Keywords: passive safety, railway interiors, biomechanics injury, occupants kinematics, multibody systems.

The aim of this work is to present a systematic approach to the improvement of the passive safety of railway interiors. Though the current injury criteria [1] have been identified in road and aerospace occupant passive safety, in which the occupants are belted and have their kinematics guided, they are also used in railway transportation where seat belts are not used and where different interior layouts are present. These layouts may include standing passengers, front and side facing occupants, a diverse furniture such as tables, poles and partitions as potential target surfaces during impact and no particular position for their resting positions. During the primary collision, the vehicle is subjected to an abrupt deceleration causing the unrestrained occupants to continue the original motion. Then the occupants are projected through the vehicle until the secondary collision occurs with their contact with some part of the interior of the vehicle or with other occupants. Due to its importance in terms of railway vehicle interiors, in this work the particular layout of the inline seating with backrest table is investigated with the objective of identifying the potential sources of injury for the railway occupants and to suggest directions for the improvement of such interiors. The numerical model of this layout is developed using the MADYMO [2] code, which includes a multibody description [3] for the dummies and a finite element approach for the seats and structural features of the vehicle interior. The crash pulse used for the virtual testing corresponds to that accepted by the industry and operators as being that representative of the most relevant accidents [4]. Of particular importance is the identification of the most relevant injuries [5] for this type of scenario and their variability with occupant size, backrest table dimensions and the distance between the seats, denoted as the pitch. Furthermore it is shown that front occupants, which are represented by Hybrid III 50 percentile, are put at a higher risk of injury to the knee, tibia, femur and neck. Rear occupants, which are represented by Hybrid III 95 percentile, are at a higher risk of injury at the head level. The scenarios of high risk for these occupants are those with the seat pitch below 800mm, corresponding to the second class pitch, and for variations of table length greater than 120mm, with a consequent reduction of space in the direction of the pitch. In terms of the kinematics of the occupant, the major difference resides on the fact that the passenger seated closer to the wall exhibits a rotation after the knee contact, suggesting differences on the exposure of the inside and outside occupants to injury. The virtual testing developed for the different configurations scenario suggests that any improvement in the passive safety features of the vehicle interior should be obtained with the characteristics of the upper part of the back of the seat structure and introducing hinges on the backrest table, allowing the enlargement of its length, without constraining the kinematics of the occupants in case of accident.

1

K.-U. Schmitt, P.F. Niederer, F., Walz, "Trauma Biomechanics: Introduction to Accidental Injury", Springer, Berlin, 2004.

2

Madymo version 6.2, Theory Manual, TNO Madymo BV, Delft, Netherlands, 2004.

3

P. Nikravesh, "Computer-aided analysis of mechanical systems", Prentice-Hall, Englewood Cliffs, New Jersey, 1988.

4

Project Report Workpackage No 2.5.2, "Pulse Construction", Safeinteriors - Train Interior Passive Safety for Europe, 2008.

5

Project Report Workpackage No 3.1.3, "Identify Suitable Criteria", Safeinteriors - Train Interior Passive Safety for Europe, 2008.

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