Fractal Analysis of Cutting Force and Acoustic Emission Signals During CFRP Machining

AbstractCutting forces and acoustic emissions signals while machining Fiber Reinforced Plastics (FRP) depends strongly on the tool wear. Fractal analysis can be adapted to those signals to characterize their variations. This tool wear monitoring technique is presented herein for the carbon FRP (CFRP) orbital drilling. Fractal parameters, characterizing the signal complexity and ruggedness, are very efficient for machining quality estimation and to follow the tool wear evolution

Surface profile topography of trimmed and drilled carbon/epoxy composite

ABSTRACT: The surface finish of Fiber Reinforced Plastic (FRP) laminate is challenging to characterize, due to the heterogeneous structure of the composite. Profile roughness parameters are highly impacted by the different layer properties, and their distributions are relatively spread out. In this paper, the surface topography of a 24-ply quasi-isotropic Carbon FRP (CFRP) is observed through primary profiles and the roughness parameter Ra in the transverse direction on trimmed and drilled CFRP surfaces. The surface characterization using the Ra parameter is found inadequate in providing useful information as to the machined surface quality

Surface profile topography of trimmed and drilled carbon/epoxy composite

ABSTRACT: The surface finish of Fiber Reinforced Plastic (FRP) laminate is challenging to characterize, due to the heterogeneous structure of the composite. Profile roughness parameters are highly impacted by the different layer properties, and their distributions are relatively spread out. In this paper, the surface topography of a 24-ply quasi-isotropic Carbon FRP (CFRP) is observed through primary profiles and the roughness parameter Ra in the transverse direction on trimmed and drilled CFRP surfaces. The surface characterization using the Ra parameter is found inadequate in providing useful information as to the machined surface quality

Self-healing UV curable acrylate coatings for wood finishing system, part 1: impact of the formulation on self-healing efficiency

ABSTRACT: In the wood flooring sector, good surface mechanical properties, such as abrasion and scratch resistance, are prerequisite. Surface wood protection is provided by finishing systems. Despite coating improvement, scratches formation on wood flooring is unavoidable. A new approach to increase service life is to confer the self-healing property to the finishing system. The most common coatings used for prefinished wood flooring are acrylate UV curable 100% solids coatings. They usually have good mechanical properties and high cross-linking density. The objective of this study was to develop and evaluate an intrinsic self-healing formulation, which is applicable to wood flooring. For this purpose, acrylate formulations were developed with monomers and oligomers carrying hydroxyl groups. To meet the requirements of wood application, hardness, and polymerization conversion of coatings were evaluated. König pendulum damping tests provide information on coating hardness and flexibility. Results around 80 oscillations is acceptable for UV curable wood sealer. The chemical composition was studied by FT-IR spectroscopy while dynamical mechanical analysis (DMA) was performed to determine glass transition temperature and cross-linking density. The self-healing behavior was evaluated by gloss and scratch depth measurements. The formulation’s composition impacted the hydrogen binding quantity, the conversion, the Tg and the cross-linking density. The (hydroxyethyl)methacrylate (HEMA) monomer provided self-healing and acrylated allophanate oligomer allowed self-healing and cross-linking. This study demonstrated that it is possible to combine high cross-linking density and self-healing property, using components with low steric hindrance

Alumina coatings on Ni-based superalloys: the impact of annealing on heavy oil fouling

ABSTRACT: As the sweet crude oil reserves decline, refiners must treat sulfur-rich heavy oil, requiring harsher operating conditions, which are detrimental to process equipment. Application of coatings on critical components protects surfaces against sulfidation, corrosion, and fouling, extends the equipment's lifetime, and reduces the frequency of costly turnarounds. In the present work, we coated Inconel 625 and Inconel 718 substrates with amorphous alumina thin films at room temperature using reactive RF magnetron sputtering. Annealing of the deposited coatings at 800, 900, and 1000 °C increased hardness, improved adhesion, and generated crystalline polymorphs, predominantly γ-Al2O3 at lower temperatures, while α-Al2O3 was present at 1000 °C. The annealed substrates formed thermally grown oxides (TGOs), which interacted with the alumina coatings. The TGOs followed grain boundaries in the case of IN718 and a crater-like pattern on IN625. Annealed substrate precipitates generated columnar-like protrusions responsible for inducing crack propagation, which exhibited TGO formation. After 2 h exposure to heavy oil (containing 0.06 g g−1 sulfur) at 450°C and 11.3 MPa the as-deposited amorphous alumina presented no clear sign of adherent fouling, while the 1000°C annealed crystalline alumina surfaces presented evidence of fouling

Spectral effects and enhancement quantification in healthy human saliva with surface-enhanced Raman spectroscopy using silver nanopillar substrates

ABSTRACT: Objectives Raman spectroscopy as a diagnostic tool for biofluid applications is limited by low inelastic scattering contributions compared to the fluorescence background from biomolecules. Surface-enhanced Raman spectroscopy (SERS) can increase Raman scattering signals, thereby offering the potential to reduce imaging times. We aimed to evaluate the enhancement related to the plasmonic effect and quantify the improvements in terms of spectral quality associated with SERS measurements in human saliva. Methods Dried human saliva was characterized using spontaneous Raman spectroscopy and SERS. A fabrication protocol was implemented leading to the production of silver (Ag) nanopillar substrates by glancing angle deposition. Two different imaging systems were used to interrogate saliva from 161 healthy donors: a custom single-point macroscopic system and a Raman micro-spectroscopy instrument. Quantitative metrics were established to compare spontaneous RS and SERS measurements: the Raman spectroscopy quality factor (QF), the photonic count rate (PR), the signal-to-background ratio (SBR). Results SERS measurements acquired with an excitation energy four times smaller than with spontaneous RS resulted in improved QF, PR values an order of magnitude larger and a SBR twice as large. The SERS enhancement reached 100×, depending on which Raman bands were considered. Conclusions Single-point measurement of dried saliva with silver nanopillars substrates led to reproducible SERS measurements, paving the way to real-time tools of diagnosis in human biofluids

Tribocorrosion test protocols for sliding contacts

ABSTRACT: Tribocorrosion is a term used to refer to material degradation resulting from a combination of tribological and corrosion processes. To understand better the interaction between wear and corrosion, and consequently to develop highly resistant materials, the materials development and testing community is in need of new experimental instruments and testing protocols. In this chapter, we present tribocorrosion rigs where electrochemical and tribological loadings can be applied simultaneously. Tribocorrosion testing protocols for sliding contact are discussed with the emphasis on advantages and disadvantages of using imposed vs free potential measurements. The imposed potential technique creates artificial oxidizing conditions and provides more quantitative data on synergism between wear and corrosion, whereas the free potential technique reproduces more closely the field conditions with less quantitative data