Biodegradable magnesium alloys, owing to their mechanical compatibility with vascular tissues, excellent biocompatibility, and biodegradability, have broad application prospects in implantable biomedical devices such as cardiovascular stents. However, when the degradation rate is not well matched to the required duration of radial support, or when degradation exhibits significant spatial heterogeneity, premature deterioration of mechanical integrity or even structural failure may occur before the stent has fulfilled its intended support function. Computational modeling serves as a core technological approach for stent design and performance prediction. Corrosion damage models based on finite element analysis (FEA) and continuum damage mechanics (CDM) can quantitatively analyze morphological evolution and time-dependent changes in mechanical performance during stent degradation, predict degradation rates and critical failure locations, and provide crucial theoretical support for stent structural optimization and degradation rate regulation. This paper systematically reviews the research progress in numerical simulation corrosion models for biodegradable magnesium alloy stents (MAS), focusing on summarizing the core methods and limitations of existing models. Based on this, it proposes future research directions to achieve accurate prediction and mechanistic analysis of MAS degradation behavior.

To investigate the coupling effects of Al–5Ti–1B-xCe (x = 0, 1, 5, and 10 wt%) refiners and cooling rate on A356 aluminum alloy, wedge-shaped castings with different thicknesses were prepared to obtain various cooling rates. The effects of refiner composition and cooling rate on microstructural evolution and mechanical properties were systematically studied. Compared with conventional Al–5Ti–1B, rare-earth composite refiners more effectively improved the microstructure and mechanical properties of A356 alloy. The Ce content strongly influenced the microstructure of the refiner and its subsequent refinement efficiency. With increasing Ce content, the refinement effect was gradually enhanced, and the finest secondary dendrite arm spacing (SDAS) was obtained using the Al–5Ti–1B–10Ce refiner. Increasing cooling rate directly refined the alloy microstructure and also acted synergistically with the composite refiner, further improving SDAS refinement. As a result, the mechanical properties were significantly enhanced. The alloy refined by Al–5Ti–1B–10Ce at a cooling rate of 22.1 °C/s exhibited the best overall properties, with an ultimate tensile strength of 229.6 MPa, yield strength of 98.4 MPa, and elongation of 12.0%. In-situ tensile observations revealed that microcracks preferentially initiated at second-phase particles, such as Si and Mg2Si phases, phase boundaries, and grain boundaries. Crack propagation mainly occurred along second phases and grain boundaries, with limited transgranular propagation, eventually leading to fracture. Plastic deformation near the crack tip was mainly governed by single-slip and double-slip mechanisms.

Cu/Al/Cu laminated composites fabricated by high-temperature oxygen-free roll bonding contain a pre-existing, continuously distributed trilayer intermetallic compounds (IMCs) structure perpendicular to the rolling direction. In this work, annealing, in-situ SEM heating, TEM/SAED, kinetic analysis, shear testing and molecular dynamics simulations were combined to clarify the stage-dependent growth and shear properties of the composite. The IMCs were identified as Al2Cu, AlCu and Al4Cu9 from the Al side to the Cu side, with their formation mechanism aligning with the solid-state reaction diffusion theory. In-situ observations revealed an asymmetric and stage-dependent growth mode: Al4Cu9 grew faster in the early stage, whereas Al2Cu became dominant in the later stage, accompanied by preferential growth toward the Al side and Kirkendall-void formation. Kinetic analysis confirmed that temperature is the dominant factor controlling IMCs thickening, while holding time mainly follows parabolic diffusion-controlled growth. Additionally, a moderate extension of the holding time creates favorable conditions for the diffusion of elements, a finding that aligns with the results of molecular dynamics simulations. Shear performance tests indicate that interfacial fracture primarily occurs in two modes: aluminum layer fracture and intermetallics fracture. Research has demonstrated that excessively high annealing temperatures and prolonged holding times can result in the excessive growth of intermetallics at the interface, thereby compromising the mechanical properties of the interface. The implementation of medium-temperature and short-time heat treatment processes effectively improves the mechanical properties of the interfacial layer. To determine the optimal heat treatment process, a comprehensive analysis of the effects of heat treatment on the microstructure and mechanical properties of the interface was conducted. The optimal annealing parameters were established as holding at 320 °C for 1 h followed by air cooling.

Lower-limb arterial stents implanted in the femoropopliteal segment are exposed to repeated axial shortening, bending, and torsion during daily limb motion. These coupled deformation modes may induce strain localization at connector and crown-transition regions, promote fatiguecrack initiation, and reduce long-term structural reliability. This study investigated the fatigue failure mechanism and crack-growth reliability of a self-expanding nitinol lower-limb arterial stent under coupled multiaxial loading. A three-dimensional stent-vessel finite element model was developed to reproduce crimping, self-expansion, and service-related dynamic deformation. The assessment framework combined nitinol-specific local mean/alternating-strain screening, comparative high-cycle fatigue evaluation using fe-safe, corrected Paris-law crack-growth analysis, and a competing-failure reliability model incorporating cyclic degradation and single-event overload. The maximum equivalent strain increased from 2.134E to 3 under bending-torsion loading to 2.912E-3 under coupled compression-bending-torsion loading. The corresponding fatigue life decreased from approximately 1.82E9 cycles to 1.39E8 cycles, and the safety factor decreased from 7.55 to 2.894. Crack-growth analysis indicated that torsional shear accelerated the transition from stable crack extension to rapid crack growth, whereas axial compression governed the formation of connector-dominated fatigue-critical regions. Reliability analysis further showed that high-activity loading scenarios produced earlier reliability degradation because overload events were superimposed on cyclic crack growth. These results suggest that femoropopliteal stent failure should be interpreted as a progressive sequence of local strain concentration, microcrack initiation, stable crack growth, overload-assisted damage accumulation, and final reliability degradation. The proposed framework provides a mechanics-based basis for connector optimization, fatigue-risk screening, and individualized postoperative activity management. However, its clinical translation requires further validation through device-specific bench fatigue testing, fracture-surface analysis, and long-term follow-up observations.

Wave energy is a promising sustainable energy yet to be fully exploited due to the low frequency and broad-banded wave fields, so much so that difficult to capture, resulting in low efficiency and limited power output from current many wave energy harvesters. Here, a topological defect gyro-multigrid triboelectric nanogenerator (TD-GM-TENG) is proposed that harnesses the mechanical energy of ocean waves to generate electricity and promotes the accumulation of triboelectric charge on the basis of realized from low to high rotation speed under the precession and gravitation acceleration effects. It benefited from topological defect strategy, TD-GM-TENG offers a charge transfer rate of 3.1 & micro;C s(-1) that when can reach to a speed of nearly 1000 rpm at the wave frequency of 1 Hz. Furthermore, the charge density reaches 90 & micro;C m(-)(2) in a cycle of 0.06 s, which is 1.6 times higher than the same kind of spherical-TENGs in the field of ocean energy harvesting. Finally, TD-GM-TENG unit outputs a peak power of 3.7 mW at the simulated water wave environment of 1 Hz and demonstrates its applicability and feasibility of being used as a distributed emergency power supply in the offshoring observation and early warning services.

This study investigates how trace Ce/Gd additions (0.5 wt%) affect the corrosion behavior of ZK61 magnesium alloy by combining first-principles calculations with experimental validation. The results reveal that both elements transform binary Mg-Zn phases into ternary Mg-Zn-RE compounds. These new phases exhibit a lower work function and electrode potential closer to the α -Mg matrix than the cathodic MgZn _2 phase, thereby reducing the micro-galvanic driving force. Consequently, the corrosion resistance is significantly improved, as confirmed by hydrogen evolution and electrochemical tests, with the performance ranking as ZK61-0.5Gd > ZK61-0.5Ce> ZK61. This work establishes a clear structure–property relationship, demonstrating that rare earth elements enhance corrosion resistance by mitigating galvanic coupling through controlled phase transformation.

The electrical performance of triboelectric nanogenerators (TENGs) is often influenced by environmental humidity. This paper presents a nanomaterial composite fiber membrane (PVDF/TM-S) designed to enhance electrical performance while improving hydrophobicity for better performance in high-humidity environments. By combining electrospinning and electrostatic spraying techniques, tourmaline and SiO2 are incorporated into PVDF, resulting in a material that not only improves the electrical performance of TENGs but also exhibits excellent hydrophobic properties. The addition of tourmaline improves the uniformity of the fiber structure and increases the (3-phase content in PVDF. Meanwhile, the incorporation of SiO2 creates larger pores and a micro/ nanosphere support structure, which increases the surface area of the fiber membrane. This enhancement leads to a higher charge transfer, resulting in a short-circuit current of 8.3 mu A and an open-circuit voltage of 308.4 V. The instantaneous output power density reaches 624.97 mW/m2. Additionally, the surface morphology of the fiber membrane is altered, with a water contact angle of 147.2 degrees, an increase of 131 %. Under an environmental humidity of 80 %, the charge transfer increases to 78 nC, a 14.7-fold improvement. The TENG based on the PVDF/TM-S fiber membrane generates a stable output signal at areas of the human body prone to sweating. In high-humidity environments, it can power a thermometer and, after energy collection, successfully light up 200 LED lights. Therefore, the PVDF/TM-S fiber membrane developed in this study holds significant potential for applications in energy harvesting, powering electronic devices, and signal sensing in high-humidity environments.

Nitinol stents are extensively utilized in the treatment of peripheral arterial stenosis due to their exceptional material properties. However, the risk of stent fatigue failure increases due to complex arterial deformation in daily activities. To explore the effect of physiological loads on the fatigue failure of stents, the implantation process and the service process of the nitinol stent are simulated based on the finite element method. The fatigue crack propagation life and reliability of the stent under physiological loads are analyzed based on fracture mechanics and probability theory. Moreover, fatigue tests (bending, torsion, and bending-torsion) are conducted on the nitinol stent with the aid of self-designed multi-axis fatigue testing equipment. Furthermore, the results are compared and verified with simulation calculations. The results indicate that the superimposed load exerts a significant impact on the fatigue and reliability of stents, with the bending load playing a dominant role. The larger the initial crack, the smaller the fatigue life of stents. Additionally, it is demonstrated that the experimental results related to the influence of the fracture position and load of the stent are basically consistent with the numerical simulation results, but the fatigue life is shorter than the predicted result. These findings may provide a scientific basis for the fatigue assessment and reliability application of nitinol stents.

The corrosion kinetics and the influence of Ce content on the corrosion performance of ZK61-xCe (x = 0, 0.5, 1.0, 1.5, wt%) magnesium alloys in NaCl (0.1 mol l ^−1 ) solution were investigated using hydrogen evolution tests combined with observations of corrosion morphology. The role of compound on the corrosion of the alloy was analyzed based on changes in the microstructure, electrode potentials of compounds and matrix, and electrochemical properties of the corrosion product film. The results show that the corrosion rate of the experimental alloy is faster in the first 3 h, then the corrosion rate is gradually reduced, and the corrosion process fits the power-exponential dynamics equation. The corrosion rate constants k and exponential n in the corrosion kinetic equations first decrease and then increase with the increase of Ce content, with the Ce content is 0.5wt%, the alloy has the slowest corrosion rate and the best corrosion resistance. The corrosion rate of the alloy is controlled by the micro-galvanic corrosion. After adding Ce to the ZK61 alloy, the MgZn _2 in the alloy is converted to (Mg, Zn) _12 Ce with more negative electrode potential, and the electrode potential decreases from −0.811 V to −1.002 V. The electrode potential of the α -Mg matrix in the alloy is about −1.451 V, and the potential difference between the compounds and the α -Mg matrix decreases, the corrosion driving force of micro-galvanic corrosion decreases, and the corrosion resistance increases. With the increase of Ce content, the amount of (Mg, Zn) _12 Ce compounds increases, resulting in an increased number of micro-galvanic couples, increased migration charge density, and decreased corrosion resistance. As the corrosion proceeds, the number of (Mg, Zn) _12 Ce exposed on the surface of the substrate increases, blocking the contact between the substrate and the corrosion medium, himpeded lateral corrosion propagation and longitudinal corrosion extension of the α -Mg matrix.

The corrosion kinetics and the influence of Gd content on the corrosion performance of ZK61-xGd (x = 0, 0.5, 1.0, 1.5, wt%) magnesium alloys in NaCl (0.1 mol/L) solution were investigated using hydrogen evolution tests combined with observations of corrosion morphology. Based on the analysis of the impact of compounds on alloy corrosion, changes in microstructure, electrode potential of compounds and matrix, as well as the electrochemical properties of the corrosion product film were studied. The results show that the corrosion rate of the test alloy is relatively fast in the first 3 h in the corrosive solution, gradually decreasing with the progression of the reaction, and follows a power-law kinetic equation. When the Gd content is 0.5 wt%, the corrosion rate of the alloy is the slowest, with a decrease of 20.6 % compared to ZK61 after 3 h of corrosion. The corrosion rate of the alloy is controlled by micro-electrolytic corrosion. After adding Gd, MgZn2 in ZK61 gradually transforms into ternary phases, namely W-phase (Mg3Gd2Zn3) and I-phase (Mg3GdZn6), with electrode potentials of -1.112 V and -0.961 V, respectively, showing a significant downward trend compared to the electrode potential of ZK61 (-0.811 V). In the experimental alloy, the electrode potential of the alpha-Mg matrix is approximately-1.451 V, with a smaller potential difference between W-phase and I-phase and the alpha-Mg matrix, resulting in a smaller driving force for micro-electrolytic corrosion. With the increase of Gd addition, the number of compounds in the alloy increases, and the number of micro-electrodes increases, which has a negative impact on the improvement of the corrosion resistance of the alloy. With the advancement of the corrosion process, the number of compounds exposed to the corrosion interface increases, and the obstruction effect of corrosion is enhanced, which has a positive impact on the improvement of the corrosion resistance of the alloy.

The complex deformation of a peripheral arterial stent during limb movements is the main reason for its fatigue fracture. The aim of this study is to explore the impact of complex loads on the fatigue behavior and life of lower limb arterial stents. Specifically, the finite element simulation was adopted to compare and analyze the fatigue performance of three stent sunder five superimposed loads. Besides, the life and the fatigue crack growth life of these stents were predicted. It demonstrated that the bending load superimposed on other loads exerted a significant impact on the fatigue performance of these stents. The "spiral" structure design of the stent helped to improve the fatigue durability under complex deformations. Moreover, the prediction method for fatigue crack growth life is relatively conservative, which accounted for approximately 65-97%of the full life. The work provides important references for the fracture assessment and the optimization design of structure of stents.

The study investigates the interaction between vertebral artery stenosis and pulsatile blood flow, with a focus on the mechanical properties and internal dynamics of blood flow. First, an asymmetrical stenosis mathematical model was established to reveal the relationship between the resistance ratio and shear stress ratio and their dependence on stenosis height and length. Next, various stenosis models were constructed using medical imaging data and analyzed through computational fluid dynamics (CFD) and fluid-structure interaction (FSI) methods. Finally, hemodynamic parameters, such as blood flow velocity and time-averaged wall shear stress (TAWSS), along with solid mechanics indicators, including total deformation and von Mises stress, were evaluated. The results indicate that changes in stenosis length and height significantly affect the resistance ratio and shear stress. Whole-segment stenosis in the vertebral artery may lead to thrombosis and intimal damage. In contrast, stenosis at the ostium of the vertebral artery increases the risk of platelet deposition on the vessel wall, potentially triggering atherosclerosis. This could ultimately lead to insufficient blood flow to the brain due to impaired vertebral artery circulation. FSI simulations revealed that elastic vessel walls are more sensitive to high-velocity flows, especially in stenotic and downstream regions. These findings provide critical insights into the effects of stenosis on blood flow and are crucial for developing effective clinical intervention strategies.

Stent implantation depth significantly influences the hemodynamics of the vertebral and subclavian arteries in treating vertebral artery stenosis. This study utilized computational fluid dynamics (CFD) to analyze key hemodynamic parameters in a vertebral artery model with a stent implanted at different depths. Results showed that excessive stent extension into the subclavian artery alters local blood flow, increasing the risk of thrombosis and plaque formation. An optimal implantation depth of 1-2 mm minimizes these risks. These findings provide a theoretical basis for optimizing stent placement, improving the efficacy and safety of interventional treatments for vertebral artery stenosis.

When performing stent intervention for iliac vein compression syndrome, the operator selects the appropriate stent and determines its implantation depth according to the type and severity of iliac vein stenosis in the patient. However, there is still uncertainty regarding how the structure of the stent and its implantation depth affect hemodynamics at the site of lesion. In this paper, we analyzed three commonly used stents (Vena stent from Venmedtch, Venovo from Bard, and Smart stent from Cordis) with different implantation depths (0, 10, 20 mm) using computational fluid dynamics (CFD). We focused on evaluating hemorheological parameters such as time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), etc., within one pulsatile cycle after stent implantation. The correlation between geometric parameters of the stents and hemodynamic indicators was assessed using Pearson correlation coefficient (r), which was further validated through PIV velocity measurement experiment. The results revealed that an increase in implantation depth led to a more pronounced disturbance effect on blood flow at bifurcation for densely arranged support body-type stents. This effect was particularly significant during periods of smooth blood flow. On the other hand, crown-shaped Vena stents exhibited relatively less disruption to blood flow post-implantation. Implantation depth showed a strong negative correlation with TAWSS but a strong positive correlation with OSI and RRT. These findings suggest an increased risk of thrombosis at iliac vein bifurcation following stent placement. Amongst all three tested stents, Vena Stent demonstrated more favorable periodic parameters after implantation compared to others. These results provide valuable theoretical insights into understanding contralateral circulation thrombosis associated with iliac vein stenting.

Owing to its low incidence, small trauma, fast recovery, and high efficiency, left atrial appendage occlusion has become a new strategy for preventing stroke caused by atrial fibrillation. Due to a lack of relevant research information on this emerging technology, the effectiveness, stability, or related complications of occluders are mostly observed from a clinical perspective. However, there are fewer studies on the mechanical properties and safety of these occluders. In this study, a new left atrial appendage occluder is proposed, and a complete numerical simulation analysis framework is established through the finite element method to simulate the actual implantation and service process of the left atrial appendage occluder. Besides, the influence of the structural size and release scale of the occluder on its support performance, occluding effect, and safety is also explored. The results demonstrate that the structural size and release scale exert a significant impact on the support performance, occluding effect, and safety of the occluder. The structural optimization of the occluder contributes to enhancing its mechanical performance, thus ensuring its stability and effectiveness after implantation. Overall, these efforts may lay a scientific foundation for the structural optimization, safety evaluation, and effectiveness prediction of the occluder. Furthermore, these findings also provide effective reference for the application of numerical simulation technology in the research on the left atrial appendage occlusion.

Magnesium alloy is one of the most widely used lightweight structural materials, and the development of high strength-toughness magnesium alloy is an important research field at present and even in the future. The preparation process parameters of magnesium alloy directly affect the microstructure of the magnesium alloy, and then determine the properties of the magnesium alloy. The cooling rate has important effects on the microstructure and properties of the magnesium alloy, and is an important preparation process parameter that cannot be ignored. Both the cooling rate from liquid phase to solid phase and the cooling rate of the magnesium alloy after heat treatment will change the microstructure of the magnesium alloy. Furthermore, the properties of magnesium alloy will be affected. In this paper, the effects of cooling rate on the solidification behavior, the rheological behavior, the change of microstructure (the solid solution of alloying elements in matrix, the composition, size, distribution and morphology of second phase, the diffusion and segregation of alloying elements, the grain size, the formation and morphology of dendrite, etc.), and the effects of cooling rate of magnesium alloy after heat treatment on the microstructure and stress distribution are reviewed. The reasons for the divergence about the influence of cooling rate on the microstructure of magnesium alloy are analyzed in detail. The effects of cooling rate on the mechanical properties, corrosion resistance and oxidation resistance of magnesium alloy are also analyzed and discussed deeply. Finally, the new methods and approaches to study the effects of cooling rate on the microstructure and properties of magnesium alloy are prospected.

After the implantation of lower limb artery stents, the complex loading conditions imposed on the limb can lead to fatigue failure, which may induce inflammation and restenosis. To investigate the effect of multi-axial loading conditions on the fatigue performance of stents, five stents, namely APsolute Pro (APbott Vascular, USA), Complete SE (Medtronic, USA), Protege EverFlex (PE3, USA), Pulsar-35 (Biotronik, Germany), and E-luminexx-B (Bard, USA), were analyzed based on the finite element method (FEM). Besides, their fatigue strength was determined under three levels of loading conditions, including tension-bending-torsion and compression-bending-torsion. Based on that, the fatigue life of these stents was predicted. The results showed that based on the nominal stress method, tension-bending-torsion loading had a more significant impact on the fatigue life of stents than compression-bending-torsion loading. Besides, two different types of initial cracks were analyzed by the fracture mechanics method. The results suggested that both the initial crack and the external load were the main causes of stent fatigue fractures. Compared with the loading nature, the influence of the initial crack on stent fatigue life was more significant. Under the same loading condition, the APsolute Pro stent had the longest fatigue life, while the E-luminexx-B stent had the shortest. Moreover, the mechanism of stent fatigue failure was revealed by exploring the fatigue performance and life prediction of stents under complex loading conditions. These findings have important implications for improving the structural design of stents and their clinical selection.

BACKGROUND AND OBJECTIVE:The lower extremity movement involves a complex and large amplitude extremity movement process, and arterial stents implanted in the lower extremity are prone to complex mechanical deformation behavior. Hence, the lower extremity arterial stent is required to have favorable comprehensive mechanical properties.METHODS:In this study, a new lower extremity arterial stent (New) was proposed, and its deformation behavior and mechanical properties were analyzed by numerical simulations under different deformation modes, such as radial compression, axial compression/tension, bending, and torsion. Stents with different diameters were modeled to compare the effect of diameter size on their biomechanical properties. Additionally, a comparative analysis was conducted between this new stent and seven commercially available stents.RESULTS:The results demonstrated that the stent diameter exerted a significant effect on its deformation behavior and mechanical properties. Specifically, with the increase of the stent diameter, the radial expansion rate, radial shrinkage rate, radial support stiffness, axial compression stiffness, and axial tensile stiffness tended to decrease, and the expansion inhomogeneity, stenosis rate, bending stiffness, and torsional stiffness tended to increase. In contrast, the stent diameter exerted a small effect on the stent axial shortening rate and ellipticity. The new lower extremity arterial stent was validated to outperform other stents in terms of most performance indicators. Especially, the radial expansion rate and ellipticity of the New stent were better than those of all commercially available stents. Moreover, the New stent presented favorable mechanical properties and flexibility under the premise of ensuring the support performance.CONCLUSIONS:Based on these findings, this lower extremity arterial stent may play a better therapeutic effect in clinical application. Furthermore, these analysis results may provide reference for the clinical application and selection of the stent.

The deformation of arterial stents in lower limbs during limb movement is the main cause of fracture failure. At present, it has been revealed in most studies that the fatigue strength and life of stents are closely related to the deformation behavior and structure of stents. In this study, the FEM was used to simulate the deformation behavior of three typical lower limb arterial stents under pulsating load, axial tension, axial compression, bending, and torsion. The association of deformation behavior with the fatigue strength and life of stents was analyzed based on the fatigue strain theory and fracture mechanics. In addition, a new life prediction method of the stent is proposed based on the fitting method of the fatigue life curve of high cycle fatigue materials. The prediction method can provide a new solution for the evaluation of the fracture failure of the stent. These findings are expected to lay a referential foundation for the evaluation of stent fracture failure and provide guidance for the clinical application and selection of stents.

In order to study the effects of REs (Ce, Y and Gd) on the grain size and the grain refinement mechanism of AZ91 as-cast magnesium alloy at different cooling rates, the AZ91- x RE(Ce, Y, Gd, x = 0, 0.3, 0.6, 0.9) alloys with different cooling rates were prepared by die casting. The results show that the addition of REs to AZ91 magnesium alloy and the increase in cooling rate both can refine the grain size of the alloy, but the grain refinement effects of REs on AZ91 magnesium alloy will be weakened when the alloy is solidified at a faster cooling rate. The grain refinement effects of REs on AZ91 magnesium alloy are mainly due to the rare earth compounds of Al 4 Ce, Al 2 Y and Al 2 Gd which can act as heterogeneous nucleation particle to promote nucleation and the inhibitory effects of rare earth compounds distributed near grain boundaries on the grain growth. Increasing the cooling rate of the alloy will reduce the effective constitutional supercooling zone and increase the proportion of nucleation-free zone, which will weaken the heterogeneous nucleation particle effect of Al 4 Ce, Al 2 Y and Al 2 Gd, thereby weakening the grain refinement effects of REs on the AZ91 magnesium alloy at a faster cooling rate.