W型辐射管的燃烧优化以及流固耦合分析方法研究

采用Fluent软件模拟W型辐射管内部流体的燃烧状况,在不同空气过剩系数、不同燃气流量以及不同空气预热温度工况下,对辐射管内燃烧流场进行了数值模拟,得出合理可行的空气过剩系数、燃气流量和空气预热温度.在此基础上通过流固耦合分析求出辐射管的结构变形及应力分布.比较全面地对辐射管进行了分析,对类似问题具有一定的参考价值.     

基于平均应力的直埋供热管道预热温度

针对大直径、高温、高压预热安装供热直埋管道,在冷水试运行、降温等过程中被拉断、补偿器被撕裂等问题,提出基于"平均应力温度"的预热温度.从升温压应力等于降温拉应力出发,建立起预热温度函数式,绘出"平均应力温度"随压力和管径的变化曲线,并用于事故管道分析.结果表明:大管径的预热安装温度高,是降温断裂的主要原因.预热温度不仅要考虑循环最高温、循环最低温,还应考虑管道内压力、管径大小及其壁厚等因素."平均应力温度"随内压力和管径的增大而显著降低,而"循环中间温度"与这些因素无关.用"平均应力温度"取代"循环中间温度"来计算各项预热参数,能使预热安装直埋管道的降温拉应力显著减小.     

基于Simufact的低温环境T形平角焊的温度场仿真

在低温环境下焊接时,为了防止冷裂纹的产生,运用Simufact-Welding软件对T形接头用焊条电弧焊在环境温度为-15℃时进行了焊接仿真,分析了焊件预热到80℃和未预热时的温度场.结果表明:未预热情况下焊件的温度范围为-14~1 330℃,焊缝处的最高温度为1 330℃;预热情况下焊件的温度范围为62~1 402℃,焊缝处的最高温度为1 402℃;焊件预热时的t8/5时间比未预热时的t8/5时间长,同理,焊缝处的变形量增大,除焊缝起始点和终止点外,其余采样点处的等效应力减小.因此,合理地控制预热温度,适当增大t8/5时间,有利于缓解接头的冷却速度,减小淬硬倾向.     

沉积温度和速率对电子束沉积ZnSe薄膜应力特性的影响

在不同沉积温度和速率下,采用电子束蒸发法制备ZnSe薄膜样品,利用ZYGO GPI型干涉仪测试样品的应力行为,并采用X射线衍射（XRD）技术测试样品的晶向特征.实验结果表明,在不同条件下制备的ZnSe薄膜均呈现压应力,应力随着沉积温度升高而增大,在200 ℃应力达到最大值,之后应力随沉积温度升高呈下降趋势.XRD结果表明,沉积速率直接影响ZnSe薄膜的晶向结构,进而改变ZnSe薄膜内应力;当沉积速率为1.5 nm/s时,薄膜应力最小.     

自蔓延高温合成TiB2微粉的热力学计算

从热力学上对Mg-Ti-B-O体系的自蔓延反应进行了理论分析,计算了稀释剂MgO、TiB2含量和预热温度对反应绝热温度的影响.结果表明,随着稀释剂MgO、TiB2含量和预热温度的不同反应绝热温度也不同,在同一预热温度下,随着稀释剂含量的增加绝热温度降低;同一体系中在稀释剂含量相同时,随着预热温度的升高绝热温度也升高;随着预热温度的不断升高,燃烧反应能自我维持的稀释剂的临界值也逐渐升高.     

Surface composites fabricated by vacuum infiltration casting technique

Alumina （Al2O3） particles reinforced copper matrix surface composites were fabricated on the bronze substrate using the vacuum infiltration casting technique. Three cases were obtained in the vacuum infiltration casting technique： no infiltration, partial infiltration and full infiltration （the thickness of preforms do not exceed 3.5mm）. The reason of no infiltration is that the vacuum degree is not enough so that the force acting on the liquid metal is lower than the resistance due to the surface tension. Partial infiltration is because of somewhat lower vacuum degree and pouring temperature. Full desired infiltration is on account of suitable infiltration casting conditions, such as vacuum degree, pouring temperature, grain size and preheating temperature of the preform. The most important factor of affecting formation of surface composites is the vacuum degree, then pouring temperature and particle size. The infiltration mechanism was discussed on the bases of different processing conditions. The surface composite up to 3.5 mm in thickness with uniformly distributed Al2O3 particles could be fabricated via the vacuum infiltration casting technique.     

离心铸造条件对Mg_2Si/Al梯度复合材料组织与性能的影响

采用离心铸造法制备了内外层特别是内层富含细小Mg2Si颗粒的铝基梯度复合材料。研究了模具离心转速和预热温度对Mg2Si/Al梯度复合材料内层显微组织和性能的影响。研究结果表明,随着模具离心转速的增大,铸件内层Mg2Si颗粒相分布趋于均匀,颗粒相体积分数、显微硬度和耐磨性能均有较大幅度提高。而模具预热温度对铸件内层颗粒相体积分数及性能影响较小。在模具离心转速为1560 r/min,预热温度为300℃的条件下,铸件内层性能达到最佳值,磨损率仅为相同干滑动摩擦磨损条件下HT200的1/30~1/40。     

Microstructure and properties of novel polarization maintaining fiber

An improved type of elliptical jacket polarization maintaining fiber was developed by using a modified chemical vapor deposition method with special treatment. Different from conventional elliptical jacket, the shape of the stress jacket was transmuted. The cross-section of fiber consists of 5 layers: substrate, outer cladding, stress jacket, inner cladding and core. The cross sectional component distribution was investigated by electron probe microscopy and energy dispersive spectrum. The finite element method was used to calculate the stress birefringence.Based on the analyses of the microstructure, the technological process is improved. The temperature cycling test of the fiber wound into gyroscope coils was performed. The results show that the fiber possesses superior performance at high and low temperatures compared with other fibers. The high homogeneity is achieved by well-controlled modified chemical vapor deposition process. A homogeneous length of 8 km fiber is obtained. With advantages in homogeneity and length, the fiber has great potential in applications such as fiber gyroscopes, fiber hydrophone and other optical fiber sensors.     

熔融堆积成型制件中层间应力及翘曲变形研究

熔融堆积成型(FDM)是一种典型的快速成型技术,由于无污染适合办公环境下使用而得到广泛应用。分析了层间应力及翘曲变形产生的原因,并在一定的假设条件下,得出了层间应力的计算公式及其在截平面上的分布情况。建立了翘曲变形的数学模型,讨论了各种工艺参数(层数、扫描线长、成型室温度、层厚等)对翘曲变形量的影响。最后提出了减小翘曲变形的措施。     

预热温度对铝合金搭接激光焊焊缝成形及组织的影响

采用Nd:YAG激光器和1.4 mm厚的5A03H24铝合金板材,在不同预热温度下用相同的激光焊参数进行了搭接激光焊试验。结果表明:焊缝的熔深、熔宽随温度的升高而增大,并在T≥250℃时增大显著;焊缝成形和焊接过程稳定性在T≤250℃时随温度的升高而变好;焊缝组织随温度的升高而粗化,但T≤200℃时粗化不明显;焊缝、热影响区和母材的显微硬度随温度的升高而下降,但T≤100℃时焊缝的显微硬度下降不明显,T≤200℃时热影响区的显微硬度下降不明显,T≤300℃时母材的显微硬度下降不明显。     

底充胶导热系数预测及对倒装焊温度场的影响

根据导热的基本理论和Haiying Li的研究数据拟合出填加了碳纤维、Silica的环氧树脂封装材料的导热系数预测公式，依此公式可预测出相关复合材料的导热系数．利用有限元方法对电子封装倒装焊中不同导热系数的底充胶材料对温度场的影响进行了分析比较．表明高导热系数的底充胶可明显降低在芯片和基板之间的温度差，降低底充胶的热应力，进而提高电子封装的可靠性．     

Preparation of Fe-Al Intermetallie /TiC-Al2O3 Ceramie Composites from llmenite by SHS

Fe-Al intermetallic/TiC-Al2O3 ceramic composites were successfully prepared by selfpropagating high-temperature synthesis （SHS） from natural ilmenite, aluminium and carbon as the raw materials. The effects of carbon sources, preheating time and heat treatment temperature on synthesis process and products were investigated in detail, and the reaction process of the FeTiO3-Al-C system was also discussed. It is shown that the temperature and velocity of the combustion wave are higher when graphite is used as the carbon source, which can reflect the effect of the carbon source structure on the combustion synthesis; Prolonging the preheating time or heat treatment temperature is beneficial to the formation of the ordered intermetallics; The temperature and velocity of the combustion wave are improved, but the disordered alloys are difficult to eliminate with the preheating time prolonged. The compound powders mainly containing ordered Fe3Al intermetallic can be prepared through heat treatment at 750 ℃.     

玻璃衬底沉积氮化硅薄膜性能研究

为了改善玻璃衬底上制备的薄膜太阳电池的转换效率,采用高纯氮气作为等离子体气源,以质量分数为5%的SiH_4(Ar稀释)作为前驱气源,利用电子回旋共振-等离子体增强化学气相沉积技术在玻璃衬底上低温制备了氮化硅薄膜;利用各种测试设备分析了薄膜的成分、光学性能和表面形貌.结果表明:实验制备的非晶薄膜含氢量较低;薄膜的折射率随着衬底温度和微波功率的增加而增加.在衬底温度为350℃、微波功率为650 W时,薄膜的折射率在2.0左右,平均粗糙度为1.45 nm,还说明薄膜具有良好的光学性能和较高的表面质量.在此条件下,薄膜的沉积速率达到10.7 nm/min,表明本实验能在较高的沉积速率下制备均匀、平整、优质的SiN薄膜.     

Influence of methane on hot filament CVD diamond films deposited on high-speed steel substrates with WC-Co interlayer

Diamond films were deposited on high-speed steel substrates by hot filament chemical vapor deposition (HFCVD) method. To minimize the early formation of graphite and to enhance the diamond film adhesion, a WC-Co coating was used as an interlayer on the steel substrates by high velocity oxy-fuel spraying. The effects of methane content on nucleation, quality, residual stress and adhesion of diamond films were investigated. The results indicate that the increasing methane content leads to the increase in nucleation density, residual stress, the degradation of quality and adhesion of diamond films. Diamond films deposited on high-speed steel (HSS) substrate with a WC-Co interlayer exhibit high nucleation density and good adhesion under the condition of the methane content initially set to be a higher value (4%, volume fraction) for 30 min, and then reduced to 2% for subsequent growth at pressure of 3 kPa and substrate temperature of 800 °C.     

Thickness and component distributions of yttrium-titanium alloy films in electronbeam physical vapor deposition

Thickness and component distributions of large-area thin films are an issue of international concern in the field of material processing. The present work employs experiments and direct simulation Monte Carlo (DSMC) method to investigate three-dimensional low-density, non-equilibrium jets of yttrium and titanium vapor atoms in an electron-beams physical vapor deposition (EBPVD) system furnished with two or three electron-beams, and obtains their deposition thickness and component distributions onto 4-inch and 6-inch mono-crystal silicon wafers. The DSMC results are found in excellent agreement with our measurements, such as evaporation rates of yttrium and titanium measured in-situ by quartz crystal resonators, deposited film thickness distribution measured by Rutherford backscattering spectrometer (RBS) and surface profilometer and deposited film molar ratio distribution measured by RBS and inductively coupled plasma atomic emission spectrometer (ICP-AES). This can be taken as an indication that a combination of DSMC method with elaborate measurements may be satisfactory for predicting and designing accurately the transport process of EBPVD at the atomic level. Supported by the National Natural Science Foundation of China (Grant Nos. 90205024, 10502051 and 10621202)     

离心铸造铝-铬自生梯度复合材料梯度结构研究

为获得具有较好梯度结构的梯度功能材料，提出并采用了一种新的离心力一多孔金属中间层法制备铝—铬自生(in-suit)梯度复合材料，进行了制备过程的实验研究，主要内容包括：工艺(材料)设计、正交实验主体、数据处理及结果分析等．重点进行了工艺参数对梯度结构影响的分析，实验结果表明，在离心转速、中间层厚度、预热温度、金属温度4个工艺参数中，中间层的板差为次大值，表明中间层的存在对梯度结构的形成有较大的贡献．     

Analysis of adiabatic shearing failure mechanism for aluminum matrix composites based on experimental and numerical simulation

Adiabatic shear behavior and the corresponding mechanism of TiB2/Al composites were researched by split Hopkinson pressure bar (SHPB).Results show that the flow stresses of the TiB2/Al composites exhibit softening tendency with the increasing of strain rates. All the composites fail in splitting and cutting with a 45 degree, and the phase transformed bands of molten aluminum are found on the adiabatic shear layers. The deformation behavior and shear localization of the TiB2/Al composites specimens were simulated by finite element code MSC.Marc. The Johnson-Cook model was used to describe the thermo-viscoplastic response of the specimen material. There was unanimous between the numerical result and the experimental result on the location of the adiabatic shear band. From the numerical simulation and experiment, it was concluded that the instantaneous failure of the composite was ascribed due to the local low strength area where the formation of adiabatic shear band was, and the stress condition had significant effect on the initiation and propagation of adiabatic shear band (ASB).     

电弧喷涂涂层温度场及应力应变分析

为了分析电弧喷涂层的沉积过程，采用有限元分析软件ANSYS计算不同时刻以及不同位置涂层内的温度场、应力场，在建立传热模型过程中考虑了金属液滴向涂层的传热以及涂层向系统外的热量散失等问题.采用在厚度方向以微小层逐层叠加来模拟涂层的增厚，并以此为基础构造涂层有限元计算模型，应用单元生与死逐层激活层单元参与计算过程.实现移动边界以充分模拟真实的喷涂沉积过程，获得了涂层温度场、应力场的分布情况.并在此计算的基础上，分析了应力分布对涂层失稳的影响.     

Diagnosis of gas phase near the substrate surface in diamond film deposition by high-power DC arc plasma jet CVD

Optical emission spectroscopy （OES） was used to study the gas phase composition near the substrate surface during diamond deposition by high-power DC arc plasma jet chemical vapor deposition （CVD）. C2 radical was determined as the main carbon radical in this plasma atmosphere. The deposition parameters, such as substrate temperature, anode-substrate distance, methane concentration, and gas flow rate, were inspected to find out the influence on the gas phase. A strong dependence of the concentrations and distribution of radicals on substrate temperature was confirmed by the design of experiments （DOE）. An explanation for this dependence could be that radicals near the substrate surface may have additional ionization or dissociation and also have recombination, or are consumed on the substrate surface where chemical reactions occur.     

水热温度对碳/碳复合材料表面HAp/壳聚糖生物复合涂层的影响

以声化学法合成的纳米羟基磷灰石(HAp)为起始原料,以异丙醇作为分散介质,采用水热电泳沉积法在经壳聚糖(CS)溶液改性后的碳/碳复合材料(C/C)表面沉积HAp/CS生物复合涂层.重点研究水热温度对复合涂层晶相、形貌的影响及涂层的沉积动力学机理.采用X射线衍射仪(XRD)、透射电子显微镜(TEM)、傅立叶变换红外光谱分析仪(FTIR)和扫描电子显微镜(SEM)对所制备的涂层进行表征.结果表明:随着水热温度的升高,涂层表面由微晶疏松结合的多孔结构向紧密结合的多孔结构转变,涂层的内聚力增强;涂层的沉积速率随水热温度的升高而增加,涂层的沉积活化能为43.58 kJ/mol.