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1.
为了确定钢渣混凝土是否具有感知应力的功能,研究了钢渣混凝土在不同荷载条件下的电阻变化规律,即压敏性.通过模拟试验测试了不同加载速率、循环加载、突然加载和卸载等加载条件下钢渣混凝土的压敏性.结果表明,随着钢渣掺量的增加,钢渣混凝土的压敏效应更加明显;压力较小时,电阻率随压力增大而迅速降低;压力增大到一定程度后,电阻率下降十分缓慢;压力达到极限荷载时,电阻率迅速升高;在循环加载情况下,第一次加载循环时钢渣混凝土电阻变化率高于第二次加载循环时的变化率.钢渣混凝土成本很低,制备方法简单,与碳纤维增强水泥一样具有良好的压敏性,因此具有较好的应用前景.  相似文献   

2.
掺工业废弃料水泥砂浆压敏性能研究   总被引:1,自引:1,他引:0  
赵若红  庄志勇  傅继阳  区浩文 《材料导报》2014,28(18):113-116,120
选择具有良好导电性的钢屑和铁砂作为导电介质,制备得到水泥基复合材料,并在测定其抗压、抗折强度的基础上采用四电极法研究其压敏性能,分析研究了导电介质的掺量、加载速率以及循环荷载对其压敏性的影响。试验结果表明,钢屑和铁砂水泥基复合材料具备良好的力学性能与压敏性能;随着外荷载变化,钢屑砂浆的电阻率变化率呈二次曲线变化规律,铁砂砂浆的电阻率变化率呈近似直线变化规律。  相似文献   

3.
镀铜钢纤维具有良好的电学性能、力学性能和电导率,而废弃陶瓷粉具有内养护作用和低碳属性。在镀铜钢纤维分散良好的情况下,两者的协同作用易在混凝土基体中形成良好且化学稳定的增强、增韧和导电网络。采用均匀筛入法分散镀铜钢纤维,制备了镀铜钢纤维增强废弃陶瓷粉超高性能混凝土并研究了其压敏性能。研究结果表明,在不同镀铜钢纤维掺量、不同加载幅值和不同加载速率下,镀铜钢纤维均可提高废弃陶瓷粉超高性能混凝土的压敏性能,2.50%(体积分数)的镀铜钢纤维增强废弃陶瓷粉超高性能混凝土的电阻率变化率和应力/应变灵敏度相比于对照组分别提升了650.0%、614.3%和1 223.0%。相比纤维掺量和加载速率,加载幅值对压敏性能的影响最大。且由力-电模型表明,废弃陶瓷粉超高性能混凝土在循环荷载的电阻率变化率和应力/应变之间均服从指数函数关系,拟合度均在0.90以上。因此,通过测试镀铜钢纤维增强废弃陶瓷粉超高性能混凝土的电阻率即可实现混凝土结构的应力/应变监测。  相似文献   

4.
水泥基纳米复合材料压敏特性研究   总被引:1,自引:0,他引:1  
李惠  肖会刚  欧进萍 《功能材料》2004,35(Z1):2653-2656
研究了添加纳米TiO2粒子砂浆在单调荷载及循环荷载下的压敏特性,及添加碳黑的水泥净浆的单调加载下的压敏特性.实验结果表明在单调单向压力荷载时,添加纳米TiO2砂浆具有良好的压敏性能,其体积电阻率与压应力具有稳定而线性的对应关系;循环加载时,其体积电阻率的变化规律又能反映出材料的疲劳损伤情况.添加纳米碳黑砂浆在单调荷载下也具有较好的压敏特性,但稳定性稍差.在实验的基础上,本文探讨了水泥基纳米复合材料的压敏特性机理,分析了两种不同纳米复合材料压敏性能差异性产生的原因.  相似文献   

5.
为探讨乙炔炭黑水泥基复合材料的压敏性 , 验证了利用基于埋入式环状电极的四电极法测试复合材料电阻的可行性; 研究了一次加载至破坏时乙炔炭黑水泥基复合材料的电阻率变化规律 , 并通过在弹性阶段的加载考察了乙炔炭黑水泥基复合材料压敏性的重现性 ; 分析了测试电流和试件偏压对压敏性的影响。研究结果表明 ,基于埋入式环状电极的四电极法测试压敏水泥基材料的电阻误差小于 10 % , 用于复合材料电阻的测试是可行的。掺量 15 vol %的乙炔炭黑水泥基复合材料一次加载至破坏 , 电阻率变化率最大可达 55 % , 弹性阶段电阻率变化率可达 35 %以上 , 且其压敏性基本不受测试电流和试件偏压的影响。乙炔炭黑是制备具有高感知灵敏度的压敏水泥基材料的一种有效功能组分。  相似文献   

6.
利用四电极法研究了内掺水泥基渗透结晶防水材料(CCCW)的碳纤维石墨水泥基复合材料试样(40 mm×40 mm×40 mm)的导电特性及其在循环荷载作用下的压阻特性,分析讨论了碳纤维石墨水泥砂浆的体积电阻率及压阻特性随石墨掺量的变化规律。碳纤维和CCCW的掺量分别为水泥质量的1%和4%;石墨掺量分别为水泥质量的0%、10%、20%、30%、40%和50%。结果表明,添加CCCW的碳纤维石墨砂浆试样的体积电阻率随石墨掺量的增加迅速下降,并存在渗滤现象,渗滤阈值为20%左右。在循环荷载作用下,不同石墨掺量试样的电阻和应力存在一定的对应关系。石墨掺量为水泥质量的20%~30%时,碳纤维石墨水泥砂浆试样的体积电阻率与压应力呈现良好的可重复性,电阻值在应力加载时几乎呈线性下降,而卸载时增加。  相似文献   

7.
轴向压力作用下钢渣混凝土的压敏性研究   总被引:1,自引:1,他引:0  
在不同加载速率、突然加载和卸载以及三向约束等加载条件下,钢渣混凝土具有良好的导电性和压敏性;随着钢渣掺量的增加,钢渣混凝土的压敏效应更加明显;施加压力较小时,电阻率随压力增大而迅速降低;压力增大到一定程度后,电阻率下降十分缓慢;压力达到极限荷载时,电阻率迅速升高;受到三向约束时,钢渣混凝土仍然具有压敏特性,相对于单轴受?其压力敏感性较低.  相似文献   

8.
为研究圆钢管玄武岩纤维再生混凝土(BFRRC)短柱的轴压力学性能,以再生粗骨料取代率和玄武岩纤维掺量为变化参数,设计并完成了15根圆钢管BFRRC短柱试件的轴压试验。观察了试件的受力全过程及破坏形态,获取了试件的荷载-位移曲线及荷载-应变曲线,分析了变化参数对圆钢管BFRRC短柱轴压性能的影响,建立了可行的组合截面应力-应变全过程曲线方程。研究表明:试件均发生鼓曲破坏,但核心混凝土在钢管约束下处于碎而不散状态;随着再生粗骨料取代率的增大,试件的耗能性能、延性系数逐渐增大,耗能因子、延性系数提升幅度最高可达1.84%和10.36%,承载力逐渐降低,降低幅度最大达5.03%;随着玄武岩纤维掺量的增大,试件的耗能性能、延性系数逐渐增大,增加幅度最高可达2.97%和4.93%,承载力提高幅度不大;不同的玄武岩纤维掺量下,试件实测的荷载-位移曲线饱满,且具有较长的变形流幅,延性较好。   相似文献   

9.
魏亚  梁思明  高翔 《复合材料学报》2018,35(6):1609-1618
水泥基材料是一种应变率敏感性材料,充分掌握水泥基材料的应变率效应对其力学性能和变形的影响可保障混凝土结构的安全设计。采用连续刚度测试(CSM)研究不同应变率下硬化水泥净浆微观徐变特征,试样的水灰比为0.3、0.4和0.5,CSM的最大压入深度为30 μm,应变率分别为0.01 s-1、0.05 s-1、0.1 s-1和0.5 s-1,并讨论土体的isotache模型表征硬化水泥净浆微观徐变行为的适用性。结果表明,在0.01~0.5 s-1应变率范围内,微观尺度上的硬化水泥净浆存在唯一的hvp-P-ε关系,与土体isotache模型的εvp-σ-ε关系类似,该关系可由归一化后的hvp-P/(PN/PN0.05)曲线和PN/PN0.05-ε曲线来表征。采用hvp-P/(PN/PN0.05)曲线和PN/PN0.05-ε曲线可预测不同应变率下硬化水泥净浆加载阶段的hvp-P曲线,预测结果与实测结果基本吻合,表明可以采用土体的isotache模型来预测硬化水泥净浆微观尺度上的徐变行为。  相似文献   

10.
为探讨镍粉-水泥基复合材料的压敏性及其产生机理,首先验证了采用埋入式环状四电极进行镍粉-水泥基复合材料电阻测试的可行性,然后探讨了镍粉-水泥基复合材料的伏安特性,最后研究了一次加载至破坏时和弹性加载阶段镍粉-水泥基复合材料的电阻率变化规律.研究结果表明:基于埋入式环状电极的四电极法适用于镍粉-水泥基复合材料压敏性的测试;在测试电流<10mA时,镍粉-水泥基复合材料的伏-安特性为线性,隧道导电具有欧姆特性;镍粉-水泥基复合材料一次加载至破坏,电阻率变化率最大达70%,弹性阶段电阻率变化率可达60%以上,量子隧道效应是致使其具有优异压敏性能的原因.  相似文献   

11.
In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.  相似文献   

12.
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……  相似文献   

13.
14.
We associate a variety of innovations with the term "Industry 4.0". The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...  相似文献   

15.
A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.  相似文献   

16.
On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……  相似文献   

17.
Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.  相似文献   

18.
ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.  相似文献   

19.
In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M2(B,C), (W,Mo)2(B,C), M3(B,C), M23(B,C)6 type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm2. The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K1 mill housing of bar mill.  相似文献   

20.
The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...  相似文献   

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