Material Characteristics Research Articles

Experimental study of friction coefficient of graphite for high-temperature gas-cooled reactors

High-temperature gas-cooled reactors, as highly regarded fourth-generation reactors, extensively utilize graphite materials. It is necessary to perform a study of the characteristics of the graphite materials aiming at optimizing the structural design and neutron physics calculation for the reactor. Thus, the investigation of the graphite friction coefficient is a crucial aspect of the research. This paper presents experiments on the graphite friction coefficient conducted using a specially designed experimental device that closely replicates the operational conditions of high-temperature gas-cooled reactors. The experimental data on the graphite friction coefficients under various atmospheric and temperature conditions are obtained. The graphite friction coefficient under a helium atmosphere demonstrates an initial increase followed by a decrease with rising temperature, reaching a maximum value of 0.17 at 200 °C. However, beyond 400 °C, the friction coefficient stabilizes gradually and fluctuates within the range of 0.03 to 0.06. Under a nitrogen atmosphere, the graphite friction coefficient exhibits the same temperature-dependent pattern as observed in helium. The peak value likewise occurs at 200 °C, measuring 0.23. At temperatures below 400 °C, the graphite friction coefficients in a nitrogen atmosphere surpass those in helium. While beyond 400 °C, the friction coefficients in a nitrogen atmosphere likewise fluctuate within the range of 0.03 to 0.06.

Research on Multi-objective Optimization Model of Power Storage Materials Based on NSGA-II Algorithm

Aiming at the problems of slow convergence speed and low precision probability of multi-objective optimization of energy storage materials, a multi-objective optimization model of energy storage materials based on NSGA-II algorithm was proposed. The association rule set of storage materials in the joint supply chain operation performance management system is extracted, and the rough vector feature distribution set multi-objective optimization method is used to decompose and optimize the characteristics of storage materials in the joint supply chain operation performance management system. Using NSGA-II optimization analysis method, this paper summarizes the power storage materials under the joint supply chain operation performance management system, and summarizes three kinds of inventory control: periodic inventory, inventory coding, and computerized inventory. Combined with the positive regression learning method of organizational operational performance, the multi-objective optimization decision of electric storage materials under the joint supply chain operational performance management system is realized. The simulation results show that under the joint supply chain operation performance management system, the proposed method reaches the optimal convergence after 65 iterations, the convergence speed is fast, and the accuracy probability reaches 1.000 after 80 iterations, which solves the problems of slow convergence speed and low accuracy probability, and has a good scheduling ability of energy storage materials.

Effect of Fire Exposure on the Properties of Self-Compacting Concrete reinforced by Glass Fibers

The optimal design of any structural elements requires examining all environmental risks, emergency accidents, and standard load cases. Exposure to fire is one of the most common safety threats. Nowadays wide developments are achieved in the field of concrete technology, therefore, experimental and theoretical investigations should be performed on the characteristics of such developed materials under different loading conditions. This study investigates the impact of fire exposure on the mechanical characteristics of self-compacting concrete, specifically compressive and tensile strength, modulus of elasticity, and stress-strain relation. The adopted fire exposure consisted of six steady-state temperatures (300, 400, 500, 600, 700, and 800°C) for one hour and a sudden cooling method. Four glass fiber volume fractions were adopted: 0, 0.5, 1, and 1.5%. The glass fiber volume fractions considered (0.5-1.5%) improved the mechanical properties investigated. Two states were detected for the effect of fire exposure. The effect of fire exposure was inversely proportional to fiber content in burning temperatures of 300-700°C, while the reduction in mechanical properties of 1.5% fiber content was greater than those of 0.5 and 1% when the temperature increased to 800°C. Furthermore, the addition of glass fiber changed the brittle mode stress-strain relation to semi-ductile for the non-burned and burned up to 600°C specimens, whereas a brittle behavior was detected when the temperature increased above 600°C. In general, a similar effect was noticed for all the glass fiber ratios considered regarding the slope of the stress-strain linear stage compared to the non-burned specimens, which was more salient when the burning temperature increased.

Characterization of Pure and Doped ZnO Nanostructured Powders elaborated in Solar Reactor

The synthesis of nano-oxides is an important field of nanotechnology, as these materials possess unique properties and applications. Several methods have been developed for synthesizing nano-oxides, each offering advantages and disadvantages depending on the desired material characteristics. Solar energy focused on solar reactors can be utilized for nano-oxide elaboration, offering a sustainable and environmentally friendly approach. The current article presents the research carried out for the elaboration of pure and doped nanostructured zinc oxides using solar energy. The morphostructural characteristics were determined by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and the Brunauer-Emmett-Teller method. The attenuated total reflectance Fourier transform infrared spectroscopy confirmed the synthesis of pure and doped nanostructured ZnO. The optical properties were highlighted by UV-VIS Spectroscopy. The research points out that crystallite sizes vary between 37 and 51 nm due to the influence of doping metal. The morphology associated with these particles is predominantly whiskers with elongated parts between 0.18 and 1.4 um. Doping with Fe, Si, Yb, and Ce causes a wider band gap compared to pure ZnO nanoparticles. As solar energy becomes more accessible and efficient, solar-driven synthesis of pure and doped ZnO is poised to be a crucial factor in shaping the future of material science and technology.

Effects of ferrite and graphite phases on scratch characteristics of nodular cast iron

In this work, we conduct micro-scratch tests of nodular cast iron with Vickers indenter under constant normal load and investigate the effects of individual phases (i.e., ferrite and graphite phases) on the scratch characteristics of nodular cast iron. Using a bimodal Gaussian model to fit the experimental data of penetration depth, residual depth, elastic recovery rate, and scratch hardness, we calculate the contribution percentages of individual phases to scratch variables. The scratch variables are independent of the scratch speed used in this work, while the penetration depth increases linearly with increasing the normal load. There exists a large difference between the contribution percentages and the volume fractions calculated from SEM images and XRD pattern. Such a large difference suggests that the bimodal Gaussian distribution analysis does not include the effect of the interaction between two phases on the scratch characteristics of dual-phase materials with significantly distinct mechanical properties and geometrical dimensions. A more refined method taking into account the interaction between two phases needs to be developed for the analysis of the scratch characteristics of dual-phase materials.

Effects of cutting conditions on materials properties of austenitic stainless steels

Austenitic stainless steel SUS304 is widely used in various engineering applications, including semiconductor manufacturing equipment and food processing machinery, owing to its exceptional material characteristics such as non-magnetic properties, high corrosion resistance, strength, and ductility. However, concerns have arisen in recent years regarding potential alterations in the material properties of austenitic stainless steel after machining processes. As the cutting process was conducted widely to make various engineering applications with different machining conditions, an examination of the effect of machining conditions on the material properties is important. In the present study, the influence of cutting conditions on the microstructure and mechanical of SUS304 was experimentally and numerically investigated, where three types of ball-end mills with rake angles (- 20°, − 3°, and 5°) and different cutting speeds (50 m･min−1 and 100 m･min−1) were conducted with plane and side machining to investigate the cutting properties. Material properties of SUS304 can be changed by the cutting resistance of the above cutting process, in particular the low rake angles under plane machining, where the high cutting resistance makes high dislocation density and strain-induced martensite formation. This occurrence made the low corrosion resistance as well as low ductility. On the contrary, no significant effect of the cutting speeds on the cutting resistance was detected compared to the condition of the rake angle on the plane machining. The reasons behind this will be discussed in detail systematically in this paper. From this approach, it could be clarified to maintain the high material properties of SUS304 even after the cutting process, which could be useful to make design of the engineering applications.

Effect of Magnetic Flow and Convective Heat Transfer Enhancement Using Hybrid Nanofluid: A Structured Review

Convective heat transfer is vital in a variety of engineering applications, including thermal management systems, electronic refrigeration, and energy conversion devices. Improving the rate of heat transfer in these systems is of the utmost significance for increasing their efficiency. This review focuses on the single and combined effects of these parameters on improving heat transmission in such systems. The heat and mass transfer of nanofluid is greatly influenced by various factors, including the intrinsic features of the nanofluid, the process used for synthesising the nanofluid, the impact of magnetic force, the concentration and size of nanoparticles, and the Reynolds number (Re). Furthermore, it is important to note that the material characteristics, thermal properties, and performance of magnetic nanofluids are significantly influenced by slight variations in the magnetic force and magnetic field gradient. Multiple research projects have reached the agreement that the inclusion of a magnetic field within magnetic nanoparticles enhances the convective heat transfer capabilities of a nanofluid, resulting in an improvement ranging from around 13% to 75%. Moreover, several applications of hybrid nanofluids in thermal systems have been introduced.

Effects of various beverages on characteristics of provisional restoration materials.

To investigate the effect of common beverages on four currently used provisional restoration materials: Protemp®4, Integrity®, polymethyl methacrylate(PMMA) block, and acrylic resin. Flowable resin composite is included as a control group. Each material was formed into disks of 10-mm diameter and 4-mm thickness (N = 40) by loading the material into acrylic molds. The exposed surface in the mold was covered using a glass slide to prevent an oxygen inhibition layer, and polymerization then proceeded. The solidified disks were placed in distilled water for 24 h. These samples (n = 8) were then immersed for 14 days in one of four different beverages: water, orange juice, cola, and coffee. Changes in color dimension, hardness, and roughness were observed and then analyzed using two-way repeated analysis of variance. The provisional materials had more obvious changes in all three color dimensions than the flowable resin composite. Integrity showed the biggest changes, followed by acrylic resin and PMMA block, whereas Protemp had the smallest changes. The hardness of all the materials significantly decreased after immersion in any of the beverages for 14 days. There were no changes in surface roughness when the materials were immersed in distilled water. The surface roughness of the PMMA block significantly decreased in orange juice whereas that of Integrity and acrylic resin significantly increased in cola. Different kinds of provisional materials had different degrees of staining due to their composition. Moisture had a significant influence on the hardness of materials, and the acidity of cola significantly roughened the surface of the provisional materials.

Study on the melting characteristics of composite phase change materials and the power generation performance of coupled thermoelectric systems under supergravity conditions

Miniaturization and integration of electronic equipment in aircraft have resulted in a substantial increase in thermal load. However, aircraft often experience acceleration maneuvering flights in supergravity environments, which makes comprehensive research on thermal management under supergravity conditions necessary. The influence of gravity on the thermal storage properties of composite phase change materials doped with graphene nanoparticles (GNP-PCM) was investigated in this study by simulation. Under 2g, 4g, 6g, 8g, and 10g gravity conditions, the melting time is reduced by 14.86%, 27.05%, 33.31%, 37.00%, and 39.79%, respectively, compared with normal gravity conditions. Moreover, the integration of the PCM with a thermoelectric power system facilitated waste heat utilization. Incorporating GNPs markedly enhances power generation efficiency under 10g supergravity conditions. With an open-circuit voltage of 0.8 V and a maximum output power of 0.11 W, the power generation reached 81.62 J, which is 53.91% higher than that of pure PCM. This enhancement can be attributed to the improved natural convection and accelerated melting rate facilitated by the GNPs. This study elucidates the underlying physical mechanisms affecting the melting rate of PCM under increased gravity conditions. Furthermore, coupling PCM with a thermal power generation system provides a rational approach for the reuse of waste heat.

Electrical characterization of interfacial transition zone in concrete during freeze-thaw process

The interfacial transition zones (ITZs) between aggregates and mortar are weak regions of concrete, which are more critical to the frost resistance of concrete due to a larger localized water-to-cement ratio. The effective conductivity of the ITZ was determined by separating electrical parameters in the AC impedance spectrum (ACIS), and the changes in microstructure within ITZ during the freeze-thaw (F-T) process were studied. First, based on the microstructure characteristics of Cement-Based Materials (CBMs), a circuit model of conduction path of conductive unit was established. The microstructure changes of CBMs during the F-T process (−50 °C to 10 °C) were characterized using ion conduction activation energy and the impedance of the constant phase element (CPE), which were classified into different regions in the F-T process. Circuit simplification and impedance parameters of CPE in different regions were analyzed. Subsequently, the composite effective conductivity formula (CECF) was proposed to separate the ITZ conductivity from the mortar or concrete conductivity. The relative change rate of conductivity during F-T process was used to define the freezing degree of CBMs, and the freezing degree of ITZ was calculated by CECF. The results indicated that in the F-T process of mortar and concrete, despite the volume fractions of ITZ being only 15.8% and 10.6%, its contribution to the freezing degree of the overall sample was 66%−70% and 57%−60%, respectively. This method can quantitatively characterize the effect of ITZ during F-T process and help understand the damage mechanism of F-T process.

Analysis of load-bearing characteristics of bi-modulus composite stiffened plates: Numerical simulation method and large-scale experimental verification

A large number of experiments show that composite materials usually show different modulus properties in tension and compression (bi-modulus). However, for actual composite engineering structures, especially complex models, the numerical simulation calculation is usually based on a single modulus. In order to consider the different modulus characteristics of composite materials in tension and compression, researchers put forward simplified constitutive models of dual-modulus materials. However, these constitutive models have not been verified by a large number of experiments, especially by complex models. In this paper, the GWFMM model is simplified and used to analyze complex structures with different modulus in tension and compression. The experimental results of stiffened plate show that the improved GWFMM model can be used to analyze different modulus of tension and compression of complex stiffened structures. In addition, the influence of elastic modulus ratio in tension and compression under different experimental load conditions is further explored, and the influence law of bending and torsion on structures with bi-modulus is discussed. The relevant conclusions provide reference for the design and optimization of full-scale composite structures in marine engineering.

Stress–Strain Properties and Structural Characteristics of a Gamma-Irradiated Polymer Composite Material Based on Low-Molecular-Mass Rubbers

Stress–Strain Properties and Structural Characteristics of a Gamma-Irradiated Polymer Composite Material Based on Low-Molecular-Mass Rubbers

Comparative Study on the Electrochemical Behaviors of Positive Electrode Materials of Lithium-ion Batteries during Overdischarge

As lithium-ion battery (LIB) use rises, recycling becomes imperative. Efficiently overdischarging LIBs for residual energy extraction is crucial for safe recycling. Our study analyzes the electrochemical behavior during overdischarge for positive electrode materials, including LiNi0.6Co0.2Mn0.2O2 (NCM622), LiNi0.8Co0.1Mn0.1O2 (NCM811), LiFePO4 (LFP), LiCoO2 (LCO), and LiMn2O4 (LMO). Electrochemical evaluations involve half cells and full cells subjected to constant current overdischarge beyond normal operating ranges. In positive electrode half-cells, a material-dependent conversion reaction was observed, while full cells exhibited similar behaviors during overdischarge to 0 V due to increasing voltage at the negative electrode. Distinct electrochemical variations emerged under forced discharge below 0 V, particularly in the NCM series, showing a gradual voltage decrease to −2 V followed by an internal short circuit. In contrast, LFP, LCO, and LMO swiftly stabilized near 0 V, attributed to the lower initial Coulombic efficiency of NCM materials leading to an early rise in negative electrode potential. To recycle used lithium-ion batteries (LIBs), it’s crucial to optimize conditions that ensure both efficient and safe overdischarge, considering the characteristics of positive electrode materials.

Poisson's ratio testing method and multi-factor influence quantification model of asphalt pavement materials

The current standard in China does not specify the standard test method for determining Poisson's ratio, and the Poisson's ratio used in pavement design is often roughly fixed, which can result in large errors in the calculations and analysis of road structure. In this paper, the research on different test methods for Poisson's ratio is carried out and the non-linear characteristics of tensile and compressive Poisson's ratio on pavement materials under different influencing factors are analyzed. The results indicate that the absolute value of the ratio between transverse rebound strain and longitudinal rebound strain under 50% of the maximum destructive load can objectively characterize the mechanical properties of Poisson's ratio, and it is the optimal measurement method for Poisson's ratio in asphalt pavement materials. The Poisson's ratio of two pavement materials both decreases with the increase of loading rate and gradually tends to a constant value. Cement dosage and temperature are the most significant factors affecting the tensile and compressive Poisson's ratio of cement stabilized crushed stone and asphalt mixture, respectively. Specifically, when cement dosage increases by 1%, the Poisson's ratio of cement stabilized crushed stone decreases by approximately 10%, and the temperature has a significant influence on the difference in tension and compression for Poisson's ratio of asphalt mixture (up to 40%). The asphalt content corresponding to the minimum Poisson's ratio is basically consistent with the optimal asphalt content obtained by the Marshall volume method. Based on these, a quantification value-taking model is established of the tensile and compressive Poisson's ratios of typical asphalt pavement materials varying with multiple factors. The research results can serve as a reference for the scientific value-taking of pavement structural design parameters considering the different mechanical characteristics of materials in tension and compression.

Surrogate metamodels from digital image correlation for testing high-performance composite vessels

In this work, a workflow has been developed for the generation of surrogate metamodels to predict and evaluate failure with a confidence above 95 % in initial service conditions of high-performance cylindrical vessels manufactured in composites by Roll Wrapping technology. Currently, there is no specific testing standardization for this type of vessel and to fill this gap probabilistic numerical models were developed, performed by the Finite Element Method, fed with the material characteristics obtained experimentally by 2D digital image correlation from flat specimens. From the initial numerical model, a surrogate metamodel was generated by stochastic approximations. Once the metamodels were obtained by robust engineering, an experimental ring-ring tensile test was developed under service conditions and deformations were measured by high-precision 3D digital image correlation. Parametric and robust tests showed that the results of the metamodel did not show statistically significant differences, with errors in the rupture part of less than 2 % with respect to the results obtained in the test, being proposed as a basis for new test procedures.

Printing Parameters and Material Characteristics Affecting Mechanical Properties of FDM Printed Parts

Printing Parameters and Material Characteristics Affecting Mechanical Properties of FDM Printed Parts

台湾地区职业院校的通识音乐教育体系研究

With the continuous deepening of education reform, educational achievements and experiences on an international scale are overlapping, from learning to actively demonstrating advantages or taking the lead. Through field research on general music education in vocational colleges in Taiwan, this paper summarizes the advantages and characteristics of music curriculum objectives, course materials, course contents, teaching methods and course evaluation in Taiwan, and analyzes the system model of general music education. Combining with the actual situation of general music education in vocational colleges of our country, this paper considers the criticism of general music education in vocational colleges of our country and probes into its development model, in order to promote the development of general music in vocational colleges of our country.

Energy Absorption Characteristics of Composite Material with Fiber-Foam Metal Sandwich Structure Subjected to Gas Explosion.

Based on the previous research on the energy absorption of foam metal materials with different structures, a composite blast-resistant energy-absorbing material with a flexible core layer was designed. The material is composed of three different fiber materials (carbon fiber, aramid fiber, and glass fiber) as the core layer and foamed iron-nickel metal as the front and rear panels. The energy absorption characteristics were tested using a self-built gas explosion tube network experimental platform, and the energy absorption effects of different combinations of blast-resistant materials were analyzed. The purpose of this paper is to evaluate the performance of blast-resistant materials designed with flexible fiber core layers. The experimental results show that the composite structure blast-resistant material with a flexible core layer has higher energy absorption performance. The work performed in this paper shows that the use of flexible core layer materials has great research potential and engineering research value for improving energy absorption performance, reducing the mass of blast-resistant materials, and reducing production costs. It also provides thoughts for the research of biomimetic energy-absorbing materials.

Vibration analysis of Timoshenko microbeams made of functionally graded materials on a Winkler-Pasternak elastic foundation

In this work, the free vibration analysis of Timoshenko microbeams made of the Functionally Graded Material (FGM) on the Winkler-Paternak elastic foundation based on the Modified Coupled Stress Theory (MCST) is investigated. Material characteristics of the beam vary throughout the thickness according to the power distribution and are estimated through Mori–Tanaka, Hashin-Shtrikman and Voigt homogenization techniques. The Timoshenko microbeam model considering the length scale parameter is applied. The free vibration differential equations of FGM microbeams are established based on the Finite Element Method (FEM) and Kosmatka’s shape functions. The influences of the size-effect, foundation, material, and geometry parameters on the vibration frequency are then analyzed. It is shown that the study can be applied to other FGMs as well as more complex beam structures.

Determination of the diameter variation peculiarities along the path of distribution drainage pipe-line

This article presents a methodology for calculating the hydraulic characteristics and structural parameters of variable (decreasing) cross-sectional distribution pressure drainage pipelines. The approach is based on analyzing a system of differential equations describing fluid flow with a variable flow rate in the investigated pipes. The study explores the most general case of distributor operation, considering a horizontal groundwater level above the pipeline. The analysis of the original equations includes a scenario where a constant average fluid flow rate is maintained along the length of the pressure channel. The velocity magnitude is influenced by the granulometric features of the surrounding soil and the filtration characteristics of the pipeline's side walls material. The investigation employs the concept of a conditional distribution infinitely long pipeline or a pipeline with limited length and infinite permeability of the side walls surface. This allows assuming a pressure close to zero at the pipeline's final cross-section, which minimally impacts the obtained results. The analysis is presented in a dimensionless form, and the resulting computational formulas are both simple and convenient. The article includes corresponding graphs to illustrate the presented dependencies.