列车作用下大跨径悬索桥纵向运动响应分析方法对比研究

随着我国铁路事业的发展,近年来设计和建造了一些大跨径铁路悬索桥。悬索桥属于典型的柔性结构,加之列车荷载大、运行速度快,列车过桥时加劲梁纵向运动问题突出。准确地计算出列车过桥时梁端纵向运动响应是进行悬索桥结构设计和梁端位移控制的前提。该文通过有限元仿真,采用4种不同的分析方法,对运行列车作用下大跨径铁路悬索桥纵向运动响应特征进行对比研究。首先,分别介绍移动静载法、移动荷载法、移动质量法、车-桥动力相互作用法的计算理论及其有限元实现方法;随后,以某主跨1060m铁路悬索桥为例,分别采用4种方法进行纵向运动响应计算;最后,对4种分析方法的计算结果进行对比分析。结果表明:大跨径铁路悬索桥纵向运动分析应考虑动力效应;通过移动荷载法、移动质量法及车-桥动力相互作用法分析得到的纵向运动响应接近;采用移动荷载法进行大跨径铁路悬索桥纵向运动响应分析可以简化计算且满足计算精度要求。

Static and dynamic responses of a microcantilever with a T-shaped tip mass to an electrostatic actuation

In this study, nonlinear static and dynamic responses of a microcantilever with a T-shaped tip mass excited by electrostatic actuations are investigated. The electrostatic force is generated by applying an electric voltage between the horizontal part of T-shaped tip mass and an opposite electrode plate. The cantilever microbeam is modeled as an Euler-Bernoulli beam. The T-shaped tip mass is assumed to be a rigid body and the nonlinear effect of electrostatic force is considered. An equation of motion and its associated boundary conditions are derived by the aid of combining the Hamilton principle and Newton’s method. An exact solution is obtained for static deflection and mode shape of vibration around the static position. The differential equation of nonlinear vibration around the static position is discretized using the Galerkin method. The system mode shapes are used as its related comparison functions. The discretized equations are solved by the perturbation theory in the neighborhood of primary and subharmonic resonances. In addition, effects of mass inertia, mass moment of inertia as well as rotation of the T-shaped mass, which were ignored in previous works, are considered in the analysis. It is shown that by increasing the length of the horizontal part of the T-shaped mass, the amount of static deflection increases, natural frequency decreases and nonlinear shift of the resonance frequency increases. It is concluded that attaching an electrode plate with a T-shaped configuration to the end of the cantilever microbeam results in a configuration with larger pull-in voltage and smaller nonlinear shift of the resonance frequency compared to the configuration in which the electrode plate is directly attached to it.

南水北调中线北京段岩体隧洞围岩变形模量分析研究

岩体力学参数是影响地下工程围岩稳定的重要因素,确定合理的岩体变形模量对隧洞设计至关重要。结合南水北调中线北京段西甘池试验洞工程,对岩体进行静载荷试验分析研究,详细介绍试验点岩体的加卸载变形关系曲线,获得西甘池隧洞岩体变形模量参数建议值,为工程设计提供依据,并以期为类似工程的设计和施工提供参考。研究结果表明:试验压力较小时,各试点岩体变形或弹性模量的变化曲线有的升、有的降,试验压力大于0.4 MPa以后,各试点的变形模量和弹性模量逐渐趋于稳定;隧洞围岩变形控制及支护结构设计时,应根据各段围岩的岩性(大理岩、滑石片岩)、结构完整性、节理裂隙的空间展布方式以及发育充填情况等综合考虑,结合工程类比和地质经验最终确定岩体弹性参数的基本代表值。研究的方法和结论可为类似条件下隧洞工程的设计、施工提供参考和借鉴。

用于夹层梁静动力及屈曲分析的新型组合结构单元

推导出新型组合结构单元,用于考虑界面滑移的3层部分作用夹层组合梁的静动力及屈曲特性分析.基于铁木辛柯梁理论,建立考虑夹层梁部分作用效应的能量原理.针对其受力特性,在节点位移、横截面转角和界面滑移插值时均采用含内部自由度的高阶插值函数,以解决含界面有限元数值分析中常遇到的“滑移锁定”现象.通过变分原理得到夹层梁的刚度矩阵、质量矩阵以及几何刚度矩阵的显示表达式.基于MATLAB编译相应夹层结构的有限元程序并验证其准确性.对不同截面3层夹层组合梁进行不同荷载条件和边界条件下的静动力及屈曲特性分析,并探讨不同夹层组合梁跨高比和不同界面抗剪连接刚度下的计算结果及其误差的变化规律.所推导的显示表达式新型组合结构单元计算效率高,并便于推广应用于其他有限元程序或商业软件子程序中.

聚烯烃颗粒在气力输送中静电起电特性研究

为了探究不同聚烯烃粉体颗粒在气力输送过程中起电特性,采用一套自制气力输送实验系统,探究了气力输送过程中不同气固浓度参数对PETG、PP、ABS这3种聚烯烃颗粒静电起电特性的影响规律。结果表明:气力输送过程中PETG与PP颗粒带负电荷,ABS颗粒带正电荷,质量流量和输送空气速度对PETG、PP颗粒的荷质比变化呈类似的变化规律,而ABS颗粒的规律则有所不同。随着颗粒质量流量增大,PETG和PP分别表现为总负电荷量减小;而相同质量流量条件下ABS颗粒则表现为总正电荷量增加。随着输送空气速度增加,3种聚烯烃颗粒所带电荷也会增加,但PETG和PP颗粒电荷极性则会出现极大值。

范伏元教授从“络脉不和”论治肺结节经验

范伏元教授基于络脉沟通内外、渗灌气血、联系脏腑的生理特点,从肺痹、肺积认识肺结节,以络脉不和为肺结节根本病机,从伏邪凝痰痹络、胃络不和痰瘀结为窠囊进行阐发,以“通络开痹,和荣散结”“和胃逐瘀,安神化浊”为核心治法,分别以疏风宣肺汤、加味温胆汤处方辨治,将宏观脏腑辨证调和诸脏与微观络脉辨证调和络脉营卫气血津液沟通渗灌相结合,临床疗效确切。

分级侧向膨胀型锚杆结构力学性能及锚固机理

为了更好地应对传统锚杆在边坡、隧道灾害防治领域锚固性能的不足,研发了一种具有分级侧向膨胀性能的锚杆结构。首先,基于弹性力学理论与物理圆环模型,得到了分级侧向膨胀锚杆径向承载变形的本构关系与极限抗拉拔力公式;然后,通过静态拉拔试验,揭示了锚杆的承载力传递规律与承载变形机理;最后,通过对分级侧向膨胀锚杆与NPR锚杆的结构特性进行对比,发现分级侧向膨胀锚杆不仅在抗剪切、扭转和吸能等方面具有更优异的性能,且相比较NPR锚杆的单次膨胀特性,其分级膨胀与可控变形的特性在提高围岩整体稳定性,释放围岩变形能方面更具优势。结果表明,分级侧向膨胀锚杆的特性更加适合稳定性较差的地质环境,为灾害防治工程提供了新的解决方案。

静动载条件下深部破碎巷道支护设计及稳定性分析

深部破碎围岩稳定性控制是制约深部金属矿安全高效开采的难题之一。以金川二矿区深部某中段破碎围岩条件下的采准巷道稳定性控制为工程背景,应用Q、RMR、GSI进行岩体质量分级与岩体力学参数估算,分别应用经验法和工程类比法进行采准巷道支护设计,并依据收敛约束法确定合理的释能支护时机。在此基础上,应用UNWEDGE软件对释能支护设计进行安全性评价,并通过RS2数值方法分析支护效果。研究结果表明:对于深部破碎采准巷道一次支护采用锚网喷支护,二次支护采用混凝土衬砌,最佳衬砌支护时机应满足巷道帮位移小于38 mm且顶板位移小于15 mm;静动载下有无支护数值分析结果表明,锚网喷支护满足巷道安全要求,同时对采准巷道围岩结构控制型、应力控制型破坏以及动力失稳破坏等起到良好的控制效果。研究结果为金川二矿区深部破碎采准巷道围岩稳定性控制提供了理论依据与技术支撑。

探究缝编工艺参数对玻纤复合材料性能的影响

通过设计并制备6种不同编织工艺参数的单轴向玻纤经编织物,探究涤纶丝缝编针距、缝编线粗细旦数、缝编线针脚长度以及缝编方式和纬线的交叉与平行铺纬方式对玻纤复合材料的厚度、纤维质量分数和静态力学性能的影响。研究结果表明:不同编织工艺参数对玻纤复合材料的厚度与纤维质量分数的影响主要取决于单轴向玻纤经编织物中涤纶丝体积分数高低,涤纶丝体积分数高者其玻纤复合材料厚度偏厚,反之偏小,但是对玻纤复合材料静态力学性能影响微乎其微。

塔吉克斯坦某金矿全尾砂静动态絮凝沉降规律试验研究

塔吉克斯坦某金矿使用深锥浓密技术进行全尾砂深度脱水。为探究尾砂浆给料稀释浓度、给料速度以及絮凝剂单耗对全尾砂絮凝沉降效果的影响规律,掌握浓密机运行的适宜参数范围,依据静态沉降理论,开展了静动态絮凝沉降试验,对底流、溢流及沉降过程进行了多指标检测分析。研究结果表明:静态絮凝沉降情况下,边界稀释浓度为10%~12.5%,超过此范围,絮凝沉降效率降低,上清液澄清度降低显著;对应最优絮凝剂单耗为25 g/t,所能达到的最大固体通量为1.70 t/(m^(2)·h);较合理的给料速度为0.28~0.59 t/(m^(2)·h),考虑泥层压密时长12 h,拟合计算最终排放底流浓度可达到66%左右。研究结果为塔吉克斯坦某金矿深锥浓密机运行参数优化提供了参考。

Static-deformation based fault diagnosis for damping spring of large vibrating screen

Based on the statics theory, a novel and feasible twice-suspended-mass method(TSMM) was proposed to deal with the seldom-studied issue of fault diagnosis for damping springs of large vibrating screen(LVS). With the static balance characteristic of the screen body/surface as well as the deformation compatibility relation of springs considered, static model of the screen surface under a certain load was established to calculate compression deformation of each spring. Accuracy of the model was validated by both an experiment based on the suspended mass method and the properties of the 3D deformation space in a numerical simulation. Furthermore, by adopting the Taylor formula and the control variate method, quantitative relationship between the change of damping spring deformation and the change of spring stiffness, defined as the deformation sensitive coefficient(DSC), was derived mathematically, from which principle of the TSMM for spring fault diagnosis is clarified. In the end, an experiment was carried out and results show that the TSMM is applicable for diagnosing the fault of single spring in a LVS.

Effect of Manufacturing Errors on Static Characteristics of Externally Pressurized Spherical Air Bearings

Externally pressurized spherical air bearings are the key component of the three-axis air bearing table, and the manufacturing errors of the bearing affects the performance of the air bearing table. However, the manufacturing errors are unavoidable, and the pursuit to enhance the manufacturing accuracy will increase the cost greatly. In order to provide some theoretical guideline for the tolerance choice in the design of the externally pressurized spherical air bearings with inherent compensation, the effects of several manufacturing errors on the static characteristics of the air bearing are studied. Due to the complex geometry of the computational domain, an unstructured meshing technology is used for mesh generation. A finite-volume method is adopted to discretize the three-dimensional steady-state compressible Navier-Stokes equations. A modified SIMPLE algorithm which is suitable for compressible flows is applied to solve the discretized governing equations. The effects of the dimension error and the roundness error of the ball head and the ball socket on the static characteristics are investigated. The investigation result shows that the positive dimension error and the oblate spheroid-type roundness error of the ball head as well as the negative dimension error and the prolate spheroid-type roundness error of the ball socket can improve the bearing capacity and static stiffness of the air bearings by reducing the mass flow. The calculation method proposed in this paper fits well for the general principle, which can be extended to the characteristics analysis of other air bearings.

浅析油品蒸发损耗及发展趋势

油品蒸发损耗不仅影响环境质量,还影响油品质量。除了该问题之外,蒸发损耗将促进汽油氧化,辛烷值减小,长时间运行对汽车发动机造成不利影响。此外,油品蒸发损耗还有一定的安全隐患,易造成局部火灾,并对人类和动植物也有毒害性。目前,国内外正结合油品蒸发损耗的相关因素,发掘降耗措施,比如对输送和储油设备的结构进行设计和改进,尽可能加大对烃蒸气的回收力度,并采取合适的方法来抑制油品蒸发损耗。

Failure behavior of highly stressed rocks under quasi-static and intensive unloading conditions

Unloading failure of rocks,especially highly stressed rocks,is one of the key issues in construction of underground structures.Based on this,analytical models for rocks under quasi-static and intensive unloading conditions are established to study the failure behavior of highly stressed rocks.In case of rock failure under quasi-static unloading,the rock mass ahead of working face is regarded as an elasto-brittle material,and the stress-displacement curves are used to characterize the tensile fracture of peak-stress area.It is observed that,when intensive unloading happens,there is an elastic unloading wave（perturbation wave） propagating in the rock mass.If the initial stress exceeds the critical stress,there will be a fracture wave,following the elastic unloading wave.To study the propagation feature of fracture wave,the conservation laws of mass,momentum and energy are employed.Results show that the post-peak deformation,strength and energy dissipation are essential to the failure process of highly stressed rocks.

基于静态气体质谱仪的Xe稳定同位素高精度分析

为解决氙(Xe)的九种稳定同位素质量差异大(约9.6%),质谱探测器接收难的问题,利用Helix MC Plus静态气体质谱仪,建立一种测量Xe全部稳定同位素丰度比的高精度质谱分析方法,快速、准确获得Xe的全部稳定同位素丰度。首先对混合气体样品中的Xe进行提取分离与纯化等条件实验,减小其他惰性气体及活性组分对Xe同位素分析测量的影响,再使用跳峰和多接收两种方式相结合的测量方法,实现在进样量极小时,基于Helix MC Plus型静态气体质谱仪的Xe全部稳定同位素的高精度测量,并利用天然丰度Xe标准气体对配制的混合气体样品测量结果进行线性校正。结果表明,在进样量约1.12×10^(-12)mol条件下,法拉第杯测量129 Xe/^(132)Xe、^(130)Xe/^(132)Xe、^(131)Xe/^(132)Xe、^(134)Xe/^(132)Xe、^(136)Xe/^(132)Xe丰度比的相对标准偏差≤0.24%,对于使用计数法测量124 Xe/^(132)Xe、126 Xe/^(132)Xe丰度比的相对标准偏差分别为0.22%和0.39%。本方法稳定性好、精度高,可以实现痕量Xe稳定同位素的丰度比质谱分析测试。

Sensitivity analysis for a type of statically stable sailcrafts

Two types of sensitivities are proposed for stat- ically stable sailcrafts. One type is the sensitivities of solar-radiation-pressure force with respect to position of the center of mass, and the other type is the sensitivities of solar-radiation-pressure force with respect to attitude. The two types of sensitivities represent how the solar-radiation- pressure force changes with the position of mass center and the attitude. Sailcrafts with larger sensitivities undergo larger error of the solar-radiation-pressure force, leading to larger orbit error, as demonstrated by simulation. Then as a case study, detailed formulas are derived to calculate the sensi- tivities for sailcrafts with four triangular sails. According to these formulas, in order to reduce both types of sensitivities, the angle between opposed sails should not be too large, and the center of mass should be as close to the axis of symmetry of the four sails as possible and as far away from the center of pressure of the sailcraft as possible.

BMI和性别对中老年人静动态平衡能力的研究

目的:探讨BMI和性别对中老年人静动态平衡能力的影响.方法:根据BMI和性别选取160名中老年人,其中,体重偏瘦、正常、超重、肥胖的人数均为40人,且男女比例均为1∶1.使用平衡仪测试受试者的静动态平衡能力,采用4×2双因素方差分析检验BMI和性别对平衡能力的影响效果.结果:在静态平衡方面,睁眼单足站立时平衡在组别间的差异具有统计学意义(P<0.05).在动态平衡方面,睁眼双足站立时的平衡在组别和性别间的差异具有统计学意义(P<0.05).结论:随着BMI等级的升高,中老年人的静动态平衡能力逐渐变差,超重、肥胖中老年人的静动态平衡能力更差.对同一BMI类型的中老年人,男性的静态平衡能力与女性相当;但是,男性的动态平衡能力却略优于女性,尤其是BMI偏小时.

静态顶空-气相色谱-质谱法分析不同产地大红袍花椒中挥发性成分

3个省份9个产地的大红袍花椒样品经筛选、自然晾干后过孔径为0.425 mm筛网。分取1.0 g置于20 mL顶空瓶中,用卷边器封口,在加热箱温度100℃、定量环温度110℃条件下平衡30 min。所得挥发性成分进入气相色谱仪,在DB-17MS毛细管色谱柱上进行程序升温分离,并用附电子轰击离子源的质谱仪检测,以保留时间和定性离子定性,以峰面积归一法半定量,以主成分分析法寻找区分不同产地的差异性物质。结果显示:在9个产地样品中共检出120种挥发性成分,烯烃、芳香烃、烷烃、醇、醛、酚、酮、酯类化合物分别有56,2,10,24,7,1,12,8种;共有成分12种,其中柠檬烯相对含量较高(9.646%~48.985%);2-甲基-5-(1-甲基乙烯基)-2-环己烯-1-醇和乙酸松油酯可作为区分不同产地样品的差异性物质,对甲-α-甲基苯乙烯、石竹烯可作为辅助差异性物质。

较破碎岩石地基中嵌岩桩竖向承载力分析

嵌岩桩的分析基于桩端置于完整岩体中的研究较多,而本文更偏向于较破碎岩体中的桩的竖向承载力分析。结合武汉某高层项目现场静载荷试验,对较破碎岩体中的嵌岩桩承载力进行分析,研讨此类岩体中桩基的承载性状。结果表明:较破碎岩石中嵌岩桩的Q-s曲线呈陡降型,桩顶沉降主要由桩身压缩引起,达到了90%以上;在有效桩长范围内,桩身轴力随埋深增加呈递减趋势;侧摩阻力分布曲线呈“上小下大”,其发挥具有异步性;极限荷载下,试桩端阻比平均值为30.59%,呈端承摩擦型桩特性。此外,通过对嵌岩段承载力进行修正,提出了较破碎岩体中嵌岩桩的承载力计算方法,并通过实例验证的结果与实测值相差较小。试验成果可为较破碎岩体中桩基设计提供借鉴。

气流参数对多孔质空气静压轴承静态特性及性能影响研究

空气静压轴承在精密机床和计量设备等制造业领域应用广泛.多孔质空气静压轴承是一种特殊类型的空气静压轴承,其由于使用了多孔质材料,因此更加稳定和坚固.目前针对这类轴承有关气流参数对轴承静态特性及性能影响的研究还较为欠缺.为此,本文提出了一个数学模型用于模拟多孔质空气静压推力轴承的静态特性,包括承载能力、刚度及质量流率等.通过使用基于Navier-Stokes方程的计算,对轴承内部的压力分布进行了分析.随后,研究了对轴承静态特性可能产生影响的相关气流参数及其影响情况.研究结果表明,轴承气膜层厚度的增加会导致轴承承载能力和刚度的下降,但增加多孔质层的厚度可以提高轴承刚度.此外,增加气膜层厚度会使得进入轴承的空气质量流率得以提升.这些结果可用于帮助设计更为高效且能够承担更高负载的多孔质空气静压轴承.