Polymers are essential for the automotive industry, the aircraft industry and medical devices due to their combination of lightness and strength. However, performance of polymers might decrease with their degradation and wear studies become necessary to ensure both usefulness and safety during their operation time. This article studies the physical phenomena involved in the abrasion of nine common polymers using surface topography. Polymer disks are cut from polymer rods, followed by a mirror-polishing and then by abrasion with silicon carbide abrasive papers from grades 80-4000. A white light interferometer is used to measure high-resolution over a large field-of-view topographies of the polymer disk surfaces thanks to stitching. To determine the scale of applications of physical phenomena involved in the abrasion process, four multiscale roughness decompositions are applied on topography and compared: the patchwork method, the box Sa method, the box Sz method and the motif method. All multiscale analyses have detected a cross-over separating micro and macro abrasion for all polymers and abrasive paper grades. A new parameter, the Abrasive Ratio Ar, is introduced, representing the ratio between the penetration depth of the abrasive grain into the polymer disk over the abrasive grain size. This parameter helps the identification of four abrasion wear mechanisms and their scale of applications: the hydrostatic limit stage (80 mu m and higher), the strain hardening stage (30 mu m - 80 mu m), the localized adhesion stage (10 mu m - 30 mu m) and the grit size effect stage (10 mu m and smaller).

This study presents a robust methodology for analyzing 3D roughness parameters to characterize sandblasted surfaces, identifying the most relevant descriptors for process optimization. Sandblasting with irregularly shaped corundum particles is performed using five grit sizes (25, 50, 90, 125, and 250 µm) and three pressure levels (2, 3, and 4 bar). The resulting surfaces are characterized through eight 3D roughness parameters: Sa, Spc, Sal, Sfd, Sdq, Sdr, Spd, and Str. A linear model of the form Q = a + b.D + d.D.P, where Q represents the roughness parameter, D is the average grit size, and P is the sandblasting pressure, is employed. For Spd, a nonlinear model, Spd = (a + b.D + d.D.P)2, yields a significantly improved determination coefficient, demonstrating the model’s enhanced ability to capture the complexity of the Spd parameter. The double-bootstrap analysis validates the statistical significance of all models, providing confidence intervals for each parameter. This approach emphasizes the importance of advanced 3D roughness descriptors for accurately analyzing surface textures in sandblasting processes, offering a reliable framework for surface characterization and industrial optimization.

Surfaces are the privileged places of interaction between physical phenomena and objects. Roughness studies, especially when performing multiscale analysis, are tools of choice to understand physical phenomena and their scales of application. However, profilometers, especially optical systems, must compromise between field of measurement and resolutions. Stitching is an assembling technique aiming to solve this compromise by combining elementary maps, such as images or topographies. Stitching generates high resolution over a large field of measurement maps, which increases the measurable scale range and facilitates the correct identification of physical phenomena at their scales of application. This article proposes a review of 3D topography stitching algorithms. After explanations on the use cases of 3D topography stitching, the stitching procedure from elementary maps acquisition to the obtention of the stitched map is described step-by-step. Secondly, errors in measurement and stitching are presented with the sources of errors and the error evaluation methods. Lastly, the mathematical modelling of 3D topography is detailed to better understand the optimization process used in the in-plane and out-of-plane registration steps of the stitching algorithms. Comparison of algorithms involved in stitching are proposed so that researchers might find the most suitable algorithm to their needs. Overall, this work aims at introducing researchers and metrologists to important multidisciplinary notions for the use and design of 3D topography stitching algorithms and offers a tutorial-based approach.

Distinguishing between right-handed and left-handed painters in the realm of painting is a question approached from various angles across different disciplines. Each approach, whether it's from neuropsychology, the study of the artwork itself, or the artist's imprint on the work, contributes insights to the burning question of whether the myth of the left-handed painter being more talented than their right-handed counterparts holds true. In this study, we introduce an experimental method involving both left-handed and right-handed painters to determine if the surface topography of brushstrokes presents relevant parameters for differentiating handedness. After conducting an analysis of variance (ANOVA), we isolated relevant roughness parameters, the most significant are the mean hill roundness (Shrn) and the maximum dale aspect ratio (Sdarx). These parameters exhibit significant differences based on the painter's dominant hand. Other parameters also provide insights into the reliability of our study, specifically the texture direction (Std), which shows no difference among the painters. The results are discussed. These findings pave the way for a more comprehensive understanding of the painter's stroke in the process of art painting creation.

Identification of an individual artist’s touch on paintings is studied using surface metrology. Paintings’ topographies were measured using focus variation and stitching, creating 13 × 13 mm maps with 1 μ m sampling intervals, and 169 megapixels, with a 10X objective lens. Topographic characterization parameters were analyzed for their ability to differentiate different painters’ renderings. Statistical treatments from data mining were used to discriminate, by optimization, multiscale topographic signatures characterized by a multitude of areal texture parameters. It appears that a fractal dimension can define 3 characteristic scale ranges. One from 3 to 70 μ m corresponds to brushstroke details. Another, from 70 to 700 μ m, corresponds to the topography of the material of the canvas fabric. Finally, scales greater than 700 μ m correspond to undulations of the canvas. For scales less than 50 μ m, the fractal structure of the topography left by brushstrokes follows a power law characterized by the slopes of the topography. The topography of the clouds painted on the canvas has an Sdq (topographic slopes) increasing with the clarity of the clouds at scales of 3–500 μ m. According to the Torrance-Sparrow theory, the higher the Sdq, the more diffuse the light on the surface. The painter therefore wanted to show, by his brushstroke, that the light clouds diffuse more light giving an impression of local brightness. This study is confirmed by the analysis of the painting of Max Savy, a French painter from Carcassonne (1918–2009), which was measured with a white light interferometer Zygo NewView 7300, a X100 objective lens giving a 517 μ m × 517 μ m stitched surface, with a sampling interval of 0.109 μ m. The box-counting method for estimating the fractal dimension of the topography of an oil painting appears optimal by the fact that it morphologically integrates scale variations of the local slopes of the surface morphology. This method thus characterizes the multiscale aspects, as well as the scale changes, of the topography.

There is a growing interest in cultural heritage preservation. The notion of HyperHeritage highlights the creation of new means of communication for the perception and data processing in cultural heritage. This article presents the Digital Surface HyperHeritage approach, an academic project to identify the topography of art painting surfaces at the scale at which the elementary information of sensorial rendering is contained. High-resolution roughness and imaging measurement tools are then required. The high-resolution digital model of painted surfaces provides a solid foundation for artwork-related information and is a source of many potential opportunities in the fields of identification, conservation, and restoration. It can facilitate the determination of the operations used by the artist in the creative process and allow art historians to define, for instance, the meaning, provenance, or authorship of a masterpiece. The Digital Surface HyperHeritage approach also includes the development of a database for archiving and sharing the topographic signature of a painting.

Rough surfaces are in contact locally by the peaks of roughness. At this local scale, the pressure of contact can be sharply superior to the macroscopic pressure. If the roughness is assumed to be a random morphology, a well-established observation in many practical cases, mechanical indicators built from the contact zone are then also random variables. Consequently, the probability density function (PDF) of any mechanical random variable obviously depends upon the morphological structure of the surface. The contact pressure PDF, or the probability of damage of this surface can be determined for example when plastic deformation occurs. In this study, the contact pressure PDF is modeled using a particular probability density function, the generalized Lambda distributions (GLD). The GLD are generic and polymorphic. They approach a large number of known distributions (Weibull, Normal, and Lognormal). The later were successfully used to model damage in materials. A semi-analytical model of elastic contact which takes into account the morphology of real surfaces is used to compute the contact pressure. In a first step, surfaces are simulated by Weierstrass functions which have been previously used to model a wide range of surfaces met in tribology. The Lambda distributions adequacy is qualified to model contact pressure. Using these functions, a statistical analysis allows us to extract the probability density of the maximal pressure. It turns out that this density can be described by a GLD. It is then possible to determine the probability that the contact pressure generates plastic deformation.

Surface gradient characterization by light reflectance (SGCLR) is used for the first time for multiscale curvature calculations and discrimination of worn surfaces on six damaged ceramic–metal composites. Measurements are made using reflectance transformation imaging (RTI). Slope and curvature maps, generated from RTI, are analyzed instead of heights. From multiscale decompositions, bootstrapping, and analysis of variance (ANOVA), a strong correlation (R² = 0.90) is found between the density of furrows of Mehlum curvatures, with a band pass filter at 5.4 µm, present in ceramic grains and their mechanical properties. A strong correlation is found between the mean curvatures of the metal and the ceramics, with a high pass filter at 1286 µm.

Short-fibre-reinforced thermoplastic polymers (SFRT) are appealing materials for use in technical applications, due to high rigidity/density ratio, in particular. However, SFRT have complex anisotropic mechanical behaviour, because of specificities of thermoplastic matrix behaviour and heterogeneous reinforcement characteristics, in particular in terms of fibre orientation. For instance, matrix behaviour can be viscoelastic and/or viscoplastic (i.e. sensitive to strain rate) pressure sensitive, damageable, etc. Moreover, mechanisms of load transmission from matrix to fibres, at fibre/matrix interface, are still not very well known, although they play a crucial role in SFRT mechanical behaviour. For instance, there is no information about their eventual strain-rate sensitivity. In this study, the 3D microstructure of an injection moulded short-fibre-reinforced polypropylene is reconstructed using micro-computed tomography. The tensile macroscopic behaviour of the composite is then studied under different angles of loading with respect to injection flow direction and different displacement rates, in quasi-static and dynamic range (from 1 min/min to 1 m/s). The anisotropy of the composite behaviour can therefore be analysed not only in terms of dependence on macroscopic loading direction, but also on actual fibre distribution of orientation relatively to tensile direction, at the microscopic scale. In an original way, coupled influence of fibre orientation and strain rate is then studied. One of the most significant results is that fibre/matrix interfacial behaviour, which governs load transmission from matrix to fibres, does not show strain rate sensitivity for the considered composite and strain-rate range (5.10(-4) to 50 s(-1)). (C) 2016 Elsevier Ltd. All rights reserved.

This two-part paper described the results of the research programme PROCAB for train driver protection during rail collisions. In Part I, a methodology was proposed to analyse driver survivability in train crash. Appropriate experimental devices and associated numerical models were developed which were able to reproduce the loads and accelerations imparted to the train driver and on the interior elements of the driver's cabin. A full validation programme was realised involving correlation between experimental methods and computer model outputs. Experiments and computer results indicated that during a collision, the driver was likely to strike the desk at the lower chest. Since actual desk was extremely rigid due to maintenance requirements, chest deflection exceeded human tolerance. Part II deals with the development of an interior driver protection.

This two-part paper described the results of the research programme PROCAB (French acronym for PROtection CABine) for train driver protection in rail collisions. In the part I, virtual and physical testing were developed to predict the train driver dynamics and related injuries due to secondary impact with cabin furniture. The conclusion was that the desk represented a hostile secondary impact environment for the locomotive engineer by inducing severe thoracic injuries. Part II included the design, fabrication and testing of an improved command desk. The concept selected was a movable rigid desk with energy-absorbing aluminium honeycomb to slow the desk motion, coupled with knee bolsters. A prototype of the protection device was fabricated and evaluated in a dynamical sled test under a 5g, 0.1s deceleration pulse. Preliminary results demonstrated the effectiveness of this concept in reducing the thoracic injury risk without increasing risk in another area (head, neck, chest, femurs and tibias).

Click to increase image sizeClick to decrease image sizeKeywords:: train collisionsecondary impactdriver protectionimpact biomechanicsinjury mechanisms AcknowledgementsThis research was supported by the Nord-Pas-de-Calais Region, the European Community, the Regional Delegation for Research and Technology, the Ministry of Higher Education and Research and the National Center for Scientific Research.