Search

The hydraulic circuit in hydraulic mechanisms may be the cause of several vibration anomalies. Flexible pipes, in particular, commonly used in test rigs, may be the source of vibration issues due to their relatively low natural frequencies altering the pump noise, vibration, and harshness (NVH) performance. The purpose of this study is to detail a methodology based on lumped parameter modeling and experiments to analyze the circuit NVH behavior. An experimental study is carried out on two pump designs to determine the outlet pressure fluctuation of various test rig configurations. Numerical simulations are also performed to simulate the actual behavior of the hydraulic system considering these different test configurations. The tests are carried out at a chosen frequency range with a hydraulic circuit configuration representing realistic layouts. In these situations, the hydraulic circuit layout can be the source of NVH anomalies. Realistic design solutions are proposed to modify the test rig NVH behavior in order to achieve a flat response throughout the desired working range. [ABSTRACT FROM AUTHOR]

Background: Worm gear sets are used in many applications of the transmission field. These mechanisms have interesting advantages. Despite this, its modelization is still challenging. This is due to its complex geometry. The goal behind this is to have an accurate model that allows improvement of the design of worm gear sets. Purpose: In this context, the paper presents a new mathematical model of a worm gear drive under rotational external excitations. Methods: Dynamic model is defined by fourteen degrees of freedom describing all rotations and translations of worm gear set, AQ1 bearings, a motor and a receiver connected together. First, equations of motion are developed to describe the dynamic behavior. Lagrange formula is, thus, employed. Elastic deformations of meshed teeth are considered. The normal load associated with the meshing is established as function of the model degrees of freedom through the elastic deflection. Second, a numerical simulation is carried out. Newmark Beta method is used to solve equations. Results: Numerical results are presented to discuss the model accuracy. The impact of the variation of friction coefficient and the stiffness of the worm gear is finally studied to discuss the consistency of the new formulation developed through this work. [ABSTRACT FROM AUTHOR]