Search Results (723)

The nanoindentation analysis of zirconium carbide (ZrC) has been studied through molecular dynamics simulations, focusing on various factors such as temperature, stoichiometric ratio, and crystal orientation. The findings show that as temperature increases, both the critical pop-in load and the maximum load decrease, while atomic strain, von Mises stress, and residual indentation depth increase. High temperatures facilitate the nucleation and propagation of 1/2<110> dislocations, which enhance the material’s ability to undergo plastic deformation. Both indentation hardness and Young’s modulus decrease linearly as temperature rises or the concentration of C vacancy increases. For stoichiometric ZrC, as the temperature rises from 10 K to 2100 K, the hardness decreases from 45.04 GPa to 20.36 GPa, and Young’s modulus drops from 396.28 GPa to 254.45 GPa. At 10 K, when the C/Zr ratio is reduced to 0.5, the hardness and Young modulus decrease to 25.32 GPa and 192.09 GPa, respectively. This reduction is attributed to the weakening of Zr-C bonds, which also reduces stress concentration. At elevated temperatures, the impact of C vacancies on the nanoindentation process diminishes due to the thermal softening of the substrate, which lessens the effects of vacancy-induced softening. Regarding anisotropy, Young’s modulus at room temperature decreases from 383.39 GPa on the (001) plane to 335.93 GPa on the $(1\stackrel{\mathrm{-}}{1}0)$ plane, and it reduces further to 303.31 GPa on the $(1\stackrel{\mathrm{-}}{1}1)$ plane; hardness shows a similar decreasing trend. This trend is primarily due to differences in slip systems, surface energies, and the angles between the plane normal and the Zr-C bond axis located directly beneath the surface atoms. Overall, these results may provide theoretical support for the processing and application of ZrC. Full article

In order to study the optimal size and sealing performance of the foot-shaped slip ring for reciprocating seal, the loading method of fluid pressure penetration is used to simulate the effect of fluid medium pressure on the seal, and the multi-objective optimization of the geometry of the slip ring is carried out based on optimization software to obtain the best combination of parameters for the foot-shaped slip ring. The effects of slip ring geometry, pre-compression and working pressure on Von Mises stress and contact pressure were investigated using the finite element method. The results show that the optimized geometry of the foot-shaped slip ring can reduce the maximum contact stress on the main sealing surface from 108.5 MPa to 75.22 MPa (a reduction of 30.7%) and decrease the maximum Von Mises stress of the slip ring from 62.84 MPa to 41.57 MPa (a reduction of 33.8%), thereby greatly reducing the wear of the slip ring while ensuring reliable sealing. In the static sealing condition, a smaller pre-compression (1.2–1.3 mm) leads to stress concentration in the O-ring, and the recommended pre-compression range is 1.4–1.6 mm. In the dynamic sealing condition, the effect of pre-compression on the sealing performance is greater than that of reciprocating motion speed on the sealing performance, and the foot-shaped slip ring seal is found to be more suitable for low-speed operation at 0.1–0.2 m/s. The optimized design provides a data-driven methodology for enhancing the reliability and service life of reciprocating seals in high-pressure environments. Full article

This study investigated the dynamic performance of laminated veneer lumber (LVL) shear-walled structures retrofitted with an aluminum oxide (Al₂O₃) nanocoating through finite element analysis (FEA) using SAP2000 software. Later, the ground motion data from the 1968 Takochi-Oki earthquake was used to conduct linear assessments of the structure. LVL, a sustainable and high-performance timber material, was selected for its favorable strength-to-weight ratio and environmental advantages. Two structural models—a reference uncoated LVL structure and an Al₂O₃-coated counterpart—were analyzed to evaluate the influence of the nanocoating on modal and structural behavior. The Al₂O₃ coating, applied as a thin surface layer (0.002 m per side), was modeled to enhance stiffness and damping characteristics. Modal analysis revealed an increase in natural frequencies from 0.75–1.72 Hz to 1.19–2.85 Hz after coating, indicating improved rigidity. The maximum top displacement decreased by approximately 18%, from 77 mm to 65 mm, without significant mass addition. Additionally, von Mises stresses were reduced from 86.65 MPa to 8.03 MPa, confirming stress redistribution and improved structural stability. These results demonstrate that the Al₂O₃ nanocoating effectively enhances the stiffness, damping, and overall dynamic response of LVL shear walls. The proposed method offers a lightweight, non-invasive, and sustainable alternative to conventional retrofitting techniques, contributing to the development of resilient and eco-efficient timber construction systems. Full article

Fully integrated MITC4 (mixed interpolation of tensorial components) shells remain costly for large-deformation sheet-metal forming benchmarks at production mesh sizes. This paper presents a GPU-resident explicit MITC4 shell solver, implemented as a single CUDA pipeline in which co-rotational kinematics, assumed natural strain transverse shear, through-thickness J2 elasto-plasticity, and rigid-surface penalty contact remain in device memory. The study is positioned as computational verification and benchmarking for the Nakajima hemispherical-dome forming benchmark. Canonical shell tests verify the element kernel through membrane and bending patches and a force-driven cantilever, with the cantilever deflection agreeing with the MacNeal–Harder reference within about 2%. On the 10K-element Nakajima benchmark, the present solver agrees with Abaqus/Explicit with a mean von Mises error of 2.95% over 94% of specimen elements and a maximum shell thickness error of 2.08%. In the clamped/binder transition band, section-mean von Mises agrees to +1.0%, whereas section-maximum stress is under-predicted by 10.9%. A 50K-element Abaqus check remains bounded at 80 mm stroke, with section-mean von Mises differences of +0.6% globally and +0.4% in the transition band. For throughput, a separate 500K-element deck over 1.0 × 10⁻³ s and 15,808 steps give per-step speed-ups of 43.7×, 17.7×, and 13.5× versus 1-, 8-, and 32-core LS-DYNA MPP. Full article

High-speed permanent magnet synchronous motors (PMSMs) used in electric pump-fed liquid rocket engines require stator shielding sleeves to prevent corrosive propellants from causing harm under cyclic pressure. However, metallic sleeves suffer significant losses due to eddy currents. Conversely, pure carbon fiber reinforced polymer (CFRP) sleeves have failed when exposed to 98% H₂O₂. Micro-CT analysis of a failed pump sleeve reveals a four-stage failure mechanism. Manufacturing defects caused matrix cracking, which propagated under pressure and thermal cycling. This progression resulted in the formation of through-thickness leakage paths, which ultimately triggered catalytic decomposition and explosion. To address these issues, an improved dual-layer sleeve is proposed, featuring a 2.5 mm PEEK 450G liner and a 2.0 mm T700S/epoxy CFRP overwrap. Finite Element Analysis (FEA) indicates peak von-Mises stresses of 86.25 MPa and 112.16 MPa, yielding Tsai–Wu safety factors of 2.9 and 1.7. Furthermore, various tests, including immersion, fatigue, burst, hydraulic, and thermal evaluations, demonstrate a burst margin of 2.37× at 7.12 MPa, with only 0.19% increase in mass. This design effectively eliminates leakage pathways while preserving zero eddy-current loss and ensuring a low weight. Full article

Punching is a fundamental and extensively employed process in the field of cold forming, prized for its operational simplicity, high performance, and ability to produce components of superior quality. However, the process is inherently complex, as the selection of optimal punching parameters remains a challenging endeavor. Achieving a high-quality punched product is critically dependent on the precise and validated choice of these parameters, which directly influence the mechanical and geometrical integrity of the final component. In this study, the shear zone height, a key indicator of punched part quality, is systematically investigated. The finite element method (FEM), integrated with the Johnson-Cook material model, is employed to simulate and analyze the influence of various punching parameters on the shear zone height, with particular emphasis on the effect of different punch shaft shapes. The Johnson-Cook model, renowned for its accuracy in capturing material behavior under high strain rates and temperatures, enables a robust and reliable simulation framework. The results of this investigation reveal that punch tools featuring a pointed shaft shape exhibit an almost constant distribution of shear zone height across a range of punching parameters. This consistency suggests that such designs are less sensitive to parameter variations, thereby offering a more stable and predictable performance. Consequently, the pointed punch shape is identified as the optimal configuration for achieving superior punched part quality, minimizing defects, and enhancing process reliability. This work contributes to the advancement of cold forming technology by providing insights into the relationship between punch geometry and shear zone characteristics, ultimately facilitating the selection of punching parameters for improved product quality and process efficiency. Full article

Tooth-supported fixed partial dentures (FPDs) exhibit complex biomechanical behaviour because occlusal loads are transferred through the periodontal ligament (PDL) and heterogeneous mandibular bone. This pilot study aimed to develop a patient-specific NURBS-based finite element analysis (FEA) workflow for anatomically realistic mandibular reconstruction and to evaluate the biomechanical effect of geometric simplification in tooth-supported FPD simulations. Cone beam computed tomography data from a single subject were segmented and reconstructed into a layered three-dimensional model of the mandible and dentition, including cortical bone, cancellous bone, teeth, and PDL. A high-fidelity reference model (V0) and four simplified variants (V1–V4) were analysed under static 500 N loads applied at 0° and 30°. The reference model yielded a maximum von Mises stress of 507 MPa and a peak displacement of 0.74 mm, with stress concentrations consistently localised at the retainer–pontic connector region. Inclusion of the PDL markedly affected the mechanical response, doubling denture displacement in simplified comparative models. Among the simplified configurations, V4, which preserved cortical morphology and PDL representation while omitting detailed trabecular architecture, showed the closest agreement with the reference model, with mean deviations of 6.1% and 5.8% under the two loading conditions, respectively. These findings suggest that patient-specific NURBS–FEA modelling provides a robust framework for biomechanical assessment of tooth-supported FPDs, while controlled simplification may improve computational efficiency without substantially compromising accuracy under static loading conditions. Full article

EMAT technology for Non Destructive testing is an important method for materials testing in several industries. In EMAT tools, a key issue is the EMAT coils design and implementation. Depending on the type of inspection, the coil type should be selected, and then, its dimensions should be calculated. This paper describes a methodology to select, design and implement EMAT coils based on Lorentz Force for applications such as thickness measurement and crack detection. Unlike previous works that focus on a single coil topology, this study integrates coil selection, dimensional design, COMSOL-based radiation-pattern simulation and experimental validation within a single workflow. Four Lorentz-force coil designs are covered: PCB spiral (CSPCB), 3D-printed spiral (CS3D), PCB meander-line (CMPCB) and 3D-printed meander-line (CM3D). Key design parameters are explicitly addressed: number of turns N, outer and inner radii R and $r_0$, track width w and spacing s for spiral coils, and meander length and inter-trace distance for meander-line coils. Simulation verification is performed in COMSOL Multiphysics by evaluating the von Mises stress along a semicircular path around the coil to obtain the angular radiation pattern. Experimentally, polar radiation patterns are measured at 500 kHz, 1.9 MHz and 4 MHz on a steel specimen, matching the simulation frequencies, with maximum amplitudes of 32.2, 46.4, 47.9 and 10.6 mV for CSPCB, CS3D, CMPCB and CM3D, respectively, showing consistent agreement between simulated and measured lobe shape and directivity. This work also uses an analogy with radio frequency antennas to better understand the operation of coils through the concept of radiation patterns, in this case in solid materials such as steel. Full article

Background/Objectives: Due to the inherent rotational instability of the proximal fragment in unstable basicervical intertrochanteric (IT) fractures, the biomechanical effect of lag screw position may differ from that observed in typical unstable IT fractures. This study aimed to evaluate the influence of lag screw positioning on proximal fragment displacement and stress distribution after cephalomedullary nailing (CMN) in unstable basicervical IT fractures using finite element analysis. Methods: Twelve finite element models of unstable basicervical IT fractures fixed with a CM nail were constructed with lag screws placed in four anteroposterior (AP) positions (superior 5 mm, center, inferior 5 mm, and inferior 10 mm) and three axial positions (anterior, center, and posterior). The positional change of the proximal fragment and stress concentration on the nail construct were measured. Results: In this computational model, proximal fragment displacement and stress concentration, including peak von Mises stress and mean stress over a region of interest, increased as the lag screw was positioned more inferiorly on the AP view and more posteriorly on the axial view. Conversely, a relatively superior-anterior lag screw position was associated with the lowest proximal fragment displacement and reduced stress concentration on the nail construct and around the lag screw tip. Conclusions: Within the limitations of this finite element analysis using a single femoral model and axial loading condition, a relatively superior-anterior lag screw position was associated with more favorable biomechanical behavior compared with more inferior or posterior positions. These findings should be interpreted as hypothesis-generating biomechanical observations rather than direct clinical guidance. Full article

Wind–wave misalignment is a pervasive environmental phenomenon that significantly affects the structural integrity of floating offshore wind turbines (FOWTs). For a Spar-type FOWT across the full 0°–90° misalignment range, this study systematically conducts dynamic response characterization and parameter sensitivity analysis, quantifying the directional modulation effects on five critical dynamic indicators, including tower-base Fore-Aft (F-A) and side-to-side (S-S) bending moments, maximum Von Mises stress, and fairlead tensions. Results demonstrate that wind–wave misalignment triggers a significant redistribution of structural energy, where side-to-side bending moments and fairlead tensions exhibit distinct peak characteristics at specific non-collinear headings. Rather than merely evaluating structural responses, this study emphasizes the sensitivity of environmental parameters to reveal a dominance-switching mechanism. As the misalignment angle increases, the governing factors of structural response dynamically shift from wind variables to wave variables. This research provides a rigorous mechanical explanation for complex response evolution and offers a scientific basis for the robust design of floating wind turbines in multi-directional sea states. Full article

Railway screw couplings are safety-critical, yet service failures show fatigue cracking at geometric discontinuities. This work assesses the response of two UIC screw-coupling components—the shackle and trunnion—under longitudinal forces from Traction–Emergency Braking (TEB) manoeuvres. A linear-elastic 3D finite element model was built for 42CrMo4/AISI 4140 steel, idealising the threaded load transfer with an RBE2 condensation and the hook–shackle interface with a tied contact to provide a repeatable baseline. Longitudinal force histories were generated in TrainDy for a freight consist and mapped to Regions of Interest; fatigue was evaluated in Altair HyperLife using rainflow counting, Goodman mean-stress correction, and Palmgren–Miner accumulation on a uniaxial S-N curve. For the 636 kN envelope case, the model predicts an axial displacement of 0.985 mm and von Mises stresses in several relevant regions near the nominal yield strength. Fatigue results rank the trunnion pin fillet as the governing hotspot: representative TEB sequences yield damage indices greater than 1 (often of order 20), while a lower-amplitude braking block shows negligible damage. Overall, the analysed spectra leave little endurance margin for the current geometry and support redesign of critical radii and more realistic contact/boundary modelling. Full article

The long-term success of implant-supported prostheses (ISPs) is strongly influenced by material selection, which affects stress distribution within the implant system and surrounding cortical bone. This study aimed to assess the biomechanical behavior of a four-unit ISP supported by two implants in the posterior region, using different framework and superstructure material combinations through dynamic finite element analysis (FEA). Methods: A three-dimensional (3D) edentulous mandibular model was created using Mimics software, with two implants placed in the first premolar and second molar regions. Four framework materials—titanium (Ti), glass fiber–reinforced composite (GFRC), 3Y-TZP zirconia, and polyether ether ketone (PEEK)—were combined with two superstructure materials, 5Y-TZP zirconia and resin-matrix ceramic (RMC), forming eight groups. Dynamic loading simulated chewing forces, and stress distribution was analyzed using the von Mises criterion. Results: The results demonstrated that 3Y-TZP zirconia frameworks generated the highest stress values across implants, abutments, and cortical bone. RMC crowns consistently produced lower stress than 5Y-TZP zirconia across all the groups. PEEK showed the highest displacement, followed by GFRC, zirconia, and Ti. Conclusion: Materials with higher Young’s modulus tended to exhibit greater stress transfer to the implant, implant components, and cortical bone. In contrast, polymer-based materials may show a tendency toward greater deformation and displacement compared with metallic and ceramic materials. Full article

Background: An exaggerated curve of Spee is a common finding in malocclusions with a deep overbite and requires correction to achieve functional occlusion and long-term stability. Leveling of the curve of Spee using continuous archwire mechanics generates complex force systems, the biomechanical effects of which depend on archwire material properties, cross-sectional dimensions, and the depth of the curvature being corrected. Quantitative data describing stress distribution within the teeth and periodontal ligament during this process remain limited. Objective: To evaluate and compare the stresses generated in the mandibular teeth and periodontal ligament during leveling of the curve of Spee using orthodontic archwires of different materials and dimensions through three-dimensional finite element analysis. Materials and Methods: A three-dimensional finite element model of the mandibular dentition, periodontal ligament, and supporting alveolar bone was constructed from computed tomography data. Orthodontic brackets and archwires of stainless steel, nickel–titanium, and titanium–molybdenum alloy were modeled in four dimensions: 0.014-inch, 0.016-inch, 0.016 × 0.022-inch, and 0.019 × 0.025-inch. Leveling of the curve of Spee was simulated at incremental depths ranging from 2 mm to 6 mm using displacement-controlled activation. Von Mises stresses generated within the teeth and periodontal ligament were recorded and compared across all simulations. Results: Stress magnitudes increased with increasing depth of the curve of Spee, larger archwire dimensions, and greater wire stiffness. Stainless steel archwires produced the highest stresses, followed by titanium–molybdenum alloy, while nickel–titanium archwires consistently generated the lowest stresses in both teeth and periodontal ligament. Conclusions: Archwire material and dimension significantly influence stress generation during leveling of the curve of Spee. Flexible archwires produce lower stress levels and may be advantageous during early correction of deeper curves. Full article

Background/Objectives: Peri-implantitis is a common complication affecting approximately 24% of dental implants and is characterized by progressive bone loss and reduced implant stability. Implantoplasty, an intraoral procedure used to remove biofilm by machining the titanium implant surface, has become increasingly common in clinical practice. However, this procedure may compromise the mechanical integrity of implants, especially when combined with peri-implant bone loss, potentially leading to premature fatigue failure. This study evaluated the effect of different marginal bone resection depths, with and without implantoplasty, on the cyclic mechanical behavior of dental implants. Methods: A total of 200 commercially pure grade 4 titanium implants were embedded in resin simulating human bone at depths of 3, 4, and 5 mm. A subset of implants underwent implantoplasty with a 0.4 mm surface reduction corresponding to the thread width. Finite element analysis was performed to evaluate von Mises stress distribution and predict fatigue behavior. Numerical results were experimentally validated using a servo-hydraulic MTS Bionix system under ISO 14801:2016 conditions. Fatigue limits were determined from the asymptotic region of the load–cycles-to-failure (S–N) curves, and fracture surfaces were examined by scanning electron microscopy. Results: Maximum von Mises stresses were concentrated at the thread–body transition and increased with greater marginal resection depth, with additional stress amplification observed after implantoplasty. Fatigue limits for untreated implants were approximately 351 N, 285 N, and 210 N for 3-, 4-, and 5 mm resections, respectively. Implants subjected to 0.4 mm implantoplasty showed fatigue limits of 311 N, 270 N, and 90 N, respectively. Failure patterns were load-dependent: higher loads produced coronal fractures, whereas lower loads resulted in failure at the implant–abutment connection. Finite element predictions showed strong agreement with the experimental results. Conclusions: Excessive marginal resection significantly decreases the fatigue resistance and long-term mechanical reliability of dental implants, particularly when combined with implantoplasty. The main limitations of this study include is in vitro design, the assumptions inherent to the numerical models, and the variability associated with implantoplasty procedures. Full article

Background: Hip implant fractures are rare, yet difficult to correct once they occur. For cemented implants, fracture is often associated with increased stresses at the implant stem when proximal regions of the implant have debonded. While deterministic analyses offer predictive power by using averages for model inputs, averages fail to capture the variability inherent in device manufacturing and musculoskeletal biology. This study developed a probabilistic finite element model of a debonded hip implant to better account for some of these variabilities to predict the most likely failure mode. The hypothesis was that fatigue would be more likely to occur than overloading. Methods and Materials: Monte Carlo sampling generated 1000 simulations varying the material elastic modulus (implant, cement, and bone) and loading magnitude at stance phase of the gait. The resultant distributions of maximum von Mises stress at the stem were compared to distributions for failure properties in the literature. Results: The analysis found the likelihood of the implant failing due to overloading was remote. In contrast, fatigue failure had a 99.4% chance of occurring. Fracture mechanics predicted that the debonded implant would reach critical flaw length between 1.8 and 26.4 months, with a mean of 7.2 months. Conclusions: The results show good agreement with the findings of the case study the model was based on, particularly in predicting the location of failure and fatigue life. The results of this study provide a framework for developing future decision-making tools that ultimately may assist clinicians in deciding when interventions are necessary to minimize the risk of implant or periprosthetic fracture. Full article