Elastic stability of bi-axially loaded rectangular plates with a single circular hole

The finite-element method has been employed to determine the elastic buckling stresses of a bi-axially loaded perforated rectangular plate with dimensions a and b in the x- and y-directions, respectively. The considered perforation is a single circular hole whose center is located along the longitudinal axis of the plate. The considered plate has simply supported edges in the out-of-plane direction and is subjected to bi-axial uniformly distributed end loads (compressive load σ_x in the x-direction, and compressive or tensile load σ_y in the y-direction). Parameters considered in the study are the plate's aspect ratio a/b, the stress ratio ξ between the applied stresses in the y- and x-directions (ξ=σ_y/σ_x), the circular hole size d and location e_x.The study shows that, in most of the considered cases, the bigger the hole size d, the lesser the plate stability and the lesser the buckling stresses. It also shows that the plate aspect ratios, a/b, between 0.6 and 1.2 should be avoided for plates with large holes and negative ξ, due to the large reduction in the buckling stresses. The hole location should also be selected to be away from the loaded edge of the plate as much as possible (better to have e_x/b>1.0) to increase the buckling stresses and improve stability. The study demonstrates also that the increase in tension in the y-direction in bi-axially loaded plate with large hole (d/b>0.4) reduces its stability. This is in contrary to the expected increase in the stability due to the increase in tension which can be seen clearly in the cases of solid plates and plates with small holes.     

矩形钢管混凝土的局部屈曲性能研究

本文用能量法对刚性基底矩形钢板的屈曲性能进行了理论分析研究,利用满足边界条件的屈曲位移函数得到屈曲系数的计算公式,然后进一步用于矩形钢管混凝土轴心受压局部屈曲问题的分析和计算,得到矩形钢管混凝土屈曲系数计算公式,最后根据修正的温特(G.Winter)公式,推导矩形钢管混凝土全截面有效的宽厚比限值及其局部屈曲强度计算公式,计算结果与试验结果进行了比较,吻合较好。本文的研究成果可为相关研究提供参考。     

Study of flow pattern in open channel flow passages

The uniform flow distribution in the upstream side of open channel flow passages is to be ensured at different flow rates. This finds critical importance in many industrial applications including chemical plants and nuclear reactors. This paper describes the method for achieving the uniform flow pattern in open channel flow passages with the aid of stream equaliser plates of different lengths and porosities.     

裂解汽油加氢装置脱壬烷系统改造

介绍了盘锦乙烯有限责任公司裂解汽油加氢装置脱壬烷系统改造实施的原因及改造效果。在实施改造前,脱壬烷系统的C9产品中含有34%的甲苯和二甲苯。为了回收这部分混合苯,该厂在2004年8月对脱壬烷系统进行了改造。改造后,提高了混合苯收率,解决了在C9产品中混合苯损失的难题。     

轧制304/Q235复合板工艺研究

通过对热轧工艺的试验研究及组织性能分析与测试,开发了一种采用轧制复合的新复合板304/Q235,试验研究取得的工艺参数对工业化生产板面尺寸大的复合板具有参考价值.     

辊式校平过程对船用大尺寸10Ni5CrMoV钢板材初始残余应力的影响

用实验和数值模拟相结合的方法,研究了辊式校平过程对10Ni5CrMoV钢大尺寸船用板材残余应力的影响规律。实验结果和有限元结果的对比表明,大尺寸板材的辊式校平的有限元分析过程可以用平面应变问题来处理,并能保持相当的精度;校平过程对于板材上表面的长度方向应力影响很大。有限元分析的结果表明,校平过程中板材承受反复的拉压,从而在板材表面形成一层关于中性层对称的塑性变形。     

铺设角度对层合板结构声功率的影响分析*

针对层合板结构铺设角度对前二阶声辐射模态幅值和辐射声功率的影响进行分析。利用分层理论结合有限元模型求解层合板的铺设角度与振动速度信息之间关系。通过声辐射模态理论,以某12层层合板结构为例,研究固定边界条件下的层合板辐射模态数、对称铺设角度、单向铺设角度以及激励力位置对声辐射模态幅值和辐射总声功率的影响。计算结果表明,在相同角度下,对称铺设层合板结构最大声功率值要小于单向角度铺设层合板结构最大声功率值;另外在低频时,对层合板结构辐射声功率起主要贡献的是前两阶辐射模态。并以某16层零度铺设的固定边界条件下的层合板结构为例,对复合材料层合板结构的声辐射模态幅值及声功率进行试验分析。     

外贴预应力玻璃钢板加固混凝土梁试验研究

本文针对外贴复合材料加固混凝土梁存在的不足,将玻璃纤维材料(GFRP)先施加预应力,再将其外贴到混凝土梁受拉面以提高混凝土梁的承载能力.针对GFRP板横向抗剪切挤压强度低的缺点,研究对GFRP板的预应力施加方法,在此基础上完成了9根不同预应力度,不同混凝土强度等级混凝土梁的抗弯试验;同时完成了4根预应力GFRP板在梁侧立面不同粘贴方式抗剪试验研究.试验结果表明,外贴预应力GFRP板加固混凝土梁可大幅度提高混凝土梁的开裂弯矩、极限承载力及GFRP板的强度利用率,改善梁的裂缝开展情况及提高梁的抗变形能力.     

应用超声波技术评价氧化膜类缺陷检出率的可行性研究

重点讨论了超声波技术检测铝合金预拉伸板材中氧化膜类缺陷的可行性和检出率,从理论和实际两个方面分析了影响氧化膜缺陷检出率的主要因素,并提出科研性结论。     

Poly(m‐phenylenediamine)‐coated 316L SS: A promising material for bipolar plates in PEMFC environment

The applicability of conducting polymer coatings to enhance corrosion resistance of bipolar plates in proton exchange membrane fuel cells (PEMFC) is gaining greater significance as electrical conductivity is as important as corrosion resistance. Metaphenylenediamine (mPD) monomer was electropolymerized to poly(m‐phenylenediamine) (PmPD) conducting polymer over 316L SS and characterized by attenuated total reflectance infrared spectroscopy to confirm the formation of P mPD polymer. Scanning electron microscopy was used to study the surface morphology of the polymer. Open‐circuit potential, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization studies were conducted to assess the corrosion protection performance of the PmPD polymer coating in PEMFC environment. The charge‐transfer resistance measured from EIS for the coated substrates was higher than the uncoated substrate. Potentiodynamic polarization studies showed lower corrosion current density for the PmPD‐coated substrates. All the results proved that the PmPD‐coated substrates could exhibit enhanced corrosion resistance in PEMFC environment.