Advanced Materials Research Vols. 199-200

Abstract: On the basis of the discrete element method (DEM), the non-linear mechanical model of the wear-resistant body surfaces was established. The step, convexity, and scale arranged structures of the wear-resistant surfaces and their abrasive wear systems were established with the software PFC2D®. Through the qualitative analysis on the morphology, the contact-bond fields and the contact-force chains, the minor injuries and the breakaway of the debris of the wear behaviors are observed. Besides, the dynamic force acted on the wear-resistant structures was studied through the quantitative analysis. Numeral simulation shows that the step structure was worn dramatically in its tip part, the convexity structure distributes the stress prominently and the scale structure shows the best wear-resistant function. The wear loss of the front monomers of the step, convexity, and scale structures are 2.43%, 2.02%, and 1.12% respectively after being worn for eight minutes in the simulation, which are in accordance with the experimental results. The numerical simulation on the abrasive wear behavior of the biological wear-resistant structures by DEM helps to reveal the wearable mechanism of the wear-resistant surfaces. Moreover, it provides a new method for studying the bionic wear-resistant surfaces and structures.

Abstract: Surface texturing has been successfully employed in some tribological applications in order to diminish friction and wear. This technology may be used in a piston ring to decrease the friction and wear of the contact between a piston ring and cylinder liner. A numerical simulation of lubrication between a surface textured piston ring and cylinder liner based on the hydrodynamic lubrication theory was conducted. The influence of surface texture parameters on piston ring lubrication performance was obtained by solving the mathematical equations with a multi-grid method. The results show that under the micro-dimple area density of 5%-40% the minimum oil film thickness increases and the dimensionless friction force decreases with the increasing of it. Under the dimple area density of 40%-60%, the minimum oil film thickness and the dimensionless friction force change slightly. Under various dimple area densities the optimum dimple depth at the given working condition in this paper is about 5µm.

Abstract: When two surfaces are brought into contact or at small separations, the liquid between them forms meniscus, which contributes to adhesion and friction. The increased adhesive force and friction are always the substantial cause leading to micro/nanodevices’s failure. In this study, a dynamic contact model of sphere-on-sphere surfaces during nanoscale separation is presented. A numerical analysis of meniscus and viscous forces based on the dynamic contact model has been carried out. During the separation process, the effects of separation distance, initial meniscus height, surface wettability and separating time on meniscus and viscous forces between the contact surfaces are investigated. The results of numerical solution revealed the adhesion mechanism of sphere-on-sphere surfaces during the separation with liquid mediated. The analyses provide a fundamental understanding of the separating process of two sphere surfaces. It is also useful for the design of the de-wetting and antisticking micro/nanoscale surfaces in various devices.

Abstract: A general fuzzy clustering analysis theory method is introduced at first, then a GAFCM algorithm and its implement steps are given. The diagnosis types of the test samples are judged by getting across the most of the Euclid pressing close degree choosing approximately principle. Practice proves that this method can be used to diagnose the diesel engine vibration faulty.

Abstract: The static performance of an aerostatic bearing with angled surface self-slot-compensation is analyzed. The consistent condition was applied to unitize the Reynolds equation of different forms and the finite element method (FEM) was used to solve the equation. The load carrying capacity (LCC) and the stiffness of the bearing was obtained and the influence of the geometric parameters was discussed. It is concluded that this self-compensating aerostatic bearing can achieve a good performance; the geometric parameters of the gap are interactive, and should be rationally matched.

Abstract: Fracture accidents often take place along the whole clapboard or block in cylinder block of diesel engine during its stand test. From the analysis of the macroscope fractography of the fracture plane and stress, it indicates that the failure of cylinder block was induced by the generation and extension of crack and local plastic deformation and the inching fretting fatigue are the main causes of crack initiation, while alternating cyclic load is the power of crack propagation. The paper represents some corresponding methods to prevent or avoid fracture accidents based on our profound research, and the study lays the reference and foundation for diesel engine design and testing.

Abstract: The subject relationship between the AM500 Shearer malfunction omen and reason is fuzzy, therefore, in the thesis we draw fuzzy mathematic method into Shearer malfunction diagnosis, bring forward setting up the fuzzy membership grade method which is based on the history data and expert preferential ordinal number, found the fuzzy diagnostic model, carry out the fuzzy diagnosis on AM500 Shearer malfunction in computer.

Abstract: The friction and wear behaviors of three kinds of spherical plain bearings with PTFE woven liners were investigated by a high oscillating frequency and heavy load tribo-tester. Dry sliding tests were carried out at an oscillating frequency of 1.2Hz and four different loads. With the help of SEM and EDS, the differences of worn surfaces of the three kinds were investigated. The results indicate that the wear depth and friction temperature for the three kinds of bearings show increasing trend with the increasing of load, while the friction coefficient is the opposite. The comprehensive performance of bearing II is the best in the whole course of experiment, while the bearing III is the worst. The adhesive and abrasive wear mechanisms are appeared on the surface of liners. The quality of boning influences the tribological property of the spherical plain bearing.

Abstract: Abuse conditions of torsion and vibration occurred on crankshaft should be eliminated or diminished during the engine design process. 3D model of the crankshaft is set up by means of the simplified crankshaft system, using the concentrated quality method. FEA software was used for analyzing the different vibration amplitude orders. Two models with absorber and without absorber were compared and tested. The results of torsional vibration amplitudes-speed and so on are benefit to the new product development for eliminating the potential mechanical harm.

Abstract: The analysis of underwater structure vibration and noise control has been paid more attention now. The problem about propeller exciting force transfers from shafting, the bearing supporting to structure, causing structure radiated noise is less studied. It is necessary to study the characteristic of coupled system for solving such problem. In this paper, the characteristic of shafting and underwater structure coupled system vibration power flow is analyzed by numerical method and experimental method. The finite element method was adopted to build the analysis model. The force transfer ratio at each bearing supporting are calculated. The transfer function from propeller force to structure response are studied. The vibration characteristics of coupled system are got by numerical method and experimental method. The results show that the coupling vibration effect of shafting and shell are significantly especially at low frequency. The whole coupled system can be excited by propeller force. Some methods should be proposed to reduce this kind of vibration.