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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]

In order to investigate the behaviour of worm drives, a new dynamic model, composed of two blocks, is established and used to extract numerical results. The tooth deflection of the worm drive, bearings, and wheels inertias are taken into consideration. New mark solving method is applied to solve motion equations. The state of contact of teeth is what enables these signals to manifest themselves. Modal analysis is developed to investigate the different natural modes of the model. Furthermore, modal energetic analysis is used to understand the distribution of strain and kinetic energies. It is also applied to classify natural models into "teeth modes" and "bearing modes". These two modes constitute two different frequency bands. The dynamic coefficient is measured simultaneously with the gradual increase of the turning speed of the motor. This allows for the evaluation of the overload of the system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Using an existing metal worm drive dynamic model and adapt it to a polymer-metal one. • The use of generalized Maxwell model to simulate the viscoelastic behaviour of POM. • An optimization procedure based on Nelder-Mead simplex method is introduced to improve the numerical results. • The sidebands at the meshing frequency are the result of the creep phenomena occurring in the polymer gear teeth. • An accuracy of 94% is reached between numerical and experimental results. Polymer-metal worm drives are common in automotives and mechatronic systems. Despite this, there is a lack of studies on this type of transmission, especially when it comes to their dynamic behaviour. With the modern orientation of Industry 4.0 towards advancing technology in predictive maintenance, it is of a great importance to consider the study of the dynamic behaviour of this mechanism. It is first proposed to introduce an appropriate dynamic model to correctly simulate, by numerical means, the behaviour of a non-defective polymer-metal worm drive. For this purpose, it is necessary to correctly model the Gear Mesh Stiffness (GMS) of the gearing system. The GMS depends on the nature of the worm and worm gear materials. It is assumed that no deformation occurs in the steel worm, in contrast to the polymer worm whose viscoelastic behaviour must be accurately modelled. Generalized Maxwell Model (GMM) is chosen to model this behaviour. Eventually, the vibration signals from the numerical model are compared with those determined by the experimental tests. To obtain more similarities between the numerical and experimental signals, it is proposed to perform an optimisation. The procedure consists in using the Nelder-Mead simplex method to obtain a minimum residual objective function. After optimisation, an accuracy of 94% between the experimental and numerical results is achieved. [ABSTRACT FROM AUTHOR]

• Using rheology in a polymer-metallic spur gear system. • Simulating the viscoelastic behavior of nylon 6,6 using generalized Maxwell model. • Identifying parameters using parameter identification method Poel-zero formulation. • Deducing gear mesh stiffness of polymer-metallic gear for different temperatures. Polymer-metal gears become increasingly interesting to manufacturers and researchers for their advantages to combine the two material's efficiencies. Despite the variety of studies in the literature, there is a significant drop in the number of studies concerning the Gear Mesh Stiffness (GMS). The variation of the GMS by time has a major influence on the dynamic response of transmission. Therefore, this study proposes to take into consideration the viscoelastic behavior of polymer in order to model effectively the GMS of a gear system. The suggested rheological model is the Generalized Maxwell Model (GMM). It is first used to model the viscoelastic behavior of the plastic material of the pinion. Then, Pole Zero Formulation (PZF) is employed to identify parameters of the proposed model. A numerical simulation is then carried out to illustrate the results of this new approach adopted on a pure Nylon 6,6-steel pinions. The evolution of the GMS is illustrated to highlight the viscoelastic behavior's model presented in this paper. Finally, the influence of the change in the temperature is investigated. [ABSTRACT FROM AUTHOR]