Analysis of Asphalt Oxidation by Means of Accelerated Testing and Environmental Conditions

2018 ◽  
Vol 2672 (28) ◽  
pp. 244-255 ◽  
Author(s):  
Rafael E. Villegas-Villegas ◽  
Alejandra Baldi-Sevilla ◽  
José Pablo Aguiar-Moya ◽  
Luis Loria-Salazar
Keyword(s):  
Mechanical Response ◽  
Chemical Species ◽  
Accelerated Testing ◽  
Elastic Response ◽  
Pavement Performance ◽  
Specific Chemical ◽  
Environmental Process ◽  
Asphalt Oxidation ◽  
Ultraviolet Aging

The chemical changes that occur to asphalt with oxidation include an increase in oxygen content, as well as the unsaturation of the molecules. This change raises the polarity and stiffness of the material. As a consequence, the elastic response increases, altering its rheology. These transformations are essential to determine pavement performance during its service life. However, the characterization of these chemical and rheological processes cannot be completed because of the inefficiency of current procedures that simulate asphalt oxidation. For this reason, the objective of this study is to characterize asphalt oxidation fundamentally and to relate the observed changes in the materials’ mechanical response. To achieve this goal, a representative group of asphalt samples has been exposed to environmental oxidation, and alternatively to thermal and ultraviolet aging in the laboratory. The samples were characterized chemically and rheologically before the start of the experiment. It was possible to find a correlation between the content of specific chemical species in the material and their mechanical behavior at low and intermediate temperatures. In addition, the present study helps to understand the oxidation phenomena, and helps verify the ineffectiveness of traditional aging techniques, so that they can be modified to simulate the environmental process better.

Zeolite-Based Optical Detectors

2019 ◽  
pp. 1-16
Author(s):  
Fabian N. Murrieta-Rico ◽  
Vitalii Petranovskii ◽  
Rosario I. Yocupicio-Gaxiola ◽  
Vera Tyrsa
Keyword(s):  
Chemical Sensors ◽  
Chemical Compound ◽  
Chemical Species ◽  
Alternative Methods ◽  
Specific Chemical ◽  
Optical Detectors ◽  
Specialized Equipment ◽  
Optical Chemical Sensors ◽  
Zeolitic Materials

The detection of chemical species is a common and required task in several areas of technology. Currently, measurements in dedicated labs are the predominant tools for detection and characterization of chemicals and materials. Although these techniques are available in specialized equipment, their use is often bounded by cost of application or the operator's expertise. Also, in many applications rather than an analysis of all the detectable chemical species, it is only of interest to determine the presence of a particular chemical compound, and if it is present, to quantify its concentration. For these reasons, alternative methods for detecting specific chemical species are required. One case of such methods are the optical chemical sensors, particularly the ones based on the materials known as zeolites. In a broad sense, these sensors are constituted by an optical detector that is modified with zeolites. This combination allows the detection of specific chemical compounds if the zeolitic materials is properly modified to have an optical response for the analyte.

Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride

1996 ◽  
Vol 54 ◽  
pp. 636-637
Author(s):  
D. L. Callahan
Keyword(s):  
Plastic Deformation ◽  
Aluminum Nitride ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Bright Field Image ◽  
Perfectly Plastic ◽  
Contrast Analysis ◽  
Deformation Patterns

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.

scholarly journals Vocabulary of radioanalytical methods (IUPAC Recommendations 2020)

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Zhifang Chai ◽  
Amares Chatt ◽  
Peter Bode ◽  
Jan Kučera ◽  
Robert Greenberg ◽  
...  
Keyword(s):  
Nuclear Reactions ◽  
Hyperfine Interactions ◽  
Chemical Species ◽  
Radiation Detectors ◽  
Nuclear Analysis ◽  
Characterization Of Materials ◽  
Nuclear Effects ◽  
Nuclear Processes ◽  
Radioanalytical Methods

AbstractThese recommendations are a vocabulary of basic radioanalytical terms which are relevant to radioanalysis, nuclear analysis and related techniques. Radioanalytical methods consider all nuclear-related techniques for the characterization of materials where ‘characterization’ refers to compositional (in terms of the identity and quantity of specified elements, nuclides, and their chemical species) and structural (in terms of location, dislocation, etc. of specified elements, nuclides, and their species) analyses, involving nuclear processes (nuclear reactions, nuclear radiations, etc.), nuclear techniques (reactors, accelerators, radiation detectors, etc.), and nuclear effects (hyperfine interactions, etc.). In the present compilation, basic radioanalytical terms are included which are relevant to radioanalysis, nuclear analysis and related techniques.

scholarly journals Chemical Evaluation of Eumelanin Maturation by ToF-SIMS and Alkaline Peroxide Oxidation HPLC Analysis

2020 ◽  
Vol 22 (1) ◽  
pp. 161
Author(s):  
Martin Jarenmark ◽  
Peter Sjövall ◽  
Shosuke Ito ◽  
Kazumasa Wakamatsu ◽  
Johan Lindgren
Keyword(s):  
Molecular Structure ◽  
Secondary Ion Mass Spectrometry ◽  
Chemical Characterization ◽  
Experimental Treatment ◽  
Negative Ion ◽  
Pressure Treatment ◽  
Peroxide Oxidation ◽  
Specific Chemical ◽  
Tof Sims

Residual melanins have been detected in multimillion-year-old animal body fossils; however, confident identification and characterization of these natural pigments remain challenging due to loss of chemical signatures during diagenesis. Here, we simulate this post-burial process through artificial maturation experiments using three synthetic and one natural eumelanin exposed to mild (100 °C/100 bar) and harsh (250 °C/200 bar) environmental conditions, followed by chemical analysis employing alkaline hydrogen peroxide oxidation (AHPO) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Our results show that AHPO is sensitive to changes in the melanin molecular structure already during mild heat and pressure treatment (resulting, e.g., in increased C-C cross-linking), whereas harsh maturation leads to extensive loss of eumelanin-specific chemical markers. In contrast, negative-ion ToF-SIMS spectra are considerably less affected by mild maturation conditions, and eumelanin-specific features remain even after harsh treatment. Detailed analysis of ToF-SIMS spectra acquired prior to experimental treatment revealed significant differences between the investigated eumelanins. However, systematic spectral changes upon maturation reduced these dissimilarities, indicating that intense heat and pressure treatment leads to the formation of a common, partially degraded, eumelanin molecular structure. Our findings elucidate the complementary nature of AHPO and ToF-SIMS during chemical characterization of eumelanin traces in fossilized organismal remains.

scholarly journals Visco-Hyperelastic Characterization of the Equine Immature Zona Pellucida

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1223
Author(s):  
Elisa Ficarella ◽  
Mohammad Minooei ◽  
Lorenzo Santoro ◽  
Elisabetta Toma ◽  
Bartolomeo Trentadue ◽  
...  
Keyword(s):  
Zona Pellucida ◽  
Soft Matter ◽  
Mechanical Response ◽  
Mechanical Characterization ◽  
Nonlinear Material ◽  
Prony Series ◽  
Critical Comparison ◽  
Highly Nonlinear ◽  
Good Agreement

This article presents a very detailed study on the mechanical characterization of a highly nonlinear material, the immature equine zona pellucida (ZP) membrane. The ZP is modeled as a visco-hyperelastic soft matter. The Arruda–Boyce constitutive equation and the two-term Prony series are identified as the most suitable models for describing the hyperelastic and viscous components, respectively, of the ZP’s mechanical response. Material properties are identified via inverse analysis based on nonlinear optimization which fits nanoindentation curves recorded at different rates. The suitability of the proposed approach is fully demonstrated by the very good agreement between AFM data and numerically reconstructed force–indentation curves. A critical comparison of mechanical behavior of two immature ZP membranes (i.e., equine and porcine ZPs) is also carried out considering the information on the structure of these materials available from electron microscopy investigations documented in the literature.

scholarly journals Numerical Characterization of Cohesive and Non-Cohesive ‘Sediments’ under Different Consolidation States Using 3D DEM Triaxial Experiments

Processes ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1252
Author(s):  
Hadar Elyashiv ◽  
Revital Bookman ◽  
Lennart Siemann ◽  
Uri ten Brink ◽  
Katrin Huhn
Keyword(s):  
Mechanical Response ◽  
Burial Depth ◽  
Cohesive Sediments ◽  
Third Order ◽  
First Order ◽  
Numerical Characterization ◽  
Response To Stress ◽  
Bond Strengths ◽  
Individual Bond

The Discrete Element Method has been widely used to simulate geo-materials due to time and scale limitations met in the field and laboratories. While cohesionless geo-materials were the focus of many previous studies, the deformation of cohesive geo-materials in 3D remained poorly characterized. Here, we aimed to generate a range of numerical ‘sediments’, assess their mechanical response to stress and compare their response with laboratory tests, focusing on differences between the micro- and macro-material properties. We simulated two endmembers—clay (cohesive) and sand (cohesionless). The materials were tested in a 3D triaxial numerical setup, under different simulated burial stresses and consolidation states. Variations in particle contact or individual bond strengths generate first order influence on the stress–strain response, i.e., a different deformation style of the numerical sand or clay. Increased burial depth generates a second order influence, elevating peak shear strength. Loose and dense consolidation states generate a third order influence of the endmember level. The results replicate a range of sediment compositions, empirical behaviors and conditions. We propose a procedure to characterize sediments numerically. The numerical ‘sediments’ can be applied to simulate processes in sediments exhibiting variations in strength due to post-seismic consolidation, bioturbation or variations in sedimentation rates.

Mechanical Response of Different Lattice Structures Fabricated Using the CLIP Technology

2016 ◽  
Author(s):  
Anil Saigal ◽  
John R. Tumbleston ◽  
Hendric Vogel
Keyword(s):  
Additive Manufacturing ◽  
Mechanical Response ◽  
Elastic Response ◽  
Lattice Structures ◽  
Rhombic Dodecahedron ◽  
Structured Materials ◽  
Specific Strength ◽  
Strain Behavior ◽  
End Use ◽  
Continuous Liquid Interface Production

In the rapidly growing field of additive manufacturing (AM), the focus in recent years has shifted from prototyping to manufacturing fully functional, ultralight, ultrastiff end-use parts. This research investigates the mechanical behavior of octahedral, octet, vertex centroid, dode, diamond, rhombi octahedron, rhombic dodecahedron and solid lattice structured polyacrylate fabricated using Continuous Liquid Interface Production (CLIP) technology based on 3D printing and additive manufacturing processes. The compressive stress-strain behavior of the lattice structures observed is typical of cellular structures which include a region of nominally elastic response, yielding, plastic strain hardening to a peak in strength, followed by a drop in flow stress to a plateau region and finally rapid hardening associated with contact of the deformed struts with each other as part of densification. It was found that the elastic modulus and strength of the various lattice structured materials are proportional to each other. In addition, it was found that the octahedral, octet and diamond lattice structures are amongst the most efficient based on the measured specific stiffness and specific strength.

Virtual trabecular bone models and their mechanical response

2008 ◽  
Vol 222 (8) ◽  
pp. 1185-1195 ◽  
Author(s):  
F E Donaldson ◽  
P Pankaj ◽  
A H Law ◽  
A H Simpson
Keyword(s):  
Finite Element ◽  
Trabecular Bone ◽  
Mechanical Behaviour ◽  
Mechanical Response ◽  
Elastic Response ◽  
Anatomical Site ◽  
Virtual Samples ◽  
Micro Level ◽  
Architectural Characteristics

The study of the mechanical behaviour of trabecular bone has extensively employed micro-level finite element (μFE) models generated from images of real bone samples. It is now recognized that the key determinants of the mechanical behaviour of bone are related to its micro-architecture. The key indices of micro-architecture, in turn, depend on factors such as age, anatomical site, sex, and degree of osteoporosis. In practice, it is difficult to acquire sufficient samples that encompass these variations. In this preliminary study, a method of generating virtual finite element (FE) samples of trabecular bone is considered. Virtual samples, calibrated to satisfy some of the key micro-architectural characteristics, are generated computationally. The apparent level elastic and post-elastic mechanical behaviour of the generated samples is examined: the elastic mechanical response of these samples is found to compare well with natural trabecular bone studies conducted by previous investigators; the post-elastic response of virtual samples shows that material non-linearities have a much greater effect in comparison with geometrical non-linearity for the bone densities considered. Similar behaviour has been reported by previous studies conducted on real trabecular bone. It is concluded that virtual modelling presents a potentially valuable tool in the study of the mechanical behaviour of trabecular bone and the role of its micro-architecture.

Preparation and Characterization of γ-Fe2O3-ZnFe2O4 Composite Nanoparticles

2013 ◽  
Vol 873 ◽  
pp. 152-157
Author(s):  
Long Long Chen ◽  
Jun Ming Li ◽  
Xiao Min Gong ◽  
Jian Li
Keyword(s):  
Photoelectron Spectroscopy ◽  
Chemical Species ◽  
Composite Nanoparticles ◽  
X Ray Diffraction ◽  
Ferrite Core ◽  
Phase Synthesis ◽  
X Ray ◽  
Transmission Electron ◽  
Chemically Induced

Using a chemically induced transition in an FeCl2 solution, γ-Fe2O3 nanoparticles can be prepared from an amorphous precursor composed of FeOOH and Mg (OH)2. Surface modification by adding ZnCl2 during liquid-phase synthesis was attempted. The magnetization, morphology, crystal structure, and chemical species of as-prepared samples were characterized by vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray energy-dispersive spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The experimental results showed that the surface of the γ-Fe2O3 nanoparticles can be modified by adding ZnCl2 to form composite nanoparticles with a γ-Fe2O3/ZnFe2O4 ferrite core coated with Zn (OH)2 and absorbed FeCl36H2O; this modification can be enhanced by additional NaOH.

scholarly journals Mechanical assessment of defects in welded joints: morphological classification and data augmentation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hugo Launay ◽  
François Willot ◽  
David Ryckelynck ◽  
Jacques Besson
Keyword(s):  
Welded Joints ◽  
Spherical Harmonic ◽  
Data Augmentation ◽  
Mechanical Response ◽  
Training Data ◽  
Distance Functions ◽  
Elastic Response ◽  
Reduction Techniques ◽  
Harmonic Decomposition ◽  
Spherical Harmonic Decomposition

AbstractWe develop a methodology for classifying defects based on their morphology and induced mechanical response. The proposed approach is fairly general and relies on morphological operators (Angulo and Meyer in 9th international symposium on mathematical morphology and its applications to signal and image processing, pp. 226-237, 2009) and spherical harmonic decomposition as a way to characterize the geometry of the pores, and on the Grassman distance evaluated on FFT-based computations (Willot in C. R., Méc. 343(3):232–245, 2015), for the predicted elastic response. We implement and detail our approach on a set of trapped gas pores observed in X-ray tomography of welded joints, that significantly alter the mechanical reliability of these materials (Lacourt et al. in Int. J. Numer. Methods Eng. 121(11):2581–2599, 2020). The space of morphological and mechanical responses is first partitioned into clusters using the “k-medoids” criterion and associated distance functions. Second, we use multiple-layer perceptron neural networks to associate a defect and corresponding morphological representation to its mechanical response. It is found that the method provides accurate mechanical predictions if the training data contains a sufficient number of defects representing each mechanical class. To do so, we supplement the original set of defects by data augmentation techniques. Artificially-generated pore shapes are obtained using the spherical harmonic decomposition and a singular value decomposition performed on the pores signed distance transform. We discuss possible applications of the present method, and how medoids and their associated mechanical response may be used to provide a natural basis for reduced-order models and hyper-reduction techniques, in which the mechanical effects of defects and structures are decorrelated (Ryckelynck et al. in C. R., Méc. 348(10–11):911–935, 2020).

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