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关键词： 谐波传动   双圆弧齿廓   齿廓参数   共轭齿廓   优化设计  

摘要： "双共轭"啮合区间对提高双圆弧谐波齿轮传动扭转刚度和传动精度有重要作用,提出一种增大"双共轭"啮合区间的方法。综合利用分段函数和啮合不变矩阵建立柔轮齿廓弧长参数方程和理论啮合方程,可有效简化谐波传动理论共轭齿廓的求解过程。基于此,以缩小共轭齿廓间差异为目标建立优化目标函数,对柔轮齿廓分别以公切线倾角、公切线纵向长度和凹圆弧齿廓半径为自变量进行单参数及多参数优化设计。研究结果表明,该优化设计方法可实现柔轮齿廓参数的合理选择,保证谐波传动"双共轭"运动的精度。

关键词： 双卧轴搅拌机   传动花键轴   安全系数  

摘要： 通过理论计算和利用三维建模软件Solidworks Simulation对两种形式的传动花键轴进行静力学计算和分析,得到两种花键轴的强度条件和安全系数,从而对搅拌机的优化设计起到一定的指导作用。

关键词： Monte Carlo   Sensitivity analysis   Nuclear data   F-CLUTCH   RMC  

摘要： Recently, there is a need to develop advanced methods of computing eigenvalue sensitivity coefficients to nuclear data in the continuous-energy Monte Carlo codes. One of these methods is the iterated fission probability (IFP) method, which is adopted by most of Monte Carlo codes of having the capabilities of computing sensitivity coefficients, including the Reactor Monte Carlo code RMC. Though it is accurate theoretically, the IFP method faces the challenge of huge memory consumption. Therefore, it may sometimes produce poor sensitivity coefficients since the number of particles in each active cycle is not sufficient enough due to the limitation of computer memory capacity. In this work, two algorithms of the Contribution-Linked eigenvalue sensitivity/Uncertainty estimation via Tracklength importance CHaracterization (CLUTCH) method, namely, the collision-event-based algorithm (C-CLUTCH) which is also implemented in SCALE and the fission-event-based algorithm (F-CLUTCH) which is put forward in this work, are investigated and implemented in RMC to reduce memory requirements for computing eigenvalue sensitivity coefficients. While the C-CLUTCH algorithm requires to store concerning reaction rates of every collision, the F-CLUTCH algorithm only stores concerning reaction rates of every fission point. In addition, the fission matrix method is put forward to generate the adjoint fission source distribution for the CLUTCH method to compute sensitivity coefficients. These newly proposed approaches implemented in RMC code are verified by a SF96 lattice model and the MIT BEAVRS benchmark problem. The numerical results indicate the accuracy of the F-CLUTCH algorithm is the same as the C-CLUTCH algorithm while the F-CLUTCH algorithm requires less memory and has higher computational efficiency. (c) 2015 Elsevier Ltd. All rights reserved.

关键词： Boundary lubrication thermal effects   Thermal analysis   Heat capacity   Thermal conductivity   Automatic transmissions   Self-lubricating composites   TRIBOLOGICAL PROPERTIES   MECHANICAL-PROPERTIES   WEAR PERFORMANCE   DISK CLUTCH   FRICTION   COMPOSITES   PARAMETERS   BEHAVIOR   ROUGH  

摘要： The temperature plays a significant role in the tribology properties and failure of friction materials during engagement of wet clutch. In order to obtain the temperature field of carbon fabric wet clutch, the thermal model was developed and the finite element analysis was conducted with the heat flux, convective and conductive heat-transfer taken into account. The predicted temperatures of thermometer hole were compared with experimental values. The effects of the thermal parameters on the temperatures of engagement and the damage of carbon fabric composites were investigated. Results show the thermal is evaluated as effective and can well predict the temperature field. The lower skeletal density, lower specific heat capacity and higher thermal conductivity are indispensable for the purpose of lowering the temperature of engagement. The highest temperature appears at R = 0.0509 m, where the damage of friction lining easily occurs. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Clutch drum   Material flow   Tooth extrusion   Tooth filling   Two-step extrusion   PROCESS DESIGN   MATERIAL FLOW   SHEET   GEAR  

摘要： The formation of the gear drum clutch involves bulk and sheet forming, and filling the tooth is a key difficulty during the forming process. In this study, four tooth extrusion processes with various extrusion ratios and preform shape were developed, and they were simulated using AFDEX software for examining how the clutch drum influenced tooth forming. Various tooth-filling results were obtained by controlling the extrusion ratio and die cavity in each process. A comparison of the deformation, material flow, and mean stress state among the processes revealed that the stress state was the main determinant of the local flowing material, and it was used to improve the degree of tooth filling. The optimal tooth-filling result was obtained using a two-step extrusion process with an appropriate extrusion ratio and a preform shape.

关键词： Carbon fabric friction materials   Tribological properties   Operating conditions   Wear mechanisms   WEAR PERFORMANCE   POLYETHERIMIDE COMPOSITES   FRICTION MATERIALS   ENGAGEMENT   BEHAVIOR  

摘要： Carbon fabric/phenolic composites with the filaments counts of 12,000 were prepared by dip-coating and hot-press techniques. The effects of operating conditions on the tribological properties were investigated. Results show that the dynamic friction coefficient (u) firstly increases and then decreases as the rotating speed and total inertia increase. However, the friction stability and shudder phenomenon become gradually poor. The influence of braking pressure on u is the largest, followed by the total inertia among the above three operating conditions. The adhesive wear and abrasive wear are the main wear mechanisms during 1000 continuous braking cycles. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Tidal turbine   Counter-rotating   Tandem propellers   CFD   MARINE CURRENT TURBINES   HYDRODYNAMIC PERFORMANCE   FLOW CONDITIONS   DESIGN   POWER   WIND   CURRENTS   BLADE  

摘要： In order to exploit renewable energies form tidal currents, a unique counter-rotating type horizontal-axis tidal turbine was proposed in this paper. Although a counter-rotating type horizontal-axis wind turbine can be taken as a reference in designing the proposed counter-rotating tidal turbine, there are some different characteristics such as the effects of the free surface and the occurrence of cavitation. The unique tidal turbine in this paper was preliminarily designed on the basis of the in-house wind turbine, and then CFD analysis and experimental test were carried out to evaluate its performance. For the extreme conditions where severe flow separation and vortex exist, the comparison of the power coefficients generated by the turbine between the CFD predictions and the experimental data shows not so good. However, good agreement has been obtained for the comfortable blade pitch setting angles and over a range of tip speed ratios, which provides an evidence of validation of CFD analysis. Such results give sufficient confidence that the CFD model set up here is suitable for the further works.

关键词： Aggressive behavior   Maternal care   Orb-weaver spiders   Reproductive investment   EGG-SAC   REPRODUCTIVE SUCCESS   SPIDERS ARANEAE   PARENTAL CARE   NEST DEFENSE   ARANEIDAE   STABILIMENTA   HYMENOPTERA   BIOLOGY   SILK  

摘要： Maternal care in spiders often involves behaviors associated with the protection of eggs and spiderlings against parasitoids and predators (including conspecifics). The females of several species have been documented to move their egg sacs away from natural enemies or to invest in active defense behaviors against web invaders, such as parasitoid wasps or araneophagic spider species, to protect their brood. In this study, we present observations of protective behavior by Uloborus sp. females carrying egg sacs. We also investigated whether brood size and female size influence female aggressive behaviors and response time against an artificial source of disturbance. Females carrying egg sacs almost immediately perceived and reacted aggressively against the artificial stimulus, whereas females without egg sacs moved away or ran to the web margins, avoiding the source of disturbance. The aggressive response was independent of clutch size and female body size, indicating that all females will risk interacting with potential agents of egg mortality. This systematic response by all females with egg sacs may be important for reducing the incidence of attack by the egg predator wasp Bathyzonus sp. (Ichneumonidae).

关键词： Dual clutch transmission   Adaptive optimal control   Starting process   Level of jerk   Frictional energy loss   ENGAGEMENT  

摘要： An optimal control based on the minimum principle is proposed to solve the problems with the starting process of the self-developed five-speed dry dual clutch transmission (DCT). For the slipping phase, the minimum principle and improved engine constant speed control are adopted to obtain the optimal clutch and engine torques and their rotating speeds, with the minimum jerk intensity and friction work as optimization indices. For the stable running phase, the engine torque is converted to the driver's level of demand. The Matlab/Simulink software platform was used to simulate the DCT vehicle in the starting stage. The simulation and related analysis were conducted for different engine speeds and intentions of the driver. The results showed that the proposed clutch starting control strategy not only reduces the level of jerk and the frictional energy loss but also follows the different starting intentions of the driver. The optimum clutch engagement principle was transformed into the clutch position principle, and a test was carried out on the test bench to validate the effectiveness of the optimum clutch position curve. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Wave generation   Wave propagation   Experimental study   Experimental wave flume   Savonius rotor   Renewable energy   ORBITAL MOTION   WATER   DRIVE   FLOW  

摘要： The present experimental study investigates the generation and propagation of regular water waves and their interactions with an in-house fabricated horizontal-axis 3-bladed Savonius rotor in an experimental wave flume (EWF) equipped with a piston-type wave maker with active absorption capability to assess the rotor performance for different parametric conditions namely, wave height, wave period and submergence level in intermediate-to-shallow water depths. The motion of the wave particles around the Savonius rotor is observed during the experiments as well as measuring the power and torque performance of the rotor to make a reliable assessment of the water movement with the rotor positioning for different inflow wave boundary conditions. The wave-to-mechanical energy conversion efficiency (ECE) of the present device is determined for each case to suggest a possible optimum positioning accompanied with optimum wave heights and frequencies for the manufactured small scale prototype. The present results suggest that experimental solutions within the wave flume can provide a proper guideline for performance analysis of such devices in intermediate-to-shallow water depths for further studies of optimization of design of Savonius rotor type sea and/or ocean wave energy conversion devices for different operating conditions provided that optimum physical flow conditions are satisfied. (C) 2015 Elsevier Ltd. All rights reserved.