the significant influence of temperature-dependent(TD)material properties on metal foam beams'buckling and vibration responses.

Size-dependent thermomechanical vibration characteristics of rotating pre-twisted functionally graded shear deformable microbeams

A three-dimensional(3D)thermomechanical vibration model is developed for rotating pre-twisted functionally graded(FG)microbeams according to the refined shear deformation theory(RSDT)and the modified couple stress theory(MCST).The material properties are assumed to follow a power-law distribution along the chordwise direction.The model introduces one axial stretching variable and four transverse deflection variables including two pure bending components and two pure shear ones.The complex modal analysis and assumed mode methods are used to solve the governing equations of motion under different boundary conditions(BCs).Several examples are presented to verify the effectiveness of the developed model.By coupling the slenderness ratio,gradient index,rotation speed,and size effect with the pre-twisted angle,the effects of these factors on the thermomechanical vibration of the microbeam with different BCs are investigated.It is found that with the increase in the pre-twisted angle,the critical slenderness ratio and gradient index corresponding to the thermal instability of the microbeam increase,while the critical material length scale parameter(MLSP)and rotation speed decrease.The sensitivity of the fundamental frequency to temperature increases with the increasing slenderness ratio and gradient index,and decreases with the other increasing parameters.Moreover,the size effect can suppress the dynamic stiffening effect and enhance the Coriolis effect.Finally,the mode transition is quantitatively demonstrated by a modal assurance criterion(MAC).