Salah Mezlini

Anti-fingerprint properties of engineering surfaces: a review

ABSTRACT Various applications require surfaces with anti-fingerprint properties. This article reviews the surface properties that govern the fingerprinting process. The achievement of surfaces free of fingerprints deals with the construction of amphiphobic surfaces that repel water and oil. Based on wetting theories, two key parameters (Surface energy and Roughness) show significant effects on surface wettability. We address in this paper, the basic requirements and strategies of designing and manufacturing amphiphobic surfaces using different substrates. The synergetic effect of low surface energy and functional surface morphology leads to reduced wettability, resulting in anti-fingerprint properties. The trends of future investigations and fundamental conclusions are drawn. The remaining challenges and future outlook of this field are also highlighted.

Effect of Skewness and Roughness Level on the Mechanical Behavior of a Rough Contact

In this work, we investigate the effects of roughness level and asymmetry of profile on the mechanical behavior of an engineering surface. A numerical model was performed to simulate bi-dimensional surfaces with different roughness parameters (The arithmetic average height parameter Ra and skewness) values. This model predicts the contact load, real area and interfacial stiffness. It takes into account the elastic-plastic material behavior, asperities interactions and more realistic geometry than the analytical models. Both symmetric and asymmetric profiles were simulated. Symmetric (Gaussian) profiles were generated through experimentally measured surfaces. These profiles were artificially edited in order to put forward the effect of roughness parameters on the contact performances. The Pearson system of frequency curves is used to produce asymmetric profiles with the same roughness level. The effect of crushing and roughness level as well as the skewness parameter on the contact performance in terms of real area, contact load and interfacial stiffness was analyzed.

Sensitivity of GFRP Composite Integrity to Machining-Induced Heat: A Numerical Approach

This paper aims at investigating the temperature effects during abrasive milling of glass fiber reinforced plastic composites (GFRP). A 3D thermal model using volumetric heat source with Gaussian distributed cylindrical flux was developed as DFLUX subroutine and implemented into Abaqus/Standard code. The model employs linear power law for simulating the temperature variation during tool advance. The composite plate is made of glass fibers oriented perpendicular to the tool trajectory. The tool feed was simulated by the source constant motion while speed was taken variable. Four equidistant thermocouples were simulated within the medium plan of the specimen in order to record the temperature evolution. The predictions highlighted the sensitivity of temperature histories to cutting speed. The conductivity and heat capacity played for controlling heating and cooling phases of the curves. The peak temperature exhibited maximum value at TC3 irrespective to speed value. The pure thermal analysis showed sufficient ability to predict the heat affected zone in the GFRP, which is, in turn, a function of tool spindle speed.

FE Modeling of Wear Mechanisms in UD-GFRP Composites Using Single-Indenter Scratch Test: A Micromechanical Approach

This paper addresses the sensitivity of the elementary wear mechanisms of UD-GFRP composite to the tribological parameters. A scanning electron microscope (SEM) was used to assess the wear mechanisms on the scratched UD-GFRP composite for different test conditions. A 3D FE micromechanical models was developed using ABAQUS/Explicit to simulate single indenter scratch test (SST). Both material behavior and damage of fibers and matrix are described using Johnson Cook behavior law. However, the fiber/matrix interface was modeled using the cohesive zone approach by the mean of the cohesive elements. The numerical results show a good agreement with the experimental wear mechanisms.

On the Elementary Wear Mechanisms of UD-GFRP Composites Using Single Indenter Scratch Test

This paper deals with the investigation of friction and wear mechanisms involved when scratching parallel to fiber orientation of unidirectional glass fiber reinforced polymers (UD-GFRP) composite. A single indenter scratch test (SST) was performed at room temperature and constant sliding speed, using high speed steel conical indenter. The dominant damage modes owing to SST were inspected at different attack angle and load using scanning electron microscope (SEM). The apparent friction and the damage modes were investigated as function of the test parameters, particularly, the attack angle and the normal load. The experimental findings reveal that the attack angle has a most important role in controlling apparent friction if compared with applied normal load. However the wear mechanisms were more sensitive to both attack angle and normal load. The correlation between wear modes and tribological parameters was emphasized and the scratch map was parallel to fiber orientation built. Six domains were identified and the different wear mechanism transitions were detailed.

Effects of Pretextured Surface Topography on Friction and Wear of AA5083/AISI52100 Materials’ Pair

This paper covers the study of the effect of surface topography on tribological behavior in the early stage of repetitive sliding under dry condition. Reciprocating sliding tests were conducted on AA5083 sample against smooth AISI52100 ball bearing. Unidirectional polishing was adopted for the surface preparation of AA5083 samples. Experiments were performed at a pressure of 200 MPa for a maximum number of 1000 cycles. The sliding velocity and the sliding track were kept constant at 50 mm/s and 15 mm, respectively. Evolution of friction coefficient as a function of the sliding distance was monitored. Wear was characterized using scanning electron microscope (SEM), energy-dispersive X-ray spectroscope (EDS), and profilometer. Experimental results have shown that the friction coefficient as well as wear mechanisms, significantly, depends on the initial surface topography. Particular focus was put in the study of the effect of the mean absolute profile slope \(\Delta_{a}\). Results showed that the mean absolute profile slope \(\Delta_{a}\) played a major role in friction and wear.

Study of the Anti-fingerprint Function: Effect of Some Texture Properties on the Finger Contact Area

Recently, anti-fingerprint surfaces have attracted wide attention due to their self-clean and esthetic performances. The surface texture is a determinant parameter that governs such properties. In this paper, the anti-fingerprint function of microstructured surfaces has been investigated. We have studied the effect of some topographic parameters on the mechanical behavior of the finger contact. Our analysis is mainly focused on the effect of the pitch value and the aspect ratio of the surface patterns on the anti-fingerprint function. A numerical approach has been employed to model dry contacts between the human fingertip and differently microstructured surfaces. The fingertip was modeled taking into account the topography of the finger skin (finger ridges) and the mechanical properties of the finger tissues. Results indicate that the pitch value has a critical effect on the anti-fingerprint function particularly for low aspect ratio surfaces. This highlights the relevance of the texture properties on the surface functionality.