鳞板式输送机链传动系统的改进

针对板式输送机片式链和链轮的主要失效形式,阐述了采用跨齿啮合和减小链传动中的动载荷以减少链轮轮齿磨损及链传动的多边形效应引起的冲击疲劳破坏。     

弧齿锥齿轮在φ2.2M圆锥破碎机的应用

φ2.2M弹簧圆锥破碎机传动轴部的传动齿轮为直齿锥齿轮传动,相互啮合的轮齿是线接触,由于齿轮制造,安装的误差以及传动时的变形,容易产生仅轮齿一端接触的现象,从而引起载荷集中,传动不平稳,承载能力低,传动效率也比较低,容易产生断齿等现象.通过改造直齿锥齿轮传动为格里森弧齿锥齿轮传动,提高齿轮的重合度,从而增大了接触比,减轻了冲击,使传动更平稳,并且降低了噪音:负荷比压降低,磨损较均匀,相应增大了齿轮的负载能力,使用寿命更长:并且可以进行齿面的研磨,以降低噪音,改善接触区和提高齿面光洁度.     

惠斯顿杠杆的设计分析

就包钢轨梁型钢加工线所用的惠斯顿杠杆的结构、原理做简单介绍,详细论述了惠斯顿杠杆的几个设计关键点,包括两链轮的齿数关系、转轴的转速变化规律、链条的拉力、转轴的临界转速,并从设备安装角度做一些说明。     

电渣重熔小型冷轧辊

一、前言冷轧辊是冷轧机上的重要部件,在很大程度上决定着产品质量。冷轧机的工作条件相当苛刻,轧制速度和轧制力迫使它承受可观的动载荷和静载荷,运行中经受冲击和扭     

面齿轮传动系统参数激励振动特性分析

为研究各参数对面齿轮传动系统动态特性的影响,建立了包含齿侧间隙、传动误差、时变啮合刚度、阻尼、支承和外激励等参数的系统弯-扭耦合非线性动力学模型,结合非线性动力学数值分析理论求解并得到了系统在不同参数下的分岔特性.计算结果表明,增加齿侧间隙、时变啮合刚度和传动误差会导致系统动载荷明显增大,而增加啮合阻尼则能有效降低系统的动载荷.     

提高650轧机人字齿轮轴寿命的探讨

人字齿轮轴是轧机的重要另件,轮齿在接触处受交变的接触应力,在齿根部则受交变的弯曲应力,外界载荷的交变性质及齿轮本身的制造与装配精度均产生附加的动力载荷。因此齿轮要有高的接触强度和抗弯强度;足够的冲击韧性;高耐磨性;高传动精度和最低的工作音响。     

合理选择啮合齿轮的模数和齿数

在保证啮合齿轮中心距不变、传动速比近似的情况下，通过合理减小啮合齿轮模数、增加啮合齿轮齿数的方法，可以适量提高啮合齿轮的齿面接触强度。在实际应用中，用上述方法对啮合齿轮进行设计改进，可以解决齿轮由点蚀引发疲劳而失效的问题。     

美国金属粉末工业联合会颁发2002年年度奖

目前 ,美国金属粉末工业联合会颁发了 2 0 0 2年年度奖 ,现根据其网站公布的信息将各种奖项简介如下 :1 加拿大Stackpole有限公司汽车齿轮部制作的链轮齿获粉末冶金制品铁基类大奖。这种 2 8kg重的链轮齿可向驱动链轮传送达 2 1 1 0N·m的转距 ,为了在工作时能承受作用于其上的强大的弯曲应力 ,这种链轮齿被设计的较宽 ,链轮齿的基体由一种特殊的MoMnCr钢制成 ,新产品的主要技术指标是 :最小抗拉强度为 862MPa,最小屈服强度为 82 8MPa,链轮齿的基体密度为 7 0 g/cm3 ,链轮齿齿部的密度为 7 75 g/cm3 ,链轮齿采用CNC液压机压制成形 ,…     

啮合齿轮的模数和齿数的合理选择

齿轮强度的校核计算可以得出，在保证啮合齿轮中心距不变、传动速比相近似的情况下，通过合理减小啮合齿轮模数和增加啮合齿轮齿数的方法，可以适量提高啮合齿轮的齿面接触强度。在实际应用中，用上述方法对啮合齿轮进行设计改进，可以解决齿轮由点蚀而引发疲劳失效的问题。     

变工况过程中球轴承保持架的稳定性

建立了球轴承ADAMS多体动力学模型，考虑轴承各元件之间的相互碰撞作用及摩擦力，分析了变工况下动量轮用球轴承的保持架质心的涡动行为，对保持架的运行稳定性做出了定量的分析。讨论了轴承启动加速度大小、轴向载荷和有无重力场对保持架稳定性的影响。结果表明轴承启动加速度增加，缩短了轴承启动过程的时间，引导面对保持架的引导作用增强，较高的转速更有利于保持架运行的稳定，但较大的启动加速度使得轴承摩擦力矩较大；轴向载荷升高加剧了滚动体与保持架的碰撞，增加了保持架的涡动状态，而且轴向载荷的增加使得轴承摩擦力矩增加；失重状态下保持架与套圈的碰撞加剧，保持架涡动增加。      

宝钢3 BF 高炉大修无料钟炉顶装料设备优化设计

宝钢3 BF高炉大修重建工程中，炉顶装料设备采用旋转受料罐＋吊挂式称量料罐的串罐式无料钟炉顶形式，并优化了各部件的结构。其中旋转受料罐采用大齿圈＋支撑轮＋导向轮取代原设计的带齿回转轴承，上料闸采用单侧油缸驱动取代原设计的双侧油缸驱动，称量压头设计安装在吊杆上，过渡短管代替眼镜阀。     

Determination of Bridge Design Parameters through Field Evaluation of the Route 601 Bridge Utilizing Fiber-Reinforced Polymer Girders

The Route 601 Bridge in Sugar Grove, Virginia, spans 11.89?m (39?ft) over Dickey Creek. The bridge is the first to use the Strongwell 91.4?cm (36?in.) deep fiber-reinforced polymer double web beam in a vehicular bridge superstructure. Construction of the new bridge was completed in October 2001 and field testing was undertaken shortly thereafter, as well as in June of 2002, to assess any potential changes in structural performance. This paper details the field evaluation of the Route 601 Bridge. Using midspan deflection and strain data from the October 2001 and June 2002 field tests, AASHTO bridge design parameters were determined—namely, wheel load distribution factor g, dynamic load allowance IM, and maximum deflection. The wheel load distribution factor was determined to be S/4, a dynamic load allowance was determined to be 0.36, and the maximum deflection of the bridge was L/1,110. Deflection results were lower than the AASHTO L/800 limit. This discrepancy is attributed to partial composite action of the deck-to-girder connections, bearing restraint at the supports, and contribution of guardrail stiffness. It was found that diaphragm removal had a small effect on the wheel load distribution factor.     

Dynamic Performance Simulation of Long-Span Bridge under Combined Loads of Stochastic Traffic and Wind

Slender long-span bridges exhibit unique features which are not present in short and medium-span bridges such as higher traffic volume, simultaneous presence of multiple vehicles, and sensitivity to wind load. For typical buffeting studies of long-span bridges under wind turbulence, no traffic load was typically considered simultaneously with wind. Recent bridge/vehicle/wind interaction studies highlighted the importance of predicting the bridge dynamic behavior by considering the bridge, the actual traffic load, and wind as a whole coupled system. Existent studies of bridge/vehicle/wind interaction analysis, however, considered only one or several vehicles distributed in an assumed (usually uniform) pattern on the bridge. For long-span bridges which have a high probability of the presence of multiple vehicles including several heavy trucks at a time, such an assumption differs significantly from reality. A new “semideterministic” bridge dynamic analytical model is proposed which considers dynamic interactions between the bridge, wind, and stochastic “real” traffic by integrating the equivalent dynamic wheel load (EDWL) approach and the cellular automaton (CA) traffic flow simulation. As a result of adopting the new analytical model, the long-span bridge dynamic behavior can be statistically predicted with a more realistic and adaptive consideration of combined loads of traffic and wind. A prototype slender cable-stayed bridge is numerically studied with the proposed model. In addition to slender long-span bridges which are sensitive to wind, the proposed model also offers a general approach for other conventional long-span bridges as well as roadway pavements to achieve a more realistic understanding of the structural performance under probabilistic traffic and dynamic interactions.     

不同类型塑料螺旋轮啮合强度研究（英文）

This study investigates the strength of plastic helical wheels meshed with enveloping and cylindrical worms whose tooth profiles mesh in line contact with helical wheels.R unning fatigue tests of plastic helical wheels together with a conventional cylindrical involute worm,a line contact enveloping worm,and a line contact cylindrical worm were conducted.T he tooth bearings,tooth temperatures,and fatigue lives of plastic helical wheels meshed with the different worms were examined at various center distances.Main results obtained are as follows:T he lives of both line and point contact wheels depended upon backlash,but the lives of line contact wheels are more sensitive to backlash than those of point contact wheels.At the backlash that maximizes the wheel life,the line contact wheels last longer than point contact wheels at smaller applied torques,but the influence of worm type on wheel life reduced at higher applied torque.     

Spiral CT. Better resolution by increased pitch?

The longitudinal resolution of spiral CT has been investigated in dependence on table increment and beam collimation by use of a phantom. The results show clearly that the pitch (ratio of table increment per tube rotation to beam collimation) alone does not allow one to draw any conclusions about the resolution. Thus, a large pitch can yield a better resolution than the pitch of 1. The individual parameters table increment and beam collimation are more relevant with regard to the resolution than the rate of pitch. An alteration of the pitch can be achieved in two different ways. An increase of the pitch by a decreased beam collimation improves the resolution. In contrast, an increase of the pitch by an increased table increment decreases the resolution. A good spatial resolution of objects with high contrast (bone, lung, enhanced vessels) needs a narrow beam collimation, even if a pitch as high as 2 is necessary for a given scanning coverage. A large pitch does not cause gaps in the data set. Moreover, the patient's radiation dose decreases.     

Evaluation of In-Service Performance of Tom’s Creek Bridge Fiber-Reinforced Polymer Superstructure

The Tom’s Creek Bridge is a small-scale demonstration project involving the use of fiber-reinforced polymer (FRP) composite girders as the main load-carrying members. The project is intended to serve two purposes. First, by calculating bridge design parameters such as the dynamic load allowance, transverse wheel load distribution, and deflections under service loading, the Tom’s Creek Bridge aids in modifying current American Association of State Highway and Transportation Officials bridge design standards for use with FRP composite materials. Second, by evaluating the FRP girders after exposure to service conditions, the project begins to answer questions about the long-term performance of these advanced composite material beams when used in bridge design. This paper details the in-service analysis of the Tom’s Creek Bridge. Five load tests, at 6-month intervals, were conducted on the bridge. Using midspan strain and deflection data gathered from the FRP composite girders during these tests, the aforementioned bridge design parameters have been determined. The Tom’s Creek Bridge was determined to have a maximum dynamic load allowance, IM, of 0.90, a transverse wheel load distribution factor, g, of 0.101, and a maximum deflection of L/490. Two bridge girders were removed from the Tom’s Creek Bridge after 15 months of service loading. These FRP composite girders were tested at the Structures and Materials Research Laboratory at Virginia Tech for stiffness and ultimate strength and compared to preservice values for the same beams. These measurements indicate that, after 15 months of service, the FRP composite girders have not significantly changed in stiffness or ultimate moment capacity.     

Performance Evaluation of Double-Hub Paddle Wheel Aerator

Aeration performance of a 500?mm diameter double-hub paddle wheel aerator was tested in a brick masonry tank of 5.9×2.9×1.6?m3. The prime objective of the present study is to evaluate the aeration performance of double-hub paddle wheels at different dynamic conditions. The results showed that the oxygen transfer simulation curve for double hub almost matched that of a single-hub paddle wheel. However, the power consumption simulation curve for double hub distinctly deviated from that of a single-hub paddle wheel due to the fact that if geometric and process conditions remain the same, a double-hub paddle wheel consumes more power than a single hub. Hence, a separate power consumption simulation equation was developed for a double-hub paddle wheel. The optimum dynamic condition producing maximum standard aeration efficiency is also presented along with a sample calculation.     

Seasonal Deterioration of Unsurfaced Roads

Seasonal deformation of unsurfaced roads was observed over several years and was studied using pavement deterioration models and finite-element analysis. The Mathematical Model of Pavement Performance is a model designed for pavement deterioration prediction and was successfully used for seasonal deterioration modeling because of its flexibility in defining the pavement structure, properties, and seasonal impact. However, these types of models are designed for highways and are somewhat limited in soils characterization and manipulation of the forces at the road–tire interface. Therefore, a three-dimensional dynamic finite-element model of a wheel rolling over soil was applied to simulate local vehicle traffic on a secondary unpaved road. These simulations were used to study the effects of vehicle speed, load, suspension system, wheel torque, and wheel slip on rutting and washboard formation. Modeling results are compared to field measurements and observations.     

Influence of Inclusion on Crack Initiation in Wheel Rim

 Speed increase and heavy-haul of the railway freight car are the effective measures to raise the transport ability of railway, and they have been the new trend for railway freight car development. The increase of speed and axle load will lead to the increase of wheel-rail contact stress, which will make a great change of stress distribution in the whole wheel rim. Goodier equation was employed to analyze the stress state around inclusion and cavity. In the operation of wheel-rail contact stress, stress concentration occurred in the pole of Al2O3 spherical inclusion, while it appeared on the equator of cavity. The critical inclusion sizes of 25t axle load freight car wheel at different velocities, a certain distance away from the tread, were calculated by Murakami equation. By contrast the inclusion state in cast-steel wheel and rolled-steel wheel, the inclusion character in cast-steel wheel determined that it has much more excellent crack resistance than that of rolled-steel wheel. In the meantime, in order to reduce the probability of rim crack, some suggestions were put forward.