Search Results (1,261)

Erosion wear is a major cause of surface degradation in metallic materials exposed to harsh marine environments. In this study, the erosion wear resistance of the 18Ni300 maraging steel repaired by underwater direct metal deposition (UDMD) is investigated. Results show that UDMD is successfully applied to repair the 18Ni300 samples in underwater environment. Full groove filling and sound metallurgical bonding without cracks are achieved, demonstrating its potential for underwater structural repair. Microstructural analyses reveal good forming quality with fine cellular structures and dense lath martensite in the deposited layer, attributed to rapid solidification under water cooling. Compared to in-air DMD, the UDMD sample exhibits higher surface microhardness due to increased dislocation density and microstructural refinement. Erosion wear behavior is evaluated at 30° and 90° impingement angles, showing that wear mechanisms shift from micro-cutting and plowing at 30° to indentation, crack propagation, and spallation at 90°. The UDMD samples demonstrate superior erosion wear resistance with lower mass loss, particularly at 30°, benefiting from surface work hardening and microstructural advantages. Progressive surface hardening occurs during erosion due to severe plastic deformation, reducing wear rates over time. The combination of refined microstructure, high dislocation density, and enhanced work hardening capability makes UDMD-repaired steel highly resistant to erosive degradation. These findings confirm that UDMD is a promising technique for repairing marine steel structures, offering enhanced durability and long-term performance in harsh offshore environments. Full article

In this paper, the austenite grains growth behavior in the austenitizing process of Nb–Ti micro-alloyed medium manganese steel was studied through in situ observation by high temperature laser confocal microscope. The results show that the average austenite grain sizes change from about 3 μm at 1050 °C to over 50 μm at 1250 °C. When the grain boundary is a small-angle grain boundary, one grain boundary will split into several dislocations. With the extension of heating time, the lattice orientation difference further decreases, and the remaining dislocations may merge into new grain boundaries. The most suitable heating temperature for the medium manganese steel in this paper is from 1100 °C to 1150 °C, taking into account influences such as grain size, grain boundary damage, and deformation resistance. Full article

This study investigates the development of axial force in micro anti-slide piles under soil movement during slope stabilization. Axial force arises from two primary mechanisms: axial soil displacement ($z_{\mathrm{s}}$) and pile kinematics. The former plays a dominant role, producing either tensile or compressive axial force depending on the direction of $z_{\mathrm{s}}$, while the kinematically induced component remains consistently tensile. A sliding angle of $\alpha =5°$ represents an approximate transition point where these two effects balance each other. Furthermore, the two mechanisms exhibit distinct mobilization behaviors: $z_{\mathrm{s}}$-induced axial force mobilizes earlier than both bending moment and shear force, whereas kinematically induced axial force mobilizes significantly later. The study reveals two distinct pile–soil interaction mechanisms depending on proximity to the slip surface: away from the slip surface, axial soil resistance is governed by rigid cross-section translation, whereas near the slip surface, rotation-dominated displacement accompanied by soil–pile separation introduces significant complexity in predicting both the magnitude and direction of axial friction. A hyperbolic formulation was adopted to model both the lateral soil resistance relative to lateral pile–soil displacement (p-y behavior) and the axial frictional resistance relative to axial pile–soil displacement (t-z behavior). Soil resistance equations were derived to explicitly incorporate the effects of cross-sectional rotation and pile–soil separation. A novel beam-spring finite element method (BSFEM) that incorporates both geometric and material nonlinearities of the pile behavior was developed, using a soil displacement-driven solution algorithm. Validation against both numerical simulations and field monitoring data from an engineering application demonstrates the model’s effectiveness in capturing the distribution and evolution of axial deformation and axial force in micropiles under varying soil movement conditions. Full article

A quasi-static FEM framework for wheel–rail contact is presented, aimed at large parametric analyses including independently rotating wheel (IRW) configurations. Unlike half-space formulations such as CONTACT, the FEM approach resolves global deformations and strongly non-Hertzian geometries while remaining computationally tractable through three key features: (i) a tailored mesh transition around the contact patch, (ii) solver settings optimized for frictional contact convergence, and (iii) an integrated post-processing pipeline for creep forces, micro-slip, and wear. The model is verified against CONTACT, an established surface-discretization reference based on the Boundary Element Method (BEM), demonstrating close agreement in contact pressure, shear stress, and stick–slip patterns across the Manchester Contact Benchmark cases. Accuracy is quantified using error metrics (MAE, RMSE), with discrepancies analyzed in high-yaw, near-flange conditions. Compared with prior FEM-based contact models, the main contributions are: (i) a rigid–flexible domain partition, which reduces 3D computational cost without compromising local contact accuracy; (ii) a frictionless preconditioning step followed by friction restoration, eliminating artificial shear-induced deformation at first contact and accelerating convergence; (iii) an automated selection of the elastic slip tolerance (slto) based on frictional-energy consistency, ensuring numerical robustness; and (iv) an IRW-oriented parametrization of toe angle, camber, and wheel spacing. The proposed framework provides a robust basis for large-scale studies and can be extended to transient or elastoplastic analyses relevant to dynamic loading, curved tracks, and wheel defects. Full article

Precious metals play an important role in various fields, from industry to jewelry and finance. In the industrial field, it is often necessary to know their mechanical properties. Micro-hardness measurement is a suitable test. In this type of test, the results are usually influenced by the Indentation Size Effect (ISE). The paper addresses the problem of micro-hardness measurement and the subsequent interpretation of the measured values using Meyer’s index n, the PSR method, and the Hays–Kendall approach in order to determine the true, test-load-independent micro-hardness values of gold, silver, palladium, and platinum. The tester Hanemann (manufactured by Carl Zeiss, Jena, Germany) was used to measure micro-hardness. The loads applied during the micro-hardness test were between 0.09807 N and 0.9807 N. Investment precious metals with a declared purity of at least 99.95% were used for the measurements. Palladium and silver have a Meyer index close to the validity of Kick’s law, with neutral ISE. Gold and platinum show a slightly “normal” ISE. This may be the influence of the previous deformation of the sample. Full article

Gallium-based room-temperature liquid metal is a promising multifunctional material for microfluidics and precision machining due to its high mobility and deformability. However, precise motion control of gallium-based liquid metal droplets, especially in abrasive particle-laden fluids, remains challenging. This study presents a hybrid control framework for regulating droplet motion in a one-dimensional PMMA channel filled with NaOH-based SiC abrasive suspensions. A dynamic model incorporating particle size and concentration effects on the damping coefficient was established. The system combines a setpoint controller, high-resolution voltage source, and vision feedback to guide droplets to target positions with high accuracy. Experimental validation and MATLAB simulations confirm that the proposed dynamic damping control strategy ensures stable, rapid, and precise positioning of droplets, minimizing motion fluctuations. This approach offers new insights into the manipulation of gallium-based liquid metal droplets for targeted material removal in micro-manufacturing, with potential applications in microelectronics and high-precision surface finishing. Full article

Amidst environmental concerns regarding the use of petroleum-based materials, wood and wood-based products are among the key players in the pursuit of green construction practices. However, environmental degradation of these materials remains a concern during structural design, particularly for outdoor applications. Borrowed from anatomy to preserve human body parts, this study applies and assesses a technique called ‘plastination’ as a new means for moisture management of Western Red Cedar (WRC). Specifically, the proposed technique includes acetone dehydration of WRC, followed by SS-151 silicone vacuum-assisted impregnation and silicone curing. To evaluate the method’s effectiveness, Micro X-ray Computed Tomography (μCT), Fourier Transform Infrared (FTIR) Spectroscopy, Thermogravimetric Analysis (TGA), and static water contact angle measurements were employed. Tensile testing was also performed to quantify the treatment’s effect on WRC’s mechanical properties under moisture conditioning. μCT confirmed an impregnation depth of 21.5%, while FTIR and TGA results showed reduced moisture retention (3.6 wt%) in plastinated WRC due to the absence of hydroxyl groups. Mechanical testing revealed enhanced deformability in treated samples without compromising tensile strength. Upon moisture conditioning, plastinated WRC retained its tensile properties and showed 59% lower moisture absorption and 15% lower weight as compared to conditioned virgin samples. Full article

Total hip arthroplasty (THA) is a widely performed and successful surgical treatment for degenerative joint disease. With increasing use in younger and more active patients, the demand for durable, biocompatible, and low-wear implant materials has grown. Oxidized zirconium (Oxinium, Zr2.5Nb) was introduced as a promising femoral head material, combining the strength of metal with the low-friction properties of ceramic. Despite encouraging early results, clinical reports have documented complications including head wear, especially after dislocation, and metallosis. We present the case of a 64-year-old male who underwent primary THA in 2009 and required revision in 2021 due to severe metallosis. Notably, no dislocation was observed that could explain the damage to the Oxinium head. Surface and subsurface analyses using X-ray photoelectron spectroscopy (XPS) and micro-indentation hardness testing revealed wear and deformation inconsistent with Oxinium’s anticipated durability. These findings highlight the importance of the femoral head–polyethylene liner interface in implant longevity. Although Oxinium–XLPE articulations remain promising, risks such as damage to the femoral head, liner dislocation, impingement, and metallosis must be carefully considered. Surgical technique, liner placement, and locking mechanisms play critical roles in preventing failure. Further biomechanical and clinical studies are needed to optimize implant design and improve long-term outcomes. Full article

Silica-reinforced chitosan/collagen hydrogels are useful for biomedical applications. In this study, thermosensitive chitosan/collagen hydrogels were prepared with different amounts of rice husk ash-derived silica (RHA-Si). Fourier-transform infrared (FTIR) spectroscopy was used to analyze the chemical structure. Results showed that adding RHA-Si did not change the main chemical groups but caused slight shifts, indicating physical interactions. Micro-Computed Tomography (Micro-CT) revealed that RHA-Si altered the shape and size of the pores in the hydrogel. The pore structure became more spherical at certain RHA-Si levels, but not consistently. Rheological tests showed that increasing RHA-Si made the hydrogel stiffer and reduced the gelation time. However, the hydrogel weakened under high strain due to broken physical bonds. Compression tests indicated that low RHA-Si (1% w/v) improved the hydrogel’s strength during small deformations. In contrast, the hydrogel was less resistant to compression at higher RHA-Si levels (2–3% w/v). In summary, adding RHA-Si can improve the structure and strength of chitosan/collagen hydrogels, but excessive RHA-Si may reduce flexibility. The RHA-Si content should be adjusted to match the intended application of the hydrogel. Full article

Micro-pillar compression is a popular experimental technique used for characterizing the mechanical behavior of nano- and micro-laminates. The compressive stress–strain response of the column-shaped thin-film composite can be measured, and the deformation and damage features can be revealed by post-test cross-section microscopy. The development of plastic instability in the form of localized strain concentration (shear bands), leading to eventual failure, is frequently observed. In the present study, a computational approach is used to illustrate the commonality of shear band formation from a continuum standpoint. Systematic finite element analyses are conducted, showing that the strain field tends to become localized once plastic yielding commences. Distinct shear offsets of the layered structure can be revealed from the numerical model, which is similar to those observed in experiments. The actual appearance of shear bands depends on the materials’ constitutive behavior and precise geometries. Post-yield strain hardening reduces the propensity of shear band formation, while strain softening enhances it. Imperfections such as the undulated layer geometry, as well as the frictional characteristics between the specimen and test apparatus, can also influence the shear band morphology and overall stress–strain response. Full article

As a key component of aero transmission systems, internal splines suffer from problems of low efficiency and poor precision in traditional lapping processes due to geometric deformation and high hardness after heat treatment. To address this, this study proposes an ultrasonic vibration lapping technology, which combines the synergistic mechanism of high-frequency vibration and free abrasive particles to achieve efficient and precise machining of small-sized hardened internal splines. By establishing an abrasive grain impact trajectory model and a rolling abrasive grain material removal model, the mechanisms of micro-cutting and impact removal of abrasive particles under ultrasonic vibration are revealed. Based on the local resonance theory, a longitudinal ultrasonic vibration system is designed, and its resonant frequency is optimized through finite element modal analysis. An ultrasonic lapping experimental platform is built, and heat-treated 9310 internal spline samples are used for experimental verification. The results show that, compared with traditional manual lapping, ultrasonic vibration lapping significantly improves the tooth profile and tooth lead deviations. After measurement, following ultrasonic vibration lapping, both the total tooth profile deviation and tooth lead deviation of the internal spline meet the Grade 6 accuracy requirements specified in GB/T 3478.1-2008 Cylindrical straight-tooth involute splines (Metric Module, Tooth Side Fit)—Part 1: General. This study confirms that ultrasonic vibration lapping can effectively correct the geometric accuracy of tooth surfaces and suppress thermal damage, and provides an innovative solution for the high-quality repair of aero transmission components. Full article

In this study, specimens cured with an epoxy adhesive were subjected to fatigue tests, which were conducted under air and water atmospheres at room temperature, because few studies have been conducted on the deformation behavior versus time (number of cycles) of the combined degradation due to moisture and cyclic stress. The epoxy adhesive was cured into plates and then cut into dumbbell-shaped specimens. Micro surface cracks were introduced into the specimen surfaces. The fatigue limit of smooth specimens without cracks in water improved compared to that in air. However, when a pre-crack was introduced at the specimen surface, all specimens fractured from the crack in water and showed the same strength as in air. Fracture toughness showed no significant difference in values between the fatigue tests in air and water. The loss factor, compliance, and creep deformation increased significantly in the fatigue tests in water compared to those for the tests in air. The specimens after testing showed that the C=O peak intensity was the same for immersion in water, fatigue in water, and fatigue in air. Therefore, no change in the chemical structure occurred during any of the loading tests. Full article

In flank milling of thin-walled workpieces, machining deformation is a key issue affecting workpiece accuracy and process stability. Although the traditional finite element method (FEM) offers high accuracy, its low computational efficiency makes it difficult to meet the requirements for rapid prediction in engineering practice. For this purpose, this paper proposes an efficient method for predicting workpiece deformation based on the voxel octree model. First, based on the analysis of the contact position between the cutting tool and the workpiece, the thin-walled workpiece is divided into six levels of voxel units, using a voxel octree model. Then, the stiffness matrix and update model of the voxel units are established. Finally, the deformation prediction is completed by calculating the micro-milling force and the voxel stiffness matrix. The experimental results show that the workpiece deformation predicted by the proposed method is highly consistent with the actual machining measurement. At the same time, compared with traditional FEM and voxel model methods, the calculation time is reduced by 90% and 13.2%, respectively. This method can provide rapid decision support for the optimization of thin-walled workpiece machining processes and effectively improve the efficiency of preliminary research in actual machining. Full article

The present study investigates passive microdroplet generation in a T-junction microchannel using microscopic observations, microscale particle image velocimetry (Micro-PIV) visualization, and lattice Boltzmann simulations. The key flow regimes, i.e., dripping, threading, and parallel flow, are characterized by analyzing the balance between hydrodynamic forces and surface tension, revealing the critical role of the flow rate ratio of the continuous to dispersed fluids in regime transitions. Micro-PIV visualizes velocity fields and vortex structures during droplet formation, while a lattice Boltzmann model with wetting boundary conditions captures interface deformation and flow dynamics, showing good agreement with experiments in the dripping and threading regimes but discrepancies in the parallel flow regime due to neglected surface roughness. The present experimental results highlight non-monotonic trends in the maximum head interface and breakup positions of the dispersed fluid under various flow rates, reflecting the competition between the squeezing and shearing forces of the continuous fluid and the hydrodynamic and surface tension forces of the dispersed fluid. Quantitative analysis shows that the droplet size increases with the flow rate of continuous fluid but decreases with the flow rate of dispersed fluid, while generation frequency rises monotonically with the flow rate of dispersed fluid. The dimensionless droplet length correlates with the flow rate ratio, enabling tunable control over droplet size and flow regimes. This work enhances understanding of T-junction microdroplet generation mechanisms, offering insights for applications in precision biology, material fabrication, and drug delivery. Full article

Background/Objectives: To prevent flap failure, adequate tissue perfusion and effective regenerative processes, undisturbed wound healing are essential, among others. To improve wound healing, various locally and systematically administered pharmacons can be used. This study investigated the effect of PACAP 1-38 (pituitary adenylate cyclase activating polypeptide) and BGP-15 (a nicotinic amidoxime derivative) on the healing of epigastric fasciocutaneous flaps exposed to ischemia–reperfusion (I/R). Methods: Wistar rats were randomly divided into control (no substance), PACAP 1-38, and BGP-15 groups. Groin flaps were prepared bilaterally. The left flap was exposed to 120 min of ischemia prior to suturing it back. We applied wound gels containing substances. Laboratory tests (hematology, erythrocyte deformability, and aggregation) were performed before surgery on the 1st, 3rd, and 7th postoperative days. Lastly, flap skin samples were taken for histological and tensile strength measurements. Results: Impaired erythrocyte deformability and enhanced aggregation were found because of flap I/R. The pharmacons were able to reduce the systemic micro-rheological impairment to varying degrees. The tensile strength increased in the areas of better perfusion. Conclusions: The anti-inflammatory effects of PACAP 1-38 and BPG-15, as well as the impact of PACAP 1-38 on collagen and elastic fiber composition, have been demonstrated. Full article