齿轮泵困油压力抵消部分径向力的方法与措施

为缓解径向力对齿轮泵造成的危害,从考虑困油压力的介质压力分布、径向力计算和径向力抵消结构3个方面提出困油力抵消部分径向力的方法和一款浮动侧板内侧面上的实施结构,并进行实例运算和分析。结果表明:困油抵消法是通过进油侧的部分困油力去弥补该区域进油方向上的介质作用力,从而实现该方向上的径向力趋于0;抵消结构的顶缘导油槽为初步减少径向力的措施,偏置八字形卸荷槽能提供很大的卸荷面积,避免气穴现象的发生,偏置圆形卸荷槽仅能提供较小的卸荷面积,从而获得抵消径向力所需的困油力;案例中的抵消率达46.15%,八字形、圆形卸荷槽的偏置值分别为0.32、0.56 mm,得到困油抵消法在理论上和实施上可行的结论。     

基于CFD的齿轮泵流场解析

卸荷槽的设计是外啮合齿轮泵设计中最重要的部分之一,卸荷槽设计是否合理直接关系到齿轮泵的工作性能和使用寿命。以CBG型齿轮泵为研究对象,运用CFD技术进行流场解析,仿真研究了卸荷槽结构参数和不可控因素对困油压力的影响。结果表明:齿轮泵困油区压力影响因素较多,需要结合卸荷槽结构参数和环境性能参数综合考虑,为卸荷槽的优化设计提供参考。     

齿轮泵的困油研究

在齿轮泵中,常在侧板上开卸荷槽以避免困油,卸荷槽的位置对齿轮泵的性能有很大的影响。然而,关于卸荷槽的位置还未给出一个确定的设计准则。为了确定卸荷槽的位置,必须弄清楚齿轮泵工作中的困油现象。在本研究中,用一个特制的固定侧板型外啮合齿轮泵作被试件,通过其上安装的半导体型压力传感器测量了主动齿轮和从动齿轮所形成的困油区中的压力。试验揭示了卸荷槽的位置和侧隙尺寸对困油区中的压力上升幅值和泵的性能的影     

泵高速用平底直U形卸荷槽的研究与分析

为解决高速齿轮泵困油的卸荷问题,提出了一款极易加工的平底直U形卸荷槽及形位尺寸;并与传统的矩形卸荷槽进行卸荷面积和困油压力的实例对比。结果表明:U形最大卸荷面积增加了13.5%,能有效解决最小困油容积附近的卸荷能力不足问题,且其结构与加工简单;在8 000 r/min高转速下, U形卸荷槽困油的压力峰值增加率为15.9%,压力谷值为-0.26 MPa,其困油现象相对轻微;而矩形卸荷槽的压力峰值增加率和压力谷值分别为25.1%和-0.61 MPa,其困油现象相对严重。     

基于振动与流场耦合齿轮泵困油现象分析

为了解决困油现象的历程和困油压力对齿轮泵工作状态的影响,根据困油条件下齿轮泵齿轮的振动模型,由内部流场数值分析,将困油压力作为耦合的条件,建立了困油条件下的齿轮副振动和内部流场耦合的动态模型,并通过对模型解耦,分析困油压力对齿轮副振动的影响以及困油压力的具体表现形式。通过齿轮泵内部流场进行仿真,和对通过传感器采集的振动信号处理分析,明确了困油压力的大小及位置和困油产生冲击的程度,表明所建耦合模型正确可靠,能够用于困油压力预测、振动冲击分析与困油历程的仿真分析。     

变量齿轮泵的新机制研究与微圆槽的卸荷能力分析

为实现功率和排量的同步变化以节省资源,提出一款齿轮泵变量的新机构,该机构原理简单,由变量弹簧力和高压油压力的动态平衡驱动齿轮副有效啮合宽度的自动变化,从而实现泵功率和排量随有效啮合宽度的同步变化;并就其困油性能与困油卸荷进行深入研究和分析,提出具有微圆结构的卸荷槽;最后,进行实例运算和分析。结果表明:微圆卸荷槽具有更大的卸荷面积和卸荷能力;有效啮合宽度越小,困油压力峰值越小,困油性能越好;反之,困油性能越差,但影响不大。     

泵高速用端楔主环形新槽及卸荷能力研究

为满足齿轮泵高速下的困油卸荷需要,提出一种新的卸荷面积更大、加工更简单的端楔主环形的新卸荷槽。基于齿轮泵的小侧隙困油卸荷原理,给出该槽的结构与尺寸;由三维模型的面积测量方法,测出一个困油周期内若干啮合位置处的卸荷面积;由所建立且被验证的困油压力模型,计算新槽、矩/圆形旧槽在3 000 r/min常速下及新槽在6 000 r/min高速、9 000 r/min超高速下的困油压力。结果表明:新槽的全程卸荷能力强,其中,主环形段的最大卸荷面积较矩、圆形卸荷槽分别增加31%、165%,端楔段的卸荷面积具有近似的直线特征,符合困油流量的线性卸荷要求;新槽常速、高速、超高速下的困油压力峰值使得出口压力分别增加2%、7.7%、14%,困油冲击小;困油压力谷值分别为0.03、-0.22、-0.61 MPa,高速下能避免气穴现象的发生,超高速下须结合较大的侧隙卸荷,方能满足气穴性能的要求等。得出楔环形槽能满足泵高速化下的卸荷要求,且结构简单、易加工。     

泵用双斜型卸荷槽及困油性能分析

为满足渐开线外啮合齿轮泵困油卸荷之需要,提出了一种具有更大卸荷面积、易加工的双斜型卸荷槽。基于常用的矩形卸荷槽,针对双齿啮合区与单齿啮合区之间不同的困油特点和卸荷措施,首先给出了双斜型卸荷槽的结构和形位设计;其次,由三维模型旋转面积的测量方法,得到一个困油周期内的卸荷面积,最后通过所建立的困油模型,进行双斜型、矩形卸荷槽下两类区域内的困油压力仿真。结果表明:双斜型较矩形能大幅提升卸荷面积,其中,双区的最大卸荷面积提升1.17倍,单区提升11.7倍;最大困油压力峰值,双区降低46.2%,对排油压力仅增加4.3%;单区则降低60.2%和仅增加1.6%,可视为无困油现象;双斜型两侧的型线轮廓,均由5个直线段和3个?2.0 mm圆弧段组成,结构简单、易加工等。为卸荷槽创新提供一种新的途径。     

齿轮泵的圆形卸荷槽及其计算——谈CB-B型齿轮泵卸荷槽的改进

一、CB-B型齿轮泵的卸荷槽在外啮合齿轮泵中,两齿轮的重叠系数通常大于1(ε>1),所以在其相啮合的两对齿之间所封闭的容积部分,会产生困油现象(图1)。若不采取措施来消除这种困油现象,将会引起困油容积中的油液压力急剧上升,使泵轴轴承的负荷也急剧增加,并产生振动、压力波动、噪音及工作油液发热等现象;同     

一种异齿数齿轮泵的困油分析

分析具有3个从动轮的异齿数齿轮泵的结构原理;采用扫过容积法,以主动齿轮的转角为变量,建立该异齿数齿轮泵困油体积的计算式,利用相关软件描述具有较小流量脉动率的齿轮泵在3个位置的困油体积变化情况,为卸荷槽的开设及配流盘的设计提供依据。     

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.     

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.     

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.     

Formulas of Tension of Continuous Rolling Process

The development of computer controlled continuous rolling process calls for a mathematical expression that can express the inequality condition of "constant flow". Tension is the link of the continuous rolling process. From the condition of dynamic equilibrium, a differential equation of tension is given out. On the basis of the physical rules established from the industrial practice and experimental studies, the law of volume constancy, the linear relation of forward slip and tension, the state equation of continuous rolling, the formula of dynamic tension, and the formula of static tension have been obtained. These formulae reflect the functional relations between tensions, thickness, roll velocity, and time in the continuous rolling process. It is implied that the continuous rolling process is a gradually steady, controllable, and measurable dynamic system. An assumption of predicting the thickness of a steel plate using these tension formulae is also put forward.