Increasing the wear resistance of reworked parts of transport engines

The article describes new mixed technology for increasing the wear resistance of parts of transport engines based on the example of a crankshaft. The basis of the new mixed technology is the heat treatment of crankshaft pins and the application of a multilayer antifriction coating in one technological cycle. Laboratory tests on mixed technology application revealed an increase of wear resistance of crankshaft pins, a reduction in the coefficient of friction, a reduction in the running-in period, and an increase in the scoring resistance and operating life of the crankshaft.     

Refined simulation of friction power loss in crank shaft slider bearings considering wear in the mixed lubrication regime

Friction reduction is a fundamental factor in decreasing fuel consumption of internal combustion engines. During the design stage of the engine the simulation of friction in the crank mechanism plays a vital role to develop optimum solutions. Due to the interaction of oil and elastic structures with rough surfaces in slider bearings, complex simulation models have to be used for representing the relevant physical behavior. The following article is focused on crank shaft slider bearings of large engines.The article describes a procedure evaluated by measurements showing how to model wear profiles of slider bearings to reach a high quality friction forecast. A fundamental influencing factor of bearing friction is given by the mixed lubrication regime and it is considered in the simulation model as part of asperity contact friction and hydrodynamic friction. Further effects result from the compliance in radial and width directions of the bearing structure and the wear of the bearing surface. Furthermore, the specific operating conditions of the slider bearing such as load, temperature, shaft speed and oil characteristics are essential and have to be taken into account.The objective of this investigation is to propose the wear profile of the bearing surface for the simulation model to be treated iteratively, where simulation results for the amount of mixed lubrication are successively assessed. For this purpose an iterative procedure is introduced and validated by measurements on a slider bearing test rig.The applied simulation method is based on elastic multi-body systems; the lubrication film contact is calculated based on Reynolds differential equation via the pressure balance calculated iteratively in the time domain. The model accounting for the mixed lubrication regime is based on the theory of Greenwood and Tripp.     

Tribotechnical properties of thin-film coatings obtained by the tribomodifcation of crankshaft pins for ship diesel engines

The tribotechnical properties of thin-film coatings obtained as a result of the tribomodification of 40Kh steel by various organic-inorganic tribotechnical materials (natural inorganic and synthetic polymers), as well as the compositions and composites created based on vermiculite are considered in the work. Comparative tribotechnical tests have made it possible to establish that the most promising materials for the tribomodification of the friction surfaces of steels are nanostructured composites based on vermiculite, which make it possible to get the minimum coefficient of friction and high wear resistance of the conjugation under the friction condition at boundary lubrication.     

Predicting the propagation of damage in roller bearings of aircraft engines by vibration analysis

This work represents the results of testing roller bearings for wear. In this study, we have measured vibration overloads and analyzed them with regard to the occurrence of damage in bearing parts. We have determined the relationship between the vibration intensity and the type of damage in working surfaces of roller bearing parts.     

基于轴心轨迹分析的热真空齿轮机构磨损监测系统

在空间齿轮机构热真空实验中,轴心运动轨迹能够反映轴承的磨损程度.由于空间齿轮的轴心位移很微小,传统的电涡流传感器测量法并不适宜,据此提出采用加速度信号测量和二次积分的方法测量轴心的运动轨迹,并根据该原理设计验证了一个基于轴心轨迹分析的热真空齿轮机构磨损监测系统:采用3个位于不同测试点的3轴加速度传感器作为敏感元件,并采用"同时采样,分时转换"方法,使用一个经济型采集卡实现九路信号的同步采样,在低成本条件下精确实现了被测点的运动合成.文末给出并分析了该系统应用于空间齿轮机构的实测轴心轨迹.     

基于虚拟样机的D-100/8-c型空压机曲柄连杆机构的运动学仿真

用Pro/Engineer,建立D-100/8-c型空压机曲柄连杆机构的实体模型,利用机械系统动力学仿真分析软件ADAMS,对曲柄连杆机构进行仿真;得出活塞的位移、速度、加速度曲线图;为进一步优化设计和技术改造提供参考。     

基于虚拟样机的D-100/8-c型空压机曲柄连杆机构的动力学仿真

本文用Pro/Ensineer,建立D-100/8-0型空压机曲柄连杆机构的实体模型,利用机械系统动力学仿真分析软件ADAMS,对曲柄连杆机构进行动力学仿真;得出活塞的位移、速度、加速度以及各运动副处的力,曲线图;为进一步优化设计和技术改造提供参考.     

Analysis of the abrasive wear mechanism by successive observations of wear processes in a scanning electron microscope

Single-point scratch tests, using a semispherical pin made of hardened steel, on the flat surfaces of brass (60Cu-40Zn) and S45C (0.45C steel) and SUS304 (18Cr-8Ni austenitic stainless steel) steels were carried out under dry and lubricated conditions in a scanning electron microscope. Successive observations in the scanning electron microscope show that the abrasive wear mechanism can be classified into the following four types: cutting, flaking, wedge formation and ploughing. The transitions between the different types of abrasive wear occurred at critical degrees of penetration which are strongly dependent on the conditions of lubrication. The ratio of the wear volume to the groove volume was highly dependent on the four types of wear.     

采用微分法确定曲柄滑块机构最大行程速比系数

曲柄滑块机构,瞬间传动角愈大,其运动性能愈好;单向工作的曲柄滑块机构,行程速比系数愈大,急回特性愈强,工作效率愈高.采用微分法,以机构允许的最小传动角[γ]为设计依据,以机构行程速比系数为函数,对设计变量求导联立,导出机构能够实现最大行程速比系数kmax的函数表达式,绘制出函数曲线,并得出结论:机构最大行程速比系数k一只与许用传动角[γ]有关,且随着[γ]增大而减小.     

用双重曲柄滑块机构范成加工高速凸轮的研究

通过对高速凸轮的设计加工问题进行研究,提出了一种新型的由双重曲柄滑块机构组成轮轮廓范成装置。对该范成凸轮的运动动力学进行了分析,并对加工刀具的误差补偿及其它主要的加工工艺进行了简要讨论。     

Reduction of the scanning time by total variation minimization reconstruction for X‐ray tomography in a SEM

Total variation minimization is applied to the particular case of X‐ray tomography in a scanning electron microscope. To prove the efficiency of this reconstruction method, noise‐free and noisy data based on the Shepp & Logan phantom have been simulated. These simulations confirm that Total variation minimization‐reconstruction algorithm better manages data containing low number of projections with respect to simultaneous iterative reconstruction technique or filtered backprojection, even in the presence of noise. The algorithm has been applied to real data sets, with a low angular sampling and a high level of noise. Two samples containing micro‐interconnections have been analyzed and 3D reconstructions show that Total variation minimization‐based algorithm performs well even with 60 projections in order to properly recover a 500 nm diameter void inside a copper interconnection.