相背夹持两点接触应力场特殊位置的极值应力

点接触夹持是最常见的夹持形式,也是研究线接触与面接触夹持的基础。点接触可以用集中力模型来模拟,在极限状态下点接触产生的摩擦力与法向集中力通过材料的摩擦系数相关联。摩擦力与法向集中力符合库仑摩擦定律。弹性理论中已经给出了半无限体受二维集中力作用模型应力场的公式,借助这些公式可以对点接触的夹持进行应力分析。当然,点接触可以分为相向夹持与相背夹持,相向夹持的情况已经讨论过[1]。本文对摩擦极限状态情况下相背夹持两点接触应力场的分布进行分析,并给出若干特殊线、点的极值应力的大小和主方向。     

同向夹持两点接触应力场特殊位置的极值应力

夹持是一种依靠摩擦力工作的约束形式。法向力自身平衡,摩擦力与外力平衡。点接触夹持是最常见的夹持形式,也是研究线接触与面接触夹持的基础。点接触可以用集中力模型来模拟,在极限状态下点接触产生的摩擦力与法向集中力通过材料的摩擦系数相关联。摩擦力与法向集中力符合库仑摩擦定律。弹性理论中已经给出了半无限体受二维集中力作用模型应力场的公式,借助这些公式可以对点接触的夹持进行应力分析。本文从一点接触应力场的分布规律开始,对在摩擦极限状态情况下同向夹持两点接触应力场的分布进行了分析。并给出了若干特殊线、点的极值应力的大小和主方向。     

新型装配式剪力墙水平连接装置的力学性能

装配式剪力墙结构连接节点/水平接缝的力学性能对装配式结构起着至关重要的作用,为了提高装配式剪力墙结构的抗震性能,本文结合消能减震技术设计研发了一种新型装配式剪力墙水平连接装置。通过该设计,制作了2种不同螺栓数量的水平连接装置,并对其进行了不同正弦加载频率下的动态力学性能试验,探究了不同螺栓预紧力、加载频率及螺栓数量对装置力学性能的影响规律;探究了装置摩擦升温对其力学性能的影响规律。结果表明:该装置在保证结构可靠连接的同时,又能依靠装置的内部摩擦消耗大量地震能量,从而有效减小结构地震响应,保护主体结构。此外,螺栓预紧力与装置的耗能能力和割线刚度基本呈线性关系,但对等效阻尼比影响不大;水平连接装置的力学性能几乎不受加载频率的影响;增加螺栓数量可大幅提高装置耗能能力;螺栓预紧力与加载频率均是装置温度升高的重要影响因素,但装置温度变化对其力学性能影响不大。     

被动消能混合式交错桁架单元滞回性能有限元分析

为了增强交错桁架耗能能力,可在桁架单元的斜腹杆上设置摩擦耗能器,形成被动消能交错桁架结构。采用有限元软件ANSYS12.1分析摩擦耗能器在不同摩擦系数、螺栓孔长以及螺栓等级下的荷载位移关系,并将摩擦耗能器的荷载-位移关系转化为等效应力-应变关系,定义到斜腹杆上的等效耗能器单元的材料本构关系中,对被动消能桁架单元进行水平方向循环加载,得到各桁架单元的滞回曲线、骨架曲线以及耗能能力图。有限元分析结果表明:摩擦系数使耗能器的滑移力达到斜腹杆屈曲荷载的96%时,结构的耗能能力最好;耗能器孔长越大,桁架的耗能能力和延性越好,滑移量达到桁架节间距的1%时,延性系数可满足一般框架的抗震要求;螺栓等级越高,其预紧力越稳定,桁架耗能能力越好。     

新型锻造操作机主运动机构控制系统设计(邀请论文)

基于运动链图拓扑图库,提出一种新型六自由度前后双提升驱动锻造操作机工作装置.该装置不仅可以控制夹钳提升的同步性,还能更好地适应偏载工况.基于虚功原理建立了该新型锻造操作机主运动机构的动力学模型,并结合液压缸系统模型,设计模糊PID控制器实现对锻造操作机夹钳末端的运动跟踪.对夹钳在竖直平面运动进行轨迹规划并确定运动过程中液压驱动各单元所需提供的驱动力.基于Matlab/Simulink平台搭建控制系统仿真模型,在给定负载情况下,分别对夹钳的竖直提升运动、水平运动以及俯仰运动进行仿真分析,得到系统单位阶跃响应与正弦响应跟踪曲线及误差曲线.研究结果表明:基于该新型锻造操作机,采用模糊PID控制器能够快速、精确地获得新机构的性能参数并高效地完成跟踪,使系统保持良好的稳态性能与动态特性.     

Passive control experiment of building with spacious first story by magnet-friction energy dissipation device

Based on the former performance capacity experiments of the magnet-friction energy dissipation devices, including the permanent magnet-friction energy dissipation device （PMF） and electromagnet-friction energy dissipation devices （EMF） , a 5-story steel frame model with spacious first story, is designed and made according to a scale of 1/4. The magnet-friction energy dissipation devices can realize continuously varied controlling force, with rapid response and reverse recognition. Therefore, they overcome shortcomings usually found in energy dissipation devices whose force models are invariable. The two kinds of devices were fixed on the flexible first story of the structure model, and the shaking table tests have been carried out, respectively. In these tests, the performance of the devices and their effectiveness in structural control were confirmed. In this paper, the test results and analysis are discussed.     

用于自复位支撑的槽孔摩擦板耗能器力学性能试验研究

为研究不同槽孔尺寸、摩擦板材料、垫片种类对自复位支撑中槽孔摩擦板耗能器力学性能的影响,对12组试件进行了低周往复试验研究.结果表明:相对标准孔钢摩擦板-槽孔钢摩擦板和标准孔碳纤维摩擦板-槽孔钢摩擦板,标准孔黄铜摩擦板-槽孔钢摩擦板组合耗能最稳定,适合工程应用;不同槽孔尺寸的槽孔摩擦板耗能器承载力相差不大,最大差值仅为2.27%;加载过程中高强螺栓预紧力平均损失为3.7%,摩擦系数平均损失为2.16%;槽孔摩擦板耗能器承载力(即稳定滑动摩擦力均值)与理论摩擦承载力比值为92.01%;碟形垫片可通过回弹适当减小摩擦力损失,建议工程中使用.给出了槽孔摩擦板耗能器用于自复位支撑时,其承载力计算公式,为工程实际应用提供参考.     

强震区多跨长联连续梁桥减隔震设计

为了给高烈度地区多跨长联连续梁桥抗震设计提供参考,以一座（55+4×90+55）m的连续梁桥为工程背景.采用ANSYS软件建立全桥分析模型,基于非线性时程分析方法,对比研究结构采用双曲面摩擦摆支座、黏滞阻尼器和速度锁定装置3种减隔震装置下的地震响应.结果表明：黏滞阻尼器在罕遇地震作用下形成了完整的滞回环,每个阻尼器耗能能力明显;采用双曲面摩擦摆支座、黏滞阻尼器和速度锁定装置时,结构的地震响应相对于传统抗震体系都有一定程度地降低,固定墩内力相对减震率分别为63.44%、6.90%、42.32%,位移相对减震率为65.70%、9.34%、43.77%;采用双曲面摩擦摆支座作为减隔震措施时,墩底内力和墩顶位移远小于黏滞阻尼器和速度锁定装置2种减隔震措施.     

A stretchable triboelectric generator with coplanar integration design of energy harvesting and strain sensing

The rapid development of flexible triboelectric nanogenerators (TENGs) has become an alternative to batteries for wearable devices. Stretchable, multifunctional, and low-cost are the primary development directions for these wearable devices based on TENG. Herein, a stretchable triboelectric generator with coplanar integration was designed for energy harvesting and force sensing. The industrial conductive silicone and silicone were used to fabricate the TENG with a thickness of less than 0.9 mm. When the elongation was less than 150%, TENG exhibited excellent linear characteristics in the resistance-tensile strain correspondence, and the coefficient of determination was 0.99. This stretchable TENG with a sufficient contact area of 9 cm² could generate a short-circuit current of 2 μA when it was in contact with the skin. Lastly, an intelligent tension monitoring wearable device that can effectively measure the tensile force was developed. Such a stretchable, coplanar integration-based, and low-cost wearable device has excellent applicability in wearable electronics.

     

低周反复试验轴力加载装置的系统摩擦力

在柱、剪力墙等的低周反复加载试验中,与施加轴压力的竖向作动器相连的钢铰轴处或滑动导轨处存在的摩擦力会导致加载水平力的测量结果不同程度地较真实值偏高。通过试验和有限元计算,分析了该摩擦力的规律和量化取值。为了消除材料非线性并准确考虑几何非线性的影响,设计两个型钢柱进行了材料弹性状态下的低周反复试验,并在OpenSees平台上建立了能够准确计算二阶效应的有限元模型。根据试验测量结果、有限元分析结果对该试验的轴力加载装置引起的摩擦力进行计算,研究了摩擦系数的取值方法,并考察了摩擦力对柱试验结果的影响。研究结果表明：由轴力加载装置引起的摩擦力主要受轴压力值影响,柱顶位移的影响较小;随着轴压力增大,摩擦力增大、摩擦系数变小;最大摩擦力、最小摩擦系数均趋于较稳定的取值;对于轴压力为350~900 kN的钢筋混凝土柱,由该装置摩擦力引起的低周反复试验的柱顶水平力测量结果误差约为5~13 kN。     

紫外线处理胶辊物理性能变化的探讨

对紫外线处理胶辊表面的动摩擦系数、硬度、冲击弹性和静态握持力进行了测试.通过讨论这些指标处理前后和不同方法下的变化情况,得出光照处理胶辊后表面性能的一系列变化与纺纱质量的关系.     

大直径超长后注浆钢筋砼桩身应变分布式光纤监测

后注浆条件下大直径超长桩荷载传递机理十分复杂,而传统监测技术得到的成果不连续,不能准确反映桩基的荷载传递机理。结合工程实例现场静载荷试验,采取BOTDR分布式光纤技术监测桩身应变分布,研究超长桩端阻、侧阻分布。发现桩侧摩阻力呈中间大、两端小的趋势;桩侧负摩阻使摩阻力曲线上出现波峰和波谷交替现象;桩侧摩阻力在桩体下部很难发挥出来,直接把基坑底标高处桩的轴力作为极限承载力是不合理的。     

新型二维压电移动机构

采用双压电晶片振子为移动机构的驱动源,提出可以实现二维平面移动的新型压电驱动机构。分析了压电驱动机构的工作特点,探讨了实现驱动运动的工作机理。指出该机构是通过控制机构驱动"足"产生的驱动力和接触面之间的摩擦力之差实现机构的定向运动的。设计研制了新型二维压电移动机构的载物工作台实验装置,并进行了实验研究。实验证明该装置可以实现沿规定方向的运动,并可以通过电路设计进行控制,且具有一定的承载能力。     

Electromechanical coupling properties of a self-powered vibration sensing device for near-surface observation tower monitoring

The wind-induced vibration of a remote sensing tower is the key factor affecting the stability of image sensing and structural reliability. Monitoring the vibration of a long-time unattended tower is critical to its proper operation. Currently, most monitoring devices are supplied with wired power or battery, significantly limiting their practical applications in remote areas. In this paper, a self-powered vibration sensing device based on hybrid electromechanical conversion mechanisms is proposed. The device depends on a cylindrical magnetic levitation structure sensitive to ambient vibration for transferring mechanical energy and takes as a dual-functional heterogeneous integrated system comprising electromagnetic, piezoelectric, and triboelectric generators. When the device vibrates under environmental force driving, the suspension magnet reciprocates vertically and generates induced electromagnetic energy, which is used to power the device. Moreover, the triboelectric and piezoelectric voltages, respectively originating from magnet impact on two separation friction materials and magnetic field repulsion-induced strain deformation of a piezoelectric sheet, are used as the synergistic sensing signals. To improve the output energy, a set of dual-segmented annular coils is designed in an electromagnetic generator, which greatly avoids the obstructive effect of the suspended magnet on the magnetic flux change at its end. Compared with a whole isochoric coil, it increases the output voltage by 78.3%. For the triboelectric sensing module, a silicone film with a large specific surface area is fabricated via 3D modification, which improves the output voltage by 29.4%. Furthermore, a pair of piezoelectric sensing modules is set to improve the accuracy of comparative sensing data. The experimental measurement shows that the device maintains a high sensitivity of 6.711 V (m s^?2)^?1 and excellent linearity of 0.991 in the range of 0–14 m s^?2. This work provides a practical strategy for the vibration monitoring of remote sensing tower and exhibits attractive potential in early warning and data analysis.

     

利用局部加载法冷精锻圆柱直齿轮

冷精锻圆柱直齿轮具有齿腔充填困难、成形力大及模具寿命低等技术难题。对此,提出了传统封闭式冷锻-局部加载终锻二步锻造工艺。利用数值模拟方法分析了局部加载终锻的变形过程、等效应变和成形载荷,并与封闭式冷锻成形圆柱直齿轮进行了对比,结果表明：利用局部锻造工艺作为终锻,不但齿腔充填良好,而且能极大地降低成形力和单位压强;局部加载成形的齿轮齿形部分变形大、组织好。     

深井延迟长脉冲燃爆压裂火药优配与评价

针对燃爆压裂火药爆燃加载速率快、措施安全与裂缝规模难以平衡的问题,基于对成熟火箭推进剂配方的深入考察,借助密闭爆发器、燃速测试仪、落锤仪、摩擦感度仪和差热分析仪等实验设备,筛选优化了延迟长脉冲燃爆压裂火药配方,测试并得到了其从低压到高压的燃速图版,评价了其爆燃加载特性.结果表明,相对传统燃爆压裂火药,该延迟长脉冲火药燃速更低、持压时间更长,且具有较强的耐撞击、摩擦和高温性能,适用于深层、超高压地层油气井.在20℃下测试,延迟长脉冲火药在7 MPa下爆燃加载持压时间78.1ms,为传统燃爆火药的2.12倍;45~70MPa超高压环境下燃速36.4~39.5mm/s,低于传统燃爆火药燃速一半,可有效提高燃爆压裂火药最大装药量、扩大裂缝延伸长度和破裂规模.     

摩擦加载式电液负载模拟器大幅值加载机构

为在紧凑的结构尺寸下利用现有的摩擦材料大幅度提高摩擦加载式电液负载模拟器的加载幅值,提出利用大幅值力矩加载机构进行加载的方法.给出加载机构的工作原理,设计并研制一个加载机构样机;利用ABAQUS软件建立该机构的有限元模型,并对该机构进行动态热-力耦合仿真研究,验证该机构的可行性,研究摩擦热的产生特征及其对该机构的影响,发现实际应用时需要对该机构进行充分的散热;利用研制的加载机构,将原有的单向摩擦加载式电液负载模拟器样机改造为大幅值摩擦加载式电液负载模拟器,基于改造的负载模拟器,在PID控制器控制下进行了大幅值力矩加载实验.实验结果表明:改造后的负载模拟器能够精确跟踪高达70 N·m的力矩,该机构能够按设计预期将原有负载模拟器样机力矩加载幅值提高3倍左右,验证了该机构的有效性.     

Numerical study on flow and heat transfer characteristics of microchannel designed using topological optimizations method

Microchannel has demonstrated advantages in the thermal management of integrated chip. In this study, the topology optimization method is applied for designing a topological microchannel to optimize the performances of both heat dissipation and pressure drop. To validate the performance of the topological structure, the flow and heat transfer characteristics of topological microchannel under non-uniform heating flux are numerically studied. The topological structure is designed to cool a heating area of 10 mm × 10 mm with 4 hotspots. Heat flux is 40 W/cm~2 in the hotspot area, while it is only 15 W/cm~2 in the rest heating area. The results of heat dissipation performance and pressure drop are compared with those of conventional straight microchannel. Numerical result shows that, compared to the straight microchannel, the hotspot temperature and pressure drop of topological microchannel can be reduced by 4 and 0.6 k Pa, respectively, under the flow rate of 2.2×10~(–4) kg/s. The coefficient of performance(COP) of topological microchannel can be 16.1% better than that of straight microchannel, which can be attributed to the effects of optimized bifurcation and confluence structural of topological microchannel.     

序列模式挖掘在网络告警分析中的应用

序列模式挖掘可以用来有效地发现网络系统中的告警关联知识.论文研究了序列模式挖掘在网络告警分析中的具体应用.首先,将挖掘过程分成了特定设备告警序列挖掘、同类设备告警序列挖掘和互联设备告警序列挖掘等3类,根据不同的用户意图来有效地确定挖掘范围,避免对无关数据的访问.为了进一步提高挖掘算法的执行效率,又提出了用于描述网络拓扑信息的拓扑约束,并设计了基于拓扑约束的互联设备告警序列模式挖掘算法.     

测定金刚石膜断裂强度及断裂韧性的力控制法研究

人造金刚石膜是一种新材料。断裂强度及断裂韧性是其主要力学性能指标,目前国内、外尚无相应的强度测试方法标准,一般采用类比陶瓷测定断裂强度与断裂韧性的方法进行,即采用位移控制法进行检测。基于金刚石膜是一种硬度比陶瓷更高的材料,本文首次对金刚石膜提出用一种力控制法进行检测。在试验时采用专用的弹性压力头加载,加载速度可调,加载平稳、可靠,收到了很好的效果。