TTCI's well-known railway multi-body dynamics computer program, NUCARS®, simulates the dynamic response of a railroad vehicle to specified track conditions. NUCARS® is capable of predicting the rsponse of any rail vehicle; locomotive, passenger, transit, or freight car on any type of track geometry, including special track work such as turnouts and guardrails. The program is ideal for evaluating and comparing new vehicle designs as well as performing failure analyses such as derailment studies. NUCARS® is also used to investigate and improve ride quality.
NUCARS® is a general multi-body rail vehicle dynamics computer simulation model. It is designed to simulate the dynamic interaction of any rail vehicle with virtually any track. The user may select any number of bodies, degrees of freedom, and connection elements to describe a vehicle and track system. NUCARS® can be used to analyze the dynamic interaction of rail vehicles and track to predict stability, ride quality, vertical and lateral dynamics, and steady state and dynamic curving response. The program includes detailed nonlinear models of wheel/rail interaction and suspension response, with wheel/rail interaction based on Kalker's complete non-linear creep theory. Applications are in the areas of vehicle design, safety performance evaluation, rail vehicle and track research, derailment investigation, and general simulation of mechanical systems. Simulations of any type of freight, passenger, transit and locomotive rail vehicles are possible. Track simulations may include hypothetical track geometries or measured track supplied by the user, including turnouts and guard rails.
Typical NUCARS® Applications
Changes to suspension characteristics and vehicle geometry can be quickly simulated and the effects on ride quality, vehicle curving and safety performance are easily determined. A wide range of suspension elements can be included in a NUCARS® model including a number of detailed friction models designed to simulate specific railroad vehicle suspension components, as well as normal spring and damping components. Advanced vehicle designs that include items such as articulation, self steering axles, independently rotating wheels, air bag suspensions and viscous dampers are just a few of the possibilities. Special connection elements are included to represent tilting and active suspensions.
Derailment conditions can be simulated with the input of measured track geometry data, actual wheel and rail profile shapes. The specifications of actual vehicle suspension conditions and the presence of unusual conditions and external forces acting on the car can be input to the NUCARS® model to permit the user to explore the wheel/rail interaction forces and other dynamic conditions that lead to derailment.
NUCARS® can be used to explore changes in track design such as turnout geometry and guard rail configuration. The wheel/rail interaction forces can be calculated and track designs optimized to minimize their effects on the track structure.
NUCARS® is an especially useful tool in evaluating vehicle safety performance. NUCARS® can significantly enhance the certification tests such as the AAR Chapter XI tests for new freight cars by permitting prediction actual tests as well as conditions not possible to test. NUCARS® simulations can be conducted up to the point of derailment to establish overall windows of performance.
NUCARS® wheel/rail interaction calculations permit the user to explore the effects of profile shapes on wheel/rail forces, wheel/rail wear, and vehicle dynamic performance. The trade off between high conicity wheel profiles for good curving performance and low conicity profiles for high-speed stability can be quickly quantified. Output of various wheel/rail contact parameters such as creep forces, contact angles and wheel rolling radii allow a detailed study of the wheel/rail interaction.
Passenger comfort evaluations and lading damage studies can be performed with NUCARS® by simulation of vehicles running over measured track data. Output variables allow the simulation of actual transducers such as accelerometers mounted anywhere on the car structure to simulate actual test instrumentation.
By varying the coefficient of friction in the tread, flange and flange back regions analyses can be made of the effects of lubrication on wheel and rail wear, rolling resistance and vehicle curving performance.
Small variations of wheel and rail profile shapes, wheel/rail lubrication, in combination with vehicle curving dynamics have been shown to have significant impact on RCF. NUCARS® has the ability to evaluate all these parameters singly or in combination, allowing detailed studies of the RCF mechanisms.
Clearances between moving vehicles on adjacent tracks, and between vehicles and stationary objects such as bridges, poles and platforms can be calculated from NUCARS® from NUCARS® simulations of vehicles running over track curves, super elevation and track perturbations.
NUCARS® has been available under license from TTCI since the late 1980's. Current licensees of the NUCARS® program include North American Railroads, North American car builders, locomotive builders, and component manufacturers, as well as overseas railways, car builders and track suppliers.