诱导孔对AL–CFRP混合管轴向压缩变形行为影响

为了研究了不同数量、位置和尺寸的诱导孔对铝–碳纤维复合材料混合管(AL–CFRP混合管)压缩变形模式与吸能特性的影响,建立了AL–CFRP混合管的有限元模型,并利用试验对有限元模型进行了验证。结果表明:诱导孔的数量、位置和尺寸均对AL–CFRP混合管压缩变形与吸能特性有较大影响;单排诱导孔时,混合管的变形模式随孔的数量增多逐渐由混合模式变化为手风琴模式,降低了初始峰值载荷,提高了吸能特性,但诱导孔数量不能过多;多排诱导孔时,诱导孔开设在管件端部能够使AL–CFRP混合管吸收更多的碰撞能量;同时,诱导孔尺寸从上往下依次降低能够使AL–CFRP混合管的吸能过程更加稳定,吸能效率更高,吸收的能量也越多;但过大的诱导孔尺寸,将降低管件的吸能能力,同时改变其变形模式。     

CFRP制孔技术的研究现状与发展趋势

由于碳纤维复合材料(CFRP)具有较高的比模量和强度,CFRP在科学和工业领域引起了足够的重视,并在航空航天领域中得到了广泛的应用。孔加工在航空制造业中占有极其重要的地位,然而由于CFRP的各向异性,使其制孔质量难以控制。介绍了CFRP制孔过程中几种典型的制孔缺陷,指出了缺陷产生的原因及抑制方法;详细阐述了CFRP制孔技术的最新进展,包括制孔刀具、钻削运动方式和特种加工制孔方式三个方面;综述了CFRP制孔技术的发展趋势。     

介孔TiO_2的结构分析

研究了热处理过程中介孔TiO2 的结构及晶粒尺寸、比表面积间的相互关系,为纳米结构材料的定量研究奠定了基础。借助GWShere的圆柱通孔模型,将有孔氧化物视为立方结构体,通过比表面积、孔径、密度等参数的计算,对介孔TiO2 的微结构进行了分析,结果说明其高比表面积主要来自于纳米晶和孔结构两者共同作用。并在晶粒尺寸、比表面积、孔容之间建立了定量关系模型,不仅解释了其比表面积的变化规律,也使得预测孔结构数据成为了可能。     

紧凑式换热器开孔翅片流动传热特性分析

对锯齿翅片和波纹翅片的不同开孔方式建立了多种三维模型,结合数值仿真方法和已有经验公式,分析开孔翅片的流动传热特性,研究翅片开孔的强化传热机理,比较不同开孔方式对流场和温度场的影响,并通过已有的实验拟合公式对仿真结果进行校验。结果表明,对锯齿形翅片,不同开孔参数对流动、散热都有不同的影响。当孔径达到一定范围后,再增加开孔尺寸并不能显著提高换热性能,却仍会导致流动阻力大大增加。对波纹形翅片,不同的开孔位置也会对空气侧流动阻力和传热性能产生显著影响。开孔位于波纹顶峰的翅片比开孔位于波纹腰部的翅片传热性能大约提高1.1%～3.8%,而空气侧压降增加了5.8%～16%。     

含孔损伤复合材料层合板固有频率研究

建立了舍圆形穿孔和方形穿孔损伤复合材料层舍板的有限元计算模型.随着开孔损伤尺寸的变化,计算出含圆形穿孔或方形穿孔损伤复合材料层合板的各阶固有频率.拟合出开孔大小和固有频率之间的关系,得到了层合板固有频率随孔的尺寸和形状变化规律.结果表明,随着损伤程度增加,层合板固有频率都将减小;方孔损伤层合板固有频率减小的幅度和速度都比圆孔损伤层舍板的大;小尺寸穿孔损伤对层合板固有频率的影响很小.     

复合材料开孔平板剪切稳定性研究

本文对复合材料开孔平板试验件进行剪切载荷下的稳定性分析。对厚度为2mm,铺层为16层的开孔平板进行剪切稳定性试验。采用工程算法对复合材料平板的临界屈曲载荷与剪切屈曲应变进行计算，该方法考虑了铺层与边界条件的影响。通过有限元仿真软件建立剪切平板模型，计算模型的屈曲模态，并将模态作为初始缺陷引入模型，通过有限元弧长法计算复合材料平板模型的非线性屈曲载荷及屈曲应变。对于平板模型，工程算法得到的剪切屈曲载荷、屈曲应变与有限元模型计算的结果基本吻合。对于带孔平板模型，利用有限元弧长法仿真得到剪切载荷作用下的应力分布及非线性屈曲载荷，与试验结果对比较好。通过有限元结果与试验、工程算法结果对比，验证了有限元模型的可靠性。基于验证过的有限元模型进行了参数化研究，评估了不同开孔直径对复合材料平板剪切屈曲稳定性的影响。研究结果表明，开孔会导致结构剪切屈曲载荷显著下降，孔边比为0.3时，为临界屈曲载荷最优的结构模型。开孔直径越大，结构的剪切屈曲载荷越小，孔边应变逐渐增大。     

国产碳纤维CCF300增强QY8911双马树脂含孔复合材料拉压疲劳试验研究

碳纤维树脂基复合材料（CFRP）层合板的疲劳性能决定了结构的安全性和可靠性。其寿命预测的研究具有重要的工程意义。依据碳纤维复合材料拉压疲劳试验标准,对含孔国产碳纤维CCF300／QY8911复合材料进行了5个不同应力水平下拉压疲劳试验,分析了疲劳试样断口,表征了中央含孔国产碳纤维CCF300／QY8911复合材料在疲劳载荷作用下的破坏过程,获得含孔复合材料层合板的条件疲劳极限,在此基础上,建立了复合材料的S-N曲线。利用该曲线可对中央含孔复合材料进行疲劳寿命预测。10^6下的条件疲劳极限为平均应力的48％（即150．3MPa）。     

基于电阻响应的CFRP加固结构的无损检测

提出一种利用加固材料自身的功能特性实施碳纤维增强塑料(CFRP)加固结构分层检测的方法,并针对该方法开展了虚拟仿真实验。基于含预制分层损伤的CFRP加固钢梁有限元模型,采用APDL命令流计算并提取了集中力作用下具有不同分层位置和不同分层长度的CFRP加固梁的电位响应,由此建立了碳纤维加固梁损伤响应样本库,通过BP神经网络技术对损伤位置和尺寸进行识别。采用16电极的虚拟仿真实验验证了该方法对分层检测的有效性。     

微介孔复合材料孔径分析方法对比

采用不同分析理论和计算方法对一种新型的孔径分布范围较广的电池碳材料进行比表面积和孔径分析计算。结果表明,传统的HK法(假定孔模型为狭缝型)只适用于分析含狭缝微孔的活性炭材料;BJH法(Barrett-Joyner-Halenda)只能适用于分析含柱状模型类中孔的介孔材料;DFT法(密度函数理论)具有获得微孔和介孔材料真实比表面的能力,并且可以在微孔—介孔全范围内区分微孔、介孔孔径。     

微-介孔复合材料的工业放大

考察了采用溶胶-凝胶化学合成法制备微-介复合材料的制备条件对复合材料制备的影响。采用XRD、SEM以及N2物理吸附-脱附等表征手段对复合材料进行了表征。结果表明,在加入异丙醇的情况下,采用超声震荡和机械搅拌的混合方式均可以很好地制备壳层均匀的微-介孔复合材料;而在没有异丙醇时,采用两种混合方式制备的微-介孔复合材料的表面比较粗糙,而且壳层结构参数也不相同。在优化了实验室制备条件的基础上,对微-介孔复合材料进行了工业放大。结果表明,采用优化的制备条件制备的微-介孔复合材料完全满足指标要求,并且制备过程重复性好。     

Performance evaluation of the incorporation of different wire meshes in between perforated current collectors and membrane electrodeassembly on the Passive Direct methanol fuel cell

Passive Direct methanol fuel cells (DMFC) are more suitable for charging small capacity electronic devices. In passive DMFC, the fuel and oxidant are supplied by diffusion and natural convection process on the anode and cathode sides respectively. Current collectors (CC) play a vital importance in fuel cell performance. This paper presents the combined impact of perforated and wire mesh current collectors (WMCC) on passive DMFC performance. Three types of open ratios of perforated current collectors (PCC), such as 45.40％, 55.40％and 63.40％and two types of wire mesh current collectors with open ratios of 38.70％and 45.40％were chosen for the experimental work. A combination of Taguchi-L9 rule is con-sidered. A combination of three PCC and two WMCC on both anode and cathode was used. Methanol con-centration was varied from 1 mol·L-1–5 mol·L-1 for nine combinations of PCC and WMCC. From the experimental results, it is noticed that the combination of PCC and WMCC with an open ratio of 55.40％ and 38.70％ incorporated passive DMFC produced peak power density at 5 mol·L-1 of methanol concentration. The passive DMFC performance was evaluated in terms of maximum power density and maximum current density. The combined current collectors of PCC and WMCC open ratios of 55.40％+38.70％ have more stable voltage than single PCC of open ratio 63.40％ at 4 mol·L-1 of methanol concentration.     

基于力阻效应的CFRP试件传感特性的试验研究

基于碳纤维复合材料传感原理,推导电阻变化率与应变的关系公式,通过CFRP试件轴向拉伸试验,得到试件的初始电阻和伏安特性曲线,研究了在三个不同的应变阶段,试件电阻变化率随应变的变化关系,并通过线性拟合得到初始阶段CFRP试件的灵敏度。试验结果表明:当应变小于0.8%时,电阻变化率随应变变化较快,表现出良好的线性关系,具有良好的力阻效应;当应变在0.8%~2.4%之间时,电阻变化率随应变的变化速度降低,电阻-应变关系曲线出现波动;当应变大于2.4%时,电阻变化率急剧增长,试件破坏。     

Study on flow fields in a bioreactor with perforated blades

Flow fields of a gas–liquid fluid in a bioreactor with perforated blades were evaluated with the computational fluid dynamics and particle image velocimetry (PIV). The flow pattern of the fluid was the complex turbulence, and the fluid had preferable flow fields for fermentations. Using a rotating coordinate system and a sliding mesh method, a mesh of 24 × 16 × 80 (X × Y × Z) was selected due to its high accuracy and appropriate workload. The numerical results of the two‐phase flow model agreed well with the experimental results of the PIV, such as flow field characteristics and data curves. The RNG k–ε model was adopted, which could precisely simulate anisotropic flow fields around higher‐speed blades. Whole deviations of X‐, Y‐ and Z‐direction velocities ranged only from 5.4% to 10.5%, and continuous turbulence models could effectively simulate transfer procedures of the fluid. Because of its low cost, simplicity and easy of scale‐up, the bioreactor with perforated blades and its models mechanism of fluid microelements are expected to be efficient for its industrial amplification and application in food industry. © 2012 Canadian Society for Chemical Engineering     

Numerical study on notched steel plate with center hole strengthened by CFRP

Steel members could be damaged and fail to fulfill the requirements of safety after long-term service. Carbon fiber reinforced polymer (CFRP) strengthening turns out to be an excellent method for prolonging its service life. The strengthening technique has been extensively studied in recent decades, however, few researchers concerned about the simulation of steel plates with center hole strengthened by CFRP. Therefore, its mechanical performance was investigated numerically in this study. The numerical results were compared with the experimental results and an acceptable agreement was reached, which verified the validity of the numerical model. A parametric study was conducted, in which the interfacial stress distribution change with CFRP elastic modulus, thickness and strengthening form was analyzed. For fully covered CFRP strengthening, increasing of elastic modulus and thickness of CFRP plates can enhance the stiffness of steel plates, however, it has insignificant effect on debonding load and obvious decrease on ultimate load. While the partially covered CFRP bonding strengthening can also upgrade the stiffness with CFRP elastic modulus and thickness, the effect to both of debonding load and ultimate load is minimal.     

Longitudinal mixing in the dispersed phase in pulsed perforated-plate columns

A method is presented to identify flow model parameters from radioactive signals with a high noise content. The method is based on the two detection points method with a highly accurate identification of the parameters by optimization in the frequency domain. The study of dispersed phase of a pulsed column with perforated plate using this method has shown evidence that there are operating conditions for which the piston-diffusion flow does not describe well the behavior of the dispersed phase.     

喷射流扩展半径及喷射火后果模拟计算方法研究

根据喷射能量守恒关系推导出喷射流扩展口半径计算式,该表达式体现扩展半径与泄漏口半径、喷射物密度之间的关系。采用HSE（Health and Safety Executive）的MHAU（Major Hazards Assessment Unit）程序中的通用喷射火模型程序SHELF2案例验证文章推导的扩展半径计算式代入API喷射火模型模拟计算喷射火的准确性,结果表明文章中的模拟方法能较准确地模拟喷射火,模拟计算结果符合L.T.Cowley总结CEC（Commission of European Communities）实验数据得出的结论。     

纤维增强复合材料汽车保险杠防撞梁的轻量化研究

探讨了用于车身结构的两种常用纤维增强型复合材料——长玻璃纤维增强聚丙烯复合材料(LGFT)和连续碳纤维增强环氧树脂基复合材料(CFRP)在汽车保险杠防撞梁上的轻量化应用。开展了LGFT和CFRP材料的制备及相关力学性能测试,基于实验与反求分析获取有限元仿真分析相关参数。以某车型铝制保险杠防撞梁为原型,采用LGFT及CFRP复合材料进行等刚度设计,综合分析了复合材料保险杠防撞梁相对于铝制防撞梁的耐撞性和轻量化性能。结果表明,在满足耐撞性能要求下,LGFT与CFRP防撞梁轻量化效果明显,相对于原铝制保险杠防撞梁质量分别减轻了11.2%和46.1%。因此,在等刚度设计条件下,纤维增强型复合材料能更好地实现汽车保险杠防撞梁的轻量化要求。     

Insights into the weep performance and modeling of perforated plates

Weeping is an important hydraulic parameter for the design and optimization of perforated plates because it determines the lower limit of the tray operation (vapor load). Therefore, an accurate prediction of the weep rate is very important. First, according to our theoretical analysis of the weeping phenomena of large-scale perforated trays, we proposed three weep modes on a perforated tray: (1) random weeping in the bubbling zone, (2) dumping in the nonbubbling zone, and (3) liquid fluctuation-induced weeping. Second, a weep rate model was developed, and the literature data were correlated to determine model parameters. Results showed the fractional hole area substantially affects the model parameters. We also examined the effects of the tray structure, flow parameter, and fluid physical properties on the weep rate. Finally, the developed model was used to predict the weep rate of different scale trays reported in references, and the prediction results showed good agreements.     

An electrochemical investigation of sintered thick metal hydride electrodes for oxygen-metal hydride semi-fuel cell applications

Based on a conventional pasting method, a sintering process was applied to fabricate thick metal hydride electrodes for oxygen–metal hydride semi-fuel cell. It was found that, after sintering, the activation and the high-rate dischargeability of the electrodes are greatly improved. The sintering parameters were optimized by measuring the electrochemical properties of the metal hydride electrode sintered in the temperature range 650–900 °C for 10–60 min under mixed argon and hydrogen gases. It was found that to make a thick metal hydride electrode, the use of perforated copper foil as a current collector is better than using perforated nickel strip and copper mesh. A new type of structure is designed for the thick metal hydride electrode, that is, by folding the perforated foil that had been prepasted with active materials into a sandwich structure. This fold-type sandwich electrode was further clamped and held together by copper mesh.