抗磁性高密度物质的磁悬浮密度测量方法

为了克服现有磁悬浮密度测量方法存在测量范围小（0.8~2.3 g/cm³）的缺点,提出全新的针对抗磁性高密度物质的密度测量方法.该方法将高密度物质通过一定长度的细线悬挂,并将高密度物质置于水平放置的磁悬浮装置中,高密度物质在重力、浮力、拉力和磁力的综合作用下产生横向悬浮位移.在分析顺磁溶液中物质受力情况的基础上,建立物质横向悬浮位移与密度的关联函数关系,基于该函数关系实现高密度物质密度的精确测量.实验结果表明,采用该方法可以测量小尺寸高密度样品（如铜、铝和玻璃等）的密度,测量精度为0.028~0.165 g/cm³.随着样品密度的增加,测量偏差呈现增大的趋势.     

物质抗磁性的经典统计解释

采用经典统计的方法得到了物质抗磁性的另一种解释。     

物质抗磁性的经典统计解释

采用经典统计的方法得到了物质抗磁性的另一种解释.     

物质抗磁性和顺磁性的物理机制

抗磁质和顺磁质虽然都是弱磁质 ,但两者在磁化的物理机制上有着本质的不同 .按照朗之万模型 ,根据经典电子论 ,运用统计方法解释了抗磁质和顺磁质的磁化过程 ,并导出相应的磁化率 .     

斥力型磁悬浮平台建模及仿真

针对吸力型磁悬浮平台尺寸大、刚度低以及承载力小等缺点,提出一种斥力型磁悬浮平台。采用等效方法推导出永磁导轨对悬浮永磁体和悬浮电磁铁的磁斥力数学模型,并通过实验验证了该模型的准确性。通过对计算实例的Matlab仿真分析,表明所建的磁斥力模型是可控的,可实现斥力型磁悬浮平台的稳定悬浮。     

磁悬浮轴承磁场分布的测量

该文介绍了磁悬浮轴承磁场分布测量的硬件结构和软件设计方案。该系统将单片机为核心的小系统,结合霍尔传感器作为前端的数据采集系统,将采集到的数据利用串口传送到PC主系统。在LabVIEW环境下对数据进行分析、处理、显示并保存。经测试,系统能方便灵活地测量磁悬浮轴承磁场,并通过三维图形显示该磁场分布。     

从电子配对看物质的“抗磁性”和“顺磁性”

不同物质的分子在磁场中表现出不同的磁性质。多数的物质在磁场中会产生一个对着外磁场方向的磁矩,有的成为抗磁性物质,有的成为顺磁性物质。如果一种物质中的电子都已经配对,没有未成对的电子,这样的物质就是抗磁性物质。一种物质中存在未成对的电子,在磁场中能顺着磁场的方向产生一个磁矩的物质就成为顺磁性物质。简单的用有没有未成对电子判断抗磁性和顺磁性是存在局限性的,但大部分时候是有效的。     

单轴磁悬浮系统控制器的仿真研究

介绍了单轴磁悬浮系统的组成及基本工作原理,通过线性化方法建立了系统的力学模型,并基于此模型设计了闭环控制器的四种控制方案。通过对这四种控制方案在受到阶跃扰动时的仿真研究,分析了它们的稳态情况及抗干扰能力,得出了性能比较良好的控制方案,并相应给出了计算机的仿真结果。     

磁悬浮转子位移测量传感器的研究

在磁力轴承系统中,磁悬浮转子的位移信号是控制磁力轴承稳定悬浮并能够高速旋转的重要依据,因此,位移传感器测量数据的可靠性、稳定性和精确性直接影响到磁力轴承的整体性能。针对磁悬浮转子对位移传感器的特殊要求,从理论上分析了涡流位移传感器的设计原理,并根据理论分析设计制作了传感器;还介绍了传感器的实验方法和实验步骤,并对实验结果进行了分析。     

磁悬浮硬盘驱动器研发中的磁场测量

研究磁力轴承磁场分布对硬盘记录磁场的影响,探讨磁悬浮硬盘磁力轴承磁场分布的可行性,然后测量并分析微型磁力轴承结构中的磁场分布,为磁悬浮硬盘驱动器的研发提供必要的实验依据．     

Geometric optimization of electrostatic fields for stable levitation of metallic materials

Experimental and computational methods are used to optimize the electrostatic field for levitating metallic materials.The calculated launch voltage increases linearly with the distance between top and bottom electrodes.The combination of a larger top electrode diameter with a smaller bottom diameter may enhance the levitation ability because the electric field intensity near the levitated sample is strengthened.Top convex and bottom concave electrodes can guarantee good levitation stability but decrease the levitation force.The design of bottom electrode is crucial to attain not only a stable levitation state but also a higher levitation capability.As a measure characterizing the intrinsic levitation ability of various materials,the product of density and diameter of levitated samples can be used to determine the launch voltage for counteracting gravity according to a power relationship.     

Magnetic levitation using diamagnetism: Mechanism,applications and prospects

As a typical contact-free manipulation technique that removes friction and contamination risk, levitation has gradually become a preferred candidate for various applications. Magnetic levitation using diamagnetism, beyond Earnshaw's theorem, is a kind of passive stable levitation that can be achieved at normal temperatures with no energy input. Appealingly, most seemingly nonmagnetic materials can be levitated in a magnetic field and can stabilize free levitation of magnetic materials. This review focuses on the fundamental principles of magnetic levitation using diamagnetism, with emphasis on its burgeoning applications.The theoretical basis associated with the magnetic levitation using diamagnetism is discussed by elucidating the characteristics of diamagnetic materials, and the key levitation mechanisms are clarified. Afterwards, state-of-the-art applications in various aspects, including sensing and measurement, actuating and micromanipulation, energy harvesting and magnetic gravity compensation, are summarized and compared. Finally, the review concludes with a brief outlook on future perspectives.     

Laguerre simulation and visualization for microstructure of metal materials

Simulation method was designed to divide Laguerre diagram for right circle group with different weight; out-of-core incremental algorithm for Laguerre diagram was constructed; simulation program development and visualization was done and simulation was realized in user-specified arbitrary area for simulation of metal materials microstructure, which facilitated the practical application and secondary development of Laguerre diagram in the field of material science engineering. Finally, the utilization of a developed software package exemplified the simulation application of microstructure about metal materials and proved its validity.     

金属材料干摩擦特性的实验与仿真研究

基于单自由度弹簧阻尼器模型和Mindlin理论模型,通过金属材料干摩擦动态特性实验,得到了干摩擦迟滞特性曲线以及等效刚度与等效阻尼变化规律.随着两接触面间相对位移幅值的增大,摩擦力等效刚度单调下降,并且趋于平缓,而摩擦力等效阻尼则随位移幅值的增大而单调上升,并且在无量纲相对位移幅值为2.0附近达到最大值后随位移幅值的增大而单调下降.通过比较分析实验数据和两种理论模型的计算结果发现,当无量纲相对位移幅值小于1.0时理论模型无法反映系统的刚度与阻尼特性.利用有限元分析软件MARC建立了与实验相一致的有限元预测模型.对比分析表明,有限元模拟结果与实验结果具有较好的吻合程度,有限元方法可以帮助分析工程实际中金属材料的干摩擦特性.     

铁路散堆装货物密度计量装置的研究

散堆装货物在单位容器内的密度 ,是确定装载该货物车厢装载参数的依据 ,提出了利用单片机实现散堆装货物密度计量的方法 ,介绍了其工作原理及软、硬件设计过程 该装置将大大提高散堆装货物计量的工作效率 ,可应用于需进行散堆装货物密度计量的各行业和部门     

碳纤维复合材料周铣加工过程的数值模拟研究

为了对碳纤维铣削过程进行研究,建立了碳纤维复合材料三维周铣加工的有限元计算模型,并研究了切削层简化及材料去除等建模关键技术。通过将周铣力施加到碳纤维复合材料的有限元计算模型,研究了铣削力对碳纤维复合材料的周铣加工过程。通过数值模拟获得了碳纤维复合材料铣削过程中的应力分布情况,数值模拟为碳纤维复合材料切削参数及刀具参数优化研究提供了参考。     

脆性多裂纹扩展问题的近场动力学建模分析

针对脆性多裂纹扩展问题,基于近场动力学（PD）理论开展本构建模与数值方法研究.在常规微弹脆性本构模型基础上引入物质点对的转动,同时在本构力模型中增加能够反映物质点间长程力尺寸效应的核函数,提高计算精度、效率和结果的稳定性.构建能够以统一的模型和算法自然模拟脆性多裂纹扩展全过程的PD数值体系.通过定量分析确定最佳近场尺寸及核函数,通过双裂纹巴西圆盘和多裂纹脆性板的破坏过程模拟验证所提模型和算法,结果表明：改进型PD模型和数值方法可以定性、定量分析脆性多裂纹扩展问题.模拟单轴拉伸荷载作用下双裂纹脆性板的裂纹扩展过程,得到了初始裂纹分布情况对结构破坏形式和承载能力的影响规律.     

Metastable liquid properties and rapid crystal growth of Ti-Ni-Al alloy investigated by electrostatic levitation and molecular dynamics simulation

Electrostatic levitation technique and molecular dynamics simulation were performed to investigate the thermophysical properties, liquid structure and crystal growth dependence on undercooling of Ti₈₅Ni₁₀Al₅ alloy. The liquid Ti₈₅Ni₁₀Al₅ alloy was substantially undercooled up to 335 K (0.18T_L). As undercooling increased, the potential energy of the liquid alloy decreased and the alloy entered into a high metastable state. At this state, the atoms tended to bond with each other and the clusters were inclined to convert into high-coordinated clusters, as confirmed by the fraction of the high-coordinated clusters variation. The enlarged clusters and enhanced local structure stability contributed to the increase of the thermophysical parameters and crystal growth velocity, and eventually dendrite refinement. The density, the specific heat and the surface tension of liquid alloy exhibited a linear relation with temperature and the shear viscosity of liquid alloy showed exponential variation which showed good agreement with the calculation results by molecular dynamics simulation. The growth velocity first increased slowly and then dramatically once the undercooling exceeded the threshold. The achieved maximum crystal growth velocity was 12.4 ms⁻¹ and it was up to 326 times of the value at 94 K undercooling.

     

二元扰动有限元法和应变软化材料的数值模拟

提出二元扰动有限元方法,对具有应变软化的三维复合材料构件进行二元扰动有限元分析.推导基于二元扰动理论(Theory of Duality Disturbance-TDD)的有限元方法(FEM)的基本方程,提出求解基本方程的"相对无扰动结果修正法",开发出二元扰动有限元分析软件-FEAD.测量具有弹塑性软化行为的损伤材料的应力-应变关系,建立扰动函数与塑性应变迹的关系,对具有弹塑性软化行为的三维构件进行有限元分析.材料进入应变软化阶段以后,材料的承载能力下降.有限元分析结果与实验结果相一致.基于二元扰动理论建立的模型能够很好地模拟损伤结构的力学行为,对软化材料力学行为的预测具有优越性.