This paper investigates the process of destruction of parts of the connecting rod-piston group of the engine due to hydraulic lock after the ingress of liquid into the cylinders of the engine. Comparing expert data on actual engine destruction due to hydrolock with existing estimation models has made it possible to identify a number of significant contradictions affecting the objectivity and accuracy of the destruction assessment. To resolve the existing contradictions, a mathematical model for reconstructing the destruction of the connecting rod-piston group of the engine during a hydraulic lock has been improved. Unlike the existing ones, the model makes it possible to take into consideration not only the static deformation of the connecting rod but also to give a comprehensive assessment of the deformations of the connecting rod, piston pin, and piston at different volumes of hydrolock fluid. Underlying the model is the hypothesis assuming that the deformation of the piston pin under excessive load caused by hydraulic lock leads to the emergence of tension and an increase in the friction in the mated pin-piston. The calculation from the condition of differential change in the amount of friction in the mated pin-piston produced a satisfactory result that does not contradict the practical data and has confirmed the working hypothesis. By calculation, the onset of the destruction of engine parts during hydrolock at a pressure in the cylinder close to 17.3 MPa, at a crankshaft angle of about 346°, was revealed. In addition, it was found that in the case of violating the operating conditions, due to friction, the mated pin-piston is exposed to the lateral force on the skirt that reaches 17.2 MPa, which exceeds the permissible one, calculated according to known procedures, by 2.8 times. The results reported here are confirmed by known practical data, which makes the devised model applicable to the practice of expert studies into the causes of engine malfunctions when violating the operating conditions of a car
This paper considers the task to clarify the circumstances of a traffic accident (TA) involving two vehicles as a result of their lateral tangential collision at low angles. The aim of the study is to construct a mathematical model of a tangential collision of vehicles for the reconstruction of TA circumstances. Owing to the combination of the law of conservation of momentum and the theory of impact using the coefficient of recovery, it was possible to construct a mathematical model that describes the development of such an accident and makes it possible to determine the main parameters of the movement of vehicles after and before the collision. An answer is given regarding the possibility of losing the directional stability of the vehicle and its movement in the lateral direction because of a collision. Based on the mathematical model, the basic parameters of vehicles motion after their side collision at angles of 5–15° were analytically determined, when there are no slip marks on the road surface. A numerical experiment was conducted on the example of a specific accident. The findings make it possible to argue about the possibility of losing the directional stability of vehicles and shifting them to the oncoming lane or curb as a result of collision. A comparison of the results of the numerical calculation with the results of software modeling of accidents and the circumstances that were established in the process of studying a real accident was carried out. It was concluded that the results obtained are consistent and make it possible to more accurately assess the parameters of the movement of vehicles after their lateral tangential collision. In general, this produces more objective results of the reconstruction of TA mechanism in cases where there are no traces of slipping and braking on the road surface. The proposed mathematical model could be used in collisions accompanied by minor deformations or damage to vehicles
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