转速和不平衡量对轴颈涡动中心影响的比较

首先运用达朗伯原理结合里茨法建立了非线性油膜力作用下的多自由度转子一轴承系统的运动方程,对转子部分进行模态降阶,然后运用变步长的Newmark数值积分方法研究了转速和不平衡量对轴颈涡动中心的影响.通过理论分析和实验测试发现:轴颈涡动中心不仅决定于轴颈转速和静载荷,而且还受不平衡量和振动幅值的影响,并且与转速的影响相比是同数量级的,因此在进行无试重动平衡时,采用只考虑转速影响的轴承动力系数,识别结果就会产生较大的误差.     

高速磨削中的快速现场动平衡技术

本文研究高速高精度磨削中的快速现场动平衡技术。利用线性系统的基本理论对砂轮一主轴系统的不平衡响应进行了分析。论证了快速现场动平衡技术的基本原理并提出了一种实用的快速现场动平衡方法。平衡过程由预平衡和现场动平衡两个步骤构成。对一定安装条件的砂轮-主轴系统，通过预平衡测定不平衡量与轴承座振动幅值的比例常数及振动量相对于不平衡量的滞后角。利用测出的比例常数和滞后角，对高速磨削过程中出现的不平衡振动，可实现转子系统一次试加重的快速动平衡。可在数分钟内使转子的残余不平衡量降低至原始不平衡量的5％以下。实验表明该方法具有平衡精度高，平衡速度快，易实施的特点。     

弯曲转子系统的模态动平衡方法研究

针对具有初始弯曲转子系统的动平衡,提出一种基于模态平衡的单平面加校正量的方法.算例验证结果表明:该方法可以在转子系统一阶临界转速左右及以下的转速范围内很好地平衡转子系统的初始弯曲,而且在该转速范围内也能很好地平衡转子系统可能同时具有的质量不平衡.但在用该方法平衡转子系统的初始弯曲时,由于在不同转速下所求得的校正量是不同的,所以从严格意义上来说,每一个校正量只能平衡相应的一个转速,但可以结合采用转子系统自动平衡头来达到比较完善的动平衡效果.     

各向异性支撑的单元盘转子系统的不平衡响应研究

转子各向同性的理论无法解释许多不平衡相关的振动现象,基于转子系统中刚度和阻尼各向异性的特点,建立了具有非线性刚度的转子系统动力学模型。分别研究了在忽略和考虑非线性刚度系数的情况下不平衡响应的变化规律。结果表明:对于线性模型,不同的不平衡量下其不平衡响应为一组同心椭圆,椭圆的初始相位角随偏心角度变化;对于非线性模型,不平衡响应椭圆的方位角和离心率随着不平衡量的变化而改变,表现出较强的非线性。该结论为全矢动平衡的应用提供了理论基础。     

基于LabVIEW的现场动平衡在线测试系统

为了适应转子现场动平衡的需要,提高测试精度,开发基于虚拟仪器技术的现场动平衡测试系统,利用相关法准确提取出振动信号的幅值和相位,采用影响系数平衡的方法进行动平衡实验。在车床主轴上进行多次转子动平衡试验,试验结果表明:转子在加适当的试重后不平衡振动得到了有效的抑制,振动幅度明显减小,达到了旋转机械所要求的平衡精度。这对于减小机器噪声和轴承磨损、提高机器的性能和寿命有着重要意义,同时也有助于提高机器的工作效率和保障机械加工操作者的安全。     

无试重的动平衡技术的研究

平衡配重过程作为动平衡的一个重要步骤,会直接影响到动平衡的质量。探索了平衡配重与平衡量之间的关系,不平衡量与振动之间的关系。经理论分析与实验研究,导出了关于平衡配重的数学表达式。依据该式,机械仅停车一次,可实现无试重的动平衡。最后,在转子上随机增加不平衡量后,使用现场动平衡技术,对该结论进行了验证。     

稳态和非稳态油膜力模型下的转子系统非线性特征比较

以多自由度转子系统为对象，运用模态降阶和变步长的Newmark积分方法，分析了油膜力模型按稳态和非稳态短轴承理论计算时的非线性振动特征，同时比较了两种油膜力模型下转子不平衡量的大小和转速对轴颈振动的涡动轨迹、频谱及其稳定性的影响，通过与实验比较分析了两种油膜力模型的实用性。     

平衡面轴向位置对影响系数动平衡法的影响

影响系数动平衡法原理简单,易于操作,但因未涉及到不平衡振动的力学本质,使得平衡效果波动较大。通过对配重质量求解过程的分析,指出了动平衡不稳定性与平衡方程组的病态本质有关。利用模态叠加法对影响系数进行描述,并建立了平衡面轴向位置参数与方程组病态特性之间的联系。在此基础上以多叶片转子系统为例,进行有限元仿真计算。计算结果表明:影响系数方程组的病态特性受平衡面位置的影响较大,合理选择位置参数可降低动平衡中的误差干扰。     

高速主轴在线动平衡调控实验研究与特性分析

为了解决高速主轴运行过程中产生的振动造成主轴加工精度低、零件表面质量差等问题,运用NI虚拟仪器对振动信号采集、处理,通过输出信号控制电磁式平衡装置内部的铁齿与配重盘上的永磁体相互作用,实现主轴在线动平衡。搭建实验平台,通过多次实验找到了主轴共振转速范围,并分析机械主轴转速与实验平台振动之间关系。改进了旋转机械初次试加质量块经验公式,分析初次试加质量大小与主轴振幅之间关系。结果表明:运用影响系数平衡方法,主轴振动降幅明显、平衡效率提高,残余不平衡量降低,电磁式平衡装置在线动平衡实验结果为高速主轴平衡调控提供理论依据与实验支持。     

全矢动平衡方法平衡精度的实验研究

在全矢谱理论基础上,参考转子动平衡的影响系数法,提出全矢动平衡方法;并提出基于主振矢的动平衡效率计算公式,以平衡效率作为平衡精度的度量值,通过转子实验台的单面和双面动平衡实验对分别以水平振动、垂直振动和全矢不平衡响应为测量项的动平衡方法的平衡效率进行横向比较。实验结果表明,全矢动平衡方法较传统动平衡方法具有较高的平衡精度。     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

INTRODUCTION TO PATENTS

The invention provides a method of making a mold which can reduce SOx generation rate while preventing decrease in hardening rate in the case of using sulfuric acid for a hardener composition. The method has a mixture step in which fire-resistant particles, a hardener composition and a binder composition are mixed to obtain a composition for a mold. The hardener composition contains sulfuric acid. In the mixture step, sodium carbonate is added. A molar ratio of the sulfuric acid to the sodium carbonate is 0.5 or more and 4.0 or less.     

China Foundry Week 2014

China Foundry Week, hosted by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） each year, is a large academic event in China. It is one of the ten high-impact activities sponsored by the Chinese Mechanical Engineering Society.     

17th Conference of Hydrodynamic and Electromechanical Control Engineering Call for papers

正1.Contents In order to promote the academic exchanges and technical communication of the research in the field of fluid power transmission and control,fluid control engineering specialized committee of the Chinese Society of Theoretical and Applied Mechanics will hold the 17th Conference of Hydrodynamic and Electromechanical Control Engineering on July 27-29,2014 in Tibet,Lhasa city.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.     

Rheology Feature of Simple Metal Melt

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.