PSI - Issue 17

João Morais et al. / Procedia Structural Integrity 17 (2019) 448–455 João Morais et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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obtain information related to the deformability of the railway. When the vehicle deforms the railway line under the wheels, due to its weight, the distance between the middle section of the chassis and the railway diminishes proportionally to the average railway stiffness on the measurement point. Then, by taking into account and removing the relative movement between the chassis and the rails due to the presence of the vehicle’s suspension system, it is possible to obtain an adequate estimate of the deformation imposed on the rails by the passage of the vehicle. This relative movement is measured on four points between the shafts of the vehicle's wheels and its chassis. The railway vertical stiffness is translated by the ratio between the vertical force applied by each wheel and the elastic vertical deflection of the rail. Regarding the identification of railway defects that affect the vehicle-railway dynamic interaction, this is accomplished by measuring the accelerations transmitted to the vehicle with accelerometers installed on each wheelset and on both cabins. The developed system is also capable of measuring railway physical parameters that are usually not evaluated by conventional auscultation vehicles. The solution is based on an integrated system consisting of four subsystems, which are embedded in the vehicle, namely: • Instrumentation subsystem, responsible for measurement of relevant physical quantities related to the vehicle railway interactions, through a set of sensors and transducers; • Data acquisition subsystem, intended for the collection and conversion of the sensors data to digital format; • Data collection subsystem, responsible for communication with the data acquisition system and management, command and import of data acquired by it. It also performs a preliminary data processing and allows for on board data visualization by the system operator and data storage; • Computer application intended to process the acquired data, transforming it into useful information regarding the management of railway infrastructures. The prototype system was installed in a self-propelled vehicle, model DD 450B, manufactured by SVI. After studying and analyzing several solutions, it was considered that the most suitable solution for measuring the deformation of the rails in relation to the chassis consisted in six laser displacement transducers (reference NCDT 1402). Four of these transducers are intended to measure the distance between the vehicle chassis and the wheel shafts, and the other two are intended to measure the distance between the middle of the vehicle chassis and each corresponding railhead (Fig. 1).

Fig. 1. Schematic view of the instrumentation locations in the railway vehicle.

Two high-sensitivity ±4 g triaxial accelerometers (reference FBA ES-T) are installed inside the vehicle's cabins and arranged symmetrically in the front and rear areas. Four high-range ±500 g accelerometers (reference PCB 356A02) are mounted on the wheel boxes. These sensors are used to complement the relative position measurements