Adhesion between side surface of an elastic beam and flat surface of a rigid body

A theory of adhesion between an elastic beam and a rigid body is proposed using linear beam theory. Normalized force between the elastic beam and the rigid body considering adhesion of the side surface of the elastic beam is investigated theoretically. Adhesion of an elastic beam is important to analyze gecko adhesion, and peeling mechanism of an adhered film. This adhesion is also important in design of grip-and-release devices. The force between an elastic beam and a rigid body is investigated by considering shear force and total energy, and is obtained as a function of the displacement of the elastic beam. The proposed theory is different from Kendall’s thin-film peeling theory in terms of the elastic energy. The proposed theory considers bending elastic energy, whereas Kendall’s theory considers extension elastic energy. Two different contacts, line contact and area contact, are taken into account to discuss the loading and unloading processes in terms of the relation between the force and the displacement. Non-dimensional parameter, which relates to the work of adhesion and the specifications of the elastic beam, is introduced to explain the normalized maximum tensile force.     

弹性棒对仿生学柔性反应器的流体混合强化

在柔性反应器底部放置竖直的弹性硅胶棒（弹性棒），通过弹性棒运动对周围流体产生扰动，强化流体混合。基于酸碱中和脱色法和图像分析方法，研究了柔性反应器的混合过程和混合时间；通过混合时间定量评估了弹性棒的强化效果；并分别研究了弹性棒的位置和高度及柔性反应器系统的最大挤压深度和频率对流体混合行为的影响。结果表明：弹性棒的放置能够使柔性反应器内隔离区结构改变，混合时间减少。弹性棒位置靠近挤压头一侧时，对流体混合强化最明显。在弹性棒高度低于柔性反应器内液面时，弹性棒高度增加，强化效果增加。超过液面之后，继续增加弹性棒高度，强化效果没有进一步增加。当弹性棒靠近挤压头、高度超过液面且最大挤压深度为2.5cm，与没有弹性棒时相比混合时间减少了57%。在其他实验条件不变的前提下，最大挤压深度增加，强化效果增加。     

Studies on poly (iso-butene oxide): 3. Elastic hard fibre of poly (iso-butene oxide)

Poly(iso-butene oxide), a highly crystalline polyether, gives an ‘elastic hard fibre’, having excellent elastic recovery, on melt-spinning under appropriate drafting conditions. The interrelation between fabricating conditions and elastic recovery has been studied and the mechanism of the appearance of the elastic recovery is discussed. The mechanical, thermal and chemical properties of the fibre have been investigated.     

动力载荷作用下橡胶混凝土的力学性能

采用体积分数分别为15%、30%和45%的橡胶粉或橡胶块颗粒对混凝土中粗骨料进行替换,并用自由振动法对橡胶混凝土简支梁的振动频率和阻尼性能进行测试,考察了小变形时阻尼比与橡胶颗粒大小和数量之间的关系。采用弹性波法和梁单元法对橡胶混凝土的动力模量进行了测量,并对其静弹性模量与动弹性模量进行了对比。结果表明,橡胶混凝土的动力弹性模量低于普通混凝土。橡胶块对橡胶混凝土动、静弹性模量的影响均大于橡胶粉。普通混凝土的动弹性模量比静弹性模量高37.4%,而橡胶混凝土的动弹性模量比静弹性模量高约50%。橡胶混凝土的阻尼比随最大响应幅值的增大而增大。相比于普通混凝土,橡胶混凝土的阻尼对振动的响应更为敏感。橡胶混凝土的阻尼比随橡胶含量的增加而显著增大。当橡胶的体积分数为30%时,橡胶混凝土综合性能较佳。     

含Y2O3玻璃的弹性模量

根据硬盘基板用材料的要求，借助Makishima-Mackenzie理论设计了MgO-Al2O3-SiO2-TiO2-Y2O3玻璃，获得具有较高弹性模量（120GPa)的玻璃，并研究了玻璃的弹性模量与其组成之间的关系，玻璃的弹性模量随组成的变化服从Makishima-Mackenzie理论，但玻璃弹性模量的理论计算值比测试值低约10GPa，这是因为Makishima-Mackenzie理论没有考虑玻璃内阳离子的具体配位状态，对MgO,Y2O3堆积密度因子的推导存在误差，利用Bocherulle公式改进氧化物堆积密度因子的计算后，Makishima-Mackenie理论数据与含Y2O3玻璃的实验结果能够很好地吻合。     

Effect of temperature and age on the relationship between dynamic and static elastic modulus of concrete

This study investigates the effects of cement type, curing temperature, and age on the relationships between dynamic and static elastic moduli or compressive strength. Based on the investigation, new relationship equations are proposed. The impact-echo method is used to measure the resonant frequency of specimens from which the dynamic elastic modulus is calculated. Types I and V cement concrete specimens with water-cement ratios of 0.40 and 0.50 are cured isothermally at 10, 23, and 50 °C and tested at 1, 3, 7, and 28 days.Cement type and age do not have a significant influence on the relationship between dynamic and static elastic moduli, but the ratio of static to dynamic elastic modulus approaches 1 as temperature increases. The initial chord elastic modulus, which is measured at low strain level, is similar to the dynamic elastic modulus. The relationship between dynamic elastic modulus and compressive strength has the same tendency as the relationship between dynamic and static elastic moduli for various cement types, temperatures, and ages.     

微细钢纤维对高弹性模量混凝土力学性能的影响

基于修正的Furnas堆积模型和骨料紧密堆积试验设计了一种高弹性模量混凝土,并利用微细钢纤维改善高弹性模量混凝土的韧性,研究了钢纤维体积掺量对骨料紧密堆积状态下混凝土流动性能、强度、弹性模量及弯曲韧性的影响规律。结果表明:采用紧密堆积骨料和适量微细钢纤维可以构筑高弹性模量韧性混凝土,其静弹性模量和动弹性模量最高分别可达50.15 GPa和53.23 GPa,断裂能可达5 680.45 N/m,残余弯曲韧度比从0增加到0.43;高弹性模量混凝土的流动性能随着钢纤维掺量的增加而降低,抗折强度、弹性模量及弯曲韧性则均随着钢纤维掺量的增加而增加,混凝土的抗压强度随着钢纤维掺量增加先增加后降低。在骨料紧密堆积状态下,综合考虑流动性能、力学性能和工程经济性,高弹性模量混凝土中微细钢纤维的合理掺量为0.4%(体积分数)。     

Instantaneous elastic recovery of poly(trimethylene terephthalate) filament

The instantaneous elastic recoveries of poly(trimethylene terephthalate) (PTT), PET, and PBT filaments were comparatively analyzed by a tensile testing machine. The conditions of the measurement were studied and the mechanism of instantaneous elastic recovery of these three aromatic polyester filaments is discussed. The instantaneous elastic recovery of PTT filaments was significantly higher than those of PBT and PET filaments. Moreover, PTT filaments had a high instantaneous elastic recovery even at a high elongation of 20%. The outstanding instantaneous elastic recovery of PTT filaments resulted from its helical conformation in crystal lattice, which responded immediately to the applied stress and deformed as though it was a coiled spring; we suggest it was a quasispring elastic recovery mechanism. When we measured the instantaneous elastic recovery of, PTT filaments with the tensile testing machine, it was appropriate to set up the crosshead speed at 500 mm/min with an elongation of 20% and a load of 0.5 cN/tex. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1967–1975, 2004     

纳米TiO_2对氨纶蠕变性能的影响

为了探究纳米TiO2对氨纶蠕变性能的影响,设计试验,对33.3 dtex普通氨纶和混有适量纳米TiO2的氨纶蠕变性能进行测试,结果表明:纳米TiO2不会改变氨纶的蠕变规律,但是可以减弱氨纶的蠕变速率和蠕变变形率,同时,可以提高氨纶的蠕变回复能力,一定程度上改善了氨纶的蠕变性能。     

三异细旦高弹涤纶复合纱的生产工艺

对细旦T400复合弹性纤维的纺丝工艺以及以细旦T400复合弹性纤维与细旦涤纶POY复合生产三异细旦高弹涤纶复合纱的假捻变形工艺进行了分析。实验证明:控制好纺丝工艺制得合适的双组分并列复合弹性纤维T400POY,然后在假捻变形加工过程中与细旦涤纶POY网络复合,可以制得弹性好、手感柔软、绒感风格独特的异成分、异线密度、异收缩的三异细旦高弹涤纶复合纱。     

轻骨料混凝土弹性模量计算模型分析

轻骨料混凝土具有轻质抗渗、保温隔热、耐火抗冻等优势,具有良好的应用前景.但破坏机理与普通混凝土存在本质差异,导致弹性模量低且缺少合理的计算分析模型.针对已有研究进展,分析轻骨料混凝土弹性模量计算模型,建立数据库,基于大数据评估模型的准确性,通过分析强度和表观密度对弹性模量的影响,提出了新的建议计算公式.研究表明:建议模型计算结果与试验结果吻合较好,可用于对轻骨料混凝土弹性模量进行预测,研究成果为后续轻骨料混凝土结构的理论分析提供依据,为实际工程应用提供理论基础.     

Viscoelastic properties of young and old human dermis: A proposed molecular mechanism for elastic energy storage in collagen and elastin

We have studied the strain‐rate dependency of the viscoelastic mechanical properties of human dermis from young (23‐year‐old) and old (87‐year‐old) donors using incremental stress–strain measurements. The elastic spring constant for elastic fibers was found to be strain‐rate and age dependent, whereas that for collagen was only age dependent. Fibril lengths were observed to decrease with increased strain rates and age for both elastic and collagen fibers; however, the large decrease in collagen fibril viscosity was hypothesized to be a result of thixotropy that results when neighboring collagen fibrils slide by each other. It is concluded that the elastic spring constant measured for elastic fibers may be higher than previously reported and is consistent with stretching of α‐helical segments of elastin into a more extended conformation during the initial part of the elastic stress–strain curve. The decrease in the elastic spring constant with increased age observed is consistent with disruption of the elastic fibers and loss of α‐helical structure. The pH dependency of the elastic modulus reported previously for collagen suggests that charge–charge interactions within and between collagen molecules are involved in energy storage during stretching. Elastic energy storage is consistent with the stretching of charged pairs located in flexible regions of the collagen molecule. Shear thinning, or thixotropy of skin, is hypothesized to reflect breakage of bonds that occur between collagen fibrils. It is hypothesized that both collagen and elastin are complex macromolecules that are hybrids of flexible and rigid regions. The flexible regions reversibly store elastic energy during stretching by breakage of secondary bonds. After stretching, the flexible regions become extended and transfer stress to the rigid regions of these molecules. This prevents premature mechanical failure of collagen and elastic fibers in the dermis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1978–1985, 2002     

中空硬弹聚丙烯单丝超分子结构和物理—机械性能的研究

研究了单、双两种组分的中空硬弹聚丙烯单丝在不同纺丝温度和拉伸倍数下的超分子结构及性质变化,并与硬弹、普通中空聚丙烯单丝进行了比较。发现单、双两种组分的中空硬弹聚丙烯单丝与普通中空聚丙烯单丝在结构和性质上有很大的差别,而与硬弹聚丙烯单丝基本相似。随着拉伸倍数的增加,单、双两组分的中空硬弹聚丙烯单丝,其取向,断裂强度均有一个最小值;回弹率有一最大值;单丝的晶轴取向与硬弹处理有关,而晶型变化与硬弹处理无直接联系,结晶度高于普通单丝。纺丝温度低,有利于取向和弹性的提高。     

弹性体在非织造布中的开发应用

阐述了用单一高聚物弹性体、高聚物共混共聚、弹性非织造布与其他材料复合等方式开发弹性非织造布产品的情况。介绍了弹性非织造布在服装、医疗卫生等领域的应用现状     

CdGeAs2晶体的结构、弹性和电子性能的模拟计算和分析

利用基于密度泛函理论的平面波赝势法对CdGeAs2晶体的结构,弹性和电子性能进行了研究.CdCeAs2晶体具有6个独立的弹性常数,利用计算的弹性性能可以判断晶体具有机械稳定性、延性和弹性各向异性等力学特点.通过总的和部分态密度分析了不同能带的贡献成分.计算的结构参数及弹性常数与实验值基本吻合.CdGeAs2晶体具有直接...     

Relation of Single-Crystal Elastic Constants to Polycrystalline Isotropic Elastic Moduli of MgO: II, Temperature Dependence

The technical adiabatic elastic moduli E_[hkl] and G_hkl of single crystals of magnesium oxide were measured over the temperature range 298° to about 1600°K by a Förster-type resonance method. These data were compared with the low-temperature values (80° to 560°K) of the principal elastic constants c_ij and coefficients Sy reported by Durand. Combining Durand's data and the present data, the elastic moduli for single-crystal magnesium oxide were evaluated for the temperature range 80° to 1600°K. Young's modulus and the shear modulus of densely formed isotropic polycrystalline magnesium oxide were measured over the temperature range 298° to 1600°K. The data on the elastic constants of the single crystals were compared with the measured elastic moduli of the isotropic polycrystalline magnesium oxide on the basis of the Voigt-Reuss-Hill approximation. The temperature dependence of the elastic moduli was fitted into the expression M = M_c— BT exp (—T_c/T) suggested by Wachtman et al. ; mean deviations were less than 0.4% for the temperature range considered. The significance of the present data is discussed with particular emphasis on the following points: (1) the temperature variation of the elastic modulus is a function of thermal expansion, (2) the temperature dependence of the elastic modulus can be well described by the foregoing expression for a wide range of temperature, (3) the expression gives a value of the elastic modulus at 0°K, and (4) it may be possible to make use of measurements on the elastic properties of a densely sintered polycrystalline material to obtain information heretofore obtainable only from the corresponding single-crystal data.     

肘杆合模机构弹性变形关联特性的研究（上）

研究了注塑机肘杆合模机构系统与机构内零件两者之间弹性变形量的关联特性,研究了拉杆与肘杆两者之间弹性变形量的关联特性,论证了弹性变形与机构运行性能之间的关系,分析了机构刚度之间的关联特征,提出了肘杆机构、拉杆直径、肘杆载面、模板绕度值等弹性变形量关联的设计理论依据、设计准则和设计方法,并举例说明了设计准则及应用效果。     

注塑机肘杆合模机构弹性变形关联特性的研究（下）

研究了注塑机肘杆合模机构系统与机构内零件两者之间弹性变形量的关联特性,研究了拉杆与肘杆两者之间弹性变形量的关联特性,论证了弹性变形与机构运行性能之间的关系,分析了机构刚度之间的关联特征,提出了肘杆机构、拉杆直径、肘杆载面、模板绕度值等弹性变形量关联的设计理论依据、设计准则和设计方法,并举例说明了设计准则及应用效果。     

PE基木塑复合材料动态弹性模量优势因素分析

以聚乙烯（PE）基木塑复合材料为研究对象,利用弯曲振动法和纵向振动法对PE基木塑复合材料进行了动态弹性模量的检测。研究了木塑比与偶联剂等主要因素对动态弹性模量的影响规律。对比了加工因素对密度和动态弹性模量影响的关系曲线,并进行了加工因素和密度对动态弹性模量的相关性分析。结果表明,木塑比是影响动态弹性模量的首要因素;在木塑比55：45~70：30的范围内,PE基木塑复合材料的动态弹性模量与木塑比成正比关系;偶联剂含量为2 %~5 %时,随着偶联剂含量的增加,PE基木塑复合材料的动态弹性模量也随之升高;利用成型温度、偶联剂含量和密度对PE基木塑复合材料的动态弹性模量进行预测是可行的。     

Elastic properties of adhesive polymers. II. Polymer films and bond lines by means of nanoindentation

Seven different polymers used frequently as adhesives and/or matrix polymers in wood, wood composites, and natural fiber‐reinforced composites were studied by uniaxial tensile tests and nanoindentation. It was shown that the elastic modulus, the hardness, the creep factor, and the elastic‐, plastic‐, and viscoelastic work of indentation of the seven different polymers is essentially the same regardless whether the polymers were tested in the form of pure films or in situ, i.e., in an adhesive bond line with spruce wood. An excellent correlation was found between the elastic modulus measured by tensile tests and the elastic modulus measured by nanoindentation. In spite of the good correlation, the elastic modulus measured by nanoindentation is significantly higher than the elastic modulus measured by tensile tests. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1234–1239, 2006