曲柄增力机构的模拟设计

对曲柄增力机构的增力原理、数学模型等进行了较为详细的分析 ,并用数值模拟的方法求得了增力比的变化规律。结果表明 ,曲柄增力机构可获得较大的增力比 ,其值与铰链 D到连杆 2及 4的距离 l及 m的关系分别为呈正态分布的指数关系和双曲线反比关系     

煤矿井下空调蒸发器对流传热特性试验

对恒定控制制冷剂R407C工作温度为9℃、额定制冷量为45k W条件下的蒸发器进行了模拟矿井条件湿空气的对流传热试验。研究结果表明:蒸发器的制冷量随进口空气温度的升高而增加,随进口空气相对湿度的增加而增加;出口空气温降随进口空气温度的升高而增加,随进口空气相对湿度的增加而缓慢降低;对流传热的Nu数随Re数的增加而增加,随进口空气相对湿度的增加而降低。     

封隔器金属密封元件设计及密封特性研究

采用NiTi合金材料设计一种用于压缩扩张式的封隔器的新型金属密封元件,建立密封元件及其组件的数值模型;提出采用最大应力、坐封力和接触应力对密封元件密封性能进行评价,并分析结构参数变化对其密封性能的影响规律。结果表明:最大应力随膨胀环半径和拱形半径单调增加,随承压环宽度、拱形厚度和卸载槽半径先减小再增大;坐封力随承压环宽度、膨胀环半径、拱形半径和拱形厚度单调增加,随卸载槽半径单调减小;接触应力随承压环宽度、膨胀环半径和拱形厚度非线性增大,随拱形半径和卸载槽半径非线性减小。拱形半径和拱形厚度对密封元件密封性能影响较为显著,且适当减小拱形半径或增大拱形厚度可提高其密封性能。     

退火时间对Cu-Al-O薄膜性能影响的研究

通过制备Cu-Al-O薄膜并对其进行退火处理,研究了退火时间对薄膜形貌、结构以及紫外-可见透过率、带隙、中红外透过率的影响。研究结果表明:随着退火时间的增加,薄膜开始晶化,5.0 h时薄膜中出现裂纹,同时出现AlCu合金相;紫外-可见透过率随退火时间的增加而降低;中红外透过率随退火时间的增加先增加后降低;Cu-Al-O薄膜的直接带隙随退火时间的增加而降低。     

FeSiB非晶薄带的磁感应效应

研究了频率、磁场强度对Fe78Si9B13非晶薄带的磁感应效应及影响磁感应效应变化幅度的因素。结果表明,磁感应效应随着频率的升高而增强,随着磁场强度的增大而减弱;磁感应效应变化幅度随着磁场强度的增大而增大,当频率低于35kHz时,磁感应效应变化幅度随着频率的升高而增大,当频率高于35kHz时,磁感应效应变化幅度随着频率的升高而减小。     

The Effectiveness of Boundary and Hydrodynamic Lubrication when Cold Rolling Aluminum Metal

How hydrodynamic and boundary lubrication affect a lubricant's film strength when cold rolling aluminum was studied using a laboratory mill. The film strength of the lubricant was determined by increasing the amount of reduction until a rapid rise in load and temperature produced a herringbone pattern on the surface of the metal. The hydrodynamic lubrication was changed by increasing the viscosity of the base oil or by increasing the rolling speed. The boundary lubrication was changed by increasing the concentration of the additives or by changing the type of additives. The results of the test showed that either increasing the amount of the hydrodynamic lubrication or increasing the amount of the boundary lubrication were effective ways to increase the film strength of the lubricant; however, the effectiveness of each decreased as the calculated film thickness of the lubricant increased. It is proposed that this can be explained by the decrease in contact area between the work roll asperities and the surface of the sheet as the thickness of the lubricant film increases.     

钢球增力液压夹具的力学计算

介绍了两种应用于液(气)夹其中的钢球增力机构,推出了其理论增力系数和实际增力系数的计算公式,并对它们进行了性能比较.钢球增力机构与无杆液压缸组合而成的夹具,具有力传递效率高,结构简单,制造工艺简便的优点。     

On springback of double-curved autobody panels

The springback of double curved autobody panels is studied theoretically and experimentally. Both steel and aluminium sheets are included in this investigation. The obtained results show that the springback is decreased with increasing binder force, increasing curvature, increasing sheet thickness and decreasing yield strength. This paper comprises also a discussion on the plastic strains and their influence on the springback.     

制动参数对制动系统稳定性的影响

以汽车的制动盘与摩擦片构成的制动系统为研究对象,建立了基于Stribeck摩擦模型的制动系统动力学模型。采用数值仿真的方法就制动系统的初速度、制动压力、阻尼和刚度等制动参数对系统稳定性的影响做了定性的分析,提出了提高系统稳定性的方法。研究结果表明:随着制动初速度的增大,系统的振动幅值也变大,但系统达到稳定状态的时间越短;系统的振动幅值随着制动压力的增大而减小,适当地提高压力可以减小振动;系统的阻尼越大,系统越快达到稳定状态;系统的刚度越大,系统达到稳态运动所需的时间就越长,达到稳定前振动的幅值随着刚度的增大而变小。     

矿用对旋式轴流通风机扩散器结构多目标优化设计

以矿用对旋式轴流通风机为研究对象,应用粒子群优化算法对其扩散器结构设计参数进行了优化。首先,应用实验设计方法研究了通风机扩散器结构设计参数与通风机全压及效率之间的关系。研究结果表明：随着扩散器芯筒尾部半径R1的增大,通风机全压会先降低而后增高;通风机全压随着扩散器出口截面半径R2的增大而减小,随扩散器长度L1的增大而增大。通风机效率随R1、L1的增大而增大,随R2的增大而减小,且L1对通风机效率的影响最为显著。然后,以通风机全压及效率为优化目标,以扩散器结构设计参数为设计变量,应用粒子群优化算法对其进行多目标优化。
     

一种计算低比转速离心泵加大系数的方法

依据离心泵叶轮出口宽度、比转速的计算式推导得出了计算低比转速离心泵流量、扬程及比转速放大系数的计算公式,公式体现了放大系数和叶轮水力参数间的关系。提出了建立在离心泵性能预测基础上的理论计算低比转速离心泵最佳流量、扬程及比转速放大系数的方法,解决了泵行业一直依据经验统计值确定其放大系数不能使低比转速离心泵在设计点效率最高这一问题。实例表明:提出的方法能够提高低比转速离心泵在设计工况点的效率,充实了低比转速离心泵的设计理论。     

并联六坐标测量机的工作空间及其仿真研究

介绍了并联坐标测量机的特点 ,分析了影响并联坐标测量机工作空间的主要因素 ,推导出并联杆长度、运动副转角、并联杆干涉和结构限制等的约束条件。采用一维搜索方法确定了工作空间的边界并推导出其体积公式 ,明确了增大工作空间的途径是增大运动副转角和并联杆行程、适当减小动平台半径     

中浓纸浆泵运行性能试验研究*

中浓纸浆泵是中浓输送环节的核心设备,其运行性能直接影响着输送系统的效率。为了研究不同运行条件对中浓纸浆泵运行特点和性能的影响,设计一种基于声纳流量测试系统的中浓纸浆泵性能试验台。研究分析了纸浆浓度(质量分数)为7.52%, 9.3%, 12.1%,转速为960 r/min, 1 140 r/min, 1 500 r/min和不同排气抽吸真空度时,泵的扬程、效率、出口含气率及最大极限流量变化特征。试验结果表明：随着纸浆浓度的增加,同一流量下扬程、效率逐渐下降。真空度对泵的性能特性有显著的影响,在不抽真空条件下,中浓纸浆泵可实现7.52%浓度纸浆的输送,但随着流量的增加,扬程、效率明显下降;随着抽吸真空度的增大,扬程逐渐升高,且存在一个最佳真空度值使得泵效率最高,泵出口纸浆的含气率逐渐降低。扬程随转速的增加而升高,泵出口纸浆的含气率降低;所需真空度随转速的增加而减小,表明提高泵转速有利于纸浆中气液的分离从而降低所需的真空度值。泵出口纸浆中含气率随着纸浆浓度的增加而升高,同时所需的抽吸真空度也迅速增加。最大流量极限值随着纸浆浓度的增加而减小,随转速的增加而增加。     

转速对直叶片升力型风轮动力特性影响数值研究

采用非定常k-ω湍流模型和滑移网格技术,对旋转直径3 m、高3 m和叶片弦长0.44 m的直叶片升力型风轮动力特性进行二维数值研究,分析在三种不同转速下单叶片动力特性、叶轮动力特性及叶片表面压力特性的变化规律。研究发现：随转速增加,上盘面叶片动力矩极高值先增加后减小存在最大值,下盘面动力矩极低值在逐渐减小且范围变广,证明上盘面为风轮的主要做功区域,下盘面对风轮出力贡献少甚至为负值;随转速增加,上盘面叶片表面压力差在增大,吸力面负压增加幅度较明显,压力面增加幅度较缓,证明吸力面对出力增加的贡献更大;叶轮整体出力由上盘面力矩、下盘面力矩和转速三个因素决定,只有均衡三者关系才能增大风轮整体出力。     

Tribotechnical properties of sintered bronze strengthened by aluminide of Ti–46Al–8Cr

The influence of ultrafine powder Ti–46Al–8Cr intermetellic addition obtained by MASHS on tribotechnical properties of Bro10 sintered bronze has been investigated. The addition of aluminide makes it possible to decrease the instantaneous friction coefficient of sintered bronze under concentrated loading upon friction with 40X hardened steel by 1.2–1.3 times upon continuously increasing loads by two times and to reduce temperature in the friction area by 1.15–1.6 times while increasing the wear resistance by 20 times upon permanent loadings and by 35–40 times upon continuously increasing loading.     

某水下热动力系统热爆事故的润滑失效原因分析

针对某水下热动力系统换速试验中多次出现的旋转燃烧室头部的热爆事故，基于流体力学、传热学以及数值计算的理论和方法，充分考虑了密封环节在整个系统中的工作环境变化，给出了一种关于旋转密封失效原因的工程分析方法。得出以下主要结论：(1)缓慢的系统升速过程不会引起摩擦面处温度的超调，系统的安全性可以得到保证；(2)过快的系统升速过程会造成摩擦面处的温度超调，超调量随换速过程的加快而增大，且较大幅度的温度超调会造成润滑失效，从而引发热爆事故。根据以上分析将系统过渡过程放慢，热爆事故得以有效地避免，多次热乍试验证明了文中理论和分析的正确性。分析方法和采取的措施已经应用于工程实践。     

Dry-sliding tribological behavior of Fe–Ni alloys

The paper reports the dry-sliding tribological behavior of Fe_100−x–Ni_x (x=20,23,25,30) alloys with various martensite fractions. For all the alloys, the friction coefficient decreased with increasing applied load and increased with increasing sliding speed, but there was nearly no difference between the different alloys. The wear rate of the alloys increased with increasing applied load and decreased slightly with increasing sliding speed. Microstructures had great influence on the wear behavior of these alloys. The Fe₇₇Ni₂₃ alloy with well-proportioned martensite exhibited the best wear resistance.     

气氛压力对水下高压干法全位置焊缝成形的影响

研究水下干焊空气环境压力对全位置打底焊接参数及焊缝质量的影响规律。研究表明,环境压力对焊接熔深有一定影响,在环境压力由0.1 MPa增至0.7 MPa时,平焊时的打底焊电流需相应线性递减,上坡焊、仰焊打底电流在0.1～0.3 MPa范围下降较快,之后变化不大,而下坡焊焊接电流在0.1～0.7 MPa范围内呈平缓下降趋势。环境压力对接头力学性能有较大的影响,随着环境压力的增加,焊接接头的抗拉强度、冲击韧度有下降的趋势,而焊缝和热影响区的硬度有上升的趋势。     

Effects of extrusion variables on temperature distribution in axisymmetric extrusion process

A numerical method was developed to simulate the non-steady-state temperature distributions during forward extrusion process. The velocity, strain rates, and strain fields within the deformation zones during extrusion were obtained, using upper bound method of analysis to obtain internal heat generations coupled to the necessary heat transfer conduction equations. The computer program written in C++ language essentially simulates the extrusion process and takes into account extrusion variables such as material properties, friction conditions, extrusion velocity, extrusion ratio, die preheat temperature, billet height, percentage reduction in area, and die land length. The effects of billet height and percentage reduction in area on the temperature distributions within the dead metal zone give good agreements with experimental results. It is found that the higher the billet's heights and higher the percentages reduction in areas, the higher the temperature rises during the extrusion process. The die land zone shows increasing temperature rise with increasing friction coefficient, while increasing friction coefficient has no effect on the dead zone temperature. Also, increasing speed of deformation shows an increasing dead zone temperature rise than a more gradual die land temperature rise. It can be stated that the extrusion temperature increases proportionally to the increase of the container temperature.     

铰孔孔径增大的工艺探析

通过对铰孔孔径增大，误差大产生原因的工艺探讨、分析，提出了有效、切实可行的避免措施，通过灵活应用，提高了产品质量。