钢—混凝土组合梁的分析方法

本文对钢—混凝土组合梁在长期荷载作用下的内力和变形的计算方法进行了分析。文中采用按龄期调整的有效模量法并结合有限单元步进法来计算钢—混凝土组合截面的应力和变形,从而将混凝土的收缩徐变等非弹性时效问题转化为相应的弹性计算问题。文末以一组合框架为例,对其在持续荷载作用下的结构内力重分布及截面应力重分布等长期行为进行了分析讨论。     

Synthesis of poly(3,4-propylenedioxythiophene)/MnO2 composites and their applications in the adsorptive removal of methylene blue

The poly(3,4-propylenedioxythiophene)/Mn O_2 composites(PPro DOT/Mn O_2) were prepared successfully by soaking the PPro DOT powders into potassium permanganate(KMn O_4) solution, with the mass ratio of PPro DOT and KMn O_4 from 2:1 to 1:2. The structure and morphology of composites were characterized by Fourier transform infrared spectroscopy(FTIR), Raman spectroscopy, ultraviolet–visible absorption spectra(UV), X-ray diffraction(XRD), energy-dispersive X-ray spectroscopy(EDX) and field emission scanning electron microscope(FE-SEM).Furthermore, PPro DOT/Mn O_2 composites were tested as the adsorbents for removal of methylene blue(MB) from aqueous solution. The results revealed that the composites were successfully synthesized, and the thiophene sulfur was oxidized into sulfoxide by KMn O_4. The highest percentage removal of MB after 30 min was 91% for PPro DOT/Mn O_2(1:2) composite, and the percentage removal of MB was 12 mg g(~-1)after 60 min at initial concentrations of MB dye of 5.6 mg L~(-1)in the case of PPro DOT/Mn O_2(1:2) composite. Besides, the adsorption process of PPro DOT/Mn O_2(1:2) composite was described by pseudo-second-order and Langmuir models.     

高拉速连铸低碳铝镇静钢铸坯中夹杂物

针对高拉速板坯连铸生产的低碳铝镇静钢铸坯,采用Aspex自动扫描电镜对铸坯表层夹杂物进行大面积的扫描分析,得到不同拉速下夹杂物的变化规律,并探究流场和S含量对夹杂物分布的影响。结果表明：随着拉速增大,钩状坯壳的深度和长度逐渐减小。对拉速大于2 m·min-1的铸坯,由于钩状坯壳不是很发达,铸坯表层没有发现大于200μm的夹杂物。铸坯表层尺寸介于50~200μm的夹杂物主要是由凝固坯壳所捕获,而夹杂物在凝固前沿的受力决定了夹杂物的捕获行为。随着拉速提高,凝固前沿的钢液流速增加,随着冲刷力的增加、捕获力的减少,夹杂物被捕获的数量减少。在高拉速连铸下,如果钢液中S含量较大,夹杂物受到明显的温度Marangoni力,会更容易被凝固坯壳捕获。     

连铸板坯轻压下过程中间裂纹产生机理

针对板坯连铸过程中间裂纹严重的问题,对中间裂纹的形貌、元素偏析等情况进行分析.通过建立有限元模型,对不同压下位置和不同压下量凝固前沿的受力情况进行计算并与临界应力值进行对比.结果表明：C、P、S等元素在晶界处富集只是促使中间裂纹开裂的内因,真正造成铸坯开裂的原因是凝固前沿所承受的拉应力.铸坯通过矫直段时,多处位置的凝固前沿所承受的拉应力超过钢的临界值,导致凝固前沿容易开裂延伸,形成中间裂纹;而弧形段和水平段处凝固前沿所承受的拉应力不超过钢的临界值,无裂纹产生.统计现场大量轻压下的实验结果显示：轻压下避开矫直区进行时,中间裂纹的发生率降低约41.3%.     

Research on Design Optimization Strategy in Virtual Product Development

Introduction WiththeadvanceofComputeraideddesign(CAD), Computeraidedengineering(CAE)andVirtualreality technology(VR),virtualproductdevelopment(VPD)is emergingasanewtechnologyusedbyleadingindustrytodevelopnewproductwithouttime consumingandexpensive physicalprototypetest.Virtualproduct,ordigitalmock up,isacomputersimulationofaphysicalproductthatcanbepresented,analyzed,andtestedfromconcernedproduct life cycleaspectssuchasdesign,manufacturing,service, andrecyclingasifonarealphysicalmodel.T…     

Mechanical, deformation and fracture behaviors of bulk metallic glass composites reinforced by spherical B2 particles

Ti_(45)Cu_(40)Ni_7Zr_5Sn_(2.5)Si_(0.5) alloys were prepared under various cooling rate conditions during solidification.The alloys exhibited different volume fractions of B2 particles with 0～40 vol%in an amorphous matrix.Monolithic bulk metallic glass of 1 mm diameter showed no macroscopic plasticity and exhibited the typical vein patterns in a maximum shear stress plane on the fracture surface.However,a bulk metallic glass composite containing the B2 particles revealed obvious plasticity(～5.6%)with a remarkable work-hardening behavior that resulted from a stress-induced martensitic transformation of the B2 particles.Moreover,the composite displayed the complicated fracture morphologies containing of three types of fracture features.Through detailed investigations on the microstructural evolution,mechanical,deformation and fracture characteristics,the influence of B2 particle on overall behavior of the TiCu-based bulk metallic glass composites was elucidated.     

河南省复合地基应用现状及评价——以许昌地区为例

随着河南省建设行业的飞速发展,我省的地基基础专业技术有了长足的进步。研究、设计、施工水平都有了较大的提高,新的复合地基形式不断出现,新的施工工艺不断开发和引进,给工程建设带来了较大的经济效益和社会效益。但由于国家相关规范标准的改进,以及我省基础工程技术力量和技术水平的限制,我省基础工程技术领域还存在很多技术和管理问题急需解决。为提高河南省地基基础行业的技术、管理水平,本文针在分析我省地基基础行业现状基础上,提出我省目前地基基础专业存在的主要问题,分析其原因并提出相应对策,供行业内同行参考。     

橡胶-硅藻精土复合改性沥青的制备及机理

为了改善沥青的高温性能,采用橡胶和硅藻精土制备多种掺量的复合改性沥青。利用针入度、软化点、延度、旋转粘度试验,对不同改性沥青性能进行表征,通过曲面响应法得出改性剂最佳掺量比例,并对比橡胶沥青、橡胶-SBS复合改性沥青进行改性效果评估。采用旋转薄膜烘箱老化试验、热重分析法、差示扫描热量法、红外光谱扫描试验、扫描电镜试验、研究了橡胶-硅藻精土复合改性沥青的老化性能、高温性能、微观结构和反应机理。结果表明,22%橡胶和4%硅藻精土的复合改性沥青综合性能最好。与橡胶沥青、橡胶-SBS复合改性沥青相比,橡胶-硅藻精土复合改性沥青表现出了更好的高温稳定性;橡胶粉、硅藻精土与基质沥青之间主要存在物理共混,沥青与两者形成了相互稳定的整体。     

含氢聚硅氧烷/丙烯酸丁酯复合乳液的研究——影响乳液流变性及反应速率的因素

详细讨论了在一次加料法制备含氢聚硅氧烷（PHMS）／丙烯酸丁酯（BA）复合乳液中,单体、乳化剂、引发剂及反应温度对聚合反应速率、转化率和乳液流变性能的影响．结果表明：PHMS／BA复合乳液的表观活化能和聚合速率方程分别为：Ea＝132．77KJ／mol,（I为引发剂,E为乳化剂）该乳液呈假塑性流体特征,随PHMS、功能单体N-羟甲基丙烯酰胺（NMA）用量增加,乳液粘度增加;乳化剂用量增加,反应温度升高,粘度降低．选择适当的原料配比和反应条件,可在较高的反应速率下,制得转化率高、性能稳定PHMS／BA复合乳液．     

CFG桩复合地基不同参数沉降影响分析

结合兰永一级公路软弱路基处治技术研究项目,为分析不同设计参数下CFG桩复合地基处治软土路基的沉降变化规律,利用非线性有限元软件ADINA建立三维模型,结合比奥固结理论,地基土体按多孔介质材料考虑,采用Mohr-coulomb理想弹塑性模型做固结分析,将填土视为荷载逐级施加,采用生死单元对CFG桩复合地基进行数值模拟。结果表明,相比提高垫层模量与桩身模量,选择较大桩长与合理的桩距、桩径对减小软土路基沉降更为明显,裙桩效应对于减小软土路基沉降起积极作用,软土路基经过CFG桩复合地基处理后满足一级公路工后沉降要求,加固效果明显。