Rochdi El Abdi

Indentation Behavior of Silica Optical Fibers Aged in Hot Water

Vickers indentations were performed on silica optical fibers subjected to water interaction by a hydrothermal treatment. The observation of the Vickers impression provided direct evidence of a piling-up of material of the fiber submitted to the hydrothermal treatment. This indentation behavior is consistent with a structural relaxation promoted by the water and the glass network interaction. It is suggested that the water could act as a modifier since the deformation combines the densification and the shear flow of the material. When the relaxed surface layer is chemically etched, the anomalous behavior of silica under indentation is restored as the deformation is controlled only by densification. The chemical etched samples exhibited an increase in hardness.

The effect of the temperature on the wear and resistance of automotive connectors subjected to vibration tests

A connector is designed to allow the passage of a current across different electrical systems. A connector subjected to car vibrations and a high temperature can suffer damage. This damage leads to a rapid degradation in the electrical performance, which results in a considerable increase in the electrical contact resistance. This work aims to address the influences of a variety of factors such as the fretting amplitude, the frequency, the temperature and the current on the performance of tin-plated automotive connectors. The changes due to the degradation in the electric conduction of the connectors under mechanical vibrations and temperature cycles are analysed. A detailed analysis of the contact surface is made using a profilometer, an optical microscope and a scanning electron microscope.

Reliability Evolution of Optical Fibre Subjected to Chemical Environment

The increased optical fiber development for a variety of physical and chemical measurements using smart structures and sensors leads to investigate the mechanical and chemical reliability of standard commercial acrylate polymer coated fibers. A comparison of mean failure strength of as-aged fibres to the water influence for similar exposure duration has revealed the highest sensitivity to dimethyl sulfoxide reagent (DMSO). SEM investigation revealed different damage levels in function of the aging conditions.

Strength of silica optical fibre subjected to chemical environment

Based on the increased interest for optical fibres development for the use in smart structures and sensors, this study has aimed to investigate the chemical reliability of standard commercial epoxy-acrylate polymer coated fibres subjected to aggressive chemical reagents in gaseous and liquid phase, such as acetylene, ammoniac, dimethyl sulfoxide. Multimode optical fibre was exposed to gaseous reagents for different durations after prior vide exposure. Tensile testing results were treated using Weibull statistics. A comparison of mean failure strength of as-aged fibres to the water influence for similar exposure duration has revealed the highest sensitivity to dimethyl sulfoxide reagent.

Effect of Vibration Frequency on Mechanical Behavior of Automotive Sensor

Due to repetitive micro-displacements, the fretting phenomenon was defined as an electrical and mechanical degradation of the electrical contact interface in automotive sensors. Commonly, the electrical degradation was quantified by the increase of contact resistance deduced from the contact voltage. This work aims to address the analysis of relative displacements according to three space directions between sensor components in contact for different vibration frequencies for a Top Dead Center sensor. Particular attention was paid to measurements of displacements near crimping zones.

Stress corrosion in silica optical fibers: Review of fatigue testing procedures

The expected lifetime of optical fibers used either in telecommunication technologies or smart applications are closely related to the chemical reaction on the silica network. Due to the manufacturing processes or the handling procedures, the flaws spread on the fiber surface are inherently present. The aging mechanism is assumed to enlarge or to extend these flaws. Based on systematic experiments one may notice that water may induce a certain curing effect. Silica optical fibers have been aged in water; series of samples have been subjected to overlapped stretching or bending. Other series have been subjected to overlapped aging effect of microwaves and hot water. Finally, samples were submitted to dynamic tensile testing. The Weibull’s diagram analysis shows mono or bimodal dispersions of flaws on the fiber surface, but the polymer coating appears vital for fiber lifetime. While humidity usually affects the fiber strength, the series of testing has revealed that in controlled conditions of chemical envi...

Fluctuation of Contact Voltage During Fretting Phases

Due to repetitive micro-displacements, the fretting phenomenon was defined as an electrical and mechanical degradation of the electrical contact interface in telecommunications and more recently in power automotive connectors. Commonly, the electrical degradation was quantified by the increase of contact resistance deduced from the contact voltage. This work aims to address the analysis of the change of contact temperature and the contact voltage during the three successive fretting phases at low and high level contacts. U-shape samples of cooper with a tin protective coating were used and fixed on a vibration system.

Aging of Silica Optical Fiber in Static Fatigue Tests

During their use, optical fibers are subject to harsh installation and environmental conditions. To evaluate more precisely the lifetime of an optical fiber, it is necessary to study the mechanical behavior of optical fibers under extreme conditions, in particular under mechanical and thermal stress.This paper presents the results of new silica optical fibers aged in hot water between 20°C and 70°C and subjected to mechanical static bending stresses from 3 GPa to 3.5 GPa. Thermal dependence of the time to failure was observed. This dependence can be described by the Arrhenius model, where the activation energy is one of the main physical characteristic.

Electrical resistance change of automotive connectors submitted to vibrations and temperature

For automotive applications, the stability of the supplied electric power depends of the change of electrical resistance. For the case of automotive connectors, an electrical current goes through the connector wire and can be perturbed by the mechanical behaviour of the connector contact area under vibrations and temperature. Such vibrations on the bulk contact device are typically in the range of 10 Hz-2000 Hz and result in displacements of only a few microns at the contact interface. In the present study, a bench test has been developed to control motions down to 1μm. The objective is to determine the minimum amplitude for fretting-corrosion degradation based on the evolution of contact resistance and to study the effects of the temperature. It was found that the fretting degradation depends on vibration displacements, used materials, loading and applied temperature.

Change of Thermo-Mechanical Properties of Optical Fibers Aged in CTAC Aqueous Solution

Fiber-optic sensors are mostly used for in situ measurements of diverse chemical composition of industrial surfactants employed in industry as detergents, emulsifying and dispersing agents, coatings, and pharmaceutical adjuvants. These optical sensors are often used in wet chemical environments in which the temperature can be high.The purpose of this work is to study the mechanical behaviour of optical fibers in contact with CetylTrimethylAmmonium Chloride in aqueous solution (CTAC) at different immersion durations and different temperatures.Optical fibers were submitted to dynamic bending test under different velocities.Result analysis demonstrates that immersion in CTAC drastically decreases the fiber strength particularly when immersed for long aging periods at high temperatures.