Variation Of Material Properties Research Articles

Thermal performance evaluation of bio-bricks and conventional bricks in residential buildings in Aswan city, Egypt

From raw material extraction to final product disposal, the construction industry is integrally involved in every stage of the greenhouse gas emissions life cycle. One of the main causes of the climate catastrophe is the increasing use of polluting energy sources to power our homes and businesses. This massive problem of global warming has now forced countries to act. To further address sustainability, they seek to reduce energy consumption and CO2 emissions by adopting more sustainable materials. The current trend in scientific research is to use waste resources to improve the properties of various materials to exacerbate the problems of climate change because of the use of traditional building materials. Therefore, one of the most environmentally friendly alternatives to the standard procedure is the use of agricultural residues to improve the quality of building materials. This improvement will modify the thermal properties of building materials such as bricks, which will lead to an improvement in energy efficiency inside buildings, especially residential buildings. As a result, the research focused solely on simulating several bio-brick alternatives that had been discovered in earlier studies in order to test their viability in terms of increasing the energy efficiency of residential buildings in one of the hot cities. The study demonstrated that using bio-building materials can lower energy usage. In addition to saving energy in residential constructions, rice straw cement bricks and sugarcane bricks have operating efficiency rates of roughly 7% and 12%, respectively. All these advancements over conventional brick reduce greenhouse gas emissions and carbon dioxide.

Spatial stochastic D-RBA and limit equilibrium analysis of unreinforced masonry pier-spandrel structures

This study investigates the effect of spatially varying material properties on the in-plane seismic behaviour and capacity of an unreinforced pier-spandrel masonry system. The discontinuous nature of masonry is represented via a system of rigid blocks that can mechanically interact with each other along their boundaries. In the discontinuous modelling strategy, denoted as discrete rigid block analysis (D-RBA), deformations are lumped at the joints, and masonry units are replicated using two rigid blocks with a potential crack plane using the discrete element method (DEM). The obtained collapse mechanisms are automatically classified into two main categories via an algorithm processing the results of D-RBA. The adopted methodology offers a robust and time-efficient categorization of different collapse modes obtained from the computational model, which is required for better understanding the possible mechanisms developing in pier-spandrel structures and their occurrence rate. Accordingly, the most recurrent failure mechanisms are further investigated via upper- and lower-bound theorems of limit equilibrium analysis (LEA) by adopting an ad hoc coded optimization algorithm to ensure the solution's uniqueness. The results show that the DEM-based modelling approach provides a comprehensive understanding of the structural behaviour and capacity of pier-spandrel systems subjected to in-plane lateral loads. Further, the proposed probabilistic assessment workflow offers a broader perspective than deterministic analysis.

Performance and influencing mechanisms of magnetically separable Ni-M layered double hydroxides (M = Fe, Al) for catalytic ozonation

From a preliminary performance comparison of several layered double hydroxides (LDHs), magnetically separable Ni-M LDHs (M = Fe, Al) were synthesized and applied as efficient ozonation catalysts for degrading dye Rhodamine B (RhB). As proved by various characterizations, the micromorphology, nanostructure size, and porous feature of the synthesized Ni-M LDHs significantly varied with different metal components. Among them, Ni3-Fe LDH and Ni2-Al LDH possessed a relatively larger specific surface area to react with O3 interfacially, thereby exhibiting excellent catalytic ozonation performance. The RhB was almost completely degraded within 60 min, and the removal efficiencies of COD and TOC reached above 70% and 50%, respectively. The effects of catalyst dosage, initial dye concentration, solution pH, and coexisting inorganic anions on RhB degradation were studied systematically. ESR measurements and radical quenching experiments indicated that OH, O2−, and 1O2 are primary reactive oxygen species (ROS), while 1O2 induced the most dominant degradation contribution. According to the variations of ROS formation and material properties during the catalytic ozonation process, the possible reaction mechanisms were proposed. Moreover, the differences involved in the redox of multivalent metals and the transformation of surface hydroxyls over Ni-Fe and Ni-Al LDHs were further revealed.

A Pulsed Current Application to the Deformation Processing of Materials.

A review of studies on the electroplastic effect on the deformation process in various conductive materials and alloys for the last decade has been carried out. Aspects, such as the mode and regimes of electric current, the practical methods of its introduction into materials with different deformation schemes, features of deformation behavior accompanied by a pulsed current of different materials, structural changes caused by the combined action of deformation and current, the influence of structural features on the electroplastic effect, changes in the physical, mechanical, and technological properties of materials subjected to plastic deformation under current, possible mechanisms and methods of physical and computer modeling of the electroplastic effect, and potential and practical applications of the electroplastic effect are considered. The growing research interest in the manifestation of the electroplastic effect in such new modern materials as shape-memory alloys and ultrafine-grained and nanostructured alloys is shown. Various methods of modeling the mechanisms of electroplasticity, especially at the microlevel, are becoming the most realistic approach for the prediction of the deformation behavior and physical and mechanical properties of various materials. Original examples of the practical application of electropulse methods in the processes of drawing, microstamping, and others are given.

Space–time method for analyzing transient heat conduction in functionally graded materials

In this study, a novel approach is presented for simulating transient heat conduction in functionally graded materials (FGM) with varying material properties only in the z direction. The proposed collocation method employs a meshless localized space–time radial basis function (LSTRBF), which yields a linear sparse matrix system, offering advantages over the global method in terms of scalability and suitability for multidimensional problems. Additionally, a novel shape parameter strategy, known as variable leave-one-out cross-validation (LOOCV), is introduced to enhance accuracy while overcoming conventional LOOCV limitations. Four benchmark numerical examples are utilized to demonstrate the simplicity, efficiency, accuracy, and stability of the method. Overall, the proposed LSTRBF method presents a promising alternative for efficiently and accurately simulating transient heat conduction in FGMs.

An Investigation into the Free Vibration of Intact and Cracked FGM Plates

In this study, the linear free vibration of intact and cracked functionally graded material plates is investigated numerically and experimentally. The experimental work is limited to the isotropic materials. The numerical work is based on finite element, where a code is developed to obtain the natural frequencies of intact plates based on the first-order shear deformation theory (FSDT) using MATLAB software. Also, a model of through-cracked FGM plate is developed using ANSYS Workbench with the help of APDL coding. The material properties of the plates under study are graded in one, two, and three directions. The novelty of this study emerges through its examination of the synergistic impacts resulting from variations in FGM material properties, crack length, crack orientation, and crack location. These effects are comprehensively discussed in the results section. The result of the present model shows that the use of three-directional FGM reduces the natural frequency compared with the other cases of two-directional and unidirectional FGM. Also, the results show that the effect of FGM gradient on the frequency of intact and cracked plate is high when the gradient index n < 3 . The present paper results are useful for the design of FGM plates especially when cracks exist.

Local and global sensitivity analysis of a coupled heat and moisture transfers model: effect of the variability of cob material properties

Local and global sensitivity analysis of a coupled heat and moisture transfers model: effect of the variability of cob material properties

Fabrication of polymer-based stents: Impact of test specimen manufacturing protocol

Abstract Various manufacturing techniques are available for polymer stent fabrication. Polymer semi-finished products can be prepared using solvent based methods, e.g. dip coating, as well as thermal processes, e.g. extrusion. These different methods may lead to an altered polymer crystal structure, resulting in a different deformation mechanism during mechanical stress. For the material property characterization needed for implant development, the test specimens usually are prepared using laser-cut or die-cut methods. Due to these different preparation protocols, a change in polymer microstructure, causing a material property variation, may also result. For this purpose, comparison of laser-cut versus die-cut of PLLA films has been performed. PLLA films have been prepared by dip-coating and were evaluated with respect to structural, thermal, and mechanical properties. In this study, a combination of uniaxial tensile tests, SEM and DSC studies was used. The results of the mechanical tests showed drastic differences in the elongations at break of die-cut specimens compared to laser-cut ones. The results point out formation of complex crystal structures during the manufacturing process. By the use of SEM imaging and DSC measurements, we were able to attribute these changes to the different plastic deformation mechanisms.

Optimal structures for focusing and energy accumulation: mathematical models and intuition

Metamaterials and composite structures are able to manipulate waves and focus fields and currents in desirable directions. Designs based on spatial and temporal variation of material properties create structures forcing fluxes into specified parts of the domain or concentrating energy into arrays of progressively sharpening pulses. The paper discusses examples of focusing structures, mathematical and intuitive considerations that influence optimal design theory. The optimality requirement introduces zones of optimal composites with variable microgeometry. The observed absence of classical solutions motivates the extension of the class of optimal partitions to composites. Such materials also provide a solution to the problem of optimal design of a thermal lens focusing thermal fluxes when the incoming fluxes are not completely known in advance. An extension of designs to dynamical materials such as space–time checkerboard composites introduces metamaterials with additional capabilities that control the accumulation of energy in the propagating waves. The discussed mathematical methods of focusing and suitable properties alternation targeted on optimality are illustrated by physical examples.

Dynamic Crack-Front Deformations in Cohesive Materials.

Crack fronts deform due to heterogeneities, and inspecting these deformations can reveal local variations of material properties, and help predict out-of-plane damage. Current models neglect the influence of a finite dissipation length scale behind the crack tip, called the process zone size. The latter introduces scale effects in the deformation of the crack front, that are mitigated by the dynamics of the crack. We provide and numerically validate a theoretical framework for dynamic crack-front deformations in heterogeneous cohesive materials, a key step toward identifying the effective properties of a microstructure.

Equivalent initial damage sizes (EIDS) for type 1C anodised aluminium alloy 7085-T7452 under variable amplitude loading

Aluminium alloy (AA) 7085-T7452 is a high strength, low weight alloy used in large forgings in primary airframe applications. For corrosion protection, airframe components are anodised and this study looks at the influence of type 1C anodising on the fatigue crack growth behaviour in AA 7085-T7452 specimens that were fatigue tested with fighter wing spectrum loading. Surface etch pits formed during essential anodising preparatory processes were the primary cause of fatigue crack nucleation. The severity of the early crack growth caused by those etch pits that nucleated the worst crack in each specimen was evaluated using quantitative fractography-based fatigue crack growth measurements and the equivalent initial damage size (EIDS) of those etch pits was determined. Characterising the EIDS distribution of aircraft alloys with representative surface treatments is a fundamental input into Linear Elastic Fracture Mechanics (LEFM) based fleet failure analysis of aircraft structures. In this study, a notable increase in the average EIDS value for the worst crack present was observed whenever material or loading condition changes led to a significantly increased number of crack nucleation sites. In particular, an increase in the cyclic stress spectrum’s severity increased the number of nucleation sites in a specimen and significantly increased the average EIDS. It appears that due to variable nucleating discontinuity properties (e.g. size, shape and orientation) and material property variations, an increased number of nucleation sites increases the probability that the worst crack present will nucleate at a location that is conducive for relatively fast early crack growth. This will potentially cause shorter overall airframe component fatigue lives and so both the mechanisms and conditions of etch pit fatigue nucleation in this material and material finish shall be discussed for the benefit of failure analysts evaluating unexpected fleet fatigue cracking.

Study of the geometry and structure of a thermoelectric leg with variable material properties and side heat dissipation based on thermodynamic, economic, and environmental analysis

Thermoelectric generator (TEG) without moving parts, refrigerants, and direct carbon emissions is the most promising way to reduce carbon dioxide. The economy and thermal efficiency of TEG are seriously inhibited by geometry and structure, while existing studies have not investigated the effect of geometric and structure on output characteristics when the model considers the effect of side leg dissipation and variable properties. This paper proposes a one-dimensional model considering the effect of Peltier heat, conductive heat, Joule heat, Thomson heat, side leg dissipation, and temperature dependence for variable and conventional geometric and structures for 8 different materials. The effects of operation parameters, geometry parameters, and structures on thermodynamic, economic, and environmental performances are studied. The higher hot source temperature and shorter leg length benefit comprehensive performance. Increasing side leg dissipation decreases efficiency. When the fin parameter (L(heP/λA)0.5) is below a specific value, increasing side leg dissipation can promote the output power, economic and environmental performance. Compared to the traditional structure, the output power and efficiency of new configurations are increased by 1.01–3.59 and 1.03–4.57 times, respectively; The cost and CO2 emission reduce by 1.0–72.1% for low hot source temperature and figure of merit (ZT) material.

Performance analysis of functionally graded multifunctional piezoelectric energy harvesting microgyroscopes

Functionally graded materials (FGMs) are composite materials with varying material properties in one or more directions. These materials possess distinct characteristics compared to their constituent components. The ability to control material distribution and compositions in FGMs offers improved constraints over the natural frequencies of the system, making them highly suitable for energy harvesting applications. In this study, we focus on a piezoelectric FGM composed of Platinum (Pt) and Lead Titanate Zirconate (PZT). By utilizing FGMs for energy harvesting, we simplify the system from a multilayer structure to a single-layer system, thereby increasing power density by reducing volume. In this work, a power law distribution is used to model the material variation throughout the thickness of the single-layered beam. The governing equations of motion and boundary conditions for FG energy harvesting microgyroscope are derived using Euler-Bernoulli beam theory, the constitutive piezoelectric principle, and the extended Hamilton's principle. To simulate the nonlinear motion of the FG energy harvester, we employ the differential quadrature method (DQM). Subsequently, an investigation is carried out to examine the effects of various factors including material distribution, platinum percentage, base rotation, DC voltage, and electrical load resistance on the energy harvesting microgyroscope with functionally graded materials. The findings suggest that functionally graded energy harvesting gyroscopes can be adjusted to obtain effective energy harvesting and sensing capabilities by carefully selecting the material distribution, input voltage, and electrical load resistance.

Comparative analysis of photovoltaic thermoelectric systems using different photovoltaic cells

The photovoltaic-thermoelectric (PV-TE) system has emerged as a focal point in research endeavors aimed at harnessing the full spectrum of solar energy and enhancing the efficacy of solar power generation. Owing to the variations in bandgap and inherent material properties across diverse photovoltaic cells, the capacity to utilize the solar spectrum of PV-TE systems can be significantly affected when using different photovoltaic cells. Historically, investigations into the influence of photovoltaic cells on PV-TE systems have been predominantly rooted in theoretical simulations. These examinations have primarily concentrated on the holistic system efficiency under varying temperature conditions. In this study, we integrated three distinct types of photovoltaic cells into PV-TE systems. Both simulation and experimental methodologies were employed to evaluate the impact of these photovoltaic cell types on the PV-TE systems' performance. Additionally, we compared the back temperatures of standard PV systems with those of PV-TE systems. The average photovoltaic conversion efficiencies of PV-TE systems equipped with CIGS, CdTe, and a-Si photovoltaic cells were 21.9%, 19.7%, and 12.7%, respectively. Meanwhile, the average efficiencies of TEG were 0.256%, 0.102%, and 0.083% respectively, with average backplate temperatures of 39.3 °C, 44.0 °C, and 40.5 °C. The temperature disparities between the back of standard photovoltaic systems and PV-TEG-PCM systems stood at 4.70 °C, 2.32 °C, and 3.43 °C, respectively. Notably, CIGS photovoltaic cells, which harness a specific range of the solar spectrum more effectively, showcased superior performance. Furthermore, a broader usable solar spectrum band for a PV cell doesn't always translate to enhanced performance. These findings offer valuable insights for optimizing the power generation capabilities of photovoltaic-thermoelectric systems leveraging full-spectrum solar energy.

Automatically Predicting Material Properties with Microscopic Images: Polymer Miscibility as an Example.

Many material properties are manifested in the morphological appearance and characterized using microscopic images, such as scanning electron microscopy (SEM). Polymer miscibility is a key physical quantity of polymer materials and is commonly and intuitively judged using SEM images. However, human observation and judgment of the images is time-consuming, labor-intensive, and hard to be quantified. Computer image recognition with machine learning methods can make up for the defects of artificial judging, giving accurate and quantitative judgment. We achieve automatic miscibility recognition utilizing a convolutional neural network and transfer learning methods, and the model obtains up to 94% accuracy. We also put forward a quantitative criterion for polymer miscibility with this model. The proposed method can be widely applied to the quantitative characterization of the microstructure and properties of various materials.

Structural and optoelectronic properties of LiYP (Y = Ca, Mg, and Zn) half-Heusler alloy under pressure: A DFT study

By adjusting the lattice geometry through pressure engineering, it is possible to further enhance and customize various properties of materials even at zero pressure. The utilization of pressure allows for the modification of the electronic structure of materials, presenting a relatively new approach to creating essential features for advanced technological applications. These intriguing applications have served as the driving force behind this research, which investigates the behavior of the LiYP (Y = Ca, Mg, and Zn) Half-Heusler (HH) semiconductor. We shed light on the effects of pressure on the optoelectronic and structural characteristics of LiYP (Y = Ca, Mg, and Zn) using the DFT-based Wien2K code. HHs belong to the F 4‾ 3 m space group (No. 216) and are denoted by the chemical symbol XYZ. The calculations were performed by fitting the computed total energy and atomic volume to the Murnaghan equation of state, allowing us to obtain the bulk modulus, first derivatives, and lattice constant. Through the analysis of the partial density of states (PDOS), we evaluated the electronic band structure of LiYP (Y = Ca, Mg, and Zn) under pressures ranging from 0 to 10 GPa. Finally, we examined the optical properties of LiYP and relevant parameters (real part, imaginary part, absorption coefficient and reflectivity coefficient) at different pressure levels. The results obtained from the analysis of optoelectronic properties demonstrate that LiYP (Y = Ca, Mg, and Zn) is suitable for applications in renewable energy devices.

Surrogate recycling for structures with spatially uncertain stiffness

This study expands the existing methods for non-destructively identifying the spatially varying material properties of a structure using modal data. It continues a recently published approach to this inverse problem that employed Bayesian inference in conjunction with the Karhunen-Loève expansion to solve it. Here, we present two developments. Firstly, eigenvectors are used instead of eigenvalues, improving the results significantly. Secondly, a generalized polynomial chaos surrogate accelerates the inversion procedure. Finally, we develop a methodology for reusing the surrogate model across inversion tasks. We demonstrate the efficacy and efficiency of this methodology via the field of additive manufacturing and the fused deposition modeling process. The good results promise profound computational cost saving potential for large-scale applications.

Correlation of Microstructure and Nanomechanical Properties of Additively Manufactured Inconel 718

Abstract Additive manufacturing (AM) has emerged as a crucial technology in recent decades, particularly within the aerospace industry. However, the thermally cyclic nature of these processes introduces significant variations and defects in microstructure, which can adversely affect final part performance and hinder the widespread adoption of the technology. Traditionally, characterization of AM parts has relied on conventional bulk testing methods, which involve analyzing many samples to gather sufficient data for statistical analysis. Unfortunately, these methods are unable to account for local nanoscale variations in material properties caused by the microstructure, as they measure a single averaged property for each tested sample. In this work, we use AM Inconel 718 as a model system in developing a novel approach to correlate nanomechanical properties obtained through nanoindentation with microstructure obtained through electron backscatter diffraction (EBSD). By associating mechanical properties obtained from each indent with the corresponding crystallographic direction, we calculate the weighted average hardness and modulus for each orientation. This enables us to generate inverse pole figure maps depicting the relationship between mechanical properties and crystallographic direction. Our method yields results in good agreement with literature when calculating the part modulus and hardness, while effectively capturing nanoscale variations in properties across the microstructure. The key advantage of this methodology is its capability to rapidly test a single AM part and generate a large dataset for statistical analysis. Complementing existing macroscale characterization techniques, this method can help improve AM part performance prediction and contribute to the wider adoption of AM technologies in the future.

A study on the vibration characteristics of functionally graded cylindrical beam in a thermal environment using the Carrera unified formulation

The displacement function was constructed using Carrera unified formulation (CUF) in combination with Taylor polynomials and the improved Fourier series method (IFSM). This study investigated the vibration characteristics of cylindrical beam made of functionally graded materials (FGM) in a thermal environment. The accuracy of the theoretical model was verified by comparing the calculation results with those obtained using the finite element method. Subsequently, the influential factors were investigated. The variations in material properties with temperature and volume rate index were studied. Additionally, the effects of temperature changes and volume rate index on the thermoelastic vibration of the FGM cylindrical beam were examined. The results indicate that in a uniform temperature field, temperature and volume rate index variations result in changes in the material’s physical properties. The modal frequency of the FGM cylindrical beam decreases gradually with increasing temperature and volume rate index.

HTS Tape Mechanical Behavior Sensitivity on Material Properties and Thickness of Material Layers

Multilayer 2G high-temperature superconductor (HTS) tapes undergo various mechanical loading steps as part of a superconducting magnet operation. The mechanical loading steps include cool-down to cryogenic temperatures and Lorentz forces when powering up the magnets. Studying the mechanical behavior of the constituent layers in a HTS tape can reveal the strain or stress level in each layer and help in predicting the probability of mechanical failure or critical current degradation. A detailed finite element method (FEM) -based simulation models enable us to estimate the mechanical behavior in each layer. However, defining the model parameters for material mechanical properties or thickness of each material layer can have consid-erable uncertainty due to variation in manufacturing processes and missing measurements of material properties within these tapes. The material properties in thin layers may not exactly comply with bulk materials of the same kind. In this paper we present a sensitivity analysis for mechanical behavior dependence on material properties variation in the constituent layers of a HTS tape. The results give important insight about the accuracy and reliability of mechanical simulation results and guide the priorities in future material characterization. In addition, we will investigate the effect of the thickness of Hastelloy layer on effective macroscopic mechanical behavior of the tape. A nonlinear elastoplastic FEM model is used for performing the simulations.