Theoretical prediction for Young''''s modulus and yield strength of high-density foamed plastics

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Determination of Hyaluronan by Spectroscopic Methods

1 IntroductionHyaluronic acid,HA,is a macromolecule non-albu-minoid acidic polysaccharide widely existing in humanbody and other creaturesinvivo.The viscosity of HAen-ables it to act aslubricate and bufferinthe articular cavi-ty,and afillinginthe connectiveissue .This material al-so playsthe role of adjustingcell function byactingontheHAreceptor inthe cell and the intercellular matrix,andexerts animportant role inthe process of tissue generationand renovation,tumor attack,etc.The relation b…     

Determination of paclitaxel in southern yew tree by HPLC

Paclitaxel in southern yew tree was quantitatively determined by high performance liquid chromatography (HPLC) with ODS-C18 column. A mixture of CH3OH-H2O-CH3COOH(volume ratio: 55 :44 :1) is used as mobile phase and UV detection is carried out at 227 nm, and the column temperature is 20℃. The results show that there is a good linear felationship between the area of paclitaxel and the concentration of the sample in the range 50-500 mg/L for paclitaxel. The corresponding regression equation is Y= 13 021. 7 + 1. 01 × 106X, r=0. 9990. The average recovery is 95. 3% and the relative standard deviation is 2. 08%.     

Determination of plastic equation of state by indentation method on 304 stainless steel

An indentation method for determining the plastic mechanical equation of state (PES) was studied. The constant loading rate and constant loading rate/load indentation tests were carried out. The method for determining the work-hardening coefficient and the strain rate sensitivity coefficient of PES were discussed in detail. 304 stainless steel hot-treated at 1100℃ was used to verify the method. The work-hardening coefficient and strain rate sensitivity coefficient of 304 stainless steel were respectively determined as 0.30 and 0.015. These values are very close to those achieved by tensile tests. From the establishment of the PES of 304 stainless steel it is shown that the PES obtained by the indentation method is easier than that by the tensile test.     

Determination of constituents of essential oil from Angelica sinensis by gas chromatographymass spectrometry

1INTRODUCTION TraditionalChinesemedicines(TCMs)are veryimportantduetotheirextensiveuseinpre ventingandcuringmanydiseasesforhumans.Al thoughonlysomecompoundsmightberesponsible forpharmaceuticaleffects,traditionalChinese medicinesusuallycontaintoomanycomponentsandformaverycomplexsystem,whichmakesthe screeningandanalysisofbioactivecomponentsex tremelydifficult[1]comparedwiththoseofwesternmedicines.Whensuchcomplexsamplesareana lyzed,itiscommonthatdifferentcontentsof multi componentsandgreatd…     

Determination of effective thermal conductivity for polyurethane foam by use of fractal method

1 Introduction Polyurethane foam is a good thermal insulation material widely used in daily life and many industries, such as chemical engineering, refrigeration and architecture owing to its very low thermal conductivity and lightweight. In the past two decades, the technology and chemistry of the rigid urethane foam have been developed to an industrial level, but its thermal conductivity, which is recognized as the most important parameter to design the insulation structure, cannot be calcul…     

Determination of constituents of essential oil from Angelica sinensis by gas chromatography-mass spectrometry

Gas chromatography-mass spectrometry （GC-MS） coupled with chemometric resolution upon twodimensional data was employed to analyze the constituents of essential oils of Angelica sinensis. Constituents in essential oils of Angelica sinensis root were identified by GC-MS with the help of subwindow factor analysis （SFA） method resolving two-dimensional original data into mass spectra and chromatograms. 76 of 97 separated constituents in essential oil of Angelica sinensis root were identified and quantified, and they account for about 91.36% of the total content. The results show that ligustilide, butylene phthalide, 2-methoxy-4-vinylphenol, carvacrol, alloocimene, 2,6,6-trimethylbicyclo-[3,1,1] hept-2-ene are the main constituents in essential oil of Angelica sinensis root.     

Determination of the Micro Stress Field in Composite by Homogenization Method

1 IntroductionThe stresses in composite determined by taking thecomposite as macro homogeneous material is in fact thenominal stresses or effective stresses . They can only re-flect the response of the composite to external macro en-vironments but not the effects of micro heterogeneity.Forcomposites are widely used as high qualitystructure mate-rials that have to satisfy strict engineering requirements ,detailedinformation of stress distribution is necessary forstructural designand optimizatio…     

Simultaneous Spectrophotometric Determination of Four Components including Acetaminophen by Taget Factor Analysis

UV Spectrophotometric Target Factor Analysis （TFA） was used for the simultaneous determination of four components （acetaminophen, guuaifenesin, caffeine, Chlorphenamine maleate） in cough syrup. The computer Frogram of TFA is based on VC＋＋ language. The difficulty of overlapping of absorption spectra of four compounds was overcome by this procedure. The experimental results show that the average recovery of each component is all in the range from 98.9% to 106.8% and each component obtains satisfactory results without any pre-separation.     

Simultaneous Spectrophotometric Determination of Three Components Including Deoxyschizandrin by Partial Least Squares Regression

1IntroductionWuweizi is a traditional Chinese herb,usually usedto cure cough,asthma,neurasthenic,hepatitisetc.Theactive ingredients in wuweizi are5%-22%lignan,themain components of which include deoxyschizandrin,schizandrin andγ-Schizandrin.Forthe purpos…     

基于纳米压痕技术的电子玻璃微观力学性能研究

为了研究不同电子玻璃的微观力学性能,采用先进的纳米压痕技术记录钠钙硅、无碱硼铝硅和碱铝硅等典型电子玻璃的载荷-位移曲线,利用Oliver-Pharr方法和经典的弹塑性变形理论,计算玻璃的硬度和弹性模量. 玻璃的硬度主要与结构的键合度相关,平均非桥氧数越高,外力作用下越容易致密化,硬度越小;弹性模量主要取决于质点间的化学键强度,化学键力越强,变形越小,弹性模量越大;九点法测得的弹性模量与硬度的变化趋势不完全相同,借助硬度-弹性模量-能量耗散之间的本征关系,评价玻璃样品的微观均匀性,其中无碱硼铝硅玻璃的恢复阻力大,局部能量耗散大,不容易引起整体破坏,力学性能最好;与浮法工艺相比,溢流下拉法制备样品的局部力学性能波动较小,微观均匀性较好.     

利用努氏硬度表征金属的弹性模量和屈服强度

为利用努氏硬度表征金属材料弹性模量和屈服强度,提出了Marshall和Conway的修正模型表征弹性模量,以及Lockett、Yu、Marsh、Johnson和Vandeperre的修正模型表征屈服强度,开拓了努氏硬度表征金属材料力学性能的新应用。选取35种金属进行努氏硬度试验,利用Meyer定律、弹塑性变形模型、Hays-Kendall模型和比例试样模型对努氏硬度的正压痕尺寸效应(硬度随载荷的减小而增大)进行了分析,可以用大载荷下趋于稳定的硬度值代表材料的真硬度。首次考虑金属材料在努氏压痕短对角线处材料堆积的影响,Marshall模型和Conway模型进行了修正：Marshall模型中原有的常参数α修正为b/d(努氏压痕短对角线与长对角线的比值)的二次函数;Conway模型引入了与b/d的平方呈线性关系修正系数β。通过比较文献中与原模型计算的屈服强度,引入修正系数k,首次获得了基于努氏硬度利用Lockett、Yu、Marsh、Johnson和Vandeperre模型计算金属屈服强度的修正模型。结果表明：除Ti6Al4V和Sn外,修正模型与仪器化压入得到的弹性模量一致,置信度不低于0....     

焦炭扬氏模量的动态测量

用悬丝共振法测量焦炭的扬氏模量时,虽然在同一种焦炭里 E 值变化范围较大,但在其中任一小区域内 E 值仍较集中。仪器经过改进后,测量误差达到规定要求,并与焦样加工精度、焦样长度、悬丝悬吊位置及焦样的均匀性有关。     

激光直射式放大测量杨氏弹性模量的研究

金属丝杨氏弹性模量测量的关键在于对于金属丝的微小长度量的精确测量．光杠杆放大测量法是一种常用方法，这种测量方法对于光路的调整有着严格地要求，测量难度大且不易掌握．在分析了光杠杆放大测量方法的特点后，对于测量装置进行了改进，建立了一种激光直射式放大测量杨氏弹性模量法．这种方法摒弃了光杠杆放大测量方法中光路调整复杂、望远镜测量精度不高等缺点．使得测量不仅方便、易调节，而且具有直观性强、精度高的特点，是测量杨氏弹性模量的一种新方法．     

The Young's moduli prediction of random distributed short-fiber-reinforced polypropylene foams using finite element method

The elastic moduli of short-fiber-reinforced foams depend critically on the fiber content and fiber length, as well as on the fiber orientation distribution. Based on periodic tetrakaidecahedrons, the finite element models with short-fiber reinforcement were proposed in this paper to examine the effects of the fiber content and fiber length on Young's modulus. The fiber length distribution and fiber orientation distribution were also considered. The proposed models featured in a three-dimensional diorama with random short-fiber distribution within or on the surfaces of the walls and edges of the closed-cells of polypropylene (PP) foams. The fiber length/orientation distributions were modeled by Gaussian prob-ability density functions. Different fiber volume fractions, different lengths, and different distributions were investigated. The predicted Young's moduli of the PP foams with short-glass-fiber or short-carbon-fiber reinforcement were compared with other theoretic and experimental results, and the agreement was found to be satisfactory. The proposed finite element models were proved to be acceptable to predict the Young's moduli of the grafted closed-cell PP foams with short-fiber reinforcement.     

Mechanical properties of 3D carbon/carbon composites by nanoindentation technique

Nanoindentation tests were conducted to investigate the near-surface mechanical properties of the individual components (fiber and matrix) for three-dimensional reinforced carbon/carbon composites (3D C/C). Optical microscope and polarizing light microscope were used to characterize the microstructure of 3D C/C. The microscopy results show that large number of pores and cracks exist at both bundle/matrix interface and pitch carbon matrix. These defects have important effect on the mechanical behavior of 3D C/C. The in situ properties for components of 3D C/C were acquired by nanoindentation technique. Relative to the matrix sample, the fiber samples have more larger values for modulus, stiffness and hardness. However, there is no significant difference of modulus and stiffness among fiber samples with different directions.     

光的衍射法测量金属的杨氏弹性模量

给出测量金属杨氏弹性模量的一种新方法。利用光的衍射法可以精确测量长度变化这一特点,对碳钢的杨氏弹性模量进行了测量。     

单壁碳纳米管力学性质的分子动力学模拟

用分子动力学方法研究了在"拉伸"和"悬臂梁"两种模型下单壁碳纳米管的力学性质。通过对扶手椅形式的单壁碳纳米管进行分子动力学计算,得出半径在0.35nm~0.69nm之间的碳纳米管的杨氏模量在1.32623Tpa~1.03947TPa范围内波动。从模拟结果可以看出,在"拉伸"和"悬臂梁"两种模型下得到的单壁碳纳米管的杨氏模量不但在数值上有所差异,而且随其半径的变化趋势相反。     

沥青混合料动态剪切模量主曲线的确定

为了克服条件评价的局限性,采用动态剪切流变仪对沥青混合料进行了连续动态频率扫描。获得了跨越15个数量级的动态模量随频率变化的主曲线,进行了沥青混合料全温全频分析,掌握了材料的黏弹性力学行为。通过讨论与分析,提出了极限频率、流变区、稳态区、低频转折点、高频转折点等概念。研究表明,动态流变试验是获得沥青混合料主曲线的有效方法,主曲线为全温全频分析提供了基础条件,基于主曲线形态提出的5个概念能够客观地反映混合料的本质特性。     

Nano-indentation profiles of intrinsic hardness and modulus of films based on silsesquioxane modified with titanium tetrabutoxide

This study is to analyze the influence of the modifier, 5 -25 wt % titanium tetrabutoxide (TBO),on the hardness and elastic modulus of the films based on SSO deriving from hydrolytic condensation of (3-glycidoxypropyl) trimethoxysilane (GPMS) and vinyltrimethoxysilane (VMS), by the continuous stiffness measurement (CSM) technique of an instrumented-indentation testing (ⅡT) device. Films were synthesized by adding the stoichiometric amount of ethylenediamine (EDA) and benzoyl proxide (BPO) to SSO solutions in ethanol, dip-coating over glass substrates, and curing using an appropriate thermal cycle. Intrinsic values of hardness and elastic modulus were determined with the average values in “plateau region” from “four-layer”explanation. And the brittle index of the modified coating systems was analyzed.