Buckling analysis of shear deformable composite conical shells reinforced by CNTs subjected to combined loading on the two-parameter elastic foundation

The main objective of this study is to investigate the buckling analysis of CCSs reinforced by CNTs subjected to combined loading of hydrostatic pressure and axial compression resting on the twoparameter elastic foundation(T-P-EF).It is one of the first attempts to derive the governing equations of the CCSs reinforced with CNTs,based on a generalized first-order shear deformation shell theory(FSDST)which includes shell-foundation interaction.By adopting the extended mixing rule,the effective material properties of CCSs reinforced by CNTs with linear distributions are approximated by introducing some efficiency parameters.Three carbon nanotube distribution in the matrix,i.e.uniform distribution(U)and V and X-types linear distribution are taken into account.The stability equations are solved by using the Galerkin procedure to determine the combined buckling loads(CBLs)of the structure selected here.The numerical illustrations cover CBLs characteristics of CCSs reinforced by CNTs in the presence of the T-P-EF.Finally,a parametric study is carried out to study the influences of the foundation parameters,the volume fraction of carbon nanotubes and the types of reinforcement on the CBLs.

Postbuckling of Imperfect Stiffened Cylindrical Shells Under Combined External Liquid Pressure and Axial Compression

posthuckling analysis is presented for the stilTened cylindrical shell of finite length subjected to combined loading of external liquid pressure and axial compression. The formulations are based on a boundary layer theory of shell buckling, which includes the effects of nonlinear prebuckling deformations, nonlinear large deflections in the postbuckling range and initial geometrical imperfections of the shell. The 'smeared stifl'cner' approach is adopted for the stiffencrs. In the analysis a singular perturbation technique is used (o determine the interactive buckling loads and the postbuckling paths. Numerical examples cover the performance of perfect and imperfect, stringer and ring stiffened cylindrical shells. Typical results arc presented in the dimcnsionless graphical form.

Analytical modeling and vibration analysis of fiber reinforced composite hexagon honeycomb sandwich cylindrical-spherical combined shells

This study analyzes and predicts the vibration characteristics of fiberreinforced composite sandwich(FRCS)cylindrical-spherical(CS)combined shells with hexagon honeycomb core(HHC)for the first time based on an analytical model developed,which makes good use of the advantage of the first-order shear deformation theory(FSDT),the multi-segment decomposition technique,the virtual spring technology,the Jacobi-Ritz approach,and the transfer function method.The equivalent material properties of HHC are firstly determined by the modified Gibson’s formula,and the related energy equations are derived for the HHC-FRCS-CS combined shells,from which the fundamental frequencies,the mode shapes,and the forced vibration responses are solved.The current model is verified through the discussion of convergence and comparative analysis with the associated published literature and finite element(FE)results.The effects of geometric parameters of HHC on the dynamic property of the structure are further investigated with the verified model.It reveals that the vibration suppression capability can be greatly enhanced by reducing the ratio of HHC thickness to total thickness and the ratio of wall thickness of honeycomb cell to overall radius,and by increasing the ratio of length of honeycomb cell to overall radius and honeycomb characteristic angle of HHC.

POSTBUCKLING OF IMPERFECT STIFFENED CYLINDRICAL SHELLS UNDER COMBINED EXTERNAL PRESSURE AND HEATING

A postbuckling analysis is presented for a stiffened cylindrical shell of finite length subjected to combined loading of external pressure and a uniform temperature rise. The formulations are based on a boundary layer theory of shell buckling, which includes the effects of nonlinear prebuckling deformations, nonlinear large deflections in the postbuckling range and initial geometrical imperfections of the shell. The 'smeared stiffener' approach is adopted for the stiffeners. The analysis uses a singular perturbation technique to determine the interactive buckling loads and the postbuckling equilibrium paths. Numerical examples cover the performances of perfect and imperfect, stringer and ring stiffened cylindrical shells. Typical results are presented in dimensionless graphical form.

Research on Strengthening Method of Concave Cone-toroid-cylinder Combined Shell with Initial Imperfection

As a new joint structure,the impact of initial imperfection to stress of Concave cone-toroid-cylinder combined shell was analyzed. Firstly the location and shape of combined shell's initial imperfection caused by welding was studied. Secondly dominated stress was chosen after comparing varioustypical stress. Then it was analyzed that the influence of imperfection to dominated stress via changing the shape of frame's deflection and shell's concave-convex. At last the strengthening case for combined shell with imperfection was pointed out. The conclusions are:(1) Stress of frame 9 is more sensitive to initial imperfection than circumferential stress of toroidmidsurface,which is a new concern;(2) To strength the frames in the sides of toroid not only can decrease the stress of frame,but also can reduce the circumference stress of toroid's midsurface.

Waste oyster shell as a kind of active filler to treat the combined wastewater at an estuary

Estuaries have been described as one of the most difficult environments on Earth. It is difficult to know how to treat the combined wastewater in tidal rivers at the estuary, where the situation is very different from ordinary fresh water rivers. Waste oyster shell was used as the active filler in this study in a bio-contact oxidation tank to treat the combined wastewater at the Fengtang Tidal River. With a middle-experimental scale of 360 ma/day, the average removal efficiency of COD, BOD, NH3-N, TP and TSS was 80.05%, 85.02%, 86.59%, 50.58% and 85.32%, respectively, in this bio-contact oxidation process. The living microbes in the biofilms on the waste oyster shell in this bio-contact oxidation tank, which were mainly composed of zoogloea, protozoa and micro-metazoa species, revealed that waste oyster shell as the filler was suitable material for combined wastewater degradation. This treatment method using waste oyster shell as active filler was then applied in a mangrove demonstration area for water quality improvement near the experiment area, with a treatment volume of 5 × 10^3 m^3/day. Another project was also successfully applied in a constructed wetland, with a wastewater treatment volume of 1 ×10^3 m^3/day. This technology is therefore feasible and can easily be applied on a larger scale,

温度场下功能梯度圆锥壳-环板振动特性分析

针对功能梯度圆锥壳-环板组合结构振动问题,本文采用一阶剪切变形理论和Rayleigh-Ritz法分析了温度场下组合结构的振动特性。组合结构位移变量采用谱几何法来表征,考虑材料参数与温度相关并引入人工边界弹簧建立了组合结构振动特性分析模型。数值算例中,通过将文中求解结果与文献解和有限元法结果进行对比验证了模型的正确性,进而分析尺寸、材料、温度和连接位置等参数对结构振动特性的影响。研究结果表明:组合结构基频随厚度增加而增加,随着幂律指数、半顶角和温度场参数增加而降低,随环板内径和连接位置变化会呈现非单一变化趋势。

Buckling of 2D-FG Cylindrical Shells under Combined External Pressure and Axial Compression

This paper presents the stability of two-dimensional functionally graded(2D-FG)cylindrical shells subjected to combined external pressure and axial compression loads,based on classical shell theory.The material properties of functionally graded cylindrical shell are graded in two directional(radial and axial)and determined by the rule of mixture.The Euler’s equation is employed to derive the stability equations,which are solved by GDQ method to obtain the critical mechanical buckling loads of the 2D-FG cylindrical shells.The effects of shell geometry,the mechanical properties distribution in radial and axial direction on the critical buckling load are studied and compared with a cylindrical shell made of 1D-FGM.The numerical results reveal that the 2D-FGM has a significant effect on the critical buckling load.

进口压缩机冷却器泄漏原因分析与维修方法的应用研究

压缩机冷却器对于限制气体温度、减少压缩机功耗、分离气体杂质具有重要作用,冷却器维保管理工作有助于保障设备性能和安全稳定运行。着重阐述引发冷却器泄漏的原因和适应性修复方法,总结正确选择维修方法并评估应用效果,期望对压缩机冷却器维修管理提供经验。

可调节式秸秆粉碎抛撒还田机设计与试验

针对秸秆粉碎还田机粉碎后的秸秆抛撒均匀度差和幅宽不可调节等问题,设计了一种可调节式秸秆粉碎抛撒还田机。该机主要由曲面机壳、粉碎装置、抛撒装置和传动装置等组成,可以实现玉米、小麦秸秆的粉碎和粉碎后秸秆的抛撒还田。曲面机壳包括对数螺旋线型前壳体、左侧板、右侧板和后挡板等。Fluent仿真分析结果表明,曲面机壳相比传统折线型机壳有利于提高秸秆在机壳内的流动性。粉碎装置包括粉碎刀轴、组合甩刀、定刀等,其中粉碎刀轴两端装有扇形叶片,提高了曲面机壳内流体流动速度和曲面机壳入口处秸秆喂入性能。在曲面机壳出口处增加了装有导向叶片的导流板,并设计了一种同步调节所有导向叶片的导向叶片同步调节装置,实现了粉碎后秸秆抛撒幅宽、均匀度的可调节。田间试验表明,在拖拉机前进速度为1.8 m/s,秸秆平均含水率为78.4%,拖拉机动力输出轴转速为540 r/min的未收获玉米地里,秸秆粉碎长度合格率达90.01%,平均抛撒幅宽达2 223.3 mm,平均留茬高度为62.0 mm,抛撒不均匀度为22.95%,各项性能指标均满足要求。

虾类剥壳加工现状及预处理便捷剥壳技术

快速剥壳是虾深加工过程中的关键环节,也是制约虾类加工产业工业化发展的技术难题。文章探讨了虾体壳肉结合特点及虾类剥壳加工现状,并就传统预处理手段及高压处理、酶辅助、超声、微波高新前沿技术在虾壳快速剥离中的研究应用及可行性进行分析论述,展望未来虾类剥壳产业的发展趋势,为解决虾剥壳的瓶颈问题、提升虾机械加工产业的技术水平提供参考。

复杂载荷作用下圆柱壳的弹塑性动力屈曲研究

对复杂载荷作用下圆柱壳的弹塑性动力屈曲问题进行了研究。基于Hamilton变分原理导出圆柱壳的运动方程 ,本构关系采用增量理论 ,借助增量数值算法求解动力方程组。结果表明 ,均匀径向外压对圆柱壳的轴向冲击的过程或冲击性态有较大的影响 ,并讨论了径向压力与轴向冲击载荷的幅值对结构临界动力屈曲载荷和临界动力失效载荷的影响。

基于组合圆柱壳理论的大型油罐应力分析

为准确获得大型石油储罐的壁板应力分布,提出了一种长-短圆柱壳解析方法.当考虑到底板与第1层壁板连接处边缘力系对第2层壁板的影响,将第1层壁板视为短圆柱壳,其他各层壁板视为长圆柱壳,同时采用刚性-弹性地基梁耦合模型模拟底板时,导出了大型油罐壁板的应力表达式.以15×104m3浮顶油罐为研究对象,进行充水试验的现场应力测试,获得了实测应力分布.结果表明,由该方法得到的理论值与实测值吻合得较好,最大误差为6.02%,满足工程误差精度的要求,可为油罐进一步大型化提供技术支持.

椰子壳苯酚液化的研究

研究了催化剂种类、浓硫酸催化剂用量、液化反应温度、苯酚与椰子壳质量比、液化反应时间对液化产物残渣率及结合酚的影响。结果表明,浓硫酸是椰子壳液化反应较佳的催化剂;当浓硫酸用量为6%,反应温度为150℃,质量比为4∶1时,液化反应30 min可较好地将椰子壳液化;随着液化反应时间的延长,液化产物结合酚含量上升。

多肋式梁桥在全过程中应力重分布研究

为了考察多肋式梁在全过程中受力性能,利用非线性实体退化壳单元理论研究了多肋式梁的应力重分布规律.混凝土和普通钢筋采用分层壳单元模拟,预应力钢筋采用组合壳单元模拟,推导了预应力钢筋对组合壳单元刚度矩阵的贡献和统一的非线性壳单元模式.利用Owen屈服准则、Hinton压碎准则和弹塑性强化模型考虑了混凝土和钢筋的非线性效应,有效模拟了预应力混凝土多肋式梁的开裂、屈服和失效全过程,并编制了相应的三维非线性全过程计算程序.结合破坏性试验资料可知,理论计算结果与试验数据吻合良好,并对预应力钢筋应力发展规律进行研究.结果表明,用实体退化壳单元模拟预应力混凝土多肋式梁是合适的,研制的非线性单元和非线性程序是正确的.

激励力对双层圆柱壳声辐射性能的影响

研究了不同激励力对流场中敷设阻尼材料的有限长加筋双层圆柱壳的振动和声辐射性能的影响。壳体的振动用Flügge壳体方程描述,将加强构件等价为对内外壳体的支持力,粘弹性阻尼层的运动用三维Navier方程描述,壳体受到的激励力可以归结成轴向力、周向力、径向力、轴向弯距、周向弯距和扭矩的作用,点激励用啄函数表示,然后将其引入壳体振动方程,最后求解双壳体声-流体-结构耦合方程,计算结果用辐射声功率和表面振动均方速度级的形式表示。在数值分析部分,讨论了六种不同性质激励力、两个力联合作用以及阻尼材料对双层圆柱壳的辐射声功率和表面振动速度级的影响。得出结论:同一位置受单位力激励时,Mx激励的声功率最高,Fr居第二,Fx最低;联合激励力产生的辐射声功率级和外壳振动速度级比单个力激励时都要大;阻尼材料能有效地抑制壳体的辐射噪声。

高压开关壳体用高强铸造铝合金的研究

为了提高高压开关壳体用铸造合金的材质水平以满足超高压大容量输变电设备对壳体材料性能的要求,进行了高强铸造铝合金的研究。试验在AlSi10Mg合金的基础上,主要考查了合金元素Cu及变质剂RE、Sr对合金热处理后力学性能的影响。试验结果表明:RE变质可同时提高AlSi10Mg合金热处理后的抗拉强度和伸长率;合金元素Cu提高合金的抗拉强度,但使得伸长率大大降低;在加入1%RE变质的同时复合加入Sr变质剂,可在进一步提高合金性能的同时,明显提高合金的伸长率。在含1%Zn、0.15%Ti的AlSi10Mg合金Cu含量3%时,复合加入1%RE和0.015%Sr变质,热处理后的力学性能可达到:σb=370MPa,δ5=2%,可以满足目前对高压开关壳体性能的要求。

3个不同地理群体红壳色文蛤杂交的配合力分析

从采自江苏如东(S)、广西北海(G)、日本本州(J)的3个不同地理群体文蛤(Meretrix meretrix)中选取红壳色个体组成亲贝群,并以5%的选择压力从中挑选最大壳长个体作为育种基础群,按照双列杂交的方式,建立9个交配组合,每组3个家系。实际获得6个交配组合(Gs、Gj、Sg、Sj、Gg、Ss),共18个家系,比较各家系的育种值,对家系进行综合评价,并进行配合力的测定和杂交优势分析,筛选最优杂交组合。结果表明,早期存在母本效应,自13日龄之后,杂交组合(Gs、Gj、Sg和Sj)的壳长均大于自繁组合(Gg和Ss),且杂交优势越来越显著。杂交组的Kung育种值和综合评定值均大于自繁组,其中,杂交组合Gs(广西♀×江苏♂)的Kung育种值和综合评定值均最大,分别为6.341、0.716。母本中,广西红壳色文蛤(G)为母本的一般配合力最大,为1 966.862;父本中,江苏红壳色文蛤(s)和日本红壳色文蛤(j)为父本的一般配合力较大,分别为49.819、185.216。由江苏红壳色文蛤和广西红壳色文蛤组配的Gs的特殊配合力及配合力总效应值均最高(927.191,90.348),是理想的杂交组合。因此,Gs组合为最具优势的杂交组合。

加肋锥—环—柱结合壳试验研究

加肋锥—环—柱结合壳是柱壳与锥壳连接的一种新型的、优越的结构形式,它能大幅降低锥、柱壳结合部的应力峰值,提高承压能力,结合部结构重量较现在采用的加强结构重量小,最大应力不出现在结合部焊缝上。文中展示系列模型试验结果,通过比较分析,验证加肋锥—环—柱结合壳的优越性,验证课题组提出的计算加肋轴对称结合壳应力和稳定性的"分区样条等参元方法"和"ARSASS"程序的正确性。

凹型加肋锥—环—柱结合壳强度的模型试验研究

为考察凹型加肋锥—环—柱结合壳的力学行为,设计制作了3个凹型加肋锥—柱/锥—环—柱结合壳系列精车模型,采用分区样条等参元方法对它们进行了应力计算。分别对3个模型进行了静水外压试验,测量其应力,计算应力与实测应力吻合较好。模型试验和计算结果表明,凹型加肋锥—环—柱结合壳能有效降低锥、柱壳结合部的应力峰值。通过对模型试验结果的分析,得出了一些对指导凹型加肋锥—环—柱结合壳结构设计有实用价值的结论。