Multi-scale Modeling and Finite Element Analyses of Thermal Conductivity of 3D C/SiC Composites Fabricating by Flexible-Oriented Woven Process

Thermal conductivity is one of the most significant criterion of three-dimensional carbon fiber-reinforced SiC matrix composites(3D C/SiC).Represent volume element(RVE)models of microscale,void/matrix and mesoscale proposed in this work are used to simulate the thermal conductivity behaviors of the 3D C/SiC composites.An entirely new process is introduced to weave the preform with three-dimensional orthogonal architecture.The 3D steady-state analysis step is created for assessing the thermal conductivity behaviors of the composites by applying periodic temperature boundary conditions.Three RVE models of cuboid,hexagonal and fiber random distribution are respectively developed to comparatively study the influence of fiber package pattern on the thermal conductivities at the microscale.Besides,the effect of void morphology on the thermal conductivity of the matrix is analyzed by the void/matrix models.The prediction results at the mesoscale correspond closely to the experimental values.The effect of the porosities and fiber volume fractions on the thermal conductivities is also taken into consideration.The multi-scale models mentioned in this paper can be used to predict the thermal conductivity behaviors of other composites with complex structures.

Ultrasonic Welding of Magnesium–Titanium Dissimilar Metals:A Study on Thermo-mechanical Analyses of Welding Process by Experimentation and Finite Element Method

Ultrasonic welding is an effective ways to achieve a non-reactive/immiscible heterogeneous metal connection, such as the connection of magnesium alloy and titanium alloy. But the thermal mechanism of magnesium alloy/titanium alloy ultrasonic welding has not been defined clearly. In this paper, the experimental and the finite element analysis were adopted to study the thermal mechanism during welding. Through the test, the temperature variation law during the welding process is obtained, and the accuracy of the finite element model is verified. The microscopic analysis indicates that at the welding time of 0.5 s, the magnesium alloy in the center of the solder joint is partially melted and generates the liquid phase. Through the finite element analysis, the friction coefficient of the magnesium–titanium ultrasonic welding interface can be considered as an average constant value of 0.28. The maximum temperature at the interface can exceed 600 ℃ to reach the melting point temperature of the magnesium alloy. The plastic deformation begins after 0.35 s and occurs at the magnesium side at the center of the interface.

Weathering and accumulation of trace elements in the soils of the Porali Plain, Balochistan: repercussions in agriculture

This study is thefirst attempt to assess the nature of the soil,especially on the western side of the Porali Plain in Balochistan;a new emerging agriculture hub,using weathering and pollution indices supplemented by multi-variate analysis based on geochemical data.The outcomes of this study are expected to help farmers in soil manage-ment and selecting suitable crops for the region.Twenty-five soil samples were collected,mainly from the arable land of the Porali Plain.After drying and coning-quarter-ing,soil samples were analyzed for major and trace ele-ments using the XRF technique;sieving and hydrometric methods were employed for granulometric analysis.Esti-mated data were analyzed using Excel,SPSS,and Surfer software to calculate various indices,correlation matrix,and spatial distribution.The granulometric analysis showed that 76%of the samples belonged to loam types of soil,12%to sand type,and 8%to silt type.Weathering indices:CIA,CIW,PIA,PWI,WIP,CIX,and ICV were calculated to infer the level of alteration.These indices reflect mod-erate to intense weathering;supported by K_(2)O/AI_(2)O_(3),Rb/K_(2)O,Rb/Ti,and Rb/Sr ratios.Assessment of the geo-ac-cumulation and Nemerow Pollution indices pinpoint rela-tively high concentrations of Pb,Ni,and Cr concentration in the soils.The correlation matrix and Principal Compo-nent Analysis show that the soil in this study area is mainly derived from the weathering of igneous rocks of Bela Ophiolite(Cretaceous age)and Jurassic sedimentary rocks of Mor Range having SEDEX/MVT type mineralization.Weathering may result in the undesirable accumulation of certain trace elements which adversely affects crops.

Finite Element Analyses and Instrumentation Layout for Single Coil Testing of TF Coils in HT-7U

The HT-7U tokamak is a magnetically-confined full superconducting fusion device, consisting of superconducting toroidal field (TF) coils and superconducting poloidal field (PF) coils. These coils are wound with cable-in-conductor (CICC) which is based on UNK NbTi wires made in Russian '. A single D-shaped toroidal field magnet coil will be tested for large and expensive magnets systems before assembling them in the toroidal configuration. This paper describes the layout of the instrumentation for a superconducting test facility based on the results of a finite element modeling of the single coil of toroidal magnetic field (TF) coils in HT-7U tokamak device. At the same time, the design of coil support structure in the test facility is particularly discussed in some detail.

Finite element analysis of dynamic response and structure borne noise of gearbox

A dynamic finite element method combined with finite element mixed formula for contact problem is used to analyze the dynamic characteristics of gear system. Considering the stiffness excitation, error excitation and meshing shock excitation, the dynamic finite element model is established for the entire gear system which includes gears, shafts, bearings and gearbox housing. By the software of I-DEAS, the natural frequency, normal mode, dynamic time-domain response, frequency-domain response and one-third octave velocity grade structure borne noise of gear system are studied by the method of theoretical modal analysis and dynamic response analysis. The maximum values of vibration and structure borne noise are occurred at the mesh frequency of output grade gearing.

Portable fiber-optic laser-induced breakdown spectroscopy system for the quantitative analysis of minor elements in steel

In this paper, we developed a portable laser-induced breakdown spectroscopy(LIBS) using an optical fiber to deliver laser energy and used it to quantitatively analyze minor elements in steel.The R^2 factors of calibration curves of elements Mn, Ti, V, and Cr in pig iron were 0.9965,0.9983, 0.9963, and 0.991, respectively, and their root mean square errors of cross-validation were 0.0501, 0.0054, 0.0205, and 0.0245 wt%, respectively. Six test samples were used for the validation of the performance of the calibration curves established by the portable LIBS. The average relative errors of elements Mn, Ti, V, and Cr were 2.5%, 11.7%, 13.0%, and 5.6%,respectively. These results were comparable with most results reported in traditional LIBS in steel or other matrices. However, the portable LIBS is flexible, compact, and robust, providing a promising prospect in industrial application.

FINITE ELEMENT ANALYS IS AND OPTIMUM DESIGN FOR THE FRONT－FUSELAGE WITH SANDWICH CONSTRUCTIONS

AbstractFinite element analysis and optimization subject to stress, displacement and side con-straints for composite sandwich structures are mainly treated. The square isoparametricsandwich plate / shell elements are used to perform structural analysis. The thickness ofthe faceplates and the depth of the core are taken as design variables in optimization pro-cess. The number of layers for each laminate is also taken as design variables if the compo-site faceplates are used. A few widely applied approximation concepts, such as design vari-able linking, regionalization method and temporary deletion technique of passive con-straints are employed to reduce the number of both design variables and constraints. Theadvanced hybrid approximation techniques combining with dual solutions are cmployed inoptimization. The corresponding software is applied to the analysis of experimental modeland to the optimum design for the composite sandwich front-fuselage, and satisfactory re-sults are obtained.

A Pragmatic Approach to Coping with Matrix Effects during ICP-MS Analysis of Trace Elements in Silicate Rocks and Calibration of REE Interferences

Operating an Agilent 7700X ICP-MS spectrometer under robust plasma conditions (1550 W) with a He-filled octopole collision cell and analysing solutions (?1 total dissolved solids) still suffered analyte peak suppression due to matrix effects. International reference rocks BCR-1, BHVO-1, AGV-1, G-2 and BCR-2 all showed count rate reductions for 36 elements (mass range 7Li to 238U) averaging ~10% but with no dependence on isotope mass. Use of an internal standard (103Rh) and/or using a ten-fold dilution of sample solutions reduced these effects but problems with reduced count rates combined with larger errors for some elements introduced other problems. The best approach was to normalise the count rates for each element in the other samples against those for BCR-1 as an external standard;thus the count suppression due to the matrix effect is corrected for each individual element. This approach provides standardization “traceability” in line with the ERM ISO/IEC requirement. Experiments are also reported on quantifying the proportions of Ba and selected REE oxide/hydroxide components versus parent isotopes (XO/X and XOH/X). This information is essential for correcting peak interferences on higher mass number REE for the rock samples, and equations are developed to use measured CeO/Ce and CeOH/Ce ratios to predict such values for any other member of the REE suite. Concentrations obtained show excellent agreement with recommended values for the international reference materials especially for the REE. Robust data are also provided for two other standard rocks: nepheline syenite STM-1 and quartz syenite CAAS-1;the latter shows exceptional enrichments of Zr, REE, Th, and U.

BPMA矿物元素分析工具在含金、含铌钽矿样品分析中的应用

工艺矿物学分析采用自动系统处理后,通常仍有部分精细分析数据需要人工采集,重复劳动工作量大。采用基于扫描电子显微镜(SEM)-X射线能谱(EDS)的BPMA(BGRIMM Process Mineralogy Analyzing System)系统矿物元素分析工具,针对目标矿物进行多点EDS元素分析,通过图像特征信息校正保障目标位置精准,通过高计数谱图信息尽量保障后续元素分析的精度。使用工具软件对含金样品进行位置回溯和元素分析统计的测试,并利用工具软件及BPMA系统对某含铌钽矿样品进行工艺矿物学分析测试,实验表明:样品中含量极少的铌钽矿物主要分布在2~5μm,粒度极细,且60%以上被其他矿物包裹,其中,90%的铌分布于褐钇铌矿、铌钙矿;超过80%的钽分布于铌钙矿和铌易解石。工具软件实现的精度可以代替手动操作,批量回找和自动统计显著提高效率;且工具软件对重要矿物元素含量的分析数据则可进一步提高BPMA最终结果数据的精确度。

Major and trace element geochemistry of the mid-Bay of Bengal surface sediments: implications for provenance

The major and trace elements in 110 surface sediment samples collected from the middle of the Bay of Bengal（mid-Bay of Bengal） are analyzed to investigate provenance. Si levels are highest, followed by Al, and the distributions of these two elements are identical. The average CIA＊（chemical index of alteration） value is 72.07,indicating that the degree of weathering of the sediments in the study area is intermediate between those of sediments of the Himalayan and Indian rivers. Factor analyses and discrimination function analyses imply that the two main provenances are the Himalayan and the Indian continent. The inverse model calculation of the Tinormalized element ratios of the Bay of Bengal sediments indicate an estimated average contribution of 83.5%and 16.5% from the Himalayan and peninsular Indian rivers to the study area, respectively. The Himalayan source contributes more sediment to the eastern part of the study area, whereas the western part receives more sediment from the Indian Peninsula than did the eastern part. The primary mechanisms for deposition of sediments in the study area are the transport of Himalayan matter by turbidity currents and river-diluted water and the transport of Indian matter to the study area by a surface circulation in the Bay of Bengal, particularly the East India Coastal Current.

Elemental variations in glacier cryoconites of Indian Himalaya and Spitsbergen,Arctic

Cryoconite samples were collected from two different climatic domains i.e.,the Sutri Dhaka glacier,western Himalaya India and Svalbard glaciers,the Spitsbergen,Arctic,to understand the elemental source and elemental deposition patterns.The data of geochemical analysis suggest that the Himalayan cryoconite samples accumulate higher concentrations as compared to the cryoconite samples of the Arctic glaciers.The concentration of lithophile elements(Cs,Li,Rb and U)was recorded higher in the cryoconite holes of the Himalayas,especially,in the lower to the higher parts of the glacier,whereas,lower concentrations were recorded in the Arctic samples.Chalcophile elements in the Himalayan cryoconites are enriched in As and Bi while the Arctic cryoconite samples show a higher concentration of Bi,Pb and As.The higher concentrations are responsible for influencing the ecosystem and in human health related issues.Siderophile elements(Co,Fe,Mn and Ni)show high concentrations in the Himalayan samples,whereas,the Arctic samples show minor variations and low elemental concentration in these elements,respectively.In addition,a few elements,such as Ag,Mg,and Ca show higher concentration in the Himalayan glacier samples.Ca also occurs in high concentrations in Arctic glacier samples.R-mode factor analysis of the Himalayas(Arctic)samples indicate that the elements are distributed in four(three)factors,explaining 89%(90%)of the variance in their elemental distribution.The Factor 1 suggests statistically significant positive loadings for most of the lithophile,chalcophile and siderophile elements of the "Himalayan" and the Arctic cryoconite samples.The sample-wise factor score distribution shows a considerable variation in the sampling locations along the glaciers of both the regions.Factors 2 and 3,demonstrate insignificant loading for most of the elements,except statistically significant positive loading in some of the elements of the both,Himalayan and Arctic "cryoconites".The higher elemental concentration in the cryoconites of the Himalayan region may be an indicator of the natural processes and/or attributed to the rapid industrialization in the Asian countries.

Identifying Pathfinder Elements for Gold in Multi-Element Soil Geochemical Data from the Wa-Lawra Belt, Northwest Ghana: A Multivariate Statistical Approach

A multivariate statistical analysis was performed on multi-element soil geochemical data from the Koda Hill-Bulenga gold prospects in the Wa-Lawra gold belt, northwest Ghana. The objectives of the study were to define gold relationships with other trace elements to determine possible pathfinder elements for gold from the soil geochemical data. The study focused on seven elements, namely, Au, Fe, Pb, Mn, Ag, As and Cu. Factor analysis and hierarchical cluster analysis were performed on the analyzed samples. Factor analysis explained 79.093% of the total variance of the data through three factors. This had the gold factor being factor 3, having associations of copper, iron, lead and manganese and accounting for 20.903% of the total variance. From hierarchical clustering, gold was also observed to be clustering with lead, copper, arsenic and silver. There was further indication that, gold concentrations were lower than that of its associations. It can be inferred from the results that, the occurrence of gold and its associated elements can be linked to both primary dispersion from underlying rocks and secondary processes such as lateritization. This data shows that Fe and Mn strongly associated with gold, and alongside Pb, Ag, As and Cu, these elements can be used as pathfinders for gold in the area, with ferruginous zones as targets.

卧式多层热压机机架热力耦合分析及结构改进设计

卧式多层热压机较立式多层热压机在生产能力方面实现了新的突破,更适用于胶合板产业的发展。为研究热力耦合效应对卧式多层热压机机架力学性能的影响,以80层4′×8′卧式多层热压机为研究对象,根据胶合板热压工艺及卧式多层热压机的结构特点,确定闭合保压阶段机架的受载情况;利用有限元方法分别对力载荷和热力耦合效应作用下的机架状态进行分析。结果表明:在热力耦合效应作用下,机架的应力值和变形量显著增加,实际工况下机架不能满足卧式多层热压机闭合保压阶段所需要的强度和刚度要求。基于分析结果,对机架结构进行改进设计;经验证,改进后机架结构满足设计要求,为卧式多层热压机机架结构改进设计提供新的设计思路和手段,具有实际工程应用价值。

电子探针分析锆石Hf和Ti含量的结果意义与技术优势

锆石是一种重要的定年矿物,其微量元素地球化学行为是解释锆石年龄地质意义的重要依据。锆石微量元素分析一般采用的是在大束斑条件下(10~50μm)的质谱仪测试方法,其结果反映的是在该束斑范围内,元素的平均含量信息。相比之下,电子探针显微分析可以在极小微区范围内(<5μm)进行元素的定量分析,更能有效地揭示元素的地球化学行为,可作为研究锆石微量元素的重要技术补充。本文以锆石定年中常用标准锆石(TEMORA、Qinghu和Ple2ovice)作为研究对象,在20kV加速电压、50~300nA轰击电流以及2~5μm束斑条件下,对其中的Hf和Ti进行了定量分析,包括常规的点和线分析(Point/Line Analysis)以及网格分析(Grid Analysis),并以此为基础进行了线性拟合并建模,对元素的面分布情况进行了探讨。在较长的计数时间条件下(300s),本文得到了20μg/g(1σ)的Ti含量检测限。实验结果表明:锆石中的Zr与Hf之间具有负相关性,反映了两者的类质同象替代;其次,在概率统计方面,电子探针Hf和Ti的定量分析结果明显高于LA-ICP-MS方法,反映了其在更小微区下的含量信息以及地球化学行为,须在诸如(锆石)Ti温度计的应用中特别注意。再者,测试所用标准锆石样品的Hf含量(和Zr/Hf比值)在微区下具有环带分布特征,表现为从核部到边部具有升高(降低)的趋势,这与锆石结晶生长过程中的熔体分异程度有关。另一方面,标准锆石样品中的Ti并未表现出类似Hf的分布特征,且Hf(和Zr/Hf比值)与Ti含量之间也没有发现明显的相关性。因此,对于前人提出的Hf具有类似Ti一样的温度计指示功能的观点仍有待进一步探讨。

Strain localization analyses of idealized sands in biaxial tests by distinct element method

This paper presents a numerical investigation on the strain localization of an idealized sand in biaxial compression tests using the distinct element method(DEM).In addition to the dilatancy and material frictional angle,the principal stress field,and distributions of void ratio,particle velocity,and the averaged pure rotation rate(APR)in the DEM specimen are examined to illustrate the link between microscopic and macroscopic variables in the case of strain localization.The study shows that strain localization of the granular material in the tests proceeds with localizations of void ratio,strain and APR,and distortions of stress field and force chains.In addition,both thickness and inclination of the shear band change with the increasing of axial swain,with the former valued around 10-14 times of mean grain diameter and the later overall described by the Mohr-Coulomb theory.

基于有限元分析技术的自行车鞍座人机工程设计

为缓解自行车鞍座对人体坐骨的压力影响,基于人机工程学和有限元分析技术设计了轻量、舒适及安全的新型自行车鞍座及支撑杆。通过人体测量软件IDMATCH建立了人体骨盆骨距及接触点样本,并对载体结构进行法向力模拟与分析,得到鞍座支撑载体结构模型;采用鞍座压力测试系统MEDILOGIC对鞍座结构模型进行受力分析,给出不同人体百分位尺寸的鞍座布局极限尺寸范围和设计方案;结合有限元分析技术对最终方案进行测试、改进和验证。结果表明:基于人机工程和有限元分析技术设计的特殊鞍座结构能有效提升骑行舒适性,为自行车鞍座的人机工程应用和结构改进提供参考。

汽车吊具有限元分析与优化设计

汽车吊具是汽车装配车间不可缺少的重要设备。在原汽车吊具框架不变的前提下,优化设计了门型汽车吊具和三种L型汽车吊具。通过ANSYS软件对汽车吊具进行有限元分析,得到汽车吊具的应力和应变。通过分析确认,门型汽车吊具虽然性能最优,但是不满足工位需要,L型汽车吊具中的L型正吊具满足工位条件,应力与变形在三种L型汽车吊具中最优,相比原汽车吊具,安全性能得到有效改善。

基于典型操作质量问题的通用控制要素研究

本文从航天产品典型操作质量问题入手,查找了当前控制的薄弱环节,提出开展通用控制要素建立。结合薄弱环节,建立了人、机、料、法、环、测六大基本控制要素和以螺纹紧固力矩施加、多余物防控、非正常(突发)过程等为代表的八大典型环节控制要素;并针对各项要素,从设计、工艺及操作维度提出了通用控制要求。同时,聚焦后续操作质量控制提出了三方面的发展方向,包括开展基于问题的控制准则知识库建设、开展三维模装仿真技术的应用、开展面向制造与装配的设计方法的应用。通过通用控制要素及发展方向研究可为进一步提高产品操作质量提供技术支撑。

中老年高血压患者血清中钾钠钙镁锌铜铁锰的含量分析

用原子吸收法对 4 8名高血压患者和 5 2名正常健康人进行血清中K ,Na ,Ca ,Mg ,Zn ,Cu ,Fe和Mn的测定。结果表明 ,患高血压组血清中Na ,Mg ,Zn ,Fe和Mn的水平含量均高于健康对照组 ,K ,Ca和Cu的水平含量均低于健康对照组。患高血压组血清Na/K比值均高于健康对照组 ,Ca/Mg ,Cu/Zn比值均低于健康对照组。建议 ,患者适当增补人体内K ,Ca,Mg和Cu的含量 ,减少Na的过多摄入 ,科学地控制Zn ,Fe和Mn的增加 ;注意体内Na/K ,Ca/Mg和Cu/Zn比值的平衡关系 ,降低Na/K比 ,提高Cu/Zn比 ,补Ca的同时一定要注意适当补充Mg ,有利于高血压病的预防和治疗。

七彩山鸡肌肉及肝脏中12种矿物元素测定分析

为了探讨七彩山鸡体内矿物元素的含量 ,开发安全的绿色营养食品 ,以及为其人工饲养的饲料添加剂配方与微量元素疾病的诊断提供科学依据。本研究采用火焰原子吸收光谱法测定分析了七彩山鸡胸肌、腿肌以及肝脏中Ca、Cu、Fe、Zn、Mn、Mo、Se、Co、Cd、Cr、Pb、Ag 12种矿物元素的含量。结果表明 ,肝脏中Ca、Cu、Fe、Zn、Mn、Cd和Cr的含量极显著高于胸肌和腿肌 (P <0 .0 1) ,其他元素差异不显著 (P >0 .0 5 )。Cu、Zn在胸肌与腿肌中的含量差异显著 (P <0 .0 5 ) ,其他元素均无明显差异 (P >0 .0 5 )。