Designing metallic surfaces in contact with hardening fresh concrete: A review

Concrete, a commonly used material in the construction industry, interacts with metallic surfaces such as formwork during pouring and reinforced bar during lifespan. Formworks are designed to minimize hardened concrete adherence in order to avoid wall defects after formwork removal. In opposite, reinforced bar designs aim at maximizing their adherence to concrete for optimizing the transmission of mechanical solicitations. The present review investigates the surface properties that govern bonding of freshly poured concrete onto metallic surfaces. Identifying the underlying mechanisms of adhesion highlighted the importance of substrate characteristics (roughness, composition), concrete curing and compaction), and interfacial additives (release agents, wetting). This paper addresses the basic requirements in designing a functional surface interacting with concrete and emphasizes today challenges

Features selection approaches for an objective control of cosmetic quality of coated surfaces

The cosmetic aspect is one of the main functions of industrial surfaces in numerous applications. Even the smallest surface defects may have a critical effect on the cosmetic tolerability of such industrial surfaces. Thus, surfaces are generally coated at the last manufacturing process stage to cover existing defects and to certify their cosmetic quality. The surface quality is however constantly controlled after coating that induces an increase of lead-time increase and production costs. This is due to a various flaw patterns and a lack of uncoated surfaces specifications. Hence, the identification of relevant surface morphological parameters underlies an objective and automatic cosmetic control performance. In fact, this relevant parameter selection allows tracking surface flaws during the coating finishing operation. This paper presents a comprehensive overview of various feature selection tools for data analysis (Neighbourhood Component Analysis (NCA), ReliefF, Sequential wrapper method, Decision tree) to extract relevant information out of physical data. A design of experiment based on scratches test on amorphous polymers to generate typical controlled defects has been performed. Then, several cosmetic defects characteristics were extracted from experimental measurements. Feature selection approaches were applied and compared to determine the most relevant parameters. The advantages and limitations of each method for data analysis have been highlighted in the case of real engineering surface quality control

New ionic conducting ceramics of NASICON type: synthesis and characterizations

In this work, we present a study of two NaSICON families of general formula Na2.800M1.775Si0.900P2.100O12 with M=Zr or Hf. The synthesis was carried out using sol-gel process and the synthesized precursors were characterized using coupled DTA-TG. The obtained oxides after pyrolysis of precursors were identified by X-ray diffraction. The electric properties of the sintered oxides were carried out by impedance spectroscopy (SIC). The obtained results at this conditions highlight a good improvement of electrical conductivity (σtot around 10-4S.cm-1). This value is comparable to total electrical conductivity at 300K given in the literature.In this work, we present a study of two NaSICON families of general formula Na2.800M1.775Si0.900P2.100O12 with M=Zr or Hf. The synthesis was carried out using sol-gel process and the synthesized precursors were characterized using coupled DTA-TG. The obtained oxides after pyrolysis of precursors were identified by X-ray diffraction. The electric properties of the sintered oxides were carried out by impedance spectroscopy (SIC). The obtained results at this conditions highlight a good improvement of electrical conductivity (σtot around 10-4S.cm-1). This value is comparable to total electrical conductivity at 300K given in the literature

Influence de l'échelle de rugosité sur le frottement dans les contacts lubrifiés

La réduction du frottement, de la consommation d'huile et la limitation des émissions de gaz à effet de serre sont les principaux objectifs de l'industrie automobile afin d'améliorer l'efficacité environnementale des moteurs de véhicules. Cette efficience énergétique passe par une fonctionnalisation de la surface de la chemise du tribosystème segment piston chemise, responsable d’environ 45% des pertes par frottement dans le moteur. La surface rodée et le segment du piston constituent donc un système tribologique qui influe sur la longévité du moteur. En général, la surface rodée est obtenue par une succession de procédé d’abrasion (rectification, rodage, polissage…) permettant de répondre aux fonctionnalités requises relatives à leur durabilité et leur fiabilité. Ces procédés utilisent des grains abrasifs de différentes tailles allant du plus grossier au plus fin générant ainsi une texture de surface multi-échelle. La texture ainsi générée affecte de manière significative la performance du triplet piston segment chemise (SPC), bien que les effets de la topographie n’est pas clairement comprise. Dans cette étude, une caractérisation avancée de la surface est utilisée pour étudier les effets d’échelle de rugosité dans les contacts lubrifiés. La topographie de surface est basée sur la décomposition de la surface en deux éléments: la rugosité superficielle (reliée au frottement et à l’usure) et les vallées (servant de réservoirs). Les résultats montrent une dépendance entre l’exposant d’Hölder et le frottement ainsi qu’une échelle critique inversant l’influence de la profondeur des vallées sur le frottement