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681.
682.
More than 40% of the registered fatigue cracks in ship structures are observed to occur in the side shell, more specifically in the connections of longitudinals to transverse web frames. The fatigue damage is caused partly by vertical and horizontal wave-induced hull bending and partly by outside water pressure on the side shell. Due to the non-linear nature of the outside water pressure the fatigue damage of the combined stress cannot be solved via a traditional frequency domain analysis. This paper solves the combination problem by application of a realistic wave model. The proposed model is used to analyze a segregated ballast tanker, and the results are compared to previously registered fatigue cracks. The analysis shows that it is very important to include the water pressure in the fatigue analysis, as this accounts for the majority of the expected fatigue damage. The analysis is performed for both I-shaped and L-shaped stiffeners. 相似文献
683.
Design of Optimal Four-Wheel Steering System 总被引:6,自引:0,他引:6
Young H. Cho Graduate Student J. Kim Assistant Professor 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1995,24(9):661-682
Optimal design of the four wheel steering (4WS) system of the ground vehicle is studied. 4WS vehicles with the optimal control scheme are considered first. General formulation of the optimal control law is developed based on the linear quadratic regulator theory. The vehicle speed function (VSF) based 4WS vehicle with a simple feedback controller is considered as a special case of the optimal system. Two new designs of the VSF 4WS system are proposed and their performances are compared with the optimal 4WS systems and the existing VSF 4WS system. The first system is designed for the maximum stability while the second system is designed to emulate the response of the optimal 4WS vehicle. Advantages of the new VSF designs are discussed. 相似文献
684.
This paper describes a comparative study between full scale measurements recorded on a fast patrol boat encountering heavy winter seas, south of the Isle of Wight and theoretical predictions accounting for the slamming behaviour of the flexible hull. A hydroelastic approach is adopted and satisfactory agreement between measured and predicted responses demonstrated. 相似文献
685.
T. H. Young C. Y. Li 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2003,40(5):329-349
Summary This paper studies the vertical vibration of a vehicle traveling on an imperfect track system. The car body and sleepers are modeled as Timoshenko beams with finite length, and the rail is assumed as an infinite Timoshenko beam with discrete supports. Imperfection of the track system comes from a sleeper lost partial support by the ballast. Since deflection of the rail is limited within a certain interval where the vehicle is passing over, the infinite domain problem can be transformed into a finite domain problem with moving boundary. In this work, the equations of motion of the car body, rail and sleepers are discretized first by the finite element method. The discretized equations of motion for the vehicle and track systems are then assembled, respectively. Finally, the Newmark method is applied to obtain the response of the vehicle and track systems at each time step. The effect of the vehicle speed on the response of the vehicle and track systems is investigated. 相似文献
686.
B.M. Eickhoff J.R. Evans A.J. Minnis 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1995,24(6):469-496
The dynamic behaviour of railway vehicles has been the subject of study for over a century but the advances in computing technology in the last few years have led to a very rapid development in the use of numerical techniques for solving railway vehicle dynamics problems. As these techniques have developed, and have been applied to ever more complex problems, the modelling of the vehicle components has increased in importance. Mathematical models of railway vehicles may now include components such as swing links, air-springs, trailing arm suspensions, load sensitive friction dampers, rubber bushes with hysteresis etc, all of which require sophisticated modelling techniques to produce accurate results. This paper looks at the developments that have taken place in this area, the background to the need for sophisticated models, the improvements in accuracy that can result and some of the difficulties in applying these techniques to the modelling of real situations. 相似文献
687.
A. Sanyal R. Karmakar 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1995,24(8):617-637
The present state of knowledge on the handling behaviour of truck-dolly-trailer system is based on parametric studies made through simulation or eigen value analysis. Any convincing study using the equations to the stability boundaries have not been reported so far due to algebraic complexities. This paper fills the gap. Effects of system parameters are assessed using equations to the stability boundaries obtained from Routh-Hurwitz criterion. The system equations of motion are derived from a bondgraph model of a linearised system. 相似文献
688.
R. S. Sharp lecturer C. J. Jones research student 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1980,9(1):45-57
A simple system capable of wheel shimmy is analysed in three different ways and the results are compared. The tyre in each case is taken to be representable by a “taut string”, and the three ways involve (a) developing a digital tyre simulation which operates sequentially with a digital simulation of the mechanical system, (b) representing the tyre responses by linear constant coefficient differential equations derived empirically to match the string responses, and (c) as in (b) but employing fundamentally derived equations which approximate the exact string responses. The approximations are shown to give good results at reduced frequencies typical of the wheel shimmy phenomenon. 相似文献
689.
T. R. O'Brien 《Maritime Policy and Management》1980,7(4):271-281
The purpose of this paper is to consider some of the issues arising from currency fluctuations or currency disparities and in particular their effects upon freight earnings through the application of a currency adjustment factor (CAF).
The operation of CAFs has been a source of great concern to shippers and shipper's councils since their introduction some seven years ago. The basis of this concern has been the widening differential of applicable CAFs as a surcharge on basic freight rates. The CAF system has been regarded by many as iniquitous and punitive. Conferences have been accused of insulating themselves from currency losses due to exchange-rate variability consequent upon the introduction of flexible exchange rates in 1971. However, this mounting pressure has brought the operation of the CAF formula under close scrutiny especially from four sources.
(a) Some member Councils of the European Shippers' Council (ESC).
(b) The Japanese Shippers' Council (JSC).
(c) The question of the legality of differential CAFs under the Treaty of Rome
(d) Complaints from North Continental Maltsters. 相似文献
The operation of CAFs has been a source of great concern to shippers and shipper's councils since their introduction some seven years ago. The basis of this concern has been the widening differential of applicable CAFs as a surcharge on basic freight rates. The CAF system has been regarded by many as iniquitous and punitive. Conferences have been accused of insulating themselves from currency losses due to exchange-rate variability consequent upon the introduction of flexible exchange rates in 1971. However, this mounting pressure has brought the operation of the CAF formula under close scrutiny especially from four sources.
(a) Some member Councils of the European Shippers' Council (ESC).
(b) The Japanese Shippers' Council (JSC).
(c) The question of the legality of differential CAFs under the Treaty of Rome
(d) Complaints from North Continental Maltsters. 相似文献
690.
This paper describes a set of specialized spreadsheets that model the cost and performance of transit system options including light rail transit, guideway bus, express bus, and ride sharing. These spreadsheets are demonstrated by comparing a guideway bus (GWB) transit system and a light rail transit (LRT) system proposed for construction in an active rail corridor. The comparisons for assumed levels of transit ridership include guideway geometry, travel time, headways, vehicle requirements, grade crossing protection, and capital and operating costs. The planned GWB system runs on an exclusive dual guideway in the rail right-of-way, and the alternative LRT system operates on the existing rails with new bridges and track as needed for a dual guideway system. The analysis compares the two options for mode splits between 0.5% and 50%. Results show that while both options have approximately the same travel time, the GWB system costs approximately 30% less than the LRT system. The cost difference results primarily from lower GWB vehicle purchase and operating costs. The spreadsheets are available through the McTrans Center at the University of Florida, Gainesville, Florida. 相似文献