Variation Of Material Properties Research Articles

Anti-radiation protection of astronauts in the process of working on the surface of the Moon in a short-term mission

Introduction. The issue of assessing the types of ionizing radiation characteristic of the lunar surface, the anti-radiation properties of various materials, and factors ensuring the anti-radiation safety of astronauts when placed on the lunar surface, taking into account the radiation safety standards for personnel, remains insufficiently studied.
 The study aims to analyze the factors that determine the features of anti-radiation protection of astronauts in future lunar settlements.
 Materials and methods. During the study, experts used analytical methods to generalize and systematize materials on the levels of dose load on astronauts at the stages of space flight and on the surface of the Moon. The researchers also used computational methods taking into account the anti-radiation properties of various materials, depending on the type of ionizing radiation, to develop approaches to the organization of anti-radiation protection of astronauts in conditions of short-term (up to 14 days) stay on the surface of the Moon.
 Results. The researchers have carried out the analysis of the factors determining the radiation hazard for astronauts during their stay and work in lunar settlements. It is proved that when developing anti-radiation protection, it is necessary to use the housing of the lunar module (aluminum frame), lunar regolith and polyethylene. With the multilayer protection of the lunar module, it is necessary to take into account the attenuation coefficients of materials for various types of ionizing radiation, which will reduce the doses from both direct gamma radiation, protons and neutrons, and from scattered secondary radiation.
 Conclusion. Various design options for the protection of the lunar station modules by the thickness of their constituent layers will provide anti-radiation protection of premises for various purposes, depending on the possible options for solar activity and the required levels for residential, working, emergency compartments.
 Ethics. The study was conducted in compliance with Ethical standards.

Failure analysis and structural reliability of unreinforced masonry veneer walls: Influence of wall tie corrosion

Corrosion appears to be a very common problem in historical and aged structures with steel ties and anchorages. A potential rapid deterioration of the wall tie due to the corrosion leading to a premature structural failure poses a serious threat to the built heritage infrastructures’ safety. This paper describes an overview of the probabilistic failure analysis of the unreinforced masonry (URM) veneer wall system with flexible backup under uniformly distributed out-of-plane loadings. Moreover, a framework is proposed to consider the wall tie corrosion in the stochastic finite element analysis (FEA) while estimating the structural reliability. A probabilistic experimental study where 18 full-scale URM veneer wall systems with theoretically identical geometries and properties were tested under inward and outward lateral loading. Wall failure statistics along with the probabilistic characterisation of veneer wall constituent materials including mortar, wall tie and timber were accomplished. A stochastic computational model was then developed which combines the FEA and Monte Carlo simulation to evaluate the failure progression and system peak load (veneer capacity) while considering the spatial variability of veneer wall material properties. Two scenarios, with and without wall tie corrosion, are considered, and the probabilistic characterisation of the veneer capacities for these scenarios under inward and outward out-of-plane loading is also reported. The model error statistics were combined with the probabilistic load models to determine the reliability index corresponding to the Australian Standard for Masonry Structures AS 3700. Annual reliabilities are compared to target reliabilities recommended by ISO 2394. Capacity reduction factor and design minimum tie strength consideration for corroded wall tie is also discussed.

Charpy absorbed energy in simulated heat-affected zone of laser-arc hybrid welded joints by high-strength steel for bridge structures

The application of laser-arc hybrid welding (so-called, hybrid welding) to the fabrication of steel bridge members has recently been investigated. One-pass full-penetration butt joints of steels for bridge high-performance structure (SBHS400 and SBHS500) with a thickness of 15 mm were performed by hybrid welding. The sound butt joints by hybrid welding were confirmed by a series of tests. The Charpy impact test was performed on the test pieces extracted from the hybrid welded butt joints with specified test temperatures. A phenomenon known as fracture path deviation (FPD) occurred in most test pieces, due to a large variation in material properties of the heat-affected zone (HAZ), resulting in the difficulty of estimating the toughness of HAZ in hybrid welded joints. Therefore, the Charpy impact test was conducted on the test pieces subjected to the welding thermal cycle tests of hybrid welding, which can exclude the heterogeneity of material properties and obtain the Charpy absorbed energy of the HAZ with high accuracy. The test results indicated that FPD was not observed in all thermal cycle simulated test pieces because the uniform metallographic structures in the vicinity of the notch were formed by the simulated thermal cycle tests, and all thermal cycle simulated test pieces satisfied 47 J at the specified test temperatures, a value that prevents brittle fracture for SBHS. Besides, for investigating the effect of the high Charpy absorbed energy guaranteed by SBHS on the toughness of hybrid welded joints, the Charpy absorbed energy of the thermal cycle simulated test pieces of SBHS and those of conventional steel (SM400B) were compared. The results showed that some of the thermal cycle simulated test pieces of SM400B failed to satisfy 27 J, suggesting that SBHS may ensure a Charpy absorbed energy of 47 J or more in the HAZ of hybrid welded joints.

Predicting Ballast Fouling Conditions Through RGB-Based Statistical Quantity Analysis

Evaluating railway ballast fouling is critical to assessing track conditions and planning proper ballast maintenance. Varying material properties associated with different ballast fouling conditions can be used to evaluate the severity of fouling. Although approaches using ground penetration radar, impulse response, surface wave, and SmartRock have been developed to estimate the fouling conditions, these methods require special sensors and equipment, or well-trained technicians. Recently, convolutional neural network (CNN) based computer vision approaches have become popular in performing particle segmentation to obtain the ballast grain size distribution. The coarse aggregate fraction can be evaluated by the CNN method, but it is not easy to segment fine particles accurately with these approaches. This study proposes a novel image analysis approach to directly estimate the ballast fouling conditions. First, fouled ballast images with different fouling conditions are taken as references. The RGB (red, green, blue) color distributions of the fouled ballast images are then processed through statistical analysis. A strong linear correlation is found between Fouling Index (FI) and variance and this is used to establish the FI prediction model. The established FI prediction model is tested and validated by additional fouled ballast samples. The FI prediction model proposed in this study can be used to quantify ballast fouling conditions with promising performance.

Temperature effect on buckling behavior of prestressed CFRP-reinforced steel columns

Prestressed carbon fiber reinforced polymer (CFRP)-reinforced steel columns behave differently under extreme temperature conditions because CFRP prestress changes with temperatures varying and is a key factor influencing the buckling behavior of such columns. This paper deeply studies the temperature effect on the buckling behavior of the composite columns. First, varying material properties from −80 to 80 °C are studied, and the temperature effect mechanism on the buckling behavior of such column is investigated. Moreover, analyses of two temperature situations are conducted using finite element modeling. When the column is loaded at a certain temperature, the buckling capacity maintains almost constant with temperature varying from 20 to 80 °C, while it increases 3%–7% when the temperature drops from 20 to −80 °C. When the column is preloaded and then the temperature changes, from 20 to 80 °C, the column extends, and the deformation is first symmetric and global and then changes to local and asymmetric when the temperature reaches a turning point; from 20 to −80 °C, the column shrinks, and the deformation is symmetric and global. Additionally, varying temperature may lead to a large change in CFRP stress (as high as 321.9 MPa), which causes significant reduction in the buckling capacity (as much as 18%). These findings provide valuable references for the design of such columns and related thin-walled structures under extreme temperature conditions.

Prediction of concrete compressive strength employing machine learning techniques

Machine learning (ML) methods have proven to be reliable techniques in estimating, classifying, and predicting material strength based on varying material properties. It is observed that the nature of the problem and the data at hand governs the selection of an appropriate ML method. Therefore, to determine the accuracy of ML models to predict concrete compressive strength, fifteen different ML algorithms were applied to a given concrete compressive strength dataset. Among all the ML algorithms used, the prediction accuracy of the Support Vector Regressor (SVR) was the highest (88.18%) due to its effective performance when dealing with continuous target variables and nonlinear relationships among the features and the target.

Material variability effects on automotive part production process

The current efforts to reduce the carbon footprint throughout the chain in the automotive industry by increased use of recycled materials poses new challenges for materials production and their use. The increase of steel scrap fraction in the current primary steel making processes, used for producing steel sheet metal for automotive components, possibly affects the material properties variability beyond the limits observed in the materials produced today despite mitigating actions in steel production. In this paper material variability increase was modelled by selecting deterministic values outside the range of the material grade used to design and manufacture an automotive part. The values were selected from an experimental data set representing the cold rolled mild steels material class range. The effects were studied numerically on a reverse engineered model of an existing automotive part production process. It was found that the manufacturing feasibility in this particular case is mainly affected by the weighted average plastic strain ratio and less by the degree of planar anisotropy.

Development of mechanical property prediction model and optimization for dissimilar aluminum alloy joints with the friction stir welding (FSW) process

Friction stir welding (FSW) is a solid-state joining process used to weld dissimilar aluminum alloys with varying material properties and compositions. Unlike traditional welding methods, FSW does not involve melting the materials being welded but instead uses a rotating tool to heat and stir the materials until they are in a plastic state. The process results in a welded joint with high strength, excellent ductility, and minimal distortion, making it a popular choice in various industries, including aerospace, automotive, and marine. AA6061-T6 (Mg-Si) and AA7075 (Al-Zn-Mg-Cu) aluminum alloys are one of the most popular grades of aluminum alloys used in current manufacturing industries, such as aerospace and automotive, joined by the Friction Stir Welding Process (FSW) technique. Taguchi orthogonal array (L9) experimental design was applied to reduce the number of insignificant factors in the process. First, the study determines three welding factors: rotation speed, travel speed, and pin eccentricity. Investigations found that travel speeds significantly on tensile strength (Ts) and elongation ( %El), but the rotational speed and tool eccentricity did not affect Ts and %El. Furthermore, considering the fabricated parameters on the hardness (HV) of the joint, it was found that all factors unaffected the HV of the joint zone at a 95 % confidence level. Next, examine the microstructure; Mg2Al3 and Al2O3 intermetallic compounds were found in the weld. Therefore, investigating the crystallite size found that welding significantly affects the crystallite size. Finally, consider the fracture surface, experimental condition A2B1C2 (optimal parameter), which is the parameter with the highest tensile strength having dimple fracture characteristics. On the other hand, the welding condition A1B3C3, the parameter with the lowest tensile strength, Small and fine dimple fracture with cleavage fracture. Because the material is highly ductile and can undergo large deformations before it is damaged. On the other hand, materials with low tensile strength exhibiting cleavage fracture indicate that the materials are brittle and can break easily under stress

A Dynamic Analysis of Porous Coated Functionally Graded Nanoshells Rested on Viscoelastic Medium

Theoretical research has numerous challenges, particularly about modeling structures, unlike experimental analysis, which explores the mechanical behavior of complex structures. Therefore, this study suggests a new model for functionally graded shell structures called “Tri-coated FGM” using a spatial variation of material properties to investigate the free vibration response incorporating the porosities and microstructure-dependent effects. Two types of tri-coated FG shells are investigated, hardcore and softcore FG shells, and five distribution patterns are proposed. A novel modified field of displacement is proposed by reducing the number of variables from five to four by considering the shear deformation effect. The shell is rested on a viscoelastic Winkler/Pasternak foundation. An analytical solution based on the Galerkin approach is developed to solve the equations of motion derived by applying the principle of Hamilton. The proposed solution is addressed to study different boundary conditions. The current study conducts an extensive parametric analysis to investigate the influence of several factors, including coated FG nanoshell types and distribution patterns, gradient material distribution, porosities, length scale parameter (nonlocal), material scale parameter (gradient), nanoshell geometry, and elastic foundation variation on the fundamental frequencies. The provided results show the accuracy of the developed technique using different boundary conditions.

An analysis of the sensitivity of the rate of buoyancy-driven flame spread on a solid material to uncertainties in the pyrolysis and combustion properties. Is accurate prediction possible?

In this study, upward flame spread over a combustible solid in a vertical corner configuration was simulated using two widely used computational tools – ThermaKin2Ds and the Fire Dynamics Simulator (FDS) – and predicted sensitivity of fire growth dynamics to variations in material properties was examined to determine which ones carry measurement uncertainties that translate into the largest errors in predicted behavior. The nominal value of each material property was calculated as the average of measured values of a balanced set of 26 materials that represent the combustible polymeric solids widely used in industrial, transportation, and construction applications. The upper and lower boundaries of each property were defined based on an uncertainty quantification of each specific measurement. These average material properties and related uncertainties were determined based on an extensive literature review presented in this work.A measure of average flame spread velocity was defined (based on the time derivative of pyrolysis front location) as the model output to characterize fire growth dynamics. Overall, ThermaKin2Ds and FDS generally demonstrate similar sensitivity to model inputs. For both simulation tools, uncertainties in reaction kinetics (Ea/ln(A)) and heat capacity of the virgin material, had the most significant effect on calculated average flame spread velocity, resulting in changes in this output (on average, for both simulation tools) of approximately 20%. FDS simulations also demonstrated a strong sensitivity to variations in heat of combustion when it was adjusted from its mean value to its lower or upper uncertainty bounds (17% change in average flame spread velocity; 2, 3 times as sensitive as ThermaKin2Ds results). In ThermaKin2Ds, an approximate 10% sensitivity in predicted average flame spread velocity was observed to variations in thermal conductivity of the virgin material, while in FDS this output demonstrated limited sensitivity to this parameter change. Uncertainties in the density of the virgin material and its char yield also showed a notable impact on predicted average flame spread velocity in both simulation tools. All other material properties considered in this work were found to demonstrate negligible influence on average flame spread velocity, which indicates that these parameters are measured with sufficient accuracy to deliver reasonably accurate predictions of flame spread dynamics.

Deep learning operator network for plastic deformation with variable loads and material properties

Deep learning operator network for plastic deformation with variable loads and material properties

Uncertainty quantification of wood floor system modal frequencies resulting from variable densities in members

Low-frequency vibration in a multi-story wood building is of concern because failure in mitigation of such vibration may lead to occupant discomfort. Ultimately, it may cause damage to their health. Variability in material properties of the members of a wooden floor system significantly influences vibration response characteristics such as eigenfrequencies and mode shapes. In this study, we investigate the uncertainty in low-frequency characteristics of a selected wood floor system, resulting from uncertainty in the members’ material properties. We use a surrogate model developed using polynomial chaos expansion, based on a few training samples computed using a finite element model of an experimental-scale structure comprised of seven load-bearing joists of spruce. We estimate the hyperparameters needed for accurate surrogate model development and, with these, we predict probability distributions for each of the floor-system modal frequencies. Also, we perform local and global sensitivity analyses to assess how material property variation affects the modal frequencies. Results confirm the accuracy and efficiency of the developed surrogate models in prediction of the modal frequencies, resulting from uncertainty in wood material properties. The accuracy of the results is comparable to those based on more expensive Monte Carlo simulation.

Design for Recycling: Polyester- and Polycarbonate-Based A–B–A Block Copolymers and Their Recyclability Back to Monomers

Chemical recycling to monomers (CRMs) of A–B–A block copolymers is governed by the chemical structure and thereby the thermodynamic behavior of different block constituents. Here, we show how a thermodynamic toolkit based on a cyclic monomer structure and solvent properties can be utilized in the design of recyclable A–B–A block copolymers with varying material properties. By combining four cyclic monomers lactide, ε-decalactone, 2,2-diethyltrimethylene carbonate, and trimethylene carbonate, three different block copolymers were created, suitable for different CRM scenarios. The chemical structure of the soft midblock (ε-decalactone or trimethylene carbonate) appeared to have a critical impact both on the ring-closing depolymerization behavior and mechanical properties, where changing from a polyester to a polycarbonate soft block increased Young’s modulus from 14 to 200 MPa. Hence, this work demonstrates the complexity as well as the opportunities in the design of macromolecular structures for a circular economy.

Grain Boundary Wetting by the Second Solid Phase: 20 Years of History

Grain boundaries (GBs) can be wetted by a second phase. This phase can be not only liquid (or melted), but it can also be solid. GB wetting can be incomplete (partial) or complete. In the case of incomplete (partial) wetting, the liquid forms in the GB droplets, and the second solid phase forms a chain of (usually lenticular) precipitates. Droplets or precipitates have a non-zero contact angle with the GB. In the case of complete GB wetting, the second phase (liquid or solid) forms in the GB continuous layers between matrix grains. These GB layers completely separate the matrix crystallites from each other. GB wetting by a second solid phase has some important differences from GB wetting by the melt phase. In the latter case, the contact angle always decreases with increasing temperature. If the wetting phase is solid, the contact angle can also increase with increasing temperature. Moreover, the transition from partial to complete wetting can be followed by the opposite transition from complete to partial GB wetting. The GB triple junctions are completely wetted in the broader temperature interval than GBs. Since Phase 2 is also solid, it contains GBs as well. This means that not only can Phase 2 wet the GBs in Phase 1, but the opposite can also occur when Phase 1 can wet the GBs in Phase 2. GB wetting by the second solid phase was observed in the Al-, Mg-, Co-, Ni-, Fe-, Cu-, Zr-, and Ti-based alloys as well as in multicomponent alloys, including high-entropy ones. It can seriously influence various properties of materials.

A phase field model to simulate crack initiation from pitting site in isotropic and anisotropic elastoplastic material

A multiphysics phase field framework for coupled electrochemical and elastoplastic behaviors is presented, where the evolution of complex solid-electrolyte is described by the variation of the phase field variable with time. The solid-electrolyte interface kinetics nonlinearly depends on the thermodynamic driving force and can be accelerated by mechanical straining according to the film rupture-dissolution mechanism. A number of examples in two- and three- dimensions are demonstrated based on the finite element-based MOOSE framework. The model successfully captures the pit-to-crack transition under simultaneous electrochemical and mechanical effects. The crack initiation and growth has been demonstrated to depend on a variety of materials properties. The coupled corrosion and crystal plasticity framework also predict the crack initiation away from the perpendicular to the loading direction.

Multiscale mechanical characterization and computational modeling of fibrin gels.

Fibrin is a naturally occurring protein network that forms a temporary structure to enable remodeling during wound healing. It is also a common tissue engineering scaffold because the structural properties can be controlled. However, to fully characterize the wound healing process and improve the design of regenerative scaffolds, understanding fibrin mechanics at multiple scales is necessary. Here, we present a strategy to quantify both the macroscale (1-10mm) stress-strain response and the deformation of the mesoscale (10-1000µm) network structure during unidirectional tensile tests. The experimental data were then used to inform a computational model to accurately capture the mechanical response of fibrin gels. Simultaneous mechanical testing and confocal microscopy imaging of fluorophore-conjugated fibrin gels revealed up to an 88% decrease in volume coupled with increase in volume fraction in deformed gels, and non-affine fiber alignment in the direction of deformation. Combination of the computational model with finite element analysis enabled us to predict the strain fields that were observed experimentally within heterogenous fibrin gels with spatial variations in material properties. These strategies can be expanded to characterize and predict the macroscale mechanics and mesoscale network organization of other heterogeneous biological tissues and matrices. STATEMENT OF SIGNIFICANCE: Fibrin is a naturally-occurring scaffold that supports cellular growth and assembly of de novo tissue and has tunable material properties. Characterization of meso- and macro-scale mechanics of fibrin gel networks can advance understanding of the wound healing process and impact future tissue engineering approaches. Using structural and mechanical characteristics of fibrin gels, a theoretical and computational model that can predict multiscale fibrin network mechanics was developed. These data and model can be used to design gels with tunable properties.

Ice-Templated Method to Promote Electrochemical Energy Storage and Conversion: A Review

The ice-templated method (ITM) has drawn significant attention to the improvement of the electrochemical properties of various materials. The ITM approach is relatively straightforward and can produce hierarchically porous structures that exhibit superior performance in mass transfer, and the unique morphology has been shown to significantly enhance electrochemical performance, making it a promising method for energy storage and conversion applications. In this review, we aim to present an overview of the ITM and its applications in the electrochemical energy storage and conversion field. The fundamental principles underlying the ITM will be discussed, as well as the factors that influence the morphology and properties of the resulting structures. We will then proceed to comprehensively explore the applications of ITM in the fabrication of high-performance electrodes for supercapacitors, batteries, and fuel cells. We intend to find the key advances in the use of ITM and evaluate its potential to overcome the existing challenges in the development of efficient energy storage and conversion systems.

Structural optimisation for controlled deflections of additively manufactured single material beams

Closely controlling the mechanical behaviour and characterization of the deflection of a beam structure is a well-known and widely studied engineering problem. The progress in additive manufacturing methods and the possibilities to closely control the material property variations with the controlled placement of materials further widen the opportunities to achieve given beam deflection criteria. The multi-material additive manufacturing solutions suffer from the lack of real engineering material options, and the quality and performance of the printed parts are usually unsuitable for producing functional parts. A novel cellular structured solution is proposed here, which utilises optimisation of geometries of individual cells of a single material structured beam to obtain deflection profiles closely matched with preset conditions under different loading conditions. The cellular geometry of the structured beam is continually altered for searching and converging on the optimal structure of the cells by the covariance matrix adaptation evolution strategy algorithm in an iterative manner. The optimised beam structures could also be physically produced with single material additive manufacturing methods and the experimental and numerical beam deflection responses correlated closely.

Tensile strength and modulus of FRP pultruded composites at varying load angles relative to the pultrusion direction

Tensile strength and modulus are key material properties for the design of pultruded fiber reinforced polymer (FRP) composite members and connections. Pultruded FRP composites are orthotropic materials and thus both the tensile strength and modulus vary with the angle between the pultrusion direction and the applied force. In current design standards, the variation of material properties with load direction is addressed by prescribing the use of longitudinal properties for angles between zero and five degrees, and the use of transversal properties for angles greater than five degrees. To derive a more precise and representative equational relationship between load angle and tensile material properties, 228 coupons extracted from pultruded FRP profiles were tested in tension in accordance with ASTM D638-22 to determine the resulting average tensile strength and tensile modulus values. Coupons were taken from different profiles from different manufacturers, different section locations (e.g., web versus flange), as well as varying angles between the pultrusion direction and the applied force. The characteristic design value of the tensile strength and tensile modulus at each tested angle was determined in accordance with ASTM D7290-22. Using this dataset, a predictive relationship based on a generalized form of Hankinson’s equation was developed for both average and characteristic tensile strength and both average and characteristic tensile modulus as a function of three factors: 1) the differential angle between the pultrusion direction and the applied force, 2) the longitudinal tensile property (i.e., strength or modulus), and 3) the transverse tensile property (i.e., strength or modulus). The average relative difference between tested and predicted values using the developed equations varied between 4.4% and 8.3%, depending on the considered mechanical property.

Three-Dimensional Printing Process for Musical Instruments: Sound Reflection Properties of Polymeric Materials for Enhanced Acoustical Performance.

Acoustical properties of various materials were analyzed in order to determine their potential for the utilization in the three-dimensional printing process of stringed musical instruments. Polylactic acid (PLA), polyethylene terephthalate with glycol modification (PET-G), and acrylonitrile styrene acrylate (ASA) filaments were studied in terms of sound reflection using the transfer function method. In addition, the surface geometry parameters (Sa, Sq, Sz, and Sdr) were measured, and their relation to the acoustic performance of three-dimensional-printed samples was investigated. It was found that a higher layer height, and thus a faster printing process, does not necessarily mean poor acoustical properties. The proposed methodology also proved to be a relatively easy and rapid way to test the acoustic performance of various materials and the effect of three-dimensional printing parameters to test such a combination at the very beginning of the production process.