Sharif Digital Repository

A new criterion for prediction of train derailment is presented in this paper. A 2 DOF wheel-set model is used to identify the main dynamic parameters that affect wheel-set derailment. Using these parameters and conventional definition of derailment coefficient, a new criterion for prediction of wheelset derailment is introduced. The proposed criterion, in addition to providing the required precision in prediction of wheelset derailment, it requires measurements which are easy to perform. To evaluate the capability of the new criterion in prediction of derailment, a full wagon model with 48 DOF was used. The wagon model is a 3-D, non-linear model of a train passenger car. The model includes... 

A new criterion for prediction of train derailment is presented in this article. A three-degrees-of-freedom (3 DOF) wheelset model is used to identify the main dynamic parameters that affect wheelset derailment. Using these parameters and conventional definition of derailment coefficient, a new criterion for prediction of wheelset derailment is introduced. The proposed criterion, in addition to providing the required precision in prediction of wheel set derailment, requires measurements that are easy to perform. To evaluate the capability of the new criterion in prediction of derailment, a full wagon model with 48 DOF moving on a track with different random irregularities was used. The track... 

A new criterion for prediction of train derailment is presented in this paper. A 2 DOF wheel-set model is used to identify the main dynamic parameters that affect wheel-set derailment. Using these parameters and conventional definition of derailment coefficient, a new criterion for prediction of wheelset derailment is introduced. The proposed criterion, in addition to providing the required precision in prediction of wheelset derailment, it requires measurements which are easy to perform. To evaluate the capability of the new criterion in prediction of derailment, a full wagon model with 48 DOF was used. The wagon model is a 3-D, non-linear model of a train passenger car. The model includes... 

This article presents a new method in determining long train derailment. A new strategy for building train models with large number of wagons has been developed. Previous studies have shown that in a train model, some of the details in the model of the wagons neighboring the wagon under study play minor role in dynamic behavior of the spotted wagon. To reduce the size of the overall model, one would tend to eliminate some of the details of the complex neighboring model having minor effect on overall behavior and trade a small approximation in results for large saving in computation time. In this research this idea is used to develop a train model with one full detail wagon model linked in a... 

Rail irregularity is one of the most effective factors in train derailment. theste irregularities have generally random distribution that are assumed to be stationary random and ergodic processes in space, with Gaussian amplitude probabiliy densities and zero mean values. The quality of irregularities, their distribution along the rails and wagon speed are the main factors for train derailment which is investigated in this article. The car model is nonlinear and three-dimensional with 48 DOF. Using simulation results, the safe speed for moving wagon on different types of random rail irregularities is also determined  

The rail-wheel interactions and their effects on the wagon dynamics has been studied in this article. Also the effects of braking on wagon and rail vibrations are studied. The model consists of a wagon with body, two bogies and four wheels having 21 degrees of freedom in a planar arrangement. The rail system is treated as a Timoshenko beam supported by sleepers, ballast, subballast, and subgrade. To determine rail-wheel contact forces, Hertzian nonlinear contact theory and Kalker theory have been used. The model is simulated for a number of working conditions and the results are validated by comparing to previous works in the literature. Copyright © 2005 by ASME  

In this article a train model is developed for studying train derailment in passing through bends. The model is three dimensional, nonlinear, and considers 43 degrees of freedom for each wagon. All nonlinear characteristics of suspension elements as well as flexibilities of wagon body and bogie frame, and the effect of coupler forces are included in the model. The equations of motion for the train are solved numerically for different train conditions. A neural network was constructed as an element in solution loop for determination of wheel-rail contact geometry. Derailment factor was calculated for each case. The results are presented and show the major role of coupler forces on possible... 

This article presents a method for determination of meshing force distribution on contact region of spur gear teeth. In this method it is assumed that there are inter-connected springs on the teeth profile. These springs treat as capacitive fields. The compliance matrices of these fields are determined from the results of finite element analysis done on 3-D model of a gear. The tooth compliance matrix is used as a reference data to determine the tooth deformations for any meshing situation. The meshing force distribution is calculated using this reference data and Hertz theory for contacting bodies. The results of this analysis help in stress analysis under real operation conditions and more... 

This article presents a new method for determination of meshing stiffness of the gear teeth using three dimensional analysis of tooth stiffness. The teeth are treated as explicit capacitive fields and their compliance matrix is determined by considering virtual interconnected springs located at defined nodes on tooth profile. The stiffness of any arbitrary point on the profile can then be determined as a linear function of neighboring nodes stiffness. The results of this analysis help in determination of load distribution for a pair of meshing gears under real operation conditions where deflections and misalignments are inevitable. Copyright © 2005 by ASME  

Widespread use of adaptive mounts depends on their cost, simplicity, and reliability. In this paper, a new adaptive hydraulic mount is introduced that its upper chamber compliance is changed using shape memory alloy (SMA) wires. Sensitivity analysis is used to show the effectiveness of changing the compliance on the dynamic stiffness of the mount. The finite element technique is applied to the main rubber of the hydraulic mount in which the SMA wires are embedded to calculate the maximum change in the compliance. It is shown that SMA wires can effectively modify the compliance of the upper chamber. It is also shown that a simple on-off control is sufficient for the adaptive mount. Copyright... 

In this paper, the sensitivity analysis is applied to the development of high performance adaptive hydraulic mounts. The analysis allows us to select the most effective design parameters for tuning an adaptive mount to different road and engine conditions. It is shown that in the low frequency road excitation, the upper chamber compliance and inertia of the fluid column in the inertia track are the most influential properties in changing the dynamic stiffness of the hydraulic mount. These properties for the high frequency engine excitations are the upper compliance and the inertia of the fluid column of the decoupler. For tuning the adaptive mount to different road and engine excitation, a... 

In this paper an experimental/numerical technique is developed for engine mount optimization. The method is general and can be applied to optimize active and passive vibration isolators or absorbers in any mechanical systems or civil structures. Engine mount optimization techniques mostly rely on an accurate mathematical model of the whole vehicle, which in most cases is not available or is too difficult to develop. As a result, the current approach for selecting engine mounts for a vehicle is based upon trial and error which is very time-consuming and expensive. The proposed technique counts upon experimental data for optimization and does not require any mathematical model of the vehicle... 

In this paper, we introduce a new high-performance adaptive hydraulic engine mount. The mount is tuned to road and engine conditions by changing the length of the inertia track and effective decoupler area in low-frequency road and high-frequency engine excitations. A single actuator is used to tune the mount in both low-frequency and high-frequency regimes. Sensitivity analysis is used to show that changing the length of the inertia track and decoupler area is the most effective way to tune an adaptive mount. Numerical simulations indicate that the proposed design can significantly improve the performance of a passive hydraulic mount  

The meshless element-free Galerkin method was generalized and an algorithm was developed for 3D dynamic modeling of deformable bodies in real time. The efficacy of the algorithm was investigated in a 3D linear viscoelastic model of human spleen subjected to a time-varying compressive force exerted by a surgical grasper. The model remained stable in spite of the considerably large deformations occurred. There was a good agreement between the results and those of an equivalent finite element model. The computational cost, however, was much lower, enabling the proposed algorithm to be effectively used in real-time applications  

The need for service passenger cars, like taxies and governmental vehicles, to work in central Tehran that can produce less emission has been the main drive behind this research. A series hybrid pneumatic vehicle based on Iran manufactured Samand Passenger car was developed using commercially available components. The idea is to use as much standard parts as possible to reduce the development and manufacturing costs of the developed hybrid car. The vehicle space and weight limitations and the fixed geometry have been the main constraint in adoption of the components. The calculations show that the designed vehicle succeeds to satisfy the requirements set by driving cycle, but requires... 

Development of hybrid cars is the most popular subject among automotive engineers both in production and research. The need for service passenger cars, like taxies and governmental vehicles, to work in central Tehran that produce less emission has been the main drive behind this paper. A parallel hybrid pneumatic vehicle based on Iran manufactured Samand passenger car was developed using commercially available components. The idea is to use as many standard components as possible to reduce development and manufacturing costs. The vehicle space and weight limitations and fixed geometry have been the main constraint in adoption of the components. In this design the 75 kW engine of the Samand... 

One of the main subjects under consideration of automotive companies seeking for higher efficiency and lower atmospheric pollution is the usage of hybrid vehicles instead of usual internal combustion engine driven cars. Developing a service car for commutation in the city centers that can produce less emission has been the main idea behind this research. The preliminary design of a series Hybrid-Pneumatic vehicle based on Samand platform satisfying the requirements of ECE-15 driving cycle is presented in this paper. One of the main goals is to use as much standard parts as possible to reduce the development and manufacturing costs. The vehicle space, fix geometry and weight limitations have... 

In this paper, the transient motion of a three unit intelligent Pipe Inspection Gauge (PIG) while moving across anomalies and bends inside gas/oil pipeline has been investigated. The pipeline fluid has been considered as isothermal and compressible. In addition, the pipeline itself has also been considered to be flexible. The fluid continuity and momentum equations along with the 3D multi body dynamic equations of motion of the pig comprise a system of coupled dynamic differential equations which have been solved numerically. Pig's position and velocity profiles as well as upstream and downstream fluid's pressure waves are presented as simulation results which provide a better understanding... 

A general modeling framework is presented for the development of the frequency equation of a microgyroscope, which is modeled as a suspended cantilever beam with a tip mass under general base excitation. Specifically, the beam is considered to vibrate in all the three directions, while subjected to a base rotational motion around its longitudinal direction. This is a common configuration utilized in many vibrating beam gyroscopes and well drilling systems. The governing equations are derived by using the Extended Hamilton's Principle with a general 6-dof base motion. The natural frequency equation is then extracted in a closed-form for the case where the beam support undergoes longitudinal... 

This paper presents the kinematic and dynamic modeling of a two degrees of freedom manipulator attached to a vehicle with a two degrees of freedom suspension system. The vehicle is considered to move with a constant linear speed over an irregular ground-surface while the end-effector tracks a desired trajectory in a fixed reference frame. In addition, the effects of highly coupled dynamic interaction between the manipulator and vehicle (including the suspension system's effects) have been studied. Finally, simulation results for the end-effector's straight-line trajectory are presented to illustrate these effects