PSI - Issue 37

Rogério Lopes et al. / Procedia Structural Integrity 37 (2022) 115–122 R. F. Lopes et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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2. Procedure It is intended to perform a preliminary of a bus sub-system. This essay aims to gain technical experience at the computational and experimental level. This test will be an initial investment in the future of the continuous improvement of passive safety of passengers traveling in the vehicle. The configuration, previously presented, will be analyzed in relation to its structural behavior in view of the reality of the bus as a whole in frontal. The main pillars of the front section of the bus will absorb the largest percentage of the energy from the collision. In this way, we assume a minimum fraction that will be responsible for the deformation of the door. The impact fraction is defined as an equivalent mass, being a rigid body of about 45 kg, which reaches the door. This value will be a virtual parameter in the pseudo-dynamic method. With the regard of the door sub-system instrumentation, 6 unidirectional strain gauges of 120 Ω were strategically placed in previous chosen locations. These locations represent the zones where the stress is highest, and comes from the initial iterations carried out with the numerical modelling software. The chosen strain gauges are from HBM company which model is 1-LY41-3/120 and these will measure the perpendicular loading direction strain variation using a National Instruments acquisition module. The location of the all strain gauge are represented in the

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Fig. 2. Location of strain gauges on the door: a) Front view and b) Back view

A 3D digital image correlation (DIC) test was setup in order to acquire full-field measurements for displacement and strain of the main front panel. The two cameras used for this purpose were positioned in front of the door, capturing the aluminum panel. The space available in front of the panel for the camera assembly was limited, which heavily conditioned the camera system’s configuration. The cameras were set up with a stereo angle of 28°, at a distance of approximately 2.2 m from the panel. Regarding the experimental set-up, in order to simulate the closest behavior to a real collision, a system was designed that applies the load evenly on the outer door frame that fits the geometry perfectly. Thus, the entire load is concentrated in a single actuation point. The fixation is done by means of 3 supports whose restriction of degrees of freedom is done identically to the position of the door on the bus. The supports are fastened to the frame by means of 12 M12 screws, please see the attached Fig. 3 representing the designed system to compress the door.

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b) Fig. 3. a) CAD set-up of the door. 1) impactor, 2) supports, 3) frame and 4) door sub-system and b) Assembly of the adaptor