Train Carbody Research Articles

Fatigue design of various type spot welded lap joints using the maximum stress

Recently, a new issue in designing spot welded structures such as automobile and train car bodies is to predict an economical fatigue design criterion. One of the most typical and traditional methods is to use a ΔP—Nf curve. However, since the fatigue data on the ΔP—Nf curve vary according to the welding conditions, materials, geometry of joint and fatigue loading conditions, it is necessary to perform the additional fatigue tests for determining a new fatigue design criterion of spot-welded lap joint having specific dimension and geometry. In this study, the stress distributions around spot welds of various spot welded lap joints such as in-plane bending type (IB type), tension shear type (TS type) and cross tension type (CT type) were numerically analyzed. Using these results, the ΔP—Nf curves previously obtained from the fatigue tests for each type were rearranged into the Δσ -N f relations with the maximum stresses at the nugget edge of the spot weld.

A Study on Predicting Shinkansen Noise Levels Using the Sound Intensity Method

The purpose of this paper is to demonstrate a new method developed to predict track wayside noise levels resulting from the passage of high-speed trains. The method calculates noise levels based on data acquired by the sound intensity method developed by the Central Japan Railway Company. This measurement method allows one to identify each sound source and its characteristics as well as identify how much each source contributes to the overall resulting noise level. Structure borne noise and multiple reflected noise between train car bodies and noise barriers are also studied. As a result of this study, a prediction method was created which can calculate and predict noise levels resulting from such various factors as structure, train type, train speed and noise barrier. Noise levels predicted during this study agreed well with those actually measured under various conditions, thus indicating the prediction method model resulting from the study is a useful tool to verify noise levels occurring at receiver positions. Furthermore, it can also verify in advance how much effect noise barriers or train source noise level reduction devices would have on noise reduction.

A multibody methodology for the design of anti-climber devices for train crashworthiness simulation

The impact of train sets is characterized by a very high potential for the longitudinal instability of the train resulting in overriding of the individual car-bodies. Consequently, the end-underframe structural mechanisms for crash energy management are not loaded and the train kinetic energy has to be dissipated by structural components not designed for that purpose. In this work, a multibody-based methodology is presented for the study of train crashworthiness including the anti-climber devices. The simulation of train impact requires models for the structures of the individual train car-bodies, contact forces between train components, systems and mechanisms responsible for the connections between vehicles. The most important motions of the train set are developed in the vertical plane, therefore, the methodology now developed uses a planar dynamics formulation. The vehicles are described by a set of rigid bodies with their relative motions constrained by kinematic joints. The forces that develop during contact, except for the joint reactions are modelled by nonlinear deformable elements. The mechanical characteristics of such elements represent the force-deformation structural response of each train car-body end, obtained by experimental testing or through detailed finite element models. The nonlinear characteristics of the suspension systems, the structural behaviour of the couplers and the friction forces between wheel-sets and rail arc also represented in these models. The anti-climber mechanical devices are modelled using the description of the contact between the train car-bodies ends. This is represented by a continuous contact force model, which accounts for the relative geometry between the car-body ends and material characteristics of the structural devices. The formulation is finally applied to train impacts in various crash scenarios, which are characterized by the collision of complete train sets with different velocities against stopped trains. The modelling assumptions and the suitability of the numerical tools developed are discussed in the framework of their application to the design of train crashworthy components.

Distributed and discrete nonlinear deformations on multibody dynamics

Two different multibody dynamics formulations for the simulation of systems experiencing material and geometric nonlinear deformations while undergoing gross motion are presented in this paper. In the first, an updated Lagrangean formulation is used to derive the equilibrium equations of the flexible body while the finite element method is subsequently applied to obtain a numerical description for the equations of motion. The computational efficiency of the formulation is increased by using a lumped mass description of the flexible body mass matrix and referring the nodal accelerations to the inertial frame. In the resulting equations of motion the flexible body mass matrix is constant and diagonal while the full nonlinear deformations and the inertia coupling description are still preserved. In some cases the flexible components present zones of concentrated deformations resulting from local instabilities. The remaining structure of the system behaves either as rigid bodies or as linear elastic bodies. The second formulation presents a discrete model where all the nonlinear deformations are concentrated in the plastic hinges assuming the multibody components are as being either rigid or flexible with linear elastodynamics. The characteristics of the plastic hinges are obtained from numerical or experimental crush tests of specific structural components. The structural impact of a train carbody against a rigid wall and the performance of its end underframe in a collision situation is studied with the objective of assessing the relative merits of the formulations presented herein. The results are compared with those obtained by experimental testing of a full scale train and conclusions on the application of these methodologies to large size models are drawn.

Dynamics of structures undergoing gross motion and nonlinear deformations: A multibody approach

The formulation and application of a flexible multibody dynamic formulation to the study structural systems experiencing geometric and material nonlinear deformations, while its components undergo large relative rotations and displacements, are presented in this paper. The description of a flexible structure able to undergo a large rigid body motion is based on the finite element description of its geometric and material nonlinear deformations. The choice of the generalized coordinates used to describe the body flexibility with emphasis on their influence over the explicit nonlinearity of the numerical model of a structure is discussed. Subsequently, the relative motion between different structural and rigid system components is described using a multibody formalism based on joint coordinates and velocity transformations. The capability of this methodology to describe nonlinear geometric effects is illustrated with an example of a rotating beam. Finally the procedure is applied to the crashworthiness and structural impact of a train carbody the results being compared with those obtained by the use of a commercial nonlinear finite element code. Furthermore, the results obtained in an experimental test of a full scale model of the train carbody are used to validate the application of this method to large scale multibody systems.