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Organisationseinheit der BAM
While there is a large body of literature on the micro-mechanical behavior of metal matrix composites (MMCs) under uniaxial applied stress, very little is available on multi-phase MMCs. In order to cast light on the reinforcement mechanisms and damage processes in such multi-phase composites, materials made by an Al-based piston alloy and containing one and two ceramic reinforcements (planar-random oriented alumina fibers and SiC particles) were studied. In-situ compression tests during neutron diffraction experiments were used to track the load transfer among phases, while X-ray computed tomography on pre-strained samples was used to monitor and quantify damage. We found that damage progresses differently in composites with different orientations of the fiber mat. Because of the presence of intermetallic network, it was observed that the second ceramic reinforcement changed the load transfer scenario only at very high applied load, when also intermetallic particles break. We rationalized the present results combining them with previous investigations and using a micromechanical model.
This paper describes a theoretical model to simulate the effects of a sloshing cargo on the safety performance of a vehicle that performs a braking-in-a-turn maneuver when travels at a partial fill level. The fundamental assumption of the model consists of the superposition of the effects of two simplified mechanical-analogy models that represent a liquid cargo on a vehicle, including one for the roll motion and another one for the pitch motion. The distinctive characteristics of the mechanical models, however, is that they are based upon a validated formulation to establish the properties of the pendulum (length).
The results suggest a small effect of the sloshing cargo on the braking efficiency of the cargo, while the load transfer is moderately affected. However, such results should be put into a perspective, according to which such small variations can represent the avoidance of a rear-end crash or a rollover. In this respect, a specialized ABS system could be considered to improve the performance of such kind of vehicles when performing such maneuvers.
Validation of the proposed methodology should be performed as a continuation of this research effort.
Vehicle’s components damage
(2020)
The failure of vehicle’s suspension components has contributed to road crashes, while their defective operation can deteriorate the fuel efficiency of the vehicles. In this context, and when compared with solid cargo transporters, the road tankers would tend to produce larger roll forces during turning, as the curved shape of the liquid cargo container, shifts upwards the centre of gravity of the cargo. With reference to a rectangular cargo container representing the solid cargo situation, the increase in the position due to elliptical and circular tank shapes, can attain a value of 17% (100% fill, circular tank). In this study, experimental results comparing the lateral load transfer due to solid and liquid cargoes, indicate that the average force increase on the vehicle’s load-receiver side due to a liquid cargo, is 4.3%. To analyse the fullscale situation of both situations, that is, the higher position of the centre of gravity and the shifting of the liquid cargo, a simplified model is developed. The outputs from such a model when subjected to realistic operating conditions (speed
and turning radius), suggest that the higher position of the centre of gravity due to using a non-rectangular cargo container generates an average force increase of 4.9% on the side receiving the load transfer. The incorporation of the effect of the liquid cargo, through the simple pendulum analogy, suggests that such an average increases to 6.76%, with a maximum of 8.35% in the case of the elliptical tank at 75% fill level. It is found that the average liquid cargo effect is 5.44%, which should be compared with the 4.3% of the experiments. Road tankers components would thus have a relatively shorter load cycle life than those of the solid cargo trucks.