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In Situ EBSD Observation and Numerical Simulation of Microstructure Evolution and Strain Localization of DP780 Dual-Phase Steel

To reveal the microstructural evolution and stress–strain distribution of 780 MPa-grade ferrite/martensite dual-phase steel during a uniaxial tensile deformation process, the plastic deformation behavior under uniaxial tension was studied using in situ EBSD and crystal plastic finite element method (CPFEM). The results showed that the geometrically necessary dislocations (GND) in ferrite accumulated continuously, which is conducive to the formation of grain boundaries, but the texture distribution did not change significantly. The average misorientation angle decreased and the proportion of low-angle grain boundaries increased with the increase of strain. At high strain, the plastic deformation mainly occurred in the soft ferrite region within a 45° distribution from the loading direction. In the undeformed state, the texture of the dual-phase steel was characterized by α-fibers and γ-fibers. Interfacial debonding was caused by the accumulation of geometrically necessary dislocations. The fracture morphologies showed that the specimens had typical ductile fracture characteristics.

Compositionally gradient Al2O3–B4C/Al composites with interpenetrating structure and tailored properties via material extrusion-based additive manufacturing and pressure infiltration

ABSTRACT Traditional fabrication methods for metal–ceramic composites often struggle to achieve the level of control needed for material on-demand design and property optimisation, despite the potential for enhanced performance. This study presents a novel approach that overcomes these limitations by combining material extrusion-based additive manufacturing and pressure infiltration techniques, which enables the fabrication of compositionally graded Al2O3–B4C/Al layered composites with tailored properties. Precise control over the B4C/Al2O3 ratio allows for the fine-tuning of key mechanical properties, including bending strength, fracture toughness, and fracture work. The composites exhibit anisotropic behaviour, with performance influenced by the ceramic composition, loading direction, and layer spacing. A notable observation is the enhancement of damage tolerance through multi-crack propagation as the Al2O3 content in the ceramic layers increases. Additionally, wear tests demonstrate exceptional abrasion resistance, highlighting the synergistic effects of B4C hardness and Al2O3 toughness. This research establishes novel strategies for the design and fabrication of metal–ceramic composites with tailored properties, paving the way for their implementation in demanding applications where a combination of strength, toughness, and wear resistance is critical.

Enhanced RTP method for nonlinear statistical prediction of ship structural response

Abstract In this study, the Enhanced RAO-based Translation Process (ERTP) method, which is an enhanced version of the RAO-based Translation Process (RTP) method proposed in the previous study, is newly proposed. The RTP method approximates the Extreme Value Distribution (EVD) in arbitrary irregular waves from the nonlinear response in regular waves based on the idea of the transformation process, in which the nonlinear process is regarded as a transformation of a linear process. However, it was found that the RTP method is inaccurate when the response spectrum has multiple peaks, which is often the case for stresses in ship structures in waves. To solve this problem, the author developed the ERTP method, which defines a nonlinear transformation based on the L p-norm of the response spectrum. Direct Load and Structure Analysis considering the nonlinearity of wave loads was conducted and confirmed that the proposed method can reasonably estimate the EVD even for structural elements with a multi-peaked response spectrum with respect to the wave direction.

Drug-Loaded Hydrogel Microneedles for Sustainable Transdermal Delivery of Macromolecular Proteins.

Poly(methyl vinyl ether co-maleic acid) (PMVE/MA) hydrogel microneedles (HMN) are investigated for transdermal delivery of macromolecular drugs owing to their biocompatibility and super-swelling properties. However, the drug delivery efficacy reduces with increasing molecular weight due to the entrapment within the HMN matrices. Furthermore, integrating external drug reservoirs extends the drug diffusion path and reduces the efficiency of drug permeation. A direct drug loading approach in the HMN matrix was introduced in this work following a pH modification step. The effect of pH modification on the physicochemical properties of HMN was studied. Then, bovine serum albumin (BSA), a model protein, was loaded into the pH-modified HMN, and the morphological changes in HMN and protein stability were also assessed. Finally, the efficacy of BSA-loaded HMN in the transdermal delivery was evaluated ex vivo. A significant increase in swelling was recorded following the pH modification of HMN (p < 0.001). The structure of pH-modified hydrogel was highly porous, and ATR-FTIR spectra indicated a shift in the carboxylic peak. The secondary structure of BSA loaded in the pH-modified HMN was also preserved. The BSA-loaded HMN mediated a sustained ex-vivo drug release with a cumulative release of 64.70% (3.88 mg) in 24 h. Hence, the model drug-incorporated PMVE/MA HMN system shows potential for sustainable transdermal delivery of proteins.

Shock compression of [101¯0]-axis zinc single crystal

Zinc single crystals have been shocked by planar impact along the [101¯0] axis as well as in the off-axis direction. The evolution of compression waves has been analyzed from the free surface velocity profiles of zinc single crystal samples. A slip on the primary system is activated by impact loading in directions making angles of θ = 17°–64° with respect to the [101¯0] axis. The phenomenon of the formation of two plastic compression waves propagating at different velocities is observed in samples oriented at angles of 53° and 64°. The spall fracture of single crystal zinc samples oriented in different directions has been measured. It is shown that the highest value of spall strength is recorded along the highly symmetric axis of the crystal. The experimental results presented are consistent with the data published in the scientific literature on beryllium and magnesium and confirm the important role of crystalline anisotropy in the process of inelastic deformation of single crystals.

Quantification of 3D microstructures in Achilles tendons during in situ loading reveals anisotropic fiber response.

While the number of studies investigating Achilles tendon pathologies has grown exponentially, more research is needed to gain a better understanding of the complex relation between its hierarchical structure, mechanical response, and failure. At the microscale, collagen fibers are, with some degree of dispersion, primarily aligned along the principal loading direction. However, during tension, rearrangements and reorientations of these fibers are believed to occur. As 3D micro-movements are hard to capture, the precise nature of this fiber reorganization remains unknown. This study aimed to visualize and quantify the intricate fiber changes occurring within rat Achilles tendons under tension. Rat tendons were in situ loaded with concurrent synchrotron phase contrast microCT imaging. The results are heterogenous and show that collagen fibers' response to loading is nonuniform and depends on anatomical orientation. Furthermore, damage propagation could be visualized, revealing that in the presence of heterotopic ossification damage proceeds within the ossified deposits rather than at the interface between hard and soft tissues. Our approach could effectively capture the microstructural changes occurring during loading and shows promise in understanding the relation between microstructure and mechanical response for ex-vivo Achilles tendons and other biological tissues. STATEMENT OF SIGNIFICANCE: Achilles tendons endure high mechanical loads during daily motion and physical activities. Understanding the structural and mechanical responses of Achilles tendons to such loads is vital for elucidating their function in health and pathology. We have combined the use of synchrotron phase contrast microCT with in situ mechanical loading contributing a better understanding of the relation between microstructural response and organ scale mechanical properties. The proposed methodology will be valuable for future research into the interplay between structure, mechanics, and pathology of tendons, and for the development of more effective strategies to preserve tendon function and possibly mitigating musculoskeletal disorders.

Ecofriendly and biocompatible biochars derived from waste-branches for direct and efficient solid-phase extraction of benzodiazepines in crude urine sample prior to LC-MS/MS.

Biochars (BCs) derived from waste-branches of apple tree, grape tree, and oak were developed for direct solid-phase extraction (SPE) of five benzodiazepines (BZDs) in crude urine samples prior to liquid chromatography-tandem mass spectrometry (LC-MS/MS)determination. Scanning electron microscopy, elemental analyzer, X-ray diffractometry, N2 adsorption/desorption experiments, and Fourier transform infrared spectrometry characterizations revealed the existence of their mesoporous structure and numerous oxygen-containing functional groups. The obtained BCs not only possessed high affinity towards BZDs via π-π and hydrogen bond interactions, but also afforded the great biocompatibility of excluding interfering components from undiluted urine samples when using SPE adsorbents. Variables affecting SPE of target analytes were systematically optimized including pH, ionic strength, dilution ratio, washing solution, desorption solvent, and its volume. The method of BC-based SPE combined with LC-MS/MS exhibited awide linear range of 0.03-100ng/mL, alow detection limit of 0.01-0.08ng/mL, and satisfactory recovery of 77.6-106% for the studied BZDs. Notably, this method allowed the possibility of direct loading of undiluted urine samples and avoided tedious filtration and dilution steps, which significantly simplified the pretreatment process. Additionally, these BC sorbents derived from waste-branches were ecofriendly and cost-effective, providing a sustainable alternative for the traditional SPE sorbents. Thus, the proposed method has promising application for ecofriendly, simple, efficient, and reliable monitoring of BZDs in urine samples.

Orientation effect and locational variation in elastic-plastic compressive properties of bovine cortical bone.

Bone is a highly heterogeneous and anisotropic material with a hierarchical structure. The effect of diaphysis locations and directions of loading on elastic-plastic compressive properties of bovine femoral cortical bone was examined in this study. The impact of location and loading directions on elastic-plastic compressive properties of cortical bone was found to be statistically insignificant in this study. The variances of most of the compressive properties were also observed to be location and directionality independent except for the locational differences in modulus of resilience (distal to central for longitudinal loading) and plastic work (central to distal for transverse loading) as well as differences in variances of the modulus of resilience and elastic modulus values for two directions of loading. The micro-mechanisms of cortical bone failure for longitudinal and transverse directions of loading were considered to be responsible for the difference in variances in the later properties values as well as for the maximum and minimum coefficient of variation (CV) obtained for compressive properties in two directions of loading. The representative cubical volume at the tested hierarchical level contained all unique microstructural features of the plexiform bone and therefore produced the homogeneous and isotropic elastic-plastic compressive properties of cortical bone. It is expected that the outcome of this study may be helpful in the area of bone tissue engineering and finite element simulation of cortical bone.

Experimental study and numerical simulation on the bearing behavior of the modified suction caisson under misalignment lateral cyclic and monotonic loadings

Suction caissons for offshore wind turbines are subjected to lateral misalignment wind and wave loads during service life, leading to the occurrence of accumulate deflection and changes in lateral bearing capacity. Experimental studies and numerical simulations were performed to investigate the motion mode, accumulated lateral deflection, and bearing capacity of a modified suction caisson (MSC) under misalignment lateral cyclic and monotonic loadings. Under misalignment lateral cyclic and monotonic loadings, the motion behavior of the MSC is combined with the translation, rotation, and torsion. The direction of MSC motion lies between cyclic and monotonic loading directions. The angle between the motion direction and cyclic loading direction is far less than that between the motion direction and monotonic loading direction. Under the same cyclic and monotonic load values, the maximum accumulated deflection was obtained when the angle between lateral cyclic and monotonic loading directions (which is defined as the misalignment angle) equals 30°. In addition, the lateral bearing capacity of the MSC after misalignment cyclic and monotonic loading was found to decrease with increasing the misalignment angle. The minimum lateral bearing capacity of the MSC after misalignment loading was obtained when the misalignment angle equals 180°. Based on the model test and simulation results, the method applying the model test results to the practical engineering is proposed.

Significant reduction of anisotropy in stress relaxation aging and mechanical properties improvement for 2195 Al-Cu-Li alloy subjected to plastic loading

Although the plastic loading can enhance creep deformation and yield strength, the anisotropic Stress Relaxation Aging (SRA) behavior and mechanism under plastic loading remain unclear, which presents a significant challenge in accurately shaping aluminum alloy panels. In this study, the SRA behavior of 2195-T4 Al-Cu-Li alloys were thoroughly studied under initial loading stresses within the elastic (210/250 MPa) and plastic (380/420 MPa) ranges at 180 ℃ by stress relaxation and tensile tests as well as microstructure characterization. The findings reveal that compared with those under elastic loadings, in-plane anisotropy (IPA) values of the stress relaxation amount, yield strength and fracture elongation under plastic loadings are reduced by 60%-80%, 70%-90% and 72%-89%, respectively. Similarly, IPA values of precipitate size in grains and Precipitation-Free Zones (PFZ) width at grain boundaries under plastic loading decrease by 31.4% and 94.4% respectively. These results indicate plastic loading significantly weakens the anisotropic SRA behavior, owing to numerous uniformly distributed fine T1 phases and small IPA values of both T1 precipitates size and PFZ width in various loading directions. Compared with those of elastic loading-aged alloys, yield strength of plastic loading-aged alloys shows high strength-ductility because of the combined effect of closely dispersed fine T1 precipitates, narrowed PFZ and numerous sheared and rotated T1 phases at different locations during tensile process. The uniformly distributed larger Kernel Average Misorientation (KAM) and Schmidt factor values of the plastic loading-aged alloy, as well as the cross-slip generated, also help to enhance the strength and ductility of the alloy.

Highly controllable micro-forging to enhance the anti-fatigue performance of components with edges

Shot peening (SP) may cause defects known as “rolled edges” because of random shots. Micro-forging (MF) can avoid this problem due to its high controllability, which further improves fatigue properties of components. In this study, specimens with rounded edges were subjected to either MF or SP treatments. During MF process, to avoid lips, smaller shot energy was used near edges. The DFRcutoff of MF-treated samples is 260 MPa, significantly higher than that of the shot-peened ones (228 MPa), and the milled specimens (207 MPa). The MF-treated specimens showed smoother surface (Sa below to 0.25 μm), which inhibited the crack initiation. While the surface topography of SP-treated samples was worse compared with the milled one (Sa increased from 0.287 μm to 5.523 μm). Moreover, although a smaller CRS near the edges was introduced to maintain shape precision, the larger CRS and lower roughness in other areas constrain the direction of crack propagation along the load direction, which extends the crack propagation path and results in a higher fatigue life. In the future, micro-forging has the potential to be widely used in the aerospace, marine, and automotive industries to enhance the fatigue performance of key components, especially with detailed structure.

Fracture and fatigue characteristics of monodomain and polydomain liquid crystal elastomers.

Liquid crystal elastomers (LCEs), a class of elastomers combining liquid crystals with a polymer network, have garnered significant interest for applications in the field of soft robotics. However, the fracture and fatigue characteristics of LCEs remain poorly understood. This study presents a comprehensive investigation into the fracture and fatigue characteristics of LCEs, focusing on polydomain and monodomain variants subjected to different loading directions. The fracture energy (also called toughness) and fatigue threshold of polydomain and monodomain LCEs were quantitatively measured and compared with selected elastomers. Our experimental results demonstrate that polydomain LCEs exhibit superior fracture energy and fatigue threshold compared to monodomain LCEs. Within the monodomain category, LCEs subjected to parallel loading exhibit larger fracture energy than those under vertical loading, while their fatigue thresholds remain comparable. These findings enhance our understanding of the deformation and failure characteristics of LCEs, which are crucial for their applications in various fields.

Progressive Collapse of Steel Structures Under Blast Loads Considering Soil‐Structure Interaction

This study focuses on the effect of soil‐structure interaction on the occurrence of progressive collapse due to an external blast. Therefore, a 3‐story fixed base steel moment‐resisting frame structure was first modeled and subjected to an external blast load. Then, the same structure was modeled considering soil‐structure interaction. In another stage of this study, the effect of plan irregularity on progressive failure resulting from the explosion was investigated, assuming the presence or absence of soil‐structure interaction. The direct simulation method and alternative load path method are all employed to simulate the progressive collapse process of steel frames using the commercial finite element program LS‐DYNA. The results of the numerical simulations demonstrated that the presence of soil‐structure interaction, significantly influences the response of the structure to the blast and this interaction increases the likelihood of progressive failure occurring even at symmetric and asymmetric structures. It was also shown that silty sand soil yields more critical conditions than other types of soil in the event of failure after the occurrence of an explosion in the structure.

Multi-hazard performance assessment of monopile offshore wind turbine considering coupled corrosion and fatigue damage

Monopile offshore wind turbine (OWT) often suffer from chloride corrosion and wind–wave fatigue during service. However, studies focus on the impact of pitting or uniform corrosion on fatigue damage, with less attention to their interaction as well as the coexistence of pitting and uniform corrosion, which produces errors in the estimation of the local defects caused by coupling damage and the residual performance of the structure. Most OWT monopiles are constructed with flexible thin-walled structural systems, which are sensitive to local defects and prone to local buckling failure. Thus, insufficient consideration of the corrosion fatigue effect clearly reduces the reliability of OWT failure mode identification and multi-hazard vulnerability analysis. To solve this problem, Faraday's law and continuous damage mechanics were used to establish models for pitting and uniform corrosion damage. A cross-sectional segmentation strategy was employed to consider nonuniform fatigue damage caused by directional fatigue loads. Then, the corrosion and fatigue coupling damage of OWT was evaluated. The results show that considering coupling damage causes the failure mode of the OWT to change from overall bending to local buckling. Quantifying OWT vulnerability under earthquake-hurricane action shows a 9.57% collapse probability with coupling damage, compared to 3.18% without it.

Multi-scale finite element analysis of the strengthening and damage behavior of carbides with different characteristics in nickel-based superalloys

This study proposes a novel multi-scale numerical approach to explore the mechanical behavior and damage evolution in nickel (Ni)-based superalloys containing various carbide particles. At the nanoscale, the elastic properties of two distinct carbides are determined using first-principles calculations. At the microscale, finite element simulations (FEM) in ABAQUS are used to analyze the stress–strain relationship and local stress distribution within a three-dimensional representative volume element, as well as damage and fracture behavior. The model integrates the elastic–plastic response of the Ni matrix, the elastic-brittle fracture of micro-scale carbides, and the interface behavior between carbide and matrix. FEM findings are consistent with tensile test data, indicating that skeletal carbide promotes plasticity while blocky carbide elevates strength. The interface between blocky carbide and matrix is susceptible to cracking. When the carbide is oriented at 45° to the load direction, offering a balance of strength and plasticity. Stress concentration is reduced when carbides are uniformly distributed and present in high-volume fractions. The numerical method is well-suited for a thorough analysis of the comprehensive behavior of reinforced phase/metal-matrix composites.

Manually directional splitting of in-situ intact igneous rocks into large sheets

This paper presents a directional large-area rock fracturing method. The method had distinctive features compared with other common fracturing methods. The area of the fracturing surface could reach 10–500 m2. The fractured rock was sheet-like in shape, with a thickness of 6–8 cm. The main fracturing tools and procedures used were described in the paper. This paper analysed the reason for controllable and directional (also mode-I) rupturing in rock from the view of fracture mechanics. Counter-intuitively, the fracturing surface of the rock sheet had an angle (approximately 25°) to the loading direction (i.e., the orientation of the maximum principal compressive stress). The rupture behavior was controlled by the relationship between the load and the geometric boundary of the rock. It is found that the fracturing surface can suddenly and rapidly propagate after a certain strike by calculating the energies of the rock sheet. The striking energy could be converted into elastic strain energy, which accumulates in a very-slightly bent rock sheet step by step until exceeds the bearing limit of rock sheet. Most of the stored elastic strain energy was subsequently released in the form of splitting energy, leading to rock fracturing. This study provides insights into the occurrence of tectonic earthquakes.

Achieving excellent ductility with increased Schmid Factor but decreased direct strain contribution of basal slip in an intergranular misorientation tailored magnesium alloy

Weakening the basal texture was a commonly used method to improve the ductility and formability of magnesium alloys. The easier activation of basal slip was often considered to be an important reason for the improved ductility of the weak basal textured magnesium alloys. However, basal slip alone cannot well satisfy the Von Mises criterion and its activation was nearly saturated in strong basal textured magnesium alloys. The deformation mechanisms of weak basal textured magnesium alloys are still open to debate. In this work, the Schmid Factor (SF) of the basal slip is obviously increased and a high fracture elongation of ∼35% is achieved in AZ31 alloy by careful tailoring of grain orientation and rational selection of loading direction. Grain size scale strain distribution by high-resolution digital image correlation (DIC) and slip activation based on the slip trace method were used to in-depth analyze the deformation mechanisms. Although the basal slip’ average SF increases, the strain statistics show that the direct strain contribution of the basal slip to the deformation gets decrease, contrary to conventional expectation. This is mainly attributed to the coupling effect of the increased basal slip’ SF with the large intergranular misorientation, which significantly promotes the activation of non-basal slip and increases its contribution to the deformation, thus leading to a lower direct strain contribution of the basal slip. The results of the study may help to further reveal the plastic deformation mechanism of magnesium alloys and improve the plasticity of magnesium alloys.

Atomistic Study on the Mechanical Behaviors of Nanoporous Glassy Alloys under Shear Loading: Effects of Porosity and Specific Surface Area

Nanoporous glassy alloys (NPGAs) have recently garnered considerable interest across various disciplines due to their exceptional and tailored functional properties. The practical applications of NPGAs necessitate a deep understanding of their mechanical behaviors under various types of loads, yet research on their mechanical responses under shear loading remains insufficient. Herein, the mechanical properties and deformation mechanisms of representative Cu50Zr50 NPGA under shear loading are investigated through molecular dynamics simulations. The results demonstrate that the relationship between the shear modulus and the solid fraction of NPGA can be well described by a modified Gibson–Ashby scaling law . The shear yield strength is linearly proportional to the solid fraction. During shear deformation, two major cracks are triggered from the two free surfaces due to the drastic strain concentration. The two cracks then propagate along the loading direction with some deflections. Eventually, the NPGA sample fractures once one crack penetrates the sample entirely. The sensitivity of shear strength to strain rate is significantly lower than the sensitivity of tensile strength to strain rate. As the temperature increases, the shear modulus, shear yield strength, and ultimate shear strength decrease monotonically.

Fatigue Behaviour of PA66 GF30 at Different Temperatures.

A comprehensive experimental investigation to understand the mechanical properties and fatigue behaviour of glass-reinforced polyamide (PA66 GF30) at different temperatures is presented in this paper. The specimens for quasi-static and fatigue testing were machined from previously extruded plates, where two orientations were considered: (i) the extrusion direction (ED) and (ii) the direction perpendicular to extrusion (PED). Both the quasi-static and fatigue tests were performed under different temperatures (22 °C and 100 °C). The fatigue tests were performed in a load control regime under pulsating loading (R = 0.1) to create S-N curves for all the temperatures and loading directions. The experimental results of the quasi-static tests showed that the test specimens manufactured in the extrusion direction have better mechanical properties when compared to those of the specimens manufactured perpendicular to the extrusion direction. Furthermore, the analysis of the quasi-static tensile test results showed that tensile strength, yield strength, and the modulus of elasticity are significantly dependent on the temperature and deteriorate when the temperature is increased from 22 °C to 100 °C. The results of the fatigue tests showed that at both the temperatures (22 °C and 100 °C), the samples produced in the direction of extrusion exhibited higher fatigue strength than those produced perpendicular to the direction of extrusion. For all the sample orientations, the fatigue strength decreased significantly with increasing temperature. The obtained experimental results could be very useful when designing and dimensioning different dynamically loaded engineering components made of PA66 GF30 subjected to high temperatures.

Разработка рабочего органа роторного экскаватора с ковшами сферической формы

Relevance of research. The Russian Federation currently disposes of enormous coal reserves ranging from lignite to anthracite. At the same time a significant part of coal in Russia is mined by the surface method, more than half of coal mining is done using the bucketwheel excavators. Design and manufacture of advanced bucket-wheel excavators and increasing their productivity is a topical task. The article proposes a design solution for the working tool of the bucket-wheel excavator, that uses spherically-shaped buckets, which makes it possible to increase the fill factor of the bucket at different directions of the bucket loading. This will not only increase the efficiency of the mining operations, but also significantly reduce the cycle time. Methods used. A complex approach that included a system scientific analysis and generalization of previously published studies was used in addressing the tasks set. Results. The working tool of the bucket-wheel excavator with spherically shaped buckets has been designed and simulated. Practical value. This approach can be implemented in the development of promising designs of the bucket-wheel excavators