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Under in-situ conditions, natural hydraulic fractures (NHF) can occur in permeable rock structures as a result of a rapid decrease of pore water accompanied by a local pressure regression. Obviously, these phenomena are of great interest for the geo-engineering community, as for instance in the framework of mining technologies. Compared to induced hydraulic fractures, NHF do not evolve under an increasing pore pressure resulting from pressing a fracking fluid in the underground but occur and evolve under local pore-pressure reductions resulting in tensile stresses in the rock material. The present contribution concerns the question under what quantitative circumstances NHF emerge and evolve. By this means, the novelty of this article results from the combination of numerical investigations based on the Theory of Porous Media with a tailored experimental protocol applied to saturated porous sandstone cylinders. The numerical investigations include both pre-existing and evolving fractures described by use of an embedded phase-field fracture model. Based on this procedure, representative mechanical and hydraulic loading scenarios are simulated that are in line with experimental investigations on low-permeable sandstone cylinders accomplished in the Porous Media Lab of the University of Stuttgart. The values of two parameters, the hydraulic conductivity of the sandstone and the critical energy release rate of the fracture model, have turned out essential for the occurrence of tensile fractures in the sandstone cores, where the latter is quantitatively estimated by a comparison of experimental and numerical results. This parameter can be taken as reference for further studies of in-situ NHF phenomena and experimental results. [ABSTRACT FROM AUTHOR]

Fine powders of yttrium orthoniobate activated by Eu, Sm, Tb, Er have been synthesized by the sol-gel. The synthesized powders have been calcined at different temperatures (1000, 1100 and 1180 °C). Luminescent ceramics (Y 0.96 Еu 0.01 Sm 0.01 Tb 0.01 Er 0.01)NbO 4 were prepared from fine powders by uniaxial hot pressing (UHP) via various technological modes. For the first time, the crystal structure, microstructure, spectral composition, photoluminescence properties of (Y 0.96 Еu 0.01 Sm 0.01 Tb 0.01 Er 0.01)NbO 4 ceramics have been studied depending on the temperature conditions of the synthesis of powders and UHP conditions during sintering of ceramics. The mechanical properties of these ceramics (Young's modulus, microhardness and critical stress intensity factor for the mode I K IC) have been evaluated. [ABSTRACT FROM AUTHOR]

• Propose a novel flexible-rigid hybridizing strategy to address the cracking issues in siloxane-based consolidants. • Synthesize a flexible-rigid hybrid siloxane material through self-catalyzed copolymerization. • Put forward one consolidation mechanism based on three-dimensional continuous network. • Successfully strengthen the weathered stone of Tianlong Mountain Grottoes. Siloxane oligomers produced through the hydrolysis of tri-alkoxysilanes or tetra-alkoxysilanes have been widely used as consolidants for stone heritage. However, the resulting xerogels tend to crack due to the volume shrinkage after curing. In this study, a novel flexible-rigid hybrid siloxane oligomer material is designed by the self-catalyzed copolymerization of di-alkoxysilane (3-Aminopropyl) dimethoxymethylsilane with tetra-alkoxysilane tetraethyl orthosilicate. The flexible linear Si O Si segments produced by di-alkoxysilane are inserted into the tetra-alkoxysilane derived rigid three-dimensional silicon-oxygen domains, as confirmed by spectroscopic characterizations. This unique structure alleviates the shrinkage stress during curing and enables the formation of crack-free xerogels. Therefore, the hybrid siloxane oligomer can invade into the interior of weathered stone to form one three-dimensional continuous network to strengthen its fragile structure. As a result, the flexible-rigid hybrid siloxane oligomer outperforms both as-made polysiloxane consolidant and commercial consolidant for the consolidation of the weathered Tianlong Mountain Grottoes stone samples. The consolidation treatment was evaluated in terms of effectiveness (Leeb hardness, ultrasonic velocity and compressive strength) and compatibility (pore size distribution, water vapor transmission rate and color variation). Following the treatment, the consolidated samples demonstrate remarkable improvements in mechanical properties, reaching a Leeb hardness of 410 HL and a compressive strength of 8.98 Mpa. Additionally, permeability and color variation of the stone after consolidation are all within acceptable ranges. The results confirm the positive consolidation performance of the flexible-rigid hybrid siloxane oligomer on weathered Tianlong Mountain Grottoes stone, indicating promising practical applications. A novel flexible-rigid hybrid siloxane oligomer that can produce flexible linear Si O Si segments mediated rigid three-dimensional silicon-oxygen domains during curing is designed by the self-catalyzed copolymerization of di-alkoxysilane with tetra-alkoxysilane. This unique structure enables the formation of the crack-free xerogel on flat substrate and the continuous three-dimensional reinforcement network within the porous weathered stone, resulting in a superior consolidation effect for the weathered Tianlong Mountain Grottoes stone heritage. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] The industry has always strived to design "hard" and "crack-resistant" glass. However, simultaneously realizing these properties in oxide glasses has been rare. Although Al 2 O 3 -rich hard and crack-resistant oxide glasses have been reported in the last decade, they exhibit two significant technological challenges that hinder their translation from laboratory to industry: (1) high processing temperatures (>2000 °C) and (2) small glass-forming regions (near eutectic). The present study reports the structural design of a hard and high modulus glass with high crack initiation resistance designed in the peraluminous region of rare-earth containing MgO–Al 2 O 3 –B 2 O 3 –SiO 2 system. The glass can be processed at a temperature ≤1650 °C and exhibits Vickers hardness (H v) of 7.84 GPa (at 1.96 N load) and indentation crack resistance (ICR) of 26.5 N. These H v and ICR values are significantly higher than most commercial or non-commercial glasses (prior to thermal tempering, densification near T g , or chemical strengthening). The glass has been scaled up to successfully produce slabs of dimensions 100 mm × 100 mm × 8 mm at laboratory scale with optical transmission of 90 ± 2 %. The results presented here are scientifically intriguing and have considerable tangible implications, as they pave the path for the design and development of stronger glasses for functional applications. [ABSTRACT FROM AUTHOR]

The brittleness of oxide glasses remains a critical problem, limiting their suitability for high‐performance and safety‐critical applications. In this study, we attempt to address this by synthesizing nanostructures in sodium borosilicate glasses through phase separation. While most previous work on the mechanical properties of phase‐separated glasses has focused on phase separation through nucleation and growth, we here create interconnected structures through spinodal decomposition. Interestingly, this leads to improvements in Vickers hardness (from 5.8 to 6.2 GPa), crack initiation resistance (from 4.9 to 8.1 N), and fracture toughness (from 0.85 to 1.09 MPa⋅m1/2). We show that the interconnected glassy phases deflect the propagating cracks, causing the required energy for cracks to cross phase boundaries to increase when subjected to external stress. This study deepens the understanding of how to address the brittleness problem of oxide glasses and provides a promising way to design high‐performance glass materials. [ABSTRACT FROM AUTHOR]

This study introduces a novel design of self-adhesive basalt fiber mesh geotextile, aiming to significantly enhance the crack resistance of asphalt pavements. Reflective cracks from environmental and traffic stresses in traditional semi-rigid asphalt pavements, compounded by current geotextiles' mechanical and adhesion limitations, reduce service life. This study explores the mechanical properties, adhesion to asphalt, and resistance to simulated cracking of self-adhesive basalt fiber mesh geotextiles within pavement structures. This is accomplished through a series of mechanical tests, interfacial adhesion tests, and advanced characterization using Digital Image Correlation. The results indicate that the distinctive pore structure of basalt fiber mesh geotextiles introduces an embedded interlocking reinforcement effect, which significantly enhances the strength of the composite geotextile. The SAM-160M specimen demonstrates a maximum tensile strength of 3.599 kN, surpassing that of the plain fabric specimen by over 34%. The twisted weaving process of the mesh fabric improves adhesion to asphalt by 14.54% compared to plain fabric, thereby enhancing the performance of the pavement structure's interlayer and its resistance to cracking. The mesh fabric excels at dispersing concentrated stresses, enhancing weak interface zones, and increasing the structural capacity and longevity of pavements. These improvements support sustainable road construction with broad engineering applications. • Developed self-adhesive composite geotextiles using basalt fiber mesh and modified asphalt. • Demonstrated the enhanced crack resistance of innovative geotextiles in pavement structures. • Identified the embedding locking effect of mesh cloth that improves tensile strength. • Showcased a reduction in raw material consumption and maintenance costs with new geotextiles. [ABSTRACT FROM AUTHOR]

An experimental investigation of interlaminar toughness for post-cured through-thickness reinforcement (PTTR) skin–stringer sub-element is presented. The improvement in the crack resistance capability of skin–stringer samples was shown through experimental testing and finite element analysis (FEA) modeling. The performance of PTTR was evaluated on a pristine and initial-disbond of the skin–stringer specimen. A macro-scale pin–spring modeling approach was employed in FEA using a non-linear spring to capture the pin failure under the mixed-mode load. The experimental results showed a 15.5% and 20.9% increase in strength for the pristine-PTTR and initial-disbond PTTR specimens, respectively. The modeling approach accurately represents the overall structural response of PTTR laminate, including stiffness, adhesive strength, crack extension scenarios and progressive pin failure modes. This modeling approach can be beneficial for designing damage-tolerant structures by exploring various PTTR arrangements for achieving improved structural responses. [ABSTRACT FROM AUTHOR]

The effects of moisture and drying shrinkage can lead to uneven settlement, cracking, and other diseases in loess subgrade. The objective of this study was to investigate the effects of amide polymer (AP) on the permeability, mechanical properties and crack resistance of loess by orthogonal experiments. The basic properties of AP and the permeability, mechanical properties, and dry–wet variation properties of polymer-modified loess were tested, and a scale model verification and simulation analysis were conducted. In this paper, water migration in subgrade is regulated by improving the water sensitivity of loess. By reducing the variation range of subgrade water content, the stress accumulation in subgrade caused by water is weakened. The results show that the curing time and mechanical properties of AP are directly affected by the oxidant and reducing agent, and the mechanical properties of AP are compatible with the characteristics of loess. AP filled the grain gap and reduced the permeability of loess by 34.05–280.83%. The ductility of polymer-modified loess is significantly increased, and the strain of peak strength is increased by 17.21–126.36%. AP can regulate moisture change, reduce the surface tension between particles, and reduce stress concentration. The strength loss rate was reduced by 19.98–51.21% by enhancing the cracking resistance and weakening the strength loss caused by dry and wet cycling. The increase of upper layer moisture content in the scale model of polymer-modified loess subgrade is reduced by 31.38–36.11%. [ABSTRACT FROM AUTHOR]

The poor early shrinkage and cracking performances of manufactured sand concrete, waste powder concrete, and recycled aggregate concrete are the main difficulties in engineering applications. To solve these problems, early shrinkage and cracking, strength, and impermeability tests were performed on high-volume stone powder manufactured sand concrete mixed with fly ash and slag powder (FS), a shrinkage-reducing agent (SRA), polyvinyl alcohol (PVA) fibers, and a superabsorbent polymer (SAP). Furthermore, the microstructures and pore structures of these concretes were revealed using nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). The results showed that the mixture of FS, SRA, PVA fibers, and SAP could effectively inhibit the shrinkage strain and cracking area of the concrete. The effect of the SAP on reducing the early shrinkage of the concrete is the greatest, and the shrinkage strain can be reduced by 76.49%. The PVA fibers had the most obvious effect on inhibiting the early cracking of the concrete, and the total cracking area was reduced by 66.91%. Significantly, the incorporation of the FS can improve the particle gradation and the pore structure and improve its compactness. The PVA fibers not only provide good carriers for cement-based materials but also enhance the bonding force between the particles inside the concrete, filling the pores inside the concrete, inhibiting the loss of water, and reducing the generation of internal microcracks. The FS and PVA can reduce the shrinkage and cracking risk and improve the strength and impermeability of the concrete. Although the SRA and SAP can reduce the shrinkage and cracking risks, it will lead to a significant decrease in the later strength and impermeability. The main reason is that the SRA leads to an increase in micropores in the matrix and microcracks near the aggregate, which are not conducive to the development of the strength and penetration resistance of the MS. Similarly, the SAP can promote the rapid formation of ettringite (Aft) at an early age and improve the early shrinkage, early cracking, and early strength of the concrete. However, with an increase in age, the residual pores, after SAP dehydration, will cause the deterioration of the concrete pore structure, resulting in the deterioration of the strength and impermeability. [ABSTRACT FROM AUTHOR]

The crack resistance of concrete structures with low reinforcement ratios requires a broader examination. It is particularly important in the case of foundations working in changing subsoil conditions. Unfavorable phenomena occurring in the subsoil (e.g., ground subsidence, landslips, non-uniform settlement) can lead to unexpected cracking. Therefore, it is necessary to check the effectiveness of the low reinforcement provided. As there are limited studies on lightly reinforced concrete structures, we performed our own experimental investigation and numerical calculations. In the beams analyzed, the reinforcement ratio varied from 0.05% to 0.20%. It was found that crack resistance in concrete members depends on the reinforcement ratio and steel bar distribution. A comprehensive method was proposed for estimating the crack resistance of lightly reinforced concrete members in which both the reinforcement ratio and the reinforcement dispersion ratio were taken into account. Furthermore, the method considered the size effect and the fracture properties of concrete. The proposed method provides the basis for extrapolation of the test results obtained for small elements and conclusions for members with large cross-sections, such as foundations, which frequently use lightly reinforced concrete. [ABSTRACT FROM AUTHOR]

The effect of cold isostatic pressing of WC-15Co powder blanks on the sintered alloy strength in threepoint bending was evaluated. The specimens treated or nontreated by cold isostatic pressing (CIP) before sintering were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), strength and Vickers and Rockwell hardness test equipment. The strength of CIP-treated specimens in three-point bending was found to be 2410 MPa, which is 13% higher than that of the CIP-nontreated ones and 30% higher than the standardized strength of a VK15 hard alloy of a similar composition. The hardness was shown to be the highest for the specimens CIP-treated before sintering, while average WC grain sizes remained unchanged compared to the CIP-nontreated ones. The predominant crystal modification of cobalt in the CIPtreated specimens was revealed to be HCP-Co, in contrast to the CIP-nontreated ones, where cobalt was mainly in the metastable FCC modification. It is shown that in the specimens CIP-treated before sintering, the cobalt content on the fracture surface is 3-4 times higher than for the nontreated ones, and the fracture crack propagates mainly along the WC matrix phase–Co binder interface. In the CIP-nontreated specimens, the crack propagates in the Co volume, and WC grains on the fracture surface are covered with cobalt interlayers of different thicknesses. Cold isostatic pressing has been proposed as a requisite additional operation of standard hard alloy technology since already at the pressing stage, it provides essential conditions for enhancing the strength of sintered specimens. [ABSTRACT FROM AUTHOR]

This study aims to develop a prefabricated flexible ultrathin overlay that can quickly and effectively repair cracks, particularly reticulation cracks, in old asphalt pavements while improving skid resistance. The overlay consists of a combination of an aggregate, a binder, and a geotextile; its unique structure results in a thickness of only about one-third of that of traditional ultrathin overlays. Its tensile strength, skid resistance, flexibility, waterproofing, interlayer bonding, and long-term service performance were evaluated through a series of tests. The results indicated that basalt, styrene butadiene styrene–modified emulsified asphalt, and warp-knitted polyester fiberglass fabric was the best combination. The proposed steady-state equation could reduce the test duration by more than 20%. The best interlayer binder was rubber asphalt with an optimum dosage of 0.9 kg/m2. The effect of temperature on interlayer bonding properties was more significant than that of the loading rate. The overlay maintained good waterproofing, skid and crack resistance, and interlayer bonding properties after a medium-scale accelerated loading test. [ABSTRACT FROM AUTHOR]

Binder plays an important role in maintaining the integrity of sulfur electrode in lithium‐sulfur (Li‐S) battery. However, cracks are easily generated inside the electrode and compromise its performance due to the volume change of sulfur during redox reaction and continuous vibration originated from the external environments. It is a challenge yet crucial to develop tough binders with crack‐insensitivity and damping performance. Herein, a polymeric binder is designed with special viscoelastic behavior by tailoring its electrolyte‐philic and electrolyte‐phobic domains. The loss modulus of the binder is regulated to be highly close to its storage modulus within a wide range of frequency, generating an ultra‐high loss factor and equilibrium of viscosity‐elasticity. Based on such rheological behavior, the binder holds 1) high damping ability across a wide frequency to suppress crack generation, 2) high toughness with crack blunting behavior to resist crack propagation, 3) efficient healing capability to repair the cracks. Besides, the pendant zwitterionic groups can immobilize the lithium polysulfides and promote ion transfer. Benefiting from these advantages, the obtained Li‐S battery delivers high specific capacity with considerable capacity retention after long‐term cycling. The viscoelastic design and crack management strategy illustrated here would provide new insights into the binder design. [ABSTRACT FROM AUTHOR]

Previous studies have shown that with increasing service life of shipbuilding steels, a strong hydrogen charging of their internal near-surface layers occurs, especially if the service life exceeds 3 years or more. This is known to cause changes in the mechanical properties of steels. Therefore, there is a need to conduct additional experimental studies on the effect of hydrogen in a wide temperature range on the degradation of the structural and phase states of steels, in particular, on changes in the crystal lattice and redistribution of cementite, which directly leads to a decrease in the ductile and deformation properties of the metal, especially at subzero air temperatures. The effect of service life and subzero temperatures on the stress state of the a-matrix lattice and its parameters for the 10KhSND and D32 steels was investigated. A tendency to increase in the value of lattice distortion stresses and decrease in the mass fraction of cementite in specimens of these steels after long-term operation was revealed. Metallographic studies showed that with decrease in the temperature of the cooling medium, the volume fraction of hydrides increases significantly, which leads to embrittlement and softening of steels. [ABSTRACT FROM AUTHOR]

To study the crack resistance of steel slag crumb rubber modified asphalt mixture (CR-steel slag) under salt freeze–thaw cycles, we selected styrene-butadiene-styrene (SBS)-steel slag and CR-basalt as the reference group. The relationship between CR-steel slag interfacial adhesion properties and crack resistance under salt freeze–thaw (FT) cycles was investigated through semicircular bending (SCB), pull-out, and contact angle tests. The results show that the salt FT will accelerate the process of micro-cracks in the mixture to macro-cracks. With the increase of FT cycles, the crack resistance will gradually deteriorate, and significant damage will occur in the mixture at 15 freeze–thaw cycles. The mutation point of freeze–thaw times will move forward in different degrees under the action of salt solution. At the same time, with the increase of salt solution concentration, its anticracking performance first decreases and then increases, reaching an extreme value of 8%. The magnitude of the crack resistance of the three asphalt mixtures is CR-steel slag > SBS-steel slag > CR-basalt. The macroscopic cracking index of asphalt mixtures has an excellent positive correlation with the matching index, and the matching index model has sufficient accuracy in evaluating the cracking resistance of three asphalt mixtures under the action of salt freeze–thaw cycles. Based on the surface energy theory to evaluate the crack resistance of the mixture from a microscopic perspective, combined with macroscopic evaluation indexes, the evaluation results are accurate and more reliable. [ABSTRACT FROM AUTHOR]

Simulation of a 3-point bending of a square beam located on supports by an edge but not on a flat side is carried out. The calculation is based on the fundamental relationship between the specific fracture energy G and the change in the sample compliance during crack propagation. In the ANSYS system, the dependence of the compliance on the crack length was obtained using the ORIGIN program. The derivative of this function along the crack length determines the change in the sample compliance. A universal equation for determining G in a wide range of geometric dimensions is obtained. [ABSTRACT FROM AUTHOR]

Steel 30KhGSA is studied after a quenching and partitioning (Q&P) heat treatment and after traditional quenching. Structural and x-ray analyses are performed and mechanical properties are determined. The Q&P treatment produces a martensite-austenite structure with 10 vol.% retained austenite. The use of Q&P instead of the traditional quenching elevates the impact toughness by a factor of 3 and the resistance to fatigue crack growth by a factor of 2. A long hold at room temperature (for more than a month) reduces the content of retained austenite in the Q&P-steel to 7.5 vol.% and lowers its impact toughness and crack resistance by a factor of 1.5 as compared to the state right after the hardening. [ABSTRACT FROM AUTHOR]

This paper reports an experimental on the flexural performance of prestressed concrete-encased high-strength steel beams (PCEHSSBs). To study the applicability of high-strength steel (HSS) in prestressed concrete-encased steel beams (PCESBs), one simply supported prestressed concrete-encased ordinarystrength steel beam (PCEOSSB) and eight simply supported PCEHSSBs were tested under a four-point bending load. The influence of steel strength grade, I-steel ratio, reinforcement ratio and stirrup ratio on the flexural performance of such members was investigated. The test results show that increasing the I-steel grade and I-steel ratio can significantly improve the bearing capacity of PCESB. Increasing the compressive reinforcement ratio of PCEHSSB can effectively improve its bearing capacity and ductility properties, making full use of the performance of HSS in composite beams. Increasing the hoop ratio has a small improvement on the load capacity of the test beams; setting up shear connectors can improve the ductile properties of the specimens although it does not lead to a significant increase in the load capacity of the combined beams. Then, combined with the test data, the comprehensive reinforcement index considering the location of reinforcement was proposed to evaluate the crack resistance of specimens. The relationship between the comprehensive reinforcement index and the crack resistance of specimens was given. [ABSTRACT FROM AUTHOR]

Plastic shrinkage cracking is a complex and multifaceted process that occurs in the period between placement and the final setting. During this period, the mixture is viscoplastic in nature and therefore possesses rheological properties. The investigation of the relationship between rheological behavior and its propensity to undergo cracking during the plastic phase presents an intriguing subject of study. However, many factors influence plastic cracking, and the corresponding interaction of its effects is complex in nature. This study aimed to evaluate the impact of rheological and physicomechanical properties on the occurrence of plastic cracking in high-performance shotcrete containing various supplementary cementitious materials. To achieve this, plastic cracking was evaluated employing the ASTM C 1579 standard and a smart crack viewer FCV-30, and the rheological parameters were controlled using an ICAR rheometer. In addition, a study was conducted to assess the strength development and fresh properties. Further, a relationship was established via statistical evaluation, and the best predicting models were selected. According to the study results, it can be concluded that high-yield stress and low plastic viscosity for colloidal silica mixtures are indicators of plastic cracking resistance owing to improved fresh microstructure and accelerated hydration reaction. However, earlier strength development and the presence of a water-reducing admixture allowed mixtures containing silica fume to achieve crack reduction. A higher indicator of yield stress is an indicator of the capillary pressure development of these mixtures. In addition, a series containing ultrafine fly ash (having high flow resistance and torque viscosity) exhibited a risk of early capillary pressure build-up and a decrease in strength characteristics, which could be stabilized with the addition of colloidal silica. Consequently, the mixture containing both silica fume and colloidal silica exhibited the best performance. Thus, the results indicated that rheological characteristics, compressive strength, and water-reducer content can be used to control the plastic shrinkage cracking of shotcrete. [ABSTRACT FROM AUTHOR]

Cement-stabilized macadam (CEM-SM) base layers on highways are prone to early shrinkage cracking in extremely cold and arid regions, mainly caused by the large drying shrinkage of traditional cement-stabilized base materials. A multi-component solid waste cementitious material (SWCM) was designed based on the response surface method. The synergistic reaction mechanism of SWCM was analyzed using X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TG). A shrinkage testing system was developed to evaluate the anti-cracking characteristics of stable macadam using multiple solid waste cementitious materials (SWCM-SM), and the strength growth law and frost resistance were analyzed. The results show that the Box–Behnken response surface model was used to obtain the optimal parameter combination for SWCM, including 60% slag, 30% steel slag, and 10% desulfurization gypsum. The compressive strength and flexural strength of SWCM-SM were 24.1% and 26.7% higher than those of CEM-SM after curing 180 days. The frost resistance of SWCM-SM was basically equivalent to that of CEM-SM, and the dry shrinkage strain of SWCM-SM was reduced by 30.7% compared to CEM-SM. It can be concluded that steel slag and desulfurization gypsum stimulate the hydration reaction of slag, thereby improving the bonding strength. Compared to CEM-SM, SWCM-SM exhibits slower hydration reaction and longer hydration duration, exhibiting characteristics of low early strength and high later strength. The early microstrain of the semi-rigid base layer is mainly caused by the occurrence of early water loss shrinkage, and the water loss rate of SWCM-SM is lower than that of CEM-SM. This study concludes that SWCM has good early crack resistance performance for stabilized crushed stones. [ABSTRACT FROM AUTHOR]

Steel slag is used instead of gravel, and five kinds of cement stabilized steel slag gravel mixtures are designed. The optimum mixing ratio of steel slag and stone was obtained through the experiments of mechanics and crack resistance. The results show that the compressive strength and splitting strength of cement-stabilized macadam mixture can be greatly improved by using steel slag instead of local coarse aggregate. The dry shrinkage coefficient decreases with the increase of steel slag content. The dry shrinkage deformation caused by water loss can be significantly reduced after steel slag is added, but the steel slag content should not be too much, otherwise the temperature shrinkage deformation of cement stabilized crushed stone mixture will increase. After comprehensive evaluation, the alternative combination of coarse steel and fine stone (steel slag for coarse aggregate and limestone for fine aggregate) is recommended. [ABSTRACT FROM AUTHOR]

This paper characterizes the efficacy of borax on different properties of alkali-activated materials (AAMs). Fly ash (FA) and ground granulated blast slag (GGBS) were used as base substances at different ratios. The effects of borax on workability, compressive strength, efflorescence formation and crack resistance are the main ideas of the study. The results indicated the positive effects of borax on the properties of one-part fly ash/slag-based alkali-activated materials such as increasing workability and decreasing efflorescence. The microscopic images and scanning electron microscope (SEM) showed that the addition of borax reduced the cracks and a higher amount of slag made the samples denser with less unreacted raw materials, respectively. The compressive strength test results showed that borax had a detrimental impact at early ages with a positive effect at later ages. Binders with borax and 20-25% replacement of FA with GGBS were found to have the best performance when workability, compressive strength, efflorescence formation, and cracks on the samples were taken into account. [ABSTRACT FROM AUTHOR]

The advantages of rubber concrete (RC) are good ductility, fatigue resistance, and impact resistance, but few studies have been conducted on the effects of different rubber admixtures on the strength of RC and the cracking performance of rubber mortar. In this study, the compressive and flexural tests of rubber concrete and the crack resistance test of rubber mortar were carried out by changing the rubber content and adding expansion agent and retarder in this test. The test results show that the strength of RC decreases with the increase in rubber admixture. At 15% of rubber admixture, the expansion agent and retarder increase the compressive strength and flexural strength of RC the most; the compressive strength increased to 116% (22.6 MPa) and 109% (21.2 MPa), and the flexural strength increased to 111% (4.02 MPa) and 116%. (4.21 MPa). At the same rubber admixture, the expander improves the cracking time of the rubber mortar by about 3 times, and the retarder improves the cracking time of the rubber mortar by about 1.6 times. The BP neural network (BPNN) was established to simulate and predict the compressive and flexural strengths of RC with different admixtures and the cracking time of rubber mortar. The simulation results show that the predicted 7-day compressive strength of RC fits best with the actual value, with a value of 0.994, and the predicted 28-day flexural strength was closest to the measured value, with an average relative error of 1.7%. It was shown that the calculation results of the artificial intelligence prediction model are more accurate. The simulation results and test results show that the expander and retarder significantly improve the strength of RC as well as the cracking performance of rubber mortar. [ABSTRACT FROM AUTHOR]

A mechanophysical model for crack growth kinetics computation on stress corrosion fracture of modified 06G2BA and 08KhMCHA pipe steels is adequately expressed through the plane stress-strain state dα/dt and dJ/dt ratios that are dependent on the strain crack tip rate. The crack growth accelerated by an aggressive environment occurs under static and cyclic loading due to transient dissolution and repassivation processes at the crack tip. Such accelerations are divided into three categories, determined by the strain rate: mechanical cracking (fatigue crack and stationary plastic crack), corrosion-accelerated mechanical cracking (corrosion fatigue and corrosion-accelerated plastic crack), and sulfide stress corrosion fracture. Metallographic studies revealed the change in the crack nucleation and propagation mechanisms, from transcrystalline to intercrystalline, related to the viscoplastic and brittle structure of steel specimens cyclically loaded and simultaneously affected by a corrosive environment. [ABSTRACT FROM AUTHOR]

A systematic evaluation of the interlayer crack resistance in the modes I and II loadings of a glass fiber epoxy laminated composite by experimental and computational methods using the cohesive zone model was carried out. The local properties (the ultimate stress σC, the maximum displacement δmax, and the specific work of fracture γF) of the cohesive zone were determined experimentally by the methods of separation and shear of the layer contact zone; the critical intensities of elastic energy release (GIC and GIIC) were found by the method of linear elastic fracture mechanics. Based on the experimental data obtained, the critical length of the cohesive zone was calculated by the Barenblatt micromechanical theory. A numerical evaluation of the crack resistance of a laminated composite under conditions of static loading in the modes I and II was carried out using 3D finite-element models of a double-cantilever beam and end-notched flexure specimens with an implemented cohesive zone obeying the exponential law. The optimal number of interface elements in the finite-element mesh was determined for the cohesive zone calculated based on experimental data, which ensured a sufficient accuracy of numerical calculating the ultimate load of the onset of crack growth and the stress distribution along the length of the cohesive zone with a minimum number of calculations. The approach proposed and the results obtained showed a good agreement between the calculated and experimentally determined characteristics of standard specimens of glass fiber epoxy composite and can be used to calculate the interlayer strength and crack resistance of structural members with a complex geometry made of layered polymer composites. [ABSTRACT FROM AUTHOR]

The objective of this study was to explore the engineering application potential of waste cigarette butts and to investigate the effect of waste cellulose acetate (WCA) as reinforcement material on the performance of asphalt mixtures. A performance prediction model was also constructed to explore the optimal mixture preparation scheme. In this study, a scanning electron microscope (SEM) was used to visually characterize the surface morphology of WCA. The elemental composition of the cellulose surface was determined semiquantitatively using an energy dispersive spectrometer (EDS). The experimental design was carried out following the face-centered central composite design (FCCD) of the response-surface methodology (RSM), taking WCA shearing time, WCA content, and asphalt-aggregate ratio as variable factors, and the splitting strength (Rdry), freeze–thaw splitting strength (Rsaturated), and tensile strength ratio (TSR) of the mixtures as response variables. The software Design-Expert was adopted to construct and optimize the model under multiple responses. The road performance was verified by rutting test, low-temperature bending test, and water immersion Marshall test. The results showed that WCA is a kind of organic cellulose with a smooth surface and cloverlike cross section, which can significantly improve the mixture's crack resistance and water stability. The performance prediction models all achieved a fit of 90% or higher. The best parameters recommended by Design-Expert were WCA content of 0.201%, WCA shearing time of 11.847 min, and asphalt-aggregate ratio of 5.683%, and the WCA-reinforced asphalt mixture Rdry , Rsaturated , and TSR values were 1.38 MPa, 1.24 MPa, and 89.86%, respectively, all of which were within the 95% prediction interval of the model predicted values. In addition, the road performance tests showed that WCA significantly improved the mixture's flexural strength and water stability, but harmed the high-temperature rutting resistance. WCA has a significant reinforcing effect on asphalt mixture, which has a certain reference value for recycling waste cigarette butts and developing green road materials. In addition, the FCCD model has high accuracy and can effectively guide the road material preparation process. [ABSTRACT FROM AUTHOR]

Fiber muddied cement concrete mortar was prepared by selecting glass fiber as the additive phase and natural fiver sand as the line aggregate, and introducing glass fiber with different volume additions (0.5 %-2. 0%). The effect of glass fiber doping on the mechanical properties, crack resistance and wear resistance of cement mortar was studied. The results show that as the amount of glass fiber doping creases, the consistency of the mortar mixture gradually increases, and the compressive strength and flexural strength first increase and then decrease. When the doping amount of glass fiber Is 1.5vol%, the compressive strength and flexural strength of the mortar reach their maximum values, which are 60.3 and 8.9 MPa, respectively. At this point, the phenomenon of penetrating cracks and surface peeling decreases, and the axial compressive strength, elastic modulus, crack resistance index, deflection, and stress of the mortar reach their maximum values, which are 47.6 MPa, 29.2 GPa, 99.6%, 3.2 mm and 17.3 kN, respectively, indicating the best crack resistance performance. When the doping amount of glass fiber 1.5vol%, the minimum wear amount of mortar as 0.83 kg/m2, and the maximum reduction percentage of wear amount 62.44%, indicating a significant improvement in wear resistance. Overall, the optimal doping amount for glass fibers as 1.5vol%. [ABSTRACT FROM AUTHOR]

The article provides a substantiation for the use of the wear resistance criterion NF determined by the number of loading cycles before the separation of large wear particles and taking into account the indicators of fracture toughness, yield strength, friction coefficient, and also taking into account the dimensional characteristics of the initial cracks to predict the contact endurance of heavy-loaded friction pairs hardened by induction surfacing with powder hard alloys. It is shown that the use of this criterion can be extended for various types of loading, including combined ones. A method of experimental confirmation of analytical dependences for determining NF is described, the scheme of the test rig and the results of experiments for powder surfacing materials of various grades are presented. [ABSTRACT FROM AUTHOR]

Pure self-compacting concrete has many disadvantages, such as early shrinkage and cracking. The addition of fibers can effectively improve the properties of resistance to tension and cracking of self-compacting concrete, thereby the effect of improving its strength and toughness can be achieved. Basalt fiber is a "new green industrial material" that has unique advantages, such as high crack resistance and being lightweight compared with other fiber materials. In order to study the mechanical properties and crack resistance of basalt fiber self-compacting high-strength concrete intensively, the self-compacting high-strength concrete of C50 was designed and obtained using the absolute volume method with multiple proportions. Orthogonal experimental methods were used to study the influence of the water binder ratio, fiber volume fraction, fiber length, and fly ash content on the mechanical properties of the basalt fiber self-compacting high-strength concrete. Meanwhile, the efficiency coefficient method was used to determine the best experiment plan (water binder ratio 0.3, fiber volume ratio 0.2%, fiber length 12 mm, fly ash content 30%), and the effect of fiber volume fraction and fiber length on the crack resistance of the self-compacting high-performance concrete was investigated using improved plate confinement experiments. The results show that (1) the water binder ratio had the greatest impact on the compressive strength of basalt fiber self-compacting high-strength concrete, and as the fiber volume fraction increased, the splitting tensile strength and flexural strength both increased; (2) there was an optimal value for the effect of the fiber length on the mechanical properties; (3) with the increase in fiber volume fraction, the total crack area of the fiber self-compacting high-strength concrete significantly decreased. When the fiber length increased, the maximum crack width first decreased and then slowly increased. The best crack resistance effect was achieved when the fiber volume fraction was 0.3% and the fiber length was 12 mm. Therefore, basalt fiber self-compacting high-strength concrete can be widely used in engineering fields, such as national defense construction, transportation, and building structure reinforcement and repair, due to its excellent mechanical and crack resistance properties. [ABSTRACT FROM AUTHOR]

Experimental and computational methods to assess the fracture toughness of 15Kh2NMFA-A reactor vessel steel are analyzed based on the local fracture models: Rice–Tracey and developed in Pisarenko Institute of Problems of Strength of the National Academy of Sciences of Ukraine. The master curve was experimentally constructed, and parameters used in examined models were obtained. The Rice–Tracey model modification, which takes into account the averaging of the relative void radius in the vicinity of the crack tip, extending at each loading step, is shown to confirm a previously made assumption as to the fracture toughness assessment regardless of the finite element size near the crack tip. Since in the ductile-brittle transition region, the crack initiation is ductile, i.e., through void nucleation, growth, and coalescence, the fracture toughness assessment based on local ductile fracture models gained theoretical substantiation and demonstrated satisfactory agreement with experimental results. [ABSTRACT FROM AUTHOR]

Introduction of lanthanum oxide into an aluminum-zirconium matrix leads to the formation of LaAl11O18 during sintering in air at 1520°C for 2 h. The grain size of aluminum oxide is at the level of 0.75 μm. The highest crack resistance (6.2 ± 0.3 MPa·m1/2) with the selected technological parameters for obtaining the materials is found for the material with 3 wt.% LaAl11O18. The critical stress intensity coefficient of such material is 24% higher than that of aluminum-zirconium ceramics without additives. [ABSTRACT FROM AUTHOR]

Results are provided for determining standard mechanical properties, cold resistance, and crack resistance properties of base metal and a heat-affected zone, and corrosion-mechanical strength of new cold-resistant steels with yield strength of at least 420, 460, 890 and 960 MPa. Results are given for studying ferritic-bainitic and bainitic-martensitic parameters of the structure of sheets from low- and sparingly-alloyed high-strength steels of various thicknesses. The low-alloy steel developed with a yield strength of at least 420 and 460 MPa with the code Arc may be used for any components of marine Arctic structures without restriction at operating temperatures down to –40°C. The high-strength steel with a yield strength of at least 890 and 960 MPa is recommended as a promising material for constructing underwater mining complexes and deep-water marine equipment. [ABSTRACT FROM AUTHOR]

Fiber metal laminate (FML) is a hybrid composite typical in aircraft industry. It is necessary to effectively characterize the quasi‐static fracture performance of FML, considering the importance of damage tolerance design of aircraft structures and the complicated fracture mechanism of FML. In present investigation, glass fiber reinforced aluminum laminates (Glare) with middle cracks were tested under quasi‐static tensile load. The experimental crack resistance curve (R curve) based on the special crack opening displacement at original crack tip (δ5) was used for revealing the superior crack resistance of Glare laminate to aluminum sheet, which expressed in crack extension aspect was the extended critical crack length. This was thought to be benefit from the contributions of glass fiber layers and fiber/metal delamination, by performing the progressive damage analysis. Since δ5 can embody the elastic–plastic response of the crack but without need to interactively correct for crack tip plasticity. The δ5‐R curve‐based macro and meso fracture models were proposed to accurately predict the residual strength and stable crack extension of Glare laminate, which gave further evidence for the effectiveness of δ5‐R curve in characterizing the quasi‐static fracture performance of FML. [ABSTRACT FROM AUTHOR]

Although the interactions among glass formers and modifiers, for example, connectivity and charge distribution, have been studied extensively in oxide glasses, the impact of a particular modifier species on the mechanical performance of aluminoborosilicate (ABS) glasses is not well understood. This work compares the indentation properties of six ABS glasses, each of which contains a different network modifier (NWM) with varying field strength (FS). Three alkali and three alkaline earth ABS glasses were designed with low NWM content and [NWM] ≈ [Al2O3], to test the modifier FS effect at low concentrations and to maximize three‐coordinated boron. It has been found that both hardness and crack resistance increase with increasing FS in these ABS systems, which is surprising in the context of historical reports. Using 11B, 27Al, and 29Si solid‐state nuclear magnetic resonance, this work provides evidence of how charge distributions differ as a function of NWM species, and how this relates to the observed indentation behaviors. [ABSTRACT FROM AUTHOR]

It is shown that it is necessary to take into account biaxial loading and short cracks in crack resistance tests of specimens for a more accurate assessment of the residual life of nuclear reactor vessels. To implement this, a special design of small cross-shaped specimens with linear and semi-elliptical cracks and tooling for their biaxial bending loading on a uniaxial servohydraulic machine was developed. On the basis of a series of finite element calculations, dependences for calculating stress intensity factors and J-integral for a strip for three-point bending with a semi-elliptical crack and for linear and semi-elliptical cracks in a cross-shaped specimen during its biaxial bending tests were obtained. Using the obtained data, experimental data on the influence of biaxial loading on the fracture toughness characteristics of reactor vessel steels were specified and plotted on a graph of fracture toughness versus temperature. It is shown that the crack resistance of specimens with linear and semi-elliptical short cracks is greater than that obtained on standard specimens, and that the biaxial loading of cross-shaped specimens, taking into account the moment of crack initiation, reduces the crack resistance compared to the uniaxial loading of specimens with short cracks. To generalize the experimental data and build a model for predicting the effect of biaxial loading on the characteristics of crack resistance, it is necessary to perform additional experimental studies to obtain a statistically significant result. [ABSTRACT FROM AUTHOR]

This article examines the characteristics of shotcrete from the standpoint of resistance to plastic shrinkage cracking. The effects of 2%, 3%, and 4% replacement with colloidal silica (CS) with a 10-nm particle size on the performance of shotcrete was examined, as were the effects of addition of supplementary cement materials in combination with CS, such as silica fume (SF) and ultra-fine fly ash (UFFA). Plastic cracking was examined from three perspectives: its effect on strength development (especially at the initial stage), assessment of plastic shrinkage in accordance with the ASTM C1579, and related issues of bleeding and evaporation. Compressive and flexural strength tests were conducted to gain an understanding of the processes involved, and the Intelligent Crack Viewer FCV-30 was used to estimate crack widths. The results show that the replacement with CS increases the compressive and flexural strength during hardening, which increases its resistance to tensile shrinkage stresses. The practical assessment of cracks showed that a significant reduction in the width of plastic shrinkage cracks was also achieved. The combination of 4% SF and 2% CS significantly reduced the risk of cracking and improved strength characteristics. The application of CS reduced the effect of 20% UFFA on plastic cracking. [ABSTRACT FROM AUTHOR]

An analytical approach that provides obtaining conservative estimates for the probability of fatigue brittle failure in the structural components of technical systems taking into account the scatter in the initial size of cracklike defects described by an exponential probabilistic distribution is presented. The operational loading is considered both as a deterministic process (with the loading cycles of constant amplitude and frequency) and as a random one (a steady-state narrowband Gaussian random loading). The crack growth kinetics is described on the basis of the modified Paris equation that takes into account the effects of the stress ratio (the loading cycle asymmetry). The parameters of the Paris law are considered as deterministic quantities. An example of the assessment of fatigue failure probability for an element of a linear pipeline section containing an axial crack on the inner surface and loaded by an internal pressure is presented. A comparative analysis of the results obtained with and without taking into account the random nature of the operational loading is performed. It is shown that neglecting the random nature of the operational loading leads to nonconservative estimates obtained for the fatigue failure probability, which can differ by an order of magnitude from calculation data taking into account the stochastic nature of the loading process. The developed method can be used in the implementation of probabilistic and risk-based approaches to providing strength, service life, and safety for technical systems under real operation conditions and in adjusting standard operating programs in terms of choosing the frequency and scope of nondestructive testing. [ABSTRACT FROM AUTHOR]

Due to the strong interface effect of continuous steel–concrete composite beams with conventional shear connectors, the efficiency of applying pre-stress in the negative moment zone is greatly reduced, which leads to a difficulty of anti-cracking design in the negative moment zone of pre-stressed steel–concrete composite box girder. In order to study the feasibility and the working mechanism of improving the crack resistance of continuous steel–concrete composite bridges by releasing the interfacial slip effect within the negative bending moment region, two groups of model tests were carried out in the paper. Two steel–concrete composite beams were used for model test, one of them using the conventional stud shear connectors, another one using the new shear connectors, named uplift-restricted and slip-permitted shear connectors. The results show that, compared with the composite beam with conventional shear studs, the composite beams with uplift-restricted and slip-permitted shear connectors have a higher pre-stress application efficiency, and the new connector could release the interface slip, which can make the tensile stress distribution in concrete slab more uniform within the negative moment zone, thus increasing the cracking load of concrete slab and reducing the subsequent crack width effectively. This study is helpful to understand the relationship between the interface slip and the anti-crack characteristics in negative moment zones, and a new anti-crack design method is proposed for the design of continuous composite girder. [ABSTRACT FROM AUTHOR]

Porous asphalt pavement have been widely employed for various functions. However, due to its large voids and small contact area between particles, the reflective cracks results from semirigid base layer shrinkage cracking and buttom-up fatigue cracking are easy to occur, under long-term multifield coupling influenced by load, temperature, water, light and other factors of natural conditions. Therefore, improving asphalt crack resistance is a key issue. Using an overlay test with a high-viscosity porous asphalt mixture (HPA-13) as a control object, a multi-index evaluation was performed to test the anticracking performance of an epoxy porous asphalt mixture (EPA-13) under different temperatures and aging conditions. Results showed that epoxy asphalt binders can considerably improve the anticracking performance of porous asphalt mixtures; under the standard condition of 25°C, the number of loading cycles (N) of EPA-13 was 7.5 times higher than that of HPA-13. However, EPA-13 was greatly affected by low temperature and aging conditions; in particular, under the low temperature condition of 10°C, N decreased by 93.5%. In the multi-index evaluation of crack resistance, the gray correlation degree of each evaluation index followed the order of the allowable failure times with (J) > cumulative fracture energy (G) > displacement at the maximum load of the first cycle (LF) > fracture energy of the first cycle (GF) > average fracture energy (G*) > maximum load of the first cycle (F). It is recommended to use N , J , and G to evaluate the crack resistance of porous asphalt mixtures. [ABSTRACT FROM AUTHOR]

An epoxy resin modified with polysulfone (PSU) and active diluent furfuryl glycidyl ether (FGE) was studied. Triethanolaminotitanate (TEAT) and iso-methyltetrahydrophthalic anhydride (iso-MTHPA) were used as curing agents. It is shown that during the curing of initially homogeneous mixtures, heterogeneous structures are formed. The type of these structures depends on the concentration of active diluent and the type of hardener. The physico-mechanical properties of the hybrid matrices are determined by the structure formed. The maximum resistance to a growing crack is provided by structures with a thermoplastic-enriched matrix-interpenetrating structures. The main mechanism for increasing the energy of crack propagation is associated with the implementation of microplasticity of extended phases enriched in polysulfone and their involvement in the fracture process. [ABSTRACT FROM AUTHOR]

Aiming at improving the driving safety problems caused by the functional deterioration of the original pavement surface or early diseases when the pavement structure diseases are not prominent and the strength is sufficient, the post blending process is applied to study the ultra-thin cover of skeleton dense SMA-10 warm mix epoxy asphalt. Through a series of tests, the mechanical properties, water stability, crack resistance, sliding durability and interlayer bonding properties were systematically evaluated. The results show that the ultra-thin cover of warm mixed epoxy asphalt has stable and good mechanical properties and serviceability; Basalt fiber has significantly improved its crack resistance. Compared with wood fiber, its bending tensile strain, impact toughness and crack resistance index have increased by 16.7%, 93.9% and 130.4% respectively; Epoxy asphalt mixture has better skid resistance and durability than SBS modified asphalt, which can significantly improve the rapid decline of asphalt pavement functionality; At the same time, epoxy asphalt as binder, its bonding performance is significantly better than matrix asphalt and SBS modified asphalt, and it is suggested that the amount of binder material should be reasonably reduced in high-temperature areas. [ABSTRACT FROM AUTHOR]

Cementitious materials, defined by their brittle nature and specific composition, are typically susceptible to thermal attack in various engineering scenarios. Basalt fibre (BF), employed as an inorganic silicate additive in cement, has garnered significant attention due to its exceptional mechanical and thermal stability. However, there exists a shortage of essential experimental data regarding the performance of BF-modified cement at elevated temperatures, and, more importantly, a lack of understanding of the key mechanisms involved in the reinforcement processes. In this study, the mechanical behavior of cementitious composites with various contents of BF is investigated at both ambient and elevated temperature conditions (up to 200 °C) to determine the optimal dosage of BF in cement and crucially the role of BF in stability of cement paste at elevated temperatures. Microstructure and phase composition analyses are performed to reveal the mechanisms of reinforcement. The results indicate that the addition of 0.05–0.1 wt% BF to cement can significantly enhance overall mechanical strength of cement paste and crucially its crack resistance at elevated temperatures, i.e., flexural strength improved by up to 60 % at 200 °C. This was primarily attributed to multiple energy-consumption processes, including the bridging effect, breaking effect, pulling out effect, crack deflection effect, and adhesive effect. Notably, the adhesion between BF and cement matrix improved after subjected to elevated temperatures, owing to the increased formation of hydration products on BF surface. While needle-shaped hydration products were commonly observed at ambient conditions, contributing to a slight increase in the surface friction of BF, the accelerated growth of hydration products at higher temperature conditions as the result of BF addition to cement was found to be the most dominant factor for enhancement of mechanical strength and improved ductility of cement composite. The outcomes of this study provide further insights and promising future for the application of BF-modified cement composite where the structure is exposed to high temperatures, including deep geothermal wells, CO 2 storage wells, radioactive waste disposal, and many other deep geo-energy applications. [Display omitted] • Incorporating 0.05–0.1 wt% BF into cement markedly improves its mechanical properties. • Multiple energy-consumption processes contribute to the crack resistance of cement. • Elevated temperatures enhanced the bonding between BF and the cement matrix. [ABSTRACT FROM AUTHOR]

• Designed a heat-treated Ni/Cr multilayer composite coating for strip casting roll. • The Ni layer as the middle layer enhanced heat transfer capacity. • The heat-treated Ni/Cr coating significantly improved crack resistance. • The heat-treated Ni/Cr coating exhibited superior wear resistance. A new heat-treated Ni/Cr multilayer composite coating for strip casting rolls was designed in this contribution. The results revealed that the addition of the middle layer of the Ni layer was conducive to enhancing the heat transfer capacity. Insignificant improvement was found in the crack resistance of the Ni/Cr coating when compared to the Cr coating. However, the heat-treated Ni/Cr coating exhibited remarkable cracking resistance due to intensified binding force with the matrix. Also, the wear resistance of Ni/Cr and heat-treated Ni/Cr was superior to that of Cr coating. [ABSTRACT FROM AUTHOR]

Reinforced glass beam (RG beam) is a type of structural glass member that has been developed in recent years. This RG beam consists of a glass beam to which reinforcement material, such as steel, is adhesively attached in the tensile side to improve crack resistance. The adhesive plays a critical role in the structural performance of RG beam. However, the effect of non-linear shear-slip behavior of the adhesive layer remains unclear and has been neglected in most previous studies, which can result in inaccurate estimations. To address this issue, this paper presents a finite difference model (FDM) that utilizes an explicit step-by-step method and trial-and-error iterative method for interfacial stress analysis. The model predicts the static structural response of a simply-supported RG beam that simulates the adhesive with non-linear stress-slip behavior. Furthermore, the model describes the adherend's shear deformation in elastic. The FDM results are then compared with the finite element method (FEM), adopting discrete nonlinear connectors (springs) to simulate the adhesion, and available analytical methods. Detailed parametric studies are further conducted to investigate the influences of glass strength, load pattern, reinforcement ratio and height-to-span ratio for proposing design recommendations. [ABSTRACT FROM AUTHOR]

Incorporating carbon nanotubes (CNTs) into concrete can improve its fracture toughness. The crack resistance properties of reinforced concrete with CNTs were tested by ring test and three-point bending beam fracture test. The fracture parameters of reinforced concrete with CNTs were analysed by using double-K fracture parameters and the results showed that CNTs can improve the crack resistance properties. When the CNT content was 0.10 wt%, the compressive strength at 28 days and the splitting tensile strength of concrete were increased by 1.7 and 11.7%, respectively. When the CNT content was 0.15 wt%, the cracking time of concrete under semi-closed and closed conditions was extended by 42.1 and 41.2%, respectively. The initiation fracture toughness, the unstable fracture toughness and the fracture energy of concrete were increased by 31.0, 32.4 and 24.6%, respectively. It was found that CNTs delay the propagation of micro-cracks by bridging across the micro-cracks in concrete and strengthening the interfacial transition zone. [ABSTRACT FROM AUTHOR]

The solid solution Ce0.8Y0.2O2–δ was obtained by three methods: sol-gel, glycine-nitrate, and solid-phase reactions. The synthesis temperature was 1350°C for the sol-gel method and 1500°C for the remaining samples. The x-ray method showed that all samples have a cubic lattice with fluorite structure. The microstructure, density, electrical conductivity, microhardness, and crack resistance of the resulting ceramics were studied. It was found by means of impedance spectroscopy that the Ce0.8Y0.2O2–δ system obtained by the sol-gel method has the highest electrical conductivity, 5.37 mS/cm at 550°C, and the lowest activation energy, equal to 0.83 eV in the temperature range of 300 – 550°C. The contribution made to the conductivity by grains and grain boundaries is determined. It is shown that the total conductivity for all samples decreases due to the resistance along the grain boundaries. [ABSTRACT FROM AUTHOR]

A method for determining the crack resistance of refractory products via a wedge splitting test was investigated. The possibility of using the method on existing equipment under the complex conditions of the Magnezit Group laboratory was evaluated. Products of various grades were tested, and the reproducibility and repeatability of the results were assessed. [ABSTRACT FROM AUTHOR]

The crack resistance of ion-exchange strengthened sheet silicate glass under bending strains is analyzed numerically using finite-element software for studying the thermal stress state of structures. The results show that the fracture of real sheet glass under tensile stresses during bending depends on crack-like surface defects. If the depth of the zone of compressive stresses from ion-exchange strengthening is much less than the depth of the surface crack, the glass strength slightly depends on the maximum compressive stresses on the surface. The ion-exchange strengthening effect becomes much stronger with decrease in the surface crack depth. The proposed method allows solving important practical problems of the destruction of multilayer aircraft glassworks with internal defects and selecting optimal methods for eliminating such defects. [ABSTRACT FROM AUTHOR]

In view of the easy cracking of the high-performance concrete (HPC) of the subway underground station floor, the effects of fly ash, basalt fiber, expansive agent, and water reducer on the compressive strength, initial crack time, through-crack time, and crack area of the HPC on a subway underground station floor at different ages by orthogonal experiment are examined. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP) are used to further analyze the microstructure and product composition of the optimal ratio HPC and reference concrete. The results show that with the increase in the content of fly ash and expander, the 7 d and 28 d compressive strength of the HPC gradually decreased. However, as the content of basalt fiber increased, the 7 d and 28 d compressive strength of the HPC gradually increased. The 7 d and 28 d compressive strength of the HPC increased and then decreased with the increase in water-reducer content. When the content of fly ash, basalt fiber and expander increased, the initial crack and through-crack time of the HPC delayed gradually, and the crack area gradually decreased. When the fly-ash content reached 30%, the cracking area accounted for 65.1% of the concrete with 15% fly-ash content. When the basalt fiber content reached 0.4%, the cracking area accounted for 56.5% of the concrete with 0.1% basalt fiber content. When the expander content reached 10%, the cracking area accounted for 60.5% of the concrete with 4% expander content. With the increase in the content of water reducer, the initial crack and through-crack time of the HPC gradually advanced, and the crack area gradually increased. When the water-reducer content reached 1.3%, the cracking area accounted for 105.7% of the concrete with 1.0% water-reducer content. The addition of fly ash and expander can produce a large number of crystalline products to fill the pores, and the disordered distribution of the added basalt fibers increases the compactness of the structure; moreover, the internal micro-pores increase, and the macro-pores decrease, thus improving the crack resistance. [ABSTRACT FROM AUTHOR]

The object of research is chromium-nickel cast iron of the working layer of two-layer sheet-rolling rolls of the LPKhNd design. At present, chromium-nickel cast iron is widely used for the manufacture of rolls for sheet and section rolling mills. One of the ways to improve the operational properties of products made of chromium-nickel cast iron is the refining of molten metal by vacuum. The existing problem is that information on the effect of vacuuming on the performance of chromium-nickel iron is very limited. Rolls with the most characteristic concentration of alloying elements for LPKhNd performance were selected for the study. When evaluating the properties of vacuumed cast iron and cast iron by traditional technology, the level of strength, hardness, as well as special properties were determined, the study of which is caused by the peculiarities of the operation of rolling rolls (thermal wear resistance and crack resistance). It has been established that there is no significant difference in the structures of rolls made of vacuumed and non-vacuumed cast iron. The structure of the rolls consists of martensite, bainite and carbides. With an increase in the content of graphite-forming elements (C, Si, Ni), graphite inclusions appear in the structure, and with their decrease, individual troostite colonies appear. The physical and mechanical properties of vacuumed and non-vacuumed cast iron are on the same level. The crack resistance of the chilled zone of vacuum cast iron is 12.35 % higher than that of cast iron of the traditional production method, and the transition zone is 11.96 %. The thermal endurance of the chilled zone of the roll material increased by 14.95 % as a result of vacuuming of the molten metal, and the transition zone – by 14.56 %. An increase in crack resistance and heat resistance can help reduce the chipping of the working layer of chromium-nickel rolls of sheet mills during operation and increase their resource indicators. The obtained results of research indicate a positive effect of vacuuming on individual indicators (crack resistance and heat resistance) of the working layer of the forming tools of sheet rolling mills. [ABSTRACT FROM AUTHOR]