腿式着陆器用不同拓扑结构金属蜂窝吸能特性优化设计

作为一种多孔固体材料的,由于其结构和功能的特殊性,金属蜂窝在缓冲吸能领域应用广泛。为了得到不同拓扑结构下金属蜂窝的异面压缩特性及缓冲特性,为其用于缓冲吸能领域提供依据,本文应用数值仿真软件Patran/DYNA对5种不同拓扑结构的金属蜂窝进行了压缩仿真。由于蜂窝结构的多样性,基于PCL语言编写金属蜂窝参数化有限元分析程序,实现有限元模型自动建立。采用全因素实验设计法对仿真点进行了规划,基于仿真结果,使用响应面方法建立了金属蜂窝吸能特性的近似函数模型,并分析模型精度。以金属蜂窝比吸能为优化目标,蜂窝主要结构参数为设计变量,针对腿式着陆器用金属蜂窝缓冲结构进行了优化设计, 结果表明正六边形金属蜂窝在五种蜂窝结构中吸能效果最优。     

工字梁型蜂窝芯材共面冲击性能的有限元模拟

目的研究双壁厚工字梁型金属蜂窝芯材的共面冲击性能。方法借助有限元软件Ansys/LSDYNA,建立工字梁型蜂窝芯材的有限元模型,并进行CAE分析。结果在不同冲击速度下,工字梁型蜂窝芯材表现出不同的变形模式。当工字梁型金属蜂窝芯材的其他结构参数固定时,其共面动态峰应力与冲击速度的平方成线性关系;当冲击速度一定时,其共面动态峰应力与壁厚边长比成幂指数关系。同时,拟合得到了工字梁型金属蜂窝芯材共面动态峰应力关于壁厚边长比和冲击速度的经验计算公式。结论工字梁型蜂窝具有优良的结构和吸能能力,研究工字梁型蜂窝的冲击性能具有重要的科学研究和工程应用价值。     

正方形金属蜂窝材料共面力学性能的仿真分析

建立了正方形金属蜂窝铝芯13×8的蜂窝单元阵列有限元分析模型,研究了正方形金属蜂窝在共面压缩载荷作用下的变形形态,并分析了速度在3～250m/s时,正方形金属蜂窝铝芯的共面力学性能与其结构参数和速度之间的关系.当结构参数固定时,正方形金属蜂窝铝芯的峰应力与速度的平方成线性关系,而当速度固定时,峰应力与壁厚边长比成幂指数关系.     

金属蜂窝夹芯板疲劳行为的试验研究

金属蜂窝夹芯板结构在航空、航天领域中已得到了广泛的应用.本文首先简单介绍了金属蜂窝夹芯板的结构及特点,然后针对两个不同方向的金属蜂窝夹芯板进行了三点弯曲疲劳试验,测试了在不同应力水平下夹芯板的疲劳寿命,得到了该夹芯板的三点弯曲疲劳极限.试验结果表明,在W方向,夹芯板的主要疲劳破坏模式为蜂窝芯子之间的脱粘断裂,在L方向,夹芯板的主要疲劳破坏模式为蜂窝芯子和盖板之间焊点的开裂.     

浮冰碰撞下蜂窝金属夹芯板动态响应研究EI北大核心CSCD

采用非线性有限元软件ANSYS/LS-DYNA,结合混凝土冰材料数值模型,建立了楔形冰碰撞下蜂窝金属夹芯板动态响应数值仿真模型,得到了碰撞过程的冲击力时间曲线和冲击力位移曲线、蜂窝金属夹芯板的变形以及冲击能量分配情况,并开展了楔形冰-蜂窝金属夹芯板碰撞冲击试验验证。研究结果表明,楔形冰碰撞下蜂窝金属夹芯板上面板表现为局部凹陷与整体弯曲的耦合变形模式,下面板表现为整体弯曲变形模式,冲击能量转化为蜂窝金属夹芯板的变形能和楔形冰的回弹动能以及冰体破碎耗散能量,数值仿真与试验结果吻合较好,验证了数值计算模型的准确性。在此基础上,研究了浮冰碰撞冲击位置以及蜂窝芯层厚度对其动态响应及能量分配的影响规律。     

金属蜂窝平板加热过程的数值模拟及试验研究

对某种金属蜂窝平板进行了模拟气动加热试验，测定了加热表面和非加热表面的瞬态温度。在试验结果的基础上，考虑传导和辐射传热的偶合作用，建立了该金属蜂窝平板传热的有限元分析模型。计算结果与试验结果吻合较好，表明该数值模拟方法可用于计算传导和辐射偶合问题。对有限元计算结果和试验结果的进一步分析表明，温度沿厚度方向呈规则的线性分布，该规律对于金属蜂窝的设计和使用有重要的指导意义。     

金属蜂窝板参数对其传热性能的影响

采用ANSYS有限元方法模拟金属蜂窝板的传热性能,并采用控制变量法和极差分析法研究了金属蜂窝板参数对其传热性能的影响。利用Swann&Pittman经验公式对蜂窝板传热模型进行验证,并深入研究蜂窝板参数对其传热性能的影响。结果表明:公式计算结果和模拟结果十分吻合,本实验建立的模型是合理的;增加蜂窝芯边长和蜂窝芯高度会降低当量热导率,而蜂窝芯厚度、上下蒙皮厚度及内表面发射率的增加会加大当量热导率;随着施加热流密度的增加,蜂窝芯厚度和下蒙皮厚度对当量热导率的影响几乎不变,而蜂窝芯高度、蜂窝单元边长、内表面发射率及上蒙皮厚度会加大对当量热导率的影响,而且各参数对当量热导率影响大小的排序会随着施加热流密度的改变而变化。     

异面冲击下金属蜂窝结构平均塑性坍塌应力模型

在已有的蜂窝结构静态平均塑性坍塌应力理论模型和Cowper-Symonds本构模型的基础上,考虑应变强化效应和双壁厚黏结层,建立了在异面冲击载荷下的金属蜂窝结构平均塑性坍塌应力理论模型。使用LS-DYNA动力学软件模拟了铝合金蜂窝结构在冲击载荷作用下的异面变形,采用仿真和实验数据对理论模型进行了对比验证。结果表明:应用所建立的平均塑性坍塌应力理论模型能够更准确地计算金属蜂窝结构在异面冲击载荷下的平均塑性坍塌应力。     

蜂窝纸板

蜂窝纸板是指以仿生正六边形蜂窝结构的纸芯为中间层、上下覆有纸张的板材。蜂窝技术的发明和应用始于５０多年前的西方国家 ,开始时为金属蜂窝板材 ,广泛应用于航空领域和飞机机翼的制造等。二战后 ,各种金属的和非金属的蜂窝板材逐步发展应用于民品领域 ,１９９３年 ,蜂窝纸板被列入世界１００项新技术、新产品。蜂窝纸板性能优异 ,具体表现在 :比强度和比刚度高 ,材耗少、重量轻、内芯密度几可与发泡塑料相当。由于内芯中充满空气且互不流通 ,因此具有良好的防震、隔热、隔音性能 ,内芯可采用再生纸 ,成本也就低廉。且回收再生容易 ,完全…     

蜂窝金属夹芯板重复冲击动态响应研究

蜂窝金属及其夹芯结构是一种物理功能与结构一体化的新型轻质高强结构,广泛应用于结构轻量化与碰撞冲击防护领域。采用ABAQUS非线性有限元软件建立了蜂窝金属夹芯板(honeycomb sandwich panel,HSP)结构动态冲击数值仿真模型,数值仿真计算结果与文献实验结果吻合较好,验证了数值仿真模型的正确性。在此基础上,开展了重复冲击载荷作用下蜂窝金属夹芯板结构动态响应研究,得到了重复冲击力时程曲线、动态变形时程曲线、冲击力位移曲线以及最终挠度,分析了冲击能量、蜂窝壁厚以及上、下面板厚度分配对蜂窝金属夹芯板结构重复冲击动态响应的影响规律。研究结果表明,重复冲击载荷作用下蜂窝金属夹芯板结构上、下面板弯曲变形以及蜂窝芯层压缩变形逐渐积累,蜂窝芯层薄壁结构逐渐达到密实化,结构抗弯刚度逐渐上升,变形增量逐渐减小,结构整体能量吸收率下降。通过调节蜂窝壁厚和上、下面板厚度分配可以显著调节蜂窝金属夹芯板结构重复冲击动态响应与能量吸收性能。     

P／MCs新型复合材料制备、结构及阻尼性能

采用特殊的渗流法所制备的新型Ｐ／ＭＣｓ复合材料，由高分子聚合物与蜂窝状铝架组成，它具有优异的阻尼性能，并简述了结构对阻尼的影响     

Heat exchange in a flat solar collector with heat pipes and honeycombed fill

A flat solar collector with honeycombed fill and a system of heat pipes has been developed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 4, pp. 546–552, October, 1987.     

Kinetic and morphological study of sulphidation of monocrystalline nickel oxide

The sulphidation of monocrystals of nickel oxide by hydrogen sulphide leads to the formation of a compact protective layer of nickel monosulphide. The rate of sulphidation is fixed by the diffusion of oxygen and nickel ions in the sulphide layer. As in metal corrosion a honeycombed zone is formed at the internal interface by ionic diffusion towards the external interface.     

Sintering behavior of alumina rich cordierite porous ceramics

Porous ceramics are increasingly becoming important in particulate gas filtration. They are an effective alternative to the honeycombed structure in the case of diesel engines. Porous ceramics are made by infiltrating ceramic slurry into a polymeric sponge followed by drying and heating to burn out the polymeric sponge and obtain a ceramic sponge with large open porosity. In this paper we report optimized drying and sintering conditions for alumina cordierite porous ceramics. The microwave drying time ranging from 5–30 min depending on the power and the amount of loading. The shapes of the object was maintained in most of the structures. The sintering temperature was optimized around 1380°C. These results were analyzed using XRD data and SEM micrographs.     

Flexible Honeycombed Nanoporous/Glassy Hybrid for Efficient Electrocatalytic Hydrogen Generation

Hydrogen evolution reaction (HER) in alkaline media urgently requires electrocatalysts concurrently possessing excellent activity, flexible free‐standing capability, and low cost. A honeycombed nanoporous/glassy sandwich structure fabricated through dealloying metallic glass (MG) is reported. This free‐standing hybrid shows outstanding HER performance with a very small overpotential of 37 mV at 10 mA cm^?2 and a low Tafel slope of 30 mV dec^?1 in alkaline media, outperforming commercial Pt/C. By alloying 3 at% Pt into the MG precursor, a honeycombed Pt₇₅Ni₂₅ solid solution nanoporous structure, with fertile active sites and large contact areas for efficient HER, is created on the dealloyed MG surface. Meanwhile, the surface compressive lattice‐strain effect is also introduced by substituting the Pt lattice sites with the smaller Ni atoms, which can effectively reduce the hydrogen adsorption energy and thus improve the hydrogen evolution. Moreover, the outstanding stability and flexibility stemming from the ductile MG matrix also make the hybrid suitable for practical electrode application. This work not only offers a reliable strategy to develop cost‐effective and flexible multicomponent catalysts with low Pt usage for efficient HER, but also sheds light on understanding the alloying effects of the catalytic process.     

Synthesis process and hydrodynamic behavior of a new filtration material for passive wastewater dephosphatation

The preparation optimization of a filter material intended to be used as a phosphate sorbent in flow-through conditions is investigated. The mixing of ferrihydrite (Fh) and pozzolana (Pz) using a “dry contact method” is found to be the most efficient and leads to the formation of a micrometric thick Fh coating deposited into the honeycombed structure of Pz. The maximal Fh content of ~ 8.5 wt.% is significantly higher than the quantity deposited on other classical substrates such as sand. The phosphate sorption kinetics and isotherms, under dynamic conditions in batch experiments, are best described by pseudo-second-order and Freundlich models respectively. Moreover, under static conditions, sorption kinetics reveals intra-aggregate diffusion process. Phosphate ion retention in packed columns, and especially the breakthrough point, can be adequately predicted when coupling the classical convection dispersion equation and the surface complexation model. Breakthrough curves of phosphate ions are strongly dependent on flow rate; which is important for future industrial applications. Finally, and unexpectedly, a high value of phosphate adsorption capacity (80 mg PO₄ g^− 1) is observed when phosphate-containing wastewater is used as feed solution. This is mostly explained by soluble calcium ions, which favors the phosphate fixation onto the filter material surface.     

Characterization and use of high surface area activated carbons prepared from cane pith for liquid-phase adsorption

Carbonaceous adsorbents with controllable surface areas were chemically activated with KOH at 780 degrees C from char that had been carbonized from cane pith at 450 degrees C. The pore properties including the BET surface area, pore volume, pore size distribution, and mean pore diameter of these activated carbons were characterized and derived using the t-plot method based on N(2) adsorption isotherms. The activated cane pith carbons, with KOH/char ratios of 2-6, exhibited BET surface areas ranging from 912 to 2299 m(2) g(-1). The scanning electron microscopic (SEM) observations revealed that the surface morphology of honeycombed holes on all activated cane pith carbons was significantly influenced by the KOH/char ratio. The adsorption kinetics and equilibrium isotherms of acid blue 74, methylene blue, basic brown 1, p-nitrophenol, p-chlorophenol, p-cresol, and phenol from water at 30 degrees C on the activated carbons were studied. The adsorption kinetics were suitably described by a simplified kinetic model, the Elovich equation. All adsorption equilibrium isotherms were in agreement with the Langmuir equation, and were used to compare the covered area (S(c)/S(p)) of the activated carbons at different KOH/char ratios. The high-surface-area activated carbons were proven to be promising adsorbents for pollution control and for other applications.     

蜂窝板换热器内部流动传热特性研究

建立了蜂窝板换热器湍流流动的物理数学模型,并应用数值分析方法模拟了蜂窝板换热器的三维流动传热过程;分析了不同雷诺数下通道内流动阻力和换热性能及其随雷诺数的变化规律,并与相同当量直径的平行平板通道的流动换热性能进行了对比。结果表明,蜂窝板换热器在换热系数提高的同时流动阻力也增大了,在雷诺数Re=3000~15000的范围内,其传热努塞尔数比平行平板增大了0.93~2.12倍,阻力系数增大了2.24~2.35倍。最后从场协同理论的角度分析了蜂窝板强化传热的机理。     

High-temperature phase transition behavior and magnetocaloric effect in a sub-rapidly solidified La–Fe–Si plate produced by centrifugal casting

A sub-rapidly solidified La Fe_(11.6)Si_(1.4)plate was fabricated directly from liquid by centrifugal casting method.The phase constitution,microstructure and magnetocaloric effect were investigated using backscatter scanning electron microscopy,X-ray diffraction,differential scanning calorimetry and physical property measurement system.When the plate was annealed at 1373 K,1 phase was formed by a solid-state peritectoid reaction.A first-order magnetic phase transition occurred in the vicinity of188 K,and the effective refrigeration capacities reached 203.5 J/kg and 209.7 J/kg in plates annealed for1 h and 3 h,respectively,under a magnetic field change of 3 T.It is suggested that centrifugal casting may become a new approach to prepare high-performance La–Fe–Si magnetocaloric plates for practical applications,which could largely accelerate the formation of 1 phase during high-temperature heat-treatment process due to refined and homogeneous honeycombed microstructure.