Applied Mechanics and Materials Vols. 52-54

Abstract: This paper presents an experimental study on engine control strategy during gear shifting for a Unimog U4000 equipped with an automated mechanical transmission (AMT) based on the controller area network (CAN) bus. First, an integrated powertrain control system based on the CAN bus is introduced. Second, the ideal AMT gear shifting process is described, and the engine control strategy during gear shifting is proposed. Then, the communication information for the engine control unit (ECU) and transmission control unit (TCU) during gear shifting is determined based on the SAE J1939 protocol. Finally, effectiveness is verified by the experimental results. The experimental results show that: engine control during gear shifting based on the CAN bus can meet the requirement for real-time operation; the engine control strategy presented in this paper during gear shifting can achieve good shift quality with shorter shifting time and less vehicle speed loss.

Abstract: The thermal characteristics of the motorized spindle determines maching qualities and cutting capabilities, and is one of the important factors influencing the precision of the high speed NC machine tool. To improve the performance of the high speed machine tool, it is important to study the thermal characteristics of the motorized spindle. It had been studied in two ways: one is finite element analysis by Ansys software, in which the finite element analysis model was built. According to the actual working condition, the heat source and the heat transfer coefficient of every part are calculated. On this basis, the temperature field and temperature rises were gotten in Ansys software. The other way is temperature rises experiment on the motorized spindle test platform. The result was shown in the form of curve. These two ways shown the same result: the highest temperature rise appears in the area of electromotor, then followed by the rolling bearing .The result provides the necessary theory basis for optimizing the structure of the motorized spindle and establishes a basis for the research and application about the high speed spindle.

Abstract: This paper proposes an improved wavelet threshold denoising method, threshold function by selecting different thresholds to filter out the noisy signal. Firstly, do the wavelet transformation for noisy signal, and then use soft threshold, hard threshold and the improved threshold algorithm to denoising the signal, finally realized by Matlab simulation of wavelet thresholding. Threshold denoising via different methods of simulation experiments show that the improved threshold denoising algorithm can effectively filter plate bonding ultrasonic echo signal in the noise detection and can be a good feature to retain the original signal.

Abstract: Current popular search engines are built to serve all users, independent of the needs of any individual user. A personalized query expansion method based on user's historical interested Web pages (UHIWPs) and user’s historical query terms (UHQTs) is proposed in this paper. When a user submits a query keyword to a search engine, the new algorithm can automatically locate the current user’s implicit search intention and compute the term-term associations dynamically according to the user’s UHIWPs and UHQTs. More personalized expansion terms then will be generated and submitted to the search engine together with the query keyword. As a result, different search results can be returned to different users even though they input the same query keywords. Experimental results show that this method is better than the current algorithm in average precision.

Abstract: How to model a dynamic road network has great practical significance in a vehicle navigation system. This paper has proposed a simplified time-division based on road network model which implicitly takes into account the delay time at various intersections, the degree of a road congestion and the different road quality, but avoids a complicated calculation and collection for these traffic data. An improved Dijkstra algorithm based on the new model has also been given. The simulation results show that the model can work well and the algorithm is efficient.

Abstract: Combined with the supercell technique, the plane wave expansion method is used to calculate the band structures for the in-plane wave of the two-dimensional solid-solid phononic crystals with line defects and the random disorders in either radius or location of the scatterers. The influences of the random disorders on the band structures and guided waves will be discussed. Propagation of the wave with one certain frequency in the waveguiding phononic crystals with different disorder degree is studied.

Abstract: Glass fiber/microcellular unsaturated polyester composites (GF/MCUP) were prepared using the supersaturated gas technology. Technological process included three stages. The effect of processing parameters on average cell size, cell density, impact strength and tensile strength was investigaed by orthogonal experiment. The results indicated that the major factor affecting them was the temperature in stageⅡ(T2). Under the optimizing processing condition, the average cell size of GF/MCUP was about 8 μm and the cell density was 1.57×109 cells/cm3. It was found that impact strength of GF/MCUP increased 88.81 and 188.12 % than that of glass fiber/unsaturated polyester composites (GF/UP) and unsaturated polyester plastics (UP), respectively. The corresponding 16.56 and 69.25 % increase in tensile strength-to-weight ratio were gained over that of GF/UP and UP, respectively.

Abstract: The components in slurry pump suffer serious corrosion abrasion under H3PO4 medium. Presently, High chromium cast irons are often used to produce the components in slurry pump. New high vanadium high speed steel(HVHSS) has been proved to be a more excellent wear resistance material than high chromium cast irons under abrasive wear and rolling wear. In order to apply HVHSS in slurry pump to replace high chromium cast irons, the corrosion properties of HVHSS were tested under different H3PO4 medium concentration conditions. Using back-propagation (BP) neural network, the non-linear relationship between the corrosion weight losses (W) and H3PO4 concentration, corrosion time (C, t) is established on the base of the dealing with experimental data. The results show that the well-trained BP neural network can predict the wear weight loss precisely according to H3PO4 concentration and corrosion time. The prediction results reveal that the corrosion time and H3PO4 concentration have obvious effect on corrosion weight loss of HVHSS. And corrosion weight loss takes on linear relationship with corrosion time and H3PO4 concentration, respectively.

Abstract: The effect of microstructure and mechanical properties on abrasion resistance of the medium-carbon low-alloy steel has been investigated under two body abrasive wear conditions. The results show that the microstructure of the test steel is mastenite and bainite/mastenite when the specimen subjected to water quenching and blow cooling respectively. The hardness of the test steel was over 52HRC when the specimen subjected to water quenching and blow cooling, however, effect of tempering temperature on hardness is slightly. The strength of the test steel is increased with the tempering temperature increased and the impact toughness change slightly under the blow cooling condition. The tensile strength of the test steel is decreased and the yield strength is increased with the tempering temperature increased when the specimen subjected to water quenching and followed tempering. The wear rate is increased with load and the wear mechanism is micro-cutting and microploughing. The wear resistance of bainite/martensite is better than single-phase martensite. The hardness and impact toughness are important factor under two body abrasive wear condition.

Abstract: Opportunistic networks is one of the newest hot research spots in wireless networks after mobile ad hoc net-works(MANET) and wireless sensor networks(WSN). Mobility model describes mobility manners of nodes. It has been widely used in research on wireless network. This paper firstly introduced, classifies, and compares the current familiar mobility models. Secondly, it classifies, and compares the current familiar mobility models. Next, it was discussed that current research focus on new mobility models, analysis of nodes mobility features, trace strategy, and evaluation of mobility model. Finally, this paper involved what calls for further study.