Ductile Behavior Research Articles

Complete stress-strain analysis of masonry prisms under compressive loading-unloading cycles through digital image correlation

This paper presents the findings of an experimental study focused on the behaviour of masonry structures subjected to uniaxial loading-unloading compression. The study's primary objective is to examine the impact of joint mortar on the failure mode and the development of permanent strains using the digital image correlation technique (DIC). Masonry prisms were constructed using two types of fired bricks and five different mortars, each with varying cement and lime contents. The prisms were instrumented with a linear variable differential transformer (LVDT) for displacement measurements and prepared for image processing using DIC. The prisms were then subjected to compression testing until failure to capture their complete behaviour. The experimental results obtained through DIC and LVDT measurements showed good agreement. The DIC technique proved its effectiveness in providing comprehensive strain evaluations of the brick prisms, enabling a detailed stress-strain analysis at a full-scale level. Furthermore, the study revealed that prisms with lower cement content exhibited a more ductile behaviour in the post-peak region, with strain localisation observed at the joint mortar interface.To validate DIC's reliability in characterising masonry's cyclic behaviour, the results obtained from analytical modelling were compared with those derived from DIC. This comparison aimed to confirm the accuracy and consistency of DIC measurements. Overall, this study contributes to our understanding of masonry behaviour under compression and highlights the capabilities of DIC in capturing strain patterns and providing valuable insights into the influence of joint mortar on the structural response of masonry elements.

Experimental and Numerical Analysis of Fracture Mechanics Behavior of Heterogeneous Zones in S690QL1 Grade High Strength Steel (HSS) Welded Joint.

The heterogeneity of welded joints' microstructure affects their mechanical properties, which can vary significantly in relation to specific weld zones. Given the dimensional limitations of the available test volumes of such material zones, the determination of mechanical properties presents a certain challenge. The paper investigates X welded joint of S690QL1 grade high strength steel (HSS), welded with slightly overmatching filler metal. The experimental work is focused on tensile testing to obtain stress-strain properties, as well as fracture mechanics testing. Considering the aforementioned limitations of the material test volume, tensile testing is carried out with mini tensile specimens (MTS), determining stress-strain curves for each characteristic weld zone. Fracture mechanical testing is carried out to determine the fracture toughness using the characteristic parameters. The experimental investigation is carried out using the single edge notch bend (SENB) specimens located in several characteristic welded joint zones: base metal (BM), heat affected zone (HAZ), and weld metal (WM). Fractographic analysis provides deeper insight into crack behavior in relation to specific weld zones. The numerical simulations are carried out in order to describe the fracture behavior of SENB specimens. Damage initiation and evolution is simulated using the ductile damage material behavior. This paper demonstrates the possibility of experimental and numerical determination of fracture mechanics behavior of characteristic heterogeneous welded joint zones and their influence on crack path growth.

Unveiling mechanisms of self-healing in CoCrFeMnNi/HfNbTaTiZr dual-phase high-entropy alloys: A molecular dynamics simulation study

This study investigates the mechanical properties and self-healing behavior of FCC CoCrFeMnNi/BCC HfNbTaTiZr dual-phase high-entropy alloy (DP-HEA) multilayers using molecular dynamics simulations. The relaxed DP-HEA multilayers have low hexagonal close-packed (HCP) percentages and decreasing "Other" fractions with increasing thickness. DP-HEA multilayers exhibit ductile behavior under uniaxial tensile loading, with stress increasing linearly until the yield strain and then gradually decreasing. Dislocation motion, twinning in the FCC phase, and BCC to HCP local structural transformation contribute to this behavior. Single crystal FCC CoCrFeMnNi and BCC HfNbTaTiZr alloys show different stress-strain responses, while DP-HEAs exhibit no significant stress drop beyond the ultimate strain. Self-healing is observed in DP-HEAs with 5 and 10 nm thickness, with a transformation from HCP to BCC structures. The DP-HEA with 15 nm thickness shows less pronounced self-healing. The interlayer distance between BCC/FCC interfaces influences the self-healing ability of the BCC phase. These findings enhance our understanding of the mechanical behavior and self-healing mechanisms in DP-HEA multilayers, facilitating the design of advanced materials with improved properties.

Temperature dependence of thermodynamic and mechanical properties of Fe2RhSi and Fe2RhGe: An ab-initio investigation

In this research, we conducted an exploration of the thermodynamic and mechanical properties of ferromagnetic inverse Heusler alloys Fe2RhSi and Fe2RhGe employing computational methods based on pseudopotentials, plane waves, density-functional theory and density-functional Perturbation theory. Our study indicates that the alloys are dynamically stable, as evidenced by the presence of positive phonon frequencies for all modes. Moreover, our computational results of specific heat and Debye temperature exhibited a remarkable agreement with experimental measurements, confirming to the accuracy of our approach. Both alloys displayed positive thermal expansion and demonstrated a decrease in elastic constants with increasing temperature, consistent with the Born–Huang criteria for mechanical stability. These alloys also exhibit an anisotropic and ductility behavior. The ductility is attributed to their metallic bonds.

Computational study of effects of doping Ni and Pd on CoAl for hydrogen storage capacity, elastic and electronic properties

Intermetallic compounds in B2 structure which have low density, fracture, and high strength have important applications in different engineering applications. For energy storage apparatus, the researchers have investigated new materials to improve effective efficiency in energy storage devices such as batteries and green energy technologies. The investigation of transition metal–aluminide alloys has increased due to their attractive elastic features. Like many hydrogen storage alloys, B2-type hydrogen storage alloys such as ZrCo utilize the systems of hydrogen storage in atomic gaps. If hydrogen atoms settle in the interstitial spaces, lattice expansion forms due to lattice distortion. Since plastic and elastic deformations change pressure and temperature, they are important for the material during hydrogen desorption and absorption. According to the literature, element doping effects boost hydrogen storage sufficiency. The effects of Ni- and Pd-substituted dopants on hydrogen storage, electronic and elastic features of a Cobalt-Aluminum alloy were performed using the first-principles calculations with and without spin-polarized configurations. Obtained lattice parameters for Co8Al8 are good agreement with literature values. Interstitial H doping has changed the crystal structure from cubic (BCC) to tetragonal. It is concluded that all investigated CoAl alloys included H doping has negative formation energies showing thermodynamically stabilities. All investigated alloys are stable mechanically and dynamically. Doping of H2 atoms to CoAl changes from a brittle to ductile nature. Also, Ni contributions improve ductility behavior to improve the cycle performance of the Co7NiAl8 and Co8Al7Ni alloy. It can be concluded from electronic band structure that they exhibite metallic behavior. Our obtained gravimetric and volumetric capacities which are comparable with B2 hydrogen storage material such as ZrCo, FeAl, indicate that CoAl alloys may be suitable for hydrogen storage applications.

Ab initio insight into the physical properties of MgXH3 (X = Co, Cu, Ni) lead-free perovskite for hydrogen storage application.

Renewable energy systems are vital for a sustainable future, where solid-state hydrogen storage can play a crucial role. Perovskite hydride materials have attracted the scientific community for hydrogen storage applications. The current work focuses on the theoretical study using density functional theory (DFT) to evaluate the characteristics of MgXH3 (X = Co, Cu, Ni) hydrides. The structural, vibrational, electronic, mechanical, thermodynamic, and hydrogen storage properties of these hydrides were investigated. The equilibrium lattice parameters were calculated using the Birch-Murnaghan equation of state-to-energy volume curves. The elastic constants (Cij) and relevant parameters, such as Born criteria, were calculated to confirm the mechanical stability of the hydrides. The Cauchy pressure (Cp) revealed brittle or ductile behavior. The outcomes of the Pugh ratio, Poisson ratio, and anisotropy were also calculated and discussed. The absence of negative lattice vibrational frequencies in phonon dispersion confirmed the lattice's dynamic stability. The heat capacity curves of thermodynamic properties revealed that hydrides can conduct thermal energy. The metallic character and ample interatomic distances of hydrides were confirmed by the band structure and population analysis, which confirmed that hydrides can conduct electrical energy and adsorb hydrogen. The density of state (DOS) and partial DOS unveiled the role of specific atoms in the DOS of the crystal. The calculated gravimetric hydrogen storage capacity of MgCoH3, MgCuH3, and MgNiH3 hydrides was 3.64, 3.32, and 3.49wt%, respectively. Our results provide a deeper understanding of its potential for hydrogen storage applications through a detailed analysis of MgXH3 (X = Co, Cu, Ni) perovskite hydride material.

Ductile failure behaviour characterisation of HRT with GISSMO and crashworthiness optimisation design of VRB-HRT

In this paper, a generalised incremental stress state dependent damage model (GISSMO) is used to accurately characterise the ductile failure behaviour of hot formed steel under collision, which is the excellent material selection to improve the crashworthiness and lightweight level of car body frames. The deformation patterns, structural failure patterns, and key crashworthiness indexes of B1500HS hot-rolled tube (HRT) are validated by the comparative researches between experiments and simulations. To fully exploit the lightweight potential of HRT, a variable-thickness rolled blanks hot rolled tube (VRB-HRT) is proposed to perform its crashworthiness optimisation design with considering the ductile failure by the extended hybrid cellular automaton for VRB thin-walled structures (eHCA-VRB) algorithm. It is found that the optimal case of VRB-HRT with considering the ductile failure is easier to meet the actual performance constraints, even though possesses a lower weight reduction ratio. Therefore, the ductile failure of VRB-HRT should be considered to guarantee the structural reliability by a more reasonable optimal design.

Punching shear performance of star-shaped steel plates reinforced RC slab-column connections

The progressive collapse of flat plate structures due to brittle punching shear failure of reinforced concrete (RC) slab-column connections is a major concern in structural engineering. This paper proposed an innovative star-shaped steel plates (SSPs) system to achieve an effective yet practical enhancement of the punching and post-punching performance of RC slab-column connections. SSPs were fabricated from thin steel plates, welded together, and placed in the centre of the joint. Engineering cementitious composite (ECC) was also adopted to replace the joint core concrete and work with the SSPs further to improve the punching shear behaviour of the joint. To evaluate the effectiveness of the proposed system, five large-scale RC slab-column connections with different SSPs configurations and concrete materials were tested under monotonic load. The results showed that the initial stiffness of the joint was minimally affected by the presence of SSPs, but the system significantly improved the punching shear strength, post-punching load-bearing capacity, and deformation capacity of the joint. Specimens with ECC and SSPs exhibited an even higher punching shear strength and more ductile post-punching behaviour. The study also found that the optimum enhancement of the punching shear behaviour of the slab-column joint can be realised when the SSPs yield just before the joint experiences punching shear damage. Finally, formulas were developed to reasonably predict the punching shear strength and post-punching load-carrying capacity of the SSPs reinforced slab-column connections.

Effect of interfacial coatings on mechanical properties of 2.5D Nextel™ 720 fiber toughened zirconia-mullite matrix composites

In this study, 2.5D bent shallow cross-linked structure Nextel™ 720 (N720) fiber-reinforced yttria-stabilized zirconia-mullite composites with pyrolytic carbon (PyC) and fugitive pyrolytic carbon (FC) interfacial coatings were prepared by using a precursor infiltration and pyrolysis approach (called as N720f/PyC/YSZ-Mu and N720f/FC/YSZ-Mu, respectively). The effects of PyC and FC coatings on the failure mechanisms and mechanical properties of the composites were investigated. The N720f/PyC/YSZ-Mu composite shows ductile fracture behavior while the N720f/FC/YSZ-Mu composite shows brittle fracture behavior. The fracture toughness and flexural strength of the N720f/PyC/YSZ-Mu composite reach ∼7.00 MPa·m1/2 and ∼ 120.79 MPa, respectively. In contrast, the corresponding properties of the N720f/FC/YSZ-Mu composite are ∼3.66 MPa·m1/2 and ∼ 59.02 MPa, respectively. Microstructure analysis indicates that the weak PyC interfacial layer contributes to toughening by promoting fiber pull-out and debonding, thus enhancing the mechanical properties of the N720f/PyC/YSZ-Mu composite. The retrogression of the mechanical properties of the N720f/FC/YSZ-Mu composite originates from the damage to N720 fibers during the preparation procedure. This paper provides a new idea for the development of high-performance oxide CMCs with a 2.5D structure.

Computational and experimental investigation of a new non equiatomic FCC single-phase Cr15Cu5Fe20Mn25Ni35 high-entropy alloy

The structural, mechanical, and thermal properties of a new non-equiatomic face-centered cubic (FCC) structured high entropy alloy (HEA) were examined computationally using density functional theory (DFT) calculations and validated experimentally. To identify potential single phase HEA candidates, the composition space of the CrCuFeMnNi alloy system, including 1451 alloys, was investigated using the CALculation of PHAse Diagrams (CALPHAD) method and Thermo-Calc software. The CALPHAD approach successfully predicted an FCC single-phase Cr15Cu5Fe20Mn25Ni35 alloy. Elastic constants and thermal properties of the Cr15Cu5Fe20Mn25Ni35 HEA were determined through DFT calculations using a 100-atom supercell. To validate the DFT calculations, HEA samples were prepared by the arc melting technique, and X-ray diffraction (XRD) analysis confirmed a single-phase FCC structure.The DFT calculated elastic constants values satisfied the Born stability conditions for stability of a cubic crystal structure. Pugh's theory indicated that this alloy exhibits ductility and metallic behavior due to its B/G ratio exceeding 1.75 and positive Cauchy pressure. Additionally, Poisson's ratio exceeded 0.26, further confirming its ductile nature. Experimental tests confirmed these findings by measuring bulk modulus, shear modulus, Young's modulus, and Poisson's ratio. The calculated CV values showed good agreement with experimental data at different temperatures. The linear coefficient of thermal expansion increased rapidly at lower temperatures before becoming linear. Both XRD as well as DFT calculations yielded similar lattice constant results for this HEA. These findings provide insights into various properties of the Cr15Cu5Fe20Mn25Ni35 HEA, including its structural stability, mechanical behavior and thermal characteristics.

Cost-effective methods for flexural strengthening of one-way RC precast flat slab bridges in South Carolina

In South Carolina, there are one-way precast RC flat slab bridges that were constructed in the 1950 s for H-10 and H-15 design trucks (lower than the current design standards) and have deteriorated over time. To ensure public safety and continued usage, strengthening the bridges is imperative. Various methods exist for flexural strengthening, including application of UHPC from above and strengthening from below with FRP, steel plates, and external prestressing. However, these methods may compromise the ductile behavior of the slabs and they are also challenging, labor-intensive, and expensive to apply. The innovation of this paper lies in investigating the methods for strengthening from above that have the potential to improve both the flexural strength and ductility of slabs, while offering advantages in terms of ease of implementation and cost-effectiveness compared to existing methods. Five slabs obtained from decommissioned bridges in South Carolina were tested under monotonic loading to failure: one reference slab; one slab strengthened with steel channel sections from above; one slab strengthened with steel plate sections from above, and two slabs connected at the joint by near surface mounted steel rebars for strengthening. Strengthening the slabs with steel channel sections from above effectively improved the flexural strength and ductility of the slabs while being more economical and easier to implement than other methods of strengthening. Following strengthening, some slabs may require overlays to cover the steel sections and ensure that bridge traffic may go on them. Even after accounting for reduction in strength gain due to the deadload of the overlay, a positive net strength gain in measured peak moment was observed in the strengthened slabs. The moment capacities of the slabs, as determined through design calculations following the ACI 318–19 code, exhibit a good agreement with the measured peak moment observed in experimental tests, thus validating their reliability as a dependable alternative to solely relying on experimental tests.

Ductile behavior of a penta-boron nitride nanosheet triggered by structure transition for enhancing hydrogels

Boron nitride nanosheet (BNNS) is an attractive nanomaterial to improve polymeric materials in hydrogels due to their high mechanical properties, robust interfacial properties with polymer, and non-toxicity. However, the mismatching deformation capacity between BNNS and hydrogels results in damage to the BNNS-hydrogels interface and deteriorates the tensile properties of BNNS reinforced hydrogels. By adopting nanotechnology, the brittle nature of BNNSs can be modified. A novel penta-BNNS exhibits pentagonal rings, presenting ductile behavior under tensile deformation. The tensile test is performed by molecular dynamics simulations. The simulation results show that the ultimate failure strain of the penta-BNNS is significantly increased, which is attributed to the structure transition of the pentagonal rings in the penta-BNNS under tensile deformation. Due to the structure transition, the deformation capacity of the penta-BNNS is significantly improved with respect to the hexa-BNNS. This study links the structure to ductile behavior, which helps to devise advanced two-dimensional nanomaterials for improving hydrogels.

Axial compression behavior of thin-walled steel partially encased fibre-reinforced self-compacting lightweight aggregate concrete columns

This study presents the mixture design method of fibre-reinforced self-compacting lightweight aggregate concrete (FSLC) and combines it with cold-formed steel (CFS) to propose a novel thin-walled steel partially encased FSLC (TPEC) column. The axial compression behavior of the TPEC column was revealed by test and finite element analysis. The test results showed that FSLC did not experience brittle failure when constrained by CFS. The presence of FSLC in CFS also restricted the occurrence of buckling, resulting in improved ductile behavior of the TPEC columns. However, the connection between the web separated at the peak load, at which time the column no longer satisfied the requirements for the serviceability limit state. Finite element analysis demonstrated the transverse constraint effect of the thin-walled steel frame on FSLC, and through parametric analysis, more rational arrangements for web connections can be obtained. The cross-section of the TPEC column can be divided into three constraint zones based on the strength of the transverse constraint on the FSLC. A compressive strength calculation model for FSLC under the constraint of a thin-walled steel frame was proposed. A calculation method of the axial carrying capacity of the TPEC column was proposed, and the corresponding calculation model demonstrated better applicability.

Analytical and numerical studies on flexural resistance of fold-fastened multi-cellular steel panels

Fold-fastened multi-cellular steel panel (FMSP) is a novel type of cold-formed steel (CFS) built-up member, which is manufactured by connecting multiple FMSP cells. When connecting these cells, folded regions can be formed by lapping the FMSPs cells end to end, and indentations are used as fasteners during the manufacturing process. In this study, the flexural resistance of FMSPs was numerically and analytically investigated. Firstly, the refined finite element (FE) models were developed to simulate the flexural behavior of FMSPs. The accuracy of FE modeling method was validated by comparing the numerical results with experimental results obtained from the published literature about these investigations for CFS built-up members in terms of their moment capacities, moment-deflection curves and failure modes. Then, substantial parametric analyses involving a total of 105 different FE models of FMSPs were carried out to study the effects of steel thickness and strength, cellular dimension, width of fold-fastened regions and indented spacing on the flexural behavior of FMSPs. Finally, a sectional analysis based on the effective width method (EWM) was adopted to predict the ultimate flexural resistance of FMSPs. The results revealed that steel thickness and web plate depth have a great effect on the flexural behavior of FMSPs, while there was little influence on the ultimate load in other parameters. Moreover, the decrease in both width-to-thickness ratio and aspect ratio will lead to better ductile behavior for FMSPs. In addition, the EWM adopted in this study can agree well with the FE results, achieving better predicting results compared with other methods; therefore, this method is valid and well fits the practical needs.

Seismic Behavior and Modeling of Ductile Composite Steel-Trussed Concrete Beam to Column Joints

This paper presents an experimental and numerical study on a ductile beam-column connection between a composite reinforced concrete truss (CRCT) beam and a reinforced concrete (RC) or concrete-filled tube (CFT) column subjected to bending and shear loads. Two experimental models with different beam-column joint testing schemes, extracted from the same prototype three-dimensional structure designed according to the rules of the capacity design provided by seismic code, were subjected to quasi-static cyclic tests by applying gravitational loads and the horizontal seismic force. The main objective of this paper is to verify the ductile behavior of both specimens experimentally and to simulate the experimental global and local responses by nonlinear static analysis, considering different modeling approaches. The comparison between the experimental and numerical results highlights, for both models considered, the ductile and dissipative capacity of the connection system, designed following the criteria of the hierarchy of resistances proposed by the current Italian code. The results of different experimental setups demonstrate that the tests can be repeated and the results can be reproduced by means of simple nonlinear models.

Behaviour of FRP-ECC-HSC composite stub columns under axial compression: Experimental and mathematical approach

The composite stub column composed of fiber-reinforced polymer (FRP), Eco engineered cementitious composite (ECC), and high-strength concrete (HSC) core is experimentally investigated in this study. The ductile performance of HSC-FRP is enhanced by proving an ECC ring of 30 mm thickness as sandwich layer between HSC and FRP. During experimentation the premature failure of the FRP-HSC column is observed at the initial phase, which exhibits brittle nature of the column. The material properties of FRP, ECC, and HSC were characterized. The performance of composite columns was observed with four FEH (FRP-ECC-HSC) columns, four HE (HSC-ECC) columns, and two FH (FRP-HSC) columns. The parameters such as uniform hoop strain distribution, ultimate load-carrying capacity, axial and hoop strain, and confining efficiency of the FRP were investigated to understand the behaviour of composite columns. From results, the ultimate load-carrying capacity of FH columns was 15.56 % higher than the FEH columns. The FEH columns showed the enhanced confining efficiency of FRP and 21% increase in uniform hoop strain distribution than the FH columns. The hoop strain capacity of FEH columns were increased twice the times of FH columns, which indicates the increased ductile behaviour of the FEH columns. In addition, experimental results of composite columns were highly correlated with the existing theoretical equation from literatures

Inferring mechanical properties of the SARS-CoV-2 virus particle with nano-indentation tests and numerical simulations

The pandemic caused by the SARS-CoV-2 virus has claimed more than 6.5 million lives worldwide. This global challenge has led to accelerated development of highly effective vaccines tied to their ability to elicit a sustained immune response. While numerous studies have focused primarily on the spike (S) protein, less is known about the interior of the virus. Here we propose a methodology that combines several experimental and simulation techniques to elucidate the internal structure and mechanical properties of the SARS-CoV-2 virus. The mechanical response of the virus was analyzed by nanoindentation tests using a novel flat indenter and evaluated in comparison to a conventional sharp tip indentation. The elastic properties of the viral membrane were estimated by analytical solutions, molecular dynamics (MD) simulations on a membrane patch and by a 3D Finite Element (FE)-beam model of the virion's spike protein and membrane molecular structure. The FE-based inverse engineering approach provided a reasonable reproduction of the mechanical response of the virus from the sharp tip indentation and was successfully verified against the flat tip indentation results. The elastic modulus of the viral membrane was estimated in the range of 7–20 MPa. MD simulations showed that the presence of proteins significantly reduces the fracture strength of the membrane patch. However, FE simulations revealed an overall high fracture strength of the virus, with a mechanical behavior similar to the highly ductile behavior of engineering metallic materials. The failure mechanics of the membrane during sharp tip indentation includes progressive damage combined with localized collapse of the membrane due to severe bending. Furthermore, the results support the hypothesis of a close association of the long membrane proteins (M) with membrane-bound hexagonally packed ribonucleoproteins (RNPs). Beyond improved understanding of coronavirus structure, the present findings offer a knowledge base for the development of novel prevention and treatment methods that are independent of the immune system.

Numerical and analytical investigations on punching shear performance of UHTCC-enhanced RC slab-column joints

The excellent tensile strain-hardening behavior of ultra-high toughness cementitious composite (UHTCC) makes it applicable for enhancing the punching shear performance of reinforced concrete (RC) slab-column joints. However, construction of an entire slab-column structure employing UHTCC would inevitably lead to uneconomical designs. To balance the economic benefits with the punching performance, utilizing UHTCC in the core region of a slab-column joint is a promising approach. In this study, the impact of UHTCC application range (UAR) on the punching shear performance of UHTCC-enhanced RC slab-column joints (USCJs) was investigated, and an approach for determining the optimal UAR was also presented. Two USCJ specimens with different UAR were tested, and experimental results were compared with the counterpart numerical results to validate the finite element (FE) models. Twenty FE USCJ models with different UAR were established. Then the impact of UAR on development of critical cracks, ultimate resistance, and ductile behavior was examined. Analytical approaches based on the critical shear crack theory as well as on the combination of critical shear crack theory and yield line theory were adopted to predict the ultimate and flexural resistances, respectively. The failure mode was determined by comparing these two resistances and considering the ductile coefficient, based on which the effect of UAR on the failure mode was determined. The results show that the location of critical shear cracks and the appearance of flexural cracks vary with UAR. By increasing UAR, the ultimate resistance increases, but the ductile coefficient first increases and then slightly decreases. Provided that the UAR is increased to some extent, the growth rate of the ultimate resistance evidently slows down and the ductile coefficient peaks, indicating the optimal UAR considering both the economic efficiency and the punching performance. The presented approach shows promise for determining the optimal UAR in practical engineering designs.

Isotropic pressure induced structural, electronic, photocatalytic, elastic and mechanical properties of RbPbF3: GGA-PBE and HSE03 based computational estimation

The main objective of this study is to present a comprehensive computational analysis, with Generalized Gradient Approximations (GGA) and Heyd–Scuseria–Ernzerhof (HSE03) correlation functionals, of the structural, optoelectronic, photocatalytic and elastic properties of Rubidium Lead Fluoride (RbPbF3) under the systematic isotropic pressure range of 0–55 GPa. Under stress a systematic decrease in lattice parameters and band gap (4.869 eV − 1.105 eV) is observed upto 55 GPa. For comprehensive evaluation of band gap, PDOS and EPDOS have also been determined. Photocatalytic properties of RbPbF3 under stress demonstrate the best photocatalytic water-splitting potential, aligning with the band gap estimation. The significant variation in optical parameters is found with a varying stress array from 0–55 GPa. Optically this compound can be utilized as a UV detector because absorption bands are seen in the UV spectrum. The material exhibits mechanical stability, and ductile behavior, with ionic and covalent bonding. The anisotropic nature is observed in our estimated results.

Recycled Fine and Coarse Aggregates' Contributions to the Fracture Energy and Mechanical Properties of Concrete.

This paper investigates the fracture mechanical properties of concrete, using crushed concrete aggregates (CCA) and granulated blast furnace slag (GGBS) for partial cement replacement. CCAs made from prefabricated concrete replace 100% of the fine and coarse fractions in concrete recipes with w/c ratios of 0.42 and 0.48. Two pre-treatment methods, mechanical pre-processing (MPCCA) and accelerated carbonation (CO2CCA), are investigated for quality improvements in CCA. The resulting aggregates show an increased density, contributing to an increase in the concrete's compressive strength. The novelty of this paper is the superposition of the effects of the composite parts of concrete, the aggregate and the cement mortar, and their contributions to concrete fracture. Investigations are directed toward the influence of fine aggregates on mortar samples and the influence of the combination of coarse and fine aggregates on concrete samples. The physical and mechanical properties of the aggregates are correlated with mortar and concrete fracture properties. The results show that CCA concrete achieves 70% of the fracture energy values of concrete containing natural aggregates, and this value increases to 80% for GGBS mixes. At lower w/c ratios, MPCCA and CO2CCA concretes show similar fracture energies. CO2CCA fine aggregates are the most effective at strengthening the mortar phase, showing ductile concrete behavior at a w/c ratio of 0.48. MPCCA aggregates contribute to higher compressive strengths for w/c ratios of 0.42 and 0.48. Thus, mechanical pre-processing can be improved to produce CCA, which contributes to more ductile concrete behavior.