ANALYTICAL EVALUATION OF PERMANENT DEFLECTION OF A THIN CIRCULAR PLATE STRUCK NORMALLY AT ITS CENTER BY A PROJECTILE

The permanent deflection of a thin circular plate struck normally at its center by a projectile is studied by an approximate theoretical analysis, FEM simulation and experiment. The plate made of rate sensitive and strain-hardening material undergoes serious local deformation but is not perforated during the impact. The theoretical analysis is based on an energy approach, in which the Cowper-Symonds equation is used for the consideration of strain rate sensitive effects and the parameters involved are determined with the aid of experimental data. The maximum permanent deflections predicted by the theoretical model are compared with those of FEM simulation and published papers obtained both by theory and experiment, and good agreement is achieved for a wide range of thickness of the plates and initial impact velocities.

Transverse Vibration Analysis of Concentrated Mass-Loaded Thin Circular Plate Based on Strcutural Circumferential Periodicity

The structural circumferential periodicity of inertial excitation produced by concentrated mass was utilized to establish the mathematical model of thin circular plate carrying eccentric concentrated mass and to analyze its transverse vibration. The fundamental frequency coefficient, natural frequency and mode shape function are determined by this method. A clamped thin circular plate was taken as an example to study the mass effect on the vibrating system.Comparison between the present results and published ones exhibits excellent agreement, which shows that the analytical method in this paper can be used to predict the transverse vibration parameters accurately.

A NEW TECHNIQUE FOR SOLVING NON-AXIALLY SYMMETRICALLARGE DEFLECTION OF ELASTIC AND THIN CIRCULAR PLATES

A new technique for solving large deflection problem of circular plates flexural non-axisymmetrically is proposed in this paper. The large deflection problem of a circular plate with built-in edge under non-axisymmetrical load is taken as an example to clarify the principle and procedure of the technique mentioned here. The technique given here can also be used to solve large deflection problem of circular plates under other non-axisymmetrical loads and boundary conditions.

LARGE DEFLECTION PROBLEM OF THIN ORTHOTROPIC CIRCULAR PLATE ON ELASTIC FOUNDATION WITH VARIABLE THICKNESS UNDER UNIFORM PRESSURE

Basic equations for large deflection theory of thin orthotropic circular plate on elastic foundation with variable thickness under uniform pressure are derived in this paper. The second opproximation solutions are obtained by means of the modified iteration method. The relation curves of the nondimensional loading and foe deflection, as to the differential ε and μrθ and λ are shown in Figs. 2, 3, 4. In special circumstance, the results are in accordance with those in [1], [6].

Iterative technique for circular thin plates on Gibson elastic foundation using modified Vlasov model

In this paper, to investigate the influence of soil inhomogeneity on the bending of circular thinplates on elastic foundations, the static problem of circular thin plates on Gibson elasticfoundation is solved using an iterative method based on the modified Vlasov model. On the basisof the principle of minimum potential energy, the governing differential equations and boundaryconditions for circular thin plates on modified Vlasov foundation considering the characteristics ofGibson soil are derived. The equations for the attenuation parameter in bending problem are alsoobtained, and the issue of unknown parameters being difficult to determine is solved using theiterative method. Numerical examples are analyzed and the results are in good agreement withthose form other literatures. It proves that the method is practical and accurate. Theinhomogeneity of modified Vlasov foundations has some influence on the deformation andinternal force behavior of circular thin plates. The effects of various parameters on the bending ofcircular plates and characteristic parameters of the foundation are discussed. The modified modelfurther enriches and develops the elastic foundations. Relevant conclusions that are meaningful toengineering practice are drawn.

THE ELASTIC-PLASTIC BENDING AND WRINKLING OF THIN CIRCULAR PLATES

Ⅰ. INTRODUCTIONThin circular plates, a kind of the basic structural element widely used in engineering,are of the simplest plane-stress mechanical model with double curvatures. Hence, the investigation on the fundamental mechanical properties of the thin circular plates has been attracting great attention and brought about many results. Due to the difficulties

A STUDY ON THE EFFECT OF RADIAL INERTIA ON THE ELASTO-PLASTIC COMBINED STRESS WAVE PROPAGATION IN THIN-WALLED TUBES

An in-depth analysis of propagation characteristics ofelasto-plastic combined stress waves in circular thin-walled tubeshas been made. In obtaining the simple-wave solution, however, mostresearches have ignored the influence of the circumferential stressrelated to the radial inertial ef- fect in the tubes. In this paperthe incremental elasto-plastic constitutive relations which areconve- nient for dynamic numerical analysis are adopted, and thefinite-difference method is used to study the evolution adpropagation of elasto-plastic combined stress waves in a thin-walledtube with the radial inertial effect of the tube considered. Thecalculation results are compared with those obtained when the radialinertial effect is not considered. The calculation results show thatthe radial inertial effect of a tube has a fairly great influence onthe propagation of elasto-plastic combined stress waves.

THE GENERAL SOLUTION FOR AXIAL SYMMETRICAL BENDING OF NONHOMOGENEOUS CIRCULAR PLATES RESTING ON AN ELASTIC FOUNDATION

In this paper, a new method, the exact analytic method, is presented on the basis of step reduction method. By this method, the general solution for the bending of nonhomogenous circular plates and circular plates with a circular hole at the center resting, on an elastfc foundation is obtained under arbitrary axial symmetrical loads' and boundary conditions. The uniform convergence of the solution is proved. This general solution can also he applied directly to the bending of circular plates without elastic foundation. Finally, it is only necessary to solve a set of binary linear algebraic equation. Numerical examples are given at the end of this paper which indicate satisfactory results of stress resultants and displacements can be obtained by the present method.

木工超薄圆锯片消音缝多目标优化设计

针对超薄圆锯片消音缝设计问题,提出并实施了一种基于MATLAB/ANSYS联合仿真协同非支配排序遗传算法(NSGA-Ⅱ)的多目标优化设计方法。通过Inspire软件采用变密度法进行拓扑优化,确定消音缝的设计域。构建以消音缝位置、角度及缝宽等形状参数为设计变量,以最大变形量、最大等效应力及整体振幅最小化为目标的多目标优化模型。通过MATLAB/ANSYS联合仿真协同NSGA-Ⅱ的策略,进行模型的优化求解。结果表明:4个优化解均能有效减少锯切过程中锯片的变形和整体振幅,为决策者提供了更广泛的选择空间。研究为圆锯片消音缝的多目标优化设计问题提供了可行的解决方案。

基于回归分析法的矩形槽圆管吸能特性研究

为了研究矩形槽圆管吸能特性规律,提出了一种基于回归分析法的结构参数与吸能特性关系的拟合方法。针对轴向冲击下的圆管动态响应,首先,建立了6005A-T6材料的Cowper-Symonds本构模型,并验证了仿真模型的准确性;其次,设计了正交试验,建立了吸能特性与结构参数之间的计算模型;然后,利用多元线性与非线性回归分析方法对计算模型参数求解,并对比了两种拟合结果,得到了峰值力和吸能量的经验公式;接着,对比经验公式与有限元数值计算值表明,经验公式在研究范围内具有较高准确性,误差在8%以内;最后,引入吸能性能指标并使用遗传算法对圆管进行了结构优化,优化结果表明,在研究范围内当直径和槽端距最小、壁厚和槽宽最大、槽深最浅时,矩形槽圆管的吸能性能最优。

机车前端薄壁吸能管仿真模型模糊参数的支持向量回归反求

为了获得影响耐撞性结构有限元计算精度的准确模型参数,提高冲击仿真的准确性,提出一种基于支持向量回归(support vector regression,SVR)模型进行参数优化反求的方法。以一种机车前端防爬结构中的预压薄壁吸能圆管为研究对象建立有限元模型,进行台车冲击试验验证仿真模型准确性。通过拉丁超立方试验设计驱动有限元模型进行少量计算获得数据集,有限元模型中的模糊参数为输入变量,计算与试验载荷的差异为目标响应,通过SVR方法构建映射关系,并采用增强精英保留遗传算法(strengthen elitist genetic algorithm,SEGA)对超参数进行优化,确定SVR模型最佳配置;通过该最优SVR模型再次使用SEGA优化反求,获得最佳模糊参数组合。使用这组参数组合设置有限元模型,其仿真结果相较初始计算耐撞性指标和载荷曲线匹配程度都得到了提高。研究结果为有限元模型中模糊参数的准确设定、碰撞仿真的精度提升提供了一种新的思路。

A DONNELL TYPE THEORY FOR FINITE DEFLECTION OF STIFFENED THIN CONICAL SHELLS COMPOSED OF COMPOSITE MATERIALS

A Donnell type theory is developed for finite deflection of closely stiffened truncated laminated composite conical shells under arbitrary loads by using the variational calculus and smeared-stiffener theory. The most general bending-stretching coupling and the effect of eccentricity of stiffeners are considered. The equilibrium equations, boundary conditions and the equation of compatibility are derived. The new equations of the mixed-type of stiffened laminated composite conical shells are obtained in terms of the transverse deflection and stress function. The simplified equations are also given for some commonly encountered cases.

木材加工超薄圆锯片基体结构对其稳定性的影响

木材加工超薄圆锯片的稳定性是影响锯切质量的重要因素之一,圆锯片的稳定性会随着锯身厚度的减小而降低。在切削木材过程中产生大量切削热会使锯身发生热形变,进而导致锯片稳定性降低。提高圆锯片切削稳定性传统的方法主要在生产工艺上通过对锯身施加预应力,抵消切削热对锯身形变的影响。本文通过改变锯身的基体结构,对不同基体材料的木工圆锯片进行基体几何处理,使其能够在切削木材过程中抵消热应力,从而提高切削稳定性。

预应力薄壁圆钢管约束混凝土短柱轴压性能初探

为提高薄壁钢管混凝土柱轴心受压性能,提出了预应力薄壁圆钢管约束混凝土柱,即采用对拉螺栓对薄壁圆钢管施加环向预应力,形成对内部混凝土初始约束围压,以提高内部混凝土的轴心抗压强度及承载力性能。为探究其轴向受压性能提升效果,进行了预应力薄壁圆钢管约束混凝土短柱轴心受压试验;并采用ABAQUS有限元计算软件建立了相应的非线性有限元数值模型,基于试验所获得荷载-位移数据,验证了模型的可靠性。在合理可靠试验模型的基础上,进行了不同预应力度(k=0、0.1、0.2、0.3、0.4和0.5)和不同钢管厚度(t=1.5mm、2.0mm、2.5mm和3.0mm)情况下的轴心受压性能影响分析。结果表明:采用对拉螺栓对薄壁圆钢管混凝土柱施加环向预应力,可有效提高其轴心抗压强度、刚度和延性;在合适预应力范围内,预应力度(k=0~0.4)越大,预应力薄壁钢约束混凝土短柱轴心受压性能提升越明显;但较大的预应力度(k=0.5)会让构件在达到峰值荷载后,其承载力降低较为明显,从而使构件延性降低;当预应力度k不变,构件的轴心受压性能随钢管厚度t的增大而增大。

用于液体容器内液位测量的金属薄壁梁振动模态仿真研究

为实现用于液体容器内液位测量的金属薄壁梁振动模态的准确模拟,构建金属薄壁梁的有限元圆梁模型。该模型采用有限元法对金属薄壁梁纵向振动模型的特征频率进行分析,从而对金属薄壁梁暴露于外部刺激时所产生的纵向振动进行准确模拟。在所开展研究中,对薄壁梁采用圆梁分布质量模型,分析模型的前4种振动模态的特征频率。为验证该模型的有效性,将该模型对金属薄壁梁前4种纵向振动模态的模拟结果与理论模型结果、实际金属薄壁梁试验结果及其他两种仿真模型的模拟结果进行了对比。对比结果表明,所构建圆梁模型对金属薄壁梁纵向振动模态的模拟结果与理论、试验分析结果高度一致,且模拟结果效果明显优于其他两种模型。

周期变半径薄圆环模态实验研究

针对变半径法向等厚薄圆环的面内振动模态问题,依据振动测试理论,提出了定测量点、变激振点的实验方法,以简化实验操作流程。利用激光多普勒测振仪和LMS振动测试系统进行测振实验,得到了变半径圆环前八阶振动的固有频率和振型,并将结果与有限元仿真及现有文献相关结论对比,验证了实验方法的可行性。归纳了半径变化周期p和模态阶数n不同关系时结构固有频率的分裂规律,并总结了法向厚度h和半径变化幅度Δ对圆环固有频率的影响。

基于有限元分析的薄壁圆环零件加工工艺研究

目的针对薄壁圆环零件刚性差、强度弱、加工过程中易发生受力变形的难题,基于薄壁圆环零件加工成形工艺,优化零件的加工工艺和装夹方式。方法考虑到工艺对零件加工质量的影响,对零件的加工方法和装夹方式进行研究,提出一种新的加工工装,运用ANSYS软件对零件装夹受力情况和振动变形进行有限元模拟仿真分析。结果该工装不仅能够防止零件发生应力集中,还提升了零件加工精度和表面质量,工装设计为一夹一顶方式,只需调整顶尖压紧力便可确保圆环件在加工中不会发生变形,同时拆装方便,提高了生产效率。结论对于薄壁圆环件的数控加工,可通过科学设计零件加工工艺流程和装夹工装,解决零件受力变形问题,保证薄壁圆环零件的尺寸、形位公差和表面粗糙度符合要求,提高了生产加工效率,满足产品批量生产使用要求,为类似薄壁件的加工提供了参考。

负泊松比手性结构圆薄板的参数设计

薄膜张紧在曲线边界上必然产生反枕效应,这会降低网状可展开天线的型面精度。为了减少影响,通常采用增加径向肋或者网面牵引索等措施,但这些方法会增加可展开天线的复杂程度。王一鸣、黄鹏飞提出了一种弱刚度复合膜,通过调整厚度使其具有一定的弯曲刚度降低反枕效应的影响,但厚度的增加会增加天线的质量。根据薄板的弯曲刚度方程可知,为了在不改变材料厚度的情况下改变弯曲刚度,通过调节材料的泊松比可以达到这个目的。文章利用等效法计算了伞天线反射面形成时两肋间材料需要施加的位移;将天线反射面等效为薄板,计算了在此位移下为消除反枕效应圆薄板所需的弯曲刚度;选取了合适的负泊松比结构,即手性结构,计算了为实现这一弯曲刚度所需的手性结构胞元的几何参数;最后,利用有限元对胞元进行强度校核,以保证设计的手性结构能满足后续实验加载需求。

矿用防冲击液压支架的吸能构件研究

为解决刚性支护防冲击性能差的问题,业内提出了吸能防冲击液压支架。对金属薄壁吸能机构进行了研究,分析了金属薄壁吸能构件的设计要点与存在问题,并对金属薄壁圆管吸能构件的结构进行了改进设计和参数优化。

基于差集的综合孔径圆环天线阵稀疏优化方法

稀疏天线阵列设计是综合孔径微波辐射计的一个重要研究内容。圆环阵因其可实现(u,v)平面基线矢量零冗余、结构简单以及共形、波束旋转对称等特点而备受关注。针对均匀圆环阵(UCA)基线长度(基线矢量的模)冗余量大的问题,提出了两种稀疏优化方法:一种是基于受限差集的半圆环阵稀疏方法;一种是基于循环差集的全圆环阵稀疏方法。这两种方法均可大大减少阵元数,节约硬件成本;且均可解析地求出稀疏阵元位置,运算量极小,适于任意大阵元数的圆环阵稀疏优化。通过阵列旋转和分时测量,这两种圆环稀疏阵可获得与UCA相同的空间频率采样。