Advanced Materials Research Vols. 479-481

Abstract: In most cases, the normal force applied to mechanical systems with friction is supposed to be constant for convenience. However, through experiments, normal vibration has been proved to have an effect on the stability of mechanical systems. Aiming at uncover the effects of the varying normal force on the stick slip motion, a belt driven system with LuGre friction is investigated. The driving velocity is considered as the critical parameter for stick slip occurrence. By means of the Jacobian matrix and the Taylor expansion, the critical driving velocity is achieved analytically as a function of frequency and acceleration of the varying normal force. In addition, the influence of the varying normal force on the size of limit cycles is also studied numerically. Results show that the variation of the applied normal force has an obviously effect on the stability of mechanical systems, and it should not be ignored in the structure design and the stability analysis for high precision mechanical systems.

Abstract: The LuGre friction model well captures most of the friction behavior, but it was very difficult to identify the parameters of the LuGre model. The LuGre friction model, theory of static and dynamic parameters identification of the LuGre model as well as the algorithm based on particle swarm optimization are summarized according to the previous work. Then the programs for the static and dynamic parameters identification are made and analyzed in the environment of Matlab software in detail, and the identification results are given. The work mentioned above will lay the theoretical foundation for the future experimental validations and provide the detailed models, algorithms and programs for the corresponding research issues.

Abstract: Using non-parametric Data Envelopment Analysis (DEA) method, the paper evaluates the efficiency of foreign-invested manufacturing enterprises in Hubei. The results indicate that the efficiency of foreign-invested manufacturing enterprises in Hubei is not high, and the trend is increasing returns to scale.Finally,through the projection analysis, the paper puts forward the countermeasure.

Abstract: The friction coefficient changes of water lubricated rubber bearing according to the temperature under different pressures are tested in the tribology test. The vibration data are collected and processed by B&K PULSE Analyzer Platform and the influences of temperature on the friction coefficient and vibration are analyzed. The results show that the influences of temperature on friction coefficient and vibration are immense; the friction coefficient increases along with temperature rising, especially when the bearing is at a low speed. And the vibration of the bearing is more serious.

Abstract: The tribological behaviour of precipitation-hardening stainless steel 0Cr17Ni4Cu4Nb against 30CrMnSiA steel under sliding condition was tested using the M2000A model wear tester. The surface roughness, hardness and load under the dry or grease lubricated conditions were studied. It indicated that the volume wear, mass wear, wear rate and friction coefficient were all large, and the main wear mechanism was the adhesive wear under the dry friction. The grease lubrication can effectively reduce the volume wear and friction coefficient, and enhance the wear resistance properties of 0Cr17Ni4Cu4Nb. The tribological properties were the best when the surface roughness was 0.8μm under the grease lubricated friction. Meanwhile the volume wear was also small when its hardness was low. The hardness was higher and the friction coefficient was more stable after the heat treatment on 0Cr17Ni4Cu4Nb. The volume wear and friction coefficient were both increased with the increasing of the loads under the grease lubricated friction.

Abstract: Based on ANSYS software and combined with the theory trends on stern shaft seal performance, the steady-state thermal structure coupling and transient thermal structure coupling analysis of stern shaft mechanical seal had been carried on. It showed that the transient thermal structure coupling analysis was more close to the actual condition of stern shaft seal. The result of transient state analysis indicated the thermal-mechanical effect on seal face during starting, and showed that the contact area was decreased especially the temperture rise rapidly inside of the seal.

Abstract: Based on micro-image, the material identification of iron and copper debris in working oil of engineering equipment is researched. By selecting four characteristic parameters of debris image, a debris recognition classifier is designed based on multi-SVM. The materials and types of debris can be fast identified after the model is trained and the identification accuracy is high, thus a new method for fault diagnosis of engineering equipment is provided.

Abstract: To predict and analyze accurately the lubrication characteristics and its influencing factors of main bearing for large low-speed two-stroke marine diesel engine, based on EHD lubrication model of dynamically loaded bearing, coupling simulation between EHD and MBD for main bearing of marine diesel engine was carried out. Systemic models were established separately considering the independent crankshaft of diesel engine and the full shafting of propulsion power plant. Main bearing load, peak oil film pressure, oil film pressure distribution, MOFT and orbital path in one working cycle under rated working conditions were investigated, and simulation results were compared based on both models. The results show that, if the impact of full shafting was considered, the lubrication characteristics of No.8 main bearing changed significantly, the lubrication characteristics of other main bearings were similar as the simulation results of the independent crankshaft model.

Abstract: The wear experimental project on main influencing factor with load, sliding speed, surface hardness and lubrication was instituted by the uniform design, the wear properties were investigated on a MMW-1 friction and wear tester. The predication formula for wear rate was defined. The wear rate predication model was established by the partial least squares based on the test data, the influencing degree on the main influencing factors was analyzed, the results show the influence on wear rate from big to small is in turn load, lubrication, surface hardness and sliding speed. The lubrication property improved is a handy valid path to decrease the wear rate. The check results show that it is a valid method by partial least squares to establish wear predication model based on test data.

Abstract: This paper gives an overview of erosion mechanisms in elbows in oil and gas production systems. The nature of the erosion process itself makes it very difficult to develop some definitive methods or models to prevent or predict the erosion in elbows in all conditions. This paper provides a review of the subject which will help petroleum engineers to handle the erosion problems in oil and gas industry. This review is given of different erosion mechanisms connected with sand erosion and the factors that influence them, and then the review goes on to look at particulate erosion in elbows in more details. Conclusions are then drawn based on the above analyses.