Changes In Mechanical Properties Research Articles

Study on the gas pressure impact test of gun propellant and fluid-solid coupling dynamics simulation

Abstract In order to reveal the mechanical response characteristics of high-energy propellant under high pressure gas impact, the gas pressure impact test and fluid-solid coupling dynamics simulation of propellant are carried out. The propellant gas pressure impact test device is established. The propellant gas pressure impact tests are conducted under different quality of depressant and thickness of iron pressure relief fragments. The gas pressure-time curve, gas pressure rise and decreasing rate are obtained. It is found that longitudinal and transverse cracks occur locally in propellant under high pressure impact. In order to reveal that mechanical property change of propellant under gas impact, the simulation study on fluid-solid coupling dynamics of gas pressure impact test is carried out using ANSYS Workbench multi-field coupling platform. The flow field pressure in the device and the change process of fixed propellant stress and deformation are obtained. The error of monitoring point simulation and test pressure is 5.3%. The maximum peak value of internal flow field pressure reaches 71.6MPa. The average value of maximum stress and maximum deformation of fixed propellant reaches 220MPa and 1.77mm respectively. It reveals the mechanical response characteristics of propellant under high pressure gas impact.

Investigation of ion irradiation effects on mineral analogues of concrete aggregates

Irradiation can cause prominent damage to reactor concrete aggregates leading to amorphization, strength and modulus decrease, radiation induced volume expansion (RIVE) and micro-cracking, which limits their long-term performance. To develop an improved understanding of irradiation effects in concrete, three mineral analogues of concrete aggregates (limestone, marble and quartzite) were irradiated by 5.5 MeV He ions and 13 MeV Ni ions to surface doses of 0.011 displacements per atom (dpa) and 0.23 dpa, respectively, at room temperature. The two different ion species allow irradiation spectrum effects (ionizing and displacive) to be examined. Irradiation induced cracks were observed in He irradiated limestone and marble, and Ni irradiated quartzite. Full amorphization was observed in Ni irradiated quartzite with 14.3 % RIVE, and ∼25 % hardness and modulus decrease, while almost no change was observed in He irradiated quartzite except 4.35 % RIVE, revealing a possible ionization enhanced diffusion effect for high energy light ions. Furthermore, partial amorphization was observed in Ni irradiated marble and limestone matrix with a 12 % hardness decrease in marble while no amorphization was observed for He irradiation with a 20 % hardness increase in limestone matrix. The role of knock-on damage and irradiation spectrum on amorphization, volumetric expansion and mechanical property changes are discussed. Moreover, the onset and critical doses for amorphization and RIVE in quartz are obtained for ion irradiations at room temperature. The dose dependence of RIVE exhibits a delay compared to the amorphization behavior. The superior irradiation resistance of calcite phase compared to quartz phase implies there could be advantages to using calcareous aggregates and lowering the usage of siliceous aggregates for concrete in nuclear power plants for extended operation beyond 60 years. However, other effects such as corrosion, aging and reactions during severe accidents should also be considered, and further investigations are needed.

Исследование влияния жидкой среды на механические характеристики полимерных композиционных материалов

The problem of determining the ability of a liquid to penetrate into the structure of a composite material prepared using reinforcing glass fabrics and a polyester binder is solved. The determination of the ability of water to penetrate into the structure of samples cut from a common plate of polymer composite materials (PCM) is carried out by determining the change in weight of samples before and after their immersion in a container with a liquid medium (water) for a certain period of time. The ability of water penetration into the composition of this material has been established depending on its structure, that is, on the location of the reinforcing material. The mechanical properties (tensile, compressive and bending strength) of a composite material after its removal from a liquid container are presented. The problem of the possibility of the effect of processing the ends of cut test samples with polyester resin on the ability of liquid penetration into the composition of a PCM is solved. For this purpose, samples cut from a common plate were immersed in containers with water, while the ends of one batch of samples were coated with polyester resin, and the other batch was uncoated. The influence of the presence of samples in a liquid medium (water) with a certain ratio of layers of reinforcing material (glass wool and roving fiberglass) on their mechanical characteristics during bending, stretching and compression has been established. The test results of the samples are presented, which showed a direct dependence of the tensile strength and destructive force on the number of roving layers in the PCM structure of the samples whose edges were treated with polyester resin. During the experiments, the ability of liquid penetration into the structure of composite materials and changes in mechanical properties as a result of immersion of these materials in a liquid medium were determined. The obtained results of experimental tests of samples made of PCM with various reinforcement schemes will justify their widespread use in ship hull structures, in particular, as a material for the manufacture of ship tanks.

Molecular dynamics simulation of water absorption and mechanical weakening in coal rocks based on Monte Carlo methods

Aiming at the problem of roadway destabilization in water encountered in the roadway of the back mining roadway of an extra-thick coal seam in Xinjiang Dabei Coal Mine, this paper used molecular dynamics simulation to study the interaction between coal and water and analyzed the adsorption characteristics of water molecules and the change of mechanical properties of coal. Firstly, the model of C181H138N2O24 bituminous coal was constructed by test, the coal-water adsorption was simulated based on the Monte Carlo method, and the coal-water adsorption configuration was analyzed. The results showed that: the saturation adsorption capacity was about 60 water molecules/cell, and the water molecule adsorption was concentrated in the vicinity of oxygen-containing groups and hydrogen atoms; the increase of water molecule content led to the decrease of heat of adsorption and diffusion capacity, and the heat of adsorption decreased by 9.1 %, and the diffusion coefficient of the early stage of adsorption was about three times of that of the final stage; the mechanical parameters of the coal body were significantly decreased, and the bulk modulus, Young's modulus, and shear modulus were respectively decreased by 21.90 %, 36.76 %, and 38.87 %, Poisson's ratio increased by 14.81 %, Poisson's ratio variability was low, volumetric modulus variability was medium, Young's modulus and shear modulus variability was high. The decrease in strength after coal water adsorption is due to the significant volume expansion of the coal body, the saturation expansion rate reaches 12.47 %, and at the same time, the total energy of the coal model decreases, where the weakening effect produced by the changes in the bonding and non-bonding energies results in the decrease in the mechanical strength of the coal molecules, and the weakening of the stability of the coal rock. The results of the study reveal the deformation and damage mechanism of the softening and deformation of the back-mining roadway in contact with water in Xinjiang Dabei Coal Mine, which provides a basis for the subsequent disaster prevention and control.

Unraveling the Composition Effects in Chemo-Mechanical Behavior for Single-Crystal Ni Rich Cathodes

Nickel-rich lithium layered oxides (LiNi x Mn y Co z O2 (NMC), x + y + z = 1, x ≥ 0.6) with high accessible capacity, have received tremendous attention as the most promising cathode candidate for next-generation lithium-ion batteries1. To obtain cathode materials with superior electrochemical performance, substantial efforts have focused on optimizing materials’ chemical compositions. However, regardless of chemical compositions, most commercial NMC materials are typically agglomerates composed of primary nanograins (polycrystalline (PC) NMC) which suffer from severe anisotropic expanding or shrinking and thus rapid mechanical failure in the form of intergranular cracking2. To enhance the structural stability, single crystal (SC) NMC with pore-free and high-strength micron-scale particles have received considerable attention3. Owing to the changes in mechanical properties and degradation mechanisms, uncertainties persist regarding the applicability of established compositional design principles and structural degradation indicators in PC Ni rich cathodes to the newly developed SC counterparts4-5. Here we elucidate the intricate correlation between chemical composition and structural properties in SC Ni-rich cathodes using Co-free and Mn-free cathodes as the models. In this case, Mn and Co exhibit significantly different roles for SC cathodes in electrochemical behaviors compared to their PC analogues. By leveraging multi-scale and high dimensional characterization techniques, we reveal the composition effects in lattice strain generation, phase evolution and microcrack formation. This study deepens understanding of the relationship between chemical composition and chemo-mechanical behaviors for SC Ni rich cathodes, contributing to relevant development of rational design strategies and refined characterization methodology. References M. Li, J. Lu, Z. Chen, K. Amine. Adv. Mater. 2018, 30, e1800561.T. Liu, L. Yu, J. Lu, T. Zhou, X. Huang, Z. Cai, A. Dai, J. Gim, Y. Ren, X. Xiao, M. V. Holt, Y. S. Chu, I. Arslan, J. Wen, K. Amine. Nat. Commun. 2021, 12, 6024.J. Langdon, A. Manthiram. Energy Storage Mater. 2021, 37, 143-160.T. Liu, L. Yu, J. Liu, J. Lu, X. Bi, A. Dai, M. Li, M. Li, Z. Hu, L. Ma, D. Luo, J. Zheng, T. Wu, Y. Ren, J. Wen, F. Pan, K. Amine. Nat. Energy 2021, 3, 277-286.A. Aishova, G-T. Park, C. S. Yoon, Y-K Sun. Adv. Energy Mater. 2020, 10, 1903179.

Prrx1-driven LINC complex disruption in vivo reduces osteoid deposition but not bone quality after voluntary wheel running.

The Linker of Nucleoskeleton and Cytoskeleton (LINC) complex serves to connect the nuclear envelope and the cytoskeleton, influencing cellular processes such as nuclear arrangement, architecture, and mechanotransduction. The role LINC plays in mechanotransduction pathways in bone progenitor cells has been well studied; however, the mechanisms by which LINC complexes govern in vivo bone formation remain less clear. To bridge this knowledge gap, we established a murine model disrupting LINC using transgenic Prx-Cre mice and floxed Tg(CAG-LacZ/EGFP-KASH2) mice. Prx-Cre mice express the Cre recombinase enzyme controlled by the paired-related homeobox gene-1 promoter (Prrx1), a pivotal regulator of skeletal development. Prx-Cre animals have been widely used in the bone field to target bone progenitor cells. Tg(CAG-LacZ/EGFP-KASH2) mice carry a lox-stop-lox flanked LacZ gene allowing for the overexpression of an EGFP-KASH2 fusion protein via cre recombinase mediated deletion of the LacZ cassette. This disrupts endogenous Nesprin-Sun binding in a dominant negative manner disconnecting nesprin from the nuclear envelope. By combining these lines, we generated a Prrx1(+) cell-specific LINC disruption model to study its impact on the developing skeleton and subsequently exercise-induced bone accrual. The findings presented here indicate Prx-driven LINC disruption (PDLD) cells exhibit no change in osteogenic and adipogenic potential compared to controls in vitro nor are there bone quality changes when compared to in sedentary animals at 8 weeks. While PDLD animals displayed increased voluntary running activity andPrrx1(+) cell-specific LINC disruption abolished the exercise-induced increases in osteoid volume and surface after a 6-week exercise intervention, no other changes in bone microarchitecture or mechanical properties were found.

Achilles Tendon Mechanical But Not Morphological Properties Change with Rehabilitation in Patients with Chronic Midportion Achilles Tendinopathy.

Achilles tendinopathy (AT) is associated with altered tendon's morphological and mechanical properties, yet it is unclear whether these properties are reversed upon mechanical loading to promote tendon healing. This study aims to determine the extent to which pathological tendon's morphological and mechanical properties adapt throughout a 12-week eccentric rehabilitation protocol. Forty participants with midportion AT were recruited and participated in a 12-week eccentric rehabilitation program. Function and symptoms were recorded through the Victorian Institute of Sports Assessment-Achilles (VISA-A) and hopping. The tendon's morphological (i.e. volume, midportion cross-sectional area (CSA) and anteroposterior (AP) diameter) and mechanical (i.e. stiffness, Young's modulus, and tendon non-uniform displacement) properties were measured at baseline and at 6 and 12 weeks of the intervention. Significant functional improvements were observed, with VISA-A scores and hopping results showing marked improvements (p < 0.001). Morphologically, no significant changes in volume, midportion CSA, or AP diameter were found, although a trend toward decreased CSA between 30-70% of tendon length was noted. Mechanically, significant increases in Achilles tendon stiffness (p = 0.001) and Young's modulus (p < 0.001) were observed over the course of the rehabilitation program. No differences in tendon non-uniform displacement were found following a 12-week rehabilitation program. These findings suggest that tendon adaptation in response to mechanical loading primarily involves changes in mechanical properties rather than morphology, highlighting the complexity and variability in tendon adaptation. Clinically, these mechanical properties could be considered in the load progression throughout rehabilitation as potentially higher strains will be induced when clinical improvements precede mechanical adaptations.

Advancement in Laser‐Based Directed Energy Deposition of Stainless Steel on Microstructural Changes in Mechanical and Wear Properties

Advancement in Laser‐Based Directed Energy Deposition of Stainless Steel on Microstructural Changes in Mechanical and Wear Properties

Moisture-induced mechanical property changes in natural hybrid composites with mwcnt fillers

ABSTRACT This study investigates the moisture absorption behaviour and its effects on the mechanical properties of polyester composites reinforced with jute and hemp fibres. The differences in moisture absorption between distilled water and saltwater are examined. Tensile and flexural tests are conducted on pure jute fibre-reinforced polyester composite, pure hemp fibre-reinforced polyester composite, and jute (J-P) and hemp (H-P) fibre-reinforced polyester composite. Changes in mechanical properties due to varying moisture conditions are analysed. Furthermore, the impact of a synthetic nano filler, multiwall carbon nanotubes (MWCNTs), on these composites is assessed. The study reveals that MWCNTs enhance mechanical properties, particularly in moist conditions. Fracture behaviour analysis aids in understanding the interaction between natural fibres, the matrix, and nano-reinforcement. At maximum natural fibre weight fractions (40%), moisture absorption reaches 8.17% for the J-P composite in distilled water and 9.61% in saltwater, while the H-P composite shows maximum absorptions of 6.61% and 8.27%, respectively. The hybrid composite records 4.18% and 7.17% under similar conditions. Compared to the plain jute fibre-reinforced composite, the addition of multiwall carbon tubes into the polymer matrix significantly reduces the moisture absorption capacity of the jute composite to 34.89% and 31.30% for distilled water and saltwater, respectively.

Experimental and Numerical Investigation on the Bearing Capacity of Axially Compressive Concrete-Filled Steel Tubular Columns with Local Corrosion

This study aims to examine the effects of local corrosion on the axial compression performance of concrete-filled steel tubular (CFST) members. Nineteen CFST short columns with local corrosion were designed and fabricated to undergo axial compression mechanical property tests, with the radial corrosion depth of the local corrosion area as the key test parameter. The failure mechanism and mechanical property change laws of CFST axial compression short columns with circumferential full corrosion at the ends and middle were studied. Combined with finite element modeling, the influence laws of the three-dimensional geometrical characteristics of the local corrosion zone, i.e., the axial length, the annular width and the radial depth, on the structural bearing performance were thoroughly explored and discussed. The results revealed that the main reason for the reduction in load-carrying capacity of circular CFST axial columns due to local corrosion is attributed to the reduction of the effective cross-sectional area of the steel tube in the corrosion area. When local corrosion occurs at different axial positions, the variation range of the bearing capacity of CFST columns is within 10%. Regarding the impact of the three dimensions of local corrosion on the axial load-carrying capacity of CFST, the radial corrosion depth was identified as the most influential factor, followed by the annular corrosion width, and finally by the axial corrosion length. When the axial corrosion length exceeds 20% of the specimen length, its further influence on the load-carrying capacity is considered limited. Finally, a practical calculation formula for the bearing capacity of locally corroded CFST columns is proposed. The predicted results of this formula fit well with the test results and can quickly estimate the remaining bearing capacity of the structure by measuring the geometric parameters of the local corrosion area, providing a reference for the assessment and maintenance of CFST structures.

Iron-Induced Lipid Oxidation Alters Membrane Mechanics Favoring Permeabilization.

Ferroptosis is a form of regulated necrosis characterized by the iron-dependent accumulation of lipid peroxides in cell membranes. However, how lipid oxidation via iron-mediated Fenton reactions affects the biophysical properties of cellular membranes and how these changes contribute to the opening of plasma membrane pores are major questions in the field. Here, we characterized the dynamics of membrane alterations during lipid oxidation induced onsite by Fenton reactions in chemically defined in vitro model membrane systems. We find that lipid vesicle permeabilization kinetically correlates with the appearance of malondialdehyde (MDA), a product of lipid oxidation. Iron-induced lipid oxidation also alters the lateral organization of supported lipid bilayers (SLBs) with lipid phase coexistence in a time-dependent manner, reducing the lipid phase mismatch and the circularity of liquid ordered domains, which indicates a decrease in line tension at the phase boundaries. Further analysis of oxidized SLBs by force spectroscopy reveals a significant decrease in the average membrane breakthrough force upon oxidation, resulting from changes in lipid bilayer organization that make it more susceptible to permeabilization. Our findings suggest that lipid oxidation via iron-mediated Fenton-like reactions induces strong changes in membrane lipid interactions and mechanical properties leading to reduced line tension in the permeabilized state of the bilayer, which promotes membrane pore formation.

Next-generation 3D printed multipurpose prevention intravaginal ring for prevention of HIV, HSV-2, and unintended pregnancy

Globally, nearly half of all pregnancies are unintended, ∼1.3 million new human immunodeficiency virus (HIV) infections are reported every year, and more than 500 million people are estimated to have a genital herpes simplex virus (HSV-2) infection. Here we report the first 3D printed multipurpose prevention technology (MPT) intravaginal ring (IVR) for prevention of HIV, HSV-2, and unintended pregnancy. The IVRs were fabricated using state-of-the-art Continuous Liquid Interface Production (CLIP™) 3D printing technology using a biocompatible silicone-urethane based resin. Anti-HIV drug (Dapivirine, DPV), anti-herpes drug (Pritelivir, PTV) and a contraceptive drug (Levonorgestrel, LNG) were loaded in a macaque size IVR (25 mm outer diameter, OD; 6.0 mm cross-section, CS) allometrically scaled from the human size (54 mm OD; 7.6 mm CS) IVR analogue. All three active pharmaceutical ingredients (APIs) were loaded in the IVR using a single-step drug loading process driven by absorption. DPV, PTV, and LNG elicited zero-order release kinetics in vitro in simulated vaginal fluid (SVF) at pH 4 and pH 8 relevant to human and macaque vaginal pH respectively. CLIP 3D printed MPT IVRs remained stable after 6 months of storage at 4 °C with no change in physical, dimensional, or mechanical properties and no change in drug concentration and absence of drug degradation byproducts. The MPT IVRs elicited sustained release of all three APIs in macaques for 28 days with median plasma concentrations of 138 pg/mL (DPV), 18,700 pg/mL (PTV), and 335 pg/mL (LNG). Safety studies demonstrated that the MPT IVRs were safe and well tolerated in the macaques with no observed change or abnormalities in vaginal pH and no significant changes in any of the 22 mucosal cytokines and chemokines tested including pro-inflammatory (IL-1β, IL-6, IL-8, IFN-γ, TNF-α, IL-17, IL-18) and anti-inflammatory (IL-10, IL-12) cytokines while the MPT IVR was in place or after its removal. Additionally, MPT IVRs elicited no observed alterations in systemic CD4+ and CD8+ T cells during the entire study. Collectively, the proposed MPT IVR has potential to expand preventative choices for young women and girls against unintended pregnancy and two highly prevalent sexually transmitted infections (STIs).

MXene/Bacterial Cellulose Hybrid Materials for Sustainable Soft Electronics.

This work evaluated bacterial cellulose (BC) as a possible biodegradable soft electronics substrate in comparison to polyethylene terephthalate (PET), while also focusing on evaluating hybrid MXene/BC material as potential flexible electronic sensor. Material characterization studies revealed that the BC material structure consists of nanofibers with diameters ranging from 70 to 140 nm, stacked layer-by-layer. BC samples produced are sensitive to post-treatment with isopropanol resulting in a change of structural and mechanical properties. The viscoelastic properties of the BC substrates have been studied experimentally in comparison with the PET film. Aged BC substrate showcased similar viscoelastic properties stability, while exhibiting better properties above 70 °C, with total storage modulus change of -15% and loss modulus change of 21%. MXenes prepared using the Minimally Intensive Layer Delamination (MILD) method were screen-printed onto BC substrates and PET films to form MXene/BC (MX/BC) and MXene/PET (MX/PET) devices. The electrical properties results showcased different resistive behavior on both BC and PET substrate samples with different impedance moduli. MX/PET presented lower sheet resistance of around 156 Ω·sq-1, while MX/BC was 2733 Ω·sq-1. Finally, the MX/BC and MX/PET devices were subjected to repeatable quasi-static load tests and the piezoresistive sensing behavior of the devices has been reported.

Effects of argon plasma treatment on carbon fiber surface characteric and its reinforcing polyimide composites interfacial properties at room and elevated temperatures

In high temperature conditions, this can cause considerable changes in the mechanical properties of the composite. In order to determine the structural and mechanical property changes that occur in composite materials at elevated temperatures, to elucidate the damage mechanisms at elevated temperatures, and to improve the stability and durability of the materials. This paper studies how plasma treatment time affects the surface polarity, roughness, wettability and mechanical properties of carbon fibers. The results showed that the best wettability was attained after 10 min of plasma treatment, and new oxygen-containing functional groups (COO- and -C=O) developed on the fiber surface. The fundamental explanation is that during plasma surface treatment, the CH group in the bisphenol A part chain segment present in the epoxy resin sizing agent's composition is oxidized, forming an organic oxide layer. In this paper, the plasma modification technology was utilized to improve the interfacial compatibility of carbon fiber and Polyimide (PI) resin, and the interlaminar shear strength reached 103.98 MPa, up 10.49 %, and the strength retention rate was 84.3 % at 300 °C. In this paper, the plasma modification technique was employed to increase the interfacial compatibility of carbon fiber and PI resin. It was found that the Inductively Coupled Plasma (ICP) treated carbon fiber surfaces underwent physical and chemical changes that effectively enhanced the interfacial compatibility with the resin. However, the chemical groups and physically etched regions on the surface of the plasma-modified fibers are able to impede the relative motion of the resin to a certain extent, thus improving the interfacial strength.

Effect of moisture on mechanical and physical properties of coals: a uniaxial compression study

The estimation of mechanical and physical properties of coal reservoirs is important for the successful exploration and development of coalbed methane (CBM). Unlike conventional sandstone reservoirs, coal reservoirs exhibit greater sensitivity to stress, resulting in distinct mechanical and physical behaviors. In this study, uniaxial compression tests were performed on both low-rank and high-rank coal samples under different moisture conditions to reveal the mechanical and physical property changes with stress. The results indicate that during axial stress loading (up to 2.8 MPa), axial strain initially increases rapidly and subsequently at a slower rate, with an axial strain of 0.13–0.25% observed at the maximum axial stress. The instantaneous Young’s modulus increases linearly before stabilizing, ranging from 618.01 to 4861.10 MPa, while the Poisson’s ratio remains relatively constant or increases linearly, ranging from 0.002 to 0.165. This results in a negative exponential decrease in both porosity and permeability, with maximum reductions of 1.77–4.21% and 5.38–12.25%, respectively. The mechanical properties of coal are influenced by both the cementation effect of water at low water saturation and the softening effect at high water saturation, which results in axial strain decreases and then increases as the water saturation increases. Concurrently, the elastic modulus initially increases and then decreases, while the Poisson’s ratio exhibits a less pronounced change or tends to increase. Consequently, there is a trend in which porosity and permeability first increase and then decrease. In addition, during stress unloading, the influence of water in coal induces a notable strain hysteresis phenomenon in water-containing coal samples, and this phenomenon is more obvious in the low-rank coals.

Unveiling the electronic structure-mechanical properties correlation in nanocomposites: A nanoindentation and DFT analysis of PMMA/TiO2

polymer nanocomposites play a critical role in various industries, including packaging, sensors, biomedicine, sports equipment, and automotive manufacturing, due to their unique properties and customizable design. To maximize their performance and reliability, a comprehensive understanding of their mechanical behavior is paramount. The evolution of mechanical properties by incorporation of nanoparticles is still far from well understood even for very common polymer nanocomposite like PMMA/TiO2. The aim of the current work is to study the change in mechanical properties of PMMA/TiO2 due to the change in electronic structure of nanocomposite as a result of systematic variation of TiO2. In this research, the electronic structure of the PMMA/TiO2 nanocomposite at different wt% of TiO2 are studied and the mechanical properties of these nanocomposites are also estimated using Density Functional Theory (DFT). The mechanical properties of PMMA/TiO2 thin films with different TiO2 wt% are meticulously examined experimentally using the nanoindentation technique at various loading rates. The mechanical properties obtained from DFT analysis matches well with the experimental study which indicates a strong correlation between the electronic structure and the mechanical properties. The study reveals that there exist an optimum TiO2 wt% beyond which the mechanical properties are not increasing due to the electronic configuration of the nanocomposite.

First-principles study of Y, Ca microalloyed Mg-Zn alloy

This article investigates the complex effects of Y and Ca alloying on the G.P. zones ( parallel to {0001}Mg)and G.P.1 zones ( parallel to {2−1−10}Mg) in Mg-Zn alloys, as well as their corresponding changes in thermal stability, electronic structure, and mechanical properties, using first-principles calculations. The addition of Y significantly enhances the thermal stability of both the G.P. and G.P.1 zones, whereas the effect of Ca is more limited, mainly enhancing the thermal stability of the one-atomic layer G.P. zones, but possibly decreasing the thermal stability in other areas. In the combined alloying of Y and Ca, the cooperative effect optimizes the thermal stability of the one-atomic layer and half-atomic layer G.P.1 zones, but reduces the thermal stability of other G.P. zones. Through studying the local density of states and the atomic radial distribution function, it is revealed that the higher stability of the half-atomic layer G.P. zones compared to the one-atomic layer G.P. zones is due to more Mg-Zn and Mg-Mg bonds, whereas the one-atomic layer G.P.1 zones exhibits higher stability because of shorter and more stable Zn-Zn, Mg-Zn, and Zn-Mg bonds. The electronic structure analysis shows that Y mainly appears in the alloy in the form of electron localization, readily forming ionic bonds with Mg and Zn, which is a key reason for its effective alloying results. In contrast, Ca, as well as the alloying of Y and Ca, do not form effective bonds on the energy levels from −8 eV to −5 eV, explaining their weaker alloying effects. Additionally, the study of mechanical properties indicates that the G.P. zones of pure Zn, due to its significant difference in shear modulus from the magnesium matrix, is not easily strengthened by dislocation shearing and thus mainly strengthened through the Orowan mechanism. The addition of Y significantly increases the strength and hardness of the one-atomic layer G.P. zones, but decreases the ductility. The addition of Ca changes the anisotropy of the Young's modulus of the one-atomic layer G.P. zones, while the combined effect of Y and Ca greatly alters the anisotropy of the shear modulus of this phase. These findings provide important theoretical guidance and insights for the design and application of Mg-Zn alloys.

Validation of assessment methods for creep crack growth rates in irradiated components from Nimonic PE16 Tie-Bar tests

Creep crack growth is a life-limiting failure mechanism in high-temperature metallic components. The creep crack growth response is linked to the underlying creep deformation and failure properties, such as creep ductility. Irradiation effects such as helium (He) embrittlement in high-temperature reactor components trigger decreases in creep ductility. Creep crack growth (CCG) data obtained from unirradiated and irradiated Nimonic PE16 tie-bars confirm the accelerated crack growth rates under neutron irradiated conditions. The exact same data were also used to validate the analytical defect assessment procedure for transient creep crack growth in Code Case N-934 of ASME BPVC Section XI Division 2, developed from unirradiated material data. To do so, the mechanics-based creep crack growth law of Nikbin-Smith-Webster (NSW) is adopted to estimate the crack growth rates in unirradiated PE16, and then adjusted through changes in bulk mechanical properties in the irradiated case to estimate the changes in crack growth rates. The estimated ȧ-C∗ trend was employed as part of the analytical defect assessment procedure for transient creep crack growth in Code Case N-934 of ASME BPVC Section XI Division 2. Evaluation of results via the procedure and the estimated trends confirm the validity of the approach to predict increases in creep crack growth in neutron irradiated components, as observed in experimental data. The approach yields moderately conservative predictions for crack growth rates, and accurately captures the relative increase in creep crack growth rates for the irradiated case. The predictions were independently validated by predicting the C*-values expected in the loading configuration for a given recorded crack growth rate ȧ. The validation of the defect assessment method introduced in Code Case N-934 against both unirradiated and irradiated PE16 CCG data provides a practical path to its implementation in metallic components across high-temperature reactor designs. This is particularly useful where crack growth data in irradiated material may not be readily available. The technique also allows for propagating uncertainties in crack growth predictions which stems from compounding effects such as variability in unirradiated properties, degree of irradiation and corresponding embrittling effects, crack size and load perturbations. The relevance of mechanical properties accurately depicting aspects of the He embrittlement process for practical applications in plant and the importance of creep crack growth testing are discussed.

Accounting for decarbonization impacts across the full life cycle of alternative concrete materials: A case-study for graphene-amended cementitious composites

Concrete's extensive use worldwide comes with significant environmental cost, contributing to 8% of annual global carbon emissions. This study investigates the use of life cycle assessment (LCA) and technoeconomic assessment (TEA) as tools to quantify anticipated reductions in global warming potential (GWP) arising from use of novel concrete mixtures or innovative production techniques, with specific focus on a case study related to graphene nanoplatelets (GNPs) as functional fillers. LCA and TEA results are reported for several choices of functional unit (FU) and system boundaries (SB). This approach illustrates how various LCA and TEA framings are differently useful to articulate how changes in technical performance properties such as mechanical strength and durability influence overall life-cycle environmental impacts. Framing 1 make use of a nominal volume-based FU (1 m3) and cradle-to-gate SB. Under this framing, addition of GNPs to the base mix seems to increase GWP and production cost. Framing 2 makes use of a strength-normalized FU and cradle-to-gate SB. Under this framing, life-cycle GWP and production cost for the GNP-amended mortars are decreased relative to the control, due to the appreciable increase in mechanical strength of the GNP-amended mortars. Finally, Framing 3 makes use of the nominal volume-based FU (1 m3) and cradle-to-grave SB. Under this framing, GWP and production cost for the GNP-amended mortars again seem to decrease, due to improved durability which gives rise to longer estimated service life and reduced maintenance. This study illustrates that use of GNPs as functional filler is a seemingly promising strategy for decarbonizing concrete. More broadly, it is concluded that LCAs and TEAs of novel concretes should be framed in a way that articulates how changes in mechanical strength and/or durability properties contribute to changes in environmental impacts over all stages of the concrete life-cycle (i.e., cradle-to-grave). Such framing will help ensure that results that are meaningful to support decision-making in the area of sustainable construction materials.

Experimental Investigations of the Influence of Spent Coffee Grounds Content on PLA Based Composite for 3D Printing

Nowadays Fused Deposition Modeling, a widely utilized additive manufacturing technology, is significantly transforming as modern production processes. Beyond basic uses to it role in sustainability, Fused Deposition Modeling offers processing potential for implanting circular economy by reducing virgin materials consumption and enhance the integration of waste food for sustainable 3D printing. This research paper investigated the production of new composite materials based on spent coffee grounds. In addition, PLA and SCG at various contents (0, 3, 5, 10, and 15 wt%) were dried and premixed, then processed into PLA/SCG composite pellets using twin-screw extrusion. These pellets were successfully converted into filaments and subsequently used for 3D printing. The effect of spent coffee grounds in PLA composites was investigated via physical and mechanical analysis of 3D printed samples. Regarding density measurements, results revealed that adding up to 5 wt% of spent coffee grounds increased the density while further additions led to a decrease which due to the printing parameters such as extrusion temperature and nozzle diameter. Considering the mechanical properties, the Young’s modulus increased once the spent coffee grounds content reached 3 wt% and then decreased. In the other hand, there was no enhancement in tensile strength and elongation at break which corroborating with density measurements. This mainly contributed to the changes in mechanical properties caused by printing parameters. This study demonstrates that coffee waste can be used as a filler in environmentally friendly composites for 3D printing, with a maximum SCG content of 15 wt%. This approach not only promotes the reuse of coffee waste but also reduces the cost of traditional PLA filaments.