1,720,979 research outputs found
Uncertainty evaluation of small wear measurements on complex technological surfaces by machine vision-aided topographical methods
No full textWear assessment is an essential feature within the Industry 4.0 framework to optimise machining and control durability of components made of innovative materials. Complex topographies often make wear measurement a challenging task. Literature tackles it by comparing the final topography with the unworn state, either by empirical methods or by registration via machine vision algorithms. This paper develops a framework to evaluate the related measurement uncertainty, so far lacking, by exploiting instruments metrological characteristics and statistical modelling. This framework is applied to an industrially relevant case study to compare the performances of accredited methods for wear measurement available in literature
Augmented multi-scale instrumented indentation test characterization of complex multi-layered coatings for tribological application
Full text linkMulti-layer coatings for steel bushings consisting of an innermost layer of sintered bronze and an outermost composite layer of lead-reinforced polytetrafluoroethylene (PTFE+Pb) have been used in several power transmission applications. The PTFE+Pb layer provides lubrication by material transfer on the counter-body reducing friction and smoothing motion. The mechanical characterization of such a complex system is challenging and essential to provide input data necessary to design and predict the service life of the components. This work innovatively mechanically characterizes the coating by augmented multi-scale Instrumented Indentation Test (IIT). Nano-IIT will evaluate the uniformity of the Pb particles dispersion. Dynamic nano-IIT will investigate the damping properties of the material as a function of load frequency. Micro-IIT will tackle the layer thickness evaluation and the gradient of mechanical properties through the layers, by continuous multi-cycle and by data augmentation provided by electric contact resistance
Digital Metrology for Nanoindentation: Synthetic Data Generator for Error Identification
Full text linkDigital metrology enables precise, real-time measurement and data analysis using digital tools, which enhances accuracy and efficiency in manufacturing and quality control. Among key enabling technologies, Digital Twins allow continuous control, enabling predictive maintenance, faster error detection, and optimised performance of the measurement system. A current challenge is establishing traceability for the Digital Twins and for the data processing algorithms implemented in digital metrology. Nanoindentation is a challenging measurement technique that may be susceptible to several random and systematic measurement errors. This work presents a parametric synthetic dataset generator for quasi-static, room-temperature nanoindentation that incorporates correlation and covariance among simulated quantities. The method models indentation responses through a power-law formulation fitted via Orthogonal Distance Regression, allowing for traceable and physics-informed datasets. The generator enables the association of uncertainty with simulated results, supporting its use within a metrological framework. Its performance is benchmarked against non-parametric methods such as bootstrapping, showing comparable accuracy with significantly reduced computational cost and improved representativeness. Furthermore, the methodology can simulate main measurement errors for advanced material characterisation and develops a traceable tool based on synthetic data which could be used to train advanced quality control tools for the detection of main measurement errors
Nanoscale topographical characterization of permeability-related features in the production of polymeric films for food packaging
No full textPolymeric films play a vital role in food packaging, offering protective barriers that reserve the quality, safety, and shelf life of food products. Their performance depends on properties such as mechanical strength, thermal stability and permeability. Permeability is particularly important as it regulates the transfer of gases from the environment to food. Thus, permeability affects the shelf life, taste and safety of food products. The interaction between nanoscale surface features and permeability is a critical but under-explored aspect of film design. This study aims to test capability of surface topographical characterization as an alternative quality inspection tool for permeability in commercial polymer films. Advanced techniques such as Atomic Force Microscopy (AFM) are used to characterize surface features including roughness and morphology. The results will provide an alternative route for the permeability quality control in manufacturing processes of state-of-the-art commercial polymer films for food packaging
Metrological Comparison of Indirect Calibration Methods for Nanoindentation: A Bootstrap-Based Approach
Full text linkArea shape function and frame compliance are the most critical parameters in nanoindentation, as they control measurement accuracy and represent the largest contributions to measurement uncertainty. Despite the availability of direct calibration methods, indirect calibrations are the most practical and fast. Thus, the indirect calibration methods proposed in ISO 14577-2 are most typically applied in academic and industrial research, as well as in quality controls. Previous research has highlighted some criticalities, but a holistic metrological framework was missing. This work aims to compare the performances of indirect calibration methods for area shape function and frame compliance in the nano-range, considering different alternatives suggested in the standard and most recent literature. The comparison will be based on uncertainty estimation using bootstrap estimation, which will innovatively highlight and introduce the effect of the nanoindentation dataset in the uncertainty estimation. The results show that the optimization of accuracy and uncertainty in mechanical characterization is achieved by indenting pairs of certified reference materials, resulting in a more robust approach to calibration experimental conditions than methods that require a single sample to be indented
Uncertainty-based comparison of conventional and surface topography-based methods for wear volume evaluation in pin-on-disc tribological test
No full textPrecise wear evaluation is essential to develop prediction models, applied to design materials, components and to optimise new manufacturing processes. Pin-on-disc is a widespread standardised conventional sliding wear test. Conventional characterisation of resulting wear exploits gravimetric or profilometric techniques. These have inadequate precision and accuracy for applications characterised by low-wear and uneven morphology and are being replaced with high-resolution and information-rich inspections to measure surface topography. Metrological characterisation of topography-based methods still lacks in literature, which prevents the performance comparison with conventional techniques. This paper develops a framework to evaluate topography-based methods’ measurement uncertainty and compare methods’ performances accordingly on experimental wear data on PTFE and Aluminium. Results show that topographic methods improve pin-on-disc characterisation's reliability
An artificial intelligence classifier for electron beam powder bed fusion as-built surface topographies
Full text linkCalibration of machine platform nonlinearity in Instrumented Indentation Test in the macro range
Full text linkInstrumented Indentation Test (IIT) is a non-conventional mechanical characterization technique to evaluate hardness, Young modulus, creep and relaxation of materials. In the macro range, it represents a cheaper and faster alternative to conventional tensile-based tests. IIT is a metrological scale; thus, to establish traceability, calibration is essential. Frame compliance calibration is critical because it is a major contribution to the measurement uncertainty. This work discusses the limits of the current state-of-the-art and proposes a novel methodology for frame compliance calibration. The introduced approach demonstrates the source of common systematic errors in the mechanical characterization reported in the literature, i.e. edge effect, while first highlighting a relevant frame compliance nonlinearity. The proposed procedure is cost-effective and relies upon constitutive spring modelling of IIT and calibration of reference block by nanoindentation. Results show that the novel approach corrects systematic trends in the characterization and yields a relative measurement uncertainty of 5%
Grinding performance and theoretical analysis for a high volume fraction SiCp/Al composite
No full textSiCp/Al composite is widely used in space shuttle slides, automotive and machine tools. In this paper, ground surfaces of SiCp/Al composite, obtained with different grinding process parameters, are characterized in terms of friction and wear performances under dry and lubricated conditions. The wear mechanism of SiCp/Al composite is firstly found the combination of cohesive and abrasive wear, then a method to calculate the wear volume of SiCp/Al composite is proposed, and a comprehensive wear evaluation system of SiCp/Al composite is established, in which the three indicators of friction coefficient, wear depth, and equivalent wear section area are adopted to evaluate usability performance. The prediction models of the wear indicators were established and the errors between the experimental and predicted results are within 7%. Finally, the NSGA-II multi-objective algorithm is used to optimize surface performance of the SiCp/Al composite, and the optimized grinding process parameters are obtained as the wheel speed of 33 m/s, the table speed of 0.4 m/min and the grinding depth of 9 μm
Uncertainty-based comparison of the effect of the area shape function on material characterisation in nanoindentation testing
Full text linkInstrumented Indentation Test (IIT) is largely exploited in industry and academia to achieve multi-scale mechanical characterisation, i.e. ranging from nano- and micro-structure to bulk, of several properties, e.g. Young's modulus, stress-strain curve, creep, and relaxation. IIT is particularly suited to cope with the challenges of the current industrial framework to achieve multi-objective characterisation and requirements of zero-defect manufacturing and zero waste. In fact, IIT requires limited sample preparation and is a non-destructive technique with high throughput. IIT consists of applying a loading-unloading force cycle on the specimen. The capability of continuously measuring the indenter displacement in the material, i.e. being a depth-sensing technique, is the essential feature of IIT. This allows the mechanical characterisation by knowing the shape of the indenter and hence the relationship between the indentation depth and the projected area of the surface in contact between the indenter and the specimen. The relationship is described by the area shape function, whose parameters require calibration according to ISO 14577-2:2015. For a given indenter geometry, several alternative models are available in the literature. These describe both the geometry and the possible presence of errors, e.g. blunt tip and wear effect. However, a comparison of the choice of the different alternatives, when they are equally nominally applicable, is lacking in the literature, although it prescribes some applicability ranges. This work exploits a simulative approach based on bootstrap sampling to estimate the uncertainty of the calibration of area shape function parameters in the nano-range, where the effect is critical. The uncertainty is then propagated to compare performances of different area shape function models on the mechanical characterisation, i.e. indentation hardness and Young's modulus estimate, within a rigorous metrological framework. Results are shown for standard reference materials, i.e. SiO2 and W, to ensure proper composition homogeneity and neglect edge effects, i.e. pile-up and sink-in
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