齿轮传动滑动系数分析和等磨损变位系数选择

1．1 滑动系数计算相啮合的一对渐开线齿廓齿轮传动,由于两齿廓在啮合点处的线速度不同,所以齿廓间必然要产生相对滑动,齿轮啮合传动过程中在法向压力的作用下。

基于TBM刀盘剖面轮廓的滚刀极径优化布置设计

为解决目前滚刀极径布置研究中多采用V型滚刀、未考虑边滚刀变切深的特性并忽略了全断面岩石掘进机(TBM)刀盘剖面轮廓与滚刀极径布置的耦合机制问题,提出了一种基于刀盘剖面轮廓的滚刀极径布置的适应性设计方法.基于CSM受力模型,以最外侧边缘滚刀的轴承受力为评价指标,根据刀盘过渡区域大小、过渡圆弧半径及安装倾角范围之间的关系,确定其剖面轮廓.推导出常截面滚刀的破岩量公式和基于变切深的边滚刀磨损量公式.采用遗传算法,基于等寿命原则,对中心刀和正刀的极径进行优化设计;基于等磨损原则,建立非线性数学模型,对边刀的倾斜角进行优化设计.以MB264-311-8030mm型TBM刀盘为例,计算结果表明,与原始滚刀极径相比,51把滚刀中最大差距仅有25.8,mm,为刀盘半径的0.64%,可忽略不计,充分验证了该方法的可行性和有效性.

大口径牙轮钻头设计中存在的问题及其改进方法

硬岩中钻进是基桩孔钻进中的一大难题．不少工地试图用牙轮钻头钻进基岩，但一直未取得理想的效果。大口径牙轮钻头在硬岩中钻整低，磨损快．不少研究者指出，其原因主要是钻压过低而又无法加压所致．但在现场，一些用石油钻牙轮装配的钻头，不加压时难以转动，因而无法增加钻压．本文从运动学方面分析了钻头所存在的这一问题．提出了纯滚动牙轮钻头的设计方法．并考虑了如何使钻头上内外周牙轮等磨损以提高钻头寿命的问题。

Tribological properties of nanostructured Al_2O_3-40%TiO_2 multiphase ceramic particles reinforced Ni-based alloy composite coatings

The Ni-based alloy composite coatings reinforced by nanostructured Al2O3-40%TiO2 multiphase ceramic particles were prepared on the surface of 7005 aluminum alloy by plasma spray technology. The microstructure and tribological properties of the composite coatings were researched. The results show that the composite coatings mainly consist of γ-Ni, α-Al2O3, γ-Al2O3 and rutile-TiO2 etc, and exhibit lower friction coefficients and wear losses than the Ni-based alloy coatings at different loads and speeds. The composite coating bears low contact stress at 3 N and its wear mechanism is micro-cutting wear. As loads increase to 6-12 N, the contact stress is higher than the elastic limit stress of worn surface, and the wear mechanisms change into multi-plastic deformation wear, micro-brittle fracture wear and abrasive wear. With the increase of speeds, the contact temperature of worn surface increases. The composite coating experiences multi-plastic deformation wear, fatigue wear and adhesive wear.

Effects of graphite content on microstructure and tribological properties of graphite/TiC/Ni-base alloy composite coatings

In order to reduce the friction coefficients and further improve the anti-wear properties of Ni-base alloy coatings reinforced by TiC particles,graphite/TiC/Ni-base alloy（GTN） coatings were prepared on the surface of 45 carbon steel.The effects of graphite content on the microstructure and tribological properties of the GTN coatings were investigated.The results show that the addition of graphite to the GTN coatings may greatly reduce the friction coefficients and improve their wear resistance.The 6.56GTN and 12.71GTN coatings exhibit excellent integrated properties of anti-friction and wear resistance under low and high loads,respectively.Under a low load,the wear mechanisms of the GTN coatings are mainly multi-plastic deformation with slight abrasive wear and gradually change into mixture of multi-plastic deformation,delamination and micro-cutting wear with the increase of graphite fraction.As the load increases,the main wear mechanisms gradually change from micro-cracks,micro-cutting and adhesive wear to micro-cutting and micro-fracture with the increase of graphite fraction.

卵砾石地层隧道盾构刀具选型研究

从国外引进的盾构机刀具配置不能适应我国部分城市砂卵石地层卵石粒径大和石英含量高的特点,刀具磨损及冲击崩裂严重。本文总结我国砂卵石地层中盾构刀具布置的常用形式及其效果,结合南京纬七路过江隧道穿越砂卵石地层中盾构刀具选型与布置,提出盾构刀具布置不仅要遵循几何对称和力学对称原则,而且要遵循等磨损原则,注意不同刀具之间的协同作用;砂卵石地层中,正面刮刀(切削刀)和贝型先行刀组合,再辅以其他刀具;在刀具配置中,要慎重考虑贝型先行刀的布置间距和贝型先行刀与刮刀高差的取值。

二段旋流器使用乐泰陶瓷防护剂

旋流器运转中充满给定密度的悬浮液，二段旋流器的内壁、入料短节及矸石出口短节等磨损非常大。一般使用周期为8个月，入料短节使用周期12个月，而矸石出口短节使用周期仅6个月。二段旋流器内壁贴有陶瓷片（图1），一般入料口处磨损较大，

大口径牙轮钻头设计存在的问题及其改进方法

硬岩中钻进是基桩孔钻进中的一大难题，不少工地试图用牙轮钻头钻进基岩，但一直未取得理想的效果，大口径牙轮钻头在硬岩中钻速低，磨损快。不少研究者指出，其原因主要是由钻压过低而又无法加压所致，便在现场，一些用石油钻牙轮装配的钻头，不加压也难以转动，因而根本无法增加钻。本文从运动学方面分析了钻头所存在的这一问题，提出了纯滚动牙轮钻头的设计方法，并考虑了如何使钻头上内外周牙轮等磨损以提高钻头寿命的问题。

几种非金属材料在水泥行业的应用

在水泥厂，普遍采用普通钢板或铸铁作为耐磨材料，应用于非标溜子、钢仓等磨损较为严重的部位；但是在水泥厂的有些地方，因工作环境条件的限制，存在局限性。如：下料钢仓，因物料本身物性、经常出现粘仓，堵塞下料口，造成配料不匀，影响产质量；粉煤灰输送，要求管道耐磨、不堵料等。

Wear and corrosion resistant coatings on surface of cast A356 aluminum alloy by plasma electrolytic oxidation in moderately concentrated aluminate electrolytes

Plasma electrolytic oxidation of a cast A356 aluminum alloy was carried out in aluminate electrolytes to develop wear and corrosion resistant coatings. Different concentrations of 2, 16 and 24 g/L NaAlO2 solutions and a silicate electrolyte （for comparison） were employed for the investigation. Wear performance and corrosion resistance of the coatings were evaluated by WC （tungsten carbide） ball-on-flat dry sliding tests and electrochemical methods, respectively. The results show that the coating formed for a short duration of 480 s in 24 g/L NaAlO2 solution generated the best protection. The coating sustained 30 N load for sliding time of 1800 s, showing very low wear rate of -4.5×10^-7 mm3/（N· m）. A low corrosion current density of -8.81×10^-9 A/cm2 was also recorded. Despite low α-Al2O3 content of the coating, the compact and nearly single layer nature of the coating guaranteed the excellent performances.

Layout design for disc cutters based on analysis of TBM cutter-head structure

Studies to date have failed to consider gage disc cutters’variable cutting depth and the constraints of cutter-head welds,and have ignored the coupling mechanism between the profile of the full-face rock tunnel-boring machine(TBM)cutter-head and the assembled radius layout of the disc cutters.To solve these problems,an adaptive design method for studying cutter layout was proposed.Taking the bearing stress of the outermost gage disc cutter as an index,the profile of the cutter-head was determined.Using a genetic algorithm and based on the principles of equal life and equal wear,the assembled radii of the cutters were optimally designed.Boundary conditions of non-interference between the cutters,manholes,muck buckets and welding lines were given when a star layout pattern was used on cutters.The cutter-head comprehensive evaluation model was established by adopting relative optimization improvement degree of evaluation indices to achieve dimensional consistency.Exemplifying the MB264-311-8030 mm tape TBM cutter-head,the calculations show that compared with the original layout scheme,among the 51 disc cutters,the largest gap of the cutters’assembled radiuses is only 25.8 mm,which is 0.64%of the cutter-head’s radius and is negligible.The cutter-head’s unbalanced radial force decreases by 62.41%,the overturning moment decreases by 33.22%,and the cutter group’s centroid shift increases by only 18.48%.Each index is better than or approximately equal to the original cutter-head layout scheme,and the equivalent stress and deformation are both smaller;these results fully verify the feasibility and effectiveness of the method.

Wear modes in open porosity titanium matrix composites with TiC addition processed by spark plasma sintering

This work focused on the influence of TiC reinforcing particles on the tribological properties of titanium matrix composites(TMCs)with open porosity,processed by spark plasma sintering(SPS).Materials composed of an equimolar mixture of Ti and TiH2 with 0,3,10 and 30 vol.% of TiC were sintered at 850 ℃.Nanoindentation and wear tests were carried out to assess the nanohardness and the wear resistance in a tribometer with a reciprocating sliding ball-on-flat configuration.Results showed a nanohardness increment from 5 to 14 GPa with increasing TiC content.The coefficient of friction(CoF)showed a minimum of 0.2 for 10% TiC grade,which also showed the lowest wear rate.For the low TiC content sample,adhesive wear with severe plastic deformation was identified.Meanwhile,medium content TiC sample showed a mechanical mixed layer(MML),whereas high TiC content composite showed abrasive as the main wear mechanism.In conclusion,the wear mechanisms,CoFs and wear volume changed with TiC content.

Mechanical properties and wear resistance of medium entropy Fe40Mn40Cr10Co10/TiC composites

The Fe40Mn40Cr10Co10/TiC (volume fraction of TiC, 10%) composites were synthesized in combination of ball milling and spark plasma sintering (SPS) in the present work. Mechanical properties and wear resistance of the Fe40Mn40Cr10Co10/TiC composites were individually investigated. It was found that TiC particles homogenously distributed in the Fe40Mn40Cr10Co10/TiC composite after being sintered at 1373 K for 15 min. Meanwhile, grain refinement was observed in the as-sintered composite. Compared with the pure Fe40Mn40Cr10Co10 medium entropy alloy (MEA) matrix grain, addition of 10% TiC particles resulted in an increase in the compressive strength from 1.571 to 2.174 GPa, and the hardness from HV 320 to HV 872. Wear resistance results demonstrated that the friction coefficient, wear depth and width of the composite decreased in comparison with the Fe40Mn40Cr10Co10 MEA matrix. Excellent mechanical properties and wear resistance could offer the Fe40Mn40Cr10Co10/TiC composite a very promising candidate for engineering applications.

Wear and corrosion behavior of clay containing coating on AM 50 magnesium alloy produced by aluminate-based plasma electrolytic oxidation

This study aims to examine the effect of clay micro particles addition on the microstructure,wear and corrosion behavior of PEO coatings on AM 50 magnesium alloy.PEO coatings were prepared using an aluminate-based electrolyte with and without the presence of 5 g/L clay particles.The structure and composition of the coatings were evaluated using SEM,EDS and XRD.The wear investigations were conducted using a ball-on-disk tribometer at 2,5 and 10 N loads.The corrosion behavior of the coatings was examined using polarization and EIS tests in 0.5 wt.%NaCl.The results revealed that the addition of clay particles deteriorated the wear resistance of the coatings under the loads of 5 and 10 N.The SEM examinations of the worn surfaces indicated that a combination of adhesive and abrasive wear mechanisms was activated for the coating with clay particles.The poor wear performance of the clay-incorporated coating was related to its lower adhesion strength and higher roughness.The potentiodynamic polarization examinations revealed that the addition of clay particles slightly decreased the corrosion rate of the coatings.Corrosion resistance of the clay-containing coating was attributed to its compactness,as indicated by the results of EIS tests.

Comparative study on tribological properties of isostatic graphite and carbon graphite under dry sliding and water-lubricated conditions

The tribological properties of isostatic graphite and carbon graphite under dry sliding and water lubricated conditions were studied.The friction test was conducted by using a pin-on-disc tribometer.The friction coefficient and the wear rate were employed to evaluate the tribological performances of the two materials,and wear morphology was used to analyze the wear mechanism.The results show that the friction coefficient of the isostatic graphite is larger than that of the carbon graphite under the dry sliding condition,and the wear rate is lower than that of the carbon graphite.Under the water lubricated condition,the friction coefficients and the wear rates of the isostatic graphite decrease obviously.The main wear form of the isostatic graphite is abrasive wear,while the main wear form of the carbon graphite is spalling wear.Finally,the tribological mechanism of the isostatic graphite under dry sliding and water lubricated conditions were systematically analyzed.

Analysis on cavitation erosion resistance of isostatic graphite

Isostatic graphite materials with 8%porosity and 14%porosity were prepared by the cold isostatic pressing process.Cavitation erosion resistance of the isostatic graphite was evaluated through cavitation tests in an ultrasonic vibration system.The volume loss and erosion morphology of the isostatic graphite were adopted to investigate the cavitation erosion resistance of the isostatic graphite.The cavitation test results show that after ultrasonic vibration of 14 h,the volume loss of the isostatic graphite materials with 8%porosity and 14%porosity are 35%and 46%of the carbon graphite material,respectively.The isostatic graphite material with 8%porosity exhibits an outstanding capability to resist cavitation erosion damage,and the cavitation erosion resistance of the isostatic graphite enhances with the decrease in porosity.The damage mechanism of isostatic graphite is brittle fracture attributed to the shock wave and micro jet.The isostatic graphite with low porosity exhibits excellent cavitation erosion resistance due to its fine graphite particles,homogeneous structure and high degree of hardness.

Optimization of shearer sliding boots by plasma cladding with Cr_4MnTi

Severe production conditions in coal mines cause damage and failure problems with the oriented sliding boots of the mechanical shearer. Wear has been an especially vexing problem. Plasma cladding methods were used to study optimized sliding boot design. By cladding the substrate steel the surface may be made of a material more resistant to wear. The iron based alloy Cr4MnTi was coated onto a modified 45 steel matrix material in these tests. The results show that the alloy cladding layer is high strength, has high hardness, and is highly resistant to wear. After hardening and tempering, 45 steel substrate has great tenacity so the combined structure meets the performance requirements for the construction of shearer sliding boots.

如此自用是否该办营运手续

最近我们在稽查工作中发现一辆货车无道路运输证，其行驶证是2004年落户，在检查中该车上没有货物，而该车主以自用为由拒不配合。执法人员对此情况有不同处理意见。一种认为该车没有载货，如车主从事营运，应主动到运管机构申请办理营运手续；另一种认为该车从箱体等磨损情况看，车主以自用不载货为借口是说不通的，请问我们对该车应如何处理？