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321.
层间水对水下双层结构撞击历程的影响分析 总被引:1,自引:1,他引:0
双层壳体结构是潜艇等大型水下结构的重要结构形式,潜艇结构的水下碰撞是潜艇的主要事故形式,然而,针对双层壳体的潜艇结构水下碰撞问题的研究工作目前却极为有限.文中首先提出潜艇碰撞问题,并对其碰撞特征进行分析,然后针对潜艇水下碰撞环境下,层间水对碰撞历程的影响和双层结构的碰撞特点进行了理论分析,在数值仿真计算的基础上,着重讨论了双层板结构在碰撞过程中,层间水对撞击速度、碰撞力以及双层板吸能特性的影响,分析结果显示,层间水对双层壳板撞击历程的影响主要体现在两方面:一是接触初始阶段,耐压壳板将由于层间水的存在,与非耐压壳板组成抗冲击弹簧体系参与抗冲击作用,吸收冲击能量,这对于双层壳板的防撞性能是有利的;二是非耐压壳板穿透后,层间水的影响主要体现为水对耐压壳板的粘附作用,耐压壳板的抗撞能力显著下降. 相似文献
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324.
H.?-Z.?Li L.?LiEmail author L.?He M.?-X.?Kang J.?Song L.?-Y.?Yu C.?Wu 《International Journal of Automotive Technology》2012,13(3):441-450
A Traction Control System (TCS) is used to control the driving force of an engine to prevent excessive slip when a vehicle
starts suddenly or accelerates. The torque control strategy determines the driving performance of the vehicle under various
drive-slip conditions. This paper presents a new torque control method for various drive-slip conditions involving abrupt
changes in the road friction. This method is based on a PID plus fuzzy logic controller for driving torque regulation, which
consists of a PID controller and a fuzzy logic controller. The PID controller is the fundamental component that calculates
the elementary torque for traction control. In addition, the fuzzy logic controller is the compensating component that compensates
for the abrupt change in the road friction. The simulation results and the experimental vehicle tests have validated that
the proposed controller is effective and robust. Compared with conventional PID controllers, the driving performance under
the proposed controller is greatly improved. 相似文献
325.
Y. L. Qi L. C. Dong H. Liu P. V. Puzinauskas K. C. Midkiff 《International Journal of Automotive Technology》2012,13(6):861-872
It is well known that in-cylinder flow is very important factor for the performance of SI engine. An appropriate in-cylinder flow pattern can enhance the turbulence intensity at spark time, therefore increasing the stability of combustion, reducing emission and improving fuel economy. In this paper, the effect of intake port design on in-cylinder flow is studied. It is found a vortex existed at the upper side of intake port of a production SI engine used in the study, during the intake stroke, which will reduce both tumble ratio and volumetric efficiency. A minor modification on intake port is made to eliminate the vortex and increase tumble ratio while keeping volumetric efficiency at the same level. It is demonstrated that the increase in tumble in the new design results in a 20 per cent increase in the fuel vaporization. In this study, both KIVA and STAR-CD are used to simulate the engine cold flow, as well as ICEM CFD and es-ice used as pre-processor respectively due to the complexity of engine geometry. Simulation results from KIVA and STAR-CD are compared and analyzed. 相似文献
326.
S. M. Zhang F. Tian G. F. Ren L. Yang 《International Journal of Automotive Technology》2012,13(5):693-699
The paper presents an innovative method combining artificial neural networks (ANNs) with Fuzzy PID to demonstrate the advantages of this control approach for meeting both NOx emission requirements and NH3 slip targets. An ANN model was utilized to simulate the formation of NOx emissions under various engine operating conditions. Next, an effective closed-loop control strategy with a type of feedback known as fuzzy PID is adopted for on-line, real-time control of 32.5% aqueous urea dosing in the exhaust stream. The new strategy explores the benefits by simulation and testing in the environments of Matlab/Simulink and ESC/ETC, respectively. The notable achievement of considerable NOx reduction and an acceptably small NH3 slip is obtained based on this new, feasible and effective strategy. 相似文献
327.
双层圆柱壳典型基座振动波传递特性优化分析 总被引:1,自引:0,他引:1
采用波动分析法,根据不均质结构中的阻抗特性和波型转换,分析振动噪声在典型双层壳结构中的传递特性。以此为切入点,采用有限元/边界元(FEM/BEM)耦合法分析人为构造的传递损失基座的减振降噪性能。通过对组合板振动波的传递特性的分析可以得出,当定常结构发生突变时,结构阻抗也会随之发生变化,导致结构之间的阻抗失配,从而使得振动波在突变截面处发生反射和透射,降低振动波的传递效率,阻隔振动波能量向下游结构传递。然后,据此理论设计了传递损失基座,并用有限元/边界元耦合法验证了传递损失基座的减振降噪性能。 相似文献
328.
Yan Xing Susan L. Handy Patricia L. Mokhtarian 《Transportation Research Part D: Transport and Environment》2010,15(2):73-81
The majority of bicycling in the US is for recreation rather than transportation purposes but few studies have examined the question of bicycling purpose. We use data from an online survey conducted in 2006 in six small cities in the western US to examine factors affecting bicycling for transportation compared to bicycling for recreation. The results indicate that individual, social-environment, and physical-environment factors have important influences on the balance between transportation and recreational bicycling and on miles of bicycling for each purpose. Bicycling comfort and an aversion to driving are associated with more transportation bicycling. A culture of utilitarian bicycling and short distances to destinations are also key factors for transportation bicycling. Bicycle infrastructure appears to play an indirect role through its effect on perceived bicycling safety and through the self-selection effect, by attracting bicycling-inclined people to bicycling-supportive communities. 相似文献
329.
The practical use of fracture mechanics has been established for use on large turbine and electric generator rotor components used in the atomic power generation and the aircraft industry. Application areas in the offshore industry have also been identified. Fracture mechanics is currently used at the design stage of offshore facilities. It provides the basis for fatigue life prediction, steel selection and tolerance setting on allowable weld imperfections. Fracture mechanics is also used during the operational stage of a structure to make important decisions on inspection scheduling and repair strategies and as a tool for establishing limits on operational conditions. Linear elastic fracture mechanics relies on the use of the stress intensity factor concept. The stress intensity factor is a very important fracture mechanics parameter. Therefore, the accuracy of any fracture mechanics model for the prediction of fatigue crack growth in offshore structures for example will depend very much on the accuracy of the stress intensity factor solution used. Several empirical and semi-empirical solutions have been developed over the years with varying degrees of accuracy. This paper presents a review of some of these methods and attempts to assess their accuracy in predicting Y factors for welded tubular joints by comparing predicted results with experimental data obtained from fatigue tests conducted on large scale welded tubular joints. The experimental results were conducted under simulated service conditions, using a jack-up offshore standard load history (JOSH). A comparison between the experimental and predicted results shows that there may be other factors, which influence fatigue crack growth under variable amplitude conditions. Some of these factors have been identified and discussed in this paper. 相似文献
330.