High-efficient low-cost characterization of materials properties using domain-knowledge-guided self-supervised learning

Modern AI-assisted approaches have helped material scientists revolutionize their abilities to better understand the properties of materials. However, current machine learning (ML) models would perform awful for materials with a lengthy production window and a complex testing procedure because only a limited amount of data can be produced to feed the model. Here, we introduce self-supervised learning (SSL) to address the issue of lacking labeled data in material characterization. We propose a generalized SSL-based framework with domain knowledge and demonstrate its robustness to predict the properties of a candidate material with the fewest data. Our numerical results show that the performance of the proposed SSL model can match the commonly-used supervised learning (SL) model with only 5 % of data, and the SSL model is also proven with ease of implementation. Our study paves the way to expand further the usability of ML tools for a broader material science community.

Some Theoretical and Experimental Extensions Based on the Properties of the Intrinsic Transfer Matrix

The work approaches new theoretical and experimental studies in the elastic characterization of materials, based on the properties of the intrinsic transfer matrix. The term ‘intrinsic transfer matrix’ was firstly introduced by us in order to characterize the system in standing wave case, when the stationary wave is confined inside the sample. An important property of the intrinsic transfer matrix is that at resonance, and in absence of attenuation, the eigenvalues are real. This property underlies a numerical method which permits to find the phase velocity for the longitudinal wave in a sample. This modal approach is a numerical method which takes into account the eigenvalues, which are analytically estimated for simple elastic systems. Such elastic systems are characterized by a simple distribution of eigenmodes, which may be easily highlighted by experiment. The paper generalizes the intrinsic transfer matrix method by including the attenuation and a study of the influence of inhomogeneity. The condition for real eigenvalues in that case shows that the frequencies of eigenmodes are not affected by attenuation. For the influence of inhomogeneity, we consider a case when the sound speed is varying along the layer’s length in the medium of interest, with an accompanying dispersion. The paper also studies the accuracy of the method in estimating the wave velocity and determines an optimal experimental setup in order to reduce the influence of frequency errors.

A Multi-Tool Analysis to Assess the Effectiveness of Passive Ice Protection Materials to Assist Rotorcraft Manual De-Icing

Search and rescue missions using rotorcrafts need to be reliable all year long, even in winter conditions. In some cases of deployment prior to take off, the crew may need to manually remove accumulated contaminant from the critical surfaces using tools at their disposal. However, icy contaminant may be hard to remove since the rotorcrafts critical surfaces could be cooler than the environment, thus promoting adhesion. Currently, there exists several passive ice protection materials that could reduce the ice adhesion strength and assist the manual de-icing. The aim of this paper is to propose a detailed comparative procedure to assess the ability of materials to assist the manual de-icing of rotorcrafts. The proposed procedure consists of the characterization of materials using several laboratory tests in order to determine their characteristics pertaining to wettability, their icephobic behavior, and finally their assessment under a multi-tool analysis to evaluate if they can assist. The multi-tool analysis uses different mechanical tools, which are currently used during normal operation, to execute a gradual de-icing procedure, which begins with the softest to the hardest tool using a constant number of passes or strokes, under different types of simulated precipitation. Five different materials were used to evaluate the proposed procedure: Aluminum (used as a reference), two silicone-based coatings (Nusil and SurfEllent), an epoxy-based coating (Wearlon), and finally a commercial ski wax (Swix). All of the tested materials could assist the manual de-icing, within a certain limit, when compared to the bare aluminum. However, SurfEllent was the material that obtained the best overall results. This procedure could be easily adapted to different fields of application and could be used as a development tool for the optimization and the assessment of new materials aimed to reduce ice adhesion.

NONLINEAR ACOUSTIC TECHNIQUE FOR MONITORING POROSITY IN ADDITIVELY MANUFACTURED PARTS

Ultrasonic wave based techniques are widely used for damage detection, and for quantitative and qualitative characterization of materials. In this study, ultrasonic waves are used for probing the response of additively manufactured 316L stainless steel samples as their porosity changes. The additively manufactured stainless steel specimens were fabricated using a laser powder bed fusion (LPBF) metal 3D printer. Four different levels of porosity were obtained by suitably controlling the LPBF process parameters. For generating ultrasonic waves, lead zirconate titanate (PZT) transducers were used. The signals were generated and propagated through the specimens in a transmission mode setup. Both linear and nonlinear analyses were used during the signal processing of the recorded signals for damage characterization. Linear ultrasonic parameters such as the time-of-flight (related to wave velocity) and signal amplitude (related to wave attenuation) were recorded. The nonlinear ultrasonic parameter, Sideband Peak Count - Index (SPC-I), was obtained by a newly developed nonlinear analysis technique called the SPC-I technique. Results obtained for the specimens were analyzed and compared for both linear and nonlinear ultrasonic analyses. Finally, the effectiveness of the SPC-I technique in monitoring porosity levels in additively manufactured specimens is discussed.

Extended characterization of materials based on continuous instrumented indentation diagrams

In addition to the traditional determination of hardness and elastic moduli from continuous diagrams of instrumental indentation, it is proposed to determine the yield stress, the characteristic of plasticity, the characteristic relative size of the elastoplastic zone under the indenter, and the volumetric deformation of the material in the area of contact of the indenter with the sample. The indentation diagram shows the transition point to the unconstrained material flow under the indenter. Keywords: indentation, hardness, elastic moduli, contact stiffness, elastic-plastic strains.

Characterization of materials used for earth architecture in Eastern Croatia

Even though earthen architecture is recognized as cultural heritage in Croatia, most of existing buildings are in deteriorated and heavily damaged state. Until today, there has been no conducted research on earthen architecture in Croatia, nor was any preservation act proclaimed. Therefore, the purpose of this research is to learn more about behaviour of traditional earthen architecture to highlight the importance of sustainable building. For that purpose, earthen houses in Eastern Croatia, mainly Slavonia and Baranja area, were studied and in-situ samples were collected. In order to learn about characteristics and composition of mixtures, five samples were tested. Results gathered within this research will be the first step towards creation of national standard for designing rammed earth structures. In scope of future research, authors are planning to use verified recipe in making of walls that will be tested for seismic resistance.

Thermal Lens Technique as a Potential Optical Tool

The spectroscopic characterization of materials involves the use of various optical tools. Spectrometers, interferometers etc, are some of the examples of optical tools. Thermal lens technique is one of the potential optical tools for the thermal characterization of different materials. The thermal lens effect is a photothermal effect which results when energy from a laser beam is absorbed by a sample, causing heating of the sample along the beam path. In this paper an overview of thermal lensing, its significance as potential optical tool and its applications are discussed. Index Terms: Optical tool, Photothermal spectroscopy, TLS application, Thermal diffusivity

Advances in Multi-Scale Mechanical Characterization of Materials with Optical Methods

The mechanical characterization of materials embraces many different aspects, such as, for example, (i) to assess materials’ constitutive behavior under static and dynamic conditions; (ii) to analyze material microstructure; (iii) to assess the level of damage developed in the material; (iv) to determine surface/interfacial properties; and (v) to optimize manufacturing processes in terms of process speed and reliability and obtain the highest quality of manufactured products [...]