Comparative analysis of the influence of labyrinth seal configuration on leakage behavior

This study analyzed the influence of configuration and clearance on the leakage behavior of labyrinth seals. Both computational fluid dynamics (CFD) and an analytical tool were used to predict the leakage flow of two different (straight and stepped) seal configurations with various clearances. The predicted results were compared with experimental data. The CFD gives a better agreement with the experimental result than the analytical model on average. In the straight seal, the dependence of the discharge coefficient on the clearance is considerable, while it is much smaller in the stepped seal. The CFD captures the entire behavior sufficiently well, but the analytical model overpredicts the clearance dependence in the stepped seal. The CFD also predicts well the influence of the flow direction on the leakage flow. The advantage of the stepped seal over the straight seal becomes more evident as the clearance gets larger. As the clearance becomes sufficiently small, the advantage of the stepped seal reduces.     

Static and dynamic characteristics of the multilayer electromagnetoelastic converter in nano- and microdrives

A generalized structural and parametric model of a multilayer electromagnetic converter is constructed, and the influence of the geometric and dynamic parameters of the converter and the external load on the static and dynamic characteristics is obtained. The transfer functions of the multilayer electromagnetoelastic converter for electromechanical nano- and microdrives are determined.     

Hiper Strut悬架与Macpherson悬架对整车操稳的影响对比分析

Hiper Strut悬架是由Macpherson悬架改进而来,为比较两者对整车操纵稳定性的影响,根据一款国产运动型多用途汽车(Sport Utility Vehicle,SUV)的Macpherson前悬架,设计出适用于该车的Hiper Strut前悬架,保持整车参数不变,利用Adams/Car软件分别建立原型车和改型车的整车模型,通过仿真试验,分析对比两种悬架在整车操纵稳定性上的表现。试验结果表明,Hiper Strut悬架综合性能优于Macpherson悬架。     

Mechanical and control characteristics of simple and multilayer nano- and micro-scale piezo motors

Statistical and dynamic characteristics of simple and multilayer nano- and micro-scale piezo motors with longitudinal and transverse piezo effects are determined.     

Comparative analysis of the characteristics of a low-pressure gas-phase injector

The paper presents the results of comparative research of selected most popular vapor phase LPG pulse injectors. A group of brand new injectors was compared with the ones already in service. The investigations aimed at determining of the parameters of the electromagnetic circuit, involved flow tests and the response time to the pulse. The coil parameters were determined using an RLC bridge for different feed frequencies. For the flow tests, where, for safety reasons, air was applied instead of vapor phase LPG, an original test stand was applied. The same test stand was used for the assessment of the response time. In the flow tests, volumetric flow rate reduced to normal conditions was analyzed at different feed frequencies. The maximum variant of the volumetric flow was also analyzed. The determined response times for the pulse have shown differences depending on the design of the actuator, coil parameters or rigidity of the springs. As a result, only some of the injectors realized their tasks in the pulse-response relation. The presented results may be useful in simulation research as a source of data for the initiation of calculations as well as in the global aspect when estimating the fuel flow rate.     

铸造式和焊接式主轴箱体的动态特性对比分析

利用有限元法和试验模态法对立式加工中心的铸造式和焊接式两种结构的主轴箱体进行了模态分析,分别获得了其前六阶固有频率和振型。通过对比两种方法获得的结果,验证了有限元分析模型的有效性。研究表明,两种主轴箱体的阻尼比接近,但焊接式主轴箱体的各阶固有频率均要高于铸造式主轴箱体的各阶固有频率。并且铸造式主轴箱体的固有频率更接近于机床主轴的常用工作频率,焊接式主轴箱体的则远离此频率。因此对于常用主轴转速而言,焊接式主轴箱体的动态性能要优于铸造式主轴箱体的动态性能。     

Comparative study of micro- and nano-ZnO reinforced UHMWPE composites under dry sliding wear

This is a comparative study between ultra-high molecular weight polyethylene (UHMWPE) reinforced with micro-zinc oxide (ZnO) and nano-ZnO under different filler loads. These composites were subjected to dry sliding wear test under abrasive conditions. The micro- and nano-ZnO/UHMWPE composites were prepared by using a hot compression mould. The wear and friction behaviours were monitored using a pin-on-disc (POD) test rig. The pin-shaped samples were slid against 400 grit SiC abrasive papers, which were pasted, on the stainless steel disc under dry sliding conditions. The worn surfaces and transfer film formed were observed under the scanning electron microscope (SEM). Experimental results showed that UHMWPE reinforced with micro- and nano-ZnO would improve the wear behaviour. The average coefficient of friction (COF) for both micro- and nano-ZnO/UHMWPE composites were comparable to pure UHMWPE. The weight loss due to wear for nano-ZnO/UHMWPE composites are lower compared to micro-ZnO/UHMWPE and pure UHMWPE. The optimum filler loading of nano-ZnO/UHMWPE composites is found to be at 10 wt%. The worn surface of ZnO/UHMWPE composites shows the wear mechanisms of abrasive and adhesive wear. Upon reinforcement with micro- and nano-ZnO, the abrasive and adhesive wear of worn surfaces transited from rough to smooth.     

用矢量方法分析角锥棱镜直角误差对其光路反射特性的影响

通过矢量分析的方法分析了角锥棱镜的直角误差对其光路反射特性的影响。并定量给出了直角误差和出射光的关系     

Comparative analysis of the performance characteristics of mini-drift tubes with different design

Two types of mini-drift tubes differing in desig n of their cathodes-with open and closed geometries-have been experimentally compared. Though their main characteristics are practically identical, two coordinates can be read out of a single tube with the open cathode geometry by recording the signal from the anode wires and the signal induced on the external strip electrodes. This feature will be used to develop the muon system of the PANDA setup (FAIR).     

Adhesive strength and physical, mechanical, and triboengineering properties of nano- and microstructural Al2O3 coatings

The methods of atom-force microscopy and measurement of the nanohardness, elasticity modulus, cohesion forces, and friction coefficient with scratch testing (the scratching method) are applied to study the Al₂O₃ oxide coatings produced by magnetron deposition on Al targets. The morphologies of the coatings are compared when they are produced by the reactive synthesis and magnetron target sputtering and application of oxygen ions in high-frequency plasma. The accomplished study of the tribological and mechanical characteristics demonstrates that the resulting coatings possess stronger hardness and elasticity modulus. Application of the oxide coatings reduces the friction coefficient considerably compared with the substrate; the scratch test reveals higher strength and better adhesion to the substrate. Comparative analysis shows that the Al₂O₃ coatings applied to the nanostructural TiN film are 1.5 times harder than the coatings deposited on steel.     

Studies of thick boundary lubrication — influence of zddp and oxidized hexadecane

The requirements of a test machine to simulate asperity lubrication are discussed. It is shown that if one test specimen is reciprocated against the other at a realistic rate (50 Hz) over a small stroke (±0.5 mm) and at a suitable temperature, the necessary requirements are fulfilled. Electrical resistance is found to be important. The reproducibility of the results is excellent. A thick boundary layer was formed when zinc dialkyl dithiophosphate was added to hexadecane and it was found that there was a considerable improvement in lubrication when the hexadecane was oxidized. The temperature of formation of the thick boundary layer was strongly dependant on the alkyl group and fell with increasing number of carbon atoms. Straight chains were more effective than branched chains     

Wear and bending strain characteristics of artificial hip joint with non-glued stem and UHMWPE femur

The aim of this study was to experimentally assess the effects of loosening between the stem of a cementless artificial hip joint and the femur on the wear and bending strain of the stem during the initial embedding term. The behavior of an ultrahigh-molecular-weight polyethylene (UHMWPE) femur model with this stem was then investigated. The interface between the stem and the UHMWPE femur model is either glued or not glued. Evaluation of differences between the two gluing conditions was conducted using testing equipment equipped with a reciprocating stage for an artificial hip joint. Total wear between the Co–Cr alloy head and UHMWPE socket was measured using a laser displacement meter installed in the axis direction on a main shaft of the tester. We measured the bending strain waveforms of the flexural direction, which was shown by three strain gauges on the upper, middle and lower part of the stem. The present results indicate that the rate of wear was markedly greater for non-glued stems than for the glued stems. In addition, the results indicate that the bending strain in the upper part of the non-glued stem tended to reach the maximum value of bending strain immediately after the femur model section stood upright, whereas the bending strain in the upper and middle of the glued stem tended to reach the maximum value of bending strain immediately before the femur model section stood upright. Furthermore, when the non-glued and glued stems had the same value of bending strain, the average amplitude was smaller for the non-glued stem than for the glued stem by 2–3 dB.     

Conductive composite of UHMWPE and CB as a dynamic contact analysis sensor

There has long been a need to experimentally measure the dynamic contact conditions of important engineering tribological systems, especially those with polymeric bearing surfaces that prove difficult to model. In order to experimentally quantify the dynamic contact conditions of geometrically complex polymeric bearing surfaces, a composite sensor material has been developed. In this study, qualitative morphological analysis of virgin ultrahigh molecular weight polyethylene (UHMWPE) and carbon black (CB) powders, as well as UHMWPE and CB powder mixtures of varying percentages was performed using field emission scanning electron microscopy (FESEM). Quantitative structure and friction analysis using atomic force microscopy (AFM) was performed on cryoultrasectioned block surfaces of compression-molded CB/UHMWPE composite. In addition, the mechanical properties of the composites were quantified using tensile testing, and the force dependence of the electrical properties was examined under dynamic compressive loading.     

Interfacial reaction and its influence on the mechanical properties of the ASZ short fibre-reinforced Al alloy composite

The effect of interfacial reaction on the mechanical properties of the AC8A Al alloy reinforced with ASZ short fibres (ASZ/AC8A composite) was studied. In the ASZ/AC8A composite, the interfacial reaction was observed to proceed between the SiO₂ binder layer and Mg of the matrix to form MgAl₂O₄ at the interface. Formation of MgAl₂O₄ was believed to enhance the interfacial bonding strength, resulting in the improved composite strength. However, the interfacial reaction in the ASZ/AC8A composite always took place at the expense of Mg in the matrix, resulting in the composite devoid of the Mg bearing precipitates such as Al₂CuMg and Mg₂Si. Interfacial reaction mechanisms were investigated for composites containing various Mg contents. The resultant mechanical properties of the composite were measured to determine the adequate amount of Mg within the composite. Microstructural changes of the composite were observed using transmission electron microscopy and differential scanning calorimetry to provide qualitative analyses on the experimental observations.     

Research on the influence of dielectric characteristics on the EDM of titanium alloy

This study investigated the influences of dielectric characteristics, namely, electrical conductivity, oxidability, and viscosity on the electrical discharge machining (EDM) of titanium alloy. A new kind of compound dielectric with optimal processing effect was developed based on the identified effects. Comparative experiments on titanium alloy EDM in compound dielectric, distilled water, and kerosene were performed to analyze the difference in material removal rate (MRR), relative electrode wear ratio (REWR), and surface roughness (SR). The experimental results revealed that titanium alloy EDM in compound dielectric achieved the highest MRR, a lower REWR than that in kerosene, and better SR and fewer micro-cracks than that in distilled water.     

Adhesive wear and frictional characteristics of UHMWPE and HDPE sliding against different counterfaces under dry contact condition

Abstract

The current work evaluates the wear and frictional performance of ultrahigh molecular weight polyethylene (UHMWPE) and high density polyethylene (HDPE) sliding against different metal counterfaces, stainless steel(SS), mild steel (MS) and aluminium (Al), under dry contact condition. The experiments were conducted using pin on disc machine at different sliding distances (0–40·32 km), 15 N applied load and 2·8 m s^–1 sliding velocity. Interface temperatures and frictional forces were measured simultaneously during the sliding, while specific wear rates were determined for every 1·68 km sliding distance. Based on the optical microscopy of the worn surface and wear track, frictional and wear results were analysed and discussed. The experimental results showed that the type of counterface material significantly influences both frictional and wear performances of the selected polymers. This was mainly due to the film transfer characteristics. Higher temperature and friction coefficient for UHMWPE and HDPE were evident when sliding took place against Al counterface. Sliding the polymers against stainless steel showed low friction coefficients compared to other counterfaces.     

The influence of contact geometry on friction and wear characteristics

This paper describes some results of evaluating the influence of contact geometry on tribological characteristics. Friction characteristics obtained for a distributed contact (pin‐on‐disc and block‐on‐ring), a linear concentrated contact (pin and vee‐block and block‐on‐ring) and a point concentrated contact (ball‐on‐disc and three cylinder‐cone) are presented. The wear scars were analysed using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results show different values of friction and wear coefficients for the different types of contact geometry. The paper also assesses the effect of non‐test characteristics, e. g., vibration.     

Antifrictional composites based on chemically modified UHMWPE. Part 2. The effect of nanofillers on the mechanical and triboengineering properties of chemically modified UHMWPE

The mechanical and tribological properties of nanocomposites based on chemically modified ultra-high molecular weight polyethylene are determined. The super-molecular and chemical structure of the nanocomposites based on the block copolymers UHMWPE-grafted UHMWPE and UHMWPE-grafted HDPE are studied by the methods of X-ray structural analysis, IR spectroscopy, scanning differential calorimetry, and electron microscopy. The mechanical and tribological properties of the nanocomposites based on the block copolymers are found to differ insignificantly from those of the nanocomposites on the base of non-modified UHMWPE. The crystallization and formation of super-molecular structure in the heterogeneous materials under study are shown to depend on the heterogeneity of the distribution of the nanofillers. The authors believe that chemical modification in terms of grafting polar monomers is unable to improve the adhesion of the nanofillers to the high-molecular matrix (UHMWPE). Thus, the wear resistance of the UHMWPE-based nanocomposites is mostly governed by the crystallization conditions and type of supermolecular structure formed during crystallization (either spherulitic or lamellar).     

Modeling and analysis of the effects of machining parameters on the performance characteristics in the EDM process of Al2O3+TiC mixed ceramic

Electric discharge machining (EDM) has achieved remarkable success in the manufacture of conductive ceramic materials for the modern metal industry. Mathematical models are proposed for the modeling and analysis of the effects of machining parameters on the performance characteristics in the EDM process of Al₂O₃+TiC mixed ceramic which are developed using the response surface methodology (RSM) to explain the influences of four machining parameters (the discharge current, pulse on time, duty factor and open discharge voltage) on the performance characteristics of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The experiment plan adopts the centered central composite design (CCD). The separable influence of individual machining parameters and the interaction between these parameters are also investigated by using analysis of variance (ANOVA). This study highlights the development of mathematical models for investigating the influences of machining parameters on performance characteristics and the proposed mathematical models in this study have proven to fit and predict values of performance characteristics close to those readings recorded experimentally with a 95% confidence interval. Results show that the main two significant factors on the value of the material removal rate (MRR) are the discharge current and the duty factor. The discharge current and the pulse on time also have statistical significance on both the value of the electrode wear ratio (EWR) and the surface roughness (SR).     

Antifriction nanocomposites based on chemically modified UHMWPE. Part 1. Mechanical and tribological properties of chemically modified UHMWPE

The mechanical and tribological properties of chemically modified UHMWPE are studied. X-ray diffraction analysis, IR spectroscopy, scanning differential calorimetry, and electron emission are used to study the permolecular structure and friction surface of polymers with different amounts of copolymers UHMWPE and LDPE grafted with maleic anhydride. Addition of grafted UHMWPE is shown to have no effect on the viscoelastic properties of the polymer-polymer composite, while the addition of grafted LDPE noticeably improves its performance (ductility, plasticity) while retaining its strength. Chemical modification of UHMWPE significantly improves its wear resistance (two to three times), which is due to the features of polymer crystallization and the formation of a permolecular structure.