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Granite is a heterogeneous material characterized by a significant population of mechanically distinct grain boundaries, which exert a substantial influence on crack propagation. An extended grain-based model was developed by integrating the geometric heterogeneity, represented by Voronoi tessellations, and the mechanical heterogeneity of grain boundary, as described by Weibull distribution. This study numerically investigates the influence of mechanical heterogeneity in grain boundary on the mechanical properties and microcracking behavior of semi-circular bend granite samples under mode I loading. The mechanical heterogeneity of grain boundary was assessed by independently varying the heterogeneity index, defined by the shape parameter m in the Weibull distribution. The findings indicate that the force–displacement curve and fracture toughness are primarily influenced by the parallel bond tensile strength and cohesion of grain boundary contacts. When the value of m in Weibull distribution is between 1.5 and 2, a compromise between failure patterns and diverse grain boundaries characterization can be reached. Considering the heterogeneous mechanical properties of grain boundary numerically is able to simulate the local stress concentration of the real rocks, thus accelerating the generation of microcracks and reflecting the brittleness of rock failure. Otherwise, the fracture toughness of the rock will may be overestimated. Generally speaking, models that consider grain boundary heterogeneity will produce larger fracture process zone and microscopically complex crack propagation patterns during loading, and these phenomena are more consistent with experimental observations than those models in which grain boundaries are homogeneous.HighlightsThe mechanical heterogeneity of grain boundary in granite is quantitatively characterized by the Weibull distribution; The heterogeneous grain boundary could favor the local stress concentration, thus accelerating the generation of microcracks;Considering both geometric heterogeneity of granite and mechanical heterogeneity of grain boundary result in the generation of larger fracture process zone and microscopically complex crack propagation patterns under mode I loading.

Fracture and mechanical properties of the water saturated sedimentary rocks have been experimentally investigated in the present paper. Three types of sandstones and one type of shale were saturated in water for different periods of time. They were then tested for their index geomechanical properties such as Brazilian tensile strength (BTS), Young’s modulus (YM), P-wave velocity and all pure and mixed-mode fracture toughness (FT). FT was measured using semicircular bend specimens in a three-point bend set-up. All the geomechanical and fracture properties of the saturated rocks were compared together to investigate their interrelations. Further, statistical methods were employed to measure the statistical significance of such relationships. Next, three types of fracture criteria were compared with the present experimental results. Results show that degree of saturation has significant effect on both the strength and fracture properties of sedimentary rock. A general decrease in the mechanical and fracture toughness was noticed with increasing saturation levels. But, t -test confirmed that FT, BTS, P-wave velocity and YM are strongly dependent on each other and linear relationships exist across all the saturation values. Calculation of the ‘degradation degree’ (DD) appeared to be a difficult task for all types of sedimentary rocks. While in sandstone, both the BTS and mode-I FT overestimated the DD calculated by YM method, in shale BTS was found to give a closure value.

Asymptotic equations for stresses are presented and used for numerical modeling and graphical representation of elastoplastic properties of circular SD-plates. A numerical solution of the plate bend is obtained after calculating the system of fifth-order differential equations. Euler difference method and software package COMSOL 5.6 are applied to solve the problem for biological tissue.

The rapid developments in conductive polymers with flexible electronics over the past years have generated noteworthy attention among researchers and entrepreneurs. Conductive polymers have the distinctive capacity to conduct electricity while still maintaining the lightweight, flexible, and versatile characteristics of polymers. They are crucial for the creation of flexible electronics or gadgets that can stretch, bend, and adapt to different surfaces have sparked momentous interest in electronics, energy storage, sensors, smart textiles, and biomedical applications. This review article offers a comprehensive overview of recent advancements in conductive polymers over the last 15 years, including a bibliometric analysis. The properties of conductive polymers are summarized. Additionally, the fabrication processes of conductive polymer-based materials are discussed, including vacuum filtering, hydrothermal synthesis, spray coating, electrospinning, in situ polymerization, and electrochemical polymerization. The techniques have been presented along with their advantages and limitations. The multifunctional applications of conductive polymers are also discussed, including their roles in energy storage and conversion (e.g., supercapacitors, lithium-ion batteries (LIBs), and sodium-ion batteries (SIBs)), as well as in organic light-emitting diodes (OLEDs), organic solar cells (OSCs), conductive textiles, healthcare monitoring, and sensors. Future scope and associated challenges have also been mentioned for further development in this field.

The rapid development of new classes of automotive steels such as the 3rd generation of advanced high-strength steels has created the need for the efficient characterization of their mechanical properties in loading scenarios other than uniaxial tension. The VDA 238-100 tight radius bend test has gained widespread acceptance in recent years for characterizing performance in plane strain bending, but there is uncertainty surrounding the use of the bend angle and its interrelation with the test parameters. The objective of the present study is to investigate the intertwined effects of the sheet thickness, bend radius, and tensile properties upon the bendability of seven advanced high-strength steels in different thicknesses for a total of 83 conditions. Practical correlations are developed to predict the bend angle and plane strain fracture strain as functions of the bending conditions and tensile mechanical properties. An extensive dataset comprising 26 additional advanced high-strength steel test cases was compiled from the literature to evaluate the proposed correlation for the plane strain fracture strain.

Storage canisters used in nuclear power plants operating in seaside areas—where the salt content in the atmosphere is high—may be susceptible to chloride-induced stress corrosion cracking (CISCC). Chloride-induced stress corrosion cracking is one of the ways in which dry storage canisters made of stainless steel can degrade. Stress corrosion cracking depends on the microstructure and residual stress, and it is therefore very important to improve the surface properties of materials. Laser shock peening both greatly deforms the material surface and refines grains, and it generates compressive residual stress in the deep part from the surface of the material. This study focused on the effect of laser shock peening on the stress corrosion cracking of 304L stainless steel. The laser shock peening was found to induce compressive residual stress from the surface to a 1 mm depth, and the SCC properties were evaluated by a U-bend test. The results showed that the SCC resistance of laser-peened 304L stainless steel in a chloride environment was enhanced, and that it was closely related to grain size, the pitting potential of the cross section, and residual stress.

To further reduce the confinement loss of hollow-core anti-resonant fibers (HC-ARFs), broaden the low-loss operating bandwidth, and decrease the bending losses, this paper proposes a novel double-single-layer nested HC-ARF. The influence of structural parameters on its optical performance is analyzed using the full-vector finite element method, and the relevant structural parameters are optimized accordingly. The results indicate that, after optimizing the structural parameters, the HC-ARF exhibits extremely low confinement loss (on the order of 10 –8  dB/km) at the wavelength of 1.55 μm. When the bending radius is 10 cm, the bending loss is also very low (on the order of 10 –4  dB/km), which demonstrates an excellent bend-resistant property. Moreover, the HC-ARF possesses a very flat dispersion characteristic, with a low-loss operating bandwidth of approximately 945 nm, covering all the communication bands (O + E + S + C + L band). Graphical Abstract Cross section of the proposed double-single-layer nested HC-ARF and its Performance under the optimized structural parameters. This paper presents a new type of hollow - core anti - resonant fiber. The optical properties of this fiber, including confinement loss, bending loss and dispersion, etc., are numerically calculated by using the full-vector finite-element method. On this basis, the structural parameters of the fiber are optimized, and excellent optical properties are finally obtained.

Understanding the microstructure–property relationship in aluminum extrusions is crucial to leverage their potential in automotive lightweighting. The sensitivity of the processing history to the microstructure and through-thickness variations poses a major challenge since it leads to strong directionality in plasticity and fracture. Reliable characterization of the mechanical response under relevant stress states is crucial for the development of modeling strategies and performance ranking in alloy design. To this end, tensile and 3-point bend tests were performed for an aluminum extrusion produced on a laboratory-scale extrusion press at Rio Tinto Aluminium. Direct measurements of surface strains during bending using stereoscopic digital image correlation revealed that a larger bend angle in the VDA238-100 test does not necessarily imply a higher fracture strain. The T4 sample tested in the extrusion direction sustained a bend angle of 104° compared to 68° in T6 for the same nominal bend severity (ratio of sheet thickness to punch radius), despite comparable major fracture strains of 0.60 and 0.58, respectively. It is proposed that the work-hardening behavior governs the strain distribution on the outer bend surface. The higher hardening rate in the T4 condition helped distribute deformation in the bend zone more uniformly. This delayed fracture to larger bend angles since strain is accumulated at a lower rate. To assess whether the effect of the hardening behavior is manifest at a microstructural lengthscale, microcomputed tomography (μ-CT) scans were conducted on interrupted bend samples. The distribution and severity of damage in the form of cracks on the outer bend surface were distinct to the temper and thus the hardening rate.

Pipeline connection is the main connection of hydraulic parts. For the study of pipe diameter, turning Angle and the turning radius of pipe, the influence law of the internal flow characteristics. this paper adopts CFD 3D simulation technology to explore the influence law of 5 kinds of bending radius, 6 kinds of bending Angle and 4 kinds of pipe diameter on the pressure loss of the pipeline. The results show that there are pressure difference and velocity difference in the inner wall and the outer wall of the bend, due to the impact of the fluid inertia force on the bend, when the fluid flows in the bend. As bending radius and pipe diameter increases, the pressure difference and speed difference of the inner and outer walls at the turning point of the pipeline are reduced, the local pressure loss at the bending is reduced, the internal pressure loss of the pipeline is reduced, and the flow is more uniform. With the increase of bending angle, the pressure difference and velocity difference of the inner and outer walls of the pipeline bending increase, the local pressure loss increases, and the overall pipeline pressure loss increases. The research results of this paper can provide some reference for pipeline hydraulic design and optimization.

The fracture mechanics of frozen rock are important to engineering in cold regions, yet the basic properties and influences remain unclear. The fracture toughness of semi-circular bend (SCB) samples with different initial saturation degrees (ISDs) was tested at − 20 ℃. Acoustic emission (AE) and digital image correlation (DIC) systems were used to capture AE signals and surface deformation under load testing. In addition, the phase composition in rock pores was measured by low-field nuclear magnetic resonance (LF-NMR). It was found that: (1) Fracturing of frozen sandstone generally consists of three stages: pore or microcrack closing, elastic deformation and microcrack propagation which is evidenced by the variation of AE counts and the maximum horizontal strain within the fracture process zone (FPZ) under loading. (2) The ISD has a great influence on fracture toughness and the microcrack propagation process. With increases in ISD, both the fracture toughness and fracture energy of frozen sandstone varies in a mode of slow increase (ISD < 40%), rapid increase (ISD 40–90%) and slight decrease (ISD 90–100%). (3) The phase composition in pores of frozen rock with low ISD (< 40%) is significantly different from that with high ISD (40–100%). At ISDs of < 40%, the ice in rock pores mainly originates from adsorbed water; however, at ISDs of 40–100%, the ice increasingly comes from free and capillary water. Based on the test results, the difference in fracture mechanical properties of frozen sandstone introduced by different ISDs can be attributed to the changes in pore phase composition, which determines the interaction between pore ice/unfrozen water and rock skeleton involving three processes: strengthening due to the filling effect of pore ice, strengthening due to the adhesion force and tensile strength of pore ice, and weakening due to frost damage.HighlightsFreezing strengthens water-bearing sandstone significantly, and the fracture toughness of frozen sandstone increases with its initial saturation degree.Initial saturation degree differs the fracturing process of frozen sandstone in terms of energy release and range of fracture process zone.Pore phase composition primarily determines the fracturing behaviour of frozen sandstone involving ice–pore interactions.The ice–pore cementation and tensile strength of ice are the main contributors to the increase of fracture toughness of frozen rock.