Compression Curves Research Articles

Novel pseudo-hexagonal montmorillonite model and microsecond MD simulations of hydrate formation in mixed clay sediments with surface defects.

Both CH4 hydrate accumulation and hydrate-based CO2 sequestration involve hydrate formation in mixed clay sediments. The development of realistic clay models and a nanoscale understanding of hydrate formation in mixed clay sediments are crucial for energy recovery and carbon sequestration. Here, we propose a novel molecular model of pseudo-hexagonal montmorillonite nanoparticles. The stress-strain curves of tension, compression, and shear of pseudo-hexagonal montmorillonite nanoparticles exhibit linear characteristics, with tension, compression, and shear moduli of ∼435, 410, and 137GPa, respectively. We perform microsecond molecular dynamics simulations to study CH4 and CH4/CO2 hydrate formation in montmorillonite-illite mixed clay sediments with surface defects. The results indicate that hydrate formation in mixed clay sediments is significantly influenced by the presence of clay defects. CH4 and CH4/CO2 mixed hydrates are challenging to form at the junction between the inside and outside clay defects. CH4 and CH4/CO2 mixed hydrates exhibit a preference for forming outside the clay defects rather than inside the clay defects. Some CH4 and CO2 molecules from the inside clay defect migrate to the outside clay defect, thereby promoting CH4 and CH4/CO2 mixed hydrate formation outside the clay defects. This molecular insight advances the development of clay particle models and expands an understanding of natural gas hydrate accumulation and hydrate-based CO2 sequestration.

One stone three birds: Multifunctional epoxy composites based on rice-granular nickel/iron bimetallic phyllosilicates enable excellent compression, anti-wear and lubricating properties under wet-sliding conditions

Epoxy resin (EP) is a versatile thermoset resin extensively employed as protective coatings. However, its brittleness causes poor wear resistance and presents a significant challenge in the application under harsh environmental circumstances. The preparation of EP composites by rationally selecting functional inorganic fillers offers a promising strategy for enhancing mechanical and tribological properties. In this paper, multifunctional EP composites were successfully fabricated with varying mass fractions of rice-granular nickel/iron bimetallic phyllosilicate (NiFePS). The compressive properties, water contact angles, wet-sliding responses, and the morphological analysis of worn surfaces for EP composites were carried out and discussed in detail. Results indicate that the incorporated NiFePS scarcely alters the compressive stress-strain curves, still exhibiting the representative stages including elastic transformation, stress yielding and strain hardening throughout the entire compressive process. The compressive strength, elastic modulus and fracture energy initially increase and then decrease, attaining the maximum values of 266.3 MPa, 4.43 GPa, and 72.1 J/cm², respectively, with the addition of merely 1 % NiFePS. Furthermore, the introduction of NiFePS significantly reduces the water contact angle, transforming the surface of EP composite from hydrophobic to hydrophilic. The friction coefficient and wear rate of EP composites decrease sharply with the addition of NiFePS, achieving the lowest values of 0.136 and 1.24×10⁻⁶ mm³/Nm simultaneously at a filler concentration of 1 %, which represent reductions of 17.07 % and 70.55 %, respectively, compared to the resin matrix. Additionally, the wet-sliding responses affected by various applied loads, rotating speeds and abrasive durations are comprehensively discussed. Finally, the wear mechanism of EP composites is elucidated through in-depth examinations of the evolving morphologies and chemical compositions of the worn surfaces. This work presents a feasible three-in-one technology for developing multifunctional materials with significant potential in high-performance composites and coatings.

Analysis of stress-strain curve of POM fiber reinforced concrete

ABSTRACT As a new type of synthetic fiber, polyoxymethylene (POM) fiber has the advantages of high tensile strength, good dispersibility, and high bonding strength with cement interface. It has broad application prospects. However, there is limited research on POM fiber reinforced concrete. In order to provide scientific basis for promoting the application of POM fiber, this paper adopts a combination of indoor experiments and numerical simulations to obtain the axial stress-strain complete curves of POM fiber reinforced concrete with different volume dosages and studies the uniaxial compressive properties of POM fiber reinforced concrete. Finally, the constitutive equation parameters of POM fiber reinforced concrete were fitted using the Guo Zhenhai model, and the optimal fiber content was determined. The results indicate that at a POM fiber content of 1.5 kg/m3, the load-displacement curve exhibits optimal shape with the highest residual strength. With increasing fiber content, compressive stress-strain curve parameters initially increase and then decrease, peaking at 1.5 kg/m3, optimizing the mechanical properties of concrete. POM fiber has minimal impact on initial elastic modulus. Thus, optimal mechanical property enhancement is achieved with 1.5 kg/m3 POM fiber content.

Study on eccentric compressive performance of circular double skin concrete filled steel tube connected by thread through inside lining tube

Connection method of lengthening the steel tube of circular hollow sandwich concrete-filled steel tube by inside lining tube and thread is proposed. Twelve circular hollow sandwich concrete filled steel tubular beam-column connected by thread through inside lining tube are designed and fabricated using the length of the thread along the axial direction, the working height of the thread, and the position of the thread as parameters; In addition, one unconnected specimen and two welded specimens also are designed and fabricated to conduct controlled experimental research. The test phenomena and failure modes, axial compressive load-compression curve, axial compressive load-lateral deflection curve, and axial compressive load-strain in steel tube curve, as well as bearing capacity, strength reservation, deflection curve shape, lateral stiffness, ductility and plane section assumption are analyzed. The research results indicate that, within the parameter range studied, the thread connection through inside lining tube is reliable before tripping, and the experimental phenomenon of specimens connected by thread is basically consistent with that of the unconnected specimens. The axial compressive load-compression curve and axial compressive load-lateral deflection curve of all specimens can be approximately divided into elastic stage, elasto-plastic stage, and descending stage. The peak load of all specimens is relatively close, while although experiencing almost the same loading process, the strength reserve of the specimens connected by thread is insufficient. During the entire loading process, the shape of the deflection curve of all specimens is close to the sine half wave curve, and the distribution of longitudinal strain in the steel tube along the height of the middle cross-section basically conforms to the plane section assumption. Calculation method for bearing capacity of circular hollow sandwich concrete filled steel tubular beam-column connected by thread through inside lining tube is suggested.

Influence of fiber shapes on the compressive behaviors of ultra-high performance concrete containing coarse aggregate

The addition of coarse aggregate in ultra-high performance concrete (UHPC-CA) has the potential to reduce autogenous shrinkage and improve mechanical properties. However, it also affects the fiber distribution and crack propagation, thereby compressive relationship of UHPC. This study investigated the effects of different fiber shapes on the compressive behaviors of UHPC-CA. Three fiber shapes (straight fiber, hooked fiber, and hybrid fiber) and six coarse aggregate content (0–1200 kg/m3) are the main variables. The test results have indicated that the addition of coarse aggregate in UHPC rendered wider main cracks. Hybrid fiber was preferred over the hooked-end and straight fibers to optimize ductility in UHPC-CA. An increase in compressive strength of up to 17.7 % and elastic modulus of UHPC of up to 23.7 % after moderate addition of coarse aggregate contents, The fiber shape affected peak strain and ultimate strain values for UHPC-CA. Their peak and ultimate strains were improved by 12.8 %–15.3 % and 38.2%–127.4 % with the inclusion of 2 % hooked and hybrid fibers. Based on the experimental data and relevant equations, a proper rational equation from the existing literature is used to generate the complete compressive stress-strain curves of UHPC-CA with different fiber shapes. In summary, this study establishes that hybrid fiber shapes significantly enhance the compressive properties of UHPC-CA. The high elastic modulus and ductility of the UHPC-CA with hybrid fiber are particularly promising for blast and impact applications.

In situ temperature-preserved coring for deep oil and gas reservoir: Thermal insulation materials

Deep oil and gas reservoirs exist under high-temperature conditions. In situ temperature-preserved coring (ITP-Coring) is an innovative and crucial method for evaluating and exploiting deep oil and gas resources. Thermal insulation materials are key to achieving successful ITP-Coring. Materials composed of hollow glass microspheres (HGMs) as fillers and epoxy resin (EP) as the matrix are promising thermal insulation materials for application in ITP-Coring to exploit deep resources. The compressive mechanical properties of these materials significantly influence their applicability and reliability. However, few studies have focused on the compressive mechanical behavior of the materials under high-temperature and high-pressure (HTHP) coupled conditions. Therefore, compressive mechanical tests on materials under temperatures and pressures of up to 150 °C and 140 MPa were conducted innovatively. The compressive stress-strain curves of the materials were divided into three stages: elastic, yield, and failure, at temperatures ranging from 25 °C to 100 °C. Increasing temperature and pressure resulted in a decrease in compressive mechanical properties. Notably, high pressure damaged the HGMs, increasing compressive strain as the temperature rose. Additionally, the compressive failure mode shifted from compound failure to shear failure at different thresholds of HTHP conditions. Finally, a constitutive model of compressive mechanics that considered multiple coupled factors was established, demonstrating good agreement with the experimental results. These findings provide both experimental and theoretical support for the optimization and engineering application of HGMs/EP materials.

Large rupture strain cotton ropes hybridized with affordable fiberglass chopped strand mat sheets for enhanced compressive behavior of reinforced concrete columns

The hybrid confinement system combines various fiber types within a single matrix, allowing for the adjustment of volumetric ratios to optimize confinement performance. Synthetic FRPs are more expensive and have a higher carbon footprint due to significant CO2 emissions during production. In response, this study presents an innovative hybrid confinement approach using two natural materials: cotton ropes and FSMS (CFS) to improve concrete strength and ductility. Specimens, standardized at 300 mm height and 150 mm diameter with longitudinal steel bars and stirrups, were divided into two groups based on CFS configurations. The stress-strain response of CFS-confined concrete displayed distinctive behavior: an initial parabolic phase leading to peak compressive stress (ultimate strength), followed by a linearly degrading phase. Across all subgroups, CFS confinement significantly enhanced ultimate strength and corresponding compressive strains, with Subgroup 2A achieving the highest improvements of 246 % in ultimate strength and 1477 % in strain. Moreover, the ductility gain was reported as high as 20 for CFS-confined concrete. A non-proportional enhancement in the compressive behavior was observed with the increase in confinement ratio. Predictive models were developed for the idealized two-branch response of CFS-confined concrete, encompassing expressions based on nonlinear regression for ultimate strength, corresponding strain, ultimate strain, and elastic modulus. Two existing models were modified to trach each branch of the response. Integrating these two adjusted models closely replicated the experimental compressive curves.

Unified uniaxial compressive constitutive model for C20–C120 concrete based on stochastic damage theory

The concrete uniaxial compressive stress-strain model is essential for analyzing reinforced concrete members and structures. However, models applicable to C20–C120 concrete are still relatively rare. Moreover, the previous empirical model construction methods may not reflect the physical mechanisms and randomness of concrete failure well. To this end, the database was constructed by collecting and analyzing uniaxial compressive stress-strain curve test results from different scholars. The cubic compressive strength in the database ranges from 9.9 MPa to 137.3 MPa. The adaptability of the stochastic damage model was validated using the database of test curves. Subsequently, stochastic damage models for C20–C120 concrete were calibrated based on concrete compressive strength grouping curves, and practical analysis models were suggested. The results indicate that the calculated curves closely match the test curves when the plastic strain evolution parameters η1,c and η2,c in the stochastic models are taken as 0.001–0.30 and 0.19–0.25, respectively. The adaptability of the stochastic damage model is satisfactory, but the plastic strain evolution laws vary for different concrete compressive strengths, influenced by mix proportions and the probability of failure of each component on the meso-scale. When η1,c is calculated by the empirical formula proposed in this paper and η2,c is approximated as 0.22, the calculated curves for C20–C120 concrete are consistent with the mean values of the test curves. The proposed practical analysis models provide comparable accuracy to stochastic damage models, eliminating the need for iterative calculations, making them convenient for engineering applications.

Early age time-dependent mechanical properties of 3D-printed concrete with coarse aggregates

Incorporating coarse aggregate into 3D-printed concrete is essential for promoting its practical application, yet the impact on the early age time-dependent mechanical properties, crucial for the multilayer structure stability and quality, is underexplored. In this study, 3D-printed concrete with coarse aggregate (3DPCA) with varying mortar-to-coarse aggregate ratios (M/A) and coarse aggregate gradations were prepared, of which uniaxial unconfined compression and direct shear performance were experimentally investigated. The fundamental formulations between the early age mechanical parameters and the resting time of 3DPCA were characterized and then utilized in a digital model simulating actual printing. Results indicated that the 3DPCA early age mechanical properties, including compressive strength, Young's modulus, cohesion, and friction angle, increased with longer resting time and decreasing M/A, and higher proportions of aggregates above 9.5 mm. High coarse aggregate content caused three distinct compressive strength-displacement curve stages and complicated strength eigenvalue extraction. Coarse aggregate gradation affected shear properties more than content, with larger aggregates improving cohesion and friction angles. The failure mode prediction model based on ABAQUS could accurately predict the maximum collapse layer of 3DPCA that occurred in overall unstable collapse and over-expansion failure but was incapable of localized deformation.

Study of the concordance between various concrete deformation models and experimental data for uniaxial compression cases

There are various equations describing concrete stress-strain curves, each yielding different theoretical curves. An important scientific question is achieving the best correspondence to experimental data. The Geniyev theory inherently includes equations for three components of stress and strain. In contrast, the Eurocode and the Russian Building Code equations are provided for uniaxial stress conditions. This paper presents a comparison of theoretical curves for uniaxial compression based on Eurocode equations, the Russian Building Code, and Geniyev theory with experimental results from tests on prism and cube samples. The analysis includes deviations of the maximum stress points of theoretical curves from the corresponding experimental data. Numerical analysis is provided for both stresses and strains. A distinguishing feature of this work compared to existing research on Geniyev theory equations is that they are presented in a resolute form, incorporating three parameters: concrete compressive strength, tensile strength, and the initial modulus of elasticity. The importance of using secondary resources on the basis of industrial waste is understood by both governments of developed countries and business (production of Portland cement using ground metallurgical slag as a mineral additive at Novotroitsk, Magnitogorsk, Sterlitamak, Katav-Ivanovsk and other plants in the South Urals). The use of secondary raw materials requires the creation of technological infrastructure for processing of secondary raw materials, the costs of which can be quickly recouped due to the cheapness and availability of industrial secondary raw materials and freeing the territory from environmental pollution. In order to recoup the costs of the infrastructure, it is necessary to guarantee full compliance of the quality of pavement elements with the requirements of GOST R 59120-2021. Secondary raw materials have a great variety and laboratory analysis of the quality of pavement elements is required in order to design compositions with the best quality, satisfying all regulatory requirements. In our work the authors present the results of laboratory research and evaluation of the possibility of using clinker-free lime-slag binder based on the mineral product of soda production and metallurgical slags to strengthen and stabilize soils for their use in pavement structures in the construction of roads for various purposes and climatic zones. It is experimentally shown that the addition of lime-slag binder in the amount of 8-10% of the dry weight of both cohesive (loamy soil, loamy sand) and non-cohesive (fine sand) soil allows to obtain reinforced soil with improved strength and elastic-deformative characteristics, which can be used instead of scarce natural crushed stone and gravel in the construction of underlying layers of pavements in the construction and reconstruction of highways. This technology can be used not only in the Russian Federation, but also in a number of other countries, including those with hot dry climates (e.g., the Republic of Egypt).

Mechanical Characteristics of Hardened Concrete with Different Types of Cement and Aggregate Available in Bangladesh

This paper presents the results of an investigation on the influence of aggregate and binding material type on the mechanical properties of hardened concrete. To perform this investigation, four different types of coarse aggregate (Brick Aggregate, Recycled Brick Aggregate, Black Stone and Shingles) and eight types of binding material [Ordinary Portland Cement (OPC), CEM Type II B-M, CEM Type II B-M-SL, 40% OPC – 60% Slag CEM IIIA, 80% OPC – 20% Slag(CEM II/A-S), 70% OPC – 30% Slag(CEM II/B-S), 30% OPC –70% Slag(CEM-IIIB), 15% OPC –85% Slag(CEM-IIIC)] have been used. Aggregates were collected and prepared according to grading requirements of ASTM C33-03. Several tests as specific gravity, absorption capacity, unit weight and abrasion resistance were performed for coarse aggregate. Cylindrical concrete specimens of diameter 100 mm and length 200 mm were made with different W/C ratio (0.45 and 0.5) and cement content (340 kg/m3 and 400 kg/m3). A total of 42 different cases were considered for testing. The specimens were tested for compressive strength, stress-strain curve and Young’s modulus at the age of 28 days. Non-destructive test as Ultrasonic Pulse Velocity (UPV) were also performed. To conduct UPV test Portable Ultrasonic Non-destructive Digital Indicating Tester (PUNDIT) were used. The major objective of this study was to investigate the mechanical characteristics of concrete for different types of aggregate and binding materials. The significance of those results is discussed here.

Mechanical properties of reactive powder concrete under compression at ultra-low temperatures

In this paper, the mechanical properties of reactive powder concrete (RPC) at ultra-low temperatures were studied. RPC prisms (300 mm × 100 mm × 100 mm) were tested at ultra-low temperatures (20 °C, 0 °C, −20 °C, −40 °C, −80 °C, −120 °C, −165 °C) and resulting prism compressive strength, compressive stress-strain curve, and toughness were determined. The increase in prismatic compressive strength of RPC at ultra-low temperatures is greater than that of ordinary concrete, with an overall strength of about 2.12 times that of ordinary concrete. Pore water freezing behavior was also studied to assess the effects on the mechanical properties of RPC in ultra-low temperatures. The water-ice phase transition further improved the RPC strength. With the reduction in temperature, The change in elastic modulus of RPC change is small, the peak strain of specimens at different temperatures increases with the decrease in temperature. The peak strain of RPC showed an overall linear increase with decreasing temperatures, and the water-ice phase transition at negative temperature increases the peak strain of RPC, adding steel fibers improves the RPC ductility, limiting the fracture. With the temperature reduction, RPC toughness first increases and then decreases. The toughness is lowest at room temperature, and highest at −120 °C, which is 2.26 times higher than at room temperature. RPC has better toughness than normal concrete at different temperatures, the reduction of temperature relatively improves the toughness of RPC, and the addition of steel fibers plays a vital role in improving the toughness. This study can serve as technical support for using RPC to design liquefied natural gas full-capacity tanks.

Research on the performance of high-strength explosive ink and application of direct writing technology in micro-explosive network

With the widespread application of 3D direct writing technology in the field of energetic materials, it has become a current research topic to design an explosive ink with excellent micro-size detonation performance and high-strength mechanical properties and combining it with explosion network technology to improve detonation synchronization has become a research hotspot. This article uses FEVE-F2311 and PF as the composite bonding system, submicron CL-20 as the main explosive, and adds an appropriate amount of TDI as the curing agent to prepare an explosive ink with excellent micro-size detonation performance and high-strength mechanical properties. Research shows that the explosive ink has a detonation velocity of 7322 m·s−1 at a charge density of 1.621 g·cm−3, a critical propagation size of 0.3×0.3 mm, a critical propagation thickness of 1×0.040 mm, and a maximum detonation Corners can reach 160°. The error of detonation synchronization in the "one in and six out" micro-explosion network is within 150 ns, showing excellent detonation synchronization. The nano-indentation test shows that the average elastic modulus of CL-20-based explosive ink is 6.991 GPa and the average hardness is 0.200 GPa, showing excellent mechanical properties; the compressive stress-strain curve shows that its average compressive stress is 7.62 MPa, showing excellent Compressive strength. It not only greatly improves the mechanical properties of explosive ink, but also provides a method to improve the synchronization performance of micro-explosive networks.

Performance Assessment on the Manufacturing of Zn-22Al-2Cu Alloy Foams Using Barite by Melt Route

A barium-rich Celestine (Sr,Ba)SO4 concentrate from the primary Mexican ore production was used as a thickening agent to produce closed-cell Zn-22Al-2Cu alloy foams, while calcium carbonate was used as a foaming agent. The microstructure and mechanical properties of the foams were analyzed by optical microscopy, scanning electron microscopy, and compression tests, respectively. The Zn-22Al-2Cu alloy foams showed a typical lamellar eutectic microstructure, constituted by a zinc-rich phase (η) and a (α) solid solution that was richer in aluminum, while a copper-rich (ε) phase was formed in the interdendritic regions. The SEM micrographs show the presence of small particles and aggregates that are randomly scattered in the cell walls and correspond to unreacted calcite and Celestine–Barian particles, especially for the higher barite addition. The compressive curves showed smooth behavior, wherein the particles at the cell walls did not affect the foam’s compressive behavior. The trial containing 1.5 wt. % of BaSO4 and 1.0 wt. % of CaCO3 showed a higher energy absorption capacity of 5.64 MJ m−3 because of its highest relative density and lowest porosity values. The Celestine–Barian concentrate could be used as a foaming agent for high melt-point metals or alloys based on the TGA results.

Доклинические испытания отечественных устройств, применяемых при внегоспитальной остановке кровообращения

Summary. The aim of the study was to evaluate the effectiveness of domestic devices for supporting blood circulation in case of out-of-hospital circulatory arrest during preclinical trials. Research materials and methods. The study assessed the effectiveness of the Russian cardiac massager “CardioRobot” – an automated device for performing indirect cardiac massage of domestic design. This device has the following technical characteristics: piston type design; compression depth – (50-60±2) mm; compression frequency – (102±2) compressions/min; 2 operating modes – continuous and 30:2; weight – 6.5 kg; continuous battery life – 45 min; trapezoidal compression curve. To evaluate the device, a comparative experiment was conducted on large mammals (pigs), during which the work of the domestic prototype and the foreign device “LUCAS-2” was compared by comparing the indicators of central hemodynamics and gas exchange. During the clinical trials of LifeStream ECMO, postmortem extracorporeal membrane oxygenation (ECMO) of two donors was performed. During the experiment, the following were assessed: pO2, pH, pCO2, arterial blood lactate and creatinine concentrations. Research results and their analysis. During preclinical trials, domestically produced devices demonstrated experimental effectiveness comparable to similar foreign-made products. Currently, the LIFESTREAM ECMO perfusion emergency circulatory restoration complex for human resuscitation has received a certificate and is actively used in the Russian Federation, and the CardioRobot automated chest compression device is undergoing state registration.

Long-Term One-Dimensional Compression Tests and Fractional Creep Model of Compacted Snow

Compacted snow is a primary construction material in polar regions and experiences persistent deformation during loading, which considerably affects the safety of snow structures. This study conducts a series of one-dimensional compression tests to investigate the effect of initial densities and stress levels on the long-term deformation of compacted snow samples over 90 days. The compression curve of compacted snow can be divided into three stages: instantaneous, primary, and secondary compressions. Instantaneous compression occurs at pressurization; primary compression occurs within 10 to 40 min of loading; secondary compression occurs when snow remains unstable for 90 days. Secondary compression is the main cause of long-term deformation of the samples and the secondary compression coefficient tends to decrease with a higher initial density and lower normal pressure. A fractional creep model is developed to describe the experimental data and a good agreement was obtained. The proposed model adopts the fractional deviation approach to modify the classic Burgers model, and the density-dependent parameters are calibrated using the experimental data. The proposed model is verified as a useful tool in describing the creep behavior of snow, and the results of this study contribute to the safe operation of building structures on snow foundations.

Study on the effect of lightweight aggregate types and steel fibers on the mechanical properties of lightweight engineered geopolymer composites (LW-EGC)

In this paper, the effects of the content of steel fiber and lightweight aggregate types on the mechanical properties of lightweight engineered geopolymer composites (LW-EGC) were investigated by uniaxial compression tests. The effect on compressive strength, stress-strain curves, elasticity modulus, peak strain, and energy absorption were discussed. The results showed that the type of lightweight aggregate had a significant effect on the mechanical properties of LW-EGC. LW-EGC-C had higher compressive strength, elasticity modulus, and energy absorption capacity. LW-EGC-S had a higher peak strain. Adding steel fibers could greatly increase the compressive strength, peak strain, and energy absorption. Meanwhile, there was an optimal range for the volume content of steel fiber, so the best improvement effect was achieved when the content of steel fiber was 1.0 %. Compared with LW-EGC-M, the above mechanical properties were improved by 39.28 %, 15.32 %, and 26.17 %, respectively. In addition, based on the existing constitutive models and test results, a stress-strain model for LW-EGC suitable for incorporating steel fibers is proposed. The constitutive model was divided into a rising phase and a falling phase, which could describe the falling curve more accurately than the existing constitutive models, indicating that it could reliably describe the compressive stress-strain response of LW-EGC.

Size shrinkage and compressive behaviour of Al2O3 honeycomb structures fabricated via Digital Light Processing technology

Al2O3 ceramic have excellent chemical inertness, superior heat resistance, and excellent corrosion resistance, so they are considered ideal materials for manufacturing high-performance components such as thermal end devices in aerospace, heat dissipation panels in electronic communication, and exhaust filters in the automotive industry. Digital Light Processing (DLP) is a useful technology to fabricate complex Al2O3 ceramic components. However, the size shrinkage effect of DLP-fabricated components need to be investigated deeply before its further application. In this work, we utilized DLP technology to fabricate Al2O3 ceramic honeycomb structures and systematically investigated their microstructure, size shrinkage, and mechanical properties. Our findings revealed that the Al2O3 ceramic grains exhibit flake-like structures with an average diameter of 1–2 μm, and the ceramic particles are tightly bonded. The shrinkage rates in the X and Y axes were 7.54 % and 7.42 %, respectively, while the Z-axis exhibited a more significant shrinkage of 13.04 %. This anisotropic shrinkage in different direction was attributed to accumulation of the interlayer bonding under gravity action during debinding and sintering process. The compressive stress-strain curve of the honeycomb structures demonstrated a typical brittle compressive behavior, including elastic, stress plateau, and brittle fracture stages. The honeycomb structures exhibited an elastic modulus of 54.49 ± 1.22 MPa and a compressive strength of 10.22 ± 0.42 MPa. The fracture analysis indicated that the fractures region of honeycomb structures initiated at the corners of the honeycomb structures, indicating their easy-broken compared to the walls. These findings provide valuable guidance for the high-precision and high-performance manufacturing of complex Al2O3 ceramic components.

An analysis of the high-homogeneity preparation, thermo-mechanical deformation and recrystallization behavior of a novel superalloy with γ′ content reaching 73%

A deformed superalloy with γ′ content reaching 73% has been designed by ourselves. In this work, the problems of preparation and deformation caused by the high γ′ phase content were solved by the electron beam smelting layered solidification technique (EBS-LST) and hot extrusion. Initially, the superalloy with low segregation and fine microstructure was prepared by EBS-LST, followed by conducting hot deformation experiments at different temperatures and strain rates. The compression curves are corrected, and the constitutive model, recrystallization models and thermo-mechanical processing maps were established based on the corrected curves, and the recrystallization mechanisms were analyzed by TEM and EBSD. Finally, the suitable hot extrusion parameters were obtained indirectly through the hot processing map, and the designed alloy was hot extruded. The microstructure of the extruded alloy is free of cracks and is characterized by fine equiaxed grains.

Constitutive modeling and extended performance evaluation of concrete reinforced with non-hybrid waste tire steel fibers

This paper investigates the extended performance and constitutive modeling of waste tire steel fiber reinforced concrete (WFRC), making notable contributions to civil engineering materials. The study assesses constitutive modeling, reinforcement indices, and the long-term performance of concrete reinforced with varying percentages of waste tire steel fiber (WSF) ranging from 0.30 % to 1.75 %. A modified analytical model for predicting compressive stress-strain curves of WFRC is introduced and compared with previous analytical models for fiber-reinforced concrete. Additionally, a novel waste tire steel fiber reinforcing index, based on WSF properties, is proposed. Empirical relationships between strength properties and reinforcement indices are established. Experimental strength properties at the standard age, as well as water absorption, carbonation depth, and split-tensile strength of specimens aged beyond the standard age at 600 days and fiber-matrix interaction obtained by SEM analysis, are reported. Prediction models are proposed for estimating the mechanical properties of WFRC at the standard age, with results compared against existing codes. The proposed modified analytical model for the uniaxial compressive stress-strain curve demonstrates better coherence with experimental curves than existing models. Furthermore, empirical equations developed in terms of the waste tire steel fiber reinforcing index demonstrate satisfactory alignment between predicted and experimental strength properties. Significant improvements are observed in specimens aged 600 days, indicating the promising role of WSF in enhancing the long-term performance and serviceability of structures. Further studies are recommended to explore the performance of WFRC in aggressive environmental conditions.