Shuguang Yao

Improved Multibody Dynamics for Investigating Energy Dissipation in Train Collisions Based on Scaling Laws

This study aimed to investigate energy dissipation in train collisions. A 1/8 scaled train model, about one-dimensional in longitudinal direction, was used to carry out a scaled train collision test. Corresponding multibody dynamic simulations were conducted using traditional and improved method model (IMM) in ADAMS. In IMM, the connection between two adjacent cars was expressed by a nonlinear spring and energy absorbing structures were equivalently represented by separate forces, instead of one force. IMM was able to simulate the motion of each car and displayed the deformation of structures at both ends of the cars. IMM showed larger deformations and energy absorption of structures in moving cars than those in stationary cars. Moreover, the asymmetry in deformation proportion in main energy absorbing structures decreased with increasing collision speed. The asymmetry decreased from 11.69% to 3.60% when the collision speed increased from 10 km/h to 36 km/h.

Numerical and experimental study on the design strategy of a new collapse zone structure for railway vehicles

ABSTRACT This study proposes the design strategy of a new collapse zone structure for railway vehicles and explores its crashing performance through numerical simulation and experiments. Starting from the one-dimensional (1D) collision analysis of two train sets, the force–displacement characteristics of each vehicle-end can be expressed in the form of a non-linear spring and the energy absorption distribution for each vehicle interface was achieved. Then, the present paper moves on to the three-dimensional (3D) finite element analysis (FEA) for the detail design of the collapse zone structure which primarily consists of front beams, rolled hollow sections (RHSs), channels and collapse initiators. The 3D resultant force–displacement response matches well with 1D characteristics. Additionally, the energy absorption of 3D computation is larger than the required value. Finally, dynamic impact tests were conducted to validate the crashworthiness of the designed energy-absorbing structure. The results showed that all the critical indicators are within 10% of both methods, which satisfies the correlation requirements of EN15227. The deformed shapes are also comparable and with reasonable agreement between the test outcomes and FEA predictions. Therefore, the design strategy is well performed and the new designed collapse zone structure is recommended as a potential absorber of impact energy.

Energy-absorption optimisation of locomotives and scaled equivalent model validation

ABSTRACT In order to improve crashworthiness, the optimum energy-absorption design of locomotives was performed in MADYMO multibody dynamics software, and a three-dimensional computational model for locomotive vehicles was built. The results of calculations using the model were then fitted by multiple linear-regression functions, and a scaled equivalent model test was carried out to validate the fitting formula results. The results showed how to influence the energy absorption of a locomotive by studying the mass and velocity of the locomotive, as well as the plastic deformation platform force of the middle cars crushing tube. The fitting formula related to the plastic deformation platform force of the crushing of the middle cars tube and the kinetic energy of the locomotive was also obtained. The fitting accuracy of the model was 99.98%, and the error between the calculation results from the fitting formula and the scaled equivalent model test results was less than 5%. These results reveal the mode of energy dissipation, and they can be applied to the preliminary conceptual design of train. The dynamic tests of prototype are essential before serial production.

Crashworthiness analysis and multiobjective optimization for circular tubes with functionally graded thickness under multiple loading angles

In this article, the nonlinear finite-element analysis software LS-DYNA is used to study the crashworthiness of functionally graded thickness circular tubes under multiple loading angles (0°, 10°, 20°, 30°, and 40°). The specific energy absorption (SEA) and maximum crashing force ( F max ) are used as evaluation indices with which to analyze the effect of the length-to-diameter ratio and thickness gradient index P on the crashworthiness characteristics of functionally graded thickness circular tubes. Taking the length-to-diameter ratio and thickness gradient as design variables, the full factorial experiment was designed. A surrogate model of the integrated specific energy absorption ( SE A α ) and maximum crashing force ( F max 0 ∘ ) when the impact angle is 0° was constructed using the response surface method; the nondominated sorting genetic algorithm II was used to optimize the surrogate model, and the Pareto-front solution set was obtained. The results show that the thickness gradient index and the length-to-diameter ratio have a greater influence on the crashworthiness characteristics of functionally graded thickness circular tubes under oblique impact load, and the appropriate geometric parameters can improve the crashworthiness characteristics of functionally graded thickness circular tubes.

Energy absorption design study of subway vehicles based on a scaled equivalent model test

To obtain the characteristics of collision energy absorption and improve the passive safety of subway vehicles, the energy absorption design of subway vehicles was studied based on a one-seventh-scale model crash test. A full-size three-dimensional model of a subway vehicle was established using the multibody dynamics software MADYMO. The simulation results of the dynamics model were scaled down according to the similarity coefficients. By comparing the simulation results with the scaled model test results, the maximum error of deformation was 2.10 and 4.35% for the head car and the maximum deforming middle car, respectively, and the energy absorption error was found to be 8.75 and 5.70% for the head car and the maximum deforming middle car, respectively. The results indicate that the collision dynamics model of subway vehicles is relatively accurate. Next, based on this dynamics model, a full factorial experiment was designed to study the effects of the marshalling, mass and crushing tube’s plastic deformation platform force on the energy absorption of subway vehicles. The calculation results were fitted by multiple linear regression functions. Finally, the authors obtained the crash energy absorption formulas for the subway head car with an accuracy of 98.42% and for the maximum deforming middle car with an accuracy of 95.31%. These formulas can be applied to the preliminary design of subway vehicles and offer guiding significance for the parameter design of subway vehicles’ energy-absorbing devices.

Study on Impact Performance of Energy Absorbing Structures under Horizontal Offset Loading

When a train collision occurs, it is impossible for the vehicle to produce a completely axial collision. To improve the energy absorption performance of the energy-absorbing structure under an eccentric collision, in this paper, the collision performance of a subway vehicle energy absorption structure under a horizontal offset of 0-40 mm is studied via simulation. The results show that the original structure is prone to instability when the horizontal offset is large, so it is necessary to perform an optimization. Based on the concept of gradient material, the honeycomb strength in the structure is changed into a gradient distribution, and the results show that the improved structure did not show any instability phenomenon under all horizontal offsets. Under the horizontal offset of 40 mm, compared with the original structure, the energy absorption increased by 171.88% and the peak force decreased by 1.92% at the same time.