Friction of fuel-rod casings and spacing cells in the pile of a water-cooled,water-moderated reactor

Fuel-rod casings and spacing cells are subjected to frictional tests, with variation in the technological and operational factors.     

Friction and wear of fuel assemblies in water-moderated reactors

Static and dynamic processes that involve frictional forces are experimentally studied. The frictional forces affect the stress of the fuel assembly in all stages of the life cycle.     

Three-dimensional inspection of grid spacers of fuel assemblies of nuclear reactors using diffractive optical elements

The method for inspecting grid spacers (GSs) using diffractive optical elements is considered. Synthesis of diffractive elements, calculation of projecting optics, and also adjustment and calibration of the measurement system are presented. Methods for processing images obtained on different GS elements are described.     

长庆油田套管腐蚀与防腐技术研究

针对长庆油田套管腐蚀的特征和现状,分析了油田套管的腐蚀机理和腐蚀模拟试验的研究情况,归纳总结了长庆油田采取的一系列套管防腐措施和技术。     

Finite element analysis of the three-dimensional transient temperature field in steam turbine casings

One of the important considerations going into the process of optimization of start-up schedules for steam turbines is the estimation of thermal stresses during the transients. This in turn requires prediction of the transient temperature fields. In the case of the turbine casing, the procedures are complex in view of the irregular geometrical shape. Finite element analysis offers better scope in this regard and has been employed in the present work to compute the 3-D transient temperature distribution in the casing metal. The results obtained by a code developed for a specific type of turbine casing have been compared with the values measured by experiment and have been found to validate the code. Time-temperature histories for two typical locations inside the casing metals are presented. Isotherm surfaces across the metal at a given instant are shown.     

Stress-strain state and thermal state of rubber-cord casings of highly elastic couplings

A solution of the steady thermoelastic problem is proposed, taking account of the dependence of the elastic and thermophysical constants of the material on the temperature and strain. As an illustration, the stress-strain state and thermal state of rubber-cord casings for highly elastic couplings (of diaphragm and toroidal type) and cylinders for pneumatic-tire couplings are calculated.     

Strength and working parameters of covers with rubber-cord casings of different designs

A method is proposed for calculating the basic structural parameters, operational characteristics, and strength of covers with rubber-cord casings. The method may be used in developing new designs for temporary covers of petroleum pipelines and covers for sewage and heating pipes.     

摩擦圆辊直径与摩擦包角对板成形摩擦系数测量的影响

基于Duncan方法设计了一种板料成形摩擦系数测试装置,用以考察摩擦圆辊的直径和摩擦包角对摩擦系数计算的影响。正交试验分析表明:随着摩擦圆辊直径和摩擦包角的增大,由板料弯曲和包角边界造成的摩擦系数计算干扰效应将逐级减小,进而计算摩擦系数也逐步减小,并且最终趋向真实摩擦系数。基于最终试验分析结果,得出包角在90°,圆辊直径在30 mm左右时,测得的摩擦系数可以忽略弯曲效应和包角边界效应,能反映真实摩擦状态,可以用于后续的金属板料成形有限元模拟。     

湿式制动轴对称摩擦生热与摩擦因数/热磨损特性分析

多片式湿式摩擦制动器工作中产生大量的摩擦热,引起摩擦工作表面产生局部高温、表面氧化和材料系数变化。其中热疲劳磨损和热摩擦因数两者的变化对制动稳定性的影响非常重要,通过建立基于"轴对称"梯度变化的摩擦热流及对流换热热传导数学模型和摩擦因数及热磨损与相关参数响应特性函数模型,分析了摩擦副的瞬态温度、制动时间与摩擦因数、热磨损量、热磨损率之间的对应分布。分析结果表明:温度、时间的变化对摩擦因数、热磨损有很大的影响,通过控制温度、时间可以改变摩擦副材料的摩擦因数、热磨损量,从而在紧急制动、持续制动过程能够减少事故的发生率,同时在研究新材料的摩擦特性及磨损相关性提供了一定的理论依据。     

Stribeck Curve Under Friction of Copper Samples in the Steady Friction State

The friction and wear of a pure copper block (99.98 wt% Cu) against a hardened steel disc were studied. The effect of sliding velocity and load on the friction coefficient and wear rate of Cu samples during steady tests was studied. Elasto-hydrodynamic (EHL), mixed (ML) and boundary lubrication (BL) regions were analyzed using the Stribeck curve. The lubrication number of Schipper, Z, was used in the analysis of the Stribeck curve. The transitions from one lubrication region to another are discussed. The mixed EHL region is characterized by stable low values of the friction coefficient, wear rate and temperature. Straight asperity contact is the dominant mechanism under friction of Cu–steel pair in the BL region. High-friction coefficients and wear rates, thin lubricant films and large wear grooves indicate straight asperity contact between rubbed surfaces in the BL region. Although the dominant mechanisms in the mixed EHL and BL regions are different in principle, a steady friction state is preserved in both cases. It is expected that the steady friction state in the BL and mixed EHL regions is associated with deformation and fracture of surface layers but these process occur at different scale levels. It was shown that under friction of Cu–steel pair, two types of ML regions are observed. The first is the stable steady friction of mixed EHL with low values of the friction coefficient and wear rate. The second type of the ML region is the region of unstable friction and wear when a decrease of lubricant film leads to a change of external (roughness, temperature, friction and wear) and internal (strain and stress) parameters. It was found out that a transition to the unstable ML region occurs within a narrow range of Z parameter under definite values of the load and sliding velocity.     

Friction and the bowed string

Some aspects of bowed string vibration are discussed with particular emphasis on a regime which is sensitive to details of the friction-velocity characteristics. Apart from its intrinsic interest this study may shed light on the behaviour of other friction-driven oscillators since the rather successful theoretical modelling developed for the bowed string may be applicable to other problems. Conversely, bowed string studies may be able to benefit from the interaction with other work on friction.     

纳米CaCO3半金属摩擦材料摩擦磨损性能的研究

使用定速摩擦试验机研究了纳米CaCO3对半金属摩擦材料性能的影响。结果表明：在半金属材料中，用纳米CaCO3代替普通的CaCO3粉体，在混料过程中，纳米CaCO3粒子粘附在其他颗粒和钢纤维表面上，热压成型过程中，作为粘结剂的树脂材料与这些材料之间的结合强度降低。在摩擦过程中，造成表面颗粒在剪切力的作用下，很容易与基体脱离，从而使得摩擦材料的摩擦因数偏小，而磨损率却大大增加。     

Flow visualisation studies and the effect of tongue area on the performance of volute casings of centrifugal machines

The present paper deals with flow visualization studies and the effect of tongue area on the performance of the volute casings of centrifugal machines with a swirling flow free from jets and wakes at their inlet. The flow visualization studies by wool tuft movements were conducted in the volute channel as well as in the exit diffuser and interpreted according to Moore and Kline[1]. Flow separation was observed at high inlet swirl angles near the volute tongue as well as in the exit diffuser. It was found that the volute performance was strongly dependent on the tongue area at low and high inlet swirl angles.     

Study of Friction and Wear Characteristics of the Friction Pair of Centrifugal Brake Rollers

In the article, the structure of a bench for testing the friction characteristics of a friction pair of centrifugal brake rollers has been considered. The dependences of the coefficient of friction and wear on the temperature of the materials of the friction pair, viz., a brake insert manufactured by Huzhou Jiutong Logistics Machinery Co., Ltd (China) and a domestic friction pair of the 6KV-10 rolled brake band of the EM-2 grade over St.3 steel grade (A537Gr.58), were obtained for temperature ranges that do not exceed 100°C. It has been shown that the rubber–PA6 friction pair widely used in brake rollers of foreign manufacture cannot be employed at high values of the slip velocity and the normal force applied to the friction lining, as it results in rapid heating to the critical temperature and, as a consequence, intensive wear. The domestic 6KV-10 brake band of the EM-2 grade, along with a metallic roller shell is proposed as the material of the friction pair. The frictional material proposed for the friction lining has a high coefficient of friction and a high wear resistance in a wide range of operating temperatures, normal forces, and temperatures of the frictional contact.     

液体分散剂-辐射器条件下液压马达中摩擦副摩擦磨损性能研究

在加有特制添加剂的工作液体条件下,在液压实验台上进行了液体分散荆.辐射器实验,考察了轴向柱塞马达的缸体(钢)-配流盘(青铜合金)摩擦副的磨损特性,得到摩擦副磨损化学成分中子有效分析的结果,实验表明依靠合适的液体添加剂,利用金属选择传导可以有效减小摩擦副磨损.     

聚氨酯弹性体摩擦衬垫材料的摩擦特性研究

本文研究了聚氨酯弹性体摩擦衬垫材料的摩擦特性,发现聚氨酯弹性体材料的动摩擦系数是和滑动速度有关的,在0．0l-0．4mm／s的速度范围内,速度提高摩擦系数上升,在更高的速度下摩擦系数还会下降。聚氨酯弹性体材料的静摩擦系数是比较难以确定的,本文建议把滑动量较小而滑动速度又很低的这一时期的摩擦称为“初期摩擦”,它是界于静摩擦与动摩擦之间的一种特殊的摩擦状态。文中还分析了粘着摩擦机理,提出了接点化学粘接机理。并根据这种机理对实验结果进行了分析和讨论。     

湿式摩擦副滑摩过程摩擦热计算

针对湿式离合器摩擦副的结构特点,研究离合器摩擦副表面粗糙接触情况,改进平均流量模型,建立修正的雷诺方程用于计算滑摩过程中油膜压力和油膜厚度的变化规律。采用Greenwood-Tripp接触模型,建立摩擦副摩擦热方程,模拟湿式摩擦副在滑摩过程中油膜厚度、相对滑摩转速、接合油压以及摩擦转矩变化规律,对摩擦副滑摩过程中微凸体和油膜剪切作用产生的摩擦热进行分析,得到它们径向呈线性和抛物线的分布规律,讨论接合油压和相对滑摩转速对微凸体和油膜剪切作用产生摩擦热的影响,并通过钢片的温度场实验对模拟结果加以验证。研究表明:接合油压越大,单位时间内微凸体和油膜剪切作用产生的摩擦热越大,单位时间产生摩擦热峰值的时间越提前;相对转速差越大,微凸体在滑摩过程中单位时间产生的摩擦热越大,油膜则与之相反,且相对转速的变化对单位时间产生摩擦热峰值的时间无影响。     

摩擦对橡胶胀管的影响及减摩研究

1　前言橡胶胀管机是一种新型的胀管机械 ,它以液压为动力 ,以橡胶为胀管介质 ,通过挤压置于换热管内橡胶弹性体 ,完成换热器、锅炉等的胀管作业 ,其胀头结构如图 1所示[1] 。图 1　胀头结构图胀头的芯轴上套装一个橡胶弹性体 ,两端依次为密封圈和挡圈 ,工作时将胀头伸入欲胀接的管端内 ,胀接时液压活塞抽动芯轴 ,使得橡胶弹性体轴向受压 ,径向发生膨胀 ,迫使管子端部与管板发生弹塑性变形而胀合 ,液压活塞动力撤除后 ,橡胶弹性体立即恢复原状 ,管子与管板仍留有残余接触压力 ,管端与管板结合在一起 ,完成胀接。胀接过程中 ,橡胶弹性体在轴…     

Friction variation in the cold-rolling process

Friction variation along the rolling contact interface was measured by a ‘sensor roll’ embedded with sensors on an experimental rolling mill. The measured results show that the friction coefficient is not constant along the contact length. Empirical formulae describing the friction variation for certain rolling condition were obtained. Experiments were also carried out to study the surface roughness of the strip. It was found that the roll and strip surface roughness can be transferred to each other along the rolling direction. Only slight change of roughness in the transverse direction was observed.     

机械密封端面摩擦机制与摩擦状态

机械密封端面摩擦状态是决定机械密封工作寿命和密封性能好坏的关键因素.从微观角度探讨了机械密封端面摩擦机制,分析了机械密封端面分别处于干摩擦、边界摩擦、流体摩擦和混合摩擦状态时的工作特性,介绍了机械密封端面摩擦状态的判断方法,分析了端面摩擦状态对机械密封性能的影响.对于普通机械密封,端面的最佳摩擦状态应该是混合摩擦状态,如密封性能要求较高,则应该是边界摩擦状态.