Sadok Sassi - Academia.edu (original) (raw)

Papers by Sadok Sassi

Vibroengineering PROCEDIA

Gear failure is considered the main alarming and undesirable event in gearboxes. Usually, cracks ... more Gear failure is considered the main alarming and undesirable event in gearboxes. Usually, cracks happen by fatigue caused due to cyclic loading. Fatigue stress is focused on the teeth root because of the small tooth fillet radius. This causes progressive damage to gear teeth which causes teeth failure, and hence, a damaged gear. This work shows a numerical framework to identify and quantify cracks' existence at the teeth root of spur gears. The problem is numerically analysed through finite element-based simulation with ANSYS by conducting a modal analysis. There are nine cases of gears with different cracks on their tooth; these cracks are varied by their number (single or multiple), Crack Length Percentage (CLP %), and location. The FEA is used to simulate all nine cases to predict the bending natural frequency of teeth and to investigate the effects of the variation of the crack by looking at the natural frequency of the teeth bending as well as the deformation level. Results...

Comptes Rendus. Mécanique

Lecture Notes in Mechanical Engineering, 2020

Active Noise Control (ANC) is used in controlling low frequency noise where passive control is in... more Active Noise Control (ANC) is used in controlling low frequency noise where passive control is ineffective. This paper presents the main results obtained from the development of an active noise control earplug for use in industry. A simple analogue feedback control system is used to demonstrate the potential of the system. Experimental results show that with existing miniature microphones and loudspeakers characteristics, adequate active noise reduction occurs in the frequency range between 100 Hz to 1000 Hz. The peak noise attenuation of about 15 dB occurs around 400 Hz. A model of the electroacoustic control system is provided and used to predict the performance. Simulation results show that the system secondary path frequency response dictates the closed-loop performance. The response in turn depends mainly on the frequency responses of the microphone and loudspeaker. The controller is used to maximize the noise reduction and its bandwidth. If lower frequency noise reduction is d...

Materials Research Express, 2021

Computational Fluid Dynamics (CFD) analysis is conducted on mono-tube vehicle MRF damper investig... more Computational Fluid Dynamics (CFD) analysis is conducted on mono-tube vehicle MRF damper investigated experimentally in a previous study. In this study, the fluid of the type MRF-132DG was inserted inside a damper of a car rear suspension system. The CFD analysis describes the fluid flow through the internal orifices between the compression and the rebound chambers. Averaged Navier–Stokes equations were solved by the SIMPLE method, and the RNG k-ε was used to model the turbulence at the fluid crossing through the orifices. All the CFD model boundary conditions’ values were set to the same values reported in the previous experimental study, except for the viscosity values. When varying the applied magnetic field density, the changes of MRF’s viscosity values were assessed by using a viscosity meter. Results showed a viscosity increase of 70% when the magnetic field excitation current was elevated from 0 A to 5 A. The damping forced and damping values were calculated using the rebound...

Journal of Vibration and Control, 2021

One of the least investigated approaches in passive vibration control is the possibility of combi... more One of the least investigated approaches in passive vibration control is the possibility of combining different types of dampers that use different damping principles. Such a combination process, if wisely designed and implemented, has the potential to increase the damping performance and extend the damper’s application. The primary purpose of this work is to experimentally and numerically investigate the damping behavior of a novel Fluid-Impact Hybrid Damper. This damper combines a conventional Viscous Fluid Damper with a Particle-Impact Damper. The Fluid-Impact Hybrid Damper comprises a 3D-printed plastic box attached to the Viscous Fluid Damper’s moving rod and filled with stainless steel balls. An experimental setup was designed to drive the Viscous Fluid Damper’s rod into harmonic oscillations at different frequencies (1, 2, 4, 6, and 8 Hz). The number of balls was changed three times (5, 10, and 15) to assess the effect of this parameter on the damping performance of the Fluid...

World Academy of Science, Engineering and Technology, International Journal of Aerospace and Mechanical Engineering, 2017

World Academy of Science, Engineering and Technology, International Journal of Mechanical and Mechatronics Engineering, 2017

Journal of Vibration and Acoustics, 2021

During the drilling process in oil and gas fields, slender drill strings often experience a multi... more During the drilling process in oil and gas fields, slender drill strings often experience a multitude of complex and simultaneous vibrational phenomena. Drill string vibrations hinder the drilling process and can cause premature wear and damage to the drilling equipment. Here, the suppression of drill string vibrations during drilling operations is experimentally investigated using a novel drill string design, based on the use of innovative periodic inserts that control the vibration transmissibility in different directions. These inserts are equipped with viscoelastic rings that act as sources of local resonances, surrounding piezoelectric actuators that generate internal axial loading when electrically excited. An experimental prototype that combined all these details was constructed and tested to demonstrate the periodic drill string's feasibility and effectiveness in minimizing undesirable vibrations. The obtained results indicate that the periodic inserts’ careful design ca...

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2019

This main purpose of this work is to investigate, through a finite-element simulation, the effect... more This main purpose of this work is to investigate, through a finite-element simulation, the effect of tire blowout on the collision of a light pickup truck with a guardrail, at a speed of 100 km/h. The finite-element model was calibrated against a dynamic test carried out by the Texas Transportation Institute. Four cases of individual tire blowout were considered. Among these, the case of the left front tire was found to be the most critical one, resulting in a pitch angle of 24°, a roll angle of 12°, and a yaw angle of 30°. For this critical case, the results showed that the deflated tire trapped in the guardrail, which created more interaction between the vehicle and the guardrail beam. These challenging crash conditions were found to be more crucial for the stability of the pickup compared with the fully inflated tire scenario.

Wave Motion, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of Sound and Vibration, 2018

The stop and pass bands (i.e. the band gaps) characteristics are determined for gyroscopic system... more The stop and pass bands (i.e. the band gaps) characteristics are determined for gyroscopic systems by developing an approach which is compatible with such class of systems which is based on the concept of Bloch wave propagation in periodic structures. In this approach, the dispersion curves of the periodic gyroscopic systems are determined for different rotational speeds. The obtained characteristics are compared with non-rotating systems in an attempt to quantify the effect of the gyroscopic forces on the "band gap" characteristics. The developed approach is illustrated by a new class of drill strings with passive periodic inserts. These inserts are utilized to filter out the vibration transmission along the drill string. Such mechanical filtering capabilities allow the vibrations to propagate along the periodic drill string only within specific frequency bands called the 'pass bands' and completely block it within other frequency bands called the 'stop bands'. The inserts introduce impedance mismatch zones along the vibration transmission path to impede the propagation of vibration along the drill string. The design and the location of the inserts are selected to confine the dominant modes of vibration of the drill string

Journal of Vibration and Acoustics, 2017

A new class of drill strings is investigated whereby strategically designed and placed periodic i... more A new class of drill strings is investigated whereby strategically designed and placed periodic inserts are utilized to filter out the vibration transmission along the drill strings. Such mechanical filtering capabilities allow the vibrations to propagate along the periodic drill string only within specific frequency bands called the “pass bands” and completely block it within other frequency bands called the “stop bands.” The design and the location of the inserts are selected to confine the dominant modes of vibration of the drill string within the stop bands generated by the periodic arrangement of the inserts in order to completely block the propagation of the vibrations. A finite element model (FEM) that simulates the operation of this new class of drill strings is developed to describe the complex nature of the vibration encountered during drilling operations. Experimental prototype of the passive periodic drill string was built and tested to demonstrate the feasibility and ef...

International Journal of Crashworthiness, 2016

ABSTRACT Since the performance of the guardrail system depends in part on the compatibility of ve... more ABSTRACT Since the performance of the guardrail system depends in part on the compatibility of vehicle-to-roadside hardware, it is important to improve the interaction of the vehicle with the guardrail system by adding more compliance to the guardrail system. In this paper, a finite-element baseline model of a guardrail system consisting of a light truck (2000 kg) travelling at 100 km/h and striking a guardrail was developed in accordance with the NCHRP Report 350 guidelines for Test Level 3 safety performance. The model was validated through comparison to a full-scale test conducted by the Texas Transportation Institute. In order for the guardrail system to absorb more energy and offer better stability to the vehicle, a rigid wooden blockout was replaced by a new crushable blockout design that was evaluated at the component level. The new blockout was formed by three crash cans and triggered at the corner, then was implemented in the full-scale model. The results of the analysis indicate that the both models satisfy the requirements of NCHRP Report 350 for the Test 3-11 conditions and show that the crushable blockout offers better vehicle stability in terms of roll angle and vehicle deceleration.

International Journal of Vehicle Systems Modelling and Testing, 2015

In this paper, the dynamic behaviour of a vehicle having one of its tyres burst is examined throu... more In this paper, the dynamic behaviour of a vehicle having one of its tyres burst is examined through a model-based analysis. The model considered in this study is a classical one, considering only straight line motion in Z-direction. In total, nine degrees of freedom are analysed: four translations of the un-sprung masses, one translation of the centre of gravity, two rotations of the body and two translations of the seat and its support. When a tyre blows out (for example in the front-left side), several changes are observed to occur. These changes affect the vehicle stability and geometry, the operating conditions and the tyre-road interaction. The numerical simulation of the effects of tyre deflations on vehicle behaviour was achieved by using MATLAB/Simulink. It is concluded that the blast coming from the tyre blowout generates enough energy to excite the wheel structure resonances but has relatively little effect on the comfort of the driver. The main effect is observed to be on the safety of the vehicle which, under the action of a lateral push, is deviated from its trajectory towards the side of the deflated tyre.